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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1569-1571 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN:Mg/AlGaN single-heterojunction light-emitting diodes were grown on Si(111) substrates by plasma-assisted molecular-beam epitaxy. High-quality Mg-doped GaN layers with hole concentrations up to 1.2×1017 holes/cm3 and intense low-temperature photoluminescence, which increases in annealed samples, were obtained. Smooth AlGaN layers, with surface roughness below 5 nm, were used as buffer layers. Continuous-wave room-temperature ultraviolet electroluminescence was observed at 365 nm with a full width at half maximum of 8 nm. An estimated optical power output of 1.5 μW was achieved under 15 V/35 mA operation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The optical, spectroscopic infrared remote imaging system (OSIRIS) is an instrument carried on board the European Space Agency spacecraft Rosetta that will be launched in January 2003 to study in situ the comet Wirtanen. The electronic design of the mechanism controller board (MCB) system of the two OSIRIS optical cameras, the narrow angle camera, and the wide angle camera, is described here. The system is comprised of two boards mounted on an aluminum frame as part of an electronics box that contains the power supply and the digital processor unit of the instrument. The mechanisms controlled by the MCB for each camera are the front door assembly and a filter wheel assembly. The front door assembly for each camera is driven by a four phase, permanent magnet stepper motor. Each filter wheel assembly consists of two, eight filter wheels. Each wheel is driven by a four phase, variable reluctance stepper motor. Each motor, for all the assemblies, also contains a redundant set of four stator phase windings that can be energized separately or in parallel with the main windings. All stepper motors are driven in both directions using the full step unipolar mode of operation. The MCB also performs general housekeeping data acquisition of the OSIRIS instrument, i.e., mechanism position encoders and temperature measurements. The electronic design application used is quite new due to use of a field programmable gate array electronic devices that avoid the use of the now traditional system controlled by microcontrollers and software. Electrical tests of the engineering model have been performed successfully and the system is ready for space qualification after environmental testing. This system may be of interest to institutions involved in future space experiments with similar needs for mechanisms control. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 3698-3705 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A detailed ab initio study on the torsional potential of two heterobutadienes (nitrosoformaldehyde and N-nitrosomethanimine) it is performed by using state-of-the-art coupled-cluster methodologies. Special emphasis is given to basis set incompleteness with a profuse comparison of several cc-pVnZ basis sets and to the performance of common extrapolation formulas for estimating the complete basis set limit. We give high quality torsional functions from a fit to our best calculations for its use in current force field methods. We analyze similarities and differences between the present heterobutadienes and similar compounds such as 1,3-butadiene and glyoxal. Finally, we provide accurate estimates to the proton affinities of nitrosoformaldehyde and N-nitrosomethanimine. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Using two cultivars of Pisum sativum L. with different sensitivity to NaCl, the effect of long-term (15 d) NaCl (70 m M) treatments on the activity and expression of the foliar ascorbate–glutathione cycle enzymes, superoxide dismutase isozymes and their mRNAs was evaluated and related to their ascorbate and glutathione contents. High-speed supernatant (soluble) fractions, enriched for cytosolic components of the antioxidant system, were used. In this fraction from the NaCl-tolerant variety (cv Granada), the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), Mn-superoxide dismutase (Mn-SOD) and dehydroascorbate reductase (DHAR) increased, while CuZn-SOD activity remained constant. In the NaCl-sensitive plants (cv Challis), salinity did not produce significant changes in APX, MDHAR and GR activities. Only DHAR activity was induced in cv Challis, whereas soluble CuZn-SOD activity decreased by about 35%. Total ascorbate and glutathione contents decreased in both cultivars, but the decline was greater in NaCl-sensitive plants. This difference between the two cultivars was more pronounced when the transcript levels of some these enzymes were examined. Transcript levels for mitochondrial Mn-SOD, chloroplastic CuZn-SOD and phospholipid hydroperoxide glutathione peroxidase (PHGPX), cytosolic GR and APX were strongly induced in the NaCl-tolerant variety but not in the NaCl-sensitive variety. These data strongly suggest that induction of antioxidant defences is at least one component of the tolerance mechanism of peas to long-term salt-stress.