Science.gov

Sample records for group size cohesion

  1. Unit-level voluntary turnover rates and customer service quality: implications of group cohesiveness, newcomer concentration, and size.

    PubMed

    Hausknecht, John P; Trevor, Charlie O; Howard, Michael J

    2009-07-01

    Despite substantial growth in the service industry and emerging work on turnover consequences, little research examines how unit-level turnover rates affect essential customer-related outcomes. The authors propose an operational disruption framework to explain why voluntary turnover impairs customers' service quality perceptions. On the basis of a sample of 75 work units and data from 5,631 employee surveys, 59,602 customer surveys, and organizational records, results indicate that unit-level voluntary turnover rates are negatively related to service quality perceptions. The authors also examine potential boundary conditions related to the disruption framework. Of 3 moderators studied (group cohesiveness, group size, and newcomer concentration), results show that turnover's negative effects on service quality are more pronounced in larger units and in those with a greater concentration of newcomers. PMID:19594245

  2. Unit-level voluntary turnover rates and customer service quality: implications of group cohesiveness, newcomer concentration, and size.

    PubMed

    Hausknecht, John P; Trevor, Charlie O; Howard, Michael J

    2009-07-01

    Despite substantial growth in the service industry and emerging work on turnover consequences, little research examines how unit-level turnover rates affect essential customer-related outcomes. The authors propose an operational disruption framework to explain why voluntary turnover impairs customers' service quality perceptions. On the basis of a sample of 75 work units and data from 5,631 employee surveys, 59,602 customer surveys, and organizational records, results indicate that unit-level voluntary turnover rates are negatively related to service quality perceptions. The authors also examine potential boundary conditions related to the disruption framework. Of 3 moderators studied (group cohesiveness, group size, and newcomer concentration), results show that turnover's negative effects on service quality are more pronounced in larger units and in those with a greater concentration of newcomers.

  3. Group Cohesion in Experiential Growth Groups

    ERIC Educational Resources Information Center

    Steen, Sam; Vasserman-Stokes, Elaina; Vannatta, Rachel

    2014-01-01

    This article explores the effect of web-based journaling on changes in group cohesion within experiential growth groups. Master's students were divided into 2 groups. Both used a web-based platform to journal after each session; however, only 1 of the groups was able to read each other's journals. Quantitative data collected before and…

  4. Behavioural Contagion Explains Group Cohesion in a Social Crustacean

    PubMed Central

    Broly, Pierre; Deneubourg, Jean-Louis

    2015-01-01

    In gregarious species, social interactions maintain group cohesion and the associated adaptive values of group living. The understanding of mechanisms leading to group cohesion is essential for understanding the collective dynamics of groups and the spatio-temporal distribution of organisms in environment. In this view, social aggregation in terrestrial isopods represents an interesting model due to its recurrence both in the field and in the laboratory. In this study, and under a perturbation context, we experimentally tested the stability of groups of woodlice according to group size and time spent in group. Our results indicate that the response to the disturbance of groups decreases with increases in these two variables. Models neglecting social effects cannot reproduce experimental data, attesting that cohesion of aggregation in terrestrial isopods is partly governed by a social effect. In particular, models involving calmed and excited individuals and a social transition between these two behavioural states more accurately reproduced our experimental data. Therefore, we concluded that group cohesion (and collective response to stimulus) in terrestrial isopods is governed by a transitory resting state under the influence of density of conspecifics and time spent in group. Lastly, we discuss the nature of direct or indirect interactions possibly implicated. PMID:26067565

  5. Using and misusing factor analysis to explore group cohesion.

    PubMed

    Cota, A A; Longman, R S; Evans, C R; Dion, K L; Kilik, L

    1995-03-01

    Group cohesion is an important construct in understanding the behavior of different types of groups. However, controversy exists about how to conceptualize and measure cohesion, and a central issue is its dimensionality. Consequently, researchers have used factor analysis to examine the structure of the construct of cohesion and measures of it. Our goals in writing this article were to review critically how factor analysis has been used to understand group cohesion, make some recommendations for future factor analytic work, and point out some weaknesses and strengths in using factor analysis to explore cohesion.

  6. Exploring Group Cohesion in a Higher Education Field Experience

    ERIC Educational Resources Information Center

    Malcarne, Brian Keith

    2012-01-01

    The purpose of this study was to gain understanding into the experience of group cohesion for university students participating in an academic field experience. A mixed methods approach was used following a two-phase, sequential research design to help provide a more complete explanation of how group cohesion was impacted by the field experience.…

  7. The role of biophysical cohesion on subaqueous bed form size

    NASA Astrophysics Data System (ADS)

    Parsons, Daniel R.; Schindler, Robert J.; Hope, Julie A.; Malarkey, Jonathan; Baas, Jaco H.; Peakall, Jeffrey; Manning, Andrew J.; Ye, Leiping; Simmons, Steve; Paterson, David M.; Aspden, Rebecca J.; Bass, Sarah J.; Davies, Alan G.; Lichtman, Ian D.; Thorne, Peter D.

    2016-02-01

    Biologically active, fine-grained sediment forms abundant sedimentary deposits on Earth's surface, and mixed mud-sand dominates many coasts, deltas, and estuaries. Our predictions of sediment transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt, sand, and gravel. This approach underpins many paleoenvironmental reconstructions of sedimentary successions, which rely on analysis of cross-stratification and bounding surfaces produced by migrating bed forms. Here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology. The results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships. The findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record.

  8. Relationship Between Group Cohesion and Anxiety in Soccer

    PubMed Central

    Borrego, Carla Chicau; Cid, Luis; Silva, Carlos

    2012-01-01

    Group cohesion in sport is a widely spread theme today. Research has found cohesion to be influenced by several individual and group components. Among the cognitive variables that relate to cohesion we found competitive anxiety. The purpose of this study was to examine the relation between task cohesion (ATG-T, and GI-T) and competitive state anxiety (A-state), and also if there would be a relation between cohesion and self-confidence. Participants were 366 football players of both genders male and female, aged between 15 to 23 years old, from Portugal’s championships. Cohesion was measured using the Portuguese version of the Group Environment Questionnaire, and to assess competitive anxiety, we used the Portuguese version of the Competition State Anxiety Inventory 2. Our results show that female athletes report experiencing more cognitive anxiety and less self-confidence than male athletes. Only cognitive anxiety relates in a significantly negative way with the perception of cohesion (GI-T e ATG-T) in the total number of participants and in male athletes. Relatively to the somatic anxiety, it only relates negatively with the perception of the integration of the group in the total number of participants and in the male gender. PMID:23487008

  9. The role of biophysical cohesion on subaqueous bed form size

    PubMed Central

    Schindler, Robert J.; Hope, Julie A.; Malarkey, Jonathan; Baas, Jaco H.; Peakall, Jeffrey; Manning, Andrew J.; Ye, Leiping; Simmons, Steve; Paterson, David M.; Aspden, Rebecca J.; Bass, Sarah J.; Davies, Alan G.; Lichtman, Ian D.; Thorne, Peter D.

    2016-01-01

    Abstract Biologically active, fine‐grained sediment forms abundant sedimentary deposits on Earth's surface, and mixed mud‐sand dominates many coasts, deltas, and estuaries. Our predictions of sediment transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt, sand, and gravel. This approach underpins many paleoenvironmental reconstructions of sedimentary successions, which rely on analysis of cross‐stratification and bounding surfaces produced by migrating bed forms. Here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology. The results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships. The findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record. PMID:27011393

  10. Root Cohesion Controls on Shallow Landslide Size, Shape and Location

    NASA Astrophysics Data System (ADS)

    Douglas, M.; Bellugi, D. G.; Perron, J.; Coe, J. A.; Schmidt, K. M.

    2013-12-01

    Many environmental factors, including ground cover, local hydrology, and recent weather events interact to cause shallow landslides and determine landslide characteristics. Vegetation is of particular interest, because changes in vegetation density, age, and composition are expected consequences of human land use and climate change. These changes alter effective cohesion due to root reinforcement, which is known to impact landslide abundance, but the effects of root cohesion on landslide size, shape and location have not been quantified. The Elliott State Forest, a 376 km2 managed forest in Douglas County, Oregon, provides an ideal venue to study these effects. There, a single storm in November 1996 triggered 154 shallow landslides, which were subsequently mapped using aerial images onto laser altimetry data, in an area with a range of vegetation ages but relatively uniform soil properties, topography, and lithology. We used aerial imagery to categorize areas with different land use histories into 3 vegetation classes, ranging from clear-cuts to forest with mature trees over 100 years old. Each mapped landslide was then assigned to a class, and its size, shape and location was recorded. Our results show that, in addition to the expected decrease in landslide abundance in more-vegetated areas (which could be influenced by a bias against detecting landslides under trees), landslides in those areas were also larger and more elongated in the down-slope direction. Although landslides in all three classes generally occurred at locations with similar drainage area and slope, we observed that slides with a larger ratio of drainage area to slope were slightly more abundant in areas with lower vegetation cover. To investigate the causes of these variations, we used a new shallow landslide model calibrated for the Oregon Coast Range to predict the size, shape and location of landslides triggered by the 1996 storm under a range of root cohesion values in a subset of the study

  11. The Role of Communication and Cohesion in Reducing Social Loafing in Group Projects

    ERIC Educational Resources Information Center

    Lam, Chris

    2015-01-01

    This study examines previously untested variables that influence social loafing in professional and technical communication group projects by determining the influence of communication quality and task cohesion on social loafing. A set-up factors model, which included group size, peer review, project scope, and method of team formation, was also…

  12. Examining the Relationship between Emotional Intelligence and Group Cohesion

    ERIC Educational Resources Information Center

    Moore, Amanda; Mamiseishvili, Ketevan

    2012-01-01

    Collaborative learning experiences increase student learning, but what happens when students fail to collaborate? The authors investigated the relationship between emotional intelligence and group cohesion by studying 44 undergraduate teams who were completing semester-long projects in their business classes at a small private university in the…

  13. Groupthink: Effects of Cohesiveness and Problem-Solving Procedures on Group Decision Making.

    ERIC Educational Resources Information Center

    Callaway, Michael R.; Esser, James K.

    1984-01-01

    Tested Janis' groupthink formulation with 126 students by manipulating group cohesiveness and adequacy of decision procedures in a factorial design. Results showed highest quality decisions were produced by groups of intermediate cohesiveness. Highly cohesive groups without adequate decision procedures (the groupthink condition) tended to make the…

  14. Dynamic Relationships of Therapist Alliance and Group Cohesion in Transdiagnostic Group CBT for Anxiety Disorders

    PubMed Central

    Norton, Peter J.; Kazantzis, Nikolaos

    2015-01-01

    Objective Little is known about the temporal variability of the alliance-symptom change and cohesion-symptom change relationships over the course of group therapy. These questions were examined in a sample of 373 clients receiving a transdiagnostic cognitive behavior therapy (tCBT), which culled the principle research-supported mechanisms of change for anxiety disorders. Method We examined relationships between the client versions of the Working Alliance Inventory and Group Cohesion Scale in predicting subsequent symptom change, as assessed by the state scale of the State-Trait Anxiety Inventory. Results Alliance and cohesion were significant predictors of next session anxiety scores. The alliance was consistently associated with anxiety symptoms (rs = −.152 to −.198, ps < .05), but cohesion only showed significant relationships with anxiety symptoms at sessions 8 and 10 (Session 8, r = −.233, p = .020, and 10, r = −.236, p = .027). Alliance-anxiety relations remained constant, whereas cohesion-anxiety relations substantially increased from earlier to later sessions. Discussion Differences that were obtained in the relation of alliance and cohesion with anxiety symptoms suggests that these processes have different roles within group tCBT. If replicated, the present findings would suggest that the dynamic relationships between alliance and cohesion and symptoms within group CBT for anxiety disorders have been an important omission in process-outcome studies. PMID:26689305

  15. Internal character dictates transition dynamics between isolation and cohesive grouping

    NASA Astrophysics Data System (ADS)

    Manrique, Pedro D.; Hui, Pak Ming; Johnson, Neil F.

    2015-12-01

    We show that accounting for internal character among interacting heterogeneous entities generates rich transition behavior between isolation and cohesive dynamical grouping. Our analytical and numerical calculations reveal different critical points arising for different character-dependent grouping mechanisms. These critical points move in opposite directions as the population's diversity decreases. Our analytical theory may help explain why a particular class of universality is so common in the real world, despite the fundamental differences in the underlying entities. It also correctly predicts the nonmonotonic temporal variation in connectivity observed recently in one such system.

  16. Group Climate, Cohesion, Alliance, and Empathy in Group Psychotherapy: Multilevel Structural Equation Models

    ERIC Educational Resources Information Center

    Johnson, Jennifer E.; Burlingame, Gary M.; Olsen, Joseph A.; Davies, D. Robert; Gleave, Robert L.

    2005-01-01

    This study examined the definitional and statistical overlap among 4 key group therapeutic relationship constructs--group climate, cohesion, alliance, and empathy--across member-member, member-group, and member-leader relationships. Three multilevel structural equation models were tested using self-report measures completed by 662 participants…

  17. Leader behaviors, group cohesion, and participation in a walking group program

    PubMed Central

    Izumi, Betty T.; Schulz, Amy J.; Mentz, Graciela; Israel, Barbara A.; Sand, Sharon L.; Reyes, Angela G.; Hoston, Bernadine; Richardson, Dawn; Gamboa, Cindy; Rowe, Zachary; Diaz, Goya

    2015-01-01

    Background Fewer than half of all U.S. adults meet the 2008 Physical Activity Guidelines. Leader behaviors and group cohesion have been associated with increased participation or adherence in sports team and exercise class settings. Physical activity interventions in community settings that encompass these factors may enhance intervention adherence. Purpose To examine the impact of Community Health Promoter leader behaviors and group cohesion on participation in a walking group intervention among racially/ethnically diverse adults in low-to-moderate income communities in Detroit, Mich. Design Data for the current study were drawn from the Walk Your Heart to Health (WYHH) data set. WYHH was a multi-site cluster randomized controlled study with a lagged intervention and outcome measurements at baseline, four, eight, and 32 weeks. Pooled survey data from both intervention arms is used for the current study. Data were analyzed between August 2013 and October 2014. Setting/participants A total of 603 non-Hispanic Black, non-Hispanic White, and Hispanic adults across five cohorts that began the 32-week WYHH intervention between March 2009 and October 2011. Intervention A 32-week long walking group program hosted by community- and faith-based organizations and facilitated by Community Health Promoters. Walking groups met three times per week for 90-minutes per session. To promote participation in or adherence to WYHH, Community Health Promoters used evidence-based strategies to facilitate group cohesion. Group members assumed increasing leadership responsibility for facilitating sessions over time. Main outcome measures Participation in WYHH as measured by consistency of attendance. Results Community Health Promoter leader behaviors were positively associated with participation in WYHH. Social but not task cohesion was significantly associated with consistent participation. Social cohesion may mediate the relationship between leader behaviors and walking group

  18. Effects of a Low-Element Challenge Course on Abstinence Self-Efficacy and Group Cohesion

    ERIC Educational Resources Information Center

    Clem, Jamie M.; Smith, Thomas E.; Richards, Kristin V.

    2012-01-01

    Substance abuse researchers identify self-efficacy and group cohesion as important components in alcohol and other drug-dependency treatment. Objectives: The purpose of this single-group, pretest-posttest study is to explore the therapeutic value of a challenge course intervention on the self-efficacy and group cohesion of nine chemically…

  19. The Use of Collaborative Writing To Enhance Cohesion in Poetry Therapy Groups.

    ERIC Educational Resources Information Center

    Golden, Karina M.

    2000-01-01

    Examines the effect of collaborative writing on cohesion in poetry therapy groups with 33 graduate students. Finds that post test scores on the Group Environment Scale indicated a significant difference in cohesion for those groups using collaborative writing compared to those without collaborative writing. (SR)

  20. Comparison of Group Cohesion, Class Participation, and Exam Performance in Live and Online Classes

    ERIC Educational Resources Information Center

    Galyon, Charles E.; Heaton, Eleanore C. T.; Best, Tiffany L.; Williams, Robert L.

    2016-01-01

    Though class participation and group cohesion have shown some potential to promote student performance in conventional classrooms, their efficacy has not yet been demonstrated in an online-class setting. Group cohesion, defined as member attraction to and self-identification with a group, is thought to promote positive interdependence and the…

  1. Redefining Group Cohesiveness and Effectiveness: Replicating and Extending within New Perspectives.

    ERIC Educational Resources Information Center

    Keyton, Joann; Springston, Jeffery K.

    A study examining small group performance replicated and extended a previous study by L. Kelly and R. L. Duran to reanalyze their operationalization of cohesiveness. To test the hypotheses of the original study and to explore questions about using the polarization index as an indication of group cohesiveness, the study used a large number of…

  2. Influence of Sport Education on Group Cohesion in University Physical Education

    ERIC Educational Resources Information Center

    Jenkins, Jayne M.; Alderman, Brandon L.

    2011-01-01

    The Sport Education ("SE") curricular model incorporated within university physical education Basic Instruction Program (BIP) may increase group cohesion. This study's purpose was to identify student perceptions of a BIP course taught within "SE," and investigate group cohesion in differing activity content. Participants included 430 students…

  3. Family Cohesion and Its Relationship to Psychological Distress among Latino Groups

    ERIC Educational Resources Information Center

    Rivera, Fernando I.; Guarnaccia, Peter J.; Mulvaney-Day, Norah; Lin, Julia Y.; Torres, Maria; Alegria, Margarita

    2008-01-01

    This article presents analyses of a representative sample of U.S. Latinos (N = 2,540) to investigate whether family cohesion moderates the effects of cultural conflict on psychological distress. The results for the aggregated Latino group suggest a significant association between family cohesion and lower psychological distress, and the…

  4. Moderating effects of group status, cohesion, and ethnic composition on socialization of aggression in children's peer groups.

    PubMed

    Shi, Bing; Xie, Hongling

    2014-09-01

    We explored the effects of 3 group features (i.e., status, cohesion, and ethnic composition) on socialization processes of aggression in early adolescents' natural peer social groups. Gender differences in these effects were also determined. A total of 245 seventh-grade individuals belonging to 65 peer groups were included in the analyses. All 3 group features moderated the strength of group socialization on physical aggression with the exception of group status on girls' physical aggression. Stronger socialization of physical aggression occurred in higher status, more cohesive, or ethnically more homogeneous groups. In contrast, only group cohesion moderated the strength of group socialization on social aggression among girls. These findings suggest that somewhat different processes may be involved in peer group influences on different forms of aggression. Future intervention and prevention efforts for adolescent aggression should consider peer group membership and group features simultaneously.

  5. Great Expectations: How Role Expectations and Role Experiences Relate to Perceptions of Group Cohesion.

    PubMed

    Benson, Alex J; Eys, Mark A; Irving, P Gregory

    2016-04-01

    Many athletes experience a discrepancy between the roles they expect to fulfill and the roles they eventually occupy. Drawing from met expectations theory, we applied response surface methodology to examine how role expectations, in relation to role experiences, influence perceptions of group cohesion among Canadian Interuniversity Sport athletes (N = 153). On the basis of data from two time points, as athletes approached and exceeded their role contribution expectations, they reported higher perceptions of task cohesion. Furthermore, as athletes approached and exceeded their social involvement expectations, they reported higher perceptions of social cohesion. These response surface patterns-pertaining to task and social cohesion-were driven by the positive influence of role experiences. On the basis of the interplay between athletes' role experiences and their perception of the group environment, efforts to improve team dynamics may benefit from focusing on improving the quality of role experiences, in conjunction with developing realistic role expectations.

  6. The Relationship between Organizational Citizenship Behavior, Group Cohesiveness and Workplace Deviance Behavior of Turkish Teachers

    ERIC Educational Resources Information Center

    Apaydin, Çigdem; Sirin, Hüseyin

    2016-01-01

    This study aims to develop a structural model for organizational citizenship behavior, group cohesiveness and workplace deviance behavior. The study group consists of 639 Turkish teachers working in primary and secondary public schools. In the study, the "Organizational Citizenship Behavior Scale" and the "Group Cohesiveness…

  7. Effect of a Collective Project on Group Cohesion.

    ERIC Educational Resources Information Center

    Shipley, Robert H.

    Immediately before their second group therapy session, 10 newly formed inpatient therapy groups were randomly assigned to complete either collective or individual art projects. The members of a group in the collective-project condition completed a single art project as a group. Each member of a group assigned to the individual project condition…

  8. Using Expressive Arts in Group Supervision to Enhance Awareness and Foster Cohesion

    ERIC Educational Resources Information Center

    Newsome, Debbie W.; Henderson, Donna A.; Veach, Laura J.

    2005-01-01

    Counselor educators and supervisors can enhance the group supervision process by intentionally selecting expressive arts activities designed to help supervisees develop personal awareness. Expressive arts activities also can serve to increase group understanding and cohesion. The authors provide a rationale for using expressive arts in…

  9. Moderating Effects of Group Status, Cohesion, and Ethnic Composition on Socialization of Aggression in Children's Peer Groups

    ERIC Educational Resources Information Center

    Shi, Bing; Xie, Hongling

    2014-01-01

    We explored the effects of 3 group features (i.e., status, cohesion, and ethnic composition) on socialization processes of aggression in early adolescents' natural peer social groups. Gender differences in these effects were also determined. A total of 245 seventh-grade individuals belonging to 65 peer groups were included in the analyses.…

  10. Regolith grain size and cohesive strength of near-Earth Asteroid (29075) 1950 DA

    NASA Astrophysics Data System (ADS)

    Gundlach, B.; Blum, J.

    2015-09-01

    Due to its fast rotation period of 2.12 h, about half of the surface of near-Earth Asteroid (29075) 1950 DA experiences negative (i.e., outward directed) acceleration levels (Rozitis, B., Maclennan, E., Emery, J.P. [2014]. Nature 512, 174-176). Thus, cohesion of the surface material is mandatory to prevent rotational breakup of the asteroid. Rozitis et al. (Rozitis, B., Maclennan, E., Emery, J.P. [2014]. Nature 512, 174-176) concluded that a grain size of ∼6 cm or lower is needed to explain the required cohesive strength of 64-20+12Pa . Here, we present another approach to determine the grain size of near-Earth Asteroid (29075) 1950 DA by using the thermal inertia value from Rozitis et al. (Rozitis, B., Maclennan, E., Emery, J.P. [2014]. Nature 512, 174-176) and a model of the heat conductivity of the surface regolith (Gundlach, B., Blum, J. [2013]. Icarus 223, 479-492). This method yields a mean particle radius ranging from 32 μm to 117 μm. The derived grain sizes are then used to infer the cohesive strength of the surface material of Asteroid (29075) 1950 DA (ranging from 24 Pa to 88 Pa), by using laboratory measurements of the tensile strength of powders.

  11. Psychological Sense of Community and Group Cohesion on Wilderness Trips

    ERIC Educational Resources Information Center

    Breunig, Mary; O'Connell, Tim; Todd, Sharon; Young, Anderson; Anderson, Lynn; Anderson, Dale

    2008-01-01

    A primary purpose of many wilderness trip programs is the development of positive interpersonal relationships and group experiences that lead to enhanced sense of community among group members. Although there is anecdotal evidence to support the development of sense of community on wilderness trips, there is little empirical evidence to support…

  12. Rescuing Community: Sociality and Cohesion in Writing Groups.

    ERIC Educational Resources Information Center

    Foster, David

    Group strategies--group discussion, feedback, collaboration--seem so widely used in postsecondary writing as to have attained the status of lore. In seeking pedagogical community, writing teachers too often gloss over or deny the reality of competing voices. To understand the traditional appeal of the trope "community" for American educational…

  13. Improving Participation Rates for Women of Color in Health Research: The Role of Group Cohesion

    PubMed Central

    Mama, Scherezade; Reese-Smith, Jacqueline Y.; Estabrooks, Paul A.; Lee, Rebecca E.

    2015-01-01

    Adherence to physical activity and dietary interventions is a common challenge. Interventions that use group cohesion strategies show promise for increasing adherence, but have not been tested among women of color. The purpose of this study was to determine whether dimensions of group cohesion mediate the association between intervention condition and attendance within a community physical activity program for women of color. African American and Hispanic or Latina women (N=310) completed measurements at baseline and post-intervention and participated in a social cohesion intervention to improve physical activity and dietary habits. Women were assigned to a physical activity or fruit and vegetable intervention group. Social and task cohesion was measured using the Physical Activity Group Environment Questionnaire (PAGE-Q). Attendance was recorded at each of six intervention sessions. Women were generally middle-age (M age = 46.4 years, SD=9.1) and obese (M BMI = 34.4 kg/m2, SD=7.7). The estimate of the mediated effect was significant for all group cohesion constructs, indicating both task constructs—attraction to the group’s task (SE=0.096, CI: −0.599 to −0.221) and group integration around the task (SE=0.060, CI: −0.092 to −0.328)—and social constructs—attraction to the group’s social aspects (SE=0.046, CI: −0.546 to −0.366) and group integration around social aspects (SE=0.046, CI: −0.546 to −0.366)—significantly mediated the association between group assignment and attendance. Both task and social constructs are important to improve attendance in health promotion interventions for women of color. PMID:21826476

  14. Group size, grooming and fission in primates: a modeling approach based on group structure.

    PubMed

    Sueur, Cédric; Deneubourg, Jean-Louis; Petit, Odile; Couzin, Iain D

    2011-03-21

    In social animals, fission is a common mode of group proliferation and dispersion and may be affected by genetic or other social factors. Sociality implies preserving relationships between group members. An increase in group size and/or in competition for food within the group can result in decrease certain social interactions between members, and the group may split irreversibly as a consequence. One individual may try to maintain bonds with a maximum of group members in order to keep group cohesion, i.e. proximity and stable relationships. However, this strategy needs time and time is often limited. In addition, previous studies have shown that whatever the group size, an individual interacts only with certain grooming partners. There, we develop a computational model to assess how dynamics of group cohesion are related to group size and to the structure of grooming relationships. Groups' sizes after simulated fission are compared to observed sizes of 40 groups of primates. Results showed that the relationship between grooming time and group size is dependent on how each individual attributes grooming time to its social partners, i.e. grooming a few number of preferred partners or grooming equally or not all partners. The number of partners seemed to be more important for the group cohesion than the grooming time itself. This structural constraint has important consequences on group sociality, as it gives the possibility of competition for grooming partners, attraction for high-ranking individuals as found in primates' groups. It could, however, also have implications when considering the cognitive capacities of primates.

  15. Grooming network cohesion and the role of individuals in a captive chimpanzee group.

    PubMed

    Kanngiesser, Patricia; Sueur, Cédric; Riedl, Katrin; Grossmann, Johannes; Call, Josep

    2011-08-01

    Social network analysis offers new tools to study the social structure of primate groups. We used social network analysis to investigate the cohesiveness of a grooming network in a captive chimpanzee group (N = 17) and the role that individuals may play in it. Using data from a year-long observation, we constructed an unweighted social network of preferred grooming interactions by retaining only those dyads that groomed above the group mean. This choice of criterion was validated by the finding that the properties of the unweighted network correlated with the properties of a weighted network (i.e. a network representing the frequency of grooming interactions) constructed from the same data. To investigate group cohesion, we tested the resilience of the unweighted grooming network to the removal of central individuals (i.e. individuals with high betweenness centrality). The network fragmented more after the removal of individuals with high betweenness centrality than after the removal of random individuals. Central individuals played a pivotal role in maintaining the network's cohesiveness, and we suggest that this may be a typical property of affiliative networks like grooming networks. We found that the grooming network correlated with kinship and age, and that individuals with higher social status occupied more central positions in the network. Overall, the grooming network showed a heterogeneous structure, yet did not exhibit scale-free properties similar to many other primate networks. We discuss our results in light of recent findings on animal social networks and chimpanzee grooming.

  16. Moving calls: a vocal mechanism underlying quorum decisions in cohesive groups.

    PubMed

    Bousquet, Christophe A H; Sumpter, David J T; Manser, Marta B

    2011-05-22

    Members of social groups need to coordinate their behaviour when choosing between alternative activities. Consensus decisions enable group members to maintain group cohesion and one way to reach consensus is to rely on quorums. A quorum response is where the probability of an activity change sharply increases with the number of individuals supporting the new activity. Here, we investigated how meerkats (Suricata suricatta) use vocalizations in the context of movement decisions. Moving calls emitted by meerkats increased the speed of the group, with a sharp increase in the probability of changing foraging patch when the number of group members joining the chorus increased from two up to three. These calls had no apparent effect on the group's movement direction. When dominant individuals were involved in the chorus, the group's reaction was not stronger than when only subordinates called. Groups only increased speed in response to playbacks of moving calls from one individual when other group members emitted moving calls as well. The voting mechanism linked to a quorum probably allows meerkat groups to change foraging patches cohesively with increased speed. Such vocal coordination may reflect an aggregation rule linking individual assessment of foraging patch quality to group travel route.

  17. Moving calls: a vocal mechanism underlying quorum decisions in cohesive groups.

    PubMed

    Bousquet, Christophe A H; Sumpter, David J T; Manser, Marta B

    2011-05-22

    Members of social groups need to coordinate their behaviour when choosing between alternative activities. Consensus decisions enable group members to maintain group cohesion and one way to reach consensus is to rely on quorums. A quorum response is where the probability of an activity change sharply increases with the number of individuals supporting the new activity. Here, we investigated how meerkats (Suricata suricatta) use vocalizations in the context of movement decisions. Moving calls emitted by meerkats increased the speed of the group, with a sharp increase in the probability of changing foraging patch when the number of group members joining the chorus increased from two up to three. These calls had no apparent effect on the group's movement direction. When dominant individuals were involved in the chorus, the group's reaction was not stronger than when only subordinates called. Groups only increased speed in response to playbacks of moving calls from one individual when other group members emitted moving calls as well. The voting mechanism linked to a quorum probably allows meerkat groups to change foraging patches cohesively with increased speed. Such vocal coordination may reflect an aggregation rule linking individual assessment of foraging patch quality to group travel route. PMID:21047853

  18. Achievement of group cohesion through the development of a psychiatric nursing seminar.

    PubMed

    Singhaus, M S; Brennan, I; Mackay, C K

    1990-01-01

    The purpose of this paper is to describe the process by which group cohesion emerged around the task of developing a psychiatric nursing seminar at the Palo Alto (California) V.A. Medical Center. This paper will discuss how group cohesion evolved, describe the seminar, and offer suggestions to other nurses wanting to work together more collaboratively. As clinical nurse specialists (CNS) assigned to the inpatient psychiatric units of a Veterans Administration Medical Center, we were asked by nursing administration to develop an educational course. The purpose of the course was to provide registered nurses with a common knowledge base that would facilitate communication related to patient care. While we were aware that teaching discreet areas of content commensurate with our individual interests and expertise would get the job done rapidly, our combined experience taught us that this approach to learning did little to bring about a change in clinical practice. We viewed the selection of a conceptual framework to which we could all be committed as an essential step prior to the content development. What is significant about this experience was that the group process of achieving cohesiveness was so closely related to the conceptual framework that finally evolved. We chose a framework that reflected our own perspectives towards working with others and about psychiatric nursing. In turn, the major concepts of the chosen framework guided many of our interactions with each other. PMID:2207976

  19. Both information and social cohesion determine collective decisions in animal groups.

    PubMed

    Miller, Noam; Garnier, Simon; Hartnett, Andrew T; Couzin, Iain D

    2013-03-26

    During consensus decision making, individuals in groups balance personal information (based on their own past experiences) with social information (based on the behavior of other individuals), allowing the group to reach a single collective choice. Previous studies of consensus decision making processes have focused on the informational aspects of behavioral choice, assuming that individuals make choices based solely on their likelihood of being beneficial (e.g., rewarded). However, decisions by both humans and nonhuman animals systematically violate such expectations. Furthermore, the typical experimental paradigm of assessing binary decisions, those between two mutually exclusive options, confounds two aspects common to most group decisions: minimizing uncertainty (through the use of personal and social information) and maintaining group cohesion (for example, to reduce predation risk). Here we experimentally disassociate cohesion-based decisions from information-based decisions using a three-choice paradigm and demonstrate that both factors are crucial to understanding the collective decision making of schooling fish. In addition, we demonstrate how multiple informational dimensions (here color and stripe orientation) are integrated within groups to achieve consensus, even though no individual is explicitly aware of, or has a unique preference for, the consensus option. Balancing of personal information and social cues by individuals in key frontal positions in the group is shown to be essential for such group-level capabilities. Our results demonstrate the importance of integrating informational with other social considerations when explaining the collective capabilities of group-living animals. PMID:23440218

  20. Effects of particle size and cohesive properties on mixing studied by non-contact NIR.

    PubMed

    Bellamy, Luke J; Nordon, Alison; Littlejohn, David

    2008-09-01

    A scaled-down convective blender was used along with non-invasive NIR spectrometry to study the mixing of citric acid, aspirin, aspartame or povidone with microcrystalline cellulose. NIR mixing profiles were generated in real time using measurements at the 2nd overtone wavelength of the added compounds. Trends demonstrated previously for aspirin were confirmed for additions of citric acid: the magnitude of the 2nd overtone NIR measurements is less affected by changes in particle size than that of the 1st overtone; the peak-to-peak noise of the 2nd overtone NIR mixing profile increases with the particle size of the added compound. The study has demonstrated the usefulness of continuous NIR measurements for rapid evaluation of the mixing process when deciding the best particle size of microcrystalline cellulose to mix with compounds of different particle shape and cohesive properties. Smaller particle sizes of microcrystalline cellulose (53-106 microm) were better for aspirin (212-250 microm), whereas larger particles (212-250 microm) were better for aspartame (212-250 microm). The characteristics of the compounds also need to be considered when deciding the order of addition of secondary compounds when mixed with microcrystalline cellulose. The time required to achieve a uniform mixture was much less when povidone was added before aspirin, rather than vice versa.

  1. [The impact of size and diversity on group process and outputs].

    PubMed

    Osca Segovia, Amparo; García-Salmones Fernández, Lourdes

    2010-02-01

    The impact of size and diversity on group process and outputs. This study has analyzed the impact of size and diversity on group processes (group cohesion, effective management of conflicts, and group norms) and outputs (work satisfaction and group effectiveness) in a sample (N= 407) of Mexican workers. It considered two types of diversity: functional and social diversity. Hierarchical regression analysis revealed main effects for size and functional diversity. Size is negatively associated with group norms, effective management of conflicts and job satisfaction. Functional diversity is positively related to group norms and cohesion. However, social diversity was not related to group process and outcomes. The analysis revealed a moderating effect of functional diversity on the relationship between size and job satisfaction. The practical implications of these results are analyzed.

  2. Evidence for contact calls in fish: conspecific vocalisations and ambient soundscape influence group cohesion in a nocturnal species

    PubMed Central

    van Oosterom, L.; Montgomery, J. C.; Jeffs, A. G.; Radford, C. A.

    2016-01-01

    Soundscapes provide a new tool for the study of fish communities. Bigeyes (Pempheris adspersa) are nocturnal planktivorous reef fish, feed in loose shoals and are soniferous. These vocalisations have been suggested to be contact calls to maintain group cohesion, however direct evidence for this is absent, despite the fact that contact calls are well documented for many other vertebrates, including marine mammals. For fish, direct evidence for group cohesion signals is restricted to the use of visual and hydrodynamic cues. In support of adding vocalisation as a contributing cue, our laboratory experiments show that bigeyes significantly increased group cohesion when exposed to recordings of ambient reef sound at higher sound levels while also decreasing vocalisations. These patterns of behaviour are consistent with acoustic masking. When exposed to playback of conspecific vocalisations, the group cohesion and vocalisation rates of bigeyes both significantly increased. These results provide the first direct experimental support for the hypotheses that vocalisations are used as contact calls to maintain group cohesion in fishes, making fish the evolutionarily oldest vertebrate group in which this phenomenon has been observed, and adding a new dimension to the interpretation of nocturnal reef soundscapes. PMID:26750559

  3. Competition in human groups-Impact on group cohesion, perceived stress and outcome satisfaction.

    PubMed

    Boos, Margarete; Franiel, Xaver; Belz, Michael

    2015-11-01

    This study on competition in human groups was performed within the context of the competitive outcome interdependence concept: the degree to which personal outcomes among group members are affected by the consequences of task performance of others, e.g. when one group member gains a high reward for a task, this lowers the available reward for other group members. Our computer-based multi-participant game empirically assessed how competitive versus neutral conditions influenced the reward-maximising behaviour of 200 undergraduate students functioning in ten-person groups - each playing two games (1 neutral and 1 competitive), their perceived pay satisfaction as well as perceived stress levels and sense of calmness within the games' task to search for coins. Participants were represented by black dots moving on a virtual playground. Results showed that competition led to reward-maximising but fellow group member disadvantaging behaviour, and all participants experienced lower pay satisfaction, higher stress levels and less calmness. We conclude that short-term behavioural consequences of positive individual competitive behaviour were gained at the above-mentioned potential long-term negative costs for all group members. This implies group paradigms aimed at sustainability should avoid introducing competitive factors that at best result in short-lived gains and at worst cause widespread dissatisfaction, stress and a pervasive lack of calmness.

  4. Competition in human groups-Impact on group cohesion, perceived stress and outcome satisfaction.

    PubMed

    Boos, Margarete; Franiel, Xaver; Belz, Michael

    2015-11-01

    This study on competition in human groups was performed within the context of the competitive outcome interdependence concept: the degree to which personal outcomes among group members are affected by the consequences of task performance of others, e.g. when one group member gains a high reward for a task, this lowers the available reward for other group members. Our computer-based multi-participant game empirically assessed how competitive versus neutral conditions influenced the reward-maximising behaviour of 200 undergraduate students functioning in ten-person groups - each playing two games (1 neutral and 1 competitive), their perceived pay satisfaction as well as perceived stress levels and sense of calmness within the games' task to search for coins. Participants were represented by black dots moving on a virtual playground. Results showed that competition led to reward-maximising but fellow group member disadvantaging behaviour, and all participants experienced lower pay satisfaction, higher stress levels and less calmness. We conclude that short-term behavioural consequences of positive individual competitive behaviour were gained at the above-mentioned potential long-term negative costs for all group members. This implies group paradigms aimed at sustainability should avoid introducing competitive factors that at best result in short-lived gains and at worst cause widespread dissatisfaction, stress and a pervasive lack of calmness. PMID:26222550

  5. Group cohesion and between session homework activities predict self-reported cognitive-behavioral skill use amongst participants of SMART Recovery groups.

    PubMed

    Kelly, Peter J; Deane, Frank P; Baker, Amanda L

    2015-04-01

    SMART Recovery groups are cognitive-behaviorally oriented mutual support groups for individuals with addictions. The aim of the study was to assess the extent to which the quality of group facilitation, group cohesion and the use of between session homework activities contribute to self-rated use of cognitive-behavioral skills amongst group participants. Participants attending SMART Recovery groups in Australia completed a cross sectional survey (N=124). The survey included measures of cognitive and behavioral skill utilization, group cohesion, quality of group facilitation and a rating of how frequently participants leave group meetings with an achievable between session homework plan. On average, participants had been attending SMART Recovery meetings for 9 months. Participants were most likely to attend SMART Recovery for problematic alcohol use. Regression analyses indicated that group cohesion significantly predicted use of cognitive restructuring, but that only provision of homework at the end of each group session predicted self-reported behavioral activation. Both group cohesion and leaving a group with an achievable homework plan predicted participant use of cognitive behavioral skills. The concrete actions associated with homework activities may facilitate behavioral activation. There is a need for longitudinal research to examine the relationship between the utilization of cognitive and behavioral skills and participant outcomes (e.g. substance use, mental health) for people attending SMART Recovery groups. PMID:25535099

  6. Floc morphology and size distributions of cohesive sediment in steady-state flow.

    PubMed

    Stone, M; Krishnappan, B G

    2003-06-01

    Fractal dimensions of particle populations of cohesive sediment were examined during deposition experiments in an annular flume at four conditions of steady-state flow (0.058, 0.123, 0.212 and 0.323Pa). Light microscopy and an image analysis system were used to determine area, longest axis and perimeter of suspended solids. Four fractal dimensions (D, D(1), D(2), D(k)) were calculated from the slopes of regression lines of the relevant variables on double log plots. The fractal dimension D, which relates the projected area (A) to the perimeter (P) of the particle (P proportional, variant A(D/2)), increased from 1.25+/-0.005 at a shear stress of 0.058Pa to a maximum of 1.36+/-0.003 at 0.121Pa then decreased to 1.34+/-0.001 at 0.323Pa. The change in D indicated that particle boundaries became more convoluted and the shape of larger particles was more irregular at higher levels of shear stress. At the highest shear stress, the observed decrease in D resulted from floc breakage due to increased particle collisions. The fractal dimension D(1), which relates the longest axis (l) to the perimeter of the particle (P proportional to l(D1)), increased from 1.00+/-0.006 at a shear stress of 0.058Pa to a maximum of 1.25+/-0.003 at 0.325Pa. The fractal dimension D(2), which relates the longest axis with the projected area of the particle (A proportional to l(D(2)), increased from 1.35+/-0.014 at a shear stress of 0.058Pa to a maximum of 1.81+/-0.005 at 0.323Pa. The observed increases in D(1) and D(2) indicate that particles became more elongated with increasing shear stress. Values of the fractal dimension D(k), resulting from the Korcak's empirical law for particle population, decreased from 3.68+/-0.002 at a shear stress of 0.058Pa to 1.33+/-0.001 at 0.323Pa and indicate that the particle size distribution changed from a population of similar sized particles at low shear to larger flocculated particles at higher levels of shear. The results show that small particle clusters

  7. Teamwork Orientation, Group Cohesiveness, and Student Learning: A Study of the Use of Teams in Online Distance Education

    ERIC Educational Resources Information Center

    Williams, Ethlyn A.; Duray, Rebecca; Reddy, Venkateshwar

    2006-01-01

    This research examines computer-supported collaborative learning. Master's of business administration (MBA) students in an online program were surveyed to examine the extent to which an orientation toward teamwork and the development of group cohesiveness affect overall student learning and the learning that results specifically from team…

  8. Two ways related to performance in elite sport: the path of self-confidence and competitive anxiety and the path of group cohesion and group goal-clarity.

    PubMed

    Kjørmo, Odd; Halvari, Hallgeir

    2002-06-01

    A model tested among 136 Norwegian Olympic-level athletes yielded two paths related to performance. The first path indicated that self-confidence, modeled as an antecedent of competitive anxiety, is negatively correlated with anxiety. Competitive anxiety in turn is negatively correlated with performance. The second path indicated that group cohesion is positively correlated with group goal-clarity, which in turn is positively correlated with performance. Competitive anxiety mediates the relation between self-confidence and performance, whereas group goal-clarity mediates the relation between group cohesion and performance. Results from multiple regression analyses supported the model in the total sample and among individual sport athletes organized in training groups (n = 100). Among team sport athletes (n = 36), personality and group measures are more strongly intercorrelated than among individual sport athletes, and the relation with performance is more complex for the former group. The interaction of self-confidence and competitive anxiety is related to performance among team sport athletes.

  9. Group Size Effects in Employment Testing

    ERIC Educational Resources Information Center

    Hillery, Joseph M.; Fugita, Stephen S.

    1975-01-01

    Effects of the number of individuals coacting while taking two standardized motor performance tests were examined. Increases in aptitude scores corresponding to increases in group size were predicted based upon the summation hypothesis of social facilitation theory. Results indicated a group size effect. (Author/BJG)

  10. Group cohesion and organizational commitment: protective factors for nurse residents' job satisfaction, compassion fatigue, compassion satisfaction, and burnout.

    PubMed

    Li, Angela; Early, Sean F; Mahrer, Nicole E; Klaristenfeld, Jessica L; Gold, Jeffrey I

    2014-01-01

    Stress can have detrimental effects on nurse residents' levels of job satisfaction, compassion, fatigue, and burnout. This can lead to high turnover rates and poor quality of care among novice nurses. Therefore, it is critical to identify protective factors to prevent the onset of negative nurse outcomes (compassion fatigue, burnout, and job dissatisfaction) and to promote positive nurse outcomes (job satisfaction, compassion satisfaction). This study aimed to determine whether factors such as group cohesion and organizational commitment would be protective and moderate the association between stress exposure and posttraumatic stress symptoms and other negative nurse outcomes, thus facilitating positive outcomes. Findings showed that group cohesion was effective in moderating the negative effects of current stress exposure and posttraumatic stress symptoms on negative nurse outcomes, specifically on increased compassion fatigue and burnout, and reduced compassion satisfaction. In addition, organizational commitment was determined to promote positive nurse outcomes such as job satisfaction and compassion satisfaction. The study findings are promising, as retention of quality nurses is a significant problem for hospitals. Nurse managers and hospital administrators should be aware of the benefits of group cohesion and organizational commitment and strive to make the promotion of these factors a priority.

  11. Simulation of granular packing of frictional cohesive particles with Gaussian size distribution

    NASA Astrophysics Data System (ADS)

    Jia, Tao; Gao, Di

    2016-09-01

    The granular packing of frictional cohesive particles with Gaussian distribution is investigated based on distinct element method. Different sliding frictional coefficients are considered in the simulation. Due to the inelastic collision between the particles, the agglomeration of the particles occurs and the packing structure is formed finally. The range of the diameter of the particle is between 50 and 100 μm, and the distribution of the particle diameter is Gaussian. The inelastic interaction is caused by the viscoelastic force and the frictional force. The internal structure of the granular matter is quantified by the coordination number, packing density, and the force distribution. It is found that the increase in the sliding frictional coefficient looses the packing structure, and the distribution range of the contact force is larger than that of the van der Waals force.

  12. Cohesion Group Approach for Evolutionary Analysis of TyrA, a Protein Family with Wide-Ranging Substrate Specificities

    PubMed Central

    Bonner, Carol A.; Disz, Terrence; Hwang, Kaitlyn; Song, Jian; Vonstein, Veronika; Overbeek, Ross; Jensen, Roy A.

    2008-01-01

    Summary: Many enzymes and other proteins are difficult subjects for bioinformatic analysis because they exhibit variant catalytic, structural, regulatory, and fusion mode features within a protein family whose sequences are not highly conserved. However, such features reflect dynamic and interesting scenarios of evolutionary importance. The value of experimental data obtained from individual organisms is instantly magnified to the extent that given features of the experimental organism can be projected upon related organisms. But how can one decide how far along the similarity scale it is reasonable to go before such inferences become doubtful? How can a credible picture of evolutionary events be deduced within the vertical trace of inheritance in combination with intervening events of lateral gene transfer (LGT)? We present a comprehensive analysis of a dehydrogenase protein family (TyrA) as a prototype example of how these goals can be accomplished through the use of cohesion group analysis. With this approach, the full collection of homologs is sorted into groups by a method that eliminates bias caused by an uneven representation of sequences from organisms whose phylogenetic spacing is not optimal. Each sufficiently populated cohesion group is phylogenetically coherent and defined by an overall congruence with a distinct section of the 16S rRNA gene tree. Exceptions that occasionally are found implicate a clearly defined LGT scenario whereby the recipient lineage is apparent and the donor lineage of the gene transferred is localized to those organisms that define the cohesion group. Systematic procedures to manage and organize otherwise overwhelming amounts of data are demonstrated. PMID:18322033

  13. The use of group dynamics strategies to enhance cohesion in a lifestyle intervention program for obese children

    PubMed Central

    Martin, Luc J; Burke, Shauna M; Shapiro, Sheree; Carron, Albert V; Irwin, Jennifer D; Petrella, Robert; Prapavessis, Harry; Shoemaker, Kevin

    2009-01-01

    Background Most research pertaining to childhood obesity has assessed the effectiveness of preventative interventions, while relatively little has been done to advance knowledge in the treatment of obesity. Thus, a 4-week family- and group-based intervention utilizing group dynamics strategies designed to increase cohesion was implemented to influence the lifestyles and physical activity levels of obese children. Methods/Design This paper provides an overview of the rationale for and implementation of the intervention for obese children and their families. Objectives of the intervention included the modification of health behaviors and cohesion levels through the use of group dynamics strategies. To date, a total of 15 children (7 boys and 8 girls, mean age = 10.5) and their families have completed the intervention (during the month of August 2008). Physiological and psychological outcomes were assessed throughout the 4-week intervention and at 3-, 6-, and 12-month follow-up periods. Discussion It is believed that the information provided will help researchers and health professionals develop similar obesity treatment interventions through the use of evidence-based group dynamics strategies. There is also a need for continued research in this area, and it is our hope that the Children's Health and Activity Modification Program (C.H.A.M.P.) will provide a strong base from which others may build. PMID:19646259

  14. A universal approximation to grain size from images of non-cohesive sediment

    USGS Publications Warehouse

    Buscombe, D.; Rubin, D.M.; Warrick, J.A.

    2010-01-01

    The two-dimensional spectral decomposition of an image of sediment provides a direct statistical estimate, grid-by-number style, of the mean of all intermediate axes of all single particles within the image. We develop and test this new method which, unlike existing techniques, requires neither image processing algorithms for detection and measurement of individual grains, nor calibration. The only information required of the operator is the spatial resolution of the image. The method is tested with images of bed sediment from nine different sedimentary environments (five beaches, three rivers, and one continental shelf), across the range 0.1 mm to 150 mm, taken in air and underwater. Each population was photographed using a different camera and lighting conditions. We term it a “universal approximation” because it has produced accurate estimates for all populations we have tested it with, without calibration. We use three approaches (theory, computational experiments, and physical experiments) to both understand and explore the sensitivities and limits of this new method. Based on 443 samples, the root-mean-squared (RMS) error between size estimates from the new method and known mean grain size (obtained from point counts on the image) was found to be ±≈16%, with a 95% probability of estimates within ±31% of the true mean grain size (measured in a linear scale). The RMS error reduces to ≈11%, with a 95% probability of estimates within ±20% of the true mean grain size if point counts from a few images are used to correct bias for a specific population of sediment images. It thus appears it is transferable between sedimentary populations with different grain size, but factors such as particle shape and packing may introduce bias which may need to be calibrated for. For the first time, an attempt has been made to mathematically relate the spatial distribution of pixel intensity within the image of sediment to the grain size.

  15. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 1 2011-07-01 2011-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  16. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  17. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  18. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  19. 36 CFR 13.905 - Group size.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Group size. 13.905 Section 13.905 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Denali National Park and Preserve General...

  20. Differences in conative characteristics and perceived group cohesion of the basketball players playing in different positions in the team.

    PubMed

    Sindik, Josko; Nazor, Damir

    2011-09-01

    Identification of differences in individual conative characteristics and in perceived group cohesion of the basketball players playing in different positions in the team could provide guidelines for a better selection of basketball players and better coaching work. The aim of our study was to determine the differences in relation to the positions of guards and forwards/centres, and the four major positions in the team. The final sample of subjects (74 basketball players) is selected from the initial sample of 107 subjects, selected from nine men's senior basketball teams that played in A-1 Croatian men's basketball league championship in 2006/2007. The results showed no statistically significant difference between basketball players who play in different positions in the team, neither in relation to two basic positions in the team (guards as opposed to forwards/centres), nor in relation to the four positions in the team (point guard, shooting guard, small forward, power forward/centre).

  1. The Impact of Homogeneity on Intra-Group Cohesion: A Macro-Level Comparison of Minority Communities in a Western Diaspora

    ERIC Educational Resources Information Center

    Deffa, Oromiya-Jalata

    2016-01-01

    Contrary to earlier studies dealing with the cultural identity development of diasporic minorities, this paper assesses the impact of homogeneity on intra-group cohesion and ethnic orientation. To this end, Oromo-Americans, an ethnic group originally located within the national borders of Ethiopia, will be compared to Armenian-Americans,…

  2. The Discursive Construction of Group Cohesion in Problem-Based Learning Tutorials

    ERIC Educational Resources Information Center

    Hendry, Gillian; Wiggins, Sally; Anderson, Tony

    2016-01-01

    Research has shown that educators may be reluctant to implement group work in their teaching due to concerns about students partaking in off-task behaviours. However, such off-task interactions have been shown to promote motivation, trust, and rapport-building. This paper details a study in which student groups were video recorded as they engaged…

  3. Entitativity and intergroup bias: How belonging to a cohesive group allows people to express their prejudices.

    PubMed

    Effron, Daniel A; Knowles, Eric D

    2015-02-01

    We propose that people treat prejudice as more legitimate when it seems rationalistic-that is, linked to a group's pursuit of collective interests. Groups that appear to be coherent and unified wholes (entitative groups) are most likely to have such interests. We thus predicted that belonging to an entitative group licenses people to express prejudice against outgroups. Support for this idea came from 3 correlational studies and 5 experiments examining racial, national, and religious prejudice. The first 4 studies found that prejudice and discrimination seemed more socially acceptable to third parties when committed by members of highly entitative groups, because people could more easily explain entitative groups' biases as a defense of collective interests. Moreover, ingroup entitativity only lent legitimacy to outgroup prejudice when an interests-based explanation was plausible-namely, when the outgroup could possibly threaten the ingroup's interests. The last 4 studies found that people were more willing to express private prejudices when they perceived themselves as belonging to an entitative group. Participants' perceptions of their own race's entitativity were associated with a greater tendency to give explicit voice to their implicit prejudice against other races. Furthermore, experimentally raising participants' perceptions of ingroup entitativity increased explicit expressions of outgroup prejudice, particularly among people most likely to privately harbor such prejudices (i.e., highly identified group members). Together, these findings demonstrate that entitativity can lend a veneer of legitimacy to prejudice and disinhibit its expression. We discuss implications for intergroup relations and shifting national demographics. (PsycINFO Database Record (c) 2015 APA, all rights reserved). PMID:25603374

  4. Entitativity and intergroup bias: How belonging to a cohesive group allows people to express their prejudices.

    PubMed

    Effron, Daniel A; Knowles, Eric D

    2015-02-01

    We propose that people treat prejudice as more legitimate when it seems rationalistic-that is, linked to a group's pursuit of collective interests. Groups that appear to be coherent and unified wholes (entitative groups) are most likely to have such interests. We thus predicted that belonging to an entitative group licenses people to express prejudice against outgroups. Support for this idea came from 3 correlational studies and 5 experiments examining racial, national, and religious prejudice. The first 4 studies found that prejudice and discrimination seemed more socially acceptable to third parties when committed by members of highly entitative groups, because people could more easily explain entitative groups' biases as a defense of collective interests. Moreover, ingroup entitativity only lent legitimacy to outgroup prejudice when an interests-based explanation was plausible-namely, when the outgroup could possibly threaten the ingroup's interests. The last 4 studies found that people were more willing to express private prejudices when they perceived themselves as belonging to an entitative group. Participants' perceptions of their own race's entitativity were associated with a greater tendency to give explicit voice to their implicit prejudice against other races. Furthermore, experimentally raising participants' perceptions of ingroup entitativity increased explicit expressions of outgroup prejudice, particularly among people most likely to privately harbor such prejudices (i.e., highly identified group members). Together, these findings demonstrate that entitativity can lend a veneer of legitimacy to prejudice and disinhibit its expression. We discuss implications for intergroup relations and shifting national demographics. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

  5. Lexical Cohesion in Students' Argumentative Essay among a Select Group of Filipino College Students

    ERIC Educational Resources Information Center

    Alarcon, Josephine B.

    2013-01-01

    This study analyzed the lexical devices used by undergraduate students in their argumentative text using Halliday and Hasan (1976) and Halliday's (2004) taxonomy. One hundred forty-eight argumentative essays were analyzed. The essays underwent interrating by three independent raters using a 20-point rubric and were grouped according to rating.…

  6. Verbal and Nonverbal Student Interaction in the College Classroom as a Function of Group Cohesion.

    ERIC Educational Resources Information Center

    von Raffler-Engel, Walburga; And Others

    The correlation of verbal, paralinguistic, and kinesic features in the context of student-student and student-teacher interaction is studied in a semester linguistics course at Vanderbilt University. The purpose of the research is to delineate some of the major problems of group interaction in the college classroom and to show how the various…

  7. Examining the Effects of Campus Climate, Ethnic Group Cohesion, and Cross-Cultural Interaction on Filipino American Students' Sense of Belonging in College

    ERIC Educational Resources Information Center

    Maramba, Dina C.; Museus, Samuel D.

    2013-01-01

    The purpose of this study is to explore how campus climate, ethnic group cohesion and cross cultural interaction influence Filipino American college students' sense of belonging in college. Specifically, we examine the impact of three environmental and behavioral factors on students' sense of belonging: 1) campus racial climate, 2) ethnic group…

  8. Behavioural ecology and group cohesion of juvenile western lowland gorillas (Gorilla g. gorilla) during rehabilitation in the Batéké Plateaux National Park, Gabon.

    PubMed

    Le Flohic, Guillaume; Motsch, Peggy; DeNys, Hélène; Childs, Simon; Courage, Amos; King, Tony

    2015-01-01

    Rehabilitation of animals followed by reintroduction into the wild can benefit conservation by supplementing depleted wild populations or reintroducing a species in an area where it has been extirpated or become extinct. The western lowland gorilla (WLG, Gorilla g. gorilla) is persistently poached; infants are often illegally traded and used as pets. Some are confiscated and rehabilitated, then kept in sanctuaries or reintroduced into the wild. Prior to reintroduction, the ability of the orphans to survive independently in their environment needs to be assessed. Here, we performed a multivariate analysis, including diet composition, activity-budget, and pattern of strata using of a group of five juvenile WLG in the process of rehabilitation and distinguished three sub-periods of ecological significance: the high furgivory period, the Dialium fruits consumption period, and the high folivory period. The consequences of these variations on their well-being (play behaviour) and the group cohesion (spatial proximity and social interactions) were examined. Like wild WLGs, diets shifted seasonally from frugivorous to folivorous, while the same staple foods were consumed and large amounts of Dialium fruits were seasonally gathered high in trees. When succulent fruit intake was the highest, thus providing high energy from sugar, juveniles spent less time feeding, more time playing and group cohesion was the highest. Conversely, the cohesion decreased with increasing folivory, individuals spent more time feeding and less time playing together. Nonetheless, the group cohesion also decreased after the death of one highly social, wild-born orphan. This may underscore the importance of skilled individuals in the cohesion and well-being of the entire group and, ultimately, to rehabilitation success. This study evaluates the rehabilitation success with regards to the methods used and highlights the need to consider a set of individual and environmental factors for enhancing

  9. Behavioural Ecology and Group Cohesion of Juvenile Western Lowland Gorillas (Gorilla g. gorilla) during Rehabilitation in the Batéké Plateaux National Park, Gabon

    PubMed Central

    Le Flohic, Guillaume; Motsch, Peggy; DeNys, Hélène; Childs, Simon; Courage, Amos; King, Tony

    2015-01-01

    Rehabilitation of animals followed by reintroduction into the wild can benefit conservation by supplementing depleted wild populations or reintroducing a species in an area where it has been extirpated or become extinct. The western lowland gorilla (WLG, Gorilla g. gorilla) is persistently poached; infants are often illegally traded and used as pets. Some are confiscated and rehabilitated, then kept in sanctuaries or reintroduced into the wild. Prior to reintroduction, the ability of the orphans to survive independently in their environment needs to be assessed. Here, we performed a multivariate analysis, including diet composition, activity-budget, and pattern of strata using of a group of five juvenile WLG in the process of rehabilitation and distinguished three sub-periods of ecological significance: the high furgivory period, the Dialium fruits consumption period, and the high folivory period. The consequences of these variations on their well-being (play behaviour) and the group cohesion (spatial proximity and social interactions) were examined. Like wild WLGs, diets shifted seasonally from frugivorous to folivorous, while the same staple foods were consumed and large amounts of Dialium fruits were seasonally gathered high in trees. When succulent fruit intake was the highest, thus providing high energy from sugar, juveniles spent less time feeding, more time playing and group cohesion was the highest. Conversely, the cohesion decreased with increasing folivory, individuals spent more time feeding and less time playing together. Nonetheless, the group cohesion also decreased after the death of one highly social, wild-born orphan. This may underscore the importance of skilled individuals in the cohesion and well-being of the entire group and, ultimately, to rehabilitation success. This study evaluates the rehabilitation success with regards to the methods used and highlights the need to consider a set of individual and environmental factors for enhancing

  10. Behavioural ecology and group cohesion of juvenile western lowland gorillas (Gorilla g. gorilla) during rehabilitation in the Batéké Plateaux National Park, Gabon.

    PubMed

    Le Flohic, Guillaume; Motsch, Peggy; DeNys, Hélène; Childs, Simon; Courage, Amos; King, Tony

    2015-01-01

    Rehabilitation of animals followed by reintroduction into the wild can benefit conservation by supplementing depleted wild populations or reintroducing a species in an area where it has been extirpated or become extinct. The western lowland gorilla (WLG, Gorilla g. gorilla) is persistently poached; infants are often illegally traded and used as pets. Some are confiscated and rehabilitated, then kept in sanctuaries or reintroduced into the wild. Prior to reintroduction, the ability of the orphans to survive independently in their environment needs to be assessed. Here, we performed a multivariate analysis, including diet composition, activity-budget, and pattern of strata using of a group of five juvenile WLG in the process of rehabilitation and distinguished three sub-periods of ecological significance: the high furgivory period, the Dialium fruits consumption period, and the high folivory period. The consequences of these variations on their well-being (play behaviour) and the group cohesion (spatial proximity and social interactions) were examined. Like wild WLGs, diets shifted seasonally from frugivorous to folivorous, while the same staple foods were consumed and large amounts of Dialium fruits were seasonally gathered high in trees. When succulent fruit intake was the highest, thus providing high energy from sugar, juveniles spent less time feeding, more time playing and group cohesion was the highest. Conversely, the cohesion decreased with increasing folivory, individuals spent more time feeding and less time playing together. Nonetheless, the group cohesion also decreased after the death of one highly social, wild-born orphan. This may underscore the importance of skilled individuals in the cohesion and well-being of the entire group and, ultimately, to rehabilitation success. This study evaluates the rehabilitation success with regards to the methods used and highlights the need to consider a set of individual and environmental factors for enhancing

  11. Item wording and internal consistency of a measure of cohesion: the group environment questionnaire.

    PubMed

    Eys, Mark A; Carron, Albert V; Bray, Steven R; Brawley, Lawrence R

    2007-06-01

    A common practice for counteracting response acquiescence in psychological measures has been to employ both negatively and positively worded items. However, previous research has highlighted that the reliability of measures can be affected by this practice (Spector, 1992). The purpose of the present study was to examine the effect that the presence of negatively worded items has on the internal reliability of the Group Environment Questionnaire (GEQ). Two samples (N = 276) were utilized, and participants were asked to complete the GEQ (original and revised) on separate occasions. Results demonstrated that the revised questionnaire (containing all positively worded items) had significantly higher Cronbach alpha values for three of the four dimensions of the GEQ. Implications, alternatives, and future directions are discussed.

  12. An Engineering Solution for Solving Mesh Size Effects in the Simulation of Delamination with Cohesive Zone Models

    NASA Technical Reports Server (NTRS)

    Turon, A.; Davila, C. G.; Camanho, P. P.; Costa, J.

    2007-01-01

    This paper presents a methodology to determine the parameters to be used in the constitutive equations of Cohesive Zone Models employed in the simulation of delamination in composite materials by means of decohesion finite elements. A closed-form expression is developed to define the stiffness of the cohesive layer. A novel procedure that allows the use of coarser meshes of decohesion elements in large-scale computations is also proposed. The procedure ensures that the energy dissipated by the fracture process is computed correctly. It is shown that coarse-meshed models defined using the approach proposed here yield the same results as the models with finer meshes normally used for the simulation of fracture processes.

  13. Music listening in families and peer groups: benefits for young people's social cohesion and emotional well-being across four cultures.

