Sensors

718 KiB

Open AccessReview

Applications of Nanomaterials in Electrogenerated Chemiluminescence Biosensors

by Honglan Qi, Yage Peng, Qiang Gao and Chengxiao Zhang

Sensors 2009, 9(1), 674-695; https://doi.org/10.3390/s90100674 - 23 Jan 2009

Cited by 105 | Viewed by 16453

Electrogenerated chemiluminescence (also called electrochemiluminescence and abbreviated ECL) involves the generation of species at electrode surfaces that then undergo electron-transfer reactions to form excited states that emit light. ECL biosensor, combining advantages offered by the selectivity of the biological recognition elements and the [...] Read more.

Electrogenerated chemiluminescence (also called electrochemiluminescence and abbreviated ECL) involves the generation of species at electrode surfaces that then undergo electron-transfer reactions to form excited states that emit light. ECL biosensor, combining advantages offered by the selectivity of the biological recognition elements and the sensitivity of ECL technique, is a powerful device for ultrasensitive biomolecule detection and quantification. Nanomaterials are of considerable interest in the biosensor field owing to their unique physical and chemical properties, which have led to novel biosensors that have exhibited high sensitivity and stability. Nanomaterials including nanoparticles and nanotubes, prepared from metals, semiconductor, carbon or polymeric species, have been widely investigated for their ability to enhance the efficiencies of ECL biosensors, such as taking as modification electrode materials, or as carrier of ECL labels and ECL-emitting species. Particularly useful application of nanomaterials in ECL biosensors with emphasis on the years 2004-2008 is reviewed. Remarks on application of nanomaterials in ECL biosensors are also surveyed. Full article

(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)

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Schematic diagrams of immobilization of BSA (a) and IgG (b) on the gold electrode with gold nanoparticle amplification. Reprinted from Ref [<a href="#b20-sensors-09-00674" class="html-bibr">20</a>] with permission from The American Chemical Society. Full article ">
Schematic diagram of the ECL detection for DNA hybridization. Reprinted from Ref [<a href="#b58-sensors-09-00674" class="html-bibr">58</a>] with permission from Elsevier. Full article ">
Schematic diagram of DNA hybridization on a polystyrene bead as the ECL label carrier and a magnetic bead for the separation of analyte-contained ECL label/polystyrene beads. Reprinted from Ref [<a href="#b62-sensors-09-00674" class="html-bibr">62</a>] with permission from The American Chemical Society. Full article ">
Schematic diagram showing the formation of a sandwich-type aggregate between an antibody-coated MB and an antibody-coated PSB containing entrapped ECL labels in the presence of the antigen species, and the separation of the newly formed aggregate with a magnet as well as the subsequent dissolution and ECL detection in MeCN using TPA as the coreactant. Reprinted from Ref [<a href="#b63-sensors-09-00674" class="html-bibr">63</a>] with permission from The American Chemical Society. Full article ">
Schematic representation of preparation Ru(bpy)32+-doped silica nanoparticles oligonucleotides probes (A) and the electrogenerated chemiluminescence detection of DNA hybridization based on the Ru(bpy)32+-doped silica nanoparticles labeled oligonucleotides probes (B). Reprinted from Ref [<a href="#b72-sensors-09-00674" class="html-bibr">72</a>] with permission from Elsevier. Full article ">
Schematic representations of PL and ECL process of nanoparticle in the core and on the surface. Reprinted from Ref [<a href="#b100-sensors-09-00674" class="html-bibr">100</a>] with permission from The American Chemical Society. Full article ">
Fabricating Steps of the ECL Immunosensor. Reprinted from Ref [<a href="#b101-sensors-09-00674" class="html-bibr">101</a>] with permission from The American Chemical Society. Full article ">

363 KiB

Open AccessArticle

Use of Reflectance Ratios as a Proxy for Coastal Water Constituent Monitoring in the Pearl River Estuary

by Li-Gang Fang, Shui-Sen Chen, Dong Li and Hong-Li Li

Sensors 2009, 9(1), 656-673; https://doi.org/10.3390/s90100656 - 23 Jan 2009

Cited by 11 | Viewed by 13850

Abstract

Spectra, salinity, total suspended solids (TSS, in mg/L) and colored dissolved organic matter (CDOM, ag(400) at 400 nm) sampled in stations in 44 different locations on December 18, 19 and 21, in 2006 were measured and analyzed. The studied field covered a large [...] Read more.

Spectra, salinity, total suspended solids (TSS, in mg/L) and colored dissolved organic matter (CDOM, ag(400) at 400 nm) sampled in stations in 44 different locations on December 18, 19 and 21, in 2006 were measured and analyzed. The studied field covered a large variety of optically different waters, the absorption coefficient of CDOM ([ag(400)] in m^-1) varied between 0.488 and 1.41 m^-1, and the TSS concentrations (mg/L) varied between 7.0 and 241.1 mg/L. In order to detect salinity of the Pearl River Estuary, we analyzed the spectral properties of TSS and CDOM, and the relationships between field water reflectance spectra and water constituents’ concentrations based on the synchronous in-situ and satellite hyper-spectral image analysis. A good correlation was discovered (the positive correlation by linear fit), between in-situ reflectance ratio R₆₈₀/R₅₂₇ and TSS concentrations (R² = 0.65) for the salinity range of 1.74-22.12. However, the result also showed that the absorption coefficient of CDOM was not tightly correlated with reflectance. In addition, we also observed two significant relationships (R²> 0.77), one between TSS concentrations and surface salinity and the other between the absorption coefficient of CDOM and surface salinity. Finally, we develop a novel method to understand surface salinity distribution of estuarine waters from the calibrated EO-1 Hyperion reflectance data in the Pearl River Estuary, i.e. channels with high salinity and shoals with low salinity. The EO-1 Hyperion derived surface salinity and TSSconcentrations were validated using in-situ data that were collected on December 21, 2006, synchronous with EO-1 Hyperion satellite imagery acquisition. The results showed that the semi-empirical relationships are capable of predicting salinity from EO-1 Hyperion imagery in the Pearl River Estuary (RMSE < 2‰). Full article

(This article belongs to the Section Remote Sensors)

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Map of water system in the Pearl River Estuary (PRE) and the black frame outlines map of EO-1 Hyperion footprint. Sample for spectra, salinity, TSS and CDOM in stations including 44 locations were measured and analyzed on December 18, 19 and 21, in 2006. There were 16 sampling locations in the Humen riverway (H1-H16), 16 locations in the Modaomen riverway (M1-M16) and 12 locations in the Lingding Bay (S1-S12). Additionally, triangles indicate the ten sampling sites synchronous with EO-1 Hyperion satellite imagery acquisition. Full article ">
Variance range of water spatial reflectance profile at a Hyperion NIR band (864.35 nm). Full article ">
The comparison of the FLAASH-derived reflectance with the apparent reflectance, and with the measured Hyperion remote sensing reflectance of surface water in the PRE. The three vertical lines indicate blue, green and visible light bands from left to right in the Figure. Full article ">
Correlation between ag(400) and reflectance ratio. Full article ">
Correlation between TSS concentration and reflectance ratio. Full article ">
Correlation between salinity (‰) and CDOM absorption coefficients. Squares present five in-situ data, which were from the Shenwan River way and were controlled by severe pollution of the Xihe waterway by industry and life. Full article ">
Correlation between salinity (‰) and total suspended solids (TSS) concentration (mg/L), and the black full line represent linear relationship between salinity and total suspended solids (TSS) concentration (R2 = 0.51). Full article ">
The left graph is sea graph of Lingding Bay; the right graph is products from the semi-empirical algorithms on December 21, 2006. (a) total suspended solid (mg/L). (b) salinity (‰). Full article ">
Correlations between the in-situ TSS concentrations and salinity data and estimated from an atmospherically corrected Hyperion image of PRE (Dec. 2006) using <a href="#FD4" class="html-disp-formula">Equations (4)</a> and <a href="#FD6" class="html-disp-formula">(6)</a>. Ten stations data synchronous with EO-1 Hyperion imagery were used to validate TSS concentrations and salinity. Full article ">

295 KiB

Open AccessArticle

Reduction of Non-Specific Protein Adsorption Using Poly(ethylene) Glycol (PEG) Modified Polyacrylate Hydrogels In Immunoassays for Staphylococcal Enterotoxin B Detection

by Paul T. Charles, Veronte R. Stubbs, Carissa M. Soto, Brett D. Martin, Brandy J. White and Chris R. Taitt

Sensors 2009, 9(1), 645-655; https://doi.org/10.3390/s90100645 - 23 Jan 2009

Cited by 69 | Viewed by 15124

Abstract

Three PEG molecules (PEG-methacrylate, -diacrylate and -dimethacrylate) were incorporated into galactose-based polyacrylate hydrogels and their relative abilities to reduce non-specific protein adsorption in immunoassays were determined. Highly crosslinked hydrogels containing amine-terminated functionalities were formed and used to covalently attach antibodies specific for staphylococcal [...] Read more.

