Annealing of nylon-1010 under high pressure

Full Paper: A study has been made on the annealing of nylon-1010 under high pressures. Heat treatment of melt-crystallized nylon-1010 was performed at 250degreesC for 30 min in the pressure range 0.7 similar to 2.5 GPa. It was found that the triclinic crystals of virgin nylon-1010 were retained at pressures less than 1.0 GPa or larger than 1.2 GPa. The X-ray diffraction intensity of (100) planes decreased with increasing pressure. The diffraction peaks shifted slightly to higher angles (2theta) relative to the virgin nylon-1010, indicating dense packing of polymer chains at high pressures. The highest melting temperature was 208degreesC for the sample annealed at 1.5 GPa. No extended-chain crystals were formed under the experimental conditions. Crosslinking occurred in the pressure range 1.0 similar to 1.2 GPa. The structure of the crosslinked samples was characterized by means of infrared spectroscopy and X-ray photoelectron spectroscopy. It is concluded that a mechanism of crosslinking via carbodiimide can explain the nature of crosslinking of nylon-1010 annealed at high pressures. The remarkable changes of the structure of annealed nylon-1010 are also discussed in this article.

Crystallization and Crosslinking of polyamide-1010 under elevated pressure

The structure and thermal properties of polyamide-1010 (PA1010), treated at 250degreesC for 30 min under pressures of 0.7-2.5 GPa, were studied with wide-angle X-ray diffraction (WAXD), infrared (IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Crystals were formed when the pressures were less than 1.0 GPa or greater than 1.2 GPa. With increasing pressure, the intensity of the diffraction peak at approximately 24degrees was enhanced, whereas the peak at approximately 20degrees was depressed. The triclinic crystal structure of PA1010 was preserved. The highest melting temperature of the crystals obtained in this work was 208degreesC for PA1010 treated at 1.5 GPa. Crosslinking occurred under pressures of 1.0-1.2 GPa. Only a broad diffraction peak centered at approximately 20degrees was observed on WAXD patterns, and no melting and crystallization peaks were found on DSC curves. IR spectra of crosslinked PA1010 showed a remarkable absorption band at 1370 cm(-1). The N-H stretching vibration band at 3305 cm(-1) was weakened. Crystallized PA1010 had a higher thermal stability than crosslinked PA1010, as indicated on TGA curves by a higher onset temperature of decomposition.

Synthesis and properties of novel organosoluble polyimides derived from 1,4-bis[4-(3,4-dicarboxylphenoxy)]triptycene dianhydride and various aromatic diamines

A novel triptycene-based dianhydride, 1,4-bis[4-(3,4-dicarboxylphenoxy)]triptycene dianhydride, was prepared from 4-nitro-N-methylphthalimide and potassium phenolate of 1,4-dihydroxytriptycene (1). The aromatic nucleophilic substitution reaction between 4-nitro-N-methylphthalimide and I afforded triptycene-based bis(N-methylphthalimide) (2), which hydrolyzed and subsequently dehydrated to give the corresponding dianhydride (3). A series of new polyimides containing triptycene moieties were prepared from the dianhydride monomer (3) and various diamines in in-cresol via conventional one-step polycondensation method. Most of the resulting polyimides were soluble in common organic solvents, such as chloroform, THF, DMAc and DMSO. The polyimides exhibited excellent thermal and thermo-oxidative stabilities with the onset decomposition temperature and 10% weight loss temperature ranging from 448 to 486 degrees C and 526 to 565 degrees C in nitrogen atmosphere, respectively. The glass transition temperatures of the polyimides were in the range of 221-296 degrees C. The polyimide films were found to be transparent, flexible, and tough. The films had tensile strengths, elongations at break, and tensile moduli in the ranges 95-118 MPa, 5.3-16.2%, and 1.03-1.38 GPa, respectively. Wide-angle X-ray diffraction measurements revealed that these polyimides were amorphous.

High-pressure sintering study of a novel hard material (W0.5Al0.5)C-0.5 without binder metal

A novel hard material of (W0.5Al0.5)C-0.5 has been successfully sintered under high-pressure (4.5 GPa). The influence of sintering time and temperature on the microstructure, Vickers microhardness and density of the as-prepared specimens are well described. Interestingly, sintering temperature has an amazing influence on the hardness, density and microstructure of the specimen while the sintering time does not. It is found that the most suitable sintering condition from our work is 1600 degrees C and 10 min under pressure of 4.5 GPa. The hardness and relative density of the as-prepared sample can reach 2340 kg mm(-2) and 98.62%, respectively. The cell parameters of the sintered specimen is found to be little smaller than that of the powder, which we propose is related to the high pressure.

