Sample records for direct colorimetric detection

  1. Polymeric assay film for direct colorimetric detection

    DOEpatents

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

    2002-01-01

    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.

  2. Polymeric assay film for direct colorimetric detection

    DOEpatents

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

    1999-01-01

    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.

  3. Direct colorimetric detection of a receptor-ligand interaction by a polymerized bilayer assembly

    SciTech Connect

    Charych, D.H.; Nagy, J.O.; Bednarski, M.D. (Lawrence Berkeley Laboratory, CA (United States)); Spevak, W. (Univ. of California, Berkeley (United States))

    1993-07-30

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

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

    NASA Astrophysics Data System (ADS)

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

    1993-07-01

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

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

    PubMed

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

    2015-03-11

    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

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

    PubMed

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

    2014-01-01

    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

  7. Label free colorimetric and fluorimetric direct detection of methylated DNA based on silver nanoclusters for cancer early diagnosis.

    PubMed

    Dadmehr, Mehdi; Hosseini, Morteza; Hosseinkhani, Saman; Reza Ganjali, Mohammad; Sheikhnejad, Reza

    2015-11-15

    Epigenetic changes such as DNA methylation of CpG islands located in the promoter region of some tumor suppressor genes are very common in human diseases such as cancer. Detection of aberrant methylation pattern could serve as an excellent diagnostic approach. Recently, the direct detection of methylated DNA sequences without using chemical and enzymatic treatments or antibodies has received great deal of attentions. In this study, we report a colorimetric and fluorimetric technique for direct detection of DNA methylation. Here, the DNA is being used as an effective template for fluorescent silver nanoclusters formation without any chemical modification or DNA labeling. The sensitivity test showed that upon the addition of target methylated DNA, the fluorescence intensity is decreased in a linear range when the concentration of methylated DNA has increased from 2.0×10(-9) to 6.3 ×10(-7)M with the detection limit of 9.4×10(-10)M. The optical and fluorescence spectral behaviors were highly reproducible and clearly discriminated between unmethylated, methylated and even partially methylated DNA in CpG rich sequences. The results were also reproducible when the human plasma was present in our assay system. PMID:26056954

  8. Optical colorimetric sensor strip for direct readout glucose measurement.

    PubMed

    Wang, Xu-dong; Chen, Hai-xu; Zhou, Ting-yao; Lin, Zhi-jie; Zeng, Jing-bin; Xie, Zhao-xiong; Chen, Xi; Wong, Kwok-yin; Chen, Guo-nan; Wang, Xiao-ru

    2009-08-15

    A novel direct readout colorimetric optical glucose sensor strip was constructed based on a three-layer film, including a green-emitted CdTe/CdS quantum dots (QDs) layer as a stable color background, a red-fluorescent platinum-porphyrin oxygen-sensing layer and a glucose oxidase layer. The sensor achieved high resolution (up to 0.2 mmol L(-1)) glucose determination with a detection range from 0 to 3.0 mmol L(-1). A "glucose ruler" which acts as a glucose standard colorimetric card was obtained. Glucose concentration could easily be directly readout using the "glucose ruler", which made the glucose determination rapid, convenient and easy. The effects of pH, salinity and temperature were systematically investigated. The prepared sensor was finally applied for glucose sample analysis, compared with the "glucose ruler", accurate results could be directly readout. PMID:19523808

  9. A colorimetric sensor array for detection of triacetone triperoxide vapor.

    PubMed

    Lin, Hengwei; Suslick, Kenneth S

    2010-11-10

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

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

    E-print Network

    Suslick, Kenneth S.

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

  11. Colorimetric Method for Beryllium Surface Contamination Detection

    Microsoft Academic Search

    2004-01-01

    To address the need for real-time accurate total beryllium analyses, Savannah River Technology Center Analytical Development Section personnel evaluated and modified a colorimetric screening method developed at Los Alamos National Lab to measure beryllium on surfaces. This method was based on a color complex formed by beryllium and chromium azurol s . SRTC converted this visual method to a quantitative

  12. Optical fiber waveguide sensor for the colorimetric detection of ammonia

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    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.

  13. Colorimetric resonant reflection as a direct biochemical assay technique

    Microsoft Academic Search

    Brian Cunningham; Peter Li; Bo Lin; J. Pepper

    2002-01-01

    A novel approach for the detection of molecular interactions is presented in which a colorimetric resonant diffractive grating surface is used as a surface binding platform. A guided mode resonant phenomenon is used to produce an optical structure that, when illuminated with white light, is designed to reflect only a single wavelength. When molecules are attached to the surface, the

  14. Preoxidation for colorimetric sensor array detection of VOCs.

    PubMed

    Lin, Hengwei; Jang, Minseok; Suslick, Kenneth S

    2011-10-26

    A disposable preoxidation technique that dramatically improves the detection and identification of volatile organic compounds (VOCs) by a colorimetric sensor array is reported. Passing a vapor stream through a tube packed with chromic acid on silica immediately before the colorimetric sensor array substantially increases the sensitivity to less-reactive VOCs and improves the limits of detection (LODs) ~300-fold, permitting the detection, identification, and discrimination of 20 commonly found indoor VOC pollutants at both their immediately dangerous to life or health (IDLH) and permissible exposure limit (PEL) concentrations. The LODs of these pollutants were on average 1.4% of their respective PELs. PMID:21967478

  15. Colorimetric detection of uranium in water

    DOEpatents

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

    2012-03-13

    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.

  16. A gold nanoparticle-based colorimetric probe for rapid detection of 1-hydroxypyrene in urine.

    PubMed

    Hu, Yaqi; Du, Chunyan; Li, Yunchao; Fan, Louzhen; Li, Xiaohong

    2015-06-15

    Direct and rapid detection of 1-hydroxypyrene (1-OHP) is of great importance owing to its high carcinogenicity, teratogenicity and toxicity. In this study, a simple colorimetric assay for rapid determination of 1-OHP is reported, which is based on non-crosslinking aggregation of gold nanoparticles (Au NPs) induced by 1-OHP in the presence of formic acid (FA). Initially, Au NPs were synthesized with citrate as the capping agent and exhibited red color. Subsequently, the addition of FA did not cause aggregation of Au NPs, but a proton transfer process occurred from FA to carboxylic anions on the surface of Au NPs with a decreased zeta potential. The subsequent addition of 1-OHP resulted in a further decreased zeta potential and an intensely hydrophobic environment, which led to a strong and rapid non-crosslinking aggregation of Au NPs within 5 min with the color changing from red to violet blue. Based on this principle, sensitive and selective detection of 1-OHP was achieved. The detection limit was 3.3 nM. Finally, the colorimetric assay was successfully applied to detect 1-OHP in a urine sample. This strategy provides new insights into developing colorimetric methods for on-site and real-time detection of polycyclic aromatic hydrocarbons. PMID:25988203

  17. Colorimetric Detection and Identification of Natural and Artificial Sweeteners

    Microsoft Academic Search

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

    2009-01-01

    A disposable, low-cost colorimetric sensor array has been created by\\u000a pin-printing onto a hydrophilic membrane 16 chemically responsive\\u000a nanoporous pigments that are comprised of indicators immobilized in an\\u000a organic-ally modified silane (ormosil). The array has been used to\\u000a detect and identify 14 different natural and artificial sweeteners at\\u000a millimolar concentrations, as well as commonly used individual-serving\\u000a sweetener packets. The array

  18. Light regulation of peroxidase activity by spiropyran functionalized carbon nanotubes used for label-free colorimetric detection of lysozyme.

    PubMed

    Song, Yujun; Xu, Can; Wei, Weili; Ren, Jinsong; Qu, Xiaogang

    2011-08-28

    Spiropyran dye-modified multi-walled carbon nanotubes have been synthesized and used to regulate horseradish peroxidase activity by light irradiation. This design has been developed for a label-free colorimetric assay of lysozyme with a direct detection limit of 30 nM. PMID:21748199

  19. A Colorimetric Technique for Detecting Trichothecenes and Assessing Relative Potencies

    PubMed Central

    Engler, Kathryn H.; Coker, Raymond D.; Evans, Ivor H.

    1999-01-01

    We tested a novel colorimetric toxicity test, based on inhibition of ?-galactosidase activity in the yeast Kluyveromyces marxianus, for sensitivity to a range of mycotoxins. A variety of trichothecene mycotoxins could be detected. The order of toxicity established with this bioassay was verrucarin A > roridin A > T-2 toxin > diacetoxyscirpenol > HT-2 toxin > acetyl T-2 toxin > neosolaniol > fusarenon X > T-2 triol > scirpentriol > nivalenol > deoxynivalenol > T-2 tetraol. The sensitivity of detection was high, with the most potent trichothecene tested, verrucarin A, having a 50% effective concentration (concentration of toxin causing 50% inhibition) of 2 ng/ml. Other mycotoxins (cyclopiazonic acid, fumonisin B1, ochratoxin A, patulin, sterigmatocystin, tenuazonic acid, and zearalenone) could not be detected at up to 10 ?g/ml, nor could aflatoxins B1 and M1 be detected at concentrations up to 25 ?g/ml. This test should be useful for trichothecene detection and for studies of relevant interactions—both between trichothecenes themselves and between trichothecenes and other food constituents. PMID:10223969

  20. Colorimetric detection of catalytic reactivity of nanoparticles in complex matrices.

    PubMed

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

    2015-03-17

    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

  1. Miniaturized 96-well ELISA chips for staphylococcal enterotoxin B detection using portable colorimetric detector

    Microsoft Academic Search

    Kim E. Sapsford; Jesse Francis; Steven Sun; Yordan Kostov; Avraham Rasooly

    2009-01-01

    A previously developed fluorescence sensing platform, combining spatial illumination using electroluminescence (EL) semiconductor\\u000a strips with charge coupled device (CCD)-based detection (EL-CCD), was adapted to a new 96-well chip for colorimetric immunological\\u000a assays, enhancing the capabilities of the EL-CCD platform. The modified system was demonstrated using a colorimetric-based\\u000a enzyme linked immunosorbent assay (ELISA) for detection of staphylococcal enterotoxin B (SEB). Limits

  2. Direct colorimetric monoclonal antibody enzyme immunoassay for estradiol-17 beta in saliva.

    PubMed

    Tamate, K; Charleton, M; Gosling, J P; Egan, D; Ishikawa, M; Fottrell, P F; Kane, M M

    1997-07-01

    We developed a direct microtiter plate enzyme immunoassay to measure estradiol-17 beta in saliva. The assay has a commercially available monoclonal antibody, raised against estradiol-17 beta-6-carboxymethyloximebovine serum albumin, and a homologous horseradish peroxidase conjugate measured colorimetrically. The detection limit (equivalent to B0-3 SD) is 365 amol/well or 7.3 pmol/L when 50-microL samples are assayed. Cross-reactivity with estrone and estriol, testosterone, or progesterone is < 0.2%. Estradiol-17 beta was measured in daily samples over five natural menstrual cycles and eight cycles stimulated as a preliminary to in vitro fertilization, and the concentrations and fluctuations found agreed with previously published data. This method gives results in approximately 3 h and may be useful for fertility monitoring and management. PMID:9216451

  3. Development of Colorimetric Ozone Detection Papers with High Ultraviolet Resistance Using Ultraviolet Absorbers

    Microsoft Academic Search

    Takashi Miwa; Yasuko Yamada Maruo; Kunihiko Akaoka; Tatsuya Kunioka; Jiro Nakamura; Remedios ez; Sebastian Caparro´s; Manuel Díaz; Johanna Gietl; Otto Klemm; Xinke Wang; Yinping Zhang; Jace Bauer; Xiao-Ying Yu; Robert Cary; Nels Laulainen; Carl Berkowitz; Juan Goncalves; Rakesh Govind; Chatchawan Vongmahadlek; Pham Thao; Boonsong Satayopas; Narisara Thongboonchoo; H. Frey; Po-Yao Kuo; Mohammad Al-Hamdan; William Crosson; Ashutosh Limaye; Douglas Rickman; Dale Quattrochi; Maurice Estes; Judith Qualters; Amber Sinclair; Dennis Tolsma; Kafayat Adeniyi; Amanda Niskar; Meng Yao; Qiong Zhang; David Hand; David Perram; Roy Taylor

    2009-01-01

    Two types of colorimetric ozone detection paper with high resistance to ultraviolet (UV) light have been developed for outdoor ozone detection. These detection papers incorporate indigo carmine and UV absorbers (UVAs). When exposed to ozone, the papers change color from blue to white, and the ozone concentration can be determined by measuring the reflectance of the papers. However, indigo carmine

  4. 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...

  5. A Colorimetric Sensor Array for Detection of Triacetone Triperoxide Vapor

    Microsoft Academic Search

    Hengwei Lin; Kenneth S. Suslick

    2010-01-01

    Triacetone triperoxide (TATP), one of the most dangerous primary\\u000a explosives, has emerged as an explosive of choice for terrorists in\\u000a recent years. Owing to the lack of UV absorbance, fluorescence, or\\u000a facile ionization, TATP is extremely difficult to detect directly.\\u000a Techniques that are able to detect generally require expensive\\u000a instrumentation, need extensive sample preparation, or cannot detect\\u000a TATP in the

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    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.

  8. Gold nanoparticle-mediated detection of melamine based on a dual colorimetric and turbidometric readouts

    Microsoft Academic Search

    Na Li; Fang Wei; Robert Lam; Jiaqi Zou; Stacy Cheng; Steven Lu; Dean Ho

    2010-01-01

    A simple method for rapid detection of melamine in the food is presented. Citrate-coated gold nanoparticles (AuNPs) and cyanuric acid were utilized to generate melamine-concentration dependent colorimetric and turbidometric signals, respectively. As low as 0.4 ppm of melamine can be detected from the whole milk within 15 minutes with this new detection method and a simple acid precipitation based milk

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

    NASA Astrophysics Data System (ADS)

    Wen, Junlin; Zhou, Shungui; Chen, Junhua

    2014-06-01

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

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

    PubMed

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

    2014-01-01

    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

  11. Ultrasensitive colorimetric detection of Cu2+ ion based on catalytic oxidation of L-cysteine.

    PubMed

    Yin, Kun; Li, Bowei; Wang, Xiaochun; Zhang, Weiwei; Chen, Lingxin

    2015-02-15

    As an essential element, copper ion (Cu(2+)) plays important roles in human beings for its participation in diverse metabolic processes as a cofactor and/or a structural component of enzymes. However, excessive uptake of Cu(2+) ion gives rise to the risk of certain diseases. So, it is important to develop simple ways to monitor and detect Cu(2+) ion. In this study, a simple, facile colorimetric sensor for the ultrasensitive determination of Cu(2+) ion was developed based on the following principle: L-cysteine and 1-chloro-2,4-dinitrobenzene (CDNB) could be conjugated to form the yellow product 2,4-dinitrophenylcysteine (DNPC), which was measurable at 355nm; however, upon addition of Cu(2+) ion, the absorbance of DNPC would be decreased owing to the Cu(2+) ion catalytic oxidation of L-cysteine to L-cystine in the presence of O2. Thus, the colorimetric detection of Cu(2+) ion could be achieved. The optimal pH, buffer, temperature and incubation time for the colorimetric sensor were obtained of pH 6.8 in 0.1M HEPES solution, 90 °C and 50 min, respectively. A good linearity within the range of 0.8-10 nM (r = 0.996) was attained, with a high detectability up to 0.5nM. Analyses of Cu(2+) ion in drinking water, lake water, seawater and biological samples were carried out and the method performances were found to agree well with that obtained by ICP-MS. The developed simple colorimetric sensor proved applicable for Cu(2+) ion determination in real samples with high sensitivity and selectivity. PMID:25194800

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

    PubMed

    R?zicka, F; Holá, V

    2008-02-01

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

  13. Highly sensitive and specific colorimetric detection of cancer cells via dual-aptamer target binding strategy.

    PubMed

    Wang, Kun; Fan, Daoqing; Liu, Yaqing; Wang, Erkang

    2015-11-15

    Simple, rapid, sensitive and specific detection of cancer cells is of great importance for early and accurate cancer diagnostics and therapy. By coupling nanotechnology and dual-aptamer target binding strategies, we developed a colorimetric assay for visually detecting cancer cells with high sensitivity and specificity. The nanotechnology including high catalytic activity of PtAuNP and magnetic separation & concentration plays a vital role on the signal amplification and improvement of detection sensitivity. The color change caused by small amount of target cancer cells (10 cells/mL) can be clearly distinguished by naked eyes. The dual-aptamer target binding strategy guarantees the detection specificity that large amount of non-cancer cells and different cancer cells (10(4) cells/mL) cannot cause obvious color change. A detection limit as low as 10 cells/mL with detection linear range from 10 to 10(5) cells/mL was reached according to the experimental detections in phosphate buffer solution as well as serum sample. The developed enzyme-free and cost effective colorimetric assay is simple and no need of instrument while still provides excellent sensitivity, specificity and repeatability, having potential application on point-of-care cancer diagnosis. PMID:26042871

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    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.

  15. A dual colorimetric-ratiometric fluorescent probe NAP-3 for selective detection and imaging of endogenous labile iron(III) pools in C. elegans.

    PubMed

    Goel, Atul; Umar, Shahida; Nag, Pankaj; Sharma, Ashutosh; Kumar, Lalit; Shamsuzzama; Hossain, Zakir; Gayen, Jiaur R; Nazir, Aamir

    2015-03-25

    The discovery of an iron(III)-selective ratiometric fluorescent probe to detect and visualize endogenous labile iron pools in living organisms at the molecular level has been long awaited. Herein we report the first dual colorimetric and ratiometric fluorescent probe naphtho[2,1-b][1,10]phenanthroline for selective and 'direct' visualization of labile iron(III) pools in a multicellular organism, Caenorhabditis elegans. PMID:25633904

  16. Iodide-Responsive Cu-Au Nanoparticle-Based Colorimetric Platform for Ultrasensitive Detection of Target Cancer Cells.

    PubMed

    Ye, Xiaosheng; Shi, Hui; He, Xiaoxiao; Wang, Kemin; He, Dinggeng; Yan, Lv'an; Xu, Fengzhou; Lei, Yanli; Tang, Jinlu; Yu, Yanru

    2015-07-21

    Colorimetric analysis is promising in developing facile, fast, and point-of-care cancer diagnosis techniques, but the existing colorimetric cancer cell assays remain problematic because of dissatisfactory sensitivity as well as complex probe design or synthesis. To solve the problem, we here present a novel colorimetric analytical strategy based on iodide-responsive Cu-Au nanoparticles (Cu-Au NPs) combined with the iodide-catalyzed H2O2-TMB (3,3,5,5-tetramethylbenzidine) reaction system. In this strategy, bimetallic Cu-Au NPs prepared with an irregular shape and a diameter of ?15 nm could chemically absorb iodide, thus indirectly inducing colorimetric signal variation of the H2O2-TMB system. By further utilizing its property of easy biomolecule modification, a versatile colorimetric platform was constructed for detection of any target that could cause the change of Cu-Au NPs concentration via molecular recognition. As proof of concept, an analysis of human leukemia CCRF-CEM cells was performed using aptamer Sgc8c-modified Cu-Au NPs as the colorimetric probe. Results showed that Sgc8c-modified Cu-Au NPs successfully achieved a simple, label-free, cost-effective, visualized, selective, and ultrasensitive detection of cancer cells with a linear range from 50 to 500 cells/mL and a detection limit of 5 cells in 100 ?L of binding buffer. Moreover, feasibility was demonstrated for cancer cell analysis in diluted serum samples. The iodide-responsive Cu-Au NP-based colorimetric strategy might not only afford a new design pattern for developing cancer cell assays but also greatly extend the application of the iodide-catalyzed colorimetric system. PMID:26100583

  17. Prussian blue nanoparticles as peroxidase mimetics for sensitive colorimetric detection of hydrogen peroxide and glucose.

    PubMed

    Zhang, Weimin; Ma, Diao; Du, Jianxiu

    2014-03-01

    Prussian blue nanoparticles (PB NPs) exhibits an intrinsic peroxidase-like catalytic activity towards the hydrogen peroxide (H2O2)-mediated oxidation of classical peroxidase substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt to produce a colored product. The catalysis follows Michaelis-Menen kinetics and shows strong affinity for H2O2. Using PB NPs as a peroxidase mimetics, a colorimetric method was developed for the detection of 0.05-50.0 ?M H2O2, with a detection limit of 0.031 ?M. When the catalytic reaction of PB NPs was coupled with the reaction of glucose oxidation catalyzed by glucose oxidase, a sensitive and selective colorimetric method for the detection of glucose was realized. The limit of detection for glucose was determined to be as low as 0.03 ?M and the linear range was from 0.1 ?M to 50.0 ?M. The method was successfully applied to the determination of glucose in human serum. Compared with other nanomaterials-based peroxidase mimetics, PB NPs provides 10-100 times higher sensitivity toward the detection of H2O2 and glucose. The detection platform developed showed great potential applications in varieties of physiological importance substances when merged with appropriate H2O2-producing oxidases. PMID:24468383

  18. A Colorimetric Sensor Array for Detection and Identification of Sugars

    E-print Network

    Suslick, Kenneth S.

    sweeteners were differentiated without error in 80 trials. Limits of detection at pH 7.4 for glucose were Va 2007, 30, 677. (b) Suslick, K. S. MRS Bull. 2004, 29, 720. (5) (a) Rakow, N. A.; Suslick, K. S. Nature

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

    PubMed Central

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

    2014-01-01

    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

  20. Utilization of unmodified gold nanoparticles in colorimetric detection

    NASA Astrophysics Data System (ADS)

    He, Sha; Liu, Dingbin; Wang, Zhuo; Cai, Kaiyong; Jiang, Xingyu

    2011-10-01

    This review begins with an overview of the appealing properties and various applications of gold nanoparticles, and briefly summarizes recent advances in using unmodified gold nanoparticles to detect different kinds of targets including nucleic acids, proteins, metal ions and small organic molecules. The key point to the unmodified gold nanoparticle-based visual detection assay is to control dispersion and aggregation of colloidal nanoparticles by targets of interest, which usually relies on affinities between gold nanoparticles and targets. The degree of dispersion or aggregation can be visualized through the change of the solution color or the precipitation of nanoparticles from the solution. Thus, the existence of the target molecules can be translated into optical signals and monitored by the naked eye conveniently. Finally, some future prospects of this research field are given.

  1. A G-quadruplex DNAzyme-based colorimetric method for facile detection of Alicyclobacillus acidoterrestris.

    PubMed

    Liu, Tao; Zhang, Xiao; Zhu, Wenxin; Liu, Wei; Zhang, Daohong; Wang, Jianlong

    2014-09-01

    The rapid and sensitive detection of Alicyclobacillus acidoterrestris (AA) has become very important due to the frequent occurrence of fruit juice spoilage by AA. In the present study, using guaiacol, both as the metabolic product of AA related to its concentration and as a green colorimetric substrate of G-quadruplex DNAzyme, a novel G-quadruplex DNAzyme-based colorimetric method for a rapid detection of AA has been developed for the first time. Under optimal conditions, AA has been successfully detected in the concentration range of 10(2)-10(5) cfu mL(-1) with a detection limit of 85 cfu mL(-1). The recoveries ranging from 71.8% to 115.7% with relative standard deviation from 1.2% to 6.6% in spiked apple and orange juice samples were obtained. Results demonstrate that the sensitivity and precision of the developed method is comparable with most other analytical methods and is prominently rapid than them. We believe that the work provides a novel and effective approach and is beneficial for monitoring and reducing the risk of AA contaminations during the process of fruit juice production. PMID:24989256

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

    PubMed

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

    2011-03-01

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

  3. Preparation of a novel colorimetric luminescence sensor strip for the detection of indole-3-acetic acid

    Microsoft Academic Search

    Yan Liu; Haitao Dong; Wenzhu Zhang; Zhiqiang Ye; Guilan Wang; Jingli Yuan

    2010-01-01

    A novel colorimetric luminescence sensor strip for the detection of indole-3-acetic acid (IAA) has been fabricated by using green emissive quantum dots of cadmium telluride (CdTe QDs) as a background layer and a red emissive europium chelate, [4?-(9-anthryl)-2,2?:6?,2?-terpyridine-6,6?-diyl]bis(methylenenitrilo) tetrakis(acetate)-Eu3+ (ATTA-Eu3+), as a specific sensing layer coated on the surface of glass slide, respectively. The luminescence response of the sensor strip

  4. A colorimetric and fluorescent probe for detecting intracellular GSH.

    PubMed

    Chen, Chunyang; Liu, Wei; Xu, Cong; Liu, Weisheng

    2015-09-15

    A new rapid and highly sensitive coumarin-based probe (probe 1) has been designed and synthesized for detecting intracellular GSH. Probe 1 was prepared from 4-methylumbelliferone using a 3-step procedure. It was converted into a latent fluorescence probe, which allowed it to achieve high sensitivity (LOD 122nM) and fluorescence turn-on response (F/F0>15) toward GSH over other various natural amino acids in PBS buffer solution at pH 7.4. Owing to a specific Michael addition between thiols and the double bond of nitroolefin moiety, probe 1 displayed a high selectivity toward GSH. Afterwards, probe 1 was successfully used for fluorescence imaging of GSH in Hela and Hek-293a cells, and a rapid response was observed in the Hek-293a cells after incubating with probe 1 for 1min. Simultaneously, a quantitative determination was achieved in Hela cells in the range of 8-48?M. Specific fluorescence imaging of plants tissue was obtained for proving the permeability of probe 1. Finally, the viability was measured to be more than 80%, which shows probe 1 can serve as a rapid and biocompatible probe for GSH in cells. PMID:25889346

  5. A novel colorimetric biosensor for monitoring and detecting acute toxicity in water.

    PubMed

    Zhai, Junfeng; Yong, Daming; Li, Jing; Dong, Shaojun

    2013-01-21

    This work presents a new colorimetric microorganism biosensor for monitoring and detecting acute toxicity in water, where prussian blue (PB) is used as the colorimetric indicator and E. coli as the model bacterial. In this biosensor, the electron mediator, ferricyanide, accepts electrons from E. coli during respiration to produce ferrocyanide, which subsequently reacts with ferric ions to yield PB, a famous material with a blue color. Since toxicants can inhibit the respiratory activity of E. coli and then reduce the ferrocyanide and consequent PB production, toxicity can be easily detected by measuring the decrease in the production of PB induced by toxicants. Three important toxicants, 3,5-dichlorophenol (DCP), As(3+), Cr(6+) are tested and the detection limits are 3.2, 25, and 3.2 ppm, respectively. Moreover, we could identify the yellow green to dark green color change by naked eye even at concentrations as low as 12.5 ppm for both DCP and Cr(6+). Subsequently, the acute toxicities of groundwater and south lake water are successfully determined by this sensor. This biosensor is rapid, sensitive and cost-effective, and can thus be regarded as a promising biosensor for giving an early warning of acute water toxicity. PMID:23187797

  6. Colorimetric test-systems for creatinine detection based on composite molecularly imprinted polymer membranes.

    PubMed

    Sergeyeva, T A; Gorbach, L A; Piletska, E V; Piletsky, S A; Brovko, O O; Honcharova, L A; Lutsyk, O D; Sergeeva, L M; Zinchenko, O A; El'skaya, A V

    2013-04-01

    An easy-to-use colorimetric test-system for the efficient detection of creatinine in aqueous samples was developed. The test-system is based on composite molecularly imprinted polymer (MIP) membranes with artificial receptor sites capable of creatinine recognition. A thin MIP layer was created on the surface of microfiltration polyvinylidene fluoride (PVDF) membranes using method of photo-initiated grafting polymerization. The MIP layer was obtained by co-polymerization of a functional monomer (e.g. 2-acrylamido-2-methyl-1-propanesulfonic acid, itaconic acid or methacrylic acid) with N, N'-methylenebisacrylamide as a cross-linker. The choice of the functional monomer was based on the results of computational modeling. The creatinine-selective composite MIP membranes were used for measuring creatinine in aqueous samples. Creatinine molecules were selectively adsorbed by the MIP membranes and quantified using color reaction with picrates. The intensity of MIP membranes staining was proportional to creatinine concentration in an analyzed sample. The colorimetric test-system based on the composite MIP membranes was characterized with 0.25 mM detection limit and 0.25-2.5mM linear dynamic range. Storage stability of the MIP membranes was estimated as at least 1 year at room temperature. As compared to the traditional methods of creatinine detection the developed test-system is characterized by simplicity of operation, small size and low cost. PMID:23498699

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  8. Colorimetric detection of clinical DNA samples using an intercalator-conjugated polydiacetylene sensor.

    PubMed

    Jung, Yun Kyung; Park, Hyun Gyu

    2015-10-15

    We herein developed a novel colorimetric polydiacetylene (PDA) sensor for very convenient detection of clinical DNA samples based on the interaction between an intercalator and dsDNA. We modified the terminal carboxyl group of a diacetylene monomer (10,12-pentacosadiynoic acid; PCDA) with the intercalator 9-aminoacridine (9AA) and prepared 9AA-modified PDA liposomes containing PCDA-9AA/PCDA/phospholipid (1,2-dimyristoyl-rac-glycero-3-phosphocholine) at a molar ratio of 1.5:6.5:2.0. The PDA sensor underwent an obvious color transition from blue to red in the presence of dsDNA molecules that were PCR-amplified from genomic DNA due to the insertion of the 9AA head group of PDA into the dsDNA. DNA concentrations as low as 20nM and relatively small molecules (around 100 base pairs) could be detected by the sensor within 1h without DNA electrophoresis. This novel colorimetric method is simple, does not require any instrument, and is therefore appropriate for POCT or portable molecular diagnostic kit. PMID:25978440

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

    PubMed

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

    2014-07-15

    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

  10. Colorimetric detection of urine glucose based ZnFe2O4 magnetic nanoparticles.

    PubMed

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

    2012-07-01

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

  11. Colorimetric detection of dichlorvos using polydiacetylene vesicles with acetylcholinesterase and cationic surfactants.

    PubMed

    Pimsen, Rungnapa; Khumsri, Akachai; Wacharasindhu, Sumrit; Tumcharern, Gamolwan; Sukwattanasinitt, Mongkol

    2014-12-15

    Widespread use of dichlorvos in agriculture has posed serious concern for food and water contamination. A new colorimetric method for the detection of dichlorvos based on polydiacethylene and acetylcholinesterase inhibition is developed. The blue-to-red color transition of poly(10,12-pentacosadynoic acid) vesicles can be induced by myristoylcholine which is enzymatically hydrolyzed by acetylcholinesterase to myristic acid and choline to prevent the color transition. In the presence of dichlorvos, the hydrolytic activity of the enzyme is inhibited that the blue-to-red color transition is restored with a linear correlation to the dichlorvos concentration. Using UV-vis absorption spectrometer, the limit of dichlorvos detection is 6.7 ppb. A naked eye detection of 50 ppb dichlorvos is achievable by using dimiristoylphosphatidylcholine to the diacetylene mixed lipid vesicles. PMID:24973536

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

    PubMed

    Zhang, Li; Zhang, Xianhong

    2014-12-10

    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

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

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhang, Xianhong

    2014-12-01

    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.

  14. Nylon 6-Gold Nanoparticle Composite Fibers for Colorimetric Detection of Urinary 1-Hydroxypyrene

    NASA Astrophysics Data System (ADS)

    Ifegwu, O. Clinton; Anyakora, C.; Torto, N.

    2015-05-01

    A one-step in situ synthesis of nylon 6 nanofibers filled with gold nanoparticles for the colorimetric probe of 1-hydroxypyrene, a biomarker associated with the largest class of cancer-causing chemical compounds polycyclic aromatic hydrocarbons (PAHs) is proposed in this study. The gold nanoparticles (AuNPs) were successfully embedded on the surface of the nylon 6 fibers where the gold particles were chemisorbed onto the amide groups in the nylon 6 backbones. By electrospinning the nylon 6/gold nanocomposite, the gold nanoparticles were uniformly dispersed on the polymer fibers to give a photostable reddish white fiber which turned purple/blue when brought in contact with a standard solution of the biomarker. The TEM revealed the formation of spherical AuNPs with an average diameter of 8 nm well arrayed within the nanofibers, but no significant change in the morphology of the nanofibers was observed. The thermal properties of the composite fibers were greatly improved compared to the electrospun nylon 6 fiber. The developed method described herein is simple, effective, requires no post-treatments, and is highly sensitive (100 ng/ml) hence the nanocomposite fibers can be employed as a test strip for the colorimetric detection of 1-hydroxypyrene in human urine or other diagnostic probe biosensors.

  15. A colorimetric and ratiometric fluorescent probe for selective detection and cellular imaging of glutathione.

    PubMed

    Xu, Chang; Li, Hongda; Yin, Bingzhu

    2015-10-15

    A new colorimetric and ratiometric fluorescent probe 1 based on a chlorinated coumarinyl aldehyde was developed for selective detection and cellular imaging of glutathione (GSH) over cysteine (Cys) and homocysteine (Hcy). Probe 1 exhibits a dramatic colorimetric and ratiometric fluorescence responses toward biothiols Cys, Hcy and GSH with high selectivity over other amino acids. Cys (or Hcy) induces a tandem SNAr-rearrangement reaction to form the corresponding amino-coumarins (2a or 2b), which result in about 75nm and 35nm blue-shifts in absorption and emission, respectively. By comparison, the thio-coumarin (3') derived from the SNAr reaction with GSH, which does not occur rearrangement because of steric hindrance, undergoes an intramolecular aldimine condensation lead to a cyclic iminium cation (3) with 47nm and 39nm red-shifts in absorption and emission, respectively. The significantly difference of photophysical properties enable excellent selectivity towards GSH over Cys and Hcy. Further application to cellular imaging indicates that the probe has appreciable cell permeability and is highly responsive to the changes of GSH level. As a result, it is applicable to monitor GSH level in living cells. PMID:25988996

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

    PubMed Central

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

    2013-01-01

    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

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

    PubMed

    Kumar, Naveen; Seth, Raman; Kumar, Harish

    2014-07-01

    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

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

    PubMed

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

    2014-11-01

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

  19. Highly sensitive colorimetric detection of lead using maleic acid functionalized gold nanoparticles.

    PubMed

    Ratnarathorn, Nalin; Chailapakul, Orawon; Dungchai, Wijitar

    2015-01-01

    Highly sensitive colorimetric detection for Pb(2+) has been developed using maleic acid (MA) functionalized GNP. The -COOH on MA was used to modify GNP surface whereas the other -COOH functional group have strong affinity to coordination behavior of Pb(2+) allowing the selective formation more than other ions. MA-GNPs solution changed from red to blue color after the addition of Pb(2+) due to nanoparticle aggregation. The different optical absorption and discriminate of particle size between the MA-GNPs solution with and without Pb(2+) were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM), respectively. The color intensity as a function of Pb(2+) concentration gave a linear response in the range of 0.0-10.0 µg L(-1) (R(2)=0.990). The detection limit was found at 0.5 µg L(-1) by naked eye and can be completed the analysis within 15 min. The MA-GNPs aggregated with Pb(2+) showed high selectivity when was compared to other metal ions (As(3+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Hg(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+)) and anions (Cl(-), NO3(-) and SO4(2-)). Our proposed method was also applied for the determination of Pb(2+) in real drinking water samples from 5 sources. The result of real water samples were not statistically significant different from the standard methods at the 95% confidence level (pair t-test method). Moreover, we evaluated our proposed method for the determination of trace Pb(2+) concentration in real breast milk samples. The recoveries were acceptable and ranged from 101 to 104% for spiked Pb(2+) in real breast milk samples. Thus, MA-GNP colorimetric sensing provides a simple, rapid, sensitive, easy-to-use, inexpensive and low detection limit for the monitoring of Pb(2+). PMID:25476352

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

    PubMed

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

    2013-08-21

    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

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

    PubMed Central

    2013-01-01

    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

  2. Colorimetric-Based Detection of TNT Explosives Using Functionalized Silica Nanoparticles

    PubMed Central

    Idros, Noorhayati; Ho, Man Yi; Pivnenko, Mike; Qasim, Malik M.; Xu, Hua; Gu, Zhongze; Chu, Daping

    2015-01-01

    This proof-of-concept study proposes a novel sensing mechanism for selective and label-free detection of 2,4,6-trinitrotoluene (TNT). It is realized by surface chemistry functionalization of silica nanoparticles (NPs) with 3-aminopropyl-triethoxysilane (APTES). The primary amine anchored to the surface of the silica nanoparticles (SiO2-NH2) acts as a capturing probe for TNT target binding to form Meisenheimer amine–TNT complexes. A colorimetric change of the self-assembled (SAM) NP samples from the initial green of a SiO2-NH2 nanoparticle film towards red was observed after successful attachment of TNT, which was confirmed as a result of the increased separation between the nanoparticles. The shift in the peak wavelength of the reflected light normal to the film surface (?peak) and the associated change of the peak width were measured, and a merit function taking into account their combined effect was proposed for the detection of TNT concentrations from 10?12 to 10?4 molar. The selectivity of our sensing approach is confirmed by using TNT-bound nanoparticles incubated in AptamerX, with 2,4-dinitrotoluene (DNT) and toluene used as control and baseline, respectively. Our results show the repeatable systematic color change with the TNT concentration and the possibility to develop a robust, easy-to-use, and low-cost TNT detection method for performing a sensitive, reliable, and semi-quantitative detection in a wide detection range. PMID:26046595

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

    PubMed

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

    2014-07-15

    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

  4. Colorimetric-Based Detection of TNT Explosives Using Functionalized Silica Nanoparticles.

    PubMed

    Idros, Noorhayati; Ho, Man Yi; Pivnenko, Mike; Qasim, Malik M; Xu, Hua; Gu, Zhongze; Chu, Daping

    2015-01-01

    This proof-of-concept study proposes a novel sensing mechanism for selective and label-free detection of 2,4,6-trinitrotoluene (TNT). It is realized by surface chemistry functionalization of silica nanoparticles (NPs) with 3-aminopropyl-triethoxysilane (APTES). The primary amine anchored to the surface of the silica nanoparticles (SiO2-NH2) acts as a capturing probe for TNT target binding to form Meisenheimer amine-TNT complexes. A colorimetric change of the self-assembled (SAM) NP samples from the initial green of a SiO2-NH2 nanoparticle film towards red was observed after successful attachment of TNT, which was confirmed as a result of the increased separation between the nanoparticles. The shift in the peak wavelength of the reflected light normal to the film surface and the associated change of the peak width were measured, and a merit function taking into account their combined effect was proposed for the detection of TNT concentrations from 10-12 to 10-4 molar. The selectivity of our sensing approach is confirmed by using TNT-bound nanoparticles incubated in AptamerX, with 2,4-dinitrotoluene (DNT) and toluene used as control and baseline, respectively. Our results show the repeatable systematic color change with the TNT concentration and the possibility to develop a robust, easy-to-use, and low-cost TNT detection method for performing a sensitive, reliable, and semi-quantitative detection in a wide detection range. PMID:26046595

  5. Sensitive colorimetric detection of protein by gold nanoparticles and rolling circle amplification.

    PubMed

    Chen, Chaohui; Luo, Ming; Ye, Tai; Li, Ningxing; Ji, Xinghu; He, Zhike

    2015-06-15

    An ultrasensitive method for the detection of protein is critically important in fundamental research and practical applications due to the low abundance of disease markers in body fluids or tissues. To detect the trace levels of disease markers with high sensitivity and specificity, a sensitive colorimetric biosensor for protein assay was developed using gold nanoparticles (AuNPs) and rolling circle amplification (RCA). After binding the biotinylated primer/circular template to the streptavidin-conjugated sandwich ELISA immunocomplex, the biotinylated primer was isothermally extended to generate single-stranded DNA (ssDNA). Sequentially, the padlock DNA was added and hybridized with the RCA products. The aggregation of the additional AuNPs in the supernatant containing the surplus padlock DNA and a certain concentration of salt could then be observed. The established sensor allowed for the specific detection of ?-fetoprotein (AFP) with a detection limit of 33.45 pg mL(-1). It was also demonstrated that this method could distinguish 500 pg mL(-1) AFP with the naked eye. In addition, this biosensor could be applied to complex sample analysis and could be further used as a universal method for any protein or virus determination by changing the corresponding antibodies. PMID:25988199

  6. Recent progress in fluorescent and colorimetric chemosensors for detection of precious metal ions (silver, gold and platinum ions).

    PubMed

    Zhang, Jun Feng; Zhou, Ying; Yoon, Juyoung; Kim, Jong Seung

    2011-07-01

    Due to the wide range of applications and biological significance, the development of optical probes for silver, gold and platinum ions has been an active research area in the past few years. This tutorial review focuses on the recent contributions concerning the fluorescent or colorimetric sensors for these metal ions, and is organized according to their structural classifications (for Ag(+) detection) and unique mechanisms between the sensors and metal ions (for Au(3+) and Pt(2+) detection). PMID:21491036

  7. Enzyme-free colorimetric detection of DNA by using gold nanoparticles and hybridization chain reaction amplification.

    PubMed

    Liu, Pei; Yang, Xiaohai; Sun, Shan; Wang, Qing; Wang, Kemin; Huang, Jin; Liu, Jianbo; He, Leiliang

    2013-08-20

    A novel, high sensitive, and specific DNA assay based on gold nanoparticle (AuNP) colorimetric detection and hybridization chain reaction (HCR) amplification has been demonstrated in this article. Two hairpin auxiliary probes were designed with single-stranded DNA (ssDNA) sticky ends which stabilize AuNPs and effectively prevent them from salt-induced aggregation. The target DNA hybridized with the hairpin auxiliary probes and triggered the formation of extended double-stranded DNA (dsDNA) polymers through HCR. As a result, the formed dsDNA polymers provide less stabilization without ssDNA sticky ends, and AuNPs undergo aggregation when salt concentration is increased. Subsequently, a pale purple-to-blue color variation is observed in the colloid solution. The system is simple in design and convenient in operation. The novel strategy eliminates the need for enzymatic reactions, separation processes, chemical modifications, and sophisticated instrumentation. The detection and discrimination process can be seen with the naked eye. The detection limit of this method is lower than or at least comparable to previous AuNP-based methods. Importantly, the protocol offers high selectivity for the determination between perfectly matched target oligonucleotides and targets with single base-pair mismatches. PMID:23895103

  8. Analyte-induced photoreduction method for visual and colorimetric detection of tyrosine.

    PubMed

    Satheeshkumar, Elumalai; Yang, Jyisy

    2015-06-16

    A new method based on photochemical formation of silver nanoparticles (AgNPs) was developed for detection of tyrosine (Tyr). To selectively detect Tyr and to simplify the detection procedure, the photoactivity of Tyr was utilized to trigger the photochemical reduction in production of AgNPs. The drastic change of solution color caused by the surface plasmon resonance (SPR) absorption band of the formed AgNPs was used to extract the quantitative information of Tyr. This developed method is simple in detection, while both the sensitivity and selectivity are significant improved. Meanwhile, the solution color was changed from colorless to dark yellow after the formation of AgNPs, which allows a much higher sensitivity in visual identification when compared with the SPR band shifting technique commonly, used in conventional colorimetric methods. To optimize the detection system and to understand the mechanism in this proposed method, parameters such as irradiation time, intensity of light source, and the concentration of Tyr were systematically examined. Results indicated that these factors mainly affected the reaction rate of photoreduction. The morphologies of the formed AgNPs were similar, but with small differences in particle sizes. In the examination of selectivity, sixteen other amino acids were examined. Results indicated that only amino acids of tryptophan, cysteine and histidine are photoactive and possess potential interferences in analysis of Tyr. Quantitative studies indicated that a linear response up to 10?M with a detection limit of 100nM could be obtained. For visually detection, color change could be observed with a concentration as low as 500nM of Tyr. PMID:26002485

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    In this research, folic acid functionalized silver nanoparticles (FA-AgNPs) were selected as a colorimetric and a ‘turn on’ fluorescent sensor for detecting Hg2+. After being added into Hg2+, 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 Hg2+ ions. Thus, we developed a simple, sensitive analytical method to detect Hg2+ based on the colorimetric and fluorescence enhancement of FA-AgNPs. The sensor exhibits two linear response ranges between absorbance and fluorescence intensity with Hg2+ concentration, respectively. Meanwhile, a detection limit of 1 nM is estimated based on the linear relationship between responses with a concentration of Hg2+. The high specificity of Hg2+ with FA-AgNPs interactions provided the excellent selectivity towards detecting Hg2+ over other metal ions (Pb2+, Mg2+, Zn2+, Ni2+, Cu2+, Co2+, Ca2+, Mn2+, Fe2+, Cd2+, Ba2+, Cr6+ and Cr3+). This will provide a simple, effective and multifunctional colorimetric and fluorescent sensor for on-site and real-time Hg2+ ion detection. The proposed method can be applied to the analysis of trace Hg2+ in lake water. Additionally, the FA-AgNPs can be used as efficient catalyst for the reduction of 4-nitrophenol and potassium hexacyanoferrate (III).

