新农村建设中面源污染控制的社会经济问题研究

在分析研究我国典型的"二元"社会结构特征、城乡人口结构性矛盾、悬殊的城乡经济发展水平等的基础上,深入研究了农村面源污染产生的更深层次的社会经济学原因,指出需要建立城市补偿农村的新机制来帮助解决农村面源污染问题,这种补偿新机制是全方位的,包括资金、技术和人员等。在此基础上,提出了"环境反哺"的理念,并指出"环境反哺"是城市对农村的一种责任和义务。     

农村土地产权非私有化改革

文章从产权的不同属性来论证中国“新土改”的农村土地产权公有(共有)性不变。通过对“新土改”政策下农村土地产权治理与制定农村土地产权制度一般原则探索,论证“新土改”政策是科学发展观一部分,是新时期具体的马克思主义中国化。     

Theoretical organometallic chemistry

Organometallic chemists have synthesized a remarkable variety of new structural types. In these structures ligands, which are organic or inorganic molecules of variable independent stability, bind to one or more transition metal atoms. An approach to an understanding of the electronic structure, geometrical preferences, and reactivity of these complexes may be made if the molecule is "decomposed" conceptually into a metal fragment, ML(n), and a ligand. A library of the molecular orbitals of these fragments is becoming available. One then "reconstructs" the molecule by examining the interaction of the orbitals of the ligand, typically an organic molecule, with the orbitals of the ML(n), fragment.     

Molecular heterogeneity of human lymphoid (HL-A) alloantigens

Soluble preparations of HL-A alloantigens were separated by gel filtration into components having either the "LA" series or the "4" series of alloantigenic determinants. This separation may indicate that several different structural cistrons within the HL-A (locus) control the expression of these two series of determinants. The alternative possibility, in which one structural cistron with multiple mutational sites controls the synthesis of a single molecule cannot be excluded.     

Reconstitution of diphtheria toxin from two nontoxic cross-reacting mutant proteins

The isolation of a new type of mutant Corynephage beta, which carries a missense mutation in the structural gene for diphtheria toxin synthesis is described. The lysogenic C7(8)(beta(197))(tox-crm+) strain of Corynebacterium diphtheriae produces a nontoxic, extracellular protein of molecular weight 62,000. This protein is immunologically indistinguishable from toxin itself but inhibits the action of toxin on HeLa cells, probably by competing for attachment sites on the cell membrane. In contrast to fragment A derived from diphtheria toxin, fragment A(197) is unable to catalyze the inactivation of eucaryotic polypeptidyl-transfer RNA-transferase II. When mixtures of the two nontoxic mutant proteins, enzymically active crm(45) protein and enzymically inactive crm(197) protein, are subjected to mild treatment with trypsin in the presence of a thiol and then allowed to reoxidize after dialysis to remove excess thiol, "diphtheria toxin" is reconstituted in high yield.     

Nonequilibrium phase transitions in cuprates observed by ultrafast electron crystallography

Nonequilibrium phase transitions, which are defined by the formation of macroscopic transient domains, are optically dark and cannot be observed through conventional temperature- or pressure-change studies. We have directly determined the structural dynamics of such a nonequilibrium phase transition in a cuprate superconductor. Ultrafast electron crystallography with the use of a tilted optical geometry technique afforded the necessary atomic-scale spatial and temporal resolutions. The observed transient behavior displays a notable "structural isosbestic" point and a threshold effect for the dependence of c-axis expansion (Deltac) on fluence (F), with Deltac/F = 0.02 angstrom/(millijoule per square centimeter). This threshold for photon doping occurs at approximately 0.12 photons per copper site, which is unexpectedly close to the density (per site) of chemically doped carriers needed to induce superconductivity.     

