Unstable topography of biphasic surfactant monolayers

We study the conformation of a heterogeneous surfactant monolayer at a fluid-fluid interface, near a boundary between two lateral regions of differing elastic properties. The monolayer attains a conformation of shallow, steep `mesas' with a height difference of up to 10 nm. If the monolayer is progressively compressed (e.g. in a Langmuir trough), the profile develops overhangs and finally becomes unstable at a surface tension of about K(delta c_0)^2, where (delta c_0) is the difference in spontaneous curvature and K a bending stiffness. We discuss the relevance of this instability to recently observed folding behavior in lung surfactant monolayers, and to the absence of domain structures in films separating oil and water in emulsions.Comment: 7 pages, 7 figures, LaTex using epl.cls, accepted for Europhys Let

Path Planning in the Presence of Dynamically Moving Obstacles with Uncertainty

In this paper, the problem of path-planning with dynamically moving elliptical obstacles is addressed. A new analytical result for computing the axes aligned bounding box for the ellipses with bounded uncertainty in the position of the centre and the orientation is presented. Genetic algorithm is utilised for finding the shortest path from the initial to goal position avoiding the moving obstacles.Defence Science Journal, 2010, 60(1), pp.55-60, DOI:http://dx.doi.org/10.14429/dsj.60.10

Further evidence for intra-night optical variability of radio-quiet quasars

Although well established for BL Lac objects and radio-loud quasars, the occurrence of intra-night optical variability (INOV) in radio-quiet quasars is still debated, primarily since only a handful of INOV events with good statistical significance, albeit small amplitude, have been reported so far. This has motivated us to continue intra-night optical monitoring of bona-fide radio-quiet quasars (RQQs). Here we present the results for a sample of 11 RQQs monitored by us on 19 nights. On 5 of these nights a given RQQ was monitored simultaneously from two well separated observatories. In all, two clear cases and two probable case of INOV were detected. From these data, we estimate an INOV duty cycle of $\sim$8% for RQQs which would increase to 19% if the `probable variable' cases are also included. Such comparatively small INOV duty cycles for RQQs, together with the small INOV amplitudes ($\sim$1%), are in accord with the previously deduced characteristics of this phenomenon.Comment: 15 Pages, 4 Tables, 24 Figures; Accepted in BAS

Do Life Style Factors And Socioeconomic Variables Explain Why Black Women Have A Remarkably Higher Body Mass Index (BMI) Than White Women In The United States? Findings From The 2010 National Health Interview Survey

Objective: There are marked inequalities in body mass index (BMI), overweight, and obesity across ethnic groups. We sought to examine the extent to which lifestyle factors and socioeconomic variables explain the higher BMI in Black women compared to White women in the United States. Methods: We used data from the 2010 National Health Interview Survey (NHIS) and limited the sample to non-Hispanic Black and non-Hispanic White women (n = 9,491). We employed normal regression and compared the association of race with BMI before and after adjusting for lifestyle factors (diet, physical activity, smoking, and drinking) and socioeconomic variables (education, ratio of income to poverty threshold, occupation, and home ownership). Data analysis was performed in 2012. Results: The difference between the BMI of Black and White women decreased from 2.91 to 2.17 Kg/m2 (i.e. a decrease of 27.2%) after adjusting for lifestyle factors and socioeconomic variables. Multivariate results also showed that higher consumption of fruit/vegetables and beans, lower consumption of red meat and sugar sweetened beverages, physical activity, smoking, regular drinking, and higher socioeconomic status were associated with lower BMI. Conclusions: Lifestyle factors and socioeconomic variables explain about a quarter of the BMI inequality between Black and White women. Thus, interventions that promote healthy eating and physical activity among Blacks as well as social policies that ameliorate socioeconomic inequalities between races might be able to reduce the current BMI inequality between Black and White women