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

    PubMed

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

    2014-09-01

    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

  11. Colorimetric sensor array for detection and identification of organophosphorus and carbamate pesticides.

    PubMed

    Qian, Sihua; Lin, Hengwei

    2015-05-19

    Due to relatively low persistence and high effectiveness for insect and pest eradication, organophosphates (OPs) and carbamates are the two major classes of pesticides that broadly used in agriculture. Hence, the sensitive and selective detection of OPs and carbamates is highly significant. In this current study, a colorimetric sensor array comprising five inexpensive and commercially available thiocholine and H2O2 sensitive indicators for the simultaneous detection and identification of OPs and carbamates is developed. The sensing mechanism of this array is based on the irreversible inhibition capability of OPs and carbamates to the activity of acetylcholinesterase (AChE), preventing production of thiocholine and H2O2 from S-acetylthiocholine and acetylcholine and thus resulting in decreased or no color reactions to thiocholine and H2O2 sensitive indicators. Through recognition patterns and standard statistical methods (i.e., hierarchical clustering analysis and principal component analysis), the as-developed array demonstrates not only discrimination of OPs and carbamates from other kinds of pesticides but, more interestingly, identification of them exactly from each other. Moreover, this array is experimentally confirmed to have high selectivity and sensitivity, good anti-interference capability, and potential applications in real samples for OPs and carbamates. PMID:25913282

  12. Colorimetric detection of pathogenic bacteria using platinum-coated magnetic nanoparticle clusters and magnetophoretic chromatography.

    PubMed

    Kwon, Donghoon; Lee, Sanghee; Ahn, Myung Mo; Kang, In Seok; Park, Ki-Hwan; Jeon, Sangmin

    2015-07-01

    A colorimetric method that uses platinum-coated magnetic nanoparticle clusters (Pt/MNCs) and magnetophoretic chromatography is developed to detect pathogenic bacteria. Half-fragments of monoclonal Escherichia coli O157:H7 (EC) antibodies were functionalized to Pt/MNCs and used to capture E. coli bacteria in milk. After magnetic separation of free Pt/MNCs and Pt/MNC-EC complexes from the milk, a precision pipette was used to imbibe the E. coli-containing solution, then a viscous polyethylene glycol solution. Due to difference in viscosities, the solutions separate into two liquid layers inside the pipette tip. The Pt/MNC-EC complexes were separated from the free Pt/MNCs by applying an external magnetic field, then added to a tetramethylbenzidine (TMB) solution. Catalytic oxidation of TMB by Pt produced color changes of the solution, which enabled identification of the presence of 10cfumL(-1)E. coli bacteria with the naked eye. The total assay time including separation, binding and detection was 30min. PMID:26088777

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

    PubMed

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

    2014-09-01

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

  14. A label-free colorimetric sensor for Pb2+ detection based on the acceleration of gold leaching by graphene oxide.

    PubMed

    Shi, Xinhao; Gu, Wei; Zhang, Cuiling; Zhao, Longyun; Peng, Weidong; Xian, Yuezhong

    2015-03-14

    In this work, we developed a novel, label-free, colorimetric sensor for Pb(2+) detection based on the acceleration of gold leaching by graphene oxide (GO) at room temperature. Gold nanoparticles (AuNPs) can be dissolved in a thiosulfate (S2O3(2-)) aqueous environment in the presence of oxygen; however, the leaching rate is very slow due to the high activation energy (27.99 kJ mol(-1)). In order to enhance the reaction rate, some accelerators should be added. In comparison with the traditional accelerators (metal ions or middle ligands), we found that GO could efficiently accelerate the gold leaching reaction. Kinetic data demonstrate that the dissolution rate of gold in the Pb(2+)-S2O3(2-)-GO system is 5 times faster than that without GO at room temperature. In addition, the effects of surface modification and the nanoparticle size on the etching of AuNPs were investigated. Based on the GO-accelerated concentration-dependent colour changes of AuNPs, a colorimetric sensor for Pb(2+) detection was developed with a linear range from 0.1 to 20 ?M and the limit of detection (LOD) was evaluated to be 0.05 ?M. This colorimetric assay is simple, low-cost, label-free, and has numerous potential applications in the field of environmental chemistry. PMID:25656247

  15. Colorimetric detection of influenza A virus using antibody-functionalized gold nanoparticles.

    PubMed

    Liu, Yuanjian; Zhang, Linqun; Wei, Wei; Zhao, Hongyu; Zhou, Zhenxian; Zhang, Yuanjian; Liu, Songqin

    2015-06-21

    Early and accurate diagnosis is considered the key issue to prevent the further spread of viruses and facilitate influenza therapy. Herein, we report a colorimetric immunosensor for influenza A virus (IAV) based on gold nanoparticles (AuNPs) modified with monoclonal anti-hemagglutinin antibody (mAb). The immunosensor allows for a fast, simple, and selective detection of IAV. In this assay, influenza-specific antibodies are conjugated to AuNPs to create mAb-AuNP probes. Since IAV has multiple recognition sites for probes on the surface, the mAb-AuNP probes can be specifically arranged on the virus surface due to their very specific antigen recognition. In this case, this aggregation of the mAb-AuNP probes produces a red shift in the absorption spectrum due to plasmon coupling between adjacent AuNPs, and it can be detected with the naked eye as a color change from red to purple and quantified with the absorption spectral measurements. The aggregate formation is also confirmed with transmission electron microscopy (TEM) imaging and dynamic light scattering (DLS). Under the optimal conditions, the present immunoassay can sensitively measure H3N2 IAV (A/Brisbane/10/2007) with a detection limit of 7.8 hemagglutination units (HAU). This proposed immunosensor revealed high specificity, accuracy, and good stability. Notably, it is a single-step detection using AuNP probes and UV-vis spectrophotometer for readout, and no additional amplification, e.g., enzymatic, is needed to read the result. This assay depends on an ordered AuNP structure covering the virus surface and can be applied to any virus pathogen by incorporating the appropriate pathogen-specific antibody. PMID:25899840

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    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.

  18. A colorimetric sensor array for detection and discrimination of biothiols based on aggregation of gold nanoparticles.

    PubMed

    Ghasemi, Forough; Hormozi-Nezhad, M Reza; Mahmoudi, Morteza

    2015-07-01

    Developments of sensitive, rapid, and cheap systems for identification of a wide range of biomolecules have been recognized as a critical need in the biology field. Here, we introduce a simple colorimetric sensor array for detection of biological thiols, based on aggregation of three types of surface engineered gold nanoparticles (AuNPs). The low-molecular-weight biological thiols show high affinity to the surface of AuNPs; this causes replacement of AuNPs' shells with thiol containing target molecules leading to the aggregation of the AuNPs through intermolecular electrostatic interaction or hydrogen-bonding. As a result of the predetermined aggregation, color and UV-vis spectra of AuNPs are changed. We employed the digital mapping approach to analyze the spectral variations with statistical and chemometric methods, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The proposed array could successfully differentiate biological molecules (e.g., cysteine, glutathione and glutathione disulfide) from other potential interferences such as amino acids in the concentration range of 10-800?molL(-1). PMID:26043092

  19. Dual-channel detection of Cu(2+) and F(-) with a simple Schiff-based colorimetric and fluorescent sensor.

    PubMed

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

    2014-10-24

    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 Cu(2+) 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. PMID:25459728

  20. An engineered nano-plasmonic biosensing surface for colorimetric and SERS detection of DNA-hybridization events

    NASA Astrophysics Data System (ADS)

    Heydari, Esmaeil; Thompson, David; Graham, Duncan; Cooper, Jonathan M.; Clark, Alasdair W.

    2015-03-01

    We report a versatile nanophotonic biosensing platform that enables both colorimetric detection and enhanced Raman spectroscopy detection of molecular binding events. Through the integration of electron-beam lithography, dip-pennanolithography and molecular self-assembly, we demonstrate plasmonic nanostructures which change geometry and plasmonic properties in response to molecularly-mediated nanoparticle binding events. These biologically-active nanostructured surfaces hold considerable potential for use as multiplexed sensor platforms for point-of-care diagnostics, and as scaffolds for a new generation of molecularly dynamic metamaterials.

  1. Low cost, disposable colorimetric sensor for quantitative detection of ammonia gas

    NASA Astrophysics Data System (ADS)

    Srivastava, Ruchi; Verma, Abhishek; Jain, V. K.

    2012-10-01

    The development of a simple, fast, disposable and low cost method for sensing and differentiating a wide range of concentration of toxic ammonia vapor by using colorimetric sensor is reported. A large dynamic range from 10 ppm to 1,00,000 ppm is successfully classified at ambient temperature with reproducible results. The CSA strip is consists of the dots of chemo-responsive materials, which are environmental friendly and react specifically with ammonia at different thresholds. The pattern of color change of colorimetric sensor array is unique for reported concentration range of ammonia gas.

  2. Multiplexed Colorimetric Solid-Phase Extraction

    NASA Technical Reports Server (NTRS)

    Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.

    2009-01-01

    Multiplexed colorimetric solid-phase extraction (MC-SPE) is an extension of colorimetric solid-phase extraction (C-SPE) an analytical platform that combines colorimetric reagents, solid phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water. In CSPE, analytes are extracted and complexed on the surface of an extraction membrane impregnated with a colorimetric reagent. The analytes are then quantified directly on the membrane surface using a handheld diffuse reflectance spectrophotometer. Importantly, the use of solid-phase extraction membranes as the matrix for impregnation of the colorimetric reagents creates a concentration factor that enables the detection of low concentrations of analytes in small sample volumes. In extending C-SPE to a multiplexed format, a filter holder that incorporates discrete analysis channels and a jig that facilitates the concurrent operation of multiple sample syringes have been designed, enabling the simultaneous determination of multiple analytes. Separate, single analyte membranes, placed in a readout cartridge create unique, analyte-specific addresses at the exit of each channel. Following sample exposure, the diffuse reflectance spectrum of each address is collected serially and the Kubelka-Munk function is used to quantify each water quality parameter via calibration curves. In a demonstration, MC-SPE was used to measure the pH of a sample and quantitate Ag(I) and Ni(II).

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

    NASA Astrophysics Data System (ADS)

    He, Yi; Peng, Rufang

    2014-11-01

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

  4. Colorimetric assay for protein detection based on "nano-pumpkin" induced aggregation of peptide-decorated gold nanoparticles.

    PubMed

    Wei, Luming; Wang, Xiaoying; Li, Chao; Li, Xiaoxi; Yin, Yongmei; Li, Genxi

    2015-09-15

    Small peptide can be used as an effective biological recognition element and provide an alternative tool for protein detection. However, the development of peptide-based detecting strategy still remains elusive due to the difficulty of signal transduction. Herein, we report a peptide-based colorimetric strategy for the detection of disease biomarker by using vascular endothelial growth factor receptor 1 (Flt-1) as an example. In this strategy, N-terminal aromatic residue-containing peptide modified gold nanoparticles (GNPs) can form bulky aggregate by the introduction of cucurbit[8]uril (CB[8]) that can selectively accommodate two N-terminal aromatic residue of peptides simultaneously regardless of their sequences. However, in the presence of Flt-1, the peptide can specifically bind to the protein molecule and the N-terminal aromatic residue will be occupied, resulting in little aggregation of GNPs. By taking advantage of the highly affinitive peptide and efficiency cross-linking effect of CB[8] to GNPs, colorimetric assay for protein detection can be achieved with a detection limit of 0.2nM, which is comparable with traditional methods. The feasibility of our method has also been demonstrated in spiked serum sample, indicating potential application in the future. PMID:25932793

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

    PubMed

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

    2013-05-21

    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

  6. Study on a colorimetric sensor with color switching: Naked-eye detection for Cu(II) ion

    NASA Astrophysics Data System (ADS)

    Gao, Yang; Ma, Wenzhong

    2012-12-01

    In this paper, we synthesize and report a Cu(II)-sensing probe of N'1,N'2-bis(4-(diethylamino)-2-hydroxybenzylidene)oxalohydrazide (BDHO) with two detection channels. Its colorimetric and fluorescence spectrophotometric responses towards Cu(II) ion are fully investigated. It is found that the absorption and emission spectra of BDHO are both sensitive towards Cu(II) ion with high sensitivity as well as excellent selectivity. In addition, the recognition of BDHO towards Cu(II) ion is also very quick and can be accomplished within less than 1 min. The actual sensing performance of BDHO towards Cu(II) ion is also tentatively explored.

  7. Multifunctional Janus Hematite-Silica Nanoparticles: Mimicking Peroxidase-Like Activity and Sensitive Colorimetric Detection of Glucose.

    PubMed

    Lu, Chang; Liu, Xiangjiang; Li, Yunfeng; Yu, Fang; Tang, Longhua; Hu, Yanjie; Ying, Yibin

    2015-07-22

    The design and engineering of multifunctional nanostructures with multiple components and synergistic properties are in urgent demand for variety of acceptable biosensing platforms, enabling users to fulfill multiple tasks in a single nanosystem. Herein, we report using an asymmetric hematite-silica hybrid of Janus ?-Fe2O3/SiO2 nanoparticles (JFSNs) as a multifunctional biosensing platform for sensitive colorimetric detection of H2O2 and glucose. It was demonstrated that JFSNs exhibit an intrinsic peroxidase-like catalytic activity. Compared with natural enzyme, JFSNs nanoenzymes could be used over a wider range of pH and temperatures and were more stable over time. Importantly, besides its excellent catalytic activity, the asymmetric properties of the Janus nanoparticle enable it to form the multiple functional utilities for various biosensing applications, including the ease of surface modification without deactivation of catalytic activity and recoverable use by magnetic separation. Thus, we utilized JFSNs with glucose oxidase (GOx) immobilization for glucose-sensitive colorimetric detection, which exhibited both catalytic activity of glucose oxidase and peroxidase with high selectivity and acceptable reproducibility. By combining these two analysis systems into Janus particles, an all-in-one and reusable sensor for blood glucose was formed and has the capability for determination of glucose in complex samples such as serum. These results suggest that such Janus nanosystems have the potential to construct robust nanoarchitecture with multiple functionalities for various biosensing applications. PMID:26110779

  8. Colorimetric monitoring of rolling circle amplification for detection of H5N1 influenza virus using metal indicator.

    PubMed

    Hamidi, Seyed Vahid; Ghourchian, Hedayatollah

    2015-10-15

    A new colorimetric method for monitoring of rolling circle amplification was developed. At first H5N1 target hybrids with padlock probe (PLP) and then PLP is circularized upon the action of T4 ligase enzyme. Subsequently, the circular probe is served as a template for hyperbranched rolling circle amplification (HRCA) by utilizing Bst DNA polymerase enzyme. By improving the reaction, pyrophosphate is produced via DNA polymerization and chelates the Mg(2+) in the buffer solution. This causes change in solution color in the presence of hydroxy naphthol blue (HNB) as a metal indicator. By using pH shock instead of heat shock and isothermal RCA reaction not only the procedure becomes easier, but also application of HNB for colorimetric detection of RCA reaction further simplifies the assay. The responses of the biosensor toward H5N1 were linear in the concentration range from 0.16 to 1.20pM with a detection limit of 28 fM. PMID:25974174

  9. Colorimetric detection of controlled assembly and disassembly of aptamers on unmodified gold nanoparticles.

    PubMed

    Gopinath, Subash C B; Lakshmipriya, Thangavel; Awazu, Koichi

    2014-01-15

    Aptamers are nucleic acid ligands that are generated artificially by in vitro selection and behave similar to antibodies. The development of aptamer-based sensing systems or strategies has been in vogue for the past few decades, because aptamers are smaller in size, stable, cheaper and undergo easier modifications. Owing to these advantages, several facile aptamer-based colorimetric strategies have been created by controlling the assembly and disassembly of aptamers on unmodified gold nanoparticle probes. As these kinds of assay systems are rapid and can be visualized unaided by instruments, they have recently become an attractive method of choice. The formation of purple-colored aggregates (attraction) from the red dispersed (repulsion) state of GNPs in the presence of mono- or divalent ions is the key principle behind this assay. Due to its simplicity and versatility, this assay can be an alternative to existing diagnostic assays. Here, we have investigated the critical elements involved in colorimetric assays, and have screened different proteins and small ligands to evaluate biofouling on GNPs. PMID:23948242

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

    PubMed

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

    2014-06-01

    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

  11. A FRET ratiometric fluorescence sensing system for mercury detection and intracellular colorimetric imaging in live Hela cells.

    PubMed

    Hu, Bo; Hu, Lin-Lin; Chen, Ming-Li; Wang, Jian-Hua

    2013-11-15

    The detection of mercury in biological systems and its imaging is of highly importance. In this work, a ratiometric fluorescence sensor is developed based on fluorescence resonance energy transfer (FRET) with N-acetyl-L-cysteine functionalized quantum dots (NAC-QDs) as donor and Rhodamine 6G derivative-mercury conjugate (R6G-D-Hg) as acceptor. Mercury annihilates the fluorescence of NAC-QDs at 508 nm and meanwhile interacts with R6G derivative to form a fluorescent conjugate giving rise to emission at 554 nm. Resonance energy transfer from NAC-QDs to R6G-D-Hg is triggered by mercury resulting in concentration-dependent variation of fluorescence ratio F508/F554. A linear calibration of F508/F554 versus mercury concentration is obtained within 5-250 ?g L(-1), along with a detection limit of 0.75 ?g L(-1) and a RSD of 3.2% (175 ?g L(-1)). The sensor generates colorimetric images for mercury within 0-250 ?g L(-1), facilitating visual detection of mercury with a distinguishing ability of 50 ?g L(-1). This feature is further demonstrated by colorimetric imaging of intracellular mercury. On the other hand, the NAC-QDs/R6G-D FRET sensing system is characterized by a combination of high sensitivity and selectivity. The present study provides an approach for further development of ratiometric sensors dedicated to selective in vitro or in vivo sensing some species of biologically interest. PMID:23811485

  12. Colorimetric and plasmonic detection of lectins using core-shell gold glyconanoparticles prepared by copper-free click chemistry.

    PubMed

    Hu, Xi-Le; Jin, Hong-Ying; He, Xiao-Peng; James, Tony D; Chen, Guo-Rong; Long, Yi-Tao

    2015-01-28

    This study describes the simple preparation of core-shell glycosyl gold nanoparticles (AuNPs) using stepwise, copper-free click chemistry-promoted self-assembly. The as-formed glyco-AuNPs can be used for the selective detection of sugar-lectin interactions, which are vital to many important physiological and pathological processes. The approach uses AuNPs as bioprobes since they produce, sensitively, changes in both color visible to the naked eye and surface plasmon resonance (SPR), on aggregation. Strain-promoted click reaction of an azido galactoside with a lipid cyclooctyne affords a galactolipid that can be embedded into polyethylene glycol (PEG)-coated AuNP via self-assembly. Subsequently, using naked-eye and plasmon resonance scattering spectroscopy, we were able to observe the colorimetric and plasmonic variations of the glyco-AuNPs, respectively, in the presence of a selective lectin over other proteins. PMID:25531131

  13. A new colorimetric platform for ultrasensitive detection of protein and cancer cells based on the assembly of nucleic acids and proteins.

    PubMed

    Chen, Chaohui; Liu, Yufei; Zheng, Zhenhua; Zhou, Guohua; Ji, Xinghu; Wang, Hanzhong; He, Zhike

    2015-06-23

    An amplified colorimetric method has been developed for the detection of protein and cancer cells based on the assembly of nucleic acids and proteins for the first time. In this process, the assembly of nucleic acids was triggered by a biotinylated DNA strand after a sandwich immunoreaction. The biotinylated DNA strand and sandwich immunocomplex were connected by streptavidin. Then, the assembly of biotinylated bovine serum albumin (Biotin-BSA) and streptavidin-horseradish peroxidase (SA-HRP) occurred at a node of the assembled products of nucleic acids through the biotin-streptavidin reaction. Under the catalysis of horseradish peroxidase, 3,3',5,5'-tetramethylbenzidine (TMB) was oxidized by H2O2 and the oxidized product was analyzed by its UV-vis absorbance signal and sensitive colorimetric detection. This colorimetric sensor could not only achieve the quantitative determination of protein by UV-vis absorbance but could also be applied for semiquantitative determination by digital visualization. Using alpha-fetoprotein (AFP) as the model target, this proposed colorimetric method showed a wide linear range from 5pg/mL to 1ng/mL with a detection limit of 1.95pg/mL by the instrument, and even 5pg/mL target protein could be distinguished simply by the naked eye. This approach was then expanded to detect cancer cells based on the recognition of folic acid receptors that were over-expressed on the cancer cells by folic acid-tethered DNA. More importantly, this strategy can be further used as a universal colorimetric method for the determination of viruses or other proteins by changing the corresponding antibodies. PMID:26092332

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

    PubMed

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

    2015-02-21

    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

  15. Real-time detection of hypochlorite in tap water and biological samples by a colorimetric, ratiometric and near-infrared fluorescent turn-on probe.

    PubMed

    Ding, Shuangshuang; Zhang, Qiong; Xue, Shuanghong; Feng, Guoqiang

    2015-06-15

    In this paper, we report a highly selective and sensitive ratiometric NIR fluorescent probe that can be used for real-time detection of the biologically important hypochlorite with colorimetric and significant NIR fluorescent turn-on signal changes at NIR excitation wavelength. In addition, experiments showed that this probe can be applied to detect hypochlorite in tap water, serum samples, and living cells with low cytotoxicity. PMID:26030158

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  17. Direct visual detection of Salmonella genomic DNA using gold nanoparticles.

    PubMed

    Kalidasan, Kamaladasan; Neo, Jia Ling; Uttamchandani, Mahesh

    2013-04-01

    Gold nanoparticles (AuNPs) are well recognized tools for visual DNA detection. Most reports on their use have however been restricted to synthetic or PCR amplified DNA sequences. Herein, we describe a visual DNA detection method that can detect unamplified genomic DNA sequences specifically, using simple reagents and AuNPs, without the need for PCR. This strategy applies thiolated probes and AuNPs to detect genomic DNA. The thiolated probes, in the presence of target Salmonella genomic sequences, cause the AuNPs to aggregate irreversibly, producing a red to purple colorimetric change. As little as 608?000 copies (at 37 fM) of the Salmonella genome were thus detected visually, by eye, without the need for a power source or sophisticated instrumentation. This method thus opens in-roads to direct visual detection, bringing sophisticated DNA analysis capabilities to the point of need. PMID:23407714

  18. Colorimetric detection of Bi (III) in water and drug samples using pyridine-2,6-dicarboxylic acid modified silver nanoparticles.

    PubMed

    Mohammadi, Somayeh; Khayatian, Gholamreza

    2015-09-01

    A new selective, simple, fast and sensitive method is developed for sensing assay of Bi (III) using pyridine-2,6-dicarboxylic acid or dipicolinic acid (DPA) modified silver nanoparticles (DPA-AgNPs). Silver nanoparticles (AgNPs) were synthesized by reducing silver nitrate (AgNO3) with sodium borohydride (NaBH4) in the presence of DPA. Bismuth detection is based on color change of nanoparticle solution from yellow to red that is induced in the presence of Bi (III). Aggregation of DPA-AgNPs has been confirmed with UV-vis absorption spectra and transmission electron microscopy (TEM) images. Under the optimized conditions, a good linear relationship (correlation coefficient r=0.995) is obtained between the absorbance ratio (A525/A390) and the concentration of Bi (III) in the 0.40-8.00?M range. This colorimetric probe allows Bi (III) to be rapidly quantified with a 0.01?M limit of detection. The present method successfully applied to determine bismuth in real water and drug samples. Recoveries of water samples were in the range of 91.2-99.6%. PMID:25919329

  19. Intrinsic enzyme mimicking activity of gold nanoclusters upon visible light triggering and its application for colorimetric trypsin detection.

    PubMed

    Wang, Guang-Li; Jin, Lu-Yi; Dong, Yu-Ming; Wu, Xiu-Ming; Li, Zai-Jun

    2015-02-15

    In this research, a novel enzyme mimetics based on the photochemical property of gold nanoclusters was demonstrated. It was found that the bovine serum albumin (BSA) stabilized red or blue emitting gold nanoclusters (Au NCs) exhibited enzyme-like activity under visible light irradiation. The BSA-Au NCs had better stability against stringent conditions compared to natural enzyme. In addition, the photostimulated enzyme mimetics of BSA-Au NCs showed several unprecedented advantages over natural peroxidase or other existing alternatives based on nanomaterials, such as the independence of hydrogen peroxide on activity and the easily regulated activity by light irradiation. The mechanism of the photoresponsive enzyme-like activity of BSA-Au NCs was investigated. The photoactivated BSA-Au NCs was designed to develop a facile, cheap, and rapid colorimetric assay to detect trypsin through trypsin digestion of the protein template of BSA-stabilized Au NCs. The limit of detection for trypsin was 0.6 ?g/mL, which was much lower than the average level of trypsin in patient's urine or serum. PMID:25310483

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

    PubMed

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

    2014-12-01

    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

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

    E-print Network

    Jelinek, Raz

    , bioterrorism alerts, and anthrax scares. Numerous technologies for bacterial detection have been developed.1 describe a bacterial detection platform based on Langmuir-Schaeffer films containing lipids

  2. Directional antineutrino detection.

    PubMed

    Safdi, Benjamin R; Suerfu, Burkhant

    2015-02-20

    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

  3. Directional Antineutrino Detection

    NASA Astrophysics Data System (ADS)

    Safdi, Benjamin R.; Suerfu, Burkhant

    2015-02-01

    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.

  4. Directional Antineutrino Detection

    E-print Network

    Benjamin R. Safdi; Burkhant Suerfu

    2014-10-30

    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.

  5. Directional Antineutrino Detection

    NASA Astrophysics Data System (ADS)

    Safdi, B. R.; Suerfu, J.

    2014-12-01

    We propose the first truly directional antineutrino detector for antineutrinos near the threshold for the inverse beta decay (IBD) of hydrogen, with potential applications including the spatial mapping of geo-neutrinos, searches for stellar antineutrinos, and the monitoring of nuclear reactors. The detector consists of adjacent and separated target and neutron-capture layers. The IBD events, which result in a neutron and a positron, take place in the target layers. These layers are thin enough so that the neutrons escape without scattering elastically. The neutrons are detected in the thicker neutron-capture layers. The location of the IBD event is determined from the energy deposited by the positron as it slows in the medium and from the two gamma rays that come from the positron annihilation. Since the neutron recoils in the direction of the antineutrino's motion, a line may then be drawn between the IBD event location and the neutron-capture location to approximate the antineutrino's velocity. In some events, we may even measure the positron's velocity, which further increases our ability to reconstruct the antineutrino's direction of motion. Our method significantly improves upon previous methods by allowing the neutron to freely travel a long distance before diffusing and being captured. Moreover, our design is a straightforward modification of existing antineutrino detectors; a prototype could easily be built with existing technology. We verify our design through Monte Carlo simulations in Geant4, using commercially-available boron-loaded plastic scintillators for the target and neutron-capture layer materials. We are able to discriminate from background using multiple coincidence signatures within a short, ~microsecond time interval. We conclude that the detector could likely operate above ground with minimal shielding.

  6. Multiplexed colorimetric detection of Kaposi's sarcoma associated herpesvirus and Bartonella DNA using gold

    E-print Network

    Erickson, David

    for each target and a multi-color change system is developed capable of detecting both targets down-of-care KS detection. Introduction With the onset of the acquired immunodeciency syndrome (AIDS) epidemic

  7. Femtomolar DNA detection by parallel colorimetric darkfield microscopy of functionalized gold nanoparticles.

    PubMed

    Verdoold, Remco; Gill, Ron; Ungureanu, Felicia; Molenaar, Robert; Kooyman, Rob P H

    2011-09-15

    We introduce a sensing platform for specific detection of DNA based on the formation of gold nanoparticles dimers on a surface. The specific coupling of a second gold nanoparticle to a surface bound nanoparticle by DNA hybridization results in a red shift of the nanoparticle plasmon peak. This shift can be detected as a color change in the darkfield image of the gold nanoparticles. Parallel detection of hundreds of gold nanoparticles with a calibrated true color camera enabled us to detect specific binding of target DNA. This enables a limit of detection below 1.0×10(-14) M without the need for a spectrometer or a scanning stage. PMID:21752628

  8. A reversible fluorescent-colorimetric imino-pyridyl bis-Schiff base sensor for expeditious detection of Al(3+) and HSO3(-) in aqueous media.

    PubMed

    Ghorai, Anupam; Mondal, Jahangir; Chandra, Rukmani; Patra, Goutam K

    2015-07-14

    A reversible fluorescent-colorimetric imino-pyridyl bis-Schiff base receptor (N(1)E,N(4)E)-N(1),N(4)-bis(pyridine-4-ylmethylene)benzene-1,4-diamine for the detection of both Al(3+) and HSO3(-) in aqueous medium has been developed. Receptor exhibits an excellent selective fluorescent-colorimetric response toward Al(3+). The sensitivity of the fluorescent based assay (0.903 ?M) for Al(3+) is far below the limit recommended in the World Health Organization (WHO) guidelines for drinking water (7.41 ?M). From (1)H NMR data, the Job plot and the ESI-MS spectrum, 1?:?2 stoichiometric complexation between and Al(3+) has been established. Receptor shows remarkable detection ability in a wide pH range of 4-11 and was successfully utilised in the determination of Al(3+) in aqueous solution of bovine serum albumin protein, and of HSO3(-) in real food samples. Moreover, shows a highly selective colorimetric response to HSO3(-) by changing its colour from yellow to colorless immediately without any interference from other anions. PMID:26126410

  9. Femtomolar DNA detection by parallel colorimetric darkfield microscopy of functionalized gold nanoparticles

    Microsoft Academic Search

    Remco Verdoold; Ron Gill; Felicia Ungureanu; Robert Molenaar; Rob P. H. Kooyman

    2011-01-01

    We introduce a sensing platform for specific detection of DNA based on the formation of gold nanoparticles dimers on a surface. The specific coupling of a second gold nanoparticle to a surface bound nanoparticle by DNA hybridization results in a red shift of the nanoparticle plasmon peak. This shift can be detected as a color change in the darkfield image

  10. 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...

  11. Dithizone nanofiber-coated membrane for filtration-enrichment and colorimetric detection of trace Hg(II) ion.

    PubMed

    Takahashi, Yukiko; Danwittayakul, Supamas; Suzuki, Toshishige M

    2009-07-01

    Dithizone nanofiber-coated membranes (dithizone membranes), which are useful for sensitive and selective determination of Hg(II), were fabricated. Simply by filtration of the aqueous dispersion of dithizone nanofiber through a cellulose ester membrane filter, a dithizone nanofiber layer of less than 500 nm thickness was coated firmly and uniformly over the membrane filter surface. The steel blue color of the membrane remained unchanged for more than three months when fabricated in the presence of ascorbic acid and stored with an oxygen absorber in an evacuated aluminium bag. Determination at the parts per billion level of Hg(II) was achieved by filtration-enrichment of a sample solution and simultaneous colorimetric analysis using a TLC scanner (500 nm). Consequently, Hg(II) ion was concentrated in the dithizone layer as reddish brown complexes by filtration of a sample solution at pH 2.7. More than 90% of 10 ppb Hg(II) was retained in the dithizone layer at the filtration rate of 1.3-9.3 ml min(-1). The presence of Na+ (10,000 ppm), K+ (5000 ppm), Ca(II) (5000 ppm), Cu(II) (6.4 ppm), Fe(II) (100 ppm), Zn(II) (100 ppm), Pb(II) (100 ppm) and Cd(II) (10 ppm) by using 2.5 x 10(-4) M of ethylenediamine tetraacetic acid (EDTA) as a masking reagent did not interfere with the detection of Hg(II) (10 ppb). Most of anions did not interfere with the determination of Hg(II). The present method was tested for the detection of simulated wastewater, river water and seawater spiked with 10 ppb of Hg(II). PMID:19562205

  12. Colorimetric detection of mutations in epidermal growth factor receptor using gold nanoparticle aggregation

    Microsoft Academic Search

    Hosub Lee; Taegyeong Kang; Kyong-Ah Yoon; So Yeong Lee; Sang-Woo Joo; Kangtaek Lee

    2010-01-01

    We have detected mutations in the epidermal growth factor receptor (EGFR) of non-small cell lung cancer cells using the selective aggregations of gold nanoparticles. Mutations in exon 19 and exon 21 of EGFR gene were detected in non-amplified genomic DNAs that were isolated from both the lung cancer cell lines and the cancer tissues of non-small cell lung cancer patients.

  13. A simple visual and highly selective colorimetric detection of Hg2+ based on gold nanoparticles modified by 8-hydroxyquinolines and oxalates.

    PubMed

    Gao, Yuexia; Li, Xing; Li, Yonglong; Li, Tianhua; Zhao, Yayun; Wu, Aiguo

    2014-06-21

    Gold nanoparticles (AuNPs) modified by 8-hydroxy-quinoline (8-HQ) and stabilized by polyvinylpyrrolidone (PVP) were used for highly selective and sensitive colorimetric detection of Hg(2+) based on the quick aggregation of AuNPs leading to a color change from wine red to gray. The limit of Hg(2+) detection in real environmental water samples is 4.0 × 10(-7) M by the naked eyes and 1.0 × 10(-8) M by UV-vis spectroscopy. PMID:24622578

  14. Multiplexed colorimetric detection of Kaposi's sarcoma associated herpesvirus and Bartonella DNA using gold and silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Mancuso, Matthew; Jiang, Li; Cesarman, Ethel; Erickson, David

    2013-01-01

    Kaposi's sarcoma (KS) is an infectious cancer occurring most commonly in human immunodeficiency virus (HIV) positive patients and in endemic regions, such as Sub-Saharan Africa, where KS is among the top four most prevalent cancers. The cause of KS is the Kaposi's sarcoma-associated herpesvirus (KSHV, also called HHV-8), an oncogenic herpesvirus that while routinely diagnosed in developed nations, provides challenges to developing world medical providers and point-of-care detection. A major challenge in the diagnosis of KS is the existence of a number of other diseases with similar clinical presentation and histopathological features, requiring the detection of KSHV in a biopsy sample. In this work we develop an answer to this challenge by creating a multiplexed one-pot detection system for KSHV DNA and DNA from a frequently confounding disease, bacillary angiomatosis. Gold and silver nanoparticle aggregation reactions are tuned for each target and a multi-color change system is developed capable of detecting both targets down to levels between 1 nM and 2 nM. The system developed here could later be integrated with microfluidic sample processing to create a final device capable of solving the two major challenges in point-of-care KS detection.

  15. 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...

  16. A colorimetric and fluorescent turn on chemodosimeter for Pd2+ detection

    NASA Astrophysics Data System (ADS)

    Li, Lianqing; Liu, Zhihong

    2015-03-01

    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 Pd2+ 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.

  17. Comparative Evaluation of Colorimetric Microtiter Plate Systems for Detection of Herpes Simplex Virus in Cerebrospinal Fluid

    Microsoft Academic Search

    YI-WEI TANG; PAUL N. RYS; BARBARA J. RUTLEDGE; P. SHAWN MITCHELL; THOMAS F. SMITH; DAVID H. PERSING

    1998-01-01

    In the past few years, application of the PCR to the detection of herpes simplex virus (HSV) DNA in the cerebrospinal fluid (CSF) from patients with encephalitis and meningitis has become standard laboratory practice. However, from an operational perspective, the true diagnostic value of PCR in this setting is yet to be realized because most laboratories subject the amplification products

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

    PubMed

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

    2014-12-15

    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

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

    E-print Network

    Du, Pingwu

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

  20. Polydiacetylene liposomes functionalized with sialic acid bind and colorimetrically detect influenza virus

    SciTech Connect

    Reichert, A.; Nagy, J.O.; Spevak, W.; Charych, D. (Lawrence Berkeley Lab., CA (United States))

    1995-01-18

    In this paper we have demonstrated that polymerized liposomes are biomolecular materials that provide a molecular recognition function (sialic acid) and a detection element (polydiacetylene backbone), all within a single supramolecular assembly. The binding event is transduced to a visible color change, readily seen with the naked eye and quantified by absorption spectroscopy. Specificity of the color change was demonstrated by competitive inhibition studies. In addition, nonspecific adsorption, if it occurs. does not appear to affect the color of the liposome solutions. 28 refs., 2 figs.

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

    NASA Astrophysics Data System (ADS)

    Narayanan, Kannan Badri; Park, Hyun Ho

    2014-10-01

    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.

  2. Cell damage detection using Escherichia coli reporter plasmids: fluorescent and colorimetric assays.

    PubMed

    Padilla-Martínez, Felipe; Carrizosa-Villegas, Luz Adriana; Rangel-Serrano, Ángeles; Paramo-Pérez, Itzel; Mondragón-Jaimes, Verónica; Anaya-Velázquez, Fernando; Padilla-Vaca, Felipe; Franco, Bernardo

    2015-08-01

    Bacterial reporter assays are powerful tools used to study the effect of different compounds that affect the physiology of cellular processes. Most bacterial reporters are luciferase based and can be monitored in real time. In the present study we designed and implemented two sets of Escherichia coli bacterial reporter assays, using a multicopy plasmid system. Each reporter strain was constructed using either green fluorescent protein or ?-galactosidase (LacZ) proteins. The designed reporter strains are capable of responding in a specific manner to molecules that either oxidative stress, or membrane, protein, or DNA damage. In order to respond to the desired stimulus, promoter sequences from E. coli were used. These sequences correspond to the promoter of the major catalase (KatG) activated with cellular oxidative damage, the promoter of the ?-hydroxydecanoyl-ACP dehydrase (FabA) which is activated with membrane perturbation, the promoter of DNA recombinase (RecA) which is activated by DNA lesions. For protein misfolding, the promoter of the heat-shock responsive chaperon (DnaK) was used. Our constructs displayed activation to damage from specific stimuli, and low response to nonspecific stimuli was detected. Our results suggest that these types of bacterial reporter strains can be used in semiquantitative (fluorometric) and qualitative (?-galactosidase activity) studies of different xenobiotic substances and pollutants. PMID:25983135

  3. Direct WIMP detection in directional experiments

    SciTech Connect

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

    2007-03-01

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

  4. Dark Matter: Direct Detection

    SciTech Connect

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

    2009-12-16

    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.

  5. [Fe(CN)6]4- decorated mesoporous gelatin thin films for colorimetric detection and as sorbents of heavy metal ions.

    PubMed

    Shi, Li; Huang, Hubiao; Sun, Luwei; Lu, Yanping; Du, Binyang; Mao, Yiyin; Li, Junwei; Ye, Zhizhen; Peng, Xinsheng

    2013-09-28

    [Fe(CN)6](4-) decorated mesoporous gelatin films, acting as colorimetric sensors and sorbents for heavy metal ions, were prepared by incorporating [Fe(CN)6](4-) ions into the mesoporous gelatin films through electrostatic interaction. Gelatin-Prussian blue (PB) and gelatin-PB analogue composite films were successfully synthesized by immersing the [Fe(CN)6](4-) decorated gelatin films into aqueous solutions of metal ions, such as Fe(3+), Cu(2+), Co(2+), Pb(2+) and Cd(2+) (all as nitrates). The in situ formation process of PB or its analogues in the films was investigated using quartz crystal microbalance (QCM) measurements. According to the different colors of the PB nanoparticles and its analogues, the [Fe(CN)6](4-) decorated mesoporous gelatin films demonstrated colorimetric sensor abilities for detecting the corresponding metal ions by the naked eye with sufficient sensitivity at 1 ppm level and a quite short response time of 5 minutes. Moreover, due to the [Fe(CN)6](4-) functionality and other functional groups of gelatin itself, this [Fe(CN)6](4-) decorated mesoporous gelatin film shows a tens times higher adsorption ability for heavy metal ions in water than that of activated carbon. Due to both the efficient detection and high adsorption ability for heavy metal ions, this film has wide potential applications for the detection and purification of heavy metal ions from polluted water. PMID:23887280

  6. A nanosized metal-organic framework of Fe-MIL-88NH? as a novel peroxidase mimic used for colorimetric detection of glucose.

    PubMed

    Liu, Ya Li; Zhao, Xi Juan; Yang, Xiao Xi; Li, Yuan Fang

    2013-08-21

    In this paper, a nanosized porous metal-organic framework, Fe-MIL-88NH?, was facilely prepared with a uniform octahedral shape by the addition of acetic acid, and for the first time was demonstrated to possess intrinsic peroxidase-like activity. Kinetic analysis and electron spin resonance measurements indicated that the catalytic behavior was consistent with typical Michaelis-Menten kinetics and follows a ping-pong mechanism. As a novel peroxidase mimic material, Fe-MIL-88NH? shows the advantages of high catalytic efficiency, ultrahigh stability and high biocompatibility in aqueous medium compared with natural enzymes and other peroxidase nanomimetics. Here, Fe-MIL-88NH? was used to quickly catalyze oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H?O? to produce a colored product, which provided a simple, sensitive and selective method for the colorimetric detection of glucose. Glucose could be linearly detected in the range from 2.0 × 10?? to 3.0 × 10?? M with a detection limit of 4.8 × 10?? M, and the color variation for glucose response was also obvious by visual observation at concentrations as low as 2.0 × 10?? M. More importantly, the colorimetric method could be successfully applied to the determination of glucose in diluted serum samples. PMID:23775015

  7. MicroRNA-triggered, cascaded and catalytic self-assembly of functional ``DNAzyme ferris wheel'' nanostructures for highly sensitive colorimetric detection of cancer cells

    NASA Astrophysics Data System (ADS)

    Zhou, Wenjiao; Liang, Wenbin; Li, Xin; Chai, Yaqin; Yuan, Ruo; Xiang, Yun

    2015-05-01

    The construction of DNA nanostructures with various sizes and shapes has significantly advanced during the past three decades, yet the application of these DNA nanostructures for solving real problems is still in the early stage. On the basis of microRNA-triggered, catalytic self-assembly formation of the functional ``DNAzyme ferris wheel'' nanostructures, we show here a new signal amplification platform for highly sensitive, label-free and non-enzyme colorimetric detection of a small number of human prostate cancer cells. The microRNA (miR-141), which is catalytically recycled and reused, triggers isothermal self-assembly of a pre-designed, G-quadruplex sequence containing hairpin DNAs into ``DNAzyme ferris wheel''-like nanostructures (in association with hemin) with horseradish peroxidase mimicking activity. These DNAzyme nanostructures catalyze an intensified color transition of the probe solution for highly sensitive detection of miR-141 down to 0.5 pM with the naked eye, and the monitoring of as low as 283 human prostate cancer cells can also, theoretically, be achieved in a colorimetric approach. The work demonstrated here thus offers new opportunities for the construction of functional DNA nanostructures and for the application of these DNA nanostructures as an effective signal amplification means in the sensitive detection of nucleic acid biomarkers.

  8. Integrated microdevice of reverse transcription-polymerase chain reaction with colorimetric immunochromatographic detection for rapid gene expression analysis of influenza A H1N1 virus.

    PubMed

    Kim, Yong Tae; Chen, Yuchao; Choi, Jong Young; Kim, Won-Jung; Dae, Hyun-Mi; Jung, Jaean; Seo, Tae Seok

    2012-03-15

    An integrated microdevice of a reverse transcription-polymerase chain reaction (RT-PCR) reactor and an immunochromatographic strip was constructed for colorimetric detection of gene expression of influenza A virus subtype H1N1. An RT-PCR cocktail, which included Texas Red-labeled primers, dNTP including biotin-labeled dUTP, and RNA templates of influenza A H1N1 virus, was filled in the PCR chamber through the micropump, and the RT-PCR was performed to amplify the target H1 gene (102 bp). The resultant amplicons bearing biotin moieties and Texas Red haptens were subsequently eluted to the immunochromatographic strip, in which they were first conjugated with the gold nanoparticle labeled anti-hapten antibody in the conjugation pad, and then captured on the streptavidin coated test line through the biotin-streptavidin interaction. By observing a violet color in the test line which was derived from the gold nanoparticle, we confirmed the H1N1 target virus. The entire process on the integrated microdevice consisting of a micropump, a 2 ?L PCR chamber, and an immunochromatographic strip was carried out on the portable genetic analyzer within 2.5h, enabling on-site colorimetric pathogen identification with detection sensitivity of 14.1 pg RNA templates. PMID:22265877

  9. Ratiometric and colorimetric "naked eye" selective detection of CN(-) ions by electron deficient Ni(ii) porphyrins and their reversibility studies.