    PubMed

    Boer, Diana; Abubakar, Amina

    2014-01-01

    Families are central to the social and emotional development of youth, and most families engage in musical activities together, such as listening to music or talking about their favorite songs. However, empirical evidence of the positive effects of musical family rituals on social cohesion and emotional well-being is scarce. Furthermore, the role of culture in the shaping of musical family rituals and their psychological benefits has been neglected entirely. This paper investigates musical rituals in families and in peer groups (as an important secondary socialization context) in two traditional/collectivistic and two secular/individualistic cultures, and across two developmental stages (adolescence vs. young adulthood). Based on cross-sectional data from 760 young people in Kenya, the Philippines, New Zealand, and Germany, our study revealed that across cultures music listening in families and in peer groups contributes to family and peer cohesion, respectively. Furthermore, the direct contribution of music in peer groups on well-being appears across cultural contexts, whereas musical family rituals affect emotional well-being in more traditional/collectivistic contexts. Developmental analyses show that musical family rituals are consistently and strongly related to family cohesion across developmental stages, whereas musical rituals in peer groups appear more dependent on the developmental stage (in interaction with culture). Contributing to developmental as well as cross-cultural psychology, this research elucidated musical rituals and their positive effects on the emotional and social development of young people across cultures. The implications for future research and family interventions are discussed. PMID:24847296

  14. Music listening in families and peer groups: benefits for young people's social cohesion and emotional well-being across four cultures

    PubMed Central

    Boer, Diana; Abubakar, Amina

    2014-01-01

    Families are central to the social and emotional development of youth, and most families engage in musical activities together, such as listening to music or talking about their favorite songs. However, empirical evidence of the positive effects of musical family rituals on social cohesion and emotional well-being is scarce. Furthermore, the role of culture in the shaping of musical family rituals and their psychological benefits has been neglected entirely. This paper investigates musical rituals in families and in peer groups (as an important secondary socialization context) in two traditional/collectivistic and two secular/individualistic cultures, and across two developmental stages (adolescence vs. young adulthood). Based on cross-sectional data from 760 young people in Kenya, the Philippines, New Zealand, and Germany, our study revealed that across cultures music listening in families and in peer groups contributes to family and peer cohesion, respectively. Furthermore, the direct contribution of music in peer groups on well-being appears across cultural contexts, whereas musical family rituals affect emotional well-being in more traditional/collectivistic contexts. Developmental analyses show that musical family rituals are consistently and strongly related to family cohesion across developmental stages, whereas musical rituals in peer groups appear more dependent on the developmental stage (in interaction with culture). Contributing to developmental as well as cross-cultural psychology, this research elucidated musical rituals and their positive effects on the emotional and social development of young people across cultures. The implications for future research and family interventions are discussed. PMID:24847296

  15. Optimal group size in a highly social mammal.

    PubMed

    Markham, A Catherine; Gesquiere, Laurence R; Alberts, Susan C; Altmann, Jeanne

    2015-12-01

    Group size is an important trait of social animals, affecting how individuals allocate time and use space, and influencing both an individual's fitness and the collective, cooperative behaviors of the group as a whole. Here we tested predictions motivated by the ecological constraints model of group size, examining the effects of group size on ranging patterns and adult female glucocorticoid (stress hormone) concentrations in five social groups of wild baboons (Papio cynocephalus) over an 11-y period. Strikingly, we found evidence that intermediate-sized groups have energetically optimal space-use strategies; both large and small groups experience ranging disadvantages, in contrast to the commonly reported positive linear relationship between group size and home range area and daily travel distance, which depict a disadvantage only in large groups. Specifically, we observed a U-shaped relationship between group size and home range area, average daily distance traveled, evenness of space use within the home range, and glucocorticoid concentrations. We propose that a likely explanation for these U-shaped patterns is that large, socially dominant groups are constrained by within-group competition, whereas small, socially subordinate groups are constrained by between-group competition and predation pressures. Overall, our results provide testable hypotheses for evaluating group-size constraints in other group-living species, in which the costs of intra- and intergroup competition vary as a function of group size.

  16. Optimal group size in a highly social mammal

    PubMed Central

    Markham, A. Catherine; Gesquiere, Laurence R.; Alberts, Susan C.; Altmann, Jeanne

    2015-01-01

    Group size is an important trait of social animals, affecting how individuals allocate time and use space, and influencing both an individual’s fitness and the collective, cooperative behaviors of the group as a whole. Here we tested predictions motivated by the ecological constraints model of group size, examining the effects of group size on ranging patterns and adult female glucocorticoid (stress hormone) concentrations in five social groups of wild baboons (Papio cynocephalus) over an 11-y period. Strikingly, we found evidence that intermediate-sized groups have energetically optimal space-use strategies; both large and small groups experience ranging disadvantages, in contrast to the commonly reported positive linear relationship between group size and home range area and daily travel distance, which depict a disadvantage only in large groups. Specifically, we observed a U-shaped relationship between group size and home range area, average daily distance traveled, evenness of space use within the home range, and glucocorticoid concentrations. We propose that a likely explanation for these U-shaped patterns is that large, socially dominant groups are constrained by within-group competition, whereas small, socially subordinate groups are constrained by between-group competition and predation pressures. Overall, our results provide testable hypotheses for evaluating group-size constraints in other group-living species, in which the costs of intra- and intergroup competition vary as a function of group size. PMID:26504236

  17. Understanding and Teaching Cohesion Comprehension.

    ERIC Educational Resources Information Center

    Irwin, Judith W., Ed.

    Concerned with improving student comprehension of text, this book focuses particularly on teaching students how sentences tie together. Articles in the three sections are grouped as follows: Part 1, What Is Cohesion Comprehension? contains "Cohesion, Coherence, and Comprehension" (Alden J. Moe and Judith W. Irwin); "Identifying Types of Anaphoric…

  18. Cohesive energy and structural parameters of binary oxides of groups IIA and IIIB from diffusion quantum Monte Carlo

    DOE PAGESBeta

    Santana, Juan A.; Krogel, Jaron T.; Kent, Paul R. C.; Reboredo, Fernando A.

    2016-05-03

    We have applied the diffusion quantum Monte Carlo (DMC) method to calculate the cohesive energy and the structural parameters of the binary oxides CaO, SrO, BaO, Sc2O3, Y2O3 and La2O3. The aim of our calculations is to systematically quantify the accuracy of the DMC method to study this type of metal oxides. The DMC results were compared with local and semi-local Density Functional Theory (DFT) approximations as well as with experimental measurements. The DMC method yields cohesive energies for these oxides with a mean absolute deviation from experimental measurements of 0.18(2) eV, while with local and semi-local DFT approximations themore » deviation is 3.06 and 0.94 eV, respectively. For lattice constants, the mean absolute deviation in DMC, local and semi-local DFT approximations, are 0.017(1), 0.07 and 0.05 , respectively. In conclusion, DMC is highly accurate method, outperforming the local and semi-local DFT approximations in describing the cohesive energies and structural parameters of these binary oxides.« less

  19. Understanding improved dissolution of indomethacin through the use of cohesive poorly water-soluble aluminium hydroxide: effects of concentration and particle size distribution.

    PubMed

    Tay, Tracy; Allahham, Ayman; Morton, David A V; Stewart, Peter J

    2011-10-01

    The objective of this study was to explore the effects of concentration and particle size distribution of an added poorly water-soluble inorganic salt, aluminium hydroxide, on the dissolution of a poorly water-soluble drug, indomethacin (IMC), from lactose interactive mixtures. Dissolution was studied using the United States Pharmacopeia paddle method in buffer pH 5.0 and the data most aptly fitted a bi-exponential dissolution model which represented dissolution occurring from dispersed and agglomerated particles. The dispersion of IMC mixtures was measured in dissolution media under non-sink conditions by laser diffraction. The dissolution of IMC increased as a function of the concentration of aluminium hydroxide (5-20%) added to the mixtures. Increasing the proportion of larger particles of the cohesive aluminium hydroxide increased the dissolution rate of IMC. The enhanced dissolution was attributed to increases in both the dissolution rate constant and initial concentration of dispersed particles. Mechanistically, the aluminium hydroxide was found to facilitate the detachment of IMC particles from the carrier surface, forming a complex interactive mixture that more readily deagglomerated than the cohesive drug agglomerates. The outcomes of this work would therefore allow more careful control and selection of the excipient specifications in producing solid dosage formulations with improved dissolution of poorly water-soluble drugs.

  20. Modeling group size and scalar stress by logistic regression from an archaeological perspective.

    PubMed

    Alberti, Gianmarco

    2014-01-01

    Johnson's scalar stress theory, describing the mechanics of (and the remedies to) the increase in in-group conflictuality that parallels the increase in groups' size, provides scholars with a useful theoretical framework for the understanding of different aspects of the material culture of past communities (i.e., social organization, communal food consumption, ceramic style, architecture and settlement layout). Due to its relevance in archaeology and anthropology, the article aims at proposing a predictive model of critical level of scalar stress on the basis of community size. Drawing upon Johnson's theory and on Dunbar's findings on the cognitive constrains to human group size, a model is built by means of Logistic Regression on the basis of the data on colony fissioning among the Hutterites of North America. On the grounds of the theoretical framework sketched in the first part of the article, the absence or presence of colony fissioning is considered expression of not critical vs. critical level of scalar stress for the sake of the model building. The model, which is also tested against a sample of archaeological and ethnographic cases: a) confirms the existence of a significant relationship between critical scalar stress and group size, setting the issue on firmer statistical grounds; b) allows calculating the intercept and slope of the logistic regression model, which can be used in any time to estimate the probability that a community experienced a critical level of scalar stress; c) allows locating a critical scalar stress threshold at community size 127 (95% CI: 122-132), while the maximum probability of critical scale stress is predicted at size 158 (95% CI: 147-170). The model ultimately provides grounds to assess, for the sake of any further archaeological/anthropological interpretation, the probability that a group reached a hot spot of size development critical for its internal cohesion.

  1. Group size and social conflict in complex societies.

    PubMed

    Shen, Sheng-Feng; Akçay, Erol; Rubenstein, Dustin R

    2014-02-01

    Conflicts of interest over resources or reproduction among individuals in a social group have long been considered to result in automatic and universal costs to group living. However, exploring how social conflict varies with group size has produced mixed empirical results. Here we develop a model that generates alternative predictions for how social conflict should vary with group size depending on the type of benefits gained from being in a social group. We show that a positive relationship between social conflict and group size is favored when groups form primarily for the benefits of sociality but not when groups form mainly for accessing group-defended resources. Thus, increased social conflict in animal societies should not be viewed as an automatic cost of larger social groups. Instead, studying the relationship between social conflict and the types of grouping benefits will be crucial for understanding the evolution of complex societies.

  2. Effects of Group Size on Students Mathematics Achievement in Small Group Settings

    ERIC Educational Resources Information Center

    Enu, Justice; Danso, Paul Amoah; Awortwe, Peter K.

    2015-01-01

    An ideal group size is hard to obtain in small group settings; hence there are groups with more members than others. The purpose of the study was to find out whether group size has any effects on students' mathematics achievement in small group settings. Two third year classes of the 2011/2012 academic year were selected from two schools in the…

  3. Modeling Group Size and Scalar Stress by Logistic Regression from an Archaeological Perspective

    PubMed Central

    Alberti, Gianmarco

    2014-01-01

    Johnson’s scalar stress theory, describing the mechanics of (and the remedies to) the increase in in-group conflictuality that parallels the increase in groups’ size, provides scholars with a useful theoretical framework for the understanding of different aspects of the material culture of past communities (i.e., social organization, communal food consumption, ceramic style, architecture and settlement layout). Due to its relevance in archaeology and anthropology, the article aims at proposing a predictive model of critical level of scalar stress on the basis of community size. Drawing upon Johnson’s theory and on Dunbar’s findings on the cognitive constrains to human group size, a model is built by means of Logistic Regression on the basis of the data on colony fissioning among the Hutterites of North America. On the grounds of the theoretical framework sketched in the first part of the article, the absence or presence of colony fissioning is considered expression of not critical vs. critical level of scalar stress for the sake of the model building. The model, which is also tested against a sample of archaeological and ethnographic cases: a) confirms the existence of a significant relationship between critical scalar stress and group size, setting the issue on firmer statistical grounds; b) allows calculating the intercept and slope of the logistic regression model, which can be used in any time to estimate the probability that a community experienced a critical level of scalar stress; c) allows locating a critical scalar stress threshold at community size 127 (95% CI: 122–132), while the maximum probability of critical scale stress is predicted at size 158 (95% CI: 147–170). The model ultimately provides grounds to assess, for the sake of any further archaeological/anthropological interpretation, the probability that a group reached a hot spot of size development critical for its internal cohesion. PMID:24626241

  4. Fluctuating survival selection explains variation in avian group size

    USGS Publications Warehouse

    Brown, Charles B.; Brown, Mary Bomberger; Roche, Erin A.; O'brien, Valerie A; Page, Catherine E.

    2016-01-01

    Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark–recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in cliff swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population.

  5. Predation as a determinant of minimum group size in baboons.

    PubMed

    Bettridge, Caroline M; Dunbar, R I M

    2012-01-01

    Predation risk places a pressure on animals to adopt mechanisms by which they reduce their individual risk of being preyed on. However, a consensus on methods of determining predation risk has yet to be reached. One of the most widespread ways in which animals respond to predation risk is by living in groups. Minimum permissible group size is the smallest group size that animals are able to live in, given the habitat-specific predation risk they face. We explore ways in which predation risk can be measured and analyse its effect on minimum observed group size in baboons. Using data on predator density, habitat composition and baboon body size, we investigate the impact of the components of predation risk on baboon group size, and derive an equation that best predicts minimum group size. Minimum group size in baboons is related to predator density and female body mass. Both of these elements can, in turn, be estimated from environmental variables. These findings present support for the argument that group living in primates is a response to predation risk and offer potentially new ways of investigating carnivore and primate ecology. PMID:23363593

  6. Boundaries around Group Interaction: The Effect of Size and Status.

    ERIC Educational Resources Information Center

    Knowles, Eric S.

    The stimulus value of group boundaries was investigated in a field experiment. It was hypothesized that the size of a group and the status of its members would reduce the permeability of a boundary around an interacting group. Two or 4 interacting people of high or low status interrupted the traffic flow in a university hallway. Results indicate…

  7. Epidemiological effects of group size variation in social species

    PubMed Central

    Caillaud, Damien; Craft, Meggan E.; Meyers, Lauren Ancel

    2013-01-01

    Contact patterns in group-structured populations determine the course of infectious disease outbreaks. Network-based models have revealed important connections between group-level contact patterns and the dynamics of epidemics, but these models typically ignore heterogeneities in within-group composition. Here, we analyse a flexible mathematical model of disease transmission in a hierarchically structured wildlife population, and find that increased variation in group size reduces the epidemic threshold, making social animal populations susceptible to a broader range of pathogens. Variation in group size also increases the likelihood of an epidemic for mildly transmissible diseases, but can reduce the likelihood and expected size of an epidemic for highly transmissible diseases. Further, we introduce the concept of epidemiological effective group size, which we define to be the group size of a hypothetical population containing groups of identical size that has the same epidemic threshold as an observed population. Using data from the Serengeti Lion Project, we find that pride-living Serengeti lions are epidemiologically comparable to a homogeneous population with up to 20 per cent larger prides. PMID:23576784

  8. A Systematic Review of Therapeutic Alliance, Group Cohesion, Empathy, and Goal Consensus/Collaboration in Psychotherapeutic Interventions in Cancer: Uncommon Factors?

    PubMed Central

    Schnur, Julie B.; Montgomery, Guy H.

    2010-01-01

    The effects of four empirically supported therapeutic relationship factors (therapeutic alliance, empathy, goal consensus/collaboration, and group cohesion) on the outcome of psychotherapeutic interventions conducted with individuals living with cancer were systematically reviewed. PubMed, PsycINFO, and CINAHL were searched from their inception through November 13, 2008. Studies of psychotherapeutic interventions targeted to individuals living with cancer, which also empirically assessed the association between any of these therapeutic relationship factors and psychotherapy outcome were included in the review (8 of 742 papers initially reviewed). Information on study methodology and results were abstracted independently by the authors using a standardized form. Results indicated that therapist-rated rapport and group cohesion were significantly related to positive psychotherapeutic outcomes. No studies examined empathy. The literature on collaboration was mixed, but showed some support for increased collaboration being related to positive therapeutic outcomes. Overall the current literature on the role of therapeutic relationship factors in the context of individuals living with cancer is scant, and much more research is needed to determine the overall contribution of these four relationship elements to the outcomes of psychotherapeutic interventions for individuals living with cancer. Results of such studies could have important clinical and research implications. PMID:20006414

  9. Dunbar's number: group size and brain physiology in humans reexamined.

    PubMed

    de Ruiter, Jan; Weston, Gavin; Lyon, Stephen M

    2011-01-01

    Popular academic ideas linking physiological adaptations to social behaviors are spreading disconcertingly into wider societal contexts. In this article, we note our skepticism with one particularly popular—in our view, problematic—supposed causal correlation between neocortex size and social group size. The resulting Dunbar's Number, as it has come to be called, has been statistically tested against observed group size in different primate species. Although there may be reason to doubt the Dunbar's Number hypothesis among nonhuman primate species, we restrict ourselves here to the application of such an explanatory hypothesis to human, culture-manipulating populations. Human information process management, we argue, cannot be understood as a simple product of brain physiology. Cross-cultural comparison of not only group size but also relationship-reckoning systems like kinship terminologies suggests that although neocortices are undoubtedly crucial to human behavior, they cannot be given such primacy in explaining complex group composition, formation, or management.

  10. The Influence of Group Size on Nonmandatory Asynchronous Instructional Discussion Groups.

    ERIC Educational Resources Information Center

    Caspi, Avner; Gorsky, Paul; Chajut, Eran

    2003-01-01

    Examines the effect of group size on students' behavior in asynchronous, nonmandatory instructional discussion groups. Focuses on four main questions on whether group size: affects the proportion of learner-learner and instructor-learner interactions; influences number of messages instructors post; have an effect on number of contributions that…

  11. Maintaining social cohesion is a more important determinant of patch residence time than maximizing food intake rate in a group-living primate, Japanese macaque (Macaca fuscata).

    PubMed

    Kazahari, Nobuko

    2014-04-01

    Animals have been assumed to employ an optimal foraging strategy (e.g., rate-maximizing strategy). In patchy food environments, intake rate within patches is positively correlated with patch quality, and declines as patches are depleted through consumption. This causes patch-leaving and determines patch residence time. In group-foraging situations, patch residence times are also affected by patch sharing. Optimal patch models for groups predict that patch residence times decrease as the number of co-feeding animals increases because of accelerated patch depletion. However, group members often depart patches without patch depletion, and their patch residence time deviates from patch models. It has been pointed out that patch residence time is also influenced by maintaining social proximity with others among group-living animals. In this study, the effects of maintaining social cohesion and that of rate-maximizing strategy on patch residence time were examined in Japanese macaques (Macaca fuscata). I hypothesized that foragers give up patches to remain in the proximity of their troop members. On the other hand, foragers may stay for a relatively long period when they do not have to abandon patches to follow the troop. In this study, intake rate and foraging effort (i.e., movement) did not change during patch residency. Macaques maintained their intake rate with only a little foraging effort. Therefore, the patches were assumed to be undepleted during patch residency. Further, patch residence time was affected by patch-leaving to maintain social proximity, but not by the intake rate. Macaques tended to stay in patches for short periods when they needed to give up patches for social proximity, and remained for long periods when they did not need to leave to keep social proximity. Patch-leaving and patch residence time that prioritize the maintenance of social cohesion may be a behavioral pattern in group-living primates.

  12. [The effect of group size on salience of member desirability].

    PubMed

    Sugimori, S

    1993-04-01

    This study tested the hypothesis that undesirable members are salient in a small group, while desirable members become salient in a larger group. One hundred and forty-five students were randomly assigned to twelve conditions, and read sentences desirably, undesirably, or neutrally describing each member of a college student club. The twelve clubs had one of three group sizes: 13, 39, or 52, and the proportion of the desirable or undesirable to the neutral was either 11:2 or 2:11, forming a three-way (3 x 2 x 2) factorial. Twelve subjects each were asked to make proportion judgments and impression ratings. Results indicated that proportion of the undesirable members was over estimated when the group size was 13, showing negativity bias, whereas proportion of the desirable was overestimated when the size was 52, displaying positivity bias. The size 39 showed neither positivity nor negativity bias. These results along with those from impression ratings suggested that salience of member desirability interacted with group size. It is argued that illusory correlation and group cognition studies may well take these effects into consideration. PMID:8355426

  13. [The effect of group size on salience of member desirability].

    PubMed

    Sugimori, S

    1993-04-01

    This study tested the hypothesis that undesirable members are salient in a small group, while desirable members become salient in a larger group. One hundred and forty-five students were randomly assigned to twelve conditions, and read sentences desirably, undesirably, or neutrally describing each member of a college student club. The twelve clubs had one of three group sizes: 13, 39, or 52, and the proportion of the desirable or undesirable to the neutral was either 11:2 or 2:11, forming a three-way (3 x 2 x 2) factorial. Twelve subjects each were asked to make proportion judgments and impression ratings. Results indicated that proportion of the undesirable members was over estimated when the group size was 13, showing negativity bias, whereas proportion of the desirable was overestimated when the size was 52, displaying positivity bias. The size 39 showed neither positivity nor negativity bias. These results along with those from impression ratings suggested that salience of member desirability interacted with group size. It is argued that illusory correlation and group cognition studies may well take these effects into consideration.

  14. Infants use relative numerical group size to infer social dominance

    PubMed Central

    Pun, Anthea; Birch, Susan A. J.; Baron, Andrew Scott

    2016-01-01

    Detecting dominance relationships, within and across species, provides a clear fitness advantage because this ability helps individuals assess their potential risk of injury before engaging in a competition. Previous research has demonstrated that 10- to 13-mo-old infants can represent the dominance relationship between two agents in terms of their physical size (larger agent = more dominant), whereas younger infants fail to do so. It is unclear whether infants younger than 10 mo fail to represent dominance relationships in general, or whether they lack sensitivity to physical size as a cue to dominance. Two studies explored whether infants, like many species across the animal kingdom, use numerical group size to assess dominance relationships and whether this capacity emerges before their sensitivity to physical size. A third study ruled out an alternative explanation for our findings. Across these studies, we report that infants 6–12 mo of age use numerical group size to infer dominance relationships. Specifically, preverbal infants expect an agent from a numerically larger group to win in a right-of-way competition against an agent from a numerically smaller group. In addition, this is, to our knowledge, the first study to demonstrate that infants 6–9 mo of age are capable of understanding social dominance relations. These results demonstrate that infants’ understanding of social dominance relations may be based on evolutionarily relevant cues and reveal infants’ early sensitivity to an important adaptive function of social groups. PMID:26884199

  15. Infants use relative numerical group size to infer social dominance.

    PubMed

    Pun, Anthea; Birch, Susan A J; Baron, Andrew Scott

    2016-03-01

    Detecting dominance relationships, within and across species, provides a clear fitness advantage because this ability helps individuals assess their potential risk of injury before engaging in a competition. Previous research has demonstrated that 10- to 13-mo-old infants can represent the dominance relationship between two agents in terms of their physical size (larger agent = more dominant), whereas younger infants fail to do so. It is unclear whether infants younger than 10 mo fail to represent dominance relationships in general, or whether they lack sensitivity to physical size as a cue to dominance. Two studies explored whether infants, like many species across the animal kingdom, use numerical group size to assess dominance relationships and whether this capacity emerges before their sensitivity to physical size. A third study ruled out an alternative explanation for our findings. Across these studies, we report that infants 6-12 mo of age use numerical group size to infer dominance relationships. Specifically, preverbal infants expect an agent from a numerically larger group to win in a right-of-way competition against an agent from a numerically smaller group. In addition, this is, to our knowledge, the first study to demonstrate that infants 6-9 mo of age are capable of understanding social dominance relations. These results demonstrate that infants' understanding of social dominance relations may be based on evolutionarily relevant cues and reveal infants' early sensitivity to an important adaptive function of social groups. PMID:26884199

  16. Energy-dependent cell cohesion in myxobacteria.

    PubMed

    Gilmore, D F; White, D

    1985-01-01

    Cohesion in the myxobacterium Stigmatella aurantiaca was characterized. Two classes of cohesion were revealed, termed class A and class B. Class A cohesion is a characteristic of vegetative cells grown in tryptone or casitone (Difco Laboratories, Detroit, Mich.), whereas class B cohesion requires the addition of calcium ion for induction. Class A cohesion occurs in the presence of any cation and is temperature independent. Class B cohesion requires the presence of a cation in the calcium group and is energy dependent. We conclude that S. aurantiaca responds to calcium ion by synthesizing the molecular components of a system of cell cohesion (class B) and that the functioning of this system requires the expenditure of metabolic energy.

  17. Effect of Work Group Size and Task Size on Observers' Job Characteristics Ratings.

    ERIC Educational Resources Information Center

    Greenberg, Carl I.; And Others

    The Job Characteristics Model proposed by Hackman and his associates postulates that positive personal and work outcomes are derived from five core job dimensions: skill variety, task identity, task significance, autonomy, and feedback from the job. The effects of the number of workers (work group size) and the number of tasks (task size) on…

  18. Learning Together while Designing: Does Group Size Make a Difference?

    ERIC Educational Resources Information Center

    Apedoe, Xornam S.; Ellefson, Michelle R.; Schunn, Christian D.

    2012-01-01

    As the use of project-based learning becomes more frequent in the K-12 science classroom, and in chemistry classrooms in particular, teachers have begun to identify practical questions about implementation that should be addressed empirically. One such question concerns whether there is an ideal group size that fosters individual student…

  19. The Influence of Group Size on Children's Competitive Behavior.

    ERIC Educational Resources Information Center

    Benenson, Joyce F.; Nicholson, Catherine; Waite, Angela; Roy, Rosanne; Simpson, Anna

    2001-01-01

    Tested hypothesis that children would compete more playing competitive games in tetrads than in dyads. Found that male target children competed more in tetrads than in dyads; female target children did not show different levels of competition based on group size. Based on a global measure of smiling, the emotional atmosphere was less positive in…

  20. Specialization and group size: brain and behavioural correlates of colony size in ants lacking morphological castes

    PubMed Central

    Amador-Vargas, Sabrina; Gronenberg, Wulfila; Wcislo, William T.; Mueller, Ulrich

    2015-01-01

    Group size in both multicellular organisms and animal societies can correlate with the degree of division of labour. For ants, the task specialization hypothesis (TSH) proposes that increased behavioural specialization enabled by larger group size corresponds to anatomical specialization of worker brains. Alternatively, the social brain hypothesis proposes that increased levels of social stimuli in larger colonies lead to enlarged brain regions in all workers, regardless of their task specialization. We tested these hypotheses in acacia ants (Pseudomyrmex spinicola), which exhibit behavioural but not morphological task specialization. In wild colonies, we marked, followed and tested ant workers involved in foraging tasks on the leaves (leaf-ants) and in defensive tasks on the host tree trunk (trunk-ants). Task specialization increased with colony size, especially in defensive tasks. The relationship between colony size and brain region volume was task-dependent, supporting the TSH. Specifically, as colony size increased, the relative size of regions within the mushroom bodies of the brain decreased in trunk-ants but increased in leaf-ants; those regions play important roles in learning and memory. Our findings suggest that workers specialized in defence may have reduced learning abilities relative to leaf-ants; these inferences remain to be tested. In societies with monomorphic workers, brain polymorphism enhanced by group size could be a mechanism by which division of labour is achieved. PMID:25567649

  1. Specialization and group size: brain and behavioural correlates of colony size in ants lacking morphological castes.

    PubMed

    Amador-Vargas, Sabrina; Gronenberg, Wulfila; Wcislo, William T; Mueller, Ulrich

    2015-02-22

    Group size in both multicellular organisms and animal societies can correlate with the degree of division of labour. For ants, the task specialization hypothesis (TSH) proposes that increased behavioural specialization enabled by larger group size corresponds to anatomical specialization of worker brains. Alternatively, the social brain hypothesis proposes that increased levels of social stimuli in larger colonies lead to enlarged brain regions in all workers, regardless of their task specialization. We tested these hypotheses in acacia ants (Pseudomyrmex spinicola), which exhibit behavioural but not morphological task specialization. In wild colonies, we marked, followed and tested ant workers involved in foraging tasks on the leaves (leaf-ants) and in defensive tasks on the host tree trunk (trunk-ants). Task specialization increased with colony size, especially in defensive tasks. The relationship between colony size and brain region volume was task-dependent, supporting the TSH. Specifically, as colony size increased, the relative size of regions within the mushroom bodies of the brain decreased in trunk-ants but increased in leaf-ants; those regions play important roles in learning and memory. Our findings suggest that workers specialized in defence may have reduced learning abilities relative to leaf-ants; these inferences remain to be tested. In societies with monomorphic workers, brain polymorphism enhanced by group size could be a mechanism by which division of labour is achieved.

  2. Mountain gorilla ranging patterns: influence of group size and group dynamics.

    PubMed

    Caillaud, Damien; Ndagijimana, Felix; Giarrusso, Anthony J; Vecellio, Veronica; Stoinski, Tara S

    2014-08-01

    Since the 1980s, the Virunga mountain gorilla population has almost doubled, now reaching 480 individuals living in a 430-km(2) protected area. Analysis of the gorillas' ranging patterns can provide critical information on the extent and possible effects of competition for food and space. We analyzed 12 years of daily ranging data and inter-group encounter data collected on 11 gorilla groups monitored by the Karisoke Research Center in Rwanda. During that period, the study population increased in size by almost 50% and the number of groups tripled. Groups had small yearly home ranges compared to other known gorilla populations, with an average 90% kernel density estimate of 8.07 km2 and large between-group variations (3.17-23.59 km2). Most groups had consistent home range location over the course of the study but for some, we observed gradual range shifts of up to 4 km. Neighboring groups displayed high home range overlap, which increased dramatically after the formation of new groups. On average, each group used only 28.6% of its 90% kernel home range exclusively, and in some areas up to six different groups had overlapping home ranges with little or no exclusive areas. We found a significant intra-group positive relationship between the number of weaned individuals in a group and the home range size, but the fitted models only explained 17.5% and 13.7% of the variance in 50% and 90% kernel home range size estimates, respectively. This suggests that despite the increase in size, the study population is not yet experiencing marked effects of feeding competition. However, the increase in home range overlap resulting from the formation of new groups led to a sixfold increase in the frequency of inter-group encounters, which exposes the population to elevated risks of fight-related injuries and infanticide.

  3. Parietal cortex mediates perceptual Gestalt grouping independent of stimulus size.

    PubMed

    Grassi, Pablo R; Zaretskaya, Natalia; Bartels, Andreas

    2016-06-01

    The integration of local moving elements into a unified gestalt percept has previously been linked to the posterior parietal cortex. There are two possible interpretations for the lack of involvement of other occipital regions. The first is that parietal cortex is indeed uniquely functionally specialized to perform grouping. Another possibility is that other visual regions can perform grouping as well, but that the large spatial separation of the local elements used previously exceeded their neurons' receptive field (RF) sizes, preventing their involvement. In this study we distinguished between these two alternatives. We measured whole-brain activity using fMRI in response to a bistable motion illusion that induced mutually exclusive percepts of either an illusory global Gestalt or of local elements. The stimulus was presented in two sizes, a large version known to activate IPS only, and a version sufficiently small to fit into the RFs of mid-level dorsal regions such as V5/MT. We found that none of the separately localized motion regions apart from parietal cortex showed a preference for global Gestalt perception, even for the smaller version of the stimulus. This outcome suggests that grouping-by-motion is mediated by a specialized size-invariant mechanism with parietal cortex as its anatomical substrate.

  4. Team cohesion and team success in sport.

    PubMed

    Carron, Albert V; Bray, Steven R; Eys, Mark A

    2002-02-01

    The main aim of this study was to examine the relationship between task cohesiveness and team success in elite teams using composite team estimates of cohesion. A secondary aim was to determine statistically the consistency (i.e. 'groupness') present in team members' perceptions of cohesion. Elite university basketball teams (n = 18) and club soccer teams (n = 9) were assessed for cohesiveness and winning percentages. Measures were recorded towards the end of each team's competitive season. Our results indicate that cohesiveness is a shared perception, thereby providing statistical support for the use of composite team scores. Further analyses indicated a strong relationship between cohesion and success (r = 0.55-0.67). Further research using multi-level statistical techniques is recommended.

  5. Group size adjustment to ecological demand in a cooperative breeder

    PubMed Central

    Zöttl, Markus; Frommen, Joachim G.; Taborsky, Michael

    2013-01-01

    Environmental factors can determine which group size will maximize the fitness of group members. This is particularly important in cooperative breeders, where group members often serve different purposes. Experimental studies are yet lacking to check whether ecologically mediated need for help will change the propensity of dominant group members to accept immigrants. Here, we manipulated the perceived risk of predation for dominant breeders of the cooperatively breeding cichlid fish Neolamprologus pulcher to test their response to unrelated and previously unknown immigrants. Potential immigrants were more readily accepted if groups were exposed to fish predators or egg predators than to herbivorous fish or control situations lacking predation risk. Our data are consistent with both risk dilution and helping effects. Egg predators were presented before spawning, which might suggest that the fish adjust acceptance rates also to a potential future threat. Dominant group members of N. pulcher apparently consider both present and future need of help based on ecological demand. This suggests that acceptance of immigrants and, more generally, tolerance of group members on demand could be a widespread response to ecological conditions in cooperatively breeding animals. PMID:23390105

  6. Risk allocation and competition in foraging groups: reversed effects of competition if group size varies under risk of predation.

    PubMed Central

    Bednekoff, Peter A.; Lima, Steven L.

    2004-01-01

    Animals often feed more quickly when in larger groups. This group-size effect is often explained by safety advantages for groups but an alternative explanation is that animals feed faster in larger groups because of greater scramble competition for limited food. We show that predation risk enhances the group-size effect if groups vary in size. By contrast, competition leads to the group-size effect only when individuals feed in groups of constant size. When individuals feed in groups that vary in size, the best strategy for dealing with competition is to feed intensely when in smaller groups and feed little when in larger (more competitive) groups. In all situations, the effects of competition interact with the effects of predation risk in a simple multiplicative way. Our results suggest that scramble competition is not a general explanation for the group-size effect on vigilance in situations where group size changes relatively rapidly. PMID:15306321

  7. Exploring the role of vision in social foraging: what happens to group size, vigilance, spacing, aggression and habitat use in birds and mammals that forage at night?

    PubMed

    Beauchamp, Guy

    2007-08-01

    I examined the role of vision in social foraging by contrasting group size, vigilance, spacing, aggression and habitat use between day and night in many species of birds and mammals. The literature review revealed that the rate of predation/disturbance was often reduced at night while food was considered more available. Social foraging at night was prevalent in many species suggesting that low light levels at night are not sufficient to prevent the formation and cohesion of animal groups. Group sizes were similar or larger at night than during the day in more than half the bird populations and in the majority of mammal populations. Factors such as calls, feeding noises or smells may contribute to the formation and cohesion of groups at night. Larger numbers of foragers at night may also facilitate the aggregation of more foragers. Vigilance levels were usually lower at night perhaps as a response to the lower predation risk or to the decreased value of scanning for predators that are difficult to locate. Low light levels may also make visual cues that promote aggression less conspicuous, which may be a factor in the lower levels of aggression documented at night. Spacing varied as a function of time of day in response to changes in foraging mode or food availability. Habitats that are avoided during the day were often used at night. Foraging at night presents birds and mammals with a new set of constraints that influence group size, time budgeting and habitat use.

  8. Correlation between the latent heats and cohesive energies of metal clusters

    NASA Astrophysics Data System (ADS)

    Starace, Anne K.; Neal, Colleen M.; Cao, Baopeng; Jarrold, Martin F.; Aguado, Andrés; López, José M.

    2008-10-01

    Dissociation energies have been determined for Aln+ clusters (n=25-83) using a new experimental approach that takes into account the latent heat of melting. According to the arguments presented here, the cohesive energies of the solidlike clusters are made up of contributions from the dissociation energies of the liquidlike clusters and the latent heats for melting. The size-dependent variations in the measured dissociation energies of the liquidlike clusters are small and the variations in the cohesive energies of solidlike clusters result almost entirely from variations in the latent heats for melting. To compare with the measured cohesive energies, density-functional theory has been used to search for the global minimum energy structures. Four groups of low energy structures were found: Distorted decahedral fragments, fcc fragments, fcc fragments with stacking faults, and "disordered." For most cluster sizes, the measured and calculated cohesive energies are strongly correlated. The calculations show that the variations in the cohesive energies (and the latent heats) result from a combination of geometric and electronic shell effects. For some clusters an electronic shell closing is responsible for the enhanced cohesive energy and latent heat (e.g., n =37), while for others (e.g., n =44) a structural shell closing is the cause.

  9. Traversing the Lexical Cohesion Minefield

    ERIC Educational Resources Information Center

    McGee, Iain

    2009-01-01

    When teachers hear the word "cohesion", they usually think of grammatical cohesion--an aspect of cohesion reasonably well covered in student books and teacher materials. However, occupying an area that straddles both lexis "proper" and cohesion lies "lexical cohesion". In what follows, it is argued that the teaching and learning of certain aspects…

  10. Habitat patch size and mating system as determinants of social group size in coral-dwelling fishes

    NASA Astrophysics Data System (ADS)

    Thompson, V. J.; Munday, P. L.; Jones, G. P.

    2007-03-01

    It is thought that the size and dispersion of habitat patches can determine the size and composition of animal social groups, however, this has rarely been tested. The relationship between group size, the mating system, and habitat patch size in six species of coral-dwelling gobies was examined. For all species, there was a positive correlation between coral colony size and social group size, however the strength of this relationship varied among species. Paragobiodon xanthosomus exhibited the strongest relationship and a manipulative field experiment confirmed that coral colony size limited group size in this species. For other species including Paragobiodon melanosomus and Eviota bifasciata, either a highly conservative mating system ( P. melanosomus), or increased mobility ( E. bifasciata) appeared to disrupt the relationship between habitat patch size and group size. There was no consistent relationship between the mating system exhibited and group size among the species investigated. These results demonstrate that habitat patch size, mobility, and mating systems can interact in complex ways to structure group size even among closely related species.

  11. Group size of a permanent large group of agile mangabeys (Cercocebus agilis) at Bai Hokou, Central African Republic.

    PubMed

    Devreese, Lieven; Huynen, Marie-Claude; Stevens, Jeroen M G; Todd, Angelique

    2013-01-01

    White-eyelid mangabeys (genus Cercocebus) live in groups of highly variable size. Because of their semi-terrestrial behaviour and preference for dense forest habitats, re-liable data on group size are scarce. During a 5-month study, we collected 17 group counts on a habituated group of agile mangabeys (C. agilis) at Bai Hokou in the Central African Republic. We found a stable group size of approximately 135 individuals. This permanent large grouping pattern is known to occur among several populations of white-eyelid mangabeys and is congruent with extreme group sizes reported in mandrills at Lopé in Gabon.

  12. Diversity and Social Cohesion

    ERIC Educational Resources Information Center

    Pagani, Camilla

    2014-01-01

    The issue of diversity, in its broadest sense, is discussed here in its relation to social cohesion, cross-cultural relations, ingroup-outgroup relations and educational interventions. The main thesis of the paper is that real social cohesion in an ingroup rests on the acknowledgment of and the dialog with the diversities of the members of the…

  13. Group size, individual role differentiation and effectiveness of cooperation in a homogeneous group of hunters.

    PubMed

    Escobedo, R; Muro, C; Spector, L; Coppinger, R P

    2014-06-01

    The emergence of cooperation in wolf-pack hunting is studied using a simple, homogeneous, particle-based computational model. Wolves and prey are modelled as particles that interact through attractive and repulsive forces. Realistic patterns of wolf aggregation readily emerge in numerical simulations, even though the model includes no explicit wolf-wolf attractive forces, showing that the form of cooperation needed for wolf-pack hunting can take place even among strangers. Simulations are used to obtain the stationary states and equilibria of the wolves and prey system and to characterize their stability. Different geometric configurations for different pack sizes arise. In small packs, the stable configuration is a regular polygon centred on the prey, while in large packs, individual behavioural differentiation occurs and induces the emergence of complex behavioural patterns between privileged positions. Stable configurations of large wolf-packs include travelling and rotating formations, periodic oscillatory behaviours and chaotic group behaviours. These findings suggest a possible mechanism by which larger pack sizes can trigger collective behaviours that lead to the reduction and loss of group hunting effectiveness, thus explaining the observed tendency of hunting success to peak at small pack sizes. They also explain how seemingly complex collective behaviours can emerge from simple rules, among agents that need not have significant cognitive skills or social organization. PMID:24694897

  14. Group size, individual role differentiation and effectiveness of cooperation in a homogeneous group of hunters.

    PubMed

    Escobedo, R; Muro, C; Spector, L; Coppinger, R P

    2014-06-01

    The emergence of cooperation in wolf-pack hunting is studied using a simple, homogeneous, particle-based computational model. Wolves and prey are modelled as particles that interact through attractive and repulsive forces. Realistic patterns of wolf aggregation readily emerge in numerical simulations, even though the model includes no explicit wolf-wolf attractive forces, showing that the form of cooperation needed for wolf-pack hunting can take place even among strangers. Simulations are used to obtain the stationary states and equilibria of the wolves and prey system and to characterize their stability. Different geometric configurations for different pack sizes arise. In small packs, the stable configuration is a regular polygon centred on the prey, while in large packs, individual behavioural differentiation occurs and induces the emergence of complex behavioural patterns between privileged positions. Stable configurations of large wolf-packs include travelling and rotating formations, periodic oscillatory behaviours and chaotic group behaviours. These findings suggest a possible mechanism by which larger pack sizes can trigger collective behaviours that lead to the reduction and loss of group hunting effectiveness, thus explaining the observed tendency of hunting success to peak at small pack sizes. They also explain how seemingly complex collective behaviours can emerge from simple rules, among agents that need not have significant cognitive skills or social organization.

  15. Group size, individual role differentiation and effectiveness of cooperation in a homogeneous group of hunters

    PubMed Central

    Escobedo, R.; Muro, C.; Spector, L.; Coppinger, R. P.

    2014-01-01

    The emergence of cooperation in wolf-pack hunting is studied using a simple, homogeneous, particle-based computational model. Wolves and prey are modelled as particles that interact through attractive and repulsive forces. Realistic patterns of wolf aggregation readily emerge in numerical simulations, even though the model includes no explicit wolf–wolf attractive forces, showing that the form of cooperation needed for wolf-pack hunting can take place even among strangers. Simulations are used to obtain the stationary states and equilibria of the wolves and prey system and to characterize their stability. Different geometric configurations for different pack sizes arise. In small packs, the stable configuration is a regular polygon centred on the prey, while in large packs, individual behavioural differentiation occurs and induces the emergence of complex behavioural patterns between privileged positions. Stable configurations of large wolf-packs include travelling and rotating formations, periodic oscillatory behaviours and chaotic group behaviours. These findings suggest a possible mechanism by which larger pack sizes can trigger collective behaviours that lead to the reduction and loss of group hunting effectiveness, thus explaining the observed tendency of hunting success to peak at small pack sizes. They also explain how seemingly complex collective behaviours can emerge from simple rules, among agents that need not have significant cognitive skills or social organization. PMID:24694897

  16. 48 CFR 1602.170-13 - Similarly sized subscriber groups.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... criteria specified in the rate instructions issued by OPM. (b) Any group with which an FEHB carrier enters... business, government entities, groups that have multi-year contracts, and groups having...

  17. Effects of group size, gender, and ability grouping on learning science process skills using microcomputers

    NASA Astrophysics Data System (ADS)

    Berge, Zane L.

    What are the effects of group size (individuals, pairs, and quads of students), gender, and ability grouping of 245 seventh- and eighth-grade students on achievement within an environment that uses microcomputers as tools in learning science process skills? A split-plot, multivariate factorial design was used to analyze the above factors and interactions among the factors. Analyses indicated that the only statistically significant result was a main effect on ability for the two response variables measured in the study. Major conclusions included: (1) teams of two and four members working together solved problems as effectively as individuals, (2) the lessons and procedures implemented in the manner described generated a gender-neutral achievement outcome in science, and (3) microcomputer, using a file-management program and structured activities, can be used as a tool to promote student learning of science process skills.

  18. Coagulation-Fragmentation Model for Animal Group-Size Statistics

    NASA Astrophysics Data System (ADS)

    Degond, Pierre; Liu, Jian-Guo; Pego, Robert L.

    2016-10-01

    We study coagulation-fragmentation equations inspired by a simple model proposed in fisheries science to explain data for the size distribution of schools of pelagic fish. Although the equations lack detailed balance and admit no H-theorem, we are able to develop a rather complete description of equilibrium profiles and large-time behavior, based on recent developments in complex function theory for Bernstein and Pick functions. In the large-population continuum limit, a scaling-invariant regime is reached in which all equilibria are determined by a single scaling profile. This universal profile exhibits power-law behavior crossing over from exponent -2/3 for small size to -3/2 for large size, with an exponential cutoff.

  19. Intergroup Discrimination in Positive and Negative Outcome Allocations: Impact of Stimulus Valence, Relative Group Status, and Relative Group Size.

    ERIC Educational Resources Information Center

    Otten, Sabine; And Others

    1996-01-01

    Three studies investigated the determination of social discrimination by the valence of stimuli that are allocated between groups. The studies were based on either the minimal group paradigm or a more reality-based laboratory intergroup setting, with stimulus valence, group status, and group size as factors and with pull scores on Tajfel matrices…

  20. Grouping for reading instruction: does one size fit all?

    PubMed

    Schumm, J S; Moody, S W; Vaughn, S

    2000-01-01

    Twenty-nine third-grade teachers and selected students from their classes participated. Study 1 used teacher interviews and classroom observations to examine teachers' perceptions and practices for grouping for reading instruction; Study 2 examined the impact of these grouping practices on the academic progress, social progress, and attitudes about reading of students representing a range of achievement levels, including students with learning disabilities. Results indicated that, overall, teachers used whole class instruction for reading and the same materials for all students, including students with learning disabilities. Students with learning disabilities made little academic progress and their attitudes about reading did not improve over time. PMID:15495549

  1. Density-dependent effects on group size are sex-specific in a gregarious ungulate.

    PubMed

    Vander Wal, Eric; van Beest, Floris M; Brook, Ryan K

    2013-01-01

    Density dependence can have marked effects on social behaviors such as group size. We tested whether changes in population density of a large herbivore (elk, Cervus canadensis) affected sex-specific group size and whether the response was density- or frequency-dependent. We quantified the probability and strength of changes in group sizes and dispersion as population density changed for each sex. We used group size data from a population of elk in Manitoba, Canada, that was experimentally reduced from 1.20 to 0.67 elk/km(2) between 2002 and 2009. Our results indicated that functional responses of group size to population density are sex-specific. Females showed a positive density-dependent response in group size at population densities ≥0.70 elk/km(2) and we found evidence for a minimum group size at population density ≤0.70 elk/km(2). Changes in male group size were also density-dependent; however, the strength of the relationship was lower than for females. Density dependence in male group size was predominantly a result of fusion of solitary males into larger groups, rather than fusion among existing groups. Our study revealed that density affects group size of a large herbivore differently between males and females, which has important implications for the benefits e.g., alleviating predation risk, and costs of social behaviors e.g., competition for resources and mates, and intra-specific pathogen transmission. PMID:23326502

  2. Density-Dependent Effects on Group Size Are Sex-Specific in a Gregarious Ungulate

    PubMed Central

    Vander Wal, Eric; van Beest, Floris M.; Brook, Ryan K.

    2013-01-01

    Density dependence can have marked effects on social behaviors such as group size. We tested whether changes in population density of a large herbivore (elk, Cervus canadensis) affected sex-specific group size and whether the response was density- or frequency-dependent. We quantified the probability and strength of changes in group sizes and dispersion as population density changed for each sex. We used group size data from a population of elk in Manitoba, Canada, that was experimentally reduced from 1.20 to 0.67 elk/km2 between 2002 and 2009. Our results indicated that functional responses of group size to population density are sex-specific. Females showed a positive density-dependent response in group size at population densities ≥0.70 elk/km2 and we found evidence for a minimum group size at population density ≤0.70 elk/km2. Changes in male group size were also density-dependent; however, the strength of the relationship was lower than for females. Density dependence in male group size was predominantly a result of fusion of solitary males into larger groups, rather than fusion among existing groups. Our study revealed that density affects group size of a large herbivore differently between males and females, which has important implications for the benefits e.g., alleviating predation risk, and costs of social behaviors e.g., competition for resources and mates, and intra-specific pathogen transmission. PMID:23326502

  3. Determination of flow-regime boundaries for cohesive particles

    NASA Astrophysics Data System (ADS)

    Knowlton, T. M.; Findlay, J. G.; Arastoopour, H.; Gidaspow, D.

    1992-10-01

    Cohesive particles (Geldart Group C powders) are fine particles generally less than 30 microns in size. Interparticle forces are large relative to inertial forces in these particles, and cause clumping, sticking, and channeling when attempts are made to fluidize them. These solids do not flow easily through pipes, and bridge extremely easily. The objectives of the work in this program were (1) to develop a hydrodynamic model which can be applied to cohesive solids, and (2) to obtain data in a large-scale (30-cm-diameter) riser to test the model. The work was divided into six tasks: Task 1. Preparation of a Project Work Plan; Task 2. Hydrodynamic Model Development; Task 3. Determination of Rheological Properties for Incorporation into the Model; Task 4. Small-Scale Flow Tests; Task 5. Large-Scale Flow Tests; and Task 6. Comparison of Model With Data. The work was conducted by the Institute of Gas Technology (IGT) in collaboration with the Illinois Institute of Technology (IIT). This work combined the expertise of IIT in model development, with the large-scale experimental capabilities of IGT. IIT researchers developed the hydrodynamic model in the program, while the large-scale data were generated by IGT. Following the preparation of the Project Work Plan in Task 1, work was started on the development of a two-dimensional hydrodynamic model to enable the behavior of cohesive solids in a dilute-phase riser to be simulated. In Task 2, two hydrodynamic models were developed based on the kinetic theory model of granular flow. The models were used to predict data presented in the literature, as well as data generated in Task 5 of this study. In Task 3, rheological data on cohesive oil shale with an average particle size of approximately 12 microns was obtained using a unique device called a cohetester.

  4. A phylogenetic analysis of body size evolution in the Anolis roquet group (Sauria: Iguanidae): character displacement or size assortment?

    PubMed

    Giannasi, N; Thorpe, R S; Malhotra, A

    2000-02-01

    The important role that competition plays in structuring communities is well documented; however, the role of competition in an evolutionary context remains unclear. Evolutionary investigations into the role of competition have often focused on the process of character displacement, and a good example of this is the evolution of body size in the Anolis lizards of the Caribbean islands. Previous work on the A. roquet species group has taken a phylogenetic approach and concluded that patterns of body size differences are not caused by character displacement but are a result of size assortment. Using a phylogenetic reconstruction based on the sequence of the cytochrome b gene (cyt-b) and ancestral character-state reconstruction methods, we investigated the roles of character displacement and size assortment. Our results indicated that size assortment alone was insufficient to explain the observed patterns of body size differences. Furthermore, we found that change in body size was associated with a change in allopatry/sympatry, thus supporting the character-displacement hypothesis. We conclude that patterns of body size differences in the A. roquet species group appear to be the result of a combination of character displacement and size assortment because character displacement was only found to be possible on three occasions.

  5. Parasite infection and host group size: a meta-analytical review.

    PubMed

    Patterson, Jesse E H; Ruckstuhl, Kathreen E

    2013-06-01

    Many studies have identified various host behavioural and ecological traits that are associated with parasite infection, including host gregariousness. By use of meta-analyses, we investigated to what degree parasite prevalence, intensity and species richness are correlated with group size in gregarious species. We predicted that larger groups would have more parasites and higher parasite species richness. We analysed a total of 70 correlations on parasite prevalence, intensity and species richness across different host group sizes. Parasite intensity and prevalence both increased positively with group size, as expected. No significant relationships were found between host group size and parasite species richness, suggesting that larger groups do not harbour more rare or novel parasite species than smaller groups. We further predicted that the mobility of the host (mobile, sedentary) and the mode of parasite transmission (direct, indirect, mobile) would be important predictors of the effects of group sizes on parasite infection. It was found that group size was positively correlated with the prevalence and intensity of directly and indirectly transmitted parasites. However, a negative relationship was observed between group size and mobile parasite intensity, with larger groups having lower parasite intensities. Further, intensities of parasites did not increase with group size of mobile hosts, suggesting that host mobility may negate parasite infection risk. The implications for the evolution and maintenance of sociality in host species are discussed, and future research directions are highlighted.

  6. Activity and social factors affect cohesion among individuals in female Japanese macaques: A simultaneous focal-follow study.

    PubMed

    Nishikawa, Mari; Suzuki, Mariko; Sprague, David S

    2014-07-01

    Understanding cohesion among individuals within a group is necessary to reveal the social system of group-living primates. Japanese macaques (Macaca fuscata) are female-philopatric primates that reside in social groups. We investigated whether individual activity and social factors can affect spatio-temporal cohesion in wild female Japanese macaques. We conducted behavioral observation on a group, which contained 38 individuals and ranged over ca. 60 ha during the study period. Two observers carried out simultaneous focal-animal sampling of adult female pairs during full-day follows using global positioning system which enabled us to quantify interindividual distances (IIDs), group members within visual range (i.e., visual unit), and separation duration beyond visual range as indicators of cohesion among individuals. We found considerable variation in spatio-temporal group cohesion. The overall mean IID was 99.9 m (range = 0-618.2 m). The percentage of IIDs within visual range was 23.1%, within auditory range was 59.8%, and beyond auditory range was 17.1%. IIDs varied with activity; they were shorter during grooming and resting, and longer during foraging and traveling. Low-ranking females showed less cohesion than high-ranking ones. Kin females stayed nearly always within audible range. The macaques were weakly cohesive with small mean visual unit size (3.15 counting only adults, 5.99 counting all individuals). Both-sex units were the most frequently observed visual unit type when they were grooming/resting. Conversely, female units were the most frequently observed visual unit type when they were foraging. The overall mean visual separation duration was 25.7 min (range = 3-513 min). Separation duration was associated with dominance rank. These results suggest that Japanese macaques regulate cohesion among individuals depending on their activity and on social relationships; they were separated to adapt food distribution and aggregated to maintain social

  7. An ecometric analysis of neighbourhood cohesion

    PubMed Central

    Fone, David L; Farewell, Daniel M; Dunstan, Frank D

    2006-01-01

    Background It is widely believed that the social environment has an important influence on health, but there is less certainty about how to measure specific factors within the social environment that could link the neighbourhood of residence to a health outcome. The objectives of the study were to examine the underlying constructs captured by an adapted version of Buckner's neighbourhood cohesion scale, and to assess the reliability of the scale at the small-area-level by combining ecometric methodology with ordinal modelling of a five-point scale. Methods Data were analysed from 11,078 participants in the Caerphilly Health and Social Needs Study, who were sampled from within 325 UK census enumeration districts in Caerphilly county borough, Wales, UK. The responses of interest came from 15 question items designed to capture different facets of neighbourhood cohesion. Factor analysis was used to identify constructs underlying the neighbourhood cohesion item responses. Using a multilevel ecometric model, the variability present in these ordinal responses was decomposed into contextual, compositional, item-level and residual components. Results Two constructs labelled neighbourhood belonging and social cohesion were identified, and variability in both constructs was modelled at each level of the multilevel structure. The intra-neighbourhood correlations were 6.4% and 1.0% for the neighbourhood belonging and social cohesion subscales, respectively. Given the large sample size, contextual neighbourhood cohesion scores can be estimated reliably. The wide variation in the observed frequency of occurence of the scale item activities suggests that the two subscales have desirable ecometric properties. Further, the majority of between-neighbourhood variation is not explained by the socio-demographic characteristics of the individual respondents. Conclusion Assessment of the properties of the adapted neighbourhood cohesion scale using factor analysis and ecometric analysis

  8. Kinship-based politics and the optimal size of kin groups

    PubMed Central

    Hammel, E. A.

    2005-01-01

    Kin form important political groups, which change in size and relative inequality with demographic shifts. Increases in the rate of population growth increase the size of kin groups but decrease their inequality and vice versa. The optimal size of kin groups may be evaluated from the marginal political product (MPP) of their members. Culture and institutions affect levels and shapes of MPP. Different optimal group sizes, from different perspectives, can be suggested for any MPP schedule. The relative dominance of competing groups is determined by their MPP schedules. Groups driven to extremes of sustainability may react in Malthusian fashion, including fission and fusion, or in Boserupian fashion, altering social technology to accommodate changes in size. The spectrum of alternatives for actors and groups, shaped by existing institutions and natural and cultural selection, is very broad. Nevertheless, selection may result in survival of particular kinds of political structures. PMID:16091466

  9. Interactions among social monitoring, anti-predator vigilance and group size in eastern grey kangaroos

    PubMed Central

    Favreau, François-René; Goldizen, Anne W.; Pays, Olivier

    2010-01-01

    Group size is known to affect both the amount of time that prey animals spend in vigilance and the degree to which the vigilance of group members is synchronized. However, the variation in group-size effects reported in the literature is not yet understood. Prey animals exhibit vigilance both to protect themselves against predators and to monitor other group members, and both forms of vigilance presumably influence group-size effects on vigilance. However, our understanding of the patterns of individual investment underlying the time sharing between anti-predator and social vigilance is still limited. We studied patterns of variation in individual vigilance and the synchronization of vigilance with group size in a wild population of eastern grey kangaroos (Macropus giganteus) subject to predation, in particular focusing on peripheral females because we expected that they would exhibit both social and anti-predator vigilance. There was no global effect of group size on individual vigilance. The lack of group-size effect was the result of two compensating effects. The proportion of time individuals spent looking at other group members increased, whereas the proportion of time they spent scanning the environment decreased with group size; as a result, overall vigilance levels did not change with group size. Moreover, a degree of synchrony of vigilance occurred within groups and that degree increased with the proportion of vigilance time peripheral females spent in anti-predator vigilance. Our results highlight the crucial roles of both social and anti-predator components of vigilance in the understanding of the relationship between group size and vigilance, as well as in the synchronization of vigilance among group members. PMID:20219737

  10. Interactions among social monitoring, anti-predator vigilance and group size in eastern grey kangaroos.

    PubMed

    Favreau, François-René; Goldizen, Anne W; Pays, Olivier

    2010-07-01

    Group size is known to affect both the amount of time that prey animals spend in vigilance and the degree to which the vigilance of group members is synchronized. However, the variation in group-size effects reported in the literature is not yet understood. Prey animals exhibit vigilance both to protect themselves against predators and to monitor other group members, and both forms of vigilance presumably influence group-size effects on vigilance. However, our understanding of the patterns of individual investment underlying the time sharing between anti-predator and social vigilance is still limited. We studied patterns of variation in individual vigilance and the synchronization of vigilance with group size in a wild population of eastern grey kangaroos (Macropus giganteus) subject to predation, in particular focusing on peripheral females because we expected that they would exhibit both social and anti-predator vigilance. There was no global effect of group size on individual vigilance. The lack of group-size effect was the result of two compensating effects. The proportion of time individuals spent looking at other group members increased, whereas the proportion of time they spent scanning the environment decreased with group size; as a result, overall vigilance levels did not change with group size. Moreover, a degree of synchrony of vigilance occurred within groups and that degree increased with the proportion of vigilance time peripheral females spent in anti-predator vigilance. Our results highlight the crucial roles of both social and anti-predator components of vigilance in the understanding of the relationship between group size and vigilance, as well as in the synchronization of vigilance among group members.

  11. Developing Cohesive Leadership Means Addressing All Parts of the System

    ERIC Educational Resources Information Center

    Fisher, Troyce

    2010-01-01

    In her role with the School Administrators of Iowa leading Iowa's leadership grant from The Wallace Foundation, the author works with a coalition of individuals and groups striving to implement a cohesive leadership system for school leaders. Efforts to create a cohesive leadership system in Iowa for the past nine years have resulted in many…

  12. Cohesion in Online Student Teams versus Traditional Teams

    ERIC Educational Resources Information Center

    Hansen, David E.

    2016-01-01

    Researchers have found that the electronic methods in use for online team communication today increase communication quality in project-based work situations. Because communication quality is known to influence group cohesion, the present research examined whether online student project teams are more cohesive than traditional teams. We tested…

  13. Cohesion and Adaptability in Mexican-American and Anglo Families.

    ERIC Educational Resources Information Center

    Vega, William A.; And Others

    1986-01-01

    Examined cohesion and adaptability as two dimensions of family functioning in 294 Anglo- and Mexican-American parents of school-age children. Revealed no significant differences in mean scores or distributions between ethnic groups for cohesion or adaptability, even when acculturation was controlled. (Author/NB)

  14. Cohesive Elements for Shells

    NASA Technical Reports Server (NTRS)

    Davila, Carlos G.; Camanho, Pedro P.; Turon, Albert

    2007-01-01

    A cohesive element for shell analysis is presented. The element can be used to simulate the initiation and growth of delaminations between stacked, non-coincident layers of shell elements. The procedure to construct the element accounts for the thickness offset by applying the kinematic relations of shell deformation to transform the stiffness and internal force of a zero-thickness cohesive element such that interfacial continuity between the layers is enforced. The procedure is demonstrated by simulating the response and failure of the Mixed Mode Bending test and a skin-stiffener debond specimen. In addition, it is shown that stacks of shell elements can be used to create effective models to predict the inplane and delamination failure modes of thick components. The results indicate that simple shell models can retain many of the necessary predictive attributes of much more complex 3D models while providing the computational efficiency that is necessary for design.

  15. Effect of group size on behavior, health, production and welfare of veal calves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of the present study was to determine the effect of group size on behavior, health, growth, and welfare of veal calves. Holstein-Friesian bull calves (n = 168), 44 ± 3 days of age, were used to investigate the effect of group size. Calves were randomly assigned into 1 of 3 treatments o...

  16. Ranging behavior, group size and behavioral flexibility in Ethiopian hamadryas baboons (Papio hamadryas hamadryas).

    PubMed

    Swedell, Larissa

    2002-01-01

    This study reports group size, home range size, daily path lengths, seasonal effects on ranging behavior and qualitative information on diet for a population of hamadryas baboons inhabiting the lowlands of the northern Rift Valley in central Ethiopia. The minimum home range size and daily path length for this population are similar to those reported for other populations of hamadryas baboons in Ethiopia and Saudi Arabia. Group sizes, however, are much larger than those in most other hamadryas populations for which published data are available. The large group sizes in this area may be related to the abundance of one food resource in particular, doum palm nuts. Overall, this study suggests that hamadryas baboons may be more flexible in some aspects of their behavioral ecology (e.g. group size) than in others (e.g. ranging behavior).

  17. Domain-general mechanisms: what they are, how they evolved, and how they interact with modular, domain-specific mechanisms to enable cohesive human groups.

    PubMed

    MacDonald, Kevin

    2014-08-01

    Domain-general mechanisms are evolutionarily ancient, resulting from the evolution of affective cues signaling the attainment of evolutionary goals. Explicit processing is a particularly important set of domain-general mechanisms for constructing human groups - enabling ideologies specifying future goal states and rationalizing group aims, enabling knowledge of others' reputations essential to cooperation, understanding the rights and obligations of group membership, monitoring group members, and providing appropriate punishments to those who deviate from group aims. PMID:25162875

  18. Validation of the Child Sport Cohesion Questionnaire

    ERIC Educational Resources Information Center

    Martin, Luc J.; Carron, Albert V.; Eys, Mark A.; Loughead, Todd

    2013-01-01

    The purpose of the present study was to test the validity evidence of the Child Sport Cohesion Questionnaire (CSCQ). To accomplish this task, convergent, discriminant, and known-group difference validity were examined, along with factorial validity via confirmatory factor analysis (CFA). Child athletes (N = 290, M[subscript age] = 10.73 plus or…

  19. Nonlinear effects of group size on the success of wolves hunting elk

    USGS Publications Warehouse

    MacNulty, D.R.; Smith, D.W.; Mech, L.D.; Vucetich, J.A.; Packer, C.