Three PEG molecules (PEG-methacrylate, -diacrylate and -dimethacrylate) were incorporated into galactose-based polyacrylate hydrogels and their relative abilities to reduce non-specific protein adsorption in immunoassays were determined. Highly crosslinked hydrogels containing amine-terminated functionalities were formed and used to covalently attach antibodies specific for staphylococcal enterotoxin B (SEB). Patterned arrays of immobilized antibodies in the PEG-modified hydrogels were created with a PDMS template containing micro-channels for use in sandwich immunoassays to detect SEB. Different concentrations of the toxin were applied to the hydrogel arrays, followed with a Cy3-labeled tracer antibody specific for the two toxins. Fluorescence laser scanning confocal microscopy of the tracer molecules provided both qualitative and quantitative measurements on the detection sensitivity and the reduction in non-specific binding as a result of PEG incorporation. Results showed the PEG-modified hydrogel significantly reduced non-specific protein binding with a detection limit for SEB of 1 ng/mL. Fluorescence signals showed a 10-fold decrease in the non-specific binding and a 6-fold increase in specific binding of SEB. Full article

(This article belongs to the Special Issue Toxin Sensors)

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Graphical abstract

Graphical abstract
Full article ">
Chemical structures of (a) Poly(ethylene glycol) methacrylate, (b) Poly(ethylene glycol) diacrylate, and (c) Poly(ethylene glycol) dimethacrylate. Full article ">
Patterned fluorescence array images of sandwich immunoassay for SEB using galactose-based hydrogels. (a) Representative image of SEB immunoassay using hydrogel containing no PEG. (b) Representative image of SEB immunoassay with PEG-diacrylate-modified hydrogel. SEB concentrations ranged from 0.03 to 1.0 μg/mL. Regions highlighted with the orange box indicate areas of non-specific protein adsorption, whereas green-highlighted areas indicate immobilized capture antibody and represent target-specific binding regions. (c) Line plot showing fluorescence signals due to non-specific and specific protein binding in SEB immunoassays (n = 6, ± SD). Full article ">
Fluorescence measured from non-specific binding in sandwich immunoassays for SEB. Unmodified hydrogels, PEG-diacrylate, PEG-methacrylate and PEG-dimethacrylate modified hydrogels were compared (i.e., areas highlighted in orange rectangle in <a href="#f2-sensors-09-00645" class="html-fig">Figures 2A and 2B</a>). Images of the fluorescence arrays were analyzed using Adobe Photoshop CS3 Extended (from RGB color values). Values reported represent replicate of six (± SD). Full article ">
Comparison of net fluorescence signal responses obtained in sandwich immunoassays using control (no PEG) and three different PEG-incorporated hydrogels. The three PEG candidates ([img]), PEG-diacrylate ([img]), PEG-methacrylate and ([img]) PEG-dimethacrylate were incorporated into galactose-based polyacrylate hydrogels. Rabbit anti-SEB (capture antibody) was bound within the hydrogel and fluorescence was obtained with Cy3-labeled sheep anti-SEB (tracer molecule). Values reported represent replicates of six (± SD). Full article ">

675 KiB

Open AccessArticle

A Two-Dimensional Micro Scanner Integrated with a Piezoelectric Actuator and Piezoresistors

by Chi Zhang, Gaofei Zhang and Zheng You

Sensors 2009, 9(1), 631-644; https://doi.org/10.3390/s90100631 - 23 Jan 2009

Cited by 26 | Viewed by 11108

Abstract

A compact two-dimensional micro scanner with small volume, large deflection angles and high frequency is presented and the two-dimensional laser scanning is achieved by specular reflection. To achieve large deflection angles, the micro scanner excited by a piezoelectric actuator operates in the resonance [...] Read more.

A compact two-dimensional micro scanner with small volume, large deflection angles and high frequency is presented and the two-dimensional laser scanning is achieved by specular reflection. To achieve large deflection angles, the micro scanner excited by a piezoelectric actuator operates in the resonance mode. The scanning frequencies and the maximum scanning angles of the two degrees of freedom are analyzed by modeling and simulation of the structure. For the deflection angle measurement, piezoresistors are integrated in the micro scanner. The appropriate directions and crystal orientations of the piezoresistors are designed to obtain the large piezoresistive coefficients for the high sensitivities. Wheatstone bridges are used to measure the deflection angles of each direction independently and precisely. The scanner is fabricated and packaged with the piezoelectric actuator and the piezoresistors detection circuits in a size of 28 mm×20 mm×18 mm. The experiment shows that the two scanning frequencies are 216.8 Hz and 464.8 Hz, respectively. By an actuation displacement of 10 μm, the scanning range of the two-dimensional micro scanner is above 26º × 23º. The deflection angle measurement sensitivities for two directions are 59 mV/deg and 30 mV/deg, respectively. Full article

(This article belongs to the Section Chemical Sensors)

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637 KiB

Open AccessArticle

Observation of a Large Landslide on La Reunion Island Using Differential Sar Interferometry (JERS and Radarsat) and Correlation of Optical (Spot5 and Aerial) Images

by Christophe Delacourt, Daniel Raucoules, Stéphane Le Mouélic, Claudie Carnec, Denis Feurer, Pascal Allemand and Marc Cruchet

Sensors 2009, 9(1), 616-630; https://doi.org/10.3390/s90100616 - 21 Jan 2009

Cited by 31 | Viewed by 15013

Abstract

Slope instabilities are one of the most important geo-hazards in terms of socio-economic costs. The island of La Réunion (Indian Ocean) is affected by constant slope movements and huge landslides due to a combination of rough topography, wet tropical climate and its specific [...] Read more.

Slope instabilities are one of the most important geo-hazards in terms of socio-economic costs. The island of La Réunion (Indian Ocean) is affected by constant slope movements and huge landslides due to a combination of rough topography, wet tropical climate and its specific geological context. We show that remote sensing techniques (Differential SAR Interferometry and correlation of optical images) provide complementary means to characterize landslides on a regional scale. The vegetation cover generally hampers the analysis of C–band interferograms. We used JERS-1 images to show that the L-band can be used to overcome the loss of coherence observed in Radarsat C-band interferograms. Image correlation was applied to optical airborne and SPOT 5 sensors images. The two techniques were applied to a landslide near the town of Hellbourg in order to assess their performance for detecting and quantifying the ground motion associated to this landslide. They allowed the mapping of the unstable areas. Ground displacement of about 0.5 m yr^-1 was measured. Full article

(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))

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Left: one of the most coherent Radarsat C-band interferograms (15/05/2001 – 23/11/2001, perpendicular baseline=68 m). Right: one of the most coherent JERS-1 (02/01/1997-14/05/1997, perpendicular baseline=187 m) interferograms obtained for the whole island. The white rectangles on Figure 1 indicate the Circles sector and the Piton de la Fournaise volcano. The yellow rectangle shows the area displayed in <a href="#f2-sensors-09-00616" class="html-fig">Figure 2</a>. No coherence loss is observed in the L-band despite the dense vegetal cover of the island. The SAR intensity image is used as background. Full article ">
JERS-1 interferogram–left: 02/01/1997-31/03/1997. Right: 15/02/1997-14/05/1997. One color cycle corresponds to 11.25 cm displacement in line of sight (LOS), whose direction is represented by the arrows. White frames give the limits and maxima of the observed displacements. Full article ">
Up: stacking sum of two 3–months L-Band JERS-1 interferograms (1 fringe = 5.6 cm in line of sight). The boundaries (white frames) of the landslide are clearly delimited by the fringe pattern. Circles correspond to GPS points (blue less than 6 cm displacement, red: more than 12 cm displacement). Down: 08/06/2001-26/07/2001 Radarsat C-Band interferogram (1 fringe=2.8 cm in line of sight). The white arrows indicate an unstable area on the left border of the landslide. Despite the poor coherence level in C-band, this interferogram confirms the detection made using the L-band. Background: aerial photograph (source IGN). Full article ">
Sum of two 3 months JERS-1 interferograms (1 fringe = 5.6 cm in line of sight) overlain on the topographic map of the landslide (source: Cruchet, 2000). In red, GPS displacements for the period 1995-1999. Black lines represent positions of crack boundaries of the landslide observed by Cruchet. Black-and-yellow line shows the position of the Hellbourg road severely affected by the landslide. Full article ">
Displacement map along the north-south direction for the Hellbourg area during the 1997-2002 period. The red contour corresponds to a landslide located north of the river, sliding in the southern direction. The white contour corresponds to the boundaries of the main landslide, moving northward. A and B are the profiles presented in <a href="#f6-sensors-09-00616" class="html-fig">Figures 6</a> and <a href="#f7-sensors-09-00616" class="html-fig">7</a>. Black areas correspond to low correlation value. Full article ">
Displacement profile A in <a href="#f4-sensors-09-00616" class="html-fig">Figure 4</a>, along the North-South direction during the 1997-2002 period. Horizontal axis corresponds to distance (in m) along the profile. Full article ">
Displacement profile B in <a href="#f5-sensors-09-00616" class="html-fig">Figure 5</a>, along the North-South direction during the 1997-2002 period. Horizontal axis corresponds to distance (in m) along the profile. Full article ">

