Presentación

La idea de que el ahorro desempeña un papel crucial en el proceso de desarrollo económico ha permeado a la literatura económica desde hace ya varias décadas. Se ha postulado que el ahorro determina la tasa de financiamiento de la acumulación de capital, lo que a su vez es determinante del crecimiento en el largo plazo. Si bien es cierto que la causalidad precisa entre ahorro, inversión y crecimiento está aún en debate, existe evidencia empírica de que hay una correlación positiva entre dichas variables. Por ejemplo, durante el periodo conocido como del Desarrollo Estabilizador en México (1959-1967), el crecimiento del producto interno bruto real, que fue de 6.5% anual en promedio, estuvo acompañado de un aumento en la propensión marginal a ahorrar de los individuos. De acuerdo con Ortiz Mena (1970), esta propensión aumentó de 0.13 entre 1951-1958 a 0.21 entre 1959-1967. Otro ejemplo es el observado en Chile durante la década de 1980, lapso en el cual coexistieron altas tasas de crecimiento de producto y del ahorro, como ha sido documentado en diversos estudios. Finalmente, tenemos el ejemplo de los países del sudeste asiático, los cuales mantuvieron durante muchos años un crecimiento sostenido acompañado de altas tasas de ahorro. En México este tema ha cobrado especial importancia en los últimos años, en particular a partir de la crisis del peso en diciembre de 1994. Las repercusiones negativas que tuvo la alta volatilidad de los flujos externos de capital obligó a las autoridades a subrayar la necesidad de aumentar el ahorro interno como elemento crucial para un crecimiento sostenido en el mediano y largo plazos. En el Plan Nacional de Desarrollo, el actual gobierno establece como uno de los puntos centrales de su proyecto económico recuperar los niveles pasados de ahorro interno para evitar que éste se constituya en una restricción para el crecimiento económico. Incluso se plantea un crecimiento en esta variable para el año 2000 de alrededor de 6 puntos porcentuales del producto. La posibilidad de lograr esta meta depende en gran medida del conocimiento que se tenga en la determinación del ahorro y de sus componentes, así como del entendimiento sobre su comportamiento, lo que permitirá diseñar las políticas adecuadas para su promoción. El contenido de este número de la revista Economía Mexicana, Nueva Época es el resultado de un esfuerzo conjunto realizado por el Centro de Investigación y Docencia Económicas (CIDE) y la Comisión Nacional del Sistema de Ahorro para el Retiro (Consar), por contribuir a una mayor comprensión y discusión sobre este importante tema. Los estudios aquí presentados forman parte del proyecto “Perspectivas del Ahorro en México” y fueron presentados y discutidos en un Seminario Internacional realizado en la ciudad de Puebla el 30 y 31 de octubre de 1998, al cual fueron invitados destacados especialistas nacionales e internacionales de los sectores académico, privado y público.

Vision and Reading Difficulties Part 1: Specific learning difficulties and vision

This article is the first in a series of five about vision and reading difficulties, and provides an introduction and an overview of learning disabilities and specific learning difficulties. It outlines the role of the optometrist in helping people with such problems; it describes the symptoms that optometrists should look for and it provides an introduction of the evidence-based approach. The second article in this series will cover the optometric and orthoptic correlates of reading difficulties. Articles three and four will describe the use of coloured filters, including background, techniques, evidence, and mechanism. The final article will draw together the themes in the series of articles and discuss the clinical protocol and the role of the eye care practitioner in managing visual factors associated with reading difficulties

Rapid learning of an abstract language-specific category: Polish children's acquisition of the instrumental construction

Rapid acquisition of linguistic categories or constructions is sometimes regarded as evidence of innate knowledge. In this paper, we examine Polish children's early understanding of an idiosyncratic, language-specific construction involving the instrumental case – which could not be due to innate knowledge. Thirty Polish-speaking children aged 2 ; 6 and 3 ; 2 participated in a elicited production experiment with novel verbs that were demonstrated as taking nouns in the instrumental case as patients. Children heard the verbs in sentences with either masculine or feminine nouns (which take different endings in the instrumental case), and were tested with new nouns of the same and of the opposite gender. In both age groups, a substantial majority of children succeeded in generalizing from one gendered form of the instrumental case to the other (especially to the masculine), thus indicating that they have some kind of abstract understanding of the instrumental case in this construction. This relatively early abstract knowledge of an idiosyncratic construction casts doubt on the view that early acquisition requires innate linguistic knowledge

