Study of D_s~±→μ~±V_μ at Belle

We present a preliminary measurement of the B(D_s→μν_μ)with the Belle experiment at the KEKB collider.We select D~s→μV_μdecays with a method that provides a high-purity of the selected sample and an absolute measurement of the branching fraction.The results are based on a data sample of 550 fb~(-1)and are compared to similar measurements by other experiments as well as to the predictions of LQCD.We conclude with short prospects for improvements in the accuracy of the measurement.     

Selective and Efficient Removal of Fluoride from Water: In Situ Engineered Amyloid Fibril/ZrO2 Hybrid Membranes

We report a new strategy for efficient removal of F^? from contaminated water streams, and it relies on carbon hybrid membranes made of amyloid fibril/ZrO₂ nanoparticles (<10 nm). These membranes exhibit superior selectivity for F^? against various competitive ions, with a distribution coefficient (K_d) as high as 6820 mL g^?1, exceeding commercial ion‐exchange resins (IRA‐900) by 180 times and outdoing the performance of most commercial carbon‐activated aluminum membranes. At both low and high (ca. 200 mg L^?1) F^? concentrations, the membrane efficiency exceeds 99.5 % removal. For real untreated municipal tap water (ca. 2.8 mg L^?1) under continuous operating mode, data indicates that about 1750 kg water m^?2 membrane can be treated while maintaining drinking water quality, and the saturated membranes can be regenerated and reused several times without decrease in performance. This technology is promising for mitigating the problem of fluoride water contamination worldwide.     

Synthesis and biological activity of diastereoisomeric octahydro-1H-indole-5,6,7-triols,analogues of castanospermine

A straightforward stereoselective route towards (3aR,5R,6S,7R,7aR)- and (3aR,5R,6S,7R,7aR)-octahydro-1H-indole-5,6,7-triol, analogues of castanospermine, starting from the corresponding shikimic acid derivatives is described. The key transformations of this approach are the Overman rearrangement and ring-closing metathesis to form the diastereoisomeric cis-fused (5R,6S,7R)-octahydro-1H-indole-5,6,7-triols in good overall yields. Evaluation for in vitro cytotoxicity revealed for some prepared compounds significant antiproliferative activity and weak glycosidase inhibition.     

Experimental and theoretical studies of the C2F4 + O reaction: nonadiabatic reaction mechanism

In this work, the C(2)F(4)(X(1)A(g)) + O((3)P) reaction was investigated experimentally using molecular beam-threshold ionization mass spectrometry (MB-TIMS). The major primary products were observed to be CF(2)O (+ CF(2)) and CF(3) (+ CFO), with measured approximate yields of % versus %, respectively, neglecting minor products. Furthermore, the lowest-lying triplet and singlet potential energy surfaces for this reaction were constructed theoretically using B3LYP, G2M(UCC, MP2), CBS-QB3, and G3 methods in combination with various basis sets such as 6-31G(d), 6-311+G(3df), and cc-pVDZ. The primary product distribution for the multiwell multichannel reaction was then determined by RRKM statistical rate theory and weak-collision master equation analysis. It was found that the observed production of CF(3) (+ CFO) can only occur on the singlet surface, in parallel with formation of ca. 5 times more CF(2)O(X) + CF(2)(X(1)A(1)). This requires fast intersystem crossing (ISC) from the triplet to the singlet surface at a rate of ca. 4 x 10(12) s(-1). The theoretical calculations combined with the experimental results thus indicate that the yield of triplet CF(2)(?(3)B(1)) + CF(2)O formed on the triplet surface prior to ISC is < or =35%, whereas singlet CF(2)(X(1)A(1)) + CF(2)O is produced with yield > or =60%, after ISC. In addition, the thermal rate coefficients k(O + C(2)F(4)) in the T = 150-1500 K range were computed using multistate transition state theory and can be expressed as k(T) = 1.67 x 10(-16) x T(1.48) cm(3) molecule(-1) s(-1); they are in agreement with the available experimental results in the T = 298-500 K range.     

