Uncertanties in Air-showers from Small-x pQCD Mini-Jets

To investigate uncertainties in air shower simulations caused by the small-x regime, a model including leading-twist hard pQCD plus soft processes was built, which are separated by an energy dependent transverse momentum cut-off. We provide a fit of the cut-off to the total pp cross section for different PDFs using the eikonal formalism and show that for modern PDF sets there is only a small uncertainty in the mini-jet cross section, and hence in the final-state multiplicity and the number of produced muons.Comment: 4 pages, 2 figures, contribution to QM2005 proceedings, revised version after referee comment

Exact simulation of coined quantum walks with the continuous-time model

The connection between coined and continuous-time quantum walk models has been addressed in a number of papers. In most of those studies, the continuous-time model is derived from coined quantum walks by employing dimensional reduction and taking appropriate limits. In this work, we produce the evolution of a coined quantum walk on a generic graph using a continuous-time quantum walk on a larger graph. In addition to expanding the underlying structure, we also have to switch on and off edges during the continuous-time evolution to accommodate the alternation between the shift and coin operators from the coined model. In one particular case, the connection is very natural, and the continuous-time quantum walk that simulates the coined quantum walk is driven by the graph Laplacian on the dynamically changing expanded graph

The Portuguese Disinflation Process: Analysis of Some Costs and Benefits

This study aims to analyse the Portuguese economic policy of disinflation through a nominal stabilization policy of the Portuguese escudo. We study the pegging of the Portuguese escudo (PTE) to the Deutsch mark (DM) knowing the reputation of the Bundesbank for its anti- inflationary record and the role played by the Deutsch mark in the stability processes of foreign exchange and European price levels. The study was based on the attainment of co-integrating relations using Johansen’s methodology, the construction of a Near-VAR model and the establishment of a simulation analysis. The acceptance of German monetary policy and the pegging of the escudo to the Deutsch mark allowed the Portuguese economy to achieve its primary goal of price stability. However, despite the credibility and stability gains obtained, the adoption of a disinflation policy led to a real appreciation of the escudo. This study tries to clarify the influence that an appreciation of the real exchange rate can have on GDP and price levels. It cannot be denied that Portugal has made great progress in its European integration, successfully integrating into the group of EMU member-states. However we can point to a decrease in Portuguese competitiveness as the price paid for the disinflation process. This reflects itself in lower wages, which in turn limit output growth. We find that it is of primary importance to realise both the benefits of disinflation, and the costs of the policies in terms of output.Monetary Policy, European Union, Disinflation, Co-Integration, Near-VAR and Simulation

Changes to cholesterol trafficking in macrophages by Leishmania parasites infection

Leishmania spp. are protozoan parasites that are transmitted by sandfly vectors during blood sucking to vertebrate hosts and cause a spectrum of diseases called leishmaniases. It has been demonstrated that host cholesterol plays an important role during Leishmania infection. Nevertheless, little is known about the intracellular distribution of this lipid early after internalization of the parasite. Here, pulse‐chase experiments with radiolabeled cholesteryl esterified to fatty acids bound to low‐density lipoproteins indicated that retention of this source of cholesterol is increased in parasite‐containing subcellular fractions, while uptake is unaffected. This is correlated with a reduction or absence of detectable NPC1 (Niemann–Pick disease, type C1), a protein responsible for cholesterol efflux from endocytic compartments, in the Leishmania mexicana habitat and infected cells. Filipin staining revealed a halo around parasites within parasitophorous vacuoles (PV) likely representing free cholesterol accumulation. Labeling of host cell membranous cholesterol by fluorescent cholesterol species before infection revealed that this pool is also trafficked to the PV but becomes incorporated into the parasites’ membranes and seems not to contribute to the halo detected by filipin. This cholesterol sequestration happened early after infection and was functionally significant as it correlated with the upregulation of mRNA‐encoding proteins required for cholesterol biosynthesis. Thus, sequestration of cholesterol by Leishmania amastigotes early after infection provides a basis to understand perturbation of cholesterol‐dependent processes in macrophages that were shown previously by others to be necessary for their proper function in innate and adaptive immune responses

Purchasing power parity: an empirical study of three EMU countries

We apply Purchasing Power Parity (PPP) theory to the analysis of long- run equilibrium in the foreign exchange market. We study the case of Portugal vis-à-vis Germany and Spain, and the case of Spain vis-à-vis Germany, in the period 1960-1990. The empirical analysis was based on unit-root testing (using ADF tests) and Johansen’s methodology for the study of co-integration. We worked with linear long-run relationships based exclusively on PPP, as well as with long-run relations that also allowed for the effect of interest rates. In a situation in which PPP does not hold, one could think that on account of some “natural reason” agents believe that, as time goes by, the dominant currency, which is also the reference currency of the EMS (the German Mark), will appreciate. We concluded, on the contrary, that the weaker currencies were the ones that with the passing of time appreciated in real terms. The fact that PPP theory was applied to two southern European countries deserves a special mention, because it may serve as an example for other countries that come to be in a position similar to that of Portugal and Spain before their adhered to the European Union.Purchasing Power Parity, Unit Roots, EMU, Economic Integration and Co-integration

An Algorithm to Simplify Tensor Expressions

The problem of simplifying tensor expressions is addressed in two parts. The first part presents an algorithm designed to put tensor expressions into a canonical form, taking into account the symmetries with respect to index permutations and the renaming of dummy indices. The tensor indices are split into classes and a natural place for them is defined. The canonical form is the closest configuration to the natural configuration. In the second part, the Groebner basis method is used to simplify tensor expressions which obey the linear identities that come from cyclic symmetries (or more general tensor identities, including non-linear identities). The algorithm is suitable for implementation in general purpose computer algebra systems. Some timings of an experimental implementation over the Riemann package are shown.Comment: 15 pages, Latex2e, submitted to Computer Physics Communications: Thematic Issue on "Computer Algebra in Physics Research

Networks for change: How networks influence organizational change

This paper contributes to the literature on organizational change by examining organizations as social entities embedded in inter-organizational networks. In contrast to extant research that focuses on macro environment and internal factors to explain organizational change we put forth the social network surrounding the firm as a major driver of any change process. In specific we examine organization change as driven by the organizations? positions and relations in an interorganizational network. Our conceptual framework demonstrates that inter-organizational networks are important mid-level environmental factors that complement the macro-environment and internal organizational factors for the study of organizational changes. We conclude with a discussion on normative implications for organizations and avenues for future research.organizational change, social networks