Comment on "Single-crystal X-ray structure of 1,3-dimethylcyclobutadiene by confinement in a crystalline matrix"

Legrand et al. (Reports, 16 July 2010, p. 299) reported the experimental observation of square-planar and rectangular-bent geometries of 1,3-dimethylcyclobutadiene (Me(2)CBD) confined within a crystalline matrix. However, we found no evidence for the Me(2)CBD formation. We argue that the experimental x-ray density data are better attributed to the bicyclic β-lactone intermediate where carbon dioxide is covalently bound to cyclobutadiene.     

Target-selected inactivation of the zebrafish rag1 gene

The zebrafish has become a favorite organism for genetic analysis of vertebrate development, but methods for generating mutants by reverse genetic approaches have been lacking. We report a method to obtain stable mutants of a gene based on knowledge of the gene sequence only. Parental fish were mutagenized with N-ethyl-N-nitrosourea; in 2679 F1 fish, the rag1 gene was analyzed for heterozygous mutations by resequencing. In total, we found 15 mutations: 9 resulted in amino acid substitutions and 1 resulted in a premature stop codon. This truncation mutant was found to be homozygous viable and defective in V(D)J joining. Although presumably immune deficient, these homozygous rag1 mutant fish are able to reach adulthood and are fertile. As sperm samples from all 2679 F1 fish were collected and cryopreserved, we have in principle generated a mutant library from which mutants of most zebrafish genes can be isolated.     

Nuclear magnetic resonance studies and water "ordering" in the crystalline lens

Nuclear magnetic resonance studies of the relaxation times of the water in the crystalline lens show that, as in all interfacial systems, these parameters are markedly reduced from their values in pure water, that T(2) is less than T(1), and that both depend on water content. Determination of diffusion coefficients and studies on physiologically inert lenses indicate that reduced relaxation times do not provide direct evidence for ordering of the bulk of the cell water.     

Gamma-A cold agglutinin: importance of disulfide bonds in activity and structure

Cleavage of disulfide bonds caused by mild reduction with mercaptoethanol produces a reversible loss of cold agglutinin activity and antigen-binding ability in a gamma-A polymer cold agglutinin. Return of agglutination and antigen-binding ability occur only in those molecules that have not been depolyimerized by reduction. Loss of activity becomes irreversible if reduction is followed immediately by alkylation.     

烤烟烟叶淀粉晶体结构的光谱分析

利用固体核磁共振波谱仪(CP/MAS 13C NMR)、粉末X–射线衍射仪(XRD)和扫描电子显微镜(SEC)研究了烤烟烟叶淀粉晶体的结构特性。结果表明:烤烟烟叶淀粉晶体CP/MAS 13C NMR波谱显示在C1区域,在化学位移99.3和100.2处有2个明显的结晶峰,同时,XRD波谱2θ在17o处有较强的衍射峰,在5.6o、15o、20o、22o和24o附近有较弱的衍射峰,均表现出典型的B–型晶体特征。根据CP/MAS 13C NMR波谱计算出的烟叶淀粉晶体的相对结晶度和双螺旋含量分别为36.1%和21.3%,其结晶度比采用XRD波谱计算值略高。     

Changed lyotropic liquid crystalline structure due to polymerization of the amphiphilic component

Optical patterns in polarized light and x-ray reflections in the low-angle region were used to detect a shift from one liquid crystalline structure to another during polymerization. The polymerization took place in a Iotropic liquid crystal of water and sodium undecenoate, with a structure consisting of cylinders in a two-dimensional hexagonal close packing. After polymerization, a lamellar liquid crystalline structure was obtained.     

畜禽钼中毒

畜禽钼中毒是由于畜禽采食了高钼饲料或因工业污染土壤﹑饲料﹑饮水引起的一种畜禽微量元素中毒病。钼是机体必需微量元素,但过量钼往往与铜﹑磷﹑钨﹑锰等矿物元素有颉颃作用,引起矿物元素缺乏,从而发生相应的缺乏症状。钼中毒主要以持续性腹泻﹑消瘦﹑贫血为特征,多发生于反刍动物,以牛最为敏感,羊次之,猪和家禽很少发生。     

The structure and symmetry of crystalline solid solutions: a general revision

Mixed single crystals composed of host and guest organic molecules of similar structures and shapes are shown to comprise sectors with different host-guest distributions and to have symmetries lower than that of the host crystal. These properties are determined by the structure of the guest and the surface structures of the crystal faces through which the guest molecules are occluded. This general concept is illustrated by studies of three mixed crystal systems,(E)-cinnamamide-(E)-2-thienylacrylamide, (E)-cinnamamide-(E)-3-thienylacrylamide, and(S)-asparagine-(S)-aspartic acid, with x-ray and neutron diffraction and solid-state photochemistry.     

