The Early Neolithic–Middle Bronze Age environmental history of the Mamakan archaeological area, Eastern Siberia

This study presents the first radiocarbon-dated palynological record from a peat section (57°49′10.03"N; 114°03′31.37"E, 251 m above sea level) in the Mamakan area located in the lower Vitim River valley, about 350 km northeast of Lake Baikal. While the area is particularly renowned for its numerous multi-layered Upper Palaeolithic (ca. 50,000–14,000/10,000 cal yr BP) archaeological sites with rich cultural assemblages, there is also evidence for human occupation during the Mesolithic–Neolithic–Bronze Age period (ca. 14,000/10,000–3000 cal yr BP). However, the absence of accurately dated palaeoenvironmental records does not allow discussion of prehistoric human–environment interactions in this area. The records of pollen, spores and other non-pollen palynomorphs (NPPs) from the Mamakan site presented in this article document changes in the vegetation and climate of the study area between 6570 and 3630 cal yr BP. From 6570 to 6200 cal yr BP the vegetation around the site was dominated by sparse forests of mainly spruce and larch, indicating that the permafrost layer was located relatively close to the surface. Fir was part of the forest communities in habitats with a milder microclimate and a deeper permafrost layer. Around 6200 cal yr BP Scots pine started to spread across the study area. Until 4670 cal yr BP it dominated the pollen spectra of the Mamakan record, indicating warmer conditions. Climate cooling and higher soil moisture is indicated by the spread of Siberian pine and Siberian dwarf pine at the expense of Scots pine between 4670 and 3840 cal yr BP. From 3840 cal yr BP the Mamakan record suggests a landscape opening associated with the spread of Sphagnum-dominated bog vegetation and an increase in the occurrence of wildfires (3870–3820 cal yr BP), which were either natural in origin or caused by human activities. The spread of Scots pine paralleled by a decline in dark conifers (spruce and fir) and larch in the Lake Baikal Region (LBR) has been linked to a ‘hiatus’ in the Cis-Baikal archaeological records of the Middle Neolithic (6660–6060 cal yr BP). Around the Mamakan site this vegetation change occurred comparatively late, about 600 years later than in the regions around and east (e.g. Lake Baunt area) of Lake Baikal. The Mamakan pollen and NPP records, together with the available archaeological data, suggest that the environmental conditions in the lower Vitim River area may have sustained the hunter-gatherer lifestyle also during the ‘hiatus’ interval

Estimation of radiation non-regulatory stochastic risks for meadow plants of the semipalatinsk test site

An algorithm and formulas to estimate non-regulatory stochastic risks (for biota and humans) have been derived. These were used to assess radiation risks for meadow plants within the Semipalatinsk Test Site (STS). It has been shown that on small plots with relatively high radiation levels (∼ 0.25 mGy/h) the radiation risks of death of radiosensitive plants (leguminous and coniferous shrubs) have a noticeable value (> 2%). In the other STS area, radiation is not a danger to the vegetation

Regulatory radiation risks for the population and natural objects within the semipalatinsk test site

Advisability of using risks as indicators for estimating radiation impacts on environmental objects and humans has been justified. Results are presented from identification of dose burdens distribution to various cohorts of the population living within the Semipalatinsk Test Site (STS) and consuming contaminated farm products. Parameters of dose burden distributions are estimated for areas of livestock grazing and the most contaminated sectors within these areas. Dose distributions to meadow plants for the above areas have been found. Regulatory radiation risks for the STS population and meadow ecosystem components have been calculated. Based on the parameters estimated, levels of radiation exposure of the population and herbaceous plants have been compared

Three-dimensional model and characterization of the iron stress-induced CP43'-photosystem I supercomplex isolated from the cyanobacterium Synechocystis PCC 6803.

The cyanobacterium Synechocystis PCC 6803 has been subjected to growth under iron-deficient conditions. As a consequence, the isiA gene is expressed, and its product, the chlorophyll a-binding protein CP43', accumulates in the cell. Recently, we have shown for the first time that 18 copies of this photosystem II (PSII)-like chlorophyll a-binding protein forms a ring around the trimeric photosystem I (PSI) reaction center (Bibby, T. S., Nield, J., and Barber, J. (2001) Nature, 412, 743-745). Here we further characterize the biochemical and structural properties of this novel CP43'-PSI supercomplex confirming that it is a functional unit of approximately 1900 kDa where the antenna size of PSI is increased by 70% or more. Using electron microscopy and single particle analysis, we have constructed a preliminary three-dimensional model of the CP43'-PSI supercomplex and used it as a framework to incorporate higher resolution structures of PSI and CP43 recently derived from x-ray crystallography. Not only does this work emphasize the flexibility of cyanobacterial light-harvesting systems in response to the lowering of phycobilisome and PSI levels under iron-deficient conditions, but it also has implications for understanding the organization of the related chlorophyll a/b-binding Pcb proteins of oxychlorobacteria, formerly known as prochlorophytes