The influence of iodide on glass transition temperature of high-pressure nuclear waste glasses

The glass transition temperature (T_g) is a key parameter to investigate for application in nuclear waste immobilization in borosilicate glasses. T_g for several glasses containing iodine (I) has been measured in order to determine the I effect on T_g. Two series of glass composition (ISG and NH) containing up to 2.5 mol% I and synthesized under high pressure (0.5 to 1.5 GPa) have been investigated using differential scanning calorimetry (DSC). The I local environment in glasses has been determined using X-ray photoelectron spectroscopy and revealed that I is dissolved under its iodide form (I⁻). Results show that T_g is decreased with the I addition in the glass in agreement with previous results. We also observed that this T_g decrease is a strong function of glass composition. For NH, 2.5 mol% I induces a decrease of 24°C in T_g, whereas for ISG, 1.2 mol% decreases the T_g by 64°C. We interpret this difference as the result of the I dissolution mechanism and its effect on the polymerization of the boron network. The I dissolution in ISG is accompanied by a depolymerization of the boron network, whereas it is the opposite in NH. Although ISG corresponds to a standardized glass, for the particular case of I immobilization it appears less adequate than NH considering that the decrease in T_g for NH is small in comparison to ISG.     

Effects of Solvents in the Polyethylene Glycol Series on the Bonding of Copper Joints Using Ag2O Paste

The effects of reducing solvents on the bonding process using silver oxide paste in a copper joint were investigated. Three solvent types were tested: diethylene glycol (DEG), triethylene glycol (TEG), and polyethylene glycol (PEG). The strength of the joints was assessed by fracturing, which occurred at the interface of the copper oxide layer and the copper substrate in DEG and TEG samples and at the bonded interface in the PEG sample. Analysis of the samples revealed that, in the DEG and TEG samples, the copper substrate was oxidized during the bonding process, which compromised the shear strength of the joints. In contrast, the PEG sample exhibited nonuniform sintering of the silver layer while retaining good shear strength. It was found that the combination of DEG and PEG produced optimum shear strength in the copper joint, as PEG suppressed the growth of copper oxide and DEG promoted the formation of a dense sintered silver layer. The bonding strength achieved was higher than that of the gold-to-gold joint made using standard Pb-5Sn solder.     

Delamination growth mechanisms in woven glass fiber reinforced polymer composites under Mode II fatigue loading at cryogenic temperatures

The purpose of this research is to characterize the cryogenic delamination growth behavior in woven glass fiber reinforced polymer (GFRP) composite laminates subjected to Mode II fatigue loading. Mode II fatigue delamination tests were performed at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K) using the four-point bend end-notched flexure (4ENF) test method, and the delamination growth rate data for the woven GFRP laminates were obtained. The energy release rate range was determined by the finite element method. Microscopic examinations of the specimen sections and fracture surfaces were also carried out. The present results are discussed to obtain an understanding of the fatigue delamination growth mechanisms in the woven GFRP laminates under Mode II loading at cryogenic temperatures.     

Dietary CLA and DHA modify skin properties in mice

This study investigated the influence of PUFA on the properties of mouse skin. Mice (3 wk old) were given free access to oils high in linoleic acid, CLA, or DHA for 4 wk. At the end of the experiment, their skins were compared by both biochemical and histological methods. No significant differences in lipid and collagen contents were detected among treatments, although the FA composition in the skin was altered depending upon the FA composition of the supplemented oils. Electron microscopy revealed that the subcutaneous tissue layers in the CLA and DHA groups were significantly thinner than that in the high linoleic acid group, whereas no differences in the thickness of dermis layers were observed among the three groups. These results suggest that skin properties in mice are readily modified by dietary FA sources within 4 wk of dietary oil supplementation.     

Conjugated‐Polymer‐Based Lateral Heterostructures Defined by High‐Resolution Photolithography

Solution processing of polymer semiconductors provides a new paradigm for large‐area electronics manufacturing on flexible substrates, but it also severely restricts the realization of interesting advanced device architectures, such as lateral heterostructures with defined interfaces, which are easily accessible with inorganic materials using photolithography. This is because polymer semiconductors degrade, swell, or dissolve during conventional photoresist processing. Here a versatile, high‐resolution photolithographic method is demonstrated for patterning of polymer semiconductors and exemplify this with high‐performance p‐type and n‐type field‐effect transistors (FETs) in both bottom‐ and top‐gate architectures, as well as ambipolar light‐emitting field‐effect transistors (LEFETs), in which the recombination zone can be pinned at a photolithographically defined lateral heterojunction between two semiconducting polymers. The technique therefore enables the realization of a broad range of novel device architectures while retaining optimum materials performance.     

Crack growth characteristics of carbon nanotube-based polymer composites subjected to cyclic loading

This paper presents the characterization of crack growth in carbon nanotube (CNT)-based polymer composites under fatigue loading. Fatigue crack growth tests were performed on single-edge cracked plate specimens of CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K). An elastic–plastic finite element analysis was also conducted to determine the J-integral range. The crack growth rate data were expressed in terms of the J-integral range, and the effect of nanotube addition on the fatigue crack growth behavior was examined. In addition, possible mechanisms of the crack growth in the nanocomposites are discussed based on microscopic observations of the specimen fracture surfaces.     

Problems in pharmacological evaluation of patients with paroxysmal atrial fibrillation: clinical analysis of more than 100 consecutive patients

To address the problems of pharmacological evaluation in paroxysmal atrial fibrillation (PAf), we interviewed 108 consecutive patients with documented PAf regarding symptoms, frequency and trigger factors of PAf and analyzed the 24-hour ambulatory electrocardiographic monitoring (Holter monitoring) records in relation to symptoms. Twenty-nine patients were totally asymptomatic, while 79 patients were symptomatic of which 49 patients had obvious trigger factors. PAf was documented by Holter monitoring in 22 of 79 symptomatic patients. On analysis of PAf-documented 25 Holter monitoring records, the patients checked event marks as PAf in only 20 of 155 PAf episodes. Six episodes of 26 event marks that patients thought to be PAf proved to be premature atrial or ventricular contractions. Nine patients in whom PAf persisted for more than 24 hours became asymptomatic. Patients suitable for pharmacological evaluation constituted about one-fifth of the PAf patients in our consecutive study. Even with the selection of these patients, pharmacological evaluation based on symptoms is difficult because disappearance of PAf may be associated with persistent atrial fibrillation.     

用4道脉冲幅度甄别器[φ4×4英寸 NaI(Tl)为探测器]测量环境天然辐射水平

本文主要介绍以φ4×4英寸 NaI(Tl)为探测器的4道脉冲甄别器,用以测量和区分包括宇宙射线在内的不同成分的环境天然辐射水平的方法。4道:Disr、Ch1、Ch2、Ch3的甄别阈范围设定为使其能记录的γ射线的能量范围(主要包括天然辐射成分)依次约为0.58MeV—∞(~(40)K、铀、钍系核素的γ射线,宇宙射线)、2.0—4.2MeV(铀系~(214)Bi 中能量为2.2MeV 的γ射线,钍系~(208)Tl 中能量为2.61MeV 的γ射线,少量低能宇宙射线)、>4.2 MeV(除少量低能宇宙射线外的全部宇宙射线)、>12.5MeV(能量较高的宇宙射线)。用此方法在中国辐射防护研究院低本底放射性实验室和地下铁室进行了测量,评价了地下铁室的屏蔽效果。文中还给出了在广州—太原和北京—大阪航线的飞机上的测量结果。