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1

Polymeric assay film for direct colorimetric detection  

DOEpatents

A lipid bilayer with affinity to an analyte, which directly signals binding by a changes in the light absorption spectra. This novel assay means and method has special applications in the drug development and medical testing fields. Using a spectrometer, the system is easily automated, and a multiple well embodiment allows inexpensive screening and sequential testing. This invention also has applications in industry for feedstock and effluent monitoring.

Charych, Deborah (Albany, CA); Nagy, Jon (Bozeman, MT); Spevak, Wayne (Albany, CA)

2002-01-01

2

Polymeric assay film for direct colorimetric detection  

DOEpatents

A lipid bilayer with affinity to an analyte, which directly signals binding by a changes in the light absorption spectra. This novel assay means and method has special applications in the drug development and medical testing fields. Using a spectrometer, the system is easily automated, and a multiple well embodiment allows inexpensive screening and sequential testing. This invention also has applications in industry for feedstock and effluent monitoring.

Charych, Deborah (Albany, CA); Nagy, Jon (Rodeo, CA); Spevak, Wayne (Albany, CA)

1999-01-01

3

Sol-gel matrices for direct colorimetric detection of analytes  

DOEpatents

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

2000-01-01

4

Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes  

DOEpatents

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

2002-11-26

5

Direct Colorimetric Detection of a Receptor-Ligand Interaction by a Polymerized Bilayer Assembly  

NASA Astrophysics Data System (ADS)

Detection of receptor-ligand interactions is generally accomplished by indirect assays such as enzyme-linked immunosorbent assay. A direct colorimetric detection method based on a polydiacetylene bilayer assembled on glass microscope slides has been developed. The bilayer is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene. The polydiacetylene layer is functionalized with an analog of sialic acid, the receptor-specific ligand for the influenza virus hemagglutinin. The sialic acid ligand serves as a molecular recognition element and the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. Direct colorimetric detection by polydiacetylene films offers new possibilities for diagnostic applications and screening for new drug candidates or binding ligands.

Charych, Deborah H.; Nagy, Jon O.; Spevak, Wayne; Bednarski, Mark D.

1993-07-01

6

A colorimetric sensor array for detection of triacetone triperoxide vapor.  

PubMed

Triacetone triperoxide (TATP), one of the most dangerous primary explosives, has emerged as an explosive of choice for terrorists in recent years. Owing to the lack of UV absorbance, fluorescence, or facile ionization, TATP is extremely difficult to detect directly. Techniques that are able to detect generally require expensive instrumentation, need extensive sample preparation, or cannot detect TATP in the gas phase. Here we report a simple and highly sensitive colorimetric sensor for the detection of TATP vapor with semiquantitative analysis from 50 ppb to 10 ppm. By using a solid acid catalyst to pretreat a gas stream, we have discovered that a colorimetric sensor array of redox sensitive dyes can detect even very low levels of TATP vapor from its acid decomposition products (e.g., H(2)O(2)) with limits of detection (LOD) below 2 ppb (i.e., <0.02% of its saturation vapor pressure). Common potential interferences (e.g., humidity, personal hygiene products, perfume, laundry supplies, volatile organic compounds, etc.) do not generate an array response, and the array can also differentiate TATP from other chemical oxidants (e.g., hydrogen peroxide, bleach, tert-butylhydroperoxide, peracetic acid). PMID:20949933

Lin, Hengwei; Suslick, Kenneth S

2010-11-10

7

A Colorimetric Sensor Array for Detection of Triacetone Triperoxide Vapor Hengwei Lin and Kenneth S. Suslick*  

E-print Network

A Colorimetric Sensor Array for Detection of Triacetone Triperoxide Vapor Hengwei Lin and Kenneth S triperoxide (TATP), one of the most danger- ous primary explosives, has emerged as an explosive of choice is extremely difficult to detect directly. Techniques that are able to detect generally require expensive

Suslick, Kenneth S.

8

Highly sensitive colorimetric detection of organophosphate pesticides using copper catalyzed click chemistry.  

PubMed

Highly sensitive colorimetric detection of organophosphate pesticides (OPs) was developed using Cu (I)-catalyzed click chemistry as the colorimetric signal amplification process between the acetylcholine esterase-acetylthiocholine system (AChE-ATCl) and azide- terminal alkyne-functionalized Au NPs as the colorimetric probe. It was demonstrated that the involvement of Cu (I)-catalyzed click chemistry allowed greatly improved colorimetric sensitivity for OPs detection based on the indirect modulation of click chemistry-induced Au NPs aggregation by the AChE-ATCl system. Paraoxon as the model OPs in the concentration range from 10(-6) to 10(-4)g/L can be directly detected using the naked-eye-based colorimetric assay without the aid of any complex instruments. The results for paraoxon detection in spiked apple juice were found to be in good agreement with that obtained by the conventional UV-vis spectroscopy. This simple and reliable assay would greatly improve the public safety and environmental protection in an on-site and real-time detection format. PMID:23200365

Fu, Guanglei; Chen, Wenwen; Yue, Xiuli; Jiang, Xingyu

2013-01-15

9

Colorimetric Aptasensor Using Unmodified Gold Nanoparticles for Homogeneous Multiplex Detection  

PubMed Central

Colorimetric aptasensors using unmodified gold nanoparticles (AuNPs) have attracted much attention because of their low cost, simplicity, and practicality, and they have been developed for various targets in the past several years. However, previous research has focused on developing single-target assays. Here, we report the development of a homogeneous multiplex aptasensor by using more than one class of aptamers to stabilize AuNPs. Using sulfadimethoxine (SDM), kanamycin (KAN) and adenosine (ADE) as example targets, a KAN aptamer (750 nM), an SDM aptamer (250 nM) and an ADE aptamer (500 nM) were mixed at a 1?1?1 volume ratio and adsorbed directly onto the surface of unmodified AuNPs by electrostatic interaction. Upon the addition of any of the three targets, the conformation of the corresponding aptamer changed from a random coil structure to a rigid folded structure, which could not adsorb and stabilize AuNPs. The AuNPs aggregated in a specific reaction buffer (20 mM Tris-HCl containing 20 mM NaCl and 5 mM KCl), which led to a color change from red to purple/blue. These results demonstrate that the multiplex colorimetric aptasensor detected three targets simultaneously while maintaining the same sensitivity as a single-target aptasensor for each individual target. The multiplex aptasensor could be extended to other aptamers for various molecular detection events. Due to its simple design, easy operation, fast response, cost effectiveness and lack of need for sophisticated instrumentation, the proposed strategy provides a powerful tool to examine large numbers of samples to screen for a small number of potentially positive samples containing more than one analyte, which can be further validated using sophisticated instruments. PMID:25279730

Niu, Shucao; Lv, Zhenzhen; Liu, Jinchuan; Bai, Wenhui; Yang, Shuming; Chen, Ailiang

2014-01-01

10

Catalyst screening for oxidative reforming of methane in direct route using high pressure HTS reactor with syngas detection system by colorimetric reaction and gas chromatograph.  

PubMed

A high-throughput screening (HTS) reactor for high-pressure oxidative reforming of methane in a direct reaction route was developed. With a combination of catalyst preparation by a split-and-pool method and HTS, Ni-K/alpha-Al(2)O(3) catalyst was found to show high activity under 1 MPa at 650 degrees C with high selectivity even when O(2) conversion is less than 100%. The HTS reactor required a new simple syngas detector operable under high pressure because the number of parallel reactor is limited when equipped with the conventional detection system. The complexity of the pressure reducing unit is the main reason of the limitation. Reduction of metal oxide accompanied with the color change was applied to the detection system. Copper oxide was supported on the filter disk made of alumina, and the filter was placed underneath the catalyst bed. After the methane was oxidatively reformed under 1 MPa at 650 degrees C, color change of spots from dark brown to light brown was observed just under the catalyst which produced hydrogen. Color change of the disk can be used to detect hydrogen formation from the reforming catalyst under pressure. PMID:19133839

Omata, Kohji; Ishii, Hidetomo; Horiguchi, Junpei; Kobayashi, Seishiro; Yamazaki, Yuichiro; Yamada, Muneyoshi

2009-01-01

11

Beryllium colorimetric detection for high speed monitoring of laboratory environments.  

PubMed

The health consequences of beryllium (Be2+) exposure can be severe. Beryllium is responsible for a debilitating and potentially fatal lung disease, chronic beryllium disease (CBD) resulting from inhalation of beryllium particles. The US Code of Federal Register (CFR), 10 CFR 850, has established a limit of 0.2 microg beryllium/100 cm(2) as the maximum amount of beryllium allowable on surfaces to be released from beryllium work areas in Department of Energy (DOE) facilities. The analytical technique described herein reduces the time and cost of detecting beryllium on laboratory working surfaces substantially. The technique provides a positive colorimetric response to the presence of beryllium on a 30.5 cm x 30.5 cm (1 ft(2)) surface at a minimum detection of 0.2 microg/100 cm(2). The method has been validated to provide positive results for beryllium in the presence of excess iron, calcium, magnesium, copper, nickel, chromium and lead at concentrations 100 times that of beryllium and aluminum and uranium (UO2(2+)) at lesser concentrations. The colorimetric detection technique has also been validated to effectively detect solid forms of beryllium including Be(OH)2, BeCl2, BeSO4, beryllium metal and BeO. PMID:12137989

Taylor, Tammy P; Sauer, Nancy N

2002-08-01

12

Colorimetric Detection and Identification of Natural and Artificial Sweeteners  

PubMed Central

A disposable, low-cost colorimetric sensor array has been created by pin-printing onto a hydrophilic membrane 16 chemically responsive nanoporous pigments made from indicators immobilized in an organically modified silane (ormosil). The array has been used to detect and identify 14 different natural and artificial sweeteners at millimolar concentrations as well as commonly used individual serving sweetener packets. The array has shown excellent reproducibility and long shelf-life and has been optimized to work in the biological pH regime. PMID:20337402

Musto, Christopher J.; Lim, Sung H.; Suslick, Kenneth S.

2009-01-01

13

Development of the colorimetric sensor array for detection of explosives and volatile organic compounds in air  

E-print Network

Development of the colorimetric sensor array for detection of explosives and volatile organic for detecting explosives, such as ammonium nitrate, mineral explosives, and DNT in low concentrations [4 of Denmark (DTU) we are developing a simple colorimetric sensor array which can be useful in detection

14

Masking nanoparticle surfaces for sensitive and selective colorimetric detection of proteins.  

PubMed

We have developed a convenient and efficient colorimetric detection system for protein targets using aptamer-gold nanoparticle conjugates. We take advantage of the correlation between the catalytic properties and the exposed surface area of the nanoparticles, which is inversely proportional to the amount of the aptamer-bound protein targets. As the concentration of the protein target increases, the nanoparticle surface area becomes more masked, thus increasing the reduction time of 4-nitrophenol for the color change. We also reduce the detection time by either redesigning the aptamer sequences or regulating their density. This detection system is highly selective, discriminating the target protein even at a concentration 1000 times higher than the limit of detection (LOD). Importantly, to the best of our knowledge, the LOD with the unaided eye in this work is the lowest for a colorimetric detection system using lysozyme as a model protein (16 nM). Lysozyme in chicken egg whites is directly analyzed using our detection system, whose results are in excellent agreement with the enzyme-linked immunosorbent assay (ELISA) analysis. PMID:24079726

Kim, Byung-Ho; Yoon, In Seon; Lee, Jae-Seung

2013-11-01

15

Colorimetric and fluorescent detection of protamines with an anionic polythiophene derivative.  

PubMed

We have developed a novel approach for the colorimetric and fluorescent detection of protamines based on an anionic polythiophene derivative. This probe has high sensitivity and selectivity toward protamines with a linear detectable range from 0.1 to 30 ?g mL(-1), and can be used for protamine detection in serum samples. PMID:23963479

Yao, Zhiyi; Ma, Wenjuan; Yang, Yan; Chen, Xueliang; Zhang, Li; Lin, Chen; Wu, Hai-Chen

2013-10-14

16

Colorimetric and fluorescent dual detection of paraquat and diquat based on an anionic polythiophene derivative.  

PubMed

We have developed a colorimetric and fluorescent dual-response probe for the detection of paraquat and diquat in aqueous solutions based on an anionic polythiophene derivative. The detection limit of this approach can be as low as 10(-9) M by fluorescence measurements. PMID:23912221

Yao, Zhiyi; Hu, Xianping; Ma, Wenjuan; Chen, Xueliang; Zhang, Li; Yu, Junhua; Zhao, Yuliang; Wu, Hai-Chen

2013-10-01

17

Recent progress in the development of fluorometric and colorimetric chemosensors for detection of cyanide ions.  

PubMed

The presence of cyanide ions in surface water is not only caused by industrial waste but also by biological processes. Owing to the extreme toxicity of cyanide in physiological systems and its widespread presence in the environment, considerable attention has been given to the development of methods for the detection of cyanide. Among the most simple, inexpensive and rapid methods to detect cyanide ions are chemosensors that rely on fluorometric and colorimetric responses. This review, which focuses on CN(-) fluorescence and colorimetric chemosensors that have been developed since 2010, follows a format in which the sensors are classified according to their structural features and reaction mechanisms. Finally, a general overview of the design of fluorometric and colorimetric chemosensors for CN(-) is provided. PMID:24668230

Wang, Fang; Wang, Li; Chen, Xiaoqiang; Yoon, Juyoung

2014-07-01

18

A colorimetric receptor combined with a microcantilever sensor for explosive vapor detection  

NASA Astrophysics Data System (ADS)

Substantial effort has been devoted to the synthesis of molecular receptors that can function as chemosensors for nitroaromatic explosives. In spite of several advantages, these receptors suffer from low sensitivity and difficulties translating the response into the gas phase. We have combined tetrathiafulvalene-functionalized calix[4]pyrrole, a colorimetric receptor, with a polyimide microcantilever, that includes a mechanical stress sensing element. The resulting system is capable of detecting 10 ppb trinitrobenzene vapor. This represents a 30-fold improvement relative to the receptor in halogenated solvents, suggesting that this approach can provide a solution to translating the chemical response of colorimetric chemosensors into practical devices.

Zhu, Weibin; Park, Jung Su; Sessler, Jonathan L.; Gaitas, Angelo

2011-03-01

19

Colorimetric microwell plate reverse-hybridization assay for detection and genotyping of hepatitis C virus.  

PubMed

This study describes a colorimetric method for detecting and genotyping hepatitis C virus (HCV) in which four different oligonucleotide probes are fixed onto microwell plates and hybridized separately with biotinylated PCR amplification products derived from clinical samples. The first probe capable of hybridizing with all seven known HCV genotypes was used for overall detection, and the remaining probes were used to recognize specifically genotypes 1-3. When combined with an improved silica-based RNA extraction method, the sensitivity of the test was 50 IU/mL. Eighty-five of the 86 samples analyzed (98.8%) yielded results in agreement with reference detection methods. The remaining sample was HCV-RNA positive in the COBAS Amplicor qualitative assay, but was negative using the reverse-hybridization method. The usefulness of the new genotyping test was confirmed by comparison with direct sequencing of PCR products: 98% of samples tested (54/55) were in agreement using the two methods (21, 7 and 27 from genotypes 1-3, respectively). The single discrepancy might have been due to a mixed HCV infection. The new method is an alternative to the use of commercially available genotyping kits and should be particularly convenient in developing countries where genotypes 1-3 represent a high proportion of HCV isolates. PMID:19643142

Costi, Cintia; da Silva, Cláudia Maria Dornelles; Da Fré, Nicole Nascimento; Grandi, Tarciana; Hamester, Fernanda Irma; Zaha, Arnaldo; Niel, Christian; Rossetti, Maria Lucia Rosa

2009-12-01

20

A colorimetric method for point mutation detection using high-fidelity DNA ligase  

Microsoft Academic Search

The present study reported proof-of-principle for a genotyping assay approach that can detect single nucleotide polymorphisms (SNPs) through the gold nanoparticle assembly and the ligase reaction. By incorporating the high-fidelity DNA ligase (Tth DNA ligase) into the allele-specific ligation-based gold nanoparticle assembly, this assay provided a conve- nient yet powerful colorimetric detection that enabled a straightforward single-base discrimination without the

Jishan Li; Xia Chu; Yali Liu; Jian-Hui Jiang; Zhimin He; Zhiwei Zhang; Guoli Shen; Ru-Qin Yu

2005-01-01

21

Molecularly imprinted photonic hydrogels as colorimetric sensors for rapid and label-free detection of vanillin.  

PubMed

A novel colorimetric sensor for the rapid and label-free detection of vanillin, based on the combination of photonic crystal and molecular imprinting technique, was developed. The sensing platform of molecularly imprinted photonic hydrogel (MIPH) was prepared by a noncovalent and self-assembly approach using vanillin as a template molecule. Morphology characterization by scanning electron microscope (SEM) showed that the MIPH possessed a highly ordered three-dimensional (3D) macroporous structure with nanocavities. The vanillin recognition events of the created nonocavities could be directly transferred into readable optical signals through a change in Bragg diffraction of the ordered macropores array of MIPH. The Bragg diffraction peak shifted from 451 to 486 nm when the concentration of the vanillin was increased from 10?¹² to 10?³ mol L?¹ within 60 s, whereas there were no obvious peak shifts for methyl and ethyl vanillin, indicating that the MIPH had high selectivity and rapid response for vanillin. The adsorption results showed that the hierarchical porous structure and homogeneous layers were formed in the MIPH with higher adsorption capacity. The application of such a label-free sensor with high selectivity, high sensitivity, high stability, and easy operation might offer a potential method for rapid real-time detection of trace vanillin. PMID:22292481

Peng, Hailong; Wang, Shenqi; Zhang, Zhong; Xiong, Hua; Li, Jinhua; Chen, Lingxin; Li, Yanbin

2012-02-29

22

Colorimetric detection of Shewanella oneidensis based on immunomagnetic capture and bacterial intrinsic peroxidase activity  

NASA Astrophysics Data System (ADS)

Rapid detection and enumeration of target microorganisms is considered as a powerful tool for monitoring bioremediation process that typically involves cleaning up polluted environments with functional microbes. A novel colorimetric assay is presented based on immunomagnetic capture and bacterial intrinsic peroxidase activity for rapidly detecting Shewanella oneidensis, an important model organism for environmental bioremediation because of its remarkably diverse respiratory abilities. Analyte bacteria captured on the immunomagnetic beads provided a bacterial out-membrane peroxidase-amplified colorimetric readout of the immunorecognition event by oxidizing 3, 3', 5, 5'-tetramethylbenzidine (TMB) in the present of hydrogen peroxide. The high-efficiency of immunomagnetic capture and signal amplification of peroxidase activity offers an excellent detection performance with a wide dynamic range between 5.0 × 103 and 5.0 × 106 CFU/mL toward target cells. Furthermore, this method was demonstrated to be feasible in detecting S. oneidensis cells spiked in environmental samples. The proposed colorimetric assay shows promising environmental applications for rapid detection of target microorganisms.

Wen, Junlin; Zhou, Shungui; Chen, Junhua

2014-06-01

23

Colorimetric detection of Shewanella oneidensis based on immunomagnetic capture and bacterial intrinsic peroxidase activity  

PubMed Central

Rapid detection and enumeration of target microorganisms is considered as a powerful tool for monitoring bioremediation process that typically involves cleaning up polluted environments with functional microbes. A novel colorimetric assay is presented based on immunomagnetic capture and bacterial intrinsic peroxidase activity for rapidly detecting Shewanella oneidensis, an important model organism for environmental bioremediation because of its remarkably diverse respiratory abilities. Analyte bacteria captured on the immunomagnetic beads provided a bacterial out-membrane peroxidase-amplified colorimetric readout of the immunorecognition event by oxidizing 3, 3?, 5, 5?-tetramethylbenzidine (TMB) in the present of hydrogen peroxide. The high-efficiency of immunomagnetic capture and signal amplification of peroxidase activity offers an excellent detection performance with a wide dynamic range between 5.0 × 103 and 5.0 × 106?CFU/mL toward target cells. Furthermore, this method was demonstrated to be feasible in detecting S. oneidensis cells spiked in environmental samples. The proposed colorimetric assay shows promising environmental applications for rapid detection of target microorganisms. PMID:24898751

Wen, Junlin; Zhou, Shungui; Chen, Junhua

2014-01-01

24

A cellulose-based bioassay for the colorimetric detection of pathogen DNA.  

PubMed

Cellulose-paper-based colorimetric bioassays may be used at the point of sampling without sophisticated equipment. This study reports the development of a colorimetric bioassay based on cellulose that can detect pathogen DNA. The detection was based on covalently attached single-stranded DNA probes and visual analysis. A cellulose surface functionalized with tosyl groups was prepared by the N,N-dimethylacetamide-lithium chloride method. Tosylation of cellulose was confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. Sulfhydryl-modified oligonucleotide probes complementary to a segment of the DNA sequence IS6110 of Mycobacterium tuberculosis were covalently immobilized on the tosylated cellulose. On hybridization of biotin-labelled DNA oligonucleotides with these probes, a colorimetric signal was obtained with streptavidin-conjugated horseradish peroxidase catalysing the oxidation of tetramethylbenzamidine by H2O2. The colour intensity was significantly reduced when the bioassay was subjected to DNA oligonucleotide of randomized base composition. Initial experiments have shown a sensitivity of 0.1 ?M. A high probe immobilization efficiency (more than 90 %) was observed with a detection limit of 0.1 ?M, corresponding to an absolute amount of 10 pmol. The detection of M. tuberculosis DNA was demonstrated using this technique coupled with PCR for biotinylation of the DNA. This work shows the potential use of tosylated cellulose as the basis for point-of-sampling bioassays. PMID:25354892

Saikrishnan, Deepika; Goyal, Madhu; Rossiter, Sharon; Kukol, Andreas

2014-12-01

25

Rapid colorimetric detection of proteins and bacteria using silver reduction\\/precipitation catalyzed by gold nanoparticles  

Microsoft Academic Search

A colorimetric immunoassay has been developed based on the reduction and precipitation of silver ions catalyzed by colloidal\\u000a gold. This method was evaluated for a noncompetitive heterogeneous immunoassay to detect ovalbumin as a model protein and\\u000a Escherichia coli as model bacterium. The influence of relevant experimental variables, including the reaction time of antigen with antibody,\\u000a the dilution ratio of the

Pravin A. Betala; Suganya Appugounder; Sudipto Chakraborty; Preedarat Songprawat; William J. Buttner; Victor H. Perez-Luna

2008-01-01

26

PDMS gold nanoparticle composite film-based silver enhanced colorimetric detection of cardiac troponin I  

Microsoft Academic Search

This paper described poly(dimethylsiloxane) (PDMS)-gold nanoparticles (AuNPs) composite film as basis with silver enhancement for colorimetric detection of cardiac troponin I (cTnI). Stable PDMS-AuNPs composite film was simply prepared with dropping HAuCl4 solution in PDMS microchip, gold nanoparticles were both used as nuclei for silver enhancement and as basis for adsorption of antibody, immunoassay was implemented after BSA blocking. Because

Wen-Ya Wu; Zhi-Ping Bian; Wei Wang; Jun-Jie Zhu

2010-01-01

27

``Red-to-blue'' colorimetric detection of cysteine via anti-etching of silver nanoprisms  

NASA Astrophysics Data System (ADS)

The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I-) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I- attack. In that case, the color of the AgNPR dispersion containing I- and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I- incubated with AgNPRs, incubation time of AgNPRs and I-, and pH of AgNPR dispersions are optimized to 5.0 ?M, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples.The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I-) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I- attack. In that case, the color of the AgNPR dispersion containing I- and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I- incubated with AgNPRs, incubation time of AgNPRs and I-, and pH of AgNPR dispersions are optimized to 5.0 ?M, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03309d

Li, Yonglong; Li, Zihou; Gao, Yuexia; Gong, An; Zhang, Yujie; Hosmane, Narayan S.; Shen, Zheyu; Wu, Aiguo

2014-08-01

28

"Red-to-blue" colorimetric detection of cysteine via anti-etching of silver nanoprisms.  

PubMed

The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I(-)) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I(-) attack. In that case, the color of the AgNPR dispersion containing I(-) and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I(-) incubated with AgNPRs, incubation time of AgNPRs and I(-), and pH of AgNPR dispersions are optimized to 5.0 ?M, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples. PMID:25083798

Li, Yonglong; Li, Zihou; Gao, Yuexia; Gong, An; Zhang, Yujie; Hosmane, Narayan S; Shen, Zheyu; Wu, Aiguo

2014-09-21

29

[Detection of viable metabolically active yeast cells using a colorimetric assay].  

PubMed

The increasing concern of yeasts able to form biofilm brings about the need for susceptibility testing of both planktonic and biofilm cells. Detection of viability or metabolic activity of yeast cells after exposure to antimicrobials plays a key role in the assessment of susceptibility testing results. Colorimetric assays based on the color change of the medium in the presence of metabolically active cells proved suitable for this purpose. In this study, the usability of a colorimetric assay with the resazurin redox indicator for monitoring the effect of yeast inoculum density on the reduction rate was tested. As correlation between the color change rate and inoculum density was observed, approximate quantification of viable cells was possible. The assay would be of relevance to antifungal susceptibility testing in both planktonic and biofilm yeasts. PMID:18318392

R?zicka, F; Holá, V

2008-02-01

30

A Simple and Highly Sensitive Colorimetric Detection Method for Gaseous Formaldehyde  

PubMed Central

A colorimetric detection method using amine functionalized polymer films doped with a pH indicator has been developed for the rapid, sensitive and quantitative detection of gaseous formaldehyde at concentrations well below the IDLH (immediately dangerous to life or health). In one minute, visible color changes are easily observed even down to the PEL (permissible exposure limit) at 750 ppb. The limit of detection is below 50 ppb (7% of PEL) after 10 min exposure. This sensor is essentially unaffected by changes in humidity or temperature (4 to 50 °C) and is not sensitive to common interferents. PMID:20218682

Feng, Liang; Musto, Christopher J.; Suslick, Kenneth S.

2010-01-01

31

[Colorimetric detection of HPV6 and HPV16 by loop mediated isothermal amplification].  

PubMed

A simple, rapid and sensitive colorimetric loop mediated isothermal amplification (LAMP) method was established to detect HPV6 and HPV 16 respectively. The method employed a set of four specially designed primers that recognized six distinct sequences of HPV6-E6 or HPV16-E7 for amplification of nucleic acid under isothermal conditions at 63 degrees C for one hour. The amplification process of LAMP was monitored by the addition of HNB (hydroxy naphthol blue) dye prior to amplification. A positive reaction was indicated by a color change from violet to sky blue and confirmed by real-time turbidimeter and agarose electrophoresis. Thirteen cervical swab samples having single infection with 13 different HPV genotypes were examined to evaluate the specificity. A serial dilution of a cloned plasmid containing HPV-E6 or HPV-E7 gene was examined to evaluate the sensitivity. The results showed that no cross-reaction with other HPV genotypes was observed. The colorimetric LAMP assay could achieve a sensitivity of 1000 copies, 10-20 times lower than that of real-time PCR. The assay was further evaluated with 62 clinical specimens and consistent results were obtained compared with the detection using Kai Pu HPV Genotyping Kit. We concluded that this colorimetric LAMP assay had potential usefulness for the rapid screening of the HPV6 or HPV16 infection in the laboratories and hospitals of provincial and municipal region in China. PMID:21462508

Lu, Chun-bin; Luo, Le; Yang, Meng-jie; Nie, Kai; Wang, Miao; Ma, Xue-Jun

2011-01-01

32

Quantitative PCR for Listeria monocytogenes with colorimetric detection.  

PubMed

An enzyme-linked immunosorbent assay (ELISA)-mediated polymerase chain reaction (PCR) technique was developed to detect and quantify Listeria monocytogenes in food products. The bacterial DNA was extracted from artificially contaminated food and co-amplified with a synthetic internal standard (IS) using primers specific for the target gene coding for the invasive-associated protein (i.a.p.), a virulence factor of L. monocytogenes (i.a.p.) or IS in the presence of fluorescein-dUTP PCR products were hybridized with biotinylated probes designed for the i.a.p. or IS, and then the hybrids were bound to a streptavidin-coated ELISA plate. An alkaline phosphatase-conjugated antibody to fluorescein was added to the plate and in the presence of substrate, PCR products were quantitated based on an optical density reading. The detection limit for L. monocytogenes experimentally inoculated into milk samples and channel catfish fillets was 20 CFU/ml and 1-2 CFU/g, respectively. Little or no cross reaction was detected in the presence of other spoilage and pathogenic organisms such as Pseudomonas aeruginosa, Aeromonas hydrophila, Escherichia coli, and Staphylococcus aureus. The ELISA-mediated PCR technique, when compared to traditional methods, is more rapid (2 working days) for detecting and quantifying L. monocytogenes. PMID:9921826

Wang, C; Hong, C

1999-01-01

33

Colorimetric Detection Of Substances In Liquids And Gases  

NASA Technical Reports Server (NTRS)

Thin polymer films containing solvatochromic dyes used as sensing elements to detect substances dissolved in liquids and gases. Dyes do not react with liquids in which dissolved, but do respond to changes in chemical compositions by changing color. Concentration determined visually by comparison of color with predetermined standard chart, or spectrophotometrically.

Harris, J. Milton; Mcgill, R. Andrew; Paley, Mark S.

1992-01-01

34

Sensitive colorimetric detection of Listeria monocytogenes based on isothermal gene amplification and unmodified gold nanoparticles.  

PubMed

Listeria monocytogenes (L. monocytogenes), one of most problematic food-borne bacteria, is mainly transmitted through the food chain and may cause listeriosis. Therefore, the development of rapid and sensitive L. monocytogenes detection technique has become an urgent task. In this study, we proposed a method using hyperbranching rolling circle amplification (HRCA) combined with gold nanoparticle (GNP) based colorimetric strategy to offer an isothermal, highly sensitive and specific assay for the detection of L. monocytogenes. First, a linear padlock probe targeting a specific sequence in the hly gene was designed and followed with a ligation by Taq DNA ligase. After ligation, further amplification by HRCA with a thiolated primer and an unlabeled primer is performed. The resulting thiolated HRCA products were then captured onto GNP surface and made GNP more salt-tolerant. Detection of the bacteria can be achieved by a facilitated GNP based colorimetric testing using naked eyes. Through this approach, as low as 100 aM synthetic hly gene targets and about 75 copies of L. monocytogenes can be detected. The specificity is evaluated by distinguishing target L. monocytogenes from other bacteria. The artificial contaminated food samples were also detected for its potential applications in real food detection. This method described here is ideal for bacteria detection due to its simplicity and high sensitivity. PMID:23948710

Fu, Zhongyu; Zhou, Xiaoming; Xing, Da

2013-12-15

35

Colorimetric detection of loop-mediated isothermal amplification reaction by using hydroxy naphthol blue.  

PubMed

Loop-mediated isothermal amplification (LAMP), a novel gene amplification method, enables the synthesis of larger amounts of both DNA and a visible byproduct--namely, magnesium pyrophosphate--without thermal cycling. A positive reaction is indicated by the turbidity of the reaction solution or the color change after adding an intercalating dye to the reaction solution, but the use of such dyes has certain limitations. Hydroxy naphthol blue (HNB), a metal indicator for calcium and a colorimetric reagent for alkaline earth metal ions, was used for a new colorimetric assay of the LAMP reaction. Preaddition of 120 microM HNB to the LAMP reaction solution did not inhibit amplification efficiency. A positive reaction is indicated by a color change from violet to sky blue. The LAMP reaction with HNB could also be carried out in a 96-well microplate, and the reaction could be measured at 650 nm with a microplate reader. The colorimetric LAMP method using HNB would be helpful for high-throughput DNA and RNA detection. PMID:19317660

Goto, Motoki; Honda, Eiichi; Ogura, Atsuo; Nomoto, Akio; Hanaki, Ken-Ichi

2009-03-01

36

Cationic Surfactant-Based Colorimetric Detection of Plasmodium Lactate Dehydrogenase, a Biomarker for Malaria, Using the Specific DNA Aptamer  

PubMed Central

A simple, sensitive, and selective colorimetric biosensor for the detection of the malarial biomarkers Plasmodium vivax lactate dehydrogenase (PvLDH) and Plasmodium falciparum LDH (PfLDH) was demonstrated using the pL1 aptamer as the recognition element and gold nanoparticles (AuNPs) as probes. The proposed method is based on the aggregation of AuNPs using hexadecyltrimethylammonium bromide (CTAB). The AuNPs exhibited a sensitive color change from red to blue, which could be seen directly with the naked eye and was monitored using UV-visible absorption spectroscopy and transmission electron microscopy (TEM). The reaction conditions were optimized to obtain the maximum color intensity. PvLDH and PfLDH were discernible with a detection limit of 1.25 pM and 2.94 pM, respectively. The applicability of the proposed biosensor was also examined in commercially available human serum. PMID:24992632

Lee, Seonghwan; Manjunatha, D H; Jeon, Weejeong; Ban, Changill

2014-01-01

37

Colorimetric immuno-protein phosphatase inhibition assay for specific detection of microcystins and nodularins of cyanobacteria.  

PubMed

A novel immunoassay was developed for specific detection of cyanobacterial cyclic peptide hepatotoxins which inhibit protein phosphatases. Immunoassay methods currently used for microcystin and nodularin detection and analysis do not provide information on the toxicity of microcystin and/or nodularin variants. Furthermore, protein phosphatase inhibition-based assays for these toxins are not specific and respond to other environmental protein phosphatase inhibitors, such as okadaic acid, calyculin A, and tautomycin. We addressed the problem of specificity in the analysis of protein phosphatase inhibitors by combining immunoassay-based detection of the toxins with a colorimetric protein phosphatase inhibition system in a single assay, designated the colorimetric immuno-protein phosphatase inhibition assay (CIPPIA). Polyclonal antibodies against microcystin-LR were used in conjunction with protein phosphatase inhibition, which enabled seven purified microcystin variants (microcystin-LR, -D-Asp3-RR, -LA, -LF, -LY, -LW, and -YR) and nodularin to be distinguished from okadaic acid, calyculin A, and tautomycin. A range of microcystin- and nodularin-containing laboratory strains and environmental samples of cyanobacteria were assayed by CIPPIA, and the results showed good correlation (R2 = 0.94, P < 0.00001) with the results of high-performance liquid chromatography with diode array detection for toxin analysis. The CIPPIA procedure combines ease of use and detection of low concentrations with toxicity assessment and specificity for analysis of microcystins and nodularins. PMID:11157261

Metcalf, J S; Bell, S G; Codd, G A

2001-02-01

38

Colorimetric Immuno-Protein Phosphatase Inhibition Assay for Specific Detection of Microcystins and Nodularins of Cyanobacteria  

PubMed Central

A novel immunoassay was developed for specific detection of cyanobacterial cyclic peptide hepatotoxins which inhibit protein phosphatases. Immunoassay methods currently used for microcystin and nodularin detection and analysis do not provide information on the toxicity of microcystin and/or nodularin variants. Furthermore, protein phosphatase inhibition-based assays for these toxins are not specific and respond to other environmental protein phosphatase inhibitors, such as okadaic acid, calyculin A, and tautomycin. We addressed the problem of specificity in the analysis of protein phosphatase inhibitors by combining immunoassay-based detection of the toxins with a colorimetric protein phosphatase inhibition system in a single assay, designated the colorimetric immuno-protein phosphatase inhibition assay (CIPPIA). Polyclonal antibodies against microcystin-LR were used in conjunction with protein phosphatase inhibition, which enabled seven purified microcystin variants (microcystin-LR, -D-Asp3-RR, -LA, -LF, -LY, -LW, and -YR) and nodularin to be distinguished from okadaic acid, calyculin A, and tautomycin. A range of microcystin- and nodularin-containing laboratory strains and environmental samples of cyanobacteria were assayed by CIPPIA, and the results showed good correlation (R2 = 0.94, P < 0.00001) with the results of high-performance liquid chromatography with diode array detection for toxin analysis. The CIPPIA procedure combines ease of use and detection of low concentrations with toxicity assessment and specificity for analysis of microcystins and nodularins. PMID:11157261

Metcalf, James S.; Bell, Steven G.; Codd, Geoffrey A.

2001-01-01

39

Selective and sensitive colorimetric detection of stringent alarmone ppGpp with Fenton-like reagent.  

PubMed

Stringent alarmone, namely, guanosine 3'-diphosphate-5'-diphosphate (ppGpp), is a global regulator that plays a critical role in the survival, growth, metabolism, and many other vital processes of microorganisms. Because of its structural similarity to normal nucleotides, it is also a challenge for the selective and sensitive detection of ppGpp nowadays. Herein, we developed a colorimetric method for the selective detection of ppGpp by inhibiting the redox reaction between Fenton-like reagent (composed of Fe(3+) and H2O2) with 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). Owing to the strong coordination affinity between ppGpp and Fe(3+), the chromogenic reaction between ABTS and Fenton-like reagent, occurred in aqueous medium at 37 °C and resulted in a bluish-green solution, which was inhibited with the addition of ppGpp. This phenomenon forms the basis for the colorimetric detection of ppGpp, with a detection limit of 0.19 ?M and good selectivity for ppGpp over other nucleotides and anions. Furthermore, the results could be visualized by the naked eye, and the sensitivity of the naked-eye observation could even be further improved with the aid of the introduction of a background color. PMID:25315398

Zheng, Lin Ling; Huang, Cheng Zhi

2014-10-27

40

Paper-based vapor detection of hydrogen peroxide: colorimetric sensing with tunable interface.  

PubMed

Vapor detection of hydrogen peroxide still remains challenging for conventional sensing techniques, though such vapor detection implies important applications in various practical areas, including locating IEDs. We report herein a new colorimetric sensor system that can detect hydrogen peroxide vapor down to parts per billion level. The sensory materials are based on the cellulose microfibril network of paper towels, which provide a tunable interface for modification with Ti(IV) oxo complexes for binding and reacting with H(2)O(2). The Ti(IV)-peroxide bond thus formed turns the complex from colorless to bright yellow with an absorption maximum around 400 nm. Such complexation-induced color change is exclusively selective for hydrogen peroxide, with no color change observed in the presence of water, oxygen, common organic reagents or other chelating reagents. This paper-based sensor material is disposable and one-time use, representing a cheap, simple approach to detect peroxide vapors. The reported sensor system also proves the technical feasibility of developing enhanced colorimetric sensing using nanofibril materials that will provide plenty of room to enlarge the surface area (by shrinking the fiber size), so as to enhance the surface interaction with gas phase. PMID:21355618

Xu, Miao; Bunes, Benjamin R; Zang, Ling

2011-03-01

41

Nucleic acid-coupled colorimetric analyte detectors  

DOEpatents

The present invention relates to methods and compositions for the direct detection of analytes and membrane conformational changes through the detection of color changes in biopolymeric materials. In particular, the present invention provide for the direct colorimetric detection of analytes using nucleic acid ligands at surfaces of polydiacetylene liposomes and related molecular layer systems.

Charych, Deborah H. (Albany, CA); Jonas, Ulrich (Mainz, DE)

2001-01-01

42

Detection of sprouted wheat by a rapid colorimetric determination of alpha-amylase.  

PubMed

A method is described for the rapid, convenient detection or estimation of sprout-damaged wheat by determining its alpha-amylase content colorimetrically. A commercially available substrate in the form of dyed amylose tablets is used. The extent of sprout damage can be determined qualitatively, or quantitatively when actual alpha-amylase concentration is required. Amylase content is determined by visual comparison with prepared colored standards or by spectrophotometric analysis. The method requires only 5 min incubation time and no elaborate equipment, and is sufficiently simple for use at locations having minimal laboratory facilities. PMID:833092

Mathewson, P R; Pomeranz, Y

1977-01-01

43

Simple colorimetric detection of doxycycline and oxytetracycline using unmodified gold nanoparticles  

NASA Astrophysics Data System (ADS)

The interaction between tetracycline antibiotics and gold nanoparticles was studied. With citrate-coated gold nanoparticles as colorimetric probe, a simple and rapid detection method for doxycycline and oxytetracycline has been developed. This method relies on the distance-dependent optical properties of gold nanoparticles. In weakly acidic buffer medium, doxycycline and oxytetracycline could rapidly induce the aggregation of gold nanoparticles, resulting in red-to-blue (or purple) colour change. The experimental parameters were optimized with regard to pH, the concentration of the gold nanoparticles and the reaction time. Under optimal experimental conditions, the linear range of the colorimetric sensor for doxycycline/oxytetracycline was 0.06-0.66 and 0.59-8.85 ?g mL-1, respectively. The corresponding limit of detection for doxycycline and oxytetracycline was 0.0086 and 0.0838 ?g mL-1, respectively. This assay was sensitive, selective, simple and readily used to detect tetracycline antibiotics in food products.

Li, Jie; Fan, Shumin; Li, Zhigang; Xie, Yuanzhe; Wang, Rui; Ge, Baoyu; Wu, Jing; Wang, Ruiyong

2014-08-01

44

Rapid detection of Pseudomonas aeruginosa in mouse feces by colorimetric loop-mediated isothermal amplification.  

PubMed

A colorimetric loop-mediated isothermal amplification (LAMP) assay with hydroxy naphthol blue was designed to amplify a region in the outer membrane lipoprotein (oprL) gene of Pseudomonas aeruginosa. The LAMP assay showed 100% specificity for the serogroup and other bacteria, and the sensitivity was 10-fold higher than that of the PCR assays. The LAMP assay could detect P. aeruginosa inoculated in mouse feces at 130 colony-forming units (CFU)/0.1g feces (3.25 CFU/reaction). The assay was completed within 2h from DNA extraction. In a field trial, the LAMP assay revealed that none of the 27 samples was obtained from 2 specific pathogen-free (SPF) mouse facilities that were monitoring infection with P. aeruginosa; 1 out of 12 samples from an SPF mouse facility that was not monitoring infection with P. aeruginosa and 2 out of 7 samples from a conventional mouse facility were positive for P. aeruginosa. In contrast, P. aeruginosa was not detected in any of the samples by a conventional culture assay. Thus, this colorimetric LAMP assay is a simple and rapid method for P. aeruginosa detection. PMID:20298724

Goto, Motoki; Shimada, Kayo; Sato, Ayako; Takahashi, Eri; Fukasawa, Takafumi; Takahashi, Tomoki; Ohka, Seii; Taniguchi, Takahide; Honda, Eiichi; Nomoto, Akio; Ogura, Atsuo; Kirikae, Teruo; Hanaki, Ken-Ichi

2010-06-01

45

Multianalyte immunoassay chip for detection of tumor markers by chemiluminescent and colorimetric methods.  

PubMed

Most cancers developed an elevation of the level of at least two markers associated with their incidence. Simultaneous detection of multi-tumor markers associated with a particular type of cancer plays an important role in cancer diagnostic. Here, a multianalyte immunoassay chip for simple and sensitive detection of tumor markers with chemiluminescent and colorimetric methods was proposed, in which carcinoembryonic antigen (CEA) and carbohydrate antigen (CA19-9) that associated with colorectal cancer were detected as model. The immunoassay chip was fabricated by co-immobilization of CEA/CA19-9 antibody on a glass slide with ?-glycidoxypropyltrimethoxysilane as linkage. Through sandwiched immunoreactions, CEA, CA19-9, and their corresponding enzyme tracers, alkaline phosphatase-labeled anti-CEA and horseradish peroxidase-labeled anti-CA19-9, were introduced on the chip. Then, they were sequentially detected by chemiluminescent method in the range of 0.5-80 ?g/L and 0.5-80 kU/L with the detection limits of 0.41 ?g/L and 0.36 kU/L at 3? for CEA and CA19-9, respectively. They could also be detected by colorimetric method in the range of 1-200 ?g/L and 5-200 kU/L with the detection limits of 0.25 ?g/L and 1.25 kU/L at 3? for CEA and CA19-9, respectively. All these results demonstrated that the present work provided a promising analytical method for tumor markers' analysis with the advantages of simple analytical procedure, small sample volume and lower cost, which made the proposed method potential for high-throughput detection. PMID:21928078

Wei, Wei; Zhang, Chunyan; Qian, Jing; Liu, Songqin

2011-12-01

46

Gold nanoparticles with asymmetric polymerase chain reaction for colorimetric detection of DNA sequence.  

PubMed

We developed a novel strategy for rapid colorimetric analysis of a specific DNA sequence by combining gold nanoparticles (AuNPs) with an asymmetric polymerase chain reaction (As-PCR). In the presence of the correct DNA template, the bound oligonucleotides on the surface of AuNPs selectively hybridized to form complementary sequences of single-stranded DNA (ssDNA) target generated from As-PCR. DNA hybridization resulted in self-assembly and aggregation of AuNPs, and a concomitant color change from ruby red to blue-purple occurred. This approach is simpler than previous methods, as it requires a simple mixture of the asymmetric PCR product with gold colloid conjugates. Thus, it is a convenient colorimetric method for specific nucleic acid sequence analysis with high specificity and sensitivity. Most importantly, the marked color change occurs at a picogram detection level after standing for several minutes at room temperature. Linear amplification minimizes the potential risk of PCR product cross-contamination. The efficiency to detect Bacillus anthracis in clinical samples clearly indicates the practical applicability of this approach. PMID:22243128

Deng, Hua; Xu, Yi; Liu, Yanhua; Che, Zhijun; Guo, Huilin; Shan, Shuxian; Sun, Yun; Liu, Xiaofang; Huang, Keyang; Ma, Xiaowei; Wu, Yan; Liang, Xing-Jie

2012-02-01

47

Capillary-driven toner-based microfluidic devices for clinical diagnostics with colorimetric detection.  

PubMed

The fabrication of toner-based microfluidic devices to perform clinical diagnostics with capillary action and colorimetric detection is described in this report. Test zones and microfluidic channels were drawn in a graphic software package and laser printed on a polyester film. The printed layout and its mirror image were aligned with an intermediary cut-through polyester film and then thermally laminated together at 150 °C at 60 cm/min to obtain a channel with ca. 100-?m depth. Colorimetric assays for glucose, protein, and cholesterol were successfully performed using a desktop scanner. The limit of detection (LD) values found for protein, cholesterol, and glucose were 8, 0.2, and 0.3 mg/mL, respectively. The relative standard deviation (RSD) values for an interdevices comparison were 6%, 1%, and 3% for protein, cholesterol, and glucose, respectively. Bioassays were successfully performed on toner-based devices stored at different temperatures during five consecutive days without loss of activity. PMID:23072590

de Souza, Fabrício Ribeiro; Alves, Guilherme Liberato; Coltro, Wendell Karlos Tomazelli

2012-11-01

48

Colorimetric detection of copper ions based on a supramolecular complex of water-soluble polythiophene and ATP.  

PubMed

A colorimetric probe for the detection of copper(II) ions in aqueous media by the naked eye has been developed based on a supramolecular complex comprised of a cationic polythiophene derivative and ATP with a detection limit as low as 0.05 mM. PMID:23377260

Yao, Zhiyi; Huang, Binghuan; Hu, Xianping; Zhang, Li; Li, Depeng; Guo, Ming; Zhang, Xiaohui; Yuan, Hui; Wu, Hai-Chen

2013-03-21

49

Colorimetric detection of DNA hybridization based on a dual platform of gold nanoparticles and graphene oxide.  

PubMed

The unique property of gold nanoparticles (Au NP) to induce colour change and the versatility of graphene oxides (GO) in surface modification makes them ideal in the application of colorimetric biosensor. Thus we developed a label free optical method to detect DNA hybridization through a visually observed colour change. The Au NP is conjugated to a DNA probe and is allowed to hybridize with the DNA target to the GO thus causing a change in colour from pinkish-red to purplish blue. Spectrophometry analysis gave a wavelength shift of 22 nm with 1 µM of DNA target. Sensitivity testing using serially diluted DNA conjugated GO showed that the optimum detection was at 63 nM of DNA target with the limit at 8 nM. This proves the possibility for the detection of DNA hybridization through the use of dual nanoparticle system by visual observation. PMID:24368225

Thavanathan, Jeevan; Huang, Nay Ming; Thong, Kwai Lin

2014-05-15

50

Colorimetric detection of urine glucose based ZnFe2O4 magnetic nanoparticles.  

PubMed

In this paper, we discovered that ZnFe(2)O(4) magnetic nanoparticles (MNPs) possess intrinsic peroxidase-like activity. ZnFe(2)O(4) MNPs exhibit several advantages such as high catalytic efficiency, good stability, monodispersion, and rapid separation over other peroxidase nanomimetics and horseradish peroxidase (HRP). ZnFe(2)O(4) MNPs were used as a colorimetric biosensor for the detection of urine glucose. This method is simple, inexpensive, highly sensitive, and selective for glucose detection using glucose oxidase (GOx) and ZnFe(2)O(4) MNPs with a linear range from 1.25 × 10(-6) to 1.875 × 10(-5) mol L(-1) with a detection limit of 3.0 × 10(-7) mol L(-1). The color change observable by the naked eyes based on the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) is the principle for the sensing of urine glucose level. PMID:22702236

Su, Li; Feng, Jie; Zhou, Ximin; Ren, Cuiling; Li, Honghong; Chen, Xingguo

2012-07-01

51

A selectively fluorescein-based colorimetric probe for detecting copper(II) ion  

NASA Astrophysics Data System (ADS)

A novel fluorescein derivative 3-bromo-5-methylsalicylaldehyde fluorescein hydrazone (BMSFH) has been synthesized by reacting fluorescein hydrazide with 3-bromo-5-methylsalicylaldehyde and was developed as a new colorimetric probe for detection of Cu2+. In the presence of Cu2+ the BMSFH exhibits a rapid color change from colorless to yellow together with an obvious new band appeared at 502 nm in the UV-vis absorption spectra. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. This change is attributed to BMSFH via coordination with Cu2+ in a 1:1 stoichiometry and this binding to Cu2+ is reversible, as indicated by the bleaching of the color when the Cu2+ is extracted with EDTA. Experimental results indicate that the BMSFH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 3.0-330 ?mol/L and can be used as a potential Cu2+ colorimetric probe in aqueous solution.

Zhang, Li; Zhang, Xianhong

2014-12-01

52

A selectively fluorescein-based colorimetric probe for detecting copper(II) ion.  

PubMed

A novel fluorescein derivative 3-bromo-5-methylsalicylaldehyde fluorescein hydrazone (BMSFH) has been synthesized by reacting fluorescein hydrazide with 3-bromo-5-methylsalicylaldehyde and was developed as a new colorimetric probe for detection of Cu(2+). In the presence of Cu(2+) the BMSFH exhibits a rapid color change from colorless to yellow together with an obvious new band appeared at 502nm in the UV-vis absorption spectra. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. This change is attributed to BMSFH via coordination with Cu(2+) in a 1:1 stoichiometry and this binding to Cu(2+) is reversible, as indicated by the bleaching of the color when the Cu(2+) is extracted with EDTA. Experimental results indicate that the BMSFH can provide a rapid, selective and sensitive response to Cu(2+) with a linear dynamic range 3.0-330?mol/L and can be used as a potential Cu(2+) colorimetric probe in aqueous solution. PMID:24929315

Zhang, Li; Zhang, Xianhong

2014-12-10

53

Beetroot-Pigment-Derived Colorimetric Sensor for Detection of Calcium Dipicolinate in Bacterial Spores  

PubMed Central

In this proof-of-concept study, we describe the use of the main red beet pigment betanin for the quantification of calcium dipicolinate in bacterial spores, including Bacillus anthracis. In the presence of europium(III) ions, betanin is converted to a water-soluble, non-luminescent orange 1?1 complex with a stability constant of 1.4×105 L mol–1. The addition of calcium dipicolinate, largely found in bacterial spores, changes the color of the aqueous solution of [Eu(Bn)+] from orange to magenta. The limit of detection (LOD) of calcium dipicolinate is around 2.0×10–6 mol L–1 and the LOD determined for both spores, B. cereus and B. anthracis, is (1.1±0.3)×106 spores mL–1. This simple, green, fast and low cost colorimetric assay was selective for calcium dipicolinate when compared to several analogous compounds. The importance of this work relies on the potential use of betalains, raw natural pigments, as colorimetric sensors for biological applications. PMID:24019934

Goncalves, Leticia Christina Pires; Da Silva, Sandra Maria; DeRose, Paul C.; Ando, Romulo Augusto; Bastos, Erick Leite

2013-01-01

54

Beetroot-pigment-derived colorimetric sensor for detection of calcium dipicolinate in bacterial spores.  

