Allan Sørensen

Protein-leverage in Mice : The Geometry of Macronutrient Balancing and Consequences for Fat Deposition

Objective: The Protein‐Leverage Hypothesis proposes that humans regulate their intake of macronutrients and that protein intake is prioritized over fat and carbohydrate intake, causing excess energy ingestion when diets contain low %protein. Here we test in a model animal, the mouse: (i) the extent to which intakes of protein and carbohydrate are regulated; (ii) if protein intake has priority over carbohydrates so that unbalanced foods low in %protein leads to increased energy intake; and (iii) how such variations in energy intake are converted into growth and storage.

Balancing of protein and lipid intake by a mammalian carnivore, the mink, Mustela vison.

Many herbivores and omnivores can balance their intake of macronutrients when faced with nutritionally variable environments. Carnivores, however, are widely believed to optimize their rates of prey capture and energy intake rather than balancing nutrients. We tested nutrient balancing in captive mink and found a pronounced ability to balance and regulate intake of protein and lipid. When faced with one of several different pairings of complementary foods varying in protein to lipid composition, mink apportioned intake between the two foods to defend a near constant ratio and amount (intake target) of the two macronutrients. When given only one food of fixed nutrient composition, mink balanced macronutrient intake relative to the intake target, without showing the excessive energy intake on diets with a low percentage of protein and energy deficit on diets with a high percentage of protein previously reported for herbivores and omnivores, including humans. This demonstration of nutrient balancing in a carnivorous mammal indicates that the capacity for nutrient balancing is a more general phenomenon across trophic levels than was hitherto believed to be the case.

Export Market Exit and Firm Survival: Theory and First Evidence

This paper deploys a dynamic extension of the Melitz (2003) model to generate predictions on export market exit and firm survival in a setting where firms endogenously make exit decisions. The central driver of the model dynamics is the inclusion of exogenous economy wide technological progress. The model predicts – inter alia – that a higher relative productivity not only increases the likelihood of exporting, but also the chances of firm survival and continued export market engagements. We relate these predictions to the empirical stylized facts of export market exit and firm survival based on Danish firm-level data. We find strong evidence that firms experience a decline in market share prior to export market exit and prior to death and that the firms discontinuing their exporting activity or closing down tend to be small. Overall, our empirical results support the central predictions from the model.

Barkas effect at low velocities

Abstract The energy loss rates of protons and antiprotons at energies below the stopping maximum are determined in an electron gas model. For silicon and germanium targets the stopping power for antiprotons is found to be less than half of the proton stopping power. An analytical second-order Born expression pertaining to electron scattering in a Yukawa potential is obtained and compared to results of exact calculations for a self-consistent potential.

Temperature dependence of axial-channeling radiation

Abstract The 2p-1s and 3p-1s lines of channeling radiation have been measured at three different temperatures, 110 K, 300 K, and 500 K, for 3.5 MeV electrons channeled along a 〈111〉 direction in silicon. A variation of about 20% of the photon energy is observed, in good agreement with calculations. The variation reflects a temperature dependence of the 1s level due to the thermal smearing of the continuum string potential. The measured linewidths also agree with theoretical estimates. They are dominated by thermal scattering, with an estimated contribution of ~ 10% from electronic scattering.

A Welfare Ranking of Multilateral Reductions in Real and Tariff Trade Barriers when Firms are Heterogenous

Trade liberalization comes about through reductions in various types of trade barriers. This paper introduces, apart from the customary real trade costs (i.e. iceberg and fixed export costs), two revenue generating trade barriers (i.e. an ad valorem tariff and a trade license) into a standard heterogeneous-firms-trade model with Pareto distributed productivities. We derive analytical welfare rankings of all four liberalization channels for an equal effect on two openness measures, for any trade cost level and while all four barriers are simultaneously present, i.e. for any initial equilibrium. We show that when openness is measured at retail prices, not border prices, the welfare rankings are sensitive to the degree of efficiency in revenue redistribution, e.g. the share of tariff revenues wasted on rent-seeking activities. As a result, multilateral tariff reductions can switch from the least to the most preferred mode of liberalization. Among the other three barriers we establish a universal welfare ranking for any strictly positive level of revenue redistribution and for either measure of openness.

Globalisation Squeezes the Public Sector - Is it so Obvious?

It is widely perceived that globalization squeezes public sector activities by making taxation more costly. This is attributed to increased factor mobility and to a more elastic labour demand due to improved scope for relocation of production and thus employment across countries. We argue that this consensus view overlooks that gains from trade unambiguously work to lower the marginal costs of public funds, and moreover that globalization via increased trade in intermediaries may actually lower the labour demand elasticity.

Energy-loss straggling of (200–1000) MeV/u uranium ions

Abstract The charge-exchange contribution can dominate the energy-loss straggling of partially stripped heavy ions depending on the charge-changing cross sections and the partial stopping powers. We have studied the energy-loss straggling of few-electron uranium ions in different solids in the energy range of (200–1000) MeV/u. Our experimental data are compared with a new model taking into account realistic screening for relativistic scattering of target electrons at close impacts to derive partial stopping powers. Screening of the projectile nucleus by inner-shell electrons reduces the charge-exchange straggling compared to that pertaining to a point-like charge distribution.

Globalization, Tax Distortions, and Public‐Sector Retrenchment

It is widely perceived that globalization is a threat to tax financed public sector activities. The argument is that public activities (public consumption and transfers) financed by income taxes distort labour markets and cause higher wages and thus a loss of competitiveness. Since this link is strengthened by globalization, it is inferred that the marginal costs of public funds increase and a retrenchment of the public sector follows. We challenge whether these conclusions have support in a general equilibrium model featuring standard effects from open macroeconomics and trade theory. Even though income taxation unambiguously worsens wage competitiveness, it does not follow that marginal costs of public funds increase with product market integration due to gains from trade. Moreover, non-cooperative fiscal policies do not have a race-to-the-bottom bias despite that taxes harm competitiveness. In fact we identify an expansionary bias in ?scal policies that is likely to increase with globalization when taxes finance either public consumption or transfers.

Second thoughts on the exporter productivity premium

Contrary to the prevailing interpretation, this paper shows that the central models of trade with heterogeneous firms ( Melitz 2003 ; Bernard et al. 2003 ) exhibit ambiguous predictions for the exporter productivity premium. This prospect arises because of differences between theoretical and empirical representations of firm productivity. Instead of marginal productivity, we examine in both models the theoretical equivalent of empirically observable productivity (value-added per employee). Given the presence of fixed export costs or heterogeneous mark-ups and trade costs, the observable productivity of exporters in proximity to the export-indifferent firm turns out to be lower than that of non-exporters; that is, the productivity distributions overlap. The paper reviews empirical literature that reports non-positive exporter productivity premia in firm-level data and discusses implications for empirical research on exporter performance, including learning and the role of non-parametric regressions (stochastic dominance, quantile regressions), fixed costs, and productivity distributions.