Geochemical composition and ages of sediment core BELQ300 obtained from Lake Belau, north Germany

Geochemical and palynological data from an annually laminated core sequence (Lake Belau, Schleswig-Holstein) are interpreted with respect to vegetation and settlement history on the basis of a chronostratigraphical model and archaeological evidence. Most settlement periods indicated by pollen and archaeological data can be geochemically identified in the sediment sequence using tracer elements such as K, Rb, Zr and the K/Zr ratio. Whilst air-borne pollen carry a more regional signal, the sedimentary flux of these trace elements is determined by the allogenic input from the catchment area of the lake and, therefore, provides information about the local history of settlement and agricultural land use in the lake's vicinity. This is exemplified for the period of the middle Neolithic Funnel Beaker Culture ('Iversen landnam'), where a time offset of 250 years between both signals has been detected. In contrast, both geochemical and pollen signals are highly synchronous during the Early Migration Period and the High Medieval Period. Additionally, the Fe/Ca and/or U/Fe ratio may serve as a sensitive tracer for human impact on the trophic state of the lake. The suggested impact of the Romans and the High Medieval civilization can clearly be seen (and quantified) from elevated lead input into Lake Belau sediments at this time. Effects of secular climatic changes on the sedimentary chemistry have not been detected and, if present, seem to have been obliterated by anthropogenic activity.

Targeted mutation reveals a central role for SR-BI in hepatic selective uptake of high density lipoprotein cholesterol

Scavenger receptor BI (SR-BI) is a cell surface receptor that binds high density lipoproteins (HDL) and mediates selective uptake of HDL cholesteryl esters (CE) in transfected cells. To address the physiological role of SR-BI in HDL cholesterol homeostasis, mice were generated bearing an SR-BI promoter mutation that resulted in decreased expression of the receptor in homozygous mutant (designated SR-BI att) mice. Hepatic expression of the receptor was reduced by 53% with a corresponding increase in total plasma cholesterol levels of 50–70% in SR-BI att mice, attributable almost exclusively to elevated plasma HDL. In addition to increased HDL-CE, HDL phospholipids and apo A-1 levels were elevated, and there was an increase in HDL particle size in mutant mice. Metabolic studies using HDL bearing nondegradable radiolabels in both the protein and lipid components demonstrated that reducing hepatic SR-BI expression by half was associated with a decrease of 47% in selective uptake of CE by the liver, and a corresponding reduction of 53% in selective removal of HDL-CE from plasma. Taken together, these findings strongly support a pivotal role for hepatic SR-BI expression in regulating plasma HDL levels and indicate that SR-BI is the major molecule mediating selective CE uptake by the liver. The inverse correlation between plasma HDL levels and atherosclerosis further suggests that SR-BI may influence the development of coronary artery disease.

Expression of scavenger receptor class B type 1 (SR-BI) promotes microvillar channel formation and selective cholesteryl ester transport in a heterologous reconstituted system

In the “selective” cholesteryl ester (CE) uptake process, surface-associated lipoproteins [high density lipoprotein (HDL) and low density lipoprotein] are trapped in the space formed between closely apposed surface microvilli (microvillar channels) in hormone-stimulated steroidogenic cells. This is the same location where an HDL receptor (SR-BI) is found. In the current study, we sought to understand the relationship between SR-BI and selective CE uptake in a heterologous insect cell system. Sf9 (Spodoptera frugiperda) cells overexpressing recombinant SR-BI were examined for (i) SR-BI protein by Western blot analysis and light or electron immunomicroscopy, and (ii) selective lipoprotein CE uptake by the use of radiolabeled or fluorescent (BODIPY-CE)-labeled HDL. Noninfected or infected control Sf9 cells do not express SR-BI, show microvillar channels, or internalize CEs. An unexpected finding was the induction of a complex channel system in Sf9 cells expressing SR-BI. SR-BI-expressing cells showed many cell surface double-membraned channels, immunogold SR-BI, apolipoprotein (HDL) labeling of the channels, and high levels of selective HDL-CE uptake. Thus, double-membraned channels can be induced by expression of recombinant SR-BI in a heterologous system, and these specialized structures facilitate both the binding of HDL and selective HDL-CE uptake.

