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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 (Rodeo, CA); Spevak, Wayne (Albany, CA)

1999-01-01

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 (Bozeman, MT); Spevak, Wayne (Albany, CA)

2002-01-01

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)

2002-11-26

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)

2000-01-01

5

Direct visualization of lead corona and its nanomolar colorimetric detection using anisotropic gold nanoparticles.  

PubMed

The study presents dithiothreitol (DTT) functionalized anisotropic gold nanoparticles (GNP) based colorimetric sensor for detection of toxic lead ions in water. Our results demonstrate the selectivity and sensitivity of the developed sensor over various heavy metal ions with detection limit of ?9 nM. The mechanism of sensing is explained on the basis of unique corona formation around the DTT functionalized anisotropic GNP. PMID:25719820

Dwivedi, Charu; Chaudhary, Abhishek; Gupta, Abhishek; Nandi, Chayan K

2015-03-11

6

Gum kondagogu reduced/stabilized silver nanoparticles as direct colorimetric sensor for the sensitive detection of Hg²? in aqueous system.  

PubMed

A highly sensitive and selective method is reported for the colorimetric detection of Hg(2+) in aqueous system by using label free silver nanoparticles (Ag NPs). Ag NPs used in this method were synthesized by gum kondagogu (GK) which acted as both reducing and stabilizing agent. The average size of the GK-Ag NPs was found to be 5.0 ± 2.8 nm as revealed by transmission electron microscope (TEM) analysis and the nanoparticles were stable at various pH conditions (pH 4-11) and salt concentrations (5-100 mM). The GK reduced/stabilized Ag NPs (GK-Ag NPs) were directly used for the selective colorimetric reaction with Hg(2+) without any further modification. The bright yellow colour of Ag NPs was found to fade in a concentration dependent manner with the added Hg(+) ions. The fading response was directly correlated with increasing concentration of Hg(2+). More importantly, this response was found to be highly selective for Hg(2+) as the absorption spectra were found to be unaffected by the presence of other ions like; Na(+), K(+), Mg(2+), Ca(2+), Cu(2+), Ni(2+), Co(2+), As(3+), Fe(2+), Cd(2+), etc. The metal sensing mechanism is explained based on the turbidometric and X-ray diffraction (XRD) analysis of GK-Ag NPs with Hg(2+). The proposed method was successfully applied for the determination of Hg(2+) in various ground water samples. The reported method can be effectively used for the quantification of total Hg(2+) in samples, wherein the organic mercury is first oxidized to inorganic form by ultraviolet (UV) irradiation. The limit of quantification for Hg(2+) using the proposed method was as low as 4.9 × 10(-8) mol L(-1) (50 nM). The proposed method has potential application for on-field qualitative detection of Hg(2+) in aqueous environmental samples. PMID:24274277

Rastogi, Lori; Sashidhar, R B; Karunasagar, D; Arunachalam, J

2014-01-01

7

Colorimetric Immunoassay for Detection of Tumor Markers  

PubMed Central

Tumor markers are substances, usually proteins, produced by the body in response to cancer growth, or by the cancer tissue itself. They can be detected in blood, urine, or tissue samples, and the discovery and detection of tumor markers may provide earlier diagnosis of cancer and improved therapeutic intervention. Colorimetric immunoassays for tumor marker detection have attracted considerable attention, due to their simplicity and high efficiency. The traditionally used colorimetric immunoassays for the detection of tumor markers are based on enzyme-linked immunosorbent assays, and the great achievement of nanotechnology has further opened opportunities for the development of such kind of immunoassays. This paper will summarize recent advances in the field of colorimetric immunoassays for detecting tumor markers, which is aimed to provide an overview in this field, as well as experimental guidance for the learner. PMID:21614193

Yin, Yongmei; Cao, Ya; Xu, Yuanyuan; Li, Genxi

2010-01-01

8

Direct colorimetric detection of copper(II) ions in sampling using diffusive gradients in thin-films.  

PubMed

A novel binding phase was developed for use in diffusive gradients in thin-film (DGT) sampling for Cu(II) by employing methylthymol blue as a chelating and chromogenic agent. Methylthymol blue was adsorbed onto beads of Dowex 1 x 8 resin (200-400 mesh) and the resin beads were then immobilised onto an adhesive disc. Analysis of exposed binding discs by either UV-vis spectrophotometry or computer imaging densitometry provided robust quantification of adsorbed Cu(II) in the 0.2-1 microg cm(-2) range, allowing detection at microg L(-1) concentrations in the test solution (ca. 17 microg L(-1) for a 24 h deployment), and in good agreement with established DGT theory. The method was shown to be a potential replacement for binding phases based on Chelex 100 where a colorimetric response to a specific metal is desired. PMID:20152264

McGifford, Russell W; Seen, Andrew J; Haddad, Paul R

2010-03-01

9

Emergency First Responders' Experience with Colorimetric Detection Methods  

SciTech Connect

Nationwide, first responders from state and federal support teams respond to hazardous materials incidents, industrial chemical spills, and potential weapons of mass destruction (WMD) attacks. Although first responders have sophisticated chemical, biological, radiological, and explosive detectors available for assessment of the incident scene, simple colorimetric detectors have a role in response actions. The large number of colorimetric chemical detection methods available on the market can make the selection of the proper methods difficult. Although each detector has unique aspects to provide qualitative or quantitative data about the unknown chemicals present, not all detectors provide consistent, accurate, and reliable results. Included here, in a consumer-report-style format, we provide “boots on the ground” information directly from first responders about how well colorimetric chemical detection methods meet their needs in the field and how they procure these methods.

Sandra L. Fox; Keith A. Daum; Carla J. Miller; Marnie M. Cortez

2007-10-01

10

Optical fiber waveguide sensor for the colorimetric detection of ammonia  

NASA Astrophysics Data System (ADS)

We present the development and characterization of a fiber-optic colorimetric gas sensor combined with the electronic circuitry for measurement control and RFID communication. The gas sensor detects ammonia using a 300 ?m polyolefin fiber coated with a gas-sensitive polymer film. The spectral and time-dependent sensitivity of various polymer films was tested in transmission measurements. Light from a standard LED at ? = 590 nm was coupled into the polyolefin fiber through the front face. A prototype of the gas sensor with the direct coupling method was tested under realistic measurement conditions, i.e. battery-driven and in a completely autonomous mode. The sensor system showed good sensitivity to the ammonia concentrations and response times in the order of minutes. The achievable power consumption was below 100?W.The films contained the pH-sensitive dyes bromocresol purple or bromophenol blue embedded in either ethyl cellulose or polyvinyl butyral, and optionally tributyl phosphate as plasticizer. The bromophenol blue based films showed a strong reaction to ammonia, with saturation concentrations around 1000 ppm and response times of about 15 seconds to 100ppm. The colorimetric reaction was simulated using a simple kinetic model which was in good agreement with the experimental results.

Schmitt, Katrin; Rist, Jonas; Peter, Carolin; Wöllenstein, Jürgen

2011-06-01

11

Colorimetric detection of uranium in water  

DOEpatents

Disclosed are methods, materials and systems that can be used to determine qualitatively or quantitatively the level of uranium contamination in water samples. Beneficially, disclosed systems are relatively simple and cost-effective. For example, disclosed systems can be utilized by consumers having little or no training in chemical analysis techniques. Methods generally include a concentration step and a complexation step. Uranium concentration can be carried out according to an extraction chromatographic process and complexation can chemically bind uranium with a detectable substance such that the formed substance is visually detectable. Methods can detect uranium contamination down to levels even below the MCL as established by the EPA.

DeVol, Timothy A. (Clemson, SC); Hixon, Amy E. (Piedmont, SC); DiPrete, David P. (Evans, GA)

2012-03-13

12

Method for colorimetric detection of double-stranded nucleic acid using leuco triphenylmethane dyes.  

PubMed

Because loop-mediated isothermal amplification (LAMP) can amplify substantial amounts of DNA under isothermal conditions, its applications for simple genetic testing have attracted considerable attention. A positive LAMP reaction is indicated by the turbidity caused by by-products or by the color change after adding a metallochromic indicator to the reaction solution, but these methods have certain limitations. Leuco crystal violet (LCV), a colorless dye obtained after sodium sulfite treatment of crystal violet (CV), was used as a new colorimetric method for detecting LAMP. LCV is reconverted into CV through contact with double-stranded DNA (dsDNA). Therefore, the positive reaction of LAMP is indicated by color change from colorless to violet. The assay is sensitive enough to detect LAMP products, with a detection limit of 7.1ng/?l for dsDNA. It is also highly selective to dsDNA, and interference with single-stranded DNA and deoxynucleotide triphosphates (dNTPs) is not observed. LCV facilitates direct colorimetric detection of the main product rather than a by-product of the LAMP reaction; therefore, this method can be used under various reaction conditions such as those with added pyrophosphatase in solution. This colorimetric LAMP detection method using LCV is useful for point-of-care genetic testing given its simplicity. PMID:25575759

Miyamoto, Shigehiko; Sano, Sotaro; Takahashi, Koji; Jikihara, Takaaki

2015-03-15

13

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

E-print Network

Colorimetric Detection and Fingerprinting of Bacteria by Glass-Supported Lipid applied for visual detection and colorimetric fingerprinting of bacteria. The sensor films comprise bacteria. An important feature of the new film platform is the feasibility of either naked-eye detection

Jelinek, Raz

14

A colorimetric and fluorometric microplate assay for the detection of microcystin-LR in drinking water without preconcentration  

Microsoft Academic Search

Protein phosphatase inhibition assays currently used for the detection of cyanobacterial peptide hepatotoxins in drinking water require an enrichment step using C18 cartridges to achieve lower the detection limit. This paper describes a colorimetric and fluorometric protein phosphatase inhibition method for the direct detection of microcystin-LR (MCYST-LR) in drinking water without complex clean-up steps and preconcentration procedures. In this assay

I Maatouk; G Vincent; Y Levi

2002-01-01

15

Colorimetric detection of catalytic reactivity of nanoparticles in complex matrices.  

PubMed

There is a need for new methodologies to quickly assess the presence and reactivity of nanoparticles (NPs) in commercial, environmental, and biological samples since current detection techniques require expensive and complex analytical instrumentation. Here, we investigate a simple and portable colorimetric detection assay that assesses the surface reactivity of NPs, which can be used to detect the presence of NPs, in complex matrices (e.g., environmental waters, serum, urine, and in dissolved organic matter) at as low as part per billion (ppb) or ng/mL concentration levels. Surface redox reactivity is a key emerging property related to potential toxicity of NPs with living cells, and is used in our assays as a key surrogate for the presence of NPs and a first tier analytical strategy toward assessing NP exposures. We detect a wide range of metal (e.g., Ag and Au) and oxide (e.g., CeO2, SiO2, VO2) NPs with a diameter range of 5 to 400 nm and multiple capping agents (tannic acid (TA), polyvinylpyrrolidone (PVP), branched polyethylenimine (BPEI), polyethylene glycol (PEG)). This method is sufficiently sensitive (ppb levels) to measure concentrations typically used in toxicological studies, and uses inexpensive, commercially available reagents. PMID:25635807

Corredor, Charlie; Borysiak, Mark D; Wolfer, Jay; Westerhoff, Paul; Posner, Jonathan D

2015-03-17

16

Nanodiagnostic Method for Colorimetric Detection of Mycobacterium tuberculosis 16S rRNA  

Microsoft Academic Search

A nanodiagnostic method using nucleic acid sequence-based amplification (NASBA) and gold nanoparticle probes (AuNP probes)\\u000a was developed for colorimetric detection of Mycobacterium tuberculosis. The primers targeting 16S rRNA were used for the amplification of mycobacterial RNA by the isothermal NASBA process. The\\u000a amplicons were hybridized with specific gold nanoparticle probes. The RNA–DNA hybrids were colorimetrically detected by the\\u000a accumulation of

Pooria Gill; Mostafa Ghalami; Amir Ghaemi; Nader Mosavari; Hossein Abdul-Tehrani; Majid Sadeghizadeh

2008-01-01

17

Gold nanoparticles-based colorimetric assay for rapid detection of Salmonella species in food samples  

Microsoft Academic Search

A rapid, sensitive and cost-effective method was developed for detection of foodborne pathogens, particularly Salmonella species. The method utilizes single stranded DNA (ssDNA) probes and non-functionalized gold nanoparticles to provide a colorimetric\\u000a assay for the detection of PCR amplified DNA. Different food samples were tested with the PCR-based colorimetric assay parallel\\u000a with the conventional culture method. The sensitivity and specificity

Dinesh Prasad; Shankaracharya; Ambarish Sharan Vidyarthi

18

Colorimetric microwell plate reverse-hybridization assay for Mycobacterium tuberculosis detection.  

PubMed

Direct smear examination using Ziehl-Neelsen staining for pulmonary tuberculosis (PTB) diagnosis is inexpensive and easy to use, but has the major limitation of low sensitivity. Rapid molecular methods are becoming more widely available in centralized laboratories, but they depend on timely reporting of results and strict quality assurance obtainable only from costly commercial kits available in high burden nations. This study describes a pre-commercial colorimetric method, Detect-TB, for detecting Mycobacterium tuberculosis DNA in which an oligonucleotide probe is fixed onto wells of microwell plates and hybridized with biotinylated polymerase chain reaction amplification products derived from clinical samples. The probe is capable of hybridising with the IS6110 insertion element and was used to specifically recognise the M. tuberculosis complex. When combined with an improved silica-based DNA extraction method, the sensitivity of the test was 50 colony-forming units of the M. tuberculosis reference strain H37Rv. The results that were in agreement with reference detection methods were observed in 95.2% (453/476) of samples included in the analysis. Sensitivity and specificity for 301 induced sputum samples and 175 spontaneous sputum samples were 85% and 98%, and 94% and 100%, respectively. This colorimetric method showed similar specificity to that described for commercially available kits and may provide an important contribution for PTB diagnosis. PMID:21537680

Michelon, Candice Tosi; Rosso, Franciele; Schmid, Karen Barros; Sperhacke, Rosa Dea; Oliveira, Martha Maria; Kritski, Afrânio Lineu; Rezende Jr, Leonides; Costa, Elis Regina Dalla; Ribeiro, Andrezza Woloski; Verza, Mirela; Cafrune, Patrícia Izquierdo; Silva, Márcia Susana Nunes; Kuhleis, Daniele; Zaha, Arnaldo; Rossetti, Maria Lucia Rosa

2011-03-01

19

Point-of-care colorimetric detection with a smartphone.  

PubMed

Paper-based immunoassays are becoming powerful and low-cost diagnostic tools, especially in resource-limited settings. Inexpensive methods for quantifying these assays have been shown using desktop scanners, which lack portability, and cameras, which suffer from the ever changing ambient light conditions. In this work, we introduce a novel approach of quantifying colors of colorimetric diagnostic assays with a smartphone that allows high accuracy measurements in a wide range of ambient conditions, making it a truly portable system. Instead of directly using the red, green, and blue (RGB) intensities of the color images taken by a smartphone camera, we use chromaticity values to construct calibration curves of analyte concentrations. We demonstrate the high accuracy of this approach in pH measurements with linear response ranges of 1-12. These results are comparable to those reported using a desktop scanner or silicon photodetectors. To make the approach adoptable under different lighting conditions, we developed a calibration technique to compensate for measurement errors due to variability in ambient light. This technique is applicable to a number of common light sources, such as sun light, fluorescent light, or smartphone LED light. Ultimately, the entire approach can be integrated in an "app" to enable one-click reading, making our smartphone based approach operable without any professional training or complex instrumentation. PMID:22996728

Shen, Li; Hagen, Joshua A; Papautsky, Ian

2012-11-01

20

Colorimetric One-Tube Nested PCR for Detection of Trichomonas vaginalisin Vaginal Discharge  

Microsoft Academic Search

A colorimetric one-tube nested PCR was developed for the detection of Trichomonas vaginalis in clinical vaginal discharge specimens. A family of 650-bp specific DNA repeats from the T. vaginalis genome was targeted. There was no cross-reaction with human DNA or other infectious agents, includingPentatrichomonas hominisandGiardia lamblia. The colorimetric assay was applied as an adjunct to nested PCR for semiquan- titative

MEN-FANG SHAIO; PEY-RU LIN; ANDJAH-YAO LIU

21

DNA based gold nanoparticles colorimetric sensors for sensitive and selective detection of Ag(I) ions.  

PubMed

In this work, we reported both unlabeled and labeled sensing strategies for Ag(I) ions detection by using the DNA based gold nanoparticles (AuNPs) colorimetric method. In the unlabeled strategy, C-base riched single strand DNA (C-ssDNA) enwinded onto AuNPs to form AuNPs/C-ssDNA complex. In the labeled method, sulfhydryl group modified C-ssDNA (HS-C-ssDNA) was covalently labeled on AuNPs to produce AuNPs-S-C-ssDNA complex. In both strategies, C-ssDNA or HS-C-ssDNA could enhance the AuNPs stability against the salt-induced aggregation. However, the presence of Ag(I) ions in the obtained AuNPs/C-ssDNA or AuNPs-S-C-ssDNA complex would decrease such stability to display purple even blue colors due to the formation of Ag(I) ions mediated C-Ag(I)-C base pairs. Through this phenomenon, Ag(I) ions could be detected qualitatively and quantitatively using both unlabeled and labeled sensing strategies. Compared with the labeled method, the unlabeled strategy avoided the label and separation steps in common sensors, which may thus save both the time and cost for the detection. Nevertheless, the labeled strategy provided more sensitive, stable and controllable sensing results compared with the unlabeled method. By the labeled strategy, 12 nM Ag(I) ions could be observed directly by naked eyes, and the lowest detectable concentration of 0.59 nM was gotten under by the UV-vis spectra measurement, which was one of the most sensitive results among DNA based AuNPs colorimetric sensors for metal ions. PMID:19463566

Li, Bingling; Du, Yan; Dong, Shaojun

2009-06-30

22

A colorimetric assay for detecting haloalkane dehalogenase activity  

Microsoft Academic Search

A pH indicator dye-based colorimetric assay was adapted to measure haloalkane dehalogenase activity quantitatively in cell extracts of bacteria using the microplate format. The assay is based on a decrease in the pH of a weakly-buffered medium when protons and chloride ions are released by the enzyme. Our assay is more convenient than other instrumental or chemical assay methods presently

Paul Holloway; Jack T Trevors

1998-01-01

23

Detection of beer spoilage bacteria Megasphaera and Pectinatus by polymerase chain reaction and colorimetric microplate hybridization  

Microsoft Academic Search

Anaerobic bacteria of the genera Megasphaera and Pectinatus cause beer spoilage by producing off flavours and turbidity. Detection of these organisms is complicated by the strict anaerobic conditions and lengthy incubation times required for their cultivation, consequently there is a need for more rapid detection methods. A polymerase chain reaction (PCR) method and a colorimetric microplate hybridization assay were developed

Reetta Satokari; Riikka Juvonen; Kirstie Mallison; Atte von Wright; Auli Haikara

1998-01-01

24

Colorimetric Phage-Based Assay for Detection of Rifampin-Resistant Mycobacterium tuberculosis  

Microsoft Academic Search

Tests based on bacteriophage replication enable rapid screening of Mycobacterium tuberculosis for drug resistance. We describe a novel broth-based colorimetric method for detecting phage replication. When clinical isolates were tested by this novel method, high concordance was observed with both the traditional phage assay and gene mutation analysis for detection of resistance to rifampin. The emergence of drug-resistant tuberculosis that

Ruth McNerney; Kim Mallard; Honorathy M. R. Urassa; Eshetu Lemma; Helen D. Donoghue

2007-01-01

25

Identification of Escherichia coli O157 by Using a Novel Colorimetric Detection Method with DNA Microarrays  

Technology Transfer Automated Retrieval System (TEKTRAN)

Shiga toxin-producing Escherichia coli O157:H7 is a leading cause of foodborne illness worldwide. To evaluate better methods to rapidly detect and genotype E. coli O157 strains, the present study evaluated the use of ampliPHOX, a novel colorimetric detection method based on photopolymerization, for...

26

Simple Colorimetric Method for Detecting Degenerate Strains of the Cultivated Basidiomycete Flammulina velutipes (Enokitake)  

PubMed Central

Degeneration of cultivated strains of Flammulina velutipes is a serious problem. We developed a simple colorimetric method to detect degenerate strains by using a liquid medium supplemented with bromothymol blue and lactose. The ability of a strain to develop normal mushrooms could be determined by the color of the medium. PMID:16204563

Magae, Yumi; Akahane, Kobun; Nakamura, Kimiyoshi; Tsunoda, Shigeyuki

2005-01-01

27

A new rapid and simple colorimetric method to detect pyrazinamide resistance in Mycobacterium tuberculosis using nicotinamide  

Microsoft Academic Search

Objectives: The purpose of this study was to develop and assess a rapid method for pyrazinamide resistance detection in Mycobacterium tuberculosis using nicotinamide in a colorimetric resazurin assay. Methods: We have tested M. tuberculosis isolates using nicotinamide in a 96-well format with the redox indicator resazurin (REMA) and compared results using the BACTEC 460-TB system with two concentra- tions of

Anandi Martin; Howard Takiff; Peter Vandamme; Jean Swings; Juan Carlos Palomino; Francoise Portaels; Mycobacteriology Unit

2006-01-01

28

Carbon nanotube-based labels for highly sensitive colorimetric and aggregation-based visual detection of nucleic acids  

NASA Astrophysics Data System (ADS)

A novel carbon nanotube (CNT) derived label capable of dramatic signal amplification of nucleic acid detection and direct visual detection of target hybridization has been developed. Highly sensitive colorimetric detection of human acute lymphocytic leukemia (ALL) related oncogene sequences amplified by the novel CNT-based label was demonstrated. Atomic force microscope (AFM) images confirmed that a monolayer of horseradish peroxidase and detection probe molecules was immobilized along the carboxylated CNT carrier. The resulting CNT labels significantly enhanced the nucleic acid assay sensitivity by at least 1000 times compared to that of conventional labels used in enzyme-linked oligosorbent assay (ELOSA). An excellent detection limit of 1 × 10-12 M (60 × 10-18 mol in 60 µl) and a four-order wide dynamic range of target concentration were achieved. Hybridizations using these labels were coupled to a concentration-dependent formation of visible dark aggregates. Targets can thus be detected simply with visual inspection, eliminating the need for expensive and sophisticated detection systems. The approach holds promise for ultrasensitive and low cost visual inspection and colorimetric nucleic acid detection in point-of-care and early disease diagnostic application.

Lee, Ai Cheng; Ye, Jian-Shan; Ngin Tan, Swee; Poenar, Daniel P.; Sheu, Fwu-Shan; Kiat Heng, Chew; Meng Lim, Tit

2007-11-01

29

A colorimetric sensor based on anodized aluminum oxide (AAO) substrate for the detection of nitroaromatics.  

SciTech Connect

Simple and low cost colorimetric sensors for explosives detection were explored and developed. Anodized aluminum oxide (AAO) with large surface area through its porous structure and light background color was utilized as the substrate for colorimetric sensors. Fabricated thin AAO films with thickness less than {approx} 500 nm allowed us to observe interference colors which were used as the background color for colorimetric detection. AAO thin films with various thickness and pore-to-pore distance were prepared through anodizing aluminum foils at different voltages and times in dilute sulfuric acid. Various interference colors were observed on these samples due to their difference in structures. Accordingly, suitable anodization conditions that produce AAO samples with desired light background colors for optical applications were obtained. Thin film interference model was applied to analyze the UV-vis reflectance spectra and to estimate the thickness of the AAO membranes. We found that the thickness of produced AAO films increased linearly with anodization time in sulfuric acid. In addition, the growth rate was higher for AAO anodized using higher voltages. The thin film interference formulism was further validated with a well established layer by layer deposition technique. Coating poly(styrene sulfonate) sodium salt (PSS) and poly(allylamine hydrochloride) (PAH) layer by layer on AAO thin film consistently shifted its surface color toward red due to the increase in thickness. The red shift of UV-vis reflectance was correlated quantitatively to the number of layers been assembled. This sensitive red shift due to molecular attachment (increase in thickness) on AAO substrate was applied toward nitroaromatics detection. Aminopropyltrimethoxysilane (APTS) which can be attached onto AAO nanowells covalently through silanization and attract TNT molecules was coated and applied for TNT detection. UV-vis spectra of AAO with APTS shifted to the longer wavelength side due to TNT attachment. This red shift implied AAO thickness increased and positive detection of TNT molecules. It was also observed that both APTS and polyethyleneimine (PEI) were electron rich polymers which formed Meisenheimer complexes with TNT in solution and changed its color abruptly. This strong color change due to chemical reaction was applied as another approach for direct TNT detection. Commercial AAO films with long pores (60 {mu}m) and white background color were coated with APTS or PEI and then exposed to TNT in solution. These membranes turned to pink rapidly and eventually became visibly orange after a few hours with a strong absorption around 500 nm that was consistent with the formation of Meisenheimer complexes. The visible color change can be observed by unaided eyes and is suitable for nitroaromatics detection at higher concentration while interference color red shift in AAO thin film is designed for nitroaromatics detection at monolayer (nm) level.

Liu, Y.; Wang, H. H.; Indacochea, J. E.; Wang, M. L. (Materials Science Division); (Northeastern Univ.); (Univ. of Illinois at Chicago)

2011-12-15

30

Highly sensitive colorimetric detection of 17?-estradiol using split DNA aptamers immobilized on unmodified gold nanoparticles  

PubMed Central

Gold nanoparticle (AuNP) based colorimetric aptasensor have been developed for many analytes recently largely because of the ease of detection, high sensitivity, and potential for high-throughput analysis. Most of the target aptamers for detection have short sequences. However, the approach shows poor performance in terms of detection sensitivity for most of the long-sequence aptamers. To address this problem, for the first time, we split the 76?mer aptamer of 17?-estradiol into two short pieces to improve the AuNP based colorimetric sensitivity. Our results showed that the split P1 + P2 still retained the original 76?mer aptamer's affinity and specificity but increased the detection limit by 10-fold, demonstrating that as low as 0.1?ng/mL 17?-estradiol could be detected. The increased sensitivity may be caused by lower aptamer adsorption concentration and a lower affinity to the AuNPs of a short single-strand DNA (ssDNA) sequence. Our study provided a new way to use long-sequence aptamers to develop a highly sensitive AuNP-based colorimetric aptasensor. PMID:25524368

Liu, Jinchuan; Bai, Wenhui; Niu, Shucao; Zhu, Chao; Yang, Shuming; Chen, Ailiang

2014-01-01

31

An enzyme-free and amplified colorimetric detection strategy: assembly of gold nanoparticles through target-catalytic circuits.  

PubMed

Herein we introduce an enzyme-free and amplified colorimetric detection strategy, which is based on gold nanoparticle (AuNP) aggregation through target-catalytic DNA circuits (HCR and CHA). PMID:25562066

Quan, Ke; Huang, Jin; Yang, Xiaohai; Yang, Yanjing; Ying, Le; Wang, He; Wang, Kemin

2015-02-21

32

Rapid colorimetric detection of Salmonella typhimuriumusing a selective filtration technique combined with antibody-magnetic nanoparticle nanocomposites.  

PubMed

Detection of pathogenic bacteria that pose a great risk to human health requires a rapid, convenient, reliable, and sensitive detection method. In this study, we developed a selective filtration method using monoclonal antibody (MAb)-magnetic nanoparticle (MNP) nanocomposites for the rapid and sensitive colorimetric detection of Salmonella typhimurium. The method contains two key steps: the immunomagnetic separation of the bacteria using MAb-MNP nanocomposites and the filtration of the nanocomposite-bound bacteria. Color signals from the nanocomposites remaining on the membrane were measured, which reflected the amount of bacteria in test samples. Immunomagnetic capture efficiencies of 8 to 90 % for various concentrations of the pathogen (2?×?10(4)-2?×?10(1) cells) were obtained. After optimization of the method, 2?×?10(1) cells of S. typhimurium in pure culture solution was detectable as well as in artificially inoculated vegetables (100 cells/g). The method was confirmed to be highly specific to S. typhimurium without cross-reaction to other pathogenic bacteria and could be concluded within 45 min, yielding results in a shorter or similar time period as compared with recently reported antibody immobilized on magnetic-particle-based methods. This study also demonstrated direct application of MAb-MNP nanocomposites without a dissociation step of bacteria from magnetic beads in colorimetric assays in practice. PMID:24337136

Shim, Won-Bo; Song, Jeong-Eon; Mun, Hyoyoung; Chung, Duck-Hwa; Kim, Min-Gon

2014-01-01

33

Label-free colorimetric aptasensor for sensitive detection of ochratoxin A utilizing hybridization chain reaction.  

PubMed

The combination of high selectivity of aptamer with the peroxidase-mimicking property of DNAzyme has presented considerable opportunities for designing colorimetric aptasensor for detection of ochratoxin A (OTA). The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. Hybridization chain reaction (HCR) between two hairpin DNAs was employed to further improve the sensitivity of this method. The presence of OTA triggers the opening of the hairpin structure and the beginning of HCR, which results in the release of many DNAzyme, and generates enhanced colorimetric signals, which is correlated to the amounts of OTA with linear range between 0.01 to 0.32nM, and the limit of detection is 0.01nM under optimal conditions. OTA in yellow rice wine and wheat flour samples was also detected using this method. We demonstrate that a new colorimetric method for the detection of OTA has been established, which is simple, easy to conduct, label-free, sensitive, high throughput, and cost-saving. PMID:25682251

Wang, Chengke; Dong, Xiaoya; Liu, Qian; Wang, Kun

2015-02-20

34

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

35

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

Microsoft Academic Search

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

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

2010-01-01

36

The Disassembly of a Core-Satellite Nanoassembled Substrate for Colorimetric Biomolecular Detection  

PubMed Central

The disassembly of a core-satellite nanostructured substrate is presented as a colorimetric biosensor observable under dark field illumination. The fabrication method described herein utilizes thiol-mediated adsorption and streptavidin-biotin binding to self-assemble core-satellite nanostructures with a sacrificial linking peptide. Biosensing functionality is demonstrated with the protease trypsin and the optical properties of the nanoassemblies are characterized. A figure of merit is presented to determine the optimal core and satellite size for visual detection. Nanoassemblies with 50 nm cores and 30 nm or 50 nm satellites are superior as these structures achieve an orange to green color shift greater than 70 nm that is easily discernible by naked eye. This colorimetric substrate may prove to be a favorable alternative to liquid-based colloidal sensors and a useful visual readout mechanism for microfluidic diagnostic assays. PMID:21667984

Waldeisen, John R.; Wang, Tim; Ross, Benjamin M.; Lee, Luke P.

2012-01-01

37

[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

38

NANOSENSOR DETECTS MERCURY IN WATER J.-S. Lee, M. S. Han, C. A. Mirkin, "Colorimetric Detection of Mercuric Ion (Hg2+  

E-print Network

NANOSENSOR DETECTS MERCURY IN WATER J.-S. Lee, M. S. Han, C. A. Mirkin, "Colorimetric Detection ­ 0647560 Mercuric ion (Hg2+ ) is one of the most stable inorganic forms of mercury. It is also a caustic

Shull, Kenneth R.

39

A Simple Colorimetric Assay for Specific Detection of Glutathione-S Transferase Activity Associated with DDT Resistance in Mosquitoes  

PubMed Central

Background Insecticide-based methods represent the most effective means of blocking the transmission of vector borne diseases. However, insecticide resistance poses a serious threat and there is a need for tools, such as diagnostic tests for resistance detection, that will improve the sustainability of control interventions. The development of such tools for metabolism-based resistance in mosquito vectors lags behind those for target site resistance mutations. Methodology/Principal Findings We have developed and validated a simple colorimetric assay for the detection of Epsilon class Glutathione transferases (GST)-based DDT resistance in mosquito species, such as Aedes aegypti, the major vector of dengue and yellow fever worldwide. The colorimetric assay is based on the specific alkyl transferase activity of Epsilon GSTs for the haloalkene substrate iodoethane, which produces a dark blue colour highly correlated with AaGSTE2-2-overexpression in individual mosquitoes. The colour can be measured visually and spectrophotometrically. Conclusions/Significance The novel assay is substantially more sensitive compared to the gold standard CDNB assay and allows the discrimination of moderate resistance phenotypes. We anticipate that it will have direct application in routine vector monitoring as a resistance indicator and possibly an important impact on disease vector control. PMID:20824165

Rajatileka, Shavanti; Steven, Andrew; Hemingway, Janet; Ranson, Hilary; Paine, Mark; Vontas, John

2010-01-01

40

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

41

Multi-colorimetric sensor array for detection of explosives in gas and liquid phase  

NASA Astrophysics Data System (ADS)

In the framework of the research project "Xsense" at the Technical University of Denmark (DTU) we are developing a simple colorimetric sensor array which can be useful in detection of explosives like DNT, TATP, HMX, RDX and identification of reagents needed for making homemade explosives. The technology is based on an array of chemoselective compounds immobilized on a solid support. Upon exposure to the analyte in suspicion the colorimetric array changes color. Each chosen compound reacts chemo-selectively with analytes of interest. A change in a color signature indicates the presence of unknown explosives and volatile organic compounds (VOCs). We are working towards the selection of compounds that undergo color changes in the presence of explosives and VOCs, as well as the development of an immobilization method for the molecules. Digital imaging of the colorimetric array before and after exposure to the analytes creates a color difference map which gives a unique fingerprint for each explosive and VOCs. Such sensing technology can be used for screening relevant explosives in a complex background as well as to distinguish mixtures of volatile organic compounds distributed in gas and liquid phases. This sensor array is inexpensive, and can potentially be produced as single use disposable.

Kostesha, N.; Alstrøm, T. S.; Johnsen, C.; Nielsen, K. A.; Jeppesen, J. O.; Larsen, J.; Boisen, A.; Jakobsen, M. H.

2011-05-01

42

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

43

Colorimetric peroxidase mimetic assay for uranyl detection in sea water.  

PubMed

Uranyl (UO2(2+)) is a form of uranium in aqueous solution that represents the greatest risk to human health because of its bioavailability. Different sensing techniques have been used with very sensitive detection limits especially the recently reported uranyl-specific DNAzymes systems. However, to the best of our knowledge, few efficient detection methods have been reported for uranyl sensing in seawater. Herein, gold nanoclusters (AuNCs) are employed in an efficient spectroscopic method to detect uranyl ion (UO2(2+)) with a detection limit of 1.86 ?M. In the absence of UO2(2+), the BSA-stabilized AuNCs (BSA-AuNCs) showed an intrinsic peroxidase-like activity. In the presence of UO2(2+), this activity can be efficiently restrained. The preliminary quenching mechanism and selectivity of UO2(2+) was also investigated and compared with other ions. This design strategy could be useful in understanding the binding affinity of protein-stabilized AuNCs to UO2(2+) and consequently prompt the recycling of UO2(2+) from seawater. PMID:25658750

Zhang, Dingyuan; Chen, Zhuo; Omar, Haneen; Deng, Lin; Khashab, Niveen M

2015-03-01

44

Colorimetric sensor for label free detection of porcine PCR product  

Microsoft Academic Search

Summary form only given. Selective detection of specific DNA sequences is increasingly getting momentum in clinical diagnosis, pathology, genetics and food analysis. The polymerase chain reaction (PCR) is a commonly used technique to amplify specific sequence segment in nearly all DNA-based assays. The use of PCR addresses both the sensitivity issues and sample purification steps producing a large quantity DNA

M. E. Ali; U. Hashim; M. F. Bari; T. S. Dhahi

2010-01-01

45

Detection of Mycoplasma pneumoniae by colorimetric loop-mediated isothermal amplification.  

PubMed

Mycoplasma pneumoniae (M. pneumoniae) is one of the most important pathogens that cause respiratory tract infection in children and adults. In this study, we describe a rapid and sensitive colorimetric loop mediated isothermal amplification (LAMP) method to detect M. pneumoniae. The specificity and sensitivity of this assay were detected with 21 common respiratory pathogens and 39 M. pneumoniae DNA. The sensitivity of LAMP was 100% among 39 M. pneumoniae isolates and the specificity was 100% among 9 members of other Mycoplasma and 12 common respiratory pathogens. The lowest detectable limit (LDL) of this assay was 102 copies, which detected by a series of standard M. pneumoniae DNA. To evaluate the clinical applicability of the LAMP assay, a total of 80 clinical samples were examined by conventional PCR, real-time PCR and the LAMP assays, respectively. The positive rates were 15.0%, 32.5% and 26.3%, respectively. This colorimetric LAMP assay demonstrated a high level of sensitivity comparable with that of conventional PCR for the detection of M. pneumoniae. It is a valuable method for simple, cost-effective and rapid detection of M. pneumoniae in the rural areas and basic clinical of China. PMID:23529294

Zhao, Fei; Liu, Zhong; Gu, Yixin; Yang, Yuelian; Xiao, Di; Tao, Xiaoxia; Meng, Fanliang; He, Lihua; Zhang, Jianzhong

2013-03-01

46

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

47

Ultrasensitive colorimetric detection of 17?-estradiol: the effect of shortening DNA aptamer sequences.  

PubMed

We report a strategy enabling ultrasensitive colorimetric detection of 17?-estradiol (E2) in water and urine samples using DNA aptamer-coated gold nanoparticles (AuNPs). Starting from an established sensor format where aggregation is triggered when target-bound aptamers dissociate from AuNP surfaces, we demonstrated that step-change improvements are easily accessible through deletion of excess flanking nucleotides from aptamer sequences. After evaluating the lowest energy two-dimensional configuration of the previously isolated E2 binding 75-mer aptamer (KD ?25 nM), new 35-mer and 22-mer aptamers were generated with KD's of 14 and 11 nM by simply removing flanking nucleotides on either side of the inner core. The shorter aptamers were found to improve discrimination against other steroidal molecules and to improve colorimetric sensitivity for E2 detection by 25-fold compared with the 75-mer to 200 pM. In comparing the response of all sequences, we find that the excess flanking nucleotides suppress signal transduction by causing target-bound aptamers to remain adhered to AuNPs, which we confirm via surface sensitive electrochemical measurements. However, comparison between the 22-mer and 35-mer systems show that retaining a small number of excess bases is optimal. The performance advances we achieved by specifically considering the signal transduction mechanism ultimately resulted in facile detection of E2 in urine, as well as enabling environmental detection of E2 at levels approaching biological relevance. PMID:25803717

Alsager, Omar A; Kumar, Shalen; Zhu, Bicheng; Travas-Sejdic, Jadranka; McNatty, Kenneth P; Hodgkiss, Justin M

2015-04-21

48

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

2014-12-01

49

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

50

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

51

Direct colorimetric determination of formaldehyde in textile fabrics and other materials  

SciTech Connect

A colorimetric method for direct determination of formaldehyde in textile fabrics and other materials is described. Color development and breaking formaldehyde bonds of the analyzed material occur simultaneously in the same reaction mixture without destruction of the material. The method is based on the color reaction of formaldehyde with indole-3-acetic acid or tryptophan. Common inorganic salts, higher aliphatic aldehydes, carbohydrates, amino acids (except tryptophan), and many other organic compounds do not react and do not interfere with the color reaction. Some interferences have been exhibited by acetaldehyde and glyoxal. The method was simple, accurate, and relatively insensitive to the reaction conditions. Only very small amounts of material are needed, and the reaction proceeds at room temperature. Different kinds of polymeric materials have been analyzed successfully (cotton, wool, plastics, collagen, wood, and furs). Most of the dyed fabrics or other materials could be analyzed in the same manner because under the reaction conditions the dyes were not extracted in the reaction mixture.

Chrastil, J.; Reinhardt, R.M.

1986-11-01

52

Direct Quantification of Carotenoids in Low Fat Baby Foods Via Laser Photoacoustics and Colorimetric Index *  

NASA Astrophysics Data System (ADS)

Carotenoids are important antioxidants found in various foods including those for nutrition of infants. In this investigation, the total carotenoid content (TCC) of nine different commercially available baby foods was quantified using colorimetric index * obtained via reflectance colorimetry (RC) and by laser photoacoustic spectroscopy (LPAS) at 473 nm. The latter requires a minimum of sample preparation and only a one time calibration step which enables practically direct quantification of TCC. Results were verified versus UV-Vis spectrophotometry (SP) as the reference technique. It was shown that RC and LPAS (at 473 nm) provide satisfactory results for *, = 0.9925 and = 0.9972, respectively. Other color indices do not show a correlation with TCC. When determining the TCC in baby foods containing tomatoes, it is necessary to select a different analytical wavelength to compensate for the effect of lycopene's presence in the test samples.