530 KiB

Open AccessArticle

An Approach for Rapid Assessment of Seismic Hazards in Turkey by Continuous GPS Data

by Haluk Ozener, Asli Dogru and Ahmet Unlutepe

Sensors 2009, 9(1), 602-615; https://doi.org/10.3390/s90100602 - 20 Jan 2009

Cited by 19 | Viewed by 12714

Abstract

The Earth is being monitored every day by all kinds of sensors. This leads an overflow of data in all branches of science nowadays, especially in Earth Sciences. Data storage and data processing are the problems to be solved by current technologies, as [...] Read more.

The Earth is being monitored every day by all kinds of sensors. This leads an overflow of data in all branches of science nowadays, especially in Earth Sciences. Data storage and data processing are the problems to be solved by current technologies, as well as by those accessing and analyzing these large data sources. Once solutions have been created for collecting, storing and accessing data, then the challenge becomes how to effectively share data, applications and processing resources across many locations. The Global Positioning System (GPS) sensors are being used as geodetic instruments to precisely detect crustal motion in the Earth’s surface. Rapid access to data provided by GPS sensors is becoming increasingly important for deformation monitoring and rapid hazard assessments. Today, reliable and fast collection and distribution of data is a challenge and advances in Internet technologies have made it easier to provide the needed data. This study describes a system which will be able to generate strain maps using data from continuous GPS stations for seismic hazard analysis. Strain rates are a key factor in seismic hazard analyses. Turkey is a country prone to earthquakes with a long history of seismic hazards and disasters. This situation has resulted in the studies by Earth scientists that focus on Turkey in order to improve their understanding of the Earth’s crust structure and seismic hazards. Nevertheless, the construction of models, data access and analysis are often not fast as expected, but the combination of Internet technologies with continuous GPS sensors can be a solution to overcome this problem. This system would have the potential to answer many important questions to assess seismic hazards such as how much stretching, squashing and shearing is taking place in different parts of Turkey, and how do velocities change from place to place? Seismic hazard estimation is the most effective way to reduce earthquake losses. It is clear that reliability of data and on-line services will support the preparation of strategies for disaster management and planning to cope with hazards. Full article

(This article belongs to the Section Remote Sensors)

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2689 KiB

Open AccessReview

State-of-The-Art and Applications of 3D Imaging Sensors in Industry, Cultural Heritage, Medicine, and Criminal Investigation

by Giovanna Sansoni, Marco Trebeschi and Franco Docchio

Sensors 2009, 9(1), 568-601; https://doi.org/10.3390/s90100568 - 20 Jan 2009

Cited by 518 | Viewed by 35823

Abstract

3D imaging sensors for the acquisition of three dimensional (3D) shapes have created, in recent years, a considerable degree of interest for a number of applications. The miniaturization and integration of the optical and electronic components used to build them have played a [...] Read more.

3D imaging sensors for the acquisition of three dimensional (3D) shapes have created, in recent years, a considerable degree of interest for a number of applications. The miniaturization and integration of the optical and electronic components used to build them have played a crucial role in the achievement of compactness, robustness and flexibility of the sensors. Today, several 3D sensors are available on the market, even in combination with other sensors in a “sensor fusion” approach. An importance equal to that of physical miniaturization has the portability of the measurements, via suitable interfaces, into software environments designed for their elaboration, e.g., CAD-CAM systems, virtual renders, and rapid prototyping tools. In this paper, following an overview of the state-of-art of 3D imaging sensors, a number of significant examples of their use are presented, with particular reference to industry, heritage, medicine, and criminal investigation applications. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)

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508 KiB

Open AccessArticle

Modeling Impact-induced Failure of Polysilicon MEMS: A Multi-scale Approach

by Stefano Mariani, Aldo Ghisi, Alberto Corigliano and Sarah Zerbini

Sensors 2009, 9(1), 556-567; https://doi.org/10.3390/s90100556 - 19 Jan 2009

Cited by 43 | Viewed by 11151

Abstract

Failure of packaged polysilicon micro-electro-mechanical systems (MEMS) subjected to impacts involves phenomena occurring at several length-scales. In this paper we present a multi-scale finite element approach to properly allow for: (i) the propagation of stress waves inside the package; (ii) the dynamics of [...] Read more.

Failure of packaged polysilicon micro-electro-mechanical systems (MEMS) subjected to impacts involves phenomena occurring at several length-scales. In this paper we present a multi-scale finite element approach to properly allow for: (i) the propagation of stress waves inside the package; (ii) the dynamics of the whole MEMS; (iii) the spreading of micro-cracking in the failing part(s) of the sensor. Through Monte Carlo simulations, some effects of polysilicon micro-structure on the failure mode are elucidated. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)

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222 KiB

Open AccessArticle

Ricin Detection Using Phage Displayed Single Domain Antibodies

by Ellen R. Goldman, Jinny L. Liu, Rachael D. Bernstein, Marla D. Swain, Stanley Q. Mitchell and George P. Anderson

Sensors 2009, 9(1), 542-555; https://doi.org/10.3390/s90100542 - 19 Jan 2009

Cited by 32 | Viewed by 12566

Abstract

Phage-displayed single domain antibodies (sdAb) were compared to monomeric solubly expressed sdAb and llama polyclonal antibodies for the detection of ricin. SdAb are comprised of the variable domain derived from camelid heavy chain only antibodies (HcAb). Although HcAb lack variable light chains, they [...] Read more.

Phage-displayed single domain antibodies (sdAb) were compared to monomeric solubly expressed sdAb and llama polyclonal antibodies for the detection of ricin. SdAb are comprised of the variable domain derived from camelid heavy chain only antibodies (HcAb). Although HcAb lack variable light chains, they as well as their derivative sdAb are able to bind antigens with high affinity. The small size of sdAb (~16 kDa), while advantageous in many respects, limits the number of labels that can be incorporated. The ability to incorporate multiple labels is a beneficial attribute for reporter elements. Opportunely, sdAb are often selected using phage display methodology. Using sdAb displayed on bacteriophage M13 as the reporter element gives the potential for incorporating a very high number of labels. We have demonstrated the use of both sdAb and phage- displayed sdAb for the detection of ricin using both enzyme linked immunosorbent assays (ELISAs) and Luminex fluid array assays. The phage-displayed sdAb led to five to ten fold better detection of ricin in both the ELISA and Luminex assays, resulting in limits of detection of 1 ng/mL and 64 pg/mL respectively. The phage-displayed sdAb were also dramatically more effective for the visualization of binding to target in nitrocellulose dot blot assays, a method frequently used for epitope mapping. Full article

(This article belongs to the Special Issue Toxin Sensors)

