347 research outputs found
Classical Boundary-value Problem in Riemannian Quantum Gravity and Self-dual Taub-NUT-(anti)de Sitter Geometries
The classical boundary-value problem of the Einstein field equations is
studied with an arbitrary cosmological constant, in the case of a compact
() boundary given a biaxial Bianchi-IX positive-definite three-metric,
specified by two radii For the simplest, four-ball, topology of the
manifold with this boundary, the regular classical solutions are found within
the family of Taub-NUT-(anti)de Sitter metrics with self-dual Weyl curvature.
For arbitrary choice of positive radii we find that there are three
solutions for the infilling geometry of this type. We obtain exact solutions
for them and for their Euclidean actions. The case of negative cosmological
constant is investigated further. For reasonable squashing of the three-sphere,
all three infilling solutions have real-valued actions which possess a ``cusp
catastrophe'' structure with a non-self-intersecting ``catastrophe manifold''
implying that the dominant contribution comes from the unique real
positive-definite solution on the ball. The positive-definite solution exists
even for larger deformations of the three-sphere, as long as a certain
inequality between and holds. The action of this solution is
proportional to for large and hence larger radii are
favoured. The same boundary-value problem with more complicated interior
topology containing a ``bolt'' is investigated in a forthcoming paper.Comment: 20 pages, 11 figures; Latex; Revised version with important new
results on real infilling solutions and corrections. To appear in Nuclear
Physics B, issue 648 (1,2), pp. 397-41
Increasing the heme-dependent respiratory efficiency in Lactococcus lactis by inhibition of lactate dehydrogenase
The discovery of heme-induced respiration in Lactococcus lactis has radically improved the industrial processes used for the biomass production of this species. Here, we show that inhibition of the lactate dehydrogenase activity of L. lactis during growth under respiration-permissive conditions can stimulate aerobic respiration, thereby increasing not only growth efficiency but also the robustness of this organism
Worldwide experience with a totally subcutaneous implantable defibrillator: Early results from the EFFORTLESS S-ICD registry
Aims The totally subcutaneous implantable-defibrillator (S-ICD) is a new alternative to the conventional transveno
Grain Surface Models and Data for Astrochemistry
AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of âź25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions
Application of the Hybrid-Maize model for limits to maize productivity analysis in a semiarid environment
Density functional theory based screening of ternary alkali-transition metal borohydrides: A computational material design project
The dissociation of molecules, even the most simple hydrogen molecule, cannot be described accurately within density functional theory because none of the currently available functionals accounts for strong on-site correlation. This problem led to a discussion of properties that the local Kohn-Sham potential has to satisfy in order to correctly describe strongly correlated systems. We derive an analytic expression for the nontrivial form of the Kohn-Sham potential in between the two fragments for the dissociation of a single bond. We show that the numerical calculations for a one-dimensional two-electron model system indeed approach and reach this limit. It is shown that the functional form of the potential is universal, i.e., independent of the details of the two fragments.We acknowledge funding by the Spanish MEC (Grant No. FIS2007-65702-C02-01), âGrupos Consolidados UPV/EHU del Gobierno Vascoâ (Grant No. IT-319-07), and the European Community through e-I3 ETSF project (Grant Agreement No. 211956).Peer reviewe
Density functional theory based screening of ternary alkali-transition metal borohydrides: A computational material design project
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