The rational reconstruction of the research program on classic rationalism: Locke and the empiricist approach

This article intends to rationally reconstruct Locke`s theory of knowledge as incorporated in a research program concerning the nature and structure of the theories and models of rationality. In previous articles we argued that the rationalist program can be subdivided into the classical rationalistic subprogram, which includes the knowledge theories of Descartes, Locke, Hume and Kant, the neoclassical subprogram, which includes the approaches of Duhem, Poincare and Mach, and the critical subprogram of Popper. The subdivision results from the different views of rationality proposed by each one of these subprograms, as well as from the tools made available by each one of them, containing theoretical instruments used to arrange, organize and develop the discussion on rationality, the main one of which is the structure of solution of problems. In this essay we intend to reconstruct the assumptions of Locke`s theory of knowledge, which in our view belongs to the classical rationalistic subprogram because it shares with it the thesis of the identity of (scientific) knowledge and certain knowledge.

The stability of the equilibrium outcomes in the admission games induced by stable matching rules

A stable matching rule is used as the outcome function for the Admission game where colleges behave straightforwardly and the students` strategies are given by their preferences over the colleges. We show that the college-optimal stable matching rule implements the set of stable matchings via the Nash equilibrium (NE) concept. For any other stable matching rule the strategic behavior of the students may lead to outcomes that are not stable under the true preferences. We then introduce uncertainty about the matching selected and prove that the natural solution concept is that of NE in the strong sense. A general result shows that the random stable matching rule, as well as any stable matching rule, implements the set of stable matchings via NE in the strong sense. Precise answers are given to the strategic questions raised.

Thoracic vibrations in stingless bees (Melipona seminigra): resonances of the thorax influence vibrations associated with flight but not those associated with sound production

Bees generate thoracic vibrations with their indirect flight muscles in various behavioural contexts. The main frequency component of non-flight vibrations, during which the wings are usually folded over the abdomen, is higher than that of thoracic vibrations that drive the wing movements for flight. So far, this has been concluded from an increase in natural frequency of the oscillating system in association with the wing adduction. In the present study, we measured the thoracic oscillations in stingless bees during stationary flight and during two types of non-flight behaviour, annoyance buzzing and forager communication, using laser vibrometry. As expected, the flight vibrations met all tested assumptions for resonant oscillations: slow build-up and decay of amplitude; increased frequency following reduction of the inertial load; and decreased frequency following an increase of the mass of the oscillating system. Resonances, however, do not play a significant role in the generation of non-flight vibrations. The strong decrease in main frequency at the end of the pulses indicates that these were driven at a frequency higher than the natural frequency of the system. Despite significant differences regarding the main frequency components and their oscillation amplitudes, the mechanism of generation is apparently similar in annoyance buzzing and forager vibrations. Both types of non-flight vibration induced oscillations of the wings and the legs in a similar way. Since these body parts transform thoracic oscillations into airborne sounds and substrate vibrations, annoyance buzzing can also be used to study mechanisms of signal generation and transmission potentially relevant in forager communication under controlled conditions.

Integrability and exact solution of an electronic model with long range interactions

We present an electronic model with long range interactions. Through the quantum inverse scattering method, integrability of the model is established using a one-parameter family of typical irreducible representations of gl(211). The eigenvalues of the conserved operators are derived in terms of the Bethe ansatz, from which the energy eigenvalues of the Hamiltonian are obtained.

Females of the weevil Zabrotes subfasciatus manipulate the size and number of eggs according to the host seed availability

In some insects, the finding of oviposition substrate triggers the uptake into oocytes of yolk proteins that are stored in the fat body during post-embryonic development. The main host of the bean weevil Zabrotes subfasciatus (Coleoptera; Chrysomelidae; Bruchinae; Amblycerini), in which larval resources are the sole source for future egg maturation, is Phaseolus vulgaris. Despite not feeding as adults, females of this species are able to lay eggs after encountering host seeds but it is not known how females react to changes in the availability of bean seeds. In the present study, the behaviour of Z. subfasciatus facing two very different environments for oviposition is investigated, as well as how this influences offspring fitness. The results obtained show that females of Z. subfasciatus react to variations in the availability of seeds belonging to the same host species by adjusting egg size and number. Females on low bean seed density lay larger and fewer eggs than those on high bean seed density, demonstrating a trade-off between these reproductive traits. Moreover, females can adjust egg size to changing levels of host availability during the first 4 days of their oviposition period. Although no difference in offspring weight is found, those from small eggs (low competition environment) result in larger adults. No response to selection on these traits after rearing beetles on the same host for 40 generations is observed. This unresponsiveness may indicate that beetle populations behave according to their reaction norm that already allows rapid adaptation to a varying amount of host-seed availability and better exploitation of the environments of this widespread stored-seed pest.

