Signature of superfluid density in the single-particle excitation spectrum of Bi(2)Sr(2)CaCu(2)O(8+delta)

We report that the doping and temperature dependence of photoemission spectra near the Brillouin zone boundary of Bi(2)Sr(2)CaCu(2)O(8+delta)exhibit unexpected sensitivity to the superfluid density. In the superconducting state, the photoemission peak intensity as a function of doping scales with the superfluid density and the condensation energy. As a function of temperature, the peak intensity shows an abrupt behavior near the superconducting phase transition temperature where phase coherence sets in, rather than near the temperature where the gap opens. This anomalous manifestation of collective effects in single-particle spectroscopy raises important questions concerning the mechanism of high-temperature superconductivity.     

藤牧一号苹果引种栽培试验

藤牧一号（Mato）又名＂南部魁＂,是美国PURDUE等3所大学联合育成的早熟苹果品种,20世纪70年代末引入日本,获专利生产繁育权,1986年从日本引入我国山东栽培,1998年获山东省品种审定.目前在山西、河南、辽宁、安徽、湖北、四川、云南等省有引种栽培,商品名＂巨森＂、＂南明星＂、＂南方苹果＂等,普遍反映良好,是公认的早熟优良苹果品种.     

Ferromagnetism stabilized by lattice distortion at the surface of the p-wave superconductor Sr(2)RuO(4)

Ferromagnetic (FM) spin fluctuations are believed to mediate the spin-triplet pairing for the p-wave superconductivity in Sr(2)RuO(4). Our experiments show that, at the surface, a bulk soft-phonon mode freezes into a static lattice distortion associated with an in-plane rotation of the RuO(6) octahedron. First-principle calculations confirm this structure and predict a FM ground state at the surface. This coupling between structure and magnetism in the environment of broken symmetry at the surface allows a reconsideration of the coupling mechanism in the bulk.     

Micropylar pollen tube guidance by egg apparatus 1 of maize

Pollen tube guidance precedes the double fertilization of flowering plants. Here, we report the identification of a small maize protein of 94 amino acids involved in short-range signaling required for pollen tube attraction by the female gametophyte. ZmEA1 is exclusively expressed in the egg apparatus, consisting of the egg cell and two synergids. Chimeric ZmEA1 fused to green fluorescent protein (ZmEA1:GFP) was first visible within the filiform apparatus and later was localized to nucellar cell walls below the micropylar opening of the ovule. Transgenic down-regulation of the ZmEA1 gene led to ovule sterility caused by loss of close-range pollen tube guidance to the micropyle.     

Single-Crystal Epitaxial Thin Films of the Isotropic Metallic Oxides Sr1-xCaxRuO3 (0 le x le 1)

Single-crystal epitaxial thin films of the isotropic metallic oxides Sr1-xCaxRuO(3) (0 相似文献   

Sr lattice clock at 1 x 10(-16) fractional uncertainty by remote optical evaluation with a Ca clock

Optical atomic clocks promise timekeeping at the highest precision and accuracy, owing to their high operating frequencies. Rigorous evaluations of these clocks require direct comparisons between them. We have realized a high-performance remote comparison of optical clocks over kilometer-scale urban distances, a key step for development, dissemination, and application of these optical standards. Through this remote comparison and a proper design of lattice-confined neutral atoms for clock operation, we evaluate the uncertainty of a strontium (Sr) optical lattice clock at the 1 x 10(-16) fractional level, surpassing the current best evaluations of cesium (Cs) primary standards. We also report on the observation of density-dependent effects in the spin-polarized fermionic sample and discuss the current limiting effect of blackbody radiation-induced frequency shifts.     

用荧光定量RT-PCR方法分析B型和ZHJ-1型烟粉虱热休克基因hsp70和hsp90的表达

【目的】比较温度胁迫对两种生物型烟粉虱体内hsps诱导表达的差异。【方法】根据烟粉虱hsp70基因、hsp90基因和18S rRNA序列,设计并合成引物用于实时定量RT-PCR,扩增产物连接到质粒pMD18-T载体上,重组质粒经筛选、签定和10×梯度稀释后作为模板,用于标准曲线的制作和样品检测,检测温度胁迫对B型和ZHJ-1型烟粉虱hsp70和hsp90 mRNA转录水平的诱导情况。【结果】在受到34℃、37℃、40℃和43℃的高温胁迫时,两者hsps的诱导水平无显著差异(P＞0.05);在受到4℃、7℃、10℃和13℃的低温胁迫时,B型烟粉虱体内hsps的诱导表达水平显著超过了ZHJ-1型烟粉虱(P＜0.05)。【结论】经检验所建立的荧光定量RT-PCR体系特异性好,灵敏度高,符合检测烟粉虱hsps mRNA转录水平的要求。低温胁迫下B型烟粉虱体内hsps的高表达可能是其较强的耐受低温能力的主要机制之一。     

RAPD鉴定番茄一代杂种遗传纯度的研究

以番茄优良一代杂交种毛粉８０８、毛粉８１８和强选一号为材料,提取ＤＮＡ进行ＲＡＰＤ分析,在３００个ＲＡＰＤ随机引物中筛选出了可鉴定３个品种一代杂种遗传纯度的特异性引物。其中Ｓ１０１９,Ｓ１３８８和Ｓ１４２２可用于这３个品种的纯度鉴定;Ｓ１０７２用于毛粉８０８和毛粉８１８的纯度鉴定;Ｓ１３８８用于区分３个品种的父本和子代。     