Dóka, O.; Ajtony, Zs.; Bicanic, D.; Valinger, D.; Végvári, Gy.

2014-12-01

53

Ultrasensitive colorimetric DNA detection using a combination of rolling circle amplification and nicking endonuclease-assisted nanoparticle amplification (NEANA).  

PubMed

A combination of rolling circle amplification and nicking endonuclease-assisted nanoparticle amplification (NEANA) is used for the rapid, colorimetric detection of DNA. The integration of rolling circle amplification into the NEANA approach allows for detection of oligonucleotides with arbitrary sequences at ultralow concentrations. PMID:22461378

Xu, Wei; Xie, Xiaoji; Li, Dawei; Yang, Zhaoqi; Li, Tianhu; Liu, Xiaogang

2012-06-25

54

Selective colorimetric NO(g) detection based on the use of modified gold nanoparticles using click chemistry.  

PubMed

A new colorimetric system for NO(g) detection is described. The detection method is based on the aggregation of modified AuNPs through a Cu(i) catalyzed click reaction promoted by the in situ reduction of Cu(ii) by NO. PMID:25613775

Martí, Almudena; Costero, Ana M; Gaviña, Pablo; Parra, Margarita

2015-02-01

55

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

56

Colorimetric Detection of Specific DNA Segments Amplified by Polymerase Chain Reactions  

NASA Astrophysics Data System (ADS)

The polymerase chain reaction (PCR) procedure has many potential applications in mass screening. We describe here a general assay for colorimetric detection of amplified DNA. The target DNA is first amplified by PCR, and then a second set of oligonucleotides, nested between the first two, is incorporated by three or more PCR cycles. These oligonucleotides bear ligands: for example, one can be biotinylated and the other can contain a site for a double-stranded DNA-binding protein. After linkage to an immobilized affinity reagent (such as a cloned DNA-binding protein, which we describe here) and labeling with a second affinity reagent (for example, avidin) linked to horseradish peroxidase, reaction with a chromogenic substrate allows detection of the amplified DNA. This amplified DNA assay (ADA) is rapid, is readily applicable to mass screening, and uses routine equipment. We show here that it can be used to detect human immunodeficiency virus sequences specifically against a background of human DNA.

Kemp, David J.; Smith, Donald B.; Foote, Simon J.; Samaras, N.; Peterson, M. Gregory

1989-04-01

57

A simple colorimetric DNA detection by target-induced hybridization chain reaction for isothermal signal amplification.  

PubMed

A novel DNA detection method is presented based on a gold nanoparticle (AuNP) colorimetric assay and hybridization chain reaction (HCR). In this method, target DNA hybridized with probe DNA modified on AuNP, and triggered HCR. The resulting HCR products with a large number of negative charges significantly enhanced the stability of AuNPs, inhibiting aggregation of AuNPs at an elevated salt concentration. The approach was highly sensitive and selective. Using this enzyme-free and isothermal signal amplification method, we were able to detect target DNA at concentrations as low as 0.5 nM with the naked eye. Our method also has great potential for detecting other analytes, such as metal ions, proteins, and small molecules, if the target analytes could make HCR products attach to AuNPs. PMID:24780220

Ma, Cuiping; Wang, Wenshuo; Mulchandani, Ashok; Shi, Chao

2014-07-15

58

Colorimetric detection and fingerprinting of bacteria by glass-supported lipid/polydiacetylene films.  

PubMed

Glass-supported films of lipids and polydiacetylene were applied for visual detection and colorimetric fingerprinting of bacteria. The sensor films comprise polydiacetylene domains serving as the chromatic reporter interspersed within lipid monolayers that function as a biomimetic membrane platform. The detection schemes are based on either visible blue-red transitions or fluorescence transformations of polydiacetylene, induced by amphiphilic molecules secreted by proliferating bacteria. An important feature of the new film platform is the feasibility of either naked-eye detection of bacteria or color analysis using conventional scanners. Furthermore, we find that the degrees of bacterially induced color transformations depend both on the bacterial strains examined and the lipid compositions of the films. Accordingly, bacterial fingerprinting can be achieved through pattern recognition obtained by recording the chromatic transformations in an array of lipid/PDA films having different lipid components. PMID:17371063

Scindia, Yogesh; Silbert, Liron; Volinsky, Roman; Kolusheva, Sofiya; Jelinek, Raz

2007-04-10

59

Antibody modified gold nanoparticles for fast and selective, colorimetric T7 bacteriophage detection.  

PubMed

Herein, we report a colorimetric immunosensor for T7 bacteriophage based on gold nanoparticles modified with covalently bonded anti-T7 antibodies. The new immunosensor allows for a fast, simple, and selective detection of T7 virus. T7 virions form immunological complexes with the antibody modified gold nanoparticles which causes them to aggregate. The aggregation can be observed with the naked eye as a color change from red to purple, as well as with a UV-vis spectrophotometer. The aggregate formation was confirmed with SEM imaging. Sensor selectivity against the M13 bacteriophage was demonstrated. The limit of detection (LOD) is 1.08 × 10(10) PFU/mL (18 pM) T7. The new method was compared with a traditional plaque test. In contrast to biological tests the colorimetric method allows for detection of all T7 phages, not only those biologically active. This includes phage ghosts and fragments of virions. T7 virus has been chosen as a model organism for adenoviruses. The described method has several advantages over the traditional ones. It is much faster than a standard plaque test. It is more robust since no bacteria-virus interactions are utilized in the detection process. Since antibodies are available for a large variety of pathogenic viruses, the described concept is very flexible and can be adapted to detect many different viruses, not only bacteriophages. Contrary to the classical immunoassays, it is a one-step detection method, and no additional amplification, e.g., enzymatic, is needed to read the result. PMID:24679221

Lesniewski, Adam; Los, Marcin; Jonsson-Niedzió?ka, Martin; Krajewska, Anna; Szot, Katarzyna; Los, Joanna M; Niedziolka-Jonsson, Joanna

2014-04-16

60

Gold-nanoparticle-based colorimetric array for detection of dopamine in urine and serum.  

PubMed

A highly selective method is presented for the colorimetric determination of dopamine (DA) using gold nanoparticles (AuNPs). DA caps on the surface of AuNPs (DA-AuNPs) induces the aggregation of AuNPs in alkaline solution. The DA-AuNPs are modified by the hydrolysate of thioglycolic acid (TGA(2)(-)) through Au-S bonds. The aggregation of AuNPs is accelerated by TGA(2-), due to the strong hydrogen-bonds (NH?OC and OH?OC) formed between TGA(2)(-) and DA. Upon the addition of DA, the solution shows a color change from red to purple (or yellow), which is also monitored to detect DA in human urine and fetal bovine serum samples. Here, the limits of colorimetric detection are as low as 10(-7)M observed in Milli-Q water, urine and serum. Based on UV-vis absorption spectra, the limits of detection have been calculated to be 3.3×10(-8)M, 1.0×10(-7)M and 9.4×10(-8)M in Milli-Q water, urine, and serum, respectively. All the limits of detection are lower than the lowest abnormal concentrations of DA in urine (5.7×10(-7)M) and blood (1.6×10(-5)M). The good linear ranges from 0 to 10(-6)M are used for the quantitative assay of DA in urine and serum samples. The applicability of our detection system is also verified by analysis of DA in urine and serum samples. The developed approach is without using complex financial instruments. PMID:25882412

Leng, Yumin; Xie, Kun; Ye, Liqun; Li, Genquan; Lu, Zhiwen; He, Junbao

2015-07-01

61

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

62

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

63

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

64

Label-free colorimetric detection of biothiols utilizing SAM and unmodified Au nanoparticles.  

PubMed

Herein, a sensitive and selective sensor for biothiols based on colorimetric assay is reported. S-adenosyl-l-methionine (SAM) could induce the selective aggregation of unmodified gold nanoparticles (AuNPs) by electrostatic interaction. In the presence of biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), AuNPs prefer to react with thiols of biothiols rather than SAM due to the formation of Au-S bond. Thus, the AuNPs turn from the aggregation to the dispersion state, and the corresponding color variation in the process of anti-aggregation of AuNPs can be used for the quantitative screening of biothiols through UV-vis spectroscopy or by the naked eye. Under optimized conditions, a good linear relationship in the range of 0.4-1.2µM is obtained for Cys, 0.2-0.9µM for GSH, and 0.6-3.0µM for Hcys. The detection limits of this assay for GSH, Cys and Hcys are 35.8nM, 21.7nM, and 62.4nM, respectively. This colorimetric assay exhibits rapid operation (within 5min), high selectivity and sensitivity towards biothiols with tunable dynamic ranges. PMID:25660511

Li, Zhi-Jian; Zheng, Xiang-Juan; Zhang, Li; Liang, Ru-Ping; Li, Zhi-Mei; Qiu, Jian-Ding

2015-06-15

65

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

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

2013-01-01

66

A gold nanoparticle-based label free colorimetric aptasensor for adenosine deaminase detection and inhibition assay.  

PubMed

A novel strategy for the fabrication of a colorimetric aptasensor using label free gold nanoparticles (AuNPs) is proposed in this work, and the strategy has been employed for the assay of adenosine deaminase (ADA) activity. The aptasensor consists of adenosine (AD) aptamer, AD and AuNPs. The design of the biosensor takes advantage of the special optical properties of AuNPs and the interaction between AuNPs and single-strand DNA. In the absence of ADA, the AuNPs are aggregated and are blue in color under appropriate salt concentration because of the grid structure of an AD aptamer when binding to AD, while in the presence of the analyte, AuNPs remain dispersed with red color under the same concentration of salt owing to ADA converting AD into inosine which has no affinity with the AD aptamer, thus allowing quantitative investigation of ADA activity. The present strategy is simple, cost-effective, selective and sensitive for ADA with a detection limit of 1.526 U L(-1), which is about one order of magnitude lower than that previously reported. In addition, a very low concentration of the inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) could generate a distinguishable response. Therefore, the AuNP-based colorimetric biosensor has great potential in the diagnosis of ADA-relevant diseases and drug screening. PMID:25597304

Cheng, Fen; He, Yue; Xing, Xiao-Jing; Tan, Dai-Di; Lin, Yi; Pang, Dai-Wen; Tang, Hong-Wu

2015-03-01

67

Colorimetric detection of melamine in milk by citrate-stabilized gold nanoparticles.  

PubMed

Here, we report a simple and sensitive colorimetric method for detection of melamine in milk using gold nanoparticles (AuNPs). AuNPs of 21-nm size were synthesized by the citrate reduction method. The method is based on the principle that the melamine causes the aggregation of AuNPs and, hence, the wine red color of AuNPs changes to blue or purple. This change in color can be visualized with the naked eye or an ultraviolet-visible (UV-Vis) spectrometer. Under optimized conditions, AuNPs are highly specific for melamine and can detect melamine down to a concentration of 0.05 mg L(-1). PMID:24727351

Kumar, Naveen; Seth, Raman; Kumar, Harish

2014-07-01

68

[Rapid enzymatic-colorimetric method for detecting organophosphorous insecticide residues in milk].  

PubMed

The authors developed a new enzymatic-colorimetric rapid method for testing milk for residues of organophosphorous insecticides. The test is based on the colour reaction of indoxyl acetate with the esterase of the OROSERAN (Dessau) horse serum which is inhibited by organophosphorous insecticides. Calibration curves were established for Trichlorphon and Dichlorphos (DDVP). The limit of detection lies at 0.02 mg/kg. The time actually needed per sample is about 15 min. The result is obtained within 90 min. Since this procedure requires no clean-up operations, it is labour-saving compared to other thin-layer or gas chromatographic methods. It may be recommended as a screening test for the detection of organophosphorous insecticides in milk samples. PMID:988909

Konrad, H; Gabrio, T

1976-01-01

69

Detecting Optic Atrophy in Multiple Sclerosis Patients Using New Colorimetric Analysis Software: From Idea to Application.  

PubMed

Abstract Neuro-ophthalmologists typically observe a temporal pallor of the optic disc in patients with multiple sclerosis. Here, we describe the emergence of an idea to quantify these optic disc color changes in multiple sclerosis patients. We recruited 12 multiple sclerosis patients with previous optic neuritis attack and obtained photographs of their optic discs. The Laguna ONhE, a new colorimetric software using hemoglobin as the reference pigment in the papilla, was used for the analysis. The papilla of these multiple sclerosis patients showed greater pallor, especially in the temporal sector. The software detected the pallor and assigned hemoglobin percentages below normal reference values. Measurements of optic disc hemoglobin levels obtained with the Laguna ONhE software program had good ability to detect optic atrophy and, consequently, axonal loss in multiple sclerosis patients. This new technology is easy to implement in routine clinical practice. PMID:25392265

Bambo, Maria Pilar; Garcia-Martin, Elena; Perez-Olivan, Susana; Larrosa, Jose Manuel; Polo, Vicente; Gonzalez-De la Rosa, Manuel

2014-11-13

70

[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

71

An enzyme-free and amplified colorimetric detection strategy via target-aptamer binding triggered catalyzed hairpin assembly.  

PubMed

Here we introduce an enzyme-free and colorimetric detection strategy for small molecule adenosine. The approach is based on the adenosine-aptamer binding triggered liberation of an initiator strand that consecutively catalyzes DNA hairpins hybridized from singles to couples. These couples induce gold nanoparticles assembled via crosslinking, which could be visualized by a color change. PMID:25435498

Quan, Ke; Huang, Jin; Yang, Xiaohai; Yang, Yanjing; Ying, Le; Wang, He; He, Yong; Wang, Kemin

2015-01-18

72

Synthesis of a mixed valence state Ce-MOF as an oxidase mimetic for the colorimetric detection of biothiols.  

PubMed

We demonstrate a facile and rapid in situ partial oxidation synthetic strategy for the fabrication of a mixed valence state Ce-MOF (MVCM) which exhibits intrinsic oxidase-like activity. Furthermore, on the basis of the excellent catalytic activity of the MCVM, a colorimetric approach for the high-throughput detection of biothiols in serum samples was established. PMID:25690559

Xiong, Yuhao; Chen, Siheng; Ye, Fanggui; Su, Lingjing; Zhang, Cong; Shen, Shufen; Zhao, Shulin

2015-03-01

73

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

74

Apyrase-based colorimetric test for detection of Shigella and enteroinvasive Escherichia coli in stool.  

PubMed

For lack of simple inexpensive early detection methods for Shigella spp. and enteroinvasive Escherichia coli (EIEC), bacillary dysentery remains a major cause of childhood mortality and morbidity in India and other developing countries. Rapid stool testing for apyrase, a specific periplasmic enzyme essential for the pathogen's intracellular spread, may provide a solution. We have developed a whole-cell colorimetric pyrophosphate hydrolysis assay based on cheap, stable, and locally available reagents. An innovative filtration-cum-inoculation step eliminates interfering stool solids and ensures sufficient bacterial growth and apyrase expression in 6 to 7 h at 37 degrees C. In a limited double-blind study of 57 clinical isolates of common enterobacteria, the test showed 100% sensitivity and 80% specificity for Shigella spp. and EIEC. Requiring only widely available equipment and inexpensive consumables, this affordable test is readily adaptable for determining antibiograms and for surveillance of food and water samples for the presence of Shigella and EIEC. PMID:19216937

Sankaran, Krishnan; Banerjee, Sanchari; Pavankumar, Asalapuram R; Jesudason, Mary; Reissbrodt, Rolf; Williams, Peter H

2009-03-01

75

Smartphone based health accessory for colorimetric detection of biomarkers in sweat and saliva.  

PubMed

The mobile health market is rapidly expanding and portable diagnostics tools offer an opportunity to decrease costs and increase the availability of healthcare. Here we present a smartphone based accessory and method for the rapid colorimetric detection of pH in sweat and saliva. Sweat pH can be correlated to sodium concentration and sweat rate in order to indicate to users the proper time to hydrate during physical exercise and avoid the risk of muscle cramps. Salivary pH below a critical threshold is correlated with enamel decalcification, an acidic breakdown of calcium in the teeth. We conduct a number of human trials with the device on a treadmill to demonstrate the ability to monitor changes in sweat pH due to exercise and electrolyte intake and predict optimal hydration. Additionally, we perform trials to measure salivary pH over time to monitor the effects of diet on oral health risks. PMID:23784453

Oncescu, Vlad; O'Dell, Dakota; Erickson, David

2013-08-21

76

New colorimetric screening assays for the directed evolution of fungal laccases to improve the conversion of plant biomass  

PubMed Central

Background Fungal laccases are multicopper oxidases with huge applicability in different sectors. Here, we describe the development of a set of high-throughput colorimetric assays for screening laccase libraries in directed evolution studies. Results Firstly, we designed three colorimetric assays based on the oxidation of sinapic acid, acetosyringone and syringaldehyde with ?max of 512, 520 and 370 nm, respectively. These syringyl-type phenolic compounds are released during the degradation of lignocellulose and can act as laccase redox mediators. The oxidation of the three compounds by low and high-redox potential laccases evolved in Saccharomyces cerevisiae produced quantifiable and linear responses, with detection limits around 1 mU/mL and CV values below 16%. The phenolic substrates were also suitable for pre-screening mutant libraries on solid phase format. Intense colored-halos were developed around the yeast colonies secreting laccase. Furthermore, the oxidation of violuric acid to its iminoxyl radical (?max of 515 nm and CV below 15%) was devised as reporter assay for laccase redox potential during the screening of mutant libraries from high-redox potential laccases. Finally, we developed three dye-decolorizing assays based on the enzymatic oxidation of Methyl Orange (470 nm), Evans Blue (605 nm) and Remazol Brilliant Blue (640 nm) giving up to 40% decolorization yields and CV values below 18%. The assays were reliable for direct measurement of laccase activity or to indirectly explore the oxidation of mediators that do not render colored products (but promote dye decolorization). Every single assay reported in this work was tested by exploring mutant libraries created by error prone PCR of fungal laccases secreted by yeast. Conclusions The high-throughput screening methods reported in this work could be useful for engineering laccases for different purposes. The assays based on the oxidation of syringyl-compounds might be valuable tools for tailoring laccases precisely enhanced to aid biomass conversion processes. The violuric assay might be useful to preserve the redox potential of laccase whilst evolving towards new functions. The dye-decolorizing assays are useful for engineering ad hoc laccases for detoxification of textile wastewaters, or as indirect assays to explore laccase activity on other natural mediators. PMID:24159930

2013-01-01

77

Detection of mercury(II) ions using colorimetric gold nanoparticles on paper-based analytical devices.  

PubMed

An on-field colorimetric sensing strategy employing gold nanoparticles (AuNPs) and a paper-based analytical platform was investigated for mercury ion (Hg(2+)) detection at water sources. By utilizing thymine-Hg(2+)-thymine (T-Hg(2+)-T) coordination chemistry, label-free detection oligonucleotide sequences were attached to unmodified gold nanoparticles to provide rapid mercury ion sensing without complicated and time-consuming thiolated or other costly labeled probe preparation processes. Not only is this strategy's sensing mechanism specific toward Hg(2+), rather than other metal ions, but also the conformational change in the detection oligonucleotide sequences introduces different degrees of AuNP aggregation that causes the color of AuNPs to exhibit a mixture variance. To eliminate the use of sophisticated equipment and minimize the power requirement for data analysis and transmission, the color variance of multiple detection results were transferred and concentrated on cellulose-based paper analytical devices, and the data were subsequently transmitted for the readout and storage of results using cloud computing via a smartphone. As a result, a detection limit of 50 nM for Hg(2+) spiked pond and river water could be achieved. Furthermore, multiple tests could be performed simultaneously with a 40 min turnaround time. These results suggest that the proposed platform possesses the capability for sensitive and high-throughput on-site mercury pollution monitoring in resource-constrained settings. PMID:24932699

Chen, Guan-Hua; Chen, Wei-Yu; Yen, Yu-Chun; Wang, Chia-Wei; Chang, Huan-Tsung; Chen, Chien-Fu

2014-07-15

78

Colorimetric detection of melamine based on methanobactin-mediated synthesis of gold nanoparticles.  

PubMed

A simple and rapid field-portable colorimetric method for the detection of melamine in liquid milk was reported. Methanobactin (Mb) could reduce Au (III) to Au (0) and mediate the synthesis of gold nanoparticles (Au-NPs). Upon the addition of melamine, melamine interacted with oxazolone ring of Mb, which interrupted the formation of Au-NPs. Melamine could also stimulate the aggregation of formed Au-NPs. In this paper, these characteristics have been used to detect melamine in liquid milk by naked eyes observation with a detection limit of 5.56 × 10(-6)M (0.7 mg/kg). Further, the plasmon absorbance of the formed Au-NPs allowed the quantitative detection of melamine by UV-vis spectrometer. A linear correlation was existed between the absorbance and the melamine concentration ranging from 3.90 × 10(-7)M to 3.97 × 10(-6)M with a correlation coefficient of 0.9685. The detection limit (3?) obtained by UV-vis spectrum was as low as 2.38 × 10(-7)M (i.e., 0.03 mg/kg). PMID:25529708

Xin, Jia-ying; Zhang, Lan-xuan; Chen, Dan-dan; Lin, Kai; Fan, Hong-chen; Wang, Yan; Xia, Chun-gu

2015-05-01

79

Bio-functionalized silver nanoparticles: a novel colorimetric probe for cysteine detection.  

PubMed

Chemical interactions between nanoparticles and biomolecules are vital for applying nanoparticles in medicine and life science. Development of sensitive, rapid, low-cost, and eco-friendly sensors for the detection of molecules acting as disease indicator is need of an hour. In the present investigation, a green trend for silver nanoparticle synthesis was followed using leaf extract of Calotropis procera. Silver nanoparticles exhibited surface plasmon absorption peak at 421 nm, spherical shape with average size of 10 nm, and zeta potential of -22.4 mV. The as-synthesized silver nanoparticles were used for selective and sensitive detection of cysteine. Cysteine induces aggregation in stable silver nanoparticles owing to selective and strong interaction of -SH group of cysteine with silver nanoparticle surface. Cysteine-induced silver nanoparticle aggregation can be observed visually by change in color of silver nanoparticles from yellow to pink. Cysteine concentration was estimated colorimetrically by measuring absorption at surface plasmon wavelength. Limit of detection for cysteine using silver nanoparticles is ultralow, i.e., 100 nM. The mechanistic insight into cysteine detection by silver nanoparticles was investigated using FT-IR, TEM, DLS, and TLC analysis. Proposed method can be applied for the detection of cysteine in blood plasma and may give rise to a new insight into development of eco-friendly fabricated nanodiagnostic device in future. PMID:25637511

Borase, Hemant P; Patil, Chandrashekhar D; Salunkhe, Rahul B; Suryawanshi, Rahul K; Kim, Beom S; Bapat, Vishwas A; Patil, Satish V

2015-04-01

80

G-quadruplex based two-stage isothermal exponential amplification reaction for label-free DNA colorimetric detection.  

PubMed

A novel G-quadruplex based two-stage isothermal exponential amplification reaction (GQ-EXPAR) was developed for label-free DNA colorimetric detection in this work. The exponential amplified trigger DNA in the first stage can convert into G-quadruplex sequence EAD2 by a linear amplification circuit in the second stage. Created EAD2 can form G-quadruplex/hemin DNAzyme to act as a direct signal readout element. The GQ-EXPAR combines the exponential amplification of DNA sequence and the peroxidase-mimicking DNAzyme induced signal amplification, which achieves tandem dual-amplification. Taking advantages of isothermal incubation, this label-free homogeneous assay obviates the need of thermal cycling . As no complex synthesis or extra downstream operation is needed, the whole easy handling procedure can be finished in no more than 1h. This assay allows the sensing of the model DNA with the limit of detection to be 2.5pM. Moreover, it demonstrates good discrimination of mismatched sequences. The strategy has also been successfully implemented to sensitively detect Tay-Sachs genetic disorder mutant. PMID:24508547

Nie, Ji; Zhang, De-Wen; Tie, Cai; Zhou, Ying-Lin; Zhang, Xin-Xiang

2014-06-15

81

Colorimetric paper-based detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from large volumes of agricultural water.  

PubMed

This protocol describes rapid colorimetric detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from large volumes (10 L) of agricultural waters. Here, water is filtered through sterile Modified Moore Swabs (MMS), which consist of a simple gauze filter enclosed in a plastic cartridge, to concentrate bacteria. Following filtration, non-selective or selective enrichments for the target bacteria are performed in the MMS. For colorimetric detection of the target bacteria, the enrichments are then assayed using paper-based analytical devices (µPADs) embedded with bacteria-indicative substrates. Each substrate reacts with target-indicative bacterial enzymes, generating colored products that can be detected visually (qualitative detection) on the µPAD. Alternatively, digital images of the reacted µPADs can be generated with common scanning or photographic devices and analyzed using ImageJ software, allowing for more objective and standardized interpretation of results. Although the biochemical screening procedures are designed to identify the aforementioned bacterial pathogens, in some cases enzymes produced by background microbiota or the degradation of the colorimetric substrates may produce a false positive. Therefore, confirmation using a more discriminatory diagnostic is needed. Nonetheless, this bacterial concentration and detection platform is inexpensive, sensitive (0.1 CFU/ml detection limit), easy to perform, and rapid (concentration, enrichment, and detection are performed within approximately 24 hr), justifying its use as an initial screening method for the microbiological quality of agricultural water. PMID:24962090

Bisha, Bledar; Adkins, Jaclyn A; Jokerst, Jana C; Chandler, Jeffrey C; Pérez-Méndez, Alma; Coleman, Shannon M; Sbodio, Adrian O; Suslow, Trevor V; Danyluk, Michelle D; Henry, Charles S; Goodridge, Lawrence D

2014-01-01

82

Sensitive and specific colorimetric DNA detection by invasive reaction coupled with nicking endonuclease-assisted nanoparticles amplification.  

PubMed

Colorimetric DNA detection is preferable to methods in clinical molecular diagnostics, because no expensive equipment is required. Although many gold nanoparticle-based colorimetric DNA detection strategies have been developed to analyze DNA sequences of interest, few of them can detect somatic mutations due to their insufficient specificity. In this study, we proposed a colorimetric DNA detection method by coupling invasive reaction with nicking endonuclease-assisted nanoparticles amplification (IR-NEANA). A target DNA firstly produces many flaps by invasive reaction. Then the flaps are converted to targets of nicking reaction-assisted nanoparticles amplification by ligation reaction to produce the color change of AuNPs, which can be observed by naked eyes. The detection limit of IR-NEANA was determined as 1pM. Most importantly, the specificity of the method is high enough to pick up as low as 1% mutant from a large amount of wild-type DNA backgrounds. The EGFR gene mutated at c.2573 T>G in 9 tissue samples from non-small cell lung cancer patients were successfully detected by using IR-NEANA, suggesting that our proposed method can be used to detect somatic mutations in biological samples. PMID:25460881

Zou, Bingjie; Cao, Xiaomei; Wu, Haiping; Song, Qinxin; Wang, Jianping; Kajiyama, Tomoharu; Kambara, Hideki; Zhou, Guohua

2015-04-15

83

ampliPHOX colorimetric detection on a DNA microarray for influenza.  

PubMed

DNA microarrays have emerged as a powerful tool for pathogen detection. For instance, many examples of the ability to type and subtype influenza virus have been demonstrated. The identification and subtyping of influenza on DNA microarrays has applications in both public health and the clinic for early detection, rapid intervention, and minimizing the impact of an influenza pandemic. Traditional fluorescence is currently the most commonly used microarray detection method. However, as microarray technology progresses towards clinical use, replacing expensive instrumentation with low cost detection technology exhibiting similar performance characteristics to fluorescence will make microarray assays more attractive and cost-effective. The ampliPHOX colorimetric detection technology is intended for research applications, and has a limit of detection within one order of magnitude of traditional fluorescence, with a main advantage being an approximate ten-fold lower instrument cost compared to the confocal microarray scanners required for fluorescence microarray detection. Another advantage is the compact size of the instrument which allows for portability and flexibility, unlike traditional fluorescence instruments. Because the polymerization technology is not as inherently linear as fluorescence detection, however, it is best suited for lower density microarray applications in which a yes/no answer for the presence of a certain sequence is desired, such as for pathogen detection arrays. Currently the maximum spot density compatible with ampliPHOX detection is ˜1800 spots/array. Because of the spot density limitations, higher density microarrays are not suitable for ampliPHOX detection. Here, we present ampliPHOX colorimetric detection technology as a method of signal amplification on a low density microarray developed for the detection and characterization of influenza viruses (FluChip). Although this protocol uses the FluChip (a DNA microarray) as one specific application of ampliPHOX detection, any microarray incorporating biotinylated target can be labeled and detected in a similar manner. The microarray design and biotinylation of the target to be captured are the responsibility of the user. Once the biotinylated target has been captured on the array, ampliPHOX detection can be performed by first tagging the array with a streptavidin-label conjugate (ampliTAG). Upon light exposure using the ampliPHOX Reader instrument, polymerization of a monomer solution (ampliPHY) occurs only in regions containing ampliTAG-labeled targets. The polymer formed can be subsequently stained with a non-toxic solution to improve visual contrast, followed by imaging and analysis using a simple software package (ampliVIEW). The entire FluChip assay from un-extracted sample to result can be performed in about 6 hours, and the ampliPHOX detection steps described above can be completed in about 30 min. PMID:21694688

Moulton, Kevin R; Taylor, Amber W; Rowlen, Kathy L; Dawson, Erica D

2011-01-01

84

Field-deployable colorimetric biosensor system for the rapid detection of pathogenic organisms  

NASA Astrophysics Data System (ADS)

The rapid identification of pathogenic organisms is necessary for recognizing and managing human and environmental health risks. Numerous detection schemes are available, but most are difficult to employ in non-laboratory settings due to their need for bulky, specialized equipment, multiple reagents, or highly trained personnel. To address this problem, a rapid, field-compatible biosensor system based on the colorimetric detection of nucleic acid hybrids was developed. Peptide nucleic acid (PNA) probes were used to capture ribosomal RNA sequences from environmental samples. Non-target nucleic acids, including single-base mismatches flanked by adenines and uracils, were removed with a micrococcal nuclease digestion step. Matched PNA-RNA hybrids remained intact and were indicated by the cyanine dye DiSC2(5). PNA-containing duplexes function as templates for the aggregation of DiSC2(5), visualized as a change in solution color from blue to purple. This transition can be measured as an increase in the solution absorbance at 540 nm (dye aggregate) at the expense of the dye monomer peak at 650 nm. These concomitant spectral changes were used to calculate a "hybridization signal" using the ratio A aggregate/Amonomer ? A540/A650. Testing with pathogenic environmental samples was accomplished using two model organisms: the harmful algal bloom-causing dinoflagellate Alexandrium species, and the potato wart disease-causing fungus Synchytrium endobioticum. In both cases, the colorimetric approach was able to distinguish the targets with sensitivities rivaling those of established techniques, but with the advantages of decreased hands-on time and cost. Assay fieldability was tested with a portable colorimeter designed to quantify the dye-indicated hybridization signal and assembled from commercially available components. Side-by-side testing revealed no difference in the sensing performance of the colorimeter compared to a laboratory spectrophotometer (Pearson's r=0.99935). Assay results were obtained within 15 minutes, with a limit of detection down to 10--17 mole. This quick, inexpensive and robust system has the potential to replace laborious pathogen identification schemes in field environments, and is easily adapted for the detection of different organisms.

Duy, Janice

85

Colorimetric detection of copper in water using a Schiff base derivative  

NASA Astrophysics Data System (ADS)

Organic molecular sensors have the advantage of being used through an easy, fast, economical and reliable optical method for detecting toxic metal ions in our environment. In this work, we present a simple but highly specific organic ligand compound 5-Chloro-2-((E)-((E)-3-(4-(dimethylamino)phenyl)allylidene)amino)phenol (L1) that acts as a colorimetric sensor for ions in a mixture of acetonitrile/water (ratio 10:1, v:v). Binding interaction between L1 and various metal-ions has been established by ultraviolet-visible spectroscopic measurements that indicate favorable coordination of the ligand with selective metal ions, particularly, with copper. These results showed that the electronic transition band shape of L1 change after binding with copper in aqueous solution. L1 exhibited binding-induced color changes from yellow to pink one detected by the naked eye. This new sensor presented 2.5 × 10-6 M as limit detection, even under the presence of other metal ions.

Peralta Domínguez, D.; Ramos-Ortiz, G.; Maldonado, J. L.; Rodriguez, M.; Meneses-Nava, M. A.; Barbosa-Garcia, O.; Santillan, R.; Farfán, N.

2013-09-01

86

Identification of Escherichia coli O157 by using a novel colorimetric detection method with DNA microarrays.  

PubMed

Shiga toxin-producing Escherichia coli O157 is a leading cause of foodborne illness worldwide. To evaluate better methods to rapidly detect and genotype E. coli O157 strains, the present study evaluated the use of ampliPHOX, a novel colorimetric detection method based on photopolymerization, for pathogen identification with DNA microarrays. A low-density DNA oligonucleotide microarray was designed to target stx1 and stx2 genes encoding Shiga toxin production, the eae gene coding for adherence membrane protein, and the per gene encoding the O157-antigen perosamine synthetase. Results from the validation experiments demonstrated that the use of ampliPHOX allowed the accurate genotyping of the tested E. coli strains, and positive hybridization signals were observed for only probes targeting virulence genes present in the reference strains. Quantification showed that the average signal-to-noise ratio values ranged from 47.73?±?7.12 to 76.71?±?8.33, whereas average signal-to-noise ratio values below 2.5 were determined for probes where no polymer was formed due to lack of specific hybridization. Sensitivity tests demonstrated that the sensitivity threshold for E. coli O157 detection was 100-1000 CFU/mL. Thus, the use of DNA microarrays in combination with photopolymerization allowed the rapid and accurate genotyping of E. coli O157 strains. PMID:21288130

Quiñones, Beatriz; Swimley, Michelle S; Taylor, Amber W; Dawson, Erica D

2011-06-01

87

A field-deployable colorimetric bioassay for the rapid and specific detection of ribosomal RNA.  

PubMed

Rapid and specific on-site detection of disease-causing or toxin-producing organisms is essential to public health and safety. Many molecular recognition methods target ribosomal RNA sequences due to their specificity and abundance in the cell. In this work RNA targets were identified and quantified using a colorimetric bioassay. Peptide nucleic acid (PNA) probes were used to capture RNA targets, and a micrococcal nuclease digestion was performed to remove all non-target nucleic acids, including single base mismatches flanked by adenines or uracils. Perfectly-matched PNA-RNA hybrids remained intact and were detected using the symmetrical cyanine dye 3,3'-diethylthiadicarbocyanine iodide (DiSC2(5)). Assay applicability to complex samples was demonstrated using mixtures containing RNA sequences from two related, harmful algal bloom-causing Alexandrium species. Target RNA was detected even in mixtures with mismatched sequences in excess of the perfect match. The fieldability of the assay was tested with a portable two-wavelength colorimeter developed to quantify the dye-indicated hybridization signal. The colorimeter sensing performance was shown to be comparable to a laboratory spectrophotometer. This quick, inexpensive and robust system has the potential to replace laborious identification schemes in field environments. PMID:22749775

Duy, Janice; Smith, Rosemary L; Collins, Scott D; Connell, Laurie B

2014-02-15

88

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

89

Colorimetric detection of Hg2+ ions in aqueous media using CA-Au NPs  

NASA Astrophysics Data System (ADS)

Based on the selective interaction between Hg2+ ions and cyanuric acid (CA) and the anti-aggregation of CA stabilized gold nanoparticles (CA-Au NPs), a simple colorimetric method was developed for detecting Hg2+ ions. In a medium of pH 7.4 tris-HCl buffer containing 8 × 10-3 M NaCl, the CA-Au NPs solution was red, which was due to CA adsorbed onto the surface of Au NPs, stabilizing Au NPs against aggregation. When CA-HgII-CA complex was formed in the presence of Hg2+, the stability of CA-Au NPs reduced, and then aggregation of Au NPs occurred. Consequently, the color of the solution changed from red to blue and could easily be measured with a common spectrophotometer. The aggregation of Au NPs was also validated using transmission electron microscopy (TEM). The controlled experiment showed that other ions including Ba2+, Ca2+, Zn2+, Cd2+, Co2+, Mn2+, Cu2+, Mg2+, and Ni2+ ions did not induce any distinct spectral changes, which constituted a Hg2+-selective sensor. A dynamic range of 1.6-16 × 10-6 M Hg2+ ions was observed at the optimized reaction condition. This method provides a potentially useful tool for Hg2+ detection.

Liu, Zening; Hu, Jiao; Tong, Sijia; Cao, Qihua; Yuan, Hong

2012-11-01

90

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

91

Optimization of trichloroethylene oxidation by methanotrophs and the use of a colorimetric assay to detect soluble methane monooxygenase activity  

Microsoft Academic Search

Methylosinus trichosporium OB3b biosynthesizes a broad specificity soluble methane monooxygenase that rapidly oxidizes trichloroethylene (TCE). The selective expression of the soluble methane monooxygenase was followed in vivo by a rapid colorimetric assay. Naphthalene was oxidized by purified soluble methane monooxygenase or by cells grown in copper-deficient media to a mixture of 1-naphthol and 2-naphthol. The naphthols were detected by reaction

Gregory A. Brusseau; Hsien-Chyang Tsien; Richard S. Hanson; Lawrence P. Wackett

1990-01-01

92

Convenient, inexpensive quantification of elemental sulfur by simultaneous in situ reduction and colorimetric detection.  

PubMed

Rapid, inexpensive, and convenient methods for quantifying elemental sulfur (S(0)) with low or sub-?gg(-1) limits of detection would be useful for a range of applications where S(0) can act as a precursor for noxious off-aromas, e.g., S(0) in pesticide residues on winegrapes or as a contaminant in drywall. However, existing quantification methods rely on toxic reagents, expensive and cumbersome equipment, or demonstrate poor selectivity. We have developed and optimized an inexpensive, rapid method (?15 min per sample) for quantifying S(0) in complex matrices. Following dispersion of the sample in PEG-400 and buffering, S(0) is quantitatively reduced to H(2)S in situ by dithiothreitol and simultaneously quantified by commercially available colorimetric H(2)S detection tubes. By employing multiple tubes, the method demonstrated linearity from 0.03 to 100 ?g S(0) g(-1) for a 5 g sample (R(2)=0.994, mean CV=6.4%), and the methodological detection limit was 0.01 ?g S(0) g(-1). Interferences from sulfite or sulfate were not observed. Mean recovery of an S(0) containing sulfur fungicide in grape macerate was 84.7% with a mean CV of 10.4%. Mean recovery of S(0) in a colloidal sulfur preparation from a drywall matrix was 106.6% with a mean CV of 6.9%. Comparable methodological detection limits, sensitivity, and recoveries were achieved in grape juice, grape macerate and with 1g drywall samples, indicating that the methodology should be robust across a range of complex matrices. PMID:21843674

Kwasniewski, Misha T; Allison, Rachel B; Wilcox, Wayne F; Sacks, Gavin L

2011-10-01

93

Optimization of the reactional medium and a food impact study for a colorimetric in situ Salmonella spp. detection method.  

