Dynamical spin susceptibility of the d–p model in the over doping region

Dynamical spin susceptibility χ^s(q,ω) of the d–p model in the over doping region is investigated by using the auxiliary boson technique. It includes higher order terms of the 1/N-expansion within the random phase approximation (RPA) of the local vertex, where frequency dependence of the quasi-particle interaction is taken into account. The incommensurate spin fluctuation is obtained due to the nesting effect in the low energy region (ωω^*), whereas the commensurate one in the high energy region (ωω^*), the characteristic energy ω^* is estimated to be about 30 meV. Both of the spin–lattice relaxation rate 1/T₁ and the spin–spin relaxation rate 1/T_g monotonically increase as T decreases, while the spin Knight shift K is almost independent of T.     

Heterogeneous nucleation on the crystallization poly(ethylene terephthalate)

The crystallization behavior of poly(ethylene terephthalate) (PET) with disodium terephthalate (DST) as nucleating agent was investigated. A detailed analysis of the crystallization course from the melt was made with the Avrami expression. The results demonstrated that DST additive can promote the PET crystallization rate in its entire crystallizable temperature range, and the acceleration degree of DST decreases with increasing temperature after a temperature higher than 180 °C. The values of the Avrami exponent indicated that the crystallization mode in Avrami theory is not suitable for the crystallization of these polymers, and the mechanism of the heterogeneous nucleation on PET crystallization is discussed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2135–2144, 2003     

Epoxy/amine‐functionalized short‐length vapor‐grown carbon nanofiber composites

Short length vapor‐grown carbon nanofibers (VGCNFs) were functionalized with 4‐aminobenzoic acid in polyphosphoric acid/phosphorous phentoxide medium via “direct” Friedel‐Crafts acylation reaction to afford aminobenzoyl‐functionalized VGCNFs (AF‐VGCNFs). The AF‐VGCNFs as a cocuring agent were mixed with epoxy resin by simple mechanical stirring in methanol which was added to help efficient mixing. After evaporation of methanol, 4,4′‐methylenedianiline as a curing agent was added to the mixture, which was then cured at elevated temperatures. The resultant composites displayed uniform dispersion of AF‐VGCNFs into cured epoxy matrix. During curing process, the amine functionalities on AF‐VGCNF together with 4,4′‐methylenedianiline were expected to be involved in covalent attachment to the epoxy resin. As a result, both tensile modulus and strength of the composites were improved when compared with those of pure epoxy resin. Thus, the AF‐VGCNFs play a role as an outstanding functional additive, which could resolve both dispersion and interfacial adhesion issues at the same time by functionalization of VGCNFs and covalent bonding between the additive and matrix, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7473–7482, 2008     

Nonisothermal crystallization behaviors of polypropylene with α/β nucleating agents

In this work, the nonisothermal crystallization and subsequent melting behaviors of polypropylene (PP) nucleated with different nucleating agents (NAs) have been studied. α‐phase NA 1,3:2,4‐bis (3,4‐dimethylbenzylidene) sorbitol (DMDBS, Millad 3988), β‐phase NA aryl amides compound (TMB‐5), and their compounds were introduced into PP matrix, respectively. The results show that the nonisothermal crystallization behaviors and crystalline structures of PP with compounded NAs are dependent on the composition of NAs. In the sample of PP with 0.1 wt % DMDBS and 0.1 wt % TMB‐5, the nucleation efficiency (NE) of TMB‐5 is much higher than that of DMDBS and PP crystallizes mainly nucleated by TMB‐5, and in this condition, β‐phase PP is the main crystallization structure. For the sample of PP with 0.2 wt % DMDBS and 0.2 wt % TMB‐5, 0.2 wt % DMDBS has higher NE than 0.2 wt % TMB5, and α‐phase is the main crystalline structure. The cooling rate is proved to be very important in controlling the nonisothermal crystallization behavior and the final crystalline structure of nucleated PP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1853–1867, 2008     

Effect of AlN content on the performance of brominated epoxy resin for printed circuit board substrate

Polymer matrix composites, based on brominated epoxy, a type of material widely used in printed circuit boards (PCBs), as matrix and AlN particle as filler were prepared. The influences of AlN content on the mechanical, thermal, and electrical properties of the composites were investigated by uniaxial tensile test, TMA, thermal conductivity measurement, DMA, and dielectric properties measurement. It was found that the properties of composites monotonically varied with AlN content except that maximum tensile strength and strain of composites corresponded to a filler content of 10 wt %. The results of DMA also showed the AlN reinforcement was more pronounced above T_g, and the peak area of tan δ versus T curves decreased with AlN content, which implied the damping capacity of the composite gradually decreased. The increase in T_g and decrease in damping were probably due to strong interaction between the AlN and epoxy matrix inhibiting the mobility of the epoxy chain. In addition, different theoretical models reported in the literature were used to predict the E, CTE, k, and D_k, and compared with the experimental data. Finally, suitable models were recommended in the present materials system. For the significant improvement of performance of epoxy, we can conclude that these composite materials may be promising for PCB substrate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1662–1674, 2007     