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Cartoon showing conventional antibodies, heavy chain antibodies, and their cloned binding elements. Variable domains have been colored red and blue for the conventional VH and VL respectively, and purple for the VHH. Full article ">
Evaluating the role of biotinylation extent or linker length. Various biotinylated llama anti-ricin IgG were examined in a direct binding assay to ricin A chain-coated microspheres; Panel A shows signal with increasing number of biotins per antibody (D/P) as determined using sureLINK biotin, while Panel B shows labeling with Lc and Lc-Lc biotin at different ratios of biotin-NHS to antibody. Results indicated that high biotin to protein ratios and longer linker lengths produce superior reagents. Full article ">
ELISA based ricin detection. Phage-displayed sdAb and llama polyclonal anti-ricin IgG were compared as the reporter reagents using a llama anti-ricin capture surface. Panel A shows results of phage-displayed sdAb followed with an anti-M13 –HRP conjugate for color generation and biotinylated llama anti-ricin IgG followed with a Streptavidin – HRP conjugate. Panel B show the results using biotinylated phage-displayed sdAb and biotinylated soluble sdAb reporter elements followed with a Streptavidin –HRP conjugate. Data is plotted as the average of 3 wells, with error bars representing the standard deviation. Results indicate phage-displayed sdAb can act as highly sensitive detection reagents. Full article ">
Binding of soluble and phage-displayed C8 to antigen coated microspheres. The binding of various biotinylated tracer reagents was evaluated: (A) sl-Bt-C8 sdAb, (B) sl-Bt-C8 phage, (C) Bt-Lc-Lc-C8 phage. As a control the binding of phage-displayed sdAb A4, a clone known to be specific toward botulinum toxid A complex (Bot Ac-td) is shown, (D) Bt-Lc-Lc-A4 phage. The molar concentration of soluble C8 (MW ∼ 16,000 kDa) used in these experiments varied from 10 nM to 625 nM. Molar concentration of phage varied from to 27 pM to 1.7 nM. Results indicate phage-displayed sdAb bind with high specificity toward their target antigen, with minimal nonspecific binding observed. Full article ">
Luminex detection of ricin using llama polyclonal anti-ricin IgG (panel A) and sdAb F11 (panel B) conjugated to polystyrene beads. The data is plotted as the median fluorescence intensity with the error bars representing the range between duplicate analyses. Results show the enhanced signal generated by using the phage-displayed sdAb as the biotinylated tracer reagent relative to soluble sdAb or conventional antibody. Full article ">
Dot blot assay for ricin, ricin A chain, and ricin B chain using C8-phage (left) and C8-sdAb (right). C8-phage binding was visualized using HRP labeled anti M13 IgG while the C8-sdAb was visualized using HRP labeled anti-His. Color formation was generated using sigmafast Diaminobenzidine (DAB). 5 or 2 μL of ricin, ricinA, ricin B or BSA (10 μg/ mL) were spotted onto nitrocellulose as the target for both phage-displayed and soluble sdAb. Full article ">

486 KiB

Open AccessArticle

Simultaneous Measurements of Chlorophyll Concentration by Lidar, Fluorometry, above-Water Radiometry, and Ocean Color MODIS Images in the Southwestern Atlantic

by Milton Kampel, João A. Lorenzzetti, Cristina M. Bentz, Raul A. Nunes, Rodolfo Paranhos, Frederico M. Rudorff and Alexandre T. Politano

Sensors 2009, 9(1), 528-541; https://doi.org/10.3390/s90100528 - 16 Jan 2009

Cited by 12 | Viewed by 13687

Abstract

Comparisons between in situ measurements of surface chlorophyll-a concentration (CHL) and ocean color remote sensing estimates were conducted during an oceanographic cruise on the Brazilian Southeastern continental shelf and slope, Southwestern South Atlantic. In situ values were based on fluorometry, above-water radiometry [...] Read more.

Comparisons between in situ measurements of surface chlorophyll-a concentration (CHL) and ocean color remote sensing estimates were conducted during an oceanographic cruise on the Brazilian Southeastern continental shelf and slope, Southwestern South Atlantic. In situ values were based on fluorometry, above-water radiometry and lidar fluorosensor. Three empirical algorithms were used to estimate CHL from radiometric measurements: Ocean Chlorophyll 3 bands (OC3M_RAD), Ocean Chlorophyll 4 bands (OC4v4_RAD), and Ocean Chlorophyll 2 bands (OC2v4_RAD). The satellite estimates of CHL were derived from data collected by the MODerate-resolution Imaging Spectroradiometer (MODIS) with a nominal 1.1 km resolution at nadir. Three algorithms were used to estimate chlorophyll concentrations from MODIS data: one empirical - OC3M_SAT, and two semi-analytical - Garver, Siegel, Maritorena version 01 (GSM01_SAT), and Carder_SAT. In the present work, MODIS, lidar and in situ above-water radiometry and fluorometry are briefly described and the estimated values of chlorophyll retrieved by these techniques are compared. The chlorophyll concentration in the study area was in the range 0.01 to 0.2 mg·m^-3. In general, the empirical algorithms applied to the in situ radiometric and satellite data showed a tendency to overestimate CHL with a mean difference between estimated and measured values of as much as 0.17 mg/m³ (OC2v4_RAD). The semi-analytical GSM01 algorithm applied to MODIS data performed better (rmse 0.28, rmse-L 0.08, mean diff. -0.01 mg/m³) than the Carder and the empirical OC3M algorithms (rmse 1.14 and 0.36, rmse-L 0.34 and 0.11, mean diff. 0.17 and 0.02 mg/m³, respectively). We find that rmsd values between MODIS relative to the in situ radiometric measurements are < 26%, i.e., there is a trend towards overestimation of R_RS by MODIS for the stations considered in this work. Other authors have already reported over and under estimation of MODIS remotely sensed reflectance due to several errors in the bio-optical algorithm performance, in the satellite sensor calibration, and in the atmospheric-correction algorithm. Full article

(This article belongs to the Special Issue Ocean Remote Sensing)

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Study area and field stations occupied during November 2004 at the Brazilian Southeastern continental margin. Water sampling, above-water radiometry and lidar stations labeled with an “s” (black squares). Stations without water sampling labeled with an “i” (white triangles). Isobaths in meters. Full article ">
Scatter plots of chlorophyll concentration estimates obtained with (a) above-water radiometric data (three algorithms), and (b) MODIS ocean color remote sensing data (three algorithms) against in situ fluorometric estimates. Full article ">
Surface distributions of chlorophyll concentration estimated with OC3M (left), GSM01 (center), and Carder (right) algorithms applied to MODIS data acquired on 11/25/2004 (see text for details). Isobaths in meters. Color table in logarithmic scale. Land and clouds are masked in white. Black square on the left indicates the in situ sampled area. Full article ">
Histograms of MODIS chlorophyll concentration estimates obtained with OC3M, GSM01, and Carder algorithms for the in situ sampled area on 11/25/2004 (see text for details). Full article ">
Surface remote sensing reflectance spectra obtained by above-water radiometry during the cruise FITOSAT I cruise, November 2004, in the Brazilian Southeastern continental shelf and slope. Stations S-5 and S-21 in red and green, respectively (see text). Full article ">
Scatter plot of MODIS remote sensing reflectance (RRS) with respect to in situ above-water RRS for 15 stations where inter-comparison were made. Full article ">
Surface chlorophyll concentration estimated with the along-track lidar sampling during the cruise FITOSAT I cruise, November 2004, in the Brazilian Southeastern continental shelf and slope compared with fluorometric estimates (grey crosses – Lidar measurements; black line – Lidar processed; red circles – fluorometric). Full article ">

292 KiB

Open AccessArticle

Sensitivity Improvement of a Humidity Sensor Based on Silica Nanospheres on a Long-Period Fiber Grating

by Diana Viegas, Javier Goicoechea, José Luís Santos, Francisco Moita Araújo, Luís Alberto Ferreira, Francisco J. Arregui and Ignacio R. Matias

Sensors 2009, 9(1), 519-527; https://doi.org/10.3390/s90100519 - 16 Jan 2009

Cited by 37 | Viewed by 12483

Abstract

This work addresses a new configuration that improves the sensitivity of a humidity sensor based on a long-period fiber grating coated with a SiO₂-nanospheres film. An intermediate higher refractive index overlay, deposited through Electrostatic Self-Assembly, is placed between the fiber cladding [...] Read more.

This work addresses a new configuration that improves the sensitivity of a humidity sensor based on a long-period fiber grating coated with a SiO₂-nanospheres film. An intermediate higher refractive index overlay, deposited through Electrostatic Self-Assembly, is placed between the fiber cladding and the humidity sensitive film in order to increase the total effective refractive index of the coating. With this intermediate design, a three-fold improvement in the sensitivity was obtained. Wavelength shifts up to 15 nm against 5 nm were achieved in a humidity range from 20% to 80%. Full article

(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)

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1648 KiB

Open AccessArticle

A Study of Ground Deformation in the Guangzhou Urban Area with Persistent Scatterer Interferometry

by Qing Zhao, Hui Lin, Liming Jiang, Fulong Chen and Shilai Cheng

Sensors 2009, 9(1), 503-518; https://doi.org/10.3390/s90100503 - 15 Jan 2009

Cited by 53 | Viewed by 13875

Abstract

TheInterferometric Point Target Analysis (IPTA) technique and Advanced Synthetic Aperture Radar (ASAR) images acquired over Hong Kong from 2007–2008 were used to detect ground deformation in the urban area of Guangzhou city in South China. A ground deformation rate map with scattered distribution [...] Read more.

