Retrofit Of Gas Lubricated Face Seals In A Centrifugal Compressor.

LecturePg. 75-84There are significant advantages in using gas lubricated face seals (dry gas seals) in centrifugal compressor service. Foremost among these are the elimination of the seal oil system resulting in lower maintenance, increased safety, and higher operating availability. For these reasons, one of four identical compressors at an installation having severe problems with seal oil contamination was selected for trial conversion to dry gas seals. The rotordynamic engineering portion of this job was done by the compressor manufacturer in conjunction with the gas seal supplier. The seal assembly was designed so that it would be essentially a drop-in conversion from a mechanical standpoint. Rotordynamic studies indicated that the conversion would result in a "better" machine. Unfortunately, sustained operations were not possible, due to excessive vibration levels at startup with the new seals. The shaft vibration exceeded 0.007 in, peak-to-peak, at a subsynchronous frequency of 4900 rpm (the machine rated speed is in excess of 10,000 rpm). These levels were sufficiently high to cause extensive damage to all internal labyrinths. The midspan labyrinths were wiped open in excess of 0.060 in, radial. Analysis of tape recorded data indicated that the vibration was due to a rotor/bearing system dynamic instability. Additional computer simulations of the compressor rotordynamics revealed that the oil seals had provided sufficient damping to the system to bound the instability. This extra damping was not being provided by the gas seals. Bearing redesign to increase stability and realignment of the rotor within the bundle to remove suspected excitation appear to have eliminated the problem

Michigan's Continuing Abolition of the Death Penalty and the Conceptual Components of Symbolic Legislation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68316/2/10.1177_096466399300200304.pd

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Racial disparity trends in childrens dental visits: US National Health Interview Survey, 1964-2010.

BACKGROUND AND OBJECTIVE: Research that has repeatedly documented marked racial/ethnic disparities in US childrens receipt of dental care at single time points or brief periods has lacked a historical policy perspective, which provides insight into how these disparities have evolved over time. Our objective was to examine the im-pact of national health policies on African American and white childrens receipt of dental care from 1964 to 2010. METHODS: We analyzed data on race and dental care utilization for children aged 2 to 17 years from the 1964, 1976, 1989, 1999, and 2010 National Health Interview Survey. Dependent variables were as follows: childs receipt of a dental visit in the previous 12 months and childs history of never having had a dental visit. Primary independent variable was race (African American/white). We calculated sample prevalences, and χ(2) tests compared African American/white prevalences by year. We age-standardized estimates to the 2000 US Census. RESULTS: The percentage of African American and white children in the United States without a dental visit in the previous 12 months declined significantly from 52.4% in 1964 to 21.7% in 2010, whereas the percentage of children who had never had a dental visit declined significantly (P < .01) from 33.6% to 10.6%. Pronounced African American/white disparities in childrens dental utilization rates, whereas large and statistically significant in 1964, attenuated and became nonsignificant by 2010. CONCLUSIONS: We demonstrate a dramatic narrowing of African American/white disparities in 2 measures of childrens receipt of dental services from 1964 to 2010. Yet, much more needs to be done before persistent racial disparities in childrens oral health status are eliminated

An examination of racial/ethnic disparities in children's oral health in the United States.

ObjectiveTo assess the extent factors other than race/ethnicity explain apparent racial/ethnic disparities in children's oral health and oral health care.MethodsData were from the 2007 National Survey of Children's Health, for children 2-17 years (n=82,020). Outcomes included parental reports of child's oral health status, receiving preventive dental care, and delayed dental care/unmet need. Model-based survey-data-analysis examined racial/ethnic disparities, controlling for child, family, and community/state (contextual) factors.ResultsUnadjusted results show large racial/ethnic oral health disparities. Compared with non-Hispanic White people, Hispanic and non-Hispanic-Black people were markedly more likely to be reported in only fair/poor oral health [odds ratios (ORs) (95% confidence intervals) 4.3 (4.0-4.6), 2.2 (2.0-2.4), respectively], lack preventive care [ORs 1.9 (1.8-2.0), 1.4 (1.3-1.5)], and experience delayed care/unmet need [ORs 1.5 (1.3-1.7), 1.4 (1.3-1.5)]. Adjusting for child, family, and community/state factors reduced racial/ethnic disparities. Adjusted ORs (AORs) for Hispanics and non-Hispanic Blacks attenuated for fair/poor oral health, to 1.6 (1.5-1.8) and 1.2 (1.1-1.4), respectively. Adjustment eliminated disparities for lacking preventive care [AORs 1.0 (0.9-1.1), 1.1 (1.1-1.2)] and in Hispanics for delayed care/unmet need (AOR 1.0). Among non-Hispanic Blacks, adjustment reversed the disparity for delayed care/unmet need [AOR 0.6 (0.6-0.7)].ConclusionsRacial/ethnic disparities in children's oral health status and access were attributable largely to socioeconomic and health insurance factors. Efforts to decrease disparities may be more efficacious if targeted at social, economic, and other factors associated with minority racial/ethnic status and may have positive effects on all who share similar social, economic, and cultural characteristics