“一带一路”背景下我国农业对外开放的文献研究

我国高质量地进行农业对外开放,是新时代的需要。以“一带一路”倡议为实践契机, 不断完善保障机制、加强农业供给侧结构性改革、资源优化配置,开启“一带一路”沿线农业对外 开放新格局。     

建筑形象创作中结构形态的表现模式初探

结构形态设计突破了只把结构作为技术手段的传统观念。结合典型案例,从多元化的结构形态表现中,总结了结构形态在建筑形象创作中的表现模式,分析了结构技术对建筑形象的塑造产生的影响。对结构形态的具体表现特征进行了进一步的探讨,提出以结构形态为出发点构筑建筑形象的新思路。     

无核雪柑与普通雪柑种胚发育过程蛋白质的差异

采用考马斯亮蓝G 250法测定胚胎蛋白质含量,并用双向电泳技术分析胚胎的特异蛋白质。结果表明:无核雪柑种胚早期的蛋白质含量相对较高,其胚胎不同发育阶段出现了P1~P6 6个特异蛋白质;另外发现了4个特异于普通雪柑胚胎发育的蛋白质P11~P14。认为P11~P14与无核雪柑的无核密切相关,分别是P11(67.0 kD,pI 5.1)、P12(65.5 kD,pI 5.4)、P13(97.0 kD,pI 5.8)及P14(64.3 kD,pI 5.9)。     

Space, stars, c60, and soot

Although carbon has been subjected to far more study than all other elements put together, the buckminsterfullerene hollow-cage structure, recently proposed to account for the exceptional stability of the C(60) cluster, has shed a totally new and revealing light on several important aspects of carbon's chemical and physical properties that were quite unsuspected and others that were not previously well understood. Most significant is the discovery that C(60) appears to form spontaneously, and this has particularly important implications for particle formation in combustion and in space as well as for the chemistry of polyaromatic compounds. The intriguing revelation that 12 pentagonal "defects" convert a planar hexagonal array of any size into a quasi-icosahedral cage explains why some intrinsically planar materials form quasi-crystalline particles, as appears to occur in the case of soot. Although the novel structural proposal has still to be unequivocally confirmed, this article pays particular attention to the way in which it provides convincing explanations of puzzling observations in several fields, so lending credence to the structure proposed for C(60).     

Watching a protein as it functions with 150-ps time-resolved x-ray crystallography

We report picosecond time-resolved x-ray diffraction from the myoglobin (Mb) mutant in which Leu29 is replaced by Phe (L29Fmutant). The frame-by-frame structural evolution, resolved to 1.8 angstroms, allows one to literally "watch" the protein as it executes its function. Time-resolved mid-infrared spectroscopy of flash-photolyzed L29F MbCO revealed a short-lived CO intermediate whose 140-ps lifetime is shorter than that found in wild-type protein by a factor of 1000. The electron density maps of the protein unveil transient conformational changes far more dramatic than the structural differences between the carboxy and deoxy states and depict the correlated side-chain motion responsible for rapidly sweeping CO away from its primary docking site.     

基于SSR的光敏型饲草高粱分子辅助育种体系

【目的】利用分子标记技术对光敏型饲草高粱新品种传统选育方法进行改良,构建分子辅助育种体系,从而提高品种选育效率,降低育种成本,为形成新的育种体系奠定理论基础。【方法】以光敏型(不抽穗)饲草高粱品种晋光1R去雄后为母本、非光敏型(抽穗)饲草高粱BMRC-3-2为父本进行杂交,构建F2群体。按照光敏与非光敏性状将群体分为两类,各选30株,取叶片提取DNA,利用微卫星分子标记技术(SSR)和集团分离分析法(BSA)对晋光1R/BMRC-3-2的F2群体进行光敏感基因定位分析,以及特异性SSR引物的设计、筛选;将筛出的特异性引物对F1杂交种(以晋光1R为亲本选育的高代稳定恢复系作为父本与其他不育系测配得到的F1代杂交种)进行光敏性鉴定,通过与田间表型对照,确定最终目标引物,从而构建新的光敏型饲草高粱新品种选育体系。【结果】经过SNP index分析,选取99%阈值线最高点前后约250 kb的区域作为性状相关的候选区域,区域总长度为500 kb,共400个SNP位点,对这些SNP位点注释,其中非同义突变或者stop-gain或者stop-loss的SNP位点有6个,最终确定2个候选基因与高粱光敏...     

