Quantum relaxation in random magnets

We present a comprehensive study of the low-temperature magnetic relaxation in random magnets. The first part of the paper contains theoretical analysis of the expected features of the relaxation, based upon current theories of quantum tunneling of magnetization. Models of tunneling, dissipation, the crossover from the thermal to the quantum regime, and the effect of barrier distribution on the relaxation rate are discussed. It is argued that relaxation-type experiments are ideally suited for the observation of magnetic tunneling, since they automatically provide the condition of very low barriers. The second part of the paper contains experimental results on transition-metal¿rare-earth amorphous magnets. Structural and magnetic characterization of materials is presented. The temperature and field dependence of the magnetic relaxation is studied. Our key observation is a nonthermal character of the relaxation below a few kelvin. The observed features are in agreement with theoretical suggestions on quantum tunneling of magnetization.

Quantum tunneling of vortices in the Tl2CaBa2Cu2O8 superconductor

Magnetic-relaxation measurements of a Tl-based high-Tc superconductor show temperature-independent flux creep below 6 K. The effect is analyzed in terms of the overdamped quantum diffusion of two-dimensional vortices. Good agreement between theory and experiment is found.

Mossbauer and magnetization studies of amorphous NdFeB compositionally modulated thin films

Several NdFeB compositionally modulated thin films are studied by using both conversion electron Mossbauer spectra and SQUID (superconducting quantum-interference-device) magnetometry. Both the hyperfine fields and the easy magnetization magnitude are not correlated with the modulation characteristic length (lambda) while the magnetization perpendicular to the thin-film plane decreases as lambda increases. The spectra were recorded at room temperature being the gamma rays perpendicular to the substrate plane. The magnetization measurements were recorded by using a SHE SQUID magnetometer in applied magnetic fields up to 5.5 T and in the temperature range between 1.8 and 30 K.

Agglomeration and labour productivity in Spanish industry: a long-term analysis

This paper analyzes the relationship between spatial density of economic activity and interregional differences in the productivity of industrial labour in Spain during the period 1860-1999. In the spirit of Ciccone and Hall (1996) and Ciccone (2002), we analyze the evolution of this relationship over the long term in Spain. Using data on the period 1860-1999 we show the existence of an agglomeration effect linking the density of economic activity with labour productivity in the industry. This effect was present since the beginning of the industrialization process in the middle of the 19th century but has been decreasing over time. The estimated elasticity of labour productivity with respect to employment density was close to 8% in the subperiod 1860-1900, reduces to a value of around 7% in the subperiod 1914-1930, to 4% in the subperiod 1965-1979 and becomes insignificant in the final subperiod 1985-1999. At the end of the period analyzed there is no evidence of the existence of net agglomeration effects in the industry. This result could be explained by an important increase in the congestion effects in large industrial metropolitan areas that would have compensated the centripetal or agglomeration forces at work. Furthermore, this result is also consistent with the evidence of a dispersion of industrial activity in Spain during the last decades.

New Estimates of Regional GDP in Spain, 1860-1930

This paper presents a new regional database on GDP in Spain for the years 1860, 1900, 1914 and 1930. Following Geary and Stark (2002), country level GDP estimates are allocated across Spanish provinces. The results are then compared with previous estimates. Further, this new evidence is used to analyze the evolution of regional inequality and convergence in the long run. According to the distribution dynamics approach suggested by Quah (1993, 1996) persistence appears as a main feature in the regional distribution of output. Therefore, in the long run no evidence of regional convergence in the Spanish economy is found.

Cotton manufacturers as bankers: the textile trade and credit in spain, 1840-1913

[cat] La historiografia ha assenyalat que en el segle XIX el crèdit que els fabricants cotoners catalans oferien als seus clients era de caràcter informal i, per tant, impossible de ser transferit al sistema bancari. Això hauria tingut un efecte negatiu en la rendibilitat de les empreses cotoneres. A partir de l’anàlisi de diversos arxius empresarials, així com de fonts judicials i notarials, aquest treball confirma aquesta descripció dels fets però proposa una interpretació més optimista. Els fabricants feien de banquers dels seus clients perquè eren els millor situats per a exercir aquesta funció. Havien construït una bona estructura d’informació, gestionaven eficientment el risc creditici i obtenien beneficis d’aquesta activitat.

