Oxygen isotopic and species composition of planktonic foraminiferas in sediment cores from the North Atlantic

Paleotemperature curves were drawn from oxygen-isotope ratios in CaCO3 of planktonic foraminiferal tests and by the micropaleontological method using quantitative relationships of their species. Two series of curves yield similar results. These data confirm that isotope composition of oxygen reflects primarily temperature, and not isotope composition in ocean water. Temperature of the upper layer of ocean water increased from north to south both during the last two glaciations and in the interglacials. All three sediment cores collected from different latitudes show approximately the same amplitudes of fluctuation of mean annual temperature during times of their accumulation, as determined independently by different methods; these amplitudes are estimated as 5-7°C.

Mineral composition of 0.1-0.05 mm grain size fraction from the surface layer of bottom sediments in the West European province of the Atlantic Ocean

Rock material sampled from the Mir manned deep-sea submersibles and by dradges, grabs, and sediment cores over a vast area of the North Atlantic was analyzed to show that this material is of continental origin, unlike original rocks of the ocean floor. It is proved to be related to iceberg rafting during Quaternary glaciations. Independent data on distribution and composition of sandy and silty grains in sediment cores also support this relation to the recent glaciation. New criteria for identification of iceberg rock matter in pelagic sediments are presented on the base of analysis of all available data.

(Table 1) Pigments isolated from DSDP Leg 56 Holes

A relatively well documented record of intermediate and late chlorophyll diagenesis in marine sediments now exists. Intermediate diagenetic stages include conversion of chlorins to DPEP-series porphyrins and subsequent chelation with nickel, vanadyl, and, in special cases, copper. Increasing thermal stress leads to etio-series generation and transalkylation (Baker, 1969; Baker and Smith, 1975; Baker et al., 1977; Palmer and Baker, in press). In contrast, the early transformations of clorophyll are still largely unknown. Very early diagenetic reactions must certainly include loss of magnesium, deesterification, decarboxylation, reduction of ring-conjugating groups, and finally, oxidative-aromatization of carbons 7 and 8 in ring IV to yield free-base porphyrins (Baker and Smith, 1973; Smith and Baker, 1974). Chlorins (7,8-dihydroporphyrins) are very difficult to isolate and identify, because of hydrocarbon impurities which absorb in the blue to violet region of the electromagnetic spectrum and which co-chromatograph with the pigments. Further complications possibly can arise from artifact formation during isolation. In the present study, twelve DSDP Leg 56 core samples, ranging in sub-bottom depth from 4 to 420 meters and in age from Pleistocene to middle Miocene, were analyzed for tetrapyrrole pigments. Chlorins, in concentrations ranging from about 4 to less than 0.002 µg/g sediment, wet weight, were the only tetrapyrroles found. A carotenoid (tetraterpene) was isolated from Section 434-1-3.

Global compilation of benthic data sets I

Approaches to quantify the organic carbon accumulation on a global scale generally do not consider the small-scale variability of sedimentary and oceanographic boundary conditions along continental margins. In this study, we present a new approach to regionalize the total organic carbon (TOC) content in surface sediments (<5 cm sediment depth). It is based on a compilation of more than 5500 single measurements from various sources. Global TOC distribution was determined by the application of a combined qualitative and quantitative-geostatistical method. Overall, 33 benthic TOC-based provinces were defined and used to process the global distribution pattern of the TOC content in surface sediments in a 1°x1° grid resolution. Regional dependencies of data points within each single province are expressed by modeled semi-variograms. Measured and estimated TOC values show good correlation, emphasizing the reasonable applicability of the method. The accumulation of organic carbon in marine surface sediments is a key parameter in the control of mineralization processes and the material exchange between the sediment and the ocean water. Our approach will help to improve global budgets of nutrient and carbon cycles.

Matters Arising: Zhu et al, "A novel gene variation of TNFα associated with ankylosing spondylitis: A reconfirmed study"

In a recently published study1 involving 79 ankylosing spondylitis (AS) patients and 132 unrelated healthy blood donors, Zhu et al report association of a tumour necrosis factor α (TNFα) single nucleotide polymorphism (SNP), rs1799724, with AS.1 I have many concerns with this paper and its conclusions...

