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Optimal b value of diffusion-weighted imaging on a 3.0T magnetic resonance scanner in Crohn's disease

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World Journal of Gastroenterology 2014年第35期20卷 12621-12627页

作者： Qi Feng Yun-Qi Yan Jiong Zhu Jin-Lu Tong Jian-Rong Xu Department of Radiology Renji HospitalSchool of MedicineShanghai Jiao Tong University Department of Gastroenterology Renji HospitalSchool of MedicineShanghai Jiao Tong University

AIM: To determine the optimal b value of diffusion-weighted imaging for detecting active inflammation in Crohn’s disease.

关键词： Crohn’ s disease Diffusion-weighted imaging b value Magnetic resonance image 3.0 Tesla

Cumulative　frequency　b　value　without　upper　bound　magnitude　and　its　regression　determination

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Earthquake Science 1994年第S1期7卷 80-89页

作者：沈建文

This paper points out that it is theoretically wrong for the traditional method to determine cumulatiove b value using linear regression and derive earthquake recurrence relation according to probability distribution or density function. As a result, it always systematically overestimated b value so as to underestimate the frequencies of the part of larger earthquakes. The smaller the actual b in the research area, or the smaller the magnitude range of the data in regression, or the smaller the magnitude interval, the larger the above deviation. So for an area with lower upper bound magnitude, if only historic earthquake data are used to determine b value by regression method, the b value will be obviously overestimated and systematic deviation of seismic hazard will be arised because the lower bound magnitude of reliable data is high and the magnitude range of data is small. In this paper, it is suggested to substitude cumulative b value without upper bound magnitude for conventional cumulative b value with upper bound magnitude, and the regression method is devloped to determine b value without upper bound magnitude.

关键词： b value earthquake recurrence relation seismic hazard analysis

Diffusion-weighted Single-shot Echo Planar MR Imaging of Normal Human Prostate Using Different b values

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Journal of Huazhong University of Science and Technology(Medical Sciences) 2008年第6期28卷 737-740页

作者：石浩军孔祥泉冯敢生徐海波刘定西于群 Department of Radiology Union HospitalTongji Medical CollegeHuazhong University of Science and Technology

This study examined the effect of different b values on diffusion-weighted MR imaging （DWI） of human prostate by using single-shot spin echo echo planar imaging （SE-EPI） sequences, observed the normal appearances and measured apparent diffusion coefficient （ADC） values in anatomical regions of normal prostate. Twenty-four healthy volunteers （mean age： 32 y） were studied by using a 1.5T system with a phased array surface multicoil. Two kinds of single-shot SE-EPI sequence were used to perform DWI in the prostate in volunteers, with five b values being 0, 30, 300, 500 to 1000 s/mm2. The image quality with different imaging parameters was analyzed and the ADC values in anatomical regions of normal prostate were measured. DWI of prostate was successfully obtained in all volunteers. The images were of good quality, without artifacts containing pixels within the prostate. The contrast was good between the different anatomical regions of the prostatic gland, i.e., the peripheral zone （PZ）, which exhibited higher signal intensity, and the central gland （CG）. Signal intensity contrast was related to the magnitude of b values. The ADC values in PZ and CG were （1.27±0.22）×10-3 mm2/s and （1.01±0.17）×10-3 mm2/s,respectively. The ADC values were found to be significantly higher in PZ than in CG （P〈0.05, paired t-test）. Significant differences were found between the slice-selecting component and both the read-out and phase-encoding components of the ADC values. It is concluded that SE-EPI is a suitable DWI sequence for human prostate. The contrast between PZ and CG is good when b values are low, while the diffusion and ADC values are accurate when b values are high. ADC values are higher in PZ than in CG in normal prostate. Diffusional anisotropy is present in normal prostatic tissue.

关键词： prostate magnetic resonance imaging diffusion-weighted imaging b value apparentdiffusion coefficient

Al(III) speciation distribution and transformation in high concentration PACl solutions

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Journal of Environmental Sciences 2006年第5期18卷 872-879页

作者： HUANG Li TANG Hong-xiao WANG Dong-sheng WANG Shui-feng DENG Zai-jun State Key Lab of Environmental Aqueous Chemistry Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China Analytical and Testing Center Beijing Normal University Beijing 100875 China

Effects of Al（Ⅲ） concentration and pH on the speciation of Al（Ⅲ） in polyaluminum chloride （PACl） solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al（Ⅲ） concentration from 0.01 to 2.0 mol/L with the b （OH/Al ratio） value from 1.0 to 2.5 by forced hydrolysis of AICl3. The samples were characterized by ferron assay, pH and 27^Al NMR. It was shown that the Al（Ⅲ） concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb （or Al13） decreased and Al0 increased with increase of total Al（Ⅲ） concentration. Under the condition of Al（Ⅲ） 2.0 reel/L, b = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evoIved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.

关键词： PACl Al13 b value pH speciation

Influence of statistical time range on estimating seismicity parameters

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Acta Seismologica Sinica(English Edition) 2001年第6期14卷 626-633页

作者：黄玮琼吴宣 Institute of Geophysics China Seismological Bureau Beijing China

The influence of non-uniqueness in selecting statistical time ranges on seismicity parameters of b value and annual mean occurrence rate ν4 is widely analyzed and studied. The studied result states that the influence of statistical time range on the b value is generally smaller than on the annual mean rate. Owing to the exponentially functional relation between the annual mean rate and b value, the variation of b value by varying statistical time range brings about decrease or increase in the annual mean rates of each magnitude interval with power progression law. These results will exert a synthetic effect on seismic safety evaluation results in various regions in our country.

