Encryption methods using formal power series rings

Recently there has been a great deal of work on noncommutative algebraic cryptography. This involves the use of noncommutative algebraic objects as the platforms for encryption systems. Most of this work, such as the Anshel-Anshel-Goldfeld scheme, the Ko-Lee scheme and the Baumslag-Fine-Xu Modular group scheme use nonabelian groups as the basic algebraic object. Some of these encryption methods have been successful and some have been broken. It has been suggested that at this point further pure group theoretic research, with an eye towards cryptographic applications, is necessary.In the present study we attempt to extend the class of noncommutative algebraic objects to be used in cryptography. In particular we explore several different methods to use a formal power series ring R && x1; :::; xn && in noncommuting variables x1; :::; xn as a base to develop cryptosystems. Although R can be any ring we have in mind formal power series rings over the rationals Q. We use in particular a result of Magnus that a finitely generated free group F has a faithful representation in a quotient of the formal power series ring in noncommuting variables.

Co-movements between US and UK stock prices: the roles of macroeconomic information and time-series varying conditional correlations

This paper provides evidence on the sources of co-movement in monthly US and UK stock price movements by investigating the role of macroeconomic and financial variables in a bivariate system with time-varying conditional correlations. Crosscountry communality in response is uncovered, with changes in the US Federal Funds rate, UK bond yields and oil prices having similar negative effects in both markets. Other variables also play a role, especially for the UK market. These effects do not, however, explain the marked increase in cross-market correlations observed from around 2000, which we attribute to time variation in the correlations of shocks to these markets. A regime-switching smooth transition model captures this time variation well and shows the correlations increase dramatically around 1999-2000. JEL classifications: C32, C51, G15 Keywords: international stock returns, DCC-GARCH model, smooth transition conditional correlation GARCH model, model evaluation.

Series enlazadas de algunos agregados económicos nacionales y regionales, 1955-2007 Versión 2.1

I construct "homogeneous" series of GVA at current and constant prices, employment and population for the Spain and its regions covering the period 1955-2007. The series are obtained by linking the Regional Accounts of the National Statistical Institute with the series constructed by Julio Alcaide and his team for the BBVA Foundation. The "switching point" at which this last source stops being used as a reference to construct the linked series is determined using a procedure that allows me to estimate which of the two competing series would produce an estimator with the lowest MSE when it is used as dependent variable in a regression on an arbitrary independent variable. To the extent that it is possible, the difference between the two series found at the point of linkage is distributed between the initial levels of the older series and its subsequent growth using external estimates of the relevant variables at the beginning of the sample period.

A mixed splicing procedure for economic time series

This note develops a flexible methodology for splicing economic time series that avoids the extreme assumptions implicit in the procedures most commonly used in the literature. It allows the user to split the required correction to the older of the series being linked between its levels and growth rates on the basis what he knows or conjectures about the persistence of the factors that account for the discrepancy between the two series that emerges at their linking point. The time profile of the correction is derived from the assumption that the error in the older series reflects the inadequate coverage of emerging sectors or activities that grow faster than the aggregate.

Series enlazadas de empleo asalariado y rentas del trabajo regionales (RegDat versión 2.2)

I construct "homogeneous" series of salaried employment, employee compensation and total labor income for Spain and its regions covering the period 1955-2008. I also estimate labor's share in regional and national GVA and construct an indicator of the average cost of labor including both employees and non-salaried workers.

Series anuales de algunos agregados económicos y demográficos regionales, 1955-2009 (RegDat versión 2.3)

En una serie de trabajos anteriores he construido series largas de diversos agregados económicos regionales enlazando las distintas bases de la Contabilidad Regional de España entre sí y con las series históricas elaboradas por la Fundación BBVA. Puesto que esta última fuente sólo ofrece datos para años impares, las series enlazadas heredan esta característica desde 1955 hasta 1989. En la presente nota se construyen series anuales completas de las variables de interés utilizando un sencillo procedimiento de interpolación que incorpora la información anual disponible a nivel nacional para estas variables.

Wiener type theorems for Jacobi series with nonnegative coefficients

"Vegeu el resum a l'inici del document del fitxer ajunt."

CO2 emissions and economic activity: heterogeneity across countries and non stationary series

This paper explores the homogeneity of the functional form, the parameters, and the turning point, when appropriate, of the relationship between CO2 emissions and economic activity for 31 countries (28 OECD, Brazil, China, and India) during the period 1950 to 2006 using cointegration analysis. With a sample highly overlapped over time between countries, the result reveals that the homogeneity across countries is rejected, both in functional form and in the parameters of long term relationship. This confirms the relevance of considering the heterogeneity in exploring the relationship between air pollution and economic activity to avoid spurious parameter estimates and infer a wrong behavior of the functional form, which could lead to induce that the relationship is reversed when in fact it is direct.

Series largas de algunos agregados demográficos regionales, 1950-2009

El presente trabajo resume los resultados de la primera fase de un proyecto cuyo objetivo es el de ofrecer series homogéneas de los principales agregados económicos y demográficos de las regiones españolas para el período desde 1950 hasta nuestros días. En él se recopilan, extienden o construyen series de movimientos naturales de población, población de derecho y residente habitual, saldos migratorios netos y estructura por edades de la población.

