This paper considers the upper orthant and extremal tail dependence indices for multivariate t-copula. Where, the multivariate t-copula is defined under a correlation structure. The explicit representations of the tai...This paper considers the upper orthant and extremal tail dependence indices for multivariate t-copula. Where, the multivariate t-copula is defined under a correlation structure. The explicit representations of the tail dependence parameters are deduced since the copula of continuous variables is invariant under strictly increasing transformation about the random variables, which are more simple than those obtained in previous research. Then, the local monotonicity of these indices about the correlation coefficient is discussed, and it is concluded that the upper extremal dependence index increases with the correlation coefficient, but the monotonicity of the upper orthant tail dependence index is complex. Some simulations are performed by the Monte Carlo method to verify the obtained results, which are found to be satisfactory. Meanwhile, it is concluded that the obtained conclusions can be extended to any distribution family in which the generating random variable has a regularly varying distribution.展开更多
AIM： To investigate whether the small bowel transit time （SBTT） influences the diagnostic yield of capsule endoscopy （CE）. METHODS： Six hundred and ninety-one consecutive CE procedures collected in a database we...AIM： To investigate whether the small bowel transit time （SBTT） influences the diagnostic yield of capsule endoscopy （CE）. METHODS： Six hundred and ninety-one consecutive CE procedures collected in a database were analyzed. SBTT and CE findings were recorded. A running mean for the SBl-I- was calculated and correlated to the diagnostic yield with a Spearman＇s correlation test. Subgroup anal- yses were performed for the various indications for the procedure. RESULTS： There was a positive correlation between the diagnostic yield and SBT1- （Spearman＇s rho 0.58, P 〈 0.01）. Positive correlations between diagnostic yield and SB-FI-were found for the indication obscure gastro- intestinal bleeding （r = 0.54, P 〈 0.01）, for polyposis and carcinoid combined （r = 0.56, P 〈 0.01） and for the other indications （r = 0.90, P 〈0.01）, but not for suspected Crohn＇s disease （r = -0.40） CONCLUSION： The diagnostic yield in small bowel capsule endoscopy is positively correlated with the small bowel transit time. This is true for all indications except for suspected Crohn＇s disease.展开更多
Background Atrial fibrillation （AF） is associated with inflammation and endothelial dysfunction. However, the association between inflammation （as indexed by high-sensitivity C-reactive protein, hs-CRP） and endoth...Background Atrial fibrillation （AF） is associated with inflammation and endothelial dysfunction. However, the association between inflammation （as indexed by high-sensitivity C-reactive protein, hs-CRP） and endothelial function [as indexed by big endothelin-1 （ET-1）] in AF patients remains unclear. Methods We enrolled 128 patients with lone AF, among which 83 had paroxysmal AF, and 45 had persistent AF. Eighty-two age- and gender-matched controls of paroxysmal supraventricular tachycardia without AF history were evaluated. Plasma hs-CRP, big ET-1 levels and other clinical characteristics were compared among the groups. Results Patients with persistent AF had higher hs-CRP concentrations than those with paroxysmal AF （P 〈 0.05）, both groups had higher hs-CRP level than controls （P 〈 0.05）. Patients with persistent AF had higher big ET-1 level than those with paroxysmal AF, although the difference did not reach the statistical significance （P 〉 0.05）, and both groups had higher big ET-1 levels than controls （P 〈 0.05）. Multiple regression analyses revealed hs-CRP as an inde- pendent determinant of AF （P 〈 0.001）. Further adjusted for big ET-1, both big ET-1 and hs-CRP were independent predictors for AF （P 〈 0.001）, but the odds ratio for hs-CRP in predicting AF attenuated from 8.043 to 3.241. There was a positive relation between hs-CRP level and big ET-1 level in paroxysmal AF patients （r = 0.563, P 〈 0.05）, however, the relationship in persistent AF patients was poor （r = 0.094, P 〈 0.05）. Conclusions Both plasma hs-CRP and big ET-1 levels are elevated in lone AF patients, and are associated with AF. In paroxysmal lone AF patients, there were significant positive correlations between plasma hs-CRP level and big ET- 1 level.展开更多
基金The National Natural Science Foundation of China(No.11001052,11171065)the National Science Foundation of Jiangsu Province(No.BK2011058)the Science Foundation of Nanjing University of Posts and Telecommunications(No.JG00710JX57)
文摘This paper considers the upper orthant and extremal tail dependence indices for multivariate t-copula. Where, the multivariate t-copula is defined under a correlation structure. The explicit representations of the tail dependence parameters are deduced since the copula of continuous variables is invariant under strictly increasing transformation about the random variables, which are more simple than those obtained in previous research. Then, the local monotonicity of these indices about the correlation coefficient is discussed, and it is concluded that the upper extremal dependence index increases with the correlation coefficient, but the monotonicity of the upper orthant tail dependence index is complex. Some simulations are performed by the Monte Carlo method to verify the obtained results, which are found to be satisfactory. Meanwhile, it is concluded that the obtained conclusions can be extended to any distribution family in which the generating random variable has a regularly varying distribution.
