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1Chinese Stroke Center Alliance:a national effort to improve healthcare quality for acute stroke and transient ischaemic attack:rationale,design and preliminary findings显示文摘Background In June 2015,the Chinese Stroke Association(CSA)initiated the Chinese Stroke Center Alliance(CSCA)to establish the national hospital-based stroke care quality assessment and improvement platform.This article outlines its objectives,operational structure,patient population,quality improvement(QI)intervention tools,data elements,data collection methodology and current patient and hospital data.Methods The CSCA is a national,hospital-based,multicentre,voluntary,multifaceted intervention and continuous QI initiative.This multifaceted intervention includes stroke centre development,written care protocols,workshops and a monitoring/feedback system of evidencebased performance measures.The data coordinating centre of the CSCA resides at the China National Clinical Research Center for Neurological Diseases,Beijing Tiantan Hospital.results As of July 2017,1576 hospitals in China have contributed detailed clinical information to serve as a benchmark for the stroke care quality of 433264 patients with acute stroke/transient ischaemic attacks(TIA),including 352572(81.38%)acute ischaemic stroke,30362(7.01%)TIA,42080(9.71%)spontaneous intracranial haemorrhage,5505(1.27%)subarachnoid haemorrhage and 2745(0.63%)not specified stroke.Conclusion The CSCA programme is designed to establish a continuous national stroke registry and help healthcare providers develop stroke centres and treat patients in a consistent manner in accordance with accepted national guidelines and,ultimately,improve patient outcomes.It supports the CSA mission to reduce stroke burden in China.Yongjun Wang Zixiao Li Yilong Wang Xingquan Zhao Liping Liu Xin Yang Caiyun Wang Hongqiu Gu Fuying Zhang Chunjuan Wang Ying Xian David Z Wang Qiang Dong Anding Xu Jizong Zhao Chinese Stroke Center Alliance investigators 2018Stroke & Vascular Neurology2018,3,4:38
2Transient elastography(Fibro Scan~?) with controlled attenuation parameter in the assessment of liver steatosis and fibrosis in patients with nonalcoholic fatty liver disease- Where do we stand?显示文摘Non-alcoholic fatty liver disease(NAFLD) is the most common cause of chronic liver disease worldwide. Currently, the routinely used modalities are unable to adequately determine the levels of steatosis and fibrosis(laboratory tests and ultrasonography) or cannot be applied as a screening procedure(liver biopsy). Among the non-invasive tests, transient elastography(Fibro Scan?, TE) with controlled attenuation parameter(CAP) has demonstrated good accuracy in quantifying the levels of liver steatosis and fibrosis in patients with NAFLD, the factors associated with the diagnosis and NAFLD progression. The method is fast, reliable and reproducible, with good intra- and interobserver levels of agreement, thus allowing for population-wide screening and disease follow-up. The initial inability of the procedure to accurately determine fibrosis and steatosis in obese patients has been addressed with the development of the obese-specific XL probe. TE with CAP is a viable alternative to ultrasonography, both as an initial assessment and during follow-up of patients with NAFLD. Its ability to exclude patients with advanced fibrosis may be used to identify low-risk NAFLD patients in whom liver biopsy is not needed, therefore reducing the risk of complications and the financial costs.Ivana Mikolasevic Lidija Orlic Neven Franjic Goran Hauser Davor Stimac Sandra Milic 2016World Journal of Gastroenterology2016,22,32:33
3Cardiovascular risk factors for acute stroke: Risk profiles in the different subtypes of ischemic stroke显示文摘Timely diagnosis and control of cardiovascular risk factors is a priority objective for adequate primary and secondary prevention of acute stroke. Hypertension, atrial fibrillation and diabetes mellitus are the most common risk factors for acute cerebrovascular events, although novel risk factors, such as sleep-disordered breathing, inflammatory markers or carotid intima-media thickness have been identified. However, the cardiovascular risk factors profile differs according to the different subtypes of ischemic stroke. Atrial fibrillation and ischemic heart disease are more frequent in patients with cardioembolic infarction, hypertension and diabetes in patients with lacunar stroke, and vascular peripheral disease, hypertension, diabetes, previous transient ischemic attack and chronic obstructive pulmonary disease in patients with atherothrombotic infarction. This review aims to present updated data on risk factors for acute ischemic stroke as well as to describe the usefulness of new and emerging vascular risk factors in stroke patients.Adrià Arboix 2015World Journal of Clinical Cases2015,3,5:29
