Physicochemical comparison of electroslag remelting with consumable electrode and electroslag refining with liquid metal

The paper is devoted to comparison of electroslag remelting (ESR) with consumable electrode and electroslag refining with liquid metal (ESR LM) processes. The possibility of rearrangement of the heat contributions coming from the consumable electrode and current supplying mould (non-consumable electrode, CSM) makes the core of the ESR process organisation in the CSM. The usage of liquid metal instead of consumable electrodes allows to reduce liquid bath temperature and volume in order to provide low segregation ingot. The formal assessment of physico-chemical conditions and experimental measurements of desulphurisation have shown the same level of refining ability of both processes. Replacing the classic ESR by the ESR LM is a prospective way to produce high-quality ingots from sophisticated and hard-to-deform materials, whereas manufacturing of the consumable electrodes is technically problematic and costly.     

Anatomic variations in underdeveloped right ventricle related to tricuspid atresia and stenosis

In the anatomy of 416 hearts, the seat of tricuspid stenosis or atresia is examined, with special reference to Fontan-like surgical procedures. A classification is offered which includes cases with and without regular or inverted transposition, and with decreased or increased pulmonary flow. The size and thickness of the right atrium, the size and architecture of the right ventricle, the size of the pulmonary tree, the types of atrial and ventricular septal defects, the condition of the mitral valve, and the size and thickness of the left atrium and left ventricle are analyzed. In addition the various intracardiac and extracardiac abnormalities are enumerated. Reference is also made to the tendency of the aorta and pulmonary trunk to override the septum, in some cases producing double-outlet left ventricle. It is considered that many cases of tricuspid valve atresia and stenosis with or without transposition may be amenable to Fontan-like procedures in the proper age group. All the above anatomic considerations have a bearing on the suitability and type of operative tricuspid bypass procedures, and they may influence the prognosis of surgical therapy.     

Mitral valve malformation of Ebstein type in absence of corrected transposition

Coffee and its most important constituent, caffeine, may not only stimulate the function of many organs but also increase the metabolism in the body. These effects require a higher energy production which is mainly obtained from striated muscles by glycogenolysis and from fat tissue by lipolysis. Sutherland and Butcher were able to demonstrate that these degradation processes are primarily caused by an increase of cyclic 3,5-AMP. - In this connection caffeine and other methylxanthines are of special interest because these compounds also increase the intracellular amount of cyclic 3,5-AMP. This effect may be caused by an inhibition of phosphodiesterase, a release of catecholamines with resulting stimulation of adenylcyclase or by competitive inhibition of adenosine. At the present time it cannot be said which of these mechanisms primarily is involved in the in vivo effects of caffeine and other methylxanthines.     

Amino acid composition of protein termini are biased in different manners

An exhaustive statistical analysis of the amino acid sequencesat the carboxyl (C) and amino (N) termini of proteins and ofcoding nucleic acid sequences at the 5' side of the stop codonswas undertaken. At the N ends, Met and Ala residues are over-representedat the first (+1) position whereas at positions 2 and 5 Thris preferred. These peculiarities at N-termini are most probablyrelated to the mechanism of initiation of translation (for Met)and to the mechanisms governing the life-span of proteins viaregulation of their degradation (for Ala and Thr). We assumethat the C-terminal bias facilitates fixation of the C endson the protein globule by a preference for charged and Cys residues.The terminal biases, a novel feature of protein structure, haveto be taken into account when molecular evolution, three-dimensionalstructure, initiation and termination of translation, proteinfolding and life-span are concerned. In addition, the bias ofprotein termini composition is an important feature which shouldbe considered in protein engineering experiments.     

First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives: Design,synthesis, crystal structures,electronic and electrical properties

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1·2 and 1·3₂, respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1·2 and 1·3₂ and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV–Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1·2 and 0.40 eV for 1·3₂. Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.     

A study of cooling water requirements for the protection of metal surfaces against thermal radiation

Among the hazards posed to storage tanks by thermal radiation are the effects of changes in the mechanical strength of the metal at high temperatures that may lead ultimately to failure. Alarge-scale experimental study has been made of the water cooling requirements for metal surfaces exposed to thermal radiation. A two meter square radiation furnace and commercial water spray equipment were used in the study, which included trials on both vertical and inclined target surfaces. Water application rates between 1.4 and 10.4 L/min per square meter and incident heat fluxes up to 70 kW per square meter were employed. The experimental work was supported by a theoretical model of the cooling process.The results indicate that a metal plate, exposed to a nearby radiating source, can be kept below the temperature at which its mechanical properties become impaired as long as a water film, of minimal thickness, can be maintained over it.     

Dialkyldithiophosphate substituted on poly(vinylchloride): Synthesis and performance

Preparation of sodium salt of di(2-ethylhexyl)dithiophosphoric acid (DTPANa) by reaction of the corresponding DTPA with sodium hydride has been described. Nucleophilic substitution of chlorine on poly(vinylchloride) (PVC) by a di(2-ethylhexyl)dithiophosphate group resulting in modified polymer (MP) was characterized by the second order rate constant equal to 6.6 × 10^?5 M^?1 s^?1. Formation of homogeneous stable gelled phases composed of MP and DTPA, as well as MP, PVC, and DTPA, was demonstrated. The gelled material is capable of selective separation of metal ions under the conditions of extraction chromatography. © 1993 John Wiley & Sons, Inc.     

Material transfer during machining of aluminum alloys with polycrystalline diamond cutting tools

An analysis of a polycrystalline diamond (PCD)-tipped tool after drilling 40,000 holes in aluminum (Al) 319 alloy under fully lubricated conditions is reported. It is found that aluminum adheres to the PCD tip surface during the machining process under lubricated condition. The aluminum transferring leads to poor surface finishing. Surface morphology analysis and element mapping suggests that the cobalt (Co) binder in the PCD tips is responsible for the adhesion of aluminum to the PCD surface, due to the chemical affinity between aluminum and cobalt. Approaches to prevent the adhesion of aluminum to the tool are discussed.