Synthesis and Structure Determination of 1, 4, 7, 11, 14, 17, 21, 24, 27-Nonaoxatriacontan-8, 10, 18, 20, 28, 30-Esaone

The title compound crystallizes in the trigonal space group R-3, with unit-cell parameters: a = 23.261(4), c = 9.537(2) Å; λ(MoKα) = 0.71073 Å, V = 4469(2) Å³, and Z = 6. The structure has been solved by direct methods using X-ray diffraction techniques. The final reliability index for the computed structure is 0.0826 for 929 observed reflections and 121 refined parameters. Crown ether adopts an almost circular shape and macrocycles are piled up in a columnar arrangement forming tubular nanochannels. The channels are filled with guest CDCl₃ molecules, characterised by rotational disorder.     

Apparent entropy,residual entropy,causality, metastability,constraints, and the glass transition

A thermodynamic framework for the investigation of ‘residual entropy’ and related phenomena is developed, expanding and clarifying the work of Kivelson and Reiss and the important work of several other investigators. The main difficulties encountered in the development of such a framework are the need to deal with constrained equilibrium as well as to include irreversible processes in the overall study. These challenges are met by using the device of auxiliary constraints and the equivalent equilibrated states that they produce. The importance of a thermodynamic framework is tied to the fact that evolving molecular theories of residual entropy, which also impact the glass transition, no matter how sophisticated, invariably contain approximations whose effects are hard to assess. Thus a thermodynamic framework provides a vehicle within which the internal consistency of a theory can be tested. Phenomena that are treated in such a framework, along with others, are those mentioned in the title of this paper. The concept of residual entropy, its reality or unreality, is often considered to be an unimportant issue. The findings of this paper, besides emphasizing the unreality of residual entropy, show that the question of its existence is a significant one. Among other things, the fundamental principle of causality is involved and we should not be so cavalier as to dispense with it. Among other rigorous analysis we present an argument involving an ideal binary solution whose behavior as the limiting behavior of a real solution provides access, in principle, to experiment. The argument does make the generally accepted assumption that, at equilibrium at 0 K, pure crystals of the binary system’s components have zero entropy. It strongly suggests that residual entropy, in general, is an impression that stems from the inclusion of an irreversible step in an experimental thermodynamic cycle.     

Glass foams: formation, transport properties, and heat, mass, and radiation transfer

Energy efficiency, environmental impact, and quality of the final product in glass manufacturing depend, to a large extent, on foams formed on the surface of the molten glass and of the batch due to entrapment of gas bubbles generated by the batch fusion and refining chemical reactions during the melting process. Hence, understanding the mechanisms of foam formation as well as development of theoretical models for thermophysical and transport properties and heat, mass, and radiation transfer in glass foams are not only a problem of significant fundamental interest but also of tremendous practical impact. In this paper, the review of the current state-of-the-art in our understanding of glass foams is provided, including some of our recent results in modeling the dynamics of the foam growth and its steady-state thickness, prediction of gas diffusion through glass foams, and thermal radiative properties of glass foams. In addition, the new results on simulation of combined conduction and radiation heat transfer in glass foams and radiative transfer in primary (batch) foams are presented and discussed in some detail. The paper also presents practical means available for reducing foaming in glass melting and concludes with the discussion of unresolved problems and summary of the directions for the future work in the area.     

D-β,β-dimethylcysteic acid,its preparation,structure, and spectroscopic properties

The X-ray crystal structure ofd-,-dimethylcysteic acid, C₅H₁₁NO₅S, has been determined. The compound is monoclinic, space groupP2₁₄ (No. 4), with cell dimensionsa=8.133(1),b=8.094(1),c=6.3138(7) Å,=96.36(1)° andZ=2. The structure was solved by Patterson and electron density difference methods and refined toR=0.025,R _w=0.022 for 1081 reflections. Bond lengths and angles do not differ from those in similar structures. The crystal is held together by intermolecular hydrogen bonds. The vibrational spectra have been recorded and assigned and the¹ H and¹³C NMR spectra were measured.     

Intermetallic Compounds LikMn (M = Ag,Au, Pt,Pd, Ir,Rh): Geometrical and Topological Analysis,Tetrahedral Cluster Precursors,and Self-Assembly of Crystal Structures

Crystallography Reports - A combinatorial and topological analysis has been performed and self-assembly of the crystal structures of intermetallic compounds formed in the Li–M (M = Ag, Au,...     

Influence of oxygen, hydrogen, helium, argon and vacuum on the surface behavior of molten InSb, other semiconductors, and metals on silica

Sessile drop experiments were performed on molten indium antimonide on clean quartz (fused silica) surfaces. A cell was constructed through which argon, helium, oxygen, hydrogen or a mixture of these was flowed at 600 °C. Some of the InSb was doped with 0.1% Ga. The surface tension σ of oxide-free molten InSb was smaller in Ar than in He, may have increased with increasing O₂ in the gas, and was not influenced by Ga or H₂. The contact angle θ on silica was higher in the presence of Ar, was lowered by O₂, and was not influenced by H₂ or Ga. The work of adhesion W and the surface energy σ_sv of the silica were higher in He than in Ar. The surface remained free of solid oxide only in flowing gas containing 0.8 ppm O₂. This behavior is attributed to reaction of O₂ at the surface of the melt to form In₂O gas. When solid oxide formed on Ga-doped material, it was strongly enriched in Ga, with the Ga/In ratio increasing with the concentration of O₂ in the gas.

Examination of published sessile-drop results for liquid metals and semiconductors on silica revealed that W and σ_sv were highest for reactive melts, in which SiO₂ dissolves. For non-reactive melts, W and σ_sv were lower and θ higher in a gas than in a vacuum, regardless of whether the experiments had been carried out in sealed ampoules, a flowing gas, or dynamic vacuum. The implication is that the surface of silica was different in a vacuum than in a gas at 1 bar.     

