bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interaction of Excitatory Amino Acid Agonists with Cortical Afterdischarges in Developing Rats
Authors: Mareš P. , Haugvicová R. , Kubová H. 
Published: March 2003

Summary:  Purpose: To determine the role of excitatory amino acids (EAAs) in genesis of two types of epileptic afterdischarges.Methods: Cortical stimulation and recording electrodes were implanted in 12‐, 18‐, and 25‐day‐old rats. Epileptic afterdischarges were induced by rhythmic stimulation of sensorimotor cortex. The stimulation was repeated 6 times with 20‐min intervals. Ten minutes after the first afterdischarge, N‐methyl‐d‐aspartate, homocysteine, or kainic acid was injected. The doses were chosen individually for different age groups to be subconvulsive. Type and duration of afterdischarges as well as type and severity of motor correlates were evaluated. Results: N
‐methyl‐
d
‐aspartate prolonged afterdischarges only in 12‐day‐old rats, whereas two other drugs did it in all age groups. Motor correlates of afterdischarges were changed to flexion seizures in 12‐day‐old rats after
N
‐methyl‐
d ‐aspartate and homocysteine; in 25‐day‐old rats homocysteine led to generalized tonic–clonic seizures (i.e., both patterns seen after substantially higher doses of these drugs in nonstimulated rats). Seizures lasted tens of minutes. Kainic acid did not change the motor pattern in any age group, but nonconvulsive EEG seizures were recorded in the interstimulation periods mainly in 18‐ and 25‐day‐old rats. Increased transition into the limbic type of afterdischarges appeared only after homocysteine in 18‐ and 25‐day‐old rats.Conclusions: A mutual potentiation of epileptic phenomena was induced by two agents. The actions of N‐methyl‐d‐aspartate and kainic acid differ in all age groups; the effects of homocysteine were identical with those of N‐methyl‐d‐aspartate in 12‐day‐old rats but not later. Only homocysteine augmented transition into the limbic type of afterdischarges.
Evidence That ATP Participates in the Pathophysiology of Pilocarpine‐Induced Temporal Lobe Epilepsy: A Fluorimetric, Immunohistochemical, and Western Blot Studies
Authors: Vianna E. P. M. , Ferreira A. T. , Naffah‐Mazzacoratti M. G. , Sanabria E. R. G. , Funke M. , Cavalheiro E. A. , Fernandes M. J. S. 
Published: March 2003

Summary:  Purpose: This study was performed to study the role of adenosine triphosphate (ATP) in the brain of pilocarpine‐induced chronic epileptic rats.Methods: ATP‐mediated changes in intracellular calcium were studied by the fura‐2 method. Immunohistochemistry and Western blotting methods were used to localize and quantify P2X7 receptors in these animals.Results: The fluorimetric study in chronic rats revealed a biphasic response indicating the presence of P2X7 receptors. The Western blotting study showed an increase of 80% of P2X7 expression in chronic rats compared with the control group. P2X7 immunoreactivity resembled mossy fiber sprouting at the dentate gyrus of epileptic animals.Conclusions: These results suggest that purinergic receptors may participate in the pathophysiology of temporal lobe epilepsy.
Dynamic Changes of Status Epilepticus‐Induced Neuronal Degeneration in the Mediodorsal Nucleus of the Thalamus During Postnatal Development of the Rat
Authors: Kubová H. , Druga R. , Haugvicová R. , Suchomelová L. , Pitkanen A. 
Published: March 2003

