~3H—藻酸双酯钠的药物动力学研究     

刘忠敏  姜国华  仪明光  车璟 《中国海洋大学学报(自然科学版)》1992,(Z1)

研究了不同剂量~3H-藻酸双酯钠(PSS)在小鼠及大鼠体内的吸收,分布、排泄及药物代谢动力学参数。无论口服或静注小鼠组织分布较广,12h以肝、肾最高,脑、脂肪、骨骼较低,大脑、小脑、脑干放射性分布未见明显差异。静注72h自小鼠尿排泄60％,粪排泄20％。大鼠口服24h由胆汁排泄15.3％。小鼠及人血血浆蛋白结合率24h为98％。PSS0.8％CMC混悬液口服的绝对生物利用度为75.6％,具有吸收好,分布广,排泄快等特点。  相似文献   

Changes in sediment processes across the western Irish Sea front     

M. Trimmer  R. J. Gowen  B. M. Stewart 《Estuarine, Coastal and Shelf Science》2003,56(5-6):1011-1019

Sediment characteristics, sediment respiration (oxygen uptake and sulphate reduction) and sediment–water nutrient exchange, in conjunction with water column structure and phytoplankton biomass were measured at five stations across the western Irish Sea front in August 2000. The transition from thermally stratified (surface to bottom temperature difference of 2.3 °C) to isothermal water (14.3 °C) occurred over a distance of 13 km. The influence of the front on phytoplankton biomass was limited to a small region of elevated near surface chlorophyll (2.23 mg m⁻³; 50% > biomass in mixed waters). The front clearly marked the boundary between depositional sediments (silt/clays) with elevated sediment pigment levels (≈60 mg m⁻²) on the western side, to pigment impoverished (<5 mg m⁻²) sand, through to coarse sand and shell fragments on the eastern side. Maximal rates of sedimentary respiration on the western stratified side of the front e.g. oxygen uptake S2 (852 μmol O₂ m⁻² h⁻¹) and sulphate reduction at S1 (149 μmol SO₄²⁻ m⁻² h⁻¹), coupled to significant efflux of nitrate and silicate at the western stations indicate closer benthic–pelagic coupling in the western Irish Sea. Whether this simply reflects the input of phytodetritus from the overlying water column or entrapment and settlement of pelagic production from other regions of the Irish Sea cannot yet be resolved.  相似文献   

锌绿钾铁矾——一种硫酸盐新矿物     

李万茂  陈国英  孙淑荣 《矿物学报》1987,(4)

锌绿钾铁矾是一种含K、Zn、Fe和Al的硫酸盐新矿物。共生矿物为粒铁矾、水绿矾、石英和黄铁矿等。矿物呈分散的晶粒或粒状集合体产出,晶体一般1—2mm。单晶体常见,主要单形有o{111},c{100},d{110},n{211}。颜色绿黑到油绿色,灰绿色条痕。沥青到玻璃光泽,透明到微透明。硬度3.0,性脆,无解理,断口贝壳状。实测比重2.759g/cm~3,计算比重2.767g/cm~3。光性均质,N=1.605(3)。等轴晶系,空间群Fd3c,a=27.180,Z=16。粉末衍射图最强线为:5.54(48),4.26(28),3.53(67),3.39(100),3.13(39),3.03(28),2.84(32)。化学式为K_2Zn_5Fe_3~(3+)Al(SO_4)_(12)·18H_2O。差热分析显示,在249和702℃处有两个强吸收峰,在278和826℃处有两个弱吸收峰。红外吸收光谱曲线在3402—3065和1138—1004cm~(-1)处有两个主要吸收带,在1686—1637,625—590和442cm~(-1)处有三个次要吸收带。  相似文献   

Laboratory simulation of rock weathering by salt crystallization and hydration processes in hot,arid environments     

C. H. B. Sperling  R. U. Cooke 《地球表面变化过程与地形》1985,10(6):541-555

The results of a series of experiments are reported in this paper which were designed to differentiate between the forces of crystal growth and hydration in salt weathering, using a single salt-hydrate system (sodium sulphate), five contrasting rock types, and several diurnal temperature-relative humidity cycles which permitted or inhibited these processes and simulated ground surface climates in hot, arid environments. It was shown that hydration of sodium sulphate is an effective mechanism of rock disintegration but that it is significantly less destructive than crystal growth pressure. Crystallization of thenardite (Na₂SO₄) is, in turn, more effective in rock weathering than the crystal growth of mirabilite (Na₂SO₄.10H₂O). In general, rates of disintegration were most rapid where the diurnal temperature range was extreme and relative humidity lowest.  相似文献   

Laboratory simulation of salt weathering processes in arid environments     

R. U. Cooke 《地球表面变化过程与地形》1979,4(4):347-359

The equipment and techniques being used at Bedford College, London to simulate salt weathering processes in deserts are described in the context of a general discussion of the nature of salt weathering processes and approaches to studying them. An experiment based on the equipment and techniques is described: it is designed to test the durability of three building stones in the presence of several different saline solutions under conditions of surface temperature and relative humidity that are considered typical of hot deserts. The experiment, the first of a series, shows that Na₂SO₄ is the most effective of the salts used, and that susceptibility of the rocks to weathering is related to such rock properties as porosity, microporosity and water absorption capacity.  相似文献   