Impedance characteristics of the diamond/carbon fiber electrodes for electrical double-layer capacitor

The electrochemical performance of carbon fibers (CF) and boron-doped diamond electrodes grown on carbon fiber substrate (BDD/CF) was studied. CF substrates were obtained from polyacrylonitrile precursor heat treated at two different temperatures of 1000 and 2000 degrees C to produce the desirable CF carbon graphitization index. This graphitization process influenced the CF conductivity and its chemical surface, also analyzed from X-ray photoelectron spectroscopy measurements. These three-dimensional CF structures allowed a high incorporation of diamond films compared to other carbon substrates such as glass carbon or HOPG. The electrochemical responses, from these four classes of electrodes, were evaluated focusing their application as electrical double-layer capacitors using cyclic voltammetry and impedance measurements. Cyclic voltammetry results revealed that the electrode formed from BDD grown on CF-2000 presented a typical capacitor behavior with the best rectangular shape, compared to those electrodes of CF or BDD/CF-1000. Furthermore, the BDD/CF-2000 electrode presented the lowest impedance, associated to its significant capacitance value of 1940 mu F/cm(2) taking into account the BDD films. This behavior was attributed to the strong dependence between diamond coating texture and the CF graphitization temperature. The largest surface area of BDD/CF-2000 was promoted by its singular film growth mechanism associated to the substrate chemical surface. (c) 2008 Elsevier B.V. All rights reserved.

Regulation by the exogenous polyamine spermidine of Na,K-ATPase activity from the gills of the euryhaline swimming crab Callinectes danae (Brachyura, Portunidae)

Euryhaline crustaceans rarely hyporegulates and employ the driving force of the Na,K-ATPase, located at the basal surface of the gill epithelium, to maintain their hemolymph osmolality within a range compatible with cell function during hyper-regulation. Since polyamine levels increase during the adaptation of crustaceans to hyperosmotic media, we investigate the effect of exogenous polyamines on Na,K-ATPase activity in the posterior gills of Callinectes danae, a euryhaline swimming crab. Polyamine inhibition was dependent on cation concentration, charge and size in the following order: spermine > spermidine > putrescine. Spermidine affected K-0.5 values for Na+ with minor alterations in K-0.5 values for K+ and N-H-4(+), causing a decrease in maximal velocities under saturating Na+, K+ and NH4+ concentrations. Phosphorylation measurements in the presence of 20 mu M ATP revealed that the Na,K-ATPase possesses a high affinity site for this substrate. In the presence of 10 mM Na+, both spermidine and spermine inhibited formation of the phosphoenzyme; however, in the presence of 100 mM Na+, the addition of these polyamines allowed accumulation of the phosphoenzyme. The polyamines inhibited pumping activity, both by competing with Na+ at the Na+-binding site, and by inhibiting enzyme dephosphorylation. These findings suggest that polyamine-induced inhibition of Na,K-ATPase activity may be physiologically relevant during migration to fully marine environments. (c) 2008 Elsevier Inc. All rights reserved.

Non-diagonal solutions of the reflection equation for the trigonometric A((1)) (n-1) vertex model

We obtain a class of non-diagonal solutions of the reflection equation for the trigonometric A(n-1)((1)) vertex model. The solutions can be expressed in terms of intertwinner matrix and its inverse, which intertwine two trigonometric R-matrices. In addition to a discrete (positive integer) parameter l, 1 less than or equal to l less than or equal to n, the solution contains n + 2 continuous boundary parameters.

Characterization of temperature dependent and substrate-binding cleft movements in Bacillus circulans family 11 xylanase: A molecular dynamics investigation

Background: Xylanases (EC 3.2.1.8) hydrolyze xylan, one of the most abundant plant polysaccharides found in nature, and have many potential applications in biotechnology. Methods: Molecular dynamics simulations were used to investigate the effects of temperature between 298 to 338 K and xylobiose binding on residues located in the substrate-binding cleft of the family 11 xylanase from Bacillus circulans (BcX). Results: In the absence of xylobiose the BcX exhibits temperature dependent movement of the thumb region which adopts an open conformation exposing the active site at the optimum catalytic temperature (328 K). In the presence of substrate, the thumb region restricts access to the active site at all temperatures, and this conformation is maintained by substrate/protein hydrogen bonds involving active site residues, including hydrogen bonds between Tyr69 and the 2` hydroxyl group of the substrate. Substrate access to the active site is regulated by temperature dependent motions that are restricted to the thumb region, and the BcX/substrate complex is stabilized by extensive intermolecular hydrogen bonding with residues in the active site. General significance: These results call for a revision of both the ""hinge-bending"" model for the activity of group 11 xylanases, and the role of Tyr69 in the catalytic mechanism. (C) 2009 Elsevier B.V. All rights reserved.

