Fundamentals of interface phenomena in advanced bulk nanoscale materials

The review is devoted to a study of interface phenomena influencing advanced properties of nanoscale materials processed by means of severe plastic deformation, high-energy ball milling and their combinations. Interface phenomena include processes of interface defect structure relaxation from a highly nonequilibrium state to an equilibrium condition, grain boundary phase transformations and enhanced grain boundary and triple junction diffusivity. On the basis of an experimental investigation, a theoretical description of the key interfacial phenomena controlling the functional properties of advanced bulk nanoscale materials has been conducted. An interface defect structure investigation has been performed by TEM, high-resolution x-ray diffraction, atomic simulation and modeling. The problem of a transition from highly non-equilibrium state to an equilibrium one, which seems to be responsible for low thermostability of nanoscale materials, was studied. Also enhanced grain boundary diffusivity is addressed. Structure recovery and dislocation emission from grain boundaries in nanocrystalline materials have been investigated by analytical methods and modeling

Rate and duration of hospitalisation for acute pulmonary embolism in the real-world clinical practice of different countries : Analysis from the RIETE registry

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Evaluation of crystal nucleation and growth from kinetics and viscosity data of new halide glasses

The understanding of glass devitrification and melt crystallization has received considerable interest from the point of view of controlling the total number of scattering centres in drawn fibers and glass preforms. In recent investigations [1] on bulk glass thermal properties we have evaluated the stability and the devitrification kinetic parameters, by means of differential scanning calorimetry (DSC). The results obtained by the use of isothermal techniques are in good agreement with those obtained by continuous heating procedures. The thermal characteristics indicate that the glasses have a good combination of casting and devitrification properties and are expected to be suitable for high quality glass preform and fibre fabrication. The aim of this work is the calculation of the viscosity of the glass-forming melts and its dependence on temperature, by using an appropriate model; and also the use of the kinetics data to construct the temperature-heating rate-transformation curves (T-HR-T), which will account for the heating cycle of a glass preform in a fibre drawing furnace. The classical theory of crystal nucleation and simultaneous three dimensional crystal growth models have been used in the Johnson-Mehl-Avrami-Erofe'ev equation for transformation kinetics to calculate the time-temperature-transformation curves. The significance of the stability parameters is interpreted in the context of the nucleation, crystal growth and transformation kinetics. We also report on the comparison of measured crystal growth rate in one of the types of cadmium mixed halide glasses (CdF2-BaF2-NaCl) with the theoretically predicted value. Work partially supported by RACE: R-2038 and CICYT:MAT92-0501

International symposium on mechanically alloyed, metastable and nanocrystalline materials

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

A dimer of bis(N-heterocyclic carbene)-rhodium(I) centres spanned by a dibenzo-18-crown-6 bridge from synchrotron radiation

The compound (μ-3,3′,3′′,3′′′-{[2,5,8,15,18,21-hexaoxatricyclo[20.4.0.09,14]hexacosa-1(22),9,11,13,23,25-hexaene-11,12,24,25-tetrayl]tetrakis(methylene)}tetrakis(1-methyl-1H-imidazol-2-yl))bis[(η4-cycloocta-1,4-diene)rhodium(I)] bis(hexafluoridophosphate) acetonitrile sesquisolvate dihydrate, [Rh2(C8H12)2(C40H42N8O6)](PF6)2·1.5CH3CN·2H2O, crystallized from acetonitrile under an atmosphere of diethyl ether. In the crystal structure, the complex cation exhibits two square-planar RhI centres, each bound by a cyclooctadiene (COD) ligand and by two adjacent imidazolylidene N-heterocyclic carbene (NHC) donors from the same phenoxy ring of the {[dibenzo-18-crown-6-11,12,24,25-tetrayl]tetrakis(methylene)}tetrakis(1-methyl-1H-imidazol-2-yl) (L) ligand. The dibenzo-crown ether bridge of L spans the Rh centres and forms hydrogen bonds with water molecules. One water molecule with half occupancy bridges adjacent macrocycles in the lattice. Another water with full occupancy forms weak hydrogen bonds to the crown ether O atoms and is, in turn, part hydrogen bonded by a lattice water with half occupancy. The latter water is within hydrogen-bonding distance of a fourth water also with partial occupancy. The result of these interactions is the formation of a layer in the ab plane. Two PF6− ions, one of which is twofold disordered, and one ordered and one twofold disordered (with 0.5 occupancy) lattice acetonitrile molecules complete the crystal structure

Calorimetric measurements of grain growth in ultrafine-grained nickel

The process of grain growth in ultrafine-grained nickel was studied using differential scanning calorimetry. Samples of nickel, with mean grain sizes in the range from 100 to 400 nm, were prepared by equal-channel angular pressing, high pressure torsion or combinations of both. It is shown using differential scanning calorimetry that grain growth in these structures begins at temperatures in the range from 500 to 700K and the measured activation energy for grain growth is close to the activation energy for grain boundary self-diffusion. There was also evidence for a decreasing activation energy in the samples prepared by high pressure torsion

Calorimetric and X-ray measurements in ultrafine-grained nickel

The procedures of X-ray diffractometry and peak profile analysis, together with differential scanning calorimetry (DSC), were used to measure the grain size, dislocation density and corresponding elastic energy stored in ultrafine-grained (UFG) nickel processed by different methods: equal channel angular pressing, high pressure torsion and their combinations. It has been shown that grain growth in these samples begins at temperatures in the range from 500 to 700 K and the measured activation energy for grain growth is close to the activation energy for grain boundary self-diffusion. A difference between the released enthalpy in DSC experiments and the elastic energy evaluated by x-ray diffractometry is attributed to the decrease in surface energy during grain growth in UFG nickel. The grain boundary (GB) surface energy of high angle boundaries was also evaluated

Platelet Count and Major Bleeding in Patients Receiving Vitamin K Antagonists for Acute Venous Thromboembolism, Findings From Real World Clinical Practice.

The outcome of patients with acute venous thromboembolism (VTE) and abnormal platelet count (PlC) at baseline has not been consistently studied. In real-world clinical practice, a number of patients with abnormal PlC receive vitamin K antagonists (VKAs) to treat acute VTE despite their higher risk of bleeding.We used the Registro Informatizado de Enfermedad TromboEmbólica registry database to compare the rate of major bleeding in patients receiving VKA for long-term therapy of acute VTE according to PlC levels at baseline. Patients were categorized as having very low (<100,000/μL), low (100,000-150,000/μL), normal (150,000-300,000/μL), high (300,000-450,000/μL), or very high (>450,000/μL) PlC at baseline.Of 55,369 patients recruited as of January 2015, 37,000 (67%) received long-term therapy with VKA. Of these, 611 patients (1.6%) had very low PlC, 4006 (10.8%) had low PlC, 25,598 (69%) had normal PlC, 5801 (15.6%) had high PlC, and 984 (2.6%) had very high PlC at baseline. During the course of VKA therapy (mean, 192 days), there were no differences in the duration or intensity (as measured by international normalized ratio levels) of treatment between subgroups. The rate of major bleeding was 3.6%, 2.1%, 1.9%, 2.1%, and 3.7%, respectively, and the rate of fatal bleeding was 0.98%, 0.17%, 0.29%, 0.34%, and 0.50%, respectively. Patients with very low or very high PlC levels were more likely to have severe comorbidities.We found a nonlinear "U-shaped" relationship between PlC at baseline and major bleeding during therapy with VKA for VTE. Consistent alteration of PlC values at baseline suggested a greater frailty