PubMed

Foodborne pathogens are still a major concern for public health authorities. In this paper, we describe the optimization of a previously reported method which combines a highly specific capture of targeted food pathogens with an intracellular staining method. The reaction medium was optimized to simultaneously allow specific enrichment of Salmonella and maximize the staining of the target pathogen. This in situ colorimetric concept was evaluated with a broad range of food samples artificially contaminated with low levels of stressed Salmonella to mimic natural contamination conditions. This direct detection method compared favorably to a commercially available immunoassay system (Vidas® UP Salmonella), for cooked meat, dry milk powder and egg products. Globally 88% agreement was obtained between the two methods with a sensitivity of 80% and a specificity of 100% for the tested method. Main discordances were obtained with food matrices having high levels of competitive Gram negative microflora. These observations show that the design of an adapted culture medium is necessary to enhance the specific in situ capture and revelation system. PMID:24819412

Junillon, Thomas; Mosticon, David; Mallen, Benoît; Baril, Florent; Morand, Lucie; Michel, Déborah; Flandrois, Jean-Pierre

2014-07-01

94

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

NASA Astrophysics Data System (ADS)

In the framework of the research project 'Xsense' at the Technical University of Denmark (DTU) we are developing a simple colorimetric sensor array which can be useful in detection of explosives like DNT and TNT, and identification of volatile organic compounds in the presence of water vapor in air. The technology is based on an array of chemo-responsive dyes immobilized on a solid support. Upon exposure to the analyte in suspicion the dye array changes color. Each chosen dye reacts chemo selectively with analytes of interest. A change in a color signature indicates the presence of unknown explosives and volatile organic compounds (VOCs). We are working towards the selection of dyes that undergo color changes in the presence of explosives and VOCs, as well as the development of an immobilization method for the molecules. Digital imaging of the dye array before and after exposure to the analytes creates a color difference map which gives a unique fingerprint for each explosive and volatile organic compound. Such sensing technology can be used to screen for relevant explosives in a complex background as well as to distinguish mixtures of volatile organic compounds distributed in gas phase. This sensor array is inexpensive, and can potentially be produced as single use disposable.

Kostesha, N. V.; Alstrøm, T. S.; Johnsen, C.; Nilesen, K. A.; Jeppesen, J. O.; Larsen, J.; Jakobsen, M. H.; Boisen, A.

2010-04-01

95

G-quadruplex-hemin DNAzyme-amplified colorimetric detection of Ag+ ion.  

PubMed

A G-quadruplex-hemin DNAzyme-amplified Ag(+)-sensing method was developed based on the ability of Ag(+) to stabilize C-C mismatches by forming C-Ag(+)-C base pairs. In this method, only one unlabelled oligonucleotide strand was used. In the absence of Ag(+), the oligonucleotide strand formed an intramolecular duplex. The G-rich sequence in the oligonucleotide was partially caged in this duplex structure and cannot fold into the G-quadruplex structure. The addition of Ag(+) promoted the formation of another intramolecular duplex in which C-C mismatches were stabilized by C-Ag(+)-C base pairs, leading to the release of the G-rich sequence which can fold into a G-quadruplex capable to bind hemin to form a catalytically active G-quadruplex-hemin DNAzyme. As a result, a UV-vis absorbance increasing was observed in the H(2)O(2)-ABTS (2,2'-azinobis(3-ethylbenzothiozoline)-6-sulfonic acid) reaction system. This "turn-on" process allowed the detection of aqueous Ag(+) at concentrations as low as 6.3 nM using a simple colorimetric technique, showing a high selectivity over a range of other metal ions. PMID:20869513

Zhou, Xue-Hui; Kong, De-Ming; Shen, Han-Xi

2010-09-23

96

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

NASA Astrophysics Data System (ADS)

A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by reacting rhodamine B hydrazide with 3-bromo-5-methylsalicylaldehyde and developed as a new colorimetric probe for the selective and sensitive detection of Cu2+. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV-vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 3.2 × 104 L mol-1. Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 0.667-240 ?mol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis.

Zhang, Jiangang; Zhang, Li; Wei, Yanli; Chao, Jianbing; Shuang, Shaomin; Cai, Zongwei; Dong, Chuan

2014-11-01

97

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

98

A colorimetric aptamer biosensor based on cationic polymer and gold nanoparticles for the ultrasensitive detection of thrombin.  

PubMed

A colorimetric assay for the ultrasensitive determination of thrombin based on cationic polymer and gold nanoparticles was presented, in which unmodified gold nanoparticles (AuNPs) was used as probes and 21-mer thrombin-binding aptamer (TBA) as sensing elements. Upon the addition of thrombin, TBA interacted specifically with thrombin to form a G-quadruplex structure. As a result, the conformation change facilitated the cationic polymer, poly(diallyldimethylammonium chloride) (PDDA)-induced AuNP aggregation. Thus, the visible change in color from wine-red to blue-purple was readily seen by the naked eye. The colorimetric sensor could detect thrombin down to 1 pM with high selectivity in the presence of other interferring proteins. Furthermore, the assay was successfully employed to determine thrombin in human serum sample, which suggested its great potential for diagnostic purposes. PMID:24463195

Chen, Zhengbo; Tan, Yuan; Zhang, Chenmeng; Yin, Lu; Ma, He; Ye, Nengsheng; Qiang, Hong; Lin, Yuqing

2014-06-15

99

Dual-channel detection of Cu2+ and F- with a simple Schiff-based colorimetric and fluorescent sensor  

NASA Astrophysics Data System (ADS)

A simple and easily synthesized colorimetric and fluorescent receptor 1, based on 4-diethylaminosalicylaldehyde moieties as a binding and signaling unit, has been synthesized and characterized. The receptor 1 has a selective colorimetric sensing ability for copper (II) ion by changing color from colorless to yellow in aqueous solution, and could be utilized to monitor Cu(II) over a wide pH range of 4-11. In addition, the detection limit (12 ?M) of 1 for Cu2+ is much lower than that (30 ?M) recommended by WHO in drinking water, and its copper complex could be reversible simply through treatment with a proper reagent such as EDTA. Moreover, receptor 1 exhibited both a color change from colorless to yellow and fluorescence enhancement with a red shift upon addition to F- in DMSO. The recognition mechanism was attributed to the intermolecular proton transfer between the hydroxyl group of the receptor and the fluoride.

Na, Yu Jeong; Choi, Ye Won; Yun, Jin Yeong; Park, Kyung-Min; Chang, Pahn-Shick; Kim, Cheal

2015-02-01

100

Colorimetric detection of hepatitis E virus based on reverse transcription loop mediated isothermal amplification (RT-LAMP) assay.  

PubMed

Hepatitis E virus (HEV) infection is a common communicable disease in the third world countries. The early diagnosis of HEV is important for the prognosis and prevention of the spread of the disease. Conventional methods for HEV detection need expensive equipment and cannot meet the needs of point of care (POC) use. In the present study, a gold nanoparticle (AuNP) based RT-LAMP assay was developed for colorimetric detection of HEV. As low as 10(1) copies of HEV RNA were detected visually. With reduced handling and less equipment requirement, this assay provided a simple and rapid alternative to other available methods. PMID:24269797

Chen, Qiuhua; Yuan, Lu; Wan, Jun; Chen, Yanlin; Du, Chaoyang

2014-03-01

101

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

102

Simple, field portable colorimetric detection device for organic peroxides and hydrogen peroxide  

DOEpatents

A simple and effective system for the colorimetric determination of organic peroxides and hydrogen peroxide. A peroxide pen utilizing a swipe material attached to a polyethylene tube contains two crushable vials. The two crushable vials contain a colorimetric reagent separated into dry ingredients and liquid ingredients. After swiping a suspected substance or surface the vials are broken, the reagent is mixed thoroughly and the reagent is allowed to wick into the swipe material. The presence of organic peroxides or hydrogen peroxide is confirmed by a deep blue color.

Pagoria, Philip F. (Livermore, CA); Mitchell, Alexander R. (Livermore, CA); Whipple, Richard E. (Livermore, CA); Carman, M. Leslie (San Ramon, CA); Reynolds, John G. (San Ramon, CA); Nunes, Peter (Livermore, CA); Shields, Sharon J. (San Ramon, CA)

2010-11-09

103

Synthetic multivalent DNAzymes for enhanced hydrogen peroxide catalysis and sensitive colorimetric glucose detection.  

PubMed

A peroxidase-mimic DNAzyme is a G-quadruplex (G4) DNA-hemin complex, in which the G4-DNA resembles an apoenzyme, and hemin is the cofactor for hydrogen peroxide (H2O2) catalysis. Twenty-one-mer CatG4 is a well-proven G4-DNA as well as a hemin-binding aptamer for constituting a DNAzyme. This work studied if a multivalent DNAzyme with accelerated catalysis could be constructed using a multimeric CatG4 with hemin. We compared CatG4 monomer, dimer, trimer, and tetramer, which were prepared by custom oligo synthesis, for G4 structure formation. According to circular dichroism (CD) analysis, we found that a CatG4 multimer exhibited more active G4 conformation than the sum effect of equal-number CatG4 monomers. However, the DNAzyme kinetics was not improved monotonically along with the subunit number of a multimeric CatG4. It was the trivalent DNAzyme, trimeric CatG4:hemin, resulting in the rapidest H2O2 catalysis instead of a tetravalent one. We discovered that the trivalent DNAzyme's highest catalytic rate was correlated to its most stable hemin-binding G4 structure, evidenced by CD melting temperature analysis. Finally, a trivalent DNAzyme-based colorimetric glucose assay with a detection limit as low as 10 ?M was demonstrated, and this assay did not need adenosine 5'-tri-phosphate disodium salt hydrate (ATP) as a DNAzyme boosting agent. PMID:25542363

Yang, Deng-Kai; Kuo, Chia-Jung; Chen, Lin-Chi

2015-01-26

104

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 HAuCl? 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

105

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

Technology Transfer Automated Retrieval System (TEKTRAN)

Postharvest applications of potassium sorbate (PS) to fresh citrus fruit control fungal decay pathogens, such as Penicillium digitatum, cause of green mold. Although PS effectiveness has been examined repeatedly, little is known about PS residues. A colorimetric method that employed extraction of th...

106

Glyconanoparticles for colorimetric bioassays.  

PubMed

Carbohydrate molecules are involved in many of the cellular processes that are important for life. By combining the specific analyte targeting of carbohydrates with the multivalent structure and change of solution colour as a consequence of plasmonic interactions with the aggregation of metal nanoparticles, glyconanoparticles have been used extensively for the development of bioanalytical assays. The noble metals used to create the nanocore, the methodologies used to assemble the carbohydrates on the nanoparticle surface, the carbohydrate chosen for each specific target, the length of the tether that separates the carbohydrate from the nanocore and the density of carbohydrates on the surface all impact on the structural formation of metal based glyconanoparticles. This tutorial review highlights these key components, which directly impact on the selectivity and sensitivity of the developed bioassay, for the colorimetric detection of lectins, toxins and viruses. PMID:25277069

Marín, María J; Schofield, Claire L; Field, Robert A; Russell, David A

2015-01-01

107

Colorimetric detection of Escherichia coli O157:H7 using functionalized Au@Pt nanoparticles as peroxidase mimetics.  

PubMed

The presence of Escherichia coli (E. coli) in food and drinking water is a chronic problem worldwide. Protecting food against bacterial contamination and rapid diagnosis of infection require simple and rapid assays for detection of bacterial pathogens, including E. coli O157:H7. Here we report a rapid and novel colorimetric method for detecting E. coli O157:H7. This colorimetric method is based on the catalytic oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine by hydrogen peroxide using 4-mercaptophenylboronic acid-functioned Au@Pt nanoparticles adsorbed on the surface of E. coli O157:H7. The assay showed excellent sensitivity both with the naked eye and based on absorbance measurements. The absorbance at 652 nm was proportional to the concentration of E. coli O157:H7 ranging from 7 to 6 × 10(6) cfu mL(-1) with a limit of detection of 7 cfu mL(-1). The total detection time was less than 40 min. PMID:23577341

Su, Haichao; Zhao, Han; Qiao, Fengmin; Chen, Lijian; Duan, Ruihuan; Ai, Shiyun

2013-05-21

108

Label-free and ultrasensitive colorimetric detection of DNA based on target-triggered quadratic amplification strategy.  

PubMed

Highly sensitive detection of DNA plays a crucial role in biomedical research and clinical diagnosis. Herein, we developed a simple, label-free, isothermal, and ultrasensitive colorimetric method for amplified detection of DNA on the basis of a new quadratic amplification strategy. With the presence of three ingeniously designed hairpin structures and Exonuclease III (Exo III), the target DNA can trigger two independent cycles of reactions: hairpin assembly reaction and Exo III cleavage reaction, which are designed to initiate target DNA recycling amplification and reporter DNA amplification, respectively. Therefore, the proposed method exhibits a high sensitivity toward target DNA with a detection limit of as low as 81 fM, and it can discriminate mismatched DNA from completely matched target DNA. Furthermore, this method could be used as a universal tool for the detection of various DNA sequences and might be further extended for the detection of aptamer-binding molecules. PMID:25437364

Wu, Hao; Liu, Yaling; Wang, Hongyong; Wu, Jun; Zhu, Feifan; Zou, Pei

2015-04-15

109

A colorimetric sensor array for the detection of the date-rape drug ?-hydroxybutyric acid (GHB): a supramolecular approach.  

PubMed

?-Hydroxybutyric acid (GHB), a colourless, odourless and tasteless chemical, has become one of the most dangerous illicit drugs of abuse today. At low doses, this drug is a central nervous system depressant that reduces anxiety and produces euphoria and relaxation, sedating the recipient. There is an urgent need for simple, easy-to-use sensors for GHB in solution. Here, we present a colorimetric sensor array based on supramolecular host-guest complexes of fluorescent dyes with organic capsules (cucurbiturils) for the detection of GHB. PMID:20309968

Baumes, Laurent A; Buaki Sogo, Mireia; Montes-Navajas, Pedro; Corma, Avelino; Garcia, Hermenegildo

2010-04-19

110

Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification  

NASA Astrophysics Data System (ADS)

A novel unmodified gold nanoparticles (AuNPs)-based colorimetric strategy for label-free, specific and sensitive mercury ion (Hg2+) detection was demonstrated by using thymine-Hg2+-thymine (T-Hg2+-T) recognition mechanism and hybridization chain reaction (HCR) amplification strategy. In this protocol, a structure-switching probe (H0) was designed to recognize Hg2+ and then propagated a chain reaction of hybridization events between two other hairpin probes (H1 and H2). In the absence of Hg2+, all hairpin probes could stably coexist in solution, the exposed sticky ends of hairpin probes were capable of stabilizing AuNPs. As a result, salt-induced AuNPs aggregation could be effectively prevented. In the presence of Hg2+, thymine bases of H0 could specifically interact with Hg2+ to form stable T-Hg2+-T complex. Consequently, the hairpin structure of H0 probe was changed. As H1/H2 probes were added, the HCR process could be triggered and nicked double-helixes were formed. Since it was difficult for the formed nicked double-helixes to inhibit salt-induced AuNPs aggregation, a red-to-blue color change was observed in the colloid solution as the salt concentration increased. With the elegant amplification effect of HCR, a detection limit of around 30 nM was achieved (S/N = 3), which was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods. By using the T-Hg2+-T recognition mechanism, high selectivity was also obtained. As an unmodified AuNPs-based colorimetric strategy, the system was simple in design, convenient in operation, and eliminated the requirements of separation processes, chemical modifications, and sophisticated instrumentations.

Wang, Qing; Yang, Xiaohan; Yang, Xiaohai; Liu, Pei; Wang, Kemin; Huang, Jin; Liu, Jianbo; Song, Chunxia; Wang, Jingjing

2015-02-01

111

Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification.  

PubMed

A novel unmodified gold nanoparticles (AuNPs)-based colorimetric strategy for label-free, specific and sensitive mercury ion (Hg(2+)) detection was demonstrated by using thymine-Hg(2)(+)-thymine (T-Hg(2)(+)-T) recognition mechanism and hybridization chain reaction (HCR) amplification strategy. In this protocol, a structure-switching probe (H0) was designed to recognize Hg(2+) and then propagated a chain reaction of hybridization events between two other hairpin probes (H1 and H2). In the absence of Hg(2+), all hairpin probes could stably coexist in solution, the exposed sticky ends of hairpin probes were capable of stabilizing AuNPs. As a result, salt-induced AuNPs aggregation could be effectively prevented. In the presence of Hg(2+), thymine bases of H0 could specifically interact with Hg(2+) to form stable T-Hg(2)(+)-T complex. Consequently, the hairpin structure of H0 probe was changed. As H1/H2 probes were added, the HCR process could be triggered and nicked double-helixes were formed. Since it was difficult for the formed nicked double-helixes to inhibit salt-induced AuNPs aggregation, a red-to-blue color change was observed in the colloid solution as the salt concentration increased. With the elegant amplification effect of HCR, a detection limit of around 30 nM was achieved (S/N=3), which was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods. By using the T-Hg(2)(+)-T recognition mechanism, high selectivity was also obtained. As an unmodified AuNPs-based colorimetric strategy, the system was simple in design, convenient in operation, and eliminated the requirements of separation processes, chemical modifications, and sophisticated instrumentations. PMID:25448931

Wang, Qing; Yang, Xiaohan; Yang, Xiaohai; Liu, Pei; Wang, Kemin; Huang, Jin; Liu, Jianbo; Song, Chunxia; Wang, Jingjing

2015-02-01

112

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; Göransson, Jenny; Lindegren, Gunnel; Sharifi-Mood, Batool; Chinikar, Sadegh; Mardani, Masoud; Mirazimi, Ali; Nilsson, Mats

2011-01-01

113

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

114

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

115

WIMP direct detection overview  

E-print Network

This review on weakly interacting massive particle (WIMP) dark matter direct detection focuses on experimental approaches and the corresponding physics basics. The presentation is intended to provide a quick and concise introduction for non-specialists to this fast evolving topic of astroparticle physics.

Y. Ramachers

2002-11-22

116

Enhanced Colorimetric Immunoassay Accompanying with Enzyme Cascade Amplification Strategy for Ultrasensitive Detection of Low-Abundance Protein  

PubMed Central

Methods based on enzyme labels have been developed for colorimetric immunoassays, but most involve poor sensitivity and are unsuitable for routine use. Herein, we design an enhanced colorimetric immunoassay for prostate-specific antigen (PSA) coupling with an enzyme-cascade-amplification strategy (ECAS-CIA). In the presence of target PSA, the labeled alkaline phosphatase on secondary antibody catalyzes the formation of palladium nanostructures, which catalyze 3,3?,5,5?-tetramethylbenzidine-H2O2 system to produce the colored products, thus resulting in the signal cascade amplification. Results indicated that the ECAS-CIA presents good responses toward PSA, and allows detection of PSA at a concentration as low as 0.05?ng mL?1. Intra- and inter-assay coefficients of variation are below 9.5% and 10.7%, respectively. Additionally, the methodology is validated for analysis of clinical serum specimens with consistent results obtained by PSA ELISA kit. Importantly, the ECAS-CIA opens a new horizon for protein diagnostics and biosecurity. PMID:24509941

Gao, Zhuangqiang; Hou, Li; Xu, Mingdi; Tang, Dianping

2014-01-01

117

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

118

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

119

Adaptation of Ti(III)-NTA colorimetric assay for use in detecting microbial demethylation of lignin and lignin derived compounds in aerobic conditions.  

PubMed

An anaerobic colorimetric assay for quantifying microbial demethylation activity was adapted for aerobic use in studying lignin and lignin-derived compounds. Standard curves of 0-500?M pyrocatechol with and without 0.3% lignin demonstrated the use in either case. This method detects demethylation products up to 500?M without using additional dilutions. PMID:24681305

Gibson, A; Dekker, R F H; Malek, L

2014-06-01

120

[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

121

A new gel tube method for the direct detection, identification and susceptibility testing of bacteria in clinical samples  

Microsoft Academic Search

We recently developed a simple new method which is designed to separate and concentrate bacteria from a sample by centrifugation in a gel system. Bacterial enzyme activity is then detected inside the gel without further manipulation using a colorimetric or fluorogenic substrate. The method provides a rapid, direct means of detecting bacteria in clinical samples, dispensing with the 24-h period

S. Langlet; F. Beaupère; G. Contant; J. M. Scheftel

1999-01-01

122

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

123

A colorimetric nitrite detection system with excellent selectivity and high sensitivity based on Ag@Au nanoparticles.  

PubMed

Excessive uptake of NO2(-) is detrimental to human health, but the currently available methods used to sensitively detect this ion in the environment are cumbersome and expensive. In this study, we developed an improved NO2(-) detection system based on a redox etching strategy of CTAB-stabilized Ag-Au core-shell nanoparticles (Ag@AuNPs). The detection mechanism was verified by UV-Vis spectroscopy, TEM and XPS. The detection system produces a color change from purple to colorless in response to an increase of NO2(-) concentration. The selectivity of detection of NO2(-), both with the unaided eye and by measurement of UV-Vis spectra, is excellent in relation to other ions, including Cu(2+), Co(2+), Ni(2+), Cr(3+), Al(3+), Pb(2+), Cd(2+), Ca(2+), Ba(2+), Zn(2+), Mn(2+), Mg(2+), Fe(3+), Hg(2+), Ag(+), K(+), F(-), PO4(3-), C2O4(2-), SO3(2-), CO3(2-), SO4(2-), NO3(-) and CH3-COO(-) (Ac(-)). The limit of detection (LOD) for NO2(-) is 1.0 ?M by eye and 0.1 ?M by UV-Vis spectroscopy. The LOD by eye is lower than the lowest previously reported value (4.0 ?M). There is a good linear relationship between A/A0 and the concentration of NO2(-) from 1.0 to 20.0 ?M NO2(-), which permits a quantitative assay. The applicability of our detection system was also verified by analysis of NO2(-) in tap water and lake water. The results demonstrate that our Ag@AuNP-based detection system can be used for the rapid colorimetric detection of NO2(-) in complex environmental samples, with excellent selectivity and high sensitivity. PMID:25564225

Li, Tianhua; Li, Yonglong; Zhang, Yujie; Dong, Chen; Shen, Zheyu; Wu, Aiguo

2015-02-01

124

Evaluation of colorimetric methods using nicotinamide for rapid detection of pyrazinamide resistance in Mycobacterium tuberculosis.  

PubMed

The direct detection of pyrazinamide resistance in Mycobacterium tuberculosis is sufficiently difficult that many laboratories do not attempt it. Most pyrazinamide resistance is caused by mutations that inactivate the pyrazinamidase enzyme needed to convert the prodrug pyrazinamide to its active form. We evaluated two newer and simpler methods to assess pyrazinamidase activity, the nitrate reductase and malachite green microtube assays, using nicotinamide in place of pyrazinamide. A total of 102 strains were tested by these methods and the results compared with those obtained by the classic Wayne assay. Mutations in the pncA gene were identified by sequencing the pncA genes from all isolates in which pyrazinamide resistance was detected by any of the three methods. Both the nitrate reductase and malachite green microtube assays showed sensitivities of 93.75% and specificities of 97.67%. Mutations in the pncA gene were found in 14 of 16 strains that were pyrazinamide resistant and in 1 of 4 strains that were sensitive by the Wayne assay. Both of these simple methods, used with nicotinamide, are promising and inexpensive alternatives for the rapid detection of pyrazinamide resistance in limited-resource countries. PMID:20554826

Mirabal, Niuris C; Yzquierdo, Sergio L; Lemus, Dihadenys; Madruga, Mariela; Milián, Yoslaine; Echemendía, Miguel; Takiff, Howard; Martin, Anandi; Van der Stuyf, Patrick; Palomino, Juan Carlos; Montoro, Ernesto

2010-08-01

125

Directional Antineutrino Detection  

NASA Astrophysics Data System (ADS)

We propose the first event-by-event directional antineutrino detector using inverse beta decay (IBD) interactions on hydrogen, with potential applications including monitoring for nuclear nonproliferation, spatially mapping geoneutrinos, characterizing the diffuse supernova neutrino background and searching for new physics in the neutrino sector. The detector consists of adjacent and separated target and capture scintillator planes. IBD events take place in the target layers, which are thin enough to allow the neutrons to escape without scattering elastically. The neutrons are detected in the thicker boron-loaded capture layers. The location of the IBD event and the momentum of the positron are determined by tracking the positron's trajectory through the detector. Our design is a straightforward modification of existing antineutrino detectors; a prototype could be built with existing technology.

Safdi, Benjamin R.; Suerfu, Burkhant

2015-02-01

126

Directional Antineutrino Detection  

E-print Network

We propose the first truly directional antineutrino detector for antineutrinos above the hydrogen inverse beta decay (IBD) threshold, with potential applications including monitoring for nuclear nonproliferation, spatially mapping geo-neutrinos, characterizing the diffuse supernova neutrino background, and searching for new physics in the neutrino sector. The detector consists of adjacent and separated target and capture scintillator planes. IBD events take place in the target layers, which are thin enough to allow the neutrons to escape without scattering elastically. The neutrons are detected in the thicker, boron-loaded capture layers. The location of the IBD event and the momentum of the positron are determined by tracking the positron's trajectory through the detector. Our design is a straightforward modification of existing antineutrino detectors; a prototype could be built with existing technology.

Benjamin R. Safdi; Burkhant Suerfu

2014-10-30

127

Directional antineutrino detection.  

PubMed

We propose the first event-by-event directional antineutrino detector using inverse beta decay (IBD) interactions on hydrogen, with potential applications including monitoring for nuclear nonproliferation, spatially mapping geoneutrinos, characterizing the diffuse supernova neutrino background and searching for new physics in the neutrino sector. The detector consists of adjacent and separated target and capture scintillator planes. IBD events take place in the target layers, which are thin enough to allow the neutrons to escape without scattering elastically. The neutrons are detected in the thicker boron-loaded capture layers. The location of the IBD event and the momentum of the positron are determined by tracking the positron's trajectory through the detector. Our design is a straightforward modification of existing antineutrino detectors; a prototype could be built with existing technology. PMID:25763953

Safdi, Benjamin R; Suerfu, Burkhant

2015-02-20

128

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

129

Visual and highly sensitive detection of cancer cells by a colorimetric aptasensor based on cell-triggered cyclic enzymatic signal amplification.  

PubMed

Rapid and efficient detection of cancer cells at their earliest stages is one of the central challenges in cancer diagnostics. We developed a simple, cost-effective, and highly sensitive colorimetric method for visually detecting rare cancer cells based on cell-triggered cyclic enzymatic signal amplification (CTCESA). In the absence of target cells, hairpin aptamer probes (HAPs) and linker DNAs stably coexist in solution, and the linker DNA assembles DNA-AuNPs, producing a purple solution. In the presence of target cells, the specific binding of HAPs to the target cells triggers a conformational switch that results in linker DNA hybridization and cleavage by nicking endonuclease-strand scission cycles. Consequently, the cleaved fragments of linker DNA can no longer assemble into DNA-AuNPs, resulting in a red color. UV-vis spectrometry and photograph analyses demonstrated that this CTCESA-based method exhibited selective and sensitive colorimetric responses to the presence of target CCRF-CEM cells, which could be detected by the naked eye. The linear response for CCRF-CEM cells in a concentration range from 10(2) to 10(4) cells was obtained with a detection limit of 40 cells, which is approximately 20 times lower than the detection limit of normal AuNP-based methods without amplification. Given the high specificity and sensitivity of CTCESA, this colorimetric method provides a sensitive, label-free, and cost-effective approach for early cancer diagnosis and point-to-care applications. PMID:24819867

Zhang, Xianxia; Xiao, Kunyi; Cheng, Liwei; Chen, Hui; Liu, Baohong; Zhang, Song; Kong, Jilie

2014-06-01

130

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

131

Colorimetric microtiter plate receptor-binding assay for the detection of freshwater and marine neurotoxins targeting the nicotinic acetylcholine receptors  

USGS Publications Warehouse

Anatoxin-a and homoanatoxin-a, produced by cyanobacteria, are agonists of nicotinic acetylcholine receptors (nAChRs). Pinnatoxins, spirolides, and gymnodimines, produced by dinoflagellates, are antagonists of nAChRs. In this study we describe the development and validation of a competitive colorimetric, high throughput functional assay based on the mechanism of action of freshwater and marine toxins against nAChRs. Torpedo electrocyte membranes (rich in muscle-type nAChR) were immobilized and stabilized on the surface of 96-well microtiter plates. Biotinylated ?-bungarotoxin (the tracer) and streptavidin-horseradish peroxidase (the detector) enabled the detection and quantitation of anatoxin-a in surface waters and cyclic imine toxins in shellfish extracts that were obtained from different locations across the US. The method compares favorably to LC/MS/MS and provides accurate results for anatoxin-a and cyclic imine toxins monitoring. Study of common constituents at the concentrations normally found in drinking and environmental waters, as well as the tolerance to pH, salt, solvents, organic and inorganic compounds did not significantly affect toxin detection. The assay allowed the simultaneous analysis of up to 25 samples within 3.5 h and it is well suited for on-site or laboratory monitoring of low levels of toxins in drinking, surface, and ground water as well as in shellfish extracts.

Rubio, Fernando; Kamp, Lisa; Carpino, Justin; Faltin, Erin; Loftin, Keith A.; Molgó, Jordi; Aráoz, Rómulo

2014-01-01

132

Microsystem-assisted synthesis of carbon dots with fluorescent and colorimetric properties for pH detection  

NASA Astrophysics Data System (ADS)

The present paper describes the use of a microfluidic system to synthesize carbon dots (Cdots) and their use as optical pH sensors. The synthesis is based on the thermal decomposition of ascorbic acid in dimethyl sulfoxide. The proposed microsystem is composed of a fluidic and a thermal platform, which enable proper control of synthesis variables. Uniform and monodispersed 3.3 nm-sized Cdots have been synthesized, the optical characterization of which showed their down/upconversion luminescence and colorimetric properties. The obtained Cdots have been used for pH detection with down and upconverison fluorescent properties as excitation sources. The naked eye or a photographic digital camera has also been implemented as detection systems with the hue parameter showing a linear pH range from 3.5 to 10.2. On the other hand, experiments on the cytotoxicity and permeability of the Cdots on human embryonic kidney cells revealed their adsorption on cells without causing any impact on the cellular morphology.

Pedro, S. Gómez-De; Salinas-Castillo, A.; Ariza-Avidad, M.; Lapresta-Fernández, A.; Sánchez-González, C.; Martínez-Cisneros, C. S.; Puyol, M.; Capitan-Vallvey, L. F.; Alonso-Chamarro, J.

2014-05-01

133

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

134

Colorimetric microtiter plate receptor-binding assay for the detection of freshwater and marine neurotoxins targeting the nicotinic acetylcholine receptors.  

PubMed

Anatoxin-a and homoanatoxin-a, produced by cyanobacteria, are agonists of nicotinic acetylcholine receptors (nAChRs). Pinnatoxins, spirolides, and gymnodimines, produced by dinoflagellates, are antagonists of nAChRs. In this study we describe the development and validation of a competitive colorimetric, high throughput functional assay based on the mechanism of action of freshwater and marine toxins against nAChRs. Torpedo electrocyte membranes (rich in muscle-type nAChR) were immobilized and stabilized on the surface of 96-well microtiter plates. Biotinylated ?-bungarotoxin (the tracer) and streptavidin-horseradish peroxidase (the detector) enabled the detection and quantitation of anatoxin-a in surface waters and cyclic imine toxins in shellfish extracts that were obtained from different locations across the US. The method compares favorably to LC/MS/MS and provides accurate results for anatoxin-a and cyclic imine toxins monitoring. Study of common constituents at the concentrations normally found in drinking and environmental waters, as well as the tolerance to pH, salt, solvents, organic and inorganic compounds did not significantly affect toxin detection. The assay allowed the simultaneous analysis of up to 25 samples within 3.5 h and it is well suited for on-site or laboratory monitoring of low levels of toxins in drinking, surface, and ground water as well as in shellfish extracts. PMID:25260255

Rubio, Fernando; Kamp, Lisa; Carpino, Justin; Faltin, Erin; Loftin, Keith; Molgó, Jordi; Aráoz, Rómulo

2014-12-01

135

Binding-induced and label-free colorimetric method for protein detection based on autonomous assembly of hemin/G-quadruplex DNAzyme amplification strategy.  

PubMed

In this work, a new binding-induced and label-free colorimetric method for protein detection has been developed on the basis of an autonomous assembly of hemin/G-quadruplex DNAzyme amplification strategy. The system consists of two proximity probes carrying two aptamer sequences as recognition elements for target, and two hairpin structures include three-fourths and one-fourth of the G-quadruplex sequences in inactive configuration as functional elements. In the presence of target protein, two proximity probes bind to the protein simultaneously, forming a stable DNA-protein complex. Then the complex triggers an autonomous cross-opening of the two functional hairpin structures, leading to the formation of numerous hemin/G-quadruplex DNAzymes. The resulting DNAzymes catalyze the oxidation of colorless 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(2-)) to the green-colored ABTS(•-) with the presence of H2O2, thus providing the amplified colorimetric detection of target. Using human ?-thrombin as the protein target, this binding-induced DNAzyme amplification colorimetric method affords high sensitivity with a detection limit of 1.9 pM. Furthermore, this method might be further extended to sensitive detection of other proteins by simply replacing recognition elements of proximity probes. PMID:25310491

Wu, Hao; Zhang, Kai; Liu, Yaling; Wang, Hongyong; Wu, Jun; Zhu, Feifan; Zou, Pei

2015-02-15

136

Rapid detection of human rotavirus using colorimetric nucleic acid sequence-based amplification (NASBA)–enzyme-linked immunosorbent assay in sewage treatment effluent  

Microsoft Academic Search

A colorimetric nucleic acid sequence-based amplification–enzyme-linked immunosorbent assay (NASBA-ELISA) was developed for rapid detection and identification of human rotavirus. Oligonucleotide primers targeting gene 9 encoding a serotype-specific antigen VP7 were selected and used for the amplification of viral RNA by the isothermal NASBA process, resulting in the accumulation of biotinylated RNA amplicons. Amplicons were hybridized with a specific amino-linked oligonucleotide

Julie Jean; Burton Blais; André Darveau

2002-01-01

137

Genotoxic activity detected in soils from a hazardous waste site by the Ames test and an SOS colorimetric test  

SciTech Connect

Ten soil samples from a hazardous waste site were compared for their genotoxic activity by the Ames test (Salmonella reverse mutation assay) and a modified SOS colorimetric test. Polynuclear aromatic hydrocarbons known to produce frameshift mutations were found in high levels in the soils. Salmonella typhimurium TA98, sensitive to frameshift mutations, was selected as the Ames tester strain. Escherichia coli K12 PQ37 (sulA::lacZ) was the SOS tester strain. Organic extracts were prepared from the soil samples by Soxhlet extraction. One set of the soil samples was extracted with methylene chloride and a second set with cyclohexane. Two criteria from reproducible dose-related increases in response to the soil were used to compare the positive responses: 1. the concentrations required for doubling responses and 2. a minimum concentration required to produce statistically significant increases from background controls. Analysis of variance indicated that with S9 mix, Ames and SOS results were similar for the same soils and solvent extractions. However, without S9 mix, the SOS test was significantly more sensitive than the Ames test to the genotoxins extracted from the soils. Both the Ames and SOS tests detected lower concentrations of genotoxins in methylene chloride than in cyclohexane extracts. The simplicity of the method, reduction in expenses, and results within 1 working day all contribute to the advantages of the SOS test.

McDaniels, A.E.; Reyes, A.L.; Wymer, L.J.; Rankin, C.C.; Stelma, G.N. Jr. (Environmental Protection Agency, Cincinnati, OH (United States))

1993-01-01

138

A novel heterogeneous colorimetric and spectrophotometric chemosensor for detection and adsorption of Hg0 and Hg2+.  

PubMed

Functionalized mesoporous silica with an immobilized azobenzene-coupled receptor 1 (FMS-1) as heterogeneous "naked-eye" colorimetric and spectrophotometric chemosensor was prepared by sol-gel reaction. The optical sensing ability of FMS-1 was studied by addition of metal ions such as K+, Ca2+, Sr2+, Co2+, Cd2+, Pb2+, Zn2+, Fe3+, Cu2+ and Hg2+ in aqueous solution. Interestingly, upon the addition of Hg2+ in aqueous suspension, FMS-1 resulted in a color change from maroon to red within 10 s. On the other hand, no significant color changes were observed with the other metal ions. These findings confirm that FMS-1 can be useful as a chemosensor for selective detection of Hg2+ over a range of metal ions. Furthermore, the adsorption ability of the FMS-1 was also estimated by measuring the amount of Hg2+ and Hg0 adsorbed on the FMS-1, resulting in 95% for Hg2+ and 75% for Hg0, respectively, suggesting that the FMS-1 is potentially useful as the adsorbent for separation of Hg0 and Hg2+ in chromatography. PMID:21125828

Kim, Eunjeong; Cho, Namjun; Vittal, Jagadese J; Lee, Shim Sung; Han, Won Seok; Jung, Jong Hwa

2010-08-01

139

Sensitive colorimetric detection of cyromazine in cucumber samples by using label-free gold nanoparticles and polythymine.  

PubMed

Cyromazine (CYR) can cause serious damage to the organs of animals or human beings, and it was found to bind to polythymine (polyT10) via multiple hydrogen bonding interactions. Based on this novel finding, a highly sensitive and simple colorimetric method was developed for CYR detection by using label-free gold nanoparticles (AuNPs) and polyT10. Under the optimized conditions, excellent linearity was acquired for CYR within the range of 1-500 ng mL(-1). In addition, the spectra and color changes of the AuNP solution were measured by spectrophotometry and observed by the naked eye, and the results showed that as low as 1 and 5 ng mL(-1) of CYR could be detected, depending upon the measurement methods. Afterwards, cucumber was selected to investigate the sample matrix effect and a sample pretreatment procedure was developed with simple homogenization and filtration. Even after 200 times dilution, the limit of detection (LOD) and limit of quantitation (LOQ) reached 252 ng g(-1) and 500 ng g(-1), respectively. The LOD and LOQ satisfied the Chinese requirement for the maximum residue limit (MRL), which is 0.5-1 ?g g(-1) of CYR in most vegetables. The assay also showed a good average recovery of 83.7-104.8% with the RSD of less than 7% and good selectivity for cyromazine over other pesticides that may exist in vegetable samples. The method proposed in this study was simple, fast, and highly sensitive and accurate, and the test result with this method was visible to the naked eye. Therefore, it could be used for routine determination of CYR residues in cucumber samples. PMID:25741673

Liu, Jinchuan; Bai, Wenhui; Zhu, Chao; Yan, Mengmeng; Yang, Shuming; Chen, Ailiang

2015-05-01

140

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

141

Immunosorbent analysis of ricin contamination in milk using colorimetric, chemiluminescence, and electrochemiluminescence detection  

Technology Transfer Automated Retrieval System (TEKTRAN)

Analytical methodology to detect ricin in food matrices is important because of the potential use of foodborne ricin as a terrorist weapon. Monoclonal antibodies (mAbs) that bind ricin were used for both capture and detection in sandwich enzyme-linked immunosorbent assay (ELISA) and electrochemilumi...

142

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...

143

Colorimetric detection of Ehrlichia canis via nucleic acid hybridization in gold nano-colloids.  

PubMed

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

144

A fluorescent and colorimetric sensor for nanomolar detection of Co2+ in water.  

PubMed

A new disulfide-based, imine-linked fluorescent receptor 1 was processed into organic nanoparticles (ONPs) with an average particle size of 79 nm. The photophysical properties of the ONPs were evaluated by UV/Vis absorption spectroscopy. Receptor 1 selectively recognized Co(2+) ions in water with a detection limit down to 88 nm. PMID:25319078

Kuwar, Anil; Patil, Rahul; Singh, Amanpreet; Bendre, Ratnamala; Singh, Narinder

2014-12-15

145

Simple Colorimetric Method for Detecting Degenerate Strains of the Cultivated Basidiomycete Flammulina velutipes (Enokitake)  

Microsoft Academic Search

The primary objective of this study was to develop a simple method for detecting degenerate Flammulina velutipes (Eno- kitake) cultures. Cultural degeneration of cultivated strains of Enokitake similar to the degeneration observed for Agaricus bisporus (1, 2) has become a serious problem in Japan. Previ- ous efforts to evaluate the fruiting potential of Enokitake have been made using isozyme electrophoresis

Yumi Magae; Kobun Akahane; Kimiyoshi Nakamura; Shigeyuki Tsunoda

2005-01-01

146

DETECTION OF ESCHERICHIA COLI IN WATER USING A COLORIMETRIC GENE PROBE ASSAY  

EPA Science Inventory

A commercially available DNA hydribization assay (Gene-trak , Framingham, MA. USA) was compared with the EC-MUG procedure for the detection of Escherichia coli in water. The gene probe gave positive responses for pure cultures of E. coli 0157:H7, E. fergusonii, Shigella sonnei, S...

147

Colorimetric detection of single nucleotide polymorphisms in the presence of 10(3)-fold excess of a wild-type gene.  

