Dielectric–Semiconductor Interface Limits Charge Carrier Motion at Elevated Temperatures and Large Carrier Densities in a High‐Mobility Organic Semiconductor

The fundamental nature of charge transport in highly ordered organic semiconductors is under constant debate. At cryogenic temperatures, effects within the semiconductor such as traps or the interaction of charge carriers with the insulating substrate (dipolar disorder or Fröhlich polarons) are known to limit carrier motion. In comparison, at elevated temperatures, where charge carrier mobility often also decreases as function of temperature, phonon scattering or dynamic disorder are frequently discussed mechanisms, but the exact microscopic cause that limits carrier motion is debated. Here, the mobility in the temperature range between 200 and 420 K as function of carrier density is explored in highly ordered perylene‐diimide from 3 to 9 nm thin films. It is observed that above room temperature increasing the gate electric field or decreasing the semiconducting film thickness leads to a suppression of the charge carrier mobility. Via X‐ray diffraction measurements at various temperatures and electric fields, changes of the thin film structure are excluded as cause for the observed mobility decrease. The experimental findings point toward scattering sites or traps at the semiconductor–dielectric interface, or in the dielectric as limiting factor for carrier mobility, whose role is usually neglected at elevated temperatures.     

Modeling of Work Hardening During Hot Rolling of Vanadium and Niobium Microalloyed Steels in the Low Temperature Austenite Region

This work extends the application of the well-established Estrin and Mecking (EM) work-hardening model in unstable low temperature austenite region. The interaction between work hardening, recovery and softening attributed to recrystallization and transformation to ferrite under dynamic conditions is considered. Experimental parameters were varied to study the effects of strain, strain rate and temperature during hot rolling in the low temperature austenite region. Hot compression tests were performed two microalloyed steels—one containing V and the other Nb—at strain rates between 0.1 and 10 s^?1 over a temperature range of 750-1000 °C. A model is presented that describes the influence of dynamic recovery on flow behavior in the unstable austenite region. The modified work-hardening model incorporates an additional fitting parameter to the EM model and is dependent on the recovery and softening rates. The new model improved prediction in the unstable austenite region, while the original EM model gave better correlation at relatively higher temperatures when dynamic recrystallization is dominant or at relatively lower temperatures when only dynamic recrystallization to ferrite was the softening mechanism.     

An empirical analysis of the simultaneous effects of nitrogen, phosphorus and potassium in millet production on spatially variable fields in SW Niger

Low soil fertility is a major constraint for increasing millet production on the acid sandy soils of the West African Sahel. On these soils, all three macronutrients: nitrogen (N), phosphate (P) and potassium (K), may be expected to limit crop yields. The important question is therefore: which of them is the most critical and would, if applied in small amounts, increase yields significantly? This paper addresses this question with an empirical approach, thus avoiding the commonly observed difficulty in the interpretation of agronomic research, caused by the extreme local soil variability which characterizes Sahelian coversands. We actually exploit soil variability by using novel non-parametric techniques for data exploration in combination with spatial methods of parametric model estimation. Apart from N, P and K, the effects of surface crusting, local topography, manure levels, farmer behaviour and spatial dependence are taken into account, since these may confound the true effects of N, P and K. A quadratic formulation conforms best to the data and explains 81 percent of the yield variation. The equation highlights the importance of interactions among variables and thus confirms the possible impact of native soil conditions on the outcome of fertilizer treatments in experimental research. The results of much earlier, multi-year, research are confirmed remarkably well by this single year study. In addition, a spatially explicit assessment on the crop response to increasing nutrient levels highlights that blanket fertilizer applications are inefficient, because yield increases in some places will be accompanied by yield decreases at other sites. Cash-constrained farmers therefore have to resort to precision farming techniques to maximize returns from minimal external input packages. However, a large part of the good explanation of millet yield variability over space derives from spatial autocorrelation, and not directly from topsoil N, P and K. This calls for further research on the factors that affect millet yield and on the characterization and classification of sites, followed by experimental work to design site-specific fertilizer technologies.     

Modeling the Tensile Strain Hardening Behavior of a Metastable AISI 301LN Austenitic Stainless Steel Pre-strained in Compression

Metallurgical and Materials Transactions A - Boltzmann-type sigmoidal equations to model the tensile strain hardening and flow stress behavior of a metastable AISI 301LN austenitic stainless steel...     

循环用水对复杂硫化矿浮选的影响

研究循环水对某复杂矿化矿浮选的影响,同时对利用两种重金属吸附剂减轻循环水不利影响的效果进行试验评价.结果表明,循环水的使用降低了浮铅的选择性.重金属吸附剂的使用可基本恢复浮选选择性至使用新鲜水的水平.     

利用磷灰石实现硫化矿浮选废水回用的试验评价

出于环境的考虑,越来越多的选矿厂均利用回水以减轻废水对环境的冲击和对水资源的依赖.工业生产经验表明,回水使用量的增加会对浮选带来不利的影响,尤其是对复杂矿化矿的优先浮选.浮选选择性降低的主要原因是溶液中重金属离子对闪锌矿或黄铁矿的意外活化.本文应用微型浮选试验,吸附试验和表面测试研究了利用磷灰石来实现硫化矿浮选废水回用的可行性.试验表明,磷灰石可增强对闪锌矿的抑制而提高浮选的选择性.微型浮选和表面测试表明,磷灰石与闪锌矿竞争吸附溶液中的重金属, 从而降低闪锌矿表面的重金属浓度.     

Amorphous azithromycin with improved aqueous solubility and intestinal membrane permeability

Azithromycin (AZM) is a poorly soluble macrolide antibacterial agent. Its low solubility is considered as the major contributing factor to its relatively low oral bioavailability. The aim of this study was to improve the solubility of this active pharmaceutical ingredient (API) by preparing an amorphous form by quench cooling of the melt and to study the influence of the improved solubility on membrane permeability. The amorphous azithromycin (AZM-A) exhibited a significant increase in water solubility when compared to the crystalline azithromycin dihydrate (AZM-DH). The influence that the improved solubility could have on membrane permeability was also studied. The apparent permeability coefficient (P_app) values of AZM-A were statistically significantly higher (p?相似文献