Racial disparity trends in children's dental visits: US National Health Interview Survey, 1964-2010.

Background and objectiveResearch that has repeatedly documented marked racial/ethnic disparities in US children's receipt of dental care at single time points or brief periods has lacked a historical policy perspective, which provides insight into how these disparities have evolved over time. Our objective was to examine the im-pact of national health policies on African American and white children's receipt of dental care from 1964 to 2010.MethodsWe analyzed data on race and dental care utilization for children aged 2 to 17 years from the 1964, 1976, 1989, 1999, and 2010 National Health Interview Survey. Dependent variables were as follows: child's receipt of a dental visit in the previous 12 months and child's history of never having had a dental visit. Primary independent variable was race (African American/white). We calculated sample prevalences, and χ(2) tests compared African American/white prevalences by year. We age-standardized estimates to the 2000 US Census.ResultsThe percentage of African American and white children in the United States without a dental visit in the previous 12 months declined significantly from 52.4% in 1964 to 21.7% in 2010, whereas the percentage of children who had never had a dental visit declined significantly (P < .01) from 33.6% to 10.6%. Pronounced African American/white disparities in children's dental utilization rates, whereas large and statistically significant in 1964, attenuated and became nonsignificant by 2010.ConclusionsWe demonstrate a dramatic narrowing of African American/white disparities in 2 measures of children's receipt of dental services from 1964 to 2010. Yet, much more needs to be done before persistent racial disparities in children's oral health status are eliminated

An examination of racial/ethnic disparities in children's oral health in the United States

ObjectiveTo assess the extent factors other than race/ethnicity explain apparent racial/ethnic disparities in children's oral health and oral health care.MethodsData were from the 2007 National Survey of Children's Health, for children 2-17 years (n=82,020). Outcomes included parental reports of child's oral health status, receiving preventive dental care, and delayed dental care/unmet need. Model-based survey-data-analysis examined racial/ethnic disparities, controlling for child, family, and community/state (contextual) factors.ResultsUnadjusted results show large racial/ethnic oral health disparities. Compared with non-Hispanic White people, Hispanic and non-Hispanic-Black people were markedly more likely to be reported in only fair/poor oral health [odds ratios (ORs) (95% confidence intervals) 4.3 (4.0-4.6), 2.2 (2.0-2.4), respectively], lack preventive care [ORs 1.9 (1.8-2.0), 1.4 (1.3-1.5)], and experience delayed care/unmet need [ORs 1.5 (1.3-1.7), 1.4 (1.3-1.5)]. Adjusting for child, family, and community/state factors reduced racial/ethnic disparities. Adjusted ORs (AORs) for Hispanics and non-Hispanic Blacks attenuated for fair/poor oral health, to 1.6 (1.5-1.8) and 1.2 (1.1-1.4), respectively. Adjustment eliminated disparities for lacking preventive care [AORs 1.0 (0.9-1.1), 1.1 (1.1-1.2)] and in Hispanics for delayed care/unmet need (AOR 1.0). Among non-Hispanic Blacks, adjustment reversed the disparity for delayed care/unmet need [AOR 0.6 (0.6-0.7)].ConclusionsRacial/ethnic disparities in children's oral health status and access were attributable largely to socioeconomic and health insurance factors. Efforts to decrease disparities may be more efficacious if targeted at social, economic, and other factors associated with minority racial/ethnic status and may have positive effects on all who share similar social, economic, and cultural characteristics