Causality Constraints on Massive Gravity

The de Rham-Gabadadze-Tolley massive gravity admits pp-wave backgrounds on which linear fluctuations are shown to undergo time advances for all values of the parameters. The perturbations may propagate in closed time-like curves unless the parameter space is constrained to a line. These classical phenomena take place well within the theory's validity regime.Comment: 6 pages, 4 figures; to appear in PR

Stacking the Equiangular Spiral

We present an algorithm that adapts the mature Stack and Draw (SaD) methodology for fabricating the exotic Equiangular Spiral Photonic Crystal Fiber. (ES-PCF) The principle of Steiner chains and circle packing is exploited to obtain a non-hexagonal design using a stacking procedure based on Hexagonal Close Packing. The optical properties of the proposed structure are promising for SuperContinuum Generation. This approach could make accessible not only the equiangular spiral but also other quasi-crystal PCF through SaD

Overcoming access barriers for facility-based delivery in low-income settings: insights from Bangladesh and Uganda.

Women in both Bangladesh and Uganda face a number of barriers to delivery in professional health facilities, including costs, transportation problems, and sociocultural norms to deliver at home. Some women in both the countries manage to overcome these barriers. This paper reports on a comparative qualitative study investigating how some women and their families were able to use professional delivery services. The study provides insights into the decision-making processes and overcoming access barriers. Husbands were found to be particularly important in Uganda, while, in Bangladesh, a number of individuals could influence care-seeking, including unqualified local healers or traditional birth attendants. In both the settings, cost and transport barriers were often overcome through social networks. Social prohibitions on birth in the health facility did not feature strongly in women's accounts, with several Ugandan women explaining that friends or peers also used facilities, while, in Bangladesh, perceived complications apparently justified the use of professional medical care. Investigating the ways in which some women can overcome common barriers can help inform policy and planning to increase the use of health facilities for child delivery