Use of maximum temperature for correction of alanine dosimetry in electron beams

Alanine dosimetry is well characterized for irradiation temperature response. In use, alanine absorbed dose response is corrected for the irradiation temperature. The temperature used to correct alanine dosimetry absorbed dose response in electron beams has historically been the mean temperature occurring during irradiation (Sharpe and Miller, 2009). At lower absorbed doses, the change in temperature is relatively low; thus the absorbed dose response correction due to temperature is small. However, industrial electron beam processing often requires higher absorbed dose measurements where the change in temperature can be very large and the corresponding dose response correction for alanine becomes significant. This paper compares the impact of the temperature correction based on the use of a mean irradiation temperature (Sharpe and Miller, 2009) versus the use of a maximum irradiation temperature on the absorbed dose measurement. The results of this comparison indicate that the use of a mean temperature correction for higher absorbed doses measured with temperature corrected alanine dosimetry introduces a bias in the absorbed dose estimate.     

Control of the electrode temperature for electrochemical studies: A new approach illustrated on porous anodizing of aluminium

A new approach for studying the effect of temperature on electrochemical processes is presented in this paper. Using an in-house developed electrode holder, experiments are performed under conditions of applied and controlled electrode temperature. This new approach provides an improved temperature control during the experimental study and, additionally, allows distinguishing both the influences of the electrolyte and electrode temperatures. The advantages of the applied electrode temperature approach are illustrated by considering porous anodizing of aluminium. In a broad temperature range the electrochemical behaviour of the aluminium electrodes, recorded during the new and the conventional way of anodizing, are compared. Differences between the anodic potential evolutions in both approaches are observed, and are explained by a heat flux to the surroundings during the experiments at uncontrolled electrode temperature. These results illustrate the advantage of applying the electrode temperature. If the influence of temperature on a process is investigated by merely varying the electrolyte temperature, the electrode temperature is only indirectly influenced and can significantly differ from the electrolyte temperature. Therefore, when evaluating the influence of temperature on an electrochemical system the electrode temperature should be considered, and preferentially also controlled.     

Thermally-regulated molecular selectivity of organosilica sol-gels

The feasibility of using temperature as a control mechanism for altering the selectivity of organosilica sol-gels for a specific molecule is demonstrated in this communication. The porous organosilica sol-gels act as reversible thermoresponsive materials which become hydrophobic at higher temperature and hydrophilic at lower temperature. When exposed to a mixture of molecules, the gels selectively intake the more hydrophobic species at higher temperature. A particularly remarkable feature of these gels is their ability to preferentially sequester the hydrophobic molecule at high temperature and the hydrophilic species at low temperature. Finally, these gels selectively intake hydrophobic molecules at high temperature and then preferentially release them when the temperature is lowered.     

Synthesis of Segmented Silica Rods by Regulation of the Growth Temperature

The control of the diameter of colloidal structures is of fundamental interest and practical importance. We synthesized segmented silica rods by regulating the reaction temperature while the rods were growing. With higher growth temperatures, the segment diameter became smaller. Longer incubation times gave longer segments at the same temperature. Similarly, high temperature for the same incubation time gave longer segments. It appears that the correlation between temperature and diameter results from the relation between temperature and the size of the emulsion droplet, that is, the higher the temperature, the smaller the emulsion droplet.     

不同灰化温度下生物质混煤灰的烧结特性研究

选取晋城无烟煤和麦秆作为研究对象,利用压差法烧结温度测定装置测量不同灰化温度下煤和麦秆混合灰的烧结温度,再利用SEM-EDS以及XRD对灰样进行烧结特性分析。结果表明,不论灰化温度高低,随着麦秆的添加,煤和麦秆混合灰的烧结温度都呈现降低趋势,其降低幅度略有差别。灰化温度较低时,煤和麦秆混合灰的烧结温度低于灰化温度较高情况下混合灰的烧结温度。SEM-EDS分析表明,低温灰化得到的样品中出现较多不规则的纤维结构;较高温度下获得的灰样中出现较多致密的球状颗粒,这表明矿物质发生熔融形成球状颗粒。XRD分析表明,低温灰化烧结后的煤和麦秆混合灰样中因含有较多的含钾等碱金属系助融矿物质,导致混合灰样的烧结温度降低。然而,像钙长石等含钙矿物质本身具有较高的熔点,因此,在1 100℃时混合灰样具有较高的烧结温度。     

