Isospin bounds for energy partition in ee and NN annihilation

In reactions such as $\text{e}$e → anything, $\text{N}$N → anything, the final state (neglecting secondary isospin violating decays) is customarily supposed to have isospin zero or one. We show that for such states the average fraction (X) of the energy carried away by neutral pions is bounded by $\text{X<}\text{(9+√41)}\text{20}\text{≈0.77}$, when I₃ = 0 (e.g., for ee, pp, nn) and by $\text{X>}\text{(11?√41)}\text{40}\text{≈0.115}$, when I₃=±1 (e.g., for pn or np).     

Biosynthesis of the unique amino acid side chain of butirosin: possible protective-group chemistry in an acyl carrier protein-mediated pathway

Butirosins A and B are naturally occurring aminoglycoside antibiotics that have a (2S)-4-amino-2-hydroxybutyrate (AHBA) side chain. Semisynthetic addition of AHBA to clinically valuable aminoglycoside antibiotics has been shown both to improve their pharmacological properties and to prevent their deactivation by a number of aminoglycoside-modifying enzymes involved in bacterial resistance. We report here that the biosynthesis of AHBA from L-glutamate, encoded within a previously identified butirosin biosynthetic gene cluster, proceeds via intermediates tethered to a specific acyl carrier protein (ACP). Five components of the pathway have been purified and characterized, including the ACP (BtrI), an ATP-dependent ligase (BtrJ), a pyridoxal phosphate-dependent decarboxylase (BtrK), and a two-component flavin-dependent monooxygenase system (BtrO and the previously unreported BtrV). The proposed biosynthetic pathway includes a gamma-glutamylation of an ACP-derived gamma-aminobutyrate intermediate, possibly a rare example of protective group chemistry in biosynthesis.     

The growth of a single crystal of Sr3CuIrO6 and its magnetic behavior compared to polycrystals

We have grown single crystals of the psuedo-one-dimensional compound Sr₃CuIrO₆, a K₄CdCl₆-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence for at least two magnetic transitions, at 5 K (T ₁) and 19 K (T ₂), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of both the forms is found to be widely different, exhibiting unexpected time dependence.     

The chromatographic analysis of organic peroxides

Organic peroxides can be identified by reversed-phase chromatography on siliconc-treated paper, a chloroform-ethanol-water mixture is used as solvent, and the spray reagent is acidified ferrous thiocyanate.Peroxides of low molecular weight are lost from the paper by volatilisation, these can be identified and estimated by vapour-phase chromatography.     

Emanation thermal analysis study of synthetic gibbsite

Emanation thermal analysis (ETA) was used for thermal characterization of microstructure changes taking place during heating of synthetic gibbsite sample in argon in the range of 25–1200°C. Microstructure development and the increase of the surface area under in-situ conditions of the sample heating were characterized. The increase of the radon release rate from 130–330°C monitored the increase of the surface area due to the dehydration of Al(OH)₃. During heating of the sample in the range 450–1080°C the ETA results characterized the annealing of surface and near surface structure irregularities of intermediate products of gibbsite heat treatment. The mathematical model for the evaluation of the ETA experimental results was proposed. From the comparison of the experimental ETA results with the model curves it followed that the model is suitable for the quantitative characterization of microstructure changes taking place on heating of gibbsite sample. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nucleophilicity in ionic liquids. 2.(1) Cation effects on halide nucleophilicity in a series of bis(trifluoromethylsulfonyl)imide ionic liquids

In this work, the nucleophilicities of chloride, bromide, and iodide have been determined in the ionic liquids [bmim][N(Tf)(2)], [bm(2)im][N(Tf)(2)], and [bmpy][N(Tf)(2)] (where bmim = 1-butyl-3-methylimidazolium, bm(2)im = 1-butyl-2,3-dimethylimidazolium, bmpy = 1-butyl-1-methylpyrrolidinium, and N(Tf)(2) = bis(trifluoromethylsulfonyl)imide). It was found that in the [bmim](+) ionic liquid, chloride was the least nucleophilic halide, but that changing the cation of the ionic liquid affected the relative nucleophilicities of the halides. The activation parameters DeltaH(), DeltaS(), and DeltaG() have been estimated for the reaction of chloride in each ionic liquid, and compared to a similar reaction in dichloromethane, where these parameters were found for reaction by both the free ion and the ion pair.