Geometric and homological finiteness in free abelian covers

We describe some of the connections between the Bieri-Neumann-Strebel-Renz invariants, the Dwyer-Fried invariants, and the cohomology support loci of a space X. Under suitable hypotheses, the geometric and homological finiteness properties of regular, free abelian covers of X can be expressed in terms of the resonance varieties, extracted from the cohomology ring of X. In general, though, translated components in the characteristic varieties affect the answer. We illustrate this theory in the setting of toric complexes, as well as smooth, complex projective and quasi-projective varieties, with special emphasis on configuration spaces of Riemann surfaces and complements of hyperplane arrangements.Comment: 30 pages; to appear in Configuration Spaces: Geometry, Combinatorics and Topology (Centro De Giorgi, 2010), Edizioni della Normale, Pisa, 201

Quasiparticle spectral weights of Gutzwiller-projected high T_c superconductors

We analyze the electronic Green's functions in the superconducting ground state of the t-J model using Gutzwiller-projected wave functions, and compare them to the conventional BCS form. Some of the properties of the BCS state are preserved by the projection: the total spectral weight is continuous around the quasiparticle node and approximately constant along the Fermi surface. On the other hand, the overall spectral weight is reduced by the projection with a momentum-dependent renormalization, and the projection produces electron-hole asymmetry in renormalization of the electron and hole spectral weights. The latter asymmetry leads to the bending of the effective Fermi surface which we define as the locus of equal electron and hole spectral weight.Comment: 6 pages, 5 figures; x-labels on Figs. 1 and 2 corrected, footnote on particle number corrected, references adde

The effect of magnetic fields on properties of the circumgalactic medium

We study the effect of magnetic fields on a simulated galaxy and its surrounding gaseous halo, or circumgalactic medium (CGM), within cosmological 'zoom-in' simulations of a Milky Way-mass galaxy as part of the Simulating the Universe with Refined Galaxy Environments (SURGE) project. We use three different galaxy formation models, each with and without magnetic fields, and include additional spatial refinement in the CGM to improve its resolution. The central galaxy's star formation rate and stellar mass are not strongly affected by the presence of magnetic fields, but the galaxy is more disc dominated and its central black hole is more massive when B > 0. The physical properties of the CGM change significantly. With magnetic fields, the circumgalactic gas flows are slower, the atomic hydrogen-dominated extended discs around the galaxy are more massive and the densities in the inner CGM are therefore higher, the temperatures in the outer CGM are higher, and the pressure in the halo is higher and smoother. The total gas fraction and metal mass fraction in the halo are also higher when magnetic fields are included, because less gas escapes the halo. Additionally, we find that the CGM properties depend on azimuthal angle and that magnetic fields reduce the scatter in radial velocity, whilst enhancing the scatter in metallicity at fixed azimuthal angle. The metals are thus less well-mixed throughout the halo, resulting in more metal-poor halo gas. These results together show that magnetic fields in the CGM change the flow of gas in galaxy haloes, making it more difficult for metal-rich outflows to mix with the metal-poor CGM and to escape the halo, and therefore should be included in simulations of galaxy formation

Ultrastructural changes in chemically induced preneoplastic focal lesions in the rat liver: a stereological study

Ultrastructural changes were investigated and quantified, using a stereological approach, in early gamma-glutamyl transpeptidase (GGT)-positive focal lesions, induced in the rat liver by treatment with a single initiating dose of diethylnitrosamine (DENA) followed by promotion with phenobarbitone (PB) for 30 weeks. Within the extra-hepato cyte environment of focal tissue, the mean volume occupied by Ito cells was markedly decreased, whilst that occupied by endothelial and Kupffer cells was increased, when compared to uninvolved tissue from the same rat livers. The bile canalicull were dilated, but nosignificant differences in the mean volume occupkd by the sinusoidal and Disse spaces were noted. In focal hepatocytes there was a striking overproduction of lipid droplets and proliferation of smooth endoplasmic reticulum (sER). Whorls of concentrically arranged, parallel ER membranes were found only in the hepatocytes of preneoplastic foci, in association with the proliferated sER, and never in the surrounding, uninvolved tissue. The Increase In mean volume of the sER, lipid droplet and cytoplasmic matrix compartments, together with the appearance of whorls, were the major contributing factors to the marked hypertrophy seen in focal hepatocytes. The mean volume of the rough endoplasmic reticulum, mitochondrial, lysosomal, peroxisomal and nuclear compartments per hepatocyte also Increased, but contributed to a lesser extent to the cellular hypertrophy. It is speculated that whorls may be structural adaptations, resulting from a possible alteration in the normalfeedback control of cholesterol synthesis, for the production of sterols and the biogenesis of sER in eosinophilic-type focal cells. The significance of changes observed in focal tissue, and the high biological variation noted between foci, is discussed in relation to the hepatocarcinogenic proces

New tensorial estimates in Besov spaces for time-dependent (2+1)(2 + 1)-dimensional problems