Una nova estimació retrospectiva del VAB regional industrial. Espanya, 1860-1930

[cat] En aquest treball, es realitza una nova estimació del VAB industrial espanyol a un nivell de desagregació territorial corresponent a les províncies (NUTSIII) i les Comunitats Autònomes (NUTS II). Per assolir aquest objectiu es planteja una nova metodologia d’estimació de les xifres històriques de VAB industrial regional. Front a les aproximacions tradicionals, basades en la utilització de fonts fiscals com a forma d’aproximar la capacitat productiva industrial, en aquest treball s’ofereix una estimació que també es basa en les rendes generades per la producció industrial de les regions. Amb aquest objectiu, es fa servir la metodologia proposada per Geary i Stark (2002) i les millores proposades per Crafts (2005). La utilització d’aquesta metodologia permet elaborar una nova estimació retrospectiva del VAB industrial de les regions espanyoles a diversos talls temporals corresponents al període 1860-1930.

Vertical Syndication-Proof Competitive Prices in Multilateral Markets

[eng] A multi-sided Böhm-Bawerk assignment game (Tejada, to appear) is a model for a multilateral market with a finite number of perfectly complementary indivisible commodities owned by different sellers, and inflexible demand and support functions. We show that for each such market game there is a unique vector of competitive prices for the commodities that is vertical syndication-proof, in the sense that, at those prices, syndication of sellers each owning a different commodity is neither beneficial nor detrimental for the buyers. Since, moreover, the benefits obtained by the agents at those prices correspond to the nucleolus of the market game, we provide a syndication-based foundation for the nucleolus as an appropriate solution concept for market games. For different solution concepts a syndicate can be disadvantageous and there is no escape to Aumman’s paradox (Aumann, 1973). We further show that vertical syndicationproofness and horizontal syndication-proofness – in which sellers of the same commodity collude – are incompatible requirements under some mild assumptions. Our results build on a self-interesting link between multi-sided Böhm-Bawerk assignment games and bankruptcy games (O’Neill, 1982). We identify a particular subset of Böhm-Bawerk assignment games and we show that it is isomorphic to the whole class of bankruptcy games. This isomorphism enables us to show the uniqueness of the vector of vertical syndication-proof prices for the whole class of Böhm-Bawerk assignment market using well-known results of bankruptcy problems.

On the coincidence between the Shimomura's bargaining sets and the core

[cat] En l'article es dona una condició necessària per a que els conjunts de negociació definits per Shimomura (1997) i el nucli d'un joc cooperatiu amb utilitat transferible coincideixin. A tal efecte, s'introdueix el concepte de vectors de màxim pagament. La condició necessària consiteix a verificar que aquests vectors pertanyen al nucli del joc.

Hindleg muscle energy and substrate balances in cold-exposed rats

Rats chronically cannulated in the carotid artery and the muscular branch of the femoral vein were subjected to a cold (4 °C) environment for up to 2 h. The changes in blood flow (measured with 46Sc microspheres) and arterio-venous differences in the concentrations of glucose, lactate, triacylglycerols and amino acids allowed the estimation of substrate (and energy) balances across the hindleg. Mean glucose uptake was 0.28mmol min21, mean lactate release was 0.33mmol min21 and the free fatty acid basal release of 0.31mmol min21 was practically zero upon exposure to the cold; the initial uptake of triacylglycerols gave place to a massive release following exposure. The measurement of PO·, PCO· and pH also allowed the estimation of oxygen, CO2 and bicarbonate balances and respiratory quotient changes across the hindleg. The contribution of amino acids to the energy balance of the hindleg was assumed to be low. These data were used to determine the sources of energy used to maintain muscle shivering with time. Three distinct phases were observed in hindleg substrate utilization. (1) The onset of shivering, with the use of glucose/glycogen and an increase in lactate efflux. Lipid oxidation was practically zero (respiratory quotient near 1), but the uptake of triacylglycerols from the blood remained unchanged. (2) A substrate-energy shift, with drastically decreased use of glucose/glycogen, and of lactate efflux; utilization of triacylglycerol as practically the sole source of energy (respiratory quotient approximately 0.7); decreasing uptake of triacylglycerol and increased tissue lipid mobilization. (3) The onset of a new heat-homeostasis setting for prolonged cold-exposure, with maintenance of muscle energy and heat production based on triacylglycerol utilization and efflux from the hindleg (muscle plus skin and subcutaneous adipose masses) contributing energy to help sustain heat production by the core organs and surrounding brown adipose tissue.