Effects of microinjections of apomorphine and haloperidol into the inferior colliculus on the latent inhibition of the conditioned emotional response

Electrical or chemical stimulation of the inferior colliculus (IC) induces fear-like behaviors. More recently, consistent evidence has shown that electrical stimulation of the central nucleus of the IC supports Pavlovian conditioning and latent inhibition (Li). LI is characterized by retardation in conditioning and also by an impaired ability to ignore irrelevant stimuli, after a non-reinforced pre-exposure to the conditioned stimulus. LI has been proposed as a behavioral model of cognitive abnormalities seen in schizophrenia. The aim of the present study was to determine whether dopaminergic mechanisms in the IC are involved in LI of the conditioned emotional response (CER). To induce LI, a group of rats was pre-exposed (PE) to six tones in two sessions, while rats that were not pre-exposed (NPE) had two sessions without tone presentations. The conditioning consisted of two tone presentations to the animal, followed immediately by a foot shock. PE and NPE rats received IC microinjections of physiological saline, the dopaminergic agonist apomorphine (9.0 mu g/0.5 mu L/side), or the dopaminergic antagonist haloperidol (0.5 mu g/0.5 mu L/side) before both pre-exposure and conditioning. During the test, the PE rats that received saline or haloperidol had a lower suppression of the licking response compared to NPE rats that received vehicle or haloperidol, indicating that latent inhibition was induced. There was no significant difference in the suppression ratio in rats that received apomorphine injections into the IC, indicating reduced latent inhibition. These results suggest that dopamine-mediated mechanisms of the IC are involved in the development of LI. (C) 2008 Elsevier Inc. All rights reserved.

Anxiety-like symptoms induced by morphine withdrawal may be due to the sensitization of the dorsal periaqueductal grey

Withdrawal from morphine leads to the appearance of extreme anxiety accompanied of several physical disturbances, most of them linked to the activation of brainstem regions such as the locus coeruleus, ventral tegmental area, hypothalamic nuclei and periaqueductal grey (PAG). As anxiety remains one of the main components of morphine withdrawal the present study aimed to evaluating the influence of the dorsal aspects of the PAG on the production of this state, since this structure is well-known to be involved in defensive behaviour elicited by anxiety-evoking stimuli. Different groups of animals were submitted to 10 days of i.p. morphine injections, challenged 2 h after with an i.p. injection of naloxone (0.1 mg/kg), and submitted to the plus-maze, open-field and light-dark transition tests. The effects of morphine withdrawal on anxiety-induced Fos immunolabelling were evaluated in four animals that passed by the light-dark transition test randomly chosen for Fos-protein analysis. Besides the PAG, Fos neural expression was conducted in other brain regions involved in the expression of anxiety-related behaviours. Our results showed that morphine withdrawn rats presented enhanced anxiety accompanied of few somatic symptoms. Increased Fos immunolabelling was noted in brain regions well-known to modulate these states as the prelimbic cortex, nucleus accumbens, amygdala and paraventricular hypothalamus. Increased Fos labelling was also observed in the ventral and dorsal aspects of the PAG, a region involved in anxiety-related processes suggesting that this region could be a common neural substrate enlisted during anxiety evoked by dangerous stimuli as well as those elicited by opiate withdrawal. (c) 2008 Elsevier Inc. All rights reserved,

Comparative Analysis of the Performance of Various Crystalloid Cardioplegic Solutions on Myocardial Protection After Prolonged Cold Ischemia

