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  • Physics (General)
  • Pathogens & Pathogenicity
  • Nucleic acid structure, RNA characterisation and manipulation, Computational Methods
  • 1
    Publication Date: 2016-02-20
    Description: Culture medium from an isolate of the fungus Aspergillus candidus was extracted, fractionated and examined to discover compounds antagonistic to plant-parasitic nematodes that are important pathogens of agricultural crops. Column, thin layer and preparative chromatographies and spectral and elemental analyses, were used to isolate and identify two major constituents of an active fraction (Fraction F) obtained from the medium. Compound 1 was identified as 2-hydroxypropane-1, 2, 3-tricarboxylic acid (citric acid). Compound 2 was identified as 3-hydroxy-5-methoxy-3-(methoxycarbonyl)-5-oxopentanoic acid, an isomer of 1, 2-dimethyl citrate. Compound 1 and a citric acid standard, each tested at 50 mg mL –1 in water, decreased hatch from eggs of the plant-parasitic nematode Meloidogyne incognita by more than 94%, and completely immobilized second-stage juveniles after 4–6 days exposure. Fraction F and Compounds 1 and 2 decreased the mobility of adults of the plant-parasitic nematode Ditylenchus destructor in vitro . Fraction F (25 mg mL –1 ) inhibited mobility 〉99% at 72 hrs. Compounds 1 and 2 (50 mg mL –1 ) each inhibited mobility more than 25% at 24 hr and more than 50% at 72 hr. This is the first assignment of nematode-antagonistic properties to specifically identified A. candidus metabolites.
    Keywords: Pathogens & Pathogenicity
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
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  • 2
    Publication Date: 2016-04-21
    Description: RNA–RNA interactions are fast emerging as a major functional component in many newly discovered non-coding RNAs. Basepairing is believed to be a major contributor to the stability of these intermolecular interactions, much like intramolecular basepairs formed in RNA secondary structure. As such, using algorithms similar to those for predicting RNA secondary structure, computational methods have been recently developed for the prediction of RNA–RNA interactions. We provide the first comprehensive comparison comprising 14 methods that predict general intermolecular basepairs. To evaluate these, we compile an extensive data set of 54 experimentally confirmed fungal snoRNA–rRNA interactions and 102 bacterial sRNA–mRNA interactions. We test the performance accuracy of all methods, evaluating the effects of tool settings, sequence length, and multiple sequence alignment usage and quality. Our results show that—unlike for RNA secondary structure prediction—the overall best performing tools are non-comparative energy-based tools utilizing accessibility information that predict short interactions on this data set. Furthermore, we find that maintaining high accuracy across biologically different data sets and increasing input lengths remains a huge challenge, causing implications for de novo transcriptome-wide searches. Finally, we make our interaction data set publicly available for future development and benchmarking efforts.
    Keywords: Nucleic acid structure, RNA characterisation and manipulation, Computational Methods
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 3
    Publication Date: 2018-06-06
    Description: We present the results of experimental investigations of gradient driven fluctuations induced in a liquid mixture with a concentration gradient and in a single-component fluid with a temperature gradient. We also describe the experimental apparatus being developed to carry out similar measurement under microgravity conditions.
    Keywords: Physics (General)
    Type: 2004 Photon Correlation and Scattering Conference; 50-51; NASA/CP-2004-213207
    Format: application/pdf
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  • 4
    Publication Date: 2019-07-12
    Description: No abstract available
    Keywords: Physics (General)
    Type: GRC-E-DAA-TN37909
    Format: application/pdf
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  • 5
    Publication Date: 2019-07-13
    Description: The attached slides are for an invited talk (invitation from Ken Savins at CASIS) to be given July 19 at the "2018 Microgravity Molecular Crystal Growth Workshop". Ken Savins indicated that the protein crystal growth community would benefit from knowing more about what is available on ISS for microscopy. It is especially important that the folks growing protein crystals start to use the microscopes on ISS as diagnostic tools so that when their samples are returned to Earth and the results are unexpected, they are able to determine whether or not the return flight had an impact. In additional to preparing this presentation describing present and possible future LMM capabilities (if it is refurbished), we worked with Rachel A Ormsby (techshot) and Devin Ridgley (HNu Photonics) to add slides and a movie they provided of their capacities. Contact information for the NASA GRC Liquid Crystal Facility (LCF) will be included, and a couple of slides for LCF may be added when the contractor (James Kolibas at ZIN Technology) returns from vacation.
    Keywords: Physics (General)
    Type: GRC-E-DAA-TN58674 , Microgravity Molecular Crystal Growth Workshop; Jul 19, 2018; Buffalo, NY; United States
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  • 6
    Publication Date: 2019-07-13
    Description: Increment 57-58 Science Symposium presentation of Advanced Colloids Experiment (ACE-T12) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators. This flight experiment was added after the Science Symposium, so these charts for more for reference, than presentation.
    Keywords: Physics (General)
    Type: GRC-E-DAA-TN63790 , Post - Increment 57 - 58 Science Symposium; Dec 31, 2018; Web Ex
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  • 7
    Publication Date: 2019-08-13
    Description: Increment 53 - 54 Science Symposium presentation of Advanced Colloids Experiment (ACE-T6) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.
    Keywords: Physics (General)
    Type: GRC-E-DAA-TN44673
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  • 8
    Publication Date: 2019-08-13
    Description: Increment 53 - 54 Science Symposium presentation of Advanced Colloids Experiment (ACE-T9) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.
    Keywords: Physics (General)
    Type: GRC-E-DAA-TN44672
    Format: application/pdf
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  • 9
    Publication Date: 2019-07-10
    Description: The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17)/cu cm. The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.
    Keywords: Physics (General)
    Type: SUDAAR-679
    Format: text
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  • 10
    Publication Date: 2019-07-11
    Description: Numerical simulation studies are reported for the convection of a supercritical fluid, He-3, in a Rayleigh-Benard cell. The calculations provide the temporal profile DeltaT(t) of the temperature drop across the fluid layer. In a previous article, systematic delays in the onset of the convective instability in simulations relative to experiments were reported, as seen from the DeltaT(t) profiles. They were attributed to the smallness of the noise which is needed to start the instability. Therefore i) homogeneous temperature noise and ii) spatial lateral periodic temperature variations in the top plate were programmed into the simulations, and DeltaT(t) compared with that of an experiment with the same fluid parameters. An effective speed-up in the instability onset was obtained, with the best results obtained through the spatial temperature variations with a period of 2L, close to the wavelength of a pair of convections rolls. For a small amplitude of 0.5 micro-K, this perturbation gave a semiquantitative agreement with experimental observations. Results for various noise amplitudes are presented and discussed in relation to predictions by El Khouri and Carl es.
    Keywords: Physics (General)
    Type: Proceedings of the 2004 NASA/JPL Workshop on Physics for Planetary Exploration; JPL-Publ-05-4
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