The identification and distribution of major biogenic amines in the central nervous system of Aedes triseriatus (Say) (Diptera: Culicidae) and studies on their regulation of adult mosquito behavior

The major biogenic amines of the insect nervous system (dopamine, octopamine, and serotonin) were identified and quantified by high performance liquid chromatography in the brain and thoracic ganglia of female Aedes triseriatus mosquitoes. Octopamine was quantitatively dominant in both tissues while dopamine and serotonin were found in smaller but generally similar amounts. Noradrenaline was not found in measurable quantities. Amine levels in the brain and thoracic ganglia increased significantly between days 1-14 of adult life while total protein content remained unchanged. No statistically significant circadian changes in brain amine levels were observed. When brains were divided by region (midbrain, optic lobes, subesophageal ganglion), octopamine was more abundant in the optic lobes, relative to the distribution of dopamine and serotonin;Biogenic amine concentrations were depleted in A. triseriatus when administered a single oral dose (approximately 4 [mu]g) of [alpha]-methyl tyrosine (AMT) or [alpha]-methyl tryptophan (AMTP). AMTP treatment selectively lowered the brain concentration of serotonin through the 14 days monitored following treatment. During the first week, serotonin levels in AMTP-treated mosquitoes were approximately 10% of control levels. Administration of AMT significantly depleted dopamine through 14 days post-treatment; dopamine was reduced by 50% in AMT-treated mosquitoes during the first week. Octopamine concentration was also lowered by AMT (determined on Day 3 post-treatment), but not to the degree of dopamine depression. Treatment with AMT or AMTP elicited statistically significant decreases in the spontaneous, circadian flight-activity of A. triseriatus for several days but flight activity of treated mosquitoes returned to control levels prior to evidence of amine pool repletion. Amine reductions did not alter the circadian pattern of flight activity;Host-seeking ability (evaluated with an olfactometer) was not altered by treatment with either AMT or AMTP. However, bloodfeeding success was significantly reduced by either oral administration or injection of AMTP. AMTP-treated mosquitoes responded positively when placed in close proximity to a host (rabbit) but fewer mosquitoes fed to repletion or fed at all. Those that fed to repletion took longer to do so. No differences were observed between control and AMT-treated mosquitoes. These observations suggest that serotonin plays a role in modulating bloodfeeding behavior in A. triseriatus

Student Role Supports for Younger and Older Middle- Aged Women: Application of a Life Event Model

This paper is a report on a study of 276 women aged 35 to 64 who have re-entered university. We used the life-event framework to focus on the stress of university life, on the methods these women use to cope with stress and on their adaptations to the demands of school. We compared the re-entry experience of two sub-groups in our population: students aged 35 to 44 (with young families) and those aged 45 to 64 (with mature families). We found that each group had different motives for attending school, each group felt different strains during the school year and each group used different methods and resources to cope with the demands of student life. The paper concludes with a review of the literature on programs that meet the needs of re-entry women. We note the applicability of these programs to the distinct needs of younger and older re-entry women and we encourage the development of more programs to meet both groups' needs.Cet article rend compte d'une étude menée à partir du témoignage de 276 femmes de 35 à 64 ans qui ont repris des études universitaires. Nous avons eu recours à une approche tenant compte des cycles de la vie pour analyser le montant de stress généré chez ces femmes par la vie universitaire et pour mettre en lumière les méthodes que celles-ci utilisent pour faire face à ce stress et s'adapter aux exigences propres aux études universitaires. Nous avons ce faisant comparé cette expérience au sein de deux sous-groupes: d'une part les étudiantes âgées de 35 à 44 ans, mères de jeunes enfants, et d'autre part celles de 45 à 64 ans dont les enfants avaient atteint l'âge adulte. Nous avons découvert que les raisons qui poussaient les personnes de ces deux groupes à reprendre des études étaient très différentes de même que les difficultés qu'elles éprouvaient pendant l'année scolaire et les moyens qu'elles utilisaient pour être à la hauteur de ce qu'on exigeait d'elles en tant qu'étudiantes. Cet article présente ensuite un éventail de programmes parmi ceux qui répondent le mieux aux besoins des femmes qui reprennent des études. Nous y soulignons dans quelle mesure ces programmes conviennent aux besoins spécifiques soit des femmes les plus jeunes soit des femmes les plus âgées et nous sollicitons la création d'un plus grand nombre de programmes susceptibles de répondre aux besoins des deux groupes

Predator feeding rates may often be unsaturated under typical prey densities

Predator feeding rates (described by their functional response) must saturate at high prey densities. Although thousands of manipulative functional response experiments show feeding rate saturation at high densities under controlled conditions, it remains unclear how saturated feeding rates are at natural prey densities. The general degree of feeding rate saturation has important implications for the processes determining feeding rates and how they respond to changes in prey density. To address this, we linked two databases—one of functional response parameters and one on mass–abundance scaling—through prey mass to calculate a feeding rate saturation index. We find that: (1) feeding rates may commonly be unsaturated and (2) the degree of saturation varies with predator and prey taxonomic identities and body sizes, habitat, interaction dimension and temperature. These results reshape our conceptualization of predator–prey interactions in nature and suggest new research on the ecological and evolutionary implications of unsaturated feeding rates

