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Sensors, Volume 14, Issue 7 (July 2014) , Pages 11278-13307

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Open AccessArticle
Enhanced Response of a Proteinase K-Based Conductometric Biosensor Using Nanoparticles
Sensors 2014, 14(7), 13298-13307; https://doi.org/10.3390/s140713298
Received: 7 April 2014 / Revised: 17 June 2014 / Accepted: 17 July 2014 / Published: 23 July 2014
Cited by 5 | Viewed by 2395 | PDF Full-text (308 KB) | HTML Full-text | XML Full-text
Abstract
Proteinases are involved in a multitude of important physiological processes, such as protein metabolism. For this reason, a conductometric enzyme biosensor based on proteinase K was developed using two types of nanoparticles (gold and magnetic). The enzyme was directly adsorbed on negatively charged [...] Read more.
Proteinases are involved in a multitude of important physiological processes, such as protein metabolism. For this reason, a conductometric enzyme biosensor based on proteinase K was developed using two types of nanoparticles (gold and magnetic). The enzyme was directly adsorbed on negatively charged nanoparticles and then deposited and cross-linked on a planar interdigitated electrode (IDE). The biosensor was characterized with bovine serum albumin (BSA) as a standard protein. Higher sensitivity was obtained using gold nanoparticles. The linear range for BSA determination was then from 0.5 to 10 mg/L with a maximum response of 154 µs. These results are greater than that found without any nanoparticles (maximum response of 10 µs). The limit of detection (LOD) was 0.3 mg/L. An inter-sensor reproducibility of 3.5% was obtained. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle
Strategy for Making a Superior Quenchbody to Proteins: Effect of the Fluorophore Position
Sensors 2014, 14(7), 13285-13297; https://doi.org/10.3390/s140713285
Received: 27 May 2014 / Revised: 3 July 2014 / Accepted: 16 July 2014 / Published: 23 July 2014
Cited by 9 | Viewed by 2585 | PDF Full-text (3562 KB) | HTML Full-text | XML Full-text
Abstract
Antibody-based sensors have made outstanding contributions to the fields of molecular biology and biotechnology. Our group recently developed a novel powerful fluorescent immunosensor strategy named Quenchbody (Q-body), which has been applied to the detection of a range of antigens in a rapid, simple, [...] Read more.
Antibody-based sensors have made outstanding contributions to the fields of molecular biology and biotechnology. Our group recently developed a novel powerful fluorescent immunosensor strategy named Quenchbody (Q-body), which has been applied to the detection of a range of antigens in a rapid, simple, and sensitive manner. However, there were some Q-bodies whose fluorescence response was limited, especially for detecting protein antigens. With the aim of improving this issue, here we made twelve types of Q-bodies incorporated with different number and position of TAMRA fluorophore in the single chain Fv of HyHEL-10, an anti-hen egg lysozyme antibody, as a model. By measuring the fluorescence intensity and its antigen dependency, it was revealed that VL-VH type Q-bodies labeled at a non-CDR loop region of the VL shows the highest fluorescence response. This position locates close to the quenching Trp35 in VL, while it is far from Trp residues in the bound antigen. This result clearly suggests the importance of dye position to maximize the fluorescence quenching and antigen-dependent de-quenching. The discovery may open a way to make many other Q-bodies with superior response. Full article
(This article belongs to the Special Issue Immunosensors 2014)
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Open AccessArticle
The Optical Property of Core-Shell Nanosensors and Detection of Atrazine Based on Localized Surface Plasmon Resonance (LSPR) Sensing
Sensors 2014, 14(7), 13273-13284; https://doi.org/10.3390/s140713273
Received: 22 April 2014 / Revised: 17 June 2014 / Accepted: 17 July 2014 / Published: 23 July 2014
Cited by 9 | Viewed by 2523 | PDF Full-text (1428 KB) | HTML Full-text | XML Full-text
Abstract
Three different nanosensors with core-shell structures were fabricated by molecular self-assembly and evaporation techniques. Such closely packed nanoparticles exhibit fine optical properties which are useful for biochemical sensing. The refractive index sensitivity (RIS) of nanosensors was detected by varying the refractive index of [...] Read more.
Three different nanosensors with core-shell structures were fabricated by molecular self-assembly and evaporation techniques. Such closely packed nanoparticles exhibit fine optical properties which are useful for biochemical sensing. The refractive index sensitivity (RIS) of nanosensors was detected by varying the refractive index of the surrounding medium and the decay length of nanosensors was investigated using a layer-by-layer polyelectrolyte multilayer assembly. The results showed that the thickness of the Au shell plays an important role in determining the RIS and the decay length. A system based on localized surface plasmon resonances (LSPR) sensing was constructed in our study. The core-shell nanosensors can detect 10 ng/mL atrazine solutions and are suitable for pesticide residue detection. Full article
(This article belongs to the Special Issue Nanoparticle-Based Biosensors)
Open AccessArticle
Detecting Cannabis Use on the Human Skin Surface via an Electronic Nose System
Sensors 2014, 14(7), 13256-13272; https://doi.org/10.3390/s140713256
Received: 9 April 2014 / Revised: 17 June 2014 / Accepted: 17 July 2014 / Published: 23 July 2014
Cited by 10 | Viewed by 3214 | PDF Full-text (3871 KB) | HTML Full-text | XML Full-text
Abstract
The most commonly used drug testing methods are based on the analysis of hair and urine using gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry or immunoassay screening. These methods are time-consuming and partly expensive. One alternative method could be the application of an “electronic [...] Read more.
