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  • 11
    ISSN: 1420-9136
    Keywords: Electromagnetic field ; Vertical magnetic dipole ; Thin conductive sheet ; Lateral conductivity variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An analytical formulation is developed for the resultant electromagnetic field of an oscillating vertical magnetic dipole located over a thin conductive sheet of infinite extent. The sheet is characterized by a conductivity-thickness product or conductance σd that may be a function of the horizontal coordinates. The system of integral equations arising in the general formulation is simplified greatly when azimuthal symmetry prevails. Numerical results for a Gaussian variation of σd in the radial direction are presented for the case of a symmetrically located source. These results are for the fields at the level of the source dipole over the conductive sheet. It is shown that the quadrature response of the sheet is enhanced when there is rapid variation of the conductance. The null in the resultant wave tilt is also found to be shifted toward the direction of increasing conductance.
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  • 12
    ISSN: 1432-0630
    Keywords: 61.12Dw ; 72.10 ; 78.50G
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Czochralski grown silicon crystals contain interstitially dissolved oxygen which diffuses on heating to form precipitates of silica. We have examined these precipitates by small angle neutron scattering (SANS) in the Q-range 0.05 Å−1〈Q〈0.4 Å−1. The obtained SANS patterns reveal pronounced anisotropic intensity distributions which resemble the symmetry of the host crystal. The SANS spectra show an anisotropic central peak at Q〈0.1 Å−1 due to the single particle shape and a number of weak intensities for larger Q-values. These weak side maxima are considered correlation peaks or quasi-elastic interference peaks. They show, however, an unexpected and distinct temperature dependence: with decreasing temperature below values of 220 K their intensity is lost slowly, but reversibly. At T = 50 K only the central peak from the single-particle scattering remains unchanged. Upon heating, the correlation peaks regain their former value of intensity and Q-position without any evidence of thermal hysteresis.
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  • 13
    ISSN: 1432-0630
    Keywords: 61.12Dw ; 72.10 ; 78.50G
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The formation of silicon oxide precipitates from Czochralski grown silicon depends on the time and temperature of the heat treatment as well as on the initial content of interstitially dissolved oxygen. Samples containing between 5×1017 Oi/cm3 and 13×1017 Oi/cm3 have been heated at 750° C for 96 h. SiO2 precipitates of various shape and size have been obtained and investigated by means of small angle neutron scattering (SANS) in the Q-range 0.05 Å−1〈Q〈0.2 Å−1. The obtained SANS patterns reveal a typical anisotropy of their intensity distribution, which splits into a central peak at Q〈0.1 Å−1 due to the shape of the individual particles and a number of weak intensities for large Q-values, originating from a correlation between defects, possibly between the precipitates. While these correlation peaks in the SANS patterns are seen best for rather low values of about (5–7)×1017 Oi/cm3 oxygen content, the central peak anisotropy is most pronounced for higher values of ca 10×1017 Oi/cm3. The integrated intensity of the central peak increases with increasing initial oxygen content. For comparison, untreated samples of the same initial oxygen content do not reveal any anisotropic SAN scattering or a broadened central peak beam.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 11 (1960), S. 499-513 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The first spermatocyte division has been investigated in Rhabdophaga batatas Walsh and Wachtliella persicariae L. It was shown that the course of this division cannot be described as mitosis, either “unipolar” or “modified bipolar”. Its essential features are: complete absence of pairing and the segregation of the chromosomes into two groups composed of 4 and 30-odd chromosomes. The segregation is accomplished by a peculiar expulsion of the group of 4 chromosomes from the main nucleus followed by an unequal cytokinesis. The spindle is absent and the nuclear membrane remains present during the entire course of the division. The second spermatocyte division occurs only in the smaller cell, which contains 4 chromosomes and bears all features of normal mitosis. For the description of the course of the first spermatocyte division and chromosome distribution, which occurs in this division, the terms “segregating division” and “monocentric configuration” were proposed. The available descriptions of the first spermatocyte division in other species of Cecidomyiidae have been analyzed. The pattern of this division in all so far investigated cecidomyiid species is very uniform and the terms “unipolar” or “modified bipolar” mitoses are here also inadequate. The cases were discussed in which the peculiar chromosome arrangements arise merely as a result of positive or negative interrelations between the centriole and the chromosome parts. With this as background, the monocentric configurations in Cecidomyiidae were explained in terms of an attraction between the centriole and centromeres, operating in one group, and a repulsion between the centriole and the chromosome ends acting in the second. The other so-called unipolar mitoses have been analyzed. It was shown that under this term at least three intrinsically different configurations have been described. For the cases of Sciara, Micromalthus debilis and Cecidomyiidae, the common denominator can be found: the chromosome movements in Sciara and M. debilis can also be explained as set forth above for Cecidomyiidae, i.e. in terms of two kinds of forces operating between the centriole and the chromosomes. The several spindle fibers present in Sciara and Micromalthus do not seem to be crucial for the chromosome movements.
