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The motion of glaciers over their bedrock or drops of fluid along a solid surface can vary dramatically when these substrates are lubricated. We investigate the coupled flow of a gravity current (GC) of a strain-rate softening fluid that is lubricated by a denser, lower-viscosity Newtonian fluid. We present a set of experiments in which such GCs are discharged axisymmetrically and at constant flux over a flat surface. Using imaging techniques, we follow the evolution of the front and thickness field of each fluid. We find that, unlike purely Newtonian lubricated GCs, the fronts of the non-Newtonian and lubricating Newtonian fluids have a power-law time evolution with different exponents. Each of these exponents is similar to that of a non-lubricated GC of the same fluid. Nevertheless, the fronts of our lubricated GCs evolve faster than those of the corresponding non-lubricated GCs owing to larger intercepts. In addition, in contrast with the monotonically declining thickness of non-lubricated GCs, the thickness of the lubricated, non-Newtonian fluid is nearly uniform, and that of the lubricating fluid is non-monotonic with localised spikes. Despite these complex thickness patterns, lubricated GCs remain axisymmetric as long as the flux of the lubricating fluid is sufficiently smaller than that of the non-Newtonian fluid.
Political scientists have largely overlooked the democratic challenges inherent in the governance of U.S. public education—despite profound implications for educational delivery and, ultimately, social mobility and economic growth. In this study, we consider whether the interests of adult voters who elect local school boards are likely to be aligned with the needs of the students their districts educate. Specifically, we compare voters and students in four states on several policy-relevant dimensions. Using official voter turnout records and rich microtargeting data, we document considerable demographic differences between voters who participate in school board elections and the students attending the schools that boards oversee. These gaps are most pronounced in majority nonwhite jurisdictions and school districts with the largest racial achievement gaps. Our novel analysis provides important context for understanding the political pressures facing school boards and their likely role in perpetuating educational and, ultimately, societal inequality.
For African American emerging adult men, developmental challenges are evident in their escalating substance abuse and depressive symptoms; this is particularly true for men from low-resource communities. The present study tests a developmental model linking childhood adversity and contemporaneous contextual stressors to increases in emerging adults’ substance use and depressive symptoms, indirectly, via increases in defensive/hostile relational schemas and social developmental risk factors (e.g., risky peers and romantic partners, lack of involvement in school or work). We also advance exploratory hypotheses regarding DNA methylation in the oxytocin receptor gene (OXTR) as a moderator of the effects of stress on relational schemas. Hypotheses were tested with three waves of data from 505 rural African American men aged 19–25 years. Adverse childhood experiences predicted exposure to emerging adult contextual stressors. Contextual stressors forecast increases in defensive/hostile relational schemas, which increased social developmental risk factors. Social developmental risk factors proximally predicted increases in substance abuse and depressive symptoms. OXTR DNA methylation moderated the effects of contextual stressors on defensive/hostile relational schemas. Findings suggest that early exposures to stress carry forward to affect the development of social developmental risk factors in emerging adulthood, which place rural African American men at risk for increased substance abuse and depressive symptoms during the emerging adult years.
Dans le cadre du développement de la classification internationale des maladies (CIM-11), les groupes de travail ont développé des propositions avec pour objectif d’améliorer l’utilité clinique de la classification. Ces propositions sont testées via la plateforme internet « Réseau Mondial de Pratique Clinique (RMPC) » permettant de conduire à des études cliniques électroniques dans les langues officielles de l’OMS, dont le français. Cette étude s’intéresse aux catégories diagnostiques des troubles de l’alimentation et des conduites alimentaires (TCA). Des nouveaux diagnostics ont été proposés tels que le trouble d’hyperphagie et le trouble d’évitement et de restriction de l’apport alimentaire.
– évaluer l’impact des changements spécifiques des TCA entre la CIM-10 et la CIM-11 auprès des membres francophones du RMPC ;
– évaluer la validité, l’utilité clinique des nouvelles propositions et l’accord inter-juges des participants.
Étude mixte, internationale, conduite par internet auprès des membres francophones du RMPC.
Membres du RMPC maîtrisant le français (environ 1000 professionnels) et exerçant une activité clinique.
La population cible recevra un email d’invitation. Les participants seront amenés à lire deux vignettes puis à poser des diagnostics et à répondre à des questions complémentaires, en se basant sur la CIM-10 ou la CIM-11 qu’ils auront reçu de façon aléatoire.
Les vignettes représenteront des cas cliniques réels et reflèteront les changements spécifiques entre la CIM-10 et la CIM-11. Elles seront ainsi présentées par pair (8 pairs possibles).
– interparticipants portant sur l’utilisation du système diagnostique (10 ou 11) et l’attribution du diagnostic en fonction des changements spécifiques ;
– intra-participant sur l’évaluation des pairs de vignettes.
Cette étude doit permettre d’évaluer les nouvelles propositions CIM en français, en tenant compte des spécificités culturelles et linguistiques de la francophonie.
