Toward an understanding of aging in plutonium from direct measurements of stored energy

ABSTRACT

We present here the first direct measurement of the radiation-damage-induced energy stored in δ-phase plutonium. The primary mode of radioactive decay of ²³⁹Pu occurs with a time constant of τ=1.1?×?10¹²?s. Each decay imparts about 85?keV of recoil energy to the uranium byproduct, 5.2?Mev to the alpha particle, and a spectrum of mostly low energy gamma rays with the most probable at 51?keV [1]. Most of the decay energy is converted immediately to heat, releasing about 1.9?mW/g. However, some thermally-recoverable energy remains trapped. Reported here are measurements of that stored energy using differential scanning calorimetry (DSC) applied to ²³⁹Pu-2.0 at.%Ga δ-phase alloy. Retained energy of ～2 J/g saturates at about 5 months and is unchanged after 30 years. The magnitude of the stored energy agrees with a short-bond defect model that that we present here. This model treats radiation damage as a Pu impurity with shortened bond lengths. It explains the change in known properties with age and predicts that density increases with age, contrary to current thinking. The short-bond impurities proposed are expected to act like other impurities, affecting strength, phase transitions, grain boundaries and other metallurgical properties.     

Crystal growth and defect study of BiSbTe3

BiSbTe₃ single crystals have been grown by the Bridgman technique. Microscopic observations of the as-grown crystals reveal typical features, such as striations on the top free surface, which are attributed to the effect of growth conditions. A nitric-acid-based reagent capable of revealing dislocations has been developed and tested. Etch pits are produced at the dislocation sites, but some discrepancies have been observed on matched cleavage surfaces. The structural difference between the matched cleavage surfaces is discussed.     

三维适形放疗治疗晚期腹部恶性肿瘤的临床受益和毒副反应

为观察三维适形放疗治疗晚期腹部恶性肿瘤的临床受益情况和毒副反应。对38例晚期腹部恶性肿瘤患者进行三维适形放疗,疗中和疗后进行临床受益情况和毒副反应的观察和评价。结果临床受益情况：有效为28．9％,稳定为42．1％,疼痛缓解率为28．9％;毒副反应主要为骨髓抑制、胃肠道反应、生化指标改变,除少数病例出现Ⅳ度生化指标改变外,其余均在Ⅲ度以下。结论三维适形放疗可以提高晚期腹部恶性肿瘤患者的生存质量,毒副反应轻微,是一种有效的姑息治疗手段。     

局限期小细胞肺癌放疗中预防野照射和累及野照射的疗效分析

局限期小细胞肺癌综合治疗中采用三维适型或调强放疗技术,按不同照射范围分为累及野照射和预防野照射2个组进行比较,分析不同照射野对预后的影响。 67例局限期小细胞肺癌患者,随机分为累及野照射组37例和预防野照射组30例。累及野照射组照射范围包括化疗前CT所见肿瘤及转移淋巴结范围,预防野照射组照射范围包括原发灶、同侧肺门、纵隔及锁骨上淋巴引流区。两组均采用三维适形或调强技术,放疗剂量为DT50Gy～66Gy/5周～6周。结果全组总有效率为82.1%,局部复发率为29.9%,远处转移率为56.7%,1年、2年、3年生存率分别为68.7%、36.2%和20.1%,分组比较以上指标均无显著性差异（P＞0.05）。而两组病例急性放射性肺炎和食道炎发生率分别为5.4%、16.7%和2.7%、20.0%,累及野照射食管炎发生率显著低于预防野（P＜0.05）。     

心理干预在放疗患者中的应用

探讨通过实施恰当的心理行为治疗,尤其是教育性干预措施,达到改善放疗患者情绪、提高其生活质量以及降低治疗负反应的效果.采用病例对照的临床研究方法,选用生活质量和心境问卷对160名正在进行放射治疗的住院癌症病人进行了心理干预的比较研究.结果表明,干预组患者的总体情绪和总体生活质量状况,比对照组患者有明显的改善,但愤怒、认知功能以及恶心呕吐症状在两组间的差异不显著;干预组组内比较中,角色功能没有显著性差别.其原因有待于进一步研究.     