TheInterferometric Point Target Analysis (IPTA) technique and Advanced Synthetic Aperture Radar (ASAR) images acquired over Hong Kong from 2007–2008 were used to detect ground deformation in the urban area of Guangzhou city in South China. A ground deformation rate map with scattered distribution of point targets shows the maximum subsidence (rise) rate as high as -26 to -20 mma^-1 (16–21 mma^-1), implying that the study area is an active zone for ground deformation. Based on the point target map, a contour ground deformation rate map is generated. The map shows three major subsidence zones located in the middle-west, the east, and the southwest of the study area, respectively. All the six ground collapse accidents that occurred in 2007–2008 fall within the subsidence zones, qualitatively validating the IPTA results. Ground subsidence and geological conditions on Datansha Island are examined. The results indicate that the local geological conditions, such as limestone Karst geomorphology as well as silt layers characterized by high water content, high void ratio, high compressibility, low bearing capacity and low shear strength, and underground engineering projects are responsible for ground subsidence and ground collapse accidents occurred there. Full article

(This article belongs to the Section Remote Sensors)

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(a) Location of study area in Guangdong Province. (b) Map of study area. Active faults are marked in red (partially referred to [<a href="#b5-sensors-09-00503" class="html-bibr">5</a>, <a href="#b13-sensors-09-00503" class="html-bibr">13</a>]). Full article ">
Distribution of ground collapse and ground subsidence in Guangzhou City (partially referred to [<a href="#b5-sensors-09-00503" class="html-bibr">5</a>]). Full article ">
The spatial distribution of ground collapse accidents in 2007–2008 are coded from 1 to 6. The underground metro-lines and district boundary lines are also marked. (The background image is Landsat TM false color composite image. The spatial resolution is 30m.). Full article ">
A ground deformation rate map of IPTA-derived point targets in Guangzhou using ASAR data listed in <a href="#t1-sensors-09-00503" class="html-table">Table 1</a>. Deformation rates are color-coded, as shown on the right-hand side. Numbers 1–6 as marked in <a href="#f3-sensors-09-00503" class="html-fig">Figure 3</a> show the locations of ground collapse accidents that occurred in 2007–2008. (The background image is Landsat TM false color composite image. The spatial resolution is 30 m.). Full article ">
A contour map of ground deformation in Guangzhou city. Full article ">
An ASAR-derived ground deformation map in Datansha Island area. PT1–PT8 are test sites along metro-lines 5 and 6. Numbers 2–6 are sites of ground collapse accidents occurred in 2007–2008. Full article ">
Datansha Island area and underground metro-lines (partially referred to [<a href="#b23-sensors-09-00503" class="html-bibr">23</a>]). Full article ">

390 KiB

Open AccessArticle

Multi-Line Fit Model for the Detection of Methane at ν₂ + 2ν₃ Band using Hollow-Core Photonic Bandgap Fibres

by Ana M. Cubillas, Jose M. Lazaro, Olga M. Conde, Marco N. Petrovich and Jose M. Lopez-Higuera

Sensors 2009, 9(1), 490-502; https://doi.org/10.3390/s90100490 - 14 Jan 2009

Cited by 18 | Viewed by 62748

Abstract

Hollow-core photonic bandgap fibres (HC-PBFs) have emerged as a novel technology in the field of gas sensing. The long interaction pathlengths achievable with these fibres are especially advantageous for the detection of weakly absorbing gases. In this work, we demonstrate the good performance [...] Read more.

Hollow-core photonic bandgap fibres (HC-PBFs) have emerged as a novel technology in the field of gas sensing. The long interaction pathlengths achievable with these fibres are especially advantageous for the detection of weakly absorbing gases. In this work, we demonstrate the good performance of a HC-PBF in the detection of the ν₂ + 2ν₃ band of methane, at 1.3 μm. The Q-branch manifold, at 1331.55 nm, is targeted for concentration monitoring purposes. A computationally optimized multi-line model is used to fit the Q-branch. Using this model, a detection limit of 98 ppmv (parts per million by volume) is estimated. Full article

(This article belongs to the Section Chemical Sensors)

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Graphical abstract

1484 KiB

Open AccessArticle

Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations

by Jesús Álvarez-Mozos, Niko E.C. Verhoest, Arantzazu Larrañaga, Javier Casalí and María González-Audícana

Sensors 2009, 9(1), 463-489; https://doi.org/10.3390/s90100463 - 13 Jan 2009

Cited by 48 | Viewed by 15210

Abstract

Radar-based surface soil moisture retrieval has been subject of intense research during the last decades. However, several difficulties hamper the operational estimation of soil moisture based on currently available spaceborne sensors. The main difficulty experienced so far results from the strong influence of [...] Read more.

Radar-based surface soil moisture retrieval has been subject of intense research during the last decades. However, several difficulties hamper the operational estimation of soil moisture based on currently available spaceborne sensors. The main difficulty experienced so far results from the strong influence of other surface characteristics, mainly roughness, on the backscattering coefficient, which hinders the soil moisture inversion. This is especially true for single configuration observations where the solution to the surface backscattering problem is ill-posed. Over agricultural areas cultivated with winter cereal crops, roughness can be assumed to remain constant along the growing cycle allowing the use of simplified approaches that facilitate the estimation of the moisture content of soils. However, the field scale spatial variability and temporal variations of roughness can introduce errors in the estimation of soil moisture that are difficult to evaluate. The objective of this study is to assess the impact of roughness spatial variability and roughness temporal variations on the retrieval of soil moisture from radar observations. A series of laser profilometer measurements were performed over several fields in an experimental watershed from September 2004 to March 2005. The influence of the observed roughness variability and its temporal variations on the retrieval of soil moisture is studied using simulations performed with the Integral Equation Model, considering different sensor configurations. Results show that both field scale roughness spatial variability and its temporal variations are aspects that need to be taken into account, since they can introduce large errors on the retrieved soil moisture values. Full article

(This article belongs to the Section Remote Sensors)

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174 KiB

Open AccessArticle

An Energy-Aware Routing Protocol in Wireless Sensor Networks

by Ming Liu, Jiannong Cao, Guihai Chen and Xiaomin Wang

Sensors 2009, 9(1), 445-462; https://doi.org/10.3390/s90100445 - 13 Jan 2009

Cited by 174 | Viewed by 17513

Abstract

The most important issue that must be solved in designing a data gathering algorithm for wireless sensor networks (WSNS) is how to save sensor node energy while meeting the needs of applications/users. In this paper, we propose a novel energy-aware routing protocol (EAP) [...] Read more.

The most important issue that must be solved in designing a data gathering algorithm for wireless sensor networks (WSNS) is how to save sensor node energy while meeting the needs of applications/users. In this paper, we propose a novel energy-aware routing protocol (EAP) for a long-lived sensor network. EAP achieves a good performance in terms of lifetime by minimizing energy consumption for in-network communications and balancing the energy load among all the nodes. EAP introduces a new clustering parameter for cluster head election, which can better handle the heterogeneous energy capacities. Furthermore, it also introduces a simple but efficient approach, namely, intra-cluster coverage to cope with the area coverage problem. We use a simple temperature sensing application to evaluate the performance of EAP and results show that our protocol significantly outperforms LEACH and HEED in terms of network lifetime and the amount of data gathered. Full article

(This article belongs to the Section Chemical Sensors)

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482 KiB

Open AccessReview

CMOS Image Sensors for High Speed Applications

by Munir El-Desouki, M. Jamal Deen, Qiyin Fang, Louis Liu, Frances Tse and David Armstrong

Sensors 2009, 9(1), 430-444; https://doi.org/10.3390/s90100430 - 13 Jan 2009

Cited by 171 | Viewed by 27703

Abstract

Recent advances in deep submicron CMOS technologies and improved pixel designs have enabled CMOS-based imagers to surpass charge-coupled devices (CCD) imaging technology for mainstream applications. The parallel outputs that CMOS imagers can offer, in addition to complete camera-on-a-chip solutions due to being fabricated [...] Read more.

