Geodesic Transport Barriers in Jupiter's Atmosphere: A Video-Based Analysis

Jupiter's zonal jets and Great Red Spot are well known from still images. Yet the planet's atmosphere is highly unsteady, which suggests that the actual material transport barriers delineating its main features should be time-dependent. Rare video footages of Jupiter's clouds provide an opportunity to verify this expectation from optically reconstructed velocity fields. Available videos, however, provide short-time and temporally aperiodic velocity fields that defy classical dynamical systems analyses focused on asymptotic features. To this end, we use here the recent theory of geodesic transport barriers to uncover finite-time mixing barriers in the wind field extracted from a video captured by NASA's Cassini space mission. More broadly, the approach described here provides a systematic and frame-invariant way to extract dynamic coherent structures from time-resolved remote observations of unsteady continua

Detecting invariant manifolds, attractors, and generalized KAM tori in aperiodically forced mechanical systems

We show how the recently developed theory of geodesic transport barriers for fluid flows can be used to uncover key invariant manifolds in externally forced, one-degree-of-freedom mechanical systems. Specifically, invariant sets in such systems turn out to be shadowed by least-stretching geodesics of the Cauchy-Green strain tensor computed from the flow map of the forced mechanical system. This approach enables the finite-time visualization of generalized stable and unstable manifolds, attractors and generalized KAM curves under arbitrary forcing, when Poincaré maps are not available. We illustrate these results by detailed visualizations of the key finite-time invariant sets of conservatively and dissipatively forced Duffing oscillator

Predictors of women's occupational attainment

This research examined the determinants of occupational attainment of American working women. Of particular interest was the development of causal models to explain women's occupational status attainment. Since women's occupations were hypothesized to be dependent upon their marital status, two models were constructed, one for married and one for single women. The models incorporated the following variables: education, family socioeconomic status, husband's socioeconomic status (for married women), ethnicity, age, length of job experience, birth order, and number of siblings; among these variables, education was hypothesized to have the greatest direct impact on occupational attainment, with the others hypothesized to have both a direct and indirect effect on educational and occupational attainment. The level of occupational attainment was measured using an index of occupational prestige scale developed by Treiman. Ethnicity was coded dichotomously as whites (Anglo) and non-whites (others). The index of family socioeconomic status incorporated father's occupation, mother's education, and the interaction of father's occupation and mother's education, while husband's socioeconomic status was a composite of occupation and education. The analysis utilized data collected from full-time women employees of the University of Houston Central Campus. Correlation analysis was used to investigate the relationship between individual variables hypothesized as determinants of women's occupational attainment. Multiple linear regression analysis assessed the strength of relationships between the linear combinations of the independent variables and women's occupational status attainment. Path analysis was used to test the theoretical causal relationships among independent variables, and revealed the strength and the weaknesses of the hypothesized models of women's occupational attainment. There were significant correlation coefficients between family socioeconomic status, ethnicity, age, education, and husband's socioeconomic status and married women's occupational attainment. It was indicated, also, that family socioeconomic status, number of siblings, and birth- order significantly contributed to married women's education. However, education and ethnicity were the only significant variables in predicting single women's occupational attainment . This study indicated that married women with a low level of education tended to attain relatively higher level occupations than single women with the same education. However, for women with moderate to high levels of education single women have a slightly higher level of occupational attainment with respect to their education than do their married counterparts. Since the married women tended to be older, their greater longevity in the work force might explain their greater attainment. This study showed that with increases in age, the gap between the occupational status of married and single women widened. The empirical data for this study showed that children from families with high socioeconomic status tended to attain higher levels in the occupational hierarchy than those from families with low socioeconomic status. The study also indicated that the degree of association between family socioeconomic status and occupational attainment was relatively smaller for single women than for married women. Thus single women appear to reap greater benefits in occupational attainment from investment in further education than do married women. Ethnicity was significant in the process of occupational attainment for both married and single women. Ethnicity also was significantly correlated with family socioeconomic status, and family socioeconomic status in turn effectively determined educational attainment for both married and single women. Further, the results of the study indicated that other variables being equal, education had almost equal explanatory power in the determination of occupational attainment for whites and non-whites. Thus it appeared that differential educational attainment is one of the mechanisms by which ascribed variables such as family socioeconomic status, number of siblings, birth order, ethnicity, and husbandtesocioeconomic status (for married women) influence occupational attainment. Education as an achieved characteristic accounted for the major portion of the variance in women's occupational status attainment. Although ascribed factors were significantly related to women's occupational differences, their effect was not decisive. In conclusion, a strong emphasis on education for women seems to be a rational response to increasing their position in the occupational status hierarchy in the United States of America. Such findings support the existence of increasing meritocracy in the status attainment patterns of American working women. Examination of the indirect effects of ascribed variables, however, indicated that these factors may operate to affect the status attainment of women to a greater extent than they do for men, in that they affect the amount of education women are able to attain.Education, College o

Defining coherent vortices objectively from the vorticity

Rotationally coherent Lagrangian vortices are formed by tubes of deforming fluid elements that complete equal bulk material rotation relative to the mean rotation of the deforming fluid volume. We show that the initial positions of such tubes coincide with tubular level surfaces of the Lagrangian-averaged vorticity deviation (LAVD), the trajectory integral of the normed difference of the vorticity from its spatial mean. The LAVD-based vortices are objective, i.e. remain unchanged under time-dependent rotations and translations of the coordinate frame. In the limit of vanishing Rossby numbers in geostrophic flows, cyclonic LAVD vortex centres are precisely the observed attractors for light particles. A similar result holds for heavy particles in anticyclonic LAVD vortices. We also establish a relationship between rotationally coherent Lagrangian vortices and their instantaneous Eulerian counterparts. The latter are formed by tubular surfaces of equal material rotation rate, objectively measured by the instantaneous vorticity deviation (IVD). We illustrate the use of the LAVD and the IVD to detect rotationally coherent Lagrangian and Eulerian vortices objectively in several two- and three-dimensional flows.ISSN:0022-1120ISSN:1469-764

Coherent Lagrangian swirls among submesoscale motions

The emergence of coherent Lagrangian swirls (CLSs) among submesoscale motions in the ocean is illustrated. This is done by applying recent nonlinear dynamics tools for Lagrangian coherence detection on a surface flow realization produced by a data-assimilative submesoscale-permitting ocean general circulation model simulation of the Gulf of Mexico. Both mesoscale and submesoscale CLSs are extracted. These extractions prove the relevance of coherent Lagrangian eddies detected in satellite-altimetry-based geostrophic flow data for the arguably more realistic ageostrophic multiscale flow