关键词： statistical time range b value annual mean occurrence rate uncertainty

Numerical simulation of the segmentation of the stress state of the Anninghe-Zemuhe-Xiaojiang faults

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Science China Earth Sciences 2016年第12期59卷 384-396页

作者： ZHU AiYu ZHANG DongNing JIANG ChangSheng Institute of Geophysics China Earthquake Administration

We established a three-dimensional finite element model of the Anninghe-Zemuhe-Xiaojiang faults region using contact surfaces of different sizes to describe the spatial segmentation characteristics of the faults. Our model is based on constraints from GPS observations, models of the crust and upper mantle, precise earthquake locations, the tectonic stress field, the slip rate of the faults, and the rheology of the lithosphere in the Sichuan-Yunnan area. Considering the influence of strong earthquakes since A.D. 1327, we analyzed the main controlling factors of the characteristics of the strong earthquakes and also studied by numerical simulation the possible areas of future earthquake risk and their relationship with tectonic stress. The numerical results showed that the gravitational potential energy of the Qinghai-Tibet Plateau and the interaction of adjacent blocks are the main kinetic factors affecting the characteristics of the tectonic stress distribution. There appears to be some correspondence between the distribution of tectonic stress and the b value; however, we also found that some low b value locations correspond to regions of lower stress. This contradiction may be the result of some comprehensive factors, such as the release of strain energy caused by strong earthquakes.

关键词： Anninghe-Zemuhe-Xiaojiang faults Stress state Gravitational potential energy b value Numerical simulation

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Evaluation of diffusion weighted imaging of magnetic resonance imaging in small focal hepatic lesions:a quantitative study in 56 cases

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Hepatobiliary & Pancreatic Diseases International 2005年第3期4卷 406-409页

作者： Xian-Yue Quan, Xi-Jie Sun, Zhi-Jian Yu and Ming Tang Imaging Center, Affiliated Zhujiang Hospital of Southern Medical University, Guangzhou 510282, China Imaging Center Affiliated Zhujiang Hospital of Southern Medical University Guangzhou 510282 China. quanxianyue@***

Diffusion-weighted imaging (DWI) as a new technique of magnetic resonance imaging (MRI) is used to detect focal hepatic lesions. This study was designed to evaluate the significance of DWI to differentiate focal hepatic lesions less than 3 cm in diameter by the quantitation of apparent diffusion coefficient (ADC) values. METHODS:DWI using 1.5T MRI scanner unit was performed with a spin-echo single-shot echo planar imaging (EPI) in 56 cases of small focal hepatic lesions, including hepatocellular carcinoma (11), hepatic metastatic tumor (15 ), hepatic cavernous hemangioma (14), and hepatic cyst (16).The ADC values of these lesions were calculated respectively. The ratios of the ADC values of lesion/liver in hepatocellular carcinomas and hepatic metastatic tumors were also estimated. RESULTS:The mean ADC values (mm2/s) were (0.93±0.06) ×10-3 in hepatocellular carcinomas, (1.09±0.18)×10-3 in hepatic metastatic tumors,(1.95±0.38)×10-3 in hepatic cavernous hemangiomas, and (3.18±0.33) ×10-3 in hepatic cysts. The ratios of ADC values of lesion/liver were 0.90±0.06 and 1.15±0.14 in hepatocellular carcinoma and hepatic metastatic tumors respectively, which were significantly different (Pvalues and the ratios of ADC values of lesion/liver are helpful in MR diagnosis and differentiation of focal hepatic lesions.

关键词： quantitative study diffusion-weighted imaging apparent diffusion coefficient magnetic resonance imaging b value

Research on Strong Earthquake Tendency on Active Tectonic block boundaries in the Chinese Mainland

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Earthquake Research in China 2011年第2期25卷 189-200页

作者： Zhang Langping Li Zhixiong Shao Zhigang Yin Xiangchu Institute of Earthquake Science China Earthquake Administration Beijing 100036 China State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

Previous studies have shown that the active tectonic block boundaries in the Chinese mainland are the main belts and concentration areas of strong earthquakes occurring in the Chinese *** is essential to carry out follow-up analysis of strong earthquake risk of active tectonic block *** this paper,we carry out the analysis on the tendency of strong earthquakes along each active tectonic block boundary from three aspects respectively,including the evolutionary characteristics of the Load/Unload Response Ratio time series,the probability method based on the log-normal distribution function,and variation of b *** estimation of strong earthquake criticality on each active tectonic block boundary is done based on the evolutionary characteristics of the Load/Unload Response Ratio time series,the cumulative probability and conditional probability,and the decrease of the b ***,according to the results of analyses on the above three aspects,the potential strong earthquake areas in the forthcoming 5 years in the Chinese mainland are discussed.

关键词： Active tectonic-block boundary Load/Unload Response Ratio (LURR) Log-normal distribution b value Strong earthquake tendency Chinese mainland

Study on Uncertainties of Seismicity Parameters b and ν_4 in Seismic Statistical Zones

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Earthquake Research in China 2007年第3期21卷 318-326页

作者： Pan Hua Li Jinchen Li Zhiguo Institute of Geophysics China Earthquake Administration Beijing 100081 China

For several seismic statistical zones in North China, the key factors causing uncertainties in the important seismicity parameters b and v4 and the features of their uncertainties are discussed in this paper. The magnitude of uncertainty is also analyzed. It can be seen that the key influencing factors are statistical period, methods of processing statistical samples, lower limit magnitude and the annual average occurrence ratio of large earthquakes. The variation ranges of b and v4 in the Tancheng-Lujiang zone are as high as 0.2 and 1. 4 respectively, which are similar to those in the Fenwei zone. They are much smaller however in the Hebei zone because of its sufficient statistical samples.

关键词： Seismic statistical zone Seismicity parameters b value v4 Uncertainty