The Middle to Upper Paleolithic transition: dating, stratigraphy, and isochronous markers

Accurate and precise dating is vital to our understanding of the Middle to Upper Paleolithic transition. There are, however, a number of uncertainties in the chronologies currently available for this period. We attempt to examine these uncertainties by utilizing a number of recent developments in the field. These include: the precise dating of the Campanian Ignimbrite (CI) tephra by 40Ar/39Ar; the tracing of this tephra to a number of deposits that are radiocarbon dated; the publication of revised radiocarbon calibration data for the period, showing a much better convergence with other available data than during the recent IntCal comparison; and a layer-counted ice-core chronology extending beyond 40,000cal BP. Our data comparisons suggest that a reasonable overall convergence between calibrated radiocarbon ages and calendar dates is possible using the new curves. Additionally, we suggest that charcoal-based radiocarbon ages, as well as bone-based radiocarbon determinations, require cautious interpretation in this period. Potentially, these issues extend far beyond the sites in this study and should be of serious concern to archaeologists studying the Middle to Upper Paleolithic. We conclude by outlining a strategy for moving the science forward by a closer integration of archaeology, chronology, and stratigraphy.     

Climatic water deficit,tree species ranges,and climate change in Yosemite National Park

Aim (1) To calculate annual potential evapotranspiration (PET), actual evapotranspiration (AET) and climatic water deficit (Deficit) with high spatial resolution; (2) to describe distributions for 17 tree species over a 2300‐m elevation gradient in a 3000‐km² landscape relative to AET and Deficit; (3) to examine changes in AET and Deficit between past (c. 1700), present (1971–2000) and future (2020–49) climatological means derived from proxies, observations and projections; and (4) to infer how the magnitude of changing Deficit may contribute to changes in forest structure and composition. Location Yosemite National Park, California, USA. Methods We calculated the water balance within Yosemite National Park using a modified Thornthwaite‐type method and correlated AET and Deficit with tree species distribution. We used input data sets with different spatial resolutions parameterized for variation in latitude, precipitation, temperature, soil water‐holding capacity, slope and aspect. We used climate proxies and climate projections to model AET and Deficit for past and future climate. We compared the modelled future water balance in Yosemite with current species water‐balance ranges in North America. Results We calculated species climatic envelopes over broad ranges of environmental gradients – a range of 310 mm for soil water‐holding capacity, 48.3°C for mean monthly temperature (January minima to July maxima), and 918 mm yr^?1 for annual precipitation. Tree species means were differentiated by AET and Deficit, and at higher levels of Deficit, species means were increasingly differentiated. Modelled Deficit for all species increased by a mean of 5% between past (c. 1700) and present (1971–2000). Projected increases in Deficit between present and future (2020–49) were 23% across all plots. Main conclusions Modelled changes in Deficit between past, present and future climate scenarios suggest that recent past changes in forest structure and composition may accelerate in the future, with species responding individualistically to further declines in water availability. Declining water availability may disproportionately affect Pinus monticola and Tsuga mertensiana. Fine‐scale heterogeneity in soil water‐holding capacity, aspect and slope implies that plant water balance may vary considerably within the grid cells of kilometre‐scale climate models. Sub‐grid‐cell soil and topographical data can partially compensate for the lack of spatial heterogeneity in gridded climate data, potentially improving vegetation‐change projections in mountainous landscapes with heterogeneous topography.     

The Medieval Climate Anomaly and Little Ice Age in Chesapeake Bay and the North Atlantic Ocean

A new 2400-year paleoclimate reconstruction from Chesapeake Bay (CB) (eastern US) was compared to other paleoclimate records in the North Atlantic region to evaluate climate variability during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Using Mg/Ca ratios from ostracodes and oxygen isotopes from benthic foraminifera as proxies for temperature and precipitation-driven estuarine hydrography, results show that warmest temperatures in CB reached 16-17 °C between 600 and 950 CE (Common Era), centuries before the classic European Medieval Warm Period (950-1100 CE) and peak warming in the Nordic Seas (1000-1400 CE). A series of centennial warm/cool cycles began about 1000 CE with temperature minima of ~ 8 to 9 °C about 1150, 1350, and 1650-1800 CE, and intervening warm periods (14-15 °C) centered at 1200, 1400, 1500 and 1600 CE. Precipitation variability in the eastern US included multiple dry intervals from 600 to 1200 CE, which contrasts with wet medieval conditions in the Caribbean. The eastern US experienced a wet LIA between 1650 and 1800 CE when the Caribbean was relatively dry. Comparison of the CB record with other records shows that the MCA and LIA were characterized by regionally asynchronous warming and complex spatial patterns of precipitation, possibly related to ocean-atmosphere processes.     

云南植物上冰核活性细菌鉴定

从云南植物上分离到９２株冰核活性细菌,并进行了鉴定。其中菠萝欧文氏菌６１株,占６６．３％;草生欧文氏菌２株,占２．２％;丁香假单胞菌２１株,占２２．８％;黄瓜角斑病菌２株,占２．２％;菜豆荚斑假单胞菌６株,占６．５％。云南省冰核活性细菌的优势种类是菠萝欧文氏菌,其次是丁香假单胞菌类。     

Bovine Oocytes Cryoinjury and How to Improve Their Development Following Cryopreservation

Bovine oocytes are less likely to undergo successful cryopreservation than cleavage-stage embryos. Bovine oocytes characteristically contain high levels of lipids that represent one of the major obstacles limiting efficient cryopreservation. These droplets together with structures such as cumulus cells, zona pellucida, cytoplasm membrane, cortical granules, mitochondria, spindle, and cytoskeleton (microtubles and microfilaments) often incur serious damage during cooling and warming. The cryoinjury could, to some extent, be decreased by selection of proper permeable and non-permeable cryoprotectants, and of vitrification with high cooling and warming rates. Additionally, such measures may also enhance their cryotolerance as partial removal of cumulus cells, modification of oocyte membrane constituents, polarization of the cytoplasmic lipid droplets by centrifugation, and addition of cytoskeleton relaxants or ice blockers into vitrification solutions. The improvement in cryopreservation methodology for bovine oocytes will no doubt augment other technologies such as bovine cloning and the establishment of gene bank for transgenic cattle.     