A quantitative evaluation of pyrite weathering     

Alwyn Vear  Charles Curtis 《地球表面变化过程与地形》1981,6(2):191-198

Namurian sediments at Mam Tor, Derbyshire are cut by a major landslide and a geological fault. Both channel oxygenated waters into fragmented pyritic shales. Pyrite is rapidly oxidized to sulphuric acid, 1.5 g being destroyed by each litre of water passing through the fault-crush. More than 99 per cent of the acid, however, is immediately consumed in clay-mineral transformation and carbonate dissolution reactions. The typical acid-sulphate ‘ochre’ springs thus retain less than 1 per cent of the acid generated in the crush zone. These very rapid and large scale chemical transformations probably contribute to the slide's continuing activity.  相似文献   

化学成分和键价对矿物晶体结构形式的影响     

史红云 《地质科技情报》1992,11(4):41-45,50

本文从晶体化学观点出发,以硫酸盐矿物为例,探讨了影响矿物晶体结构形式的因素——化学成分因素(z/x比值)和原子键价(S)因素。它们直接制约着矿物的晶体结构形式。利用矿物的化学组成,原子的键价数据以及键价规则既可解释已有的结构,同时在某种程度上也可预测未知的矿物结构。  相似文献   

Inhibition of dissolution within shallow water carbonate sediments: impacts of terrigenous sediment input on syn-depositional carbonate diagenesis   总被引：2，自引：0，他引：2  

CHRISTOPHER T. PERRY  KEVIN G. TAYLOR 《Sedimentology》2006,53(3):495-513

The early diagenetic chemical dissolution of skeletal carbonates has previously been documented as taking place within bioturbated, shallow water, tropical carbonate sediments. The diagenetic reactions operating within carbonate sediments that fall under the influence of iron‐rich (terrigenous) sediment input are less clearly understood. Such inputs should modify carbonate diagenetic reactions both by minimizing bacterial sulphate reduction in favour of bacterial iron reduction, and by the reaction of any pore‐water sulphide with iron oxides, thereby minimizing sulphide oxidation and associated acidity. To test this hypothesis sediment cores were taken from sites within Discovery Bay (north Jamaica), which exhibit varying levels of Fe‐rich bauxite sediment contamination. At non‐impacted sites sediments are dominated by CaCO₃ (up to 99% by weight). Pore waters from the upper few centimetres of cores show evidence for active sulphate reduction (reduced SO₄/Cl^? ratios) and minor CaCO₃ dissolution (increased Ca²⁺/Cl^? ratios). Petrographic observations of carbonate grains (specifically Halimeda and Amphiroa) show clear morphological evidence for dissolution throughout the sediment column. In contrast, at bauxite‐impacted sites, the sediment is composed of up to 15% non‐carbonate and contains up to 6000 μg g^?1 Fe. Pore waters show no evidence for sulphate reduction, but marked levels of Fe(II), suggesting that bacterial Fe(III) reduction is active. Carbonate grains show little evidence for dissolution, often exhibiting pristine surface morphologies. Samples from the deeper sections of these cores, which pre‐date bauxite influence, commonly exhibit morphological evidence for dissolution implying that this was a significant process prior to bauxite input. Previous studies have suggested that dissolution, driven by sulphate reduction and sulphide oxidation, can account for the loss of as much as 50% of primary carbonate production in localized platform environments. The finding that chemical dissolution is minor in a terrigenous‐impacted carbonate environment, therefore, has significant implications for carbonate budgets and cycling, and the preservation of carbonate grains in such sediment systems.  相似文献   

中国芒硝类矿产资源及硫酸钠产业状况   总被引：3，自引：0，他引：3       下载免费PDF全文

宣之强 《盐湖研究》1994,2(3):60-64

中国芒硝类矿产矿类齐全、资源丰富，硫酸钠资源居世界首位．硫酸钠产业起步于五十年代，八十年代得到迅速发展．至今，硫酸钠生产能力已跃居世界前列．改革开放和科技进步将为中国硫酸钠工矿业带来新的机遇．  相似文献   

三元体系MgSO_4─CH_3CONHCONH_2─H_2O及Mg（NO_3）－          下载免费PDF全文

崔斌  张逢星  张军  宗建华  郭志箴 《盐湖研究》1995,(3)

本文研究了三元体系ＭｇＳＯ４—ＣＨ３ＣＯＮＨＣＯＮＨ２—Ｈ２Ｏ（Ⅰ）和Ｍｇ（ＮＯ３）２─ＣＨ３ＣＯＮＨＣＯＮＨ２—Ｈ２Ｏ（Ⅱ）在３０℃的相平衡，测定了饱和溶液溶解度及其折光指数，绘制了相应的溶度图和折光指数─组成关系图。两个体系均为简单共饱型。溶度曲线及折光指数曲线均由两支组成，分别与ＭｇＳＯ４·７Ｈ２Ｏ（Ⅰ）或Ｍｇ（ＮＯ２）２·６Ｈ２Ｏ（Ⅱ）和ＣＨ２ＣＯＮＨＣＯＮＨ２相对应。共饱点的组成分别为（Ⅰ）中ＭｇＳｏ４２７．３５％，ＣＨ３ＣＯＮＨＣＯＮＨ２　４．７％；（Ⅰ）中Ｍｇ（ＮＯ３）２４２．７５％，ＣＨ３ＣＯＮＨＣＯＮＨ２１２．２４％。这项工作对开发缓释肥料具有重要意义。  相似文献