基金Supported by A clinical fellow grant(90700281)from the Netherlands Organization for Scientific Research(NWO)
文摘AIM： To investigate whether the small bowel transit time （SBTT） influences the diagnostic yield of capsule endoscopy （CE）. METHODS： Six hundred and ninety-one consecutive CE procedures collected in a database were analyzed. SBTT and CE findings were recorded. A running mean for the SBl-I- was calculated and correlated to the diagnostic yield with a Spearman＇s correlation test. Subgroup anal- yses were performed for the various indications for the procedure. RESULTS： There was a positive correlation between the diagnostic yield and SBT1- （Spearman＇s rho 0.58, P 〈 0.01）. Positive correlations between diagnostic yield and SB-FI-were found for the indication obscure gastro- intestinal bleeding （r = 0.54, P 〈 0.01）, for polyposis and carcinoid combined （r = 0.56, P 〈 0.01） and for the other indications （r = 0.90, P 〈0.01）, but not for suspected Crohn＇s disease （r = -0.40） CONCLUSION： The diagnostic yield in small bowel capsule endoscopy is positively correlated with the small bowel transit time. This is true for all indications except for suspected Crohn＇s disease.
文摘Background Atrial fibrillation （AF） is associated with inflammation and endothelial dysfunction. However, the association between inflammation （as indexed by high-sensitivity C-reactive protein, hs-CRP） and endothelial function [as indexed by big endothelin-1 （ET-1）] in AF patients remains unclear. Methods We enrolled 128 patients with lone AF, among which 83 had paroxysmal AF, and 45 had persistent AF. Eighty-two age- and gender-matched controls of paroxysmal supraventricular tachycardia without AF history were evaluated. Plasma hs-CRP, big ET-1 levels and other clinical characteristics were compared among the groups. Results Patients with persistent AF had higher hs-CRP concentrations than those with paroxysmal AF （P 〈 0.05）, both groups had higher hs-CRP level than controls （P 〈 0.05）. Patients with persistent AF had higher big ET-1 level than those with paroxysmal AF, although the difference did not reach the statistical significance （P 〉 0.05）, and both groups had higher big ET-1 levels than controls （P 〈 0.05）. Multiple regression analyses revealed hs-CRP as an inde- pendent determinant of AF （P 〈 0.001）. Further adjusted for big ET-1, both big ET-1 and hs-CRP were independent predictors for AF （P 〈 0.001）, but the odds ratio for hs-CRP in predicting AF attenuated from 8.043 to 3.241. There was a positive relation between hs-CRP level and big ET-1 level in paroxysmal AF patients （r = 0.563, P 〈 0.05）, however, the relationship in persistent AF patients was poor （r = 0.094, P 〈 0.05）. Conclusions Both plasma hs-CRP and big ET-1 levels are elevated in lone AF patients, and are associated with AF. In paroxysmal lone AF patients, there were significant positive correlations between plasma hs-CRP level and big ET- 1 level.
