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  • Articles  (354)
  • Biology  (354)
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  • Articles  (354)
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  • 1
    Electronic Resource
    Electronic Resource
    A MEMBRANE SEPARATOR/BIOREACTOR COUPLED WITH ABSORBANCE MEASUREMENT FOR DETECTION OF Escherichia coli O157:H7 (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of rapid methods and automation in microbiology 9 (2001), S. 0 
    Details
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A membrane separator/bioreactor system was developed for rapid detection of Escherichia coli O157:H7. The system consisted of a membrane separator/bioreactor (0.45 μm of the pore size) to separate the-complexes of E. coli O157:H7 and alkaline phosphatase-conjugated anti-E. coli O157:H7 antibodies from the sample and to produce p-nitrophenol through the enzymatic reaction (p-nitrophenyl phosphate hydrolysis), and an optical detector for measuring the p-nitrophenol absorbance at 400 nm. The membrane material and the flow rate of the substrate for the enzymatic hydrolysis had great effects on the absorbance of p-nitrophenol. The optimum conditions for the enzymatic reaction were determined as 1.0 M Tris buffer, pH 8.0, and 0.1 M MgCl2 for this system. The detection range was 104± 107 CFU/mL with a relative standard deviation of 4.3 ± 14.2%, and whole procedure could be completed in 50 min without any enrichment and culture. Other bacteria such as Salmonella typhimurium, Campylobacter jejuni and Listeria monocytogenes had no significant interference with the detection of E. coli O157:H7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4581.2001.tb00232.x
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  • 2
    Electronic Resource
    Electronic Resource
    DETECTION OF VIABLE LISTERIA MONOCYTOGENES IN MILK USING AN ELECTROCHEMICAL METHOD (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of rapid methods and automation in microbiology 11 (2003), S. 0 
    Details
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  Growth of Listeria monocytogenes in a Listeria enrichment broth (LEB) was automatically monitored by electrochemical cyclic voltammetric scan using a gold working electrode. Changes in cyclic voltammograms were observed during growth of L. monocytogenes in LEB. The reduction peak at −0.4 V (vs Ag/AgCl) corresponding to the reduction of oxygen dissolved in LEB on cyclic voltammograms was decreasing with proliferation of L. monocytogenes, and disappeared eventually. A pair of reversible redox peaks appeared during growth of L. monocytogenes in LEB. These cyclic voltammetric characteristics can be used to detect L. monocytogenes in various samples. Threshold values (detection time) obtained from the oxygen consumption curves were inversely related to the concentrations of L. monocytogenes in the broth. A calibration curve was obtained by plotting initial cell concentrations (CFU/mL) determined by conventional plate counting, as a function of the detection time. A linear response was found on the calibration curve for L. monocytogenes between 1 ∼ 9 times 100 and 1 ∼ 9 times 105 cells/mL. The detection time was approximately 17 and 6 h for 1 ∼ 9 times 100 and 1 ∼ 9 × 105 cells/mL of viable L. monocytogenes in the broth, respectively. The method was evaluated in detection of L. monocytogenes in milk samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4581.2003.tb00404.x
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  • 3
    Electronic Resource
    Electronic Resource
    PCR-BASED FLUORESCENT METHOD FOR RAPID DETECTION OF SALMONELLA TYPHIMURIUM IN POULTRY SAMPLES (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of rapid methods and automation in microbiology 10 (2002), S. 0 
    Details
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A DNA binding fluorescence method based on polymerase chain reaction (PCR) products was evaluated for rapid detection of Salmonella Typhimurium in poultry products. Wash water samples of chicken carcasses and ground turkey were inoculated with S. Typhimurium to obtain final concentrations of 10° - 105 CFU/mL. One mL of each sample was used to get the DNA template and 5 μL of the sample template was added into 25 μL of SYBR Green PCR Master Mix and two specific Salmonella ompC gene primers. The negative control was the same except 5 μL of each wash solution was added instead of 5 μL sample template. The reaction was carried out in a thermocycler. Finally, the fluorescence signal of each PCR product was measured using a fluorometer. The PCR products were also confirmed by ethidium bromide agarose gel, and the DNA concentrations of the PCR products were measured by a filter fluorescence photometer. The results showed that when bacterial cells increased from 0 to 2 CFU/mL, the fluorescence signal increased significantly. The PCR-based fluorescence method could detect the target bacteria in minutes after PCR amplification compared to hours by gel electrophoresis and also could be done at an earlier time during PCR amplification. The detection limit of this method for S. Typhimurium in the poultry samples was 2 CFU/mL without any enrichment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4581.2002.tb00014.x
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  • 4
    Electronic Resource
    Electronic Resource