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  • 15
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Currently available data on chromosome elimination in Cecidomyiidae are still inadequate to support any definite conclusions regarding its immediate causes. It seems that some evidence on the mechanism of elimination could be obtained from observation of the behavior of E chromosomes in complete absence of spindle. To bring about such absence of spindle, ultraviolet microbeams would appear promising, since they have already been used to destroy spindles in cells of other organisms. 2. For irradiation the embryos of Rhabdophaga batatas Walsh were chosen. It was established that in this species 2 S+E=40 and 2 S (for female)=8. Elimination of 30-odd chromosomes regularly occurs in the fifth cleavage. Embryos were irradiated with 8μ and 16μ heterochromatic ultraviolet microbeams not only in this fifth cleavage but also in the fourth, in which elimination was never observed. The irradiated regions were small parts of somatic cytoplasm or small parts of germ cells. 3. The effects of irradiation were multifold: complete degeneration of nuclei in the vicinity of irradiated cytoplasm; disappearance of spindle and formation of quasi-rosettes; multipolar mitosis. The polar substance present in germ cells was often severely damaged and fragmented. All these effects are evidently indirect. 4. In mitoses thus deprived of spindles, the separation of chromosomes into daughter chromatids was suppressed but some of their active movements persisted. All chromosomes were gathered into a quasirosette, which afterwards divided into two quasi-rosettes. The daughter quasi-rosettes moved apart and formed telophase nuclei. In both irradiated divisions (fourth and fifth) E chromosomes behaved in exactly the same manner as S chromosomes; they showed the same kind of peculiar movement and were incorporated into telophase nuclei. Suppression of elimination of E chromosomes in the fifth division can be regarded as one more indirect effect of irradiation to be added to the list above. 5. These results show that elimination of E chromosomes does not result from failures in chromosomal spindle fibers or from intrinsic morphological defects in the centromeres. The fact that elimination can be suppressed by indirect action of ultraviolet light strongly supports the assumption that elimination occurs because of chemical changes in adjacent cytoplasm that are injurious to the centromeres of E chromosomes. Most probably the indirect action of ultraviolet interferes with the production of some substance that is normally injurious to the centromeres in the fifth division. 6. Since in Cecidomyiidae the general features of the metabolism are known to be stable up to the mid-blastoderm stage, it would appear that the chemical changes involved in elimination cleavage are probably quite specific.
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  • 16
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We present a direct approach for the calculation of functional determinants of the Laplace operator on balls. Dirichlet and Robin boundary conditions are considered. Using this approach, formulas for any value of the dimension,D, of the ball, can be obtained quite easily. Explicit results are presented here for dimensionsD=2,3,4,5 and 6.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 46 (1963), S. 9-12 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary The action of ultrasonic waves on the tryptophanase in Escherichia coli is described. The proteine of the tryptophanase is changed by ultrasonic waves, whereas the coenzyme pyridoxalphosphate is stable. In vitro pyridoxalphosphate is changed by ultrasonic waves.
    Notes: Zusammenfassung In der vorliegenden Arbeit wurde die Wirkung des Ultraschalls auf die Tryptophanase in Escherichia coli untersucht. Es konnte nachgewiesen werden, daß Ultraschall das Tryptophanase-Protein angreift, während das Coenzym Pyridoxalphosphat nicht verändert wird. Weiterhin wurde die Veränderung des Pyridoxalphosphats durch Ultraschall in vitro festgestellt.
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  • 18
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary The estimation of pyridoxalphosphate in Escherichia coli after irradiation is described. The investigations are made with resting and growing cells. A dose of 10, 40 or 80 kr does not change the pyridoxal-content of the cell. In all cultures of E. coli starts the synthesis of pyridoxalphosphate at the same time on the end of the log-phase.
    Notes: Zusammenfassung Um zu klären, ob der Tod von lebenden Zellen nach Röntgenbestrahlung auf eine Zerstörung des in der Zelle vorhandenen Pyridoxalphosphats und damit auf eine Blockierung der pyridoxalabhängigen Enzyme zurückzuführen ist, wurde in bestrahlten und unbestrahlten Escherichia coli der Pyridoxalphosphat-Gehalt bestimmt. Die Untersuchung wurde an ruhenden und wachsenden Zellen durchgeführt. Durch Bestrahlung mit 10,40 und 80 kr wird der Pyridoxalphosphat-Gehalt der Zelle nicht verändert. Alle Kulturen begannen zur gleichen Zeit am Ende der log-Phase des Wachstums mit der Neubildung von Pyridoxalphosphat.
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  • 19
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new variant of the nonlocal light-cone expansion in QCD is proposed. The anomalous dimension of the corresponding fermion flavour nonsinglet operator is calculated in the one-loop approximation and shown to coincide (up to a trivial diagonal factor) with the Brodsky-Lepage kernel. The connection of our approach with the standard local conformal light-cone expansion is briefly discussed. An exclusive light-cone dominated process is considered within the framework of our formalism. The evolution equation obtained earlier by different methods is recovered in a particularly straightforward and compact manner.
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  • 20
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Scheinbare Divergenzen zwischen den seinerzeit aufgestellten Phosphatbilanzen in Säureextrakten aus phosphatangereicherter und-verarmter Hefe und den in der letzten Mitteilung dieser Reihe erhobenen Befunden über den Gehalt an freien Nucleotiden in demselben Material, veranlaßten eine genauere Überprüfung der Frage, inwieweit die Extraktionsmethoden die Ergebnisse der Nucleotidbestimmung und der Phosphatbilanzen beeinflussen. Es zeigte sich, daß bei Bestimmung der freien Nucleotide, trotz Verwendung verschiedener Extraktionsmittel, sowohl qualitativ als auch quantitativ weitgehend entsprechende Ergebnisse erhalten wurden. Die Resultate können wieder in dem Sinne erklärt werden, daß während der Phosphatanreicherung eine Synthese von Nucleinsäure auf Kosten der freien Nucleotide erfolgt. Gleichzeitig durchgeführte Phosphatbilanzen in den Säureextrakten aus phosphat-verarmter und-angereicherter Hefe ergaben je nach den Extraktionsbedingungen starke, zur Zeit noch schwer deutbare Konzentrationsunterschiede in den einzelnen Phosphatfraktionen.
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