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  • 1
    ISSN: 1432-0983
    Keywords: Key words Petite mutation ; Error-prone repair ; Paraquat ; Psoralen photo-induced DNA-damage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The original pso3-1 mutant isolate of the yeast Saccharomyces cerevisiae exhibits a pleiotropic mutagen-sensitivity phenotype that includes sensitivity to UVA-activated 3-carbethoxypsoralen, to UVC-light, to mono- and bi-functional nitrogen mustard, to paraquat, and to cadmium; on the other hand, it shows hyper-resistance (HYR) to nitrosoguanidine when compared to established wild-type strains. Also, the original pso3-1 mutant exhibits a low UVC-induced mutability and mitotic gene conversion and a high rate of spontaneous and UVC-induced petite mutations. Since the HYR to the nitrosoguanidine (MNNG) phenotype resembles that of low glutathione-containing yeast cells, the original pso3-1 mutant was crossed to a gsh1 knock-out mutant that lacks the enzyme for the first step in glutathione biosynthesis and the resulting diploid was tested for complementation. While there was none for HYR to nitrosoguanidine, and other low glutathione-related phenotypes, some other phenotypic characteristics of pso3-1, e.g. UVC sensitivity and UVC-induced mutability were restored to a wild-type level. Tetrad analysis of a diploid derived from a cross of the original haploid pso3-1 isolate with a repair-proficient, normal glutathione-containing, PSO3 GSH1 wild-type led to the separation of a leaky gsh1 mutation phenotype from that of the repair-deficient pso3-1 phenotype. Linkage studies by tetrad and random spore analyses indicated no linkage of the two genes. This shows that the low glutathione content in the original pso3-1 isolate is due to a second, additional, mutation in the GSH1 locus and is unrelated to the pso3-1 mutation. Thus, the original pso3-1 isolate is a pso3-1 gsh1 double mutant with most of the particular characteristics of the pleiotropic sensitivity phenotype contributed by either the pso3-1 or the gsh1-leaky mutant allele. The expression of a few phenotypic characteristics of pso3, however, were most pronounced in pso3-1 mutants with a low glutathione pool.
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  • 2
    ISSN: 1090-6487
    Keywords: 52.50.Jm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The x-ray spectra of a plasma produced by heating CO2 clusters with intense femtosecond laser pulses with λ=0.8 μm and λ=0.4 μm are investigated. Spatially resolved x-ray spectra of the cluster plasma are obtained. The observed characteristic features of the x-ray emission spectra show unequivocally that such a plasma contains quite a large relative number of ions (≃10−2–10−3) with energies of 0.1–1 MeV. The contour of the OVIII Lyα line is found to have characteristic features that are especially conspicuous when the clusters are heated with second-harmonic pulses. These features cannot be explained by any mechanisms known to the authors.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 3099-3110 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation two-dimensional dipolar vortices by the interaction between two shielded monopolar vortices with opposite vorticity, as shown in a numerical study by Couder and Basdevant,〈citeref RID="R1" STYLE="SUPERIOR"〉1 is investigated in detail, both experimentally, in a nonrotating stratified fluid and numerically by direct solutions of the two-dimensional Navier–Stokes equations. A comparative study between the laboratory experiments and numerical simulations is performed. The vorticity distribution measured in the early stage of the evolution in the laboratory is used as initial data for the simulations, and an additional damping term in the Navier–Stokes equations, that accounts for the vertical diffusion in the laboratory experiments, is used. The results show that, depending on the initial separation between the vortices, the shields of the monopoles are peeled off and indeed a compact dipole with a linear (ω,ψ)-relationship is formed, or when the monopoles are further apart the shields of the monopoles are perturbed and two tripoles are formed. The characteristics of the emerged dipole are analyzed and a dye visualization of the dipole formation is performed. A second, more general numerical study yields a relationship between the formation time of the dipole and the initial separation distance between the monopoles and it shows that the deshielding process can be explained by the domination of strain over vorticity. © 1998 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2696-2703 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: With the increasing popularity of the scanning tunneling microscope (STM) in surface science, many ideas for additional and new technical features have been proposed. The work herein contributes to this evolution with a special STM design. The STM described is part of an experimental apparatus for thin film growth investigations in ultrahigh vacuum. Besides the STM, the apparatus includes facilities for thermal desorption spectroscopy and Auger electron spectroscopy and a Kelvin probe for measuring dynamic work function changes. The Kelvin probe is optimized for gas adsorption experiments as well as for in situ film growth investigations during metal deposition. These added features combined with the STM and easy sample transfer yield a new powerful tool for in situ controlled preparation and extensive characterization of thin films. In the present work we describe the novel features of this STM and we demonstrate the efficiency of the whole system by giving a few representative results. © 1998 American Institute of Physics.