    2012-01-01

    Despite the popular view that social predators live in groups because group hunting facilitates prey capture, the apparent tendency for hunting success to peak at small group sizes suggests that the formation of large groups is unrelated to prey capture. Few empirical studies, however, have tested for nonlinear relationships between hunting success and group size, and none have demonstrated why success trails off after peaking. Here, we use a unique dataset of observations of individually known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to show that the relationship between success and group size is indeed nonlinear and that individuals withholding effort (free riding) is why success does not increase across large group sizes. Beyond 4 wolves, hunting success leveled off, and individual performance (a measure of effort) decreased for reasons unrelated to interference from inept hunters, individual age, or size. But performance did drop faster among wolves with an incentive to hold back, i.e., nonbreeders with no dependent offspring, those performing dangerous predatory tasks, i.e., grabbing and restraining prey, and those in groups of proficient hunters. These results suggest that decreasing performance was free riding and that was why success leveled off in groups with >4 wolves that had superficially appeared to be cooperating. This is the first direct evidence that nonlinear trends in group hunting success reflect a switch from cooperation to free riding. It also highlights how hunting success per se is unlikely to promote formation and maintenance of large groups. ?? 2011 The Author.

  20. Nonlinear effects of group size on the success of wolves hunting elk

    USGS Publications Warehouse

    MacNulty, Daniel R.; Smith, Douglas W.; Mech, L. David; Vucetich, John A.; Packer, Craig

    2012-01-01

    Despite the popular view that social predators live in groups because group hunting facilitates prey capture, the apparent tendency for hunting success to peak at small group sizes suggests that the formation of large groups is unrelated to prey capture. Few empirical studies, however, have tested for nonlinear relationships between hunting success and group size, and none have demonstrated why success trails off after peaking. Here, we use a unique dataset of observations of individually known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to show that the relationship between success and group size is indeed nonlinear and that individuals withholding effort (free riding) is why success does not increase across large group sizes. Beyond 4 wolves, hunting success leveled off, and individual performance (a measure of effort) decreased for reasons unrelated to interference from inept hunters, individual age, or size. But performance did drop faster among wolves with an incentive to hold back, i.e., nonbreeders with no dependent offspring, those performing dangerous predatory tasks, i.e., grabbing and restraining prey, and those in groups of proficient hunters. These results suggest that decreasing performance was free riding and that was why success leveled off in groups with >4 wolves that had superficially appeared to be cooperating. This is the first direct evidence that nonlinear trends in group hunting success reflect a switch from cooperation to free riding. It also highlights how hunting success per se is unlikely to promote formation and maintenance of large groups.

  1. A Small Group Model for Early Intervention in Literacy: Group Size and Program Effects.

    ERIC Educational Resources Information Center

    Homan, Susan; King, James R.; Hogarty, Kris

    Over the last 2 years, Accelerated Literacy Learning (ALL) has experimented with the small group model in early literacy intervention, with success comparable to that in one-to-one intervention. There can be little doubt that intervention provided to struggling readers is most effectively initiated at an early stage. The ALL program was conceived…

  2. Group size alters postures, and maintenance, oral, locomotor and social behaviors of veal calves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to evaluate the effect of group size on behavior of veal calves. Holstein-Friesian bull calves (n = 168; 44 ± 3 d of age), were randomly assigned to 1 of 3 treatments of group housing with 2, 4, or 8 calves per pen (1.82 m2 per calf for all groups). Behavior was obser...

  3. Prior Knowledge, Reading Skill, and Text Cohesion in the Comprehension of Science Texts

    ERIC Educational Resources Information Center

    Ozuru, Yasuhiro; Dempsey, Kyle; McNamara, Danielle S.

    2009-01-01

    This study examined how text features (i.e., cohesion) and individual differences (i.e., reading skill and prior knowledge) contribute to biology text comprehension. College students with low and high levels of biology knowledge read two biology texts, one of which was high in cohesion and the other low in cohesion. The two groups were similar in…

  4. The Effects of Group Size, Memory Instruction, and Session Length on the Creative Performance in Electronic Brainstorming Groups

    ERIC Educational Resources Information Center

    Coskun, Hamit

    2011-01-01

    In the literature, there has been a focus on the effectiveness of larger sized electronic brainstorming groups; however, mechanisms for its effectiveness still remain open to question and some methodological concerns (e.g., the evaluation of ideas and the typing speed, and the use of different formats) continue to be important problems. To…

  5. Social complexity can drive vocal complexity: group size influences vocal information in Carolina chickadees.

    PubMed

    Freeberg, Todd M

    2006-07-01

    One hypothesis to explain variation in vocal communication in animal species is that the complexity of the social group influences the group's vocal complexity. This social-complexity hypothesis for communication is also central to recent arguments regarding the origins of human language, but experimental tests of the hypothesis are lacking. This study investigated whether group size, a fundamental component of social complexity, influences the complexity of a call functioning in the social organization of Carolina chickadees, Poecile carolinensis. In unmanipulated field settings, calls of individuals in larger groups had greater complexity (more information) than calls of individuals in smaller groups. In aviary settings manipulating group size, individuals in larger groups used calls with greater complexity than individuals in smaller groups. These results indicate that social complexity can influence communicative complexity in this species. PMID:16866738

  6. The role of micro size computing clusters for small physics groups

    NASA Astrophysics Data System (ADS)

    Shevel, A. Y.

    2014-06-01

    A small physics group (3-15 persons) might use a number of computing facilities for the analysis/simulation, developing/testing, teaching. It is discussed different types of computing facilities: collaboration computing facilities, group local computing cluster (including colocation), cloud computing. The author discuss the growing variety of different computing options for small groups and does emphasize the role of the group owned computing cluster of micro size.

  7. Rearing-group size determines social competence and brain structure in a cooperatively breeding cichlid.

    PubMed

    Fischer, Stefan; Bessert-Nettelbeck, Mathilde; Kotrschal, Alexander; Taborsky, Barbara

    2015-07-01

    Social animals can greatly benefit from well-developed social skills. Because the frequency and diversity of social interactions often increase with the size of social groups, the benefits of advanced social skills can be expected to increase with group size. Variation in social skills often arises during ontogeny, depending on early social experience. Whether variation of social-group sizes affects development of social skills and related changes in brain structures remains unexplored. We investigated whether, in a cooperatively breeding cichlid, early group size (1) shapes social behavior and social skills and (2) induces lasting plastic changes in gross brain structures and (3) whether the development of social skills is confined to a sensitive ontogenetic period. Rearing-group size and the time juveniles spent in these groups interactively influenced the development of social skills and the relative sizes of four main brain regions. We did not detect a sensitive developmental period for the shaping of social behavior within the 2-month experience phase. Instead, our results suggest continuous plastic behavioral changes over time. We discuss how developmental effects on social behavior and brain architecture may adaptively tune phenotypes to their current or future environments. PMID:26098344

  8. Collectivism, Individualism, and Cohesion in a Team-based Occupation.

    ERIC Educational Resources Information Center

    Workman, Michael

    2001-01-01

    Ethnographic interviews with 3 teams of 26 computer programmers revealed how levels of collectivism or individualism differed as groups solved problems. Cultural cohesion was identified as a separate construct from collectivism. (Contains 53 references.) (SK)

  9. Infectious disease and group size: more than just a numbers game

    PubMed Central

    Nunn, Charles L.; Jordán, Ferenc; McCabe, Collin M.; Verdolin, Jennifer L.; Fewell, Jennifer H.

    2015-01-01

    Increased risk of infectious disease is assumed to be a major cost of group living, yet empirical evidence for this effect is mixed. We studied whether larger social groups are more subdivided structurally. If so, the social subdivisions that form in larger groups may act as barriers to the spread of infection, weakening the association between group size and infectious disease. To investigate this ‘social bottleneck’ hypothesis, we examined the association between group size and four network structure metrics in 43 vertebrate and invertebrate species. We focused on metrics involving modularity, clustering, distance and centralization. In a meta-analysis of intraspecific variation in social networks, modularity showed positive associations with network size, with a weaker but still positive effect in cross-species analyses. Network distance also showed a positive association with group size when using intraspecific variation. We then used a theoretical model to explore the effects of subgrouping relative to other effects that influence disease spread in socially structured populations. Outbreaks reached higher prevalence when groups were larger, but subgrouping reduced prevalence. Subgrouping also acted as a ‘brake’ on disease spread between groups. We suggest research directions to understand the conditions under which larger groups become more subdivided, and to devise new metrics that account for subgrouping when investigating the links between sociality and infectious disease risk. PMID:25870397

  10. An examination of the relationship between athlete leadership and cohesion using social network analysis.

    PubMed

    Loughead, Todd M; Fransen, Katrien; Van Puyenbroeck, Stef; Hoffmann, Matt D; De Cuyper, Bert; Vanbeselaere, Norbert; Boen, Filip

    2016-11-01

    Two studies investigated the structure of different athlete leadership networks and its relationship to cohesion using social network analysis. In Study 1, we examined the relationship between a general leadership quality network and task and social cohesion as measured by the Group Environment Questionnaire (GEQ). In Study 2, we investigated the leadership networks for four different athlete leadership roles (task, motivational, social and external) and their association with task and social cohesion networks. In Study 1, the results demonstrated that the general leadership quality network was positively related to task and social cohesion. The results from Study 2 indicated positive correlations between the four leadership networks and task and social cohesion networks. Further, the motivational leadership network emerged as the strongest predictor of the task cohesion network, while the social leadership network was the strongest predictor of the social cohesion network. The results complement a growing body of research indicating that athlete leadership has a positive association with cohesion.

  11. Cohesion to the Group and Its Association with Attendance and Early Treatment Response in an Adult Day-Hospital Program for Eating Disorders: A Preliminary Clinical Investigation

    ERIC Educational Resources Information Center

    Crino, Natalie; Djokvucic, Ivana

    2010-01-01

    Treatment outcome studies demonstrate that day-hospital programs are effective in the treatment of eating disorders. Few descriptions are available on the specifics of treatment, particularly the process of therapy. The group therapy modality is thought to provide important therapeutic benefits. The present study aimed to examine the association…

  12. A Life-Cycle Model of Human Social Groups Produces a U-Shaped Distribution in Group Size

    PubMed Central

    Salali, Gul Deniz; Whitehouse, Harvey; Hochberg, Michael E.

    2015-01-01

    One of the central puzzles in the study of sociocultural evolution is how and why transitions from small-scale human groups to large-scale, hierarchically more complex ones occurred. Here we develop a spatially explicit agent-based model as a first step towards understanding the ecological dynamics of small and large-scale human groups. By analogy with the interactions between single-celled and multicellular organisms, we build a theory of group lifecycles as an emergent property of single cell demographic and expansion behaviours. We find that once the transition from small-scale to large-scale groups occurs, a few large-scale groups continue expanding while small-scale groups gradually become scarcer, and large-scale groups become larger in size and fewer in number over time. Demographic and expansion behaviours of groups are largely influenced by the distribution and availability of resources. Our results conform to a pattern of human political change in which religions and nation states come to be represented by a few large units and many smaller ones. Future enhancements of the model should include decision-making rules and probabilities of fragmentation for large-scale societies. We suggest that the synthesis of population ecology and social evolution will generate increasingly plausible models of human group dynamics. PMID:26381745

  13. A Life-Cycle Model of Human Social Groups Produces a U-Shaped Distribution in Group Size.

    PubMed

    Salali, Gul Deniz; Whitehouse, Harvey; Hochberg, Michael E

    2015-01-01

    One of the central puzzles in the study of sociocultural evolution is how and why transitions from small-scale human groups to large-scale, hierarchically more complex ones occurred. Here we develop a spatially explicit agent-based model as a first step towards understanding the ecological dynamics of small and large-scale human groups. By analogy with the interactions between single-celled and multicellular organisms, we build a theory of group lifecycles as an emergent property of single cell demographic and expansion behaviours. We find that once the transition from small-scale to large-scale groups occurs, a few large-scale groups continue expanding while small-scale groups gradually become scarcer, and large-scale groups become larger in size and fewer in number over time. Demographic and expansion behaviours of groups are largely influenced by the distribution and availability of resources. Our results conform to a pattern of human political change in which religions and nation states come to be represented by a few large units and many smaller ones. Future enhancements of the model should include decision-making rules and probabilities of fragmentation for large-scale societies. We suggest that the synthesis of population ecology and social evolution will generate increasingly plausible models of human group dynamics. PMID:26381745

  14. Group Size Regulates Self-Assertive versus Self-Deprecating Responses to Interpersonal Competition.

    ERIC Educational Resources Information Center

    Benenson, Joyce F.; Maiese, Rebecca; Dolenszky, Eva; Dolenszky, Michole; Sinclair, Nancy; Simpson, Anna

    2002-01-01

    This study examined the hypothesis that group size can influence whether 9- to 10-year-olds display self-assertive versus self-deprecating responses to interpersonal competition, especially under stress. Findings indicated that individuals displayed more assertive behaviors during competitive game-playing in groups than in dyads, and more…

  15. Influence of Group Size on Students' Participation in Online Discussion Forums

    ERIC Educational Resources Information Center

    Kim, Jungjoo

    2013-01-01

    This study attempts to examine how students participate and interact in different discussion modules organized with different group size in an online environment. It adopts a case study methodology where full semester online course with two small-group and three class-wide discussion forums was examined. The researcher counted the number of…

  16. Horizontal transfer of fipronil is enhanced with increased group size in Coptotermes formosanus (Isoptera: Rhinotermitidae).

    PubMed

    Wang, Cai; Henderson, Gregg; Chen, Xuan; Gautam, Bal K

    2013-12-01

    Fipronil is a widely used insecticide for termite control. Although transfer of fipronil among termite cohorts has been investigated in previous studies, no study has yet focused on the influence of termite group size (density) on horizontal transfer. In this study, the mortality of donor and recipient Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) was compared among groups of 10, 25, and 50 workers. Most donor termites were dead within 20 h. There was a significantly higher mortality of recipient termites starting at 44 h when in bigger groups. LT50 and LT90 of recipient termites decreased with increase in group size, being significantly shorter in groups of 50 termites compared with groups of 10 termites. Moreover, the variance (within-group difference) of recipient mortality and lethal time estimations was lowest in the groups of 50 termites, indicating a more uniform horizontal transfer of fipronil by termites in bigger groups. Our findings suggest that group size has an influence on fipronil transfer among C. formosanus workers and should be considered as a variable of importance.

  17. Referential Cohesion in Law Cases.

    ERIC Educational Resources Information Center

    Badger, Richard

    A study examined cohesive reference in a newspaper report of a law case, with the intention of helping students read such texts. Occurrences of two classes of items signaling referential cohesion were analyzed: personals (personal pronouns and possessive adjectives) and demonstratives (including the definite article). Factors that might lead a…

  18. Ecological correlates of group-size variation in a resource-defense ungulate, the sedentary guanaco.

    PubMed

    Marino, Andrea; Baldi, Ricardo

    2014-01-01

    For large herbivores, predation-risk, habitat structure and population density are often reported as major determinants of group size variation within and between species. However, whether the underlying causes of these relationships imply an ecological adaptation or are the result of a purely mechanistic process in which fusion and fragmentation events only depend on the rate of group meeting, is still under debate. The aim of this study was to model guanaco family and bachelor group sizes in contrasting ecological settings in order to test hypotheses regarding the adaptive significance of group-size variation. We surveyed guanaco group sizes within three wildlife reserves located in eastern Patagonia where guanacos occupy a mosaic of grasslands and shrublands. Two of these reserves have been free from predators for decades while in the third, pumas often prey on guanacos. All locations have experienced important changes in guanaco abundance throughout the study offering the opportunity to test for density effects. We found that bachelor group size increased with increasing density, as expected by the mechanistic approach, but was independent of habitat structure or predation risk. In contrast, the smaller and territorial family groups were larger in the predator-exposed than in the predator-free locations, and were larger in open grasslands than in shrublands. However, the influence of population density on these social units was very weak. Therefore, family group data supported the adaptive significance of group-size variation but did not support the mechanistic idea. Yet, the magnitude of the effects was small and between-population variation in family group size after controlling for habitat and predation was negligible, suggesting that plasticity of these social units is considerably low. Our results showed that different social units might respond differentially to local ecological conditions, supporting two contrasting hypotheses in a single species, and

  19. Ecological Correlates of Group-Size Variation in a Resource-Defense Ungulate, the Sedentary Guanaco

    PubMed Central

    Marino, Andrea; Baldi, Ricardo

    2014-01-01

    For large herbivores, predation-risk, habitat structure and population density are often reported as major determinants of group size variation within and between species. However, whether the underlying causes of these relationships imply an ecological adaptation or are the result of a purely mechanistic process in which fusion and fragmentation events only depend on the rate of group meeting, is still under debate. The aim of this study was to model guanaco family and bachelor group sizes in contrasting ecological settings in order to test hypotheses regarding the adaptive significance of group-size variation. We surveyed guanaco group sizes within three wildlife reserves located in eastern Patagonia where guanacos occupy a mosaic of grasslands and shrublands. Two of these reserves have been free from predators for decades while in the third, pumas often prey on guanacos. All locations have experienced important changes in guanaco abundance throughout the study offering the opportunity to test for density effects. We found that bachelor group size increased with increasing density, as expected by the mechanistic approach, but was independent of habitat structure or predation risk. In contrast, the smaller and territorial family groups were larger in the predator-exposed than in the predator-free locations, and were larger in open grasslands than in shrublands. However, the influence of population density on these social units was very weak. Therefore, family group data supported the adaptive significance of group-size variation but did not support the mechanistic idea. Yet, the magnitude of the effects was small and between-population variation in family group size after controlling for habitat and predation was negligible, suggesting that plasticity of these social units is considerably low. Our results showed that different social units might respond differentially to local ecological conditions, supporting two contrasting hypotheses in a single species, and

  20. Does group size have an impact on welfare indicators in fattening pigs?

    PubMed

    Meyer-Hamme, S E K; Lambertz, C; Gauly, M

    2016-01-01

    Production systems for fattening pigs have been characterized over the last 2 decades by rising farm sizes coupled with increasing group sizes. These developments resulted in a serious public discussion regarding animal welfare and health in these intensive production systems. Even though large farm and group sizes came under severe criticism, it is still unknown whether these factors indeed negatively affect animal welfare. Therefore, the aim of this study was to assess the effect of group size (30 pigs/pen) on various animal-based measures of the Welfare Quality(®) protocol for growing pigs under conventional fattening conditions. A total of 60 conventional pig fattening farms with different group sizes in Germany were included. Moderate bursitis (35%) was found as the most prevalent indicator of welfare-related problems, while its prevalence increased with age during the fattening period. However, differences between group sizes were not detected (P>0.05). The prevalence of moderately soiled bodies increased from 9.7% at the start to 14.2% at the end of the fattening period, whereas large pens showed a higher prevalence (15.8%) than small pens (10.4%; P<0.05). With increasing group size, the incidence of moderate wounds with 8.5% and 11.3% in small- and medium-sized pens, respectively, was lower (P<0.05) than in large-sized ones (16.3%). Contrary to bursitis and dirtiness, its prevalence decreased during the fattening period. Moderate manure was less often found in pigs fed by a dry feeder than in those fed by a liquid feeding system (P<0.05). The human-animal relationship was improved in large in comparison to small groups. On the contrary, negative social behaviour was found more often in large groups. Exploration of enrichment material decreased with increasing live weight. Given that all animals were tail-docked, tail biting was observed at a very low rate of 1.9%. In conclusion, the results indicate that BW and feeding system are determining factors for

  1. Does group size have an impact on welfare indicators in fattening pigs?

    PubMed

    Meyer-Hamme, S E K; Lambertz, C; Gauly, M

    2016-01-01

    Production systems for fattening pigs have been characterized over the last 2 decades by rising farm sizes coupled with increasing group sizes. These developments resulted in a serious public discussion regarding animal welfare and health in these intensive production systems. Even though large farm and group sizes came under severe criticism, it is still unknown whether these factors indeed negatively affect animal welfare. Therefore, the aim of this study was to assess the effect of group size (30 pigs/pen) on various animal-based measures of the Welfare Quality(®) protocol for growing pigs under conventional fattening conditions. A total of 60 conventional pig fattening farms with different group sizes in Germany were included. Moderate bursitis (35%) was found as the most prevalent indicator of welfare-related problems, while its prevalence increased with age during the fattening period. However, differences between group sizes were not detected (P>0.05). The prevalence of moderately soiled bodies increased from 9.7% at the start to 14.2% at the end of the fattening period, whereas large pens showed a higher prevalence (15.8%) than small pens (10.4%; P<0.05). With increasing group size, the incidence of moderate wounds with 8.5% and 11.3% in small- and medium-sized pens, respectively, was lower (P<0.05) than in large-sized ones (16.3%). Contrary to bursitis and dirtiness, its prevalence decreased during the fattening period. Moderate manure was less often found in pigs fed by a dry feeder than in those fed by a liquid feeding system (P<0.05). The human-animal relationship was improved in large in comparison to small groups. On the contrary, negative social behaviour was found more often in large groups. Exploration of enrichment material decreased with increasing live weight. Given that all animals were tail-docked, tail biting was observed at a very low rate of 1.9%. In conclusion, the results indicate that BW and feeding system are determining factors for

  2. Processing power limits social group size: computational evidence for the cognitive costs of sociality.

    PubMed

    Dávid-Barrett, T; Dunbar, R I M

    2013-08-22

    Sociality is primarily a coordination problem. However, the social (or communication) complexity hypothesis suggests that the kinds of information that can be acquired and processed may limit the size and/or complexity of social groups that a species can maintain. We use an agent-based model to test the hypothesis that the complexity of information processed influences the computational demands involved. We show that successive increases in the kinds of information processed allow organisms to break through the glass ceilings that otherwise limit the size of social groups: larger groups can only be achieved at the cost of more sophisticated kinds of information processing that are disadvantageous when optimal group size is small. These results simultaneously support both the social brain and the social complexity hypotheses.

  3. Processing power limits social group size: computational evidence for the cognitive costs of sociality

    PubMed Central

    Dávid-Barrett, T.; Dunbar, R. I. M.

    2013-01-01

    Sociality is primarily a coordination problem. However, the social (or communication) complexity hypothesis suggests that the kinds of information that can be acquired and processed may limit the size and/or complexity of social groups that a species can maintain. We use an agent-based model to test the hypothesis that the complexity of information processed influences the computational demands involved. We show that successive increases in the kinds of information processed allow organisms to break through the glass ceilings that otherwise limit the size of social groups: larger groups can only be achieved at the cost of more sophisticated kinds of information processing that are disadvantageous when optimal group size is small. These results simultaneously support both the social brain and the social complexity hypotheses. PMID:23804623

  4. Rheotaxis performance increases with group size in a coupled phase model with sensory noise. The effects of noise and group size on rheotaxis

    NASA Astrophysics Data System (ADS)

    Chicoli, A.; Bak-Coleman, J.; Coombs, S.; Paley, D. A.

    2015-12-01

    Many fish exhibit rheotaxis, a behavior in which fish orient themselves relative to flow. Rheotaxis confers many benefits, including energetic cost savings and interception of drifting prey. Despite the fact that most species of fish school during at least some portion of their life, little is known about the importance of rheotactic behavior to schooling fish and, conversely, how the presence of nearby conspecifics affects rheotactic behavior. Understanding how rheotaxis is modified by social factors is thus of ecological importance. Here we present a mathematical model in the form of an all-to-all, coupled-oscillator framework over the non-Euclidean space of fish orientations to model group rheotactic behavior. Individuals in the model measure the orientation of their neighbors and the flow direction relative to their own orientation. These measures are corrupted by sensory noise. We study the effect of sensory noise and group size on internal (i.e., within the school) and external (i.e., with the flow) disagreement in orientation. We find that under noisy environmental conditions, increased group size improves rheotaxis. Results of this study have implications for understanding animal behavior, as well as for potential applications in bio-inspired engineering.

  5. Correlation of automorphism group size and topological properties with program-size complexity evaluations of graphs and complex networks

    NASA Astrophysics Data System (ADS)

    Zenil, Hector; Soler-Toscano, Fernando; Dingle, Kamaludin; Louis, Ard A.

    2014-06-01

    We show that numerical approximations of Kolmogorov complexity (K) of graphs and networks capture some group-theoretic and topological properties of empirical networks, ranging from metabolic to social networks, and of small synthetic networks that we have produced. That K and the size of the group of automorphisms of a graph are correlated opens up interesting connections to problems in computational geometry, and thus connects several measures and concepts from complexity science. We derive these results via two different Kolmogorov complexity approximation methods applied to the adjacency matrices of the graphs and networks. The methods used are the traditional lossless compression approach to Kolmogorov complexity, and a normalised version of a Block Decomposition Method (BDM) based on algorithmic probability theory.

  6. Mating group size and evolutionarily stable pattern of sexuality in barnacles.

    PubMed

    Yamaguchi, Sachi; Yusa, Yoichi; Yamato, Shigeyuki; Urano, Satoru; Takahashi, Satoshi

    2008-07-01

    Barnacles, marine crustaceans, have various patterns of sexuality depending on species including simultaneous hermaphroditism, androdioecy (hermaphrodites and dwarf males), and dioecy (females and dwarf males). We develop a model that predicts the pattern of sexuality in barnacles by two key environmental factors: (i) food availability and (ii) the fraction of larvae that settle on the sea floor. Populations in the model consist of small individuals and large ones. We calculate the optimal resource allocation toward male function, female function and growth for small and large barnacles that maximizes each barnacle's lifetime reproductive success using dynamic programming. The pattern of sexuality is defined by the combination of the optimal resource allocations. In our model, the mating group size is a dependent variable and we found that sexuality pattern changes with the food availability through the mating group size: simultaneous hermaphroditism appears in food-rich environments, where the mating group size is large, protandric simultaneous hermaphroditism appears in intermediate food environments, where the mating group size also takes intermediate value, the other sexuality patterns, androdioecy, dioecy, and sex change are observed in food-poor environments, where the mating group size is small. Our model is the first one where small males can control their growth to large individuals, and hence has ability to explain a rich spectrum of sexual patterns found in barnacles.

  7. The Influence of Social Comparison and Peer Group Size on Risky Decision-Making

    PubMed Central

    Wang, Dawei; Zhu, Liping; Maguire, Phil; Liu, Yixin; Pang, Kaiyuan; Li, Zhenying; Hu, Yixin

    2016-01-01

    This study explores the influence of different social reference points and different comparison group sizes on risky decision-making. Participants were presented with a scenario describing an exam, and presented with the opportunity of making a risky decision in the context of different information provided about the performance of their peers. We found that behavior was influenced, not only by comparison with peers, but also by the size of the comparison group. Specifically, the larger the reference group, the more polarized the behavior it prompted. In situations describing social loss, participants were led to make riskier decisions after comparing themselves against larger groups, while in situations describing social gain, they become more risk averse. These results indicate that decision making is influenced both by social comparison and the number of people making up the social reference group. PMID:27582723

  8. The Influence of Social Comparison and Peer Group Size on Risky Decision-Making.

    PubMed

    Wang, Dawei; Zhu, Liping; Maguire, Phil; Liu, Yixin; Pang, Kaiyuan; Li, Zhenying; Hu, Yixin

    2016-01-01

    This study explores the influence of different social reference points and different comparison group sizes on risky decision-making. Participants were presented with a scenario describing an exam, and presented with the opportunity of making a risky decision in the context of different information provided about the performance of their peers. We found that behavior was influenced, not only by comparison with peers, but also by the size of the comparison group. Specifically, the larger the reference group, the more polarized the behavior it prompted. In situations describing social loss, participants were led to make riskier decisions after comparing themselves against larger groups, while in situations describing social gain, they become more risk averse. These results indicate that decision making is influenced both by social comparison and the number of people making up the social reference group. PMID:27582723

  9. Information-based sample size re-estimation in group sequential design for longitudinal trials.

    PubMed

    Zhou, Jing; Adewale, Adeniyi; Shentu, Yue; Liu, Jiajun; Anderson, Keaven

    2014-09-28

    Group sequential design has become more popular in clinical trials because it allows for trials to stop early for futility or efficacy to save time and resources. However, this approach is less well-known for longitudinal analysis. We have observed repeated cases of studies with longitudinal data where there is an interest in early stopping for a lack of treatment effect or in adapting sample size to correct for inappropriate variance assumptions. We propose an information-based group sequential design as a method to deal with both of these issues. Updating the sample size at each interim analysis makes it possible to maintain the target power while controlling the type I error rate. We will illustrate our strategy with examples and simulations and compare the results with those obtained using fixed design and group sequential design without sample size re-estimation.

  10. Sample Size under Inverse Negative Binomial Group Testing for Accuracy in Parameter Estimation

    PubMed Central

    Montesinos-López, Osval Antonio; Montesinos-López, Abelardo; Crossa, José; Eskridge, Kent

    2012-01-01

    Background The group testing method has been proposed for the detection and estimation of genetically modified plants (adventitious presence of unwanted transgenic plants, AP). For binary response variables (presence or absence), group testing is efficient when the prevalence is low, so that estimation, detection, and sample size methods have been developed under the binomial model. However, when the event is rare (low prevalence <0.1), and testing occurs sequentially, inverse (negative) binomial pooled sampling may be preferred. Methodology/Principal Findings This research proposes three sample size procedures (two computational and one analytic) for estimating prevalence using group testing under inverse (negative) binomial sampling. These methods provide the required number of positive pools (), given a pool size (k), for estimating the proportion of AP plants using the Dorfman model and inverse (negative) binomial sampling. We give real and simulated examples to show how to apply these methods and the proposed sample-size formula. The Monte Carlo method was used to study the coverage and level of assurance achieved by the proposed sample sizes. An R program to create other scenarios is given in Appendix S2. Conclusions The three methods ensure precision in the estimated proportion of AP because they guarantee that the width (W) of the confidence interval (CI) will be equal to, or narrower than, the desired width (), with a probability of . With the Monte Carlo study we found that the computational Wald procedure (method 2) produces the more precise sample size (with coverage and assurance levels very close to nominal values) and that the samples size based on the Clopper-Pearson CI (method 1) is conservative (overestimates the sample size); the analytic Wald sample size method we developed (method 3) sometimes underestimated the optimum number of pools. PMID:22457714

  11. Dolphin underwater bait-balling behaviors in relation to group and prey ball sizes.

    PubMed

    Vaughn-Hirshorn, Robin L; Muzi, Elisa; Richardson, Jessica L; Fox, Gabriella J; Hansen, Lauren N; Salley, Alyce M; Dudzinski, Kathleen M; Würsig, Bernd

    2013-09-01

    We characterized dusky dolphin (Lagenorhynchus obscurus) feeding behaviors recorded on underwater video, and related behaviors to variation in prey ball sizes, dolphin group sizes, and study site (Argentina versus New Zealand, NZ). Herding behaviors most often involved dolphins swimming around the side or under prey balls, but dolphins in Argentina more often swam under prey balls (48% of passes) than did dolphins in NZ (34% of passes). This result may have been due to differences in group sizes between sites, since groups are larger in Argentina. Additionally, in NZ, group size was positively correlated with proportion of passes that occurred under prey balls (p<0.001). Prey-capture attempts most often involved capturing fish from the side of prey balls, but dolphins in Argentina more often swam through prey balls (8% of attempts) than did dolphins in NZ (4% of attempts). This result may have been due to differences in prey ball sizes between sites, since dolphins fed on larger prey balls in Argentina (>74m(2)) than in NZ (maximum 33m(2)). Additionally, in NZ, dolphins were more likely to swim through prey balls to capture fish when they fed on larger prey balls (p=0.025).

  12. Nitrogen limitation as a driver of genome size evolution in a group of karst plants.

    PubMed

    Kang, Ming; Wang, Jing; Huang, Hongwen

    2015-06-25

    Genome size is of fundamental biological importance with significance in predicting structural and functional attributes of organisms. Although abundant evidence has shown that the genome size can be largely explained by differential proliferation and removal of non-coding DNA of the genome, the evolutionary and ecological basis of genome size variation remains poorly understood. Nitrogen (N) and phosphorus (P) are essential elements of DNA and protein building blocks, yet often subject to environmental limitation in natural ecosystems. Using phylogenetic comparative methods, we test this hypothesis by determining whether leaf N and P availability affects genome sizes in 99 species of Primulina (Gesneriaceae), a group of soil specialists adapted to limestone karst environment in south China. We find that genome sizes in Primulina are strongly positively correlated with plant N content, but the correlation with plant P content is not significant when phylogeny history was taken into account. This study shows for the first time that N limitation might have been a plausible driver of genome size variation in a group of plants. We propose that competition for nitrogen nutrient between DNA synthesis and cellular functions is a possible mechanism for genome size evolution in Primulina under N-limitation.

  13. Nitrogen limitation as a driver of genome size evolution in a group of karst plants

    NASA Astrophysics Data System (ADS)

    Kang, Ming; Wang, Jing; Huang, Hongwen

    2015-06-01

    Genome size is of fundamental biological importance with significance in predicting structural and functional attributes of organisms. Although abundant evidence has shown that the genome size can be largely explained by differential proliferation and removal of non-coding DNA of the genome, the evolutionary and ecological basis of genome size variation remains poorly understood. Nitrogen (N) and phosphorus (P) are essential elements of DNA and protein building blocks, yet often subject to environmental limitation in natural ecosystems. Using phylogenetic comparative methods, we test this hypothesis by determining whether leaf N and P availability affects genome sizes in 99 species of Primulina (Gesneriaceae), a group of soil specialists adapted to limestone karst environment in south China. We find that genome sizes in Primulina are strongly positively correlated with plant N content, but the correlation with plant P content is not significant when phylogeny history was taken into account. This study shows for the first time that N limitation might have been a plausible driver of genome size variation in a group of plants. We propose that competition for nitrogen nutrient between DNA synthesis and cellular functions is a possible mechanism for genome size evolution in Primulina under N-limitation.

  14. Predator biomass, prey density, and species composition effects on group size in recruit coral reef fishes

    USGS Publications Warehouse

    DeMartini, Edward E.; Anderson, Todd W.; Friedlander, Alan M.; Beets, James P.

    2011-01-01

    Group incidence and size are described for recruit parrotfishes, wrasses, and damselfishes on Hawaiian reefs over 3 years (2006–2008) at sites spanning the archipelago (20–28°N, 155–177°W). Coral-poor and coral-rich areas were surveyed at sites with both low (Hawaii Island) and high (Midway Atoll) predator densities, facilitating examination of relations among predator and recruit densities, habitat, and group metrics. Predator and recruit densities varied spatially and temporally, with a sixfold range in total recruit densities among years. Group (≥2 recruits) metrics varied with time and tracked predator and recruit densities and the proportion of schooling species. Groups often included heterospecifics whose proportion increased with group size. A non-saturating relationship between group size and recruit density suggests that the anti-predator benefits of aggregation exceeded competitive costs. Grouping behavior may have overarching importance for recruit survival—even at high recruit densities—and merits further study on Hawaiian reefs and elsewhere.

  15. Cohesion influences on erosion and bed load transport

    NASA Astrophysics Data System (ADS)

    Jain, Rajesh K.; Kothyari, Umesh C.

    2009-06-01

    Studies on erosion and transport rates of cohesive sediment mixtures containing gravel are not reported so far in the literature to the best of our knowledge. Results from laboratory experiments on the process of erosion of cohesive sediment mixtures by open-channel flow are presented. The sediment used for experimentation consisted of fine gravel mixed with clay in proportions varying from 10% to 50% and fine gravel, fine sand in equal proportion (by weight) mixed with clay proportions again varying from 10% to 50% by weight. Experimental observations have revealed that the process of detachment of cohesive sediment mixtures containing gravel is significantly different from that of cohesionless sediments. Also, it is different from the detachment process of cohesive sediment mixtures not containing coarser-size material. Experimental data on transport rates of the bed load of the cohesive sediment mixtures are presented. On the basis of dimensional considerations, a computational procedure is proposed to determine the bed load transport rates generated from erosion of the different size fractions of sediment mixtures. Clay percentage and unconfined compressive strength of the sediment bed were the main parameters controlling bed load transport rate of such sediments. In the absence of cohesion, the proposed method reduces to the Patel and Ranga Raju (1996) method for bed load transport rate computation of nonuniform cohesionless sediments.

  16. Effect of group size on performance of growing-finishing pigs.

    PubMed

    Schmolke, S A; Li, Y Z; Gonyou, H W

    2003-04-01

    Six hundred forty growing-finishing pigs (initial BW = 23.2 +/- 4.8 kg) were used in a 12-wk study (final BW = 95.5 +/- 10.2 kg) to quantify the effects of group size (10, 20, 40, and 80 pigs/pen) on performance, tail biting, and use of widely distributed feed resources. One single-space wet/dry feeder was provided for every 10 pigs, and floor allowance was 0.76 m2/pig in all treatment groups. Weight gain and feed intake were measured every 2 wk. At weighing, a tail-biting injury score was given to each pig. Blood samples were collected and analyzed for neutrophil:lymphocyte ratio before regrouping at the beginning of the experiment, 24 to 48 h after regrouping, and on the last day of each trial. The use of feeders by individual pigs was assessed by behavioral observations. Average daily gain for the entire 12-wk trial did not differ among group sizes (861, 873, 854, and 845 g/d for groups of 10, 20, 40, and 80, respectively; P > 0.10). During the first 2 wk, ADG was lower for pigs in groups of 40 (554 g/d) than pigs in groups of 10 (632 g/d; P < 0.05), but not pigs in groups of 20 or 80 (602 and 605 g/d, respectively). Average daily feed intake, feed efficiency, and variability in final BW within a pen also did not differ among group sizes. Tail-biting injury scores increased throughout the study, but did not differ among group sizes. Similar proportions of pigs were removed from the trial for health reasons, primarily due to tail biting, in all treatments. Individual pigs in each group size ate from most, if not all, of the feeders in the pen. There was no evidence of spatial subgrouping within the larger groups. The results suggest that housing growing-finishing pigs in groups of up to 80 pigs is not detrimental to productivity and health if space allowance is adequate and feed resources are evenly distributed. PMID:12723074

  17. Determination of flow-regime boundaries for cohesive particles

    SciTech Connect

    Knowlton, T.M.; Findlay, J.G.

    1992-01-01

    The overall objective of this program is the development of a hydrodynamic model to predict the choking/non-choking flow regime boundary of fine, cohesive (i.e., Geldart Group C) powders. Specific objectives are to: (1) Develop a two-dimensional hydrodynamic model that can be applied to cohesive solids. (2) Generate large-scale solids-flows data that will be used to verify the model.

  18. Effect of Group-Selection Opening Size on Breeding Bird Habitat Use in a Bottomland Forest

    SciTech Connect

    Moorman, C.E.; D.C. Guynn, Jr.

    2001-12-01

    Research on the effects of creating group-selection openings of various sizes on breeding birds habitat use in a bottomland hardwood forest of the Upper Coastal Plain of South Carolina. Creation of 0.5-ha group selection openings in southern bottomland forests should provide breeding habitat for some field-edge species in gaps and habitat for forest-interior species and canopy-dwelling forest-edge species between gaps provided that enough mature forest is made available.

  19. Group Size as a Determinant of Preschool Children's Frequency of Asking Questions.

    ERIC Educational Resources Information Center

    Endsley, Richard C.; Gupta, Sadhana

    This study presents an evaluation of the effect of group size on the frequency with which young children ask questions. Subjects for the study were 32 preschool children (16 boys, 16 girls) ranging in age from 3.1 to 6.2 years. The children were divided into two non-overlapping age groups with mean ages of 3.6 and 5.2 years respectively. Each…

  20. Social structure mediates environmental effects on group size in an obligate cooperative breeder, Suricata suricatta.

    PubMed

    Bateman, A W; Ozgul, A; Nielsen, J F; Coulson, T; Clutton-Brock, T H

    2013-03-01

    Population dynamics in group-living species can be strongly affected both by features of sociality per se and by resultant population structure. To develop a mechanistic understanding of population dynamics in highly social species we need to investigate how processes within groups, processes linking groups, and external drivers act and interact to produce observed patterns. We model social group dynamics in cooperatively breeding meerkats, Suricata suricatta, paying attention to local demographic as well as dispersal processes. We use generalized additive models to describe the influence of group size, population density, and environmental conditions on demographic rates for each sex and stage, and we combine these models into predictive and individual-based simulation models of group dynamics. Short-term predictions of expected group size and simulated group trajectories over the longer term agree well with observations. Group dynamics are characterized by slow increases during the breeding season and relatively sharp declines during the pre-breeding season, particularly after dry years. We examine the demographic mechanisms responsible for environmental dependence. While individuals appear more prone to emigrate after dry years, seasons of low rainfall also cause reductions in reproductive output that produce adult-biased age distributions in the following dispersal season. Adult subordinates are much more likely to disperse or be evicted than immature individuals, and demographic structure thus contributes to crashes in group size. Our results demonstrate the role of social structure in characterizing a population's response to environmental variation. We discuss the implications of our findings for the population dynamics of cooperative breeders and population dynamics generally.

  1. Social structure mediates environmental effects on group size in an obligate cooperative breeder, Suricata suricatta.

    PubMed

    Bateman, A W; Ozgul, A; Nielsen, J F; Coulson, T; Clutton-Brock, T H

    2013-03-01

    Population dynamics in group-living species can be strongly affected both by features of sociality per se and by resultant population structure. To develop a mechanistic understanding of population dynamics in highly social species we need to investigate how processes within groups, processes linking groups, and external drivers act and interact to produce observed patterns. We model social group dynamics in cooperatively breeding meerkats, Suricata suricatta, paying attention to local demographic as well as dispersal processes. We use generalized additive models to describe the influence of group size, population density, and environmental conditions on demographic rates for each sex and stage, and we combine these models into predictive and individual-based simulation models of group dynamics. Short-term predictions of expected group size and simulated group trajectories over the longer term agree well with observations. Group dynamics are characterized by slow increases during the breeding season and relatively sharp declines during the pre-breeding season, particularly after dry years. We examine the demographic mechanisms responsible for environmental dependence. While individuals appear more prone to emigrate after dry years, seasons of low rainfall also cause reductions in reproductive output that produce adult-biased age distributions in the following dispersal season. Adult subordinates are much more likely to disperse or be evicted than immature individuals, and demographic structure thus contributes to crashes in group size. Our results demonstrate the role of social structure in characterizing a population's response to environmental variation. We discuss the implications of our findings for the population dynamics of cooperative breeders and population dynamics generally. PMID:23687885

  2. Effect of group size on behavior, health, production, and welfare of veal calves.

    PubMed

    Abdelfattah, E M; Schutz, M M; Lay, D C; Marchant-Forde, J N; Eicher, S D

    2013-11-01

    The objective of this study was to investigate the effect of group size on behavior, growth, health, and welfare of veal calves. Holstein-Friesian bull calves (n=168; 44±3 d of age) were assigned randomly to 1 of 3 treatments of group housing with 2, 4, or 8 calves per pen. The pens used for housing were 3 by 1.20 m (2 calves per pen), 3 by 2.40 m (4 calves per pen), and 3 by 4.80 m (8 calves per pen), supplying a total pen space allowance of 1.82 m2/calf, regardless of pen size. Behavior was recorded from video data throughout the day from 0700 to 1900 h during a single day each month for 5 mo using scan sampling every 5 min within 30-min observation sessions. On d 0, 1, 5, 14, 42, and 70 after grouping, continuous focal sampling around feeding time (30-min intervals before, during, and after feeding) focused on oral and aggressive behaviors. Calves housed in large groups (4 or 8 calves per pen) showed more (P≤0.001) conspecific contact, walking, and standing and less (P<0.001) manipulation of objects, self-licking, and lying when compared to calves housed in small groups (2 calves per pen). Group size had no effect on play behavior (P=0.11) throughout the experiment. During feeding times group size had no (P≥0.07) effect on any behavioral patterns except for duration of conspecific contact (P<0.01). Aggression at feeding time was not (P>0.23) affected by treatment. Group size treatments were similar for hip height change (P=0.41) and heart girth change (P=0.18) over the duration of the experiment; however, both hip height and heart girth increased (P=0.001) with calf age. During mo 1, calves in groups of 8 or 4 coughed more than calves in groups of 2 whereas calves in groups of 8 coughed more than calves in groups of 4 or 2 in mo 2 (treatment×month, P=0.03). Furthermore, during mo 4, calves in groups of 8 had less nasal discharge than calves in groups of 2 or 4 (treatment×month, P=0.02). Ocular discharge, ears, and fecal scores did not differ (P≥0

  3. Effect of Habitat Size, Quality, and Isolation on Functional Groups of Beetles in Hollow Oaks

    PubMed Central

    Pilskog, Hanne Eik; Birkemoe, Tone; Framstad, Erik; Sverdrup-Thygeson, Anne

    2016-01-01

    One of the largest threats to biodiversity is land use change and habitat loss. Hollow oaks (Quercus spp. L.) are well-defined patches that are hotspots for biodiversity and red-listed species, but they are often rare and fragmented in the landscape. We investigated the effect of patch size, habitat quality, and isolation on functional groups and red-listed saproxylic beetles in hollow oaks (n = 40) in Norway. The groups were defined by host tree association, trophic grouping, and red-listed status. Habitat quality, represented by tree form was most important in explaining species richness for most groups. Patch size, represented by circumference and amount of dead branches, was most important in explaining abundance. Isolation, that is single oaks compared with oaks in groups, had a negative effect on the abundance of beetles feeding both on wood and fungi (xylomycethopagous), as well as on species associated with broadleaved trees (oak semi-specialists), but did not affect species richness. This indicates that at this scale and in this landscape, isolated oaks are as species rich and valuable for conservation as other oaks, although some functional groups may be more vulnerable to isolation than others. The red-listed species only responded to patch size, indicating that oaks with large circumference and many dead branches are especially important for red-listed species and for conservation. PMID:26945089

  4. Effect of Habitat Size, Quality, and Isolation on Functional Groups of Beetles in Hollow Oaks.

    PubMed

    Pilskog, Hanne Eik; Birkemoe, Tone; Framstad, Erik; Sverdrup-Thygeson, Anne

    2016-01-01

    One of the largest threats to biodiversity is land use change and habitat loss. Hollow oaks (Quercus spp. L.) are well-defined patches that are hotspots for biodiversity and red-listed species, but they are often rare and fragmented in the landscape. We investigated the effect of patch size, habitat quality, and isolation on functional groups and red-listed saproxylic beetles in hollow oaks (n = 40) in Norway. The groups were defined by host tree association, trophic grouping, and red-listed status. Habitat quality, represented by tree form was most important in explaining species richness for most groups. Patch size, represented by circumference and amount of dead branches, was most important in explaining abundance. Isolation, that is single oaks compared with oaks in groups, had a negative effect on the abundance of beetles feeding both on wood and fungi (xylomycethopagous), as well as on species associated with broadleaved trees (oak semi-specialists), but did not affect species richness. This indicates that at this scale and in this landscape, isolated oaks are as species rich and valuable for conservation as other oaks, although some functional groups may be more vulnerable to isolation than others. The red-listed species only responded to patch size, indicating that oaks with large circumference and many dead branches are especially important for red-listed species and for conservation. PMID:26945089

  5. Tooth Size in Patients with Mild, Moderate and Severe Hypodontia and a Control Group

    PubMed Central

    Khalaf, Khaled

    2016-01-01

    Objectives: To compare tooth size between subjects with mild, moderate and severe hypodontia and a control group. Material and Methods: The study comprised 120 patients with hypodontia divided into three groups of 40 mild (≤2 teeth congenitally missing), 40 moderate (3-5 teeth congenitally missing) and 40 severe (≥6 teeth congenitally missing) hypodontia; and 40 age and sex matched controls. Tooth size was recorded by measuring the mesiodistal and buccolingual dimensions of all fully erupted teeth on study models using digital callipers and compared between all hypodontia and control groups using Two-way ANOVA and Post Hoc Tests of subgroup comparison. Results: Two-way ANOVA revealed patients with hypodontia had significantly smaller mesiodistal and buccolingual tooth dimensions compared with controls (p<0.05). Furthermore patients with more severe hypodontia demonstrated significantly smaller tooth dimensions than those in the mild and moderate hypodontia subgroups (p<0.05). The most affected tooth in terms of tooth size reduction was the maxillary lateral incisor and the least affected tooth was the mandibular first molar. Conclusion: Patients with hypodontia have smaller tooth dimensions than control. Tooth size appears to be affected by the degree of hypodontia, with severe hypodontia having a greater effect on tooth size reduction. The findings of this study may contribute to understanding the aetiology of hypodontia and aid the multidisciplinary management of this complex condition. PMID:27583048

  6. Spatial-size scaling of pedestrian groups under growing density conditions

    NASA Astrophysics Data System (ADS)

    Zanlungo, Francesco; Brščić, Dražen; Kanda, Takayuki

    2015-06-01

    We study the dependence on crowd density of the spatial size, configuration, and velocity of pedestrian social groups. We find that, in the investigated density range, the extension of pedestrian groups in the direction orthogonal to that of motion decreases linearly with the pedestrian density around them, both for two- and three-person groups. Furthermore, we observe that at all densities, three-person groups walk slower than two-person groups, and the latter are slower than individual pedestrians, the differences in velocities being weakly affected by density. Finally, we observe that three-person groups walk in a V-shaped formation regardless of density, with a distance between the pedestrians in the front and back again almost independent of density, although the configuration appears to be less stable at higher densities. These findings may facilitate the development of more realistic crowd dynamics models and simulators.

  7. INFLUENCE OF SPAWNING GROUP SIZE AND SPACE ON REPRODUCTION BY SHEEPSHEAD MINNOWS, CYPRINODON VARIEGATUS

    EPA Science Inventory

    Cripe, G.M., R.L. Hemmer and L.R. Goodman. In press. Influence of Spawning Group Size and Space on Reproduction Variability of Sheepshead Minnows, Cyprinodon variegatus (Abstract). To be presented at the SETAC Fourth World Congress, 14-18 November 2004, Portland, OR. 1 p. (ERL,GB...

  8. Group Size and Organisational Conditions for Children's Learning in Preschool: A Teacher Perspective

    ERIC Educational Resources Information Center

    Sheridan, Sonja; Williams, Pia; Pramling Samuelsson, Ingrid

    2014-01-01

    Background: There is a limited amount of research about group size in preschool, and how it impacts on teachers' working conditions and their ability to support children's learning and knowledge development in line with curriculum intentions. Purpose: From a perspective on quality, this article examines the organisational conditions for…

  9. The Relationships among Group Size, Participation, and Performance of Programming Language Learning Supported with Online Forums

    ERIC Educational Resources Information Center

    Shaw, Ruey-Shiang

    2013-01-01

    This study examined the relationships among group size, participation, and learning performance factors when learning a programming language in a computer-supported collaborative learning (CSCL) context. An online forum was used as the CSCL environment for learning the Microsoft ASP.NET programming language. The collaborative-learning experiment…

  10. Cohesive Zone Model User Element

    2007-04-17

    Cohesive Zone Model User Element (CZM UEL) is an implementation of a Cohesive Zone Model as an element for use in finite element simulations. CZM UEL computes a nodal force vector and stiffness matrix from a vector of nodal displacements. It is designed for structural analysts using finite element software to predict crack initiation, crack propagation, and the effect of a crack on the rest of a structure.

  11. Group Size Effect on Cooperation in One-Shot Social Dilemmas II: Curvilinear Effect

    PubMed Central

    Capraro, Valerio; Barcelo, Hélène

    2015-01-01

    In a world in which many pressing global issues require large scale cooperation, understanding the group size effect on cooperative behavior is a topic of central importance. Yet, the nature of this effect remains largely unknown, with lab experiments insisting that it is either positive or negative or null, and field experiments suggesting that it is instead curvilinear. Here we shed light on this apparent contradiction by considering a novel class of public goods games inspired to the realistic scenario in which the natural output limits of the public good imply that the benefit of cooperation increases fast for early contributions and then decelerates. We report on a large lab experiment providing evidence that, in this case, group size has a curvilinear effect on cooperation, according to which intermediate-size groups cooperate more than smaller groups and more than larger groups. In doing so, our findings help fill the gap between lab experiments and field experiments and suggest concrete ways to promote large scale cooperation among people. PMID:26182247

  12. What about N? A methodological study of sample-size reporting in focus group studies

    PubMed Central

    2011-01-01

    Background Focus group studies are increasingly published in health related journals, but we know little about how researchers use this method, particularly how they determine the number of focus groups to conduct. The methodological literature commonly advises researchers to follow principles of data saturation, although practical advise on how to do this is lacking. Our objectives were firstly, to describe the current status of sample size in focus group studies reported in health journals. Secondly, to assess whether and how researchers explain the number of focus groups they carry out. Methods We searched PubMed for studies that had used focus groups and that had been published in open access journals during 2008, and extracted data on the number of focus groups and on any explanation authors gave for this number. We also did a qualitative assessment of the papers with regard to how number of groups was explained and discussed. Results We identified 220 papers published in 117 journals. In these papers insufficient reporting of sample sizes was common. The number of focus groups conducted varied greatly (mean 8.4, median 5, range 1 to 96). Thirty seven (17%) studies attempted to explain the number of groups. Six studies referred to rules of thumb in the literature, three stated that they were unable to organize more groups for practical reasons, while 28 studies stated that they had reached a point of saturation. Among those stating that they had reached a point of saturation, several appeared not to have followed principles from grounded theory where data collection and analysis is an iterative process until saturation is reached. Studies with high numbers of focus groups did not offer explanations for number of groups. Too much data as a study weakness was not an issue discussed in any of the reviewed papers. Conclusions Based on these findings we suggest that journals adopt more stringent requirements for focus group method reporting. The often poor and

  13. Aposematism and gregariousness: the combined effect of group size and coloration on signal repellence

    PubMed Central

    Gamberale, G.; Tullberg, B. S.

    1998-01-01

    Many aposematic species have evolved an aggregated lifestyle, and one possible advantage of grouping in warningly coloured prey is that it makes the aposematic signal more effective by generating a greater aversion in predators. Here we investigate the effect of prey group size on predator behaviour, both when prey are aposematic and when they are not aposematic, to separate the effects of warning coloration and prey novelty. Naive domestic chicks (Gallus gallus domesticus) were presented with either solitary or groups of 3, 9 or 27 live larvae of the aposematic bug Tropidothorax leucopterus. Other naive chicks were presented with larvae of the non-aposematic bug Graptostethus servus either solitary or in groups of 27. Attack probability decreased with increasing group size of aposematic prey, both when birds were naive and when they had prior experience, whereas prey gregariousness did not affect the initial attack probability on the G. servus larvae. In a separate experiment, groups of mealworms were shown to be even more attractive than solitary mealworms to naive chicks. We conclude that the aversiveness of prey grouping in this study can be explained as increased signal repellence of specific prey coloration, in this case a classical warning coloration. These experiments thus support the idea of gregariousness increasing the signalling effect of warning coloration.

  14. The effect of boldness on decision-making in barnacle geese is group-size-dependent.

    PubMed

    Kurvers, Ralf H J M; Adamczyk, Vena M A P; van Wieren, Sipke E; Prins, Herbert H T

    2011-07-01

    In group-living species, decisions made by individuals may result in collective behaviours. A central question in understanding collective behaviours is how individual variation in phenotype affects collective behaviours. However, how the personality of individuals affects collective decisions in groups remains poorly understood. Here, we investigated the role of boldness on the decision-making process in different-sized groups of barnacle geese. Naive barnacle geese, differing in boldness score, were introduced in a labyrinth in groups with either one or three informed demonstrators. The demonstrators possessed information about the route through the labyrinth. In pairs, the probability of choosing a route prior to the informed demonstrator increased with increasing boldness score: bolder individuals decided more often for themselves where to go compared with shyer individuals, whereas shyer individuals waited more often for the demonstrators to decide and followed this information. In groups of four individuals, however, there was no effect of boldness on decision-making, suggesting that individual differences were less important with increasing group size. Our experimental results show that personality is important in collective decisions in pairs of barnacle geese, and suggest that bolder individuals have a greater influence over the outcome of decisions in groups.

  15. Social group size affects Mycobacterium bovis infection in European badgers (Meles meles).

    PubMed

    Woodroffe, Rosie; Donnelly, Christl A; Wei, Gao; Cox, D R; Bourne, F John; Burke, Terry; Butlin, Roger K; Cheeseman, C L; Gettinby, George; Gilks, Peter; Hedges, Simon; Jenkins, Helen E; Johnston, W Thomas; McInerney, John P; Morrison, W Ivan; Pope, Lisa C

    2009-07-01

    1. In most social animals, the prevalence of directly transmitted pathogens increases in larger groups and at higher population densities. Such patterns are predicted by models of Mycobacterium bovis infection in European badgers (Meles meles). 2. We investigated the relationship between badger abundance and M. bovis prevalence, using data on 2696 adult badgers in 10 populations sampled at the start of the Randomized Badger Culling Trial. 3. M. bovis prevalence was consistently higher at low badger densities and in small social groups. M. bovis prevalence was also higher among badgers whose genetic profiles suggested that they had immigrated into their assigned social groups. 4. The association between high M. bovis prevalence and small badger group size appeared not to have been caused by previous small-scale culling in study areas, which had been suspended, on average, 5 years before the start of the current study. 5. The observed pattern of prevalence might occur through badgers in smaller groups interacting more frequently with members of neighbouring groups; detailed behavioural data are needed to test this hypothesis. Likewise, longitudinal data are needed to determine whether the size of infected groups might be suppressed by disease-related mortality. 6. Although M. bovis prevalence was lower at high population densities, the absolute number of infected badgers was higher. However, this does not necessarily mean that the risk of M. bovis transmission to cattle is highest at high badger densities, since transmission risk depends on badger behaviour as well as on badger density. PMID:19486382

  16. Social group size affects Mycobacterium bovis infection in European badgers (Meles meles).

    PubMed

    Woodroffe, Rosie; Donnelly, Christl A; Wei, Gao; Cox, D R; Bourne, F John; Burke, Terry; Butlin, Roger K; Cheeseman, C L; Gettinby, George; Gilks, Peter; Hedges, Simon; Jenkins, Helen E; Johnston, W Thomas; McInerney, John P; Morrison, W Ivan; Pope, Lisa C

    2009-07-01

    1. In most social animals, the prevalence of directly transmitted pathogens increases in larger groups and at higher population densities. Such patterns are predicted by models of Mycobacterium bovis infection in European badgers (Meles meles). 2. We investigated the relationship between badger abundance and M. bovis prevalence, using data on 2696 adult badgers in 10 populations sampled at the start of the Randomized Badger Culling Trial. 3. M. bovis prevalence was consistently higher at low badger densities and in small social groups. M. bovis prevalence was also higher among badgers whose genetic profiles suggested that they had immigrated into their assigned social groups. 4. The association between high M. bovis prevalence and small badger group size appeared not to have been caused by previous small-scale culling in study areas, which had been suspended, on average, 5 years before the start of the current study. 5. The observed pattern of prevalence might occur through badgers in smaller groups interacting more frequently with members of neighbouring groups; detailed behavioural data are needed to test this hypothesis. Likewise, longitudinal data are needed to determine whether the size of infected groups might be suppressed by disease-related mortality. 6. Although M. bovis prevalence was lower at high population densities, the absolute number of infected badgers was higher. However, this does not necessarily mean that the risk of M. bovis transmission to cattle is highest at high badger densities, since transmission risk depends on badger behaviour as well as on badger density.

  17. Group size effect on vigilance: evidence from Tibetan gazelle in Upper Buha River, Qinghai-Tibet Plateau.

    PubMed

    Li, Zhongqiu; Jiang, Zhigang

    2008-05-01

    Tibetan gazelle Procapra picticaudata is a threatened and endemic species to the Qinghai-Tibet Plateau. With the method of group scan sampling, we observed the behaviours of males and females of the gazelle in the two summers of 2005 and 2006, in order to test the group size effect on group vigilance. We found that male gazelles were significantly more vigilant than the females at both group scan level (percentage of individuals scanning during a session) and group scan frequency (percentage of intervals with at least one individual scanning). We also found a negative correlation between group scan level and group size and a positive correlation between group scan frequency and group size, showing the group size effect on vigilance was testified in Tibetan gazelle. The predation factor might be the main driving force for the group size effect. PMID:18215472

  18. Effects of group size and floor space allowance on grouped sows: aggression, stress, skin injuries, and reproductive performance.

    PubMed

    Hemsworth, P H; Rice, M; Nash, J; Giri, K; Butler, K L; Tilbrook, A J; Morrison, R S

    2013-10-01

    A total of 3,120 sows, in 4 time replicates, were used to determine the effects of group size and floor space on sow welfare using behavioral, physiological, health, and fitness variables. Within 1 to 7 d postinsemination, sows were assigned randomly to treatments of a 3 by 6 factorial arrangement, with 3 group sizes (10, 30, or 80 sows/pen) and 6 floor space allowances (1.4, 1.8, 2.0, 2.2, 2.4, or 3.0 m(2)/sow). Sows were housed on partially slatted concrete floors, and overhead feeders delivered 4 times/day to provide a total of 2.5 kg of feed/sow. As pen space increased from 1.4 to 3.0 m(2)/sow, aggression at feeding decreased from about 9 to 7 bouts/sow (linear, P = 0.029) and plasma cortisol concentrations decreased from about 28 to 21 ng/mL (linear, P = 0.0089) at 2 d. Although the results are in accord with a linear decline from 1.4 to 3 m(2)/sow, the results are also in accord with a decline in these measurements from 1.4 to 1.8 m(2)/sow and no further decline greater than 1.8 m(2)/sow. Farrowing rate (percentage of inseminated sows that farrowed) also increased from about 60 to 75% as space increased from 1.4 to 3.0 m(2)/sow (linear, P = 0.012). Group size was related to skin injuries on d 9 (P = 0.0017), 23 (P = 0.0046), and 51 (P = 0.0006), with groups of 10 consistently having the lowest number of total injuries over this period. Based on the aggression and cortisol results, it is credible to judge that, within the range of floor space allowances studied, sow welfare improves with increased space. However, from a sow welfare perspective, the experiment had insufficient precision to determine what is an adequate space allowance for sows. Thus, although the results definitely support a space allowance of 1.4 m(2)/sow being too small, it is not possible to give guidance on an actual space allowance at mixing that is adequate. PMID:23893983

  19. Separating the impact of group size, density, and enclosure size on broiler movement and space use at a decreasing perimeter to area ratio.

    PubMed

    Leone, Erin Hoerl; Christman, Mary C; Douglass, Larry; Estevez, Inma

    2010-01-01

    The goal of this study was to determine the impact of enclosure size on space use and movement patterns of domestic fowl (Gallus gallus domesticus), independent of group size and density. Research designed to estimate the effects of group size, density, or enclosure size involves inherent confounding between factors, clouding their individual effects. This experimental design enabled us to conduct multiple contrasts in order to tease apart the specific impacts. Treatments consisted of five combinations of three square enclosures: small (S; 1.5m(2)), medium (M; 3.0m(2)), and large (L; 4.5m(2)), and three group sizes of 10, 20, and 30 birds. We made comparisons while holding group size constant, holding density constant, and the third while maintaining a constant enclosure size. Nearest neighbor distances increased with enclosure size but appeared to be constrained by density. Net displacement and minimum convex polygons increased with enclosure size regardless of group size or density. We found no evidence of social restriction on space use. Results indicate that broilers adapted their use of space and movement patterns to the size of the enclosures, spreading out and utilizing a greater amount of space when it was available.

