Mirror conversion of gaussian beams with simple astigmatism

The surface of an inclined mirror, which converts Gaussian beams with simple astigmatism hase been found within the quasi-optical approximation. The beam reflected from the found mirror was examined. Power losses of the reflected beam, when the beam is incident on a selective system, which transmits a Gaussian beam of one polarization only have been found.     

Sources of intensive noise signals of millimeter wave band

The new method of the CW intensive noise signals excitation in millimeter wave band has been studied. With this aim in mind the O-type Backward Wave Oscillators, operating in chaotic oscillation regime, are proposed to use. The noise sources, based onBWO, have a high efficiency, universal power spectrums and feasibility of electronic tuning of the noise signal frequency in the relative range of 4–10%. Low voltage noise sources, operating in the bands needed over the range from 30to 60GHz, make possible output power of 8 – 25W and 4W respectively and 3 –dB power spectrum width more than 300M H z. Application of the suitableBWO offers to excite the noise signals in decimeter and centimeter ranges too.     

Magneto‐sensitive Elastomers in a Homogeneous Magnetic Field: A Regular Rectangular Lattice Model

A theory of mechanical behaviour of the magneto‐sensitive elastomers is developed in the framework of a linear elasticity approach. Using a regular rectangular lattice model, different spatial distributions of magnetic particles within a polymer matrix are considered: isotropic, chain‐like and plane‐like. It is shown that interaction between the magnetic particles results in the contraction of an elastomer along the homogeneous magnetic field. With increasing magnetic field the shear modulus, G, for the shear deformation perpendicular to the magnetic field increases for all spatial distributions of magnetic particles. At the same time, with increasing magnetic field the Young's modulus, E, for tensile deformation along the magnetic field decreases for both chain‐like and isotropic distributions of magnetic particles and increases for the plane‐like distribution of magnetic particles.

     

Fe valence state at the surface of the Fe0.5Cu0.5Cr2S4 spinel

Here we present X‐ray absorption measurements of a vacuum cleaved Fe_0.5Cu_0.5Cr₂S₄ single crystal. Measurements at different positions on the cleaved sample surface clearly reveal a difference between the valence state of the Fe ions in the sur‐ face layers and the valency of the Fe ions present in the bulk. These results confirm the findings of recent measurements outlined previously. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hierarchical genetic networks and noncoding RNAs

In eukaryotic cells, many genes are transcribed into noncoding RNAs. Such RNAs may associate with mRNAs and inhibit their translation and facilitate degradation. To clarify what may happen in this case, we propose a kinetic model describing the effect of noncoding RNAs on a mRNA-protein network with the hierarchical three-layer architecture. For positive regulation of the layers, our model predicts either bistability with a fairly narrow hysteresis loop or a unique steady state. For negative or mixed regulation, the steady state is found to be unique.     

Bell-type inequalities and tomographic entropies of multiqudit states

Tomographic entropies of multiqudit systems are studied. A comparison of Shannon and von Neumann entropic inequalities with analogous inequalities for tomographic entropies is presented. An attempt to associate the violation of these and Bell-type inequalities of multipartite states is done within the framework of tomographic probability theory.     

Inverse spin-<Emphasis Type="Italic">s</Emphasis> portrait and representation of qudit states by single probability vectors

Using the tomographic probability representation of qudit states and the inverse spin-portrait method, we suggest a bijective map of the qudit density operator onto a single probability distribution. Within the framework of the approach proposed, any quantum spin-j state is associated with the (2j+1)(4j+1)-dimensional probability vector whose components are labeled by spin projections and points on the sphere S². Such a vector has a clear physical meaning and can be relatively easily measured. Quantum states form a convex subset of the 2j(4j + 3) simplex, with the boundary being illustrated for qubits (j = 1/2) and qutrits (j = 1). A relation to the (2j +1)^2_ and (2j +1)(2j +2)-dimensional probability vectors is established in terms of spin-s portraits. We also address an auxiliary problem of the optimum reconstruction of qudit states, where the optimality implies a minimum relative error of the density matrix due to the errors in measured probabilities.     

Exoelectron emission from solid nitrogen

Solid nitrogen was investigated by activation spectroscopy methods – thermally stimulated luminescence and thermally stimulated exoelectron emission (TSL and TSEE) in combination with luminescence analysis. TSEE from solid nitrogen pre-irradiated by an electron beam was measured and investigated for the first time. A set of peaks both in TSL and TSEE were observed. It was found that one of the peaks in the TSEE curve is caused by release of electrons in the course of the α-β phase transition of solid nitrogen. The corresponding activation energy was estimated.     

Thermodynamics of the rupture in a Morse lattice

The rupture of a Morse lattice is considered in the presentpaper. The critical rupture force F _cr is found todecrease with the number of particles N as F _cr ~ 1/\(\sqrt{N}\). The partition function is obtained for two states ofthe lattice – with all equal bond lengths and one broken bond.In the first case an accurate expressions for thermodynamicparameters are obtained, and thermodynamic expressions arederived in the harmonic approximation in the latter case. Theanalytical predictions are confirmed by extensive MD simulations.Cis-trans isomerization is considered as an example. Volumefractions of trans- and cis-isomers versus number ofmonomer units N are found depending on the torsion stiffnesses.