The most commonly used drug testing methods are based on the analysis of hair and urine using gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry or immunoassay screening. These methods are time-consuming and partly expensive. One alternative method could be the application of an “electronic nose” (eNose). We have developed an eNose to detect directly on the human skin surface metabolic changes in the human body odor caused by cannabis consumption. Twenty cannabis-smoking and 20 tobacco-smoking volunteers were enrolled in this study. For the sensor signal data processing, two different methods were applied: Principle component analysis (PCA) with discriminant analysis, and the method of pattern recognition with subsequent support vector machines (SVM) processing. The PCA analysis achieved a correct classification of 70%, whereas the SVM obtained an accuracy of 92.5% (sensitivity 95%, specificity 90%) between cannabis-consuming volunteers and tobacco-smoking subjects. This study shows evidence that a low-cost, portable and fast-working eNose system could be useful for health protection, security agencies and for forensic investigations. The ability to analyze human body odor with an eNose opens up a wide field for diagnosing other drugs and also various diseases. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle
Vertical Soil Profiling Using a Galvanic Contact Resistivity Scanning Approach
Sensors 2014, 14(7), 13243-13255; https://doi.org/10.3390/s140713243
Received: 22 July 2013 / Revised: 3 June 2014 / Accepted: 18 June 2014 / Published: 23 July 2014
Cited by 5 | Viewed by 2960 | PDF Full-text (3110 KB) | HTML Full-text | XML Full-text
Abstract
Proximal sensing of soil electromagnetic properties is widely used to map spatial land heterogeneity. The mapping instruments use galvanic contact, capacitive coupling or electromagnetic induction. Regardless of the type of instrument, the geometrical configuration between signal transmitting and receiving elements typically defines the [...] Read more.
Proximal sensing of soil electromagnetic properties is widely used to map spatial land heterogeneity. The mapping instruments use galvanic contact, capacitive coupling or electromagnetic induction. Regardless of the type of instrument, the geometrical configuration between signal transmitting and receiving elements typically defines the shape of the depth response function. To assess vertical soil profiles, many modern instruments use multiple transmitter-receiver pairs. Alternatively, vertical electrical sounding can be used to measure changes in apparent soil electrical conductivity with depth at a specific location. This paper examines the possibility for the assessment of soil profiles using a dynamic surface galvanic contact resistivity scanning approach, with transmitting and receiving electrodes configured in an equatorial dipole-dipole array. An automated scanner system was developed and tested in agricultural fields with different soil profiles. While operating in the field, the distance between current injecting and measuring pairs of rolling electrodes was varied continuously from 40 to 190 cm. The preliminary evaluation included a comparison of scan results from 20 locations to shallow (less than 1.2 m deep) soil profiles and to a two-layer soil profile model defined using an electromagnetic induction instrument. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Small Infrared Target Detection by Region-Adaptive Clutter Rejection for Sea-Based Infrared Search and Track
Sensors 2014, 14(7), 13210-13242; https://doi.org/10.3390/s140713210
Received: 8 May 2014 / Revised: 24 June 2014 / Accepted: 15 July 2014 / Published: 22 July 2014
Cited by 28 | Viewed by 3348 | PDF Full-text (6123 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a region-adaptive clutter rejection method for small target detection in sea-based infrared search and track. In the real world, clutter normally generates many false detections that impede the deployment of such detection systems. Incoming targets (missiles, boats, etc.) can be [...] Read more.
This paper presents a region-adaptive clutter rejection method for small target detection in sea-based infrared search and track. In the real world, clutter normally generates many false detections that impede the deployment of such detection systems. Incoming targets (missiles, boats, etc.) can be located in the sky, horizon and sea regions, which have different types of clutters, such as clouds, a horizontal line and sea-glint. The characteristics of regional clutter were analyzed after the geometrical analysis-based region segmentation. The false detections caused by cloud clutter were removed by the spatial attribute-based classification. Those by the horizontal line were removed using the heterogeneous background removal filter. False alarms by sun-glint were rejected using the temporal consistency filter, which is the most difficult part. The experimental results of the various cluttered background sequences show that the proposed region adaptive clutter rejection method produces fewer false alarms than that of the mean subtraction filter (MSF) with an acceptable degradation detection rate. Full article
Open AccessArticle
A Large Response Range Reflectometric Urea Biosensor Made from Silica-Gel Nanoparticles
Sensors 2014, 14(7), 13186-13209; https://doi.org/10.3390/s140713186
Received: 21 December 2013 / Revised: 3 July 2014 / Accepted: 14 July 2014 / Published: 22 July 2014
Cited by 11 | Viewed by 2546 | PDF Full-text (961 KB) | HTML Full-text | XML Full-text
Abstract
A new silica-gel nanospheres (SiO2NPs) composition was formulated, followed by biochemical surface functionalization to examine its potential in urea biosensor development. The SiO2NPs were basically synthesized based on sol–gel chemistry using a modified Stober method. The SiO2NPs [...] Read more.