Introduction. The quality and effectiveness of myocardial protection are fundamental problems to expand the use of and consequently good outcomes of donated hearts for transplantation. Objective. The purpose of this investigation was to compare the cardioprotective effects of Krebs-Henseleit, Bretschneider-HTK, St Thomas, and Celsior solutions using a modified nonrecirculating Langendorff column model of isolated perfused rat heart during prolonged cold storage. Materials and Methods. After removal 36 rat hearts underwent isolated perfusion into a Langendorff apparatus using Krebs-Henseleit solution for a 15-minute period of recovery; we excluded organs that did not maintain an aortic pressure above 100 m Hg. Subsequently, we equally distributed the hearts into four groups according to the cardioprotection solution; group 1, Krebs-Henseleit (control); group II, Bretschneider-HTK; group III, St Thomas; and group IV, Celsior. Each heart received the specific cardioplegic solution at 10 C for 2-hour storage at 20 C, before a 15 minutes perfusion with Krebs-Henseleit solution for recovery and stabilization. After 60 additional minutes of perfusion, every 5 minutes we determined heart rate (HR), coronary flow (CF), left ventricular systolic pressure (LVSP), and positive and negative peak of the first derivative of left ventricular pressure (+dP/dt and dP/dt, respectively). Results. Comparative analysis by Turkey`s test showed the following performances among the groups at 60 minutes of reperfusion: HR: II = IV > III > I; CF: II = IV > I = III; LVSP: IV > I = II = III; +dP/dt: IV > I = II = III; and dP/dt: IV = II > I = II. Conclusion. Cardioprotective solutions generally used in clinical practice are not able to avoid hemodynamic alterations in hearts exposed to prolonged ischemia. Celsior solution showed better performance than Bretschneider-HTK, St Thomas, and Krebs-Henseleit.

Self-defocusing effects in an ethanol solution of chlorophyll

The thermally induced optical nonlinearity in a chlorophyll ethanol solution is examined. A theory is presented which shows good agreement with experiment. The theory models an optically thick but physically thin medium whose only heat transport mechanism is conduction. An average nz was found for the medium which corresponds well with previous results but the thermal medium is shown to be fundamentally different from a Kerr medium.

Bioactivation of Phenytoin by Human Cytochrome P450: Characterization of the Mechanism and Targets of Covalent Adduct Formation

The cytochrome P450-dependent covalent binding of radiolabel derived fi om phenytoin (DPH) and its phenol and catechol metabolites, 5-(4'-hydroxyphenyl)-5-phenylhydantoin (HPPH) and 5-(3',4'-dihydroxyphenyl)-5-phenylhydantoin (CAT), was examined in liver microsomes. Radiolabeled HPPH and CAT and unlabeled CAT were obtained from microsomal incubations and isolated by preparative HPLC. NADPH-dependent covalent binding was demonstrated in incubations of human liver microsomes with HPPH. When CAT was used as substrate, covalent adduct formation was independent of NADPH, was enhanced in the presence of systems generating reactive oxygen species, and was diminished under anaerobic conditions or in the presence of cytoprotective reducing agents. Fluorographic analysis showed that radiolabel derived from DPH and HPPH was selectively associated with proteins migrating with approximate relative molecular weights of 57-59 kDa and at the dye front (molecular weights < 23 kDa) on denaturing gels. Lower levels of radiolabel were distributed throughout the molecular weight range. In contrast, little selectivity was seen in covalent adducts formed from CAT. HPPH was shown to be a mechanism-based inactivator of P450, supporting the contention that a cytochrome P450 is one target of covalent binding. These results suggest that covalent binding of radiolabel derived from DPH in rat and human Liver microsomes occurs via initial P450-dependent catechol formation followed by spontaneous oxidation to quinone and semiquinone derivatives that ultimately react with microsomal protein. Targets for covalent binding may include P450s, though the catechol appears to be sufficiently stable to migrate out of the P450 active site to form adducts with other proteins. In conclusion, we have demonstrated that DPH can be bioactivated in human liver to metabolites capable of covalently binding to proteins. The relationship of adduct formation to DPH-induced hypersensitivity reactions remains to be clarified.

Down-regulation of the amyloid protein precursor of Alzheimer's disease by antisense oligonucleotides reduces neuronal adhesion to specific substrata

The hallmark of Alzheimer's disease is the cerebral deposition of amyloid which is derived from the amyloid precursor protein (APP). The function of APP is unknown but there is increasing evidence for the role of APP in cell-cell and/or cell-matrix interactions. Primary cultures of murine neurons were treated with antisense oligonucleotides to down-regulate APP. This paper presents evidence that APP mediates a substrate-specific interaction between neurons and extracellular matrix components collagen type I, laminin and heparan sulphate proteoglycan but not fibronectin or poly-L-lysine. It remains to be determined whether this effect is the direct result of APP-matrix interactions, or whether an intermediary pathway is involved. (C) 1997 Elsevier Science B.V.