High energy radiation from the direction of the galactic black hole Sgr A

X-ray observations indicate that the Galactic black hole Sgr A^∗ is inactive now, however, we suggest that Sgr A^∗ can become active when a captured star is tidally disrupted and matter is accreted into the black hole. Consequently the Galactic black hole could be a powerful source of relativistic protons with a characteristic energy ∼10⁵² erg per capture. The diffuse GeV and TeV γ-rays emitted in the direction of the Galactic Center (GC) are the direct consequences of p–p collisions of such relativistic protons ejected by very recent capture events occurred ?10⁵ yr ago. On the other hand, the extended electron-positron annihilation line emission observed from GC is a phenomenon related to a large population of thermalized positrons, which are produced, cooled down and accumulated through hundreds of past capture events during a period of ∼10⁷ yr. In addition to explaining GeV, TeV and 511 keV annihilation emissions we also estimate the photon flux of several MeV resulting from in-flight annihilation process.     

Spaceflight results in increase of thick filament but not thin filament proteins in the paramyosin mutant of Caenorhabditis elegans

We have investigated the effect of microgravity during spaceflight on body-wall muscle fiber size and muscle proteins in the paramyosin mutant of Caenorhabditis elegans. Both mutant and wild-type strains were subjected to 10 days of microgravity during spaceflight and compared to ground control groups. No significant change in muscle fiber size or quantity of the protein was observed in wild-type worms; where as atrophy of body-wall muscle and an increase in thick filament proteins were observed in the paramyosin mutant unc-15(e73) animals after spaceflight. We conclude that the mutant with abnormal muscle responded to microgravity by increasing the total amount of muscle protein in order to compensate for the loss of muscle function.     

New index of long-term variations of galactic cosmic ray intensity

We find that the soft rigidity spectrum of the Galactic Cosmic Ray (GCR) intensity variations for the maximum epoch and the hard rigidity spectrum for the minimum epoch calculated based on the neutron monitors experimental data (1960–2002) are related with the various dependence of the diffusion coefficient on the GCR particle’s rigidity for different epoch of solar activity. This dependence is stronger in the maximum epoch than in the minimum epoch of solar activity, and is provided by the essential temporal rearrangements of the structure of the Interplanetary Magnetic Field (IMF) turbulence from the maxima to minima epoch of solar activity. We also show that the rigidity spectrum of GCR intensity variations is harder for the effective rigidities ∼(10–15) GV (by neutron monitors data), than for the effective rigidities ∼(25–30) GV (by neutron monitors and muon telescopes data). A general scenario of GCR modulation versus solar activity is settled on the essential temporal rearrangements of the structure of the IMF turbulence. Therefore, the temporal changes of the power law rigidity spectrum exponent can be considered as a vital (new) index to explain the 11-year variations of the GCR intensity. We assume that ∼(70–80)% of the changes of the amplitudes of the 11-year variations of GCR intensity is related with the changes of the IMF turbulence versus solar activity.     

Recent studies of the optical counterpart of GX 1+4

The galactic X-ray source GX 1+4 has been undergoing remarkable changes since early 1991. The X-ray pulsar has shown fast spin down accompanied by an increase in the hard X-ray intensity. We have obtained 1.6Å resolution spectra of the optical counterpart extending the known spectrum to 8500Å. The Ca II (8498Å) line seen for the first time from this source is indicative of a nova burst scenario. Other lines detected for the first time are detailed and the significance of these features is discussed.     

Computational methods for the HZETRN code.

Asymptotic expansion has been used to simplify the transport of high charge and energy ions for broad beam applications in the laboratory and space. The solution of the lowest order asymptotic term is then related to a Green's function for energy loss and straggling coupled to nuclear attenuation providing the lowest order term in a rapidly converging Neumann series for which higher order collisions terms are related to the fragmentation events including energy dispersion and downshift. The first and second Neumann corrections were evaluated numerically as a standard for further analytic approximation. The first Neumann correction is accurately evaluated over the saddle point whose width is determined by the energy dispersion and located at the downshifted ion collision energy. Introduction of the first Neumann correction leads to significant simplification of the second correction term allowing application of the mean value theorem and a second saddle point approximation. The regular dependence of the second correction spectral dependence lends hope to simple approximation to higher corrections. At sufficiently high energy nuclear cross-section variations are small allowing non-perturbative methods to all orders and renormalization of the second corrections allow accurate evaluation of the full Neumann series.     

