Highly enantioselective hydrogenation of (E)-beta-(acylamino)acrylates catalyzed by Rh(i)-complexes of electron-rich P-chirogenic diphosphines

Excellent enantioselectivities up to 99.7% were achieved in the hydrogenation of (E)-beta-(acylamino)acrylates by the use of Rh(I)-complexes of electron-rich diphosphines, t-Bu-BisP and t-Bu-MiniPHOS. Low-temperature NMR experiments testify that monohydrides with beta-carbon atom of the substrate bound to rhodium are involved in the catalytic cycle.     

Promoted random orientation of the phenyl substituent of phenylhydroquinone–terephthalic acid polyesters prepared with a diphenyl chlorophosphate/pyridine condensing agent

The reaction of sterically hindered hydroxyl groups at the 2-position of methylhydroquinone and phenylhydroquinone (PhHQ) to form esters was largely promoted by their slow addition to benzoic acid activated by diphenyl chlorophosphate in pyridine. A modification of this reaction was applied to the preparation of thermotropic terephthalic acid/PhHQ and 2,5-dichloroterephthalic acid/PhHQ polymers with randomly oriented phenyl substituents, and the properties of the polymers were studied in terms of their transition temperatures, which were determined by differential scanning calorimetry and microscopic observation. The melting points were lowered by about 30–50 °C by the dropwise addition of PhHQ over 10–30 min. The molecular structures of the 2,5-dichloroterephthalic acid/PhHQ polymers were studied by ¹³C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1726–1732, 2001     

Shock wave detection in two-dimensional flow based on the theory of characteristics from CFD data

A method to detect the discontinuity of a shock wave from computational fluid dynamics (CFD) data was developed based on the theory of characteristics and was adopted to replace the inaccurate method that involves observation of the location of steep spatial gradient with respect to the primitive variables, such as pressure. A shock wave is mathematically defined as a convergence of characteristics, in which each type of Riemann invariant is conserved within each characteristic. In the vector field of the characteristics, such convergences are interpreted as critical lines of the streamlines, which are easily identified by calculating the eigenvectors of the vector field of propagation velocity of the Riemann invariant. The use of a triangular cell system enables unique determination of the linearized vector field in each cell and enables analytical identification of the critical line within this field. Shock waves can be successfully extracted using this method. The method can be extended to the detection of moving shock waves by considering the coordinate moving with the shock.     

A novel microreactor approach for analysis of ketones and aldehydes in breath

We report a fabricated microreactor with thousands of micropillars in channels. Each micropillar surface is chemically functionalized to selectively preconcentrate gaseous ketones and aldehydes of exhaled breath and to enhance ultra-trace, rapid analysis by direct-infusion Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry (MS). The micropillar reactive coating contains the quaternary ammonium aminooxy salt 2-(aminooxy)ethyl-N,N,N-trimethylammonium iodide (ATM) for capturing trace carbonyl VOCs by means of an oximation reaction. We demonstrate the utility of this approach for detection of C(1) to C(12) aldehydes and ketones in exhaled breath, but the approach is applicable to any gaseous sample.     

Effect of polymer addition amount and type on thermal decomposition behavior of spray-dried particles comprising ammonium nitrate,potassium nitrate,and polymer

Certain properties of ammonium nitrate (AN), such as high hygroscopicity and the thermal transformation of the crystal structure accompanied by volume changes, pose problems for industrial applications of AN. To solve these problems, we previously prepared AN-based particles by spray-drying. The particles contained potassium nitrate (PN) as a phase stabilizer and a polymer (e.g., PVA, CMCs, and Latex) to produce a moisture-resistant material. Herein, we investigate the thermal decomposition of spray-dried AN/PN/polymer particles by differential scanning calorimetry and Thermogravimetry–Differential thermal analysis. Comparison of the thermal decomposition of AN/PN/polymer materials with different amounts and types of polymers suggested that thermal decomposition at lower temperatures resulted from the reaction of AN with the molten polymer or decomposition products derived from the polymer. Therefore, it can be concluded that the thermal stability of the AN/PN/polymer was exclusively determined by the thermal properties of the polymer components.     

Synthesis of cyclodextrin‐based radial polycatenane cyclized by amide bond and subsequent fabrication of water‐soluble derivatives

Journal of Inclusion Phenomena and Macrocyclic Chemistry - In recent years, functional materials using cyclodextrin (CD)-based polyrotaxanes have attracted considerable attention, and...     

Preparation of high molecular weight polyhydrazides from hydrazine monohydrochloride using phenylphosphonic dichloride and phosphorus compounds as additives

Significantly high molecular weight poly(isophthalic dihydrazide) of inherent viscosity up to 1.6 (DMSO) was prepared by the reaction of isophthalic acid and hydrazine monohydrochloride using phenylphosphonic dichloride in the presence of phosphorus compounds such as phosphine oxides. The phosphorus compounds used as additives were assumed to be involved in the reaction through a complexation with the monohydrochloride, enhancing the reactivity of the hydrazine. It was attempted to prepare copoly(hydrazide-amides) with different monomer sequences by changing the relative reactivity between diamines and the hydrazine using the phosphorus compounds. The copoly(hydrazide-amide)s were studied in terms of the dehydration reaction of hydrazide groups into 1,3,4-oxadiazole groups. © 1993 John Wiley & Sons, Inc.     

Strong evidence of alpha-particle doorway states in 28Si observed in alpha-decays to low-lying states of 24Mg

Four ratios of alpha-particle decay probabilities to specific members of the K-bands of ²⁴Mg were measured at bombarding energies E_cm = 19.7 to 28.2 MeV. The energies for enhancement of these ratios correspond quite well to the 0⁺ resonances reported.     

超细纹理超塑性材料Zn-Al合金及其在无铅和地震减振装置方面的应用(英文)

pacc:7850C SincetheGreatHanshinEarthquakein 1995,manyinvestigationsontheseismicdamper havebeenmade.Ontheotherhand,italsotheo reticallyprojectedthatultrafinegrainedZn-Al alloyscouldshowsuperplasticityatlowtempera tures[1-4].Authorstriedtomakeamassiveultr…