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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 133 (1990), S. 149-165 
    ISSN: 1420-9136
    Keywords: Volcanic seismicity ; volcanic gravity anomaly ; volcanic tectonics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Subduction induced compressional stress, lateral displacement faults probably linked to the NW extension of the Polochic-Motagua fault system, and local magma emplacement create a complex geological setting for the El Chichon volcano. Gravity analysis reveals that the principal structures in the area correspond to synclines and anticlines. Downward continuation of the gravity field suggests the presence of magma emplacement SE of the volcano. This magmatic emplacement appears to be the principal cause of the truncation of the syncline in which the volcano lies. Analyses of earthquakes occurring after eruptions show that the vertical distribution of events is confined to a roughly cylindrical zone which correlates well with the region of magmatic emplacement inferred from the gravity analysis. Even though more than 350 km separate the volcano from the Middle American trench, the compressional stress regime reported for the area may correlate with subduction stress (N30°E). However, the strike direction for the principal faults in the zone, N60°W, permits us to postulate that the NW extension of the Polochic-Motagua fault system is implicated in the local tectonics of the El Chichon area.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 49 (1989), S. 729-737 
    ISSN: 1432-0630
    Keywords: 68.55.+ b ; 82.40.Dm ; 61.14.Hg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A new development of molecular beam epitaxy (MBE) for III–V compounds is described, based on cyclic perturbation of the growth front at atomic layer level by periodic pulsing, alternating or interrupting the molecular beams. The modification of the growth mechanism caused by this perturbations is discussed and related to periodic changes of surface stoichiometry which induce 2D growth mechanism by enhanced layer nucleation. Under appropriate modulation conditions, an atomic layer by layer growth mode can be achieved. A practical implementention of this mode, that we denote atomic layer MBE (ALMBE), is considered in which only group V beams are pulsed in a specially designed effusion cell. A number of growth applications of ALMBE are presented, including growth of highly mismatched heterostructures and short period superlattices containing two different group V elements such as arsenic and phosphorous.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: TiSiN coatings have been prepared by reactive DC magnetron co-sputtering on Corning glass and carbon steel substrates, using Ti-Si targets, with a constant Si:Ti area ratio of 0.2. The flow rate of nitrogen has been varied from 1.6 to 7.0 sccm, for a fixed argon flow rate of 25.0 sccm. We present a study of structure (texture, crystallite size and microstrain), chemical composition, and mechanical properties of the coatings and their dependence on the argon/nitrogenratio. Moreover, a study of the thermal stability of the coatings has been performed by means of thermal annealing under oxidizing conditions (air atmosphere) at 500 and 600 °C. Coatings with the smallest crystallite size (∼2 nm) present the highest hardness (26 GPa) and the best thermal stability
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 11134-11142 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Starting from optimal control, various series of infrared, ultrashort laser pulses with analytical shapes are designed in order to drive a preoriented molecule from its ground torsional state, which represents the coherent superposition of left and right atropisomers, towards a single enantiomer. Close analysis of the population dynamics, together with the underlying symmetry selection rules for the laser induced transitions, yields the mechanism. Namely, the molecule is driven from its ground vibrational state towards the coherent superposition of the lowest doublet of states via a doublet of excited torsional states with opposite symmetries. This pump-and-dump mechanism can be achieved by simpler series of analytical laser pulses. This decomposition of the optimal pulse into analytical subpulses allows us to design different scenarios for the selective preparation of left or right enantiomers. Exemplary this is demonstrated by quantum simulations of representative wave packets for the torsional motions of the model system, H2POSH, in the electronic ground state, based on the ab initio potential energy surface, and with ab initio dipole couplings. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 2373-2376 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The orbital free ab initio molecular dynamics method is applied to study the static and dynamic structure of liquid Al near the triple point. The method uses a new kinetic energy functional, along with a local pseudopotential constructed within the same kinetic energy functional. The results obtained for the dynamic structure factor are compared with recent experimental data. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Samples of skin tissue were collected by biopsy darting from humpback whales (Megaptera novaeangliae) in six seasonal habitats representing three stocks and four regions: Groups IV (western Australia), V western component (eastern Australia), V eastern component (New Zealand and Tonga) and VI (the Antarctic Peninsula and Gorgona Island, Colombia, South America) of the Southern Hemisphere. A variable section of the mitochondrial DNA control region was amplified and sequenced from 84 of these individuals, distinguishing a total of 48 unique sequences (i. e., mtDNA nucleotypes). Phylogenetic reconstructions suggested that these nucleotypes form three clades, corresponding to those previously described in a world-wide survey of humpback whale mtDNA variation, although bootstrap support for two of the clades was relatively low (〈50%). An analysis of variance adapted for molecular information showed significant differentiation of nucleotypes among the three Groups (Stocks) and heterogeneity of haplotype diversity among the four regions. A pattern of interchange within and between oceanic basins was demonstrated by the presence of shared identical nucleotypes among humpback whales in regions of the Southern and Northern Hemispheres.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Gerodontology 6 (1987), S. 0 
    ISSN: 1741-2358
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Alzheimer's disease, or pre-senile dementia, may occur as early as 40 years. Pathologically, there is, besides a loss of brain weight, a conical atrophy with ventricular dilatation and typical microscopic lesions in the cortex and the hippocampus. Previously, the authors [Sanchez & Gonzalez, 1986] have studied the modifications of the amino acids (AA) composition in the cerebrospinal fluid (CSF), Even if some were increased without specificity, three of them were decreased significantly in this type of dementia (Serine, Glutamate and Aspartate). Twenty subjects were studied (15 with Alzheimer's disease and 5 non-patients) having a mean age of 72 years. For each subject, two samples were tested (one blood and one saliva sample). In this study we tried to determine if our results would be similar to those previously obtained in the CSF, but in a different biological fluid, the saliva. Of the 13 AA of the saliva, tested by gas-liquid chromatology (Spectra Physics 7100), 3 were increased significantly, and curiously, these were similar to those found to be decreased in CSF. We attempted to find the possible biological and oral repercussions of this dementia, which is the most frequent type in elderly patients.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Forest Ecology and Management 70 (1994), S. 113-119 
    ISSN: 0378-1127
    Keywords: Afforestation ; Implantation ; Prosopis spp. ; Seedling survival ; Survival
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0378-1119
    Keywords: Nitrogen and carbon regulation ; glutamate dehydrogenase ; mRNA levels ; primer extension ; recombinant DNA ; site-directed mutagenesis
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Plasmid 30 (1993), S. 131-140 
    ISSN: 0147-619X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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