It has been suggested that human communities that share their basic cultural foundations evince no remarkable differences concerning the characterization of core concepts. However, the small but existing differences among them reflect their sociocultural diversity. This study compares 219 concrete concepts common to both Spanish and English semantic feature norms in order to assess whether core features of concepts follow a universal or cultural language-specific pattern. Concepts were compared through a geometric technique of vector comparison in the Euclidean n-dimensional space alongside the calculation of the network’s degree of centrality. The role of cognate status was also explored by repeating the former analysis separating cognate from noncognate words. Taken together, our data show that languages are structurally similar independent of the cognate status of words, further suggesting that there are some sort of core features common to both languages.
The article investigates the broken pural in the Modern South Arabian language Soqotri (island of Soqotra, Gulf of Aden, Yemen). It is based on extensive field research and rich collections of lexical evidence. Primarily synchronic in its approach, the article pays attention to historical problems of Modern South Arabian and Semitic phonology and morphology whenever appropriate.
This paper reviews the neurocognitive particularities of subjects with sustained experience in simultaneous interpreting, a highly demanding form of bilingual processing. The literature converges into three broad empirical patterns. First, significant neurocognitive differences, including behavioral enhancements in verbal and executive domains, are observable after only one or two years of training. Second, such effects, both in interpreting students and/or professional interpreters, seem robust for crucial linguistic (e.g., translation) and executive (e.g., working memory) aspects of the activity, but not for more marginally relevant ones (e.g., conflict resolution) – suggesting that they are non-generalizable beyond directly taxed functions. Third, though more tentatively, some of the observed verbal and executive effects seem to be mutually independent and uninfluenced by other bilingual-experience-related factors (e.g., L2 competence), which could highlight their distinctive relation with interpreting practice. In sum, this particular model of expertise sheds novel light on the adaptive capacity of cognitive systems in bilinguals.
Exposure to armed conflict and forced displacement constitute significant risks for mental health. Existing evidence-based psychological interventions have limitations for scaling-up in low-resource humanitarian settings. The WHO has developed a guided self-help intervention, Self Help Plus (SH+), which is brief, implemented by non-specialists, and designed to be delivered to people with and without specific mental disorders. This paper outlines the study protocol for an evaluation of the SH+ intervention in northern Uganda, with South Sudanese refugee women.
A two-arm, single-blind cluster-randomised controlled trial will be conducted in 14 villages in Rhino Camp refugee settlement, with at least 588 women experiencing psychological distress. Villages will be randomly assigned to receive either SH+ with enhanced usual care (EUC), or EUC alone. SH+ is a five-session guided self-help intervention delivered in workshops with audio-recorded materials and accompanying pictorial guide. The primary outcome is reduction in overall psychological distress over time, with 3 months post-treatment as the primary end-point. Secondary outcomes are self-defined psychosocial concerns, depression and post-traumatic stress disorder symptoms, hazardous alcohol use, feelings of anger, interethnic relations, psychological flexibility, functional impairment and subjective wellbeing. Psychological flexibility is a hypothesised mediator, and past trauma history and intervention attendance will be explored as potential moderators.
This trial will provide important information on the effectiveness of a scalable, guided self-help intervention for improving psychological health and wellbeing among people affected by adversity.
Emerging developmental perspectives suggest that adverse rearing environments promote neurocognitive adaptations that heighten impulsivity and increase vulnerability to risky behavior. Although studies document links between harsh rearing environments and impulsive behavior on substance use, the developmental hypothesis that impulsivity acts as mechanism linking adverse rearing environments to downstream substance use remains to be investigated. The present study investigated the role of impulsivity in linking child abuse and neglect with adult substance use using data from (a) a longitudinal sample of youth (Study 1, N = 9,421) and (b) a cross-sectional sample of adults (Study 2, N = 1,011). In Study 1, the links between child abuse and neglect and young adult smoking and marijuana use were mediated by increases in adolescent impulsivity. In Study 2, indirect links between child abuse and neglect and substance use were evidenced via delayed reward discounting and impulsivity traits. Among impulsivity subcomponents, robust indirect effects connecting childhood experiences to cigarette use emerged for negative urgency. Negative urgency, positive urgency, and sensation seeking mediated the effect of child abuse and neglect on cannabis and alcohol use. Results suggest that child abuse and neglect increases risk for substance use in part, due to effects on impulsivity. Individuals with adverse childhood experiences may benefit from substance use preventive intervention programs that target impulsive behaviors.
The distribution of income lies at the intersection of states and markets, both influencing and responding to government policy. Reflecting this reality, increasing research focuses on the political origins of inequality in the United States. However, the literature largely assumes—rather than tests—the political mechanisms thought to affect the income gap. This study provides a timely reassessment of one such mechanism. Leveraging variation in labor laws between states and differences in the timing of adoption of right-to-work (RTW) legislation, I examine one political mechanism blamed by many for contributing to inequality. Using a variety of panel designs, I find little evidence that RTW laws have been a major cause of growing income inequality, pointing to the importance of grounding theoretical arguments about the interrelationships between states and markets in a sound empirical reality.
