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Sensors, Volume 13, Issue 4 (April 2013) – 80 articles , Pages 3998-5405

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184 KiB  
Correction
Correction: Lee, Y. et al. Geosensor Data Representation Using Layered Slope Grids. Sensors 2012, 12, 17074-17093
by Yongmi Lee, Young Jin Jung, Kwang Woo Nam, Silvia Nittel, Kate Beard and Keun Ho Ryu
Sensors 2013, 13(4), 5404-5405; https://doi.org/10.3390/s130405404 - 22 Apr 2013
Viewed by 5004
Abstract
There are four mistakes at the table derived from the (c) surface slope of Figure 4 in [1]. The direction numbers are derived according to (a) slope directions. The overall direction number should be changed from 6 to 4. The distinct direction number [...] Read more.
There are four mistakes at the table derived from the (c) surface slope of Figure 4 in [1]. The direction numbers are derived according to (a) slope directions. The overall direction number should be changed from 6 to 4. The distinct direction number between the 1st and 2nd subcells should be changed from 0 to 8. The distinct direction number between the 2nd and 3rd subcells should be changed from 8 to 4. The distinct direction number between the 3rd and 4th subcells should be changed from 4 to 6. The authors would like to apologize for any inconvenience this may have caused to the readers of this journal. [...] Full article
(This article belongs to the Section Chemical Sensors)
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Figure 4

Figure 4
<p>The layered slopes for data abstraction in a cell.</p> Full article ">
114 KiB  
Correction
Correction: Zarzo, M. et al. Long-Term Monitoring of Fresco Paintings in the Cathedral of Valencia (Spain) through Humidity and Temperature Sensors in Various Locations for Preventive Conservation. Sensors 2011, 11, 8685-8710
by Manuel Zarzo, Angel Fernández-Navajas and Fernando-Juan García-Diego
Sensors 2013, 13(4), 5403; https://doi.org/10.3390/s130405403 - 22 Apr 2013
Viewed by 5042
Abstract
A typo has been found in our paper [1]. It is stated on page 8698 that the range of acceptable temperature for the conservation of frescoes is 6–25 °C while in the case of RH, this range is 45%–60%, according to the Italian [...] Read more.
A typo has been found in our paper [1]. It is stated on page 8698 that the range of acceptable temperature for the conservation of frescoes is 6–25 °C while in the case of RH, this range is 45%–60%, according to the Italian Standard UNI 10829 (1999). These recommended ranges of temperature (6–25 °C) and RH (45%–60%) correspond to the Standard DM 10/2001 [2], not to UNI 10829. The authors would like to apologize for any inconvenience this may have caused to the readers of this journal. [...] Full article
(This article belongs to the Section Chemical Sensors)
1323 KiB  
Article
Computational Burden Resulting from Image Recognition of High Resolution Radar Sensors
by Patricia López-Rodríguez, Raúl Fernández-Recio, Ignacio Bravo, Alfredo Gardel, José L. Lázaro and Elena Rufo
Sensors 2013, 13(4), 5381-5402; https://doi.org/10.3390/s130405381 - 22 Apr 2013
Cited by 10 | Viewed by 9927
Abstract
This paper presents a methodology for high resolution radar image generation and automatic target recognition emphasizing the computational cost involved in the process. In order to obtain focused inverse synthetic aperture radar (ISAR) images certain signal processing algorithms must be applied to the [...] Read more.
This paper presents a methodology for high resolution radar image generation and automatic target recognition emphasizing the computational cost involved in the process. In order to obtain focused inverse synthetic aperture radar (ISAR) images certain signal processing algorithms must be applied to the information sensed by the radar. From actual data collected by radar the stages and algorithms needed to obtain ISAR images are revised, including high resolution range profile generation, motion compensation and ISAR formation. Target recognition is achieved by comparing the generated set of actual ISAR images with a database of ISAR images generated by electromagnetic software. High resolution radar image generation and target recognition processes are burdensome and time consuming, so to determine the most suitable implementation platform the analysis of the computational complexity is of great interest. To this end and since target identification must be completed in real time, computational burden of both processes the generation and comparison with a database is explained separately. Conclusions are drawn about implementation platforms and calculation efficiency in order to reduce time consumption in a possible future implementation. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)
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<p>Basic principle of a radar system.</p> Full article ">
<p>Example of scattering centers in a target.</p> Full article ">
<p>High resolution range profile.</p> Full article ">
<p>Scattering centers in an ISAR image.</p> Full article ">
<p>RDA Algorithm.</p> Full article ">
<p>System identification flowchart.</p> Full article ">
<p>ISAR image formation flowchart.</p> Full article ">
<p>Profile alignment process; (<b>a</b>) initially misaligned HRRP; (<b>b</b>) pre-aligned HRRP; (<b>c</b>) aligned HRRP after translational motion compensation.</p> Full article ">
<p>Profile alignment processm—2D; (<b>a</b>) initially misaligned HRRP; (<b>b</b>) aligned HRRP after translational motion compensation.</p> Full article ">
1020 KiB  
Article
Validation of Noninvasive MOEMS-Assisted Measurement System Based on CCD Sensor for Radial Pulse Analysis
by Karolis Malinauskas, Paulius Palevicius, Minvydas Ragulskis, Vytautas Ostasevicius and Rolanas Dauksevicius
Sensors 2013, 13(4), 5368-5380; https://doi.org/10.3390/s130405368 - 22 Apr 2013
Cited by 19 | Viewed by 10396
Abstract
Examination of wrist radial pulse is a noninvasive diagnostic method, which occupies a very important position in Traditional Chinese Medicine. It is based on manual palpation and therefore relies largely on the practitioner’s subjective technical skills and judgment. Consequently, it lacks reliability and [...] Read more.
Examination of wrist radial pulse is a noninvasive diagnostic method, which occupies a very important position in Traditional Chinese Medicine. It is based on manual palpation and therefore relies largely on the practitioner’s subjective technical skills and judgment. Consequently, it lacks reliability and consistency, which limits practical applications in clinical medicine. Thus, quantifiable characterization of the wrist pulse diagnosis method is a prerequisite for its further development and widespread use. This paper reports application of a noninvasive CCD sensor-based hybrid measurement system for radial pulse signal analysis. First, artery wall deformations caused by the blood flow are calibrated with a laser triangulation displacement sensor, following by the measurement of the deformations with projection moiré method. Different input pressures and fluids of various viscosities are used in the assembled artificial blood flow system in order to test the performance of laser triangulation technique with detection sensitivity enhancement through microfabricated retroreflective optical element placed on a synthetic vascular graft. Subsequently, the applicability of double-exposure whole-field projection moiré technique for registration of blood flow pulses is considered: a computational model and representative example are provided, followed by in vitro experiment performed on a vascular graft with artificial skin atop, which validates the suitability of the technique for characterization of skin surface deformations caused by the radial pulsation. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
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<p>Different spots of radial artery on the wrist of the left and right hands represent different human organ in traditional Chinese pulse diagnosis.</p> Full article ">
<p>Forward pulse wave is higher in amplitude, while backward wave is lower in amplitude and shifted in phase.</p> Full article ">
<p>(<b>A</b>–<b>C</b>) pulse patterns of young healthy persons: (A) taut, (B) slippery, (C) moderate. Plot (<b>D</b>) illustrates abnormal pulse pattern containing BAD Notch.</p> Full article ">
<p>Scheme for measurement of artificial radial pulses by means of laser triangulation technique.</p> Full article ">
<p>Experimental setup for registration of artificial radial blood flow pulsation: (1) measurement location (test point); (2) vascular graft; (3) flow speed controller; (4) laser triangulation sensor; (5) digital oscilloscope; (6) PC for data management.</p> Full article ">
<p>Plots of registered data for different values of pressure applied to artificial blood flow system: (<b>A</b>), (<b>C</b>) 120 mmHg; (<b>B</b>), (<b>D</b>) 140 mmHg ((A), (B) artificial blood; (C), (D) water).</p> Full article ">
<p>One-dimensional geometrical representation of optical projection on a diffuse surface. <span class="html-italic">F(y)</span> projected image, <span class="html-italic">G(x)</span> diffuse deformed surface, <span class="html-italic">H(z)</span> observed image.</p> Full article ">
<p>Schematic representation of the projection process.</p> Full article ">
<p>Illustration of surface described by function <span class="html-italic">G(x)</span>.</p> Full article ">
405 KiB  
Article
Cramer-Rao Bounds and Coherence Performance Analysis for Next Generation Radar with Pulse Trains
by Xiaowei Tang, Jun Tang, Qian He, Shuang Wan, Bo Tang, Peilin Sun and Ning Zhang
Sensors 2013, 13(4), 5347-5367; https://doi.org/10.3390/s130405347 - 22 Apr 2013
Cited by 35 | Viewed by 7852
Abstract
We study the Cramer-Rao bounds of parameter estimation and coherence performance for the next generation radar (NGR). In order to enhance the performance of NGR, the signal model of NGR with master-slave architecture based on a single pulse is extended to the case [...] Read more.
We study the Cramer-Rao bounds of parameter estimation and coherence performance for the next generation radar (NGR). In order to enhance the performance of NGR, the signal model of NGR with master-slave architecture based on a single pulse is extended to the case of pulse trains, in which multiple pulses are emitted from all sensors and then integrated spatially and temporally in a unique master sensor. For the MIMO mode of NGR where orthogonal waveforms are emitted, we derive the closed-form Cramer-Rao bound (CRB) for the estimates of generalized coherence parameters (GCPs), including the time delay differences, total phase differences and Doppler frequencies with respect to different sensors. For the coherent mode of NGR where the coherent waveforms are emitted after pre-compensation using the estimates of GCPs, we develop a performance bound of signal-to-noise ratio (SNR) gain for NGR based on the aforementioned CRBs, taking all the estimation errors into consideration. It is shown that greatly improved estimation accuracy and coherence performance can be obtained with pulse trains employed in NGR. Numerical examples demonstrate the validity of the theoretical results. Full article
(This article belongs to the Section Physical Sensors)
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<p>The master-slave architecture of NGR.</p> Full article ">
<p>The logarithmic MSE and CRB of (<b>a</b>) the time delay difference and (<b>b</b>) the normalized time delay difference <span class="html-italic">vs.</span> input SNR.</p> Full article ">
<p>The logarithmic MSE and CRB of (<b>a</b>) the total phase difference and (<b>b</b>) the Doppler frequency <span class="html-italic">vs.</span> input SNR.</p> Full article ">
<p>SNR gain <span class="html-italic">vs.</span> input SNR with different number of pulses.</p> Full article ">
<p>Comparisons between total phase differences and T/R phase differences: (<b>a</b>) the logarithmic CRB (<b>b</b>) SNR gain <span class="html-italic">vs.</span> input SNR.</p> Full article ">
266 KiB  
Article
Open-Source Colorimeter
by Gerald C. Anzalone, Alexandra G. Glover and Joshua M. Pearce
Sensors 2013, 13(4), 5338-5346; https://doi.org/10.3390/s130405338 - 19 Apr 2013
Cited by 99 | Viewed by 25638
Abstract
The high cost of what have historically been sophisticated research-related sensors and tools has limited their adoption to a relatively small group of well-funded researchers. This paper provides a methodology for applying an open-source approach to design and development of a colorimeter. A [...] Read more.
The high cost of what have historically been sophisticated research-related sensors and tools has limited their adoption to a relatively small group of well-funded researchers. This paper provides a methodology for applying an open-source approach to design and development of a colorimeter. A 3-D printable, open-source colorimeter utilizing only open-source hardware and software solutions and readily available discrete components is discussed and its performance compared to a commercial portable colorimeter. Performance is evaluated with commercial vials prepared for the closed reflux chemical oxygen demand (COD) method. This approach reduced the cost of reliable closed reflux COD by two orders of magnitude making it an economic alternative for the vast majority of potential users. The open-source colorimeter demonstrated good reproducibility and serves as a platform for further development and derivation of the design for other, similar purposes such as nephelometry. This approach promises unprecedented access to sophisticated instrumentation based on low-cost sensors by those most in need of it, under-developed and developing world laboratories. Full article
(This article belongs to the Section Chemical Sensors)
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<p>The open-source colorimeter: (<b>a</b>) schematic of case design in OpenSCAD, and (<b>b)</b> the assembled case with electronics.</p> Full article ">
<p>The open-source colorimeter circuit schematic.</p> Full article ">
<p>Comparison of the results from the commercial and open-source colorimeter.</p> Full article ">
1015 KiB  
Article
Classification of Sporting Activities Using Smartphone Accelerometers
by Edmond Mitchell, David Monaghan and Noel E. O'Connor
Sensors 2013, 13(4), 5317-5337; https://doi.org/10.3390/s130405317 - 19 Apr 2013
Cited by 134 | Viewed by 13617
Abstract
In this paper we present a framework that allows for the automatic identification of sporting activities using commonly available smartphones. We extract discriminative informational features from smartphone accelerometers using the Discrete Wavelet Transform (DWT). Despite the poor quality of their accelerometers, smartphones were [...] Read more.
