Use of the fluorescent antibody technique in the detection of bacterial bean blight organisms in Kansas

Call number: LD2668 .T4 1969 B3688Master of Scienc

Dirac Fields in Loop Quantum Gravity and Big Bang Nucleosynthesis

Big Bang nucleosynthesis requires a fine balance between equations of state for photons and relativistic fermions. Several corrections to equation of state parameters arise from classical and quantum physics, which are derived here from a canonical perspective. In particular, loop quantum gravity allows one to compute quantum gravity corrections for Maxwell and Dirac fields. Although the classical actions are very different, quantum corrections to the equation of state are remarkably similar. To lowest order, these corrections take the form of an overall expansion-dependent multiplicative factor in the total density. We use these results, along with the predictions of Big Bang nucleosynthesis, to place bounds on these corrections.Comment: 15 pages, 2 figures; v2: new discussion of relevance of quantum gravity corrections (Sec. II) and new estimates (Sec. V

Salitsülaadi ning metüülsalitsülaatide lagundamine erinevates perekonna Pseudomonas liikides

Salitsülaat on polütsüklilise aromaatse ühendi, naftaleeni, lagundamise käigus tekkiv vaheühend, millel on toksiline toime isegi seda lagundavatele mikroorganismidele. P. pseudoalcaligenes tüvi C70 omab redundantseid salitsülaadi 1-hüdroksülaase ja redundantseid katehhooli 2,3-dioksügenaase, mis on võtmeensüümid salitsülaadi edasises lagundamises. Käesolevas töös võrreldi tüve C70 kasvuparameetreid ning geeniekspressiooni tasemeid ilma redundantsete salitsülaadi lagundamise geenideta referentstüvedega, P. fluorescens PC20 ja P. putida NCIB 9816-4. Lisaks selgitati MGE insertsiooni mõju P. putida võimele lagundada salitsülaati ja metüülsalitsülaate. Kasutatud tingimustel ei olnud tüvel C70 eelist salitsülaadi ega metüülsalitsülaatide lagundamisel referentstüvede suhtes. Märksõnad: Salitsülaadi 1-hüdroksülaas, katehhooli dioksügenaasid, aromaatsed ühendid, redundantsus, Na-salitsülaat, qRT-PC

Models for Little Rip Dark Energy

We examine in more detail specific models which yield a little rip cosmology, i.e., a universe in which the dark energy density increases without bound but the universe never reaches a finite-time singularity. We derive the conditions for the little rip in terms of the inertial force in the expanding universe and present two representative models to illustrate in more detail the difference between little rip models and those which are asymptotically de Sitter. We derive conditions on the equation of state parameter of the dark energy to distinguish between the two types of models. We show that coupling between dark matter and dark energy with a little rip equation of state can alter the evolution, changing the little rip into an asymptotic de Sitter expansion. We give conditions on minimally-coupled phantom scalar field models and on scalar-tensor models that indicate whether or not they correspond to a little rip expansion. We show that, counterintuitively, despite local instability, a little-rip cosmology has an infinite lifetime.Comment: LaTeX, 10 pages, no figure, version to appear in Phys.Lett

Future Asymptotic Behaviour of Tilted Bianchi models of type IV and VIIh

Using dynamical systems theory and a detailed numerical analysis, the late-time behaviour of tilting perfect fluid Bianchi models of types IV and VII$_h$ are investigated. In particular, vacuum plane-wave spacetimes are studied and the important result that the only future attracting equilibrium points for non-inflationary fluids are the plane-wave solutions in Bianchi type VII$_h$ models is discussed. A tiny region of parameter space (the loophole) in the Bianchi type IV model is shown to contain a closed orbit which is found to act as an attractor (the Mussel attractor). From an extensive numerical analysis it is found that at late times the normalised energy-density tends to zero and the normalised variables 'freeze' into their asymptotic values. A detailed numerical analysis of the type VII$_h$ models then shows that there is an open set of parameter space in which solution curves approach a compact surface that is topologically a torus.Comment: 30 pages, many postscript figure

Big Bang Nucleosynthesis Constraints on Brane Cosmologies

We examine constraints from Big Bang nucleosynthesis on type II Randall-Sundrum brane cosmologies with both a dark radiation component and a quadratic term that depends on the 5-dimensional Planck mass, M_5. Using limits on the abundances of deuterium and helium-4, we calculate the allowed region in the M_5-dark radiation plane and derive the precise BBN bound on M_5 alone with no dark radiation: M_5 > 13 TeV.Comment: 3 pages, 1 figure, references added, to appear in Phys. Lett.