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Simulating the Weekly Cycle of NO-VOC-HO-O Photochemical System in the South Coast of California During CalNex-2010 Campaign
Get PDFUnited States Environmental Protection Agency guidance on the use of photochemical models for assessing the efficacy of an emissions control strategy for ozone requires that modeling be used in a relative sense. Consequently, testing a modeling system's ability to predict changes in ozone resulting from emission changes is critical. We evaluate model simulations for precursor species (NO, CO, and volatile organic compounds [VOCs]), radicals (OH and HO), a secondary pollutant (O), and the model response of these compounds to weekend/weekday emission changes during California Nexus study in 2010. The modeling system correctly simulated the broad spatial and temporal variation of NO and O in California South Coast. Although the model generally underpredicted the daytime mixing ratios of NO at the surface and overpredicted the NO column, the simulated weekend to weekday ratios are consistent with each other and match the observed ratios well. The modeling system exhibited reasonable performance in simulating the VOC compounds with fossil fuel origins but has larger bias in simulating certain species associated with noncombustion sources. The modeling system successfully captured the weekend changes of the enhancement ratios for various VOC species to CO and the relative changes of HO, which are indicators of faster chemical processing on weekends. This work demonstrates satisfactory model performances for O and most relevant chemical compounds with more robust performance in simulating weekend versus weekday changes. Improved planetary boundary layer height simulations, a better understanding of OH‐HO cycling, continued improvement of emissions, especially urban biogenic emissions and emissions of oxygenated VOCs, are important for future model improvement
Discovery of a Double Blue Straggler Sequence in M15: New Insight into the Core-collapse Process
Get PDFIn this paper we report the discovery of a double blue straggler star (BSS) sequence in the core of the core-collapsed cluster M15 (NGC 7078). We performed a detailed photometric analysis of the extremely dense core of the cluster using a set of images secured with the Advanced Camera for Survey in the High Resolution Channel mode on board the Hubble Space Telescope. The proper combination of the large number of single frames in the near-UV (F220W), and blue (F435W) filters allowed us to perform a superb modeling of the point-spread function and an accurate deblending procedure. The color–magnitude diagram revealed the presence of two distinct parallel sequences of blue stragglers. In particular, the blue BSS sequence is characterized by the intriguing presence of two different branches. The first branch appears extremely narrow, it extends up to 2.5 mag brighter than the cluster main-sequence turnoff (MS-TO) point, and it is nicely reproduced by a 2 Gyr old collisional isochrone. The second branch extends up to 1.5 mag from the MS-TO and it is reproduced by a 5.5 Gyr old collisional isochrone. Our observations suggest that each of these branches is mainly constituted by a population of nearly coeval collisional BSSs of different masses generated during two episodes of high collisional activity. We discuss the possibility that the oldest episode corresponds to the core-collapse (CC) event (occurred about 5.5 Gyr ago), while the most recent one (occurred about 2 Gyr ago) is associated with a core oscillation in the post-CC evolution. The discovery of these features provides further strong evidence in support of the connection between the BSS properties and globular cluster dynamical evolution, and it opens new perspectives on the study of CC and post-CC evolution
The X chromosome is necessary for ovule production in Silene latifolia
No full textSex chromosomes stop recombining and accumulate differences over time. In particular, genes on the chromosome restricted to the heterogametic sex degenerate and become non-functional. Here, we investigated whether or not the degeneration of a plant Y chromosome was sufficient to cause ovules containing a Y to fail to develop, thereby eliminating the possibility of YY individuals. We used two genotypic assays to determine the genotype—XX, XY, or YY—of offspring from a single fruit of an otherwise normal male XY plant of Silene latifolia. The fruit contained fewer ovules than normal pistillate flowers, produced an equal offspring sex ratio, and generated no YY offspring. The results indicate that ovaries must contain an X chromosome to develop properly. While haploid selection has slowed down Y-chromosome degeneration in S. latifolia, we find that it has progressed sufficiently to prevent the proper development of ovules, and hence prevent the presence of YY individuals
Interpreting Pattern in Plant-Soil Feedback Experiments with Co-occurring Invasive Species: A Graphical Framework and Case Study
No full textDespite the ubiquity of multiple plant invasions, the underlying mechanisms of invasive-invasive interactions remain relatively unknown. Given the importance of plant–soil feedback (PSF) in contributing to single species invasions, it may be an important factor influencing invasive–invasive species interactions as well. PSF between multiple invaders has rarely been examined, but could inform the nature of invasive–invasive interactions and advance understanding of how multiple invaders impact plant communities. Alternative mechanisms of plant invasions include novel weapons and enemy escape. We develop graphical PSF predictions based on these mechanisms and other possible invasive–invasive dynamics. Comparing these predictions to observed results is a first step in interpreting PSF among co-occurring invasive species. We illustrate this with a case study of net pairwise PSF among three common invaders of tallgrass prairie: Lotus corniculatus (birdsfoot trefoil), Phalaris arundinacea (reed canarygrass), and Cirsium arvense (Canada thistle). We found that feedback among all pairwise combinations of these invasive species was neutral. Neutral feedback can arise from a mutual lack of soil borne pathogens, consistent with the enemy escape hypothesis, although we cannot rule out shared benefit from generalist mutualists. While both facilitative and competitive interactions among these three species have previously been shown, our data suggest that such interactions are unlikely to operate through a legacy effect of PSF. Our results inform follow-up PSF experiments that would help to confirm the existence and nature of PSF interactions among these species