    PubMed

    Kumar, Ravi; Chaudhri, Nivedita; Sankar, Muniappan

    2015-05-01

    Highly electron deficient ?-substituted Ni(ii) porphyrins () were synthesized and utilized as novel sensors for selective rapid visual detection of CN(-) ions. This article describes the single crystal X-ray structures, electronic spectral and electrochemical redox properties of these sensors. The ratiometric and colorimetric responses of these porphyrins were monitored by the change in optical absorption spectra. These sensors were found to be highly selective for cyanide ions with extremely high binding constants (10(16)-10(8) M(-2)) through axial ligation of CN(-) ions and are able to detect <0.11 ppm of CN(-) ions. were recovered from ·2CN(-) adducts by acid treatment and reused without loss of sensing ability. CN(-) binding strongly perturbs the redox properties of the parent porphyrin ?-system. The applicability of as practical visible colorimetric test kits for CN(-) ions in aqueous and non-aqueous media has also been explored. The mode of binding was confirmed by single crystal X-ray, spectroscopic studies and DFT calculations. PMID:25901694

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

    PubMed

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

    2015-04-15

    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

  11. Highly selective colorimetric detection and estimation of Hg2+ at nano-molar concentration by silver nanoparticles in the presence of glutathione.

    PubMed

    Alam, Ayesha; Ravindran, Aswathy; Chandran, Preethy; Sudheer Khan, S

    2015-02-25

    The present study investigated the colorimetric detection of mercury (Hg(2+)) ions by using silver nanoparticles (Ag NPs) in the presence of glutathione. The nanoparticles used in the study were synthesized biologically by using Polyalthia longifolia leaf extract. The synthesized nanoparticles were characterized by UV-visible spectrophotometer, transmission electron microscope, X-ray diffraction, particle size analyzer and zeta sizer. The particles were spherical in shape and it possesses the effective diameter of 5 nm. The zeta potential of the particles was determined to be -28.6 mV. Ag NPs-glutathione conjugates were able to detect Hg(2+) in nanomolar level. Ag NPs-glutathione conjugates upon interaction with Hg(2+) changes from yellowish brown to pale yellow and finally colorless. The study may be applied for the qualitative and quantitative estimation of mercury at very low concentration. PMID:25240142

  12. Low-cost preparation of photoluminescent carbon nanodots and application as peroxidase mimetics in colorimetric detection of H2O2 and glucose.

    PubMed

    Wu, Di; Deng, Xiang; Huang, Xiaomei; Wang, Kun; Liu, Qingye

    2013-10-01

    A low-cost and facile preparation of water-soluble photoluminescent carbon nanodots (CDs) with a quantum yield of approximately 12.4% by hydrothermal method utilizing the leaves of Olea Europaea, a large number of planted trees in southwest of China, as a carbon source is developed for the first time. The prepared photoluminescent CDs not only show favorable photoluminescent properties, but also possess intrinsic peroxidase-like activity for colorimetric and UV-Vis absorption detection of hydrogen oxide (H2O2) and glucose. This sensing system exhibits excellent sensitivity toward H2O2 and glucose with the limit of detection as low as 0.6 microM and 5.2 microM. The practical use of this system for glucose determination in serum samples is also demonstrated successfully. The stability and low cost of photoluminescent CDs make them a powerful tool for a wide range of potential applications in biochemical analysis. PMID:24245121

  13. Direct detection of beta-1,3-glucanase in plant extracts by polyacrylamide gel electrophoresis.

    PubMed

    Kalix, S; Buchenauer, H

    1995-06-01

    By using carboxymethyl (CM)-curdlan, a polysaccharide linked with the dye Remazol Brilliant Blue (RBB) as a substrate in polyacrylamide gels, the beta-1,3-glucanase in plant extracts can be detected directly by native polyacrylamide gel electrophoresis. In contrast to the usually used procedures for the detection of glucanases, e.g., colorimetric assay, overlay technique, enzyme activity staining using laminarin as a substrate, this method is rapid and allows both the determination of the activity and the location of the relative position of the multiple forms of beta-1,3-glucanases. PMID:7498122

  14. Direct Detection with Dark Mediators

    E-print Network

    David Curtin; Ze'ev Surujon; Yuhsin Tsai

    2014-11-11

    We introduce dark mediator Dark matter (dmDM) where the dark and visible sectors are connected by at least one light mediator $\\phi$ carrying the same dark charge that stabilizes DM. $\\phi$ is coupled to the Standard Model via an operator $\\bar q q \\phi \\phi^*/\\Lambda$, and to dark matter via a Yukawa coupling $y_\\chi \\overline{\\chi^c}\\chi \\phi$. Direct detection is realized as the $2\\rightarrow3$ process $\\chi N \\rightarrow \\bar \\chi N \\phi$ at tree-level for $m_\\phi \\lesssim 10 \\ \\mathrm{keV}$ and small Yukawa coupling, or alternatively as a loop-induced $2\\rightarrow2$ process $\\chi N \\rightarrow \\chi N$. We explore the direct-detection consequences of this scenario and find that a heavy $\\mathcal{O}(100 \\ \\mathrm{GeV})$ dmDM candidate fakes different $\\mathcal{O}(10 \\ \\mathrm{GeV})$ standard WIMPs in different experiments. Large portions of the dmDM parameter space are detectable above the irreducible neutrino background and not yet excluded by any bounds. Interestingly, for the $m_\\phi$ range leading to novel direct detection phenomenology, dmDM is also a form of Self-Interacting Dark Matter (SIDM), which resolves inconsistencies between dwarf galaxy observations and numerical simulations.

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

    PubMed

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

    2014-04-01

    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

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

    SciTech Connect

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

    1997-03-19

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

  17. Colorimetric Biosensors Based on DNAzyme-Assembled Gold Nanoparticles

    Microsoft Academic Search

    Juewen Liu; Yi Lu

    2004-01-01

    Taking advantage of recent developments in the field of metallic nanoparticle-based colorimetric DNA detection and in the field of in vitro selection of functional DNA\\/RNA that can recognize a wide range of analytes, we have designed highly sensitive and selective colorimetric biosensors for many analytes of choice. As an example of the sensor design strategy, a highly sensitive and selective

  18. 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)

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

    2011-07-01

    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.

  19. Design and characterization of a recombinant colorimetric SAG1-alkaline phosphatase conjugate to detect specific antibody responses against Toxoplasma gondii.

    PubMed

    Chahed Bel-Ochi, Nouha; Bouratbine, Aïda; Mousli, Mohamed

    2013-08-30

    The purpose of this study was to design a novel in vitro tool by using recombinant protein technology to detect specific antibody responses against Toxoplasma gondii in a simple, rapid and highly sensitive reagent. The surface T. gondii SAG1 protein is an important immunodominant target, which provides a great interest as a diagnostic antigen. To further exploit its immunodetection capacity, in the present study, the full length sag1 gene was inserted into the pLIP6 prokaryotic expression vector so as to produce a SAG1 antigen genetically fused to the bacterial alkaline phosphatase (AP). After expression optimization, the recombinant fusion protein folded correctly in soluble form in the periplasmic space and preserved both the AP enzymatic activity and the SAG1 immunoreactivity. Subsequently, direct-ELISA and dot-blot immunoassays were designed, using crude preparation SAG1-AP conjugate, to explore its value in serodiagnosis of human toxoplasmosis. We demonstrate that the recombinant SAG1-AP can detect specific T. gondii antibodies in one-step procedure and can successfully discriminate between T. gondii immune and non-immune patients, in agreement with the standard gold test. In conclusion, the present study shows that the genetic fusion protein provides a new tool for one-step T. gondii immunodetection, which was easily, quickly and reproducibly produced as homogeneous bi-functional reagent. Thus, this recombinant immunoconjugate is a promising marker for Toxoplasma serodiagnosis, requiring further evaluation on a larger series and could provide the basis for direct antibody capture enzyme-immunoassay for specific immunoglobulin M and G detection. PMID:23727049

  20. Detection and differentiation of Campylobacter jejuni and Campylobacter coli in broiler chicken samples using a PCR/DNA probe membrane based colorimetric detection assay.

    PubMed

    O'Sullivan, N A; Fallon, R; Carroll, C; Smith, T; Maher, M

    2000-02-01

    Campylobacter enteritis in humans has been linked to consumption of poultry meat. Surveys show that 30-100% of poultry harbour Campylobacter as normal flora of the digestive tract which indicates a need to identify prevalent organism types in flocks and trace their epidemiology. In this study we describe a Campylobacter genus specific polymerase chain reaction (PCR) assay, amplifying the 16 S-23 S rRNA intergenic spacer region with an internal Campylobacter genus specific DNA probe and species specific probes for Campylobacter jejuni and Campylobacter coli designed for confirmation of the amplified PCR products by Southern blot and colorimetric reverse hybridization assays. The specificity of this assay was established by testing a range of food pathogens. Broiler chicken samples were tested following presumptive positive identification by the Malthus System V analyser (Malthus Instruments, UK). The combined PCR and colorimetric reverse hybridization assay is easy to perform and faster than conventional methods for confirmation and identification of Campylobacter species. PMID:10725058

  1. dmdd: Dark matter direct detection

    NASA Astrophysics Data System (ADS)

    Gluscevic, Vera; McDermott, Samuel D.

    2015-06-01

    The dmdd package enables simple simulation and Bayesian posterior analysis of recoil-event data from dark-matter direct-detection experiments under a wide variety of scattering theories. It enables calculation of the nuclear-recoil rates for a wide range of non-relativistic and relativistic scattering operators, including non-standard momentum-, velocity-, and spin-dependent rates. It also accounts for the correct nuclear response functions for each scattering operator and takes into account the natural abundances of isotopes for a variety of experimental target elements.

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

    PubMed

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

    2015-04-21

    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

  3. SDS-MoS2 nanoparticles as highly-efficient peroxidase mimetics for colorimetric detection of H2O2 and glucose.

    PubMed

    Zhao, Kai; Gu, Wei; Zheng, Sisi; Zhang, Cuiling; Xian, Yuezhong

    2015-08-15

    In this work, we find that the peroxidase-like activity of MoS2 nanoparticles (NPs) is dependent on the surface charge. Negatively charged sodium dodecyl sulfate modified MoS2 nanoparticles (SDS-MoS2 NPs) possess highly-efficient peroxidase-like activity. MoS2 NPs with intrinsic peroxidase-like activity were synthesized through a simple one-pot hydrothermal route. The peroxidase-like activities of different surfactants modified MoS2 NPs were discussed. Compared with bare MoS2 NPs and positively charged cetyltrimethyl ammonium bromide modified MoS2 NPs, SDS-MoS2 NPs have the best peroxidase-like activity. SDS-MoS2 NPs can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue product. On basis of this, we have successfully established a novel platform for colorimetric detection of H2O2, and the detection limit is 0.32?M. Furthermore, the SDS-MoS2 NPs based platform can also be used for high sensitivity and selectivity detection of glucose with a wide linear range of 5.0-500?M by controlling the generation of H2O2 in the presence of glucose oxidase. PMID:25966379

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

    PubMed

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

    2013-09-21

    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

  5. 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

    Sedghi, Roya; Heidari, Bahareh; Behbahani, Mohammad

    2015-03-21

    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

  6. Colorimetric detection of the flux of hydrogen peroxide released from living cells based on the high peroxidase-like catalytic performance of porous PtPd nanorods.

    PubMed

    Ge, Shenguang; Liu, Weiyan; Liu, Haiyun; Liu, Fang; Yu, Jinghua; Yan, Mei; Huang, Jiadong

    2015-09-15

    One-dimensional PtPd porous nanorods (PtPd PNRs) were successfully synthesized through a bromide-induced galvanic replacement reaction between Pd nanowires and K2PtCl6. The PtPd PNRs were porous and alloy-structured with Pt/Pd atomic ratio up to 1:1 which were demonstrated by spectroscopic methods. We had also proved that the nanorods could function as peroxidase mimetic for the detection of H2O2, with the detection limit of 8.6nM and the linear range from 20nM to 50mM. The result demonstrated that PtPd PNRs exhibited much higher affinity to H2O2 over other peroxidase mimetics due to synergistically integrating highly catalytic activity of two metals. On the basis of the peroxidase-like activity, the PtPd PNRs were used as a signal transducer to develop a novel and simple colorimetric method for the study of the flux of H2O2 released from living cell. By using 3,3,5,5-tetramethylbenzidine as substrate, the H2O2 concentration could be distinguished by naked-eye observation without any instrumentation or complicated design. The method developed a new platform for a reliable collection of information on cellular reactive oxygen species release. And the nanomaterial could be used as a power tool for a wide range of potential applications in biotechnology and medicine. PMID:25982545

  7. Colorimetric determination of dimethoate or omethoate.

    PubMed

    Bhaskar, S U; Nandakumar, N V

    1980-09-01

    A simple, sensitive and rapid colorimetric method is described for determining dimethoate [O,O-dimethyl-S-(N-methylcarbanoylmethyl)phosphorodithioate] and omethoate by an enzymatic method using pig liver acetone powder as enzyme source and p-nitrobenzenediazonium fluoroborate as the chromogenic reagent. This colorimetric method is more sensitive than non-enzymatic methods. Inhibition can be detected at ng levels and amounts ranging from 50 to 1000 ng of omethoate and from 1 to 10 mug of dimethoate can be estimated. PMID:18962774

  8. A new rapid colorimetric detection method of Al³? with high sensitivity and excellent selectivity based on a new mechanism of aggregation of smaller etched silver nanoparticles.

    PubMed

    Yang, Ningning; Gao, Yuexia; Zhang, Yujie; Shen, Zheyu; Wu, Aiguo

    2014-05-01

    As a pathogenic factor of the Alzheimer?s disease, aluminum has been associated with the damage of the central nervous system in humans. In this study, we propose a new facile and rapid colorimetric detection method of Al(3+) with excellent selectivity and high sensitivity based on silver nanoparticles (AgNPs) stabilized by reduced glutathione (GSH) in the presence of l-cysteine (Cys). The new mechanism of our Al(3+) detection system based on GSH-AgNPs, i.e., aggregation of smaller etched GSH-AgNPs, are confirmed by TEM, EDS and DLS. The aggregation of smaller etched GSH-AgNPs results in obvious color change of the nanoparticle dispersion from yellow to reddish brown, and red shift and intensity decrease of the surface plasmon resonance (SPR) absorption. The GSH concentration, Cys concentration and pH value of the GSH-AgNPRs-based detection system are respectively optimized to be 10.0 mM, 50.0 mM and 6.0 according to the sensing effect of Al(3+). At the optimized conditions, the selectivity of the GSH-AgNPs detection system for Al(3+) is excellent compared with other ions including K(+), Mg(2+), Fe(3+), Co(2+), Mn(2+), Zn(2+), Cd(2+), Pb(2+), Ca(2+), Ba(2+), Cu(2+), Cr(3+), Hg(2+), Ni(2+), [Formula: see text] , [Formula: see text] , [Formula: see text] , [Formula: see text] and [Formula: see text] . Furthermore, this detection system is very sensitive for Al(3+). The limit of detection (LOD) is 1.2 µM by the naked eyes and 0.16 µM by UV-vis spectra, which are both much lower than the national drinking water standards (7.4 µM). Furthermore, the UV-vis detection offers a good linear detection range from 0.4 to 4.0 µM (R(2)=0.9924), which indicates that our developed detection system can also be used for the quantitative analysis of Al(3+). The detection results of real water samples indicate that this method can be used for real water detection. PMID:24720995

  9. Model Independent Direct Detection Analyses

    E-print Network

    A. Liam Fitzpatrick; Wick Haxton; Emanuel Katz; Nicholas Lubbers; Yiming Xu

    2012-11-12

    Following the construction of the general effective theory for dark matter direct detection in 1203.3542, we perform an analysis of the experimental constraints on the full parameter space of elastically scattering dark matter. We review the prescription for calculating event rates in the general effective theory and discuss the sensitivity of various experiments to additional nuclear responses beyond the spin-independent (SI) and spin-dependent (SD) couplings: an angular-momentum-dependent (LD) and spin-and-angular-momentum-dependent (LSD) response, as well as a distinction between transverse and longitudinal spin-dependent responses. We consider the effect of interference between different operators and in particular look at directions in parameter space where such cancellations lead to holes in the sensitivity of individual experiments. We explore the complementarity of different experiments by looking at the improvement of bounds when experiments are combined. Finally, our scan through parameter space shows that within the assumptions on models and on the experiments' sensitivity that we make, no elastically scattering dark matter explanation of DAMA is consistent with all other experiments at 90%, though we find points in parameter space that are ruled out only by about a factor of 2 in the cross-section.

  10. Facile synthesis of enzyme-inorganic hybrid nanoflowers and its application as a colorimetric platform for visual detection of hydrogen peroxide and phenol.

    PubMed

    Lin, Zian; Xiao, Yun; Yin, Yuqing; Hu, Wenli; Liu, Wei; Yang, Huanghao

    2014-07-01

    This study reports a facile approach for the synthesis of horseradish peroxidise (HRP)-inorganic hybrid nanoflowers by self-assembly of HRP and copper phosphate (Cu3(PO4)2·3H2O) in aqueous solution. Several reaction parameters that affect the formation of the hybrid nanoflowers were investigated and a hierarchical flowerlike spherical structure with hundreds of nanopetals was obtained under the optimum synthetic conditions. The enzymatic activity of HRP embedded in hybrid naonflowers was evaluated based on the principle of HRP catalyzing the oxidation of o-phenylenediamine (OPD) in the presence of hydrogen peroxide (H2O2). The results showed that 506% enhancement of enzymatic activity in the hybrid nanoflowers could be achieved compared with the free HRP in solution. Taking advantages of the structural feature with catalytic property, a nanoflower-based colorimetric platform was newly designed and applied for fast and sensitive visual detection of H2O2 and phenol. The limits of detection (LODs) for H2O2 and phenol were as low as 0.5 ?M and 1.0 ?M by the naked-eye visualization, which meet the requirements of detection of both analytes in clinical diagnosis and environmental water. The proposed method has been successfully applied to the analysis of low-level H2O2 in spiked human serum and phenol in sewage, respectively. The recoveries for all the determinations were higher than 92.6%. In addition, the hybrid nanoflowers exhibited excellent reusability and reproducibility in cycle analysis. These primary results demonstrate that the hybrid nanoflowers have a great potential for applications in biomedical and environmental chemistry. PMID:24937087

  11. Bio-inspired Maillard-Like reactions enable a simple and sensitive assay for colorimetric detection of methylglyoxal.

    PubMed

    Wang, Shih-Ting; Lin, Yiyang; Spicer, Christopher D; Stevens, Molly M

    2015-06-25

    A simple and selective assay for detecting methylglyoxal (MGO), a metabolite associated with diabetes, was developed by combining a bio-inspired chemical reaction with the anti-aggregation of gold nanoparticles. This assay could detect MGO at as low as 1 ?M by the naked eye and 0.05 ?M by UV/vis spectrometry, within the clinical range marking oxidative stress in diabetes, and demonstrated high selectivity over other physiologically relevant ketones and aldehydes. PMID:26073427

  12. Colorimetric determination of methyl parathion and oxygen analog.

    PubMed

    Nanda Kumar, N V; Ramasundari, M

    1980-05-01

    A simple, sensitive, and rapid colorimetric method is described for determining methyl parathion (O,O-dimethyl-O-p-nitrophenyl phosphorothioate) and methyl paraoxon (O,O-dimethyl-O-p-nitrophenyl phosphate), using p-nitrobenzene diazonium fluoroborate as the chromogenic salt. This colorimetric method is more sensitive than are other colorimetric methods based on non-enzymatic reactions. Pig liver acetone powder cholinesterase was found to be sensitive to methyl parathion. Inhibition can be detected at picogram levels, and 50-80 ng methyl paraoxon and 1-9 micrograms methyl parathion can be estimated. PMID:7430041

  13. Control of metal nanoparticles aggregation and dispersion by PNA and PNA-DNA complexes, and its application for colorimetric DNA detection.

    PubMed

    Su, Xiaodi; Kanjanawarut, Roejarek

    2009-09-22

    We have demonstrated that mixed-base PNA oligomers are effective coagulants of citrate ion-coated gold and silver nanoparticles (AuNPs and AgNPs), and PNA-induced particle aggregation can be disrupted by hybridization of PNA with a specific DNA. Using particles' aggregation/dispersion as a measure, we have investigated how PNA and PNA-DNA complexes bind to AuNPs and AgNPs and modulate particles' stability differently relative to their DNA counterparts. We have made the following original discoveries: (1) mix-base PNA oligomers can induce immediate particle aggregation in a concentration- and chain-length-dependent manner; (2) PNA oligomers have a higher affinity to AuNPs and AgNPs than its ssDNA counterpart; (3) PNA-DNA complexes, although having a stable double helix structure similar to dsDNA, can effectively protect the particles from salt induced aggregation, and the protection effect of different nucleic acids are in the order of PNA-DNA complex > ssDNA > dsDNA; (4) all the characteristics are identical for AuNPs and AgNPs; and (5) AgNPs is more sensitive in response to destabilization effect and is proven a more sensitive platform for colorimetric assays. The control of particle aggregation and dispersion by PNA and PNA-DNA complexes has been used to detect a specific DNA sequence with single-base-mismatch resolution. zeta potential measurements have been conducted to reveal how distinct backbone properties of PNA and PNA-DNA complexes relative to their DNA counterparts contribute to the distinct binding characteristics. PMID:19708641

  14. Size-specific, colorimetric detection of counteranions by using helical poly(phenylacetylene) conjugated to L-leucine groups through urea acceptors.

    PubMed

    Kakuchi, Ryohei; Nagata, Sachiko; Sakai, Ryosuke; Otsuka, Issei; Nakade, Hiroshi; Satoh, Toshifumi; Kakuchi, Toyoji

    2008-01-01

    A colorimetric detection susceptible to the dimensions of guest counteranions has been demonstrated by using poly(phenylacetylene) with L-leucine and urea functionalities (poly-PA-Leu). Poly-PA-Leu was prepared from N-(4-ethynylphenylcarbamoyl)-L-leucine ethyl ester (PA-Leu) by using [Rh(+){eta(6)-C(6)H(5))B(-)(C(6)H(5))(3)}(2,5-norbornadiene)] as a catalyst. The biased helical conformation of poly-PA-Leu was demonstrated through Cotton effects in the circular dichroism (CD) spectra. The addition of ammonium salts, including tetra-n-butylammonium acetate, tetra-n-butylammonium chloride, and tetra-n-butylammonium bromide anions (CH(3)COO(-), Cl(-), and Br(-)), into the poly-PA-Leu solution intensified the CD responses of poly-PA-Leu, which is indicative of the chiral adjustability of anion recognition by using urea groups. In addition, the combination of poly-PA-Leu with the CH(3)COO(-), Cl(-), and Br(-) anions promoted large redshifts in the absorption spectra, thus providing dramatic color changes from pale yellow to red. Guest dependency in the CD and UV/Vis spectra was clearly correlated with the size of the counteranions. Fundamentally, the addition of tetra-n-butylammonium nitrate, tetra-n-butylammonium hydrogen sulfate, tetra-n-butylammonium perchlorate, tetra-n-butylammonium azide, tetra-n-butylammonium fluoride, and tetra-n-butylammonium iodide anions (NO(3) (-), HSO(4) (-), ClO(4) (-), N(3) (-), F(-), and I(-)) has no effect on either the CD or UV/Vis profiles of poly-PA-Leu. The guest specificity observed in the CD and UV/Vis spectra clearly demonstrated the guest-dimension selectivity of poly-PA-Leu in counteranion recognition. PMID:18846603

  15. Water-dispersible silicon dots as a peroxidase mimetic for the highly-sensitive colorimetric detection of glucose.

    PubMed

    Chen, Qiong; Liu, Meiling; Zhao, Jiangna; Peng, Xue; Chen, Xiaojiao; Mi, Naxiu; Yin, Bangda; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2014-06-28

    We demonstrate that photoluminescent Si-dots exhibit intrinsic peroxidase-like activity, and can catalyze the oxidization of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2, and produce a color change. This strategy can be used to detect glucose with high sensitivity and selectivity. PMID:24834912

  16. Novel colorimetric sensor for oral malodour.

    PubMed

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

    2010-02-19

    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

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

    PubMed

    Sommers, Cynthia D; Keire, David A

    2011-09-15

    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

  18. A novel rapid colorimetric assay of carcinoembryonic antigen levels in the abdominal cavity to detect peritoneal micrometastasis during gastric cancer surgery

    Microsoft Academic Search

    Souichi Tsutsumi; Takayuki Asao; Tatsuo Shimura; Erito Mochiki; Ryouji Kato; Hiroyuki Kuwano

    2000-01-01

    We showed that the carcinoembryonic antigen (CEA) level in a peritoneal washing is an indicator of the postoperative survival of gastric cancer patients. On the premise that the polyvinylidine difluoride membrane adsorbs a fixed quantity of protein, this study was designed to produce a rapid, colorimetric, semi-quantitative assay of peritoneal CEA levels by using anti-CEA antibodies. At the time of

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

    PubMed

    Xue, Dingshuai; Wang, Hongyue; Zhang, Yanbin

    2014-02-01

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

  20. 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...

  1. Disentangling dark matter dynamics with directional detection

    SciTech Connect

    Lisanti, Mariangela; Wacker, Jay G. [Theory Group, SLAC, Menlo Park, California 94025 (United States)

    2010-05-01

    Inelastic dark matter reconciles the DAMA anomaly with other null direct detection experiments and points to a nonminimal 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.

  2. Disentangling Dark Matter Dynamics with Directional Detection

    SciTech Connect

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

    2009-12-16

    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.

  3. A novel technique for rapid evaluation of fish freshness using colorimetric sensor array

    Microsoft Academic Search

    Xingyi Huang; Junwei Xin; Jiewen Zhao

    2011-01-01

    An olfaction system based on colorimetric sensor array was developed for fish freshness evaluation. Nine chemically responsive dyes were selected according to their sensitivity to volatile compounds typically occurring during spoilage in fish. The colorimetric sensor array was made by printing selected dyes on a reverse phase silica gel plate. Detection on fish of chub was made every 24h within

  4. Directional detection of dark matter streams

    E-print Network

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

    2014-11-11

    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.

  5. Directional detection of dark matter streams

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  6. Edge detection using directional wavelet transform

    Microsoft Academic Search

    Javad Musevi Niya; Ali Aghagolzadeh

    2004-01-01

    In this paper we propose a new wavelet-based approach for solving the edge detection problem. A primary knowledge about the magnitude and the direction of the edges extracted by the ordinary wavelet-based edge detector is used to classify the image pixels as edge points, candidate edge points, or not edge points by double thresholding using extended Otsu's thresholding method explained

  7. Direct fast neutron detection: A status report

    Microsoft Academic Search

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

    1997-01-01

    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

  8. A Colorimetric Enzyme-Linked Immunosorbent Assay (ELISA) Detection Platform for a Point-of-Care Dengue Detection System on a Lab-on-Compact-Disc

    PubMed Central

    Thiha, Aung; Ibrahim, Fatimah

    2015-01-01

    The enzyme-linked Immunosorbent Assay (ELISA) is the gold standard clinical diagnostic tool for the detection and quantification of protein biomarkers. However, conventional ELISA tests have drawbacks in their requirement of time, expensive equipment and expertise for operation. Hence, for the purpose of rapid, high throughput screening and point-of-care diagnosis, researchers are miniaturizing sandwich ELISA procedures on Lab-on-a-Chip and Lab-on-Compact Disc (LOCD) platforms. This paper presents a novel integrated device to detect and interpret the ELISA test results on a LOCD platform. The system applies absorption spectrophotometry to measure the absorbance (optical density) of the sample using a monochromatic light source and optical sensor. The device performs automated analysis of the results and presents absorbance values and diagnostic test results via a graphical display or via Bluetooth to a smartphone platform which also acts as controller of the device. The efficacy of the device was evaluated by performing dengue antibody IgG ELISA on 64 hospitalized patients suspected of dengue. The results demonstrate high accuracy of the device, with 95% sensitivity and 100% specificity in detection when compared with gold standard commercial ELISA microplate readers. This sensor platform represents a significant step towards establishing ELISA as a rapid, inexpensive and automatic testing method for the purpose of point-of-care-testing (POCT) in resource-limited settings. PMID:25993517

  9. Direct optical detection in bioanalysis: an update

    Microsoft Academic Search

    Günter Gauglitz

    2010-01-01

    In biomolecular interaction analysis, direct optical detection is attracting increasing interest in academia and industry.\\u000a Therefore, a previous review has been updated. Optical principles are given in brief, focussing especially on modern and frequently\\u000a used techniques. Commercialized methods are listed with some specific applications. In addition, some of the many applications\\u000a found in the literature are listed; others which have

  10. Direct detection of dark matter axions with directional sensitivity

    SciTech Connect

    Irastorza, Igor G.; García, Juan A., E-mail: Igor.Irastorza@cern.ch, E-mail: jagarpas@unizar.es [Laboratorio de Física Nuclear y Astropartículas, Departamento de Física Teórica, Universidad de Zaragoza, C/ Pedro Cerbuna 12, 50009, Zaragoza (Spain)

    2012-10-01

    We study the directional effect of the expected axion dark matter signal in a resonant cavity of an axion haloscope detector, for cavity geometries not satisfying the condition that the axion de Broglie wavelength ?{sub a} is sufficiently larger than the cavity dimensions L for a fully coherent conversion, i.e. ?{sub a}?>2?L. We focus on long thin cavities immersed in dipole magnets and find, for appropriately chosen cavity lengths, an O(1) modulation of the signal with the cavity orientation with respect the momentum distribution of the relic axion background predicted by the isothermal sphere model for the galactic dark matter halo. This effect can be exploited to design directional axion dark matter detectors, providing an unmistakable signature of the extraterrestrial origin of a possible positive detection. Moreover, the precise shape of the modulation may give information of the galactic halo distribution and, for specific halo models, give extra sensitivity for higher axion masses.

  11. Ink-jet printed colorimetric gas sensors on plastic foil

    NASA Astrophysics Data System (ADS)

    Courbat, Jerome; Briand, Danick; de Rooij, Nico F.

    2010-08-01

    An all polymeric colorimetric gas sensor with its associated electronics for ammonia (NH3) detection targeting low-cost and low-power applications is presented. The gas sensitive layer was inkjet printed on a plastic foil. The use of the foil directly as optical waveguide simplified the fabrication, made the device more cost effective and compatible with large scale fabrication techniques, such as roll to roll processes. Concentrations of 500 ppb of NH3 in nitrogen with 50% of RH were measured with a power consumption of about 868 ?W in an optical pulsed mode of operation. Such sensors foresee applications in the field of wireless systems, for environmental and safety monitoring. The fabrication of the planar sensor was based on low temperature processing. The waveguide was made of PEN or PET foil and covered with an ammonia sensitive layer deposited by inkjet printing, which offered a proper and localized deposition of the film. The influence of the substrate temperature and its surface pretreatment were investigated to achieve the optimum deposition parameters for the printed fluid. To improve the light coupling from the light source (LED) to the detectors (photodiodes), polymeric micro-mirrors were patterned in an epoxy resin. With the printing of the colorimetric film and additive patterning of polymeric micro-mirrors on plastic foil, a major step was achieved towards the implementation of full plastic selective gas sensors. The combination with printed OLED and PPD would further lead to an integrated all polymeric optical transducer on plastic foil fully compatible with printed electronics processes.

  12. Direct Electron Detection And Imaging Using CCD

    E-print Network

    S. R. Mirfayzi

    2013-01-13

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

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

    PubMed

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

    2015-05-15

    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

  14. Passive colorimetric dosimeter tubes for ammonia, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen dioxide, and sulfur dioxide

    Microsoft Academic Search

    E. S. McKee; I. M. Pritts

    1981-01-01

    Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an 8-h period for several inorganic airborne contaminants in the range of their threshold limit values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NHâ), carbon monoxide (CO), carbon dioxide (COâ), hydrogen sulfide (HâS), nitrogen dioxide

  15. Ion Channeling in Direct Dark Matter Detection

    NASA Astrophysics Data System (ADS)

    Bozorgnia, Nassim

    The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger signal than otherwise expected. We give estimates of the fraction of channeled recoiling ions in NaI (Tl), Si, Ge, CsI, and solid Xe, Ar and Ne crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects. We find that the channeling fraction of recoiling lattice nuclei is smaller than that of ions that are injected into the crystal and that it is strongly temperature dependent. Channeling is a directional effect which depends on the velocity distribution of WIMPs in the dark halo of our Galaxy and could lead to a daily modulation of the signal. We compute upper bounds to the expected amplitude of daily modulation due to channeling using our estimates of the channeling fractions. After developing the general formalism, we examine the possibility of finding a daily modulation due to channeling in the data already collected by the DAMA experiment. We find that even the largest daily modulation amplitudes would not be observable for WIMPs in the standard halo in the 13 years of data taken by the DAMA collaboration. For these to be observable the DAMA total rate should be 1/40 of what it is or the total DAMA exposure should be 40 times larger. The daily modulation due to channeling will be difficult to measure in future experiments.

  16. Determination of cysteine, homocysteine, cystine, and homocystine in biological fluids by HPLC using fluorosurfactant-capped gold nanoparticles as postcolumn colorimetric reagents.

    PubMed

    Zhang, Lijuan; Lu, Biqi; Lu, Chao; Lin, Jin-Ming

    2014-01-01

    We have demonstrated for the first time the suitability of fluorosurfactant-capped spherical gold nanoparticles as HPLC postcolumn colorimetric reagents for the direct assay of cysteine, homocysteine, cystine, and homocystine. The success of this work was based on the use of an on-line tris(2-carboxyethyl)phosphine reduction column for cystine and homocystine. Several parameters affecting the separation efficiency and the postcolumn colorimetric detection were thoroughly investigated. Under the optimized conditions, cysteine, homocysteine, cystine, and homocystine in human urine and plasma samples were determined. Detection limits for cysteine, homocysteine, cystine, and homocystine ranged from 0.16-0.49 ?M. The accuracy in terms of recoveries ranged between 94.0-102.1%. This proposed method was rapid, inexpensive, and simple. PMID:24302617

  17. Colorimetric characterization of LED luminaires

    NASA Astrophysics Data System (ADS)

    Costa, C. L. M.; Vieira, R. R.; Pereira, R. C.; Silva, P. V. M.; Oliveira, I. A. A.; Sardinha, A. S.; Viana, D. D.; Barbosa, A. H.; Souza, L. P.; Alvarenga, A. D.

    2015-01-01

    The Optical Metrology Division of Inmetro – National Institute of Metrology, Quality and Technology has recently started the colorimetric characterization of lamps by implementing Correlated Color Temperature (CCT) and Color Rendering Index (CRI) measurements of incandescent lamps, followed by the CFL, and LED lamps and luminaires. Here we present the results for the verification of the color characterization of samples of SSL luminaires for public as well as indoor illumination that are sold in Brazil.

  18. A novel highly selective colorimetric sensor for aluminum (III) ion using Schiff base derivative

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Fang; Ke, Ying-Chang; Guo, Hong-Xu; Chen, Jianhua; Weng, Wen

    2014-03-01

    A novel colorimetric sensor, 2-hydroxy naphthaldehyde isonicotinoyl hydrazone (HINH), was easily synthesized by the condensation of isoniazid and 2-hydroxy-1-naphthaldehyde. The as-prepared compound showed effective colorimetric single selectivity and high sensitivity for aluminum cation in CH3CN/H2O (1:3) binary solutions. The detection limit is 1.0 × 10-8 M Al3+ based on UV-vis changes.

  19. 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

  20. Particle stability in polymer-assisted reverse colorimetric DNA assays

    Microsoft Academic Search

    Weiming Zheng; Lin He

    2009-01-01

    “Reverse” colorimetric DNA detection by the formation of core-shell particles upon DNA hybridization is described. Specifically,\\u000a the assay is based on a strategy to covalently link polymer reaction initiators to suspended nanoparticles upon DNA hybridization.\\u000a These initiators then prompt polymer chain growth to form a thick polymer shell outside of particles, acting as the physical\\u000a barrier to keep Au particles

  1. Portable paper-based device for quantitative colorimetric assays relying on light reflectance principle.

    PubMed

    Li, Bowei; Fu, Longwen; Zhang, Wei; Feng, Weiwei; Chen, Lingxin

    2014-04-01

    This paper presents a novel paper-based analytical device based on the colorimetric paper assays through its light reflectance. The device is portable, low cost (<20 dollars), and lightweight (only 176 g) that is available to assess the cost-effectiveness and appropriateness of the original health care or on-site detection information. Based on the light reflectance principle, the signal can be obtained directly, stably and user-friendly in our device. We demonstrated the utility and broad applicability of this technique with measurements of different biological and pollution target samples (BSA, glucose, Fe, and nitrite). Moreover, the real samples of Fe (II) and nitrite in the local tap water were successfully analyzed, and compared with the standard UV absorption method, the quantitative results showed good performance, reproducibility, and reliability. This device could provide quantitative information very conveniently and show great potential to broad fields of resource-limited analysis, medical diagnostics, and on-site environmental detection. PMID:24375226

  2. Colorimetric Solid-Phase Extractor

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The heart of a colorimetric solid phase extractor (CSPE) test kit quickly measures the concentration of the biocides silver or iodine in astronauts' drinking water to determine whether concentrations are safe. When 10 milliliters (ml) of water is drawn through the disk, the disk will turn color (yellow in this picture for iodine) indicating the presence of the biocides. The device could someday be used to test water safety at reservoirs and water treatment plants on Earth. (photo credit: Microanalytical Instrumentation Center, Iowa State University).

  3. Biomolecular Sensing with Colorimetric Vesicles

    Microsoft Academic Search

    Raz Jelinek; Sofiya Kolusheva

    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

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

    Microsoft Academic Search

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

    2011-01-01

    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

  5. Systematic aspects of direct extrasolar planet detection

    NASA Technical Reports Server (NTRS)

    Brown, Robert A.

    1988-01-01

    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.

  6. DIRECTIONAL DETECTION OF A NEUTRON SOURCE.

    SciTech Connect

    VANIER, P.E.; FORMAN, L.

    2006-10-23

    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.

  7. Avalanche photodiode detection statistics for direct detection laser radar

    Microsoft Academic Search

    Douglas G. Youmans

    1992-01-01

    The detection statistics of avalanche photodiode detectors when used in laser radar systems are examined. In the laser radar systems considered here, a diffuse hard target is illuminated by a transmitted laser beam and the photons subtended by the receiving aperture and focused onto the detector obey negative-binomial statistics. The specific negative-binomial distribution is determined by the coherence length of

  8. Dark matter effective field theory scattering in direct detection experiments

    E-print Network

    Schneck, K.

    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 ...

  9. Fault detection of multivariable system using its directional properties 

    E-print Network

    Pandey, Amit Nath

    2006-04-12

    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 ...

  10. Direct detection of linearized bursts in turbulence

    NASA Astrophysics Data System (ADS)

    Jiménez, Javier

    2015-06-01

    The relevance of linear transitional mechanisms in fully turbulent shear flows, and in particular of the Orr-like inviscid transient amplification of disturbances, is explored in the context of the prediction of bursting behavior. Although the logarithmic layer of wall-bounded turbulence is used as the primary example, most conclusions should apply to other flows with linearly stable mean profiles that are dominated by large-scale streamwise-velocity streaks and intermittent bursts of the cross-shear velocity. When the linearised problem is solved in the limit of small viscosity, it has previously been shown that statistical properties, such as the bursting time- and length-scales, the energy fluxes between components, and the mean inclination angles, are consistent in linear and nonlinear systems. The question addressed here is whether the individual structures predicted by the linearised solution can be detected in fully nonlinear simulations, and whether the linearized approximation can be used to predict their evolution. It is found that strong bursting of the largest scales is well described linearly, comprising about 65%-70% of the total time, but that weaker fluctuations are not. It is also found that adding an eddy viscosity does not substantially improve predictions.

  11. Detecting a trajectory embedded in random-direction motion noise

    Microsoft Academic Search

    Scott N. J. Watamaniuk; Suzanne P. McKee; Norberto M. Grzywacz

    1995-01-01

    Human observers can easily detect a signal dot moving, in apparent motion, on a trajectory embedded in a background of random-direction motion noise. A high detection rate is possible even though the spatial and temporal characteristics (step size and frame rate) of the signal are identical to the noise, making the signal indistinguishable from the noise on the basis of

  12. Direct electrochemical sensor for fast reagent-free DNA detection

    Microsoft Academic Search

    Elena Komarova; Matt Aldissi; Anastasia Bogomolova

    2005-01-01

    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

  13. Passive Colorimetric Dosimeter Tubes for Ammonia, Carbon Monoxide, Carbon Dioxide, Hydrogen Sulfide, Nitrogen Dioxide and Sulfur Dioxide

    Microsoft Academic Search

    PAUL W. McCONNAUGHEY; ELMER S. McKEE; IRVIN M. PRITTS

    1985-01-01

    Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an eight-hour period for several inorganic airborne contaminants in the range of their Threshold Limit Values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH3), carbon monoxide (CO), carbon dioxide (CO2), hydrogen sulfide (H2S), nitrogen dioxide

  14. Directional Dark Matter Detection Beyond the Neutrino Bound Philipp Grothaus

    E-print Network

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

  15. Direction finding antenna system for spark detection and localization

    NASA Astrophysics Data System (ADS)

    Topor, Raluca E.; Bucuci, Stefania C.; Tamas, Razvan D.; Danisor, Alin; Dumitrascu, Ana; Berescu, Serban

    2015-02-01

    This paper proposes a novel UWB antenna system for spark detection and localization by using the amplitude comparison direction finding (DF) method. The proposed design consists of two identical axially crossed "padlock" shaped UWB antennas, with unbalanced feeding. Simulation results show that such radiating systems can be used for assessing the direction of arrival for short pulses.

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

    PubMed Central

    Wang, Xu; Niessner, Reinhard; Knopp, Dietmar

    2014-01-01

    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

  17. DNA transducer-triggered signal switch for visual colorimetric bioanalysis

    PubMed Central

    Chen, Wenhong; Yan, Yurong; Zhang, Ye; Zhang, Xuemei; Yin, Yibing; Ding, Shijia

    2015-01-01

    A simple and versatile colorimetric biosensor has been developed for sensitive and specific detection of a wide range of biomolecules, such as oligonucleotides and aptamer-recognized targets. Combining the signal transducer and catalyzed hairpin assembly (CHA)-based signal amplification, the target DNA binds with the hairpin DNA to form a new nucleic acid sequence and creates a toehold in the transducer for initiating the recycle amplification reaction of CHA. The catalyzed assembly process produces a large amount of G-rich DNA. In the presence of hemin, the G-rich DNA forms G-quadruplex/hemin complex and mimic horseradish peroxidase activity, which catalyzes a colorimetric reaction. Under optimal conditions, the calibration curve of synthetic target DNA has good linearity from 50?pM to 200?nM with a detection limit of 32?pM. This strategy has been successfully applied to detect S. pneumoniae as low as 156?CFU mL?1, and shows a good specificity against closely related streptococci and major pathogenic bacteria. In addition, the developed method enables successful visual analysis of S. pneumoniae in clinical samples by the naked eye. Importantly, this method demonstrates excellent assay versatility for sensitively detecting oligonucleotides or aptamer-recognized targets. PMID:26060886

  18. DNA transducer-triggered signal switch for visual colorimetric bioanalysis.

    PubMed

    Chen, Wenhong; Yan, Yurong; Zhang, Ye; Zhang, Xuemei; Yin, Yibing; Ding, Shijia

    2015-01-01

    A simple and versatile colorimetric biosensor has been developed for sensitive and specific detection of a wide range of biomolecules, such as oligonucleotides and aptamer-recognized targets. Combining the signal transducer and catalyzed hairpin assembly (CHA)-based signal amplification, the target DNA binds with the hairpin DNA to form a new nucleic acid sequence and creates a toehold in the transducer for initiating the recycle amplification reaction of CHA. The catalyzed assembly process produces a large amount of G-rich DNA. In the presence of hemin, the G-rich DNA forms G-quadruplex/hemin complex and mimic horseradish peroxidase activity, which catalyzes a colorimetric reaction. Under optimal conditions, the calibration curve of synthetic target DNA has good linearity from 50?pM to 200?nM with a detection limit of 32?pM. This strategy has been successfully applied to detect S. pneumoniae as low as 156?CFU mL(-1), and shows a good specificity against closely related streptococci and major pathogenic bacteria. In addition, the developed method enables successful visual analysis of S. pneumoniae in clinical samples by the naked eye. Importantly, this method demonstrates excellent assay versatility for sensitively detecting oligonucleotides or aptamer-recognized targets. PMID:26060886

  19. On the Direct Detection of Dark Matter Annihilation

    E-print Network

    Cherry, John F; Shoemaker, Ian M

    2015-01-01

    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...

  20. On the Direct Detection of Dark Matter Annihilation

    E-print Network

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

    2015-05-21

    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 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 $E_{{\\rm min}}$ space without making assumptions about DM astrophysics, mass, or scattering form factors. 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 detection by more than three orders of magnitude for masses in a 2-7 GeV window.

