1alpha-Hydroxyvitamin D2: a potent synthetic analog of vitamin D2

A hydroxy analog of vitamin D(2), 1alpha-hydroxyvitamin D(2), has been synthesized and tested for biological activity. This vitamin derivative is active in stimulating intestinal calcium transport and bone calcium mobilization in the rat and exhibits antirachitic activity. Its biopotency is comparable to that of the corresponding vitamin D(3) analog, 1alpha-hydroxyvitamin D(3).     

Intercalated clay catalysts

Recent advances in the intercalation of metal complex cations in smectite clay minerals are leading to the development of new classes of selective heterogeneous catalysts. The selectivity of both metal-catalyzed and proton-catalyzed chemical conversions in clay intercalates can often be regulated by controlling surface chemical equilibria, interlamellar swelling, or reactant pair proximity in the interlayer regions. Also, the intercalation of polynuclear hydroxy metal cations and metal cluster cations in smectites affords new pillared clay catalysts with pore sizes that can be made larger than those of conventional zeolite catalysts.     

Pecoraite, Ni6Si4O10(OH)8, Nickel Analog of Clinochrysotile, Formed in the Wolf Creek Meteorite

Pecoraite is a new phase in the natural system H(2)O-NiO-MgOSiO(2), the nickel analog of clinochrysotile. It occurs in cracks in the Wolf Creek meteorite in Australia where it was formed under hydrothermal conditions. Particles of pecoraite are very small curved plates which have begun to coil; some have achieved spiral form.     

Melting of two-dimensional solids

Recent theoretical predictions indicate that melting of a two-dimensional solid may be caused by spontaneous creation of dislocations. The theory predicts that melting occurs by a two-step process involving an intermediate phase, called the hexatic phase, in which there is order in the local crystalline axes but not in the positions of atoms. These ideas are being tested by numerical simulations and by experiments on electrons on liquid helium, liquid crystal films, and rare gas layers adsorbed on graphite. Experiments on liquid crystal films indicate that the three-dimensional analog of the hexatic phase exists, and xenon on graphite exhibits a melting transition close to the form predicted.     

Soldier determination in ants: new role for juvenile hormone

Topical application of juvenile hormone analog induces soldier development in the ant Pheidole bicarinata. Soldier induction takes place if the juvenile hormone analog is present during a period of sensitivity that occurs during the last larval instar. Control of worker dimorphism seems to be accomplished through control of timing of metamorphosis. The smallest size at which metamorphosis can be initiated is shifted upwardfrom 1.2 to 1.7 millimeters by exposure to the juvenile hormone analog during the sensitive period.     

Enzymatic O-methylation of N-acetylserotonin to melatonin

An enzyme, hydroxyindole-O-methyl transferase, that can transfer the methyl group of S-adenosylmethionine to the hydroxy group of N-acetylserotonin to form the hormone melatonin is described. This enzyme, which is highly localized in the pineal gland, also O-methylates serotonin.     

山东潮土高产农田的供磷特性

潮土表层土壤中全磷以无机磷为主,无机磷中以Ca—P为主,Ca—P中又以Ca10-P为主,有机磷中以MLOP（中度活性有机磷）含量最高;灰色关联分析结果表明,潮土中的Ca2-P、A1-P、Ca8-P和LOP（活性有机磷）的相对有效性较高。潮土吸附和固定的主要基质是物理性粘粒,其次是CaCO3;解吸则主要受物理性粘粒的影响。潮土的3种磷酸化酶以碱性磷酸化酶的活性最高;有机解磷细菌数量大于无机解磷细菌数量,土壤微生物转化有机磷强度大于转化无机磷强度。高产农田的有效磷、缓效磷、Ca2-P含量均极显著高于中低产田,有机质、A1-P、供磷强度均显著高于中低产田;3种磷酸化酶的活性、解磷细菌数量和土壤微生物转化有机磷和无机磷强度,高产田均高于中低产田;高产农田比中低产田对磷的吸附能力强,固磷能力差异不显著,对吸附磷的解吸较易。     

5-Diazo-4-oxo-L-norvaline: reactive asparagine analog with biological specificity

The L-asparagine analog, 5-diazo-4-oxo-L-norvaline, specifically inactivates L-asparaginase and inhibits the growth of L-asparagine-dependent or L-asparaginase-sensitive tumor cells in culture. With 5-(14)C-labeled compound, a biphasic incorporation into sensitive cells occurs, but the inhibition of cell multiplication is manifest much later than the rapid phase of incorporation of the analog.     

