When Does Less Equal More? Assessing The Mechanisms Driving Compensatory Mortality And The Hydra Effect

Many populations across taxa are regulated by negative density-dependence, wherein increased population sizes lead to decreased birth rates and/or increased mortality. By releasing such populations from some level of these density-dependent effects, extrinsic mortality can lead to counter-intuitive results, such as no change in population size (compensation), or an increase in population size (overcompensation). These results have been documented experimentally, but there currently exists a dearth of empirical studies exploring the mechanisms behind the phenomenon. We tested the relationship between extrinsic mortality level and (over)compensation in four mosquito species – Aedes aegypti, A. albopictus, A. triseriatus, and Culex pipiens – by exposing larvae to a range of mortality by artificial harvest and predation and analyzing the numbers of adults produced. Additionally, we examined the ability of three functionally diverse predators – Mesocyclops longisetus, Anopheles barberi, and Corethrella appendiculata – to induce (over)compensation in A. aegypti by exposing larvae to predation by either single or multiple predator species treatments. We found overcompensation across all ranges of mortality in A. triseriatus and C. pipiens and at intermediate levels of mortality in A. aegypti. Low-to-intermediate levels of mortality was compensatory in A. albopictus, followed by a decrease in adult production at the highest mortality level. Predation induced compensation in the second experiment and an increase in population equilibrium, a phenomenon known as the ‘hydra effect.’ These results provide a better understanding of the conditions under which mortality may increase adult production or population equilibrium. Because overcompensation and the hydra effect are predicted to affect a wide range of taxa and food webs, our findings present implications for developing proper population management and pest reduction strategies

Being Different Yet Feeling Similar: The Influence Of Demographic Composition And Organizational Culture On Work Processes And Outcomes

Drawing from self-categorization theory, we tested hypotheses on the effects of an organization's demographic composition and cultural emphasis on work processes and outcomes. Using an organizational simulation, we found that the extent to which an organization emphasized individualistic or collectivistic values interacted with demographic composition to influence social interaction, conflict, productivity, and perceptions of creativity among 258 MBA students. Our findings suggest that the purported benefits of demographic diversity are more likely to emerge in organizations that, through their culture, make organizational membership salient and encourage people to categorize one another as having the organization's interests in common, rather than those that emphasize individualism and distinctiveness among members.(.)Managemen

Yield and protein variation within a controlled traffic system

Controlled Traffic systems aim to minimise wheel traffic impact on the cropping system. In this study, on-farm research was employed to investigate the impact of several wheel tracks on grain yield and protein in a planter width within a 7-year-old Controlled Traffic Farming (CTF) system. This was achieved by using a plot harvester. Results from the study of grain sorghum (Sorghum bicolor) and maize (Zea mays) showed lower establishment rates adjacent to wheel tracks, resulting in lower yield and higher protein. Further studies investigating a change to a system with fewer wheel tracks show that reducing the number of wheel tracks appears to have led to increased grain yield

Genetic and environmental risk factors for sexual distress and its association with female sexual dysfunction

A. Burri, Q. Rahman and T. Spector (2011). Genetic and environmental risk factors for sexual distress and its association with female sexual dysfunction. Psychological Medicine, 41, pp 2435-2445. Copyright © Cambridge University Press 2011. http://dx.doi.org/10.1017/S003329171100049

Micromanipulation of InP lasers with optoelectronic tweezers for integration on a photonic platform

The integration of light sources on a photonic platform is a key aspect of the fabrication of self-contained photonic circuits with a small footprint that does not have a definitive solution yet. Several approaches are being actively researched for this purpose. In this work we propose optoelectronic tweezers for the manipulation and integration of light sources on a photonic platform and report the positional and angular accuracy of the micromanipulation of standard Fabry-Pérot InP semiconductor laser die. These lasers are over three orders of magnitude bigger in volume than any previously assembled with optofluidic techniques and the fact that they are industry standard lasers makes them significantly more useful than previously assembled microdisk lasers. We measure the accuracy to be 2.5 ± 1.4 µm and 1.4 ± 0.4° and conclude that optoelectronic tweezers are a promising technique for the micromanipulation and integration of optoelectronic components in general and semiconductor lasers in particular

Associations between diurnal preference, sleep quality and externalizing behaviours: a behavioural genetic analysis

Background - Certain aspects of sleep co-occur with externalizing behaviours in youth, yet little is known about these associations in adults. The present study: (1) examines the associations between diurnal preference (morningness versus eveningness), sleep quality and externalizing behaviours; (2) explores the extent to which genetic and environmental influences are shared between or are unique to these phenotypes; (3) examines the extent to which genetic and environmental influences account for these associations. Method - Questionnaires assessing diurnal preference, sleep quality and externalizing behaviours were completed by 1556 young adult twins and siblings. Results - A preference for eveningness and poor sleep quality were associated with greater externalizing symptoms [r=0.28 (95% CI 0.23–0.33) and 0.34 (95% CI 0.28–0.39), respectively]. A total of 18% of the genetic influences on externalizing behaviours were shared with diurnal preference and sleep quality and an additional 14% were shared with sleep quality alone. Non-shared environmental influences common to the phenotypes were small (2%). The association between diurnal preference and externalizing behaviours was mostly explained by genetic influences [additive genetic influence (A)=80% (95% CI 0.56–1.01)], as was the association between sleep quality and externalizing behaviours [A=81% (95% CI 0.62–0.99)]. Non-shared environmental (E) influences accounted for the remaining variance for both associations [E=20% (95% CI −0.01 to 0.44) and 19% (95% CI 0.01–0.38), respectively]. Conclusions - A preference for eveningness and poor sleep quality are moderately associated with externalizing behaviours in young adults. There is a moderate amount of shared genetic influences between the phenotypes and genetic influences account for a large proportion of the association between sleep and externalizing behaviours. Further research could focus on identifying specific genetic polymorphisms common to both sleep and externalizing behaviours