  1. COLORIMETRICRESONANT REFLECTIONAS A DIRECT BIOCHEMICAL,ASSAY TECHNIQUE Brian Cunningham, Peter Li, Bo Lin, Jane Pepper

    E-print Network

    Cunningham, Brian

    to produce an optical structure that, when illuminated with white light, is designed to reflect only a single and proteins that are not readily labeled. Direct optical methods include surface plasmon resonance (SPR)9 A novel approach for the detection of molecular interactions is presented in which a colorimetric resonant

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

    PubMed

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

    2007-02-01

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

  3. Global limits and interference patterns in dark matter direct detection

    E-print Network

    Catena, Riccardo

    2015-01-01

    We compare the general effective theory of one-body dark matter nucleon interactions to current direct detection experiments in a global multidimensional statistical analysis. We derive exclusion limits on the 28 isoscalar and isovector coupling constants of the theory, and show that current data place interesting constraints on dark matter-nucleon interaction operators usually neglected in this context. We characterize the interference patterns that can arise in dark matter direct detection from pairs of dark matter-nucleon interaction operators, or from isoscalar and isovector components of the same operator. We find that commonly neglected destructive interference effects weaken standard direct detection exclusion limits by up to one order of magnitude in the coupling constants.

  4. Directional detection as a strategy to discover Galactic Dark Matter

    NASA Astrophysics Data System (ADS)

    Billard, J.; Mayet, F.; Macías-Pérez, J. F.; Santos, D.

    2010-07-01

    Directional detection of Galactic Dark Matter is a promising search strategy for discriminating WIMP events from background. Technical progress on gaseous detectors and read-outs has permitted the design and construction of competitive experiments. However, to take full advantage of this powerful detection method, one need to be able to extract information from an observed recoil map to identify a WIMP signal. We present a comprehensive formalism, using a map-based likelihood method allowing to recover the main incoming direction of the signal and its significance, thus proving its Galactic origin. This is a blind analysis intended to be used on any directional data. Constraints are deduced in the (?,m) plane and systematic studies are presented in order to show that, using this analysis tool, unambiguous Dark Matter detection can be achieved on a large range of exposures and background levels.

  5. Can the Existence of Dark Energy Be Directly Detected?

    E-print Network

    Martin L. Perl

    2008-10-06

    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?

  6. Closing supersymmetric resonance regions with direct detection experiments

    SciTech Connect

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

    2014-01-01

    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 ??} 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 ??} 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.

  7. Halo Independent Direct Detection of Momentum-Dependent Dark Matter

    E-print Network

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

    2014-10-13

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

  8. 3D graphene network@WO3 nanowire composites: a multifunctional colorimetric and electrochemical biosensing platform.

    PubMed

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

    2014-10-01

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

  9. Diagnosis of lung cancer by the analysis of exhaled breath with a colorimetric sensor array

    Microsoft Academic Search

    Peter J Mazzone; Jeffrey Hammel; Raed Dweik; Jie Na; Carmen Czich; Daniel Laskowski; Tarek Mekhail

    2007-01-01

    Background: The pattern of volatile organic compounds (VOCs) in the exhaled breath of patients with lung cancer may be unique. New sensor systems that detect patterns of VOCs have been developed. One of these sensor systems, a colorimetric sensor array, has 36 spots composed of different chemically sensitive compounds impregnated on a disposable cartridge. The colours of these spots change

  10. Gold-nanorod-based colorimetric and fluorescent approach for sensitive and specific assay of disease-related gene and mutation.

    PubMed

    Wang, Wenhong; Zhao, Yina; Jin, Yan

    2013-11-27

    Sensitive and specific detection of disease-related gene and single nucleotide polymorphism (SNP) is of great importance in cancer diagnosis. Here, a colorimetric and fluorescent approach is described for detection of the p53 gene and SNP in homogeneous solution by using gold nanorods (GNRs) as both colorimetric probe and fluorescence quencher. Hairpin oligonucleotide was utilized as DNA probe to ensure highly sequence-specific detection of target DNA. In the presence of target DNA, the formation of DNA duplex greatly changed the electrostatic interaction between GNR and DNAs, leading to an obvious change in fluorescence and colorimetric response. The detection limit of fluorescent and colorimetric assay is 0.26 pM and 0.3 nM, respectively. Both fluorescence and colorimetric strategies were able to effectively discriminate complementary DNA from single-base mismatched DNA, which is meaningful for cancer diagnosis. More important, target DNA can be detected as low as 10 nM by the naked eye. Furthermore, transmission electron microscopy and fluorescence anisotropy measurements demonstrated that the color change as well as fluorescence quenching is ascribed to the DNA hybridization-induced aggregation of GNRs. Therefore, the assay provided a fast, sensitive, cost-effective, and specific sensing platform for detecting disease-related gene and SNP. PMID:24151993

  11. Direct IR Interferometric Detection of Extra Solar Planets

    NASA Technical Reports Server (NTRS)

    Shao, Michael

    1989-01-01

    This paper describes a concept for the direct detection of extra solar planets. The concept is based on a decade old idea from Bracewell but expanded. A long baseline interferometer is examined with two three meter telescopes, cooled to 70K and a baseline of 30-50 meters. In space, this instrument would be able to detect an Earth sized planet around a solar like star at 10 parsec in approximately 1 hour of integration (5 sigma). The total number of candidate stars with detectable "Earths" number in the thousands.

  12. Colorimetric Sensor Arrays for Volatile Organic Michael C. Janzen, Jennifer B. Ponder, Daniel P. Bailey, Crystal K. Ingison, and Kenneth S. Suslick*

    E-print Network

    Suslick, Kenneth S.

    -reactive sensors based primarily on changes in properties (e.g., mass, volume, conductivity) of some set-cost, sensitive colorimetric sensor array for the detection and identification of volatile organic compounds (VOCs

  13. Comparison of direct and heterodyne detection optical intersatellite communication links

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  14. Stokes vector direct detection for short-reach optical communication.

    PubMed

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

    2014-06-01

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

  15. Synchronization Helps Robots to Detect Black Holes in Directed Graphs

    E-print Network

    Pinotti, Maria Cristina

    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

  16. Channel simulation for direct detection optical communication systems

    NASA Technical Reports Server (NTRS)

    Tycz, M.; Fitzmaurice, M. W.

    1974-01-01

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

  17. Channel simulation for direct-detection optical communication systems

    NASA Technical Reports Server (NTRS)

    Tycz, M.; Fitzmaurice, M. W.

    1974-01-01

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

  18. Direct detection of the inflationary gravitational-wave background

    SciTech Connect

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

    2006-01-15

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

  19. ccsd00003303, Dark Matter Direct Detection using Cryogenic

    E-print Network

    ccsd­00003303, version 1 ­ 17 Nov 2004 Dark Matter Direct Detection using Cryogenic Detectors cryogenic experiments currently provide the best sensitivity, by nearly one order of magnitude, to WIMP of cryogenic exper- iments promises two orders of magnitude increase in sensitivity over the next few years

  20. Directed energy active illumination for near-Earth object detection

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  1. Calorimetry with Nonequilibrium Phonon Sensors for Dark Matter Direct Detection

    SciTech Connect

    Dragowsky, Michael [Physics Department, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH (United States)

    2006-10-27

    Low-temperature calorimetric particle detectors are applied to the problem of dark matter detection. These semiconductor crystal-based devices operate at sub-Kelvin temperatures. Nuclear-recoil interactions can be distinguished from electron-recoils by comparing the thermal energy yield with that in another channel, such as ionization or scintillation, essential in the search for dark matter and potentially quite useful in measuring neutrino-nucleus scattering cross-sections. The Cryogenic Dark Matter Search collaboration has demonstrated in phase two (CDMS II) that athermal phonon sensors instrumented with direct-current SQUID arrays achieve additional background rejection encoded in the pulse shape, particularly associated with leading edge features. This talk will present the general ideas of applying calorimetry to dark matter detection. It will also present CDMS II detector design and performance, and discuss future plans for dark matter direct detection with this approach.

  2. Direct Detection of Sub-GeV Dark Matter

    E-print Network

    Rouven Essig; Jeremy Mardon; Tomer Volansky

    2012-03-01

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

  3. Directional statistics for realistic weakly interacting massive particle direct detection experiments. II. 2D readout

    SciTech Connect

    Morgan, Ben; Green, Anne M. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH (United Kingdom)

    2005-12-15

    The direction dependence of the WIMP direct detection rate provides a powerful tool for distinguishing a WIMP signal from possible backgrounds. We study the number of events required to discriminate a WIMP signal from an isotropic background for a detector with 2-d readout using nonparametric circular statistics. We also examine the number of events needed to (i) detect a deviation from rotational symmetry, due to flattening of the Milky Way halo and (ii) detect a deviation in the mean direction due to a tidal stream. If the senses of the recoils are measured then of order 20--70 events (depending on the plane of the 2-d readout and the detector location) will be sufficient to reject isotropy of the raw recoil angles at 90% confidence. If the senses can not be measured these number increase by roughly 2 orders of magnitude (compared with an increase of 1 order of magnitude for the case of full 3-d readout). The distributions of the reduced angles, with the (time-dependent) direction of solar motion subtracted, are far more anisotropic, however, and if the isotropy tests are applied to these angles then the numbers of events required are similar to the case of 3-d readout. A deviation from rotational symmetry will only be detectable if the Milky Way halo is significantly flattened. The deviation in the mean direction due to a tidal stream is potentially detectable, however, depending on the density and direction of the stream. The meridian plane (which contains the Earth's spin axis) is, for all detector locations, the optimum readout plane for rejecting isotropy. However readout in this plane can not be used for detecting flattening of the Milky Way halo or a stream with direction perpendicular to the galactic plane. In these cases the optimum readout plane depends on the detector location.

  4. Directional statistics for realistic weakly interacting massive particle direct detection experiments

    SciTech Connect

    Morgan, Ben; Spooner, Neil J.C. [Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH (United Kingdom); Green, Anne M. [Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, United Kingdom, Astronomy Centre, University of Sussex, Brighton BN1 9QH, United Kingdom, and Physics Department, Stockholm University, Stockholm, S106 91 (Sweden)

    2005-05-15

    The direction dependence of the event rate in WIMP direct detection experiments provides a powerful tool for distinguishing WIMP events from potential backgrounds. We use a variety of (nonparametric) statistical tests to examine the number of events required to distinguish a WIMP signal from an isotropic background when the uncertainty in the reconstruction of the nuclear recoil direction is included in the calculation of the expected signal. We consider a range of models for the Milky Way halo, and also study rotational symmetry tests aimed at detecting nonsphericity/isotropy of the Milky Way halo. Finally we examine ways of detecting tidal streams of WIMPs. We find that if the senses of the recoils are known then of order ten events will be sufficient to distinguish a WIMP signal from an isotropic background for all of the halo models considered, with the uncertainties in reconstructing the recoil direction only mildly increasing the required number of events. If the senses of the recoils are not known the number of events required is an order of magnitude larger, with a large variation between halo models, and the recoil resolution is now an important factor. The rotational symmetry tests require of order a thousand events to distinguish between spherical and significantly triaxial halos, however a deviation of the peak recoil direction from the direction of the solar motion due to a tidal stream could be detected with of order a hundred events, regardless of whether the sense of the recoils is known.

  5. The Direct Detectability of Giant Exoplanets in the Optical

    E-print Network

    Greco, Johnny P

    2015-01-01

    (abridged) Motivated by the possibility that an optical coronagraph will be put on WFIRST/AFTA, we present an exploration of the general character of the direct detectability of extrasolar giant planets (EGPs) in the optical. We quantify a planet's direct detectability by the fraction of its orbit for which it is in an observable configuration--defined to be its observability fraction ($f_{obs}$). Using a suite of Monte Carlo experiments, we study the dependence of $f_{obs}$ upon various technological and astrophysical parameters, including the inner working angle (IWA) and minimum achievable contrast ($C_{min}$) of the direct-imaging observatory; the planet's scattering phase function, geometric albedo, single-scattering albedo, radius, and distance from Earth; and the semi-major axis distribution of EGPs. We assume cloud-free, homogeneous atmospheres and calculate phase functions for a given geometric or single-scattering albedo, assuming various scattering mechanisms. We find that the often-assumed Lambert...

  6. Directional Detection of Fast Neutrons Using a Time Projection Chamber

    SciTech Connect

    Bowden, N; Heffner, M; Carosi, G; Carter, D; Foxe, M; Jovanovic, I

    2009-06-03

    Spontaneous fission in Special Nuclear Material (SNM) such as plutonium and highly enriched uranium (HEU) results in the emission of neutrons with energies in the MeV range (hereafter 'fast neutrons'). These fast neutrons are largely unaffected by the few centimeters of intervening high-Z material that would suffice for attenuating most emitted gamma rays, while tens of centimeters of hydrogenous materials are required to achieve substantial attenuation of neutron fluxes from SNM. Neutron detectors are therefore an important complement to gamma-ray detectors in SNM search and monitoring applications. The rate at which SNM emits fast neutrons varies from about 2 per kilogram per second for typical HEU to some 60,000 per kilogram per second for metallic weapons grade plutonium. These rates can be compared with typical sea-level (cosmogenic) neutron backgrounds of roughly 5 per second per square meter per steradian in the relevant energy range [1]. The fact that the backgrounds are largely isotropic makes directional neutron detection especially attractive for SNM detection. The ability to detect, localize, and ultimately identify fast neutron sources at standoff will ultimately be limited by this background rate. Fast neutrons are particularly well suited to standoff detection and localization of SNM or other fast neutrons sources. Fast neutrons have attenuation lengths of about 60 meters in air, and retain considerable information about their source direction even after one or two scatters. Knowledge of the incoming direction of a fast neutron, from SNM or otherwise, has the potential to significantly improve signal to background in a variety of applications, since the background arriving from any one direction is a small fraction of the total background. Imaging or directional information therefore allows for source detection at a larger standoff distance or with shorter dwell times compared to nondirectional detectors, provided high detection efficiency can be maintained. Directional detection of neutrons has been previously considered for applications such as controlled fusion neutron imaging [2], nuclear fuel safety research [3], imaging of solar neutrons and SNM [4], and in nuclear science [5]. The use of scintillating crystals and fibers has been proposed for directional neutron detection [6]. Recently, a neutron scatter camera has been designed, constructed, and tested for imaging of fast neutrons, characteristic for SNM material fission [7]. The neutron scatter camera relies on the measurement of the proton recoil angle and proton energy by time of flight between two segmented solid-state detectors. A single-measurement result from the neutron scatter camera is a ring containing the possible incident neutron direction. Here we describe the development and commissioning of a directional neutron detection system based on a time projection chamber (TPC) detector. The TPC, which has been widely used in particle and nuclear physics research for several decades, provides a convenient means of measuring the full 3D trajectory, specific ionization (i.e particle type) and energy of charged particles. For this application, we observe recoil protons produced by fast neutron scatters on protons in hydrogen or methane gas. Gas pressures of a few ATM provide reasonable neutron interaction/scattering rates.

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

    PubMed Central

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

    2013-01-01

    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

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

    PubMed

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

    2015-04-21

    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

  9. Using the Griess colorimetric nitrite assay for measuring aliphatic ?-nitroalcohols

    PubMed Central

    Wen, Quan; Paik, David C.

    2012-01-01

    Our recent studies suggest that aliphatic ?-nitroalcohols (BNAs) may represent a useful class of compounds for topical therapeutic corneoscleral cross-linking agents. Thus, this study was undertaken in order to standardize a simple method for nitroalcohol quantitation based on a denitration step followed by colorimetric Griess nitrite assay. Conditions necessary for denitration included a pH of 7-9 and heating for 1 hour at 100°C. Standard curves for two mono-nitroalcohols (2-nitroethanol and 2-nitro-1-propanol), a nitro-diol (2-methyl-2-nitro-1,3-propanediol), and a nitro-triol (2-hydroxymethyl-2-nitro-1,3-propanediol) showed excellent linearity in the 100-500 M range with absorbance values <1.0 and R2 values >0.98. The lower limit of detection was ~20 M. Recovery from tissue homogenates (10mg/mL wet weight) of rabbit cornea and sclera as well as solutions of gelatin B (1mg/mL) ranged from 89-103% for scleral tissue, 68-106% for corneal tissue, and 90-99% for gelatin B. The Griess colorimetric nitrite assay can be successfully used for the quantitative determination of BNAs and is simpler to use than conventional chromatographic techniques. PMID:22406005

  10. Future directions for H sub x O sub y detection

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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?

  11. An Automated Directed Spectral Search Methodology for Small Target Detection

    NASA Astrophysics Data System (ADS)

    Grossman, Stanley I.

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

  12. Colorimetric plasmon sensors with multilayered metallic nanoparticle sheets.

    PubMed

    Shinohara, Shuhei; Tanaka, Daisuke; Okamoto, Koichi; Tamada, Kaoru

    2015-07-01

    Colorimetric plasmon sensors for naked-eye detection of molecular recognition events have been proposed. Here, 3-layered Ag nanoparticle (NP) sheets on a Au substrate fabricated using the Langmuir-Schaefer method were utilized as the detection substrates. A drastic color change was observed following the binding of Au NPs via avidin-biotin interactions at less than 30% surface coverage. The color change was attributed not only to the localized surface plasmon resonance (LSPR) of the adsorbed Au NPs but also to the multiple light trapping effect derived from the stratified Au and Ag NPs, as predicted by a finite-difference time-domain (FDTD) simulation. This plasmonic multi-color has great potential in the development of simple and highly sensitive diagnostic systems. PMID:26113242

  13. Analysis of microsatellites by direct blotting electrophoresis and chemiluminescence detection.

    PubMed

    Mekus, F; Dörk, T; Deufel, T; Morral, N; Tümmler, B

    1995-10-01

    We describe a fast and reliable method for the nonradioactive analysis of microsatellites. For three dinucleotide repeats within the cystic fibrosis transmembrane conductance regulator (CFTR) gene, the separation of polymerase chain reaction (PCR) products generated with biotinylated primers on a direct blotting electrophoresis system and subsequent chemiluminescence detection is shown. In direct blotting electrophoresis, the separation of DNA fragments depended linearly on size. The reproducible resolution allowed reliable assignment of allele lengths to a given signal. The nonradioactive detection protocol was advantageous compared to radioactive methods: samples could be analyzed within one day due to the fast signal development by 3-(4-methoxyspiro[1,2-dioxetane-3,2'-(5'- chloro)tricyclo[3.3.1.1.3,7]decan]-4-yl)phenylphosphate disodium salt (CSPD). Variation of exposure times enabled differentiation between major bands and byproducts of comparable intensity that are due to the slippage of the Taq polymerase during PCR amplification. PMID:8586058

  14. Hunting electroweakinos at future hadron colliders and direct detection experiments

    NASA Astrophysics Data System (ADS)

    di Cortona, Giovanni Grilli

    2015-05-01

    We analyse the mass reach for electroweakinos at future hadron colliders and their interplay with direct detection experiments. Motivated by the LHC data, we focus on split supersymmetry models with different electroweakino spectra. We find for example that a 100 TeV collider may explore Winos up to ˜ 7 TeV in low scale gauge mediation models or thermal Wino dark matter around 3 TeV in models of anomaly mediation with long-lived Winos. We show moreover how collider searches and direct detection experiments have the potential to cover large part of the parameter space even in scenarios where the lightest neutralino does not contribute to the whole dark matter relic density.

  15. Dark matter effective field theory scattering in direct detection experiments

    NASA Astrophysics Data System (ADS)

    Schneck, K.; Cabrera, B.; Cerdeño, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; Basu Thakur, R.; 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.; Lopez Asamar, E.; Lukens, P.; Mahapatra, R.; McCarthy, K. A.; Mirabolfathi, N.; Moffatt, R. A.; Morales Mendoza, J. D.; 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.; SuperCDMS Collaboration

    2015-05-01

    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.

  16. Hunting electroweakinos at future hadron colliders and direct detection experiments

    E-print Network

    Giovanni Grilli di Cortona

    2015-05-06

    We analyse the mass reach for electroweakinos at future hadron colliders and their interplay with direct detection experiments. Motivated by the LHC data, we focus on split supersymmetry models with different electroweakino spectra. We find for example that a 100 TeV collider may explore Winos up to ~ 7 TeV in low scale gauge mediation models or thermal Wino dark matter around 3 TeV in models of anomaly mediation with long-lived Winos. We show moreover how collider searches and direct detection experiments have the potential to cover large part of the parameter space even in scenarios where the lightest neutralino does not contribute to the whole dark matter relic density.

  17. Dark matter effective field theory scattering in direct detection experiments

    E-print Network

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

    2015-03-11

    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.

  18. Direct Detection of Intermediate Mass Compact Objects via Submillilensing

    Microsoft Academic Search

    Kaiki Taro Inoue; Masashi Chiba

    2005-01-01

    A galaxy-sized halo may contain a large number of intermediate mass (10^{2-4} solar mass) compact objects (IMCOs), which can be intermediate mass black holes (IMBHs) or the CDM subhalos. We propose to directly detect the IMBHs by observing multiply imaged QSO-galaxy lens systems with a high angular resolution (~ 0.03mas), which would be achieved by the next-VLBI space missions. The

  19. Future Directions for the Early Detection of Recurrent Breast Cancer

    PubMed Central

    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

    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

  20. Review of Dark Matter Direct Detection Using Cryogenic Detectors

    SciTech Connect

    Brink, P.L.; /SLAC

    2012-06-13

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

  1. Future directions for the early detection of recurrent breast cancer.

    PubMed

    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

    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

  2. WIMP Dark Matter Direct-Detection Searches in Noble Gases

    E-print Network

    Laura Baudis

    2014-08-19

    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.

  3. Direct Imaging Detectability of Tidally Heated ExoMoons (THEM)

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  4. (In)direct Detection of Boosted Dark Matter

    E-print Network

    Kaustubh Agashe; Yanou Cui; Lina Necib; Jesse Thaler

    2014-12-31

    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.

  5. Highly Sensitive Detection of Staphylococcus aureus Directly from Patient Blood

    PubMed Central

    Banada, Padmapriya P.; Chakravorty, Soumitesh; Shah, Darshini; Burday, Michele; Mazzella, Fermina M.; Alland, David

    2012-01-01

    Background Rapid detection of bloodstream infections (BSIs) can be lifesaving. We investigated the sample processing and assay parameters necessary for highly-sensitive detection of bloodstream bacteria, using Staphylococcus aureus as a model pathogen and an automated fluidic sample processing – polymerase chain reaction (PCR) platform as a model diagnostic system. Methodology/Principal Findings We compared a short 128 bp amplicon hemi-nested PCR and a relatively shorter 79 bp amplicon nested PCR targeting the S. aureus nuc and sodA genes, respectively. The sodA nested assay showed an enhanced limit of detection (LOD) of 5 genomic copies per reaction or 10 colony forming units (CFU) per ml blood over 50 copies per reaction or 50 CFU/ml for the nuc assay. To establish optimal extraction protocols, we investigated the relative abundance of the bacteria in different components of the blood (white blood cells (WBCs), plasma or whole blood), using the above assays. The blood samples were obtained from the patients who were culture positive for S. aureus. Whole blood resulted in maximum PCR positives with sodA assay (90% positive) as opposed to cell-associated bacteria (in WBCs) (71% samples positive) or free bacterial DNA in plasma (62.5% samples positive). Both the assays were further tested for direct detection of S. aureus in patient whole blood samples that were contemporaneous culture positive. S. aureus was detected in 40/45 of culture-positive patients (sensitivity 89%, 95% CI 0.75–0.96) and 0/59 negative controls with the sodA assay (specificity 100%, 95% CI 0.92–1). Conclusions We have demonstrated a highly sensitive two-hour assay for detection of sepsis causing bacteria like S. aureus directly in 1 ml of whole blood, without the need for blood culture. PMID:22363564

  6. Direct Real-Time Detection of Vapors from Explosive Compounds

    SciTech Connect

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

    2013-10-03

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

  7. Direct real-time detection of vapors from explosive compounds.

    PubMed

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

    2013-11-19

    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

  8. Passive, Direct-Read Monitoring System for Selective Detection and Quantification of Hydrogen Chloride

    NASA Technical Reports Server (NTRS)

    Chapman, K. B.; Mihaylov, G. M.; Kirollos, K. S.

    2000-01-01

    Monitoring the exposure of an employee to hydrogen chloride or hydrochloric acid in the presence of other acids has been a challenge to the industrial hygiene community. The capability of a device to differentiate the levels of acid vapors would allow for more accurate determinations of exposure and therefore improved occupational health. In this work, a selective direct-read colorimetric badge system was validated for Short Term Exposure Limit (STEL) monitoring of hydrogen chloride. The passive colorimetric badge system consists of a direct reading badge and a color scale. The badge has a coated indicator layer with a diffusive resistance in the shape of an exclamation mark. An exclamation mark will appear if hydrogen chloride is present in the atmosphere at concentrations at or above 2.0 ppm. By using the color scale, the intensity of the color formed on the badge can be further quantified up to 25 ppm. The system was validated according to a protocol based on the NIOSH Protocol for the Evaluation of Passive Monitors. The badge was exposed to relative humidities ranging from 11% to 92%, temperatures ranging from 7 C to 400 C and air velocities ranging from 5 cm/sec to 170 cm/sec. All experiments were conducted in a laboratory vapor generation system. Hydrofluoric acid, nitric acid, sulfuric acid, chlorine, hydrogen sulfide and organic acids showed no effect on the performance of the hydrogen chloride monitoring system. The passive badge and color scale system exceeded the accuracy requirements as defined by NIOSH. At ambient conditions, the mean coefficient of variation was 10.86 and the mean bias was 1.3%. This data was presented previously at the American Industrial Hygiene Conference and Exposition in Toronto, Canada in June 1999.

  9. Colorimetric sensor array for soft drink analysis.

    PubMed

    Zhang, Chen; Suslick, Kenneth S

    2007-01-24

    Fourteen commercial soft drinks have been analyzed using colorimetric sensor arrays made from a set of 25 chemically responsive dyes printed on a hydrophobic membrane. Digital imaging of the dye array before and after immersion provides a color change profile as a unique fingerprint for each specific analyte. The digital data library generated was analyzed with statistical and chemometric methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). Facile identification of all of the soft drinks was readily achieved using comparison of the color change profiles or a PCA score plot. Using a HCA dendrogram, the misclassification rate was <2%, and even very similar sodas were easily differentiated. In addition, the monitoring of soft drinks as they degas or upon dilution also proved to be possible. This work demonstrates the potential of our colorimetric sensor array technology for quality assurance/control applications of sodas and perhaps other beverages as well. PMID:17227048

  10. Direct and indirect detection of dissipative dark matter

    NASA Astrophysics Data System (ADS)

    Fan, JiJi; Katz, Andrey; Shelton, Jessie

    2014-06-01

    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.

  11. Toward Direct Detection of Hot Jupiters with Precision Closure Phase

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  12. Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  13. Theoretical direct WIMP detection rates for transitions to excited states

    E-print Network

    Vergados, J D; Savvidy, K G

    2013-01-01

    The recent WMAP and Planck data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Many extensions of the standard model provide dark matter candidates, in particular Weakly Interacting Massive Particles (WIMPs). %Supersymmetry provides a natural dark matter candidate, the lightest supersymmetric particle (LSP). Thus the direct dark matter detection is central to particle physics and cosmology. Most of the research on this issue has hitherto focused on the detection of the recoiling nucleus. In this paper we study transitions to the excited states, possible in some nuclei, which have sufficiently low lying excited states. Good examples are the first excited states of I-127 and Xe-129. %focusing on the first excited state at 50 keV of Iodine A=127. We find appreciable branching ratios for the inelastic scattering mediated by the spin cross sections. %find that the transition rate to this excited state is about 5 %percent of the transiti...

  14. Problem detection during tripping operations in horizontal and directional wells

    SciTech Connect

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

    1995-06-01

    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.

  15. Direct Detection of Gravity Waves from Neutron Stars

    E-print Network

    Redouane Al Fakir; William G. Unruh

    2008-05-24

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

  16. Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength.

    PubMed

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

    2014-01-01

    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

  17. Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength

    PubMed Central

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

    2014-01-01

    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

  18. Theoretical antineutrino detection, direction and ranging at long distances

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  19. WIMP physics with ensembles of direct-detection experiments

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  20. The past and future of light dark matter direct detection

    NASA Astrophysics Data System (ADS)

    Davis, Jonathan H.

    2015-05-01

    We review the status and future of direct searches for light dark matter. We start by answering the question: "Whatever happened to the light dark matter anomalies?" i.e. the fate of the potential dark matter signals observed by the CoGeNT, CRESST-II, CDMS-Si and DAMA/LIBRA experiments. We discuss how the excess events in the first two of these experiments have been explained by previously underestimated backgrounds. For DAMA, we summarize the progress and future of mundane explanations for the annual modulation reported in its event rate. Concerning the future of direct detection, we focus on the irreducible background from solar neutrinos. We explain broadly how it will affect future searches and summarize efforts to mitigate its effects.

  1. The Past and Future of Light Dark Matter Direct Detection

    E-print Network

    Jonathan H. Davis

    2015-06-12

    We review the status and future of direct searches for light dark matter. We start by answering the question: `Whatever happened to the light dark matter anomalies?' i.e. the fate of the potential dark matter signals observed by the CoGeNT, CRESST-II, CDMS-Si and DAMA/LIBRA experiments. We discuss how the excess events in the first two of these experiments have been explained by previously underestimated backgrounds. For DAMA we summarise the progress and future of mundane explanations for the annual modulation reported in its event rate. Concerning the future of direct detection we focus on the irreducible background from solar neutrinos. We explain broadly how it will affect future searches and summarise efforts to mitigate its effects.

  2. The Past and Future of Light Dark Matter Direct Detection

    E-print Network

    Davis, Jonathan H

    2015-01-01

    We review the status and future of direct searches for light dark matter. We start by answering the question: `Whatever happened to the light dark matter anomalies?' i.e. the fate of the potential dark matter signals observed by the CoGeNT, CRESST-II, CDMS-Si and DAMA/LIBRA experiments. We discuss how the excess events in the first two of these experiments have been explained by previously underestimated backgrounds. For DAMA we summarise the progress and future of mundane explanations for the annual modulation reported in its event rate. Concerning the future of direct detection we focus on the irreducible background from solar neutrinos. We explain broadly how it will affect future searches and summarise efforts to mitigate its effects.

  3. Assessing Alternatives for Directional Detection of a WIMP Halo

    E-print Network

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

    2005-08-30

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

  4. A strongly coupled Au/Fe3O4/GO hybrid material with enhanced nanozyme activity for highly sensitive colorimetric detection, and rapid and efficient removal of Hg2+ in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Shouting; Li, Hua; Wang, Zhiyi; Liu, Jian; Zhang, Haoli; Wang, Baodui; Yang, Zhengyin

    2015-04-01

    We have developed an efficient strategy for synthesizing a strongly coupled Au/Fe3O4/GO hybrid material to improve the catalytic activity, stability, and separation capability of Au nanoparticles (NPs) and Hg2+. The hybrid material can be synthesized by the direct anchoring of Au and Fe3O4 NPs on the functional groups of GO. This approach affords strong chemical attachments between the NPs and GO, allowing this hybrid material to ultrasensitively detect Hg2+ in aqueous solutions with a detection limit as low as 0.15 nM. In addition, the deposition of Hg0 on the surface of Au/Fe3O4/GO could be quickly (within 30 min) and efficiently (>99% elimination efficiency) removed by the simple application of an external magnetic field and then Au/Fe3O4/GO could be subsequently reused at least 15 times, with the elimination efficiency remaining high (>96%).We have developed an efficient strategy for synthesizing a strongly coupled Au/Fe3O4/GO hybrid material to improve the catalytic activity, stability, and separation capability of Au nanoparticles (NPs) and Hg2+. The hybrid material can be synthesized by the direct anchoring of Au and Fe3O4 NPs on the functional groups of GO. This approach affords strong chemical attachments between the NPs and GO, allowing this hybrid material to ultrasensitively detect Hg2+ in aqueous solutions with a detection limit as low as 0.15 nM. In addition, the deposition of Hg0 on the surface of Au/Fe3O4/GO could be quickly (within 30 min) and efficiently (>99% elimination efficiency) removed by the simple application of an external magnetic field and then Au/Fe3O4/GO could be subsequently reused at least 15 times, with the elimination efficiency remaining high (>96%). Electronic supplementary information (ESI) available: Scheme S1, Fig. S1-S9 and Tables S1 and S2. See DOI: 10.1039/c5nr00527b

  5. Direct Detection of Intermediate Mass Compact Objects via Submillilensing

    E-print Network

    Inoue, K T; Inoue, Kaiki Taro; Chiba, Masashi

    2005-01-01

    A galaxy-sized halo may contain a large number of intermediate mass (10^{2-4} solar mass) compact objects (IMCOs), which can be intermediate mass black holes (IMBHs) or the CDM subhalos. We propose to directly detect the IMBHs by observing multiply imaged QSO-galaxy lens systems with a high angular resolution (~ 0.03mas), which would be achieved by the next-VLBI space missions. The silhouette of the IMBHs would appear as an either monopole-like or dipole-like variation at the scale of the Einstein radius against the QSO jets. As a byproduct, we can also directly detect the 10^{4-5} solar mass CDM subhalos. From a measurement of the local distortion in the surface brightness of the QSO jet, we can make a distinction between a point mass (corresponding to an IMBH) and an extended structure (corresponding to a CDM subhalo). It would be a unique probe of the IMCOs whose nature has been under the veil of mistery.

  6. Direct Detection of Intermediate Mass Compact Objects via Submillilensing

    E-print Network

    Kaiki Taro Inoue; Masashi Chiba

    2005-12-30

    A galaxy-sized halo may contain a large number of intermediate mass (10^{2-4} solar mass) compact objects (IMCOs), which can be intermediate mass black holes (IMBHs) or the CDM subhalos. We propose to directly detect the IMBHs by observing multiply imaged QSO-galaxy lens systems with a high angular resolution (~ 0.03mas), which would be achieved by the next-VLBI space missions. The silhouette of the IMBHs would appear as an either monopole-like or dipole-like variation at the scale of the Einstein radius against the QSO jets. As a byproduct, we can also directly detect the 10^{4-5} solar mass CDM subhalos. From a measurement of the local distortion in the surface brightness of the QSO jet, we can make a distinction between a point mass (corresponding to an IMBH) and an extended structure (corresponding to a CDM subhalo). It would be a unique probe of the IMCOs whose nature has been under the veil of mistery.

  7. DIAMUND: Direct Comparison of Genomes to Detect Mutations

    PubMed Central

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

    2014-01-01

    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

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

    Microsoft Academic Search

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

    2008-01-01

    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

  9. A benzobisimidazolium-based fluorescent and colorimetric chemosensor for CO2.

    PubMed

    Guo, Zhiqian; Song, Na Ri; Moon, Jong Hun; Kim, Myounwoo; Jun, Eun Jin; Choi, Jiyoung; Lee, Jin Yong; Bielawski, Christopher W; Sessler, Jonathan L; Yoon, Juyoung

    2012-10-31

    A new sensor for the fluorescent and colorimetric detection of CO(2) is described. The system utilizes fluoride to activate a tetrapropyl benzobisimidazolium salt and operates in the absence of an exogenous base. On the basis of spectroscopic and theoretical analyses, the mode of action of the present system is ascribed to the fluoride-induced formation of an N-heterocyclic carbene intermediate that reacts with CO(2) to form an imidazolium carboxylate. PMID:22931227

  10. A Colorimetric Estimation of Polyethyleneglycol-Conjugated Phospholipid in Stealth Liposomes

    Microsoft Academic Search

    Alo Nag; Gargi Mitra; Prahlad C. Ghosh

    1997-01-01

    The paper describes a colorimetric method for estimation of polyethyleneglycol (PEG)-conjugated phospholipid in either form, free or bound to liposomes. It provides a rapid, highly reproducible, and sensitive tool to detect PEG-coupled phospholipid in amounts as low as 1 ?g giving a linear response over a range of 1–100 ?g. The method makes use of the biphasic system comprising aqueous

  11. Mesoporous silica-coated gold nanorods: towards sensitive colorimetric sensing of ascorbic acid via target-induced silver overcoating

    NASA Astrophysics Data System (ADS)

    Wang, Guoqing; Chen, Zhaopeng; Chen, Lingxin

    2011-04-01

    This article describes a nonaggregation-based colorimetric assay of ascorbic acid by tailoring the optical properties of mesoporous silica-coated gold nanorods (MS GNRs) via silver overcoating. The colorimetric measurement of ascorbic acid (AA) concentration strongly relies on the fact that the blue shift effect of localized surface plasmon resonance (LSPR) peak of MS GNRs is gradually enlarged with the increase of AA amount. The limit of detection is determined to be 49 nM, which is comparable to that of quantum dots (QDs)-based fluorimetric methods.

  12. Detecting Tsunami Genesis and Scales Directly from Coastal GPS Stations

    NASA Astrophysics Data System (ADS)

    Song, Y. Tony

    2013-04-01

    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).

  13. Improving Detection Accuracy for a Direct Brain Interface Based on Detection of Event Related Potentials in Electrocorticogram

    E-print Network

    Fessler, Jeffrey A.

    Improving Detection Accuracy for a Direct Brain Interface Based on Detection of Event Related collection can be found in Levine et al.(1999). The basic method for the direct brain interface is based, B. Graimann Background A direct brain interface is defined as a human-computer interface

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

    E-print Network

    Jin Li

    2015-03-25

    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 resolutions and thresholds for a columnar recombination detector that detects two channel recombination and ionization processes from gaseous xenon. We find that with a $5\\times 10^{-46} \\mathrm{cm}^2$ spin-independent WIMP-nucleon cross-section and a 30 GeV WIMP, a $636$ kg$\\cdot$year's exposure with a columnar recombination detector can make a three sigma discovery of directional WIMPs in the isothermal galactic dark matter halo.

  15. Tropospheric Wind Profile Measurements with a Direct Detection Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce M.; Li, Steven X.; Korb, C. Laurence; Chen, Huailin; Mathur, Savyasachee

    1998-01-01

    Research has established the importance of global tropospheric wind measurements for large scale improvements in numerical weather prediction. In addition, global wind measurements provide data that are fundamental to the understanding and prediction of global climate change. These tasks are closely linked with the goals of the NASA Earth Science Enterprise and Global Climate Change programs. NASA Goddard has been actively involved in the development of direct detection Doppler lidar methods and technologies to meet the wind observing needs of the atmospheric science community. In this paper we describe a recently developed prototype wind lidar system using a direct detection Doppler technique for measuring wind profiles from the surface through the troposphere. This system uses a pulsed ND:YAG laser operating at 1064 nm as the transmitter. The laser pulse is directed to the atmosphere using a 40 cm diameter scan mirror. The portion of the laser energy backscattered from aerosols and molecules is collected by a 40 cm diameter telescope and coupled via fiber optics into the Doppler receiver. Single photon counting APD's are used to detect the atmospheric backscattered signal. The principle element of the receiver is a dual bandpass tunable Fabry Perot etalon which analyzes the Doppler shift of the incoming laser signal using the double edge technique. The double edge technique uses two high resolution optical filters having bandpasses offset relative to one another such that the 'edge' of the first filter's transmission function crosses that of the second at the half power point. The outgoing laser frequency is located approximately at the crossover point. Due to the opposite going slopes of the edges, a Doppler shift in the atmospheric backscattered laser frequency produces a positive change in signal for one filter and a negative change in the second filter. Taking the ratio of the two edge channel signals yields a result which is directly proportional to the component of the wind along the line-of-sight of the laser. Measuring the radial wind in several directions provides sufficient information to determine the true wind speed and direction. The lidar has operated from our laboratory at Goddard since June, 1997. Wind profiles have been obtained to altitudes of 12 km with a vertical resolution of 330 in. Vector wind data are obtained by rotating the scan mirror to measure line-of-sight wind profiles for at least two azimuth angles at an elevation angle of 45 degrees. The precision of the data as determined from the standard deviation of multiple independent lidar profiles is in the range of 1 to 3 m/sec up to 10 km. Good agreement is obtained when the lidar data are compared with the upper air rawinsonde soundings taken at Dulles airport. Examples of the wind lidar data will be presented along with a description of the instrument and future developments.

  16. 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

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

    2007-01-01

    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…

  17. Comparison of HPLC and colorimetric methods for measuring cellulolytic activity

    Microsoft Academic Search

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

    1988-01-01

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

  18. Masking Model for Accurate Colorimetric Characterization of LCD

    Microsoft Academic Search

    Nobuhiko Tamura; Norimichi Tsumura; Yoichi Miyake

    2002-01-01

    A color management system (CMS) such as ICC profile or sRGB space have been proposed for color transformation and reproduction of cross media. In such a CMS, accurate colorimetric char- acterization of a display device plays a critical role in achieving device-independent color reproduc- tion. In the case of a CRT, colorimetric characterization based on a GOG model is accurate

  19. Rapid, colorimetric quantification of lipid from algal cultures.

    PubMed

    Wawrik, Boris; Harriman, Brian H

    2010-03-01

    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

  20. Paper-based bioassays using gold nanoparticle colorimetric probes.

    PubMed

    Zhao, Weian; Ali, M Monsur; Aguirre, Sergio D; Brook, Michael A; Li, Yingfu

    2008-11-15

    The majority of bioassays utilize thermosensitive reagents (e.g., biomolecules) and laboratory conditions for analysis. The developing world, however, requires inexpensive, simple-to-perform tests that do not require refrigeration or access to highly trained technicians. To address this need, paper-based bioassays using gold nanoparticle (AuNP) colorimetric probes have been developed. In the two prototype DNase I and adenosine-sensing assays, blue (or black)-colored DNA-cross-linked AuNP aggregates were spotted on paper substrates. The addition of target DNase I (or adenosine) solution dissociated the gold aggregates into dispersed AuNPs, which generated an intense red color on paper within one minute. Both hydrophobic and (poly(vinyl alcohol)-coated) hydrophilic paper substrates were suitable for this biosensing platform; by contrast, uncoated hydrophilic paper caused "bleeding" and premature cessation of the assay due to surface drying. The assays are surprisingly thermally stable. During preparation, AuNP aggregate-coated papers can be dried at elevated temperatures (e.g., 90 degrees C) without significant loss of biosensing performance, which suggests the paper substrate protects AuNP aggregate probes from external nonspecific stimuli (e.g., heat). Moreover, the dried AuNP aggregate-coated papers can be stored for at least several weeks without loss of the biosensing function. The combination of paper substrates and AuNP colorimetric probes makes the final products inexpensive, low-volume, portable, disposable, and easy-to-use. We believe this simple, practical bioassay platform will be of interest for use in areas such as disease diagnostics, pathogen detection, and quality monitoring of food and water. PMID:18847216

  1. 2001 Progress on a Direct Brain Interface Based on Detection of ERPs in ECoG

    E-print Network

    Fessler, Jeffrey A.

    2001 Progress on a Direct Brain Interface Based on Detection of ERPs in ECoG The University partnership focuses on the development of a direct brain interface based on event detection obtained from 39 subjects. The basic method for the direct brain interface is based on the detection

  2. Filtered Back Projection Type Direct Edge Detection of Real Synthetic Aperture Radar Images

    E-print Network

    Qiao, Zhijun "George" - Department of Mathematics, University of Texas

    Filtered Back Projection Type Direct Edge Detection of Real Synthetic Aperture Radar Images Noe American, Edinburg, TX 78539 USA ABSTRACT Edge detection algorithms applied to Synthetic Aperture Radar with significant results. Keywords: Synthetic Aperture Radar, Backprojection, Edge Detection, Imaging 1

  3. Direct Detection of Stealth Dark Matter through Electromagnetic Polarizability

    E-print Network

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

    2015-01-01

    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...

  4. On the annual modulation signal in dark matter direct detection

    SciTech Connect

    Herrero-Garcia, Juan; Schwetz, Thomas [Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg (Germany); Zupan, Jure, E-mail: juan.a.herrero@uv.es, E-mail: schwetz@mpi-hd.mpg.de, E-mail: jure.zupan@cern.ch [Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221 (United States)

    2012-03-01

    We derive constraints on the annual modulation signal in Dark Matter (DM) direct detection experiments in terms of the unmodulated event rate. A general bound independent of the details of the DM distribution follows from the assumption that the motion of the earth around the sun is the only source of time variation. The bound is valid for a very general class of particle physics models and also holds in the presence of an unknown unmodulated background. More stringent bounds are obtained, if modest assumptions on symmetry properties of the DM halo are adopted. We illustrate the bounds by applying them to the annual modulation signals reported by the DAMA and CoGeNT experiments in the framework of spin-independent elastic scattering. While the DAMA signal satisfies our bounds, severe restrictions on the DM mass can be set for CoGeNT.

  5. Direct-detection wind lidar operating with a multimode laser.

    PubMed

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

    2013-07-10

    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

  6. Colorimetric biosensing of targeted gene sequence using dual nanoparticle platforms.

    PubMed

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

    2015-01-01

    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. PMID:25897217

  7. Subcarrier multiplexing with dispersion reduction and direct detection

    DOEpatents

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

    1997-01-01

    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.

