Chemical characteristics of degraded soils in Uzbekistan and remediation by cyanobacteria

Nutrient Cycling in Agroecosystems - Precipitation in Uzbekistan is limited, so irrigation must be used widely in local agriculture. However, irrigation is carried out with inadequate drainage...     

Electrical,mechanical, and crystallization properties of ethylene‐tetrafluoroethylene copolymer/multiwalled carbon nanotube composites

Multiwalled carbon nanotubes (MWCNTs) were melt‐mixed in a conical twin‐screw extruder with a random copolymer of ethylene and tetrafluoroethylene. Surprisingly, the electrical percolation threshold of the resultant composites was quite low; ～0.9 wt %. In fact, this value is as low or lower than the value for most MWCNT/semicrystalline polymer composites made with roughly equivalent aspect ratio tubes mixed in a similar manner, for example, melt mixing. This low percolation threshold, suggestive of good dispersion, occurred even though the polymer surface energy is quite low which should make tubes more difficult to disperse. Dynamic mechanical measurements confirmed the rather low percolation threshold. The effect of nanotubes on crystallization kinetics was quite small; suggesting perhaps that a lack of nucleation which in turn reduces/eliminates an insulating crystalline polymer layer around the nanotubes might explain the low percolation threshold. Finally, the modulus increased with the addition of nanotubes and the strain at break decreased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41052.     

Effects of H2O2 under low- and high-aeration-level conditions on growth and catalase activity in Exiguobacterium oxidotolerans T-2-2T

The effects of H2O2 under low- and high-aeration-level conditions on growth and catalase activity in Exiguobacterium oxidotolerans T-2-2T were investigated. Continuous addition of 5-200 mM H2O2 to the culture medium from the mid-exponential growth phase enhanced the growth of the strain under the low-aeration-level condition, whereas the addition of 5-50 mM H2O2 decreased intracellular specific catalase activity and extracellular total catalases activity. The detection of extracellular catalase by the cells and the decrease in intracellular specific catalase activity and extracellular total catalase activity under the high-aeration-level condition account for the stimulation of growth by the introduced H2O2 and the decrease in catalase activities induced by O(2) from H2O2 in the medium. On the other hand, the addition of H2O2 to the medium prior to the initiation of growth inhibited the growth but increased the specific activity of intracellular catalase in the stationary growth phase. Strain T-2-2T grew when 10 mM H2O2 was added to the medium prior to growth. However, the growth was completely inhibited by the catalase inhibitor 3-amino-1,2,4-triazole (3-AT). The continuous addition of H2O2 at an appropriate concentration from prior to the initiation of growth to the stationary growth phase under the low-aeration-level condition resulted in higher intracellular specific catalase activity and cell growth rate than single H2O2 addition prior to growth.     

注射成型流道温度分布的测量分析方法

树脂温度的分布对注射成型过程的充填平衡具有重要影响。由于型腔中传感器的安装空间有限,至今为止还没有合适的方法来测量注射成型过程中流道和小尺寸型腔中树脂温度场的分布。为了解决这一问题,文中设计了一套新式的移动式温度测量系统,该系统采用常规尺寸红外线传感器和红外线纤维传感器来测量注射模具流道内树脂温度场分布。测量结果显示,...     

Tiny-scale “stealth” current sensor to probe power semiconductor device failure

“Stealth” electric current probing technique for power electronics circuits, power device modules and chips makes it possible to measure electric current without any change or disassembling the circuit and the chip connection for the measurement. The technique consists of a tiny-scale magnetic-field coil, a high speed analog amplifier and a digitizer with numerical data processing. This technique can be applied to a single bonding wire current measurement inside IGBT modules, chip scale current redistribution measurement and current measurement for surface mount devices. The “stealth” current measurement can be utilized in the failure mechanism understanding of power devices including IGBT short circuit destruction.     

The thermochemical hydrogen program at N.C.L.I.

This short communication describes work now underway at the National Chemical Laboratory for Industry (N.C.L.I.) in Tokyo, Japan on the production of hydrogen from H₂S or H2O by thermochemical processes. Emphasis is placed on the chemistry of the processes and the use of catalysts in various reactions.     

Fundamental Oscillation up to 1.42 THz in Resonant Tunneling Diodes by Optimized Collector Spacer Thickness

We report an increase in the oscillation frequency of terahertz oscillators using AlAs/InGaAs double-barrier resonant tunneling diodes (RTDs) by optimizing the collector spacer thickness. For high-frequency oscillation of RTDs, the electron delay time, which is composed of the dwell time in the resonance region and the transit time in the collector depletion region, must be reduced. Although the transit time is reduced by a thin collector spacer, the capacitance increases. Thus, an optimum thickness of collector spacer layer exists. In this report, we investigate the dependence of oscillation frequency on the collector spacer thickness. The RTDs were integrated with 20-μm-long slot antennas, and oscillations up to 1.1, 1.42, and 1.29 THz were obtained for spacer thicknesses of 25, 12, and 6 nm, respectively. The optimum spacer thickness for high-frequency oscillation was around 12 nm. The highest frequency in this experiment was 1.42 THz oscillation, with an output power of ~1 μW. We also extracted the electron velocity in the collector depletion region and the dwell time from the dependence of the delay time on the collector spacer thickness.     

Effect of primary structure on permselectivity of ultrathin semipermeable polybenzimidazole membrane

A series of polybenzimidazoles (PBIs) with different main chains and sulfonated PBI were successfully synthesized from the corresponding dicarboxylic acids and 3,3'‐diaminobenzidine for the formation of ultrathin, single‐component, and semipermeable membranes. Furthermore, the covalently crosslinked PBI membrane was prepared by the reaction of sulfonated PBI with divinyl sulfone. Their water transport properties were evaluated under a reverse osmosis mode and compared with the primary structure based on the water permeability (A) and salt permeability (B) values normalized by the membrane thickness. It was found that the A and B values of the PBIs were improved with increasing the weight ratio of the imidazole rings per repeating unit, the introduction of sulfonate group as the hydrophilic group to the PBI was an effective way to enhance the A value, and the crosslinked structure enhanced the salt rejection rate (R) value while maintaining the water flux. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41531.