Summary:  Purpose: Status epilepticus (SE) was previously found to induce damage in the mediodorsal nucleus of the thalamus (MD) in both adult and immature rats. This study was designed to describe age‐related changes of SE‐induced neuronal degeneration in this part of the brain.Methods: SE was induced by LiCl/pilocarpine in five age groups of rats (P12–P25). Distribution of degenerating neurons was studied at various time intervals from 4 h up to 1 week using Fluoro Jade B (FJB) staining. For P12 and P25 rats, an interval of 3 months was added.Results: Damaged neurons were found in all age groups during a 1‐week period after SE. Patterns of neuronal degeneration, however, changed in an age‐related manner. In animals at P12 and P15, FJB‐labeled neurons were located in the central and lateral segment of the MD. In the P18 group, degenerating neurons occurred in all three segments of the MD, with a prevalence in central and lateral subdivisions. In contrast, in P21 and P25 rats, FJB‐labeled neurons were predominantly located in the central and medial segments. Degenerating neurons were still present 3 months after SE in the medial segment in P25 animals, whereas no labeled neurons were detected in the P12 group at this time.Conclusions: Our data demonstrate that the pattern of neuronal degeneration in MD is mainly related to age at SE onset. In addition to damage occurring during the acute phase of SE, a population of degenerating neurons was detected in P25 animals during the chronic period 3 months after SE.
Helicobacter pylori und nichtsteroidale Antirheumatika
Authors: Knoflach P. 
Published: March 2003

Zusammenfassung:Beobachtungen über die Wechselwirkungen zwischen den beiden wesentlichen Ursachen von gastroduodenalen Läsionen – Einnahme von nichtsteroidalen Antirheumatika (NSAR) und Infektion mit Helicobacter pylori (H.p.) – sind zum Teil noch kontroversiell. Dabei muss die H. p.‐Infektion nicht unbedingt einen additiv oder synergistisch schädigenden Effekt entfalten, sondern kann möglicherweise auch protektiv gegenüber der NSAR‐Wirkung auf die Schleimhaut sein. Daraus leiten sich spezifische therapeutische Strategien für verschiedene klinische Situationen ab.
Cerebrospinal‐Fluid Lactate in Adult Mitochondriopathy with and without Encephalopathy
Authors: Finsterer J. 
Published: March 2003

Summary: Despite improved diagnostic facilities, the diagnosis of mitochondriopathy (MCP) is sometimes difficult to establish. This study aimed to investigate whether CSF lactate can be of diagnostic help in this respect. Cerebrospinal‐fluid (CSF) lactate and its relation to resting lactate and lactate stress testing were investigated in 26 MCP patients, aged 30 – 84 years. The upper reference limit of CSF lactate, obtained from 28 healthy subjects, was 1.6 mmol/l. Seven MCP patients (27 %) had elevated CSF lactate. Five of these patients had central nervous system (CNS) abnormalities other than elevated CSF lactate. In two patients with increased cerebrospinal‐fluid lactate, lactate stress testing was normal or could not be carried out. In conclusion, CSF lactate is elevated in one quarter of adult MCP patients. CSF lactate is preferentially elevated in patients with additional CNS abnormalities other than elevated CSF lactate. If the results for resting lactate or lactate stress testing are normal or unavailable, determination of CSF lactate may be of diagnostic support in single cases.
Adhesively bonded joints under cyclic loading spectra
Authors: Jones R. , Kotousov A. , Marshall I. H. 
Published: March 2003

Abstract Current designs which involve the use of composite materials in primary aircraft structures are often conservative. This, in turn, significantly lowers the weight advantage that composites have over established metallic airframe materials. Strain restrictions are often applied because the failure mechanism(s) in (fibre) composite joints and stiffener runouts where the stress state is often complex, are not fully understood. Nevertheless, from the airworthiness perspective it is essential that both the static strength and the fatigue behaviour of the components subjected to complex multiaxial stress conditions are both understood and predicted. This topic is extremely complex, and numerous criteria ranging from the purely empirical to the theoretical have been proposed. In both cases, it is necessary to know the localised stress–strain history.One common design methodology is to keep the stresses so low that fatigue will not be an issue. However, this can lead to an overly conservative design. On the other hand, while a detailed (nonlinear) finite element analysis can be performed it is often both resource‐intensive and time‐consuming. The present paper shows that Glinka's hypothesis can be used in order to calculate the localised stresses and strains for a bonded joint subjected to cyclic loading.This is a new result and has not previously been noted. It has the potential to extend the Hart‐Smith design methodology to the adhesively bonded joints in order to encompass durability considerations. This formulation also raises the possibility of enabling the degree of conservatism inherent in traditional joint design to be relaxed provided that failure occurs in the adhesive.This paper also addresses the problem of variable adhesive thickness. We show that while variable adhesive thickness can change the stress and the energy fields, the peak in the strain energy density is relatively insensitive to the stress–strain relationship for the adhesive and that Glinka's hypothesis still appears to be true. This means that, for the present class of problems, even if there is variability in the thickness of the adhesive bond the energy field and, hence, the strength of the joint can be estimated from a purely linear elastic analysis of the joint, provided that failure occurs in the adhesive.
CEO pay, firm size, and corporate performance: evidence from Canada
Authors: Zhou Xianming 
Published: March 2003

