Malthus and Ricardo on Economic Methodology

The paper is a comparative study of the methodologies of Malthus and Ricardo. Its claims are: (i) economic laws almost always admit of exceptions for Malthus; for Ricardo even contingent predictions allow no exception apart from random temporary variations; (ii) both rely on the prestigious Newtonian paradigm, while interpreting it according to two distinct methodological traditions (the one deriving from MacLaurin, the other from Priestley); (iii) the choice of stressing what happens during intervals or in permanent states leads to opposing definitions of the main problem of economic science in so far as equilibrium is always already given for Ricardo and is never given for Malthus; (iv) their use of the ambiguous notion of "tendency" leaves unclear for both the degree of predictive power with which theories are endowed; (v) what both share is the idea of a natural order and this idea is the source of both shortcomings and endless disagreement

Persuasion and Argument in the Malthus-Ricardo Correspondence

We reconstruct the text, that is, we analyse the development of the discussion between Malthus and Ricardo both in the correspondence and in published works, paying special attention to (a) the use of methodological statements, (b) some pragmatic features of the controversy, (c) considerations pertaining to the meta-level of the controversy (assessments of the status of the controversy, of ways of solving it, etc.); then, we reconstruct the co-text, that is, unpublished papers by each opponent that were not made available to the other, records of exchanges between each of these and third parties, etc.; thirdly, we describe the essential features of the context, focusing on events that influenced the course of the controversy; (iv) we draw lessons from our case study on the role of co-text and context, on pragmatic and semantic interpretation, and on "casts of mind”

The Unitarian Connection and Ricardo's Scientific Style

We reply to Philippe Depoortère’s paper “On Ricardo’s method: The Unitarian influence examined. Some comments on Cremaschi and Dascal’s article ‘Malthus and Ricardo on Economic Methodology’”. Depoortère asks two questions: (1) was Ricardo’s ‘conversion’ to Unitarianism sincere? (2) did Ricardo follow the methodologies of Priestley and Belsham? His answers are that he was a ‘religious skeptic’ and he was not an ‘empiricist’ like Priestley and Belsham. We reply that the sincerity of Ricardo’s religious beliefs is irrelevant since we start with the evidence that he was exposed for a long time to the intellectual influence of Belsham, primarily in matters of philosophy, and to deny this would imply a negative answer to a different question, namely, did Ricardo attend Unitarian meetings for 15 years? Then we reply that Ricardo inherited Belsham’s version of Newtonian methodology which omitted the fourth rule, that is the most anti-Cartesian and anti-systematic rule, and this has little to do with empiricism but instead with apriorism

Modulation of cardiac Ca2+ channels in Xenopus oocytes by protein kinase C

L-Type calcium channel was expressed in Xenopus laevis oocytes injected with RNAs coding for different cardiac Cu2+ channel subunits, or with total heart RNA. The effects of activation of protein kinase C (PKC) by the phorbol ester PMA (4β-phorbol 12-myristate 13-acetate) were studied. Currents through channels composed of the main (1) subunit alone were initially increased and then decreased by PMA. A similar biphasic modulation was observed when the 1 subunit was expressed in combination with 2/δ, β and/or γ subunits, and when the channels were expressed following injection of total rat heart RNA. No effects on the voltage dependence of activation were observed. The effects of PMA were blocked by staurosporine, a protein kinase inhibitor. β subunit moderated the enhancement caused by PMA. We conclude that both enhancement and inhibition of cardiac L-type Ca2+ currents by PKC are mediated via an effect on the 1 subunit, while the β subunit may play a mild modulatory role

Aspects of a Watermark Solution

Although watermarking is a relatively new technology, there are many ways of applying it on an electronic data set with the purpose of ensuring copyright integrity and authenticity of the electronic data. But, bearing in mind the evolution of information technology and of communication, a watermark may be the target of several attacks which aim at its robustness, its form and even at its removal. In order to reduce these threats, this paper proposes a solution - digital watermarking completed by a hash function which has an important role in the authenticity of the content of a message and in the security of the transmission of this message through computer networks which are the main support of collaborative systems.Digital Watermarking, Hash Functions, Digital Information Security, Collaborative Systems

Las imágenes culinarias como metonimia del deseo y la sensualidad en el Libro de Buen Amor : Un aporte a la comprensión de la cultura de la España medieval