A new silica-gel nanospheres (SiO2NPs) composition was formulated, followed by biochemical surface functionalization to examine its potential in urea biosensor development. The SiO2NPs were basically synthesized based on sol–gel chemistry using a modified Stober method. The SiO2NPs surfaces were modified with amine (-NH2) functional groups for urease immobilization in the presence of glutaric acid (GA) cross-linker. The chromoionophore pH-sensitive dye ETH 5294 was physically adsorbed on the functionalized SiO2NPs as pH transducer. The immobilized urease determined urea concentration reflectometrically based on the colour change of the immobilized chromoionophore as a result of the enzymatic hydrolysis of urea. The pH changes on the biosensor due to the catalytic enzyme reaction of immobilized urease were found to correlate with the urea concentrations over a linear response range of 50–500 mM (R2 = 0.96) with a detection limit of 10 mM urea. The biosensor response time was 9 min with reproducibility of less than 10% relative standard deviation (RSD). This optical urea biosensor did not show interferences by Na+, K+, Mg2+ and NH4+ ions. The biosensor performance has been validated using urine samples in comparison with a non-enzymatic method based on the use of p-dimethylaminobenzaldehyde (DMAB) reagent and demonstrated a good correlation between the two different methods (R2 = 0.996 and regression slope of 1.0307). The SiO2NPs-based reflectometric urea biosensor showed improved dynamic linear response range when compared to other nanoparticle-based optical urea biosensors. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle
Bio-Inspired Micro-Fluidic Angular-Rate Sensor for Vestibular Prostheses
Sensors 2014, 14(7), 13173-13185; https://doi.org/10.3390/s140713173
Received: 16 June 2014 / Revised: 1 July 2014 / Accepted: 9 July 2014 / Published: 22 July 2014
Cited by 8 | Viewed by 3342 | PDF Full-text (2281 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an alternative approach for angular-rate sensing based on the way that the natural vestibular semicircular canals operate, whereby the inertial mass of a fluid is used to deform a sensing structure upon rotation. The presented gyro has been fabricated in [...] Read more.
This paper presents an alternative approach for angular-rate sensing based on the way that the natural vestibular semicircular canals operate, whereby the inertial mass of a fluid is used to deform a sensing structure upon rotation. The presented gyro has been fabricated in a commercially available MEMS process, which allows for microfluidic channels to be implemented in etched glass layers, which sandwich a bulk-micromachined silicon substrate, containing the sensing structures. Measured results obtained from a proof-of-concept device indicate an angular rate sensitivity of less than 1 °/s, which is similar to that of the natural vestibular system. By avoiding the use of a continually-excited vibrating mass, as is practiced in today’s state-of-the-art gyroscopes, an ultra-low power consumption of 300 μW is obtained, thus making it suitable for implantation. Full article
(This article belongs to the Special Issue Implantable Sensors)
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Open AccessCorrection
Correction: Deng, F., et al. A CMOS Humidity Sensor for Passive RFID Sensing Applications. Sensors 2014, 14, 8728–8739
Sensors 2014, 14(7), 13171-13172; https://doi.org/10.3390/s140713171
Received: 27 June 2014 / Accepted: 30 June 2014 / Published: 22 July 2014
Viewed by 2029 | PDF Full-text (715 KB) | HTML Full-text | XML Full-text
Abstract
The authors wish to make the following corrections to this paper [1]. [...] Full article
(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)
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Open AccessArticle
An Integrated Environment Monitoring System for Underground Coal Mines—Wireless Sensor Network Subsystem with Multi-Parameter Monitoring
Sensors 2014, 14(7), 13149-13170; https://doi.org/10.3390/s140713149
Received: 1 May 2014 / Revised: 9 July 2014 / Accepted: 14 July 2014 / Published: 21 July 2014
Cited by 32 | Viewed by 3017 | PDF Full-text (1122 KB) | HTML Full-text | XML Full-text
Abstract
Environment monitoring is important for the safety of underground coal mine production, and it is also an important application of Wireless Sensor Networks (WSNs). We put forward an integrated environment monitoring system for underground coal mine, which uses the existing Cable Monitoring System [...] Read more.
Environment monitoring is important for the safety of underground coal mine production, and it is also an important application of Wireless Sensor Networks (WSNs). We put forward an integrated environment monitoring system for underground coal mine, which uses the existing Cable Monitoring System (CMS) as the main body and the WSN with multi-parameter monitoring as the supplementary technique. As CMS techniques are mature, this paper mainly focuses on the WSN and the interconnection between the WSN and the CMS. In order to implement the WSN for underground coal mines, two work modes are designed: periodic inspection and interrupt service; the relevant supporting technologies, such as routing mechanism, collision avoidance, data aggregation, interconnection with the CMS, etc., are proposed and analyzed. As WSN nodes are limited in energy supply, calculation and processing power, an integrated network management scheme is designed in four aspects, i.e., topology management, location management, energy management and fault management. Experiments were carried out both in a laboratory and in a real underground coal mine. The test results indicate that the proposed integrated environment monitoring system for underground coal mines is feasible and all designs performed well as expected. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle
An Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator for Dielectric Sensing Applications
Sensors 2014, 14(7), 13134-13148; https://doi.org/10.3390/s140713134
Received: 29 April 2014 / Revised: 18 June 2014 / Accepted: 3 July 2014 / Published: 21 July 2014
Cited by 35 | Viewed by 2733 | PDF Full-text (1219 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the design and development of a planar Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator (SRR) for microwave sensors that operates at a resonance frequency around 5 GHz. The sensor consists of a microstrip transmission line loaded with two elements [...] Read more.
This paper presents the design and development of a planar Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator (SRR) for microwave sensors that operates at a resonance frequency around 5 GHz. The sensor consists of a microstrip transmission line loaded with two elements of rectangular SRR on both sides. The proposed metamaterial sensors were designed and fabricated on Rogers RT5880 substrate having dielectric constant of 2.2 and thickness of 0.787 mm. The final dimension of the proposed sensor was measured at 35 × 14 mm2. Measured results show good agreement with simulated ones as well as exhibiting high Q-factor for use in sensing application. A remarkably shift of resonance frequency is observed upon introduction of several sample with different dielectric value. Full article
Open AccessArticle
Distributed Power-Line Outage Detection Based on Wide Area Measurement System
Sensors 2014, 14(7), 13114-13133; https://doi.org/10.3390/s140713114
Received: 16 April 2014 / Revised: 12 July 2014 / Accepted: 14 July 2014 / Published: 21 July 2014
Cited by 15 | Viewed by 2420 | PDF Full-text (1265 KB) | HTML Full-text | XML Full-text
Abstract
In modern power grids, the fast and reliable detection of power-line outages is an important functionality, which prevents cascading failures and facilitates an accurate state estimation to monitor the real-time conditions of the grids. However, most of the existing approaches for outage detection [...] Read more.