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

    PubMed

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

    2013-12-01

    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

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

    PubMed

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

    2014-01-01

    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

  10. Direct Detection Doppler Lidar for Spaceborne Wind Measurement

    NASA Technical Reports Server (NTRS)

    Korb, C. Laurence; Flesia, Cristina

    1999-01-01

    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.

  11. Chemically responsive nanoporous pigments: colorimetric sensor arrays and the identification of aliphatic amines.

    PubMed

    Bang, Jin Ho; Lim, Sung H; Park, Erwin; Suslick, Kenneth S

    2008-11-18

    A general method has been developed for the preparation of microspheres of nanoporous pigments, their formulation into chemically responsive pigment inks, and the printing of these inks as colorimetric sensor arrays. Using an ultrasonic-spray aerosol-gel synthesis from chemically responsive dyes and common silica precursors, 16 different nanoporous pigment microspheres have been prepared and characterized. New colorimetric sensor arrays have been created by printing inks of these chemically responsive pigments as primary sensor elements; these arrays have been successfully tested for the detection, identification, and quantitation of toxic aliphatic amines. Among 11 structurally similar amines, complete identification of each analyte without confusion was achieved using hierarchical cluster analysis (HCA). Furthermore, visual identification of ammonia gas was easily made at the IDLH (immediately dangerous to life or health), PEL (permissible exposure limits), and 0.1 PEL concentrations with high reproducibility. PMID:18950204

  12. Colorimetric cholesterol sensor based on peroxidase like activity of zinc oxide nanoparticles incorporated carbon nanotubes.

    PubMed

    Hayat, Akhtar; Haider, Waqar; Raza, Yousuf; Marty, Jean Louis

    2015-10-01

    A sensitive and selective colorimetric method based on the incorporation of zinc oxide nanoparticles (ZnO NPs) on the surface of carbon nanotubes (CNTs) was shown to posses synergistic peroxidase like activity for the detection of cholesterol. The proposed nanocomposite catalyzed the oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) in the presence of hydrogen peroxide (H2O2) to produce a green colored product which can be monitored at 405nm. H2O2 is the oxidative product of cholesterol in the presence of cholesterol oxidase. Therefore, the oxidation of cholesterol can be quantitatively related to the colorimetric response by combining these two reactions. Under the optimal experimental conditions, the colorimetric response was proportional to the concentration of cholesterol in the range of 0.5-500nmol/L, with a detection limit of 0.2nmol/L. The applicability of the proposed assays was demonstrated for the determination of cholesterol in milk powder samples with good recovery results. PMID:26078143

  13. Direct Detection of Stealth Dark Matter through Electromagnetic Polarizability

    E-print Network

    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

    2015-05-28

    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.

  14. Direct Sequence Detection of Structured H5 Influenza Viral RNA

    PubMed Central

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

    2008-01-01

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

  15. NEW COMPLETENESS METHODS FOR ESTIMATING EXOPLANET DISCOVERIES BY DIRECT DETECTION

    SciTech Connect

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

    2010-05-20

    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.

  16. Direct detection rates of dark matter coupled to dark energy

    SciTech Connect

    Tetradis, N. [Department of Physics, University of Athens, Zographou 157 84 (Greece); Vergados, J. D. [Theoretical Physics Division, University of Ioannina, Ioannina, Gr 451 10 (Greece); Institute of Theoretical Physics, University of Tuebingen, Tuebingen (Germany); Faessler, Amand [Institute of Theoretical Physics, University of Tuebingen, Tuebingen (Germany)

    2007-01-15

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

  17. Direct detection of light anapole and magnetic dipole DM

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  18. High-resolution direct-detection x-ray imagers

    NASA Astrophysics Data System (ADS)

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

    2000-04-01

    We report on a-Si direct detection x-ray image sensors with polycrystalline PbI2, and more recently with HgI2. The arrays have 100 micron pixel size and, we study those aspects of the detectors that mainly determine the DQE, such as sensitivity, effective fill factor, dark current noise, noise power spectrum, and x-ray absorption. Line spread function data show that in the PbI2 arrays, most of the signal in the gap between pixels is collected, which is important for high,DQE. The leakage current noise agrees with the expected shot noise value with only a small enhancement at high bias voltages. The noise power spectrum under x-ray exposure is reported and compared to the spatial resolution information. The MTF is close to the ideal sinc function, but is reduced by the contribution of K-fluorescence in the PbI2 film for which we provide new experimental evidence. The role of noise power aliasing in the DQE and the effect of slight image spreading are discussed. Initial studies of HgI2 as the photoconductor material show very promising results with high x-ray sensitivity and low leakage current.

  19. Prospects for direct detection of primordial gravitational waves

    SciTech Connect

    Chongchitnan, Sirichai; Efstathiou, George [Institute of Astronomy, Madingley Road, Cambridge, CB3 OHA (United Kingdom)

    2006-04-15

    We study the primordial gravitational wave background produced in models of single-field inflation. Using the inflationary flow approach, we investigate the amplitude of gravitational wave spectrum, {omega}{sub gw}, in the frequency range 1 mHz-1 Hz pertinent to future space-based laser interferometers. For models that satisfy the current observational constraint on the tensor-to-scalar ratio, r < or approx. 0.36, we derive a strict upper bound of {omega}{sub gw} < or approx. 1.6x10{sup -15} independent of the form of the inflationary potential. Applying, in addition, the observational constraints on the spectral index n{sub s} and its running, {omega}{sub gw} is expected to be considerably lower than this bound unless the shape of the potential is finely tuned. We contrast our numerical results with those based on simple power-law extrapolation of the tensor power spectrum from cosmic microwave background (CMB) scales. In addition to single-field inflation, we summarize a number of other possible cosmological sources of primordial gravitational waves and assess what might be learned from direct detection experiments such as LISA, Big Bang Observer and beyond.

  20. Prospects for direct detection of primordial gravitational waves

    NASA Astrophysics Data System (ADS)

    Chongchitnan, Sirichai; Efstathiou, George

    2006-04-01

    We study the primordial gravitational wave background produced in models of single-field inflation. Using the inflationary flow approach, we investigate the amplitude of gravitational wave spectrum, ?gw, in the frequency range 1 mHz 1 Hz pertinent to future space-based laser interferometers. For models that satisfy the current observational constraint on the tensor-to-scalar ratio, r?0.36, we derive a strict upper bound of ?gw?1.6×10-15 independent of the form of the inflationary potential. Applying, in addition, the observational constraints on the spectral index ns and its running, ?gw is expected to be considerably lower than this bound unless the shape of the potential is finely tuned. We contrast our numerical results with those based on simple power-law extrapolation of the tensor power spectrum from cosmic microwave background (CMB) scales. In addition to single-field inflation, we summarize a number of other possible cosmological sources of primordial gravitational waves and assess what might be learned from direct detection experiments such as LISA, Big Bang Observer and beyond.

  1. Colorimetric consideration of transparencies for a typical LACIE scene

    NASA Technical Reports Server (NTRS)

    Juday, R. D. (principal investigator)

    1979-01-01

    The production film converter used to produce LACIE imagery is described as well as schemes designed to provide the analyst with operational film products. Two of these products are discussed from the standpoint of color theory. Colorimetric terminology is defined and the mathematical calculations are given. Topics covered include (1) history of product 1 and 3 algorithm development; (2) colorimetric assumptions for product 1 and 3 algorithms; (3) qualitative results from a colorimetric analysis of a typical LACIE scene; and (4) image-to-image color stability.

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

    E-print Network

    Peters, Achim

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

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

    E-print Network

    Li, Jin

    2015-01-01

    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...

  4. The Use of Colorimetric Sensor Arrays to Discriminate between Pathogenic Bacteria

    PubMed Central

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

    2013-01-01

    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

  5. Identifying the Theory of Dark Matter with Direct Detection

    E-print Network

    Vera Gluscevic; Moira I. Gresham; Samuel D. McDermott; Annika H. G. Peter; Kathryn M. Zurek

    2015-06-15

    Identifying the true theory of dark matter depends crucially on accurately characterizing interactions of dark matter (DM) with other species. In the context of DM direct detection, we present a study of the prospects for correctly identifying the low-energy effective DM-nucleus scattering operators connected to UV-complete models of DM-quark interactions. We take a census of plausible UV-complete interaction models with different low-energy leading-order DM-nuclear responses. For each model (corresponding to different spin-, momentum-, and velocity-dependent responses), we create a large number of realizations of recoil-energy spectra, and use Bayesian methods to investigate the probability that experiments will be able to select the correct scattering model within a broad set of competing scattering hypotheses. We conclude that agnostic analysis of a strong signal (such as Generation-2 would see if cross sections are just below the current limits) seen on xenon and germanium experiments is likely to correctly identify momentum dependence of the dominant response, ruling out models with either "heavy" or "light" mediators, and enabling downselection of allowed models. However, a unique determination of the correct UV completion will critically depend on the availability of measurements from a wider variety of nuclear targets, including iodine or fluorine. We investigate how model-selection prospects depend on the energy window available for the analysis. In addition, we discuss accuracy of the DM particle mass determination under a wide variety of scattering models, and investigate impact of the specific types of particle-physics uncertainties on prospects for model selection.

  6. Results on Discrete-Time, Decision-Directed Integrated Detection, Estimation, and Identification 

    E-print Network

    Painter, John H.; Jones, S.

    1977-01-01

    New results are presented for symbol-by-symbol detection with decision-directed tracking of colored channel disturbances. Recursive sampled-data algorithms are shown for Maximum A Posteriori Probability of detection under colored additive...

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

    E-print Network

    Bermingham, Eldredge

    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

  8. Direct detection of intermolecular forces by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Skulason, Hjalti

    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.

  9. Direct and indirect polarimetry for detection in microbore liquid chromatography

    SciTech Connect

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

    1984-09-01

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

  10. Colorimetric determination of reducing normality in the Purex process

    SciTech Connect

    Baumann, E.W.

    1983-07-01

    Adjustment of the valence state of plutonium from extractable Pu(IV) to nonextractable Pu(III) in the Purex process is accomplished by addition of reductants such as Fe(II), hydroxylamine nitrate (HAN), or U(IV). To implement on-line monitoring of this reduction step for improved process control at the Savannah River Plant, a simple colorimetric method for determining excess reductant (reducing normality) was developed. The method is based on formation of a colored complex of Fe(II) with FerroZine (Hach Chemical Company). The concentration of Fe(II) is determined directly. The concentration of HAN or U(IV), in addition to Fe(II), is determined indirectly as Fe(II), produced through reduction of Fe(III). Experimental conditions for a HAN-Fe(III) reaction of known stoichiometry were established. The effect of hydrazine, which stabilizes U(IV), was also determined. Real-time measurements of color development were made that simulated on-line performance. A laboratory analytical procedure is included. 5 references, 8 figures.

  11. White emission magnetic nanoparticles as chemosensors for sensitive colorimetric and ratiometric detection, and degradation of ClO(-) and SCN(-) in aqueous solutions based on a logic gate approach.

    PubMed

    Zhi, Lihua; Wang, Zhiyi; Liu, Jian; Liu, Weisheng; Zhang, Haoli; Chen, Fengjuan; Wang, Baodui

    2015-07-21

    Fluorescent chemosensors for detecting single anions have been largely synthesized. However, the simultaneous detection and degradation of multiple anions remain a major challenge. Herein we report the synthesis of a white emission nanoprobe on the basis of a Coumarin-Rhodamine CR1-Eu complex coordinated to dipicolinic acid (dpa)-PEG-Fe3O4 nanoparticles for the selective detection of ClO(-) and SCN(-) ions on controlling by a logic gate. The obtained nanoprobe exhibits three individual primary colors (blue, green, and red) as well as white emission at different excitation energies. Interestingly, this nanoprobe shows a marked rose red to violet emission color change in response to ClO(-), a reversible violet to rose red emission color change in response to SCN(-), and high ClO(-) and SCN(-) selectivity and sensitivity with a detection limit of 0.037 and 0.250 nM, respectively. Furthermore, the SCN(-) and ClO(-) can degrade simultaneously through the redox reaction between ClO(-) and SCN(-). PMID:26102484

  12. Bed bug detection: current technologies and future directions.

    PubMed

    Vaidyanathan, Rajeev; Feldlaufer, Mark F

    2013-04-01

    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

  13. Enhancing spectral efficiency and receiving sensitivity in a direct-detected OFDM system

    Microsoft Academic Search

    Kai-Ming Feng; Wei-Ren Peng

    2010-01-01

    In this paper, we will review our latest developments in improving the spectral efficiency and receiving sensitivity in a direct-detected OFDM transmission system. An RF-tone assisted virtual single sideband (VSSB) OFDM modulation format is proposed to enhance the spectral efficiency in both electrical and optical domains for direct detected OFDM applications. The receiving sensitivity can be improved by using an

  14. Early detection of Pseudomonas aeruginosa – comparison of conventional versus molecular (PCR) detection directly from adult patients with cystic fibrosis (CF)

    Microsoft Academic Search

    Jiru Xu; John E Moore; Philip G Murphy; B Cherie Millar; J Stuart Elborn

    2004-01-01

    BACKGROUND: Pseudomonas aeruginosa (PA) is the most important bacterial pathogen in patients with cystic fibrosis (CF) patients. Currently, routine bacteriological culture on selective\\/non- selective culture media is the cornerstone of microbiological detection. The aim of this study was to compare isolation rates of PA by conventional culture and molecular (PCR) detection directly from sputum. METHODS: Adult patients (n = 57)

  15. Basic design principles of colorimetric vision systems

    NASA Astrophysics Data System (ADS)

    Mumzhiu, Alex M.

    1998-10-01

    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.

  16. Direct detection of trimethylamine in meat food products using ion mobility spectrometry

    Microsoft Academic Search

    Gheorghe M. Bota; Peter B. Harrington

    2006-01-01

    Biogenic amines are degradation products generated by bacteria in meat products. These amines can indicate bacterial contamination or have a carcinogenic effect to humans consuming spoiled meats; therefore, their rapid detection is essential. Trimethylamine (TMA) is a good target for the detection of biogenic amines because its volatility. TMA was directly detected in meat food products using ion mobility spectrometry

  17. Detection of regions of interest and camouflage breaking by direct convexity estimation

    Microsoft Academic Search

    Ariel Tankus; Yehezkel Yeshurun

    1998-01-01

    Detection of regions of interest is usually based on edge maps. We suggest a novel nonedge-based mechanism for detection of regions of interest, which extracts 3D information from the image. Our operator detects smooth 3D convex and concave objects based on direct processing of intensity values. Invariance to a large family of functions is mathematically proved. It follows that our

  18. Face Detection by Direct Convexity Estimation Ariel Tankus, Hezy Yeshurun and Nathan Intrator

    E-print Network

    Yeshurun, Hezy

    on direct processing of in­ tensity values. The operator detects the regions of the eyes and hair background. It is employed for face detection, namely to detect the eyes and hair, from which the scale) as Y­Phase. 2.2 Mathematical Formulation of Y­Phase Reaction to Paraboloids The projection of concave

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

    PubMed

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

    2015-04-01

    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 0.005 ng mL(-1) (0.025 nM) 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

  20. Direct detection of extra-solar planetary systems from the ground and space

    NASA Technical Reports Server (NTRS)

    Terrile, R. J.

    1986-01-01

    This paper discusses recent work in the development of instrumentation used for the direct detection of planetary systems from ground-based and space-based observatories. Direct methods such as CCD coronagraphic imaging of nearby stars must overcome the large contrast differences between parent star and the circumstellar material. However, these methods have the advantage over indirect methods in that more advanced space-based direct detection instrumentation can lead to a significantly greater science return.

  1. Direct detection of RDX vapor using a conjugated polymer network.

    PubMed

    Gopalakrishnan, Deepti; Dichtel, William R

    2013-06-01

    1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) is a principal component of plastic explosives used in acts of terrorism and within improvised explosive devices, among others. Approaches to detect RDX compatible with remote, "stand-off" sampling that do not require preconcentration strategies, such as the swabs commonly employed in airports, will benefit military and civilian security. Such detection remains a significant challenge because RDX is 10(3) less volatile than 1,3,5-trinitrotoluene (TNT), corresponding to a parts-per-trillion vapor pressure under ambient conditions. Therefore, while fluorescence quenching of conjugated polymers is sufficiently sensitive to detect TNT vapors, RDX vapor detection is undemonstrated. Here we report a cross-linked phenylene vinylene polymer network whose fluorescence is quenched by trace amounts of RDX introduced from solution or the vapor phase. Fluorescence quenching is reduced, but remains significant, when partially degraded RDX is employed, suggesting that the polymer responds to RDX itself. The polymer network also responds to TNT and PETN similarly introduced from solution or the vapor phase. Pure solvents, volatile amines, and the outgassed vapors from lipstick or sunscreen do not quench polymer fluorescence. The established success of TNT sensors based on fluorescence quenching makes this a material of interest for real-world explosive sensors and will motivate further interest in cross-linked polymers and framework materials for sensing applications. PMID:23641956

  2. Fraud Detection from a Business Perspective: Future Directions and Challenges

    E-print Network

    Flegel, Ulrich

    and Julien Vayssière1 and Gunter Bitz2 1 SAP Research Center Karlsruhe, Germany 2 SAP Fraud Prevention Competence Center, Walldorf, Germany {ulrich.flegel|julien.vayssiere|gunter.bitz}{@}sap.com Abstract approaches over the years to the problem of fraud detection: data mining, machine learning, signature

  3. PoS(ICHEP2010)539 Dark Matter direct detection searches

    E-print Network

    Boyer, Edmond

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

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

    Microsoft Academic Search

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

    2003-01-01

    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

  5. 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

    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

    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

  6. Direct broad-range detection of alphaviruses in mosquito extracts

    Microsoft Academic Search

    Mark W. Eshoo; Chris A. Whitehouse; Scott T. Zoll; Christian Massire; Thuy-Trang D. Pennella; Lawrence B. Blyn; Rangarajan Sampath; Thomas A. Hall; Joseph A. Ecker; Anjali Desai; Leonard P. Wasieloski; Feng Li; Michael J. Turell; Amy Schink; Karl Rudnick; Glen Otero; Scott C. Weaver; George V. Ludwig; Steven A. Hofstadler; David J. Ecker

    2007-01-01

    Members of the genus Alphavirus are a diverse group of principally mosquito-borne RNA viruses. There are at least 29 species and many more subtypes of alphaviruses and some are considered potential bioweapons. We have developed a multi-locus RT-PCR followed by electrospray ionization mass spectrometry (RT-PCR\\/ESI-MS) assay that uses the amplicon base compositions to detect and identify alphaviruses. A small set

  7. Direct broad-range detection of alphaviruses in mosquito extracts.

    PubMed

    Eshoo, Mark W; Whitehouse, Chris A; Zoll, Scott T; Massire, Christian; Pennella, Thuy-Trang D; Blyn, Lawrence B; Sampath, Rangarajan; Hall, Thomas A; Ecker, Joseph A; Desai, Anjali; Wasieloski, Leonard P; Li, Feng; Turell, Michael J; Schink, Amy; Rudnick, Karl; Otero, Glen; Weaver, Scott C; Ludwig, George V; Hofstadler, Steven A; Ecker, David J

    2007-11-25

    Members of the genus Alphavirus are a diverse group of principally mosquito-borne RNA viruses. There are at least 29 species and many more subtypes of alphaviruses and some are considered potential bioweapons. We have developed a multi-locus RT-PCR followed by electrospray ionization mass spectrometry (RT-PCR/ESI-MS) assay that uses the amplicon base compositions to detect and identify alphaviruses. A small set of primer pairs targeting conserved sites in the alphavirus RNA genome were used to amplify a panel of 36 virus isolates representing characterized Old World and New World alphaviruses. Base compositions from the resulting amplicons could be used to unambiguously determine the species or subtype of 35 of the 36 isolates. The assay detected, without culture, Venezuelan equine encephalitis virus (VEEV), Eastern equine encephalitis virus (EEEV), and mixtures of both in pools consisting of laboratory-infected and -uninfected mosquitoes. Further, the assay was used to detect alphaviruses in naturally occurring mosquito vectors collected from locations in South America and Asia. Mosquito pools collected near Iquitos, Peru, were found to contain an alphavirus with a very distinct signature. Subsequent sequence analysis confirmed that the virus was a member of the Mucambo virus species (subtype IIID in the VEEV complex). The assay we have developed provides a rapid, accurate, and high-throughput assay for surveillance of alphaviruses. PMID:17655905

  8. Hollow PDA-Au nanoparticles-enabled signal amplification for sensitive nonenzymatic colorimetric immunodetection of carbohydrate antigen 125.

    PubMed

    Zhao, Yan; Zheng, Yiqun; Zhao, Caiyun; You, Jinmao; Qu, Fengli

    2015-09-15

    A novel colorimetric immunoassay was designed for the sensitive detection of carbohydrate antigen 125 (CA125). The success of this immunoassay relies on the use of hollow polydopamine-gold nanoparticles (PDA-Au) for signal amplification to achieve sensitive nonenzymatic colorimetric detection. In particular, PDA-Au was used as a stable and sensitive label and aminated-Fe3O4 magnetic nanoparticles (Fe3O4 NPs) were employed to immobilize capture antibody (Ab1) and acted as a separable immunosensing probe. PDA-Au exhibited high catalytic performance towards p-nitrophenol reduction and thus resulted in significant color change and UV/vis signal variations. The immunoassay was performed based on sandwich protocol. As compared to pure Au nanoparticles, the signal amplification and sensitivity of PDA-Au-based assay was significantly improved. For instance, the dynamic range of the developed colorimetric immunoassay for CA125 was 0.1-100U/mL with a detection limit of 0.1U/mL at S/N=3. In addition, this immunoassay was also tested for the analysis of clinical serum samples, which demonstrated its potential for practical diagnostic applications. PMID:25909340

  9. A colorimetric probe for online analysis of sulfide based on the red shifts of longitudinal surface plasmon resonance absorption resulting from the stripping of gold nanorods

    Microsoft Academic Search

    Jia-Ming Liu; Xin-Xing Wang; Fei-Ming Li; Li-Ping Lin; Wen-Lian Cai; Xuan Lin; Li-Hong Zhang; Zhi-Ming Li; Shao-Qin Lin

    A gold nanorods (GNRs) nonaggregation-based colorimetric probe has been developed for the detection of S2? based on that the longitudinal surface plasmon resonance absorption wavelength (LPAW) of GNRs red shifts (??) and the color of the solution distinctly changes on account of the faster stripping of GNRs along longitudinal axis than transverse axis in the process of GNRs reacting with

  10. A prototype direct-detection CCD for protein crystallography

    PubMed Central

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

    2013-01-01

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

  11. Direct detection at FIR frequencies with niobium tunnel junctions

    Microsoft Academic Search

    J. D. Prince; B. S. Deaver Jr.; S. Withington

    1993-01-01

    Measurements have been made on an array of six niobium\\/aluminum-aluminum oxide\\/niobium junctions with an integrated bow-tie antenna at 584 GHz. These measurements include examining the response of current-voltage curves at different incident radiation powers, both with and without an applied magnetic field. The measurements also include the responsivity and the noise of the devices as direct detectors. A planar SQUID

  12. Size- and shape-dependent peroxidase-like catalytic activity of MnFe2O4 Nanoparticles and their applications in highly efficient colorimetric detection of target cancer cells.

    PubMed

    Peng, Yunhua; Wang, Zhiyi; Liu, Weisheng; Zhang, Haoli; Zuo, Wei; Tang, Huiang; Chen, Fengjuan; Wang, Baodui

    2015-07-01

    The catalytic activity of nanocrystal catalysts depends strongly on their chemical composition, size, and shape. Herein, we report four different sizes and shapes of MnFe2O4 nanoparticles (NPs) prepared by a hydrothermal procedure. In addition, the size- and shape-dependent peroxidase-like activity of these NPs was first explored using 3,3',5,5'-tetramethyl-benzidine and H2O2 as peroxidase substrates. The results showed that the peroxidase-like activities of the MnFe2O4 NPs were size- and shape-dependent and followed the order of 4 nm (spherical) > 18 nm (plate-like) > 27 nm (near-cubic) > 16 nm (spherical); this order was closely related to their surface-to-volume ratio and atom arrangements. Such an investigation is of great significance for peroxidase nanomimetics with enhanced activity and utilization. Furthermore, folic acid (FA)-conjugated MnFe2O4 NPs allow the detection of folate receptor-rich cancer cells. Such investigation can be widely utilized for the identification of important target molecules. PMID:26102593

  13. Detection of nucleic acid sequences by invader-directed cleavage

    DOEpatents

    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

    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.

  14. Dark matter direct detection in the MSSM with heavy scalars

    SciTech Connect

    Bernal, Nicolás, E-mail: bernal@ecm.ub.es [High Energy Physics Group, Dept. ECM, and Institut de Ciències del Cosmos, Univ. de Barcelona, Av. Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

    2009-08-01

    We explore the dark matter detection prospects in the Minimal Supersymmetric Standard Model in the scenario where the scalar partners of the fermions and the Higgs particles (except for the Standard-Model-like one) are assumed to be very heavy and are removed from the low-energy spectrum. We analyse the neutralino LSP (?{sub 1}{sup 0}) in scenarios where the gaugino mass parameters are universal at the GUT scale and also the case where they are non-universal. This analysis is carried out in the framework of a Xenon-like 100 kg experiment. In general, an important fraction of the parameter space giving rise to the dark matter relic density measured by WMAP can be probed and excluded in the case of not detecting any WIMP. In the opposite case, once a WIMP signal has been found, we show that for a light ?{sub 1}{sup 0} which is a higgsino-gaugino mixture it is possible to reconstruct efficiently the mass and the scattering cross-section of the neutralino LSP. Moreover, we show that it is also feasible to put strong constraints over some of the parameters of the Lagrangian, e.g. the higgsino and the gaugino mass parameters.

  15. Colorimetric calibration of CCD cameras for self-luminous images

    NASA Astrophysics Data System (ADS)

    Chang, Gao-Wei; Chen, Yung-Chang

    1998-06-01

    Reproducing colors with rich saturation, from illuminating objects, is usually recognized as an essential issue for CCD camera imaging. In this paper, we propose a colorimetric calibration scheme regarding self-luminous images for CCD cameras. And, an efficient algorithm to generate highly saturated color stimuli is devised for investigating the CCD camera performance of image reproduction. In this scheme, a set of color samples containing highly saturated colors is generated, from an advanced CRT, as color stimuli for colorimetric characterization. To demonstrate the effectiveness of this algorithm, a realization of color samples, uniformly distributed in CIE LAB, are presented for illustration.

  16. Molecular detection of human adenovirus in sediment using a direct detection method compared to the classical polyethylene glycol precipitation.

    PubMed

    Staggemeier, Rodrigo; Bortoluzzi, Marina; da Silva Heck, Tatiana Moraes; da Silva, Tiago; Spilki, Fernando Rosado; de Matos Almeida, Sabrina Esteves

    2015-03-01

    Various effective methods have been developed to measure the concentration of viruses in sediment samples. However, there is need to standardize less laborious and simpler techniques. The objective of the present study was to compare two different methods to measure the concentration of viruses in soil samples. The use of polyethylene glycol (PEG) was compared with a direct extraction of viral nucleic acids from the samples diluted in modified Eagle's minimal essential medium (E-MEM). The presence of adenovirus in the samples was detected by real-time quantitative polymerase chain reaction (qPCR). Only six samples (30%) were positive for adenovirus when PEG technique was used. The direct method showed 16 (80%) samples positive for adenovirus. Therefore, direct detection (i.e. without previous concentration) demonstrated a higher rate of detection, better effectiveness, and shorter execution time. Furthermore, direct detection uses reagents that are often readily available in virology laboratories. Thus, it is an attractive alternative to other methods of detection of virus particles in sediments. PMID:25486079

  17. Self-assembled, functionalized graphene and DNA as a universal platform for colorimetric assays.

    PubMed

    Tao, Yu; Lin, Youhui; Ren, Jinsong; Qu, Xiaogang

    2013-07-01

    We have demonstrated a robust sensing strategy by employing single-stranded probe DNA and the hemin-graphene hybrid (GH) to detect a broad range of targets including metal ions, DNA and small molecules. This nearly "universal" biosensor approach is based on the DNA-mediated assembly of the hemin-graphene composite upon addition of the targets. Afterwards, GH aggregate resulting from DNA hybridization will occur. The DNA-GH hybrids will settle on the bottom of the vial after centrifugation, leaving behind a transparent supernatant. After incubation with TMB and H2O2, the colorimetric signal of the centrifugal supernatant will be significantly lower compared to that in the absence of targets. Therefore, mediation of the assembly of DNA on GH by targets can yield a facile means with tunable optical properties in response to concentration changes of the targets. This colorimetric "readout" offers great advantages such as the simple operation process, low-cost portable instrument and easy-to-use applications. Therefore, we believe that this method promises a great potential of becoming a routine tool for quantitative detection of a wide spectrum of analytes for specific applications in biodiagnostics, nanoelectronics, and bionanotechnology. PMID:23548641

  18. Improving spectral efficiency and receiving sensitivity in a direct-detected OFDM system

    Microsoft Academic Search

    Kai-Ming Feng; Wei-Ren Peng

    2010-01-01

    We'll bring out our latest developments in improving the spectral efficiency and receiving sensitivity in a direct-detected OFDM transmission. The analytical model, numerical simulations and experimental results of the proposed architectures will be presented.

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

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli; Abshire, James B.

    2011-01-01

    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

  20. Direct (13)C NMR detection in HPLC hyphenation mode: analysis of Ganoderma lucidum terpenoids.

    PubMed

    Wubshet, Sileshi G; Johansen, Kenneth T; Nyberg, Nils T; Jaroszewski, Jerzy W

    2012-05-25

    Solid phase extraction (SPE) was introduced as a crucial step in the HPLC-SPE-NMR technique to enable online analyte enrichment from which proton-detected NMR experiments on submicrogram amounts from complex mixtures were possible. However, the significance of direct-detected (13)C NMR experiments is indubitable in simplifying structural elucidations. In the current study, we demonstrated direct (13)C NMR detection of triterpenoids from a Ganoderma lucidum extract in hyphenation mode. The combined advantage of a cryogenically cooled probe, miniaturization, and multiple trapping enabled the first reported application of HPLC-SPE-NMR analysis using direct-detected (13)C NMR spectra. HPLC column loading, accumulative SPE trappings, and the effect of different elution solvents were evaluated and optimized. A column loading of approximately 600 ?g of a prefractionated triterpenoid mixture, six trappings, and an acquisition time of 13 h resulted in spectra with adequate signal-to-noise ratios to detect all C-13 signals. PMID:22515483

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

    SciTech Connect

    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

    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.

  2. Method of detecting the direction of arcing faults on power distribution feeders

    E-print Network

    Fernando, W. Anand Krisantha

    1992-01-01

    METHOD OF DETECTING THE DIRECTION OF ARCING FAULTS ON POWER DISTRIBUTION FEEDERS A Thesis by W. ANAND KRISANTHA FERNANDO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1992 Major Subject: Electrical Engineering METHOD OF DETECTING THE DIRECTION OF ARCING FAULTS ON POWER DISTRIBUTION FEEDERS A Thesis by W. ANAND KRISANTHA FERNANDO Approved as to style and content by: B. Don...

  3. Method of detecting the direction of arcing faults on power distribution feeders 

    E-print Network

    Fernando, W. Anand Krisantha

    1992-01-01

    METHOD OF DETECTING THE DIRECTION OF ARCING FAULTS ON POWER DISTRIBUTION FEEDERS A Thesis by W. ANAND KRISANTHA FERNANDO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1992 Major Subject: Electrical Engineering METHOD OF DETECTING THE DIRECTION OF ARCING FAULTS ON POWER DISTRIBUTION FEEDERS A Thesis by W. ANAND KRISANTHA FERNANDO Approved as to style and content by: B. Don...

  4. Direct surface plasmon resonance immunosensor for in situ detection of benzoylecgonine, the major cocaine metabolite

    Microsoft Academic Search

    Eva M. Munoz; Silvia Lorenzo-Abalde; África González-Fernández; Oscar Quintela; Manuel Lopez-Rivadulla; Ricardo Riguera

    2011-01-01

    In this paper the development of the first direct surface plasmon resonance (SPR) immunoassay for the detection of benzoylecgonine (BZE) is described. Immunosensor chips consisting of a high affinity monoclonal anti-BZE-antibody (anti-BZE–Ab) immobilized at high density to a sensor chip were prepared. First, BZE detection in Hepes buffer was achieved by direct, real time monitoring of the binding between BZE

  5. Colorimetric blood-gas monitoring sensors

    NASA Astrophysics Data System (ADS)

    Proctor, Keith J.; Seifert, George P.

    1993-05-01

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

  6. First Direct Detection of Clay Minerals on Mars

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  7. Direct In-Gel Fluorescence Detection and Cellular Imaging of O-GlcNAc-Modified Proteins

    E-print Network

    Hsieh-Wilson, Linda

    Direct In-Gel Fluorescence Detection and Cellular Imaging of O-GlcNAc-Modified Proteins Peter M fluorescence detection of O-GlcNAc proteins in gels would facilitate proteomic studies and greatly extend an anti-TAMRA antibody to remove nonglycosylated proteins, resolved by 1D or 2D gel electrophoresis

  8. Optimal geometrical conditions of photoacoustic signal detection with a cylindrical direct coupling cell for liquids

    Microsoft Academic Search

    Takehiko Kitamori; Masaaki Fujii; Tsuguo Sawada; Yohichi Gohshi

    1985-01-01

    The general description of photoacoustic (PA) signal generation in liquids developed in our earlier paper [J. Appl. Phys. 55, 4005 (1984)] was extended to analyze PA signal detection. The dependence of detected PA signal magnitude on the excitation beam profile and cell geometry of the cylindrical direct coupling cell was obtained theoretically. The thermal lens effect was clarified to be

  9. Direct Nitric Oxide Detection in Aqueous Solution by Copper(II) Fluorescein Complexes

    E-print Network

    Baik, Mu-Hyun

    Direct Nitric Oxide Detection in Aqueous Solution by Copper(II) Fluorescein Complexes Mi Hee Lim nitrogen atoms of the FLn ligands most likely bind to Cu(II). Introduction of nitric oxide (NO) to pH 7-time detection of nitric oxide production in living cells. Introduction Nitric oxide (NO) is produced

  10. STATE OF CALIFORNIA FAULT DETECTION AND DIAGNOSTICS (FDD) FOR PACKAGED DIRECT EXPANSION UNITS

    E-print Network

    STATE OF CALIFORNIA FAULT DETECTION AND DIAGNOSTICS (FDD) FOR PACKAGED DIRECT EXPANSION UNITS CEC-MECH-12A (Revised 08/09) CALIFORNIA ENERGY COMMISSION CERTIFICATE OF ACCEPTANCE MECH-12A NA7.5.11 Fault Signed: Position With Company (Title): #12;STATE OF CALIFORNIA FAULT DETECTION AND DIAGNOSTICS (FDD

  11. BUILDING DETECTION USING DIRECTIONAL SPATIAL CONSTRAINTS H. Gokhan Akcay, Selim Aksoy

    E-print Network

    Aksoy, Selim

    BUILDING DETECTION USING DIRECTIONAL SPATIAL CONSTRAINTS H. G¨okhan Akc¸ay, Selim Aksoy Department,saksoy}@cs.bilkent.edu.tr ABSTRACT We propose an algorithm for automatic detection of buildings with complex shapes and roof is obtained. Then, candidate building regions are found using shadow and sun azimuth angle information. Fi

  12. Direct Detection of Reactive Nitrogen Species in Experimental Autoimmune Uveitis

    PubMed Central

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

    2007-01-01

    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

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

    E-print Network

    Boyer, Edmond

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

  14. A Biosensor for Direct Detection of DNA Sequences Based on Capacitance Measurements

    E-print Network

    Bogliolo, Alessandro

    A Biosensor for Direct Detection of DNA Sequences Based on Capacitance Measurements C.Guiducci1 , C-to-perform assays. We developed and performed preliminary assessments of an integrable biosensor for the direct the reproducibility of the experimental results and the reusability of the DNA biosensor. 1. Introduction Molecular

  15. Testing of Colorimetric Tubes for Nitrogen Dioxide and Monomethylhydrazine.

    ERIC Educational Resources Information Center

    Diamond, Philip

    Colorimetric tubes for nitrogen dioxide (NO2) and monomethylhydrazine (MMH) were tested for accuracy and results indicate that at the levels checked the tubes' average deviation was plus or minus 20 percent. Tube NO2 concentrations all read lower than the analyzed concentrations. MMH tubes read much higher than the analyzed concentration of 0.28…

  16. Evaluation of a Colorimetric Personal Dosimeter for Nitrogen Oxide.

    ERIC Educational Resources Information Center

    Diamond, Philip

    A personal colorimetric dosimeter for nitrogen dioxide was developed. Tests were performed to determine the response of these strips to various concentrations of NO2. The dosimeter strips were satisfactory for approximate determinations of total exposure (concentration + time) of nitrogen dioxide. The total exposure was calculated in terms of time…

  17. A Colorimetric Method for the Determination of Sugars

    Microsoft Academic Search

    M. Dubois; K. Gilles; J. K. Hamilton; P. A. Rebers; F. Smith

    1951-01-01

    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

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

    PubMed

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

    2015-01-15

    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

  19. Direct Detection Phenomenology in Models Where the Products of Dark Matter Annihilation Interact with Nuclei

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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 nonstandard and/or even absent annual modulation, and the ability to probe DM masses as low as a ˜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 Emin space without making assumptions about DM astrophysics, mass, or scattering form factors. 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 nonrelativistic direct detection by more than 3 orders of magnitude for masses in a 2-7 GeV window.

  20. Deciphering Inflation with Gravitational Waves: Cosmic Microwave Background Polarization vs. Direct Detection with Laser Interferometers

    E-print Network

    Smith, T L; Cooray, A R; Smith, Tristan L.; Peiris, Hiranya V.; Cooray, Asantha

    2006-01-01

    A detection of the primordial gravitational wave background is considered to be the ``smoking-gun '' evidence for inflation. While super-horizon 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 three orders of magnitude over current plans.

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

    SciTech Connect

    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

    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.

  2. Colorimetric determination of sildenafil citrate (Viagra) through ion-associate complex formation.

    PubMed

    Amin, Alaa S; Moustafa, Moustafa E; El-Dosoky, Reham

    2009-01-01

    A simple, quick, accurate, and sensitive colorimetric method is described for the determination of sildenafil citrate (SLD). The method is based on the reaction of SLD with Congo Red, Sudan II, and Gentian Violet in buffered aqueous solutions at pH 2.5, 6.5, and 11.0, respectively, to give highly colored soluble ion-associate complex species; the colored products are quantitated colorimetrically at 523, 554, and 569 nm, respectively. The various experimental conditions were optimized. The stoichiometric ratio was found to be 1:1 for all ion associates; the calculated logarithmic stability constants were 8.51, 7.79, and 5.58, respectively. Beer's law was obeyed over the concentration range of 0.2-7.0 microg/mL, whereas the Ringbom optimum concentration range was 0.4-6.5 microg/mL. Values for molar absorptivity, Sandell sensitivity, and detection and quantification limits were also calculated. The proposed method was successfully applied to the determination of SLD in Viagra tablets and in serum samples by using the technique of standard additions with mean accuracy values of 100.06 +/- 1.14, 99.87 +/- 0.70, and 99.86 +/- 0.97% for Viagra tablets and 99.88 +/- 0.60, 99.90 +/- 0.90, and 100.24 +/- 0.80% for serum samples, respectively. PMID:19382569

  3. Acquisition algorithm for direct-detection ladars with Geiger-mode avalanche photodiodes.

    PubMed

    Milstein, Adam B; Jiang, Leaf A; Luu, Jane X; Hines, Eric L; Schultz, Kenneth I

    2008-01-10

    An optimal algorithm for detecting a target using a ladar system employing Geiger-mode avalanche photodiodes (GAPDs) is presented. The algorithm applies to any scenario where a ranging direct detection ladar is used to determine the presence of a target against a sky background within a specified range window. A complete statistical model of the detection process for GAPDs is presented, including GAPDs that are inactive for a fixed period of time each time they fire. The model is used to develop a constant false alarm rate detection algorithm that minimizes acquisition time. Numerical performance predictions, simulation results, and experimental results are presented. PMID:18188212

  4. Acquisition algorithm for direct-detection ladars with Geiger-mode avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Milstein, Adam B.; Jiang, Leaf A.; Luu, Jane X.; Hines, Eric L.; Schultz, Kenneth I.

    2008-01-01

    An optimal algorithm for detecting a target using a ladar system employing Geiger-mode avalanche photodiodes (GAPDs) is presented. The algorithm applies to any scenario where a ranging direct detection ladar is used to determine the presence of a target against a sky background within a specified range window. A complete statistical model of the detection process for GAPDs is presented, including GAPDs that are inactive for a fixed period of time each time they fire. The model is used to develop a constant false alarm rate detection algorithm that minimizes acquisition time. Numerical performance predictions, simulation results, and experimental results are presented.

  5. Urchin-like (gold core)@(platinum shell) nanohybrids: A highly efficient peroxidase-mimetic system for in situ amplified colorimetric immunoassay.

    PubMed

    Gao, Zhuangqiang; Xu, Mingdi; Lu, Minghua; Chen, Guonan; Tang, Dianping

    2015-08-15

    The development of signal-amplified colorimetric immunoassay relies on the design of highly efficient signal-transduction tags. One promising route is to exploit a novel enzyme mimetic system as the signal label. Herein, we report that urchin-like (gold core)@(platinum shell) nanohybrids (Au@PtNHs) can be utilized as a highly efficient peroxidase mimetic system for in situ amplified colorimetric immunoassay of prostate-specific antigen (PSA, one kind of tumor marker). Initially, urchin-like Au@PtNHs were discovered to outperform horseradish peroxidase (HRP) by a vast margin in terms of the turnover number toward hydrogen peroxide (H2O2)-3,3',5,5'-tetramethylbenzidine (TMB) system and the stability against high temperatures and HRP inhibitors. Based on this discovery, the assay was simply carried out on a capture antibody-immobilized microplate by using the Au@PtNH-labeled detection antibody as a signal-transduction tag with a sandwich-type assay mode. The colorimetric signal stemmed from the labeled Au@PtNHs toward catalytic oxidation of TMB-H2O2 system. Experimental results indicated that the Au@PtNH-based colorimetric immunoassay could display a good colorimetric response toward PSA in the dynamic working range of 5-500pgmL(-)(1) with a low detection limit of 2.9pgmL(-)(1). Meanwhile, the developed immunoassay exhibited good precision and reproducibility, high specificity and acceptable accuracy for the detection of clinical serum samples. These results open up a new horizon for the development of highly sensitive, highly stable and inexpensive non-enzyme immunoassay platforms as an alternative to conventional enzyme-based immunoassay platforms. PMID:25814409

  6. Filling carbon nanotubes with Prussian blue nanoparticles of high peroxidase-like catalytic activity for colorimetric chemo- and biosensing.

