Grafting acrylic acid onto polypropylene by reactive extrusion with pre-irradiated PP as initiator

In this paper, the modification of polypropylene (PP) with acrylic acid (AA) by reactive extrusion using pre-irradiated PP (rPP) as initiator was investigated. It was found the relatively high graft degree (Gd) and slight degradation of modified PP was obtained when 20 wt% rPP was used. This result can be explained in terms of effective concentration of free radicals.

Preparation and Characterization of Melt Grafting 2-acrylamido-2-methyl-1-propanesulfonic Acid onto Pre-Irradiated Linear Low Density Polyethylene

Linear low density polyethylene (LLDPE) was functionalized with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) by using -ray pre-irradiation in air in a twin-screw extruder. Fourier-transformed infrared spectroscopy (FT-IR) and electron spectroscopy for chemical analysis (ESCA) were used to characterize the formation of LLDPE-g-AMPS copolymers. The content of AMPS in LLDPE-g-AMPS was determined by using element analysis instrument. The effects of concentrations of monomer, reaction temperature and pre-irradiation dose on degree of grafting were investigated. The critical surface tension of LLDPE-g-AMPS was measured by using contact angle method. The influences of the degree of grafting on crystallization properties were studied by using DSC. Compared with neat LLDPE, the crystallization temperature increased about 4C, and crystallinity decreased with increasing degree of grafting. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at the same crystallization temperature.

Graft chain propagation rate coefficients of acrylic acid in melt graft copolymerization with linear low density polyethylene

Graft chain propagation rate coefficients (k(p.g)) for grafting AA onto linear low density polyethylene (LLDPE) in the melt in ESR tubes have been measured via Fourier transform infrared (FTIR) spectroscopy and electron spin resonance (ESR) spectroscopy in the temperature range from 130 to 170 degrees C. To exclude the effect of homopolymerization on the grafting. the LLDPE was pre-irradiated in the air by electron beam to generate the peroxides and then treated with iodide solution to eliminating one kind of peroxides, hydroperoxide. The monomer conversion is determined by FTIR and the chain propagation free-radical concentration is deduced from the double integration of the well-resolved ESR spectra, consisting nine lines in the melt. The temperature dependence of k(p.g) is expressed:The magnitude of k(p.g) from FTIR and ESR analysis is in good agreement with the theoretical data deduced from ethylene-AA copolymerization, suggesting this method could reliably and directly provide the propagation rate coefficient. The comparison of k(p.g) with the data extrapolated from solution polymerization at modest temperature indicates that the extrapolated data might not be entirely fitting to discuss the kinetics behavior in the melt.

The preparation of high activity DMFC Pt/C electrocatalysts using a pre-precipitation method

It is suggested that a Pt/C cathodic catalyst for the direct methanol fuel cell (DMFC) can be prepared with a pre-precipitation method, in which, H2PtCl6 is precipitated onto the carbon black as (NH4)(2)PtCl6 before H2PtCl6 is reduced to Pt. The electrocatalytic activity of this Pt/C-A catalyst for oxygen reduction is excellent because the Pt/C catalyst prepared with this pre-precipitation method possesses a small average particle size, low relative crystalinity and a large electrochemically active surface area. In addition, the pre-precipitation method is simple and economical and it can be used to prepare a Pt/C catalyst on a large scale.

Electrochemical H2S sensor with H2SO4 pre-treated Nafion membrane as solid polymer electrolyte

It is reported for the first time that the performance of the electrochemical H2S sensor with the Nation membrane pre-treated with the concentrated H2SO4 as the solid electrolyte is much more stable than that for the sensor with the Nation membrane without H2SO4 pretreatment. The sensitivity of the sensor is about 2.92 muA/ppm. The response time of the sensor is about 9 s. The detection limit is about 0.1 ppm. Therefore, this kind of the electrochemical H2S gas sensor may be desirable for the practical application.

Self-assembly of the pre-formed inclusion complexes between cyclodextrins and alkanethiols on gold electrodes

A new kind of self-assembled monolayer (SAM) formed in aqueous solution through the pre-formed inclusion complexes (abbreviated CD . C-n) between alpha-, beta-cyclodextrins (CDs) and alkanethiols (CH3(CH2)(n-1)SH, n = 10, 14 and 18) was prepared successfully on gold electrodes. High-resolution H-1 NMR was used to confirm the formation of CD . C-n. X-ray photoelectron spectroscopy, cyclic voltammetry and chronoamperometry were used to characterize the resulting SAMs (denoted as M-CD . Cn). It was found that M-CD . Cn were more stable against repeated potential cycling in 0.5 M H2SO4 than SAMs of CH3(CH2)(n-1)SH (denoted as M-Cn), with a relative sequence of Mbeta-CD . Cn > Malpha-CD . Cn > M-Cn. In addition, an order of blocking the electron transfer between gold electrodes and redox couples (both Fe(CN)(6)(3-) and Ru(NH3)(6)(3+)) in solution, M-CD . C10 > M-CD . C14 > M-CD . C18, was observed. A plausible explanation is provided to elucidate some of the observations. (C) 1997 Elsevier Science S.A.

