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1

Monographie ausleihbar

Superhard materials, convection, and optical devices (1988)

Heimann, Robert Bertram [Mitverf.]

Berlin [u.a.] : Springer

Dazugehörige Bände

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Signatur: FHD 210 ; 14598

In: Crystals

Materialart: Monographie ausleihbar

Seiten: 196 S. : Ill., graph. Darst.

ISBN: 3540186026

Serie: Crystals 11

Standort: Kompaktmagazin oben

Zweigbibliothek: GFZ Bibliothek

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Ferromagnetic switching in elongated γ-Fe2O3 particles (1988)

Schabes, Manfred E. ; Bertram, H. Neal

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 64 (1988), S. 5832-5834

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Results of numerical micromagnetic calculations of the switching process in elongated γ-Fe2O3 particles are reported. The particles are represented by square rectangular prisms of aspect ratio 3:1 and 5:1, respectively. The crystalline anisotropy is cubic with K1=−4.6×104 erg/cm3 and with the [110] direction in the long particle axis. The application of a reverse field leads to formation of vortices at the ends of the particle. As the reverse field is increased in magnitude the vortices expand from the ends of the particle inwards. Equilibrium and transient magnetization states are computed as a function of particle size. The resulting dependence of the switching field on the particle size and on the angle of the applied field is similar to what has been suggested by experimental evidence.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.342222

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Magnetization processes in ferromagnetic cubes (1988)

Schabes, Manfred E. ; Bertram, H. Neal

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 64 (1988), S. 1347-1357

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A cubic discretization procedure of the micromagnetic energy functional is used to carry out numerical studies of the magnetization process in ferromagnetic cubes. Equilibrium magnetization configurations and their switching behavior are calculated for particle sizes in the range from 100 to 550 A(ring). In the model calculations the particles are assumed to have uniaxial crystalline anisotropy with an anisotropy constant of 18 500 erg/cm3, a saturation magnetization of 370 emu/cm3, and an exchange constant of 10−6 erg/cm. For particle sizes smaller than 520 A(ring) the remanent state has a flowerlike magnetization configuration. Beyond 520 A(ring) this state is replaced by a vortex structure about the easy axis. For particles smaller than 450 A(ring) switching occurs by approximately uniform rotation of the flower state. The switching fields are larger than the corresponding Stoner–Wohlfarth value. Beyond 450 A(ring) the application of an external field leads to the formation of a vortex configuration. The switching of the vortex configuration involves rotation of the vortex axis at a reduced value of the switching field. The angular dependence of the coercive field is calculated for particle sizes of 200, 400, and 550 A(ring).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.341858

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Micromagnetic studies of thin metallic films (invited) (1988)

Zhu, Jian-Gang ; Bertram, H. Neal

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 63 (1988), S. 3248-3253

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A computer simulation model has been developed to conduct micromagnetic studies of thin magnetic films. Thin-film media are modeled as a planar hexagonal array of hexagonally shaped grains. Each grain is a single domain particle whose magnetization reverses by coherent rotation. The computation utilizes coupled gyromagnetic dynamic equations with phenomenological Landau–Lifshitz damping. In particular, the effects of particle interactions are investigated. The effect of media microstructure on magnetic hysteresis is examined as well as the effect of intergranular exchange coupling. The difference between planar and completely random orientation of the crystalline anisotropy axes is discussed. Recorded transitions are simulated by allowing a pair of perfect transitions to relax. With no intergranular exchange coupling, the transitions show profound irregularity and zig-zag structure. Intergranular exchange coupling produces more uniform transitions with increased zig-zag structure amplitude. For a closely spaced transition pair, the equilibrium configuration yields percolated transition boundaries with stable reverse island domains. The effect of gyromagnetic precession also has been examined.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.341167

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Action of gamma endonuclease on clustered lesions in irradiated DNA (1988)

Kohfeldt, E. ; Bertram, H. ; Hagen, U.

Springer

Radiation and environmental biophysics 27 (1988), S. 123-132

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ISSN: 1432-2099

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Physik

Notizen: Summary Irradiation of DNA in situ i.e. in phage particles or in the cell leads to alterations of single DNA nucleotides as well as to clustered lesions such as double strand breaks or unpaired DNA regions the latter being sensitive to digestion by S 1 nuclease. A contribution will be made to the configuration of such S 1-nuclease-sensitive sites (S 1 sites). DNA from irradiated lambda phage containing S 1 sites was treated with gamma endonuclease fromM. luteus which is known to split the nucleotide strand at the position of oxidized pyrimidine base. It was found that the gamma endonuclease induces double-strand breaks at some of the S 1 sites indicating double base damage within this site. However, half of the S 1 sites are not converted into a double-strand break by the gamma endonuclease, indicating base damage only on one strand within the unpaired region.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01214602

