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Stereoselective, intramolecular, formal hydroamination of dienamines via directed hydroboration is reported. Four stereocenters are set in the process. Natural and unnatural indolizidine alkaloids can be synthesized from simple unsaturated amines using the title process.

We have measured the magnetization and specific heat of multiferroic CoCr2O4 in magnetic fields up to 14 T. The high-field magnetization measurements indicate a new phase transition at T* = 5 - 6 K. The phase between T* and the lock-in transition at 15 K is characterized by magnetic irreversibility. At higher magnetic fields, the irreversibility increases. Specific-heat measurements confirm the transition at T*, and also show irreversible behavior. We construct a field-temperature phase diagram of CoCr2O4.

It was shown using the model of L2-dependent proliferation of T-cells that IL2 forms complexes with gamma-globulin inhibiting IL2 activity. In this interaction IL2 acts as lectin binding with two-antenna terminals of 5 or 6 mannose residues in one and the same region of immunoglobulin. Similar effect is observed in vivo in case of induction of DTH to listerial antigens. This phenomenon accounts for suppression of the immune response after passive injection of autoantibodies and for the inverse relationship between humoral and cellular immunity. Reduction of IL2 activity after its interaction with IgG or immune complexes may be regarded as a universal feedback immunoregulatory mechanism. External and internal factors showing affinity to mannose, e.g. sodium polyprenyl phosphate or lactobacillus, can interfere with this process and exert immunomodulating effect.

Inhibition of bacterial transcription represents an effective and clinically validated anti-infective chemotherapeutic strategy. We describe the evolution of our approach to the streptolydigin class of antibiotics that target bacterial RNA polymerases (RNAPs). This effort resulted in the synthesis and biological evaluation of streptolydigin, streptolydiginone, streptolic acid, and a series of new streptolydigin-based agents. Subsequent biochemical evaluation of RNAP inhibition demonstrated that the presence of both streptolic acid and tetramic acid subunits was required for activity of this class of antibiotics. In addition, we identified 10,11-dihydrostreptolydigin as a new RNAP-targeting agent, which was assembled with high synthetic efficiency of 15 steps in the longest linear sequence. Dihydrostreptolydigin inhibited three representative bacterial RNAPs and displayed in vitro antibacterial activity against S. salivarius . The overall increase in synthetic efficiency combined with substantial antibacterial activity of this fully synthetic antibiotic demonstrates the power of organic synthesis in enabling design and comprehensive in vitro pharmacological evaluation of new chemical agents that target bacterial transcription.

We have measured the complex dynamical conductivity, $\ensuremath{\sigma}={\ensuremath{\sigma}}_{1}+i{\ensuremath{\sigma}}_{2}$, of superconducting $\text{Ba}{({\text{Fe}}_{0.9}{\text{Co}}_{0.1})}_{2}{\text{As}}_{2}$ $({T}_{c}=22\text{ }\text{K})$ at terahertz frequencies and temperatures 2--30 K. In the frequency dependence of ${\ensuremath{\sigma}}_{1}$ below ${T}_{c}$, we observe clear signatures of the superconducting energy gap opening. The temperature dependence of ${\ensuremath{\sigma}}_{1}$ demonstrates a pronounced coherence peak at frequencies below $15\text{ }{\text{cm}}^{\ensuremath{-}1}$ (1.8 meV). The temperature dependence of the penetration depth, calculated from ${\ensuremath{\sigma}}_{2}$, shows power-law behavior at the lowest temperatures. Analysis of the conductivity data with a two-gap model, gives the smaller isotropic $s$-wave gap of ${\ensuremath{\Delta}}_{A}=3\text{ }\text{meV}$, while the larger gap is highly anisotropic with possible nodes and its rms amplitude is ${\ensuremath{\Delta}}_{0}=8\text{ }\text{meV}$. Overall, our results are consistent with a two-band superconductor with an ${s}_{\ifmmode\pm\else\textpm\fi{}}$ gap symmetry.