    PubMed

    Wang, Ting; Fu, Yingchun; Chai, Liyuan; Chao, Long; Bu, Lijuan; Meng, Yue; Chen, Chao; Ma, Ming; Xie, Qingji; Yao, Shouzhuo

    2014-02-24

    Facile filling of multiwalled carbon nanotubes (MWCNTs) with Prussian blue nanoparticles (PBNPs) of high peroxidase-like catalytic activity was performed to develop novel colorimetric sensing protocols for assaying H2O2 and glucose. Fine control of PBNP growth was achieved by modulating the concentration ratio of K3 [Fe(CN)6] and FeSO4 precursors in an acidic solution containing ultrasonically dispersed MWCNTs, and thus size-matched PBNPs could be robustly immobilized in the cavities of the MWCNTs (MWCNT-PBin). Unlike other reported methods involving complicated procedures and rigorous preparation/separation conditions, this mild one-pot filling method has advantages of easy isolation of final products by centrifugation, good retention of the pristine outer surface of the MWCNT shell, and satisfactory filling yield of (24±2)?%. In particular, encapsulation of PBNPs of poor dispersibility and limited functionality in dispersible and multifunctional MWCNT shells creates new and valuable opportunities for quasihomogeneous-phase applications of PB in liquid solutions. The MWCNT-PBin nanocomposites were exploited as a peroxidase mimic for the colorimetric assay of H2O2 in solution by using 3,3',5,5'-tetramethylbenzidine (TMB) as reporter, and they gave a linear absorbance response from 1??M to 1.5?mM with a limit of detection (LOD) of 100?nM. Moreover, glucose oxidase (GOx) was anchored on the outer surface of MWCNT-PBin to form GOx/MWCNT-PBin bionanocomposites. The cooperation of outer-surface biocatalysis with peroxidase-like catalysis of interior PB resulted in a novel cooperative colorimetric biosensing mode for glucose assay. The use of GOx/MWCNT-PBin for colorimetric biosensing of glucose gave a linear absorbance response from 1??M to 1.0?mM and an LOD of 200?nM. The presented protocols may be extended to other multifunctional nanocomposite systems for broad applications in catalysis and biotechnology. PMID:24482045

  7. G-quadruplex DNAzymes-induced highly selective and sensitive colorimetric sensing of free heme in rat brain.

    PubMed

    Li, Ruimin; Jiang, Qin; Cheng, Hanjun; Zhang, Guoqiang; Zhen, Mingming; Chen, Daiqin; Ge, Jiechao; Mao, Lanqun; Wang, Chunru; Shu, Chunying

    2014-04-21

    Direct selective determination of free heme in the cerebral system is of great significance due to the crucial roles of free heme in physiological and pathological processes. In this work, a G-quadruplex DNAzymes-induced highly sensitive and selective colorimetric sensing of free heme in rat brain is established. Initially, the conformation of an 18-base G-rich DNA sequence, PS2.M (5'-GTGGGTAGGGCGGGTTGG-3'), in the presence of K(+), changes from a random coil to a "parallel" G-quadruplex structure, which can bind free heme in the cerebral system with high affinity through ?-? stacking. The resulted heme/G-quadruplex complex exhibits high peroxidase-like activity, which can be used to catalyze the oxidation of colorless ABTS(2-) to green ABTS?(-) by H2O2. The concentration of heme can be evaluated by the naked eye and determined by UV-vis spectroscopy. The signal output showed a linear relationship for heme within the concentration range from 1 to 120 nM with a detection limit of 0.637 nM. The assay demonstrated here was highly selective and free from the interference of physiologically important species such as dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), ascorbate acid (AA), cysteine, uric acid (UA), glucose and lactate in the cerebral system. The basal dialysate level of free heme in the microdialysate from the striatum of adult male Sprague-Dawley rats was determined to be 32.8 ± 19.5 nM (n = 3). The analytic protocol possesses many advantages, including theoretical simplicity, low-cost technical and instrumental demands, and responsible detection of heme in rat brain microdialysate. PMID:24600682

  8. L-cysteine protected copper nanoparticles as colorimetric sensor for mercuric ions.

    PubMed

    Soomro, Razium A; Nafady, Ayman; Sirajuddin; Memon, Najma; Sherazi, Tufail H; Kalwar, Nazar H

    2014-12-01

    This report demonstrates a novel, simple and efficient protocol for the synthesis of copper nanoparticles in aqueous solution using L-cysteine as capping or protecting agent. UV-visible (UV-vis) spectroscopy was employed to monitor the LSPR band of L-cysteine functionalized copper nanoparticles (Cyst-Cu NPs) based on optimizing various reaction parameters. Fourier Transform Infrared (FTIR) spectroscopy provided information about the surface interaction between L-cysteine and Cu NPs. Transmission Electron Microscopy (TEM) confirmed the formation of fine spherical, uniformly distributed Cyst-Cu NPs with average size of 34 ± 2.1 nm. X-ray diffractometry (XRD) illustrated the formation of pure metallic phase crystalline Cyst-Cu NPs. As prepared Cyst-Cu NPs were tested as colorimetric sensor for determining mercuric (Hg(2+)) ions in an aqueous system. Cyst-Cu NPs demonstrated very sensitive and selective colorimetric detection of Hg(2+) ions in the range of 0.5 × 10(-6)-3.5 × 10(-6) mol L(-1) based on decrease in LSPR intensity as monitored by a UV-vis spectrophotometer. The developed sensor is simple, economic compared to those based on precious metal nanoparticles and sensitive to detect Hg(2+) ions with detection limit down to 4.3 × 10(-8) mol L(-1). The sensor developed in this work has a high potential for rapid and on-site detection of Hg(2+) ions. The sensor was successfully applied for assessment of Hg(2+) ions in real water samples collected from various locations of the Sindh River. PMID:25159429

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

    SciTech Connect

    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

    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.

  10. Direct detection of optical radiation through a sampling orifice for inductively coupled plasma atomic emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Lafreniere, B. R.

    1987-08-01

    The direct optical viewing of an argon inductively coupled plasma (ICP) through a sampling orifice inserted directly into the plasma has been accomplished. A copper cone with a sampling orifice is attached to the entrance slit chamber of a monochromator and inserted directly into an ICP to obtain optical spectra in the vacuum ultraviolet (VUV). With solar-blind photomultiplier tube (PMT) detection, detection limits are 50 ng mL-1 for the resonance lines of Br and Cl during injection into the plasma of aerosols of aqueous solutions generated by pneumatic nebulization. With ultrasonic nebulization, the detection limits improve to 8 ng mL-1 for Br and 15 ng mL-1 for Cl. Detection limits for Br and Cl in the form of an aqueous sample were superior to the best reported values in the Ar and He ICP, and in the microwave-induced plasma atomic emission spectroscopy (MIP-AES) literature. Another significant breakthrough in the present work includes the determination of nonmetals in gases by their direct injection into the ICP by a device called a direct injection probe (DIP). This low dead volume interface (less than 40 microL) is used for the introduction of gaseous samples directly into the axial channel of the ICP. Injection of a gaseous mixture of compounds containing the elements Br, Cl, S, and C results in detection limits of 0.1, 0.3, 0.05, and 1 ng, respectively. These detection limits are by far the best obtained for these elements in a gaseous form by ICP-AES. The extension of ICP-AES analysis to the determination of nonmetals, metalloids, and/or selected metals in aqueous and gaseous samples illustrates the value of this optical sampling approach in the VUV.

  11. FET-Based Biosensors for The Direct Detection of Organophosphate Neurotoxins

    Microsoft Academic Search

    J. R. Wildc

    2004-01-01

    Recent world-wide terrorist events associated with the threat of hazardous chemical agent proliferation, and outbreaks of chemical contamination in the food supply has demonstrated an urgent need for sensors that can directly detect the presence of dangerous chemical toxins.Such sensors must enable real-time detection and accurate identification of different classes of pesticides (e.g., carbamates and organophosphates) but must especially discriminate

  12. Application of IS900 PCR for Detection of Mycobacterium avium subsp. paratuberculosis Directly from Raw Milk

    Microsoft Academic Search

    S. R. Pillai; B. M. Jayarao

    2002-01-01

    A polymerase chain reaction (PCR)-based assay was developed for detection of insertion sequence 900 (IS900 )o fMycobacterium avium subsp. paratuberculo- sis in raw milk. This IS900 PCR assay included DNA extraction and PCR assay using commercially available kits. The DNA extraction and PCR assay were opti- mized to detect the IS900 sequence directly from raw milk. The IS900 PCR assay

  13. Detection and identification of bacteria using direct injection inductively coupled plasma mass spectroscopy

    Microsoft Academic Search

    C. M Gikunju; S. M Lev; A Birenzvige; D. M Schaefer

    2004-01-01

    In this study, an inductively coupled plasma mass spectrometer (ICP-MS) was used for the inorganic chemical characterization of biological materials by direct injection. ICP-MS has the advantage of sub-nanogram\\/gram detection limits for most elements making it a sensitive tool for the detection and characterization of aerosolized biological material. Suspended, microgram-sized samples of Bacillus subtilis spores (BG), Bacillus subtilis vegetative cells

  14. Directed Design of Experiments (DOE) for Determining Probability of Detection (POD) Capability of NDE Systems (DOEPOD)

    NASA Technical Reports Server (NTRS)

    Generazio, Ed

    2007-01-01

    This viewgraph presentation reviews some of the issues that people who specialize in Non destructive evaluation (NDE) have with determining the statistics of the probability of detection. There is discussion of the use of the binominal distribution, and the probability of hit. The presentation then reviews the concepts of Directed Design of Experiments for Validating Probability of Detection of Inspection Systems (DOEPOD). Several cases are reviewed, and discussed. The concept of false calls is also reviewed.

  15. A phase-modulated direct-detection fiber optical CATV transport system

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Yi; Lu, Hai-Han; Lin, Chun-Yu; Wu, Kuan-Hung; Jhang, Tai-Wei; Ying, Cheng-Ling

    2014-05-01

    A fiber optical CATV transport system based on phase modulation (PM) and direct-detection schemes to reduce noise and distortion induced by systems is proposed and experimentally demonstrated. The architecture of the proposed systems is simplified by the fiber-dispersion-induced PM-to-intensity modulation (IM) conversion technique. As a result, the optical signal is detected directly by a photodiode (PD), without using the sophisticated and expensive delay interferometer (DI). Impressive performances of carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) were obtained in our proposed systems over a 100-km single-mode fiber (SMF) transport.

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

    SciTech Connect

    Garny, Mathias [Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22603 Hamburg (Germany); Ibarra, Alejandro; Pato, Miguel; Vogl, Stefan, E-mail: mathias.garny@desy.de, E-mail: ibarra@tum.de, E-mail: miguel.pato@tum.de, E-mail: stefan.vogl@tum.de [Physik-Department T30d, Technische Universität München, James-Franck-Straße, 85748 Garching (Germany)

    2012-11-01

    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 orthogonal to ongoing collider searches at the Large Hadron Collider, making it feasible to close in on degenerate dark matter scenarios within the next years.

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

    PubMed

    Ford, N B; Low, J R

    1984-08-01

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

  18. Poker face of inelastic dark matter: Prospects at upcoming direct detection experiments

    SciTech Connect

    Alves, Daniele S. M.; Lisanti, Mariangela [Theory Group, SLAC, Menlo Park, California 94025 (United States); Physics Department, Stanford University, Stanford, California 94305 (United States); Wacker, Jay G. [Theory Group, SLAC, Menlo Park, California 94025 (United States)

    2010-08-01

    The XENON100 and CRESST experiments will directly test the inelastic dark matter explanation for DAMA's 8.9{sigma} anomaly. This article discusses how predictions for direct detection experiments depend on uncertainties in quenching factor measurements, the dark matter interaction with the standard model, and the halo velocity distribution. When these uncertainties are accounted for, an order of magnitude variation is found in the number of expected events at CRESST and XENON100.

  19. Azomethine H colorimetric method for determining dissolved boron in water

    USGS Publications Warehouse

    Spencer, R.R.; Erdmann, D.E.

    1979-01-01

    An automated colorimetric method for determining dissolved boron in water is described. The boron is complexed with azomethine H, which is readily available as the condensation product of H acid (8-amino-1-naphthol-3,6-disulfonic acid) and salicylaldehyde. The absorbance of the yellow complex formed is then measured colorimetrically at 410 nm. Interference effects from other dissolved species are minimized by the addition of diethylenetriaminepentaacetic acid (DTPA); however, iron, zinc, and bicarbonate interfere at concentrations above 400 ??g/L, 2000 ??g/L, and 200 mg/L, respectively. The bicarbonate interference can be eliminated by careful acidification of the sample with concentrated HCl to a pH between 5 and 6. Thirty samples per hour can be routinely analyzed over the range of from 10 to 400 ??g/L, boron.

  20. Optimal geometrical conditions of photoacoustic signal detection with a cylindrical direct coupling cell for liquids

    NASA Astrophysics Data System (ADS)

    Kitamori, Takehiko; Fujii, Masaaki; Sawada, Tsuguo; Gohshi, Yohichi

    1985-07-01

    The general description of photoacoustic (PA) signal generation in liquids developed in our earlier paper [J. Appl. Phys. 55, 4005 (1984)] was extended to analyze PA signal detection. The dependence of detected PA signal magnitude on the excitation beam profile and cell geometry of the cylindrical direct coupling cell was obtained theoretically. The thermal lens effect was clarified to be one of the dominant factors for determination of an acoustic source profile in liquids. These theoretical results were confirmed experimentally. Theoretical, optimized detection conditions for a highly sensitive cell (under a near-field condition) and a wide dynamic range cell (under a far-field condition) were proposed.

  1. A SETI metapolicy: New directions towards comprehensive policies concerning the detection of extraterrestrial intelligence

    NASA Astrophysics Data System (ADS)

    Baxter, Stephen; Elliott, John

    2012-09-01

    At present we have only one agreed public policy for handling the detection of an extraterrestrial intelligence (ETI), the 'First SETI Protocol' of 1989, which guides action in the immediate aftermath of detection, even though SETI (the Search for Extraterrestrial Intelligence) constitutes an active search for such a detection. The purpose of this paper is to set out areas in which policies might fruitfully be developed, including reviewing the rationale and investment in SETI, handling ETI artefacts, and approaches to direct contact. 'Negative' possibilities will be examined, for example, whether an ETI artefact or data should be purposefully destroyed.

  2. A rapid colorimetric method for measuring arsenic concentrations in groundwater

    Microsoft Academic Search

    R. K. Dhar; Y. Zheng; J. Rubenstone; A. van Geen

    2004-01-01

    The arsenic content of groundwater consumed by millions of people in the developing world has become a major health concern. We report here an optimization of the colorimetric method of Johnson and Pilson (1972) to accurately measure As concentrations in the <0.03–5.3?molL?1 (<2–400?gL?1) range in groundwater containing 2–30?molL?1 dissolved phosphate. The optimization includes increases in the concentrations of potassium iodate,

  3. Assessment of methodologies for colorimetric cholesterol assay of meats

    E-print Network

    Bohac, Cynthia Kay Edwards

    1987-01-01

    density lipoprotein-cholesterol (Grundy and Ahrens, 1970; Grundy, 1983; Krause and Hartman, 1984), and may (Vega et al. , 1982; Mattson and Grundy, 1985) or may not (Oh and Monaco, 1985) subsequently decrease serum high density lipoprotein (HDL)-cholesterol.... Kube a (Co-Chair of Committee) J. R. Lupton (Member) J. D. Williams (Member) G. C. Smith (Head of Department) May 1987 1 1x ABSTRACT Assessment of Methodologies for Colorimetric Cholesterol Assay of Meats. (May 1987) Cynthia Kay Edwards...

  4. Chapter 4: Direct In-Gel Fluorescence Detection and Cellular Imaging of O-GlcNAc-Modified Proteins

    E-print Network

    Winfree, Erik

    Chapter 4: Direct In-Gel Fluorescence Detection and Cellular Imaging of O-GlcNAc-Modified Proteins for direct in-gel detection and mass spectrometric identification of O-GlcNAc proteins, identifying 146 novel fluorescence detection of O-GlcNAc proteins in gels would permit monitoring of changes in glycosylation levels

  5. Ionic Liquid-Based Fluorescein Colorimetric pH Nanosensors

    PubMed Central

    Das, Susmita; Magut, Paul K. S.; de Rooy, Sergio L.; Hasan, Farhana; Warner, Isiah M.

    2014-01-01

    A novel pH sensitive, colorimetric ionic liquid nanosensor based on phosphonium salts of fluorescein is reported. Herein, fluorescein salts of various stoichiometries were synthesized by use of a trihexyltetradecylphosphonium cation [TTP]+ in combination with dianionic [FL]2? and monoanionic [FL]? fluorescein. Nanomaterials derived from these two compounds yielded contrasting colorimetric responses in neutral and acidic environments. Variations in fluorescence spectra as a function of pH were also observed. Examination of TEM and DLS data revealed significant expansion in the diameter of [TTP]2[FL] nanodroplets in acidic environments of variable pHs. A similar trend was also observed for [TTP][FL] nanoparticles. The pH dependent colorimetric and other optical properties of these nanomaterials are attributed to alterations in molecular orientations and stacking as suggested by measuring the absorption, fluorescence, and zeta potential. Since the pH is an important indicator for many diseases, including cancer, these nanosensors are considered to be potential candidates for biomedical applications. PMID:25264488

  6. Simple Colorimetric Determination of the Manganese Content in Photosynthetic Membranes

    SciTech Connect

    Semin, B. K.; Seibert, M.

    2009-01-01

    The functional Mn content of intact photosystem II membrane fragments was measured as 4.06 {+-} 0.13 Mn/reaction center when determined using a simple, sensitive colorimetric assay that will also work with thylakoids and core complexes. This procedure requires minimal sample material, does not need expensive assay equipment, requires four simple steps, and only takes 20-30 min to perform. These include (a) removal of the adventitious Mn ions by CaCl{sub 2} treatment of the membranes, (b) extraction of the Mn from the O{sub 2}-evolving complex with hydrochloric acid, (c) purification of the extract by centrifugation followed by filtration of the supernatant through an Acrodisc syringe filter (0.2 {micro}m nylon membrane), and (d) colorimetric determination of Mn in the extract using the reaction of the chromogenic agent, 3,3',5,5'-tetramethylbenzidine, with previously oxidized Mn(II) cations carried out at high pH. The colorimetric assay itself has been used previously by Serrat (Mikrochim Acta 129:77-80, 1998) for assaying Mn concentrations in sea water and drinking water.

  7. Latent fingerprint and trace explosives detection by photoluminescence and time-resolved imaging

    NASA Astrophysics Data System (ADS)

    Bouldin, Kimberly Kay

    Latent fingerprint detection by photoluminescence is a well-developed field. Many development techniques exist and are currently being employed in forensic laboratories to detect fingerprints by making them luminescent. However, in forensic science, time-resolved imaging techniques, designed to suppress background fluorescence that interferes with fingerprint detectability, are to date not used outside of the research laboratory, and the chemistry necessary to use time-resolved imaging for fingerprint detection is somewhat limited. For this reason, the first section of this dissertation deals with fingerprint detection methods that have direct application to time-resolved imaging techniques. Trace explosive detection field methods based on chemical reactions have until recently utilized only colorimetric products. To increase the sensitivity of such detection, a field explosive test kit which produces a product that is both colorimetric and luminescent is studied. Detection sensitivity can be gained by taking advantage of the luminescence of these products, something that has not been done to date. When the appropriate chemistry is chosen for explosive detection, time-resolved imaging techniques may again be applicable. This dissertation thus looks at possibilities of taking trace explosives detection to this next level.

  8. Channeling in direct dark matter detection III: channeling fraction in CsI crystals

    NASA Astrophysics Data System (ADS)

    Bozorgnia, Nassim; Gelmini, Graciela B.; Gondolo, Paolo

    2010-11-01

    The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger signal scintillation or ionization than otherwise expected. We give estimates of the fraction of channeled recoiling ions in CsI crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects.

  9. Detection of Regions of Interest and Camouflage Breaking by Direct Convexity Ariel Tankus Yehezkel Yeshurun

    E-print Network

    Yeshurun, Hezy

    Detection of Regions of Interest and Camouflage Breaking by Direct Convexity Estimation Ariel camouflaged in noisy areas. An extensive comparison with edge-based attentional operators is delineated. 1, including camouflage which might delude a human viewer. The invariance and robustness fea- tures

  10. Direct Detection of Diverse Metabolic Changes in Virally Transformed and Tax-Expressing Cells by Mass

    E-print Network

    Vertes, Akos

    Direct Detection of Diverse Metabolic Changes in Virally Transformed and Tax-Expressing Cells Oncology, National Institutes of Health/National Cancer Institute, Bethesda, Maryland, United States in the proteome and the metabolome of the host. There is limited information on the broad metabolic changes

  11. A compact direct detection receiver for L-band STAR radiometry

    Microsoft Academic Search

    Line van Nieuwstadt; Roger De Roo; David Boprie; Ron Rizor; Peter Hansen; Anthony W. England; Hanh Pham; Boon Lim

    2003-01-01

    An L-band total power receiver for use in a synthetic thinned array radiometer (STAR) is described. The total power architecture of a radiometer receiver requires special considerations to control gain fluctuations due to small temperature drifts. The STAR application requires consistent passband and stable phase between receivers. The design presented incorporates direct detection to eliminate distributed local oscillators for phase

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

    E-print Network

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

    2014-09-23

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

  13. Automated DNA mutation detection using universal conditions direct sequencing: application to ten muscular dystrophy genes

    Microsoft Academic Search

    Richard R Bennett; Hal E Schneider; Elicia Estrella; Stephanie Burgess; Andrew S Cheng; Caitlin Barrett; Va Lip; Poh San Lai; Yiping Shen; Bai-Lin Wu; Basil T Darras; Alan H Beggs; Louis M Kunkel

    2009-01-01

    BACKGROUND: One of the most common and efficient methods for detecting mutations in genes is PCR amplification followed by direct sequencing. Until recently, the process of designing PCR assays has been to focus on individual assay parameters rather than concentrating on matching conditions for a set of assays. Primers for each individual assay were selected based on location and sequence

  14. Exonuclease enhances hybridization efficiency: Improved direct cycle sequencing and point mutation detection

    Microsoft Academic Search

    Veerle A. M. C Somers; Darcy A Leimbach; James J Murtagh; Frederik B. J. M Thunnissen

    1998-01-01

    Solution hybridization is an essential step in sequencing and some point mutation detection methods. In practice, this hybridization is hampered resulting in the need of additional purification of the amplification products. The use of T7 gene 6 exonuclease may lead to efficient production of single-stranded DNA. In this study, the effect of pretreatment with exonuclease on direct cycle sequencing and

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

    Microsoft Academic Search

    Alvarado Tarun; Julius Jecong; Caesar Saloma

    2005-01-01

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

  16. Experiment on operating methods of an electric wheelchair for a system of detecting position and direction

    Microsoft Academic Search

    Takashi Asakawa; Kazue Nishihara; Tadashi Yoshidome

    2007-01-01

    In this paper, we propose a voice-controlled electric wheelchair with a system for detecting the position and direction. Thus far, we have studied systems that incorporated voice instructions with our indoor navigation equipment using RF tags. An operating method which is different in order to clarify the problem of the operation method of an existing wheelchair was measured in the

  17. Direction of Arrival Detection System for Radio Surveillance: Frequency Spectrum Analysis of CDMA and Jamming Waves

    Microsoft Academic Search

    Koichi Ichiget; Mitsuharu Imai; Hiroyuki Arai; Masayuki Nakano; Masafumi Hirono

    2006-01-01

    This paper introduces DOA (direction of arrival) detection system of jamming waves used for radio surveillance of 900 MHz, featuring its function of frequency spectrum analysis to distinguish CDMA (code division multiple access) and jamming waves. There exist many jamming waves arising from illegal (non-licensed) repeating antennas or wireless cameras that seriously interfere to CDMA signals especially in urban districts.

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

    E-print Network

    Gelb, Michael

    Direct Assay of Enzymes in Heme Biosynthesis for the Detection of Porphyrias by Tandem Mass porphyria cutanea tarda and hereditary copro- porphyria, respectively. Electrospray ionization tandem mass, and em- ploy commercially available substrates and internal stan- dards. Porphyrias are a group of rare

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

    E-print Network

    Gelb, Michael

    Direct Assay of Enzymes in Heme Biosynthesis for the Detection of Porphyrias by Tandem Mass activity causes acute intermittent porphyria, the most common disorder of heme biosynthesis. The assay%) is significantly lower than the decrease due to acute intermittent porphyria (50%). Acute intermittent porphyria

  20. Ultrasensitive colorimetric carcinoembryonic antigen biosensor based on hyperbranched rolling circle amplification.

    PubMed

    Liang, Kai; Zhai, Shuiting; Zhang, Zhidong; Fu, Xiaoyang; Shao, Jingwei; Lin, Zhenyu; Qiu, Bin; Chen, Guo-nan

    2014-09-01

    In this study, a hyperbranched rolling circle amplification (HRCA)-based colorimetric biosensor for carcinoembryonic antigen (CEA) is developed with high sensitivity and specificity. A CEA aptamer can bind with its target (CEA) to form a complex due to their high affinity, and the introduced CDNA cannot hybridize with the aptamer. Thus, free CDNA can propagate the HRCA reaction to form a large number of single-stranded DNA (ss-DNA). ss-DNA can be easily adsorbed onto AuNPs and prevent salt-induced AuNPs aggregation, which causes the change in the color of the system. It is found that the absorbance intensity ratio (A520/A660) has a linear relationship with the concentration of the target in the range of 5 pM-0.5 nM, and the detection limit is as low as 2 pM (S/N = 3). PMID:24996292

  1. Colorimetric and Fluorescent Bimodal Ratiometric Probes for pH Sensing of Living Cells.

    PubMed

    Liu, Yuan-Yuan; Wu, Ming; Zhu, Li-Na; Feng, Xi-Zeng; Kong, De-Ming

    2015-06-01

    pH measurement is widely used in many fields. Ratiometric pH sensing is an important way to improve the detection accuracy. Herein, five water-soluble cationic porphyrin derivatives were synthesized and their optical property changes with pH value were investigated. Their pH-dependent assembly/disassembly behaviors caused significant changes in both absorption and fluorescence spectra, thus making them promising bimodal ratiometric probes for both colorimetric and fluorescent pH sensing. Different substituent identity and position confer these probes with different sensitive pH-sensing ranges, and the substituent position gives a larger effect. By selecting different porphyrins, different signal intensity ratios and different fluorescence excitation wavelengths, sensitive pH sensing can be achieved in the range of 2.1-8.0. Having demonstrated the excellent reversibility, good accuracy and low cytotoxicity of the probes, they were successfully applied in pH sensing inside living cells. PMID:25779219

  2. Laser desorption with corona discharge ion mobility spectrometry for direct surface detection of explosives.

    PubMed

    Sabo, M; Malásková, M; Matej?ík, S

    2014-10-21

    We present a new highly sensitive technique for the detection of explosives directly from the surface using laser desorption-corona discharge-ion mobility spectrometry (LD-CD-IMS). We have developed LD based on laser diode modules (LDM) and the technique was tested using three different LDM (445, 532 and 665 nm). The explosives were detected directly from the surface without any further preparation. We discuss the mechanism of the LD and the limitations of this technique such as desorption time, transport time and desorption area. After the evaluation of experimental data, we estimated the potential limits of detection of this method to be 0.6 pg for TNT, 2.8 pg for RDX and 8.4 pg for PETN. PMID:25118619

  3. Directional templates for real-time detection of coronal axis rotated faces

    NASA Astrophysics Data System (ADS)

    Perez, Claudio A.; Estevez, Pablo A.; Garate, Patricio

    2004-10-01

    Real-time face and iris detection on video images has gained renewed attention because of multiple possible applications in studying eye function, drowsiness detection, virtual keyboard interfaces, face recognition, video processing and multimedia retrieval. In this paper, a study is presented on using directional templates in the detection of faces rotated in the coronal axis. The templates are built by extracting the directional image information from the regions of the eyes, nose and mouth. The face position is determined by computing a line integral using the templates over the face directional image. The line integral reaches a maximum when it coincides with the face position. It is shown an improvement in localization selectivity by the increased value in the line integral computed with the directional template. Besides, improvements in the line integral value for face size and face rotation angle was also found through the computation of the line integral using the directional template. Based on these results the new templates should improve selectivity and hence provide the means to restrict computations to a fewer number of templates and restrict the region of search during the face and eye tracking procedure. The proposed method is real time, completely non invasive and was applied with no background limitation and normal illumination conditions in an indoor environment.

  4. A high-throughput, precipitating colorimetric sandwich ELISA microarray for Shiga toxins.

    PubMed

    Gehring, Andrew; He, Xiaohua; Fratamico, Pina; Lee, Joseph; Bagi, Lori; Brewster, Jeffrey; Paoli, George; He, Yiping; Xie, Yanping; Skinner, Craig; Barnett, Charlie; Harris, Douglas

    2014-06-01

    Shiga toxins 1 and 2 (Stx1 and Stx2) from Shiga toxin-producing E. coli (STEC) bacteria were simultaneously detected with a newly developed, high-throughput antibody microarray platform. The proteinaceous toxins were immobilized and sandwiched between biorecognition elements (monoclonal antibodies) and pooled horseradish peroxidase (HRP)-conjugated monoclonal antibodies. Following the reaction of HRP with the precipitating chromogenic substrate (metal enhanced 3,3-diaminobenzidine tetrahydrochloride or DAB), the formation of a colored product was quantitatively measured with an inexpensive flatbed page scanner. The colorimetric ELISA microarray was demonstrated to detect Stx1 and Stx2 at levels as low as ~4.5 ng/mL within ~2 h of total assay time with a narrow linear dynamic range of ~1-2 orders of magnitude and saturation levels well above background. Stx1 and/or Stx2 produced by various strains of STEC were also detected following the treatment of cultured cells with mitomycin C (a toxin-inducing antibiotic) and/or B-PER (a cell-disrupting, protein extraction reagent). Semi-quantitative detection of Shiga toxins was demonstrated to be sporadic among various STEC strains following incubation with mitomycin C; however, further reaction with B-PER generally resulted in the detection of or increased detection of Stx1, relative to Stx2, produced by STECs inoculated into either axenic broth culture or culture broth containing ground beef. PMID:24921195

  5. A High-Throughput, Precipitating Colorimetric Sandwich ELISA Microarray for Shiga Toxins

    PubMed Central

    Gehring, Andrew; He, Xiaohua; Fratamico, Pina; Lee, Joseph; Bagi, Lori; Brewster, Jeffrey; Paoli, George; He, Yiping; Xie, Yanping; Skinner, Craig; Barnett, Charlie; Harris, Douglas

    2014-01-01

    Shiga toxins 1 and 2 (Stx1 and Stx2) from Shiga toxin-producing E. coli (STEC) bacteria were simultaneously detected with a newly developed, high-throughput antibody microarray platform. The proteinaceous toxins were immobilized and sandwiched between biorecognition elements (monoclonal antibodies) and pooled horseradish peroxidase (HRP)-conjugated monoclonal antibodies. Following the reaction of HRP with the precipitating chromogenic substrate (metal enhanced 3,3-diaminobenzidine tetrahydrochloride or DAB), the formation of a colored product was quantitatively measured with an inexpensive flatbed page scanner. The colorimetric ELISA microarray was demonstrated to detect Stx1 and Stx2 at levels as low as ~4.5 ng/mL within ~2 h of total assay time with a narrow linear dynamic range of ~1–2 orders of magnitude and saturation levels well above background. Stx1 and/or Stx2 produced by various strains of STEC were also detected following the treatment of cultured cells with mitomycin C (a toxin-inducing antibiotic) and/or B-PER (a cell-disrupting, protein extraction reagent). Semi-quantitative detection of Shiga toxins was demonstrated to be sporadic among various STEC strains following incubation with mitomycin C; however, further reaction with B-PER generally resulted in the detection of or increased detection of Stx1, relative to Stx2, produced by STECs inoculated into either axenic broth culture or culture broth containing ground beef. PMID:24921195

  6. The AMIDAS Website: An Online Tool for Direct Dark Matter Detection Experiments

    E-print Network

    Chung-Lin Shan

    2009-09-08

    Following our long-term work on development of model-independent data analysis methods for reconstructing the one-dimensional velocity distribution function of halo WIMPs as well as for determining their mass and couplings on nucleons by using data from direct Dark Matter detection experiments directly, we combined the simulation programs to a compact system: AMIDAS (A Model-Independent Data Analysis System). For users' convenience an online system has also been established at the same time. AMIDAS has the ability to do full Monte Carlo simulations, faster theoretical estimations, as well as to analyze (real) data sets recorded in direct detection experiments without modifying the source code. In this article, I give an overview of functions of the AMIDAS code based on the use of its website.

  7. Impedimetric immunosensor for human serum albumin detection on a direct aldehyde-functionalized silicon nitride surface.

    PubMed

    Caballero, David; Martinez, Elena; Bausells, Joan; Errachid, Abdelhamid; Samitier, Josep

    2012-03-30

    In this work we report the fabrication and characterization of a label-free impedimetric immunosensor based on a silicon nitride (Si(3)N(4)) surface for the specific detection of human serum albumin (HSA) proteins. Silicon nitride provides several advantages compared with other materials commonly used, such as gold, and in particular in solid-state physics for electronic-based biosensors. However, few Si(3)N(4)-based biosensors have been developed; the lack of an efficient and direct protocol for the integration of biological elements with silicon-based substrates is still one of its the main drawbacks. Here, we use a direct functionalization method for the direct covalent binding of monoclonal anti-HSA antibodies on an aldehyde-functionalized Si-p/SiO(2)/Si(3)N(4) structure. This methodology, in contrast with most of the protocols reported in literature, requires less chemical reagents, it is less time-consuming and it does not need any chemical activation. The detection capability of the immunosensor was tested by performing non-faradaic electrochemical impedance spectroscopy (EIS) measurements for the specific detection of HSA proteins. Protein concentrations within the linear range of 10(-13)-10(-7) M were detected, showing a sensitivity of 0.128 ? ?M(-1) and a limit of detection of 10(-14) M. The specificity of the sensor was also addressed by studying the interferences with a similar protein, bovine serum albumin. The results obtained show that the antibodies were efficiently immobilized and the proteins detected specifically, thus, establishing the basis and the potential applicability of the developed silicon nitride-based immunosensor for the detection of proteins in real and more complex samples. PMID:22365119

  8. Rapid quantification of microalgal lipids in aqueous medium by a simple colorimetric method.

    PubMed

    Mishra, Sanjiv K; Suh, William I; Farooq, Wasif; Moon, Myounghoon; Shrivastav, Anupama; Park, Min S; Yang, Ji-Won

    2014-03-01

    Identification of novel microalgal strains with high lipid productivity is one of the most important research topics in renewable biofuel research. However, the major bottleneck in the strain screening process is that currently known methods for the estimation of microalgal lipid are laborious and time-consuming. The present study successfully employed sulpho-phospho-vanillin (SPV) colorimetric method for direct quantitative measurement of lipids within liquid microalgal culture. The SPV reacts with lipids to produce a distinct pink color, and its intensity can be quantified using spectrophotometric methods by measuring absorbance at 530nm. This method was employed for a rapid quantification of intracellular lipid contents within Chlorella sp., Monoraphidium sp., Ettlia sp. and Nannochloropsis sp., all of which were found to have lipid contents ranging in between 10% and 30%. Subsequent analysis of the biomass using gas chromatography confirmed that our protocol is highly accurate (R(2)=0.99). PMID:24463407

  9. Electrical percolation-based biosensor for real-time direct detection of staphylococcal enterotoxin B (SEB).

    PubMed

    Yang, Minghui; Sun, Steven; Bruck, Hugh Alan; Kostov, Yordan; Rasooly, Avraham

    2010-08-15

    Electrical percolation-based biosensing is a new technology. This is the first report of an electrical percolation-based biosensor for real-time detection. The label-free biosensor is based on electrical percolation through a single-walled carbon nanotubes (SWNTs)-antibody complex that forms a network functioning as a "Biological Semiconductor" (BSC). The conductivity of a BSC is directly related to the number of contacts facilitated by the antibody-antigen "connectors" within the SWNT network. BSCs are fabricated by immobilizing a pre-functionalized SWNTs-antibody complex directly on a poly(methyl methacrylate) (PMMA) and polycarbonate (PC) surface. Each BSC is connected via silver electrodes to a computerized ohmmeter, thereby enabling a continuous electronic measurement of molecular interactions (e.g. antibody-antigen binding) via the change in resistance. Using anti-staphylococcal enterotoxin B (SEB) IgG to functionalize the BSC, we demonstrate that the biosensor was able to detect SEB at concentrations as low as 5 ng/mL at a signal to baseline (S/B) ratio of 2. Such measurements were performed on the chip in wet conditions. The actuation of the chip by SEB is immediate, permitting real-time signal measurements. In addition to this "direct" label-free detection mode, a secondary antibody can be used to "label" the target molecule bound to the BSC in a manner analogous to an immunological sandwich "indirect" detection-type assay. Although a secondary antibody is not needed for direct detection, the indirect mode of detection may be useful as an additional measurement to verify or amplify signals from direct detection in clinical, food safety and other critical assays. The BSC was used to measure SEB both in buffer and in milk, a complex matrix, demonstrating the potential of electrical percolation-based biosensors for real-time label-free multi-analyte detection in clinical and complex samples. Assembly of BSCs is simple enough that multiple sensors can be fabricated on the same chip, thereby creating "Biological Central Processing Units (BCPUs)" capable of parallel processing and sorting out information on multiple analytes simultaneously which may be used for complex analysis and for point of care diagnostics. PMID:20447819

  10. Impact of dark matter microhalos on signatures for direct and indirect detection

    NASA Astrophysics Data System (ADS)

    Schneider, Aurel; Krauss, Lawrence; Moore, Ben

    2010-09-01

    Detecting dark matter as it streams through detectors on Earth relies on knowledge of its phase space density on a scale comparable to the size of our Solar System. Numerical simulations predict that our galactic halo contains an enormous hierarchy of substructures, streams and caustics, the remnants of the merging hierarchy that began with tiny Earth-mass microhalos. If these bound or coherent structures persist until the present time, they could dramatically alter signatures for the detection of weakly interacting elementary particle dark matter. Using numerical simulations that follow the coarse grained tidal disruption within the Galactic potential and fine grained heating from stellar encounters, we find that microhalos, streams, and caustics have a negligible likelihood of impacting direct detection signatures implying that dark matter constraints derived using simple smooth halo models are relatively robust. We also find that many dense central cusps survive, yielding a small enhancement in the signal for indirect detection experiments.

  11. Impact of dark matter microhalos on signatures for direct and indirect detection

    SciTech Connect

    Schneider, Aurel; Moore, Ben [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); Krauss, Lawrence [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); School of Earth and Space Exploration and Department of Physics, Arizona State University, PO Box 871404, Tempe, Arizona 85287 (United States)

    2010-09-15

    Detecting dark matter as it streams through detectors on Earth relies on knowledge of its phase space density on a scale comparable to the size of our Solar System. Numerical simulations predict that our galactic halo contains an enormous hierarchy of substructures, streams and caustics, the remnants of the merging hierarchy that began with tiny Earth-mass microhalos. If these bound or coherent structures persist until the present time, they could dramatically alter signatures for the detection of weakly interacting elementary particle dark matter. Using numerical simulations that follow the coarse grained tidal disruption within the Galactic potential and fine grained heating from stellar encounters, we find that microhalos, streams, and caustics have a negligible likelihood of impacting direct detection signatures implying that dark matter constraints derived using simple smooth halo models are relatively robust. We also find that many dense central cusps survive, yielding a small enhancement in the signal for indirect detection experiments.

  12. Using a large area CMOS APS for direct chemiluminescence detection in Western blotting electrophoresis

    NASA Astrophysics Data System (ADS)

    Esposito, Michela; Newcombe, Jane; Anaxagoras, Thalis; Allinson, Nigel M.; Wells, Kevin

    2012-03-01

    Western blotting electrophoretic sequencing is an analytical technique widely used in Functional Proteomics to detect, recognize and quantify specific labelled proteins in biological samples. A commonly used label for western blotting is Enhanced ChemiLuminescence (ECL) reagents based on fluorescent light emission of Luminol at 425nm. Film emulsion is the conventional detection medium, but is characterized by non-linear response and limited dynamic range. Several western blotting digital imaging systems have being developed, mainly based on the use of cooled Charge Coupled Devices (CCDs) and single avalanche diodes that address these issues. Even so these systems present key drawbacks, such as a low frame rate and require operation at low temperature. Direct optical detection using Complementary Metal Oxide Semiconductor (CMOS) Active Pixel Sensors (APS)could represent a suitable digital alternative for this application. In this paper the authors demonstrate the viability of direct chemiluminescent light detection in western blotting electrophoresis using a CMOS APS at room temperature. Furthermore, in recent years, improvements in fabrication techniques have made available reliable processes for very large imagers, which can be now scaled up to wafer size, allowing direct contact imaging of full size western blotting samples. We propose using a novel wafer scale APS (12.8 cm×13.2 cm), with an array architecture using two different pixel geometries that can deliver an inherently low noise and high dynamic range image at the same time representing a dramatic improvement with respect to the current western blotting imaging systems.

  13. Cu(I)-MOF: naked-eye colorimetric sensor for humidity and formaldehyde in single-crystal-to-single-crystal fashion.

    PubMed

    Yu, Yang; Zhang, Xiao-Meng; Ma, Jian-Ping; Liu, Qi-Kui; Wang, Peng; Dong, Yu-Bin

    2014-02-11

    A porous Cu(I)-MOF was constructed from CuI and 1-benzimidazolyl-3,5-bis(4-pyridyl)benzene. This Cu(I)-MOF can be a highly sensitive naked-eye colorimetric sensor to successively detect water and formaldehyde species in a single-crystal-to-single-crystal fashion. Solid-state guest-responsive luminescence is also used to monitor the sensing process. PMID:24352589

  14. Novel salicylic acid-oriented thiourea-type receptors as colorimetric chemosensor: Synthesis, characterizations and selective naked-eye recognition properties

    NASA Astrophysics Data System (ADS)

    Li, Shaowei; Cao, Xiufang; Chen, Changshui; Ke, Shaoyong

    2012-10-01

    Based on the salicylic acid backbone, three highly sensitive and selective colorimetric chemosensors with an acylthiourea binding unit have been designed, synthesized and characterized. These chemosensors have been utilized for selective recognition of fluoride anions in dry DMSO solution by typical spectroscopic titration techniques. Furthermore, the obtained chemosensors AR1-3 have shown naked-eye sensitivity for detection of biologically important fluoride ion over other anions in solution.

  15. Direct detection of Marek's disease virus in poultry dust by loop-mediated isothermal amplification.

    PubMed

    Wo?niakowski, Grzegorz; Samorek-Salamonowicz, El?bieta

    2014-11-01

    Marek's disease virus (MDV) is a serious concern for poultry production and represents a unique herpesvirus model. MDV can be shed by doubly infected chickens despite vaccination. The fully infectious MDV particles are produced in the feather follicle epithelium (FFE), and MDV remains infectious for many months in fine skin particles and feather debris. Molecular biology methods including PCR and real-time PCR have been shown to be valuable for the detection of MDV DNA in farm dust. Recently, loop-mediated isothermal amplification (LAMP) was found to be useful in the detection of MDV in feathers and internal organs of infected chickens. LAMP is also less affected by the inhibitors present in DNA samples. Taking into account the advantages of LAMP, direct detection of MDV DNA in poultry dust has been conducted in this research. The detection of MDV DNA was possible in 11 out of the 12 examined dust samples without DNA extraction. The DNA was retrieved from dust samples by dilution and incubation at 95 °C for 5 min. The direct detection of MDV DNA in the dust was possible within 30 min using a water bath and UV light. The results were confirmed by electrophoresis and melting curve analysis of the LAMP products. Our results show that LAMP may be used to test for the presence of virulent MDV in poultry farm dust without DNA extraction. PMID:24986718

  16. A novel chemical detector using colorimetric sensor array and pattern recognition methods for the concentration analysis of NH3

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-gang; Liu, Ping; Hou, Chang-jun; Huo, Dan-qun; Dong, Jia-le; Fa, Huan-bao; Yang, Mei

    2010-10-01

    With a colorimetric sensor array comprising chemoresponsive dyes, a simple, rapid, and cost-effective integrated system for differentiating low-concentration gases was described. The system could be used to identify gases by detecting the color change information of the chemoresponsive dyes based on porphyrins before and after reaction with the target gas; the colorimetric sensor array images were collected by a charge coupled device and processed with image analysis to get the color changes of the dyes in the array. Temperature, humidity, and flux of the chamber could be detected and displayed on the personal computer screen. A low-concentration [30-210 ppb (parts per 109)] NH3 was detected by the system. This prototype successfully differentiated four concentration levels of NH3 in less than 1 min. Pattern recognition methods, such as the backpropagation neural network and the radial basis function neural network, validated the effect of the developed sensor system both with 100% classification with feature vectors at single time point as inputs.

  17. A novel chemical detector using colorimetric sensor array and pattern recognition methods for the concentration analysis of NH3.

    PubMed

    Luo, Xiao-gang; Liu, Ping; Hou, Chang-jun; Huo, Dan-qun; Dong, Jia-le; Fa, Huan-bao; Yang, Mei

    2010-10-01

    With a colorimetric sensor array comprising chemoresponsive dyes, a simple, rapid, and cost-effective integrated system for differentiating low-concentration gases was described. The system could be used to identify gases by detecting the color change information of the chemoresponsive dyes based on porphyrins before and after reaction with the target gas; the colorimetric sensor array images were collected by a charge coupled device and processed with image analysis to get the color changes of the dyes in the array. Temperature, humidity, and flux of the chamber could be detected and displayed on the personal computer screen. A low-concentration [30-210 ppb (parts per 10(9))] NH(3) was detected by the system. This prototype successfully differentiated four concentration levels of NH(3) in less than 1 min. Pattern recognition methods, such as the backpropagation neural network and the radial basis function neural network, validated the effect of the developed sensor system both with 100% classification with feature vectors at single time point as inputs. PMID:21034125

  18. Reduced electrical bandwidth receivers for direct detection 4-ary PPM optical communication intersatellite links

    NASA Technical Reports Server (NTRS)

    Davidson, Frederic M.; Sun, Xiaoli

    1993-01-01

    One of the major sources of noise in a direct detection optical communication receiver is the shot noise due to the quantum nature of the photodetector. The shot noise is signal dependent and is neither Gaussian nor wide sense stationary. When a photomultiplier tube (PMT) or an avalanche photodiode (APD) is used, there is also a multiplicative excess noise due to the randomness of the internal photodetector gain. Generally speaking, the radio frequency (RF) communication theory cannot be applied to direct detection optical communication systems because noise in RF communication systems is usually additive and Gaussian. A receiver structure which is mathematically optimal for signal dependent shot noise is derived. Several suboptimal receiver structures are discussed and compared with the optimal receiver. The objective is to find a receiver structure which is easy to implement and gives close to optimal performance.