In modern power grids, the fast and reliable detection of power-line outages is an important functionality, which prevents cascading failures and facilitates an accurate state estimation to monitor the real-time conditions of the grids. However, most of the existing approaches for outage detection suffer from two drawbacks, namely: (i) high computational complexity; and (ii) relying on a centralized means of implementation. The high computational complexity limits the practical usage of outage detection only for the case of single-line or double-line outages. Meanwhile, the centralized means of implementation raises security and privacy issues. Considering these drawbacks, the present paper proposes a distributed framework, which carries out in-network information processing and only shares estimates on boundaries with the neighboring control areas. This novel framework relies on a convex-relaxed formulation of the line outage detection problem and leverages the alternating direction method of multipliers (ADMM) for its distributed solution. The proposed framework invokes a low computational complexity, requiring only linear and simple matrix-vector operations. We also extend this framework to incorporate the sparse property of the measurement matrix and employ the LSQRalgorithm to enable a warm start, which further accelerates the algorithm. Analysis and simulation tests validate the correctness and effectiveness of the proposed approaches. Full article
(This article belongs to the Special Issue Sensor Computing for Mobile Security and Big Data Analytics)
Open AccessArticle
A New Electrochemical Sensor Based on Task-Specific Ionic Liquids-Modified Palm Shell Activated Carbon for the Determination of Mercury in Water Samples
Sensors 2014, 14(7), 13102-13113; https://doi.org/10.3390/s140713102
Received: 19 May 2014 / Revised: 4 July 2014 / Accepted: 7 July 2014 / Published: 21 July 2014
Cited by 9 | Viewed by 2296 | PDF Full-text (736 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a potentiometric sensor composed of palm shell activated carbon modified with trioctylmethylammonium thiosalicylate (TOMATS) was used for the potentiometric determination of mercury ions in water samples. The proposed potentiometric sensor has good operating characteristics towards Hg (II), including a relatively [...] Read more.
In this study, a potentiometric sensor composed of palm shell activated carbon modified with trioctylmethylammonium thiosalicylate (TOMATS) was used for the potentiometric determination of mercury ions in water samples. The proposed potentiometric sensor has good operating characteristics towards Hg (II), including a relatively high selectivity; a Nernstian response to Hg (II) ions in a concentration range of 1.0 × 10−9 to 1.0 × 10−2 M, with a detection limit of 1 × 10−10 M and a slope of 44.08 ± 1.0 mV/decade; and a fast response time (~5 s). No significant changes in electrode potential were observed when the pH was varied over the range of 3–9. Additionally, the proposed electrode was characterized by good selectivity towards Hg (II) and no significant interferences from other cationic or anionic species. Full article
(This article belongs to the Special Issue Ion Selective Electrodes for Bioavailable Ions)
Open AccessArticle
An Optical Fibre-Based Sensor for Respiratory Monitoring
Sensors 2014, 14(7), 13088-13101; https://doi.org/10.3390/s140713088
Received: 29 April 2014 / Revised: 29 April 2014 / Accepted: 15 July 2014 / Published: 21 July 2014
Cited by 38 | Viewed by 4542 | PDF Full-text (1031 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a textile-based respiratory sensing system is presented. Highly flexible polymeric optical fibres (POFs) that react to applied pressure were integrated into a carrier fabric to form a wearable sensing system. After the evaluation of different optical fibres, different setups were [...] Read more.
In this paper, a textile-based respiratory sensing system is presented. Highly flexible polymeric optical fibres (POFs) that react to applied pressure were integrated into a carrier fabric to form a wearable sensing system. After the evaluation of different optical fibres, different setups were compared. To demonstrate the feasibility of such a wearable sensor, the setup featuring the best performance was placed on the human torso, and thus it was possible to measure the respiratory rate. Furthermore, we show that such a wearable system enables to keep track of the way of breathing (diaphragmatic, upper costal and mixed) when the sensor is placed at different positions of the torso. A comparison of the results with the output of some commercial respiratory measurements devices confirmed the utility of such a monitoring device. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
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Open AccessArticle
Influence of Segmentation of Ring-Shaped NdFeB Magnets with Parallel Magnetization on Cylindrical Actuators
Sensors 2014, 14(7), 13070-13087; https://doi.org/10.3390/s140713070
Received: 4 May 2014 / Revised: 11 July 2014 / Accepted: 11 July 2014 / Published: 21 July 2014
Cited by 2 | Viewed by 2527 | PDF Full-text (1100 KB) | HTML Full-text | XML Full-text
Abstract
This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and [...] Read more.
This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines. Full article
Open AccessArticle
Reduction of the Dimensionality of the EEG Channels during Scoliosis Correction Surgeries Using a Wavelet Decomposition Technique
Sensors 2014, 14(7), 13046-13069; https://doi.org/10.3390/s140713046
Received: 20 March 2014 / Revised: 23 June 2014 / Accepted: 4 July 2014 / Published: 21 July 2014
Cited by 6 | Viewed by 2680 | PDF Full-text (1696 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a comparison between the electroencephalogram (EEG) channels during scoliosis correction surgeries. Surgeons use many hand tools and electronic devices that directly affect the EEG channels. These noises do not affect the EEG channels uniformly. This research provides a complete system [...] Read more.