Fluxes of low-energy particles in quiet periods of solar activity and the <Emphasis Type="Italic">MgII</Emphasis> index

Low fluxes of protons with energies 0.3–10 MeV were studied during 21–23 solar cycles as a function of the MgII index using the data of the instruments CPME, EIS (IMP8), and EPHIN (SOHO). It has been shown that a) during quiet time of solar activity the fluxes of protons (background protons) have a positive correlation with the MgII index value throughout the solar cycle, b) specific features of variations of the MgII index during the solar minima of 1986–1987 and 1996–1997 can be considered, as well as variations of background fluxes of low energy charged particles, to be manifestations of the 22-year magnetic cycle of the Sun, and c) periods of the lowest value of the MgII index are also characterized by the smaller values of the ratio of intensities of protons and helium nuclei than in other quiet periods. A hypothesis is put forward that acceleration in a multitude of weak solar flares is one of the sources of background fluxes of low energy particles in the interplanetary space.     

Particle acceleration in solar flares and some related phenomena

Observational features concerning solar energetic particles are compactly reviewed with some emphasis on the spectra and time histories. Velocity dependent characteristics in the energy spectra are pointed out, and compared to the results of the interplanetary shocks. A shock drift acceleration is introduced in order to interpret the observational features, especially a very fast acceleration to MeV energies within an order of second. There is a strong evidence of the shock drift acceleration in the interplanetary shocks. When some conditions are satisfied in the corona, only one or several encounters of particles with a near perpendicular shock accelerates protons to gamma-ray emitting energies (> 10 MeV). Pre-acceleration is inevitable for any kind of acceleration mechanisms in solar flares. To fulfill the requirements from the abundance ratios between various species of accelerated ions, pre-acceleration to the same velocities before the injection into a main acceleration process turns out to be absolutely necessary.     

Use of measurements from an imaging sensor for precision targettracking

The extraction of measurements for precision tracking of the centroid of a target from a forward-looking infrared imaging sensor is presented. The size of the image of the target is assumed to be small, i.e. around 10 pixels. The statistical characterization of the centroid of the target is obtained. Similarly, the statistical properties of the image correlation of two frames, which measures the target offset, are derived. Explicit expressions that map the video noise statistics into measurement noise statistics are obtained. The offset measurement noise is shown to be autocorrelated. State variable models for tracking the target centroid with these measurements are then presented. Simulation results and quantitative conclusions about achievable subpixel tracking accuracy are given. It is shown that the filter that models the autocorrelated measurement noise provides the best performance     

Plant cell plasma membrane structure and properties under clinostatting.

Structural-functional organization of plasma membrane of pea roots seedling was investigated by methods of chemiluminescence, fluorescence probes, chromatography and freeze-fracture studies under normal conditions and clinostatting. Phase character of lipid peroxidation intensity was fixed. The initial phase of this process is characterized by lipid peroxidation decreasing with its next induction. The primary changes depending on free-radical mechanisms of lipid peroxidation were excellently revealed by chemiluminescence. Plasmalemma microviscosity increased on the average of 15-20% under microgravity at the initial stages of its phenomenon. There were major changes of phosphatidilcholine and phosphatidilethanolamine contents. The total quantity of phospholipids remained rather stable. Changes of phosphatide acid concentration point to degradation and phospholipids biosynthesis. There were increases of unsaturated fatty acids mainly at the expense of linoleic and linolenic acids and also a decrease of saturated fatty acid content at the expense of palmitic and stearic acids. Unsaturation index of fatty acids increased as well. On the whole fatty acid composition was variable in comparison with phospholipids. Probably it is one of mechanisms of maintaining of microviscosity within definite limits. Considerable structural changes in organization of plasmalemma protein-lipid complex were not revealed by the freeze-fracture studies.