叶用莴苣热激蛋白90（LsHsp90）基因的克隆及其在热激下的表达

【目的】克隆叶用莴苣热激蛋白Hsp90基因并探讨其响应热胁迫的相关机制,为揭示叶用莴苣抗热分子机制奠定理论基础。【方法】采用同源克隆和RACE 技术相结合,从叶用莴苣叶片总RNA 中克隆LsHsp90 cDNA 序列。通过实时荧光定量 PCR (qRT-PCR) 分析LsHsp90在叶用莴苣耐热品种Z36和热敏品种S106受37℃和42℃热激后叶片的表达差异。【结果】该基因cDNA序列全长2 330 bp,开放阅读框2 097 bp,编码698个氨基酸,推导的蛋白质分子量约79.8 kD。蛋白质结构预测及同源比对分析表明,LsHsp90基因编码蛋白含ATPase位点和Hsp90保守结构域,并与拟南芥（AY081302.1）、紫茎泽兰（EU269070.1）等多种物种的热激蛋白90高度同源;进化树分析表明,LsHsp90与紫茎泽兰Hsp90基因（EU269070.1）聚为一类。qRT-PCR分析表明,37℃热胁迫下,该基因在耐热品种和热敏品种的叶片中均上调表达;42℃高温胁迫下,热敏品种S106 中下调表达,而耐热品种Z36上调表达。【结论】成功从叶用莴苣叶片中分离克隆到LsHsp90,该基因具有已知物种Hsp90基因的特征,该基因在热胁迫下有不同的表达特征,预示该基因其可能在抗高温胁迫中起重要作用。     

曲周作物施肥模型与系统(3HCCFS-90-曲周)的研究

本研究采用盆栽试验和田间试验方法对国内常用的2种施肥模型(二次和平方根)和3种试验设计(D饱和设计、3×3设计,5×5设计)进行了比较研究.确定灌溉农田以二次模型最优,旱地以平方根模型最佳.3×3设计简单、实用、准确、易于在农户中推广应用.研究认为对多点分散试验的结果,可采用动态聚类分析的方法,获得类肥料效应方程以指导推荐施肥.研究中建立的3HCCFS-90曲周施肥系统可实现90%的预报吻合度.     

Structural and Electronic Role of Lead in (PbBi)2Sr2CaCu2O8 Superconductors by STM

The structural and electronic effects of lead substitution in the high-temperature superconducting materials Pb(x)Bi(2-x)Sr(2)CaCu(2)O(8) have been characterized by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Large-area STM images of the Bi(Pb)-O layers show that lead substitution distorts and disorders the one-dimensional superlattice found in these materials. Atomic-resolution images indicate that extra oxygen atoms are present in the Bi(Pb)-O layers. STS data show that the electronic structure of the Bi(Pb)-O layers is insensitive to lead substitution within +/-0.5 electron volt of the Fermi level; however, a systematic decrease in the density of states is observed at approximately 1 electron volt above the Fermi level. Because the superconducting transition temperatures are independent of x(Pb) (x 相似文献   

Structural basis for DNA damage-dependent poly(ADP-ribosyl)ation by human PARP-1

Poly(ADP-ribose) polymerase-1 (PARP-1) (ADP, adenosine diphosphate) has a modular domain architecture that couples DNA damage detection to poly(ADP-ribosyl)ation activity through a poorly understood mechanism. Here, we report the crystal structure of a DNA double-strand break in complex with human PARP-1 domains essential for activation (Zn1, Zn3, WGR-CAT). PARP-1 engages DNA as a monomer, and the interaction with DNA damage organizes PARP-1 domains into a collapsed conformation that can explain the strong preference for automodification. The Zn1, Zn3, and WGR domains collectively bind to DNA, forming a network of interdomain contacts that links the DNA damage interface to the catalytic domain (CAT). The DNA damage-induced conformation of PARP-1 results in structural distortions that destabilize the CAT. Our results suggest that an increase in CAT protein dynamics underlies the DNA-dependent activation mechanism of PARP-1.     

(1+1)维呼吸子的可视化

呼吸子是局域在空间的一种特殊的孤立子.用可视化方法研究了它的两种(1+1)维呼吸.     

(1+1)维呼吸子的可视化

呼吸子是局域在空间的一种特殊的孤立子.用可视化方法研究了它的两种（1＋1）维呼吸.     

石蒜属植物种质资源ISSR-PCR反应体系的建立

为进一步开展石蒜属Lycoris植物种质资源遗传多样性研究,利用正交试验设计的方法,从Taq酶、Mg2 、模板DNA、dNTP和引物等5因素4水平,对石蒜属植物ISSR(intersimple sequence repeats)反应体系进行优化,确立了石蒜属植物ISSR的最佳反应体系:在20μL反应体系中,含1×Buffer,模板DNA 50 ng,2.5 mmol.L-1氯化镁(MgCl2),0.15 mmol.L-1dNTP,25.05 nkatTaq聚合酶,0.5μmol.L-1引物。进一步进行梯度退火试验,确定最适宜退火温度为57℃。图7表2参23     

PCR和IFA测定猪圆环病毒2型半数细胞培养感染量的比较

采用聚合酶链式反应（PCR）和间接免疫荧光法（IFA）测定PCV2 SN07-1 2株的半数细胞培养感染量(TCID₅₀),初步比较两种方法测定病毒滴度的差异。参照Reed-Muench法计算TCID₅₀,并采用荧光定量PCR（Real-time PCR）法对试验结果进行验证。对于同一病毒样品,IFA法测出的TCID₅₀为10^6.5/mL,PCR法测出的TCID₅₀为10^5.0/mL,结果表明:IFA法比PCR法更敏感,更适宜用于测定PCV2的效价。