明代铜镜科学考察

通过对部分明代铜镜的科学分析,了解到明代也使用过与战国汉唐成分相近的合金来铸镜;除了锡汞齐外,此时还使用了铅汞齐和铅锡汞齐来开镜或磨镜。     

Burning Libraries: A Community Response

ABSTRACT

The first decade of the twenty-first century has seen a growing recognition that widespread impacts of climate change (erosion, sea level rise, wildfires, warming soil temperatures) are rapidly destroying archaeological sites and permanently wiping out millennia of cultural heritage and important scientific data on a global scale. This paper provides a brief overview of the efforts of the international archaeological community and its allies to organise a broad and coordinated response to this widespread and urgent threat to our basic record by mobilising at the local, national and international level. The work of the archaeological professional societies has supplemented a growing host of initiatives on multiple scales by national and local governmental agencies, regional research teams, local and Indigenous heritage groups and the international global change scientific community. This paper provides some reflections on the Society for American Archaeology’s Climate Change Strategies and the Archaeological Record team effort from 2015 to 2018, some links to more contacts and resources and some suggestions for future directions.     

The Diffraction of Rayleigh Waves by Twin Circular Cavities in a Poroelastic Half-Space

The diffraction of Rayleigh waves by twin circular cavities in a poroelastic half-space is investigated using the indirect boundary integral equation method (IBIEM). To satisfy the boundary conditions on the free surface, Green’s functions of compressional and shear wave sources in a poroelastic half-space are derived based on Biot’s theory. It is verified that the IBIEM has great accuracy and numerical stability. Then, the influences of the drainage boundary condition, incident wave frequency, porosity, and cavity spacing on the dynamic responses are investigated by numerical examples. The results show that the amplification effect of the twin cavities is greater in the case of undrained boundary conditions, lower frequencies, and smaller cavity spacings. The porosity of the saturated medium also influences the dynamic responses because the velocity of the Rayleigh wave will change with the porosity of the saturated medium.     

传统西藏壁画表面涂层材质与工艺研究

在前期对甘肃拉卜楞寺壁画表面涂层结构分析基础上,以桐油、亚麻油、胡麻油等干性油为基础材料,试验重现了制作西藏壁画表面涂层的"古法"清漆熬制方法和工艺。同时,提出了一种源于"古法",吸收现代油基树脂漆优点,具有良好材料结构且组成可知、可控、兼容等特点的清漆材料及其工艺("新古法")。研究表征了"古法""新古法"清漆的结构,评价了清漆涂层的颜色、外观、光学性质、艺术效果、耐候性等,并与现代合成的醇酸清漆、氟碳清漆、酚醛清漆等做了对比。结果表明,"古法""新古法"清漆在达到与合成清漆相同化学稳定性、耐候性的同时,具有更好的兼容性和表现效果,可用于今后西藏壁画表面涂层材料的修复。     

Soil and organic carbon losses from varying land uses: a global meta‐analysis

Soil (SL) and organic carbon losses (SOC_L) have increased with human population and climate change linked extreme events. While SL and SOC_L are clearly associated with surface run‐off, the impact of land use is still not well understood. This article elucidates the effects of land use, surface cover, and other environmental factors on SL and SOC_L using data from 55 published studies. The overall SL (12.34 ± 2.25 Mg ha^?1 year^?1) and SOC_L (21.80 ± 0.91 g C m^?2 year^?1) suggests substantial losses of the fertile topsoil globally. Grasslands (4.19 ± 1.22 Mg ha^?1 year^?1) had 77%, 66%, and 41% lower SL than orchards, croplands, and forests, respectively, which is attributable to higher soil organic matter and surface cover. Croplands had the highest SOC_L at 22.78 ± 2.22 g C m^?2 year^?1. Natural vegetation had 98% and 70% lower run‐off and SL than did plant residue mulched plots, indicating its great potential for surface run‐off and soil erosion control. Rainfall and slope were key drivers of soil erosion, while soil surface cover, SOC, and clay content decreased. These findings improve our knowledge on soil and organic carbon losses, which is useful for fostering sustainable management of soils and natural vegetation to enhance ecosystems functionality.     

Intrasite features distribution as a source of social information: The case of Djaba-Hosséré (Northern Cameroon)

The spatial organization of Dìì settlements has been considered as the reflection of the peculiar social organization of Dìì chiefdoms: a model based on an association of several lineages, most of them being necessary for the working of the whole. The distribution of thousands of surface remains (features and ceramics) located on the eastern foot of the Djaba massif, the site of the eponymous chieftaincy in the early 19th century, together with stratigraphic data, is likely to provide information about the age and the foundation process of a Dìì chiefdom. Following the spatial analysis, we will see that, locally, the growth of political complexity began about the 18th century and that this process may have resulted in the arrival of ‘foreigners’ among one or more of the autochthonous communities, one of what appears to have been strongly involved in metallurgical activities. Archaeological data seems thus to indicate that the foundation myth of the ‘generous foreigner’ shared by most of the Dìì chieftaincies was based on historical events.     

