Cytochemical localization of calcium in soybean root cap cells in microgravity.

The antimonate precipitation technique was used to evaluate the effects of microgravity and ethylene on the cellular and subcellular distribution of free calcium ions in soybean root apices. Soybean (Glycine max L. [Merr.]) dry seeds were launched, activated by hydration, and germinated in the presence of KMnO4 (to remove ethylene) and in its absence onboard the space shuttle Columbia during the STS-87 mission. Primary root apices of 6-day old seedlings were fixed for electron microscopy after landing. Ultrastructural studies indicated that antimonate precipitation appeared as individual electron-dense particles which were more or less round in shape and varied in diameter from 10 nm (minimum size beginning from which the particles were well identified) to 90 nm. It was revealed that analyzed root cap cells varied in both the precipitate particle sizes and the amount particles per unit of the cellular area. In both flight and ground control treatments, antimonate precipitation level increases from apical meristem cells to peripheral (secretory) cells of root apices. In root cap statocytes, subcellular localization of precipitate particles was revealed in the cytoplasm, nucleus and small vacuoles. The quantitative analysis showed a reduction of precipitate density in the cytoplasm and the nucleus, and an increase in precipitate density in the vacuoles from statocytes of both spaceflight treatments in comparison with ground controls.     

Signal Sequence Detection Given Noisy, Common Background Image Sets

The optimum processing (likelihood functional) is found for a set of M images {Zm = Sm + Y + Nm}, each the sum of a member Sm of a signal sequence {Sm}, due to an object to be detected and its parameters estimated, a sample function Nm of a noise field {Nm}, and a sample function Y of a common background field {Y}. The noise fields {{Nm}} are independent, zero mean, white Gaussian fields, all independent of the background field {Y}; the latter is assumed to be either 1} completely unknown or of known mean and covariance functions with 2) a certain fluctuation property or 3) Gaussian. Three equivalent forms of the optimum processing are found: 1) a summation of generalized matched filterings of the images, 2) a summation of matched filtering of certain generalized differences of the images, 3) a summation of ?estimator-correlator? type filterings. The detection performance and optimum signal/image selection under the Neyman-Pearson criterion is given and the singularity of the ({{Nm = O}} and M > 1) case noted. It is shown that optimum processor and signal design can completely eliminate any effect of the background on detectability (M > 1). The Cramer-Rao lower bound for the signal parameter estimates meansquare error is given along with an example; optimum signal/image selection in the single parameter case is discussed.     

A study of angular motion of the Chibis-M microsatellite with three-axis flywheel control

We study the controlled angular motion of the Chibis-M microsatellite. Executive elements are three pairs of flywheels, whose axes are mutually perpendicular. The task of the control system is realization of a required program motion and support of its asymptotic stability. In this paper, we synthesize a control algorithm and study the evolution of the angular momentum of flywheels on long time intervals. The attitude accuracy is estimated for the case when disturbances act upon the spacecraft.     

Investigation of low-energy proton effects on aptamer performance for astrobiological applications

Biochips are promising instruments for the search for organic molecules in planetary environments. Nucleic acid aptamers are powerful affinity receptors known for their high affinity and specificity, and therefore are of great interest for space biochip development. A wide variety of aptamers have already been selected toward targets of astrobiological interest (from amino acids to microorganisms). We present a first study to test the resistance of these receptors to the constraints of the space environment. The emphasis is on the effect of cosmic rays on the molecular recognition properties of DNA aptamers. Experiments on beam-line facilities have been conducted with 2 MeV protons and fluences much higher than expected for a typical mission to Mars. Our results show that this irradiation process did not affect the performances of DNA aptamers as molecular recognition tools.     