This paper presents a comparison between the electroencephalogram (EEG) channels during scoliosis correction surgeries. Surgeons use many hand tools and electronic devices that directly affect the EEG channels. These noises do not affect the EEG channels uniformly. This research provides a complete system to find the least affected channel by the noise. The presented system consists of five stages: filtering, wavelet decomposing (Level 4), processing the signal bands using four different criteria (mean, energy, entropy and standard deviation), finding the useful channel according to the criteria’s value and, finally, generating a combinational signal from Channels 1 and 2. Experimentally, two channels of EEG data were recorded from six patients who underwent scoliosis correction surgeries in the Pusat Perubatan Universiti Kebangsaan Malaysia (PPUKM) (the Medical center of National University of Malaysia). The combinational signal was tested by power spectral density, cross-correlation function and wavelet coherence. The experimental results show that the system-outputted EEG signals are neatly switched without any substantial changes in the consistency of EEG components. This paper provides an efficient procedure for analyzing EEG signals in order to avoid averaging the channels that lead to redistribution of the noise on both channels, reducing the dimensionality of the EEG features and preparing the best EEG stream for the classification and monitoring stage. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle
On Bandwidth Characteristics of Tuning Fork Micro-Gyroscope with Mechanically Coupled Sense Mode
Sensors 2014, 14(7), 13024-13045; https://doi.org/10.3390/s140713024
Received: 29 April 2014 / Revised: 14 July 2014 / Accepted: 14 July 2014 / Published: 21 July 2014
Cited by 7 | Viewed by 2490 | PDF Full-text (2165 KB) | HTML Full-text | XML Full-text
Abstract
The bandwidth characteristics of a tuning fork micro-gyroscope with mechanically coupled sense mode were investigated in this paper to provide some references for mechanical bandwidth design. The concept of sense mode mechanical coupling is introduced first. Theoretical frequency response analyses were then carried [...] Read more.
The bandwidth characteristics of a tuning fork micro-gyroscope with mechanically coupled sense mode were investigated in this paper to provide some references for mechanical bandwidth design. The concept of sense mode mechanical coupling is introduced first. Theoretical frequency response analyses were then carried out on the mechanical part of the gyroscope. Equations representing the relationships between the differential output signal and the frequency of the input angular rate were deduced in full frequency range and further simplified in low frequency range. Based on these equations, bandwidth characteristics under ideal and non-ideal conditions are discussed. Analytical results show that under ideal conditions, the bandwidth characteristics of a tuning fork micro-gyroscope are similar to those of a single mass micro-gyroscope, but under non-ideal conditions, especially when sense mass and/or stiffness are asymmetric, the bandwidth characteristics would be quite different because the in-phase mode would participate in the anti-phase vibration response. Experimental verifications were carried out on two micro-gyroscope prototypes designed in our laboratory. The deduced equations and analytical results can be used in guiding the mechanical bandwidth design of tuning fork micro-gyroscopes with mechanically coupled sense mode. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A Bionic Camera-Based Polarization Navigation Sensor
Sensors 2014, 14(7), 13006-13023; https://doi.org/10.3390/s140713006
Received: 10 March 2014 / Revised: 20 June 2014 / Accepted: 3 July 2014 / Published: 21 July 2014
Cited by 26 | Viewed by 2635 | PDF Full-text (1693 KB) | HTML Full-text | XML Full-text
Abstract
Navigation and positioning technology is closely related to our routine life activities, from travel to aerospace. Recently it has been found that Cataglyphis (a kind of desert ant) is able to detect the polarization direction of skylight and navigate according to this information. [...] Read more.
Navigation and positioning technology is closely related to our routine life activities, from travel to aerospace. Recently it has been found that Cataglyphis (a kind of desert ant) is able to detect the polarization direction of skylight and navigate according to this information. This paper presents a real-time bionic camera-based polarization navigation sensor. This sensor has two work modes: one is a single-point measurement mode and the other is a multi-point measurement mode. An indoor calibration experiment of the sensor has been done under a beam of standard polarized light. The experiment results show that after noise reduction the accuracy of the sensor can reach up to 0.3256°. It is also compared with GPS and INS (Inertial Navigation System) in the single-point measurement mode through an outdoor experiment. Through time compensation and location compensation, the sensor can be a useful alternative to GPS and INS. In addition, the sensor also can measure the polarization distribution pattern when it works in multi-point measurement mode. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A Hybrid Spatio-Temporal Data Indexing Method for Trajectory Databases
Sensors 2014, 14(7), 12990-13005; https://doi.org/10.3390/s140712990
Received: 4 February 2014 / Revised: 8 July 2014 / Accepted: 14 July 2014 / Published: 21 July 2014
Cited by 14 | Viewed by 2588 | PDF Full-text (995 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, there has been tremendous growth in the field of indoor and outdoor positioning sensors continuously producing huge volumes of trajectory data that has been used in many fields such as location-based services or location intelligence. Trajectory data is massively increased [...] Read more.
In recent years, there has been tremendous growth in the field of indoor and outdoor positioning sensors continuously producing huge volumes of trajectory data that has been used in many fields such as location-based services or location intelligence. Trajectory data is massively increased and semantically complicated, which poses a great challenge on spatio-temporal data indexing. This paper proposes a spatio-temporal data indexing method, named HBSTR-tree, which is a hybrid index structure comprising spatio-temporal R-tree, B*-tree and Hash table. To improve the index generation efficiency, rather than directly inserting trajectory points, we group consecutive trajectory points as nodes according to their spatio-temporal semantics and then insert them into spatio-temporal R-tree as leaf nodes. Hash table is used to manage the latest leaf nodes to reduce the frequency of insertion. A new spatio-temporal interval criterion and a new node-choosing sub-algorithm are also proposed to optimize spatio-temporal R-tree structures. In addition, a B*-tree sub-index of leaf nodes is built to query the trajectories of targeted objects efficiently. Furthermore, a database storage scheme based on a NoSQL-type DBMS is also proposed for the purpose of cloud storage. Experimental results prove that HBSTR-tree outperforms TB*-tree in some aspects such as generation efficiency, query performance and query type. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Improved Artificial Bee Colony Algorithm Based Gravity Matching Navigation Method
Sensors 2014, 14(7), 12968-12989; https://doi.org/10.3390/s140712968
Received: 25 March 2014 / Revised: 9 July 2014 / Accepted: 16 July 2014 / Published: 18 July 2014
Cited by 13 | Viewed by 2706 | PDF Full-text (1620 KB) | HTML Full-text | XML Full-text
Abstract
Gravity matching navigation algorithm is one of the key technologies for gravity aided inertial navigation systems. With the development of intelligent algorithms, the powerful search ability of the Artificial Bee Colony (ABC) algorithm makes it possible to be applied to the gravity matching [...] Read more.