4Esophageal motility abnormalities in gastroesophageal reflux disease显示文摘Esophageal motility abnormalities are among the main factors implicated in the pathogenesis of gastroesophageal reflux disease. The recent introduction in clinical and research practice of novel esophageal testing has markedly improved our understanding of the mechanisms contributing to the development of gastroesophageal reflux disease, allowing a better management of patients with this disorder. In this context, the present article intends to provide an overview of the current literature about esophageal motility dysfunctions in patients with gastroesophageal reflux disease. Esophageal manometry, by recording intraluminal pressure, represents the gold standard to diagnose esophagealmotility abnormalities. In particular, using novel techniques, such as high resolution manometry with or without concurrent intraluminal impedance monitoring, transient lower esophageal sphincter (LES) relaxations, hypotensive LES, ineffective esophageal peristalsis and bolus transit abnormalities have been better defined and strongly implicated in gastroesophageal reflux disease development. Overall, recent findings suggest that esophageal motility abnormalities are increasingly prevalent with increasing severity of reflux disease, from nonerosive reflux disease to erosive reflux disease and Barrett's esophagus. Characterizing esophageal dysmotility among different subgroups of patients with reflux disease may represent a fundamental approach to properly diagnose these patients and, thus, to set up the best therapeutic management. Currently, surgery represents the only reliable way to restore the esophagogastric junction integrity and to reduce transient LES relaxations that are considered to be the predominant mechanism by which gastric contents can enter the esophagus. On that ground, more in depth future studies assessing the pathogenetic role of dysmotility in patients with reflux disease are warranted.Irene Martinucci Nicola de Bortoli Maria Giacchino Giorgia Bodini Elisa Marabotto Santino Marchi Vincenzo Savarino Edoardo Savarino 2014World Journal of Gastrointestinal Pharmacology and Therapeutics2014,5,2:24
5Effect of alcohol consumption on liver stiffness measured by transient elastography显示文摘AIM:To determine the evolution of transient elastography(TE) in patients with alcoholic liver disease according to alcohol cessation or continuation.METHODS:We retrospectively selected in our local database all patients who had two TE between June 2005 and November 2010 with chronic alcohol excessive consumption and excluded those with associated cause of liver disease.TE was performed at least one week apart by senior operator.TE examinations with less than ten successful measures or with an interquartile range above 30% were excluded.We retrospectively reviewed file of all patients to include only patient followed up by trained addictologist and for which definite information on alcohol consumption was available.Concomitant biological parameters [aspartate amino transferase(AST),alanine amino transferase and gamma-glutamyl transpeptidase(GGT)] within 4 wk of initial and final TE were recorded.Putative fibrosis score according to initial and final TE were determined with available cut-off for alcoholic liver disease and hepatitis C.Initial and final putative fibrosis score were compared according to alcohol consumption during follow-up.RESULTS:During the study period 572 patients had TE examination for alcoholic liver disease and 79 of them had at least two examinations.Thirty-seven patients met our criteria with a median follow-up of 32.5 wk.At the end of the study,13(35%) were abstinent,and 24(65%) relapsers.Eight patients had liver biopsy during follow-up.TE decreased significantly during follow-up in 85% of abstinent patients [median(range):-4.9(-6.1,-1.9)],leading to a modification of the putative fibrosis stage in 28%-71% of patient according to different cut-off value.In relapsers TE increased in 45% and decreased in 54% of patient.There was no statistical difference between initial and final TE in relapsers.In the overall