An Efficient Method for the Preparation of Nitriles via the Dehydration of Aldoximes with Phthalic Anhydride

A new and highly efficient method for the conversion of aldoximes to nitriles was established. By fusing with phthalic anhydride, aldoximes were efficiently and smoothly converted into nitriles, in high yields (over 85%) and in a short time (within 5 minutes). The mixture of phthalic anhydride, a cyclic anhydride, and aldoximes in fusing state set up an ideal transition state for a selective [3.3]‐sigmatropic rearrangement of the acylated aldoximes to nitriles.     

Probe-induced native oxide decomposition and localized oxidation on 6H-SiC (0001) surface: an atomic force microscopy investigation

We report, for the first time, the native oxide decomposition/etching and direct local oxide growth on 6H-SiC (0001) surface induced by atomic force microscopy (AFM). Surface native oxide was decomposed and assembled into protruded lines when the negatively biased AFM tip was scanned over surface areas. The mechanism of decomposition was found to be governed by the Fowler-Nordheim emission current enhanced by the negatively biased AFM tip. Direct oxide growth on the SiC surface was achieved when the AFM tip was immobilized and longer bias duration applied. In particular, the aspect ratio of oxide grown on SiC was found to be several times higher than that on the Si surface. The improved aspect ratio on SiC was attributed to the anisotropic OH(-) diffusion involved in vertical and lateral oxidation along the polar and nonpolar directions such as [0001] and [110] axis in SiC crystal. The electron transport in the above AFM grown oxide on SiC was further investigated by I-V characteristics. The dielectrical strength of AFM oxide against degradation and breakdown under electrical stressing was evaluated.     

Determination of the inelastic mean-free-path and mean inner potential for AlAs and GaAs using off-axis electron holography and convergent beam electron diffraction.

The mean-free-paths for inelastic scattering of high-energy electrons (200 keV) for AlAs and GaAs have been determined based on a comparison of thicknesses as measured by electron holography and convergent-beam electron diffraction. The measured values are 77 +/- 4 nm and 67 +/- 4 nm for AlAs and GaAs, respectively. Using these values, the mean inner potentials of AlAs and GaAs were then determined, from a total of 15 separate experimental measurements, to be 12.1 +/- 0.7 V and 14.0 +/- 0.6 V, respectively. These latter measurements show good agreement with recent theoretical calculations within experimental error.     

Smectic Bimetallomesogens: Synthesis and Mesomorphic Properties in Oxygen-Bridged Dicopper and Divanadyl Complexes

The synthesis and mesomorphic properties of a homologous series of N-(3-hydroxypropyl)-4-alkoxylsalicylaldimine, N-(3-hydroxypropyl)-4-(4′-alkoxybenzoxy)salicylaldimine, and their dicopper(II) and di-oxovanadium(VI) complexes are reported. Copper complexes exhibited monotropic smectic A phases; however, vanadyl complexes showed no mesomorphism. A systematic comparison revealed that the meso-genie behaviors of these bimetallic complexes are induced by the weak intermolecular force and determined mainly by the central metal. The effects on the structural variations near the metal central cores and side chain density are also discussed.     

Design of passive mixers utilizing microfluidic self-circulation in the mixing chamber

This paper proposes the design of a passive micromixer that utilizes the self-circulation of the fluid in the mixing chamber for applications in the Micro Total Analysis Systems (microTAS). The micromixer with a total volume of about 20 microL and consisting of an inlet port, a circular mixing chamber and an outlet port was designed. The device was actuated by a pneumatic pump to induce self-circulation of the fluid. The self-circulation phenomenon in the micromixer was predicted by the computational simulation of the microfluidic dynamics. Flow visualization with fluorescence tracer was used to verify the numerical simulations and indicated that the simulated and the experimental results were in good agreement. Besides, an index for quantifying the mixing performance was employed to compare different situations and to demonstrate the advantages of the self-circulation mixer. The mixing efficiencies in the mixer under different Reynolds numbers (Re) were evaluated numerically. The numerical results revealed that the mixing efficiency of the mixer with self-circulation was 1.7 to 2 times higher than that of the straight channel without a mixing chamber at Re= 150. When Re was as low as 50, the mixing efficiency of the mixer with self-circulation in the mixing chamber was improved approximately 30% higher than that in the straight channel. The results indicated that the self-circulation in the mixer could enhance the mixing even at low Re. The features of simple mixing method and fabrication process make this micromixer ideally suitable for microTAS applications.     