JCV-specific T-cells producing IFN-gamma are differently associated with PmL occurrence in HIV patients and liver transplant recipients

Aim of this work was to investigate a possible correlation between the frequency of JCV-specific T-cells and PML occurrence in HIV-infected subjects and in liver transplant recipients. A significant decrease of JCV-specific T-cells was observed in HIV-PML subjects, highlighting a close relation between JCV-specific T-cell immune impairment and PML occurrence in HIV-subjects. Interestingly, liver-transplant recipients (LTR) showed a low frequency of JCV-specific T-cells, similar to HIV-PML subjects. Nevertheless, none of the enrolled LTR developed PML, suggesting the existence of different immunological mechanisms involved in the maintenance of a protective immune response in LT

Cause-specific mortality as a sentinel indicator of current socioeconomic conditions in Italy

This study aims to assess whether simple, widely available demographic indexes, like mortality measures, may serve as sentinel indicators of the economic development and the social wellbeing in Italy. We analyze and compare the geographical patterns of all-cause mortality indexes and those of the mortality rates for leading causes of death, with the spatial pattern found for a more complex index, the vulnerability index, recently introduced by the Italian National Institute for Statistics, at provincial level in the contemporary Italy. We show that mortality data are a straightforward and powerful tool for driving policy makers in planning appropriate interventions

Lipopolysaccharide-specific acyloxyacyl hydrolase

" An acyloxyacyl hydrolase from the human promyelocyte cell line HL-60 has been found to specifically hydrolyze fatty acids from their ester linkages to hydroxy groups of 3-hydroxyfatty acids, the latter being being bound in turn to lipopolysaccharide glycosaminyl residues. The hydrolyzed fatty acids may include dodecanoic acid, tetradecanoic acid and hexadecanoic acid. This enzyme showed a molecular weight by gel exclusion chromatography between about 50,000 Daltons and about 70,000 Daltons, and a molecular weight by polyacrylamide gel electrophoresis with sodium dodecylsulphate, using reduced molecular weight standards, of approximately 54,000 to 60,000 Daltons. Altered bacterial lipopolysaccharide substantially without fatty acids bound in ester linkage to hydroxy groups of 3-hydroxyfatty acids covalently linked to a glucosaminyl moiety of lipopolysaccharide lipid A are produced. Since the structure of the lipid A moiety is highly conserved, acyloxyacyl hydrolase may act on lipopolysaccharide of many different pathogenic bacteria (for example Salmonella, Escherichia, Hemophilus, and Neisseria). Such altered bacterial lipopolysaccharide, having toxicity reduced more than immunostimulatory activity, may be therapeutically useful: (1) as vaccines to prevent Gram-negative bacterial diseases by inducing antibodies to lipopolysaccharide O-polysaccharide or R-core antigens, (2) as antidotes to treat or prevent Gram-negative bacterial sepsis (""septic shock""), or (3) as adjuvants to enhance formation of antibodies to other antigens. the acyloxyacyl hydrolase itself may be prophylactically or therapeutically useful to detoxify endogenous lipopolysaccharide in patients with Gram-negative bacterial diseases. The enzyme may also be used to remove toxic lipopolysaccharide from therapeutic injectants. "Board of Regents, University of Texas Syste

Source-specific routing

Source-specific routing (not to be confused with source routing) is a routing technique where routing decisions depend on both the source and the destination address of a packet. Source-specific routing solves some difficult problems related to multihoming, notably in edge networks, and is therefore a useful addition to the multihoming toolbox. In this paper, we describe the semantics of source-specific packet forwarding, and describe the design and implementation of a source-specific extension to the Babel routing protocol as well as its implementation - to our knowledge, the first complete implementation of a source-specific dynamic routing protocol, including a disambiguation algorithm that makes our implementation work over widely available networking APIs. We further discuss interoperability between ordinary next-hop and source-specific dynamic routing protocols. Our implementation has seen a moderate amount of deployment, notably as a testbed for the IETF Homenet working group

Specific wavelength colorimeter

A self contained, specific wavelength, single beam colorimeter is described for direct spectrophotometric measurement of the concentration of a given solute in a test sample. An electrical circuit employing a photoconductive cell converts the optical output into a linear, directly readable meter output. The colorimeter is simple to operate and is adapted for use in zero gravity conditions. In a specific application, the colorimeter is designed to analyze the concentration of iodine in potable water carried aboard a space vehicle such as the 4B stage of Skylab