Covalent polymers of water

A new covalent structural scheme for water polymers is proposed. The observed properties of "polywater" are related to the structures of the suggested homologous series of molecules. Mechanisms of formation are suggested.     

Evolution of a protein fold in vitro

A "switch" mutant of the Arc repressor homodimer was constructed by interchanging the sequence positions of a hydrophobic core residue, leucine 12, and an adjacent surface polar residue, asparagine 11, in each strand of an intersubunit beta sheet. The mutant protein adopts a fold in which each beta strand is replaced by a right-handed helix and side chains in this region undergo significant repacking. The observed structural changes allow the protein to maintain solvent exposure of polar side chains and optimal burial of hydrophobic side chains. These results suggest that new protein folds can evolve from existing folds without drastic or large-scale mutagenesis.     

Single-cell gene expression profiling

A key goal of biology is to relate the expression of specific genes to a particular cellular phenotype. However, current assays for gene expression destroy the structural context. By combining advances in computational fluorescence microscopy with multiplex probe design, we devised technology in which the expression of many genes can be visualized simultaneously inside single cells with high spatial and temporal resolution. Analysis of 11 genes in serum-stimulated cultured cells revealed unique patterns of gene expression within individual cells. Using the nucleus as the substrate for parallel gene analysis, we provide a platform for the fusion of genomics and cell biology: "cellular genomics."     

Memory Glass: An Amorphous Material Formed from AlPO4

A glass exhibiting structural memory has been produced through the compression of a single crystal of AlPO(4) berlinite to 18 gigapascals at 300 kelvin. The unique and extraordinary characteristic of this glass is that upon decompression below 5 gigapascals it transforms back into a single crystal with the same orientation as the starting crystal. This glass has a "memory" of the previous crystallographic orientation of the crystal from which it forms.     

Conserved residues make similar contacts in two repressor-operator complexes

Comparison of a lambda repressor-operator complex and a 434 repressor-operator complex reveals that three conserved residues in the helix-turn-helix (HTH) region make similar contacts in each of the crystallographically determined structures. These conserved residues and their interactions with phosphodiester oxygens help establish a frame of reference within which other HTH residues make contacts that are critical for site-specific recognition. Such "positioning contacts" may be important conserved features within families of HTH proteins. In contrast, the structural comparisons appear to rule out any simple "recognition code" at the level of detailed side chain-base pair interactions.     

小麦幼胚体细胞无性系及其继代过程的微观结构观察

利用扫描电子显微镜,观察了由小麦“千斤早”和“小偃22”幼胚离体培养产生的体细胞胚性无性系继代过程中微观结构的变化,以及胚性无性系和非胚性无性系的结构差异。结果发现,小麦“千斤早”和“小偃22”的幼胚体细胞胚性无性系的微观结构存在较大差异,主要表现在体细胞之间的组织形式上,胚性无性系发生能力强的小麦具有较好的细胞组织形式,胚性无性系发生能力弱的小麦其体细胞组织形式也较差。随着继代次数的增加,体细胞胚性无性系在组织结构上趋于无序化,且这种无序化的进程也受到小麦基因型的影响:对于耐离体培养小麦,在经历多次继代后,组织的有序化程度仍然保持着较高的水平;对于胚性无性系产生频率低的小麦,不仅其早期培养过程中胚性细胞所占的比例较低,且组织间的有序性很快在有限的继代过程中趋于崩溃。     

“三·三教练法”模式下大学新生“破冰训练”的探索与实践

在大学生新生的入学教育中,以素质拓展培训为载体,开展体验式的思想教育工作是一种新的尝试和探索。以江西农业大学为例,初步分析了拓展培训的特点及意义,以及开展新生"破冰训练"的目标及思路。自创了"三.三教练法",即素质拓展培训师对大学生助理教练、大学新生兼职辅导员进行分层培训,培训大学新生"破冰训练"的教练队伍。就项目选择、项目实施进行了探索和实践,强化了"以生为本"的教育理念,培养了"自我服务"的师资队伍,探索了"有效沟通"的工作方式。