In this paper we present a framework that allows for the automatic identification of sporting activities using commonly available smartphones. We extract discriminative informational features from smartphone accelerometers using the Discrete Wavelet Transform (DWT). Despite the poor quality of their accelerometers, smartphones were used as capture devices due to their prevalence in today’s society. Successful classification on this basis potentially makes the technology accessible to both elite and non-elite athletes. Extracted features are used to train different categories of classifiers. No one classifier family has a reportable direct advantage in activity classification problems to date; thus we examine classifiers from each of the most widely used classifier families. We investigate three classification approaches; a commonly used SVM-based approach, an optimized classification model and a fusion of classifiers. We also investigate the effect of changing several of the DWT input parameters, including mother wavelets, window lengths and DWT decomposition levels. During the course of this work we created a challenging sports activity analysis dataset, comprised of soccer and field-hockey activities. The average maximum F-measure accuracy of 87% was achieved using a fusion of classifiers, which was 6% better than a single classifier model and 23% better than a standard SVM approach. Full article
(This article belongs to the Section Physical Sensors)
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<p>Location of Smartphone.</p> Full article ">
<p>DWT decomposition of signal <span class="html-italic">x</span>[<span class="html-italic">n</span>].</p> Full article ">
<p>System overview of the DWT decomposition and classification process.</p> Full article ">
<p>Average classifier family accuracy for experiment 2.</p> Full article ">
<p>Effect of DWT Levels on classification accuracy.</p> Full article ">
<p>Effect of window length on average accuracy.</p> Full article ">
<p>Effect of choice of wavelet.</p> Full article ">
<p>Average model accuracy for each experiment.</p> Full article ">
<p>Single activity accuracy results for each approach.</p> Full article ">
315 KiB  
Article
A PARALIND Decomposition-Based Coherent Two-Dimensional Direction of Arrival Estimation Algorithm for Acoustic Vector-Sensor Arrays
by Xiaofei Zhang, Min Zhou and Jianfeng Li
Sensors 2013, 13(4), 5302-5316; https://doi.org/10.3390/s130405302 - 19 Apr 2013
Cited by 18 | Viewed by 6944
Abstract
In this paper, we combine the acoustic vector-sensor array parameter estimation problem with the parallel profiles with linear dependencies (PARALIND) model, which was originally applied to biology and chemistry. Exploiting the PARALIND decomposition approach, we propose a blind coherent two-dimensional direction of arrival [...] Read more.
In this paper, we combine the acoustic vector-sensor array parameter estimation problem with the parallel profiles with linear dependencies (PARALIND) model, which was originally applied to biology and chemistry. Exploiting the PARALIND decomposition approach, we propose a blind coherent two-dimensional direction of arrival (2D-DOA) estimation algorithm for arbitrarily spaced acoustic vector-sensor arrays subject to unknown locations. The proposed algorithm works well to achieve automatically paired azimuth and elevation angles for coherent and incoherent angle estimation of acoustic vector-sensor arrays, as well as the paired correlated matrix of the sources. Our algorithm, in contrast with conventional coherent angle estimation algorithms such as the forward backward spatial smoothing (FBSS) estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm, not only has much better angle estimation performance, even for closely-spaced sources, but is also available for arbitrary arrays. Simulation results verify the effectiveness of our algorithm. Full article
(This article belongs to the Special Issue Last Trends in Acoustic Sensing)
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<p>The structure of acoustic-vector sensor array [<a href="#b14-sensors-13-05302" class="html-bibr">14</a>].</p> Full article ">
<p>Angle estimation of our algorithm for ULA in SNR = 15 dB (<span class="html-italic">M</span> = 12, <span class="html-italic">J</span> = 100, and <span class="html-italic">K</span> = 3).</p> Full article ">
<p>Angle estimation performance comparison for ULA (<span class="html-italic">M</span> = 12, <span class="html-italic">J</span> = 100, and <span class="html-italic">K</span> = 3).</p> Full article ">
<p>Angle estimation of our algorithm in SNR = 5 dB (<span class="html-italic">M</span> = 12, <span class="html-italic">J</span> = 100, and <span class="html-italic">K</span> = 3).</p> Full article ">
<p>Angle estimation of our algorithm in SNR = 15 dB (<span class="html-italic">M</span> = 12, <span class="html-italic">J</span> = 100, and <span class="html-italic">K</span> = 3).</p> Full article ">
<p>Angle estimation performance comparison (<span class="html-italic">M</span> = 12, <span class="html-italic">J</span> = 100, and <span class="html-italic">K</span> = 3).</p> Full article ">
<p>Angle estimation performance comparison (<span class="html-italic">M</span> = 10, <span class="html-italic">J</span> = 50, and <span class="html-italic">K</span> = 3).</p> Full article ">
<p>Angle estimation performance of our algorithm with different <span class="html-italic">J</span>. (<span class="html-italic">M</span> = 12, and <span class="html-italic">K</span> = 3).</p> Full article ">
<p>Angle estimation performance of our algorithm with different <span class="html-italic">K</span> (<span class="html-italic">M</span> = 12, and <span class="html-italic">J</span> = 100).</p> Full article ">
965 KiB  
Article
Amperometric Immunosensor for Carbofuran Detection Based on MWCNTs/GS-PEI-Au and AuNPs-Antibody Conjugate
by Ying Zhu, Yaoyao Cao, Xia Sun and Xiangyou Wang
Sensors 2013, 13(4), 5286-5301; https://doi.org/10.3390/s130405286 - 19 Apr 2013
Cited by 36 | Viewed by 9156
Abstract
In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs) and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au) nanocomposites were modified onto the surface of a glass carbon electrode (GCE) via self-assembly. The nanocomposites can increase the surface [...] Read more.
In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs) and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au) nanocomposites were modified onto the surface of a glass carbon electrode (GCE) via self-assembly. The nanocomposites can increase the surface area of the GCE to capture a large amount of antibody, as well as produce a synergistic effect in the electrochemical performance. Then the modified electrode was coated with gold nanoparticles-antibody conjugate (AuNPs-Ab) and blocked with BSA. The monoclonal antibody against carbofuran was covalently immobilized on the AuNPs with glutathione as a spacer arm. The morphologies of the GS-PEI-Au nanocomposites and the fabrication process of the immunosensor were characterized by X-ray diffraction (XRD), ultraviolet and visible absorption spectroscopy (UV-vis) and scanning electron microscopy (SEM), respectively. Under optimal conditions, the immunosensor showed a wide linear range, from 0.5 to 500 ng/mL, with a detection limit of 0.03 ng/mL (S/N = 3). The as-constructed immunosensor exhibited notable performance features such as high specificity, good reproducibility, acceptable stability and regeneration performance. The results are mainly due to the excellent properties of MWCNTs, GS-PEI-Au nanocomposites and the covalent immobilization of Ab with free hapten binding sites for further immunoreaction. It provides a new avenue for amperometric immunosensor fabrication. Full article
(This article belongs to the Section Biosensors)
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<p>(<b>A</b>) The experimental procedure in the preparation of GS-PEI-Au nanocomposites; (<b>B</b>) Steps involved in the preparation of AuNPs-Ab conjugate; (<b>C</b>) Construction of the immunosensor.</p> Full article ">
<p>(<b>A</b>) The XRD pattern of GS-PEI-Au nanocomposites; (<b>B</b>) The UV-vis absorbances pectrum of GS-PEI-Au nanocomposites.</p> Full article ">
<p>The SEM images of (<b>A</b>) GS-PEI-Au nanocomposites; (<b>B</b>) MWCNTs/GCE; (<b>C</b>) GS-PEI-Au/MWCNTs/GCE; and (<b>D</b>) AuNPs-Ab/GS-PEI-Au/MWCNTs/GCE.</p> Full article ">
<p>CVs of (<b>A</b>): (a) bare GCE, (b) MWCNTs/GCE, (c) GS-PEI-Au/GCE, (d) GS-PEI-Au/MWCNTs/GCE, (e) BSA/AuNPs-Ab/GS-PEI-Au/MWCNTs/GCE, and (f) carbofuran/BSA/AuNPs-Ab/GS-PEI-Au/MWCNTs/GCE; EIS of (<b>B</b>): (a) bare GCE, (b) MWCNTs/GCE, (c) GS-PEI-Au/MWCNTs/GCE, (d) BSA/AuNPs-Ab/GS-PEI-Au/ MWCNTs/GCE, and (e) carbofuran/BSA/AuNPs-Ab/GS-PEI-Au/MWCNTs/GCE; (<b>C</b>) Amperometric responses of the immunosensor with the various antibodies toward different carbofuran concentrations: (a) AuNPs-Ab conjugate, (b) anti-carbofuran Ab. All of these curves were obtained in 5.0 mM [Fe(CN)6]<sup>3−/4−</sup> (pH 7.0) containing 0.1 M KCl at 50 mV/s.</p> Full article ">
<p>Effect of the thickness of the GS-PEI-Au layer (<b>A</b>) (from a to e: 2 μL, 4 μL, 6 μL, 8 μL, 10 μL), the pH of the detection solution (<b>B</b>) and the incubation time (<b>C</b>) on the immunosensor response in 5.0 mM [Fe(CN)6]<sup>3−/4−</sup> (pH 7.0) containing 0.1 M KCl.</p> Full article ">
<p>(<b>A</b>) The CVs responses of the fabricated immunosensor to the different concentration of carbofuran (from a to g): 0.5, 1, 5, 10, 50, 100, 500 ng/mL under the optimal conditions; (<b>B</b>) The calibration curve of the ΔI of the proposed immunosensor <span class="html-italic">vs.</span> the logarithm of carbofuran concentration.</p> Full article ">
<p>(<b>A</b>) The ΔI of proposed immunosensor to: (1) 100 ng/mL carbofuran, (2) 100 ng/mL carbofuran+100 ng/mL chlorpyrifos, (3) 100 ng/mL carbofuran+100 ng/mL dichlorphos, (4) 100 ng/mL carbofuran+100 ng/mL 3-hydroxycarbofuran, (5) 100 ng/mL carbofuran+100 ng/mL carbaryl; (<b>B</b>) Regeneration performance of the immunosensor.</p> Full article ">
956 KiB  
Article
Development of Robust and Standardized Cantilever Sensors Based on Biotin/Neutravidin Coupling for Antibody Detection
by Jiayun Zhang, Hans Peter Lang, Felice Battiston, Natalija Backmann, Francois Huber and Christoph Gerber
Sensors 2013, 13(4), 5273-5285; https://doi.org/10.3390/s130405273 - 19 Apr 2013
Cited by 11 | Viewed by 7283
Abstract
A cantilever-based protein biosensor has been developed providing a customizable multilayer platform for the detection of antibodies. It consists of a biotin-terminated PEG layer pre-functionalized on the gold-coated cantilever surface, onto which NeutrAvidin is adsorbed through biotin/NeutrAvidin specific binding. NeutrAvidin is used as [...] Read more.
