Photodegradation of polypropylene thermal bonded non-woven fabric

Samples of thermal bonded polypropylene non-woven fabrics were exposed to light from two TUV 30W G30T8 Philips lamps (λ = 253.7 nm) in a covered open-air chamber at room temperature (25 °C and 55% relative humidity) for different periods of time. In order to determine the state of degradation, the samples were examined by optical microscopy, scanning electron microscopy, staining with an isopropanol solution of methylene blue and Sudan III, colourimetry, Fourier transform infrared (FTIR) spectroscopy and density measurements. Although the bonded areas formed under complex thermal and mechanical deformations during the fabric production, no localized staining was observed. The colour of the irradiated and stained fabrics changed uniformly due to the even production of polar groups in the process of irradiation. It was found that the change of redness and blueness of degraded and stained samples can be correlated linearly with the evolution of POOH groups as determined by FTIR spectroscopy. Products containing carbonyl (CO), hydroxyl and/or hydroperoxide (POOH) groups increase with time of degradation with a non-linear relation. It was also observed that the density and 997 cm⁻¹/972 cm⁻¹ FTIR absorbance ratio increases with degradation time. Density fluctuation and the build up of degradation products caused fibre cracks and embrittlement.     

Synthesis of a Tweezer—like Bis（Phenylthiapropoxy）calix[4]—arene as a Cation／π Enhanced Sensor for Ion—Selective Electrodes

Two novel 25,27-dihydroxy-26,28-bis(3-phenylthiapropxy)-calix[4]arene(3) and 25,27-dihydroxy-26,28-bis(3-phenylthiapropoxy)-5,11,17,23-tetra-tert-butylcalix[4] arene (4) were synthesized for the evaluation of their ion-selectivity in ion-selective electrodes(ISEs).ISEs based on 3 and 4 as neutral ionophores were prepared,and their selectivity coefficients for Ag^ (lg KAg,M^pot)were investigated against other alkali metal,alkaline-earth metal,aluminum,thallium(Ⅰ）,Lead and some transition metal ions using the separate solution method (SSM).These ISEs showed excellent Ag^ seletivity over most of the interfering cations examined,except for Hg^2 and Fe^2 having relative smaller interference(lg KAg,M^pot≤-2.1).     

高能强子–强子碰撞中喷注性质的蒙特卡洛研究

在喷注“圆锥判定法”的基础上,对高能强子–强子碰撞中产生的喷注(微喷注)的性质进行了蒙特卡洛研究.采用以喷注动量为z轴的“喷注坐标系”,给出了表征喷注性质的各物理量在新坐标系中的分布情况.结果表明,圆锥判定法能够作为一种有效手段来对高能强子–强子碰撞和相对论重离子碰撞中发生的硬和半硬过程开展实验研究.由有喷注事件和无喷注事件的多重数分布可以看到,E_t=2GeV是用圆锥法确定喷注的合理的横能截断值.     

Spatiotemporal stochastic resonance and its consequences in neural model systems

The realization of spatiotemporal stochastic resonance is studied in a two-dimensional FitzHugh-Nagumo system, and in a one-dimensional system of integrate-and-fire neurons. We show that spatiotemporal stochastic resonance occurs in these neural model systems, independent of the method of modeling. Moreover, the ways of realization are analogous in the two model systems. The biological implications and open questions are discussed. (c) 2001 American Institute of Physics.     

Laser-hole boring into overdense plasmas measured with soft X-Ray laser probing

A laser self-focused channel formation into overdense plasmas was observed using a soft x-ray laser probe system with a grid image refractometry (GIR) technique. 1.053 &mgr;m laser light with a 100 ps pulse duration was focused onto a preformed plasma at an intensity of 2x10(17) W/cm (2). Cross sections of the channel were obtained which show a 30 &mgr;m diameter in overdense plasmas. The channel width in the overdense region was kept narrow as a result of self-focusing. Conically diverging density ridges were also observed along the channel, indicating a Mach cone created by a shock wave due to the supersonic propagation of the channel front.     

Structural characterization and mechanical properties of electrospun silk fibroin nanofiber mats

The regenerated silk fibroin dissolved in formic acid was electrospun into nanofiber mats. Structural characteristics of the spun as received and methanol and ethanol treated fibers were examined using the Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction. Mechanical properties and air permeability of the electrospun mats were also studied. IR spectroscopy and X-ray diffractometry showed random coil conformation and amorphous structure for as-spun fibers while typical FTIR spectra and X-ray diffractograms of β-sheet crystalline structure were recorded for the methanol and ethanol treated fibers. The mechanical properties of the mats were found to be dependent on fiber diameter. The mats containing fibers with smaller diameter had higher tensile strength but lower breaking strain. Methanol and ethanol treatment enhanced tensile strengths of the mats at the expenses of their breaking strain. Air permeability and pore size of the mats are strongly associated with diameter of the electrospun fibers.     

Dark matter results from 100 live days of XENON100 data

We present results from the direct search for dark matter with the XENON100 detector, installed underground at the Laboratori Nazionali del Gran Sasso of INFN, Italy. XENON100 is a two-phase time-projection chamber with a 62 kg liquid xenon target. Interaction vertex reconstruction in three dimensions with millimeter precision allows the selection of only the innermost 48 kg as the ultralow background fiducial target. In 100.9 live days of data, acquired between January and June 2010, no evidence for dark matter is found. Three candidate events were observed in the signal region with an expected background of (1.8 ± 0.6) events. This leads to the most stringent limit on dark matter interactions today, excluding spin-independent elastic weakly interacting massive particle (WIMP) nucleon scattering cross sections above 7.0 × 10(-45) cm(2) for a WIMP mass of 50 GeV/c(2) at 90% confidence level.     

Modification of poly(ethylene terephthalate) fibers,fabrics, and films by amination reactions—A review

Currently, many of our living facilities are dependent on poly(ethylene terephthalate) (PET). It is utilized in the production of textiles, beverage bottles, food packaging, implants, and so forth. Although PET has desirable properties, it has to be amended for certain applications that have been modified by different methods. For modifications, aminolysis is used by several investigators, and this report reviews critically the related literature. Amines can be applied to impart the desired properties and produce active sites to be used for further alterations by successive reactions. Amine treatments alone enhance wettability, increase dyeability, and most applicable, produce functionality on the surface. By further reactions with several other chemicals, a spectrum of properties was endowed to PET products, such as flame retarding, anti-fouling property, highest hygroscopicity, silk-like character, biocompatibility, and so forth. There are a large number of works, mainly to change the surface properties, but the literature on the in vivo or common everyday evaluation of the amended products is scarce. Most of the modifications of PET products by amines are accompanied by a decrease in some other properties. Then the process of aminolysis and modifications have to be optimized with respect to several production parameters.     

Curing theory of A_f-A_g type free radical polymerization (I)──Distribution function and its invariant property

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