PubMed

In this proof-of-concept study, we describe the use of the main red beet pigment betanin for the quantification of calcium dipicolinate in bacterial spores, including Bacillus anthracis. In the presence of europium(III) ions, betanin is converted to a water-soluble, non-luminescent orange 1?1 complex with a stability constant of 1.4 × 10(5) L mol(-1). The addition of calcium dipicolinate, largely found in bacterial spores, changes the color of the aqueous solution of [Eu(Bn)(+)] from orange to magenta. The limit of detection (LOD) of calcium dipicolinate is around 2.0 × 10(-6) mol L(-1) and the LOD determined for both spores, B. cereus and B. anthracis, is (1.1 ± 0.3)× 10(6) spores mL(-1). This simple, green, fast and low cost colorimetric assay was selective for calcium dipicolinate when compared to several analogous compounds. The importance of this work relies on the potential use of betalains, raw natural pigments, as colorimetric sensors for biological applications. PMID:24019934

Gonçalves, Letícia Christina Pires; Da Silva, Sandra Maria; DeRose, Paul C; Ando, Rômulo Augusto; Bastos, Erick Leite

2013-01-01

55

[Colorimetric detection of norovirus genotype GII by reverse transcription loop-mediated isothermal amplification].  

PubMed

A simple, rapid and sensitive colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) method was established to detect norovirus genotype GII. The method employed a set of six specially designed primers that recognized eight distinct sequences of RNA-dependant RNA polymerase and capsid protein gene for amplification of nucleic acid under isothermal conditions at 65 degrees C for 60 minutes. The amplification process of RT-LAMP was monitored by the addition of HNB (Hydroxy naphthol blue) dye prior to amplification. A positive reaction was indicated by a color change from violet to sky blue and confirmed by agarose electrophoresis. The specificity of the RT-LAMP was validated by detecting several different diarrhea viruses including norovirus genotype GII. The sensitivity was determined by serial dilutions of RNA molecules from in vitro transcription of norovirus genotype GII in parallel with conventional RT-PCR detection. The assay was further evaluated with 93 clinical specimens of diarrhea patients. The results showed that the sensitivity of RT-LAMP was 1 000 copies/microL with a high specificity and the relative sensitivity was at the same level as that of conventional RT-PCR. Positive rate of RT-LAMP in analysis of clinical specimens was approximately the same as that of conventional RT-PCR as well. This colorimetric RT-LAMP assay was potential for rapid detection of norovirus genotype GII on spot due to the observation of visual result with high specificity and sensitivity, time-saving and cost benefit. PMID:22519179

Luo, Jian-Ming; Wu, Xi-Yang; Xu, Zi-Qian; Luo, Le; Nie, Kai; Yang, Meng-Jie; Zeng, Ya-Lan; Duan, Zhao-Jun; Ma, Xue-Jun

2012-03-01

56

A fast, sensitive and easy colorimetric assay for chitinase and cellulase activity detection  

PubMed Central

Background Most of the current colorimetric methods for detection of chitinase or cellulase activities on the insoluble natural polymers chitin and cellulose depend on a chemical redox reaction. The reaction involves the reducing ends of the hydrolytic products. The Schales’ procedure and the 3,5-dinitrosalicylic acid (DNS) method are two examples that are commonly used. However, these methods lack sensitivity and present practical difficulties of usage in high-throughput screening assays as they require boiling or heating steps for color development. Results We report a novel method for colorimetric detection of chitinase and cellulase activity. The assay is based on the use of two oxidases: wild-type chito-oligosaccharide oxidase, ChitO, and a mutant thereof, ChitO-Q268R. ChitO was used for chitinase, while ChitO-Q268R was used for cellulase activity detection. These oxidases release hydrogen peroxide upon the oxidation of chitinase- or cellulase-produced hydrolytic products. The hydrogen peroxide produced can be monitored using a second enzyme, horseradish peroxidase (HRP), and a chromogenic peroxidase substrate. The developed ChitO-based assay can detect chitinase activity as low as 10 ?U within 15 minutes of assay time. Similarly, cellulase activity can be detected in the range of 6 to 375 mU. A linear response was observed when applying the ChitO-based assay for detecting individual chito-oligosaccharides and cello-oligosaccharides. The detection limits for these compounds ranged from 5 to 25 ?M. In contrast to the other commonly used methods, the Schales’ procedure and the DNS method, no boiling or heating is needed in the ChitO-based assays. The method was also evaluated for detecting hydrolytic activity on biomass-derived substrates, that is, wheat straw as a source of cellulose and shrimp shells as a source of chitin. Conclusion The ChitO-based assay has clear advantages for the detection of chitinase and cellulase activity over the conventional Schales’ procedure and DNS method. The detection limit is lower and there is no requirement for harsh conditions for the development of the signal. The assay also involves fewer and easier handling steps. There is no need for boiling to develop the color and results are available within 15 minutes. These aforementioned features render this newly developed assay method highly suitable for applications in biorefinery-related research. PMID:24612932

2014-01-01

57

Ultrafast colorimetric detection of nucleic acids based on the inhibition of the oxidase activity of cerium oxide nanoparticles.  

PubMed

A label-free colorimetric method to detect nucleic acids, which relies on target DNA induced shielding of the oxidase activity of CeO2 NPs, is developed. With this novel strategy, target nucleic acids can be identified within a few minutes and without the need for post-purification of PCR products. PMID:25012452

Kim, Moon Il; Park, Ki Soo; Park, Hyun Gyu

2014-08-28

58

One-pot synthesized DNA-templated Ag/Pt bimetallic nanoclusters as peroxidase mimics for colorimetric detection of thrombin.  

PubMed

We developed a facile one-step approach to synthesize DNA-templated Ag/Pt bimetallic nanoclusters (DNA-Ag/Pt NCs), which possess highly-efficient peroxidase-like catalytic activity. With this finding, an aptamer based sandwich-type strategy is employed to design a label-free colorimetric aptasensor for the protein detection with high sensitivity and selectivity. PMID:25223346

Zheng, Cheng; Zheng, Ai-Xian; Liu, Bo; Zhang, Xiao-Long; He, Yu; Li, Juan; Yang, Huang-Hao; Chen, Guonan

2014-11-01

59

Homogeneous detection of unamplified genomic DNA sequences based on colorimetric scatter of gold nanoparticle probes.  

PubMed

Nucleic acid diagnostics is dominated by fluorescence-based assays that use complex and expensive enzyme-based target or signal-amplification procedures. Many clinical diagnostic applications will require simpler, inexpensive assays that can be done in a screening mode. We have developed a 'spot-and-read' colorimetric detection method for identifying nucleic acid sequences based on the distance-dependent optical properties of gold nanoparticles. In this assay, nucleic acid targets are recognized by DNA-modified gold probes, which undergo a color change that is visually detectable when the solutions are spotted onto an illuminated glass waveguide. This scatter-based method enables detection of zeptomole quantities of nucleic acid targets without target or signal amplification when coupled to an improved hybridization method that facilitates probe-target binding in a homogeneous format. In comparison to a previously reported absorbance-based method, this method increases detection sensitivity by over four orders of magnitude. We have applied this method to the rapid detection of mecA in methicillin-resistant Staphylococcus aureus genomic DNA samples. PMID:15170215

Storhoff, James J; Lucas, Adam D; Garimella, Viswanadham; Bao, Y Paul; Müller, Uwe R

2004-07-01

60

Colorimetric detection of human chorionic gonadotropin using catalytic gold nanoparticles and a peptide aptamer.  

PubMed

We combined catalytic gold nanoparticles (AuNPs) with an hCG-specific peptide aptamer to create a simple, sensitive, label-free colorimetric assay for hCG. The applications of this colorimetric biosensor may be expanded by changing the peptide aptamer. PMID:25302679

Chang, Chia-Chen; Chen, Chie-Pein; Lee, Chung-Han; Chen, Chen-Yu; Lin, Chii-Wann

2014-10-23

61

Colorimetric detection of DNA, small molecules, proteins, and ions using unmodified gold nanoparticles and conjugated polyelectrolytes  

PubMed Central

We have demonstrated a novel sensing strategy employing single-stranded probe DNA, unmodified gold nanoparticles, and a positively charged, water-soluble conjugated polyelectrolyte to detect a broad range of targets including nucleic acid (DNA) sequences, proteins, small molecules, and inorganic ions. This nearly “universal” biosensor approach is based on the observation that, while the conjugated polyelectrolyte specifically inhibits the ability of single-stranded DNA to prevent the aggregation of gold-nanoparticles, no such inhibition is observed with double-stranded or otherwise “folded” DNA structures. Colorimetric assays employing this mechanism for the detection of hybridization are sensitive and convenient—picomolar concentrations of target DNA are readily detected with the naked eye, and the sensor works even when challenged with complex sample matrices such as blood serum. Likewise, by employing the binding-induced folding or association of aptamers we have generalized the approach to the specific and convenient detection of proteins, small molecules, and inorganic ions. Finally, this new biosensor approach is quite straightforward and can be completed in minutes without significant equipment or training overhead. PMID:20534499

Xia, Fan; Zuo, Xiaolei; Yang, Renqiang; Xiao, Yi; Kang, Di; Vallee-Belisle, Alexis; Gong, Xiong; Yuen, Jonathan D.; Hsu, Ben B. Y.; Heeger, Alan J.; Plaxco, Kevin W.

2010-01-01

62

Facile colorimetric detection of Hg2+ based on anti-aggregation of silver nanoparticles.  

PubMed

This paper describes an investigation of a facile colorimetric sensor for Hg(2+) in aqueous solution based on the anti-aggregation of silver nanoparticles (AgNPs). In the absence of Hg(2+), the addition of 6-Thioguanine to AgNPs solution led to the aggregation of AgNPs, resulting in a color change from yellow to brown with a red shift of absorption spectra. However, the presence of Hg(2+) inhibited the 6-Thioguanine-induced aggregation of AgNPs accompanying with a color change from brown to yellow. Under the optimal conditions, the ratio between the absorbance at 530 nm and 394 nm (A530/A394) was linearly proportional to the Hg(2+) concentration in a range from 0 to 333 nM with a detection limit of 4 nM. Other environmentally relevant metal ions did not interfere with the detection of Hg(2+). The proposed method was simple, cost-effective and rapid without any complicated modifying step. It was successfully applied to detect Hg(2+) in environmental water samples. PMID:24583318

Duan, Junling; Yin, Hongzong; Wei, Ranran; Wang, Weiwei

2014-07-15

63

A colorimetric sandwich-type assay for sensitive thrombin detection based on enzyme-linked aptamer assay.  

PubMed

A colorimetric sandwich-type assay based on enzyme-linked aptamer assay has been developed for the fast and sensitive detection of as low as 25 fM of thrombin with high linearity. Aptamer-immobilized glass was used to capture the target analyte, whereas a second aptamer, functionalized with horseradish peroxidase (HRP), was employed for the conventional 3,5,3',5'-tetramethylbenzidine (TMB)-based colorimetric detection. Without the troublesome antibody requirement of the conventional enzyme-linked immunosorbent assay (ELISA), as low as 25 fM of thrombin could be rapidly and reproducibly detected. This assay has superior, or at least equal, recovery and accuracy to that of conventional antibody-based ELISA. PMID:24937288

Park, Jun Hee; Cho, Yea Seul; Kang, Sungmuk; Lee, Eun Jeong; Lee, Gwan-Ho; Hah, Sang Soo

2014-10-01

64

Probing phosphatase activity using redox active nanoparticles: a novel colorimetric approach for the detection of enzyme activity.  

PubMed

A new colorimetric assay for the detection of alkaline phosphatase (ALP) activity is reported based on the surface reactivity and optical properties of redox active nanoparticles of cerium oxide, or nanoceria. The method takes advantage of nanoceria color changes after interaction with products of the ALP catalyzed reaction, resulting in charge transfer complexes with very strong absorption characteristics. The developed assay is easy-to-use, robust and cost effective and does not involve labeled reagents, secondary enzymes or soluble dyes. Hydrolytic products of more stable substrates (catechol monophosphate, ascorbic 2-phosphate and hydroquinone diphosphate) that could previously not be used in ALP assays can be conveniently colorimetrically detected with this assay. A detection limit of 0.04 U/L ALP with a linear range up to 2U/L was obtained with ascorbic 2-phosphate substrate. The proposed assay can eliminate multistep procedures and minimize problems associated with the poor stability of substrates and enzyme labels of conventional ALP assays. The assay has been adapted to a paper platform and has demonstrated functionality for ALP detection in human serum. This sensing concept can find wide applications as a general approach for improving sensitivity and simplifying detection schemes of colorimetric bioassays, e.g. enzyme, gene, immuno and aptamer assays and related affinity sensing methods. PMID:24531308

Hayat, Akhtar; Gonca Bulbul; Andreescu, Silvana

2014-06-15

65

Folic acid functionalized silver nanoparticles with sensitivity and selectivity colorimetric and fluorescent detection for Hg2+ and efficient catalysis.  

PubMed

In this research, folic acid functionalized silver nanoparticles (FA-AgNPs) were selected as a colorimetric and a 'turn on' fluorescent sensor for detecting Hg(2+). After being added into Hg(2+), AgNPs can emit stable fluorescence at 440 nm when the excitation wavelength is selected at 275 nm. The absorbance and fluorescence of the FA-AgNPs could reflect the concentration of the Hg(2+) ions. Thus, we developed a simple, sensitive analytical method to detect Hg(2+) based on the colorimetric and fluorescence enhancement of FA-AgNPs. The sensor exhibits two linear response ranges between absorbance and fluorescence intensity with Hg(2+) concentration, respectively. Meanwhile, a detection limit of 1 nM is estimated based on the linear relationship between responses with a concentration of Hg(2+). The high specificity of Hg(2+) with FA-AgNPs interactions provided the excellent selectivity towards detecting Hg(2+) over other metal ions (Pb(2+), Mg(2+), Zn(2+), Ni(2+), Cu(2+), Co(2+), Ca(2+), Mn(2+), Fe(2+), Cd(2+), Ba(2+), Cr(6+) and Cr(3+)). This will provide a simple, effective and multifunctional colorimetric and fluorescent sensor for on-site and real-time Hg(2+) ion detection. The proposed method can be applied to the analysis of trace Hg(2+) in lake water. Additionally, the FA-AgNPs can be used as efficient catalyst for the reduction of 4-nitrophenol and potassium hexacyanoferrate (III). PMID:25116278

Su, Dongyue; Yang, Xin; Xia, Qingdong; Zhang, Qi; Chai, Fang; Wang, Chungang; Qu, Fengyu

2014-09-01

66

Colorimetric detection of DNA damage by using hemin-graphene nanocomposites  

NASA Astrophysics Data System (ADS)

A colorimetric method for detection of DNA damage was developed by using hemin-graphene nanosheets (H-GNs). H-GNs were skillfully synthesized by adsorping of hemin on graphene through ?-? interactions. The as-prepared H-GNs possessed both the ability of graphene to differentiate the damage DNA from intact DNA and the catalytic action of hemin. The damaged DNA made H-GNs coagulated to different degrees from the intact DNA because there were different amount of negative charge exposed on their surface, which made a great impact on the solubility of H-GNs. As a result, the corresponding centrifugal supernatant of H-GNs solution showed different color in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2, which could be discriminated by naked eyes or by ultraviolet (UV)-visible spectrometer. Based on this, the damaged effects of styrene oxide (SO), NaAsO2 and UV radiation on DNA were studied. Results showed that SO exerted most serious damage effect on DNA although all of them damaged DNA seriously. The new method for detection of DNA damage showed good prospect in the evaluation of genotoxicity of new compounds, the maximum limit of pesticide residue, food additives, and so on, which is important in the fields of food science, pharmaceutical science and pesticide science.

Wei, W.; Zhang, D. M.; Yin, L. H.; Pu, Y. P.; Liu, S. Q.

2013-04-01

67

Colorimetric detection of ractopamine and salbutamol using gold nanoparticles functionalized with melamine as a probe.  

PubMed

A highly selective and sensitive method is developed for colorimetric detection of ractopamine and salbutamol using gold nanoparticles (AuNPs) functionalized with melamine (MA), respectively. The presence of these ?-agonists induces the aggregation of gold nanoparticles through hydrogen-bonding interaction that was accompanied by a distinct change in color and optical properties, which could be monitored by a UV-vis spectrophotometer or even naked eyes. This process caused a significant decrease in the absorbance ratio (A670 nm/A520 nm) of melamine-gold nanoparticles (MA-AuNPs), and the color changed from wine red to blue. The systems exhibited a wide liner range, from 1×10(-10)M to 5×10(-7)mol/L with a correlation coefficient of 0.995 for ractopamine, and 1×10(-10)M to 1×10(-5)mol/L with a correlation coefficient of 0.996 for salbutamol, with measuring the absorbance ratio (A670 nm/A520 nm). The detection limit of these ?-agonists is as low as 1×10(-11)mol/L. Particularly, the developed method has been applied to the analysis of real swine feed samples and has achieved satisfactory results. PMID:23708531

Zhou, Ying; Wang, Peilong; Su, Xiaoou; Zhao, Hong; He, Yujian

2013-08-15

68

Direct Detection of Exoplanets  

Microsoft Academic Search

Direct detection of exoplanets from the ground is now within reach of existing astronomical instruments. Indeed, a few planet candidates have already been imaged and analyzed and the capability to detect (through imaging or interferometry) young, hot, Jupiter-mass planets exists. We present here an overview of what such detection methods can be expected to do in the near and far

J.-L. Beuzit; D. Mouillet; B. R. Oppenheimer; J. D. Monnier

2007-01-01

69

A portable lab-on-a-chip system for gold-nanoparticle-based colorimetric detection of metal ions in water.  

PubMed

Heavy metal ions released into various water systems have a severe impact on the environment and human beings, and excess exposure to toxic metal ions through drinking water poses high risks to human health and causes life-threatening diseases. Thus, there is high demand for the development of a rapid, low-cost, and sensitive method for detection of metal ions in water. We present a portable analytical system for colorimetric detection of lead (Pb(2+)) and aluminum (Al(3+)) ions in water based on gold nanoparticle probes and lab-on-a-chip instrumentation. The colorimetric detection of metal ions is conducted via single-step assays with low limits of detection (LODs) and high selectivity. We design a custom-made microwell plate and a handheld colorimetric reader for implementing the assays and quantifying the signal readout. The calibration experiments demonstrate that this portable system provides LODs of 30?ppb for Pb(2+) and 89?ppb for Al(3+), both comparable to bench-top analytical spectrometers. It promises an effective platform for metal ion analysis in a more economical and convenient way, which is particularly useful for water quality monitoring in field and resource-poor settings. PMID:25332734

Zhao, Chen; Zhong, Guowei; Kim, Da-Eun; Liu, Jinxia; Liu, Xinyu

2014-09-01

70

Colorimetric Sensor Array Allows Fast Detection and Simultaneous Identification of Sepsis-Causing Bacteria in Spiked Blood Culture  

PubMed Central

Sepsis is a medical emergency demanding early diagnosis and tailored antimicrobial therapy. Every hour of delay in initiating effective therapy measurably increases patient mortality. Blood culture is currently the reference standard for detecting bloodstream infection, a multistep process which may take one to several days. Here, we report a novel paradigm for earlier detection and the simultaneous identification of pathogens in spiked blood cultures by means of a metabolomic “fingerprint” of the volatile mixture outgassed by the organisms. The colorimetric sensor array provided significantly faster detection of positive blood cultures than a conventional blood culture system (12.1 h versus 14.9 h, P < 0.001) while allowing for the identification of 18 bacterial species with 91.9% overall accuracy within 2 h of growth detection. The colorimetric sensor array also allowed for discrimination between unrelated strains of methicillin-resistant Staphylococcus aureus, indicating that the metabolomic fingerprint has the potential to track nosocomial transmissions. Altogether, the colorimetric sensor array is a promising tool that offers a new paradigm for diagnosing bloodstream infections. PMID:24478493

Mix, Samantha; Xu, Zeyu; Taba, Brian; Budvytiene, Indre; Berliner, Anders N.; Queralto, Nuria; Churi, Yair S.; Huang, Richard S.; Eiden, Michael; Martino, Raymond A.; Rhodes, Paul

2014-01-01

71

Colorimetric Sensor for Label Free Detection of Porcine PCR Product (ID: 18)  

NASA Astrophysics Data System (ADS)

This report described the use of 40±5 nm in diameter citrate-coated gold nanoparticles (GNPs) as colorimetric sensor to visually detect the presence of a 17-base swine specific conserved sequence and nucleotide mismatch in the mixed PCR products of pig, deer and shad cytochrome b genes. The size of these PCR amplicons was 109 base-pair and was amplified with a pair of common primers. Colloidal GNPs changed color from pinkish- red to purple-gray in 2 mM PBS buffer by losing its characteristic surface plasmon resonance peak at 530 nm and gaining new features between 620 and 800 nm in the absorption spectrum indicating strong aggregation. The particles were stabilized against salt induced aggregation, retained spectral features and characteristic color upon adsorption of single-stranded DNA. The PCR products without any additional processing were hybridized with a 17-nucleotide swine probe prior to exposure to GNPs. At a critical annealing temperature (55° C) that differentiated between the match and mismatch pairing, the probe was hybridized with the pig PCR product and dehybridized from the deer's and shad's. The interaction of dehybridized probe to GNPs prevented them from salt-induced aggregation, retaining their characteristic red color. The assay did not need any surface modification chemistry or labeling steps. The results were determined visually and validated by absorption spectroscopy. The entire assay (hybridization plus visual detection) was performed in less than 10 min. The assay obviated the need of complex RFLP, sequencing or blotting to differentiate the same size PCR products. We find the application of the assay for species assignment in food analysis, mismatch detection in genetic screening and homology study among closely related species.

Ali, M. E.; Hashim, U.; Bari, M. F.; Dhahi, Th. S.

2011-05-01

72

Label-free detection of specific DNA sequence-telomere using unmodified gold nanoparticles as colorimetric probes  

NASA Astrophysics Data System (ADS)

A simple and sensitive label-free colorimetric detection of telomere DNA has been developed. It was based on the color change of gold nanoparticles (AuNPs) due to DNA hybridization. UV-vis spectra and transmission electron microscopy (TEM) were used to investigate the change of AuNPs. Under the optimized conditions, the linear range for determination of telomere DNA was 5.7 × 10 -13 to 4.5 × 10 -6 mol/L. The detection limit (3 ?) of this method has decreased to pico-molar level.

Qi, Yingying; Li, Li; Li, Baoxin

2009-09-01

73

Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline  

NASA Astrophysics Data System (ADS)

In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl4 with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (?25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 ?g for colorimetric detection and from 10 ng to 1.0 ?g for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng.

He, Yi; Peng, Rufang

2014-11-01

74

Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline.  

PubMed

In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl4 with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (?25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 ?g for colorimetric detection and from 10 ng to 1.0 ?g for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng. PMID:25327146

He, Yi; Peng, Rufang

2014-11-14

75

Gold nanoparticles for the colorimetric and fluorescent detection of ions and small organic molecules  

NASA Astrophysics Data System (ADS)

In recent years, gold nanoparticles (AuNPs) have drawn considerable research attention in the fields of catalysis, drug delivery, imaging, diagnostics, therapy and biosensors due to their unique optical and electronic properties. In this review, we summarized recent advances in the development of AuNP-based colorimetric and fluorescent assays for ions including cations (such as Hg2+, Cu2+, Pb2+, As3+, Ca2+, Al3+, etc) and anions (such as NO2-, CN-, PF6-, F-, I-, oxoanions), and small organic molecules (such as cysteine, homocysteine, trinitrotoluene, melamine and cocaine, ATP, glucose, dopamine and so forth). Many of these species adversely affect human health and the environment. Moreover, we paid particular attention to AuNP-based colorimetric and fluorescent assays in practical applications.

Liu, Dingbin; Wang, Zhuo; Jiang, Xingyu

2011-04-01

76

Use of Colorimetric Culture Methods for Detection of Mycobacterium tuberculosis Complex Isolates from Sputum Samples in Resource-Limited Settings  

PubMed Central

Despite recent advances, tuberculosis (TB) diagnosis remains imperfect in resource-limited settings due to its complexity and costs, poor sensitivity of available tests, or long times to reporting. We present a report on the use of colorimetric methods, based on the detection of mycobacterial growth using colorimetric indicators, for the detection of Mycobacterium tuberculosis in sputum specimens. We evaluated the nitrate reductase assay (NRA), a modified NRA using para-nitrobenzoic acid (PNB) (NRAp), and the resazurin tube assay using PNB (RETAp) to differentiate tuberculous and nontuberculous mycobacteria. The performances were assessed at days 18 and 28 using mycobacterium growth indicator tube (MGIT) and Löwenstein-Jensen (LJ) medium culture methods as the reference standards. We enrolled 690 adults with suspected pulmonary tuberculosis from a regional referral hospital in Uganda between March 2010 and June 2011. At day 18, the sensitivities and specificities were 84.6% and 90.0% for the NRA, 84.1% and 92.6% for the NRAp, and 71.2% and 99.3% for the RETAp, respectively. At day 28, the sensitivity of the RETAp increased to 82.6%. Among smear-negative patients with suspected TB, sensitivities at day 28 were 64.7% for the NRA, 61.3% for the NRAp, and 50% for the RETAp. Contamination rates were found to be 5.4% for the NRA and 6.7% for the RETAp, compared with 22.1% for LJ medium culture and 20.4% for MGIT culture. The median times to positivity were 10, 7, and 25 days for colorimetric methods, MGIT culture, and LJ medium culture,respectively. Whereas the low specificity of the NRA/NRAp precludes it from being used for TB diagnosis, the RETAp might provide an alternative to LJ medium culture to decrease the time to culture results in resource-poor settings. PMID:23658270

Orikiriza, Patrick; Rojas-Ponce, Gabriel; Riera-Montes, Margarita; Atwine, Daniel; Nansumba, Margaret; Bazira, Joel; Tuyakira, Eleanor; De Beaudrap, Pierre; Bonnet, Maryline; Page, Anne-Laure

2013-01-01

77

Facile colorimetric method for simple and rapid detection of endotoxin based on counterion-mediated gold nanorods aggregation.  

PubMed

Existence of endotoxin in food and injection products indicates bacterial contaminations and therefore poses threat to human health. Herein, a simple and rapid colorimetric method for the effective detection of endotoxin in food and injections based on counterion-mediated gold nanorods aggregation is first proposed. By taking advantage of the color change of unmodified gold nanorods resulted from endotoxin mediated gold nanorods aggregation, endotoxin could be detected in the concentration range of 0.01-0.6 ?M. Further, we studied the performance of gold nanorods with different aspect ratios (2.7 and 3.3) in determination of endotoxin and found that gold nanorods with higher aspect ratio (AR) showed superiority in the sensing sensitivity of endotoxin. A good specificity for endotoxin, a detection limit of 0.0084 ?M and recoveries ranging from 84% to 109% in spiked food and injection samples are obtained with the colorimetric method. Results demonstrate that the present method provides a novel and effective approach for on-site screening of endotoxin in common products, which is beneficial for monitoring and reducing the risk of bacterial contaminations in food and injections production. PMID:24388905

Wang, Yashan; Zhang, Daohong; Liu, Wei; Zhang, Xiao; Yu, Shaoxuan; Liu, Tao; Zhang, Wentao; Zhu, Wenxin; Wang, Jianlong

2014-05-15

78

A novel colorimetric method for the detection of Escherichia coli using cytochrome c peroxidase-encoding bacteriophage.  

PubMed

A new rapid and simple method was developed for the detection of Escherichia coli by constructing a recombinant T4 phage carrying the cytochrome c peroxidase gene derived from Saccharomyces cerevisiae (T4ccp) using which, the colorimetric detection of E. coli K12 was examined. The oxidation activity toward the chromogenic substrate cytochrome c was demonstrated by the cytochrome c peroxidase (CCP) produced from the T4ccp genome. The color change caused by the oxidation of the substrate could be visually perceived. The possibility of interference in the detection by the coexistence of other bacteria was assessed using Pseudomonas aeruginosa as a nontarget bacterium, and it was confirmed that the coexistence of P. aeruginosa caused no interference in the detection of E. coli K12. PMID:24417350

Hoang, Hoang A; Abe, Michiharu; Nakasaki, Kiyohiko

2014-03-01

79

Colorimetric Nucleic Acid Testing Assay for RNA Virus Detection Based on Circle-to-Circle Amplification of Padlock Probes?  

PubMed Central

We developed a molecular diagnostic method for detection of RNA virus based on padlock probes and colorimetric readout. The feasibility of our approach was demonstrated by using detection of Crimean-Congo hemorrhagic fever (CCHF) virus as a model. Compared with conventional PCR-based methods, our approach does not require advanced equipment, involves easier assay design, and has a sensitivity of 103 viral copies/ml. By using a cocktail of padlock probes, synthetic templates representing different viral strain variants could be detected. We analyzed 34 CCHF patient samples, and all patients were correctly diagnosed when the results were compared to those of the current real-time PCR method. This is the first time that highly specific padlock probes have been applied to detection of a highly variable target sequence typical of RNA viruses. PMID:21956984

Ke, Rongqin; Zorzet, Anna; Goransson, Jenny; Lindegren, Gunnel; Sharifi-Mood, Batool; Chinikar, Sadegh; Mardani, Masoud; Mirazimi, Ali; Nilsson, Mats

2011-01-01

80

Direct Detection of Exoplanets  

NASA Astrophysics Data System (ADS)

Direct detection of exoplanets from the ground is now within reach of existing astronomical instruments. Indeed, a few planet candidates have already been imaged and analyzed and the capability to detect (through imaging or interferometry) young, hot, Jupiter-mass planets exists. We present here an overview of what such detection methods can be expected to do in the near and far term. These methods will provide qualitatively new information about exoplanets, including spectroscopic data that will mature the study of exoplanets into a new field of comparative exoplanetary science. Spectroscopic study of exoplanet atmospheres promises to reveal aspects of atmospheric physics and chemistry as well as internal structure. Astrometric measurements will complete orbital element determinations partially known from the radial velocity surveys. We discuss the impact of these techniques, on three different timescales, corresponding to the currently available instruments, the new "Planet Finder" systems under development for 8- to 10-m telescopes, foreseen to be in operation in 5-10 years, and the more ambitious but more distant projects at the horizon of 2020.

Beuzit, J.-L.; Mouillet, D.; Oppenheimer, B. R.; Monnier, J. D.

81

Architecture based on the integration of intermolecular G-quadruplex structure with sticky-end pairing and colorimetric detection of DNA hybridization  

NASA Astrophysics Data System (ADS)

An interesting discovery is reported in that G-rich hairpin-based recognition probes can self-assemble into a nano-architecture based on the integration of an intermolecular G-quadruplex structure with the sticky-end pairing effect in the presence of target DNAs. Moreover, GNPs modified with partly complementary DNAs can intensively aggregate by hybridization-based intercalation between intermolecular G-quadruplexes, indicating an inspiring assembly mechanism and a powerful colorimetric DNA detection. The proposed intermolecular G-quadruplex-integrated sticky-end pairing assembly (called GISA)-based colorimetric system allows a specific and quantitative assay of p53 DNA with a linear range of more than two orders of magnitude and a detection limit of 0.2 nM, suggesting a considerably improved analytical performance. And more to the point, the discrimination of single-base mismatched target DNAs can be easily conducted via visual observation. The successful development of the present colorimetric system, especially the GISA-based aggregation mechanism of GNPs is different from traditional approaches, and offers a critical insight into the dependence of the GNP aggregation on the structural properties of oligonucleotides, opening a good way to design colorimetric sensing probes and DNA nanostructure. An interesting discovery is reported in that G-rich hairpin-based recognition probes can self-assemble into a nano-architecture based on the integration of an intermolecular G-quadruplex structure with the sticky-end pairing effect in the presence of target DNAs. Moreover, GNPs modified with partly complementary DNAs can intensively aggregate by hybridization-based intercalation between intermolecular G-quadruplexes, indicating an inspiring assembly mechanism and a powerful colorimetric DNA detection. The proposed intermolecular G-quadruplex-integrated sticky-end pairing assembly (called GISA)-based colorimetric system allows a specific and quantitative assay of p53 DNA with a linear range of more than two orders of magnitude and a detection limit of 0.2 nM, suggesting a considerably improved analytical performance. And more to the point, the discrimination of single-base mismatched target DNAs can be easily conducted via visual observation. The successful development of the present colorimetric system, especially the GISA-based aggregation mechanism of GNPs is different from traditional approaches, and offers a critical insight into the dependence of the GNP aggregation on the structural properties of oligonucleotides, opening a good way to design colorimetric sensing probes and DNA nanostructure. Electronic supplementary information (ESI) available: Experimental section, supplementary Figures and perspectives. See DOI: 10.1039/c3nr03547f

Li, Hongbo; Wu, Zai-Sheng; Shen, Zhifa; Shen, Guoli; Yu, Ruqin

2014-01-01

82

[Colorimetric detection of human influenza A H1N1 virus by reverse transcription loop mediated isothermal amplification].  

PubMed

A simple, rapid and sensitive colorimetric Reverse Transcription Loop Mediated Isothermal Amplification (RT-LAMP) method was established to detect human influenza A H1N1 virus. The method employed a set of six specially designed primers that recognized eight distinct sequences of the HA gene for amplification of nucleic acid under isothermal conditions at 65 degrees C for one and half hour. The amplification process of RT-LAMP was monitored by the addition of HNB (Hydroxy naphthol blue) dye prior to amplification. A positive reaction was indicated by a color change from violet to sky blue and confirmed by agarose electrophoresis. The specificity of the RT-LAMP assay was validated by cross-reaction with different swine and human influenza virus including human seasonal influenza A /H1N1 A /H3N2, influenza B and swine A /H1N1. The sensitivity of this assay was evaluated by serial dilutions of RNA molecules from in vitro transcription of human influenza A H1N1 HA gene. The assay was further evaluated with 30 clinical specimens with suspected pandemic influenza A H1N1 virus infection in parallel with RT-PCR detection and 26 clinical specimens with seasonal influenza virus infection. Our results showed that the RT-LAMP was able to achieve a sensitivity of 60 RNA copies with high specificity, and detection rate was comparable to that of the RT-PCR with the clinical samples of pandemic influenza A H1N1 infection. The RT-LAMP reaction with HNB could also be measured at 650nm in a microplate reader for quantitative analysis. Thus, we concluded that this colorimetric RT-LAMP assay had potential for the rapid screening of the human influenza A H1N1 virus infection in National influenza monitoring network laboratories and sentinel hospitals of provincial and municipal region in China. PMID:20480635

Nie, Kai; Wang, Da-Yan; Qin, Meng; Gao, Rong-Bao; Wang, Miao; Zou, Shu-Mei; Han, Feng; Zhao, Xiang; Li, Xi-Yan; Shu, Yue-Long; Ma, Xue-Jun

2010-03-01

83

Fe3O4 magnetic nanoparticle peroxidase mimetic-based colorimetric assay for the rapid detection of organophosphorus pesticide and nerve agent.  

PubMed

Rapid and sensitive detection methods are in urgent demand for the screening of extensively used organophosphorus pesticides and highly toxic nerve agents for their neurotoxicity. In this study, we developed a novel Fe(3)O(4) magnetic nanoparticle (MNP) peroxidase mimetic-based colorimetric method for the rapid detection of organophosphorus pesticides and nerve agents. The detection assay is composed of MNPs, acetylcholinesterase (AChE), and choline oxidase (CHO). The enzymes AChE and CHO catalyze the formation of H(2)O(2) in the presence of acetylcholine, which then activates MNPs to catalyze the oxidation of colorimetric substrates to produce a color reaction. After incubation with the organophosphorus neurotoxins, the enzymatic activity of AChE was inhibited and produced less H(2)O(2), resulting in a decreased catalytic oxidation of colorimetric substrates over MNP peroxidase mimetics, accompanied by a drop in color intensity. Three organophosphorus compounds were tested on the assay: acephate and methyl-paraoxon as representative organophosphorus pesticides and the nerve agent Sarin. The novel assay displayed substantial color change after incubation in organophosphorus neurotoxins in a concentration-dependent manner. As low as 1 nM Sarin, 10 nM methyl-paraoxon, and 5 ?M acephate are easily detected by the novel assay. In conclusion, by employing the peroxidase-mimicking activity of MNPs, the developed colorimetric assay has the potential of becoming a screening tool for the rapid and sensitive assessment of the neurotoxicity of an overwhelming number of organophosphate compounds. PMID:23153113

Liang, Minmin; Fan, Kelong; Pan, Yong; Jiang, Hui; Wang, Fei; Yang, Dongling; Lu, Di; Feng, Jing; Zhao, Jianjun; Yang, Liu; Yan, Xiyun

2013-01-01

84

Hydroxamate-based colorimetric method for direct screening of transglutaminase-producing bacteria.  

PubMed

Microbial transglutaminase (MTGase) is a commercial enzyme that has been applied to many protein containing foods to improve their textural property. The screening of MTGase-producing microorganisms from various sources might lead to the discovery of a new MTGase with different characteristics. This report demonstrates the use of a direct detection method for MTGase-producing bacteria grown on an agar plate by filter paper disc (FPD) assay. The principle of the assay is the formation of a red burgundy color by the hydroxamate-ferric complex. The color developed intensity was linearly correlated by the concentration of hydroxamic acid in the range of 0.1-0.8 ?M and was visually scored at 4 levels: 0, 1, 2 and 3. Streptoverticillium mobaraense DSM 40847, a positive MTGase-producer, was chosen for the verification and improving of the proposed method. The colonies grown on the nutrient agar plate at 37°C for 24 h were covered with FPDs and 30 ?l of substrates (CBZ-Gln-Gly and hydroxylamine). After incubation, 10 ?l of the ferric-TCA-HCl solution was placed on the FPD. The optimal time taken to catalyze the formation of CBZ-Gln-Gly-hydroxamic acid by the MTGase and the time taken for the hydroxamate-ferric complex to form color were 180 and 60 min, respectively. Using this assay, 30 of 189 colonies isolated from wastewater and floating-floc samples showed MTGase-positive colonies which were well correlated to the quantitative screening of MTGase activity (R(2) = 0.9758). The results revealed that the FPD assay could be used for the qualitative screening of MTGase-producing bacteria. PMID:22806051

Bourneow, Chaiwut; Benjakul, Soottawat; H-Kittikun, Aran

2012-05-01

85

Highly sensitive and selective colorimetric detection of glutathione based on Ag [I] ion-3,3',5,5'-tetramethylbenzidine (TMB).  

PubMed

Glutathione (GSH) plays an important role in the biological system and serves many cellular functions. Since all of the biothiols possess similar functional groups, it is still challenging to selectively detect GSH over cysteine (Cys) and homocysteine (Hcy). In this work, a novel and simple colorimetric method for discriminative detection of glutathione (GSH) over Cys and Hcy is developed. The proposed method is based on the fact that Ag [I] ion could oxidize 3,3',5,5',-tetramethylbenzidine (TMB) to the oxidized TMB to induce a blue color and an absorption peak centered at 652 nm. However, the introduction of GSH could cause the reduction of oxidized TMB and it could also combine with Ag(+), both of which result in a blue color fading and a decrease of the absorbance at 652 nm. Based on this finding, we propose a method to qualitatively and quantitatively detect GSH by naked eyes and UV-vis spectroscopy, respectively. The proposed method shows a low detection limit of 0.1 µM by naked eyes and 0.05 µM with the help of UV-vis spectroscopy. In addition, this method has great potential in discriminatively detecting GSH over other amino acid and biothiols. More importantly, this method is simple and fast without the preparation of nanomaterials and has also been successfully applied to the detection of GSH in biological fluids. PMID:25058938

Ni, Pengjuan; Sun, Yujing; Dai, Haichao; Hu, Jingting; Jiang, Shu; Wang, Yilin; Li, Zhuang

2015-01-15

86

Peptide functionalized gold nanoparticles for colorimetric detection of matrilysin (MMP-7) activity  

NASA Astrophysics Data System (ADS)

A peptide with two cleavage sites for MMP-7 has been synthesized and immobilized on gold nanoparticles (AuNPs) through a cysteine residue. Digestion of the peptide by MMP-7 decreases its size and net charge, which leads to the aggregation of the AuNPs. The color shift caused by aggregation enables a direct and quantitative measurement of the concentration and activity of MMP-7 with an estimated limit of detection of ~5 nM (0.1 ?g mL-1).A peptide with two cleavage sites for MMP-7 has been synthesized and immobilized on gold nanoparticles (AuNPs) through a cysteine residue. Digestion of the peptide by MMP-7 decreases its size and net charge, which leads to the aggregation of the AuNPs. The color shift caused by aggregation enables a direct and quantitative measurement of the concentration and activity of MMP-7 with an estimated limit of detection of ~5 nM (0.1 ?g mL-1). Electronic supplementary information (ESI) available: Experimental section, structure and MALDI-TOF spectrum of MMP-7, TEM images, digestion scheme of peptide, photos of peptide functionalized gold nanoparticles before and after incubation with MMP-7. See DOI: 10.1039/c3nr03006g

Chen, Peng; Selegård, Robert; Aili, Daniel; Liedberg, Bo

2013-09-01

87

Efficient reaction based colorimetric probe for sensitive detection, quantification, and on-site analysis of nitrite ions in natural water resources.  

PubMed

We have developed a novel aza-BODIPY probe for the sensitive colorimetric detection of the nitrite ions in the aqueous medium by a simple and direct method. This probe selectively recognizes the nitrite ions through a distinct visual color change from bright blue to intense green with a sensitivity of 20 ppb. Uniquely, this probe can be coated on a glass surface to fabricate a simple solid-state dipstick device that can be used for the visual detection of the nitrite ions in the presence of other competing anions in distilled as well as natural water resources like a sea, lake, and river. Furthermore, this probe can be used for the sensitive detection of the nitrate ions when coupled to a reduction step. Our results demonstrate that this probe not only can be used for the on-site analysis and quantification but also can replace the conventional spot test carried out for the nitrite ions in the laboratory practical experiments. PMID:24144080

Adarsh, Nagappanpillai; Shanmugasundaram, Madhesh; Ramaiah, Danaboyina

2013-11-01

88

The colorimetric detection of Pb2+ by using sodium thiosulfate and hexadecyl trimethyl ammonium bromide modified gold nanoparticles.  

PubMed

A simple, rapid colorimetric detection method for Pb(2+) in aqueous solution has been developed by using sodium thiosulfate (Na2S2O3) and hexadecyl trimethyl ammonium bromide (CTAB) modified gold nanoparticles (Au NPs). Na2S2O3 was added into the Au NP solution and thiosulfate ions (S2O3(2-)) were adsorbed on the surface of the Au NPs due to electrostatic interactions. Au atoms on the surface of the Au NPs were then oxidized to Au(i) by the O2 that existed in the solution in presence of thiosulfate. The addition of Pb(2+) (the final concentration was lower than 10 ?M), accelerated the leaching of the Au NPs, and Pb-Au alloys also formed on the surface of the Au NPs. There was an obvious decrease in the surface plasmon resonance (SPR) absorption of the Au NPs. The lowest concentration for Pb(2+) that could be detected by the naked eye was 0.1 ?M and using UV-vis spectroscopy was 40 nM. This is lower than the lead toxic level defined by the US Environmental Protection Agency (US EPA), which is 75 nM. In this method, CTAB, as a stabilizing agent for Au NPs, can accelerate the adsorption of S2O3(2-) on the surface of the Au NPs, which shortened the detection time to within 30 min. Moreover, this detection method is simple, cheap and environmentally friendly. PMID:23426019

Zhang, Yujie; Leng, Yumin; Miao, Lijing; Xin, Junwei; Wu, Aiguo

2013-04-21

89

Sensitive and selective colorimetric detection of Cu(2+) in aqueous medium via aggregation of thiomalic acid functionalized Ag nanoparticles.  

PubMed

A simple and effective colorimetric method for determination of Cu(2+) in real samples was developed. In this method, thiomalic acid functionalized silver nanoparticles (TMA-AgNPs) were prepared and changes in solution color, induced by the aggregation of TMA-AgNPs in the presence of Cu(2+), were employed for quantitative analysis. The surface plasmon resonance (SPR) band of our synthesized TMA-AgNPs was located at 392 nm and shifted to a longer wavelength after aggregation due to the interactions between carboxylate and Cu(2+). A band intensity ratio of A455/(A392-A455) was constructed and used to correlate with the concentration of Cu(2+). A linear relationship was found with a linear response up to 50 nM of Cu(2+). Due to the formation of a stable carboxylate Cu(2+) complex, highly sensitive detection of Cu(2+) was achieved with the estimated detection limit approaching 1 nM. Moreover, the formation of the stable complex leads to high selectivity in the detection of Cu(2+), which was verified by examination of 12 other metal ions. In the detection of Cu(2+) in real samples, results indicated that our proposed method is simple, sensitive and selective for application in such measurements. PMID:25316548

Tharmaraj, Vairaperumal; Yang, Jyisy

2014-12-01

90

Colorimetric detection of in situ metal acetates and fluorides by a bipyridyl-linked Schiff base.  

PubMed

Here, we present a new bipyridyl moiety linked Schiff base (bipy-1) that is well characterized using spectroscopic techniques. Colorimetric and UV-vis titrations were used to study the photophysical properties of bipy-1 in the presence of various tetrabutyl ammonium salt of anions and metal salts containing different counter cations. bipy-1 showed selective recognition of dimethyl sulphoxide solution of tetrabutyl ammonium salt of F(-) ion accompanied with a UV-vis band at 529?nm and interesting binding of aqueous Co, Ni, and Cu acetates/fluorides, as confirmed by distinct color changes from fluorescent green to pink or orange and a strong band around 480-510?nm in the UV-vis spectrum. However, in the presence of Co, Ni, and Cu countercations, any form of metal acetate/fluorides was found to be able to respond to similar color changes from fluorescent green to pink or orange, showing a band around 480-510?nm. This type of output clearly indicates that the in situ formation of Co, Ni, and Cu acetates/fluorides also coordinates with bipyridyl nitrogen atoms. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25319616

Suganya, Sivalingam; Zo, Hye Jin; Park, Jong S; Velmathi, Sivan

2014-12-01

91

Potassium sorbate residue levels and persistence in citrus fruit as detected by a simple colorimetric method.  

PubMed

A colorimetric method that employed extraction of the macerated fruit, followed by a reaction with 2-thiobarbituric acid, was used to quantify potassium sorbate residues in citrus fruit. A recovery of more than 90% in oranges and lemons was obtained. Potassium sorbate residues determined by this method and a standard high-performance liquid chromatography (HPLC) method were similar. Residues were proportionate to the potassium sorbate concentration in the treatment solution. In oranges stored at 15 degrees C, following the potassium sorbate treatments, residues declined initially rapidly and later more slowly, until residues stopped declining after 6 days. A brief double-dip rinse in tap water applied immediately after immersion of lemons in a 2% (wt/vol) potassium sorbate removed more than 90% of the potassium sorbate residue. The influence of high-pressure water washing (HPWW) on potassium sorbate residues in potassium-sorbate-treated fruit was determined. Potassium sorbate residues were more effectively reduced by rinsing oranges than lemons. PMID:19334786

Montesinos-Herrero, Clara; Smilanick, Joseph L; Hurley, J Michael; Palou, Lluís

2009-05-13

92

A sensitive and selective colorimetric method for detection of copper ions based on anti-aggregation of unmodified gold nanoparticles.  

PubMed

A highly sensitive and selective colorimetric method for detection of copper ions, based on anti-aggregation of D-penicillamine (D-PC) induced aggregated gold nanoparticles (AuNPs) was developed. Copper ions can hinder the aggregation of AuNPs induced by D-PC, through formation of mixed-valence complex with D-PC that is a selective copper chelator. In the presence of a fixed amount of D-PC, the aggregation of AuNPs decreases with increasing concentrations of Cu(2+) along with a color change from blue to red in AuNPs solution and an increase in the absorption ratio (A520/A650). Under the optimum experimental conditions (pH 7, [AuNPs] =3.0 nmol L(-1) and [NaCl]=25 mmol L(-1)), a linear calibration curve for Cu(2+) was obtained within the range of 0.05-1.85 µmol L(-1) with a limit of detection (3Sb) of 30 nmol L(-1). Excellent selectivity toward Cu(2+) was observed among various metal ions due to a specific complex formation between Cu(2+) and D-PC. The proposed method has been successfully applied for the detection of Cu(2+) in various real samples. PMID:25127588

Hormozi-Nezhad, M Reza; Abbasi-Moayed, Samira

2014-11-01

93

Non-aggregation based label free colorimetric sensor for the detection of Cu2+ based on catalyzing etching of gold nanorods by dissolve oxygen.  

PubMed

A label-free non-aggregation colorimetric sensor has been designed for the detection of Cu(2+), based on Cu(2+) catalyzing etching of gold nanorods (AuNRs) along longitudinal axis induced by dissolve oxygen in the presence of S2O3(2-), which caused the aspect ratio (length/width) of AuNRs to decrease and the color of the solution to distinctly change. The linear range and the detection limit (LD, calculated by 10 Sb/k, n=11) of this sensor were 0.080-4.8 µM Cu(2+) and 0.22 µM Cu(2+), respectively. This sensor has been utilized to detect Cu(2+) in tap water and human serum samples with the results agreeing well with those of inductively coupled plasma-mass spectroscopy (ICP-MS), showing its remarkable practicality. In order to prove the possibility of catalyzing AuNRs non-aggregation colorimetric sensor for the detection of Cu(2+), the morphological structures of AuNRs were characterized by high resolution transmission electron microscopy (HRTEM) and the sensing mechanism of colorimetric sensor for the detection of Cu(2+) was also discussed. PMID:24209363

Liu, Jia-Ming; Jiao, Li; Lin, Li-Ping; Cui, Ma-Lin; Wang, Xin-Xing; Zhang, Li-Hong; Zheng, Zhi-Yong; Jiang, Shu-Lian

2013-12-15

94

Sun Direction Detection System.  

National Technical Information Service (NTIS)

A sun sensor detection system is described which includes an illumination detector and a sun angle detector. The illumination detector provides a low resistance output whenever the sun is within a selected field of view and a high resistance output whenev...

L. F. Schmidt, G. D. Pace

1975-01-01

95

A Cu@Au nanoparticle-based colorimetric competition assay for the detection of sulfide anion and cysteine.  

PubMed

As an extension of our previous work, which described the unique ability of the core/shell Cu@Au nanoparticle (NP) to selectively recognize iodide, (1) herein, we wish to report the development of an alternatively sensitive and selective colorimetric detection for sulfide anion and cysteine based upon the Cu@Au NP by a competition avenue. In the absence of sulfide anion or cysteine, iodide can induce an appreciable color change of the Cu@Au NP solution from purple to red by transforming the clusters of NP to single, nearly spherical, and larger ones. However, the transformation is severely interfered by the presence of sulfide or cysteine because of a higher binding strength of the S-Au bond than the I-Au one. As a result, the clear purple-to-red color change induced by iodide is affected as a correlation with the concentration of sulfide or cysteine. By taking advantage of this fact, we can detect a concentration of 3 ?M for sulfide and 0.4 ?M for cysteine with the naked eye or 0.3 ?M (10 ppb) for sulfide and 50 nM (6 ppb) for cysteine aided by a UV/vis spectrometer. Given the detrimental effect of hydrogen sulfide and the biological importance of cysteine, the assay may become useful in the environment monitoring, water quality inspection and biomedical diagnosis as well. PMID:21786826

Zhang, Jia; Xu, Xiaowen; Yuan, Yue; Yang, Cheng; Yang, Xiurong

2011-08-01

96

Colorimetric detection of copper and efficient removal of heavy metal ions from water by diamine-functionalized SBA-15.  

