Reluctance of the YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>x</Subscript> oxygen-deficient ceramics

Influence of an external magnetic field on the reluctance of the YBa ₂ Cu ₃ O _x ceramics is investigated. A significant reluctance of the oxygen-deficient ceramics (with critical temperature T_c < 77 K) is established for a sample in the normal state at T < 160 K. It is demonstrated that after ceramics annealing that restores the oxygen content to a nearly optimum value, the magnetic field has essentially no effect on the sample reluctance at temperatures exceeding T_c. To explain the revealed mechanisms, a model involving ferromagnetic clusters effectively decreasing the free carrier density is used. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 68–71, April, 2007.     

Dimethylmalonoyl peroxide – the neglected lowest homologue: simple synthesis and high reactivity

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Self-oscillations of two bodies in the case of nonlinear friction

The motion of two bodies is studied. One of them is attached to a fixed base by a spring, whereas the other one is attached to a body moving at a constant velocity. The interaction of the bodies is described by a nonlinear friction law with a falling section of the characteristic. The averaged equations of motion are obtained in terms of the canonical action-angle variables. The stationary points corresponding to self-oscillation modes are found and their stability is studied.     

Measuring optical characteristics of the atmosphere with a laser heterodyne system

A laser heterodyne system for measuring optical characteristics of a turbulent atmosphere is described. Continuous readout data on the fluctuations in the phase of the radiation propagating in a channel in the atmosphere are presented. These data can be used to determine the major parameters of the turbulent state. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 906–908, November–December, 2008.