High energy factorization predictions for the charm structure function F2^c at HERA

High energy factorization predictions for F2^c are derived using BFKL descriptions of the proton structure function F2 at HERA. The model parameters are fixed by a fit of F2 at small x. Two different approaches of the non perturbative proton input are shown to correspond to the factorization at the gluon or quark level, respectively. The predictions for F2^c are in agreement with the data within the present error bars. However, the photon wave-function formulation (factorization at quark level) predicts significantly higher F2^c than both gluon factorization and a next-leading order DGLAP model.Comment: latex file + 6 encapsulated figures, 28 page

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

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

Mixed ionic-electronic conduction in K1/2Bi1/2TiO3

Recently, it has been reported that the Pb-free piezoelectric perovskite Na1/2Bi1/2TiO3 (NBT) can be compositionally tuned by close control of the A-site starting stoichiometry to exhibit high levels of oxide-ion conduction. The related K1/2Bi1/2TiO3 (KBT) perovskite has also drawn considerable interest as a promising Pb-free piezoelectric material; however, its conduction properties have been less extensively investigated. Here we report on the influence of the K/Bi ratio in the starting composition on the electrical properties using a combination of impedance spectroscopy and ion-transport property measurements. KBT ceramics exhibit mixed ionic-electronic (oxide-ion) conduction with tion similar 0.5 at 600-800 degreeC and although variations in the A-site starting stoichiometry can create a similar1 order of magnitude difference in the bulk conductivity at >500 degree C, the conductivity is low (ca. 0.1 to 1 mS cm-1 at 700 degree C) and the activation energy for bulk conduction remains in the range similar1.2 to 1.5 eV. The high temperature electrical transport properties of KBT are therefore much less sensitive to the starting A-site stoichiometry as compared to NBT. However, KBT ceramics exhibit non-negligible proton conduction at lower temperatures (<300 degree C). For K/Bi greater-than-or-equal 1 the total conductivity of KBT ceramics at room temperature can be as high as similar0.1 mS cm-1 under wet atmospheric conditions. This study demonstrates ionic conduction to be a common feature in A1/2Bi1/2TiO3 perovskites, where A = Na, K

Functional determinants of forest recruitment over broad scales

11 páginas.-- 3 figuras.-- 2 tablas.-- referencias.--Aim The drivers of tree recruitment over large spatial scales remain unexplored. Here, we ask whether species potential for recruitment and the strength of densitydependent processes, both inferred from species relative abundances, show emerging patterns that can be explained upon the basis of information about climate and functional traits. Location Eastern forests of the USA. Methods We document the geographical distributions and magnitudes of seedling recruitment and the strength of density dependence and conspecific density dependence for the forests of the eastern USA spanning > 1.2 million km2 across 88,854 local communities comprising 164 tree species. We also compiled climatic variables and 16 traits representing several important ecological axes of tree functional strategies to assess which factors were most strongly associated with the emerging broad-scale spatial patterns. Results Strong geographical variation in the potential for seedling recruitment and a latitudinal change from negative to positive density dependence moving northward were associated with adaptation to seasonal freezing temperatures and seed size.Wood density and leaf nitrogen, in contrast,were related to the magnitude of the negative density dependence and conspecific density dependence, respectively, which were prevalent over most of the region. Main conclusions Our results provide strong evidence that tree recruitment and the strength of density-dependent processes have broad-scale patterns that can be explained by a few key species functional traits.We thank Lorena Gómez-Aparicio, Irena Šímová, Pedro Villar, Jeff Diez and Elena Granda for their comments. O.G. and M.R. acknowledge post-doctoral financial support provided by the Spanish Ministry of Education and Science and Fulbright Commission (FU-2009-0039 and BVA-2010-0596, respectively).Peer reviewe

Advancing marine conservation in European and contiguous seas with the MarCons Action

Cumulative human impacts have led to the degradation of marine ecosystems and the decline of biodiversity in the European and contiguous seas. Effective conservation measures are urgently needed to reverse these trends. Conservation must entail societal choices, underpinned by human values and worldviews that differ between the countries bordering these seas. Social, economic and political heterogeneity adds to the challenge of balancing conservation with sustainable use of the seas. Comprehensive macro-regional coordination is needed to ensure effective conservation of marine ecosystems and biodiversity of this region. Under the European Union Horizon 2020 framework programme, the MarCons COST action aims to promote collaborative research to support marine management, conservation planning and policy development. This will be achieved by developing novel methods and tools to close knowledge gaps and advance marine conservation science. This action will provide support for the development of macro-regional and national policies through six key actions: to develop tools to analyse cumulative human impacts; to identify critical scientific and technical gaps in conservation efforts; to improve the resilience of the marine environment to global change and biological invasions; to develop frameworks for integrated conservation planning across terrestrial, freshwater, and marine environments; to coordinate marine conservation policy across national boundaries; and to identify effective governance approaches for marine protected area management. Achieving the objectives of these actions will facilitate the integration of marine conservation policy into macro-regional maritime spatial planning agendas for the European and contiguous seas, thereby offsetting the loss of biodiversity and ecosystem services in this region