Why do legislative parties emerge in democracies where elections are contested by individual candidates, rather than national party organizations? And can parties survive in the absence electoral pressure for their members to work on shared political goals? In this article, we examine the emergence and maintenance of party discipline in an atypical legislative context: California's 1878–79 constitutional convention. The unusual partisan alignments among the delegates at the California convention provide us with a unique empirical opportunity to test election- and policy-based explanations for legislative discipline. Our study combines a careful reading of the historical record with a statistical analysis of roll call votes cast at the convention to show how leaders of the “Nonpartisan” majority held together their disparate coalition of Democratic and Republican members in the face of conflicting preferences, ideological divisions, and well-organized political opponents. Our findings provide evidence that cohesive parties can exist even in the absence of broadly shared electoral pressures or policy goals.
We show that business microloans to U.S. subprime borrowers have a very large
impact on subsequent firm success. Using data on startup loan applicants from a
lender that employed an automated algorithm in its application review, we
implement a regression discontinuity design assessing the causal impact of
receiving a loan on firms. Startups receiving funding are dramatically more
likely to survive, enjoy higher revenues, and create more jobs. Loans are more
consequential for survival among subprime business owners with more education
and less managerial experience.
The present investigation extends research on Gene × Environment interactions and youth risk behavior by linking multilevel contextual factors, such as community disadvantage and protective parenting practices, to both parental and youth dopamine D4 receptor (DRD4) genotypes. We expected community disadvantage to influence youth risk behavior via a series of indirect effects involving protective parenting and youth's planful future orientation when both parents’ and youth's DRD4 status was considered. Genetic moderation processes also were tested to determine whether they conformed to a diathesis–stress or a differential susceptibility model. Hypotheses were investigated with data from 361 rural African American youth and their parents assessed 3 times when youth were ages 16 to 19. Community disadvantage interacted with parental DRD4 status to predict low levels of protective parenting. Protective parenting, in turn, interacted with youth DRD4 status to forecast increases in youth's planful future orientations, a proximal influence on changes in risk behavior. The Parental DRD4 × Community Disadvantage interaction, but not youth DRD4 × Protective Parenting, conformed to a differential susceptibility model. Indirect effect analyses revealed a significant indirect path linking community disadvantage to youth risk behavior through a series of multilevel Gene × Environment interaction processes.
In this paper we review a recently developed approximate method for investigation of dynamics of compressible ellipsoidal figures. Collapse and subsequent behaviour are described by a system of ordinary differential equations for time evolution of semi-axes of a uniformly rotating, three-axis, uniform-density ellipsoid. First, we apply this approach to investigate dynamic stability of non-spherical bodies. We solve the equations that describe, in a simplified way, the Newtonian dynamics of a self-gravitating non-rotating spheroidal body. We find that, after loss of stability, a contraction to a singularity occurs only in a pure spherical collapse, and deviations from spherical symmetry prevent the contraction to the singularity through a stabilizing action of nonlinear non-spherical oscillations. The development of instability leads to the formation of a regularly or chaotically oscillating body, in which dynamical motion prevents the formation of the singularity. We find regions of chaotic and regular pulsations by constructing a Poincaré diagram. A real collapse occurs after damping of the oscillations because of energy losses, shock wave formation or viscosity. We use our approach to investigate approximately the first stages of collapse during the large scale structure formation. The theory of this process started from ideas of Ya. B. Zeldovich, concerning the formation of strongly non-spherical structures during nonlinear stages of the development of gravitational instability, known as ‘Zeldovich’s pancakes’. In this paper the collapse of non-collisional dark matter and the formation of pancake structures are investigated approximately. Violent relaxation, mass and angular momentum losses are taken into account phenomenologically. We estimate an emission of very long gravitational waves during the collapse, and discuss the possibility of gravitational lensing and polarization of the cosmic microwave background by these waves.
This study investigated the influences of neighborhood factors (residential stability and neighborhood disadvantage) and variants of the serotonin transporter linked polymorphic region (5-HTTLPR) genotype on the development of substance use among African American children aged 10–24 years. To accomplish this, a harmonized data set of five longitudinal studies was created via pooling overlapping age cohorts to establish a database with 2,689 children and 12,474 data points to span ages 10–24 years. A description of steps used in the development of the harmonized data set is provided, including how issues such as the measurement equivalence of constructs were addressed. A sequence of multilevel models was specified to evaluate Gene × Environment effects on growth of substance use across time. Findings indicated that residential instability was associated with higher levels and a steeper gradient of growth in substance use across time. The inclusion of the 5-HTTLPR genotype provided greater precision to the relationships in that higher residential instability, in conjunction with the risk variant of 5-HTTLPR (i.e., the short allele), was associated with the highest level and steepest gradient of growth in substance use across ages 10–24 years. The findings demonstrated how the creation of a harmonized data set increased statistical power to test Gene × Environment interactions for an under studied sample.