  19. Prospects for direct detection of the circular polarization of the gravitational-wave background.

    PubMed

    Seto, Naoki

    2006-10-13

    We discuss the prospects for directly detecting a circular polarization signal of the gravitational-wave background. We find it is generally difficult to probe the monopole mode of the signal due to the broad directivity of the gravitational-wave detectors. But the dipole (l=1) and octupole (l=3) modes of the signal can be measured in a simple manner by combining outputs of two unaligned detectors, and we can dig them deeply under confusion and detector noises. Around f approximately 0.1 mHz the Laser Interferometer Space Antenna will provide ideal data streams to detect these patterns whose magnitudes are as small as approximately 1 percent of the detector noise level in terms of the nondimensional energy density OmegaGW(f). PMID:17155312

  20. First direct detection limits on sub-GeV dark matter from XENON10.

    PubMed

    Essig, Rouven; Manalaysay, Aaron; Mardon, Jeremy; Sorensen, Peter; Volansky, Tomer

    2012-07-13

    The first direct detection limits on dark matter in the MeV to GeV mass range are presented, using XENON10 data. Such light dark matter can scatter with electrons, causing ionization of atoms in a detector target material and leading to single- or few-electron events. We use 15??kg?day of data acquired in 2006 to set limits on the dark-matter-electron scattering cross section. The strongest bound is obtained at 100 MeV where ?(e)<3×10(-38)??cm2 at 90% C.L., while dark-matter masses between 20 MeV and 1 GeV are bounded by ?(e)<10(-37)??cm2 at 90% C.L. This analysis provides a first proof of principle that direct detection experiments can be sensitive to dark-matter candidates with masses well below the GeV scale. PMID:23030151

  1. First Direct Detection Limits on sub-GeV Dark Matter from XENON10

    E-print Network

    Rouven Essig; Aaron Manalaysay; Jeremy Mardon; Peter Sorensen; Tomer Volansky

    2012-06-12

    The first direct detection limits on dark matter in the MeV to GeV mass range are presented, using XENON10 data. Such light dark matter can scatter with electrons, causing ionization of atoms in a detector target material and leading to single- or few-electron events. We use 15 kg-days of data acquired in 2006 to set limits on the dark-matter-electron scattering cross section. The strongest bound is obtained at 100 MeV where sigma_e < 3 x 10^{-38} cm^2 at 90% CL, while dark matter masses between 20 MeV and 1 GeV are bounded by sigma_e < 10^{-37} cm^2 at 90% CL. This analysis provides a first proof-of-principle that direct detection experiments can be sensitive to dark matter candidates with masses well below the GeV scale.

  2. First Direct Detection Limits on sub-GeV Dark Matter from XENON10

    E-print Network

    Essig, Rouven; Mardon, Jeremy; Sorensen, Peter; Volansky, Tomer

    2012-01-01

    The first direct detection limits on dark matter in the MeV to GeV mass range are presented, using XENON10 data. Such light dark matter can scatter with electrons, causing ionization of atoms in a detector target material and leading to single- or few-electron events. We use 15 kg-days of data acquired in 2006 to set limits on the dark-matter-electron scattering cross section. The strongest bound is obtained at 100 MeV where sigma_e < 3 x 10^{-38} cm^2 at 90% CL, while dark matter masses between 20 MeV and 1 GeV are bounded by sigma_e < 10^{-37} cm^2 at 90% CL. This analysis provides a first proof-of-principle that direct detection experiments can be sensitive to dark matter candidates with masses well below the GeV scale.

  3. Colorless ONU implementation for WDM-PON using direct-detection optical OFDM

    NASA Astrophysics Data System (ADS)

    Feng, Min; Luo, Qing-long; Bai, Cheng-lin

    2013-03-01

    A novel architecture for the colorless optical network unit (ONU) is proposed and experimentally demonstrated with direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM). In this architecture, polarization-division multiplexing is used to reduce the cost at ONU. In optical line terminal (OLT), quadrature amplitude modulation (QAM) intensity-modulated OFDM signal with x-polarization at 10 Gbit/s is transmitted as downstream. At each ONU, the optical OFDM signal is demodulated with direct detection, and ?-polarization signal is modulated for upstream on-off keying (OOK) data at 5 Gbit/s. Simulation results show that the power penalty is negligible for both optical OFDM downstream and the on-off keying upstream signals after over 50 km single-mode fiber (SMF) transmission.

  4. Modeling the Performance of Direct-Detection Doppler Lidar Systems in Real Atmospheres

    NASA Technical Reports Server (NTRS)

    McGill, Matthew J.; Hart, William D.; McKay, Jack A.; Spinhirne, James D.

    1999-01-01

    Previous modeling of the performance of spaceborne direct-detection Doppler lidar systems has assumed extremely idealized atmospheric models. Here we develop a technique for modeling the performance of these systems in a more realistic atmosphere, based on actual airborne lidar observations. The resulting atmospheric model contains cloud and aerosol variability that is absent in other simulations of spaceborne Doppler lidar instruments. To produce a realistic simulation of daytime performance, we include solar radiance values that are based on actual measurements and are allowed to vary as the viewing scene changes. Simulations are performed for two types of direct-detection Doppler lidar systems: the double-edge and the multi-channel techniques. Both systems were optimized to measure winds from Rayleigh backscatter at 355 nm. Simulations show that the measurement uncertainty during daytime is degraded by only about 10-20% compared to nighttime performance, provided a proper solar filter is included in the instrument design.

  5. Prospects for Direct Detection of the Circular Polarization of the Gravitational-Wave Background

    NASA Astrophysics Data System (ADS)

    Seto, Naoki

    2006-10-01

    We discuss the prospects for directly detecting a circular polarization signal of the gravitational-wave background. We find it is generally difficult to probe the monopole mode of the signal due to the broad directivity of the gravitational-wave detectors. But the dipole (l=1) and octupole (l=3) modes of the signal can be measured in a simple manner by combining outputs of two unaligned detectors, and we can dig them deeply under confusion and detector noises. Around f˜0.1mHz the Laser Interferometer Space Antenna will provide ideal data streams to detect these patterns whose magnitudes are as small as ˜1 percent of the detector noise level in terms of the nondimensional energy density ?GW(f).

  6. Prospects for direct detection of circular polarization of gravitational-wave background

    E-print Network

    Naoki Seto

    2006-09-18

    We discussed prospects for directly detecting circular polarization signal of gravitational wave background. We found it is generally difficult to probe the monopole mode of the signal due to broad directivity of gravitational wave detectors. But the dipole (l=1) and octupole (l=3) modes of the signal can be measured in a simple manner by combining outputs of two unaligned detectors, and we can dig them deeply under confusion and detector noises. Around f~0.1mHz LISA will provide ideal data streams to detect these anisotropic components whose magnitudes are as small as ~1 percent of the detector noise level in terms of the non-dimensional energy density \\Omega_{GW}(f).

  7. Directed Design of Experiments for Validating Probability of Detection Capability of NDE Systems (DOEPOD)

    NASA Technical Reports Server (NTRS)

    Generazio, Edward R.

    2008-01-01

    The capability of an inspection system is established by applications of various methodologies to determine the probability of detection (POD). One accepted metric of an adequate inspection system is that there is 95% confidence that the POD is greater than 90% (90/95 POD). Directed design of experiments for probability of detection (DOEPOD) has been developed to provide an efficient and accurate methodology that yields observed POD and confidence bounds for both Hit- Miss or signal amplitude testing. Specifically, DOEPOD demands utilization of observance of occurrences. Directed DOEPOD does not assume prescribed POD logarithmic or similar functions with assumed adequacy over a wide range of flaw sizes and inspection system technologies, so that multi-parameter curve fitting or model optimization approaches to generate a POD curve are not required.

  8. Detection of human cytomegalovirus DNA: how, when and where?

    PubMed

    Gerna, G; Baldanti, F; Zella, D; Furione, M

    1995-01-01

    Although several methods have been utilized for the detection and quantification of human cytomegalovirus (HCMV) DNA, all of them can be divided into three groups: (i) detection of HCMV DNA directly in tissues by in situ hybridization or in situ polymerase chain reaction (PCR); (ii) detection of HCMV DNA in cell or tissue lysates by hybridization with DNA or RNA probes differently labelled-labels were progressively modified in order to provide an increasing sensitivity (hybridization products were revealed by radioactive, colorimetric or chemiluminescent procedures); (iii) detection of HCMV DNA in cell or tissue lysates by qualitative (single-step and nested) and quantitative (semiquantitative, competitive or noncompetitive) PCR. The selection of the methods to be employed depends primarily on the clinical situation which must be evaluated. Clinical samples for HCMV genome detection must vary accordingly. PMID:8668932

  9. Colorimetric Method for the Estimation of Total Limonoid Aglycones and Glucoside Contents in Citrus Juices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method for estimating the total limonoid aglycone and glucoside concentrations in Citrus samples in terms of limonin and limonin glucoside equivalents is presented. The method consists of extraction followed by colorimetric quantification. The colorimetric quantification was based on the formatio...

  10. Fetal head detection and measurement in ultrasound images by a direct inverse randomized Hough transform

    NASA Astrophysics Data System (ADS)

    Lu, Wei; Tan, Jinglu; Floyd, Randall C.

    2005-04-01

    Object detection in ultrasound fetal images is a challenging task for the relatively low resolution and low signal-to-noise ratio. A direct inverse randomized Hough transform (DIRHT) is developed for filtering and detecting incomplete curves in images with strong noise. The DIRHT combines the advantages of both the inverse and the randomized Hough transforms. In the reverse image, curves are highlighted while a large number of unrelated pixels are removed, demonstrating a "curve-pass filtering" effect. Curves are detected by iteratively applying the DIRHT to the filtered image. The DIRHT was applied to head detection and measurement of the biparietal diameter (BPD) and head circumference (HC). No user input or geometric properties of the head were required for the detection. The detection and measurement took 2 seconds for each image on a PC. The inter-run variations and the differences between the automatic measurements and sonographers" manual measurements were small compared with published inter-observer variations. The results demonstrated that the automatic measurements were consistent and accurate. This method provides a valuable tool for fetal examinations.

  11. Commercial Systems for the Direct Detection of Explosives for Explosive Ordnance Disposal Tasks

    Microsoft Academic Search

    Claudio Bruschini

    2001-01-01

    There are a number of Explosive Ordnance Disposal (EOD) tasks in which it is necessary to discriminate and identify UneXploded Ordnance (UXO) already detected by other means. What we seek is the capacity to characterize in a non-destructive way the munition's content, usually either explosive or inert (e.g., practice munition), if possible using a fairly mobile system and without direct

  12. Direct-detection polarization division multiplexed orthogonal frequency-division multiplexing transmission systems without polarization tracking.

    PubMed

    Wang, Chih-Yun; Wei, Chia-Chien; Lin, Chun-Ting; Chi, Sien

    2012-12-15

    We experimentally demonstrate a direct-detection polarization division multiplexed (PDM) orthogonal frequency-division multiplexing (OFDM) scheme without dynamic polarization tracking. Simply using a polarization-diverse receiver, the proposed multiple-input multiple-output assisted system can achieve bit-error rate of 10(-) over all possible received states of polarization. Moreover, 50 Gbps PDM-OFDM transmission over 100 km single-mode fiber is successfully demonstrated without dispersion-induced penalty. PMID:23258008

  13. Halo-Independent analysis of direct dark matter detection data for any WIMP interaction

    E-print Network

    Graciela B. Gelmini

    2014-11-04

    The halo independent comparison of direct dark matter detection data eliminates the need to make any assumption on the uncertain local dark matter distribution and is complementary to the usual data comparison which required assuming a dark halo model for our galaxy. The method, initially proposed for WIMPs with spin-independent contact interactions, has been generalized to any other interaction and applied to recent data on "Light WIMPs".

  14. Direct mecA Detection from Blood Culture Bottles by Branched-DNA Signal Amplification

    Microsoft Academic Search

    X. ZHENG; C. P. KOLBERT; P. VARGA-DELMORE; J. ARRUDA; M. LEWIS; J. KOLBERG; F. R. COCKERILL; D. H. PERSING; Bayer Diagnostics

    1999-01-01

    A branched-DNA (bDNA) signal amplification method was used to detect the mecA gene directly from blood culture broth growing staphylococci. BACTEC blood culture bottles with positive growth indices and contain- ing staphylococcus-like organisms as shown by Gram stain were tested for the presence of the mecA gene. Comparison of test results was done among 225 patients (one blood culture from

  15. Electrical percolation-based biosensor for real-time direct detection of staphylococcal enterotoxin B (SEB)

    Microsoft Academic Search

    Minghui Yang; Steven Sun; Hugh Alan Bruck; Yordan Kostov; Avraham Rasooly

    2010-01-01

    Electrical percolation-based biosensing is a new technology. This is the first report of an electrical percolation-based biosensor for real-time detection. The label-free biosensor is based on electrical percolation through a single-walled carbon nanotubes (SWNTs)–antibody complex that forms a network functioning as a “Biological Semiconductor” (BSC). The conductivity of a BSC is directly related to the number of contacts facilitated by

  16. Performance analysis of direct-detection optical CDMA communication systems with avalanche photodiodes

    Microsoft Academic Search

    Alex W. Lam; Awais M. Hussain

    1992-01-01

    Direct-detection optical code-division multiple-access (CDMA) communication systems with avalanche photodiode (APD) photodetectors are investigated. A Chernoff upper bound, modified Chernoff upper bound, and Gaussian approximation on the probability of bit error are presented for general APDs and arbitrary {0,1}-valued optical signature sequences. Multiple-user interference, shot-noise, and receiver thermal noise effects on the bit error probability are studied in detail. One-coincidence

  17. Probing WIMP particle physics and astrophysics with direct detection and neutrino telescope data

    NASA Astrophysics Data System (ADS)

    Kavanagh, Bradley J.; Fornasa, Mattia; Green, Anne M.

    2015-05-01

    With positive signals from multiple direct detection experiments, it will, in principle, be possible to measure the mass and cross sections of weakly interacting massive particle (WIMP) dark matter. Recent work has shown that, with a polynomial parametrization of the WIMP speed distribution, it is possible to make an unbiased measurement of the WIMP mass, without making any astrophysical assumptions. However, direct detection experiments are not sensitive to low-speed WIMPs and, therefore, any model-independent approach will lead to a bias in the cross section. This problem can be solved with the addition of measurements of the flux of neutrinos from the Sun. This is because the flux of neutrinos produced from the annihilation of WIMPs which have been gravitationally captured in the Sun is sensitive to low-speed WIMPs. Using mock data from next-generation direct detection experiments and from the IceCube neutrino telescope, we show that the complementary information from IceCube on low-speed WIMPs breaks the degeneracy between the cross section and the speed distribution. This allows unbiased determinations of the WIMP mass and spin-independent and spin-dependent cross sections to be made, and the speed distribution to be reconstructed. We use two parametrizations of the speed distribution: binned and polynomial. While the polynomial parametrization can encompass a wider range of speed distributions, this leads to larger uncertainties in the particle physics parameters.

  18. Predicting direction detection thresholds for arbitrary translational acceleration profiles in the horizontal plane

    PubMed Central

    Soyka, Florian; Robuffo Giordano, Paolo; Beykirch, Karl

    2011-01-01

    In previous research, direction detection thresholds have been measured and successfully modeled by exposing participants to sinusoidal acceleration profiles of different durations. In this paper, we present measurements that reveal differences in thresholds depending not only on the duration of the profile, but also on the actual time course of the acceleration. The measurements are further explained by a model based on a transfer function, which is able to predict direction detection thresholds for all types of acceleration profiles. In order to quantify a participant’s ability to detect the direction of motion in the horizontal plane, a four-alternative forced-choice task was implemented. Three types of acceleration profiles (sinusoidal, trapezoidal and triangular) were tested for three different durations (1.5, 2.36 and 5.86 s). To the best of our knowledge, this is the first study which varies both quantities (profile and duration) in a systematic way within a single experiment. The lowest thresholds were found for trapezoidal profiles and the highest for triangular profiles. Simulations for frequencies lower than the ones actually measured predict a change from this behavior: Sinusoidal profiles are predicted to yield the highest thresholds at low frequencies. This qualitative prediction is only possible with a model that is able to predict thresholds for different types of acceleration profiles. Our modeling approach represents an important advancement, because it allows for a more general and accurate description of perceptual thresholds for simple and complex translational motions. PMID:21234751

  19. A theoretical look at the direct detection of giant planets outside the Solar System

    NASA Astrophysics Data System (ADS)

    Burrows, Adam

    2005-01-01

    Astronomy is at times a science of unexpected discovery. When it is, and if we are lucky, new intellectual territories emerge to challenge our views of the cosmos. The recent indirect detections using high-precision Doppler spectroscopy of more than 100 giant planets orbiting more than 100 nearby stars is an example of such rare serendipity. What has been learned has shaken out preconceptions, for none of the planetary systems discovered so far is like our own. The key to unlocking a planet's chemical, structural, and evolutionary secrets, however, is the direct detection of the planet's light. Because there have been as yet no confirmed detections, a theoretical analysis of such a planet's atmosphere is necessary for guiding our search.

  20. Direct detection of Theileria annulata in bovine blood samples using standard and isothermal DNA amplification approaches.

    PubMed

    Gomes, Jacinto; Inácio, João

    2015-01-01

    Tropical theileriosis is a tick-borne disease responsible for important health problems in cattle, caused by the hemoprotozoan Theileria annulata. Traditionally, detection of Theileria pathogens in infected animals requires the microscopic examination of stained-blood smears and serological methods. Molecular diagnostic assays have been developed for the detection of Theileria parasites, including PCR-based and reverse line blotting approaches, but these methods usually demand qualified personnel, complex instrumentation, and expensive materials. Loop-mediated isothermal amplification (LAMP) can facilitate the design of molecular assays independent of the use of sophisticated equipment. In this chapter we describe the application of two molecular assays for the direct detection of T. annulata in bovine blood samples, based in real-time PCR and LAMP, both targeting the Tams1-encoding gene of this parasite. PMID:25399096

  1. Evaluation of a colorimetric reagent strip assay for urine specific gravity.

    PubMed

    Kirschbaum, B B

    1983-06-01

    N-Multistix SG provides a convenient colorimetric assay for the determination of the specific gravity (sp. gr.) of freshly voided urine. When compared with results obtained by standard hydrometry, the colorimetric assay sp. gr. was observed to decrease by as much as 0.010 units as urine pH increased from 5 to 7. Moderate levels of proteinuria that did not alter hydrometer readings effectively raised the colorimetric sp. gr. by 0.005-0.010 units. The colorimetric assay was almost completely insensitive to clinically encountered concentrations of glucose and urea but responded appropriately to monovalent salts. The magnitude of these observed discrepancies places serious limitations on the value of the colorimetric sp. gr. measurement. PMID:6846262

  2. Detection of short tandem repeat polymorphisms from human nails using direct polymerase chain reaction method.

    PubMed

    Tie, Jian; Uchigasaki, Seisaku

    2014-11-01

    Human nail is an important forensic material for parental testing and individual identification in large-scale disasters. Detection of STR polymorphism from hard tissues generally requires DNA purification, which is technically complicated and time consuming. In the present study, we attempted to detect STR polymorphisms from untreated human nail samples by direct PCR amplification method using the primer mixture supplied with the GenePrint® SilverSTR® III System or the AmpF?STR® Identifiler® PCR Amplification Kit, and Tks Gflex DNA polymerase known to be effective for amplification from crude samples. A nail fragment measuring approximately 1.5 mm in breadth and 0.5 mm in length was placed directly into a PCR tube, and various PCR conditions were tested. The PCR products were analyzed by denaturing acrylamide gel electrophoresis or CE. Multiple STR polymorphisms were detected successfully. This method that detects STR polymorphisms not only from fresh human fingernails, but also from old nail fragments stored at room temperature for up to 10 years is expected to become a novel DNA analytical method in forensic medicine and genetic studies. PMID:24934775

  3. Chemical Methods for the Direct Detection and Labeling of S-Nitrosothiols

    PubMed Central

    Bechtold, Erika

    2012-01-01

    Abstract Significance: Posttranslational modification of proteins through phosphorylation, glycosylation, and oxidation adds complexity to the proteome by reversibly altering the structure and function of target proteins in a highly controlled fashion. Recent Advances: The study of reversible cysteine oxidation highlights a role for this oxidative modification in complex signal transduction pathways. Nitric oxide (NO), and its respective metabolites (including reactive nitrogen species), participates in a variety of these cellular redox processes, including the reversible oxidation of cysteine to S-nitrosothiols (RSNOs). RSNOs act as endogenous transporters of NO, but also possess beneficial effects independent of NO-related signaling, which suggests a complex and versatile biological role. In this review, we highlight the importance of RSNOs as a required posttranslational modification and summarize the current methods available for detecting S-nitrosation. Critical Issues: Given the limitations of these indirect detection methods, the review covers recent developments toward the direct detection of RSNOs by phosphine-based chemical probes. The intrinsic properties that dictate this phosphine/RSNO reactivity are summarized. In general, RSNOs (both small molecule and protein) react with phosphines to yield reactive S-substituted aza-ylides that undergo further reactions leading to stable RSNO-based adducts. Future Directions: This newly explored chemical reactivity forms the basis of a number of exciting potential chemical methods for protein RSNO detection in biological systems. Antioxid. Redox Signal. 17, 981–991. PMID:22356122

  4. Direct detection of exoplanets in the 3-10 ?m range with E-ELT/METIS

    NASA Astrophysics Data System (ADS)

    Quanz, Sascha P.; Crossfield, Ian; Meyer, Michael R.; Schmalzl, Eva; Held, Jenny

    2015-04-01

    We quantify the scientific potential for exoplanet imaging with the mid-infrared E-ELT Imager and Spectrograph (METIS) foreseen as one of the instruments of the European Extremely Large Telescope (E-ELT). We focus on two main science cases: (1) the direct detection of known gas giant planets found by radial velocity (RV) searches; and (2) the direct detection of small (1-4 R?) planets around the nearest stars. Under the assumptions made in our modelling, in particular on the achievable inner working angle and sensitivity, our analyses reveal that within a reasonable amount of observing time METIS is able to image >20 already known, RV-detected planets in at least one filter. Many more suitable planets with dynamically determined masses are expected to be found in the coming years with the continuation of RV-surveys and the results from the GAIA astrometry mission. In addition, by extrapolating the statistics for close-in planets found by Kepler, we expect METIS might detect ~10 small planets with equilibrium temperatures between 200 and 500 K around the nearest stars. This means that (1) METIS will help constrain atmospheric models for gas giant planets by determining for a sizable sample their luminosity, temperature and orbital inclination; and (2) METIS might be the first instrument to image a nearby (super-) Earth-sized planet with an equilibrium temperature near that expected to enable liquid water on a planet surface.

  5. Detection of Bi-Directionality in Strain-Gage Balance Calibration Data

    NASA Technical Reports Server (NTRS)

    Ulbrich, Norbert

    2012-01-01

    An indicator variable was developed for both visualization and detection of bi-directionality in wind tunnel strain-gage balance calibration data. First, the calculation of the indicator variable is explained in detail. Then, a criterion is discussed that may be used to decide which gage outputs of a balance have bi- directional behavior. The result of this analysis could be used, for example, to justify the selection of certain absolute value or other even function terms in the regression model of gage outputs whenever the Iterative Method is chosen for the balance calibration data analysis. Calibration data of NASA s MK40 Task balance is analyzed to illustrate both the calculation of the indicator variable and the application of the proposed criterion. Finally, bi directionality characteristics of typical multi piece, hybrid, single piece, and semispan balances are determined and discussed.

  6. A novel prediction methodology for detecting failures and instabilities in directional wireless networks

    NASA Astrophysics Data System (ADS)

    Coleman, David M.; Milner, Stuart D.; Davis, Christopher C.

    2012-10-01

    Even though advances in wireless technology have yielded lower power consumption, higher data rates, and numerous other improvements, the ability to develop a proactive strategy towards handling degradations and failures in directional wireless networks has evaded the research community. In this paper, we introduce a methodology using an analogy to molecular systems in which a directional wireless network utilizing free space optical (FSO) or RF links is modeled as a molecule whose links can grow/retract similarly to bonds. A normal mode analysis (NMA) is performed to identify link instabilities (degradations and failures) and an N-dimensional potential energy surface (PES) is derived with respect to network and environmental parameters to aide in the detection of when a new topology is available ahead of the topology computation stage. Together, the NMA and PES form a basis for a proactive network methodology aimed at improving performance in directional wireless networks.

  7. An acid dissociation bridging ELISA for detection of antibodies directed against therapeutic proteins in the presence of antigen

    Microsoft Academic Search

    Aaron Patton; Michael C. Mullenix; Steven J. Swanson; Eugen Koren

    2005-01-01

    Bridging Enzyme-Linked Immunosorbent Assay (ELISA) is commonly used in detection of antibodies directed against therapeutic proteins. Advantages of the bridging ELISA include the capability to detect antibodies regardless of their isotype or the species of origin. However, detection of antibodies can be difficult, if not impossible, in the presence of high levels of the antigen in the sample matrix. This

  8. Visual & reversible sensing of cyanide in real samples by an effective ratiometric colorimetric probe & logic gate application.

    PubMed

    Bhardwaj, Shubhrajyotsna; Singh, Ashok Kumar

    2015-10-15

    A novel anion probe 3 (2,4-di-tert-butyl-6-((2(2,4-dinitrophenyl) hydrazono) methyl) phenol) has been unveiled as an effective ratiometric and colorimetric sensor for selective and rapid detection of cyanide. The sensing behavior was demonstrated by UV-vis experiments and NMR studies. This sensory system exhibited prominent visual color change toward cyanide ion over other testing anions in DMSO (90%) solvent, with a 1:1 binding stoichiometry and a detection limit down to 3.6×10(-8)molL(-1). Sensor reveals specific anti-jamming activity and reversible in the presence of Cu(2+) ions. This concept has been applied to design a logic gate circuit at the molecular level. Further we developed coated graphite electrode using probe 3 as ionophore and studied the performance characteristics of electrode. The sensitivity of ratiometric-based colorimetric assay is below the 1.9?M, accepted by the World Health Organization as the highest permissible cyanide concentration in drinking water. So it can be applied for both quantitative determination and qualitative supervising of cyanide concentrations in real samples. PMID:25913671

  9. An optofluidic nanoplasmonic biosensor for direct detection of live viruses from biological media.

    PubMed

    Yanik, Ahmet A; Huang, Min; Kamohara, Osami; Artar, Alp; Geisbert, Thomas W; Connor, John H; Altug, Hatice

    2010-12-01

    Fast and sensitive virus detection techniques, which can be rapidly deployed at multiple sites, are essential to prevent and control future epidemics and bioterrorism threats. In this Letter, we demonstrate a label-free optofluidic nanoplasmonic sensor that can directly detect intact viruses from biological media at clinically relevant concentrations with little to no sample preparation. Our sensing platform is based on an extraordinary light transmission effect in plasmonic nanoholes and utilizes group-specific antibodies for highly divergent strains of rapidly evolving viruses. So far, the questions remain for the possible limitations of this technique for virus detection, as the penetration depths of the surface plasmon polaritons are comparable to the dimensions of the pathogens. Here, we demonstrate detection and recognition of small enveloped RNA viruses (vesicular stomatitis virus and pseudotyped Ebola) as well as large enveloped DNA viruses (vaccinia virus) within a dynamic range spanning 3 orders of magnitude. Our platform, by enabling high signal to noise measurements without any mechanical or optical isolation, opens up opportunities for detection of a broad range of pathogens in typical biology laboratory settings. PMID:21053965

  10. Direction identification in radio images of cosmic-ray air showers detected with LOPES and KASCADE

    E-print Network

    A. Nigl

    2008-09-16

    AIMS: We want to understand the emission mechanism of radio emission from air showers to determine the origin of high-energy cosmic rays. Therefore, we study the geometry of the air shower radio emission measured with LOPES and search for systematic effects between the direction determined on the radio signal and the direction provided by the particle detector array KASCADE. METHODS: We produce 4D radio images on time-scales of nanoseconds using digital beam-forming. Each pixel of the image is calculated for three spatial dimensions and as a function of time. The third spatial dimension is obtained by calculating the beam focus for a range of curvature radii fitted to the signal wave front. We search this multi-dimensional parameter space for the direction of maximum coherence of the air shower radio signal and compare it to the direction provided by KASCADE. RESULTS: The maximum radio emission of air showers is obtained for curvature radii being larger than 3 km. We find that the direction of the emission maximum can change when optimizing the curvature radius. Furthermore, we find a tentative increase of the curvature radius to lower elevations, where the air showers pass through a larger atmospheric depth. CONCLUSIONS: We conclude that the angular resolution of LOPES is sufficient to determine the direction which maximizes the observed electric field amplitude. However, the statistical uncertainty of the directions is not determined by the resolution of LOPES, but by the uncertainty of the curvature radius. We do not find any systematic deviation between the directions determined from the radio signal and from the detected particles. This result places a strong supportive argument for the use of the radio technique to study the origin of high-energy cosmic rays.

  11. Poker Face of Inelastic Dark Matter: Prospects at Upcoming Direct Detection Experiments

    SciTech Connect

    Alves, Daniele S.M.; Lisanti, Mariangela; /SLAC /Stanford U., Phys. Dept.; Wacker, Jay G.; /SLAC

    2011-08-12

    The XENON100 and CRESST experiments will directly test the inelastic dark matter explanation for DAMA's 8.9{sigma} anomaly. This article discusses how predictions for direct detection experiments depend on uncertainties in quenching factor measurements, the dark matter interaction with the Standard Model and the halo velocity distribution. When these uncertainties are accounted for, an order of magnitude variation is found in the number of expected events at CRESST and XENON100. The process of testing the DAMA anomaly highlights many of the challenges inherent to direct detection experiments. In addition to determining the properties of the unknown dark matter particle, direct detection experiments must also consider the unknown flux of the incident dark matter, as well as uncertainties in converting a signal from one target nucleus to another. The predictions for both the CRESST 2009 run and XENON100 2010 run show an order of magnitude uncertainty. The nuclear form factor for {sup 184}W, when combined with additional theoretical and experimental uncertainties, will likely prevent CRESST from refuting the iDM hypothesis with an exposure of {Omicron}(100 kg-d) in a model-independent manner. XENON100, on the other hand, will be able to make a definitive statement about a spin-independent, inelastically scattering dark matter candidate. Still, the CRESST 2009 data can potentially confirm iDM for a large range of parameter space. In case of a positive signal, the combined data from CRESST and XENON100 will start probing the properties of the Milky Way DM profile and the interaction of the SM with the dark matter.

  12. Interfacial Polymerization for Colorimetric Labeling of Protein Expression in Cells

    PubMed Central

    Lilly, Jacob L.; Sheldon, Phillip R.; Hoversten, Liv J.; Romero, Gabriela; Balasubramaniam, Vivek; Berron, Brad J.

    2014-01-01

    Determining the location of rare proteins in cells typically requires the use of on-sample amplification. Antibody based recognition and enzymatic amplification is used to produce large amounts of visible label at the site of protein expression, but these techniques suffer from the presence of nonspecific reactivity in the biological sample and from poor spatial control over the label. Polymerization based amplification is a recently developed alternative means of creating an on-sample amplification for fluorescence applications, while not suffering from endogenous labels or loss of signal localization. This manuscript builds upon polymerization based amplification by developing a stable, archivable, and colorimetric mode of amplification termed Polymer Dye Labeling. The basic concept involves an interfacial polymer grown at the site of protein expression and subsequent staining of this polymer with an appropriate dye. The dyes Evans Blue and eosin were initially investigated for colorimetric response in a microarray setting, where both specifically stained polymer films on glass. The process was translated to the staining of protein expression in human dermal fibroblast cells, and Polymer Dye Labeling was specific to regions consistent with desired protein expression. The labeling is stable for over 200 days in ambient conditions and is also compatible with modern mounting medium. PMID:25536421

  13. [Colorimetric characterization of LCD based on wavelength partition spectral model].

    PubMed

    Liu, Hao-Xue; Cui, Gui-Hua; Huang, Min; Wu, Bing; Xu, Yan-Fang; Luo, Ming

    2013-10-01

    To establish a colorimetrical characterization model of LCDs, an experiment with EIZO CG19, IBM 19, DELL 19 and HP 19 LCDs was designed and carried out to test the interaction between RGB channels, and then to test the spectral additive property of LCDs. The RGB digital values of single channel and two channels were given and the corresponding tristimulus values were measured, then a chart was plotted and calculations were made to test the independency of RGB channels. The results showed that the interaction between channels was reasonably weak and spectral additivity property was held well. We also found that the relations between radiations and digital values at different wavelengths varied, that is, they were the functions of wavelength. A new calculation method based on piecewise spectral model, in which the relation between radiations and digital values was fitted by a cubic polynomial in each piece of wavelength with measured spectral radiation curves, was proposed and tested. The spectral radiation curves of RGB primaries with any digital values can be found out with only a few measurements and fitted cubic polynomial in this way and then any displayed color can be turned out by the spectral additivity property of primaries at given digital values. The algorithm of this method was discussed in detail in this paper. The computations showed that the proposed method was simple and the number of measurements needed was reduced greatly while keeping a very high computation precision. This method can be used as a colorimetrical characterization model. PMID:24409730

  14. One-step homogeneous magnetic nanoparticle immunoassay for biomarker detection directly in blood plasma.

    PubMed

    Ranzoni, Andrea; Sabatte, Gwenola; van Ijzendoorn, Leo J; Prins, Menno W J

    2012-04-24

    Assay technologies capable of detecting low biomarker concentrations in complex biological samples are fundamental for biological research and for applications in medical diagnostics. In this paper we address the challenge to perform protein biomarker detection homogeneously in one single step, applying a minute amount of reagent directly into whole human blood plasma, avoiding any sample dilution, separation, amplification, or fluid manipulation steps. We describe a one-step homogeneous assay technology based on antibody-coated magnetic nanoparticles that are spiked in very small amount directly into blood plasma. Pulsed magnetic fields and a double-linker molecular architecture are used to generate high biomarker-induced binding and low nonspecific binding between the nanoparticles. We demonstrate dose-response curves for prostate specific antigen (PSA) measured in undiluted human blood plasma with a detection limit of 400-500 femtomol/L, in a total assay time of 14 min and an optically probed volume of only 1 nL. We explain the dose-response curves with a model based on discrete binding of biomarker molecules onto the nanoparticles, which allows us to extract reaction parameters for the binding of biomarker molecules onto the nanoparticles and for the biomarker-induced binding between nanoparticles. The demonstrated analytical performance and understanding of the nanoparticle assay technology render it of interest for a wide range of applications in quantitative biology and medical diagnostics. PMID:22414272

  15. Real-time PCR detection of Plasmodium directly from whole blood and filter paper samples

    PubMed Central

    2011-01-01

    Background Real-time PCR is a sensitive and specific method for the analysis of Plasmodium DNA. However, prior purification of genomic DNA from blood is necessary since PCR inhibitors and quenching of fluorophores from blood prevent efficient amplification and detection of PCR products. Methods Reagents designed to specifically overcome PCR inhibition and quenching of fluorescence were evaluated for real-time PCR amplification of Plasmodium DNA directly from blood. Whole blood from clinical samples and dried blood spots collected in the field in Colombia were tested. Results Amplification and fluorescence detection by real-time PCR were optimal with 40× SYBR® Green dye and 5% blood volume in the PCR reaction. Plasmodium DNA was detected directly from both whole blood and dried blood spots from clinical samples. The sensitivity and specificity ranged from 93-100% compared with PCR performed on purified Plasmodium DNA. Conclusions The methodology described facilitates high-throughput testing of blood samples collected in the field by fluorescence-based real-time PCR. This method can be applied to a broad range of clinical studies with the advantages of immediate sample testing, lower experimental costs and time-savings. PMID:21851640

  16. Fabrication of SERS swab for direct detection of trace explosives in fingerprints.

    PubMed

    Gong, Zhengjun; Du, Hongjie; Cheng, Fansheng; Wang, Cong; Wang, Canchen; Fan, Meikun

    2014-12-24

    Swab sampling is of great importance in surface contamination analysis. A cotton swab (cotton Q-tip) was successfully transformed into surface-enhanced Raman scattering (SERS) substrate (SERS Q-tip) through a bottom-up strategy, where Ag NPs were first self-assembled onto the Q-tip followed by in situ growing. The capability for direct swab detection of Raman probe Nile Blue A (NBA) and a primary explosive marker 2,4-dinitrotoluene (2,4-DNT) using the SERS Q-tip was explored. It was found that at optimum conditions, a femotogram of NBA on glass surface could be swab-detected. The lowest detectable amount for 2,4-DNT is only ?1.2 ng/cm(2) (total amount of 5 ng) on glass surface, 2 orders of magnitude more sensitive than similar surface analysis achieved with infrared technique, and comparable even with that obtained by ion mobility spectrometry-mass spectrometry. Finally, 2,4-DNT left on fingerprints was also analyzed. It was found that SERS signal of 2,4-DNT from 27th fingerprint after touching 2,4-DNT powder can still be clearly identified by swabbing with the SERS Q-tip. We believe this is the first direct SERS swabbing test of explosives on fingerprint on glass. Considering its relative long shelf life (>30 d), the SERS Q-tip may find great potential in future homeland security applications when combined with portable Raman spectrometers. PMID:25455731

  17. Direct Detection of the Hydrolysis of Nerve Agent Model Compounds Using a Fluorescent Probe

    PubMed Central

    Zheng, Xueying; Okolotowicz, Karl; Wang, Beilin; MacDonald, Mary; Cashman, John R.; Zhang, Jun

    2010-01-01

    Nerve agents are highly toxic organophosphorus compounds (OP) that are used as chemical warfare agents. Developing a catalytic bioscavenger to efficiently detoxify nerve agents in the bloodstream of affected individuals has been recognized as an attractive approach to prevent nerve agent toxicity. However, the search for nerve agent catalysts has been hindered by the lack of efficient direct assays for nerve agent hydrolysis. In addition, authentic nerve agents are restricted and access to use for experiments by the general research community is prohibited. Herein we report development of a method that combines use of novel nerve agent model compounds possessing a thiocholine leaving group that reacts with the fluorescent thio-detection probe, BES-Thio, to afford detection of sub-micromolar amounts of nerve agent model compounds hydrolysis products. The detection sensitivity of BES-Thio assay was approximately 10 times better than the Ellman assay. This developed method is useful as a direct, sensitive screening method for evaluating OP hydrolysis efficiency from catalytic cholinesterases. When the assay was assembled in the presence of oxime, OP-inhibited cholinesterases that were able to be reactivated by specific oxime showed oxime-assisted enzyme-mediated OP hydrolysis. Therefore, this method is also useful to screen oxime analogs to identify novel agents that can reactivate OP-inhibited cholinesterases or to screen various enzymes to identify pseudo-catalytic bioscavengers that can be readily reactivated by clinically approved oximes. PMID:20097185

  18. Dynamics of WIMPs in the solar system and implications for direct and indirect detection

    E-print Network

    Annika H. G. Peter; Scott Tremaine

    2008-10-14

    Semi-analytic treatments of the evolution of orbits of weakly interacting massive particles (WIMPs) in the solar system suggest that the WIMPs bound to the solar system may enhance the direct detection rate relative to that of the unbound population by up to a factor of order unity, and boost the flux of neutrinos from WIMP annihilation in the Earth by up to two orders of magnitude. To test these important but uncertain results, we perform a suite of numerical orbit integrations to explore the properties of the bound WIMP population as a function of the WIMP mass and the scattering cross section with baryonic matter. For regions of WIMP parameter space presently allowed by experiments, we find that (i) the bound WIMP population enhances the direct detection rate by at most ~1% relative to the rate from unbound halo WIMPs; (ii) it is unlikely that planned km^3-scale neutrino telescopes will detect neutrinos from WIMP annihilation in the Earth; (iii) the event rate from neutrinos produced by WIMP annihilation in the Sun may be much smaller than implied by the usual calculations, which assume that WIMPs scattered onto bound orbits are rapidly thermalized in the Sun.

  19. Direct detection of expanded trinucleotide repeats using PCR and DNA hybridization techniques

    SciTech Connect

    Petronis, A.; Tatuch, Y.; Klempan, T.A.; Kennedy, J.L. [Hospital for Sick Children, Toronto (Canada)] [and others] [Hospital for Sick Children, Toronto (Canada); and others

    1996-02-16

    Recently, unstable trinucleotide repeats have been shown to be the etiologic factor in seven neuropsychiatric diseases, and they may play a similar role in other genetic disorders which exhibit genetic anticipation. We have tested one polymerase chain reaction (PCR)-based and two hybridization-based methods for direct detection of unstable DNA expansion in genomic DNA. This technique employs a single primer (asymmetric) PCR using total genomic DNA as a template to efficiently screen for the presence of large trinucleotide repeat expansions. High-stringency Southern blot hybridization with a PCR-generated trinucleotide repeat probe allowed detection of the DNA fragment containing the expansion. Analysis of myotonic dystrophy patients containing different degrees of (CTG){sub n} expansion demonstrated the identification of the site of trinucleotide instability in some affected individuals without any prior information regarding genetic map location. The same probe was used for fluorescent in situ hybridization and several regions of (CTG){sub n}/(CAG){sub n} repeats in the human genome were detected, including the myotonic dystrophy locus on chromosome 19q. Although limited at present to large trinucleotide repeat expansions, these strategies can be applied to directly clone genes involved in disorders caused by large expansions of unstable DNA. 33 refs., 4 figs.

  20. Evaluation of a Semiautomated System for Direct Fluorescent Antibody Detection of Salmonellae

    PubMed Central

    Thomason, Berenice M.; Hebert, G. Ann; Cherry, William B.