Streptolydigin is a highly potent, broad-spectrum antibiotic produced by Streptomyces lydicus, which inhibits bacterial RNA polymerase. We describe the first synthesis of streptolydigin, which was assembled in a highly convergent and fully stereocontrolled fashion with a longest linear sequence of 24 steps starting from commercially available precursors. The assembly process entailed preparation of fully elaborated streptolic and ydiginic subunits of the natural product, followed by a highly efficient union in a three-step one-pot procedure, which included Dieckmann cyclization with a concomitant imide opening, Horner-Wadsworth-Emmons olefination, and desilylation.

We report on a method, which allows accurate measurements of complex reflection coefficient of a solid at frequencies 1 to 50 cm-1 (30 GHz - 1.5 THz). Backward-wave oscillators (BWOs) are used as sources of monochromatic coherent radiation, tunable in frequency. The amplitude of the complex reflection (the reflectivity) is measured in a standard way, while the phase shift, introduced by the reflection from the sample surface, is measured using a polarizing Michelson interferometer. This method is particular useful for not-transparent samples (such as metals, superconductors, etc.), where phase-sensitive transmission measurements are not possible. The method requires no Kramers-Kronig transformation in order to extract the sample's electrodynamic properties (such as complex dielectric function or complex conductivity). Another area of application of this method is the study of magnetic materials with complex dynamic permeability different from unity at the measurement frequencies (for example, metamaterials). Measuring both, the phase-sensitive transmission and the phase-sensitive reflection, would allow a straight-forward model-independent determination of the dielectric permittivity and magnetic permeability of such materials.

In this article we describe a method which allows accurate measurements of the complex reflection coefficient r = absolute value(r) x exp(i phi(R)) of a solid at frequencies of 1-50 cm(-1) (30 GHz-1.5 THz). Backward-wave oscillators are used as sources for monochromatic coherent radiation tunable in frequency. The amplitude of the complex reflection (the reflectivity) is measured in a standard way, while the phase shift, introduced by the reflection from the sample surface, is measured using a Michelson interferometer. This method is particular useful for nontransparent samples, where phase-sensitive transmission measurements are not possible. The method requires no Kramers-Kronig transformation in order to extract the sample's electrodynamic properties (such as the complex dielectric function or complex conductivity). Another area of application of this method is the study of magnetic materials with complex dynamic permeabilities different from unity at the measurement frequencies (for example, colossal-magnetoresistance materials and metamaterials). Measuring both the phase-sensitive transmission and the phase-sensitive reflection allows for a straightforward model-independent determination of the dielectric permittivity and magnetic permeability of such materials.

The purpose of the current research was to estimate the range of angular sizes of incomplete images across which the perception of the given images does not depend on scale. We have measured thresholds of recognition of the identities of objects across a wide range of angular sizes from 0.19 to 50 degrees of visual angle. The methodology derived from the Gollin-test which has been used as a method for studying the perception of objects presented as incomplete contour and pattern recognition. Results demonstrated that there is a wide range of angular sizes (from 1 .0 up to 50 degrees of visual angle) across which thresholds perception of incomplete images does not depend on object size. However, there was found a narrow range of small sizes of stimulus (0.19-1.0 degrees of visual angle) at which there was found dependence of performance on object size. We assume that increase of thresholds and occurrence of undistinguished images (when they have small size) depends on increase of the contribution of sampling noise at the observer's eye retina.

The search for new materials with extremely high ("colossal") dielectric constants, required for future electronics, is one of the most active fields of modern materials science. However, the applicability of the colossal-epsilon' materials, discovered so far, suffers from the fact that their dielectric constant, epsilon', only is huge in a limited frequency range below about 1 MHz. In the present report, we show that the dielectric properties of La15/8Sr1/8NiO4 surpass those of other materials. Especially, epsilon' retains its colossal magnitude of >10000 well into the GHz range. This material is prone to charge order and this spontaneous ordering process of the electronic subsystem can be assumed to play an important role in the generation of the observed unusual dielectric properties., 4 pages, 4 figures. Shortened version, Abstract, text, and Fig. 1 revised

Multipurpose modular software for an analog interface based on Lcard 761 is considered. Algorithms for pipeline processing of medical signals under Windows with dynamic control of computational resources are suggested. The software consists of user-friendly completable modifiable modules. The module hierarchy is based on object-oriented heritage principles, which make it possible to construct various real-time systems for long-term detection, processing, and imaging of multichannel medical signals.

