In vitro degradation properties of ion-beam irradiated poly(lactide-co-glycolic acid) mesh

Scaffolds for tissue regeneration must be biocompatible and biodegradable. Ion-beam irradiation is useful for making polymers biocompatible, but the process by which the irradiated polymers biodegradable is not yet well understood. We investigated this phenomenon by Kr⁺-irradiated poly(lactide-co-glycolic acid) (PLGA) mesh substrate at an acceleration energy of 50 keV with fluences of 1 × 10¹³ and 1 × 10¹⁴ ions/cm². We then measured the electronic states of the constituent elements on the irradiated surface by X-ray photoelectron microscopy (XPS) and evaluated the hydrolytic degradation properties (weight loss, media pH, and tensile strength) of the mesh in phosphate buffer solution. New functional groups and carbonization were induced on the irradiated surface. Degradation rate and tensile strength remain unchanged by ion-beam irradiation. Ion-beam irradiation should, thus, be a promising modification technique for tissue engineering scaffolds.     

Progress in ECRF antenna development for JT-60SA

Structural, mechanical and optical design work on antennas/launchers for the electron cyclotron range of frequency heating and current drive system in JT-60 Super Advanced (JT-60SA) have been advanced based on a linear motion antenna concept. A CAD model of the launcher was built with realistic component sizes. A mock-up of the steering structure consisting of two different bellows sections for poloidal and toroidal beam scanning was fabricated to test movement of the bellows. The poloidal (?40° to +20°) and toroidal (?15° to +15°) injection angle ranges required in JT-60SA were shown to be realized by this steering structure and mirrors.     

Less Carcinogenic Chlorinated Estrogens Applicable to Hormone Replacement Therapy

Human estrogens prescribed for hormone replacement therapy (HRT) are known to be potent carcinogens. To find safer estrogens, several chlorinated estrogens were synthesized and their carcinogenic potential were determined. A pellet containing either 2-chloro-17β-estradiol (2-ClE₂) or 4-chloro-17β-estradiol (4-ClE₂) was implanted subcutaneously for 52 weeks into August Copenhagen Irish (ACI) rats, a preferred animal model for human breast cancer. 17β-Estradiol (E₂) frequently induced mammary tumors while both 2-ClE₂ and 4-ClE₂ did not. Their 17α-ethinyl forms, thought to be orally active estrogens, were also synthesized. Neither 2-chloro-17α-ethinylestradiol (2-ClEE₂) nor 4-chloro-17α-ethinylestradiol (4-ClEE₂) induced tumors. The less carcinogenic effects were supported by histological examination of mammary glands of ACI rats treated with the chlorinated estrogens. A chlorine atom positioned at the 2- or 4-position of E₂ may prevent the metabolic activation, resulting in reducing the carcinogenicity. 2-ClE₂ and 4-ClE₂ administered subcutaneously and 2-ClEE₂ and 4-ClEE₂ given orally to ovariectomized rats all showed uterotrophic potency, albeit slightly weaker than that of E₂. Our results indicate that less carcinogenic chlorinated estrogens retaining estrogenic potential could be safer alternatives to the carcinogenic estrogens now in use for HRT.     

Rheological characterization of konjac glucomannan in concentrated solutions

Dynamic viscoelasticity measurements were performed for concentrated solutions of konjac glucomannan in an ionic liquid. The entanglement coupling appeared in the rheological data for each solution was characterized in terms of the molecular weight between entanglements (M _e) as an average size of the transient entanglement network. The value of M _e for konjac glucomannan in the molten state was estimated to be 1.8 × 10³ (in g mol^?1), being significantly smaller than that for cellulose, although the molecular weight and linkage of the repeating units were the same between these polysaccharides. This result suggested that the configuration of the repeating monosaccharide unit affected the entanglement network of these polysaccharides reflecting the single chain characteristics.     

Emissions of toxic pollutants from compressed natural gas and low sulfur diesel-fueled heavy-duty transit buses tested over multiple driving cycles

The number of heavy-duty vehicles using alternative fuels such as compressed natural gas (CNG) and new low-sulfur diesel fuel formulations and equipped with after-treatment devices are projected to increase. However, few peer-reviewed studies have characterized the emissions of particulate matter (PM) and other toxic compounds from these vehicles. In this study, chemical and biological analyses were used to characterize the identifiable toxic air pollutants emitted from both CNG and low-sulfur-diesel-fueled heavy-duty transit buses tested on a chassis dynamometer over three transient driving cycles and a steady-state cruise condition. The CNG bus had no after-treatment, and the diesel bus was tested first equipped with an oxidation catalyst (OC) and then with a catalyzed diesel particulate filter (DPF). Emissions were analyzed for PM, volatile organic compounds (VOCs; determined on-site), polycyclic aromatic hydrocarbons (PAHs), and mutagenic activity. The 2000 model year CNG-fueled vehicle had the highest emissions of 1,3-butadiene, benzene, and carbonyls (e.g., formaldehyde) of the three vehicle configurations tested in this study. The 1998 model year diesel bus equipped with an OC and fueled with low-sulfur diesel had the highest emission rates of PM and PAHs. The highest specific mutagenic activities (revertants/microg PM, or potency) and the highest mutagen emission rates (revertants/mi) were from the CNG bus in strain TA98 tested over the New York Bus (NYB) driving cycle. The 1998 model year diesel bus with DPF had the lowest VOCs, PAH, and mutagenic activity emission. In general, the NYB driving cycle had the highest emission rates (g/mi), and the Urban Dynamometer Driving Schedule (UDDS) had the lowest emission rates for all toxics tested over the three transient test cycles investigated. Also, transient emissions were, in general, higher than steady-state emissions. The emissions of toxic compounds from an in-use CNG transit bus (without an oxidation catalyst) and from a vehicle fueled with low-sulfur diesel fuel (equipped with DPF) were lower than from the low-sulfur diesel fueled vehicle equipped with OC. All vehicle configurations had generally lower emissions of toxics than an uncontrolled diesel engine. Tunnel backgrounds (measurements without the vehicle running) were measured throughout this study and were helpful in determining the incremental increase in pollutant emissions. Also, the on-site determination of VOCs, especially 1,3-butadiene, helped minimize measurement losses due to sample degradation after collection.     