Simultaneous determination of monoamine and amino acid neurotransmitters in rat endbrain tissues by pre-column derivatization with high-performance liquid chromatographic fluorescence detection and mass spectrometric identification

A sensitive and efficient method for simultaneous determination of glutamic acid (Glu), gamma-amino-butyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in rat endbrains was developed by high-performance liquid chromatography (HPLC) with fluorescence detection and on-line mass spectrometric identification following derivatization with 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC). Different parameters which influenced derivatization and separation were optimized. The complete separation of five neurotransmitter (NT) derivatives was performed on a reversed-phase Hypersil BDS-C-18 column with a gradient elution. The rapid structure identification of five neurotransmitter derivatives was carried out by on-line mass spectrometry with electrospray ionization (ESI) source in positive ion mode, and the BCEOC-labeled derivatives were characterized by easy-to-interpret mass spectra. Stability of derivatives, repeatability, precision and accuracy were evaluated and the results were excellent for efficient HPLC analysis. The quantitative linear range of five neurotransmitters were 2.441-2 x 10(4) nM, and limits of detection were in the range of 0.398-1.258 nM (S/N = 3:1). The changes of their concentrations in endbrains of three rat groups were also studied using this HPLC fluorescence detection method. The results indicated that exhausting exercise could obviously influence the concentrations of neurotransmitters in rat endbrains. The established method exhibited excellent validity, high sensitivity and convenience, and provided a new technique for simultaneous analysis of monoamine and amino acid neurotransmitters in rat brain. (C) 2008 Elsevier B.V. All rights reserved.

Determination of aliphatic amines from soil and wastewater of a paper mill by pre-column derivatization using HPLC and tandem mass spectrometry (HPLC-MS/MS)

A pre-column derivatization method for the sensitive determination of aliphatic amines using the labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) followed by HPLC with fluorescence detection and APCI/NIS identification in positive-ion mode has been developed. The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent was replaced by the 1,2-benzo-3,4-dihydrocarbazole functional group, which resulted in a sensitive fluorescence derivatizing reagent, BCEOC, that could easily and quickly label amines. Derivatives were stable enough to be efficiently analyzed by HPLC and showed an intense protonated molecular ion corresponding m/z [M + H](+) with APCI/MS in positive-ion mode. The collision induced dissociation of the protonated molecular ion formed characteristic fragment ions at m/z 264.1, m/z 246.0 and m/z 218.1, corresponding to the cleavages of CH2CH2O-CO, CH2CH2-OCO, and N-CH2CH2O bonds. Studies on derivatization conditions demonstrated that excellent derivatization yields close to 100% were observed with a 3 to 4-fold molar reagent excess in acetonitrile solvent, in the presence of borate buffer (pH 9.0) at 40 degrees C for 10 min. In addition, the detection responses for BCEOC derivatives were compared with those obtained with CEOC and FMOC as labeling reagents. The ratios I-BCEOC/I-CEOC and I-BCEOC/I-FMOC were, respectively, 1.40-2.76 and 1.36-2.92 for fluorescence responses (here, I was the relative fluorescence intensity). Separation of the amine derivatives had been optimized on an Eclipse XDB-C-8 column. Detection limits calculated from an 0.10 pmol injection, at a signal-to-noise ratio of 3, were 18.65-38.82 fmol (injection volume 10 mu L for fluorescence detection. The relative standard deviations for intraday determination (n = 6) of standard amine derivatives (50 pmol) were 0.0063-0.037% for retention times and 3.36-6.93% for peak areas. The mean intra-and inter-assay precision for all amines were <5.4% and 5.8%, respectively. The recoveries of amines ranged from 96 to 113%. Excellent linear responses were observed with correlation coefficients of >0.9994. The established method provided a simple and highly sensitive technique for the quantitative analysis of trace amounts of aliphatic amines from biological and natural environmental samples.

