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  • 1
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dielectric and electro-optic properties of phenyl ester FLC mixture have been studied in detail. Dielectric relatation spectroscopy was used to study the molecular dynamics and dipolar ordering. In the SmA* phase, this is accompanied by a sharp increase in the dielectric strength Δεs on approaching T c. At such high frequency (2 MHz) Δε is usually negative in the SmC* and SmA* phase. In the N* phase, at lower frequencies, Δε had a weakly positive value. In the SmC* phase, δε is positive and its maximum value is less than 0.1. The dielectric biaxiality is discussed as an order parameter of the tilted smectic phase. It is verified that if the tilt angle increases according to θ ∝ (T C − T)β, the biaxiality increases according to δε ∝ (T C − T)2β. A critical exponent for θ and δε are 0.27 and 0.54, respectively. The rotational viscosity γθ for soft mode is of 10 Nsec/m2 in the SmA* phase. The activation energy for the rotational dynamics of Goldstone mode is estimated to be 1.4 eV from an Arrhenius plot. Optical response time is of about 50 μs at room temperature in SmC* phase, and is on the order of 10 μs in the N* phase and almost independent of the applied field.
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  • 2
    ISSN: 1573-6822
    Keywords: anthrax lethal toxin ; cytotoxicity ; macrophage ; phospholipase A2 ; protein kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The molecular mechanism of cytotoxic effect exerted by the lethal toxin (LeTx) of Bacillus anthracis is not well understood. In the present study, using primary culture of mouse peritoneal macrophages, we have investigated possible cytotoxic mechanisms. LeTx was not found to induce high levels of nitric oxide (NO) production for NO-mediated toxicity. Fragmentation of DNA, a biochemical marker of apoptosis, was not observed in LeTx-treated cells. Pretreatment of cells with antioxidants such as melatonin and dehydroepiandrosterone (DHEA) did not protect the LeTx-induced cytotoxicity. However, addition of phospholipase A2 (PLA2) inhibitors (quinacrine, p-bromophenacyl bromide, manoalide, butacaine) to the culture medium resulted in the inhibition of cytotoxicity of LeTx in a dose-dependent manner. LeTx-induced cytotoxicity was also inhibited by the tyrosine-specific protein kinase inhibitor genistein, but not by the protein kinase C inhibitors staurosporine or H-7. The results of these studies indicate a role for PLA2 and protein kinase in the cytotoxic mechanism of macrophages by anthrax lethal toxin.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Nonlinear dynamics 1 (1990), S. 221-241 
    ISSN: 1573-269X
    Keywords: Nonlinear ; rotor ; clearance ; chaos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A HB (Harmonic Balance)/AFT (Alternating Frequency/Time) technique is developed to obtain synchronous and subsynchronous whirling motions of a horizontal Jeffcott rotor with bearing clearances. The method utilizes an explicit Jacobian form for the iterative process which guarantees convergence at all parameter values. The method is shown to constitute a robust and accurate numerical scheme for the analysis of two dimensional nonlinear rotor problems. The stability analysis of the steady-state motions is obtained using perturbed equations about the periodic motions. The Floquet multipliers of the associated Monodromy matrix are determined using a new discrete HB/AFT method. Flip bifurcation boundaries were obtained which facilitated detection of possible rotor chaotic (irregular) motion as parameters of the system are changed. Quasi-periodic motion is also shown to occur as a result of a secondary Hopf bifurcation due to increase of the destabilizing cross-coupling stiffness coefficients in the rotor model.
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  • 4
    ISSN: 1573-6822
    Keywords: ethylvinyl sulfone ; glyceraldehyde-3-phosphate dehydrogenase ; lymphocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Recently, vinyl sulfones have been observed to selectively inhibit glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is an important ATP-generating enzyme in glycolysis. The possibility of using GAPDH as a biochemical parameter of cytotoxicity by vinyl sulfones was investigated using mouse lymphocytes. Incubation of lymphocyte GAPDH with ethylvinyl sulfone resulted in a pseudo-first-order loss of enzyme activity. The exposure of lymphocytes to ethylvinyl sulfone resulted in the decrease of GAPDH activity followed by ATP depletion and cell death, which were both dependent on the concentration of ethylvinyl sulfone. A further study on the time-dependent change indicated that cell death was preceded by ATP loss. Compared to ethylvinyl sulfone, divinyl sulfone was more than 8 times more potent in causing either ATP depletion or cell death.
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  • 5
    ISSN: 1573-6822
    Keywords: anthrax lethal toxin ; cytotoxicity ; intracellular calcium antagonist ; macrophage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The lethal toxin ofBacillus anthracis is central to the pathogenesis of anthrax. Using primary cultures of mouse peritoneal macrophages, we have demonstrated that intracellular calcium release inhibitors protect against anthrax lethal toxin-induced cytotoxicity. The cytolytic effect of anthrax lethal toxin was markedly reduced by dantrolene, an inhibitor of calcium release from intracellular calcium stores. Pretreatment of macrophages with cyclosporin A, which has been shown to be a potent inhibitor of calcium release from mitochondria, also protected cells against cytotoxicity. These results indicate that calcium release from intracellular store may be an essential step for the propagation of anthrax lethal toxin-induced cell damage in macrophages. Thus our findings suggest that dantrolene, cyclosporin A, and possibly other drugs affecting intracellular calcium pools might be effectively preventing the toxicity from anthrax lethal toxin.