Spectral analysis and control to obtain sub-5 fs pulses by femtosecond filamentation

A spectral-filter method is numerically demonstrated to obtain sub-5 fs pulses by using femtosecond filamentation in fused silica. Instead of employing spectral phase compensation, by properly employing a high-pass filter to select the broadened high-frequency spectra that are located almost in phase in the tailing edge of the self-compressed pulses owing to self-steepening, as short as single-cycle pulses can be obtained. For instance, for an input pulse with a duration of 50 fs and energy 2.2 mu J, the minimum pulse duration can reach to similar to 4 fs (about 1.5 cycles) by applying a proper spectral filter. (C) 2008 Optical Society of America

The spectroscopic properties of Er3(+)-doped TeO2-Nb2O5 glasses with high mechanical strength performance

(100 - x)TeO2 - xNb(2)O(5) (x=5-20) mobic tellurite glasses doped with 0.5 mol.% Er2O3 were synthesized, and their thermal, mechanical, and spectroscopic properties were measured and compared to the properties of the typical 75TeO(2)-20ZnO-5Na(2)O (TZN) tellurite glass. The refractive index (n(d)), density (p), and glass transition temperature (T-g) of bulk glasses increase with the Nb2O5 content. The Vickers microhardness (H-v) of bulk glass in niobic tellurite glasses also increases with the Nb2O5 content. The values (2.5-3.2 GPa) of H, in the niobic tellurite glasses are 47-88% larger than that (1.7 GPa) in TZN glass. The effect of Nb2O5 content on absorption spectra, the Judd-Ofelt parameters Omega(t) (t = 2, 4, 6), fluorescence spectra and the lifetimes of Er3+ :I-13/2 level were also investigated, and the stimulated emission crosssection was calculated from McCumber theory. With increasing Nb2O5 content in the glass composition, the Omega(t) (t = 2, 4, 6) parameters, fluorescence full width at half maximum (FWHM) Of I-13/2 of Er3+ increase, while the I-4(13/2) lifetimes of Er3+ decreases. Compared with TZN glass, the gain bandwidth properties of Er3+-doped TeO2-Nb2O5 glass is much larger than in tellurite glass based TeO2-ZnO-Na2O system, bismush-based glass, germanate, and silicate glasses, which indicates that TeO2-Nb2O5 glasses are better choice as a practical available host material for broadband Er3+-doped amplifier. (c) 2005 Elsevier B.V. All rights reserved.

Intense upconversion and infrared emissions in Er3+;Yb3+ codoped Lu2 Si O5 and (Lu0.5 Gd0.5)2 Si O5 crystals

High optical quality Lu2SiO5 (LSO) and (Lu0.5Gd0.5)(2)SiO5 (LGSO) laser crystals codoped with Er3+ and Yb3+ have been fabricated by the Czochralski method. Intense upconversion (UC) and infrared emission (1543 nm) are observed under excitation of 975 nm. The luminescence processes are explained and the emission efficiencies are quantitatively obtained by measuring the UC efficiency and calculating the emission cross section. The temperature-dependent optical properties of the crystals are also investigated. Our study indicates that Er3+-Yb3+ : LSO and Er3+-Yb3+: LGSO crystals are promising gain media for developing the solid-state 1.5 mu m optical amplifiers and tunable UC lasers. (c) 2008 American Institute of Physics.

中国5种珍稀绢蝶非损伤性取样的mtDNA序列及系统进化

应用非损伤性取样DNA测序技术测定了4种来自云南白马雪山和1种来自新疆天山的5种珍稀绢蝶的线粒体DNA细胞色素b基因部分DNA序列。PAUP3.1.1(简约法)数据分析软件构建该5个种绢蝶的分子系统树显示,爱珂绢蝶(Parnassius acco)和巴裔绢蝶(Parnassius baileyi)的亲缘关系比较接近,阿波罗绢蝶(Parnassius apollo)、珍珠绢蝶(Parnassius orlears)和西猴绢蝶(Parnassius simo)3种绢蝶均为相对独立的一支,其中西猴绢蝶分化较早,与形态学研究结果相吻合。

Anti-human Immunodeficiency Virus-1 Constituents of the Bark of Poncirus trifoliata

A total of 36 compounds (1-36) were obtained from the stem bark of Poncirus trifoliata including three new prenylated flavonoids, (-)-5,4'-dihydroxy-7,8-[(3 '',4 ''-cis-dihydroxy-3 '',4 ''-dihydro)-2 '',2 ''-dimethylpyrano]-flavone (1), (-)-5,4'-dihydroxy-7,8-[(3 ''-hydroxy-4 ''-one)-2 '',2 ''-dimethylpyrano]-flavone (2), and (-)-5,4'-dihydroxy-7,8-[(cis-3 ''-hydroxy-4 ''-ethoxy-3 '',4 ''-dihydro)-2 '',2 ''-dimethylpyrano]-flavone (3). The new structures were elucidated by means of spectroscopic methods. Compounds 1-20 were evaluated for their anti-human immunodeficiency virus-1 (HIV-1) activity, in which 2 showed significant anti-HIV-1 activity with high therapeutic index (T1) of 143.65.