The size of particle aggregates produced by flocculation with PNIPAM, as a function of temperature

This work investigates the effect of temperature on the size of alumina aggregates formed by flocculation with temperature responsive Poly(N-Isopropylacrylamide)(PNIPAM). The results are discussed in terms of the effects of temperature on particle collision, particle adhesion and aggregate breakage. It was found that the size of alumina aggregates increases with increasing solution temperature. Particle/particle collision and aggregate breakage are largely unaffected by increasing solution temperature and therefore could not account for the change in aggregate size. The dominant factor in aggregate growth with increasing temperature was found to be the increase in the force of adhesion between alumina particles. The appearance of the adhesive force is triggered by the increase in temperature above the lower critical solution temperature of PNIPAM.     

Prediction of the enthalpy of vaporization of metals and metalloids

A simple correlation equation without adjustable parameters is used to obtain the enthalpy of vaporization of 10 metals and 2 metalloids as a function of the temperature. Besides the critical temperature, this equation requires knowing of the enthalpy of vaporization at two reference temperatures: the lowest available temperature and the normal boiling temperature. Average relative deviations are less than 0.75% for the available ranges of temperature. A comparison is made with three other well-known empirical equations based only on the normal boiling point.     

Thermal characteristics of gelatin extracted from shaari fish skin

Gelatin extraction yield increased with the increase of acetic acid concentration and temperature. Gelatin extracted from shaari skin using 0.1 N acid solutions and temperatures of 323 and 353 K gave highest protein content comparable to that of commercial bovine and porcine gelatins. In general, gelatin extracted from shaari gelatin showed lower onset of glass transition temperature than mammalian gelatins. For shaari skin gelatin, the onset of glass transition temperature decreased with the increase of extraction temperature up to 323 K and then remained nearly constant. The decrease in glass transition was more pronounced for gelatin extracted at 0.01 N compared to the 0.1 and 1.0 N samples. Unfolding temperature decreased exponentially with the increase of extraction temperature. The unfolding temperature shifted to lower temperature, and the decrease was more pronounced in the case of higher (1.0 N) concentrated samples. The extraction concentration and temperature did not show significant effect on the onset solids-melting temperature.     

BN掺杂钛酸钡基NTC材料的研究

钛酸钡基材料在居里温度以下呈优异的NTC特性,围绕BN掺杂制备钛酸钡基NTC功能陶瓷材料,分别对不同掺杂量、烧结工艺过程进行了研究.结果表明,随着烧结温度的升高,NTC材料的致密化程度增强,其室温电阻率和NTC效应也会有一些变化,随着烧结温度的提高,NTC材料的居里温度也会有微小的变化;加入BN采用传统固相烧结法在烧结...     

Determination of the temperature of the graphite probe surface in graphite probe furnace atomic absorption spectrometry

An apparatus for determining the temperature of a graphite probe in graphite probe furnace atomic absorption spectrometry has been developed and tested. By measuring the change in the reflection of a laser beam from various pure metals which are deposited on the probe surface at the usual location for sample deposition, it has been found that the heating of the graphite probe surface occurs in two stages. When the probe is inserted into a pulse-heated, commercial graphite furnace after it has been heated to a steady-state temperature, the probe surface is initially rapidly heated by the radiation from the heated graphite tube wall, and thereafter the probe maintains that steady-state temperature for a short time. For a given graphite probe, the heating rate at the initial stage and the corresponding steady-state temperature at the final stage are mainly determined by the final tube wall temperature; the steady-state temperature of the probe is considerably lower than the final tube wall temperature because of thermal conduction by the probe to that part of its body which is lying outside the tube wall. The higher the final tube wall temperature, the higher is the heating rate of the probe at the initial stage, the higher is its steady-state temperature at the final stage, and the less is the difference between the final tube wall temperature and the steady-state temperature of the probe surface. The heating rate of the probe surface at 1600 K is 180 K s⁻¹, whereas at 2300 K it is 3600 K s⁻¹; the differences between the probe surface and tube wall temperatures at the former temperature is 700 K, whereas at the latter temperature it is 250 K.     

