951 resultados para Slow potentials
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Recent evidence suggests that slow anion channels in guard cells need to be activated to trigger stomatal closing and efficiently inactivated during stomatal opening. The patch-clamp technique was employed here to determine mechanisms that produce strong regulation of slow anion channels in guard cells. MgATP in guard cells, serving as a donor for phosphorylation, leads to strong activation of slow anion channels. Slow anion-channel activity was almost completely abolished by removal of cytosolic ATP or by the kinase inhibitors K-252a and H7. Nonhydrolyzable ATP, GTP, and guanosine 5'-[gamma-thio]triphosphate did not replace the ATP requirement for anion-channel activation. In addition, down-regulation of slow anion channels by ATP removal was inhibited by the phosphatase inhibitor okadaic acid. Stomatal closures in leaves induced by the plant hormone abscisic acid (ABA) and malate were abolished by kinase inhibitors and/or enhanced by okadaic acid. These data suggest that ABA signal transduction may proceed by activation of protein kinases and inhibition of an okadaic acid-sensitive phosphatase. This modulation of ABA-induced stomatal closing correlated to the large dynamic range for up- and down-regulation of slow anion channels by opposing phosphorylation and dephosphorylation events in guard cells. The presented opposing regulation by kinase and phosphatase modulators could provide important mechanisms for signal transduction by ABA and other stimuli during stomatal movements.
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The collective behavior of interconnected spiking nerve cells is investigated. It is shown that a variety of model systems exhibit the same short-time behavior and rapidly converge to (approximately) periodic firing patterns with locally synchronized action potentials. The dynamics of one model can be described by a downhill motion on an abstract energy landscape. Since an energy landscape makes it possible to understand and program computation done by an attractor network, the results will extend our understanding of collective computation from models based on a firing-rate description to biologically more realistic systems with integrate-and-fire neurons.
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Contractile proteins are encoded by multigene families, most of whose members are differentially expressed in fast- versus slow-twitch myofibers. This fiber-type-specific gene regulation occurs by unknown mechanisms and does not occur within cultured myocytes. We have developed a transient, whole-animal assay using somatic gene transfer to study this phenomenon and have identified a fiber-type-specific regulatory element within the promoter region of a slow myofiber-specific gene. A plasmid-borne luciferase reporter gene fused to various muscle-specific contractile gene promoters was differentially expressed when injected into slow- versus fast-twitch rat muscle: the luciferase gene was preferentially expressed in slow muscle when fused to a slow troponin I promoter, and conversely, was preferentially expressed in fast muscle when fused to a fast troponin C promoter. In contrast, the luciferase gene was equally well expressed by both muscle types when fused to a nonfiber-type-specific skeletal actin promoter. Deletion analysis of the troponin I promoter region revealed that a 157-bp enhancer conferred slow-muscle-preferential activity upon a minimal thymidine kinase promoter. Transgenic analysis confirmed the role of this enhancer in restricting gene expression to slow-twitch myofibers. Hence, somatic gene transfer may be used to rapidly define elements that direct myofiber-type-specific gene expression prior to the generation of transgenic mice.
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The mitochondrial matrix flavoproteins electron transfer flavoprotein (ETF) and electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) are responsible for linking fatty acid β-oxidation with the main mitochondrial respiratory chain. Electrons derived from flavoprotein dehydrogenases are transferred sequentially through ETF and ETF-QO to ubiquinone and then into the respiratory chain via complex III. In this study, the effects of changes in ETF-QO redox potentials on its activity and the conformational flexibility of ETF were investigated. ETF-QO contains one [4Fe-4S]2+,1+ and one flavin adenine dinucleotide (FAD). In the porcine protein, threonine 367 is hydrogen bonded to N1 and O2 of the flavin ring of the FAD. The analogous site in Rhodobacter sphaeroides ETF-QO is asparagine 338. Mutations N338T and N338A were introduced into the R. sphaeroides protein by site-directed mutagenesis to determine the impact of hydrogen bonding at this site on redox potentials and activity. FAD redox potentials were measured by potentiometric titration probed by electron paramagnetic resonance (EPR) spectroscopy. The N338T and N338A mutations lowered the midpoint potentials, which resulted in a decrease in the quinone reductase activity and negligible impact on disproportionation of ETF1e- catalyzed by ETF-QO. These observations indicate that the FAD is involved in electron transfer to ubiquinone, but not in electron transfer from ETF to ETF-QO. Therefore it is proposed that the iron-sulfur cluster is the immediate acceptor from ETF. It has been proposed that the αII domain of ETF is mobile, allowing promiscuous interactions with structurally different partners. Double electron-electron resonance (DEER) was used to measure the distance between spin labels at various sites and an enzymatically reduced FAD cofactor in Paracoccus denitrificans ETF. Two or three interspin distance distributions were observed for spin-labels in the αI (A43C) and βIII (A111C) domains, but only one is observed for a label in the βII (A210C) domain. This suggests that the αII domain adopts several stable conformations which may correspond to a closed/inactive conformation and an open/active conformation. An additional mutation, E162A, was introduced to increase the mobility of the αII domain. The E162A mutation doubled the activity compared to wild-type and caused the distance distributions to become wider. The DEER method has the potential to characterize conformational changes in ETF that occur when it interacts with various redox partners.
