In many of the high-precision optical frequency standards with trapped atoms or ions that are under development to date, the AC Stark shift induced by thermal radiation leads to a major contribution to the systematic uncertainty. We present an analysis of the inhomogeneous thermal environment experienced by ions in various types of ion traps. Finite element models which allow the determination of the temperature of the trap structure and the temperature of the radiation were developed for 5 ion trap designs, including operational traps at PTB and NPL and further optimized designs. Models were refined based on comparison with infrared camera measurement until an agreement of better than 10% of the measured temperature rise at critical test points was reached. The effective temperature rises of the radiation seen by the ion range from 0.8 K to 2.1 K at standard working conditions. The corresponding fractional frequency shift uncertainties resulting from the uncertainty in temperature are in the 10 -18 range for optical clocks based on the Sr + and Yb + E2 transitions, and even lower for Yb + E3, In + and Al + . Issues critical for heating of the trap structure and its predictability were identified and design recommendations developed.
Relying upon a content analysis of one specific type of medium to which young people are exposed beginning at an early age, on a regular basis, and for many years (i.e., animated cartoons), the present study examines what types of messages are provided about being underweight, overweight and normal weight. This research examines the following issues: (1) How prevalent is weight-related content in animated cartoons? (2) Has this prevalence changed over time? (3) What "types" of characteristics tend to be associated with being thinner-than-normal or heavier-than normal? Results indicate that the prevalence of both underweight and overweight characters has changed dramatically over the course of the past several decades. These relationships are both curvilinear in nature, but in recent decades have demonstrated a significant increase in the proportion of all cartoons showing characters that are underweight and a simultaneous decrease in the prevalence of characters that are overweight. Many variables were found to differ based on cartoon characters' body weight including gender, age, intelligence, physical attractiveness, emotional states experienced, prosocial behaviors, antisocial behaviors, and overall goodness/badness. Whenever differences were found, the overriding tendency was for cartoons to provide positive messages about being thin and negative messages about being overweight.
Older women's risk of acquiring HIV should not be discounted, because researchers have noted that older women may be at an increased risk of contracting HIV due to their heterosexual sexual practices and/or substance use behaviors. HIV prevention efforts must be directed at older adults who engage in high-risk sexual and drug behaviors, particularly those who may not perceive themselves to be at risk for HIV infection. This study is based on 183 women, mostly African American, divided into two age cohorts (ages 18 to 29, and ages 40 and older). The authors investigate factors associated with HIV risk perception in several domains, including individual, psychosocial, and sociodemographic characteristics as well as sexual and drug use behaviors. Multivariate analyses revealed differences in factors associated with younger and older women's HIV risk perceptions. Our findings indicate a need for HIV risk prevention programs to take age into consideration when developing intervention messages and strategies.
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