population,using 22.6 kPa as cut-off for cirrhosis,4 patients had cirrhosis at initial TE and 3 patients had cirrhosis at final TE.Using 19.5 kPa as cut-off for cirrhosis,7 patients had cirrhosis at initial TE and 5 patients had cirrhosis at final TE.Using 12.5 kPa as cut-off for cirrhosis,16 patients had cirrhosis at initial TE and 15 patients had cirrhosis at final TE.Evolution of biological data was in accordance with the relapse or abstinent status:abstinence ratio(duration of abstinence/duration follow-up) was correlated with AST ratio(r =-0.465,P = 0.007) and GGT ratio(r =-0.662,P<0.0001).GGT was correlated with initial(r = 0.488,P = 0.002) and final TE(r = 0.49,P<0.005).Final TE was correlated with AST(r = 0.362,P<0.05).Correlation between TE ratio and AST ratio(r = 0.44,P = 0.01) revealed that TE varied proportionally to AST for all patients irrespective of their alcohol status.The same relationship was observed between TE ratio and GGT ratio(r = 0.65,P<0.0001).Evolution of TE was significantly correlated with the ratio of time of abstinence to observation time(r =-0.387,P = 0.016) and the evolution of liver enzymes.CONCLUSION:TE significantly decreased with abstinence.Results of TE in alcoholic liver disease cannot be interpreted without taking into account alcohol consumption and liver enzymes.Edouard Bardou-Jacquet Ludivine Legros Draman Soro Marianne Latournerie Anne Guillygomarc'h Caroline Le Lan Pierre Brissot Dominique Guyader Romain Moirand 2013World Journal of Gastroenterology2013,19,4:20
6Performance of liver stiffness measurements by transient elastography in chronic hepatitis显示文摘AIM:To compare results of liver stiffness measurements by transient elastography(TE) obtained in our patients population with that used in a recently published meta-analysis.METHODS:This was a single center cross-sectional study.Consecutive patients with chronic viral hepatitis scheduled for liver biopsy at the outpatient ward of our Infectious Diseases Department were enrolled.TE was carried out by using FibroScan(Echosens,Paris,France).Liver biopsy was performed on the same day as TE,as day case procedure.Fibrosis was staged according to the Metavir scoring system.The diagnostic performance of TE was assessed by using receiver operating characteristic(ROC) curves and the area under the ROC curve analysis.RESULTS:Two hundred and fifty-two patients met the inclusion criteria.Six(2%) patients were excluded due to unreliable TE measurements.Thus,246(171 men and 75 women) patients were analyzed.One hundred and ninety-five(79.3%) patients had chronic hepatitis C,41(16.7%) had chronic hepatitis B,and 10(4.0%) were coinfected with human immunodeficiency virus.ROC curve analysis identified optimal cut-off value of TE as high as 6.9 kPa forF ≥ 2;7.9 kPa forF ≥ 3;9.6 kPa for F = 4 in all patients(n = 246),and as high as 6.9 kPa for F ≥ 2;7.3 kPa for F ≥ 3;9.3 kPa for F = 4 in patients with hepatitis C(n = 195).Cut-off values of TE obtained by maximizing only the specificity were as high as 6.9 kPa for F ≥ 2;9.6 kPa for F ≥ 3;12.2 kPa for F = 4 in all patients(n = 246),and as high as 7.0 kPa forF ≥ 2;9.3 kPa forF ≥ 3;12.3 kPa forF = 4 in patients with hepatitis C(n = 195).CONCLUSION:The cut-off values of TE obtained in this single center study are comparable to that obtained in a recently published meta-analysis that included up to 40 studies.Giovanna Ferraioli Carmine Tinelli Barbara Dal Bello Mabel Zicchetti Raffaella Lissandrin Gaetano Filice Carlo Filice Elisabetta Above Giorgio Barbarini Enrico Brunetti Willy Calderon Marta Di Gregorio Roberto Gulminetti Paolo Lanzarini Serena Ludovisi Laura Maiocchi Antonello Malfitano Giuseppe Michelone Lorenzo Minoli Mario Mondelli Stefano Novati Savino FA Patruno Alessandro Perretti Gianluigi Poma Paolo Sacchi Domenico Zanaboni Marco Zaramella 2013World Journal of Gastroenterology2013,19,1:18
7The Queue Length Distribution for M/G/1 Queue with Delay Single Server VacationTANG Ying\|hui,\ TANG Xiao\|woSichuan University, Chengdu 610064 University of Electronic Science & Technology of China, Chengdu 610054 2000Systems Science and Systems Engineering2000,10,2:16