PubMed

SBA-15 functionalized with N-[3-(trimethoxysilyl)propyl]ethylene-diamine (TPED) was synthesized and used for the colorimetric detection of Cu(2+) and removal of heavy metal ions in aqueous solutions. Compared to free SBA-15, the adsorption ability of diamine-functionalized SBA-15 (depicted as SBA-TPED) increased remarkably, the maximum adsorption capacity of SBA-TPED for Cu(2+), Pb(2+) and Zn(2+) was 27.22, 96.43 and 12.16 mg g(-1), respectively. Furthermore, SBA-TPED exhibits high selectivity for Cu(2+) with the relative selectivity coefficient of SBA-TPED for Cu(2+)/Pb(2+) being over 10 and for Cu(2+)/Zn(2+) being over 60. The naked-eye detection limit of SBA-TPED for Cu(2+) is 0.95 ppm, and the determination of Cu(2+) in real water samples also displays satisfactory results. Moreover, SBA-TPED possesses fast kinetics for removing Cu(2+) with a saturation time of less than 30 min, and can be regenerated by simple acid treatment. PMID:24745033

Wang, Zhuqing; Wang, Min; Wu, Genhua; Wu, Dayu; Wu, Aiguo

2014-06-14

97

Direct WIMP detection in directional experiments  

SciTech Connect

The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Thus the direct dark matter search, consisting of detecting the recoiling nucleus, is central to particle physics and cosmology. Modern particle theories naturally provide viable cold dark matter candidates with masses in the GeV-TeV region. Supersymmetry provides the lightest supersymmetric particle (LSP), theories in extra dimensions the lightest Kaluza-Klein particle (LKP) etc. Unfortunately, however, in nuclear recoil measurements the interesting signal cannot be easily distinguished from the background. So, to minimize the background problems, one should exploit characteristic signatures of the reaction, such as the modulation effect and, in directional experiments, the correlation of the event rates with the sun's motion. In standard nondirectional experiments the modulation is small, less than two per cent and the location of the maximum depends on the unknown particle's mass. In directional experiments, in addition to the forward-backward asymmetry due to the sun's motion, one expects a larger modulation, which depends on the direction of observation. We study such effects both in the case of a light and a heavy target. Furthermore, since it now appears that the planned experiments may be only partly directional, in the sense that they can only detect the line of the recoiling nucleus, but not the sense of direction on it, we study which of the above mentioned interesting features, if any, will persist in these less ambitious experiments.

Vergados, J. D. [Theoretical Physics Division, University of Ioannina, Ioannina, Gr 451 10 (Greece); Institute of Theoretical Physics, University of Tuebingen, Tuebingen (Germany); Faessler, Amand [Institute of Theoretical Physics, University of Tuebingen, Tuebingen (Germany)

2007-03-01

98

p-Dimethylaminocinnamaldehyde Derivatization for Colorimetric Detection and HPLC-UV/Vis-MS/MS Identification of Indoles  

PubMed Central

Cytochrome P450 2A13 is a lung specific enzyme known to activate the potent tobacco procarcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) into two carcinogenic metabolites. CYP2A13 has been crystallized and X-ray diffraction experiments illuminated the structure of this enzyme, but with an unknown ligand present in the enzyme active site. This unknown ligand was suspected to be indole but a selective method had to be developed to differentiate among indole and its metabolites in the protein sample. We successfully modified a microbiological colorimetric assay to spectrophotometrically differentiate between indole and a number of possible indole metabolites in nanomolar concentrations by derivatization with p-dimethylaminocinnamaldehyde (DMACA). Further differentiation of indoles was made by mass spectrometry (HPLC-UV/Vis-MS/MS) utilizing the chromophore generated in the DMACA conjugation as a UV signature for HPLC detection. The ligand in the crystallized protein was identified as unsubstituted indole, which facilitated refinement of two alternate conformations in the CYP2A13 crystal structure active site. PMID:18423367

Porubsky, Patrick R.; Scott, Emily E.; Williams, Todd D.

2008-01-01

99

p-dimethylaminocinnamaldehyde derivatization for colorimetric detection and HPLC-UV/vis-MS/MS identification of indoles.  

PubMed

Cytochrome P450 2A13 (CYP2A13) is a lung specific enzyme known to activate the potent tobacco procarcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) into two carcinogenic metabolites. CYP2A13 has been crystallized and X-ray diffraction experiments illuminated the structure of this enzyme, but with an unknown ligand present in the enzyme active site. This unknown ligand was suspected to be indole but a selective method had to be developed to differentiate among indole and its metabolites in the protein sample. We successfully modified a microbiological colorimetric assay to spectrophotometrically differentiate between indole and a number of possible indole metabolites in nanomolar concentrations by derivatization with p-dimethylaminocinnamaldehyde (DMACA). Further differentiation of indoles was made by mass spectrometry (HPLC-UV/vis-MS/MS) utilizing the chromophore generated in the DMACA conjugation as a UV signature for HPLC detection. The ligand in the crystallized protein was identified as unsubstituted indole, which facilitated refinement of two alternate conformations in the CYP2A13 crystal structure active site. PMID:18423367

Porubsky, Patrick R; Scott, Emily E; Williams, Todd D

2008-07-01

100

BacT\\/Alert: anAutomated Colorimetric Microbial Detection System  

Microsoft Academic Search

BacT\\/Alert (Organon Teknika Corp., Durham, N.C.) isanautomated microbial detection system based on thecolorimetric detection ofC02produced bygrowing microorganisms. Results ofanevaluation ofthemedia, sensor, detection system, anddetection algorithm indicate thatthesystem reliably growsanddetects awide variety ofbacteria andfungi. Results ofalimited pilot clinical trial withaprototype research instrument indicate thatthesystem iscomparable totheradiometric BACTEC460system initsability togrowanddetect microorganisms inblood. Onthebasis ofthese initial findings, large-scale clinical trials comparing BacT\\/Alert withother

THURMAN C. THORPE; MICHAEL L. WILSON; JAMES E. TURNER; L. BARTH RELLER

1990-01-01

101

Catalytic formation of silver nanoparticles by bovine serum albumin protected-silver nanoclusters and its application for colorimetric detection of ascorbic acid  

NASA Astrophysics Data System (ADS)

We established a simple spectrophotometric and colorimetric method for detection of ascorbic acid based on the growth of silver nanoparticles in bovine serum albumin protected-silver nanoclusters (BSA-AgNCs) and Ag+ mixture. Due to the catalysis of BSA-AgNCs, ascorbic acid could reduce Ag+ to silver nanoparticles (NPs) at room temperature. The color of the mixture changed from colorless to yellow and a strong absorption band near 420 nm could be found in their absorption spectra owing to localized surface plasmon resonance (LSPR) of produced silver NPs. The absorbance changes at 420 nm had a good relationship with ascorbic acid concentration. Thus, we proposed a spectrophotometric and colorimetric method to determine ascorbic acid in concentration range from 2.0 to 50.0 ?M, with the corresponding limits of determination (3?) of 0.16 ?M.

Yang, Xiu-Hua; Ling, Jian; Peng, Jun; Cao, Qiu-E.; Wang, Lei; Ding, Zhong-Tao; Xiong, Jie

2013-04-01

102

A SIMPLE COLORIMETRIC METHOD TO DETECT BIOLOGICAL EVIDENCE OF HUMAN EXPOSURE TO MICROCYSTINS  

EPA Science Inventory

Toxic cyanobacteria are contaminants of surface waters worldwide. Microcystins are some of the most commonly detected toxins. Biological evidence of human exposure may be difficult to obtain due to limitations associated with cost, laboratory capacity, analytic support, and exp...

103

Colorimetric Detection and Fingerprinting of Bacteria by Glass-Supported Lipid/Polydiacetylene Films  

E-print Network

compositions of the films. Accordingly, bacterial fingerprinting can be achieved through pattern recognition as a biomimetic membrane platform. The detection schemes are based on either visible blue-red transitions

Jelinek, Raz

104

A Simple and Highly Sensitive Colorimetric Detection Method for Gaseous Formaldehyde  

E-print Network

, and formaldehyde-based resins.1 Formaldehyde is a probable human carcinogen, an allergen, and an intense irritant with formaldehyde. An amine-terminated polymer was used to create a reactive matrix for formaldehyde detection

Suslick, Kenneth S.

105

A simple colorimetric method to detect biological evidence of human exposure to microcystins.  

PubMed

Toxic cyanobacteria are contaminants of surface waters worldwide. Microcystins are some of the most commonly detected cyanotoxins. Biological evidence of human exposure may be difficult to obtain due to limitations associated with cost, laboratory capacity, analytic support, and expertise. We investigated the application of an enzyme-linked immunosorbant assay (ELISA) to detect microcystins in human serum. We analyzed ten serum samples collected from dialysis patients who were known to be exposed to a mixture of microcystins during a 1996 outbreak in Brazil. We applied a commercially available ELISA method to detect microcystins in serum, and we compared the ELISA results to a more specific method, liquid chromatography/mass spectrometry (LC/MS) that was also used to detect microcystins in serum. The Spearman correlation coefficient was calculated using serum microcystin concentrations in split samples obtained by the two methods. Serum microcystin concentrations were similar, and we found good correlation of microcystin concentrations between the two methods. The ELISA detected total microcystins, median=19.9 ng/ml; LC/MS detected microcystin-LR equivalents, median=21.2 ng/ml; Spearman r=0.96, p<0.0001. We found that ELISA is a simple, accessible method to screen human serum for evidence of microcystin exposure. PMID:15963544

Hilborn, Elizabeth D; Carmichael, Wayne W; Yuan, Moucun; Azevedo, Sandra M F O

2005-08-01

106

A fluorescence-based colorimetric droplet platform for biosensor application to the detection of ?-fetoprotein.  

PubMed

Droplet methods have been successfully applied in DNA hybridization analysis and protein-protein interaction. Existing assay methods implemented in droplet platforms are severely limited by expensive and high-maintenance equipment. As a convenient detection method, colorimetry provides a new path for microscale assay since it can enhance assay efficiency and simplify the detection procedure. Here, a microscale immunoassay for ?-fetoprotein (AFP) was developed for the first time by the incorporation of colorimetry and droplet platform. Ru(bpy)(2)(mcbpy-O-Su-ester)(PF(6))(2) complex (Ru) was coupled with the monoclonal antibody (Ab) of AFP to form a stable red Ru-Ab complex both as a quencher for green CdTe quantum dots (QDs) and as a capture probe for AFP. In the absence of AFP, the mixed droplet showed a red color. With the increase of AFP concentration, the color change of the droplet was from red to green as a result of the competition of AFP with QDs for Ru-Ab. The biosensor exhibited not only good sensitivity and specificity for AFP with a detection limit of 0.06 ng ml(-1), but also satisfactory performance in diluted human sera with a detection limit of 0.4 ng ml(-1). Notably, a visual droplet platform for screening cancer biomarkers by the naked eye based on this principle is anticipated. PMID:23059448

Xiang, Xia; Chen, Lu; Zhang, Cuiling; Luo, Ming; Ji, Xinghu; He, Zhike

2012-12-01

107

Colorimetric Detection of Ehrlichia Canis via Nucleic Acid Hybridization in Gold Nano-Colloids  

PubMed Central

Canine monocytic ehrlichiosis (CME) is a major thick-bone disease of dog caused by Ehrlichia canis. Detection of this causal agent outside the laboratory using conventional methods is not effective enough. Thus an assay for E. canis detection based on the p30 outer membrane protein gene was developed. It was based on the p30 gene amplification using loop-mediated isothermal DNA amplification (LAMP). The primer set specific to six areas within the target gene were designed and tested for their sensitivity and specificity. Detection of DNA signals was based on modulation of gold nanoparticles' surface properties and performing DNA/DNA hybridization using an oligonucleotide probe. Presence of target DNA affected the gold colloid nanoparticles in terms of particle aggregation with a plasmonic color change of the gold colloids from ruby red to purple, visible by the naked eye. All the assay steps were completed within 90 min including DNA extraction without relying on standard laboratory facilities. This method was very specific to target bacteria. Its sensitivity with probe hybridization was sufficient to detect 50 copies of target DNA. This method should provide an alternative choice for point of care control and management of the disease. PMID:25111239

Muangchuen, Ajima; Chaumpluk, Piyasak; Suriyasomboon, Annop; Ekgasit, Sanong

2014-01-01

108

Gold nanoflowers based colorimetric detection of Hg2+ and Pb2+ ions  

NASA Astrophysics Data System (ADS)

An optical detection method based on the interaction of gold nanoflowers with Hg2+ and Pb2+ has been described. After interaction, gold nanoflowers change the color from violet to wine red. The nanoflowers are capable of determining Hg2+ and Pb2+ over a dynamic range of 1.0 × 10-6 and 1.0 × 10-5 M, respectively. The response time of nanoflowers depends on the concentration of ions. The presence of both Hg2+ and Pb2+ ions in the mixture having Au nanoflowers induced color changes of the solution within several seconds even at 1.0 × 10-6 M. Common metal ions were chosen to investigate their interference in Hg2+ and Pb2+ detection, and the concentration of each metal ion studied was 1.0 × 10-5 M. Other metallic ions could not induce color change even at 1.0 × 10-5 M. The feasibility of our method to detect Hg2+ and Pb2+ ions at high concentration in real water samples was verified. Water samples were from our own laboratory and no pretreatment was made. As the particles are stable they can be used for more than 3 months without observing any major deviation.

Nalawade, Pradnya; Kapoor, Sudhir

2013-12-01

109

A colorimetric chemosensor for Cu(2+) ion detection based on an iridium(III) complex.  

PubMed

We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1-3 bearing a rhodamine-linked NˆN ligand for the detection of Cu(2+) ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu(2+) ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu(2+) ions in tap water or natural river water samples was demonstrated. PMID:25348724

Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W J; Leung, Chung-Hang; Ma, Dik-Lung

2014-01-01

110

A colorimetric chemosensor for Cu2+ ion detection based on an iridium(III) complex  

NASA Astrophysics Data System (ADS)

We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1-3 bearing a rhodamine-linked NˆN ligand for the detection of Cu2+ ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu2+ ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu2+ ions in tap water or natural river water samples was demonstrated.

Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W. J.; Leung, Chung-Hang; Ma, Dik-Lung

2014-10-01

111

A colorimetric chemosensor for Cu2+ ion detection based on an iridium(III) complex  

PubMed Central

We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1?3 bearing a rhodamine-linked NˆN ligand for the detection of Cu2+ ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu2+ ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu2+ ions in tap water or natural river water samples was demonstrated. PMID:25348724

Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W. J.; Leung, Chung-Hang; Ma, Dik-Lung

2014-01-01

112

A Highly Selective Turn-On Colorimetric, Red Fluorescent Sensor for Detecting Mobile Zinc in Living Cells  

E-print Network

We describe ZRL1, a turn-on colorimetric and red fluorescent zinc ion sensor. The Zn2+-promoted ring opening of the rhodamine spirolactam ring in ZRL1 evokes a 220-fold fluorescence turn-on response. In aqueous media, ZRL1 ...

Du, Pingwu

113

Colorimetric detection of manganese(II) ions using gold/dopa nanoparticles  

NASA Astrophysics Data System (ADS)

We report here a one-pot, greener, eco-friendly strategy for the synthesis of gold nanoparticles using L-dopa. The as-prepared dopa-functionalized gold nanoparticles (AuNPs/dopa) can detect low concentrations of manganese(II) metal ions in aqueous solution. The binding forces between dopa and Mn2+ ions cause dopa-functionalized gold nanoparticles to come closer together, decreasing the interparticle distance and aggregating it with a change in color of colloidal solution from red to purplish-blue. Dynamic light scattering (DLS) analysis showed a decreased surface charge on the surface of gold nanoparticles when exposed to Mn2+ ions, which caused cross-linking aggregation. Transmission electron microscopic (TEM) images also revealed the aggregation of gold nanoparticles with the addition of Mn2+ ions. The extinction ratio of absorbance at 700-550 nm (A700/A550) was linear against the concentration of [Mn2+] ions. Thus, the optical absorption spectra of gold colloidal solution before and after the addition of Mn2+ ions reveal the concentration of Mn2+ ions in solution.

Narayanan, Kannan Badri; Park, Hyun Ho

2014-10-01

114

Colorimetric detection of manganese(II) ions using gold/dopa nanoparticles.  

PubMed

We report here a one-pot, greener, eco-friendly strategy for the synthesis of gold nanoparticles using L-dopa. The as-prepared dopa-functionalized gold nanoparticles (AuNPs/dopa) can detect low concentrations of manganese(II) metal ions in aqueous solution. The binding forces between dopa and Mn(2+) ions cause dopa-functionalized gold nanoparticles to come closer together, decreasing the interparticle distance and aggregating it with a change in color of colloidal solution from red to purplish-blue. Dynamic light scattering (DLS) analysis showed a decreased surface charge on the surface of gold nanoparticles when exposed to Mn(2+) ions, which caused cross-linking aggregation. Transmission electron microscopic (TEM) images also revealed the aggregation of gold nanoparticles with the addition of Mn(2+) ions. The extinction ratio of absorbance at 700-550nm (A700/A550) was linear against the concentration of [Mn(2+)] ions. Thus, the optical absorption spectra of gold colloidal solution before and after the addition of Mn(2+) ions reveal the concentration of Mn(2+) ions in solution. PMID:24825666

Narayanan, Kannan Badri; Park, Hyun Ho

2014-10-15

115

Colorimetric biosensing using smart materials.  

PubMed

In recent years, colorimetric biosensing has attracted much attention because of its low cost, simplicity, and practicality. Since color changes can be read out by the naked eye, colorimetric biosensing does not require expensive or sophisticated instrumentation and may be applied to field analysis and point-of-care diagnosis. For transformation of the detection events into color changes, a number of smart materials have been developed, including gold nanoparticles, magnetic nanoparticles, cerium oxide nanoparticles, carbon nanotubes, graphene oxide, and conjugated polymers. Here, we focus on recent developments in colorimetric biosensing using these smart materials. Along with introducing the mechanisms of color changes based on different smart materials, we concentrate on the design of biosensing assays and their potential applications in biomedical diagnosis and environmental monitoring. PMID:21800383

Song, Yujun; Wei, Weili; Qu, Xiaogang

2011-10-01

116

Surface-plasmon-based colorimetric detection of Cu(II) ions using label-free gold nanoparticles in aqueous thiosulfate systems  

NASA Astrophysics Data System (ADS)

We report colorimetric, label-free and non-aggregation-based gold nanoparticle (AuNP) probes for the highly selective detection of Cu(II) ions in aqueous environments. This detection scheme relies on the ability of Cu(II) ions to catalyze the leaching of gold at room temperature in the presence of thiosulfate species and ammonia. This simple and cost-effective probe provides rapid detection of Cu(II) ions at concentrations as low as 10 ppm. A similar detection method using AuNPs in ammonia-free thiosulfate solution is also viable at moderate reaction temperature (50?°C). The ammonia-free method also leads to marked damping and red-shifting of the surface plasmon resonance signal of the AuNP dispersion. The two methods clearly differ in the nature of the surface plasmon damping phenomenon, and their working mechanisms are plausibly explained based on the experimental investigations.

Tripathy, Suraj Kumar; Woo, Ju Yeon; Han, Chang-Soo

2012-08-01

117

'Naked-eye' detection of fluoride and acetate anions by using simple and efficient urea and thiourea based colorimetric sensors  

NASA Astrophysics Data System (ADS)

Simple and efficient sensors 1 and 2 possessing azo and nitrophenyl as signaling units and urea and thiourea moieties as binding sites were designed and synthesized. These sensors were characterized by combination of 1H, 13C, APT, COSY NMR, FTIR, elemental analysis, and UV-vis spectral data. The interaction and colorimetric sensing properties of receptor 1 and 2 with different anions were investigated by the naked eye, as well as UV-visible and 1H NMR experiments. It was found that the receptor 1 and 2 are highly selective toward fluoride and acetate anions in CHCl3.

Okudan, Ahmet; Erdemir, Serkan; Kocyigit, Ozcan

2013-09-01

118

A Highly Selective Turn-On Colorimetric, Red Fluorescent Sensor for Detecting Mobile Zinc in Living Cells  

PubMed Central

We describe ZRL1, a turn-on colorimetric and red fluorescent zinc ion sensor. The Zn2+-promoted ring opening of the rhodamine spirolactam ring in ZRL1 evokes a 220-fold fluorescence turn-on response. In aqueous media, ZRL1 turn-on luminescence is highly selective for Zn2+ ions, with no significant response to other competitive cations, including Na+, K+, Ca2+, Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Cd2+, or Hg2+. In addition to these characteristics, preliminary results indicate that ZRL1 can be delivered to living cells and monitor changes in intracellular Zn2+ levels. PMID:21028775

Du, Pingwu; Lippard, Stephen J.

2010-01-01

119

Paper-based colorimetric array test strip for selective and semiquantitative multi-ion analysis: simultaneous detection of hg(2+), ag(+), and cu(2+).  

PubMed

A novel approach is presented in this article to qualitatively and semiquantitatively analyze multiple heavy metal ions simultaneously by a colorimetric array test strip. As a proof-of-concept application, a multi-ion analysis array test strip (for Hg(2+), Ag(+), and Cu(2+)) was fabricated through immobilizing five specifically responsive indicators in typical matrixes with tunable sensitivities. The as-obtained test strip shows not only high selectivity for Hg(2+), Ag(+), and Cu(2+), respectively, but also can be applied for their mixtures. The detection limit of the test strip is well below the Chinese wastewater discharge standard concentrations. Moreover, the array test strip demonstrates excellent anti-interference capability, detection, and production reproducibility, long-term storage stability, and real water sample applicability. PMID:25070403

Liu, Li; Lin, Hengwei

2014-09-01

120

Label-free colorimetric detection of trace atrazine in aqueous solution by using molecularly imprinted photonic polymers.  

PubMed

Based on the combination of colloidal-crystal templating and a molecular imprinting technique, a sensor platform for efficient detection of atrazine in aqueous solution has been developed. The sensor is characterized by a 3D-ordered interconnected macroporous structure in which numerous nanocavities derived from atrazine imprinting are distributed in the thin wall of the formed inverse polymer opal. Owing to the special hierarchical porous structure, the molecularly imprinted polymer opals (or molecularly imprinted photonic polymer; MIPP) allow rapid and ultrasensitive detection of the target analyte. The interconnected macropores are favorable for the rapid transport of atrazine in polymer films, whereas the inherent high affinity of nanocavites distributed in thin polymer walls allows MIPP to recognize atrazine with high specificity. More importantly, the atrazine recognition events of the created nanocavities can be directly transferred (label-free) into a readable optical signal through a change in Bragg diffraction of the ordered macropores array of MIPP and thereby induce color changes that can be detected by the naked eye. With this novel sensory system, direct, ultrasensitive (as low as 10(-8) ng mL(-1)), rapid (less than 30 s) and selective detection of atrazine with a broad concentration range varying from 10(-16) M to 10(-6) M in aqueous media is achieved without the use of label techniques and expensive instruments. PMID:19016562

Wu, Zhen; Tao, Cheng-an; Lin, Changxu; Shen, Dezhong; Li, Guangtao

2008-01-01

121

Molecular recognition and colorimetric detection of cholera toxin by poly(diacetylene) liposomes incorporating G{sub m1} ganglioside  

SciTech Connect

Molecular recognition sites on cell membranes serve as the main communication channels between the inside of a cell and its surroundings. Upon receptor binding, cellular messages such as ion channel opening or activation of enzymes are triggered. In this report, we demonstrate that artificial cell membranes made from conjugated lipid polymers (poly(diacetylene)) can, on a simple level, mimic membrane processes of molecular recognition and signal transduction. The ganglioside GM1 was incorporated into poly(diacetylene) liposomes. Molecular recognition of cholera toxin at the interface of the liposome resulted in a change of the membrane color due to conformational charges in the conjugated (ene-yne) polymer backbone. The `colored liposomes` might be used as simple colorimetric sensors for drug screening or as new tools to study membrane-membrane or membrane-receptor interactions. 21 refs., 3 figs.

Pan, J.J.; Charych, D. [Lawrence Berkeley Lab., CA (United States)] [Lawrence Berkeley Lab., CA (United States)

1997-03-19

122

Colorimetric detection with aptamer-gold nanoparticle conjugates coupled to an android-based color analysis application for use in the field.  

PubMed

The feasibility of using aptamer-gold nanoparticle conjugates (Apt-AuNPs) to design colorimetric assays for in the field detection of small molecules was investigated. An assay to detect cocaine was designed using two clones of a known cocaine-binding aptamer. The assay was based on the AuNPs difference in affinity for single-stranded DNA (non-binding) and double stranded DNA (target bound). In the first assay, a commonly used design was followed, in which the aptamer and target were incubated to allow binding followed by exposure to the AuNPs. Interactions between the non-bound analytes and the AuNPs surface resulted in a number of false positives. The assay was redesigned by incubating the AuNPs and the aptamer prior to target addition to passivate the AuNPs surface. The adsorbed aptamer was able to bind the target while preventing non-specific interactions. The assay was validated with a number of masking and cutting agents and other controlled substances showing minimal false positives. Studies to improve the assay performance in the field were performed, showing that assay activity could be preserved for up to 2 months. To facilitate the assay analysis, an android application for automatic colorimetric characterization was developed. The application was validated by challenging the assay with cocaine standards of different concentrations, and comparing the results to a conventional plate reader, showing outstanding agreement. Finally, the rapid identification of cocaine in mixtures mimicking street samples was demonstrated. This work established that Apt-AuNPs can be used to design robust assays to be used in the field. PMID:24607135

Smith, Joshua E; Griffin, Daniel K; Leny, Juliann K; Hagen, Joshua A; Chávez, Jorge L; Kelley-Loughnane, Nancy

2014-04-01

123

New colorimetric and fluorometric sensing strategy based on the anisotropic growth of histidine-mediated synthesis of gold nanoclusters for iodide-specific detection.  

PubMed

Iodide, as a biologically important anion, it remains a worthwhile yet challenging undertaking to find a sensitive and specific approach to provide a technically simple iodide detection. In this article, it was found that no other ions than iodide-induced anisotropic growth of gold nanocrystals (AuNCs) originated from a small molecule, histidine-mediated synthesis of AuNCs, were observed. Simultaneously, it is accompanied by the fluorescence quenching of AuNCs and the naked-eye visible color change. Therefore, a new colorimetric and fluorometric sensing strategy was developed for the iodide-specific detection. Compared with currently reported methods, the present one displays the advantages of the visual detection and simplicity. The quenched fluorescence and enhanced surface plasmon resonance absorbance were found to be proportional to the iodide concentration over the range of 0.8-60 and 1.2-50 ?M with a detection limit (3?) of 118 nM and 215 nM, respectively. PMID:23393644

Wang, Yifeng; Zhu, Haiyan; Yang, Xiaoming; Dou, Yao; Liu, Zhongde

2013-04-01

124

Rapid colorimetric sensing of tetracycline antibiotics with in situ growth of gold nanoparticles.  

PubMed

A colorimetric assay utilizing the formation of gold nanoparticles was developed to detect tetracycline antibiotics in fluidic samples. Tetracycline antibiotics showed the capability of directly reducing aurate salts into atomic gold which form gold nanoparticles spontaneously under proper conditions. The resulted gold nanoparticles showed characteristic plasmon absorbance at 526 nm, which can be visualized by naked eyes or with a spectrophotometer. UV-vis absorbance of the resulted gold nanoparticles is correlated directly with the concentrations of tetracycline antibiotics in the solution, allowing for quantitative colorimetric detection of tetracycline antibiotics. Reaction conditions, such as pH, temperature, reaction time, and ionic strength were optimized. Sensitivity of the colorimetric assay can be enhanced by the addition of gold nanoparticle seeds, a LOD as low as 20 ng mL(-1) can be achieved with the help of seed particles. The colorimetric assay showed minimum interference from ethanol, methanol, urea, glucose, and other antibiotics such as sulfonamides, amino glycosides etc. Validity of the method was also evaluated on urine samples spiked with tetracycline antibiotics. The method provides a broad spectrum detection method for rapid and sensitive detection of reductive substances such as tetracycline antibiotics in liquid and biological samples. PMID:25066722

Shen, Li; Chen, Jing; Li, Na; He, Pingli; Li, Zhen

2014-08-11

125

Colorimetric and dynamic light scattering detection of DNA sequences by using positively charged gold nanospheres: a comparative study with gold nanorods  

NASA Astrophysics Data System (ADS)

We introduce a new genosensing approach employing CTAB (cetyltrimethylammonium bromide)-coated positively charged colloidal gold nanoparticles (GNPs) to detect target DNA sequences by using absorption spectroscopy and dynamic light scattering. The approach is compared with a previously reported method employing unmodified CTAB-coated gold nanorods (GNRs). Both approaches are based on the observation that whereas the addition of probe and target ssDNA to CTAB-coated particles results in particle aggregation, no aggregation is observed after addition of probe and nontarget DNA sequences. Our goal was to compare the feasibility and sensitivity of both methods. A 21-mer ssDNA from the human immunodeficiency virus type 1 HIV-1 U5 long terminal repeat (LTR) sequence and a 23-mer ssDNA from the Bacillus anthracis cryptic protein and protective antigen precursor (pagA) genes were used as ssDNA models. In the case of GNRs, unexpectedly, the colorimetric test failed with perfect cigar-like particles but could be performed with dumbbell and dog-bone rods. By contrast, our approach with cationic CTAB-coated GNPs is easy to implement and possesses excellent feasibility with retention of comparable sensitivity—a 0.1 nM concentration of target cDNA can be detected with the naked eye and 10 pM by dynamic light scattering (DLS) measurements. The specificity of our method is illustrated by successful DLS detection of one-three base mismatches in cDNA sequences for both DNA models. These results suggest that the cationic GNPs and DLS can be used for genosensing under optimal DNA hybridization conditions without any chemical modifications of the particle surface with ssDNA molecules and signal amplification. Finally, we discuss a more than two-three-order difference in the reported estimations of the detection sensitivity of colorimetric methods (0.1 to 10-100 pM) to show that the existing aggregation models are inconsistent with the detection limits of about 0.1-1 pM DNA and that other explanations should be developed.

Pylaev, T. E.; Khanadeev, V. A.; Khlebtsov, B. N.; Dykman, L. A.; Bogatyrev, V. A.; Khlebtsov, N. G.

2011-07-01

126

Sensitive and specific colorimetric dot assay to detect eastern equine encephalomyelitis viral RNA in mosquitoes (Diptera: Culicidae) after polymerase chain reaction amplification.  

PubMed

A sensitive and specific colorimetric dot assay following polymerase chain reaction (PCR) method has been developed to detect 0.1 pg of eastern equine encephalomyelitis viral (EEEV) RNA. The assay is 250-fold more sensitive than analysis by electrophoresis and is based on converting a 291-nucleotide sequence of the viral coat protein amino terminus into a double-stranded DNA (dsDNA) and amplifying the DNA using a specific primer pair and PCR. The amplified complementary DNA (cDNA) is denatured adsorbed onto a nylon strip, baked, and detected with a digoxigenin-labeled probe. Dots with viral cDNA are stained dark red, whereas controls do not stain or stain lightly. The assay is very specific and sensitive and detects only EEEV. RNA of Venezuelan equine encephalitis, St. Louis encephalitis, Keystone, Flanders, Tensaw, and western equine encephalitis viruses were not detected. EEEV (Ten Broeck) RNA was detected at the 10-ng level, indicating that the prototype we used may have different nucleotides in the region where the primer pair binds. The PCR amplified EEEV cDNA that was 92% homologous to the consensus sequence of EEEV. The detection of EEEV in the liver of an infected Emu bird and in field-collected mosquitoes from Florida and Massachusetts that were analyzed concurrently as blind samples by tissue culture plaque assay and by PCR dot analysis proved that the assay is sensitive and can be used to detect infected mosquitoes. The assay can detect at least 1 infected mosquito in a pool of 1,000 uninfected mosquitoes. PMID:7869341

Armstrong, P; Borovsky, D; Shope, R E; Morris, C D; Mitchell, C J; Karabatsos, N; Komar, N; Spielman, A

1995-01-01

127

Doped colorimetric assay liposomes  

DOEpatents

The present invention provides compositions comprising colorimetric assay liposomes. The present invention also provides methods for producing colorimetric liposomes and calorimetric liposome assay systems. In preferred embodiments, these calorimetric liposome systems provide high levels of sensitivity through the use of dopant molecules. As these dopants allow the controlled destabilization of the liposome structure, upon exposure of the doped liposomes to analyte(s) of interest, the indicator color change is facilitated and more easily recognized.

Charych, Deborah (Albany, CA); Stevens, Raymond C. (Albany, CA)

2001-01-01

128

A simple green route to prepare stable silver nanoparticles with pear juice and a new selective colorimetric method for detection of cysteine.  

PubMed

In this work, a new cost-effective, rapid and simple method for the preparation of stable silver nanoparticles (AgNPs) was developed, which can be completed within 15 minutes at room temperature by oxidizing the reductants in pear juice with AgNO3. Compared with the most used citrate-capped AgNPs, the as-prepared AgNPs showed high stability, good biocompatibility and enhanced antibacterial activity. Based on the formation of Ag-S covalent bonds between cysteine and AgNPs as well as the electrostatic interaction of COO(-) and NH4(+) between cysteine molecules, which selectively lead to the aggregation of the as-prepared AgNPs and give a specific yellow-to-red colour change, a new selective colorimetric method for detection of cysteine was proposed with the as-prepared AgNPs by coupling the decrease of the characteristic localized surface plasmon resonance (LSPR) absorption at 406 nm of the as-prepared AgNPs and the increase of the new aggregation-induced band at 530 nm. The ratio of the absorbance at 530 nm to 406 nm (A530/A406) was found to be linearly dependent on the cysteine concentrations in the range of 5.0 × 10(-7) to 1.0 × 10(-5) M with a limit of detection of 6.8 × 10(-8) M. PMID:23869382

Huang, Jing Tao; Yang, Xiao Xi; Zeng, Qiao Ling; Wang, Jian

2013-09-21

129

4-(8-Quinolyl)amino-7-nitro-2,1,3-benzoxadiazole as a new colorimetric probe for rapid and visual detection of Hg2+.  

PubMed

4-Amino-7-nitro-2,1,3-benzoxadiazole (ANBD) usually serves as a scaffold for developing fluorescent probes. In this paper, however, ANBD has been used as a chromogenic unit to design a new colorimetric probe, 4-(8-quinolyl)amino-7-nitro-2,1,3-benzoxadiazole (1), for rapid and visual detection of Hg(2+). The reaction of 1 with Hg(2+) in NaH(2)PO(4)-Na(2)HPO(4) buffer (pH 7.0) containing 70% (v/v) acetonitrile forms a 1:1 complex, accompanying a red shift of the absorption maximum from 482 nm to 557 nm and a distinct color change from orange to violet. Moreover the color reaction exhibits a high selectivity and sensitivity to Hg(2+) only, instead of other common metal ions. This behavior may be ascribed to the formation of a specific 1-Hg(2+) complex, which is supported by (1)H NMR titration experiments. The present study is not only a supplement to the detection method of Hg(2+), but also a merit to the chemistry of 4-amino-7-nitro-2,1,3-benzoxadiazole. PMID:23291198

Wang, Ke; Yang, Lixue; Zhao, Chuan; Ma, Huimin

2013-03-15

130

A Colorimetric Bioassay for Perchlorate  

NASA Astrophysics Data System (ADS)

Recognition of perchlorate (ClO4-) as a widespread contaminant across the United States and its potential adverse affects towards human health has motivated the EPA to place ClO4- on its contaminant candidate list for drinking water supplies. While a federal MCL has not yet been set, a recommended public health goal of 1 ppb (?g.L-1) was established by the US EPA in 2002. To date, methods of detection require use of sensitive ion chromatographic equipment that are expensive, time consuming, and require highly trained personnel for use. Our studies are focused on the development of a highly sensitive, simple, and robust colorimetric bioassay based on the primary enzyme involved in microbial ClO4- reduction, the perchlorate reductase (Pcr). A previously published assay used reduced methyl viologen (MV, the dye is reduced with sodium hydrosulfite) as an electron donor to demonstrate Pcr activity. The assay directly correlates the amount of MV oxidized with the amount of ClO4- reduced by assuming a transfer of four electrons. To test this assumption, we compared actual concentrations of MV oxidized to ClO4- reduced in this assay. ClO4- concentrations were determined using a Dionex ICS-500 ion chromatography system, while MV concentrations were determined using a standard curve generated at 578 nm. Comparisons between the two revealed that twelve molecules of MV were oxidized for each molecule of ClO4- reduced. The oxidation of these additional eight MV molecules is explained by the interaction of the dye with chlorite (the product of the Pcr reaction) and other contaminants that could be present in the enzyme prep. This unsettling result indicated this assay would be problematic for the detection of ClO4- in soil, which has many chemicals that could react with MV. To improve upon this assay, we have tried to reduce ClO4- using less reactive dyes and reductants. The reductants ascorbic acid, NADH, and dithiothreitol drive Pcr catalyzed ClO4- reduction, however, they are not effective unless an accompanying dye is used as a shuttle. N-methylphenazinium methosulfate (PMS) was selected as the most suitable dye because of its interaction with NADH, an oxygen stable reductant. In addition, the positive redox potential of PMS (E°' = +80 mV), makes it significantly less reactive than MV (E°' = -450 mV). A comparison of actual concentrations of ClO4- reduced vs. NADH oxidized show exactly four molecules of NADH oxidized for each molecule of ClO4- that is reduced (8 electrons). These studies have resulted in the successful development of a method that can accurately determine ClO4- concentrations with a small error using the enzyme Pcr and indicate the great potential for the ultimate development of a simple, robust, and highly sensitive colorimetric bioassay for perchlorate that can be widely used to screen laboratory and environmental samples .

Heinnickel, M. L.; Smith, S.; Coates, J. D.

2007-12-01

131

A simple cassette as point-of-care diagnostic device for naked-eye colorimetric bacteria detection.  

PubMed

Effective pathogen detection is necessary for treatment of infectious diseases. Point of care (POC) devices have tremendously improved the global human heath. However, design criteria for sample processing POC devices for pathogen detection in limited infrastructure are challenging and can make a significant contribution to global health by providing rapid and sensitive detection of bacteria in food, water, and patient samples. In this paper, we demonstrate a novel portable POC diagnostic device that is simple to assemble for genetic detection of bacterial pathogens by isothermal DNA amplification. The device is fabricated with very low production cost, using simple methods and easy-to-access materials on a flexible ribbon polyethylene substrate. We showed that the device is capable of detection of 30 CFU mL(-1) of E. coli and 200 CFU mL(-1) of S. aureus in less than 1 hour. Through numerical simulations, we estimated that the device can be extended to high-throughput detection simultaneously performing a minimum of 36 analyses. This robust and sensitive detection device can be assembled and operated by non-specialist personnel, particularly for multiple bacterial pathogen detections in low-resource settings. PMID:24300967

Safavieh, Mohammadali; Ahmed, Minhaz Uddin; Sokullu, Esen; Ng, Andy; Braescu, Liliana; Zourob, Mohammed

2014-01-21

132

A FRET-based ratiometric fluorescent and colorimetric probe for the facile detection of organophosphonate nerve agent mimic DCP.  

PubMed

A FRET ratiometric fluorescent probe enabling a fast and highly sensitive response to OP nerve agent mimic DCP within 1 min and with as low as 0.17 ppm concentration detection limit has been developed. Moreover, the probe exhibits noticeable color changes under UV light and even with the naked eye. It is also demonstrated that it can detect both liquid and gas nerve agents. PMID:24080856

Xuan, Weimin; Cao, Yanting; Zhou, Jiahong; Wang, Wei

2013-11-18

133

Dark Matter -- Possible Candidates and Direct Detection  

E-print Network

The cosmological observations coupled with theoretical calculations suggest the existence of enormous amount of unseen and unknown matter or dark matter in the universe. The evidence of their existence, the possible candidates and their possible direct detections are discussed.

Debasish Majumdar

2007-03-29

134

A Label Free Colorimetric Assay for the Detection of Active Botulinum Neurotoxin Type A by SNAP-25 Conjugated Colloidal Gold  

PubMed Central

Botulinum neurotoxins are one of the most potent toxins known to man. Current methods of detection involve the quantification of the toxin but do not take into account the percentage of the toxin that is active. At present the assay used for monitoring the activity of the toxin is the mouse bioassay, which is lengthy and has ethical issues due to the use of live animals. This report demonstrates a novel assay that utilises the endopeptidase activity of the toxin to detect Botulinum neurotoxin in a pharmaceutical sample. The cleaving of SNAP-25 is monitored via UV-Visible spectroscopy with a limit of detection of 373 fg/mL and has been further developed into a high throughput method using a microplate reader detecting down to 600 fg/mL of active toxin. The results show clear differences between the toxin product and the placebo, which contains the pharmaceutical excipients human serum albumin and lactose, showing that the assay detects the active form of the toxin. PMID:23925142

Halliwell, Jennifer; Gwenin, Christopher

2013-01-01

135

Direct Detection of Galactic Halo Dark Matter  

E-print Network

Direct Detection of Galactic Halo Dark Matter B. R. Oppenheimer,1 * N. C. Hambly,2 A. P. Digby,2 S detection of galactic halo dark matter. Dark matter in the spherical halo of the Milky Way galaxy has been as half of this "dark matter" may be in the form of old, very cool white dwarfs, the remnants

Oppenheimer, Ben R.

136

Portable sick house syndrome gas monitoring system based on novel colorimetric reagents for the highly selective and sensitive detection of formaldehyde.  

PubMed

Formaldehyde (HCHO) emitted from the furniture and the walls in the rooms injures the eyes, nose, and respiratory organs and causes allergies, which is called sick house syndrome. We designed and synthesized novel colorimetric HCHO-sensing molecules (KD-XA01 and KD-XA02) which possess an enaminone structure and developed a hand-held instrument to monitor indoor HCHO gas with the use of KD-XA01. These sensing molecules produced speedy color changes from colorless to yellow under mild conditions, which was caused by the fact that the enaminone structure in the reagent reacts with HCHO to give a lutidine derivative. This reaction took place not only in the solution phase but also in the solid phase (surface of the cellulose paper). To take advantage of this phenomena, a handy and rapid monitoring system has been developed for detecting indoor HCHO gas using a highly sensitive and selective detection tablet constructed from the porous cellulose paper that contains silica gel as an adsorbent, KD-XA01, and phosphoric acid under optimum conditions. This instrument detected the surface color change of the tablet from white to yellow, which was monitored as a function of the intensity of the reflected light illuminated by an LED (475 nm). The response was proportional to the HCHO concentration at a constant sampling time and flow rate; 0.05 ppm HCHO, which is under the standard value set by the World Health Organization, was able to be detected in 5 min. The detection limit was 0.005 ppm. This monitoring system was not interfered by carbonyl compounds such as acetaldehyde and acetone, alcohols, hydrocarbons, and typical gases such as carbon monoxide, carbon dioxide, nitrogen dioxide, etc., which contributes to the measurement of correct HCHO concentrations. It was possible to monitor the HCHO gas in the room of a new apartment and school using this instrument; the response values were in good agreement with those obtained by the standard DNPH method. This highly sensitive, selective, and handy HCHO gas monitor is widely applicable and convenient for users who are not specialists in this field. PMID:14717182

Suzuki, Yoshio; Nakano, Nobuo; Suzuki, Koji

2003-12-15

137

Median recoil direction as a WIMP directional detection signal  

SciTech Connect

Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP 'smoking gun'. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of {approx}2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

Green, Anne M. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Morgan, Ben [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)

2010-03-15

138

Detection of possible economically motivated adulterants in heparin sodium and low molecular weight heparins with a colorimetric microplate based assay.  

PubMed

Recently, we described a 96-well plate format assay for visual detection of oversulfated chondroitin sulfate A (OSCS) contamination in heparin samples based on a water-soluble cationic polythiophene polymer (3-(2-(N-(N'-methylimidazole))ethoxy)-4-methylthiophene (LPTP)) and heparinase digestion of heparin. Here, we establish the specificity of the LPTP/heparinase test with a unique set of reagents that define the structural requirements for significant LPTP chemosensor color change. For example, we observed a biphasic behavior of larger shifts to the red in the UV absorbance spectra with decreasing average molecular weight of heparin chains with a break below 12-mer chain lengths. In addition, the oversulfation of chondroitin sulfate A (CSA) to a partially (PSCS) or fully (OSCS) sulfated form caused progressively less red shift of LPTP solutions. Furthermore, glycosaminoglycans (GAGs) containing glucuronic acid caused distinct spectral patterns compared to iduronic acid containing GAGs. We applied the LPTP/heparinase test to detection of OSCS (?0.03% (w/w) visually or 0.01% using a plate reader) in 10 ?g amounts of low molecular weight heparins (LMWHs; i.e. dalteparin, tinzaparin, or enoxaparin). Furthermore, because other oversulfated GAGs are possible economically motivated adulterants (EMAs) in heparin sodium, we tested the capacity of the LPTP/heparinase assay to detect oversulfated dermatan sulfate (OSDS), heparin (OSH), and heparan sulfate (OSHS). These potential EMAs were visually detectable at a level of ?0.1% when spiked into heparin sodium. We conclude that the LPTP/heparinase test visually detects oversulfated GAGs in heparin sodium and LMWHs in a format potentially amenable to high-throughput screening. PMID:21819047

Sommers, Cynthia D; Keire, David A

2011-09-15

139

Au nanoparticles and polyaniline coated resin beads for simultaneous catalytic oxidation of glucose and colorimetric detection of the product.  

PubMed

In this letter, we report the synthesis of Au nanoparticles (NPs) and polyaniline (PANI) on the same cation-exchange resin beads and demonstrate their use in catalyzing the oxidation of glucose to gluconic acid by Au NPs and simultaneously in detecting the formation of the acid by the color change of PANI. The synthesis was carried out by exchanging the cations of the resins with HAuCl4 and anilinuium chloride and then reducing the metal ions by NaBH4 to produce Au NPs followed by polymerization of aniline using H2O2. The green emeraldine salt form of PANI thus obtained was treated with NaOH to be converted to blue emeraldine base before use. The deposition of Au NPs was confirmed by a change in color of the bead, visible spectroscopy, X-ray diffraction, and scanning electron microscopic measurements. On the other hand, the presence of PANI was confirmed by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. The formation of gluconic acid from glucose was confirmed by FTIR spectroscopy. We could detect the presence of glucose of a minimum 1.0 mM concentration in water, using the present method. Our experimental observations demonstrate the possibility of the incorporation of multifunctional components on the surfaces of resins for carrying out a chemical reaction as well as detection of the product. PMID:15723451

Majumdar, Gitanjali; Goswami, Mausumi; Sarma, Tridib Kumar; Paul, Anumita; Chattopadhyay, Arun

2005-03-01

140

Specific and sensitive colorimetric detection of Al3+ using 5-mercaptomethyltetrazole capped gold nanoparticles in aqueous solution.  

PubMed

Contamination of food and drinking water by health-risk levels of Al(3+) calls for convenient assays. Here, we report a method to visibly detect Al(3+) at room temperature. Firstly, the chelating ligand of 5-mercaptomethyltetrazole (MMT) was synthesized and modified on the surface of AuNPs through the strong Au-S interaction to form a MMT-AuNP probe, which can remain well-dispersed and stable in an aqueous solution for a long time. Upon the addition of Al(3+), the interparticle crosslinking induced aggregation (color change from red to blue) of MMT-AuNPs was triggered through the Al(3+)-MMT interaction. Under optimal conditions, the absorbance ratio (A620/A520) of MMT-AuNPs is linear within the Al(3+) concentration range from 1.0 to 10.0 ?M, and the detection limit (3?) was as low as 0.53 ?M. Moreover, an interference study showed that this MMT-AuNP probe discriminated Al(3+) from a wide range of environmentally dominant metal ions and anions. The practical utility of the new method was demonstrated by determining Al(3+) in several environmental water and human urine specimens, obtaining satisfactory results. Being a rapid, convenient and cost-effective method, it should become a powerful alternative to conventional methods for selective quantification of Al(3+) in routine laboratory practice or rapid on-site assay. PMID:24401419

Xue, Dingshuai; Wang, Hongyue; Zhang, Yanbin

2014-02-01

141

Disentangling Dark Matter Dynamics with Directional Detection  

SciTech Connect

Inelastic dark matter reconciles the DAMA anomaly with other null direct detection experiments and points to a non-minimal structure in the dark matter sector. In addition to the dominant inelastic interaction, dark matter scattering may have a subdominant elastic component. If these elastic interactions are suppressed at low momentum transfer, they will have similar nuclear recoil spectra to inelastic scattering events. While upcoming direct detection experiments will see strong signals from such models, they may not be able to unambiguously determine the presence of the subdominant elastic scattering from the recoil spectra alone. We show that directional detection experiments can separate elastic and inelastic scattering events and discover the underlying dynamics of dark matter models.

Lisanti, Mariangela; Wacker, Jay G.; /SLAC

2009-12-16

142

Directional detection of dark matter streams  

E-print Network

Directional detection of WIMPs, in which the energies and directions of the recoiling nuclei are measured, currently presents the only prospect for probing the local \\textit{velocity} distribution of Galactic dark matter. We investigate the extent to which future directional detectors would be capable of probing dark matter substructure in the form of streams. We analyse the signal expected from a Sagittarius-like stream and also explore the full parameter space of stream speed, direction, dispersion and density. Using a combination of non-parametric directional statistics, a profile likelihood ratio test and Bayesian parameter inference we find that within acceptable exposure times ($\\mathcal{O}(10)$ kg yr for cross sections just below the current exclusion limits) future directional detectors will be sensitive to a wide range of stream velocities and densities. We also examine and discuss the importance of the energy window of the detector.

O'Hare, Ciaran A J

2014-01-01

143

Novel colorimetric sensor for oral malodour.  

PubMed

Volatile sulphur compounds are the primary constituents of oral malodour. Quantitative tools for the detection of oral malodour are beneficial to evaluate the intensity of malodour, analyse its causes and monitor the effectiveness of customized treatments. We have developed an objective, cost effective, do-it-yourself colorimetric sensor for oral malodour quantification. The sensor consisted of a sensing solution, a gas sampling unit for collecting a known volume of mouth air and a photometric detector. The sensing solution was iodine and the depletion of iodine on reaction with hydrogen sulphide was detected colorimetrically using starch. The detection limit of the sensor is 0.05 microg L(-1) of hydrogen sulphide, which is fit-for-purpose for oral malodour detection in healthy subjects as well as halitosis patients. Volatile sulphur compounds in mouth air were quantified in healthy human volunteers using this portable sensor and the detected levels were in the range of 0.2-0.4 microg L(-1). There was a good correlation between the VSC levels detected by the colorimetric sensor and halimeter (R(2)=0.934). The developed sensor can be easily fabricated in the laboratory, and it shows high potential to be used as a clinical evaluation tool for oral malodour assessments. PMID:20113721

Alagirisamy, Nethaji; Hardas, Sarita S; Jayaraman, Sujatha

2010-02-19

144

Probing light WIMPs with directional detection experiments  

E-print Network

The CoGeNT and CRESST WIMP direct detection experiments have recently observed excesses of nuclear recoil events, while the DAMA/LIBRA experiment has a long standing annual modulation signal. It has been suggested that these excesses may be due to light mass, m_chi ~ 5-10 GeV, WIMPs. The Earth's motion with respect to the Galactic rest frame leads to a directional dependence in the WIMP scattering rate, providing a powerful signal of the Galactic origin of any recoil excess. We investigate whether direct detection experiments with directional sensitivity have the potential to observe this anisotropic scattering rate with the elastically scattering light WIMPs proposed to explain the observed excesses. We find that the number of recoils required to detect an anisotropic signal from light WIMPs at 5 sigma significance varies from 7 to more than 190 over the set of target nuclei and energy thresholds expected for directional detectors. Smaller numbers arise from configurations where the detector is only sensitive to recoils from the highest speed, and hence most anisotropic, WIMPs. However, the event rate above threshold is very small in these cases, leading to the need for large experimental exposures to accumulate even a small number of events. To account for this sensitivity to the tail of the WIMP velocity distribution, whose shape is not well known, we consider two exemplar halo models spanning the range of possibilities. We also note that for an accurate calculation the Earth's orbital speed must be averaged over. We find that the exposures required to detect 10 GeV WIMPs at a WIMP-proton cross-section of 10^-4 pb are of order 10^3 kg day for a 20 keV energy threshold, within reach of planned directional detectors. Lower WIMP masses require higher exposures and/or lower energy thresholds for detection.