Pre-column derivatization of amines with 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl chloroformate followed by LC-fluorescence and LC-APCI-MS

A pre-column derivatization method for the sensitive determination of amines using the labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl chloroformate (BCIC-Cl) followed by high-performance liquid chromatography with fluorescence detection has been developed. Identification of derivatives is carried out by high performance liquid chromatography/atmospheric pressure chemical ionization (LC-APCl-MS-MS). The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent is replaced by 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl functional group, which results in a sensitive fluorescence derivatizing reagent BCIC-Cl. BCIC-Cl can easily and quickly label amines. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography and show an intense protonated molecular ion corresponding m/z [MH](+) under APCl in positive-ion mode. The collision-induced dissociation of protonated molecular ion formed a product at m/z 260 corresponding to the cleavage of CH2-OCO bond. Studies on derivatization demonstrate excellent derivative yields over the pH 9.0-10.0. Maximal yields close to 100% are observed with a 3 to 4-fold molar reagent excess. In addition, the detection responses for BCIC derivatives are compared with those obtained using CEOC and FMOC as derivatization reagents. The ratios of l(BCIC)/l(CEOC) and l(BCIC)/l(FMOC) are, respectively, 1.23-3.14 and 1.25-3.08 for fluorescent (FL) responses (here, l is relative fluorescence intensity). Separation of the derivatized amines had been optimized on reversed-phase Eclipse XDB-C-8 column. Detection limits are calculated from 1.0 pmol injection, at a signal-to-noise ratio of 3, are 10.6-37.8 fmol. The mean interday accuracy ranges from 94 to 105% for fluorescence detection with the largest mean %CV < 7.5. The mean interday precision for all standards is < 6.0% of the expected concentration. Excellent linear responses are observed with coefficients of > 0.9997.

北山及邻区古生代-早中生代增生与碰撞大地构造格局

The Beishan orogenic collage locates at the triple-joint among Xinjiang, Gansu, and Inner Mongolia Provinces, at which the Siberian, Tarim and North China plates join together. It also occupies the central segment of the southern Central Asian Orogenic Belt (CAOB). The main study area in the present suty focused on the southwest part of the Beishan Mountain, which can be subdivided into four units southernward, the Mazhongshan continental block, Huaniushan Arc, Liuyuan suture zone and Shibanshan-Daqishan Arc. 1. The Huaniushan Arc was formed by northernward dipping subduction from the Orcovician to Permian, in which volcanic rocks ranging from basic to acidic with island arc affinity were widely developed. The granitiod intrusions become smaller and younger southward, whichs indicates a southward rollback of slab. The granitiod intrusions are mainly composed of I type granites, and their geochemical compositions suggest that they have affinities of island arc settings. In the early Paleozoic（440Ma-390Ma）. The Shibanshan-Daqishan Arc, however, were produced in the southernward dipping subduction system from Carboniferous to Permian. Volcanic rocks from basic to acidic rocks are typical calcic-alkaline rocks. The granitiod intrusions become smaller and younger northernward, indicating subdution with a northernward rollback. The granitiod intrusions mainly consist of I-type granites, of which geochemical data support they belong to island arc granite. 2. Two series of adakite intrusions and eruptive rocks have been discovered in the southern margin of the Huaniushan Island Arc. The older series formed during Silurian (441.7±2.5Ma) are gneiss granitoid. These adakite granites intruded the early Paleozoic Liuyuan accretionary complex, and have the same age as most of the granite intrusions in the Huanniushan Arc. Their geochemical compostions demonstrate that they were derived from partial melting of the subudcted oceanic slab. These characteristics indicate a young oceanic crust subduction in the early Paleozoic. The late stage adakites with compositons of dacites associate with Nb-enriched basalts, and island arc basalts and dacites. Their geochemistries demonstrate that the adakites are the products of subducted slab melts, whereas the Nb-enriched basalt is products of the mantle wedge which have metasomatized by adakite melts. Such a association indicates the existences of a young ocean slab subduction. 3. The Liuyuan suture zone is composed of late Paleozoic ophiolites and two series of accretionary complexes with age of early Paleozoic. The early Paleozoic accretionary complex extensively intruded by early Palozioc granites is composed of metamorphic clastics, marble, flysch, various metamorphic igneous rocks (ultramafic, mafic and dacite), and eclogite blocks, which are connected by faults. The original compositions of the rocks in this complex are highly varied, including MORB, E-MORB, arc rocks. Geochronological study indicates that they were formed during the Silurian (420.9±2.5Ma and 421.1±4.3Ma). Large-scale granitiods intruded in the accretionary complex suggest a fast growth effect at the south margin of the Huaniushan arc. During late Paleozoic, island arc were developed on this accretionary complex. The late Paleozoic ophiolite has an age of early Permian (285.7±2.2Ma), in which the rock assemblage includes ultra-mafic, gabbros, gabbros veins, massive basalts, pillow basalt, basaltic clastic breccias, and thin layer tuff, with chert on the top.These igneous rocks have both arc and MORB affinities, indicating their belonging to SSZ type ophiolite. Therefore, oceanic basins area were still existed in the Liuyuan area in the early Permian. 4. The mafic-ultramafic complexes are distributed along major faults, and composed of zoned cumulate rocks, in which peridotites are surrounded by pyroxenite, hornblendites, gabbros norite and diorite outward. They have island-arc affinities and are consistent with typical Alaska-type mafic-ultramafic complexes. The geochronological results indicate that they were formed in the early Permian. 5. The Liuyuan A-type granite were formed under post-collisional settings during the late Triassic (230.9±2.5Ma), indicating the persistence of orogenic process till the late Triassic in the study area. Geochronological results suggested that A-type granites become younger southward from the Wulungu A-type granite belt to Liuyuan A-type granite belt, which is in good agreement with the accretionary direction of the CAOB in this area, which indicate that the Liuyuan suture is the final sture of the Paleo-Asin Ocean. 6. Structural geological evidence demonstrate the W-E spreading of main tectonic terrenes. These terrenes had mainly underwent through S-N direction contraction and NE strike-faulting. The study area had experienced a S-N direction compression after the Permian, indicating a collisional event after the Permian. Based on the evidene from sedimentary geology, paleontology, and geomagnetism, our studies indicate that the orogenic process can be subdivided into five stages: (1) the pre-orogenic stage occurred before the Ordovicain; (2) the subduction orogenic stage occurred from the Orcovician to the Permian; (3) the collisional orogenic stage occurred from the late Permian to the late Triassic; (4) the post-collision stage occurred after the Triassic. The Liuyuan areas have a long and complex tectonic evolutional history, and the Liuyuan suture zone is one of the most important sutures. It is the finally suture zone of the paleo-Asian ocean in the Beishan area.