Local Knowledge and Economic Realities Affecting Soil Erosion in the Rach Rat Catchment,Vietnam

Several parts of Binh Phuóc Province, southern Vietnam, suffer from degraded soils and vegetation as a result of both natural erosion of weak mud rocks and sandstones and intensive human activity, especially through land clearing for agriculture on unstable slopes, deforestation, and abandonment of poor farmland. The underlying cause of this land degradation has been the farming habits of migrants of varying ethnic groups who have settled in the area since 1980. The indigenous farming knowledge of these people and the role of that knowledge in soil erosion were examined by a series of household surveys. They enabled farming practices to be related to ground cover established from a 2002 Landsat 7 ETM (Enhanced Thematic Mapper), and erosion data from a series of erosion bridge measurements. A GIS (Geographical Information System) approach was piloted as a means of identifying areas vulnerable to erosion. This could then be combined with the understanding of farming practices to reveal the relative roles of farmer behaviour, crop cover, and slope and soil characteristics in the erosion process. Land use, local people's knowledge and economic realities are the main factors, as well as natural conditions, that drive this land degradation.     

饱水木质文物的细菌病害及其诊断技术的进展

为了促进微生物学理论与技术在我国文物保护领域中的应用,使我国的文物保护与国际先进水平接轨,本文通过对国内外有关文物保护微生物学研究进展的综述,阐述了饱水木质文物细菌性病害的成因和机理.侵蚀细菌、钻管细菌和空化细菌是饱水木质文物细菌性病害的病原体,但它们的作用方式有一定的区别.在饱水木质文物细菌性病害诊断上,国外已较为普遍地使用了光镜技术、电镜技术、细菌培养技术以及多种分子生物学技术.根据众多样本分析的结果,国外学者已建立评价饱水木质文物腐蚀状态的定性指标体系.文中还结合目前我国有关饱水木质文物保护的现状,阐述了文物保护微生物学在我国饱水木质文物保护中的应用前景,并建议尽快开展相关的研究工作.     

A Survey of Soil Erosion in Australia using Caesium‐137

A survey of soil erosion was conducted in Australia using the fallout radioisotope caesium‐137 as an indicator of topsoil redistribution. Two hundred and six sites were sampled, 100 within rotational cropping and horticultural use, 52 within uncultivated permanent pasture and forest, and 54 in rangelands. Average net soil losses were approximately equal for cultivated cropping lands and rangelands (ca. 5.5 t ha^?1 yr^?1), and just over 1 t ha^?1 yr^?1 for pasture and forest. The Mann Whitney U Test revealed that losses under cropping and rangeland conditions were significantly higher (p < 0.05) than under uncultivated pasture and forest. Soil loss was negatively correlated with mean annual rainfall and slope gradient, and positively correlated with slope length (Spearman's rank correlation). There was no correlation between rates of soil loss and a rainfall erosi‐vity index. An assessment of erosional events was provided by landholders for 104 sites, with their ranking being weakly but significantly correlated with soil loss estimates (r =+0.35). Sixty percent of sites had net soil losses greater than 1 t ha^?1 yr^?1, and 74% of sites had losses of more than 0.5 t ha^?1 yr^?1. This latter rate may be regarded as a limit for a tolerable level of soil loss. These high rates of soil loss have occurred since the mid‐1950s despite there being significant landholder awareness of the soil erosion hazard.     

几件西沙华光礁I号沉船遗址出水瓷器的保护研究

为了对8件西沙华光礁I号沉船遗址出水瓷器进行表面凝结物去除、脱盐清洗和残缺补全等保护处理,采用X射线衍射(XRD),对瓷器表面凝结物进行了成分分析;用三维视频显微镜对瓷器进行脱盐前、后的显微照相对比;对瓷器表面微孔内的物质,用扫描电镜分析(SEM)方法进行成分检测;用电导率仪测量瓷器脱盐过程中电导率变化情况。结果表明,出水瓷器表面凝结物,容易机械去除的样品,其成分主要是镁方解石及文石;不容易机械去除的样品,其成分主要是锰白云石及文石。瓷器微孔内的白色物质为含氯盐分。经两周时间的脱盐清洗,出水瓷器的脱盐电导率值降至较低水平。本工作结果可为西沙海域出水瓷器的后续保护提供资料。