A cantilever-based protein biosensor has been developed providing a customizable multilayer platform for the detection of antibodies. It consists of a biotin-terminated PEG layer pre-functionalized on the gold-coated cantilever surface, onto which NeutrAvidin is adsorbed through biotin/NeutrAvidin specific binding. NeutrAvidin is used as a bridge layer between the biotin-coated surface and the biotinylated biomolecules, such as biotinylated bovine serum albumin (biotinylated BSA), forming a multilayer sensor for direct antibody capture. The cantilever biosensor has been successfully applied to the detection of mouse anti-BSA (m-IgG) and sheep anti-BSA(s-IgG) antibodies. As expected, the average differential surface stress signals of about 5.7 ± 0.8 ´ 10−3 N/m are very similar for BSA/m-IgG and BSA/s-IgG binding, i.e., they are independent of the origin of the antibody. A statistic evaluation of 112 response curves confirms that the multilayer protein cantilever biosensor shows high reproducibility. As a control test, a biotinylated maltose binding protein was used for detecting specificity of IgG, the result shows a signal of bBSA layer in response to antibody is 5.8 ´ 10−3 N/m compared to bMBP. The pre-functionalized biotin/PEG cantilever surface is found to show a long shelf-life of at least 40 days and retains its responsivity of above 70% of the signal when stored in PBS buffer at 4 °C. The protein cantilever biosensor represents a rapid, label-free, sensitive and reliable detection technique for a real-time protein assay. Full article
(This article belongs to the Section Biosensors)
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<p>Schematics of cantilever functionalization: (<b>a</b>) gold-coated cantilevers were functionalized with a self-assembled monolayer of SH-C<sub>11</sub>-(PEG)<sub>3</sub>-biotin as a sensor to detect NeutrAvidin. Other cantilevers were coated with SH-C<sub>11</sub>-(PEG)<sub>4</sub> inert to NeutrAvidin serving as reference. (<b>b</b>) Subsequent functionalization with NeutrAvidin. (<b>c</b>) Adsorption of biotinylated BSA forms a multilayer for capturing antibodies. (<b>d</b>) Scheme depicting how antibodies are captured by the multilayer cantilever biosensor.</p> Full article ">
<p>Schematics of cantilever functionalization: (<b>a</b>) gold-coated cantilevers were functionalized with a self-assembled monolayer of SH-C<sub>11</sub>-(PEG)<sub>3</sub>-biotin as a sensor to detect NeutrAvidin. Other cantilevers were coated with SH-C<sub>11</sub>-(PEG)<sub>4</sub> inert to NeutrAvidin serving as reference. (<b>b</b>) Subsequent functionalization with NeutrAvidin. (<b>c</b>) Adsorption of biotinylated BSA forms a multilayer for capturing antibodies. (<b>d</b>) Scheme depicting how antibodies are captured by the multilayer cantilever biosensor.</p> Full article ">
<p>(<b>a</b>) Pre-functionalization of cantilevers coated with SH-C<sub>11-</sub>(PEG)<sub>3</sub>-biotin on cantilever 1-4 (biotin1 to biotin4, shown in green), and with SH-C<sub>11</sub>-(PEG)<sub>4</sub> on cantilever 5-8 (ref1 to ref4, shown in red, randomly selected). (<b>b</b>) Absolute bending signal after specific interaction of biotin and NeutrAvidin (hatched area) displaying different reactivity for sensors and reference cantilevers. (<b>c</b>) Differential bending signal showing a very reproducible negative signal that corresponds to compressive stress building up on the sensor cantilever. Differences between reference cantilevers show no signal. The periodic oscillation observed in the signals is due to the injection process (imperfection of the syringe pump gear).</p> Full article ">
<p>Bar graphs showing the stability of the pre-functionalized biosensor arrays. Each bar represents the average of differential surface stress with standard deviations produced by the response to 1.5μM of NeutrAvidin. (<b>a</b>) Stability in various storage environments. (<b>b</b>) shelf-life graph for different storage durations in PBS.</p> Full article ">
<p>Specificity test of the biotinylated BSA layer on cantilevers to m-IgG. (<b>a</b>) The average absolute bending responses of different protein coated cantilevers upon injecting of m-IgG (red hatched area) displaying different binding affinity. (<b>b</b>) The average differential bending signal of BSA to m-IgG is evaluated by subtracting of the bending signal of bMBP to IgG.</p> Full article ">
<p>The average differential surface stress of sensor cantilever exposed to three various concentrations of m-IgG in separate experiments.</p> Full article ">
<p>(<b>a</b>) shows individual measurement curves analyzed for one out of nine cantilever arrays. In this experiment, the sensor cantilevers were immobilized with bBSA as the sensing layer, only two cantilevers served as reference cantilevers. The difference in responses between a sensor and a reference cantilever shows that the sensor cantilevers bent upward (producing a positive signal), corresponding to tensile surface stress. (<b>b</b>) Bar graph showing the individual differential bending signal values for each curve. (<b>c</b>) Each bar represents the average independent measurements of the difference in responses of a sensor and a reference cantilever. Measurements were carried out on nine different arrays (displayed by nine bars). Recognition between bBSA and antibody (either s-IgG (pink bars) or m-IgG (blue including dark grey bars)) produced mean deflections that do not differ significantly for both the 4 s-IgG arrays and the 5 m-IgG arrays. The dark grey bar displays the average of differential signal corresponding to the data shown in (b).</p> Full article ">
351 KiB  
Article
Optimal Periodic Cooperative Spectrum Sensing Based on Weight Fusion in Cognitive Radio Networks
by Xin Liu, Min Jia, Xuemai Gu and Xuezhi Tan
Sensors 2013, 13(4), 5251-5272; https://doi.org/10.3390/s130405251 - 19 Apr 2013
Cited by 48 | Viewed by 6808
Abstract
The performance of cooperative spectrum sensing in cognitive radio (CR) networks depends on the sensing mode, the sensing time and the number of cooperative users. In order to improve the sensing performance and reduce the interference to the primary user (PU), a periodic [...] Read more.
The performance of cooperative spectrum sensing in cognitive radio (CR) networks depends on the sensing mode, the sensing time and the number of cooperative users. In order to improve the sensing performance and reduce the interference to the primary user (PU), a periodic cooperative spectrum sensing model based on weight fusion is proposed in this paper. Moreover, the sensing period, the sensing time and the searching time are optimized, respectively. Firstly the sensing period is optimized to improve the spectrum utilization and reduce the interference, then the joint optimization algorithm of the local sensing time and the number of cooperative users, is proposed to obtain the optimal sensing time for improving the throughput of the cognitive radio user (CRU) during each period, and finally the water-filling principle is applied to optimize the searching time in order to make the CRU find an idle channel within the shortest time. The simulation results show that compared with the previous algorithms, the optimal sensing period can improve the spectrum utilization of the CRU and decrease the interference to the PU significantly, the optimal sensing time can make the CRU achieve the largest throughput, and the optimal searching time can make the CRU find an idle channel with the least time. Full article
(This article belongs to the Section Sensor Networks)
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<p>Energy sensing model.</p> Full article ">
<p>Cognitive radio networks.</p> Full article ">
<p>Periodic cooperative sensing model.</p> Full article ">
<p>Interference and loss of spectrum access during one period.</p> Full article ">
<p>Sensing period including two state transitions.</p> Full article ">
<p>Processes of sensing spectrum and searching channel.</p> Full article ">
<p>Total sensing loss probability <span class="html-italic">vs.</span> sensing period.</p> Full article ">
<p>(<b>a</b>) Probability of spectrum utilization <span class="html-italic">vs.</span> cooperative false alarm probability (<span class="html-italic">η</span><sub>1</sub>=1 and <span class="html-italic">η</span><sub>2</sub>=0.1). (<b>b</b>) Probability of interference <span class="html-italic">vs.</span> cooperative false alarm probability (<span class="html-italic">η</span><sub>1</sub>=1 and <span class="html-italic">η</span><sub>2</sub>=0.1). (<b>c</b>) Probability of spectrum utilization <span class="html-italic">vs.</span> cooperative false alarm probability (<span class="html-italic">η</span><sub>1</sub>=0.1and <span class="html-italic">η</span><sub>2</sub>=1). (<b>d</b>) Probability of interference <span class="html-italic">vs.</span> cooperative false alarm probability (<span class="html-italic">η</span><sub>1</sub>=0.1and <span class="html-italic">η</span><sub>2</sub>=1).</p> Full article ">
<p>Average throughput <span class="html-italic">vs.</span> sensing time.</p> Full article ">
627 KiB  
Article
Identifying the Key Factors Affecting Warning Message Dissemination in VANET Real Urban Scenarios
by Manuel Fogue, Piedad Garrido, Francisco J. Martinez, Juan-Carlos Cano, Carlos T. Calafate and Pietro Manzoni
Sensors 2013, 13(4), 5220-5250; https://doi.org/10.3390/s130405220 - 19 Apr 2013
Cited by 14 | Viewed by 8071
Abstract
In recent years, new architectures and technologies have been proposed for Vehicular Ad Hoc networks (VANETs). Due to the cost and complexity of deploying such networks, most of these proposals rely on simulation. However, we find that most of the experiments made to [...] Read more.
In recent years, new architectures and technologies have been proposed for Vehicular Ad Hoc networks (VANETs). Due to the cost and complexity of deploying such networks, most of these proposals rely on simulation. However, we find that most of the experiments made to validate these proposals tend to overlook the most important and representative factors. Moreover, the scenarios simulated tend to be very simplistic (highways or Manhattan-based layouts), which could seriously affect the validity of the obtained results. In this paper, we present a statistical analysis based on the 2k factorial methodology to determine the most representative factors affecting traffic safety applications under real roadmaps. Our purpose is to determine which are the key factors affecting Warning Message Dissemination in order to concentrate research tests on such parameters, thus avoiding unnecessary simulations and reducing the amount of simulation time required. Simulation results show that the key factors affecting warning messages delivery are the density of vehicles and the roadmap used. Based on this statistical analysis, we consider that VANET researchers must evaluate the benefits of their proposals using different vehicle densities and city scenarios, to obtain a broad perspective on the effectiveness of their solution. Finally, since city maps can be quite heterogeneous, we propose a roadmap profile classification to further reduce the number of cities evaluated. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Spain 2013)
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<p>RAV visibility scheme: example scenario.</p> Full article ">
<p>Scenarios used in our simulations as street graphs in SUMO: (<b>a</b>) fragment of the city of New York (USA); (<b>b</b>) fragment of the city of Rome (Italy); and (<b>c</b>) fragment of the city of San Francisco.</p> Full article ">
<p>Cumulative histogram for the time evolution of disseminated warning messages when varying the RPM used.</p> Full article ">
<p>Evolution of the warning message dissemination process in the Rome scenario after 20 s, when using (<b>a</b>) the TwoRay Ground and (<b>b</b>) the RAV model.</p> Full article ">
<p>Warning notification time when varying the density of vehicles.</p> Full article ">
<p>Evolution of the warning message dissemination process in the Rome scenario after 20 s, when simulating (<b>a</b>) 100 and (<b>b</b>) 400 vehicles.</p> Full article ">
<p>Warning notification time when varying the roadmap.</p> Full article ">
<p>Evolution of the warning message dissemination process after 20 s, when simulating (<b>a</b>) New York; (<b>b</b>) San Francisco; and (<b>c</b>) Rome scenarios.</p> Full article ">
<p>Classification of different cities based on the density of streets and junctions.</p> Full article ">
826 KiB  
Article
An Ink-Jet Printed Eddy Current Position Sensor
by Nikola Jeranče, Nikola Bednar and Goran Stojanović
Sensors 2013, 13(4), 5205-5219; https://doi.org/10.3390/s130405205 - 18 Apr 2013
Cited by 32 | Viewed by 9945
Abstract
An eddy current sensor with an ink-jet printed flexible inductor has been designed and fabricated. The inductor has been designed by means of software developed in-house. It has been fabricated by ink-jet printing with silver ink on a flexible substrate. The inductor is [...] Read more.
An eddy current sensor with an ink-jet printed flexible inductor has been designed and fabricated. The inductor has been designed by means of software developed in-house. It has been fabricated by ink-jet printing with silver ink on a flexible substrate. The inductor is a part of the oscillator circuit whose oscillating frequency is measured by a microcontroller. The sensor characteristics have been analyzed for two types of application. The first considered application is the displacement of a large conductive target in a direction perpendicular to the inductor plane. The second considered application is the displacement of a small steel ball parallel to the inductor plane. Inductance and oscillating frequency have been measured in order to completely characterize the sensor. The obtained results validate the use of the sensor for both considered applications, and are in good agreement with the simulations. The advantages of this type of sensor are low cost, the possibility for the inductor to match any curved surface and flexibility and precision of the inductor design. Full article
(This article belongs to the Section Physical Sensors)
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<p>Sensor overview.</p> Full article ">
<p>Spiral inductor.</p> Full article ">
<p>Cross section of the printed inductor in front of a conductive target.</p> Full article ">
<p>Method of images for eddy currents (approximation).</p> Full article ">
<p>Simulation results: Inductance variation with distance inductor-target.</p> Full article ">
<p>(<b>a</b>) Top and (<b>b</b>) bottom side of the printed inductor with contacts.</p> Full article ">
<p>Complete electrical scheme of fabricated inductor as a part of oscillator circuit.</p> Full article ">
<p>Program flow chart.</p> Full article ">
<p>Measured inductance of the sensing element.</p> Full article ">
3187 KiB  
Article
Experimental Investigation on Adaptive Robust Controller Designs Applied to Constrained Manipulators
by Samuel L. Nogueira, Tatiana F. P. A. T. Pazelli, Adriano A. G. Siqueira and Marco H. Terra
Sensors 2013, 13(4), 5181-5204; https://doi.org/10.3390/s130405181 - 18 Apr 2013
Cited by 1 | Viewed by 6256
Abstract
In this paper, two interlaced studies are presented. The first is directed to the design and construction of a dynamic 3D force/moment sensor. The device is applied to provide a feedback signal of forces and moments exerted by the robotic end-effector. This development [...] Read more.
