Metric Dimension for Gabriel Unit Disk Graphs is NP-Complete

We show that finding a minimal number of landmark nodes for a unique virtual addressing by hop-distances in wireless ad-hoc sensor networks is NP-complete even if the networks are unit disk graphs that contain only Gabriel edges. This problem is equivalent to Metric Dimension for Gabriel unit disk graphs. The Gabriel edges of a unit disc graph induce a planar O(\sqrt{n}) distance and an optimal energy spanner. This is one of the most interesting restrictions of Metric Dimension in the context of wireless multi-hop networks.Comment: A brief announcement of this result has been published in the proceedings of ALGOSENSORS 201

Universal optimality of Patterson's crossover designs

We show that the balanced crossover designs given by Patterson [Biometrika 39 (1952) 32--48] are (a) universally optimal (UO) for the joint estimation of direct and residual effects when the competing class is the class of connected binary designs and (b) UO for the estimation of direct (residual) effects when the competing class of designs is the class of connected designs (which includes the connected binary designs) in which no treatment is given to the same subject in consecutive periods. In both results, the formulation of UO is as given by Shah and Sinha [Unpublished manuscript (2002)]. Further, we introduce a functional of practical interest, involving both direct and residual effects, and establish (c) optimality of Patterson's designs with respect to this functional when the class of competing designs is as in (b) above.Comment: Published at http://dx.doi.org/10.1214/009053605000000723 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Quasilocal energy for rotating charged black hole solutions in general relativity and string theory

We explore the (non)-universality of Martinez's conjecture, originally proposed for Kerr black holes, within and beyond general relativity. The conjecture states that the Brown-York quasilocal energy at the outer horizon of such a black hole reduces to twice its irreducible mass, or equivalently, to \sqrt{A} /(2\sqrt{pi}), where `A' is its area. We first consider the charged Kerr black hole. For such a spacetime, we calculate the quasilocal energy within a two-surface of constant Boyer-Lindquist radius embedded in a constant stationary-time slice. Keeping with Martinez's conjecture, at the outer horizon this energy equals the irreducible mass. The energy is positive and monotonically decreases to the ADM mass as the boundary-surface radius diverges. Next we perform an analogous calculation for the quasilocal energy for the Kerr-Sen spacetime, which corresponds to four-dimensional rotating charged black hole solutions in heterotic string theory. The behavior of this energy as a function of the boundary-surface radius is similar to the charged Kerr case. However, we show that in this case it does not approach the expression conjectured by Martinez at the horizon.Comment: 15 page

Changing Women’s Roles in Homestead Management: Mainstreaming Women in Rural Development

This paper has been prepared as part of CPD's advocacy activities with IRRI under the PETRRA project and was presented at the dialogue on Women's Contribution to Rural Economic Activities: Making the Invisible Visible. It reports the result of the focus group discussions with men and women as a supplement to the quantitative information gathered from household surveys as presented in the CPD Occasional Paper 41. Focus Group Discussions (FGD) were conducted in 8 out of the 62 villages from 57 districts included in the quantitative study.Women, Bangladesh

Exchange bias phenomenology and models of core/shell nanoparticles

Some of the main experimental observations related to the occurrence of exchange bias in magnetic systems are reviewed, focusing the attention on the peculiar phenomenology associated to nanoparticles with core/shell structure as compared to thin film bilayers. The main open questions posed by the experimental observations are presented and contrasted to existing theories and models for exchange bias formulated up to date. We also present results of simulations based on a simple model of a core/shell nanoparticle in which the values of microscopic parameters such as anisotropy and exchange constants can be tuned in the core, shell and at the interfacial regions, offering new insight on the microscopic origin of the experimental phenomenology. A detailed study of the of the magnetic order of the interfacial spins shows compelling evidence that most of the experimentally observed effects can be qualitatively accounted within the context of this model and allows also to quantify the magnitude of the loop shifts with striking agreement with the macroscopic observed values.Comment: 17 pages, 10 figures. Review article, submitted to J. Nanosci. Nanotechnol. (special Issue on Nanomagnetism), invited contribution. Suggestions and comments are welcome. A copy with higher resolution of Fig. 7 may be obtained at this web site: http://hermes.ffn.ub.es/oscar/Articles.htm

Double burden of malnutrition among urban Bengalee adolescent boys in Midnapore, West Bengal, India

Malnutrition is an important public health problem worldwide. Therefore a study was undertaken to assess the prevalence of adolescent thinness, overweight and obesity in Midnapore town, West Bengal, India. A total of 974 adolescent boys aged 10-18 years were selected following multistage cluster sampling method from three higher secondary schools. Data was collected using pretested questionnaire following standard technique. Presence of thinness was evaluated using the cut-off values of international survey as suggested by Cole et al (2007). While overweight and obesity was determine by using international cut-off values develop by Cole et al (2000) based on international surveys as recommended by IOTF. Overall the prevalence of thinness, overweight and obesity were 20.8%, 14.9% and 3.8%, respectively. This study developed age specific smooth BMI percentile values using LMS method. Moreover, the study also developed BMI cut-off values to define thinness, overweight and obesity. In conclusion, the present analyses indicated that the prevalence of adolescent undernutrition is still a major problem. In addition, there was also an emerging trend for overweight/obesity, thereby indicating a double burden of malnutrition as observed in other developing countries