Recent advances in deep submicron CMOS technologies and improved pixel designs have enabled CMOS-based imagers to surpass charge-coupled devices (CCD) imaging technology for mainstream applications. The parallel outputs that CMOS imagers can offer, in addition to complete camera-on-a-chip solutions due to being fabricated in standard CMOS technologies, result in compelling advantages in speed and system throughput. Since there is a practical limit on the minimum pixel size (4~5 μm) due to limitations in the optics, CMOS technology scaling can allow for an increased number of transistors to be integrated into the pixel to improve both detection and signal processing. Such smart pixels truly show the potential of CMOS technology for imaging applications allowing CMOS imagers to achieve the image quality and global shuttering performance necessary to meet the demands of ultrahigh-speed applications. In this paper, a review of CMOS-based high-speed imager design is presented and the various implementations that target ultrahigh-speed imaging are described. This work also discusses the design, layout and simulation results of an ultrahigh acquisition rate CMOS active-pixel sensor imager that can take 8 frames at a rate of more than a billion frames per second (fps). Full article

(This article belongs to the Special Issue Image Sensors 2009)

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(a) Fluorescence spectral response showing the excitation pulse and the emission pulse. (b) Time-resolved and fluorescence lifetime measurements [<a href="#b2-sensors-09-00430" class="html-bibr">2</a>]. Full article ">
A block-diagram categorizing some of the most relevant published high-speed imagers [<a href="#b3-sensors-09-00430" class="html-bibr">3</a>-<a href="#b14-sensors-09-00430" class="html-bibr">14</a>], showing the frame rates that can be achieved by different readout architectures. Full article ">
Array access in a simple pixel-by-pixel (PBP) sequential readout architecture. Full article ">
Array access in (a) a per-column ADC (PC-ADC) readout and (b) a PC-ADC ×2. Full article ">
Simplified schematic diagrams of (a) a 3-T active pixel sensor (APS) and (b) a digital pixel sensor (DPS) containing part of the ADC and an 8-bit memory within the pixel. Full article ">
Simulation results of <a href="#FD1" class="html-disp-formula">equations (1</a><a href="#FD3" class="html-disp-formula">3</a>) showing the FR of a pixel-by-pixel, PC-ADC and a PP-ADC readout architectures with 8-bit resolution ADCs (b=8), four 8-bit parallel outputs (n=32) and a τADC = 2 μ s. (a) The FR as a function of varying the imager resolution with a fixed clock rate of 50 MHz (1/τRO). (b) The FR as a function of the clock rate with a fixed imager resolution of H×V = 64×64. Both graphs are shown in a log-log scale. Full article ">
Simple 4-T APS with an analog storage element. Full article ">
The storage and readout of an in situ CCD imager that can store up to N frames. Full article ">
(a) The schematic diagram of the ultrahigh-speed in-situ APS containing 8 memory elements and 38 transistors and (b) the layout screen capture of a single pixel. Full article ">

652 KiB

Open AccessArticle

A Differential Pressure Instrument with Wireless Telemetry for In-Situ Measurement of Fluid Flow across Sediment-Water Boundaries

by Alan T. Gardner, Hanan N. Karam, Ann E. Mulligan, Charles F. Harvey, Terence R. Hammar and Harold F. Hemond

Sensors 2009, 9(1), 404-429; https://doi.org/10.3390/s90100404 - 9 Jan 2009

Cited by 9 | Viewed by 14283

Abstract

An instrument has been built to carry out continuous in-situ measurement of small differences in water pressure, conductivity and temperature, in natural surface water and groundwater systems. A low-cost data telemetry system provides data on shore in real time if desired. The immediate [...] Read more.

An instrument has been built to carry out continuous in-situ measurement of small differences in water pressure, conductivity and temperature, in natural surface water and groundwater systems. A low-cost data telemetry system provides data on shore in real time if desired. The immediate purpose of measurements by this device is to continuously infer fluxes of water across the sediment-water interface in a complex estuarine system; however, direct application to assessment of sediment-water fluxes in rivers, lakes, and other systems is also possible. Key objectives of the design include both low cost, and accuracy of the order of ±0.5 mm H₂O in measured head difference between the instrument’s two pressure ports. These objectives have been met, although a revision to the design of one component was found to be necessary. Deployments of up to nine months, and wireless range in excess of 300 m have been demonstrated. Full article

(This article belongs to the Special Issue Wireless Pressure Sensors)

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317 KiB

Open AccessArticle

Human NK Cell Up-regulation of CD69, HLA-DR, Interferon γ Secretion and Cytotoxic Activity by Plasmacytoid Dendritic Cells is Regulated through Overlapping but Different Pathways

by Adel Benlahrech, Heather Donaghy, George Rozis, Martin Goodier, Linda Klavinskis, Frances Gotch and Steven Patterson

Sensors 2009, 9(1), 386-403; https://doi.org/10.3390/s90100386 - 9 Jan 2009

Cited by 22 | Viewed by 16691

Abstract

Human plasmacytoid dendritic cells secrete high levels of IFNa and are thus implicated in the activation of NK cells. Activated NK cells are characterised by the up-regulation of CD69 and MHC class II DR expression, secretion of IFN g and enhanced cytotoxicity. We [...] Read more.

Human plasmacytoid dendritic cells secrete high levels of IFNa and are thus implicated in the activation of NK cells. Activated NK cells are characterised by the up-regulation of CD69 and MHC class II DR expression, secretion of IFN g and enhanced cytotoxicity. We show that pDC mediate these processes by different mechanisms, some of which overlap. Human NK cells were analysed after co-culture with immature or CpG-matured blood pDC or with supernatant from these cells. Maximal CD69 expression by NK cells was mediated by supernatant from mature pDC and did not require pDC contact. Up-regulation was due in part to IFNa but also to factors in IFNa negative supernatant from immature DC. HLA-DR expression was independent of secreted molecules but required contact with immature or mature DC. Enhanced NK cytotoxicity, measured by killing of K562 targets and expression of CD107a, was mediated by multiple factors including type I IFN, supernatant from immature pDC cultures and contact with immature or mature pDC. These factors act cumulatively to enhance cytotoxcity. Thus different parameters of pDC mediated NK cell activation are regulated by distinct pathways. Full article

(This article belongs to the Special Issue Dendritic Sensors: From Dendrimer Molecules to Dendritic Cells)

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Purity of the different isolated cell populations. A) NK cells were isolated as described in materials and methods then stained for CD56 and CD3. B) autologous pDC were magnetically isolated then stained with anti-human CD11c, a cocktail of anti-human CD3, CD14, CD16, CD19, and CD56 and HLA-DR antibodies. Contour plots are expressed with a threshold value of 0.2; percentages of purity were obtained using CellQuest Pro®. Full article ">
NK activation after a single freeze/thaw cycle. Isolated NK cells were cryopreserved and re-thawed for use in later experiments. A) NK cells cultured for 24 hours in the absence (filled histogram) or presence of IL-2 (clear histogram) were labelled with anti-CD56, CD3 and CD69 antibodies. Histograms show CD69 expression on CD56+ CD3- cells. B) NK cultured alone for 24 hours (left dot-plot) or with IL-2, 50 units/mL, (Right dot-plot) and stained for intracellular IFNγ. Dotplots show 50,000 acquired events gated on live CD56+ CD3- cells. Full article ">
NK cells up-regulate CD69 in response to pDC sensitisation through secreted type I interferons. NK cells were cultured for 24 hours in the presence or absence of anti-IFNR1 antibody. Cells were cultured alone or treated with PMA/Ionomycin, rIFNα, untreated (ipDC) or CPG-treated pDC (mpDC), or their supernatants. Cells were then stained with anti-CD3, CD56, CD69 and HLA-DR antibodies and CD69 expression shown on the CD3- CD56+ cells (clear histograms). Results from a typical experiment (total of 3) are presented with M1 region based on the isotype control (filled histograms). Full article ">
pDC induce HLA-DR up-regulation on NK cells through cellular contact. NK cells up-regulate HLA-DR in response to pDC sensitisation in a cell–contact dependent, type I interferon independent manner. NK cells were cultured for 24 hours in the presence or absence of anti-IFNR1 antibody. Cells were cultured alone or treated with PMA/Ionomycin, rIFNα, untreated (ipDC) or CPG-treated pDC (mpDC), or their supernatants. NK cells were cultured with pDC either together, or separated by transwells. Cells were then stained with anti-CD3, CD56, CD69 and HLA-DR antibodies. HLA-DR expression on the CD3- CD56+ cells is shown. Results from a typical experiment (total of 3) are presented with quadrants based on the isotype control. Full article ">
Mature pDC induce IFNγ secretion by NK cells. Full article ">
pDC stimulate NK secretion of IFNγ and is dependent on signalling through the type 1 interferon receptor. Full article ">
NK degranulation is slightly induced by type I interferons but augmented through cellular contact with pDC. Full article ">
NK specific cytotoxicity is induced by pDC in a contact dependent manner. Full article ">

130 KiB

Open AccessArticle

Immobilization of Electroporated Cells for Fabrication of Cellular Biosensors: Physiological Effects of the Shape of Calcium Alginate Matrices and Foetal Calf Serum

by Nikos Katsanakis, Andreas Katsivelis and Spiridon Kintzios

Sensors 2009, 9(1), 378-385; https://doi.org/10.3390/s90100378 - 9 Jan 2009

Cited by 7 | Viewed by 10998

Abstract

In order to investigate the physiological effect of transfected cell immobilization in calcium alginate gels, we immobilized electroporated Vero cells in gels shaped either as spherical beads or as thin membrane layers. In addition, we investigated whether serum addition had a positive effect [...] Read more.