In this paper, two interlaced studies are presented. The first is directed to the design and construction of a dynamic 3D force/moment sensor. The device is applied to provide a feedback signal of forces and moments exerted by the robotic end-effector. This development has become an alternative solution to the existing multi-axis load cell based on static force and moment sensors. The second one shows an experimental investigation on the performance of four different adaptive nonlinear H∞ control methods applied to a constrained manipulator subject to uncertainties in the model and external disturbances. Coordinated position and force control is evaluated. Adaptive procedures are based on neural networks and fuzzy systems applied in two different modeling strategies. The first modeling strategy requires a well-known nominal model for the robot, so that the intelligent systems are applied only to estimate the effects of uncertainties, unmodeled dynamics and external disturbances. The second strategy considers that the robot model is completely unknown and, therefore, intelligent systems are used to estimate these dynamics. A comparative study is conducted based on experimental implementations performed with an actual planar manipulator and with the dynamic force sensor developed for this purpose. Full article
(This article belongs to the Special Issue Piezoelectric Sensors and Actuators)
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<p>(<b>a</b>) Image taken from [<a href="#b25-sensors-13-05181" class="html-bibr">25</a>]; (<b>b</b>) Image taken from [<a href="#b26-sensors-13-05181" class="html-bibr">26</a>]; (<b>c</b>) Image taken from [<a href="#b27-sensors-13-05181" class="html-bibr">27</a>].</p> Full article ">
<p>Constrained robot manipulator.</p> Full article ">
<p>Design of the 3D dynamic forces/moments sensor: (1) Moving part; (2) Fixed part.</p> Full article ">
<p>Body of force transmission (4) and arrangement of sensor units: (<b>a</b>) Top view; (<b>b</b>) Bottom view.</p> Full article ">
<p>Schematic of sensor operation.</p> Full article ">
<p>3D dynamic forces/moments sensor.</p> Full article ">
<p>Electronic diagram.</p> Full article ">
<p>(<b>a</b>) UnderActuated Robot Manipulator; (<b>b</b>) Force sensor device coupled to the UARM end-effector.</p> Full article ">
<p>Torque disturbance.</p> Full article ">
808 KiB  
Article
Performance Evaluation of a Modular Detector Unit for X-Ray Computed Tomography
by Zhe Guo, Zhiwei Tang, Xinzeng Wang, Mingliang Deng, Guangshu Hu and Hui Zhang
Sensors 2013, 13(4), 5167-5180; https://doi.org/10.3390/s130405167 - 18 Apr 2013
Cited by 2 | Viewed by 7586
Abstract
A research prototype CT scanner is currently under development in our lab. One of the key components in this project is the CT detector. This paper describes the design and performance evaluation of the modular CT detector unit for our proposed scanner. It [...] Read more.
A research prototype CT scanner is currently under development in our lab. One of the key components in this project is the CT detector. This paper describes the design and performance evaluation of the modular CT detector unit for our proposed scanner. It consists of a Photodiode Array Assembly which captures irradiating X-ray photons and converts the energy into electrical current, and a mini Data Acquisition System which performs current integration and converts the analog signal into digital samples. The detector unit can be easily tiled together to form a CT detector. Experiments were conducted to characterize the detector performance both at the single unit level and system level. The noise level, linearity and uniformity of the proposed detector unit were reported and initial imaging studies were also presented which demonstrated the potential application of the proposed detector unit in actual CT scanners. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
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<p>Illustration diagram of the detector unit.</p> Full article ">
<p>Photo of the modular detector unit.</p> Full article ">
<p>Detector unit readout modes.</p> Full article ">
<p>Photo of the modular detector unit.</p> Full article ">
<p>Setup of the CT detector tests.</p> Full article ">
<p>Noise level of float mode and mode0.</p> Full article ">
<p>PCA accumulative curve.</p> Full article ">
<p>(<b>a</b>) Linearity property of <span class="html-italic">R</span>∼<span class="html-italic">T</span>, X-ray tube parameter is 90 kV, 80 mA; (<b>b</b>) Linearity property of <span class="html-italic">R</span> ∼ <span class="html-italic">I<sub>tube</sub></span>, integration time <span class="html-italic">T</span> = 500 <span class="html-italic">us</span>; (<b>c</b>) Sensitivity property, red line's slope is <span class="html-italic">s<sub>T</sub></span> and blue line's slope is <span class="html-italic">s<sub>I</sub></span>; (<b>d</b>) Difference between <span class="html-italic">s<sub>I</sub></span> and <span class="html-italic">s<sub>T</sub></span></p> Full article ">
<p>(<b>a</b>) Sensitivity <span class="html-italic">s<sub>T</sub></span>. (<b>b</b>) Raw data and corrected results. The blue line is a frame data of 90 kV, 32 mA, green line is 90 kV, 80 mA, red lines are corrected results. (<b>c</b>) Corrected result of a randomly selected channel, obviously, this correction procedure keeps linearity. (<b>d</b>) Uniformity <span class="html-italic">Uni</span>, which is calculated by <a href="#FD11" class="html-disp-formula">Equation (10)</a>. Red line is the corrected result, blue line is raw data's uniformity.</p> Full article ">
465 KiB  
Review
Targeting agr- and agr-Like Quorum Sensing Systems for Development of Common Therapeutics to Treat Multiple Gram-Positive Bacterial Infections
by Brian Gray, Pamela Hall and Hattie Gresham
Sensors 2013, 13(4), 5130-5166; https://doi.org/10.3390/s130405130 - 18 Apr 2013
Cited by 101 | Viewed by 18646
Abstract
Invasive infection by the Gram-positive pathogen Staphylococcus aureus is controlled by a four gene operon, agr that encodes a quorum sensing system for the regulation of virulence. While agr has been well studied in S. aureus, the contribution of agr homologues and [...] Read more.
Invasive infection by the Gram-positive pathogen Staphylococcus aureus is controlled by a four gene operon, agr that encodes a quorum sensing system for the regulation of virulence. While agr has been well studied in S. aureus, the contribution of agr homologues and analogues in other Gram-positive pathogens is just beginning to be understood. Intriguingly, other significant human pathogens, including Clostridium perfringens, Listeria monocytogenes, and Enterococcus faecalis contain agr or analogues linked to virulence. Moreover, other significant human Gram-positive pathogens use peptide based quorum sensing systems to establish or maintain infection. The potential for commonality in aspects of these signaling systems across different species raises the prospect of identifying therapeutics that could target multiple pathogens. Here, we review the status of research into these agr homologues, analogues, and other peptide based quorum sensing systems in Gram-positive pathogens as well as the potential for identifying common pathways and signaling mechanisms for therapeutic discovery. Full article
(This article belongs to the Section Biosensors)
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<p>The structure and function of the <span class="html-italic">agr</span> operon in <span class="html-italic">S. aureus</span>. AgrB is a multifunctional endopeptidase and chaperone protein, and it has been suggested that AgrB is also involved in the export of AIP. AgrD is a propeptide processed by AgrB into the small thiolactone AIP. AgrC is the integral membrane sensor part of a two-component regulatory system. AgrA is the transcription factor response regulator companion to AgrC, and acts on the divergent P2/P3 promoter to upregulate <span class="html-italic">agr</span> and RNAIII expression, in addition to several other transcriptional targets. The regulatory RNA molecule RNAIII acts on numerous gene transcripts to modulate gene expression through post-transcriptional control.</p> Full article ">
<p>Structures of thiolactone and lactone signal peptides. (<b>a</b>) Structure of the prototypical autoinducing peptide, <span class="html-italic">S. aureus</span> AIP-1. (<b>b</b>) AIP-1 from <span class="html-italic">S. pseudintermedius</span>, the only reported <span class="html-italic">Staphylococcus</span> species with a lactone autoinducing molecule. (<b>c</b>) Gelatinase biosynthesis activating peptide (GBAP) from <span class="html-italic">Enterococcus faecalis</span>.</p> Full article ">
<p>Known targets in <span class="html-italic">agr</span>-homologues and other peptide quormone QS systems with the potential for chemotherapeutic intervention to inhibit or retard virulence. Colored dots indicate which species are reported to possess <span class="html-italic">agr</span> homologues or analogues at the indicated step. (1) Binding and C′ terminal cleavage of AgrD/propeptide by AgrB/endopeptidase. (2) Cyclization of cleaved propeptide by AgrB. (3) Export of partially formed AIP/signal peptide by endopeptidase/export channel. (4) Binding of AIP by AgrC/cognate receptor module. (5) Dimerization and/or activation of the AgrC/receptor module HPK. (6) Phosphorylation and activation of AgrA/regulatory module by AgrC/receptor HPK. (7) Binding of consensus sequences by AgrA/regulatory module. (8) Binding of target mRNAs by RNAIII/<span class="html-italic">fsr</span>/VR-RNA and post-transcriptional regulation of gene expression.</p> Full article ">
393 KiB  
Article
Caffeine as a Potential Quorum Sensing Inhibitor
by Siti Nur Maisarah Norizan, Wai-Fong Yin and Kok-Gan Chan
Sensors 2013, 13(4), 5117-5129; https://doi.org/10.3390/s130405117 - 18 Apr 2013
Cited by 90 | Viewed by 13213
Abstract
Quorum sensing enables bacteria to control the gene expression in response to the cell density. It regulates a variety of bacterial physiological functions such as biofilm formation, bioluminescence, virulence factors and swarming which has been shown contribute to bacterial pathogenesis. The use of [...] Read more.
