Electron tunneling properties of outer-membrane decaheme cytochromes from Shewanella oneidensis

We have characterized the outer-membrane decaheme cytochromes OmcA and MtrC from Shewanella oneidensis MR-1 at the single-molecule level using scanning tunneling microscopy (STM) and tunneling spectroscopy (TS). These cytochrome proteins are of great interest because they are thought to mediate bacterial electron transfer reactions in anoxic waters that control the reductive dissolution of oxide minerals. In our study, to characterize the electron transfer properties of these proteins on a model surface, the purified cytochromes were chemically immobilized as molecular monolayers on Au(111) substrates via a recombinant tetra-cysteine sequence as verified by X-ray photoelectron spectroscopy. Atomic force microscopy images confirm the monolayer films were ∼5-8 nm thick which is consistent with the apparent lateral dimensions of individual cytochrome molecules obtained with STM. Current-voltage TS of single cytochrome molecules revealed that OmcA and MtrC have different abilities to mediate tunneling current despite having otherwise very similar molecular and biochemical properties. These observations suggest that, based on their electron tunneling properties, the two cytochromes could have specific roles during bacterial metal reduction. Additionally, this study establishes single-molecule STM/TS as an effective means for revealing insights into biogeochemical redox processes in the environment.     

油气聚集对石英矿物成岩演化的影响

油气在砂岩储层中的聚集会对石英矿物的胶结作用产生影响。对黄骅坳陷三马探区的石英矿物的包裹体分析以及对开放孔隙中原油抽提物和包裹体中原油的生物标志物进行分析,含油级别较低的油层与水层具有相似的均一化温度分布范围,但富含油层中流体包裹体均一化温度高值分布范围比低级别油层和水层低,包裹体中的烃类组成与开放孔隙中的主要存在成熟度上的不同。分析认为石油的充注不会使石英矿物的胶结作用立刻停止,石英的次生加大作用仍在继续,但胶结作用受到一定的抑制,当石油充注到一定程度后,胶结作用将会停止,后期进入储层的成熟度较高的原油可能未被捕获。     

高速铁路地基黄土微结构的分形研究

基于分形理论,结合Photoshop等图像分析处理软件,在图像处理过程中选择适当的阈值,本文对郑州—西安客运专线地基黄土在动荷载作用下变形前后的孔隙微观结构进行分形研究。研究表明,黄土孔隙微观结构具有分形特征,揭示了黄土孔隙分形分维同孔隙比之间有近似直线的关系,且孔隙微结构分形分维越大,土体强度越大,反之越小。     

地质雷达方法检测隧道衬砌质量研究

在铁路、公路和电站等项目的建设中,隧道隐蔽工程所占比例较大。为了严格控制隧道的施工质量,检测方法由传统的破检向无损检测转变,并对无损检测的精度要求也越来越高。由于探地雷达技术具有高效率、高分辨率和异常图像直观等突出优点,因此,该方法广泛应用于隧道隐蔽工程的质量检测中。这里从地质雷达方法原理出发,从理论上研究了电磁波在隧道衬砌内的传播规律、反射能力和基本雷达图像特征,并结合工程实例,总结了正确判识各类雷达异常的经验,提出了常用的反演计算方法。     

再论岩石圈地幔蘑菇云构造及其深部成因

根据地球物理资料的分析得到,除了东北吉辽地区太平洋板块向大陆俯冲外,当今中国东部其他地区大陆下都没有俯冲太平洋板块的证据。中生代以来中国东部发生的岩石圈巨变不是太平洋板块向中国大陆的俯冲所造成,而是由于软流圈物质上涌形成蘑菇云构造对岩石圈地幔的改造而引发的重大地质事件。软流圈物质的上涌使岩石圈地幔成为新生地幔与残剩地幔并存的结构,岩石圈被激活,稳定的克拉通地壳褶皱变形,地壳减薄,地震频发,岩浆活动活跃,地面沉降,并形成广袤的西太平洋边缘海。但是岩石圈厚度并未减薄,只是由于岩石圈地幔形成了蘑菇云结构使它的速度降低,与周遍地区的岩石圈结构产生明显差别。蘑菇云地幔发育的地区覆盖整个东南亚西太平洋地区。包括中国东北的中东部、华北的东部、华南的东南缘、马来半岛、印尼、菲律宾、日本海、黄海、东海、南海,加罗林盆地和菲律宾海盆。与这个东南亚西太平洋低速岩石圈地幔相对应,还存在一个巨大的大地椭球面正异常,它应是核幔边界的质量过剩所引起。它与印度洋—西藏地区核幔边界质量亏损引起的负大地椭球面异常孪生,并形成一个控制中国大陆构造的深层动力系统,这个动力系统产生的时代可能为中生代或晚古生代。它们之间的地幔环流造成了东南亚西太平洋岩石圈巨变,并驱动印度板块的北移和青藏高原的隆升。     