Gravity matching navigation algorithm is one of the key technologies for gravity aided inertial navigation systems. With the development of intelligent algorithms, the powerful search ability of the Artificial Bee Colony (ABC) algorithm makes it possible to be applied to the gravity matching navigation field. However, existing search mechanisms of basic ABC algorithms cannot meet the need for high accuracy in gravity aided navigation. Firstly, proper modifications are proposed to improve the performance of the basic ABC algorithm. Secondly, a new search mechanism is presented in this paper which is based on an improved ABC algorithm using external speed information. At last, modified Hausdorff distance is introduced to screen the possible matching results. Both simulations and ocean experiments verify the feasibility of the method, and results show that the matching rate of the method is high enough to obtain a precise matching position. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Short Chain N-Acyl Homoserine Lactone Production in Tropical Marine Vibrio sinaloensis Strain T47
Sensors 2014, 14(7), 12958-12967; https://doi.org/10.3390/s140712958
Received: 8 May 2014 / Revised: 30 June 2014 / Accepted: 11 July 2014 / Published: 18 July 2014
Cited by 3 | Viewed by 2177 | PDF Full-text (2357 KB) | HTML Full-text | XML Full-text
Abstract
Quorum sensing (QS), acts as one of the gene regulatory systems that allow bacteria to regulate their physiological activities by sensing the population density with synchronization of the signaling molecules that they produce. Here, we report a marine isolate, namely strain T47, and [...] Read more.
Quorum sensing (QS), acts as one of the gene regulatory systems that allow bacteria to regulate their physiological activities by sensing the population density with synchronization of the signaling molecules that they produce. Here, we report a marine isolate, namely strain T47, and its unique AHL profile. Strain T47 was identified using 16S rRNA sequence analysis confirming that it is a member of Vibrio closely clustered to Vibrio sinaloensis. The isolated V. sinaloensis strain T47 was confirmed to produce N-butanoyl-L-homoserine lactone (C4-HSL) by using high resolution liquid chromatography tandem mass spectrometry. V. sinaloensis strain T47 also formed biofilms and its biofilm formation could be affected by anti-QS compound (cathechin) suggesting this is a QS-regulated trait in V. sinaloensis strain T47. To our knowledge, this is the first documentation of AHL and biofilm production in V. sinaloensis strain T47. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle
Association Rule Extraction from XML Stream Data for Wireless Sensor Networks
Sensors 2014, 14(7), 12937-12957; https://doi.org/10.3390/s140712937
Received: 13 May 2014 / Revised: 24 June 2014 / Accepted: 2 July 2014 / Published: 18 July 2014
Cited by 2 | Viewed by 2518 | PDF Full-text (684 KB) | HTML Full-text | XML Full-text
Abstract
With the advances of wireless sensor networks, they yield massive volumes of disparate, dynamic and geographically-distributed and heterogeneous data. The data mining community has attempted to extract knowledge from the huge amount of data that they generate. However, previous mining work in WSNs [...] Read more.
With the advances of wireless sensor networks, they yield massive volumes of disparate, dynamic and geographically-distributed and heterogeneous data. The data mining community has attempted to extract knowledge from the huge amount of data that they generate. However, previous mining work in WSNs has focused on supporting simple relational data structures, like one table per network, while there is a need for more complex data structures. This deficiency motivates XML, which is the current de facto format for the data exchange and modeling of a wide variety of data sources over the web, to be used in WSNs in order to encourage the interchangeability of heterogeneous types of sensors and systems. However, mining XML data for WSNs has two challenging issues: one is the endless data flow; and the other is the complex tree structure. In this paper, we present several new definitions and techniques related to association rule mining over XML data streams in WSNs. To the best of our knowledge, this work provides the first approach to mining XML stream data that generates frequent tree items without any redundancy. Full article
(This article belongs to the Section Sensor Networks)
Open AccessReview
Automatic Fall Monitoring: A Review
Sensors 2014, 14(7), 12900-12936; https://doi.org/10.3390/s140712900
Received: 8 April 2014 / Revised: 2 July 2014 / Accepted: 7 July 2014 / Published: 18 July 2014
Cited by 81 | Viewed by 4482 | PDF Full-text (2752 KB) | HTML Full-text | XML Full-text
Abstract
Falls and fall-related injuries are major incidents, especially for elderly people, which often mark the onset of major deterioration of health. More than one-third of home-dwelling people aged 65 or above and two-thirds of those in residential care fall once or more each [...] Read more.