Quorum sensing enables bacteria to control the gene expression in response to the cell density. It regulates a variety of bacterial physiological functions such as biofilm formation, bioluminescence, virulence factors and swarming which has been shown contribute to bacterial pathogenesis. The use of quorum sensing inhibitor would be of particular interest in treating bacterial pathogenicity and infections. In this work, we have tested caffeine as quorum sensing inhibitor by using Chromobacterium violaceum CV026 as a biosensor. We verified that caffeine did not degrade the N-acyl homoserine lactones tested. In this work, it is shown that caffeine could inhibit N-acyl homoserine lactone production and swarming of a human opportunistic pathogen, namely Pseudomonas aeruginosa PA01. To the best of our knowledge, this is the first documentation providing evidence on the presence of anti-quorum sensing activity in caffeine. Our work will allow caffeine to be explored as anti-infective drugs. Full article
(This article belongs to the Section Biosensors)
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<p>Antibacterial assay. (<b>A</b>) Disc without treatment; (<b>B</b>) 20% DMSO; (<b>C</b>) Ultrapure water; (<b>D</b>) 100% DMSO; (<b>E</b>) 0.1 mg/mL caffeine; (<b>F</b>) 0.2 mg/mL caffeine; (<b>G</b>) 0.3 mg/mL caffeine; (<b>H</b>) 0.4 mg/mL caffeine; (<b>I</b>) 0.1 mg/mL; (<b>J</b>) 0.2 mg/mL (+)-catechin; (<b>K</b>) 0.3 mg/mL (+)-catechin; (<b>L</b>) 0.4 mg/mL (+)-catechin. None of the tested caffeine concentrations showed growth inhibition zones except for paper disc treated with 100% DMSO (positive control). This assay was conducted in three independent triplicates.</p> Full article ">
<p>Anti-QS properties of caffeine. (<b>A</b>) untreated well; (<b>B</b>) 20% DMSO; (<b>C</b>) ultrapure water; (<b>D</b>) 0.1 mg/mL (+)-catechin; (<b>E</b>) 0. 2 mg/mL (+)-catechin; (<b>F</b>) 0.3 mg/mL (+)-catechin; (<b>G</b>) 0.1 mg/mL caffeine; (<b>H</b>) 0.2 mg/mL caffeine; (<b>I</b>) 0.3 mg/mL caffeine. Result showed that caffeine promoted QS inhibitory effect in concentration dependent manner. This assay was conducted in three independent triplicates.</p> Full article ">
<p>Caffeine inhibits CV026 violacein production by anti-QS. The violacein production was measured spectrophotometrically as described in Materials and Methods and quantified by reading the OD values of the solution at (<b>a</b>) 585nm and (<b>b</b>) bacterial growth at 600 nm.The statistical significant of each test (n = 3) was evaluated by conducting one-way ANOVA test and a P value of P &lt; 0.05 being significant. Inset: Structure of caffeine.</p> Full article ">
<p>Caffeine did not degrade C6-HSL. Disc (<b>A</b>) C6-HSL treated with ultrapure water (negative control); (<b>B</b>) C6- HSL treated with 20% DMSO (negative control); (<b>C</b>) PBS; (<b>D</b>) C6-HSL treated with 0.1 mg/mL caffeine; (<b>E</b>) C6-HSL treated with 0.2 mg/mL caffeine; (<b>F</b>) C6-HSL treated with 0.3 mg/mL caffeine; (<b>G</b>) C6-HSL treated with 0.1 mg/mL (+)-catechin; (<b>H</b>) C6-HSL treated with 0.2 mg/mL (+)-catechin; (<b>I</b>) C6-HSL treated with 0.3 mg/mL (+)-catechin. The result showed that both caffeine and (+)-catechin have no effect on C6-HSL. This assay was conducted in three independent triplicates.</p> Full article ">
<p>(<b>a</b>) Caffeine inhibited <span class="html-italic">P. aeruginosa</span> PA01 QS signal production. Filter paper A and B were added with 20 μL AHL extracted from <span class="html-italic">P. aeruginosa</span> PA01 culture (A); <span class="html-italic">P. aeruginosa</span> PA01 culture treated with ultrapure water (B). In (C) only PBS buffer (20 μL) was spotted on the CV026 lawn. Filter paper (D); (E); (F); (G); (H); (I); (J); (K); (L); and (M) were added with 20 μL AHLs extracted from <span class="html-italic">P. aeruginosa</span> PA01 culture treated with 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 mg/mL caffeine, respectively. This assay was conducted in three independent triplicates and representative data are shown. This result shows that caffeine interfered AHLs production of <span class="html-italic">P. aeruginosa</span> PA01 in a concentration dependent manner as evident. (<b>b</b>) OD<sub>600nm</sub> reading of <span class="html-italic">P. aeruginosa</span> PA01 overnight culture treated with various concentrations of caffeine. The statistical significant of each test (n = 3) was evaluated by conducting one-way ANOVA test and a P value of P &lt; 0.05 being significant. Our result indicated no significant differences between the treatments and the control at P &lt; 0.05 suggesting that caffeine at these concentrations did not exhibit any antibacterial activity in <span class="html-italic">P. aeruginosa</span> PA01.</p> Full article ">
<p>Swarming inhibition assays. Swarming agars of <span class="html-italic">P. aeruginosa</span> PA01 (<b>a</b>); supplemented with ultrapure water (<b>b</b>); (v/v, negative control); and caffeine of 0.1 mg/mL (<b>c</b>); 0.2 mg/mL (<b>d</b>); and 0.3 mg/mL (<b>e</b>). Images shown are <span class="html-italic">P. aeruginosa</span> PA01 swarming patterns and inhibition effects after 16 hours of incubation at 37 °C. This assay was conducted in three independent triplicates.</p> Full article ">
543 KiB  
Article
Performance Improvement of the One-Dot Lateral Flow Immunoassay for Aflatoxin B1 by Using a Smartphone-Based Reading System
by Sangdae Lee, Giyoung Kim and Jihea Moon
Sensors 2013, 13(4), 5109-5116; https://doi.org/10.3390/s130405109 - 18 Apr 2013
Cited by 93 | Viewed by 12279
Abstract
This study was conducted to develop a simple, rapid, and accurate lateral flow immunoassay (LFIA) detection method for point-of-care diagnosis. The one-dot LFIA for aflatoxin B1 (AFB1) was based on the modified competitive binding format using competition between AFB1 and colloidal gold-AFB1-BSA conjugate [...] Read more.
This study was conducted to develop a simple, rapid, and accurate lateral flow immunoassay (LFIA) detection method for point-of-care diagnosis. The one-dot LFIA for aflatoxin B1 (AFB1) was based on the modified competitive binding format using competition between AFB1 and colloidal gold-AFB1-BSA conjugate for antibody binding sites in the test zone. A Smartphone-based reading system consisting of a Samsung Galaxy S2 Smartphone, a LFIA reader, and a Smartphone application for the image acquisition and data analysis. The detection limit of one-dot LFIA for AFB1 is 5 μg/kg. This method provided semi-quantitative analysis of AFB1 samples in the range of 5 to 1,000 μg/kg. Using combination of the one-dot LFIA and the Smartphone-based reading system, it is possible to conduct a more fast and accurate point-of-care diagnosis. Full article
(This article belongs to the Special Issue Biosensors and Rapid Testing Bio-Analytical Platforms for Food and Water Analysis)
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<p>Schematic description of the one-dot LFIA for AFB1.</p> Full article ">
<p>Smartphone-based reading system.</p> Full article ">
<p>Typical photo image and intensity profile of detection area.</p> Full article ">
<p>Detection limit of AFB1 with the one-dot LFIA.</p> Full article ">
<p>(<b>a</b>) Peak and (<b>b</b>) Area test results measured by the Smartphone-based reading system.</p> Full article ">
<p>Cross-reactivity test results using OTA.</p> Full article ">
877 KiB  
Article
A Low-Cost, Computer-Interfaced Drawing Pad for fMRI Studies of Dysgraphia and Dyslexia
by Frederick Reitz, Todd Richards, Kelvin Wu, Peter Boord, Mary Askren, Thomas Lewis and Virginia Berninger
Sensors 2013, 13(4), 5099-5108; https://doi.org/10.3390/s130405099 - 17 Apr 2013
Cited by 11 | Viewed by 15515
Abstract
We have developed a pen and writing tablet for use by subjects during fMRI scanning. The pen consists of two jacketed, multi-mode optical fibers routed to the tip of a hollowed-out ball-point pen. The pen has been further modified by addition of a [...] Read more.
We have developed a pen and writing tablet for use by subjects during fMRI scanning. The pen consists of two jacketed, multi-mode optical fibers routed to the tip of a hollowed-out ball-point pen. The pen has been further modified by addition of a plastic plate to maintain a perpendicular pen-tablet orientation. The tablet is simply a non-metallic frame holding a paper print of continuously varying color gradients. The optical fibers are routed out of the MRI bore to a light-tight box in an adjacent control room. Within the box, light from a high intensity LED is coupled into one of the fibers, while the other fiber abuts a color sensor. Light from the LED exits the pen tip, illuminating a small spot on the tablet, and the resulting reflected light is routed to the color sensor. Given a lookup table of position for each color on the tablet, the coordinates of the pen on the tablet may be displayed and digitized in real-time. While simple and inexpensive, the system achieves sufficient resolution to grade writing tasks testing dysgraphic and dyslexic phenomena. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
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<p>The pen assembly shown prior to securing with glue and enclosure in heat-shrink tubing.</p> Full article ">
<p>Computer-pen interface circuit diagram. DI0, DI1, and PFI9 are digital inputs of the PCI-6025E.</p> Full article ">
<p>The color map.</p> Full article ">
<p>Run time display.</p> Full article ">
<p>Tablet in use near the bore of the MRI scanner. The pen is connected to a fiber optic cable that goes through a waveguide that is positioned in the wall of the scanner room.</p> Full article ">
<p>Subject response of letter “H”.</p> Full article ">
<p>Dysgraphic and dyslexic subjects.</p> Full article ">
701 KiB  
Review
Progress in Infrared Photodetectors Since 2000
by Chandler Downs and Thomas E. Vandervelde
Sensors 2013, 13(4), 5054-5098; https://doi.org/10.3390/s130405054 - 16 Apr 2013
Cited by 205 | Viewed by 18522
Abstract
The first decade of the 21st-century has seen a rapid development in infrared photodetector technology. At the end of the last millennium there were two dominant IR systems, InSb- and HgCdTe-based detectors, which were well developed and available in commercial systems. While these [...] Read more.
The first decade of the 21st-century has seen a rapid development in infrared photodetector technology. At the end of the last millennium there were two dominant IR systems, InSb- and HgCdTe-based detectors, which were well developed and available in commercial systems. While these two systems saw improvements over the last twelve years, their change has not nearly been as marked as that of the quantum-based detectors (i.e., QWIPs, QDIPs, DWELL-IPs, and SLS-based photodetectors). In this paper, we review the progress made in all of these systems over the last decade plus, compare the relative merits of the systems as they stand now, and discuss where some of the leading research groups in these fields are going to take these technologies in the years to come. Full article
(This article belongs to the Special Issue Photodetectors)
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<p>A plot of the atmosphere's absorption spectrum [<a href="#b16-sensors-13-05054" class="html-bibr">16</a>]. Note that light emitted in the 2.5–3.5 and 5–7 μm ranges are rapidly absorbed by the atmosphere.</p> Full article ">
<p>A lattice constant <span class="html-italic">vs.</span> band gap plot of common semiconductor materials.</p> Full article ">
<p>A band diagram of a quantum well in a QWIP. Carriers are excited by incident photons from the ground energy state of the well (<span class="html-italic">E<sub>1</sub></span>) to the excited energy state of the well (<span class="html-italic">E<sub>2</sub></span>).</p> Full article ">
<p>A band diagram of a quantum cascade detector. Incident light excites a carrier from the ground energy state of the absorbing well to an excited energy state. The carrier then tunnels through the barrier layers into the adjacent wells. This continues until the carrier reaches the ground state of the next period of the superlattice.</p> Full article ">
<p>A band diagram of a InAs(blue)/GaSb(red) SLS. Carrier electrons are excited from the valence band of the GaSb layers to the conduction band of the InAs layers.</p> Full article ">
<p>A band diagram of a InAs(blue)/GaSb(red)/AlSb(green) M-SLS. The inclusion of AlSb into the device gives this structure its eponymous band structure.</p> Full article ">
<p>A band diagram of an nBn IRPD without applied bias. With the barrier in the middle, the left hand side acts as the photo-absorber. Absorbed photons create carrier pairs, which are unimpeded by the barrier. Thermally generated pairs on the right-hand side are blocked by the conduction band barrier, however.</p> Full article ">
<p>A band diagram of a pBn photodiode. A carrier electron is excited from the valence band of the n-type material and swept away from the barrier. The carrier hole is swept past the barrier layer, as it does not produce a potential barrier in the valence band of the p-n junction.</p> Full article ">
<p>A band diagram of a DWELL structure, with a barrier layer (blue), well layer (red), and dot layer (green).</p> Full article ">
2403 KiB  
Article
3D Image Acquisition System Based on Shape from Focus Technique
by Bastien Billiot, Frédéric Cointault, Ludovic Journaux, Jean-Claude Simon and Pierre Gouton
Sensors 2013, 13(4), 5040-5053; https://doi.org/10.3390/s130405040 - 15 Apr 2013
Cited by 36 | Viewed by 10751
Abstract
This paper describes the design of a 3D image acquisition system dedicated to natural complex scenes composed of randomly distributed objects with spatial discontinuities. In agronomic sciences, the 3D acquisition of natural scene is difficult due to the complex nature of the scenes. [...] Read more.
This paper describes the design of a 3D image acquisition system dedicated to natural complex scenes composed of randomly distributed objects with spatial discontinuities. In agronomic sciences, the 3D acquisition of natural scene is difficult due to the complex nature of the scenes. Our system is based on the Shape from Focus technique initially used in the microscopic domain. We propose to adapt this technique to the macroscopic domain and we detail the system as well as the image processing used to perform such technique. The Shape from Focus technique is a monocular and passive 3D acquisition method that resolves the occlusion problem affecting the multi-cameras systems. Indeed, this problem occurs frequently in natural complex scenes like agronomic scenes. The depth information is obtained by acting on optical parameters and mainly the depth of field. A focus measure is applied on a 2D image stack previously acquired by the system. When this focus measure is performed, we can create the depth map of the scene. Full article
(This article belongs to the Section Physical Sensors)
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<p>Sharp and unsharp image formation.</p> Full article ">
<p>Acquisition system.</p> Full article ">
<p>Acquisition process.</p> Full article ">
<p>Optical scheme for the 1st and the nth image.</p> Full article ">
<p>Gaussian approximation.</p> Full article ">
<p>Merged images of two different sequences (<b>a</b>,<b>e</b>), associated depth maps (<b>b</b>,<b>f</b>) and 3D visualizations with (<b>d</b>,<b>h</b>) and without (<b>c</b>,<b>g</b>) texture mapping</p> Full article ">
<p>Merged images of two different sequences (<b>a</b>,<b>e</b>), associated depth maps (<b>b</b>,<b>f</b>) and 3D visualizations with (<b>d</b>,<b>h</b>) and without (<b>c</b>,<b>g</b>) texture mapping</p> Full article ">
282 KiB  
Article
Optimization of Hydrogen Peroxide Detection for a Methyl Mercaptan Biosensor
by Zhan-Hong Li, Houssemeddine Guedri, Bruno Viguier, Shi-Gang Sun and Jean-Louis Marty
Sensors 2013, 13(4), 5028-5039; https://doi.org/10.3390/s130405028 - 15 Apr 2013
Cited by 19 | Viewed by 8553
Abstract
Several kinds of modified carbon screen printed electrodes (CSPEs) for amperometric detection of hydrogen peroxide (H2O2) are presented in order to propose a methyl mercaptan (MM) biosensor. Unmodified, carbon nanotubes (CNTs), cobalt phthalocyanine (CoPC), Prussian blue (PB), and Os-wired [...] Read more.