Ben Morgan; Anne M. Green

2012-08-24

145

A label-free activatable aptamer probe for colorimetric detection of cancer cells based on binding-triggered in situ catalysis of split DNAzyme.  

PubMed

A novel label-free tailed hairpin-shaped activatable aptamer probe (THAAP) was developed by rationally integrating an aptamer and a split G-quadruplex into one sequence. Based on target recognition-triggered in situ catalysis of split DNAzyme, the THAAP strategy achieved a simple, fast, washing-free, specific and quantitative colorimetric assay of human leukemic CCRF-CEM cells. PMID:25037636

Shi, Hui; Li, Duo; Xu, Fengzhou; He, Xiaoxiao; Wang, Kemin; Ye, Xiaosheng; Tang, Jinlu; He, Chunmei

2014-09-01

146

Colorimetric redox-indicator methods for the rapid detection of multidrug resistance in Mycobacterium tuberculosis: a systematic review and meta-analysis  

Microsoft Academic Search

Objectives: With the spread of multidrug-resistant tuberculosis (MDR-TB) there is increasing demand for new accurate and cost-effective tools for rapid drug susceptibility testing (DST), particularly for developing countries. The reference standard method used today for DST is very slow and cumbersome. Colorimetric assays using redox indicators have been proposed to be used in low-resource countries as rapid alternative culture methods

Anandi Martin; Francoise Portaels; Juan Carlos Palomino

2007-01-01

147

DIRECTIONAL DETECTION OF FISSION-SPECTRUM NEUTRONS.  

SciTech Connect

Conventional neutron detectors consisting of {sup 3}He tubes surrounded by a plastic moderator can be quite efficient in detecting fission spectrum neutrons, but do not indicate the direction of the incident radiation. We have developed a new directional detector based on double proton recoil in two separated planes of plastic scintillators. This method allows the spectrum of the neutrons to be measured by a combination of peak amplitude in the first plane and time of flight to the second plane. It also allows the determination of the angle of scattering in the first plane. If the planes are position-sensitive detectors, then the direction of the scattered neutron is known, and the direction of the incident neutron can be determined to lie on a cone of s fixed angle. The superposition of many such cones generates an image that indicates the presence of a localized source. Typical background neutron fluences from the interaction of cosmic rays with the atmosphere are low and fairly uniformly distributed in angle. Directional detection helps to locate a manmade source in the presence of natural background. Monte Carlo simulations are compared with experimental results.

VANIER,P.E.

2007-05-04

148

Direct optical nanoscopy with axially localized detection  

E-print Network

Evanescent light excitation is widely used in super-resolution fluorescence microscopy to confine light and reduce background noise. Herein we propose a method of exploiting evanescent light in the context of emission. When a fluorophore is located in close proximity to a medium with a higher refractive index, its near-field component is converted into light that propagates beyond the critical angle. This so-called Supercritical Angle Fluorescence (SAF) can be captured using a hig-NA objective and used to determine the axial position of the fluorophore with nanometer precision. We introduce a new technique for 3D nanoscopy that combines direct STochastic Optical Reconstruction Microscopy (dSTORM) imaging with dedicated detection of SAF emission. We demonstrate that our approach of a Direct Optical Nanoscopy with Axially Localized Detection (DONALD) yields a typical isotropic 3D localization precision of 20 nm.

Bourg, N; Dupuis, G; Barroca, T; Bon, P; Lécart, S; Fort, E; Lévêque-Fort, S

2014-01-01

149

Direct detection of dark matter polarizability  

E-print Network

We point out that the direct detection of dark matter via its electro-magnetic polarizability is described by two new nuclear form factors, which are controlled by the 2-nucleon nuclear density. The signature manifests a peculiar dependence on the atomic and mass numbers of the target nuclei, as well as on the momentum transfer, and can differ significantly from experiment to experiment. We also discuss UV completions of our scenario.

Ovanesyan, Grigory

2014-01-01

150

Direct detection submillimeter spectrometer for CCAT  

Microsoft Academic Search

We present a trade study for a submillimeter direct-detection spectrometer operating at the background limit for the Cornell Caltech Atacama Telescope (CCAT). In this study we compare the classical echelle spectrometer ZEUS with the waveguide grating spectrometer Z-Spec. The science driver for this instrument is spectroscopic investigation of high redshift galaxies as their far-IR fine structure line emission is redshifted

Thomas Nikola; Gordon J. Stacey; C. Matt Bradford

2008-01-01

151

Direct detection of dark matter polarizability  

E-print Network

We point out that the direct detection of dark matter via its electro-magnetic polarizability is described by two new nuclear form factors, which are controlled by the 2-nucleon nuclear density. The signature manifests a peculiar dependence on the atomic and mass numbers of the target nuclei, as well as on the momentum transfer, and can differ significantly from experiment to experiment. We also discuss UV completions of our scenario.

Grigory Ovanesyan; Luca Vecchi

2014-10-02

152

Direct detection submillimeter spectrometer for CCAT  

NASA Astrophysics Data System (ADS)

We present a trade study for a submillimeter direct-detection spectrometer operating at the background limit for the Cornell Caltech Atacama Telescope (CCAT). In this study we compare the classical echelle spectrometer ZEUS with the waveguide grating spectrometer Z-Spec. The science driver for this instrument is spectroscopic investigation of high redshift galaxies as their far-IR fine structure line emission is redshifted into the telluric submillimeter windows. The baseline detector consists of SQUID multiplexed TES bolometers and the ideal spectrometer to detect weak lines from distant extragalactic sources is a grating with a resolution of ~103 and a large bandwidth, covering an entire telluric submillimeter window instantaneously. Since the density of high-z sources on the sky is ~100 within a 10'×10' field of view and a redshift range of ?z~0.2 we also explore multi-object (~50 objects) capability, including articulated mirrors and flexible waveguide fibers.

Nikola, Thomas; Stacey, Gordon J.; Bradford, C. Matt

2008-07-01

153

Direct Electron Detection And Imaging Using CCD  

E-print Network

The purpose of this project is to investigate the use of charge couple devices (CCDs) to detect electrons directly. This can be done in transmission electron microscopy (TEM) for electrons over 100 KeV, but for space plasma instruments, lower energies are of interest. At the entrance surface of a back illuminated CCD, there is an insensitive layer of oxide and silicon. This layer needs to be kept as thin as possible, in order to detect the electrons of interest, which have short absorption depths. Following analysis of the parameters, we are going to measure the least amount of energy we can detect from electron interaction with the thinned layer. The detection process is simulated by combining two separate models: First: Mulasses, using Geant4, to simulate the interaction of the incident electron with the silicon, giving the energy absorption as a function of depth; Second A model from Stern et al. of the charge collection efficiency as a function of depth. Combining these models gives a measure of the charge collected as a function of incident electron energy, which is the relationship of interest.

S. R. Mirfayzi

2012-10-09

154

Miniature laser direct-detection radar  

NASA Astrophysics Data System (ADS)

A miniature laser with a total volume less than 15 cu cm and weight less than 100 g has been designed, fabricated, and assembled. The laser uses a composite rod consisting of Nd:Cr:GSGG material rod cladded with an Er:Cr:YSGG tube. The laser provides output at 1 and 3 micron wavelengths. The size and weight reduction is obtained by chemical pumping which eliminates the prime power and the power supply. The laser is used as an illuminator in a direct detection radar.

Acharekar, Madhu; Lebeau, Robert

1992-06-01

155

Complementarity of dark matter direct detection targets  

SciTech Connect

We investigate the reconstruction capabilities of the dark matter mass and spin-independent cross section from future ton-scale direct detection experiments using germanium, xenon, or argon as targets. Adopting realistic values for the exposure, energy threshold, and resolution of dark matter experiments which will come online within 5 to 10 years, the degree of complementarity between different targets is quantified. We investigate how the uncertainty in the astrophysical parameters controlling the local dark matter density and velocity distribution affects the reconstruction. For a 50 GeV WIMP, astrophysical uncertainties degrade the accuracy in the mass reconstruction by up to a factor of {approx}4 for xenon and germanium, compared to the case when astrophysical quantities are fixed. However, the combination of argon, germanium, and xenon data increases the constraining power by a factor of {approx}2 compared to germanium or xenon alone. We show that future direct detection experiments can achieve self-calibration of some astrophysical parameters, and they will be able to constrain the WIMP mass with only very weak external astrophysical constraints.

Pato, Miguel [Institute for Theoretical Physics, University of Zuerich, Winterthurerst. 190, 8057 Zuerich CH (Switzerland); Institut d'Astrophysique de Paris, UMR 7095-CNRS, University Pierre and Marie Curie, 98bis Bd Arago 75014 Paris (France); Dipartimento di Fisica, Universita degli Studi di Padova, via Marzolo 8, I-35131, Padova (Italy); Baudis, Laura [Physics Institute, University of Zuerich, Winterthurerst. 190, 8057 Zuerich CH (Switzerland); Bertone, Gianfranco [Institute for Theoretical Physics, University of Zuerich, Winterthurerst. 190, 8057 Zuerich CH (Switzerland); Institut d'Astrophysique de Paris, UMR 7095-CNRS, University Pierre and Marie Curie, 98bis Bd Arago 75014 Paris (France); Ruiz de Austri, Roberto [Instituto de Fisica Corpuscular, IFIC-UV/CSIC, Valencia (Spain); Strigari, Louis E. [Kavli Institue for Particle Astrophysics and Cosmology, Stanford University, Stanford, California, 94305 (United States); Trotta, Roberto [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)

2011-04-15

156

The Earth's velocity for direct detection experiments  

E-print Network

The Earth's velocity relative to the Sun in galactic coordinates is required in the rate calculation for direct detection experiments. We provide a rigorous derivation of this quantity to first order in the eccentricity of the Earth's orbit. We also discuss the effect of the precession of the equinoxes, which has hitherto received little explicit discussion. Comparing with other expressions in the literature, we confirm that the expression of Lee, Lisanti and Safdi is correct, while the expression of Lewin and Smith, the de facto standard expression, contains an error. For calculations of the absolute event rate, the leading order expression is sufficient while for modulation searches, an expression with the eccentricity is required for accurate predictions of the modulation phase.

Christopher McCabe

2013-12-04

157

EXTRAGALACTIC DARK MATTER AND DIRECT DETECTION EXPERIMENTS  

SciTech Connect

Recent astronomical data strongly suggest that a significant part of the dark matter content of the Local Group and Virgo Supercluster is not incorporated into the galaxy halos and forms diffuse components of these galaxy clusters. A portion of the particles from these components may penetrate the Milky Way and make an extragalactic contribution to the total dark matter containment of our Galaxy. We find that the particles of the diffuse component of the Local Group are apt to contribute {approx}12% to the total dark matter density near Earth. The particles of the extragalactic dark matter stand out because of their high speed ({approx}600 km s{sup -1}), i.e., they are much faster than the galactic dark matter. In addition, their speed distribution is very narrow ({approx}20 km s{sup -1}). The particles have an isotropic velocity distribution (perhaps, in contrast to the galactic dark matter). The extragalactic dark matter should provide a significant contribution to the direct detection signal. If the detector is sensitive only to the fast particles (v > 450 km s{sup -1}), then the signal may even dominate. The density of other possible types of the extragalactic dark matter (for instance, of the diffuse component of the Virgo Supercluster) should be relatively small and comparable with the average dark matter density of the universe. However, these particles can generate anomaly high-energy collisions in direct dark matter detectors.

Baushev, A. N., E-mail: baushev@gmail.com [DESY, D-15738 Zeuthen (Germany); Institut fuer Physik und Astronomie, Universitaet Potsdam, D-14476 Potsdam-Golm (Germany)

2013-07-10

158

A novel and efficient colorimetric chemosensor for detection and determination of biologically important ions in DMSO/H2O media using bromo pyrogallol red chemosensors with analytical applications.  

PubMed

An efficient colorimetric chemosensor with bromo pyrogallol red (BPR) as an easily available dye demonstrated a high chromogenic selectivity for Fe(3+) over other cations with detection limit of 5.1 ?mol L(-1). The complex of Fe(3+) with BPR displayed ability to detect of up to 4.4 and 25.6 ?mol L(-1) for acetate (AcO(-)) and benzoate ions (BzO(-)) in DMSO/H(2)O (9:1 v/v) media respectively over a large number of other anions. Both processes proceeded with distinct visual color changes in DMSO/H(2)O (9:1 v/v). The linear dynamic ranges for the determinations of Fe(3+), AcO(-) and BzO(-) were 2.5-24.0, 2.5-20.5 and 28.0-42.0 ?g mL(-1) respectively. This chemosensor was successfully applied for the determination of Fe(3+) and of carboxylate anions in environmental samples. This is the first article of a chemosensor capable of detecting both Fe(3+) and anions (AcO(-) and BzO(-)) using single detection method in a single cell. PMID:22847073

Tavallali, Hossein; Deilamy Rad, Gohar; Parhami, Abolfath; Abbasiyan, Elham

2012-10-01

159

Colorimetric Disposable Paper Coated with ZnO@ZnS Core-Shell Nanoparticles for Detection of Copper Ions in Aqueous Solutions.  

PubMed

In this study, we have proposed a new nanoparticle-containing test paper sensor that could be used as an inexpensive, easy-to-use, portable, and highly selective sensor to detect Cu(2+) ions in aqueous solutions. This disposable paper sensor is based on ZnO@ZnS core-shell nanoparticles. The core-shell nanoparticles were synthesized using a chemical method and then they were used for coating the paper. The synthesis of the ZnO@ZnS core-shell nanoparticles was performed at a temperature as low as 60 °C, and so far this is the lowest temperature for the synthesis of such core-shell nanoparticles. The sensitivity of the paper sensor was investigated for different Cu(2+) ion concentrations in aqueous solutions and the results show a direct linear relation between the Cu(2+) ions concentration and the color intensity of the paper sensor with a visual detection limit as low as 15 ?M (?0.96 ppm). Testing the present paper sensor on real river turbulent water shows a maximum 5% relative error for determining the Cu(2+) ions concentration, which confirms that the presented paper sensor can successfully be used efficiently for detection in complex solutions with high selectivity. Photographs of the paper sensor taken using a regular digital camera were transferred to a computer and analyzed by ImageJ Photoshop software. This finding demonstrates the potential of the present disposable paper sensor for the development of a portable, accurate, and selective heavy metal detection technology. PMID:25275616

Sadollahkhani, Azar; Hatamie, Amir; Nur, Omer; Willander, Magnus; Zargar, Behrooz; Kazeminezhad, Iraj

2014-10-22

160

DMTPC: a new apparatus for directional detection of Dark Matter  

E-print Network

Directional detection of Dark Matter allows for unambiguous direct detection of WIMPs as well as discrimination between various Dark Matter models in our galaxy. The DMTPC detector is a low-pressure TPC with optical readout designed for directional direct detection of WIMPs. By using CF4 gas as the active material, the detector also has excellent sensitivity to spin-dependent interactions of Dark Matter on protons.

G. Sciolla; A. Lee; J. Battat; T. Caldwell; B. Cornell; D. Dujmic; P. Fisher; S. Henderson; R. Lanza; J. Lopez; A. Kaboth; G. Kohse; J. Monroe; T. Sahin; R . Vanderspek; R. Yamamoto; H. Yegoryan; S. Alhen; D. Avery; K. Otis; A. Roccaro; H. Tomita; A. Dushkin; H. Wellenstein

2008-10-01

161

CCMR: VOC Capture on Fibrous Substrates: Colorimetric Sensors  

NSDL National Science Digital Library

Volatile Organic Compounds (VOCs) such as chloroform, toluene and trichloroethylene can cause health hazards and affect indoor air quality. Therefore, cost effective and reusable sensors for the detection of these volatile gases are required. In this study, the potential use of diacetylene monomers as colorimetric sensors combined with electrospinning is investigated in order to develop sensor membranes from biodegradable Polylactic Acid (PLA).

Molina, Anna M.

2007-08-29

162

Colorimetric barbiturate sensing with hybrid spin crossover assemblies.  

PubMed

Spin crossover complexes based on either iron(II) or iron(III) give a colorimetric response upon self-assembly with barbituric acids. They can be used as visible sensors for these narcotics, selectively detecting barbiturates in the presence of other biologically-relevant hydrogen bonding species. PMID:24715100

Young, Michael C; Liew, Erica; Hooley, Richard J

2014-05-21

163

DIRECTIONAL DETECTION OF A NEUTRON SOURCE.  

SciTech Connect

Advantages afforded by the development of new directional neutron detectors and imagers are discussed. Thermal neutrons have mean free paths in air of about 20 meters, and can be effectively imaged using coded apertures. Fission spectrum neutrons have ranges greater than 100 meters, and carry enough energy to scatter at least twice in multilayer detectors which can yield both directional and spectral information. Such strategies allow better discrimination between a localized spontaneous fission source and the low, but fluctuating, level of background neutrons generated by cosmic rays. A coded aperture thermal neutron imager will be discussed as well as a proton-recoil double-scatter fast-neutron directional detector with time-of-flight energy discrimination.

VANIER, P.E.; FORMAN, L.

2006-10-23

164

Paper-based colorimetric immunosensor for visual detection of carcinoembryonic antigen based on the high peroxidase-like catalytic performance of ZnFe2O4-multiwalled carbon nanotubes.  

PubMed

A new paper-based colorimetric immunosensor for the detection of carcinoembryonic antigen (CEA) was developed based on the intrinsic peroxidase activity of ZnFe2O4-multiwalled carbon nanotubes (ZnFe2O4@MWNTs). The immunosensor platform was prepared by depositing chitosan and porous gold onto filter paper and entrapping the primary antibodies (Ab1) onto the layers. Secondary antibodies (Ab2) were assembled on the surface of the functionalized ZnFe2O4@MWNTs. The immunosensor response was quantified as a color change resulting from ZnFe2O4@MWNTs catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H2O2. The catalytic performance of ZnFe2O4@MWNTs was higher than ZnFe2O4 due to the high electrical conductance of MWNTs, moreover, the electron communications between ZnFe2O4@MWNTs and substrates are electrically "wired". Detection was achieved by measuring the color change when the concentrations of CEA were different. The color change can be quantified with the naked eye but a digitalized picture can also be used to provide more sensitive comparison to a calibrated color scheme. This method was simple for CEA detection with a linear range from 0.005 to 30 ng mL(-1) and a detection limit of 2.6 pg mL(-1). Such an equipment-free immunoassay has great potential in resource-limited environments. PMID:24205509

Liu, Weiyan; Yang, Hongmei; Ding, Yanan; Ge, Shenguang; Yu, Jinghua; Yan, Mei; Song, Xianrang

2014-01-01

165

Direct Detection of Exoplanets J.-L. Beuzit  

E-print Network

Direct Detection of Exoplanets J.-L. Beuzit Laboratoire d'Astrophysique de Grenoble D. Mouillet of Michigan, Ann Arbor Direct detection of exoplanets from the ground is now within reach of existing. These methods will provide qualitatively new information about exoplanets, including spectroscopic data

Paris-Sud XI, Université de

166

ccsd00003303, Dark Matter Direct Detection using Cryogenic  

E-print Network

ccsd­00003303, version 1 ­ 17 Nov 2004 Dark Matter Direct Detection using Cryogenic Detectors. Solving the Dark Matter enigma represents one of the key objectives of contemporary physics. Recent Matter gap, and direct detection Dark Matter experiments have recently reached sensitivities allowing

167

Direct detection searches for axion dark matter  

NASA Astrophysics Data System (ADS)

The axion is both a compelling dark matter candidate and provides an elegant solution to the strong CP problem. The axion haloscope technique has the potential to detect dark matter axions. ADMX (the Axion Dark Matter eXperiment) is an implementation of the axion haloscope technique, and has undergone a series of sensitivity-improving upgrades. With the impending addition of a dilution refrigerator, ADMX is poised to search a large region of plausible dark matter axion masses. Meanwhile, a number of other axion experimental techniques are being considered to explore other axion masses relevant to dark matter.

Rybka, Gray

2014-09-01

168

Direct detection of momentum flux in atomic and molecular beams  

Microsoft Academic Search

We describe the use of a microphone for detection of atomic and molecular beams in a high-vacuum environment. Two experiments were carried out to demonstrate this detection method. Pulsed beams of argon were detected using a conventional electret microphone where the output of the microphone was displayed directly on an oscilloscope or processed with a boxcar averager to remove the

J. G. Choi; J. S. Hayden; M. T. O’Connor; G. J. Diebold

1981-01-01

169

Direct and Indirect Detection of Dark Matter  

NASA Astrophysics Data System (ADS)

The gravitationally required dark matter may consist of three components: hadronic, hot, and cold, each requiring specific detection techniques. Since visible matter is <1% of the universe critical density, but 2--8% is allowed by nucleosynthesis, much of the missing hadronic matter is likely to be in the form of objects between 10(-7) and 10(-1) solar masses. These are being searched for by microlensing using ~ 10(7) stars in the LMC as sources. Hot dark matter has to be deduced from terrestrial non-accelerator and accelerator neutrino experiments. Cold dark matter (CDM) in the form of axions is being searched for via conversion to microwave photons in a magnetic field. If the CDM is made up of WIMPs, the massive particles may annihilate in the sun or earth and produce neutrinos which can be detected underground. Alternatively, these particles can hit detector nuclei underground and the recoil energy measured in the form of ionization and phonons. The status of all these experiments will be discussed.

Caldwell, D. O.

1993-05-01

170

Colorimetric method for phase evaluation.  

PubMed

Measurements of very small phase changes in optical measurement techniques are usually performed with interferometric methods that are based on evaluation of interference patterns, which correspond to a phase change of the investigated wave field. If values of the phase change are small, it is difficult to determine accurately the phase values, and one needs very expensive measurement systems. We present a simple method for evaluation of small phase variations that uses the interference of polychromatic light. The phase change affects the color of the interference pattern, and the color of the interference pattern corresponds to a specific phase change that can be evaluated using colorimetric analysis. We describe and analyze our colorimetric phase evaluation method. The proposed method offers accurate results, and it may be suitable for practical utilization in the optical industry. PMID:16604772

Miks, Antonin; Novak, Jiri; Novak, Pavel

2006-04-01

171

Measurement of microbial activity in soil by colorimetric observation of in situ dye reduction: an approach to detection of extraterrestrial life  

Microsoft Academic Search

BACKGROUND: Detecting microbial life in extraterrestrial locations is a goal of space exploration because of ecological and health concerns about possible contamination of other planets with earthly organisms, and vice versa. Previously we suggested a method for life detection based on the fact that living entities require a continual input of energy accessed through coupled oxidations and reductions (an electron

Ronald L Crawford; Andrzej Paszczynski; Qingyong Lang; Daniel P Erwin; Lisa Allenbach; Giancarlo Corti; Tony J Anderson; I Francis Cheng; Chien Wai; Bruce Barnes; Richard Wells; Touraj Assefi; Mohammad Mojarradi

2002-01-01

172

A one-step colorimetric method of analysis detection of Hg2+ based on an in situ formation of Au@HgS core-shell structures.  

PubMed

A new approach for the detection of Hg(2+) is reported based on color changes from which gold nanoparticles (Au NPs) are surrounded by a layer of HgS quantum dots to form in situ Au@HgS core-shell nanostructures. The surface plasmon resonance (SPR) absorption of the gold core was changed due to a shell layer of HgS formed on the surface of the Au NPs, which brings the colour change of the aqueous solution. Therefore, Hg(2+) can be recognized by visualizing the colour change of the Au@HgS core-shell nanostructures, and can be detected quantitatively by measurement of the UV-vis spectra. Some effects on the detection of Hg(2+) were investigated in detail. This method was used to detect Hg(2+) with excellent selectivity and high sensitivity. In our method, the lowest detected concentrations for mercury ions were 5.0 × 10(-6) M observed by the naked eye and 0.486 nM as measured by UV-vis spectra. At the range from 8.0 × 10(-5) to 1.0 × 10(-8) M of Hg(2+), this method was shown to have a good linear relationship. PMID:21611650

Zhang, Fuqiang; Zeng, Leyong; Yang, Cui; Xin, Junwei; Wang, Haiyan; Wu, Aiguo

2011-07-01

173

Colorimetric detection of copper and chloride in DMSO/H?O media using bromopyrogallol red as a chemosensor with analytical applications.  

PubMed

We report bromopyrogallol red (BPR) as an easily available dye for detection of copper and chloride with distinct visual color changes in DMSO/H(2)O (9:1 v/v). The chemosensor has a high chromogenic selectivity for Cu(2+) over other cations with detection limit of 0.07 ?g mL(-1). The obtained complex of Cu(2+) with BPR displayed ability to detect Cl(-) up to 0.79 ?g mL(-1) in DMSO/H(2)O (9:1v/v) media over a large number of other anions. The linear dynamic ranges for the determinations of Cu(2+) and Cl(-) were 0.53-14.60 and 6.00-36.00 ?g mL(-1), respectively. This receptor was successfully applied for the determination of Cl(-) and Cu(2+) in water samples. PMID:22750338

Tavallali, Hossein; Deilamy Rad, Gohar; Parhami, Abolfath; Abbasiyan, Elham

2012-11-01

174

Colorimetric detection of copper and chloride in DMSO/H2O media using bromopyrogallol red as a chemosensor with analytical applications  

NASA Astrophysics Data System (ADS)

We report bromopyrogallol red (BPR) as an easily available dye for detection of copper and chloride with distinct visual color changes in DMSO/H2O (9:1 v/v). The chemosensor has a high chromogenic selectivity for Cu2+ over other cations with detection limit of 0.07 ?g mL-1. The obtained complex of Cu2+ with BPR displayed ability to detect Cl- up to 0.79 ?g mL-1 in DMSO/H2O (9:1 v/v) media over a large number of other anions. The linear dynamic ranges for the determinations of Cu2+ and Cl- were 0.53-14.60 and 6.00-36.00 ?g mL-1, respectively. This receptor was successfully applied for the determination of Cl- and Cu2+ in water samples.

Tavallali, Hossein; Deilamy Rad, Gohar; Parhami, Abolfath; Abbasiyan, Elham

2012-11-01

175

Directional Local Contrast Based Blood Vessel Detection in Retinal Images  

Microsoft Academic Search

In this paper, we proposed a novel algorithm to detect blood vessels on retinal images. By using directional local contrast as its detection feature, our algorithm is highly sensitive, fast and accurate. The algorithm only needs integral computing with very simple parameter adjustments and highly suitable for parallelization. It is much more robust to illumination conditions than intensity based counterparts

Ming Zhang; Jyh-charn Liu

2007-01-01

176

A selective colorimetric and ratiometric fluorescent probe for hydrogen sulfide.  

PubMed

A reaction-based colorimetric and ratiometric fluorescent probe based on an ICT-strategy for selective detection of H(2)S that exploited the H(2)S-mediated reduction of nitrocompound to amines was explored. And it displayed high selectivity for H(2)S over other relevant reactive sulfur, oxygen, nitrogen species and other anions with more than 120 nm blue shift and the change of emission intensity ratio inducted by H(2)S was over 4750. PMID:22965805

Wu, Ming-Yu; Li, Kun; Hou, Ji-Ting; Huang, Zheng; Yu, Xiao-Qi

2012-10-01

177

Directional Dark Matter Detection Beyond the Neutrino Bound Philipp Grothaus  

E-print Network

Directional Dark Matter Detection Beyond the Neutrino Bound Philipp Grothaus and Malcolm Fairbairn creates an irreducible background for direct dark matter experiments with sensitivities to WIMP the potential to study dark matter beyond the neutrino bound by fitting event distributions in multiple dimen

178

Direct Detection of Interstellar Neutrals from Earth Orbit  

Microsoft Academic Search

From December 2000 to early March 2001, the IMAGE Low Energy Neutral Atom (LENA) imager detected a temporally variable signal that had a peak count rate in the direction of the velocity vector of the Earth around the Sun. The direction of arrival and the timing of the signal are consistent with interstellar neutrals whose motion through the solar system

S. A. Fuselier; O. W. Lennartsson; A. G. Ghielmetti; M. R. Collier; T. E. Moore; D. Simpson; J. Quinn; E. Moebius; P. Wurz; D. Rucinski

2001-01-01

179

A "light-on" colorimetric assay for anion detection using the inhibitory effect of anions on the catalytic activity of metal nanoparticles for the degradation of methyl orange.  

PubMed

In this communication, we studied the inhibitory effects of anions on the catalytic activity of metal nanoparticles for the degradation of methyl orange (MO). Some anions have great affinity with specific metal nanoparticles, thus resulting in the change of surface state and inhibition of catalytic activity, which can be observed with the naked eye or manifested in the UV spectrum of MO for anion detection. PMID:25317955

Lu, Lixia; Yang, Fan; Yang, Xiurong

2014-10-27

180

Gold nanoparticle-based simple colorimetric and ultrasensitive dynamic light scattering assay for the selective detection of Pb(II) from paints, plastics, and water samples.  

PubMed

Pb (II) is a common water pollutant with high toxicity. According to the CDC, about 310,000 U.S. children of ages 1-5 have high levels of lead in their blood that it is due to the exposure to lead from plastic toys and other products. As a result, the development of ultrasensitive assays for the real-time detection of Pb(II) from plastic toys and paints is very important for water controlling, clinical toxicology and industrial processes. Driven by the need to detect trace amounts of Pb(II) from water samples, we report a label-free, highly selective and ultra sensitive glutathione modified gold nanoparticle based dynamic light scattering (DLS) probe for Pb(II) recognition in 100 ppt level from aqueous solution with excellent discrimination against other heavy metals. The sensitivity of our assay to detect Pb(II) level in water is almost 2 orders of magnitude higher than the EPA standard limit. We have also demonstrated that our DLS assay is capable of measuring the amount of Pb(II) in paint, plastic toys, and water from MS river. A possible mechanism and operating principles of our DLS assay have been discussed. Ultimately, this nanotechnology driven assay could have enormous potential applications in rapid, on-site monitoring of Pb(II) from day-to-day sample. PMID:21306127

Beqa, Lule; Singh, Anant Kumar; Khan, Sadia Afrin; Senapati, Dulal; Arumugam, Sri Ranjini; Ray, Paresh Chandra

2011-03-01

181

Simple colorimetric method determines uranium in tissue  

NASA Technical Reports Server (NTRS)

Simple colorimetric micromethod determines concentrations of uranium in tissue. The method involves dry ashing organic extraction, and colorimetric determination of uranyl ferrocyanide. This uranium determination technique could be used in agricultural research, tracer studies, testing of food products, or medical research.

Doran, D.; Frigerio, N. A.

1967-01-01

182

Fault detection of multivariable system using its directional properties  

E-print Network

properties of the MIMO systems such as the transmission zeros, input zero direction, output zero direction etc was utilized. Neither were the directional properties of MIMO systems utilized in the various previously developed popular fault detection... Invariant Zeros System Zeros 13 However throughout this present work the zeros refer to transmission zero satisfying the definitions provided by the MacFarlane and Karcanias in 1976. One fundamental difference between SISO and the MIMO system...

Pandey, Amit Nath

2006-04-12

183

Colorimetric phosphorescence measurements with a color camera for oxygen determination  

NASA Astrophysics Data System (ADS)

We developed a simple oxygen imaging platform with phosphorescent oxygen sensor films to demonstrate a quantitative oxygen determination method utilizing a color CCD camera. Phosphorescence quenching of a luminophore Pt(II) meso-tetrakis (pentafluorophenyl) porphyrin complex (PtTFPP) immobilized in poly (dimethylsiloxane) (PDMS) matrix, is the principal detection mechanism. This sensor material was cast to form a film on the bottom surface of a transparent Petri dish. As levels of dissolved oxygen increased, phosphorescence of the complex decreased, allowing for measurement of oxygen levels which developed in the sensor film. A camera with a charge-coupled device (CCD) was used in conjunction with processing software to quantify oxygen levels colorimetrically. Microscopic images were collected using a CCD camera and stored as a set of red/green/blue (RGB) images. Phosphorescence excitation (390 nm peak) is limited to the blue (B) pixels of the CCD chip, and these values were discarded; while retaining the oxygen-responsive phosphorescence emission (645 nm peak) almost identical with the response range of the red (R) pixels. Red pixel intensity analysis effectively extracts color intensity information, which can be in turn directly related to oxygen contents. Color CCD cameras allow simultaneous acquisition of many types of chemical information by combining the merits of digital imaging with the attributes of spectroscopic measurement. Therefore, use of color CCD cameras is considered as an inexpensive alternative to time-resolved imaging for relatively short-term monitoring.

Bhagwat, Prajakta; Achanta, Gowthami Satya; Henthorn, David; Kim, Chang-Soo

2011-05-01

184

Highly selective colorimetric detection and preconcentration of Bi(III) ions by dithizone complexes anchored onto mesoporous TiO2  

PubMed Central

We successfully developed a single-step detection and removal unit for Bi(III) ions based on dithizone (DZ) anchored on mesoporous TiO2 with rapid colorometric response and high selectivity for the first time. [(DZ)3-Bi] complex is easily separated and collected by mesoporous TiO2 as adsorbent and preconcentrator without any color change of the produced complex onto the surface of mesoporous TiO2 (TiO2-[(DZ)3-Bi]) at different Bi(III) concentrations. This is because highly potent mesoporous TiO2 architecture provides proficient channeling or movement of Bi(III) ions for efficient binding of metal ion, and the simultaneous excellent adsorbing nature of mesoporous TiO2 provides an extra plane for the removal of metal ions. PMID:24502680

2014-01-01

185

Can the Existence of Dark Energy be Directly Detected?  

SciTech Connect

The majority of astronomers and physicists accept the reality of dark energy and also believe that it can only be studied indirectly through observation of the motions of stars and galaxies. In this paper I open the experimental question of whether it is possible to directly detect dark energy through the presence of dark energy density. Two thirds of this paper outlines the major aspects of dark energy density as now comprehended by the astronomical and physics community. The final third summarizes various proposals for direct detection of dark energy density or its possible effects. At this time I do not have a fruitful answer to the question: Can the Existence of Dark Energy Be Directly Detected?

Perl, Martin L.; /SLAC /KIPAC, Menlo Park

2011-11-23

186

Halo Independent Direct Detection of Momentum-Dependent Dark Matter  

E-print Network

We show that the momentum dependence of dark matter interactions with nuclei can be probed in direct detection experiments without knowledge of the dark matter velocity distribution. This is one of the few properties of DM microphysics that can be determined with direct detection alone, given a signal of dark matter in multiple direct detection experiments with different targets. Long-range interactions arising from the exchange of a light mediator are one example of momentum-dependent DM. For data produced from the exchange of a massless mediator we find for example that the mediator mass can be constrained to be $\\lesssim 10$ MeV for DM in the 20-1000 GeV range in a halo-independent manner.

John F. Cherry; Mads T. Frandsen; Ian M. Shoemaker

2014-05-06

187

65 nm CMOS Sensors Applied to Mathematically Exact Colorimetric Reconstruction  

E-print Network

Extracting colorimetric image information from the spectral characteristics of image sensors is a key issue in accurate image acquisition. Technically feasible filter/sensor combinations usually do not replicate colorimetric responses with sufficient accuracy to be directly applicable to color representation. A variety of transformations have been proposed in the literature to compensate for this. However, most of those rely on heuristics and/or introduce a reconstruction dependent on the composition of the incoming illumination. In this work, we present a spectral reconstruction method that is independent of illumination and is derived in a mathematically strict way. It provides a deterministic method to arrive at a least mean squared error approximation of a target spectral characteristic from arbitrary sensor response curves. Further, we present a new CMOS sensor design in a standard digital 65nm CMOS technology. Novel circuit techniques are used to achieve performance comparable with much larger-sized spe...

Mayr, C; Krause, A; Schlüßler, J -U; Schüffny, R

2014-01-01

188

Direct detection of the current in a magnetotail flux rope  

SciTech Connect

The field-aligned current densities in the core of a magnetotail flux rope were directly detected with plasma instrumentation on board the Geotail spacecraft at a downstream distance of about 96 R{sub E} (Earth radii). The axis of the flux rope and the core magnetic fields were detected cross-tail, and the magnitudes of these core magnetic fields were similar to that in the magnetotail lobe at these distances. The radius of the core cross-section was about 0.7 R{sub E}, and the total current was 500,000 A. Together with a recently reported, similar measurement with the Galileo spacecraft these direct detections of current greatly strengthen the previous identifications in favor of flux ropes that were solely based on their magnetic signatures. The detection of the flux rope with the Geotail spacecraft occurred during a period of relative magnetic quiescence. 20 refs., 4 figs.

Frank, L.A.; Paterson, W.R.; Kokubun, S. [and others] [and others

1995-10-15

189

The Maximum Patch Method for Directional Dark Matter Detection  

E-print Network

Present and planned dark matter detection experiments search for WIMP-induced nuclear recoils in poorly known background conditions. In this environment, the maximum gap statistical method provides a way of setting more sensitive cross section upper limits by incorporating known signal information. We give a recipe for the numerical calculation of upper limits for planned directional dark matter detection experiments, that will measure both recoil energy and angle, based on the gaps between events in two-dimensional phase space.

Shawn Henderson; Jocelyn Monroe; Peter Fisher

2008-01-10

190

Direct detection of biotinylated proteins by mass spectrometry.  

PubMed

Mass spectrometric strategies to identify protein subpopulations involved in specific biological functions rely on covalently tagging biotin to proteins using various chemical modification methods. The biotin tag is primarily used for enrichment of the targeted subpopulation for subsequent mass spectrometry (MS) analysis. A limitation of these strategies is that MS analysis does not easily discriminate unlabeled contaminants from the labeled protein subpopulation under study. To solve this problem, we developed a flexible method that only relies on direct MS detection of biotin-tagged proteins called "Direct Detection of Biotin-containing Tags" (DiDBiT). Compared with conventional targeted proteomic strategies, DiDBiT improves direct detection of biotinylated proteins ?200 fold. We show that DiDBiT is applicable to several protein labeling protocols in cell culture and in vivo using cell permeable NHS-biotin and incorporation of the noncanonical amino acid, azidohomoalanine (AHA), into newly synthesized proteins, followed by click chemistry tagging with biotin. We demonstrate that DiDBiT improves the direct detection of biotin-tagged newly synthesized peptides more than 20-fold compared to conventional methods. With the increased sensitivity afforded by DiDBiT, we demonstrate the MS detection of newly synthesized proteins labeled in vivo in the rodent nervous system with unprecedented temporal resolution as short as 3 h. PMID:25117199

Schiapparelli, Lucio Matias; McClatchy, Daniel B; Liu, Han-Hsuan; Sharma, Pranav; Yates, John R; Cline, Hollis T

2014-09-01

191

A colorimetric "naked-eye" Cu(II) chemosensor and pH indicator in 100% aqueous solution.  

PubMed

A new, highly selective and sensitive colorimetric chemosensor 1 for detection of Cu(2+) ions in aqueous solution was developed. Receptor 1 detected Cu(2+) ions by changing its color from colorless to yellow. Moreover, the Cu(2+)-sensitive compound was used as a colorimetric pH detector based on a color change due to 1-Cu(2+) complex formation identifiable by the naked eye. PMID:24599223

Noh, Jin Young; Park, Gyeong Jin; Na, Yu Jeong; Jo, Hyun Yong; Lee, Seul Ah; Kim, Cheal

2014-04-21

192

Direct detection of the inflationary gravitational wave background  

E-print Network

Inflation generically predicts a stochastic background of gravitational waves over a broad range of frequencies, from those accessible with cosmic microwave background (CMB) measurements, to those accessible directly with gravitational-wave detectors, like NASA's Big-Bang Observer (BBO) or Japan's Deci-Hertz Interferometer Gravitational-wave Observer (DECIGO), both currently under study. Here we investigate the detectability of the inflationary gravitational-wave background at BBO/DECIGO frequencies. To do so, we survey a range of slow-roll inflationary models consistent with constraints from the CMB and large-scale structure (LSS). We go beyond the usual assumption of power-law power spectra, which may break down given the 16 orders of magnitude in frequency between the CMB and direct detection, and solve instead the inflationary dynamics for four classes of inflaton potentials. Direct detection is possible in a variety of inflationary models, although probably not in any in which the gravitational-wave signal does not appear in the CMB polarization. However, direct detection by BBO/DECIGO can help discriminate between inflationary models that have the same slow-roll parameters at CMB/LSS scales.

Tristan L. Smith; Marc Kamionkowski; Asantha Cooray

2005-06-17

193

Generalized Halo Independent Comparison of Direct Dark Matter Detection Data  

E-print Network

We extend the halo-independent method to compare direct dark matter detection data, so far used only for spin-independent WIMP-nucleon interactions, to any type of interaction. As an example we apply the method to magnetic moment interactions.

Eugenio Del Nobile; Graciela Gelmini; Paolo Gondolo; Ji-Haeng Huh

2013-06-21

194

Analysis of the theoretical bias in dark matter direct detection  

NASA Astrophysics Data System (ADS)

Fitting the model ''A'' to dark matter direct detection data, when the model that underlies the data is ``B'', introduces a theoretical bias in the fit. We perform a quantitative study of the theoretical bias in dark matter direct detection, with a focus on assumptions regarding the dark matter interactions, and velocity distribution. We address this problem within the effective theory of isoscalar dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle. We analyze 24 benchmark points in the parameter space of the theory, using frequentist and Bayesian statistical methods. First, we simulate the data of future direct detection experiments assuming a momentum/velocity dependent dark matter-nucleon interaction, and an anisotropic dark matter velocity distribution. Then, we fit a constant scattering cross section, and an isotropic Maxwell-Boltzmann velocity distribution to the simulated data, thereby introducing a bias in the analysis. The best fit values of the dark matter particle mass differ from their benchmark values up to 2 standard deviations. The best fit values of the dark matter-nucleon coupling constant differ from their benchmark values up to several standard deviations. We conclude that common assumptions in dark matter direct detection are a source of potentially significant bias.

Catena, Riccardo

2014-09-01

195

Direct detection of the inflationary gravitational-wave background  

SciTech Connect

Inflation generically predicts a stochastic background of gravitational waves over a broad range of frequencies, from those accessible with cosmic microwave background (CMB) measurements, to those accessible directly with gravitational-wave detectors, like NASA's Big-Bang Observer (BBO) or Japan's Deci-Hertz Interferometer Gravitational-wave Observer (DECIGO), both currently under study. Here we investigate the detectability of the inflationary gravitational-wave background at BBO/DECIGO frequencies. To do so, we survey a range of slow-roll inflationary models consistent with constraints from the CMB and large-scale structure (LSS). We go beyond the usual assumption of power-law power spectra, which may break down given the 16 orders of magnitude in frequency between the CMB and direct detection, and solve instead the inflationary dynamics for four classes of inflaton potentials. Direct detection is possible in a variety of inflationary models, although probably not in any in which the gravitational-wave signal does not appear in the CMB polarization. However, direct detection by BBO/DECIGO can help discriminate between inflationary models that have the same slow-roll parameters at CMB/LSS scales.

Smith, Tristan L.; Kamionkowski, Marc [California Institute of Technology, Mail Code 130-33, Pasadena, California 91125 (United States); Cooray, Asantha [California Institute of Technology, Mail Code 130-33, Pasadena, California 91125 (United States); Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697 (United States)

2006-01-15

196

Source Direction Detection based on Stationary Electronic Nose System  

Microsoft Academic Search

Electronic nose (array of chemical sensors) are widely used in food industry and pollution control. Also it could be used to locate or detect the direction of the source of emission odors. Usually this task is performed by electronic nose (ENose) cooperated with mobile vehicles, but when a source is instantaneous or surrounding is hard for vehicles to reach, problem

Jie Cai; David C. Levy

2006-01-01

197

Synchronization Helps Robots to Detect Black Holes in Directed Graphs  

E-print Network

Synchronization Helps Robots to Detect Black Holes in Directed Graphs Adrian Kosowski1,2 , Alfredo, pinotti}@dmi.unipg.it Abstract. The paper considers a team of robots which has to explore a graph G where some nodes can be harmful. Robots are initially located at the so called home base node. The dangerous

Pinotti, Maria Cristina

198

Analysis of the theoretical bias in dark matter direct detection  

E-print Network

Fitting the model "A" to dark matter direct detection data, when the model that underlies the data is "B", introduces a theoretical bias in the fit. We perform a quantitative study of the theoretical bias in dark matter direct detection, with a focus on assumptions regarding the dark matter interactions, and velocity distribution. We address this problem within the effective theory of isoscalar dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle. We analyze 24 benchmark points in the parameter space of the theory, using frequentist and Bayesian statistical methods. First, we simulate the data of future direct detection experiments assuming a momentum/velocity dependent dark matter-nucleon interaction, and an anisotropic dark matter velocity distribution. Then, we fit a constant scattering cross section, and an isotropic Maxwell-Boltzmann velocity distribution to the simulated data, thereby introducing a bias in the analysis. The best fit values of the dark matter particle mass differ from their benchmark values up to 2 standard deviations. The best fit values of the dark matter-nucleon coupling constant differ from their benchmark values up to several standard deviations. We conclude that common assumptions in dark matter direct detection are a source of potentially significant bias.

Riccardo Catena

2014-07-01

199

Stokes vector direct detection for short-reach optical communication.  

PubMed

We propose the Stokes vector direct detection (SV-DD) scheme which simultaneously achieves receiver phase diversity and the cancellation of photodetection nonlinearity. An 80??Gb/s single-polarization modulated SV-DD signal is successfully received after 160 km SSMF transmission with 11.64??bit/s/Hz electrical spectrum efficiency. PMID:24875989

Che, Di; Li, An; Chen, Xi; Hu, Qian; Wang, Yifei; Shieh, William

2014-06-01

200

Channel simulation for direct detection optical communication systems  

NASA Technical Reports Server (NTRS)

A technique is described for simulating the random modulation imposed by atmospheric scintillation and transmitter pointing jitter on a direct detection optical communication system. The system is capable of providing signal fading statistics which obey log normal, beta, Rayleigh, Ricean or chi-squared density functions. Experimental tests of the performance of the Channel Simulator are presented.

Tycz, M.; Fitzmaurice, M. W.

1974-01-01

201

Channel simulation for direct-detection optical communication systems  

NASA Technical Reports Server (NTRS)

A technique is described for simulating the random modulation imposed by atmospheric scintillation and transmitter pointing jitter on a direct-detection optical communication system. The system is capable of providing signal fading statistics which obey log-normal, beta, Rayleigh, Ricean, or chi-square density functions. Experimental tests of the performance of the channel simulator are presented.

Tycz, M.; Fitzmaurice, M. W.

1974-01-01

202

Directed energy active illumination for near-Earth object detection  

NASA Astrophysics Data System (ADS)

On 15 February 2013, a previously unknown ~20 m asteroid struck Earth near Chelyabinsk, Russia, releasing kinetic energy equivalent to ~570 kt TNT. Detecting objects like the Chelyabinsk impactor that are orbiting near Earth is a difficult task, in part because such objects spend much of their own orbits in the direction of the Sun when viewed from Earth. Efforts aimed at protecting Earth from future impacts will rely heavily on continued discovery. Ground-based optical observatory networks and Earth-orbiting spacecraft with infrared sensors have dramatically increased the pace of discovery. Still, less than 5% of near-Earth objects (NEOs) >=100 m/~100 Mt TNT have been identified, and the proportion of known objects decreases rapidly for smaller sizes. Low emissivity of some objects also makes detection by passive sensors difficult. A proposed orbiting laser phased array directed energy system could be used for active illumination of NEOs, enhancing discovery particularly for smaller and lower emissivity objects. Laser fiber amplifiers emit very narrow-band energy, simplifying detection. Results of simulated illumination scenarios are presented based on an orbiting emitter array with specified characteristics. Simulations indicate that return signals from small and low emissivity objects is strong enough to detect. The possibility for both directed and full sky blind surveys is discussed, and the resulting diameter and mass limits for objects in different observational scenarios. The ability to determine both position and speed of detected objects is also discussed.

Riley, Jordan; Lubin, Philip; Hughes, Gary B.; O'Neill, Hugh; Meinhold, Peter; Suen, Jonathan; Bible, Johanna; Johansson, Isabella E.; Griswold, Janelle; Cook, Brianna

2014-09-01

203

Direct Detection of Sub-GeV Dark Matter  

SciTech Connect

Direct detection strategies are proposed for dark matter particles with MeV to GeV mass. In this largely unexplored mass range, dark matter scattering with electrons can cause single-electron ionization signals, which are detectable with current technology. Ultraviolet photons, individual ions, and heat are interesting alternative signals. Focusing on ionization, we calculate the expected dark matter scattering rates and estimate the sensitivity of possible experiments. Backgrounds that may be relevant are discussed. Theoretically interesting models can be probed with existing technologies, and may even be within reach using ongoing direct detection experiments. Significant improvements in sensitivity should be possible with dedicated experiments, opening up a window to new regions in dark matter parameter space.

Essig, Rouven; Mardon, Jeremy; Volansky, Tomer

2012-03-20

204

Colorimetric Analysis of Ammonia in Water.  

National Technical Information Service (NTIS)

An accurate, reliable method of determing concentration of ammonia in water solution was developed using colorimetric techniques. The procedure involves formation of a colored complex of ammonia with 2,5-dimethoxyoxolane and (E)-p-dimethylamino-cinnamalde...

F. W. Carson, R. L. Gross

1977-01-01

205

Colorimetric Correction for Stereoscopic Camera Arrays  

E-print Network

, i.e. gain, brightness or shutter speed may not solve the problem. Moreover, the camera response between multiple cameras of a camera array. 2 Related Work The problem of transferring the colorimetric

Paris-Sud XI, Université de

206

Directional dark matter detection beyond the neutrino bound  

NASA Astrophysics Data System (ADS)

Coherent scattering of solar, atmospheric, and diffuse supernovae neutrinos creates an irreducible background for direct dark matter experiments with sensitivities to WIMP-nucleon spin-independent scattering cross sections of 10-46-10-48 cm2, depending on the WIMP mass. Even if one could eliminate all other backgrounds, this "neutrino floor" will limit future experiments with projected sensitivities to cross sections as small as 10-48 cm2. Direction-sensitive detectors have the potential to study dark matter beyond the neutrino bound by fitting event distributions in multiple dimensions: recoil kinetic energy, recoil track angle with respect to the sun, and event time. This work quantitatively explores the impact of direction sensitivity on the neutrino bound in dark matter direct detection.

Grothaus, Philipp; Fairbairn, Malcolm; Monroe, Jocelyn

2014-09-01

207

Sensitive colorimetric visualization of perfluorinated compounds using poly(ethylene glycol) and perfluorinated thiols modified gold nanoparticles.  

PubMed

In this work, we have developed a novel sensing strategy employing mixed poly(ethylene glycol)-terminated (PEG-thiols) and perfluoroalkyl-terminated (F-thiols) alkanethiols modified gold nanoparticles (Au@PEG-F NPs) as a probe to detect perfluorinated compounds (PFCs) from water samples. PEG-thiols with high density and long carbon chains make the Au NPs probe well-dispersed in solution and stable even in high concentration of salt solution; F-thiols provide specific fluorous-fluorous interactions to PFCs, which results in adsorption of PFCs on Au@PEG-F NPs. The adsorbed PFCs cause the aggregation of Au@PEG-F NPs probes and thus induce the insolubility of probes and precipitation directly from reaction solution due to the superhydrophobicity of perfluorocarbon monolayers, leading to color and absorbance response of the assay to PFCs. The preparation of the Au@PEG-F NPs probe is very simple, and the colorimetric assay based on this mechanism for the detection of PFCs is selective and convenient. Combined with UV-vis spectrophotometry, the assay demonstrates good sensitivities to PFCs with wide linear range. In the designed concentration range, the response of the colorimetric assay to long-chain PFCs (perfluoroalkyl chain ?7) is discerned even as the concentration of these PFCs is as low as 10 ?g L(-1). This low-cost and sensitive assay shows great potential to measure total PFCs in water samples. To the best of our knowledge, this is the first application of the specific fluorous-fluorous interactions and Au NPs based probes for colorimetric recognition for PFCs. PMID:24684731

Niu, Hongyun; Wang, Saihua; Zhou, Zhen; Ma, Yurong; Ma, Xunfeng; Cai, Yaqi

2014-05-01

208

Nanoparticle-catalyzed reductive bleaching for fabricating turn-off and enzyme-free amplified colorimetric bioassays.  