In this paper, we consider various tensorial estimates in geometric Besov-type norms on a one-parameter foliation of surfaces with evolving geometries. Moreover, we wish to do this with only very weak control on these geometries. Several of these estimates were established in previous works by S. Klainerman and I. Rodnianski, but in very specific settings. A primary objective of this paper is to significantly simplify and make more robust the proofs of the estimates. Another goal is to generalize these estimates to more abstract settings. In upcoming papers (joint with S. Alexakis), we will apply these estimates in order to study truncated null cones in an Einstein-vacuum spacetime extending to infinity. This analysis will then be used to study and to control the Bondi mass and the angular momentum under minimal conditions.Comment: Corrected typo

Variable echo time imaging for detecting the short T2* components of the sciatic nerve: a validation study

OBJECTIVE: The aim of this study was to develop and validate an MRI protocol based on a variable echo time (vTE) sensitive to the short T2* components of the sciatic nerve. MATERIALS AND METHODS: 15 healthy subjects (M/F: 9/6; age: 21-62) were scanned at 3T targeting the sciatic nerve at the thigh bilaterally, using a dual echo variable echo time (vTE) sequence (based on a spoiled gradient echo acquisition) with echo times of 0.98/5.37 ms. Apparent T2* (aT2*) values of the sciatic nerves were calculated with a mono-exponential fit and used for data comparison. RESULTS: There were no significant differences in aT2* related to side, sex, age, and BMI, even though small differences for side were reported. Good-to-excellent repeatability and reproducibility were found for geometry of ROIs (Dice indices: intra-rater 0.68-0.7; inter-rater 0.70-0.72) and the related aT2* measures (intra-inter reader ICC 0.95-0.97; 0.66-0.85) from two different operators. Side-related signal-to-noise-ratio non-significant differences were reported, while contrast-to-noise-ratio measures were excellent both for side and echo. DISCUSSION: Our study introduces a novel MR sequence sensitive to the short T2* components of the sciatic nerve and may be used for the study of peripheral nerve disorders

Energy dissipation downstream of Piano Key Weirs – Case of study of Gloriettes Dam (France)

The Gloriettes concrete arch dam in the French Pyrenees showed a deficit of 80 m3/s for the new design flood of 150 m3/s. To address the problem, a Piano Key Weir (PKW) as an additional spillway was designed. The existence of a geotechnically unstable zone downstream of the PKW site, as well as requirements for environmental integration, did not allow a direct trajectory of the tailrace channel, but imposed an abrupt change in direction halfway. A stepped channel including an intermediate stilling basin was conceived for this purpose. The energy dissipation over the total length of the restitution channel for this condition was found to be about 90 per cent. Since the construction works could only be carried out in summer, the works were split into two stages: summer 2009 (excavation of the stepped reaches and the stilling basin) and summer 2010 (construction of the PKW and completion)

Flood retention in alpine catchments equipped with complex hydropower schemes - A case study of the upper Aare catchment in Switzerland

The simulation of run-off in alpine catchment areas is an important issue for the optimal operation of hydropower plants for normal flow conditions, but also during flood events. A semi-lumped numerical approach combines hydrological modelling and operation of hydraulic elements. It allows simulation of operating mode of complex storage hydropower plants and its impacts on the downstream river system for different scenarios. The modelling of the upper Aare catchment with the Oberhasli hydropower scheme in Switzerland is presented. The effect of the existing reservoirs and their management, taking into account preventive turbining, on flood routing in the Aare River upstream of Lake Brienz is presented for the 2005 and 1987 flood events. The enhancement project KWOplus, which contains a considerable increase of storage volume in the main reservoir as well as in turbining capacity, is estimated

Spillway discharge capacity upgrade at Gloriettes dam

In many countries dams are found to have insufficient flood discharge capacity with respect to updated design floods. Upgradig of spillway discharge capacity has therefore become a significant issue for operators of hydropower plants. The Gloriettes concrete arch dam in the French Pyrenees, operated by EDF, shows a deficit of 80m3/s for the new design flood of 150m3/s. Therefore a complementary spillway on the right bank is to be implemented. The type of labyrinth weir known as the Piano Key Weir (PKW) was selected

The impact of natal kicks on galactic r-process enrichment by neutron star mergers

We study galactic enrichment with rapid neutron capture (r-process) elements in cosmological, magnetohydrodynamical simulations of a Milky Way-mass galaxy. We include a variety of enrichment models, based on either neutron star mergers or a rare class of core-collapse supernova as sole r-process sources. For the first time in cosmological simulations, we implement neutron star natal kicks on-the-fly to study their impact. With kicks, neutron star mergers are more likely to occur outside the galaxy disc, but how far the binaries travel before merging also depends on the kick velocity distribution and shape of the delay time distribution for neutron star mergers. In our fiducial model, the median r-process abundance ratio is somewhat lower and the trend with metallicity is slightly steeper when kicks are included. In a model 'optimized' to better match observations, with a higher rate of early neutron star mergers, the median r-process abundances are fairly unaffected by kicks. In both models, the scatter in r-process abundances is much larger with natal kicks, especially at low metallicity, giving rise to more r-process enhanced stars. We experimented with a range of kick velocities and find that with lower velocities, the scatter is reduced, but is still larger than without natal kicks. We discuss the possibility that the observed scatter in r-process abundances is predominantly caused by natal kicks removing the r-process sources far from their birth sites, making enrichment more inhomogeneous, rather than the usual interpretation that the scatter is set by the rarity of its production source