    A CHEMILUMINESCENCE BIOSENSOR COUPLED WITH IMMUNOMAGNETIC SEPARATION FOR RAPID DETECTION OF SALMONELLA TYPHIMURIUM (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of rapid methods and automation in microbiology 11 (2003), S. 0 
    Details
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A chemiluminescence biosensor, using a fiber-optic-linked photometer and a data acquisition unit connected to a PC, was developed in conjunction with immunomagnetic separation for rapid detection of Salmonella Typhimurium. Magnetic microbeads coated with Anti-Salmonella antibodies and anti-Salmonella antibodies conjugated with horseradish peroxidase (HRP) were added to artificially-inoculated samples, and the immuno-reaction was completed in 60 min resulting in a sandwich complex. A magnetic field was applied to collect magnetic beads and the addition of luminol to HRP-conjugated antibodies resulted in a chemiluminescence reaction. The signal was collected through a fiber optic light guide, measured with a photometer, and recorded in the data acquisition unit. The minimum detection limit of the chemiluminescence biosensor for S. Typhimurium was 1.97 × 103 CFU/mL and the range of the detectable signal was from 8.6 to 350 mV for cell numbers from 1.97 × 103 to 1.97 × 106 CFU/mL. Signal values for 106 CFU/mL of S. Typhimurium were at least 97 and 394% higher than the corresponding values for S. enteritidis and four times the signal values for others including S. montevideo, S. california, S. heidlberg, and S. seftenberg, respectively. The biosensor response showed a significant difference (P 〈 0.05) between 103 CFU/mL S. Typhimurium and 106 CFU/mL of commonly-occurring bacteria in foods including Listeria monocytogenes, Pseudomonas aeruginosa, Citrobacter freundii, Campylobacter jejuni, Escherichia coli O157, and generic Escherichia coli. A regression equation, V = 0.0262 N 5.7713, with R2= 0.9713 was obtained for the calibration curve over the detection range for S. Typhimurium. The whole procedure could be completed within 90 min.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4581.2003.tb00034.x
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  • 5
    Electronic Resource
    Electronic Resource
    RAPID DETECTION OF SALMONELLA TYPHIMURIUM IN FOOD SAMPLES USING A BIENZYME ELECTROCHEMICAL BIOSENSOR WITH FLOW INJECTION (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of rapid methods and automation in microbiology 9 (2001), S. 0 
    Details
    ISSN: 1745-4581
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A bienzyme (tyrosinase and horseradish peroxidase) electrochemical biosensor was developed for detection of Salmonella typhimurium, and evaluated for application in a flow injection system coupled with immunomagnetic separation for food samples. Parameters for immunomagnetic separation, enzymatic reaction, flow injection and electrochemical detection were determined using pure culture samples. The selectivity was tested in the presence of Listeria monocytogenes, Campylobacter jejuni and E. coli 0157:H7. The results showed a linear relationship for logarithmic values between peak current ratio and the cell number of S. typhimurium in the range of 103 105 cfu/mL, with R2= 0.99. The detection limit of this method was 1.09 × 103 cfu/mL for S. typhimurium and the detection time was 2.5 h. Samples of chicken carcass wash water and ground beef were used to evaluate the biosensor. The results demonstrated that this biosensor has a potential for rapid detection of different pathogens in various food samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4581.2001.tb00249.x
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  • 6
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    Programmable active kirigami metasheets with more freedom of actuation (2019)
    National Academy of Sciences
    Details
    Publication Date: 2019-12-16
    Description: Kirigami (cutting and/or folding) offers a promising strategy to reconfigure metamaterials. Conventionally, kirigami metamaterials are often composed of passive cut unit cells to be reconfigured under mechanical forces. The constituent stimuli-responsive materials in active kirigami metamaterials instead will enable potential mechanical properties and functionality, arising from the active control of cut unit cells. However, the planar features of hinges in conventional kirigami structures significantly constrain the degrees of freedom (DOFs) in both deformation and actuation of the cut units. To release both constraints, here, we demonstrate a universal design of implementing folds to reconstruct sole-cuts–based metamaterials. We show that the supplemented folds not only enrich the structural reconfiguration beyond sole cuts but also enable more DOFs in actuating the kirigami metasheets into 3 dimensions (3D) in response to environmental temperature. Utilizing the multi-DOF in deformation of unit cells, we demonstrate that planar metasheets with the same cut design can self-fold into programmable 3D kirigami metastructures with distinct mechanical properties. Last, we demonstrate potential applications of programmable kirigami machines and easy-turning soft robots.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 7
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    Beyond sixfold coordinated Si in SiO2glass at ultrahigh pressures (2017)
    National Academy of Sciences
    Details
    Publication Date: 2017-09-05