Element concentrations of bulk sediment from the Southern Cape Basin

High-resolution records of Ca and Sr were obtained from shipboard XRF analyses of bulk sediments in five gravity cores from the southern Cape Basin, South Atlantic Ocean. Sr/Ca ratios display regular glacial/interglacial variations of 14-40% and reveal a close correlation with the SPECMAP record, minimum Sr/Ca ratios appearing during glacial (delta18 O) maxima, distinct increases during periods of deglaciation, and highest ratios in interstadials. Shifts in carbonate-producing phytoplankton and/or zooplankton assemblages over glacial/interglacial cycles are suggested to be the main cause for the observed variations in Sr/Ca patterns. Quick assessment of the relationship between Sr/Ca ratios and the SPECMAP record made it possible to easily transfer an age model to the newly collected cores already during the cruise.

(Table 1) Water chemistry of groundwater and snow samples from three sites in Ontario, Canada

Snow samples collected from hand-dug pits at two sites in Simcoe County, Ontario, Canada were analysed for major and trace elements using the clean lab methods established for polar ice. Potentially toxic, chalcophile elements are highly enriched in snow, relative to their natural abundance in crustal rocks, with enrichment factor (EF) values (calculated using Sc) in the range 107 to 1081 for Ag, As, Bi, Cd, Cu, Mo, Pb, Sb, Te, and Zn. Relative to M/Sc ratios in snow, water samples collected at two artesian flows in this area are significantly depleted in Ag, Al, Be, Bi, Cd, Cr, Cu, Ni, Pb, Sb, Tl, V, and Zn at both sites, and in Co, Th and Tl at one of the sites. The removal from the waters of these elements is presumably due to such processes as physical retention (filtration) of metal-bearing atmospheric aerosols by organic and mineral soil components as well as adsorption and surface complexation of ionic species onto organic, metal oxyhydroxide and clay mineral surfaces. In the case of Pb, the removal processes are so effective that apparently ''natural'' ratios of Pb to Sc are found in the groundwaters. Tritium measurements show that the groundwater at one of the sites is modern (ie not more than 30 years old) meaning that the inputs of Pb and other trace elements to the groundwaters may originally have been much higher than they are today; the M/Sc ratios measured in the groundwaters today, therefore, represent a conservative estimate of the extent of metal removal along the flow path. Lithogenic elements significantly enriched in the groundwaters at both sites include Ba, Ca, Li, Mg, Mn, Na, Rb, S, Si, Sr, and Ti. The abundance of these elements can largely be explained in terms of weathering of the dominant silicate (plagioclase, potassium feldspar, amphibole and biotite) and carbonate minerals (calcite, dolomite and ankerite) in the soils and sediments of the watershed. Arsenic, Mo, Te, and especially U are also highly enriched in the groundwaters, due to chemical weathering: these could easily be explained if there are small amounts of sulfides (As, Mo, Te) and apatite (U) in the soils of the source area. Elements neither significantly enriched nor depleted at both sites include Fe, Ga, Ge, and P.

The effect of Yb addition in bi2sr2ca 1-xybxcu2oy partial melted thick films

To study the phase relations in the Bi-2212 and Yb2O3 system, Bi2Sr2Ca1-xYbxCu 2Oy thick films are prepared by partial melt processing via an intermediate reaction between Bi-2212 and Yb2O3. When Bi-2212 and Yb2O3 are partially melted and then slowly cooled, solid solutions of Bi2Sr2Ca 1-xYbxCu2Oy, form by reactions between liquid and solid phases which contain Yb. Following these reactions, Ca is partially replaced in Bi-2212 matrix and participates in the formation of secondary phases, such as Bi-free, (Ca, Sr)Ox and CaO. Variation of the Bi-2212-Yb2O3 ratios and processing parameters changes the balance between the phases and leads to different Yb:Ca ratios in the Bi-2212 matrix of processed thick films. When the partial melting process is optimized for each sample to minimize the growth of secondary phases, x = 0.42-0.46 for the samples prepared at pO2 = 0.01 atm, x = 0.24-0.29 for the samples prepared at pO2 = 0.21 atm, x = 0.18-0.23 for the samples prepared at pO2 = 0.99 atm are obtained regardless to the starting compositions. It is found that superconducting properties of Bi 2Sr2Ca1-xYbxCu2O y thick films strongly depend on the processing conditions, because the conditions result in different Yb content in the Bi-2212 matrix and the volume fraction of the secondary phases. The highest Tc(0) of 77, 90 and 91 K were obtained for the samples processed at 0.01, 0.21 and 0.99 atm of O2, respectively.

