Dysbiosis in the intestinal microflora can affect the gut production of microbial metabolites,and toxic substances can disrupt the barrier function of the intestinal wall,leading to the development of various diseases...Dysbiosis in the intestinal microflora can affect the gut production of microbial metabolites,and toxic substances can disrupt the barrier function of the intestinal wall,leading to the development of various diseases.Decreased levels of Clostridium subcluster XIVa(XIVa)are associated with the intestinal dysbiosis found in inflammatory bowel disease(IBD)and Clostridium difficile infection(CDI).Since XIVa is a bacterial group responsible for the conversion of primary bile acids(BAs)to secondary BAs,the proportion of intestinal XIVa can be predicted by determining the ratio of deoxycholic acid(DCA)/[DCA+cholic acid(CA)]in feces orserum.For example,serum DCA/(DCA+CA)was significantly lower in IBD patients than in healthy controls,even in the remission period.These results suggest that a low proportion of intestinal XIVa in IBD patients might be a precondition for IBD onset but not a consequence of intestinal inflammation.Another report showed that a reduced serum DCA/(DCA+CA)ratio could predict susceptibility to CDI.Thus,the BA profile,particularly the ratio of secondary to primary BAs,can serve as a surrogate marker of the intestinal dysbiosis caused by decreased XIVa.展开更多
Hybrid clustering combines partitional and hierarchical clustering for computational effectiveness and versatility in cluster shape. In such clustering, a dissimilarity measure plays a crucial role in the hierarchical...Hybrid clustering combines partitional and hierarchical clustering for computational effectiveness and versatility in cluster shape. In such clustering, a dissimilarity measure plays a crucial role in the hierarchical merging. The dissimilarity measure has great impact on the final clustering, and data-independent properties are needed to choose the right dissimilarity measure for the problem at hand. Properties for distance-based dissimilarity measures have been studied for decades, but properties for density-based dissimilarity measures have so far received little attention. Here, we propose six data-independent properties to evaluate density-based dissimilarity measures associated with hybrid clustering, regarding equality, orthogonality, symmetry, outlier and noise observations, and light-tailed models for heavy-tailed clusters. The significance of the properties is investigated, and we study some well-known dissimilarity measures based on Shannon entropy, misclassification rate, Bhattacharyya distance and Kullback-Leibler divergence with respect to the proposed properties. As none of them satisfy all the proposed properties, we introduce a new dissimilarity measure based on the Kullback-Leibler information and show that it satisfies all proposed properties. The effect of the proposed properties is also illustrated on several real and simulated data sets.展开更多
文摘Dysbiosis in the intestinal microflora can affect the gut production of microbial metabolites,and toxic substances can disrupt the barrier function of the intestinal wall,leading to the development of various diseases.Decreased levels of Clostridium subcluster XIVa(XIVa)are associated with the intestinal dysbiosis found in inflammatory bowel disease(IBD)and Clostridium difficile infection(CDI).Since XIVa is a bacterial group responsible for the conversion of primary bile acids(BAs)to secondary BAs,the proportion of intestinal XIVa can be predicted by determining the ratio of deoxycholic acid(DCA)/[DCA+cholic acid(CA)]in feces orserum.For example,serum DCA/(DCA+CA)was significantly lower in IBD patients than in healthy controls,even in the remission period.These results suggest that a low proportion of intestinal XIVa in IBD patients might be a precondition for IBD onset but not a consequence of intestinal inflammation.Another report showed that a reduced serum DCA/(DCA+CA)ratio could predict susceptibility to CDI.Thus,the BA profile,particularly the ratio of secondary to primary BAs,can serve as a surrogate marker of the intestinal dysbiosis caused by decreased XIVa.
文摘Hybrid clustering combines partitional and hierarchical clustering for computational effectiveness and versatility in cluster shape. In such clustering, a dissimilarity measure plays a crucial role in the hierarchical merging. The dissimilarity measure has great impact on the final clustering, and data-independent properties are needed to choose the right dissimilarity measure for the problem at hand. Properties for distance-based dissimilarity measures have been studied for decades, but properties for density-based dissimilarity measures have so far received little attention. Here, we propose six data-independent properties to evaluate density-based dissimilarity measures associated with hybrid clustering, regarding equality, orthogonality, symmetry, outlier and noise observations, and light-tailed models for heavy-tailed clusters. The significance of the properties is investigated, and we study some well-known dissimilarity measures based on Shannon entropy, misclassification rate, Bhattacharyya distance and Kullback-Leibler divergence with respect to the proposed properties. As none of them satisfy all the proposed properties, we introduce a new dissimilarity measure based on the Kullback-Leibler information and show that it satisfies all proposed properties. The effect of the proposed properties is also illustrated on several real and simulated data sets.
