Collective Gradient Sensing in Fish Schools

Throughout the animal kingdom, animals frequently benefit from living in groups. Models of collective behaviour show that simple local interactions are sufficient to generate group morphologies found in nature (swarms, flocks and mills). However, individuals also interact with the complex noisy environment in which they live. In this work, we experimentally investigate the group performance in navigating a noisy light gradient of two unrelated freshwater species: golden shiners (Notemigonuscrysoleucas) and rummy nose tetra (Hemigrammus bleheri). We find that tetras outperform shiners due to their innate individual ability to sense the environmental gradient. Using numerical simulations, we examine how group performance depends on the relative weight of social and environmental information. Our results highlight the importance of balancing of social and environmental information to promote optimal group morphologies and performance

Testing a Thermodynamic Approach to Collective Animal Behavior in Laboratory Fish Schools

Collective behaviors displayed by groups of social animals are observed frequently in nature. Understanding and predicting the behavior of complex biological systems is dependent on developing effective descriptions and models. While collective animal systems are characteristically nonequilibrium, we can employ concepts from equilibrium statistical mechanics to motivate the measurement of material-like properties in laboratory animal aggregates. Here, we present results from a new set of experiments that utilize high speed footage of two-dimensional schooling events, particle tracking, and projected static and dynamic light fields to observe and control the behavior of negatively phototaxic fish schools (Hemigrammus bleheri). First, we use static light fields consisting of dark circular regions to produce visual stimuli that confine the schools to a range of areas. We find that schools have a maximum density which is independent of group size, and that a swim pressurelike quantity, Π increases linearly with number density, suggesting that unperturbed schools exist on an isotherm. Next, we use dynamic light fields where the radius of the dark region shrinks linearly with time to compress the schools. We find that an effective temperature parameter depends on the compression time and our results are thus consistent with the school having a constant heat flux. These findings further evidence the utility of effective thermodynamic descriptions of nonequilibrium systems in collective animal behavior

A pilot study of cardiac MRI in breast cancer survivors after cardiotoxic chemotherapy and three-dimensional conformal radiotherapy

Purpose/Objectives: Node-positive breast cancer patients often receive chemotherapy and regional nodal irradiation. The cardiotoxic effects of these treatments, however, may offset some of the survival benefit. Cardiac magnetic resonance (CMR) is an emerging modality to assess cardiac injury. This is a pilot trial assessing cardiac damage using CMR in patients who received anthracycline-based chemotherapy and three-dimensional conformal radiotherapy (3DCRT) regional nodal irradiation using heart constraints. Materials and Methods: Node-positive breast cancer patients (2000-2008) treated with anthracycline-based chemotherapy and 3DCRT regional nodal irradiation (including the internal mammary chain nodes) with heart ventricular constraints (V25 \u3c 10%) were invited to participate. Cardiac tissues were contoured and analyzed separately for whole heart (pericardium) and for combined ventricles and left atrium (myocardium). CMR obtained ventricular function/dimensions, late gadolinium enhancement (LGE), global longitudinal strain (GLS), and extracellular volume fraction (ECV) as measures of cardiac injury and/or early fibrosis. CMR parameters were correlated with dose-volume constraints using Spearman correlations. Results: Fifteen left-sided and five right-sided patients underwent CMR. Median diagnosis age was 50 (32-77). No patients had baseline cardiac disease before regional nodal irradiation. Median time after 3DCRT was 8.3 years (5.2-14.4). Median left-sided mean heart dose (MHD) was 4.8 Gy (1.1-11.2) and V25 was 5.7% (0-12%). Median left ventricular ejection fraction (LVEF) was 63%. No abnormal LGE was observed. No correlations were seen between whole heart doses and LVEF, LV mass, GLS, or LV dimensions. Increasing ECV did not correlate with increased heart or ventricular doses. However, correlations between higher LV mass and ventricular mean dose, V10, and V25 were seen. Conclusion: At a median follow-up of 8.3 years, this cohort of node-positive breast cancer patients who received anthracycline-based chemotherapy and regional nodal irradiation had no clinically abnormal CMR findings. However, correlations between ventricular mean dose, V10, and V25 and LV mass were seen. Larger corroborating studies that include advanced techniques for measuring regional heart mechanics are warranted

New Introductions, Spread of Existing Matrilines, and High Rates of Pyrethroid Resistance Result in Chronic Infestations of Bed Bugs (Cimex lectularius L.) in Lower-Income Housing