PubMed

Herein, we proposed a simple colorimetric assay for highly sensitive and specific detection of single nucleotide polymorphisms (SNPs). Briefly, SNP specific capture probes (CPs) were immobilized onto magnetic beads. The hybridization of a target SNP with the CPs and detection probes containing multiple DNAzyme sequences (DNAzyme-DPs) brought the target SNP and the DNAzyme-DPs onto the magnetic beads. Meanwhile, a mismatch-specific CEL II enzyme (Surveyor(®) nuclease) cleaved the imperfectly hybridized wild-type gene together with all other mismatched sequences off the magnetic beads, leaving only the perfectly matched SNP strands on the magnetic beads. Amplified colorimetric detection was carried out through the DNAzyme-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H2O2. The excellent selectivity of Surveyor(®) nuclease toward all imperfectly-matched DNA duplexes produced an ultrahigh selectivity - one mutant in 1000 copies of the wild-type gene can be detected. In addition, the cumulative nature of the DNAzyme-amplified signal generation process produced a detection limit as low as 0.40fM and a dynamic range from 1.0 to 200fM. The simple protocol and its high sensitivity and selectivity allowed the proposed assay to be used in the detection of SNPs in genomic DNA samples. PMID:25596559

Deng, Huimin; Shen, Wei; Gao, Zhiqiang

2015-06-15

148

Dark Matter: Direct Detection  

SciTech Connect

The identification of Dark Matter is an outstanding question of contemporary physics. I summarize the main experimental strategies developed to answer this question, focusing on cryogenic detectors and comparing these detectors to their double-phase xenon and argon competitors. I discuss in particular the main developments in charge-phonon (CDMS, EDELWEISS) and light-phonon detectors (CRESST, ROSEBUD). Finally, I discuss the prospects of WIMP detection within the next few years by the CDMS, CRESST, EDELWEISS and XENON experiments, and their successors EURECA, GEODM and XENON-1 ton.

Chardin, G. [CSNSM, CNRS/IN2P3 and Universite Paris-Sud, Orsay (France)

2009-12-16

149

A Novel Porphyrin-Containing Polyimide Nanofibrous Membrane for Colorimetric and Fluorometric Detection of Pyridine Vapor  

PubMed Central

A novel zinc porphyrin-containing polyimide (ZPCPI) nanofibrous membrane for rapid and reversible detection of trace amounts of pyridine vapor is described. The membrane displays a distinct color change, as well as dramatic variations in absorption and fluorescent emission spectra, upon exposure to pyridine vapor. This condition allows the detection of the analyte at concentrations as low as 0.041 ppm. The vapochromic and spectrophotometric responses of the membrane are attributed to the formation of the ZPCPI-pyridine complex upon axial coordination. From surface plasmon resonance analysis, the affinity constant of ZPCPI-pyridine complex was calculated to be (3.98 ± 0.25) × 104 L·mol?1. The ZPCPI nanofibrous membrane also showed excellent selectivity for pyridine vapor over other common amines, confirming its applicability in the manufacture of pyridine-sensitive gas sensors. PMID:24256976

Lv, Yuanyuan; Zhang, Yani; Du, Yanglong; Xu, Jiayao; Wang, Junbo

2013-01-01

150

BODIPY based colorimetric fluorescent probe for selective thiophenol detection: theoretical and experimental studies.  

PubMed

A BODIPY-based selective thiophenol probe capable of discriminating aliphatic thiols is reported. The fluorescence off-on effect upon reaction with thiol is elucidated with theoretical calculations. The sensing of thiophenol is associated with a color change from red to yellow and 63-fold enhancement in green fluorescence. Application of the probe for selective thiophenol detection is demonstrated by live cell imaging. PMID:22751002

Kand, Dnyaneshwar; Mishra, Pratyush Kumar; Saha, Tanmoy; Lahiri, Mayurika; Talukdar, Pinaki

2012-09-01

151

A colorimetric and fluorescent turn on chemodosimeter for Pd(2+) detection.  

PubMed

A novel rhodamine derivative L had been successfully developed and well characterized by NMR, and Mass spectroscopy. Chemodosimeter L is a naked-eye fluorescent chemodosimeter for Pd(2+) in aqueous solution. More over the detection limit of Chemodosimeter L is in 10(-7)M level. The Ligand to L ratio was determined to be 1:2 according to the job's plot. PMID:25534416

Li, Lianqing; Liu, Zhihong

2015-03-01

152

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

153

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

154

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

155

Label-free colorimetric detection of Hg(2+) based on Hg(2+)-triggered exonuclease III-assisted target recycling and DNAzyme amplification.  

PubMed

This work reported a label-free colorimetric assay for sensitive detection of Hg(2+) based on Hg(2+)-triggered hairpin DNA probe (H-DNA) termini-binding and exonuclease ? (Exo ?)-assisted target recycling, as well as hemin/G-quadruplex (DNAzyme) signal amplification. The specific binding of free Hg(2+) with the thymine-thymine (T-T) mismatches termini of H-DNA could immediately trigger the Exo ? digestion, and then set free G-quadruplex segments and Hg(2+). The Exo ? impellent recycling of ultratrace Hg(2+) produced numerous G-quadruplexes. The corresponding DNAzymes catalyzed efficiently the H2O2-mediated oxidation of the ABTS(2-) to the colored product in the presence of hemin. Using the color change as the output signal, and the Exo ?-aided Hg(2+) recycling and DNAzyme as the signal amplifier, the ultrasensitive assay system successfully achieved visual detection of Hg(2+) as low as 1.0nM by the naked eye, and was suitable for field monitoring. The calibration curve was linear in the range of 50.0pM to 20.0nM for Hg(2+) (R=0.9962) with a detection limit of 10.0pM. Moreover, this proposed strategy showed excellent selectivity, portability and low-cost, and was successfully applied to colorimetric detection of Hg(2+) in laboratory tap water and Jialing river water samples. PMID:25590972

Ren, Wang; Zhang, Ying; Huang, Wei Tao; Li, Nian Bing; Luo, Hong Qun

2015-06-15

156

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

157

Self-assembly of core-satellite gold nanoparticles for colorimetric detection of copper ions.  

PubMed

Molecule-coated nanoparticles are hybrid materials which can be engineered with novel properties. The molecular coating of metal nanoparticles can provide chemical functionality, enabling assembly of the nanoparticles that are important for applications, such as biosensing devices. Herein, we report a new self-assembly of core-satellite gold nanoparticles linked by a simple amino acid l-Cysteine for biosensing of Cu(2+). The plasmonic properties of core-satellite nano-assemblies were investigated, a new red shifted absorbance peak from about 600 to 800 nm was found, with specific wavelength depending on ratios with assembly of large and small gold nanoparticles. The spectral features obtained using surface-enhanced Raman spectroscopy (SERS) provided strong evidence for the assembly of the Cu(2+) ions to the L-Cysteine molecules leading to the successful formation of the core-satellite Cu(l-Cysteine) complex on the gold surfaces. In addition, a linear relationship between the concentration of mediating Cu(2+) and absorbance of self-assembled gold nanoparticles (GNPs) at 680 nm was obtained. These results strongly address the potential strategy for applying the functionalized GNPs as novel biosensing tools in trace detections of certain metal ions. PMID:24216206

Weng, Ziqing; Wang, Hongbin; Vongsvivut, Jitraporn; Li, Runqing; Glushenkov, Alexey M; He, Jin; Chen, Ying; Barrow, Colin J; Yang, Wenrong

2013-11-25

158

A simplified approach to the determination of N-nitroso glyphosate in technical glyphosate using HPLC with post-derivatization and colorimetric detection  

Microsoft Academic Search

A simple and sensitive HPLC post-derivatization method with colorimetric detection has been developed for the determination of N-nitroso glyphosate in samples of technical glyphosate. Separation of the analyte was accomplished using an anionic exchange resin (2.50mm×4.00mm i.d., 15?m particle size, functional group: quaternary ammonium salt) with Na2SO4 0.0075M (pH 11.5) (flow rate: 1.0mLmin?1) as mobile phase. After separation, the eluate

Manuela Kim; Jorge Stripeikis; Fernando Iñón; Mabel Tudino

2007-01-01

159

Intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots and their application in the colorimetric detection of H2O2 and glucose.  

PubMed

In this paper, the highly intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots (N-GQDs) is revealed. This activity was greatly dependent on pH, temperature and H2O2 concentration. The experimental results showed that the stable N-GQDs could be used for the detection of H2O2 and glucose over a wide range of pH and temperature, offering a simple, highly selective and sensitive approach for their colorimetric sensing. The linearity between the analyte concentration and absorption ranged from 20 to 1170?M for H2O2 and 25 to 375?M for glucose with a detection limit of 5.3?M for H2O2 and 16?M for glucose. This assay was also successfully applied to the detection of glucose concentrations in diluted serum and fruit juice samples. PMID:25818144

Lin, Liping; Song, Xinhong; Chen, Yiying; Rong, Mingcong; Zhao, Tingting; Wang, Yiru; Jiang, Yaqi; Chen, Xi

2015-04-15

160

Colorimetric detection of anions in aqueous media using N-monosubstituted diaminomaleonitrile-based azo-azomethine receptors: real-life applications.  

PubMed

New N-monosubstituted diaminomaleonitrile-based azo-azomethine dyes have been synthesized in order to develop colorimetric sensors for detection of biologically important anions in aqueous media. Importantly, the reported sensor decorated with strong electron-withdrawing group can detect inorganic fluoride in water even at 0.037 ppm level, which is lower than WHO permissible level (below 1 ppm). Successfully, the prepared dyes were used for qualitative and quantitative detection of inorganic fluoride in toothpaste and mouthwash. The anion recognition mechanism was also investigated by detailed UV-Vis and (1)H NMR experiments. The detailed (1)H NMR experiments corroborated that anion recognition is based on the deprotonation phenomenon. PMID:25576937

Khanmohammadi, Hamid; Rezaeian, Khatereh; Abdollahi, Alieh

2015-03-15

161

Colorimetric detection of trace Hg2+ with near-infrared absorbing squaraine functionalized by dibenzo-18-crown-6 and its mechanism  

NASA Astrophysics Data System (ADS)

In this contribution, an improved near-infrared absorbing colorimetric detection of Hg2+ ion with high selectivity and sensitivity had been developed by using bis-dibenzo-18-crown-6-based squaraine (BCSQ) as sensor in aqueous media. The proposed method was applied to analyze trace Hg2+ in synthetic Hg2+ samples and natural Hg2+ samples. Under the optimum conditions, the detection had a linear range of 7.5-150 × 10-8 mol L-1 with a correlation coefficient (R) of 0.9983 combining a limit detection (3?, n = 20) of 5.6 × 10-9 mol L-1. The relative standard deviation (RSD) was lower than 2.4% (n = 5). The proposed method possesses the advantages of simplicity, rapidity, high selectivity and sensitivity. The action mechanism between BCSQ and Hg2+ was discussed in details.

Hu, Lei; Zhang, Yafei; Nie, Li; Xie, Chenggen; Yan, Zhengquan

2013-03-01

162

Selective and sensitive detection of free bilirubin in blood serum using human serum albumin stabilized gold nanoclusters as fluorometric and colorimetric probe.  

PubMed

We report here a fluorescence quenching based non-enzymatic method for sensitive and reliable detection of free bilirubin in blood serum samples using human serum albumin (HSA) stabilized gold nanoclusters (HSA-AuNCs) as fluorescent probe. The fluorescence of the nanoclusters was strongly quenched by bilirubin in a concentration dependent manner by virtue of the inherent specific interaction between bilirubin and HSA. A strong binding constant of 0.55×10(6) L mole(-1) between the HSA-AuNC and bilirubin was discerned. The nano clusters each with size ~1.0 nm (in diameter) and a core of Au18 were homogeneously distributed in HSA molecules as revealed from the respective high resolution transmission electron microscopic and mass spectroscopic studies. The fluorescence quenching phenomena which obeyed a simple static quenching mechanism, was utilized for interference free detection of bilirubin with minimum detection limit (DL) of 248±12 nM (S/N=3). The fluorescence response of HSA-AuNCs against bilirubin was practically unaltered over a wide pH (6-9) and temperature (25-50 °C) range. Additionally, peroxidase-like catalytic activity of these nanoclusters was exploited for colorimetric detection of bilirubin in serum sample with a DL of 200±19 nM by following the decrease in absorbance (at ?440 nm) of the reaction and its rate constant (Kp) of 2.57±0.63 mL ?g(-1) min(-1). Both these fluorometric and colorimetric methods have been successfully used for detection of free bilirubin in blood serum samples. PMID:24752148

Santhosh, Mallesh; Chinnadayyala, Somasekhar R; Kakoti, Ankana; Goswami, Pranab

2014-09-15

163

Paper-based colorimetric array test strip for selective and semiquantitative multi-ion analysis: simultaneous detection of Hg²?, Ag?, and Cu²?.  

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

164

A new pyrene-based Schiff-base: A selective colorimetric and fluorescent chemosensor for detection of Cu(II) and Fe(III)  

NASA Astrophysics Data System (ADS)

A new receptor 1 was prepared, for the detection of Cu2+ and Fe3+ in solutions as a colorimetric and fluorescent sensor, respectively. Receptor 1 shows highly selective and sensitive recognition toward Cu2+ and Fe3+ by naked eye UV-Vis and fluorescent color changes in aqueous solution (DMSO/H2O = 8/2, v/v), respectively. The sensitivity toward Cu2+ or Fe3+ was not interfered with by the presence of other metal ions such as Mg2+, Cd2+, Ag+, Zn2+, Ni2+, Co2+, Mn2+, Cr3+, Ca2+, Na+, Pb2+, K+, Fe2+, Li+ and Hg2+ ions. Receptor 1 can be used for semi-quantitative recognition of Cu2+ ions at ppm level. The fluorescence microscopy experiments showed that the receptor is efficient for detection of Fe3+ in vitro, developing a good image of the biological organelles.

Bhorge, Yeshwant Ramchandra; Tsai, Haw-Tyng; Huang, Keh-Feng; Pape, Albert J.; Janaki, Sudhakar Narasimha; Yen, Yao-Pin

2014-09-01

165

COLORIMETRIC DETERMINATION OF MANGANESE  

E-print Network

1 COLORIMETRIC DETERMINATION OF MANGANESE (Chemistry 51 Version) The objective of this experiment is to determine the percentage of manganese in a steel sample, using colorimetric methods of analysis. PRINCIPLES This analysis is accomplished by dissolving the steel sample, converting all of the manganese to the intensely

Bertsch George F.

166

A reversible and reusable selective chemosensor for fluoride detection using a phenolic OH-containing BODIPY dye by both colorimetric 'naked-eye' and fluorometric modes.  

PubMed

A novel BODIPY-based probe 1 was designed and synthesized as a selective fluorescent and colorimetric chemosensor for fluoride. The spectral responses of 1 to fluoride in acetonitrile were studied: an approximately 118 nm red shift in absorption and 'turn-off' emission response was observed. The striking pink to indigo change in ambient light was thought to be due to the deprotonation of the phenol moiety by way of O-H?·?·?·?F hydrogen bonding interactions. Interestingly, when the nonfluorescent 1-F(-) solution treated with trifluoroacetic acid (TFA) resulted in color change from indigo to pink and a significant enhancement of fluorescence intensity (10-fold). Furthermore, the reversibility and reusability of probe 1 for the detection of F(-) ion was tested for four cycles indicating the probe 1 could be used in reversible manner. PMID:25257399

Wang, Lingyun; Fang, Guipo; Cao, Derong

2014-11-01

167

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

168

Colorimetric Method of Loop-Mediated Isothermal Amplification with the Pre-Addition of Calcein for Detecting Flavobacterium columnare and its Assessment in Tilapia Farms.  

PubMed

Abstract Flavobacterium columnare, the causative agent of columnaris disease in fish, affects many economically important freshwater fish species. A colorimetric method of loop-mediated isothermal amplification with the pre-addition of calcein (LAMP-calcein) was developed and used to detect the presence of F. columnare in farmed tilapia (Nile Tilapia Oreochromis niloticus and red tilapia [Nile Tilapia × Mozambique Tilapia O. mossambicus]) and rearing water. The detection method, based on a change in color from orange to green, could be performed within 45 min at 63°C. The method was highly specific, as it had no cross-detections with 14 other bacterial species, including other fish pathogens and two Flavobacterium species. The method has a minimum detection limit of 2.2 × 10(2) F. columnare CFU; thus, it is about 10 times more sensitive than conventional PCR. With this method, F. columnare was detected in gonad, gill, and blood samples from apparently healthy tilapia broodstock as well as in samples of fertilized eggs, newly hatched fry, and rearing water. The bacteria isolated from the blood were further characterized biochemically and found to be phenotypically identical to F. columnare. The amplified products from the LAMP-calcein method had 97% homology with the DNA sequence of F. columnare. Received May 21, 2014; accepted August 10, 2014. PMID:25584663

Suebsing, Rungkarn; Kampeera, Jantana; Sirithammajak, Sarawut; Withyachumnarnkul, Boonsirm; Turner, Warren; Kiatpathomchai, Wansika

2015-03-01

169

Specific detection of reverse transcription-loop-mediated isothermal amplification amplicons for Taura syndrome virus by colorimetric dot-blot hybridization.  

PubMed

The goal of this study was to develop a field diagnosis system based on isothermal reverse transcription-loop-mediated amplification (RT-LAMP) for shrimp Taura syndrome virus (TSV), placing emphasis on specific and simple detection of the LAMP amplicons. After a single-tube RT-LAMP reaction for TSV was established, colorimetric dot-blot hybridization (DBH) was adopted to detect signals only from the target-derived amplicons. The results showed that the modified DBH offered unambiguous and sensitive detection of the TSV RT-LAMP amplicons without the UV cross-linking and denaturation steps. Together, TSV RT-LAMP-DBH assay reached the same dilution point as reverse transcription-nested polymerase chain reaction-agarose gel electrophoresis (RT-nPCR-AGE) for TSV detection. Specificity of the assay was demonstrated by the absence of DBH signal from yeast tRNA and various shrimp viruses. TSV RT-LAMP-DBH was applied to 125 Penaeus vannamei and demonstrated a very good concordance (kappa value, 0.823) with RT-nPCR-AGE assay in detection efficiency. Furthermore, a one-step guanidinium thiocyanate (GuSCN) homogenization method was established to provide RNA extraction efficiency comparable to that of the TRIzol Reagent for RT-LAMP. Requiring simply a heating apparatus, the GuSCN RNA extraction-isothermal RT-LAMP-DBH protocol has the potential for further development for diagnosis of diseases in the field. PMID:17868915

Teng, Ping-Hua; Chen, Chu-Liang; Sung, Ping-Feng; Lee, Fu-Chun; Ou, Bor-Rung; Lee, Pei-Yu

2007-12-01

170

Selective and sensitive detection of pectin lyase activity using a colorimetric test: application to the screening of microorganisms possessing pectin lyase activity.  

PubMed

Several methods have been described for the detection and quantification of polygalacturonase (PG) and pectin lyase (PL) activities. The most frequently used tests are the Nelson method using copper(II) and an arsenomolybdate reagent to detect PG activity, and the colorimetric method using thiobarbituric acid (TBA) to detect PL activity. We observed that none of these methods are suitable to differentiate between these two enzymatic activities. Therefore, we optimized the test conditions of the TBA method. As a result, the detection of the enzymatic beta-elimination (PL activity) became sensitive and selective. A basic pretreatment at 80 degrees C for 5 min of the solution which contains the pectin fragments of the PL activity furnished aldehydes which were condensed with TBA or its derivatives. After acidification of the medium, a pink fluorescent dye was detected spectrophotochemically (lambda = 550 nm). The interference of galacturonic acid or oligomers resulting from PG activity was completely eliminated. The most sensitive reagent was N-(pyridin-2-yl)-thiobarbituric acid. The application of this method with the new reagent was extended to the screening of microorganisms possessing the PL activity. The obtained results confirm that Aspergillus niger strain and a Saccharomyces cerevisiae SCPP strain possess this activity. PMID:11401303

Nedjma, M; Hoffmann, N; Belarbi, A

2001-04-15

171

Direct Fast-Neutron Detection  

SciTech Connect

Direct fast-neutron detection is the detection of fast neutrons before they are moderated to thermal energy. We have investigated two approaches for using proton-recoil in plastic scintillators to detect fast neutrons and distinguish them from gamma-ray interactions. Both approaches use the difference in travel speed between neutrons and gamma rays as the basis for separating the types of events. In the first method, we examined the pulses generated during scattering in a plastic scintillator to see if they provide a means for distinguishing fast-neutron events from gamma-ray events. The slower speed of neutrons compared to gamma rays results in the production of broader pulses when neutrons scatter several times within a plastic scintillator. In contrast, gamma-ray interactions should produce narrow pulses, even if multiple scattering takes place, because the time between successive scattering is small. Experiments using a fast scintillator confirmed the presence of broader pulses from neutrons than from gamma rays. However, the difference in pulse widths between neutrons and gamma rays using the best commercially available scintillators was not sufficiently large to provide a practical means for distinguishing fast neutrons and gamma rays on a pulse-by-pulse basis. A faster scintillator is needed, and that scintillator might become available in the literature. Results of the pulse-width studies were presented in a previous report (peurrung et al. 1998), and they are only summarized here.

DC Stromswold; AJ Peurrung; RR Hansen; PL Reeder

2000-01-18

172

Highly sensitive colorimetric detection of Hg(II) and Cu(II) in aqueous solutions: from amino acids toward solid platforms.  

PubMed

A chemosensor (NBD-H) based on an amino acid with 7-nitro-2,1,3-benzoxadiazole was used for selective detection of Hg(II) and Cu(II) among 15 metal ions in aqueous solutions by a colorimetric change. NBD-H sensitively differentiated Hg(II) and Cu(II) in aqueous solutions by a color change; a pink color for Hg(II) and an orange color for Cu(II). NBD-H showed nanomolar detection limits for Hg(II) (176 nM, R2 = 0.996) and Cu(II) (163 nM, R2 = 0.996). The detection limit for Cu(II) was much lower than the maximum allowable level of Cu(II) in drinking water recommended by the U.S. EPA. The binding mode study showed that deprotonation of the NH group of NBD-H played a critical role in the binding and sensing of metal ions. NBD-H immobilized on PEG-PS resin maintained the potent binding affinity and sensing ability for the metal ions. The resin with NBD-H was recyclable for the detection of metal ions in 100% aqueous solutions. PMID:25471472

Park, Jooyoung; In, Byunggyu; Neupane, Lok Nath; Lee, Keun-Hyeung

2015-02-01

173

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

174

Image Noise and Colorimetric Precision in Multispectral Image Capture  

Microsoft Academic Search

The performance of a multispectral (more than three color-records) camera is addressed from the standpoint of pixel-to-pixel error introduced by image detection. Matrix equations are given for the propagation of this image noise from camera signal through colorimetric transformations. Results of the analysis are shown to agree with experimental results, allowing the prediction of system colorimetric precision.

Peter D. Burns; Roy S. Berns

1998-01-01

175

Colorimetric assay for Lindane dechlorination by bacteria  

Microsoft Academic Search

A colorimetric microtitre plate-based assay that detects haloalkane dehalogenase activity was modified to detect dechlorination of ?-hexachlorocyclohexane (Lindane). Dechlorination is indicated by the colour change of phenol red from red to yellow, in a weakly buffered solution, as the solution becomes acidic due to HCl formed during dechlorination. Enzyme activity can be monitored by reading the absorbance of each well

Theresa M Phillips; Alan G Seech; Hung Lee; Jack T Trevors

2001-01-01

176

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

177

Colorimetric and fluorometric dual-modal probes for cyanide detection based on the doubly activated Michael acceptor and their bioimaging applications.  

PubMed

In this study, we synthesized CTB and CB probes based on doubly activated Michael acceptors to selectively detect cyanide (CN(-)) anions through a one-step condensation reaction of coumarinyl acrylaldehyde with the corresponding derivatives of malonyl urea (thiourea). Through the conjugated addition of CN(-) to the ?-site of the Michael acceptor, both probes displayed colorimetric and fluorometric dual-modal responses that were highly reactive and selective. CTB generates an active fluorescent response, whereas CB displays a ratiometric fluorescent response. The fluorescent signal of the probes reached its maximum given only 1 CN(-) equivalent and the signal change was linearly proportional to CN(-) concentrations ranging from 0 to 5 ?M with the detection limits 18 and 23 nM, respectively. The reaction rate of the probes is highly dependent on the methylene acidity of malonyl urea derivatives. Thus, the response rate of CTB to CN(-) is 1.2-fold faster than that of CB, and the response rate of CB to CN(-) is 1.2-fold faster than that of the previously examined CM. We then verified the highly reactive nature of the ?-site of the probes through density functional reactivity theory calculations. In addition, according to proof-of-concept experiments, these probes may be applied to analyze CN(-) contaminated water and biomimetic samples. Finally, cell cytotoxicity and bioimaging studies revealed that the probes were cell-permeable and could be used to detect CN(-) with low cytotoxicity. PMID:25441899

Li, Hongda; Chen, Tie; Jin, Longyi; Kan, Yuhe; Yin, Bingzhu

2014-12-10

178

Hemin-functionalized WS2 nanosheets as highly active peroxidase mimetics for label-free colorimetric detection of H2O2 and glucose.  

PubMed

Hemin-functionalized WS2 nanosheets (hemin/WS2-NSs) were first obtained by hemin assembled on the surface of few-layered WS2 nanosheets (WS2-NSs) via van der Waals interactions. Significantly, this new material possessed the advantages of both hemin and WS2 nanosheets and exhibited some unique properties. Firstly, hemin/WS2-NSs had intrinsic peroxidase-like activity, which could effectively catalyze oxidation of the substrate 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce a typical blue colored reaction. Secondly, the activity of hemin/WS2-NSs was much higher than the activity of hemin or WS2-NSs alone. The catalytic activity followed the typical Michaelis-Menten kinetics and was dependent on the temperature, pH, H2O2 concentration, as well as reaction time. Based on this finding, a new highly sensitive and selective colorimetric method for H2O2 and glucose detection was developed. This method was simple and inexpensive for glucose detection using glucose oxidase (GOx) and hemin/WS2-NSs with a linear range of 0.5 × 10(-5) to 2.0 × 10(-4) mol L(-1) with a detection limit of 1.5 × 10(-6) mol L(-1). The good catalytic activity and low-cost make the hemin/WS2-NSs a useful biocatalyst for a wide range of potential applications in environmental chemistry, biotechnology and clinical diagnostics. PMID:25742312

Chen, Qiao; Chen, Jia; Gao, Cunji; Zhang, Mingliang; Chen, Junying; Qiu, Hongdeng

2015-04-21

179

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

180

Synthesis, characterization and application of poly(acrylamide-co-methylenbisacrylamide) nanocomposite as a colorimetric chemosensor for visual detection of trace levels of Hg and Pb ions.  

PubMed

In this study, a new colorimetric chemosensor based on TiO2/poly(acrylamide-co-methylenbisacrylamide) nanocomposites was designed for determination of mercury and lead ions at trace levels in environmental samples. The removal and preconcentration of lead and mercury ions on the sorbent was achieved due to sharing an electron pair of N and O groups of polymer chains with the mentioned heavy metal ions. The hydrogel sensor was designed by surface modification of a synthesized TiO2 nanoparticles using methacryloxypropyltrimethoxysilan (MAPTMS), which provided a reactive C=C bond that polymerized the acrylamide and methylenbisacrylamide. The sorbent was characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), EDS analysis and Fourier transform in frared (FT-IR) spectrometer. This nanostructured composite with polymer shell was developed as a sensitive and selective sorbent for adsorption of mercury and lead ions from aqueous solution at optimized condition. This method involves two-steps: (1) preconcentration of mercury and lead ions by the synthesized sorbent and (2) its selective monitoring of the target ions by complexation with dithizone (DZ). The color of the sorbent in the absence and presence of mercury and lead ions shifts from white to violet and red, respectively. The detection limit of the synthesized nanochemosensor for mercury and lead ions was 1 and 10 ?g L(-1), respectively. The method was successfully applied for trace detection of mercury and lead ions in tap, river, and sea water samples. PMID:25497023

Sedghi, Roya; Heidari, Bahareh; Behbahani, Mohammad

2015-03-21

181

Ni(II)NTA AuNPs as a low-resource malarial diagnostic platform for the rapid colorimetric detection of Plasmodium falciparum Histidine-Rich Protein-2.  

PubMed

Diagnosing infectious diseases remains a challenge in the developing world where there is a lack of dependable electricity, running water, and skilled technicians. Although rapid immunochromatographic tests (RDTs) have been deployed to diagnose diseases such as malaria, the extreme climate conditions encountered in these regions compounded with the discrepancies in test manufacturing have yielded varying results, so that more innovative and robust technologies are sought. Devoid of antibodies and thermally sensitive materials, we present a robust, colorimetric diagnostic platform for the detection of a malarial biomarker, Plasmodium falciparum Histidine-Rich Protein 2 (PfHRP-II). The assay exploits the optical properties of gold nanoparticles, covalently coupling them to a Ni(II)NTA recognition element specific for PfHRP-II. In the presence of the recombinant malarial biomarker (rcHRP-II), the Ni(II)NTA AuNPs begin to crosslink and aggregate in as little as one minute, triggering a red-to-purple color change in solution. To increase assay sensitivity and platform stability suitable for low-resource regions, the Ni(II)NTA AuNPs were assembled with varying spacer ligands in a mixed monolayer presentation. When assembled with a negatively charged Peg4-thiol ligand, the Ni(II)NTA AuNPs demonstrate low nanomolar limits of rcHRP-II detection in physiological concentrations of human serum albumin and maintain excellent stability at 37°C when stored for four weeks. Detection of the malaria biomarker is also measured by capturing and processing images of aggregated gold nanoparticles with a smartphone camera. By utilizing a smartphone camera and image processing application, there is no significant difference in assay sensitivity and rcHRP-II limit of detection in comparison to a spectrophotometer, further making this diagnostic platform applicable for use in low-resource regions. PMID:25640131

Gulka, Christopher P; Swartz, Joshua D; Wright, David W

2015-04-01

182

One-tube loop-mediated isothermal amplification combined with restriction endonuclease digestion and ELISA for colorimetric detection of resistance to isoniazid, ethambutol and streptomycin in Mycobacterium tuberculosis isolates.  

PubMed

In this study, we designed a simple and rapid colorimetric detection method, a one-tube loop-mediated isothermal amplification (LAMP)-PCR-hybridization-restriction endonuclease-ELISA [one-tube LAMP-PCR-HY-RE-ELISA] system, to detect resistance to isoniazid, ethambutol and streptomycin in strains of Mycobacterium tuberculosis isolated from clinical specimens. The clinical performance of this method for detecting isoniazid-resistant, ethambutol-resistant and streptomycin-resistant isolates of M. tuberculosis showed 98.9%, 94.3% and 93.8%, respectively. This assay is rapid and convenient that can be performed within one working day. One-tube LAMP-PCR-HY-RE-ELISA system was designed based on hot spot point mutations in target drug-resistant genes, using LAMP-PCR, hybridization, digestion with restriction endonuclease and colorimetric method of ELISA. In this study, LAMP assay was used to amplify DNA from drug-resistant M. tuberculosis, and ELISA was used for colorimetrical determination. This assay will be a useful tool for rapid diagnosis of mutant codons in strains of M. tuberculosis for isoniazid at katG 315 and katG 463, ethambutol at embB 306 and embB 497, and streptomycin at rpsL 43. PMID:20673837

Lee, Mei-Feng; Chen, Yen-Hsu; Hsu, Hui-Jine; Peng, Chien-Fang

2010-10-01

183

Novel colorimetric sensor for oral malodour  

Microsoft Academic Search

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

Nethaji Alagirisamy; Sarita S. Hardas; Sujatha Jayaraman

2010-01-01

184

Direct dark matter detection: The diurnal variation in directional experiments  

E-print Network

We present some theoretical results relevant to the direct dark matter detection experiments, paying particular attention to directional experiments, i.e. experiments in which, not only the energy but the direction of the recoiling nucleus is observed. In directional experiments the detection rate depends on the angle between the line observation and the sun's direction of motion. Since, however, the direction of observation is fixed with respect the earth, while the Earth is rotating around its axis, in a directional experiment the angle between the direction of observation and the Sun's direction of motion will change during the day. So the observed signal in such experiments will exhibit a very interesting and characteristic periodic diurnal variation.

Vergados, J D

2010-01-01

185

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

186

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

187

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

188

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of some fluoroquinolone antibacterials using ammonium reineckate  

NASA Astrophysics Data System (ADS)

Three accurate, rapid and simple atomic absorption spectrometric (AAS), conductometric and colorimetric methods were developed for the determination of gatifloxacin (GTF), moxifloxacin (MXF) and sparfloxacin (SPF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at ?max 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone. The optimizations of various experimental conditions were described. Optimum concentration ranges for the determination of GTF, MXF and SPF were 5.0-150, 40-440 ?g mL -1 and 0.10-1.5 mg mL -1 using atomic absorption (AAS), conductometric and colorimetric methods, respectively. Detection and quantification limits are ranges from 1.5 to 2.3 ?g mL -1 using AAS method or 30-45 ?g mL -1 using colorimetric method. The proposed procedures have been applied successfully to the analysis of these drugs in pharmaceutical formulations and the results are favourably comparable to the reference methods.

Al-Ghannam, Sheikha M.

2008-04-01

189

Comparison of colorimetric, fluorescent, and enzymatic amplification substrate systems in an enzyme immunoassay for detection of DNA-RNA hybrids.  

PubMed Central

The monoclonal antibody solution hybridization assay is a novel enzyme immunoassay for detection of RNA with a biotinylated DNA probe. To increase the sensitivity of this test, a fluorescent substrate and an enzymatic amplification cycling system were compared with a conventional colorigenic substrate for alkaline phosphatase. The fluorescent, cycling, and colorigenic substrates detected, respectively, 10, 10, and 100 amol of unbound alkaline phosphatase in 2 h. With a prolonged incubation period of 16.6 h, the conventional substrate measured 10 amol of the enzyme. In the immunoassay for RNA detection, the fluorescence and cycling assays were faster than that using the colorigenic substrate and reached an endpoint sensitivity of 3.2 pg/ml (0.16 pg per assay) of cRNA. However, longer incubation periods (16.6 h) for optimal generation of the colorigenic product led to a comparable level of sensitivity for the conventional substrate. PMID:2473088

Coutlee, F; Viscidi, R P; Yolken, R H

1989-01-01

190

[3] DIRECT DETECTION OF SINGLET OXYGEN 41 [3] Direct Detection of Singlet Oxygen via Its  

E-print Network

[3] DIRECT DETECTION OF SINGLET OXYGEN 41 [3] Direct Detection of Singlet Oxygen via Its be detected directly by its emission (phosphorescence), although this emission is extremely weak due to spin- fer from tO2 to the O-H vibrations in water molecules and by partial reabsorption of the emitted

Daub, Margaret

191

Pd/V.sub.2O.sub.5 device for colorimetric H.sub.2 detection  

DOEpatents

A sensor structure for chemochromic optical detection of hydrogen gas over a wide response range, that exhibits stability during repeated coloring/bleaching cycles upon exposure and removal of hydrogen gas, comprising: a glass substrate (20); a vanadium oxide layer (21) coated on the glass substrate; and a palladium layer (22) coated on the vanadium oxide layer.

Liu, Ping (San Diego, CA); Tracy, C. Edwin (Golden, CO); Pitts, J. Roland (Lakewood, CO); Smith, II, R. Davis (Golden, CO); Lee, Se-Hee (Lakewood, CO)

2008-09-02

192

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

193

Novel antibody/gold nanoparticle/magnetic nanoparticle nanocomposites for immunomagnetic separation and rapid colorimetric detection of Staphylococcus aureus in milk.  

PubMed

We demonstrated the new antibody/gold nanoparticle/magnetic nanoparticle nanocomposites (antibody/AuNP/MNPs) and their application in the detection of the foodborne pathogen, Staphylococcus aureus (S. aureus), in milk. The nanocomposites were synthesized by coating the MNPs with bovine serum albumin (BSA) then adsorbing the AuNPs and anti-S. aureus antibodies on their surface. Using the completed immunomagnetic nanostructures, S. aureus inoculated in the milk sample was captured and isolated from the medium using the permanent magnet. The nanoparticle-bound cells as well as the unbound cells in the supernatant were enumerated via surface plating to evaluate the target binding capacity of the nanocomposites. The capture efficiencies of the antibody/AuNP/MNPs were 96% and 78% for S. aureus in PBS and the milk sample respectively, which were significantly higher than those of the antibody-coupled MNPs without any AuNP. The captured cells were also applied to the selective filtration system to produce color signals that were used for the detection of the target pathogen. During the filtration, the cells bound to the antibody/AuNP/MNPs remained on the surface of the membrane filter while unbound nanoparticles passed through the uniform pores of the membrane. After the gold enhancement, the cells-particles complex resting on the membrane surface rendered a visible color, and the signal intensity became higher as the target cell concentration increased. The detection limits of this colorimetric sensor were 1.5×10(3) and 1.5×10(5)CFU for S. aureus in PBS and the milk sample respectively. This sensing mechanism also had the high specificity for S. aureus over the other pathogens such as Escherichia coli, Listeria monocytogenes, and Salmonella enterica. The assay required only 40min to obtain the results. With the use of the appropriate antibodies, our immunomagnetic nanocomposites-based detection strategy can provide an easy, convenient, and rapid sensing method for a wide range of pathogens. PMID:23370174

Sung, Yun Ju; Suk, Ho-Jun; Sung, Hwa Young; Li, Taihua; Poo, Haryoung; Kim, Min-Gon

2013-05-15

194

Colorimetric and ratiometric fluorescent detection of sulfite in water via cationic surfactant-promoted addition of sulfite to ?,?-unsaturated ketone.  

PubMed

Three fluorescent probes were constructed by incorporating an ?,?-unsaturated ketone to a coumarin fluorophore. The selective addition of sulfite to the alkene of TSP assisted by cetyltrimethyl ammonium bromide (CTAB) micelle can be visualized by dramatic color and ratiometric fluorescence changes. In CTAB-PBS system, the fluorescence intensity ratio at 465 nm and 592 nm (I465/I592) and the absorbance ratio at 390 nm and 470 nm (A390/A470) were linearly proportional to sulfite concentration in the range of 0.5-150 ?M, and the detection limit was 0.2 ?M. Good selectivity and competition of TSP1 towards sulfite over several anions and biological thiols were acquired. Probe TSP1 was used to detect sulfite in three realistic samples (mineral water, sugar and white wine) with good recovery. PMID:23845496

Tian, Haiyu; Qian, Junhong; Sun, Qian; Bai, Hongyan; Zhang, Weibing

2013-07-25

195

Silver-ion-mediated DNAzyme switch for the ultrasensitive and selective colorimetric detection of aqueous Ag+ and cysteine.  

PubMed

Two states, two applications! An Ag(+)-mediated DNAzyme switch has been designed to detect Ag(+) and cysteine with high sensitivity and selectivity. In the closed state, Ag(+) turns on the switch through the formation of cytosine-Ag(+)-cytosine base pairs, whereas adding cysteine turns off the open switch because it competitively binds to Ag(+). This feature endows the DNAzyme switch with two sensing applications. PMID:19222076

Li, Tao; Shi, Lili; Wang, Erkang; Dong, Shaojun

2009-01-01

196

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

197

Direct Detection of Electron Backscatter Diffraction Patterns  

NASA Astrophysics Data System (ADS)

We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data.

Wilkinson, Angus J.; Moldovan, Grigore; Britton, T. Benjamin; Bewick, Angus; Clough, Robert; Kirkland, Angus I.

2013-08-01

198

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

199

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

200

Colorimetric elastase sensor with peptide conjugated cellulose nanocrystals is interfaced to dialysis membranes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Clinical detection of human neutrophil elastase (HNE) as point of care biomarker or in situ colorimetric adjuvant to chronic wound dressings presents potential advantages in the management of chronic wounds. A colorimetric approach to the detection of HNE using cotton cellulose nanocrystals (CCN) i...

201

Field evaluation of the direct detection of multidrug resistant Mycobacterium tuberculosis by nitrate reductase assay on 7H11 agar.  

