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  • Chemistry  (46,597)
  • Inorganic Chemistry  (5,711)
  • Aerodynamics
  • Fluid Mechanics and Thermodynamics
  • SPACE SCIENCES
  • Seismicity
  • Witterung
  • 1980-1984  (33,932)
  • 1950-1954  (9,366)
  • 1945-1949  (3,876)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 15 (1980), S. 79-101 
    ISSN: 1432-1432
    Keywords: Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 118 (1980), S. 128-151 
    ISSN: 1420-9136
    Keywords: Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 122 (1984), S. 327-339 
    ISSN: 1420-9136
    Keywords: Radon ; Groundwater ; Long Valley caldera ; Seismicity ; Earth tides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In the Long Valley caldera, where seismicity has continued essentially uninterrupted since mid-1980 and uplift is documented, samples of water from hot, warm, and cold springs have been collected since September, 1982, and their222Rn concentrations analyzed. Concurrently, rocks encompassing the hydrologic systems feeding the springs were analyzed for their radioelement contents, because their uranium is the ultimate source of the222Rn in the water. The222Rn concentration in the springs varies inversely with their temperature and specific conductance. High concentrations (1500 to 2500 picocuries per liter) occur in dilute cold springs on the margins of the caldera, while low contents (12 to 25 pCi/l) occur in hot to boiling springs. Springwater radon concentrations also correlate slightly with the uranium content of the encompassing rocks. A continuous monitoring system was installed in August, 1983, at a spring issuing from basalt, to provide hourly records of radon concentration. A gamma detector is submerged in a natural pool, and we have observed that the radioactivity measured in this manner is due almost entirely to the222Rn concentration of the water. Initial operation shows diurnal and semidiurnal variations in the222Rn concentration of the springwater that are ascribed to earth tides, suggesting that those variations are responding to small changes in stress in the rocks encompassing the hydrologic system.
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  • 4
    ISSN: 1432-0827
    Keywords: Bacterial amphophile ; Purification ; Chemistry ; Resorption ; Ca influx ; Cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The bone resorptive factor and amphipathic antigen (AcA) previously identified by us in preparations fromActinomyces viscosus have been partially purified, characterized chemically, and compared. They elute at the same location on chromatography with Ac 22. The fatty acid composition of AcA and the bone resorptive factor is the same. Some differences in carbohydrate composition are observed. TheActinomyces factor does not affect calcium influx or cyclic AMP in isolated bone cells. Therefore it is concluded that AcA stimulates resorption either by gaining entrance into bone cells or by way of a yet undetermined second messenger.
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  • 5
    ISSN: 1871-4528
    Keywords: Klima ; Witterung ; Qualität ; Trockenheit ; Sorte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary The effect of chitting and planting time of potato seed on the suitability of the crop for crisp production was investigated in a 5-year trial. The second-early table variety Bintje and the two early-main crisping varieties Maritta and Saturna were used. Three chitting periods (0, 6 and 12 weeks) and two planting dates (the beginning of April and May) were investigated. The change in crisping quality over a 7–8 month storage period was checked by frying tests at two to two-and-a-half monthly intervals. The criterion of quality was the colour of the crisps. Duration of chitting had little effect on crisping quality. The effect of planting date was strongly affected by the weather in a given year. In most years, but not for the experiment overall, the colour rating of the chips was slightly but significantly better for the later rather than the earlier planting date. The two crisping varieties Maritta and Saturna reached optimum suitability for crisping about twothirds of the way through the storage period, i.e. about March, the late plantings showing a more marked improvement in quality than the early ones (Table 1, Fig. 1–4). The weather, sometimes in combination with various soil conditions, had the greatest influence on the experimental results. This is concluded since the effects of the individual experimental factors depend on the season (Fig. 1–4) and from the difference in the averaged yearly results. Statistical analysis showed highly significant years and all experimental factors but chitting. 1976 merits special attention due to the extremely warm and dry summer weather. Potatoes which at the start of storage were generally poor showed a great improvement in quality during storage, especially those from the later planting. From the results it is obvious that the producer of quality potatoes for industry faces difficulties in choosing growing methods for improving quality due to the unpredictability of the consequences of weather conditions.