Falls and fall-related injuries are major incidents, especially for elderly people, which often mark the onset of major deterioration of health. More than one-third of home-dwelling people aged 65 or above and two-thirds of those in residential care fall once or more each year. Reliable fall detection, as well as prevention, is an important research topic for monitoring elderly living alone in residential or hospital units. The aim of this study is to review the existing fall detection systems and some of the key research challenges faced by the research community in this field. We categorize the existing platforms into two groups: wearable and ambient devices; the classification methods are divided into rule-based and machine learning techniques. The relative merit and potential drawbacks are discussed, and we also outline some of the outstanding research challenges that emerging new platforms need to address. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle
Modeling and Analysis of a Microresonating Biosensor for Detection of Salmonella Bacteria in Human Blood
Sensors 2014, 14(7), 12885-12899; https://doi.org/10.3390/s140712885
Received: 8 May 2014 / Revised: 10 June 2014 / Accepted: 19 June 2014 / Published: 18 July 2014
Cited by 19 | Viewed by 2892 | PDF Full-text (1893 KB) | HTML Full-text | XML Full-text
Abstract
A new photonics biosensor configuration comprising a Double-side Ring Add-drop Filter microring resonator (DR-ADF) made from SiO2-TiO2 material is proposed for the detection of Salmonella bacteria (SB) in blood. The scattering matrix method using inductive calculation is used to determine [...] Read more.
A new photonics biosensor configuration comprising a Double-side Ring Add-drop Filter microring resonator (DR-ADF) made from SiO2-TiO2 material is proposed for the detection of Salmonella bacteria (SB) in blood. The scattering matrix method using inductive calculation is used to determine the output signal’s intensities in the blood with and without presence of Salmonella. The change in refractive index due to the reaction of Salmonella bacteria with its applied antibody on the flagellin layer loaded on the sensing and detecting microresonator causes the increase in through and dropper port’s intensities of the output signal which leads to the detection of SB in blood. A shift in the output signal wavelength is observed with resolution of 0.01 nm. The change in intensity and shift in wavelength is analyzed with respect to the change in the refractive index which contributes toward achieving an ultra-high sensitivity of 95,500 nm/RIU which is almost two orders higher than that of reported from single ring sensors and the limit of detection is in the order of 1 × 10−8 RIU. In applications, such a system can be employed for a high sensitive and fast detection of bacteria. Full article
(This article belongs to the Special Issue Advances in Optical Biosensors)
Open AccessArticle
Lamb Wave Line Sensing for Crack Detection in a Welded Stiffener
Sensors 2014, 14(7), 12871-12884; https://doi.org/10.3390/s140712871
Received: 10 June 2014 / Revised: 5 July 2014 / Accepted: 14 July 2014 / Published: 18 July 2014
Cited by 10 | Viewed by 2600 | PDF Full-text (1927 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a novel Lamb wave line sensing technique for crack detection in a welded stiffener. The proposed technique overcomes one of the biggest technical challenges of Lamb wave crack detection for real structure applications: crack-induced Lamb waves are often mixed with [...] Read more.
This paper proposes a novel Lamb wave line sensing technique for crack detection in a welded stiffener. The proposed technique overcomes one of the biggest technical challenges of Lamb wave crack detection for real structure applications: crack-induced Lamb waves are often mixed with multiple reflections from complex waveguides. In particular, crack detection in a welded joint, one of the structural hot spots due to stress concentration, is accompanied by reflections from the welded joint as well as a crack. Extracting and highlighting crack-induced Lamb wave modes from Lamb wave responses measured at multi-spatial points along a single line can be accomplished through a frequency-wavenumber domain analysis. The advantages of the proposed technique enable us not only to enhance the crack detectability in the welded joint but also to minimize false alarms caused by environmental and operational variations by avoiding the direct comparison with the baseline data previously accumulated from the pristine condition of a target structure. The proposed technique is experimentally and numerically validated in vertically stiffened metallic structures, revealing that it successfully identifies and localizes subsurface cracks, regardless of the coexistence with the vertical stiffener. Full article
Open AccessReview
Dry EEG Electrodes
Sensors 2014, 14(7), 12847-12870; https://doi.org/10.3390/s140712847
Received: 2 May 2014 / Revised: 1 July 2014 / Accepted: 14 July 2014 / Published: 18 July 2014
Cited by 78 | Viewed by 5905 | PDF Full-text (788 KB) | HTML Full-text | XML Full-text
Abstract
Electroencephalography (EEG) emerged in the second decade of the 20th century as a technique for recording the neurophysiological response. Since then, there has been little variation in the physical principles that sustain the signal acquisition probes, otherwise called electrodes. Currently, new advances in [...] Read more.
Electroencephalography (EEG) emerged in the second decade of the 20th century as a technique for recording the neurophysiological response. Since then, there has been little variation in the physical principles that sustain the signal acquisition probes, otherwise called electrodes. Currently, new advances in technology have brought new unexpected fields of applications apart from the clinical, for which new aspects such as usability and gel-free operation are first order priorities. Thanks to new advances in materials and integrated electronic systems technologies, a new generation of dry electrodes has been developed to fulfill the need. In this manuscript, we review current approaches to develop dry EEG electrodes for clinical and other applications, including information about measurement methods and evaluation reports. We conclude that, although a broad and non-homogeneous diversity of approaches has been evaluated without a consensus in procedures and methodology, their performances are not far from those obtained with wet electrodes, which are considered the gold standard, thus enabling the former to be a useful tool in a variety of novel applications. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle
Introduction and Testing of a Monitoring and Colony-Mapping Method for Waterbird Populations That Uses High-Speed and Ultra-Detailed Aerial Remote Sensing
Sensors 2014, 14(7), 12828-12846; https://doi.org/10.3390/s140712828
Received: 9 April 2014 / Revised: 2 July 2014 / Accepted: 11 July 2014 / Published: 18 July 2014
Cited by 6 | Viewed by 2783 | PDF Full-text (2399 KB) | HTML Full-text | XML Full-text
Abstract
Remote sensing is a method that collects data of the Earth’s surface without causing disturbances. Thus, it is worthwhile to use remote sensing methods to survey endangered ecosystems, as the studied species will behave naturally while undisturbed. The latest passive optical remote sensing [...] Read more.