The aim of the present work was to assess the range of angular sizes of fragmented images of objects at which perception of the images was scale-independent. Measurements were made of human subjects' recognition thresholds for the shapes of the objects over a wide range of angular sizes (0.19-50 degrees). The experiments used the Gollin test--a method for studying the recognition of fragmented outline images of objects with which the observer is familiar. The results obtained demonstrated that there is a wide range of angular sizes, from 1.0 degrees to 50 degrees, over which the perception thresholds of incomplete outline images do not change with changes in size, along with a narrow range of stimulus sizes, 0.19-1.0 degrees, over which there is a significant size dependence. We suggest that the increase in thresholds and the failure to recognize images of small size occur as a result of an increased contribution of sampling noise at the level of the human retina.

Noopept, a peptide analog of piracetam, enhanced phagocytic activity of mouse peritoneal macrophages, stimulated humoral and cellular immune response to various antigens, and markedly increased spontaneous proliferative activity of splenocytes. In animals with secondary immune deficiency caused by cyclophosphamide, noopept exhibited immunocorrector properties.

In the clinic there were examined and treated 7 patients, ageing 38-69 years, suffering false aneurism of proximal anastomosis, which occurred after performance of aorto-femoral reconstruction for Leriche syndrome. Besides clinical data, ultrasonographic investigation of aorta was of principal meaning in diagnosis. All the patients were operated on: 2--for an urgent indications because of the prosthesis suppuration and arrosive hemorrhage occurrence and 5--in elective order. The volume of operation have depended on the patient general state, the aneurism etiology, its size and interrelationship with neighboring organs. The aneurism resection with formation of anastomosis and the blood flow restoration have constituted the main kind of operation performed in elective patients. Six patients had recovered and 1 died.

This paper presents the results of a comparative computer analysis of monochromatic drawings by mentally healthy subjects and patients with schizophrenia. The contours of the images were distinguished in each of the drawings, after which the following characteristics were calculated: the total length of all the contours of the image, the mean size of the image, and the ratio of the total length of the contours to the mean size. The spatial-frequency spectra of the images were also computed. It is established that the mean size of the drawings and the relative length of the contours in the drawings by the patients with schizophrenia are less than in those of the healthy subjects—i.e., the drawings of the patients with schizophrenia are less detailed. Moreover, these drawings are characterized by a certain rise of the spectrum in the region of medium spatial frequencies. As shown by a computer experiment, on the basis of an analysis of twenty arbitrarily chosen drawings by the patients with schizophrenia, a positive diagnosis can be delivered in 92% of all the cases. When the same sample of drawings by healthy subjects is analyzed, the probability of an incorrect diagnosis was 6.5%. The resulting data are regarded as evidence of dysfunction when there is schizophrenia of the magnocellular system, which provides a global analysis of the images and an increase of the internal noise level of the visual system.

This article gives an analysis of the interconnection of the optical properties of incomplete (fragmented) images and the psychophysical recognition thresholds of objects as necessary conditions for the appearance of visual insight. A well-known method of measuring the perception thresholds of fragmented images—the Gollin test—is proposed for the first time for solving the problem of evaluating the characteristics of insight in a person. The architecture of the neural networks that ensure the appearance of insight is considered.

The work of an operator in solving two classification problems when working with one image alphabet is studied. From ninety visual stimuli, half of the images contained animate objects, and the other half contained inanimate objects. The first task was to classify the images according to a semantic attribute—whether they contained an animate or inanimate object. This alphabet of stimuli was then subjected to wavelet filtering in a low- and high-spatial-frequency region, regardless of semantic significance. The second task was to classify the stimuli according to a physical attribute—a blurred or unblurred object in the image. Electrophysiological monitoring of the operator’s work—recording of the induced visual potentials from the entire surface of the head—made it possible to detect that, from the beginning of the stimulation until the organization of the motor response, parallel processing of the observed signal occurs according to the different semantic and physical attributes. The responses of the temporal and frontal sections of the brain associated with the semantics of the images are distinguished, even under those conditions in which the subject’s task was to classify the physical properties of an image of an object.

