Ion-induced nucleation rate measurement in SO2/H2O/N2 gas mixture by soft X-ray ionization at various pressures and temperatures

This paper reports the systematic investigation of ion-induced nucleation rate measurement in a SO₂/H₂O/N₂ gas mixture, employing soft X-ray at different pressure and temperature levels. Experiments were conducted using a modified continuous flow gas-generation system employing a soft X-ray ionizer and a particle counter, with an improved integrated online temperature, pressure and a relative humidity (RH) control system. Nucleation rates were measured as a function of SO₂ concentration at different levels of RH, pressure (600–970 hPa) and temperature (5–25 °C). The results show that the nucleation rate dependence on SO₂ concentration followed a power law, and the slope varied slightly in a range from 1 to 1.26 at different RH levels (15–60%). A positive pressure effect was generally found and a power law was followed with varied scaling for different SO₂ concentrations. The trend of an increase in nucleation rate with temperature was consistent with observations in homogenous nucleation experiments, and with the behavior predicted by classical binary nucleation theory. These experimental results will be useful to explain the contribution of ion-induced nucleation in different locations and atmospheric conditions.     

Influence of addition of styrene–ethylene/butylene–styrene copolymer on rheological,mechanical, and tribological properties of polyamide nanocomposites

To develop new tribomaterials for mechanical sliding parts, investigations were carried out on the influence of adding styrene–ethylene/butylene–styrene block copolymer (SEBS) on the rheological, mechanical, and tribological properties of polyamide 6 (PA6) nanocomposite, which is a commercial product of layered silicate (clay) filled polyamide 6 (PA6/Clay). Two kinds of block copolymers, unmodified SEBS (SEBS) and maleic anhydride‐grafted SEBS (SEBS‐g‐MA), were added with PA6/Clay nanocomposite. Dynamic viscoelastic properties in the molten state of these nanocomposites and their tensile, impact, and tribological properties of these nanocomposites were evaluated. Dynamic viscoelastic properties were found to increase with the addition of SEBS and were influenced, in particular, by block copolymers containing SEBS‐g‐MA. Influence of the addition of SEBS on mechanical properties of these systems differed for each mechanical property. Although tensile properties decreased with SEBS, Izod impact properties were improved with the addition of SEBS‐g‐MA. Tribological properties were improved with the addition of block copolymer, and the influence of the amount of addition was higher than the type of block copolymer used. These results indicate that new tribomaterials developed have sufficient balance amongst moldability, mechanical, and tribological properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

热处理温度对焦宝石基喷涂料性能的影响

以焦宝石颗粒及细粉为主要原料,以硅微粉、铝酸钙水泥为结合剂,研究了不同热处理温度对焦宝石基喷涂料性能的影响。结果表明,随着热处理温度的提高,焦宝石基喷涂料的体积密度无明显变化,线变化率随热处理温度的提高而增大。焦宝石基喷涂料的抗折强度和耐压强度随着热处理温度的提高呈现先减小后增大的趋势。     

Continuously Frequency Tunable High Power Sub-THz Radiation Source—Gyrotron FU CW VI for 600 MHz DNP-NMR Spectroscopy

A high frequency gyrotron with a 15 T superconducting magnet named Gyrotron FU CW VI has achieved continuous frequency tuning through the relatively wide range of 1.5 GHz near 400 GHz. The operation is at the fundamental cyclotron resonance of the TE₀₆ cavity mode with many higher order axial modes. The output power measured at the end of the circular waveguide system ranges from 10 to 50 watts at the low acceleration voltage of 12 kV for beam electrons. The beam current is also low. It is around 250 mA. This gyrotron is designed as a demountable radiation source for the 600 MHz DNP-NMR spectroscopy. The design and operation results of the gyrotron FU CW VI are presented.     

Phytanic acid α-hydroxylation by bacterial cytochrome P450

Fatty acid α-hydroxylase, a cytochrome P450 enzyme, from Sphingomonas paucimobilis, utilizes various straight-chain fatty acids as substrates. We investigated whether a recombinant fatty acid α-hydroxylase is able to metabolize phytanic acid, a methyl-branched fatty acid. When phytanic acid was incubated with the recombinant enzyme in the presence of H₂O₂, a reaction product was detected by gas chromatography, whereas a reaction product was not detected in the absence of H₂O₂. When a heat-inactivated enzyme was used, a reaction product was not detected with any concentration of H₂O₂. Analysis of the methylated product by gas chromatography-mass spectrometry revealed a fragmentation pattern of 2-hydroxyphytanic acid methyl ester. By single-ion monitoring, the mass ion and the characteristic fragmentation ions of 2-hydroxyphytanic acid methyl ester were detected at the retention time corresponding to the time of the product observed on the gas chromatogram. The K _m value for phytanic acid was approximately 50 μM, which was similar to that for myristic acid, although the calculated V _max for phytanic acid was about 15-fold lower than that for myristic acid. These results indicate that a bacterial cytochrome P450 is able to oxidize phytanic acid to form 2-hydroxyphytanic acid.     

