On leading spiral arms in close pairs of galaxies

It is explained why one can observe a leading spiral pattern in close pairs of galaxies where the direction of the orbital momentum of the satellite is opposite to the direction of the spin of the spiral galaxy

Fast periodic oscillations in singularly perturbed relay control systems and sliding modes

As a mathematical model of chattering in the small neighbourhood of switching surface in the sliding mode systems we examine the singularly perturbed relay control systems (SPRCS). The sufficient conditions for existence of fast periodic solutions in such systems are found. Their stability is investigated. It is proved that the slow motions in such SPRCS are approximately described with equations obtained from the equations for the slow variables of SPRCS by averaging along fast periodic motions. It is shown that in the case when the original SPRCS contains the relay control linearly the averaged equations and equations which describe the motions of the reduced system in the sliding mode are coincide. The algorithm is proposed which allows to solve the problem of eigenvalues assignment for averaged equations using the additional dynamics of fast actuator

Preparation and Processing of Novel Precursors for β-BBO Nonlinear Optical Thin Films using 1) 2, 4, 6- Triphenylcyclotriboroxine, Cryptand 2.2.2, and Barium Hydride and 2) 2, 4, 6-Trimethoxycyclotriboroxane, 18- crown-6, and Barium Metal

Certain optical materials interact with high intensity light in a nonlinear way causing the emission of higher energy photons. Nonlinear optical thin films have many promising uses such as frequency converters, optical switches, and data storage devices. Betabarium borate (β-BaB204, β-BBO) was chosen for this investigation due to its large optical transparency range, high radiation damage threshold, and its ability to up-convert infrared light to the ultraviolet (UV) and visible region. The preparation and processing of two novel precursors for β-BBO nonlinear optical thin films were studied using 1) 2, 4, 6-triphenylcyclotriboroxine, cryptand 2.2.2, and barium hydride and 2) 2, 4, 6- trimethoxycyclotriboroxane, 18-crown-6, and barium metal. The precursors were analyzed by nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The solid state thermolysis products of Project 1, powders and thin films, were characterized by X-ray diffraction. The Project 1 precursor was successfully used to produce β-BBO thin film on sapphire substrate (R-plane, 1-102 orientation) via metalorganic deposition (MOD). The formation temperature of β-BBO, based on the XRD results of the thin film produced using the Project 1 precursor, was found to be as low as 550 °C. The formation temperature of β-BBO, based on the DSC results of the Project 2 precursor, was found to be near 560 °C

Tropospheric limitations on the accuracy of phase measurement of coordinates in astronomy

The effect of tropospheric fluctuation on the accuracy of phase measurements of coordinates is discussed. The nature of the averaging of the tropospheric effects, if N coordinate measurements of duration T with period mu are made, is investigated. Various averaging modes depending on the relation of the various time parameters are investigated. Equations taking into account the correlations between individual observations are presented. It is shown that the correlation interval between the individual observations is always greater than the fluctuation period of tropospheric inhomogeneities typical for a given baseline

Versioning of Digital Objects in a Fedora-based Repository

This presentation gives an overview on the complex versioning re-quirements for digital objects in the scope of the project eSciDoc and discusses our solution based on the flexible repository architecture Fedora. It describes the conceptual background of how the eSciDoc infrastructure handles versioning of digital objects. Versioning and object identification are strongly interwoven concepts. Therefore, the unique identification of objects and their versions are discussed as well

Metastatic Melanomas Express Inhibitory Low Affinity Fc Gamma Receptor and Escape Humoral Immunity

Our research, inspired by the pioneering works of Isaac Witz in the 1980s, established that 40% of human metastatic melanomas express ectopically inhibitory Fc gamma receptors (FcγRIIB), while they are detected on less than 5% of primary cutaneous melanoma and not on melanocytes. We demonstrated that these tumoral FcγRIIB act as decoy receptors that bind the Fc portion of antimelanoma IgG, which may prevent Fc recognition by the effector cells of the immune system and allow the metastatic melanoma to escape the humoral/natural immune response. The FcγRIIB is able to inhibit the ADCC (antibody dependent cell cytotoxicity) in vitro. Interestingly, the percentage of melanoma expressing the FcγRIIB is high (70%) in organs like the liver, which is rich in patrolling NK (natural killer) cells that exercise their antitumoral activity by ADCC. We found that this tumoral FcγRIIB is fully functional and that its inhibitory potential can be triggered depending on the specificity of the anti-tumor antibody with which it interacts. Together these observations elucidate how metastatic melanomas interact with and potentially evade humoral immunity and provide direction for the improvement of anti-melanoma monoclonal antibody therapy

Accretion-ejection instability in magnetized disks: Feeding the corona with Alfven waves

We present a detailed calculation of the mechanism by which the Accretion-Ejection Instability can extract accretion energy and angular momentum from a magnetized disk, and redirect them to its corona. In a disk threaded by a poloidal magnetic field of the order of equipartition with the gas pressure, the instability is composed of a spiral wave (analogous to galactic ones) and a Rossby vortex. The mechanism detailed here describes how the vortex, twisting the footpoints of field lines threading the disk, generates Alfven waves propagating to the corona. We find that this is a very efficient mechanism, providing to the corona (where it could feed a jet or a wind) a substantial fraction of the accretion energy.Comment: accepted by A&