Effect of Prolonged Thermal Exposure on Microstructure and Mechanical Properties of Zr – 1 wt.% Nb and Ti – 45 wt.% Nb Ultrafine-Grained Bioinert Alloys

Russian Physics Journal - The results on thermal stability of the microstructure and mechanical properties of Zr – 1 wt.% Nb and Ti – 45 wt.% Nb ultrafine-grained alloys subjected to...     

The Influence of Ultrafine-Grained State of Zr – 1 wt.% Nb and Ti – 45 wt.% Nb Alloys on their Thermophysical Properties and Energy Dissipation and Accumulation during Deformation

Russian Physics Journal - The results of a study of thermal conductivity and specific heat capacity of Zr – 1 wt.% Nb and Ti – 45 wt.% Nb alloys in coarse-grained and ultrafine-grained...     

Effect of cooling speed on structure and properties of rapidly solidified Pb–25wt.% Sn alloy

The effect of cooling speed on structure, hardness, mechanical and electrical transport properties of rapidly solidified Pb–25wt.% Sn alloy have been investigated. A single roller melt spinning technique with linear speeds 15.7 and 31.7 m/s, was used for the preparation of specimens. The results showed that a lower cooling speed increased the precipitation of Sn in a Pb-matrix phase as compared with the higher cooling speed. This decomposition behavior decreased the electrical resistivity and increased the internal friction, thermal diffusivity and Vickers microhardness of the lower cooling speed as compared with those of the higher cooling speed.     

The hyperfine and isotope structure of the Cd intercombination line – revisited

Careful analysis of the intercombination 5¹S₀–5³P₁ line of the ¹¹³Cd isotope with two hfs components and was carried out. The hyperfine splitting of this line was determined to uncertainty less than 10^-3 cm^-1 using neon-perturbed Doppler limited spectra.     

Microwave spectrum and structure of carbonyl gold iodide,OCAuI – ARTICLE WITHDRAWN

WITHDRAWN TO APPEAR IN SPECIAL ISSUE IN 2007     

The structure of solid salt eutectics — – Why lamellar or conglomerate?

Using KCl/ZnSO₄ eutectic it has been shown that cooling the melt into a room temperature enclosure forms a lamellar structure, whereas cooling into a heated enclosure (225 °C) forms a conglomerate structure, while an enclosure temperature of 125 °C gave a partially conglomerate structure with some lamellae in process of forming conglomerates.Consideration of the thermal gradients imposed on solidification and consequently the relative time available during which the ions are sufficiently mobile to rearrange their positions, can explain the observation that lamellar structures are formed by higher melting point eutectics, whereas eutectics of lower melting point form conglomerate structures.     

Effect of iron and silicon on structure transformations and on microhardness of Al-30 wt. % Zn alloy aged at 90 °C

The structure transformations during the ageing at 90 C of Al-30 wt. % Zn alloys prepared from Al of 99.7, 99.99 and 99.999 wt. % were studied by X-ray diffraction and by transmission electron microscopy. Simultaneously, the measurement of Vicker's microhardness was carried out. It was found that Fe and Si impurities affect substantially the structure transformations and the microhardness values during the ageing process. These impurities retard the formation of lamellar aggregates of-phase and of impoverished-matrix and thus they slow down the softening of the alloy.In conclusion we would like to express our thanks to Doc. Dr. V.Syneek CSc. for his valuable discussions. We are also indebted to Mr. V.Petr and Mr. Z.iký for their help in the microhardness and X-ray diffraction measurements, and to Mr. P.Vyhlídka for the homogeneity check of the investigated samples.     

Perception of prosodic structure of Chinese sentence

TheprojectissupportedbyNationalNaturalScienceFoundationofChinaI.IntroductionProsodicstructureisusedbylinguistsindealingwiththeinteractionbetweenphonoIogyandsyntax,thetwocomponentsofgrammar.Itisalsoadoptedandinvestigatedbyresearchersinthefieldsofpsycholinguistics,speechperception,andspeechengineeringastheydealwiththeproductionandcomprehensionofspokenlanguagebyeitherhumanbeingsormachines.Psycholinguistsworkingonthemodelsofspeechproductionconsidersyntacticandprosodicstructuresasgeneratedbydiff…     

Ferromagnetism caused by severe plastic deformation of the Fe – 35% Al alloy

Results of investigations into the structure and temperature dependence of magnetization of the Fe – 35% Al alloy subjected to severe plastic deformation are presented. It is demonstrated that after plastic deformation, this alloy becomes ferromagnetic, though before deformation it was non-ferromagnetic. The temperature interval of the ferromagnetic order stability arising due to plastic deformation is established. The revealed effect is explained.     

Continuous-cooling α-to-γ transformation behaviour of Ti–45.5 at.% Al–0.05 at.% B alloy

The continuous-cooling transformation behaviour of Ti–45.5?at.%?Al–0.05?at.%?B alloy was quantitatively measured using a real-time resistivity–temperature–time measurement apparatus operating under a high vacuum. The addition of a small amount of B does not significantly alter the α–γ-phase equilibria but significantly raises the α–γ lamellar start temperature of Ti–45.5?at.%?Al alloy at most cooling rates. Furthermore, it markedly increases the critical cooling rate for the ordering reaction. The effect of B addition, which greatly stabilizes the lamellar structure up to a fast cooling rate, is to accelerate the lamellar formation kinetics; the lamellar spacing was nevertheless distinctively larger in a B-doped alloy. This is because lamellae in B-doped alloy nucleate heterogeneously on titanium borides at the grain boundary; the borides are effective nucleation sites particularly since local Ti depletion can occur near the interface of the growing titanium borides during cooling. In the absence of B addition, the lamellar structure starts to form only at temperatures below T ₀, suggesting that a large undercooling is required for the nucleation of lamellae even at the grain boundaries. On the other hand, the B addition greatly retards the kinetics of the α-to-α₂ ordering reaction by markedly increasing its critical cooling rate without a large change in the ordering temperature. This is believed to be due to its tendency to segregate strongly to the antiphase boundaries.     