PubMed

In this study we evaluated the performance of colorimetric nitrate reductase assay (NRA) on Middlebrook 7H11 agar instead of Lowenstein-Jensen medium for detection of isoniazid (INH) and rifampin (RIF) resistance directly on 114 smear positive sputum specimens and compared the results with direct proportion method on LJ medium. The results of both methods were in 100% agreement for detection of RIF resistance while agreement for INH was 96.4%. The average turnaround time for NRA was 18.6 days and majority of the specimens gave positive results within 21 days. Thus direct NRA testing on smear positive sputum specimens by using 7H11 agar could be used as a fast, reliable and inexpensive method in resource starved settings. PMID:23507185

Satti, Luqman; Ikram, Aamer; Palomino, Juan Carlos; Martin, Anandi; Khan, Farooq Ahmad

2013-05-01

202

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

203

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

204

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 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 (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.

Ciaran A. J. O'Hare; Anne M. Green

2014-11-11

205

Directional detection of dark matter streams  

NASA Astrophysics Data System (ADS)

Directional detection of weakly interacting massive particles, in which the energies and directions of the recoiling nuclei are measured, currently presents the only prospect for probing the local 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 analyze 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 nonparametric directional statistics, a profile likelihood ratio test and Bayesian parameter inference we find that within acceptable exposure times [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.; Green, Anne M.

2014-12-01

206

Modification of a colorimetric method for histamine analysis in fish meal  

Microsoft Academic Search

This study describes the modifications necessary to apply the colorimetric method for histamine detection in fish meal. Although the original colorimetric method works well with fish flesh, diÅculties were observed during filtration of the homogenised sample and column separation when it was applied to fish meal. In this study, the reason for the problems encountered was studied by processing fish

Sevim Kose; George Hall

207

Modification of a colorimetric method for histamine analysis in fish meal  

Microsoft Academic Search

This study describes the modifications necessary to apply the colorimetric method for histamine detection in fish meal. Although the original colorimetric method works well with fish flesh, difficulties were observed during filtration of the homogenised sample and column separation when it was applied to fish meal. In this study, the reason for the problems encountered was studied by processing fish

Sevim Köse; George Hall

2000-01-01

208

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

209

Dark Matter Direct Detection and Lhc Searches  

NASA Astrophysics Data System (ADS)

Direct detection experiments are reporting intriguing indications of a possible dark matter signal, the most noticeable case being the annual modulation effect observed by the DAMA experiments. A relevant interpretation of these results is in terms of light neutralino dark matter, arising in supersymmetric models where gaugino universality is broken. These supersymmetric models possess specific features that differentiate them from more typical supersymmetric scenarios and that can be tested at the LHC.

Fornengo, N.

2015-01-01

210

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

211

Community detection in directed acyclic graphs  

E-print Network

Some temporal networks, most notably citation networks, are naturally represented as directed acyclic graphs (DAGs). To detect communities in DAGs, we propose a modularity for DAGs by defining an appropriate null model (i.e., randomized network) respecting the order of nodes. We implement a spectral method to approximately maximize the proposed modularity measure and test the method on citation networks and other DAGs. We find that the attained values of the modularity for DAGs are similar for partitions that we obtain by maximizing the proposed modularity (designed for DAGs), the modularity for undirected networks and that for general directed networks. In other words, if we neglect the order imposed on nodes (and the direction of links) in a given DAG and maximize the conventional modularity measure, the obtained partition is close to the optimal one in the sense of the modularity for DAGs.

Speidel, Leo; Masuda, Naoki

2015-01-01

212

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

PubMed Central

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 transport chain). We demonstrated using earthly soils that the identification of extracted components of electron transport chains is useful for remote detection of a chemical signature of life. The instrument package developed used supercritical carbon dioxide for soil extraction, followed by chromatography or electrophoresis to separate extracted compounds, with final detection by voltammetry and tandem mass-spectrometry. Results Here we used Earth-derived soils to develop a related life detection system based on direct observation of a biological redox signature. We measured the ability of soil microbial communities to reduce artificial electron acceptors. Living organisms in pure culture and those naturally found in soil were shown to reduce 2,3-dichlorophenol indophenol (DCIP) and the tetrazolium dye 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT). Uninoculated or sterilized controls did not reduce the dyes. A soil from Antarctica that was determined by chemical signature and DNA analysis to be sterile also did not reduce the dyes. Conclusion Observation of dye reduction, supplemented with extraction and identification of only a few specific signature redox-active biochemicals such as porphyrins or quinones, provides a simplified means to detect a signature of life in the soils of other planets or their moons. PMID:12150716

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

2002-01-01

213

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

214

Determination of Oseltamivir Quality by Colorimetric and Liquid Chromatographic Methods  

PubMed Central

We developed a colorimetric and chromatographic assay for oseltamivir to assess the authenticity of Tamiflu (F. Hoffmann-La Roche Ltd., Basel, Switzerland) because of a growing concern about counterfeit oseltamivir. The colorimetric assay is quantitative and relies on an extractable colored ion-pair complex of oseltamivir with Congo red or bromochlorophenol blue. The reverse-phase chromatographic assay uses an alkaline mobile phase with UV detection. Both methods were evaluated for variability and selectivity and subsequently applied to batches of oseltamivir products acquired through the Internet. The Congo red test showed greater assay sensitivity, linearity, and accuracy. Colorimetric and chromatographic analysis showed all batches of oseltamivir product were within ±15% of the stated amount of active ingredient. PMID:18394271

Nettey, Henry; Wirtz, Robert A.

2008-01-01

215

Bayesian analysis of multiple direct detection experiments  

NASA Astrophysics Data System (ADS)

Bayesian methods offer a coherent and efficient framework for implementing uncertainties into induction problems. In this article, we review how this approach applies to the analysis of dark matter direct detection experiments. In particular we discuss the exclusion limit of XENON100 and the debated hints of detection under the hypothesis of a WIMP signal. Within parameter inference, marginalizing consistently over uncertainties to extract robust posterior probability distributions, we find that the claimed tension between XENON100 and the other experiments can be partially alleviated in isospin violating scenario, while elastic scattering model appears to be compatible with the frequentist statistical approach. We then move to model comparison, for which Bayesian methods are particularly well suited. Firstly, we investigate the annual modulation seen in CoGeNT data, finding that there is weak evidence for a modulation. Modulation models due to other physics compare unfavorably with the WIMP models, paying the price for their excessive complexity. Secondly, we confront several coherent scattering models to determine the current best physical scenario compatible with the experimental hints. We find that exothermic and inelastic dark matter are moderatly disfavored against the elastic scenario, while the isospin violating model has a similar evidence. Lastly the Bayes' factor gives inconclusive evidence for an incompatibility between the data sets of XENON100 and the hints of detection. The same question assessed with goodness of fit would indicate a 2 ? discrepancy. This suggests that more data are therefore needed to settle this question.

Arina, Chiara

2014-12-01

216

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

217

A colorimetric and smartphone readable method for uracil-DNA glycosylase detection based on the target-triggered formation of G-quadruplex.  

PubMed

A simple, visible and smartphone readable strategy for the sensitive detection of uracil-DNA glycosylase (UDG) activity has been developed. This is based on the UDG-catalyzed removal of uracil bases, which induces the formation of a G-quadruplex-cofactor complex. The guanine-rich DNA probe can form a special G-quadruplex structure with hemin to display peroxidase activity and catalyze the H2O2-mediated oxidation of ABTS(2-) to the colored ABTS?(-), providing a visible signal for UDG detection. The proposed sensing platform exhibits a good linear response to UDG concentrations ranging from 0.008 to 0.2 U mL(-1), with a low detection limit of 0.008 U mL(-1). Based on the theory of chromatics, we can directly read out the color value using a smartphone app to reflect the content of UDG with high resolution, providing a new vision for the portable assay strategy. Furthermore, the utility of this method for screening potential UDG inhibitors has also been demonstrated. PMID:25713817

Nie, Huaijun; Wang, Wei; Li, Wang; Nie, Zhou; Yao, Shouzhuo

2015-03-30

218

Directly detecting exozodiacal dust and disk variability  

NASA Astrophysics Data System (ADS)

Dust is common throughout stellar systems. The architecture of stellar systems may be typically comprised of a distant cold debris disk, a warm exozodiacal disk, and a hot inner disk. Dust in this exozodiacal region confounds exoplanet detections by scattering light or mimicking planetary emission. This environment must be well-modelled in order to find Earth-sized exoplanets. Interferometry at the Center for High Resolution Astronomy (CHARA) Array provides the angular resolution to directly detect near-infrared (NIR) excesses originating from warm and hot dust close to the host star. The recently upgraded Fiber-Linked Unit for Optical Recombination (JouFLU) is capable of measuring interferometric visibility contrasts to a precision of <0.1% and dust disk fluxes equal to 1% of the host star. There is likely a connection between these hot interferometrically detected dust disks and the harder-to-detect warm zodiacal dust analogues. In this way interferometric studies can observe the tip-of-the-iceberg of stellar system dust, providing details such as composition and grain size of dust, as well as statistics on the correlation of dust populations and stellar properties. These inner dust regions may exhibit a high degree of variability which should also be characterized and may give hint to the dust origin and replenishment mechanisms. JouFLU is currently involved in a large survey of exozodiacal dust stars of spectral types A through K with the aim to provide statistics about dust disk occurrence in relation to their host stars and the presence of cold dust reservoirs. Complementing this survey is a project of re-observing the earliest excess detections in order to determine their variability. In addition, NASA's InfraRed Telescope Facility (IRTF) provides a method for spectrophotometric detections of excess stellar flux corresponding to the presence of hot/warm exozodiacal dust. Multiple NIR interferometric instruments as well as medium resolution spectroscopy are a sensitive and affordable method of discovering inner disks and characterizing nearby habitable zone environments.

Scott, Nicholas J.

2015-01-01

219

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

220

The Earth's velocity for direct detection experiments  

NASA Astrophysics Data System (ADS)

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.

McCabe, Christopher

2014-02-01

221

Direct fast neutron detection: A status report  

SciTech Connect

This report describes the status of efforts to develop direct fast-neutron detection via proton recoil within plastic scintillator. Since recording proton recoil events is of little practical use without a means to discriminate effectively against gamma-ray interactions, the present effort is concentrated on demonstrating a method that distinguishes between pulse types. The proposed method exploits the different pulse shapes that are to be expected primarily on the basis of the slower speed of the recoiling fission neutrons. Should this effort ultimately prove successful, the resulting novel technology will have the potential to significantly lower cost and increase capability for a number of critical neutron-detection applications. Considerable progress has been made toward a clear and compelling demonstration of this new technique. An exhaustive theoretical and numerical investigation of the method has been completed. The authors have been able to better understand the laboratory results and estimate the performance that could ultimately be achieved using the proposed technique. They have assessed the performance of a number of different algorithms for discriminating between neutron and gamma ray events. The results of this assessment will be critical when the construction of low-cost, field-portable neutron detectors becomes necessary. Finally, a laboratory effort to realize effective discrimination is well underway and has resulted in partial success.

Peurrung, A.J.; Hansen, R.R.; Craig, R.A.; Hensley, W.K.; Hubbard, C.W.; Keller, P.E.; Reeder, P.L.; Sunberg, D.S.

1997-12-01

222

MEMS and the direct detection of exoplanets  

NASA Astrophysics Data System (ADS)

Deformable mirrors, and particularly MEMS, are crucial components for the direct imaging of exoplanets for both ground-based and space-based instruments. Without deformable mirrors, coronagraphs are incapable of reaching contrasts required to image Jupiter-like planets. The system performance is limited by image quality degradation resulting from wavefront error introduced from multiple effects including: atmospheric turbulence, static aberrations in the system, non-common-path aberrations, all of which vary with time. Correcting for these effects requires a deformable mirror with fast response and numerous actuators having moderate stroke. Not only do MEMS devices fulfill this requirement but their compactness permits their application in numerous space- and ground-based instruments, which are often volume- and mass-limited. In this paper, I will briefly explain how coronagraphs work and their requirements. I then will discuss the Extreme Adaptive Optics needed to compensate for the introduced wavefront error and how MEMS devices are a good choice to achieve the performance needed to produce the contrasts necessary to detect exoplanets. As examples, I will discuss a facility instrument for the Gemini Observatory, called the Gemini Planet Imager, that will detect Jupiter-like planets and present recent results from the NASA Ames Coronagraph Experiment laboratory, in the context of a proposed space- based mission called EXCEDE. EXCEDE is planned to focus on protoplanetary disks.

Thomas, Sandrine J.; Macintosh, Bruce; Belikov, Ruslan

2014-03-01

223

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

224

Study on direction detection of automobile headlamp beam  

Microsoft Academic Search

The beam direction is one of the important items of headlamp detection, but lots of internal detection machines can not give it an accurate detection. This article analyses the factors which affect the detection result, then gives a new accurate solution. It uses an automobile position fixing system and data correction algorithm. Firstly, the beam direction angle and the automobile's

Ying Yun; Shu-Guang Dai; Pning-An Mu; Lin Wang

2009-01-01

225

A smartphone-based colorimetric reader for bioanalytical applications using the screen-based bottom illumination provided by gadgets.  

PubMed

A smartphone-based colorimetric reader (SBCR) was developed using a Samsung Galaxy SIII mini, a gadget (iPAD mini, iPAD4 or iPhone 5s), integrated with a custom-made dark hood and base holder assembly. The smartphone equipped with a back camera (5 megapixels resolution) was used for colorimetric imaging via the hood and base-holder assembly. A 96- or 24-well microtiter plate (MTP) was positioned on the gadget's screensaver that provides white light-based bottom illumination only in the specific regions corresponding to the bottom of MTP's wells. The pixel intensity of the captured images was determined by an image processing algorithm. The developed SBCR was evaluated and compared with a commercial MTP reader (MTPR) for three model assays: our recently developed human C-reactive protein sandwich enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase direct ELISA, and bicinchoninic acid protein estimation assay. SBCR had the same precision, dynamic range, detection limit and sensitivity as MTPR for all three assays. With advanced microfabrication and data processing, SBCR will become more compact, lighter, inexpensive and enriched with more features. Therefore, SBCR with a remarkable computing power could be an ideal point-of-care (POC) colorimetric detection device for the next-generation of cost-effective POC diagnostics, immunoassays and diversified bioanalytical applications. PMID:25168283

Vashist, Sandeep Kumar; van Oordt, Thomas; Schneider, E Marion; Zengerle, Roland; von Stetten, Felix; Luong, John H T

2015-05-15

226

Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors  

PubMed Central

Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

Wang, Hui; Zhang, Ke-Qin

2013-01-01

227

NULLING INTERFEROMETRY for direct exo-planet detection  

E-print Network

#12;NULLING INTERFEROMETRY for direct exo-planet detection #12;#12;NULLING INTERFEROMETRY for direct exo-planet detection Proefschrift ter verkrijging van de graad van doctor aan de Technische of Chios, 4th century B.C.. #12;Cover: One possible method to detect Earth-like planets around distant

228

Failure of direction discrimination at detection threshold for both fast  

E-print Network

Failure of direction discrimination at detection threshold for both fast and slow chromatic motion West, H 4-14, Montreal, Quebec, H3A 1A1 Canada Received April 20, 1998; accepted June 30, 1998; revised at detection threshold, whereas at higher temporal rates detection and direction discrimination threshold

Mullen, Kathy T.

229

Molecular diagnosis of ?-thalassemias by the colorimetric nanogold.  

PubMed

A new application of gold nanoparticles (AuNPs) as a colorimetric method for gene detection of ?-thalassemia 1 (SEA deletion) is reported here for the first time. This technique is based on color changes from salt-induced aggregation of un-hybridized nanogold probes after hybridization with the target DNA. Specific DNA probes were synthesized, thiol modified and conjugated on the surface of AuNPs. The target DNA was amplified and hybridized with the AuNPs-immobilized probe. Salt solution (NaCl) was added to induce aggregation of the un-hybridized nanogold probes. The color changes were visualized either by the naked eye or by UV-vis spectrophotometry at 520 nm. By this nanogold colorimetric method samples carrying normal ?-globin genes could be successfully identified from samples carrying ?-globin genes causing ?-thalassemia 1 (SEA deletion), either as a carrier or disease form. Results demonstrated that the new colorimetric nanogold method is a definite gene diagnosis of ?-thalassemia. It is accurate, simple, rapid, specific, sensitive, and cost effective. It is also a promising point-of-care testing (POCT) method for thalassemias and other genetic disorders. The new colorimetric nanogold is a method of choice for areas where access to sophisticated molecular diagnosis is limited. PMID:24383063

Chomean, Sirinart; Wangmaung, Nantawan; Sritongkham, Pornpimol; Promptmas, Chamras; Mas-Oodi, Sumana; Tanyong, Dalina; Ittarat, Wanida

2014-02-21

230

Engineering of the heme pocket of an H-NOX domain for direct cyanide detection and quantification.  

PubMed

A new cyanide sensing system, the Heme-Nitric oxide and/or OXygen binding domain (H-NOX domain) from Thermoanaerobacter tengcongensis (Tt H-NOX), has been investigated. With straightforward absorbance-based detection, we have achieved a cyanide detection limit of 0.5 microM (approximately 10 ppb) with an upper detection range that is adjustable with protein concentration. We find a linear correlation of multiple spectroscopic features with cyanide concentration. These spectroscopic features include the Soret band maximum and absorbance changes in both the Soret and alpha/beta band regions of the spectrum. Multiple probes for cyanide detection makes sensing with Tt H-NOX unique compared to other cyanide sensing methods. Furthermore, using site-directed mutagenesis, we have rationally engineered the heme pocket of Tt H-NOX to improve its cyanide sensing properties. Using a mutant that alters the heme structure of Tt H-NOX (P115A) we were able to introduce colorimetric detection of cyanide. Through substituting phenylalanine 78 with a smaller (valine, F78V) or a larger residue (tyrosine, F78Y), we demonstrate a correlation with distal pocket steric crowding and affinity for cyanide. In particular, F78V Tt H-NOX shows a significant increase in CN(-) binding affinity and selectivity. Thus, we demonstrate the ability to fine-tune the affinity and specificity of Tt H-NOX for cyanide, suggesting that Tt H-NOX can be readily tailored into a practical cyanide sensor. PMID:20684546

Dai, Zhou; Boon, Elizabeth M

2010-08-25

231

Colorimetric alamarBlue assay as a bacterial concentration and spoilage index of marine foods  

Microsoft Academic Search

The alamarBlue (resazurin) assay incorporates a colorimetric and fluorometric growth indicator based on detection of the metabolic activity of cells. We investigated the relationship between results of the colorimetric alamarBlue assay using 96-well microplates and colony-forming units (CFU) on aerobic agar plates of Escherichia coli, Staphylococcus aureus, Bacillus subtilis strains and unknown bacterial flora in spoiled foods. As bacteria grew

Takashi Kuda; Toshihiro Yano

2003-01-01

232

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

233

Indirect detection of radiation sources through direct detection of radiolysis products  

DOEpatents

A system for indirectly detecting a radiation source by directly detecting radiolytic products. The radiation source emits radiation and the radiation produces the radiolytic products. A fluid is positioned to receive the radiation from the radiation source. When the fluid is irradiated, radiolytic products are produced. By directly detecting the radiolytic products, the radiation source is detected.

Farmer, Joseph C. (Tracy, CA); Fischer, Larry E. (Los Gatos, CA); Felter, Thomas E. (Livermore, CA)

2010-04-20

234

Colorimetric bacteria sensing using a supramolecular enzyme-nanoparticle biosensor.  

PubMed

Rapid and sensitive detection of pathogens is a key requirement for both environmental and clinical settings. We report here a colorimetric enzyme-nanoparticle conjugate system for detection of microbial contamination. In this approach, cationic gold nanoparticles (NPs) featuring quaternary amine headgroups are electrostatically bound to an enzyme [?-galactosidase (?-Gal)], inhibiting enzyme activity. Analyte bacteria bind to the NP, which releases the ?-Gal and restores its activity, providing an enzyme-amplified colorimetric readout of the binding event. Using this strategy, we have been able to quantify bacteria at concentrations of 1 × 10(2) bacteria/mL in solution and 1 × 10(4) bacteria/mL in a field-friendly test strip format. PMID:21627131

Miranda, Oscar R; Li, Xiaoning; Garcia-Gonzalez, Limary; Zhu, Zheng-Jiang; Yan, Bo; Bunz, Uwe H F; Rotello, Vincent M

2011-06-29

235

Simultaneous direct detection of Shiga-toxin producing Escherichia coli (STEC) strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles  

NASA Astrophysics Data System (ADS)

A simultaneous direct detection of Shiga-toxin producing strains of E. coli (STEC; ``Big Six'' - O26, O45, O103, O111, O121, and O145) as well as O157 strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles (AuNPs) was developed. Initially, conserved regions of stx genes were amplified by asymmetric polymerase chain reaction (asPCR). Pairs of single stranded thiol-modified oligonucleotides (30-mer) were immobilized onto AuNPs and used as probes to capture regions of stx1 (119-bp) and/or stx2 (104-bp) genes from STEC strains. DNA samples from pure cultures and food samples were sandwich hybridized with AuNP-oligo probes at optimal conditions (50 °C, 30 min). A complex was formed from the hybridization of AuNP-probes and target DNA fragments that retained the initial red color of the reaction solutions. For non-target DNA, a color change from red to purplish-blue was observed following an increase in salt concentration, thus providing the basis of simultaneous direct colorimetric detection of target DNA in the samples. Enrichment and pooling systems were incorporated to efficiently process a large number of food samples (ground beef and blueberries) and detection of live targets. The detection limit was <1 log CFU g-1, requiring less than 1 h to complete after DNA sample preparation with 100% specificity. Gel electrophoresis verified AuNP-DNA hybridization while spectrophotometric data and transmission electron microscope (TEM) images supported color discrimination based on the occurrence of molecular aggregation. In conclusion, the significant features of this approach took advantage of the unique colorimetric properties of AuNPs as a low-cost and simple approach yet with high specificity for simultaneous detection of STEC strains.A simultaneous direct detection of Shiga-toxin producing strains of E. coli (STEC; ``Big Six'' - O26, O45, O103, O111, O121, and O145) as well as O157 strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles (AuNPs) was developed. Initially, conserved regions of stx genes were amplified by asymmetric polymerase chain reaction (asPCR). Pairs of single stranded thiol-modified oligonucleotides (30-mer) were immobilized onto AuNPs and used as probes to capture regions of stx1 (119-bp) and/or stx2 (104-bp) genes from STEC strains. DNA samples from pure cultures and food samples were sandwich hybridized with AuNP-oligo probes at optimal conditions (50 °C, 30 min). A complex was formed from the hybridization of AuNP-probes and target DNA fragments that retained the initial red color of the reaction solutions. For non-target DNA, a color change from red to purplish-blue was observed following an increase in salt concentration, thus providing the basis of simultaneous direct colorimetric detection of target DNA in the samples. Enrichment and pooling systems were incorporated to efficiently process a large number of food samples (ground beef and blueberries) and detection of live targets. The detection limit was <1 log CFU g-1, requiring less than 1 h to complete after DNA sample preparation with 100% specificity. Gel electrophoresis verified AuNP-DNA hybridization while spectrophotometric data and transmission electron microscope (TEM) images supported color discrimination based on the occurrence of molecular aggregation. In conclusion, the significant features of this approach took advantage of the unique colorimetric properties of AuNPs as a low-cost and simple approach yet with high specificity for simultaneous detection of STEC strains. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05869k

Quintela, Irwin A.; de Los Reyes, Benildo G.; Lin, Chih-Sheng; Wu, Vivian C. H.

2015-01-01

236

Brief Report: Eye Direction Detection Improves with Development in Autism  

ERIC Educational Resources Information Center

Eye direction detection has been claimed to be intact in autism, but the development of this skill has not been investigated. Eleven children with autism and 11 typically developing children performed a demanding face-to-face eye direction detection task. Younger children with autism demonstrated a deficit in this skill, relative to younger…

Webster, Simon; Potter, Douglas D.

2008-01-01

237

Dark matter direct detection constraints from gauge bosons loops  

NASA Astrophysics Data System (ADS)

While many interactions of dark matter (DM) with the standard model (SM) affect direct detection and LHC searches, there are only a few operators generating annihilation of DM into photons. All of these operators, except four of them, give rise to unsuppressed rates, rendering indirect detection superior to other search strategies. For two of the four effective interactions with velocity-suppressed annihilation cross sections, we identify a new type of loop effect which significantly enhances the associated direct detection rates. As a result, relevant constraints from next-generation direct detection experiments on DM-SM interactions, so far only bounded by the LHC, are obtained.

Crivellin, Andreas; Haisch, Ulrich

2014-12-01

238

Systematic aspects of direct extrasolar planet detection  

NASA Technical Reports Server (NTRS)

Using the first optical observatory in space, the Hubble Space Telescope, images of possible extrasolar planets will have poor contrast against the background of diffracted and scattered starlight. The very long exposure time required to achieve an adequate signal-to-noise ratio will make their detection infeasible. For a future telescope, a 16-fold increase in either the smoothness of the collecting area of the optics would reduce the exposure time to a tolerable value, but the contrast would remain low and the required photometric precision high. In this situation, the feasibility of detection would be contingent on the careful identification and control of systematic errors.

Brown, Robert A.

1988-01-01

239

Simultaneous direct detection of Shiga-toxin producing Escherichia coli (STEC) strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles.  

PubMed

A simultaneous direct detection of Shiga-toxin producing strains of E. coli (STEC; "Big Six" - O26, O45, O103, O111, O121, and O145) as well as O157 strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles (AuNPs) was developed. Initially, conserved regions of stx genes were amplified by asymmetric polymerase chain reaction (asPCR). Pairs of single stranded thiol-modified oligonucleotides (30-mer) were immobilized onto AuNPs and used as probes to capture regions of stx1 (119-bp) and/or stx2 (104-bp) genes from STEC strains. DNA samples from pure cultures and food samples were sandwich hybridized with AuNP-oligo probes at optimal conditions (50 °C, 30 min). A complex was formed from the hybridization of AuNP-probes and target DNA fragments that retained the initial red color of the reaction solutions. For non-target DNA, a color change from red to purplish-blue was observed following an increase in salt concentration, thus providing the basis of simultaneous direct colorimetric detection of target DNA in the samples. Enrichment and pooling systems were incorporated to efficiently process a large number of food samples (ground beef and blueberries) and detection of live targets. The detection limit was <1 log CFU g(-1), requiring less than 1 h to complete after DNA sample preparation with 100% specificity. Gel electrophoresis verified AuNP-DNA hybridization while spectrophotometric data and transmission electron microscope (TEM) images supported color discrimination based on the occurrence of molecular aggregation. In conclusion, the significant features of this approach took advantage of the unique colorimetric properties of AuNPs as a low-cost and simple approach yet with high specificity for simultaneous detection of STEC strains. PMID:25563863

Quintela, Irwin A; de los Reyes, Benildo G; Lin, Chih-Sheng; Wu, Vivian C H

2015-02-14

240

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. (authors)

Vanier, P. E. [Brookhaven National Laboratory, Bldg. 197C, Upton, NY 11973 (United States); Forman, L. [Ion Focus Technology, 52 Pardam Knoll, Miller Place, 11764 (United States)

2006-07-01

241

Biomolecular Sensing with Colorimetric Vesicles  

Microsoft Academic Search

This chapter summarizes recent studies employing colorimetric vesicle-based systems for biomolecular\\u000a sensing. Vesicular aggregates exhibit an important advantage as a biological sensing platform in that\\u000a they mimic the cell membrane—the site of molecular docking, ligand–receptor binding, and other\\u000a important processes that can be exploited as a means of signal generation. Particularly attractive\\u000a for sensing applications is the use of colour changes visible

Raz Jelinek; Sofiya Kolusheva

242

Performance evaluation of a colorimetric hydrazine dosimeter  

NASA Astrophysics Data System (ADS)

A dosimeter for real-time, colorimetric detection of hydrazine in air has been developed. The passive badge consists of a dosimeter card containing a vanillin solution coated on a thin paper substrate. The active patch consists of a thick cellulose substrate coated with a vanillin solution. When placed in a plastic sample holder attached to a personnel pump, up to 5 L/min can be drawn through the active badge substrate. Through a condensation reaction, vanillin reacts with hydrazine to form a colored product that absorbs in the visible region. The hydrazone formed in the reaction is yellow; its intensity is proportional to the dose. When exposed passively to hydrazine, the experimental detection limit is less than 20 ppb-hrs. Extrapolated results indicate a detection limit of less than 5 ppb-hrs for long sampling periods. Actively sampling of hydrazine vapors gives an experimental detection limit of less than 100 ppb-L at a sample rate of 5 L/min. Relative humidity effects on badge response were minor. High humidity enhanced the color development on the vanillin badge; while low humidity had no effect on badge response. Interference testing of the dosimeters revealed a tobacco smoke interference. Preliminary shelf life tests indicated no decrease in sensitivity to hydrazine when stored at room temperature for 6 months.

Brenner, Karen P.; Rose-Pehrsson, Susan L.

1994-06-01

243

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

2014-12-01

244

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

245

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

246

Selective turn-off phosphorescent and colorimetric detection of mercury(ii) in water by half-lantern platinum(ii) complexes.  

PubMed

The platinum(ii) half-lantern dinuclear complexes [{Pt(bzq)(?-C7H4NS2-?N,S)}2] () and [{Pt(bzq)(?-C7H4NOS-?N,S)}2] () [bzq = benzo[h]quinolinate, C7H4NS2 = 2-mercaptobenzothiazolate, C7H4NOS = 2-mercaptobenzoxazolate] in solution of DMSO-H2O undergo a dramatic color change from yellowish-orange to purple and turn-off phosphorescence in the presence of a small amount of Hg(2+), being discernible by the naked-eye and by spectroscopic methods. Other metal ions as Ag(+), Li(+), Na(+), K(+), Ca(2+), Mg(2+), Ba(2+), Pb(2+), Cd(2+), Zn(2+) and Tl(+) were tested and, even in a big excess, showed no interference in the selective detection of Hg(2+) in water. Job's plot analysis indicated a 1?:?1 stoichiometry in the complexation mode of Hg(2+) by /. The phosphorescence quenching attributed to the formation of [/?:?Hg(2+)] complexes showed binding constants of K = 1.13 × 10(5) M(-1) () and K = 1.99 × 10(4) M(-1) (). The limit of detection has been also evaluated. In addition, dried paper test strips impregnated in DMSO solutions of and can detect concentration of Hg(2+) in water as low as 1 × 10(-5) M for and 5 × 10(-5) M for , making these complexes good candidates to be used as real-time Hg(2+) detectors. The nature of the interaction of the Pt2 half-lantern complex with the Hg(2+) cation, has been investigated by theoretical calculations. PMID:25781389

Sicilia, Violeta; Borja, Pilar; Baya, Miguel; Casas, José M

2015-04-01

247

In house colorimetric reverse hybridisation assay for detection of the mutation most frequently associated with resistance to isoniazid in Mycobacterium tuberculosis.  

PubMed

Mutations in the katG gene have been identified and correlated with isoniazid (INH) resistance in Mycobacterium tuberculosis isolates. The mutation AGC-->ACC (Ser-->Thr) at katG315 has been reported to be the most frequent and is associated with transmission and multidrug resistance. Rapid detection of this mutation could therefore improve the choice of an adequate anti-tuberculosis regimen, the epidemiological monitoring of INH resistance and, possibly, the tracking of transmission of resistant strains. An in house reverse hybridisation assay was designed in our laboratory and evaluated with 180 isolates of M. tuberculosis. It could successfully characterise the katG315 mutation in 100% of the samples as compared to DNA sequencing. The test is efficient and is a promising alternative for the rapid identification of INH resistance in regions with a high prevalence of katG315 mutants. PMID:19820830

Verza, Mirela; Maschmann, Raquel de Abreu; Silva, Márcia Susana Nunes; Dalla Costa, Elis Regina; Ribeiro, Marta Osório; Rosso, Franciele; Suffys, Philip Noel; Tortoli, Enrico; Marcelli, Fiorella; Zaha, Arnaldo; Rossetti, Maria Lucia Rosa

2009-08-01

248

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

249

Self-assembly of graphene oxide with a silyl-appended spiropyran dye for rapid and sensitive colorimetric detection of fluoride ions.  

PubMed

Fluoride ion (F(-)), the smallest anion, exhibits considerable significance in a wide range of environmental and biochemical processes. To address the two fundamental and unsolved issues of current F(-) sensors based on the specific chemical reaction (i.e., the long response time and low sensitivity) and as a part of our ongoing interest in the spiropyran sensor design, we reported here a new F(-) sensing approach that, via assembly of a F(-)-specific silyl-appended spiropyran dye with graphene oxide (GO), allows rapid and sensitive detection of F(-) in aqueous solution. 6-(tert-Butyldimethylsilyloxy)-1',3',3'-trimethylspiro [chromene- 2,2'-indoline] (SPS), a spiropyran-based silylated dye with a unique reaction activity for F(-), was designed and synthesized. The nucleophilic substitution reaction between SPS and F(-) triggers cleavage of the Si-O bond to promote the closed spiropyran to convert to its opened merocyanine form, leading to the color changing from colorless to orange-yellow with good selectivity over other anions. With the aid of GO, the response time of SPS for F(-) was shortened from 180 to 30 min, and the detection limit was lowered more than 1 order of magnitude compared to the free SPS. Furthermore, due to the protective effect of nanomaterials, the SPS/GO nanocomposite can function in a complex biological environment. The SPS/GO nanocomposite was characterized by XPS and AFM, etc., and the mechanism for sensing F(-) was studied by (1)H NMR and ESI-MS. Finally, this SPS/GO nanocomposite was successfully applied to monitoring F(-) in the serum. PMID:24164279

Li, Yinhui; Duan, Yu; Zheng, Jing; Li, Jishan; Zhao, Wenjie; Yang, Sheng; Yang, Ronghua

2013-12-01

250

Detecting Blackholes and Volcanoes in Directed Networks  

E-print Network

In this paper, we formulate a novel problem for finding blackhole and volcano patterns in a large directed graph. Specifically, a blackhole pattern is a group which is made of a set of nodes in a way such that there are only inlinks to this group from the rest nodes in the graph. In contrast, a volcano pattern is a group which only has outlinks to the rest nodes in the graph. Both patterns can be observed in real world. For instance, in a trading network, a blackhole pattern may represent a group of traders who are manipulating the market. In the paper, we first prove that the blackhole mining problem is a dual problem of finding volcanoes. Therefore, we focus on finding the blackhole patterns. Along this line, we design two pruning schemes to guide the blackhole finding process. In the first pruning scheme, we strategically prune the search space based on a set of pattern-size-independent pruning rules and develop an iBlackhole algorithm. The second pruning scheme follows a divide-and-conquer strategy to fur...

Li, Zhongmou; Liu, Yanchi

2010-01-01

251

Direct electrochemical sensor for fast reagent-free DNA detection  

Microsoft Academic Search

A novel reagentless direct electrochemical DNA sensor has been developed using ultrathin films of the conducting polymer polypyrrole doped with an oligonucleotide probe. Our goal was to develop a prototype electrochemical DNA sensor for detection of a biowarfare pathogen, variola major virus. The sensor has been optimized for higher specificity and sensitivity. It was possible to detect 1.6fmol of complementary

Elena Komarova; Matt Aldissi; Anastasia Bogomolova

2005-01-01

252

On the Direct Detection of Dark Matter Annihilation  

E-print Network

We investigate the direct detection phenomenology of a class of dark matter (DM) models in which DM does not directly interact with nuclei, {but rather} the products of its annihilation do. When these annihilation products are very light compared to the DM mass, the scattering in direct detection experiments is controlled by relativistic kinematics. This results in a distinctive recoil spectrum, a non-standard and or even {\\it absent} annual modulation, and the ability to probe DM masses as low as a $\\sim$10 MeV. We use current LUX data to show that experimental sensitivity to thermal relic annihilation cross sections has already been reached in a class of models. Moreover, the compatibility of dark matter direct detection experiments can be compared directly in $E_{min}$ space without making assumptions about DM astrophysics. Lastly, when DM has direct couplings to nuclei, the limit from annihilation to relativistic particles in the Sun can be stronger than that of conventional non-relativistic direct detect...

Cherry, John F; Shoemaker, Ian M

2015-01-01

253

Comparing readout strategies to directly detect dark matter  

NASA Astrophysics Data System (ADS)

Over the past decades, several ideas and technologies have been developed to directly detect weakly interacting massive particles (WIMP) from the galactic halo. All these detection strategies share the common goal of discriminating a WIMP signal from the residual backgrounds. By directly detecting WIMPs, one can measure some or all of the observables associated to each nuclear recoil candidates, such as their energy and direction. In this study, we compare and examine the discovery potentials of each readout strategies from counting only (bubble chambers) to directional detectors (Time Projection Chambers) with 1d-, 2d-, and 3d-sensitivity. Using a profile likelihood analysis, we show that, in the case of a large and irreducible background contamination characterized by an energy distribution similar to the expected WIMP signal, directional information can improve the sensitivity of the experiment by several orders of magnitude. We also found that 1d directional detection is only less effective than a full 3d directional sensitivity by about a factor of 3, or 10 if we assume no sense recognition, still improving by a factor of 2 or more if only the energy of the events is being measured.

Billard, J.

2015-01-01

254

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

255

Gold nanoparticles based colorimetric nanodiagnostics for cancer and infectious diseases  

NASA Astrophysics Data System (ADS)

Traditional in vitro diagnostics requires specialized laboratories and costly instrumentation, both for the amplification of nucleic acid targets (usually achieved by PCR) and for the assay readout, often based on fluorescence. We are developing hybrid nanomaterials-based sensors for the rapid and low-cost diagnosis of various disease biomarkers, for applications in portable platforms for diagnostics at the point-of-care. To this aim, we exploited the size and distancedependent optical properties of gold nanoparticles (AuNPs) to achieve colorimetric detection. Moreover, in order to avoid the complexity of thermal cycles associated to traditional PCR, the design of our systems includes signal amplification schemes, achieved by the use of enzymes (nucleases, helicase) or DNAzymes. Focused on instrument-free and sensitive detection, we carefully combined the intrinsic sensitivity by multivalency of functionalized AuNPs with isothermal and non-stringent enzyme-aided reaction conditions, controlled AuNPs aggregates, universal reporters and magnetic microparticles, the latter used both as a substrate and as a means for the colorimetric detection. We obtained simple and robust assays for the sensitive (pM range or better) naked-eye detection of cancer or infectious diseases (HPV, HCV) biomarkers, requiring no instrumentation except for a simple heating plate. Finally, we are also developing non-medical applications of these bio-nanosensors, such as in the development of on-field rapid tests for the detection of pollutants and other food and water contaminants.

Valentini, Paola; Persano, Stefano; Cecere, Paola; Sabella, Stefania; Pompa, Pier Paolo

2014-03-01

256

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

257

Direct detection of classically undetectable dark matter through quantum decoherence  

NASA Astrophysics Data System (ADS)

Although various pieces of indirect evidence about the nature of dark matter have been collected, its direct detection has eluded experimental searches despite extensive effort. If the mass of dark matter is below 1 MeV, it is essentially imperceptible to conventional detection methods because negligible energy is transferred to nuclei during collisions. Here I propose directly detecting dark matter through the quantum decoherence it causes rather than its classical effects, such as recoil or ionization. I show that quantum spatial superpositions are sensitive to low-mass dark matter that is inaccessible to classical techniques. This provides new independent motivation for matter interferometry with large masses, especially on spaceborne platforms. The apparent dark matter wind we experience as the Sun travels through the Milky Way ensures interferometers and related devices are directional detectors, and so are able to provide unmistakable evidence that decoherence has Galactic origins.

Riedel, C. Jess

2013-12-01

258

Colorimetric chemosensitivity testing using sulforhodamine B.  

