Performance of Digital FM Systems in a Fading Environment

This paper investigates the effects of fading and predetection diversity on the error-rate performance of digital FM discriminator systems. Results are presented in graphs showing the relative improvement of the error rate for several types of diversity, and are compared with the well-known FSK systems. It is also shown that an optimum modulation index giving the minimum attainable probability of error for narrowband digital FM is not affected by the effect of fading, carrier-to-noise ratio, or the types and order of diversity.     

The action of simulated and true weightlessness on the digestive tract of rats

Rats on board the Soviet Cosmos 936 satellite for 18$\text{1}\text{2}$ days showed a decreased glycoprotein secretion from the salivary mucous glands, stomach and intestine, and an increased leucine aminopeptidase and acid phosphatase content from the small intestine. Grimelius positive cells were activated. One group of rats were centrifuged at 1 g during the flight to simulate terrestrial gravity. Some investigations have suggested that under these conditions muscular and cardiac disorders diminished. In the digestive tract the benefits of centrifugation at 1 g are minimal and limited to a few glycoprotein components. The digestive changes are probably the expression of a stress response, unrelated to weightlessness. Similar changes, concomitant with a glycocorticoid hypersecretion, were found in rats after 15 days of hypokinesia on Earth. These digestive changes persisted even in adrenalectomized rats.     

Estimation of plasma density from wave data of cold electron plasma

Based on the dispersion relation of electron plasma, one can expect, that the waves excited in the frequency band (f_p, f_u=sqrt(f_p^*f_p+f_c^*f_c)) should persist in experimental spectra. For wave data from a spacecraft immersed in a cold plasma such an assumption may be misleading. In measurements performed on board the INTERCOSMOS-19, ACTIVE, APEX satellites and VC36.064CE rocket the most prominent spectral structure is centered around frequency f_r fulfilling the relation f_crp and corresponds to resonant detection of Bernstein waves excited in the surrounding plasma by spacecraft systems. Input network mismatch at frequencies around fu significantly depresses natural plasma noise as well as that excited by the spacecraft. Plasma emissions in the band (f_p, f_u) are prominent if the electromagnetic excitation is preferential (topside sounders) or if the excitation introduces nonequilibrium components into the plasma e.g. particle beams or clouds. Experimental examples are presented and parameters of cold plasma spectra useful for electron density estimation are discussed. The application to other spacecraft-cold plasma configurations is suggested.     

Ontogeny of plants under various gravity condition.

The results of experiments performed under conditions of microgravity (MG) or under its simulation on the horizontal clinostat (HC) with the callus, seedlings of various species and embryogenic structures have revealed a definite role of gravity as an ecological factor in the processes of cytomorphogenesis, growth, and development. The transformation of differentiated somatic cells of arabidopsis seed into undifferentiated callus was not inhibited under MG, though modifications of the whole callus morphology and of mean cell and nucleus size were observed. The morphogenesis of polar structures such as root-hair bearing cells of Lactuca primary root has been shown to be modified in the course of differentiation under mass acceleration diminished below 0.1 g. Seed germination and seedling morphogenesis under MG follow their normal course, but a significant stimulation of shoot growth with no effect on primary root growth has been determined. A successful in vitro regeneration of Nicotiana tabacum plantlets from leaf cells and subsequent formation of shoots and roots on a continuously rotating HC as well as the formation of viable seeds during seed-to-seed growth of Arabidopsis plants under MG have indicated that gravity plays but a limited role in the processes of embryogenesis and organogenesis.     

Electron beams and their interactions with the ionosphere — A review of the E| |B series

A review is presented of results from a series of experiments which began with an attempt to reflect electrons from the potential change which is thought to generate the aurora. In order to understand the experiment, this series then expanded to study beam-plasma interactions in the laboratory as well as in the ionosphere. Results from the electron reflection experiment, as well as in situ and ground-based observations of the waves generated by beam-plasma interactions will be reviewed. Measurements bearing on modifications of the ambient plasma by the beam-emitting rocket will be presented.     