In order to investigate the physiological effect of transfected cell immobilization in calcium alginate gels, we immobilized electroporated Vero cells in gels shaped either as spherical beads or as thin membrane layers. In addition, we investigated whether serum addition had a positive effect on cell proliferation and viability in either gel configuration. The gels were stored for four weeks in a medium supplemented or not with 20% (v/v) foetal calf serum. Throughout a culture period of four weeks, cell proliferation and cell viability were assayed by optical microscopy after provision of Trypan Blue. Non-elaborate culture conditions (room temperature, non-CO₂ enriched culture atmosphere) were applied throughout the experimental period in order to evaluate cell viability under less than optimal storage conditions. Immobilization of electroporated cells was associated with an initially reduced cell viability, which was gradually increased. Immobilization was associated with maintenance of cell growth for the duration of the experimental period, whereas electroporated cells essentially died after a week in suspension culture. Considerable proliferation of immobilized cells was observed in spherical alginate beads. In both gel configurations, addition of serum was associated with increased cell proliferation. The results of the present study could contribute to an improvement of the storability of biosensors based on electroporated, genetically or membrane-engineered cells. Full article

(This article belongs to the Section Biosensors)

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153 KiB

Open AccessCorrection

Vasić, V. et al. Na⁺,K⁺-ATPase as the Target Enzyme for Organic and Inorganic Compounds. Sensors 2008, 8, 8321-8360

by Vesna Vasić, Tatjana Momić, Marijana Petković and Danijela Krstić

Sensors 2009, 9(1), 377; https://doi.org/10.3390/s90100377 - 8 Jan 2009

Viewed by 7248

Abstract

n/a Full article

114 KiB

Open AccessCorrection

Jeong, H.; Jeon, S. Determination of Dopamine in the Presence of Ascorbic Acid by Nafion and Single-Walled Carbon Nanotube Film Modified on Carbon Fiber Microelectrode. Sensors 2008, 8, 6924-6935

by Haesang Jeong and Seungwon Jeon

Sensors 2009, 9(1), 376; https://doi.org/10.3390/s90100376 - 8 Jan 2009

Cited by 1 | Viewed by 5621

Abstract

n/a Full article

1281 KiB

Open AccessArticle

Evaluation of the Convergence Region of an Automated Registration Method for 3D Laser Scanner Point Clouds

by Kwang-Ho Bae

Sensors 2009, 9(1), 355-375; https://doi.org/10.3390/s90100355 - 8 Jan 2009

Cited by 22 | Viewed by 10301

Abstract

Using three dimensional point clouds from both simulated and real datasets from close and terrestrial laser scanners, the rotational and translational convergence regions of Geometric Primitive Iterative Closest Points (GP-ICP) are empirically evaluated. The results demonstrate the GP-ICP has a larger rotational convergence [...] Read more.

Using three dimensional point clouds from both simulated and real datasets from close and terrestrial laser scanners, the rotational and translational convergence regions of Geometric Primitive Iterative Closest Points (GP-ICP) are empirically evaluated. The results demonstrate the GP-ICP has a larger rotational convergence region than the existing methods, e.g., the Iterative Closest Point (ICP). Full article

(This article belongs to the Section Remote Sensors)

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199 KiB

Open AccessArticle

An Effective Mobile Sensor Control Method for Sparse Sensor Networks

by Kriengsak Treeprapin, Akimitsu Kanzaki, Takahiro Hara and Shojiro Nishio

Sensors 2009, 9(1), 327-354; https://doi.org/10.3390/s90100327 - 8 Jan 2009

Cited by 8 | Viewed by 7837

Abstract

In this paper, we propose an effective mobile sensor control method, named DATFM (Data Acquisition and Transmission with Fixed and Mobile node) for sparse sensor networks. DATFM uses two types of sensor nodes, fixed node and mobile node. The data acquired by [...] Read more.

In this paper, we propose an effective mobile sensor control method, named DATFM (Data Acquisition and Transmission with Fixed and Mobile node) for sparse sensor networks. DATFM uses two types of sensor nodes, fixed node and mobile node. The data acquired by nodes are accumulated on a fixed node before being transferred to the sink node. In addition, DATFM transfers the accumulated data efficiently by constructing a communication route of multiple mobile nodes between fixed nodes. We also conduct simulation experiments to evaluate the performance of DATFM. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)

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721 KiB

Open AccessArticle

Emission Characteristics and Factors of Selected Odorous Compounds at a Wastewater Treatment Plant

by Eui-Chan Jeon, Hyun-Keun Son and Jae-Hwan Sa

Sensors 2009, 9(1), 311-326; https://doi.org/10.3390/s90100311 - 8 Jan 2009

Cited by 44 | Viewed by 12241

Abstract

This study was initiated to explore the emission characteristics of Reduced Sulfur Compounds (RSCs: hydrogen sulfide, methyl mercaptan, dimethyl sulfide, dimethyl disulfide), ammonia and trimethylamine from a Wastewater Treatment Plant (WWTP) located at Sun-Cheon, Chonlanam-Do in South Korea. The study also evaluates flux [...] Read more.

This study was initiated to explore the emission characteristics of Reduced Sulfur Compounds (RSCs: hydrogen sulfide, methyl mercaptan, dimethyl sulfide, dimethyl disulfide), ammonia and trimethylamine from a Wastewater Treatment Plant (WWTP) located at Sun-Cheon, Chonlanam-Do in South Korea. The study also evaluates flux profiles of the six selected odorous compounds and their flux rates (µg/m²/min) and compares their emission characteristics. A Dynamic Flux Chamber DFC was used to measure fluxes of pollutants from the treatment plant. Quality control of odor samples using a non-reactive sulfur dioxide gas determined the time taken for DFC concentration to reach equilibrium. The reduced sulfur compounds were analyzed by interfacing gas chromatography with a Pulsed Flame Photometric Detector (PFPD). Air samples were collected in the morning and afternoon on one day during summer (August) and two days in winter (December and January). Their emission rates were determined and it was observed that during summer relatively higher amounts of the selected odorous compounds were emitted compared to winter. Air samples from primary settling basin, aeration basin, and final settling basin were tested and the total amount of selected odorous compounds emitted per wastewater ton was found to be 1344 µg/m³ from the selected treatment processes. It was also observed that, in this study, the dominant odor intensity contribution was caused by dimethyl disulfide (69.1%). Full article

(This article belongs to the Section Chemical Sensors)

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168 KiB

Open AccessCommunication

Algorithmic Foundation of Spectral Rarefaction for Measuring Satellite Imagery Heterogeneity at Multiple Spatial Scales

by Duccio Rocchini

Sensors 2009, 9(1), 303-310; https://doi.org/10.3390/s90100303 - 8 Jan 2009

Cited by 5 | Viewed by 10368

Abstract

Measuring heterogeneity in satellite imagery is an important task to deal with. Most measures of spectral diversity have been based on Shannon Information theory. However, this approach does not inherently address different scales, ranging from local (hereafter referred to alpha diversity) to global [...] Read more.

