磷酸氢钙中钙含量测定方法的改进

主要研究了应用高锰酸钾滴定法测定磷酸氢钙中钙含量的方法,该方法准确度高,重现性好。     

Reduced nicotinamide-adenine dinucleotide phosphate oxidase: activity enhanced by ethanol consumption

Prolonged consumption of ethanol enhances the activities of the hepatic microsomal ethanol oxidizing system and of reduced nicotinamide-adenine dinucleotide phosphate oxidase, but not of catalase. The oxidase-catalase system is not part of the microsomal ethanol oxidizing system since catalase inhibitors dissociate ethanol oxidation by the two pathways. Enhanced reduced nicotinamide-adenine dinucleotide phosphate oxidase activity may contribute to liver injury, possibly by favoring lipoperoxidation.     

产多糖溶磷细菌对难溶性Ca-P的活化特性

以肠杆菌EnHy-401、节杆菌ArHy-505、固氮菌AzHy-510和巨大芽孢杆菌P17为材料,比较了4种溶磷细菌在摇瓶培养条件下对不同难溶性Ca-P中的磷活化能力.结果表明,4种溶磷细菌均能促使难溶性Ca-P中的磷活化, 但3种产多糖的溶磷细菌(EnHy-401、ArHy-505、AzHy-510)对难溶性Ca-P的活化能力普遍强于不产多糖的溶磷细菌(P17),肠杆菌EnHy-401对Ca3-P、Ca8-P和Ca10-P中的磷活化率分别达61.53%、63.40%和4.32%.在产多糖的溶磷细菌中,有机酸和多糖均高的菌株活化磷的能力最高,3种产多糖的溶磷细菌活化难溶磷酸钙能力的大小顺序依次为肠杆菌EnHy-401、节杆菌ArHy-505、固氮菌AzHy-510.结果还表明,产多糖的溶磷细菌对难溶磷的活化作用是由分泌有机酸和多糖的协同作用实现的,多糖对磷的吸持推动了磷的溶解平衡向溶解方向移动,且该协同作用受胞外多糖持磷能力和环境中C/N的影响,单位体积发酵液中多糖持磷量与菌株的磷活化能力呈正相关.在本试验条件下,C/N值高时,多糖产量高,有机酸分泌多,活化磷的能力就强.同一菌株只有在最适于产有机酸和产多糖的C/N值下,才能表现出最佳的溶磷效果.     

Crystal tectonics: construction of reticulated calcium phosphate frameworks in bicontinuous reverse microemulsions

The chemical construction of organized architectures is an important aspect of innovative materials synthesis. Bicontinuous water-filled microemulsions can be used as preorganized systems for the fabrication of crystalline calcium phosphate materials with extended reticulated microstructures. These macroporous materials are formed by mineralization reactions located within the interconnecting water channels of the bicontinuous network. The resulting materials represent replicas of the microemulsion architecture, but the pore sizes are incommensurate, suggesting that secondary modifications in the bicontinuous microstructure occur during crystal growth. Synthetic macroporous calcium phosphates could have uses in biomaterial implants.     

Transformation of amorphous calcium phosphate to crystalline dahillite in the radular teeth of chitons

A comparison of infrared spectra from individual teeth along the radula of a chiton (Polyplacophora, Mollusca) shows that the first-formed calcium phosphate mineral is amorphous. Over a period of weeks the mineral transforms to dahllite. The c axes of the dahllite crystals are aligned approximately perpendicular to the tooth surface.     

p-nitrophenyl phosphate hydrolysis and calcium ion transport in fragmented sarcoplasmic reticulum

The calcium ion pump of fragmented sarcoplasmic reticulum can be coupled to hydrolysis of p-nitrophenyl phosphate, in the absence of added adenosine triphosphate. Comparison of the activities obtained with the two substrates suggests an analogous mechanism of transport. Independent of the substrate, a 2 : 1 ratio between calcium ion transport and substrate hydrolysis is displayed by the system, and an identical amount of work is required for ion transport against a given gradient. A phosphate ester appears necessary for substrate utilization in the pump mechanism, whereas the structure of the substrate determines the rates of activity and the affinity of the system for calcium ion.     