  20. Group selection on population size affects life-history patterns in the entomopathogenic nematode Steinernema carpocapsae.

    PubMed

    Bashey, Farrah; Lively, Curtis M

    2009-05-01

    Selection is recognized to operate on multiple levels. In disease organisms, selection among hosts is thought to provide an important counterbalance to selection for faster growth within hosts. We performed three experiments, each selecting for a divergence in group size in the entomopathogenic nematode, Steinernema carpocapsae. These nematodes infect and kill insect larvae, reproduce inside the host carcass, and emerge as infective juveniles. We imposed selection on group size by selecting among hosts for either high or low numbers of emerging nematodes. Our goal was to determine whether this trait could respond to selection at the group level, and if so, to examine what other traits would evolve as correlated responses. One of the three experiments showed a significant response to group selection. In that experiment, the high-selected treatment consistently produced more emerging nematodes per host than the low-selected treatment. In addition, nematodes were larger and they emerged later from hosts in the low-selected lines. Despite small effective population sizes, the effects of inbreeding were small in this experiment. Thus, selection among hosts can be effective, leading to both a direct evolutionary response at the population level, as well as to correlated responses in populational and individual traits.

  1. Influence of Group Size on the Success of Wolves Hunting Bison

    PubMed Central

    MacNulty, Daniel R.; Tallian, Aimee; Stahler, Daniel R.; Smith, Douglas W.

    2014-01-01

    An intriguing aspect of social foraging behaviour is that large groups are often no better at capturing prey than are small groups, a pattern that has been attributed to diminished cooperation (i.e., free riding) in large groups. Although this suggests the formation of large groups is unrelated to prey capture, little is known about cooperation in large groups that hunt hard-to-catch prey. Here, we used direct observations of Yellowstone wolves (Canis lupus) hunting their most formidable prey, bison (Bison bison), to test the hypothesis that large groups are more cooperative when hunting difficult prey. We quantified the relationship between capture success and wolf group size, and compared it to previously reported results for Yellowstone wolves hunting elk (Cervus elaphus), a prey that was, on average, 3 times easier to capture than bison. Whereas improvement in elk capture success levelled off at 2–6 wolves, bison capture success levelled off at 9–13 wolves with evidence that it continued to increase beyond 13 wolves. These results are consistent with the hypothesis that hunters in large groups are more cooperative when hunting more formidable prey. Improved ability to capture formidable prey could therefore promote the formation and maintenance of large predator groups, particularly among predators that specialize on such prey. PMID:25389760

  2. Influence of group size on the success of wolves hunting bison.

    PubMed

    MacNulty, Daniel R; Tallian, Aimee; Stahler, Daniel R; Smith, Douglas W

    2014-01-01

    An intriguing aspect of social foraging behaviour is that large groups are often no better at capturing prey than are small groups, a pattern that has been attributed to diminished cooperation (i.e., free riding) in large groups. Although this suggests the formation of large groups is unrelated to prey capture, little is known about cooperation in large groups that hunt hard-to-catch prey. Here, we used direct observations of Yellowstone wolves (Canis lupus) hunting their most formidable prey, bison (Bison bison), to test the hypothesis that large groups are more cooperative when hunting difficult prey. We quantified the relationship between capture success and wolf group size, and compared it to previously reported results for Yellowstone wolves hunting elk (Cervus elaphus), a prey that was, on average, 3 times easier to capture than bison. Whereas improvement in elk capture success levelled off at 2-6 wolves, bison capture success levelled off at 9-13 wolves with evidence that it continued to increase beyond 13 wolves. These results are consistent with the hypothesis that hunters in large groups are more cooperative when hunting more formidable prey. Improved ability to capture formidable prey could therefore promote the formation and maintenance of large predator groups, particularly among predators that specialize on such prey. PMID:25389760

  3. Influence of group size on the success of wolves hunting bison.

    PubMed

    MacNulty, Daniel R; Tallian, Aimee; Stahler, Daniel R; Smith, Douglas W

    2014-01-01

    An intriguing aspect of social foraging behaviour is that large groups are often no better at capturing prey than are small groups, a pattern that has been attributed to diminished cooperation (i.e., free riding) in large groups. Although this suggests the formation of large groups is unrelated to prey capture, little is known about cooperation in large groups that hunt hard-to-catch prey. Here, we used direct observations of Yellowstone wolves (Canis lupus) hunting their most formidable prey, bison (Bison bison), to test the hypothesis that large groups are more cooperative when hunting difficult prey. We quantified the relationship between capture success and wolf group size, and compared it to previously reported results for Yellowstone wolves hunting elk (Cervus elaphus), a prey that was, on average, 3 times easier to capture than bison. Whereas improvement in elk capture success levelled off at 2-6 wolves, bison capture success levelled off at 9-13 wolves with evidence that it continued to increase beyond 13 wolves. These results are consistent with the hypothesis that hunters in large groups are more cooperative when hunting more formidable prey. Improved ability to capture formidable prey could therefore promote the formation and maintenance of large predator groups, particularly among predators that specialize on such prey.

  4. Gender Similarities and Differences in Preadolescent Peer Groups

    ERIC Educational Resources Information Center

    Xie, Hongling; Shi, Bing

    2009-01-01

    The Social Cognitive Mapping procedure was used to identify peer social groups in 26 fifth-grade classrooms from six elementary schools in a northeastern urban school district. Four group structural features were examined: size, the number of subcliques, cohesion, and salience hierarchy. Ethnic diversity index was calculated for each group. An…

  5. Dynamic-persistence of cooperation in public good games when group size is dynamic.

    PubMed

    Janssen, Marco A; Goldstone, Robert L

    2006-11-01

    The evolution of cooperation is possible with a simple model of a population of agents that can move between groups. The agents play public good games within their group. The relative fitness of individuals within the whole population affects their number of offspring. Groups of cooperators evolve but over time are invaded by defectors which eventually results in the group's extinction. However, for small levels of migration and mutation, high levels of cooperation evolve at the population level. Thus, evolution of cooperation based on individual fitness without kin selection, indirect or direct reciprocity is possible. We provide an analysis of the parameters that affect cooperation, and describe the dynamics and distribution of population sizes over time. PMID:16872637

  6. Fewer but better: Proportionate size of the group affects evaluation of transgressive leaders.

    PubMed

    Travaglino, Giovanni A; Abrams, Dominic; Randsley de Moura, Georgina; Yetkili, Orkun

    2016-06-01

    A group may be badly affected if its leader transgresses important rules. Nonetheless, an emerging body of evidence suggests that in intergroup contexts, group members apply a double standard when judging ingroup leaders - They respond less punitively to transgressions by their leader than by non-leaders. In this article, two experiments investigated how proportionate ingroup size affects reactions to transgressive ingroup leaders. We demonstrate that ingroup leaders from larger, but not smaller, groups benefit from the double standard. The experiments testing the effects of two different types of transgressions (nepotistic favouritism and corruption, respectively) show that transgressive leaders from larger groups are evaluated more positively than both comparable non-leaders and leaders from smaller groups. In contrast, transgressive leaders from smaller groups are evaluated similarly to comparable transgressive non-leaders. Experiment 2 investigated a potential explanation for this phenomenon. Faced with a transgressive leader, members of a smaller group report greater embarrassment than do members of larger groups in relation to the leaders' actions. Implications of these findings and directions for future research are discussed.

  7. The Effect of Group Size on the Interplay between Dominance and Reproduction in Bombus terrestris

    PubMed Central

    Amsalem, Etya; Hefetz, Abraham

    2011-01-01

    Social insects provide good model systems for testing trade-offs in decision-making because of their marked reproductive skew and the dilemma workers face when to reproduce. Attaining reproductive skew requires energy investment in aggression or fertility signaling, creating a trade-off between reproduction and dominance. This may be density-dependent because the cost of achieving dominance may be higher in larger groups. We investigated the effect of group-size in B. terrestris queenless workers on two major reproduction-dominance correlates: between-worker aggression, and pheromone production, aiming at mimicking decision-making during the transition of worker behavior from cooperation and sterility to aggressive reproductive competition in whole colonies. Despite the competition, reproductive division of labor in colonies can be maintained even during this phase through the production of a sterility signal by sterile workers that has an appeasement effect on dominant nestmates. Worker-worker aggression, ovary activation, and production of sterility-appeasement signals may therefore constitute components of a trade-off affecting worker reproduction decisions. By constructing queenless groups of different size and measuring how this affected the parameters above, we found that in all groups aggression was not evenly distributed with the α-worker performing most of the aggressive acts. Moreover, aggression by the α-worker increased proportionally with group-size. However, while in small groups the α-worker monopolized reproduction, in larger groups several workers shared reproduction, creating two worker groups: reproductives and helpers. It appears that despite the increase of aggression, this was evidently not sufficient for the α-worker to monopolize reproduction. If we compare the α-worker to the queen in full-sized colonies it can be hypothesized that worker reproduction in B. terrestris colonies starts due to a gradual increase in the worker population

  8. A cohesive granular material with tunable elasticity

    PubMed Central

    Hemmerle, Arnaud; Schröter, Matthias; Goehring, Lucas

    2016-01-01

    By mixing glass beads with a curable polymer we create a well-defined cohesive granular medium, held together by solidified, and hence elastic, capillary bridges. This material has a geometry similar to a wet packing of beads, but with an additional control over the elasticity of the bonds holding the particles together. We show that its mechanical response can be varied over several orders of magnitude by adjusting the size and stiffness of the bridges, and the size of the particles. We also investigate its mechanism of failure under unconfined uniaxial compression in combination with in situ x-ray microtomography. We show that a broad linear-elastic regime ends at a limiting strain of about 8%, whatever the stiffness of the agglomerate, which corresponds to the beginning of shear failure. The possibility to finely tune the stiffness, size and shape of this simple material makes it an ideal model system for investigations on, for example, fracturing of porous rocks, seismology, or root growth in cohesive porous media. PMID:27774988

  9. Effects of Reproductive Status, Social Rank, Sex and Group Size on Vigilance Patterns in Przewalski's Gazelle

    PubMed Central

    Li, Chunlin; Jiang, Zhigang; Li, Linlin; Li, Zhongqiu; Fang, Hongxia; Li, Chunwang; Beauchamp, Guy

    2012-01-01

    Background Quantifying vigilance and exploring the underlying mechanisms has been the subject of numerous studies. Less attention has focused on the complex interplay between contributing factors such as reproductive status, social rank, sex and group size. Reproductive status and social rank are of particular interest due to their association with mating behavior. Mating activities in rutting season may interfere with typical patterns of vigilance and possibly interact with social rank. In addition, balancing the tradeoff between vigilance and life maintenance may represent a challenge for gregarious ungulate species rutting under harsh winter conditions. We studied vigilance patterns in the endangered Przewalski's gazelle (Procapra przewalskii) during both the rutting and non-rutting seasons to examine these issues. Methodology/Principal Findings Field observations were carried out with focal sampling during rutting and non-rutting season in 2008–2009. Results indicated a complex interplay between reproductive status, social rank, sex and group size in determining vigilance in this species. Vigilance decreased with group size in female but not in male gazelles. Males scanned more frequently and thus spent more time vigilant than females. Compared to non-rutting season, gazelles increased time spent scanning at the expense of bedding in rutting season. During the rutting season, territorial males spent a large proportion of time on rutting activities and were less vigilant than non-territorial males. Although territorial males may share collective risk detection with harem females, we suggest that they are probably more vulnerable to predation because they seemed reluctant to leave rut stands under threats. Conclusions/Significance Vigilance behavior in Przewalski's gazelle was significantly affected by reproductive status, social rank, sex, group size and their complex interactions. These findings shed light on the mechanisms underlying vigilance patterns and

  10. Intraspecific variation in group size in the blackbuck antelope: the roles of habitat structure and forage at different spatial scales.

    PubMed

    Isvaran, Kavita

    2007-11-01

    The main ecological factors that are hypothesized to explain the striking variation in the size of social groups among large herbivores are habitat structure, predation, and forage abundance and distribution; however, their relative roles in wild populations are not well understood. I combined analyses of ecological correlates of spatial variation in group size with analyses of individual behaviour in groups of different sizes to investigate factors maintaining variation in group size in an Indian antelope, the blackbuck Antilope cervicapra. I measured group size, habitat structure, forage, and the occurrence of predators in ten blackbuck populations, and, at a smaller spatial scale, within an intensively studied population. To examine the processes by which these ecological factors influence group size, I used behavioural observations and an experiment to estimate the shape of the relationship between group size and potential costs and benefits to individuals. Group size varied extensively both among and within populations. Analyses of spatial variation in group size suggested that both forage and habitat structure influence group size: large-scale, among-population variation in group size was primarily related to habitat structure, while small-scale, within-population variation was most closely related to forage abundance. Analyses of individual behaviour suggested that larger groups incur greater travel costs while foraging. However, individuals in larger groups appeared to experience greater benefits, namely the earlier detection of a "predator", a reduction in vigilance, and an increase in the time spent feeding. Overall, these findings suggest that individuals in groups experience a trade-off between predation-related benefits and costs arising from feeding competition. Habitat structure and forage likely influence the nature of this trade-off; thus, variation in these ecological factors may maintain variation in group size. The role of predation pressure and

  11. Spatial selection and grouping of raindrops by size in wind gusts

    NASA Astrophysics Data System (ADS)

    Sterlyadkin, V. V.

    2015-11-01

    Results that indicate the grouping of droplets of the same size in certain regions of space have been obtained during in situ measurements of the instantaneous structure and spatial and temporal distribution of rains (using methods based on the effect of abnormally high modulation of the scattered light). Calculations that show that such a grouping can be associated with wind gusts and intense turbulence are presented. It is shown that a lateral wind gust leads to the grouping of drops of different sizes in different layers. The processes of spatial selection and grouping are considered for both the laminar flow in the case of droplets and for the turbulent flow regime in the case of the coarse fraction of drops. It is stated that the clustering of particles can lead to a sharp increase in the received signal strength and the anomalous dependence of the backscatter cross section on the wavelength. This means that not only the microstructure of scatterers, but also the dynamic state of the atmosphere should be considered in the interpretation of radar data, e.g., Z-I ratio. The considered clustering mechanism can cause the rapid formation of raindrops in the clouds.

  12. Intraspecific variation in space use, group size, and mating systems of caviomorph rodents

    PubMed Central

    Maher, Christine R.; Burger, Joseph Robert

    2012-01-01

    Intraspecific variation in social systems is widely recognized across many taxa, and specific models, including polygamy potential, resource defense, and resource dispersion, have been developed to explain the relationship between ecological variation and social organization. Although mammals from temperate North America and Eurasia have provided many insights into this relationship, rodents from the Neotropics and temperate South America have largely been ignored. In this review we focus on reports documenting intraspecific variation in spacing systems, group size, and mating systems of caviomorphs. This large group of New World hystricognath rodents occupies a diverse array of habitats; thus, members of the same species potentially exhibit different social systems in response to different ecological conditions. Spatial patterns vary in response to a diverse array of factors, including predation, food availability, population density, and soil characteristics. Changes in group size typically correlate with changes in resource availability, particularly food. Mating systems generally reflect the ability of males to control access to females, which may depend on population density or food distribution. In general, social organization in caviomorphs fits predictions of resource-based models; however, most studies have been purely observational, involving small numbers of animals over short time periods and reporting qualitative rather than quantitative levels of ecological correlates. In future studies the use of molecular techniques and controlled, experimental manipulations can increase our understanding of intraspecific variation in caviomorph social systems. This understudied group of rodents offers excellent opportunities to provide insights into the influence of ecological conditions on behavior such as social systems. PMID:22328790

  13. Referential Cohesion and Logical Coherence of Narration after Closed Head Injury

    ERIC Educational Resources Information Center

    Davis, G. Albyn; Coelho, Carl A.

    2004-01-01

    A group with closed head injury was compared to neurologically intact controls regarding the referential cohesion and logical coherence of narrative production. A sample of six stories was obtained with tasks of cartoon-elicited story-telling and auditory-oral retelling. We found deficits in the clinical group with respect to referential cohesion,…

  14. Universal size effects for populations in group-outcome decision-making problems

    NASA Astrophysics Data System (ADS)

    Borghesi, Christian; Hernández, Laura; Louf, Rémi; Caparros, Fabrice

    2013-12-01

    Elections constitute a paradigm of decision-making problems that have puzzled experts of different disciplines for decades. We study two decision-making problems, where groups make decisions that impact only themselves as a group. In both studied cases, participation in local elections and the number of democratic representatives at different scales (from local to national), we observe a universal scaling with the constituency size. These results may be interpreted as constituencies having a hierarchical structure, where each group of N agents, at each level of the hierarchy, is divided in about Nδ subgroups with δ≈1/3. Following this interpretation, we propose a phenomenological model of vote participation where abstention is related to the perceived link of an agent to the rest of the constituency and which reproduces quantitatively the observed data.

  15. The effects of familiarity and group size on mating preferences in the guppy, Poecilia reticulata.

    PubMed

    Mariette, M M; Zajitschek, S R K; Garcia, C M; Brooks, R C

    2010-08-01

    In recent years, it has become evident that frequency dependence in the attractiveness of a particular phenotype to mates can contribute to the maintenance of polymorphism. However, these preferences for rare and unfamiliar male phenotypes have only been demonstrated in small, controlled experiments. Here, we tested the preference for unfamiliar mates in groups of six to 96 individuals over 13 days, in the guppy (Poecilia reticulata). We observed individual behaviour in situ to test whether fish discriminate two unfamiliar individuals among many familiar ones. We found that unfamiliar males and females were preferred over the familiar fishes in all groups and that this effect decayed over time. Increasing group sizes and levels of sexual activity did not hamper the preference for unfamiliar mates, providing further support for the role of frequency dependent mate choice in the maintenance of trait polymorphism in natural populations.

  16. The effects of familiarity and group size on mating preferences in the guppy, Poecilia reticulata.

    PubMed

    Mariette, M M; Zajitschek, S R K; Garcia, C M; Brooks, R C

    2010-08-01

    In recent years, it has become evident that frequency dependence in the attractiveness of a particular phenotype to mates can contribute to the maintenance of polymorphism. However, these preferences for rare and unfamiliar male phenotypes have only been demonstrated in small, controlled experiments. Here, we tested the preference for unfamiliar mates in groups of six to 96 individuals over 13 days, in the guppy (Poecilia reticulata). We observed individual behaviour in situ to test whether fish discriminate two unfamiliar individuals among many familiar ones. We found that unfamiliar males and females were preferred over the familiar fishes in all groups and that this effect decayed over time. Increasing group sizes and levels of sexual activity did not hamper the preference for unfamiliar mates, providing further support for the role of frequency dependent mate choice in the maintenance of trait polymorphism in natural populations. PMID:20626544

  17. Size-constraints on intonation groups in speech: Evidence of an independent syllable-count principle

    NASA Astrophysics Data System (ADS)

    Gilbert, Annie C.; Boucher, Victor J.

    2005-04-01

    This poster examines size-limits on intonation (F0) contours in spontaneous speech and presents the results of an experiment on a syllable-count principle, which is seen to constitute, irrespective of syntax, a factor restricting the length of F0 groups. Studies of various languages indicate a general tendency to restrict stress-groups in speech to four syllables or less. In languages were stress is not lexically coded (e.g., French), syntax is not a sufficient predictor of stress. The object was to determine whether these aspects of stress patterning also apply to tonal groups. Statistics are lacking with respect to the extent of F0 contours in speech. Pitch-extracting software was used to analyze the speech of 15 native speakers of French (20 minutes each). Initial results suggest an eight-syllable limit on tonal groups. Based on these statistics an experiment was conducted where 40 Ss read and repeated visually presented sentences containing major syntactic divisions (phrase boundaries) at different locations. There are two central findings: (1) phrase boundaries placed at different points in the sentence did not serve to predict tonal grouping; (2) even when the sentence structure offered the possibility of creating large tonal groups, Ss did not create contours exceeding an eight-syllable limit.

  18. Cross (Unit)-Level Effects of Cohesion on Relationships of Suicide Thoughts to Combat Exposure, Postdeployment Stressors, and Postdeployment Social Support.

    PubMed

    Griffith, James

    2015-01-01

    A behavioral health concern for the US military has been suicide, largely due to its increased prevalence in the last several years during US involvement in the Iraq and Afghanistan wars. Using hierarchical linear modeling (HLM), the present study examined relationships among combat exposure, postdeployment stressors, social support, and unit cohesion. Survey data were obtained from 4,567 soldiers who were members of 50 company-sized units. At the individual level, combat exposure and postdeployment stressors were associated with suicidal thoughts. Postdeployment social support was associated with fewer suicidal thoughts. There was no evidence of the stress-buffering effect of social support. At the group level, reduced risk for suicidal thoughts was associated with units having higher than average cohesion. Reduced risk for suicidal thoughts in conjunction with combat experiences was observed in units having higher than average cohesion, though not reaching a traditional level of statistical significance.

  19. Cross (Unit)-Level Effects of Cohesion on Relationships of Suicide Thoughts to Combat Exposure, Postdeployment Stressors, and Postdeployment Social Support.

    PubMed

    Griffith, James

    2015-01-01

    A behavioral health concern for the US military has been suicide, largely due to its increased prevalence in the last several years during US involvement in the Iraq and Afghanistan wars. Using hierarchical linear modeling (HLM), the present study examined relationships among combat exposure, postdeployment stressors, social support, and unit cohesion. Survey data were obtained from 4,567 soldiers who were members of 50 company-sized units. At the individual level, combat exposure and postdeployment stressors were associated with suicidal thoughts. Postdeployment social support was associated with fewer suicidal thoughts. There was no evidence of the stress-buffering effect of social support. At the group level, reduced risk for suicidal thoughts was associated with units having higher than average cohesion. Reduced risk for suicidal thoughts in conjunction with combat experiences was observed in units having higher than average cohesion, though not reaching a traditional level of statistical significance. PMID:26332927

  20. Modeling Asteroid Spin-up with Cohesion

    NASA Astrophysics Data System (ADS)

    Walsh, Kevin J.; Richardson, D. C.; Michel, P.

    2008-09-01

    Recent work has shown that the gradual spin-up of cohesionless gravitational aggregates produces a wide range of outcomes depending on the specific configuration of the body, such as particle size distribution. One important outcome is the creation of binary asteroids, which requires bodies that can maintain spherical/oblate shapes as the body is spun to rapid rotation (Walsh et al., 2008, Nature, 454, 188-191). Our recent work includes a similar model which also models cohesion within the gravitational aggregate by way of a spring-like restoring force between neighboring particles that vanishes under high strain. We will present early results of gradual spin-up tests on gravitational aggregates covering a large range of starting conditions including the initial body shape and size, as well as varying configurations for the cohesion properties. These results will be compared to previous spin-up work as well as analytical theory. KJW and PM had the support of the French Programme National de Planétologie and the ACT Team of ESA and Ariadna Study 07/4111"Asteroid Rotational Fragmentation". KJW is also supported by the Henri Poincaré fellowship at the Observatoire de la Côte d'Azur, Nice, France, and Rotary International -- District 1730. DCR acknowledges support from the National Science Foundation under grant AST0708110 and the National Aeronautics and Space Administration under Grant No. NNX08AM39G.

  1. The Relationship between Task Cohesion and Competitive State Anxiety.

    ERIC Educational Resources Information Center

    Eys, Mark A.; Hardy, James; Carron, Albert V.; Beauchamp, Mark R.

    2003-01-01

    Examined the association between athlete perceptions of task cohesiveness (Individual Attractions to the Group-Task and Group Integration-Task) and the degree to which they viewed their perceptions of the presence of pre-competition anxiety symptoms as facilitative or debilitative. Survey data indicated that the more positive their perceptions of…

  2. Group size effect on cooperation in one-shot social dilemmas

    PubMed Central

    Barcelo, Hélène; Capraro, Valerio

    2015-01-01

    Social dilemmas are central to human society. Depletion of natural resources, climate protection, security of energy supply, and workplace collaborations are all examples of social dilemmas. Since cooperative behaviour in a social dilemma is individually costly, Nash equilibrium predicts that humans should not cooperate. Yet experimental studies show that people do cooperate even in anonymous one-shot interactions. In spite of the large number of participants in many modern social dilemmas, little is known about the effect of group size on cooperation. Does larger group size favour or prevent cooperation? We address this problem both experimentally and theoretically. Experimentally, we find that there is no general answer: it depends on the strategic situation. Specifically, we find that larger groups are more cooperative in the Public Goods game, but less cooperative in the N-person Prisoner's dilemma. Theoretically, we show that this behaviour is not consistent with either the Fehr & Schmidt model or (a one-parameter version of) the Charness & Rabin model, but it is consistent with the cooperative equilibrium model introduced by the second author. PMID:25605124

  3. Group size effect on cooperation in one-shot social dilemmas.

    PubMed

    Barcelo, Hélène; Capraro, Valerio

    2015-01-21

    Social dilemmas are central to human society. Depletion of natural resources, climate protection, security of energy supply, and workplace collaborations are all examples of social dilemmas. Since cooperative behaviour in a social dilemma is individually costly, Nash equilibrium predicts that humans should not cooperate. Yet experimental studies show that people do cooperate even in anonymous one-shot interactions. In spite of the large number of participants in many modern social dilemmas, little is known about the effect of group size on cooperation. Does larger group size favour or prevent cooperation? We address this problem both experimentally and theoretically. Experimentally, we find that there is no general answer: it depends on the strategic situation. Specifically, we find that larger groups are more cooperative in the Public Goods game, but less cooperative in the N-person Prisoner's dilemma. Theoretically, we show that this behaviour is not consistent with either the Fehr &Schmidt model or (a one-parameter version of) the Charness &Rabin model, but it is consistent with the cooperative equilibrium model introduced by the second author.

  4. Genome size in Hieracium subgenus Hieracium (Asteraceae) is strongly correlated with major phylogenetic groups

    PubMed Central

    Chrtek, Jindřich; Zahradníček, Jaroslav; Krak, Karol; Fehrer, Judith

    2009-01-01

    Background and Aims Hieracium subgenus Hieracium is one of the taxonomically most intricate groups of vascular plants, due to polyploidy and a diversity of breeeding systems (sexuality vs. apomixis). The aim of the present study was to analyse nuclear genome size in a phylogenetic framework and to assess relationships between genome size and ploidy, breeding system and selected ecogeographic features. Methods Holoploid and monoploid genome sizes (C- and Cx-values) of 215 cultivated plants from 89 field populations of 42 so-called ‘basic’ Hieracium species were determined using propidium iodide flow cytometry. Chromosome counts were available for all analysed plants, and all plants were tested experimentally for their mode of reproduction (sexuality vs. apomixis). For constructing molecular phylogenetic trees, the external transcribed spacer region of nuclear ribosomal DNA was used. Key Results The mean 2C values differed up to 2·37-fold among different species (from 7·03 pg in diploid to 16·67 in tetraploid accessions). The 1Cx values varied 1·22-fold (between 3·51 and 4·34 pg). Variation in 1Cx values between conspecific (species in a broad sense) accessions ranged from 0·24% to 7·2%. Little variation (not exceeding the approximate measurement inaccurracy threshold of 3·5%) was found in 33 species, whereas variation higher than 3·5% was detected in seven species. Most of the latter may have a polytopic origin. Mean 1Cx values of the three cytotypes (2n, 3n and 4n) differed significantly (average of 3·93 pg in diploids, 3·82 pg in triploids and 3·78 pg in tetraploids) indicating downsizing of genomes in polyploids. The pattern of genome size variation correlated well with two major phylogenetic clades which were composed of species with western or eastern European origin. The monoploid genome size in the ‘western’ species was significantly lower than in the ‘eastern’ ones. Correlation of genome size with latitude, altitude and selected

  5. Behavioral correlates of corpus callosum size: Anatomical/behavioral relationships vary across sex/handedness groups

    PubMed Central

    Welcome, Suzanne E.; Chiarello, Christine; Towler, Stephen; Halderman, Laura K.; Otto, Ronald; Leonard, Christiana M.

    2009-01-01

    There are substantial individual differences in the size and shape of the corpus callosum and such differences are thought to relate to behavioral lateralization. We report findings from a large scale investigation of relationships between brain anatomy and behavioral asymmetry on a battery of visual word recognition tasks. A sample of 200 individuals was divided into groups on the basis of sex and consistency of handedness. We investigated differences between sex/handedness groups in callosal area and relationships between callosal area and behavioral predictors. Sex/handedness groups did not show systematic differences in callosal area or behavioral asymmetry. However, the groups differed in the relationships between area of the corpus callosum and behavioral asymmetry. Among consistent-handed males, callosal area was negatively related to behavioral laterality. Among mixed-handed males and consistent-handed females, behavioral laterality was not predictive of callosal area. The most robust relationship was observed in mixed-handed females, in whom behavioral asymmetry was positively related to callosal area. Our study demonstrates the importance of considering brain/behavior relationships within sub-populations, as relationships between behavioral asymmetry and callosal anatomy varied across subject groups. PMID:19383501

  6. The Impact of Group Size and Proportion of Shared Information on the Exchange and Integration of Information in Groups.

    ERIC Educational Resources Information Center

    Cruz, Michael G.; Boster, Franklin J.; Rodriguez, Jose I.

    1997-01-01

    Seeks conditions that improve group performance on "hidden profiles." Finds that, among undergraduate student groups, group information sharing and decision-making effectiveness were higher in small groups with a low percentage of shared information, and lower when groups either were large or shared a high percentage of information. Notes that…

  7. Evolution of indirect reciprocity in groups of various sizes and comparison with direct reciprocity.

    PubMed

    Suzuki, Shinsuke; Akiyama, Eizo

    2007-04-01

    Recently many studies have investigated the evolution of indirect reciprocity through which cooperative action is returned by a third individual, e.g. individual A helped B and then receives help from C. Most studies on indirect reciprocity have presumed that only two individuals take part in a single interaction (group), e.g. A helps B and C helps A. In this paper, we investigate the evolution of indirect reciprocity when more than two individuals take part in a single group, and compare the result with direct reciprocity through which cooperative action is directly returned by the recipient. Our analyses show the following. In the population with discriminating cooperators and unconditional defectors, whether implementation error is included or not, (i) both strategies are evolutionarily stable and the evolution of indirect reciprocity becomes more difficult as group size increases, and (ii) the condition for the evolution of indirect reciprocity under standing reputation criterion where the third individuals distinguish between justified and unjustified defections is more relaxed than that under image scoring reputation criterion in which the third individuals do not distinguish with. Furthermore, in the population that also includes unconditional cooperators, (iii) in the presence of errors in implementation, the discriminating strategy is evolutionarily stable not only under standing but also under image scoring if group size is larger than two. Finally, (iv) in the absence of errors in implementation, the condition for the evolution of direct reciprocity is equivalent to that for the evolution of indirect reciprocity under standing, and, in the presence of errors, the condition for the evolution of direct reciprocity is very close to that for the evolution of indirect reciprocity under image scoring.

  8. The effect of group size on vigilance in a semi-solitary, fossorial marsupial (Lasiorhinus latifrons).

    PubMed

    Descovich, Kristin A; Lisle, Allan T; Johnston, Stephen; Phillips, Clive J C

    2013-11-01

    Prey species that congregate gain protection against predatory attacks and this advantage is often reflected by a reduction in vigilance behaviour by individuals in larger groups. Comparatively few studies have investigated vigilance in solitary animals, but those that have, found that vigilance increases as group size increases because of the threat posed by conspecifics and/or competition for resources. The southern hairy-nosed wombat (Lasiorhinus latifrons) is a large fossorial, nocturnal marsupial that is neither strictly solitary nor gregarious, sharing warren systems with multiple conspecifics. We investigated the effects of conspecific presence on vigilance behaviour in this semi-solitary species. We observed wild-born, adult L. latifrons wombats in three group sizes (Large (1♂, 3♀), Medium (1♂, 2♀) and Small (1♂, 1♀)) in a captive, naturalistic environment that allowed above-ground and den behaviour monitoring. Vigilance behaviours were performed less frequently by wombats in large groups (e.g. scanning, counts/day, Large: 55, Medium: 69, Small: 115, P=0.002) and more frequently as the distance from their nearest conspecific increased (r64=0.30, P= 0.016). Vigilance within burrows was also affected by social influences, with solitary wombats significantly more vigilant than those denning with a conspecific (e.g. scanning: conspecific absent: 0.13/5min, present: 0.03/5min, P<0.0001). It is concluded that the presence of conspecifics reduces vigilance in L. latifrons wombats, even within burrows, and this may partially explain the occurrence of warren sharing in the wild. PMID:24140418

  9. The effect of group size on vigilance in a semi-solitary, fossorial marsupial (Lasiorhinus latifrons).

    PubMed

    Descovich, Kristin A; Lisle, Allan T; Johnston, Stephen; Phillips, Clive J C

    2013-11-01

    Prey species that congregate gain protection against predatory attacks and this advantage is often reflected by a reduction in vigilance behaviour by individuals in larger groups. Comparatively few studies have investigated vigilance in solitary animals, but those that have, found that vigilance increases as group size increases because of the threat posed by conspecifics and/or competition for resources. The southern hairy-nosed wombat (Lasiorhinus latifrons) is a large fossorial, nocturnal marsupial that is neither strictly solitary nor gregarious, sharing warren systems with multiple conspecifics. We investigated the effects of conspecific presence on vigilance behaviour in this semi-solitary species. We observed wild-born, adult L. latifrons wombats in three group sizes (Large (1♂, 3♀), Medium (1♂, 2♀) and Small (1♂, 1♀)) in a captive, naturalistic environment that allowed above-ground and den behaviour monitoring. Vigilance behaviours were performed less frequently by wombats in large groups (e.g. scanning, counts/day, Large: 55, Medium: 69, Small: 115, P=0.002) and more frequently as the distance from their nearest conspecific increased (r64=0.30, P= 0.016). Vigilance within burrows was also affected by social influences, with solitary wombats significantly more vigilant than those denning with a conspecific (e.g. scanning: conspecific absent: 0.13/5min, present: 0.03/5min, P<0.0001). It is concluded that the presence of conspecifics reduces vigilance in L. latifrons wombats, even within burrows, and this may partially explain the occurrence of warren sharing in the wild.

  10. The oxidative costs of reproduction are group-size dependent in a wild cooperative breeder

    PubMed Central

    Cram, Dominic L.; Blount, Jonathan D.; Young, Andrew J.

    2015-01-01

    Life-history theory assumes that reproduction entails a cost, and research on cooperatively breeding societies suggests that the cooperative sharing of workloads can reduce this cost. However, the physiological mechanisms that underpin both the costs of reproduction and the benefits of cooperation remain poorly understood. It has been hypothesized that reproductive costs may arise in part from oxidative stress, as reproductive investment may elevate exposure to reactive oxygen species, compromising survival and future reproduction and accelerating senescence. However, experimental evidence of oxidative costs of reproduction in the wild remains scarce. Here, we use a clutch-removal experiment to investigate the oxidative costs of reproduction in a wild cooperatively breeding bird, the white-browed sparrow weaver, Plocepasser mahali. Our results reveal costs of reproduction that are dependent on group size: relative to individuals in groups whose eggs were experimentally removed, individuals in groups that raised offspring experienced an associated cost (elevated oxidative damage and reduced body mass), but only if they were in small groups containing fewer or no helpers. Furthermore, during nestling provisioning, individuals that provisioned at higher rates showed greater within-individual declines in body mass and antioxidant protection. Our results provide rare experimental evidence that reproduction can negatively impact both oxidative status and body mass in the wild, and suggest that these costs can be mitigated in cooperative societies by the presence of additional helpers. These findings have implications for our understanding of the energetic and oxidative costs of reproduction, and the benefits of cooperation in animal societies. PMID:26582023

  11. The sizes of elephant groups in zoos: implications for elephant welfare.

    PubMed

    Rees, Paul A

    2009-01-01

    This study examined the distribution of 495 Asian elephants (Elephas maximus) and 336 African elephants (Loxodonta africana) in 194 zoos, most of which were located in Europe (49.1%) and North America (32.6%). Cows outnumbered bulls 4 to 1 (Loxodonta) and 3 to 1 (Elephas). Groups contained 7 or fewer: mean, 4.28 (sigma = 5.73). One fifth of elephants lived alone or with one conspecific. Forty-six elephants (5.5%) had no conspecific. Many zoos ignore minimum group sizes of regional zoo association guidelines. The American Zoo and Aquarium Association recommends that breeding facilities keep herds of 6 to 12 elephants. The British and Irish Association of Zoos and Aquariums recommends keeping together at least 4 cows over 2 years old. Over 69% Asian and 80% African cow groups-including those under 2 years-consisted of fewer than 4 individuals. Recently, Europe and North America have made progress with some zoos no longer keeping elephants and with others investing in improved facilities and forming larger herds. The welfare of individual elephants should outweigh all other considerations; zoos should urgently seek to integrate small groups into larger herds.

  12. The oxidative costs of reproduction are group-size dependent in a wild cooperative breeder.

    PubMed

    Cram, Dominic L; Blount, Jonathan D; Young, Andrew J

    2015-11-22

    Life-history theory assumes that reproduction entails a cost, and research on cooperatively breeding societies suggests that the cooperative sharing of workloads can reduce this cost. However, the physiological mechanisms that underpin both the costs of reproduction and the benefits of cooperation remain poorly understood. It has been hypothesized that reproductive costs may arise in part from oxidative stress, as reproductive investment may elevate exposure to reactive oxygen species, compromising survival and future reproduction and accelerating senescence. However, experimental evidence of oxidative costs of reproduction in the wild remains scarce. Here, we use a clutch-removal experiment to investigate the oxidative costs of reproduction in a wild cooperatively breeding bird, the white-browed sparrow weaver, Plocepasser mahali. Our results reveal costs of reproduction that are dependent on group size: relative to individuals in groups whose eggs were experimentally removed, individuals in groups that raised offspring experienced an associated cost (elevated oxidative damage and reduced body mass), but only if they were in small groups containing fewer or no helpers. Furthermore, during nestling provisioning, individuals that provisioned at higher rates showed greater within-individual declines in body mass and antioxidant protection. Our results provide rare experimental evidence that reproduction can negatively impact both oxidative status and body mass in the wild, and suggest that these costs can be mitigated in cooperative societies by the presence of additional helpers. These findings have implications for our understanding of the energetic and oxidative costs of reproduction, and the benefits of cooperation in animal societies.

  13. The Effect of Grouping by Formal Reasoning Ability, Formal Reasoning Ability Levels, Group Size, and Gender on Achievement in Laboratory Chemistry.

    ERIC Educational Resources Information Center

    Moody, Judith D.; Gifford, Vernon D.

    This study investigated the grouping effect on student achievement in a chemistry laboratory when homogeneous and heterogeneous formal reasoning ability, high and low levels of formal reasoning ability, group sizes of two and four, and homogeneous and heterogeneous gender were used for grouping factors. The sample consisted of all eight intact…

  14. One is not enough: Group size modulates social gaze-induced object desirability effects.

    PubMed

    Capozzi, Francesca; Bayliss, Andrew P; Elena, Marco R; Becchio, Cristina

    2015-06-01

    Affective evaluations of objects are influenced by the preferences expressed by other people via their gaze direction, so that objects looked at are liked more than objects looked away from. But when can others' preferences be trusted? Here, we show that group size influences the extent to which individuals tend to conform to others' gaze preferences. We adopted the conventional gaze-cuing paradigm and modified the design in such a way that some objects were consistently cued by only one face (single-face condition), whereas other objects were consistently cued by several different faces (multiple-faces condition). While response time measures revealed equal gaze-cuing effects for both conditions, a boost in affective evaluation was observed only for objects looked at by several different faces. Objects looked at by a single face were not rated differently than objects looked away from. These findings suggest that observers make use of group size to evaluate the generalizability of the epistemic information conveyed by others' gaze: Objects looked at are liked more than objects looked away from, but only when they are looked at by multiple faces.

  15. A passive acoustic monitoring method applied to observation and group size estimation of finless porpoises.

    PubMed

    Wang, Kexiong; Wang, Ding; Akamatsu, Tomonari; Li, Songhai; Xiao, Jianqiang

    2005-08-01

    The present study aimed at determining the detection capabilities of an acoustic observation system to recognize porpoises under local riverine conditions and compare the results with sighting observations. Arrays of three to five acoustic data loggers were stationed across the main channel of the Tian-e-zhou Oxbow of China's Yangtze River at intervals of 100-150 m to record sonar signals of free-ranging finless porpoises (Neophocaena phocaenoides). Acoustic observations, concurrent with visual observations, were conducted at two occasions on 20-22 October 2003 and 17-19 October 2004. During a total of 42 h of observation, 316 finless porpoises were sighted and 7041 sonar signals were recorded by loggers. The acoustic data loggers recorded ultrasonic signals of porpoises clearly, and detected the presence of porpoises with a correct detection level of 77.6% and a false alarm level of 5.8% within an effective distance of 150 m. Results indicated that the stationed passive acoustic observation method was effective in detecting the presence of porpoises and showed potential in estimating the group size. A positive linear correlation between the number of recorded signals and the group size of sighted porpoises was indicated, although it is faced with some uncertainty and requires further investigation. PMID:16158672

  16. Relative group size and minority school success: the role of intergroup friendship and discrimination experiences.

    PubMed

    Baysu, Gülseli; Phalet, Karen; Brown, Rupert

    2014-06-01

    From an intergroup relations perspective, relative group size is associated with the quantity and quality of intergroup contact: more positive contact (i.e., intergroup friendship) supports, and negative contact (i.e., experienced discrimination) hampers, minority identity, and school success. Accordingly, we examined intergroup contact as the process through which perceived relative proportions of minority and majority students in school affected minority success (i.e., school performance, satisfaction, and self-efficacy). Turkish minorities (N = 1,060) were compared in four Austrian and Belgian cities which differ in their typical school ethnic composition. Across cities, minority experiences of intergroup contact fully mediated the impact of perceived relative group size on school success. As expected, higher minority presence impaired school success through restricting intergroup friendship and increasing experienced discrimination. The association between minority presence and discrimination was curvilinear, however, so that schools where minority students predominated offered some protection from discrimination. To conclude, the comparative findings reveal positive and negative intergroup contact as key processes that jointly explain when and how higher proportions of minority students affect school success.

  17. A passive acoustic monitoring method applied to observation and group size estimation of finless porpoises.

    PubMed

    Wang, Kexiong; Wang, Ding; Akamatsu, Tomonari; Li, Songhai; Xiao, Jianqiang

    2005-08-01

    The present study aimed at determining the detection capabilities of an acoustic observation system to recognize porpoises under local riverine conditions and compare the results with sighting observations. Arrays of three to five acoustic data loggers were stationed across the main channel of the Tian-e-zhou Oxbow of China's Yangtze River at intervals of 100-150 m to record sonar signals of free-ranging finless porpoises (Neophocaena phocaenoides). Acoustic observations, concurrent with visual observations, were conducted at two occasions on 20-22 October 2003 and 17-19 October 2004. During a total of 42 h of observation, 316 finless porpoises were sighted and 7041 sonar signals were recorded by loggers. The acoustic data loggers recorded ultrasonic signals of porpoises clearly, and detected the presence of porpoises with a correct detection level of 77.6% and a false alarm level of 5.8% within an effective distance of 150 m. Results indicated that the stationed passive acoustic observation method was effective in detecting the presence of porpoises and showed potential in estimating the group size. A positive linear correlation between the number of recorded signals and the group size of sighted porpoises was indicated, although it is faced with some uncertainty and requires further investigation.

  18. Development of an online database of typical food portion sizes in Irish population groups.

    PubMed

    Lyons, Jacqueline; Walton, Janette; Flynn, Albert

    2013-01-01

    The Irish Food Portion Sizes Database (available at www.iuna.net) describes typical portion weights for an extensive range of foods and beverages for Irish children, adolescents and adults. The present paper describes the methodologies used to develop the database and some key characteristics of the portion weight data contained therein. The data are derived from three large, cross-sectional food consumption surveys carried out in Ireland over the last decade: the National Children's Food Survey (2003-2004), National Teens' Food Survey (2005-2006) and National Adult Nutrition Survey (2008-2010). Median, 25th and 75th percentile portion weights are described for a total of 545 items across the three survey groups, split by age group or sex as appropriate. The typical (median) portion weights reported for adolescents and adults are similar for many foods, while those reported for children are notably smaller. Adolescent and adult males generally consume larger portions than their female counterparts, though similar portion weights may be consumed where foods are packaged in unit amounts (for example, pots of yoghurt). The inclusion of energy under-reporters makes little difference to the estimation of typical portion weights in adults. The data have wide-ranging applications in dietary assessment and food labelling, and will serve as a useful reference against which to compare future portion size data from the Irish population. The present paper provides a useful context for researchers and others wishing to use the Irish Food Portion Sizes Database, and may guide researchers in other countries in establishing similar databases of their own.

  19. Fish otoliths: do sizes correlate with taxonomic group, habitat and/or luminescence?

    PubMed Central

    Paxton, J R

    2000-01-01

    Otoliths are dense structures in the ears of fishes that function in hearing and gravity perception. Otolith (sagitta) diameters, as percentages of standard length (% SL), are calculated for 247 marine fish species in 147 families and compared by taxonomic group (usually order), habitat and presence or absence of luminescence. Otolith sizes range from 0.4-31.4 mm and 0.08-11.2% SL. The eel and spiny eel orders Anguilliformes and Notacanthiformes have small to very small otoliths, as do the triggerfish order Tetraodontiformes, pipefish order Gasterosteiformes, billfish suborder Scombroidei and many of the dragonfish order Stomiiformes. The soldierfish order Beryciformes has moderate to very large otoliths. The perch order Perciformes has a wide range of otolith sizes but most have small to moderate otoliths 2-5% SL. Only 16 out of the 247 species have the relatively largest otoliths, over 7% SL. Seven out of these 16 species are also luminous from a variety of habitats. Luminous species have slightly to much larger otoliths than non-luminous species in the same family Both beryciforms and luminous fishes live in low-light environments, where acute colour vision is probably impossible. Most fishes of the epipelagic surface waters have very small otoliths, perhaps due to background noise and/or excessive movement of heavy otoliths in rough seas. Bathypelagic species usually have small otoliths and regressed or absent swimbladders. Other habitats have species with a range of otolith sizes. While the relationship between hearing ability and otolith length is unknown, at least some groups with modified swim-bladders have larger otoliths, which may be associated with more acute hearing. PMID:11079419

  20. Social Cohesion as the Goal: Can Social Cohesion Be Directly Pursued?

    ERIC Educational Resources Information Center

    Koonce, Kelly A.

    2011-01-01

    This article establishes an understanding of social cohesion in general and discusses organizations and activities that are known to promote social cohesion before introducing organizations that claim to work toward social cohesion as one of their main priorities. The Council of Europe's Directorate General of Social Cohesion represents a…

  1. Education and Social Cohesion: Recentering the Debate.

    ERIC Educational Resources Information Center

    Green, Andy; Preston, John

    2001-01-01

    Examines the debate over education and social cohesion, reviewing relevant literature, which notes limitations of individual-level analysis of societal issues; outlining alternative models for understanding how education influences social cohesion in different societies (e.g., skills, income distribution, and indicators of social cohesion); and…

  2. Discourse Cohesion in the Verbal Interactions of Individuals Diagnosed with Autistic Disorder or Schizotypal Personality Disorder.

    ERIC Educational Resources Information Center

    Baltaxe, Christiane A. M.; And Others

    1995-01-01

    This study compared high functioning adolescents and young adults with autism (n=8) or schizotypal personality disorder (n=9) in use of social language referencing. Both groups had similar rates, types, and patterns of cohesive reference errors, though subjects with schizotypal disorder used cohesive ties of reference more often and more correctly…

  3. Correlation effects in metallic cohesion

    NASA Astrophysics Data System (ADS)

    Haydock, Roger

    2014-03-01

    The electronic contribution to the cohesive energy of a correlated metal is the sum of the transition energies for adding successive electrons at successive Fermi levels until the system reaches its final electron density. This can be computed as the integral of energy over the projected density of transitions for adding single electrons to localized orbitals. In the case of independent electrons, this reduces to the usual integral over the projected density of states. As an example, cohesive energies for some simple transition metal structures are calculated using the recursion method* with a Hubbard repulsion between electrons. * Phys. Rev. B 61, 7953-64 Work supported by the Richmond F. Snyder gift to the University of Oregon.

  4. Cohesion, coherence, and declarative memory: Discourse patterns in individuals with hippocampal amnesia.

    PubMed

    Kurczek, Jake; Duff, Melissa C

    2011-01-01

    BACKGROUND: Discourse cohesion and coherence gives our communication continuity. Deficits in cohesion and coherence have been reported in patients with cognitive-communication disorders (e.g., TBI, dementia). However, the diffuse nature of pathology and widespread cognitive deficits of these disorders have made identification of specific neural substrates and cognitive systems critical for cohesion and coherence challenging. AIMS: Taking advantage of a rare patient group with selective and severe declarative memory impairments, the current study attempts to isolate the contribution of declarative memory to the successful use of cohesion and coherence in discourse. METHODS #ENTITYSTARTX00026; PROCEDURES: Cohesion and coherence were examined in the discourse of six participants with hippocampal amnesia and six demographically matched comparison participants. Specifically, this study (1) documents the frequency, type, and completeness of cohesive ties; (2) evaluates discourse for local and global coherence; and (3) compares use of cohesive ties and coherence ratings in amnesia and healthy participants. OUTCOMES #ENTITYSTARTX00026; RESULTS: Overall, amnesia participants produced fewer cohesive ties per T-unit, the adequacy of their ties were more often judged to be incomplete, and the ratings of their local coherence were consistently lower than comparison participants. CONCLUSIONS: These findings suggest that declarative memory may contribute to the discursive use of cohesion and coherence. Broader notions of cohesion, or interactional cohesion, i.e., cohesion across speakers (two or more people), time (days, weeks), and communicative resources (gesture), warrant further study as the experimental tasks used in the literature, and here, may actually underestimate or overestimate the extent of impairment.

  5. The Politics of Britishness: Multiculturalism, Schooling and Social Cohesion

    ERIC Educational Resources Information Center

    Keddie, Amanda

    2014-01-01

    This paper is set against a backdrop of contemporary concerns about Britishness. It explores the dominant view that unprecedented levels of cultural diversity within western contexts such as the UK are undermining social cohesion and are attributable to minority groups' failure to connect or assimilate with mainstream "British"…

  6. Mode I Cohesive Law Characterization of Through-Crack Propagation in a Multidirectional Laminate

    NASA Technical Reports Server (NTRS)

    Bergan, Andrew C.; Davila, Carlos G.; Leone, Frank A.; Awerbuch, Jonathan; Tan, Tein-Min

    2014-01-01

    A method is proposed and assessed for the experimental characterization of through-the-thickness crack propagation in multidirectional composite laminates with a cohesive law. The fracture toughness and crack opening displacement are measured and used to determine a cohesive law. Two methods of computing fracture toughness are assessed and compared. While previously proposed cohesive characterizations based on the R-curve exhibit size effects, the proposed approach results in a cohesive law that is a material property. The compact tension specimen configuration is used to propagate damage while load and full-field displacements are recorded. These measurements are used to compute the fracture toughness and crack opening displacement from which the cohesive law is characterized. The experimental results show that a steady-state fracture toughness is not reached. However, the proposed method extrapolates to steady-state and is demonstrated capable of predicting the structural behavior of geometrically-scaled specimens.

  7. Dependence of micelle size and shape on detergent alkyl chain length and head group.

    PubMed

    Oliver, Ryan C; Lipfert, Jan; Fox, Daniel A; Lo, Ryan H; Doniach, Sebastian; Columbus, Linda

    2013-01-01

    Micelle-forming detergents provide an amphipathic environment that can mimic lipid bilayers and are important tools for solubilizing membrane proteins for functional and structural investigations in vitro. However, the formation of a soluble protein-detergent complex (PDC) currently relies on empirical screening of detergents, and a stable and functional PDC is often not obtained. To provide a foundation for systematic comparisons between the properties of the detergent micelle and the resulting PDC, a comprehensive set of detergents commonly used for membrane protein studies are systematically investigated. Using small-angle X-ray scattering (SAXS), micelle shapes and sizes are determined for phosphocholines with 10, 12, and 14 alkyl carbons, glucosides with 8, 9, and 10 alkyl carbons, maltosides with 8, 10, and 12 alkyl carbons, and lysophosphatidyl glycerols with 14 and 16 alkyl carbons. The SAXS profiles are well described by two-component ellipsoid models, with an electron rich outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core composed of the alkyl chains. The minor axis of the elliptical micelle core from these models is constrained by the length of the alkyl chain, and increases by 1.2-1.5 Å per carbon addition to the alkyl chain. The major elliptical axis also increases with chain length; however, the ellipticity remains approximately constant for each detergent series. In addition, the aggregation number of these detergents increases by ∼16 monomers per micelle for each alkyl carbon added. The data provide a comprehensive view of the determinants of micelle shape and size and provide a baseline for correlating micelle properties with protein-detergent interactions.

  8. Size distributions of shocks and static avalanches from the functional renormalization group.

    PubMed

    Le Doussal, Pierre; Wiese, Kay Jörg

    2009-05-01

    Interfaces pinned by quenched disorder are often used to model jerky self-organized critical motion. We study static avalanches, or shocks, defined here as jumps between distinct global minima upon changing an external field. We show how the full statistics of these jumps is encoded in the functional-renormalization-group fixed-point functions. This allows us to obtain the size distribution P(S) of static avalanches in an expansion in the internal dimension d of the interface. Near and above d=4 this yields the mean-field distribution P(S) approximately S;{-3/2}e;{-S4S_{m}} , where S_{m} is a large-scale cutoff, in some cases calculable. Resumming all one-loop contributions, we find P(S) approximately S;{-tau}exp(C(SS_{m});{1/2}-B/4(S/S_{m});{delta}) , where B , C , delta , and tau are obtained to first order in =4-d . Our result is consistent to O() with the relation tau=tau_{zeta}:=2-2/d+zeta , where zeta is the static roughness exponent, often conjectured to hold at depinning. Our calculation applies to all static universality classes, including random-bond, random-field, and random-periodic disorders. Extended to long-range elastic systems, it yields a different size distribution for the case of contact-line elasticity, with an exponent compatible with tau=2-1/d+zeta to O(=2-d) . We discuss consequences for avalanches at depinning and for sandpile models, relations to Burgers turbulence and the possibility that the relation tau=tau_{zeta} be violated to higher loop order. Finally, we show that the avalanche-size distribution on a hyperplane of codimension one is in mean field (valid close to and above d=4 ) given by P(S) approximately K_{13}(S)S , where K is the Bessel- K function, thus tau_{hyperplane}=4/3 .

  9. A sign of the times: To have or to be? Social capital or social cohesion?

    PubMed

    Carrasco, Maria A; Bilal, Usama

    2016-06-01

    Among various social factors associated with health behavior and disease, social cohesion has not captured the imagination of public health researchers as much as social capital as evidenced by the subsuming of social cohesion into social capital and the numerous studies analyzing social capital and the comparatively fewer articles analyzing social cohesion and health. In this paper we provide a brief overview of the evolution of the conceptualization of social capital and social cohesion and we use philosopher Erich Fromm's distinction between "having" and "being" to understand the current research focus on capital over cohesion. We argue that social capital is related to having while social cohesion is related to being and that an emphasis on social capital leads to individualizing tendencies that are antithetical to cohesion. We provide examples drawn from the literature where this conflation of social capital and cohesion results in non-concordant definitions and subsequent operationalization of these constructs. Beyond semantics, the practical implication of focusing on "having" vs. "being" include an emphasis on understanding how to normalize groups and populations rather than providing those groups space for empowerment and agency leading to health.

  10. Effects of Group Size and Lack of Sphericity on the Recovery of Clusters in K-Means Cluster Analysis

    ERIC Educational Resources Information Center

    de Craen, Saskia; Commandeur, Jacques J. F.; Frank, Laurence E.; Heiser, Willem J.

    2006-01-01

    K-means cluster analysis is known for its tendency to produce spherical and equally sized clusters. To assess the magnitude of these effects, a simulation study was conducted, in which populations were created with varying departures from sphericity and group sizes. An analysis of the recovery of clusters in the samples taken from these…

  11. Elongational rheology and cohesive fracture of photo-oxidated LDPE

    SciTech Connect

    Rolón-Garrido, Víctor H. Wagner, Manfred H.

    2014-01-15

    It was found recently that low-density polyethylene (LDPE) samples with different degrees of photo-oxidation represent an interesting system to study the transition from ductile to cohesive fracture and the aspects of the cohesive rupture in elongational flow. Sheets of LDPE were subjected to photo-oxidation in the presence of air using a xenon lamp to irradiate the samples for times between 1 day and 6 weeks. Characterisation methods included Fourier transform infrared spectroscopy, solvent extraction method, and rheology in shear and uniaxial extensional flows. Linear viscoelasticity was increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by the carbonyl index, acid and aldehydes groups, and gel fraction. The molecular stress function model was used to quantify the experimental data, and the nonlinear model parameter β was found to be correlated with the gel content. The uniaxial data showed that the transition from ductile to cohesive fracture was shifted to lower elongational rates, the higher the gel content was. From 2 weeks photo-oxidation onwards, cohesive rupture occurred at every strain rate investigated. The true strain and true stress at cohesive fracture as well as the energy density applied to the sample up to fracture were analyzed. At low gel content, rupture was mainly determined by the melt fraction while at high gel content, rupture occurred predominantly in the gel structure. The strain at break was found to be independent of strain rate, contrary to the stress at break and the energy density. Thus, the true strain and not the stress at break or the energy density was found to be the relevant physical quantity to describe cohesive fracture behavior of photo-oxidated LDPE. The equilibrium modulus of the gel structures was correlated with the true strain at rupture. The stiffer the gel structure, the lower was the deformation tolerated before the sample breaks.

  12. Brain Size, IQ, and Racial-Group Differences: Evidence from Musculoskeletal Traits.

    ERIC Educational Resources Information Center

    Rushton, J. Philippe; Rushton, Elizabeth W.

    2003-01-01

    Correlated brain size differences with 37 musculoskeletal variables shown in evolutionary textbooks to change with brain size. Findings from a sample of more than 6,000 U.S. military personnel indicate that racial differences in brain size are securely established and are the most likely biological mediators of race differences in intelligence.…

  13. Developing the Noncentrality Parameter for Calculating Group Sample Sizes in Heterogeneous Analysis of Variance

    ERIC Educational Resources Information Center

    Luh, Wei-Ming; Guo, Jiin-Huarng

    2011-01-01

    Sample size determination is an important issue in planning research. In the context of one-way fixed-effect analysis of variance, the conventional sample size formula cannot be applied for the heterogeneous variance cases. This study discusses the sample size requirement for the Welch test in the one-way fixed-effect analysis of variance with…

  14. Evolving trends in size and structure of group dental practices in the United States.

    PubMed

    Guay, Albert H; Wall, Thomas P; Petersen, Bradford C; Lazar, Vickie F

    2012-08-01

    In this study, the authors examined recent trends in the growth of dental establishments and dental firms, including geographic location. In this article, they also present information about the demographic characteristics of dentists who work in a dental practice that is part of a larger company that delivers dental care in multiple locations. The number of dental establishments (single locations) and the average size of these establishments grew from 1992 to 2007. Large multi-unit dental firms grew in terms of number of establishments and the percentage of total receipts. Large multi-unit dental firms represent a small but growing segment of the dental market. Dentists less than thirty-five years old were most likely to work in a practice that was part of a larger company, and females were more likely than males to work in such a setting. The percentage of dentists working in these settings was also found to vary by region and state. The authors present a typology of dental group practice and suggest that future research should take into account the differences so that appropriate conclusions can be drawn and generalizations across categories are not made.

  15. Human Activity Dampens the Benefits of Group Size on Vigilance in Khulan (Equus hemionus) in Western China.

    PubMed

    Wang, Mu-Yang; Ruckstuhl, Kathreen E; Xu, Wen-Xuan; Blank, David; Yang, Wei-Kang

    2016-01-01

    Animals receive anti-predator benefits from social behavior. As part of a group, individuals spend less time being vigilant, and vigilance decreases with increasing group size. This phenomenon, called "the many-eyes effect", together with the "encounter dilution effect", is considered among the most important factors determining individual vigilance behavior. However, in addition to group size, other social and environmental factors also influence the degree of vigilance, including disturbance from human activities. In our study, we examined vigilance behavior of Khulans (Equus hemionus) in the Xinjiang Province in western China to test whether and how human disturbance and group size affect vigilance. According to our results, Khulan showed a negative correlation between group size and the percentage time spent vigilant, although this negative correlation depended on the groups' disturbance level. Khulan in the more disturbed area had a dampened benefit from increases in group size, compared to those in the undisturbed core areas. Provision of continuous areas of high-quality habitat for Khulans will allow them to form larger undisturbed aggregations and to gain foraging benefits through reduced individual vigilance, as well as anti-predator benefits through increased probability of predator detection.

  16. 3D model of radionuclide dispersion in coastal areas with multifraction cohesive and non-cohesive sediments

    NASA Astrophysics Data System (ADS)

    Brovchenko, Igor; Maderich, Vladimir; Jung, Kyung Tae

    2015-04-01

    We developed new radionuclide dispersion model that may be used in coastal areas, rivers and estuaries with non-uniform distribution of suspended and bed sediments both cohesive and non-cohesive types. Model describes radionuclides concentration in dissolved phase in water column, particulated phase on suspended sediments on each sediment class types, bed sediments and pore water. The transfer of activity between the water column and the pore water in the upper layer of the bottom sediment is governed by diffusion processes. The phase exchange between dissolved and particulate radionuclides is written in terms of desorption rate a12 (s-1) and distribution coefficient Kd,iw and Kd,ib (m3/kg) for water column and for bottom deposit, respectively. Following (Periáñez et al., 1996) the dependence of distribution coefficients is inversely proportional to the sediment particle size. For simulation of 3D circulation, turbulent diffusion and wave fields a hydrostatic model SELFE (Roland et. al. 2010) that solves Reynolds-stress averaged Navier-Stokes (RANS) equations and Wave Action transport equation on the unstructured grids was used. Simulation of suspended sediment concentration and bed sediments composition is based on (L. Pinto et. al., 2012) approach that originally was developed for non-cohesive sediments. In present study we modified this approach to include possibility of simulating mixture of cohesive and non-cohesive sediments by implementing parameterizations for erosion and deposition fluxes for cohesive sediments and by implementing flocculation model for determining settling velocity of cohesive flocs. Model of sediment transport was calibrated on measurements in the Yellow Sea which is shallow tidal basin with strongly non-uniform distribution of suspended and bed sediments. Model of radionuclide dispersion was verified on measurements of 137Cs concentration in surface water and bed sediments after Fukushima Daiichi nuclear accident. References Peri

  17. Dislocation shielding of a cohesive crack

    NASA Astrophysics Data System (ADS)

    Bhandakkar, Tanmay K.; Chng, Audrey C.; Curtin, W. A.; Gao, Huajian

    2010-04-01

    Dislocation interaction with a cohesive crack is of increasing importance to computational modelling of crack nucleation/growth and related toughening mechanisms in confined structures and under cyclic fatigue conditions. Here, dislocation shielding of a Dugdale cohesive crack described by a rectangular traction-separation law is studied. The shielding is completely characterized by three non-dimensional parameters representing the effective fracture toughness, the cohesive strength, and the distance between the dislocations and the crack tip. A closed form analytical solution shows that, while the classical singular crack model predicts that a dislocation can shield or anti-shield a crack depending on the sign of its Burgers vector, at low cohesive strengths a dislocation always shields the cohesive crack irrespective of the Burgers vector. A numerical study shows the transition in shielding from the classical solution of Lin and Thomson (1986) in the high strength limit to the solution in the low strength limit. An asymptotic analysis yields an approximate analytical model for the shielding over the full range of cohesive strengths. A discrete dislocation (DD) simulation of a large (>10 3) number of edge dislocations interacting with a cohesive crack described by a trapezoidal traction-separation law confirms the transition in shielding, showing that the cohesive crack does behave like a singular crack at very high cohesive strengths (˜7 GPa), but that significant deviations in shielding between singular and cohesive crack predictions arise at cohesive strengths around 1GPa, consistent with the analytic models. Both analytical and numerical studies indicate that an appropriate crack tip model is essential for accurately quantifying dislocation shielding for cohesive strengths in the GPa range.