Several kinds of modified carbon screen printed electrodes (CSPEs) for amperometric detection of hydrogen peroxide (H2O2) are presented in order to propose a methyl mercaptan (MM) biosensor. Unmodified, carbon nanotubes (CNTs), cobalt phthalocyanine (CoPC), Prussian blue (PB), and Os-wired HRP modified CSPE sensors were fabricated and tested to detect H2O2, applying a potential of +0.6 V, +0.6 V, +0.4 V, −0.2 V and −0.1 V (versus Ag/AgCl), respectively. The limits of detection of these electrodes for H2O2 were 3.1 μM, 1.3 μM, 71 nM, 1.3 μM, 13.7 nM, respectively. The results demonstrated that the Os-wired HRP modified CSPEs gives the lowest limit of detection (LOD) for H2O2 at a working potential as low as −0.1 V. Os-wired HRP is the optimum choice for establishment of a MM biosensor and gives a detection limit of 0.5 μM. Full article
(This article belongs to the Special Issue Enzymatic Biosensors)
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<p>Screen printed electrode.</p> Full article ">
<p>Cyclic voltammograms of CSPEs in 0.1 M phosphate buffer solution, pH 7.5 (a); in presence of 1 mM H<sub>2</sub>O<sub>2</sub> (b). Scan rate 20 mV·s<sup>−1</sup>.</p> Full article ">
<p>Amperometric performance of CSPEs for detection of H<sub>2</sub>O<sub>2</sub> at +0.6 V in a stirred 0.1 M phosphate buffer solution, pH 7.5. The upper left inset shows the calibration curve of CSPEs for H<sub>2</sub>O<sub>2</sub> concentration; the lower right inset zooms in the part of the amperometric response of 5 μM H<sub>2</sub>O<sub>2</sub> injected.</p> Full article ">
<p>Cyclic voltammograms of CNT/CSPEs in 0.1 M phosphate buffer solution, pH 7.5 (a); in presence of 1 mM H<sub>2</sub>O<sub>2</sub> (b). Scan rate 20 mV·s<sup>−1</sup>.</p> Full article ">
<p>Cyclic voltammograms of CoPC/CSPEs in 0.1 M phosphate buffer solution, pH 7.5 (a); in presence of 0.1 mM H<sub>2</sub>O<sub>2</sub> (b). Scan rate 20 mV·s<sup>−1</sup>.</p> Full article ">
<p>Cyclic voltammograms of PPD/PB/CSPEs in 0.1 M phosphate buffer solution, pH 7.5 (a); in presence of 0.1 mM H<sub>2</sub>O<sub>2</sub> (b) and 1 mM H<sub>2</sub>O<sub>2</sub> (c). Scan rate 20 mV·s<sup>−1</sup>.</p> Full article ">
<p>Cyclic voltammograms of Os-HRP/CSPEs in 0.1 M phosphate buffer solution, pH7.5 (a____); in presence of 0.1 mM H<sub>2</sub>O<sub>2</sub> (b-----). Scan rate 20 mV·s<sup>−1</sup>.</p> Full article ">
<p>Amperometric performance of Os-HRP/CSPEs sensor in detection of H<sub>2</sub>O<sub>2</sub> at −0.1 V in a stirred 0.1 M phosphate buffer solution, pH 7.5. The upper right inset shows the calibration curve of Os-HRP/CSPEs for H<sub>2</sub>O<sub>2</sub> concentration; the lower left inset zooms in on the part of the amperometric response of 0.01 μM H<sub>2</sub>O<sub>2</sub> injected.</p> Full article ">
<p>The electrocatalytical reductive reaction process of Os-HRP towards H<sub>2</sub>O<sub>2</sub>.</p> Full article ">
1451 KiB  
Article
Application of the Electronic Nose Technique to Differentiation between Model Mixtures with COPD Markers
by Tomasz Dymerski, Jacek Gębicki, Paulina Wiśniewska, Magdalena Śliwińska, Waldemar Wardencki and Jacek Namieśnik
Sensors 2013, 13(4), 5008-5027; https://doi.org/10.3390/s130405008 - 15 Apr 2013
Cited by 23 | Viewed by 7237
Abstract
The paper presents the potential of an electronic nose technique in the field of fast diagnostics of patients suspected of Chronic Obstructive Pulmonary Disease (COPD). The investigations were performed using a simple electronic nose prototype equipped with a set of six semiconductor sensors [...] Read more.
The paper presents the potential of an electronic nose technique in the field of fast diagnostics of patients suspected of Chronic Obstructive Pulmonary Disease (COPD). The investigations were performed using a simple electronic nose prototype equipped with a set of six semiconductor sensors manufactured by FIGARO Co. They were aimed at verification of a possibility of differentiation between model reference mixtures with potential COPD markers (N,N-dimethylformamide and N,N-dimethylacetamide). These mixtures contained volatile organic compounds (VOCs) such as acetone, isoprene, carbon disulphide, propan-2-ol, formamide, benzene, toluene, acetonitrile, acetic acid, dimethyl ether, dimethyl sulphide, acrolein, furan, propanol and pyridine, recognized as the components of exhaled air. The model reference mixtures were prepared at three concentration levels—10 ppb, 25 ppb, 50 ppb v/v—of each component, except for the COPD markers. Concentration of the COPD markers in the mixtures was from 0 ppb to 100 ppb v/v. Interpretation of the obtained data employed principal component analysis (PCA). The investigations revealed the usefulness of the electronic device only in the case when the concentration of the COPD markers was twice as high as the concentration of the remaining components of the mixture and for a limited number of basic mixture components. Full article
(This article belongs to the Section Chemical Sensors)
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<p>Experimental set-up for analysis of volatile fraction of reference gaseous mixtures consisting in: 1—bottle with carrier gas, 2—flow meter, 3—scrubber, 4—prototype of electronic nose, 5—PC.</p> Full article ">
<p>Scheme of integrated circuit.</p> Full article ">
<p>Dependence between sensor signals and barbotage time for A 5 type mixture. Time instants, at which PCA was performed: 20 s (●), 60 s (■). Sensors: 1–TGS 880, 2–TGS 825, 3–TGS 826, 4–TGS 822, 5–TGS 2610, 6–TGS 2602.</p> Full article ">
<p>Result of PCA for the mixtures of type <b>A 5</b>, <b>B 5</b>, <b>C 5</b>, where A 5, B 5, C 5 are the aqueous solutions of the basic components (acetone, isoprene, carbon disulphide, propan-2-ol, formamide) having the concentration of each component in the mixture equal 10 ppb, 25 ppb and 50 ppb v/v, respectively. 1–6 are the mixtures of reference substances with the COPD markers of the respective concentrations: 0 ppb, 5 ppb, 10 ppb, 25 ppb, 50 ppb, 100 ppb v/v. Measurement was obtained for time instant 60 s.</p> Full article ">
<p>Result of PCA for the mixtures of type <b>A 10</b>, <b>B 10</b>, <b>C 10</b>, where A 10, B 10, C 10 are the aqueous solutions of the basic components (acetone, isoprene, carbon disulphide, propan-2-ol, formamide, benzene, toluene, acetonitrile, acetic acid, dimethyl ether) having the concentration of each component in the mixture equal 10 ppb, 25 ppb and 50 ppb v/v, respectively. 1–6 are the mixtures of reference substances with the COPD markers of the respective concentrations: 0 ppb, 5 ppb, 10 ppb, 25 ppb, 50 ppb, 100 ppb v/v. Measurement was obtained for time instant 60 s.</p> Full article ">
<p>Result of PCA for the mixtures of type <b>A 15</b>, <b>B 15</b>, <b>C 15</b>, where A 15, B 15, C 15 are the aqueous solutions of the basic components (acetone, isoprene, carbon disulphide, propan-2-ol, formamide, benzene, toluene, acetonitrile, acetic acid, dimethyl ether, dimethyl sulphide, acrolein, furane, propanol, pyridine) having the concentration of each component in the mixture equal 10 ppb, 25 ppb and 50 ppb v/v, respectively. 1–6 are the mixtures of reference substances with the COPD markers of the respective concentrations: 0 ppb, 5 ppb, 10 ppb, 25 ppb, 50 ppb, 100 ppb v/v. Measurement was obtained for time instant 60 s.</p> Full article ">
<p>Result of PCA for the mixtures of type <b>A 5</b>, <b>A 10</b>, <b>A 15</b>, where A 5, A 10, A 15 are the aqueous solutions of the basic components of amount 5, 10 and 15 in the mixtures of concentration 10 ppb v/v for each component. 1–6 are the mixtures of reference substances with the COPD markers of the respective concentrations: 0 ppb, 5 ppb, 10 ppb, 25 ppb, 50 ppb, 100 ppb v/v. Measurement was obtained for time instant 60 s.</p> Full article ">
<p>Result of PCA for the mixtures of type <b>B 5</b>, <b>B 10</b>, <b>B 15</b>, where B 5, B 10, B 15 are the aqueous solutions of the basic components of amount 5, 10 and 15 in the mixtures of concentration 25 ppb v/v for each component. 1–6 are the mixtures of reference substances with the COPD markers of the respective concentrations: 0 ppb, 5 ppb, 10 ppb, 25 ppb, 50 ppb, 100 ppb v/v. Measurement was obtained for time instant 60 s.</p> Full article ">
<p>Result of PCA for the mixtures of type <b>C 5</b>, <b>C 10</b>, <b>C 15</b>, where C 5, C 10, C 15 are the aqueous solutions of the basic components of amount 5, 10 and 15 in the mixtures of concentration 50 ppb v/v for each component. 1–6 are the mixtures of reference substances with the COPD markers of the respective concentrations: 0 ppb, 5 ppb, 10 ppb, 25 ppb, 50 ppb, 100 ppb v/v. Measurement was obtained for time instant 60 s.</p> Full article ">
2586 KiB  
Article
Study of the Electrocatalytic Activity of Cerium Oxide and Gold-Studded Cerium Oxide Nanoparticles Using a Sonogel-Carbon Material as Supporting Electrode: Electroanalytical Study in Apple Juice for Babies
by M. Yahia M. Abdelrahim, Stephen R. Benjamin, Laura Mª Cubillana-Aguilera, Ignacio Naranjo-Rodríguez, José L. Hidalgo-Hidalgo De Cisneros, Juan José Delgado and José Mª Palacios-Santander
Sensors 2013, 13(4), 4979-5007; https://doi.org/10.3390/s130404979 - 12 Apr 2013
Cited by 21 | Viewed by 11352
Abstract
The present work reports a study of the electrocatalytic activity of CeO2 nanoparticles and gold sononanoparticles (AuSNPs)/CeO2 nanocomposite, deposited on the surface of a Sonogel-Carbon (SNGC) matrix used as supporting electrode and the application of the sensing devices built with them [...] Read more.