Phase relations in the system BiO1.5–SrO–CuO at 1123 K

Phase relations in the system Bi-Sr-Cu-O at 1123 K have been investigated using optical microscopy, electron-probe microanalysis (EPMA) and powder X-ray diffraction (XRD) of equilibrated samples. Differential thermal analysis (DTA) was used to confirm liquid formation for compositions rich in BiO1.5. Compositions along the three pseudo-binary sections and inside the pseudo-ternary triangle have been examined. The attainment of equilibrium was facilitated by the use of freshly prepared SrO as the starting material. The loss of Bi2O3 from the sample was minimized by double encapsulation. A complete phase diagram at 1123 K is presented. It differs significantly from versions of the phase diagram published recently.

铜的多元复合物组成、结构和电学性质的研究

本论文包括三个部分的内容，第一部分研究了Y-Ba-Cu-O材料中，钙、钾、氟离子的掺入对材料结构和电、磁学性质的影响。1、在Y_(1-x)Ca_xBa_2Cu_3O_(7-y)系列中，当x ≤ 0.15时，钙离子进入了YBa_2Cu_3O_(7-y)晶格中钇离子的位置，使晶胞参数略为增大，但没有引起正交 → 四方相变。钙离子渗入导致123相中Cu~(3+)含量上升，同时材料的监界超导转变温度下降。因此，Cu~(3+)含旱管高可能是对超导电性不利的。由于钇离子位置紧邻着Cu(2)-O平面而与Cu(1)-O链相隔较远。因此，钇离子被钙离子替代时主要影响了Cu(2)-O平面的性质。少量钙离子的渗入即明显影响材料的超导电性，这说明Cu(2)-O平面的性质与超导电性密切相关，并可能起着关键的作用。2、在Y(Ba_(1-x)Ca_x)_2Cu_3O_y系的研究中，当x = 1，YCa_2Cu_3O_y是一个单一的化合物，文献未见报道，本文研究了它的结构，电学性质与热学性质，确定它的结构属正交晶系，a = 5.286 A、b = 7.636 A、c = 9.286 A。热分析表明YCa_2Cu_3O_y在1080 ℃分解，分解前于380 ℃ 和608 ℃出殃失氧现象。这个化合物是黑色n型半导体。室温电阻率1.2 * 10~5Ω·cm。与热分析中的失氧温度相对应，lnρ-1/T曲线上在370 ℃、620 ℃ 出现两个转折点。3、在Y-Ba-Cu-O材料中渗入钾离子能细化材料晶粒，降低超导转变宽度，提高零电阻温度，但由于KOH、K_2CO_3等强吸湿性杂质的存在也降低了材料的稳定性。4、在Y-Ba-Cu-O材料中间时掺入钾和氟离子时，材料的超导电性的变化与仅掺钾时相似。这种变化可能主要是钾离子的影响造成的。第二部分中，我们研究了Ca-Sr-Ca-O系的相图和新化合物Sr_3Cu_5O_(8+x)、CaSrCu_3O_(5+x)的结构和电学性质。在第三部分中，广泛研究了组成为Bi_tSr_vCa_wCu_zO_y超导材料的制备，结构和超导电性。铋系超导材料的形成貌与YBa_2Cu_3O_y材料有较大差异，前者是片状层叠的晶粒堆积而成，后者是球状小颗粒堆积而成的。我们合成的材料最高起始转变温度124K，最高零电阻温度112K，与国际上已达到的最高Tc值一致。Jc值达到131A/cm~2。

