Adsorption of benzonitrile at the air/water interface studied by sum frequency generation spectroscopy

In this investigation, the adsorption of benzonitrile at the air/water interface was addressed using vibrational sum-frequency spectroscopy. Using ppp and ssp polarization combinations, the authors detected the symmetric stretching mode of the cyano (CN) group and calculated the orientation of benzonitrile at the interface. In addition, the adsorption isotherm was determined in terms of the hyperpolarizability element by varying the bulk benzonitrile concentration. The adsorption energy was obtained from fitting this isotherm. This work will add to our understanding of chemical processes relevant to retention, degradation, and photolysis of benzonitriles in the environment.     

A 457-year reconstruction of precipitation in the southeastern Qinghai-Tibet Plateau, China using tree-ring records

This paper presents a 457-year reconstruction of precipitation in the southeastern Qinghai-Tibet Plateau using tree-ring records.Tree-ring samples were collected from the Hengduan Mountains in the southeastern part of the Qinghai-Tibet Plateau,China.A nearly 500-year chronology was developed using tree-ring width records.Correlation analysis shows moisture is the main factor limiting tree growth in this region.Ring-widths were significantly positively correlated with the Palmer Drought Severity Index(PDSI) and precipitation in many months.The highest correlation coefficient was found between the annual growth of trees and precipitation from the previous September to the current June(0.738).Based on this relationship,we reconstructed the precipitation history from 1509 to 2006.The reconstruction explains 54.4%(Radj2=53.5%,N=49,F=56.12) of the actual precipitation variation during the calibration period(1958-2006).During the reliable period of the reconstruction(1549-2006),some low-frequency climate signals are included,indicating this region has been getting wetter in the last 20 years.The reconstruction documents six apparently dry and five pluvial periods and the 17th century dry period lasted longer than any other.When compared with other recent studies,this study and these earlier reconstructions show a similar trend in the variation of drought and pluvial.Further spatial correlation analysis confirms that the reconstructed precipitation adequately represents the rainfall history of the entire Hengduan Mountain area.The Multi-taper method,a type of spectral analysis,reveals that precipitation in this area had significant(P<0.01) spectral peaks at 3-5 a,60 a and 79-85 a.     

Photocatalytic degradation of microcystin-LR using TiO2 nanotubes under irradiation with UV and natural sunlight

In order to investigate the catalytic performance of anodic TiO2 nanotubes and their practical application in the treatment of refractory microcystins(MCs) in natural-water samples,TiO2 nanotubes of diameter of 50-80 nm were fabricated by anodization in C2H2O4·2H2O containing NH4F.Under irradiation with natural sunlight,MC-LR was totally degraded after 1 d using the anodic TiO2 nanotubes.In contrast,the removal efficiency without TiO2 nanotubes was as low as 47.7% within 20 d.In addition,a mixture of anatase and rutile TiO2 gave higher photocatalytic activity than the single phase did.The pH also influenced the adsorption capacity of the TiO2 nanotubes.The order of MC-LR degradation efficiencies at different pH values was 3.5 > 8.0 > 10.0.After five repeated experiments on the degradation of MC-LR for 7 h,the degradation efficiency was still stable.     

Isolation and characterization of H7N9 viruses from live poultry markets--Implication of the source of current H7N9 infection in humans

On March 31, 2013, the National Health and Family Planning Commission announced that human infections with a previously undescribed influenza A (H7N9) virus had occurred in Shanghai and Anhui Province, China. To investigate the possible origins of the H7N9 viruses causing these human infections, we collected 970 samples, including drinking water, soil, and cloacal and tracheal swabs of poultry from live poultry markets and poultry farms in Shanghai and Anhui Province. Twenty samples were positive for the H7N9 influenza virus. Notably, all 20 viruses were isolated from samples collected from live poultry markets in Shanghai. Phylogenetic analyses showed that the six internal genes of these novel human H7N9 viruses were derived from avian H9N2 viruses, but the ancestor of their HA and NA genes is uncertain. When we examined the phylogenetic relationship between the H7N9 isolates from live poultry markets and the viruses that caused the human infections, we found that they shared high homology across all eight gene segments. We thus identified the direct avian origin of the H7N9 influenza viruses that caused the human infections. Importantly, we observed that the H7N9 viruses isolated from humans had acquired critical mutations that made them more "human-like". It is therefore imperative to take strong measures to control the spread of H7N9 viruses in birds and humans to prevent further threats to human health.     

