“Selfish worker policing” controls reproduction in a Temnothorax ant

Animal societies, including those of humans, are under constant threat by selfish individuals, who attempt to enforce their own interests at the cost of the group. In the societies of bees, wasps, and ants, such individual selfishness can be prevented by “policing,” whereby workers or queens impede the reproduction of other individuals by aggression, immobilization, or egg eating. In this study, we report on a particular kind of reproduction control in the ant Temnothorax unifasciatus, which can be considered as a selfish act itself. We experimentally induced workers to lay eggs by dividing several colonies into two halves, one with and one without a queen. In queenless colonies, workers established rank orders by aggression and several top-ranking workers started to reproduce. Upon reunification, egg-laying workers mostly stopped behaving aggressively. They were neither attacked by the queen nor by random workers, but instead received infrequent, nondestructive, targeted aggression from a few workers, most of which became fertile when the queen was later removed. The introduction of differentially stained worker-laid and queen-laid eggs in queenright fragments did not lead to a selective removal of worker-laid eggs. Hence, there appears to be no collective worker policing in T. unifasciatus. Instead, reproduction appears to be controlled mostly through a few attacks from high-ranking workers, which, in this way, might attempt to selfishly increase their chances of future reproduction.     

A new look at the psychological contract during organizational socialization: The role of newcomers' obligations at entry

Previous studies have demonstrated that the psychological contract is largely shaped during socialization. This study adopts a complementary perspective and analyzes how the psychological contract at the start of employment shapes the subsequent socialization process. Drawing upon social exchange theory, we propose that newcomers with a higher sense of their personal obligations at entry will perceive orientation training as more useful and develop better relationships with their supervisors and peers, which in turn will facilitate their work adjustment. Results of a longitudinal survey on a sample of 144 recruits from a European Army show that newcomers with a higher initial sense of their employee obligations toward their employer report higher perceived training utility, higher leader–member exchange (LMX) with their instructors, and higher team–member exchange (TMX) with their platoon peers. Moreover, perceived training utility and LMX predict the fulfillment of employers' obligations; and training utility predicts the level of newcomers' employee obligations. Finally, training utility, LMX, and TMX predict some of three indicators of newcomers' adjustment, namely, role clarity (training utility and LMX), group integration (TMX), and organizational values understanding (training utility). These results highlight how newcomers' obligations at the start of employment contribute to the social exchange dynamic underlying organizational socialization. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of an indirect-cost calculation model suitable for workplace use

Introduction: Occupational Health and Safety (OHS) stakeholders rarely factor the cost of workplace accidents into prevention spending decisions. The lack of consideration of this key information is related to the fact that the scientific literature has failed to provide OHS stakeholders with a cost-calculation tool that is both sufficiently accurate and does not require a data-collection stage ill-suited to the time constraints of workplace decision-makers. Method: This study reviews the recent literature to identify key elements that should foster the use of indirect-cost calculation methods by decision makers. Results: A “local” approach currently appears to be the best method for calculating indirect costs of workplace incidents or accidents in comparison to “bottom-up” or “top-down” approach. This paper discusses four criteria that this type of approach must satisfy to be compatible with the time constraints and accuracy demands of OHS stakeholders in organizations. In addition, four bases for the development of a new indirect cost estimation model are presented and discussed. Impact on industry: this study provides bases and criteria to help the development of indirect-cost calculation models better suited to workplace use than those currently available.     

Survival and Inactivation by Advanced Oxidative Process of Foodborne Viruses in Model Low-Moisture Foods

Enteric viruses, such as human norovirus (NoV) and hepatitis A virus (HAV), are the major causes of foodborne illnesses worldwide. These viruses have low infectious dose, and may remain infectious for weeks in the environment and food. Limited information is available regarding viral survival and transmission in low-moisture foods (LMF). LMFs are generally considered as ready-to-eat products, which undergo no or minimal pathogen reduction steps. However, numerous foodborne viral outbreaks associated with LMFs have been reported in recent years. The objective of this study was to examine the survival of foodborne viruses in LMFs during 4-week storage at ambient temperature and to evaluate the efficacy of advanced oxidative process (AOP) treatment in the inactivation of these viruses. For this purpose, select LMFs such as pistachios, chocolate, and cereal were inoculated with HAV and the norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV), then viral survival on these food matrices was measured over a four-week incubation at ambient temperature, by both plaque assay and droplet-digital RT-PCR (ddRT-PCR) using the modified ISO-15216 method as well as the magnetic bead assay for viral recovery. We observed an approximately 0.5 log reduction in viral genome copies, and 1 log reduction in viral infectivity for all three tested viruses following storage of select inoculated LMFs for 4 weeks. Therefore, the present study shows that the examined foodborne viruses can persist for a long time in LMFs. Next, we examined the inactivation efficacy of AOP treatment, which combines UV-C, ozone, and hydrogen peroxide vapor, and observed that while approximately 100% (4 log) inactivation can be achieved for FCV, and MNV in chocolate, the inactivation efficiency diminishes to approximately 90% (1 log) in pistachios and 70% (< 1 log) in cereal. AOP treatment could therefore be a good candidate for risk reduction of foodborne viruses from certain LMFs depending on the food matrix and surface of treatment.

     

Lab-scale investigation of the ability of Polar Organic Chemical Integrative Sampler to catch short pesticide contamination peaks

Environmental Science and Pollution Research - In this lab-scale study, the POCIS capacity to integrate short contamination peaks of variable intensity and duration was evaluated. POCIS were...     