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous studies have shown the existence of proliferating cells in explants from bovine (Bos Taurus) lateral ventricle walls that were maintained for several days in vitro in the absence of serum and growth factors. In this study we have characterized the nature of new cells and have assessed whether the insulin-like growth factor-1 (IGF-1) receptor regulates their survival and/or proliferation. The explants were composed of the ependymal layer and attached subependymal cells. Ependymal cells in culture were labelled with glial markers (S-100, vimentin, GFAP, BLBP, 3A7 and 3CB2) and did not incorporate bromodeoxiuridine when this molecule was added to the culture media. Most subependymal cells were immunoreactive for βIII-tubulin, a neuronal marker, and did incorporate bromodeoxiuridine. Subependymal neurons displayed immunoreactivity for IGF-1 and its receptor and expressed IGF-1 mRNA, indicating that IGF-1 is produced in the explants and may act on new neurons. Addition to the culture media of an IGF-1 receptor antagonist, the peptide JB1, did not affect the incorporation of bromodeoxiuridine to proliferating subependymal cells. However, JB1 significantly increased the number of TUNEL positive cells in the subependymal zone, suggesting that IGF-1 receptor is involved in the survival of subependymal neurons. In conclusion, these findings indicate that neurogenesis is maintained in explants from the lateral cerebral ventricle of adult bovine brains and that IGF-1 is locally produced in the explants and may regulate the survival of the proliferating neurons.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of the European Academy of Dermatology and Venereology 15 (2001), S. 0 
    ISSN: 1468-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 207 (2002), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of different carbon sources on the expression in Saccharomyces cerevisiae of the SWA2α-amylase gene from Schwanniomyces occidentalis was studied from constructs containing its 5′ region (−223 to +15), which were fused in-frame to the lacZ gene coding sequence. Maximal expression was achieved with the non-fermentable substrates ethanol and/or glycerol, whereas lower levels were found with maltose or galactose. In contrast, glucose repressed it, even in the presence of any of these other carbon sources. Deletion analyses of the −233 to −85 SWA2 promoter region permitted the identification of two fragments involved in both glucose repression and ethanol activation. A possible region required for cAMP regulation was localised. The SWA2 promoter contains a MIG1-binding GC box whose deletion caused a five-fold increase in the glucose-repressed reporter expression. Despite this, expression of the SWA2 promoter was not MIG1-dependent.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 201 (2001), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: An amylolytic industrial yeast strain of Saccharomyces cerevisiae containing the Schwanniomyces occidentalis SWA2 amylase gene was generated. The new strain contains DNA derived exclusively from yeast and expresses a high starch hydrolyzing activity. Yeast transformation was carried out by an integrative process targeted to a dispensable upstream region of the ILV2 locus, which determines sulfometuron resistance. The SWA2 enzyme was constitutively expressed under the ADH1 promoter. The growth, substrate utilization and fermentative capacity of this organism are described.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Allergy 56 (2001), S. 0 
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1438-2385
    Keywords: Key wordsOlive ; Cell wall ; Processing ; Pitting ; Hemicelluloses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Olive fruits processed as “Spanish green olives” were sorted into two batches depending on their pitting behaviour: those that broke under punch pressure, and those that were pitted without damage. Cell wall polysaccharides from both batches were isolated. The main changes were lower amounts of carbonate-soluble and 24 % KOH-soluble polysaccharides and a higher proportion of 4% KOH-soluble polysaccharides in broken olives. The carbonate-soluble fraction from broken olives was poorer in homogalacturonans, polysaccharides that could help in increasing texture. The 24% KOH-soluble fraction from the same olive batch was poorer in xylans and xyloglucans, the former being present in a higher proportion in the 4% KOH-soluble fraction and the last in cellulose residue. The new xylans of the 4% KOH-soluble fraction were of high (around 250 kDa) and low (6–40 kDa) molecular weights. Carbonate-soluble and 24% KOH-soluble fractions are very important in maintaining cell wall structure, which is responsible for vegetable product firmness.
    Type of Medium: Electronic Resource
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