    Abstract: Résumé L'influence de la durée de prégermination des plants et de la date de plantation sur l'aptitude des pommes de terre à la fabrication de pommes chips a été examinée dans un essai répété pendant 5 ans. Les cultivars ci-après ont été examinées: Bintje, variété mi-précoce de consommation, Maritta et Saturna, variétés mi-tardives présentant une très bonne aptitude à la fabrication de pommes chips. Trois procédés de prégermination (0, 6 et 12 semaines) ainsi que deux dates de plantations (début avril et début mai) ont été comparés. L'évolution de la qualité des chips au cours d'une durée de conservation de 7 à 8 mois, a été contrôlée à intervalles de deux mois à deux mois et demi, par des tests de fabrication. La couleur des pommes chips a constitué le critère de qualité. La prégermination n'a pratiquement pas influencé la qualité des chips. L'effet de la date de plantation était en relation étroite avec les conditions météorologiques de l'année. Sur un grand nombre d'années d'essais et compte tenu des exceptions, une amélioration peu importante mais néanmoins significantive de la qualité des chips, a été obtenue par la plantation tardive, par rapport à la plantation précoce. Pour les variétés spécifiquement aptes à la fabrication de chips, Maritta et Saturna, les tubercules ont atteint leur qualité optimale aux deux tiers de la durée de conservation, soit en mars environ. L'amélioration de la qualité a été plus prononcée pour les tubercules issus de la plantation tardive que pour ceux de la plantation précoce (tableau 1, fig. 1–4). Ce sont les conditions de croissance et les différences de structure du sol qui ont influencé le plus les résultats de ces essais. L'effet de l'année sur les paramètres examinés a été évident (fig. 2–4). L'analyse statistique (tableau 1) donne une interaction hautement significative entre les années et les paramètres d'essais, exception faite de la prégermination. Les résultats de l'année 1976 méritent une attention particulière, en raison des températures élevées, de la sécheresse durant l'été. La qualité des tubercules a été plutôt médiocre en début de conservation. Par la suite, plusieurs lots, et particulièrement ceux de la plantation tardive, se sont fortement améliorés (fig. 3). Ces résultats démontrent pour la production de pommes de terre destinées à la transformation industrielle, les difficultés auxquelles se heurte le choix des techniques culturales appropriées, en raison des conditions météorologiques imprévisibles.
    Notes: Zusammenfassung Die in einem mehrjährigen Versuch (1973–1977) mit den Sorten Bintje, Maritta und Saturna geprüften Faktoren Vorkeimen und Pflanzzeitpunkt des Saatgutes sowie Lagerdauer des Erntegutes, übten folgende Einflüsse auf die Farbe von daraus hergestellten Pommes Chips aus: - Spätes Pflanzen (anfangs Mai) brachte in der Mehrzahl der Versuchsjahre eine leichte Verbesserung der Chipsfarbe bei jeweils mindestens zwei der drei Versuchssorten gegenüber frühem Pflanzen (anfangs April). - Die Vorkeimdauer hatte keinen Einfluss. - Mit zunehmender Lagerdauer trat mindestens bis zum Monat März bei den beiden Chips-Sorten Maritta und Saturna eine Qualitätsverbesserung ein, die bei den spätgepflanzten Varianten etwas deutlicher ausfiel als bei den frühgepflanzten. Die Ergebnisse wurden durch die Jahreswitterung und teils auch durch die Bodenbeschaffenheit stark beeinflusst.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 823-831 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the DNA-binding oligopeptide distamycin A on the B to A transition of DNA in ethanol/water solutions has been studied by means of CD. (The overbars indicate that it does not matter which particular form of the corresponding families is considered.) The results show that increasing the concentration of distamycin A reverses the A conformation (in 82% ethanol) to the B conformation due to its strong binding and stabilization of the latter. In accordance with previous data for pure aqueous solutions, a site size of 3.5 base pairs is obtained from the studies in water/ethanolic solutions. From the data on the B to A transition in the presence of distamycin A, we estimated the length of the cooperativity ν0 = 10 base pairs.The results demonstrate that the oligopeptide systems of distamycin, as well as those of netropsin, are effective stabilizers of the DNA B-conformation.
    Additional Material: 6 Ill.
