6,340 research outputs found
Comment on ``Method to analyze electromechanical stability of dielectric elastomers" [Appl. Phys. Lett. 91, 061921 (2007)]
The model of Zhao and Suo can be readily generalized to predict the critical
breakdown electric field value of elastomers with arbitrary elastic
strain energy function. An explicit expression for is presented for
elastomeric thin films under biaxial strain and comparisons are made with
experimental data using a two term Ogden rubber elasticity model. Simplified
results for uniaxial and for equi-biaxial stress provide further insight into
the findings of Zhao and Suo.Comment: 2 page
Secular changes in mid-adulthood body mass index, waist circumference, and low HDL cholesterol between 1990, 2003, and 2018 in Great Britain
Objective:
To investigate the extent to which (1) secular changes in mid-adulthood WC are independent of BMI and (2) secular changes in low HDL-C are dependent on WC in each sex. /
Methods:
The sample comprised 19,406 adults (aged 43–47 years) from three birth cohort studies with BMI and WC measured in 1990, 2003, or 2018; 13,239 participants additionally had HDL-C measured in 2003 or 2018. Quantile regression was used to model differences between 1990–2003 and 2003–2018 in (1) BMI and WC internal Z-scores and (2) WC in cm before and after adjustment for BMI. Binary logistic regression was used to model differences between 2003 and 2018 in low HDL-C, before and after adjustment for BMI or WC. /
Results:
Secular increases in BMI and WC were larger between 1990 and 2003 than 2003 and 2018 and at the upper ends of the distributions. At the 85th quantile, effect sizes were larger for WC than BMI Z-scores in females but not males. Adjustment for BMI attenuated estimates of secular increases in WC in cm more in males than females. Odds ratios for low HDL-C in 2018 compared to 2003 were 1.73 (95% CI 1.32, 2.28) in males and 1.34 (1.01, 1.78) in females. Adjustment for WC did not substantially change the estimate in males but attenuated the estimate for females to 1.09 (0.81, 1.47). /
Conclusions:
In women much more so than in men, secular increases in mid-adulthood WC appear to have occurred independently of BMI and largely explain the observed rise in low HDL-C prevalence between 2003 and 2018
A wider audience: Turning VLBI into a survey instrument
Radio observations using the Very Long Baseline Interferometry (VLBI)
technique typically have fields of view of only a few arcseconds, due to the
computational problems inherent in imaging larger fields. Furthermore,
sensitivity limitations restrict observations to very compact and bright
objects, which are few and far between on the sky. Thus, while most branches of
observational astronomy can carry out sensitive, wide-field surveys, VLBI
observations are limited to targeted observations of carefully selected
objects. However, recent advances in technology have made it possible to carry
out the computations required to target hundreds of sources simultaneously.
Furthermore, sensitivity upgrades have dramatically increased the number of
objects accessible to VLBI observations. The combination of these two
developments have enhanced the survey capabilities of VLBI observations such
that it is now possible to observe (almost) any point in the sky with
milli-arcsecond resolution. In this talk I review the development of wide-field
VLBI, which has made significant progress over the last three years.Comment: Invited review at the General Assembly of the Astronomische
Gesellschaf
Plasma Magnetohydrodynamics and Energy Conversion
Contains reports on three research projects.National Science Foundation under Grant G-9330U. S. Air Force (Aeronautical Systems Division) under Contract AF33(616)-7624 with the Aeronautical Accessories Laboratory, Wright-Patterson Air Force Base, Ohi
The Relationship of Early-Life Adversity With Adulthood Weight and Cardiometabolic Health Status in the 1946 National Survey of Health and Development
OBJECTIVE:
Evidence linking early-life adversity with an adverse cardiometabolic profile in adulthood is equivocal. This study investigates early-life adversity in relation to weight and cardiometabolic health status at ages 60 to 64 years.
