Seasonality of tuberculosis in India: is it real and what does it tell us?

India has a third of the world’s tuberculosis cases. Large-scale expansion of a national program in 1998 has allowed for population-based analyses of data from tuberculosis registries. We assessed seasonal trends using quarterly reports from districts with stable tuberculosis control programs (population 115 million). In northern India, tuberculosis diagnoses peaked between April and June, and reached a nadir between October and December, whereas no seasonality was reported in the south. Overall, rates of new smear-positive tuberculosis cases were 57 per 100 000 population in peak seasons versus 46 per 100 000 in trough seasons. General health-seeking behavior artifact was ruled out. Seasonality was highest in paediatric cases, suggesting variation in recent transmission.

Optimal Segment Size for Fixed-sized Segment Protection in Wavelength-routed Optical Networks

Protecting a network against link failures is a major challenge faced by network operators. The protection scheme has to address two important objectives - fast recovery and minimizing the amount of backup resources needed. Every protection algorithm is a tradeoff between these two objectives. In this paper, we study the problem of segment protection. In particular, we investigate what is the optimal segment size that obtains the best tradeoff between the time taken for recovery and minimizing the bandwidth used by the backup segments. We focus on the uniform fixed-length segment protection method, where each primary path is divided into fixed-length segments, with the exception of the last segment in the path. We observe that the optimal segment size for a given network depends on several factors such as the topology and the ratio of the costs involved.

A Heuristic with Bounded Guarantee to Compute Diverse Paths under Shared Protection in WDM Mesh Networks

Establishing a fault-tolerant connection in a network involves computation of diverse working and protection paths. The Shared Risk Link Group (SRLG) [1] concept is used to model several types of failure conditions such as link, node, fiber conduit, etc. In this work we focus on the problem of computing optimal SRLG/link diverse paths under shared protection. Shared protection technique improves network resource utilization by allowing protection paths of multiple connections to share resources. In this work we propose an iterative heuristic for computing SRLG/link diverse paths. We present a method to calculate a quantitative measure that provides a bounded guarantee on the optimality of the diverse paths computed by the heuristic. The experimental results on computing link diverse paths show that our proposed heuristic is efficient in terms of number of iterations required (time taken) to compute diverse paths when compared to other previously proposed heuristics.

Distribution of Dioecious Eastern Red Cedar (Juniperus virginiana) along an Environmental Gradient in Ogallala, NE.

Abstract The purpose of this research was to study the sex distribution and energy allocation of dioecious Eastern Red Cedars (Juniperus virginiana) along an environmental resource gradient. The trees surveyed were growing in a canyon located at the University of Nebraska’s Cedar Point Biological Research Station in Ogallala, Nebraska. Due to the geography of this canyon, environmental factors necessary for plant growth should vary depending on the tree’s location within the canyon. These factors include water availability, sun exposure, ground slope, and soil nitrogen content, all of which are necessary for carbon acquisition. Juniperus virginiana is a dioecious conifer. Dioecious plants maintain male and female reproductive structures on separate individuals. Therefore, proximal spatial location is essential for pollination and successful reproduction. Typically female reproductive structures are more costly and require a greater investment of carbon and nitrogen. For this reason, growth, survival and successful reproduction are more likely to be limited by environmental resources for females than for male individuals. If this is true for Juniperus virginiana, females should be located in more nutrient and water rich areas than males. This also assumes that females can not be reproductively successful in areas of poor environmental quality. Therefore, reproductive males should be more likely to inhabit environments with relatively lower resource availability than females. Whether the environment affects sexual determination or just limits survival of different sexes is still relatively unknown. In order to view distribution trends along the environmental gradient, the position of the tree in the canyon transect was compared to its sex. Any trend in sex should correspond with varying environmental factors in the canyon, ie: sunlight availability, aspect, and ground slope. The individuals’ allocation to growth and reproduction was quantified first by comparing trunk diameter at six inches above ground to sex and location of the tree. The feature of energy allocation was further substantiated by comparing carbon and nitrogen content in tree leaf tissue and soil to location and sex of each individual. Carbon and nitrogen in soil indicate essential nutrient availability to the individual, while C and N in leaf tissue indicate nutrient limitation experienced by the tree. At the conclusion of this experiment, there is modest support that survival and fecundity of females demands environments relatively richer in nutrients, than needed by males to survive and be reproductively active. Side of the canyon appeared to have an influence on diameter of trees, frequency of sex and carbon and nitrogen leaf content. While this information indicated possible trends in the relation of sex to nutrient availability, most of the environmental variables presumed responsible for the sex distribution bias differed minutely and may not have been biologically significant to tree growth.