The Analysis of Sulfur Compounds by Solid Adsorbent Tenax GR Preconcentration and Gas Chromatography with Flameless Sulfur Chemiluminescence Detection

Gas chromatography using flameless sulfur chemiluminescence detection was applied to the analysis of sulfur compounds in air. A trap employing the solid adsorbent Tenax GR was used to enrich ambient levels of volatile sulfur compounds. The sulfur gases were then thermally released according to programmed temperature from the adsorbent trap and re-collected in a column cooled with liquid nitrogen. The sulfur compounds were revolatilized and directly transferred to the system of PLOT-column gas chromatograph/flameless sulfur chemiluminescence detector for analysis. The PTV injector has been used as a thermal resorption chamber for analysis of sulfur compounds. The sulfur gaseous compounds known to cause nuisance odors in the air from sewerage treatment works were determined.     

PEMFC催化剂的研究：自制抗CO中毒Pt-Ru/C电催化剂的性质

用胶体法制备了抗CO中毒PEMFC阳极Pt-Ru/C电催化剂（标记为THYT－2）,对 比研究了THYT－2与Johnson Matthey (JM)公司同类品牌Pt-Ru/C催化剂的电化学及 其它物理化学性能。结果表明,THYT－2电催化剂在甲醇燃料电池和CO／H_2（Φ_ (CO) = 1 * 10~(-4)）的氢氧燃料电池中的电催化行为与JM催化剂相当,但THYT－ 2在低浓度CO氢气燃料中的电池性能更好。两种催化剂的其它物理化学性质具有类 似性：XPS分析结果表明THYT－2和JM催化剂 中都有三种不同价态的Pt存在：即金 属态Pt(0)、氧化态Pt(II)和Pt(IV)。HRTEM测试结果表明两种催化剂的粒径处在2 ～3 mn左右,这可能是它们拥有良好电化学性能的主要原因之一。本文还对催化剂 中Pt与Ru组分的分布和相互作用进行了讨论,提出了改进Pt-Ru/C电催化剂的思路 。     

Effects of ultraviolet B on epidermal morphology, shedding, lipid peroxide, and antioxidant enzymes in Cope's rat snake (Elaphe taeniura)

Cope's rat snakes (Elaphe taeniura) favor to expose under sunlight in order to increase their body temperature simultaneously increasing the risk of skin damage by ultraviolet B (UVB) irradiation. We have investigated the effects of UVB irradiation on their skin. Results show that the UVB transmission of the keratinous layer was only 5.1+/-0.36%. The peak of epidermal damage and malondialdehyde (MDA) content, a product of lipid peroxidation, simultaneously occurred 72-96, 48 or 24 h after exposure to 300, 500 and 800 mJ/cm2 of UVB radiation, respectively. Superoxide dismutase (SOD) activity was inhibited by UVB and the lowest activity occurred 24, 48, 12 and 12 h after exposure to 110, 300, 500 and 800 mJ/cm2 of UVB, respectively. SOD activity recovered later to some extent but mostly remained below control level. After exposure to different doses of UVB radiation, catalase (CAT) activity was inhibited immediately, and then gradually recovered and even increased to peak levels above control level. The highest CAT levels accompanied the most serious damage of skin morphology. Later on, CAT activity decreased and recovered again close to or below control level, which was accompanied by shedding off the damaged epidermal complex. This indicated that the epidermal damage induced by UVB is closely related to lipid peroxidation, where CAT acts as a primary antioxidant enzyme. Moreover, the keratinous layer protects the viable cell layer against UVB damage as well.     

The Efficient Synthesis of the Optically Active β‐Hydroxyl‐γ‐Butyrolactone Derivatives

The optically active β‐hydroxyl‐γ‐butyrolactones were synthesized from nonchiral starting material by employing reductive cleavage reaction, sharpless asymmetric epoxidation and dihydroxylation, and Lewis acid‐catalysed cyclization as key steps. This strategy can be used to prepare many chiral β‐hydroxyl‐γ‐butyrolactone analogues.     

A detailed investigation of subsitituent effects on N-h bond enthalpies in aniline derivatives and on the stability of corresponding N-centered radicals

The N-H bond dissociation enthalpies (BDE's) of 40 anilines (pGC(6)H(4)NHY) from series 1 to 4 with alpha-Y and p-G substituents and the stability of related radicals (pGC(6)H(4)Ndot;Y) were studied using ab initio (MP2) and density functional methods (B3LYP) with large basis sets. The results show that both methods reproduce earlier experimental BDEs within 2-3 kcal/mol and satisfactorily predict the alpha and remote substituent effects on BDEs (DeltaBDEs), as they reproduced the experimental DeltaBDEs within less than 1 kcal/mol. Furthermore, the conventional radical stabilization enthalpy (RSE = - DeltaBDE) was found to be invalid to represent the trend of the radical stabilization because the molecule effect (ME) can contribute more to RSE than the radical effect (RE) for certain series (1 and 4). These radicals are in fact stabilized by electron-withdrawing groups (EWGs) but destabilized by electron-donating groups (EDGs), a phenomenon just opposite to the observed O-behavior of many other aromatic heteroatomic radicals studied so far. These radicals are thus assigned as a new radical class, Class counter-O (or O) according to Walter's terminology. Moreover, the excellent multi-parametric Hammett-type correlations indicated that the para substituent effects on BDEs originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. The atomic charge and spin population variations at a radical center due to p-G substitution were also found to correlate satisfactorily with REs. These results show that the spin delocalization effect should be explicitly considered in accounting for both DeltaBDEs and radical stabilization effects. Finally, an overall subsituent effect scale for radical stability has been proposed, and the overall substituent effect on the N-radicals was found to conform to the Capto-dative Principle.     