METHODS: We included 1059 individuals from the 1946 National Survey of Health and Development. Data on adversity between ages 0 to 15 years were used to create a cumulative childhood psychosocial adversity score and a socioeconomic adversity score. Cardiometabolic and weight/height data collected at ages 60 to 64 years were used to create four groups: metabolically healthy normal weight, metabolically unhealthy normal weight, metabolically healthy overweight/obese, and metabolically unhealthy overweight/obese. Associations between the two exposure scores and weight/health status were examined using multinomial logistic regression, with adjustment for sex and age at the outcome visit.
RESULTS: Sixty-two percent of normal-weight individuals were metabolically healthy, whereas only 34% of overweight/obese individuals were metabolically healthy. In a mutually adjusted model including both exposure scores, a psychosocial score of ≥3 (compared with 0) was associated with increased risk of being metabolically unhealthy (compared with healthy) in both normal-weight adults (relative risk = 2.49; 95% confidence interval = 0.87–7.13) and overweight/obese adults (1.87; 0.96–3.61). However, the socioeconomic adversity score was more strongly related to metabolic health status in overweight/obese adults (1.60; 0.98–2.60) than in normal-weight adults (0.95; 0.46–1.96).
CONCLUSIONS: Independently of socioeconomic adversity, psychosocial adversity in childhood may be associated with a poor cardiometabolic health profile, in both normal-weight and overweight/obese adults.
Childhood adversity might cause obesity via the adoption of unhealthy behaviors. It might also cause poor cardiometabolic health, either via obesity or via another pathway (e.g., altered stress response). Robson et al. found that childhood adversity was associated with poor cardiometabolic health at ages 60 to 64 years, in both normal-weight and overweight/obese adults. Further research is needed to understand the mechanisms by which childhood adversity might affect cardiometabolic health without necessarily increasing body weight
ac Losses in a Finite Z Stack Using an Anisotropic Homogeneous-Medium Approximation
A finite stack of thin superconducting tapes, all carrying a fixed current I,
can be approximated by an anisotropic superconducting bar with critical current
density Jc=Ic/2aD, where Ic is the critical current of each tape, 2a is the
tape width, and D is the tape-to-tape periodicity. The current density J must
obey the constraint \int J dx = I/D, where the tapes lie parallel to the x axis
and are stacked along the z axis. We suppose that Jc is independent of field
(Bean approximation) and look for a solution to the critical state for
arbitrary height 2b of the stack. For c<|x|<a we have J=Jc, and for |x|<c the
critical state requires that Bz=0. We show that this implies \partial
J/\partial x=0 in the central region. Setting c as a constant (independent of
z) results in field profiles remarkably close to the desired one (Bz=0 for
|x|<c) as long as the aspect ratio b/a is not too small. We evaluate various
criteria for choosing c, and we show that the calculated hysteretic losses
depend only weakly on how c is chosen. We argue that for small D/a the
anisotropic homogeneous-medium approximation gives a reasonably accurate
estimate of the ac losses in a finite Z stack. The results for a Z stack can be
used to calculate the transport losses in a pancake coil wound with
superconducting tape.Comment: 21 pages, 17 figures, accepted by Supercond. Sci. Techno
Hysteretic ac losses in a superconductor strip between flat magnetic shields
Hysteretic ac losses in a thin, current-carrying superconductor strip located
between two flat magnetic shields of infinite permeability are calculated using
Bean's model of the critical state. For the shields oriented parallel to the
plane of the strip, penetration of the self-induced magnetic field is enhanced,
and the current dependence of the ac loss resembles that in an isolated
superconductor slab, whereas for the shields oriented perpendicular to the
plane of the strip, penetration of the self-induced magnetic field is impaired,
and the current dependence of the ac loss is similar to that in a
superconductor strip flanked by two parallel superconducting shields. Thus,
hysteretic ac losses can strongly augment or, respectively, wane when the
shields approach the strip.Comment: 9 pages, 5 figures, submitted to PR
Plasma Magnetohydrodynamics and Energy Conversion
Contains reports on four research projects.United States Air Force, Aeronautical Systems Division (Contract AF33(616)-7624)United States Air Force, Aeronautical Systems Division, Aeronautical Accessories Laboratory, Wright-Patterson Air Force Base (Contract AF33(616)-7624
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