On the correct measurement of relative heavy charged particles to gamma thermoluminescent efficiencies

In order to better understand the most important experimental aspects for performing correct measurements of relative thermoluminescent (TL) efficiencies, an investigation has been carried out to quantify the effect of using different experimental procedures in the evaluation of 3 MeV proton-to-gamma relative efficiency (etap,gamma) of LiF:Mg,Ti. Variations in batch, presentation, annealing and reader have been studied. When the same protocol is used to measure proton and gamma TL response, efficiency values obtained range from 0.36 to 0.59 for peak 5 and from 0.44 to 0.79 for the total signal. The use of different annealings and different batches leads to 20% and 10% differences in etap,gamma respectively. Large differences (40%) are found between efficiency values measured with TLD-100 chips and those obtained using TLD-100 microcubes. When 'mixed' procedures are used to measure the proton and the gamma response, differences in etap,gamma may increase even more. The main conclusion of this work is to stress the importance of measuring an entire series of experiments in the same laboratory with a carefully defined protocol and using dosemeters from the same batch to obtain heavy charged particle TL response and gamma TL response with identical annealing and readout procedures.     

PLGA bone plates reinforced with crosslinked PPF

In this study a matrix of poly(propylene fumarate) (PPF) was crosslinked with N-vinylpyrrolidone (NVP), 2-hydroxyethylmethacrylate (HEMA), or a mixture of NVP and ethyleneglycol dimethacrylate (EGDMA) in the presence of poly(lactide-co-glycolide) (PLGA) to reinforce and preserve the form of PLGA bone plates. The degree of crosslinkage varied depending on the crosslinker as shown by the rapid and almost complete leaching of NVP upon incubation in phosphate buffered saline at 37 ° C in 900 h and retention of 92% of HEMA. With the reinforced bone plates extracted for 72 h at room temperature methylene chloride, the extracted PLGA from NVP/PPF, NVP-EGDMA/PPF, and HEMA/PPF were 75.42% (w/w), 59.52% (w/w), and 30.86% (w/w), respectively. The flexural modulus and compressive strength of the crosslinked PPF reinforced bone plates were higher than that of the unreinforced bone plate. Atomic force microscopy showed that NVP/PPF reinforced PLGA bone plates eroded substantially (a mean surface roughness of 19.319 nm) whereas NVP-EGDMA-PPF reinforced bone plate showed a distinct crystalline organization (and a higher roughness, 43.525 nm). In conclusion, we propose the consideration of NVP-EGDMA/PPF reinforced PLGA as a biodegradable orthopedic implant material that has a lower likelihood of warping or failing catastrophically than the currently available materials.     

Cytogenic investigations of serious overexposures to an industrial gamma radiography source

This paper describes the sequence of events, medical aspects and dose estimations for two radiographers and their driver who were seriously exposed to an iridium-192 industrial radiography source that became detached from its wind-out cable. The men came to medical attention about 1 month later by which time all three were severely leucopenic and one had skin burns on both hands. Doses were estimated by (i) physics calculations combined with their accounts of the event. (ii) the levels of depression of their blood neutrophils, (iii) electron spin resonance on tooth enamel and (iv) blood lymphocyte chromosomal analyses by the conventional dicentric and the fluorescence in situ hybridisation methods. Intercomparison of these methods for estimating doses showed a good level of agreement. In brief, the averaged whole body dose for the most seriously exposed man was about 2.5-3.0 Gy and for the others it was 1.0-2.0 Gy.     

用过氧化氢连续沉淀铀

研究了从含硫酸根的模拟工厂溶液中回收铀的三种不同的连续工艺流程。用这三种流程均可制得钼和钒含量低、易于过滤和干燥的高质量产品。硫酸根的存在降低了沉淀速率,产生较大的沉淀颗粒,从而有利于沉淀物的过滤和干燥。按本文给出的流程制得了大颗粒的多种形态,这说明在沉淀器中晶体的成长支配着成核过程。在60℃时过氧化铀以二水合物形式沉淀,但在50℃—60℃以下则形成四水合物,基于这种认识引出了有关沉淀速率的重要结论。研究中曾发现了各种各样的颗粒形态,其中最罕见的是由一些针状结晶聚集体,这些针状结晶以颗料中心为共同点向四周辐射。     

90年代的中频感应炉熔炼

这是一篇实用性很强的文章。作者在文中描述近几年来中频感应炉熔炼和保温方面的一些发展。本文综述了黑色金属和有色金属两方面的应用,其中包括液压倾侧炉(含屏蔽框的结构),用于有色金属熔炼的移动式坩锅炉,用于精密铸造的翻转炉,炉子开关系统以及辅助设备。其中特别有意义的是描述了一种新设计的新型的自动浇注炉。