Straightforward access to new vinca-alkaloids via selective reduction of a nitrile containing anhydrovinblastine derivative

A procedure to exclusively obtain 3′S-cyanoanhydrovinblastine 12 from two naturally occurring vinca-alkaloids (catharanthine and vindoline) in one step with good yield is described. Stereoselective reductions of 12, providing straightforward access to three new vinca-alkaloids, including two diastereomers 3′S-cyano-(4′R,5′-dihydro)-anhydrovinblastine and 3′S-cyano-(4′S,5′-dihydro)-anhydrovinblastine as well as (3′S-aminomethyl)-(4′S,5′-dihydro)-anhydrovinblastine in good yields is also reported.     

Copper ferrite superparamagnetic nanoparticles as a heterogeneous catalyst for directed phenol/formamide coupling

The copper ferrite-catalyzed, directed coupling of ortho-arylated phenols and dialkylformamides in the presence of a peroxide oxidant is described. Acyclic and cyclic amides were compatible with the reaction conditions. The copper ferrite catalyst is heterogeneous since substantial leaching was not detected and re-use of the catalyst for 9 consecutive reactions proceeded without a significant decrease in yield. To the best of our knowledge, this transformation has not been previously performed under heterogeneous catalysis conditions.     

A molecular dynamics simulation of a homogeneous organic-inorganic hybrid silica membrane

A new molecular dynamics simulation method was successfully applied to construct a homogeneous organic-inorganic hybrid silica membrane using the hybrid-pcff (h-pcff) potential function. Analysis suggested that the hybrid BTESE silica membrane provided a looser network and larger cavity size for the enhancement of gas permeability and selectivity.     

Asymmetric orbital-lattice interactions in ultrathin correlated oxide films

Using resonant x-ray spectroscopies combined with density functional calculations, we find an asymmetric biaxial strain-induced d-orbital response in ultrathin films of the correlated metal LaNiO3 which are not accessible in the bulk. The sign of the misfit strain governs the stability of an octahedral "breathing" distortion, which, in turn, produces an emergent charge-ordered ground state with an altered ligand-hole density and bond covalency. Control of this new mechanism opens a pathway to rational orbital engineering, providing a platform for artificially designed Mott materials.     

Development of a laser-based measurement system for evaluation of the scraping workpiece quality

A laser-based measurement system for evaluation of the scraping workpiece quality that can eliminate contact-induced measurement errors and increase measurement accuracy is proposed. The laser-based measurement system comprises a light-scattering-type triangulation laser, a computer numerical control (CNC) machine tool, and an analog-to-digital (A/D) card. The triangulation laser measures the depth of the scraping spots and the CNC machine tool locates their position. The 3D data of the scraping workpiece is then drawn using the least squares method. Cast iron and Turcite workpieces can be measured. Five parameters of the scraping workpiece, namely peak points per square inch, percentage of points, distribution of heights of points or depth of surroundings, edge shape of the grooves, and flatness, can be evaluated. The scanning rate and sampling rate of the laser-based measurement system are 100 mm/s and 10 KHz, respectively. In the future, an appliance machine based on the proposed system will be designed for the on-line detection of scraping workpieces.     

Atomic force microscopy-based repeated machining theory for nanochannels on silicon oxide surfaces

The atomic force microscopy (AFM)-based repeated nanomachining of nanochannels on silicon oxide surfaces is investigated both theoretically and experimentally. The relationships of the initial nanochannel depth vs. final nanochannel depth at a normal force are systematically studied. Using the derived theory and simulation results, the final nanochannel depth can be predicted easily. Meanwhile, if a nanochannel with an expected depth needs to be machined, a right normal force can be selected simply and easily in order to decrease the wear of the AFM tip. The theoretical analysis and simulation results can be effectively used for AFM-based fabrication of nanochannels.     

Energy transfer of ionic dyes in mixed surfactant vesicle

Stable vesicles composed of cationic and anionic single-tailed-surfactant were prepared, and their image obtained by electron microscopy with negative staining technique. Significant fluorescence enhancement for acridine orange in vesicle with regards to water has been observed. In heterogeneous vesicle solution composed of mixed cationic and anionic surfactants for the energy transfer between acridine orange (D) and pyronine (A), the Förster dipole-dipole model was valid, and it is interesting to note that the energy transfer rate constant (k_ET) was smaller than that in homogeneous aqueous solution. On the inside and outside of the stable vesicle, immiscible water solution of acridine orange and pyronine could be obtained, and the distance calculated from the energy transfer between D and A separated by the bilayer membrane implied that the location of ionic dye molecules was in the Gouy-Chapman layers of the vesicles. Furthermore, due to the electrostatic absorption of the dye molecules to charged headgroups of surfactants, acridine orange and pyronine accumulated and aggregated to the vesicle bilayer membrane.     

Nonisothermal crystallization kinetics of poly(ε‐caprolactone) blocks in double crystalline triblock copolymers containing poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and poly(ε‐caprolactone) units

The poly(3‐hydroxbutyrate‐co‐3‐hydroxyvalerate)/poly(ε‐caprolactone) block copolymers (PHCLs) with three different weight ratios of PCL blocks (38%, named PHCL‐38; 53%, named PHCL‐53; and 60%, named PHCL‐60) were synthesized by using PHBV with two hydroxyl end groups to initiate ring‐opening polymerization of ε‐caprolactone. During DSC cooling process, melt crystallization of PHCL‐53 at relatively high cooling rates (9, 12, and 15 °C min^?1) and PHCL‐60 at all the selected cooling rates corresponded to PCL blocks so that PHCL‐53 and PHCL‐60 were used to study the nonisothermal crystallization behaviors of PCL blocks. The kinetics of PCL blocks in PHCL‐53 and PHCL‐60 under nonisothermal crystallization conditions were analyzed by Mo equation. Mo equation was successful in describing the nonisothermal crystallization kinetics of PCL blocks in PHCLs. Crystallization activation energy were estimated using Kissinger's method. The results of kinetic parameters showed that both blocks crystallized more difficultly than corresponding homopolymers. With the increase of PCL content, the crystallization rate of PCL block increased gradually. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Hg-rich liquid-phase epitaxy of Hg1−xCdxTe

Over the past decade, liquid-phase epitaxy (LPE) has become an established technique for the growth of HgCdTe. This article reviews one of the successful LPE technologies developed for HgCdTe, specifically, “infinite-melt” vertical LPE (VLPE) from Hg-rich solutions.

In spite of the relatively low solubility of Cd in Hg-rich solutions and the relatively high Hg pressure at the usual growth temperatures, this approach has been found to offer superior results for growth of HgCdTe suitable for various compositions and layer structures.

An historical perspective and the current status of VLPE technology are presented. Particular emphasis is placed on the important role of the thermodynamic parameters (phase diagram), on control of stoichiometry (defect chemistry) and on impurity doping (distribution coefficient) for growth of HgCdTe layers from Hg solutions. Critical material characteristics, such as transport properties, minority-carrier lifetime, morphology and crystal structure, are also discussed.