High energy Li ion irradiation effects in ferroelectric PZT and SBT thin films

The ferroelectric Pb(Zr0.53Ti0.47)O-3 (PZT) and SrBi2Ta2O9 (SBT) thin films were prepared by laser ablation technique. The dielectric analysis, capacitance-voltage, ferroelectric hysteresis and DC leakage current measurements were performed before and after 50 MeV Li3+ ion irradiation. In both thin films, the irradiation produced some amount of amorphisation, considerable degradation in the ferroelectric properties and change in DC conductivity. On irradiation of these thin films, the phase transition temperature [T-c] of PZT decreased considerably from 628 to 508 K, while SBT exhibited a broad and diffuse transition with its T-c decreased from 573 to 548 K. The capacitance-voltage curve at 100 kHz showed a double butterfly loop with a large decrease in the capacitance and switching voltage. There was decrease in the ferroelectric hysteresis loop, remanant polarisation and coercive field. After annealing at a temperature of 673 K for 10 min while PZT partially regained the ferroelectric properties, while SBT did not. The DC conductivity measurements showed a shift in the onset of non-linear conduction region in irradiated SBT. The degradation of ferroelectric properties of the irradiated thin films is attributed to the irradiation-induced partial amorphization and the pinning of the ferroelectric domains by trapped charges. The regaining of properties after annealing is attributed to the thermal annealing of the defects generated during the irradiation. (C) 2003 Elsevier Science B.V. All rights reserved.

Jeans instability criterion modified by external tidal field

The well-known Jeans criterion describes the onset of instabilities in an infinite, homogeneous, self-gravitating medium supported by pressure. Most realistic astrophysical systems, however, are not isolated - instead they are under the influence of an external field such as the tidal field due to a neighbour. Here, we do a linear perturbation analysis for a system in an external field and obtain a generalized dispersion relation that depends on the wavenumber, the sound speed and also the magnitude of the tidal field. A typical, disruptive tidal field is shown to make the system more stable against perturbations, and results in a higher effective Jeans wavelength. The minimum mass that can become unstable is then higher (super-Jeans) than the usual Jeans mass. Conversely, in a compressive tidal field, perturbations can grow even when the mass is lower (sub-Jeans). This approach involving the inclusion of tidal field opens up a new way of looking at instabilities in gravitating systems. The treatment is general and the simple analytical form of the modified Jeans criterion obtained makes it easily accessible.

