Esterification of oleic acid catalayzed by an Aspergillus niger strain. Influence of water activity and alcohol concentration

Effects of water activity and 1-propanol concentration on synthesis of propyl oleate from oleic acid using Aspergillus niger cell-bound lipases in isooctane are described. A. niger produces lipases (EC 3.1.1.3) which partly bind to the mycelium during growth. Ester production was monitored for 72 hours at different 1-propanol concentrations and water activities. Aliquots were sequentially withdrawn and propyl esters were quantified using GC and methyl palmitate as an internal standard. In all assayed conditions A. niger cell-bound lipases catalysed propyl oleate synthesis, but at different degrees.

Internal promotion versus external recruitment: evidence in industrial plants

An analysis is carried out in a sample of 738 industrial plants of the determining factors in the use of internal promotion of blue-collar workers to middle managers and skilled technicians as against their external recruitment. The use of internal promotion is positively correlated with variables indicative of the efforts made by plants to measure employees' skills, and to a lesser extent, with the level of specificity of investments in human capital made by blue-collar workers. Contrary to what was expected, variables related with the use and efficiency of other incentive systems have no significant influence on the increased or decreased use of internal promotion. These results are initial evidence that internal promotions are used to protect and favour specific investments, especially those made by firms in order to discover their workers' skills.

La Industrialización en Cataluña: un balance historiográfico

Este trabajo constituye una breve presentación del caso de la industrialización de Cataluña en los siglos XIX y XX y, asimismo, una primera valoración crítica de las aportaciones de las dos últimas décadas al estudio histórico de la industria catalana, a partir de un anterior balance historiográfico realizado por el autor veinte años atrás. Esta revisión no se plantea desde una perspectiva pluridisciplinar, sino a partir de un enfoque especializado de Historia Económica. El hecho industrial ha mantenido una gran influencia durante los dos últimos siglos en todos esos ángulos de la vida social de Cataluña y en muchos más, desde el arte a la literatura o al deporte. La historia contemporánea catalana ha sido modelada en gran parte por la fuerte presencia de la industria. Pero en las secciones que siguen se ensaya, exclusivamente, una medida aproximada de la obra realizada, y de algunas tareas por hacer, con la caja de instrumentos propia de la ciencia económica desde una perspectiva histórica.

Mergers, investment decisions and internal organisation

We analyse the effects of investment decisions and firms' internal organisation on the efficiency and stability of horizontal mergers. In our framework economies of scale are endogenous and there might be internal conflict within merged firms. We show that often stable mergers do not lead to more efficiency and may even lead to efficiency losses. These mergers lead to lower total welfare, suggesting that a regulator should be careful in assuming that possible efficiency gains of a merger will be effiectively realised. Moreover, the paper offers a possible explanation for merger failures.

A general construction of internal sheaves in algebraic set theory

We present a solution to the problem of defining a counterpart in Algebraic Set Theory of the construction of internal sheaves in Topos Theory. Our approach is general in that we consider sheaves as determined by Lawvere-Tierney coverages, rather than by Grothen-dieck coverages, and assume only a weakening of the axioms for small maps originally introduced by Joyal and Moerdijk, thus subsuming the existing topos-theoretic results.

Optimal exponent heat balance and refined integral methods applied to Stefan problems

When using a polynomial approximating function the most contentious aspect of the Heat Balance Integral Method is the choice of power of the highest order term. In this paper we employ a method recently developed for thermal problems, where the exponent is determined during the solution process, to analyse Stefan problems. This is achieved by minimising an error function. The solution requires no knowledge of an exact solution and generally produces significantly better results than all previous HBI models. The method is illustrated by first applying it to standard thermal problems. A Stefan problem with an analytical solution is then discussed and results compared to the approximate solution. An ablation problem is also analysed and results compared against a numerical solution. In both examples the agreement is excellent. A Stefan problem where the boundary temperature increases exponentially is analysed. This highlights the difficulties that can be encountered with a time dependent boundary condition. Finally, melting with a time-dependent flux is briefly analysed without applying analytical or numerical results to assess the accuracy.

Application of standard and refined heat balance integral methods to one-dimensional Stefan problems

The work in this paper concerns the study of conventional and refined heat balance integral methods for a number of phase change problems. These include standard test problems, both with one and two phase changes, which have exact solutions to enable us to test the accuracy of the approximate solutions. We also consider situations where no analytical solution is available and compare these to numerical solutions. It is popular to use a quadratic profile as an approximation of the temperature, but we show that a cubic profile, seldom considered in the literature, is far more accurate in most circumstances. In addition, the refined integral method can give greater improvement still and we develop a variation on this method which turns out to be optimal in some cases. We assess which integral method is better for various problems, showing that it is largely dependent on the specified boundary conditions.

Fiscal policy, foresight and the trade balance in the U.S.

This paper investigates the effects of fiscal policy on the trade balance using a structural factor model. A fiscal policy shock worsens the trade balance and produces an appreciation of the domestic currency but the effects are quantitatively small. The findings match the theoretical predictions of the standard Mundell-Fleming model, although fiscal policy should not be considered one of the main causes of the large US external deficit. My conclusions differ from those reached using VAR models since the fiscal shock, possibly due to fiscal foresight, is nonfundamental for the variables typically used in open economy VARs.

Improving the accuracy of heat balance integral methods applied to thermal problems with time dependent boundary conditions

In this paper the two main drawbacks of the heat balance integral methods are examined. Firstly we investigate the choice of approximating function. For a standard polynomial form it is shown that combining the Heat Balance and Refined Integral methods to determine the power of the highest order term will either lead to the same, or more often, greatly improved accuracy on standard methods. Secondly we examine thermal problems with a time-dependent boundary condition. In doing so we develop a logarithmic approximating function. This new function allows us to model moving peaks in the temperature profile, a feature that previous heat balance methods cannot capture. If the boundary temperature varies so that at some time t & 0 it equals the far-field temperature, then standard methods predict that the temperature is everywhere at this constant value. The new method predicts the correct behaviour. It is also shown that this function provides even more accurate results, when coupled with the new CIM, than the polynomial profile. Analysis primarily focuses on a specified constant boundary temperature and is then extended to constant flux, Newton cooling and time dependent boundary conditions.

Institutional Balance in the EU. The Prodi Administration as a Reforming Commission

The essay looks at the Prodi Commission (1999-2004) in the context of the institutional balance in the European Union. Not only did Prodi come into office at a time of unprecedented weakness of the Executive, but the Commission operates within a changing institutional equilibrium, one made more precarious by the shifting political disposition of the Member States

Efectos en el balance de ácidos grasos y el metabolismo lipídico

En edades prematuras el cerdo tiene unos niveles de engrasamiento muy bajos y durante su crecimiento aumenta su contenido en proteína, hueso y masa grasa. Mientras que la deposición proteica viene determinada en gran medida por la capacidad genética, la deposición grasa depende de la ingesta energética.