Abstract: We show that a superconducting quantum nanowire undergoes a new type of BCS-BEC crossover each time when an electron subband approaches the Fermi surface. In this case the longitudinal Cooper-pair size drops by two-three orders of magnitude down to a few nanometers. This unconventional BCS-BEC crossover is driven by quantum-size effects rather than by tuning the fermion-fermion interaction.

Abstract: There is a type of filament that forms dosed contours encircling regions of one polarity of magnetic field, while the surrounding region has the opposite polarity One distribution of ring-filaments has sizes 2R = 40,000 to 160,000 km with the maximum around 100,000 km; the other distribution (with filaments and filament channels) has bigger sizes, with a maximum around 300,000 km. At low and mid latitudes the radial component B-rs (radial for the Sun) in the region outlined by filaments varies from 50 to 100 gauss, while the longitudinal component B-phi varies from 10 to 30 gauss. The total current inside the filament is 10(10) – 10(11) A, the ratio R/a approximate to 5 to 10, the magnetic flux crossing the surface is approximate to 10(21) – 10(22) MX; th, magnetic energy is approximate to 10(29) – 10(31) erg. Polar ring-filaments at latitudes 60 degrees-80 degrees are related to the polar magnetic field reversal and the quasi-flare processes at the poles during the field reversal. Correlation between B-rs and B-phi for the polar filament bands cannot be satisfactorily explained. A theoretical model using the conservation laws is used to study the relations between the various fields, currents, etc, of shrinking polar ring-filaments and their evolution. According to this theory ring-filaments should rise higher above the photosphere when shrinking. However, observations show that the height lowers. Presumably the discrepancy is due to the lack of dissipation in the model.

Abstract: We present a Ginzburg-Landau theory for a two-band superconductor with emphasis on MgB2. We propose experiments which lead to identification of the possible scenarios: whether both sigma- and pi-bands superconduct or sigma-alone. According to the second scenario a microscopic theory of superconducting MgB2 is proposed based on the strongly interacting or-electrons and non-correlated pi-electrons of boron ions. The kinematic and Coulomb interactions of sigma-electrons provide the superconducting state with an anisotropic gap of s(*)-wave symmetry. The critical temperature T-c has a non-monotonic dependence on the distance r between the centers of gravity of sigma- and pi-bands. The position of MgB2 on a bell-shaped curve T-c (r) is identified in the overdoped region. The derived superconducting density of electronic states is in agreement with available experimental and theoretical data. It is argued that the effects of pressure are crucial to identify the microscopic origin of superconductivity in MgB2. Possibilities for increase of T, are discussed.

Abstract: Not much about the effect of thiocyanate addition on the sulphur ripening is known, although it is used for many applications in photographic practice. Via a combination of tracer analysis and diffuse reflectance spectroscopy the effect of thiocyanate addition on the sulphur and sulphur-plus-gold ripening could be unveiled. When thiocyanate is added prior to the sulphur addition, it appears to rearrange the silver halide surface in such way that the sulphur deposition rate is enhanced, but the supply of interstitials is limited. Addition of thiocyanate after the sulphur reaction results in the formation of thiocyanate complexes with silver, from which a silver ion is more easily deposited in a surface cell of the silver sulphide clusters thus enhancing the sensitization rate. For sulphur-plus-gold sensitized emulsions it was observed that part of the gold ions could be removed out of the Ag2-xAuxS clusters by addition of thiocyanate ions and subsequent washing. Hence, it was concluded that two different types of gold ions are present in the silver sulphide clusters; 1. gold ions which are substitutional for silver (bound between sulphur and bromide ions) 2. gold ions which bridge two or three sulphur atoms. Incorporation of gold ions into silver sulphide clusters suppresses their optical absorption in diffuse reflectance spectroscopy. Since the optical absorption at 505 nm can completely be restored by addition of thiocyanate, it is assumed that the entity absorbing at this wavelength is a monomer of silver sulphide.

Abstract: Multishell tabular grains have a higher speed than pure AgBr tabular grains. Usually the shells differ in size and iodide content, but also the precipitation method for the iodide containing shells has an influence on the iodide incorporation. A TEM investigation was performed to determine the defect structure of multishell AgBr (111) tabular crystals containing a shell with a low iodide concentration and one with a high iodide concentration. The twins that induce tabular growth and stacking fault contrast in the region of the iodide shells have been observed, similar to previously studied AgBr/Ag(Br,I) coreshell crystals. Moreover in some of the crystals dislocations have been observed, sometimes even an entire network. The number of dislocations formed varies for the different methods of iodide addition. Also variations in average thickness between the different iodide addition methods have been observed. A higher number of dislocations and thicker crystals point towards a higher local concentration of iodide. These observations allow deciding which iodide incorporation method is most useful for a preferred dislocation pattern.

Abstract: Strain fields introduced by coherent Ni4Ti3 precipitates in austenitic Ni-Ti are believed to be a possible origin of why the R-phase transformation is introduced as an extra step before transforming to the B19'. The presence of this strain field was already confirmed in the past by conventional transmission electron microscopy (TEM) techniques and measured quantitatively by high resolution TEM (HRTEM). This time the geometrical phase method is applied on HRTEM micrographs to measure the full 3D strain tensor of the strain fields. Since each atomic resolution micrograph only results in a 2D measurement of the strain, observations in two different zone orientations are combined to retrieve the 3 x 3 strain tensor. In this work observations in a [1-1 1](B2) and [1 0-1](B2) zone orientation are used and this in case of precipitates with a diameter of around 50nm. In a next step the measured strain tensor is compared to the calculated eigenstrain of the R-phase in reference to the B2 matrix. This comparison shows that the introduced strain is very similar to the eigenstrain of one R-phase variant. Since for both structures, Ni4Ti3 and R-phase, four orientation variants are possible, each variant of the R-phase is thus able to accommodate the strain field of one of the Ni4Ti3 variants.

Abstract: A single crystal of Cu74.08Al23.13Be2.79 undergoes a martensitic phase transition at 246K and 232K under heating and cooling, respectively. Surprisingly, the martensite phase is elastically much harder than the austenite phase showing that interfaces between various crystallographic variants are strongly pinned and can not be moved by external stress while the phase boundary between the austenite and martensite regions in the sample remains mobile. This unusual behavior was revealed by Dynamical Mechanical Analysis and Resonant Ultrasound Spectroscopy. Transmission Electron Microscopy shows that the pinning is generated by dislocations, which are inherited from the austenite phase. Such dislocations can hinder the movement of stacking faults in the 18R martensite structure or twin boundaries between martensite variants.