PubMed

Nanoparticle-catalyzed reductive bleaching reactions of colored substrates are emerging as a class of novel indicator reactions for fabricating enzyme-free amplified colorimetric biosensing (turn-off mode), which are exactly opposite to the commonly used oxidative coloring processes of colorless substrates in traditional enzyme-catalyzed amplified colorimetric bioassays (turn-on mode). In this work, a simple theoretical analysis shows that the sensitivity of this colorimetric bioassay can be improved by increasing the amplification factor (kcat?t), or enhancing the binding affinity between analyte and receptor (Kd), or selecting the colored substrates with high extinction coefficients (?). Based on this novel strategy, we have developed a turn-off and cost-effective amplified colorimetric thrombin aptasensor. This aptasensor made full use of sandwich binding of two affinity aptamers for increased specificity, magnetic particles for easy separation and enrichment, and gold nanoparticle (AuNP)-catalyzed reductive bleaching reaction to generate the amplified colorimetric signal. With 4-nitrophenol (4-NP) as the non-dye colored substrate, colorimetric bioassay of thrombin was achieved by the endpoint method with a detection limit of 91pM. In particular, when using methylene blue (MB) as the substrate, for the first time, a more convenient and efficient kinetic-based colorimetric thrombin bioassay was achieved without the steps of acidification termination and magnetic removal of particles, with a low detection limit of 10pM, which was superior to the majority of the existing colorimetric thrombin aptasensors. The proposed colorimetric protocol is expected to hold great promise in field analysis and point-of-care applications. PMID:23962710

Li, Wei; Qiang, Weibing; Li, Jie; Li, Hui; Dong, Yifan; Zhao, Yaju; Xu, Danke

2014-01-15

209

Future directions for H sub x O sub y detection  

NASA Technical Reports Server (NTRS)

The activities and recommendations of the NASA workshop on the Future Directions for H sub x O sub y detection are given. The objective of this workshop was to access future directions for the measurement of the OH radical as well as other H sub x O sub y species. The workshop discussions were focused by two broad questions: (1) What are the capabilities of potential measurement methods? and (2) Will the results from the most promising method be useful in furthering understanding of tropospheric chemistry?

Crosley, David R. (editor); Hoell, James M. (editor)

1986-01-01

210

An Automated Directed Spectral Search Methodology for Small Target Detection  

NASA Astrophysics Data System (ADS)

Much of the current efforts in remote sensing tackle macro-level problems such as determining the extent of wheat in a field, the general health of vegetation or the extent of mineral deposits in an area. However, for many of the remaining remote sensing challenges being studied currently, such as border protection, drug smuggling, treaty verification, and the war on terror, most targets are very small in nature - a vehicle or even a person. While in typical macro-level problems the objective vegetation is in the scene, for small target detection problems it is not usually known if the desired small target even exists in the scene, never mind finding it in abundance. The ability to find specific small targets, such as vehicles, typifies this problem. Complicating the analyst's life, the growing number of available sensors is generating mountains of imagery outstripping the analysts' ability to visually peruse them. This work presents the important factors influencing spectral exploitation using multispectral data and suggests a different approach to small target detection. The methodology of directed search is presented, including the use of scene-modeled spectral libraries, various search algorithms, and traditional statistical and ROC curve analysis. The work suggests a new metric to calibrate analysis labeled the analytic sweet spot as well as an estimation method for identifying the sweet spot threshold for an image. It also suggests a new visualization aid for highlighting the target in its entirety called nearest neighbor inflation (NNI). It brings these all together to propose that these additions to the target detection arena allow for the construction of a fully automated target detection scheme. This dissertation next details experiments to support the hypothesis that the optimum detection threshold is the analytic sweet spot and that the estimation method adequately predicts it. Experimental results and analysis are presented for the proposed directed search techniques of spectral image based small target detection. It offers evidence of the functionality of the NNI visualization and also provides evidence that the increased spectral dimensionality of the 8-band Worldview-2 datasets provides noteworthy improvement in results over traditional 4-band multispectral datasets. The final experiment presents the results from a prototype fully automated target detection scheme in support of the overarching premise. This work establishes the analytic sweet spot as the optimum threshold defined as the point where error detection rate curves -- false detections vs. missing detections -- cross. At this point the errors are minimized while the detection rate is maximized. It then demonstrates that taking the first moment statistic of the histogram of calculated target detection values from a detection search with test threshold set arbitrarily high will estimate the analytic sweet spot for that image. It also demonstrates that directed search techniques -- when utilized with appropriate scene-specific modeled signatures and atmospheric compensations -- perform at least as well as in-scene search techniques 88% of the time and grossly under-performing only 11% of the time; the in-scene only performs as well or better 50% of the time. It further demonstrates the clear advantage increased multispectral dimensionality brings to detection searches improving performance in 50% of the cases while performing at least as well 72% of the time. Lastly, it presents evidence that a fully automated prototype performs as anticipated laying the groundwork for further research into fully automated processes for small target detection.

Grossman, Stanley I.

211

Review of Dark Matter Direct Detection Using Cryogenic Detectors  

SciTech Connect

The direct detection of the Universe's Dark Matter is one of the key questions in particle astrophysics. Cryogenic based detectors offer advantages in low radioactive backgrounds, target mass, sensitivity to the small energy depositions and rejection of possible background sources. I will summarize the main experimental approaches, including both cryogenic crystal and liquid targets and the options pursued for their signal readout. Recent advances from around the world and prospects for future proposed experiments will be discussed.

Brink, P.L.; /SLAC

2012-06-13

212

Gif Lectures on direct detection of Dark Matter  

E-print Network

These notes cover some of the topics associated with direct detection of dark matter at an introductory level. The general principles of dark matter search are summarized. The current status of some experiments is described, with an emphasis on bolometric and noble liquid techniques. Plots and illustrations associated to these notes may be found on transparencies presented during the lecture, on the web site of Gif school 2009.

Eric Armengaud

2010-03-11

213

PCTS Workshop Dark Matter: Direct Detection and Theoretical Developments  

E-print Network

PCTS Workshop Dark Matter: Direct Detection and Theoretical Developments November 15-16, 2010:15 - 4:40 Kathryn Zurek: The light dark matter scenario 4:40 - 5:05 Paolo Gondolo: The role of channeling:20 - 2:30 Coffee break 2:30 - 2:55 Lisa Randall: Xogenesis and Weak Scale Dark Matter 2:55 - 3:20 Neal

Torquato, Salvatore

214

High-resolution direct-detection x-ray imagers  

Microsoft Academic Search

We report on a-Si direct detection x-ray image sensors with polycrystalline PbI2, and more recently with HgI2. The arrays have 100 micron pixel size and, we study those aspects of the detectors that mainly determine the DQE, such as sensitivity, effective fill factor, dark current noise, noise power spectrum, and x-ray absorption. Line spread function data show that in the

Steve E. Ready; Jeffrey T. Rahn; Marcelo Mulato; Kanai S. Shah; Paul R. Bennett; Ping Mei; Jeng-Ping Lu; Raj B. Apte; Jackson Ho; Koenraad Van Schuylenbergh; Francesco Lemmi; James B. Boyce; Per Nylen; Michael M. Schieber; Haim Hermon

2000-01-01

215

New method for analyzing dark matter direct detection data  

NASA Astrophysics Data System (ADS)

The experimental situation of dark matter direct detection has reached an exciting crossroads, with potential hints of a discovery of dark matter (DM) from the CDMS, CoGeNT, CRESST-II and DAMA experiments in tension with null results from xenon-based experiments such as XENON100 and LUX. Given the present controversial experimental status, it is important that the analytical method used to search for DM in direct detection experiments is both robust and flexible enough to deal with data for which the distinction between signal and background points is difficult, and hence where the choice between setting a limit or defining a discovery region is debatable. In this article we propose a novel (Bayesian) analytical method, which can be applied to all direct detection experiments and which extracts the maximum amount of information from the data. We apply our method to the XENON100 experiment data as a worked example, and show that firstly our exclusion limit at 90% confidence is in agreement with their own for the 225 live days data, but is several times stronger for the 100 live days data. Secondly we find that, due to the two points at low values of S1 and S2 in the 225 days data set, our analysis points to either weak consistency with low-mass dark matter or the possible presence of an unknown background. Given the null result from LUX, the latter scenario seems the more plausible.

Davis, Jonathan H.; Enßlin, Torsten; BÅ`hm, Céline

2014-02-01

216

Direct Imaging Detectability of Tidally Heated ExoMoons (THEM)  

NASA Astrophysics Data System (ADS)

Existing and planned ground and space-based telescopes are capable of directly imaging plausible tidally heated exomoons orbiting gas-giant exoplanets. Tidally heated exomoons can easily be far more luminous than their host exoplanet and as much as 0.001 as bright as the system's stellar primary. Because emission from exomoons can be powered by tidal forces, their luminosities are independent of their separations from the system's stellar primary. Furthermore, high surface temperatures can occur in systems that are billions of years old. Tidally heated exomoons may thus be far easier targets for direct imaging studies than giant exoplanets that must be both young and at a large projected separation (typically at least tens of AU) from their primary to be accessible to direct imaging currently. For example, the (warm) Spitzer Space Telescope and the next generation of ground based instruments could detect an exomoon roughly the size of the Earth at a temperature of ~600 K and a distance ~5 parsecs in IR bands; in more favorable cases, detections are possible at distances of tens of parsecs. Future mid-infrared space telescopes, such as JWST and SPICA, will be capable of directly imaging tidally heated exomoons around the nearest two dozen stars with brightness temperatures of ~300 K and sizes similar to the Earth orbiting beyond 10 AU at a 5 sigma confidence level in a 10^4 second integration. It is also possible that some already imaged exoplanets are actually tidally heated exomoons or blends of such objects with hot young planets. If THEM exist and are sufficiently common (and thus nearby), it may be easier to directly image an exomoon with surface conditions that allow the existence of liquid water than it will be to resolve an Earth-like planet in the classical Habitable Zone of its primary. Preliminary results of a search for THEM in Spitzer archival images of nearby stars indicate that these data are sufficient to allow the detection of plausible THEM.

Turner, E. L.; Peters, M. A.

2014-03-01

217

WIMP Dark Matter Direct-Detection Searches in Noble Gases  

E-print Network

Cosmological observations and the dynamics of the Milky Way provide ample evidence for an invisible and dominant mass component. This so-called dark matter could be made of new, colour and charge neutral particles, which were non-relativistic when they decoupled from ordinary matter in the early universe. Such weakly interacting massive particles (WIMPs) are predicted to have a non-zero coupling to baryons and could be detected via their collisions with atomic nuclei in ultra-low background, deep underground detectors. Among these, detectors based on liquefied noble gases have demonstrated tremendous discovery potential over the last decade. After briefly introducing the phenomenology of direct dark matter detection, I will review the main properties of liquefied argon and xenon as WIMP targets and discuss sources of background. I will then describe existing and planned argon and xenon detectors that employ the so-called single- and dual-phase detection techniques, addressing their complementarity and science...

Baudis, Laura

2014-01-01

218

WIMP Dark Matter Direct-Detection Searches in Noble Gases  

E-print Network

Cosmological observations and the dynamics of the Milky Way provide ample evidence for an invisible and dominant mass component. This so-called dark matter could be made of new, colour and charge neutral particles, which were non-relativistic when they decoupled from ordinary matter in the early universe. Such weakly interacting massive particles (WIMPs) are predicted to have a non-zero coupling to baryons and could be detected via their collisions with atomic nuclei in ultra-low background, deep underground detectors. Among these, detectors based on liquefied noble gases have demonstrated tremendous discovery potential over the last decade. After briefly introducing the phenomenology of direct dark matter detection, I will review the main properties of liquefied argon and xenon as WIMP targets and discuss sources of background. I will then describe existing and planned argon and xenon detectors that employ the so-called single- and dual-phase detection techniques, addressing their complementarity and science reach.

Laura Baudis

2014-08-19

219

(In)direct Detection of Boosted Dark Matter  

E-print Network

We initiate the study of novel thermal dark matter (DM) scenarios where present-day annihilation of DM in the galactic center produces boosted stable particles in the dark sector. These stable particles are typically a subdominant DM component, but because they are produced with a large Lorentz boost in this process, they can be detected in large volume terrestrial experiments via neutral-current-like interactions with electrons or nuclei. This novel DM signal thus combines the production mechanism associated with indirect detection experiments (i.e. galactic DM annihilation) with the detection mechanism associated with direct detection experiments (i.e. DM scattering off terrestrial targets). Such processes are generically present in multi-component DM scenarios or those with non-minimal DM stabilization symmetries. As a proof of concept, we present a model of two-component thermal relic DM, where the dominant heavy DM species has no tree-level interactions with the standard model and thus largely evades direct and indirect DM bounds. Instead, its thermal relic abundance is set by annihilation into a subdominant lighter DM species, and the latter can be detected in the boosted channel via the same annihilation process occurring today. Especially for dark sector masses in the 10 MeV-10 GeV range, the most promising signals are electron scattering events pointing toward the galactic center. These can be detected in experiments designed for neutrino physics or proton decay, in particular Super-K and its upgrade Hyper-K, as well as the PINGU/MICA extensions of IceCube. This boosted DM phenomenon highlights the distinctive signatures possible from non-minimal dark sectors.

Kaustubh Agashe; Yanou Cui; Lina Necib; Jesse Thaler

2014-05-28

220

(In)direct detection of boosted dark matter  

NASA Astrophysics Data System (ADS)

We initiate the study of novel thermal dark matter (DM) scenarios where present-day annihilation of DM in the galactic center produces boosted stable particles in the dark sector. These stable particles are typically a subdominant DM component, but because they are produced with a large Lorentz boost in this process, they can be detected in large volume terrestrial experiments via neutral-current-like interactions with electrons or nuclei. This novel DM signal thus combines the production mechanism associated with indirect detection experiments (i.e. galactic DM annihilation) with the detection mechanism associated with direct detection experiments (i.e. DM scattering off terrestrial targets). Such processes are generically present in multi-component DM scenarios or those with non-minimal DM stabilization symmetries. As a proof of concept, we present a model of two-component thermal relic DM, where the dominant heavy DM species has no tree-level interactions with the standard model and thus largely evades direct and indirect DM bounds. Instead, its thermal relic abundance is set by annihilation into a subdominant lighter DM species, and the latter can be detected in the boosted channel via the same annihilation process occurring today. Especially for dark sector masses in the 10 MeV–10 GeV range, the most promising signals are electron scattering events pointing toward the galactic center. These can be detected in experiments designed for neutrino physics or proton decay, in particular Super-K and its upgrade Hyper-K, as well as the PINGU/MICA extensions of IceCube. This boosted DM phenomenon highlights the distinctive signatures possible from non-minimal dark sectors.

Agashe, Kaustubh; Cui, Yanou; Necib, Lina; Thaler, Jesse

2014-10-01

221

Direct real-time detection of vapors from explosive compounds.  

PubMed

The real-time detection of vapors from low volatility explosives including PETN, tetryl, RDX, and nitroglycerine along with various compositions containing these substances was demonstrated. This was accomplished with an atmospheric flow tube (AFT) using a nonradioactive ionization source coupled to a mass spectrometer. Direct vapor detection was accomplished in less than 5 s at ambient temperature without sample preconcentration. The several seconds of residence time of analytes in the AFT provided a significant opportunity for reactant ions to interact with analyte vapors to achieve ionization. This extended reaction time, combined with the selective ionization using the nitrate reactant ions (NO3(-) and NO3(-)·HNO3), enabled highly sensitive explosives detection from explosive vapors present in ambient laboratory air. Observed signals from diluted explosive vapors indicated detection limits below 10 ppqv using selected ion monitoring (SIM) of the explosive-nitrate adduct at m/z 349, 378, 284, and 289 for tetryl, PETN, RDX, and NG, respectively. Also provided is a demonstration of the vapor detection from 10 different energetic formulations sampled in ambient laboratory air, including double base propellants, plastic explosives, and commercial blasting explosives using SIM for the NG, PETN, and RDX product ions. PMID:24090362

Ewing, Robert G; Clowers, Brian H; Atkinson, David A

2013-11-19

222

Direct Real-Time Detection of Vapors from Explosive Compounds  

SciTech Connect

The real-time detection of vapors from low volatility explosives including PETN, tetryl, RDX and nitroglycerine along with various compositions containing these substances is demonstrated. This was accomplished with an atmospheric flow tube (AFT) using a non-radioactive ionization source and coupled to a mass spectrometer. Direct vapor detection was demonstrated in less than 5 seconds at ambient temperature without sample pre-concentration. The several seconds of residence time of analytes in the AFT provides a significant opportunity for reactant ions to interact with analyte vapors to achieve ionization. This extended reaction time, combined with the selective ionization using the nitrate reactant ions (NO3- and NO3-•HNO3), enables highly sensitive explosives detection. Observed signals from diluted explosive vapors indicate detection limits below 10 ppqv using selected ion monitoring (SIM) of the explosive-nitrate adduct at m/z 349, 378, 284 and 289 for tetryl, PETN, RDX and NG respectively. Also provided is a demonstration of the vapor detection from 10 different energetic formulations, including double base propellants, plastic explosives and commercial blasting explosives using SIM for the NG, PETN and RDX product ions.

Ewing, Robert G.; Clowers, Brian H.; Atkinson, David A.

2013-10-03

223

Direct Imaging Detectability of Tidally Heated ExoMoons (THEM)  

NASA Astrophysics Data System (ADS)

Existing and planned ground and space based telescopes are capable of directly imaging plausible tidally heated exomoons orbiting gas-giant exoplanets. Tidally heated exomoons can plausibly be far more luminous than their host exoplanet and as much as 0.001 as bright as the system's stellar primary. Because emission from exomoons can be powered by tidal forces, their luminosities are independent of their separations from the system's stellar primary. Furthermore, high surface temperatures can occur in systems that are billions of years old. Tidally heated exomoons may thus be far easier targets for direct imaging studies than giant exoplanets which must be both young and at a large projected separation (typically at least tens of AU) from their primary to be accessible to direct imaging currently. For example, the (warm) Spitzer Space Telescope and the next generation of ground based instruments could detect an exomoon roughly the size of the Earth at a temperature of ~600 K and a distance ~5 parsecs in IR bands; in more favorable cases, detections are possible at distances of tens of parsecs. Future mid-infrared space telescopes, such as JWST and SPICA, will be capable of directly imaging tidally heated exomoons around the nearest two dozen stars with brightness temperatures of ~300 K and sizes similar to the Earth orbiting beyond 10 AU at a 5 sigma confidence level in a 10^4 second integration. If such exomoons exist and are sufficiently common (and thus nearby), it may be easier to directly image an exomoon with surface conditions that allow the existence of liquid water than it will be to resolve an Earth-like planet in the classical Habitable Zone from its primary.

Turner, Edwin L.; Peters, Mary Anne

2013-07-01

224

Direct detection of Black Holes via electromagnetic radiation  

E-print Network

Many black hole (BH) candidates exist, ranging from supermassive ($\\sim10^{6}$--$10^{10}$ M$_{\\odot}$) to stellar masses ($\\sim 1$--$100$ M$_{\\odot}$), all of them identified by indirect processes. Although there are no known candidate BHs with sub-stellar masses, these might have been produced in the primordial Universe. BHs emit radiation composed of photons, gravitons and, later in their lifes, massive particles. We explored the detection of such BHs with present day masses from $10^{-22}$ M$_{\\odot}$ to $10^{-11}$ M$_{\\odot}$. We determined the maximum distances ($d$) at which the current best detectors should be placed in order to identify such isolated BHs. Broadly, we conclude that in the visible and ultraviolet BHs can be directly detected at $d\\lesssim 10^7$ m while in the X-ray band the distances might reach $\\sim10^8$ m (of the order of the Earth-Moon distance) and in the $\\gamma$-ray band BHs might even be detected from as far as $\\sim 0.1$ pc. Since these results give us realistic hopes of direct...

Sobrinho, J L G

2014-01-01

225

Direct and indirect detection of dissipative dark matter  

E-print Network

We study the constraints from direct detection and solar capture on dark matter scenarios with a subdominant dissipative component. This dissipative dark matter component in general has both a symmetric and asymmetric relic abundance. Dissipative dynamics allow this subdominant dark matter component to cool, resulting in its partial or total collapse into a smaller volume inside the halo (e.g., a dark disk) as well as a reduced thermal velocity dispersion compared to that of normal cold dark matter. We first show that these features considerably relax the limits from direct detection experiments on the couplings between standard model (SM) particles and dissipative dark matter. On the other hand, indirect detection of the annihilation of the symmetric dissipative dark matter component inside the Sun sets stringent and robust constraints on the properties of the dissipative dark matter. In particular, IceCube observations force dissipative dark matter particles with mass above 50 GeV to either have a small coupling to the SM or a low local density in the solar system, or to have a nearly asymmetric relic abundance. Possible helioseismology signals associated with purely asymmetric dissipative dark matter are discussed, with no present constraints.

JiJi Fan; Andrey Katz; Jessie Shelton

2013-12-04

226

Toward Direct Detection of Hot Jupiters with Precision Closure Phase  

NASA Astrophysics Data System (ADS)

Direct detection of thermal emission from nearby hot Jupiters has greatly advanced our knowledge of extrasolar planets in recent years. Since hot Jupiter systems can be regarded as analogs of high-contrast binaries, ground-based infrared long-baseline interferometers have the potential to resolve them and detect their thermal emission with precision closure phase—a method that is immune to the systematic errors induced by the Earth's atmosphere. Here we present closure phase studies toward direct detection of nearby hot Jupiters using the CHARA interferometer array outfitted with the MIRC instrument. We find much larger systematic errors than expected in our observations, most likely caused by dispersion across different wavelengths. We also find that using higher spectral resolution modes (e.g., R=150) can significantly reduce the systematics. By combining all calibrators in an observing run together, we are able to roughly re-calibrate the lower spectral resolution data, allowing us to obtain upper limits of the star-planet contrast ratios of ? And b across the H band. The data also allow us to get a refined stellar radius of 1.625±0.011R?. Our best upper limit corresponds to a contrast ratio of 2.1×103:1 with 90% confidence level at 1.52?m, suggesting that we are starting to have the capability of constraining atmospheric models of hot Jupiters with interferometry.

Zhao, M.; Monnier, J. D.; Che, X.; Pedretti, E.; Thureau, N.

2014-09-01

227

Clustering and community detection in directed networks: A survey  

NASA Astrophysics Data System (ADS)

Networks (or graphs) appear as dominant structures in diverse domains, including sociology, biology, neuroscience and computer science. In most of the aforementioned cases graphs are directed - in the sense that there is directionality on the edges, making the semantics of the edges nonsymmetric as the source node transmits some property to the target one but not vice versa. An interesting feature that real networks present is the clustering or community structure property, under which the graph topology is organized into modules commonly called communities or clusters. The essence here is that nodes of the same community are highly similar while on the contrary, nodes across communities present low similarity. Revealing the underlying community structure of directed complex networks has become a crucial and interdisciplinary topic with a plethora of relevant application domains. Therefore, naturally there is a recent wealth of research production in the area of mining directed graphs - with clustering being the primary method sought and the primary tool for community detection and evaluation. The goal of this paper is to offer an in-depth comparative review of the methods presented so far for clustering directed networks along with the relevant necessary methodological background and also related applications. The survey commences by offering a concise review of the fundamental concepts and methodological base on which graph clustering algorithms capitalize on. Then we present the relevant work along two orthogonal classifications. The first one is mostly concerned with the methodological principles of the clustering algorithms, while the second one approaches the methods from the viewpoint regarding the properties of a good cluster in a directed network. Further, we present methods and metrics for evaluating graph clustering results, demonstrate interesting application domains and provide promising future research directions.

Malliaros, Fragkiskos D.; Vazirgiannis, Michalis

2013-12-01

228

Quantitative colorimetric measurement of cellulose degradation under microbial culture conditions.  

PubMed

We have developed a simple, rapid, quantitative colorimetric assay to measure cellulose degradation based on the absorbance shift of Congo red dye bound to soluble cellulose. We term this assay "Congo Red Analysis of Cellulose Concentration," or "CRACC." CRACC can be performed directly in culture media, including rich and defined media containing monosaccharides or disaccharides (such as glucose and cellobiose). We show example experiments from our laboratory that demonstrate the utility of CRACC in probing enzyme kinetics, quantifying cellulase secretion, and assessing the physiology of cellulolytic organisms. CRACC complements existing methods to assay cellulose degradation, and we discuss its utility for a variety of applications. PMID:22391973

Haft, Rembrandt J F; Gardner, Jeffrey G; Keating, David H

2012-04-01

229

Direct Detection of Gravity Waves from Neutron Stars  

E-print Network

In light of the discovery of the first-ever double pulsar system, PSR J0737-3039, we re-examine an earlier proposal to directly detect gravity waves from neutron stars, which was predicated on a hypothetical system almost identical to the later discovered double pulsar. We re-derive the effect in more detail, and confirm the initial estimate--sometimes doubted in the literature--that it includes a 1/b dependence, where b is the impact parameter of a pulsar with respect to its foreground, gravity-wave emitting, neutron star companion. A coherent modulation in pulsar time-of-arrival measurements of 10 nano-sec/sec is possible. A one-year intermittent experiment on an instrument comparable to the SKA could thus detect the exceedingly faint gravity waves from individual neutron stars.

Redouane Al Fakir; William G. Unruh

2008-05-24

230

Direct digital radiography for caries detection and analysis.  

PubMed

Recent developments in the field of electronic imaging have provided a new set of imaging tools for intra-oral imaging and clinical diagnosis. In this chapter, we review the general structure and characteristics of image sensors used in digital radiography and their application for clinical caries detection and analysis. An overview of the literature, comparing the diagnostic accuracy of digital and film-based radiography and the impact of image-processing methods, is provided. We also describe several approaches for quantitative assessment of radiographic images for caries detection and assessment. Examples include digital subtraction radiography, and 2-D and 3-D density profiling. To increase the accuracy and reduce observer variability the use of 3-D imaging and computer-aided diagnosis is presented as future direction for clinical caries diagnosis. PMID:10949832

Analoui, M; Stookey, G K

2000-01-01

231

Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength.  

PubMed

Broadband light sources play essential roles in diverse fields, such as high-capacity optical communications, optical coherence tomography, optical spectroscopy, and spectrograph calibration. Although a nonclassical state from spontaneous parametric down-conversion may serve as a quantum counterpart, its detection and characterization have been a challenging task. Here we demonstrate the direct detection of photon numbers of an ultrabroadband (110 nm FWHM) squeezed state in the telecom band centred at 1535 nm wavelength, using a superconducting transition-edge sensor. The observed photon-number distributions violate Klyshko's criterion for the nonclassicality. From the observed photon-number distribution, we evaluate the second- and third-order correlation functions, and characterize a multimode structure, which implies that several tens of orthonormal modes of squeezing exist in the single optical pulse. Our results and techniques open up a new possibility to generate and characterize frequency-multiplexed nonclassical light sources for quantum info-communications technology. PMID:24694515

Wakui, Kentaro; Eto, Yujiro; Benichi, Hugo; Izumi, Shuro; Yanagida, Tetsufumi; Ema, Kazuhiro; Numata, Takayuki; Fukuda, Daiji; Takeoka, Masahiro; Sasaki, Masahide

2014-01-01

232

Theoretical antineutrino detection, direction and ranging at long distances  

NASA Astrophysics Data System (ADS)

In this paper we introduce the concept of what we call “NUDAR” (NeUtrino Direction and Ranging), making the point that measurements of the observed energy and direction vectors can be employed to passively deduce the exact three-dimensional location and thermal power of geophysical and anthropogenic neutrino sources from even a single detector. Earlier studies have presented the challenges of long-range detection, dominated by the unavoidable inverse-square falloff in neutrinos, which force the use of kiloton scale detectors beyond a few kilometers. Earlier work has also presented the case for multiple detectors, and has reviewed the background challenges. We present the most precise background estimates to date, all handled in full three dimensions, as functions of depth and geographical location. For the present calculations, we consider a hypothetical 138 kiloton detector which can be transported to an ocean site and deployed to an operational depth. We present a Bayesian estimation framework to incorporate any a priori knowledge of the reactor that we are trying to detect, as well as the estimated uncertainty in the background and the oscillation parameters. Most importantly, we fully employ the knowledge of the reactor spectrum and the distance-dependent effects of neutrino oscillations on such spectra. The latter, in particular, makes possible determination of range from one location, given adequate signal statistics. Further, we explore the rich potential of improving detection with even modest improvements in individual neutrino direction determination. We conclude that a 300 MWth reactor can indeed be geolocated, and its operating power estimated with one or two detectors in the hundred kiloton class at ranges out to a few hundred kilometers. We note that such detectors would have natural and non-interfering utility for scientific studies of geo-neutrinos, neutrino oscillations, and astrophysical neutrinos. This motivates the development of cost effective methods of constructing and deploying such next generation detectors.

Jocher, Glenn R.; Bondy, Daniel A.; Dobbs, Brian M.; Dye, Stephen T.; Georges, James A.; Learned, John G.; Mulliss, Christopher L.; Usman, Shawn

2013-06-01

233

Direct detection of alpha synuclein oligomers in vivo  

PubMed Central

Background Rat models of Parkinson’s disease are widely used to elucidate the mechanisms underlying disease etiology or to investigate therapeutic approaches. Models were developed using toxins such as MPTP or 6-OHDA to specifically target dopaminergic neurons resulting in acute neuronal loss in the substantia nigra or by using viral vectors to induce the specific and gradual expression of alpha synuclein in the substantia nigra. The detection of alpha- synuclein oligomers, the presumed toxic species, in these models and others has been possible using only indirect biochemical approaches to date. Here we coinjected AAVs encoding alpha-synuclein fused to the N- or C-terminal half of VenusYFP in rat substantia nigra pars compacta and describe for the first time a novel viral vector rodent model with the unique ability to directly detect and track alpha synuclein oligomers ex vivo and in vivo. Results Viral coinjection resulted in widespread VenusYFP signal within the nigrostriatal pathway, including cell bodies in the substantia nigra and synaptic accumulation in striatal terminals, suggestive of in vivo alpha-synuclein oligomers formation. Transduced rats showed alpha-synuclein induced dopaminergic neuron loss in the substantia nigra, the appearance of dystrophic neurites, and gliosis in the striatum. Moreover, we have applied in vivo imaging techniques in the living mouse to directly image alpha-synuclein oligomers in the cortex. Conclusion We have developed a unique animal model that provides a tool for the Parkinson’s disease research community with which to directly detect alpha- synuclein oligomers in vivo and screen therapeutic approaches targeting alpha-synuclein oligomers. PMID:24252244

2013-01-01

234

Two approaches in scanner-printer calibration: colorimetric space-based versus closed-loop  

NASA Astrophysics Data System (ADS)

The present paper studies two different table-based approaches for the calibration of electronic imaging systems. The first approach, which is the classical one, uses the device-independent CIE-XYZ colorimetric space as an intermediate standard space. Input and output devices such as scanners, displays and printers are calibrated separately with respect to the objective CIE-XYZ space. The calibration process requires establishing a 3-dimensional mapping between scanner's device-dependent RGB pace and a device-independent colorimetric space such as CIE-XYZ. Measured samples belonging to the calibration set are used for splitting the colorimetric space into Delaunay tetrahedrons. The second approach, the so-called closed loop approach, calibrates directly scanner-printer pairs, without any reference to an objective colorimetric space. It enables a 3D mapping to be built between the scanner's RGB space and the printer's CMY space without requiring any colorimetric measurement. It offers very accurate calibrated output for input samples having the same characteristics (halftone dot, ink spectral reflectance) as the printed samples used for the calibration process. When the desktop scanners' RGB sensibilities are not a linear transform of the CIE x, y, z matching curves, an accurate calibration can only be made if input color patches are based on the same primary inks as the patches used for device calibration.

Ostromoukhov, Victor; Hersch, Roger D.; Peraire, Cecile; Amidror, Isaac; Emmel, Patrick

1994-04-01

235

Direct detection of Vibrio cholerae in stool samples.  

PubMed Central

A direct method to detect Vibrio cholerae in stool samples was developed by using a PCR procedure that did not require a DNA purification step. Dilution (1/100) of stool samples prevented inhibition of the reaction by contaminants, and two consecutive PCRs, the second one with a nested primer, achieved the desired sensitivity. Comparison of the results obtained from stool swab samples processed by the two-step PCR and by an enzyme-linked immunosorbent assay using GM1 as the capture molecule showed that the former is more sensitive and gave positive results even when V. cholerae was not culturable or dead. Images PMID:8051251

Varela, P; Pollevick, G D; Rivas, M; Chinen, I; Binsztein, N; Frasch, A C; Ugalde, R A

1994-01-01

236

Capacity of a direct detection optical communication channel  

NASA Technical Reports Server (NTRS)

The capacity of a free space optical channel using a direct detection receiver is derived under both peak and average signal power constraints and without a signal bandwidth constraint. The addition of instantaneous noiseless feedback from the receiver to the transmitter does not increase the channel capacity. In the absence of received background noise, an optimally coded PPM system is shown to achieve capacity in the limit as signal bandwidth approaches infinity. In the case of large peak to average signal power ratios, an interleaved coding scheme with PPM modulation is shown to have a computational cutoff rate far greater than ordinary coding schemes.

Tan, H. H.

1980-01-01

237

A new colorimetric method for determining the isomerization activity of sucrose isomerase.  

PubMed

A new colorimetric method for determining the isomerization activity of sucrose isomerase was developed. This colorimetric method is based on the enzymatic reactions of invertase and glucose oxidase-peroxidase (GOD-POD). The main scheme for assaying sucrose isomerase activity is to degrade sucrose in the reaction mixture to glucose and fructose by invertase and to detect the concentration of glucose generated using GOD-POD. The concentrations of trehalulose and isomaltulose, reaction products of sucrose isomerase, are calculated from the concentration of glucose. This method allows rapid and accurate determination of the isomerization activity of sucrose isomerase without inhibition by hydrolysis activity. PMID:17284828

Park, Sang-Eun; Cho, Mee-Hyun; Lim, Jin Kyu; Kim, Jong-Sang; Kim, Jeong Hwan; Kwon, Dae Young; Park, Cheon-Seok

2007-02-01

238

Assessing Alternatives for Directional Detection of a WIMP Halo  

E-print Network

The future of direct terrestrial WIMP detection lies on two fronts: new, much larger low background detectors sensitive to energy deposition, and detectors with directional sensitivity. The former can large range of WIMP parameter space using well tested technology while the latter may be necessary if one is to disentangle particle physics parameters from astrophysical halo parameters. Because directional detectors will be quite difficult to construct it is worthwhile exploring in advance generally which experimental features will yield the greatest benefits at the lowest costs. We examine the sensitivity of directional detectors with varying angular tracking resolution with and without the ability to distinguish forward versus backward recoils, and compare these to the sensitivity of a detector where the track is projected onto a two-dimensional plane. The latter detector regardless of where it is placed on the Earth, can be oriented to produce a significantly better discrimination signal than a 3D detector without this capability, and with sensitivity within a factor of 2 of a full 3D tracking detector. Required event rates to distinguish signals from backgrounds for a simple isothermal halo range from the low teens in the best case to many thousands in the worst.

Craig J. Copi; Lawrence M. Krauss; David Simmons-Duffin; Steven R. Stroiney

2005-08-30

239

Sensitiveness of the colorimetric estimation of titanium  

USGS Publications Warehouse

The accuracy of the colorimetric estimation of titanium is practically constant over concentrations ranging from the strongest down to those containing about 1.5 mg. TiO2 in 100 cc. The change in concentration required to produce a perceptible difference in intensity between two solutions, at favorable concentrations, was found to be about 6.5 per cent, which does not differ much from the results of others with chromium and copper solutions. With suitable precautions, such as comparing by substitution and taking the mean of several settings or of the two perceptibly different extremes, the accuracy of the colorimetric comparisons appears to be about 2 per cent.

Wells, R.C.

1911-01-01

240

3D graphene network@WO3 nanowire composites: a multifunctional colorimetric and electrochemical biosensing platform.  

PubMed

A three dimensional graphene network (3DGN)@WO3 nanowire (NW) sensor is proposed which can perform colorimetric and electrochemical sensing techniques to detect H2O2, ascorbic acid and dopamine. The 3DGN provides three functions: anchoring, separating, conducting, while the WO3 NWs maximize surface area and catalyse reactions. PMID:25105515

Ma, Ye; Zhao, Minggang; Cai, Bin; Wang, Wei; Ye, Zhizhen; Huang, Jingyun

2014-10-01

241

Understanding WIMP-baryon interactions with direct detection: A Roadmap  

E-print Network

We study prospects of dark-matter direct-detection searches for probing non-relativistic effective theory for WIMP-baryon scattering. We simulate a large set of noisy recoil-energy spectra for different scattering scenarios (beyond the standard momentum-independent contact interaction), for Generation 2 and futuristic experiments. We analyze these simulations and quantify the probability of successfully identifying the operator governing the scattering, if a WIMP signal is observed. We find that the success rate depends on a combination of factors: the WIMP mass, the mediator mass, the type of interaction, and the experimental energy window. For example, for a 20 GeV WIMP, Generation 2 is only likely to identify the right operator if the interaction is Coulomb-like, and is unlikely to do so in any other case. For a WIMP with a mass of 200 GeV or higher, success is almost guaranteed. We also find that, regardless of the scattering model and the WIMP parameters, a single Generation 2 experiment is unlikely to successfully discern the momentum dependence of the underlying operator on its own, but prospects improve drastically when experiments with different target materials and energy windows are analyzed jointly. Furthermore, we examine the quality of parameter estimation and degeneracies in the multi-dimensional parameter space of the effective theory. We find in particular that the resulting WIMP mass estimates can be severely biased if data are analyzed assuming the standard (momentum-independent) operator while the actual operator has momentum-dependence. Finally, we evaluate the ultimate reach of direct detection, finding that the prospects for successful operator selection prior to reaching the irreducible backgrounds are excellent, if the signal is just below the current limits, but slim if Generation 2 does not report WIMP detection.

Vera Gluscevic; Annika H. G. Peter

2014-06-26

242

Understanding WIMP-baryon interactions with direct detection: a roadmap  

NASA Astrophysics Data System (ADS)

We study prospects of dark-matter direct-detection searches for probing non-relativistic effective theory for WIMP-baryon scattering. We simulate a large set of noisy recoil-energy spectra for different scattering scenarios (beyond the standard momentum-independent contact interaction), for Generation 2 and futuristic experiments. We analyze these simulations and quantify the probability of successfully identifying the operator governing the scattering, if a WIMP signal is observed. We find that the success rate depends on a combination of factors: the WIMP mass, the mediator mass, the type of interaction, and the experimental energy window. For example, for a 20 GeV WIMP, Generation 2 is only likely to identify the right operator if the interaction is Coulomb-like, and is unlikely to do so in any other case. For a WIMP with a mass of 200 GeV or higher, success is almost guaranteed. We also find that, regardless of the scattering model and the WIMP parameters, a single Generation 2 experiment is unlikely to successfully discern the momentum dependence of the underlying operator on its own, but prospects improve drastically when experiments with different target materials and energy windows are analyzed jointly. Furthermore, we examine the quality of parameter estimation and degeneracies in the multi-dimensional parameter space of the effective theory. We find in particular that the resulting WIMP mass estimates can be severely biased if data are analyzed assuming the standard (momentum-independent) operator while the actual operator has momentum-dependence. Finally, we evaluate the ultimate reach of direct detection, finding that the prospects for successful operator selection prior to reaching the irreducible backgrounds are excellent, if the signal is just below the current limits, but slim if Generation 2 does not report WIMP detection.

Gluscevic, Vera; Peter, Annika H. G.

2014-09-01

243

A method to auto-estimate edge detection direction  

NASA Astrophysics Data System (ADS)

In machine vision measurement, the edge is a key point for fitting geometric parameter. There are two problems in the edge detection process. First, there is redundant information for the object with complex shape in the field of the view. Second, the surface of the object is full of texture which is misidentified as the edge. The texture processes similar feature to the edge and cannot be removed by filter. To solve the above problems, vision sight is proposed to get an interesting region and remove redundant information. A new algorithm based on fuzzy entropy is used to auto-estimate the edge detection direction from the pure region to mixed region in order to avoid the textures which misidentified as the edge. Comparing the algorithm with Canny, the former gets less texture points than the latter. A mask film is used as a standard to weight the validity of the algorithm. The experimental result shows that the algorithm proposed by this paper is robust and accuracy in detecting edge.

Yin, Z.; Liu, B. G.; Chen, F. D.; Liu, G. D.; Wan, F.

2013-01-01

244

Monthly Modulation in Dark Matter Direct-Detection Experiments  

E-print Network

The count rate in dark matter direct-detection experiments should exhibit modulation signatures due to the Earth's motion with respect to the Galactic dark matter halo. The annual and daily modulations, due to the Earth's revolution about the Sun and rotation about its own axis, have been explored previously. Monthly modulation is another such feature present in rate counts, and provides a nearly model-independent method of distinguishing dark matter signal events from background. We study here monthly modulations in detail, examining both the effect of the motion of the Earth about the Earth-Moon barycenter and the gravitational focusing due to the Moon. We show that the former is the dominant source of monthly modulation, and that the amplitude of the monthly modulation varies on an annual cycle. The expected amplitude of monthly modulation is quite small which makes its detection challenging; any such detection however, would provide very strong evidence that candidate events are due to dark matter scatter...

Britto, Vivian

2014-01-01

245

Detecting Tsunami Genesis and Scales Directly from Coastal GPS Stations  

NASA Astrophysics Data System (ADS)

Different from the conventional approach to tsunami warnings that rely on earthquake magnitude estimates, we have found that coastal GPS stations are able to detect continental slope displacements of faulting due to big earthquakes, and that the detected seafloor displacements are able to determine tsunami source energy and scales instantaneously. This method has successfully replicated several historical tsunamis caused by the 2004 Sumatra earthquake, the 2005 Nias earthquake, the 2010 Chilean earthquake, and the 2011 Tohoku-Oki earthquake, respectively, and has been compared favorably with the conventional seismic solutions that usually take hours or days to get through inverting seismographs (reference listed). Because many coastal GPS stations are already in operation for measuring ground motions in real time as often as once every few seconds, this study suggests a practical way of identifying tsunamigenic earthquakes for early warnings and reducing false alarms. Reference Song, Y. T., 2007: Detecting tsunami genesis and scales directly from coastal GPS stations, Geophys. Res. Lett., 34, L19602, doi:10.1029/2007GL031681. Song, Y. T., L.-L. Fu, V. Zlotnicki, C. Ji, V. Hjorleifsdottir, C.K. Shum, and Y. Yi, 2008: The role of horizontal impulses of the faulting continental slope in generating the 26 December 2004 Tsunami, Ocean Modelling, doi:10.1016/j.ocemod.2007.10.007. Song, Y. T. and S.C. Han, 2011: Satellite observations defying the long-held tsunami genesis theory, D.L. Tang (ed.), Remote Sensing of the Changing Oceans, DOI 10.1007/978-3-642-16541-2, Springer-Verlag Berlin Heidelberg. Song, Y. T., I. Fukumori, C. K. Shum, and Y. Yi, 2012: Merging tsunamis of the 2011 Tohoku-Oki earthquake detected over the open ocean, Geophys. Res. Lett., doi:10.1029/2011GL050767 (Nature Highlights, March 8, 2012).

Song, Y. Tony

2013-04-01

246

Detections and confirmations of electromagnetic pulses directly excited by earthquakes  

NASA Astrophysics Data System (ADS)

In order to detect and confirm electromagnetic (EM) pulses directly excited by earthquakes, we have been observing EM noise in boreholes of 100 m in depth at various places such as on mountain sides and seashores, inserting EM sensor systems into the boreholes. In the observations, we detected tremendous number of EM pulses of a few kHz with duration of a few millisecond. From detailed analysis of these EM pulses, we found that almost all of these EM pulses were lightning and artificial ones, and we could not confirm any earthquake-related EM pulse at all. The reason why earthquake-related EM pulses could not be detected in the earth was considered that the amplitude of the EM pulses would be strongly decayed during their propagations in the earth due to high electrical conductivity of the earth's medium. The decay rate is generally given by a specific distance so-called 'Skin depth ' through which the amplitude decays to 1/e (e = 2.718), and the skin depth is inversely proportional to square root of EM frequency. This means that high frequency EM waves decay and fade out in a short distance but lower frequency ones can survive for a long distance. Therefore EM waves of a few kHz had been severe to propagate for long distance in the earth. So we shifted down the monitoring frequency to the range of a few tens of Hz. As the result, we have finally detected earthquake-excited EM pulses in the earth and above the ground. By simultaneous capturing of waveforms of detected EM pulses and of seismic accelerations measured at the same observation site, we have confirmed close relationship between earthquakes and EM pulses, in which the waveform of magnetic component clearly shows primary tremor corresponding to seismic P-wave although it can't be seen in the waveform of seismic acceleration. Furthermore, by a laboratory experiment on giving stress impact to a granite pillar, excitation mechanism of EM pulses from granite has been confirmed as the Piezo-electric effect. These results have proved that seismic P-wave could be easily generated even by extremely weak stress impact to earth's crusts compared to that for causing earthquakes, and that EM waves could be excited by small seismic vibrations. Furthermore, we found an analogy of situations in EM pulse excitations between in the laboratory experiment and in active faults, which means that EM pulses can be excited by the fractures of small stones in active faults before earthquakes. So we here propose a method for detecting EM pulses as a precursor of earthquakes.

Tsutsui, M.

2013-12-01

247

Plasmon-enhanced colorimetric ELISA with single molecule sensitivity.  

PubMed

Robust but ultrasensitive biosensors with a capability of detecting low abundance biomarkers could revolutionize clinical diagnostics and enable early detection of cancer, neurological diseases, and infections. We utilized a combination of localized surface plasmon resonance (LSPR) refractive index sensing and the well-known enzyme-linked immunosorbent assay to develop a simple colorimetric biosensing methodology with single molecule sensitivity. The technique is based on spectral imaging of a large number of isolated gold nanoparticles. Each particle binds a variable number of horseradish peroxidase (HRP) enzyme molecules that catalyze a localized precipitation reaction at the particle surface. The enzymatic reaction dramatically amplifies the shift of the LSPR scattering maximum, ?(max), and makes it possible to detect the presence of only one or a few HRP molecules per particle. PMID:21428275

Chen, Si; Svedendahl, Mikael; Duyne, Richard P Van; Käll, Mikael

2011-04-13

248

Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers  

ERIC Educational Resources Information Center

A colorimetric method for total capsaicinoids in chili pepper ("Capsicum") fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and…

Thompson, Robert Q.; Chu, Christopher; Gent, Robin; Gould, Alexandra P.; Rios, Laura; Vertigan, Theresa M.

2012-01-01

249

Label Free Colorimetric Biosensing Using Nanoparticles  

Microsoft Academic Search

In this review article, we discuss a class of biosensors that exploit the change in the colorimetric properties of noble metal nanoparticles in response to biomolecular binding at their surface. Several sensor fabrication techniques as well as sensor configurations are discussed with an emphasis on their strengths and limitations. We conclude by presenting the future prospects and challenges for the

Nidhi Nath; Ashutosh Chilkoti

2004-01-01

250

Ion-directed assembly of gold nanorods: a strategy for mercury detection.  

PubMed

Water-soluble gold nanorods (Au NRs) have been functionalized with an N-alkylaminopyrazole ligand, 1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole (PyL), that has been demonstrated able to coordinate heavy metal ions. The N-alkylaminopyrazole functionalized Au NRs have been characterized by electron microscopy and spectroscopic investigation and tested in optical detection experiments of different ions, namely, Zn(2+), Cd(2+), Hg(2+), Cu(2+), Pb(2+), and As(3+). In particular, the exposure of the functionalized NRs to increasing amounts of Hg(2+) ions has resulted in a gradual red-shift and broadening of the longitudinal plasmon band, up to 900 nm. Interestingly, a significantly different response has been recorded for the other tested ions. In fact, no significant shift in the longitudinal plasmon band has been observed for any of them, while a nearly linear reduction in the plasmon band intensity versus ion concentration in solution has been detected. The very high sensitivity for Hg(2+) with respect to other investigated ions, with a limit of detection of 3 ppt, demonstrates that the functionalization of Au NRs with PyL is a very effective method to be implemented in a reliable colorimetric sensing device, able to push further down the detection limit achieved by applying similar strategies to spherical Au NPs. PMID:23305173

Placido, Tiziana; Aragay, Gemma; Pons, Josefina; Comparelli, Roberto; Curri, M Lucia; Merkoçi, Arben

2013-02-01

251

Regenerating WIMPs in the light of direct and indirect detection  

E-print Network

There are several ways to explain the dark matter relic density other than by the ordinary freeze-out scenario. For example, the freeze-in mechanism may constitute an alternative for generating the correct relic density for dark matter candidates whose predicted freeze-out abundance is too low due to a large total annihilation cross section. Here we show that although such a mechanism could explain why a dark matter candidate has the correct relic density, some candidates may still be ruled out because they would lead to a large gamma ray flux in dwarf spheroidal galaxies or a large elastic scattering rate in direct detection experiments. To investigate this scenario we examine neutralino dark matter in the MSSM. However our conclusions can be generalised to other types of annihilating DM candidates with a low relic density in the freeze-out scenario but which have their relic densities generated by some other mechanism.

Andrew J. Williams; Celine Boehm; Stephen M. West; Daniel Albornoz Vasquez

2012-04-17

252

Direct detection of dark matter in universal bound states  

NASA Astrophysics Data System (ADS)

We study the signatures for internal structure of dark matter in direct detection experiments in the context of asymmetric self-interacting dark matter. The self-interaction cross section of two dark matter particles at low energies is assumed to come close to saturating the S-wave unitarity bound, which requires the presence of a resonance near their scattering threshold. The universality of S-wave near-threshold resonances then implies that the low-energy scattering properties of a two-body bound state of dark matter particles are completely determined by its binding energy, irrespective of the underlying microphysics. The form factor for elastic scattering of the bound state from a nucleus and the possibility of break up of the bound state produce new signatures in the nuclear recoil energy spectrum. If these features are observed in experiments, it will give a smoking-gun signature for the internal structure of dark matter.

Laha, Ranjan; Braaten, Eric

2014-05-01

253

Direct Detection of Light "Ge-phobic" Exothermic Dark Matter  

E-print Network

We present comparisons of direct dark matter (DM) detection data for light WIMPs with exothermic scattering with nuclei (exoDM), both assuming the Standard Halo Model (SHM) and in a halo model - independent manner. Exothermic interactions favor light targets, thus reducing the importance of upper limits derived from xenon targets, the most restrictive of which is at present the LUX limit. In our SHM analysis the CDMS-II-Si and CoGeNT regions become allowed by these bounds, however the recent SuperCDMS limit rejects both regions for exoDM with isospin-conserving couplings. An isospin-violating coupling of the exoDM, in particular one with a neutron to proton coupling ratio of $-0.8$ (which we call "Ge-phobic"), maximally reduces the DM coupling to germanium and allows the CDMS-II-Si region to become compatible with all bounds. This is also clearly shown in our halo-independent analysis.

Graciela B. Gelmini; Andreea Georgescu; Ji-Haeng Huh

2014-04-29

254

SPIFI: a direct-detection imaging spectrometer for submillimeter wavelengths.  

