A Simulation Model For Residential Location In Harare, Zimbabwe

The post-independent-period in Zimbabwe has been characterized by a number of alterations to the previous organization and structure of society. The spatial manifestation of these alterations is of particular interest to the geographer and provides many avenues for useful research which have much to contribute to the planning of the country's future. The development of a resident black population within those city suburbs formerly reserved exclusively for the white population is one example of these structural changes

In situ analysis of pH gradients in mosquito larvae using non-invasive, self-referencing, pH-sensitive microelectrodes

The alkaline environment, pH approximately 11, in the anterior midgut lumen of mosquito larvae is essential for normal nutrition and development. The mechanism of alkalization is, however, unknown. Although evidence from immunohistochemistry, electron microscopy and electrophysiology suggests that a V-ATPase is present in the basal membranes of the epithelial cells, its physiological role in the alkalization process has not been demonstrated. To investigate a possible role of the V-ATPase in lumen alkalization, pH gradients emanating from the hemolymph side of the midgut in semi-intact mosquito larvae were measured using non-invasive, self-referencing, ion-selective microelectrodes (SERIS). Large H+ concentration gradients, with highest concentrations close to the basal membrane (outward [H+] gradients), were found in the anterior midgut, whereas much smaller gradients, with concentrations lowest close to this membrane (inward [H+] gradients), were found in the gastric caeca and posterior midgut. Similar region-specific pH gradients, with consistent anterior-to-posterior profiles, were observed in individuals of two Aedes species, Aedes aegypti from semi-tropical Florida and Aedes canadensis from north-temperate Massachusetts. The gradients remained in a steady state for up to 6 h, the maximum duration of the recordings. Bafilomycin A1 (10(-5), 10(-7 )mol x l(-1)) on the hemolymph side greatly diminished the [H+] gradients in the anterior midgut but had no effect on the gradients in the gastric caecum and posterior midgut. These physiological data are consistent with the previous findings noted above. Together, they support the hypothesis that a basal, electrogenic H+ V-ATPase energizes luminal alkalization in the anterior midgut of larval mosquitoes

Access to liquidity and corporate investment in Europe during the financial crisis

We use a unique data set to show how firms in Europe used credit lines during the financial crisis. We find that firms with restricted access to credit (small, private, non-investment-grade, and unprofitable) draw more funds from their credit lines during the crisis than their large, public, investment-grade, profitable counterparts. Interest spreads increased (especially in "market-based economies"), but commitment fees remained unchanged. Our findings suggest that credit lines did not dry up during the crisis and provided the liquidity that firms used to cope with this exceptional contraction. In particular, credit lines provided the liquidity companies needed to invest during the crisis

Spacetime Energy Decreases under World-sheet RG Flow

We study renormalization group flows in unitary two dimensional sigma models with asymptotically flat target spaces. Applying an infrared cutoff to the target space, we use the Zamolodchikov c-theorem to demonstrate that the target space ADM energy of the UV fixed point is greater than that of the IR fixed point: spacetime energy decreases under world-sheet RG flow. This result mirrors the well understood decrease of spacetime Bondi energy in the time evolution process of tachyon condensation.Comment: 25 pages, 4 figures, harvma

Characterizing the metabolic effects of the selective inhibition of gut microbial β-glucuronidases in mice

The hydrolysis of xenobiotic glucuronides by gut bacterial glucuronidases reactivates previously detoxified compounds resulting in severe gut toxicity for the host. Selective bacterial β-glucuronidase inhibitors can mitigate this toxicity but their impact on wider host metabolic processes has not been studied. To investigate this the inhibitor 4-(8-(piperazin-1-yl)-1,2,3,4-tetrahydro-[1,2,3]triazino[4′,5′:4,5]thieno[2,3-c]isoquinolin-5-yl)morpholine (UNC10201652, Inh 9) was administered to mice to selectively inhibit a narrow range of bacterial β-glucuronidases in the gut. The metabolomic profiles of the intestinal contents, biofluids, and several tissues involved in the enterohepatic circulation were measured and compared to control animals. No biochemical perturbations were observed in the plasma, liver or gall bladder. In contrast, the metabolite profiles of urine, colon contents, feces and gut wall were altered compared to the controls. Changes were largely restricted to compounds derived from gut microbial metabolism. This work establishes that inhibitors targeted towards bacterial β-glucuronidases modulate the functionality of the intestinal microbiota without adversely impacting the host metabolic system