El presente trabajo plantea una línea de lectura en torno a uno de los aspectos más remarcables en la obra maestra de Juan Ruiz: las referencias a la cocina medieval española. Se analizarán las apariciones de los alimentos en el texto en cuanto a su contexto histórico y la narración, haciendo uso bibliográfico de obras pertenecientes a Lida de Malkiel, A. D. Deyermond y J. Le Goff, etc. La importancia de las referencias culinarias se aprecia por medio de tres factores: primero, los alimentos juegan un rol indispensable para la configuración del relato. Segundo, la imaginería y simbología culinaria significan un aporte sensorial y estético. Finalmente, las descripciones poseen valor histórico: el Arcipreste, mientras expone una amplia galería de oficios, nos ofrece un menú de España, ilustrando las representaciones culturales de la época

A G protein-gated K channel is activated via beta 2-adrenergic receptors and G beta gamma subunits in Xenopus oocytes

In many tissues, inwardly rectifying K channels are coupled to seven- helix receptors via the Gi/Go family of heterotrimeric G proteins. This activation proceeds at least partially via G beta gamma subunits. These experiments test the hypothesis that G beta gamma subunits activate the channel even if released from other classes of heterotrimeric G proteins. The G protein-gated K channel from rat atrium, KGA/GIRK1, was expressed in Xenopus oocytes with various receptors and G proteins. The beta 2-adrenergic receptor (beta 2AR), a Gs-linked receptor, activated large KGA currents when the alpha subunit, G alpha s, was also overexpressed. Although G alpha s augmented the coupling between beta 2AR and KGA, G alpha s also inhibited the basal, agonist-independent activity of KGA. KGA currents stimulated via beta 2AR activated, deactivated, and desensitized more slowly than currents stimulated via Gi/Go-linked receptors. There was partial occlusion between currents stimulated via beta 2AR and the m2 muscarinic receptor (a Gi/Go-linked receptor), indicating some convergence in the mechanism of activation by these two receptors. Although stimulation of beta 2AR also activates adenylyl cyclase and protein kinase A, activation of KGA via beta 2AR is not mediated by this second messenger pathway, because direct elevation of intracellular cAMP levels had no effect on KGA currents. Experiments with other coexpressed G protein alpha and beta gamma subunits showed that (a) a constitutively active G alpha s mutant did not suppress basal KGA currents and was only partially as effective as wild type G alpha s in coupling beta 2AR to KGA, and (b) beta gamma subunits increased basal KGA currents. These results reinforce present concepts that beta gamma subunits activate KGA, and also suggest that beta gamma subunits may provide a link between KGA and receptors not previously known to couple to inward rectifiers

The roles of the subunits in the function of the calcium channel

Dihydropyridine-sensitive voltage-dependent L-type calcium channels are critical to excitation-secretion and excitation-contraction coupling. The channel molecule is a complex of the main, pore-forming subunit alpha 1 and four additional subunits: alpha 2, delta, beta, and gamma (alpha 2 and delta are encoded by a single messenger RNA). The alpha 1 subunit messenger RNA alone directs expression of functional calcium channels in Xenopus oocytes, and coexpression of the alpha 2/delta and beta subunits enhances the amplitude of the current. The alpha 2, delta, and gamma subunits also have pronounced effects on its macroscopic characteristics, such as kinetics, voltage dependence of activation and inactivation, and enhancement by a dihydropyridine agonist. In some cases, specific modulatory functions can be assigned to individual subunits, whereas in other cases the different subunits appear to act in concert to modulate the properties of the channel

Expression of an atrial G-protein-activated potassium channel in Xenopus oocytes

Injection of rat atrial RNA into Xenopus oocytes resulted in the expression of a guanine nucleotide binding (G) protein-activated K+ channel. Current through the channel could be activated by acetylcholine or, if RNA encoding a neuronal 5HT1A receptor was coinjected with atrial RNA, by serotonin (5HT). A 5HT-evoked current (I5HT) was observed in oocytes injected with ventricle RNA fractions (of 2.5-5.5 kb) and 5HT1A receptor RNA. I5HT displayed strong inward rectification with very little conductance above the K+ equilibrium potential, was highly selective for K+ over Na+, and was blocked by 5-300 µM Ba2+. I5HT was suppressed by intracellular injection of the nonhydrolyzable analog of GDP, guanosine 5'-[ß-thio]diphosphate, but not by treatment with pertussis toxin (PTX), suggesting coupling of the receptor to the G-protein-activated K+ channel via a PTX-insensitive G protein, possibly endogenously present in the oocyte. Coexpression of the subunit of a PTX-sensitive G protein, Gi2, rendered I5HT sensitive to PTX inhibition. Native oocytes displayed a constitutively active inwardly rectifying K+ current with a lower sensitivity to Ba2+ block; expression of a similar current was also directed by atrial or ventricle RNA of 1.5-3 kb. Xenopus oocytes may be employed for cloning of the G-protein-activated K+ channel cDNA and for studying the coupling between this channel and G proteins