Infanticide and infant defence by males--modelling the conditions in primate multi-male groups

Infanticide by primate males was considered rare if groups contain more than one adult male because, owing to lower paternity certainty, a male should be less likely to benefit from infanticide. Guided by recent evidence for strong variation of infanticide in primate multi-male groups, we modelled the conditions for when infanticide should occur for a group with a resident and an immigrant male. Setting the parameters (e.g. infant mortality, reduction of interbirth interval, life-time reproductive success, genetic representation) to fit the conditions most commonly found in nature, we develop a game-theoretic model to explore the influence of age and dominance on the occurrence of infanticide and infant defence. Male age strongly impacts the likelihood of an attack which is modified by the father's defence. If the new male is dominant he is likely to attack under most circumstances whereas a subordinate male will only attack if the father does not defend. These model scenarios fit the conditions under which infanticide is known to occur in primate multi-male groups and offer an explanation why infanticide is common in some multi-male groups and rare in others. Overall, the benefits for infanticidal males are strongly governed by a reduced interbirth interval while advantages via improved genetic representation in the gene pool contribute but a minor fraction

Solution of fluid-structure interaction problems using a discontinuous Galerkin technique

Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2008.Includes bibliographical references (p. 57-58).The present work aims to address the problem of fluid-structure interaction using a discontinuous Galerkin approach. Starting from the Navier-Stokes equations on a fixed domain, an arbitrary Lagrangian Eulerian (ALE) approach is used to derive the equations for the deforming domain. A geometric conservation law (GCL) is then introduced, which guarantees freestream preservation of the numerical scheme. The space discretization is performed using a discontinuous Galerkin method and time integration is performed using either an explicit four stage Runge-Kutta scheme or an implicit BDF2 scheme. The mapping parameters for the ALE formulation are then obtained using algorithms based on radial basis functions (RBF) or linear elasticity. These strategies are robust and can be applied to bodies with arbitrary shapes and undergoing arbitrary motions. The robustness and accuracy of the ALE scheme coupled with these mapping strategies is then demonstrated by solving some model problems. The ability of the scheme to handle complex flow problems is demonstrated by analyzing the low Reynolds number flow over an oscillating circular cylinder.by Anshul Mohnot.S.M

Surveillance data on micro-organisms in respiratory tract infections at a tertiary care teaching hospital in South India

Background: Respiratory tract infections are the leading cause of infections and associated hospitalizations in India. Generally, there is little control on the use of antibiotics. Community awareness of the issues involved in antibiotic therapy is poor and this is compounded by over-the-counter availability. The main aim was to compare the resistance developed by respiratory microbes.Methods: A retrospective and prospective study was designed and conducted to compare the pattern of resistance developed by microorganisms affecting the respiratory tract.Results: The sensitivity of K. pneumoniae to cefepime/tazobactum has decreased from 91.9% to 47.6% and S. aureus to Linezolid has decreased from 93.4% to 80% and S. pyogenes to azithromycin from 51.4% to 24.8%. Whereas sensitivity pattern of S. pneumoniae to amoxicillin/clavulanate is increased from 65.6% to 82.3%. The prevalence of Klebsiella pneumoniae was increased 19% to 25.2% whereas the prevalence of S. pneumoniae was decreased from 66.8% to 65.2%. Our study suggests that all microorganisms isolated are susceptible to carbapenems and cefepime/tazobactum in the cephalosporin class.Conclusions: There is major shift in the sensitivity pattern of microorganisms towards antibiotics. Therefore, these results must be kept in mind by the practitioners in the study site, prior to making decisions over a medication regimen empirically for patients and also to maximize the output of medications by rational prescribing and dosing.

Female Resistance to Invading Males Increases Infanticide in Langurs

BACKGROUND: Infanticide by adult male occurs in many mammalian species under natural conditions, and it is often assumed to be a goal-directed action and explained predominately by sexual selection. Motivation of this behavior in mammals is limitedly involved. METHODOLOGY AND PRINCIPAL FINDINGS: We used long-term reproductive records and direct observation in captivity and in the field of two snub-nosed langur species on the basis of individual identification to investigate how infanticide happened and to be avoided in nonhuman primates. Our observations suggested that infanticide by invading males might be more accidental than goal-directed. The invading male seemed to monopolize all the females including lactating mothers during takeovers. Multiparous mothers who accepted the invading male shortly after takeovers avoided infanticide in most cases. Our results conjectured primiparous mothers would decrease infanticidal possibility if they sexually accepted the invading male during or immediately after takeovers. In the studied langur species, voluntary abortion or mating with the invading male was evidently adopted by females to limit or avoid infanticide by takeover males. CONCLUSIONS AND SIGNIFICANCE: The objective of the invading male was to monopolize all adult females after his takeover. It appeared that the mother's resistance to accepting the new male as a mating partner was the primary incentive for infanticide. Motivation analysis might be helpful to further understand why infanticide occurs in primate species

Infant mortality following male takeovers in wild geladas

Since Sugiyama's [1965] first observations of infanticide, empirical evidence from a multitude of primate species has supported the sexual selection hypothesis—the idea that males enhance their reproductive success by killing nonrelated, unweaned infants to hasten the mothers' return to fertility. Like other primates that live in social groups where paternity certainty is high, the social structure of geladas [ Theropithecus gelada ] suggests that infanticide by males could enhance their reproductive success. Nevertheless, empirical evidence for infanticide in this species is limited to anecdotal accounts. Using the timing of infant mortality and female reproductive and behavioral data collected across 26 months from a population of geladas living in the Simien Mountains National Park, Ethiopia, we test whether sexually selected infanticide occurs in this species. We also examine two additional hypotheses [noninfanticide hypothesis and generalized aggression hypothesis] for this population. Results suggest that sexually selected infanticide in geladas may, indeed, be a threat to females with dependent infants. First, male takeovers—the most likely time for infanticide—were associated with subsequently elevated rates of infant death [a 32-fold increase] comprising nearly 60% of all infant mortality. Second, females who lost infants during this period returned to fertility more quickly than if infants had lived [IBIs were 50% shorter], and third, all of these females were observed to mate with the new male. We found little to no support for other hypotheses. Finally, these results raise the possibility that anecdotal reports [from previous studies and this study] of pregnancy termination, accelerated weaning, and deceptive sexual swellings may represent female counterstrategies to male infanticide in geladas. Am. J. Primatol. 70:1152–1159, 2008. © 2008 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61204/1/20614_ftp.pd