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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Uranium oxides are known as nonstoichiometric compounds whose composition changes according to external conditions such as temperature and oxygen partial pressure. The change of composition caused by the formation of defect structure results in a change of their properties. In this paper, the compositional changes of UO2 and doped UO2 [(U, M)O2; M=La, Ti, Pu, Th, Nb, Cr, etc.] and also those of other uranium oxides (U4O9, U3O8) are shown against oxygen partial pressure. From the results of doped UO2, it is concluded that the valence control rule holds to a first approximation. The defect structures are estimated both from log x vs. log Po2 (x: deviation from the stoichiometric composition and Po2: oxygen partial pressure) and log σ vs. log Po2 (σ: electrical conductivity) relations. The defect structures of UO2 and doped UO2 are derived based on the Willis model for UO2+x. The detect structure of U4O9 phase is similar to that of UO2+x, but the defect structures of U3O8 phase are complicated due to the existence of many higher-order phase transitions. The thermodynamic data such as the partial molar enthalpy and entropy and the heat capacity are important to characterize the defect structure. The high temperature heat capacities of UO2 doped with Gd show pronounced increases at high temperatures the onset temperature decreases as the dopant content increases. The increase of heat capacity is interpreted to be due to the formation of lattice defects. The heat capacity measurements on U4O9 and U3O8 clucidate the presence of the phase transition. The mechanisms of these phase transitions are discussed.
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  • 2
    ISSN: 1614-7456
    Keywords: Robotic system ; Genetic algorithms ; Elastic system ; Control design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a new and practical method for a control design of a robotic system. In general, actuators in robotic systems are set with gears whose characteristics are elastic. Since a state feedback-type digital controller is usually used for such a robotic system, the design of the feedback gain of the controller is important, because undesirable vibrations or an overshoot in responses occur for high gains. Therefore the desired response, the output of a reference model, is designed first, and the feedback gains are determined so that the response will coincide with the desired response, which is an optimization problem. The gradient method works to some extent, but it takes a long time to get a satisfactory result. Thus we applied the genetic algorithm (GA) to this nonlinear optimization problem, which gave the very first convergence. The gains obtained have many useful applications. The results of a simulation are also given.
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  • 3
    ISSN: 1615-6102
    Keywords: Boodlea coacta ; Cortical microtubule ; Cell polarity ; Anchor protein ; Coenocytic green alga
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Examination was made of the structure and assembly of the cortical microtubule (MT) cytoskeleton in the coenocytic green algaBoodlea coacta (Dickie) Murray et De Toni by immunofluorescence microscopy. Cortical MTs inBoodlea protoplasts are arranged randomly but some show a meridional arrangement within 6 h after protoplast formation. At 6–9 h such MTs become highly concentrated and parallel to each other in certain areas. At 12 h the concentration is uniformly high throughout the cell, indicating the completion of high density meridional arrangement of cortical MTs. Cortical MTs exhibiting a high density, meridional arrangement show characteristic disassembly by treatment with 10 μM amiprophos-methyl (APM) or cold treatment (0 °C). Disassembly occurs by each MT unit at positions skipping 30–40 μm in the transverse direction, and neighboring MTs subsequently disassemble to form MT groups. Each group becomes slender and then disappears completely within the following 24 h. The meridional arrangement of cortical MTs is disrupted by N-ethylmaleimide (NEM) accompanied by a remarkable reduction in density. The remaining MTs form groups at 30–40 μm intervals from each other, as also occurs with drug or cold treatment, but disruption and density return to normal levels following removal of NEM. It appears that there are meridionally oriented channels, anchor-rich and anchor-poor, in the plasma membrane. The channels could be distributed alternately and anchors could be deposited in a cross-linking manner with cortical MTs to form a stable cortical MT-cytoskeleton. MTs comprising the cortical MT cytoskeleton could be oriented by meridionally oriented channels of anchors which are distributed following establishment of cell polarity.
