Model independent determination of the shape function for inclusive B decays and of the structure functions in DIS

We present a method to compute, by numerical simulations of lattice QCD, the inclusive semileptonic differential decay rates of heavy hadrons and the structure functions which occur in deep inelastic scattering. The method is based on first principles and does not require any model assumption. It allows the prediction of the differential rate in B semileptonic decays for values of the recoiling hadronic mass W ~ sqrt(M_B Lambda_QCD), which is in the relevant region to extract |V_ub| from the end-point of the lepton spectrum in inclusive decays.Comment: 16 pages, LaTeX fil

Light quark masses and pseudoscalar decay constants from Nf=2 Lattice QCD with twisted mass fermions

We present the results of a lattice QCD calculation of the average up-down and strange quark masses and of the light meson pseudoscalar decay constants with Nf=2 dynamical fermions. The simulation is carried out at a single value of the lattice spacing with the twisted mass fermionic action at maximal twist, which guarantees automatic O(a)-improvement of the physical quantities. Quark masses are renormalized by implementing the non-perturbative RI-MOM renormalization procedure. Our results for the light quark masses are m_ud^{msbar}(2 GeV)= 3.85 +- 0.12 +- 0.40 MeV, m_s^{msbar}(2 GeV) = 105 +- 3 +- 9 MeV and m_s/m_ud = 27.3 +- 0.3 +- 1.2. We also obtain fK = 161.7 +- 1.2 +- 3.1 MeV and the ratio fK/fpi=1.227 +- 0.009 +- 0.024. From this ratio, by using the experimental determination of Gamma(K-> mu nu (gamma))/Gamma(pi -> mu nu (gamma)) and the average value of |Vud| from nuclear beta decays, we obtain |Vus|=0.2192(5)(45), in agreement with the determination from Kl3 decays and the unitarity constraint.Comment: 20 pages, 5 figure

Herbig Ae/Be Stars in nearby OB associations

We have carried out a study of the early type stars in nearby OB associations spanning an age range of $\sim$ 3 to 16 Myr, with the aim of determining the fraction of stars which belong to the Herbig Ae/Be class. We studied the B, A, and F stars in the nearby ($\le 500$ pc) OB associations Upper Scorpius, Perseus OB2, Lacerta OB1, and Orion OB1, with membership determined from Hipparcos data. We obtained spectra for 440 Hipparcos stars in these associations, from which we determined accurate spectral types, visual extinctions, effective temperatures, luminosities and masses, using Hipparcos photometry. Using colors corrected for reddening, we find that the Herbig Ae/Be stars and the Classical Be stars (CBe) occupy clearly different regions in the JHK diagram. Thus, we use the location on the JHK diagram, as well as the presence of emission lines and of strong 12 microns flux relative to the visual to identify the Herbig Ae/Be stars in the associations. We find that the Herbig Ae/Be stars constitute a small fraction of the early type stellar population even in the younger associations. Comparing the data from associations with different ages and assuming that the near-infrared excess in the Herbig Ae/Be stars arises from optically thick dusty inner disks, we determined the evolution of the inner disk frequency with age. We find that the inner disk frequency in the age range 3 - 10 Myr in intermediate mass stars is lower than that in the low mass stars (< 1msun). This indicates that the time-scales for disk evolution are much shorter in the intermediate mass stars, which could be a consequence of more efficient mechanisms of inner disk dispersal (viscous evolution, dust growth and settling toward the midplane).Comment: 34 pages, 10 figure

Historical perspectives on pastoralism and land tenure transformation in Ngamiland, Botswana: What are the policy and institutional lessons?

Pastoral societies in dryland Africa continue to face changes to their pastoral systems. These systems are influenced by a range of historical factors but little use is made of this information to design policies that suit pastoralists’ landscapes. This article provides a synthesis of historical perspectives on pastoral land use and tenure transformations in Ngamiland, south of the Okavango Delta, Botswana. Little documentation of herders’ historical perspectives exists and less is known about how past experiences can be applied to sustainable pastoralism policies. In this article, current land use pressing issues are examined and analysed within the context of past experiences. We use a series of oral histories with key informants, focus group discussions, expert interviews and rangelands field observations. Ngamiland historical perspectives depict a pastoral landscape that has been shaped by a variety of factors; livestock diseases, Human-wildlife-conflicts, droughts, land tenure transformations associated with rangeland policies and the pastoral identity of the Ovaherero/Ovambanderu ethnic groups. Pastoralists have followed unique trajectories, specific to their rangeland conditions and socio-cultural context. Resilience to climate shocks and diseases has been weakened by inequitable patterns of control over rangeland resources. We recommend institutional diversity such that from experiences of the past, lessons can be drawn of the sort of processes and institutions required for pastoralism policies including targeted pastoralists’ adaptations. Using pastoralists to provide information, especially in the area of indigenous knowledge, strategies can be developed to link conservation of wildlife and rangelands with pastoral production by developing ecologically-sensitive low-volume tourism that pastoral communities can tap in to diversify their livelihoods

CarrotDiverse : understanding variation in a wild relative of carrot

Genebanks and other ex situ collections have a significant role in the conservation, management and use of crop genetic diversity, including that of crop wild relatives. Efficient management and use depends on insight into the patterning and distribution of genetic diversity as well as obtaining baseline information on phenotypic characters and traits. Wild carrot (Daucus carota L.) is the closest wild relative of cultivated carrot (Daucus carota L. subsp. sativus (Hoffm.) Arcang.), and is a potential source of useful traits for crop improvement. There are over 900 accessions of D. carota described as wild in European genebanks, however associated phenotypic and genotypic characterization data are sparse. The influence of environment on phenotype is also not well understood in this taxon, meaning that it is difficult to ascertain how data collected at different locations can be compiled and collated. We present initial results of CarrotDiverse, a collaborative project in which wild D. carota accessions are undergoing detailed phenotypic and morphological characterization in parallel at three sites of varying latitude across Europe located in Portugal, France and Sweden. This will allow us to understand which traits are affected by environmental variables. Basic phenotypic information is being collected on a further 150 accessions. Furthermore, resistance screening to Alternaria species and polyacetylene profiling will be included in the evaluation. A Genotyping by Sequencing approach will be used to generate knowledge about genetic background and trait associations. The project will result in a significant data set which will facilitate the use of crop wild relatives in carrot breeding and improvement