It is well known that an important function of binocular vision is to increase the SNR. When a signal simultaneously arrives along two channels, it is summed if the channels are statistically independent. The binocular visual acuity can then theoretically be increased by comparison with the monocular value by a factor of 2, or 1.4. This paper gives the results of experiments to measure the visual acuity by means of Landolt rings. It is established that binocular visual acuity is greater than monocular by a factor of 1.3 on the average. It is assumed that this can be associated with internal multiplicative discretization noise at the level of the retinal receptors. This result is important for understanding image processing in different channels of the visual system.

The methods of neuroiconics and functional magnetic-resonance tomography are used to investigate the factors that limit the possibilities of visual search. The influence of an image of a human face hidden in the background on the activity of the observer’s brain was recorded during the task of tracking a moving ring. It is established that images are unconsciously perceived under threshold-presentation conditions, and this is reflected in the activation of the fusiform gyrus—a region of the brain that participates in face recognition. Under above-threshold presentation conditions, the parietal and frontal regions of the brain were also activated, but activity in this case decreased in the auditory, motor, and certain other regions of the brain not occupied in signal processing. The resulting data reveal the significance of the background semantics under conditions of visual search and explain how the unconsciously perceived optical characteristics of a background image can affect the operator’s functional state.

To study the synergism between neuropeptides and lithium ions.An experimental model of stroke (chronic bilateral occlusion of the common carotid arteries in rats), neuronal culture studies, histomorphological analyses, determination of micronutrient profile of brain substrates were used.A complex of experimental studies revealed that the effect of cerebrolysin is influenced by the synergism between lithium ions and the neuropeptide contentof this drug. Pharmacokinetic synergism promotes the accumulation of lithium in brain tissues during cerebrolysin treatment. The existence of the pharmacokinetic synergism is evident from the potentiation of neuroprotective effects of the drug under the action of lithium ions established in the model of stroke.Lithium ions potentiate neuroprotective effects of cerebrolysin.Цель исследования. Изучение синергизма между нейропептидами церебролизина и ионами лития. Материал и методы. Экспериментальная модель инсульта (хроническая двусторонняя окклюзия общих сонных артерий у крыс), исследования на нейронах в культуре, гистоморфологические анализы, исследования микроэлементного профиля биосубстратов мозга. Результаты. Проведенный комплекс экспериментальных исследований показал существование синергизма между ионами лития и нейропептидами в составе церебролизина. Фармакокинетический синергизм заключается в ускоренном накоплении лития в тканях головного мозга под воздействием церебролизина. Существование фармакодинамического синергизма между нейропептидами в составе церебролизина и литием следует из установленного нами потенцирования нейропротективных эффектов препарата под воздействием ионов лития на модели инсульта. Заключение. Ионы лития потенцируют нейропротективные эффекты церебролизина.

Summary form only given. The universal laws of complex systems close to phase transitions can often be expressed by scaling relations. We measured quantum phase transition metal-insulator-transition (MIT) in yttrium hydride. Yttrium hydride YH/sub x/ shows a remarkable transitions of its electronic and optical properties upon change of hydrogen concentration. Also we demonstrate that terahertz spectroscopy is a perfect tool to explore the frequency-temperature scaling in condensed matter.

We report here our electrophysiological and psychophysiological studies of the mechanisms by which the visual system recognizes structured images with different levels of ordering. Visual stimuli consisted of textures, i.e., a set of matrixes consisting of Gabor grids. Matrixes differed in terms of the degree of ordering resulting from changes in the probability that grids with the same orientation would appear. The subject’s task was to identify the dominant orientation in the stimulus. The relationship between response accuracy, reaction time, and the main characteristics of evoked potentials on the one hand, and the number of identical grids in the matrix on the other was identified. The proportion of correct responses increased and the reaction time decreased as the degree of ordering of stimuli increased. Visual evoked potentials recorded in the occipital areas showed a relationship between the amplitudes of the N2, P2, and P3 waves, with latent periods of 180, 260, and 400 msec, respectively, and matrix parameters. The amplitudes of the P3 component and the positive component recorded in the frontal leads, with a latent period of 250 msec, increased gradually as the task became simpler. The amplitude of the N2 wave also increased with increases in the number of identically oriented elements in the matrix, though this relationship was S-shaped. The magnitude of the P2 component, conversely, was maximal in response to presentation of those matrixes which were most complex to recognize and gradually decreased as the content of identically oriented grids in the matrix increased. These relationships were compared with the statistical characteristics of the stimuli and assessed in terms of the view that the visual system contains two mechanisms, i.e., local and integral image descriptions.

