Preservation of DNA in ancient Egyptian mummies

The presence of DNA has been demonstrated in the cell nuclei of an ancient Egyptian mummy fragment. When extracted, this DNA proved to be degraded to a considerable extent and chemically modified. However, the preservation of nucleic acids in this specimen suggests that applying recombinant DNA techniques to the study of ancient mummified tissues might prove to be a fruitful future area of research.     

Variabilité et fréquence des cycles de gel‐dégel dans la région de Québec, 1977–2006

Freeze‐thaw cycles are most common at the beginning or near the end of the winter season. These cycles have various effects on the ecosystems of Eastern Canada, affecting both biotic and abiotic components of temperate cold environments. Using air temperature minima and maxima from four meteorological stations close to Québec City, we determined the frequency of daily freeze‐thaw cycles for the last 30 years. The results show no significant increase in the number of freeze‐thaw cycles despite a small increase in air temperature. Polynomial curves describing the relationship between mean air temperatures and the number of freeze‐thaw cycles were calculated. Based on these equations and anticipating a climate change scenario, we projected future freeze‐thaw cycles. Assuming a 5 °C increase in mean air temperatures by 2100, we estimated that the number of days with a freeze‐thaw cycle could increase by approximately 20 days per winter. The increase in the number of such cycles will be concentrated during the coldest months of the winter (January and February).     

硅胶在出土浸饱水漆木器脱水定型中的应用与研究

为解决出土浸饱水漆木器的脱水定型,采用硅胶法将出土浸饱水的漆耳杯和漆盒表面用75%的酒精棉球擦净,经软X射线对胎质进行无损检测后,用电火花打孔,然后放入干燥器皿内的托盘上,同时放入称量的变色球形硅胶,反复更换硅胶量,每次更换25g,每810天更换一次。待硅胶不再变色,器物不再减重,脱水定型完成。结果表明,各件器物平均脱水量为121g。其中,漆耳杯平均脱水率为140%,漆盒盖为120%。说明此法效果良好,值得进一步完善,加以推广。     

“Conducted Properly,Published Incorrectly”: The Evolving Status of Gel Electrophoresis Images Along Instrumental Transformations in Times of Reproducibility Crisis

For the last ten years, within molecular life sciences, the reproducibility crisis discourse has been embodied as a crisis of trust in scientific images. Beyond the contentious perception of “questionable research practices” associated with a digital turn in the production of images, this paper highlights the transformations of gel electrophoresis as a family of experimental techniques. Our aim is to analyze the evolving epistemic status of generated images and its connection with a crisis of trust in images within that field. From the 1980s to the 2000s, we identify two key innovations (precast gels and gel docs) leading to a “two-tiered” gel electrophoresis with different standardization procedures, different epistemic statuses of the produced images and different ways of generating (dis)trust in images. The first tier, exemplified by differential gel electrophoresis (DIGE), is characterized by specialized devices processing images as quantitative data. The second tier, exemplified by polyacrylamide gel electrophoresis (PAGE), is described as a routine technique making use of image as qualitative “virtual witnessing.” The difference between these two tiers is particularly apparent in the ways images are processed, even though both tiers involve image digitization. Our account thus highlights different views on reproducibility within the two tiers. Comparability of images is insisted upon in the first tier while traceability is expected in the second tier. It is striking that these differences occur not only within the same scientific field, but even within the same family of experimental techniques. In the second tier, digitization entails distrust, whereas it implies a collective sentiment of trust in the first tier.     

琼脂凝胶在青铜文物激光清洗中的应用研究

激光清洗应用于青铜文物上有时会使其表面颜色及其他一些物化性质发生改变。如何优化这种方法改善这种状况?为此,本工作将琼脂凝胶-激光联用作为一种可能的优化手段,首先研究了凝胶对激光能量和作用的影响,包括以能量计测量激光穿过凝胶层后的能量减弱幅度,以及通过热敏纸和文物样品上的烧蚀斑观察凝胶对激光烧蚀结果的影响。其次在不同类型的青铜文物样品上将之与普通湿法激光清洗、机械清洗等手段做清洗效果的对比实验,并以视频显微镜、扫描电镜及能谱仪、X射线衍射等手段进行分析验证。实验结果发现,凝胶能小幅度降低激光能量,减轻激光引起的青铜文物表面微观结构的改变,为清洗操作提供更灵活多样的选择。凝胶-激光联用的方法在实验的文物样品上取得了理想的清洗效果,兼顾了操作的效率性和安全性,是在今后的应用中可被考虑的手段。     

Serum Proteins in Archaeological Human Bone

Research on the decomposition of bone collagen offers the key to a wealth of hidden information, for instance, to understanding palaeoclimatic conditions; habitat-specific parameters such as altitude; and for the reconstruction of palaeodiet and subsistence patterns. Radiocarbon dating, one of the most commonly used geochronological techniques is also preferentially carried out on bone collagen. Because negatively charged ions, and especially phosphate groups, are responsible for the tight bonding between organic molecules and bone, soluble serum proteins need not necessarily be leached from buried bone. The authors' hypothesis is that intruding minerals, aided by recrystallization of the bone mineral matrix, and colloid formation, aided by humic substances, form protective layers that preserve serum proteins in bone even after long periods of burial. We have used electrophoresis and Western blotting to recover protein fractions from about 150 archaeological bones from various sites and epochs (up to 5500 BC ) and have succeeded in recovering, purifying all, and identifying some of the proteins. Molecular weight bands corresponding to albumin, transferrin and a-2HS-glycoprotein (A2HS) were frequently recovered. This paper presents the method for separating serum proteins from archaeological bone and for their identification. Twenty-five per cent of samples with the respective molecular weight band still gave a positive immunological reaction with antibodies. We conclude that non-collagenous proteins, especially serum proteins, may be well preserved in bone.     

Commentary: Visual Cultures,Publication Technologies,and Legitimation in the Life Sciences**

This paper comments on five articles in the special issue “Circulating Images in the Life Sciences.” It sees the papers as unified by two themes. The first is their attention to the processes of legitimation. The second is the embedding of the images in textual cultures, which changed over time from the mid-nineteenth century to the very recent past, most notably with the recent advent of digital culture.