Infant Feeding Patterns Of HIV Positive Mothers And Disclosure Of Status To Family And Partners In Botswana
Get PDFTransmission during breastfeeding, which is a multifactorial process, has been associated with increased HIV transmission of 35%-45% in the developing countries. Infants who are formula fed stand a higher risk of morbidity and mortality due to other causes such as malnutrition, pneumococcal infections and diarrhoeal diseases. It is against this background that this study was conducted to assess women’s decisions making process regarding PMTCT, decisions on infant feeding, infant testing and status disclosure to significant others. The results of this study will be used to develop pragmatic interventions and healthcare practices that better address the barriers to prevention of mother to child transmission of HIV while ensuring infant survival
Observation of and study of the -wave mesons
Get PDFStudies of and the -wave charmed-strange mesons are performed based on an collision data sample corresponding to an integrated luminosity of 567 pb collected with the BESIII detector at GeV. The processes of and are observed for the first time and are found to be dominated by the modes and , respectively. The Born cross sections are measured to be and , and the products of Born cross section and the decay branching fraction are measured to be and . For the and mesons, the masses and widths are measured to be , , and , . The spin-parity of the meson is determined to be . In addition, the process are searched for using the data samples taken at four (two) center-of-mass energies between 4.416 (4.527) and 4.575 GeV, and upper limits at the 90% confidence level on the cross sections are determined
Organizational Factors Influencing the Early Implementation Process of Diabetes Group Visits by Five Midwestern Community Health Centers: A Multisite Case Study Analysis
No full textThe objective was to identify facilitators and challenges of implementing diabetes group visits in 5 Midwestern community health center (CHC) settings that care for diverse patient populations. Interview data were collected from July to August 2015. An interview guide was developed to explore health center teams' initial experiences with diabetes group visit implementation. Interviews were conducted with 14 individuals who participated in a training prior to diabetes group visit implementation. Four levels of coding (open, in vivo, categorical, and thematic) were used to identify characteristics of group visit implementation in 5 CHCs. A semi-structured model encouraged interprofessional teamwork across all CHC teams. Self-appointed or chosen team champions were the "pulse" or central driving force of implementation. A designated time in the clinic for patients to receive education and psychosocial support enhanced engagement in diabetes self-management. Early buy-in from upper leadership was critical to securing fiscal and human resources as unexpected needs emerged during group visit implementation. Time commitment of clinic staff and providers for ongoing operations, socioeconomic challenges of patients, staff turnover, and billing were reported as challenges in the initial implementation process. This study acknowledges the influence of administrative and sociocultural factors on successful implementation of diabetes group visits. Future research should further explore how these factors influence successful adoption of diabetes group visits in health centers across the United States and the impact of group visit implementation on staff and patient outcomes
Prism Adaptation Deficits in Schizophrenia
No full textRecent clinical and neurobehavioral evidence suggests cerebellar dysfunction in schizophrenia (SZ). We used the prism adaptation motor task (PAT) to probe specific cerebellar circuits in the disorder. PAT requires cerebellum-dependent motor adaptation, perceptual remapping, and strategic control. A failure to engage in early corrective processes may indicate impairment within either the cerebellum or regions contributing to strategic components, such as the parietal lobe, while an inability to develop and retain a visuomotor shift with time strongly suggests cerebellar impairment. Thirty-one individuals with SZ and 31 individuals without a history of psychological disorders completed PAT. Subjects reached to a target before, during, and following prism exposure, while their movements were recorded using motion-sensing technology. The SZ group performed worse on conditions consisting of adaptation, post-adaptation, aftereffects, and reorientation, thereby demonstrating a failure to adapt to the same degree as healthy controls. SZ performance remained impaired even with visual feedback and did not differ from controls at baseline, suggesting the observed deficit is specific to adaptation. Results indicate that sensorimotor adaptation is impaired in SZ and implicate disturbances in cerebellar circuits
Where and with Whom Students Live: Impacts on Peer Belonging and Institutional Acceptance
Get PDFSENSE OF BELONGING is critical for students throughout their college experience, and even more so now, given the current concerns about undergraduate graduation rates. The purpose of this study was to explore how students’ perception of their sense of belonging on campus is affected by where and with whom they live. We utilized a multidimensional approach, defining sense of belonging with two dimensions: peer belonging and institutional acceptance. In 2014, additional items measuring these dimensions were appended to the end of the core National Survey of Student Engagement (NSSE). Overall, more than 17,000 first-year and senior students at 44 four-year colleges and universities responded. For both first-year and senior students, results suggest that living environment and with whom a student resides impact their sense of belonging on campus. For example, students living with roommates reported higher levels of peer belonging than did those living alone. First-year students living farther than walking distance from campus reported lower levels of peer belonging than did those living on campus. Additionally, off-campus seniors who lived within walking or driving distance from campus reported lower levels of institutional acceptance than did their classmates living on campus. Additional results, potential reasons, and implications for these results are also discussed