Network hierarchy evolution and system vulnerability in power grids

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.The seldom addressed network hierarchy property and its relationship with vulnerability analysis for power transmission grids from a complex-systems point of view are given in this paper. We analyze and compare the evolution of network hierarchy for the dynamic vulnerability evaluation of four different power transmission grids of real cases. Several meaningful results suggest that the vulnerability of power grids can be assessed by means of a network hierarchy evolution analysis. First, the network hierarchy evolution may be used as a novel measurement to quantify the robustness of power grids. Second, an antipyramidal structure appears in the most robust network when quantifying cascading failures by the proposed hierarchy metric. Furthermore, the analysis results are also validated and proved by empirical reliability data. We show that our proposed hierarchy evolution analysis methodology could be used to assess the vulnerability of power grids or even other networks from a complex-systems point of view.Peer ReviewedPostprint (author's final draft

Racial and ethnic variations in preventive dental care utilization among middle-aged and older Americans, 1999-2008

Objective: This study examined recent trends of preventive dental care utilization among Americans aged 50 and above, focusing on variations across racial and ethnic groups including Whites, Blacks, Hispanics, American Indians/Alaska Natives, and Asians. Methods: Self-reported information on oral health behaviors was collected from 644,635 participants in the Behavioral Risk Factor Surveillance System between 1999 and 2008. Results: Despite a significant upward trend of frequency of dental cleaning from 1999 to 2008 (OR = 1.02), in 2008 still only 56–77% of any ethnic or racial group reported having had a dental cleaning in the previous 12 months. Relative to Whites, Blacks (OR = 0.65) were less likely to have a dental cleaning in the previous 12 months. These variations persisted even when SES, health conditions, health behaviors, and number of permanent teeth were controlled. In contrast, Hispanics, Asians, and American Indians/Alaskan Natives did not differ from Whites in dental cleanings. Discussion: This is the first study to provide national estimates of the frequency of dental cleaning and associated trends over time for five major ethnic groups aged 50 and above in the U.S. simultaneously. Our findings suggest that public health programs with an emphasis on educating middle-aged and older minority populations on the benefits of oral health could have a large impact, as there is much room for improvement. Given the importance of oral health and a population that is rapidly becoming older and more diverse, the need for improved dental care utilization is significant

SAGE II Measurements of Stratospheric Aerosol Properties at Non-Volcanic Levels

Since 2000, stratospheric aerosol levels have been relatively stable and at the lowest levels observed in the historical record. Given the challenges of making satellite measurements of aerosol properties at these levels, we have performed a study of the sensitivity of the product to the major components of the processing algorithm used in the production of SAGE II aerosol extinction measurements and the retrieval process that produces the operational surface area density (SAD) product. We find that the aerosol extinction measurements, particularly at 1020 nm, remain robust and reliable at the observed aerosol levels. On the other hand, during background periods, the SAD operational product has an uncertainty of at least a factor of 2 during due to the lack of sensitivity to particles with radii less than 100 nm

Edentulism trends among middle‐aged and older adults in the United States: comparison of five racial/ethnic groups

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90571/1/j.1600-0528.2011.00640.x.pd