Sulfur in Cometary Dust

The computer-intensive project consisted of the analysis and synthesis of existing data on composition of comet Halley dust particles. The main objective was to obtain a complete inventory of sulfur containing compounds in the comet Halley dust by building upon the existing classification of organic and inorganic compounds and applying a variety of statistical techniques for cluster and cross-correlational analyses. A student hired for this project wrote and tested the software to perform cluster analysis. The following tasks were carried out: (1) selecting the data from existing database for the proposed project; (2) finding access to a standard library of statistical routines for cluster analysis; (3) reformatting the data as necessary for input into the library routines; (4) performing cluster analysis and constructing hierarchical cluster trees using three methods to define the proximity of clusters; (5) presenting the output results in different formats to facilitate the interpretation of the obtained cluster trees; (6) selecting groups of data points common for all three trees as stable clusters. We have also considered the chemistry of sulfur in inorganic compounds

Bias correction factors for near-Earth asteroids

Knowledge of the population size and physical characteristics (albedo, size, and rotation rate) of near-Earth asteroids (NEA's) is biased by observational selection effects which are functions of the population's intrinsic properties and the size of the telescope, detector sensitivity, and search strategy used. The NEA population is modeled in terms of orbital and physical elements: a, e, i, omega, Omega, M, albedo, and diameter, and an asteroid search program is simulated using actual telescope pointings of right ascension, declination, date, and time. The position of each object in the model population is calculated at the date and time of each telescope pointing. The program tests to see if that object is within the field of view (FOV = 8.75 degrees) of the telescope and above the limiting magnitude (V = +1.65) of the film. The effect of the starting population on the outcome of the simulation's discoveries is compared to the actual discoveries in order to define a most probable starting population

Heavy Metal and Rock in Space: Cluster RAPID Observations of Fe and Si

Metallic and silicate ions carry essential information about the evolution of the Earth and near-Earth small bodies. Despite this, there has so far been very little focus on ions with atomic masses higher than oxygen in the terrestrial magnetosphere. In this paper, we report on abundances and properties of energetic ions with masses corresponding to that of silicon (Si) and iron (Fe) in Earth's geospace. The results are based on a newly derived data product from the Research with Adaptive Particle Imaging Detectors on Cluster. We find traces of both Si and Fe in all of the regions covered by the spacecraft, with the highest occurrence rates and highest intensities in the inner magnetosphere. We also find that the Fe and Si abundances are modulated by solar activity. During solar maximum, the probability of observing Fe and Si in geospace increases significantly. On the other hand, we find little or no direct correlation between geomagnetic activity and Si and Fe abundance in the magnetosphere. Both Si and Fe in the Earth's magnetosphere are inferred to be primarily of solar wind origin.publishedVersio

Isolation, crystallization, and investigation of ribosomal protein S8 complexed with specific fragments of rRNA of bacterial or archaeal origin. Biochemistry 66

Study of the nature of protein-rRNA complexes is a topical problem of modern molecular biology. Structural studies of rRNA-protein complexes are the most direct and precise method of analysis of these interactions. Because ribosomal proteins are most conservative during evolution, their complexes with specific RNA fragments provide an interesting model for studying RNA-protein interactions. Ribosomal protein S8 from E. coli plays a key role in assembling the small ribosomal subunit The major region of protein S8 binding on 16S rRNA was determined by partial hydrolysis with restric tion endonucleases The binding sites of protein S8 on 16S rRNA are similar in E. coli and T. thermophilus. It was shown that ACCELERATED PUBLICATION 0006 2979/01/6609 0948$25.00 ©2001 MAIK "Nauka / Interperiodica" * To whom correspondence should be addressed. Vol. 66, No. 9, 2001, pp. 948 953. Translated from Biokhimiya, Vol. 66, No. 9, 2001, pp. 1165 1171. Original Russian Text Copyright © 2001 Abstract-The core ribosomal protein S8 binds to the central domain of 16S rRNA independently of other ribosomal proteins and is required for assembling the 30S subunit. It has been shown with E. coli ribosomes that a short rRNA fragment restrict ed by nucleotides 588 602 and 636 651 is sufficient for strong and specific protein S8 binding. In this work, we studied the complexes formed by ribosomal protein S8 from Thermus thermophilus and Methanococcus jannaschii with short rRNA frag ments isolated from the same organisms. The dissociation constants of the complexes of protein S8 with rRNA fragments were determined. Based on the results of binding experiments, rRNA fragments of different length were designed and syn thesized in preparative amounts in vitro using T7 RNA polymerase. Stable S8-RNA complexes were crystallized. Crystals were obtained both for homologous bacterial and archaeal complexes and for hybrid complexes of archaeal protein with bac terial rRNA. Crystals of the complex of protein S8 from M. jannaschii with the 37 nucleotide rRNA fragment from the same organism suitable for X ray analysis were obtained