Anti-HIV-1 Activity of Lignans from the Fruits of Schisandra rubriflora

This study investigated the 70% aqueous acetone extract of the fruits of Schisandra rubriflora which led to the isolation of eight lignans, including a new isolate, rubrisandrin C (1), and seven known lignans (2-8). The structure of 1 was established by extensive 1D and 2D NMR spectroscopy and its absolute stereochemistry was determined by CD spectrum. Compounds 1-5 and 7-8 were evaluated for their anti-HIV-1 activity that showed inhibitory activity on HIV-1(IIIB) induced syncytium formation with EC50 values in the range of 2.26 similar to 20.4 mu g/mL. Compounds 1 and 7 exerted their obvious protection of HIV-1(IIIB) inducted MT-4 host cells lytic effects with a selectivity index of 15.4 and 24.6, respectively.

Explorative study on the expression of neuregulin-1 gene in peripheral blood of schizophrenia

Neuregulin-1 (Nrg-1)(1) gene has been considered as a schizophrenia susceptibility gene. In order to observe the association of Nrg-1 gene with schizophrenia, the study was designed to investigate the effect of anti-psychotic treatment on the Nrg-1 mRNA e

HIV-1感染对T和B细胞核内UNG2 mRNA表达的影响

目的:探讨HIV-1感染是否影响细胞中UNG2的表达.方法:采用四步法SYBR green Ⅰ实时定量RT-PCR,对HIV-1感染者的T和B淋巴细胞,以及HIV-1感染的C8166细胞核内UNG2 mRNA的表达进行测定.结果:UNG2 mRNA的表达在HIV-1感染者的T细胞和HIV-1感染的C8166细胞中被明显上调,分别是对照的8.76倍和8.14倍,而在HIV-1感染者的B细胞中却没有被上调.结论:HIV-1感染导致的UNG2表达上调,可能通过减少TCR的多样性削弱Th的功能,另一方面可能有利于病毒对UNG2的包装.

First-principles study of ground-state properties and high pressure behavior of ThO2

The mechanical properties, electronic structure and phonon dispersion of ground state ThO2 as well as the structure behavior up to 240 GPa are studied using first-principles density-functional theory. Our calculated elastic constants indicate that both the ground-state fluorite structure and high pressure cotunnite structure of ThO2 are mechanically stable. The bulk modulus, shear modulus, and Young's modulus of cotunnite ThO2 are all smaller by approximately 25% compared with those of fluorite ThO2. The Poisson's ratios of both structures are approximately equal to 0.3 and the hardness of fluorite ThO2 is 22.4 GPa. The electronic structure and bonding nature of fluorite ThO2 are fully analyzed, and show that the Th-O bond displays a mixed ionic/covalent character. The phase transition from the fluorite to cotunnite structure is calculated to occur at the pressure of 26.5 GPa, consistent with recent experimental measurement by ldiri et al. [1]. For the cotunnite phase it is further predicted that an isostructural transition takes place in the pressure region of 80-130 GPa.

New observations on the pressure dependence of luminescence from Eu2+-doped MF2 (M = Ca, Sr, Ba) fluorides

The luminescence from Eu2+ ions in MF2 (M = Ca, Sr, Ba) fluorides has been investigated under the pressure range of 0-8 GPa. The emission band originating from the 4f(6)5d(1) -> 4f(7) transition of Eu2+ ions in CaF2 and SrF2 shows the red-shift as increasing pressure with pressure coefficients of -17 meV/GPa for CaF2 and -18 meV/GPa for SrF2. At atmospheric pressure, the emission spectrum of BaF2:Eu2+ comprises two peaks at 2.20 and 2.75 eV from the impurity trapped exciton (ITE) and the self-trapped exciton (STE), respectively. As the pressure is increased, both emission peaks shift to higher energies, and the shifting rate is slowed by the phase transition from the cubic to orthorhombic phase at 4 GPa. Due to the phase transition at 4-5 GPa pressure, the ITE emission disappears gradually, and the STE emission is gradually replaced by the 4f(6)5d(1) -> 4f(7) transition of Eu2+. Above 5 GPa, the pressure behavior of the 4f(6)5d(1) -> 4f(7) transition of EU2+ in BaF2: EU2+ is the same as the normal emission of Eu2+ in CaF2 and SrF2 phosphors.

Anomalous Pressure Behavior of N-Cluster Emissions in GaAs0.973Sb0.022N0.005

Photoluminescence of GaAs0.973Sb0.022N0.005 is investigated at different temperatures and pressures. Both the alloy band edge and the N-related emissions, which show different temperature and pressure dependences, are observed. The pressure coefficients obtained in the pressure range 0-1.4GPa for the band edge and N-related emissions are 67 and 45 meV/GPa, respectively. The N-related emissions shift to a higher energy in the lower pressure range and then begin to redshift at about 8.5 GPa. This redshift is possibly caused by the increase of the X-valley component in the N-related states with increasing pressure.