There were examined 32 patients with obliterating atherosclerosis of the lower extremities arteries, in whom the reperfusion syndrome have occurred after performance of the restoration operation. In 8 patients aorto-femoral shunting was performed and in 24--femoro-popliteal one. There was established that local signs of the reperfusion syndrome, as a rule, have occurred in patients with critical ischemia of the lower extremities preoperatively. Characteristic signs of the reperfusion syndrome were noted, the methods of its prophylaxis and treatment were adduced.

We measured recognition thresholds of incomplete figure perception (the Gollin test). This test we regarded as a visual masking problem. Digital image processing permits us to measure the spatial properties and spatial frequency spectrum of the absent part of the image as the mask. Using a noise paradigm, we have measured the signal/noise ratio for Incomplete Figure. Recognition was worse with better spectral "similarity" between the figure and the "invisible" mask. At threshold, the spectrum of the fragmented image was equally similar to that of the "invisible" mask and complete image. We think the recognition thresholds for Gollin stimuli reflect the signal/noise ratio.

The high-frequency mobility in disordered systems is governed by transport properties on mesoscopic length scales, which makes it a sensitive probe for the amount of local order. Here we present a method to measure the energy dependence of the high frequency mobility by combining an electrochemically gated transistor with in-situ quasi-optical measurements in the sub-terahertz domain. We apply this method to poly([2-methoxy-5-(3',7'-dimethylocyloxy)]-p-phenylene vinylene) (OC_1C_10-PPV) and find a mobility at least as high as 0.1 cm^2V^-1s^-1., Comment: 3 pages (incl. 3 figures) in Appl. Phys. Lett

Patients with acromegaly need the constant and effective medical examination due to with more frequent development of the respiratory, cardiovascular, metabolic abnormalities and neoplasia processes, causing early morbidity and premature mortality, exceeding the one in population in 2 or 4 fold. Nowadays in Russia the work is being actively done to create the Database of patients with acromegaly. It will permit to evaluate the real prevalence of acromegaly in Russia, to analyze the sufficiency of the kinds of treatment being applied before, to evaluate the efficiency of new methods of surgical and medical treatment. By the present time in the database there are included 123 patients with active and non-active phases of acromegaly, at the age from 17 to 84 years old. (Men –48, women –75). During the patients' examination the following complications were revealed: microadenoma pituitary in 65%, macroadenoma – in 35%. The arterial hypertension, cardiomegaly, hypertrophy of the left ventricle were found in 93% of patients, atherosclerosal cardiosclerosis with dilatation of heart's caverns and the development the relative valve insufficiency in 60%, diffusive and/or nodal goiter – in 69%. In 12% of cases there were revealed the polyps of the large intestine, 20% of patients had the impaired glucose tolerance or demonstrative diabetes mellitus type 2. In case of women the frequency of myoma of the uterus, fibrose-adenomatous mastopathy, the cancer of the mamma made up accordingly 17, 15 and 3%. The patients were undertaken by the following kinds of treatment: transcranial or transnasal adenomectomy –55 of them, external pituitary radiotherapy (Gamma radiotherapy, proton irradiation) –33, using the dopamine agonists (Bromocriptine, Cabergoline) –26, somatostatin analogs (Sandostatin LAR) –21 of the patients. As a result of the examination done the complete remission of the disease (circulating insulin-like growth factor-I (IGF-I) is reduces to an-adjusted normal range and nadir growth hormone (GH) after an oral glucose load is

The thresholds of recognition of line drawings of common objects were measured using the Gollin-test procedure, in which separate random line fragments are displayed cumulatively up to the point of recognition. It was shown that the mean percentage of contour displayed at threshold recognition for different images was always about 12.5%, despite inter-subject variability between 5% and 25%. The comparative and spatial-frequency analysis of the geometrical parameters of images was carried out for different levels of fragmentation (before threshold, at threshold, and for the complete contour). The magnitude information of the Fourier domain image of figures was characterized by maximum at low and high levels of fragmentation, but at recognition threshold fragmentation it was characterized by minimum variability.

