重庆北碚嘉陵江组第三—第四段碳酸盐岩碳同位素组成对古海水代表性

早三叠世海水的碳同位素组成是近年来地学研究的热点之一,但全球早三叠世碳同位素组成并没有获得统一的认识。上扬子地区早三叠世晚期普遍发育蒸发岩,地表剖面则因表生成岩作用而形成一套夹盐溶角砾岩及次生灰岩的碳酸盐地层,其地球化学信息不同程度地偏离海水,因而样品成岩蚀变性对古海水碳同位素组成的代表性的评估显得十分重要。本文以中、下三叠统界线清楚的重庆北碚剖面为对象,研究了下三叠统嘉陵江组第三、第四段和中三叠统雷口坡组底部样品的元素组成,碳、氧同位素组成及彼此之间的相互关系,选择Mn含量和氧同位素作为条件评价碳酸盐岩的成岩蚀变性及其对海水碳同位素组成的代表性,在此基础上建立了早三叠世晚期海水的碳同位素演化曲线。研究表明:(1)北碚剖面嘉陵江组第三、第四段(嘉三、嘉四段)及雷口坡组底部碳酸盐岩的Mn、Fe含量与碳同位素组成之间具有良好的负相关性,氧同位素组成和碳同位素组成之间则具有良好的正相关性,大量样品具有低δ18 O值、低δ13 C值以及较高Mn、Fe含量的特征,说明其碳同位素组成偏离海水。(2)以δ18 O-7.5‰、方解石的Mn质量分数100×10-6、白云石的Mn质量分数120×10-6为评价条件,北碚剖面嘉三、嘉四段(含雷口坡组底部)的73个样品中有38个需要在建立海水碳同位素曲线时剔除,占全部样品的52%。其中嘉四段需要剔除的样品占嘉四段样品的78%,而嘉三段的该数值为11%,说明作为原始沉积的灰岩段对海水地球化学信息保存较好,而分布盐溶角砾岩及次生灰岩的层位对海水地球化学信息保存很差。(3)氧同位素作为成岩蚀变评价标准比Mn含量更为苛刻,并可基本覆盖Mn含量评价条件,说明对于嘉三—嘉四段这样的石灰岩—白云岩—蒸发岩地层的地表剖面的样品来说,选择氧同位素作为评价条件可较好地对碳同位素的原生性进行控制。(4)白云岩对海水地球化学信息总体上保存较好,与相邻石灰岩相比,白云岩具有更高的δ18 O和δ13 C值,但其原因仍然需要进一步研究,可能与同位素分馏系数的差别以及白云岩形成于盐度更高的流体有关,因而白云岩所代表的海水地球化学信息可能不完全与伴生石灰岩相同。(5)除绿豆岩附近出现了短时间的变化超过4‰的大幅度波动以外,早三叠世晚期海水的碳同位素演化相对平稳,大致在-0.3‰~-1.8‰的范围内波动,呈现一个低幅的"V"字形,显示早三叠世晚期地球生态的恢复与碳循环系统的重建。     

Dual Binding of an Antibody and a Small Molecule Increases the Stability of TERRA G‐Quadruplex

In investigating the binding interactions between the human telomeric RNA (TERRA) G‐quadruplex (GQ) and its ligands, it was found that the small molecule carboxypyridostatin (cPDS) and the GQ‐selective antibody BG4 simultaneously bind the TERRA GQ. We previously showed that the overall binding affinity of BG4 for RNA GQs is not significantly affected in the presence of cPDS. However, single‐molecule mechanical unfolding experiments revealed a population (48 %) with substantially increased mechanical and thermodynamic stability. Force‐jump kinetic investigations suggested competitive binding of cPDS and BG4 to the TERRA GQ. Following this, the two bound ligands slowly rearrange, thereby leading to the minor population with increased stability. Given the relevance of G‐quadruplexes in the regulation of biological processes, we anticipate that the unprecedented conformational rearrangement observed in the TERRA‐GQ–ligand complex may inspire new strategies for the selective stabilization of G‐quadruplexes in cells.     