8Clinical application of liver stiffness measurement using transient elastography in chronic liver disease from longitudinal perspectives显示文摘Accurate determination of the presence and degree of fibrosis in liver is of great importance, because the prognosis and management strategies for chronic liver disease depend mainly on these factors. To date, liver biopsy (LB) remains the 'gold standard' for assessing the severity of liver fibrosis; however, LB is often limited by its invasiveness, sampling error, and intra/ inter-observer variability in histological interpretation. Furthermore, repeated LB examinations within a short time interval are indeed ineligible in a real clinical practice. Thus, due to the pressing need for non-invasive surrogates for liver fibrosis, transient elastography (TE),as a novel ultrasound based technology, has allowed a noninvasive measurement of liver stiffness and has gained in popularity over recent years. In the past few years, additional roles for transient TE beyond the initial purpose of a non-invasive surrogate for LB have included the prediction of the most two critical consequences of fibrosis progression: the development of portal hypertension-related complications and hepatocellular carcinoma. This indicates that the role of transient TE is not merely limited to reducing the need for LB, but transient TE can enable the establishment of tailored management strategies by providing more detailed prognostic information. In particular, under the concept in which the clinical course of liver fibrosis is dynamic and bidirectional, especially when appropriate intervention is commenced, transient TE can be used to track the dynamic changes in fibrotic burden during antiviral or antifibrotic treatment. This review discussed extended applications of transient TE in prediction of the development of real clinical endpoints from a longitudinal perspective.Beom Kyung Kim James Fung Man-Fung Yuen Seung Up Kim 2013World Journal of Gastroenterology2013,19,12:14
9Comparison of the Global Energy Cycle between Chinese Reanalysis Interim and ECMWF Reanalysis显示文摘The global energy cycle is a diagnostic metric widely used to gauge the quality of datasets. In this paper, the 'Mixed Space-Time Domain' method for diagnosis of energy cycle is evaluated by using newly developed datasets-the Chinese Reanalysis Interim (CRAI) and ECMWF Reanalysis version 5 (ERA5), over a 7-yr period (2010-16) on seasonal and monthly timescales. The results show that the energy components calculated from the two reanalysis datasets are highly consistent;however, some components in the global energy integral from CRAI are slightly larger than those from ERA5. The main discrepancy in the energy components stems from the conversion of baroclinic process, whereas the dominant difference originates from the conversion from stationary eddy available potential energy to stationary eddy kinetic energy (CES), which is caused by systematic differences in the temperature and vertical velocity in low-mid latitudes of the Northern Hemisphere and near the Antarctic, where there exist complex terrains. Furthermore, the monthly analysis reveals that the general discrepancy in the temporal variation between the two datasets also lie mainly in the CES as well as corresponding generation and dissipation rates.Bin ZHAO Bo ZHANG Chunxiang SHI Jingwei LIU Lipeng JIANG 2019Journal of Meteorological Research2019,33,3:14
10Tracing the first hematopoietic stem cell generation in human embryo by single-cell RNA sequencing显示文摘Tracing the emergence of the first hematopoietic stem cells(HSCs)in human embryos,particularly the scarce and transient precursors thereof,is so far challenging,largely due to the technical limitations and the material rarity.Here,using single-cell RNA sequencing,we constructed the first genome-scale gene expression landscape covering the entire course of endothelial-to-HSC transition during human embryogenesis.The transcriptomically defined HSC-primed hemogenic endothelial cells(HECs)were captured at Carnegie stage(CS)12-14 in an unbiased way,showing an unambiguous feature of arterial endothelial cells(ECs)with the up-regulation of RUNX1,MYB and ANGPTL Importantly,subcategorizing CD34+CD45-ECs into a CD44+population strikingly enriched HECs by over 10-fold.We further mapped the developmental path from arterial ECs via HSC-primed HECs to hematopoietic stem progenitor cells,and revealed a distinct expression pattern of genes that were transiently over-represented upon the hemogenic fate choice of arterial ECs#including EMCN,PROCR and RUNX1T1.We also uncovered another temporally and molecularly distinct intra-embryonic HEC population,which was detected mainly at earlier CS 10 and lacked the arterial feature.Finally,we revealed the cellular components of the putative aortic niche and potential cellular interactions acting on the HSCprimed HECs.The cellular and molecular programs that underlie the generation of the first HSCs from HECs in human embryos,together with the ability to distinguish the HSC-primed HECs from others,will shed light on the strategies for the production of clinically useful HSCs from pluripotent stem cells.Yang Zeng Jian He Zhijie Bai Zongcheng Li Yandong Gong Chen Liu Yanli Ni Junjie Du Chunyu Ma Lihong Bian Yu Lan Bing Liu 2019Cell Research2019,29,11:14
