High-dimensional Sparse Inverse Covariance Estimation using Greedy Methods

In this paper we consider the task of estimating the non-zero pattern of the sparse inverse covariance matrix of a zero-mean Gaussian random vector from a set of iid samples. Note that this is also equivalent to recovering the underlying graph structure of a sparse Gaussian Markov Random Field (GMRF). We present two novel greedy approaches to solving this problem. The first estimates the non-zero covariates of the overall inverse covariance matrix using a series of global forward and backward greedy steps. The second estimates the neighborhood of each node in the graph separately, again using greedy forward and backward steps, and combines the intermediate neighborhoods to form an overall estimate. The principal contribution of this paper is a rigorous analysis of the sparsistency, or consistency in recovering the sparsity pattern of the inverse covariance matrix. Surprisingly, we show that both the local and global greedy methods learn the full structure of the model with high probability given just $O(d\log(p))$ samples, which is a \emph{significant} improvement over state of the art $\ell_1$-regularized Gaussian MLE (Graphical Lasso) that requires $O(d^2\log(p))$ samples. Moreover, the restricted eigenvalue and smoothness conditions imposed by our greedy methods are much weaker than the strong irrepresentable conditions required by the $\ell_1$-regularization based methods. We corroborate our results with extensive simulations and examples, comparing our local and global greedy methods to the $\ell_1$-regularized Gaussian MLE as well as the Neighborhood Greedy method to that of nodewise $\ell_1$-regularized linear regression (Neighborhood Lasso).Comment: Accepted to AI STAT 2012 for Oral Presentatio

Racial/Ethnic Disparities in Provision of Dental Procedures to Children Enrolled in Delta Dental Insurance in Milwaukee, Wisconsin

Objectives: Most studies on the provision of dental procedures have focused on Medicaid enrollees known to have inadequate access to dental care. Little information on private insurance enrollees exists. This study documents the rates of preventive, restorative, endodontic, and surgical dental procedures provided to children enrolled in Delta Dental of Wisconsin (DDWI) in Milwaukee. Methods: We analyzed DDWI claims data for Milwaukee children aged 0-18 years between 2002 and 2008. We linked the ZIP codes of enrollees to the 2000 US Census information to derive racial/ethnic estimates in the different ZIP codes. We estimated the rates of preventive, restorative, endodontic, and surgical procedures provided to children in different racial/ethnic groups based on the population estimates derived from the US Census data. Descriptive and multivariable analysis was done using Poisson regression modeling on dental procedures per year. Results: In 7 years, a total of 266,380 enrollees were covered in 46 ZIP codes in the database. Approximately, 64 percent, 44 percent, and 49 percent of White, African American, and Hispanic children had at least one dental visit during the study period, respectively. The rates of preventive procedures increased up to the age of 9 years and decreased thereafter among children in all three racial groups included in the analysis. African American and Hispanic children received half as many preventive procedures as White children. Conclusion: Our study shows that substantial racial disparities may exist in the types of dental procedures that were received by children

Differences in Utilization of Dental Procedures by Children Enrolled in Wisconsin Medicaid And Delta Dental Insurance Plans

Background Few studies have directly compared dental procedures provided in public and private insurance plans for enrollees living in dental health professional shortage areas (DHPSAs). We examined the rates for the different types of dental procedures received by 0–18-year-old children living in DHPSAs and non-DHPSAs who were enrolled in Medicaid and those enrolled under Delta Dental of Wisconsin (DDW) for years 2002 to 2008. Methods Medicaid and DDW dental claims data for 2002 to 2008 was analyzed. Enrollees were divided into DDW-DHPSA and non-DHPSA and Medicaid-DHPSA and non-DHPSA groups. Descriptive and multivariable analyses using over-dispersed Poisson regression were performed to examine the effect of living in DHPSAs and insurance type in relation to the number of procedures received. Results Approximately 49 and 65 percent of children living in non-DHPSAs that were enrolled in Medicaid and DDW received at least one preventive dental procedure annually, respectively. Children in DDW non-DHPSA group had 1.79 times as many preventive, 0.27 times fewer complex restorative and 0.51 times fewer endodontic procedures respectively, compared to those in Medicaid non-DHPSA group. Children enrolled in DDW-DHPSA group had 1.53 times as many preventive and 0.25 times fewer complex restorative procedures, compared to children in Medicaid-DHPSA group. Conclusions DDW enrollees had significantly higher utilization rates for preventive procedures than children in Medicaid. There were significant differences across Medicaid and DDW between non-DHPSA and DHPSA for most dental procedures received by enrollees

Rural–Urban Differences in Dental Service Use Among Children Enrolled in a Private Dental Insurance Plan in Wisconsin: Analysis of Administrative Data