Applications and usage of the real-time Neutron Monitor Database

A high-time resolution Neutron Monitor Database (NMDB) has started to be realized in the frame of the Seventh Framework Programme of the European Commission. This database will include cosmic ray data from at least 18 neutron monitors distributed around the world and operated in real-time. The implementation of the NMDB will provide the opportunity for several research applications most of which will be realized in real-time mode. An important one will be the establishment of an Alert signal when dangerous solar cosmic ray particles are heading to the Earth, resulting into ground level enhancements effects registered by neutron monitors. Furthermore, on the basis of these events analysis, the mapping of all ground level enhancement features in near real-time mode will provide an overall picture of these phenomena and will be used as an input for the calculation of the ionization of the atmosphere. The latter will be useful together with other contributions to radiation dose calculations within the atmosphere at several altitudes and will reveal the absorbed doses during flights. Moreover, special algorithms for anisotropy and pitch angle distribution of solar cosmic rays, which have been developed over the years, will also be set online offering the advantage to give information about the conditions of the interplanetary space. All of the applications will serve the needs of the modern world which relies at space environment and will use the extensive network of neutron monitors as a multi-directional spectrographic detector. On top of which, the decreases of the cosmic ray intensity – known as Forbush decreases – will also be analyzed and a number of important parameters such as galactic cosmic ray anisotropy will be made available to the users of NMDB. A part of the NMDB project is also dedicated to the creation of a public outreach website with the scope to inform about cosmic rays and their possible effects on humans, technological systems and space-terrestrial environment. Therefore, NMDB will also stand as an informative gate on space research through neutron monitor’s data usage.     

Photoinduced catalytic synthesis of biologically important metabolites from formaldehyde and ammonia under plausible “prebiotic” conditions

The article analyzes new and previously reported data on several catalytic and photochemical processes yielding biologically important molecules. UV-irradiation of formaldehyde aqueous solution yields acetaldehyde, glyoxal, glycolaldehyde and glyceraldehyde, which can serve as precursors of more complex biochemically relevant compounds. Photolysis of aqueous solution of acetaldehyde and ammonium nitrate results in formation of alanine and pyruvic acid. Dehydration of glyceraldehyde catalyzed by zeolite HZSM-5-17 yields pyruvaldehyde. Monosaccharides are formed in the course of the phosphate-catalyzed aldol condensation reactions of glycolaldehyde, glyceraldehyde and formaldehyde. The possibility of the direct synthesis of tetroses, keto- and aldo-pentoses from pure formaldehyde due to the combination of the photochemical production of glycolahyde and phosphate-catalyzed carbohydrate chain growth is demonstrated. Erythrulose and 3-pentulose are the main products of such combined synthesis with selectivity up to 10%. Biologically relevant aldotetroses, aldo- and ketopentoses are more resistant to the photochemical destruction owing to the stabilization in hemiacetal cyclic forms. They are formed as products of isomerization of erythrulose and 3-pentulose. The conjugation of the concerned reactions results in a plausible route to the formation of sugars, amino and organic acids from formaldehyde and ammonia under presumed ‘prebiotic’ conditions.     

The Swift X-Ray Telescope

he Swift Gamma-Ray Explorer is designed to make prompt multiwavelength observations of gamma-ray bursts (GRBs) and GRB afterglows. The X-ray telescope (XRT) enables Swift to determine GRB positions with a few arcseconds accuracy within 100 s of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM-Newton/EPIC MOS CCD detector to provide a sensitive broad-band (0.2–10 keV) X-ray imager with effective area of > 120 cm² at 1.5 keV, field of view of 23.6 × 23.6 arcminutes, and angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2×10⁻¹⁴ erg cm⁻² s⁻¹ in 10⁴ s. The instrument is designed to provide automated source detection and position reporting within 5 s of target acquisition. It can also measure the redshifts of GRBs with Fe line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return for each frame as the source intensity fades. The XRT will measure spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and will follow each burst for days or weeks. Dedicated to David J. Watson, in memory of his valuable contributions to this instrument.     

Methods for calculating thermophysical properties of gas mixtures

The methods for calculating thermophysical properties of substances in high-temperature gas mixtures are considered, and the existing problems are presented.     

Possible role of electrostatic potential in formation of sharp boundaries of small-scale and middle-scale solar wind structures

Sharp boundaries of small-scale and middle-scale structures of the solar wind are an essential part of a turbulized solar wind. Such boundaries are observed near the Earth’s orbit as sharp and large-amplitude changes of parameters (in particular, ion density) of the solar wind. In this paper, the observed phenomena are briefly described, and an account of their basic properties and specific features is given. Using the kinetic approach, a possible theoretical mechanism is suggested in order to explain some peculiarities in the formation of these structures.