The present work reports a study of the electrocatalytic activity of CeO2 nanoparticles and gold sononanoparticles (AuSNPs)/CeO2 nanocomposite, deposited on the surface of a Sonogel-Carbon (SNGC) matrix used as supporting electrode and the application of the sensing devices built with them to the determination of ascorbic acid (AA) used as a benchmark analyte. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the electrocatalytic behavior of CeO2- and AuSNPs/CeO2-modified SNGC electrodes, utilizing different concentrations of CeO2 nanoparticles and different AuSNPs:CeO2 w/w ratios. The best detection and quantification limits, obtained for CeO2 (10.0 mg·mL−1)- and AuSNPs/CeO2 (3.25% w/w)-modified SNGC electrodes, were 1.59 × 10−6 and 5.32 × 10−6 M, and 2.93 × 10−6 and 9.77 × 10−6 M, respectively, with reproducibility values of 5.78% and 6.24%, respectively, for a linear concentration range from 1.5 µM to 4.0 mM of AA. The electrochemical devices were tested for the determination of AA in commercial apple juice for babies. The results were compared with those obtained by applying high performance liquid chromatography (HPLC) as a reference method. Recovery errors below 5% were obtained in most cases, with standard deviations lower than 3% for all the modified SNGC electrodes. Bare, CeO2- and AuSNPs/CeO2-modified SNGC electrodes were structurally characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). AuSNPs and AuSNPs/CeO2 nanocomposite were characterized by UV–vis spectroscopy and X-ray diffraction (XRD), and information about their size distribution and shape was obtained by transmission electron microscopy (TEM). The advantages of employing CeO2 nanoparticles and AuSNPs/CeO2 nanocomposite in SNGC supporting material are also described. This research suggests that the modified electrode can be a very promising voltammetric sensor for the determination of electroactive species of interest in real samples. Full article
(This article belongs to the Special Issue Novel Tools in Electrochemical Sensing)
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<p>Typical HAADF-STEM (<b>A</b>) and HREM (<b>B</b>) micrograph of the sample. Digital Diffraction Pattern of selected areas (<b>C</b>) in image B and the particle size distribution (<b>D</b>) are included.</p> Full article ">
<p>XRD pattern of AuSNPs/CeO<sub>2</sub> nanoparticles.</p> Full article ">
<p>UV-visible spectra recorded for AuSNPs/CeO<sub>2</sub> (5% w/w) nanoparticles at different stirring times: (<b>a</b>) AuSNPs spectrum immediately after the synthesis; AuSNPs/CeO<sub>2</sub> nanoparticles spectra after stirring (<b>b</b>) 15 min; (<b>c</b>) 30 min; (<b>d</b>) 45 min; (<b>e</b>) 1 h; (<b>f</b>) 2 h; (<b>g</b>) 8 h and (<b>h</b>) 10 h.</p> Full article ">
<p>CV voltammograms corresponding to different configurations of the SNGC electrodes tested for 1.00 M of K<sub>4</sub>Fe(CN)<sub>6</sub> recorded at 100 mV·s<sup>−1</sup> of scan rate.</p> Full article ">
<p>CV voltammograms of 1.0 mM AA, in 0.10 M PBS (pH 6.9) at AuSNPs/CeO<sub>2</sub> (2.5% w/w)-modified SNGC electrode (solid lines) at different scan rates: (<b>a</b>) 5; (<b>b</b>) 10; (<b>c</b>) 25; (<b>d</b>) 50; (<b>e</b>) 75; (<b>f</b>) 100; (<b>g</b>) 150; (<b>h</b>) 200 mVmiddot;s<sup>−1</sup>), and at bare SNGC electrode (dashed line) at 50 mV middot;s<sup>−1</sup>. The inset displays the plot of peak current against square root of scan rate.</p> Full article ">
<p>Tafel plots derived from current-potential curves obtained on the AuSNPs/CeO<sub>2</sub>(2.5% w/w)-modified SNGC electrode in the presence of different AA concentrations: (<b>a</b>) 1, (<b>b</b>) 2 and (<b>c</b>) 3 mM at a scan rate of 50 mV·s<sup>−1</sup> in PBS 0.2 M.</p> Full article ">
<p>The cyclic voltammograms of AuSNPs/CeO<sub>2</sub>(2.5% w/w)-modified SNGC electrode in 0.2 M PBS with different concentrations of ascorbic acid: (<b>a</b>) 0.01; (<b>b</b>) 0.1; (<b>c</b>) 0.5; (<b>d</b>) 1.0; (<b>e</b>) 2.0; (<b>f</b>) 3.0; (<b>g</b>) 4,0; (<b>h</b>) 5,0 mM. The inset displays the AA oxidation peak current on this electrode versus concentration of the analyte.</p> Full article ">
<p>DPV voltammograms corresponding to one calibration curve (inset) for ascorbic acid using a AuSNPs/CeO<sub>2</sub> (5% w/w)-modified SNGC electrode.</p> Full article ">
<p>SEM micrographs and example of EDS corresponding to different configurations of the SNGC electrodes used and not used: CeO<sub>2</sub>(0.75 mg·mL<sup>−1</sup>)-modified SNGC electrode (<b>A</b>) used and (<b>B</b>) not used, both obtained with the secondary electron detector; CeO<sub>2</sub>(10.0 mg·mL<sup>−1</sup>)-modified SNGC electrode (<b>C</b>) used and (<b>D</b>) not used, both obtained with the backscattered electron detector; (<b>E</b>) X-ray EDS corresponding to the CeO<sub>2</sub> nanoparticles film deposited on the surface of a SNGC electrode. All the micrographs were obtained at the magnification of 90× and operating in the range of 24-30 kV.</p> Full article ">
553 KiB  
Review
Compressive Sensing Image Sensors-Hardware Implementation
by Mohammadreza Dadkhah, M. Jamal Deen and Shahram Shirani
Sensors 2013, 13(4), 4961-4978; https://doi.org/10.3390/s130404961 - 12 Apr 2013
Cited by 34 | Viewed by 8490
Abstract
The compressive sensing (CS) paradigm uses simultaneous sensing and compression to provide an efficient image acquisition technique. The main advantages of the CS method include high resolution imaging using low resolution sensor arrays and faster image acquisition. Since the imaging philosophy in CS [...] Read more.
The compressive sensing (CS) paradigm uses simultaneous sensing and compression to provide an efficient image acquisition technique. The main advantages of the CS method include high resolution imaging using low resolution sensor arrays and faster image acquisition. Since the imaging philosophy in CS imagers is different from conventional imaging systems, new physical structures have been developed for cameras that use the CS technique. In this paper, a review of different hardware implementations of CS encoding in optical and electrical domains is presented. Considering the recent advances in CMOS (complementary metal–oxide–semiconductor) technologies and the feasibility of performing on-chip signal processing, important practical issues in the implementation of CS in CMOS sensors are emphasized. In addition, the CS coding for video capture is discussed. Full article
(This article belongs to the Section Physical Sensors)
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<p>General schematic of single-pixel camera set-up (adapted from [<a href="#b41-sensors-13-04961" class="html-bibr">41</a>]) (DMD: digital micro-mirror device; ADC: analog-to-digital converter, DSP: digital signal processor).</p> Full article ">
<p>(<b>a</b>) Schematic of single dispersive spectral imaging system (adapted from [<a href="#b49-sensors-13-04961" class="html-bibr">49</a>]); (<b>b</b>) Optical set-up for random-mask image acquisition (adapted from [<a href="#b51-sensors-13-04961" class="html-bibr">51</a>]).</p> Full article ">
<p>Block diagram for the digital implementation of CS coding.</p> Full article ">
<p>Block diagram for the analog implementation of CS coding.</p> Full article ">
<p>Block diagram of a CS encoding implementation.</p> Full article ">
<p>General schematic representation of the separable-transform imager (adapted from [<a href="#b64-sensors-13-04961" class="html-bibr">64</a>]).</p> Full article ">
<p>(<b>a</b>) Connections of each block toward the linear feedback shift register (LFSR); (<b>b</b>) Block connections for block-by-block read-out; (<b>c</b>) Block connections for column-of-blocks connections (adapted from [<a href="#b63-sensors-13-04961" class="html-bibr">63</a>]).</p> Full article ">
<p>Timing diagram for frame-by-frame video coding using consecutive image coding steps.</p> Full article ">
<p>(<b>a</b>) Multiple-capture and one read-out timing diagram; (<b>b</b>) Cube of data for <span class="html-italic">n</span> frames.</p> Full article ">
2421 KiB  
Article
Analysis and Description of HOLTIN Service Provision for AECG monitoring in Complex Indoor Environments
by Santiago Led, Leire Azpilicueta, Erik Aguirre, Miguel Martínez De Espronceda, Luis Serrano and Francisco Falcone
Sensors 2013, 13(4), 4947-4960; https://doi.org/10.3390/s130404947 - 12 Apr 2013
Cited by 30 | Viewed by 7314
Abstract
In this work, a novel ambulatory ECG monitoring device developed in-house called HOLTIN is analyzed when operating in complex indoor scenarios. The HOLTIN system is described, from the technological platform level to its functional model. In addition, by using in-house 3D ray launching [...] Read more.
In this work, a novel ambulatory ECG monitoring device developed in-house called HOLTIN is analyzed when operating in complex indoor scenarios. The HOLTIN system is described, from the technological platform level to its functional model. In addition, by using in-house 3D ray launching simulation code, the wireless channel behavior, which enables ubiquitous operation, is performed. The effect of human body presence is taken into account by a novel simplified model embedded within the 3D Ray Launching code. Simulation as well as measurement results are presented, showing good agreement. These results may aid in the adequate deployment of this novel device to automate conventional medical processes, increasing the coverage radius and optimizing energy consumption. Full article
(This article belongs to the Special Issue Select papers from UCAmI & IWAAL 2012 - the 6th International Conference on Ubiquitous Computing and Ambient Intelligence & 4th International Workshop on Ambient Assisted Living (UCAmI & IWAAL 2012))
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<p>Overview of the HOLTIN platform.</p> Full article ">
<p>Image of the HOLTIN wearable ECG recorder (<b>a</b>) placed on a patient chest (<b>b</b>) detail of the device.</p> Full article ">
<p>Principle of operation of the 3D ray launching method implemented in-house to perform indoor coverage analysis.</p> Full article ">
<p>Geometry for wedge diffraction coefficients.</p> Full article ">
<p>Image of R&amp;D Communications Center laboratory N° 2, in which simulation and measurement results of operation of the HOLTIN system have been performed</p> Full article ">
<p>(<b>a</b>) R&amp;D Communication's Center laboratory N°2, proposed for deterministic radio channel simulation; (<b>b</b>) Detail of the simplified human body model, with the different organs that are embedded within it.</p> Full article ">
<p>Spatial distribution of Received Power [dBm] for 1.30 meters height in the indoor scenario with (<b>a</b>) the presence of a human body model in the center (<b>b</b>) without the human body model.</p> Full article ">
<p>(<b>a</b>) Distribution of Power for Y = 4.67 meters along the X-axis for both cases, with and without the presence of a person (<b>b</b>) Power-Delay Profile at Point (3.41, 4.67, 1.35) meters in the indoor scenario.</p> Full article ">
<p>Layout of the measurement scenario.</p> Full article ">
412 KiB  
Article
Energy-Efficient Algorithm for Broadcasting in Ad Hoc Wireless Sensor Networks
by Naixue Xiong, Xingbo Huang, Hongju Cheng and Zheng Wan
Sensors 2013, 13(4), 4922-4946; https://doi.org/10.3390/s130404922 - 12 Apr 2013
Cited by 27 | Viewed by 8310
Abstract
Broadcasting is a common and basic operation used to support various network protocols in wireless networks. To achieve energy-efficient broadcasting is especially important for ad hoc wireless sensor networks because sensors are generally powered by batteries with limited lifetimes. Energy consumption for broadcast [...] Read more.