Remote sensing is a method that collects data of the Earth’s surface without causing disturbances. Thus, it is worthwhile to use remote sensing methods to survey endangered ecosystems, as the studied species will behave naturally while undisturbed. The latest passive optical remote sensing solutions permit surveys from long distances. State-of-the-art highly sensitive sensor systems allow high spatial resolution image acquisition at high altitudes and at high flying speeds, even in low-visibility conditions. As the aerial imagery captured by an airplane covers the entire study area, all the animals present in that area can be recorded. A population assessment is conducted by visual interpretations of an ortho image map. The basic objective of this study is to determine whether small- and medium-sized bird species are recognizable in the ortho images by using high spatial resolution aerial cameras. The spatial resolution needed for identifying the bird species in the ortho image map was studied. The survey was adjusted to determine the number of birds in a colony at a given time. Full article
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
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Graphical abstract

Open AccessCommunication
A Novel Crosstalk Suppression Method of the 2-D Networked Resistive Sensor Array
Sensors 2014, 14(7), 12816-12827; https://doi.org/10.3390/s140712816
Received: 28 April 2014 / Revised: 24 June 2014 / Accepted: 14 July 2014 / Published: 18 July 2014
Cited by 13 | Viewed by 2288 | PDF Full-text (2463 KB) | HTML Full-text | XML Full-text
Abstract
The 2-D resistive sensor array in the row–column fashion suffered from the crosstalk problem for parasitic parallel paths. Firstly, we proposed an Improved Isolated Drive Feedback Circuit with Compensation (IIDFCC) based on the voltage feedback method to suppress the crosstalk. In this method, [...] Read more.
The 2-D resistive sensor array in the row–column fashion suffered from the crosstalk problem for parasitic parallel paths. Firstly, we proposed an Improved Isolated Drive Feedback Circuit with Compensation (IIDFCC) based on the voltage feedback method to suppress the crosstalk. In this method, a compensated resistor was specially used to reduce the crosstalk caused by the column multiplexer resistors and the adjacent row elements. Then, a mathematical equivalent resistance expression of the element being tested (EBT) of this circuit was analytically derived and verified by the circuit simulations. The simulation results show that the measurement method can greatly reduce the influence on the EBT caused by parasitic parallel paths for the multiplexers’ channel resistor and the adjacent elements. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
A Self-Referencing Intensity-Based Fiber Optic Sensor with Multipoint Sensing Characteristics
Sensors 2014, 14(7), 12803-12815; https://doi.org/10.3390/s140712803
Received: 1 May 2014 / Revised: 5 July 2014 / Accepted: 14 July 2014 / Published: 18 July 2014
Cited by 12 | Viewed by 2365 | PDF Full-text (5752 KB) | HTML Full-text | XML Full-text
Abstract
A self-referencing, intensity-based fiber optic sensor (FOS) is proposed and demonstrated. The theoretical analysis for the proposed design is given, and the validity of the theoretical analysis is confirmed via experiments. We define the measurement parameter, X, and the calibration factor, β, [...] Read more.
A self-referencing, intensity-based fiber optic sensor (FOS) is proposed and demonstrated. The theoretical analysis for the proposed design is given, and the validity of the theoretical analysis is confirmed via experiments. We define the measurement parameter, X, and the calibration factor, β, to find the transfer function, , of the intensity-based FOS head. The self-referencing and multipoint sensing characteristics of the proposed system are validated by showing the measured and relative error versus the optical power attenuation of the sensor head for four cases: optical source fluctuation, various remote sensing point distances, fiber Bragg gratings (FBGs) with different characteristics, and multiple sensor heads with cascade and/or parallel forms. The power-budget analysis and limitations of the measurement rates are discussed, and the measurement results of fiber-reinforced plastic (FRP) coupon strain using the proposed FOS are given as an actual measurement. The proposed FOS has several benefits, including a self-referencing characteristic, the flexibility to determine FBGs, and a simple structure in terms of the number of devices and measuring procedure. Full article
Open AccessArticle
Classification of EEG Signals Using a Multiple Kernel Learning Support Vector Machine
Sensors 2014, 14(7), 12784-12802; https://doi.org/10.3390/s140712784
Received: 19 February 2014 / Revised: 20 June 2014 / Accepted: 10 July 2014 / Published: 17 July 2014
Cited by 40 | Viewed by 3676 | PDF Full-text (865 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a multiple kernel learning support vector machine algorithm is proposed for the identification of EEG signals including mental and cognitive tasks, which is a key component in EEG-based brain computer interface (BCI) systems. The presented BCI approach included three stages: [...] Read more.
In this study, a multiple kernel learning support vector machine algorithm is proposed for the identification of EEG signals including mental and cognitive tasks, which is a key component in EEG-based brain computer interface (BCI) systems. The presented BCI approach included three stages: (1) a pre-processing step was performed to improve the general signal quality of the EEG; (2) the features were chosen, including wavelet packet entropy and Granger causality, respectively; (3) a multiple kernel learning support vector machine (MKL-SVM) based on a gradient descent optimization algorithm was investigated to classify EEG signals, in which the kernel was defined as a linear combination of polynomial kernels and radial basis function kernels. Experimental results showed that the proposed method provided better classification performance compared with the SVM based on a single kernel. For mental tasks, the average accuracies for 2-class, 3-class, 4-class, and 5-class classifications were 99.20%, 81.25%, 76.76%, and 75.25% respectively. Comparing stroke patients with healthy controls using the proposed algorithm, we achieved the average classification accuracies of 89.24% and 80.33% for 0-back and 1-back tasks respectively. Our results indicate that the proposed approach is promising for implementing human-computer interaction (HCI), especially for mental task classification and identifying suitable brain impairment candidates. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
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