Eisenstein series for principal congruence subgroups of GL(2,Fq[T])

"Vegeu el resum a l'inici del document del fitxer adjunt"

Aproximación a la traducción de la terminología médica de series dobladas al español: el caso de "Urgencias"

A les darreres dècades, l'anglès mèdic col·loquial s'ha barrejat amb el llenguatge no especialitzat a dramatitzacions audiovisuals. Aquest argot pertany actualment a un sistema conceptual lligat a una cultura i constitueix l'oralitat prefabricada destinada a caracteritzar els personatges de ficció. Aquesta investigació verifica tant les tècniques de traducció emprades per traslladar la terminologia mèdica de la sèrie ER (Urgències) en el doblatge de l'anglès a l'espanyol, com el nivell d'adequació de la versió en la llengua meta. Acadèmicament, aquest treball està motivat per la manca d'estudis empírics de la traducció per el doblatge de la terminologia mèdica de les series televisives

Uranium reserve, nuclear fuel cycle delusion, CO2 emission from the sea, and electricity supply: reflections after the fuel meltdown of Fukushima nuclear power units

The Great Tohoku-Kanto earthquake and resulting tsunami has brought considerable attention to the issue of the construction of new power plants. We argue in this paper, nuclear power is not a sustainable solution to energy problems. First, we explore the stock of uranium-235 and the different schemes developed by the nuclear power industry to exploit this resource. Second, we show that these methods, fast breeder and MOX fuel reactors, are not feasible. Third, we show that the argument that nuclear energy can be used to reduce CO2 emissions is false: the emissions from the increased water evaporation from nuclear power generation must be accounted for. In the case of Japan, water from nuclear power plants is drained into the surrounding sea, raising the water temperature which has an adverse affect on the immediate ecosystem, as well as increasing CO2 emissions from increased water evaporation from the sea. Next, a short exercise is used to show that nuclear power is not even needed to meet consumer demand in Japan. Such an exercise should be performed for any country considering the construction of additional nuclear power plants. Lastly, the paper is concluded with a discussion of the implications of our findings.

The global uranium rush and its Africa frontier. Lessons from Namibia

Uranium mines are the - often forgotten - source of nuclear power. The promotion of nuclear energy as a clean alternative and the projected increase of electricity demand in countries such as China and India, have led to a global “uranium rush”, unseen since the peak of the Cold War. This article studies the formation of the expanding nuclear frontier looking at the interaction between the global uranium metabolism, industrial dynamics and local ecologies of resistance using Namibia as a case-study. Namibia, the world´s fourth largest producer of uranium, stands at the frontier of this rush with sixty-six recently granted prospecting licenses that could turn into mines, compared to only three currently operating mines. We focus on three generic attributes that help to explain the emergence and intensity of resistance by local communities to uranium mining: the ecology and geography of the resource; the degree and type of political and economic marginalization of the community; and crucially, the connection and integration of local concerns with broader social movements and political demands. We show with the use of empirical material how these factors play out differently in five Namibian communities that have been, or stand to be, affected by uranium mining, and explain how local ecologies of resistance shape the global uranium rush.

Traducció i estudi de documents demòtics datats del regnat d'Alexandre el Gran (332-323 aC)

Projecte de recerca elaborat a partir d’una estada a l’Oriental Institute de la University of Oxford, Regne Unit, entre juliol i octubre de 2007. Durant l’estada s’ha analitzat la documentació demòtica datada del regnat d’Alexandre el Gran com a faraó d’Egipte (332-323 aC). El conjunt de fonts que examinat està constituït per sis papirs (actes notarials que recullen diversos tipus de contractes o acords entre dues parts), un òstrakon fragmentari i una sèrie d’esteles provinents de la Necròpolis d’Animals de Saqqara Nord, en concret de la Catacumba de les Mares d’Apis. Aquesta documentació és fonamental perquè permet extreure conclusions importants sobre diversos aspectes relacionats amb l’administració i la religiositat egípcies en els moments inicials de la dominació grega d'Egipte. Cadascun d’aquests documents ha estat traduït, analitzat en profunditat i degudament contextualitzat històricament. D’una banda, en l’àmbit de l’administració, he pogut constatar la continuïtat existent amb el període històric immediatament anterior, és a dir, amb la Segona Dominació Persa del país; mentre que de l'altra, des del punt de vista religiós, l’anàlisi d’aquestes fonts m’ha permès verificar l'existència de tota una sèrie de canvis substancials, estretament vinculats a la voluntat expressa de la nova elit dirigent d'origen grec de distanciar-se dels seus predecessors aquemènides i de marcar amb força l’obertura d’una nova era que es caracteritzarà pel respecte a les tradicions autòctones i per la potenciació dels cultes nacionals.

Solitary Fibrous Tumor. Imaging findings in a series of nine cases

Es presenta un estudi retrospectiu descrivint les característiques radiològiques en una sèrie de nou casos de tumor fibrós solitari que affecta partes toves. Aquests resultats es comparen amb els resultats d’anatomia patològica i amb l’evolució clínica dels pacients