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  • 7
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrapeptides with proline in position 2, asparagine or leucine in position 3, and glycine in positions 1 and 4, with end groups free or blocked on the N-terminal side, were studied in their various ionic states in 2H2O and in Me2SO-d6 by 1H- and 13C-nmr. In order to clarify or refine some details, successive substitutions of the residues in these peptides with amino acids enriched to 85% in 13C, or to 85% 13C plus 97% 2H were carried out. The 1H and 13C chemical shifts as well as the 1H-1H, 13C-13C, and 13C-1H coupling constants and the signal intensities show strong similarity of behavior between the tetrapeptides of asparagine and leucine. The main conformational characteristics are (1) the almost total stabilization of the trans conformer in the type I β-turn structure when the peptide is in the zwitterion state dissolved in Me2SO. This is deduced from the 3JC3αH-N3H and the 3JC2′-H3α coupling constants, which both furnish a dihedral angle of φ3 = -90°, and from the positive value of the temperature coefficient of the glycine-4 amide protons, which suggests a type 4 → 1 hydrogen bond; (2) the evolution of cis and trans isomer fractions which change with the ionic state of the peptides in Me2SO, whereas they remain constant in aqueous solution; and (3) the conformation of the pyrrolidine ring as it follows the variations in cis:trans isomer populations together with the side-chain rotamer fractions of the residue in position 3. In the β-turn conformation the isomer cis is less abundant and the pyrrolidine ring is more flexible; this explains the perfect accommodation of the proline residue in position 2 of a bend. The interdependence of these phenomena where interactive forces play a predominant role underlines the importance of cooperative effects in the molecule. The results also suggest that the cis isomer of proline can adapt itself just as well as the trans isomer to position 2 of a type I β-turn.
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  • 8
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An algorithm is presented for the Monte Carlo simulation of the decay of fluorescence polarization from segmentally flexible molecules. Based on the random walk model of Brownian motion, the treatment explicitly follows the stochastic changes in the diffusion coefficients as the molecule bends. It includes the effects of a linear restoring force opposing the bending and the effects of hydrodynamic coupling between the translational, rotational, and bending motions. One application is presented: the simulation of anisotropy decay curves for hinged rods. A variety of decay curves are obtained, including single- and multiexponential behavior, and the following conclusions are reached: (1) increasing the flexibility is usually, but not always, accompanied by a more rapid rate of depolarization; (2) reducing the size of the fluorescent subunit will usually, but not always, increase the rate of depolarization; and (3) the complex interplay between the effects of molecular shape, relative sizes of the subunits, restoring force, and orientation of the transition dipoles renders it unlikely that any simple method can be used to interpret anisotrophy data without simulation. In particular, it is not possible to determine the extent of bending by fitting the data with the two-exponential approximation used by some investigators in the past.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 977-990 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C-nmr spectra of red seaweed galactans, belonging to the agar and carrageenan groups or having the “intermediate” type of structure, were interpreted on the basis of 13C-nmr spectra of model compounds. Signal assignments have been made for most of the known extreme structures of such galactans. 13C-nmr spectroscopy was shown to be a rapid and convenient method of structural analysis, which permits one to determine the type of galactan structure, the absolute configurations of its constituents (galactose and 3,6-anhydrogalactose), and the positions of the sulfate and O-methyl groups in a polysaccharide molecule.
    Additional Material: 3 Ill.
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dielectric response of human umbilical cord hyaluronic acid in various environments has been studied at microwave frquencies using a resonant microwave cavity as a probe. Both the real and imaginary parts of complex dielectric constant and the loss tangent for hyaluronate solutions are obtained by utilizing equations for perturbation of a resonant cavity. Dielectric changes at room temperature have been observed in aqueous solutions of hyaluronic acid as a function of concentration ranging from 0 to 350 mg/ml. The data indicate the existence of ordered phases in hyaluronate solutions at selective concentrations, that is, exhibiting lyotropic-type transitions. Hyaluronate solutions at 1.5 and 3 mg/ml concentrations have been studied at various pH in the range of 6-8 and at constant ionic strength 0.1. A temperature-dependent transition in hyaluronate solution of 120 mg/ml concentration has been observed at physiological temperature. It is shown that this temperature-dependent behavior can be related to the orientational polarizability term in the Debye theory of polar molecules in liquids.
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