306 research outputs found

    ROLE OF HETERONUCLEAR COMPLEXES IN SOLUTIONS FOR METALLIZATION OF PLASTICS.

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    Metallization of plastics by chemical deposition of metals is an important technological process in production of circuit boards. The usual reducing agents are formaldehyde, borohydrides, hydrazine and its derivatives, and hypophosphites in alkaline media. Since most metal ions undergo hydrolysis in such media, they are converted into complex compounds. Salts of tartaric (H//4Tart) or citric (H//4Citr) acids, whose anions act as multidentate ligands, are used in solutions for chemical coppering and coating with nickel-cobalt and nickel-copper alloys. Heteronuclear complexes (HNC) may be formed in solutions containing two or more transition-metal salts. The authors studied the systems Cu(II)-Ni(II)-H//4Citr, Cu(II)-Co(II)-H//4Citr under the concentration conditions of copper baths. Using the NMR method, whereby formation of heteronuclear species can be recorded directly, the authors detected formation of a heteronuclear complex

    Composition, properties, and structure of palladium(II) chlorides in aqueous solution

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    The composition, stability, and structure of palladium(II) chloride complexes in hydrochloric acid media have been determined using nuclear-magnetic relaxation, magnetochemical methods, and Rayleigh light scattering. The predominant form in solution for palladium(II) concentrations greater than 0.005 moles/liter is the octahedral Pd6Cl12 or Pd6Cl14 2-, which has antiferromagnetic properties in contrast with the paramagnetic properties of the mononuclear aquachloride. The polarizability anisotropy of Pd-Cl bonds with terminal and bridging chlorine atoms has been determined. © 1991 Plenum Publishing Corporation

    Hygienic assessment of educational and extracurricular activities of students in grades 9 and 11

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    The purpose of the study is a hygienic assessment of the educational and extracurricular activities of students in grades 9 and 11.Цель исследования – гигиеническая оценка учебной и вне учебной деятельности учеников 9 и 11 классов

    Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

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    The significance and nature of ion kinetic effects in D3He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects

    Two-Stage Rotational Disordering of a Molecular Crystal Surface: C60

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    We propose a two-stage mechanism for the rotational surface disordering phase transition of a molecular crystal, as realized in C60_{60} fullerite. Our study, based on Monte Carlo simulations, uncovers the existence of a new intermediate regime, between a low temperature ordered (2×2)(2 \times 2) state, and a high temperature (1×1)(1 \times 1) disordered phase. In the intermediate regime there is partial disorder, strongest for a subset of particularly frustrated surface molecules. These concepts and calculations provide a coherent understanding of experimental observations, with possible extension to other molecular crystal surfaces.Comment: 4 pages, 2 figure

    Chemical genetic screen identifies lithocholic acid as an anti-aging compound that extends yeast chronological life span in a TOR-independent manner, by modulating housekeeping longevity assurance processes

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    In chronologically aging yeast, longevity can be extended by administering a caloric restriction (CR) diet or some small molecules. These life-extending interventions target the adaptable target of rapamycin (TOR) and cAMP/protein kinase A (cAMP/PKA) signaling pathways that are under the stringent control of calorie availability. We designed a chemical genetic screen for small molecules that increase the chronological life span of yeast under CR by targeting lipid metabolism and modulating housekeeping longevity pathways that regulate longevity irrespective of the number of available calories. Our screen identifies lithocholic acid (LCA) as one of such molecules. We reveal two mechanisms underlying the life-extending effect of LCA in chronologically aging yeast. One mechanism operates in a calorie availability-independent fashion and involves the LCA-governed modulation of housekeeping longevity assurance pathways that do not overlap with the adaptable TOR and cAMP/PKA pathways. The other mechanism extends yeast longevity under non-CR conditions and consists in LCA-driven unmasking of the previously unknown anti-aging potential of PKA. We provide evidence that LCA modulates housekeeping longevity assurance pathways by suppressing lipid-induced necrosis, attenuating mitochondrial fragmentation, altering oxidation-reduction processes in mitochondria, enhancing resistance to oxidative and thermal stresses, suppressing mitochondria-controlled apoptosis, and enhancing stability of nuclear and mitochondrial DNA

    Hypergraph extensions of the Erdős-Gallai Theorem

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    Abstract We extend the Erdős-Gallai Theorem for Berge paths in r -uniform hypergraphs. We also find the extremal hypergraphs avoiding t -tight paths of a given length and consider this extremal problem for other definitions of paths in hypergraphs
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