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Existe un interés considerable en hallar métodos que nos ayuden a saber cuándo una persona miente y cuándo dice la verdad desde un punto de vista forense. Actualmente, una de las líneas de investigación se inclina hacia el uso de potenciales relacionados con eventos. Se pretende hacer una revisión de los artículos que estudian estos procedimientos mediante distintos métodos: propiedades, fiabilidad, validez y limitaciones. Los resultados indican tasas de acierto en la discriminación de culpables en un rango de 7 al 100 por ciento, y en la de inocentes de 31 a 100 por ciento. La gran variabilidad y la posibilidad de “falsear” las respuestas llevan a cuestionar la inexactitud utilizada en algunos círculos mediáticos respecto a las cualidades y finalidades de dicha prueba. Se concluye la necesidad de profundizar más la posibilidad de que esta prueba sea utilizada con fines forenses.
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The electro-oxidation of carbon materials enormously degrades their performance and limits their wider utilization in multiple electrochemical applications. In this work, the positive influence of phosphorus functionalities on the overall electrochemical stability of carbon materials has been demonstrated under different conditions. We show that the extent and selectivity of electroxidation in P-containing carbons are completely different to those observed in conventional carbons without P. The electro-oxidation of P-containing carbons involves the active participation of phosphorus surface groups, which are gradually transformed at high potentials from less-to more-oxidized species to slow down the introduction of oxygen groups on the carbon surface (oxidation) and the subsequent generation of (C*OOH)-like unstable promoters of electro-gasification. The highest-oxidized P groups (–C–O–P-like species) seem to distribute the gained oxygen to neighboring carbon sites, which finally suffer oxidation and/or gasification. So it is thought that P-groups could act as mediators of carbon oxidation although including various steps and intermediates compared to electroxidation in P-free materials.
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In this paper we discussed how the literature traces a growing involvement of the national parliaments in EU policy-making. Three phases can be distinguished: limited or no involvement was the trend until the 1980s; after the Single Act (SEA, 1987), national parliaments started to be interested in European affairs and to set up specialized committees; following the Maastricht Treaty (TUE, 1992), the involvement of national parliaments in EU affairs became a response to the question of "democratic deficit" in the EU (Norton, 1995). The growing number of policies dealt with at the EU level, the consequently increased influence of EU law in national legislations, the new powers of the Union: all of these worked together to push national legislators to seek a scrutiny role in the drafting of EU legislation. According to Laprat (1995: 1), once the TUE was formally approved, a more parliamentary climate prevailed. In more recent years, national parliaments have distinguished themselves for their increased role in the scrutiny of EU legislation (Raunio and Hix, 200I: !52); more specialized MPs sit in the committees on EU affairs; the amount of work for EU specialists has increased. Also, parliamentary scrutiny, initially only optional and ex post, is now increasingly ex ante and/or mandatory (Maurer and Wessels, 2001: 425-475).