Measuring heterogeneity in satellite imagery is an important task to deal with. Most measures of spectral diversity have been based on Shannon Information theory. However, this approach does not inherently address different scales, ranging from local (hereafter referred to alpha diversity) to global scales (gamma diversity). The aim of this paper is to propose a method for measuring spectral heterogeneity at multiple scales based on rarefaction curves. An algorithmic solution of rarefaction applied to image pixel values (Digital Numbers, DNs) is provided and discussed. Full article

(This article belongs to the Special Issue Sensor Algorithms)

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410 KiB

Open AccessArticle

A Localized Coverage Preserving Protocol for Wireless Sensor Networks

by Yuheng Liu, Juhua Pu, Shuo Zhang, Yunlu Liu and Zhang Xiong

Sensors 2009, 9(1), 281-302; https://doi.org/10.3390/s90100281 - 8 Jan 2009

Cited by 27 | Viewed by 12481

Abstract

In a randomly deployed and large scale wireless sensor network, coverage-redundant nodes consume much unnecessary energy. As a result, turning off these redundant nodes can prolong the network lifetime, while maintaining the degree of sensing coverage with a limited number of on-duty nodes. [...] Read more.

In a randomly deployed and large scale wireless sensor network, coverage-redundant nodes consume much unnecessary energy. As a result, turning off these redundant nodes can prolong the network lifetime, while maintaining the degree of sensing coverage with a limited number of on-duty nodes. None of the off-duty eligibility rules in the literature, however, are sufficient and necessary conditions for eligible nodes. Hence redundancy or blind points might be incurred. In this paper we propose a complete Eligibility Rule based on Perimeter Coverage (ERPC) for a node to determine its eligibility for sleeping. ERPC has a computational complexity of O(N²log(N)), lower than the eligibility rule in the Coverage Control Protocol (CCP), O(N³), where N is the number of neighboring nodes. We then present a Coverage Preserving Protocol (CPP) to schedule the work state of eligible nodes. The main advantage of CPP over the Ottawa protocol lies in its ability to configure the network to any specific coverage degree, while the Ottawa protocol does not support different coverage configuration. Moreover, as a localized protocol, CPP has better adaptability to dynamic topologies than centralized protocols. Simulation results indicate that CPP can preserve network coverage with fewer active nodes than the Ottawa protocol. In addition, CPP is capable of identifying all the eligible nodes exactly while the CCP protocol might result in blind points due to error decisions. Quantitative analysis and experiments demonstrate that CPP can extend the network lifetime significantly while maintaining a given coverage degree. Full article

(This article belongs to the Special Issue Sensor Algorithms)

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403 KiB

Open AccessArticle

HyBloc: Localization in Sensor Networks with Adverse Anchor Placement

by King-Yip Cheng, King-Shan Lui and Vincent Tam

Sensors 2009, 9(1), 253-280; https://doi.org/10.3390/s90100253 - 8 Jan 2009

Cited by 24 | Viewed by 10011

Abstract

To determine the geographical positions of sensors, numerous localization algorithms have been proposed in recent years. The positions of sensors are inferred from the connectivity between sensors and a set of nodes called anchors which know their precise locations. We investigate the effect [...] Read more.

To determine the geographical positions of sensors, numerous localization algorithms have been proposed in recent years. The positions of sensors are inferred from the connectivity between sensors and a set of nodes called anchors which know their precise locations. We investigate the effect of adverse placement and density of anchors on the accuracies of different algorithms. We develop an algorithm called HyBrid Localization (HyBloc) to provide reliable localization service with a limited number of clustered anchors. HyBloc is distributed in nature with reasonable message overhead. Through simulations, we demonstrate that HyBloc provides more accurate location estimates than some existing distributed algorithms when there are only a few anchors. HyBloc also performs well when anchors are clustered together. Full article

(This article belongs to the Special Issue Sensor Algorithms)

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50-node networks, 10 anchors, measurement error=5%. Full article ">
50-node networks, 5 anchors, measurement error=5%. Full article ">
200-node networks, clustered anchors, measurement error=5%. Full article ">
Uniform Network. Full article ">
C-shaped Network. Full article ">
Uniform Networks, α=0.05, 5 Anchors. Full article ">
Uniform Networks, α=0.10, 5 Anchors. Full article ">
C-shaped Networks, α=0.05, 5 Anchors. Full article ">
C-shaped Networks, α=0.10, 5 Anchors. Full article ">

471 KiB

Open AccessArticle

Simulation of Greenhouse Climate Monitoring and Control with Wireless Sensor Network and Event-Based Control

by Andrzej Pawlowski, Jose Luis Guzman, Francisco Rodríguez, Manuel Berenguel, José Sánchez and Sebastián Dormido

Sensors 2009, 9(1), 232-252; https://doi.org/10.3390/s90100232 - 8 Jan 2009

Cited by 133 | Viewed by 24023

Abstract

Monitoring and control of the greenhouse environment play a decisive role in greenhouse production processes. Assurance of optimal climate conditions has a direct influence on crop growth performance, but it usually increases the required equipment cost. Traditionally, greenhouse installations have required a great [...] Read more.

Monitoring and control of the greenhouse environment play a decisive role in greenhouse production processes. Assurance of optimal climate conditions has a direct influence on crop growth performance, but it usually increases the required equipment cost. Traditionally, greenhouse installations have required a great effort to connect and distribute all the sensors and data acquisition systems. These installations need many data and power wires to be distributed along the greenhouses, making the system complex and expensive. For this reason, and others such as unavailability of distributed actuators, only individual sensors are usually located in a fixed point that is selected as representative of the overall greenhouse dynamics. On the other hand, the actuation system in greenhouses is usually composed by mechanical devices controlled by relays, being desirable to reduce the number of commutations of the control signals from security and economical point of views. Therefore, and in order to face these drawbacks, this paper describes how the greenhouse climate control can be represented as an event-based system in combination with wireless sensor networks, where low-frequency dynamics variables have to be controlled and control actions are mainly calculated against events produced by external disturbances. The proposed control system allows saving costs related with wear minimization and prolonging the actuator life, but keeping promising performance results. Analysis and conclusions are given by means of simulation results. Full article

(This article belongs to the Section Chemical Sensors)

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120 KiB

Open AccessArticle

Determination of Antimony (III) in Real Samples by Anodic Stripping Voltammetry Using a Mercury Film Screen-Printed Electrode

by Olga Domínguez-Renedo, M. Jesús Gómez González and M. Julia Arcos-Martínez

Sensors 2009, 9(1), 219-231; https://doi.org/10.3390/s90100219 - 8 Jan 2009

Cited by 40 | Viewed by 11556

Abstract

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual [...] Read more.

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual Standard Deviation (RSD), the repeatability (3.81 %) and the reproducibility (5.07 %) of the constructed electrodes were both analyzed. The detection limit for Sb (III) was calculated at a value of 1.27×10^–8 M. The linear range obtained was between 0.99 × 10^–8 – 8.26 × 10^–8 M. An analysis of possible effects due to the presence of foreign ions in the solution was performed and the procedure was successfully applied to the determination of antimony levels in pharmaceutical preparations and sea water samples. Full article

(This article belongs to the Section Chemical Sensors)

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2280 KiB

Open AccessArticle

Multi-Channel Morphological Profiles for Classification of Hyperspectral Images Using Support Vector Machines

by Javier Plaza, Antonio J. Plaza and Cristina Barra

Sensors 2009, 9(1), 196-218; https://doi.org/10.3390/s90100196 - 8 Jan 2009

Cited by 48 | Viewed by 16295

Abstract

Hyperspectral imaging is a new remote sensing technique that generates hundreds of images, corresponding to different wavelength channels, for the same area on the surface of the Earth. Supervised classification of hyperspectral image data sets is a challenging problem due to the limited [...] Read more.

Hyperspectral imaging is a new remote sensing technique that generates hundreds of images, corresponding to different wavelength channels, for the same area on the surface of the Earth. Supervised classification of hyperspectral image data sets is a challenging problem due to the limited availability of training samples (which are very difficult and costly to obtain in practice) and the extremely high dimensionality of the data. In this paper, we explore the use of multi-channel morphological profiles for feature extraction prior to classification of remotely sensed hyperspectral data sets using support vector machines (SVMs). In order to introduce multi-channel morphological transformations, which rely on ordering of pixel vectors in multidimensional space, several vector ordering strategies are investigated. A reduced implementation which builds the multi-channel morphological profile based on the first components resulting from a dimensional reduction transformation applied to the input data is also proposed. Our experimental results, conducted using three representative hyperspectral data sets collected by NASA’s Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) sensor and the German Digital Airborne Imaging Spectrometer (DAIS 7915), reveal that multi-channel morphological profiles can improve single-channel morphological profiles in the task of extracting relevant features for classification of hyperspectral data using small training sets. Full article

(This article belongs to the Section Remote Sensors)

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Sensors, Volume 9, Issue 1 (January 2009) – 40 articles , Pages 1-695

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