Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

<p>Highly reflective dielectric mirror coatings are critical components in a range of precision optics applications including frequency combs, optical atomic clocks, precision interferometry and ring laser gyroscopes. A key limitation to the performance in these applications is thermal noise, arising from the mechanical loss of the coatings. The origins of the mechanical loss from these coatings is not well understood.</p> <p>Recent work suggests that the mechanical loss of amorphous Ta2O5 coatings can drop by as much as 40% when it is doped with TiO2. We use a combination of electron diffraction data and atomic modelling using molecular dynamics to probe the atomic structure of these coatings, and examine the correlations between changes in the atomic structure and changes in the mechanical loss of these coatings. Our results show the first correlation between changes in the mechanical loss and experimentally measured changes in the atomic structure resulting from variations in the level of TiO2 doping in TiO2-doped Ta2O5 coatings, in that increased homogeneity at the nearest-neighbour level appears to correlate with reduced mechanical loss. It is demonstrated that subtle but measurable changes in the nearest-neighbour homogeneity in an amorphous material can correlate with significant changes in macroscopic properties.</p&gt

Time and length scales in supercooled liquids

We numerically obtain the first quantitative demonstration that development of spatial correlations of mobility as temperature is lowered is responsible for the ``decoupling'' of transport properties of supercooled liquids. This result further demonstrates the necessity of a spatial description of the glass formation and therefore seriously challenges a number of popular alternative theoretical descriptions.Comment: 4 pages, 4 figs; improved version: new refs and discussion

Molecular velocity auto-correlation of simple liquids observed by NMR MGSE method

The velocity auto-correlation spectra of simple liquids obtained by the NMR method of modulated gradient spin echo show features in the low frequency range up to a few kHz, which can be explained reasonably well by a $t^{-3/2}$ long time tail decay only for non-polar liquid toluene, while the spectra of polar liquids, such as ethanol, water and glycerol, are more congruent with the model of diffusion of particles temporarily trapped in potential wells created by their neighbors. As the method provides the spectrum averaged over ensemble of particle trajectories, the initial non-exponential decay of spin echoes is attributed to a spatial heterogeneity of molecular motion in a bulk of liquid, reflected in distribution of the echo decays for short trajectories. While at longer time intervals, and thus with longer trajectories, heterogeneity is averaged out, giving rise to a spectrum which is explained as a combination of molecular self-diffusion and eddy diffusion within the vortexes of hydrodynamic fluctuations.Comment: 8 pages, 6 figur

Adolescents' experience of comments about their weight – prevalence, accuracy and effects on weight misperception

<p>Abstract</p> <p>Background</p> <p>Weight comments are commonly received by adolescents, but the accuracy of the comments and their effects on weight misperception are unclear. We assessed the prevalence and accuracy of weight comments received by Chinese adolescents from different sources and their relation to weight misperception.</p> <p>Methods</p> <p>In the Hong Kong Student Obesity Surveillance (HKSOS) project 2006–07, 22612 students aged 11–18 (41.5% boys) completed a questionnaire on obesity. Students responded if family members, peers and professionals had seriously commented over the past 30 days that they were "too fat" or "too thin" in two separate questions. The accuracy of the comments was judged against the actual weight status derived from self-reported height and weight. Self-perceived weight status was also reported and any discordance with the actual weight status denoted weight misperception. Logistic regression yielded adjusted odd ratios for weight misperception by the type of weight comments received.</p> <p>Results</p> <p>One in three students received weight comments, and the mother was the most common source of weight comments. Health professional was the most accurate source of weight comments, yet less than half the comments were correct. Adolescents receiving incorrect comments had increased risk of having weight misperception in all weight status groups. Receiving conflicting comments was positively associated with weight misperception among normal weight adolescents. In contrast, underweight and overweight/obese adolescents receiving correct weight comments were less likely to have weight misperception.</p> <p>Conclusion</p> <p>Weight comments, mostly incorrect, were commonly received by Chinese adolescents in Hong Kong, and such incorrect comments were associated with weight misperception.</p

