Synthesis and characterisation of some new stabilisers for polyvinylchloride

Some new stabilisers having a chelating polymeric structure were synthesised and characterised, i.e., 8-hydroxyquinoline-formaldehyde chelating resins of Cd, Zn, and Pb. The efficiency of these new stabilisers was studied with respect to PVC. The stabilised PVC samples showed outstanding thermal stability as studied by thermogravimetric techniques, i.e., the percentage of HCl evolved reduced remarkably with increasing polymer decomposition temperature.     

Phosphinsubstituierte Chelatliganden. XVIII. Penta- und Tetracarbonylmetall-Komplexe des Chroms,Molybdäns und Wolframs mit sekundären und tertiären Phosphinothioformamid-Liganden

Phosphine Substituted Chelate Ligands. XVIII. Penta- and Tetracarbonylmetal Complexes of Chromium, Molybdenum, and Tungsten with Secondary and Tertiary Phosphinothioformamide Ligands Mono- and bidentately coordinated phosphinothioformamide complexes are obtained by photochemical substitution of the metal hexacarbonyls M(CO)₆ (M ? Cr ( a ), Mo ( b ), W ( c )). The M(CO)₅ · THF adducts react with secondary thioamides under exclusion of light to give the P-coordinate pentacarbonyl complexes [(CO)₅MPPh₂C(S)NHR¹] (R¹ ? Ph ( 1a – c ), Me ( 2a )). The photoreaction of M(CO)₅ · THF with secondary and tertiary thioamides at low temperatures leads to the formation of the P, S-chelate complexes . The corresponding N-silylated complexes 6a – c (R¹ ? Me₃Si, R² ? Ph) are obtained by direct photosubstitution of M(CO)₆ in cyclohexane solution. The labile bis(thioformamide) complexes [(CO)₄M(PPh₂C(S)NHMe)₂] ( 7a – c , cis-trans isomers) are synthesized in low yields according to the same procedure. The attempted alkylation of the chelate complexes 3a – c remains unsuccessful, whereas the secondary thioformamides react with n-BuLi/CH₂Br₂ to give the methylene bis(thioformirnidoesters) [Ph₂PC(NR¹)S]₂CH₂ (R¹ ? Ph (8), Me ( 9 )) in quantitative yields.     

Adsorptive stripping voltammetry of sex hormones at the static mercury drop electrode

Controlled adsorptive accumulation of testosterone, methyltestosterone and progesterone on the static mercury drop electrode provides the basis for direct stripping measurement of these compounds ar nanomolar concentrations. The adsorptive stripping behavior is evaluated with respect to preconcentration time and potential, stripping mode, concentration dependence, drop size and other variables. With 5-min accumulation, peak current enhancements of 45, 18 anal 12 are observed for 5 × 10^?8 M testosterone, progesterone and methyltestosterone, respectively, relative to direct pulse voltammetry. Detection limits are 1.6 × 10^?10 M for testosterone, 2 × 10^?10 M for progesterone and 3.3 × 10^?10 M for methyltestosterone with 15-min preconcentration. The relative standard deviation for 8 × 10^?8 M progesterone is 3.4% (n=8). Applicability to direct measurements of methyltestosterone in pharmaceutical formulations is assessed.     

Koordinationschemie funktioneller Phosphorylide. VII. Pentacarbonylmetall-Komplexe des Cyanmethylen-triphenyl-phosphorans, [Ph3PCH(CN)] · M(CO)5 (M = Cr,Mo, W)

Coordination Chemistry of Functional Phosphorus Ylides. VII. Pentacarbonylmetal Complexes of Cyanomethylene Triphenylphosphorane, [Ph₃P?CH(CN)] · M(CO)₅ (M = Cr, Mo, W) The pentacarbonyl complexes [Ph₃P?CH(CN)] · M(CO)₅ ( 1a –c) are obtained by reaction of the irradiated metal hexacarbonyls M(CO)₆ (M = Cr, Mo, W) with cyanomethylene triphenylphosphorane under exclusion of light. The IR and NMR spectra indicate N-coordination of the ligand, that means a nitrile complex. The chromium complex 1a crystallizes triclinic (space group P1 , Z = 2) with the lattice constant a = 1126.5(2), b = 1153.6(3), c = 951.4(3) pm; α = 103.47(3), β = 102.04(3), γ = 84.00(2)°. The linear array of the ligand atoms C7, C6, N forms an angle of 168.1(5)° with the metal-nitrogen bond. Significant bond distances are Cr? N = 206.2(6), N? C6 = 115.3(7), C6? C7 = 137.2(8) and P? C7 = 170.9(5) pm.     

All-optical 2R-regeneration and continuous wave to pulsed signal wavelength conversion based on fiber nonlinearity

In this paper, we propose a novel all-optical 2R (re-amplification and re-shaping) regenerator based on inducing nonlinear chirp over a continuous wave probe. The regenerator also performs continuous wave to pulsed wavelength conversion. The chirp is induced in a highly nonlinear fiber by the data modulated pulsed signal that is to be regenerated. Offset filtering is employed at the output of the highly nonlinear fiber to extract the frequencies generated as a result of chirping. The regenerator performance has been evaluated with the help of bit-error-rate plots and eye diagrams at different values of optical signal to noise ratios. Apart from re-shaping and re-amplification, inclusion of the regenerator results in better resilience to amplified spontaneous emission noise.     