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  • 4
    ISSN: 1615-6102
    Keywords: Boodlea coacta ; Cortical microtubule ; Cell polarity ; Anchor protein ; Coenocytic green alga ; Cycloheximide ; 2, 6-Di-chlorobenzonitrile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of 2,6-dichlorobenzonitrile (DCB, an agent which inhibits cellulose synthesis) and cycloheximide (CHI, a known inhibitor of protein synthesis) on the construction and stability of the cortical microtubule (MT) cytoskeleton in two kinds of protoplasts (smaller protoplasts and larger ones) prepared fromBoodlea coacta (Dickie) Murray et De Toni were examined by immunofluorescence microscopy. In smaller protoplasts which develop from released protoplasmic masses in culture media, parental cortical MTs assume a convoluted configuration, but new cortical MTs appear following disassembly of convoluted MTs. New cortical MTs initially have a random arrangement but later, a rough meridional arrangement following development of cell polarity and finally, a high density meridional arrangement. In larger protoplasts which are formed within cell wall cylinders of thalli cut at 500 μm length, longitudinally oriented parental cortical MTs are preserved. Each exhibits a curving configuration just after protoplast formation, but a straight configuration after 3 h of culture. In smaller protoplasts, cortical MT orientation changes from random to rough meridional orientation but never to a high density meridional orientation following treatment with 10 μM CHI, and MT density decreases after 12 h. However, rough meridional and high density meridional arrangements of MTs ceased to be formed and MT density decreased following treatment with 10 μM DCB. In larger protoplasts, high density meridional arrangements of MTs were noted not to be affected by treatment with CHI; instead, they continued to remain oriented meridionally, but the length and density were decreased after treatment with DCB for 3–4 h. After 10 h, the MTs became fragmented and orientation was random. From these findings it is summarized that: (1) There are no putative anchors in the plasma membrane of nascent smaller protoplasts, but the meridional orientation of cortical MTs requires anchors which may be distributed in the plasma membrane following the establishment of cell polarity. (2) Plasma membranes in larger protoplasts contain parental anchors oriented meridionally. Anchors stabilize cortical MTs via their close relation to cell walls (especially to cellulose). Anchors are detached from the plasma membrane when cellulose is not formed. (3) Cellulose regeneration may be indispensable to the formation and stabilization of the MT cytoskeleton inBoodlea.
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  • 5
    ISSN: 1612-1112
    Keywords: Ion-exchange chromatography ; Titanium antimonate cation exchanger ; Trivalent metals separation ; Gallium separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ion exchange selectivity of trivalent metal ions has been determined on titanium antimonate cation exchanger prepared by coprecipitation of antimony to titanium at different mole ratios. The selectivity sequence Al3+〈Cr3+〈Ga3+〈In3+〈Fe3+ was found for trivalent metal ions at an initial concentration of 10−4 mol dm−3 in nitric acid media. A high separation factor αGa/Al = KdGa/KdAl, 4.8×103, was observed for the Ga3+−Al3+ pair on titanium antimonate with an antimony to titanium ratio of 0.34. The effective separation of Ga3+ and In3+ from Al3+ was achieved using a 3 cm×0.5 cm i.d. column containing titanium antimonate with an antimony to titanium ratio of 0.34.
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  • 6
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The immunogenicity of Leucocytozoon caulleryi sporozoites for chickens and their reactivity in vitro with specific immune sera were studied. Almost all of the chickens that had been immunized with the sporozoite antigens survived the sporozoite challenge. The degree of parasitemia observed in the immunized chickens was significantly lower than that found in the nonimmunized chickens. Specific antibodies against sporozoites were tested by the circumsporozoite precipitation (CSP) reaction. Antibodies were demonstrated in the sera of chickens that had been immunized with the sporozoite antigens or chickens that had recovered from a primary infection with L. caulleryi sporozoites. When viable mature sporozoites were incubated in vitro with serum from immune chickens, agglutination and a long, thread-like precipitate at one end of the sporozoite could be seen within a few minutes under a phase-contrast microscope. The effects of specific immune serum on the infectivitiy of sporozoites were examined by the sporozoite neutralization activity (SNA) test. Sporozoites that had been incubated in vitro with serum from immune chickens lost their infectivity to chickens. The CSP reaction and the SNA test in L. caulleryi infection were stage- and species-specific.
