Effect of magnetic field on melt flow and crystal growth of oxide crystals

The flow in an oxide melt such as LiNbO, and TiO₂ in a high magnetic field was observed by using magnetic-field-applied Czochralski equipment for oxide crystals. It was found that the flows in oxides melts were very much different from these in a semiconductor melt. The single crystals of TiO₂ were grown in a magnetic field by using this equipment.     

Rigid‐plastic hybrid element analyses of the plane strain upsetting

A rigid‐plastic hybrid element method (HEM) for simulation of metal forming is developed. This method is a mixed approach of the rigid‐plastic domain‐BEM and the rigid‐plastic FEM based on the theory of compressible plasticity. Because the compatibilities of not only velocity but also velocity's derivative between the adjoining boundary elements and finite elements can be met, the velocities and the derivatives of the velocity can be calculated with the same precision for the rigid‐plastic HEM. Then, it is considered that the rigid‐plastic HEM is a more precise method in formulation than the conventional rigid‐plastic FEMs for which the compatibilities of velocity's derivative cannot be met. The plane strain upsetting processes with two friction factors are analyzed by the rigid‐plastic HEM in this article. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 726–737, 2002; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/num.10031.     

Inter- and intramolecular differentiation of enantiotopic dioxane acetals through oxazaborolidinone-mediated enantioselective ring-cleavage reaction: kinetic resolution of racemic 1,3-alkanediols and asymmetric desymmetrization of meso-1,3-polyols

Acetals derived from racemic 1,3-alkanediols undergo kinetic resolution in chiral oxazaborolidinone-mediated ring-cleavage reaction with nucleophiles such as enol silanes and allylic silanes. Enantioselectivity of the reaction is affected by nucleophiles, the N-sulfonyl groups of oxazaborolidinones, and the substituents attached to the acetal carbon. For disubstituted acetals rac-1 and for trisubstituted acetal rac-2, derived from syn-2,4-dimethyl-1,3-pentanediol, satisfactory enantioselectivity is obtained by using methallylsilane 7b,c as a nucleophile in combination with N-mesyloxazaborolidinone 4a. On the other hand, enantioselective reaction of trisubstituted acetal rac-3b, derived from anti-2,4-dimethyl-1,3-pentanediol, is realized by using silyl ketene acetal 5e in combination with N-tosyloxazaborolidinone 4b. The reaction conditions optimized for the kinetic resolution, or enantiomer differentiating reaction, of the racemic acetals are successfully applied to asymmetric desymmetrization of meso-1,3-polyols through intramolecular differentiation of the enantiotopic acetal moieties of the bis-acetal derivatives. The utility of the ring-cleavage reaction as a method for enantioselective terminal differentiation of prochiral polyols is demonstrated in convergent asymmetric synthesis of pentol derivative 35 corresponding to the C(19)[bond]C(27) ansa-chain of rifamycin S.     

Brominated unsaturated fatty acids from marine sponge collected in Papua New Guinea

New brominated fatty acids (3, 5-8, 10) and new sterol esters (14-16) have been isolated from an unidentified marine sponge collected in Papua New Guinea. Their structures were determined on the basis of their spectroscopic data. A major component of the marine sponge (1) was tested for activities against Arutemia salina and some fungi.     

Determination of paroxetine in serum treated with simple pretreatment by pre‐column high‐performance liquid chromatography using 4‐(5,6‐dimethoxy‐2‐phthalimidinyl)‐2‐methoxyphenylsulfonyl chloride as a fluorescent labeling reagent