Executive compensation of 755 Canadian firms is examined over the period 1991–95, and evidence is obtained consistent with previous studies: CEO pay rises with firm size and compensation is tied to company performance. In addition, executives in utilities earn lower pay, and their compensation is less responsive to performance, than is true for their counterparts in other industries. Some novel findings are also documented. First, the sales elasticity of CEO compensation is greater in larger firms. Second, while CEO turnover probability is generally negatively related to the firm's stock performance, the threat of dismissal appear to be less pronounced in small firms. JEL Classification: G35, J33 Salaire des PDG, taille de l'entreprise et performance des sociétés: résultats pour le Canada. En étudiant le salaire des PDG de 755 entreprises canadiennes au cours de la période 1991–95, l'auteur confirme certains résultats d'études antérieures: le salaire du PDG croît avec la taille de l'entreprise, et il est liéà la performance de l'entreprise. Il appert aussi que les cadres dans les entreprises de service public gagnent moins relativement parlant, et que leur salaire est moins sensible aux écarts de performance que dans les autres secteurs. On met aussi à jour certains résultats inédits. D'abord, il semble que l'élasticité du salaire du PDG par rapport au niveau des ventes est plus forte dans les plus grandes entreprises. Ensuite, alors que la probabilité de roulement est en général co‐reliée négativement à la performance des actions en bourse de l'entreprise, la menace de renvoi semble moins prononcée dans les petites entreprises.
On estimating the option value of preserving a wilderness area
Authors: Forsyth Margaret 
Published: March 2003

In this paper option pricing theory is used to analyse whether or not to preserve a wilderness area. A numerical approach is demonstrated that can be applied to any generalized stochastic process. The impact of assuming that amenity value follows a logistic process, rather than geometric Brownian motion, is considered. The calculation of critical levels for amenity value necessary to justify preserving a wilderness area such as the Killarney Provincial Park in Ontario or the Headwaters Forest in California is demonstrated. The impact of changing the assumed growth and volatility of amenity value is also examined. JEL Classifcation: D81 Q26Ce mémoire utilise la théorie de la tarification d'une option pour analyser si on doit préserver un espace naturel. On utilise une approche numérique qui peut être appliquée à tout processus stochastique généralisé. On examine l'impact de possibilités que le profil de la valeur de la ressource dans la temps suive un processus logistique plutôt qu'un pattern géométrique de type Brownien. Le texte montre le calcul des niveaux critiques de la valeur de la ressource qui seraient nécessaires pour justifier la préservation d'une espace naturel comme le parc provincial Killarney en Ontario ou les forêts Headwaters en Californie. L'impact de postulats différents quant à la croissance et à la volatilité de la valeur de la ressource est examiné.
Employment and child‐care choices in Canada and the United States
Authors: Michalopoulos Charles , Robins Philip K. 
Published: March 2003

In this paper we examine employment and child‐care choices of two‐parent families with young children in the United States and Canada, using a pooled data set based on recent national surveys in each country. We find that the employment and child‐care choices of Canadian families are similar to those of U.S. families. Estimates of a model of employment and child‐care choices indicate significant effects of child‐care subsidies, child‐care prices, and wage rates on employment and child‐care choices. However, none of these factors helps to explain the differences in employment and child‐care choices between the two countries.Ce mémoire examine le choix de l'emploi et du soin des enfants dans les familles où il y deux parents aux Etats‐Unis et au Canada en utilisant des données d'études récentes dans les deux pays. Il appert que les choix des familles canadiennes sont semblables à ceux des familles américaines. Les calibrations d'un modèle de ces choix montrent les effets significatifs des subventions au soin des enfants, du prix des soins des enfants, et des taux de salaires sur ces choix. Cependant, aucun de ces facteurs n'explique les diffrences dans les patterns de choix entre les deux pays.
Renewable resource management with environmental prediction
Authors: Costello Christopher , Polasky Stephen , Solow Andrew 
Published: March 2003