两种四苯基卟啉衍生物的表观质子化常数测定

卟啉类试剂质子化常数的测定对于研究其显色性能有着重要的意义。用光度法测得两种四苯基卟啉衍生物的表观质子化常数,探讨了取代基的电子效应与空间位阻效应对表观质子化常数的影响。取代基三氟甲基的间位引入降低了两种四苯基卟啉衍生物的表观质子化常数,与四苯基卟啉相比其显色灵敏度稍微降低,但增强了其空间位阻效应,在显色研究中有望提高其选择性。     

两种四苯基卟啉衍生物的表观质子化常数测定

卟啉类试剂质子化常数的测定对于研究其显色性能有着重要的意义。用光度法测得两种四苯基卟啉衍生物的表观质子化常数,探讨了取代基的电子效应与空间位阻效应对表观质子化常数的影响。取代基三氟甲基的间位引入降低了两种四苯基卟啉衍生物的表观质子化常数,与四苯基卟啉相比其显色灵敏度稍微降低,但增强了其空间位阻效应,在显色研究中有望提高其选择性。     

Drumlin formation: a rheological model

Drumlins are formed in a layer of boulder clay separating a glacier fronm certain types of terrain. Under certain conditions the large particles in the clay form a dilatant system. When flow in the separating layer is interrupted, part of the layer packs into an obstruction and the rest of the material flows around this obstruction, giving it a streamlined form.     

Accretion of mudstone beds from migrating floccule ripples

Mudstones make up the majority of the geological record. However, it is difficult to reconstruct the complex processes of mud deposition in the laboratory, such as the clumping of particles into floccules. Using flume experiments, we have investigated the bedload transport and deposition of clay floccules and find that this occurs at flow velocities that transport and deposit sand. Deposition-prone floccules form over a wide range of experimental conditions, which suggests an underlying universal process. Floccule ripples develop into low-angle foresets and mud beds that appear laminated after postdepositional compaction, but the layers retain signs of floccule ripple bedding that would be detectable in the rock record. Because mudstones were long thought to record low-energy conditions of offshore and deeper water environments, our results call for reevaluation of published interpretations of ancient mudstone successions and derived paleoceanographic conditions.     

土壤中非代换铵的行为——Ⅳ.非代换铵的水平及垂直分布与土壤颗粒组成的关系

在西北24种的基础上,逐次递加杨陵12种、澄城县6个层次的土壤和杨陵另外20种土壤,以构成不同容量的样本。采用相关分析及卡方检验的方法,分别研究了非代换铵含量与颗粒组成、非代换铵的水平分布类型与粘粒分布类型的关系。结果表明,土壤非代换铵含量主要受土壤粘粒含量的影响。土壤粘粒是非代换铵的载体,其含量多少决定着非代换铵的水平;非代换铵的垂直分布与粘粒含量有密切关系,非代换铵的水平分布类型也受粘粒分布类型的制约。     

峄城东郊水源地地下水可采资源量研究

峄城东郊水源地具有典型的双层结构,上层为第四系粘性土,下层为奥陶系马家沟组石灰岩,石灰岩富水性较好,地下水主要接受大气降水的补给,由于受峄城断裂、吴林断裂、泥沟断裂的共同作用以及第四系覆盖层和水动力、补给条件等的制约,石灰岩单位涌水量一般大于100 m3/（d.m）。利用建立的地下水数学模型,采用2个观测井的水位进行拟合,通过模拟计算2个观测孔的水位,均与实测水位拟合较好,按6口开采井抽水量进行模拟计算,峄城东郊水源地地下水可采资源量为2.0×104m3/d,开采区内水位降深最大20 m。     