层内纵向非均质性对稠油油藏剩余油分布的影响研究

渤海某油田层内纵向非均质性严重,导致低渗透层动用程度低,影响油藏的高效开发。根据非均质油藏地质特征,利用人造物理模型制作技术制作二维物理模型,进行水驱油实验,从而明确纵向非均质性对剩余油分布规律的影响。实验表明:水驱采收率的高低主要取决于层内纵向非均质性,平均渗透率对它影响相对较小;相同级差、不同渗透率条件下,无水采收率和水驱采收率都随着渗透率的增加而增加,但增幅不明显;相同平均渗透率、不同级差条件下,无水采收率和水驱采收率都随着级差的增大而减少,变化幅度明显。     

Early Diagnostic Value of Circulating MiRNA-21 in Lung Cancer： A Meta-Analysis

To evaluate the early diagnostic value of circulating miRNA-21 in diagnosis of lung cancer, databases such as Wan Fang, VIP, PubMed, and Elsevier were systematically searched from 2005 to 2013 to collect relevant references in which the diagnostic value had been evaluated. The statistics were consolidated and the qualities of the studies were classified. The data were analyzed using Meta Disc1.4 software. The diagnostic value of circulating miRNA-21 in lung cancer was assessed by pooling sensitivity, specificity, the likelihood ratio, and the Summary Receiver Operating Characteristic(SROC) curve. Publication biases of the studies involved were analyzed using Stata 11.0 software. A total of 143 papers were collected of which 8 were included, which contained 600 cases and440 controls. A heterogeneity test proved the existence of homogeneity in this study. Upon analysis using random effects models, the weighted sensitivity was 0.68, the specificity 0.77, the positive likelihood ratio 2.84, the negative likelihood ratio 0.40, and the SROC Area Under the Curve(AUC) was 0.8133. Further analysis by subgroup showed that the 5 indicators mentioned above were 0.72, 0.84, 4.50, 0.27, and 0.8987, respectively, for the serum group and 0.63, 0.70, 1.95, 0.53, and 0.7318, respectively, for the plasma group. We conclude that circulating miRNA-21can be regarded a valuable reference in diagnosis of lung cancer. This research showed that in lung cancer the early diagnostic value of miRNA-21 in serum was better than that in plasma.     

基于地理位置预测的ETT判据路由协议

提出了基于节点位置预测的路由算法AODV-LP-ETT.该算法通过计算出在通信范围内的节点间链路的ETX值和带宽值进行路由选择,采用灰色预测模型预测节点下一时刻的地理位置,通过判断节点间的距离是否处于彼此的通信范围之内来决定是否使用ETT路由判据.QualNet仿真结果表明,与AODV路由协议相比AODV-LP-ETT路由协议提高了网络吞吐量,提高了分组投递率,降低了平均端到端延时及平均抖动,改善了网络整体性能.     

该如何理解质的研究的推广度?

在进行质的研究时,推广度成为研究者要考虑的一个因素,但质的研究推广度不同于量的研究中对于推广度的理解,也不能用衡量量的研究推广度的标准来衡量质的研究的推广度.质的研究推广度因其本身的具体内部概括性和相似性移情的特性,因此它更倾向于一种认同和共鸣.     

地表荷载对地铁车站箱体影响实测及有限元分析

对天津地铁1号线西站车站及隧道在地表荷载作用下产生的沉降进行了现场监测和有限元分析,由于变形缝的存在使结构沉降表现为非连续性;地表荷载下基底土体产生塑性应变导致卸荷后结构仍存在不可恢复的残余变形;侧向地表荷载会导致结构产生较大的倾斜差异沉降并使结构扭转。在此基础上研究了地表荷载位置、结构埋深因素对于存在变形缝的地铁结构箱体变形的影响。结果表明：变形缝的存在会削弱结构刚度、加剧结构沉降以及结构间的差异沉降,并且不同荷载位置下结构的沉降特点也各不相同。此外,对于浅埋结构,荷载位置距结构越远,结构的变形越小,且结构埋置越深地表荷载对结构的影响也越小。     

依托就业导向的民族高校计算机专业实训——以大连民族学院为例

分析计算机专业毕业生实训现状,根据大连民族学院计算机专业开展的3年实训课程经验,构建依托就业导向的专业实训体系。论述了实训体系的指导思想,介绍了教学内容与形式、师资建设和网络教学辅助平台等方面的具体措施。