PubMed

A colorimetric chemosensitivity test was investigated using sulforhodamine B (SRB), which stains protein synthesized by cells, as an end-point marker. Four cultured cell lines, 9 human tumor xenografts serially transplanted into nude mice, and 14 fresh surgical specimens were subjected to this assay. The optimal conditions for the assay were 3-5 x 10(4) cells per well in a 96-microplate, an SRB concentration of 4%, and an incubation time of more than 10 minutes. When mitomycin C, doxorubicin, cisplatin, and 5-fluorouracil were assessed by the SRB assay, the concentration-effect curves revealed a sharp slope between plateaux at low and high concentrations, suggesting that this assay has an excellent sensitivity which can assess the effect of drugs as "all or none." Although this high sensitivity resulted in good reproducibility of the assay for cultured cell lines, the predictive rate of the SRB assay for the chemosensitivity of human tumor xenografts in vivo was limited to 63.9%. As a result, this SRB assay is thought to be useful for evaluating the chemosensitivity of cultured cells as all or none, since it can assess directly cellular protein synthesis, which is one of the most important parameters of cell renewal, with excellent sensitivity. PMID:8468977

Kubota, T; Takahara, T; Nagata, M; Furukawa, T; Kase, S; Tanino, H; Ishibiki, K; Kitajima, M

1993-02-01

259

Magnetic bead-based colorimetric immunoassay for aflatoxin B1 using gold nanoparticles.  

PubMed

A competitive colorimetric immunoassay for the detection of aflatoxin B1 (AFB) has been established using biofunctionalized magnetic beads (MBs) and gold nanoparticles (GNPs). Aflatoxin B1-bovine serum albumin conjugates (AFB-BSA) modified MBs were employed as capture probe, which could specifically bind with GNP-labeled anti-AFB antibodies through immunoreaction, while such specific binding was competitively inhibited by the addition of AFB. After magnetic separation, the supernatant solution containing unbound GNPs was directly tested by UV-Vis spectroscopy. The absorption intensity was directly proportional to the AFB concentration. The influence of GNP size, incubation time and pH was investigated in detail. After optimization, the developed method could detect AFB in a linear range from 20 to 800 ng/L, with the limit of detection at 12 ng/L. The recoveries for spiked maize samples ranged from 92.8% to 122.0%. The proposed immunoassay provides a promising approach for simple, rapid, specific and cost-effective detection of toxins in the field of food safety. PMID:25405511

Wang, Xu; Niessner, Reinhard; Knopp, Dietmar

2014-01-01

260

Magnetic Bead-Based Colorimetric Immunoassay for Aflatoxin B1 Using Gold Nanoparticles  

PubMed Central

A competitive colorimetric immunoassay for the detection of aflatoxin B1 (AFB) has been established using biofunctionalized magnetic beads (MBs) and gold nanoparticles (GNPs). Aflatoxin B1-bovine serum albumin conjugates (AFB-BSA) modified MBs were employed as capture probe, which could specifically bind with GNP-labeled anti-AFB antibodies through immunoreaction, while such specific binding was competitively inhibited by the addition of AFB. After magnetic separation, the supernatant solution containing unbound GNPs was directly tested by UV-Vis spectroscopy. The absorption intensity was directly proportional to the AFB concentration. The influence of GNP size, incubation time and pH was investigated in detail. After optimization, the developed method could detect AFB in a linear range from 20 to 800 ng/L, with the limit of detection at 12 ng/L. The recoveries for spiked maize samples ranged from 92.8% to 122.0%. The proposed immunoassay provides a promising approach for simple, rapid, specific and cost-effective detection of toxins in the field of food safety. PMID:25405511

Wang, Xu; Niessner, Reinhard; Knopp, Dietmar

2014-01-01

261

Highly selective colorimetric sensing of Cu(II) ions in aqueous solution via modulation of intramolecular charge transfer transition of aminonaphthoquinone chemosensor.  

PubMed

An aminonaphthoquinone based colorimetric chemosensor has been developed and demonstrated for the highly selective detection of Cu(II) ions in aqueous solution. The intramolecular charge transfer (ICT) transition exits in amine moiety directly attached to the quinone ring is modulated by the d-d transition of a square planar Cu(II)-receptor complex resulting in a change of color from yellow to blue. No significant color change was observed upon addition of other selected metal ions. The sensing property has been investigated using various spectral techniques (UV-Vis, fluorescence) and product analysis (Elemental analysis, magnetic moment, UV-Vis, FT-IR, EPR). PMID:22750343

Madhupriya, Selvaraj; Elango, Kuppanagounder P

2012-11-01

262

Rapid colorimetric screening test for ?-hydroxybutyric acid (liquid X) in human urine  

Microsoft Academic Search

A rapid colorimetric test for the detection of ?-hydroxybutyric acid (GHB) is described. The ferric hydroxamate test for ester detection has been adapted to detect GHB in human urine samples from a healthy female and a healthy male subject. The assay can be performed within 5min and with a GHB detection limit of 0.5mg\\/ml when 0.3ml of human urine is

William C Alston; Karno Ng

2002-01-01

263

Fault detection of multivariable system using its directional properties  

E-print Network

A novel algorithm for making the combination of outputs in the output zero direction of the plant always equal to zero was formulated. Using this algorithm and the result of MacFarlane and Karcanias, a fault detection scheme was proposed which...

Pandey, Amit Nath

2006-04-12

264

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

265

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

266

Comparison of direct and heterodyne detection optical intersatellite communication links  

NASA Technical Reports Server (NTRS)

The performance of direct and heterodyne detection optical intersatellite communication links are evaluated and compared. It is shown that the performance of optical links is very sensitive to the pointing and tracking errors at the transmitter and receiver. In the presence of random pointing and tracking errors, optimal antenna gains exist that will minimize the required transmitter power. In addition to limiting the antenna gains, random pointing and tracking errors also impose a power penalty in the link budget. This power penalty is between 1.6 to 3 dB for a direct detection QPPM link, and 3 to 5 dB for a heterodyne QFSK system. For the heterodyne systems, the carrier phase noise presents another major factor of performance degradation that must be considered. In contrast, the loss due to synchronization error is small. The link budgets for direct and heterodyne detection systems are evaluated. It is shown that, for systems with large pointing and tracking errors, the link budget is dominated by the spatial tracking error, and the direct detection system shows a superior performance because it is less sensitive to the spatial tracking error. On the other hand, for systems with small pointing and tracking jitters, the antenna gains are in general limited by the launch cost, and suboptimal antenna gains are often used in practice. In which case, the heterodyne system has a slightly higher power margin because of higher receiver sensitivity.

Chen, C. C.; Gardner, C. S.

1987-01-01

267

A new adaptive switching filter with directional impulse detection  

NASA Astrophysics Data System (ADS)

A novel adaptive switching filter (ASF) based on directional detection is proposed for denoising the images that are highly corrupted by impulse noise. The proposed algorithm employs an efficient noise detection mechanism. It first employs an efficient method to estimate the differences between the current pixel and its neighbors aligned with 28 directions. The current noise pixel is replaced by a median or a mean value within an adaptive filter window with respect to different noise densities. Experimental results show that the proposed approach can not only achieve very low miss-detection ratio and false-alarm ratio even up to high noise corruption, but also preserve the detailed information of an image very well.

Sun, Jing; Liu, Hui-gang; Zhang, Fu-hai

2014-03-01

268

Direct Fast-Neutron Detection: A Progress Report  

SciTech Connect

It is widely acknowledged that Mure neutron-detection technologies will need to offer increased performance at lower cost. One clear route toward these goals is rapid and direct detection of fast neutrons prior to moderation. This report describes progress to date in an effort to achieve such neutron detection via proton recoil within plastic scintillator. Since recording proton-recoil events is of little practical use without a means to discriminate effectively against gamma-ray interactions, the present effort is concentrated on demonstrating a method that distinguishes between pulse types. The proposed method exploits the substantial difference in the speed of fission neutrons and gamma-ray photons. Should this effort ultimately prove successful, the resulting. technology would make a valuable contribution toward meeting the neutron-detection needs of the next century. This report describes the detailed investigations that have been part of Pacific Northwest National Laborato@s efforts to demonstrate direct fast-neutron detection in the laboratory. Our initial approach used a single, solid piece of scintillator along with the electronics needed for pulse-type differentiation. Work to date has led to the conclusion that faster scintillator and/or faster electronics will be necessary before satisfactory gamma-ray discrimination is achieved with this approach. Acquisition and testing of both faster scintillator and faster electronics are currently in progress. The "advanced" approach to direct fast-neutron detection uses a scintillating assembly with an overall density that is lower than that of ordinary plastic scintillator. The lower average density leads to longer interaction times for both neutrons and gamma rays, allowing easier discrimination. The modeling, optimization, and design of detection systems using this approach are described in detail.

AJ Peurrung; DC Stromswold; PL Reeder; RR Hansen

1998-10-18

269

Three-dimensional track reconstruction for directional Dark Matter detection  

NASA Astrophysics Data System (ADS)

Directional detection of Dark Matter is a promising search strategy. However, to perform such detection, a given set of parameters has to be retrieved from the recoiling tracks: direction, sense and position in the detector volume. In order to optimize the track reconstruction and to fully exploit the data of forthcoming directional detectors, we present a likelihood method dedicated to 3D track reconstruction. This new analysis method is applied to the MIMAC detector. It requires a full simulation of track measurements in order to compare real tracks to simulated ones. We conclude that a good spatial resolution can be achieved, i.e. sub-mm in the anode plane and cm along the drift axis. This opens the possibility to perform a fiducialization of directional detectors. The angular resolution is shown to range between 20° to 80°, depending on the recoil energy, which is however enough to achieve a high significance discovery of Dark Matter. On the contrary, we show that sense recognition capability of directional detectors depends strongly on the recoil energy and the drift distance, with small efficiency values (50%-70%). We suggest not to consider this information either for exclusion or discovery of Dark Matter for recoils below 100 keV and then to focus on axial directional data.

Billard, J.; Mayet, F.; Santos, D.

2012-04-01

270

Colorimetric determination of o-phenylenediamine in water samples based on the formation of silver nanoparticles as a colorimetric probe.  

PubMed

A simple, rapid and cost-effective method for visual colorimetric detection of o-phenylenediamine (OPD) based on the formation of silver nanoparticles (AgNPs) has been developed in this paper. Silver ions can be reduced to AgNPs by OPD in a few minutes, causing changes in absorption spectra and color of the reaction system. Therefore, colorimetric detection of OPD could be realized by a UV-vis spectrophotometer or even the naked eye. Results showed that the absorption intensity of AgNPs at 416nm exhibited a good linear correlation (R(2)=0.998) with OPD concentration in the range from 10(-6) to 8×10(-5)molL(-1) and the detection limit (3?/S) was calculated to be 1.61×10(-7)molL(-1). Furthermore, as low as 4×10(-6)molL(-1)OPD can be visualized by the naked eye without the requirement of any complicated or expensive instruments. This proposed method has been successfully applied to determine OPD in water samples, and may provide an innovative platform in the development of sensors for guiding environmental monitoring in the future. PMID:25615678

Li, Nan; Gu, Yu; Gao, Mengmeng; Wang, Zilu; Xiao, Deli; Li, Yun; Lin, Rui; He, Hua

2015-04-01

271

Clustering and Community Detection in Directed Networks: A Survey  

E-print Network

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 non symmetric. 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 applications. Therefore, naturally there is a recent wealth of research production in the area of mining directed graphs - with clustering being the primary method and tool for community detection and evaluation. The goal of this paper is t...

Malliaros, Fragkiskos D

2013-01-01

272

Spaceborne Simulations of Two Direct-Detection Doppler Lidar Techniques  

NASA Technical Reports Server (NTRS)

Direct-detection (or incoherent) lidar is now a proven technique for measuring winds in the atmosphere. Over the last few years, several types of direct-detection lidar have evolved. These methods rely on Fabry-Perot interferometers(also termed etalons) or other narrow-passband filters to provide the required spectral resolution. One method, now called the edge (EDG) technique, uses a sharply-sloping filter and measures changes in the filter transmission caused by Doppler shifting of the laser wavelength. A variation of the EDG method, called the double-edge (DEDG) technique, uses two filters. The molecular DEDG method was first demonstrated by Chanin et al. for stratospheric measurements and more recently Korb et al. successfully demonstrated the aerosol DEDG through the troposphere. A second method, here termed the multi-channel (MC) technique, measures Doppler shifts by observing angular displacement of a Fabry-Perot fringe in a spatially resolving detector. The EDG technique thus employs the Fabry-Perot to convert the frequency shift into an amplitude signal, while the MC technique uses the Fabry-Perot to resolve the spectral signature which is then fitted to determine the centroid. The focus of this presentation is on the DEDG and MC methods because these are viewed as the current state of the art in direct-detection lidar. Successful ground-based demonstrations of direct-detection wind measurements have resulted in proposals for spaceborne systems. With this new emphasis on spaceborne systems comes the need for accurate prediction of spaceborne direct-detection Doppler lidar performance. Previously, the EDG and MC methods have been compared although only for aerosol Doppler systems. A recent paper by McGill and Spinhirne compares the DEDG and MC methods in a non-system specific manner for both the aerosol and molecular Doppler systems. The purpose of this presentation is to extend the previous work of McGill and Spinhirne to examine the performance of spaceborne profiling systems. Particular emphasis will be placed on the molecular systems, as these are viewed as the strength of direct-detection Doppler lidar.

McGill, Matthew J.; Li, Steve X.

1998-01-01

273

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

274

Visual and Instrumental Colorimetric Assessments of Small Color Differences on Translucent Dental Porcelain  

Microsoft Academic Search

The CIELAB colorimetric system was used for the study of the relationship between measured color difference values and human observer responses. This study verified that a specific, visually meaningful and precise relationship exists between the magnitude and direction of the measurements and the average dental-observer responses. The results support the use of this system in dentistry as a means of

R. R. Seghi; E. R. Hewlett; J. Kim

1989-01-01

275

Principal direction-based Hough transform for line detection  

NASA Astrophysics Data System (ADS)

A robust and fast line detection method based on Hough transform (HT) is proposed in this paper. Edge pixels are extracted based on the summation and ratio of principal curvatures. Probabilistic sampling on the edge pixels is applied to reduce the count of voting. Then a one-to-one voting strategy is applied by taking advantages of the information of principal direction. The principal direction is also conducive for the successive accurate line segment extraction. The experiments demonstrate that the proposed method shows better locating accuracy and computation efficiency compared with several significant variations of HT.

Zhao, Yao; Pan, Haibin; Du, Changping; Zheng, Yao

2015-03-01

276

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

277

Prospects for direct dark matter detection in the Constrained MSSM  

E-print Network

We outline the WIMP dark matter parameter space in the Constrained MSSM by performing a comprehensive statistical analysis that compares with experimental data predicted superpartner masses and other collider observables as well as a cold dark matter abundance. We include uncertainties arising from theoretical approximations as well as from residual experimental errors on relevant Standard Model parameters. We present high-probability regions for neutralino dark matter direct detection cross section, and we find that 10^-10 pb < sigma_p^SI < 10^-8 for direct WIMP detection (with details slightly dependent on the assumptions made). We highlight a complementarity between LHC and WIMP dark matter searches in exploring the CMSSM parameter space. We conclude that most of the 95% probability region for the cross section will be explored by future one-tonne detectors, that will therefore cover most of the currently favoured region of parameter space.

Roberto Trotta; Roberto Ruiz de Austri; Leszek Roszkowski

2006-09-05

278

Dark matter effective field theory scattering in direct detection experiments  

E-print Network

We examine the consequences of the effective field theory (EFT) of dark matter-nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.

Schneck, K; Cerdeno, D G; Mandic, V; Rogers, H E; Agnese, R; Anderson, A J; Asai, M; Balakishiyeva, D; Barker, D; Thakur, R Basu; Bauer, D A; Billard, J; Borgland, A; Brandt, D; Brink, P L; Bunker, R; Caldwell, D O; Calkins, R; Chagani, H; Chen, Y; Cooley, J; Cornell, B; Crewdson, C H; Cushman, P; Daal, M; Di Stefano, P C F; Doughty, T; Esteban, L; Fallows, S; Figueroa-Feliciano, E; Godfrey, G L; Golwala, S R; Hall, J; Harris, H R; Hofer, T; Holmgren, D; Hsu, L; Huber, M E; Jardin, D M; Jastram, A; Kamaev, O; Kara, B; Kelsey, M H; Kennedy, A; Leder, A; Loer, B; Asamar, E Lopez; Lukens, P; Mahapatra, R; McCarthy, K A; Mirabolfathi, N; Moffatt, R A; Mendoza, J D Morales; Oser, S M; Page, K; Page, W A; Partridge, R; Pepin, M; Phipps, A; Prasad, K; Pyle, M; Qiu, H; Rau, W; Redl, P; Reisetter, A; Ricci, Y; Roberts, A; Saab, T; Sadoulet, B; Sander, J; Schnee, R W; Scorza, S; Serfass, B; Shank, B; Speller, D; Toback, D; Upadhyayula, S; Villano, A N; Welliver, B; Wilson, J S; Wright, D H; Yang, X; Yellin, S; Yen, J J; Young, B A; Zhang, J

2015-01-01

279

Future Directions for the Early Detection of Recurrent Breast Cancer  

PubMed Central

The main goal of follow-up care after breast cancer treatment is the early detection of disease recurrence. In this review, we emphasize the multidisciplinary approach to this continuity of care from surgery, medical oncology, and radiology. Challenges within each setting are briefly addressed as a means of discussion for the future directions of an effective and efficient surveillance plan of post-treatment breast cancer care. PMID:24790657

Schneble, Erika J.; Graham, Lindsey J.; Shupe, Matthew P.; Flynt, Frederick L.; Banks, Kevin P.; Kirkpatrick, Aaron D.; Nissan, Aviram; Henry, Leonard; Stojadinovic, Alexander; Shumway, Nathan M.; Avital, Itzhak; Peoples, George E.; Setlik, Robert F.

2014-01-01

280

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

281

Paper-based tuberculosis diagnostic devices with colorimetric gold nanoparticles  

NASA Astrophysics Data System (ADS)

A colorimetric sensing strategy employing gold nanoparticles and a paper assay platform has been developed for tuberculosis diagnosis. Unmodified gold nanoparticles and single-stranded detection oligonucleotides are used to achieve rapid diagnosis without complicated and time-consuming thiolated or other surface-modified probe preparation processes. To eliminate the use of sophisticated equipment for data analysis, the color variance for multiple detection results was simultaneously collected and concentrated on cellulose paper with the data readout transmitted for cloud computing via a smartphone. The results show that the 2.6 nM tuberculosis mycobacterium target sequences extracted from patients can easily be detected, and the turnaround time after the human DNA is extracted from clinical samples was approximately 1 h.

Tsai, Tsung-Ting; Shen, Shu-Wei; Cheng, Chao-Min; Chen, Chien-Fu

2013-08-01

282

Closing supersymmetric resonance regions with direct detection experiments  

SciTech Connect

One of the few remaining ways that neutralinos could potentially evade constraints from direct detection experiments is if they annihilate through a resonance, as can occur if 2m{sub ?{sup 0}} falls within about ?10% of either m{sub A/H}, m{sub h}, or m{sub Z}. Assuming a future rate of progress among direct detection experiments that is similar to that obtained over the past decade, we project that within 7 years the light Higgs and Z pole regions will be entirely closed, while the remaining parameter space near the A/H resonance will require that 2m{sub ?{sup 0}} be matched to the central value (near m{sub A}) to within less than 4%. At this rate of progress, it will be a little over a decade before multi-ton direct detection experiments will be able to close the remaining, highly-tuned, regions of the A/H resonance parameter space.

Kelso, Chris [Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112 (United States)

2014-06-24

283

Direct Detection Portals for Self-interacting Dark Matter  

E-print Network

Dark matter self-interactions can affect the small scale structure of the Universe, reducing the central densities of dwarfs and low surface brightness galaxies in accord with observations. From a particle physics point of view, this points toward the existence of a 1-100 MeV particle in the dark sector that mediates self-interactions. Since mediator particles will generically couple to the Standard Model, direct detection experiments provide sensitive probes of self-interacting dark matter. We consider three minimal mechanisms for coupling the dark and visible sectors: photon kinetic mixing, Z boson mass mixing, and the Higgs portal. Self-interacting dark matter motivates a new benchmark paradigm for direct detection via momentum-dependent interactions, and ton-scale experiments will cover astrophysically motivated parameter regimes that are unconstrained by current limits. Direct detection is a complementary avenue to constrain velocity-dependent self-interactions that evade astrophysical bounds from larger scales, such as those from the Bullet Cluster.

Manoj Kaplinghat; Sean Tulin; Hai-Bo Yu

2013-10-29

284

Direct detection portals for self-interacting dark matter  

NASA Astrophysics Data System (ADS)

Dark matter self-interactions can affect the small scale structure of the Universe, reducing the central densities of dwarfs and low surface brightness galaxies in accord with observations. From a particle physics point of view, this points toward the existence of a 1-100 MeV particle in the dark sector that mediates self-interactions. Since mediator particles will generically couple to the Standard Model, direct detection experiments provide sensitive probes of self-interacting dark matter. We consider three minimal mechanisms for coupling the dark and visible sectors: photon kinetic mixing, Z boson mass mixing, and the Higgs portal. Self-interacting dark matter motivates a new benchmark paradigm for direct detection via momentum-dependent interactions, and ton-scale experiments will cover astrophysically motivated parameter regimes that are unconstrained by current limits. Direct detection is a complementary avenue to constrain velocity-dependent self-interactions that evade astrophysical bounds from larger scales, such as those from the bullet cluster.

Kaplinghat, Manoj; Tulin, Sean; Yu, Hai-Bo

2014-02-01

285

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

286

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

287

WIMP dark matter direct-detection searches in noble gases  

NASA Astrophysics Data System (ADS)

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.

Baudis, Laura

2014-09-01

288

Direct detection of black holes via electromagnetic radiation  

NASA Astrophysics Data System (ADS)

Many black hole (BH) candidates exist, ranging from supermassive (˜106-1010 M?) to stellar masses (˜1-100 M?), all of them identified by indirect processes. Although there are no known candidate BHs with substellar masses, these might have been produced in the primordial Universe. BHs emit radiation composed of photons, gravitons and, later in their lives, massive particles. We explored the detection of such BHs with present-day masses from 10-22 to 10-11 M?. 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 ? 107 m while in the X-ray band the distances might reach ˜108 m (of the order of the Earth-Moon distance) and in the ?-ray band BHs might even be detected from as far as ˜0.1 pc. Since these results give us realistic hopes of directly detecting BHs, we suggest the scrutiny of current and future space mission data to reach this goal.

Sobrinho, J. L. G.; Augusto, P.

2014-07-01

289

(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

290

Dependence of direct detection signals on the WIMP velocity distribution  

SciTech Connect

The signals expected in WIMP direct detection experiments depend on the ultra-local dark matter distribution. Observations probe the local density, circular speed and escape speed, while simulations find velocity distributions that deviate significantly from the standard Maxwellian distribution. We calculate the energy, time and direction dependence of the event rate for a range of velocity distributions motivated by recent observations and simulations, and also investigate the uncertainty in the determination of WIMP parameters. The dominant uncertainties are the systematic error in the local circular speed and whether or not the MW has a high density dark disc. In both cases there are substantial changes in the mean differential event rate and the annual modulation signal, and hence exclusion limits and determinations of the WIMP mass. The uncertainty in the shape of the halo velocity distribution is less important, however it leads to a ? 5% systematic error in the WIMP mass. The detailed direction dependence of the event rate is sensitive to the velocity distribution. However the numbers of events required to detect anisotropy and confirm the median recoil direction do not change substantially.

Green, Anne M., E-mail: anne.green@nottingham.ac.uk [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom)

2010-10-01

291

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

292

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

293

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

294

Comparison of radiometric and chemical detection sensitivities for heterodyne and direct detection DIAL  

NASA Astrophysics Data System (ADS)

A high repetition rate, wavelength agile CO2 laser has been developed at the Air Force Research Laboratory for use as a local oscillator in a heterodyne detection receiver. Rapid wavelength selection is required for measurements of airborne chemical vapors using the differential absorption lidar (DIAL) technique. Acousto-optic modulators are used in the local oscillator to tune between different wavelengths at high speeds (greater than 100 Hz) without the need for moving mechanical parts. Other advantages obtained by the use of acousto-optic modulators are laser output power control per wavelength and rugged packaging for field applications. A series of experiments to simultaneously characterize the radiometric and chemical detection sensitivities of heterodyne and direct detection DIAL systems is being performed at Kirtland AFB, NM, and will be described. The wavelength agile local oscillator (WALO) has been incorporated into a heterodyne receiver, with the Laser Airborne Remote Sensing (LARS) system providing the laser transmitter and direct detection receiver. The experiment series is studying radiometric issues, spread spectrum operation, the effects of target-induced speckle, and the influence of atmospheric turbulence for both detection mechanisms. Measurements are being performed over a horizontal path at standoff ranges of 4 to 15 km, using both natural and man-made targets. Comparisons of the heterodyne and direct detection radiometric and chemometric results will be presented, and contrasted with predictions from simulations and models. The results will also be discussed in terms of the implications for fielding operational DIAL systems.

Senft, Daniel C.; Pierrottet, Diego F.

2004-02-01

295

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

2014-07-02

296

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

297

Automatic colorimetric calibration of human wounds  

PubMed Central

Background Recently, digital photography in medicine is considered an acceptable tool in many clinical domains, e.g. wound care. Although ever higher resolutions are available, reproducibility is still poor and visual comparison of images remains difficult. This is even more the case for measurements performed on such images (colour, area, etc.). This problem is often neglected and images are freely compared and exchanged without further thought. Methods The first experiment checked whether camera settings or lighting conditions could negatively affect the quality of colorimetric calibration. Digital images plus a calibration chart were exposed to a variety of conditions. Precision and accuracy of colours after calibration were quantitatively assessed with a probability distribution for perceptual colour differences (dE_ab). The second experiment was designed to assess the impact of the automatic calibration procedure (i.e. chart detection) on real-world measurements. 40 Different images of real wounds were acquired and a region of interest was selected in each image. 3 Rotated versions of each image were automatically calibrated and colour differences were calculated. Results 1st Experiment: Colour differences between the measurements and real spectrophotometric measurements reveal median dE_ab values respectively 6.40 for the proper patches of calibrated normal images and 17.75 for uncalibrated images demonstrating an important improvement in accuracy after calibration. The reproducibility, visualized by the probability distribution of the dE_ab errors between 2 measurements of the patches of the images has a median of 3.43 dE* for all calibrated images, 23.26 dE_ab for all uncalibrated images. If we restrict ourselves to the proper patches of normal calibrated images the median is only 2.58 dE_ab! Wilcoxon sum-rank testing (p < 0.05) between uncalibrated normal images and calibrated normal images with proper squares were equal to 0 demonstrating a highly significant improvement of reproducibility. In the second experiment, the reproducibility of the chart detection during automatic calibration is presented using a probability distribution of dE_ab errors between 2 measurements of the same ROI. Conclusion The investigators proposed an automatic colour calibration algorithm that ensures reproducible colour content of digital images. Evidence was provided that images taken with commercially available digital cameras can be calibrated independently of any camera settings and illumination features. PMID:20298541

2010-01-01

298

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

299

Virtual colorimetric sensor array: single ionic liquid for solvent discrimination.  

PubMed

There is a continuing need to develop high-performance sensors for monitoring organic solvents, primarily due to the environmental impact of such compounds. In this regard, colorimetric sensors have been a subject of intense research for such applications. Herein, we report a unique virtual colorimetric sensor array based on a single ionic liquid (IL) for accurate detection and identification of similar organic solvents and mixtures of such solvents. In this study, we employ eight alcohols and seven binary mixtures of ethanol and methanol as analytes to provide a stringent test for assessing the capabilities of this array. The UV-visible spectra of alcoholic solutions of the IL used in this study show two absorption bands. Interestingly, the ratio of absorbance for these two bands is found to be extremely sensitive to alcohol polarity. A virtual sensor array is created by using four different concentrations of IL sensor, which allowed identification of these analytes with 96.4-100% accuracy. Overall, this virtual sensor array is found to be very promising for discrimination of closely related organic solvents. PMID:25822878

Galpothdeniya, Waduge Indika S; Regmi, Bishnu P; McCarter, Kevin S; de Rooy, Sergio L; Siraj, Noureen; Warner, Isiah M

2015-04-21

300

Problem detection during tripping operations in horizontal and directional wells  

SciTech Connect

Most directional well drilling problems detected in Brazil, and also verbally reported by service companies abroad, occur during tripping operations. A comprehensive research program was undertaken to study this problem. The work is summarized in this paper, and shows the development of a field analysis procedure that proved to be reliable and thus translates into significant cost savings. The field data was obtained using an in-house mud logging offshore unit and service companies` drilling sensors. The analysis was performed using the new developed method--Two Stage Type Curve Matching: an alert hook load expert system, followed by a pseudo friction factor ``signature`` analysis. Field results showed this to be useful for early borehole detection.

Cordoso, J.V. Jr. [Petrobras, Rio de Janeiro (Brazil); Maidla, E.E.; Idagawa, L.S. [State Univ. in Campinas (Brazil)

1995-06-01

301

Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength  

PubMed Central

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

302

WIMP physics with ensembles of direct-detection experiments  

NASA Astrophysics Data System (ADS)

The search for weakly-interacting massive particle (WIMP) dark matter is multi-pronged. Ultimately, the WIMP-dark-matter picture will only be confirmed if different classes of experiments see consistent signals and infer the same WIMP properties. In this work, we review the ideas, methods, and status of direct-detection searches. We focus in particular on extracting WIMP physics (WIMP interactions and phase-space distribution) from direct-detection data in the early discovery days when multiple experiments see of order dozens to hundreds of events. To demonstrate the essential complementarity of different direct-detection experiments in this context, we create mock data intended to represent the data from the near-future Generation 2 experiments. We consider both conventional supersymmetry-inspired benchmark points (with spin-independent and -dependent elastic cross sections just below current limits), as well as benchmark points for other classes of models (inelastic and effective-operator paradigms). We also investigate the effect on parameter estimation of loosening or dropping the assumptions about the local WIMP phase-space distribution. We arrive at two main conclusions. Firstly, teasing out WIMP physics with experiments depends critically on having a wide set of detector target materials, spanning a large range of target nuclear masses and spin-dependent sensitivity. It is also highly desirable to obtain data from low-threshold experiments. Secondly, a general reconstruction of the local WIMP velocity distribution, which will only be achieved if there are multiple experiments using different target materials, is critical to obtaining a robust and unbiased estimate of the WIMP mass.

Peter, Annika H. G.; Gluscevic, Vera; Green, Anne M.; Kavanagh, Bradley J.; Lee, Samuel K.

2014-12-01

303

Direct magnetic resonance detection of neuronal electrical activity  

PubMed Central

Present noninvasive neuroimaging methods measure neuronal activity indirectly, via either cerebrovascular changes or extracranial measurements of electrical/magnetic signals. Recent studies have shown evidence that MRI may be used to directly and noninvasively map electrical activity associated with human brain activation, but results are inconclusive. Here, we show that MRI can detect cortical electrical activity directly. We use organotypic rat-brain cultures in vitro that are spontaneously active in the absence of a cerebrovascular system. Single-voxel magnetic resonance (MR) measurements obtained at 7 T were highly correlated with multisite extracellular local field potential recordings of the same cultures before and after blockade of neuronal activity with tetrodotoxin. Similarly, for MR images obtained at 3 T, the MR signal changed solely in voxels containing the culture, thus allowing the spatial localization of the active neuronal tissue. PMID:17038505

Petridou, Natalia; Plenz, Dietmar; Silva, Afonso C.; Loew, Murray; Bodurka, Jerzy; Bandettini, Peter A.

2006-01-01

304

Some implications of TCM for optical direct-detection channels  

NASA Astrophysics Data System (ADS)

Consideration is given to the optical direct-detection channel, and it is shown how simple trellis-coded modulation (TCM) can be used to improve performance or increase throughput (in bits per second) without bandwidth expansion or performance loss. In fact, a modest performance gain can be achieved. Although the approach can be used with other signal constellations, the authors concentrate on signals derived from the pulse-position modulation (PPM) format by allowing overlap. Theoretical motivation for using this signal set, known as overlapping PPM (OPPM), was recently given by David and Kaplan (1984), who showed a capacity gain when overlap is introduced.

Georghiades, Costas N.

1989-05-01

305

Is SUSY accessible by direct dark matter detection?  

E-print Network

We performed a combined analysis of the parameter space of the Minimal Supersymmetric Standard Model (MSSM) taking into account cosmological and accelerator constraints including those from the radiative $b\\rightarrow s\\gamma$ decay measured by the CLEO collaboration. Special attention is paid to the event rate, $R$, of direct dark matter neutralino detection. We have found domains of the parameter space with $R\\simeq 5-10$~events/kg/day. This would be within the reach of current dark matter experiments. The $b\\rightarrow s\\gamma$ data do not essentially reduce these large event rate domains of the MSSM parameter space.

V. A. Bednyakov; S. G. Kovalenko; H. V. Klapdor-Kleingrothaus; Y. Ramachers

1996-06-07

306

DIAMUND: Direct Comparison of Genomes to Detect Mutations  

PubMed Central

DNA sequencing has become a powerful method to discover the genetic basis of disease. Standard, widely used protocols for analysis usually begin by comparing each individual to the human reference genome. When applied to a set of related individuals, this approach reveals millions of differences, most of which are shared among the individuals and unrelated to the disease being investigated. We have developed a novel algorithm for variant detection, one that compares DNA sequences directly to one another, without aligning them to the reference genome. When used to find de novo mutations in exome sequences from family trios, or to compare normal and diseased samples from the same individual, the new method, direct alignment for mutation discovery (DIAMUND), produces a dramatically smaller list of candidate mutations than previous methods, without losing sensitivity to detect the true cause of a genetic disease. We demonstrate our results on several example cases, including two family trios in which it correctly found the disease-causing variant while excluding thousands of harmless variants that standard methods had identified. PMID:24375697

Salzberg, Steven L; Pertea, Mihaela; Fahrner, Jill A; Sobreira, Nara

2014-01-01

307

Active THz medical imaging using broadband direct detection  

NASA Astrophysics Data System (ADS)

Research in THz imaging is generally focused on three primary application areas: medical, security, and nondestructive evaluation (NDE). While work in THz security imaging and personnel screening is populated by a number of different active and passive system architectures, research in medical imaging in is generally performed with THz time-domain systems. These systems typically employ photoconductive or electro-optic source/detector pairs and can acquire depth resolved data or spectrally resolved pixels by synchronously sampling the electric field of the transmitted/reflected waveform. While time-domain is a very powerful scientific technique, results reported in the literature suggest that desired THz contrast in medical imaging may not require the volume of data accessible from time-resolved measurements and that a simpler direct detection, active technique may be sufficient for specific applications. In this talk we discuss an active direct detection reflectometer system architecture operating at a center frequency of ~ 525 GHz that uses a photoconductive source and schottky diode detector. This design takes advantage or radar-like pulse rectification and novel reflective optical design to achieve high target imaging contrast with significant potential for high speed acquisition time. Results in spatially resolved hydration mapping of burn wounds are presented and future outlooks discussed.

Taylor, Zachary D.; Garritano, James; Tewari, Priyamvada; Diebold, Eric; Sung, Shijun; Bajwa, Neha; Nowroozi, Bryan; Stojadinovic, Alexander; Llombart, Nuria; Brown, Elliott R.; Grundfest, Warren S.

2013-03-01

308

Development of a colorimetric assay for rapid quantitative measurement of clavulanic acid in microbial samples.  

PubMed

We developed a colorimetric assay to quantify clavulanic acid (CA) in culture broth of Streptomyces clavuligerus, to facilitate screening of a large number of S. clavuligerus mutants. The assay is based on a ?-lactamase-catalyzed reaction, in which the yellow substrate nitrocefin (? (max)=390 nm) is converted to a red product (? (max)=486 nm). Since CA can irreversibly inhibit ?-lactamase activity, the level of CA in a sample can be measured as a function of the A (390)/A (486) ratio in the assay mixture. The sensitivity and detection window of the assay were determined to be 50 ?g L(-1) and 50 ?g L(-1) to 10 mg L(-1), respectively. The reliability of the assay was confirmed by comparing assay results with those obtained by HPLC. The assay was used to screen a pool of 65 S. clavuligerus mutants and was reliable for identifying CA over-producing mutants. Therefore, the assay saves time and labor in large-scale mutant screening and evaluation tasks. The detection window and the reliability of this assay are markedly better than those of previously reported CA assays. This assay method is suitable for high throughput screening of microbial samples and allows direct visual observation of CA levels on agar plates. PMID:22415687

Dai, Xida; Xiang, Sihai; Li, Jia; Gao, Qiang; Yang, Keqian

2012-02-01

309

Effect of nuclear response functions in dark matter direct detection  

NASA Astrophysics Data System (ADS)

We examine the effect of nuclear response functions, as laid out by Fitzpatrick et al. [J. Cosmol. Astropart. Phys. 02 (2013) 004], on dark matter (DM) direct detection in the context of well-motivated UV completions, including electric and magnetic dipoles, anapole, spin-orbit, and pseudoscalar-mediated DM. Together, these encompass five of the six nuclear responses extracted from the nonrelativistic effective theory of Fitzpatrick et al. [J. Cosmol. Astropart. Phys. 02 (2013) 004] (with the sixth difficult to UV complete), with two of the six combinations corresponding to standard spin-independent and spin-dependent responses. For constraints from existing direct detection experiments, we find that only the COUPP constraint, due to its heavy iodine target with large angular momentum and an unpaired spin, and its large energy range sensitivity, is substantially modified by the new responses compared to what would be inferred using the standard form factors to model the energy dependence of the response. For heavy targets such as xenon and germanium, the behavior of the new nuclear responses as recoil energy increases can be substantially different from that of the standard responses, but this has almost no impact on the constraints derived from experiments such as LUX, XENON100, and CDMS since the maximum nuclear recoil energy detected in these experiments is relatively low. We simulate mock data for 80 and 250 GeV DM candidates utilizing the new nuclear responses to highlight how they might affect a putative signal, and find the new responses are most important for highly momentum-suppressed interactions such as the magnetic dipole or pseudoscalar-mediated interaction when the target is relatively heavy (such as xenon and iodine).

Gresham, Moira I.; Zurek, Kathryn M.

2014-06-01

310

Highly selective colorimetric bacteria sensing based on protein-capped nanoparticles.  

PubMed

A rapid and cost-effective colorimetric sensor has been developed for the detection of bacteria (Bacillus subtilis was selected as an example). The sensor was designed to rely on lysozyme-capped AuNPs with the advantages of effective amplification and high specificity. In the sensing system, lysozyme was able to bind strongly to Bacillus subtilis, which effectively induced a color change of the solution from light purple to purplish red. The lowest concentration of Bacillus subtilis detectable by the naked eye was 4.5 × 10(3) colony-forming units (CFU) mL(-1). Similar results were discernable from UV-Vis absorption measurements. A good specificity was observed through a statistical analysis method using the SPSS software (version 17.0). This simple colorimetric sensor may therefore be a rapid and specific method for a bacterial detection assay in complex samples. PMID:25503063

Qiu, Suyan; Lin, Zhenyu; Zhou, Yaomin; Wang, Donggen; Yuan, Lijuan; Wei, Yihua; Dai, Tingcan; Luo, Linguang; Chen, Guonan

2015-02-21

311

Absolute colorimetric characterization of a DSLR camera  

NASA Astrophysics Data System (ADS)

A simple but effective technique for absolute colorimetric camera characterization is proposed. It offers a large dynamic range requiring just a single, off-the-shelf target and a commonly available controllable light source for the characterization. The characterization task is broken down in two modules, respectively devoted to absolute luminance estimation and to colorimetric characterization matrix estimation. The characterized camera can be effectively used as a tele-colorimeter, giving an absolute estimation of the XYZ data in cd=m2. The user is only required to vary the f - number of the camera lens or the exposure time t, to better exploit the sensor dynamic range. The estimated absolute tristimulus values closely match the values measured by a professional spectro-radiometer.

Guarnera, Giuseppe Claudio; Bianco, Simone; Schettini, Raimondo

2014-03-01

312

Halo-Independent Direct Detection Analyses Without Mass Assumptions  

E-print Network

Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the $m_\\chi-\\sigma_n$ plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the $v_{min}-\\tilde{g}$ plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from $v_{min}$ to nuclear recoil momentum ($p_R$), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call $\\tilde{h}(p_R)$. The entire family of conventional halo-independent $\\tilde{g}(v_{min})$ plots for all DM masses are directly found from the single $\\tilde{h}(p_R)$ plot through a simple rescaling of axes. By considering results in $\\tilde{h}(p_R)$ space, one can determine if two experiments are inconsistent for all masses and all physically possible halos, or for what range of dark matter masses the results are inconsistent for all halos, without the necessity of multiple $\\tilde{g}(v_{min})$ plots for different DM masses. We conduct a sample analysis comparing the CDMS II Si events to the null results from LUX, XENON10, and SuperCDMS using our method and discuss how the mass-independent limits can be strengthened by imposing the physically reasonable requirement of a finite halo escape velocity.