Radiation polymerization of thermo-sensitive poly (N-vinylcaprolactam)

Temperature-sensitive poly (N-vinylcaprolactam) both in water-soluble state and in gel was prepared by γ-radiation polymerization. The effects of radiation dose, radiation dose rate and monomer concentration on polymerization and the low critical solution temperature characteristics of the polymer were studied. The results show that the polymer prepared within certain radiation dose (beyond 2 kGy) and dose rate range (2–14 Gy/min) has good temperature sensitivity and uniformity.     

Calix[2]furano[2]pyrrole and related compounds as the neutral carrier in silver ion-selective electrode

The performance of calix[2]furano[2]pyrrole and related compounds used as neutral carriers for silver selective polymeric membrane electrode was investigated. The silver ion-selective electrode based on calix[2]furano[2]pyrroles gave a good Nernstian response of 57.1 mV per decade for silver ion in the activity range 1×10⁻⁶ to 1×10⁻² M. The present silver ion-selective electrode displayed very good selectivity for Ag⁺ ion against alkali and alkaline earth metal ions, NH₄⁺, and H⁺. In particular, the present Ag⁺-selective electrode exhibited very low responses towards Hg²⁺ and Pb²⁺ ions. The potentiometric selectivity coefficients of the silver ion-selective electrode exhibited a strong dependence on the solution pH. In particular, the response of the electrode to the Hg²⁺ activity was greatly diminished at pH 2.5 compared to that at pH 5.0. Overall, the performance of the present silver ion-selective electrode based on the ionophore, calix[2]furano[2]pyrrole, is very comparable to that of the electrode prepared with the commercially available neutral carrier in terms of slope, linear range, and detection limits.     

Vinyl sulfones in solid-phase synthesis: preparation of 4,5,6,7-tetrahydroisoindole derivatives

The preparation of functionalized 4,5,6,7-tetrahydroisoindole via a traceless solid-phase sulfone linker strategy is described. Thermolytic extrusion of SO(2) from polymer-bound 3-(phenylsulfonyl)-3-sulfolene (7) generated polymer-bound 2-(phenylsulfonyl)-1,3-butadiene (9) in situ which underwent Diels--Alder cycloaddition with various dienophiles to furnish vinyl sulfone resins 10-14. To complete a traceless linker cleavage strategy, (p-tolysulfonyl)methyl isocyanide or ethyl isocyanoacetate was employed to react with the vinyl sulfone moiety to liberate functionalized 4,5,6,7-tetrahydroisoindole products from the resin. Using this chemistry, nine tetrahydroisoindole derivatives (6, 15-22) were prepared in 32-41% overall yields from polystyrene/divinylbenzene sulfinate 1.     

Modulation of the lifespan of C. elegans by the controlled release of nitric oxide

The frontier of nitric oxide biology has gradually shifted from mechanism elucidation to biomanipulation, e.g. cell-proliferation promotion, cell-apoptosis induction, and lifespan modulation. This warrants biocompatible nitric oxide (NO) donating materials, whose NO release is not only controlled by a bioorthogonal trigger, but also self-calibrated allowing real-time monitoring and hence an onset/offset of the NO release. Additionally, the dose of NO release should be facilely adjusted in a large dynamic range; flux and the dose are critical to the biological outcome of NO treatment. Via self-assembly of a PEGylated small-molecule NO donor, we developed novel NO-donating nanoparticles (PEG-NORM), which meet all the aforementioned criteria. We showcased that a low flux of NO induced cell proliferation, while a high flux induced cell oxidative stress and, ultimately, death. Notably, PEG-NORM was capable of efficiently modulating the lifespan of C. elegans. The average lifespan of C. elegans could be fine-tuned to be as short as 15.87 ± 0.29 days with a high dose of NO, or as long as 21.13 ± 0.41 days with a low dose of NO, compared to an average life-span of 18.87 ± 0.46 days. Thus, PEG-NORM has broad potential in cell manipulation and life-span modulation and could drive the advancement of NO biology and medicine.

Schematic illustration of modulating the longevity of the C. elegans by PEG-NORM nanoparticles.     

Influence of acid treatments of carbon nanotube precursors on Ni/CNT in the synthesis of carbon nanotubes

The Ni/CNT catalyst was fabricated by directly dipping carbon nanotube precursors refluxed in 4 M of nitric acid into Ni electroless plating bath, and used to synthesize new carbon nanotubes. The experimental results indicate that the duration of acid-treatment of carbon nanotubes precursors exerts a great influence on the catalysis of Ni/CNT in the synthesis of carbon nanotubes and hence the structures of the new carbon nanotubes. When the carbon nanotubes precursors were refluxed for 0.5 h in 4 M of nitric acid, bamboo-shaped carbon nanotubes (BSCNT) or Y junction carbon nanotubes in the carbon products were obtained. As the duration of acid-treatment of carbon nanotubes precursors increased to 6 h, the as-prepared Ni/CNT displayed higher activity, and the carbon nanotube products were high pure without any Y junction structure or any separation layers in hollow.