An Improved Oxidative Cleavage Method for Large Scale Preparation of Some Acid‐Labile Aglycones from Glycosides

A practical method for large‐scale preparation of acid‐labile aglycones including protopanaxadiol, protopanaxatriol, cycloastragenol, and jujubogenin from the corresponding glycoside containing fraction was developed. The key point of this improved method is to generate and maintain the critical reaction conditions, anhydrous and strongly basic, in situ. This effort over comes the weakness of the reported method for oxidative cleavage of glycones and scales up the preparation of these acid‐labile aglycones for further studies.     

Biofunctional properties of polyester fibers grafted with chitosan and collagen

Poly(ethylene terephthalate) (PET) fiber was treated with ⁶⁰Co-γ-ray and grafted with acrylic acid (AA). The resulting fibers were further grafted with chitosan (CS) via esterification. Afterward collagen (COL) was immobilized onto CS-grafting fibers. The antibacterial activity of CS against Staphylococus aureus, Escherichia coli, and Pseudomonas aeruginosa was preserved after COL-immobilization. After immobilizing COL, the L929 fibroblasts cell proliferation was promoted than CS-grafting PET fiber. The results indicate that by grafting with CS and immobilizing with COL, PET fibers exhibited both antibacterial activity against four pathological bacteria and improvement in the proliferation of fibroblast. Copyright © 2007 John Wiley & Sons, Ltd.     

Flavonol Glycosides and Cytotoxic Triterpenoids from Alphitonia Philippinensis

Three new flavonol glycosides, namely, isorhamnetin 3‐O‐(6″‐O‐(Z)‐p‐coumaroyl)‐β‐D ‐glucopyranoside ( 1 ), quercetin 3‐O‐α‐L ‐rhamnopyranosyl(1 → 2)‐α‐L ‐arabinopyranosyl(1 → 2)‐α‐L ‐rhamnopyranoside ( 2 ), and quercetin 3‐O‐α‐L ‐arabinopyranosyl(1 → 2)‐α‐L ‐rhamnopyranoside ( 3 ), were isolated from the stems of Alphitonia philippinensis. Their structures were established by spectral analysis. In addition, NMR data were assigned for ceanothenic acid ( 11 ). Some of the isolated triterpenoids and flavonoid glycosides showed cytotoxicity against human PC‐3 cells and hepatoma HA22T cells, and inhibition of replication on herpes simplex virus type‐1.     

Kinetics of free‐radical graft polymerization of 1‐vinyl‐2‐pyrrolidone onto silica

The kinetics of aqueous free‐radical graft polymerization of 1‐vinyl‐2‐pyrrolidone onto silica activated with vinyltrimethoxysilane was studied with a mechanistic polymerization model and experimental data for a temperature range of 70–90 °C. The polymerization was initiated with hydrogen peroxide with initial monomer concentrations ranging from 10 to 40 vol %. The kinetic model, which incorporates the hybrid cage–complex initiation mechanism, describes the experimental polymerization data for which the kinetic order, with respect to the monomer concentration, varies from 1 to . Surface chain growth occurs by both monomer addition and homopolymer grafting, although the latter contribution to the total polymer graft yield is less significant. Increasing the initial monomer concentration enhances both surface polymer density and average grafted chain length. Increasing reaction temperature, however, produces a denser surface layer of shorter polymer chains. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 26–42, 2002     

Heat Transport Equations with Phonons and Electrons

In the framework of Extended Irreversible Thermodynamics, a model of heat transport due to phonons and electrons is developed. Compatibility with Second Law of Thermodynamics is exploited through a generalized Coleman-Noll procedure. A?system of nonlinear partial differential equations, ruling the evolution of the partial heat fluxes, is derived. Propagation of temperature waves through one-dimensional heat conductors is investigated as well.     

Nonequilibrium temperatures and second-sound propagation along nanowires and thin layers

It is shown that the dispersion relation of heat waves along nanowires or thin layers could allow to compare two different definitions of nonequilibrium temperature, since thermal waves are predicted to propagate with different phase speed depending on the definition of nonequilibrium temperature being used. The difference is small, but it could be in principle measurable in nanosystems, as for instance nanowires and thin layers, in a given frequency range. Such an experiment could provide a deeper view on the problem of the definition of temperature in nonequilibrium situations.     

Critical temperatures of the anisotropic Heisenberg ferromagnets

High temperature series expansions for the fluctuation in the long range order M_x is obtained through order T^?7 for a spin-$\text{1}\text{2}$ anisotropic Heisenberg Hamiltonian. The critical temperatures at which the spontaneous magnetization occurs on the xy-plane are determined.     

Active Frequency-Tune Beam-Scanning Leaky-Wave Antenna Arrays

X-band active beam-scanning leaky-wave antenna arrays, including 1 × 1,1 × 2 and 1 × 4 prototypes, have been demonstrated. These antennas integrated one or several microstrip leaky-wave antenna elements with a single varactor-tuned HEMT VCO as an active source. Measured results on experimental antennas indicate that the beam scanning angle of the 1 × 1 antenna close to 40° can be achieved and the scanning range of 1 × 2 and 1 × 4 antenna arrays are both close to 32°. Furthermore, reflected wave due to the open end of each leaky-wave antenna element has been suppressed by the symmetric configuration of this antenna array and the antenna efficiency increases. When comparing with the measured radiation pattern of the single element antenna, we found that the 1 × 2 and 1 × 4 antenna arrays can effectively suppress the reflected power by more than 5.5 dB and 10.5 dB, respectively, at 10.2GHz. The power gain are more than 2 dB and 3.16 dB higher than the single element antenna with a measured EIRP of 18.67 dBm.