Random time change and recurrent boundary

The purpose of this paper is to study some properties of random time changes in recurrent potential theory. In particular we show that the Martin recurrent boundary is not invariant under a random time change. We then obtain a characterization of random time change destroying a boundary point. We also give some complement about the recurrent boundary connected with “special additive functionals”. We have for example a representation at the boundary of solutions of the Poisson's equation $\text{?(I-U}{}_1\text{)=-U}{}_1\text{(x,·)}$ by using local time at x.     

Micellar electrokinetic capillary chromatography determination of zinc bacitracin and nystatin in animal feed

An MEKC procedure was developed for the separation of zinc bacitracin (Zn-BC) and nystatin (NYS) in mixtures and in animal feedstuff. The running buffer was 15 mM borate/19 mM phosphate, pH 8.2, containing 20 mM SDS and 10% v/v methanol. Samples were run at 25 degrees C, the applied voltage was 25 kV, and an additional pressure of 5 mbar was applied. Both analytes were detected by UV simultaneously at 215 nm, Zn-BC alone at 192 and 254 nm, and NYS alone at 305 nm. The method was shown to be specific, accurate (recoveries were 100.0 +/- 0.6% and 100.1 +/- 0.6% for Zn-BC and NYS, respectively), linear over the tested range (correlation coefficients 0.9991 and 0.9994), and precise (RSD below 1.3% for both analytes). The method was applied to determine Zn-BC and NYS as additives in animal feed.     

Technological Opportunities for the Implementation of Anti-Microbial Activities into Dry-Wet Shaped Cellulose Fibres

Metal cations are valuable antimicrobial additives for controlling of bacteria growth on textile fibres. By means of multiple actions they are able to suppress the undesirable microbe action also during wound healing. Dry-wet shaping technology offers numerous opportunities for implementation of antimicrobial activities into textile structures (fibres, yarn, fabrics). The degree of load, insertion step as well as type of additive (Ag, Cu, Zn) presents a broad field of physical modification of dry-wet spun cellulose fibres. The investigation of antimicrobial activities of manufactured fibres and yarns exhibit bactericide or bacteriostatic effects against typical pathogenic germs. Ag contents higher than 30 ppm in fibres and 0.06 per cent in yarns as well as Cu contents higher than 100 ppm in fibres and about 0.5 per cent in yarns are fairly effective for a permanent antimicrobial effect. Fabrics based on the developed fibres and yarns could already been successfully commercialised by innovative small and medium sized enterprises (SME).     

Effect of chemical substitution and oxide additives on the Tc behaviour of the oxide superconductor,Bi4Sr3Ca3Cu4O16

Studies on the superconductivity behaviour of pure and doped (Pb,TI) Bi₄Sr₃Ca₃Cu₄O₁₆ phases are reported. Effect of oxide additives PbO, BaPbO₃ and BaBiO₃ has also been examined. Results show that an oxygen treatment at 600°C for 12 h during the final stages of the synthesis has the beneficial effect of sharpening the T_c ^zero of the 4334 Bi-composition. Pb and TI substitution has only a marginally beneficial effect on the T_c , though it is not definitely known whether substitution is actually occurring in the system. PbO as an additive raises the T_c ^zero to 89 K, whereas other additives do not basically affect the properties of the 4334 system.     

Tribological behavior of the low-concentration boric acid and ZDDP lubricating oil mixtures

Zinc dithiophosphate (ZDDP)-free environmental friendly lubricating oil research studies have gained importance due to the governmental regulations over the last decade. In this study, low concentration boric acid-base oil and ZDDP-base oil mixtures were investigated with a ball on flat reciprocating tribometer to evaluate their tribological performances. The tribological performances of 1, 3, and 5% additive and base oil mixtures were evaluated at boundary lubrication condition in three main contexts including wear rates, surface tribochemistry, and friction. Results showed that there was no significant difference between boric acid and ZDDP friction coefficients. However, boric acid showed poor wear resistance when compared with ZDDP and it cannot be an alternative additive alone to ZDDPs.