Experimental Evaluation of the Optical Properties of Porous Silica/Carbon Composite Particles

Light scattering by porous spheroidal silica and several silica/carbon composite particles having different carbon contents was systematically investigated using a laser particle counter coupled with a pulse height analyzer (LPC-PHA). A new and simple method for the measurements of the effective complex refractive index of silica/carbon composite particles using a conventional LPC-PHA system and a differential mobility analyzer was introduced and tested. Challenge particles, from pure silica to silica/carbon compounds having a gradually increasing porous structure, were prepared by spray-drying methods for use in testing of the inversion method. By representing the deviation of the real part of the refractive index of a porous silica particle versus the size on a topographical map, the inversion method for the determination of the real part of the refractive indices was found to have a satisfactory precision. Furthermore, the method can be applied to the measurement of the complex refractive index of silica/carbon composite particles by extending the best fitting method to complex refractive indices. The effective complex refractive index of silica/carbon composite particles as a function of their carbon content is reported. Both the real and imaginary parts of the complex refractive index were increased with increasing carbon content of the composite particles.     

Polyethyleneimine/chitosan hexamer-mediated gene transfection into intestinal epithelial cell cultured in serum-containing medium

In search of an efficient nonviral vector, polyethyleneimine (PEI)-based vectors were examined. In general, the transfection efficiency of nonviral vectors is suppressed by serum. Here we show that PEI based vectors, particularly, the chitosan hexamer-PEI vector, could perform efficient gene transfection into intestinal epithelial cells (IEC-6) in the presence of serum. The conjugation order of the two polymers with a plasmid (first, chitosan hexamer; second, PEI) was found to be an important factor in enhancing transfection efficiency.     

Interference-based electrochemical biosensor for the measurement of the concentration and isomer ratio of urocanic acid

Urocanic acid (UCA) is known to be synthesized as the trans isomer (trans-UCA) in the skin, and trans-UCA is transformed by UV light to the cis isomer (cis-UCA), which may be involved in photoimmunosuppression. An electrochemical method has been developed for the measurement of the concentration and isomer ratio of UCA. A heme peptide-modified electrode (HP electrode) reduces hydrogen peroxide at +150 mV vs Ag/AgCl, and the reduction current is inhibited by UCA. Since cis-UCA is a stronger inhibitor than trans-UCA, irradiation of a sample solution with UV light increases the percent inhibition. The concentration and isomer ratio of UCA in the sample solution can be estimated from the values of percent inhibition before and after the UV irradiation.     

Strong metal-support interactions (SMSIs) between Pt and Ti3+ on Pt/TiOx nanoparticles for enhanced degradation of organic pollutant

In this work, Pt nanoparticles were deposited onto the surface of Magnéli phase titanium suboxide (TiO_x) nanoparticles using a microwave-assisted deposition method. The effect of different concentrations of Pt nanoparticles was investigated to evaluate the strong metal-support interactions (SMSIs) between Pt and TiO_x based on their performance for the degradation of organic pollutant molecules. The adsorption and catalytic performance of the as-synthesized Pt/TiO_x nanoparticles were evaluated with respect to the degradation of rhodamine B (RhB) molecules without any external energy source. The Pt/TiO_x nanoparticles with Pt loading at 10 wt% (10%Pt/TiO_x) exhibited a remarkable performance. The XPS, CV, and FTIR analyses confirmed the presence of RhB degradation reactions under dark condition. This remarkable performance of the Pt/TiO_x nanoparticles was attributed to the SMSIs between Pt and Ti³⁺ atoms, which improves their performance compared with Pt/TiO₂ nanoparticles, and high density of active sites due to their nanometer size, which results in better performance compared with that of Pt/TiO_x submicron particles.     

AC Drive System for Tension Reel Control

Recently, adjustable-speed ac drive systems have been employed successfully for blowers, pumps, table rollers, etc., in steel plants instead of the more conventional dc drives. In processing lines many drives require speed and tension control. To confirm the suitability of an ac drive for tension control, the tension reel of an existing pilot processing line has been equipped with an adjustable-speed ac drive. An ac drive system for tension reel control, its characteristics, and performance are described and compared with a dc tension control.