Numerical analysis of crack development in structurally nonuniform composites

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 6, pp. 115–121, November–December, 1992.     

Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−x Co x Si3 alloys

Recently, the solid solution Ce₂Au_{1− x Co} xSi₃ has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce₂AuSi₃, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce₂AuSi₃ lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.     

Optical sensing quantum dot-labeled polyacrolein particles prepared by layer-by-layer deposition technique

Optical sensing polymer particles with tailored semiconductor nanocrystal (QD) loading are prepared by layer-by-layer deposition technique (LbL). Polyacrolein particles of 1.2 μm diameter are used as solid support for deposition of hydrophilic CdSe/ZnS nanocrystal/polyelectrolyte multilayers formed by electrostatic interactions. The pH-dependent fluorescence of QDs and pH-dependent conformations of polyelectrolytes, which likely passivate the surface state of nanocrystals, allow a creation of both mono- and multiplex coded polymer particles with pH-dependent fluorescence intensity. Bovine serum albumin (BSA) as outermost layer makes it possible to design the optical sensing polymer particles with reversibly responded fluorescence at pH variations. The fluorescence of such polymer particles with BSA outer layer is sensitive to copper(II) ion while the fluorescence of these particles is practically insensitive to the other divalent cations (Zn(2+), Ca(2+), Ba(2+), Co(2+), Mg(2+)). The detection limit of Cu(2+) is about 15 nM. Adaptation of LbL method to prepare QD-labeled polymer particles with enhanced complexity (e.g. several types of QDs, multiple biofunctionality) is expected to open new opportunities in biotechnological applications.     

Electron tunneling through a barrier that depends linearly on time

We discuss the creation of a negative molecular ion via the decay of a self-captured electron state — the fluctuon — in a nonideal dipole-molecule gas. The creation probability of the negative ion is evaluated in the classical approximation using Green's function methods. We assume that the potential barrier through which the electron tunnels from the potential well of the fluctuon to that of the molecule depends linearly on time.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 84–88, September, 1987.     

The growth of a single crystal of Sr3CuIrO6 and its magnetic behavior compared to polycrystals

We have grown single crystals of the psuedo-one-dimensional compound Sr₃CuIrO₆, a K₄CdCl₆-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence for at least two magnetic transitions, at 5 K (T ₁) and 19 K (T ₂), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of both the forms is found to be widely different, exhibiting unexpected time dependence.     

Fundamental solutions of the theory of unidirectional composites

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 3, pp. 120–127, May–June, 1992.     

Formation of negative ions in a nonideal gas

We consider a new mechanism of formation of a negative molecular ion: the decay of a localized state of an electron (a fluctuon) in a nonideal gas of polar molecules. The probability of forming a negative ion is calculated both in the quasi-classical approximation and from the solution of the nonstationary Schrödinger equation. The results from these two methods are compared.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, 83–89, November, 1987.