Elastic interaction between two parallel dislocations in non-parallel slip planes

The elastic interaction between two parallel dislocations which can glide in non-parallel slip planes is studied under the simplifying assumption that the dislocation glide velocity is proportional to stress. The motion of the two dislocations is represented by a motion of one reference point in a configuration plane. It is concluded that the contribution of the long-range elastic interaction between individual dislocations from different slip systems to work hardening is negligible, compared to the contribution from the formed attractive junctions. Especially, two parallel edge dislocations with mutually perpendicular Burgers vectors can co-exist in minimum energy positions, however, they can be separated by an arbitrarily small external stress.     

The ordering of crystallographic shear planes: Theory of regular arrays

In certain non-stoichiometric transition metal oxides, crystallographic shear planes are found instead of isolated oxygen vacancies. These planes tend to form arrays with regular spacings. The interactions responsible for this ordering have not been understood in the past. We propose that the major interaction comes from elastic strain, with smaller electrostatic terms: the configuration of the planes is one which minimises the elastic strain energy. Quantitative results are given for a realistic model, and agree with the main features observed experimentally. Thus the regular array of planes is stable, and the equilibrium separation of planes in the array is about half that predicted for an isolated pair of planes. The interaction between isolated planes proves an oscillatory function of their separation. One can understand from its detailed form why the observed mean spacing gets smaller as the planes come together to form larger groups.     

Field electron emission changes by face specific adsorption of aluminum oxide and corresponding decomposition products on tungsten {110} and {100} planes

After deposition of aluminum oxide on a tungsten field emission microscope (FEM) tip and stepwise heating, three stages of emission changes were observed on {100}. Stages I and II cause work function decreases of 0.28 and 0.07 eV, respectively. Stage III is characterized by a large increase (Δ??+3 eV). The changes are discussed in terms of interaction of decomposition products (oxygen and aluminum) and adsorption of aluminum oxide. On {110} only a single aluminum oxide layer growth, which results in a work function decrease to ?=4.69 eV, is observed. The field electron emission from this layer was measured between 1400°K and room temperature. The experimental values were compared with those determined from Christov's unified theory of field and thermionic emission. The {110} layer values coincide with those obtained earlier from an aluminum oxide covered tungsten {112}.     

The co-adsorption of copper and oxygen on a tungsten {100} surface

The co-adsorption of Cu on O₂ and a W{100}surface is studied by Auger electron spectroscopy (AES), thermal desorption (TD), low energy electron diffraction (LEED) and by work function change (δø) measurements. It is shown that the presence of Cu on the surface initially decreases s_O, the sticking coefficient of O₂. For longer oxygen exposures and for higher adsorption temperatures, θ_O reaches values larger than those on the clean surface for the same O₂ exposure. Except at the highest θ_O values and temperatures, the sticcking coefficient for copper, s_Cu, is unity and is independent of the oxygen coverage θ_O in the range studied (0 ? θ_O ? 2). Co-adsorption at room temperatures does not produce any long range order while co-adsorption at elevated temperature leads to the ordered structures (1 × 1), p(2 × 1), p(2 × 2) and c(2 × 2). The saturation coverage of the two dimensional co-adsorbate at 800 K is given by the relation $\text{θ}{}_{\mathrm{Cu}}\text{+}\text{8}\text{5}\text{θ}{}_{\mathrm{O}}\text{= 2}$. The work function is a complicated function of θ_O and θ_Cu and is determined predominantly by the temperature at which oxygen is adsorbed. At high temperatures the sequence of adsorption has no influence, in contrast to the room temperature behavior.     

Statistical treatment of crystallographic shear planes in WO3−x

From the analysis of recent thermodynamic data, we show that whereas oxygen vacancies are present in the whole homogeneity range of WO_3?x, crystallographic shear planes are present only for large departures from stoichiometry (x > 0.012).     

Energy dependence of {\bar{K}N} interaction in nuclear medium

When the $\bar{K}N$ system is submerged in nuclear medium the $\bar{K}N$ scattering amplitude and the final state branching ratios exhibit a strong energy dependence when going to energies below the $\bar{K}N$ threshold. A sharp increase of $\bar{K}N$ attraction below the $\bar{K}N$ threshold provides a link between shallow $\bar{K}$ -nuclear potentials based on the chiral $\bar{K}N$ amplitude evaluated at threshold and the deep phenomenological optical potentials obtained in fits to kaonic atoms data. We show the energy dependence of the in-medium K ^??? p amplitude and demonstrate the impact of energy dependent branching ratios on the Λ-hypernuclear production rates.     

