Stress concentration investigations using NASTRAN

Parametic investigations are performed using several two dimensional finite element formulations to determine their suitability for use in predicting extremum stresses in marine propellers. Comparisons are made of two NASTRAN elements (CTRIM6 and CTRAIA2) wherein elasticity properties have been modified to yield plane strain results. The accuracy of the elements is investigated by comparing finite element stress predictions with experimentally determined stresses in two classical cases: (1) tension in a flat plate with a circular hole; and (2) a filleted flat bar subjected to in-plane bending. The CTRIA2 element is found to provide good results. The displacement field from a three dimensional finite element model of a representative marine propeller is used as the boundary condition for the two dimensional plane strain investigations of stresses in the propeller blade and fillet. Stress predictions from the three dimensional analysis are compared with those from the two dimensional models. The validity of the plane strain modifications to the NASTRAN element is checked by comparing the modified CTRIA2 element stress predictions with those of the ABAQUS plane strain element, CPE4

HIV, cardiovascular disease, anti-retroviral resistance: the issue with protease inhibitors and a need for alternatives

Today, it is estimated that 35 million people are living with human immunodeficiency virus (HIV). Since its initial discovery in 1981, researchers and medical providers have worked endless hours to understand the pathology, transmission, and medical management of HIV. In the early days of HIV, life expectancy after diagnosis was 10 years. However, after the development of zidovudine (AZT) in 1987, life expectancy of HIV patients began to slowly increase, albeit still lower than that of the general population. The development of AZT opened the door for more antiretroviral drugs and more drug classes. Now, patients undergo a triple drug regimen to manage HIV. These patients are able to maintain viral suppression and are no longer experiencing opportunistic infection or other AIDS-related conditions. While HIV is medically managed, this is a chronic condition and to-date, not cured. As opposed to opportunistic infections and other AIDS-related conditions, patients are succumbing to non-AIDs related conditions such as renal, neurological, bone disorders, and liver complications. The leading non-AIDs related condition is cardiovascular disease (CVD). Even with viral suppression, HIV infection itself contributes to the pathology and development of atherosclerosis and CVD. It is clear that chronic immune activation, HIV proteins, and dyslipidemia appear to be key factors in CVD development. Since the life expectancy of HIV patients has increased, physicians are now seeing an older generation of HIV patients. Medical providers are shifting focus toward understanding the long-term effects of not just HIV, but antiretroviral therapy (ART) as well. It appears that drug interactions and long-term toxicity augment CVD development. Protease inhibitors (PIs), compared to other ART drug classes, appear to increase the risk of atherosclerosis, especially through dyslipidemia. Due to management of HIV being life-long, compliance is difficult because of high pill burden, drug-drug interactions, and drug side effects. This can result in drug failure leading HIV patients to switch to second-line ART regimens. PIs are a common component of second-line ART regimens. Compared to other ART drugs, PIs have a high genetic barrier to resistance. However, PIs have a low bioavailability requiring high dosage and/or boosting with ritonavir (RTV). Lopinavir (LPV) boosted with RTV (LPV/r) is a favorable PI as it is used in a combination pill and is the most cost effective. However, multiple studies have shown LPV/r correlates more to CVD compared to other PIs. Patients on LPV/r exhibit an increased intima-medial thickening, a hallmark characteristic of atherosclerosis and an increased risk for myocardial infarction. Unfortunately, researchers are greatly conflicted as to why this is and in general why PIs increase the risk of CVD. Future medical treatment for HIV is complex and requires long-term medical management. In recent years, integrase inhibitors (IIs) have exhibited promise to provide better lipid profiles while maintaining viral suppression. However, as this drug class is relatively new and expensive, the financial burden on HIV patients is high. The next step toward addressing the global health issue of HIV is understanding the exact mechanism of how PIs contribute to CVD. This will not only increase the life expectancy of HIV patients, but reduce drug toxicity, non-AIDS related conditions, and increase adherence and viral suppression. It is clear that future research must be focused on understanding the role PIs have in CVD development. Physicians are seeing an older generation of HIV patients, and a vast majority are on second-line regimens. By understanding this relationship, researchers could design alternative drugs to manage CVD risk, by modifying current PIs or designing entirely new drugs

