Attractive Vortex Interaction and the Intermediate-Mixed State of?Superconductors

The magnetic vortices in superconductors usually repel each other. Several cases are discussed when the vortex interaction has an attractive tail, and thus a minimum, leading to vortex clusters and chains. Decoration pictures then typically look like in the intermediate state of type-I superconductors, showing lamellae or islands of Meissner state or surrounded by Meissner state, but with the normal regions filled with Abrikosov vortices that are typical for type-II superconductors in the mixed state. Such intermediate-mixed state was observed and investigated in detail in pure Nb, TaN and other materials 40 years ago; last year it was possibly also observed in MgB₂, where it was called ??a totally new state?? and ascribed to the existence of two superconducting electron bands, one of type-I and one of type-II. The complicated electronic structure of MgB₂ and its consequences for superconductivity and vortices are discussed. It is shown that for the real superconductor MgB₂ which possesses a single transition temperature, the assumption of two independent order parameters with separate penetration depths and separate coherence lengths is unphysical.     

Density of Ni-Cr Alloy in the Mushy State

The density of Ni-Cr alloy in the mushy state has been measured using the modified sessile drop method. The density of Ni-Cr alloy in the mushy state was found to decrease with increasing temperature and Cr concentration in alloy. The molar volume of Ni-Cr alloy in the mushy state therefore increases with increasing the Cr concentration in alloy.The ratio of the difference of density divided by the temperature difference between liquidus and solidus temperatures decreases with increasing Cr concentration. The density of the alloy increased with the precipitation of a solid phase in alloy during the solidification process. The temperature dependence of the density of alloy in the mushy state was not linear but biquadratic.     

Pseudogap Ground State and Its Doping Evolution in Bi2Sr2?x La x CuO6+δ : Removing the Superconducting State by the Application of Very High Magnetic Fields

We present results for the pseudogap ground state and its doping evolution in single-layered copper-oxide Bi₂Sr_2?x La _x CuO_6+?? . We apply very high magnetic fields up to 44 T to remove the superconducting state and reveal the hidden low temperature (T) normal state. Through ⁶³Cu-NMR Knight shift and spin-lattice relaxation rate measurements, we find that there remains a finite density of states (DOS) at the Fermi level in the zero-T limit when the superconductivity is removed, which indicates that the pseudogap ground state is a metallic state with a finite volume of Fermi surface. The residual DOS in the pseudogap ground state decreases with decreasing doping (increasing x), but remains quite large even at the vicinity of the magnetically ordered phase of x?? 0.8. The result indicates that the superconductivity emerges from the remaining Fermi surface and coexists with the pseudogap.     

About the Features of Transient to Steady State Deformation of Solids

The features of transient to steady state deformation of solids are theoretically investigated.Modeling of various types of loading was carried out by the Movable Cellular Automata method.A stress state of material at the stage of transient to a steady state is shown to be essentially non-uniform, that may in its turn result in stable structures in velocity field of particles of the material. It may also influence development of deformation at the further stages.     

Modeling of the Temperature State of Large‐Size Space Structures

A procedure of modeling of the temperature state of largesize space structures is considered. Results of modeling of the temperature state of a truss structure, the reflector of a reflectortype aerial, and the concentrator of a solar power unit are reported.     

The Influence of the Interface on the Magnetic State in Two-Layer Films of the Fe–Bi System

Technical Physics Letters - Results of the experimental investigation of two-layer films in the Fe–Bi system are presented. It is found that the order of sequential deposition of the magnetic...     

Formation of Superhard State of the TiZrHfNbTaYN Vacuum–Arc High-Entropy Coating

Complex studies of the formation of the superhard state in the TiZrHfNbTaYN vacuum-arc high-entropy coating were carried out. Based on the approach of the structural surface engineering, the regularities of the formation of the triads composition–structure–physico-mechanical properties depending on the supplied potential displacement are established. It is shown that the increase of U _b at the formation of a coating leads to a decrease of the relative content of a light (Ti) and increase of a heavy (Ta, Hf) metal components, which is determined by radiationally stimulated processes in a near-surface region at the deposition. The formation of the single-phase state (based on the fcc of metal lattice) in the range U _b from–50 to–250 V and revealed the formation of the preferred orientation of the crystallites with the axis [111], which is perpendicular to the growth plane. The increase of the perfection of the texture with the [111] axis with increasing U _b is accompanied with an increase of the coatings hardness, which makes it possible to achieve the superhard state (H = 40.2 GPa) at U _b =–250 V.     