Preparation of novel silica/poly(butylene succinate-co-adipate) organic–inorganic hybrid biodegradable material via sol–gel method

Silica/poly(butylene succinate-co-adipate) organic–inorganic hybrid biodegradable materials were prepared by the sol–gel method. Fourier-transform infrared spectroscopy (FT-IR) and Thermogravimetry/differential thermal analysis (TG/DTA) indicated that the inorganic (SiO₂, C₆H₅SiO_3/2) and organic (PBSA) components were well dispersed in the hybrid material. Heat resistant test shows that the hybrid material was both heat resistant and flexible. The presence of phenyl groups and siloxane network was responsible for the flexibility and heat resistance.     

Shielding effect of double microelectrode tips in a scanning electrochemical microscope

Electrochemical interaction of coaxial double microelectrodes, in which a ring microelectrode was surrounded by another ring microelectrode, was investigated. Mass-transfer reactions that occurred on both inner and outer microelectrodes interfered with each other and showed a “shielding” effect depending on potentials and geometries of microelectrodes. Application of the inner microelectrode of the double microelectrodes for a probing tip of a scanning electrochemical microscope (SECM) revealed that the shielding effect by the outer microelectrode affected the electrochemistry on the inner microelectrode in the vicinity of the substrate surface. The effect was intensified above the insulator but attenuated above the conductor as the microelectrodes approached in feedback mode of the SECM. Approach to a critical interelectrode distance also intensified the shielding effect in the substrate generation/tip collection mode. An SECM line-scan using a platinum/epoxy resin-model substrate was carried out to investigate the shielding effect on current sensitivity and lateral resolution of an SECM image.     

Thermal and electrical conduction properties of vertically aligned carbon nanotubes produced by water-assisted chemical vapor deposition

We present both thermal and electrical conduction properties of vertically aligned carbon nanotubes (VACNTs), synthesized by the water-assisted chemical vapor deposition method using Fe–Ti–O nanoparticles as catalyst. Thermal diffusivity and electrical resistance of VACNTs have been measured by the laser flash method and direct-current four-terminal method, respectively. The VACNTs are found to have thermal diffusivities of the same order as isotropic graphite and the electrical characteristics of semiconductors. The electrical resistance shows a T^−1/4 temperature dependence, which implies that the conduction of electrons is dominated by 3D Mott variable range hopping.     

In situ binary sol–gel reaction of various trifunctional alkoxysilane in the silane‐grafted polyolefin matrix and its effect upon the mechanical properties

The vinyltrimethoxysilane‐grafted ethylene‐propylene copolymer/trifunctional methoxysilane (EPR‐g‐VTMS/RTMS) composites were prepared via in situ silica sol–gel reactions. Five trifunctional methoxysilane compounds (n‐hexyltrimethoxysilane, n‐decyltrimethoxysilane, n‐tetradecyltrimethoxysilane, n‐octadecyltrimethoxysilane, and phenyltrimethoxysilane) have been selected for this study. The water‐cross‐linked EPR‐g‐VTMS/RTMS composites were characterized by attenuated total reflectance‐Fourier transform infrared spectroscopy, gel content, solid‐state ²⁹Si CP/MAS NMR, wide‐angle x‐ray scattering, tensile strength, and field emission scanning electron microscopy measurements. The type of RTMS additive has a substantial influence on the nature of siloxane band networks and eventually the mechanical tensile properties. This finding suggests that the interaction and/or entanglement between the EPR‐g‐VTMS matrix and the substituent of the RTMS additives are crucial for the modifying mechanical properties. Moreover, for the water‐cross‐linked EPR‐g‐VTMS/CnTMS (n = 6, 10, 14, and 18) composites, the joint evidence provided by attenuated total reflectance‐Fourier transform infrared spectroscopy, ²⁹Si CP/MAS NMR, and wide‐angle x‐ray scattering results suggested the formation of ladder‐type poly(n‐alkyl silsesquioxane)s and the presence of the highly ordered structure with a thickness equal to the length of two n‐alkyl groups in all‐trans conformation. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Synthesis of Condensed Tannin Derivatives and their Protein-Precipitating Capacity

Four regiospecifically methylated condensed tannin derivatives were synthesized by the condensation of regiospecifically methylated flavan-3, 4-diols protected by benzyl groups, and subsequent debenzylation. The monomeric flavan-3,4-diols were obtained via four reaction steps starting from phloroacetophenone derivatives and protocatechualdehyde derivatives. Protein—precipitating capacity of these synthetic condensed tannin derivatives was tested and a comparision of these capacity suggests the following results: 1) Phenolic hydroxyl groups in tannins are essential sites for protein precipitation. 2) Although the A-ring has been considered not to be important for tannin—protein interactions, it was proved that the A-ring also plays an important role together with the B-ring. 3) Both hydroxyl groups of A- and B-rings may synergistically interact with proteins.