  18. Reobservation of Close QSO Groups: The Size Evolution and Shape of Lyα Forest Absorbers

    NASA Astrophysics Data System (ADS)

    Crotts, Arlin P. S.; Fang, Yihu

    1998-07-01

    In order to study the size and shape of the absorbers that lie in front of the QSOs, in particular the Lyα forest, we present an analysis of 785 absorption lines in the spectra of five QSOs in close groupings: a pair (LB 9605: 1517+2357 at z = 1.834 and LB 9612: 1517+2356 at z = 1.903, with a separation of 102" between them) and a triplet (KP 76: 1623+2651A at z = 2.467, KP 77: 1623+2653 at z = 2.526, and KP 78: 1623+2651B at z = 2.605, with separations of 127", 147", and 177" between pairs 76:78, 76:77, and 77:78, respectively). Both of these QSO groups have been observed before, but these data represent a drastic increase in signal-to-noise ratio and/or wavelength coverage over earlier data and provide a qualitatively different view of the nature of the absorbers. The pair samples a scale critical in determining the size upper bound of Lyα absorbers, with significant leverage in redshift compared to previous studies. In the case of the triplet, this represents the spatially densest sample of Lyα forest absorbers ever studied and an almost ideally suited probe of the shape of absorbers. We observe a significant number of Lyα lines in common between the triplet sight lines, for lines stronger than rest equivalent width W0 > 0.4 Å (and no detected metal lines) and velocity differences up to 200 km s-1, corresponding to a two-point correlation function ξ=1.88+0.78-0.50 on scales of 0.5-0.8 h-1 Mpc with = 2.14 and inconsistent at the 99.999% level with the absence of any clustering. These data also show that a significant fraction of the W0 > 0.4 Å Lyα forest absorbers spans all three sight lines to the KP triplet, indicating that the strong-lined absorbers are consistent with nearly round shapes, chosen from a range of possible cylinders of different elongations. This may be inconsistent with results from hydrodynamic/gravitational simulations of H I in the early Universe, indicating that the theoretical counterparts of Lyα forest clouds are long and

  19. Effect of group size and maize silage dietary levels on behaviour, health, carcass and meat quality of Mediterranean buffaloes.

    PubMed

    Masucci, F; De Rosa, G; Barone, C M A; Napolitano, F; Grasso, F; Uzun, P; Di Francia, A

    2016-03-01

    The effects of different dietary levels of maize silage (10% v. 36% DM) and group size (7 v. 14 animals) were assessed on growth performance and in vivo digestibility of 28 male fattening buffaloes. In addition, the effects of diet on meat quality and group size on behaviour and immune response were separately evaluated. Animals were weighed and assigned to three groups. The high silage - low size group (HL) was fed a total mixed ration (TMR) containing 36% DM of maize silage and consisted of seven animals (age 12.7±2.6 months; BW 382.2±67.7 kg at the start of the study). The low silage - low size group (LL) was fed a TMR containing 10% DM of maize silage and consisted of seven animals (age 13.0±2.7 months; BW 389.4±72.3 kg). The high silage - high size group (HH) was fed the 36% maize silage DM diet and consisted of 14 animals (age 13.9±3.25 months; BW 416.5±73.9 kg). Total space allowance (3.2 indoor+3.2 outdoor m2/animal) was kept constant in the three groups, as well as the ratio of animals to drinkers (seven animals per water bowl) and the manger space (70 cm per animal). Growth performance, carcass characteristics and digestibility were influenced neither by dietary treatment nor by group size, even if the group fed 36% maize silage diet showed a higher fibre digestibility. No effect of diet was found on meat quality. Group size did not affect the behavioural activities with the exception of drinking (1.04±0.35% v. 2.60±0.35%; P<0.01 for groups HL and HH, respectively) and vigilance (2.58±0.46% v. 1.20±0.46%; P<0.05 for groups HL and HH, respectively). Immune responses were not affected by group size. PMID:26549768

  20. Effect of group size and maize silage dietary levels on behaviour, health, carcass and meat quality of Mediterranean buffaloes.

    PubMed

    Masucci, F; De Rosa, G; Barone, C M A; Napolitano, F; Grasso, F; Uzun, P; Di Francia, A

    2016-03-01

    The effects of different dietary levels of maize silage (10% v. 36% DM) and group size (7 v. 14 animals) were assessed on growth performance and in vivo digestibility of 28 male fattening buffaloes. In addition, the effects of diet on meat quality and group size on behaviour and immune response were separately evaluated. Animals were weighed and assigned to three groups. The high silage - low size group (HL) was fed a total mixed ration (TMR) containing 36% DM of maize silage and consisted of seven animals (age 12.7±2.6 months; BW 382.2±67.7 kg at the start of the study). The low silage - low size group (LL) was fed a TMR containing 10% DM of maize silage and consisted of seven animals (age 13.0±2.7 months; BW 389.4±72.3 kg). The high silage - high size group (HH) was fed the 36% maize silage DM diet and consisted of 14 animals (age 13.9±3.25 months; BW 416.5±73.9 kg). Total space allowance (3.2 indoor+3.2 outdoor m2/animal) was kept constant in the three groups, as well as the ratio of animals to drinkers (seven animals per water bowl) and the manger space (70 cm per animal). Growth performance, carcass characteristics and digestibility were influenced neither by dietary treatment nor by group size, even if the group fed 36% maize silage diet showed a higher fibre digestibility. No effect of diet was found on meat quality. Group size did not affect the behavioural activities with the exception of drinking (1.04±0.35% v. 2.60±0.35%; P<0.01 for groups HL and HH, respectively) and vigilance (2.58±0.46% v. 1.20±0.46%; P<0.05 for groups HL and HH, respectively). Immune responses were not affected by group size.

  1. Increases in New Social Network Ties are Associated with Increased Cohesion among Intervention Participants

    PubMed Central

    Gesell, Sabina B.; Barkin, Shari L.; Sommer, Evan C.; Thompson, Jessica R.; Valente, Thomas W.

    2016-01-01

    Objective Many behavior change programs are delivered in group settings to manage implementation costs and to foster support and interactions among group members to facilitate behavior change. Understanding the group dynamics that evolve in group settings (e.g., weight management, Alcoholics Anonymous) is important, yet rarely measured. This paper examined the relationship between social network ties and group cohesion in a group-based intervention to prevent obesity in children. Method The data reported are process measures from an ongoing community-based randomized controlled trial. 305 parents with a child (3-6 years) at risk of developing obesity were assigned to an intervention that taught parents healthy lifestyles. Parents met weekly for 12 weeks in small consistent groups. Two measures were collected at weeks 3 and 6: a social network survey (people in the group with whom one discusses healthy lifestyles); and the validated Perceived Cohesion Scale (Bollen & Hoyle, 1990). We used lagged random and fixed effects regression models to analyze the data. Results Cohesion increased from 6.51 to 6.71 (t=4.4, p<0.01). Network nominations tended to increase over the 3-week period in each network. In the combined discussion and advice network, the number of nominations increased from 1.76 to 1.95 (z=2.59, p<0.01). Cohesion at week 3 was the strongest predictor of cohesion at week 6 (b=0.55, p<0.01). Number of new network nominations at week 6 was positively related to cohesion at week 6 (b=0.06, p<.01). In sum, being able to name new network contacts was associated with feelings of cohesion. Conclusion This is the first study to demonstrate how network changes affect perceived group cohesion within a behavioral intervention. Given that many behavioral interventions occur in group settings, intentionally building new social networks could be promising to augment desired outcomes. PMID:26286298

  2. Human Activity Dampens the Benefits of Group Size on Vigilance in Khulan (Equus hemionus) in Western China

    PubMed Central

    Wang, Mu-Yang; Ruckstuhl, Kathreen E.; Xu, Wen-Xuan; Blank, David; Yang, Wei-Kang

    2016-01-01

    Animals receive anti-predator benefits from social behavior. As part of a group, individuals spend less time being vigilant, and vigilance decreases with increasing group size. This phenomenon, called “the many-eyes effect”, together with the “encounter dilution effect”, is considered among the most important factors determining individual vigilance behavior. However, in addition to group size, other social and environmental factors also influence the degree of vigilance, including disturbance from human activities. In our study, we examined vigilance behavior of Khulans (Equus hemionus) in the Xinjiang Province in western China to test whether and how human disturbance and group size affect vigilance. According to our results, Khulan showed a negative correlation between group size and the percentage time spent vigilant, although this negative correlation depended on the groups’ disturbance level. Khulan in the more disturbed area had a dampened benefit from increases in group size, compared to those in the undisturbed core areas. Provision of continuous areas of high-quality habitat for Khulans will allow them to form larger undisturbed aggregations and to gain foraging benefits through reduced individual vigilance, as well as anti-predator benefits through increased probability of predator detection. PMID:26756993

  3. Coagulation of particles in Saturn's rings - Measurements of the cohesive force of water frost

    NASA Technical Reports Server (NTRS)

    Hatzes, A. P.; Bridges, F.; Lin, D. N. C.; Sachtjen, S.

    1991-01-01

    Experimental data are presented on the sticking force of water ice particles which are indicative of the role that the cohesive properties of such particles could play in the dynamics of Saturn ring particles. Sticking forces are dependent on particle impact velocities; a 'Velcro' model is devised to describe the surface structure involved in sticking. The data indicate that below the critical impact velocity of about 0.03 cm/sec, particle cohesion always occurs. Due to the optical depth of micron-sized grains in the Saturn rings, particles are hypothesized to be coated with a layer of frost which will render cohesion an important ring-dynamics process.

  4. Coagulation of particles in Saturn's rings - Measurements of the cohesive force of water frost

    SciTech Connect

    Hatzes, A.P.; Bridges, F.; Lin, D.N.C.; Sachtjen, S. McDonald Observatory, Austin, TX )

    1991-01-01

    Experimental data are presented on the sticking force of water ice particles which are indicative of the role that the cohesive properties of such particles could play in the dynamics of Saturn ring particles. Sticking forces are dependent on particle impact velocities; a Velcro model is devised to describe the surface structure involved in sticking. The data indicate that below the critical impact velocity of about 0.03 cm/sec, particle cohesion always occurs. Due to the optical depth of micron-sized grains in the Saturn rings, particles are hypothesized to be coated with a layer of frost which will render cohesion an important ring-dynamics process. 14 refs.

  5. [Experimental test of the ideal free distribution in humans: the effects of reinforcer magnitude and group size].

    PubMed

    Yamaguchi, Tetsuo; Ito, Masato

    2006-02-01

    The ideal free distribution (IFD) theory describes how animals living in the wild distribute themselves between two different resource sites. The IFD theory predicts that the ratio of animals in the two resource sites is equal to the ratio of resources available in those sites. The present study investigated the effects of absolute reinforcer magnitude and group size on the distribution of humans between two resource sites. Two groups of undergraduate students (N = 10 and N = 20) chose blue or red cards to earn points. The ratio of points assigned to each color varied from 1 : 1 to 4 : 1 across five conditions. In each condition, absolute reinforcer magnitude was varied. The generalized ideal free distribution equation was fit to the data obtained under the different magnitude and group size conditions. These results suggest that larger absolute reinforcer magnitude and smaller group size produce higher sensitivity to resource distribution.

  6. Relationship between the cohesion of guest particles on the flow behaviour of interactive mixtures.

    PubMed

    Mangal, Sharad; Gengenbach, Thomas; Millington-Smith, Doug; Armstrong, Brian; Morton, David A V; Larson, Ian

    2016-05-01

    In this study, we aimed to investigate the effects cohesion of small surface-engineered guest binder particles on the flow behaviour of interactive mixtures. Polyvinylpyrrolidone (PVP) - a model pharmaceutical binder - was spray-dried with varying l-leucine feed concentrations to create small surface-engineered binder particles with varying cohesion. These spray-dried formulations were characterised by their particle size distribution, morphology and cohesion. Interactive mixtures were produced by blending these spray-dried formulations with paracetamol. The resultant blends were visualised under scanning electron microscope to confirm formation of interactive mixtures. Surface coverage of paracetamol by guest particles as well as the flow behaviour of these mixtures were examined. The flow performance of interactive mixtures was evaluated using measurements of conditioned bulk density, basic flowability energy, aeration energy and compressibility. With higher feed l-leucine concentrations, the surface roughness of small binder particles increased, while their cohesion decreased. Visual inspection of the SEM images of the blends indicated that the guest particles adhered to the surface of paracetamol resulting in effective formation of interactive mixtures. These images also showed that the low-cohesion guest particles were better de-agglomerated that consequently formed a more homogeneous interactive mixture with paracetamol compared with high-cohesion formulations. The flow performance of interactive mixtures changed as a function of the cohesion of the guest particles. Interactive mixtures with low-cohesion guest binder particles showed notably improved bulk flow performance compared with those containing high-cohesion guest binder particles. Thus, our study suggests that the cohesion of guest particles dictates the flow performance of interactive mixtures.

  7. A Note on Testing for Homogeneity Among Effect Sizes Sharing a Common Control Group

    ERIC Educational Resources Information Center

    Cook, Samantha R.

    2004-01-01

    L. V. Hedges and I. Olkin (1985) presented a statistic to test for homogeneity among correlated effect sizes and L. J. Gleser and I. Olkin (1994) presented a large-sample approximation to the covariance matrix of the correlated effect sizes. This article presents a more exact expression for this covariance matrix, assuming normally distributed…

  8. Strong adhesion and cohesion of chitosan in aqueous solutions

    PubMed Central

    Lee, Dong Woog; Lim, Chanoong; Israelachvili, Jacob N.; Hwang, Dong Soo

    2014-01-01

    Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0–8.5), achieving a maximum value at pH 3.0 after a contact time of 1 hr (Wad ~6.4 mJ/m2). We also found weak or no cohesion between two opposing chitosan layers on mica in aqueous buffer until the critical contact time for maximum adhesion (chitosan-mica) was reached. Strong cohesion (Wco ~8.5 mJ/m2) between the films was measured with increasing contact times up to 1 hr at pH 3.0, which is equivalent to ~60% of the strongest, previously reported, mussel underwater adhesion. Such time-dependent adhesion properties are most likely related to molecular or molecular group reorientations and interdigitations. At high pH (8.5), the solubility of chitosan changes drastically, causing the chitosan-chitosan (cohesion) interaction to be repulsive at all separation distances and contact times. The strong contact time and pH-dependent chitosan-chitosan cohesion and adhesion properties provide new insight into the development of chitosan based load-bearing materials. PMID:24138057

  9. The Role of Context-Specific Norms and Group Size in Alcohol Consumption and Compliance Drinking During Natural Drinking Events

    PubMed Central

    Cullum, Jerry; O’Grady, Megan; Armeli, Stephen; Tennen, Howard

    2016-01-01

    Using experience sampling methods we examined how group size and context-specific drinking norms corresponded to alcohol consumption and compliance with drinking offers during natural social drinking events. For 30 days, 397 college students reported daily on their alcohol consumption during social events, the size of the group they were with, the average alcohol consumption of its’ members, and the number of drinks they accepted that came directly from the group they were with during these social drinking events. Larger groups corresponded with greater alcohol consumption, but only when context-specific norms were high. Furthermore, larger groups increased compliance with drinking offers when context-specific norms were high, but decreased compliance with drinking offers when context-specific norms were low. Thus, subtle features of the social-context may influence not only overall consumption behavior, but also compliance with more overt forms of social influence. PMID:27536009

  10. Cohesive Writing: Why Concept Is Not Enough.

    ERIC Educational Resources Information Center

    Jago, Carol

    To write cohesively means doing many things at once--wrestling with ideas, balancing form and function, pushing words this way and that, attending to syntax and diction, and employing imagery and metaphor until a coherent message emerges. Though full of promise, student writing typically lacks cohesion, and the question is whether the fault lies…

  11. Networks, space, and residents' perception of cohesion.

    PubMed

    Boessen, Adam; Hipp, John R; Smith, Emily J; Butts, Carter T; Nagle, Nicholas N; Almquist, Zack

    2014-06-01

    Community scholars increasingly focus on the linkage between residents' sense of cohesion with the neighborhood and their own social networks in the neighborhood. A challenge is that whereas some research only focuses on residents' social ties with fellow neighbors, such an approach misses out on the larger constellation of individuals' relationships and the spatial distribution of those relationships. Using data from the Twin Communities Network Study, the current project is one of the first studies to examine the actual spatial distribution of respondents' networks for a variety of relationships and the consequences of these for neighborhood and city cohesion. We also examine how a perceived structural measure of cohesion-triangle degree-impacts their perceptions of neighborhood and city cohesion. Our findings suggest that perceptions of cohesion within the neighborhood and the city depend on the number of neighborhood safety contacts as well as on the types of people with which they discuss important matters. On the other hand, kin and social friendship ties do not impact cohesion. A key finding is that residents who report more spatially dispersed networks for certain types of ties report lower levels of neighborhood and city cohesion. Residents with higher triangle degree within their neighborhood safety networks perceived more neighborhood cohesion.

  12. Effect of Parasitoid: Host Ratio and Group Size on Fitness of Spathius galinae (Hymenoptera: Braconidae): Implications for Mass-Rearing.

    PubMed

    Watt, Timothy J; Duan, Jian J; Tallamy, Douglas W; Hough-Goldstein, Judith

    2015-06-01

    Producing insect natural enemies in laboratories or insectaries for biological pest control is often expensive, and developing cost-effective rearing techniques is a goal of many biological control programs. Spathius galinae Belokobylskij and Strazenac (Hymenoptera: Braconidae), a newly described ectoparasitoid of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is currently being evaluated for environmental introduction in the United States to provide biological control of this invasive pest. To improve mass-rearing outcomes for S. galinae, we investigated the effects of parasitoid: host ratio and parasitoid and host group size (density) on parasitoid fitness. Our results showed that when 1 emerald ash borer larva was exposed to 1, 2, 4, or 8 female parasitoids, parasitism rate was positively associated with increasing parasitoid: host ratio, while brood size, sex ratio, and fitness estimates of progeny were not affected. When a constant 1:1 parasitoid: host ratio was used, but group size varied from 1 female parasitoid and 1 host, 5 parasitoids and 5 hosts, 10 of each, and 20 of each in same size rearing cages, parasitism rates were highest when at least 5 females were exposed to 5 host larvae. Moreover, the number of progeny produced per female parasitoid was greatest when group size was 10 parasitoids and 10 hosts. These findings demonstrate that S. galinae may be reared most efficiently in moderately high-density groups (10 parasitoids and hosts) and with a 1:1 parasitoid: host ratio. PMID:26470215

  13. Population sizes and group characteristics of Siberian Crane (Leucogeranus leucogeranus) and Hooded Crane (Grus monacha) in Poyang Lake Wetland

    PubMed Central

    SHAO, Ming-Qin; GUO, Hong; JIANG, Jian-Hong

    2014-01-01

    Both the Siberian Crane (Leucogeranus leucogeranus) and Hooded Crane (Grus monacha) have limited population sizes and are considered endangered by domestic Chinese and international agencies. To document the current size of their respective populations and characterize their groups, between October 2012 and April 2013 we undertook fieldwork at four nature reserve areas within the Poyang Lake wetlands. We divided Poyanghu National Nature Reserve (PYH) into the Wucheng (PWC) and Hengfeng areas (PHF), because each are each located in different counties. Our fieldwork showed that the Siberian Crane occurred mainly in PYH (364 in the PHF, 158 in the PWC) and the Nanjishan Wetland National Nature Reserve (NJS, with 200 individuals). The Hooded Crane was mainly distributed in PYH (302 in the PHF and 154 in the PWC). Family groups accounted for more than 50% of the total number of groups among both species, with Hooded Cranes forming more family groups than Siberian Cranes. Typically, these groups were formed of two adults with one offspring (Siberian Crane), and two adults with two offspring (Hooded Crane), with the mean family group size of the Siberian Crane and Hooded Crane being respectively 2.65±0.53 (n=43) and 3.09±0.86 (n=47) individuals per group. The mean collective group size of the Siberian Crane and Hooded Crane included 28.09±24.94 (n=23) and 28.94±27.97 (n=16) individuals per group, respectively, with the proportion of juveniles among Hooded Cranes being more than double that seen among the Siberian Cranes. PMID:25297076

  14. Influence of prey dispersion on territory and group size of African lions: a test of the resource dispersion hypothesis.

    PubMed

    Valeix, Marion; Loveridge, Andrew J; MacDonald, David W

    2012-11-01

    Empirical tests of the resource dispersion hypothesis (RDH), a theory to explain group living based on resource heterogeneity, have been complicated by the fact that resource patch dispersion and richness have proved difficult to define and measure in natural systems. Here, we studied the ecology of African lions Panthera leo in Hwange National Park, Zimbabwe, where waterholes are prey hotspots, and where dispersion of water sources and abundance of prey at these water sources are quantifiable. We combined a 10-year data set from GPS-collared lions for which information of group composition was available concurrently with data for herbivore abundance at waterholes. The distance between two neighboring waterholes was a strong determinant of lion home range size, which provides strong support for the RDH prediction that territory size increases as resource patches are more dispersed in the landscape. The mean number of herbivore herds using a waterhole, a good proxy of patch richness, determined the maximum lion group biomass an area can support. This finding suggests that patch richness sets a maximum ceiling on lion group size. This study demonstrates that landscape ecology is a major driver of ranging behavior and suggests that aspects of resource dispersion limit group sizes.

  15. Reciprocal Relations Between Student-Teacher Relationship and Children's Behavioral Problems: Moderation by Child-Care Group Size.

    PubMed

    Skalická, Věra; Belsky, Jay; Stenseng, Frode; Wichstrøm, Lars

    2015-01-01

    In this Norwegian study, bidirectional relations between children's behavior problems and child-teacher conflict and closeness were examined, and the possibility of moderation of these associations by child-care group size was tested. Eight hundred and nineteen 4-year-old children were followed up in first grade. Results revealed reciprocal effects linking child-teacher conflict and behavior problems. Effects of child-teacher closeness on later behavior problems were moderated by group size: For children in small groups only (i.e., ≤ 15 children), greater closeness predicted reduced behavior problems in first grade. In consequence, stability of behavior problems was greater in larger than in smaller groups. Results are discussed in light of regulatory mechanisms and social learning theory, with possible implications for organization of child care.

  16. Reciprocal Relations Between Student-Teacher Relationship and Children's Behavioral Problems: Moderation by Child-Care Group Size.

    PubMed

    Skalická, Věra; Belsky, Jay; Stenseng, Frode; Wichstrøm, Lars

    2015-01-01

    In this Norwegian study, bidirectional relations between children's behavior problems and child-teacher conflict and closeness were examined, and the possibility of moderation of these associations by child-care group size was tested. Eight hundred and nineteen 4-year-old children were followed up in first grade. Results revealed reciprocal effects linking child-teacher conflict and behavior problems. Effects of child-teacher closeness on later behavior problems were moderated by group size: For children in small groups only (i.e., ≤ 15 children), greater closeness predicted reduced behavior problems in first grade. In consequence, stability of behavior problems was greater in larger than in smaller groups. Results are discussed in light of regulatory mechanisms and social learning theory, with possible implications for organization of child care. PMID:26248001

  17. A behavioural Bayes approach to the determination of sample size for clinical trials considering efficacy and safety: imbalanced sample size in treatment groups.

    PubMed

    Kikuchi, Takashi; Gittins, John

    2011-08-01

    The behavioural Bayes approach to sample size determination for clinical trials assumes that the number of subsequent patients switching to a new drug from the current drug depends on the strength of the evidence for efficacy and safety that was observed in the clinical trials. The optimal sample size is the one which maximises the expected net benefit of the trial. The approach has been developed in a series of papers by Pezeshk and the present authors (Gittins JC, Pezeshk H. A behavioral Bayes method for determining the size of a clinical trial. Drug Information Journal 2000; 34: 355-63; Gittins JC, Pezeshk H. How Large should a clinical trial be? The Statistician 2000; 49(2): 177-87; Gittins JC, Pezeshk H. A decision theoretic approach to sample size determination in clinical trials. Journal of Biopharmaceutical Statistics 2002; 12(4): 535-51; Gittins JC, Pezeshk H. A fully Bayesian approach to calculating sample sizes for clinical trials with binary responses. Drug Information Journal 2002; 36: 143-50; Kikuchi T, Pezeshk H, Gittins J. A Bayesian cost-benefit approach to the determination of sample size in clinical trials. Statistics in Medicine 2008; 27(1): 68-82; Kikuchi T, Gittins J. A behavioral Bayes method to determine the sample size of a clinical trial considering efficacy and safety. Statistics in Medicine 2009; 28(18): 2293-306; Kikuchi T, Gittins J. A Bayesian procedure for cost-benefit evaluation of a new drug in multi-national clinical trials. Statistics in Medicine 2009 (Submitted)). The purpose of this article is to provide a rationale for experimental designs which allocate more patients to the new treatment than to the control group. The model uses a logistic weight function, including an interaction term linking efficacy and safety, which determines the number of patients choosing the new drug, and hence the resulting benefit. A Monte Carlo simulation is employed for the calculation. Having a larger group of patients on the new drug in general

  18. The Relative Effects of Group Size on Reading Progress of Older Students with Reading Difficulties

    ERIC Educational Resources Information Center

    Vaughn, Sharon; Wanzek, Jeanne; Wexler, Jade; Barth, Amy; Cirino, Paul T.; Fletcher, Jack; Romain, Melissa; Denton, Carolyn A.; Roberts, Greg; Francis, David

    2010-01-01

    This study reports findings on the relative effects from a yearlong secondary intervention contrasting large-group, small-group, and school-provided interventions emphasizing word study, vocabulary development, fluency, and comprehension with seventh- and eighth-graders with reading difficulties. Findings indicate that few statistically…

  19. The effects of group size on aggression when mixing unacquainted sows in outdoor paddocks

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aggression is a challenge when pigs are kept in groups. Sows fight at mixing when space is limited but this project sought to determine the amount and type of aggression observed when unacquainted Berkshire sows were mixed in pairs or in two established sub-groups of three in outdoor paddocks. Treat...

  20. Defensive responses by a social caterpillar are tailored to different predators and change with larval instar and group size

    NASA Astrophysics Data System (ADS)

    McClure, Melanie; Despland, Emma

    2011-05-01

    Gregariousness in animals is widely accepted as a behavioral adaptation for protection from predation. However, predation risk and the effectiveness of a prey's defense can be a function of several other factors, including predator species and prey size or age. The objective of this study was to determine if the gregarious habit of Malacosoma disstria caterpillars is advantageous against invertebrate natural enemies, and whether it is through dilution or cooperative defenses. We also examined the effects of larval growth and group size on the rate and success of attacks. Caterpillars of M. disstria responded with predator-specific behaviors, which led to increased survival. Evasive behaviors were used against stinkbugs, while thrashing by fourth instar caterpillars and holding on to the silk mat by second instar caterpillars was most efficient against spider attacks. Collective head flicking and biting by groups of both second and fourth instar caterpillars were observed when attacked by parasitoids. Increased larval size decreased the average number of attacks by spiders but increased the number of attacks by both stinkbugs and parasitoids. However, increased body size decreased the success rate of attacks by all three natural enemies and increased handling time for both predators. Larger group sizes did not influence the number of attacks from predators but increased the number of attacks and the number of successful attacks from parasitoids. In all cases, individual risk was lower in larger groups. Caterpillars showed collective defenses against parasitoids but not against the walking predators. These results show that caterpillars use different tactics against different natural enemies. Overall, these tactics are both more diverse and more effective in fourth instar than in second instar caterpillars, confirming that growth reduces predation risk. We also show that grouping benefits caterpillars through dilution of risk, and, in the case of parasitoids, through

  1. Defensive responses by a social caterpillar are tailored to different predators and change with larval instar and group size.

    PubMed

    McClure, Melanie; Despland, Emma

    2011-05-01

    Gregariousness in animals is widely accepted as a behavioral adaptation for protection from predation. However, predation risk and the effectiveness of a prey's defense can be a function of several other factors, including predator species and prey size or age. The objective of this study was to determine if the gregarious habit of Malacosoma disstria caterpillars is advantageous against invertebrate natural enemies, and whether it is through dilution or cooperative defenses. We also examined the effects of larval growth and group size on the rate and success of attacks. Caterpillars of M. disstria responded with predator-specific behaviors, which led to increased survival. Evasive behaviors were used against stinkbugs, while thrashing by fourth instar caterpillars and holding on to the silk mat by second instar caterpillars was most efficient against spider attacks. Collective head flicking and biting by groups of both second and fourth instar caterpillars were observed when attacked by parasitoids. Increased larval size decreased the average number of attacks by spiders but increased the number of attacks by both stinkbugs and parasitoids. However, increased body size decreased the success rate of attacks by all three natural enemies and increased handling time for both predators. Larger group sizes did not influence the number of attacks from predators but increased the number of attacks and the number of successful attacks from parasitoids. In all cases, individual risk was lower in larger groups. Caterpillars showed collective defenses against parasitoids but not against the walking predators. These results show that caterpillars use different tactics against different natural enemies. Overall, these tactics are both more diverse and more effective in fourth instar than in second instar caterpillars, confirming that growth reduces predation risk. We also show that grouping benefits caterpillars through dilution of risk, and, in the case of parasitoids, through

  2. A Note on Confidence Intervals for Two-Group Latent Mean Effect Size Measures

    ERIC Educational Resources Information Center

    Choi, Jaehwa; Fan, Weihua; Hancock, Gregory R.

    2009-01-01

    This note suggests delta method implementations for deriving confidence intervals for a latent mean effect size measure for the case of 2 independent populations. A hypothetical kindergarten reading example using these implementations is provided, as is supporting LISREL syntax. (Contains 1 table.)

  3. When to use social information: the advantage of large group size in individual decision making.

    PubMed

    King, Andrew J; Cowlishaw, Guy

    2007-04-22

    Correct decision making is crucial for animals to maximize foraging success and minimize predation risk. Group-living animals can make such decisions by using their own personal information or by pooling information with other group members (i.e. social information). Here, we investigate how individuals might best balance their use of personal and social information. We use a simple modelling approach in which individual decisions based upon social information are more likely to be correct when more individuals are involved and their personal information is more accurate. Our model predicts that when the personal information of group members is poor (accurate less than half the time), individuals should avoid pooling information. In contrast, when personal information is reliable (accurate at least half the time), individuals should use personal information less often and social information more often, and this effect should grow stronger in larger groups. One implication of this pattern is that social information allows less well-informed members of large groups to reach a correct decision with the same probability as more well-informed members of small groups. Thus, animals in larger groups may be able to minimize the costs of collecting personal information without impairing their ability to make correct decisions.

  4. Group size modifies the patterns and muscle carbohydrate effects of aggression in Betta splendens.

    PubMed

    Haller, J

    1992-08-01

    Aggressive encounters of previously isolated individuals were investigated in dyads and groups of five. Fights were longer and more intense when they were performed in dyads compared to fights involving five fishes. During aggressive encounters, an elevation in carbohydrate catabolism was noticed in both dyads and groups. Losing a fight resulted in a reduction in glycogen content and an increase in glycogen synthesis. Similar changes in winners did not appear; thus, the metabolic response in losers was different from that noticed in winners, both in dyads and groups. In dyadic contest winners, a marked increase in the free glucose content and glucose consumption was noticed (without changes in losers). In groups, free glucose content of the winners was not modified, while glucose consumption was enhanced both in winners and losers. Thus, the differences existing between winners and losers were greater in dyads compared to those noticed in groups. The energy cost of aggression seems to be different in dyads compared to groups of five. The rate of glucose oxidation was strongly reduced in dyads (there were no differences between winners and losers in this respect), while in groups, this parameter was not modified.

  5. Group size modifies the patterns and muscle carbohydrate effects of aggression in Betta splendens.

    PubMed

    Haller, J

    1992-08-01

    Aggressive encounters of previously isolated individuals were investigated in dyads and groups of five. Fights were longer and more intense when they were performed in dyads compared to fights involving five fishes. During aggressive encounters, an elevation in carbohydrate catabolism was noticed in both dyads and groups. Losing a fight resulted in a reduction in glycogen content and an increase in glycogen synthesis. Similar changes in winners did not appear; thus, the metabolic response in losers was different from that noticed in winners, both in dyads and groups. In dyadic contest winners, a marked increase in the free glucose content and glucose consumption was noticed (without changes in losers). In groups, free glucose content of the winners was not modified, while glucose consumption was enhanced both in winners and losers. Thus, the differences existing between winners and losers were greater in dyads compared to those noticed in groups. The energy cost of aggression seems to be different in dyads compared to groups of five. The rate of glucose oxidation was strongly reduced in dyads (there were no differences between winners and losers in this respect), while in groups, this parameter was not modified. PMID:1523255

  6. Effects of Violations of Data Set Assumptions When Using the Analysis of Variance and Covariance with Unequal Group Sizes.

    ERIC Educational Resources Information Center

    Johnson, Colleen Cook; Rakow, Ernest A.

    This research explored the degree to which group sizes can differ before the robustness of analysis of variance (ANOVA) and analysis of covariance (ANCOVA) are jeopardized. Monte Carlo methodology was used, allowing for the experimental investigation of potential threats to robustness under conditions common to researchers in education. The…

  7. Comparisons of Improvement-Over-Chance Effect Sizes for Two Groups under Variance Heterogeneity and Prior Probabilities

    ERIC Educational Resources Information Center

    Henson, Robin K.; Natesan, Prathiba; Axelson, Erika D.

    2014-01-01

    The authors examined the distributional properties of 3 improvement-over-chance, I, effect sizes each derived from linear and quadratic predictive discriminant analysis and from logistic regression analysis for the 2-group univariate classification. These 3 classification methods (3 levels) were studied under varying levels of data conditions,…

  8. Attitudes, Behaviors, and Effectiveness of Black and White Leaders of Simulated Problem Solving Groups of Varying Size and Racial Composition.

    ERIC Educational Resources Information Center

    Hill, Walter A.; Allen, William R.

    A field experiment was used to investigate the effects, if any, of changing group size and racial composition on the attitudes, behaviors, and effectiveness of black and white leaders. Subjects were 288 naval recruits, half black and half white, performing two tasks which were watched by a pair of racially mixed observers through a one-way mirror.…

  9. The Effect of Computer-Assisted Cooperative Learning Methods and Group Size on the EFL Learners' Achievement in Communication Skills

    ERIC Educational Resources Information Center

    AbuSeileek, Ali Farhan

    2012-01-01

    This study explored the effect of cooperative learning small group size and two different instructional modes (positive interdependence vs. individual accountability) on English as a Foreign Language (EFL) undergraduate learners' communication skills (speaking and writing) achievement in computer-based environments. The study also examined the…

  10. Reciprocal Relations between Student-Teacher Relationship and Children's Behavioral Problems: Moderation by Child-Care Group Size

    ERIC Educational Resources Information Center

    Skalická, Vera; Belsky, Jay; Stenseng, Frode; Wichstrøm, Lars

    2015-01-01

    In this Norwegian study, bidirectional relations between children's behavior problems and child-teacher conflict and closeness were examined, and the possibility of moderation of these associations by child-care group size was tested. Eight hundred and nineteen 4-year-old children were followed up in first grade. Results revealed reciprocal…

  11. Effect of Teacher Structure, Teacher Affect, Cognitive Level of Questions, Group Size and Student Social Status on Reading Achievement.

    ERIC Educational Resources Information Center

    Creamer, Mary; Lorentz, Jeffrey L.

    The effects of student socioeconomic status (SES) and four teacher behaviors--teacher structure, teacher affect, cognitive level of questions, and group size--on student reading achievement were analyzed. Subjects were 36 fifth and sixth grade classroom teachers and their 820 students. Data were collected with the Reading Comprehension Subtest…

  12. Mixing behaviour of cohesive and non-cohesive particle mixtures in a ribbon mixer

    NASA Astrophysics Data System (ADS)

    Musha, H.; Dong, K.; Chandratilleke, G. R.; Bridgwater, J.; Yu, A. B.

    2013-06-01

    Ribbon mixers are used in a wide range of applications involving pharmaceuticals, ceramics and cosmetics, to name a few. Here, the discrete element method is used to investigate the effect of impeller speed on the mixing behaviours of cohesive as well as non-cohesive particle mixtures in a ribbon mixer, which has a horizontal cylindrical vessel. The mixing behaviours are characterized by particle-scale and macroscopic mixing indexes. Simulations show that the mixing rate increases with the impeller speed for both the cohesive and non-cohesive mixtures up to a certain speed, beyond which it showed a reduction. There is a possibility that the mixture quality becomes poorer at higher impeller speeds for the non-cohesive particles, but it was not the case with the cohesive particles. Inspection of velocity fields shows that many local recirculation regions exist in the case of non-cohesive particle mixing, preventing the overall mixing. By contrast, in the case of the cohesive mixture, there exists a circumferential motion about the shaft and a convective motion in the horizontal axial direction, improving the particle mixing. Force analyses are also carried out, which show that the particle contact forces increase with the impeller speed for non-cohesive particles, but in the case of cohesive particles, they increase initially with the impeller speed, and then show a reduction after a certain speed. The results will be useful in selecting operation conditions of a ribbon mixer.

  13. The effects of forage provision and group size on the behavior of calves.

    PubMed

    Phillips, C J C

    2004-05-01

    The effects of providing alternative forages to individual or group-reared calves on their behavior were examined in 2 experiments. In experiment 1, 24 calves were reared in groups of 3 or individually in straw-bedded pens from age 1 to 7 wk. One-half of the calves in each treatment were provided with ad libitum cut perennial ryegrass herbage. Grass intakes and time spent eating grass were greater for grouped calves than for individual calves. Providing grass reduced concentrate intake of grouped calves and reduced the time that all calves, but particularly individual calves, spent eating straw bedding. Ruminating time was increased by offering grass to grouped calves compared with individual calves. Grass reduced the frequency of calves licking their buckets and their pen, vocalizing, and investigating their pen. Particularly for grouped calves provision of grass reduced all grooming. Group rearing reduced the frequency of calves licking their bucket, vocalizing, and investigating their pen, but had no effect on the frequency of pen licking. Calves were weaned at wk 7 and transferred to indoor silage feeding or grazing. Most effects of group rearing and grass provision were not maintained after weaning, but calves that had received grass ate for longer periods when turned out to pasture. In experiment 2, 72 calves were offered a mixture of straw, molasses, and pot ale syrup or grass hay. Calves offered the straw mixture ate more forage and concentrates and grew faster than calves offered hay. It was concluded that nontraditional forages, such as fresh grass and straw mixtures, could benefit the behavior and growth of calves compared with hay and straw.

  14. Do Neighborhood Socioeconomic Deprivation and Low Social Cohesion Predict Coronary Calcification?

    PubMed Central

    Kim, Daniel; Diez Roux, Ana V.; Kiefe, Catarina I.; Kawachi, Ichiro; Liu, Kiang

    2010-01-01

    Growing evidence suggests that neighborhood characteristics may influence the risk of coronary heart disease. No studies have yet explored associations of neighborhood attributes with subclinical atherosclerosis in younger adult populations. Using data on 2,974 adults (1,699 women, 1,275 men) aged 32–50 years in 2000 from the Coronary Artery Disease Risk Development in Young Adults (CARDIA) Study and 2000 US Census block-group-level data, the authors estimated multivariable-adjusted associations of neighborhood socioeconomic deprivation and perceived neighborhood cohesion with odds of coronary artery calcification (CAC) 5 years later. Among women, the quartiles of highest neighborhood deprivation and lowest cohesion were associated with higher odds of CAC after adjustment for individual-level demographic and socioeconomic factors (for deprivation, odds ratio = 2.49, 95% confidence interval: 1.22, 5.08 (P for trend = 0.03); for cohesion, odds ratio = 1.87, 95% confidence interval: 1.10, 3.16 (P for trend = 0.02)). Associations changed only slightly after adjustment for behavioral, psychosocial, and biologic factors. Among men, neither neighborhood deprivation nor cohesion was related to CAC. However, among men in deprived neighborhoods, low cohesion predicted higher CAC odds (for interaction between neighborhood deprivation and cohesion, P = 0.03). This study provides evidence on associations of neighborhood deprivation and cohesion with CAC in younger, asymptomatic adults. Neighborhood attributes may contribute to subclinical atherosclerosis. PMID:20610467

  15. New Analysis Techniques for Avalanches in a Conical Bead Pile with Cohesion

    NASA Astrophysics Data System (ADS)

    Tieman, Catherine; Lehman, Susan

    2015-03-01

    Avalanche statistics and pile geometry for 3 mm steel spheres dropped on a conical bead pile were studied at different drop heights and different cohesion strengths. The pile is initially built on a circular base and is subsequently slowly driven by adding one bead at a time to the apex of the pile. We investigate the dynamic response of the pile by recording avalanches off the pile over the course of tens of thousands of bead drops. The level of cohesion is tuned through use of an applied uniform magnetic field. Changes in the pile mass and geometry were investigated to determine the effect of cohesion and drop height on the angle of repose. The angle of repose increased with cohesion strength, and decreased somewhat for higher drop heights. The packing density of beads is expected to decrease as magnetic cohesion increases, but for our 20 000-bead pile, this effect has not been observed. The proportion of beads removed from the pile by different avalanche sizes was also calculated. Although larger avalanches are much rarer occurrences, they carry away a larger fraction of the total avalanched mass than small avalanches. As the pile cohesion increases, the number of small and medium avalanches decreases so that this mass loss distribution shifts more strongly to large sizes.

  16. Cohesion, granular solids, granular liquids, and their connection to small near-Earth objects

    NASA Astrophysics Data System (ADS)

    Sánchez, P.; Scheeres, D.

    2014-07-01

    form a matrix of sorts that holds the bigger boulders together. The aggregates were slowly spun up to disruption controlling for angle of friction, cohesion and global shape. Systems with no frictional forces had θ≈ 12° and are in effect granular liquids in the best case scenario. Systems with only surface-surface friction had θ≈ 25°, which is typical in laboratory experiments with spherical glass beads. Systems that also implemented rolling friction had θ≈ 35°, which is typical of non-cohesive granular media on the Earth. How much each aggregate deformed before disruption was directly related to the angle of friction. The greater θ allowed for much less deformation before disruption. Cohesive forces on the other hand controlled the mode of disruption and maximum spin rate and showed that the change from shedding to fission is continuous and therefore, they should not be seen as different disruption processes. The figure shows the deformation and disruption of three initially spherical aggregates (left) and three initially ellipsoidal aggregates (right) with increasing cohesive strength from left to right (θ≈ 35°). Through scaling arguments we could also see these aggregates as having the exact same σ_c=25 Pa but different sizes. If we do that, the aggregates measure about 1.6 km, 5 km, and 22 km, and the particles, or groups of particles being detached now have similar sizes. This has now become a problem of resolution, i.e., the number and size of particles used in a simulation. These results start to raise fundamental questions regarding the difference between shedding and fission. Is it shedding when it is dust grain by dust grain ejection from the main body or when it is in groups of 10, 100, or 100,000 dust particles? Is it fission when a 1-m piece of the asteroid detaches or when it splits in the middle? Which values of θ and σ_c are realistic? These and other questions will be explored.

  17. Textual Cohesion in Modern Standard Chinese.

    ERIC Educational Resources Information Center

    Okurowski, Mary Ellen

    1989-01-01

    Presents a description of textual cohesion in Modern standard Chinese (MSC), and describes three types of relations as discourse and text features that contribute to the overall unity or coherence of a text. (24 references) (Author/VWL)

  18. Effect Size Indices for Analyses of Measurement Equivalence: Understanding the Practical Importance of Differences between Groups

    ERIC Educational Resources Information Center

    Nye, Christopher D.; Drasgow, Fritz

    2011-01-01

    Because of the practical, theoretical, and legal implications of differential item functioning (DIF) for organizational assessments, studies of measurement equivalence are a necessary first step before scores can be compared across individuals from different groups. However, commonly recommended criteria for evaluating results from these analyses…

  19. Becoming a Scientist: The Effects of Work-Group Size and Organizational Climate

    ERIC Educational Resources Information Center

    Louis, Karen Seashore; Holdsworth, Janet M.; Anderson, Melissa S.; Campbell, Eric G.

    2007-01-01

    The purpose of this article is to explore the effects of organizational and work-group characteristics on the socialization of new scientists. It focuses on the experiences of graduate students and postdoctoral fellows in science. The authors chose to look at outcomes that reflect behaviors (early productivity) and attitudes (willingness to share…

  20. The effects of group size on aggression when mixing unacquainted sows in indoor pens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As the US swine industry moves towards group housing sows, it is important to increase our understanding of aggression. Sows fight at mixing and this project sought to determine the amount and type of aggression observed when unacquainted York × Landrace sows were mixed in pairs or in two establishe...

  1. Task-Based Cohesive Evolution of Dynamic Brain Networks

    NASA Astrophysics Data System (ADS)

    Davison, Elizabeth

    2014-03-01

    Applications of graph theory to neuroscience have resulted in significant progress towards a mechanistic understanding of the brain. Functional network representation of the brain has linked efficient network structure to psychometric intelligence and altered configurations with disease. Dynamic graphs provide us with tools to further study integral properties of the brain; specifically, the mathematical convention of hyperedges has allowed us to study the brain's cross-linked structure. Hyperedges capture the changes in network structure by identifying groups of brain regions with correlation patterns that change cohesively through time. We performed a hyperedge analysis on functional MRI data from 86 subjects and explored the cohesive evolution properties of their functional brain networks as they performed a series of tasks. Our results establish the hypergraph as a useful measure in understanding functional brain dynamics over tasks and reveal characteristic differences in the co-evolution structure of task-specific networks.

  2. DELINQUENCY AND THE STRUCTURE OF ADOLESCENT PEER GROUPS.

    PubMed

    Kreager, Derek A; Rulison, Kelly; Moody, James

    2011-02-01

    Gangs and group-level processes were once central phenomena for criminological theory and research. By the mid-1970's, however, gang research was primarily displaced by studies of individual behavior using randomized self-report surveys, a shift that also removed groups from the theoretical foreground. In this project, we return to the group level to test competing theoretical claims about delinquent group structure. We use network-based clustering methods to identify 897 friendship groups in two ninth grade cohorts of 27 Pennsylvania and Iowa schools. We then relate group-level measures of delinquency and drinking to network measures of group size, friendship reciprocity, transitivity, structural cohesion, stability, average popularity, and network centrality. We find significant negative correlations between group delinquency and all of our network measures, suggesting that delinquent groups are less solidary and less central to school networks than non-delinquent groups. Further analyses, however, reveal that these correlations are primarily explained by other group characteristics, such as gender composition and socioeconomic status. Drinking behaviors, on the other hand, show net positive associations with most of the network measures, suggesting that drinking groups have higher status and are more internally cohesive than non-drinking groups. Our findings shed light on a longstanding criminological debate by suggesting that any structural differences between delinquent and non-delinquent groups may be attributable to other attributes coincidental with delinquency. In contrast, drinking groups appear to provide peer contexts of greater social capital and cohesion.

  3. DELINQUENCY AND THE STRUCTURE OF ADOLESCENT PEER GROUPS*

    PubMed Central

    Kreager, Derek A.; Rulison, Kelly; Moody, James

    2010-01-01

    Gangs and group-level processes were once central phenomena for criminological theory and research. By the mid-1970's, however, gang research was primarily displaced by studies of individual behavior using randomized self-report surveys, a shift that also removed groups from the theoretical foreground. In this project, we return to the group level to test competing theoretical claims about delinquent group structure. We use network-based clustering methods to identify 897 friendship groups in two ninth grade cohorts of 27 Pennsylvania and Iowa schools. We then relate group-level measures of delinquency and drinking to network measures of group size, friendship reciprocity, transitivity, structural cohesion, stability, average popularity, and network centrality. We find significant negative correlations between group delinquency and all of our network measures, suggesting that delinquent groups are less solidary and less central to school networks than non-delinquent groups. Further analyses, however, reveal that these correlations are primarily explained by other group characteristics, such as gender composition and socioeconomic status. Drinking behaviors, on the other hand, show net positive associations with most of the network measures, suggesting that drinking groups have higher status and are more internally cohesive than non-drinking groups. Our findings shed light on a longstanding criminological debate by suggesting that any structural differences between delinquent and non-delinquent groups may be attributable to other attributes coincidental with delinquency. In contrast, drinking groups appear to provide peer contexts of greater social capital and cohesion. PMID:21572969

  4. The effect of body coloration and group size on social partner preferences in female fighting fish (Betta splendens).

    PubMed

    Blakeslee, C; McRobert, S P; Brown, A C; Clotfelter, E D

    2009-02-01

    Females of the fighting fish Betta splendens have been shown to associate with other B. splendens females in a manner reminiscent of shoaling behavior. Since body coloration varies dramatically in this species, and since body coloration has been shown to affect shoalmate choice in other species of fish, we examined the influence of body coloration on association preferences in female B. splendens. In dichotomous choice tests, B. splendens females spent more time swimming near groups of females (regardless of coloration) than swimming near an empty chamber, and chose to swim near fish of similar coloration to their own when choosing between two distinctly colored groups of females. When examining the interplay between body coloration and group size, focal fish spent more time swimming near larger groups (N=5) of similarly colored fish than swimming near an individual female of similar coloration. However, focal fish showed no preference when presented with an individual female of similar coloration and a larger group of females of dissimilar coloration. These results suggest that association choices in B. splendens females are strongly affected by both body coloration and by group size.

  5. The effect of body coloration and group size on social partner preferences in female fighting fish (Betta splendens).

    PubMed

    Blakeslee, C; McRobert, S P; Brown, A C; Clotfelter, E D

    2009-02-01

    Females of the fighting fish Betta splendens have been shown to associate with other B. splendens females in a manner reminiscent of shoaling behavior. Since body coloration varies dramatically in this species, and since body coloration has been shown to affect shoalmate choice in other species of fish, we examined the influence of body coloration on association preferences in female B. splendens. In dichotomous choice tests, B. splendens females spent more time swimming near groups of females (regardless of coloration) than swimming near an empty chamber, and chose to swim near fish of similar coloration to their own when choosing between two distinctly colored groups of females. When examining the interplay between body coloration and group size, focal fish spent more time swimming near larger groups (N=5) of similarly colored fish than swimming near an individual female of similar coloration. However, focal fish showed no preference when presented with an individual female of similar coloration and a larger group of females of dissimilar coloration. These results suggest that association choices in B. splendens females are strongly affected by both body coloration and by group size. PMID:19059314

  6. Group-size-dependent punishment of idle subordinates in a cooperative breeder where helpers pay to stay

    PubMed Central

    Fischer, Stefan; Zöttl, Markus; Groenewoud, Frank; Taborsky, Barbara

    2014-01-01

    In cooperative breeding systems, dominant breeders sometimes tolerate unrelated individuals even if they inflict costs on the dominants. According to the ‘pay-to-stay’ hypothesis, (i) subordinates can outweigh these costs by providing help and (ii) dominants should be able to enforce help by punishing subordinates that provide insufficient help. This requires that dominants can monitor helping and can recognize group members individually. In a field experiment, we tested whether cooperatively breeding cichlid Neolamprologus pulcher subordinates increase their help after a forced ‘idle’ period, how other group members respond to a previously idle helper, and how helper behaviour and group responses depend on group size. Previously, idle helpers increased their submissiveness and received more aggression than control helpers, suggesting that punishment occurred to enforce help. Subordinates in small groups increased their help more than those in large groups, despite receiving less aggression. When subordinates were temporarily removed, dominants in small groups were more likely to evict returning subordinates. Our results suggest that only in small groups do helpers face a latent threat of punishment by breeders as predicted by the pay-to-stay hypothesis. In large groups, cognitive constraints may prevent breeders from tracking the behaviour of a large number of helpers. PMID:24990673

  7. Group-size-dependent punishment of idle subordinates in a cooperative breeder where helpers pay to stay.

    PubMed

    Fischer, Stefan; Zöttl, Markus; Groenewoud, Frank; Taborsky, Barbara

    2014-08-22

    In cooperative breeding systems, dominant breeders sometimes tolerate unrelated individuals even if they inflict costs on the dominants. According to the 'pay-to-stay' hypothesis, (i) subordinates can outweigh these costs by providing help and (ii) dominants should be able to enforce help by punishing subordinates that provide insufficient help. This requires that dominants can monitor helping and can recognize group members individually. In a field experiment, we tested whether cooperatively breeding cichlid Neolamprologus pulcher subordinates increase their help after a forced 'idle' period, how other group members respond to a previously idle helper, and how helper behaviour and group responses depend on group size. Previously, idle helpers increased their submissiveness and received more aggression than control helpers, suggesting that punishment occurred to enforce help. Subordinates in small groups increased their help more than those in large groups, despite receiving less aggression. When subordinates were temporarily removed, dominants in small groups were more likely to evict returning subordinates. Our results suggest that only in small groups do helpers face a latent threat of punishment by breeders as predicted by the pay-to-stay hypothesis. In large groups, cognitive constraints may prevent breeders from tracking the behaviour of a large number of helpers.

  8. Modelling cohesive, frictional and viscoplastic materials

    NASA Astrophysics Data System (ADS)

    Alehossein, Habib; Qin, Zongyi

    2016-06-01

    Most materials in mining and civil engineering construction are not only viscoplastic, but also cohesive frictional. Fresh concrete, fly ash and mining slurries are all granular-frictional-visco-plastic fluids, although solid concrete is normally considered as a cohesive frictional material. Presented here is both a formulation of the pipe and disc flow rates as a function of pressure and pressure gradient and the CFD application to fresh concrete flow in L-Box tests.

  9. Cohesive Features in Argumentative Writing Produced by Chinese Undergraduates

    ERIC Educational Resources Information Center

    Liu, Meihua; Braine, George

    2005-01-01

    Because cohesion is important both to the reader and the writer to create and comprehend a text, teachers have placed much emphasis on text cohesion and coherence in their teaching and evaluation of writing. Using Halliday and Hasan's [Halliday, M.A.K., Hasan, R. (1976). "Cohesion in English." Longman, London] taxonomy of cohesive devices and…

  10. Cohesion in Teaching and Evaluation: Problems and Implications.

    ERIC Educational Resources Information Center

    Neuner, Jerome L.

    Good and poor explanatory essays of 40 college freshmen were analyzed for 18 cohesive ties and chains to determine the appropriateness of the cohesion system for teaching and evaluating writing. The questions that were specifically addressed were, (1) How do writers use the cohesive resources of the language? and (2) How is cohesion related to…

  11. Investigating Some Technical Issues on Cohesive Zone Modeling of Fracture

    NASA Technical Reports Server (NTRS)

    Wang, John T.

    2011-01-01

    This study investigates some technical issues related to the use of cohesive zone models (CZMs) in modeling fracture processes. These issues include: why cohesive laws of different shapes can produce similar fracture predictions; under what conditions CZM predictions have a high degree of agreement with linear elastic fracture mechanics (LEFM) analysis results; when the shape of cohesive laws becomes important in the fracture predictions; and why the opening profile along the cohesive zone length needs to be accurately predicted. Two cohesive models were used in this study to address these technical issues. They are the linear softening cohesive model and the Dugdale perfectly plastic cohesive model. Each cohesive model constitutes five cohesive laws of different maximum tractions. All cohesive laws have the same cohesive work rate (CWR) which is defined by the area under the traction-separation curve. The effects of the maximum traction on the cohesive zone length and the critical remote applied stress are investigated for both models. For a CZM to predict a fracture load similar to that obtained by an LEFM analysis, the cohesive zone length needs to be much smaller than the crack length, which reflects the small scale yielding condition requirement for LEFM analysis to be valid. For large-scale cohesive zone cases, the predicted critical remote applied stresses depend on the shape of cohesive models used and can significantly deviate from LEFM results. Furthermore, this study also reveals the importance of accurately predicting the cohesive zone profile in determining the critical remote applied load.

  12. Group Size and Nest Spacing Affect Buggy Creek Virus (Togaviridae: Alphavirus) Infection in Nestling House Sparrows

    PubMed Central

    O'Brien, Valerie A.; Brown, Charles R.

    2011-01-01

    The transmission of parasites and pathogens among vertebrates often depends on host population size, host species diversity, and the extent of crowding among potential hosts, but little is known about how these variables apply to most vector-borne pathogens such as the arboviruses (arthropod-borne viruses). Buggy Creek virus (BCRV; Togaviridae: Alphavirus) is an RNA arbovirus transmitted by the swallow bug (Oeciacus vicarius) to the cliff swallow (Petrochelidon pyrrhonota) and the introduced house sparrow (Passer domesticus) that has recently invaded swallow nesting colonies. The virus has little impact on cliff swallows, but house sparrows are seriously affected by BCRV. For house sparrows occupying swallow nesting colonies in western Nebraska, USA, the prevalence of BCRV in nestling sparrows increased with sparrow colony size at a site but decreased with the number of cliff swallows present. If one nestling in a nest was infected with the virus, there was a greater likelihood that one or more of its nest-mates would also be infected than nestlings chosen at random. The closer a nest was to another nest containing infected nestlings, the greater the likelihood that some of the nestlings in the focal nest would be BCRV-positive. These results illustrate that BCRV represents a cost of coloniality for a vertebrate host (the house sparrow), perhaps the first such demonstration for an arbovirus, and that virus infection is spatially clustered within nests and within colonies. The decreased incidence of BCRV in sparrows as cliff swallows at a site increased reflects the “dilution effect,” in which virus transmission is reduced when a vector switches to feeding on a less competent vertebrate host. PMID:21966539

  13. Group size and nest spacing affect Buggy Creek virus (Togaviridae: Alphavirus) infection in nestling house sparrows.

    PubMed

    O'Brien, Valerie A; Brown, Charles R

    2011-01-01

    The transmission of parasites and pathogens among vertebrates often depends on host population size, host species diversity, and the extent of crowding among potential hosts, but little is known about how these variables apply to most vector-borne pathogens such as the arboviruses (arthropod-borne viruses). Buggy Creek virus (BCRV; Togaviridae: Alphavirus) is an RNA arbovirus transmitted by the swallow bug (Oeciacus vicarius) to the cliff swallow (Petrochelidon pyrrhonota) and the introduced house sparrow (Passer domesticus) that has recently invaded swallow nesting colonies. The virus has little impact on cliff swallows, but house sparrows are seriously affected by BCRV. For house sparrows occupying swallow nesting colonies in western Nebraska, USA, the prevalence of BCRV in nestling sparrows increased with sparrow colony size at a site but decreased with the number of cliff swallows present. If one nestling in a nest was infected with the virus, there was a greater likelihood that one or more of its nest-mates would also be infected than nestlings chosen at random. The closer a nest was to another nest containing infected nestlings, the greater the likelihood that some of the nestlings in the focal nest would be BCRV-positive. These results illustrate that BCRV represents a cost of coloniality for a vertebrate host (the house sparrow), perhaps the first such demonstration for an arbovirus, and that virus infection is spatially clustered within nests and within colonies. The decreased incidence of BCRV in sparrows as cliff swallows at a site increased reflects the "dilution effect," in which virus transmission is reduced when a vector switches to feeding on a less competent vertebrate host.

  14. Long-term resource variation and group size: A large-sample field test of the Resource Dispersion Hypothesis

    PubMed Central

    Johnson, Dominic DP; Baker, Samantha; Morecroft, Michael D; Macdonald, David W

    2001-01-01

    Background The Resource Dispersion Hypothesis (RDH) proposes a mechanism for the passive formation of social groups where resources are dispersed, even in the absence of any benefits of group living per se. Despite supportive modelling, it lacks empirical testing. The RDH predicts that, rather than Territory Size (TS) increasing monotonically with Group Size (GS) to account for increasing metabolic needs, TS is constrained by the dispersion of resource patches, whereas GS is independently limited by their richness. We conducted multiple-year tests of these predictions using data from the long-term study of badgers Meles meles in Wytham Woods, England. The study has long failed to identify direct benefits from group living and, consequently, alternative explanations for their large group sizes have been sought. Results TS was not consistently related to resource dispersion, nor was GS consistently related to resource richness. Results differed according to data groupings and whether territories were mapped using minimum convex polygons or traditional methods. Habitats differed significantly in resource availability, but there was also evidence that food resources may be spatially aggregated within habitat types as well as between them. Conclusions This is, we believe, the largest ever test of the RDH and builds on the long-term project that initiated part of the thinking behind the hypothesis. Support for predictions were mixed and depended on year and the method used to map territory borders. We suggest that within-habitat patchiness, as well as model assumptions, should be further investigated for improved tests of the RDH in the future. PMID:11511326

  15. Line transect estimation of population size: the exponential case with grouped data

    USGS Publications Warehouse

    Anderson, D.R.; Burnham, K.P.; Crain, B.R.

    1979-01-01

    Gates, Marshall, and Olson (1968) investigated the line transect method of estimating grouse population densities in the case where sighting probabilities are exponential. This work is followed by a simulation study in Gates (1969). A general overview of line transect analysis is presented by Burnham and Anderson (1976). These articles all deal with the ungrouped data case. In the present article, an analysis of line transect data is formulated under the Gates framework of exponential sighting probabilities and in the context of grouped data.

  16. Genetic determination of telomere size in humans: A twin study of three age groups

    SciTech Connect

    Slagboom, P.E.; Droog, S.; Boomsma, D.I.

    1994-11-01

    Reduction of telomere length has been postulated to be a casual factor in cellular aging. Human telomeres terminate in tandemly arranged repeat arrays consisting of the (TTAGGG) motif. The length of these arrays in cells from human mitotic tissues is inversely related to the age of the donor, indicating telomere reduction with age. In addition to telemore length differences between different age cohorts, considerable variation is present among individuals of the same age. To investigate whether this variation can be ascribed to genetic influences, we have measured the size of terminal restriction fragments (TRFs) in HaeIII-digested genomic DNA from 123 human MZ and DZ twin pairs 2-95 years of age. The average rate of telomere shortening was 31 bp/year, which is similar to that observed by others. Statistical analysis in 115 pairs 2-63 years of age indicates a 78% heritability for mean TRF length in this age cohort. The individual differences in mean TRF length in blood, therefore, seem to a large extent to be genetically determined. 24 refs., 4 figs., 2 tabs.

  17. The impact of size of cooperative group on achievement, social support, and self-esteem.

    PubMed

    Bertucci, Andrea; Conte, Stella; Johnson, David W; Johnson, Roger T

    2010-01-01

    The effect of cooperative learning in pairs and groups of 4 and in individualistic learning were compared on achievement, social support, and self-esteem. Sixty-two Italian 7th-grade students with no previous experience with cooperative learning were assigned to conditions on a stratified random basis controlling for ability, gender, and self-esteem. Students participated in 1 instructional unit for 90 min for 6 instructional days during a period of about 6 weeks. The results indicate that cooperative learning in pairs and 4s promoted higher achievement and greater academic support from peers than did individualistic learning. Students working in pairs developed a higher level of social self-esteem than did students learning in the other conditions.

  18. The Reading Level Paradox: Why Children's Picture Books Are Less Cohesive than Adult Books

    ERIC Educational Resources Information Center

    Corrigan, Roberta; Surber, John R.

