Parameter estimation of wormholes beyond the Heisenberg limit

We propose to exploit the quantum properties of nonlinear media to estimate the parameters of massless wormholes. The spacetime curvature produces a change in length with respect to Minkowski spacetime that can be estimated in principle with an interferometer. We use quantum metrology techniques to show that the sensitivity is improved with nonlinear media and propose a nonlinear Mach-Zehnder interferometer to estimate the parameters of massless wormholes that scales beyond the Heisenberg limit

EQUITY SCHEMES IN SOUTH AFRICA: BENEFITS DELIVERED TO FARM WORKERS AS FUNCTION OF COMMERCIAL FARMERS' STRATEGY

With the end of Apartheid, the South African Government created and corrected agricultural factor and product market failures in its attempt to improve the distribution of wealth and incorporate previously disadvantaged farmers into the mainstream of agricultural activities. Some commercial farmers responded strategically to the new equity-based policies on factor and product markets by initiating equity-schemes with farm workers in order to maintain/increase their profits given the new local economic and political environment and global competition. Hence, most equity-schemes are organized according to the commercial farmers' capacities. The purpose of this paper is to analyze the organizational structure of the equity-schemes as a function of the commercial farmers strategy (production vs. marketing). This study is based on interviews of emerging farmers, former and present farm workers, commercial farmers, non-Governmental Organizations and Governmental agencies. The results show that equity-schemes tend to benefit commercial farmers but the degree to which farm workers' gain access to factor and product markets depends on commercial farmers' strategy. Then, the paper assesses alternative organizational structures of equity-schemes to maximize the benefits delivered to farm workers. Finally, utilizing the Peterson-Wysocki-Harsh Model, the issues of why the Government policies have not accomplished its objectives are discussed and recommendations to broaden the implementation of equity-schemes are suggested.Farm Management, Labor and Human Capital,

Interactions with water of mixed acetic-fatty cellulose esters

Cellulose powder was acylated with mixtures containing acetic, fatty and acetic-fatty anhydrides to form acetic-fatty cellulose esters. The total degree of substitution (DS) of the mixed cellulose esters (MCE) ranged from 2x10-2 to 2.92. MCE were characterized by their interactions with water. Static contact angles with water were measured on a regular smooth surface. The values found were dependent on the fatty acyl content and independent of the acetyl content. In the case of acetic-oleic cellulose esters, the minimum DS of the oleoyl moiety required to obtain permanent water repellency was 3x10-4. The microporosity of the samples may account for this exceptional hydrophobic character. Nevertheless, water vapor adsorption measurements on powder samples revealed only a limited increase in hydrophobicity of the MCE compared to cellulose acetate with the same acetyl content. It was thus demonstrated that water repellency and vapor water adsorption are not correlated

Determination of the degree of substitution (DS) of mixed cellulose esters by elemental analysis

Equations for transforming the results of elemental analysis (EA) into degree of substitution (DS) values for aliphatic cellulose esters were developed. The equations allow to determine the DS of cellulose derivatives bearing not only one but also two different acyl substituents. Error transmission studies revealed that the accuracy of the DS-values for a pure sample depends on both the number of carbon atoms in the substituents and on the uncertainty of the EA, especially from the hydrogen content. This method provides accurate DS-values (± 0.10 in most cases) if H-content determinations are within ± 0.1

Bi-acylation of cellulose: determining the relative reactivities of the acetyl and fatty-acyl moieties

The global reaction between acetic anhydride and a fatty acid yields, at equilibrium, an asymmetric acetic-aliphatic anhydride in a medium containing finally: acetic-fatty anhydride, acetic anhydride, fatty acid, acetic acid and fatty anhydride. No solvent or catalyst was used to evaluate the impact of the actual reactivity of the anhydrides. The competition between the formation of acetyl and fatty acyl ester functions was evaluated by determining the ratio of acetyl/fatty acyl groups grafted on solid cellulose. The influence of temperature, reaction time, and length of fatty chain on the total degree of substitution and on the ratio of acetyl/fatty acyl ester functions was investigated. For the first time, a correlation has been established between esterification and the length of the aliphatic chain of the fatty acid. Reactivity of the medium decreased with the number of carbons in the fatty acid, raised to the power 2.37

