Enantiospecific synthesis of optically pure (3s)-hydroxy esters by the stereocontrolled yeast reduction of α-sulfenyl-β-ketoesters

Stereocontrol in Baker's yeast reduction of β-ketoesters was successfully achieved by introducing the sulfenyl group at α-position of the esters to afford optically pure (S)-β-hydroxy esters.     

Circular dichroism of tail-to-tail bisbenzyliso-quinoline and the absolute configuration of daurisoline isolated from Menispermum dauricum

Since two asymmetric centres are usually present in the bisbenzylisoquinolines, the circular dichroism is known to be an important method to elucidate their stereochemistry. We studied the relationships of the CD spectra with the stereochemistry of synthetic RR-(1), SS-(2), RS-daurisoline (3) and SR-daurisoline (4). By comparision of the CD spectrum of natural daurisoline (1) from Menispermum dauricum (Menispermaceae) with those of synthetic enantiomers, the absolute configuration was established as RR-daurisoline (1).     

Adsorption of gas on ion exchangers. III. The pore structure of m-aminophenol–formaldehyde condensation resins

m-Aminophenol was condensed with formaldehyde in an acid medium in the presence of a water-soluble inorganic salt (NaCl, CaCl₂ etc) and/or poly(ethylene glycol). The pore structure characteristics of the condensation products were investigated by measurements of average pore size, pore size distribution of channels, total pore volume, surface area, and electron microscopic observation. The type and concentration of inorganic salts appeared to be a significant variable for the resulting pore structure, while poly(ethylene glycol) had a little effect. The nongel interstices of products were channels between many agglomerates of minute spherical gel particles with narrow pore size distribution. The diameters of these spherical gel particles were 3–10 × 10^?1µ from the scanning electron microscopic observation. Apparent dissociation constants of functional groups of resin, pK_a and pK_b, estimated by using the Henderson-Hasselbach equation, were 10.94 and 10.99, respectively. The resin had an ion-exchange capacity of 1.0 meq/g for base and 4.8 meq/g for acid.     

Layer-by-layer analysis of charge state distribution of field evaporated ions from the W(011) plane

A charge state distribution of the field evaporated ions is layer-by-layer analyzed in a W(011) plane by using an atom-probe field ion microscope. A specimen temperature is varied from ～ 20 to ～ 250 K. The results indicate that at any temperature, the surface tungsten atoms field evaporate as triply and quadruply ions from the (011) plane, and the quadruply charged ions are always detected during the final collapse of the plane. They are also discussed on the basis of the post-ionization model.     

Effect of synthesis conditions of polyallylamine-beads-glucose (PAA-Glu) on boron adsorption

In this study, we assessed the boron adsorption characteristic of our synthesized adsorbent: polyallylamine-beads-glucose (PAA-Glu) by using the adsorption amount and adsorption site availability (ASA), and determined the optimum conditions for PAA-Glu synthesis. ASA is our proposed indicator and it expresses the percentage of the experimental equilibrium adsorption in relation to the theoretical equilibrium adsorption and indicates the availability of adsorption sites (hydroxyl groups) on adsorbents. We investigated the effects of the degree of cross-linking (20, 40 and 60 %), the introduction amount of α-D-glucose (40, 60 and 80 %), and the introduction temperature (30–150 °C) as regards PAA-Glu on the boron adsorption amount. The boron adsorption amount for PAA-Glu (20 % cross-linked, 30 °C) was superior to that for another degree of cross-linked PAA-Glu. However, the ASA for PAA-Glu (60 % cross-linked, 30 °C) exhibited the best value in this synthesized PAA-Glu. Furthermore, we examined the introduction temperature at which glucose was introduced to PAA-Glu (20 % cross-linked) in the 30–150 °C range, and we confirmed that the optimum temperature range for the synthesis of PAA-Glu was 60–80 °C. We found that controlling the space between the main chains of the polymer by using a spacer such as a cross-linker allowed boron molecules to come and go and led to an improvement in the boron adsorption amount and ASA.     

Aggregation,gelation instability,and morphologies of diblock copolymers consisting of poly(p‐benzamide) and poly(m‐benzamide)

The solution, gelation, and morphological properties of monodisperse aromatic polyamide diblock copolymers consisting of poly(p‐benzamide) (PpBA), poly(m‐benzamide) (PmBA), and poly(N‐octyl m‐benzamide) (POmBA) were investigated. The block copolymers of these polymers, PpBA‐block‐POmBA and PmBA‐block‐POmBA, formed spherical micelles or amorphous aggregates in many solvents in addition to physical gels at concentrations higher than 5 wt %. A temperature‐induced sol‐gel transition was also exhibited for PpBA‐block‐POmBA in solvents with high boiling points such as N,N‐dimethylacetamide and N‐methylpyrrolidone (NMP), although the transition was not entirely thermoreversible; the transition temperature decreased by annealing at ～80 °C. Dynamic light scattering measurements of the PpBA‐block‐POmBA/NMP solutions revealed that metastable micelles in the sol state reorganized into smaller micelles upon annealing at 90 °C. The block copolymer, which forms strong associations, exhibited some transient structure as indicated by the need to sufficiently anneal the solution to reach equilibrium. Network‐like patterns with characteristic length of ～10 μm appeared on the gel surfaces upon evaporation of volatile solvents such as dichloromethane and chloroform, in which the copolymers were observed to aggregate. The unique properties of the copolymers originate from interactions between the highly polar N? H aromatic polyamide blocks. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1732–1739, 2010     

Effects of wing deformation on aerodynamic performance of a revolving insect wing

Flexible wings of insects and bio-inspired micro air vehicles generally deform remarkably during flapping flight owing to aerodynamic and inertial forces,which is of highly nonlinear fluid-structure interaction（FSI）problems.To elucidate the novel mechanisms associated with flexible wing aerodynamics in the low Reynolds number regime,we have built up a FSI model of a hawkmoth wing undergoing revolving and made an investigation on the effects of flexible wing deformation on aerodynamic performance of the revolving wing model.To take into account the characteristics of flapping wing kinematics we designed a kinematic model for the revolving wing in two-fold：acceleration and steady rotation,which are based on hovering wing kinematics of hawkmoth,Manduca sexta.Our results show that both aerodynamic and inertial forces demonstrate a pronounced increase during acceleration phase,which results in a significant wing deformation.While the aerodynamic force turns to reduce after the wing acceleration terminates due to the burst and detachment of leading-edge vortices（LEVs）,the dynamic wing deformation seem to delay the burst of LEVs and hence to augment the aerodynamic force during and even after the acceleration.During the phase of steady rotation,the flexible wing model generates more ver-tical force at higher angles of attack（40°–60°）but less horizontal force than those of a rigid wing model.This is because the wing twist in spanwise owing to aerodynamic forces results in a reduction in the effective angle of attack at wing tip,which leads to enhancing the aerodynamics performance by increasing the vertical force while reducing the horizontal force.Moreover,our results point out the importance of the fluid-structure interaction in evaluating flexible wing aerodynamics：the wing deformation does play a significant role in enhancing the aerodynamic performances but works differently during acceleration and steady rotation,which is mainly induced by inertial force in acceleration but by aerodynamic forces