    2010-01-01

    Three experiments explored how pictures in award-winning children's storybooks contribute to their cohesion. In Experiment 1, one group of college students read storybooks with pictures, and another group read them with the pictures removed. Both groups answered questions inserted periodically. The source for about one half of the questions was…

  19. Social Cohesion as Determined by the Levels and Types of Involvement.

    ERIC Educational Resources Information Center

    Grubb, Henry Jefferson

    1987-01-01

    Asserts that all behavior is result of individual-group interaction, determined by attachment to and identification with various groups to which one belongs. Presents this social cohesion as a function of member's levels and types of group involvement. Describes types ranked according to degree of involvement (identification, alienation, autonomy,…

  20. Cohesion from Conflict: Does Intergroup Conflict Motivate Intragroup Norm Enforcement and Support for Centralized Leadership?

    ERIC Educational Resources Information Center

    Benard, Stephen

    2012-01-01

    Classic work suggests that intergroup conflict increases intragroup cohesion and cooperation. But how do group members respond when their peers refuse to cooperate? Simmel ([1908] 1955) argued that groups in conflict quell dissent by sanctioning group members and supporting centralized leadership systems. This claim has important implications, but…

  1. Longitudinal analysis of minority women’s perceptions of cohesion: the role of cooperation, communication, and competition

    PubMed Central

    2014-01-01

    Background Interaction in the form of cooperation, communication, and friendly competition theoretically precede the development of group cohesion, which often precedes adherence to health promotion programs. The purpose of this manuscript was to explore longitudinal relationships among dimensions of group cohesion and group-interaction variables to inform and improve group-based strategies within programs aimed at promoting physical activity. Methods Ethnic minority women completed a group dynamics-based physical activity promotion intervention (N = 103; 73% African American; 27% Hispanic/Latina; mage = 47.89 + 8.17 years; mBMI = 34.43+ 8.07 kg/m2) and assessments of group cohesion and group-interaction variables at baseline, 6 months (post-program), and 12 months (follow-up). Results All four dimensions of group cohesion had significant (ps < 0.01) relationships with the group-interaction variables. Competition was a consistently strong predictor of cohesion, while cooperation did not demonstrate consistent patterns of prediction. Conclusions Facilitating a sense of friendly competition may increase engagement in physical activity programs by bolstering group cohesion. PMID:24779959

  2. Towards a chemistry of cohesion and adhesion

    NASA Astrophysics Data System (ADS)

    Eberhart, M. E.; Donovan, M. M.; MacLaren, J. M.; Clougherty, D. P.

    Modern chemistry frequently describes the structure and reaction dynamics of molecules in terms of the general principle of “competition for bonds”; consequently, bonding forms the basis of the language of chemistry. The actual models used to represent these bonds are frequently system specific. Organic reactions are described in terms of bonds based on pairs of atomic valence electrons. Reactions of inorganic coordination complexes are described in terms of bonds based on a molecular orbital representation. In analogy to those chemistries, a representation for a bond and bond strength, suitable for describing the cohesive and adhesive properties of all classes of materials, is introduced. This representation proves to yield an explanation for the observed cohesive properties of a specific class of materials (cleavage in bcc metals), and it also provides a framework for exploring and analyzing the more complex phenomena of cohesion and adhesion, such as environmentally-induced embrittlement. A complete chemistry of cohesion and adhesion will require the demonstration that the specific bonding model used can form the basis for consistent interpretations for a wealth of experimental phenomena beyond environmentally-induced embrittlement; thus, as presented, this model does not provide a complete chemistry of cohesion and adhesion, but does embody the first steps in that direction.

  3. Genetic differentiation and species cohesion in two widespread Central American Begonia species.

    PubMed

    Twyford, A D; Kidner, C A; Ennos, R A

    2014-04-01

    Begonia is one of the ten largest plant genera, with over 1500 species. This high species richness may in part be explained by weak species cohesion, which has allowed speciation by divergence in allopatry. In this study, we investigate species cohesion in the widespread Central American Begonia heracleifolia and Begonia nelumbiifolia, by genotyping populations at microsatellite loci. We then test for post-zygotic reproductive barriers using experimental crosses, and assess whether sterility barriers are related to intraspecific changes in genome size, indicating major genome restructuring between isolated populations. Strong population substructure was found for B. heracleifolia (FST=0.364, F'ST=0.506) and B. nelumbiifolia (FST=0.277, F'ST=0.439), and Bayesian admixture analysis supports the division of most populations into discrete genetic clusters. Moderate levels of inferred selfing (B. heracleifolia s=0.40, B. nelumbiifolia s=0.62) and dispersal limitation are likely to have contributed to significant genetic differentiation (B. heracleifolia Jost's D=0.274; B. nelumbiifolia D=0.294). Interpopulation crosses involving a divergent B. heracleifolia population with a genome size ∼10% larger than the species mean had a ∼20% reduction in pollen viability compared with other outcrosses, supporting reproductive isolation being polymorphic within the species. The population genetic data suggest that Begonia populations are only weakly connected by gene flow, allowing reproductive barriers to accumulate between the most isolated populations. This supports allopatric divergence in situ being the precursor of speciation in Begonia, and may also be a common speciation mechanism in other tropical herbaceous plant groups.

  4. Genetic differentiation and species cohesion in two widespread Central American Begonia species

    PubMed Central

    Twyford, A D; Kidner, C A; Ennos, R A

    2014-01-01

    Begonia is one of the ten largest plant genera, with over 1500 species. This high species richness may in part be explained by weak species cohesion, which has allowed speciation by divergence in allopatry. In this study, we investigate species cohesion in the widespread Central American Begonia heracleifolia and Begonia nelumbiifolia, by genotyping populations at microsatellite loci. We then test for post-zygotic reproductive barriers using experimental crosses, and assess whether sterility barriers are related to intraspecific changes in genome size, indicating major genome restructuring between isolated populations. Strong population substructure was found for B. heracleifolia (FST=0.364, F′ST=0.506) and B. nelumbiifolia (FST=0.277, F′ST=0.439), and Bayesian admixture analysis supports the division of most populations into discrete genetic clusters. Moderate levels of inferred selfing (B. heracleifolia s=0.40, B. nelumbiifolia s=0.62) and dispersal limitation are likely to have contributed to significant genetic differentiation (B. heracleifolia Jost's D=0.274; B. nelumbiifolia D=0.294). Interpopulation crosses involving a divergent B. heracleifolia population with a genome size ∼10% larger than the species mean had a ∼20% reduction in pollen viability compared with other outcrosses, supporting reproductive isolation being polymorphic within the species. The population genetic data suggest that Begonia populations are only weakly connected by gene flow, allowing reproductive barriers to accumulate between the most isolated populations. This supports allopatric divergence in situ being the precursor of speciation in Begonia, and may also be a common speciation mechanism in other tropical herbaceous plant groups. PMID:24220088

  5. An evaluation of the advantages and limitations in simulating indentation cracking with cohesive zone finite elements

    NASA Astrophysics Data System (ADS)

    Johanns, K. E.; Lee, J. H.; Gao, Y. F.; Pharr, G. M.

    2014-01-01

    A cohesive zone model is applied to a finite element (FE) scheme to simulate indentation cracking in brittle materials. Limitations of using the cohesive zone model to study indentation cracking are determined from simulations of a standard fracture toughness specimen and a two-dimensional indentation cracking problem wherein the morphology of the crack and the geometry of the indenter are simplified. It is found that the principles of linear-elastic fracture mechanics can be applied when indentation cracks are long in comparison to the size of the cohesive zone. Vickers and Berkovich pyramidal indentation crack morphologies (3D) are also investigated and found to be controlled by the ratio of elastic modulus to yield strength (E/Y), with median type cracking dominating at low ratios (e.g. E/Y = 10) and Palmqvist type cracking at higher ratios (e.g. E/Y = 100). The results show that cohesive FE simulations of indentation cracking can indeed be used to critically examine the complex relationships between crack morphology, material properties, indenter geometry, and indentation test measurements, provided the crack length is long in comparison to the cohesive zone size.

  6. In situ tensile fracture toughness of surficial cohesive marine sediments

    NASA Astrophysics Data System (ADS)

    Johnson, Bruce D.; Barry, Mark A.; Boudreau, Bernard P.; Jumars, Peter A.; Dorgan, Kelly M.

    2012-02-01

    This study reports the first in situ measurements of tensile fracture toughness, K IC, of soft, surficial, cohesive marine sediments. A newly developed probe continuously measures the stress required to cause tensile failure in sediments to depths of up to 1 m. Probe measurements are in agreement with standard laboratory methods of K IC measurements in both potter's clay and natural sediments. The data comprise in situ depth profiles from three field sites in Nova Scotia, Canada. Measured K IC at two muddy sites (median grain size of 23-50 μm) range from near zero at the sediment surface to >1,800 Pa m1/2 at 0.2 m depth. These profiles also appear to identify the bioturbated/mixed depth. K IC for a sandy site (>90% sand) is an order of magnitude lower than for the muddy sediments, and reflects the lack of cohesion/adhesion. A comparison of K IC, median grain size, and porosity in muddy sediments indicates that consolidation increases fracture strength, whereas inclusion of sand causes weakening; thus, sand-bearing layers can be easily identified in K IC profiles. K IC and vane-measured shear strength correlate strongly, which suggests that the vane measurements should perhaps be interpreted as shear fracture toughness, rather than shear strength. Comparison of in situ probe-measured values with K IC of soils and gelatin shows that sediments have a K IC range intermediate between denser compacted soils and softer, elastic gelatin.

  7. Relationships between cohesion, collective efficacy and performance in professional basketball teams: an examination of mediating effects.

    PubMed

    Heuzé, Jean-Philippe; Raimbault, Nicolas; Fontayne, Paul

    2006-01-01

    The main aim of this study was to examine mediating effects in the relationships between cohesion, collective efficacy and performance in professional basketball teams. A secondary aim was to examine the correlates of collective efficacy in a professional sport. A total of 154 French and foreign professional players completed French or English versions of questionnaires about cohesion and collective efficacy. Two composite measures of individual performance were used (pre- and post-performance). Individual-level analyses were performed. Regression analyses supported two mediating relationships with collective efficacy as a mediator of the pre-performance - Group integration-task relationship, and Group integration-task as a mediator of the pre-performance - collective efficacy relationship. Statistical analyses indicated that neither Group integration-task nor collective efficacy was a better mediator in the relationship between pre-performance and the other group variables. Results also revealed positive relationships between three dimensions of cohesion (i.e. Individual attractions to the group-task, Group integration-task, Group integration-social) and collective efficacy. These findings suggest that in professional basketball teams, staff members should look after athletes who perform at a lower or below their usual level because their performances might lead them into a downward cohesion - collective efficacy spiral. Staff members should also develop a high quality of group functioning, both on and off the basketball court, given its relationship with collective efficacy. PMID:16368614

  8. Relationships between cohesion, collective efficacy and performance in professional basketball teams: an examination of mediating effects.

    PubMed

    Heuzé, Jean-Philippe; Raimbault, Nicolas; Fontayne, Paul

    2006-01-01

    The main aim of this study was to examine mediating effects in the relationships between cohesion, collective efficacy and performance in professional basketball teams. A secondary aim was to examine the correlates of collective efficacy in a professional sport. A total of 154 French and foreign professional players completed French or English versions of questionnaires about cohesion and collective efficacy. Two composite measures of individual performance were used (pre- and post-performance). Individual-level analyses were performed. Regression analyses supported two mediating relationships with collective efficacy as a mediator of the pre-performance - Group integration-task relationship, and Group integration-task as a mediator of the pre-performance - collective efficacy relationship. Statistical analyses indicated that neither Group integration-task nor collective efficacy was a better mediator in the relationship between pre-performance and the other group variables. Results also revealed positive relationships between three dimensions of cohesion (i.e. Individual attractions to the group-task, Group integration-task, Group integration-social) and collective efficacy. These findings suggest that in professional basketball teams, staff members should look after athletes who perform at a lower or below their usual level because their performances might lead them into a downward cohesion - collective efficacy spiral. Staff members should also develop a high quality of group functioning, both on and off the basketball court, given its relationship with collective efficacy.

  9. Blood thicker than water: kinship, disease prevalence and group size drive divergent patterns of infection risk in a social mammal

    PubMed Central

    Delahay, Richard J.

    2016-01-01

    The importance of social- and kin-structuring of populations for the transmission of wildlife disease is widely assumed but poorly described. Social structure can help dilute risks of transmission for group members, and is relatively easy to measure, but kin-association represents a further level of population sub-structure that is harder to measure, particularly when association behaviours happen underground. Here, using epidemiological and molecular genetic data from a wild, high-density population of the European badger (Meles meles), we quantify the risks of infection with Mycobacterium bovis (the causative agent of tuberculosis) in cubs. The risk declines with increasing size of its social group, but this net dilution effect conceals divergent patterns of infection risk. Cubs only enjoy reduced risk when social groups have a higher proportion of test-negative individuals. Cubs suffer higher infection risk in social groups containing resident infectious adults, and these risks are exaggerated when cubs and infectious adults are closely related. We further identify key differences in infection risk associated with resident infectious males and females. We link our results to parent–offspring interactions and other kin-biased association, but also consider the possibility that susceptibility to infection is heritable. These patterns of infection risk help to explain the observation of a herd immunity effect in badgers following low-intensity vaccination campaigns. They also reveal kinship and kin-association to be important, and often hidden, drivers of disease transmission in social mammals. PMID:27440666

  10. Blood thicker than water: kinship, disease prevalence and group size drive divergent patterns of infection risk in a social mammal.

    PubMed

    Benton, Clare H; Delahay, Richard J; Robertson, Andrew; McDonald, Robbie A; Wilson, Alastair J; Burke, Terry A; Hodgson, Dave

    2016-07-27

    The importance of social- and kin-structuring of populations for the transmission of wildlife disease is widely assumed but poorly described. Social structure can help dilute risks of transmission for group members, and is relatively easy to measure, but kin-association represents a further level of population sub-structure that is harder to measure, particularly when association behaviours happen underground. Here, using epidemiological and molecular genetic data from a wild, high-density population of the European badger (Meles meles), we quantify the risks of infection with Mycobacterium bovis (the causative agent of tuberculosis) in cubs. The risk declines with increasing size of its social group, but this net dilution effect conceals divergent patterns of infection risk. Cubs only enjoy reduced risk when social groups have a higher proportion of test-negative individuals. Cubs suffer higher infection risk in social groups containing resident infectious adults, and these risks are exaggerated when cubs and infectious adults are closely related. We further identify key differences in infection risk associated with resident infectious males and females. We link our results to parent-offspring interactions and other kin-biased association, but also consider the possibility that susceptibility to infection is heritable. These patterns of infection risk help to explain the observation of a herd immunity effect in badgers following low-intensity vaccination campaigns. They also reveal kinship and kin-association to be important, and often hidden, drivers of disease transmission in social mammals. PMID:27440666

  11. Warring arthropod societies: Social spider colonies can delay annihilation by predatory ants via reduced apparency and increased group size.

    PubMed

    Keiser, Carl N; Wright, Colin M; Pruitt, Jonathan N

    2015-10-01

    Sociality provides individuals with benefits via collective foraging and anti-predator defense. One of the costs of living in large groups, however, is increased apparency to natural enemies. Here, we test how the individual-level and collective traits of spider societies can increase the risk of discovery and death by predatory ants. We transplanted colonies of the social spider Stegodyphus dumicola into a habitat dense with one of their top predators, the pugnacious ant Anoplolepis custodiens. With three different experiments, we test how colony-wide survivorship in a predator-dense habitat can be altered by colony apparency (i.e., the presence of a capture web), group size, and group composition (i.e., the proportion of bold and shy personality types present). We also test how spiders' social context (i.e., living solitarily vs. among conspecifics) modifies their behaviour toward ants in their capture web. Colonies with capture webs intact were discovered by predatory ants on average 25% faster than colonies with the capture web removed, and all discovered colonies eventually collapsed and succumbed to predation. However, the lag time from discovery by ants to colony collapse was greater for colonies containing more individuals. The composition of individual personality types in the group had no influence on survivorship. Spiders in a social group were more likely to approach ants caught in their web than were isolated spiders. Isolated spiders were more likely to attack a safe prey item (a moth) than they were to attack ants and were more likely to retreat from ants after contact than they were after contact with moths. Together, our data suggest that the physical structures produced by large animal societies can increase their apparency to natural enemies, though larger groups can facilitate a longer lag time between discovery and demise. Lastly, the interaction between spiders and predatory ants seems to depend on the social context in which spiders reside

  12. Warring arthropod societies: Social spider colonies can delay annihilation by predatory ants via reduced apparency and increased group size.

    PubMed

    Keiser, Carl N; Wright, Colin M; Pruitt, Jonathan N

    2015-10-01

    Sociality provides individuals with benefits via collective foraging and anti-predator defense. One of the costs of living in large groups, however, is increased apparency to natural enemies. Here, we test how the individual-level and collective traits of spider societies can increase the risk of discovery and death by predatory ants. We transplanted colonies of the social spider Stegodyphus dumicola into a habitat dense with one of their top predators, the pugnacious ant Anoplolepis custodiens. With three different experiments, we test how colony-wide survivorship in a predator-dense habitat can be altered by colony apparency (i.e., the presence of a capture web), group size, and group composition (i.e., the proportion of bold and shy personality types present). We also test how spiders' social context (i.e., living solitarily vs. among conspecifics) modifies their behaviour toward ants in their capture web. Colonies with capture webs intact were discovered by predatory ants on average 25% faster than colonies with the capture web removed, and all discovered colonies eventually collapsed and succumbed to predation. However, the lag time from discovery by ants to colony collapse was greater for colonies containing more individuals. The composition of individual personality types in the group had no influence on survivorship. Spiders in a social group were more likely to approach ants caught in their web than were isolated spiders. Isolated spiders were more likely to attack a safe prey item (a moth) than they were to attack ants and were more likely to retreat from ants after contact than they were after contact with moths. Together, our data suggest that the physical structures produced by large animal societies can increase their apparency to natural enemies, though larger groups can facilitate a longer lag time between discovery and demise. Lastly, the interaction between spiders and predatory ants seems to depend on the social context in which spiders reside.

  13. Too Many Friends: Social Integration, Network Cohesion and Adolescent Depressive Symptoms

    ERIC Educational Resources Information Center

    Falci, Christina; McNeely, Clea

    2009-01-01

    Using a nationally representative sample of adolescents, we examine associations among social integration (network size), network cohesion (alter-density), perceptions of social relationships (e.g., social support) and adolescent depressive symptoms. We find that adolescents with either too large or too small a network have higher levels of…

  14. Investigating Team Cohesion in COCOMO II.2000

    ERIC Educational Resources Information Center

    Snowdeal-Carden, Betty A.

    2013-01-01

    Software engineering is team oriented and intensely complex, relying on human collaboration and creativity more than any other engineering discipline. Poor software estimation is a problem that within the United States costs over a billion dollars per year. Effective measurement of team cohesion is foundationally important to gain accurate…

  15. The Corporate Stake in Social Cohesion

    ERIC Educational Resources Information Center

    Oketch, Moses O.

    2005-01-01

    Corporate Social Responsibility (CSR) is a function that transcends, but includes, making profits, creating jobs, and producing goods and services. The effectiveness with which corporations perform this function determines their contribution (or lack of contribution) to social cohesion. This article therefore presents a discussion of some of the…

  16. Building Cohesion in Positively Connected Exchange Networks

    ERIC Educational Resources Information Center

    Schaefer, David R.; Kornienko, Olga

    2009-01-01

    This research investigates the process through which individuals build cohesive relationships in positively connected exchange relations. Positive connections exist any time exchange in one relation must precede exchange in another. Such situations arise through gatekeeping, in generalized exchange contexts, and when resources diffuse across a…

  17. Cohesion in Interlanguage: A Study of Conjunction.

    ERIC Educational Resources Information Center

    Beebe, Leslie M.

    A study of textual cohesion in the oral discourse of learners of English as a second language had as subjects 19 Asians from 4 language backgrounds, who were living and, in most cases, studying English in the United States. Analysis of taped conversations focused on the use of conjunctive adjuncts of three kinds: (1) simple adverbs (e.g., and,…

  18. Role of Education in Building Social Cohesion

    ERIC Educational Resources Information Center

    Khan, Zebun Nisa

    2016-01-01

    Social Cohesion is the expression of that tradition of tolerance in all religions and cultures that are the basis of peace and progress. It is foreign to know culture and native to all nations. Tolerance and mercy have always and in all cultures being ideals of Government rules and human behavior. Professional educator often comments on the poor…

  19. Cohesive Energy of the Alkali Metals.

    ERIC Educational Resources Information Center

    Poole, R. T.

    1980-01-01

    Describes a method, considered appropriate for presentation to undergraduate students in materials science and related courses, for the calculation of cohesive energies of the alkali metals. Uses a description based on the free electron model and gives results to within 0.1 eV of the experimental values. (Author/GS)

  20. Toward a Cohesive Theory of Visual Literacy

    ERIC Educational Resources Information Center

    Avgerinou, Maria D.; Pettersson, Rune

    2011-01-01

    Despite the fact that to date Visual Literacy (VL) scholars have not arrived at a general consensus for a theoretical organization of the VL field, important conceptual investigations have emerged over the past four decades. In this paper we discuss and synthesize those studies. We then present a first attempt toward a cohesive theory of VL. The…

  1. Cohesion and Coherence in Short Expository Essays.

    ERIC Educational Resources Information Center

    Lindeberg, Ann-Charlotte

    A study to find patterns of cohesion and rhetorical structure that distinguish good from weak English essay writing is described. The corpus consisted of ten Swedish college essays written as part of the final exam in a first-year English course. Methodological problems encountered included the delimitation of units for the analysis of cohesive…

  2. Ultrasound measurement of the size of the anterior tibial muscle group: the effect of exercise and leg dominance

    PubMed Central

    2011-01-01

    Background Knowledge of normal muscle characteristics is crucial in planning rehabilitation programmes for injured athletes. There is a high incidence of ankle and anterior tibial symptoms in football players, however little is known about the effect of limb dominance on the anterior tibial muscle group (ATMG). The purpose of this study was to assess the effect of limb dominance and sports-specific activity on ATMG thickness in Gaelic footballers and non-football playing controls using ultrasound measurements, and to compare results from transverse and longitudinal scans. Methods Bilateral ultrasound scans were taken to assess the ATMG size in 10 Gaelic footballers and 10 sedentary controls (age range 18-25 yrs), using a previously published protocol. Both transverse and longitudinal images were taken. Muscle thickness measurements were carried out blind to group and side of dominance, using the Image-J programme. Results Muscle thickness on the dominant leg was significantly greater than the non-dominant leg in the footballers with a mean difference of 7.3%, while there was no significant dominance effect in the controls (p < 0.05). There was no significant difference between the measurements from transverse or longitudinal scans. Conclusions A significant dominance effect exists in ATMG size in this group of Gaelic footballers, likely attributable to the kicking action involved in the sport. This should be taken into account when rehabilitating footballers with anterior tibial pathology. Ultrasound is a reliable tool to measure ATMG thickness, and measurement may be taken in transverse or longitudinal section. PMID:21914209

  3. Challenging the wall of fast rotating asteroids - constraining internal cohesive strength for MBAs and NEAs

    NASA Astrophysics Data System (ADS)

    Polishook, David; Moskovitz, Nicholas; Binzel, Richard P.; DeMeo, Francesca E.; Aharonson, Oded; Thomas, Cristina; Lockhart, Matthew; Thirouin, Audrey; Mommert, Michael; Trilling, David; Burt, Brian

    2015-11-01

    We report an observation of a 2 km size main belt asteroid (MBA), (60716) 2000 GD65, with a lightcurve indicating a rotation period of 1.9529±0.0002 hours, i.e. challenging the ‘rubble pile spin barrier’. This adds to a handful of MBAs, recently observed by the Palomar Transient Factory (PTF) survey (Chang et al. 2014, 2015), with diameters between 0.5-1.5 km and lightcurves indicating rotation periods of 1.2-1.9 hours. These asteroids are relatively large compared to the population of small near-Earth asteroids (NEAs; D<300 m) that can reach rotation periods as fast as 15.797 seconds as is the case of NEA 2014 RC (Moskovitz and MANOS team).We apply the Holsapple (2007) model to these two distinct populations in order to constrain the cohesion within these objects and to search for monolithic asteroids. We use the lightcurve’s amplitude as indication of the triaxial shape ratio a/b, and assume b/c=1 (i.e. a>b=c). While the density is a free parameter, the given cohesion is the average of values for density ranges between 1.5 to 2.5 gr cm^-3, which are measured density values for asteroids (Carry 2012).We find that the fast rotating MBAs must have internal cohesive strength of at least ~25 to ~250 Pa in order to prevent disruption against centrifugal acceleration. Similar cohesion values have been found within lunar soils (100-1000 Pa; Mitchell et al. 1974). However, since only a few MBAs rotate so quickly, such internal cohesive strength might be rare within the population of km-size MBAs. Among NEAs, about 25% have minimal constrained cohesion values similar to those found for the fast rotating MBAs. Approximately 65% have no need for substantial cohesion values >25 Pa. Only ~10% of NEAs must have substantial internal cohesion of over 1000 Pa to prevent disruption, however none of them are rotating fast enough to require a fully monolithic body, i.e. cohesion >10 kPa.

  4. Decoupling the contribution of dispersive and acid-base components of surface energy on the cohesion of pharmaceutical powders.

    PubMed

    Shah, Umang V; Olusanmi, Dolapo; Narang, Ajit S; Hussain, Munir A; Tobyn, Michael J; Heng, Jerry Y Y

    2014-11-20

    This study reports an experimental approach to determine the contribution from two different components of surface energy on cohesion. A method to tailor the surface chemistry of mefenamic acid via silanization is established and the role of surface energy on cohesion is investigated. Silanization was used as a method to functionalize mefenamic acid surfaces with four different functional end groups resulting in an ascending order of the dispersive component of surface energy. Furthermore, four haloalkane functional end groups were grafted on to the surface of mefenamic acid, resulting in varying levels of acid-base component of surface energy, while maintaining constant dispersive component of surface energy. A proportional increase in cohesion was observed with increases in both dispersive as well as acid-base components of surface energy. Contributions from dispersive and acid-base surface energy on cohesion were determined using an iterative approach. Due to the contribution from acid-base surface energy, cohesion was found to increase ∼11.7× compared to the contribution from dispersive surface energy. Here, we provide an approach to deconvolute the contribution from two different components of surface energy on cohesion, which has the potential of predicting powder flow behavior and ultimately controlling powder cohesion.

  5. Merlin's wizardry guides cohesive migration.

    PubMed

    Zoch, Ansgar; Morrison, Helen

    2015-03-01

    Cells often migrate in tightly connected groups with coordinated movement and polarity. The collective migration of epithelial cell sheets is now shown to be mediated by a signalling axis that involves the merlin tumour-suppressor protein, the tight-junction-associated angiomotin-Rich1 complex and the Rac1 small GTPase. PMID:25720961

  6. The impact of trait emotional intelligence on nursing team performance and cohesiveness.

    PubMed

    Quoidbach, Jordi; Hansenne, Michel

    2009-01-01

    Claims about the positive influence of emotional intelligence (EI) on work team performance are very numerous, both in commercial and scientific literature. However, despite the huge interest that media and business consultants put in EI and its fast-growing use in organizations, there is very little empirical evidence to support these claims. In this study, we investigated the relationships between EI, performance, and cohesiveness in 23 nursing teams. EI was assessed using the modified version of the Schutte Emotional Intelligence Scale and cohesiveness with the Group Cohesiveness Scale. Finally, nursing team performance was measured at four different levels: job satisfaction, chief nursing executives' rating, turnover rate, and health care quality. Results showed that health care quality was positively correlated with emotion regulation. Emotion regulation was also positively correlated with group cohesiveness. Surprisingly, it also appears that emotion appraisal was negatively correlated with the health care quality provided by teams. These results suggest that EI and, more specifically, Emotional Regulation may provide an interesting new way of enhancing nursing teams' cohesion and patient/client outcomes. PMID:19161959

  7. The impact of trait emotional intelligence on nursing team performance and cohesiveness.

    PubMed

    Quoidbach, Jordi; Hansenne, Michel

    2009-01-01

    Claims about the positive influence of emotional intelligence (EI) on work team performance are very numerous, both in commercial and scientific literature. However, despite the huge interest that media and business consultants put in EI and its fast-growing use in organizations, there is very little empirical evidence to support these claims. In this study, we investigated the relationships between EI, performance, and cohesiveness in 23 nursing teams. EI was assessed using the modified version of the Schutte Emotional Intelligence Scale and cohesiveness with the Group Cohesiveness Scale. Finally, nursing team performance was measured at four different levels: job satisfaction, chief nursing executives' rating, turnover rate, and health care quality. Results showed that health care quality was positively correlated with emotion regulation. Emotion regulation was also positively correlated with group cohesiveness. Surprisingly, it also appears that emotion appraisal was negatively correlated with the health care quality provided by teams. These results suggest that EI and, more specifically, Emotional Regulation may provide an interesting new way of enhancing nursing teams' cohesion and patient/client outcomes.

  8. Cohesion enhancing effect of magnesium in aluminum grain boundary: A first-principles determination

    SciTech Connect

    Zhang Shengjun; Freeman, Arthur J.; Kontsevoi, Oleg Y.; Olson, Gregory B.

    2012-06-04

    The effect of magnesium on grain boundary cohesion in aluminum was investigated by means of first-principles calculations using the Rice-Wang model [Rice and Wang, Mater. Sci. Eng. A 107, 23 (1989)]. It is demonstrated that magnesium is a cohesion enhancer with a potency of -0.11 eV/atom. It is further determined through electronic structure and bonding character analysis that the cohesion enhancing property of magnesium is due to a charge transfer mechanism which is unusually strong and overcomes the negative result of the size effect mechanism. Consistent with experimental results, this work clarifies the controversy and establishes that Mg segregation does not contribute to stress corrosion cracking in Al alloys.

  9. A simple model of the adhesive failure of a layer: Cohesive effects

    SciTech Connect

    Ferer, M.; Smith, D.H. |

    1997-02-01

    A fine-scale model is developed for the removal of an adhesive layer by a uniform stress. The initial motivation of this modeling project was a description of the removal of a layer of filter cake from cylindrical filters by backpulse cleaning. The model includes the bonding forces of adhesion between the layer and a substrate, as well as the forces of cohesion between imaginary {open_quotes}gridblocks{close_quote}{close_quote} within the layer. For stresses greater than a threshold value, some of the layer is removed, with the fraction removed depending upon the stress, the average adhesive and cohesive forces, and the distribution of these forces about their average. The cohesive forces reduce the threshold well below the average strength of the adhesive force, because they increase the stress near broken adhesive bonds. The cohesive forces also sharpen the threshold in the cleaning pressure significantly, so that the threshold is very much sharper than the distribution of adhesive strengths. For moderate filter cake thickness (moderately strong cohesive forces), the threshold becomes steplike, with no cleaning just below the threshold and complete cleaning at the threshold and above. The model also provides the pressure dependence of the size and shape distributions for the fragments of the filter cake layer removed from the filter, enabling the model to address questions of cleaning efficiency, {open_quotes}patchy cleaning,{close_quote}{close_quote} re-entrainment, and trapping of large cake-fragments in the filter vessel. {copyright} {ital 1997 American Institute of Physics.}

  10. Corrasion of a remoulded cohesive bed by saltating littorinid shells

    NASA Astrophysics Data System (ADS)

    Amos, C. L.; Sutherland, T. F.; Cloutier, D.; Patterson, S.

    2000-07-01

    Corrasion of a standard cohesive bed due to saltating gastropod shells of the species Littorina has been examined in a laboratory mini flume. The purpose of the study was to examine the effects of shell size and number on bed erosion rate. The movement of shells by flows explain why intertidal, glacial clays in the Bay of Fundy (which are covered in places with Littorinid shells) suffer erosion because bed erosion rate increased up to 20-fold with the introduction of a single shell to the flume (27 m -2). The standard bed was made of potters clay which had an erosion threshold of 0.19 Pa and a fluid-induced erosion rate Eo=0.072( Uy- Ucrit) gm -2 s -1, where Uy is the azimuthal current speed at height y=0.10 m. Shells of seven differing sizes ( ds) were used to define the process of erosion by shell impacts. The threshold for shell motion ( Ugcrit) was linearly related to shell size in the form: Ugcrit=9.17×10 -3 ds-0.22 m s -1. Motion began by intermittent rolling, followed by continuous rolling and then by saltation. The shell speed in saltation was 68% that of Uy, thus 32% of the horizontal shell momentum was transmitted to the bed. The length/height ratio of saltations was 6.3, and was constant for all sizes, and the mean saltation frequency was 1.7 s -1. The shell erosion rate ( Es) increased with shell diameter for both the rolling and saltating phases. During the rolling phase, Es was up to 5 times greater than Eo at the same current speed. During saltation, Es was up to 20 times greater than Eo at the same current speed. The effect of shell number (1-7) was examined for the 7-10 mm size class. During rolling, Es increased linearly with shell number. For the saltating phase, Es increased in an asymptotic fashion, suggesting that groups of saltating shells affect the erosion process differently than single shells. The ballistic momentum flux ( T) of saltating shells is highly dependent on the area of impact ( Ag), which in the case of the littorinids, is

  11. Lexical Cohesion: An Issue Only in the Foreign Language?

    ERIC Educational Resources Information Center

    Kafes, Hüseyin

    2012-01-01

    The purpose of this study was to investigate Turkish EFL learners' ability in composing cohesive texts in their first language and in English as their foreign language, and to examine whether there are similarities between lexical reiteration cohesive devices they employ in composing cohesive texts both in Turkish and in English. The study was…

  12. Cohesion in Compositions of Turkish and Immigrant Students

    ERIC Educational Resources Information Center

    Coskun, Eyyup

    2011-01-01

    Cohesion refers to the relationships established between sentences and paragraphs via the units in the surface structure of the text. This study evaluated texts written by Uzbek origin immigrant students and Turkish students living in Hatay in terms of the use of cohesion devices (ellipsis, conjunctions, lexical cohesion, reference, substitution).…

  13. Intact Discourse Cohesion and Coherence Following Bilateral Ventromedial Prefrontal Cortex

    ERIC Educational Resources Information Center

    Kurczek, Jake; Duff, Melissa C.

    2012-01-01

    Discourse cohesion and coherence give communication its continuity providing the grammatical and lexical links that hold an utterance or text together and give it meaning. Researchers often link cohesion and coherence deficits to the frontal lobes by drawing attention to frontal lobe dysfunction in populations where discourse cohesion and…

  14. Effective porosity and pore-throat sizes of Conasauga Group mudrock: Application, test and evaluation of petrophysical techniques

    SciTech Connect

    Dorsch, J.; Katsube, T.J.; Sanford, W.E. |; Dugan, B.E.; Tourkow, L.M.

    1996-04-01

    Effective porosity (specifically referring to the interconnected pore space) was recently recognized as being essential in determining the effectiveness and extent of matrix diffusion as a transport mechanism within fractured low-permeability rock formations. The research presented in this report was performed to test the applicability of several petrophysical techniques for the determination of effective porosity of fine-grained siliciclastic rocks. In addition, the aim was to gather quantitative data on the effective porosity of Conasauga Group mudrock from the Oak Ridge Reservation (ORR). The quantitative data reported here include not only effective porosities based on diverse measurement techniques, but also data on the sizes of pore throats and their distribution, and specimen bulk and grain densities. The petrophysical techniques employed include the immersion-saturation method, mercury and helium porosimetry, and the radial diffusion-cell method.

  15. Standard energy metabolism of a desert harvester ant, Pogonomyrmex rugosus: Effects of temperature, body mass, group size, and humidity

    SciTech Connect

    Lighton, J.R.B.; Bartholomew, G.A. )

    1988-07-01

    Pogonomyrmex rugosus is an important seed predator in the Mojave Desert of the southwestern United States. Its standard rate of O{sub 2} consumption (Vo{sub 2}) varied significantly with temperature. The ratio of the Vo{sub 2} values at 10{degree}C increments in body temperature, Q{sub 10}, also varied with temperature; methods of calculating Vo{sub 2} from temperature with a shifting Q{sub 10} are described. Vo{sub 2} also varied with body mass. Vo{sub 2} was inversely related to relative humidity and was independent of group size. The rise in Vo{sub 2} at low relative humidities was caused by increased activity and resulted in higher rates of net water loss. The primary metabolic adaptation to xeric conditions in P. rugosus appears to be a lower-than-predicted metabolic rate.

  16. The neural basis of the bystander effect--the influence of group size on neural activity when witnessing an emergency.

    PubMed

    Hortensius, Ruud; de Gelder, Beatrice

    2014-06-01

    Naturalistic observation and experimental studies in humans and other primates show that observing an individual in need automatically triggers helping behavior. The aim of the present study is to clarify the neurofunctional basis of social influences on individual helping behavior. We investigate whether when participants witness an emergency, while performing an unrelated color-naming task in an fMRI scanner, the number of bystanders present at the emergency influences neural activity in regions related to action preparation. The results show a decrease in activity with the increase in group size in the left pre- and postcentral gyri and left medial frontal gyrus. In contrast, regions related to visual perception and attention show an increase in activity. These results demonstrate the neural mechanisms of social influence on automatic action preparation that is at the core of helping behavior when witnessing an emergency.

  17. Analyzing indirect effects in cluster randomized trials. The effect of estimation method, number of groups and group sizes on accuracy and power.

    PubMed

    Hox, Joop J; Moerbeek, Mirjam; Kluytmans, Anouck; van de Schoot, Rens

    2014-01-01

    Cluster randomized trials assess the effect of an intervention that is carried out at the group or cluster level. Ajzen's theory of planned behavior is often used to model the effect of the intervention as an indirect effect mediated in turn by attitude, norms and behavioral intention. Structural equation modeling (SEM) is the technique of choice to estimate indirect effects and their significance. However, this is a large sample technique, and its application in a cluster randomized trial assumes a relatively large number of clusters. In practice, the number of clusters in these studies tends to be relatively small, e.g., much less than fifty. This study uses simulation methods to find the lowest number of clusters needed when multilevel SEM is used to estimate the indirect effect. Maximum likelihood estimation is compared to Bayesian analysis, with the central quality criteria being accuracy of the point estimate and the confidence interval. We also investigate the power of the test for the indirect effect. We conclude that Bayes estimation works well with much smaller cluster level sample sizes such as 20 cases than maximum likelihood estimation; although the bias is larger the coverage is much better. When only 5-10 clusters are available per treatment condition even with Bayesian estimation problems occur. PMID:24550881

  18. Population Balance Modeling of Polydispersed Bubbly Flow in Continuous-Casting Using Multiple-Size-Group Approach

    NASA Astrophysics Data System (ADS)

    Liu, Zhongqiu; Li, Linmin; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa; Tsukihashi, Fumitaka

    2014-09-01

    A population balance model based on the multiple-size-group (MUSIG) approach has been developed to investigate the polydispersed bubbly flow inside the slab continuous-casting mold and bubble behavior including volume fraction, breakup, coalescence, and size distribution. The Eulerian-Eulerian approach is used to describe the equations of motion of the two-phase flow. All the non-drag forces (lift force, virtual mass force, wall lubrication force, and turbulent dispersion force) and drag force are incorporated in this model. Sato and Sekiguchi model is used to account for the bubble-induced turbulence. Luo and Svendsen model and Prince and Blanch model are used to describe the bubbles breakup and coalescence behavior, respectively. A 1/4th water model of the slab continuous-casting mold was applied to investigate the distribution and size of bubbles by injecting air through a circumferential inlet chamber which was made of the specially-coated samples of mullite porous brick, which is used for the actual upper nozzle. Against experimental data, numerical results showed good agreement for the gas volume fraction and local bubble Sauter mean diameter. The bubble Sauter mean diameter in the upper recirculation zone decreases with increasing water flow rate and increases with increasing gas flow rate. The distribution of bubble Sauter mean diameter along the width direction of the upper mold increases first, and then gradually decreases from the SEN to the narrow wall. Close agreements between the predictions and measurements demonstrate the capability of the MUSIG model in modeling bubbly flow inside the continuous-casting mold.

  19. Population Balance Modeling of Polydispersed Bubbly Flow in Continuous-Casting Using Multiple-Size-Group Approach

    NASA Astrophysics Data System (ADS)

    Liu, Zhongqiu; Li, Linmin; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa; Tsukihashi, Fumitaka

    2015-02-01

    A population balance model based on the multiple-size-group (MUSIG) approach has been developed to investigate the polydispersed bubbly flow inside the slab continuous-casting mold and bubble behavior including volume fraction, breakup, coalescence, and size distribution. The Eulerian-Eulerian approach is used to describe the equations of motion of the two-phase flow. All the non-drag forces (lift force, virtual mass force, wall lubrication force, and turbulent dispersion force) and drag force are incorporated in this model. Sato and Sekiguchi model is used to account for the bubble-induced turbulence. Luo and Svendsen model and Prince and Blanch model are used to describe the bubbles breakup and coalescence behavior, respectively. A 1/4th water model of the slab continuous-casting mold was applied to investigate the distribution and size of bubbles by injecting air through a circumferential inlet chamber which was made of the specially-coated samples of mullite porous brick, which is used for the actual upper nozzle. Against experimental data, numerical results showed good agreement for the gas volume fraction and local bubble Sauter mean diameter. The bubble Sauter mean diameter in the upper recirculation zone decreases with increasing water flow rate and increases with increasing gas flow rate. The distribution of bubble Sauter mean diameter along the width direction of the upper mold increases first, and then gradually decreases from the SEN to the narrow wall. Close agreements between the predictions and measurements demonstrate the capability of the MUSIG model in modeling bubbly flow inside the continuous-casting mold.

  20. On the relationship of inter-particle cohesiveness and bulk powder behavior: Flowability of pharmaceutical powders.

    PubMed

    Capece, Maxx; Silva, Karina Ruiz; Sunkara, Divya; Strong, John; Gao, Ping

    2016-09-10

    This study investigates the relationship between particle interactions dominated by the cohesive van der Waals force and powder flowability for materials commonly used by the pharmaceutical industry in oral solid dosage formulation. This study first sought to correlate the granular Bond number, defined as the ratio of the inter-particle cohesion force to particle weight, to the flow function coefficient, a metric commonly used to assess powder flowability. However, the granular Bond number which strictly quantifies inter-particle cohesiveness was found to correlate poorly with powder flowability due to the complexity associated with particle assemblies. To account for the multitude of interactions between particles of different sizes within a powder and to more precisely predict bulk powder behavior, a population-dependent granular Bond number was proposed. The population-dependent granular Bond number which explicitly accounts for particle size distribution and described herein as a quantification of powder cohesiveness (instead of inter-particle cohesiveness) was shown to correlate well with the flow function coefficient for a wide variety of materials including four active pharmaceutical ingredients (APIs) and fourteen common pharmaceutical excipients. Due to the success of the population-dependent granular Bond number, it was extended to predict the flowability of powder blends. This so-called population-dependent multi-component granular Bond number takes into account relevant material properties and particle interactions and was used to predict the flowability of 6-component powder blends containing acetaminophen as a model cohesive active pharmaceutical ingredient. Prediction of bulk powder behavior from individual material properties as accomplished here may be highly useful in formulation development.

  1. On the relationship of inter-particle cohesiveness and bulk powder behavior: Flowability of pharmaceutical powders.

    PubMed

    Capece, Maxx; Silva, Karina Ruiz; Sunkara, Divya; Strong, John; Gao, Ping

    2016-09-10

    This study investigates the relationship between particle interactions dominated by the cohesive van der Waals force and powder flowability for materials commonly used by the pharmaceutical industry in oral solid dosage formulation. This study first sought to correlate the granular Bond number, defined as the ratio of the inter-particle cohesion force to particle weight, to the flow function coefficient, a metric commonly used to assess powder flowability. However, the granular Bond number which strictly quantifies inter-particle cohesiveness was found to correlate poorly with powder flowability due to the complexity associated with particle assemblies. To account for the multitude of interactions between particles of different sizes within a powder and to more precisely predict bulk powder behavior, a population-dependent granular Bond number was proposed. The population-dependent granular Bond number which explicitly accounts for particle size distribution and described herein as a quantification of powder cohesiveness (instead of inter-particle cohesiveness) was shown to correlate well with the flow function coefficient for a wide variety of materials including four active pharmaceutical ingredients (APIs) and fourteen common pharmaceutical excipients. Due to the success of the population-dependent granular Bond number, it was extended to predict the flowability of powder blends. This so-called population-dependent multi-component granular Bond number takes into account relevant material properties and particle interactions and was used to predict the flowability of 6-component powder blends containing acetaminophen as a model cohesive active pharmaceutical ingredient. Prediction of bulk powder behavior from individual material properties as accomplished here may be highly useful in formulation development. PMID:27353729

  2. Group size of veal calves does not affect production, physiological, or hematological indicators of welfare and has transient effects on health

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Holstein-Friesian bull calves (n = 168; 44 ± 3 d of age), were used to investigate the effect of group size on performance, health, hematology, and welfare of veal calves. Groups of calves were assigned to 1 of 3 group housing treatments with 2, 4, or 8 calves per pen (initial BW 65.3 ± 3.7, 66.5 ± ...

  3. Determination of flow-regime boundaries for cohesive particles. Quarterly report, December 20, 1990--March 19, 1991

    SciTech Connect

    Knowlton, T.M.; Findlay, J.G.

    1992-01-01

    The overall objective of this program is the development of a hydrodynamic model to predict the choking/non-choking flow regime boundary of fine, cohesive (i.e., Geldart Group C) powders. Specific objectives are to: (1) Develop a two-dimensional hydrodynamic model that can be applied to cohesive solids. (2) Generate large-scale solids-flows data that will be used to verify the model.

  4. Relating Cohesive Zone Model to Linear Elastic Fracture Mechanics

    NASA Technical Reports Server (NTRS)

    Wang, John T.

    2010-01-01

    The conditions required for a cohesive zone model (CZM) to predict a failure load of a cracked structure similar to that obtained by a linear elastic fracture mechanics (LEFM) analysis are investigated in this paper. This study clarifies why many different phenomenological cohesive laws can produce similar fracture predictions. Analytical results for five cohesive zone models are obtained, using five different cohesive laws that have the same cohesive work rate (CWR-area under the traction-separation curve) but different maximum tractions. The effect of the maximum traction on the predicted cohesive zone length and the remote applied load at fracture is presented. Similar to the small scale yielding condition for an LEFM analysis to be valid. the cohesive zone length also needs to be much smaller than the crack length. This is a necessary condition for a CZM to obtain a fracture prediction equivalent to an LEFM result.

  5. Investigating Cohesion and Coherence Discourse Strategies of Chinese Students with Varied Lengths of Residence in Canada

    ERIC Educational Resources Information Center

    Leo, Krista

    2012-01-01

    This study examines how three age-on-arrival (AOA) groups of Chinese-background ESL students use two types of cohesive devices on a standardized essay exam. A discourse analysis of 90 first-year students' expository writing samples was conducted to ascertain how factors such as first language (L1) and length of residence (LOR) in Canada influence…

  6. Three Educational Values for a Multicultural Society: Difference Recognition, National Cohesion and Equality

    ERIC Educational Resources Information Center

    Blum, Lawrence

    2014-01-01

    Educational aims for societies comprising multiple ethnic, cultural and racial groups should involve three different values--recognizing difference, national cohesion and equality. Recognition of difference acknowledges and respects ethnocultural identities and in educational contexts also encourages mutual engagement across difference. National…

  7. Marital Cohesion, Flexibility, and Communication in the Marriages of Nontraditional and Traditional Women.

    ERIC Educational Resources Information Center

    Rhoden, J. Lyn

    2003-01-01

    Compares reported levels of marital quality, marital stability, and the marital processes of cohesion, flexibility, and communication in the marriages of nontraditional and traditional women. Results indicated many similarities between the two groups; however, nontraditional women reported greater flexibility in their marriages. Implications of…

  8. Emotional Intelligence, Communication Competence, and Student Perceptions of Team Social Cohesion

    ERIC Educational Resources Information Center

    Troth, Ashlea C.; Jordan, Peter J.; Lawrence, Sandra A.

    2012-01-01

    Students generally report poor experiences of group work in university settings. This study examines whether individual student perceptions of team social cohesion are determined by their level of emotional intelligence (EI) and whether this relationship is mediated by their communication skills. Business students (N = 273) completed the 16-item…

  9. Cluster size statistic and cluster mass statistic: two novel methods for identifying changes in functional connectivity between groups or conditions.

    PubMed

    Ing, Alex; Schwarzbauer, Christian

    2014-01-01

    Functional connectivity has become an increasingly important area of research in recent years. At a typical spatial resolution, approximately 300 million connections link each voxel in the brain with every other. This pattern of connectivity is known as the functional connectome. Connectivity is often compared between experimental groups and conditions. Standard methods used to control the type 1 error rate are likely to be insensitive when comparisons are carried out across the whole connectome, due to the huge number of statistical tests involved. To address this problem, two new cluster based methods--the cluster size statistic (CSS) and cluster mass statistic (CMS)--are introduced to control the family wise error rate across all connectivity values. These methods operate within a statistical framework similar to the cluster based methods used in conventional task based fMRI. Both methods are data driven, permutation based and require minimal statistical assumptions. Here, the performance of each procedure is evaluated in a receiver operator characteristic (ROC) analysis, utilising a simulated dataset. The relative sensitivity of each method is also tested on real data: BOLD (blood oxygen level dependent) fMRI scans were carried out on twelve subjects under normal conditions and during the hypercapnic state (induced through the inhalation of 6% CO2 in 21% O2 and 73%N2). Both CSS and CMS detected significant changes in connectivity between normal and hypercapnic states. A family wise error correction carried out at the individual connection level exhibited no significant changes in connectivity.

  10. Neighborhoods and mental health: exploring ethnic density, poverty, and social cohesion among Asian Americans and Latinos.

    PubMed

    Hong, Seunghye; Zhang, Wei; Walton, Emily

    2014-06-01

    This study examines the associations of neighborhood ethnic density and poverty with social cohesion and self-rated mental health among Asian Americans and Latinos. Path analysis is employed to analyze data from the 2002-2003 National Latino and Asian American Study (NLAAS) and the 2000 U.S. Census (N = 2095 Asian Americans living in N = 259 neighborhoods; N = 2554 Latinos living in N = 317 neighborhoods). Findings reveal that neighborhood ethnic density relates to poor mental health in both groups. Social cohesion partially mediates that structural relationship, but is positively related to ethnic density among Latinos and negatively related to ethnic density among Asian Americans. Although higher neighborhood poverty is negatively associated with mental health for both groups, the relationship does not hold in the path models after accounting for social cohesion and covariates. Furthermore, social cohesion fully mediates the association between neighborhood poverty and mental health among Latinos. This study highlights the necessity of reconceptualizing existing theories of social relationships to reflect complex and nuanced mechanisms linking neighborhood structure and mental health for diverse racial and ethnic groups.

  11. Two girls for every boy: The effects of group size and composition on the reproductive success of male and female white-faced capuchins.

    PubMed

    Fedigan, Linda Marie; Jack, Katharine M

    2011-02-01

    Many factors have been hypothesized to affect the size and adult sex ratios of primate groups and these, in turn, have been argued to influence birth rates. Using park-wide census data collected on a population of capuchins over a 25-year period, we examined whether group size and adult sex ratio affect the per capita reproductive success of male and female white-faced capuchins (Cebus capucinus) in Santa Rosa National Park, Costa Rica. We found that the reproductive success of females (measured as the observed minus the expected ratio of immatures to adult females in the group) decreased with increasing group size, whereas that of males was independent of group size. The proportion of adult males residing in groups had significant, yet contrasting effects on males and females. Male reproductive success was negatively associated with the proportion of males residing in groups whereas female reproductive success increased with the proportion of males. The latter finding supports the intersexual conflict hypothesis, which suggests that a conflict of interest occurs between males and females over adult sex ratios. The effects of group size and composition on the reproductive success of capuchins, a male-dispersed omnivorous species, are similar to those reported for howlers, a bisexually-dispersed folivorous species. One common factor between these taxa is that groups with low ratios of males to females are at greater risk of takeovers and resultant infanticide. Our results suggest that regardless of dietary preference and dispersal pattern, the threat of infanticide can constrain primate group size and composition.

  12. Direct numerical simulations of collision efficiency of cohesive sediments

    NASA Astrophysics Data System (ADS)

    Zhang, Jin-Feng; Maa, Jerome P.-Y.; Zhang, Qing-He; Shen, Xiao-Teng

    2016-09-01

    A clear understanding of the collision efficiency of cohesive sediment particles is critical for more accurate simulation of the flocculation processes. It is difficult, if not impossible, to carry out laboratory experiments to determine the collision efficiency for small particles. Direct Numerical Simulation (DNS) is a relatively feasible approach to describe the motion of spherical particles under gravity in calm water, and thus, to study the collision efficiency of these particles. In this study, the Lattice Boltzmann (LB) method is used to calculate the relative trajectories of two approaching particles with different ratios of sizes and densities. Results show that the inter-molecular forces (i.e., van der Waals attractive force, electrostatic repulsive/attractive force, and displacement force), which are usually neglected in previous studies, would affect the trajectories, and thus, lead to an overestimation of the collision efficiency. It is found that to increase the particle size ratio from 0.1 to 0.8 only slightly increases the collision efficiency, since the force caused by fluid-solid interaction between these two particles is reduced. To increase the submerged particle density ratio from 1 to 22, however, would significantly decrease the collision efficiency. Earlier analytical formulations of collision efficiency, which only consider the effects of particle size ratio, have significantly overestimated the collision efficiency (change from 0.01 to 0.6) when the particle size ratio is around 0.5.

  13. Validating Experimental Bedform Dynamics on Cohesive Sand-Mud Beds in the Dee Estuary

    NASA Astrophysics Data System (ADS)

    Baas, Jaco H.; Baker, Megan; Hope, Julie; Malarkey, Jonathan; Rocha, Renata

    2014-05-01

    Recent laboratory experiments and field measurements have shown that small quantities of cohesive clay, and in particular 'sticky' biological polymers, within a sandy substrate dramatically reduce the development rate of sedimentary bedforms, with major implications for sediment transport rate calculations and process interpretations from the sedimentary record. FURTHER INFORMATION Flow and sediment transport predictions from sedimentary structures found in modern estuaries and within estuarine geological systems are impeded by an almost complete lack of process-based knowledge of the behaviour of natural sediments that consist of mixtures of cohesionless sand and biologically-active cohesive mud. Indeed, existing predictive models are largely based on non-organic cohesionless sands, despite the fact that mud, in pure form or mixed with sand, is the most common sediment on Earth and also the most biologically active interface across a range of Earth-surface environments, including rivers and shallow seas. The multidisciplinary COHBED project uses state-of-the-art laboratory and field technologies to measure the erosional properties of mixed cohesive sediment beds and the formation and stability of sedimentary bedforms on these beds, integrating the key physical and biological processes that govern bed evolution. The development of current ripples on cohesive mixed sediment beds was investigated as a function of physical control on bed cohesion versus biological control on bed cohesion. These investigations included laboratory flume experiments in the Hydrodynamics Laboratory (Bangor University) and field experiments in the Dee estuary (at West Kirby near Liverpool). The flume experiments showed that winnowing of fine-grained cohesive sediment, including biological stabilisers, is an important process affecting the development rate, size and shape of the cohesive bedforms. The ripples developed progressively slower as the kaolin clay fraction in the sandy substrate

  14. National Assessment of Educational Progress. 1969-70 Citizenship: Group Results for Sex, Region, and Size of Community. National Assessment Report 6.

    ERIC Educational Resources Information Center

    Campbell, Vincent N.; And Others

    Information on assessment of citizenship achievement is presented in this report which compares 1970 first assessment results for the two sexes, four regions of the country, and four community sizes. Age groups assessed were 9, 13, 17, and 26 through 35 age group; geographical regions were Northeastern, Central, Western, and Southeastern; and…

  15. Size-regulated group separation of CoFe2O4 nanoparticles using centrifuge and their magnetic resonance contrast properties

    PubMed Central

    2013-01-01

    Magnetic nanoparticle (MNP)-based magnetic resonance imaging (MRI) contrast agents (CAs) have been the subject of extensive research over recent decades. The particle size of MNPs varies widely and is known to influence their physicochemical and pharmacokinetic properties. There are two commonly used methods for synthesizing MNPs, organometallic and aqueous solution coprecipitation. The former has the advantage of being able to control the particle size more effectively; however, the resulting particles require a hydrophilic coating in order to be rendered water soluble. The MNPs produced using the latter method are intrinsically water soluble, but they have a relatively wide particle size distribution. Size-controlled water-soluble MNPs have great potential as MRI CAs and in cell sorting and labeling applications. In the present study, we synthesized CoFe2O4 MNPs using an aqueous solution coprecipitation method. The MNPs were subsequently separated into four groups depending on size, by the use of centrifugation at different speeds. The crystal shapes and size distributions of the particles in the four groups were measured and confirmed by transmission electron microscopy and dynamic light scattering. Using X-ray diffraction analysis, the MNPs were found to have an inverse spinel structure. Four MNP groups with well-selected semi-Gaussian-like diameter distributions were obtained, with measured T2 relaxivities (r2) at 4.7 T and room temperature in the range of 60 to 300 mM−1s−1, depending on the particle size. This size regulation method has great promise for applications that require homogeneous-sized MNPs made by an aqueous solution coprecipitation method. Any group of the CoFe2O4 MNPs could be used as initial base cores of MRI T2 CAs, with almost unique T2 relaxivity owing to size regulation. The methodology reported here opens up many possibilities for biosensing applications and disease diagnosis. PACS 75.75.Fk, 78.67.Bf, 61.46.Df PMID:24004536

  16. Multiple Size Group Modeling of Polydispersed Bubbly Flow in the Mold: An Analysis of Turbulence and Interfacial Force Models

    NASA Astrophysics Data System (ADS)

    Liu, Zhongqiu; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa

    2015-04-01

    An inhomogeneous Multiple Size Group (MUSIG) model based on the Eulerian-Eulerian approach has been developed to describe the polydispersed bubbly flow inside the continuous-casting mold. A laboratory scale mold has been simulated using four different turbulence closure models (modified k - ɛ, RNG k - ɛ, k - ω, and SST) with the purpose of critically comparing their predictions of bubble Sauter mean diameter distribution with previous experimental data. Furthermore, the influences of all the interfacial momentum transfer terms including drag force, lift force, virtual mass force, wall lubrication force, and turbulent dispersion force are investigated. The breakup and coalescence effects of the bubbles are modeled according to the bubble breakup by the impact of turbulent eddies while for bubble coalescence by the random collisions driven by turbulence and wake entrainment. It has been found that the modified k - ɛ model shows better agreement than other models in predicting the bubble Sauter mean diameter profiles. Further, simulations have also been performed to understand the sensitivity of different interfacial forces. The appropriate drag force coefficient, lift force coefficient, virtual mass force coefficient, and turbulent dispersion force coefficient are chosen in accordance with measurements of water model experiments. However, the wall lubrication force does not have much effect on the current polydispersed bubbly flow system. Finally, the MUSIG model is then used to estimate the argon bubble diameter in the molten steel of the mold. The argon bubble Sauter mean diameter generated in molten steel is predicted to be larger than air bubbles in water for the similar conditions.

  17. Intact discourse cohesion and coherence following bilateral ventromedial prefrontal cortex.

    PubMed

    Kurczek, Jake; Duff, Melissa C

    2012-12-01

    Discourse cohesion and coherence give communication its continuity providing the grammatical and lexical links that hold an utterance or text together and give it meaning. Researchers often link cohesion and coherence deficits to the frontal lobes by drawing attention to frontal lobe dysfunction in populations where discourse cohesion and coherence deficits are reported and through attribution of these deficits to underlying cognitive impairments putatively associated with the frontal lobes. We examined the distinct contribution of a region of the frontal lobes, the ventromedial prefrontal cortex (vmPFC), to discourse cohesion and coherence across a range of discourse tasks. We found that bilateral vmPFC damage does not impair cohesion and coherence in spoken discourse. This study provides insights into the contribution of the major anatomical subdivisions of the frontal lobes to language use and furthers our understanding of the neural and cognitive underpinnings of discourse cohesion and coherence.

  18. Atomistic Cohesive Zone Models for Interface Decohesion in Metals

    NASA Technical Reports Server (NTRS)

    Yamakov, Vesselin I.; Saether, Erik; Glaessgen, Edward H.

    2009-01-01

    Using a statistical mechanics approach, a cohesive-zone law in the form of a traction-displacement constitutive relationship characterizing the load transfer across the plane of a growing edge crack is extracted from atomistic simulations for use within a continuum finite element model. The methodology for the atomistic derivation of a cohesive-zone law is presented. This procedure can be implemented to build cohesive-zone finite element models for simulating fracture in nanocrystalline or ultrafine grained materials.

  19. Retinal Nerve Fiber Layer Thicknesses in Three Different Optic Nerve Head Size Groups Measured by Cirrus Spectral Domain Optical Coherence Tomography

    PubMed Central

    Gür Güngör, Sirel; Akman, Ahmet; Küçüködük, Ali; Çolak, Meriç

    2016-01-01

    Objectives: To compare the retinal nerve fiber layer (RNFL) thicknesses in three different optic nerve head (ONH) size groups measured by Cirrus spectral domain optical coherence tomography (OCT). Materials and Methods: Between January and March 2013, 253 eyes of 253 healthy subjects were enrolled in this study (mean age: 42.7±7.4 years [28-62 years]; 121 men and 132 women). The patients were divided into 3 groups according to ONH size: 77 patients in the “small ONH” group (ONH area <1.63 mm2), 90 patients in the “medium ONH” group (ONH area 1.63-1.97 mm2), and 86 patients in the “large ONH” group (ONH area >1.97 mm2). Results: There were significant differences in superior (p=0.008), inferior (p=0.004) and average RNFL thickness (p=0.001) between the small, medium and large ONH groups. Positive correlations between ONH size and inferior/average RNFL thicknesses were significant but very weak (r=0.150, p=0.017 and r=0.157, p=0.013 respectively). Conclusion: RNFL thickness as measured by Cirrus OCT is positively correlated with ONH size and the differences in RNFL thickness were statistically significant between groups. This correlation and difference may be the result of a varying distance between the circular scan and the ONH margin. PMID:27800261

  20. Alluvial Morphology In Cohesive Sediment: The Mahakam Lowland Area

    NASA Astrophysics Data System (ADS)

    Vermeulen, B.; van Berkum, S.; Hoitink, A.; Sassi, M.; Hidayat, H.