We measure the penetration depth of optimally doped and underdoped ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ in the millimeter frequency domain (4--7 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) and for temperatures $2\mathrm{K}l~Tl~300\mathrm{K}.$ The penetration depth as a function of temperature reveals significant changes on electron doping. It shows quadratic temperature dependence in underdoped samples, but increases almost exponentially at optimal doping. Significant changes in the gap anisotropy (or even in the gap symmetry) may account for this transition.

The mechanism of non-immune inhibition of biological activity of IL-2 by IgG or its immune complexes was studied using serological analysis on the model of IL-2-dependent proliferation of Con A-induced blast cells obtained from a mouse spleen. The mechanism investigated is realized through formation of a complex between IL-2 and an effector part of IgG molecule. It is suggested that this mechanism can participate in immune regulation, formation of individual and population resistance to infections, and pathogenesis of infectious and non-infectious diseases with antigen persistence.

Immunomodulatory properties of sodium polyprenyl phosphate (PP) were studied in vivo and in vitro. After injection to mice, PP was shown to increase serum levels of TNF-alpha, IL-6, and IFN-gamma. The simultaneous inoculation of tick-born encephalitis virus (TBEV) and PP to mice resulted in earlier serum appearance of IL-6, TNF-alpha and IFN-gamma (at days 1, 2 and 3, respectively) compared with mice which have received PP only. In TBEV-infected mice (not injected with PP) cytokines in serum were registered later - at day 7 after infection. Development of the disease with subsequent death was observed in 100% of infected mice. In contrast, mortality of mice infected with TBEV and simultaneously treated with PP was decreased to 40%. The study of spleen cell proliferative activity in mice injected with PP revealed a modulating effect of the latter. In vitro PP decreased spleen cell and Con A-induced blast proliferation stimulated by Con A and rIL-2 respectively. This effect was dependent upon PP inhibition of IL-2 binding to IL-2 receptors. It was concluded that PP induced early cytokine production (IL-6, TNF-alpha) by cells of monocyte/macrophage origin and, apparently, provided protection of mice against viral infection. Thus, the main properties of PP are the following: absence of the expressed direct effect on cytokine production and co-stimulating effect in combination with a bystander stimulus (in this case - TBEV).

Polyprenols are an integral part of all living cells including prokaryotic and eukaryotic ones. These compounds take part in biosynthesis of glycoproteins. We have found that phosphates of polyprenols may act as effective antiviral agents with a wide spectrum of activity. One of such antiviral agents received from Pinus sativum polyprenols was named phosprenyl. Earlier we showed that phosprenyl expressed direct antiviral effect, while having mild immunomodulatory activity. In the present study we further evaluated influence of phosprenyl on the immune system. The drug was found to inhibit an early phase of IL-1 and Con A interaction in spleen cells as well as lypoxigenase activity and expression of IL-2 receptors. At the same time, phosprenyl induced NK cell activity and early TNF-alpha production. Basing on all these data we proposed that polyprenols could be considered as a "label" which grants a possibility to the innate immune system to recognize infection at the early stages and govern the acquired immunity.

We investigate the far-infrared and submillimeter-wave conductivity of electron-doped La_(2-x)Ce_xCuO_4 tilted 1 degree off from the ab-plane. The effective conductivity measured for this tilt angle reveals an intensive peak at finite frequency (\nu ~ 50 cm{-1}) due to a mixing of the in-plane and out-of-plane responses. The peak disappears for the pure in-plane response and transforms to the Drude-like contribution. Comparative analysis of the mixed and the in-plane contributions allows to extract the c-axis conductivity which shows a Josephson plasma resonance at 11.7 cm{-1} in the superconducting state., Comment: 4 pages, 4 figures included

