Effects of both ecdysone and the acclimation to low temperature, on growth and metabolic rate of juvenile freshwater crayfish Cherax quadricarinatus (Decapoda, Parastacidae)

Growth, metabolic rate, and energy reserves of Cherax quadricarinatus (von Martens, 1868) juveniles were evaluated in crayfish acclimated for 16 weeks to either 25ºC (temperature near optimum) or 20ºC (marginal for the species). Additionally, the modulating effect of ecdsyone on acclimation was studied. After 12 weeks of exposure, weight gain of both experimental groups acclimated to 25ºC (control: C25, and ecdysone treated: E25) was significantly higher than that of those groups acclimated to 20ºC (C20 and E20). A total compensation in metabolic rate was seen after acclimation from 25ºC to 20ºC; for both the control group and the group treated with ecdysone. A Q10value significantly higher was only observed in the group acclimated to 20ºC and treated with ecdysone. A reduction of glycogen reserves in both hepatopancreas and muscle, as well as a lower protein content in muscle, was seen in both groups acclimated to 20ºC. Correspondingly, glycemia was always higher in these groups. Increased lipid levels were seen in the hepatopancreas of animals acclimated to 20ºC, while a higher lipid level was also observed in muscle at 20ºC, but only in ecdysone-treated crayfish.

Linear stochastic differential algebraic equations with constant coefficients

We consider linear stochastic differential-algebraic equations with constant coefficients and additive white noise. Due to the nature of this class of equations, the solution must be defined as a generalised process (in the sense of Dawson and Fernique). We provide sufficient conditions for the law of the variables of the solution process to be absolutely continuous with respect to Lebesgue measure.

Growth of positive words and lower bounds of the growth rate for Thompson's group (F)p

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Collusion in growing and shrinking markets: empirical evidence from experimental duopolies

We study collusive behaviour in experimental duopolies that compete in prices under dynamic demand conditions. In one treatment the demand grows at a constant rate. In the other treatment the demand declines at another constant rate. The rates are chosen so that the evolution of the demand in one case is just the reverse in time than the one for the other case. We use a box-design demand function so that there are no issues of finding and co-ordinating on the collusive price. Contrary to game-theoretic reasoning, our results show that collusion is significantly larger when the demand shrinks than when it grows. We conjecture that the prospect of rapidly declining profit opportunities exerts a disciplining effect on firms that facilitates collusion and discourages deviation.

Interest rate determination in the interbank market

The purpose of this paper is to study the determinants of equilibrium in the market for daily funds. We use the EONIA panel database which includes daily information on the lending rates applied by contributing commercial banks. The data clearly shows an increase in both the time series volatility and the cross section dispersion of rates towards the end of the reserve maintenance period. These increases are highly correlated. With respect to quantities, we find that the volume of trade as well as the use of the standing facilities are also larger at the end of the maintenance period. Our theoretical model shows how the operational framework of monetary policy causes a reduction in the elasticity of the supply of funds by banks throughout the reserve maintenance period. This reduction in the elasticity together with market segmentation and heterogeneity are able to generate distributions for the interest rates and quantities traded with the same properties as in the data.

The behavior of money velocity in low and high inflation countries

This paper presents a general equilibrium model of money demand where the velocity of money changes in response to endogenous fluctuations in the interest rate. The parameter space can be divided into two subsets: one where velocity is constant as in standard cash-in-advance models, and another one where velocity fluctuates as in Baumol (1952). The model provides an explanation of why, for a sample of 79 countries, the correlation between the velocity of money and the inflation rate appears to be low, unlike common wisdom would suggest. The reason is the diverse transaction technologies available in different economies.

Marx's analysis of the falling rate of profit on the first version of volume III of capital

The paper provides a description and analysis of the Hodgskin section of Theories of Surplus Value and the general law section of the first version of Volume III of Capital. It then considers Part III of Volume III, the evolution of Marx's thought and various interpretations of his theory in the light of this analysis. It is suggested that Marx thought that the rate of profit must fall and even in the 1870s hoped to be able to provide a demonstration of this. However the main conclusions are: 1. Marx's major attempt to show that the rate of profit must fall occurred in the general law section. 2. Part III does not contain a demonstration that the rate of profit must fall. 3. Marx was never able to demonstrate that the rate of profit must fall and he was aware of this.

How tight should one's hands be tied? Fear of floating and credibility of exchange rate regimes

This paper analyzes the linkages between the credibility of a target zone regime, the volatility of the exchange rate, and the width of the band where the exchange rate is allowed to fluctuate. These three concepts should be related since the band width induces a trade-off between credibility and volatility. Narrower bands should give less scope for the exchange rate to fluctuate but may make agents perceive a larger probability of realignment which by itself should increase the volatility of the exchange rate. We build a model where this trade-off is made explicit. The model is used to understand the reduction in volatility experienced by most EMS countries after their target zones were widened on August 1993. As a natural extension, the model also rationalizes the existence of non-official, implicit target zones (or fear of floating), suggested by some authors.