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Studies on the deconvolution of flash-induced absorption changes into the difference spectra of individual redox steps within the water-oxidizing enzyme system (1988)

Renger, Gernot ; Hanssum, Bertram

Springer

Photosynthesis research 16 (1988), S. 243-259

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ISSN: 1573-5079

Schlagwort(e): photosystem II ; water oxidation ; difference spectra of Si-oxidation ; QAFe2+ oxidation ; pH-dependence

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The possibility to determine the difference spectra Δεi+1jλ of each univalent redox step Si→Si+1(i=0,...3) of the water-oxidizing enzyme system was analyzed by theoretical calculations and by measurements of 320 nm absorption changes induced by a train of saturating laser flashes (FWHM:7 ns) in PS II membrane fragments. It was found: a) Lipophilic quinones complicate the experimental determination of optical changes due the Si-state transitions because they lead to an additional binary oscillation probably caused by a reductant-induced oxidation of the Fe2+ at the PS II acceptor side. b) In principle, a proper separation can be achieved at sufficiently high K3[Fe(CN)6] concentrations. c) An unequivocal deconvolution into the difference spectra Δεi+1jλ of flash train-induced optical changes which are exclusively due to Si-state transitions is impossible unless the Kok parameters α, β and [Si]0 can be determined by an independent method. Measurements of the oxygen yield induced by a flash train reveals, that in thylakoids and PS II membrane fragments Si is the stable state of dark adapted samples even at alkaline pH (up to pH=9). However, in PS II membrane fragments at pH〉7.7 the misses probability α markedly increases, in contrast to the properties of intact thylakoids. Based on these data the possibility is discussed that an equilibrium exists of two types of S2-states with different properties.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00028843

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Stimulation by thyroid hormone of phosphate transport in primary cultured renal cells (1988)

Noronha-Blob, Lalita ; Lowe, Valerie ; Sacktor, Bertram

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 137 (1988), S. 95-101

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ISSN: 0021-9541

Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Medizin

Notizen: The regulation by thyroid hormone of phosphate transport in primary cultured chick renal cells was examined. The more physiologically active L-analogs of triiodothyronine and thyroxine, but not the D-analogs of the hormones, stimulated the Na+ -dependent phosphate uptake system. Na+ -independent phosphate uptake and Na+ -dependent uptakes of α-methylglucoside and L-proline were unaffected. The increase in Na+ -dependent phosphate uptake was concentration dependent, exhibited an induction period, and was blocked by inhibitors of RNA and protein synthesis. The stimulation of phosphate uptake by triiodothyronine was due to an increased Vmax rather than to an altered affinity for phosphate. These findings demonstrate that thyroid hormone acts directly on renal cells to modulate phosphate transport and suggest that the renal cell system may serve as a model to examine the mechanism by which thyroid hormone controls gene expression and regulates plasma membrane transport function.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jcp.1041370111

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8

Digitale Medien

Zur Charakterisierung des Extragitter-Aluminiums in Y-Zeolithen mittels der FerronmethodeVgl. auch Z. Chem. 27 (1987) 194. (1988)

Bertram, R. ; Lohse, U. ; Gessner, W.

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 567 (1988), S. 145-152

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ISSN: 0044-2313

Schlagwort(e): Chemistry ; Inorganic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Characterization of Non-Framework Aluminium in Zeolites Y by the Ferron MethodBy using the ferron method it is shown that the non-framework aluminium occuring in dealuminated zeolites Y exists in form of different kinds of Al-oxo-hydroxo-species. At the beginning of dealumination (673 K) besides polymeric species with relatively low degree of polymerization monomeric and a special kind of oligomeric cations occur. These special cations alter into a mixture of oligomeric species with increasing temperature of dealumination (813 K). Simultaneously the degree of polymerization of the polymeric species increases.

Notizen: Mit der Ferronmethode wird gezeigt, daß das in thermisch behandelten Y-Zeolithen auftretende Extragitter-Aluminium aus unterschiedlichen Arten von Al-oxo-hydroxo-Spezies besteht. Am Anfang der Dealuminierung (673 K) liegen neben monomeren spezielle oligomere Kationen vor; gleichzeitig werden aber auch polymere Spezies mit relativ niedrigem Polymerisationsgrad gebildet. Mit steigender Temperatur der thermischen Behandlung (813 K) entsteht aus den oligomeren Teilchen ein Gemisch niedermolekularer Kationen. Die polymeren Spezies unterliegen dabei einer Veränderung im Sinne einer zunehmenden Kondensation bzw. Polymerisation.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/zaac.19885670116

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