Experimental evidence is provided that colossal dielectric constants ${\ensuremath{\varepsilon}}^{\ensuremath{'}}g~1000,$ sometimes reported to exist in a broad temperature range, can often be explained by Maxwell-Wagner-type contributions of depletion layers at the interface between sample and contacts or at grain boundaries. We demonstrate this on a variety of different materials. We speculate that the largest intrinsic dielectric constant observed so far in nonferroelectric materials is of order ${10}^{2}.$

LiBC, a semiconducting ternary borocarbide constituted of the lightest elements only, has been synthesized and characterized by x-ray powder diffraction, dielectric spectroscopy, and conductivity measurements. Utilizing an infrared microscope the phonon spectrum has been investigated in single crystals. The in-plane B-C stretching mode has been detected at 150 meV, noticeably higher than in AlB2, a non-superconducting isostructural analog of MgB2. It is this stretching mode, which reveals a strong electron-phonon coupling in MgB2, driving it into a superconducting state below 40 K, and is believed to mediate predicted high-temperature superconductivity in hole-doped LiBC [H. Rosner, A. Kitaigorodsky, and W. E. Pickett, Phys. Rev. Lett. 88, 127001 (2002)]., 4 pages, 4 figures

Physical properties of semiconducting ${\mathrm{CdF}}_{2}$ crystals doped with In are determined from measurements of the radio-frequency response of a sample with Schottky barriers at frequencies $10\ensuremath{-}{10}^{6} \mathrm{Hz}.$ The dielectric constant, the dc conductivity, the activation energy of the amphoteric impurity, and the total concentration of the active In ions in ${\mathrm{CdF}}_{2}$ are found through an equivalent-circuit analysis of the frequency dependencies of the sample complex impedance at temperatures from 20 to 300 K. Kinetic coefficients determining the thermally induced transitions between the deep and the shallow states of the In impurity and the barrier height between these states are obtained from the time-dependent radio-frequency response after illumination of the material. The results on the low-frequency conductivity in ${\mathrm{CdF}}_{2}:\mathrm{In}$ are compared with submillimeter ${(10}^{11}\ensuremath{-}{10}^{12} \mathrm{Hz})$ measurements and with room-temperature infrared measurements of undoped ${\mathrm{CdF}}_{2}.$ The low-frequency impedance measurements of semiconductor samples with Schottky barriers are shown to be a good tool for investigation of the physical properties of semiconductors.

We present optical conductivity data for Lu(Ni 1 - x Co x ) 2 B 2 C over a wide range of frequencies and temperatures for x = 0 and 0.09. Both materials show evidence of being good Drude metals with the infrared data in reasonable agreement with dc resistivity measurements at low frequencies. An absorption threshold is seen at approximately 700 cm - 1 . In the cobalt-doped material, we see a superconducting gap in the conductivity spectrum with an absorption onset at 24′2 cm - 1 = 3.9′0.4k B T, suggestive of weak to moderately strong coupling. The pure material is in the clean limit and no gap can be seen. We discuss the data in terms of the electron-phonon interaction and find that it can be fit below 600 cm - 1 with a plasma frequency of 3.3 eV and an electron-phoon coupling constant λ t r = 0.33 using an α 2 F(ω) spectrum fit to the resistivity.

This paper discusses the process of perceiving dynamic images subjected to processing with spatial-frequency filters that simulate the characteristics of the receptive fields of the neurons of the primary visual cortex. A technique was used that makes it possible to give a quantitative estimate of how subjects perceive the emotional state of people’s faces on images presented to the subjects. It was shown that, besides the vertical and horizontal components of the spatial-frequency spectrum, a substantial role is played by the diagonal components in the process of perceiving the images of faces. Even though the visual system is less sensitive to the diagonal components than to the vertical and horizontal ones, the information contained in them makes it possible to distinguish the individual features and emotional state of a person’s face.

