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.     

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,...     

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.     

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.