Search for Pair Production of Scalar Top Quarks Decaying to a tau Lepton and a b Quark in ppbar Collisions at sqrt{s}=1.96 TeV

We search for pair production of supersymmetric top quarks (~t_1), followed by R-parity violating decay ~t_1 -> tau b with a branching ratio beta, using 322 pb^-1 of ppbar collisions at sqrt{s}=1.96 TeV collected by the CDF II detector at Fermilab. Two candidate events pass our final selection criteria, consistent with the standard model expectation. We set upper limits on the cross section sigma(~t_1 ~tbar_1)*beta^2 as a function of the stop mass m(~t_1). Assuming beta=1, we set a 95% confidence level limit m(~t_1)>153 GeV/c^2. The limits are also applicable to the case of a third generation scalar leptoquark (LQ_3) decaying LQ_3 -> tau b.Comment: 7 pages, 2 eps figure

Ocena rozwoju osobniczego (ontogenezy) chwastów w łanie lnu włóknistego

The study was conducted according to observations of ontogenesis of weeds found in the field of fibrous flax conducted in 2005–2006. The field experiments were conducted at INF Experimental Farms Stary Sielec and P tkowo (wielkopolskie district). Experiments were set on two types of soil: grey brown podsolic and black earth. The phenological development of flax and weeds was evaluated according to BBCH scale.  On black earth soil (good wheat agricultural soil complex) the full ontogenesis was recorded for the following taxa: Geranium pusillum L., Viola arvensis Murr., Stellaria media Vill., Chenopodium album L., Matricaria maritima L. ssp. inodora (L.) Dostal, Galium aparine L., Polygonum lapathifolium L., Capsella bursa-pastoris (L.) Med., Euphorbia cyparissias L., Galinsoga parviflora Cav. and Elymus repens (L.) Goud. On grey brown podsolic soil (good rye agricultural soil complex) few weed species reached flowering or green maturity stage (BBCH 60–73): Chenopodium album L., Polygonum aviculare L., Polygonum persicaria L. and Anthemis arvensis L. Most weeds senesced before completion of full development cycle on the lighter soil. Environmental conditions had stronger effect on development of weeds than on ontogenesis of fibrous flax.

Ab-initio computation of superconducting properties of elemental superconductors and MgB2

We present ab-initio predictions of superconducting properties of some elemental superconductors and of MgB2, based on the Super-Conducting Density Functional theory (SC-DFT). This formalism allows a description of superconducting properties at thermal equilibrium by means of three “densities”: the ordinary electron density, the superconducting order parameter, and the diagonal of the nuclear N-body density matrix. These quantities are determined through self-consistent solutions of Bogoliubov-de Gennes Kohn-Sham like equations, involving exchange-correlation potentials which are universal functionals of the three above-mentioned quantities. By means of approximate expressions for the relevant functionals, we obtain an ab-initio description of the superconducting state, completely free of empirical parameters. The results of our present implementation of SC-DFT for selected materials are discussed in terms of superconducting energy gap, critical temperature and specific heat, and compared with experiments