New Prenylated Flavones from the Roots of Ficus Beecheyana

Two new prenylated flavanones, ficubee A and ficubee B, respectively, as 7,8‐(2,2‐dimethylpyrano)‐6‐prenyl‐5,3′,4′‐trihydroxyflavone and 6,7‐(2,2‐dimethylpyrano)‐8‐prenyl‐5,3′,4′‐trihydroxyflavone were isolated from the roots of Ficus beecheyana together with twelve known compounds: β‐sitosterol, 5‐stigmasten‐3β,7α‐diol, 5‐stigmasten‐3β,7β‐diol, 3β‐hydroxystigmast‐5‐en‐7‐one, 4‐hydroxybenzaldehyde, 4‐hydroxy‐3‐methoxybenzaldehyde, 1‐(4‐hydroxyphenyl)‐ethanone, 4‐hydroxy‐3‐methoxybenzoic acid, 4‐hydroxy‐cinnamic acid, seseline, xanthyletin, and psoralene. The structures of these secondary metabolites were determined by spectroscopic means and in comparison with published data.     

Phantoms for Noninvasive Blood Glucose Sensing with Near Infrared Transmission Spectroscopy

In vivo spectra from human subjects can be simulated with a phantom composed of different layers of water, fat and muscle tissue. All three components are necessary to simulate in vivo spectra collected over the combination spectral region (5000–4000 cm⁻¹). Muscle tissue is not required, however, to accurately simulate overtone spectra (6600–5400 cm⁻¹). The near-IR spectral characteristics of fat and muscle tissue from several animal sources are essentially identical to those found for human tissue, hence, the animal source for these phantom components is not critical. Thickness of each tissue layer can be determined by a regression analysis where the in vivo spectrum of interest is regressed against standard absorbance spectra of the necessary model components (water, fat and muscle). In general, in vivo overtone spectra collected across human webbing tissue with a thickness of 6.7 mm can be simulated with water layer thicknesses ranging from 5.0 to 6.4 mm combined with fat layer thicknesses from 1.4 to 4.2 mm.     

Efficient gene delivery in differentiated human embryonic stem cells

Human embryonic stem (hES) cells are capable of differentiating into pluralistic cell types, however, spontaneous differentiation generally gives rise to a limited number of specific differentiated cell types and a large degree of cell heterogeneity. In an effort to increase the efficiency of specified hES cell differentiation, we performed a series of transient transfection of hES cells with EGFP expression vectors driven by different promoter systems, including human cellular polypeptide chain elongation factor 1 alpha (hEF1alpha), human cytomegalo-virus, and chicken beta-actin. All these promoters were found to lead reporter gene expression in undifferentiated hES cells, but very few drug-selectable transfectants were obtained and failed to maintain stable expression of the transgene with either chemical or electroporation methods. In an attempt to increase transfection efficiency and obtain stable transgene expression, differentiated hES cells expressing both mesodermal and ectodermal markers were derived using a defined medium. Differentiated hES cells were electroporated with a hEF1alpha promoter-driven EGFP or human noggin expression vector. Using RT-PCR, immunocytochemistry and fluorescence microscopy, the differentiated hES cells transfected with foreign genes were confirmed to retain stable gene and protein expression during prolonged culture. These results may provide a new tool for introducing exogenous genes readily into hES cells, thereby facilitating more directed differentiation into specific and homogenous cell populations.     

The association of eotaxin-2 and eotaxin-3 gene polymorphisms in a Korean population with ulcerative colitis

The eotaxin gene family (eotaxin, eotaxin-2 and eotaxin-3) have been implicated in the recruitment of eosinophils, basophiles and helper T (Th) 2 lymphocytes that is a central aspect of allergic disease. We previously suggested that Eo2+179T>C and Eo2 +275C>T of the eotaxin-2, and Eo3 +2497T>G of the eotaxin-3 were significantly associated with susceptibility to asthma. To determine whether the single nucleotide polymorphisms (SNPs) of eotaxin-2 and eotaxin-3 gene family are associated with the susceptibility of ulcerative colitis (UC), we analyzed the genotype of 119 patients with UC and 303 controls using single-base extension (SBE) method. We also calculated the haplotype frequencies among Eo2 +179T>C and Eo2 +275C >T of the eotaxin-2 and Eo3 +2497T>G of the eotaxin-3 in both control and UC patients. The genotype frequency of Eo2 +179T>C and Eo2 +275C>T between UC patients and controls were significantly different (P=0.006 and 0.022, respectively). The genotype and allele frequencies of EoA2497T>G in UC patients were not significantly different from those in the controls without UC patients. Our results suggest that Eo2 +179T>C and Eo2 +275C>T of eotaxin-2 might be associated with the susceptibility of UC.