Diphosphonates inhibit formation of calcium phosphate crystals in vitro and pathological calcification in vivo

Two diphosphonates containing the P-C-P bond, CH(3)C(OH)(PO(3)HNa)(2) and H(2)C(PO(3)HNa)(2), inhibit the crystallization of calcium phosphate in vitro and prevent aortic calcification of rats given large amounts of vitamin D(3). The diphosphonates therefore have effects similar to those described for compounds containing the P-O-P bond but are active when administered orally.     

磷酸盐和氯化钙对牛肉凝胶特性的影响

主要研究磷酸盐和氯化钙对牛肉凝胶特性及颜色的影响。结果表明,磷酸盐的使用量对凝胶硬度影响差异不显著,会显著提高凝胶弹性和粘聚性,并使亮度L值和红色度a值逐渐降低,说明磷酸盐对牛肉颜色有不良影响,会使牛肉亮度值和红色度值降低。不同部位牛肉之间的凝胶硬度、弹性和粘聚性差异显著,注射0.3mol·L-1CaCl2对凝胶特性影响不显著,能显著提高各部位的L值,但对a值影响差异不显著。     

常规阳离子存在时Mg-Al-CO3 LDH对土壤中Cd吸附迁移的影响

层状双氢氧化物(Layered double hydroxide, LDH)是土壤中常见的矿物组分,而Na~+、K~+、Ca~(2+)和Mg~(2+)更是土壤溶液中的主要阳离子,它们共存条件下对重金属污染物在土壤中的行为过程影响如何是一个需要探讨的科学问题。通过批量静态吸附实验、动力学实验和室内土柱迁移实验,研究不同阳离子与Mg-Al-CO_3 LDH共存时对重金属Cd在土壤中吸附迁移的影响。运用伪二级动力学模型、Elovich模型及内扩散模型对吸附动力学数据进行拟合,并对Mg-Al-CO_3 LDH吸附Cd前后的样品进行红外光谱分析及X射线衍射分析,以探究其吸附机理。结果表明:Mg-Al-CO_3 LDH的存在使土壤pH升高,且Mg-Al-CO_3 LDH含有大量CO_3~(2-),使得土壤对Cd的吸附能力增强;阳离子类型不同时,无论土壤中是否含有LDH,其对Cd的吸附量均表现为阳离子价态越高,吸附量越小。伪二级动力学模型拟合效果非常好,R~2均接近于1,说明土壤对Cd的吸附能力与吸附位点有关;内扩散模型拟合结果揭示土壤对Cd~(2+)吸附的速率受液膜扩散、颗粒间扩散、化学反应等综合作用的控制。不同阳离子类型对Cd在土壤中吸附迁移的影响不同,Cd迁移能力表现为随背景阳离子价态升高迁移能力增强;Mg-Al-CO_3 LDH的存在抑制了Cd的迁移。红外光谱及X射线衍射分析表明,Mg-Al-CO_3 LDH对Cd~(2+)的吸附机理主要为Cd~(2+)与Mg-Al-CO_3 LDH上的CO_3~(2-)反应生成CdCO_3沉淀。Mg-Al-CO_3 LDH对不同阳离子的吸附机制不同,影响着重金属Cd在土壤中的吸附迁移过程。     