The therapeutic drug monitoring of paroxetine could be used to optimize the pharmacological treatment of depressed patients. A simple and sensitive high‐performance liquid chromatography procedure was developed for the determination of paroxetine in serum. After simple pretreatment of serum (50 μL) with acetonitrile and o‐phthalaldehyde, paroxetine was derivatized with 4‐(5,6‐dimethoxy‐2‐phthalimidinyl)‐2‐methoxyphenylsulfonyl chloride at 70°C for 20 min in borate buffer (0.1 mol/L, pH 8.0) to produce a fluorescent product. The derivative was separated on a reversed‐phase column at 40°C for stepwise elution with (A) acetic acid (10 mmol/L) and (B) acetonitrile. The flow rate was 1.0 mL/min. The fluorescence intensity was monitored at excitation and emission wavelengths of 320 and 400 nm, respectively. The within‐day and day‐to‐day relative standard deviations were 3.0–3.4 and 2.7–8.3%, respectively. The detection limit of paroxetine was 8.3 fmol at a signal‐to‐noise ratio of 3. As the proposed method that only requires a small quantity of serum (50 μL) is simple, sensitive and reproducible, it would be useful for clinical and biochemical research as well as drug monitoring. Copyright © 2013 John Wiley & Sons, Ltd.     

Detection of peptide-phospholipid interaction sites in bilayer membranes by 13C NMR spectroscopy: observation of 2H/31P-selective 1H-depolarization under magic-angle spinning

We have developed a solid-state NMR method for observing the signals due to 13C spins of a peptide in the close vicinity of 31P and 2H spins in deuterated phospholipid bilayers. The signal intensities in 13C high-resolution NMR spectra directly indicate the depolarization of 1H by 1H-31P and 1H-2H dipolar couplings under multiple-contact cross-polarization. This method was applied to a fully 13C-, 15N-labeled 14-residue peptide, mastoparan-X (MP-X), bound to phospholipid bilayers whose fatty acyl chains are deuterated. The 13C NMR spectra for the depolarization were simulated from the chemical shifts and structure of membrane-bound MP-X previously determined and the distribution of 2H and 31P spins in lipid bilayers. The minimization of RMSD between the simulated and the experimental spectra showed that the amphiphilic alpha-helix of MP-X was located in the interface between the water layer and the hydrophobic domain of the bilayer, with nonpolar residues facing the phosphorus atoms and alkyl chains of the lipids.     

Determination of bisphenol-A in water by semi-micro column high-performance liquid chromatography using 2-methoxy-4-(2-phthalimidinyl)phenylsulfonyl chloride as a fluorescent labeling reagent.

A highly sensitive method for the determination of bisphenol-A in water with semi-micro column high-performance liquid chromatography using 2-methoxy-4-(2-phthalimidinyl)phenylsulfonyl chloride as a fluorescent labeling reagent has been developed. The labeling reaction was carried out at 70 degrees C for 20 min in borate buffer (pH 9.5). The derivative eluted at 11.6 min on a reversed-phase column with methanol-water (78:22, v/v) at a flow-rate of 0.2 ml/min. The fluorescence was monitored at 308 nm for excitation and 410 nm for emission. The detection limit (S/N = 3) was 10 fmol per injection. The labeling yield was about 95%.     

Pulsed differential optical absorption spectroscopy applied to air pollution measurement in urban troposphere

Differential optical absorption spectroscopy (DOAS) is useful for various types of trace gas measurements in the lower troposphere. In this paper, we report the DOAS measurement conducted in Chiba, Japan during 2009 and 2010. An optical path length of 5.5 km is employed to measure the average concentration of NO₂ using a xenon aviation obstruction light that flashes every 1.5 s. By virtue of the high stability of the light source intensity, the intensity measurement enables the retrieval of aerosol extinction coefficient averaged over the optical path. The results are compared with the concurrent results of ground sampling and sunphotometer measurements.     

Humidity-Induced Switching between Two Magnetic and Structural Phases in a CoII-[WV(CN)8] Molecular Magnet

The self-assembly of cobalt(II) with purine and octacyanidotungstate(V) results in the formation of the three-dimensional Co₃[W(CN)₈]₂(purine)₂ ⋅ 8.5H₂O ( 1 ) coordination polymer. This compound exhibits humidity-induced variation of the number of water molecules of crystallisation leading to a reversible structural phase transition and the alternation of the long-range ferromagnetic ordering temperature from T_C=29 K for the pristine assembly ( 1 ) to T_C=49 K for the sample stored in a low-humidity atmosphere ( 1-deh ). This phenomenon can be attributed to a reversible change in the hydrogen-bonding network resulting in the modification of the local geometries of cobalt(II) as well as the cyanido bridges.