Una exploración completa de los costes de servicio de residuos sólidos

La literatura económica sobre los servicios municipales de residuos sólidos en España es muy escasa, aun cuando estos servicios han sido objeto d'intensas reformas organizativas y regulatorias. En esta investigación se estudia su estructura de costes con el objetivo de explicar la variabilidad entre los municipios de los costes soportados por el servicio. Se determina una función de costes y se estima de forma paramétrica. Los resultados del análisis empírico permiten estudiar la existencia de economías de escala con el output, y el efecto de algunos factores directamente asociados con el servicio como el grado de residuos selectivos, la frecuencia de recogida o la existencia de instalaciones de depósito en el municipio. Además, se analiza el impacto sobre los costes de otros factores como la densidad de población, los niveles salariales, la estacionalidad y la forma de producción, pública o privada.

The Impact of Monetary Union on EU-15 Sovereign Debt Yield Spreads

With European Monetary Union (EMU), there was an increase in the adjusted spreads (corrected from the foreign exchange risk) of euro participating countries' sovereign securities over Germany and a decrease in those of non-euro countries. The objective of this paper is to study the reasons for this result, and in particular, whether the change in the price assigned by markets was due to domestic factors such as credit risk and/or market liquidity, or to international risk factors. The empirical evidence suggests that market size scale economies have increased since EMU for all European markets, so the effect of the various risk factors, even though it differs between euro and non-euro countries, is always dependent on the size of the market.

Socio-economic inequalities in reported depression in Spain : a decomposition approach

Recent evidence questions some conventional view on the existence of income-related inequalities in depression suggesting in turn that other determinants might be in place, such as activity status and educational attainment. Evidence of socio-economic inequalities is especially relevant in countries such as Spain that have a limited coverage of mental health care and are regionally heterogeneous. This paper aims at measuring and explaining the degree of socio-economic inequality in reported depression in Spain. We employ linear probability models to estimate the concentration index and its decomposition drawing from 2003 edition of the Spanish National Health Survey, the most recent representative health survey in Spain. Our findings point towards the existence of avoidable inequalities in the prevalence of reported depression. However, besides ¿pure income effects¿ explaining 37% of inequality, economic activity status (28%), education (15%) and demographics (15%) play also a key encompassing role. Although high income implies higher resources to invest and cure (mental) illness, environmental factors influencing in peoples perceived social status act as indirect path as explaining the prevalence of depression. Finally, we find evidence of a gender effect, gender social-economic inequality in income is mainly avoidable.

'Biased' Risk Perceptions of Longevity and Disability in Old Age

Rational learning theories postulate that information channels and cognitive biases such as individual optimism may influence an individual¿s assessment of the risk of undesired events, especially with regard to those that have a cumulative nature. This is the case with disability in old age, which may take place upon survival to an advanced age, and such factors have been regarded as responsible for certain individual behaviours (for example, the limited incidence of insurance purchase). This paper examines the determinants of individual perceptions with regard to disability in old age and longevity. The cumulative nature of such perceptions of risk is tested, and potential biases are identified, including `optimism¿ and a set of information determinants. Empirical evidence from a representative survey of Catalonia is presented to illustrate these effects. The findings from this research suggest a significant overestimation of disability in old age, yet this is not the case with longevity. Furthermore, individual perceptions with regard to disability in old age, unlike those with regard to longevity, exhibit on aggregate an `optimistic bias¿ and, are perceived as `cumulative risks¿. Gender influences the perceived risk of disability in old age at a population level but not at the individual level, and the opposite holds true for age. Finally, self-reported health status is the main variable behind risk perceptions at both the individual and population level.

Agglomeration and labour productivity in Spanish industry: a long-term analysis

This paper analyzes the relationship between spatial density of economic activity and interregional differences in the productivity of industrial labour in Spain during the period 1860-1999. In the spirit of Ciccone and Hall (1996) and Ciccone (2002), we analyze the evolution of this relationship over the long term in Spain. Using data on the period 1860-1999 we show the existence of an agglomeration effect linking the density of economic activity with labour productivity in the industry. This effect was present since the beginning of the industrialization process in the middle of the 19th century but has been decreasing over time. The estimated elasticity of labour productivity with respect to employment density was close to 8% in the subperiod 1860-1900, reduces to a value of around 7% in the subperiod 1914-1930, to 4% in the subperiod 1965-1979 and becomes insignificant in the final subperiod 1985-1999. At the end of the period analyzed there is no evidence of the existence of net agglomeration effects in the industry. This result could be explained by an important increase in the congestion effects in large industrial metropolitan areas that would have compensated the centripetal or agglomeration forces at work. Furthermore, this result is also consistent with the evidence of a dispersion of industrial activity in Spain during the last decades.