Micromorphological Features of Old Cultivated and Modern Soils in Guanzhong Areas, Shaanxi Province, China

Using the data obtained from the LGT soil profile, this article attempts to illustrate the process of modem soil formation in the Guanzhong areas and its micromorphological features. The micromorphology is observed under a petrographic microscope, and its image is quantitatively measured by LEICAL Qwin 2.6 software. Micromorphological observations of the thin sections show that the assemblage of minerals in different horizons is very similar, which is mainly composed of Q and P1. However, there are obvious differences in C/F15μm ratio, mineral content, and coarse features. The pedofeatures is mainly composed of clay, calcite, and amorphous Fe. Ap horizon is characterized by abundant needleshaped secondary calcite, secondary clay, and earthworm fecal pellet. BC horizon is characterized by a large quantity of secondary calcite with various shapes. Bt1and Bt2 horizons are characterized by abundant clay hypocoatings and a small quantity of secondary calcite. All the results of this research suggest that Earth-cumulic Orthic Anthrosols consist of both the upper Ap horizon, which cause loessal dung and eolian dust deposition, and cultivation occurs simultaneously during the process of Ap horizon-formation, and the lower BC horizon, which is aeolian sedimentary at the time of relative aridity during late Holocene.     

Disruption of the terrestrial plant ecosystem at the cretaceous-tertiary boundary, Western interior

The palynologically defined Cretaceous-Tertiary boundary in the western interior of North America occurs at the top of an iridium-rich clay layer. The boundary is characterized by the abrupt disappearance of certain pollen species, immediately followed by a pronounced, geologically brief change in the ratio of fern spores to angiosperm pollen. The occurrence of these changes at two widely separated sites implies continentwide disruption of the terrestrial ecosystem, probably caused by a major catastrophic event at the end of the period.     

Magnesium-iron replacement in clay minerals in anoxic marine sediments

In anoxic marine sediments iron is extracted from clay minerals to form a sulfide. Magnesium from the surrounding solution then replaces the extracted iron in the clay mineral structure. This process removes magnesium from seawater and serves as a control on the composition of interstitial waters in sediments.     

几种粘粒矿物和土壤表面吸附态磷的解吸(英文)

几种重要粘粒矿物和我国代表性土壤表面吸附态磷的解吸随pH的变化可以归纳为三种不同的曲线类型.铁铝氧化物和蒙脱石表面磷的解吸在pH4.0到10.0范围内随pH升高而增加,pH6.0到7.5以上增加更快.高岭石和以可变电荷为主的酸性红黄壤的磷解吸—pH曲线呈现“U”型特征,其解吸最低值的pH高岭石为6.5,红黄壤类样品都在4.8左右.中性和石灰性土壤磷解吸在pH酸侧类似碳酸钙的情况,即解吸随pH升高线性下降,但在pH高于6.0～7.5以上时,解吸又趋于稳定,甚至增加.pH对磷吸附和解吸的影响在本质上是一样的,但方向相反.高岭石和红黄壤等具可变电荷表面的样品的磷解吸最小值pH范围恰好都落在各样品吸附磷前后的两个PZC值之间.上述结果表明可变电荷矿物和土壤吸附态磷的解吸在很大程度上受表面电荷特性 制约.pH影响此类样品磷解吸的机理主要是改变了表面电位.至于中性和石灰性土壤,磷的释放在pH酸侧主要受磷酸钙溶解作用支配;而在较高pH条件下,粘粒矿物表面吸附磷的解吸仍然是重要的.     

新建县风景水库北坡山体滑坡机制研究

通过对滑坡体和其发生环境的调查分析,新建县风景水库北坡山体滑坡具以下因素作用和发生机制：片麻岩层理走向与坡面平行是形成滑落面的重要地质基础;坡面冲沟发育、筑坝取土造成的坡角临空面是滑坡的地貌条件;粘粒含量和渗透率随土壤深度递减的剖面特性是水份在滑落面积滞并与粘粒作用导致抗剪强度减低的主要原因;滑坡前和发生时的雷雨条件是造成土体增重和促发牵引动力的重要触发因素。