    1975-01-01

    A semi-automatic system under development by Aerojet Medical and Biological Systems for the direct fluorescent antibody detection of salmonellae was evaluated with various food, feed, and environmental samples. All samples were simultaneously examined by Automated Bioassay System (ABS), manual direct fluorescent antibody procedures and cultural procedures. The ABS gave satisfactory results with the processed samples. It detected all of the culturally positive powdered egg and candy samples with no false negative results and gave only 6.6 and 5.3% false positive rates, respectively. With meatmeal samples the ABS failed to detect one culturally positive specimen that was also positive by manual fluorescent antibody and gave one (1.1%) false-positive result. A high rate of false-negative results was obtained by ABS on unprocessed samples of creek water, poultry, and sausage. Adding another enrichment step to the protocol reduced the false-negative rate considerably but severely increased the false-positive rate. The instruments worked reasonably well, but research is needed to improve enrichment procedures for samples to be processed by the system. Images PMID:1103730

  1. Evaluation of a semiautomated system for direct fluorescent antibody detection of salmonellae.

    PubMed

    Thomason, B M; Hebert, G A; Cherry, W B

    1975-10-01

    A semi-automatic system under development by Aerojet Medical and Biological Systems for the direct fluorescent antibody detection of salmonellae was evaluated with various food, feed, and environmental samples. All samples were simultaneously examined by Automated Bioassay System (ABS), manual direct fluorescent antibody procedures and cultural procedures. The ABS gave satisfactory results with the processed samples. It detected all of the culturally positive powdered egg and candy samples with no false-negative results and gave only 6.6 and 5.3% false-positive rates, respectively. With meatmeal samples the ABS failed to detect one culturally positive specimen that was also positive by manual fluorescent antibody and gave one (1.1%) false-positive result. A high rate of false-negative results was obtained by ABS on unprocessed samples of creek water, poultry, and sausage. Adding another enrichment step to the protocol reduced the false-negative rate considerably but severely increased the false-positive rate. The instruments worked reasonably well, but research is needed to improve enrichment procedures for samples to be processed by the system. PMID:1103730

  2. Direct RNA-based detection of CTX-M ?-lactamases in human blood samples.

    PubMed

    Stein, Claudia; Makarewicz, Oliwia; Pfeifer, Yvonne; Brandt, Christian; Pletz, Mathias W

    2015-05-01

    Bloodstream infections with ESBL-producers are associated with increased mortality, which is due to delayed appropriate treatment resulting in clinical failure. Current routine diagnostics for detection of bloodstream infections consists of blood culture followed by species identification and susceptibility testing. In attempts to improve and accelerate diagnostic procedures, PCR-based methods have been developed. These methods focus on species identification covering only a limited number of ESBL coding genes. Therefore, they fail to cover the steadily further evolving genetic diversity of clinically relevant ?-lactamases. We have recently designed a fast and novel RNA targeting method to detect and specify CTX-M alleles from bacterial cultures, based on an amplification-pyrosequencing approach. We further developed this assay towards a diagnostic tool for clinical use and evaluated its sensitivity and specificity when applied directly to human blood samples. An optimized protocol for mRNA isolation allows detection of specific CTX-M groups from as little as 100CFU/mL blood via reverse transcription, amplification, and pyrosequencing directly from human EDTA blood samples as well as from pre-incubated human blood cultures with a turnaround time for test results of <7h. PMID:25769406

  3. Direct detection of chlorpropham on potato skin using desorption electrospray ionization.

    PubMed

    Berchtold, Christian; Müller, Vivian; Meier, Lukas; Schmid, Stefan; Zenobi, Renato

    2013-05-01

    Most pesticides, herbicides and other plant treatment agents are applied to the crop surface. Direct mass spectrometric methods, such as desorption electrospray ionization (DESI), offer new ways to analyze plant samples directly and rapidly. A strategy for the development and optimization of a DESI method for the direct determination of chemicals on complex surfaces is described. Chlorpropham (CP) was applied to potato surfaces as an example for a crop protection agent and analyzed using a self-made DESI source. Aspects such as instrument selectivity, sensitivity and reproducibility were investigated. The MS(4) fragmentation pattern of CP was analyzed to achieve the necessary detection selectivity, and is discussed in detail. Similar fragmentation was found in the ESI and DESI mass spectra, indicating that the mechanisms of ESI and DESI are closely related. A DESI method for semi-quantification of CP on potatoes was developed. Detection limits of 6.5?µg/kg were found using MS/MS. The reproducibility, in the range of 12% (signal variation), appears to be sufficient for semi-quantitative measurements. PMID:23674283

  4. UV Direct Detection Doppler Wind Lidar validation in the frame of ADM/Aeolus mission

    NASA Astrophysics Data System (ADS)

    Lolli, Simone; Garnier, Anne; Flamant, Pierre

    2014-05-01

    Atmospheric wind profile measurement is a critical variable to improve Numerical Weather Prediction (NWP) models accuracy and for climate studies. The European Space Agency (ESA) Atmospheric Dynamic Mission (ADM) has, as its main goal, to enhance the present meteorological observations system over sparse wind data regions and more importantly to provide direct wind information in the tropics where no geostrophic wind can be derived from mass fields obtained from passive radiometer, by deploying on a satellite a direct detection high spectral resolution 355nm Doppler wind lidar (launch expected in mid-2015). In this study are presented the results and performances of the first ground-based 355nm direct detection Doppler wind lidar prototype against other remote sensors, as lidars, 72 MHz radar and conventional balloon radio soundings during ESA VALID campaign that held at Haute Provence Observatory in July 1999, under all possible different meteorological conditions. The study presents the comparison of different remote sensors using two criteria: Pearson cross-correlation coefficient and root mean square error. The methodology discussed here may be useful in future ESA Aeolus validation campaigns involving different kinds of instruments.

  5. [Feasibility of using laser-induced fluorescence to detect directly polycyclic aromatic hydrocarbons in soil].

    PubMed

    Yang, Ren-Jie; Shang, Li-Ping; Bao, Zhen-Bo; He, Jun; Deng, Hu; Liu, Yu-Le

    2011-08-01

    Abstract In the present paper, a technique of laser-induced fluorescence(LIF)for direct assay of polycyclic aromatic hydrocarbons(PAH) in soil was put forward. The research objective of this article is anthracene. The possibility of using LIF spectra to detect directly anthracene in soil was studied. Anthracene was detected in soil by AvaSpec-3648 Fiber Optic Spectrometer of thermoelectric refrigeration. The authors drew a conclusion that in the range of certain anthracene concentration(0.000 005-0.001 g x g(-1)), the intensity of LIF fluorescence is linear with anthracene concentration in soil, with a regression coefficient of 0. 929. This showed that direct assay of anthracene in soil was feasible by laser-induced fluorescence. The study is important to developing a new analytical technique of quantitative fluorescence detector which can be applied to the analysis of PAH in soil without pretreatment, and is significant to realization of real-time, in-line, in-situ measurement of PAH in soil. PMID:22007406

  6. Direct detection of the acetate-forming activity of the enzyme acetate kinase.

    PubMed

    Fowler, Matthew L; Ingram-Smith, Cheryl J; Smith, Kerry S

    2011-01-01

    Acetate kinase, a member of the acetate and sugar kinase-Hsp70-actin (ASKHA) enzyme superfamily, is responsible for the reversible phosphorylation of acetate to acetyl phosphate utilizing ATP as a substrate. Acetate kinases are ubiquitous in the Bacteria, found in one genus of Archaea, and are also present in microbes of the Eukarya. The most well characterized acetate kinase is that from the methane-producing archaeon Methanosarcina thermophila. An acetate kinase which can only utilize PP(i) but not ATP in the acetyl phosphate-forming direction has been isolated from Entamoeba histolytica, the causative agent of amoebic dysentery, and has thus far only been found in this genus. In the direction of acetyl phosphate formation, acetate kinase activity is typically measured using the hydroxamate assay, first described by Lipmann, a coupled assay in which conversion of ATP to ADP is coupled to oxidation of NADH to NAD(+) by the enzymes pyruvate kinase and lactate dehydrogenase, or an assay measuring release of inorganic phosphate after reaction of the acetyl phosphate product with hydroxylamine. Activity in the opposite, acetate-forming direction is measured by coupling ATP formation from ADP to the reduction of NADP(+) to NADPH by the enzymes hexokinase and glucose 6-phosphate dehydrogenase. Here we describe a method for the detection of acetate kinase activity in the direction of acetate formation that does not require coupling enzymes, but is instead based on direct determination of acetyl phosphate consumption. After the enzymatic reaction, remaining acetyl phosphate is converted to a ferric hydroxamate complex that can be measured spectrophotometrically, as for the hydroxamate assay. Thus, unlike the standard coupled assay for this direction that is dependent on the production of ATP from ADP, this direct assay can be used for acetate kinases that produce ATP or PP(i). PMID:22214984

  7. Detection of shiga toxins by lateral flow assay.

    PubMed

    Ching, Kathryn H; He, Xiaohua; Stanker, Larry H; Lin, Alice V; McGarvey, Jeffery A; Hnasko, Robert

    2015-04-01

    Shiga toxin-producing Escherichia coli (STEC) produce shiga toxins (Stxs) that can cause human disease and death. The contamination of food products with STEC represents a food safety problem that necessitates rapid and effective detection strategies to mitigate risk. In this manuscript, we report the development of a colorimetric lateral flow assay (LFA) for the rapid detection of Stxs in <10 min using a pair of monoclonal antibodies that bind epitopes common to Stx1 and six Stx2 variants. This LFA provides a rapid and sensitive test for the detection of Stxs directly from STEC culture supernatants or at risk food samples with a 0.1 ng/mL limit of detection (LOD) for Stx2a. This Stx LFA is applicable for use in the rapid evaluation of Stx production from cultured E. coli strains or as a tool to augment current methods as part of food safety testing. PMID:25855129

  8. Detection of Shiga Toxins by Lateral Flow Assay

    PubMed Central

    Ching, Kathryn H.; He, Xiaohua; Stanker, Larry H.; Lin, Alice V.; McGarvey, Jeffery A.; Hnasko, Robert

    2015-01-01

    Shiga toxin-producing Escherichia coli (STEC) produce shiga toxins (Stxs) that can cause human disease and death. The contamination of food products with STEC represents a food safety problem that necessitates rapid and effective detection strategies to mitigate risk. In this manuscript, we report the development of a colorimetric lateral flow assay (LFA) for the rapid detection of Stxs in <10 min using a pair of monoclonal antibodies that bind epitopes common to Stx1 and six Stx2 variants. This LFA provides a rapid and sensitive test for the detection of Stxs directly from STEC culture supernatants or at risk food samples with a 0.1 ng/mL limit of detection (LOD) for Stx2a. This Stx LFA is applicable for use in the rapid evaluation of Stx production from cultured E. coli strains or as a tool to augment current methods as part of food safety testing. PMID:25855129

  9. DNA Functionalized Direct Electro-deposited Gold nanoaggregates for Efficient Detection of Salmonella typhi.

    PubMed

    Singh, Anu; Choudhary, Meenakshi; Singh, M P; Verma, H N; Singh, Surinder P; Arora, Kavita

    2015-10-01

    Direct electro-deposition of gold nano-aggregates (GNAs) was carried out to fabricate electrochemical DNA biosensor for the detection of Salmonella typhi in urine and blood samples. Size of depositing GNAs was controlled by regulating electro-deposition parameters at physiological pH. This facilitated achieving biocompatible GNAs with desired electrochemical behaviour and enhanced surface area to achieve higher DNA loading. Salmonella typhi (S. typhi) specific 5'amine modified single stranded DNA (ssDNA, NH2-(C6)-5'CGTGCGCGACGCCCGCCGCC3') was covalently immobilized on to GNAs-ITO (indium tin oxide) electrode. Dynamic detection range of 4 aM - 24 fM. using methylene blue (MB) redox indicator at 25°C was achieved using ssDNA-GNAs-ITO bio-electrode to detect the complimentary target sequence (5'GGCGGCGGGCGTCGCGCACG 3') through differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Selectivity of designed electrode was ascertained by response signal for complementary, non-complementary and 1 base mismatch sequences. Furthermore, clear distinction in complementary and non-complimentary targets was obtained by EIS studies for genomic DNA in culture spiked biological fluids 'CSBF' (blood and urine). This study for detection of S. typhi from urine and blood samples using fabricated ssDNA-GNA-ITO bio-electrode showed promising results and have potential to be used as sensor for real patient samples. PMID:25917793

  10. A novel method for dendritic spines detection based on directional morphological filter and shortest path.

    PubMed

    Su, Ran; Sun, Changming; Zhang, Chao; Pham, Tuan D

    2014-12-01

    Dendritic spines are tiny membranous protrusions from neuron's dendrites. They play a very important role in the nervous system. A number of mental diseases such as Alzheimer's disease and mental retardation are revealed to have close relations with spine morphologies or spine number changes. Spines have various shapes, and spine images are often not of good quality; hence it is very challenging to detect spines in neuron images. This paper presents a novel pipeline to detect dendritic spines in 2D maximum intensity projection (MIP) images and a new dendrite backbone extraction method is developed in the pipeline. The strategy for the backbone extraction approach is that it iteratively refines the extraction result based on directional morphological filtering and improved Hessian filtering until a satisfactory extraction result is obtained. A shortest path method is applied along a backbone to extract the boundary of the dendrites. Spines are then segmented from the dendrites outside the extracted boundary. Touching spines will be split using a marker-controlled watershed algorithm. We present the results of our algorithm on real images and compare our algorithm with two other spine detection methods. The results show that the proposed approach can detect dendrites and spines more accurately. Measurements and classification of spines are also made in this paper. PMID:25155696

  11. Direct detection of singlet dark matter in classically scale-invariant standard model

    E-print Network

    Endo, Kazuhiro

    2015-01-01

    Classical scale invariance is one of the possible solutions to explain the origin of the electroweak scale. The simplest extension is the classically scale-invariant standard model augmented by a multiplet of gauge singlet real scalar. In the previous study it was shown that the properties of the Higgs potential deviates substantially, which can be observed in the International Linear Collider. On the other hand, since the multiplet does not acquire vacuum expectation value, the singlet components are stable and can be dark matter. In this letter we study the detectability of the real singlet scalar bosons in the experiment of the direct detection of dark matter. It is shown that a part of this model has already been excluded and the rest of the parameter space is within the reach of the future experiment.

  12. 50 Mbps free space direct detection laser diode optical communication system with Q = 4 PPM signaling

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli; Davidson, Frederic; Field, Christopher

    1990-01-01

    A 50 Mbps direct detection optical communication system for use in an intersatellite link was constructed with an AlGaAs laser diode transmitter and a silicon avalanche photodiode photodetector. The system used a Q = 4 PPM format. The receiver consisted of a maximum likelihood PPM detector and a timing recovery subsystem. The PPM slot clock was recovered at the receiver by using a transition detector followed by a PLL. The PPM word clock was recovered by using a second PLL whose input was derived from the presence of back-to-back PPM pulses contained in the received random PPM pulse sequences. The system achieved a bit error rate of 0.000001 at less than 50 detected signal photons/information bit. The receiver was capable of acquiring and maintaining slot and word synchronization for received signal levels greater than 20 photons/information bit, at which the receiver bit error rate was about 0.01.

  13. Direct detection and speciation of trace explosives using a nanoporous multifunctional microcantilever.

    PubMed

    Lee, Dongkyu; Kim, Seonghwan; Jeon, Sangmin; Thundat, Thomas

    2014-05-20

    We have developed a highly selective and sensitive nanomechanical infrared (IR) calorimetric spectrometer for use in the direct detection of ultralow concentrations of explosive vapors using a nanoporous TiO2 cantilever. These cantilevers were fabricated using a two-step anodization and photolithography process. By patterning nanoscale wells onto a cantilever, its surface area is increased by 2 orders of magnitude and the surface is converted into a preconcentrator. Resonant excitation of adsorbed molecules using IR radiation causes the cantilever to bend due to temperature changes originating from the nonradiative decay process. The porous structure of the cantilever increases its thermomechanical sensitivity as well as the number of adsorbed molecules. The system performance was demonstrated by detecting binary explosive mixtures under ambient conditions. The TiO2 sensor surface also allows regeneration through the photocatalytic decomposition of adsorbates under UV irradiation. PMID:24766474

  14. Direct detection behavior of a superconducting hot electron bolometer measured by Fourier transform spectrometer

    NASA Astrophysics Data System (ADS)

    Miao, W.; Zhang, W.; Zhou, K. M.; Lin, Z., H.; Yao, Q. J.; Delorme, Y.; Lefevre, R.; Shi, S. C.

    2010-11-01

    In this paper, the direct detection behaviors of a superconducting hot electron bolometer integrated with a log spiral antenna are investigated by using Fourier Transform Spectrometer (FTS). We find the response of the bolometer to a modulated signal can be detected by a lock-in amplifier not only from the DC bias current, but also from the output noise power at the IF port of the HEB. We attribute the response in output noise power to Johnson noise and thermal fluctuation noise. Both the current response and the output noise power response measured at different bias voltages can be explained by one dimensional distributed hot spot model. In addition, the frequency response of the hot electron bolometer measured from the response in DC bias current is in good agreement with that in IF output noise power.

  15. Direct detection of free radicals and reactive oxygen species in thylakoids.

    PubMed

    Hideg, Eva; Kálai, Tamás; Hideg, Kálmán

    2011-01-01

    In plants, reactive oxygen species (ROS), also known as active oxygen species (AOS), are associated with normal, physiologic processes as well as with responses to adverse conditions. ROS are connected to stress in many ways: as primary elicitors, as products and propagators of oxidative damage, or as signal molecules initiating defense or adaptation. The photosynthetic electron transport is a major site of oxidative stress by visible or ultraviolet light, high or low temperature, pollutants or herbicides. ROS production can be presumed from detecting oxidatively damaged lipids, proteins, or pigments as well as from the alleviating effects of added antioxidants. On the contrary, measuring ROS by special sensor molecules provides more direct information. This chapter focuses on the application of spin trapping electron paramagnetic resonance (EPR) spectroscopy for detecting ROS: singlet oxygen and oxygen free radicals in thylakoid membrane preparations. PMID:20960131

  16. Design and Development of a Scanning Airborne Direct Detection Doppler Lidar System

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce; McGill, Matthew; Schwemmer, Geary; Hardesty, Michael; Brewer, Alan; Wilkerson, Thomas; Atlas, Robert; Sirota, Marcos; Lindemann, Scott

    2006-01-01

    In the fall of 2005 we began developing an airborne scanning direct detection molecular Doppler lidar. The instrument is being built as part of the Tropospheric Wind Lidar Technology Experiment (TWiLiTE), a three year project selected by the NASA Earth Sun Technology Office under the Instrument Incubator Program. The TWiLiTE project is a collaboration involving scientists and engineers from NASA Goddard Space Flight Center, NOAA ESRL, Utah State University Space Dynamics Lab, Michigan Aerospace Corporation and Sigma Space Corporation. The TWiLiTE instrument will leverage significant research and development investments made by NASA Goddard and it's partners in the past several years in key lidar technologies and sub-systems (lasers, telescopes, scanning systems, detectors and receivers) required to enable spaceborne global wind lidar measurement. These sub-systems will be integrated into a complete molecular direct detection Doppler wind lidar system designed for autonomous operation on a high altitude aircraft, such as the NASA WB57. The WB57 flies at an altitude of 18 km and from this vantage point the nadir viewing Doppler lidar will be able to profile winds through the full troposphere. The TWiLiTE integrated airborne Doppler lidar instrument will be the first demonstration of a airborne scanning direct detection Doppler lidar and will serve as a critical milestone on the path to a future spaceborne tropospheric wind system. In addition to being a technology testbed for space based tropospheric wind lidar, when completed the TWiLiTE high altitude airborne lidar will be used for studying mesoscale dynamics and storm research (e.g. winter storms, hurricanes) and could be used for calibration and validation of satellite based wind systems such as ESA's Aeolus Atmospheric Dynamics Mission. The TWiLiTE Doppler lidar will have the capability to profile winds in clear air from the aircraft altitude of 18 km to the surface with 250 m vertical resolution and < 2mls velocity accuracy.

  17. Defect detection and classification of machined surfaces under multiple illuminant directions

    NASA Astrophysics Data System (ADS)

    Liao, Yi; Weng, Xin; Swonger, C. W.; Ni, Jun

    2010-08-01

    Continuous improvement of product quality is crucial to the successful and competitive automotive manufacturing industry in the 21st century. The presence of surface porosity located on flat machined surfaces such as cylinder heads/blocks and transmission cases may allow leaks of coolant, oil, or combustion gas between critical mating surfaces, thus causing damage to the engine or transmission. Therefore 100% inline inspection plays an important role for improving product quality. Although the techniques of image processing and machine vision have been applied to machined surface inspection and well improved in the past 20 years, in today's automotive industry, surface porosity inspection is still done by skilled humans, which is costly, tedious, time consuming and not capable of reliably detecting small defects. In our study, an automated defect detection and classification system for flat machined surfaces has been designed and constructed. In this paper, the importance of the illuminant direction in a machine vision system was first emphasized and then the surface defect inspection system under multiple directional illuminations was designed and constructed. After that, image processing algorithms were developed to realize 5 types of 2D or 3D surface defects (pore, 2D blemish, residue dirt, scratch, and gouge) detection and classification. The steps of image processing include: (1) image acquisition and contrast enhancement (2) defect segmentation and feature extraction (3) defect classification. An artificial machined surface and an actual automotive part: cylinder head surface were tested and, as a result, microscopic surface defects can be accurately detected and assigned to a surface defect class. The cycle time of this system can be sufficiently fast that implementation of 100% inline inspection is feasible. The field of view of this system is 150mm×225mm and the surfaces larger than the field of view can be stitched together in software.

  18. Fluorescent In Situ hybridization: a new tool for the direct identification and detection of F. psychrophilum.

    PubMed

    Strepparava, Nicole; Wahli, Thomas; Segner, Helmut; Polli, Bruno; Petrini, Orlando

    2012-01-01

    F. psychrophilum is the causative agent of Bacterial Cold Water Disease (BCW) and Rainbow Trout Fry Syndrome (RTFS). To date, diagnosis relies mainly on direct microscopy or cultural methods. Direct microscopy is fast but not very reliable, whereas cultural methods are reliable but time-consuming and labor-intensive. So far fluorescent in situ hybridization (FISH) has not been used in the diagnosis of flavobacteriosis but it has the potential to rapidly and specifically detect F. psychrophilum in infected tissues. Outbreaks in fish farms, caused by pathogenic strains of Flavobacterium species, are increasingly frequent and there is a need for reliable and cost-effective techniques to rapidly diagnose flavobacterioses. This study is aimed at developing a FISH that could be used for the diagnosis of F. psychrophilum infections in fish. We constructed a generic probe for the genus Flavobacterium ("Pan-Flavo") and two specific probes targeting F. psychrophilum based on 16S rRNA gene sequences. We tested their specificity and sensitivity on pure cultures of different Flavobacterium and other aquatic bacterial species. After assessing their sensitivity and specificity, we established their limit of detection and tested the probes on infected fresh tissues (spleen and skin) and on paraffin-embedded tissues. The results showed high sensitivity and specificity of the probes (100% and 91% for the Pan-Flavo probe and 100% and 97% for the F. psychrophilum probe, respectively). FISH was able to detect F. psychrophilum in infected fish tissues, thus the findings from this study indicate this technique is suitable as a fast and reliable method for the detection of Flavobacterium spp. and F. psychrophilum. PMID:23152887

  19. Rapid detection of NBOME's and other NPS on blotter papers by direct ATR-FTIR spectrometry.

    PubMed

    Coelho Neto, José

    2015-07-01

    Blotter paper is among the most common forms of consumption of new psychotropic substances (NPS), formerly referred as designer drugs. In many cases, users are misled to believe they are taking LSD when, in fact, they are taking newer and less known drugs like the NBOMEs or other substituted phenethylamines. We report our findings in quick testing of blotter papers for illicit substances like NBOMEs and other NPS by taking ATR-FTIR spectra directly from blotters seized on the streets, without any sample preparation. Both sides (front and back) of each blotter were tested. Collected data were analyzed by single- and multi-component spectral matching and submitted to chemometric discriminant analysis. Our results showed that, on 66.7% of the cases analyzed, seized blotters contained one or more types of NBOMEs, confirming the growing presence of this novel substances on the market. Matching IR signals were detected on both or just one side of the blotters and showed variable strength. Although no quantitative analysis was made, detection of these substances by the proposed approach serves as indication of variable and possibly higher dosages per blotter when compared to LSD, which showed to be below the detection limit of the applied method. Blotters containing a mescaline-like compound, later confirmed by GC-MS and LC-MS to be MAL (methallylescaline), a substance very similar to mescaline, were detected among the samples tested. Validity of direct ATR-FTIR testing was confirmed by checking the obtained results against independent GC-MS or LC-MS results for the same cases/samples. PMID:25965305

  20. Results on Discrete-Time, Decision-Directed Integrated Detection, Estimation, and Identification

    E-print Network

    Painter, John H.; Jones, S.

    on February 18,2010 at 17:27:24 EST from IEEE Xplore. Restrictions apply. 716 IEEE TRANSACTIONS ON COMMUNICATIONS, JULY 1977 strengths, etc.) of the colored disturbances. Thus, the total process described below is called Integrated Detection... signal, during the Jth symbol interval. p(k) is [ 1, 1 ] in (3), and represents the direct path. n(k) is a two- Authorized licensed use limited to: Texas A M University. Downloaded on February 18,2010 at 17:27:24 EST from IEEE Xplore...

  1. Flipped-exponential Nyquist pulse technique to optimize the PAPR in optical direct detection OFDM system

    NASA Astrophysics Data System (ADS)

    Xiao, Jiangnan; Yu, Jianjun; Cao, Zizheng; Li, Fan; Chen, Lin

    2013-01-01

    In this paper, a novel technique based on flipped-exponential (FE) Nyquist pulse method is proposed for peak-to-average power ratio (PAPR) reduction in optical direct detection orthogonal frequency-division multiplexing (DD-OFDM) system. The method is based on a proper selection of the FE Nyquist pulses for shaping the different subcarriers of the OFDM. We experimentally demonstrated an optical DD-OFDM transmission system with this novel technique to achieve significant improvement in PAPR reduction in the optical OFDM system. The received sensitivity of the OFDM signal after suffered from strong nonlinear effects in standard single-mode fiber (SMF) has been experimentally investigated.

  2. Annual Modulation Signature for the Direct Detection of Milky Way Wimps and Supergravity Models

    E-print Network

    R. Arnowitt; Pran Nath

    1999-02-03

    An analysis is given of the annual modulation signal for the direct detection of relic neutralinos within the framework of supergravity unified models. It is shown that both the minimal and the non-minimal SUGRA models can generate neutralino-proton cross-sections at the level compatible with the signals reported in the DAMA experiment at the Gran Sasso National Laboratory. Effects of proton stability on the analysis of the DAMA data in the minimal and the non-minimal SUGRA models are also discussed.

  3. Characterization of a direct detection device imaging camera for transmission electron microscopy.

    PubMed

    Milazzo, Anna-Clare; Moldovan, Grigore; Lanman, Jason; Jin, Liang; Bouwer, James C; Klienfelder, Stuart; Peltier, Steven T; Ellisman, Mark H; Kirkland, Angus I; Xuong, Nguyen-Huu

    2010-06-01

    The complete characterization of a novel direct detection device (DDD) camera for transmission electron microscopy is reported, for the first time at primary electron energies of 120 and 200 keV. Unlike a standard charge coupled device (CCD) camera, this device does not require a scintillator. The DDD transfers signal up to 65 lines/mm providing the basis for a high-performance platform for a new generation of wide field-of-view high-resolution cameras. An image of a thin section of virus particles is presented to illustrate the substantially improved performance of this sensor over current indirectly coupled CCD cameras. PMID:20382479

  4. Precise Detection of Direct Glomerular Input Duration by the Olfactory Bulb

    PubMed Central

    Li, Anan; Gire, David H.; Bozza, Thomas

    2014-01-01

    Sensory neuron input to the olfactory bulb (OB) was activated precisely for different durations with blue light in mice expressing channelrhodopsin-2 in olfactory sensory neurons. Behaviorally the mice discriminated differences of 10 ms in duration of direct glomerular activation. In addition, a subset of mitral/tufted cells in the OB of awake mice responded tonically therefore conveying information on stimulus duration. Our study provides evidence that duration of the input to glomeruli not synchronized to sniffing is detected. This potent cue may be used to obtain information on puffs in odor plumes. PMID:25429146

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

    SciTech Connect

    Tarun, Alvarado; Jecong, Julius; Saloma, Caesar

    2005-12-01

    We demonstrate a compact in-line interferometer for direction-sensitive displacement measurement by optical feedback detection with a semiconductor laser (SL) light source. Two reflected beams from a semitransparent reference mirror and a reflecting test object interfere in the SL medium, causing a variation in its output power. The reference mirror is located between the SL output facet and the test object. The performance of the interferometer is investigated numerically and experimentally to determine its optimal operating conditions. We have verified the operating conditions where the behavior of the SL output power profile could indicate accurately the displacement magnitude and direction of the moving test object. The profile behavior is robust against variations in optical feedback and scale of the interferometer configuration.

  6. Low energy electron/recoil discrimination for directional Dark Matter detection

    SciTech Connect

    Billard, J.; Mayet, F.; Santos, D., E-mail: billard@lpsc.in2p3.fr, E-mail: mayet@lpsc.in2p3.fr, E-mail: santos@lpsc.in2p3.fr [Laboratoire de Physique Subatomique et de Cosmologie, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut Polytechnique de Grenoble, 53 rue des Martyrs, Grenoble (France)

    2012-07-01

    Directional detection is a promising Dark Matter search strategy. Even though it could accommodate to a sizeable background contamination, electron/recoil discrimination remains a key and challenging issue as for direction-insensitive detectors. The measurement of the 3D track may be used to discriminate electrons from nuclear recoils. While a high rejection power is expected above 20 keV ionization, a dedicated data analysis is needed at low energy. After identifying discriminant observables, a multivariate analysis, namely a Boosted Decision Tree, is proposed, enabling an efficient event tagging for Dark Matter search. We show that it allows us to optimize rejection while keeping a rather high efficiency which is compulsory for rare event search.With respect to a sequential analysis, the rejection is about ? 20 times higher with a multivariate analysis, for the same Dark Matter exclusion limit.

  7. Assessing alternatives for directional detection of a halo of weakly interacting massive particles

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

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

  8. Facet dependent binding and etching: ultra-sensitive colorimetric visualization of blood uric acid by unmodified silver nanoprisms.

    PubMed

    Tan, Kanghui; Yang, Guang; Chen, Huide; Shen, Pengfei; Huang, Yucheng; Xia, Yunsheng

    2014-09-15

    By combination of experiments and density functional theory calculations, we present a simple but effective "facet dependent binding and etching" strategy for non-enzymatic and non-aggregated colorimetric sensing of blood uric acid (UA), using unmodified Ag nanoprisms as the signal readout. In the absence of UA, the triangular Ag nanoprisms are etched alongside (110) facets by H2O2 and form round nanodiscs, and a more than 160 nm surface plasmon resonance (SPR) blue shift is observed. Because of special affinity between UA and side facets of the Ag nanoprisms, pre-added UA can well protect the Ag nanoprisms from etching. Such protection effect can be used for well quantifying UA in the range of 10-3000 nM, based on the inverse proportion of the SPR blue shift with the added analyte. Due to very thin plate morphology (5 nm) and facet dependent binding/etching effects of the Ag nanoprisms, the sensing system has ultrahigh sensitivity. The detection limit is only 10nM, which is about 2 to 4 orders of magnitude lower than that of previous colorimetric sensing systems. In addition to accurate quantitation, the proposed strategy can conveniently discriminate the patient of hyperuricemia from normal person by naked eyes. So, the present simple, low-cost and visualized UA chemosensor has great potential in the applications for point-of-care diagnostics. PMID:24732599

  9. Novel colorimetric sensors for cyanide based on azo-hydrazone tautomeric skeletons

    NASA Astrophysics Data System (ADS)

    Adegoke, Olajire A.; Adesuji, Temitope E.; Thomas, Olusegun E.

    2014-07-01

    The monoazo dyes, 4-carboxyl-2, 6-dinitrophenylazohydroxynaphthalenes dyes (AZ-01, AZ-03 and AZ-04), were evaluated as a highly selective colorimetric chemosensor for cyanide ion. The recognition of cyanide ion gave an obvious colour change from light yellow to brownish red and upon dilution with acetone produced a purple to lilac colour. Optimum conditions for the reaction between the azo dyes and cyanide ion were established at 30 °C for 5 min, and different variables affecting the reaction were carefully studied and optimised. Under the optimum conditions, linear relationships between the CN- concentrations and light absorption were established. Using these azo-hydrazone molecular switch entities, excellent selectivity towards the detection of CN- in aqueous solution over miscellaneous competitive anions was observed. Such selectivity mainly results from the possibility of nucleophilic attack on the azo-hydrazone chemosensors by cyanide anions in aqueous system, which is not afforded by other competing anions. The cyanide chemosensor method described here should have potential application as a new family probes for detecting cyanide in aqueous solution.

  10. Selection of DNA aptamers against Human Cardiac Troponin I for colorimetric sensor based dot blot application.

    PubMed

    Dorraj, Ghamar Soltan; Rassaee, Mohammad Javad; Latifi, Ali Mohammad; Pishgoo, Bahram; Tavallaei, Mahmood

    2015-08-20

    Troponin T and I are ideal markers which are highly sensitive and specific for myocardial injury and have shown better efficacy than earlier markers. Since aptamers are ssDNA or RNA that bind to a wide variety of target molecules, the purpose of this research was to select an aptamer from a 79bp single-stranded DNA (ssDNA) random library that was used to bind the Human Cardiac Troponin I from a synthetic nucleic acids library by systematic evolution of ligands exponential enrichment (Selex) based on several selection and amplification steps. Human Cardiac Troponin I protein was coated onto the surface of streptavidin magnetic beads to extract specific aptamer from a large and diverse random ssDNA initial oligonucleotide library. As a result, several aptamers were selected and further examined for binding affinity and specificity. Finally TnIApt 23 showed beast affinity in nanomolar range (2.69nM) toward the target protein. A simple and rapid colorimetric detection assay for Human Cardiac Troponin I using the novel and specific aptamer-AuNPs conjugates based on dot blot assay was developed. The detection limit for this protein using aptamer-AuNPs-based assay was found to be 5ng/ml. PMID:26003883

  11. Synthesis of gold-cellobiose nanocomposites for colorimetric measurement of cellobiase activity.

    PubMed

    Lai, Cui; Zeng, Guang-Ming; Huang, Dan-Lian; Zhao, Mei-Hua; Wei, Zhen; Huang, Chao; Xu, Piao; Li, Ning-Jie; Zhang, Chen; Chen, Ming; Li, Xue; Lai, Mingyong; He, Yibin

    2014-11-11

    Gold-cellobiose nanocomposites (GCNCs) were synthesized by reducing gold salt with a polysaccharide, cellobiose. Here, cellobiose acted as a controller of nucleation or stabilizer in the formation of gold nanoparticles. The obtained GCNCs were characterized with UV-visible spectroscopy; Zetasizer and Fourier transform infrared (FT-IR) spectrophotometer. Moreover, 6-Mercapto-1-hexanol (MCH) was modified on GCNCs, and the MCH-GCNCs were used to determine the cellobiase activity in compost extracts based on the surface plasmon resonance (SPR) property of MCH-GCNCs. The degradation of cellobiose on MCH-GCNCs by cellobiase could induce the aggregation, and the SPR absorption wavelength of MCH-GCNCs correspondingly red shifted. Thus, the absorbance ratio of treated MCH-GCNCs (A650/A520) could be used to estimate the cellobiase activity, and the probe exhibited highly sensitive and selective detection of the cellobiase activity with a wide linear from 3.0 to 100.0U L(-1) within 20 min. Meanwhile, a good linear relationship with correlation coefficient of R2=0.9976 was obtained. This approach successfully showed the suitability of gold nanocomposites as a colorimetric sensor for the sensitive and specific enzyme activity detection. PMID:24887498

  12. Phenylboronic acid modified silver nanoparticles for colorimetric dynamic analysis of glucose.

    PubMed

    Cao, Ke; Jiang, Xiaomei; Yan, Suting; Zhang, Laiying; Wu, Weitai

    2014-02-15

    The development of advanced nanostructures that allow dynamic quantification of glucose level can contribute to tight glucose control in diabetes management and other medical/biological fields. In this paper, we demonstrated that the assemblies of the 5-amino-2-fluorophenylboronic acid modified silver nanoparticles (FPBA-AgNPs) can be employed for highly modulating, sensitive, and selective colorimetric sensing of glucose over a physiologically important concentration range of 0-20mM at a physiological pH of 7.4. The glucose-modulated assembly of the FPBA-AgNPs occurred by the regulable formation of interparticle linkages via the bridged binding of 1,2-cis-diols and 5,6-cis-diols (for furanose form; or 4,6-cis-diols for pyranose form), respectively, of a glucose molecule to two FPBA-AgNPs. The detection limit was 89.0 ?M. The mean error of glucose detection in a macro-bio-system, blood serum of adult, was smaller than 10%. Furthermore, we show that the glucose level variations associated with a model biological reaction process can be monitored by using the FPBA-AgNPs, whilst with the reaction mechanism remaining nearly unchanged. PMID:24055932

  13. Synthesis of gold-cellobiose nanocomposites for colorimetric measurement of cellobiase activity

    NASA Astrophysics Data System (ADS)

    Lai, Cui; Zeng, Guang-Ming; Huang, Dan-Lian; Zhao, Mei-Hua; Wei, Zhen; Huang, Chao; Xu, Piao; Li, Ning-Jie; Zhang, Chen; Chen, Ming; Li, Xue; Lai, Mingyong; He, Yibin

    2014-11-01

    Gold-cellobiose nanocomposites (GCNCs) were synthesized by reducing gold salt with a polysaccharide, cellobiose. Here, cellobiose acted as a controller of nucleation or stabilizer in the formation of gold nanoparticles. The obtained GCNCs were characterized with UV-visible spectroscopy; Zetasizer and Fourier transform infrared (FT-IR) spectrophotometer. Moreover, 6-Mercapto-1-hexanol (MCH) was modified on GCNCs, and the MCH-GCNCs were used to determine the cellobiase activity in compost extracts based on the surface plasmon resonance (SPR) property of MCH-GCNCs. The degradation of cellobiose on MCH-GCNCs by cellobiase could induce the aggregation, and the SPR absorption wavelength of MCH-GCNCs correspondingly red shifted. Thus, the absorbance ratio of treated MCH-GCNCs (A650/A520) could be used to estimate the cellobiase activity, and the probe exhibited highly sensitive and selective detection of the cellobiase activity with a wide linear from 3.0 to 100.0 U L-1 within 20 min. Meanwhile, a good linear relationship with correlation coefficient of R2 = 0.9976 was obtained. This approach successfully showed the suitability of gold nanocomposites as a colorimetric sensor for the sensitive and specific enzyme activity detection.

  14. Leptophilic Dark Matter in Direct Detection Experiments and in the Sun

    SciTech Connect

    Kopp, Joachim; Niro, Viviana; Schwetz, Thomas; Zupan, Jure

    2010-11-01

    Dark matter interacting predominantly with leptons instead of nuclear matter has received a lot of interest recently. In this talk, we investigate the signals expected from such 'leptophilic Dark Matter' in direct detection experiments and in experiments looking for Dark Matter annihilation into neutrinos in the Sun. In a model-independent framework, we calculate the expected interaction rates for different scattering processes, including elastic and inelastic scattering off atomic electron shells, as well as loop-induced scattering off atomic nuclei. In those cases where the last effect dominates, leptophilic Dark Matter cannot be distinguished from conventional WIMPs. On the other hand, if inelastic scattering off the electron shell dominates, the expected event spectrum in direct detection experiments is different and would provide a distinct signal. However, we find that the signals in DAMA and/or CoGeNT cannot be explained by invoking leptophilic DM because the predicted and observed energy spectra do not match, and because of neutrino bounds from the Sun.

  15. On the existence of low-mass dark matter and its direct detection.

    PubMed

    Bateman, James; McHardy, Ian; Merle, Alexander; Morris, Tim R; Ulbricht, Hendrik

    2015-01-01

    Dark Matter (DM) is an elusive form of matter which has been postulated to explain astronomical observations through its gravitational effects on stars and galaxies, gravitational lensing of light around these, and through its imprint on the Cosmic Microwave Background (CMB). This indirect evidence implies that DM accounts for as much as 84.5% of all matter in our Universe, yet it has so far evaded all attempts at direct detection, leaving such confirmation and the consequent discovery of its nature as one of the biggest challenges in modern physics. Here we present a novel form of low-mass DM ? that would have been missed by all experiments so far. While its large interaction strength might at first seem unlikely, neither constraints from particle physics nor cosmological/astronomical observations are sufficient to rule out this type of DM, and it motivates our proposal for direct detection by optomechanics technology which should soon be within reach, namely, through the precise position measurement of a levitated mesoscopic particle which will be perturbed by elastic collisions with ? particles. We show that a recently proposed nanoparticle matter-wave interferometer, originally conceived for tests of the quantum superposition principle, is sensitive to these collisions, too. PMID:25622565

  16. Form factor effects in the direct detection of isospin-violating dark matter

    NASA Astrophysics Data System (ADS)

    Zheng, Hao; Zhang, Zhen; Chen, Lie-Wen

    2014-08-01

    Isospin-violating dark matter (IVDM) provides a possible mechanism to ameliorate the tension among recent direct detection experiments. For IVDM, we demonstrate that the results of direct detection experiments based on neutron-rich target nuclei may depend strongly on the density dependence of the symmetry energy which is presently largely unknown and controls the neutron skin thickness that reflects the relative difference of neutron and proton form factors in the neutron-rich nuclei. In particular, using the neutron and proton form factors obtained from Skyrme-Hartree-Fock calculations by varying the symmetry energy within the uncertainty region set by the latest model-independent measurement of the neutron skin thickness of 208Pb from PREX experiment at JLab, we find that, for IVDM with neutron-to-proton coupling ratio fixed to fn/fp=-0.7, the form factor effect may enhance the sensitivity of Xe-based detectors (e.g., XENON100 and LUX) to the DM-proton cross section by a factor of 3 in the DM mass region constrained by CMDS-II(Si) and even by more than an order of magnitude for heavy DM with mass larger than 80 GeV, compared with the results using the empirical Helm form factor. Our results further indicate that the form factor effect can significantly modify the recoil spectrum of Xe-based detectors for heavy IVDM with fn/fp=-0.7.

  17. Turbine Reliability and Operability Optimization through the use of Direct Detection Lidar Final Technical Report

    SciTech Connect

    Johnson, David K; Lewis, Matthew J; Pavlich, Jane C; Wright, Alan D; Johnson, Kathryn E; Pace, Andrew M

    2013-02-01

    The goal of this Department of Energy (DOE) project is to increase wind turbine efficiency and reliability with the use of a Light Detection and Ranging (LIDAR) system. The LIDAR provides wind speed and direction data that can be used to help mitigate the fatigue stress on the turbine blades and internal components caused by wind gusts, sub-optimal pointing and reactionary speed or RPM changes. This effort will have a significant impact on the operation and maintenance costs of turbines across the industry. During the course of the project, Michigan Aerospace Corporation (MAC) modified and tested a prototype direct detection wind LIDAR instrument; the resulting LIDAR design considered all aspects of wind turbine LIDAR operation from mounting, assembly, and environmental operating conditions to laser safety. Additionally, in co-operation with our partners, the National Renewable Energy Lab and the Colorado School of Mines, progress was made in LIDAR performance modeling as well as LIDAR feed forward control system modeling and simulation. The results of this investigation showed that using LIDAR measurements to change between baseline and extreme event controllers in a switching architecture can reduce damage equivalent loads on blades and tower, and produce higher mean power output due to fewer overspeed events. This DOE project has led to continued venture capital investment and engagement with leading turbine OEMs, wind farm developers, and wind farm owner/operators.

  18. Direct electron detection yields cryo-EM reconstructions at resolutions beyond ¾ Nyquist frequency

    PubMed Central

    Bammes, Benjamin E.; Rochat, Ryan H.; Jakana, Joanita; Chen, Dong-Hua; Chiu, Wah

    2012-01-01

    One limitation in electron cryo-microscopy (cryo-EM) is the inability to recover high-resolution signal from the image-recording media at the full-resolution limit of the transmission electron microscope. Direct electron detection using CMOS-based sensors for digitally recording images has the potential to alleviate this shortcoming. Here, we report a practical performance evaluation of a Direct Detection Device (DDD) for biological cryo-EM at two different microscope voltages: 200 and 300 kV. Our DDD images of amorphous and graphitized carbon show strong per-pixel contrast with image resolution near the theoretical sampling limit of the data. Single-particle reconstructions of two frozen-hydrated bacteriophages, P22 and ?15, establish that the DDD is capable of recording usable signal for 3-D reconstructions at about 4/5 of the Nyquist frequency, which is a vast improvement over the performance of conventional imaging media. We anticipate the unparalleled performance of this digital recording device will dramatically benefit cryo-EM for routine tomographic and single-particle structural determination of biological specimens. PMID:22285189

  19. WMAP constraints, supersymmetric dark matter, and implications for the direct detection of supersymmetry

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Utpal; Corsetti, Achille; Nath, Pran

    2003-08-01

    Recently WMAP has measured the cosmological parameters to a much greater accuracy. We analyze the implications of this more precise measurement for supersymmetric dark matter and for the direct detection of supersymmetry at accelerators. We consider MSUGRA including also the hyperbolic branch (HB) in the radiative breaking of the electroweak symmetry. On the part of the hyperbolic branch where the lightest neutralino is dominantly a Higgsino rather than being mostly a B-ino, the relic density constraints are satisfied by coannihilation with the next lightest neutralino and the light chargino. Including this branch the lightest neutralino mass satisfies m?01?1200 GeV for tan ??50. Constraints of b?s+?, of g?-2, and of B0s??+?- are also analyzed. It is shown that the neutralino-proton cross section in each case will fall within the reach of dark matter experiments. The possibility for the direct detection of supersymmetry is discussed in the allowed regions of the parameter space consistent with WMAP constraints. A brief discussion of the hyperbolic branch and focus point region (HB/FP) is also given.

  20. On the Existence of Low-Mass Dark Matter and its Direct Detection

    E-print Network

    James Bateman; Ian McHardy; Alexander Merle; Tim R. Morris; Hendrik Ulbricht

    2014-05-21

    Dark Matter (DM) is an elusive form of matter which has been postulated to explain astronomical observations through its gravitational effects on stars and galaxies, gravitational lensing of light around these, and through its imprint on the Cosmic Microwave Background (CMB). This indirect evidence implies that DM accounts for as much as 84.5% of all matter in our Universe, yet it has so far evaded all attempts at direct detection, leaving such confirmation and the consequent discovery of its nature as one of the biggest challenges in modern physics. Here we present a novel form of low-mass DM $\\chi$ that would have been missed by all experiments so far. While its large interaction strength might at first seem unlikely, neither constraints from particle physics nor cosmological/astronomical observations are sufficient to rule out this type of DM, and it motivates our proposal for direct detection by optomechanics technology which should soon be within reach, namely, through the precise position measurement of a levitated mesoscopic particle which will be perturbed by elastic collisions with $\\chi$ particles. We show that a recently proposed nanoparticle matter-wave interferometer, originally conceived for tests of the quantum superposition principle, is sensitive to these collisions, too.