PubMed

The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind-a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI's focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 microm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI's sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument's large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope. PMID:12009168

Bradford, C Matt; Stacey, Gordon J; Swain, Mark R; Nikola, Thomas; Bolatto, Alberto D; Jackson, James M; Savage, Maureen L; Davidson, Jacqueline A; Ade, Peter A R

2002-05-01

255

Halo independent comparison of direct dark matter detection data  

NASA Astrophysics Data System (ADS)

We extend the halo-independent method of Fox, Liu, and Weiner to include energy resolution and efficiency with arbitrary energy dependence, making it more suitable for experiments to use in presenting their results. Then we compare measurements and upper limits on the direct detection of low mass ( ~ 10 GeV) weakly interacting massive particles with spin-independent interactions, including the upper limit on the annual modulation amplitude from the CDMS collaboration. We find that isospin-symmetric couplings are severely constrained both by XENON100 and CDMS bounds, and that isospin-violating couplings are still possible at the lowest energies, while the tension of the higher energy CoGeNT bins with the CDMS modulation constraint remains. We find the CRESST-II signal is not compatible with the modulation signals of DAMA and CoGeNT.

Gondolo, Paolo; Gelmini, Graciela B.

2012-12-01

256

Protein Detection via Direct Enzymatic Amplification of Short DNA Aptamers  

PubMed Central

Aptamers are single-stranded nucleic acids that fold into defined tertiary structures to bind target molecules with high specificities and affinities. DNA aptamers have garnered much interest as recognition elements for biodetection and diagnostic applications due to their small size, ease of discovery and synthesis, and chemical and thermal stability. Herein, we describe the design and application of a short DNA molecule capable of both protein target binding and amplifiable bioreadout processes. As both recognition and readout capabilities are incorporated into a single DNA molecule, tedious conjugation procedures required for protein-DNA hybrids can be omitted. The DNA aptamer is designed to be amplified directly by either the polymerase chain reaction (PCR) or rolling circle amplification (RCA) processes, taking advantage of real-time amplification monitoring techniques for target detection. A combination of both RCA and PCR provides a wide protein target dynamic range (1 ?M to 10 pM). PMID:17980857

Fischer, Nicholas O.; Tarasow, Theodore M.; Tok, Jeffrey B.-H.

2008-01-01

257

Light magnetic dark matter in direct detection searches  

NASA Astrophysics Data System (ADS)

We study a fermionic Dark Matter particle carrying magnetic dipole moment and analyze its impact on direct detection experiments. In particular we show that it can accommodate the DAMA, CoGeNT and CRESST experimental results. Assuming conservative bounds, this candidate is shown not to be ruled out by the CDMS, XENON and PICASSO experiments. We offer an analytic understanding of how the long-range interaction modifies the experimental allowed regions, in the cross section versus Dark Matter mass parameter space, with respect to the typically assumed contact interaction. Finally, in the context of a symmetric Dark Matter sector, we determine the associated thermal relic density, and further provide relevant constraints imposed by indirect searches and colliders.

Del Nobile, Eugenio; Kouvaris, Chris; Panci, Paolo; Sannino, Francesco; Virkajärvi, Jussi

2012-08-01

258

Subcarrier multiplexing with dispersion reduction and direct detection  

DOEpatents

An SCM system is disclosed for simultaneously reducing the concomitant problems of receiver complexity and dispersion penalty and without requiring the use of an expensive, high-bandwidth optical detector. The system provides both a dispersion reduction and a direct detection to the receiver, with microwave mixers and lithium niobate external modulators that produce sidebands that are only separated by a few gigahertz from a principal laser optical carrier. Digital data streams are independently impressed upon these sidebands for transmission over an ordinary single-mode fiber. Independent high-speed data streams are upconverted to microwave frequencies. These subcarriers are then combined with a microwave power combiner and amplified with a microwave amplifier. A solid-state 1550-nm laser carrier is modulated by the microwave subcarriers. An erbium-doped fiber amplifier (EDFA) is used just prior to long-distance transmission over ordinary single-mode fiber. The transmitted optical signal may then traverse multiple EDFAs to compensate for long-haul optical fiber losses prior to detection. At a receiving end, the optical signal is split into multiple paths. The subcarrier channels are optically pre-selected using a narrowband optical filter, such as a fiber Fabry-Perot (FFP) filter. An optical detector converts the selected optical signal into a baseband electrical data stream. 2 figs.

Sargis, P.D.; Haigh, R.E.; McCammon, K.G.

1997-01-21

259

Subcarrier multiplexing with dispersion reduction and direct detection  

DOEpatents

An SCM system for simultaneously reducing the concomitant problems of receiver complexity and dispersion penalty and without requiring the use of an expensive, high-bandwidth optical detector. The system provides both a dispersion reduction and a direct detection to the receiver, with microwave mixers and lithium niobate external modulators that produce sidebands that are only separated by a few gigahertz from a principal laser optical carrier. Digital data streams are independently impressed upon these sidebands for transmission over an ordinary single-mode fiber. Independent high-speed data streams are upconverted to microwave frequencies. These subcarriers are then combined with a microwave power combiner and amplified with a microwave amplifier. A solid-state 1550-nm laser carrier is modulated by the microwave subcarriers. An erbium-doped fiber amplifier (EDFA) is used just prior to long-distance transmission over ordinary single-mode fiber. The transmitted optical signal may then traverse multiple EDFAs to compensate for long-haul optical fiber losses prior to detection. At a receiving end, the optical signal is split into multiple paths. The subcarrier channels are optically pre-selected using a narrowband optical filter, such as a fiber Fabry-Perot (FFP) filter. An optical detector converts the selected optical signal into a baseband electrical data stream.

Sargis, Paul D. (Modesto, CA); Haigh, Ronald E. (Tracy, CA); McCammon, Kent G. (Livermore, CA)

1997-01-01

260

DIRECT DETECTIONS OF YOUNG STARS IN NEARBY ELLIPTICAL GALAXIES  

SciTech Connect

Small amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identified individual young stars and star clusters in four nearby ellipticals. Ongoing star formation is detected in all galaxies, including three ellipticals that have previously exhibited potential signposts of star-forming conditions (NGC 4636, NGC 4697, and NGC 4374), as well as the typical ''red and dead'' NGC 3379. The current star formation in our closest targets, where we are most complete, is between 2.0 and 9.8 Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5) Multiplication-Sign 10{sup -4} M{sub Sun} yr{sup -1}), but decreased by a factor of several in the past 0.3 Gyr. Most star clusters have a mass between 10{sup 2} and 10{sup 4} M{sub Sun }. The specific star formation rates of {approx}10{sup -16} yr{sup -1} (at the present day) or {approx}10{sup -14} yr{sup -1} (when averaging over the past Gyr) imply that a fraction 10{sup -8} of the stellar mass is younger than 100 Myr and 10{sup -5} is younger than 1 Gyr, quantifying the level of frosting of recent star formation over the otherwise passive stellar population. There is no obvious correlation between either the presence or spatial distribution of postulated star formation indicators and the star formation we detect.

Ford, H. Alyson; Bregman, Joel N., E-mail: aford@nrao.edu [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)

2013-06-20

261

Complementarity of direct dark matter detection and indirect detection through gamma rays  

SciTech Connect

We show, by using an extensive sample of viable supersymmetric models as templates, that indirect detection of dark matter through gamma rays may have a large potential for identifying the nature of dark matter. This is, in particular, true also for models that give too weak dark matter-nucleon scattering cross sections to be probed by present and planned direct detection experiments. Also models with a mass scale too high to be accessible at CERN's LHC accelerator may show up in next-generation imaging Cherenkov telescope arrays. Based on our findings, we therefore suggest to view indirect searches as genuine particle physics experiments, complementing other strategies to probe so far unknown regions in the parameter space of e.g. supersymmetric models, and propose a new approach that would make use of telescopes dedicated for dark matter searches. As a concrete example for the potential of such an approach, we consider an array of imaging air Cherenkov telescopes, the Dark Matter Array (DMA), and show that such an experiment could extend present-day limits by several orders of magnitude, reaching a large class of models that would remain undetected in both direct detection experiments and searches at the LHC. In addition, in a sizable part of the parameter space, signals from more than one type of dark matter detection experiment would be possible, something that may eventually be necessary in order to identify the dark matter candidate.

Bergstroem, Lars; Bringmann, Torsten; Edsjoe, Joakim [Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); II. Institute for Theoretical Physics, University of Hamburg, Luruper Chausse 149, D-22761 Hamburg (Germany); Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden)

2011-02-15

262

Direct Detection Doppler Lidar for Spaceborne Wind Measurement  

NASA Technical Reports Server (NTRS)

Aerosol and molecular based versions of the double-edge technique can be used for direct detection Doppler lidar spaceborne wind measurement. The edge technique utilizes the edge of a high spectral resolution filter for high accuracy wind measurement using direct detection lidar. The signal is split between an edge filter channel and a broadband energy monitor channel. The energy monitor channel is used for signal normalization. The edge measurement is made as a differential frequency measurement between the outgoing laser signal and the atmospheric backscattered return for each pulse. As a result the measurement is insensitive to laser and edge filter frequency jitter and drift at a level less than a few parts in 10(exp 10). We have developed double edge versions of the edge technique for aerosol and molecular-based lidar measurement of the wind. Aerosol-based wind measurements have been made at Goddard Space Flight Center and molecular-based wind measurements at the University of Geneva. We have demonstrated atmospheric measurements using these techniques for altitudes from 1 to more than 10 km. Measurement accuracies of better than 1.25 m/s have been obtained with integration times from 5 to 30 seconds. The measurements can be scaled to space and agree, within a factor of two, with satellite-based simulations of performance based on Poisson statistics. The theory of the double edge aerosol technique is described by a generalized formulation which substantially extends the capabilities of the edge technique. It uses two edges with opposite slopes located about the laser frequency at approximately the half-width of each edge filter. This doubles the signal change for a given Doppler shift and yields a factor of 1.6 improvement in the measurement accuracy compared to the single edge technique. The use of two high resolution edge filters substantially reduces the effects of Rayleigh scattering on the measurement, as much as order of magnitude, and allows the signal to noise ratio to be substantially improved in areas of low aerosol backscatter. We describe a method that allows the Rayleigh and aerosol components of the signal to be independently determined using the two edge channels and an energy monitor channel. The effects of Rayleigh scattering may then subtracted from the measurement and we show that the correction process does not significantly increase the measurement noise for Rayleigh to aerosol ratios up to 10. We show that for small Doppler shifts a measurement accuracy of 0.4 m/s can be obtained for 5000 detected photon, 1.2 m/s for 1000 detected photons, and 3.7 m/s for 50 detected photons for a Rayleigh to aerosol ratio of 5. Methods for increasing the dynamic range of the aerosol-based system to more than +/- 100 m/s are given.

Korb, C. Laurence; Flesia, Cristina

1999-01-01

263

A Novel Colorimetric Immunoassay Utilizing the Peroxidase Mimicking Activity of Magnetic Nanoparticles  

PubMed Central

A simple colorimetric immunoassay system, based on the peroxidase mimicking activity of Fe3O4 magnetic nanoparticles (MNPs), has been developed to detect clinically important antigenic molecules. MNPs with ca. 10 nm in diameter were synthesized and conjugated with specific antibodies against target molecules, such as rotaviruses and breast cancer cells. Conjugation of the MNPs with antibodies (MNP-Abs) enabled specific recognition of the corresponding target antigenic molecules through the generation of color signals arising from the colorimetric reaction between the selected peroxidase substrate, 3,3?,5,5?-tetramethylbenzidine (TMB) and H2O2. Based on the MNP-promoted colorimetric reaction, the target molecules were detected and quantified by measuring absorbance intensities corresponding to the oxidized form of TMB. Owing to the higher stabilities and economic feasibilities of MNPs as compared to horseradish peroxidase (HRP), the new colorimetric system employing MNP-Abs has the potential of serving as a potent immunoassay that should substitute for conventional HRP-based immunoassays. The strategy employed to develop the new methodology has the potential of being extended to the construction of simple diagnostic systems for a variety of biomolecules related to human cancers and infectious diseases, particularly in the realm of point-of-care applications. PMID:23665902

Woo, Min-Ah; Kim, Moon Il; Jung, Jae Hwan; Park, Ki Soo; Seo, Tae Seok; Park, Hyun Gyu

2013-01-01

264

Colorimetric fluorescent cyanide chemodosimeter based on triphenylimidazole derivative.  

PubMed

In this paper, we demonstrated a highly selective colorimetric chemodosimeter for cyanide anion detection. This chemodosimeter having a triphenylimidazole group as a fluorescent signal unit and a dicyano-vinyl group as a reaction unit was synthesized by the Knoevenagel condensation of 4-(4,5-diphenyl-1H-imidazol-2-yl)benzaldehyde with malononitrile in a reasonable yield. The probe exhibited an intramolecular charge transfer (ICT) absorption band at 420 nm and emission band at 620 nm, respectively. Upon the addition of cyanide anion, the probe displayed a blue-shifted spectrum and loss in color due to the disruption of conjugation. With the aid of the fluorescence spectrometer, the chemodosimeter exhibited a detection limit of 0.11 ?M (S/N=3). Interferences from other common anions associated with cyanide anion analysis were effectively inhibited. PMID:24463246

Zheng, Wei; He, Xiangzhu; Chen, Hongbiao; Gao, Yong; Li, Huaming

2014-04-24

265

Direct Sequence Detection of Structured H5 Influenza Viral RNA  

PubMed Central

We describe the development of sequence-specific molecular beacons (dual-labeled DNA probes) for identification of the H5 influenza subtype, cleavage motif, and receptor specificity when hybridized directly with in vitro transcribed viral RNA (vRNA). The cloned hemagglutinin segment from a highly pathogenic H5N1 strain, A/Hanoi/30408/2005(H5N1), isolated from humans was used as template for in vitro transcription of sense-strand vRNA. The hybridization behavior of vRNA and a conserved subtype probe was characterized experimentally by varying conditions of time, temperature, and Mg2+ to optimize detection. Comparison of the hybridization rates of probe to DNA and RNA targets indicates that conformational switching of influenza RNA structure is a rate-limiting step and that the secondary structure of vRNA dominates the binding kinetics. The sensitivity and specificity of probe recognition of other H5 strains was calculated from sequence matches to the National Center for Biotechnology Information influenza database. The hybridization specificity of the subtype probes was experimentally verified with point mutations within the probe loop at five locations corresponding to the other human H5 strains. The abundance frequencies of the hemagglutinin cleavage motif and sialic acid recognition sequences were experimentally tested for H5 in all host viral species. Although the detection assay must be coupled with isothermal amplification on the chip, the new probes form the basis of a portable point-of-care diagnostic device for influenza subtyping. PMID:18403607

Kerby, Matthew B.; Freeman, Sarah; Prachanronarong, Kristina; Artenstein, Andrew W.; Opal, Steven M.; Tripathi, Anubhav

2008-01-01

266

A Gait Based Approach to Detect Directional Bias of Four-Legged Robots' Direct Walking Utilizing Acceleration Sensors  

Microsoft Academic Search

In this paper, we propose an effective approach to detect the directional bias of walking four-legged robots. We found that\\u000a light weight four-legged robots tend to have unstable directional bias even when walking on flat ground, thus this approach\\u000a is designed to be able to dynamically and continuously detect the directional bias. By observing and analyzing data from acceleration\\u000a sensors

Ding-jie Huang; Wei-chung Teng

2007-01-01

267

Direct detection of light anapole and magnetic dipole DM  

NASA Astrophysics Data System (ADS)

We present comparisons of direct detection data for ``light WIMPs'' with an anapole moment interaction (ADM) and a magnetic dipole moment interaction (MDM), both assuming the Standard Halo Model (SHM) for the dark halo of our galaxy and in a halo-independent manner. In the SHM analysis we find that a combination of the 90% CL LUX and CDMSlite limits or the new 90% CL SuperCDMS limit by itself exclude the parameter space regions allowed by DAMA, CoGeNT and CDMS-II-Si data for both ADM and MDM. In our halo-independent analysis the new LUX bound excludes the same potential signal regions as the previous XENON100 bound. Much of the remaining signal regions is now excluded by SuperCDMS, while the CDMSlite limit is much above them. The situation is of strong tension between the positive and negative search results both for ADM and MDM. We also clarify the confusion in the literature about the ADM scattering cross section.

Del Nobile, Eugenio; Gelmini, Graciela B.; Gondolo, Paolo; Huh, Ji-Haeng

2014-06-01

268

Direct Detection Rates of Dark Matter Coupled to Dark Energy  

E-print Network

We investigate the effect of a coupling between dark matter and dark energy on the rates for the direct detection of dark matter. The magnitude of the effect depends on the strength $\\kappa$ of this new interaction relative to gravity. The resulting isothermal velocity distribution for dark matter in galaxy halos is still Maxwell-Boltzmann (M-B), but the characteristic velocity and the escape velocity are increased by $\\sqrt{1+\\kappa^2}$. We adopt a phenomenological approach and consider values of $\\kappa$ near unity. For such values we find that: (i) The (time averaged) event rate increases for light WIMPs, while it is somewhat reduced for WIMP masses larger than 100 GeV. (ii) The time dependence of the rate arising from the modulation amplitude is decreased compared to the standard M-B velocity distribution. (iii) The average and maximum WIMP energy increase proportionally to $1+\\kappa^2$, which, for sufficiently massive WIMPs, allows the possibility of designing experiments measuring $\\gamma$ rays following nuclear de-excitation.

N. Tetradis; J. D. Vergados; Amand Faessler

2006-09-07

269

Improving colorimetric assays through protein enzyme-assisted gold nanoparticle amplification.  

PubMed

The discovery of the DNA-mediated assembly of gold nanoparticles was a great moment in the history of science; this understanding and chemical control enabled the rational design of functional nanomaterials as novel probes in biodetection. In contrast with conventional probes such as organic dyes, gold nanoparticles exhibit high photostability and unique size-dependent optical properties. Because of their high extinction coefficients and strong distance dependent optical properties, these nanoparticles have emerged over the past decade as a promising platform for rapid, highly sensitive colorimetric assays that allow for the visual detection of low concentrations of metal ions, small molecules, and biomacromolecules. These discoveries have deepened our knowledge of biological phenomena and facilitated the development of many new diagnostic and therapeutic tools. Despite these many advances and continued research efforts, current nanoparticle-based colorimetric detection systems still suffer from several drawbacks, such as limited sensitivity and selectivity. This Account describes the recent development of colorimetric assays based on protein enzyme-assisted gold nanoparticle amplification. The benefits of such detection systems include significantly improved detection sensitivity and selectivity. First, we discuss the general design of enzyme-modified nanoparticle systems in colorimetric assays. We show that a quantitative understanding of the unique properties of different enzymes is paramount for effective biological assays. We then examine the assays for nucleic acid detection based on different types of enzymes, including endonucleases, ligases, and polymerases. For each of these assays, we identify the underlying principles that contribute to the enhanced detection capability of nanoparticle systems and illustrate them with selected examples. Furthermore, we demonstrate that the combination of gold nanoparticles and specific enzymes can probe enzyme dynamics and function with high specificity, offering substantial advantages in both sensitivity and specificity over conventional detection methods. The screening of nuclease, methyltransferase, protease, and kinase activities can be colorimetrically performed in a straightforward manner. Finally, we discuss examples of colorimetric assays for metal ions and small molecules that constitute important advances toward visual monitoring of enzyme catalytic functions and gene expression. Although these enzyme-assisted assay methods hold great promise for myriad applications in biomedicine and bioimaging, the application of the described techniques in vivo faces formidable challenges. In addition, researchers do not fully understand the interactions of gold nanoparticles with enzyme molecules. This understanding will require the development of new techniques to probe enzyme substrate dynamics at the particle interface with higher spatial resolution and chemical specificity. PMID:22786666

Xie, Xiaoji; Xu, Wei; Liu, Xiaogang

2012-09-18

270

Colorimetric analysis of Carrollton water sources  

SciTech Connect

In recent years there has been a growing concern over pollution in water supplies. In the last couple of years there have been illnesses reported that were caused by pollution in the water system in the city of Carrollton. These reports of illness led to an investigation of Hardness levels in the local water supplies. The results of the Hardness test led to the investigation of fourteen possible contaminants in the city's water supplies by Colorimetric Analysis. The results of the Colorimetric test show that chlorides are present on amounts up to 700 parts per million, and total dissolved solids are present in amounts up to 190 parts per million in the local water sources. also other contaminants such as iron, lead, copper, and low pH reading were found in these water supplies.

Spidle, D.; Kay, A. (West Georgia College, Carrollton (USA))

1990-01-01

271

Selective colorimetric sensing of cysteine in aqueous solutions using silver nanoparticles in the presence of Cr³+.  

PubMed

We here in report an extensive study on the development of a highly facile, selective and sensitive colorimetric probe for cysteine detection using silver nanoparticles (Ag NPs). The efficacy of the process relies upon the surface plasmon resonance properties of Ag NPs and the interaction of Ag-cysteine complex with chromium ions (Cr(3+)) in a ratio of 2:1. In the presence of Cr(3+), cysteine was able to induce the aggregation of Ag NPs thereby resulting in a change in yellow colour of the Ag colloid to purple. The reported probe has a limit of detection down to 1 nM which is to the best of our knowledge the lowest ever reported for the colorimetric detection of cysteine. Furthermore, a remarkable feature of this method is that it involves a simple technique exhibiting high selectivity to cysteine over other tested amino acids. PMID:21645737

Ravindran, Aswathy; Mani, Vinayak; Chandrasekaran, N; Mukherjee, Amitava

2011-07-15

272

Three dimensional colorimetric assay assemblies  

DOEpatents

A direct assay is described using novel three-dimensional polymeric assemblies which change from a blue to red color when exposed to an analyte, in one case a flu virus. The assemblies are typically in the form of liposomes which can be maintained in a suspension, and show great intensity in their color changes. Their method of production is also described.

Charych, Deborah (Albany, CA); Reichart, Anke (Albany, CA)

2000-01-01

273

Three dimensional colorimetric assay assemblies  

SciTech Connect

A direct assay is described using novel three-dimensional polymeric assemblies which change from a blue to red color when exposed to an analyte, in one case a flu virus. The assemblies are typically in the form of liposomes which can be maintained in a suspension, and show great intensity in their color changes. Their method of production is also described.

Charych, D.; Reichart, A.

2000-06-27

274

Determining Properties of WIMP Dark Matter with Direct Detection Experiments as Model Independently as Possible  

E-print Network

Determining Properties of WIMP Dark Matter with Direct Detection Experiments as Model Independently) are one of the leading candidates for Dark Matter. Currently, the most promising method to detect and their couplings on nucleons from direct Dark Matter detection experiments are essential. In this talk I

Peters, Achim

275

Comparison of IPDA lidar receiver sensitivity for coherent detection and for direct detection using sine-wave and pulsed modulation.  

PubMed

We use theoretical models to compare the receiver signal to noise ratio (SNR) vs. average rate of detected signal photons for an integrated path differential absorption (IPDA) lidar using coherent detection with continuous wave (CW) lasers and direct detection with sine-wave and pulse modulations. The results show the coherent IPDA lidar has high receiver gain and narrow bandwidth to overcome the effects of detector circuit noise and background light, but the actual receiver performance can be limited by the coherent mixing efficiency, speckle and other factors. For direct detection, using sine-wave modulation allows the use of a low peak power laser transmitter and synchronous detection. The pulse modulation technique requires higher laser peak powers but is more efficient than sine-wave modulation in terms of average detected signal photon rate required to achieve a given receiver SNR. We also conducted experiments for the direct detection cases and the results agreed well with theory. PMID:23037252

Sun, Xiaoli; Abshire, James B

2012-09-10

276

2001 Progress on a Direct Brain Interface Based on Detection of ERPs in ECoG  

E-print Network

University Graz: G. Pfurtscheller, B. Graimann A direct brain interface is defined as a human partnership focuses on the development of a direct brain interface based on event detection2001 Progress on a Direct Brain Interface Based on Detection of ERPs in ECoG The University

Fessler, Jeffrey A.

277

Direct detection of intermolecular forces by atomic force microscopy  

NASA Astrophysics Data System (ADS)

The phenomenon of adhesion appears in various applications of everyday life, ranging from PostIt Notes(TM) and Scotch Tape(TM), to the assembly of aircraft and space shuttles. However, adhesion on the molecular scale is fundamentally different from the adhesion that we experience in the macroscopic world. While macroscopic objects require special adhesives or glues to bind them together, microscale and nanoscale objects and molecules commonly have a high affinity to adhere to each other. A detailed description of intermolecular forces is therefore of key importance in order to understand a wide range of phenomena, ranging from macroscopic properties of materials to molecular recognition. Two key aspects of the atomic force microscope (AFM), namely its sensitivity to sub-nanoNewton forces and its very sharp probe, offer the opportunity to measure interactions between very small numbers of molecules. Through chemical tailoring of both substrates and AFM probes with self-assembled monolayers (SAMs), measurements of forces acting between specific functional groups can be measured. Furthermore, the force required to rupture a single chemical bond can be obtained by a detailed analysis of the histograms of rupture forces. A new model was derived to examine the relationship between the various experimental variables and the shape of histograms of rupture forces when discrete chemical bonds are formed between the AFM probe and substrate. Calculations based on the model demonstrated that in measurements aimed at detecting single bond rupture forces, strict limits are put on the size of the AFM probe, the relative magnitude of the interfacial energies and the bond formation probability. These results were used in two experimental systems where the single bond rupture force was successfully measured: (i) the abstraction of a single Au-S complex from an Au coated AFM probe; and (ii) the rupture of a single charge-transfer (CT) complex between tetramethylphenylenediamine (TMPD) and tetracyanoquinodimethane (TCNQ). Measurements involving only one molecule at a time were conducted using polymer chains chemically grafted to the AFM probe and substrate. In these measurements, the effect of the solvent on the elasticity of the poly-ethylene-propylene oligomers was directly observed in the force-elongation profile.

Skulason, Hjalti

278

Direct electrical detection of target cells on a microfluidic biochip  

NASA Astrophysics Data System (ADS)

Pathogenic bacterial cell detection is currently performed using techniques such as culture enrichment and various plating methods, which are expensive and can take up to several days. In this study, we describe the design, fabrication, and testing of a rapid and inexpensive sensor for detection of target cells electrically in real-time. The sensor operates with the use of microelectrodes integrated in a micro-channel. As a proof of principle, we have successfully demonstrated real-time detection of target yeast cells with a concentration of 10 7 cells/ml. We have also demonstrated the selectivity of our sensors in responding to target cells while remaining irresponsive to non-target cells. We also perform theoretical modeling in order to determine the ultimate detection limit of the sensor. Based on our modeling results, proper optimization of the sensor can yield detection limits approaching the single cell level.

Javanmard, Mehdi; Talasaz, AmirAli H.; Nemat-Gorgani, Mohsen; Pease, Fabian; Ronaghi, Mostafa; Davis, Ronald W.

2008-02-01

279

A real-time colorimetric and ratiometric fluorescent probe for sulfite.  

PubMed

A real-time colorimetric and ratiometric fluorescent probe based on modulating the intramolecular charge transfer (ICT) of the coumarin platform for selective detection of sulfite is presented. This reaction based probe utilized the Michael addition to the dicyano-vinyl group with the detection limit of 5.8 × 10(-5) M. The probe displayed a high selectivity for sulfite over other anions and reactive sulfur especially for biothiols including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), with about 100 nm blue shift and more than 230 times intensity ratios change of the emission spectrum. Meanwhile, it could be easily observed that the probe for sulfite changes from red to pale yellow by the naked eye, and from red to blue under UV lamp immediately after the sulfite is added. To the best of our knowledge, it is the fastest response probe for sulfite ever reported, which could give a colorimetric and ratiometric fluorescent response instantly. PMID:23563108

Wu, Ming-Yu; He, Ting; Li, Kun; Wu, Ming-Bo; Huang, Zheng; Yu, Xiao-Qi

2013-05-21

280

Au@Ag core/shell nanoparticles as colorimetric probes for cyanide sensing  

NASA Astrophysics Data System (ADS)

We synthesize Au@Ag core/shell nanoparticles (NPs) using a Au NP assisted Tollens reaction. The as-synthesized NPs are used for the colorimetric cyanide sensing with a detection limit of 0.4 ?M. The bimetallic NPs are immobilized into agarose gels as portable ``test strips''.We synthesize Au@Ag core/shell nanoparticles (NPs) using a Au NP assisted Tollens reaction. The as-synthesized NPs are used for the colorimetric cyanide sensing with a detection limit of 0.4 ?M. The bimetallic NPs are immobilized into agarose gels as portable ``test strips''. Electronic supplementary information (ESI) available: Experimental procedures and Fig. S1-S14. See DOI: 10.1039/c4nr02560a

Zeng, Jing-Bin; Cao, Ying-Ying; Chen, Jing-Jing; Wang, Xu-Dong; Yu, Jian-Feng; Yu, Bin-Bin; Yan, Zi-Feng; Chen, Xi

2014-08-01

281

Direct and indirect polarimetry for detection in microbore liquid chromatography  

SciTech Connect

An optical activity detection system is described that is compatible with microbore LC (liquid chromatography). The scope of the detection scheme can be expanded to include optically inactive materials when an optically active eluent is used. In addition, with chromatograms of an analyte in two different eluents, one optically active and the other the racemic analog of the first, the volume fraction of the analyte can be determined without the need for identification or standards. A detectability of 11 ng is obtained for fructose.

Bobbitt, D.R.; Yeung, E.S.

1984-09-01

282

Bed Bug Detection: Current Technologies and Future Directions  

PubMed Central

Technologies to detect bed bugs have not kept pace with their global resurgence. Early detection is critical to prevent infestations from spreading. Detection based exclusively on bites is inadequate, because reactions to insect bites are non-specific and often misdiagnosed. Visual inspections are commonly used and depend on identifying live bugs, exuviae, or fecal droplets. Visual inspections are inexpensive, but they are time-consuming and unreliable when only a few bugs are present. Use of a dog to detect bed bugs is gaining in popularity, but it can be expensive, may unintentionally advertise a bed bug problem, and is not foolproof. Passive monitors mimic natural harborages; they are discreet and typically use an adhesive to trap bugs. Active monitors generate carbon dioxide, heat, a pheromone, or a combination to attract bed bugs to a trap. New technologies using DNA analysis, mass spectrometry, and electronic noses are innovative but impractical and expensive for widespread use. PMID:23553226

Vaidyanathan, Rajeev; Feldlaufer, Mark F.

2013-01-01

283

A System for Multiplexed Direct Electrical Detection of DNA Synthesis  

PubMed Central

An electronic system for the multiplexed detection of DNA polymerization is designed and characterized. DNA polymerization is detected by the measurement of small transient currents arising from ion diffusion during polymerization. A transimpedance amplifier is used to detect these small currents; we implemented a twenty-four channel recording system on a single printed circuit board. Various contributions to the input-referred current noise are analyzed and characterized, as it limits the minimum detectable current and thus the biological limit of detection. We obtained 8.5 pA RMS mean noise current (averaged over all 24 channels) over the recording bandwidth (DC to 2 kHz). With digital filtering, the input-referred current noise of the acquisition system is reduced to 2.4 pA, which is much lower than the biological noise. Electrical crosstalk between channels is measured, and a model for the crosstalk is presented. Minimizing the crosstalk is critical because it can lead to erroneous microarray data. With proper precautions, crosstalk is reduced to a negligible value (less than 1.4%). Using a micro-fabricated array of 24 gold electrodes, we demonstrated system functionality by detecting the presence of a target DNA oligonucleotide which hybridized onto its corresponding target. PMID:19183700

Anderson, Erik P.; Daniels, Jonathan S.; Yu, Heng; Karhanek, Miloslav; Lee, Thomas H.; Davis, Ronald W.; Pourmand, Nader

2008-01-01

284

Detection of methicillin-resistant Staphylococcus aureus directly by loop-mediated isothermal amplification and direct cefoxitin disk diffusion tests.  

PubMed

We evaluated the utility of 2 methods for detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from signal-positive blood culture bottles: loop-mediated isothermal amplification (LAMP) assay, and direct cefoxitin disk diffusion (DCDD) test using a 30 ?g cefoxitin disk. In parallel, standard microbiological identification and oxacillin susceptibility testing with MecA PCR was performed. Of 60 blood cultures positive for Gram-positive cocci in clusters, LAMP (via detection of the FemA and MecA genes) showed 100% sensitivity and specificity for identification of MRSA/MSSA. When coagulase-negative staphylococci were tested, sensitivity for detection of methicillin resistance was 91.7% and specificity was 100%. DCDD along with direct tube coagulase assay detected only 80.6% of MRSA/MSSA. LAMP showed higher diagnostic accuracy although DCDD was more cost-effective and did not require additional reagents or supplies. PMID:24952125

Metwally, L; Gomaa, N; Hassan, R

2014-04-01

285

Comparison of HPLC and colorimetric methods for measuring cellulolytic activity  

Microsoft Academic Search

The sugars released during a standard filter paper assay were quantified by colorimetric (Dinitrosalicylic acid and Nelson and Somogyi) and HPLC methods. It was found that the composition of the sugars present in the hydrolysates greatly influenced the final filter paper units of activity obtained. In a ß-glucosidase deficient cellulase system the filter paper activity reported using colorimetric methods could

W. Schwald; M. Chart; C. Breuil; J. N. Saddler

1988-01-01

286

Localized surface plasmon resonance of gold nanoparticles as colorimetric probes for determination of Isoniazid in pharmacological formulation  

NASA Astrophysics Data System (ADS)

Isoniazid is an important antibiotic, which is widely used to treat tuberculosis. This study presents a colorimetric method for the determination of Isoniazid based on localized surface plasmon resonance (LSPR) property of gold nanoparticles. An LSPR band is produced by reducing gold ions in solution using Isoniazid as the reducing agent. Influences of the following relevant variables were examined and optimized in the experiment, formation time of gold nanoparticles, pH, buffer and stabilizer. These tests demonstrated that under optimum conditions the absorbance of Au nanoparticles at 530 nm related linearly to the concentration of Isoniazid in the range of 1.0-8.0 ?g mL-1 with a detection limit of 0.98 ?g mL-1. This colorimetric method has been successfully applied to the determine Isoniazid in tablets and spiked serum samples. The proposed colorimetric assay exhibits good reproducibility and accuracy, providing a simple and rapid method for analysis of Isoniazid.

Zargar, Behrooz; Hatamie, Amir

2013-04-01

287

A ratiometric and colorimetric luminescent thermometer over a wide temperature range based on a lanthanide coordination polymer.  

PubMed

A lanthanide coordination polymer Tb0.957Eu0.043cpda was synthesized as a ratiometric and colorimetric luminescent thermometer. The high triplet excited state energy of a linker enables Tb0.957Eu0.043cpda to detect and visualize temperature over a wide range from cryogenic to room temperature (40-300 K). PMID:24287968

Cui, Yuanjing; Zou, Wenfeng; Song, Ruijing; Yu, Jiancan; Zhang, Wenqian; Yang, Yu; Qian, Guodong

2014-01-21

288

Calculations of rates for direct detection of neutralino dark matter  

NASA Technical Reports Server (NTRS)

The detection rates in cryogenic detectors of neutralinos, the most well motivated supersymmetric dark-matter candidate, are calculated. These rates can differ greatly from the special case of pure photinos and pure Higgsinos which are usually considered. In addition, a new term is found in the elastic-scattering cross section proportional to the Z-ino component which is 'spin independent', even for these Majorana particles. As a result, substantial detection rates exist for previously disfavored, mostly spinless materials such as germanium and mercury.

Griest, Kim

1988-01-01

289

Enzyme-free Detection of Hydrogen Peroxide from Cerium Oxide Nanoparticles Immobilized on Poly(4-vinylpyridine) Self-Assembled Monolayers  

SciTech Connect

A single layer of oxygen-deficient cerium oxide nanoparticles (CNPs) are immobilized on microscopic glass slide using poly(4-vinylpyridine) (PVP) self-assembled monolayers (SAMs). A specific colorimetric property of CNPs when reacted with hydrogen peroxide allows for the direct, single-step peroxide detection which can be used in medical diagnosis and explosives detection. Multiple PVP-CNP immobilized layers improve sensitivity of detection and the sensor can be regenerated for reuse.

Gaynor, James D.; Karakoti, Ajay S.; Inerbaev, Talgat; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Seal, Sudipta; Thevuthasan, Suntharampillai

2013-05-02

290

Direct Gray-Scale Minutiae Detection In Fingerprints  

Microsoft Academic Search

Most automatic systems for fingerprint comparison are based on minutiae matching. Minutiae are essentially terminations and bifurcations of the ridge lines that constitute a fingerprint pattern. Automatic minutiae detection is an extremely critical process, especially in low-quality fingerprints where noise and contrast deficiency can originate pixel configurations similar to minutiae or hide real minutiae. Several approaches have been proposed in

Dario Maio; Davide Maltoni

1997-01-01

291

Circulating tumor cells (CTC) detection: Clinical impact and future directions  

Microsoft Academic Search

Recent molecular and clinical studies have shown that invasion may occur very early in tumor development, thus emphasizing the potential importance of specific and sensitive detection of circulating tumor cells (CTC) and circulating tumor microemboli (CTM). The technical challenge in this field consists of finding “rare” tumor cells (just a few CTCs mixed with the approximately 10 million leukocytes and

Patrizia Paterlini-Brechot; Naoual Linda Benali

2007-01-01

292

Circulating tumor cells (CTC) detection: Clinical impact and future directions  

Microsoft Academic Search

Recent molecular and clinical studies have shown that invasion may occur very early in tumor development, thus emphasizing the potential importance of specific and sensitive detection of circulating tumor cells (CTC) and circulating tumor microemboli (CTM). The technical challenge in this field consists of finding ''rare'' tumor cells (just a few CTCs mixed with the approximately 10 million leukocytes and

Patrizia Paterlini-Brechot; Naoual Linda Benali; Unite INSERM; CHU Necker; Enfant Malades

2007-01-01

293

Determination of MICs forMycobacterium avium-M. intracellulare Complex in Liquid Medium by a Colorimetric Method  

Microsoft Academic Search

We investigated the potential of a rapid colorimetric microassay based on the reduction of dimethylthiazol- diphenyltetrazolium bromide (MTT) for determining the growth of Mycobacterium avium-M. intracellulare complex (MAC) and MICs of clofazimine, resorcinomycin A, and the quinolone PD 127391 against MAC. The reduction of MTT was directly proportional to the number of viable bacteria. A comparison of the MTT reductiontestwiththe(

R. GOMEZ-FLORES; S. GUPTA; R. TAMEZ-GUERRA; T. MEHTA

1995-01-01

294

Failure of direction discrimination at detection threshold for both fast  

E-print Network

Andrew B. Metha and Kathy T. Mullen McGill Vision Research, Department of Ophthalmology, 687 Pine Avenue'' pathway with a high sensitivity to chromatic tar- gets that signals the direction of slowly moving, have noted that at higher speeds the threshold gap disappears for RG tar- gets, signifying correct

Mullen, Kathy T.

295

Direct detection of variable tropospheric clouds near Titan's south pole  

Microsoft Academic Search

Atmospheric conditions on Saturn's largest satellite, Titan, allow the possibility that it could possess a methane condensation and precipitation cycle with many similarities to Earth's hydrological cycle. Detailed imaging studies, of Titan have hitherto shown no direct evidence for tropospheric condensation clouds, although there has been indirect spectroscopic evidence for transient clouds,. Here we report images and spectra of Titan

Antonin H. Bouchez; Caitlin A. Griffith; Michael E. Brown

2003-01-01

296

A comparison of two colorimetric assays, based upon Lowry and Bradford techniques, to estimate total protein in soil extracts  

PubMed Central

Soil extracts usually contain large quantities of dissolved humified organic material, typically reflected by high polyphenolic content. Since polyphenols seriously confound quantification of extracted protein, minimising this interference is important to ensure measurements are representative. Although the Bradford colorimetric assay is used routinely in soil science for rapid quantification protein in soil-extracts, it has several limitations. We therefore investigated an alternative colorimetric technique based on the Lowry assay (frequently used to measure protein and humic substances as distinct pools in microbial biofilms). The accuracies of both the Bradford assay and a modified Lowry microplate method were compared in factorial combination. Protein was quantified in soil-extracts (extracted with citrate), including standard additions of model protein (BSA) and polyphenol (Sigma H1675-2). Using the Lowry microplate assay described, no interfering effects of citrate were detected even with concentrations up to 5 times greater than are typically used to extract soil protein. Moreover, the Bradford assay was found to be highly susceptible to two simultaneous and confounding artefacts: 1) the colour development due to added protein was greatly inhibited by polyphenol concentration, and 2) substantial colour development was caused directly by the polyphenol addition. In contrast, the Lowry method enabled distinction between colour development from protein and non-protein origin, providing a more accurate quantitative analysis. These results suggest that the modified-Lowry method is a more suitable measure of extract protein (defined by standard equivalents) because it is less confounded by the high polyphenolic content which is so typical of soil extracts. PMID:24302786

Redmile-Gordon, M.A.; Armenise, E.; White, R.P.; Hirsch, P.R.; Goulding, K.W.T.

2013-01-01

297

Copolythiophene-derived colorimetric and fluorometric sensor for lysophosphatidic acid based on multipoint interactions.  

PubMed

3-Phenylthiophene-based water-soluble copolythiophenes (CPT9) were designed for colorimetric and fluorometric detection of lysophosphatidic acid (LPA) based on electrostatic interaction, hydrophobic interaction, and hydrogen bonding. Other negatively charged species gave nearly no interference, and the detection limit reached to 0.6 ?M, which is below the requisite detection limits for LPA in human plasma samples. The appealing performance of CPT9 was demonstrated to originate from the multipoint interaction-induced conformational change of conjugated backbone and weakened electron transfer effect. To our best knowledge, this is the first polythiophene based optical sensor which displays emission peak red-shift followed with fluorescence enhancement. PMID:23459452

Lan, Minhuan; Liu, Weimin; Wang, Ying; Ge, Jiechao; Wu, Jiasheng; Zhang, Hongyan; Chen, Jianhong; Zhang, Wenjun; Wang, Pengfei

2013-03-01

298

A prototype direct-detection CCD for protein crystallography  

PubMed Central

The fabrication and testing of a prototype deep-depletion direct-conversion X-ray CCD detector are described. The device is fabricated on 600?µm-thick high-resistivity silicon, with 24?×?24?µm pixels in a 4k?×?4k pixel format. Calibration measurements and the results of initial protein crystallography experiments at the Cornell High Energy Synchrotron Source (CHESS) F1 beamline are described, as well as suggested improvements for future versions of the detector. PMID:24046505

Green, Katherine S.; Szebenyi, Doletha M. E.; Boggs, Kasey; Bredthauer, Richard; Tate, Mark W.; Gruner, Sol M.

2013-01-01

299

Linear 1x2 directional coupler for electromagnetic field detection  

Microsoft Academic Search

A 1x2 directional coupler which can be used as an integrated optical electromagnetic field detector is described. Modulators have been formed from titanium-indiffused lithium niobate waveguides operating at the 1.3 micron wavelength. Linear dynamic ranges of 74.3 dB with 190 micro-W light and 76.3 dB with 760 micro-W light were observed for separate devices. Voltage sensitivity measurements are in good

Marta McWright Howerton; Catherine H. Bulmer; William K. Burns

1988-01-01

300

Linear 1×2 directional coupler for electromagnetic field detection  

Microsoft Academic Search

A 1×2 directional coupler which can be used as an integrated optical electromagnetic field detector is described. Modulators have been formed from titanium-indiffused lithium niobate waveguides operating at the 1.3 ?m wavelength. Linear dynamic ranges of 74.3 dB with 190 ?W light and 76.3 dB with 760 ?W light were observed for separate devices. Voltage sensitivity measurements are in good

Marta McWright Howerton; Catherine H. Bulmer; William K. Burns

1988-01-01

301

Direct detection of DNA conformation in hybridization processes.  

PubMed

DNA hybridization studies at surfaces normally rely on the detection of mass changes as a result of the addition of the complementary strand. In this work we propose a mass-independent sensing principle based on the quantitative monitoring of the conformation of the immobilized single-strand probe and of the final hybridized product. This is demonstrated by using a label-free acoustic technique, the quartz crystal microbalance (QCM-D), and oligonucleotides of specific sequences which, upon hybridization, result in DNAs of various shapes and sizes. Measurements of the acoustic ratio ?D/?F in combination with a "discrete molecule binding" approach are used to confirm the formation of straight hybridized DNA molecules of specific lengths (21, 75, and 110 base pairs); acoustic results are also used to distinguish between single- and double-stranded molecules as well as between same-mass hybridized products with different shapes, i.e., straight or "Y-shaped". Issues such as the effect of mono- and divalent cations to hybridization and the mechanism of the process (nucleation, kinetics) when it happens on a surface are carefully considered. Finally, this new sensing principle is applied to single-nucleotide polymorphism detection: a DNA hairpin probe hybridized to the p53 target gene gave products of distinct geometrical features depending on the presence or absence of the SNP, both readily distinguishable. Our results suggest that DNA conformation probing with acoustic wave sensors is a much more improved detection method over the popular mass-related, on/off techniques offering higher flexibility in the design of solid-phase hybridization assays. PMID:22248021

Papadakis, George; Tsortos, Achilleas; Bender, Florian; Ferapontova, Elena E; Gizeli, Electra

2012-02-21

302

Bio-functionalized silver nanoparticles for selective colorimetric sensing of toxic metal ions and antimicrobial studies  

NASA Astrophysics Data System (ADS)

Hibiscus Sabdariffa (Gongura) plant extracts (leaves (HL) and stem (HS) were used for the first time in the green synthesis of bio-functionalized silver nanoparticles (AgNPs). The bio-functionality of AgNPs has been successfully utilized for selective colorimetric sensing of potentially health and environmentally hazardous Hg2+, Cd2+ and Pb2+ metal ions at ppm level in aqueous solution. Importantly, clearly distinguishable colour for all three metal ions was observed. The influence of extract preparation condition and pH were also explored on the formation of AgNPs. Both selectivity and sensitivity differed for AgNPs synthesized from different parts of the plant. Direct correlation between the stability of green synthesized AgNPs at different pH and its antibacterial effects has been established. The selective colorimetric sensing of toxic metal ions and antimicrobial effect of green synthesized AgNPs demonstrated the multifunctional applications of green nanotechnology.

Vinod Kumar, V.; Anbarasan, S.; Christena, Lawrence Rene; SaiSubramanian, Nagarajan; Philip Anthony, Savarimuthu

2014-08-01

303

Detection of nucleic acid sequences by invader-directed cleavage  

DOEpatents

The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The 5' nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof. The present invention further relates to methods and devices for the separation of nucleic acid molecules based by charge.

Brow, Mary Ann D. (Madison, WI); Hall, Jeff Steven Grotelueschen (Madison, WI); Lyamichev, Victor (Madison, WI); Olive, David Michael (Madison, WI); Prudent, James Robert (Madison, WI)

1999-01-01

304

Edge-directed inference for microaneurysms detection in digital fundus images  

Microsoft Academic Search

Microaneurysms (MAs) detection is a critical step in diabetic retinopathy screening, since MAs are the earliest visible warning of potential future problems. A variety of algorithms have been proposed for MAs detection in mass screening. Different methods have been proposed for MAs detection. The core technology for most of existing methods is based on a directional mathematical morphological operation called

Ke Huang; Michelle Yan; Selin Aviyente

2007-01-01

305

Lumen Border Detection of Intravascular Ultrasound via Denoising of Directional Wavelet Representations  

E-print Network

speaking, on IVUS image data, detection of the external vessel wall border is relatively easier thanLumen Border Detection of Intravascular Ultrasound via Denoising of Directional Wavelet for detection of lumen border layers, which remains one of the most challenging problems in IVUS image analysis

306

Face detection directly from h.264 compressed video with convolutional neural network  

Microsoft Academic Search

Human faces provide a useful cue in indexing video content. In this paper, we propose a novel face detection algorithm based on a convolutional neural network architecture that can rapidly detect human face regions in video sequences encoded by H.264\\/AVC. By detecting faces directly in the compressed domain, we use the discrete cosine transform (DCT) coefficients in H.264 intra coding

Shin-Shan Zhuang; Shang-Hong Lai

2009-01-01

307

4-Aminothiophenol functionalized gold nanoparticle-based colorimetric sensor for the determination of nitramine energetic materials.  

PubMed

The heterocyclic nitramine compounds, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), are two most important military-purpose high explosives. Differentiation of RDX and HMX with colorimetric methods of determination has not yet been made because of their similar chemical structures. In this study, a sensitive colorimetric method for the determination of RDX and HMX was proposed on the basis of differential kinetics in the hydrolysis of the two compounds (yielding nitrite as a product) followed by their colorimetric determination using 4-aminothiophenol (4-ATP) modified gold nanoparticles (AuNPs) and naphthylethylene diamine (NED) as coupling agent for azo-dye formation, abbreviated as "4-ATP-AuNP+NED" colorimetric method. After alkaline hydrolysis in a 1 M Na2CO3 + 0.04 M NaOH mixture solution at room temperature, only RDX (but not HMX) was hydrolyzed to give a sufficient colorimetric response in neutralized solution, the molar absorptivity (?) at 565 nm and the limit of detection (LOD) for RDX being (17.6 ± 1.3) × 10(3) L mol(-1) cm(-1) and 0.55 ?g mL(-1), respectively. On the other hand, hot water bath (at 60 °C) hydrolysis enabled both nitramines, RDX and HMX, to give substantial colorimetric responses; i.e., ? and LOD for RDX were (32.8 ± 0.5) × 10(3) L mol(-1)cm(-1) and 0.20 ?g mL(-1) and for HMX were (37.1 ± 2.8) × 10(3) L mol(-1)cm(-1) and 0.24 ?g mL(-1), respectively. Unlike other AuNP-based nitrite sensors in the literature showing absorbance quenching within a relatively narrow concentration range, the developed sensor operated with an absorbance increase over a wide range of nitrite. Synthetic mixtures of (RDX + HMX) gave additive responses, and the proposed method was statistically validated against HPLC using nitramine mixtures. PMID:24299426

Üzer, Ay?em; Can, Ziya; Ak?n, Ilknur; Erça?, Erol; Apak, Re?at

2014-01-01

308

Multianalyte determination with a direct optical miltiantibody detection system  

NASA Astrophysics Data System (ADS)

Discrimination of structurally similar analytes by immunoassay is limited by antibody cross reactivity. Using a plurality of cross-reacting antibody species allows increased selectivity by application of pattern recognition methods. We present a detailed characterization of an array of monoclonal antibodies which allows analytical modeling of the performance of an antibody array in a multi-analyte system. Such well defined antibody arrays give the possibility for the systematical optimization for immunoassay applications. Affinity characterization is carried out in a simple test format: After equilibrium binding of antibody and analyte, unoccupied antibody is quantified by an optical transducer. The test result reflects directly the respective affinity constants for different analytes. A set of three monoclonal antibodies was characterized with respect to their affinity to five different s-triazines which play an important role in water contamination. The affinities were compared with results obtained by direct enzyme immunoassay. The analytical performance of the antibody array was modeled by using the affinity constants determined from the calibration curve.