The structure of pure water is commonly viewed as an openwork matrix of hydrogen-bonded H2O molecules with a Debye relaxation dynamics. The matrix is filled with free ions of low concentration, which makes water a weak electrolyte with pH = 7. Traditionally, the Debye relaxation is considered having no relevance to the dc water conductivity (or the pH index): while the Debye relaxation is caused by the dynamics of intact H2O molecules, the dc conductivity, in contrast, is due to self-dissociation of H2O into H3O+ and OH- ions. Here, we consider a microscopic mechanism, which could unify the Debye and the dc dynamics, namely the Brownian-like motion of strongly interacting ions. The model comprehensively describes the low-energy electrodynamics of water (up to 1011Hz) giving however an unexpected outcome: water behaves as if it had far more free ions than the standard model assumes. High concentration of counter charges results in a polarization structure of water. We recognize full well that such a radical model is contrary to many years of research on the dynamics, thermodynamics, and dielectric properties of water; but the results seem logically consistent and may prove stimulating.

The reflection characteristics of certain optical elements and sights have been investigated in the 0.3–20-μm wavelength region. It is shown that the reflectance increases in the UV region and depends on the design of the device. Therefore, a promising range for detecting optical devices is the UV region, operation in which makes it possible to achieve high contrast of the image of an object on the background of natural formations. The results of field experiments using laser illumination of optical devices are given.

Thorough Raman and infrared (IR) reflectivity investigations of nominally pure ${\mathrm{SrTiO}}_{3}$ ceramics in the 10--300 K range have revealed a clear presence of the polar phase whose manifestation steeply increases on cooling. The Raman strengths of the Raman-forbidden IR modes are proportional to ${\ensuremath{\omega}}_{\mathrm{TO}1}^{\ensuremath{-}\ensuremath{\alpha}}(\ensuremath{\alpha}\ensuremath{\approx}1.6)$ where ${\ensuremath{\omega}}_{\mathrm{TO}1}$ is the polar soft mode frequency. No pronounced permittivity dispersion is observed below the soft mode frequency so that, as in single crystals, the static permittivity is essentially determined by the soft mode contribution. A theory is suggested which assumes a frozen dipole moment connected with the grain boundaries which induces the polar phase in the grain bulk in correlation with the bulk soft-mode frequency. This stiffens slightly the effective soft mode response and reduces the low-temperature permittivity compared to that of single crystals. Moreover, the polar soft mode strongly couples to the ${E}_{g}$ component of the structural soft doublet showing that the polar axis is perpendicular to the tetragonal axis below the structural transition which is shifted to 132 K in our ceramics. Whereas the ${\mathrm{TiO}}_{6}$ octahedra tilt (primary order parameter) below the structural transition corresponds to that in single crystals, much smaller ${A}_{1g}\ensuremath{-}{E}_{g}$ splitting of the structural soft doublet shows that the tetragonal deformation (secondary order parameter) is nearly 10 times smaller, apparently due to the grain volume clamping in ceramics.

The dielectric response of semiconducting ${\mathrm{CdF}}_{2}$ crystals with bistable In centers in the range of ${10}^{1}\ensuremath{-}{10}^{6}\mathrm{Hz}$ reveals a quasi-Debye relaxation due to Schottky barriers at the Au/Ag contacts. These spectra can be modeled with a two- or tri-layer capacitor, the characteristics of which are determined by the conductivity and capacity of the crystal volume and the depletion layers at the contacts (the Maxwell-Wagner capacitance). Analyses of the temperature dependence of these parameters show that the volume conductivity is due to free-electron motion, whereas the depletion-layer conductivity probably is caused by electron jumps over the deep In centers. Illumination of the crystals in the photoionization absorption band of the deep centers has the same effect upon the dielectric response as an increase of the temperature since both factors increase the free-electron concentration.

The complex conductivity of a MgB2 film has been investigated in the frequency range 4 cm^{-1}< nu < 30 cm^{-1} and for temperatures 2.7 K < T, 4 pages, 4 figures

Dichoptic stimulation was used in comparison of visual evoked potentials (VEPs) with those obtained with monocular stimulation (recordings made from the occipital area). 16 subjects viewed sinusoidal gratings with the right eye while a visual noise was added via a mirror for the left eye. In presence of the noise, amplitude of the early VEP components' N1, P1b, and the late component P2 decreased, P1a is not changed in presence of the noise, and the late negative wave N2 increased for all spatial frequencies. The effect of noise on the amplitude of VEPs obtained for monocular and dichoptic stimulation was similar. The data suggest that external noise is filtered by the V1 cortical neurons--matched filters for the gratings.