Is Diversification a Suitable Option to Reduce Drought-Induced Risk of Forest Dieback? An Economic Approach Focused on Carbon Accounting

Environmental Modeling & Assessment - Extreme or recurrent drought events are the principal source of stress on forests, impairing their overall health. They result in financial losses for...     

A model for estimating the potential biomagnification of chemicals in a generic food web: Preliminary development

GOAL, SCOPE AND BACKGROUND: Bioaccumulation and biomagnification of organic pollutants have been increasingly assessed and modeled during the last years. Due to the complexity of these processes and the large variability of food webs, setting generic assessments for these parameters is really difficult. Equilibrium models, based on a compound's lipophylicity, are the main tool in regulatory proposals, such as for identifying Persistent, Bioaccumulative and Toxic Substances (PBTs), although a refinement has been claimed by the scientific community. Toxicokinetic studies offer an alternative for these estimations, where biomagnification is modeled as a succession of bioaccumulation processes, each one regulated by toxicokinetic parameters. METHODS: A review of kinetic models covering species belonging to different trophic levels and with different ecological behavior has been conducted. The results were employed for setting a conceptual model for estimating the biomagnification potential in a generic food web, which was mathematically implemented through system dynamic models developed under data sheet software. Crystal Ball was then employed for allowing Monte Carlo based probabilistic calculations. Bioaccumulation laboratory assays have been performed to estimate toxicokinetic parameters in mussels (Mytilus edulis) with two PAHs (chrysene and benzo[a]pyrene). The contamination was delivered via food. The exposure period lasted more than one month followed then by a depuration phase. The contaminant content was determined on an individual basis on five replicates. RESULTS AND DISCUSSION:. The reviewed information suggested the development of a tiered conceptual biomagnification model, starting with a simplified food chain which can be refined to more realistic and complex models in successive levels. CONCLUSIONS: The mathematical implementation of the conceptual model offers tools for estimating the potential for bioaccumulation and biomagnification of chemicals under very different conditions. The versatility of the model can be used for both comparative estimations and for validating the model. RECOMMENDATIONS AND PERSPECTIVES: Since bioaccumulation and biomagnification processes are crucial elements for a proper risk assessment of chemicals, their estimation by mathematical models has been widely tested. However, inregulatory assessments, too simplistic models are still being used quite often. The biomagnification model presented in this study should be amore accurate alternative to these models. In comparison to other previously published biomagnification models, the present one covers the time variation of bioaccumulation using just a few toxicokinetic parameters.     

Application of rough sets analysis to identify polluted aquatic sites based on a battery of biomarkers: a comparison with classical methods

The evaluation of toxicological effects at the cellular and molecular levels in organisms are often used to determine sites subjected to contamination problems that pose a threat to the long-term survival of organisms. However, the integration of multiple measurements on the health status of organisms into a model for site discrimination is challenging. This study compares two discrimination methods which are based on rule inference: rough sets (RS) analysis and classification trees (CT) with classical multivariate discriminant analysis (DA). Site classification was attempted with six biomarkers of effects: metallothionein levels, lipid peroxidation, DNA damage, levels of lipophosphoproteins (i.e., vitellins), phagocytosis activity and haemocyte cell viability on clam (Mya arenaria) populations from the Saguenay River fjord (Quebec, Canada). Rule based methods have the advantage of complete independence from data distribution constraints in contrast to the classification methods from multivariate analysis that are more commonly used in ecotoxicology. Results show that RS and CT gave better classifications than DA because they do not require strong distributional assumptions. Moreover, RS provided classification rules that could identify the most important biomarker(s) for site discrimination. RS and CT were shown to be simple and efficient methods for classifying multivariable ecotoxicological data. This methodology would be especially useful when freedom from distributional assumptions is required.     

Biodegradation of petroleum hydrocarbon vapors: laboratory studies on rates and kinetics in unsaturated alluvial sand

Predictions of natural attenuation of volatile organic compounds (VOCs) in the unsaturated zone rely critically on information about microbial biodegradation kinetics. This study aims at determining kinetic rate laws for the aerobic biodegradation of a mixture of 12 volatile petroleum hydrocarbons and methyl tert-butyl ether (MTBE) in unsaturated alluvial sand. Laboratory column and batch experiments were performed at room temperature under aerobic conditions, and a reactive transport model for VOC vapors in soil gas coupled to Monod-type degradation kinetics was used for data interpretation. In the column experiment, an acclimatization of 23 days took place before steady-state diffusive vapor transport through the horizontal column was achieved. Monod kinetic parameters Ks and vmax could be derived from the concentration profiles of toluene, m-xylene, n-octane, and n-hexane, because substrate saturation was approached with these compounds under the experimental conditions. The removal of cyclic alkanes, isooctane, and 1,2,4-trimethylbenzene followed first-order kinetics over the whole concentration range applied. MTBE, n-pentane, and chlorofluorocarbons (CFCs) were not visibly degraded. Batch experiments suggested first-order disappearance rate laws for all VOCs except n-octane, which decreased following zero-order kinetics in live batch experiments. For many compounds including MTBE, disappearance rates in abiotic batch experiments were as high as in live batches indicating sorption. It was concluded that the column approach is preferable for determining biodegradation rate parameters to be used in risk assessment models.