On the reheating stage after inflation

We point out that inflaton decay products acquire plasma masses during the reheating phase following inflation. The plasma masses may render inflaton decay kinematicaly forbidden, causing the temperature to remain frozen for a period at a plateau value. We show that the final reheating temperature may be uniquely determined by the inflaton mass, and may not depend on its coupling. Our findings have important implications for the thermal production of dangerous relics during reheating (e.g., gravitinos), for extracting bounds on particle physics models of inflation from Cosmic Microwave Background anisotropy data, for the production of massive dark matter candidates during reheating, and for models of baryogenesis or leptogensis where massive particles are produced during reheating.Comment: 8 pages, 2 figures. Submitted for publication in Phys. Rev.

Leptogenesis through direct inflaton decay to light particles

We present a scenario of nonthermal leptogenesis following supersymmetric hybrid inflation, in the case where inflaton decay to both heavy right handed neutrino and SU(2)_L triplet superfields is kinematically disallowed. Lepton asymmetry is generated through the decay of the inflaton into light particles by the interference of one-loop diagrams with right handed neutrino and SU(2)_L triplet exchange respectively. We require superpotential couplings explicitly violating a U(1) R-symmetry and R-parity. However, the broken R-parity need not have currently observable low-energy signatures. Also, the lightest sparticle can be stable. Some R-parity violating slepton decays may, though, be detectable in the future colliders. We take into account the constraints from neutrino masses and mixing and the preservation of the primordial lepton asymmetry.Comment: 11 pages including 3 figures, uses Revtex, minor corrections, references adde

Heterotic String Field Theory

We construct the Neveu-Schwarz sector of heterotic string field theory using the large Hilbert space of the superghosts and the multi-string products of bosonic closed string field theory. No picture-changing operators are required as in Wess-Zumino-Witten-like open superstring field theory. The action exhibits a novel kind of nonpolynomiality: in addition to terms necessary to cover missing regions of moduli spaces, new terms arise from the boundary of the missing regions and its subspaces. We determine the action up to quintic order and a subset of terms to all orders.Comment: 15 pages, no figures, LaTeX2e; v2: minor cosmetic change

On the phase transition in the scalar theory

The basic tool for the study of the electroweak phase transition is $V_{eff} (\phi,T)$, the one-loop finite-temperature effective potential, improved by all-loop resummations of the most important infrared contributions. In this paper we perform, as a first step towards a full analysis of the Standard Model case, a detailed study of the effective potential of the scalar theory. We show that subleading corrections to the self-energies lead to spurious terms, linear in the field-dependent mass $m(\phi)$, in the daisy-improved effective potential. Consistency at subleading order requires the introduction of superdaisy diagrams, which prevent the appearance of linear terms. The resulting $V_{eff}(\phi,T)$ for the scalar theory hints at a phase transition which is either second-order or very weakly first-order.Comment: 10 A4 pages, table and figures not included and available (by ordinary mail) upon request, plain LATEX, CERN-TH.6451/92, IEM-FT-56/9

WZW-like Action for Heterotic String Field Theory

We complete the construction of the Neveu-Schwarz sector of heterotic string field theory begun in hep-th/0406212 by giving a closed-form expression for the action and gauge transformations. Just as the Wess-Zumino-Witten (WZW) action for open superstring field theory can be constructed from pure-gauge fields in bosonic open string field theory, our heterotic string field theory action is constructed from pure-gauge fields in bosonic closed string field theory. The construction involves a simple alternative form of the WZW action which is consistent with the algebraic structures of closed string field theory.Comment: 22 pages, no figures, LaTeX2