Adam J. Anderson; Patrick J. Fox; Yonatan Kahn; Matthew McCullough

2015-04-13

313

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

314

An enzyme mediated, colorimetric method for the measurement of salicylate.  

PubMed

A novel enzymatic assay for salicylate in serum has been developed. Salicylate monooxygenase and NADH are used to convert the drug to catechol. This is reacted with 4-aminophenol at high pH to yield a blue product, which is detected colorimetrically. The assay is complete in less than seven minutes and requires no sophisticated equipment. The method is precise, sensitive and shows excellent accuracy in recovery experiments and when compared to a high performance liquid chromatography method. The assay is free from interference by coloured or turbid samples, salicylate metabolites, structurally related compounds such as benzoate and 4-hydroxybenzoate, and a range of drugs. The assay reagents demonstrate excellent stability. The formulation of the assay in two stages provides increased specificity and sensitivity compared to other emergency salicylate assays and allows the inclusion of reagents to greatly enhance the stability of the salicylate monooxygenase-NADH reagent, yet the method is simple and performs well. PMID:3708854

Chubb, S A; Campbell, R S; Ramsay, J R; Hammond, P M; Atkinson, T; Price, C P

1986-03-28

315

A sensitive colorimetric and ratiometric chemosensor for trivalent metal cations.  

PubMed

A novel hydroxyethyl piperazine functionalized cyanine derivative was designed and synthesized. It presents selective colorimetric as well as ratiometric absorption responses to trivalent metal cations (Cr(3+), Fe(3+) and Al(3+)) over a variety of divalent and monovalent metal cations in 3:7 ethanol-water solution. Detection limits of this method for Cr(3+), Fe(3+) and Al(3+) were 3.99 ?M, 4.30 ?M and 1.85 ?M, respectively. The recognition mechanism was attributed to the protonation of the organic probe, which blocked the photoinduced electron transfer (PET) process. In addition, the sensor was also successfully applied to the determination of Cr(3+) in prepared samples. PMID:25663271

Zhao, Xu; Yin, Guohui; Jin, Di; Yan, Xilong; Li, Yang; Chen, Ligong

2015-03-01

316

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

317

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

318

Higher dimensional effective operators for direct dark matter detection  

NASA Astrophysics Data System (ADS)

We discuss higher dimensional effective operators describing interactions between fermionic dark matter and Standard Model particles. They are typically suppressed compared to the leading order effective operators, which can explain why no conclusive direct dark matter detection has been made so far. The ultraviolet completions of the effective operators, which we systematically study, require new particles. These particles can potentially have masses at the TeV scale and can therefore be phenomenologically interesting for LHC physics. We demonstrate that the lowest order options require Higgsportal interactions generated by dimension six operators. We list all possible tree-level completions with extra fermions and scalars, and we discuss the LHC phenomenology of a specific example with extra heavy fermion doublets.

Krauss, Martin B.; Morisi, Stefano; Porod, Werner; Winter, Walter

2014-02-01

319

Direct-detection wind lidar operating with a multimode laser.  

PubMed

A direct-detection wind lidar that operates with a multimode laser has been developed and tested. The instrument exploits the light backscattered by particles using a Mach-Zehnder interferometer with an optical path difference matched to the free spectral range of the laser longitudinal modes. In addition to requiring no monomodal emission, the system requires no frequency locking between the interferometer and the laser. We report laboratory and atmospheric measurements that show that the lidar is capable of measuring the radial wind velocity with a systematic error lower than 1 ms(-1) and a random error lower than 2 ms(-1) for a signal-to-noise ratio of 100. The development is motivated by the possibility to probe wind with a compact system in planetary atmospheres. PMID:23852210

Bruneau, Didier; Blouzon, Frédéric; Spatazza, Joseph; Montmessin, Franck; Pelon, Jacques; Faure, Benoît

2013-07-10

320

Single molecule detection of direct, homologous, DNA/DNA pairing  

PubMed Central

Using a parallel single molecule magnetic tweezers assay we demonstrate homologous pairing of two double-stranded (ds) DNA molecules in the absence of proteins, divalent metal ions, crowding agents, or free DNA ends. Pairing is accurate and rapid under physiological conditions of temperature and monovalent salt, even at DNA molecule concentrations orders of magnitude below those found in vivo, and in the presence of a large excess of nonspecific competitor DNA. Crowding agents further increase the reaction rate. Pairing is readily detected between regions of homology of 5 kb or more. Detected pairs are stable against thermal forces and shear forces up to 10 pN. These results strongly suggest that direct recognition of homology between chemically intact B-DNA molecules should be possible in vivo. The robustness of the observed signal raises the possibility that pairing might even be the “default” option, limited to desired situations by specific features. Protein-independent homologous pairing of intact dsDNA has been predicted theoretically, but further studies are needed to determine whether existing theories fit sequence length, temperature, and salt dependencies described here. PMID:19903884

Danilowicz, C.; Lee, C. H.; Kim, K.; Hatch, K.; Coljee, V. W.; Kleckner, N.; Prentiss, M.

2009-01-01

321

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

322

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

323

Comparing Dynamical Ranges of Direct Imaging Planet Detection  

NASA Astrophysics Data System (ADS)

Direct imaging of extra-solar planets in orbit around stars is difficult because of the problem of dynamic range: Planets are much fainter then their parent stars and very close to them. One way around this problem is searching for giant planets around young nearby stars, where the planets are still self-luminous due to their own thermal emssion because of on-going contraction and accretion. We are activelly searching for young planets around young (up to 100 Myrs) nearby (up to 100 pc) stars using space- and ground-based facilities. Previously, we did detect one planet candidate near TWA-7, which could have been a few jupiter mass companion, if at the same distance and age as TWA-7. However, our follow-up H-band ISAAC/VLT spectrum has shown that this object is a background K-type star. Then, we also confirmed two brown dwarfs as companions to TWA-5 and HR 7329 by both spectroscopy and proper motion. We will show and compare the dynamical ranges (detected or detectable magnitude difference versus separation from the primary star) for HST WFPC, HST Nicmos (without coronograph), Calar Alto 3.5m ALFA (AO), ESO 3.6m Adonis (AO, with and without coronograph), ESO 3.5m NTT with the MPE speckle camera SHARP 1, ESO 3.5m NTT with the IR camera SOFI, ESO 8.2m VLT with IR camera ISAAC, and Hbar okbar upa'a (AO) at the 8.3m Gemini-North on Mauna Kea. We will also discuss the capabilities of CONICA-NAOS, soon to be available at the VLT.

Neuhäuser, R.; Huélamo, N.; Ott, T.; Guenther, E. W.; Brandner, W.; Alves, J.; Comerón, F.; Eckart, A.; Potter, D.

324

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

325

Direct detection of dark matter with liquid argon and neon  

NASA Astrophysics Data System (ADS)

There is a great deal of observational evidence across a wide variety of scales that a large fraction of the universe and most of the matter in the universe is made up of some form of non-baryonic, dark matter. The most prominent candidate for dark matter is the weakly interacting massive particle or WIMP, with a mass between 1 GeV to a few TeV, and there are many current experiments aiming to detect these particles directly. The DEAP/CLEAN program seeks to detect dark matter and pp-solar neutrinos using liquid argon and liquid neon as targets. When ionizing radiation interacts in these liquids, scintillation light is produced. The timing or pulse shape of scintillation provides pulse shape discrimination (PSD) with which to identify the type of recoil that occurred in the liquid. As WIMP-nucleus scattering events would produce nuclear recoils but most of the backgrounds produce electronic recoils, PSD provides background rejection, allowing liquid argon- and neon-based detectors to achieve excellent sensitivity to dark matter. In this work, I describe the evidence for dark matter and review the state of current detection efforts. I then discuss observations of scintillation in liquid argon and liquid neon performed in prototype detectors at Yale and underground at SNOLAB in Ontario, Canada, focusing on measurements of PSD, the nuclear recoil scintillation efficiency and alpha backgrounds in these detectors. I describe the implications of these measurements for both the argon and neon components of the DEAP/CLEAN program, including simulations of a possible 10-tonne liquid neon detector. In the first appendix, I describe efforts at Yale to build a thermal column for the separation of isotopes, with applications to both dark matter and neutrinoless double-beta decay searches. In the second appendix, I describe operation of an evaporator system.

Lippincott, W. Hugh

2010-12-01

326

Determination of chromate adulteration of human urine by automated colorimetric and capillary ion electrophoretic analyses.  

PubMed

Various chemicals can be added to urine specimens collected for drug analysis to abnormally elevate ionic concentrations and/or interfere with either immunoassay urine drug-screening procedures or gas chromatographic-mass spectrometric confirmation techniques. One such adulterant, "Urine Luck" (formula 5.3), has been identified in our previous research to contain potassium dichromate. Screening of suspected adulterated specimens and confirmation of the adulterant are important for forensic drug screening. The application and comparison of automated colorimetric and capillary ion electrophoretic techniques for the detection, confirmation, and quantitation of chromate adulteration of urine specimens were the purpose of this investigation. Thirty-six urine specimens suspected of adulteration were analyzed for chromate by colorimetric analysis with diphenylcarbazide. Duplicate aliquots were analyzed for chromate by capillary ion electrophoresis. Results of the colorimetric chromate analyses revealed a mean chromate concentration of 929 microg/mL with a standard error of 177 microg/mL and a range of 30 to 5634 microg/mL. Results of the capillary ion electrophoresis chromate analyses revealed a mean chromate concentration of 1009 microg/mL with a standard error of 218 microg/mL and a range of 20 to 7501 microg/mL. The correlation coefficient between the capillary ion electrophoretic and colorimetric chromate results was r = 0.9669. Application of the automated diphenylcarbazide colorimetric technique provides rapid determination of chromate adulteration of a urine specimen. Capillary ion electrophoresis offers a separation technique to confirm the presence of chromate in suspected adulterated specimens. The excellent correlation between these methods substantiates their application to forensic testing as screening and/or confirmation techniques. PMID:12587681

Ferslew, Kenneth E; Nicolaides, Andrea N; Robert, Timothy A

2003-01-01

327

Specific-primer-directed DNA sequencing using automated fluorescence detection.  

PubMed Central

Automated fluorescence-based DNA sequence analysis offers the possibility to undertake very large scale sequencing projects. Directed strategies, such as the specific-primer-directed sequencing approach ('gene walking'), should prove useful in such projects. Described herein is a study involving the use of this approach in conjunction with automated fluorescence detection on a commercial instrument (ABI 370A DNA sequencer). This includes procedures for the rapid chemical synthesis and purification of labeled primers, the design of primer sequences that are compatible with the commercial analysis software, and automated DNA sequence analysis using such primers. A set of four fluorophore-labeled primers can be reliably synthesized in a twenty-four hour period, and greater than 300 nucleotides of analyzed new sequence obtained using this set in an additional twenty-four hours. Scale-up of these procedures to take advantage of the full capabilities of the sequencer is, at present, too slow and costly to be suitable for routine sequencing, and therefore the use of specific-primers is best suited to the closure of gaps in extended sequence produced using random cloning and sequencing strategies. PMID:2771640

Kaiser, R J; MacKellar, S L; Vinayak, R S; Sanders, J Z; Saavedra, R A; Hood, L E

1989-01-01

328

Direct Detection of Polarized, Scattered Light from Exoplanets  

NASA Astrophysics Data System (ADS)

We propose to radically advance the state of exoplanet characterization, which lags dramatically behind exoplanet discovery. We propose to directly detect scattered light from the atmospheres of close-in, highly eccentric, and extended/non-spherical exoplanets and thereby determine the following: orbital inclination (and therefore masses free of the M sin i mass ambiguity), geometric albedo, presence or lack of hazes and cloud layers, and scattering particle size and composition. Such measurements are crucial to the understanding of exoplanet atmospheres, because observations with NASA s Hubble, Spitzer, and Kepler space telescopes present the following questions: 1) Do exoplanets have highly reflective haze layers? 2) How does the upper atmospheric composition differ between exoplanets with and without thermal inversions? 3) What are the optical manifestations of the extreme heating of highly eccentric exoplanets? 4) Are the atmospheres of certain exoplanets truly escaping their Roche lobes? Using the POLISH2 polarimeter developed by the Postdoctoral Associate (Wiktorowicz) for the Lick 3-m telescope, we propose to monitor the linear polarization state of exoplanet host stars at the part per million level. POLISH2 consistently delivers nearly photon shot noise limited measurements with this precision. In addition, the simultaneous full-Stokes measurements of POLISH2 and the equatorial mount of the Lick 3-m telescope ensure that systematic effects are mitigated to the part per million level. Indeed, we find the accuracy of the POLISH2 polarimeter to be 0.1 parts per million. This instrument and telescope represent the highest precision polarimeter in the world for exoplanet research. We present potential detection of polarized, scattered light from the HD 189733b, Tau Boo b, and WASP-12b exoplanets. We propose to observe hot Jupiters on circular orbits, highly eccentric exoplanets, exoplanets with extended or non-spherical scattering surfaces, and 55 Cnc e, the super-Earth with the highest expected polarimetric signal-to- noise ratio. These exoplanets should all produce detectable polarization, and they present unique opportunities to study the atmospheres of wildly different exoplanets. Extending the PI s (Laughlin) Monte Carlo ray-tracing code, and utilizing the Co-I s (Fortney) experience in modeling exoplanet atmospheres, we propose to fund a graduate student to model the polarization data obtained from POLISH2 and invert the above variables. This is because they affect the amplitude and shape of the periodic variability in the polarization state of light from the system. Indeed, the discovery of spherical, sulfuric acid droplets suspended in the Venusian atmosphere was made forty years ago with Mie scattering models to fit polarimetric measurements. The PI s ray-tracing code, which has been used to model the rapid heating of the eccentric HD 80606b exoplanet, currently includes Rayleigh scattering and alkali metal absorption in a self-consistent manner. The direct detection of exoplanets as well as characterization of their atmospheric compositions and structure is directly related to the goals of the Origins program and to the NASA 2010 Science Plan, which emphasizes exploration of exoplanets and exoplanetary systems.

Laughlin, Gregory

329

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

330

Colorimetric \\/ fluorescent bacterial sensing by agarose-embedded lipid \\/ polydiacetylene films  

Microsoft Academic Search

Aim: Development of a new chromatic (colorimetric ?fluorescence) bacterial sensor, for rapid, sensitive and versatile detection of bacterial proliferation. Methods and Results: We constructed agarose-embedded chromatic films which produce dramatic colour changes and fluorescence transformations in response to bacterial growth. The sensing constructs comprise glass-supported Langmuir-Schaeffer phospholipid ?polydiacetylene films that undergo both blue-red transformations and induction of intense fluorescence following

D. Meir; L. Silbert; R. Volinsky; S. Kolusheva; I. Weiser; R. Jelinek

2008-01-01

331

Development of an ultrasensitive ELISA-bienzyme colorimetric substrate recycle assay for measurement of Tau  

Microsoft Academic Search

On the basis of conventional enzyme-linked immunosorbent assay (ELISA) and bienzyme substrate recycle, ELISA-bienzyme colorimetric\\u000a substrate recycle was developed in the present study. The sensitivity of this method increased 15 times than that of ELISA\\u000a for the measurement of Tau and increased 55 times forp-Tau. The linear detective rang of this method expanded 3 times higher than that of conventional

Duan Qiu-hong; Wang Xiao-chuan; Wang Xi-ming; Zhou Xin-wen; He Shan-shu; Wang Jian-zhi

2005-01-01

332

A sensitive colorimetric high-throughput screening method for lipase synthetic activity assay.  

PubMed

A sensitive and practical high-throughput screening method for assaying lipase synthetic activity is described. Lipase-catalyzed transesterification between vinyl acetate and n-butanol in n-hexane was chosen as a model reaction. The released acetaldehyde was determined by the colorimetric method using 3-methyl-2-benzothialinone (MBTH) derivatization. In comparison with other methods, the major advantages of this process include high sensitivity, simple detection, inexpensive reagents, and low requirements for instruments. PMID:24525041

Zheng, Jianyong; Fu, Xianfeng; Ying, Xiangxian; Zhang, Yinjun; Wang, Zhao

2014-05-01

333

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

334

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

335

Direct detection of hyaluronidase in urine using cationic gold nanoparticles: a potential diagnostic test for bladder cancer.  

PubMed

Hyaluronidase (HAase) was reported as a urinary marker of bladder cancer. In this study, a simple colorimetric gold nanoparticle (AuNP) assay was developed for rapid and sensitive detection of urinary HAase activity. Charge interaction between polyanionic hyaluronic acid (HA) and cationic AuNPs stabilized with cetyl trimethyl ammonium bromide (CTAB) led to formation of gold aggregates and a red to blue color shift. HAase digests HA into small fragments preventing the aggregation of cationic AuNPs. The nonspecific aggregation of AuNPs in urine samples was overcome by pre-treatment of samples with the polycationic chitosan that was able to agglomerate all negatively charged interfering moieties before performing the assay. The developed AuNP assay was compared with zymography for qualitative detection of urinary HAase activity in 40 bladder carcinoma patients, 11 benign bladder lesions patients and 15 normal individuals, the assay sensitivity was 82.5% vs. 65% for zymography, while the specificity for both assays was 96.1%. The absorption ratio, A530/A620 of the reacted AuNP solution was used to quantify the HAase activity. The best cut off value was 93.5 ?U/ng protein, at which the sensitivity was 90% and the specificity was 80.8%.The developed colorimetric AuNP HAase assay is simple, inexpensive, and can aid noninvasive diagnosis of bladder cancer. PMID:24240162

Nossier, Ahmed Ibrahim; Eissa, Sanaa; Ismail, Manal Fouad; Hamdy, Mohamed Ahmed; Azzazy, Hassan Mohamed El-Said

2014-04-15

336

Direct Detection of Stealth Dark Matter through Electromagnetic Polarizability  

E-print Network

We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar baryon dark matter candidate -- "Stealth Dark Matter", that is based on a dark SU(4) confining gauge theory. In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest baryons in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be potentially detectable in the dark matter mass range of about 200-700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure, however the steep dependence on the dark matter mass, $1/m_B^6$, suggests the observable dark matter mass range is not appreciably modified. We briefly highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter.

Thomas Appelquist; Evan Berkowitz; Richard C. Brower; Michael I. Buchoff; George T. Fleming; Xiao-Yong Jin; Joe Kiskis; Graham D. Kribs; Ethan T. Neil; James C. Osborn; Claudio Rebbi; Enrico Rinaldi; David Schaich; Chris Schroeder; Sergey Syritsyn; Pavlos Vranas; Evan Weinberg; Oliver Witzel

2015-03-13

337

A high-throughput colorimetric assay to measure the activity of glutamate decarboxylase.  

PubMed

A pH-sensitive colorimetric assay has been established to quantitatively measure glutamate decarboxylase (GAD) activity in bacterial cell extracts using a microplate format. GAD catalyzes the irreversible ?-decarboxylation of L-glutamate to ?-aminobutyrate. The assay is based on the color change of bromocresol green due to an increase in pH as protons are consumed during the enzyme-catalyzed reaction. Bromocresol green was chosen as the indicator because it has a similar pK(a) to the acetate buffer used. The corresponding absorbance change at 620 nm was recorded with a microplate reader as the reaction proceeded. A difference in the enzyme preparation pH and optimal pH for GAD activity of 2.5 did not prevent this method from successfully allowing the determination of reaction kinetic parameters and the detection of improvements in enzymatic activity with a low coefficient of variance. Our assay is simple, rapid, requires minimal sample concentration and can be carried out in robotic high-throughput devices used as standard in directed evolution experiments. In addition, it is also applicable to other reactions that involve a change in pH. PMID:22112511

Yu, Kai; Hu, Sheng; Huang, Jun; Mei, Le-He

2011-08-10

338

Direct detection of guidance receptor activity during border cell migration.  

PubMed

Guidance receptor signaling is crucial for steering migrating cells. Despite this, we generally lack direct measurements of such signaling. Border cells in Drosophila migrate as a tightly associated group, but dynamically, with front and rear cells exchanging places. They use the receptor tyrosine kinase (RTK) PDGF/VEGF receptor (PVR) as a guidance receptor, perceiving the attractant Pvf1. Here we determine the spatial distribution of PVR signaling by generating an antibody that specifically detects activated PVR in situ. PVR activity is very low in migrating border cells, due to strong activity of cellular phosphatases. Measurements of signal at the cell cortex show variability but a strong bias for both total active PVR and specific activity of PVR to be elevated at the front versus side of the leading cell, often with several-fold difference in signal levels. This polarized active PVR signal requires the E3 ubiquitin ligase Cbl and the recycling regulator Rab11, indicating a dependency on receptor trafficking. The endogenous ligand gradient contributes to shaping of signaling by increasing the specific activity of PVR toward the source in front cells. Surprisingly, signaling is also elevated at the back versus the side of rear cells. This distally polarized distribution of active PVR is ligand independent. Thus the actual guidance signal transmitted in border cells appears to integrate perceived ligand distribution with cell polarity or cell orientation with respect to the cluster. A general implication is that both group configuration and extrinsic cues can directly modulate guidance receptor signaling during collective cell migration. PMID:20368415

Janssens, Katrien; Sung, Hsin-Ho; Rørth, Pernille

2010-04-20

339

NEW COMPLETENESS METHODS FOR ESTIMATING EXOPLANET DISCOVERIES BY DIRECT DETECTION  

SciTech Connect

We report on new methods for evaluating realistic observing programs that search stars for planets by direct imaging, where observations are selected from an optimized star list and stars can be observed multiple times. We show how these methods bring critical insight into the design of the mission and its instruments. These methods provide an estimate of the outcome of the observing program: the probability distribution of discoveries (detection and/or characterization) and an estimate of the occurrence rate of planets ({eta}). We show that these parameters can be accurately estimated from a single mission simulation, without the need for a complete Monte Carlo mission simulation, and we prove the accuracy of this new approach. Our methods provide tools to define a mission for a particular science goal; for example, a mission can be defined by the expected number of discoveries and its confidence level. We detail how an optimized star list can be built and how successive observations can be selected. Our approach also provides other critical mission attributes, such as the number of stars expected to be searched and the probability of zero discoveries. Because these attributes depend strongly on the mission scale (telescope diameter, observing capabilities and constraints, mission lifetime, etc.), our methods are directly applicable to the design of such future missions and provide guidance to the mission and instrument design based on scientific performance. We illustrate our new methods with practical calculations and exploratory design reference missions for the James Webb Space Telescope (JWST) operating with a distant starshade to reduce scattered and diffracted starlight on the focal plane. We estimate that five habitable Earth-mass planets would be discovered and characterized with spectroscopy, with a probability of zero discoveries of 0.004, assuming a small fraction of JWST observing time (7%), {eta} = 0.3, and 70 observing visits, limited by starshade fuel.

Brown, Robert A.; Soummer, Remi [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2010-05-20

340

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

341

A New Colorimetric Assay of Tabletop Sweeteners Using a Modified Biuret Reagent: An Analytical Chemistry Experiment for the Undergraduate Curriculum  

ERIC Educational Resources Information Center

A new, fast and effective colorimetric analysis of the artificial sweetener aspartame is presented for application in undergraduate laboratory courses. This new method incorporates the use of a modified biuret reagent for selective detection and analysis of aspartame in aqueous solutions. The modified reagent is less caustic than the traditional…

Fenk, Christopher J.; Kaufman, Nathan; Gerbig, Donald G., Jr.

2007-01-01

342

Rapid, colorimetric quantification of lipid from algal cultures.  

PubMed

Algae have significant potential as a source of biomass for the production of biofuels, due to their high growth rates and high cellular lipid content. Studies that address the use of algae as biofuels often require the frequent measurement of algal lipid content. Traditional methods for the quantification of lipid are, however, costly if sub-contracted, or involve the use of expensive analytical equipment that is not available in many labs. This study describes a simple, colorimetric method for the quantification of algal lipid from small amounts of culture. The technique is derived from a method for the quantification of fatty acids dissolved in chloroform. Algal lipids are saponified to fatty acids and then mixed with a copper reagent. Chloroform-extractable copper soaps of long-chain fatty acids are then colorimetrically measured by the addition of diethyldithiocarbamate to develop a yellow colored product. Linear responses for fatty acids in the range of C10:0 to C16:0 were observed for a concentration range between 0.025 and 1 micromol of fatty acid per 200 microL of sample. Fatty acids with chain lengths of less than twelve carbons produced significantly reduced signal. Decenoic acid yielded a slightly, but significantly lower signal than decanoic acid indicating that the assay underestimates the presence of unsaturated fatty acids. Lipid contents of Phaeodactylum tricornutum and Chlorella vulgaris CM2 were monitored for eight days during exponential growth to demonstrate the feasibility of the technique as a monitoring methodology. Overall, the method allowed reliable detection and quantification of fatty acid content from 1 to 2 mL of algal culture. Adaptation of the technique to micro-centrifuge format allows assaying 30 samples in less than 2h. Considering reagents and time, the total cost per assay was estimated at less than $5, representing a significant cost savings over traditional lipid quantification procedures. PMID:20093146

Wawrik, Boris; Harriman, Brian H

2010-03-01

343

Direct detection of dark matter with resonant annihilation  

E-print Network

In the scenario where the dark matter (DM) particles $\\chi\\bar\\chi$ pair annihilate through a resonance particle $R$, the constraint from DM relic density makes the corresponding cross section for DM-nuclei elastic scattering extremely small, and can be below the neutrino background induced by the coherent neutrino-nuclei scattering, which makes the DM particle beyond the reach of the conventional DM direct detection experiments. We present an improved analytical calculation of the DM relic density in the case of resonant DM annihilation for $s$- and $p$-wave cases and invesitgate the condition for the DM-nuclei scattering cross section to be above the neutrino background. We show that in Higgs-portal type models, for DM particles with $s$-wave annihilation, the spin-independent DM-nucleus scattering cross section is proportional to $\\Gamma_{R}/m_{R}$, the ratio of the decay width and the mass of $R$. For a typical DM particle mass $\\sim50$ GeV, the condition leads to $\\Gamma_{R}/m_{R} \\gtrsim \\mathcal{O}(10^...

Li, Bo

2015-01-01

344

Investigation of Possible Dark Matter Direct Detection in Electron Accelerators  

E-print Network

We investigate a possibility of neutralino dark matter (DM) direct detection in the future electron accelerators. That is counting of high p_T electron recoil events by neutralinos in halo. If selectron and neutralino masses would be precisely measured in future collider experiments, the beam energy could be tuned so that the scatterings are dominated by on-pole selectron exchange. When selectron and neutralino mass difference is smaller than O(10) GeV, the elastic cross section exceeds over micro barn. Discovery of the high p_T electron events would be a firm prove of the neutralino DM component in halo. In the experiment, the electron beam energy must be tuned within O(10) MeV and the electron beam with high currents of O(100)A is required for the detectors of the total length of a few hundred meters so that the sufficient event rate is obtained. The dependence of the event rate on the DM velocity distribution in halo is also discussed. This method might be applicable to other DM candidates.

Junji Hisano; Minoru Nagai; Mihoko M. Nojiri; Masato Senami

2006-02-13

345

The effective field theory of dark matter direct detection  

SciTech Connect

We extend and explore the general non-relativistic effective theory of dark matter (DM) direct detection. We describe the basic non-relativistic building blocks of operators and discuss their symmetry properties, writing down all Galilean-invariant operators up to quadratic order in momentum transfer arising from exchange of particles of spin 1 or less. Any DM particle theory can be translated into the coefficients of an effective operator and any effective operator can be simply related to most general description of the nuclear response. We find several operators which lead to novel nuclear responses. These responses differ significantly from the standard minimal WIMP cases in their relative coupling strengths to various elements, changing how the results from different experiments should be compared against each other. Response functions are evaluated for common DM targets — F, Na, Ge, I, and Xe — using standard shell model techniques. We point out that each of the nuclear responses is familiar from past studies of semi-leptonic electroweak interactions, and thus potentially testable in weak interaction studies. We provide tables of the full set of required matrix elements at finite momentum transfer for a range of common elements, making a careful and fully model-independent analysis possible. Finally, we discuss embedding non-relativistic effective theory operators into UV models of dark matter.

Fitzpatrick, A. Liam; Katz, Emanuel [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94305 (United States); Haxton, Wick [Dept. of Physics, University of California, and Lawrence Berkeley National Laboratory, Berkeley, 94720 (United States); Lubbers, Nicholas; Xu, Yiming, E-mail: fitzpatr@stanford.edu, E-mail: haxton@berkeley.edu, E-mail: amikatz@buphy.bu.edu, E-mail: nlubbers@bu.edu, E-mail: ymxu@bu.edu [Physics Department, Boston University, Boston, MA 02215 (United States)

2013-02-01

346

Colorimetric biosensing of targeted gene sequence using dual nanoparticle platforms  

PubMed Central

We have developed a colorimetric biosensor using a dual platform of gold nanoparticles and graphene oxide sheets for the detection of Salmonella enterica. The presence of the invA gene in S. enterica causes a change in color of the biosensor from its original pinkish-red to a light purplish solution. This occurs through the aggregation of the primary gold nanoparticles–conjugated DNA probe onto the surface of the secondary graphene oxide–conjugated DNA probe through DNA hybridization with the targeted DNA sequence. Spectrophotometry analysis showed a shift in wavelength from 525 nm to 600 nm with 1 ?M of DNA target. Specificity testing revealed that the biosensor was able to detect various serovars of the S. enterica while no color change was observed with the other bacterial species. Sensitivity testing revealed the limit of detection was at 1 nM of DNA target. This proves the effectiveness of the biosensor in the detection of S. enterica through DNA hybridization.

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

2015-01-01

347

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

348

Directional dark matter by polar angle direct detection and application of columnar recombination  

E-print Network

We report a systematic study on the directional sensitivity of a direct dark matter detector that detects the polar angle of a recoiling nucleus. A WIMP-mass independent method is used to obtain the sensitivity of a general detector in an isothermal galactic dark matter halo. By using two-dimensional distributions of energy and polar angle, a detector without head-tail information with 6.3 times the statistics is found to achieve the same performance level as a full three-dimensional tracking dark matter detector. Optimum operation orientations are obtained for various experimental configurations, with detectors that are space- or Earth-fixed, have head-tail capability or not, and use energy information or not. Earth-fixed detectors are found to have best sensitivity when the polar axis is oriented at a 45 degree angle from the Earth's pole. The WIMP-mass dependence of the performance of a detector with a 3 keV energy threshold that uses xenon as target material is reported. We apply realistic experimental re...

Li, Jin

2015-01-01

349

Colorimetric solid-phase extraction method for Cu(II) ion determination using 2-hydroxybenzaldehyde benzoylhydrazone as sensing reagent.  

PubMed

A new sensor based on the use of 2-hydroxybenzaldehyde benzoylhydrazone as a colorimetric reagent immobilized onto styrenedivinylbenzene disks has been carried out for the determination of Cu(II) ions within several minutes. The sensor is designed on a rapid and easy two-step procedure: (1) the extraction of Cu(II) ions onto a disk loaded with the copper-selective colorimetric reagent and (2) the determination of the complexed analyte directly on the surface of the disk using diffuse reflectance measurements at 400 nm. The color of the disk changed from white to green in the presence of Cu(II) ions. The work herein details the optimization of the sensing system employing a fractional factorial design 3(3-1) considering three variables (pH, immobilization time, and amount of ligand immobilized onto the disk). The Pareto chart and response surfaces in a spherical domain indicated that the optimum conditions for the sensing of copper ions were pH = 7, with a ligand immobilization time of 10 min and 6.25 mg of reagent loaded onto the disk. Under the optimum conditions, the analytical parameters of the proposed method were determined. The calibration graph was linear over the range of 0 to 2.5 mg L(-1) of Cu(II) with a detection limit of 0.21 mg L(-1). The relative standard deviation for six measurements of 1 mg L(-1) of Cu(II) was found to be 4.87%. The interference from inorganic salts and other metals was found not to be of major concern when monitoring copper ions in water samples. The simplicity and rapidity of this technique make it convenient and amenable for on-site and routine analysis. PMID:24694697

Espada-Bellido, Estrella; Galindo-Riaño, Maria Dolores; García-Vargas, Manuel; Narayanaswamy, Ramaier

2014-01-01

350

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

351

Development of a nanobody-alkaline phosphatase fusion protein and its application in a highly sensitive direct competitive fluorescence enzyme immunoassay for detection of ochratoxin A in cereal.  

PubMed

A rapid and sensitive direct competitive fluorescence enzyme immunoassay (dc-FEIA) for ochratoxin A (OTA) based on a nanobody (Nb)-alkaline phosphatase (AP) fusion protein was developed. The VHH (variable domain of heavy chain antibody) gene of Nb28 was subcloned into the expression vector pecan45 containing the AP double-mutant gene. The Nb28-AP construct was transformed into Escherichia coli BL21(DE3)plysS, and soluble expression in bacteria was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot. Both the Nb properties and AP enzymatic activity were validated by colorimetric and fluorometric analysis. The 50% inhibitory concentration and the detection limit of the dc-FEIA were 0.13 and 0.04 ng/mL, respectively, with a linear range of 0.06-0.43 ng/mL. This assay was compared with LC-MS/MS, and the results indicated the reliability of Nb-AP fusion protein-based dc-FEIA for monitoring OTA contamination in cereal. PMID:25531426

Liu, Xing; Xu, Yang; Wan, De-bin; Xiong, Yong-hua; He, Zhen-yun; Wang, Xian-xian; Gee, Shirley J; Ryu, Dojin; Hammock, Bruce D

2015-01-20

352

Sub-picomole colorimetric single nucleotide polymorphism discrimination using oligonucleotide-nanoparticle conjugates.  

PubMed

Oligonucleotide-gold nanoparticle conjugates are employed to demonstrate selective colorimetric discrimination of a cystic fibrosis-related genetic mutation in a model oligonucleotide system. Specifically, three strand oligonucleotide complexes are employed, wherein two probe oligonucleotide-gold nanoparticle conjugates are linked together by a third target oligonucleotide strand bearing the chosen CF-related mutation. By monitoring the solution optical absorption behaviour of the complexes as a function of temperature, melting profiles may be accurately acquired and reproducibly compared. Following this method, fully complementary sequences are successfully distinguished from mismatched sequences, with single base mismatch resolution, for the V232D mutation. To extend the detection sensitivity of this oligonucleotide-nanoparticle conjugate assay, a novel and compact LED-based optical monitoring system capable of sub-picomole level colorimetric SNP discrimination is also demonstrated. PMID:15457332

Murphy, Deirdre; O'Brien, Peter; Redmond, Gareth

2004-10-01

353

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

354

Bed bug detection: Current technologies and future directions  

Technology Transfer Automated Retrieval System (TEKTRAN)

This study evaluates current technologies used to detect bed bug infestations, and presents new information regarding the underlying chemical basis of canines scent detection. The manuscript also reports new and future devices that may play a part in bed bug detection in the future....

355

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

PubMed

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 Hg(2+), Cd(2+) and Pb(2+) 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. PMID:24717716

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

2014-08-14

356

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

357

Visual Motion-Detection Circuits in Flies: Parallel Direction-and Non-Direction-Sensitive Pathways between the Medulla and  

E-print Network

Visual Motion-Detection Circuits in Flies: Parallel Direction- and Non-Direction-Sensitive Pathways into parallel retinotopic pathways that subsequently are reunited at higher levels. In insects, achromatic to the lobula. Further parallel subdivisions of the retinotopic pathways to the lobula plate have been suggested

Bermingham, Eldredge

358

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

359

Direct Detection of Extra-Solar Comets is Possible  

E-print Network

The dust tails of comets similar to Hale-Bopp can scatter as much optical light as does the Earth. Space-based observatories such as the Terrestrial Planet Finder or Darwin that will detect extra-solar terrestrial planets also will be able to detect extra-solar comets.

M. Jura

2005-05-24

360

Fluorescent and colorimetric ion probes based on conjugated oligopyrroles.  

PubMed

Metal ions and anions play important roles in many industrial and biochemical processes, and thus it is highly desired to detect them in the relevant systems. Small organic molecule based sensors for selective and sensitive detection of target ions show the advantages of low cost, high sensitivity and convenient implementation. In this area, pyrrole has incomparable advantages. It can be easily incorporated into linear and macrocyclic conjugated structures such as dipyrrins, porphyrins, and N-confused porphyrins, which may utilize the imino N and amino NH moieties for binding metal ions and anions, respectively. In this tutorial review, we focus on representative examples to describe the design, syntheses, sensing mechanisms, and applications of the conjugated oligopyrroles. These compounds could be used as colorimetric or fluorescent ion probes, with the advantages of vivid colour and fluorescence changes, easy structural modification and functionalization, and tunable emission wavelengths. Compared with normal porphyrins, simple di- and tripyrrins, as well as some porphyrinoids are more suitable for designing fluorescence "turn-on" metal probes, because they may exhibit flexible confirmations, and metal coordination will improve the rigidity, resulting in vivid fluorescence enhancement. It is noteworthy that the oligopyrrolic moieties may simultaneously act as the binding unit as well as the reporting moiety, which simplifies the design and syntheses of the probes. PMID:25608833

Ding, Yubin; Tang, Yunyu; Zhu, Weihong; Xie, Yongshu

2015-03-01

361

The Use of Colorimetric Sensor Arrays to Discriminate between Pathogenic Bacteria  

PubMed Central

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

362

Bed bug detection: current technologies and future directions.  

PubMed

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

2013-04-01

363

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

364

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

365

A Neural Network Model for Detecting the Direction of EgoMotion using  

E-print Network

A Neural Network Model for Detecting the Direction of Ego­Motion using Optical Flow and Extra in the optical flow field to perform this task. Previous research has ignored extra­ocular information which can optical flow field and extra­retinal information to detect the direction of ego­motion. My approach

Mirghafori, N. Nikki

366

Highly sensitive and selective colorimetric sensing of antibiotics in milk.  

PubMed

Antibiotics residues in foods are very harmful to human beings. Determination of antibiotics residues relies largely on the availability of adequate analytical techniques. Currently, there is an urgent need for on site and real time detection of antibiotics in food. In this work, a novel one step synthesis of gold nanoparticles (AuNPs) was proposed using pyrocatechol violet (PCV) as a reducer agent. Highly sensitive and selective colorimetric detection of four antibiotics kanamycin mono sulfate (KA), neomycin sulfate (NE), streptomycin sulfate (ST) and bleomycin sulfate (BL) was realized during the formation of AuNPs. PCV has -OH groups and these antibiotics have -OH, -NH2, -NH- groups, so there may be some special hydrogen-bonding interactions between PCV and these antibiotics. Therefore, the presence of KA, NE, ST and BL would influence the synthesis of AuNPs, then the color and state of AuNPs would change, which could be observed with the naked eye or a UV-vis spectrophotometer. Results showed that A670 was linear with the logarithm of KA concentration in the range from 1.0×10(-8) to 5.0×10(-7)M and 5.0×10(-7) to 5.5×10(-5)M. The detection limit of KA was 1.0×10(-9)M (S/N=3). The coexisting substances including 1.0×10(-5)M phenylalanine, alanine, glycerol, glucose, Mg(2+), Ca(2+), Na(+), K(+), CO3(2-), SO4(2-), NO3(-), Cl(-) and Br(-) did not affect the determination of 1.0×10(-7)M antibiotics. In particular, the proposed method could be applied successfully to the detection of antibiotics in the pretreated liquid milk products. PMID:23639400

Zhang, Xiaofang; Zhang, Yang; Zhao, Hong; He, Yujian; Li, Xiangjun; Yuan, Zhuobin

2013-05-17

367

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

368

Possible direct physical detection of de Broglie waves  

Microsoft Academic Search

A modified version of the Mandel-Pfleegor experiment implies conflicting measurable predictions of the Copenhagen and statistical interpretations of quantum mechanics. Their detection would help to choose between the antagonistic positions of Bohr and Einstein in the Bohr-Einstein controversy.

