Free Bicommutative Algebras

2000 Mathematics Subject Classification: Primary 17A50, Secondary 16R10, 17A30, 17D25, 17C50.Algebras with identities a(bc)=b(ac), (ab)c=(ac)b is called bicommutative. Bases and the cocharacter sequence for free bicommutative algebras are found. It is shown that the exponent of the variety of bicommutaive algebras is equal to 2

Monitoring vibrations and microdisplacement for "pin on disc" tribology studies

The paper studies the example of applying accelerometers to evaluate tribocoupling vibration characteristics and verification methods in the testing system "pin on disc". Microelectromechanical systems (MEMS) intended for operation over a wide static and spectral ranges were applied. Accelerator spatial track recovery was implemented through the double integration algorithm. In the course of the work, the vibrations occurring through the friction between fluorocarbon and brass alloy LS59-1 under the conditions of dry friction were studied

Interband electron Raman scattering in a quantum wire in a transverse magnetic field

Electron Raman scattering (ERS) is investigated in a parabolic semiconductor quantum wire in a transverse magnetic field neglecting by phonon-assisted transitions. The ERS cross-section is calculated as a function of a frequency shift and magnetic field. The process involves an interband electronic transition and an intraband transition between quantized subbands. We analyze the differential cross-section for different scattering configurations. We study selection rules for the processes. Some singularities in the Raman spectra are found and interpreted. The scattering spectrum shows density-of-states peaks and interband matrix elements maximums and a strong resonance when scattered frequency equals to the "hybrid" frequency or confinement frequency depending on the light polarization. Numerical results are presented for a GaAs/AlGaAs quantum wire.Comment: 8 pages, 5 figure

Spectropolarimetric Observations of Herbig Ae/Be Stars. II. Comparison of Spectropolarimetric Surveys: HAeBe, Be and Other Emission-Line Stars

The polarization of light across individual spectral lines contains information about the circumstellar environment on very small spatial scales. We have obtained a large number of high precision, high resolution spectropolarimetric observations of Herbig Ae/Be, Classical Be and other emission-line stars collected on 117 nights of observations with the HiVIS spectropolarimeter at a resolution of R=13000 on the 3.67m AEOS telescope. We also have many observations from the ESPaDOnS spectropolarimeter at a resolution of R=68000 on the 3.6m CFH telescope. In roughly ~2/3 of the so-called "windy" or "disky" Herbig Ae/Be stars, the detected H-alpha linear polarization varies from our typical detection threshold near 0.1% to over 2%. In all but one HAe/Be star the detected polarization effect is not coincident with the H-alpha emission peak but is detected in and around the obvious absorptive part of the line profile. The qu-loops are dominated by the polarization in this absorptive region. In several stars the polarization varies in time mostly in the absorptive component and is not necessarily tied to corresponding variations in intensity. This is a new result not seen at lower resolution. In the Be and emission-line stars, 10 out of a sample of 30 show a typical broad depolarization effect but 4 of these 10 show weaker effects only visible at high resolution. Another 5 of 30 show smaller amplitude, more complex signatures. Six stars of alternate classification showed large amplitude (1-3%) absorptive polarization effects. These detections are largely inconsistent with the traditional disk-scattering and depolarization models.Comment: Published in ApJS 180. 47 pages, 34 figures. Small corrections made to tex

Arch vessel injury: geometrical considerations. Implications for the mechanism of traumatic myocardial infarction II

BACKGROUND: Various types of vascular injury have been reported in the medical literature; the isthmic part of the aorta is at particularly high risk of traumatic rupture. Early diagnosis results in better survival, justifying the search for potential risk factors and diagnostic tests. The aim of this research was to investigate the complex mechanism of blunt injury to the vascular wall with particular focus on the branching region of the vessels. Geometric peculiarities were investigated. METHODS: Multi-phase equations have been used. The system of equations with certain boundary conditions was solved numerically by applying the finite-difference method with order of approximation equal to 0.0001. RESULTS: The degree of curvature (the Dean number) is highly informative about the shear stress on the external surface of the vessel. An important function of the blood flow on the external wall is to destroy rouleaux. The viscosity of phase 2 (f(2)) exceeds, by many times, the viscosity of phase 1 (f(1)). The major stress created by blood flow is expressed as the shear stress of f(2). The volume fraction of rouleaux depends to a greater degree on the concentration of erythrocytes (expressed as the viscosity of the mixture) than on the shear stress. The peculiarities of rouleaux formation were assessed and their impact on the local shear stress and, therefore, on the internal wall was determined in relation to the erythrocyte concentration. CONCLUSION: The results of this research take into account certain geometrical peculiarities of the branching part of the vessel. The mathematical model created in this study will improve our understanding of the complex mechanism of blunt injury to the vascular wall and, therefore, conditions such as aortic rupture and traumatic acute myocardial infarction

Geographic altitude, ocular diseases and injuries

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Forced Vibrations of a System Consisting of a Pre-strained Highly Elastic Plate under Compressible Viscous Fluid Loading

The forced vibration of the system consisting of the pre-stretched plate made of highly-elastic material and half-plane filled by barotropic compressible Newtonian viscous fluid is considered. It is assumed that this forced vibration is caused by the lineal located time-harmonic force acting on the free face plane of the plate. The motion of the pre-stretched plate is written by utilizing of the linearized exact equations of the theory of elastic waves in the initially stressed bodies, but the motion of the compressible viscous fluid is described by the linearized Navier-Stokes equations. The elastic relations of the plate material are described with the use of the harmonic potential. Moreover, it is assumed that the velocities and stresses of the constituents are continuous on the contact plane between the plate and fluid. The dimensionless parameters which characterize the compressibility, viscosity of the fluid and elastic constants of the plate material are introduced. The plane strain state in the plate is considered and the corresponding boundary- and contact-value problem is solved by employing exponential Fourier transformation with respect to the coordinate directed along the interface line and the inverse of this transformation is determined numerically by employing the Sommerfeld contour. Numerical results on the interface stresses and velocities and the influence of the problem parameters such as initial strains and thickness of the plate, the compressibility and viscosity of the plate, as well the magnitude of the frequency of the external forces on these results are presented and discussed. Numerical results are examined in the case where the fluid is Glycerin and the values of the elastic constants which enter into the mentioned above harmonic potential and the density of the plate material are taken as Lame’s constants and density of the Plexiglass (Lucite)

Registration of CBS Effects from Wedge-shaped Samples Containing Particles of Alumina

The paper looks at recent results of research dealing with a coherent backscattering (CBS) on the particles of alumina. It was developed a system of registration of CBS with a tunable dynamic sample. During the experiment the transport mean free path over the width of the peak of angular profile of signal intensity of CBS was determined. Moreover, new scientific data about the CBS’s profiles from randomly inhomogeneous environments were obtained