Placebo: Its action and place in health research today* — Summary and conclusions

Conclusion The material presented at this conference pointed to a new dimension in the prosecution of activities that seek to relieve people of disease. While the simple instrument of the placebo may show those interested in the efficacy of physiologically active chemicals the extent to which the chemical of interest is actually active, the surprising outcome of such studies is that the placebo per se is worthy of more general study. This, when taken further, points to the ways in which mind can influence the matter of the body. Of course, mind itself is an activity of matter, so we may retain the experimental approach that has told us about the world outside ourselves to examine the world that is inside our brains. New techniques and approaches to these once intractable problems are now in train. Where they will lead us we cannot predict, but as with the emergence of all new tools, we have to adopt those ethics that will carry us forward with the expectation that we will maximise benefits and minimise harms. An International Conference held in Warsaw, April 12–13, 2003, entitled ‘Placebo: Its Action and Place in Health Research Today’ was attended by some 200 individuals who heard 25 presentations delivered by participants from the wider Europe and North America.     

Mortgaging the future: Dumping ethics with nuclear waste

On August 22, 2005 the U.S. Environmental Protection Agency issued proposed new regulations for radiation releases from the planned permanent U.S. nuclear-waste repository in Yucca Mountain, Nevada. The goal of the new standards is to provide public-health protection for the next million years — even though everyone admits that the radioactive wastes will leak. Regulations now guarantee individual and equal protection against all radiation exposures above the legal limit. Instead E.P.A. recommended different radiation exposure-limits for different time periods. It also recommended using only the arithmetic mean of the dose distribution, to assess regulatory compliance during one time period, but using only the median dose to assess compliance during another period. This piece argues that these two changes — in exposure-limits and in methods of assessing regulatory compliance — have at least four disturbing consequences. The changes would threaten equal protection, ignore the needs of the most vulnerable, allow many fatal exposures, and sanction scientifically flawed dose calculations.     

AIDR 技术在优化婴幼儿胸部 CT 扫描方案中的应用价值

该研究是探讨自适应迭代剂量降低重建技术（adaptive iterative dose reduction ,AIDR）在婴幼儿胸部 CT 扫描中的应用。本研究从拟行胸部 CT 检查的患儿中随机选取40例,分成 A 与 B 两组,A 组管电压为80kV ,用 AIDR 重建技术;B组为100kV ,用滤过反投影重建技术（FBP）。比较 A 、B 两组 CT 值、标准差（SD）、信噪比（SNR）、对比信噪比（CNR）、CT容积剂量指数（CTDIvol）、剂量长度乘积（DLP）及辐射剂量。该研究所得到的 A 、B 两组的图像质量评分、CT 值、SD 、SNR 、CNR 差异均无统计学意义。 A 组较 B 组辐射剂量降低。所以本研究认为在婴幼儿胸部扫描中采用80kV 加 ADIR重建,图像质量能达到诊断要求,且可降低辐射剂量。     

围手术期负荷剂量他汀对急性ST段抬高型心肌梗死患者预后的影响

为了探讨围手术期给予阿托伐他汀负荷剂量对急性ST段抬高型心肌梗死（STEMI）患者急诊经皮冠状动脉介入治疗（PCI）后对心血管事件的影响。选取因STEMI行急诊PCI术患者160例,其中80例于PCI术前给予阿托伐他汀负荷剂量40mg,80例术前未给予阿托伐他汀负荷剂量进行研究。分析两组患者住院期间肌酸激酶同工酶与超敏C反应蛋白值,PCI术后与术后1个月心功能情况。结果显示围手术期阿托伐他汀负荷剂量组主要心血管事件发生率优于非阿托伐他汀组（P〈0．05）。因此,围手术期给予负荷剂量的阿托伐他汀可以降低住院期间不良心血管事件的发生率,改善患者预后。