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  • 5
    ISSN: 1434-601X
    Keywords: PACS:29.25.Dz Neutron sources – 25.40.Ve Other reactions above meson production thresholds – 13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons etc.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstact: The kinetic energy spectrum and the polarization of the PSI neutron beam produced in the reaction 12C(p,n)X at 0° with 590 MeV polarized protons were investigated. A strong energy dependence of the neutron beam polarization is observed which was not expected at the time the neutron beam was built.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 182 (1998), S. 677-686 
    ISSN: 1432-1351
    Keywords: Key words Electrophysiology ; Brain ; Insect ; Histamine ; GABA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Whole-cell patch-clamp recordings were obtained from 116 freshly dissociated neuronal somata from the optic lobe of adult locusts (Schistocerca gregaria). Prerequisites were a papain treatment and the directed transfer of somata to the recording chamber by dabbing. Of the recorded somata, 65 were from lamina and 51 from other optic lobe neurons. All somata supported voltage-activated outward currents and some (24% of optic lobe, 3% of lamina neurons) also fast inward currents. Most lamina neurons supported an outward current that activated (V 1/2=−8.5 mV) and inactivated rapidly and a sustained outward current. Some lamina and most optic lobe neurons expressed only a sustained outward current (V 1/2=−9.4 mV). GABA and histamine elicited inward currents at negative holding potentials. Most optic lobe (95%) but only 18% of lamina neurons showed a γ-aminobutyric acid (GABA) current, whereas a similar percentage of optic lobe (50%) and lamina neurons (67%) expressed a histamine current. Both currents reversed near the chloride equilibrium potential, were reversibly reduced by picrotoxin, and did not show rundown. Thus, they likely represent chloride currents mediated by ionotropic receptors. Our data indicate that the lamina neurons recorded mainly represent monopolar cells postsynaptic to histaminergic photoreceptors. The optic lobe neurons, on which GABA and histamine apparently act as inhibitory neurotransmitters, are more heterogeneous.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 130 (1998), S. 162-175 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The fluid-absent reaction 12 zoisite = 3 lawsonite + 7 grossular + 8 kyanite + 1 coesite was experimentally reversed in the model system CaO-Al2O3-SiO2-H2O (CASH) using a multi-anvil apparatus. The upper pressure stability limit for zoisite was found to extend to 5.0 GPa at 700 °C and to 6.6 GPa at 950 °C. Additional experiments both in the H2O-SiO2-saturated and in the H2O-Al2O3-saturated portions of CASH provide further constraints on high pressure phase relationships of lawsonite, zoisite, grossular, kyanite, coesite, and an aqueous fluid. Consistency of the present experiments with the H2O-saturated breakdown of lawsonite is demonstrated by thermodynamic analysis using linear programming techniques. Two sets of data consistent with databases of Berman (1988) and Holland and Powell (1990) were retrieved combining experimental phase relationships, calorimetric constraints, and recently measured elastic properties of solid phases. The best fits result in G f ,1,298 ∘,zoisite=−6,499,400 J and S 1,298 ∘,zoisite=302 J/K, and G f ,1,298 ∘,lawsonite=−4,514,600 J and S 1,298 ∘,lawsonite=220 J/K for the dataset of Holland and Powell, and G f ,1,298 ∘,zoisite=−6,492,120 J and S 1,298 ∘,zoisite=304 J/K, and G f ,1,298 ∘,lawsonite=−4,513,000 J and S 1,298 ∘,lawsonite= 218 J/K for the dataset of Berman. Examples of the usage of zoisite as a geohygrometer and as a geobarometer in rocks metamorphosed at eclogite facies conditions are worked, profiting from the thermodynamic properties retrieved here.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 25 (1998), S. 37-41 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  We present a measurement technique designed to accurately measure small flow rates near atmospheric pressure, and demonstrate the ability to measure flows on the order of 10-10 mol/sec. The technique is based upon a modification of a constant-volume mass accumulation scheme where the flow rate is measured by monitoring the change in pressure of a known volume of gas. We identify two phenomena, thermally-induced fluctuations and thermodynamically-induced fluctuations, which will affect the resolution and dynamic range of the instrumentation and discuss how the problems associated with them can be mitigated. We estimate the resolution to be approximately 2.0×10-13 mol/s, and the maximum measurable flow rate to be to the order 2×10-9 mol/s.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Computational mechanics 22 (1998), S. 225-238 
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Many interesting tasks in technology need the solution of complex boundary value problems within the mathematical theory of elastoplasticity. Error controlled adaptive strategies should be used in order to achieve a prescribed accuracy of the computed solutions at minimum cost. Local error indicators in the primal form of the finite-element-method for Hencky- and Prandtl–Reußplasticity without and with nonlinear hardening are presented, controlling global errors of equilibrium, plastic strain rates, the yield condition and the numerical integration of the flow rule. A 2D finite element code was extended for the transfer of physical parameters between meshes and for a combined space and time adaptive strategy. All error indicators are tested with the benchmark example of a rectangular plane strain problem with a hole.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Microsystem technologies 4 (1998), S. 184-186 
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract  The manufacturing of pinhole arrays with diameters 10 μm up to 60 μm in 100–300 μm gold foils is described using LIGA. These structures are used to characterize the electron beam in a storage ring by means of the emitted synchrotron radiation. The source inside the bending magnet 13 at BESSY I (single bunch mode, 70 mA ring current, pinholes: ∅60 μm) is (448±40) μm in height and (768±40)μm in horizontal width. For BESSY II pinholes with ∅ 10–20 μm will be used utilizing bending magnet radiation (resolution ∼10 μm), single pinholes with 1–5 μm in diameter are dedicated to insertion device characterization (coherence).
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