The effect of cryopreservation or heating on the mechanical properties and histomorphology of rat bone-patellar tendon-bone

The effects of cryopreservation on tendon allograft have been reported, but remain unclear, particularly the potential effects on mechanical properties and histological changes by ice crystal formation. There are also few studies about effects of heating for sterilization of tendon. We evaluated the effect of cryopreservation or heating on the mechanical properties and histomorphology of rat bone-patellar tendon-bones (BTBs). BTBs were processed by cryopreservation at −80°C for 3 weeks, or heating at 80°C for 10 min. Tensile testing and histomorphological examination were performed. The cryopreservation of tendons showed less influences on their mechanical properties. When cryopreserved BTBs in frozen state were fixed by freeze-substitution method, many spaces were observed in interfibrillar substances. These results suggest that the collagen fibers of cryopreserved tendons were histomorphologically affected by ice crystals. The heating of tendons completely destroyed the collagen fibers of the tendons and is therefore thought to be inappropriate for the sterilization of BTBs.     

Extra- and intra-cellular ice formation of red seabream (Pagrus major) embryos at different cooling rates

The ice crystal formation is assumed as the most lethal factor for the failure of fish embryo cryopreservation and intracellular ice formation (IIF) plays a central role in cell injury during cooling. The objectives were to observe the morphological changes of red seabream (Pagrus major) embryo during the cooling–thawing process, and to examine the effect of cryoprotectant and cooling rate on the temperatures of oil globule ice formation (T_OIF), extra-cellular ice formation (T_EIF) and intracellular ice formation (T_IIF) using cryomicroscope. After thawing, the morphological changes of embryos were observed and recorded by the video attachment and monitor under the microscope. During the cooling process, three representative phenomena were observed: oil globule gradually turned bright firstly, then the whole field of view flashed and the embryo blackened. Cooling rate affect the temperature of both extra- and intra-cellular ice formations. T_EIF and T_IIF at high cooling rate were much lower than that at low cooling rate. And the value of T_EIF − T_IIF increased from 0.45 to 11.11 °C with the increase of cooling rate from 3 to130 °C/min. Taken together, our results suggested that high cooling rate with proper cryoprotectant would be a good option for red seabream embryo cryopreservation.     

Supercooling,ice nucleation and crystal growth: a systematic study in plant samples

This paper presents an innovative technological platform which is based on infrared video recording and is used for monitoring multiple ice nucleation events and their interactions, as they happen in 96 well microplates. Thousands of freezing curves were obtained during this study and the following freezing parameters were measured: cooling rate, nucleation point, freezing point, solidus point, degree of supercooling, duration of dendritic phase and duration of crystal growth. We demonstrate the use of this platform in the detection of ice nuclei in plant samples. Future applications of this platform may include breeding for frost tolerance, cryopreservation, frozen food technology and atmospheric sciences.     

聚乙烯醇-海藻酸盐共固定化冰核活性细菌——黄单胞菌TS206的研究

冰核活性细菌固定化在食品冷冻浓缩中的应用具有重要意义,冰核活性和抗渗漏能力是衡量其性能的两个重要技术指标。研究采用PVA和海藻酸盐作为固定化载体,通过两者优良性能的互补而建立对冰核活性细菌Xanthomonas ampelina TS206的共固定化技术。结果表明,细胞投入量对冰核活性有较大影响,基础固定化条件对固定化技术指标的综合评分影响程度大小的顺序依次为：海藻酸钠浓度＞硼酸浓度＞PVA浓度＞CaCl2浓度,各因素的较优水平是：海藻酸钠浓度1%,硼酸浓度5%,PVA浓度8%,CaCl2浓度1.1%;研究还发现冰核活性与固定化凝胶珠的添加量正相关,与固化时间相关性较小,渗漏量受固定化凝胶珠的添加量和固化时间影响不显著。     

Cryoprotectants: A review of the actions and applications of cryoprotective solutes that modulate cell recovery from ultra-low temperatures

Cryopreservation has become a central technology in many areas of clinical medicine, biotechnology, and species conservation within both plant and animal biology. Cryoprotective agents (CPAs) invariably play key roles in allowing cells to be processed for storage at deep cryogenic temperatures and to be recovered with high levels of appropriate functionality. As such, these CPA solutes possess a wide range of metabolic and biophysical effects that are both necessary for their modes of action, and potentially complicating for cell biological function. Early successes with cryopreservation were achieved by empirical methodology for choosing and applying CPAs. In recent decades, it has been possible to assemble objective information about CPA modes of action and to optimize their application to living systems, but there still remain significant gaps in our understanding. This review sets out the current status on the biological and chemical knowledge surrounding CPAs, and the conflicting effects of protection versus toxicity resulting from the use of these solutes, which are often required in molar concentrations, far exceeding levels found in normal metabolism. The biophysical properties of CPAs that allow them to facilitate different approaches to cryogenic storage, including vitrification, are highlighted. The topics are discussed with reference to the historical background of applying CPAs, and the relevance of cryoprotective solutes in natural freeze tolerant organisms. Improved cryopreservation success will be an essential step in many future areas such as regenerative medicine, seed banking, or stem cell technology. To achieve this, we will need to further improve our understanding of cryobiology, where better and safer CPAs will be key requirements.