Thermoreversible gelation of solutions of vinyl polymers

The thermoreversible gelation of solutions of isotactic poly(methyl methacrylate) is investigated. Amorphous gels can be prepared in l-butanol by a combination of a liquid-liquid demixing with an upper critical demixing temperature and a glass transition. Annealing of the demixed solutions above their glass transition temperature T_G, results in the formation of a crystalline gel. In oxylene, crystalline gels are formed by a liquid-liquid demixing with an lower critical demixing temperature and an annealing at room temperature. Very fast gelation is observed to occur far below room temperature in solvents like 2-butanone.     

Relation between the melting temperature and the temperature of maximum density for the most common models of water

Water exhibits a maximum in density at normal pressure at 4 degrees above its melting point. The reproduction of this maximum is a stringent test for potential models used commonly in simulations of water. The relation between the melting temperature and the temperature of maximum density for these potential models is unknown mainly due to our ignorance about the melting temperature of these models. Recently we have determined the melting temperature of ice I(h) for several commonly used models of water (SPC, SPC/E, TIP3P, TIP4P, TIP4P/Ew, and TIP5P). In this work we locate the temperature of maximum density for these models. In this way the relative location of the temperature of maximum density with respect to the melting temperature is established. For SPC, SPC/E, TIP3P, TIP4P, and TIP4P/Ew the maximum in density occurs at about 21-37 K above the melting temperature. In all these models the negative charge is located either on the oxygen itself or on a point along the H-O-H bisector. For the TIP5P and TIP5P-E models the maximum in density occurs at about 11 K above the melting temperature. The location of the negative charge appears as a geometrical crucial factor to the relative position of the temperature of maximum density with respect to the melting temperature.     

Comparison of two adaptive temperature-based replica exchange methods applied to a sharp phase transition of protein unfolding-folding

Temperature-based replica exchange (T-ReX) enhances sampling of molecular dynamics simulations by autonomously heating and cooling simulation clients via a Metropolis exchange criterion. A pathological case for T-ReX can occur when a change in state (e.g., folding to unfolding of a protein) has a large energetic difference over a short temperature interval leading to insufficient exchanges amongst replica clients near the transition temperature. One solution is to allow the temperature set to dynamically adapt in the temperature space, thereby enriching the population of clients near the transition temperature. In this work, we evaluated two approaches for adapting the temperature set: a method that equalizes exchange rates over all neighbor temperature pairs and a method that attempts to induce clients to visit all temperatures (dubbed "current maximization") by positioning many clients at or near the transition temperature. As a test case, we simulated the 57-residue SH3 domain of alpha-spectrin. Exchange rate equalization yielded the same unfolding-folding transition temperature as fixed-temperature ReX with much smoother convergence of this value. Surprisingly, the current maximization method yielded a significantly lower transition temperature, in close agreement with experimental observation, likely due to more extensive sampling of the transition state.     

聚硫堇半导体性质的电化学证据

聚硫堇的电导率为9.6×10－6 S•cm－1,属有机半导体.在10 ℃至60 ℃温度范围内,测定了聚硫堇的循环伏安图、恒电位下的放电曲线和交流阻抗图,并测定了电解质溶液的电导率随温度的变化.在聚硫堇的循环伏安图上有一阳极峰和一阴极峰,它们的峰电流均随温度的升高而增加;恒电位下的放电电流也随温度升高而增加;而交流阻抗的结果表明,聚硫堇的电荷传递电阻Rct随温度升高而下降,即它的交换电流i0随温度升高而增加;而溶液电阻和膜电阻也随温度的升高而下降,这同样会引起电流随温度升高而增加.所以温度对固体半导体聚硫堇的电极反应速率的影响包含了电极反应的本身和电极的电导率等因素的影响.聚硫堇的扫描电镜图证实了它的表面是一种纤维状结构.     

