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  • 1
    Electronic Resource
    Electronic Resource
    Aero-acoustic levitation: A method for containerless liquid-phase processing at high temperatures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 456-465 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method for containerless liquid-phase processing was developed which has practical application in process and property research on virtually any material which is involatile at the melting point. It combines aerodynamic and acoustic forces to support and position the levitated material. The design provides forced convection control of the thermal boundary in the gas surrounding beam-heated specimens, which stabilizes the acoustic forces and allows acoustic positioning necessary to stabilize the aerodynamic levitation forces on molten materials. Beam heating and melting at very high temperatures was achieved. Experiments were conducted on specimens with diameters in the range 0.25–0.4 cm, of density up to 9 g/cm3, at temperatures up to 2700 K, and in oxygen, air, or argon atmospheres. Unique liquid-phase processing results included deep undercooling of aluminum oxide, glass formation at exceptionally small cooling rates, complete melting and undercooling of YBa2Cu3Ox superconductor materials, direct formation of the YBa2Cu3Ox from the liquid phase, and the vaporization of volatile constituents from a low-liquefaction point glass to form a refractory, high melting material. The application of rapid containerless batch processing operations to materials synthesis is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145157
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  • 2
    Electronic Resource
    Electronic Resource
    Enantioselective hydrogenation of α-ketoesters over Pt/alumina modified with cinchonidine: theoretical investigation of the substrate-modifier interaction (1994)
    Springer
    Catalysis letters 23 (1994), S. 271-279 
    Details
    ISSN: 1572-879X
    Keywords: Enantioselective hydrogenation ; α-ketoesters ; α-hydroxyesters ; cinchonidine ; modifier ; Pt/alumina ; molecular modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Enantio-differentiation in the asymmetric hydrogenation of α-ketoesters to α-hydroxyesters over platinum catalysts modified with cinchona-alkaloid modifiers occurs through interaction of the ketoester with the cinchona modifier. The structure of the probable transition complex has been calculated for the system methyl pyruvate (substrate) cinchonidine (modifier) using molecular mechanics and quantum chemistry techniques at both ab initio and semiempirical levels. The calculations suggest that protonated cinchonidine is energetically more likely to interact with the substrate and that the crucial interaction occurs via hydrogen bonding of the quinuclidine nitrogen and the oxygen of the α-carbonyl moiety of methyl pyruvate. In this complex the methyl pyruvate is transformed into a half-hydrogenated species which is adsorbed on the platinum surface and on hydrogenation yields the product methyll actate. Theoretical studies indicate that adsorption of the complex leading to (R) -methyl lactate is energetically more favourable than that of the corresponding complex which yields (S) -methyl lactate, which may be the key for the enantio-differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811362
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  • 3
    Electronic Resource
    Electronic Resource
    Myotonic dystrophy and limb girdle muscular dystrophy in one family (1994)
    Springer
    Journal of molecular medicine 72 (1994), S. 409-413 
    Details
    ISSN: 1432-1440
    Keywords: Myotonic dystrophy ; Limb girdle muscular dystrophy ; Genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A family is reported in which a 29-year-old woman showed the clinical features of myotonic dystrophy while her 26-year-old brother presented with the clinical picture of limb girdle syndrome. In the affected female, direct genetic testing for the specific myotonic dystrophy mutation on chromosome 19 revealed abnormal expansion of a repeat unit containing the three nucleotides cytosine, thymine, and guanine (CTG) — typical for myotonic dystrophy — while her diseased brother displayed two normal alleles. This supports the hypothesis of the extremely rare occurrence of two clinically and genetically different myopathies in one family. Genetic analysis of six other family members showed that the father of the diseased siblings as well as all of his three brothers and sisters had a pathological CTG repeat expansion, and that the other two family members tested had a normal allelic pattern. The number of CTG repeats in the diseased women was approximately tenfold higher than in her asymptomatic relatives who revealed an abnormal allelic pattern. The increase in CTG repeats with transmission to a subsequent generation in this family was paralleled by a dramatic increase in the severity of myotonic dystrophy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252840
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  • 4
    Electronic Resource
