Synthesis and applications of chiral bis-THF in asymmetric synthesis

The synthesis of enantiopure bis-THF is described, starting from d-mannitol. Bis-THF is used as chiral ligand for organolithium reagents in four different reactions. The enantioselectivity provided by this ligand is moderate, and the asymmetric induction is in line with the expected model.     

Solid codes and the uniform density of fd-domains

By means of further investigation of solid codes,the problem“Is every fd-domain uni- formly dense”proposed by Yuqi Guo,C.M.Reis and G.Thierrin in 1988 is solved in this paper.     

生物小分子与铜锌超氧化物歧化酶相互作用的波谱学研究及其应用

本工作以ESR和NMR为主要手段,并结合其它生化方法,考察了氨基酸、核酸碱基、糖等生命基本物质,和抗坏血酸等生命必需物质与钢锌超氧化物歧化酶的相互作用,实验观测到氨基酸、核酸碱基和抗坏血酸在水溶液中可以与酶中的Cu²⁺作用而使其脱离活性部位,以小分子络合物形式游离在溶液中,同时使酶失活,脱离活性部位的Cu²⁺的比例和酶的失活程度取决于小分子配体的加入量及其与Cu²⁺的络合能力。此外,首次尝试使用ESR方法,并借助氨基酸与酶的作用,考察了铜锌超氧化物歧化酶在盐酸胍变性和热变性过程中的构象变化行为,结果表明这一方法是直观而有效的。     

New developments in the field of piezothermal analysis

The solid transitions of C₂₁, C₂₃ and C₂₅ n-paraffins are examined from a piezothermal point of view. The paper is divided into two parts. The first is a report of the main features of a piezothermal analyzer when pressure scanning allows the continuous record of the expansivity as a function of pressure up to 5 Kilobars. Small samples are required and the scanning speeds vary from 0.3 to 16 Kilobars per hour. The second part describes the experimental procedure appropriate for solid state determinations. The resulting piezothermograms are presented and entropies of transformation are determined. A model allows a crude statistical approach giving the entropies of transformation with the correct order of magnitude. Problems related with phase transformations under a shearing stress are considered.

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Zusammenfassung Feststoffumwandlungen bei C₂₁, C₂₃ und C₂₅ n-Paraffinen wurden unter dem Gesichtspunkt der Piezowärme untersucht. Im ersten Teil vorliegender Arbeit werden die Haupteigenschaften eines piezothermischen Analysators beschrieben, bei dem durch Druck-Scanning die kontinuierliche Aufzeichnung des Ausdehnungsvermögens als Punktion des Druckes bis zu 5 kbar ermöglicht wird. Es werden nur kleine Proben benötigt, die Scanning-Geschwindigkeit variiert zwischen 0,3 und 16 kbar/h. Der zweite Teil beschreibt das geeignete experimentelle Verfahren zur Feststoffzustandsbestimmung. Die erhaltenen Piezothermogramme werden dargestellt und die Entropien der Umwandlung bestimmt. Ein Modell liefert eine grobe statistische Näherung, die die Entropien der Umwandlung in der richtigen Grö\enordnung liefert. Probleme in Zusammenhang mit Phasenumwandlungen bei Scherbeanspruchungen werden betrachtet.

     

Melting of heterogeneous vortex matter: The vortex ‘nanoliquid’

Disorder and porosity are parameters that strongly influence the physical behavior of materials, including their mechanical, electrical, magnetic and optical properties. Vortices in superconductors can provide important insight into the effects of disorder because their size is comparable to characteristic sizes of nanofabricated structures. Here we present experimental evidence for a novel form of vortex matter that consists of inter-connected nanodroplets of vortex liquid caged in the pores of a solid vortex structure, like a liquid permeated into a nanoporous solid skeleton. Our nanoporous skeleton is formed by vortices pinned by correlated disorder created by high-energy heavy ion irradiation. By sweeping the applied magnetic field, the number of vortices in the nanodroplets is varied continuously from a few to several hundred. Upon cooling, the caged nanodroplets freeze into ordered nanocrystals through either a first-order or a continuous transition, whereas at high temperatures a uniform liquid phase is formed upon delocalization-induced melting of the solid skeleton. This new vortex nanoliquid displays unique properties and symmetries that are distinct from both solid and liquid phases.     

Covariant Newtonian and relativistic dynamics of (magneto)-elastic solid model for neutron star crust

This work develops the dynamics of a perfectly elastic solid model for application to the outer crust of a magnetised neutron star. Particular attention is given to the Noether identities responsible for energy-momentum conservation, using a formulation that is fully covariant, not only (as is usual) in a fully relativistic treatment but also (sacrificing accuracy and elegance for economy of degrees of gravitational freedom) in the technically more complicated case of the Newtonian limit. The results are used to obtain explicit (relativistic and Newtonian) formulae for the propagation speeds of generalised (Alfven type) magneto-elastic perturbation modes.     

57Fe Mössbauer spectroscopic study of (25−x)MnO–xZnO–15Fe2O3–60B2O3 glasses

The ⁵⁷Fe Mössbauer technique has been used to investigate the effect of zinc oxide substitution in (25???x)MnO–xZnO–15Fe₂O₃–60B₂O₃ glass system (x?=?0, 5, 10, 15 and 20 mol% of ZnO ). Mössbauer absorption spectra for all the samples recorded at room temperature suggest the existence of the two paramagnetic quadrupole doublets. The observed variations in hyperfine parameters have been explained on the basis of cations distribution and exchange interaction at the lattice sites and it is concluded that B–B interaction increases while the metal–metal interaction decreases due to replacement of manganese oxide by zinc oxide. These results suggest that the present glass system exhibits a paramagnetic behaviour that changes towards the weak paramagnetic when manganese oxide was replaced with zinc oxide.     

固体密度秤

根据杠杆平衡原理,使用杠杆平衡仪设计了固体密度秤.采用与液体密度计读数类似的方法,能够直接读出被测固体的密度.     

Stabilization of valence fluctuations in the cerium solid by the time-dependent collision approach

The collision-generated hybridization which has been found responsible for the on-site mixing of the atomic-likef-state and the band-liked states in mixed valence solids has been studied for the cerium solid. A practical expression which depends on the lattice constant and temperature has been obtained for the collision-generated hybridization. Numerical calculations show that the valence varies continuously with lattice constant and that temperature makes the transition smoother. The collision-generated hybridization is found to be of significant strength in the intermediate valence regime; but over a wide range of the valence near 3.5 it varies rather slowly without preferring a particular valence. Factors which can assist the collision-generated hybridization in stabilizing the mixed valence phase at a particular lattice constant are discussed.