Phase resolved study of the CRSF in MX 0656-072

MXB 0656-072 is an accreting X-ray pulsar with a Be star companion, showing notable emission in H. In October 2003 this system exhibited a large and extended X-ray outburst. RXTE observations during this outburst indicated a pulse period of 160.4 s and a cyclotron resonance scattering feature in the spectrum at 32 keV. This paper presents pulse profile analysis and phase-resolved X-ray spectroscopy of RXTE observations during this outburst.     

Chromospheric line emission in seismically active flares

Some flares are known to drive seismic transients into the solar interior. The effects of these seismic transients are seen in helioseismic observations of the Sun’s surface thousands of km from their sources in the hour succeeding the impulsive phase of the flare. Energetic particles impinging from the corona into the chromosphere are known to drive strong, downward-propagating shocks in active region chromospheres during the impulsive phases of flares. H observations have served as an important diagnostic of these shocks, showing intense emission with characteristic transient redshifts. In most flares no detectable transients penetrate beneath the active region photosphere. In those that do, there is a strong correlation between compact white-light emission and the signature of seismic emission. This study introduces the first known H observations of acoustically active flares, centered in the core of the line. The morphology of line-core emission H in the impulsive phase of the flare is similar to that of co-spatial line-core emission in NaD₁, encompassing the site of seismic emission but more extended. The latter shows a compact red shift in the region of seismic emission, but a similar feature is known to appear in a conjugate magnetic footpoint from which no seismic emission emanates. Radiative MHD modelling based on the profiles of chromospheric line emission during the impulsive phases of flares can contribute significantly to our understanding of the mechanics of flare acoustic emission penetrating into the solar interior and the conditions under which it occurs.     

Do heavy ions cause microlesions in cell membranes?

Heavy ions are a hazard in manned deep space missions. It has been theoretically postulated that when they interact with cells, localized damage in the forms of "microlesions" may occur. Purported morphological evidence of these lesions, however, has not been confirmed in the most extensively studied tissue so far, the cornea. Recent morphological evidence from rat corneas demonstrated that holes in membranes do not form as consequence of heavy ion irradiation. This does not mean, however, that some other form of damage is excluded. For example such damage may be physiological in nature, impairing the ability of cells or tissues to function properly. In order to uncover any physiological effects, we investigated the microlesion question by monitoring the electrical potential difference across the endothelium of rat corneas in vitro before, during, and after irradiation. When the corneas were exposed to 1 Gy of 56Fe ions (450 and 600 MeV/a.m.u.), we detected no effect on this parameter. These results suggest that direct physical damage to cell membranes, as predicted by the microlesion theory, does not take place.     

Polarization Studies of Contribution of Aerosol Scattering to the Glow of Twilight Sky

The paper is devoted to studies and a quantitative estimation of the influence of scattering of direct solar radiation by particles of tropospheric aerosols in the period of light twilight, close to sunrise and sunset. Polarization measurements of the twilight sky in two broad spectral bands lying near the standard bands V and R form the basis of these studies. The measurements were carried out in 2002 and 2003 at the Southern Laboratory (Crimea) of the Sternberg Astronomical Institute. The twilight period during which the single aerosol scattering becomes significant is isolated. The character of its influence on the intensity and polarization of the twilight sky is demonstrated. A method is suggested to evaluate polarization of the single aerosol scattering and its contribution to the general brightness of the twilight sky background. The method is based on differential characteristics of the background near the zenith and on their correlations with each other.     

Spatial vibration protection in a turbopump of hydrogen rocket engines

We discuss the use of multilayered annular-plate dampers as rotor supports in turbopumps of the RD-0120 and RD-0146 rocket engines. We present a technique of calculating the elastic and damping characteristics of multilayer corrugated annular supports in the case of the conical precession of the rotor.