1,597 research outputs found
Microlensing Constraints on Broad Absorption and Emission Line Flows in the Quasar H1413+117
We present new integral field spectroscopy of the gravitationally lensed
broad absorption line (BAL) quasar H1413+117, covering the ultraviolet to
visible rest-frame spectral range. We observe strong microlensing signatures in
lensed image D, and we use this microlensing to simultaneously constrain both
the broad emission and broad absorption line gas. By modeling the lens system
over the range of probable lensing galaxy redshifts and using on a new argument
based on the wavelength-independence of the broad line lensing magnifications,
we determine that there is no significant broad line emission from smaller than
~20 light days. We also perform spectral decomposition to derive the intrinsic
broad emission line (BEL) and continuum spectrum, subject to BAL absorption. We
also reconstruct the intrinsic BAL absorption profile, whose features allow us
to constrain outflow kinematics in the context of a disk-wind model. We find a
very sharp, blueshifted onset of absorption of 1,500 km/s in both C IV and N V
that may correspond to an inner edge of a disk-wind's radial outflow. The lower
ionization Si IV and Al III have higher-velocity absorption onsets, consistent
with a decreasing ionization parameter with radius in an accelerating outflow.
There is evidence of strong absorption in the BEL component which indicates a
high covering factor for absorption over two orders of magnitude in outflow
radius.Comment: 29 pages, 8 figure
Freesia groeimodel: Ontwikkeling van een groeimodel voor gebruik door telers
Abstract Wageningen UR Greenhouse Horticulture conducted in close cooperation with the Dutch freesia sector research on the effects of climate on dry matter production of Freesia plants. The relationships were established on the basis of photosynthesis, growth and climate data measured in greenhouses of Freesia growers. The relationships were incorporated in a dynamic growth model that correctly simulated the dry matter growth in a series of trials. A user-friendly interface was satisfactorily developed interactively with a number of Freesia growers. The model can be used by growers to find the most optimal combination of climate factors for Freesia growth at given plant age and greenhouse settings
Prevalence, Social Contexts, and Risks for Prepartying Among Ethnically Diverse College Students
Prepartying, also known as pre-gaming, has emerged as a high-risk drinking event among U.S. college students. Research on factors related to prepartying behavior is in its relative infancy. The present study provides prevalence rates for prepartying across ethnic groups and examines how social context (whether prepartying took place with primarily male, female, or coed groups) and demographic factors may influence prepartying behavior. Participants were students from two West Coast universities (N = 2,546) whom identified as White, Asian and Pacific Islander American (APIA), Hispanic/Latino(a), or African American. The percentage of students who reported prepartying at least once in the past month, as well as the frequency and number of drinks consumed for prepartying occasions, varied by ethnic group and sex. A greater proportion of White students (60%) reported prepartying than Hispanic/Latino(a) (52%), African American (44%), and APIA (37%) students, though Hispanic/Latino(a) students who prepartied did so as often and consumed similar amounts of alcohol as White prepartiers. Across all ethnic groups, females who reported prepartying in coed groups consumed significantly more drinks than those who prepartied in primarily female groups. Finally, prepartiers within all ethnic groups consumed more drinks per week and experienced a higher number of alcohol-related consequences than non-prepartiers. The results suggest that future research and prevention programs should target prepartying and other high-risk events in at-risk students of ethnically diverse backgrounds and also consider the effects of gender in prepartying contexts on alcohol use
Horizontal DNA transfer mechanisms of bacteria as weapons of intragenomic conflict
Horizontal DNA transfer (HDT) is a pervasive mechanism of diversification in many microbial species, but its primary evolutionary role remains controversial. Much recent research has emphasised the adaptive benefit of acquiring novel DNA, but here we argue instead that intragenomic conflict provides a coherent framework for understanding the evolutionary origins of HDT. To test this hypothesis, we developed a mathematical model of a clonally descended bacterial population undergoing HDT through transmission of mobile genetic elements (MGEs) and genetic transformation. Including the known bias of transformation toward the acquisition of shorter alleles into the model suggested it could be an effective means of counteracting the spread of MGEs. Both constitutive and transient competence for transformation were found to provide an effective defence against parasitic MGEs; transient competence could also be effective at permitting the selective spread of MGEs conferring a benefit on their host bacterium. The coordination of transient competence with cell-cell killing, observed in multiple species, was found to result in synergistic blocking of MGE transmission through releasing genomic DNA for homologous recombination while simultaneously reducing horizontal MGE spread by lowering the local cell density. To evaluate the feasibility of the functions suggested by the modelling analysis, we analysed genomic data from longitudinal sampling of individuals carrying Streptococcus pneumoniae. This revealed the frequent within-host coexistence of clonally descended cells that differed in their MGE infection status, a necessary condition for the proposed mechanism to operate. Additionally, we found multiple examples of MGEs inhibiting transformation through integrative disruption of genes encoding the competence machinery across many species, providing evidence of an ongoing "arms race." Reduced rates of transformation have also been observed in cells infected by MGEs that reduce the concentration of extracellular DNA through secretion of DNases. Simulations predicted that either mechanism of limiting transformation would benefit individual MGEs, but also that this tactic's effectiveness was limited by competition with other MGEs coinfecting the same cell. A further observed behaviour we hypothesised to reduce elimination by transformation was MGE activation when cells become competent. Our model predicted that this response was effective at counteracting transformation independently of competing MGEs. Therefore, this framework is able to explain both common properties of MGEs, and the seemingly paradoxical bacterial behaviours of transformation and cell-cell killing within clonally related populations, as the consequences of intragenomic conflict between self-replicating chromosomes and parasitic MGEs. The antagonistic nature of the different mechanisms of HDT over short timescales means their contribution to bacterial evolution is likely to be substantially greater than previously appreciated
Comparing injunctive marijuana use norms of salient reference groups among college student marijuana users and nonusers