TiO2–carbon nanotube composites for visible photocatalysts – Influence of TiO2 crystal structure

We investigated the influence of the crystal structure of TiO₂ and the use of different TiO₂ precursors on the properties and photocatalytic activity of carbon nanotube (CNTs)–titania composites. We found that the crystal structure and properties of starting TiO₂ nanomaterial significantly affected the effect of CNTs incorporation on the photocatalytic activity under simulated solar and visible light illumination (simulated solar illumination with UV-blocking filter). In case of significant photocatalytic activity under visible light illumination (anatase TiO₂), likely due to the presence of native defects, composites exhibited lower activity under visible illumination only, but higher activity under simulated solar illumination. The opposite trends were observed for P25 (anatase + rutile) and rutile TiO₂, where incorporation of CNTs resulted in a significant increase of photocatalytic activity under visible illumination. Thus, control over crystal structure and native defects is essential for the development of efficient visible light activated photocatalysts.     

The activation and the spreading of deformation in a fully lamellar Ti–47 at.% Al–1 at.% Cr–0.2 at.% Si Alloy

The spreading of deformation in a lamellar Ti–47?at.% Al–1?at.% Cr–0.2?at.% Si alloy deformed under compression is studied at 25°C and 600°C. This microstructure is largely dominated by twin-related variants which are separated by either twin interfaces or thin α ₂ slabs. The alloy deforms at both temperatures by ordinary dislocations and twins. Deformation in a particular γ variant and its adjacent twin-related variant involves the same kind of glide system, either ordinary dislocations or twins. This property is found to be true for all twin-related lamellae. The occurrence of this correlated glide is explained by the introduction of the notion of pilot and driven orientations. The lamellar orientation in which the operating glide system is activated on the basis of Schmid factor considerations is termed the pilot orientation. It imposes its deformation system on to the twin-related lamella, called the driven orientation, whose deformation may not involve the slip system most favoured by the applied stress.     

On the structure of Σ-hypernuclei

We investigate the-nucleus potential in the framework of a relativistic mean field approximation. As input for the elementaryN interaction we supplement the-repulsion by the exchange of an effective, complex-meson to account for theN N conversion. As the main result we find that the strength of ths absorptive central potential is smaller than the corresponding real part, whereas in the spin-orbit interaction, which is expected to be much weaker than for a nucleon, the imaginary component dominates.This work was partially supported by CNPq, FINEP (Brazil) and by the Bilateral Cooperation W. Germany — Brazil (KFA — CNPq).     

Efficient perturbation analysis of elastic network models – Application to acetylcholinesterase of T. californica

Elastic network models in their different flavors have become useful models for the dynamics and functions of biomolecular systems such as proteins and their complexes. Perturbation to the interactions occur due to randomized and fixated changes (in molecular evolution) or designed modifications of the protein structures (in bioengineering). These perturbations are modifications in the topology and the strength of the interactions modeled by the elastic network models. We discuss how a naive approach to compute properties for a large number of perturbed structures and interactions by repeated diagonalization can be replaced with an identity found in linear algebra. We argue about the computational complexity and discuss the advantages of the protocol. We apply the proposed algorithm to the acetylcholinesterase, a well-known enzyme in neurobiology, and show how one can gain insight into the “breathing dynamics” of a structural funnel necessary for the function of the protein. The computational speed-up was a 60-fold increase in this example.     

Luminescent properties and structure of multicomponent naphthalene-β-cyclodextrin complexes. 1. Effect of adding third parties, o-carborane or/and adamantane

Luminescence spectra of water solution of β-cyclodextrin (β-CD) inclusion complexes with naphthalene have been studied in the presence of carcass compounds (CC), adamantane and ocarborane, added in solution as the third parties. It was observed that the CC structure completely determines luminescence type displayed by the three-component complex. Adding adamantane to the solution leads to the disappearance of the spontaneous excimer fluorescence observed usually along with a monomer fluorescence of naphthalene and the appearance of the long lived phosphorescence at room temperature. At the same time, introducing o-carborane in solution of β-CD inclusion complexes with naphthalene results in the dramatic growth of intensity of the excimer band at the expense of lowering intensity of monomer fluorescence. These phenomena were explained using results of the quantum-chemical calculation of the structure and complexation energies at the semi-empirical PM3 and DFT levels of theory.     

Band structure and pressure-induced metallic transition in iodine – GW calculation

We have studied the band structure and the band gap closure in phase I of solid iodine under high pressure, using the methods based on the quasiparticle theory, i.e. GW approximation. Our calculations show that the band gap in the Cmca structure, which is the structure of the phase I of solid iodine, closes around 20 GPa. This pressure is near the upper boundary of phase I. We discuss the possible metallic transition in the molecular phase of solid iodine and the possible changes of the crystal structure.