    Electronic Resource
    Laser Doppler flowmetry of focal ischaemia and reperfusion in deep brain structures in rats (1994)
    Springer
    Acta neurochirurgica 131 (1994), S. 151-156 
    Details
    ISSN: 0942-0940
    Keywords: Middle cerebral artery occlusion ; cerebral blood flow ; ischaemia ; reperfusion ; laser Doppler flowmetry ; hydrogen clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Monitoring cerebral blood flow during focal ischaemia and reperfusion with established techniques such as hydrogen clearance and autoradiography is difficult. Laser Doppler flowmetry is a new technique, it allows one to continuously measure blood flow in small tissue samples. The objective of this study was to compare laser Doppler flowmetry with hydrogen clearance using a new single fiber probe to obtain measurements in deep brain structures and then to show the temporal profile of cerebral blood flow during focal ischaemia and after reperfusion. First, the single fiber laser Doppler method was compared with the hydrogen clearance method in ten Wistar rats. Second, focal cerebral ischaemia was induced in fifteen Wistar rats using a model of middle cerebral artery occlusion based on the intravascular insertion of a nylon suture; reperfusion occurred after withdrawal of the suture. The laser Doppler probe was placed in the lateral caudatoputamen, and local cerebral blood flow was measured continuously before and during occlusion as well as after reperfusion. The relative blood flow values obtained by the laser Doppler method and the hydrogen clearance method showed a good correlation (r=0.76) and a linear relationship. A rapid decrease in laser Doppler flowmetry to 42±16% of former baseline values was seen with occlusion of the middle cerebral artery; during occlusion cerebral blood flow remained at this level. Reperfusion resulted in a heterogeneous pattern of cerebral blood flow as laser Doppler flowmetry values ranged from 25% to 134% of baseline values. The effects of middle cerebral artery occlusion and reperfusion on cerebral blood flow can be monitored on-line with laser Doppler flowmetry. Our findings suggest that this method, with the high spatial and temporal resolution characteristics of its new single fiber probe, allows one to continuously measure microcirculatory blood flow in deep brain structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01401466
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  • 5
    Electronic Resource
    Electronic Resource
    Mucocutaneous bleeding, a rare but severe complication in nephrosialidosis (1994)
    Springer
    European journal of pediatrics 153 (1994), S. 703-704 
    Details
    ISSN: 1432-1076
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02190699
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  • 6
    Electronic Resource
    Electronic Resource
    Fourth metting of the European Neurological Society 25–29 June 1994 Barcelona, Spain (1994)
    Springer
    Journal of neurology 241 (1994), S. 1-164 
    Details
    ISSN: 1432-1459
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02333089
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  • 7
    Electronic Resource
    Electronic Resource
    lin-Benzo-ATP and-ADP: Versatile fluorescent probes for spectroscopic and biochemical studies (1994)
    Springer
    Journal of fluorescence 4 (1994), S. 247-250 
    Details
    ISSN: 1573-4994
    Keywords: lin-Benzo-ATP ; lin-benzo-ADP ; dissociation constants ; Mg2+ and Ca2+ binding ; fluorescence spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract lin-Benzo-adenine nucleotides can act not only as probes for fluorescence studies but also as structural active site probes for enzymes. To understand the basic properties oflin-benzo-ATP and-ADP, protolysis and Mg2+ and Ca2+, binding are investigated between pH 6.2 and pH 8.5 by spectrophotometric and spectrofluorometric titrations. Based on a reaction model, a set of equilibrium constants is determined which is consistent with all available experimental results. The pK values of the Mg2+ and Ca2+ complex oflin-benzo-ATP in the chosen medium are 4.6 and 4.1, respectively, and those for the corresponding diphosphate are 3.1 and 2.8, respectively. Fluorescence and absorption spectra are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01878458
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  • 8
    Electronic Resource
    Electronic Resource
    Survey of plant short tandem DNA repeats (1994)
    Springer
    Theoretical and applied genetics 88 (1994), S. 1-6 
    Details
    ISSN: 1432-2242