新型混桥配位聚合物的合成、晶体结构及表征

本论文对文献所报道的α,ω-二梭酸根的配位方式及其构象进行了概括，提出表示其配位方式的方法（暂定为琳L法）．随后报道20个新型配位聚合物的合成、晶体结构，并对部分配合物做了红外、差热热重、磁性质和元素分析等表征．配合物Zn（bpy）（CSH6O4）1和Cu（bpy）（CSH6o4）2为异质同晶结构，五配位的金属原子通过戊二酸根的桥联作用形成一条带状链，相邻链间通过4，4七联毗睫形成二维层．配合物Mll（bpy）（CSH12O4）·HZO3具有与配合物1和2类似的却由辛二酸根桥联的二维层，层间存在结晶水分子．在配合物zn（bpy）（C6HSO4）4中，4，4，一联毗睫和己二酸根桥联锌原子形成具有纳米孔洞的三维框架结构，它们两度相互穿插构筑整个晶体结构．热分析表明配合物3在82一140oC区间失去结晶水分子．配合物4在180-320℃区间内失去4，4’-联毗陡．配合物3在5-30OK区间内的磁性遵循Curie-Weiss定律Xm-l＝4.265／（T+6.3），两个异质同晶结构配合物MZ（hmt）（HZO）2（C3HZO4）2（M＝Mn（II）5，Cu（II）6）中的金属原子通过丙二酸根的桥联和鳌合作用形成二维层。继而通过六次甲基四胺桥联作用形成三维框架结构．配合物5在5一30OK区间内的磁性遵循Curie一Weiss定律Xm-1＝8.99／（T+4.5）．配合物［Mn（HZO）4（bpy）］（C4H4O4）4H207、［Mn（H2O）4（bpy）］（c4HZO4）·4H208和［Zn（H2O）4（bpy）］（C4H4O4）·4H209为异质同晶结构，属于三斜晶系，均由∞1［M（H2O）4（ bpy）2/2］2+阳离子链、结晶水分子和二狡酸根（丁二酸根或反丁烯二酸根）组成．未配位的二梭酸根和结晶水分子通过氢键作用形成带状阴离子链，阴、阳离子链间存在广泛的氢键作用．属于单斜晶系的配合物［Cu（H2O）4（bpy）］（C4H2O4）4H2O 10和｛Ni（H2O）4（bpy）〕（C4H2O4）4HZO 11，具有和配合物7－－9类似的阳离子链二〔M（H2O）4（bpy）2／2］2＋，然而结晶水分子和反丁烯二酸根在氢键作用下形成二维负电荷层．配合物Cu（imid）2（H2O）L（L＝丁二酸根12，反丁烯二酸根13）为异质同晶型化合物，双端单齿的二梭酸根桥联［Cu（工mid）；（H2O）〕2+形成的一维多聚链通过氢键作用组装成三维结构．而配合物Cu（imid）2（C6H8O4）14中五配位的cu原子通过己二酸根的桥联作用形成的一维多聚链止｛［Cu（C3C3H4］2（ C6H8O4）3／3｝．配合物Cu（imid）2（C6H9O4）2巧中双端单齿的己二酸氢根桥联Cu原子形成的带状多聚链止［Cu（C3N2H4）2(C6H9O4)4/2〕，通过氢键作用组装成两度穿插的三维框架结构．配合物12的热分析表明在25一6000c区间内先脱水形成“Cu（imid）2（C4H4O4）”中间体，继而失去咪哩，残留物为CuO．配合物13和14有相似的TG曲线，加热时失去咪哇和“已二酸醉”．配合物14和15的磁性在5300K温度范围内遵循curie－w七155定律，关系式分别为m-＝0.371／（T-4.6）和Xm-l:0.4095／（T-1.2）．在配合物N处Cu（mal）2·ZHZO 16、KZCu（mal）2·3HZO 17、RbZCu（mal）2H2O 18和C82Cu（mal）2' 4H2O19中，丙二酸根桥联铜原子分别形成二维负电荷层（16，17）、一维阴离子链和一络阴离子．在16-19在合成过程中得到的副产物为配合物［Cu（imid）4Cl］Cl 21，它由CI一和［Cu（imid为CI］＋络阳离子组成，通过氢键和芳环堆积构筑整个晶体结构，热分析表明。配合物1企19在25一500℃的温度区间内可能具有以下的热分解过程：（I）脱水，（2）脱去丙二酸醉和甲烷，（3）草酸盐分解生成碳酸盐和CO气体．酉己合物16一19的磁性在5一300K测试温度范围内遵循Curie-Wesiss定律Xm-l＝C／（T-θ） 其中的韦斯常数夕分别为4．3（5）、4．2（6）、3 ．0（6）和4．3（9）K，相应的居里常数C分别为0.434（1）、0.417（2）、0.423（2）和0.411（3）cm3·K.mol-1．

In situ FTIR spectroelectrochemistry of a microarray electrode

A thin-layer microdisk array electrode (TLMDAE) was designed for in situ reflectance FTIR spectroelectrochemical studies. A theoretical estimation, cyclic voltammetry, chronoamperometry and in situ IR measurements demonstrate that this novel design of array electrode results in advantages such as reduced ohmic potential drop, small cell constant and facility for diffusional exchange between thin layer and bulk solution. It has been suggested that the enhanced edge diffusion on the TLMDAE leads to a reduced accumulation of species in the thin layer. (C) 1997 Elsevier Science S.A.