    2011-12-01

    In the lower part of its course, the Mahakam River (Indonesia) flows through the subsiding Kutai Basin, through its own cohesive alluvium. The river is surrounded by a large number of floodplain lakes and peat domes. Its planform geometry and bed morphology reveal the presence of very sharp bends and associated deep scours. The lakes are connected to the river by small-sized tie-channels, which play a crucial role the discharge regime of the Mahakam downstream of the lake district. This study aims to establish the morphology of the sharp river bends and tie-channels, and to evaluate the contribution of sediment cohesion, riparian vegetation and the presence of peat in the area to river banks stability. Based on a detailed reconnaissance survey of the river banks, patterns of sedimentation and erosion in highly curved bends are found to be mirrored relative to those in mildly curved river stretches. Bars develop at the concave banks of sharp bends. On the convex sides, reattachment bars are often found, indicating flow separation at the inner bank. These sharp bends are thought to develop due to failure of the river to cutoff meanders due to erosion resistance of the banks. The top of the levees are located high in the landscape, forming a barrier between the surrounding swampy floodplains and the river. These levees form a buffer between the river corridor and peat domes, suggesting peat domes to be formed in areas outside the river corridor, rather than vice versa. Tie-channels are characterized by a very stable morphology and exhibit levees with decreasing height away from the river. The bed of these channels is armored with gravel and concretions of iron, organic matter and clay, suggesting that very high flow velocity can occur when the water level in the river changes abruptly. Both in the tie-channels and in the meandering part of the river, we found no apparent effect of vegetation on morphometric properties. We conclude the morphological characteristics of

  1. Improving powder flow properties of a cohesive lactose monohydrate powder by intensive mechanical dry coating.

    PubMed

    Zhou, Qi; Armstrong, Brian; Larson, Ian; Stewart, Peter J; Morton, David A V

    2010-02-01

    The objective of this study was to improve the cohesive lactose powder flowability. A cohesive lactose monohydrate powder was processed in either a tumbling blender or an intensive mechanical processor with either magnesium stearate or fumed silica. No substantial changes in particle size were detected by laser diffraction following either treatment. The untreated lactose sample exhibited very poor powder flow. Only limited improvements in powder flowability were indicated after the tumbling blending, intensive mechanical processing with the fumed silica or without additives. However, the intensive mechanical processing of the lactose sample with magnesium stearate demonstrated exceptionally large increases in both poured and tapped density as well as notable improvements in all powder flowability indicators examined. Our findings support the use of intensive mechanical processing technique as an effective method to coat cohesive pharmaceutical powders with selected additives, modify the surface nature of the particles, reduce the interparticle cohesive forces and hence improve powder flowability. The subtle differences in powder flow behaviour of lactose samples between the untreated and tumbling blended powders with magnesium stearate were only detected by the powder rheometer using its dynamic mode, indicating its potential advantages over traditional powder flow characterisation approaches.

  2. The effect of cohesive forces on the fluidization of aeratable powders

    SciTech Connect

    Galvin, Janine F.; Benyahia, Sofiane

    2014-01-01

    The effects of cohesive forces of van der Waals type in the fluidization/defluidization of aeratable type A powders in the Geldart classification are numerically investigated. The effects of friction and particle-size distribution (PSD) on some design-significant parameters, such as minimum fluidization and bubbling velocities, are also investigated. For these types of particles, cohesive forces are observed as necessary to fully exhibit the role friction plays in commonly observed phenomena, such as pressure overshoot and hysteresis around minimum fluidization. This study also shows that a full-experimental PSD consisting of a dozen particle sizes may be sufficiently represented by a few particle diameters. Reducing the number of particle types may benefit the continuum approach, which is based on the kinetic theory of granular flow, by reducing computational expense, while still maintaining the accuracy of the predictions.

  3. A visualization and characterization of microstructures of cohesive powders

    NASA Astrophysics Data System (ADS)

    Patil, Vineeth R.

    In this work, a framework for the determination of the particle positions in a fluorescent powder structure was created. The feasibility of imaging and quantifying sedimented particulate samples in air was demonstrated by using micron-sized poly-dispersed electrophotographic printing particles. Particle positions were determined by a Confocal Laser Scanning Microscope (CLSM) to capture a stack of cross-sectional images of fluorescent particle clusters. The resulting images were analyzed using Matlab image processing tools. The XYZ coordinates and radii for these particles (assumed spherical) were calculated in several selected sampling volumes, and the packing fractions were calculated. A three-dimensional visualization of the particle structure was then created. The CLSM particle results obtained from this study were compared with Scanning Electron Microscopy (SEM) particle imaging results. A difference in the average particle radii of the CLSM results from the SEM results was observed. The three-dimensional reconstruction of these particles showed a highly porous structure. The average packing fraction of 14.07% +/- 0.84% was comparable to the literature packing fraction values for cohesive particles [1]. The cohesive nature of toner was noted from this comparison. Based on this finding, the self-similar nature of the particle clusters was investigated in the samples. This methodology of three-dimensional particle mapping and visualization has the potential to lead to much needed materials and structural analyses for fine particles. The frame-by-frame particle-tracking method developed in this study can be adapted into other digital imaging methods like X-ray micro-computed tomography (muCT) where the scanned object is also digitized through layer-by-layer scanning.

  4. Pregnenolone functions in centriole cohesion during mitosis.

    PubMed

    Hamasaki, Mayumi; Matsumura, Shigeru; Satou, Ayaka; Takahashi, Chisato; Oda, Yukako; Higashiura, Chika; Ishihama, Yasushi; Toyoshima, Fumiko

    2014-12-18

    Cell division is controlled by a multitude of protein enzymes, but little is known about roles of metabolites in this mechanism. Here, we show that pregnenolone (P5), a steroid that is produced from cholesterol by the steroidogenic enzyme Cyp11a1, has an essential role in centriole cohesion during mitosis. During prometa-metaphase, P5 is accumulated around the spindle poles. Depletion of P5 induces multipolar spindles that result from premature centriole disengagement, which are rescued by ectopic introduction of P5, but not its downstream metabolites, into the cells. Premature centriole disengagement, induced by loss of P5, is not a result of precocious activation of separase, a key factor for the centriole disengagement in anaphase. Rather, P5 directly binds to the N-terminal coiled-coil domain of short-form of shugoshin 1 (sSgo1), a protector for centriole cohesion and recruits it to spindle poles in mitosis. Our results thus reveal a steroid-mediated centriole protection mechanism.

  5. Perceived coach-created and peer-created motivational climates and their associations with team cohesion and athlete satisfaction: evidence from a longitudinal study.

    PubMed

    García-Calvo, Tomás; Leo, Francisco Miguel; Gonzalez-Ponce, Inmaculada; Sánchez-Miguel, Pedro Antonio; Mouratidis, Athanasios; Ntoumanis, Nikos

    2014-01-01

    In this longitudinal study, we examined the extent to which perceived coach- and peer-created motivational climates are associated with athlete-group cohesion and satisfaction with participation among Spanish soccer players competing in the Third National Division. Multilevel modelling analyses showed that perceived coach-created task climate was positively related to perceived cohesion and players' satisfaction with their participation within their team. Also, perceived peer-created task climate related positively to perceived cohesion. The results indicate the importance of considering peer-related aspects of the motivational climate in addition to considering the coach-related aspects of the motivational climate when examining motivational group dynamics in sport.

  6. Biostabilization and Transport of Cohesive Sediment Deposits in the Three Gorges Reservoir.

    PubMed

    Fang, Hongwei; Fazeli, Mehdi; Cheng, Wei; Huang, Lei; Hu, Hongying

    2015-01-01

    Cohesive sediment deposits in the Three Gorges Reservoir, China, were used to investigate physical and geochemical properties, biofilm mass, and erosion and deposition characteristics. Biofilm cultivation was performed in a recirculating flume for three different periods (5, 10 and 15 days) under ambient temperature and with sufficient nutrients supply. Three groups of size-fractionated sediment were sequentially used, including 0-0.02 mm, 0.02-0.05 mm and 0.05-0.10 mm. Desired conditions for erosion and deposition were designed by managing high bed shear stress at the narrow part of upstream flume and low shear stress at the wide part of downstream flume. Biostabilization and transport characteristics of the biofilm coated sediment (bio-sediment) were strongly influenced by the cultivation period, and the results were compared with clean sediment. The bio-sediment was more resistant to erosion, and the mean shear stress was increased by factors of 2.65, 2.73 and 5.01 for sediment with 5, 10 and 15 days of biofilm growth compared with clean sediment, resulting in less sediment being eroded from the bed. Simultaneously, the settling velocity was smaller for bio-sediment due to higher organic content and porosity (i.e., lower density). Additionally, there was a smaller probability of deposition for sediment with a longer cultivation period after erosion, resulting in more retention time in aquatic systems. These results will benefit water management in natural rivers. PMID:26560122

  7. Biostabilization and Transport of Cohesive Sediment Deposits in the Three Gorges Reservoir

    PubMed Central

    Fang, Hongwei; Fazeli, Mehdi; Cheng, Wei; Huang, Lei; Hu, Hongying

    2015-01-01

    Cohesive sediment deposits in the Three Gorges Reservoir, China, were used to investigate physical and geochemical properties, biofilm mass, and erosion and deposition characteristics. Biofilm cultivation was performed in a recirculating flume for three different periods (5, 10 and 15 days) under ambient temperature and with sufficient nutrients supply. Three groups of size-fractionated sediment were sequentially used, including 0–0.02 mm, 0.02–0.05 mm and 0.05–0.10 mm. Desired conditions for erosion and deposition were designed by managing high bed shear stress at the narrow part of upstream flume and low shear stress at the wide part of downstream flume. Biostabilization and transport characteristics of the biofilm coated sediment (bio-sediment) were strongly influenced by the cultivation period, and the results were compared with clean sediment. The bio-sediment was more resistant to erosion, and the mean shear stress was increased by factors of 2.65, 2.73 and 5.01 for sediment with 5, 10 and 15 days of biofilm growth compared with clean sediment, resulting in less sediment being eroded from the bed. Simultaneously, the settling velocity was smaller for bio-sediment due to higher organic content and porosity (i.e., lower density). Additionally, there was a smaller probability of deposition for sediment with a longer cultivation period after erosion, resulting in more retention time in aquatic systems. These results will benefit water management in natural rivers. PMID:26560122

  8. Key Skills for Science Learning: The Importance of Text Cohesion and Reading Ability

    ERIC Educational Resources Information Center

    Hall, Sophie Susannah; Maltby, John; Filik, Ruth; Paterson, Kevin B.

    2016-01-01

    To explore the importance of text cohesion, we conducted two experiments. We measured online (reading times) and offline (comprehension accuracy) processes for texts that were high and low cohesion. In study one (n?=?60), we manipulated referential cohesion using noun repetition (high cohesion) and synonymy (low cohesion). Students showed enhanced…

  9. Macro and micro scale interactions between cohesive sediment tracers and natural mud.

    NASA Astrophysics Data System (ADS)

    Spencer, Kate; Manning, Andrew; Droppo, Ian; Leppard, Gary; Benson, Thomas

    2010-05-01

    Understanding the dispersion patterns of fine, cohesive sediment (< 63 micron) is fundamental to the sustainable management of aquatic environments. In order to develop sediment transport models and predict sediment dispersion, accurate field techniques for the measurement of sediment transport are required. Although this is relatively simple for the sand sized fraction, measuring transport pathways for cohesive sediment is more problematic. Cohesive sediment tracers developed for this purpose include synthetic tracer particles (e.g. polymers) and labelled natural clays (e.g. Mahler et al. 1998, Yin et al. 1999, Krezoski 1985; Spencer et al. 2007) and a fundamental assumption is that the tracer has the same physical properties as natural sediment. For the cohesive fraction this means that the tracer must be incorporated into and transported via floc aggregates (Black et al. 2006). A few studies have examined the physical behaviour of cohesive tracers (e.g. Manning et al. in press) but most are limited to the examination of gross settling characteristics (e.g. Louisse et al. 1986) rather than floc formation and behaviour. This work focuses on a labelled natural clay; a Ho-montmorillonite (see Spencer et al. 2007). The aims of this work were to examine the physical characteristics, internal structure and settling dynamics of the tracer and to determine whether the tracer flocculated and interacted with natural estuarine muds at both macro- and microscales. To our knowledge, this is the first study to present data examining the flocculation characteristics and structure of cohesive sediment tracers and their interaction with natural sediment. Macroscale floc characteristics such as floc size and settling velocity measurements were obtained using the LabSFLOC - Laboratory Spectral Flocculation Characteristics - instrument. Floc density, porosity, dry mass, and mass settling flux were then calculated. Floc internal microstructure (1-2 nm) and elemental floc composition

  10. Population sizes and group characteristics of Siberian Crane (Leuco-geranus leucogeranus) and Hooded Crane (Grus monacha) in Poyang Lake Wetland.

    PubMed

    Shao, Ming-Qin; Guo, Hong; Jiang, Jian-Hong

    2014-09-01

    Both the Siberian Crane (Leucogeranus leucogeranus) and Hooded Crane (Grus monacha) have limited population sizes and are considered endangered by domestic Chinese and international agencies. To document the current size of their respective populations and characterize their groups, between October 2012 and April 2013 we undertook fieldwork at four nature reserve areas within the Poyang Lake wetlands. We divided Poyanghu National Nature Reserve (PYH) into the Wucheng (PWC) and Hengfeng areas (PHF), because each are each located in different counties. Our fieldwork showed that the Siberian Crane occurred mainly in PYH (364 in the PHF, 158 in the PWC) and the Nanjishan Wetland National Nature Reserve (NJS, with 200 individuals). The Hooded Crane was mainly distributed in PYH (302 in the PHF and 154 in the PWC). Family groups accounted for more than 50% of the total number of groups among both species, with Hooded Cranes forming more family groups than Siberian Cranes. Typically, these groups were formed of two adults with one offspring (Siberian Crane), and two adults with two offspring (Hooded Crane), with the mean family group size of the Siberian Crane and Hooded Crane being respectively 2.65 ± 0.53 (n=43) and 3.09 ± 0.86 (n=47) individuals per group. The mean collective group size of the Siberian Crane and Hooded Crane included 28.09 ± 24.94 (n=23) and 28.94 ± 27.97 (n=16) individuals per group, respectively, with the proportion of juveniles among Hooded Cranes being more than double that seen among the Siberian Cranes.

  11. Population sizes and group characteristics of Siberian Crane (Leuco-geranus leucogeranus) and Hooded Crane (Grus monacha) in Poyang Lake Wetland.

    PubMed

    Shao, Ming-Qin; Guo, Hong; Jiang, Jian-Hong

    2014-09-01

    Both the Siberian Crane (Leucogeranus leucogeranus) and Hooded Crane (Grus monacha) have limited population sizes and are considered endangered by domestic Chinese and international agencies. To document the current size of their respective populations and characterize their groups, between October 2012 and April 2013 we undertook fieldwork at four nature reserve areas within the Poyang Lake wetlands. We divided Poyanghu National Nature Reserve (PYH) into the Wucheng (PWC) and Hengfeng areas (PHF), because each are each located in different counties. Our fieldwork showed that the Siberian Crane occurred mainly in PYH (364 in the PHF, 158 in the PWC) and the Nanjishan Wetland National Nature Reserve (NJS, with 200 individuals). The Hooded Crane was mainly distributed in PYH (302 in the PHF and 154 in the PWC). Family groups accounted for more than 50% of the total number of groups among both species, with Hooded Cranes forming more family groups than Siberian Cranes. Typically, these groups were formed of two adults with one offspring (Siberian Crane), and two adults with two offspring (Hooded Crane), with the mean family group size of the Siberian Crane and Hooded Crane being respectively 2.65 ± 0.53 (n=43) and 3.09 ± 0.86 (n=47) individuals per group. The mean collective group size of the Siberian Crane and Hooded Crane included 28.09 ± 24.94 (n=23) and 28.94 ± 27.97 (n=16) individuals per group, respectively, with the proportion of juveniles among Hooded Cranes being more than double that seen among the Siberian Cranes. PMID:25297076

  12. Text Structure and Patterns of Cohesion in Narrative Texts Written by Adults with a History of Language Impairment

    ERIC Educational Resources Information Center

    Mortensen, Lynne; Smith-Lock, Karen; Nickels, Lyndsey

    2009-01-01

    This paper examines text structure and patterns of cohesion in stories written by a group of adults with a history of childhood language impairment. The study aimed to extend our knowledge of writing difficulties in this group by building upon a study that examined clause level phenomena (Smith-Lock, Nickels, & Mortensen, this issue). Ten adults…

  13. The Role of Collective Efficacy, Cognitive Quality, and Task Cohesion in Computer-Supported Collaborative Learning (CSCL)

    ERIC Educational Resources Information Center

    Wang, Shu-Ling; Hwang, Gwo-Jen

    2012-01-01

    Research has suggested that CSCL environments contain fewer social context clues, resulting in various group processes, performance or motivation. This study thus attempts to explore the relationship among collective efficacy, group processes (i.e. task cohesion, cognitive quality) and collaborative performance in a CSCL environment. A total of 75…

  14. Effect of Alignment on Text Cohesion in the Continuation Task

    ERIC Educational Resources Information Center

    Jiang, Lin; Xu, Xin

    2016-01-01

    A continuation task provides learners with a text with its ending removed and requires them to complete it through writing in a most coherent and logical way. The current study investigated (a) whether the continuation task had a positive effect on text cohesion and (b) whether texts produced by pairs exhibited higher cohesion than those produced…

  15. A Reappraisal of Lexical Cohesion in Conversational Discourse

    ERIC Educational Resources Information Center

    Gomez Gonzalez, Maria De Los Angeles

    2013-01-01

    Cohesion, or the connectedness of discourse, has been recognized as playing a crucial role in both language production and comprehension processes. Researchers have debated about the "right" number and classification of cohesive devices, as well as about their interaction with coherence and/or genre. The present study proposes an integrative model…

  16. Discourse Analysis: Part I, Information Management and Cohesion.

    ERIC Educational Resources Information Center

    Lovejoy, Kim Brian; Lance, Donald M.

    Combining linguistics and composition studies, this paper (part 1 of a two-part article) proposes a model for the analysis of information management and cohesion in written discourse. It defines concepts of discourse analysis--specifically information management, syntax, semantic reference, lexicon, cohesion, and intonation, with examples taken…

  17. Forgiveness and Cohesion in Familial Perceptions of Alcohol Misuse

    ERIC Educational Resources Information Center

    Scherer, Michael; Worthington, Everett L.; Hook, Joshua N.; Campana, Kathryn L.; West, Steven L.; Gartner, Aubrey L.

    2012-01-01

    The authors examine the relationships between forgiveness, family cohesion, and alcohol. In Study 1 (N = 190), participants reported lower levels of trust and forgiveness for family members who misuse alcohol. In Study 2 (N = 141), the authors present a model demonstrating family cohesion and trait forgiveness related to state forgiveness of an…

  18. A Long Noncoding RNA Regulates Sister Chromatid Cohesion.

    PubMed

    Marchese, Francesco P; Grossi, Elena; Marín-Béjar, Oskar; Bharti, Sanjay Kumar; Raimondi, Ivan; González, Jovanna; Martínez-Herrera, Dannys Jorge; Athie, Alejandro; Amadoz, Alicia; Brosh, Robert M; Huarte, Maite

    2016-08-01

    Long noncoding RNAs (lncRNAs) are involved in diverse cellular processes through multiple mechanisms. Here, we describe a previously uncharacterized human lncRNA, CONCR (cohesion regulator noncoding RNA), that is transcriptionally activated by MYC and is upregulated in multiple cancer types. The expression of CONCR is cell cycle regulated, and it is required for cell-cycle progression and DNA replication. Moreover, cells depleted of CONCR show severe defects in sister chromatid cohesion, suggesting an essential role for CONCR in cohesion establishment during cell division. CONCR interacts with and regulates the activity of DDX11, a DNA-dependent ATPase and helicase involved in DNA replication and sister chromatid cohesion. These findings unveil a direct role for an lncRNA in the establishment of sister chromatid cohesion by modulating DDX11 enzymatic activity. PMID:27477908

  19. From Planning to Implementation: An Examination of Changes in the Research Design, Sample Size, and Precision of Group Randomized Trials Launched by the Institute of Education Sciences

    ERIC Educational Resources Information Center

    Spybrook, Jessaca; Puente, Anne Cullen; Lininger, Monica

    2013-01-01

    This article examines changes in the research design, sample size, and precision between the planning phase and implementation phase of group randomized trials (GRTs) funded by the Institute of Education Sciences. Thirty-eight GRTs funded between 2002 and 2006 were examined. Three studies revealed changes in the experimental design. Ten studies…

  20. Evidence from a Large Sample on the Effects of Group Size and Decision-Making Time on Performance in a Marketing Simulation Game

    ERIC Educational Resources Information Center

    Treen, Emily; Atanasova, Christina; Pitt, Leyland; Johnson, Michael

    2016-01-01

    Marketing instructors using simulation games as a way of inducing some realism into a marketing course are faced with many dilemmas. Two important quandaries are the optimal size of groups and how much of the students' time should ideally be devoted to the game. Using evidence from a very large sample of teams playing a simulation game, the study…

  1. Characterization of the components of the putative mammalian sister chromatid cohesion complex

    PubMed Central

    Darwiche, N.; Freeman, L.A.; Strunnikov, A.

    2009-01-01

    Establishing and maintaining proper sister chromatid cohesion throughout the cell cycle are essential for maintaining genome integrity. To understand how sister chromatid cohesion occurs in mammals, we have cloned and characterized mouse orthologs of proteins known to be involved in sister chromatid cohesion in other organisms. The cDNAs for the mouse orthologs of SMC1S.c. and SMC3S.c., mSMCB and mSMCD respectively, were cloned and the corresponding transcripts and proteins were characterized. mSMCB and mSMCD are transcribed at similar levels in adult mouse tissues except in testis, which has an excess of mSMCD transcripts. The mSMCB and mSMCD proteins, as well as the PW29 protein, a mouse homolog of Mcd1pS.c./Rad21S.p., form a complex similar to cohesin in X. laevis. mSMCB, mSMCD and PW29 protein levels show no significant cell-cycle dependence. The bulk of the mSMCB, mSMCD and PW29 proteins undergo redistribution from the chromosome vicinity to the cytoplasm during prometaphase and back to the chromatin in telophase. This pattern of intracellular localization suggests a complex role for this group of SMC proteins in chromosome dynamics. The PW29 protein and PCNA, which have both been implicated in sister chromatid cohesion, do not colocalize, indicating that these proteins may not function in the same cohesion pathway. Overexpression of a PW29-GFP fusion protein in mouse fibroblasts leads to inhibition of proliferation, implicating this protein and its complex with SMC proteins in the control of mitotic cycle progression. PMID:10375619

  2. Maternal corticosterone deposition in avian yolk: Influence of laying order and group size in a joint-nesting, cooperatively breeding species.

    PubMed

    Schmaltz, Gregory; Quinn, James S; Schoech, Stephan J

    2016-06-01

    Glucocorticoid hormones play a key role in day-to-day adjustments to fluctuating metabolic needs. These hormones also mediate physiological and behavioral responses to stressful events, allowing individuals to cope with stressors. Various environmental insults, such as a food shortages, predation attempts, and agonistic encounters often elevate plasma glucocorticoid levels in vertebrates. Because exposure to maternally-derived (via circulation or egg) glucocorticoids may be detrimental to the developing embryo, maternal stress can have negative carryover effects on offspring fitness. We examined corticosterone, the primary avian glucocorticoid, concentrations in egg yolk in a plural-breeding, joint-nesting species, the smooth-billed ani (Crotophaga ani), in which females compete among themselves to lay eggs in the final incubated clutch. We investigated whether yolk corticosterone levels varied with laying order and group size. Because egg-laying competition leads to physiological and social stress that is intensified with group size and laying order, we predicted that yolk corticosterone levels should increase from the early to the late egg-laying period and from single female to multi-female groups. In this two-year field study, we found that yolk corticosterone levels of late-laid eggs within the communal clutch were higher in multi-female groups than in single female groups. Results from this study suggest that laying females experience higher levels of stress in multi-female groups and that this maternal stress influences yolk corticosterone concentrations. This study identifies a novel cost of group-living in plural-breeding cooperatively breeding birds, namely an increase in yolk corticosterone levels with group size that may result in detrimental effects on offspring development. PMID:27118704

  3. One size does not fit all: HIV testing preferences differ among high-risk groups in Northern Tanzania

    PubMed Central

    Ostermann, Jan; Njau, Bernard; Mtuy, Tara; Brown, Derek S.; Mühlbacher, Axel; Thielman, Nathan

    2014-01-01

    In order to maximize the effectiveness of “Seek, Test, and Treat” strategies for curbing the HIV epidemic, new approaches are needed to increase the uptake of HIV testing services, particularly among high-risk groups. Low HIV testing rates among such groups suggests that current testing services may not align well with the testing preferences of these populations. Female bar workers and male mountain porters have been identified as two important high-risk groups in the Kilimanjaro Region of Tanzania. We used conventional survey methods and a Discrete Choice Experiment (DCE), a preference elicitation method increasingly applied by economists and policy makers to inform health policy and services, to analyze trade-offs made by individuals and quantify preferences for HIV testing services. Compared to 486 randomly selected community members, 162 female bar workers and 194 male Kilimanjaro porters reported 2 to 3 times as many lifetime sexual partners (p<0.001), but similar numbers of lifetime HIV tests (median 1–2 across all groups). Bivariate descriptive statistics were used to analyze differences in survey responses across groups. For the DCE, participants’ stated choices across 11,178 hypothetical HIV testing scenarios (322 female and 299 male participants × 9 choice tasks × 2 alternatives) were analyzed using gender-specific mixed logit models. Direct assessments and the DCE data demonstrated that barworkers were less likely to prefer home testing and were more concerned about disclosure issues compared with their community counterparts. Male porters preferred testing in venues where antiretroviral therapy was readily available. Both high-risk groups were less averse to traveling longer distances to test compared to their community counterparts. These results expose systematic differences in HIV testing preferences across high-risk populations compared to their community peers. Tailoring testing options to the preferences of high-risk populations should

  4. Sample size calculations for intervention trials in primary care randomizing by primary care group: an empirical illustration from one proposed intervention trial.

    PubMed

    Eldridge, S; Cryer, C; Feder, G; Underwood, M

    2001-02-15

    Because of the central role of the general practice in the delivery of British primary care, intervention trials in primary care often use the practice as the unit of randomization. The creation of primary care groups (PCGs) in April 1999 changed the organization of primary care and the commissioning of secondary care services. PCGs will directly affect the organization and delivery of primary, secondary and social care services. The PCG therefore becomes an appropriate target for organizational and educational interventions. Trials testing these interventions should involve randomization by PCG. This paper discusses the sample size required for a trial in primary care assessing the effect of a falls prevention programme among older people. In this trial PCGs will be randomized. The sample size calculations involve estimating intra-PCG correlation in primary outcome: fractured femur rate for those 65 years and over. No data on fractured femur rate were available at PCG level. PCGs are, however, similar in size and often coterminous with local authorities. Therefore, intra-PCG correlation in fractured femur rate was estimated from the intra-local authority correlation calculated from routine data. Three alternative trial designs are considered. In the first design, PCGs are selected for inclusion in the trial from the total population of England (eight regions). In the second design, PCGs are selected from two regions only. The third design is similar to the second except that PCGs are stratified by region and baseline value of fracture rate. Intracluster correlation is estimated for each of these designs using two methods: an approximation which assumes cluster sizes are equal and an alternative method which takes account of the fact that cluster sizes vary. Estimates of sample size required vary between 26 and 7 PCGs in each intervention group, depending on the trial design and the method used to calculate sample size. Not unexpectedly, stratification by baseline

  5. Cohesive Energies and Enthalpies: Complexities, Confusions, and Corrections.

    PubMed

    Glasser, Leslie; Sheppard, Drew A

    2016-07-18

    The cohesive or atomization energy of an ionic solid is the energy required to decompose the solid into its constituent independent gaseous atoms at 0 K, while its lattice energy, Upot, is the energy required to decompose the solid into its constituent independent gaseous ions at 0 K. These energies may be converted into enthalpies at a given temperature by the addition of the small energies corresponding to integration of the heat capacity of each of the constituents. While cohesive energies/enthalpies are readily calculated by thermodynamic summing of the formation energies/enthalpies of the constituents, they are also currently intensively studied by computational procedures for the resulting insight on the interactions within the solid. In supporting confirmation of their computational results, authors generally quote "experimental" cohesive energies which are, in fact, simply the thermodynamic sums. However, these "experimental" cohesive energies are quoted in many different units, atom-based or calorimetric, and on different bases such as per atom, per formula unit, per oxide ion, and so forth. This makes comparisons among materials very awkward. Additionally, some of the quoted values are, in fact, lattice energies which are distinctly different from cohesive energies. We list large numbers of reported cohesive energies for binary halides, chalcogenides, pnictogenides, and Laves phase compounds which we bring to the same basis, and identify a number as incorrectly reported lattice energies. We also propose that cohesive energies of higher-order ionic solids may also be estimated as thermodynamic enthalpy sums.

  6. Cohesive Energies and Enthalpies: Complexities, Confusions, and Corrections.

    PubMed

    Glasser, Leslie; Sheppard, Drew A

    2016-07-18

    The cohesive or atomization energy of an ionic solid is the energy required to decompose the solid into its constituent independent gaseous atoms at 0 K, while its lattice energy, Upot, is the energy required to decompose the solid into its constituent independent gaseous ions at 0 K. These energies may be converted into enthalpies at a given temperature by the addition of the small energies corresponding to integration of the heat capacity of each of the constituents. While cohesive energies/enthalpies are readily calculated by thermodynamic summing of the formation energies/enthalpies of the constituents, they are also currently intensively studied by computational procedures for the resulting insight on the interactions within the solid. In supporting confirmation of their computational results, authors generally quote "experimental" cohesive energies which are, in fact, simply the thermodynamic sums. However, these "experimental" cohesive energies are quoted in many different units, atom-based or calorimetric, and on different bases such as per atom, per formula unit, per oxide ion, and so forth. This makes comparisons among materials very awkward. Additionally, some of the quoted values are, in fact, lattice energies which are distinctly different from cohesive energies. We list large numbers of reported cohesive energies for binary halides, chalcogenides, pnictogenides, and Laves phase compounds which we bring to the same basis, and identify a number as incorrectly reported lattice energies. We also propose that cohesive energies of higher-order ionic solids may also be estimated as thermodynamic enthalpy sums. PMID:27362373

  7. Cohesion energetics of carbon allotropes: Quantum Monte Carlo study

    SciTech Connect

    Shin, Hyeondeok; Kang, Sinabro; Koo, Jahyun; Lee, Hoonkyung; Kwon, Yongkyung; Kim, Jeongnim

    2014-03-21

    We have performed quantum Monte Carlo calculations to study the cohesion energetics of carbon allotropes, including sp{sup 3}-bonded diamond, sp{sup 2}-bonded graphene, sp–sp{sup 2} hybridized graphynes, and sp-bonded carbyne. The computed cohesive energies of diamond and graphene are found to be in excellent agreement with the corresponding values determined experimentally for diamond and graphite, respectively, when the zero-point energies, along with the interlayer binding in the case of graphite, are included. We have also found that the cohesive energy of graphyne decreases systematically as the ratio of sp-bonded carbon atoms increases. The cohesive energy of γ-graphyne, the most energetically stable graphyne, turns out to be 6.766(6) eV/atom, which is smaller than that of graphene by 0.698(12) eV/atom. Experimental difficulty in synthesizing graphynes could be explained by their significantly smaller cohesive energies. Finally, we conclude that the cohesive energy of a newly proposed graphyne can be accurately estimated with the carbon–carbon bond energies determined from the cohesive energies of graphene and three different graphynes considered here.

  8. Cohesion Energetics of Carbon Allotropes: Quantum Monte Carlo Study

    SciTech Connect

    Shin, Hyeondeok; Kang, Sinabro; Koo, Jahyun; Lee, Hoonkyung; Kim, Jeongnim; Kwon, Yongkyung

    2014-01-01

    We have performed quantum Monte Carlo calculations to study the cohesion energetics of carbon allotropes, including sp3-bonded diamond, sp2-bonded graphene, sp-sp2 hybridized graphynes, and sp-bonded carbyne. The comput- ed cohesive energies of diamond and graphene are found to be in excellent agreement with the corresponding values de- termined experimentally for diamond and graphite, respectively, when the zero-point energies, along with the interlayer binding in the case of graphite, are included. We have also found that the cohesive energy of graphyne decreases system- atically as the ratio of sp-bonded carbon atoms increases. The cohesive energy of -graphyne, the most energetically- stable graphyne, turns out to be 6.766(6) eV/atom, which is smaller than that of graphene by 0.698(12) eV/atom. Experi- mental difficulty in synthesizing graphynes could be explained by their significantly smaller cohesive energies. Finally we conclude that the cohesive energy of a newly-proposed two-dimensional carbon network can be accurately estimated with the carbon-carbon bond energies determined from the cohesive energies of graphene and three different graphynes.

  9. Group Leader Development: Effects of Personal Growth and Psychoeducational Groups

    ERIC Educational Resources Information Center

    Ohrt, Jonathan H.; Robinson, E. H., III; Hagedorn, W. Bryce

    2013-01-01

    The purpose of this quasi-experimental study was to compare the effects of personal growth groups and psychoeducational groups on counselor education students' (n = 74) empathy and group leader self-efficacy. Additionally, we compared the degree to which participants in each group valued: (a) cohesion, (b) catharsis, and (c) insight. There were no…

  10. Men's preferences for women's profile waist-to-hip ratio, breast size, and ethnic group in Britain and South Africa.

    PubMed

    Swami, Viren; Jones, John; Einon, Dorothy; Furnham, Adrian

    2009-05-01

    One particular aspect of the literature on preferences for female body shapes has focused on the purported universality of preferences for a low waist-to-hip ratio (WHR), despite substantial evidence of cross-cultural variability in such preferences. In the present study, we examined the effects of manipulating women's profile WHR, breast size, and ethnicity on men's ratings of physical attractiveness and health. A total of 51 African men in South Africa, 56 British Africans, and 114 British Caucasians rated 12 line drawings that varied in two levels of ethnicity, three levels of WHR, and two levels of breast size. Overall, the results suggested that there were cross-cultural differences in preferred body shape, with the preferred body configuration varying as a function of the ethnicity of the figure being rated. In addition, there was a strong positive correlation between ratings of attractiveness and health. These findings are discussed in relation to the interplay between culture and evolution in determining ideals of attractiveness. PMID:18625082

  11. The impact of phenotypic appearance on body weight and egg production in laying hens: a group-size- and experience-dependent phenomenon.

    PubMed

    Marin, R H; Liste, M G; Campderrich, I; Estevez, I

    2014-07-01

    Alterations of birds' phenotypic appearance (PA) may lead to unwanted behaviors, potentially impairing poultry welfare, health, and productive performance. Likewise, group size may play an important role modulating the expression of adaptive behaviors. This study evaluates whether changes in the PA of Hy-line Brown laying hens may affect their BW and egg production, and if so, whether these effects depend on group size. A total of 1,050 one-day-old chicks were randomly assigned to 1 of 45 pens. Groups were of 10, 20, or 40 individuals (8 hens/m(2)). At arrival, the PA of 0, 30, 50, 70, or 100% of the birds within each group was artificially altered by marking the back of their heads black. The remaining birds within groups were unaltered. The 30% marked hens within groups of 10 individuals had a lower BW at 24 wk of age than their 70% unmarked counterparts, whereas the other groups showed similar BW. No differences were detected in egg laying performance during this phase. Next, within the initially homogeneous groups (0 and 100%), 30, 50, and 70% of the hens were either marked or unmarked (PA changed) sequentially at 34, 38, and 44 wk of age. Hens within the initially heterogeneous groups of 30, 50, and 70% marked birds remained unchanged and were used as controls. Groups of 40 individuals showed a reduction in BW gain and weekly hen-day-egg production after 30% PA changes, as compared with control counterparts. No differences were found in pens of 10 hens, and the groups of 20 showed intermediate results. A transient reduction in egg production was found after 50% PA changes. No further productive effects were observed after 70% changes. Our findings suggest that differences in hen appearance, which may occur due to variations in health status, injuries, and other natural causes, can be critical for production and welfare management practices depending both on the flock size and the birds' previous experience in exposure to group phenotypic heterogeneity.

  12. Age and gender diversity as determinants of performance and health in a public organization: the role of task complexity and group size.

    PubMed

    Wegge, Jürgen; Roth, Carla; Neubach, Barbara; Schmidt, Klaus-Helmut; Kanfer, Ruth

    2008-11-01

    The influence of age and gender composition on group performance and self-reported health disorders was examined with data from 4,538 federal tax employees working in 222 natural work unit groups. As hypothesized, age diversity correlated positively with performance only in groups solving complex decision-making tasks, and this finding was replicated when analyzing performance data collected 1 year later. Age diversity was also positively correlated with health disorders--but only in groups working on routine decision-making tasks. Gender composition also had a significant effect on group performance, such that groups with a high proportion of female employees performed worse and reported more health disorders than did gender-diverse teams. As expected, effects of gender composition were most pronounced in large groups. Effects of age diversity were found when controlling for gender diversity and vice versa. Thus, age and gender diversity seem to play a unique role in performance and well-being. The moderating role of task complexity for both effects of age diversity and the moderating role of group size for both effects of gender diversity further suggest that the impact of these 2 variables depends on different group processes (e.g., knowledge exchange, variation in gender salience).

  13. Obstacle avoiding patterns and cohesiveness of fish school.

    PubMed

    Nguyen, Linh Thi Hoai; Tạ, Việt Tôn; Yagi, Atsushi

    2016-10-01

    This paper is devoted to studying obstacle avoiding patterns and cohesiveness of fish school. First, we introduce a model of stochastic differential equations (SDEs) for describing the process of fish school's obstacle avoidance. Second, on the basis of the model we find obstacle avoiding patterns. Our observations show that there are clear four obstacle avoiding patterns, namely, Rebound, Pullback, Pass and Reunion, and Separation. Furthermore, the emerging patterns change when parameters change. Finally, we present a scientific definition for fish school's cohesiveness that will be an internal property characterizing the strength of fish schooling. There are then evidences that the school cohesiveness can be measured through obstacle avoiding patterns. PMID:27449357

  14. Evaluation of cohesive and elastic support bandages for joint immobilization.

    PubMed

    Wilder, R P; Doctor, A; Paley, R J; Saunders, T J; Edlich, R F

    1989-01-01

    The purpose of this clinical study was to compare the performance of a new cohesive bandage to that of elastic bandages for joint immobilization. The magnitude of joint immobilization by these bandages was quantitated during isokinetic exercise using a computerized dynamometer. The degree to which the cohesive and elastic bandages reduced range of motion and peak torque of plantar and dorsiflexion was not significantly different. After exercising for 1 hour, the elastic bandage loosens, reducing its ability to immobilize the joint. In contrast, the cohesive bandage maintains its configuration, despite active exercise for 1 hour.

  15. Differential introgression and effective size of marker type influence phylogenetic inference of a recently divergent avian group (Phasianidae: Tympanuchus).

    PubMed

    Galla, Stephanie J; Johnson, Jeff A

    2015-03-01

    Life history strategies can influence the effective population size (Ne) of loci differently based on their mode of inheritance. Recognizing how this may affect the rate of lineage sorting among marker types is important for studies focused on resolving phylogenetic relationships among recently divergent taxa. In this study, we use gene tree, coalescent-based species tree, and isolation-with-migration analyses to explore the differences between marker types (autosomal, Z-linked, and mitochondrial) in resolving phylogenetic relationships among North American prairie grouse (Tympanuchus). We found that Z-linked loci were more likely to identify monophyletic relationships among prairie grouse species compared to autosomal and mtDNA loci in both species and gene tree analyses, with species tree analyses outperforming gene trees. These results were further supported with isolation-with-migration analyses, where Z-linked loci largely followed a strict isolation model while autosomal loci were more likely to fit a model with gene flow between species following population divergence. While accounting for differences in inheritance pattern (or Ne) for marker type, results suggest that additional factors, such as strong sexual selection and sex-biased introgression (i.e., male-biased postzygotic hybrid behavioral isolation or "unsexy son"), may further explain the decreased diversity levels and increased rate of lineage sorting observed with the Z-linked loci relative to autosomal and mtDNA loci. In fact, to our knowledge no hybrid male prairie grouse have been observed breeding in the wild, yet hybrid females along with backcross females are known to produce viable offspring. Overall, this study highlights that more work is needed to determine how complex models of gene flow (i.e., sex biased introgression) and differences in the effective size among marker types based on differing life history strategies influence divergence date estimation and species delimitation.

  16. Repeated erosion of cohesive sediments with biofilms

    NASA Astrophysics Data System (ADS)

    Valentine, K.; Mariotti, G.; Fagherazzi, S.

    2014-04-01

    This study aims to explore the interplay between biofilms and erodability of cohesive sediments. Erosion experiments were run in four laboratory annular flumes with natural sediments. After each erosion the sediment was allowed to settle, mimicking intermittent physical processes like tidal currents and waves. The time between consecutive erosion events ranged from 1 to 12 days. Turbidity of the water column caused by sediment resuspension was used to determine the erodability of the sediments with respect to small and moderate shear stresses. Erodability was also compared on the basis of the presence of benthic biofilms, which were quantified using a Pulse-Amplitude Modulation (PAM) Underwater Fluorometer. We found that frequent erosion lead to the establishment of a weak biofilm, which reduced sediment erosion at small shear stresses (around 0.1 Pa). If prolonged periods without erosion were present, the biofilm fully established, resulting in lower erosion at moderate shear stresses (around 0.4 Pa). We conclude that an unstructured extracellular polymeric substances (EPS) matrix always affect sediment erodability at low shear stresses, while only a fully developed biofilm mat can reduce sediment erodability at moderate shear stresses.

  17. Evidence for Cohesive Dispersal in the Sea

    PubMed Central

    Ben-Tzvi, Ofer; Gaines, Steven D.; Bernardi, Giacomo; Beldade, Ricardo; Sheehy, Michael S.; Paradis, Georges L.

    2012-01-01

    As with many marine species, the vast majority of coral-reef fishes have a bipartite life cycle consisting of a dispersive larval stage and a benthic adult stage. While the potentially far-reaching demographic and ecological consequences of marine dispersal are widely appreciated, little is known of the structure of the larval pool and of the dispersive process itself. Utilizing Palindrome Sequence Analysis of otolith micro-chemistry (PaSA;) we show that larvae of Neopomacentrus miryae (Pomacentridae) appear to remain in cohesive cohorts throughout their entire pelagic larval duration (PLD; ∼28 days). Genetically, we found cohort members to be maternally (mtDNA) unrelated. While physical forcing cannot be negated as contributing to initial cohort formation, the small scale of the observed spatial structure suggests that some behavioral modification may be involved from a very early age. This study contributes to our ongoing re-evaluation of the processes that structure marine populations and communities and the spatial scales at which they operate. PMID:23028433

  18. Community-level cohesion without cooperation

    PubMed Central

    Tikhonov, Mikhail

    2016-01-01

    Recent work draws attention to community-community encounters ('coalescence') as likely an important factor shaping natural ecosystems. This work builds on MacArthur’s classic model of competitive coexistence to investigate such community-level competition in a minimal theoretical setting. It is shown that the ability of a species to survive a coalescence event is best predicted by a community-level 'fitness' of its native community rather than the intrinsic performance of the species itself. The model presented here allows formalizing a macroscopic perspective whereby a community harboring organisms at varying abundances becomes equivalent to a single organism expressing genes at different levels. While most natural communities do not satisfy the strict criteria of multicellularity developed by multi-level selection theory, the effective cohesion described here is a generic consequence of resource partitioning, requires no cooperative interactions, and can be expected to be widespread in microbial ecosystems. DOI: http://dx.doi.org/10.7554/eLife.15747.001 PMID:27310530

  19. Vibrofluidized melting of geometrically cohesive granular media

    NASA Astrophysics Data System (ADS)

    Gravish, Nick; Russell, Geoffrey; Franklin, Scott V.; Hu, David; Goldman, Daniel I.

    2011-03-01

    Dry granular media composed of particles of special shapes (e.g. long rods or c-shaped particles) can display cohesive effects through particle geometry alone. We study the solid to gas transition in piles of c-shaped particles under vertical vibration as we vary acceleration and frequency. A cylindrical solid of particles is formed with wall angles near 90° and is placed on a solid surface. For fixed frequency as acceleration increases, the pile undergoes two transitions. The first is from the solid-like state to a liquid-like state in which the wall angles relax but the mobile particles remain spatially localized. The second is from the liquid-like state to the gaseous state in which particles become separated (not entangled). Using video and accelerometer measurements, we record the temporal evolution of the spatial density and pile-plate collisional impulse. A critical energy scale, set by the particle geometry and gravitational potential energy, governs the liquid-gas transition.

  20. Family Rituals and Quality of Life in Children With Cancer and Their Parents: The Role of Family Cohesion and Hope

    PubMed Central

    Crespo, Carla; Canavarro, M. Cristina; Kazak, Anne E.

    2015-01-01

    Objective Family rituals are associated with adaptive functioning in pediatric illness, including quality of life (QoL). This article explores the role of family cohesion and hope as mediators of this association in children with cancer and their parents. Methods Portuguese children with cancer (N = 389), on- and off-treatment, and one of their parents completed self-report measures. Structural equation modeling was used to examine direct and indirect links between family rituals and QoL. Results When children and parents reported higher levels of family rituals, they also reported more family cohesion and hope, which were linked to better QoL. At the dyadic level, children’s QoL was related to parents’ family rituals through the child’s family cohesion. This model was valid across child’s age-group, treatment status, and socioeconomic status. Conclusions Family rituals are important in promoting QoL in pediatric cancer via family cohesion and hope individually and via family cohesion in terms of parent–child interactions. PMID:25775914

  1. A season-long team-building intervention: examining the effect of team goal setting on cohesion.

    PubMed

    Senécal, Julie; Loughead, Todd M; Bloom, Gordon A

    2008-04-01

    The purpose of the current study was to determine whether the implementation of a season-long team-building intervention program using team goal setting increased perceptions of cohesion. The participants were 86 female high school basketball players from 8 teams. The teams were randomly assigned to either an experimental team goal-setting or control condition. Each participant completed the Group Environment Questionnaire (GEQ; Carron, Brawley, & Widmeyer, 2002; Carron, Widmeyer, & Brawley, 1985), which assessed cohesion at both the beginning and end of the season. Overall, the results revealed a significant multivariate effect, Pillai's trace F(12, 438) = 2.68, p = .002. Post hoc analyses showed that at the beginning of the season, athletes from both conditions did not differ in their perceptions of cohesion. However, at the end of the season, athletes in the team goal-setting condition held higher perceptions of cohesion than athletes in the control condition. Overall, the results indicated that team goal setting was an effective team-building tool for influencing cohesiveness in sport teams.

  2. Facing Sorrow as a Group Unites. Facing Sorrow in a Group Divides.

    PubMed

    Rennung, Miriam; Göritz, Anja S

    2015-01-01

    Collective gatherings foster group cohesion through providing occasion for emotional sharing among participants. However, prior studies have failed to disentangle two processes that are involved in emotional sharing: 1) focusing shared attention on the same emotion-eliciting event and 2) actively sharing one's experiences and disclosing one's feelings to others. To date, it has remained untested if shared attention influences group cohesion independent of active emotional sharing. Our experiment investigated the effect of shared versus individual attention on cohesion in groups of strangers. We predicted that differences in group cohesion as called forth by shared vs. individual attention are most pronounced when experiencing highly arousing negative affect, in that the act of experiencing intensely negative affect with others buffers negative affect's otherwise detrimental effect on group cohesion. Two-hundred sixteen participants were assembled in groups of 3 to 4 people to either watch an emotion-eliciting film simultaneously on a common screen or to watch the same emotion-eliciting film clip on a laptop in front of each group member using earphones. The film clips were chosen to elicit either highly arousing negative affect or one of three other affective states representing the other poles in Russel's Circumplex model of affect. We examined self-reported affective and cognitive group cohesion and a behavioral measure of group cohesion. Results support our buffer-hypothesis, in that experiencing intense negative affect in unison leads to higher levels of group cohesion than experiencing this affect individually despite the group setting. The present study demonstrates that shared attention to intense negative emotional stimuli affects group cohesion independently of active emotional sharing. PMID:26335924

  3. Facing Sorrow as a Group Unites. Facing Sorrow in a Group Divides

    PubMed Central

    Rennung, Miriam; Göritz, Anja S.

    2015-01-01

    Collective gatherings foster group cohesion through providing occasion for emotional sharing among participants. However, prior studies have failed to disentangle two processes that are involved in emotional sharing: 1) focusing shared attention on the same emotion-eliciting event and 2) actively sharing one’s experiences and disclosing one’s feelings to others. To date, it has remained untested if shared attention influences group cohesion independent of active emotional sharing. Our experiment investigated the effect of shared versus individual attention on cohesion in groups of strangers. We predicted that differences in group cohesion as called forth by shared vs. individual attention are most pronounced when experiencing highly arousing negative affect, in that the act of experiencing intensely negative affect with others buffers negative affect’s otherwise detrimental effect on group cohesion. Two-hundred sixteen participants were assembled in groups of 3 to 4 people to either watch an emotion-eliciting film simultaneously on a common screen or to watch the same emotion-eliciting film clip on a laptop in front of each group member using earphones. The film clips were chosen to elicit either highly arousing negative affect or one of three other affective states representing the other poles in Russel’s Circumplex model of affect. We examined self-reported affective and cognitive group cohesion and a behavioral measure of group cohesion. Results support our buffer-hypothesis, in that experiencing intense negative affect in unison leads to higher levels of group cohesion than experiencing this affect individually despite the group setting. The present study demonstrates that shared attention to intense negative emotional stimuli affects group cohesion independently of active emotional sharing. PMID:26335924

  4. Experimental infectious respiratory disease in groups of calves:Lobar distribution, variance, and sample-size requirements for vaccine evaluation

    PubMed Central

    2004-01-01

    Abstract The distribution and variance of respiratory disease produced with aerosols of bovine herpesvirus 1 (BHV-1) and Mannheimia haemolytica in control (183 calves in 44 experiments) and vaccinated calves were studied in experiments conducted at the Animal Diseases Research Institute, Lethbridge, Alberta, from 1975 to 1989. All calves had been born and raised at this institute and exposed similarly for 5 min by means of a face mask to viral and bacterial aerosols produced by a Collison atomizer (particles < 3 μm in diameter). We summarized the macroscopic pathological responses of pneumonia (main end point), tonsillitis, tracheitis, and other microbiologic and experimental variables. We also summarized the lobar distribution of pneumonia in 202 control and 192 vaccinated calves with this disease model and in calves similarly exposed to parainfluenza 3 virus/M. haemolytica or BHV-1/Pasteurella multocida. Pneumonia in control calves began in ventral tissues of all lobes, with lobar preferences, and progressed dorsally, the dorsal parts of both large caudal lobes being least affected. A high variance of pneumonia was evident within and among experiments. From the magnitude of variance observed in the control groups, the number of calves per group required in vaccine-challenge studies using this BHV-1/M. haemolytica disease model was estimated. Such estimates are required for any disease model used in vaccine-challenge studies. PMID:15188956

  5. Occurrence of cohesion of metals during combined plastic deformation

    NASA Technical Reports Server (NTRS)

    Aynbinder, S. G.; Klokova, E. F.

    1980-01-01

    Experiments were conducted to study the cohesion of metals with surface films of varying thickness and hardness. It was established that the deformation necessary for the occurrence of cohesion is determined by the correlation of mechanical properties of the films and the base metal. The greater the relative hardness of the film the lower the deformation necessary for the occurrence of cohesion. The films are as plastic as the base metal prevent cohesion, since in this case it is impossible for sections of metal to appear that are free of contaminants. The physical perculiarities of metals that determine their capability for coalescence under conditions of dry friction are the relative hardness and plasticity of the oxide films formed on their surface under atmospheric conditions.

  6. A thermodynamic analysis of propagating subcritical cracks with cohesive zones

    NASA Technical Reports Server (NTRS)

    Allen, David H.

    1993-01-01

    The results of the so-called energetic approach to fracture with particular attention to the issue of energy dissipation due to crack propagation are applied to the case of a crack with cohesive zone. The thermodynamic admissibility of subcritical crack growth (SCG) is discussed together with some hypotheses that lead to the derivation of SCG laws. A two-phase cohesive zone model for discontinuous crack growth is presented and its thermodynamics analyzed, followed by an example of its possible application.

  7. Cohesions, friction angles, and other physical properties of Martian regolith from Mars Exploration Rover wheel trenches and wheel scuffs

    NASA Astrophysics Data System (ADS)

    Sullivan, R.; Anderson, R.; Biesiadecki, J.; Bond, T.; Stewart, H.

    2011-02-01

    The Mars Exploration Rovers Spirit and Opportunity investigated the physical properties of Martian regolith in 7 wheel trenches and 20 wheel scuffs distributed along traverses at Gusev crater and Meridiani Planum. Specialized wheel-trenching sequences allowed analysis of wheel motor and suspension telemetry to determine regolith friction angle $\\phi$ and cohesion c at trench sites. Friction angles were 30°-37°, and cohesions were 0-2 kPa. Simpler wheel-scuff maneuvers were analyzed for cohesion by assuming the range of $\\phi$ determined from trenches; cohesions in wheel-scuffed regoliths were from 0 to 11 kPa. Regolith $\\phi$ and c can be related to regolith origins. Grain sorting, compaction, shape, size, and angularity influence $\\phi$. Impact cratering and aeolian processes have affected grain angularity and sorting of Martian regolith at both Mars Exploration Rover (MER) landing sites and contend in opposing ways to determine grain characteristics in the regolith. Friction angles are consistent with dry, rigid, nonplaty grains with particle size frequencies dominated by very fine sand (as seen by the Microscopic Imager or MI) with at least some grain rounding (unresolved by MI), reflecting physical weathering from aeolian saltation. Friction angle results from MER trenches therefore indicate that regolith states are between fully mature aeolian materials and impact debris. MI and color Pancam views show trench tailings and trench floors are redder, brighter, and have more intermixed extremely fine (unresolved) grains than regolith closer to the surface disturbed and exposed only by rolling tracks.

  8. Social Cohesion, Social Participation, and HIV Related Risk among Female Sex Workers in Swaziland

    PubMed Central

    Fonner, Virginia A.; Kerrigan, Deanna; Mnisi, Zandile; Ketende, Sosthenes; Kennedy, Caitlin E.; Baral, Stefan

    2014-01-01

    Social capital is important to disadvantaged groups, such as sex workers, as a means of facilitating internal group-related mutual aid and support as well as access to broader social and material resources. Studies among sex workers have linked higher social capital with protective HIV-related behaviors; however, few studies have examined social capital among sex workers in sub-Saharan Africa. This cross-sectional study examined relationships between two key social capital constructs, social cohesion among sex workers and social participation of sex workers in the larger community, and HIV-related risk in Swaziland using respondent-driven sampling. Relationships between social cohesion, social participation, and HIV-related risk factors were assessed using logistic regression. HIV prevalence among the sample was 70.4% (223/317). Social cohesion was associated with consistent condom use in the past week (adjusted odds ratio [AOR]  = 2.25, 95% confidence interval [CI]: 1.30–3.90) and was associated with fewer reports of social discrimination, including denial of police protection. Social participation was associated with HIV testing (AOR = 2.39, 95% CI: 1.36–4.03) and using condoms with non-paying partners (AOR = 1.99, 95% CI: 1.13–3.51), and was inversely associated with reported verbal or physical harassment as a result of selling sex (AOR = 0.55, 95% CI: 0.33–0.91). Both social capital constructs were significantly associated with collective action, which involved participating in meetings to promote sex worker rights or attending HIV-related meetings/ talks with other sex workers. Social- and structural-level interventions focused on building social cohesion and social participation among sex workers could provide significant protection from HIV infection for female sex workers in Swaziland. PMID:24498125

  9. Tectonic and gravity extensional collapses in overpressured cohesive and frictional wedges

    NASA Astrophysics Data System (ADS)

    Yuan, X. P.; Leroy, Y. M.; Maillot, B.

    2015-03-01

    Two modes of extensional collapse in a cohesive and frictional wedge of arbitrary topography, finite extent, and resting on an inclined weak décollement are examined by analytical means. The first mode consists of the gravitational collapse by the action of a half-graben, rooting on the décollement and pushing seaward the frontal part of the wedge. The second mode results from the tectonics extension at the back wall with a similar half-graben kinematics and the landward sliding of the rear part of the wedge. The predictions of the maximum strength theorem, equivalent to the kinematic approach of limit analysis and based on these two collapse mechanisms, not only match exactly the solutions of the critical Coulomb wedge theory, once properly amended, but generalizes them in several aspects: wedge of finite size, composed of cohesive material and of arbitrary topography. This generalization is advantageous to progress in our understanding of many laboratory experiments and field cases. For example, it is claimed from analytical results validated by experiments that the stability transition for a cohesive, triangular wedge occurs with the activation of the maximum length of the décollement. It is shown that the details of the topography, for the particular example of the Mejillones peninsula (North Chile) is, however, responsible for the selection of a short length-scale, dynamic instability corresponding to a frontal gravitational instability. A reasonable amount of cohesion is sufficient for the pressures proposed in the literature to correspond to a stability transition and not with a dynamically unstable state.

  10. On the Depositional Characteristics of Natural Cohesive & Mixed Sediments: "floccin' across the USA!"

    NASA Astrophysics Data System (ADS)

    Manning, A. J.; Schoellhamer, D. H.; Mehta, A. J.; Schladow, G.; Monismith, S. G.; Huang, I. B.; Kuwabara, J. S.; Carter, J. L.; Sheremet, A.; Parsons, D. R.; Whitehouse, R. J. S.; Todd, D.; Benson, T.; Spearman, J.

    2015-12-01

    Many coastal and inland waterways are dominated by muddy sediments; typically a mixture of clay minerals and various types of organic matter. When cohesive sediment is entrained into suspension, the particles tend to flocculate. Flocs are less dense, but faster settling than their constituent particles thus affecting their depositional characteristics. As flocs grow their effective densities generally decrease, but their settling rates rise due to a Stokes' Law relationship. Flocculation effects become even more complex when purely cohesive sediments are mixed with different ratios of non-cohesive sediments, and the amount of biological activity changes, i.e. affecting the resultant cohesion. Developing instrumentation that can provide key physical and dynamical data on depositional rates of flocculating sediments is extremely important in advancing our understanding of natural flocculation processes. The data need to be both qualitative and quantitative, as the latter improves our understanding of the depositional and aggregational physical processes through parameterization. This presentation will demonstrate recent advances in the study of the flocculation process through the use of video image technology. One such device pioneered at HR Wallingford, and implemented with co-authors, is the high resolution floc video camera, LabSFLOC - Laboratory Spectral Flocculation Characteristics (developed by Prof. Manning). LabSFLOC can observe floc spectral physical properties, including: floc size, settling velocity, effective density, porosity, shape, mass, and settling flux (using controlled volume referencing). These data are highly desirable for sediment transport modelers. Examples of floc measurements from locations in estuaries, tidal lagoons, river deltas, and lakes from locations across the USA will be presented. In addition, we will demonstrate how video floc data can be used to parameterize floc settling characteristics for use in modeling.

  11. On the retreat of forested, cohesive riverbanks

    NASA Astrophysics Data System (ADS)

    Pizzuto, Jim; O'Neal, Michael; Stotts, Stephanie

    2010-04-01

    Data from the Brandywine Creek in Pennsylvania and the South River in Virginia document spatial and temporal patterns describing the retreat of gently curving bends with forested riparian zones containing a mix of very large and smaller trees, cohesive banks, and slow rates of migration (˜ 0.1 m/yr). Field data include 2.5 years of bank profile surveys, measurements of tree morphology, and ground-based laser scanner (LiDAR) surveys repeated biannually. These banks retreat through a cycle of erosion on decadal timescales. Initially, small volumes (mean = 0.173 m 3 per bank erosion event) of soil are removed between large trees growing on the bank. Near trees, the rate of bank retreat is initially negligible, creating a scalloped bank morphology buttressed by large trees. As the trees are increasingly exposed to the flow, they become slowly undercut, gradually leaning into the channel and sliding down to the toe of the bank, eventually toppling into the river after a few years, which restarts the cycle. A magnitude-frequency analysis of monitoring data from the Brandywine Creek indicates that the effective bank erosion event only 0.11 m 3; thus, forested bank retreat is dominated by small soil failures. Large erosion events, many associated with trees toppling into the river, greatly increase the variance of time-averaged rates of bank erosion, such that almost 4 years of monitoring are needed to measure time-averaged rates of erosion to within an accuracy of 10%. Because of the limited spatial extent of our survey data and the absence of large discharges, these results are provisional. Improved process-based models to predict the retreat of forested riverbanks should account for the spatial structure of riparian forests and the interactions between the flow, the gradual removal of bank soils, and the ongoing efforts of the trees to remain attached to the bank.

  12. Does relative out-group size in neighborhoods drive down associational life of Whites in the U.S.? Testing constrict, conflict and contact theories.

    PubMed

    Savelkoul, Michael; Hewstone, Miles; Scheepers, Peer; Stolle, Dietlind

    2015-07-01

    We test whether a larger percentage of non-Whites in neighborhoods decreases associational involvement and build on earlier research in three ways. First, we explicitly consider the ethnic composition of organizations, distinguishing involvement in bridging (with out-group members) and bonding (only in-group members) organizations. Second, we start from constrict theory and test competing sets of predictions derived from conflict and contact theories to explain these relationships. Third, we examine whether relative out-group size affects involvement in different types of voluntary organizations equally. Using data from the 2005 U.S. 'Citizenship, Involvement, Democracy' survey, the percentage of non-Whites in neighborhoods is largely unrelated with associational involvement or perceived ethnic threat. However, perceiving ethnic threat is consistently negatively related with involvement in bridging organizations. Simultaneously, a larger percentage of non-Whites fosters intergroup contact, which is negatively related with perceptions of ethnic threat and involvement in bonding leisure organizations. Our results shed more light on the relationship between the relative out-group size in neighborhoods and associational involvement as well as underlying explanations for this link. PMID:26004460

  13. Interparticle force based methodology for prediction of cohesive powder flow properties

    NASA Astrophysics Data System (ADS)

    Esayanur, Madhavan Sujatha Sarma

    The transport and handling of powders are key areas in the process industry that have a direct impact on the efficiency and/or the quality of the finished product. A lack of fundamental understanding of powder flow properties as a function of operating variables such as relative humidity, and particle size, leading to problems such as arching, rat-holing and segregation, is one the main causes for unscheduled down times in plant operation and loss of billions of dollars in revenues. Most of the current design strategies and characterization techniques for industrial powders are based on a continuum approach similar to the field of soil mechanics. Due to an increase in complexity of the synthesis process and reduction in size of powders to the nanoscale, the surface properties and inter particle forces play a significant role in determining the flow characteristics. The use of ensemble techniques such as direct shear testing to characterize powders are no longer adequate due to lack of understanding of the changes in the property of powders as a function of the major operating variables such as relative humidity, temperature etc. New instrumentation or techniques need to be developed to reliably characterize powder flow behavior. Simultaneously, scalability of the current models to predict powder flow needs to be revisited. Specifically, this study focuses on the development of an inter particle force based model for predicting the unconfined yield strength of cohesive powders. To understand the role of interparticle forces in determining the strength of cohesive powders, the particle scale interactions were characterized using Atomic Force Microscopy (AFM), contact angle, surface tension, and coefficient of friction. The bulk scale properties such as unconfined yield strength, packing structure, and size of the shear zone were also investigated. It was determined that an interparticle force based model incorporating the effect of particle size and packing structure

  14. Ectomycorrhizal influence on particle size, surface structure, mineral crystallinity, functional groups, and elemental composition of soil colloids from different soil origins.

    PubMed

    Li, Yanhong; Wang, Huimei; Wang, Wenjie; Yang, Lei; Zu, Yuangang

    2013-01-01

    Limited data are available on the ectomycorrhizae-induced changes in surface structure and composition of soil colloids, the most active portion in soil matrix, although such data may benefit the understanding of mycorrhizal-aided soil improvements. By using ectomycorrhizae (Gomphidius viscidus) and soil colloids from dark brown forest soil (a good loam) and saline-alkali soil (heavily degraded soil), we tried to approach the changes here. For the good loam either from the surface or deep soils, the fungus treatment induced physical absorption of covering materials on colloid surface with nonsignificant increases in soil particle size (P > 0.05). These increased the amount of variable functional groups (O-H stretching and bending, C-H stretching, C=O stretching, etc.) by 3-26% and the crystallinity of variable soil minerals (kaolinite, hydromica, and quartz) by 40-300%. However, the fungus treatment of saline-alkali soil obviously differed from the dark brown forest soil. There were 12-35% decreases in most functional groups, 15-55% decreases in crystallinity of most soil minerals but general increases in their grain size, and significant increases in soil particle size (P < 0.05). These different responses sharply decreased element ratios (C:O, C:N, and C:Si) in soil colloids from saline-alkali soil, moving them close to those of the good loam of dark brown forest soil.