Electrical Impedance Spectroscopic Study of CNT/Ethylene-alt-CO/Propylene-alt-CO Polyketones Nanocomposite

Impedance spectroscopy was utilized to investigate the dielectric properties, ac conductivity and charge transport mechanisms in propylene-alt-CO/ethylene-alt-CO (EPEC) random terpolymer filled with multi-walled carbon nanotubes (MWCNT) as a function of nanofiller content, frequency, and temperature. Equivalent resistor-capacitor (RC) circuit models were proposed to describe the impedance characteristics of the unfilled terpolymer and the nanocomposite at different temperatures. For the nanocomposites, the ac conductivity tended to be frequency independent at low frequencies. At high frequencies, the ac conductivity increased with frequency. The dc conductivity (i.e., plateau of the ac conductivity at low frequencies) at room temperature increased from 10^?9 (Ω·m)^?1 for the unfilled polymer to l0^?3 (Ω·m)^?1 for the 6 wt% MWCNT/EPEC nanocomposite. At low temperatures, the equivalent RC model for EPEC-0 and EPEC-2 was found to consist of a parallel RC circuit. However, for 6 wt% MWCNT/EPEC nanocomposite, an RC model consisting of an R/constant phase element (CPE) circuit and a resistor in series was required to describe the impedance behavior of the nanocomposite.     

Work place air particulate monitoring of automobile workshops for public health and safety

Twenty-eight pairs of coarse and fine air particulate samples were collected in front of an automotive workshop located at Tasmasipabad on Chaklala Road in Rawalpindi using a Gent sampler and polycarbonate filters. These samples were collected during the period; 7th to 27th of April 2009. The gravimetric data (PM_2.5 and PM₁₀) were obtained for these samples and were found to exceed the Pakistani standards. Black carbon (BC) was also determined using reflectance measurements and it was found that BC contributed significantly more to the fine mass than to the coarse fraction; i.e. ~10 to ~3 %, respectively. This is not surprising as soot is emitted by combustion processes and is usually found in the fine particulate mass. Using instrumental neutron activation analysis technique all 28 pairs of filters were analyzed for >30 elements. Major elements, in the coarse mass fraction, include Al, K, Fe, Sr, Na, and Zn implying soil as the major source while BC was found to be a higher contributor of PM_2.5. An episode of high PM_2.5 was observed on the 18th of April 2009. Back trajectory analysis showed that the air mass originated from the Middle East where a dust storm was in progress over Iraq.     

Tuning the physical properties of a nematic liquid crystal elastomer actuator

In this report we demonstrate the ability to tune the physical properties of a liquid crystal elastomer (LCE) by varying the amount and type of crosslinking within the elastomer network. LCE films composed of a single mesogenic compound were capable of uniaxial contraction when thermally actuated through the nematic to isotropic phase of the material. We probed the physical properties of the LCE films while varying the amount and concentration of two crosslinking agents and measured actuation strains of 10–35%, elastic moduli of 3–14 MPa, and transition temperatures ranging between 75 and 60°C. The viscous losses of the elastomers and the estimated work capable of being produced by the films were also evaluated. The ability to tune the physical properties of the LCE films allows for a wide range of applications including robotics, microelectromechanical systems (MEMS), shape‐changing membranes, and/or microfluidics.     

碳酸氢盐活化的过氧化氢：一种有机废水处理的新技术

水污染问题已成为影响我国可持续发展的关键问题之一,为有效提高现有污水处理的效率及其回收利用,各种催化氧化技术受到了广泛的关注。目前发展的各类高级氧化技术在实际的应用过程中明显受到了氧化剂的利用率、催化剂的浸出、寿命及成本等问题的严重限制。因此基于新的理念、发展新的催化氧化技术仍然受到广泛的关注。
　　最近几年,利用碳酸氢盐活化过氧化氢,应用于有机废水的降解逐渐受到环境催化领域的关注。碳酸氢盐本身是一种低毒性、广泛存在于环境及生物体系的化学物质,通过它活化过氧化氢产生过碳酸氢盐氧化剂,该氧化剂能够直接氧化有机物。同时,在各种过渡金属催化剂的存在下,通过该过碳酸氢盐可以形成氧化能力更强的各种自由基(如羟基自由基等) 及高价态的过渡金属离子参与有机废水的降解。虽然传统认为碳酸盐及碳酸氢盐对高级氧化法降解有机废水不利,原因是认为它们能捕捉羟基自由基,形成氧化能力更低的碳酸根自由基。现有的研究已充分表明,较低浓度的碳酸氢盐能够加快有机废水的氧化降解,而且通常比单独使用过氧化氢效率更高,这些新的发现已明显突破了传统意义上对碳酸氢盐作用的理解。更为重要的是,在微量碳酸氢盐的存在下,其产生的微碱性环境极大地消除了负载型氧化物催化剂在废水降解过程中的金属离子流失、从而极大地延长了催化剂的寿命。该缺点是各种基于过渡金属氧化物催化剂的高级氧化技术难以广泛推广的关键性挑战,原因是随着氧化降解的进行,废水体系由于有机酸的生成而逐渐酸化,进而引发氧化物催化剂的酸溶而流失。在这点上,碳酸氢盐活化过氧化氢系统由于其天然的微碱性环境体现出了其明显的优势。
　　本文即是在本课题组工作基础上,对该领域内国内外研究进展加以总结,以期获得国内外同行的进一步关注。综述的主要内容包括：(1)碳酸氢氧活化过氧化氢的相关知识介绍,(2)均相碳酸氢氧活化过氧化氢降解有机废水的研究进展,(3)基于金属氧化物催化剂的碳酸氢氧活化过氧化氢降解有机废水的研究进展,和(4)碳酸氢盐在其他高级氧化技术中的应用。虽然基于碳酸氢氧活化过氧化氢降解有机废水的研究还处于早期探索阶段,还有很多基础科学问题如降解机理等值得进一步探索,期望通过该综述的介绍能够让同行对碳酸氢氧活化过氧化氢降解有机废水有一个比较全面的了解,进而推动该研究方向的发展,为有机废水的催化处理提供新的机会。