生物质炭、有机肥和钙镁磷肥对三七(Panax Notoginseng) Cd含量的影响

选择生物质炭、钙镁磷肥、有机肥三种改良剂,在云南三七主产区进行田间试验,比较不同改良剂对降低五加科人参属三七(Panax Notoginseng)Cd含量的效果。结果表明,生物质炭和钙镁磷肥处理均显著降低了三七主根、剪口、茎、叶的Cd含量,降低幅度分别为25.4%~43.6%、40.2%~40.9%、34.3%~51.2%和33.0%~33.5%,且生物质炭、钙镁磷肥处理下三七主根干重较对照分别显著提高48.7%和50.4%;生物质炭和钙镁磷肥处理土壤有效Cd含量分别减少56.1%和58.1%,表明生物质炭和钙镁磷肥能有效降低土壤Cd生物有效性、抑制三七Cd吸收。这与生物质炭和钙镁磷肥处理通过降低土壤酸性、提高土壤CEC及有机质含量有关。有机肥处理三七植株生物量和三七各部位Cd含量与对照相比均无显著差异。此外,生物质炭和钙镁磷肥处理显著降低了三七主根、剪口、茎、叶Cd的富集系数(Accumulation coefficient,AF),对三七Cd转移系数(Transfer coefficient,TF)影响则不显著,而有机肥处理对三七Cd的AF与TF均无影响;各处理三七须根Cd的AF在2.84~4.64之间,显著高于其他部位,而三七主根、剪口、茎、叶等部位Cd的AF和TF均小于1,表明三七须根对土壤Cd富集能力较强而转移能力较差,Cd易集中于三七地下部,Cd污染土壤中施用生物质炭与钙镁磷肥能有效降低Cd在三七体内的富集。     

施肥和刈割间隔对杂交狼尾草钙磷镁含量的影响

施肥显著影响杂交狼尾草植株磷和镁含量,对钙含量无显著影响,植株镁含量随施肥水平的提高而升高,植株磷含量随施肥水平的提高而降低。刈割间隔对植株钙、磷和镁含量具有显著影响,植株钙、磷和镁含量随刈割间隔的变化年度间表现不一。基肥施用氮磷钾复合肥,可促进植株对钙、镁的吸收,显著提高植株磷含量。     

海泡石及钙镁磷肥对烟草主要农艺性状及吸收镉的影响

采用田间小区试验,研究海泡石和钙镁磷肥在400、800 g/m2处理水平下对烟田土壤有效态Cd含量、土壤pH值、烟草Cd含量及主要农艺性状的影响。结果表明,在本试验条件下,海泡石和钙镁磷肥均能有效降低烟田土壤中有效态Cd含量,减少土壤Cd向烟草各组织的迁移转运,2种材料的效果差异不显著;施用海泡石和钙镁磷肥均能小幅度提高土壤pH值,但不能过量施用;400 g/m2钙镁磷肥处理能提高烟叶鲜重,800 g/m2钙镁磷肥和海泡石处理对烟叶鲜重、株高、有效叶数均无显著影响。     

生石灰和钙镁磷肥对晚稻生长及稻米镉含量的影响

为研究不同培肥措施对镉污染稻田的修复效果,采用小区试验的方法,研究了生石灰和钙镁磷肥及与化肥、有机肥配施对土壤镉有效性、水稻生长和稻米镉含量的影响。结果表明:施用生石灰、钙镁磷肥可以显著提高土壤pH值,其增幅为10.5%～16.1%,其中耦合石灰、钙镁磷肥和化肥(NPKML)处理增幅最大,达到16.1%,施用生石灰次之、钙镁磷肥增幅最小。有机肥与生石灰、有机肥与化肥和生石灰配施可使土壤有效镉含量降低7.9%～23.5%、使糙米的镉含量降低35.1%～47.5%,其中NPKML对两者的降低效果最佳。施用生石灰、钙镁磷肥等对水稻生长和稻谷品质没有显著影响。研究表明,有机肥、化肥、钙镁磷肥和石灰合理配施,对镉污染稻田修复具有较好的效果。     

Decision-making in the presence of risk

Proposed in the 18th century by Cramer and Bernoulli and formally axiomatized in the 20th century by von Neumann and Morgenstern and others, the expected utility model has long been the dominant framework for the analysis of decision-making under risk. A growing body of experimental evidence, however, indicates that individuals systematically violate the key behavioral assumption of this model, the so-called independence axiom. This has led to the development and analysis of nonexpected utility models of decision-making. Although recent work in this area has shown that the analytical results of expected utility theory are more robust than previously supposed, other important issues remain unresolved.     

Diphenylhydantoin: effects on calcium metabolism in the chick

Rickets, hypocalcemia, decreased duodenal calcium transport, and reduction of calcium binding protein have been produced in chicks treated with diphenylhydantoin. These effects are directly related to diphenylhydantoin dose and inversely related to the intake of vitamin D(3) (cholecalciferol).