应用超声波装置控制害虫的研究概况

害虫综合治理的方法包括化学防控,生物防控,物理防控,植物检疫和农业防控等,但其各有利弊,当因势选择,适时防控。超声波技术因其无公害、可减轻抗性、避免残留、经济高效和操作安全等优势受到越来越多的关注。通过分析超声波防控虫害的基本原理,阐述用于控制害虫的超声波装置的研制和应用的研究进展,并讨论利用超声波技术控制害虫的应用前景。     

Nd0.7Sr0.3MnO3陶瓷中界面“陷阱态”相关电阻转变行为

通过固相烧结和高能球磨后热处理两种方法分别得到不具晶(相)界和具有明显晶(相)界的两种Nd_0.7Sr_0.3MnO₃陶瓷样品, 并用两线法和四线法分别对这两种样品的电极-块体接触界面和晶(相)界界面的I-V和电脉冲诱导电阻转变效应(EPIR)进行研究. 结果发现, 在两线法测试下, 电极-块体界面具有回滞的非线性I-V特征, 并能产生稳定的EPIR效应, EPIR的稳定性随温度的升高逐渐减弱并消失; 而对具有明显晶(相)界的陶瓷样品, 四线法测试结果表明, 虽然其I-V行为也具有非线性和回滞性特点, 但不能产生EPIR 效应. 这些奇特的界面输运行为与界面中的各种缺陷充当“陷阱”并实现对载流子的捕捉和释放过程密切相关. 而大量的晶(相)界界面及其复杂的连接方式导致较大的漏导则是晶(相)界不能出现EPIR效应的主要原因.     

Degradation of gate-recessed MOS-HEMTs and conventional HEMTs under DC electrical stress

The performance degradation of gate-recessed metal–oxide–semiconductor high electron mobility transistor(MOSHEMT) is compared with that of conventional high electron mobility transistor(HEMT) under direct current(DC) stress,and the degradation mechanism is studied. Under the channel hot electron injection stress, the degradation of gate-recessed MOS-HEMT is more serious than that of conventional HEMT devices due to the combined effect of traps in the barrier layer, and that under the gate dielectric of the device. The threshold voltage of conventional HEMT shows a reduction under the gate electron injection stress, which is caused by the barrier layer traps trapping the injected electrons and releasing them into the channel. However, because of defects under gate dielectrics which can trap the electrons injected from gate and deplete part of the channel, the threshold voltage of gate-recessed MOS-HEMT first increases and then decreases as the conventional HEMT. The saturation phenomenon of threshold voltage degradation under high field stress verifies the existence of threshold voltage reduction effect caused by gate electron injection.     

On the homogenization of some linear problems in domains weakly connected by a system of traps

The aim of the paper is to study the asymptotic behaviour of solutions of second‐order elliptic and parabolic equations, arising in modelling of flow in cavernous porous media, in a domain Ω^ε weakly connected by a system of traps ??^ε, where ε is the parameter that characterizes the scale of the microstructure. Namely, we consider a strongly perforated domain Ω^ε ?Ω a bounded open set of ?³ such that Ω^ε =Ω₁^ε ∪Ω₂^ε ∪??^ε ∪ W^ε, where Ω₁^ε, Ω₂^ε are non‐intersecting subdomains strongly connected with respect to Ω, ??^ε is a system of traps and meas W^ε → 0 as ε → 0. Without any periodicity assumption, for a large range of perforated media and by means of variational homogenization, we find the homogenized models. The effective coefficients are described in terms of local energy characteristics of the domain Ω^ε associated with the problem under consideration. The resulting homogenized problem in the parabolic case is a vector model with memory terms. An example is presented to illustrate the methodology. Copyright © 2007 John Wiley & Sons, Ltd.     

三塘湖盆地马朗凹陷火山岩储层成岩作用及成岩演化特征

通过大量的野外剖面观察、钻井岩心描述,结合室内薄片鉴定、地球化学元素测定和扫描电镜分析,确定了三塘湖盆地马朗凹陷石炭系火山岩的成岩演化阶段分为同生成岩阶段、表生成岩阶段和埋藏成岩阶段,以及交代作用、充填作用等多种成岩作用类型。冷凝收缩作用、挥发逸散作用、溶解作用、风化作用和构造作用是使储层物性变好的主要成岩作用;熔结作用、压实作用、交代作用、充填作用是使储层物性变差的主要成岩作用。     

和田河气田奥陶系碳酸盐岩成岩作用及孔隙演化

奥陶系碳酸盐岩储层是塔里木盆地和田河气田的主要产层 ,受成岩作用的改造非常强烈。通过对岩心、普通薄片、铸体薄片、阴极发光、碳氧同位素、微量元素和流体包裹体等多种资料进行综合研究 ,详细阐述了主要成岩作用的形成机理及其产物 ,分析了其对储层的影响和成岩序列。胶结作用和压实作用是原生孔隙和部分次生孔隙的主要破坏者 ;溶蚀 (岩溶 )作用、压溶作用、破裂作用和白云石化作用是次生孔隙的主要建造者 ,它们产生的溶孔、溶洞和裂缝是天然气的主要储集空间和运移通道。成岩作用是该储层物性的主要控制因素 ,它控制了孔隙的演化过程。