Background Studies on rural–urban differences in dental care have primarily focused on differences in utilization rates and preventive dental services. Little is known about rural–urban differences in the use of wider range of dental procedures. This study examined patterns of preventive, restorative, endodontic, and extraction procedures provided to children enrolled in Delta Dental of Wisconsin (DDWI). Methods We analyzed DDWI enrollment and claims data for children aged 0-18 years from 2002 to 2008. We modified and used a rural and urban classification based on ZIP codes developed by the Wisconsin Area Health Education Center (AHEC). We categorized the ZIP codes into 6 AHEC categories (3 rural and 3 urban). Descriptive and multivariable analysis using generalized linear mixed models (GLMM) were used to examine the patterns of dental procedures provided to children. Tukey-Kramer adjustment was used to control for multiple comparisons. Results Approximately, 50%, 67% and 68 % of enrollees in inner-city Milwaukee, Rural 1 (less than 2500 people), and suburban-Milwaukee had at least one annual dental visit, respectively. Children in inner city-Milwaukee had the lowest utilization rates for all procedures examined, except for endodontic procedures. Compared to children from inner-city Milwaukee, children in other locations had significantly more preventive procedures. Children in Rural 1-ZIP codes had more restorative, endodontic and extraction procedures, compared to children from all other regions. Conclusions We found significant geographic variation in dental procedures received by children enrolled in DDWI

Rural–Urban Differences in Dental Service Use Among Children Enrolled in a Private Dental Insurance Plan in Wisconsin: Analysis of Administrative Data

Background Studies on rural–urban differences in dental care have primarily focused on differences in utilization rates and preventive dental services. Little is known about rural–urban differences in the use of wider range of dental procedures. This study examined patterns of preventive, restorative, endodontic, and extraction procedures provided to children enrolled in Delta Dental of Wisconsin (DDWI). Methods We analyzed DDWI enrollment and claims data for children aged 0-18 years from 2002 to 2008. We modified and used a rural and urban classification based on ZIP codes developed by the Wisconsin Area Health Education Center (AHEC). We categorized the ZIP codes into 6 AHEC categories (3 rural and 3 urban). Descriptive and multivariable analysis using generalized linear mixed models (GLMM) were used to examine the patterns of dental procedures provided to children. Tukey-Kramer adjustment was used to control for multiple comparisons. Results Approximately, 50%, 67% and 68 % of enrollees in inner-city Milwaukee, Rural 1 (less than 2500 people), and suburban-Milwaukee had at least one annual dental visit, respectively. Children in inner city-Milwaukee had the lowest utilization rates for all procedures examined, except for endodontic procedures. Compared to children from inner-city Milwaukee, children in other locations had significantly more preventive procedures. Children in Rural 1-ZIP codes had more restorative, endodontic and extraction procedures, compared to children from all other regions. Conclusions We found significant geographic variation in dental procedures received by children enrolled in DDWI

Regioselective Reactions of Highly Substituted Arynes

The fully regioselective reactivity of four new highly substituted silyl aryl triflate aryne precursors in aryne acyl-alkylation, acyl-alkylation/condensation, and heteroannulation reactions is reported. The application of these more complex arynes provides access to diverse natural product scaffolds and obviates late-stage functionalization of aromatic rings

Cost Models for mHealth Intervention in Aged Care Diabetes Management

Governments across the globe are facing the challenges posed by ageing population. Diabetes is one of the leading causes of disease burden to the economies. A proactive management of diabetes for the elderly can offer benefits to all the stakeholders. Mobile Health (mHealth) can play a vital role to tackle the complexities associated with aged people who are living independently. While there have been several pilot studies of mHealth interventions in diabetes management, they have not made inroads into operational reality. The significant factors appear to be lack of comprehensive cost models and business case for mHealth interventions. The paper reviews some of the related research work and argues for the development of cost models for mHealth interventions in aged care diabetes management. It also presents the work-in-progress of creation of cost models and envisages that such a development will help the operational adoption of mHealth benefiting all the stakeholders

Cultural and review characteristics in the formation of trust in online product reviews: A multinational investigation

Recent changes in web technologies have given a voice to consumers in online discussion of products and services. While the web has long been a source of information about products and services, web content was controlled by those who knew how to develop for the web, or those who could hire web developers. The trend toward web software that permits novice users to contribute to conversations about products has been embraced by online retailers, who facilitate and encourage online user reviews of products. Researchers are just starting to understand the relationship between online user reviews and purchase intention, however have determined that trust is central to the development of purchase intention. In this study, we report the results of a simulation based web purchase experiment that included subjects in Colombia, the People’s Republic of China and the United States. The experiment included manipulations for both information quality and a social component of the review, and espoused culture scores of subjects where measured. We find that information quality, the social component and espoused uncertainty avoidance influence trust in the review. We were not able to support an interaction effect between information quality and uncertainty avoidance and trust, nor an interaction effect between the social component and collectivism