11Real-time transient stability assessment in power system based on improved SVM显示文摘Due to the strict requirements of extremely high accuracy and fast computational speed, real-time transient stability assessment(TSA) has always been a tough problem in power system analysis.Fortunately, the development of artificial intelligence and big data technologies provide the new prospective methods to this issue, and there have been some successful trials on using intelligent method, such as support vector machine(SVM) method.However, the traditional SVM method cannot avoid false classification, and the interpretability of the results needs to be strengthened and clear.This paper proposes a new strategy to solve the shortcomings of traditional SVM,which can improve the interpretability of results, and avoid the problem of false alarms and missed alarms.In this strategy, two improved SVMs, which are called aggressive support vector machine(ASVM) and conservative support vector machine(CSVM), are proposed to improve the accuracy of the classification.And two improved SVMs can ensure the stability or instability of the power system in most cases.For the small amount of cases with undetermined stability, a new concept of grey region(GR) is built to measure the uncertainty of the results, and GR can assessment the instable probability of the power system.Cases studies on IEEE 39-bus system and realistic provincial power grid illustrate the effectiveness and practicability of the proposed strategy.Wei HU Zongxiang LU Shuang WU Weiling ZHANG Yu DONG Rui YU Baisi LIU 2019Journal of Modern Power Systems and Clean Energy2019,7,1:14
12THE TRANSIENT SOLUTION FOR M/G/1 QUEUEWITH SERVER VACATIONS显示文摘In this paper, the transient solutions for M/G/1 queues with single server vacation and multiple server vacations are firstly studied, and the recursion expressions of their Laplace transform are given. Further the distribution and stochastic decomposition result of the queue length at a random point in equilibrium are directly obtained from the transient solution. As will be seen this paper provides a intuitive and elegant method for studying transient solutions for M/G/1 queues with single server.唐应辉 1997Acta Mathematica Scientia1997,17,3:13
13Performance of transient elastography in assessing liver fibrosis in patients with autoimmune hepatitis-primary biliary cholangitis overlap syndrome显示文摘AIM To investigate the performance of transient elastography(TE) for diagnosis of fibrosis in patients with autoimmune hepatitis-primary biliary cholangitis(AIHPBC) overlap syndrome.METHODS A total of 70 patients with biopsy-proven AIH-PBC overlap syndrome were included. Spearman correlation test was used to analyze the correlation of liver stiffness measurement(LSM) and fibrosis stage. Independent samples Student's t-test or one-way analysis of variance was used to compare quantitative variables. Receiver operating characteristics(ROC) curve was used to calculate the optimal cut-off values of LSM for predicting individual fibrosis stages. A comparison on the diagnostic accuracy for severe fibrosis was made between LSM and other serological scores.RESULTS Patients with AIH-PBC overlap syndrome had higher median LSM than healthy controls(11.3 ± 6.4 k Pa vs 4.3 ± 1.4 k Pa, P < 0.01). LSM was significantly correlated with fibrosis stage(r = 0.756, P < 0.01). LSM values increased gradually with an increased fibrosis stage. The areas under the ROC curves of LSM for stages F ≥ 2, F ≥ 3, and F4 were 0.837(95%CI: 0.729-0.914), 0.910(0.817-0.965), and 0.966(0.893-0.995), respectively. The optimal cut-off values of LSM for fibrosis stages F ≥ 2, F ≥ 3, and F4 were 6.55, 10.50, and 14.45 k Pa, respectively. LSM was significantly superior to fibrosis-4, glutaglumyl-transferase/platelet ratio, and aspartate aminotransferase-to-platelet ratio index scores in detecting severe fibrosis(F ≥ 3)(0.910 vs 0.715, P < 0.01; 0.910 vs 0.649, P < 0.01; 0.910 vs 0.616, P < 0.01, respectively).CONCLUSION TE can accurately detect hepatic fibrosis as a noninvasive method in patients with AIH-PBC overlap syndrome.Hui-Min Wu Li Sheng Qi Wang Han Bao Qi Miao Xiao Xiao Can-Jie Guo Hai Li Xiong Ma De-Kai Qiu Jing Hua 2018World Journal of Gastroenterology2018,24,6:13