Piehler, Jacob; Brecht, Andreas; Kramer, Karl-Josef; Hock, Bertold; Gauglitz, Guenter

1995-10-01

309

PoS(ICHEP2010)539 Dark Matter direct detection searches  

E-print Network

PoS(ICHEP2010)539 Dark Matter direct detection searches Jules Gascon IPNL, Université de Lyon searches for Dark Matter is presented. These experi- ments look for energetic recoiling ions produced)539 Direct Searches for Dark Matter Jules Gascon Direct searches for Dark Matter in the form of Weakly

Boyer, Edmond

310

Direct Detection of Legionella Species from Bronchoalveolar Lavage and Open Lung Biopsy Specimens: Comparison of LightCycler PCR, In Situ Hybridization, Direct Fluorescence Antigen Detection, and Culture  

Microsoft Academic Search

We developed a rapid thermocycling, real-time detection (also known as real-time PCR) method for the detection of Legionella species directly from clinical specimens. This method uses the LightCycler (Roche Molecular Biochemicals, Indianapolis, Ind.) and requires approximately 1 t o2ht operform. Both a Legionella genus PCR assay and Legionella pneumophila species-specific PCR assay were designed. A total of 43 archived specimens

R. T. Hayden; J. R. Uhl; X. Qian; M. K. Hopkins; M. C. Aubry; A. H. Limper; R. V. Lloyd; F. R. Cockerill

2001-01-01

311

A direct immunoassay for detecting diatoms in groundwater as an indicator of the direct influence of surface water  

USGS Publications Warehouse

Groundwater under the direct influence of surface water (GWUDISW) is of concern in communities where growing public demand on groundwater resources has resulted in increased withdrawals and hydraulic stress near surface water bodies. Under these conditions, contaminants such as methyl-tert butyl ether (MTBE) and biological materials have been detected in domestic wells. Other contaminants and pathogens associated with surface water are not routinely tested for in groundwater-supplied systems. To address the need for methods to easily identify potentially vulnerable supplies, a direct immunoassay for the quantitative detection of diatoms in raw water samples was developed as a measure of surface water influence on groundwater. Cell wall preparations from Nitzschia palea Ku??tzing, a freshwater diatom found throughout North America, were used to produce a polyclonal antibody that was applied in a direct enzyme-linked immunosorbent assay (ELISA) developed to detect the presence of N. palea cell wall components. The direct immunoassay allows detection at 500 cells L-1, a level similar to diatom concentrations observed in samples of groundwater collected near the test site. This investigation was the first attempt to utilize an ELISA as an indicator of surface water influence on groundwater. Further research is needed to develop more specific diatom-based monoclonal antibodies, determine cross-reactivity, and optimize sample processing and ELISA procedures for development of a standardized method. ?? Springer 2005.

Walker, C. E.; Schrock, R. M.; Reilly, T. J.; Baehr, A. L.

2005-01-01

312

Comparison of Chemicon SimulFluor Direct Fluorescent Antibody Staining with Cell Culture and Shell Vial Direct Immunoperoxidase Staining for Detection of Herpes Simplex Virus and with Cytospin Direct Immunofluorescence Staining for Detection of Varicella-Zoster Virus  

Microsoft Academic Search

A new rapid direct immunofluorescence assay, the SimulFluor direct fluorescent-antibody (DFA) assay, which can simultaneously detect herpes simplex virus types 1 and 2 (HSV-1 and -2) and varicella-zoster virus (VZV), was evaluated in comparison with our current standard procedures of (i) shell vial direct immuno- peroxidase (shell vial IP) staining and cell culture for detection of HSV and (ii) cytospin

EDWARD L. CHAN; KEN BRANDT; GREG B. HORSMAN

2001-01-01

313

Speckle identification to assist the direct detection of exoplanets  

NASA Astrophysics Data System (ADS)

Current observations in the context of exoplanet searches with coronagraphic instruments have shown that one of the main limitations to high-contrast imaging is due to residual quasi-static speckles. Speckles look like the image of a planet, but they have a different spectral behavior and are optically coherent with the star. We present two techniques to distinguish a planet from speckles. We are assuming that the optical path can be changed enough so that the speckles will change significantly between each image and therefore our model of each image having an independent source of aberrations (creating a new speckle pattern) from the other images is a good model. In the future, we would like to design and build a testbed suitable for coherent speckle detection studies. There are two techniques we want to apply to create the necessary multiple images with changing speckle patterns. The first is to use images generated using our existing deformable mirror (DM) control algorithm and the second is to put deliberate shapes on the DM to achieve the desired speckle pattern outcome.

Young, Elizabeth J.; Kasdin, N. J.; Carlotti, A.; Littman, M.; Noecker, M. C.

2011-10-01

314

Direct phosphorescent detection of primary event of photodynamic action  

NASA Astrophysics Data System (ADS)

Highly phosphorescent photosensitizer Pd-tetra (o-methoxy-p-sulfo) phenyl porphyrin (Pd-MSPP) was used to follow the primary events of photodynamic action - quenching of triplet states by free oxygen in different systems: water solutions of proteins, cells and tissues in vivo and in vitro. The photosensitizer forms complexes with proteins in solutions and biosystems showing remarkable hypsochromic shifts of band and an increase of the quantum yield and lifetime of phosphorescence at the binding to proteins. In absence of oxygen the lifetime of phosphorescence is almost single exponential, and depends on the energy of lowest triplet state of the sensitizer. The photochemical quenching of the triplets by cell components is negligible. In presence of free oxygen the quenching of the sensitizer triplets takes place. The emission spectrum of singlet oxygen with maximum 1271 nm was recorded in water protein solutions and quantum yield of sensitized luminescence was measured. In the systems studied, oxygen consumption was detected and oxygen concentration was estimated in the course of photodynamics by an increase in photosensitizer phosphorescence lifetime, using laser flash photolysis technique. At least two exponential kinetics of the phosphorescence decay shows that the distribution of the free oxygen is not uniform in tissues.

Losev, Anatoly P.; Knukshto, Valentin N.; Zhuravkin, Ivan N.

1994-07-01

315

First Direct Detection of Clay Minerals on Mars  

NASA Technical Reports Server (NTRS)

Magnesian clays or clay-type minerals were conclusively detected in the martian regolith. Near-IR spectral observations of Mars using the Mauna Kea 2.2-m telescope show weak but definite absorption bands near microns. The absorption band positions and widths match those produced by combined OH stretch and Mg-OH lattice modes and are diagnostic of minerals with structural OH such as clays and amphiboles. Likely candidate minerals include serpentine, talc, hectorite, and sponite. There is no spectral evidence for aluminous hydroxylated minerals. No distinct band occurs at 2.55 microns, as would be expected if carbonates were responsible for the 2.35 micron absorption. High-albedo regions such as Elysium and Utopia have the strongest bands near 2.35 microns, as would be expected for heavily weathered soils. Low-albedo regions such as Iapygia show weaker but distinct bands, consistent with moderate coatings, streaks, and splotches of bright weathered material. In all areas observed, the 2.35-micron absorption is at least three times weaker than would be expected if well-crystallized clay minerals made up the bulk of bright soils on Mars.

Singer, R. B.; Owensby, P. D.; Clark, R. N.

1985-01-01

316

Direct detection and solar capture of spin-dependent dark matter  

NASA Astrophysics Data System (ADS)

We investigate the implication of different elastic spin-dependent (SD) operators on both the direct and indirect detections of the weakly interacting massive particle (WIMP). Six representative building blocks of SD operators, together with their counterparts with a massless mediator, are considered to interpret the direct detection experiments (Xenon100, SIMPLE, and COUPP) in a comprehensive way. We also study the solar capture and annihilation of WIMPs with these effective SD operators and place the constraints on the relevant annihilation rate from neutrino detection experiments Super-Kamionkande and IceCube. Upper limits on the WIMP-nucleon couplings drawn from direct detections are also projected to the annihilation rate for contrast and complementarity. We find that the efficiency of these mentioned detection strategies depends specifically on the six SD operators, while the neutrino-based detections are more effective in exploring the parameter space for the massless mediator scenario.

Liang, Zheng-Liang; Wu, Yue-Liang

2014-01-01

317

Direct Detection of Cl2 in Coastal Urban Air  

NASA Astrophysics Data System (ADS)

Chlorine radicals react rapidly with a wide range of organic compounds and, if present in sufficient levels, can significantly affect ozone in urban air. Several mechanisms for the generation of Cl in air have been proposed, but there are few direct observations of reactive chlorine species. This study reports measurements of atmospheric chlorine (Cl2) in coastal urban air utilizing negative ion atmospheric pressure chemical ionization with triple quadrupole mass spectrometry. Measurements were made in Irvine, CA over a 14 day period during July and August, 2005. Fifteen minute average Cl2 mixing ratios ranged from 5-40 parts per trillion, with a two week geometric mean of 16+/-14 pptv. These levels imply significant (>15 ppb/day) ozone production from the Cl-mediated oxidation of VOC's. A consistent pattern of diurnal variability in Cl2 was observed, with low nighttime and morning Cl2 levels, and an increase shortly after local noon reaching a maximum in the early evening. Cl2 levels gradually returned to lower nighttime values between 9 and 11 PM. This pattern suggests a photochemical production mechanism for Cl2, and possibly a relationship to the local sea-breeze circulation and the levels of seasalt aerosols.

Finley, B. D.; Saltzman, E. S.

2005-12-01

318

The effect of carbonated beverages on colorimetric end-tidal CO(2) determination  

PubMed

Esophageal intubation is a significant complication of attempted airway control. Colorimetric end-tidal CO(2) monitors are highly sensitive and specific for detecting the presence of CO(2). There are reports of false-positive end-tidal CO(2) readings from esophageal intubations in patients who had ingested carbonated beverages. OBJECTIVE: To determine whether carbonated gastric contents can affect colorimetric end-tidal CO(2) readings. METHODS: End-tidal CO(2) was measured in sacrificed piglets at measured time intervals after instillation of 5-, 10-, 15-, and 20-mL aliquots of Diet Coke were placed into the stomach via a 28-French orogastric tube followed by esophageal intubation. The stomach was completely evacuated prior to each instillation and rechecked for baseline CO(2). RESULTS: Compiled data from three piglets (20-30 kg). Piglets were not ventilated or moved and determinations were measured at 20 degrees while supine. All data collected within 2 hours postmortem (table 24-1). CONCLUSIONS: The colorimetric end-tidal CO(2) turned "yellow" and did not change to blue with extended insufflations. The CO(2) of a small quantity of carbonated beverage in the stomach could be "blown off" by multiple insufflations. We conclude that esophageal intubation in the setting of recent ingestion of a carbonated beverage may result in a false-positive end-tidal CO(2) determination. PMID:11015273

Qureshi; Park; Sturmann; Hsu

2000-10-01

319

The use of colorimetric sensor arrays to discriminate between pathogenic bacteria.  

PubMed

A colorimetric sensor array is a high-dimensional chemical sensor that is cheap, compact, disposable, robust, and easy to operate, making it a good candidate technology to detect pathogenic bacteria, especially potential bioterrorism agents like Yersinia pestis and Bacillus anthracis which feature on the Center for Disease Control and Prevention's list of potential biothreats. Here, a colorimetric sensor array was used to continuously monitor the volatile metabolites released by bacteria in solid media culture in an Advisory Committee on Dangerous Pathogen Containment Level 3 laboratory. At inoculum concentrations as low as 8 colony-forming units per plate, 4 different bacterial species were identified with 100% accuracy using logistic regression to classify the kinetic profile of sensor responses to culture headspace gas. The sensor array was able to further discriminate between different strains of the same species, including 5 strains of Yersinia pestis and Bacillus anthracis. These preliminary results suggest that disposable colorimetric sensor arrays can be an effective, low-cost tool to identify pathogenic bacteria. PMID:23671629

Lonsdale, Claire L; Taba, Brian; Queralto, Nuria; Lukaszewski, Roman A; Martino, Raymond A; Rhodes, Paul A; Lim, Sung H

2013-01-01

320

Overview of Non-Liquid Noble Direct Detection Dark Matter Experiments  

E-print Network

In the last few years many advances have been made in the field of dark matter direct detection. In this article I will review the progress and status of experiments that employ detection techniques that do not use noble liquids. First, I will give an introduction to the field of dark matter and discuss the background challenges that confront all dark matter experiments. I will also discuss various detection techniques employed by the current generation and the next generation of dark matter experiments. Finally, I will discuss recent results and the status of current and future direct detection experiments.

Cooley, J

2014-01-01

321

A concise colorimetric and fluorimetric probe for sarin related threats designed via the "covalent-assembly" approach.  

PubMed

A turn-on signal from zero background allows sensitive detection of a weak signal and is highly desired. The "covalent-assembly" probe design principle is powerful in this regard. Herein, we report an embodiment of this principle (NA570) for detection of Sarin related threats, based on a phenylogous Vilsmeier-Haack reaction. NA570 bears a concise molecular construct, exhibits a colorimetric and a fluorimetric signal, and has potential for real applications. PMID:24766398

Lei, Zuhai; Yang, Youjun

2014-05-01

322

Highly Sensitive and Selective Colorimetric Sensors for Uranyl (UO22+): Development and Comparison of Labeled and Label-Free DNAzyme-Gold Nanoparticle Systems  

PubMed Central

Colorimetric uranium sensors based on uranyl (UO22+) specific DNAzyme and gold nanoparticles (AuNP) have been developed and demonstrated using both labeled and label-free methods. In the labeled method, a uranyl-specific DNAzyme was attached to AuNP, forming purple aggregates. The presence of uranyl induced disassembly of the DNAzyme functionalized AuNP aggregates, resulting in red individual AuNPs. Once assembled, such a “turn-on” sensor is highly stable and worked in a single step at room temperature and had detection limit of 50 nM after 30 min. of reaction time. The label-free method, on the other hand, utilizes the different adsorption properties of single stranded and double stranded DNA on AuNPs, which affects the stability of AuNPs in the presence of NaCl. The presence of uranyl resulted in cleavage of substrate by DNAzyme, releasing a single stranded DNA that can be adsorbed on AuNPs and protect them from aggregation. Taking advantage of this phenomenon, a “turn-off” sensor was developed, which is easy to control through reaction quenching, and has 1 nM detection limit after 6 min. of reaction at room temperature. Both sensors have excellent selectivity over other metal ions and have detection limits below the maximum contamination level of 130 nM for UO22+ in drinking water defined by the US Environmental Protection Agency (EPA). The study represents the first direct systematic comparison of these two types of sensor methods using the same DNAzyme and AuNPs, making it possible to reveal advantages, disadvantages, versatility, and limitations and potential applications of each method. The results obtained not only allow practical sensing application for uranyl, but also serve as a guide for choosing different method for designing colorimetric sensors for other targets. PMID:18837498

Lee, Jung Heon; Wang, Zidong; Liu, Juewen; Lu, Yi

2009-01-01

323

Direct determination of free cyanide in drinking water by ion chromatography with pulsed amperometric detection  

Microsoft Academic Search

Cyanide is a regulated contaminant in drinking water in the United States. This paper describes an ion chromatography method with pulsed amperometric detection (PAD) that directly determines free cyanide in drinking water. Samples are treated with sodium hydroxide to stabilize cyanide and with a cation-exchange cartridge to remove transition metals. Cyanide is separated by anion-exchange chromatography and detected by PAD

Terri T. Christison; Jeffrey S. Rohrer

2007-01-01

324

Direct detection of Salmonella typhimurium on fresh produce using phage-based magnetoelastic biosensors  

Microsoft Academic Search

Current bacterial detection methods require the collection of samples followed by preparation and analysis in the laboratory, both time and labour consuming steps. More importantly, because of cost, only a limited number of samples can be taken and analyzed. This paper presents the results of an investigation to directly detect Salmonella typhimurium on fresh tomato surfaces using phage-based magnetoelastic (ME)

Suiqiong Li; Yugui Li; Huiqin Chen; Shin Horikawa; Wen Shen; Aleksandr Simonian; Bryan A. Chin

2010-01-01

325

Direct detection of Salmonella on fresh vegetables using multiple magnetoelastic biosensors  

Microsoft Academic Search

This paper demonstrates the direct detection of Salmonella typhimurium on fresh tomatoes using multiple phage based magnetoelastic (ME) biosensors. In this investigation, the sample collection\\/preparation step that is necessary for current pathogen detection methods was eliminated. ME biosensors are wireless sensors and are composed of a ME resonator platform immobilized with E2 phage. The E2 phage is genetically engineered to

Suiqiong Li; Shin Horikawa; Wen Shen; Z.-Y. Cheng; B. A. Chin

2010-01-01

326

Ultrasensitive detection of coliforms by means of direct asymmetric PCR combined with disposable magnetic amperometric genosensors.  

PubMed

An extremely sensitive procedure for the isolation and detection of DNA from bacterial cell cultures is described. Direct asymmetric PCR amplified products from E. coli cultures are specifically detected, at a concentration level as low as 0.01 cfu mL(-1) (cfu, colony forming unit), using disposable magnetic DNA hybridization amperometric sensors with no need for culture preconcentration steps. PMID:19082171

Loaiza, Oscar A; Campuzano, Susana; Pedrero, María; García, Pedro; Pingarrón, José M

2009-01-01

327

Challenges of Detecting Directional Selection After a Bottleneck: Lessons From Sorghum bicolor  

Microsoft Academic Search

Multilocus surveys of sequence variation can be used to identify targets of directional selection, which are expected to have reduced levels of variation. Following a population bottleneck, the signal of directional selection may be hard to detect because many loci may have low variation by chance and the frequency spectrum of variation may be perturbed in ways that resemble the

Martha T. Hamblin; Alexandra M. Casa; Hong Sun; Seth C. Murray; Andrew H. Paterson; Charles F. Aquadro; Stephen Kresovich

2006-01-01

328

Detecting Blackhole and Volcano Patterns in Directed Networks Zhongmou Li1  

E-print Network

Detecting Blackhole and Volcano Patterns in Directed Networks Zhongmou Li1 , Hui Xiong1 , Yanchi and volcano patterns in a large directed graph. Specifically, a blackhole pattern is a group which is made. In contrast, a volcano pattern is a group which only has outlinks to the rest nodes in the graph. Both

Xiong, Hui

329

Contour detection based on Gabor filter and directional DoG filter  

Microsoft Academic Search

A contour detector with directional surround suppression, motivated by biological principles, is proposed in this paper. A bank of Gabor filters are used to simulate receptive filed for edge detection. The directional DoG filter is used to simulate the biological surround suppression mechanism. The resulting operator has strong response to the texture boundary, isolated edge and object contour. We use

Lu Min; Zheng Ling Xiang

2007-01-01

330

Bloodstream infections caused by Pseudomonas spp.: how to detect carbapenemase producers directly from blood cultures.  

PubMed

The Carba NP test has been evaluated to detect carbapenemase-producing Pseudomonas spp. directly from blood cultures. This rapid and cost-effective test permits an early identification of carbapenemase-producing Pseudomonas spp. directly from blood cultures with excellent sensitivity and specificity. Results may be useful in particular for guiding the first-line therapy and epidemiological purposes. PMID:24501031

Dortet, Laurent; Boulanger, Anne; Poirel, Laurent; Nordmann, Patrice

2014-04-01

331

ccsd-00003303,version1-17Nov2004 Dark Matter Direct Detection using Cryogenic  

E-print Network

ccsd-00003303,version1-17Nov2004 Dark Matter Direct Detection using Cryogenic Detectors Gabriel the Dark Matter enigma represents one of the key objectives of contemporary physics. Recent astrophysical Massive Particles (WIMPs) represent the best mo- tivated candidate to fill the Dark Matter gap, and direct

Boyer, Edmond

332

Bloodstream Infections Caused by Pseudomonas spp.: How To Detect Carbapenemase Producers Directly from Blood Cultures  

PubMed Central

The Carba NP test has been evaluated to detect carbapenemase-producing Pseudomonas spp. directly from blood cultures. This rapid and cost-effective test permits an early identification of carbapenemase-producing Pseudomonas spp. directly from blood cultures with excellent sensitivity and specificity. Results may be useful in particular for guiding the first-line therapy and epidemiological purposes. PMID:24501031

Dortet, Laurent; Boulanger, Anne; Poirel, Laurent

2014-01-01

333

PREFACE: CYGNUS 2013: 4th Workshop on Directional Detection of Dark Matter  

NASA Astrophysics Data System (ADS)

It is a great pleasure to publish the proceedings of the 4th Workshop on Directional Detection of Dark Matter held in Toyama, Japan on 10-12 June 2013 (CYGNUS 2013). These proceedings contain written versions of the presentations made at CYGNUS 2013 as scientific outputs of the directional detection of dark matter. The GYGNUS workshop started in 2007 at Boulby Underground Laboratory (UK), followed by CYGNUS 2009 (MIT in Cambridge, Massachusetts, USA) and CYGNUS 2011 (AUSSOIS, France). CYGNUS 2013 was held by the combination of a two and a half days of scientific program and a half day visit to the underground laboratory (Kamioka Observatory) as a 'tradition' of CYGNUS workshops. The name 'CYGNUS' came from the fact that the 'dark matter wind' is expected to come from the direction of the constellation Cygnus due to the motion of the Solar system in the galaxy. A general aim of these CYGNUS workshops is to bring together the theoretical and experimental studies on the directional dark matter detection. Directional detection of dark matter is a promising approach to a 'clear detection' and also to 'further investigations' of galactic dark matter, or Weakly Interacting Massive Particles (WIMPs). Directional detection requires the simultaneous detection of the energy and track of low energy recoils. Among many technological challenges for the requirement above, three of them, namely size, background, and directionality (angular resolution and head-tail detection), are most important to demonstrate and improve the quality as a dark matter detector. In the workshop, up-to-date activities by the international reserchers are discussed. The workshop was a great success thanks to the oral contributions and fruitful discussions held throughout the workshop period. We hope that readers will remember and share the great enthusiasm shown during the CYGNUS 2013 workshop. The Editors Tatsuhiro Naka and Kentaro Miuchi

Naka, Tatsuhiro; Miuchi, Kentaro

2013-12-01

334

Efficacy of the use of a colorimetric pupil light reflex device in the diagnosis of fundus disease or optic pathway disease in dogs.  

PubMed

The aim of this study was to determine the efficacy of a colorimetric pupil light reflex (PLR) device (Melan-100(®), U.S.A.) in dogs with sudden acquired retinal degeneration syndrome (SARDS; 16 cases), progressive retinal atrophy (PRA; 10 cases) and optic pathway disease (6 cases). The colorimetric device detected PLR abnormality in 32, 16 and 9 eyes with SARDS, PRA and optic pathway disease, respectively, whereas white light detected PLR abnormality in 18, 11 and 9 eyes with SARDS, PRA and optic pathway disease, respectively. SARDS dogs displayed miosis, while optic pathway disease dogs displayed mydriasis in a blue light examination. Thus, colorimetric PLR may be a useful method for determining whether electroretinography (ERG) or magnetic resonance imaging (MRI) should be performed for dogs with acute blindness. PMID:23774038

Terakado, Kunihiko; Yogo, Takuya; Nezu, Yoshinori; Harada, Yasuji; Hara, Yasushi; Tagawa, Masahiro

2013-11-01

335

Basic design principles of colorimetric vision systems  

NASA Astrophysics Data System (ADS)

Color measurement is an important part of overall production quality control in textile, coating, plastics, food, paper and other industries. The color measurement instruments such as colorimeters and spectrophotometers, used for production quality control have many limitations. In many applications they cannot be used for a variety of reasons and have to be replaced with human operators. Machine vision has great potential for color measurement. The components for color machine vision systems, such as broadcast quality 3-CCD cameras, fast and inexpensive PCI frame grabbers, and sophisticated image processing software packages are available. However the machine vision industry has only started to approach the color domain. The few color machine vision systems on the market, produced by the largest machine vision manufacturers have very limited capabilities. A lack of understanding that a vision based color measurement system could fail if it ignores the basic principles of colorimetry is the main reason for the slow progress of color vision systems. the purpose of this paper is to clarify how color measurement principles have to be applied to vision systems and how the electro-optical design features of colorimeters have to be modified in order to implement them for vision systems. The subject of this presentation far exceeds the limitations of a journal paper so only the most important aspects will be discussed. An overview of the major areas of applications for colorimetric vision system will be discussed. Finally, the reasons why some customers are happy with their vision systems and some are not will be analyzed.

Mumzhiu, Alex M.

1998-10-01

336

Functional gold nanoparticles coupled with microporous membranes: a flow controlled assay for colorimetric visualization of proteins.  

PubMed

We report a rapid and simple assay for colorimetric visualization of thrombin at nanomolar levels using functional gold nanoparticles (FAuNPs) coupled with microporous membranes. We used a 29-mer thiolated-thrombin-binding-aptamer (TBA29) to prepare TBA29 functionalized AuNPs (TBA29-AuNPs) for the selective detection of human thrombin. The sensing mechanism is based on the principle of TBA29-AuNPs flowing down through the nitrocellulose membrane (NCM) pores at different flow rates after binding to thrombin. Compared with free TBA29-AuNPs, when thrombin-TBA29-AuNPs were dropped on the NCM, the particles flowed down more easily through the NCM pores along with the buffer solution due to the increase in the gravity of particles. Therefore, color intensities of TBA29-AuNPs on the NCM depended on the concentration of thrombin; the color intensity was lighter when the concentration of thrombin was higher. Thrombin can be detected at the nanomolar level with the naked eye using this colorimetric probe. A protein G modified AuNP based probe (PG-AuNPs/NCM) was employed to detect human immunoglobulin G (hIgG) in plasma samples to demonstrate the practicality of our sensing system. Also, fibrinogen modified Au NPs were analyzed to demonstrate that this concept of detection could be extended to other proteins or systems, by functionalizing with suitable molecules. PMID:25267979

Chen, Yu-Yuan; Unnikrishnan, Binesh; Li, Yu-Jia; Huang, Chih-Ching

2014-10-15

337

Ascorbic acid-functionalized Ag NPs as a probe for colorimetric sensing of glutathione  

NASA Astrophysics Data System (ADS)

In this work, we report the use of ascorbic acid-capped silver nanoparticles (AA-Ag NPs) as a probe for selective colorimetric detection of glutathione (GSH) in aqueous solution. This detection system was based on the GSH-induced aggregation of AA-Ag NPs, resulting in drastic changes in the absorption spectra and color of the AA-Ag NPs system. The GSH-induced AA-Ag NPs aggregation was confirmed by UV-visible spectrometry, dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. Under optimal conditions, this method exhibited good linearity over the concentration ranges from 5.0 to 50 µM, with the limit of detection 2.4 × 10-7 M. This method was successfully applied to detect GSH in the presence of other biomolecules, which confirms that this probe can be used for the detection of GSH in real samples.

D'souza, Stephanie L.; Pati, Ranjan; Kailasa, Suresh Kumar

2014-10-01

338

A novel colorimetric and fluorescent sensor based on calix[4]arene possessing triphenylamine units  

NASA Astrophysics Data System (ADS)

A novel colorimetric and fluorometric calix[4]arene probe (CTP) bearing triphenylamine units was synthesized in good yield and characterized by combination of 1H, 13C, APT, COSY, FTIR, HRMS, and UV-vis spectral data. Ion-binding studies of CTP were investigated in acetonitrile with a wide range of cations and anions and the recognition process was monitored by luminescence, UV-vis and 1H NMR spectral changes. CTP exhibited naked eye detection for Hg2+ ion. Also it showed a significant fluorescence quenching towards F- ion.

Erdemir, Serkan; Malkondu, Sait; Kocyigit, Ozcan; Al?c?, Onder

2013-10-01

339

Edge-directed inference for microaneurysms detection in digital fundus images  

NASA Astrophysics Data System (ADS)

Microaneurysms (MAs) detection is a critical step in diabetic retinopathy screening, since MAs are the earliest visible warning of potential future problems. A variety of algorithms have been proposed for MAs detection in mass screening. Different methods have been proposed for MAs detection. The core technology for most of existing methods is based on a directional mathematical morphological operation called "Top-Hat" filter that requires multiple filtering operations at each pixel. Background structure, uneven illumination and noise often cause confusion between MAs and some non-MA structures and limits the applicability of the filter. In this paper, a novel detection framework based on edge directed inference is proposed for MAs detection. The candidate MA regions are first delineated from the edge map of a fundus image. Features measuring shape, brightness and contrast are extracted for each candidate MA region to better exclude false detection from true MAs. Algorithmic analysis and empirical evaluation reveal that the proposed edge directed inference outperforms the "Top-Hat" based algorithm in both detection accuracy and computational speed.

Huang, Ke; Yan, Michelle; Aviyente, Selin

2007-03-01

340

Halo-independent direct detection of momentum-dependent dark matter  

NASA Astrophysics Data System (ADS)

We show that the momentum dependence of dark matter interactions with nuclei can be probed in direct detection experiments without knowledge of the dark matter velocity distribution. This is one of the few properties of DM microphysics that can be determined with direct detection alone, given a signal of dark matter in multiple direct detection experiments with different targets. Long-range interactions arising from the exchange of a light mediator are one example of momentum-dependent DM. For data produced from the exchange of a massless mediator we find for example that the mediator mass can be constrained to be lesssim 10 MeV for DM in the 20-1000 GeV range in a halo-independent manner.

Cherry, John F.; Frandsen, Mads T.; Shoemaker, Ian M.

2014-10-01

341

New non-covalent charge–transfer complex of calix[4]pyrrole–chloranil: as a potential colorimetric anion sensor  

Microsoft Academic Search

Non-covalent calix[4]pyrrole–chloranil complex, a new class of supramolecular assembly, is reported. The formation of the complex is mainly attributed to the charge–transfer interactions between calix[4]pyrrole with electron-rich pyrrole rings and the electron-deficient chloranil subunit. As potential colorimetric anion sensors, the charge–transfer aggregation may be used for effective and selective detection of F? and H2PO4? by means of dramatic visual color

Shijun Shao; Yong Guo; Lijun He; Shengxiang Jiang; Xianda Yu

2003-01-01

342

Validation of direct plating of a stool sample as a method for Listeria monocytogenes detection.  

PubMed

The aim of current studies was to validate the direct plating of a stool sample for Listeria monocytogenes detection, using selective medium Palcam agar with Palcam selective supplement. Validation was performed using stool samples collected from healthy humans inoculated with Listeria sp. strains. Stool samples were frozen to determine the influence of freezing on method robustness. The presented research defines the Listeria monocytogenes limit of detection (LOD) as 10(3) cfu/g of stools for fresh and frozen samples. Repeatability and reproducibility of the method has been confirmed using statistical methods. We show the effectiveness of direct plating of stool samples on Palcam agar with Palcam selective supplement collected for Listeria monocytogenes detection. This method could be useful for this pathogen detection in stool samples collected from patients with diarrhoea. PMID:22462448

Madajczak, Grzegorz; Szych, Jolanta; Wójcik, Bo?ena; M?ka, ?ukasz; Formi?ska, Kamila

2012-03-23

343

Rapid Determination of Methicillin Resistance among Staphylococcus aureus Clinical Isolates by Colorimetric Methods  

PubMed Central

In the present study, the effectiveness of a rapid and colorimetric nitrate reductase analysis (NRA) method and resazurin microplate assay (REMA) for rapid determination of methicillin resistance among Staphylococcus aureus was investigated. A total of 275 clinical isolates of S. aureus were included in the present study. Among these isolates, 151 had the mecA gene and were resistant to methicillin. The remaining 124 isolates were methicillin susceptible and did not have the mecA gene. Cefoxitin MICs of all isolates were detected by NRA, REMA, and reference broth microdilution methods. Category and essential agreement were determined as 100% and 99.6%, respectively, comparing both NRA and REMA with the reference method. No minor, major, or very major discrepancy was observed for either of the methods. The time necessary to have the MIC results was 5 h for NRA, whereas it was 6 h for REMA. Early detection of MRSA is an important public health concern, and the results of this study showed that both of the colorimetric methods are easy to perform and save time in the determination of MRSA. These methods have a potential use for early detection of MRSA for laboratories unable to use molecular techniques. PMID:22518854

2012-01-01

344

Advances and new directions in plant-wide disturbance detection and diagnosis  

Microsoft Academic Search

This article reviews advances in detection and diagnosis of plant-wide control system disturbances in chemical processes and discusses new directions that look promising for the future. Causes of plant-wide disturbances include non-linear limit cycles in control loops, controller interactions and tuning problems. The diagnosis of non-linearity, especially when due to valve stiction, has been an active area. Detection of controller

Nina F. Thornhill; Alexander Horch

2007-01-01

345

Migratory birds use head scans to detect the direction of the earth's magnetic field.  

PubMed

Night-migratory songbirds are known to use a magnetic compass , but how do they detect the reference direction provided by the geomagnetic field, and where is the sensory organ located? The most prominent characteristic of geomagnetic sensory input, whether based on visual patterns or magnetite-mediated forces , is the predicted symmetry around the north-south or east-west magnetic axis. Here, we show that caged migratory garden warblers perform head-scanning behavior well suited to detect this magnetic symmetry plane. In the natural geomagnetic field, birds move toward their migratory direction after head scanning. In a zero-magnetic field , where no symmetry plane exists, the birds almost triple their head-scanning frequency, and the movement direction after a head scan becomes random. Thus, the magnetic sensory organ is located in the bird's head, and head scans are used to locate the reference direction provided by the geomagnetic field. PMID:15530397

Mouritsen, Henrik; Feenders, Gesa; Liedvogel, Miriam; Kropp, Wiebke

2004-11-01

346

MIMAC: MIcro-tpc MAtrix of Chambers for dark matter directional detection  

NASA Astrophysics Data System (ADS)

Directional detection of non-baryonic Dark Matter is a promising search strategy for discriminating WIMP events from neutrons, the ultimate background for dark matter direct detection. This strategy requires both a precise measurement of the energy down to a few keV and 3D reconstruction of tracks down to a few mm. The MIMAC (MIcro-tpc MAtrix of Chambers) collaboration has developed in the last years an original prototype detector based on the direct coupling of large pixelized micromegas with a special developed fast self-triggered electronics showing the feasibility of a new generation of directional detectors. The first bi-chamber prototype has been installed at Modane, underground laboratory in June 2012. The first undergournd background events, the gain stability and calibration are shown. The first spectrum of nuclear recoils showing 3D tracks coming from the radon progeny is presented.

Santos, D.; Bosson, G.; Bouly, J. L.; Bourrion, O.; Fourel, Ch; Guillaudin, O.; Lamblin, J.; Mayet, F.; Muraz, J. F.; Richer, J. P.; Riffard, Q.; Lebreton, L.; Maire, D.; Busto, J.; Brunner, J.; Fouchez, D.

2013-12-01

347

Three-dimensional double directional filter for tracking and detecting moving dim weak target  

Microsoft Academic Search

The aim of the present work is to assess the performance of three-dimensional Double Directional Filtering (TDDDF) algorithm for detecting and tracking a weak moving dim target against a complex cluttered background in infrared image sequences. This paper proposes an novel TDDDF to improve the integrated signal-to-clutter ratio (ISCR) and enhance the three-dimensional directional filter's (TDDF) target energy accumulation ability

Meng Li; Tianxu Zhang; Weidong Yang; Haiceng Mao

2005-01-01

348

Moving dim point target detection with three-dimensional wide-to-exact search directional filtering  

Microsoft Academic Search

We assess the performance of a novel three-dimensional wide-to-exact search directional filtering (3DWESDF) algorithm for detecting and tracking a weak moving dim target against a cluttered background in real infrared (IR) image sequence. This paper proposed a novel 3DWESDF to decrease the 3D directional filter’s (3DDF) computational requirements and increase the target energy accumulation ability further. Prior to the filtering,

Tianxu Zhang; Meng Li; Zhengrong Zuo; Weidong Yang; Xiechang Sun

2007-01-01

349

Sex pheromone source location by garter snakes: : A mechanism for detection of direction in nonvolatile trails.  

PubMed

Male plains garter snakes,Thamnophis radix, tested in a 240-cm-long arena can detect directional information from a female pheromone trail only when the female is allowed to push against pegs while laying the trail. The female's normal locomotor activity apparently deposits pheromone on the anterolateral surfaces of vertical structures in her environment. The male sensorily assays the sides of these objects and from this information determines the female's direction of travel. PMID:24318905

Ford, N B; Low, J R

1984-08-01

350

Detecting an orientation component in animal paths when the preferred direction is individual-dependent.  

PubMed

An orientation component leads to directionally biased paths, with major consequences in animal population redistribution. Classical orientation analyses, which focus on the overall direction of motion, are useless for detecting such a component when the preferred direction is not common to the whole population, but differs from one path to another. In-depth path analyses are required in this case. They consist of determining whether paths are more suitably represented as biased or unbiased random walks. The answer is not easy because most animals' paths show some forward persistence propensity that acts as a purely local directional bias and, hence, blurs the possible occurrence of an additional, consistent bias in a preferred direction. I highlight the key differences between biased and unbiased random walks and the different ways orientation mechanisms can generate a consistent directional bias. I then examine the strength and weakness of the available methods likely to detect it. Finally, I introduce a new procedure based on the backward evolution of the beeline distance, from the end of the path, which might correspond to a goal toward which the animal orients itself, to each of the animal's preceding locations. This new procedure proves to be very efficient, as it requires only a small sample of short paths for detecting a possible orientation component. PMID:16637375

Benhamou, Simon

2006-02-01

351

Detecting and Characterizing Exoplanets with Direct Imaging: Past, Present, and Future  

NASA Astrophysics Data System (ADS)

The last decade has yielded the first images of exoplanets, considerably advancing our understanding of the properties of young giant planets. In this talk I will discuss current results from ongoing direct imaging efforts as well as future prospects for detection and characterization of exoplanets via high contrast imaging. Direct detection, and direct spectroscopy in particular, have great potential for advancing our understanding of extrasolar planets. In combination with other methods of planet detection, direct imaging and spectroscopy will allow us to eventually: 1) study the physical properties of exoplanets (colors, temperatures, etc.) in depth and 2) fully map out the architecture of typical planetary systems. Direct imaging has offered us the first glimpse into the atmospheric properties of young high-mass (3-10 M Jup ) exoplanets. Deep direct imaging surveys for exoplanets have also yielded the strongest constraints to date on the statistical properties of wide giant exoplanets. A number of extremely high contrast exoplanet imaging instruments have recently come online or will come online within the next year (including Project 1640, SCExAO, SPHERE, GPI, among others). I will discuss future prospects with these instruments.

Biller, Beth

2014-01-01

352

Microneedle Biosensor: A Method for Direct Label-free Real Time Protein Detection  

PubMed Central

Here we present the development of an array of electrical micro-biosensors in a microfluidic channel, called microneedle biosensors. A microneedle biosensor is a real-time, label-free, direct electrical detection platform, which is capable of high sensitivity detection, measuring the change in ionic current and impedance modulation, due to the presence or reaction of biomolecules such as proteins and nucleic acids. In this study, we successfully fabricated and electrically characterized the sensors and demonstrated successful detection of target protein. In this study, we used biotinylated bovine serum albumin as the receptor and streptavidin as the target analyte PMID:23355762

Esfandyarpour, Rahim; Esfandyarpour, Hesaam; Javanmard, Mehdi; Harris, James S.; Davis, Ronald W.

2012-01-01

353

Design on the readout electronics for the mobile direct detection Doppler wind LIDAR  

NASA Astrophysics Data System (ADS)

A readout electronics system is presented for the mobile direct detection Doppler Wind LIDAR (DWL). The structure of the readout electronics is compact to fit the mobile DWL which is fixed on a truck. According to the wind measurement principle of double-edge technique with triple-channel Fabry-Perot etalon, the readout electronics system is designed adjustable for wind speed detection due to the multi-channel technique and reconfiguration of the FPGA. The experimental results indicate that there is good consistency between the readout electronics and the current commercial devices. The detection range of the experiments can cover the troposphere and low stratosphere even in daylight.

Gao, Xin; Wen, Fei; Yao, Yuan; Sang, Zi-ru; Jin, Ge

2013-12-01

354

Signal-carrier interleaved optical OFDM for direct detection optical communication.  

PubMed

We propose signal-carrier interleaved (SCI) optical OFDM for direct detected transmission systems. Such a scheme can be considered as a variation of self-coherent detection where the carrier and signal are supplied at the transmitter and extracted at the receiver for coherent-like detection. This provides high OSNR sensitivity while maintaining very low carrier-to-signal power ratio (CSR). Our experiment results show that with 0 dB CSR, 43.2 Gb/s 16 QAM OFDM signal can be successfully delivered over 80 km standard single mode fiber (SSMF) with 24 dB OSNR requirements at 7% FEC limit. PMID:24514843

Chen, Xi; Che, Di; Li, An; He, Jiayuan; Shieh, William

2013-12-30

355

Gene doping detection: evaluation of approach for direct detection of gene transfer using erythropoietin as a model system.  

PubMed

As clinical gene therapy has progressed toward realizing its potential, concern over misuse of the technology to enhance performance in athletes is growing. Although 'gene doping' is banned by the World Anti-Doping Agency, its detection remains a major challenge. In this study, we developed a methodology for direct detection of the transferred genetic material and evaluated its feasibility for gene doping detection in blood samples from athletes. Using erythropoietin (EPO) as a model gene and a simple in vitro system, we developed real-time PCR assays that target sequences within the transgene complementary DNA corresponding to exon/exon junctions. As these junctions are absent in the endogenous gene due to their interruption by introns, the approach allows detection of trace amounts of a transgene in a large background of the endogenous gene. Two developed assays and one commercial gene expression assay for EPO were validated. On the basis of ability of these assays to selectively amplify transgenic DNA and analysis of literature on testing of gene transfer in preclinical and clinical gene therapy, it is concluded that the developed approach would potentially be suitable to detect gene doping through gene transfer by analysis of small volumes of blood using regular out-of-competition testing. PMID:20463760

Baoutina, A; Coldham, T; Bains, G S; Emslie, K R

2010-08-01

356

Colorimetric blood-gas monitoring sensors  

NASA Astrophysics Data System (ADS)

Colorimetric fiber optic sensors have been developed for measuring the pH and pCO2 of blood. These sensors are fabricated using a single 125 micrometers diameter optical fiber. Located at the distal end of the fiber is a capsule that contains a pH sensitive dye. The pCO2 sensor is fabricated from a pH sensor with the addition of a salt, bicarbonate, and the encapsulation with an ion impermeable gas permeable membrane. The distal end of the capsule is terminated with a reflective surface. The reflective surface can either be a polished metallic surface or, in this case, a TiO2 impregnated epoxy. The disposable sensor mates with an optical connector that contains two optical fibers of the same size as the disposable sensor. The two fibers within the optical cable provide a light path for both the antegrade and retrograde optical signals. These fibers are terminated at either the LED source or the detector. A prototype sensor assembly that incorporates the measurement of three physiological parameters (pH, pCO2, and sO2) has been demonstrated to fit within a standard 20 gauge arterial catheter, typically used for radial artery blood pressure monitoring, without significant damping of the blood pressure waveform. The pH sensor has a range of 6.9 - 7.8 with a precision of 0.01 pH units and the pCO2 sensor has a range of 15 - 95 mm Hg with a precision of 3 mm Hg. The long term drift pH drift is less than 0.01 pH unit per 8 hours and the pCO2 drift is less than 1 mm Hg per 8 hours. Sensor performance in the canine has demonstrated that the pH sensor is accurate to within +/- 0.03 pH units and the pCO2 sensor is accurate to within +/- 3 mm Hg when compared to a typical blood gas analyzer.

Proctor, Keith J.; Seifert, George P.

1993-05-01

357

Halo-independent comparison of direct dark matter detection data: a review  

E-print Network

We review the halo-independent formalism, that allows to compare data from different direct dark matter detection experiments without making assumptions on the properties of the dark matter halo. We apply this method to spin-independent WIMP-nuclei interactions, for both isospin-conserving and isospin-violating couplings, and to WIMPs interacting through an anomalous magnetic moment.

Del Nobile, Eugenio

2014-01-01

358

The ?-Lacta Test for Direct Detection of Extended-Spectrum-?-Lactamase-Producing Enterobacteriaceae in Urine.  

PubMed

With the ?-Lacta test, production of extended-spectrum ?-lactamases (ESBLs) was assayed in 200 urine samples showing Gram-negative bacilli during direct microscopic examination. While 168 samples tested negative, all samples yielding ESBL-producing Enterobacteriaceae after culture gave positive (n = 30) or uninterpretable (n = 2) results. The sensitivity and specificity of ESBL detection were 94% and 100%, respectively. PMID:25078913

Gallah, Salah; Decré, Dominique; Genel, Nathalie; Arlet, Guillaume

2014-10-01

359

Response to Technical Comments regarding the paper "Direct Detection of Galactic Halo Dark Matter"  

E-print Network

We reply to the criticism of Gibson & Flynn and of Graff regarding "Direct detection of galactic halo dark matter" by Oppenheimer et al. (2001) (Science, Vol. 292, p. 698), which reported on the discovery of a significant population of halo white dwarfs found in our South Galactic Cap survey. None of their arguments against our claims withstand close scrutiny.

B. R. Oppenheimer; N. C. Hambly; A. P. Digby; S. T. Hodgkin; D. Saumon

2001-06-14

360

Direct Detection and Characterization of a Transient 1-Silaallene Derivative in Solution  

E-print Network

Direct Detection and Characterization of a Transient 1-Silaallene Derivative in Solution Corinna. West and co-workers have recently reported the first example of an isolable 1-silaallene derivative,2 derivatives have yet been characterized spectroscopically, either in solution or solid matrices. In this paper

Leigh, William J.

361

Halo-independent comparison of direct dark matter detection data: a review  

E-print Network

We review the halo-independent formalism, that allows to compare data from different direct dark matter detection experiments without making assumptions on the properties of the dark matter halo. We apply this method to spin-independent WIMP-nuclei interactions, for both isospin-conserving and isospin-violating couplings, and to WIMPs interacting through an anomalous magnetic moment.

Eugenio Del Nobile

2014-04-16

362

Interplay and Characterization of Dark Matter Searches at Colliders and in Direct Detection Experiments  

E-print Network

In this White Paper we present and discuss a concrete proposal for the consistent interpretation of Dark Matter searches at colliders and in direct detection experiments. Based on a specific implementation of simplified models of vector and axial-vector mediator exchanges, this proposal demonstrates how the two search strategies can be compared on an equal footing.

Sarah A. Malik; Christopher McCabe; Henrique Araujo; Alexander Belyaev; Celine Boehm; Jim Brooke; Oliver Buchmueller; Gavin Davies; Albert De Roeck; Kees de Vries; Matthew J. Dolan; John Ellis; Malcolm Fairbairn; Henning Flaecher; Loukas Gouskos; Valentin V. Khoze; Greg Landsberg; Dave Newbold; Michele Papucci; Timothy Sumner; Marc Thomas; Steven Worm

2014-09-14

363

Direct Detection of Radiocarbon Using Accelerator Techniques and Its Application to Age Measurements  

Microsoft Academic Search

Radiocarbon measurements by the direct detection of 14C atoms with the Tandetron accelerator mass spectrometer were begun in the autumn of 1983 at Nagoya University. The 14C dating of geological and archeological samples is routinely performed with a precision of ± 1% (± 83 years) using a carbon-silver target containing only 2-5 mg of carbon in measurements lasting 5 hours.

Toshio Nakamura; Nobuyuki Nakai; Takao Sakase; Masaya Kimura; Shoji Ohishi; Makoto Taniguchi; Shigeo Yoshioka

1985-01-01

364

In-line interferometer for direction-sensitive displacement measurements by optical feedback detection  

Microsoft Academic Search

We demonstrate a compact in-line interferometer for direction-sensitive displacement measurement by optical feedback detection with a semiconductor laser (SL) light source. Two reflected beams from a semitransparent reference mirror and a reflecting test object interfere in the SL medium, causing a variation in its output power. The reference mirror is located between the SL output facet and the test object.

Alvarado Tarun; Julius Jecong; Caesar Saloma

2005-01-01

365

Direct Assay of Enzymes in Heme Biosynthesis for the Detection of Porphyrias by Tandem Mass  

E-print Network

diseases caused by enzyme deficiencies in the heme biosynthetic pathway.1 Heme biosynthesis starts from disease caused by alcoholism, hepatitis C, or estrogen intake by women. The PCT manifests itselfDirect Assay of Enzymes in Heme Biosynthesis for the Detection of Porphyrias by Tandem Mass

Gelb, Michael

366

A new direct field oriented controller employing rotor end ring current detection  

Microsoft Academic Search

A novel direct field-oriented control scheme for induction motor drive applications that employs rotor end ring current detection and removes the dependence of the controller accuracy on temperature is presented. This field orientation scheme does not require an incremental encoder for rotor position sensing. The motor torque can be accurately controlled even down to zero frequency operation. The controller is

T. Matsuo; V. Blasko; J. C. Moreira; T.A. Lipo

1990-01-01

367

Respiratory Syncytial Virus Detection by Remel Xpect, Binax Now RSV, Direct Immunofluorescent Staining, and Tissue Culture  

Microsoft Academic Search

The performance characteristics of Xpect RSV (XP) and Binax Now RSV (BN) were compared to those of direct fluorescent-antibody staining and\\/or tissue culture for detection of respiratory syncytial virus (RSV) in nasopharyngeal aspirate and wash samples from children (n 110) and adults (n 66). The sensitivity, specificity, positive predictive value, and negative predictive value of XP were 75%, 98%, 95%,

Anita P. Borek; Susan H. Clemens; Valerie K. Gaskins; Deborah Z. Aird; Alexandra Valsamakis

2006-01-01

368

Direct Detection Doppler Lidar Wind Measurements Obtained During the 2002 International Project (IHOP).  

National Technical Information Service (NTIS)

In the spring of 2002 the Goddard Lidar Observatory for Winds (GLOW) was operated at the Homestead profiling site in western Oklahoma as part of the International H(sub2)O Project (IHOP). GLOW is a mobile direct detection Doppler lidar system which operat...

B. Gentry, S. Li H. Chen, J. Comer, S. Mathur

2005-01-01

369

Fabry-Perot etalon aperture requirements for direct detection Doppler wind lidar from Earth orbit.  

PubMed

The design of Fabry-Perot etalons for direct detection Doppler wind lidar from a satellite is considered for two direct detection methods, fringe imaging (multichannel) and double edge. The area solid-angle product of the etalon for each technique is derived and shown to be inherently larger, for a given etalon aperture, for the fringe imager than for the double-edge Doppler analyzer. Modeling of the Doppler measurement accuracy of a spaceflight direct detection wind lidar shows that a very large optical aperture, 2 m or more, is necessary. Optical throughput matching to a 2-m collector requires, for the fringe-imaging Doppler analyzer, an etalon with 60 mm aperture, whereas the double-edge technique would require two etalons of 200 mm aperture, or a split-aperture etalon of 400 mm working aperture. Because the two direct detection methods have been shown to have practically identical intrinsic sensitivities (measurement accuracies per unit signal), this difference in etalon dimensions may be a significant selection consideration. PMID:18324101

McKay, J A

1999-09-20

370

Toward directional detection of Dark Matter with the DM-TPC detector  

E-print Network

Directional detection can provide unambiguous observation of Dark Matter interactions even in presence of insidious backgrounds. The DM-TPC collaboration is developing a detector with the goal of measuring the direction and sense of nuclear recoils produced in Dark Matter interactions. The detector consists of a Time Projection Chamber with optical readout filled with CF$_4$ gas at low pressure. A collision between a WIMP and a gas molecule results in a nuclear recoil of 1-2 mm. The measurement of the energy loss along the recoil allows us to determine the sense and the direction of the recoil. Results from a prototype detector operated in a low-energy neutron beam clearly demonstrate the suitability of this approach to measure directionality. A cubic meter prototype, which is now being designed, will allow us to set competitive limits on spin-dependent Dark Matter interactions using a directional detector.

G. Sciolla; S. Ahlen; D. Dujmic; V. Dutta; P. Fisher; S. Henderson; A. Kaboth; G. Kohse; R. Lanza; J. Monroe; A. Roccaro; N. Skvorodnev; H. Tomita; R. Vanderspek; H. Wellenstein; R. Yamamoto; for the DM-TPC collaboration

2008-06-16

371

Laser desorption with corona discharge ion mobility spectrometry for direct surface detection of explosives.  

PubMed

We present a new highly sensitive technique for the detection of explosives directly from the surface using laser desorption-corona discharge-ion mobility spectrometry (LD-CD-IMS). We have developed LD based on laser diode modules (LDM) and the technique was tested using three different LDM (445, 532 and 665 nm). The explosives were detected directly from the surface without any further preparation. We discuss the mechanism of the LD and the limitations of this technique such as desorption time, transport time and desorption area. After the evaluation of experimental data, we estimated the potential limits of detection of this method to be 0.6 pg for TNT, 2.8 pg for RDX and 8.4 pg for PETN. PMID:25118619

Sabo, M; Malásková, M; Matej?ík, S

2014-10-21

372

Highly sensitive, label-free colorimetric assay of trypsin using silver nanoparticles.  