THE AIDS PATIENT SUFFERING FROM GENERALIZED MYCOBACTERIOSIS

The clinical case of mycobacteriosis caused by drug resistant strains of M. avium (subspecies of hominissuis), was observed in the patient su}ering from HIV at the stage of AIDS. The severity of immune deficiency and the absence of opportunity for antibacterial and antiviral therapy promoted the rapid progression of mycobacteriosis, early lymphogeneous generalization and the lethal outcome in 16 months from the start of the disease. Mycobacteriosis in this clinical case was specifically characterized by the massive bacterial semination, the absence of specific granulomatous changes in parenchymal organs, massive lesion of lymph nodes with extensive necrosis and the presence of para-specific changes. It highlights the similarity of mycobacteriosis pathogenesis with pathogenesis of primary tuberculosis

Генерализованный микобактериоз у пациента с ВИЧ-инфекцией на стадии СПИДа

The clinical case of mycobacteriosis caused by drug resistant strains of M. avium (subspecies of hominissuis), was observed in the patient su}ering from HIV at the stage of AIDS. The severity of immune deficiency and the absence of opportunity for antibacterial and antiviral therapy promoted the rapid progression of mycobacteriosis, early lymphogeneous generalization and the lethal outcome in 16 months from the start of the disease. Mycobacteriosis in this clinical case was specifically characterized by the massive bacterial semination, the absence of specific granulomatous changes in parenchymal organs, massive lesion of lymph nodes with extensive necrosis and the presence of para-specific changes. It highlights the similarity of mycobacteriosis pathogenesis with pathogenesis of primary tuberculosis.Наблюдали микобактериоз, вызванный лекарственно-устойчивым штаммом M. avium (подвид hominissuis), у больного ВИЧ-инфекцией на стадии СПИДа. Тяжесть иммунодефицита и невозможность провести антибактериальную и противовирусную терапию способствовали стремительному прогрессированию микобактериоза, ранней лимфогематогенной генерализации и летальному исходу спустя 16 мес. от начала заболевания. Особенностями микобактериоза в данном случае являются массивность бакте­риального обсеменения, отсутствие специфических гранулематозных изменений в паренхиматозных органах, массивное поражение лимфоузлов, некротизированных на большем протяжении, и наличие параспецифических изменений. Это подчеркивает сходство патогенеза микобактериоза с патогенезом первичного туберкулеза легких

Structure of ribosomal protein TL5 complexed with RNA provides new insights into the CTC family of stress proteins

The crystal structure of Thermus thermophilus ribosomal protein TL5 in complex with a fragment of Escherichia coli 5S rRNA has been determined at 2.3 Å resolution. The protein consists of two domains. The structure of the N-terminal domain is close to the structure of E. coli ribosomal protein L25, but the C-terminal domain represents a new fold composed of seven -strands connected by long loops. TL5 binds to the RNA through its N-terminal domain, whereas the C-terminal domain is not included in this interaction. Cd2+ ions, the presence of which improved the crystal quality significantly, bind only to the protein component of the complex and stabilize the protein molecule itself and the interactions between the two molecules in the asymmetric unit of the crystal. The TL5 sequence reveals homology to the so-called general stress protein CTC. The hydrophobic cores which stabilize both TL5 domains are highly conserved in CTC proteins. Thus, all CTC proteins may fold with a topology close to that of TL5