Analysis of the results of calibrating meteoritic olivine crystals with238U nuclei at the Bevalac accelerator

The results are presented of calibrating the sensitivity of olivine crystals from meteorites by the²³⁸U nuclei produced at the Bevalac accelerator. The comparative studies of the spectra of the etchable track lengths due to the²³⁸U nuclei and to fossil tracks in these olivines have shown that the group of the 210 m fossil tracks observed in 1980 at the LNR, JINR is due to the galactic cosmic-ray nuclei of the Th-U group. As regards the origin of the 340–360 m group of fossil tracks which were considered in [2] to be candidates for superheavy nuclei in cosmic rays the presence of the track with a length of up to 360 m in the calibrating²³⁸U track length spectra indicates that the above interpretation has to be questioned. The possible ways of the unambiguous identification of the group of the abnormally long fossil tracks are discussed.In conclusion the authors express their deep gratitude to Academician G.N. Flerov for thoughtful guidance and permanent attention to this study. The authors wish to thank Dr. G.M. Ter-Akopian for very useful discussions and advice and also for his help during the calibrations on Bevalac, Dr. R.I. Petrova for her help in preparing olivine crystal mounts and for their subsequent annealing and etching, and Mrs. G.G. Bankova and G.P. Knyazeva for the thorough microscopic measurements of the²³⁸U track spectra.     

Space structure of a fireball and the pion radius

Results of calculation of the fireball radius as measured by means of the Hanbury-Brown and Twiss (HBT) effect are interpreted in the context of Landau's hydrodynamical model. A method based on a simple geometric picture of fireball formation is used to deduce the pion radius. From available data of various \(\bar p\) p annihilations andπ ^± p,K ⁺ p collisions, it is foundr _π=0.76±0.22 fm. A derivation is given on the decoherence factor of the Kopylov formula. A discussion is presented on other applications of the HBT effect to particle physics.     

Structure, stereochemistry, and biological activity of integramycin, a novel hexacyclic natural product produced by Actinoplanes sp. that inhibits HIV-1 integrase

[structure: see text] HIV-1 integrase is a critical enzyme for viral replication, and its inhibition is an emerging target for potential antiviral chemotherapy. We have discovered a novel inhibitor, integramycin, from screening of fermentation extracts using an in vitro assay. Integramycin possesses a hexacyclic ring system and exhibited an IC50 value of 4 microM against HIV-1 integrase (strand transfer). The isolation, structure elucidation, stereochemistry, conformation, and biological activity has been described.     

Preparation of sinapinaldehyde modified mesoporous silica materials and their application in selective extraction of trace Pb(II)

A new solid phase extractant, sinapinaldehyde (SA) modified SBA-15 mesoporous silica, was developed for selective extraction and preconcentration of trace Pb(II) from aqueous solutions. The successful immobilization of SA on SBA-15 and the strong interaction between SA-SBA-15 and Pb(II) were characterized and confirmed by FTIR spectroscopy and scanning electron microscopy. Parameters such as solution pH, shaking time, eluent condition and sample volume were optimized so that the maximum removal of Pb(II) from solution could be achieved. At pH 4.0, the maximum adsorption capacity of the sorbent for Pb(II) was found to be 33.6?mg?g^?1 and the adsorbed Pb(II) could be completely eluted using a mixed solution of 2?M HCl and 5% CS(NH₂)₂. Some common metal ions such as K(I), Na(I), Mg(II), Ca(II), Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) did not interfere with the adsorption of trace Pb(II). The detection limit of the present method was found to be 1.3?ng?mL^?1 and the relative standard deviation was less than 2.0% (n?=?8). These results suggested that this new sorbent is very efficient and selective for the removal of trace Pb(II) in water samples.     

Predicting the Outcome of Photocyclisation Reactions: A Joint Experimental and Computational Investigation

Photochemical oxidative cyclodehydrogenation reactions are a versatile class of aromatic ring‐forming reactions. They are tolerant to functional group substitution and heteroatom inclusion, so can be used to form a diverse range of extended polyaromatic systems by fusing existing ring substituents. However, despite their undoubted synthetic utility, there are no existing models—computational or heuristic—that predict the outcome of photocyclisation reactions across all possible classes of reactants. This can be traced back to the fact that “negative” results are rarely published in the synthetic literature and the lack of a general conceptual framework for understanding how photoexcitation affects reactivity. In this work, we address both of these issues. We present experimental data for a series of aromatically substituted pyrroles and indoles, and show that quantifying induced atomic forces upon photoexcitation provides a powerful predictive model for determining whether a given reactant will photoplanarise and hence proceed to photocyclised product under appropriate reaction conditions. The propensity of a molecule to photoplanarise is related to localised changes in charge distribution around the putative forming ring upon photoexcitation. This is promoted by asymmetry in molecular structures and/or charge distributions, inclusion of heteroatoms and ethylene bridging and well‐separated or isolated photocyclisation sites.     

A Study of Highly Qualified Science Teachers' Career Trajectory in the Deep,Rural South: Examining a Link Between Deprofessionalization and Teacher Dissatisfaction

Science teacher retention, attrition, and migration continue to perplex educational scholars, political entities, as well as the general public. This study utilized an interpretive methodological design to generate assertions regarding career choice made by highly qualified science teachers in the deep, rural South through analysis of documents, interviews, focus groups, and observation. Generally considered “difficult to staff” because of location, socioeconomics, and demographics, Wilson County High School is an exemplar in science teacher retention and student achievement. Findings presented include how the science department at Wilson County improved student learning outcomes as well as the reasons why two of the highly qualified science teachers at this school were considering leaving the profession they love.