Large-Scale Spatio-Temporal Patterns of Mediterranean Cephalopod Diversity

Species diversity is widely recognized as an important trait of ecosystems’ functioning and resilience. Understanding the causes of diversity patterns and their interaction with the environmental conditions is essential in order to effectively assess and preserve existing diversity. While diversity patterns of most recurrent groups such as fish are commonly studied, other important taxa such as cephalopods have received less attention. In this work we present spatio-temporal trends of cephalopod diversity across the entire Mediterranean Sea during the last 19 years, analysing data from the annual bottom trawl survey MEDITS conducted by 5 different Mediterranean countries using standardized gears and sampling protocols. The influence of local and regional environmental variability in different Mediterranean regions is analysed applying generalized additive models, using species richness and the Shannon Wiener index as diversity descriptors. While the western basin showed a high diversity, our analyses do not support a steady eastward decrease of diversity as proposed in some previous studies. Instead, high Shannon diversity was also found in the Adriatic and Aegean Seas, and high species richness in the eastern Ionian Sea. Overall diversity did not show any consistent trend over the last two decades. Except in the Adriatic Sea, diversity showed a hump-shaped trend with depth in all regions, being highest between 200–400 m depth. Our results indicate that high Chlorophyll a concentrations and warmer temperatures seem to enhance species diversity, and the influence of these parameters is stronger for richness than for Shannon diversityVersión del editor4,411

Low Dynamics, High Longevity and Persistence of Sessile Structural Species Dwelling on Mediterranean Coralligenous Outcrops

There is still limited understanding of the processes underlying benthic species dynamics in marine coastal habitats, which are of disproportionate importance in terms of productivity and biodiversity. The life-history traits of long-lived benthic species in these habitats are particularly poorly documented. In this study, we assessed decadal patterns of population dynamics for ten sponge and anthozoan species that play key structural roles in coralligenous outcrops (∼25 m depth) in two areas of the NW Mediterranean Sea. This study was based on examination of a unique long-term photographic series, which allowed analysis of population dynamics over extensive spatial and time spans for the very first time. Specifically, 671 individuals were censused annually over periods of 25-, 15-, and 5-years. This long-term study quantitatively revealed a common life-history pattern among the ten studied species, despite the fact they present different growth forms. Low mortality rates (3.4% yr−1 for all species combined) and infrequent recruitment events (mean value of 3.1±0.5 SE recruits yr−1) provided only a very small fraction of the new colonies required to maintain population sizes. Overall, annual mortality and recruitment rates did not differ significantly among years; however, some species displayed important mortality events and recruitment pulses, indicating variability among species. Based on the growth rates of these 10 species, we projected their longevity and, obtained a mean estimated age of 25–200 years. Finally, the low to moderate turnover rates (mean value 0.80% yr−1) observed among the coralligenous species were in agreement with their low dynamics and persistence. These results offer solid baseline data and reveal that these habitats are among the most vulnerable to the current increases of anthropogenic disturbances

Hypoxia-Inducible Factor Directs POMC Gene to Mediate Hypothalamic Glucose Sensing and Energy Balance Regulation

Hypoxia-inducible factor (HIF) is a nuclear transcription factor that responds to environmental and pathological hypoxia to induce metabolic adaptation, vascular growth, and cell survival. Here we found that HIF subunits and HIF2α in particular were normally expressed in the mediobasal hypothalamus of mice. Hypothalamic HIF was up-regulated by glucose to mediate the feeding control of hypothalamic glucose sensing. Two underlying molecular pathways were identified, including suppression of PHDs by glucose metabolites to prevent HIF2α degradation and the recruitment of AMPK and mTOR/S6K to regulate HIF2α protein synthesis. HIF activation was found to directly control the transcription of POMC gene. Genetic approach was then employed to develop conditional knockout mice with HIF inhibition in POMC neurons, revealing that HIF loss-of-function in POMC neurons impaired hypothalamic glucose sensing and caused energy imbalance to promote obesity development. The metabolic effects of HIF in hypothalamic POMC neurons were independent of leptin signaling or pituitary ACTH pathway. Hypothalamic gene delivery of HIF counteracted overeating and obesity under conditions of nutritional excess. In conclusion, HIF controls hypothalamic POMC gene to direct the central nutrient sensing in regulation of energy and body weight balance

The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

The Mediterranean Sea is a marine biodiversity hot spot. Here we combined an extensive literature analysis with expert opinions to update publicly available estimates of major taxa in this marine ecosystem and to revise and update several species lists. We also assessed overall spatial and temporal patterns of species diversity and identified major changes and threats. Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea. However, our estimates of marine diversity are still incomplete as yet—undescribed species will be added in the future. Diversity for microbes is substantially underestimated, and the deep-sea areas and portions of the southern and eastern region are still poorly known. In addition, the invasion of alien species is a crucial factor that will continue to change the biodiversity of the Mediterranean, mainly in its eastern basin that can spread rapidly northwards and westwards due to the warming of the Mediterranean Sea. Spatial patterns showed a general decrease in biodiversity from northwestern to southeastern regions following a gradient of production, with some exceptions and caution due to gaps in our knowledge of the biota along the southern and eastern rims. Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth. Temporal trends indicated that overexploitation and habitat loss have been the main human drivers of historical changes in biodiversity. At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves (and in particular, the Strait of Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well