Computational modelling of a fluid-conveying flexible channel using oomph-lib

The objective of this paper is to assess the suitability of a new, open-source, Finite Element Modelling (FEM) program called Object-Oriented Multi-Physics Finite-Element Library (oomph-lib)to study the Fluid-Structure Interaction (FSI) mechanics of a fluid-conveying two-dimensional channel that has a flexible section. Previous studies have shown that this system contains rich dynamics that can include unstable oscillations of the flexible-wall section due to the fluid loading that itself is determined by the wall motion. The fundamental system is relevant to a host of applications in both engineered (e.g. flexible-pipes, membrane filters, and general aero-/hydro-elasticity) and biomechanical (e.g. blood flow, airway flow) systems. The computational model developed using oomph-lib accounts for unsteady laminar flow interacting with large-amplitude (nonlinear) deformations of a thin flexible wall. The fluid loading on the wall comprises both pressure and viscous stresses while the wall mechanics includes inertial, flexural and tension forces. Nonlinear effects in the wall mechanics principally arises through the tension induced by its deformation and the correct modelling of its geometry throughout its motion.The discretised equations for the coupled fluid and structural dynamics are combined to yield a single (monolithic) matrix differential equation for all of the fluid and wall variables that is solved through a time-stepping algorithm so as to generate numerical simulations of the system behaviour. In this paper we present results of a systematic validation of the computational model developed. Meanflow mechanics are validated by comparison against theory for Poiseuille flow through the channel with the flexible-wall held in its undisplaced position. Appropriate comparisons of statically-loaded deformations and in-vacuo vibrations of the flexible wall are made against linear theory and the limits of linear behaviour identified. The steady-state FSI is validated by comparing large-amplitude wall deformations, pressure and skin-friction loadings with published computational results that were obtained using a different computational scheme that is not in the public domain. Finally, some preliminary results of large amplitude dynamic FSI for the system are presented and discussed. Taken together, these results demonstrate the suitability of oomph-lib as a modelling and predictive tool for the study of fluid-conveying flexible pipes

A Gendered Analysis of Fisherfolk’s Livelihood Adaptation and Coping Responses in the Face of a Seasonal Fishing Ban in Tamil Nadu & Puducherry, India

This study investigates how people respond to economic stresses incurred as a result of natural resource regulations. Previous research has demonstrated that in some cases, men and women adapt differently to livelihood stresses. We argue that looking only at an individual’s sex is insufficient for understanding why they adapt the way they do. Instead, using the framework of intersectionality, we examine individuals’ adaptation strategies and coping responses influenced not only by their sex but also their power and class. Using the case of a closed fishing season in Tamil Nadu and Puducherry, India we employ interviews, seasonal activities calendars, and surveys to identify key variables that influence an individual’s likelihood of employing reactive strategies that may threaten their longer term livelihood sustainability. We show that if we categorize individuals only by sex, then women are more likely to resort to reactive coping than men. However, this sex divide in reactive coping is driven by particular subsets of people who also lack power and/or capital. Furthermore, we find that power and class lead to different outcomes for men and women, with networked power most helpful to women above a certain financial threshold. This study highlights the necessity of examining gender and livelihood adaptations beyond the male versus female dichotomy: considering intersecting and locally relevant measures of power, class, and sex are pivotal in understanding why people adapt and cope the way they do. This understanding of adaptation options may also have implications for resource management decisions that do not force individuals to choose between long-term livelihood resilience and response to immediate stresses

Abundance and Diversity of Organohalide-Respiring Bacteria in Lake Sediments Across a Geographical Sulfur Gradient

Across the U.S. Upper Midwest, a natural geographical sulfate gradient exists in lakes. Sediment grab samples and cores were taken to explore whether this sulfur gradient impacted organohalide-respiring Chloroflexi in lake sediments. Putative organohalide-respiring Chloroflexi were detected in 67 of 68 samples by quantitative polymerase chain reaction. Their quantities ranged from 3.5 × 104 to 8.4 × 1010 copies 16S rRNA genes g−1 dry sediment and increased in number from west to east, whereas lake sulfate concentrations decreased along this west-to-east transect. A terminal restriction fragment length polymorphism (TRFLP) method was used to corroborate this inverse relationship, with sediment samples from lower sulfate lakes containing both a higher number of terminal restriction fragments (TRFs) belonging to the organohalide-respiring Dehalococcoidetes, and a greater percentage of the TRFLP amplification made up by Dehalococcoidetes members. Statistical analyses showed that dissolved sulfur in the porewater, measured as sulfate after oxidation, appeared to have a negative impact on the total number of putative organohalide-respiring Chloroflexi, the number of Dehalococcoidetes TRFs, and the percentage of the TRFLP amplification made up by Dehalococcoidetes. These findings point to dissolved sulfur, presumably present as reduced sulfur species, as a potentially controlling factor in the natural cycling of chlorine, and perhaps as a result, the natural cycling of some carbon as well

Complexity Increases Predictability in Allometrically Constrained Food Webs

All ecosystems are subjected to chronic disturbances, such as harvest, pollution, and climate change. The capacity to forecast how species respond to such press perturbations is limited by our imprecise knowledge of pairwise species interaction strengths and the many direct and indirect pathways along which perturbations can propagate between species. Network complexity (size and connectance) has thereby been seen to limit the predictability of ecological systems. Here we demonstrate a counteracting mechanism in which the influence of indirect effects declines with increasing network complexity when species interactions are governed by universal allometric constraints. With these constraints, network size and connectance interact to produce a skewed distribution of interaction strengths whose skew becomes more pronounced with increasing complexity. Together, the increased prevalence of weak interactions and the increased relative strength and rarity of strong interactions in complex networks limit disturbance propagation and preserve the qualitative predictability of net effects even when pairwise interaction strengths exhibit substantial variation or uncertainty