Prevalence of sealants in relation to dental caries on the permanent molars of 12 and 15-year-old Greek adolescents. A national pathfinder survey

<p>Abstract</p> <p>Background</p> <p>The use of sealants as an effective measure for the prevention of pit and fissure caries in children has been well documented by several studies; either they are used on an individual or on a public health basis. In order to plan and establish a national preventive program with sealants in a community, it is mandatory to know the epidemiological pattern of caries along with other variables influencing their use and effectiveness. Aims: To assess the utilization and distribution pattern of pit and fissure sealants on the first and second permanent molars of Greek adolescents and to evaluate whether the existing usage of sealants and some socio-demographic factors are correlated to caries prevalence on the population examined</p> <p>Methods</p> <p>A stratified cluster sample of 2481 Greek adolescents was selected according to WHO guidelines (1224 twelve and 1,257 fifteen-year-old), living in urban and rural areas in 11 districts within the country. Five calibrated examiners carried out clinical examinations, recording caries experience at the dentine threshold (BASCD criteria) and presence or absence of sealants along with Socio-demographic indicators associated with oral health. Mann Whitney and Pearson's chi-square non parametric tests were utilized for assessing the data. The level of significance was p < 0.05.</p> <p>Results</p> <p>Sealants utilization varied considerably within the different districts, with 8,3% of the 12 and 8,0% of the 15-year-old adolescents having at least one sealed molar. Sealants reduced DMFS scores by 11% in the 12-year-olds and by 24% in the 15-year-olds, while 15-year-old adolescents from rural areas had a statistically significant (p = 0.002) less chance of having sealants (71%) compared to children from urban areas. Girls had higher chance to receive sealants in both age groups (26% for the 12 and 19% for the 15-year-old) as well as patients that visited the dentist for prevention compared to those visiting the dentist because they thought they needed a restoration or because they were in pain.</p> <p>Conclusions</p> <p>The finding that sealants reduced DMFS scores despite their very low utilization, along with the high prevalence of dental caries found on the occlusal surfaces of the posterior teeth of Greek adolescents, is calling for a national preventive program with sealants which could eliminate caries to a larger extent.</p

Developmental delays and dental caries in low-income preschoolers in the USA: a pilot cross-sectional study and preliminary explanatory model

Abstract Background Anecdotal evidence suggests that low-income preschoolers with developmental delays are at increased risk for dental caries and poor oral health, but there are no published studies based on empirical data. The purpose of this pilot study was two-fold: to examine the relationship between developmental delays and dental caries in low-income preschoolers and to present a preliminary explanatory model on the determinants of caries for enrollees in Head Start, a U.S. school readiness program for low-income preschool-aged children. Methods Data were collected on preschoolers ages 3–5 years at two Head Start centers in Washington, USA (N = 115). The predictor variable was developmental delay status (no/yes). The outcome variable was the prevalence of decayed, missing, and filled surfaces (dmfs) on primary teeth. We used multiple variable Poisson regression models to test the hypothesis that within a population of low-income preschoolers, those with developmental delays would have increased dmfs prevalence than those without developmental delays. Results Seventeen percent of preschoolers had a developmental delay and 51.3% of preschoolers had ≥1 dmfs. Preschoolers with developmental delays had a dmfs prevalence ratio that was 1.26 times as high as preschoolers without developmental delays (95% CI: 1.01, 1.58; P < .04). Other factors associated with increased dmfs prevalence ratios included: not having a dental home (P = .01); low caregiver education (P < .001); and living in a non-fluoridated community (P < .001). Conclusions Our pilot data suggest that developmental delays among low-income preschoolers are associated with increased primary tooth dmfs. Additional research is needed to further examine this relationship. Future interventions and policies should focus on caries prevention strategies within settings like Head Start classrooms that serve low-income preschool-aged children with additional targeted home- and community-based interventions for those with developmental delays

Mesozioc basin development and structural inversion in the external French Alps

Imperial Users onl