Synthesis of nanometric-size magnesium nitride by the nitriding of pre-activated magnesium powder

Magnesium nitride (Mg3N2) was synthesized by the reaction of magnesium in the highly reactive form (Mg*) with nitrogen at 450 degrees C under normal pressure. The effect of doping with nickel dichloride on the nitridation of Mg* was investigated. Differential thermal analysis (DTA) of Mg* systems and transmission electron microscopy (TEM) measurement of the product formed were carried out. TEM measurement showed that the particle size of the Mg3N2 synthesized was in the nanometric range. The dependence of nitridation of the NiCl2-doped Mg* on temperature was investigated at temperatures ranging from 300 to 500 degrees C. The nitridation of NiCl2-doped Mg* could occur even at temperature as low as 300 degrees C. (C) 1999 Kluwer Academic Publishers.

Application of liquid pre-column capillary electrophoresis technique to the study of interaction between drug enantiomers and human serum albumin

Based on the chiral separation of several basic drugs, dimetindene, tetryzoline, theodrenaline and verapamil, the liquid pre-column capillary electrophoresis (LPC-CE) technique was established. It was used to determine free concentrations of drug enantiomers in mixed solutions with human serum albumin (HSA). To prevent HSA entering the CE chiral separation zone, the mobility differences between HSA and drugs under a specific pH condition were employed in the LPC. Thus, the detection confusion caused by protein was totally avoided. Further study of binding constants determination and protein binding competitions was carried out. The study proves that the LPC technique could be used for complex media, particularly the matrix of protein coexisting with a variety of drugs.

Computational Consequences of Agreement and Ambiguity in Natural Language

The computer science technique of computational complexity analysis can provide powerful insights into the algorithm-neutral analysis of information processing tasks. Here we show that a simple, theory-neutral linguistic model of syntactic agreement and ambiguity demonstrates that natural language parsing may be computationally intractable. Significantly, we show that it may be syntactic features rather than rules that can cause this difficulty. Informally, human languages and the computationally intractable Satisfiability (SAT) problem share two costly computional mechanisms: both enforce agreement among symbols across unbounded distances (Subject-Verb agreement) and both allow ambiguity (is a word a Noun or a Verb?).

Computation and Pre-Parametric Design

My work is broadly concerned with the question "How can designs bessynthesized computationally?" The project deals primarily with mechanical devices and focuses on pre-parametric design: design at the level of detail of a blackboard sketch rather than at the level of detail of an engineering drawing. I explore the project ideas in the domain of single-input single-output dynamic systems, like pressure gauges, accelerometers, and pneumatic cylinders. The problem solution consists of two steps: 1) generate a schematic description of the device in terms of idealized functional elements, and then 2) from the schematic description generate a physical description.