Spectral features of laser induced plasma from YBa2Cu3O7 and GdBa2Cu3O7 highT c superconductors

Laser induced plasma emission spectra from highT _c superconducting samples of YBa₂Cu₃O₇ and GdBa₂Cu₃O₇ obtained with 1.06μm radiation from a Q switched Nd:YAG laser beam has been analysed. The results clearly show the presence of diatomic oxides in addition to ionized species of the constituent metals in the plasma thus produced.     

Diffraction of random light emission in a monochromatic sound wave field in an anisotropic disperising medium

Institute of Automated Control Systems and Radioelectronics, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 1, pp. 94–105, January, 1989.     

An interpretation of cortical maps in echolocating bats

Target parameters such as reflectivity, range, velocity, and angular position are represented by ordered maps of tuned cortical neurons in insectivorous bats. It is suggested that the response of each neuron in such a map is determined by a hypothesis test conditioned on a particular value of the mapped parameter. The excitation of each neuron is then interpreted as a sample value of a conditional log-likelihood ratio or a log-likelihood function. Interpolation between the samples, which is needed to find the parameter that maximizes the mapped function (e.g., the maximum likelihood parameter estimate), can be accomplished with overlapped tuning curves. An attempt to portray a sharp peak by a weighted sum of relatively broad neuronal tuning curves or interpolation functions results in excitatory center/inhibitory surround behavior. Facilitation or antifacilitation of neurons that are likely to be excited by succeeding observations can be used for sequential detection and tracking. Interpolation and pulse-to-pulse data storage capability are required to explain range jitter sensitivity and to allow for moving target indication in bat sonar. If a cortical map represents an ordered array of hypothesis tests, then many such tests are implemented in parallel when target parameters are unknown. Detection performance is then degraded relative to the idealized situation in which all parameters are specified. Performance in noise may thus appear to be much worse than that of an ideal detector, even if each hypothesis test is optimally implemented.     

On the feasibility of antideuteron production and storage at CERN

The new Antiproton Accumulator Complex is now in operation at CERN. We consider the possibility of using this facility to create and store antideuterons and conclude that we could achieve an accumulation rate of about 2·10⁶ particles/day. No major rebuild of the rings is envisaged, but it is thought that modification to existing components and becoming operational would take about 5 to 6 months. We stress, however, that the operation of such a facility and the use of any stack of antideuterons for particle physics would be extremely taxing.     

Binary quantum logic and generating semigroups

A refined definition of basic concepts for logic describing physical systems is proposed. Within the suggested formalism of generating semigroups the active logic of questions and passive logic of answers are introduced. The objects for which both logics are isomorphic are called self-adequate. It is shown that the assumption of self-adequacy implies that the object is either quantum or classical. The possibility of application of the theory to non-self-adequate objects is discussed.     

Vibrations of a magnet levitated over a flat superconductor

Based on a dipole-dipole interaction model, we discuss the levitation force and related vibration problems to understand the effects of flux pinning in type-II superconductors, and the applications of levitation in superconducting systems.     

The effect of oxygen ordering through controlled exposure to oxygen on the superconductive properties of LaBa2Cu3Oy

In an effort to clarify the role of controlled oxygen exposure in the synthesis of LaBa₂Cu₃O_y samples which achieve zero resistivity above 90 K, we have prepared samples of La(_1+x)Ba(_2–x)Cu₃O_y with x approximately equal to 0 and with y varying between 6.22 and 7.00. We find that for large values of y, 6.88相似文献   

Nonlinear effects of electrical transport in crystals with orbital degeneration

The influence of an electrical field on the charge transfer in crystals with orbital degeneration is investigated. An expression is obtained for the current density in crystals with narrow d-conduction bands in transition metal compounds. As the electrical field intensity increases, a current density maximum is observed with a subsequent section of negative differential conductivity. The results of the investigation agree qualitatively with experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 14–18, February, 1989.