PubMed

Herein, we report a simple, sensitive label-free colorimetric assay of trypsin based on silver nanoparticles (AgNPs) aggregation. Generally, a specially designed short peptide chain acts as both the stabilizer of AgNPs and the substrate of trypsin. In the presence of trypsin, the negatively charged part of peptides will be hydrolyzed, leaving the positively charged dipeptide capped on the surface of AgNPs. The electrostatic property alteration then leads to the AgNPs' aggregation in certain salt condition. The solution color may change correspondingly due to the localized surface plasmon resonance, which can be monitored by naked eye and UV-vis spectrophotometry. This novel AgNPs-based colorimetric method for quantitative determination of trypsin has a linear detection range from 2.5 to 200 ng mL(-1) and a rather low detection limit down to 2 ng mL(-1). The determination of trypsin can also be realized in complex biological fluids by the proposed method, demonstrating its great potential utility in the clinical applications in the future. PMID:23708813

Miao, Peng; Liu, Tao; Li, Xiaoxi; Ning, Limin; Yin, Jian; Han, Kun

2013-11-15

373

Forecast constraints on inflation from combined CMB and gravitational wave direct detection experiments  

SciTech Connect

We study how direct detection of the inflationary gravitational wave background constrains inflationary parameters and complements CMB polarization measurements. The error ellipsoids calculated using the Fisher information matrix approach with Planck and the direct detection experiment, Big Bang Observer (BBO), show different directions of parameter degeneracy, and the degeneracy is broken when they are combined. For a slow-roll parametrization, we show that BBO could significantly improve the constraints on the tensor-to-scalar ratio compared with Planck alone. We also look at a quadratic and a natural inflation model. In both cases, if the temperature of reheating is also treated as a free parameter, then the addition of BBO can significantly improve the error bars. In the case of natural inflation, we find that the addition of BBO could even partially improve the error bars of a cosmic variance-limited CMB experiment.

Kuroyanagi, Sachiko [Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Gordon, Christopher [Astrophysics Department, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Silk, Joseph [Astrophysics Department, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Institut d'Astrophysique, 98bis Boulevard Arago, Paris 75014 (France); Sugiyama, Naoshi [Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Institute for Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa City, Chiba 277-8582 (Japan)

2010-04-15

374

AND logic gate application based on colorimetric screening of enzyme activity  

NASA Astrophysics Data System (ADS)

A simple and novel DNA and gold nanoparticle (AuNPs) based colorimetric method has been developed for efficient detection of Deoxyribonuclease I (DNase-I) activity. For the detection process, the sample that contains DNase-I, which will cleave double stranded DNA into small pieces. Furthermore, the small pieces DNA sequences and water-soluble conjugated polymer cause the AuNPs aggregation (the solution change the color from red to blue). Thus, DNase-I could be detected by naked eyes or UV/Vis. Molecular substrates can be viewed as computational devices that process physical or chemical 'inputs' to generate 'outputs' based on a set of logical operators. Based on the assay, we have presented a DNA/AuNP based, multi-readout AND logic operations.

Liu, Ziheng; Zhan, Yihong; Bai, Yu; Sun, Jianwen

2012-07-01

375

Gold-nanoparticle-based colorimetric discrimination of cancer-related point mutations with picomolar sensitivity.  

PubMed

Point mutations in the Kirsten rat sarcoma viral oncogene homologue (KRAS) gene are being increasingly recognized as important diagnostic and prognostic markers in cancer. In this work, we describe a rapid and low-cost method for the naked-eye detection of cancer-related point mutations in KRAS based on gold nanoparticles. This simple colorimetric assay is sensitive (limit of detection in the low picomolar range), instrument-free, and employs nonstringent room temperature conditions due to a combination of DNA-conjugated gold nanoparticles, a probe design which exploits cooperative hybridization for increased binding affinity, and signal enhancement on the surface of magnetic beads. Additionally, the scheme is suitable for point-of-care applications, as it combines naked-eye detection, small sample volumes, and isothermal (PCR-free) amplification. PMID:23697628

Valentini, Paola; Fiammengo, Roberto; Sabella, Stefania; Gariboldi, Manuela; Maiorano, Gabriele; Cingolani, Roberto; Pompa, Pier Paolo

2013-06-25

376

DIURNAL AND ANNUAL VARIATIONS OF DIRECTIONAL DETECTION RATES OF DARK MATTER  

SciTech Connect

Direction-sensitive direct detection of weakly interacting massive particles (WIMPs) as dark matter would provide an unambiguous non-gravitational signature of dark matter. The diurnal variation of dark matter signal due to Earth's rotation around its own axis can be a significant signature for Galactic WIMPs. Because of a particular orientation of Earth's axis of rotation with respect to the WIMP wind direction, the apparent direction of WIMP wind as observed at a detector can alter widely in a day. In this work, we calculate the directional detection rates with their daily and yearly modulations in Earth-bound dark matter experiments considering detailed features of the geometry and dynamics of the Earth-Sun system along with the solar motion in a Galactic frame. A separate halo model, namely the dark disk model other than the usual standard halo model for dark matter halo, is also considered and the results for two models are compared. We demonstrate the results for two types of gas detectors, namely DRIFT (target material CS{sub 2}) and NEWAGE (target material CF{sub 4}), which use Time Projection Chamber techniques for measuring directionality of the recoil nucleus. The WIMP mass and recoil energy dependence of the daily variation of event rates are computed for a specific detector, and the sensitive ranges of mass and recoil energies for the considered detector are probed.

Bandyopadhyay, Abhijit [Department of Physics, RKM Vivekananda University, Belur Math, Howrah 711202 (India); Majumdar, Debasish, E-mail: abhi.vu@gmail.com, E-mail: debasish.majumdar@saha.ac.in [Astroparticle Physics and Cosmology Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India)

2012-02-10

377

Colorimetric and spectroradiometric characteristics of narrow-field-of-view  

E-print Network

Colorimetric and spectroradiometric characteristics of narrow-field-of-view clear skylight characteristics along four sky meridians: the solar me- ridian and three meridians at azimuths of 45°, 90 and performance of spectrally selective solar-energy devices such as photovoltaic systems. Im- proving our

Lee Jr., Raymond L.

378

Colorimetric Water Quality Sensing with Mobile Smart Phones  

E-print Network

Colorimetric Water Quality Sensing with Mobile Smart Phones by Samuel Schaefer B sensor using an approach based on integration with mobile smart phones. Mobile smart phones are advanced systems capable of running application software (apps). Integration of these features with sensor hardware

Chau, Kenneth

379

Research Paper Rapid Colorimetric Screening of Drug Interaction  

E-print Network

Research Paper Rapid Colorimetric Screening of Drug Interaction and Penetration Through Lipid on highly generic physicochemical parameters such as the partition coefficients between water and alcohol [so-called log P/log D values (1)], employ time- consuming chromatography methods (2) or artificial

Jelinek, Raz

380

A Colorimetric Method for the Determination of Sugars  

Microsoft Academic Search

VOLUMETRIC procedures have been used for the quantitative determination of sugars after separation by partition chromatography1,2. It has been our experience that these methods not only require considerable skill, but also they are lengthy and sensitive to slight variation of the conditions. We have therefore attempted to develop a simple quantitative colorimetric procedure. Preliminary experiments showed that the anthrone3 and

M. Dubois; K. Gilles; J. K. Hamilton; P. A. Rebers; F. Smith

1951-01-01

381

Testing of Colorimetric Tubes for Nitrogen Dioxide and Monomethylhydrazine.  

ERIC Educational Resources Information Center

Colorimetric tubes for nitrogen dioxide (NO2) and monomethylhydrazine (MMH) were tested for accuracy and results indicate that at the levels checked the tubes' average deviation was plus or minus 20 percent. Tube NO2 concentrations all read lower than the analyzed concentrations. MMH tubes read much higher than the analyzed concentration of 0.28…

Diamond, Philip

382

Notes & Tips Colorimetric determination of pure Mg2+  

E-print Network

.g., thin-layer chromatography) of [3 H]diacyl- glycerol from [3 H]PA [9,10]. We have developed a nonradio spectrophotometrically. This colorimetric assay is not suitable for use with cell ex- tracts or with crude PAP1

Chen, Kuang-Yu

383

Recent progress on polymer-based fluorescent and colorimetric chemosensors.  

PubMed

Recently, fluorescent or colorimetric chemosensors based on polymers have attracted great attention due to several important advantages, such as their simplicity of use, signal amplification, easy fabrication into devices, and combination of different outputs, etc. This tutorial review will cover polymer-based optical chemosensors from 2007 to 2010. PMID:21107482

Kim, Ha Na; Guo, Zhiqian; Zhu, Weihong; Yoon, Juyoung; Tian, He

2011-01-01

384

Using a large area CMOS APS for direct chemiluminescence detection in Western blotting electrophoresis  

NASA Astrophysics Data System (ADS)

Western blotting electrophoretic sequencing is an analytical technique widely used in Functional Proteomics to detect, recognize and quantify specific labelled proteins in biological samples. A commonly used label for western blotting is Enhanced ChemiLuminescence (ECL) reagents based on fluorescent light emission of Luminol at 425nm. Film emulsion is the conventional detection medium, but is characterized by non-linear response and limited dynamic range. Several western blotting digital imaging systems have being developed, mainly based on the use of cooled Charge Coupled Devices (CCDs) and single avalanche diodes that address these issues. Even so these systems present key drawbacks, such as a low frame rate and require operation at low temperature. Direct optical detection using Complementary Metal Oxide Semiconductor (CMOS) Active Pixel Sensors (APS)could represent a suitable digital alternative for this application. In this paper the authors demonstrate the viability of direct chemiluminescent light detection in western blotting electrophoresis using a CMOS APS at room temperature. Furthermore, in recent years, improvements in fabrication techniques have made available reliable processes for very large imagers, which can be now scaled up to wafer size, allowing direct contact imaging of full size western blotting samples. We propose using a novel wafer scale APS (12.8 cm×13.2 cm), with an array architecture using two different pixel geometries that can deliver an inherently low noise and high dynamic range image at the same time representing a dramatic improvement with respect to the current western blotting imaging systems.

Esposito, Michela; Newcombe, Jane; Anaxagoras, Thalis; Allinson, Nigel M.; Wells, Kevin

2012-03-01

385

Direct detection of Salmonella typhimurium on fresh produce using phage-based magnetoelastic biosensors.  

PubMed

Current bacterial detection methods require the collection of samples followed by preparation and analysis in the laboratory, both time and labour consuming steps. More importantly, because of cost, only a limited number of samples can be taken and analyzed. This paper presents the results of an investigation to directly detect Salmonella typhimurium on fresh tomato surfaces using phage-based magnetoelastic (ME) biosensors. The biosensor is composed of a ME resonator platform coated with filamentous E2 phage, engineered to bind with S. typhimurium. The ME biosensors are wireless sensors, whose resonance oscillation and resonance frequency are actuated and detected through magnetic fields. The sensors used in this study were 0.028 mm×0.2 mm×1 mm in size. In this study, the tomato surface was spiked with S. typhimurium suspensions with concentrations ranging from 5×10(1) to 5×10(8)CFU/ml and then allowed to dry in air. The detection was conducted by directly placing ME measurement biosensors and control sensors on the spiked surface for 30 min in a humid environment. The control sensors were identical to the measurement biosensors, but without phage. Both measurement and control sensors were blocked with BSA to reduce non-specific binding. The resonance frequencies of both measurement and control sensors were measured prior to and after the placement of the sensors on the tomato. Shifts in the resonance frequency of the measurement biosensors were observed, while the control sensors showed negligible change. Scanning electron microscopy (SEM) was used to verify the specific binding of S. typhimurium to the biosensor. Results of multiple biosensor detection and corresponding analyzes showed statistically different responses between the measurement and control sensors for tomatoes spiked with S. typhimurium suspensions with concentrations of 5×10(2)CFU/ml and greater. This study demonstrates the direct detection of food-borne bacteria on fresh produce. PMID:20688505

Li, Suiqiong; Li, Yugui; Chen, Huiqin; Horikawa, Shin; Shen, Wen; Simonian, Aleksandr; Chin, Bryan A

2010-12-15

386

Precision measurements, dark matter direct detection and LHC Higgs searches in a constrained NMSSM  

SciTech Connect

We reexamine the constrained version of the Next-to-Minimal Supersymmetric Standard Model with semi universal parameters at the GUT scale (CNMSSM). We include constraints from collider searches for Higgs and susy particles, upper bound on the relic density of dark matter, measurements of the muon anomalous magnetic moment and of B-physics observables as well as direct searches for dark matter. We then study the prospects for direct detection of dark matter in large scale detectors and comment on the prospects for discovery of heavy Higgs states at the LHC.

Belanger, G. [LAPTH, U. de Savoie, CNRS, 9 Chemin de Bellevue, 74940 Annecy-le-Vieux (France)] [LAPTH, U. de Savoie, CNRS, 9 Chemin de Bellevue, 74940 Annecy-le-Vieux (France); Hugonie, C. [Laboratoire Physique Theorique et Astroparticules, Universite de Montpellier II, Place Eugene Bataillon, 34095 Montpellier (France)] [Laboratoire Physique Theorique et Astroparticules, Universite de Montpellier II, Place Eugene Bataillon, 34095 Montpellier (France); Pukhov, A., E-mail: belanger@lapp.in2p3.fr, E-mail: cyril.hugonie@lpta.univ-montp2.fr, E-mail: pukhov@lapp.in2p3.fr [Skobeltsyn Institute of Nuclear Physics, Moscow State University, Leninskie gory, GSP-1, Moscow 119991 (Russian Federation)

2009-01-15

387

A new halo-independent approach to dark matter direct detection analysis  

E-print Network

Uncertainty in the local dark matter velocity distribution is a key difficulty in the analysis of data from direct detection experiments. Here we propose a new approach for dealing with this uncertainty, which does not involve any assumptions about the structure of the dark matter halo. Given a dark matter model, our method yields the velocity distribution which best describes a set of direct detection data as a finite sum of streams with optimised speeds and densities. The method is conceptually simple and numerically very efficient. We give an explicit example in which the method is applied to determining the ratio of proton to neutron couplings of dark matter from a hypothetical set of future data.

Brian Feldstein; Felix Kahlhoefer

2014-03-18

388

Modeling the Performance of Direct-Detection Doppler Lidar Systems in Real Atmospheres  

NASA Technical Reports Server (NTRS)

Previous modeling of the performance of spaceborne direct-detection Doppler lidar systems has assumed extremely idealized atmospheric models. Here we develop a technique for modeling the performance of these systems in a more realistic atmosphere, based on actual airborne lidar observations. The resulting atmospheric model contains cloud and aerosol variability that is absent in other simulations of spaceborne Doppler lidar instruments. To produce a realistic simulation of daytime performance, we include solar radiance values that are based on actual measurements and are allowed to vary as the viewing scene changes. Simulations are performed for two types of direct-detection Doppler lidar systems: the double-edge and the multi-channel techniques. Both systems were optimized to measure winds from Rayleigh backscatter at 355 nm. Simulations show that the measurement uncertainty during daytime is degraded by only about 10-20% compared to nighttime performance, provided a proper solar filter is included in the instrument design.

McGill, Matthew J.; Hart, William D.; McKay, Jack A.; Spinhirne, James D.

1999-01-01

389

Reduced electrical bandwidth receivers for direct detection 4-ary PPM optical communication intersatellite links  

NASA Technical Reports Server (NTRS)

One of the major sources of noise in a direct detection optical communication receiver is the shot noise due to the quantum nature of the photodetector. The shot noise is signal dependent and is neither Gaussian nor wide sense stationary. When a photomultiplier tube (PMT) or an avalanche photodiode (APD) is used, there is also a multiplicative excess noise due to the randomness of the internal photodetector gain. Generally speaking, the radio frequency (RF) communication theory cannot be applied to direct detection optical communication systems because noise in RF communication systems is usually additive and Gaussian. A receiver structure which is mathematically optimal for signal dependent shot noise is derived. Several suboptimal receiver structures are discussed and compared with the optimal receiver. The objective is to find a receiver structure which is easy to implement and gives close to optimal performance.

Davidson, Frederic M.; Sun, Xiaoli

1993-01-01

390

Performance of random diagonal code for OCDMA systems using new spectral direct detection technique  

NASA Astrophysics Data System (ADS)

This paper studies the performance of random diagonal (RD) code for spectral-amplitude coding OCDMA (SAC-OCDMA) system using a newly proposed spectral direct detection technique. RD code is constructed using code segment and data segment. One of the important properties of this code is that the cross correlation at data segment is always zero, which means that phase intensity induced noise (PIIN) is reduced. The weight for the RD code can be any number greater than three. By comparing the theoretical and simulation results taken from the commercial optical systems simulator " OptSim," we show that the proposed new spectral direct detection technique utilizing RD code considerably improves the performance compared with the conventional SAC complementary subtraction technique.

Fadhil, Hilal Adnan; Aljunid, S. A.; Ahmad, R. B.

2009-06-01

391

Method and apparatus for detecting the direction and distance to a target well casing  

SciTech Connect

A method and an apparatus for determining the exact direction of and distance to a nearby target well having a steel casing from a borehole are disclosed. A long solenoid having a coil wound on a high permeability core for generating a source magnetic field which, in the absence of a target well, has axial symmetry and is characterized by having a magnetic pole at each end of the core is provided. Directly adjacent to one end of the core is a 3-component ring-type fluxgate magnetometer to detect magnetic field components perpendicular to the axis of the solenoid. The detection apparatus is located in a borehole, and the magnetic field generated.

Kuckes, A.F.

1984-04-17

392

Colorimetric iodide recognition and sensing by citrate-stabilized core/shell Cu@Au nanoparticles.  

PubMed

In the light of the significance and urgency for the recognition and sensing of anions specifically, especially those of biological relevance, herein, we wish to demonstrate a novel colorimetric avenue for highly selective iodide recognition and sensing using simple citrate-stabilized core/shell Cu@Au nanoparticles. No other ions than iodide can induce an appreciable color change of the Cu@Au nanoparticles solution from purple to red by transforming the interconnected, irregularly shaped nanoparticles to the single, separated, and nearly spherical ones, as confirmed by the transmission electron microscopy (TEM). On the basis of the optical spectra and TEM studies, a mechanism of iodide-induced aggregating/fusion, fragmentation, and reorganization of atoms is proposed. With this strategy, 6 ?M (0.76 ppm) of iodide can be recognized within 20 min by naked-eye observation. This sensitive and selective colorimetric assay opens up a fresh insight of facile, rapid, and reliable detection of iodide and may find its future application in the analysis of the total iodine in edible salt as well as the clinical diagnosis of urinary iodide. PMID:21449559

Zhang, Jia; Xu, Xiaowen; Yang, Cheng; Yang, Fan; Yang, Xiurong

2011-05-15

393

Discrimination of Complex Mixtures by a Colorimetric Sensor Array: Coffee Aromas  

PubMed Central

The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 °C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures. PMID:20143838

Suslick, Benjamin A.; Feng, Liang; Suslick, Kenneth S.

2010-01-01

394

A highly selective colorimetric sensor for Hg²? based on nitrophenyl-aminothiourea.  

PubMed

A simple and highly selective colorimetric sensor (L1) bearing thiosemicarbazide moiety as binding site and nitrophenyl moiety as signal group were synthesized. Sensor L1 showed great colorimetric single selectivity and high sensitivity for mercury cation in DMSO and DMSO/H(2)O binary solutions. When Hg(2+) was added to the DMSO solution of L1, dramatic color change from brown to colorless was observed. While the cations Ca(2+), Mg(2+), Cd(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Pb(2+), Ag(+) and Cr(3+) could not cause any distinct interferer toward the recognition process for Hg(2+). The detection limit is allowable to 5.0 × 10(-6) and 1.0 × 10(-7)M level of Hg(2+) according to visual color change and UV-vis change, respectively. The recognition mechanism of the sensor toward mercury cation was evaluated in DMSO solutions by UV-vis and (1)H NMR. The sensor selectively sense Hg(2+)via the formation of a stable 1:1 complex through CS and CO group with Hg(2+). When these complex bonds formed, the sensor carried out an ICT transition induced color change. PMID:22484259

Liu, Juan; Yu, Mei; Wang, Xi-Cun; Zhang, Zhang

2012-07-01

395

Fetal head detection and measurement in ultrasound images by a direct inverse randomized Hough transform  

NASA Astrophysics Data System (ADS)

Object detection in ultrasound fetal images is a challenging task for the relatively low resolution and low signal-to-noise ratio. A direct inverse randomized Hough transform (DIRHT) is developed for filtering and detecting incomplete curves in images with strong noise. The DIRHT combines the advantages of both the inverse and the randomized Hough transforms. In the reverse image, curves are highlighted while a large number of unrelated pixels are removed, demonstrating a "curve-pass filtering" effect. Curves are detected by iteratively applying the DIRHT to the filtered image. The DIRHT was applied to head detection and measurement of the biparietal diameter (BPD) and head circumference (HC). No user input or geometric properties of the head were required for the detection. The detection and measurement took 2 seconds for each image on a PC. The inter-run variations and the differences between the automatic measurements and sonographers" manual measurements were small compared with published inter-observer variations. The results demonstrated that the automatic measurements were consistent and accurate. This method provides a valuable tool for fetal examinations.

Lu, Wei; Tan, Jinglu; Floyd, Randall C.

2005-04-01

396

Direct-detection polarization division multiplexed orthogonal frequency-division multiplexing transmission systems without polarization tracking.  

PubMed

We experimentally demonstrate a direct-detection polarization division multiplexed (PDM) orthogonal frequency-division multiplexing (OFDM) scheme without dynamic polarization tracking. Simply using a polarization-diverse receiver, the proposed multiple-input multiple-output assisted system can achieve bit-error rate of 10(-) over all possible received states of polarization. Moreover, 50 Gbps PDM-OFDM transmission over 100 km single-mode fiber is successfully demonstrated without dispersion-induced penalty. PMID:23258008

Wang, Chih-Yun; Wei, Chia-Chien; Lin, Chun-Ting; Chi, Sien

2012-12-15

397

Dispersion-supported direct-detection mode group division multiplexing using commercial multimode fiber couplers.  

PubMed

In this Letter, an intensity-modulation direct-detection mode group multiplexing system is investigated. The system does not use highly modally selective optics: multiplexing and demultiplexing is done in commercial multimode couplers and modal diversity is enhanced by modulation rates far beyond the length-bandwidth product of the fiber. Experimental and theoretical results shown for OM1 and OM2 fibers fully confirm this theory. PMID:24686612

Stepniak, Grzegorz

2014-04-01

398

Halo-Independent analysis of direct dark matter detection data for any WIMP interaction  

E-print Network

The halo independent comparison of direct dark matter detection data eliminates the need to make any assumption on the uncertain local dark matter distribution and is complementary to the usual data comparison which required assuming a dark halo model for our galaxy. The method, initially proposed for WIMPs with spin-independent contact interactions, has been generalized to any other interaction and applied to recent data on "Light WIMPs".

Gelmini, Graciela B

2014-01-01

399

Update on the Halo-Independent Comparison of Direct Dark Matter Detection Data  

E-print Network

We briefly review the halo-independent formalism, that allows to compare data from different direct dark matter detection experiments without making assumptions on the properties of the dark matter halo. We apply this method to spin-independent WIMP-nuclei interactions, for both isospin-conserving and isospin-violating couplings, updating the existing analyses with the addition of the SuperCDMS bound. We point out that this method can be applied to any type of WIMP interaction.

Eugenio Del Nobile; Graciela B. Gelmini; Paolo Gondolo; Ji-Haeng Huh

2014-05-22

400

Halo-Independent analysis of direct dark matter detection data for any WIMP interaction  

E-print Network

The halo independent comparison of direct dark matter detection data eliminates the need to make any assumption on the uncertain local dark matter distribution and is complementary to the usual data comparison which required assuming a dark halo model for our galaxy. The method, initially proposed for WIMPs with spin-independent contact interactions, has been generalized to any other interaction and applied to recent data on "Light WIMPs".

Graciela B. Gelmini

2014-11-04

401

Comparison of PCR, Culture, and Direct Fluorescent-Antibody Testing for Detection of Bordetella pertussis  

Microsoft Academic Search

We prospectively compared the performance of culture, direct fluorescent-antibody testing (DFA), and an in-house-developed PCR test targeting the repeated insertion sequence IS481 for the detection of Bordetella pertussis in nasopharyngeal swab specimens. We tested 319 consecutive paired specimens on which all three tests were performed. A total of 59 specimens were positive by one or more tests. Of these, 5

MIKE J. LOEFFELHOLZ; CURT J. THOMPSON; KARLA S. LONG; MARY J. R. GILCHRIST

1999-01-01

402

Alamouti-type space-time coding for free-space optical communication with direct detection  

Microsoft Academic Search

In optical communication systems employing direct detection at the receiver, intensity modulations such as on-off keying (OOK) or pulse-position modulation (PPM) are commonly used to convey the information. Consider the possibility of applying space-time coding in such a scenario, using, for example, an Alamouti-type coding scheme (1). Implicit in the Alamouti code is the fact that the modulation that defines

Marvin K. Simon; Victor A. Vilnrotter

2005-01-01

403

Commercial Systems for the Direct Detection of Explosives for Explosive Ordnance Disposal Tasks  

Microsoft Academic Search

There are a number of Explosive Ordnance Disposal (EOD) tasks in which it is necessary to discriminate and identify UneXploded Ordnance (UXO) already detected by other means. What we seek is the capacity to characterize in a non-destructive way the munition's content, usually either explosive or inert (e.g., practice munition), if possible using a fairly mobile system and without direct

Claudio Bruschini

2001-01-01

404

Lepton-Flavored Asymmetric Dark Matter and Interference in Direct Detection  

E-print Network

In flavored dark matter models, dark matter can scatter off of nuclei through Higgs and photon exchange, both of which can arise from renormalizable interactions and individually lead to strong constraints from direct detection. While these two interaction channels can destructively interfere in the scattering amplitude, for a thermal relic with equal abundances for the dark matter particle and its antiparticle, this produces no effect on the total event rate. Focusing on lepton-flavored dark matter, we show that it is quite natural for dark matter to have become asymmetric during high-scale leptogenesis, and that in this case the direct detection bounds can be significantly weakened due to interference. We quantify this by mapping out and comparing the regions of parameter space that are excluded by direct detection for the symmetric and asymmetric cases of lepton-flavored dark matter. In particular, we show that the entire parameter region is ruled out for symmetric dark matter, while large portions of para...

Hamze, Ali; Koeller, Jason; Trendafilova, Cynthia; Yu, Jiang-Hao

2014-01-01

405

Direct detection of bovine leukemia virus infection: practical applicability of a double polymerase chain reaction.  

PubMed

A double polymerase chain reaction (PCR) assay has been devised for the direct detection of bovine leukemia virus (BLV). The assay was directly performed on blood leukocytes, avoiding the DNA-purification procedures. The PCR products were identified by gel-electrophoresis and the specificity of the test was confirmed by hybridization with a biotinylated oligonucleotide probe. When testing the sensitivity of PCR, less than eight genome copies of the provirus were detected in the background of two million negative lymphocytes. In a BLV infected herd 22 animals of various age groups were examined by the indirect (serological) diagnostic tests of agar-gel immunodiffusion and indirect ELISA as well as by the direct detection method of PCR. The tests were repeated at monthly intervals on five occasions. When examining the specimens from cows and heifers, a close agreement was found between the results of the various methods. The newborn calves, which were the offspring of BLV infected mothers, were consequently negative in PCR throughout the experimental period. However, in the indirect tests the calves were positive during the first samplings and became negative only around four months of age. Since the indirect tests can not discriminate infection from colostral immunity, PCR proved to be a useful complementary assay for the safe diagnosis of BLV infection in young calves. PMID:1316025

Ballagi-Pordány, A; Klintevall, K; Merza, M; Klingeborn, B; Belák, S

1992-02-01

406

Probing WIMP particle physics and astrophysics with direct detection and neutrino telescope data  

E-print Network

With positive signals from multiple direct detection experiments it will, in principle, be possible to measure the mass and cross sections of weakly-interacting massive particle (WIMP) dark matter. Recent work has shown that, with a polynomial parameterisation of the WIMP speed distribution, it is possible to make an unbiased measurement of the WIMP mass, without making any astrophysical assumptions. However, direct detection experiments are not sensitive to low-speed WIMPs and, therefore, any model-independent approach will lead to a bias in the cross section. This problem can be solved with the addition of measurements of the flux of neutrinos from the Sun. This is because the flux of neutrinos produced from the annihilation of WIMPs which have been gravitationally captured in the Sun is sensitive to low-speed WIMPs. Using mock data from next-generation direct detection experiments and from the IceCube neutrino telescope, we show that the complementary information from IceCube on low-speed WIMPs breaks the ...

Kavanagh, Bradley J; Green, Anne M

2014-01-01

407

Direct optimization of LWIR systems for maximized detection range and minimized size and weight  

NASA Astrophysics Data System (ADS)

With reductions in microbolometer size and cost, long-wave infrared (LWIR) systems are increasingly being developed for platforms with challenging size, weight, power, and cost (SWAP-C) constraints, such as helmet-mounted systems and unmanned vehicles. Past optimization of imaging systems toward the simultaneous objectives of improved stand-off detection and low size, weight, and power required an iterative, multi-disciplinary design process. Here we demonstrate the direct optimization of the full LWIR system model including the optics, sensor, signal processing, and display degrees of freedom with system level metrics including SWAP-C and detection range. The end result is a system with superior size and weight for a given detection range.

Bates, Rob; Kubala, Kenneth

2014-05-01

408

Hybrid SCM SAC-OCDMA System Employing New Optical Spectral Amplitude Direct Decoding Detection Technique  

NASA Astrophysics Data System (ADS)

In this research, a hybrid subcarrier multiplexed spectral-amplitude-coding optical code-division-multiple-access (SCM SAC-OCDMA) system is proposed for the purpose of combining the advantages of both techniques. SAC-OCDMA is employed because of its ability to eliminate the Multiple Access Interference (MAI) when code sequences with fixed in-phase cross correlation are used. In order to enhance the channel data rate of the OCDMA systems, the SCM technique is used. As a result, the hybrid system is robust against interference and is much more spectrally efficient. The system utilizes double weight (DW) code that has a weight W equal to two, code length N equal to six and cross correlation ? equal to 1. A simple and new detection technique called optical spectral amplitude direct decoding is proposed. Based on the theory and experimental simulation results obtained, the new proposed detection technique provides a better performance than the conventional balanced detection technique.

Sahbudin, R. K. Z.; Abdullah, M. K.; Samad, M. D. A.; Mahdi, M. A.; Ismail, M.

409

Accelerated colorimetric immunosensing using surface-modified porous monoliths and gold nanoparticles  

NASA Astrophysics Data System (ADS)

A rapid and sensitive immunoassay platform integrating polymerized monoliths and gold nanoparticles (AuNPs) has been developed. The porous monoliths are photopolymerized in situ within a silica capillary and serve as solid support for high-mass transport and high-density capture antibody immobilization to create a shorter diffusion length for antibody-antigen interactions, resulting in a rapid assay and low reagent consumption. AuNPs are modified with detection antibodies and are utilized as signals for colorimetric immunoassays without the need for enzyme, substrate and sophisticated equipment for quantitative measurements. This platform has been verified by performing a human IgG sandwich immunoassay with a detection limit of 0.1 ng ml-1. In addition, a single assay can be completed in 1 h, which is more efficient than traditional immunoassays that require several hours to complete.

Chuag, Shao-Hsuan; Chen, Guan-Hua; Chou, Hsin-Hao; Shen, Shu-Wei; Chen, Chien-Fu

2013-08-01

410

Direct detection of exoplanets in the 3 -- 10 micron range with E-ELT/METIS  

E-print Network

We quantify the scientific potential for exoplanet imaging with the Mid-infrared E-ELT Imager and Spectrograph (METIS) foreseen as one of the instruments of the European Extremely Large Telescope (E-ELT). We focus on two main science cases: (1) the direct detection of known gas giant planets found by radial velocity (RV) searches; and (2) the direct detection of small (1 - 4 R_earth) planets around the nearest stars. Under the assumptions made in our modeling, in particular on the achievable inner working angle and sensitivity, our analyses reveal that within a reasonable amount of observing time METIS is able to image >20 already known, RV-detected planets in at least one filter. Many more suitable planets with dynamically determined masses are expected to be found in the coming years with the continuation of RV-surveys and the results from the GAIA astrometry mission. In addition, by extrapolating the statistics for close-in planets found by \\emph{Kepler}, we expect METIS might detect ~10 small planets with...

Quanz, Sascha P; Meyer, Michael R; Schmalzl, Eva; Held, Jenny

2014-01-01

411

Chemical Methods for the Direct Detection and Labeling of S-Nitrosothiols  

PubMed Central

Abstract Significance: Posttranslational modification of proteins through phosphorylation, glycosylation, and oxidation adds complexity to the proteome by reversibly altering the structure and function of target proteins in a highly controlled fashion. Recent Advances: The study of reversible cysteine oxidation highlights a role for this oxidative modification in complex signal transduction pathways. Nitric oxide (NO), and its respective metabolites (including reactive nitrogen species), participates in a variety of these cellular redox processes, including the reversible oxidation of cysteine to S-nitrosothiols (RSNOs). RSNOs act as endogenous transporters of NO, but also possess beneficial effects independent of NO-related signaling, which suggests a complex and versatile biological role. In this review, we highlight the importance of RSNOs as a required posttranslational modification and summarize the current methods available for detecting S-nitrosation. Critical Issues: Given the limitations of these indirect detection methods, the review covers recent developments toward the direct detection of RSNOs by phosphine-based chemical probes. The intrinsic properties that dictate this phosphine/RSNO reactivity are summarized. In general, RSNOs (both small molecule and protein) react with phosphines to yield reactive S-substituted aza-ylides that undergo further reactions leading to stable RSNO-based adducts. Future Directions: This newly explored chemical reactivity forms the basis of a number of exciting potential chemical methods for protein RSNO detection in biological systems. Antioxid. Redox Signal. 17, 981–991. PMID:22356122

Bechtold, Erika

2012-01-01

412

Direct detection of Mycobacterium tuberculosis complex in bovine and bubaline tissues through nested-PCR  

PubMed Central

Post-mortem bacterial culture and specific biochemical tests are currently performed to characterize the etiologic agent of bovine tuberculosis. Cultures take up to 90 days to develop. A diagnosis by molecular tests such as PCR can provide fast and reliable results while significantly decreasing the time of confirmation. In the present study, a nested-PCR system, targeting rv2807, with conventional PCR followed by real-time PCR, was developed to detect Mycobacterium tuberculosis complex (MTC) organisms directly from bovine and bubaline tissue homogenates. The sensitivity and specificity of the reactions were assessed with DNA samples extracted from tuberculous and non-tuberculous mycobacteria, as well as other Actinomycetales species and DNA samples extracted directly from bovine and bubaline tissue homogenates. Regarding the analytical sensitivity, DNA of the M. bovis AN5 strain was detected up to 1.5 pg by nested-PCR, whereas DNA of M. tuberculosis H37Rv strain was detected up to 6.1 pg. The nested-PCR system showed 100% analytical specificity for MTC when tested with DNA of reference strains of non-tuberculous mycobacteria and closely-related Actinomycetales. A clinical sensitivity level of 76.7% was detected with tissues samples positive for MTC by means of the culture and conventional PCR. A clinical specificity of 100% was detected with DNA from tissue samples of cattle with negative results in the comparative intradermal tuberculin test. These cattle exhibited no visible lesions and were negative in the culture for MTC. The use of the nested-PCR assay to detect M. tuberculosis complex in tissue homogenates provided a rapid diagnosis of bovine and bubaline tuberculosis.

Araujo, Cristina P.; Osorio, Ana Luiza A.R.; Jorge, Klaudia S.G.; Ramos, Carlos A.N.; Souza Filho, Antonio F.; Vidal, Carlos E.S.; Vargas, Agueda P.C.; Roxo, Eliana; Rocha, Adalgiza S.; Suffys, Philip N.; Fonseca, Antonio A.; Silva, Marcio R.; Barbosa Neto, Jose D.; Cerqueira, Valiria D.; Araujo, Flabio R.

2014-01-01

413

Silicon nanowire biosensor for ultrasensitive and label-free direct detection of miRNAs.  

PubMed

MicroRNA (miRNA), a large and growing class of 18-24-nucleotide long, noncoding RNA molecules in all known animal and plant genomes, is a key player in gene regulation. The functions of miRNA are yet to be understood with respect to how and where it is produced and the changes within an organism associated with variations in miRNA expression level. The expression profiles serve as molecular diagnostics for diseases and new targets in drug discovery. Consequently, highly sensitive and selective detection of miRNA is playing a significant role in understanding miRNA functions. Existing major methods of detecting miRNA are dependent on hybridization, in which a target miRNA molecule is hybridized to a complementary probe molecule. Recently developed detection methods introduce nanomaterials to the hybridized duplex to enhance the sensitivity. However, all of them are indirect, involving labeling or conjugating process. To overcome the above-mentioned issues, we have demonstrated a highly sensitive and label-free direct detection method for miRNA by using peptide nucleic acids (PNAs)-functionalized silicon nanowires (SiNWs) biosensor. The sensor is capable of detecting target miRNA as low as 1 fM (10(-15) M), as well as identifying fully matched versus mismatched miRNA sequences. More importantly, the SiNW biosensor enables miRNA detection in total RNA extracted from HeLa cells. The developed detection method shows potential applications in label-free, early detection of miRNA as a biomarker in cancer diagnostics with very high sensitivity and good specificity. PMID:20931394

Zhang, Guo-Jun

2011-01-01

414

Detection of Bi-Directionality in Strain-Gage Balance Calibration Data  

NASA Technical Reports Server (NTRS)

An indicator variable was developed for both visualization and detection of bi-directionality in wind tunnel strain-gage balance calibration data. First, the calculation of the indicator variable is explained in detail. Then, a criterion is discussed that may be used to decide which gage outputs of a balance have bi- directional behavior. The result of this analysis could be used, for example, to justify the selection of certain absolute value or other even function terms in the regression model of gage outputs whenever the Iterative Method is chosen for the balance calibration data analysis. Calibration data of NASA s MK40 Task balance is analyzed to illustrate both the calculation of the indicator variable and the application of the proposed criterion. Finally, bi directionality characteristics of typical multi piece, hybrid, single piece, and semispan balances are determined and discussed.

Ulbrich, Norbert

2012-01-01

415

A novel prediction methodology for detecting failures and instabilities in directional wireless networks  

NASA Astrophysics Data System (ADS)

Even though advances in wireless technology have yielded lower power consumption, higher data rates, and numerous other improvements, the ability to develop a proactive strategy towards handling degradations and failures in directional wireless networks has evaded the research community. In this paper, we introduce a methodology using an analogy to molecular systems in which a directional wireless network utilizing free space optical (FSO) or RF links is modeled as a molecule whose links can grow/retract similarly to bonds. A normal mode analysis (NMA) is performed to identify link instabilities (degradations and failures) and an N-dimensional potential energy surface (PES) is derived with respect to network and environmental parameters to aide in the detection of when a new topology is available ahead of the topology computation stage. Together, the NMA and PES form a basis for a proactive network methodology aimed at improving performance in directional wireless networks.

Coleman, David M.; Milner, Stuart D.; Davis, Christopher C.

2012-10-01

416

Direction identification in radio images of cosmic-ray air showers detected with LOPES and KASCADE  

E-print Network

AIMS: We want to understand the emission mechanism of radio emission from air showers to determine the origin of high-energy cosmic rays. Therefore, we study the geometry of the air shower radio emission measured with LOPES and search for systematic effects between the direction determined on the radio signal and the direction provided by the particle detector array KASCADE. METHODS: We produce 4D radio images on time-scales of nanoseconds using digital beam-forming. Each pixel of the image is calculated for three spatial dimensions and as a function of time. The third spatial dimension is obtained by calculating the beam focus for a range of curvature radii fitted to the signal wave front. We search this multi-dimensional parameter space for the direction of maximum coherence of the air shower radio signal and compare it to the direction provided by KASCADE. RESULTS: The maximum radio emission of air showers is obtained for curvature radii being larger than 3 km. We find that the direction of the emission maximum can change when optimizing the curvature radius. Furthermore, we find a tentative increase of the curvature radius to lower elevations, where the air showers pass through a larger atmospheric depth. CONCLUSIONS: We conclude that the angular resolution of LOPES is sufficient to determine the direction which maximizes the observed electric field amplitude. However, the statistical uncertainty of the directions is not determined by the resolution of LOPES, but by the uncertainty of the curvature radius. We do not find any systematic deviation between the directions determined from the radio signal and from the detected particles. This result places a strong supportive argument for the use of the radio technique to study the origin of high-energy cosmic rays.

A. Nigl

2008-09-16

417

An optofluidic nanoplasmonic biosensor for direct detection of live viruses from biological media.  

PubMed

Fast and sensitive virus detection techniques, which can be rapidly deployed at multiple sites, are essential to prevent and control future epidemics and bioterrorism threats. In this Letter, we demonstrate a label-free optofluidic nanoplasmonic sensor that can directly detect intact viruses from biological media at clinically relevant concentrations with little to no sample preparation. Our sensing platform is based on an extraordinary light transmission effect in plasmonic nanoholes and utilizes group-specific antibodies for highly divergent strains of rapidly evolving viruses. So far, the questions remain for the possible limitations of this technique for virus detection, as the penetration depths of the surface plasmon polaritons are comparable to the dimensions of the pathogens. Here, we demonstrate detection and recognition of small enveloped RNA viruses (vesicular stomatitis virus and pseudotyped Ebola) as well as large enveloped DNA viruses (vaccinia virus) within a dynamic range spanning 3 orders of magnitude. Our platform, by enabling high signal to noise measurements without any mechanical or optical isolation, opens up opportunities for detection of a broad range of pathogens in typical biology laboratory settings. PMID:21053965

Yanik, Ahmet A; Huang, Min; Kamohara, Osami; Artar, Alp; Geisbert, Thomas W; Connor, John H; Altug, Hatice

2010-12-01

418

An Optofluidic-Nanoplasmonic Biosensor for Direct Detection of Live Viruses from Biological Media  

PubMed Central

Fast and sensitive virus detection techniques, which can be rapidly deployed at multiple sites, are essential to prevent and control the future epidemics and bioterrorism threats. In this letter, we demonstrate a label-free optofluidic-nanoplasmonic sensor that can directly detect intact viruses from biological media at clinically relevant concentrations with little to no sample preparation. Our sensing platform is based on extraordinary light transmission effect in plasmonic nanoholes and utilizes group specific antibodies for highly divergent strains of rapidly evolving viruses. So far, the questions remain for the possible limitations of this technique for virus detection, as the penetration depths of the surface plasmon polaritons (SPP) are comparable to the dimensions of the pathogens. Here, we demonstrate detection and recognition of small enveloped RNA viruses (vesicular stomatitis virus and pseudo-typed Ebola) as well as large enveloped DNA viruses (vaccinia virus) within a dynamic range spanning three orders of magnitude. Our platform, by enabling high signal noise measurements without any mechanical or optical isolation, opens up opportunities for detection of a broad range of pathogens in typical biology laboratory settings. PMID:21053965

Yanik, Ahmet A.; Huang, Min; Kamohara, Osami; Artar, Alp; Geisbert, Thomas W.; Connor, John H.; Altug, Hatice

2010-01-01

419

Direct detection of cancer biomarkers in blood using a "place n play" modular polydimethylsiloxane pump  

PubMed Central

Cancer biomarkers have significant potential as reliable tools for the early detection of the disease and for monitoring its recurrence. However, most current methods for biomarker detection have technical difficulties (such as sample preparation and specific detector requirements) which limit their application in point of care diagnostics. We developed an extremely simple, power-free microfluidic system for direct detection of cancer biomarkers in microliter volumes of whole blood. CEA and CYFRA21-1 were chosen as model cancer biomarkers. The system automatically extracted blood plasma from less than 3??l of whole blood and performed a multiplex sample-to-answer assay (nano-ELISA (enzyme-linked immunosorbent assay) technique) without the use of external power or extra components. By taking advantage of the nano-ELISA technique, this microfluidic system detected CEA at a concentration of 50?pg/ml and CYFRA21-1 at a concentration of 60?pg/ml within 60?min. The combination of PnP polydimethylsiloxane (PDMS) pump and nano-ELISA technique in a single microchip system shows great promise for the detection of cancer biomarkers in a drop of blood. PMID:24404025

Zhang, Honglian; Li, Gang; Liao, Lingying; Mao, HongJu; Jin, Qinghui; Zhao, Jianlong

2013-01-01

420

Standardization of Neisseria meningitidis Serogroup B Colorimetric Serum Bactericida Assay  

PubMed Central

The correlate of protection for serogroup B meningococci is not currently known, but for serogroup C it is believed to be the serum bactericidal assay (SBA). The current SBAs are labor intensive and the variations in protocols among different laboratories make interpretation of results difficult. A colorimetric SBA (cSBA), based on the ability of Neisseria meningitidis serogroup B to consume glucose, leading to acid production, was standardized by using group B strain Cu385-83 as the target. The cSBA results were compared to those obtained for a traditional colony-counting microassay (mSBA). Glucose and bromocresol purple pH indicator were added to the medium in order to estimate growth of cSBA target cell survivors through color change. Different variants of the assay parameters were optimized: growth of target cells (Mueller Hinton agar plates), target cell number (100 CFU/per well), and human complement source used at a final concentration of 25%. After the optimization, three other group B strains (H44/76, 490/91, and 511/91) were used as targets for the cSBA. The selection of the assay parameters and the standardization of cSBA were done with 13 sera from vaccinated volunteers. The titers were determined as the higher serum dilution that totally inhibited the bacterial growth marked by the color invariability of the pH indicator. This was detected visually as well as spectrophotometrically and was closely related to a significant difference in the growth of target cell survivors determined using Student’s t test. Intralaboratory reproducibility was ±1 dilution. The correlation between bactericidal median titers and specific immunoglobulin G serum concentration by enzyme immunoassay was high (r = 0.910, P < 0.01). The bactericidal titers generated by the cSBA and the mSBA were nearly identical, and there was a high correlation between the two assays (r = 0.974, P < 0.01). The standardized cSBA allows easy, fast, and efficient evaluation of samples. PMID:11777839

Rodriguez, Tamara; Lastre, Miriam; Cedre, Barbara; Campo, Judith del; Bracho, Gustavo; Zayas, Caridad; Taboada, Carlos; Diaz, Miriam; Sierra, Gustavo; Perez, Oliver

2002-01-01

421

WIMP astronomy and particle physics with liquid-noble and cryogenic direct-detection experiments  

E-print Network

Once weakly-interacting massive particles (WIMPs) are unambiguously detected in direct-detection experiments, the challenge will be to determine what one may infer from the data. Here, I examine the prospects for reconstructing the local speed distribution of WIMPs in addition to WIMP particle-physics properties (mass, cross sections) from next-generation cryogenic and liquid-noble direct-detection experiments. I find that the common method of fixing the form of the velocity distribution when estimating constraints on WIMP mass and cross sections means losing out on the information on the speed distribution contained in the data and may lead to biases in the inferred values of the particle-physics parameters. I show that using a more general, empirical form of the speed distribution can lead to good constraints on the speed distribution. Moreover, one can use Bayesian model-selection criteria to determine if a theoretically-inspired functional form for the speed distribution (such as a Maxwell-Boltzmann distribution) fits better than an empirical model. The shape of the degeneracy between WIMP mass and cross sections and their offset from the true values of those parameters depends on the hypothesis for the speed distribution, which has significant implications for consistency checks between direct-detection and collider data. In addition, I find that the uncertainties on theoretical parameters depends sensitively on the upper end of the energy range used for WIMP searches. Better constraints on the WIMP particle-physics parameters and speed distribution are obtained if the WIMP search is extended to higher energy (~ 1 MeV).

Annika H. G. Peter

2011-03-26

422

Poker Face of Inelastic Dark Matter: Prospects at Upcoming Direct Detection Experiments  

SciTech Connect

The XENON100 and CRESST experiments will directly test the inelastic dark matter explanation for DAMA's 8.9{sigma} anomaly. This article discusses how predictions for direct detection experiments depend on uncertainties in quenching factor measurements, the dark matter interaction with the Standard Model and the halo velocity distribution. When these uncertainties are accounted for, an order of magnitude variation is found in the number of expected events at CRESST and XENON100. The process of testing the DAMA anomaly highlights many of the challenges inherent to direct detection experiments. In addition to determining the properties of the unknown dark matter particle, direct detection experiments must also consider the unknown flux of the incident dark matter, as well as uncertainties in converting a signal from one target nucleus to another. The predictions for both the CRESST 2009 run and XENON100 2010 run show an order of magnitude uncertainty. The nuclear form factor for {sup 184}W, when combined with additional theoretical and experimental uncertainties, will likely prevent CRESST from refuting the iDM hypothesis with an exposure of {Omicron}(100 kg-d) in a model-independent manner. XENON100, on the other hand, will be able to make a definitive statement about a spin-independent, inelastically scattering dark matter candidate. Still, the CRESST 2009 data can potentially confirm iDM for a large range of parameter space. In case of a positive signal, the combined data from CRESST and XENON100 will start probing the properties of the Milky Way DM profile and the interaction of the SM with the dark matter.

Alves, Daniele S.M.; Lisanti, Mariangela; /SLAC /Stanford U., Phys. Dept.; Wacker, Jay G.; /SLAC

2011-08-12

423

Azomethine H colorimetric method for determining dissolved boron in water  

USGS Publications Warehouse

An automated colorimetric method for determining dissolved boron in water is described. The boron is complexed with azomethine H, which is readily available as the condensation product of H acid (8-amino-1-naphthol-3,6-disulfonic acid) and salicylaldehyde. The absorbance of the yellow complex formed is then measured colorimetrically at 410 nm. Interference effects from other dissolved species are minimized by the addition of diethylenetriaminepentaacetic acid (DTPA); however, iron, zinc, and bicarbonate interfere at concentrations above 400 ??g/L, 2000 ??g/L, and 200 mg/L, respectively. The bicarbonate interference can be eliminated by careful acidification of the sample with concentrated HCl to a pH between 5 and 6. Thirty samples per hour can be routinely analyzed over the range of from 10 to 400 ??g/L, boron.

Spencer, R. R.; Erdmann, D. E.

1979-01-01

424

DM-TPC: a new approach to directional detection of Dark Matter  

E-print Network

Directional detection can provide unambiguous observation of Dark Matter interactions even in presence of insidious backgrounds. The DM-TPC collaboration is developing a detector with the goal of measuring the direction and sense of nuclear recoils produced in Dark Matter interactions. The detector consists of a Time Projection Chamber with optical readout filled with CF$_4$ gas at low pressure. A collision between a WIMP and a gas molecule results in a nuclear recoil of 1-2 mm. The measurement of the energy loss along the recoil allows us to determine the sense and the direction of the recoil. Results from a prototype detector operated in a low-energy neutron beam clearly demonstrate the suitability of this approach to measure directionality. A full-scale module with an active volume of about one cubic meter is now being designed. This detector, which will be operated underground in 2009, will allow us to set competitive limits on spin-dependent Dark Matter interactions using a directional detector.

G. Sciolla; S. Ahlen; D. Dujmic; V. Dutta; P. Fisher; S. Henderson; A. Kaboth; G. Kohse; R. Lanza; J. Monroe; A. Roccaro; N. Skvorodnev; H. Tomita; R. Vanderspek; H. Wellenstein; R. Yamamoto

2008-05-16

425

Newly Established Monoclonal Antibody Diagnostic Assays for Schistosoma mansoni Direct Detection in Areas of Low Endemicity  

PubMed Central

Background Current available methods for diagnosis of schistosomiasis mansoni lack sufficient sensitivity, which results in underreporting of infectious in areas of low endemicity. Methodology/Principal Findings We developed three novel diagnostic methodologies for the direct detection of schistosome infection in serum samples. These three new methods were evaluated with positive patients from a low endemicity area in southeast Brazil. The basis of the assay was the production of monoclonal antibodies against the protein backbone of heavily glycosylated Circulating Cathodic Antigen (CCA). The antibodies were also selected for having no specificity to repeating poly-Lewis x units. Assays based on the dete