Comparative study of depth-dose distributions for beams of light and heavy nuclei in tissue-like media

We study the energy deposition by beams of light and heavy nuclei in tissue-like media for their possible application in charged-particle cancer therapy. The depth-dose distributions for protons, ³He, ¹²C, ²⁰Ne and ⁵⁸Ni nuclei are calculated within a Monte Carlo model based on the GEANT4 toolkit. These distributions are compared with each other and with available experimental data. It is demonstrated that nuclear fragmentation reactions essentially reduce the peak-to-plateau ratio of the dose profiles for deeply penetrating energetic ions heavier than ³He. On the other hand, the shapes of depth-dose profiles for all projectiles up to ⁵⁸Ni were found similar at low penetration depths.     

The effect of solder paste residues on RF signal integrity

Wireless devices such as pagers and cellular phones are becoming common consumer items. These products require low loss RF signal propagation which is affected by material choices and processing conditions. This paper examines the effect of a series of no-clean solder pastes on signal integrity using an RF test circuit which sends a broadband signal through a gallium arsenide antenna switch and measures its transmission using a network analyzer. The test circuit also measures signal leakage. This paper reports on two different test vehicles, one that uses a 900 MHz antenna switch, and the other that uses a 2.0 GHz antenna switch. The transmission and leakage readings were taken daily for 16–21 days while the test vehicles were under accelerated aging conditions of 85°C and 85% RH. Average values for the readings for each solder paste were plotted to provide comparison among the pastes. The comparison data clearly distinguish solder pastes that provide consistency throughout the test period from those which do not.     

铅、银对活性碳分离富集-原子吸收法测金的干扰及消除

本文针对电鲜阳极泥、冰铜、铅、锌精矿、炉砖四种含金样品中铅银对活性碳富集－AAS测Au的干扰，提出了消除干扰的具体措施，提高了分析结果的准确性。     

Effects of poling state and pores on fracture toughness of Pb(Zr0·95Ti0·05)O3 ferroelectric ceramics

Abstract

Abstract

The effects of poling state and pores on the fracture toughness of Pb(Zr_0·95Ti_0·05)O₃ (PZT 95/5) ferroelectric ceramics were investigated. X-ray diffraction analysis and piezoelectric constant measurements reveal that the phase structures of PZT 95/5 ceramics change with the poling state, which significantly affects the fracture toughness. The poled PZT 95/5 ceramics demonstrate higher fracture toughness than the unpoled ceramics, and their fracture toughness significantly increases after the pressure depoling. As the porosity of ceramics increases with addition of poreformer during preparation, their fracture toughnesses all decrease accordingly either in poled state or unpoled state. The effect of pore size on the fracture toughness is subtle for the poled ceramics, but for the hydrostatic pressure depoled porous PZT 95/5 ceramics, their fracture toughness increases with the increase in pore size. A new stress model is proposed to explain the pore size effect on the fracture toughness of hydrostatic pressure depoled PZT 95/5 ceramics.     

Catalytic activity of Pt‐Re‐Pb/Al2O3 naphtha reforming catalysts

BACKGROUND: The main purpose of the naphtha reforming process is to obtain high octane naphtha, aromatic compounds and hydrogen. The catalysts are bifunctional in nature, having both acid and metal sites. The metal function is supplied by metal particles (Pt with other promoters like Re, Ge, Sn, etc.) deposited on the support. The influence of the addition of Pb to Pt‐Re/Al₂O₃ naphtha reforming catalysts was studied in this work. The catalysts were prepared by co‐impregnation and they were characterized by means of temperature programmed reduction, thermal programmed desorption of pyridine and several test reactions such as cyclohexane dehydrogenation, cyclopentane hydrogenolysis and n‐heptane reforming. RESULTS: It was found that Pb interacts strongly with the (Pt‐Re) active phase producing decay in the metal function activity. Hydrogenolysis is more affected than dehydrogenation. Part of the Pb is deposited over the support decreasing the acidity and the strength of the most acidic sites. CONCLUSION: The n‐heptane reforming reaction shows that Pb modifies the stability and selectivity of the Pt‐Re catalysts. Small Pb additions increase the stability and greatly improve the selectivity to C₇ isomers and aromatics while they decrease the formation of low value products such as methane and gases. Copyright © 2011 Society of Chemical Industry     

Electrodialytic remediation of soil fines (<63 μm) in suspension—Influence of current strength and L/S

Current treatment of the remaining soil fines from soil wash is onerous and expensive, and therefore, in this work, we investigated the feasibility of electrodialytic remediation (EDR) as an alternative treatment. The study focuses on EDR efficiency as a function of current strength, liquid-to-solid-ratio (L/S), pH and time. We found out that during the experiments, Pb was easily dissolved by the acidification resulting from water splitting at the anion-exchange membrane. When higher currents and/or higher L/S ratios were applied, it was found that water splitting occurring at the cation-exchange membrane increased the pH, and this resulted in decreased remediation efficiency. It was shown that complete remediation of the soil-fines is possible, with the majority of the Pb being transported into the catholyte and precipitated at the cathode. Based on the results it is recommended that EDR is implemented using a number of reactors in series, where the initial reactor works at the highest possible removal rate, and the final reactor works at the target Pb-concentration.     

Thermophysical properties of some key solids: An update

In 1985, the CODATA Bulletin published a Report of its Task Group on Thermophysical Properties of Solids which analyzed available data on, and gave recommended values for, the heat capacity of Cu, Fe, W, and Al₂O₃, the thermal expansion of Cu, Si, W, and Al₂O₃, the electrical resistivity of Cu, Fe, Pt, and W, the thermal conductivity of Al, Cu, Fe, and W, and the absolute thermopower of Pb, Cu, Pt, and W. The analysts for the different properties were R. B. Castanet, S. J. Collocott, P. D. Desai, C. Y. Ho, J. G. Hust, R. B. Roberts, C. A. Swenson, and G. K. White. The present paper is an updated version of the earlier report and includes more recent data which change some of the recommended values. notably the heat capacity of Cu and W and the thermal expansion of Si and W.     

乙二胺四乙酸络合滴定法连续快速测定高品位矿样中的铅锌

用乙二胺四乙酸络合滴定法测定铅时,需要将铅沉淀成PbSO4与其他元素分离,分析手续繁琐、耗时.采用不经分离而加多种掩蔽剂的办法消除干扰,在一份溶液中连续测铅和锌,该方法简单快速,适合铅样品的野外现场测定.