Infestations of the common bed bug (Cimex lectularius L.) have increased substantially in the United States in the past 10-15 years. The housing authority in Harrisonburg, Virginia, conducts heat-treatments after bed bugs are detected in a lower-income housing complex, by treating each infested unit at 60°C for 4-6 hours. However, a high frequency of recurrent infestations called into question the efficacy of this strategy. Genetic analysis using Bayesian clustering of polymorphic microsatellite loci from 123 bed bugs collected from 23 units from May 2012 to April 2013 in one building indicated that (a) 16/21 (73%) infestations were genetically similar, suggesting ineffective heat-treatments or reintroductions from within the building or from a common external source, followed by local spread of existing populations; and (b) up to 5 of the infestations represented new genotypes, indicating that 5 new populations were introduced into this building in one year, assuming they were not missed in earlier screens. There was little to no gene flow among the 8 genetic clusters identified in the building. Bed bugs in the U.S. often possess one or both point mutations in the voltage-gated sodium channel, termed knockdown resistance (kdr), from valine to leucine (V419L) and leucine to isoleucine (L925I) that confer target-site resistance against pyrethroid insecticides. We found that 48/121 (40%) bed bugs were homozygous for both kdr mutations (L419/I925), and a further 59% possessed at least one of the kdr mutations. We conclude that ineffective heat treatments, new introductions, reintroductions and local spread, and an exceptionally high frequency of pyrethroid resistance are responsible for chronic infestations in lower-income housing. Because heat treatments fail to protect from reintroductions, and pesticide use has not decreased the frequency of infestations, preventing new introductions and early detection are the most effective strategies to avoid bed bug infestations in multistory apartment buildings

The Psychological and Social Processes through which Internalized Heterosexism Influences Psychological Distress in Sexual Minorities

Internalized heterosexism refers to the development of a negative view of one\u27s own and others\u27 sexual minority identities as a product of living within a heterosexist society. Various negative mental health outcomes have been associated with internalized heterosexism (IH), such as anxiety, depression, and suicidality. However, little is known about the actual processes through which these outcomes take place. The current study examined the role of self-criticism (a psychological process), connectedness with other sexual minorities (a social process), and decentering (a potential coping strategy wherein someone is able to detach from their thoughts and view them as events instead of truth about themselves) in explaining the relation between IH and psychological distress. Data were collected via an online survey and analyzed using structural equation modeling (SEM) with latent variables for most study constructs. Results supported previous research, showing a significant direct relation between IH and psychological distress. In addition, higher self-criticism and lower connectedness with sexual minorities mediated this relation. The model fit for the final model which included both mediators was a significant improvement from the initial model with only the direct relation between IH and psychological distress and accounted for a significant amount of the variance in psychological distress (64.3%). In addition, decentering significantly moderated the relation between IH and psychological distress. At low levels of IH, decentering did not appear to impact the relation with psychological distress. However, at high levels of IH, high decentering was associated with lower psychological distress for participants who had lower scores on decentering. Correlational analyses also revealed that high decentering was associated with less self-criticism and more community connectedness. Most participants reported having various types of connections to other sexual minorities, with the mean being 3.49 different forms of community connections. The findings of this study revealed underlying processes that explain a significant amount of variance in the relation between IH and psychological distress. Both self-criticism and connectedness to a sexual minority community are mechanisms that could be targeted within therapy when working to improve the mental health of clients with high IH. Limitations and directions for future research are presented

Lesbian, Gay, Bisexual and Trans-sexual Butch-Femme Subcultures

The terms butch and femme refer to two gender identities that are rooted in sexual minority women\u27s communities. Butch and femme can be descriptions of gender expressions as well as gender identities. Within this article, the origins of these identities are reviewed, as well as the ways in which they have changed over time. Research on butch and femme identities, relationships, and experiences of discrimination is reviewed as is methodological issues related to this research

Lesbian, Gay, Bisexual and Trans-sexual Butch-Femme Subcultures

The terms butch and femme refer to two gender identities that are rooted in sexual minority women\u27s communities. Butch and femme can be descriptions of gender expressions as well as gender identities. Within this article, the origins of these identities are reviewed, as well as the ways in which they have changed over time. Research on butch and femme identities, relationships, and experiences of discrimination is reviewed as is methodological issues related to this research

Sexual Minority Women\u27s Gender Identity and Expression: Challenges and Supports

Sexual minority women were divided into four groups to study their gender identities (butch and femme), and genderexpression (traditionally gendered and non-traditionally gendered women who do not identify as butch or femme). Experiences of heterosexist events (discrimination, harassment, threats of violence, victimization, negative emotions associated with these events), mental health (self esteem, stress, depression), and supports for a sexual minority identity(social support, outness, internalized homophobia) were examined across these groups. Findings suggested that butch-identified women experienced more heterosexist events than femme women or women with non-traditional genderexpressions. There were no differences in mental health variables