    Keywords: Short tandem repeat (STR) ; DNA sequences ; Molecular marker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Length variations in simple sequence tandem repeats are being given increased attention in plant genetics. Some short tandem repeats (STRs) from a few plant species, mainly those at the dinucleotide level, have been demonstrated to show polymorphisms and Mendelian inheritance. In the study reported here a search for all of the possible STRs ranging from mononucleotide up to tetranucleotide repeats was carried out on EMBL and GenBank DNA sequence databases of 3026 kb nuclear DNA and 1268 kb organelle DNA in 54 and 28 plant species (plus algae), respectively. An extreme rareness of STRs (4 STRs in 1268 kb DNA) was detected in organelle compared with nuclear DNA sequences. In nuclear DNA sequences, (AT)n sequences were the most abundant followed by (A)n · (T)n, (AG)n · (CT)n, (AAT)n · (ATT)n, (AAC)n · (GTT), (AGC)n · (GCT)n, (AAG)n · (CTT)n, (AATT)n · (TTAA)n, (AAAT)n · (ATTT)n and (AC)n · (GT)n sequences. A total of 130 STRs were found, including 49 (AT)n sequences in 31 species, giving an average of 1 STR every 23.3 kb and 1 (AT)n STR every 62 kb. An abundance comparable to that for the dinucleotide repeat was observed for the tri- and tetranucleotide repeats together. On average, there was 1 STR every 64.6 kb DNA in monocotyledons versus 1 every 21.2 kb DNA in dicotyledons. The fraction of STRs that contained G-C basepairs increased as the G+C contents went up from dicotyledons, monocotyledons to algae. While STRs of mono-, di- and tetranucleotide repeats were all located in non coding regions, 57% of the trinucleotide STRs containing G-C basepairs resided in coding regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222386
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  • 9
    Electronic Resource
    Electronic Resource
    Synaptic connections of central carotid sinus afferents in the nucleus of the tractus solitarius of the rat. II. Connections with substance P-immunoreactive neurons (1994)
    Springer
    Journal of neurocytology 23 (1994), S. 313-322 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A combined transganglionic transport and immunocytochemical technique was used to study the synaptic morphology of central carotid sinus afferents and substance P-immunoreactive neurons in the commissural subnucleus of the nucleus of the tractus solitarius in rats. A large population of substance P-immunoreactive neurons (88.32%) were seen in close association with central carotid sinus afferents by light microscopy. However, many labelled central carotid sinus afferents appeared not associated with substance P-immunoreactive neurons in the nucleus of the tractus solitarius. Substance P-immunoreactive neurons were spindle, pear, or oval-shaped with a short axis ranging from 5 to 11 μm. Their long axis was oriented predominantly in a lateral-medial direction along the path of the central carotid sinus afferents from the solitary tract to the midline. Synaptic contacts between central carotid sinus afferents and substance P-structures, including dendritic profiles of different calibers and somas, were readily found by electron microscopy. Many central carotid sinus afferents were also found in synaptic contact with non-immunoreactive dendrites and somas. Appositions between central carotid sinus afferents and unlabelled axon terminals were common, but only in a few cases were morphological manifestations of synapses revealed. In the latter, the substance P-immunoreactive terminals appeared mostly presynaptic but postsynaptic ones were also encountered. Our data provide the evidence that some of the substance P-immunoreactive cells in the nucleus of the tractus solitarius are 2nd order neurons of the carotid sinus afferent pathway. The possibility that some of the substance P-immunoreactive neurons in the nucleus of the tractus solitarius may be interneurons and mediate carotid sinus afferent inputs to catecholaminergic neurons in the nucleus of the tractus solitarius is considered. Our findings also provide an anatomical substrate for a possible presynaptic modulatory role of central carotid sinus afferents on the inputs from other brain centers to the substance P-neurons in the nucleus of the tractus solitarius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188499
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  • 10
    Electronic Resource
    Electronic Resource
    Theoretical investigation of the enantioselective hydrogenation of α-ketoesters over pt/alumina modified with cinchonidine (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 191-197 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantioselective hydrogenation of α-ketoesters with cinchona-modified platinum catalysts has been studied theoretically in order to rationalize the interaction between the chiral modifier and the substrate. The structure of the probable transition complex has been calculated for the system methyl pyruvate (substrate)-cinchonidine (modifier) using quantum chemistry techniques at both ab initio and semiempirical levels and molecular mechanics. The calculations indicate that crucial interaction occurs via hydrogen bonding of the quinuclidine nitrogen and the oxygen of the α-carbonyl moiety of methyl pyruvate and confirm earlier experimental evidence that the quinuclidine nitrogen of the cinchonidine is involved in the interaction leading to enantiodifferentiation. The resulting complex, which resembles to a half-hydrogenated state of the substrate, is shown to be a possible transition state for the enantioselective hydrogenation of α-ketoesters. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520119
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