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Summary. The European electricity sector will have to deal with a huge challenge in the decades to come. On the one hand, electrical power is increasingly substituted for other forms of energy. It has been forecast that electricity demand will increase in the future (notably because of new needs in transport and heat sectors), although it is currently stagnant, mainly because of the economic crisis. Unless a major alternative energy source is discovered, electricity will become the central energy pillar in the long term. On the other hand, electricity production remains uncertain and will depend on numerous factors: the growth of renewable energy and decentralized energy, the renewal of old power generation capacities, increased external dependency, CO2 charges, etc. This increases the demand for electricity networks that are more reliable, more efficient, and more flexible. Europe’s current electricity networks are ageing, and, as already indicated by the International Energy Agency, many of them will need to be modernized or replaced in the decades to come. Finally, the growing impact of energy trading also needs to be taken into account. These considerations explain the need to modernize the electric grid through various ICT means. This modernization alone may allow the grid to become more flexible and interactive, to provide real time feedback, more adaptation to a fluctuating demand, and finally to reduce the global electricity costs. The paper begins with a description of the EU definition of the term ‘smart grid’ (§ 1) and of the body in charge of advising the Commission (§ 2). The EU legal framework applicable to smart grids is also detailed (§ 3). It is a rather complex domain, connected to various regulations. The paper then examines three critical factors in the development of smart grids (and smart meters as a precondition). Standardization is quite complex, but absolutely essential (§ 4). Innovation is not easily put into action (§ 5). Finally, as digital insecurity has worsened dramatically in recent years, the security of electricity networks, and especially their multiplied electronic components, will become increasingly important (§ 6). Lastly, the paper provides a concise overview of the progress of smart grids in the EU in recent years (§ 7). In a nutshell, the conclusion is that progress is quite slow, many obstacles remain, and, given the appearance of many new regulatory problems, it would be useful to organize a review of the present EU strategy.
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In questo elaborato si propone una traduzione per il primo capitolo del romanzo "The Slow Regard of Silent Things", un testo di narrativa fantasy per young adults. Si analizzano in oltre le particolarità del testo e alcuni punti critici della traduzione alla luce di un percorso teorico basato sul lavoro di studiosi dal diciannovesimo secolo fino ai giorni nostri.
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Consensus democracies like Switzerland are generally known to have a low innovation capacity (Lijphart 1999). This is due to the high number of veto points such as perfect bicameralism or the popular referendum. These institutions provide actors opposing a policy with several opportunities to block potential policy change (Immergut 1990; Tsebelis 2002). In order to avoid a failure of a process because opposing actors activate veto points, decision-making processes in Switzerland tend to integrate a large number of actors with different - and often diverging - preferences (Kriesi and Trechsel 2008). Including a variety of actors in a decision-making process and taking into account their preferences implies important trade-offs. Integrating a large number of actors and accommodating their preferences takes time and carries the risk of resulting in lowest common denominator solutions. On the contrary, major innovative reforms usually fail or come only as a result of strong external pressures from either the international environment, economic turmoil or the public (Kriesi 1980: 635f.; Kriesi and Trechsel 2008; Sciarini 1994). Standard decision-making processes are therefore characterized as reactive, slow and capable of only marginal adjustments (Kriesi 1980; Kriesi and Trechsel 2008; Linder 2009; Sciarini 2006). This, in turn, may be at odds with the rapid developments of international politics, the flexibility of the private sector, or the speed of technological development.
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A ‘sense of self’ is essentially the ability to distinguish between self-generated and external stimuli. It consists of at least two very basic senses: a sense of agency and a sense of ownership. Disturbances seem to provide a basic deficit in many psychiatric diseases. The aim of our study was to manipulate those qualities separately in 28 patients with schizophrenia (14 auditory hallucinators and 14 non-hallucinators) and 28 healthy controls (HC) and to investigate the effects on the topographies and the power of the event-related potential (ERP). We performed a 76-channel EEG while the participants performed the task as in our previous paper. We computed ERPs and difference maps for the conditions and compared the amount of agency and ownership between the HC and the patients. Furthermore, we compared the global field power and the topographies of these effects. Our data showed effects of agency and ownership in the healthy controls and the hallucinator group and to a lesser degree in the non-hallucinator group. We found a reduction of the N100 during the presence of agency, and a bilateral temporal negativity related to the presence of ownership. For the agency effects, we found significant differences between HC and the patients. Contrary to the expectations, our findings were more pronounced in non-hallucinators, suggesting a more profoundly disturbed sense of agency compared to hallucinators. A contemporary increase of global field power in both patient groups indicates a compensatory recruitment of other mechanisms not normally associated with the processing of agency and ownership.
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