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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 51-59 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct liquid introduction negative ion mass spectra have been studied for some kirromycin class antibiotics. A scheme for the interpretation of the mass spectral fragmentation patterns is presented and shown to be useful for structure elucidation and novelty determination. Since these spectra are obtained by liquid chromatography/mass spectrometry, antibiotic isolates need not be highly purified. However, where pure preparations are available confirmation of molecular weight assignments may be obtained with fast atom bombardment ionization.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 14 (1992), S. 69-73 
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fatigue resistance of 6 inch Schedule 40 PVC solvent-bonded pipe fittings was investigated. It has often been assumed that the performance of PVC fittings is comparable to that of the corresponding pipe. The results of this study indicate that the fatigue performance of PVC fittings is much lower than that of the pipe. Several fittings were exposed to a repetitive surge cycle of 90 to 180 psig at a rate of 0.111 hertz. Failures of several tees occurred between 13,000 and 16,000 cycles, much sooner than the predicted lifetime of pipe under these conditions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2011-03-09
    Description: A global chemistry-climate model is used to assess the impact on atmospheric composition of the regeneration and recycling of HOx in the photo-oxidation of isoprene. The impact is explored subject to present-day, pre-industrial and future climate/emission scenarios. Our calculations show that, in all cases, the inclusion of uni-molecular isomerisations of the isoprene hydroxy-peroxy radicals leads to enhanced production of HOx radicals and ozone. The global burden of ozone increases by 25–36 Tg (8–18%), depending on the climate/emissions scenario, whilst the changes in OH lead to decreases in the methane lifetime of between 11% in the future and 35% in the pre-industrial. Critically the size of the change in methane lifetime depends on the VOC/NOx emission ratio. The results of the present-day calculations suggest a certain amount of parameter refinement is still needed to reconcile the updated chemistry with field observations (particularly for HO2+RO2). However, the updated chemistry could have far-reaching implications for: future-climate predictions; projections of future oxidising capacity; and our understanding of past changes in oxidising capacity.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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  • 4
    Publication Date: 2011-08-04
    Description: An obstacle to the simultaneous use of near-infrared (NIR) and thermal infrared (TIR) observations from the Measurements of Pollution in the Troposphere (MOPITT) instrument has been a lack of understanding of NIR radiance errors. Retrieval uncertainties produced by optimal estimation-based retrieval algorithms used for satellite instruments like MOPITT are only meaningful if radiance error statistics are accurately quantified in the measurement error covariance matrix. MOPITT's gas correlation radiometers are subject to a unique form of “geophysical noise” due to the combined effects of (1) translational motion of the instrumental field of view during a single observation and (2) fine-scale spatial variability of surface radiative properties. We describe and demonstrate a new method for quantifying this source of error for each observation. Both TIR and NIR radiance errors due to this effect are highly variable, especially over land, but are qualitatively consistent with the variability of Moderate Resolution Imaging Spectroradiometer radiances in similar spectral bands. In addition, retrieval algorithm modifications are described which adjust the trade-off between smoothing error and retrieval noise within the optimal estimation framework. These modifications are necessary to fully exploit the information in MOPITT's NIR channels. A case study based on MOPITT observations over Minnesota demonstrates significant improvement in retrieval performance as the result of the retrieval algorithm modifications.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 5
    Publication Date: 2013-02-26
    Description: [1]  Thwaites Glacier, West Antarctica has the potential to directly contribute ~1 m to sea level, and currently is losing mass and thinning rapidly. Here we report on regional results for the Sea-level Response to Ice Sheet Evolution (SeaRISE) experiments and investigate the impact of i) spatial resolution within existing data sets, ii) grounding-zone processes, and iii) till rheology on the dynamics of this outlet glacier. In addition to the SeaRISE datasets, we use detailed aerogeophysical and satellite data from Thwaites Glacier as input to a coupled ice-stream/ice-shelf/ocean-plume model that includes oceanic influences across a several-kilometers-wide grounding zone suggested by new, high resolution data. Our results indicate that the ice tongue provides limited stability, and that while future atmospheric warming will likely add mass to the surface of the glacier, strong ice-stream stabilization on bedrock highs narrower than the length of the grounding zone may be ephemeral if circulating waters substantially reduce basal resistance and enhance melting beneath grounded ice within this zone. However, we find that stability is significantly enhanced by effectively-plastic till beds. Accurate projections of future sea-level changerelies on correct understanding of the till rheology as well as local basal processes near the grounding line.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 6
    Publication Date: 2014-05-09
    Description: The trypanosomatid parasite Leishmania infantum is the causative agent of visceral leishmaniasis (VL), which is usually fatal unless treated. VL has an incidence of 0.5 million cases every year and is an important opportunistic co-infection in HIV/AIDS. Tyrosine aminotransferase (TAT) has an important role in the metabolism of trypanosomatids, catalyzing the first step in the degradation pathway of aromatic amino acids, which are ultimately converted into their corresponding L-2-oxoacids. Unlike the enzyme in Trypanosoma cruzi and mammals, L. infantum TAT (LiTAT) is not able to transaminate ketoglutarate. Here, the structure of LiTAT at 2.35 Å resolution is reported, and it is confirmed that the presence of two Leishmania -specific residues (Gln55 and Asn58) explains, at least in part, this specific reactivity. The difference in substrate specificity between leishmanial and mammalian TAT and the importance of this enzyme in parasite metabolism suggest that it may be a useful target in the development of new drugs against leishmaniasis.
    Electronic ISSN: 1744-3091
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Physics
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