Marijuana is the most commonly used illicit drug among college students and has the potential for various negative outcomes. Perceptions of what constitutes typical approval/acceptability of a reference group (i.e. injunctive social norms) have been shown to have strong utility as predictors of health-risk behaviors in the college context, yet this construct remains significantly understudied for marijuana use despite its potential for use in social norms-based interventions. The current research evaluated individuals’ marijuana approval level and their perceptions of others’ marijuana approval level (i.e. injunctive norms) for various reference groups (typical student on campus, one’s close friends, one’s parents) as a function of individual user status (abstainers, experimenters, occasional users, regular users). A diverse sample of 3553 college students from two universities completed an online survey. Among all user status groups, individual approval yielded mean scores paralleling that of perceived close friends’ approval and all groups were relatively uniform in their perception of typical students’ approval. Higher levels of marijuana use tended to produce higher endorsements of individual approval, perceived close friends’ approval, and perceived parental approval. Among occasional and regular users, there were no differences between one’s own approval level for use and the perceptions of close friends’ approval, nor did they think the typical student was more approving than themselves. Abstainers and experimenters, however, perceived typical students and close friends to have more permissive attitudes than themselves. Implications and future directions for research regarding the role of injunctive marijuana use norms in the development of social norms intervention are discussed
“This would be better drunk”: Alcohol expectancies become more positive while drinking in the college social environment
The current study examined whether drinking and/or presence in the college social environment led to augmented positive alcohol expectancies among college students (N = 225). Participants were approached during popular drinking nights as they exited events at which alcohol was consumed or in front of their residence as they returned home. Participants completed a brief questionnaire that included an assessment of demographics, breath alcohol concentration (BrAC), and positive expectancies. Within 48 hours of baseline assessment, participants received via email a follow-up survey that re-assessed positive expectancies while sober. Positive sexual expectancies were more strongly endorsed while drinking in the college social environment for both males and females, while males also reported heightened liquid courage expectancies. In addition, positive expectancies were more strongly endorsed at higher doses of alcohol for males but not females. These findings suggest that interventions which seek to prevent alcohol abuse by targeting alcohol expectancies may wish to challenge positive expectancies in naturalistic college social settings
Self-Consciousness Moderates the Relationship between Perceived Norms and Drinking in College Students
The current research examines whether self-consciousness subscales have prognostic value in the relationship between perceived norms and drinking and if that differs among college men and women. Results indicate that self-consciousness moderates gender differences in the relationship between perceived social norms and drinking. A strong positive relationship was found between perceived norms (descriptive and injunctive) and drinking for men relative to women and this was more pronounced among individuals who were lower in public self-consciousness. Similarly, the relationship between perceived injunctive norms and drinking was significantly stronger among men than women and this was more pronounced among individuals who were higher in private self-consciousness or social anxiety. These results highlight the important influence of social factors in salient peer reference groups. This is promising information for future research attempting to identify useful indicators of candidates who would most benefit from social norms interventions. This also underscores the relevance of future norms based interventions using self-consciousness as a potential moderator of intervention efficacy
The prognostic power of normative influences among NCAA student-athletes
This study evaluated the predictive power of perceived descriptive and injunctive norms on intercollegiate student-athlete alcohol consumption and attitudes toward drinking-related behaviors. The sample consisted of 594 NCAA student-athletes from two geographically opposite sites. Norms variables utilized a school and gender-specific athletic peer reference group. Results indicate that respondents reported greater perceived injunctive norms than actual attitudes, and greater perceived descriptive norms than actual alcohol use. Further, after accounting for demographics and alcohol motivations, perceived injunctive norms were the strongest predictors of athletes\u27 attitudes with the final model explaining 54% of the variance. Similarly, perceived descriptive norms were among the strongest predictors of alcohol use with the final model explaining 69% of the variance. Future research may want to use both of these perceived norms constructs to create a more salient and targeted social norms intervention aimed at reducing risky behavior and permissive alcohol-related attitudes among this population. Utilizing this strong peer reference group as well as targeting both injunctive and descriptive norms may increase the power and saturation of prevention and intervention strategies
Role of gonadotropin-releasing hormone analogues in metastatic male breast cancer: Results from a pooled analysis
Background: Male breast cancer is a rare malignancy. Despite the lack of prospectively generated data from trials in either the adjuvant or metastatic setting, patients are commonly treated with hormone therapies. Much controversy exists over the use of gonadotropin-releasing hormone analogues in metastatic male breast cancer patients. We conducted this study to provide more concrete ground on the use of gonadotropin-releasing hormone analogues in this setting. Methods: We herein present results from a pooled analysis including 60 metastatic male breast cancer patients treated with either an aromatase inhibitor or cyproterone acetate as a monotherapy (23 patients) or combined with a gonadotropin-releasing hormone analogue (37 patients). Results: Overall response rate was 43.5 % in patients treated with monotherapy and 51.3 % with combination therapy (p = 0.6). Survival outcomes favored combination therapy in terms of median progression-free survival (11.6 months versus 6 months; p = 0.05), 1-year progression-free survival rate (43.2 % versus 21.7 %; p = 0.05), median overall survival (29.7 months versus 22 months; p = 0.05), and 2-year survival rate (64.9 % versus 43.5 %; p = 0.05). Conclusions: In metastatic male breast cancer patients, the combined use of gonadotropin-releasing hormone analogues and aromatase inhibitors or antiandrogens seems to be associated with greater efficacy, particularly in terms of survival outcomes, compared with monotherapy. Collectively, these results encourage considering these agents in the metastatic setting
- …