Construction of meanings related to violent contents of video games in children aged 11 to 14

Este estudio forma parte de la línea de investigación Violencia y medios de Comunicación de la Facultad de Psicología de la Uiversidad de la Sabana. Se propuso como objetivo conocer los significados que construyen los niños frente a los contenidos violentos de los videojuegos. Los participantes fueron cuatro niños de 11 a 14 años de edad de dos colegios públicos del municipio de Chía (Colombia). Se utilizó un método de carácter descriptivo explicativo con enfoque cualitativo. La estrategia empleada fue el estudio de caso único en donde a partir de la narrativa de los participantes se analizaron los significados que construyen frente a temas como el reconocimiento de la violencia, la percepción del conflicto y la resolución del mismo, la identidad de género, la relación entre familia y videojuegos, y el poder en los videojuegos. La información fue recogida a través de grupos focales, y analizada a partir de la propuesta de Strauss y Corbin. (2002). Los resultados obtenidos demuestran que existe relación entre los contenidos violentos de los videojuegos y la construcción de significados que realizan los participantes del grupo focal, lo que señala la influencia que tienen los videojuegos como generadores de valores, creencias y significados en los niños.This project was part of the research line entitled Violence and the Media developed by the Faculty of Psychology of the Universidad de la Sabana. , The aim of the study was to enquire about the meaning that children give to violent contents of videogames. Participants were four children between the ages of 11 and 14, who attended public schools in the village of Chía (Colombia). The research had a qualitative approach and used a descriptive-explanatory method, adopting the single-case study strategy. Based on the participants narratives an analysis was made of the meanings that children gave to topics such as recognition of violence, conflict perception, conflict resolution, gender identity, relationship between family and videogames and the power of videogames. Data were collected through the use of Focus Groups and analyzed according to Strauss and Corbin s theory (2002). Results show that there is a relationship between the violent contents of videogames and the meaning given to them by the participants in the focus group. This underlines the influence that videogames have on the development of values and beliefs in children

Optimal estimation for discrete time jump processes

Optimum estimates of nonobservable random variables or random processes which influence the rate functions of a discrete time jump process (DTJP) are obtained. The approach is based on the a posteriori probability of a nonobservable event expressed in terms of the a priori probability of that event and of the sample function probability of the DTJP. A general representation for optimum estimates and recursive equations for minimum mean squared error (MMSE) estimates are obtained. MMSE estimates are nonlinear functions of the observations. The problem of estimating the rate of a DTJP when the rate is a random variable with a probability density function of the form cx super K (l-x) super m and show that the MMSE estimates are linear in this case. This class of density functions explains why there are insignificant differences between optimum unconstrained and linear MMSE estimates in a variety of problems

Las tecnologías de información y comunicación en el contexto de los desequilibrios regionales de la República Argentina

From the last years of the XX century, several changes — politics, economics, social and technologic — conjectured the start a new model of society, where the technologies of information and communication — protagonists of the informational revolution — had a central place. In front of this phenomenon, we wonder: what characteristics have the process of incorporation of these technologies in Argentina, a country whit a high heterogeneity (different in structure and size) and territorial inequality (level of development)? To answer this question we approach at this issue watching that the advancement of these technologies reproduces the patron of unequal development previously existent in this country.Desde las últimas décadas del siglo XX una serie de cambios políticos, económicos, sociales y tecnológicos auguran la llegada de un nuevo modelo de sociedad, donde, las tecnologías de información y comunicación, protagonistas de la revolución informacional, ocupan un lugar central. Frente a este fenómeno nos preguntamos: ¿Qué características asumen los procesos de incorporación de estas tecnologías en la Argentina, un país con una marcada heterogeneidad (diferencias en características y tamaños relativos) y desigualdad (nivel de desarrollo) territorial? Buscando responder estos interrogantes nos acercamos al tema observando que el despliegue de estas tecnologías reproducía el patrón de desarrollo desigual existente en el país