Variations in environmental conditions affect renewable resource growth. The ability to predict such variations is improving, providing scope for improved management. We generalize a common stochastic stock recruitment model to explore how optimal management changes with environmental prediction. We obtain three main results. First, while it might seem that a prediction of adverse future conditions should lead to more conservative management, the opposite may be true. Second, optimal management requires only a one‐period‐ahead forecast, suggesting forecast accuracy is more important than forecast lead time. Finally, we derive conditions on environmental fluctuations guaranteeing positive optimal harvest in every period. Gestion d'une ressource renouvelable quand on prédit les conditions futures de l'environnement. Les variations dans les conditions de l'environnement affectent la croissance de la ressource renouvelable. La capacitéà prévoir ces variations s'améliore et ouvre la possibilité d'améliorer la gestion de la ressource. Les auteurs utilisent un modèle de ressource renouvelable avec croissance stochastique et obtiennent trois résultats. D'abord, alors qu'il peut sembler que des prévisions pessimistes de conditions difficiles dans l'avenir peuvent conduire à une gestion plus conservatrice, le contraire peut être vrai. Ensuite, la gestion optimale requiert seulement une prédiction pour la prochaine période: voilà qui suggère qu'il est plus important d'avoir une prévision exacte que d'avoir des prévisions à plus long terme. Enfin, on développe les conditions pour les fluctuations de l'environnement qui garantissent une récolte positive optimale à chaque période.
Price discrimination and quality improvement
Authors: Glass Amy Jocelyn 
Published: March 2003

This paper models quality improvements when multiple quality levels can sell, owing to differences in consumers' valuations of quality improvements. Firms can collude to price discriminate, so that consumers with high valuations pay a price premium, while others receive a quality level below the highest available. Imposing minimum quality standards or price ceilings can ensure that only the highest quality level of each product is sold. Such intervention reduces the quality‐adjusted price paid by consumers but also reduces the incentives for firms to innovate. When enough consumers have high valuations, such intervention must be welfare reducing, owing to reduced innovation. JEL Classification: O31, L16 Discrimination par les prix et amélioration de la qualité. Ce mémoire présente un modèle d'amélioration de la qualité quand on peut vendre des produits à divers niveaux de qualitéà cause des différences dans les évaluations d'amélioration de qualité par les consommateurs. Les entreprises peuvent entrer en collusion pour faire de la discrimination par les prix de manière à ce que les consommateurs qui apprécient davantage la qualité paient une prime pendant que les autres consommateurs reçoivent une qualité au‐dessous de ce qui est la meilleure qualité disponible. Si on impose des normes de qualité minimale ou des plafonds aux prix, on peut s'assurer que seuls les produits de la plus haute qualité seront vendus. De telles interventions réduisent le niveau de prix ajusté pour la qualité payé par les consommateurs, mais réduisent aussi les incitations des entreprises à innover. Quand un nombre suffisant de consommateurs apprécient beaucoup la qualité, de telles interventions peuvent réduire le niveau de bien‐être à cause des innovations moins importantes.
Does trade liberalization harm the environment? A new test
Authors: Dean Judith M. 
Published: March 2003

Some believe that relatively lenient environmental standards give developing countries a comparative advantage in pollution–intensive goods. Thus, freer trade will harm their environment. This paper brings together the literature on openness and growth, and on the environmental Kuznet’s curve, to demonstrate that the opposite may be true. A simultaneous–equations system is derived which incorporates multiple effects of trade liberalization on the environment. Estimation using pooled provincial data on Chinese water pollution, suggests that freer trade aggravates environmental damage via the terms of trade, but mitigates it via income growth. Simulations suggest that the net effect in China was beneficial. JEL Classification: Fl3, Q28, 0l9 Est–ce que la libéralisation du commerce est nuisible pour l’environnement? Un nouveau test. Certains croient que des normes environnementales relativement peu contraignantes donnent un avantage comparatif aux pays en voie de développement dans la production de biens qui polluent intensivement. Donc, un commerce plus libre contribuera à nuire à l’environnement. Ce mémoire synthétise la littérature spécialisée sur l’ouverture des marchés et la croissance, ainsi que sur la courbe de Kuznets, pour montrer que l’inverse est vrai. On dérive un système d’équations simultanées qui incorpore les multiples effets de la libéralisation du commerce sur l’environnement. La calibration de ce système, en utilisant de manière intégrée les données provinciales de pollution de l’eau en Chine, suggère qu’un commerce plus libre aggrave l’état de l’environnement par le truchement du jeu des termes d’échange, mais que cet effet est mitigé par l’effet de croissance des revenus. Des simulations suggèrent que l’effet net en Chine est positif.
Endogenous Processes in European Regional Growth: Convergence and Policy
Authors: Cheshire Paul , Magrini Stefano 
Published: March 2003

