Phase Competition in Ln0.5a0.5mno3 Perovskites

Single crystals of the systems Pr0.5(Ca1-xSrx)0.5MnO3, (Pr1-yYy)0.5(Ca1-xSrx)0.5MnO3, and Sm0.5Sr0.5MnO3 were grown to provide a series of samples with fixed ratio Mn(III)/Mn(IV)=1 having geometric tolerance factors that span the transition from localized to itinerant electronic behavior of the MnO3 array. A unique ferromagnetic phase appears at the critical tolerance factor tc= 0.975 that separates charge ordering and localized-electron behavior for t<tc from itinerant or molecular-orbital behavior for t>tc. This ferromagnetic phase, which has to be distinguished from the ferromagnetic metallic phase stabilized at tolerance factors t>tc, separates two distinguishable Type-CE antiferromagnetic phases that are metamagnetic. Measurements of the transport properties under hydrostatic pressure were carried out on a compositions t a little below tc in order to compare the effects of chemical vs. hydrostatic pressure on the phases that compete with one another near t=tc.Comment: 10 pages. To be publised in Phys. Rev.

El problema de las compensaciones : ¿Quién compensa a quién, por qué y cómo?

One problem that is probably the most complex and contentious in any process of normalization of relations between Cuba and the United States is that of "compensations." These problems must be resolved to avoid future lawsuits over property ownership, in order to minimize the uncertainty and economic paralysis that they could generate. This paper summarizes some of the elements related to the compensation problem, namely: The historical context; the claims of the United States against Cuba; the possible claims of Cuba to the United States; the legal and ethical dimensions; the alternative approaches to dealing with this problem and, finally, the Cuban-American claims (not considered by the Foreign Claims Settlement Commission) and the claims of the Cubans.Un problema que probablemente es el más complejo y contencioso en cualquier proceso de normalización de relaciones entre Cuba y los Estados Unidos es el relativo a las "compensaciones". Estos problemas deberán ser resueltos para evitar futuras demandas legales sobre la propiedad de los bienes, a fin de reducir al mínimo la incertidumbre y la parálisis económica que podrían generar. En este trabajo se resumen algunos de los elementos relativos al problema de las compensaciones, a saber: El contexto histórico; las demandas de los Estados Unidos a Cuba; las posibles demandas de Cuba a los Estados Unidos; las dimensiones legales y éticas; los enfoques alternativos para tratar este problema y, finalmente, las demandas cubano-norteamericanas (no consideradas por la Foreign Claims Settlement Commission) y las demandas de los cubanos

An Overview of Cuba’s Economy in the 2000s: Recuperation and/or Relapse – revised version: The Cuban Economy in the Twenty-first Century: Recuperation or Relapse? The Cuban Economy

This essay surveys and evaluates Cuba’s economic performance since its economic “melt-down” of 1989-1993, outlines the government’s policy responses, and explores Cuba’s economic prospects. By 1995, the Cuban economy began to recover with some positive results but also with continuing problems. An enduring economic recovery that allows for the recuperation of living standards and investment in social programs would require Cuban economic policy-makers to address a number of challenges. Among these are unifying the dualistic exchange rate system, increasing levels of savings and investment, expanding and diversifying merchandise exports, rethinking the policy environment for the sugar sector, redesigning the policy environment for micro-enterprise, and increasing the real value of budgetary revenues devoted to education, health and public services. Cuba’s economic management team does not appear to be addressing these issues effectively or seriously. Instead, Cuba will probably proceed on its current course for some time to come.Cuba; economic performance; economic development; monetary policy; exchange rate policy; liberalization; micro-enterprise; export diversification