Bi系铜酸盐的固体化学性质与超导性能

本论文基于固态化学原理，以Bi系中2223高Tc相的稳定性为中心，通过对该复合氧化物的超导电性的系统研究，从整体上来认识铜酸盐化合物的超导电性的系统研究，从整体上来认识铜酸盐化合物的超导性能。前四章侧重于对Bi(Pb,Sb)系中的一些基本性质和特殊现象的研究，后面章节则主要是对晶体中Cu-O面内、面外元素替代效应的探讨。

电感耦合等离子体发射光谱法测定大气降水中多种元素

本文研究了长白山自然保护区大气降水（雨水或雪水）中的多元素分析。采用ICP-AES法测定水中的K、Na、Ca、Mg、Mn、Fe、Sr、Ba、Cu、Zn、Ni和V等元素，用干扰系数法对光谱干扰进行修正。为该地区天气环境背景值和大气污染现状提供了富贵资料。

褐藻胶的化学结构与吸附二价金属离子功能关系的研究

本文在测定由中国产海带（Laminaria japonica）、海蒿子（Sargassum pallidum）、海黍子（S.kjellmanianum)和鼠尾藻（s.thunbergii）提取的无损褐藻胶的糖醛酸组成和嵌段结构的基础上，较系统地研究了褐藻酸及其钠盐钙盐对二价金属离子的静态交换平衡特性与褐藻胶结构的关系，初步制成了具有离子交换性能的粒状褐藻酸钙树脂，开对干燥过的褐藻酸、褐藻酸钠和褐藻酸钙在水溶液中的吸附机理进行了探讨和比较。其结果如下：1. 海带、海蒿子、海黍子和鼠尾藻提取的褐藻胶具有不同的组成和嵌段结构，其M/G比值分别为1.86、1.50、1.22和1.27。文中引入结构参数η不胜数= (F_MG))/(F_M * F_G)，η值分别为0.62、0.13、0.36和0.41。后三种马尾藻褐藻胶与海带的结构和性质有差异，而海黍子和鼠尾藻胶在结构与性质方面比较接近。2. 褐藻胶的结构对吸附二坐金属离子具有很大影响，褐藻酸钠Cd-Sr交换反应的分离因子随着M/G比值的增大而增大；褐藻酸钙对Cu~(2+)离子的交换容量随着MG-嵌段比例（或η值）的增大而增大；褐藻酸对Sr~(2+)、Ba~(2+)、Cd~(2+)混合离子的总交换量随着M-嵌段比例的增大而增大。3. 干燥进的褐藻酸、褐藻酸钙以及褐藻酸钠在水溶液中具有不同的吸附机理。褐藻酸钠在溶液中，主要是二价离子诱导G-分子链协同聚合——“蛋箱模型”~(26)，褐藻酸吸附Cu~(2+)、Sr~(2+)时，除了离子交换外，还有使分子链聚合的螯合作作，分子链上未交换的 -COOH可能参与Sr~(2+)的配位，而Cu~(2+)无此现象。褐藻酸钙吸附Cu~(2+)时，可能有部分Cu~(2+)离子进入“蛋箱”内部替代Ca~(2+)离子而重新配位，但“蛋箱”的骨架不变，而吸附Sr~(2+)时，则表现出与离子交换剂截然不同的分子吸附行为。4. 不溶性的褐藻酸和褐藻酸钙具有较高的吸附选择性，尤其是粒状褐藻酸钙树脂的选择性高、稳定性好，可能应用于贵金属的回收、分离与废水处理等。

贵州黄壤地区植物营养元素来源的Sr同位素示踪

为研究植物营养元素来源，对贵州龙里地区黄壤上生长的12种主要植物的部分营养元素含量及Sr同位素特征进行了分析。结果表明：喀斯特地区黄壤上的植物具有高钙含量，营养元素含量由高到低排序为Ca〉K〉Mg；研究区植物的Ca、K、Sr平均含量均高出报道的陆生植物的平均含量，但比贵州地区同样以灰岩为母质发育而来的石灰土上生长的植物低；植物样品的^87Sr／^86Sr同位素比值变化范围在0．70856～0．71145之间。基于锶同位素组成的端员模式计算结果表明，除了苔藓、石松的营养元素主要来源于大气输入外，其他植物的营养元素主要来源于土壤风化.