Current Account imbalances, thriftiness and the real exchange rate in a growing economy

This paper analyses the theoretical relevance of the dynamical aspects of growth on the discussion about the observed positive correlation between per capita real income and real exchange rates. With this purpose, we develop a simple exogenous growth model where the internal, external and intertemporal equilibrium conditions of a typical macroeconomic model are imposed; this last one through the inclusion of a balanced growth path for the foreign assets accumulation. The main result under this consideration is that the relationship defended by the Balassa-Samuelson hypothesis is no more so straightforward. In our particular approach, the mentioned bilateral relationship depends on a parameter measuring thriftiness in the economy. Therefore, the probability of ending up with a positive relationship between growth and real exchange rates -as the classical economic theory predicts- will be higher when the economy is able to maintain a minimum saving ratio. Moreover, given that our model considers a simple Keynesian consumption function, some explosive paths can also be possible.

A Descriptive and analytic look at Marx's own explanations of the falling rate of profit (second version)

This paper examines, both descriptively and analytically, Marx's arguments for the falling rate of profit from the Hodgskin section of Theories of Surplus Value, The General Law section of the recently published Volume 33 of the Collected Works and Chapter 3 of Volume III of Capital. The conclusions are as follows: First, Marx realised that his main attempt to give an intrinsic explanation of the falling rate of profit, which occurred in the General Law section, had failed; but he still hoped that he would be able to demonstrate it in the future. Second, the Hodgskin and General Law sections contain a number of subsidiary explanations, mostly related to resource scarcity, some of which are correct. Third, Part III of volume III does not contain a demonstration of the falling rate of profit, but a description of the role of the falling rate of profit in capitalist development. Forth, it also contains suppressed references to resource scarcity. And finally, in Chapter 3 of Volume III, Marx says that it is resource scarcity that causes the fall in the rate of profit described in Part III of the same volume. The key to all these conclusions in the careful analysis of the General Law section.

On the choice of an exchange rate regime: target zones revisited

From the classical gold standard up to the current ERM2 arrangement of the European Union, target zones have been a widely used exchange regime in contemporary history. This paper presents a benchmark model that rationalizes the choice of target zones over the rest of regimes: the fixed rate, the free float and the managed float. It is shown that the monetary authority may gain efficiency by reducing volatility of both the exchange rate and the interest rate at the same time. Furthermore, the model is consistent with some known stylized facts in the empirical literature that previous models were not able to produce, namely, the positive relation between the exchange rate and the interest rate differential, the degree of non-linearity of the function linking the exchage rate to fundamentals and the shape of the exchange rate stochastic distribution.

A proposal for a new specification for a conditionally heteroskedastic variance model: the Quadratic Moving-Average Conditional Heteroskedasticity and an application to the D. Mark-U.S. dollar Exchange Rate

Ever since the appearance of the ARCH model [Engle(1982a)], an impressive array of variance specifications belonging to the same class of models has emerged [i.e. Bollerslev's (1986) GARCH; Nelson's (1990) EGARCH]. This recent domain has achieved very successful developments. Nevertheless, several empirical studies seem to show that the performance of such models is not always appropriate [Boulier(1992)]. In this paper we propose a new specification: the Quadratic Moving Average Conditional heteroskedasticity model. Its statistical properties, such as the kurtosis and the symmetry, as well as two estimators (Method of Moments and Maximum Likelihood) are studied. Two statistical tests are presented, the first one tests for homoskedasticity and the second one, discriminates between ARCH and QMACH specification. A Monte Carlo study is presented in order to illustrate some of the theoretical results. An empirical study is undertaken for the DM-US exchange rate.

A foundation model for marxian theories of the breakdown of capitalism

Marx and the writers that followed him have produced a number of theories of the breakdown of capitalism. The majority of these theories were based on the historical tendencies: the rise in the composition of capital and the share of capital and the fall in the rate of profit. However these theories were never modeled with main stream rigour. This paper presents a constant wage model, with capital, labour and land as factors of production, which reproduces the historical tendencies and so can be used as a foundation for the various theories. The use of Chaplygins theorem in the proof of the main result also gives the paper a technical interest.

A descriptive and analytic look at Marxs own explanations for the falling rate of profit

Marxs conclusions about the falling rate of profit have been analysed exhaustively. Usually this has been done by building models which broadly conform to Marxs views and then showing that his conclusions are either correct or, more frequently, that they can not be sustained. By contrast, this paper examines, both descriptively and analytically, Marxs arguments from the Hodgskin section of Theories of Surplus Value, the General Law section of the recently published Volume 33 of the Collected Works and Chapter 3 of Volume III of Capital. It also gives a new interpretation of Part III of this last work. The main conclusions are first, that Marx had an intrinsic explanation of the falling rate of profit but was unable to give it a satisfactory demonstration and second, that he had a number of subsidiary explanations of which the most important was resource scarcity. The paper closes with an assessment of the pedigree of various currents of Marxian thought on this issue.

A descriptive and analytic look at Marxs own explanations for the falling rate of profit (Long Version)

Marxs conclusions about the falling rate of profit have been analysed exhaustively. Usually this has been done by building models which broadly conform to Marxs views and then showing that his conclusions are either correct or, more frequently, that they can not be sustained. By contrast, this paper examines, both descriptively and analytically, Marxs arguments from the Hodgskin section of Theories of Surplus Value, the General Law section of the recently published Volume 33 of the Collected Works and Chapter 3 of Volume III of Capital. It also gives a new interpretation of Part III of this last work. The main conclusions are first, that Marx had an intrinsic explanation of the falling rate of profit but was unable to give it a satisfactory demonstration and second, that he had a number of subsidiary explanations of which the most important was resource scarcity. The paper closes with an assessment of the pedigree of various currents of Marxian thought on this issue.