Factors Associated with Hepatitis B Testing Among Vietnamese Americans

Chronic hepatitis B and hepatitis B-associated liver cancer is a major health disparity among Vietnamese Americans, who have a chronic hepatitis B prevalence rate of 7–14% and an incidence rate for liver cancer six times that of non-Latino whites. Describe factors associated with hepatitis B testing among Vietnamese Americans. A population-based telephone survey conducted in 2007–2008. Vietnamese Americans age 18–64 and living in the Northern California and Washington, DC areas (N = 1,704). Variables included self-reports of sociodemographics, health care factors, and hepatitis B-related behaviors, knowledge, beliefs, and communication with others. The main outcome variable was self-reported receipt of hepatitis B testing. The cooperation rate was 63.1% and the response rate was 27.4%. Only 62% of respondents reported having received a hepatitis B test and 26%, hepatitis B vaccination. Only 54% knew that hepatitis B could be transmitted by sexual intercourse. In multivariable analyses, factors negatively associated with testing included: age 30–49 years, US residence for &gt;10 years, less Vietnamese fluency, lower income, and believing that hepatitis B can be deadly. Factors positively associated with testing included: Northern California residence, having had hepatitis B vaccination, having discussed hepatitis B with family/friends, and employer requested testing. Physician recommendation of hepatitis B testing (OR 4.46, 95% CI 3.36, 5.93) and respondent's request for hepatitis B testing (OR 8.37, 95% CI 5.95, 11.78) were strongly associated with test receipt. Self-reports of hepatitis B testing among Vietnamese Americans remain unacceptably low. Physician recommendation and patient request were the factors most strongly associated with test receipt. A comprehensive effort is needed to promote hepatitis B testing in this population, including culturally-targeted community outreach, increased access to testing, and physician education

Is obesity associated with reduced health-related quality of life in Latino, black and white children in the community?

OBJECTIVE: Few studies have examined the impact of obesity on health-related quality of life (HRQOL) in non-clinical community samples of children, and methodological limitations have hindered drawing firm conclusions, especially whether the impact is similar across racial/ethnic groups. The present aims were to examine at what levels of non-normal weight, school-aged children experience lower HRQOL and whether this differs among racial/ethnic groups, when controlling for socioeconomic status (SES) differences. DESIGN: Cross-sectional community cohort survey. SUBJECTS AND METHODS: Data are from the Healthy Passages, reporting on 4824 Latino, black and white 5th graders in a population-based survey conducted in three United States metropolitan areas. Children's weight status was classified from measured weight and height into underweight (1%), normal weight (52%), overweight (19%), obese (13%) and extremely obese (14%). Children reported their own HRQOL using the Pediatric Quality of Life Inventory and additional scales addressing global self-worth, physical appearance and body satisfaction. Parents reported children's overall health status. RESULTS: Each increment in higher non-healthy weight class—overweight to obese to extremely obese—was associated with significantly lower scores in more domains of psychosocial HRQOL compared with that in normal weight. However, only extremely obese children reported significantly lower physical HRQOL. Differences among weight classes remained when adjusting for SES and were independent of race/ethnicity. Underweight children generally reported HRQOL that was not significantly different from normal weight children. CONCLUSIONS: Overweight, obese and extremely obese 5th graders on average experience worse HRQOL than normal weight children, especially in psychosocial domains including self-worth and peer relationships, regardless of race/ethnicity. If messages can be conveyed in a sensitive and supportive manner, the desire to improve HRQOL could provide additional motivation for children and their parents in addressing unhealthy weight

Species of Ichnanthus in South America Related to I. ichnodes (Griseb.) Hitchc. & Chasease

Volume: 11Start Page: 73End Page: 8

New species of Paspalum

Volume: 14Start Page: 358End Page: 38