The Genetic and Environmental Sources of Resemblance Between Normative Personality and Personality Disorder Traits

Recent work has suggested a high level of congruence between normative personality, most typically represented by the big five factors, and abnormal personality traits. In 2,293 Norwegian adult twins ascertained from a population-based registry, the authors evaluated the degree of sharing of genetic and environmental influences on normative personality, assessed by the Big Five Inventory (BFI), and personality disorder traits (PDTs), assessed by the Personality Inventory for DSM-S-Norwegian Brief Form (PID-5NBF). For four of the five BFI dimensions, the strongest genetic correlation was observed with the expected PID-5-NBF dimension (e.g., neuroticism with negative affectivity [+], conscientiousness with disinhibition [-]). However, neuroticism, conscientiousness, and agreeableness had substantial genetic correlations with other PID-S-NBF dimensions (e.g., neuroticism with compulsivity [+], agreeableness with detachment [-]). Openness had no substantial genetic correlations with any PID-5-NBF dimension. The proportion of genetic risk factors shared in aggregate between the BFI traits and the PID-5-NBF dimensions was quite high for conscientiousness and neuroticism, relatively robust for extraversion and agreeableness, but quite low for openness. Of the six PID-S-NBF dimensions, three (negative affectivity, detachment, and disinhibition) shared, in aggregate, most of their genetic risk factors with normative personality traits. Genetic factors underlying psychoticism, antagonism, and compulsivity were shared to a lesser extent, suggesting that they are influenced by etiological factors not well indexed by the BFI

The utility of twins in developmental cognitive neuroscience research: How twins strengthen the ABCD research design

The ABCD twin study will elucidate the genetic and environmental contributions to a wide range of mental and physical health outcomes in children, including substance use, brain and behavioral development, and their interrelationship. Comparisons within and between monozygotic and dizygotic twin pairs, further powered by multiple assessments, provide information about genetic and environmental contributions to developmental associations, and enable stronger tests of causal hypotheses, than do comparisons involving unrelated children. Thus a sub-study of 800 pairs of same-sex twins was embedded within the overall Adolescent Brain and Cognitive Development (ABCD) design. The ABCD Twin Hub comprises four leading centers for twin research in Minnesota, Colorado, Virginia, and Missouri. Each site is enrolling 200 twin pairs, as well as singletons. The twins are recruited from registries of all twin births in each State during 2006–2008. Singletons at each site are recruited following the same school-based procedures as the rest of the ABCD study. This paper describes the background and rationale for the ABCD twin study, the ascertainment of twin pairs and implementation strategy at each site, and the details of the proposed analytic strategies to quantify genetic and environmental influences and test hypotheses critical to the aims of the ABCD study. Keywords: Twins, Heritability, Environment, Substance use, Brain structure, Brain functio

Tools for evaluating and monitoring effectiveness of urban landscape water conservation interventions and programs

Our research objective was to investigate ways to evaluate landscape water use to help cities more effectively direct water conservation programs to locations with capacity to conserve. Research was conducted in connection with a landscape irrigation evaluation delivered through a city-sponsored Water Check Program. Research efforts led to development of several assessment and monitoring tools including: Landscape Irrigation Ratio (LIR), Participant Outcome Evaluation Tool, and Program Evaluation Tool. We utilized these tools to identify locations with capacity to conserve water applied to landscapes, compare water use before and after the water check, and evaluate Water Check Program effectiveness. We found the LIR approach successfully distinguished residential locations efficiently or acceptably using water applied to landscapes from ones with use considered inefficient or excessive. In analyzing change in participants’ water use and eliminating explanations other than the water check, we found factors influencing landscape water use tend to be highly contextualized and the intervention itself needed to be analyzed. The majority of participants who adopted the water check recommendations successfully reduced their landscape water use, but results indicate water check programs can be designed for greater effectiveness by accommodating participants’ differing knowledge and skill levels. We argue that the tools we developed provide the water conservation field with a needed set of common assessment methods. We conclude that landscape water checks have the potential to provide people with the information and problem-solving skills necessary to maintain residential landscapes using appropriate amounts of water if they are well designed, delivered, and monitored

Effects of drought on groundwater-fed lake areas in the Nebraska Sand Hills

Study region: The Nebraska Sand Hills (NSH) lies in the western part of Nebraska, United States. We chose the north-eastern, central, and western parts of NSH with distinct climate, topography, and hydrology. Study focus: The study assesses the response of hundreds of shallow groundwater-fed lakes to drought. Total lake area (TLA), determined by classifying Landsat satellite images from 1984 to 2018, was juxtaposed with published Palmer Drought Severity Index (PDSI) and detrended cumulative PDSI (DeCumPDSI) at monthly and annual timescales. The PDSI and DeCumPDSI were time lagged to incorporate the preceding climatic effect (groundwater time lag) and evaluated against TLA using Bayesian regression analysis. New hydrologic insight for the region: TLA in the NSH respond to the seasonal as well as long-term climatic effects moderated by topography, surface, and subsurface hydrology. A higher determination coefficient R2 and lower mean square error of TLA at annual PDSI and DeCumPDSI illustrate the effect of long-term climatic fluctuations and groundwater influence: the evaporative losses from lakes are modulated by the lake-groundwater exchange, but the groundwater recharge has a longer response time to the drought. The study provides a simple method of assessment of the climate impact that results from the satellite data, gridded climate observation, and statistics for sensitive landscape of the NSH