Biaxiality Dependence of the Fracture Toughness for Glass in Plane Stress State

The fracture behaviour of glass in biaxial stress state has been investigated. Fracture toughness of disk specimen with a straight-through crack was measured under biaxial tension and uniaxial tension loads respectively. The difference between them and the reasons for the difference are discussed. The influence of the stress parallel to crack on fracture of brittle material was demonstrated in theory and experiments. The results show that plane stress fracture toughness of glass is not a material constant. and that the fracture toughness measured in biaxial tension state is higher than that measured under uniaxial tension. The conventional fracture criterion upon the stress intensity factor is questioned in the case of biaxial stress problem, and the strain dependence of crack growth is discussed.     

63,65Cu NQR Evidence for Low-Temperature Charge Ordering in the Superconducting State of YBa2Cu3O7?δ

Measurements of the nuclear quadrupole resonance (NQR) transverse relaxation rate and of the NQR spectral linewidths of ^63,65Cu in the superconducting state of YBa₂Cu₃O_7– reveal unusual features below T = 35 K. A narrow peak in the transverse relaxation rate and an increased quadrupolar line broadening with decreasing temperature are attributed to a charge density wave (CDW) ordered state below T = 35 K.     

Widening the Scope of Working of Solid‐State Nd‐Glass Lasers

With the example of the serial model of a pulsed Ndglass laser, it is shown that the use of an unstable resonator with a semireflecting homogeneous exit mirror makes it possible to significantly decrease the laserbeam divergence and increase the uniformity of the radiationintensity distribution in the near zone. We were the first to obtain a laserbeam quality of (40–50) mm·mrad for technological glass lasers and to attain a depth of fusing of of 6.3 mm for steel (aspect ratio 10) for an energy of 23 J. The obtained uniformity of the radiationintensity distribution was estimated at the level of ±10%. The beamquality level attained for the Ndglass laser beam allows us to recommend it for both realization of deepfusion regimes and laser hardening without the use of external integrating optical elements.     

Critical Aspects of the Danish Welfare State — as Revealed by Issue Tracking

The paper examines the applicability of informetric methods to trace the pattern of debate about the three main critical issues of the modern Welfare State in Denmark: economic aspects, legitimacy and functionality. The methodology of issue tracking is used to follow the developments of these issues in periods through national databases of various types covering information about the research, implementation, press and legislation aspects. The approach taken is novel in that it implements and tests issue tracking in this area of social sciences, and tries to reduce subjectivity in the analysis of trends influencing social policy and public opinion. The study aims to show how the emerging data and text mining techniques can be applied to integrate downloaded bibliographic data with other types of information in a strategic mix.     

Soliton-Like Spin State in the A-Like Phase of 3He in Anisotropic Aerogel

We have found a new stable spin state in the A-like phase of superfluid ³He confined to intrinsically anisotropic aerogel. The state can be formed by radiofrequency excitation applied while cooling through the superfluid transition temperature and its NMR properties are different from the standard A-like phase obtained in the limit of very small excitation. It is possible that this new state is formed by textural domain walls pinned by aerogel.      

Computational Modeling of the Optical Pumping of Solid‐State Lasers and the Heating of the Active Element with Allowance for Water Cooling

Twodimensional nonstationary models of optical pumping of a solidstate laser in the presence of a reflector and heating of a cylindrical or plane active element with water cooling have been described. The results of calculations of the spacetime dependence of the pumping rate and the temperature in the active element have been given for different versions of a neodymium laser with a crystalline active medium in laserdiode pumping.     

Is the water rising?

When a quantity is changing slowly it is difficult to know whetherit will continue to monotonically increase. This situation mayraise questions as to when there is a problem and what shouldbe done. Is the average level of the world's oceans rising?There is some evidence to support this contention. Is this situationa matter of concern that requires action, and what should thataction be? These are vexing questions. Ionising radiation certainly     

Is the Universe homogeneous?

The standard model of cosmology is based on the existence of homogeneous surfaces as the background arena for structure formation. Homogeneity underpins both general relativistic and modified gravity models and is central to the way in which we interpret observations of the cosmic microwave background (CMB) and the galaxy distribution. However, homogeneity cannot be directly observed in the galaxy distribution or CMB, even with perfect observations, since we observe on the past light cone and not on spatial surfaces. We can directly observe and test for isotropy, but to link this to homogeneity we need to assume the Copernican principle (CP). First, we discuss the link between isotropic observations on the past light cone and isotropic space-time geometry: what observations do we need to be isotropic in order to deduce space-time isotropy? Second, we discuss what we can say with the Copernican assumption. The most powerful result is based on the CMB: the vanishing of the dipole, quadrupole and octupole of the CMB is sufficient to impose homogeneity. Real observations lead to near-isotropy on large scales--does this lead to near-homogeneity? There are important partial results, and we discuss why this remains a difficult open question. Thus, we are currently unable to prove homogeneity of the Universe on large scales, even with the CP. However, we can use observations of the cosmic microwave background, galaxies and clusters to test homogeneity itself.