Formation and properties of RE55Al25Co20 (RE = Y,Ce, La,Pr, Nd,Gd, Tb,Dy, Ho and Er) bulk metallic glasses

We report that a series of ternary RE₅₅Al₂₅Co₂₀ (RE = Y, Ce, La, Pr, Nd, Gd, Tb, Dy, Ho and Er) alloys can be readily cast into bulk glasses by a conventional casting method. The characteristics and properties of these new bulk metallic glasses (BMGs) are studied and compared. Due to the chemical comparability and well-regulated variety in atomic size, properties and elastic constants of these rare earth elements, the RE₅₅Al₂₅Co₂₀ BMGs could be regarded as a model system to investigate the glass-forming ability, thermal stability, glass transition, crystallization behavior, liquid fragility, elastic and mechanical properties as well as their relationships. An attempt is made to highlight commonality and contrasts of the effects of various factors on the metallic glasses formation and properties.     

Crystal and molecular structure of dihydro-8b,8c-diphenyl-1H,3H,4H,5H,7H,8H,-2,6-dioxa-3a,4a,7a,8a-tetraazacyclopenta[def]fluorene-4,8-dithione

The title compound C₂₀H₁₈N₄O₂S₂ crystallizes in the monoclinic space group P2₁/n witha=8.4930(1) Å,b=11.4880(1) Å,c=20.0709(2) Å, =94.933(1)°,V=1951.01(3) ų,Z=4. The crystal structure has been solved by vector search methods and refined by fullmatrix least-squares toR=0.04 for 2888 reflections and 116 restraints. The title compound has a suitable geometry for synthesizing receptor molecules with a cleft for selective complexation.     

Intermetallic Compounds CsnMk (М = Na,K, Rb,Pt, Au,Hg, Te): Geometrical and Topological Analysis,Cluster Precursors,and Self-Assembly of Crystal Structures

Crystallography Reports - A geometrical and topological analysis has been performed, and self-assembly of the crystal structures of intermetallic compounds CsnMk (М = Na, K, Rb, Pt, Au, Hg,...     

Absolute structure of (11E, 1S, 3S, 4R, 7S, 8R, 14S)-3,7-diiodo-4,8-epoxy-euniolide

3,7-Diiodo-4,8-epoxy-euniolide (2) was synthesized from euniolide (1) by the addition reaction of iodine in the presence of triphenylphosphine in CH₂Cl₂. The absolute structure of 2 was unambiguously determined by a combination of ¹H and ¹³C NMR, HREI mass spectroscopy, and x-ray single crystal analysis as (11E, 1S, 3S, 4R, 7S, 8R, 14S)-3,7-diiodo-4,8-epoxy-cembra-11,15-dien-16,14-olide. X-ray crystallographic data for 2: Orthorhombic P2₁2₁2₁ (#19), a = 10.9688(7), b = 11.3909(8), c = 16.885(1) Å, _calcd = 1.795 g cm^–3, and for Z = 4.     

Growth,optical, photoluminescence,dielectric, second and third order nonlinear optical studies of benzoyl valine acentric crystal

A nonlinear optical material benzoyl valine (BV) was synthesized by the technique of slow evaporation process at room temperature. The single crystal X ray diffraction analysis evince that crystal corresponds to acentric space group P₂₁ with monoclinic system. The diverse optical properties assured an elevated transparency in BV crystal. Photoluminescence profile revealed the suitability of crystal for fabricating violet lasers. The Laser damage threshold and the dielectric behavior of the grown crystal were analyzed to indicate its practical applications. The second and third order nonlinear optical measurements were studied to prove its potentiality in the domain of nonlinear optical applications.     

Electrons,dislocations, and low-temperature plastic deformation

The influence of electron drag processes on the plasticity of normal state metals is demonstrated in the case of zinc crystals. These results show that dislocations move as underdamped oscillators at low temperature and that dislocations flutters as they move. This flutter motion, in contrast to kink motion which is expected to have no long range stress, is the dominant drag process at temperatures below ≈ 4.2 K.     

Microhardness,indentation toughness,elasticity, plasticity,and brittleness of Ge–Sb–Se chalcogenide glasses

Elastic/plastic properties of Ge–Se binary and Ge–Sb–Se ternary chalcogenide glasses were explored by indenting with Vickers and Brinell (spherical) microindenters using static and ‘instrumented’ (load versus penetration) recording machines and analyzed further using a non-contact profilometer. The load-dependence of microhardness, indentation fracture toughness and brittleness versus the average covalent coordination number, 〈r〉, were studied. It is concluded that the elastic recovery of deformations is maximized at ∼GeSe₄ (〈r〉 = 2.4), which is consistent with ‘optimized connectivity’ of the rigidity percolation arguments. Surprisingly, many of the extrema were nearly non-existent in the ternary glasses.     

High-Temperature Crystallization,Composition, Structure,and Certain Properties of Rare-Earth Gallium Borates

Solution-melts based on PbF₂—B₂O₃ and Bi₂O₃—B₂O₃ were used in studying the stability regions and for growth, by way of spontaneous crystallization, of crystals up to 3 mm in size of twelve compounds having the general formula RGa₃(BO₃)₄. All of these compounds are isostructural with carbonate mineral huntite. Their composition is highly dependent on that of the crystallization medium. The facing of the crystals is characterized by a small number of simple forms {101 1}, {112 0}, {21 1 0}, and less frequently {022 1}, {0112}, {404 1}. The examined parameters include the IR spectra, luminescence spectra, heat of formation from oxides, harness (6 to 8 units on the Mohs scale) and others.