Splitting of dislocations in b.c.c. metals on {110} planes

Three possible splittings of a screw dislocation on {110} planes of a metal with a b.c.c. lattice are proposed, their total elastic energy is calculated and the dependence of the splitting width on the stacking fault energy is studied.We wish to express our thanks to B. esták, CSc., and S. Libovický for valuable comments and M. Jiincová for her help in carrying out the numerical calculations.     

Self-Consistent Calculations of Probabilities for Transitions between $${3}_{1}^{{-}}$$ and $${2}_{1}^{{+}}$$ One-Phonon States in Tin Isotopes

Physics of Atomic Nuclei - For the first time, a self-consistent method for studying second-order anharmonic effects within quantum many-body theory is applied to calculating probabilities for...     

Mutually Unbiasedness between Maximally Entangled Bases and Unextendible Maximally Entangled Systems in $\mathbb {C}^{2}\otimes \mathbb {C}^{2^{k}}$

The mutually unbiasedness between a maximally entangled basis (MEB) and an unextendible maximally entangled system (UMES) in the bipartite system \(\mathbb {C}^{2}\otimes \mathbb {C}^{2^{k}} (k>1)\) are introduced and discussed first in this paper. Then two mutually unbiased pairs of a maximally entangled basis and an unextendible maximally entangled system are constructed; lastly, explicit constructions are obtained for mutually unbiased MEB and UMES in \(\mathbb {C}^{2}\otimes \mathbb {C}^{4}\) and \(\mathbb {C}^{2}\otimes \mathbb {C}^{8}\), respectively.     

The \pi h_{11/2}^{-1}\nu i_{13/2}^{-2} three-hole isomeric state and octupole core excitation in the 205 Tl nucleus

New high-spin states were identified in the ²⁰⁵Tl isotope produced in deep-inelastic heavy-ion reactions. The expected 29/2 ⁺ yrast state and 35/2^- isomeric state with 235 ns half-life were located above the 2.6 s isomer known from previous studies. Above this isomer a 7092 keV level was interpreted as a 41/2 ⁺ state arising from the coupling of the octupole vibration of the ²⁰⁸Pb core with the three-hole structure of the 35/2^- isomer.Received: 20 January 2003, Revised: 10 March 2003, Published online: 2 March 2004PACS: 21.60.Cs Shell model - 23.20.Lv Gamma transitions and level energies - 27.80. + w - 25.70.Lm Strongly damped collisions     

The Dynamics of Relativistic Strings Moving in the Minkowski Space $$\mathbb{R}^{1+n}$$

In this paper we investigate the dynamics of relativistic (in particular, closed) strings moving in the Minkowski space . We first derive a system with n nonlinear wave equations of Born-Infeld type which governs the motion of the string. This system can also be used to describe the extremal surfaces in . We then show that this system enjoys some interesting geometric properties. Based on this, we give a sufficient and necessary condition for the global existence of extremal surfaces without space-like point in with given initial data. This result corresponds to the global propagation of nonlinear waves for the system describing the motion of the string in . We also present an explicit exact representation of the general solution for such a system. Moreover, a great deal of numerical analyses are investigated, and the numerical results show that, in phase space, various topological singularities develop in finite time in the motion of the string. Finally, some important discussions related to the theory of extremal surfaces of mixed type in are given.     

Method of determing the energy of antiphase boundaries in {h0l} planes in a superstructure with an arbitrary primitive cell

An expression obtained previously by the authors for the energy of formation of an antiphase shear boundary for the {001} orientation is generalized to the case of the {h0l } orientation. The given problem is solved by examining primitive cells of an intermetallide crystal in which one face is parallel to the plane of the antiphase boundary. The energy of the defect is given in the form of an analytical expression that can be used for any ordered alloy with an arbitrary primitive cell without restrictions on the number of coordination spheres in the atomic interactions. An example is presented and the results are compared with known data.Altai Polytechnic Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 73–77, May, 1992.