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  • 7
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The thermal properties of bis-GMA-based resins containing a synthesized crystalline DME-TDC which was dissolved to bis-GAM/TEGDMA base resin by 10 or 20wt% were examined. Camphorquinone (0.5%) and a reducing agent (0.5%) were added to the base resin before the addition of DME-TDC. A thermoanalytical study using differential thermal analysis (DTA) and differential scanning calorimetry (DSC) showed that thermal change in the DTA and DSC curves depended on the composition of the bis-GMA-based resins. Heat for curing was lowest in 50/50 base resin of 40 wt% bis-GMA/60 wt% TEGDMA, 50/50 and 60/40 base resins in DTA analysis during heating. The addition of DME-TDC to each resin increased heat requirements in 50/50 resin and decreased heat requirements in 40/60 and 60/40 resins. The thermal decomposition of 50/50 bis-GMA-based resin including DME-TDC occurred at a higher temperature than that in 40/60 and 60/40 based resin. The value of activation energy for curing performance was lowest for a DME-TDC including bis-GMA-based resin.
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  • 8
    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 The continuous methanation of CO2 has been accomplished over hydrogen-reduced Ni(II)-bearing ferrite (NixFe3−xO4−δ; x=0.39, δ 〉 0) in a mixed gas flow of CO2 and H2 at 250–375 °C. The yield and the selectivity for the methanation were larger than 50% and 95%, respectively, at the initial stage of the process. They decreased to 31% and 89%, respectively, after 6 h methanation. The innovative results can be ascribed to the use of the new material; hydrogen-reduced Ni(II)-bearing ferrite. Its formation was evinced by chemical analyses and the increase in the lattice constant; the lattice constant of the Ni(II)-bearing ferrite (a0 0.8375 nm) was enlarged to 0.8379 nm by hydrogen reduction. The enlarged lattice constant was not changed during the methanation. These findings suggest that the methanation occurs at the oxygen-deficient site of the hydrogen-reduced Ni(II)-bearing ferrite, as well as the formation of water by combination of the incorporated oxygens with hydrogen. The methanation consists of three steps of the elementary reaction. First, the oxygen-deficient sites are formed by hydrogen reduction; second, CO2 is reduced to elementary carbon and two oxygen ions which are incorporated into the oxygen-deficient sites; and third, the carbon deposited on the surface of the reduced ferrite is selectively hydrogenated to CH4.
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  • 9
    ISSN: 1573-5060
    Keywords: gametogenesis ; mutagenesis ; radiosensitivity ; mutation frequency ; X-ray irradiation ; Oryza sativa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Developmental stages during gametogenesis of rice were histologically examined in the period from differentiation of reproductive organs to anthesis. Plants were exposed to acute X-rays of 20 Gy. Radiosensitivity and mutation frequency were investigated in relation to the developmental stages of reproductive organs. The most radiosensitive stage, as measured by reduction of the M1 pollen-and seed-fertilities, was the last premeiotic interphase. Mutations induced at different developmental stages were scored in M3 strains. Sterility mutants and short-culm mutants were most frequently observed. Grain shape, panicle morphology, heading-date and endosperm character mutants were induced at a relatively low frequency. The overall mutation frequency varied with the developmental stage at the time of irradiation. The highest overall mutation frequency was observed when radiation was applied 10 days before anthesis, the late tetrad stage of microspores. Radiation exposure of florets at the late tetrad stage was found to be a more efficient method of inducing a large number of mutations than radiations applied to seeds and fertilized egg cells.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 256 (1978), S. 97-97 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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