The paradox between resistance to hypoxia and liability to hypoxic damage in hyperglycemic peripheral nerves. Evidence for glycolysis involvement

Isolated ventral and dorsal rat spinal roots incubated in normal (2.5 mM) or high glucose (25 mM) concentrations or in high concentrations of other hexoses were exposed transiently to hypoxia (30 min) in a solution of low buffering power. Compound nerve action potentials, extracellular direct current potentials, and interstitial pH were continuously recorded before, during, and after hypoxia. Ventral roots incubated in 25 mM D-glucose showed resistance to hypoxia. Dorsal roots, on the other hand, revealed electrophysiological damage by hyperglycemic hypoxia as indicated by a lack of posthypoxic recovery. In both types of spinal roots, interstitial acidification was most pronounced during hyperglycemic hypoxia. The changes in the sensitivity to hypoxia induced by high concentrations of D-glucose were imitated by high concentrations of D-mannose. In contrast, D-galactose, L-glucose, D-fructose, and L-fucose did not have such effects. Resistance to hypoxia, hypoxia-generated interstitial acidification, and hypoxia-induced electrophysiological damage were absent after pharmacological inhibition of nerve glycolysis with iodoacetate. These observations indicate 1) that enhanced anaerobic glycolysis produces resistance to hypoxia in hyperglycemic peripheral nerves and 2) that acidification may impair the function of peripheral axons when anaerobic glycolysis proceeds in a tissue with reduced buffering power

Acceleration-Induced Nonlocal Electrodynamics in Minkowski Spacetime

We discuss two nonlocal models of electrodynamics in which the nonlocality is induced by the acceleration of the observer. Such an observer actually measures an electromagnetic field that exhibits persistent memory effects. We compare Mashhoon's model with a new ansatz developed here in the framework of charge & flux electrodynamics with a constitutive law involving the Levi-Civita connection as seen from the observer's local frame and conclude that they are in partial agreement only for the case of constant acceleration.Comment: LaTeX file, 3 figures, 14 page

AGRICULTURAL TRADE LIBERALIZATION AND STRATEGIC ENVIRONMENTAL POLICY: A FORMAL ANALYSIS

This paper develops an extended general equilibrium model of international trade in order to analyze the welfare effects of agricultural trade liberalization if a large country influences its terms of trade by means of environmental policy. We derive globally optimal first-best and second-best environmental and trade policy combinations as a benchmark for assessing the trade-distorting character of strategically motivated environmental policies and demonstrate that if second-best rather than first-best policies are chosen as a benchmark the conclusions may differ not only in magnitude but also in direction. We further demonstrate that if a Pigouvian instrument is transformed into a strategic environmental policy, following trade liberalization, the global welfare effect is unambiguously positive. We thereby prove that the distorting effect of an optimal tariff is generally greater than that of a strategically motivated environmental policy.International Relations/Trade,

The diurnal nature of future extreme precipitation intensification

Short‐duration, high‐impact precipitation events in the extratropics are invariably convective in nature, typically occur during the summer, and are projected to intensify under climate change. The occurrence of convective precipitation is strongly regulated by the diurnal convective cycle, peaking in the late afternoon. Here we perform very high resolution (convection‐permitting) regional climate model simulations to study the scaling of extreme precipitation under climate change across the diurnal cycle. We show that the future intensification of extreme precipitation has a strong diurnal signal and that intraday scaling far in excess of overall scaling, and indeed thermodynamic expectations, is possible. We additionally show that, under a strong climate change scenario, the probability maximum for the occurrence of heavy to extreme precipitation may shift from late afternoon to the overnight/morning period. We further identify the thermodynamic and dynamic mechanisms which modify future extreme environments, explaining both the future scaling's diurnal signal and departure from thermodynamic expectations

Agricultural Trade Liberalisation and Strategic Environmental Policy

We use an extended partial equilibrium trade model to derive optimal environmental policy responses to tariff reduction requirements and assess the impact of such policies on the welfare of trading partners. We find that countries which attribute preferential political weights to farmers' welfare have an incentive to implement environmental policies that deviate from the Pigouvian solution - even if production is not de facto linked to environmental externalities. We clarify the conditions under which trading partners do not gain from unilateral trade liberalisation if trade concessions are accompanied by strategic environmental policy changes. We postulate a role for the WTO in overseeing the process of domestic policy formulation.trade liberalisation, strategic environmental policy, multifunctionality, agri-environmental policy, WTO, Environmental Economics and Policy, D60, F11, F18, Q17,

Massive scalar fields in the early Universe

We discuss the role of gravitational excitons/radions in different cosmological scenarios. Gravitational excitons are massive moduli fields which describe conformal excitations of the internal spaces and which, due to their Planck-scale suppressed coupling to matter fields, are WIMPs. It is demonstrated that, depending on the concrete scenario, observational cosmological data set strong restrictions on the allowed masses and initial oscillation amplitudes of these particles.Comment: 6 pages, Latex2e, talk presented at the 1st International Workshop on Astronomy and Relativistic Astrophysics, 12-16 October, 2003, (IWARA2003), Olinda-PE, Brazi

Trapped surfaces in spherical expanding open universes

Consider spherically symmetric initial data for a cosmology which, in the large, approximates an open $k = -1 ,\Lambda = 0$ Friedmann-Lema{\^\i}tre universe. Further assume that the data is chosen so that the trace of the extrinsic curvature is a constant and that the matter field is at rest at this instant of time. One expects that no trapped surfaces appear in the data if no significant clump of excess matter is to be found. This letter confirms this belief by displaying a necessary condition for the existence of trapped surfaces.This necessary condition, simply stated, says that a relatively large amount of excess matter must be concentrated in a small volume for trapped surfaces to appear.Comment: 8 pages, Late