A temperature window for the synthesis of single-walled carbon nanotubes by catalytic chemical vapor deposition of CH4 over Mo-Fe/MgO catalyst

A temperature window of single-walled carbon nanotubes (SWCNTs) growth has been studied by Raman spectroscopy. The results presented when temperature lower than 750 degrees C, there were few SWCNTs formed, and when temperature higher than 900 degrees C, mass amorphous carbons were formed in the SWCNTs bundles due to the self-decomposition of CH4. The temperature window of SWCNTs efficiently growth is between 800 and 900 degrees C, and the optimum growth temperature is about 850 degrees C. These results were supported by transmission electron microscope images of samples formed under different temperature. The temperature window is important for large-scale production of SWCNTs by catalytic chemical vapor deposition method.     

Periodic crystallisation of magnesium hydroxide in agar-agar gel. Influence of temperature

The influence of temperature on periodic crystallisation of magnesium hydroxide in agar-agar gel has been studied. The increase in velocity constant with temperature is attributed to the increase in the diffusion constant with temperature. The activation energy for diffusion of aqueous ammonia is calculated from the temperature — velocity constant correlation. The solubility of Mg(OH)₂ decreases with temperature. The decrease in the spacing coefficient and fiocculation value of Mg(OH)₂ with temperature is also explained because of the increase in temperature. Matalon and Packter’s equation correlating the spacing coefficient and concentration of the inner electrolyte is suitably modified to satisfy the temperature dependence of the spacing coefficient.     

The effect of oxygen content on the melting of the eutectic of physiological salinity solution

The effect of oxygen concentration on the melting of this eutectic was investigated by DSC. In the deoxygenized solution, an endothermic peak attributed to the eutectic transition was observed in the course of heating, and its peak temperature is around ?21.5°C. Another endothermic peak appeared at lower temperature in the presence of oxygen. As the oxygen content in the solution increases, the temperature of this peak is shifted to lower temperature. The transition at the lower temperature are associated with the melting of eutectic carrying oxygen. The same results are given in the NMR data.     

Investigation of Partial Oxidation of Methane over Rh/SiO2 catalyst by TP-MS

Partial oxidation of methane (POM) was investigated over Rh/SiO₂ catalyst using several techniques combined with MS, such as temperature programmed desorption (TPD), temperature programmed reduction (TPR), temperature programmed surface reaction (TPSR), temperature programmed reaction, and CH₃I chemical trapping reaction.     

凝结热对低阶煤低温氧化过程的影响

选用Pulse Calorimeter仪器,研究了低阶煤在干燥氧气下低温氧化过程的反应热和相对湿度为80％的氮气下凝结热与温度的变化,以研究凝结热对低阶煤低温氧化过程的影响。结果表明,随着温度的上升体系的反应热增加,而凝结热减少。在26℃~60℃的低温下,体系的凝结热明显高于反应热。因此,低温下凝结热是影响低阶煤的低温氧化过程的重要因素。研究还得到了低阶煤在干燥氧气下低温氧化过程的动力学方程及活化能。     

D8X射线衍射仪简易变温加热台的研制

成功研制的简易变温加热台,在不更换D8X射线衍射仪的附件情况下,能快速方便的安装在衍射仪上,进行X射线衍射原位变温测试,满足了从室温至600℃的原位变温X射线衍射测试需求.更换附件时间从2~3天缩短至30 min即可进行变温X射线衍射测试,提高了测试效率.同时,节省了购买同类变温加热台近20万元的资金.