Broadcasting is a common and basic operation used to support various network protocols in wireless networks. To achieve energy-efficient broadcasting is especially important for ad hoc wireless sensor networks because sensors are generally powered by batteries with limited lifetimes. Energy consumption for broadcast operations can be reduced by minimizing the number of relay nodes based on the observation that data transmission processes consume more energy than data reception processes in the sensor nodes, and how to improve the network lifetime is always an interesting issue in sensor network research. The minimum-energy broadcast problem is then equivalent to the problem of finding the minimum Connected Dominating Set (CDS) for a connected graph that is proved NP-complete. In this paper, we introduce an Efficient Minimum CDS algorithm (EMCDS) with help of a proposed ordered sequence list. EMCDS does not concern itself with node energy and broadcast operations might fail if relay nodes are out of energy. Next we have proposed a Minimum Energy-consumption Broadcast Scheme (MEBS) with a modified version of EMCDS, and aimed at providing an efficient scheduling scheme with maximized network lifetime. The simulation results show that the proposed EMCDS algorithm can find smaller CDS compared with related works, and the MEBS can help to increase the network lifetime by efficiently balancing energy among nodes in the networks. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
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<p>An example network with six nodes.</p> Full article ">
<p>Network topology of the given example.</p> Full article ">
<p>Layers for the given example.</p> Full article ">
<p>MIS construction for the given example.</p> Full article ">
<p>CDS construction for the given example in EMCDS algorithm.</p> Full article ">
<p>Remove redundant nodes in the EMCDS algorithm.</p> Full article ">
<p>The size of MCDS with different transmission range. (<b>a</b>) 200 nodes; (<b>b</b>) 1,000 nodes.</p> Full article ">
<p>The size of MCDS with different transmission range. (<b>a</b>) 200 nodes; (<b>b</b>) 1,000 nodes.</p> Full article ">
<p>The size of MCDS with different number of nodes. (<b>a</b>) Transmission radius <span class="html-italic">r</span> = 25 m; (<b>b</b>) Transmission radius <span class="html-italic">r</span> = 50 m.</p> Full article ">
<p>The size of MCDS with different number of nodes. (<b>a</b>) Transmission radius <span class="html-italic">r</span> = 25 m; (<b>b</b>) Transmission radius <span class="html-italic">r</span> = 50 m.</p> Full article ">
<p>Saved rebroadcast with different transmission range.</p> Full article ">
2668 KiB  
Article
In-Situ Waviness Characterization of Metal Plates by a Lateral Shearing Interferometric Profilometer
by María Frade, José María Enguita and Ignacio Álvarez
Sensors 2013, 13(4), 4906-4921; https://doi.org/10.3390/s130404906 - 12 Apr 2013
Cited by 7 | Viewed by 7203
Abstract
Characterizing waviness in sheet metal is a key process for quality control in many industries, such as automotive and home appliance manufacturing. However, there is still no known technique able to work in an automated in-floor inspection system. The literature describes many techniques [...] Read more.
Characterizing waviness in sheet metal is a key process for quality control in many industries, such as automotive and home appliance manufacturing. However, there is still no known technique able to work in an automated in-floor inspection system. The literature describes many techniques developed in the last three decades, but most of them are either slow, only able to work in laboratory conditions, need very short (unsafe) working distances, or are only able to estimate certain waviness parameters. In this article we propose the use of a lateral shearing interferometric profilometer, which is able to obtain a 19 mm profile in a single acquisition, with sub-micron precision, in an uncontrolled environment, and from a working distance greater than 90 mm. This system allows direct measurement of all needed waviness parameters even with objects in movement. We describe a series of experiments over several samples of steel plates to validate the sensor and the processing method, and the results are in close agreement with those obtained with a contact stylus device. The sensor is an ideal candidate for on-line or in-machine fast automatic waviness assessment, reducing delays and costs in many metalworking processes. Full article
(This article belongs to the Section Physical Sensors)
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<p>General setup of the prototype system.</p> Full article ">
<p>Schematic setup as observed from the direction perpendicular to the profile, <span class="html-italic">zy</span> plane (first appeared in [<a href="#b23-sensors-13-04906" class="html-bibr">23</a>], reprinted with permission).</p> Full article ">
<p>Examples of raw profiles obtained by the stylus contact instrument (<b>top</b>) and the optical profilometer (<b>down</b>).</p> Full article ">
<p>Separation of the waviness and roughness profiles from a sample. From top to bottom: a profile of a Rubert Type 130 reference specimen of a surface machined by horizontal milling (in this case the N8) obtained with a contact stylus instrument, and the waviness and roughness profiles obtained with values of λ<span class="html-italic"><sub>c</sub></span> = 0.25, 0.8 and 2.5 respectively.</p> Full article ">
<p>Examples of the steel plates used for testing.</p> Full article ">
<p>3D surface reconstruction of a Rubert Type 130 reference specimen of a surface machined by horizontal milling (in this case the N7), where the marks of the machining process are clearly seen.</p> Full article ">
<p>Comparison of results between a contact stylus profilometer and the proposed optical sensor for each of of the waviness parameters <span class="html-italic">W<sub>a</sub>, W<sub>q</sub>, W<sub>p</sub>, W<sub>v</sub>, W<sub>z</sub></span>, and <span class="html-italic">H<sub>tp</sub></span> using a cutoff wavelength of 0.25 mm. The boxplots represent the dispersion of the parameters calculated using the optical sensor data from more than 70 profiles of each sample. The continuous lines represent the parameters calculated over three different profiles obtained from the contact stylus instrument.</p> Full article ">
<p>Comparison of results between a contact stylus profilometer and the proposed optical sensor for the waviness parameters <span class="html-italic">W<sub>a</sub></span> and <span class="html-italic">W<sub>q</sub></span> using a cutoff wavelength of 0.8 mm. The boxplots represent the dispersion of the parameters calculated using the optical sensor data from more than 70 profiles of each sample. The continuous lines represent the parameters calculated over three different profiles obtained from the contact stylus instrument. The rest of the parameters have been omitted in this case, as the results were similar to those in <a href="#f7-sensors-13-04906" class="html-fig">Figure 7</a>.</p> Full article ">
229 KiB  
Article
Estimation of Distribution Algorithm for Resource Allocation in Green Cooperative Cognitive Radio Sensor Networks
by Muhammad Naeem, Udit Pareek, Daniel C. Lee and Alagan Anpalagan
Sensors 2013, 13(4), 4884-4905; https://doi.org/10.3390/s130404884 - 12 Apr 2013
Cited by 24 | Viewed by 6556
Abstract
Due to the rapid increase in the usage and demand of wireless sensor networks (WSN), the limited frequency spectrum available for WSN applications will be extremely crowded in the near future. More sensor devices also mean more recharging/replacement of batteries, which will cause [...] Read more.
Due to the rapid increase in the usage and demand of wireless sensor networks (WSN), the limited frequency spectrum available for WSN applications will be extremely crowded in the near future. More sensor devices also mean more recharging/replacement of batteries, which will cause significant impact on the global carbon footprint. In this paper, we propose a relay-assisted cognitive radio sensor network (CRSN) that allocates communication resources in an environmentally friendly manner. We use shared band amplify and forward relaying for cooperative communication in the proposed CRSN. We present a multi-objective optimization architecture for resource allocation in a green cooperative cognitive radio sensor network (GC-CRSN). The proposed multi-objective framework jointly performs relay assignment and power allocation in GC-CRSN, while optimizing two conflicting objectives. The first objective is to maximize the total throughput, and the second objective is to minimize the total transmission power of CRSN. The proposed relay assignment and power allocation problem is a non-convex mixed-integer non-linear optimization problem (NC-MINLP), which is generally non-deterministic polynomial-time (NP)-hard. We introduce a hybrid heuristic algorithm for this problem. The hybrid heuristic includes an estimation-of-distribution algorithm (EDA) for performing power allocation and iterative greedy schemes for constraint satisfaction and relay assignment. We analyze the throughput and power consumption tradeoff in GC-CRSN. A detailed analysis of the performance of the proposed algorithm is presented with the simulation results. Full article
(This article belongs to the Section Sensor Networks)
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<p>WSN life cycle.</p> Full article ">
<p>EDA flow diagram with IGS-CSRA and IGS-CSSP.</p> Full article ">
<p>EDA thresholding.</p> Full article ">
<p>Power and sum-capacity trade-off with <math display="inline"> <semantics id="sm57"> <mrow> <mrow> <mo>(</mo> <mrow> <mi>M</mi> <mo>,</mo> <mi>K</mi> <mo>,</mo> <mi>L</mi> <mo>,</mo> <msubsup> <mi>I</mi> <mrow> <mi>m</mi> <mi>k</mi></mrow> <mrow> <mtext>max</mtext></mrow></msubsup></mrow> <mo>)</mo></mrow> <mo>=</mo> <mrow> <mo>(</mo> <mrow> <mn>1</mn> <mo>,</mo> <mn>10</mn> <mo>,</mo> <mn>20</mn> <mo>,</mo> <mn>1</mn> <mi>W</mi></mrow> <mo>)</mo></mrow></mrow></semantics></math>.</p> Full article ">
<p>Effect of threshold parameter on EDA. The parameters are <math display="inline"> <semantics id="sm58"> <mrow> <mrow> <mo>(</mo> <mrow> <mi>L</mi> <mo>,</mo> <mi>K</mi> <mo>,</mo> <mi>M</mi> <mo>,</mo> <msubsup> <mi>I</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi></mrow> <mrow> <mtext mathvariant="italic">max</mtext></mrow></msubsup> <mo>,</mo> <msub> <mi>w</mi> <mn>1</mn></msub> <mo>,</mo> <msub> <mi>w</mi> <mn>2</mn></msub></mrow> <mo>)</mo></mrow> <mo>=</mo> <mrow> <mo>(</mo> <mrow> <mn>10</mn> <mo>,</mo> <mn>10</mn> <mo>,</mo> <mn>1</mn> <mo>,</mo> <mn>1</mn> <mi>W</mi> <mo>,</mo> <mn>0.5</mn> <mo>,</mo> <mn>0.5</mn></mrow> <mo>)</mo></mrow></mrow></semantics></math>.</p> Full article ">
<p>Effect of selection probability <span class="html-italic">ρ<sub>s</sub></span> on EDA. The parameters are <math display="inline"> <semantics id="sm59"> <mrow> <mrow> <mo>(</mo> <mrow> <mi>L</mi> <mo>,</mo> <mi>K</mi> <mo>,</mo> <mi>M</mi> <mo>,</mo> <msubsup> <mi>I</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi></mrow> <mrow> <mtext mathvariant="italic">max</mtext></mrow></msubsup> <mo>,</mo> <msub> <mi>w</mi> <mn>1</mn></msub> <mo>,</mo> <msub> <mi>w</mi> <mn>2</mn></msub></mrow> <mo>)</mo></mrow> <mo>=</mo> <mrow> <mo>(</mo> <mrow> <mn>10</mn> <mo>,</mo> <mn>10</mn> <mo>,</mo> <mn>1</mn> <mo>,</mo> <mn>1</mn> <mi>W</mi> <mo>,</mo> <mn>0.5</mn> <mo>,</mo> <mn>0.5</mn></mrow> <mo>)</mo></mrow></mrow></semantics></math>.</p> Full article ">
<p>Iterations <span class="html-italic">vs.</span> Fitness plot with (<span class="html-italic">w</span><sub>1</sub>, <span class="html-italic">w</span><sub>2</sub>) = (0.5,0.5).</p> Full article ">
<p>Iterations <span class="html-italic">vs</span>. Fitness plot with (<span class="html-italic">w</span><sub>1</sub>, <span class="html-italic">w</span><sub>2</sub>) = (0.1, 0.9).</p> Full article ">
<p>Iterations <span class="html-italic">vs</span>. Fitness plot with (<span class="html-italic">w</span><sub>1</sub>, <span class="html-italic">w</span><sub>2</sub>) = (0.5, 0.5).</p> Full article ">
194 KiB  
Communication
Near Infrared Spectral Linearisation in Quantifying Soluble Solids Content of Intact Carambola
by Ahmad Fairuz Omar and Mohd Zubir MatJafri
Sensors 2013, 13(4), 4876-4883; https://doi.org/10.3390/s130404876 - 12 Apr 2013
Cited by 10 | Viewed by 6262
Abstract
This study presents a novel application of near infrared (NIR) spectral linearisation for measuring the soluble solids content (SSC) of carambola fruits. NIR spectra were measured using reflectance and interactance methods. In this study, only the interactance measurement technique successfully generated a reliable [...] Read more.
This study presents a novel application of near infrared (NIR) spectral linearisation for measuring the soluble solids content (SSC) of carambola fruits. NIR spectra were measured using reflectance and interactance methods. In this study, only the interactance measurement technique successfully generated a reliable measurement result with a coefficient of determination of (R2) = 0.724 and a root mean square error of prediction for (RMSEP) = 0.461° Brix. The results from this technique produced a highly accurate and stable prediction model compared with multiple linear regression techniques. Full article
(This article belongs to the Section Physical Sensors)
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<p>Probe configuration for (<b>a</b>) Reflectance calibration setup (<b>b</b>) interactance calibration setup.</p> Full article ">
<p>NIR reflectance and interactance spectra of an intact carambola.</p> Full article ">
<p>Calibration accuracies from different range of wavelength conducted on interactance spectra.</p> Full article ">
<p>Spectra for two different levels of carambola SSC measured through (<b>a</b>) Reflectance (<b>b</b>) Interactance.</p> Full article ">
<p>Prediction of carambola SSC through interactance spectral linearisation.</p> Full article ">
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