    Description: We investigated the structure of SiO2glass up to 172 GPa using high-energy X-ray diffraction. The combination of a multichannel collimator with diamond anvil cells enabled the measurement of structural changes in silica glass with total X-ray diffraction to previously unachievable pressures. We show that SiO2first undergoes a change in Si–O coordination number from fourfold to sixfold between 15 and 50 GPa, in agreement with previous investigations. Above 50 GPa, the estimated coordination number continuously increases from 6 to 6.8 at 172 GPa. Si–O bond length shows first an increase due to the fourfold to sixfold coordination change and then a smaller linear decrease up to 172 GPa. We reconcile the changes in relation to the oxygen-packing fraction, showing that oxygen packing decreases at ultrahigh pressures to accommodate the higher than sixfold Si–O coordination. These results give experimental insight into the structural changes of silicate glasses as analogue materials for silicate melts at ultrahigh pressures.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    Deep melting reveals liquid structural memory and anomalous ferromagnetism in bismuth (2017)
    National Academy of Sciences
    Details
    Publication Date: 2017-03-13
    Description: As an archetypal semimetal with complex and anisotropic Fermi surface and unusual electric properties (e.g., high electrical resistance, large magnetoresistance, and giant Hall effect), bismuth (Bi) has played a critical role in metal physics. In general, Bi displays diamagnetism with a high volumetric susceptibility (∼10−4). Here, we report unusual ferromagnetism in bulk Bi samples recovered from a molten state at pressures of 1.4–2.5 GPa and temperatures above ∼1,250 K. The ferromagnetism is associated with a surprising structural memory effect in the molten state. On heating, low-temperature Bi liquid (L) transforms to a more randomly disordered high-temperature liquid (L′) around 1,250 K. By cooling from above 1,250 K, certain structural characteristics of liquid L′ are preserved in L. Bi clusters with characteristics of the liquid L′ motifs are further preserved through solidification into the Bi-II phase across the pressure-independent melting curve, which may be responsible for the observed ferromagnetism.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Ultrahigh-pressure polyamorphism in GeO2 glass with coordination number 〉6 (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-03-14
    Description: Knowledge of pressure-induced structural changes in glasses is important in various scientific fields as well as in engineering and industry. However, polyamorphism in glasses under high pressure remains poorly understood because of experimental challenges. Here we report new experimental findings of ultrahigh-pressure polyamorphism in GeO2 glass, investigated using a newly developed double-stage large-volume cell. The Ge–O coordination number (CN) is found to remain constant at ∼6 between 22.6 and 37.9 GPa. At higher pressures, CN begins to increase rapidly and reaches 7.4 at 91.7 GPa. This transformation begins when the oxygen-packing fraction in GeO2 glass is close to the maximal dense-packing state (the Kepler conjecture = ∼0.74), which provides new insights into structural changes in network-forming glasses and liquids with CN higher than 6 at ultrahigh-pressure conditions.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Shallow particulate organic carbon regeneration in the South Pacific Ocean (2019)
    National Academy of Sciences
    Details
    Publication Date: 2019-04-29
    Description: Particulate organic carbon (POC) produced in the surface ocean sinks through the water column and is respired at depth, acting as a primary vector sequestering carbon in the abyssal ocean. Atmospheric carbon dioxide levels are sensitive to the length (depth) scale over which respiration converts POC back to inorganic carbon, because shallower waters exchange with the atmosphere more rapidly than deeper ones. However, estimates of this carbon regeneration length scale and its spatiotemporal variability are limited, hindering the ability to characterize its sensitivity to environmental conditions. Here, we present a zonal section of POC fluxes at high vertical and spatial resolution from the GEOTRACES GP16 transect in the eastern tropical South Pacific, based on normalization to the radiogenic thorium isotope 230Th. We find shallower carbon regeneration length scales than previous estimates for the oligotrophic South Pacific gyre, indicating less efficient carbon transfer to the deep ocean. Carbon regeneration is strongly inhibited within suboxic waters near the Peru coast. Canonical Martin curve power laws inadequately capture POC flux profiles at suboxic stations. We instead fit these profiles using an exponential function with flux preserved at depth, finding shallow regeneration but high POC sequestration below 1,000 m. Both regeneration length scales and POC flux at depth closely track the depths at which oxygen concentrations approach zero. Our findings imply that climate warming will result in reduced ocean carbon storage due to expanding oligotrophic gyres, but opposing effects on ocean carbon storage from expanding suboxic waters will require modeling and future work to disentangle.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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