土壤钼素营养状况及钼在烟草上的应用研究进展

钼是植物生长必需的微量元素,具有多种生物学功能.土壤有效钼含量反映了土壤钼养分的供应能力,钼与烟草的产量和品质的形成密切相关.总结了土壤钼状况及钼在烟草上应用的研究进展,并提出了相关的研究方向.     

植烟土壤中钼素的研究

本文就钼元素在植烟土壤中的作用以及其营养特性进行综述。分析了我国烟叶钼含量低的原因,进而提出了提高我国烟叶钼含量的若干建议。     

不同钼效率冬小麦品种钼的吸收和分配

 在缺钼酸性黄棕壤上设不施钼（CK，土壤有效钼0.112 mg·kg-1）和施钼两个处理（+Mo，施钼0.13 mg·kg-1），研究钼高效冬小麦品种97003和钼低效冬小麦品种97014钼吸收和分配的差异。结果表明，不施钼时高效品种97003在整个生育期地上部干重和钼累积量均极显著高于97014，表明在相同缺钼逆境下97003吸收钼较多；97003拔节期上部叶、抽穗期穗、成熟期籽粒中分配的钼也多；穗和种子钼含量相对较高，表明97003向繁殖器官输送较多的钼。因而在缺钼逆境下97003对钼的利用效率较高，可获得较高产量。钼的吸收能力和利用能力较高可能是冬小麦品种97003钼高效的重要机理。     

“4.30”闽东暴雨的结构分析

利用2013年4月30日8:00到5月1日8:00的MICAPS资料、NCEP1°×1°再分析资料、福建省区域自动站资料等,分析闽东一场在高空槽、低层切变和地面冷空气共同作用下的冷锋锋前暴雨天气过程。通过物理量结构分析发现,槽前西南急流为此次降水提供了充足的水汽,冷锋过境使得大气条件性不稳定,强的辐散场和锋面南压为此次暴雨提供了强的抬升条件。并浅析此次暴雨对铁观音茶青生产及品质的影响。     

家畜钼中毒研究简史浅述

较系统地阐述了有关家钼中毒的研究。１９３８年最早报道英国流行该病,此后、美国、新西兰、瑞典、加拿大、日本等国相灵报道了有关钼中毒病的流行及研究状况。国内１９８１年报道过赣南流行“钼镉中毒综合症”。陕西省１９８８年开始对南洛河钼矿污染区流行的该病进行研究。先后进行了发病调查,运行内外环境钼含量和毒源成分分析测定以及综合防治,采用天然高钼饮水复制钼中毒试验,并进行中毒超微结构病理学及超氧化物歧化酶（Ｓ     

Cytidylic acid "a" trihydrate: structure and conformation

Cytidylic acid "a" (cytidine 2'-monophosphate) crystallizes in the triclinic space group P1 with two molecules of cytidine monophosphate (C(9)H(14)O(8)N(3)P) and six molecules of water in the unit cell. X-ray analysis of this crystal shows that in both molecules, the base is in the anti conformation, the ribose ring is C(2')-endo puckered, and the hydroxyl O(5') is gauche-gauche. The two molecules are linked by a short hydrogen bond through the phosphate oxygens.     

钼营养对烤烟干物质积累、钼素分配和利用率的影响

研究不同剂量的钼营养对烟株干物质积累的影响、钼素在不同器官中的分配及钼素利用率等。盆栽试验采用4个钼剂量水平和CK(清水)共5个处理,并在黔南烟草主产区的9个地方布置统一方案进行大田试验。分别在不同生育阶段使用KCNS比色方法测定钼含量,并使用SPSS进行数据分析。结果表明:①随生育期的延长,干物质积累量也在增加,且钼含量有不同的变化规律。②不同施钼水平烟株的各器官中的铝分配都以叶中最多,施钼处理的烟叶中钼素含量均高于CK。③随供钼水平的变化,各处理被烟株吸收的钼素有效率有所差异增加,烟株中钼素积累量有所提高。钼素促进了烟株各器官干物质的积累,提高了烟株中的钼素积累量,而且适当剂量的钼营养影响着烟株不同器官中的钼素分配率,一定程度上提高了烟叶中的钼含量及分配比率。