Prompt k 0-factors and relative gamma-emission intensities for the strong non-1/v absorbers 113Cd, 149Sm, 151Eu and 155,157Gd

Prompt k ₀-factors relative to chlorine and relative g-emission intensities were determined for the strong non-1/v absorbers ¹¹³Cd, ¹⁴⁹Sm, ¹⁵¹Eu,¹⁵⁵Gd and ¹⁵⁷Gd. Measurements were performed using the SNU-KAERI prompt gamma activation analysis (PGAA) facility at the Korea Atomic Energy Research Institute (KAERI). For proper experimental determination of the prompt k ₀-factors, the effective g-factor and cadmium ratio were taken into account, in consideration of the effects from the non-1/v capture cross section and neutron spectrum in the thermal and epithermal energy region. By using the actual spectrum of the neutron beam in this study, the effective g-factor was obtained by calculation, and the influence of epithermal neutrons on the capture rate was corrected by measuring the cadmium ratio for each non-1/v target isotope. The measured prompt k ₀-factors were used to check the consistency between the existing dataset of the absolute g-emission intensity and the 2200 m/s capture cross section for these isotopes.     

Mono- and Dinuclear d(10) Metal Complexes of Hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene. Synthesis, Structures, and Unusual Solution Dynamic Behavior

Synthesis, structures, and unusual solution dynamic processes of d(10) metal complexes of hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene (L) are reported. Reaction systems with three MX(n):L mole ratios (MX(n) = d(10) metal halide) in CH(2)Cl(2) have resulted in the formation of [ICu(&mgr;,eta(3),eta(3)-L)CuI] (1), [Cl(2)Zn(&mgr;,eta(2),eta(3)-L)ZnCl(2)] (2), [Cl(2)Cd(&mgr;,eta(3),eta(3)-L)CdCl(2)] (3), and [(eta(3)-L)HgCl(2)] (4). These compounds were characterized by single crystal X-ray diffraction studies, and crystallographic data are given in the order of compound: crystal system; space group; unit cell parameters; Z; unique data (I > 2sigma(I)); R(1). 1.0.5CH(2)Cl(2): monoclinic; P2(1)/c; a = 8.268(4) ?; b = 22.365(5) ?; c = 23.325(8) ?, beta = 93.06(1) degrees; 4; 5736; 4.82. 2.CH(3)CN: monoclinic; P2(1)/c; a = 17.021(3) ?; b = 12.161(2) ?; c = 23.608(5) ?; beta = 107.72(1) degrees; 4; 5469; 3.16. 3.CH(2)Cl(2): monoclinic; P2(1)/n; a = 18.585(5) ?; b = 17.585(4) ?; c = 14.404(3) ?; beta = 102.71(2) degrees; 4; 3814; 3.65. The structure of 4 was attempted but resulted in data of low precision. Reaction of L with CuI and ZnCl(2) in an equimolar ratio afforded [ICu(&mgr;,eta(3),eta(3)-L)ZnCl(2)] (5) which crystallizes in monoclinic space group P2(1)/n with a = 22.876(5) ?, b = 21.594(4) ?, c = 9.177(2) ?, beta = 93.54(2) degrees, Z = 4, and R(1) = 7.00 for 3806 (I > 2sigma(I)) data. In all cases, metal halide centers except the Td zinc site in 2 are coordinated by L via a kappa(3)N binding core consisting of two nongeminal pyrazolyl nitrogen atoms and one phosphazene ring nitrogen atom. The eta(2)-N(2) coordination in 2 involves two geminal pyrazolyl nitrogen atoms. Factors which govern the nuclearity of the complex were partially demonstrated. The intermetallic distances in dinuclear metallophosphazenes range from 6.790 to 7.195 ?. The solution behavior of five compounds was studied by variable temperature (31)P{(1)H}, (1)H, and (113)Cd FT NMR spectroscopy. Compounds 1 and 4 are associated with fluxional motions involving A(2)B low-temperature limit spectrum while compounds 2 and 5 show solvent-dependent dynamic processes with ABX and A(2)B low-temperature limit spectral patterns. Compounds 3 constitutes a fluxional system involving three A(2)B species. Accounts of solution NMR spectra were attempted by using PANIC, by assuming the formation of new solution metallophosphazene species and by considering several types of dynamic processes such as a ring-around type hopping motion for the kappa(3)N metal site, a Td conformational change for the geminal pyrazolyl kappa(2)N metal site, and a wigwag motion for the nongeminal pyrazolyl kappa(2)N metal unit.     

Synthesis of ceramide analogues having the C(4)-C(5) bond of the long-chain base as part of an aromatic or heteroaromatic system

Two efficient and stereoselective methods are described for the preparation of aryl and heteroaryl ceramide analogues 2 and 3. The first route involves the addition of an aryllithium or a heteroaryllithium reagent (7a or 25a, respectively) to the L-serine-derived aldehyde 4, followed by hydrolysis of the oxazolidine, liberation of the amino group, and N-acylation. The second route, which was used to prepare arylceramide analogue 2 in eight steps and 28% overall yield starting with 3-bromobenzaldehyde, utilizes a Heck reaction to afford (E)-alpha,beta-unsaturated ester 16, then osmium-catalyzed asymmetric dihydroxylation for the introduction of the desired chirality at C-2 and C-3. Regioselective alpha-azidation of alpha-O-nosyl-beta-hydroxyester 18 with sodium azide, followed by LiAlH(4) reduction of the azido and ester groups and N-acylation, complete the synthesis of arylceramide analogue 2.     

Nonlinear obstacle problems with double phase in the borderline case

In this paper we study a double phase problem with an irregular obstacle. The energy functional under consideration is characterized by the fact that both ellipticity and growth switch between a type of polynomial and a type of logarithm, which can be regarded as a borderline case of the double phase functional with $(p,q)$-growth. We obtain an optimal global Calderón–Zygmund type estimate for the obstacle problem with double phase in the borderline case.     

Detection of Chemical Warfare Nerve Agents via a Beckmann Fragmentation of Aldoxime

Abstract

A new (E)-pyrene-1-carbaldehyde O-tert-butyldimethylsilyl oxime 3 was synthesized for the detection of chemical warfare nerve agents, O-isopropyl methylphosphonofluoridate (GB) and O-pinacolyl methylphosphonofluoridate (GD). ¹H NMR spectrum showed that the tert-butyldimethylsilyl (TBDMS) group was deprotected using TBAF and the oximate supernucleophile was made. Upon addition of chemical warfare agents (GB and GD) (50 mol%), the reaction was completely finished within 5 min and also the color change of reaction mixture was observed under a hand-held UV lamp with the naked eye.     

An Improved Direct Oxidation of Alkyl Halides to Aldehydes

The oxidation of alkyl chlorides and bromides with dimethyl sulfoxide has been performed in the presence of sodium iodide. This method allows a convenient one-step procedure for the preparation of aldehydes from alkyl chlorides and bromides.