14Non-invasive assessment of liver fibrosis in patients with alcoholic liver disease显示文摘Alcoholic liver disease(ALD) consists of a broad spectrum of disorders, ranging from simple steatosisto alcoholic steatohepatitis and cirrhosis. Fatty liver develops in more than 90% of heavy drinkers, however only 30%-35% of them develop more advanced forms of ALD. Therefore, even if the current 'gold standard' for the assessment of the stage of alcohol-related liver injury is histology, liver biopsy is not reasonable in all patients who present with ALD. Currently, although several non-invasive fibrosis markers have been suggested as alternatives to liver biopsy in patients with ALD, none has been sufficiently validated. As described in other liver disease, the diagnostic accuracy of such tests in ALD is acceptable for the diagnosis of significant fibrosis or cirrhosis but not for lesser fibrosis stages. Existing data suggest that the use of noninvasive tests could be tailored to first tier screening of patients at risk, in order to diagnose early patients with progressive liver disease and offer targeted interventions for the prevention of decompensation. We review these tests and critically appraise the existing evidence.Rosa Lombardi Elena Buzzetti Davide Roccarina Emmanuel A Tsochatzis 2015World Journal of Gastroenterology2015,21,39:13
15A transient energy function for power systems including the induction motor model显示文摘A construction method for power system transient energy function is studied in the paper, which is simple and universal, and can unify the forms of some current en- ergy functions. A transient energy function including the induction motor model is derived using the method. The unintegrable term is dealt with to get an approxi- mate energy function. Simulations in a 3-bus system and in the WSCC 4-generator system verify the validity of the proposed energy function. The function can be applied to direct transient stability analysis of multi-machine large power systems and provides a tool for analysis of the interaction between the generator angle stability and the load voltage stability.MIN Yong CHEN Lei 2007Science China(Technological Sciences)2007,50,5:12
16A method for the production and expedient screening of CRISPR/Cas9-mediated non-transgenic mutant plants显示文摘Developing CRISPR/Cas9-mediated non-transgenic mutants in asexually propagated perennial crop plants is challenging but highly desirable.Here,we report a highly useful method using an Agrobacterium-mediated transient CRISPR/Cas9 gene expression system to create non-transgenic mutant plants without the need for sexual segregation.We have also developed a rapid,cost-effective,and high-throughput mutant screening protocol based on Illumina sequencing followed by high-resolution melting(HRM)analysis.Using tetraploid tobacco as a model species and the phytoene desaturase(PDS)gene as a target,we successfully created and expediently identified mutant plants,which were verified as tetra-allelic mutants.We produced pds mutant shoots at a rate of 47.5%from tobacco leaf explants,without the use of antibiotic selection.Among these pds plants,17.2%were confirmed to be non-transgenic,for an overall non-transgenic mutation rate of 8.2%.Our method is reliable and effective in creating non-transgenic mutant plants without the need to segregate out transgenes through sexual reproduction.This method should be applicable to many economically important,heterozygous,perennial crop species that are more difficult to regenerate.Longzheng Chen Wei Li Lorenzo Katin-Grazzini Jing Ding Xianbin Gu Yanjun Li Tingting Gu Ren Wang Xinchun Lin Ziniu Deng Richard J.McAvoy Frederick G.Gmitter Jr. Zhanao Deng Yunde Zhao Yi Li 2018Horticulture Research2018,5,1:12
17Investigation on transient electromagnetic scattering from a randomly rough surface and the perfect electric conductor target with an arbitrary cross section above it显示文摘The Time-Domain-Integral-Equation (TDIE) method is proposed to analyze transient scattering interaction between a two-dimensional infinitely long conducting target with an arbitrary cross section and a one-dimensional rough surface. Based on the electric-field-integral-equation in time domain, the explicit and implicit solutions of MOT (Marching-on-time) are derived and presented. The current response at the center of the rough surface and the far electric field response with time in the composite model are calculated and analyzed. The numerical results are compared and verified with those obtained by conventional MOM-IDFT (Method of Moment-inverse discrete Fourier transform). Finally, the influence of the size, the location of the target and the incident angle on the current response and the far electric fields response are discussed in detail.WANG Rui GUO LiXin LI Juan LIU XiaoYong 2009Science China(Physics,Mechanics & Astronomy)2009,52,5:11