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  • 6
    ISSN: 1573-6822
    Keywords: anthrax lethal toxin ; cytokine ; dehydroepiandrosterone ; melatonin ; tumor necrosis factor α
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The lethal toxin of Bacillus anthracis, which is composed of two separate proteinaceous exotoxins, namely protective antigen and lethal factor, is central to the pathogenesis of anthrax. Low levels of this toxin are known to induce release of cytokines such as tumor necrosis factor α (TNF-α). In the present study we investigated the effect of dehydroepiandrosterone (DHEA), melatonin (MLT), or DHEA + MLT on production of lethal toxin-induced TNF-α in mouse peritoneal macrophages. We found that treatment with DHEA significantly inhibited the TNF-α production caused by anthrax lethal toxin. Exposure of MLT to anthrax lethal toxin-treated macrophages also decreased the release of TNF-α to the extracellular medium as compared to the control. However, combined use of DHEA and MLT also inhibited TNF-α release, but not more than single therapies. These results suggest that DHEA and MLT may have a therapeutic role in reducing the increased cytokine production induced by anthrax lethal toxin.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2218-2219 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surfaces of rubbed polyimide films for aligning liquid crystal have been studied by atomic force microscopy. The unrubbed films consisted of randomly distributed polyimide clusters of different sizes. On the rubbed surface, however, the clusters are aligned in long chains along the rubbing direction. The cluster chains were separated by about 100 nm for small rubbing strength. For higher strength the cluster chains coalesced into wider ones. © 1995 American Institute of Physics.
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase transformation of NdFeB melt-spun alloys with low Nd content of 4–8 at. % was investigated by thermomagnetic analysis and x-ray diffractometry. Experimental results have shown that the metastable Nd2Fe23B3 compound formed in the alloys is considered to be transformed to Nd2Fe23B3+α-Fe+Fe3B in the temperature range of 550–690 °C, α-Fe+Fe3B+Nd1+eFe4B4 in the temperature range of 690–730 °C and finally α-Fe+Nd1+eFe4B4 above 840 °C. From the results, it has been concluded that Nd2Fe14B is not formed from metastable Nd2Fe23B3. On the other hand, the melt-spun alloy of Nd2Fe23B3 (∼Nd7.1Fe82.1B10.7) annealed under optimum conditions has been found to be composed of α-Fe, Fe3B, and Nd2Fe14B phases. The alloy has a coercivity comparable to Fe3B-based Nd4Fe77B19 and relatively high-energy product of about 71.6 kJ/m3 (∼9 MG Oe). © 1995 American Institute of Physics.
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  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: NdFe10.7TiM0.3(M=B, Ti) has been studied with x-ray diffraction, Mössbauer spectroscopy, and a vibrating sample magnetometer. The alloys were prepared by arc-melting under an argon atmosphere. The NdFe10.7TiB0.3 exhibits a pure single phase, whereas the NdFe10.7Ti1.3 contains some α-Fe, from x-ray and Mössbauer measurements. The NdFe10.7TiB0.3 has the ThMn12-type tetragonal structure with a0=8.587 A(ring) and c0=4.788 A(ring). The Curie temperature (TC) is 570 K from Mössbauer spectroscopy performed at various temperatures ranging from 13 to 770 K. Each spectrum below TC was fitted with five subspectra of Fe sites in the structure (8i1, 8i2, 8j1, 8j2, and 8f ). The area fraction of the subspectra at room temperature are 16.4%, 8.2%, 14.8%, 21.3%, and 39.3%, respectively. Magnetic hyperfine fields for the Fe sites decrease on the order of Hhf(8i)(approximately-greater-than)Hhf(8j)(approximately-greater-than)Hhf(8f ). The average hyperfine field Hhf(T) of the NdFe10.7TiB0.3 shows a temperature dependence of [Hhf(T)−Hhf(O)]/Hhf(O)=−0.39(T/TC)3/2 & −0.17(T/TC)5/2 for T/TC〈0.7, indicative of spin-wave excitation. Annealing the alloy at around TC for 60 min resulted in a two phase microstructure consisting of a ThMn12-type structure and α-Fe. © 1996 American Institute of Physics.
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  • 10
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of composition and additives on the microstructures and magnetic properties of Nd-Fe-B melt-spun ribbons were studied. Experimental results have revealed that homogeneous grain structure with fine grain size was obtained on composition close to 2-14-1 stoichiometry with additives. It was also found that Nb was very effective in increasing both remanence and coercivity in a Nd-Fe-B melt-spun ribbon. A high-energy product of 151.2 kJ/m3 (19.0 MGOe) was obtained from an isotropic (Nd0.5Pr0.5)12Fe72Co8B6Nb2 melt-spun ribbon with a remanence of 0.926 T and a coercivity exceeding 1200 kA/m (∼15 kOe).
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