  15. Geometry of flexible filament cohesion: better contact through twist?

    PubMed

    Cajamarca, Luis; Grason, Gregory M

    2014-11-01

    Cohesive interactions between filamentous molecules have broad implications for a range of biological and synthetic materials. While long-standing theoretical approaches have addressed the problem of inter-filament forces from the limit of infinitely rigid rods, the ability of flexible filaments to deform intra-filament shape in response to changes in inter-filament geometry has a profound affect on the nature of cohesive interactions. In this paper, we study two theoretical models of inter-filament cohesion in the opposite limit, in which filaments are sufficiently flexible to maintain cohesive contact along their contours, and address, in particular, the role played by helical-interfilament geometry in defining interactions. Specifically, we study models of featureless, tubular filaments interacting via: (1) pair-wise Lennard-Jones (LJ) interactions between surface elements and (2) depletion-induced filament binding stabilized by electrostatic surface repulsion. Analysis of these models reveals a universal preference for cohesive filament interactions for non-zero helical skew, and further, that in the asymptotic limit of vanishing interaction range relative to filament diameter, the skew-dependence of cohesion approaches a geometrically defined limit described purely by the close-packing geometry of twisted tubular filaments. We further analyze non-universal features of the skew-dependence of cohesion at small-twist for both potentials, and argue that in the LJ model the pair-wise surface attraction generically destabilizes parallel filaments, while in the second model, pair-wise electrostatic repulsion in combination with non-pairwise additivity of depletion leads to a meta-stable parallel state.

  16. Pier and contraction scour prediction in cohesive soils at selected bridges in Illinois

    USGS Publications Warehouse

    Straub, Timothy D.; Over, Thomas M.

    2010-01-01

    This report presents the results of testing the Scour Rate In Cohesive Soils-Erosion Function Apparatus (SRICOS-EFA) method for estimating scour depth of cohesive soils at 15 bridges in Illinois. The SRICOS-EFA method for complex pier and contraction scour in cohesive soils has two primary components. The first component includes the calculation of the maximum contraction and pier scour (Zmax). The second component is an integrated approach that considers a time factor, soil properties, and continued interaction between the contraction and pier scour (SRICOS runs). The SRICOS-EFA results were compared to scour prediction results for non-cohesive soils based on Hydraulic Engineering Circular No. 18 (HEC-18). On average, the HEC-18 method predicted higher scour depths than the SRICOS-EFA method. A reduction factor was determined for each HEC-18 result to make it match the maximum of three types of SRICOS run results. The unconfined compressive strength (Qu) for the soil was then matched with the reduction factor and the results were ranked in order of increasing Qu. Reduction factors were then grouped by Qu and applied to each bridge site and soil. These results, and comparison with the SRICOS Zmax calculation, show that less than half of the reduction-factor method values were the lowest estimate of scour; whereas, the Zmax method values were the lowest estimate for over half. A tiered approach to predicting pier and contraction scour was developed. There are four levels to this approach numbered in order of complexity, with the fourth level being a full SRICOS-EFA analysis. Levels 1 and 2 involve the reduction factors and Zmax calculation, and can be completed without EFA data. Level 3 requires some surrogate EFA data. Levels 3 and 4 require streamflow for input into SRICOS. Estimation techniques for both EFA surrogate data and streamflow data were developed.

  17. Ecology and sociality in a multilevel society: ecological determinants of spatial cohesion in hamadryas baboons.

    PubMed

    Schreier, Amy L; Swedell, Larissa

    2012-08-01

    The multilevel society of hamadryas baboons, consisting of troops, bands, clans, and one-male units (OMUs), is commonly perceived to be an effective means of adapting to variable food availability while allowing spatial cohesion in response to predator pressure. The relationship between these variables, however, has never been tested quantitatively. The Filoha site in Awash National Park, Ethiopia is ideally suited to such an investigation as it contains nutrient-dense palm forests in addition to the Acacia scrublands typical of hamadryas distribution elsewhere, allowing comparisons of spatial cohesion across habitat types. Here, we use observations over a 1-year period to examine the relationship between resource availability, perceived predator pressure, and spatial cohesion in a band of wild hamadryas baboons at Filoha. Our results demonstrate that the band was more likely to break into OMUs when foraging in habitats with lower food availability, and that the band fissioned into independent clans more often when preferred resources were not available. Furthermore, the baboons remained in larger aggregations for longer periods of time (i.e., prior to embarking on their daily foraging route) on mornings after predators were heard in the vicinity, and increased cohesion in response to encounters with people who may have been perceived as predators. These results support the notion that hamadryas baboons change their social groupings in response to both food availability and predation risk and that the ability of hamadryas bands to cleave and coalesce in response to changes in these factors underlies the evolution of the hamadryas modular social structure.

  18. Acculturative Stress and Diminishing Family Cohesion Among Recent Latino Immigrants

    PubMed Central

    De La Rosa, Mario; Ibañez, Gladys E.

    2012-01-01

    This study investigates a theorized link between Latino immigrants’ experience of acculturative stress during their two initial years in the United States (US) and declines in family cohesion from pre- to post-immigration contexts. This retrospective cohort study included 405 adult participants. Baseline assessment occurred during participants’ first 12 months in the US. Follow-up assessment occurred during participants’ second year in the US. General linear mixed models were used to estimate change in family cohesion and sociocultural correlates of this change. Inverse associations were determined between acculturative stress during initial years in the US and declines in family cohesion from pre-immigration to post-immigration contexts. Participants with undocumented immigration status, those with lower education levels, and those without family in the US generally indicated lower family cohesion. Participants who experienced more acculturative stress and those without family in the US evidenced a greater decline in family cohesion. Results are promising in terms of implications for health services for recent Latino immigrants. PMID:22790880

  19. Furnished cages for laying hens: study of the effects of group size and litter provision on laying location, zootechnical performance and egg quality.

    PubMed

    Huneau-Salaün, A; Guinebretière, M; Taktak, A; Huonnic, D; Michel, V

    2011-05-01

    The furnished cage is a new housing system for layers. A current trend in furnished cage design is to increase group size and replace the litter box with a mat provided with litter. An experiment was set up to determine the effects of group size and litter provision on laying performance and egg quality of beak-trimmed ISA Brown hens housed in large furnished cages with more than 12 hens. Six treatments, each of 18 furnished cages (768 cm(2)/hen including nest and litter area) were compared in a 3 × 2 experimental trial: three group sizes (S20 (20 hens per cage), S40 (40) and S60 (60)), with or without feed as litter distributed on the mat of the litter area. The provision of facilities per hen was equal in all treatments. Mortality, laying rate, mean egg weight, feed intake and feed conversion ratio were unaffected by group size over the 53-week laying period, and performance exceeded the ISA production standards. The overall percentage of eggs laid in the nest exceeded 95% except that it was slightly lower in group S20 (92.0% ± 6.4% v. S40: 96.0% ± 3.3% and S60: 96.2% ± 2.7%) leading to a higher proportion of dirty eggs (S20: 1.6% ± 2.2%, S40: 1.4% ± 1.5%, S60: 1.0% ± 1.0%). At 66 to 70 weeks, eggs laid outside the nest had a slightly higher count of mesophilic bacteria on the eggshell (5.0 log CFU/egg ± 0.4) than those laid in the nest (4.8 log CFU/egg ± 0.5) but no difference in contamination was observed between group sizes. Litter provision had no effect on mortality, egg weight or egg quality traits except for a higher proportion of broken eggs in cages with litter (5.3% ± 6.2% v. 4.6% ± 5.7%). Providing hens with feed for litter was associated with a higher laying rate (97.3% ± 3.2% v. 94.8% ± 4.4% at 23 weeks) and an apparent improvement in feed efficiency at the beginning of the laying period (feed conversion ratio based on feed consumption at the trough: 2.18 ± 0.06 with litter v. 2.28 ± 0.09 without litter at 25 weeks). The results of

  20. Achieving high dielectric constant and low loss property in a dipolar glass polymer containing strongly dipolar and small-sized sulfone groups.

    PubMed

    Wei, Junji; Zhang, Zhongbo; Tseng, Jung-Kai; Treufeld, Imre; Liu, Xiaobo; Litt, Morton H; Zhu, Lei

    2015-03-11

    In this report, a dipolar glass polymer, poly(2-(methylsulfonyl)ethyl methacrylate) (PMSEMA), was synthesized by free radical polymerization of the corresponding methacrylate monomer. Due to the large dipole moment (4.25 D) and small size of the side-chain sulfone groups, PMSEMA exhibited a strong γ transition at a temperature as low as -110 °C at 1 Hz, about 220 °C below its glass transition temperature around 109 °C. Because of this strong γ dipole relaxation, the glassy PMSEMA sample exhibited a high dielectric constant of 11.4 and a low dissipation factor (tan δ) of 0.02 at 25 °C and 1 Hz. From an electric displacement-electric field (D-E) loop study, PMSEMA demonstrated a high discharge energy density of 4.54 J/cm(3) at 283 MV/m, nearly 3 times that of an analogue polymer, poly(methyl methacrylate) (PMMA). However, the hysteresis loss was only 1/3-1/2 of that for PMMA. This study suggests that dipolar glass polymers with large dipole moments and small-sized dipolar side groups are promising candidates for high energy density and low loss dielectric applications.

  1. Mechanical Reinforcement and Enhanced Cohesion of Streambanks Using Common Riparian Species

    NASA Astrophysics Data System (ADS)

    Collison, A. J.; Pollen, N. L.; Simon, A.

    2001-12-01

    Vegetation plays an important role in the stabilisation of riverbanks due to its effects on soil strength. Mechanical strengthening of the soil occurs as a result of their tensile strength and frictional properties. Increased cohesion due to roots (cr) is a function of the number and size of roots, the root area ratio (RAR), root-tensile strength, and the friction between the soil and the roots. Field investigations were carried out in Southeastern, Central and Northwest USA to determine the root distributions and tensile strengths of various riparian, species (Eastern Sycamore (Plantanus occidentalis), River Birch (Betula nigra), Black Willow (Salix nigra), Sweetgum (Liquidamber stryaciflua), Longleaf Pine (Pinus palustris), Cottonwood (Populus deltoids), Alamo Switch Grass (Panicum virgatum 'Alamo') and Eastern Gamma Grass (Tripsacum dactyloides)). In situ root distributions were mapped to a depth of 1.0 m. Tensile-strength measurements were made using a modified boat winch connected to a load cell and wired to a datalogger to determine the maximum load applied to a root at failure. Increased cohesion due to roots was calculated using Wu et al.'s (1979) equation The relation between tensile strength and root diameter is a non-linear decay function, with the smallest roots having the greatest strength per unit area. River birch and sycamore provide the greatest cr over the range of root diameters (about 8 kPa). In contrast, black willow, a common species used in restoration projects provides some of the lowest values of cr (about 2 kPa). For the tree species studied, although the smallest root size class (<1.0 mm) has the largest frequency of roots, and these smaller roots are stronger per unit area, the sum of their areas is insufficient to make a marked contribution to cohesion. However, of the grass species studied, Switch Grass has such a large number of these small roots that in this case the smaller roots are the main contributors to cr.

  2. Depth-dependent erodibility: representing burnt soils as a two-layered cohesive/non-cohesive system

    NASA Astrophysics Data System (ADS)

    Nyman, P.; Sheridan, G. J.; Moody, J. A.; Smith, H. G.; Lane, P. N.

    2011-12-01

    Immediately after wildfire there is an abundant supply of non-cohesive ash, soil and gravel which is easily entrained by overland flow. Under these conditions the sediment flux on hillslopes can be assumed to be equal to the transport capacity of the flow. However, the supply of material is finite and at some point the hillslope could shift towards a system where entrainment is restricted by armouring and soil cohesion. In this study we test the notion that burnt hillslopes can be represented as a two-layered system of non-cohesive and cohesive soils. Using a combination of i) shear vane measurements, ii) confined hillslope flow experiments and iii) a laboratory flume, we demonstrate how erosion on burnt hillslopes primarily takes place in a distinct layer of non-cohesive soil with erosion properties that are very different to the underlying soil matrix. Shear vane measurements were taken at 5 soil depths at more than 50 points along transects in order to quantify the depth and spatial distribution of non-cohesive soil in two small (0.5 ha) and steep (30 deg) convergent basins (SE Australia) that were burnt at high severity. The measurements showed that the recently burnt hillslopes were mantled with non-cohesive soil to an average depth of 18mm and 20mm at the two sites which were situated in different geologic terrain but in similar eucalyptus dominated forests. In the hillslope flow experiments, the rapid entrainment of non-cohesive material resulted in very high sediment concentration (50-60% by volume) in the initial surge from the test area. During the flow experiments the sediment concentration decreased exponentially with time until the erosion rate reached a steady state reflecting the erodibility of the underlying cohesive soil. The formation of shallow rills and the presence of large clasts (>16cm) within the test area resulted in incomplete removal of the non-cohesive material at shear stress < 50 Ncm-2. At shear stress > 50 Ncm-2 all material was

  3. Health and social cohesion: why care about income inequality?

    PubMed Central

    Kawachi, I.; Kennedy, B. P.

    1997-01-01

    Throughout the world, wealth and income are becoming more concentrated. Growing evidence suggests that the distribution of income-in addition to the absolute standard of living enjoyed by the poor-is a key determinant of population health. A large gap between rich people and poor people leads to higher mortality through the breakdown of social cohesion. The recent surge in income inequality in many countries has been accompanied by a marked increase in the residential concentration of poverty and affluence. Residential segregation diminishes the opportunities for social cohesion. Income inequality has spillover effects on society at large, including increased rates of crime and violence, impeded productivity and economic growth, and the impaired functioning of representative democracy. The extent of inequality in society is often a consequence of explicit policies and public choice. Reducing income inequality offers the prospect of greater social cohesiveness and better population health. PMID:9112854

  4. Health and social cohesion: why care about income inequality?

    PubMed

    Kawachi, I; Kennedy, B P

    1997-04-01

    Throughout the world, wealth and income are becoming more concentrated. Growing evidence suggests that the distribution of income-in addition to the absolute standard of living enjoyed by the poor-is a key determinant of population health. A large gap between rich people and poor people leads to higher mortality through the breakdown of social cohesion. The recent surge in income inequality in many countries has been accompanied by a marked increase in the residential concentration of poverty and affluence. Residential segregation diminishes the opportunities for social cohesion. Income inequality has spillover effects on society at large, including increased rates of crime and violence, impeded productivity and economic growth, and the impaired functioning of representative democracy. The extent of inequality in society is often a consequence of explicit policies and public choice. Reducing income inequality offers the prospect of greater social cohesiveness and better population health.

  5. Cohesiveness in financial news and its relation to market volatility.

    PubMed

    Piškorec, Matija; Antulov-Fantulin, Nino; Novak, Petra Kralj; Mozetič, Igor; Grčar, Miha; Vodenska, Irena; Smuc, Tomislav

    2014-01-01

    Motivated by recent financial crises, significant research efforts have been put into studying contagion effects and herding behaviour in financial markets. Much less has been said regarding the influence of financial news on financial markets. We propose a novel measure of collective behaviour based on financial news on the Web, the News Cohesiveness Index (NCI), and we demonstrate that the index can be used as a financial market volatility indicator. We evaluate the NCI using financial documents from large Web news sources on a daily basis from October 2011 to July 2013 and analyse the interplay between financial markets and finance-related news. We hypothesise that strong cohesion in financial news reflects movements in the financial markets. Our results indicate that cohesiveness in financial news is highly correlated with and driven by volatility in financial markets.

  6. Cohesiveness in Financial News and its Relation to Market Volatility

    PubMed Central

    Piškorec, Matija; Antulov-Fantulin, Nino; Novak, Petra Kralj; Mozetič, Igor; Grčar, Miha; Vodenska, Irena; Šmuc, Tomislav

    2014-01-01

    Motivated by recent financial crises, significant research efforts have been put into studying contagion effects and herding behaviour in financial markets. Much less has been said regarding the influence of financial news on financial markets. We propose a novel measure of collective behaviour based on financial news on the Web, the News Cohesiveness Index (NCI), and we demonstrate that the index can be used as a financial market volatility indicator. We evaluate the NCI using financial documents from large Web news sources on a daily basis from October 2011 to July 2013 and analyse the interplay between financial markets and finance-related news. We hypothesise that strong cohesion in financial news reflects movements in the financial markets. Our results indicate that cohesiveness in financial news is highly correlated with and driven by volatility in financial markets. PMID:24849598

  7. Biocompatibility, endocytosis, and intracellular trafficking of mesoporous silica and polystyrene nanoparticles in ovarian cancer cells: effects of size and surface charge groups

    PubMed Central

    Ekkapongpisit, Maneerat; Giovia, Antonino; Follo, Carlo; Caputo, Giuseppe; Isidoro, Ciro

    2012-01-01

    Background and methods Nanoparticles engineered to carry both a chemotherapeutic drug and a sensitive imaging probe are valid tools for early detection of cancer cells and to monitor the cytotoxic effects of anticancer treatment simultaneously. Here we report on the effect of size (10–30 nm versus 50 nm), type of material (mesoporous silica versus polystyrene), and surface charge functionalization (none, amine groups, or carboxyl groups) on biocompatibility, uptake, compartmentalization, and intracellular retention of fluorescently labeled nanoparticles in cultured human ovarian cancer cells. We also investigated the involvement of caveolae in the mechanism of uptake of nanoparticles. Results We found that mesoporous silica nanoparticles entered via caveolae-mediated endocytosis and reached the lysosomes; however, while the 50 nm nanoparticles permanently resided within these organelles, the 10 nm nanoparticles soon relocated in the cytoplasm. Naked 10 nm mesoporous silica nanoparticles showed the highest and 50 nm carboxyl-modified mesoporous silica nanoparticles the lowest uptake rates, respectively. Polystyrene nanoparticle uptake also occurred via a caveolae-independent pathway, and was negatively affected by serum. The 30 nm carboxyl-modified polystyrene nanoparticles did not localize in lysosomes and were not toxic, while the 50 nm amine-modified polystyrene nanoparticles accumulated within lysosomes and eventually caused cell death. Ovarian cancer cells expressing caveolin-1 were more likely to endocytose these nanoparticles. Conclusion These data highlight the importance of considering both the physicochemical characteristics (ie, material, size and surface charge on chemical groups) of nanoparticles and the biochemical composition of the cell membrane when choosing the most suitable nanotheranostics for targeting cancer cells. PMID:22904626

  8. Nonverbal Interventions in Clinical Groups.

    ERIC Educational Resources Information Center

    Shadish, William R., Jr.

    1980-01-01

    A comparison of nonverbal with verbal clinical group interventions suggested that some traditional self-report devices show less differentiation between these two interventions than do measures of group cohesion. A strong, replicable manipulation tested these findings, which were consistent with previous research. (Author/BEF)

  9. Behavioral and biological interactions with small groups in confined microsocieties

    NASA Technical Reports Server (NTRS)

    Brady, Joseph V.

    1986-01-01

    Research on small group performance in confined microsocieties was focused upon the development of principles and procedures relevant to the selection and training of space mission personnel, upon the investigation of behavioral programming, preventive monitoring and corrective procedures to enhance space mission performance effectiveness, and upon the evaluation of behavioral and physiological countermeasures to the potentially disruptive effects of unfamiliar and stressful environments. An experimental microsociety environment was designed and developed for continuous residence of human volunteers over extended time periods. Studies were then undertaken to analyze experimentally: (1) conditions that sustain group cohesion and productivity and that prevent social fragmentation and performance deterioration, (2) motivational effects performance requirements, and (3) behavioral and physiological effects resulting from changes in group size and composition. The results show that both individual and group productivity can be enhanced under such conditions by the direct application of contingency management principles to designated high-value tasks. Similarly, group cohesiveness can be promoted and individual social isolation and/or alienation prevented by the application of contingency management principles to social interaction segments of the program.

  10. Inverse correlation between cohesive energy and thermal expansion coefficient in liquid transition metal alloys.

    PubMed

    Gangopadhyay, A K; Bendert, J C; Mauro, N A; Kelton, K F

    2012-09-19

    The volume expansion coefficients (α) of twenty-five glass-forming transition metal alloy liquids, measured using the electrostatic levitation technique, are reported. An inverse correlation between α and the cohesive energy is found. The predicted values of α from this relationship agree reasonably well with the published data for thirty other transition metal and alloy liquids; some disagreement was found for a few alloys containing significant amounts of group III and IV elements. A theoretical argument for this empirical relationship is presented. PMID:22842287

  11. Fermionic quantum criticality in honeycomb and π -flux Hubbard models: Finite-size scaling of renormalization-group-invariant observables from quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Parisen Toldin, Francesco; Hohenadler, Martin; Assaad, Fakher F.; Herbut, Igor F.

    2015-04-01

    We numerically investigate the critical behavior of the Hubbard model on the honeycomb and the π -flux lattice, which exhibits a direct transition from a Dirac semimetal to an antiferromagnetically ordered Mott insulator. We use projective auxiliary-field quantum Monte Carlo simulations and a careful finite-size scaling analysis that exploits approximately improved renormalization-group-invariant observables. This approach, which is successfully verified for the three-dimensional XY transition of the Kane-Mele-Hubbard model, allows us to extract estimates for the critical couplings and the critical exponents. The results confirm that the critical behavior for the semimetal to Mott insulator transition in the Hubbard model belongs to the Gross-Neveu-Heisenberg universality class on both lattices.

  12. Group dynamics.

    PubMed

    Scandiffio, A L

    1990-12-01

    Group dynamics play a significant role within any organization, culture, or unit. The important thing to remember with any of these structures is that they are made up of people--people with different ideas, motivations, background, and sometimes different agendas. Most groups, formal or informal, look for a leader in an effort to maintain cohesiveness of the unit. At times, that cultural bond must be developed; once developed, it must be nurtured. There are also times that one of the group no longer finds the culture comfortable and begins to act out behaviorally. It is these times that become trying for the leader as she or he attempts to remain objective when that which was once in the building phase of group cohesiveness starts to fall apart. At all times, the manager must continue to view the employee creating the disturbance as an integral part of the group. It is at this time that it is beneficial to perceive the employee exhibiting problem behaviors as a special employee, as one who needs the benefit of your experience and skills, as one who is still part of the group. It is also during this time that the manager should focus upon her or his own views in the area of power, communication, and the corporate culture of the unit that one has established before attempting to understand another's point of view. Once we understand our own motivation and accept ourselves, it is then that we may move on to offer assistance to another. Once we understand our insecurities recognizing staff dysfunction as a symptom of system dysfunction will not be so threatening to the concept of the manager that we perceive ourselves to be. It takes a secure person to admit that she or he favors staff before deciding to do something to change things. The important thing to know is that it can be done. The favored staff can find a new way of relating to others, the special employee can find new modes of behavior (and even find self-esteem in the process), the group can find new ways

  13. Long Fibre Composite Modelling Using Cohesive User's Element

    NASA Astrophysics Data System (ADS)

    Kozák, Vladislav; Chlup, Zdeněk

    2010-09-01

    The development glass matrix composites reinforced by unidirectional long ceramic fibre has resulted in a family of very perspective structural materials. The only disadvantage of such materials is relatively high brittleness at room temperature. The main micromechanisms acting as toughening mechanism are the pull out, crack bridging, matrix cracking. There are other mechanisms as crack deflection etc. but the primer mechanism is mentioned pull out which is governed by interface between fibre and matrix. The contribution shows a way how to predict and/or optimise mechanical behaviour of composite by application of cohesive zone method and write user's cohesive element into the FEM numerical package Abaqus. The presented results from numerical calculations are compared with experimental data. Crack extension is simulated by means of element extinction algorithms. The principal effort is concentrated on the application of the cohesive zone model with the special traction separation (bridging) law and on the cohesive zone modelling. Determination of micro-mechanical parameters is based on the combination of static tests, microscopic observations and numerical calibration procedures.

  14. Writing Cohesion Using Content Lexical Ties in ESOL.

    ERIC Educational Resources Information Center

    Liu, Dilin

    2000-01-01

    Describes a series of exercises that have proved useful in helping students learning English to enhance their writing skills, particularly cohesion in their writing. Exercises enabled students to learn words in context or in relation to one another as synonyms, antonyms, superordinates, or hyponyms, and a better understanding of these words…

  15. Narrative Speech in Aging: Quantity, Information Content, and Cohesion

    ERIC Educational Resources Information Center

    Juncos-Rabadan, Onesimo; Pereiro, Arturo X.; Rodriguez, Maria Soledad

    2005-01-01

    This study examined age-related changes in narrative speech of 79 adults aged 40-91 who told stories from their pictorial representations. Quantity, information content and cohesion of narratives were analysed using a detailed transcription and codification system. We carried out a LISREL analysis to study relationships between narrative…

  16. All Together Now: Measuring Staff Cohesion in Special Education Classrooms

    ERIC Educational Resources Information Center

    Kratz, Hilary E.; Locke, Jill; Piotrowski, Zinnia; Ouellette, Rachel R.; Xie, Ming; Stahmer, Aubyn C.; Mandell, David S.

    2015-01-01

    This study sought to validate a new measure, the Classroom Cohesion Survey (CCS), designed to examine the relationship between teachers and classroom assistants in autism support classrooms. Teachers, classroom assistants, and external observers showed good inter-rater agreement on the CCS and good internal consistency for all scales. Simple…

  17. All Together Now: Measuring Staff Cohesion in Special Education Classrooms

    ERIC Educational Resources Information Center

    Kratz, Hilary E.; Locke, Jill; Piotrowski, Zinnia; Ouellette, Rachel R.; Xie, Ming; Stahmer, Aubyn C.; Mandell, David S.

    2014-01-01

    This study sought to validate a new measure, the Classroom Cohesion Survey (CCS), designed to examine the relationship between teachers and classroom assistants in autism support classrooms. Teachers, classroom assistants, and external observers showed good inter-rater agreement on the CCS and good internal consistency for all scales. Simple…

  18. Sense of Cohesion among Community Activists Engaging in Volunteer Activity

    ERIC Educational Resources Information Center

    Levy, Drorit; Itzhaky, Haya; Zanbar, Lea; Schwartz, Chaya

    2012-01-01

    The present article attempts to shed light on the direct and indirect contribution of personal resources and community indices to Sense of Cohesion among activists engaging in community volunteer work. The sample comprised 481 activists. Based on social systems theory, three levels of variables were examined: (1) inputs, which included personal…

  19. Long Fibre Composite Modelling Using Cohesive User's Element

    SciTech Connect

    Kozak, Vladislav; Chlup, Zdenek

    2010-09-30

    The development glass matrix composites reinforced by unidirectional long ceramic fibre has resulted in a family of very perspective structural materials. The only disadvantage of such materials is relatively high brittleness at room temperature. The main micromechanisms acting as toughening mechanism are the pull out, crack bridging, matrix cracking. There are other mechanisms as crack deflection etc. but the primer mechanism is mentioned pull out which is governed by interface between fibre and matrix. The contribution shows a way how to predict and/or optimise mechanical behaviour of composite by application of cohesive zone method and write user's cohesive element into the FEM numerical package Abaqus. The presented results from numerical calculations are compared with experimental data. Crack extension is simulated by means of element extinction algorithms. The principal effort is concentrated on the application of the cohesive zone model with the special traction separation (bridging) law and on the cohesive zone modelling. Determination of micro-mechanical parameters is based on the combination of static tests, microscopic observations and numerical calibration procedures.

  20. Coach-Initiated Motivational Climate and Cohesion in Youth Sport

    ERIC Educational Resources Information Center

    Eys, Mark A.; Jewitt, Eryn; Evans, M. Blair; Wolf, Svenja; Bruner, Mark W.; Loughead, Todd M.

    2013-01-01

    Purpose: The general purpose of the present study was to examine the link between cohesion and motivational climate in youth sport. The first specific objective was to determine if relationships demonstrated in previous research with adult basketball and handball participants would be replicated in a younger sample and with a more heterogeneous…

  1. Global expression for representing cohesive-energy curves. II

    NASA Technical Reports Server (NTRS)

    Schlosser, Herbert; Ferrante, John

    1993-01-01

    Schlosser et al. (1991) showed that the R dependence of the cohesive energy of partially ionic solids may be characterized by a two-term energy relationship consisting of a Coulomb term arising from the charge transfer, delta-Z, and a scaled universal energy function, E*(a *), which accounts for the partially covalent character of the bond and for repulsion between the atomic cores for small R; a* is a scaled length. In the paper by Schlosser et al., the normalized cohesive-energy curves of NaCl-structure alkali-halide crystals were generated with this expression. In this paper we generate the cohesive-energy curves of several families of partially ionic solids with different crystal structures and differing degrees of ionicity. These include the CsCl-structure Cs halides, and the Tl and Ag halides, which have weaker ionic bonding than the alkali halides, and which have the CsCl and NaCl structures, respectively. The cohesive-energy-curve parameters are then used to generate theoretical isothermal compression curves for the Li, Na, K, Cs, and Ag halides. We find good agreement with the available experimental compression data.

  2. Explaining Couple Cohesion in Different Types of Gay Families

    ERIC Educational Resources Information Center

    van Eeden-Moorefield, Brad; Pasley, Kay; Crosbie-Burnett, Margaret; King, Erin

    2012-01-01

    This Internet-based study used data from a convenience sample of 176 gay men in current partnerships to examine differences in outness, cohesion, and relationship quality between three types of gay male couples: first cohabiting partnerships, repartnerships, and gay stepfamilies. Also, we tested whether relationship quality mediated the link…

  3. The Impact of Cooperative Video Games on Team Cohesion

    ERIC Educational Resources Information Center

    Anderson, Greg

    2010-01-01

    In today's economy, productivity and efficiency require collaboration between employees. In order to improve collaboration the factors affecting teamwork must be examined to identify where changes can be made in order to increase performance. One factor contributing to teamwork is team cohesion and represents a process whereby members are joined…

  4. Community Cohesion in Post-16 Education: Principles and Practice

    ERIC Educational Resources Information Center

    Holden, Andrew

    2013-01-01

    Background: This paper is the product of a two year investigation into the contribution of post-16 education to community cohesion. The investigation took place between 2010 and 2012 and was funded by the University Centre at Blackburn College in England. Fieldwork was undertaken in three East Lancashire colleges and focused on students aged…

  5. Cohesive Errors in Writing among ESL Pre-Service Teachers

    ERIC Educational Resources Information Center

    Kwan, Lisa S. L.; Yunus, Melor Md

    2014-01-01

    Writing is a complex skill and one of the most difficult to master. A teacher's weak writing skills may negatively influence their students. Therefore, reinforcing teacher education by first determining pre-service teachers' writing weaknesses is imperative. This mixed-methods error analysis study aims to examine the cohesive errors in the writing…

  6. The Relationship between Social Cohesion and Computer-Internet Usage

    ERIC Educational Resources Information Center

    Balkan, Emre; Adalier, Ahmet

    2011-01-01

    The aim of this study is to analyze the relationship between social cohesion and computer-internet usage among university students. The research was conducted among university students in North Cyprus. The sample for the research consists of 38.8% (n=80) female, 61.2 % (n=126) male, 206 university students by using the criterion sampling method.…

  7. Coh-Metrix: Capturing Linguistic Features of Cohesion

    ERIC Educational Resources Information Center

    McNamara, Danielle S.; Louwerse, Max M.; McCarthy, Philip M.; Graesser, Arthur C.

    2010-01-01

    This study addresses the need in discourse psychology for computational techniques that analyze text on multiple levels of cohesion and text difficulty. Discourse psychologists often investigate phenomena related to discourse processing using lengthy texts containing multiple paragraphs, as opposed to single word and sentence stimuli.…

  8. Course Cohesion: An Elusive Goal for Tertiary Education

    ERIC Educational Resources Information Center

    Bahr, Nan; Lloyd, Margaret

    2011-01-01

    A program's development and implementation in a higher education institution is usually launched with great fanfare, goodwill and a huge effort on the part of the whole development team to ensure a worthwhile cohesive set of learning experiences aligned to the desired course learning outcomes. It is often not long before the glue starts to come…

  9. Possibilities for Social Cohesion in Education: Bosnia-Herzegovina

    ERIC Educational Resources Information Center

    Hill, Kelly

    2011-01-01

    In postwar Bosnia-Herzegovina, segregation along ethno-nationalistic lines and divergent pedagogies within the education system have presented challenges to social cohesion and the long-term stability of a society that is still struggling to rebuild, reconcile, and regain trust (Jancic, 2008). This article examines the current state of the…

  10. A Measure for the Cohesion of Weighted Networks.

    ERIC Educational Resources Information Center

    Egghe, Leo; Rousseau, Ronald

    2003-01-01

    Discusses graph theory in information science, focusing on measures for the cohesion of networks. Illustrates how a set of weights between connected nodes can be transformed into a set of dissimilarity measures and presents an example of the new compactness measures for a cocitation and a bibliographic coupling network. (Author/LRW)

  11. Spatial cohesion of adult male chimpanzees (Pan troglodytes verus) in Taï National Park, Côte d'Ivoire.

    PubMed

    Eckhardt, Nadin; Polansky, Leo; Boesch, Christophe

    2015-02-01

    Group living animals can exhibit fission-fusion behavior whereby individuals temporarily separate to reduce the costs of living in large groups. Primates living in groups with fission-fusion dynamics face numerous challenges in maintaining spatial cohesion, especially in environments with limited visibility. Here we investigated the spatial cohesion of adult male chimpanzees (Pan troglodytes verus) living in Taï National Park, Côte d'Ivoire, to better understand the mechanisms by which individuals maintain group cohesion during fission-fusion events. Over a 3-year period, we simultaneously tracked the movements of 2-4 males for 4-12 hr on up to 12 consecutive days using handheld GPS devices that recorded locations at one-minute intervals. Analyses of the male's inter-individual distance (IID) showed that the maximum, median, and mean IID values across all observations were 7.2 km, 73 m, and 483 m, respectively. These males (a) had maximum daily IID values below the limits of auditory communication (<1 km) for 63% of the observation time, (b) remained out of visual range (≥100 m) for 46% of observation time, and (c) remained within auditory range for 70% of the time when they were in different parties. We compared the observed distribution of IIDs with a random distribution obtained from permutations of the individuals' travel paths using Kolmogorov-Smirnov tests. Observation IID values were significantly smaller than those generated by the permutation procedure. We conclude that these male chimpanzees actively maintain cohesion when out of sight, and that auditory communication is one likely mechanism by which they do so. We discuss mechanisms by which chimpanzees may maintain the level of cohesion observed. This study provides a first analysis of spatial group cohesion over large distances in forest chimpanzees using high-resolution tracking, and illustrates the utility of such data for quantifying socio-ecological processes in primate ecology.

  12. Cohesion and Joint Speech: Right Hemisphere Contributions to Synchronized Vocal Production

    PubMed Central

    Jasmin, Kyle M.; McGettigan, Carolyn; Agnew, Zarinah K.; Lavan, Nadine; Josephs, Oliver; Cummins, Fred

    2016-01-01

    Synchronized behavior (chanting, singing, praying, dancing) is found in all human cultures and is central to religious, military, and political activities, which require people to act collaboratively and cohesively; however, we know little about the neural underpinnings of many kinds of synchronous behavior (e.g., vocal behavior) or its role in establishing and maintaining group cohesion. In the present study, we measured neural activity using fMRI while participants spoke simultaneously with another person. We manipulated whether the couple spoke the same sentence (allowing synchrony) or different sentences (preventing synchrony), and also whether the voice the participant heard was “live” (allowing rich reciprocal interaction) or prerecorded (with no such mutual influence). Synchronous speech was associated with increased activity in posterior and anterior auditory fields. When, and only when, participants spoke with a partner who was both synchronous and “live,” we observed a lack of the suppression of auditory cortex, which is commonly seen as a neural correlate of speech production. Instead, auditory cortex responded as though it were processing another talker's speech. Our results suggest that detecting synchrony leads to a change in the perceptual consequences of one's own actions: they are processed as though they were other-, rather than self-produced. This may contribute to our understanding of synchronized behavior as a group-bonding tool. SIGNIFICANCE STATEMENT Synchronized human behavior, such as chanting, dancing, and singing, are cultural universals with functional significance: these activities increase group cohesion and cause participants to like each other and behave more prosocially toward each other. Here we use fMRI brain imaging to investigate the neural basis of one common form of cohesive synchronized behavior: joint speaking (e.g., the synchronous speech seen in chants, prayers, pledges). Results showed that joint speech recruits

  13. Clause Relations and Macro Patterns: Cohesion, Coherence, and the Writing of Advanced ESOL Students.

    ERIC Educational Resources Information Center

    Basturkmen, Helen

    2002-01-01

    Discusses problems nonnative speakers of English may have in making their written texts cohesive and coherent and describes instructional activities designed to help students achieve greater cohesion and coherence in their writing. (Author/VWL)

  14. Lifelong Learning, Equality and Social Cohesion

    ERIC Educational Resources Information Center

    Green, Andy

    2011-01-01

    This article compares the evidence from the 2009 PISA survey on the distribution of skills amongst 15-year-olds in different regions and country groups and explores how education systems in these regions contribute to different levels of inequality. In the second part, it presents evidence from surveys on adult skills and attitudes on how skills…

  15. Riparian vegetation controls on channels formed in non-cohesive sediment

    NASA Astrophysics Data System (ADS)

    Gran, K.; Tal, M.; Paola, C.

    2002-05-01

    Riparian vegetation can significantly influence the morphology of a river, affecting channel geometry and flow dynamics. In channels formed in non-cohesive material, vegetation is the main source of bank cohesion and could affect the overall behavior of the river, potentially constraining the flow from a multi-thread channel to a single-thread channel. To examine the effects of riparian vegetation on streams formed in non-cohesive material, we conducted a series of physical experiments at the St. Anthony Falls Laboratory. The first set of experiments examines the effects of varying densities of vegetation on braided stream dynamics. Water discharge, sediment discharge, and grain size were held constant. For each run, we allowed a braided system to develop, then halved the discharge, and seeded the flume with alfalfa (Medicago sativa). After ten to fourteen days of growth, we returned the discharge to its original value and continued the run for 30-36 hours. Our results show that the influence of vegetation on the overall river pattern varied systematically with the spatial density of plant stems. The vegetation reduced the number of active channels and increased bank stability, leading to lower lateral migration rates, narrower and deeper channels, and an increase in channel relief. All these effects increased with vegetation density. Vegetation also influenced flow dynamics, increasing the variance of flow direction in the vegetated runs, and increasing scour depths through strong downwelling where the flow collided with relatively resistant banks. This oblique bank collision provides a new mechanism for producing secondary flows. We found these bank collision driven secondary flows to be more important than the classical curvature-driven mechanism in the vegetated runs. The next set of experiments examines more closely how the channel pattern evolves through time, allowing for both channel migration and successive vegetation growth. In these on-going experiments

  16. Intra-molecular cohesion of coils mediated by phenylalanine-glycine motifs in the natively unfolded domain of a nucleoporin

    SciTech Connect

    Krishnan, V V; Lau, E Y; Yamada, J; Denning, D P; Patel, S S; Colvin, M E; Rexach, M F

    2007-04-19

    The nuclear pore complex (NPC) provides the sole aqueous conduit for macromolecular exchange between the nucleus and cytoplasm of cells. Its conduit contains a size-selective gate and is populated by a family of NPC proteins that feature long natively-unfolded domains with phenylalanine-glycine repeats. These FG nucleoporins play key roles in establishing the NPC permeability barrier, but little is known about their dynamic structure. Here we used molecular modeling and biophysical techniques to characterize the dynamic ensemble of structures of a representative FG domain from the yeast nucleoporin Nup116. The results show that its FG motifs function as intra-molecular cohesion elements that impart order to the FG domain. The cohesion of coils mediated by FG motifs in the natively unfolded domain of Nup116 supports a type of tertiary structure, a native pre-molten globule, that could become quaternary at the NPC through recruitment of neighboring FG nucleoporins, forming one cohesive meshwork of intertwined filaments capable of gating protein diffusion across the NPC by size exclusion.

  17. Application of English Cohesion Theory in the Teaching of Writing to Chinese Graduate Students

    ERIC Educational Resources Information Center

    Xin-hong, Zhou

    2007-01-01

    The English cohesion theory proposed by Halliday and Hasan makes great contributions to the understanding of the coherence and cohesion of the English texts. It should be applicable in the teaching of English writing so as to improve the cohesion in the students' compositions. The present paper describes a practice of this order among non-major…

  18. Reversing the Reverse Cohesion Effect: Good Texts Can Be Better for Strategic, High-Knowledge Readers

    ERIC Educational Resources Information Center

    O'Reilly, Tenaha; McNamara, Danielle S.

    2007-01-01

    Students with low knowledge have been shown to better understand and learn more from more cohesive texts, whereas high-knowledge students have been shown to learn more from lower cohesion texts; this has been called the "reverse cohesion effect". This study examines whether students' comprehension skill affects the interaction between text…

  19. Exploring the Effect of Background Knowledge and Text Cohesion on Learning from Texts in Computer Science

    ERIC Educational Resources Information Center

    Gasparinatou, Alexandra; Grigoriadou, Maria

    2013-01-01

    In this study, we examine the effect of background knowledge and local cohesion on learning from texts. The study is based on construction-integration model. Participants were 176 undergraduate students who read a Computer Science text. Half of the participants read a text of maximum local cohesion and the other a text of minimum local cohesion.…

  20. Contributions of Self-Explanation to Comprehension of High- and Low-Cohesion Texts

    ERIC Educational Resources Information Center

    Ozuru, Yasuhiro; Briner, Stephen; Best, Rachel; McNamara, Danielle S.

    2010-01-01

    This study examined how the contribution of self-explanation to science text comprehension is affected by the cohesion of a text at a local level. Psychology undergraduates read and self-explained a science text with either low or high local cohesion. Local cohesion was manipulated by the presence or absence of connectives and referential words or…

  1. The cohesive metaschema: a higher-level abstraction of the UMLS Semantic Network.

    PubMed

    Perl, Yehoshua; Chen, Zong; Halper, Michael; Geller, James; Zhang, Li; Peng, Yi

    2002-06-01

    The Unified Medical Language System (UMLS) joins together a group of established medical terminologies in a unified knowledge representation framework. Two major resources of the UMLS are its Metathesaurus, containing a large number of concepts, and the Semantic Network (SN), containing semantic types and forming an abstraction of the Metathesaurus. However, the SN itself is large and complex and may still be difficult to view and comprehend. Our structural partitioning technique partitions the SN into structurally uniform sets of semantic types based on the distribution of the relationships within the SN. An enhancement of the structural partition results in cohesive, singly rooted sets of semantic types. Each such set is named after its root which represents the common nature of the group. These sets of semantic types are represented by higher-level components called metasemantic types. A network, called a metaschema, which consists of the meta-semantic types connected by hierarchical and semantic relationships is obtained and provides an abstract view supporting orientation to the SN. The metaschema is utilized to audit the UMLS classifications. We present a set of graphical views of the SN based on the metaschema to help in user orientation to the SN. A study compares the cohesive metaschema to metaschemas derived semantically by UMLS experts.

  2. Shear-rate Dependent Regime Transition in Homogeneously sheared systems of Frictionless Cohesive Granules

    NASA Astrophysics Data System (ADS)

    Murphy, Eric; Sundararajan, Sriram; Subramaniam, Shankar

    2013-11-01

    We study regime transition behavior in systems of cohesive micron-sized granular particles in the absence of friction via soft sphere discrete element (DEM) simulations. Previous studies, have identified a shear-rate dependent regime transition, from Bagnold to quasi-static scaling, occurring below jamming volume fractions. The transition of interest is well-described by theories for non-equilibrium phase transitions. Most notably, this regime transition is accompanied by the emergence of a diverging meso-scopic length-scale based on the formation of local contact networks indicative of clustering. We identify the relevant non-dimensional quantities, e.g. ratio of cohesive potential to granular kinetic temperature, which mark the location of the critical transition and show that the fabric tensor may serve as a promising order-parameter. The study of such simple systems has broad implications for the constitutive modeling of other athermal systems, and illuminates the growing need for the modeling of non-local effects in flows of macroscopic particles. We gratefully acknowledge the support for this work from NSF grant no. 0927660.

  3. Aggregation and sedimentation in gas-fluidized beds of cohesive powders.

    PubMed

    Castellanos, A; Valverde, J M; Quintanilla, M A

    2001-10-01

    We present measurements on the settling velocity of gas-fluidized beds of fine cohesive powders. In the solidlike regime (solid volume fraction straight phi>straight phi(c)) particles are static, sustained by enduring contacts. The settling is hindered by interparticle contacts and is a very slow process. In the fluidlike regime (straight phisize is confirmed by direct visualization of the aggregates, and shows that cohesive effects become important when the adhesion force between particles is above particle weight. Results show that aggregates form open structures with a fractal dimension close to the predicted one in the diffusion-limited-aggregation model (D=2.5).

  4. Delamination of impacted composite structures by cohesive zone interface elements and tiebreak contact

    NASA Astrophysics Data System (ADS)

    Dogan, Fatih; Hadavinia, Homayoun; Donchev, Todor; Bhonge, Prasannakumar S.

    2012-12-01

    Maximising impact protection of fibre reinforced plastic (FRP) laminated composite structures and predicting and preventing the negative effects of impact on these structures are paramount design criteria for ground and space vehicles. In this paper the low velocity impact response of these structures will be investigated. The current work is based on the application of explicit finite element software for modelling the behaviour of laminated composite plates under low velocity impact loading and it explores the impact, post impact and failure of these structures. Three models, namely thick shell elements with cohesive interface, solid elements with cohesive interface, and thin shell elements with tiebreak contact, were all developed in the explicit nonlinear finite element code LS-DYNA. The FEA results in terms of force and energy are validated with experimental studies in the literature. The numerical results are utilized in providing guidelines for modelling and impact simulation of FRP laminated composites, and recommendations are provided in terms of modelling and simulation parameters such as element size, number of shell sub-laminates, and contact stiffness scale factors.

  5. Interface Cohesive Elements to Model Matrix Crack Evolution in Composite Laminates

    NASA Astrophysics Data System (ADS)

    Shi, Y.; Pinna, C.; Soutis, C.

    2014-02-01

    In this paper, the transverse matrix (resin) cracking developed in multidirectional composite laminates loaded in tension was numerically investigated by a finite element (FE) model implemented in the commercially available software Abaqus/Explicit 6.10. A theoretical solution using the equivalent constraint model (ECM) of the damaged laminate developed by Soutis et al. was employed to describe matrix cracking evolution and compared to the proposed numerical approach. In the numerical model, interface cohesive elements were inserted between neighbouring finite elements that run parallel to fibre orientation in each lamina to simulate matrix cracking with the assumption of equally spaced cracks (based on experimental measurements and observations). The stress based traction-separation law was introduced to simulate initiation of matrix cracking and propagation under mixed-mode loading. The numerically predicted crack density was found to depend on the mesh size of the model and the material fracture parameters defined for the cohesive elements. Numerical predictions of matrix crack density as a function of applied stress are in a good agreement to experimentally measured and theoretically (ECM) obtained values, but some further refinement will be required in near future work.

  6. The darker side of groups.

    PubMed

    Thomas, Mike; Hynes, Celia

    2007-05-01

    This paper examines the role of group interaction in the workplace and the impact of anxiety on group cohesion. It takes a psychoanalytical perspective and highlights how early learning within a familial setting influences later attitudes and behaviour at work. In particular the article focuses on the signs of negative group anxiety and how the manager can recognise anti-group culture. By recognising the negative signs the leader can also come to understand how the anti-group develops and thereby prevent the resulting disruptive behaviour. In some instances the perception of anti-group feelings and behaviour can also be altered so that the team leader can reach a positive outcome for the group dynamic and resultant team cohesion and collaboration. PMID:17456166

  7. Cohesive zone model for intergranular slow crack growth in ceramics: influence of the process and the microstructure

    NASA Astrophysics Data System (ADS)

    Romero de la Osa, M.; Estevez, R.; Olagnon, C.; Chevalier, J.; Tallaron, C.

    2011-10-01

    Ceramic polycrystals are prone to slow crack growth (SCG) which is stress and environmentally assisted, similarly to observations reported for silica glasses. The kinetics of fracture are known to be dependent on the load level, the temperature and the relative humidity. In addition, evidence is available on the influence of the microstructure on the SCG rate with an increase in the crack velocity with decreasing the grain size. Crack propagation takes place beyond a load threshold, which is grain size dependent. We present a cohesive zone model for the intergranular failure process. The methodology accounts for an intrinsic opening that governs the length of the cohesive zone and allows the investigation of grain size effects. A rate and temperature-dependent cohesive model is proposed (Romero de la Osa M, Estevez R et al 2009 J. Mech. Adv. Mater. Struct. 16 623-31) to mimic the reaction-rupture mechanism. The formulation is inspired by Michalske and Freiman's picture (Michalske and Freiman 1983 J. Am. Ceram. Soc. 66 284-8) together with a recent study by Zhu et al (2005 J. Mech. Phys. Solids 53 1597-623) of the reaction-rupture mechanism. The present investigation extends a previous work (Romero de la Osa et al 2009 Int. J. Fracture 158 157-67) in which the problem is formulated. Here, we explore the influence of the microstructure in terms of grain size, their elastic properties and residual thermal stresses originating from the cooling from the sintering temperature down to ambient conditions. Their influence on SCG for static loadings is reported and the predictions compared with experimental trends. We show that the initial stress state is responsible for the grain size dependence reported experimentally for SCG. Furthermore, the account for the initial stresses enables the prediction of a load threshold below which no crack growth is observed: a crack arrest takes place when the crack path meets a region in compression.

  8. Using Telestrations™ to Illustrate Small Group Communication Principles

    ERIC Educational Resources Information Center

    Fedesco, Heather Noel

    2014-01-01

    This single class activity described here: (1) illustrates the importance of interdependence in groups; (2) can be used to measure group productivity and performance; (3) can encourage groups to engage in group learning; and (4) can facilitate group cohesion for newly formed groups. Students will be working in groups for the majority of their…

  9. Quantum Mechanical Metric for Internal Cohesion in Cement Crystals

    PubMed Central

    Dharmawardhana, C. C.; Misra, A.; Ching, Wai-Yim

    2014-01-01

    Calcium silicate hydrate (CSH) is the main binding phase of Portland cement, the single most important structural material in use worldwide. Due to the complex structure and chemistry of CSH at various length scales, the focus has progressively turned towards its atomic level comprehension. We study electronic structure and bonding of a large subset of the known CSH minerals. Our results reveal a wide range of contributions from each type of bonding, especially hydrogen bonding, which should enable critical analysis of spectroscopic measurements and construction of realistic C-S-H models. We find the total bond order density (TBOD) as the ideal overall metric for assessing crystal cohesion of these complex materials and should replace conventional measures such as Ca:Si ratio. A rarely known orthorhombic phase Suolunite is found to have higher cohesion (TBOD) in comparison to Jennite and Tobermorite, which are considered the backbone of hydrated Portland cement. PMID:25476741

  10. Coh-metrix: analysis of text on cohesion and language.

    PubMed

    Graesser, Arthur C; McNamara, Danielle S; Louwerse, Max M; Cai, Zhiqiang

    2004-05-01

    Advances in computational linguistics and discourse processing have made it possible to automate many language- and text-processing mechanisms. We have developed a computer tool called Coh-Metrix, which analyzes texts on over 200 measures of cohesion, language, and readability. Its modules use lexicons, part-of-speech classifiers, syntactic parsers, templates, corpora, latent semantic analysis, and other components that are widely used in computational linguistics. After the user enters an English text, CohMetrix returns measures requested by the user. In addition, a facility allows the user to store the results of these analyses in data files (such as Text, Excel, and SPSS). Standard text readability formulas scale texts on difficulty by relying on word length and sentence length, whereas Coh-Metrix is sensitive to cohesion relations, world knowledge, and language and discourse characteristics. PMID:15354684

  11. Cohesive fracture model for functionally graded fiber reinforced concrete

    SciTech Connect

    Park, Kyoungsoo; Paulino, Glaucio H.; Roesler, Jeffery

    2010-06-15

    A simple, effective, and practical constitutive model for cohesive fracture of fiber reinforced concrete is proposed by differentiating the aggregate bridging zone and the fiber bridging zone. The aggregate bridging zone is related to the total fracture energy of plain concrete, while the fiber bridging zone is associated with the difference between the total fracture energy of fiber reinforced concrete and the total fracture energy of plain concrete. The cohesive fracture model is defined by experimental fracture parameters, which are obtained through three-point bending and split tensile tests. As expected, the model describes fracture behavior of plain concrete beams. In addition, it predicts the fracture behavior of either fiber reinforced concrete beams or a combination of plain and fiber reinforced concrete functionally layered in a single beam specimen. The validated model is also applied to investigate continuously, functionally graded fiber reinforced concrete composites.

  12. Age-Dependent Susceptibility of Chromosome Cohesion to Premature Separase Activation in Mouse Oocytes1

    PubMed Central

    Chiang, Teresa; Schultz, Richard M.; Lampson, Michael A.

    2011-01-01

    ABSTRACT A hypothesis to explain the maternal age-dependent increase in formation of aneuploid eggs is deterioration of chromosome cohesion. Although several lines of evidence are consistent with this hypothesis, whether cohesion is actually reduced in naturally aged oocytes has not been directly tested by any experimental perturbation. To directly target cohesion, we increased the activity of separase, the protease that cleaves the meiotic cohesin REC8, in oocytes. We show that cohesion is more susceptible to premature separase activation in old oocytes than in young oocytes, demonstrating that cohesion is significantly reduced. Furthermore, cohesion is protected by two independent mechanisms that inhibit separase, securin and an inhibitory phosphorylation of separase by CDK1; both mechanisms must be disrupted to prematurely activate separase. With the continual loss of cohesins from chromosomes that occurs throughout the natural reproductive lifespan, tight regulation of separase in oocytes may be particularly important to maintain cohesion and prevent aneuploidy. PMID:21865557

  13. Modelling interfacial cracking with non-matching cohesive interface elements

    NASA Astrophysics Data System (ADS)

    Nguyen, Vinh Phu; Nguyen, Chi Thanh; Bordas, Stéphane; Heidarpour, Amin

    2016-07-01

    Interfacial cracking occurs in many engineering problems such as delamination in composite laminates, matrix/interface debonding in fibre reinforced composites etc. Computational modelling of these interfacial cracks usually employs compatible or matching cohesive interface elements. In this paper, incompatible or non-matching cohesive interface elements are proposed for interfacial fracture mechanics problems. They allow non-matching finite element discretisations of the opposite crack faces thus lifting the constraint on the compatible discretisation of the domains sharing the interface. The formulation is based on a discontinuous Galerkin method and works with both initially elastic and rigid cohesive laws. The proposed formulation has the following advantages compared to classical interface elements: (i) non-matching discretisations of the domains and (ii) no high dummy stiffness. Two and three dimensional quasi-static fracture simulations are conducted to demonstrate the method. Our method not only simplifies the meshing process but also it requires less computational demands, compared with standard interface elements, for problems that involve materials/solids having a large mismatch in stiffnesses.

  14. Modelling interfacial cracking with non-matching cohesive interface elements

    NASA Astrophysics Data System (ADS)

    Nguyen, Vinh Phu; Nguyen, Chi Thanh; Bordas, Stéphane; Heidarpour, Amin

    2016-11-01

    Interfacial cracking occurs in many engineering problems such as delamination in composite laminates, matrix/interface debonding in fibre reinforced composites etc. Computational modelling of these interfacial cracks usually employs compatible or matching cohesive interface elements. In this paper, incompatible or non-matching cohesive interface elements are proposed for interfacial fracture mechanics problems. They allow non-matching finite element discretisations of the opposite crack faces thus lifting the constraint on the compatible discretisation of the domains sharing the interface. The formulation is based on a discontinuous Galerkin method and works with both initially elastic and rigid cohesive laws. The proposed formulation has the following advantages compared to classical interface elements: (i) non-matching discretisations of the domains and (ii) no high dummy stiffness. Two and three dimensional quasi-static fracture simulations are conducted to demonstrate the method. Our method not only simplifies the meshing process but also it requires less computational demands, compared with standard interface elements, for problems that involve materials/solids having a large mismatch in stiffnesses.

  15. Packing and stability of geometrically cohesive granular media

    NASA Astrophysics Data System (ADS)

    Gravish, Nick; Franklin, Scott V.; Hu, David L.; Goldman, Daniel I.

    2011-11-01

    Granular particles with concave shapes may entangle with neighboring particles creating an effective cohesion controlled by particle geometry. We study the packing and stability of vertical columns formed from geometrically cohesive u-shaped particles (staples) of varying barb length, l. We prepare cohesive columns by packing particles in a confining cylindrical tube under vertical vibration at fixed frequency of f = 30 Hz and peak acceleration (in units of g) of Γ = 2 . The initial and final volume fraction vary with l and volume fraction increases for decreasing l. Once packed, the tube is removed and columns are subjected to vertical vibration at fixed f and variable Γ. We monitor column height, h (t) , during collapse and find that h (t) is described by a stretched exponential h (t) /h0 = exp [ -(t/τ)β ] . The characteristic collapse time, τ, is governed by an Arrhenius law with τ =τ0 exp (Γ0 / Γ) where Γ0 is a measure of the column's resistance to collapse. We find that Γ0 is a non-monotonic function of l and exhibits a maximum at intermediate l. We explain this effect through a model considering packing and entanglement.

  16. Determination of mode-I cohesive strength for interfaces

    NASA Astrophysics Data System (ADS)

    Jørgensen, J. B.; Thouless, M. D.; Sørensen, B. F.; Kildegaard, C.

    2016-07-01

    The cohesive strength is one of the governing parameters controlling crack deflection at interfaces, but measuring its magnitude is challenging. In this paper, we demonstrate a novel approach to determine the mode-I cohesive strength of an interface by using a 4-point single-edge-notch beam specimen. The test specimen is made of a glue cast onto a unidirectional, glass-fiber laminate. A crack is cut in the glue, orthogonal to the interface, which creates a high normal stress across the glue/laminate interface during loading. It is observed that a new crack can be initiated along the interface in response to this stress, before the main crack starts to grow. Observations using 2D digital-image correlation showed that an ’’apparent” strain across the interface initially increases linearly with the applied load, but becomes nonlinear upon the initiation of the interface crack. The cohesive strength is determined, using a 2D, linear-elastic, finite-element model of the experiment, as the stress value where the experimental measured ’apparent” strain value becomes non-linear across the interface.

  17. An algorithm for simulating fracture of cohesive-frictional materials

    SciTech Connect

    Nukala, Phani K; Sampath, Rahul S; Barai, Pallab

    2010-01-01

    Fracture of disordered frictional granular materials is dominated by interfacial failure response that is characterized by de-cohesion followed by frictional sliding response. To capture such an interfacial failure response, we introduce a cohesive-friction random fuse model (CFRFM), wherein the cohesive response of the interface is represented by a linear stress-strain response until a failure threshold, which is then followed by a constant response at a threshold lower than the initial failure threshold to represent the interfacial frictional sliding mechanism. This paper presents an efficient algorithm for simulating fracture of such disordered frictional granular materials using the CFRFM. We note that, when applied to perfectly plastic disordered materials, our algorithm is both theoretically and numerically equivalent to the traditional tangent algorithm (Roux and Hansen 1992 J. Physique II 2 1007) used for such simulations. However, the algorithm is general and is capable of modeling discontinuous interfacial response. Our numerical simulations using the algorithm indicate that the local and global roughness exponents ({zeta}{sub loc} and {zeta}, respectively) of the fracture surface are equal to each other, and the two-dimensional crack roughness exponent is estimated to be {zeta}{sub loc} = {zeta} = 0.69 {+-} 0.03.

  18. Does Decentralisation Enhance a School's Role of Promoting Social Cohesion? Bosnian School Leaders' Perceptions of School Governance

    ERIC Educational Resources Information Center

    Komatsu, Taro

    2014-01-01

    This study seeks to understand whether and how decentralised school governance in Bosnia and Herzegovina (BiH) enhances the schools' role of promoting social cohesion. This includes increasing "horizontal" trust among different ethnic groups and "vertical" trust between civilians and public institutes. The study examined…

  19. Simulating Intergranular Stress Corrosion Cracking in AZ31 Using Three-Dimensional Cohesive Elements for Grain Structure

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Chen, Z. H.; Dong, C. F.

    2015-12-01

    In this study, a grain boundary model with three-dimensional (3D) cohesive elements for analyzing the intergranular stress corrosion cracking (IGSCC) on the crystal level in polycrystalline materials is presented. The objectives are to characterize the grain boundary microstructure and the fracture mechanism of IGSCC in AZ31 Mg alloy. In order to investigate the development of the microcrack and its effects on macrocrack evolution, a novel model of IGSCC propagation has been developed, in which the 3D Voronoi tessellations geometry is employed to model polycrystalline grain structures. And the 3D cohesive elements with zero constitutive thickness are directly inserted on the faces of two adjacent grains. The effect of the embrittlement due to the presence of hydrogen has also been included in the cohesive model. To validate the model, an IGSCC process of AZ31 Mg alloy in NaCl solution has been simulated, with the influence of hydrogen concentration being taken into account. It is found that damage develops at the triple lines between the grains and the combinations of grains can lead to high stresses at the grains boundary, especially those that are normal to the direction of the applied strain. In this paper, the effects of damage due to hydrogen and the grain sizes in microstructure are considered. The simulation results have a good consistency with the experimental phenomenon.

  20. Drinking water biofilm cohesiveness changes under chlorination or hydrodynamic stress.

    PubMed

    Mathieu, L; Bertrand, I; Abe, Y; Angel, E; Block, J C; Skali-Lami, S; Francius, G

    2014-05-15

    Attempts at removal of drinking water biofilms rely on various preventive and curative strategies such as nutrient reduction in drinking water, disinfection or water flushing, which have demonstrated limited efficiency. The main reason for these failures is the cohesiveness of the biofilm driven by the physico-chemical properties of its exopolymeric matrix (EPS). Effective cleaning procedures should break up the matrix and/or change the elastic properties of bacterial biofilms. The aim of this study was to evaluate the change in the cohesive strength of two-month-old drinking water biofilms under increasing hydrodynamic shear stress τw (from ∼0.2 to ∼10 Pa) and shock chlorination (applied concentration at T0: 10 mg Cl2/L; 60 min contact time). Biofilm erosion (cell loss per unit surface area) and cohesiveness (changes in the detachment shear stress and cluster volumes measured by atomic force microscopy (AFM)) were studied. When rapidly increasing the hydrodynamic constraint, biofilm removal was found to be dependent on a dual process of erosion and coalescence of the biofilm clusters. Indeed, 56% of the biofilm cells were removed with, concomitantly, a decrease in the number of the 50-300 μm(3) clusters and an increase in the number of the smaller (i.e., <50 μm(3)) and larger (i.e., >600 μm(3)) ones. Moreover, AFM evidenced the strengthening of the biofilm structure along with the doubling of the number of contact points, NC, per cluster volume unit following the hydrodynamic disturbance. This suggests that the compactness of the biofilm exopolymers increases with hydrodynamic stress. Shock chlorination removed cells (-75%) from the biofilm while reducing the volume of biofilm clusters. Oxidation stress resulted in a decrease in the cohesive strength profile of the remaining drinking water biofilms linked to a reduction in the number of contact points within the biofilm network structure in particular for the largest biofilm cluster volumes (>200