Damage evolution in an expanding/contracting hollow sphere at large strains

A generalization of one of the classical problems of plasticity theory, expansion/contraction of a hollow sphere, is proposed assuming that the conventional constitutive equations for rigid plastic, hardening material are supplemented with an arbitrary ductile damage evolution law. No restriction is imposed on the hardening law in the analytic part of the solution. The initial/boundary value problem is reduced to two equations in characteristic coordinates. A numerical scheme to solve these equations is proposed. An illustrative example is given.     

Covariant Lagrange multiplier constrained higher derivative gravity with scalar projectors

We formulate higher derivative gravity with Lagrange multiplier constraint and scalar projectors. Its gauge-fixed formulation as well as vector fields formulation is developed and corresponding spontaneous Lorentz symmetry breaking is investigated. We show that the only propagating mode is higher derivative graviton while scalar and vector modes do not propagate. Despite to higher derivatives structure of the action, its first FRW equation is the first order differential equation which admits the inflationary universe solution.     

Quality control of coatings with the help of local electrochemical analysis

Local electrochemical analysis with a pressed-on electrochemical cell is suggested for the estimation of the quality of coatings protecting the surface of materials, for the detection of different defects and for the control of the thickness and composition of coatings. The suggested local electrochemical analysis allows the determination of the throwing power of the electrolytes used in electrodepositions. Received: 8 December 1997 / Accepted: 21 August 1998     

Prolonged plasma clot lysis induced by acyl-derivatives of urokinase in vitro

Two acyl-derivatives of urokinase, p-trimethylam inocinnamoyl-urokinase (TMAC-Uk) and p-guanidinobenzoyl-urokinase (GB-Uk), reactivating with different rates (k _reac were 6×10^?4/s and 6×10^?5/s, respectively) were prepared. In comparison with free urokinase, acyl-activators were more stable in human plasma, and their stability increased with the decrease in the reactivation rate. Plasma clotlysis induced by all three agents was time- and dose-dependent, but acyl-activators caused a more prolonged fibrinolysis and lengthened lag-phase than free urokinase. Slowly reactivating GB-Uk induced the most long-lasting clotlysis, whereas free urokinase was more effective for the first 3 h. A combination of GB-Uk with low dose urokinase promoted the long-lasting clotlysis with the shortened lag-phase.     

A Passive Q-Switched Microchip Er/Yb Glass Laser Pumped by Laser Diode

A laser-diode-pumped 1.54-μm passive Q-switched erbium doped glass laser was reported. We utilize a laser diode with wavelength of 973nm to pump a 1-mm Er/Yb co-doped phosphate glass with the erbium and ytterbium concentrations of 1 wt.% and 21 wt.%, respectively. A Co^2＋ ：MgAl2O4 slab crystal was used as a passive Q- switcher. Q-switched pulses with repetition frequency of 800Hz, width of 7.4ns, peak power of 2.2kW and average power of 13.3 m W were obtained when absorbed pump power was 4 75 m W. A sandwich structure of the Q- switched microchip Er/Yb glass laser was demonstrated, which shows shorter pulse width of 6.8 ns. Dependences of pulse duration and repetition frequency on pump power were also investigated.     

Kinetics of the nematic ordered phase growth during a temperature quench of an isotropic siloxane-azomethine polymer

Kinetics of the nucleus growth during a deep temperature quench across the isotropic to nematic phase transition was experimentally investigated for a siloxane-azomethine polyether at cooling rates of 10 and 20°C min^-1. Nematic droplets revealed in the optical images during the phase separation were treated statistically and the resulting statistical size distributions were described using the model of reversible aggregation. Analysis of the time-dependent distribution parameters allowed two processes involved in liquid crystal phase ordering to be identified: nucleus growth and nucleus coarsening. Both regimes are quantitatively described using the universal growth law.     

1,5-Di­amino-1H-1,2,3,4-tetrazole

In the title compound, CH₄N₆, the tetrazole ring is planar to within 0.001 (1) Å. The 5-amino group is conjugated with the π-system of the tetrazole ring. In contrast, the N atom of the 1-­amino group is sp³ hybridized and is not conjugated with the π system of the tetrazole ring. All H atoms are localized at the exocyclic N atoms. The mol­ecules are connected by N—H⃛N hydrogen bonds, forming an infinite three-dimensional framework.     

Resonance scattering on In impurity in Pb0.4Sn0.6Te solid solutions

The Hall coefficient and resistivity were measured on a series of samples of InTe in Pb_0.4Sn_0.6Te solid solutions with varying indium content from 0 to 5 molar%. All samples show a p-type conductivity with the concentration of holes 10¹⁹ cm⁻³ at 77 K. A considerable decrease of mobility calculated from the measurements was observed in the samples with high content of In. The contribution to the mobility, directly related to the scattering of holes into In atoms, was determined, and the scattering crosssection was estimated. We observed a drastic increase in the scattering crosssection with the rise of In content, which can be explained by the resonance scattering of holes into the band of quasi-local states of In. This result can also be explained with the use of the Breit–Wigner formula. The location of the In states in the valence band was also calculated using the Kane model.