The traditional empirical approaches to the analysis of economic growth,cross‐section and panel data regressions are substantially uninformative withrespect to the issue of convergence. Whether national or regional economies appear to converge in terms of per capita income or productivity levels (the so‐called β‐convergence) critically depends on the way in which the empirical model is specified. Traditional specifications witness a disproportionate presence of proxies for forces leading towards divergence among the conditioning variables. It is therefore hardly surprising that these analyses find a positive and statistically significant value for the estimate of the speed of convergence.A more constructive use of cross‐section and panel data regressions is in the analysis of the determinants of growth. The present paper therefore builds on recent work on the role of different growth determinants (Cheshire and Carbonaro 1996) and analyses the growth performance of 122 Functional Urban Regions (FURs)over the period 1978–1994. This model explicitly recognizes growth as amultivariate process. In this new formulation it incorporates a spatialized adaptation of Romer's endogenous growth model (Romer 1990), developing the work of Magrini (Magrini 1997). Magrini's model originated from the view that technological knowledge has a very important tacit component that has been neglected in formal theories of endogenous growth. This tacit component, being the non‐written personal heritage of individuals or groups, is naturally concentrated in space. As a result, technological change is profoundly influenced by the interaction between firms and their local environments.The present paper reports the results of the estimation of a fully specified model of regional growth in per capita income. Particular attention is played to the role of research and development (R&D) activities, and to the influence of factors such as Universities that shape the local environments and have important policy implications.These results are then applied to quantifying the scope for policy to influence the growth process. Several simulations are presented deriving alternative growth outcomes across European regions that would have been obtained if those variables over which policy might have control—including the contribution of human capital—had had alternative values reflecting the realistic scope of policy makers' influence. The implications for convergence/divergence in regional per capita income levels are then analyzed using a Markov chain approach (Quah 1993 and 1996; Magrini 1999).
Regularity‐based Perceptual Grouping
Authors: Feldman Jacob 
Published: March 2003

This paper investigates perceptual grouping from a logical point of view, defining a grouping interpretation as a particular kind of logical expression, and then developing an explicit inference theory in terms of such expressions. First, a regularity‐based interpretation language is presented, in which an observed configuration is characterized in terms of the regularities(special configurational classes, e.g. nonaccidental properties) it obeys. The most preferred interpretation in such a system is shown to be the most‐regular (maximum “codimension”) model the observed configuration obeys, which is also the unique model in which it is generic(typical). Inference then reduces to a straiightforward exercise in LogicProgramming. Because generic model assignment involves negation, this reduction requires that a version of the Closed World Assumption (CWA) be adopted.Next, this entire regularity‐based machinery is generalized to the grouping problem: here an interpretation is a hierarchical recursive) version of a model called a parse tree.For a given number of dots and a fixed choice of regularity set, it is possible to explicitly enumerate the complete set of possible grouping interpretations, partially ordered by their degree of regularity (codimension). The most preferred interpretation is the one with maximum codimension (i.e., the most regular interpretation), which we call the qualitative parse. An efficient procedure (worst case $O(n^2)$) for finding the qualitative parse is presented. The qualitative parse has a unique epistemic status: given a choice of regularity set, it is the only grouping interpretation that both (a) is maximally regular, and (b) satisfies the CWA. This unique status, it is argued, accounts for the perceptually compelling quality of the qualitative parse.