Analysis of NMR J couplings in partially protected galactopyranosides

[carbohydrate structure: see text] Hydrogen bond mediated NMR J couplings offer additional structural information. The interpretation of these usually small (h)J couplings are, however, not necessarily straightforward. In the present case of a carbohydrate system, a four-bond classical W coupling, (4)J(HO4,H5), is more reasonable on the basis of, in particular, density functional theory calculations of spin-spin coupling constants at the UB3LYP/6-311G** level of theory.     

Formation of the 1∶2∶3 structure in Y-Ba-Cu(Fe)-O system studied by Mössbauer spectroscopy

Annealing time and temperature dependence of Y, Ba, Cu, Fe nitrade mixture towards new phases creation was revealed by Mössbauer spectroscopy. The observed changes can be assigned to chemical decomposition of corresponding nitrades and creation of intermedial and final Y₁Baz(Cuo.o3Feo. o3)3Ox phase.     

Crystallization of some amorphous metallic alloys studied by Mössbauer spectroscopy

The present work provides an analysis of crystallization processes in amorphous metallic alloys Fe₈₀Si₄Cr_1.0B₁₄ and Fe₆₇Co₁₈B₁₄Si₁. Crystallization of the first sample started at the temperature of 648 K. The fully crystalline state was observed after annealing at 748 K. We identified four sextets. One corresponds to crystalline Fe₂B and the three others to FeSi solid solution with 10 at .% of Si. Crystallization of Fe₆₇Co₁₈B₁₄Si₁ started at the temperature of 623 K. We identified two crystalline phases. The first may have its origin as (Fe_1−xCo_x)₃B, the second one may correspond to a Fe−Co solid solution with a different Co content.     

Internal dynamics of hydroxymethyl rotation from CH2 cross-correlated dipolar relaxation in methyl-beta-D-glucopyranoside

Conventional relaxation parameters (T1(-1), T2(-1), and NOE), obtained at different temperatures and magnetic fields, are reported for the hydroxymethyl (C6) carbon in methyl-beta-D-glucopyranoside in a D2O/DMSO cryosolvent. These data are interpreted with the Lipari-Szabo model. In addition, two-field measurements of longitudinal and spin-locked relaxation rates related to the cross-correlated carbon-proton dipole-dipole interactions for the same carbon are reported. The complete data set consisting the conventional and cross-correlated relaxation parameters is interpreted using a new "hybrid" approach, in which the Lipari-Szabo model for the auto-correlated spectral densities is combined with the two-site jump model for the cross-correlated spectral densities, with the global correlation time as a common parameter. The two-site jump rates thus obtained are in reasonable agreement with the ultrasonic relaxation measurements, and have reasonable temperature dependence.     

Mechanism of the catalytic oxidation of hydrocarbons by N-hydroxyphthalimide: a theoretical study

The mechanism of the recently proposed catalytic oxidation of hydrocarbons by oxygen in the presence of N-hydroxyphthalimide (NHPI) was established by quantum chemical calculations, consistent with experiments.     

The Bellus-Claisen rearrangement

Among the reactions available to synthetic chemists for the construction of new C--C bonds, the Claisen rearrangement is one of the most powerful, elegant, and well-characterized methods. A genuinely new variant, the Bellus-Claisen rearrangement came to light a quarter of a century ago: The reaction of an allylic ether, thioether, or amine with a ketene leads through a [3,3] sigmatropic bond reorganization of a zwitterionic intermediate to an E unsaturated ester, thioester, or amide. When applied to cyclic allylic substrates, a ring-enlargement by four carbon atoms in one step provides medium-ring unsaturated E-configured lactones, thiolactones, and lactams. The scope of the Bellus-Claisen rearrangement and the optimum reaction conditions will be discussed in this Minireview.