Augusto Garuccio; Karl R. Popper; Jean-Pierre Vigier

1981-01-01

369

Pace of Discovery Direct Detection Large Contrast = Difficult  

E-print Network

­ In the Habitable Zone? #12;Mass Detected vs. Distance Extrasolar planet encyclopedia Ice Super-Earths Hot Jupiters" #12;Radial Velocity Technique Sun's reflex motion due to: Jupiter ~13 m/s Earth ~ 9 cm/s Vsun;Gliese 581c - A "Super-Earth" M >~ 5 Mearth P ~ 13 days Red Dwarf 20.3 ly #12;Gliese 581c

Shirley, Yancy

370

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

371

Identification and colorimetric determination of organic cyanates in nanomolar quantities  

SciTech Connect

A color reaction for the qualitative and quantitative determination of organic cyanates (R - O - C = N) was developed. Upon treatment of an organic cyanate with color reagent (0.75 g of 1,3-dimethylbarbituric acid in 50 mL of pyridine/water (45:5)) a purple dye formed. The mechanism of this reaction was investigated, and the purple dye was identified as a pentamethine oxonol, 5-(5-(hexahydro-1,3-dimethyl-2,4,6-trioxo-5-pyrimidinyl)-2,4-pentadienylidene)-1,3-dimethyl-2,4,6(1H,3H,5H)-pyrimidinetrione. The spot test procedure had an identification limit of 60 ng and a dilution limit of 1:833000 for phenyl cyanate. On TLC plates as little as 20 pmol of organic cyanate could be detected. The color reaction was highly selective; isocyanates (R - N = C = O) and other CN-containing functional groups were unreactive. The colorimetric procedure for the quantitative determination of organic cyanates was used in the range of 0.04-200 ..mu..mol of organic cyanate. The standard deviation for repetitive determinations (n = 8) was 2%.

Kohn, J.; Albert, E.C.; Wilchek, M.; Langer, R.

1986-12-01

372

Colorimetric nanoplasmonic assay to determine purity and titrate extracellular vesicles.  

PubMed

Extracellular Vesicles (EVs) - cell secreted vesicles that carry rich molecular information of the parental cell and constitute an important mode of intercellular communication - are becoming a primary topic in translational medicine. EVs (that comprise exosomes and microvesicles/microparticles) have a size ranging from 40 nm to 1 ?m and share several physicochemical proprieties, including size, density, surface charge, and light interaction, with other nano-objects present in body fluids, such as single and aggregated proteins. This makes separation, titration, and characterization of EVs challenging and time-consuming. Here we present a cost-effective and fast colorimetric assay for probing by eye protein contaminants and determine the concentration of EV preparations, which exploits the synergy between colloidal gold nanoplasmonics, nanoparticle-protein corona, and nanoparticle-membrane interaction. The assay hits a limit of detection of protein contaminants of 5 ng/?L and has a dynamic range of EV concentration ranging from 35 fM to 35 pM, which matches the typical range of EV concentration in body fluids. This work provides the first example of the exploitation of the nanoparticle-protein corona in analytical chemistry. PMID:25674701

Maiolo, Daniele; Paolini, Lucia; Di Noto, Giuseppe; Zendrini, Andrea; Berti, Debora; Bergese, Paolo; Ricotta, Doris

2015-04-21

373

Protein-based nanobiosensor for direct detection of hydrogen sulfide  

NASA Astrophysics Data System (ADS)

The chemically modified cytochrome c from equine heart, EC (232-700-9), was immobilized onto gold nanoparticles in order to develop a specific biosensing system for monitoring hydrogen sulfide down to the micromolar level, by means of a localized surface plasmon resonance spectroscopy. The sensing mechanism is based on the cytochrome-c conformational changes in the presence of H2S which alter the dielectric properties of the gold nanoparticles and the surface plasmon resonance peak undergoes a redshift. According to the experiments, it is revealed that H2S can be detected at a concentration of 4.0 ? \\text{M} (1.3 \\text{ppb}) by the fabricated biosensor. This simple, quantitative and sensitive sensing platform provides a rapid and convenient detection for H2S at concentrations far below the hazardous limit.

Omidi, Meisam; Amoabediny, Ghasem; Yazdian, Fatemeh; Habibi-Rezaei, M.

2015-01-01

374

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

375

Closing in on mass-degenerate dark matter scenarios with antiprotons and direct detection  

E-print Network

Over the last years both cosmic-ray antiproton measurements and direct dark matter searches have proved particularly effective in constraining the nature of dark matter candidates. The present work focusses on these two types of constraints in a minimal framework which features a Majorana fermion as the dark matter particle and a scalar that mediates the coupling to quarks. Considering a wide range of coupling schemes, we derive antiproton and direct detection constraints using the latest data and paying close attention to astrophysical and nuclear uncertainties. Both signals are strongly enhanced in the presence of degenerate dark matter and scalar masses, but we show that the effect is especially dramatic in direct detection. Accordingly, the latest direct detection limits take the lead over antiprotons. We find that antiproton and direct detection data set stringent lower limits on the mass splitting, reaching 19% at a 300 GeV dark matter mass for a unity coupling. Interestingly, these limits are orthogona...

Garny, Mathias; Pato, Miguel; Vogl, Stefan

2012-01-01

376

Fast and accurate circle detection using gradient-direction-based segmentation.  

PubMed

We present what is to our knowledge the first-ever fitting-based circle detection algorithm, namely, the fast and accurate circle (FACILE) detection algorithm, based on gradient-direction-based edge clustering and direct least square fitting. Edges are segmented into sections based on gradient directions, and each section is validated separately; valid arcs are then fitted and further merged to extract more accurate circle information. We implemented the algorithm with the C++ language and compared it with four other algorithms. Testing on simulated data showed FACILE was far superior to the randomized Hough transform, standard Hough transform, and fast circle detection using gradient pair vectors with regard to processing speed and detection reliability. Testing on publicly available standard datasets showed FACILE outperformed robust and precise circular detection, a state-of-art arc detection method, by 35% with regard to recognition rate and is also a significant improvement over the latter in processing speed. PMID:24323106

Wu, Jianping; Chen, Ke; Gao, Xiaohui

2013-06-01

377

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

378

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

379

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

380

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

2014-11-21

381

Detection of Speaker Direction Based on the On-and-Off Microphone Combination for Entertainment Robots  

Microsoft Academic Search

\\u000a An important function of entertainment robots is voice communication with humans. For realizing them, accurate speech recognition\\u000a and a speaker-direction detection mechanism are necessary. The direct-noise problem is serious in such speech processing.\\u000a The microphone attached to the robot body receives not only human voices but also motor and mechanical noises directly. The\\u000a direct noises are often larger than distance

Takeshi Kawabata; Masashi Fujiwara; Takanori Shibutani

2005-01-01

382

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

383

Spectroscopic and computational study of a naphthalene derivative as colorimetric and fluorescent sensor for bioactive anions.  

PubMed

The anion recognition property of a naphthalene based receptor (L) was investigated by naked-eye, UV-Vis, fluorescence, (1)H NMR and computational methods. The receptor L showed fluoride selective naked-eye detectable colorimetric and UV-Vis spectral changes over other tested anions due to the formation of hydrogen bonding complex in 1:1 stoichiometry and/or deprotonation between fluoride and the receptor. Interestingly, the fluorescence of L was quenched by fluoride but enhanced by acetate. PMID:23456416

Sharma, Darshna; Sahoo, Suban K; Bera, Rati Kanta; Kamal, Raj

2013-05-01

384

Direct dark matter identification with a hybrid detection technique  

E-print Network

In the quest to understand the ultimate nature of WIMPs, we propose the use of a hybrid detection technique: cylinders filled with liquefied noble gasses, acting as targets, are immersed inside a tank of Gd-doped ultra-pure water that provides an active and efficient veto against neutrons. The evaluation of the background rejection capabilities and physics potential of this instrument have been carried out through a full GEANT4 simulation, assuming the detector will be located at the Canfranc underground laboratory (in the Spanish Pyrenees). Our results compare very favourably with existing or planned experiments in the field. This technique is scalable and will allow to reach target masses of few tonnes in the next future.

Bueno, A; Melgarejo, A J

2008-01-01

385

Enzymic colorimetry-based DNA chip: a rapid and accurate assay for detecting mutations for clarithromycin resistance in the 23S rRNA gene of Helicobacter pylori.  

PubMed

Macrolide drugs, such as clarithromycin (CAM), are a key component of many combination therapies used to eradicate Helicobacter pylori. However, resistance to CAM is increasing in H. pylori and is becoming a serious problem in H. pylori eradication therapy. CAM resistance in H. pylori is mostly due to point mutations (A2142G/C, A2143G) in the peptidyltransferase-encoding region of the 23S rRNA gene. In this study an enzymic colorimetry-based DNA chip was developed to analyse single-nucleotide polymorphisms of the 23S rRNA gene to determine the prevalence of mutations in CAM-related resistance in H. pylori-positive patients. The results of the colorimetric DNA chip were confirmed by direct DNA sequencing. In 63 samples, the incidence of the A2143G mutation was 17.46 % (11/63). The results of the colorimetric DNA chip were concordant with DNA sequencing in 96.83 % of results (61/63). The colorimetric DNA chip could detect wild-type and mutant signals at every site, even at a DNA concentration of 1.53 x 10(2) copies microl(-1). Thus, the colorimetric DNA chip is a reliable assay for rapid and accurate detection of mutations in the 23S rRNA gene of H. pylori that lead to CAM-related resistance, directly from gastric tissues. PMID:19628643

Xuan, Shi-Hai; Zhou, Yu-Gui; Shao, Bo; Cui, Ya-Lin; Li, Jian; Yin, Hong-Bo; Song, Xiao-Ping; Cong, Hui; Jing, Feng-Xiang; Jin, Qing-Hui; Wang, Hui-Min; Zhou, Jie

2009-11-01

386

Ultrasensitive and rapid screening of mercury(II) ions by dual labeling colorimetric method in aqueous samples and applications in mercury-poisoned animal tissues.  

PubMed

Rapid and ultrasensitive detection of trace heavy metal mercury(II) ions (Hg(2+)) are of significant importance due to the induced serious risks for environment and human health. This presented article reports the gold nanoparticle-based dual labeling colorimetric method (Dual-COLO) for ultrasensitive and rapid detection of Hg(2+) using the specific thymine-Hg(2+)-thymine (T-Hg(2+)-T) as recognition system and the dual labeling strategy for signal amplification. Both qualitative and quantitative detections of Hg(2+) are achieved successfully in aqueous samples. More importantly, the achieved detection limit of 0.005ngmL(-1) (0.025nM) without any instruments is very competitive to other rapid detection methods even ICP-MS based methods. This Dual-COLO method is also applied directly for real water sample monitoring and, more importantly, applied in analysis of mercury poisoned animal tissues and body fluidic samples, indicating a potentially powerful and promising tool for environmental monitoring and food safety control. PMID:25813233

Deng, Yi; Wang, Xin; Xue, Feng; Zheng, Lei; Liu, Jian; Yan, Feng; Xia, Fan; Chen, Wei

2015-04-01

387

Application of Colorimetric Indicators and Thermo-Hand Method to Determine Base Permeation Through Chemical Protective Gloves  

Microsoft Academic Search

The aim of this study was to assess the use of colorimetric indicator pads and the thermo-hand method for detection of inorganic\\/organic base permeation of chemical protective gloves under simulated in-use conditions. Breakthrough times for four types of gloves were determined based on the color change of pads and ranged from 3 to 10 min for butylamine, from 4 min

Evanly Vo

2004-01-01

388

Signal to noise ratios of pulsed and sinewave modulated direct detection lidar for IPDA measurements  

Microsoft Academic Search

The signal-to-noise ratios have been derived for IPDA lidar using a direct detection receiver for both pulsed and sinewave laser modulation techniques, and the results and laboratory measurements are presented.

Xiaoli Sun; James B. Abshire

2011-01-01

389

Signal to Noise Ratios of Pulsed and Sinewave Modulated Direct Detection Lidar for IPDA Measurements  

NASA Technical Reports Server (NTRS)

The signal-to-noise ratios have been derived for IPDA lidar using a direct detection receiver for both pulsed and sinewave laser modulation techniques, and the results and laboratory measurements are presented

Sun, Xiaoli; Abshire, James B.

2011-01-01

390

Direct Detection Doppler Lidar for Spaceborne Wind Measurement  

NASA Technical Reports Server (NTRS)

The theory of double edge lidar techniques for measuring the atmospheric wind using aerosol and molecular backscatter is described. Two high spectral resolution filters with opposite slopes are located about the laser frequency for the aerosol based measurement or in the wings of the Rayleigh - Brillouin profile for the molecular measurement. This doubles the signal change per unit Doppler shift and improves the measurement accuracy by nearly a factor of 2 relative to the single edge technique. For the aerosol based measurement, the use of two high resolution edge filters reduces the effects of background, Rayleigh scattering, by as much as an order of magnitude and substantially improves the measurement accuracy. Also, we describe a method that allows the Rayleigh and aerosol components of the signal to be independently determined. A measurement accuracy of 1.2 m/s can be obtained for a signal level of 1000 detected photons which corresponds to signal levels in the boundary layer. For the molecular based measurement, we describe the use of a crossover region where the sensitivity of a molecular and aerosol-based measurement are equal. This desensitizes the molecular measurement to the effects of aerosol scattering and greatly simplifies the measurement. Simulations using a conical scanning spaceborne lidar at 355 nm give an accuracy of 2-3 m/s for altitudes of 2-15 km for a 1 km vertical resolution, a satellite altitude of 400 km, and a 200 km x 200 km spatial.

Korb, C. Laurence; Flesia, Cristina

1999-01-01

391

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

392

Comparison of the pseudorandom noise code and pulsed direct-detection lidars for atmospheric probing  

Microsoft Academic Search

The advantages and limitations of using the pseudorandom-noise (PN)-code technique in comparison with pulsed direct detection are discussed. Because the signal-to-noise ratio (SNR) of the PN codes is dependent on the average atmospheric return, strong returns from short ranges and clouds determine the SNR for all ranges. The SNR of a profile obtained by pulsed direct detection exceeds that of

Janet L. Machol

1997-01-01

393

Direct measurement of sub-wavelength interference using thermal light and photon-number-resolved detection  

SciTech Connect

We examine thermal light diffracted through a double slit using photon-number-resolved detection to directly measure high-order spatial correlations, and we see sinusoidal modulations of those correlations. The fringe width can, in principal, be made arbitrarily small, and we have experimentally obtained fringe widths as small as 30?nm with 800?nm wavelength light. This extreme sub-wavelength resolution, along with this direct detection technique, offers potential for high precision measurement applications.

Zhai, Yanhua, E-mail: yanhuazhai@gmail.com, E-mail: jfan@nist.gov; Fan, Jingyun, E-mail: yanhuazhai@gmail.com, E-mail: jfan@nist.gov; Migdall, Alan [Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, 100 Bureau Drive, Mail Stop 8441, Gaithersburg, Maryland 20899 (United States); Becerra, Francisco E. [Center for Quantum Information and Control, MSC07-4220, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

2014-09-08

394

Rapid determination of methicillin resistance among Staphylococcus aureus clinical isolates by colorimetric methods.  

PubMed

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

Coban, Ahmet Yilmaz

2012-07-01

395

The Diurnal Variation of the Wimp Detection Event Rates in Directional Experiments  

E-print Network

The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. 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 supply the lightest Kaluza-Klein particle (LKP) etc. The nature of dark matter can only be unraveled only by its direct detection in the laboratory. All such candidates will be called WIMPs (Weakly Interacting Massive Particles). In any case the direct dark matter search, which amounts to detecting the recoiling nucleus, following its collision with WIMP, is central to particle physics and cosmology. In this work we briefly review the theoretical elements relevant to the direct dark matter detection experiments, paying particular attention to directional experiments. i.e experiments in which, not only the energy but the direction of the recoiling nucleus is ob...

Vergados, J D

2009-01-01

396

Direct Detection of Reactive Nitrogen Species in Experimental Autoimmune Uveitis  

PubMed Central

Purpose Demonstrate unequivocally the generation of nitric oxide in experimental autoimmune uveoretinitis by electron spin resonance spectroscopy (ESR) using ferrous iron complex of N-methyl-D-glucamine dithiocarbamate, (MGD)2-Fe2+, as a spin trap. Methods Experimental autoimmune uveitis was induced in Lewis rats, and at the peak of the intraocular inflammation, the animals received intravitreous injections of the spin trap. The retina and choroid dissected from the enucleated globes were subjected to ESR. Similarly, the retina and choroid obtained at the peak of experimental autoimmune uveo-retinitis (EAU) were placed in a vial containing luminal, and chemiluminescence was counted on a Packard liquid scintillation analyzer. Results The ESR three-line spectrum (g=2.04; aN=12.5 G) obtained was characteristic of the adduct [(MGD)2-Fe2+-NO]. The majority of this signal was eliminated by the inducible nitric oxide synthase (iNOS) specific inhibitor aminoguanidine injected inflamed retina was detected when compared with that of the non inflamed controls. The chemiluminescent activity was further increased two-fold by the addition of bicarbonate to the inflamed retina; the phenomenon is attributable only to the presence of a high steady-state concentration of peroxynitrite. Conclusions The study shows an unequivocal presence of nitric oxide in EAU retina and choroid and the generation of peroxynitrite. High levels of these reactive nitrogen species generated in the inflamed retina and choroids are certain to cause irreversible tissue damage, especially at the susceptible sites such as photoreceptors. PMID:17460428

Wu, Guey Shuang; Sevanian, Alex; Schultz, Brian E.; Zamir, Ehud; Rao, Narsing A.

2007-01-01

397

A coumarin-indole based colorimetric and "turn on" fluorescent probe for cyanide.  

PubMed

A novel coumarin-indole based chemodosimeter with a simple structure was designed and prepared via a condensation reaction in high yield. The probe exhibited very high selectivity towards cyanide on both fluorescence and UV-vis spectra, which allowed it to quantitatively detect and imaging cyanide ions in organic-aqueous solution by either fluorescence enhancement or colorimetric changes. Confirmed by (1)H NMR and HRMS spectra, the detection mechanism was proved to be related with the Michael addition reaction induced by cyanide ions, which blocked the intramolecular charge transfer (ICT) of the probe. Moreover, the probe was able to be utilized efficiently in a wide pH range (7.5-10) with negligible interference from other anions and a low detection limit of 0.51?M. Application in 5 kinds of natural water source and accurate detection of cyanide in tap water solvent system also indicated the high practical significance of the probe. PMID:25490042

Xu, Yu; Dai, Xi; Zhao, Bao-Xiang

2015-03-01

398

A coumarin-indole based colorimetric and 'turn on' fluorescent probe for cyanide  

NASA Astrophysics Data System (ADS)

A novel coumarin-indole based chemodosimeter with a simple structure was designed and prepared via a condensation reaction in high yield. The probe exhibited very high selectivity towards cyanide on both fluorescence and UV-vis spectra, which allowed it to quantitatively detect and imaging cyanide ions in organic-aqueous solution by either fluorescence enhancement or colorimetric changes. Confirmed by 1H NMR and HRMS spectra, the detection mechanism was proved to be related with the Michael addition reaction induced by cyanide ions, which blocked the intramolecular charge transfer (ICT) of the probe. Moreover, the probe was able to be utilized efficiently in a wide pH range (7.5-10) with negligible interference from other anions and a low detection limit of 0.51 ?M. Application in 5 kinds of natural water source and accurate detection of cyanide in tap water solvent system also indicated the high practical significance of the probe.

Xu, Yu; Dai, Xi; Zhao, Bao-Xiang

2015-03-01

399

Survey and Detection of Endophytic Fungi in Lolium Germ Plasm by Direct Staining and Aphid Assays  

Microsoft Academic Search

Wilson, A. D., Clement, S. L., and Kaiser, W. J. 1991. Survey and detection of endophytic fungi in Lolium germ plasm by direct staining and aphid assays. Plant Dis. 75:169-173. Clavicipitaceous anamorphic endophytes were detected in 28 of 85 accessions from five of eight species in a collection of Lolium germ plasm. Comparative descriptions of endophytic mycelium in seeds of

A. DAN WILSON; STEPHEN L. CLEMENT; WALTER J. KAISER

400

Development of a colorimetric sensor array for squid spoilage assessment.  

PubMed

The aim of this work was to develop and evaluate a rapid, easy-to-use optoelectronic system for the shelf-life assessment of squid in cold storage. For this purpose, an optoelectronic nose was designed, which consisted of an array containing six sensing materials prepared by combining different dyes and two inorganic supports (aluminium oxide and silica gel). Samples were packaged with the colorimetric array and kept in cold storage for 12 days. Squid spoilage was monitored simultaneously by the colorimetric array and by the physico-chemical and microbial analyses during storage. Samples exceeded the acceptability limits for microbial counts on the third day. PCA analysis carried out with CIELab showed that the colorimetric array was able to discriminate between fresh squid fit for consumption and spoiled squid. The statistical models obtained by PLS, with the optoelectronic nose, successfully predicted CO2 and O2 content in the headspace as well as microbial growth. PMID:25577086

Zaragozá, Patricia; Fuentes, Ana; Ruiz-Rico, María; Vivancos, José-Luis; Fernández-Segovia, Isabel; Ros-Lis, José V; Barat, José M; Martínez-Máñez, Ramón

2015-05-15

401

Colorimetric determination of ferrous-ferric ratio in glass  

SciTech Connect

This memorandum describes a simple, rapid colorimetric procedure that can be used for analysis of vitrified melter feed. This method can replace the Moessbauer spectroscopy method for routine DWPF process control analysis. A colorimetric method has been developed that is recommended as a replacement for Moessbauer spectroscopy for process control measurements of the Fe(II)/Fe(III) ratio of melter feed for the DWPF analytical laboratory. The results agree satisfactorily with Moessbauer values. The method is suitable for remote operation and has several advantages. The total time involved is less than 30 minutes. Quantitative measurements of samples, reagents, and dilutions are unnecessary because only the ratio value is required and both Fe(II) and total Fe are measured on the same solution. Small samples (<3 mg total Fe) are required, minimizing radiation exposure, because of the high sensitivity of the colorimetric method. Relative precision and relative accuracy are about {plus minus}5%.

Baumann, E W

1987-02-20

402

An Output-Capacitorless Low-Dropout Regulator With Direct Voltage-Spike Detection  

Microsoft Academic Search

An output-capacitorless low-dropout regulator (LDO) with a direct voltage-spike detection circuit is presented in this paper. The proposed voltage-spike detection is based on capacitive coupling. The detection circuit makes use of the rapid transient voltage at the LDO output to increase the bias current momentarily. Hence, the transient response of the LDO is significantly enhanced due to the improvement of

Pui Ying Or; Ka Nang Leung

2010-01-01

403

Direct determination of glyphosate using hydrophilic interaction chromatography with coulometric detection at copper microelectrode  

Microsoft Academic Search

A simple, rapid, and low-cost coulometric method for direct detection of glyphosate using hydrophilic interaction chromatography is presented. The principle of detection is based on the enhancement of the anodic current of copper microelectrode in the presence of complexing agents, such as glyphosate, with the formation of a soluble Cu(II) complex. Under optimized conditions, the limit of detection (S\\/R=3) for

Cláudia F. B. Coutinho; Lincoln F. M. Coutinho; Luiz H. Mazo; Suzana L. Nixdorf; Carlos A. P. Camara; Fernando M. Lanças

2007-01-01

404

Is Anyone Looking at Me? Direct Gaze Detection in Children with and without Autism  

ERIC Educational Resources Information Center

Atypical processing of eye contact is one of the significant characteristics of individuals with autism, but the mechanism underlying atypical direct gaze processing is still unclear. This study used a visual search paradigm to examine whether the facial context would affect direct gaze detection in children with autism. Participants were asked to…

Senju, Atsushi; Kikuchi, Yukiko; Hasegawa, Toshikazu; Tojo, Yoshikuni; Osanai, Hiroo

2008-01-01

405

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

406

Improved direct back EMF detection for sensorless brushless DC (BLDC) motor drives  

Microsoft Academic Search

Improved back EMF detection circuits for low voltage\\/low speed and high voltage sensorless BLDC motor drives are presented in this paper. The improvements are based on the direct back EMF sensing method from our previous research work described in reference, which describes a technique for directly extracting phase back EMF information without the need to sense or re-construct the motor

Jianwen Shao; Dennis Nolan; Thomas Hopkins

2003-01-01

407

On Diurnal and Annual Variations of Directional Detection Rates of Dark Matter  

E-print Network

Direction sensitive direct detection of Weakly Interacting Massive Particles (WIMPs) as Dark matter would provide an unambiguous non-gravitational signature of Dark Matter (DM). The diurnal variation of DM signal due to earth's rotation around its own axis can be a significant signature for galactic WIMPs. Because of particular orientation of earth's axis of rotation with respect to WIMP wind direction, the apparent direction of WIMP wind as observed at a detector can alter widely over a day. In this work we calculate the directional detection rates with their daily and yearly modulations in a earth-bound dark matter experiments considering detailed features of the geometry and dynamics of the earth-sun system along with the solar motion in galactic frame. We demonstrate the results for two types of gas detectors namely DRIFT (target material CS2) and NEWAGE (target material CF4) that use Time Projection Chamber techniques for measuring directionality of the recoil nucleus.

Bandyopadhyay, Abhijit

2010-01-01

408

Prospects for detecting dark matter with neutrino telescopes in light of recent results from direct detection experiments  

SciTech Connect

Direct detection dark matter experiments, lead by the CDMS collaboration, have placed increasingly stronger constraints on the cross sections for elastic scattering of WIMPs on nucleons. These results impact the prospects for the indirect detection of dark matter using neutrino telescopes. With this in mind, we revisit the prospects for detecting neutrinos produced by the annihilation of WIMPs in the Sun. We find that the latest bounds do not seriously limit the models most accessible to next generation kilometer-scale neutrino telescopes such as IceCube. This is largely due to the fact that models with significant spin-dependent couplings to protons are the least constrained and, at the same time, the most promising because of the efficient capture of WIMPs in the Sun. We identify models where dark matter particles are beyond the reach of any planned direct detection experiments while within reach of neutrino telescopes. In summary, we find that, even when contemplating recent direct detection results, neutrino telescopes still have the opportunity to play an important as well as complementary role in the search for particle dark matter.

Halzen, Francis; /Wisconsin U., Madison; Hooper, Dan; /Fermilab

2005-10-01

409

An Illumination-Adaptive Colorimetric Measurement Using Color Image Sensor  

NASA Astrophysics Data System (ADS)

An image sensor for a use of colorimeter is characterized based on the CIE standard colorimetric observer. We use the method of least squares to derive a colorimetric characterization matrix between RGB output signals and CIE XYZ tristimulus values. This paper proposes an adaptive measuring method to obtain the chromaticity of colored scenes and illumination through a 3×3 camera transfer matrix under a certain illuminant. Camera RGB outputs, sensor status values, and photoelectric characteristic are used to obtain the chromaticity. Experimental results show that the proposed method is valid in the measuring performance.

Lee, Sung-Hak; Lee, Jong-Hyub; Sohng, Kyu-Ik

410

Characterising dark matter searches at colliders and direct detection experiments: vector mediators  

NASA Astrophysics Data System (ADS)

We introduce a Minimal Simplified Dark Matter (MSDM) framework to quantitatively characterise dark matter (DM) searches at the LHC. We study two MSDM models where the DM is a Dirac fermion which interacts with a vector and axial-vector mediator. The models are characterised by four parameters: m DM , M med , g DM and g q, the DM and mediator masses, and the mediator couplings to DM and quarks respectively. The MSDM models accurately capture the full event kinematics, and the dependence on all masses and couplings can be systematically studied. The interpretation of mono-jet searches in this framework can be used to establish an equal-footing comparison with direct detection experiments. For theories with a vector mediator, LHC mono-jet searches possess better sensitivity than direct detection searches for light DM masses (?5 GeV). For axial-vector mediators, LHC and direct detection searches generally probe orthogonal directions in the parameter space. We explore the projected limits of these searches from the ultimate reach of the LHC and multi-ton xenon direct detection experiments, and find that the complementarity of the searches remains. Finally, we provide a comparison of limits in the MSDM and effective field theory (EFT) frameworks to highlight the deficiencies of the EFT framework, particularly when exploring the complementarity of mono-jet and direct detection searches.

Buchmueller, Oliver; Dolan, Matthew J.; Malik, Sarah A.; McCabe, Christopher

2015-01-01

411

Rapid and selective lead (II) colorimetric sensor based on azacrown ether-functionalized gold nanoparticles  

NASA Astrophysics Data System (ADS)

A gold nanoparticle (AuNPs)-based simple and fast colorimetric sensor for selective detecting of Pb(II) in aqueous solution has been developed. Monodisperse AuNPs (approx. 2.0 nm diameter) has been prepared facilely and further modified with an alkanethiol-bearing monoazacrown ether terminus. These AuNPs are shown to selectively sense Pb2 + through color change, which is visually discernible by an appearance of the surface plasmon band (SPB) at 520 nm. The recognition mechanism is attributed to the unique structure of the monoazacrown ether attached to AuNPs and metal sandwich coordination between two azacrown ether moieties that are attached to separate nanoparticles. This inter-particle cross-linking results in an aggregation and apparent color change from brown to purple. Additionally, TEM experiments support the optical absorption data proving the aggregation between azacrown ether-capped gold nanoparticles. This AuNP-based colorimetric assay is a facile and robust method and allows fast detection of Pb2 + at ambient temperatures. More importantly, the developed technique does not utilize enzymatic reactions, light-sensitive dye molecules, lengthy protocols or sophisticated instrumentation.

Alizadeh, A.; Khodaei, M. M.; Karami, Ch; Workentin, M. S.; Shamsipur, M.; Sadeghi, M.

2010-08-01

412

Deciphering inflation with gravitational waves: Cosmic microwave background polarization vs direct detection with laser interferometers  

SciTech Connect

A detection of the primordial gravitational wave background is considered to be the 'smoking-gun' evidence for inflation. While superhorizon waves are probed with cosmic microwave background (CMB) polarization, the relic background will be studied with laser interferometers. The long lever arm spanned by the two techniques improves constraints on the inflationary potential and validation of consistency relations expected under inflation. If gravitational waves with a tensor-to-scalar amplitude ratio greater than 0.01 are detected by the CMB, then a direct-detection experiment with a sensitivity consistent with current concept studies should be pursued vigorously. If no primordial tensors are detected by the CMB, a direct-detection experiment to understand the simplest form of inflation must have a sensitivity improved by two to 3 orders of magnitude over current plans.

Smith, Tristan L. [California Institute of Technology, Mail Code 130-33, Pasadena, California 91125 (United States); Peiris, Hiranya V. [Kavli Institute for Cosmological Physics and Enrico Fermi Institute, University of Chicago, Chicago Illinois 60637 (United States); Cooray, Asantha [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)

2006-06-15

413

Directly measuring the concurrence of atomic two-qubit states through the detection of cavity decay  

NASA Astrophysics Data System (ADS)

We present a scheme for directly measuring the concurrence of atomic two-qubit states (including pure states and mixed states) by detecting the photons leaking from the cavities where the atoms are located. We found that it is possible to encode the concurrence of two-atom entangled states in the photon detection results on the cavities. Cavity decay usually plays a passive role in quantum information processing, but in our scheme the decay of cavity mode plays a constructive role, and the state detection for trapped atoms were replaced by the photon detection. Our scheme is more implementable and may be feasible within the current technology.

Zhang, Li-Hua; Yang, Ming; Cao, Zhuo-Liang

2014-05-01

414

Liquid core optical fiber total reflection cell as a colorimetric detector for flow injection analysis  

SciTech Connect

A hollow fiber (250 ..mu..m i.d.) was used as a colorimetric cell for detecting iodine absorption. To attain total reflection of source light inside the capillary, carbon disulfide was used as a solvent which constitutes the fiber core. A funnel-shaped glass was used for efficiency condensing the light source emission into an aperture of hollow fiber; a low-power tungsten lamp was usable as the light source. With a 5-m cell, 0.1 ..mu..g of I/mL (10 ng of I) can be detected based on the iodine absorption at 540 nm when the solution was injected into the carbon disulfide flow. An automated detection system of iodide ion was also constructed. 11 references, 8 figures.

Fujiwara, K.; Fuwa, K.

1985-05-01

415

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

416

Colorimetric logic response based on aptamer functionalized colloidal crystal hydrogels.  

PubMed

A novel colorimetric logic system based on the aptamer-cross-linked colloidal crystal hydrogel (CCH) was developed. With the input stimuli of Hg(2+) and Ag(+), the CCH displayed shrinking response and colour change corresponding to the logical "OR" and "AND" gate. The visualization of the logic output signals is realized. PMID:25874602

Ye, Baofen; Wang, Huan; Ding, Haibo; Zhao, Yuanjin; Pu, Yuepu; Gu, Zhongze

2015-04-24

417

Digital camera filter design for colorimetric and spectral accuracy  

Microsoft Academic Search

A filter optimization was investigated to design a set of filters for a five channel multi-spectral camera, three of which result in high colorimetric performance when used alone, and the full set having high quality spectral performance. Each candidate filter was selected from a set of 33 glass filters with three different thicknesses where filters may be combined in optical

Francisco H. Imai; Shuxue Quan; Mitchell R. Rosen; Roy S. Berns

2001-01-01

418

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

419

A Colorimetric Process to Visualize Erythrocyte Exovesicles Aggregates  

ERIC Educational Resources Information Center

A biochemistry laboratory class protocol is described in order to create an opportunity for students to apply by doing the theoretical concepts underlying biomolecules and vesicles properties, together with the principles of centrifugation and colorimetric methodologies. Through simple procedures the students will i) observe the segregation of the…

Saldanha, Carlota; Santos, Nuno C.; Martins-Silva, J.

2004-01-01

420

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

421

Colorimetric Quantification and in Situ Detection of Collagen  

ERIC Educational Resources Information Center

A simple multidisciplinary and inexpensive laboratory exercise is proposed, in which the undergraduate student may correlate biochemical and anatomical findings. The entire practical session can be completed in one 2.5-3 hour laboratory period, and consists of the quantification of collagen and total protein content from tissue sections--without…

Esteban, Francisco J.; del Moral, Maria L.; Sanchez-Lopez, Ana M.; Blanco, Santos; Jimenez, Ana; Hernandez, Raquel; Pedrosa, Juan A.; Peinado, Maria A.

2005-01-01

422

Doubling direct-detection data rate by polarization multiplexing of 16-QAM without active polarization control.  

PubMed

We introduce and simulate a technique enabling to utilize the polarization dimension in direct-detection optical transmission, supporting polarization multiplexing (POL-MUX) over direct-detection (DD) methods previously demonstrated for a single polarization such as direct-detection OFDM. POL-MUX is currently precluded in self-coherent DD with remotely transmitted pilot, as signal x pilot components may randomly fade out. We propose POL-MUX transmission of advanced modulation formats, such as 16-QAM and higher, by means of a novel low-complexity photonic integrated optical front-end and adaptive 3x2 MIMO DSP. The principle of operation is as follows: an additional X x Y cross-polarizations signal is generated, providing three projections onto an over-complete frame of three dependent vectors. This enables to resiliently reconstruct the received state of polarization even when the remotely transmitted pilot fades along one of the received polarization axes. PMID:24514795

Nazarathy, Moshe; Agmon, Amos

2013-12-30

423

Loop-induced dark matter direct detection signals from ?-ray lines  

SciTech Connect

Improved limits as well as tentative claims for dark matter annihilation into ?-ray lines have been presented recently. We study the direct detection cross section induced from dark matter annihilation into two photons in a model-independent fashion, assuming no additional couplings between dark matter and nuclei. We find a striking non-standard recoil spectrum due to different destructively interfering contributions to the dark matter nucleus scattering cross section. While in the case of s-wave annihilation the current sensitivity of direct detection experiments is insufficient to compete with indirect detection searches, for p-wave annihilation the constraints from direct searches are comparable. This will allow to test dark matter scenarios with p-wave annihilation that predict a large di-photon annihilation cross section in the next generation of experiments.

Frandsen, Mads T.; Haisch, Ulrich; Kahlhoefer, Felix; Mertsch, Philipp; Schmidt-Hoberg, Kai, E-mail: m.frandsen1@physics.ox.ac.uk, E-mail: u.haisch1@physics.ox.ac.uk, E-mail: felix.kahlhoefer@physics.ox.ac.uk, E-mail: p.mertsch1@physics.ox.ac.uk, E-mail: ksh@physics.ox.ac.uk [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)

2012-10-01

424

The peroxidase/catalase-like activities of MFe?O? (M=Mg, Ni, Cu) MNPs and their application in colorimetric biosensing of glucose.  

PubMed

MFe2O4 (M=Mg, Ni, Cu) magnetic nanoparticles (MNPs) were found to have catalytic activities similar to those of biological enzymes such as catalase and peroxidase. These nanomaterials, as bifunctional catalase/peroxidases (KatGs), not only could catalyze H2O2 to produce hydroxyl radicals, which oxidized peroxidase substrate to produce color, but also could catalyze the decomposition reaction of H2O2 into water and oxygen directly in the same condition through the catalase-like activity. And it was also found that the amount of generated hydroxyl radicals and oxygen was related to the concentration of MFe2O4 (M=Mg, Ni, Cu) MNPs. The peroxidase-like catalytic behavior of MFe2O4 MNPs was analyzed in detail. Under the optimized conditions, NiFe2O4 MNPs were used as a colorimetric biosensor for the detection of 9.4×10(-7)-2.5×10(-5) mol L(-1) glucose with a limit of detection (LOD) of 4.5×10(-7) mol L(-1). The sensor was successfully applied to glucose detection in urine sample. PMID:25127473

Su, Li; Qin, Wenjie; Zhang, Huige; Rahman, Zia Ur; Ren, Cuiling; Ma, Sudai; Chen, Xingguo

2015-01-15

425

Improvement on the polynomial modeling of digital camera colorimetric characterization  

NASA Astrophysics Data System (ADS)

The digital camera has become a requisite for people's life, also essential in imaging applications, and it is important to get more accurate colors with digital camera. The colorimetric characterization of digital camera is the basis of image copy and color management process. One of the traditional methods for deriving a colorimetric mapping between camera RGB signals and the tristimulus values CIEXYZ is to use polynomial modeling with 3×11 polynomial transfer matrices. In this paper, an improved polynomial modeling is presented, in which the normalized luminance replaces the camera inherent RGB values in the traditional polynomial modeling. The improved modeling can be described by a two stage model. The first stage, relationship between the camera RGB values and normalized luminance with six gray patches in the X-rite ColorChecker 24-color card was described as "Gamma", camera RGB values were converted into normalized luminance using Gamma. The second stage, the traditional polynomial modeling was improved to the colorimetric mapping between normalized luminance and the CIEXYZ. Meanwhile, this method was used under daylight lighting environment, the users can not measure the CIEXYZ of the color target char using professional instruments, but they can accomplish the task of the colorimetric characterization of digital camera. The experimental results show that: (1) the proposed method for the colorimetric characterization of digital camera performs better than traditional polynomial modeling; (2) it's a feasible approach to handle the color characteristics using this method under daylight environment without professional instruments, the result can satisfy for request of simple application.

Huang, Xiaoqiao; Yu, Hongfei; Shi, Junsheng; Tai, Yonghang

2014-11-01

426

Bearing fault detection for direct-drive wind turbines via stator current spectrum analysis  

Microsoft Academic Search

Bearing faults constitute a significant portion of all faults in wind turbine generators (WTGs). Current-based bearing fault detection has significant advantages over traditional vibration-based methods in terms of cost, implementation, and system reliability. This paper proposes a method based on stator current power spectral density (PSD) analysis for bearing fault detection of direct-drive WTGs. In the proposed method, appropriate interpolation\\/up-sampling

Xiang Gong; Wei Qiao

2011-01-01

427

Closing in on mass-degenerate dark matter scenarios with antiprotons and direct detection  

SciTech Connect

Over the last years both cosmic-ray antiproton measurements and direct dark matter searches have proved particularly effective in constraining the nature of dark matter candidates. The present work focusses on these two types of constraints in a minimal framework which features a Majorana fermion as the dark matter particle and a scalar that mediates the coupling to quarks. Considering a wide range of coupling schemes, we derive antiproton and direct detection constraints using the latest data and paying close attention to astrophysical and nuclear uncertai