18圆锥型场源瞬变电磁法测量数据反演(英文)显示文摘瞬变电磁法多匝小线圈装置是应用于地下有限空间、复杂地表地形的有效装置,但该装置的重叠绕制方式使其互感影响大,关断时间长。与之相比,我们提出的圆锥型场源的电感弱,关断时间短,可以有效兼顾减弱互感和适应复杂地形针对圆锥型场源场值,我们基于叠加原理,采用汉克尔变换和数值滤波法对层状介质中圆锥型场源进行了正演,验证了该场源的优势、探索了其激发的瞬变场特征,但由其激发的数据处理方法研究仍显不足。基于此,本文开展了根据'烟圈'反演结果设定初始模型的阻尼最小二乘反演方法研究。对瞬变电磁正演所获得的视电阻率进行'烟圈'反演,以'烟圈'反演结果设定的初始模型在频率域内进行了阻尼最小二乘反演。同时,从初始模型角度对阻尼最小二乘反演方法进行了改进,提出了以'烟圈'反演曲线的极值点和拐点为基点,建立阻尼最小二乘反演初始模型的方法。理论数据与实测数据反演结果表明,所研究的反演方法不仅使反演电阻率和层厚得到改善,也弥补了常规'烟圈'反演不具有分层效果的缺点,可以获得相对满意的层状反演结果。杨海燕 李锋平 Chen Shen-En 岳建华 郭福生 陈晓 张华 2018Applied Geophysics2018,15,3:11
19Ultrafast hydrogen bond dynamics of liquid water revealed by terahertz-induced transient birefringence显示文摘The fundamental properties of water molecules,such as their molecular polarizability,have not yet been clarified.The hydrogen bond network is generally considered to play an important role in the thermodynamic properties of water.The terahertz(THz)Kerr effect technique,as a novel tool,is expected to be useful in exploring the low-frequency molecular dynamics of liquid water.Here,we use an intense and ultrabroadband THz pulse(peak electric field strength of 14.9 MV/cm,centre frequency of 3.9 THz,and bandwidth of 1–10 THz)to resonantly excite intermolecular modes of liquid water.Bipolar THz field-induced transient birefringence signals are observed in a free-flowing water film.We propose a hydrogen bond harmonic oscillator model associated with the dielectric susceptibility and combine it with the Lorentz dynamic equation to investigate the intermolecular structure and dynamics of liquid water.We mainly decompose the bipolar signals into a positive signal caused by hydrogen bond stretching vibration and a negative signal caused by hydrogen bond bending vibration,indicating that the polarizability perturbation of water presents competing contributions under bending and stretching conditions.A Kerr coefficient equation related to the intermolecular modes of water is established.The ultrafast intermolecular hydrogen bond dynamics of water revealed by an ultrabroadband THz pump pulse can provide further insights into the transient structure of liquid water corresponding to the pertinent modes.Hang Zhao Yong Tan Liangliang Zhang Rui Zhang Mostafa Shalaby Cunlin Zhang Yuejin Zhao Xi-Cheng Zhang 2020Light(Science & Applications)2020,9,1:10
20Rainfall-induced landslide stability analysis in response to transient pore pressure——A case study of natural terrain landslide in Hong Kong显示文摘Transient pore pressure in response to short intense rainfall process plays an important role in shallow landslide occurrence. Using GIS technology, we carry out the rainfall-induced landslide stability analysis in response to transient pore pressure by means of transient and unsaturated rainfall infiltration modeling. A case study is performed on the shallow landslide stability analysis in Hong Kong. Detailed analysis and discussion reached some useful conclusions on the tempo-spatial behavior and characteristics of slope stability response and pore pressure response to typical rainfall process. Comparison analysis is performed on some important issues including landslide stability response in different types of slopes with different hydraulic properties, antecedent rainfall and landslide stability, and the nature of pore pressure response time. These studies might give us an important insight into landslide tringgering mechanism and the hydrological process in response to rainfall, and provide systematic information and evidences for effective risk assessment and warning system establishment.LAN Hengxing, ZHOU Chenghu C. F. LeeWANG Sijing & WU Faquan State Key Laboratory of Natural Resources and Environmental System, Institute of Geographical Sci-ences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China Department of Civil Engineering, Hong Kong University, Hong Kong, China 3. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 2003Science China(Technological Sciences)2003,46,z1:10
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