新疆东天山十里坡自然铜矿化区马头滩组玄武岩锆石LA-ICPMS U-Pb年龄及其意义

新疆北部东天山十里坡地区近年来新发现了与玄武岩有关的自然铜矿化这一新类型。自然铜的赋矿地层-马头滩组中的赋矿玄武岩锆石 LA-ICPMS 年龄为307±4Ma,对应于晚石炭世,显示该套赋矿地层属于上石炭统。从该区自然铜赋矿火山岩所限定的时间看,成矿背景应属于后碰撞环境。东天山十里坡地区自然铜矿化的构造背景、成矿系统和矿化类型与峨眉山玄武岩自然铜矿化和美国基威诺铜矿床均存在差异,自然铜矿化的成因可能也存在差异。     

钻孔灌注桩桩底沉渣压浆处理研究与应用

对桩底沉渣产生的原因、沉渣对灌注桩承载能力的影响以及沉渣的处理作了简要分析,讨论了灌注桩桩底压浆工艺的作用机理。重点结合实际工程介绍了该技术,经检测表明,灌注桩桩底压浆技术的使用有效地处理了沉渣,提高了桩的承载能力。     

Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinling carbonatites, China

The Lesser Qinling carbonatite dykes are mainly composed of calcites. They are characterized by unusually high heavy rare earth element concentrations (HREE; e.g. Yb > 30 ppm) and flat to weakly light rare earth element (LREE) enriched chondrite-normalized patterns (La/Yb_n = 1.0–5.5), which is in marked contrast with all other published carbonatite data. The trace element contents of calcite crystals were measured in situ by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Some crystals show reduced LREE from core to rim, whereas their HREE compositions are relatively constant. The total REE contents and chondrite-normalized REE patterns from the cores of carbonate crystals are similar to those of the whole rock. The carbon and oxygen isotopic compositions of calcites fall within the range of primary, mantle-derived carbonatites. The initial Sr isotopic compositions (0.70480–0.70557) of calcites are consistent with an EM1 source or mixing between HIMU and EM1 mantle sources. However these sources cannot produce carbonatite parental magmas with a flat or slightly LREE enrichment pattern by low degrees of partial melting. Analyses of carbonates from other carbonatites show that carbonates have nearly flat REE pattern if they crystallize from a LREE enriched carbonatite melt. This implies that when carbonates crystallize from a carbonatite melt the calcite/melt partition coefficients (D) for HREE are much greater than the D for the LREE. The nearly flat REE patterns of the Lesser Qinling carbonatites can be explained if they are carbonate cumulates that contain little trapped carbonatite melt. Strong enrichment of HREE in the carbonatites may require their derivation by small degrees of melting from a garnet-poor source.     

SHRIMP U-Pb Zircon Age of the Ka''''erjiao Intrusion in the Sawur Region in West Junggar,Xinjiang

Acid intrusions are widespread in the Sawur region, Xinjiang. The Ka'erjiao intrusion is mainly composed of albite granite porphyry, K-feldspar granite porphyry, ivernite and granite porphyry. Being a transitional product between magma intrusion and eruption in the Sawur region, the Ka'erjiao intrusion was formed at the telophase of the late Carboniferous to the begining of early Permian as determined by the SHRIMP U-Pb zircon dating, with an age of 302.6±7.6 Ma (1σ). The intrusion consists of alkali-enriched rock, whose REE distribution patterns are of the LREE enrichment type, theδEu value is low and Nd, Sr, Pb isotopes reflect its mantle source characteristics. Theδ18O value of intrusion is low as a result of isotope exchange with meteoric water. The geochemical characteristics show that it was formed in a post-collisional tectonic setting. Taking combined considerations of current studies of A-type granites and Permian volcanic rocks, we think that in the telophase of the late Carboniferous to the beginning of the early Permian, the Sawur region was within the extension or compressional to extensional period of a post-collisional stage. The Ka'erjiao intrusion from mantle sources can confirm the vertical continental crust growth in the late Paleozoic. The Sawur region in west Junggar is consistent with east Junggar in post-collisional tectonic evolution process.     

坐标投影作图法在川藏线宿瓦卡岩质边坡稳定性分析中的应用

边坡稳定性问题是川藏线工程建设面临的重要问题。野外调查发现基岩边坡失稳一般表现为块体塌落或滑动。基于岩体结构控制理论,作者以川藏线西藏境内宿瓦卡附近的人工高边坡为例,进行了块体边坡稳定性分析。对比现有理论方法的优缺点,采用坐标投影作图法及其计算机化程序CPH。坐标投影作图法是一种以正投影为基础,以分析岩体结构面的几何关系及由其切割出来的块体的稳定性为目的的图解方法。根据现场量测取得的数据,采用CPH程序确定了块体边坡的结构面方程,从而求出各结构面产状。在此基础上建立水平切面图,并求得各块体顶点坐标,计算出块体的表面积及体积。根据极限平衡理论,运用CPH程序进行块体稳定性分析,并求出块体的稳定性系数。通过分析可知,坐标投影作图法及其计算机化的CPH程序在块体边坡稳定性分析中有着很好的应用效果。