Stochastic dynamics of remote knock-on permeation in biological ion channels

Brownian dynamics simulations provide evidence for a remote knock-on mechanism facilitating the permeation of a biological ion channel by an ion that is initially trapped at the selectivity filter (SF). Unlike the case of conventional direct knock-on, the second ion that instigates permeation does not need to enter the channel. Nor does it necessarily take the place of the permeating ion at the SF, and it can even be of a different ionic species. The study is based on the simultaneous, self-consistent, solution of the coupled Poisson and Langevin equations for a simple generic model, taking account of all the charges present. The new permeation mechanism involves electrostatic amplification attributable to the permittivity mismatch between water and protein: the arrival of the instigating ion at the channel entrance reduces the exit barrier for the ion trapped at the SF, facilitating escape

Self-organized enhancement of conductivity in biological ion channels

We discuss an example of self-organization in a biological system. It arises from long-range ion–ion interactions, and it leads us to propose a new kind of enhanced conduction in ion channels. The underlying mechanism involves charge fluctuations near the channel mouth, amplified by the mismatch between the relative permittivities of water and the protein of the channel walls. We use Brownian dynamics simulations to show that, as in conventional 'knock on' permeation, these interactions can strongly enhance the channel current; but unlike the conventional mechanism, the enhancement occurs without the instigating bath ion entering the channel. The transition between these two mechanisms is clearly demonstrated, emphasizing their distinction. A simple model accurately reproduces the observed phenomena. We point out that electrolyte plus protein of low relative permittivity are universal in living systems, so that long-range ion–ion correlations of the kind considered must be common

Metgourine (Adrar) (Station rupestre, Maroc)

Ride gréseuse, à une quarantaine de kilomètres au nord de l’Oued Dra et une dizaine du village d’Akka, au Maroc présaharien. Sur cette colline dominant la feija (plaine intérieure) d’Akka et la cluse de l’oued du même nom furent signalées, dès 1935, des gravures rupestres. C’est en fait l’un des plus importants sites rupestres du Maroc méridional. On doit à A. Simoneau une première description du site. Quelques gravures furent publiées par la suite, par divers auteurs, mais jusqu’en 1989 la m..

Koudiat el-Mouissiera

La colline (koudia) El-Mouissiera (El-Moussira, sur les cartes de la Direction foncière, Rabat) est située à une dizaine de kilomètres au S/W de Marrakech et à trois kilomètres du village de Sidi Bouzid. Malgré sa faible élévation (569 m d’altitude absolue au signal géodésique), la colline est bien visible de tous les environs du Haouz. Le dôme à nu qui émerge des dépôts tertiaires est un grès primaire très dur, bleu-gris à la fracture ou à l’érosion naturelle et blanc à l’impact. Le sommet d..

Impacts Des Technologies De l’Information Et De La Communication (TIC) Sur Les Rendements Scolaires Des Apprenants De La Ville De Dassa-Zoumé Dans Le Département Des Collines Au Bénin

L’usage des TIC consiste à l’accès et à l’utilisation des technologies de l’information et de la communication dans l’éducation. L’objectif global de cette recherche est de montrer les répercutions socio-éducatives des usages des TIC sur le rendement des apprenants des établissements publics de Dassa-Zoumé. L’approche méthodologique adoptée se subdivise en trois points à savoir : la recherche documentaire, la collecte de données, le traitement des informations et l’analyse des résultats.Les résultats obtenus sur le terrain ont révélé que 37 % des enseignants ont estimé que les TIC facilitent les recherches et 65 % de ceux-ci pensent que cela contribue à l’amélioration des résultats scolaires. L’usage des TIC pour des recherches documentaires est adopté par 65 % des enquêtés. 14 % ont affirmé que cela affaiblit le niveau scolaire des apprenants parce qu’ils l’utilisent pour des fins peu orthodoxes. Malgré les multiples avantages que procurent l’usage des TIC en milieu scolaire, des défis restent à relever à savoir : la non-maîtrise des outils informatiques, le coût d’accès élevés, l’éloignement des lieux d’accès et la privation formelle de l’usage des smartphones par les parents. Enfin 18 % ont énuméré l’indisponibilité des services offerts par les TIC

Haouz

La plaine du Haouz est enserrée entre les vieilles collines des Djebilet et le Haut Atlas, délimitée à l’Est par le seuil de la Tassaout et à l’Ouest par les premières cuestas des Haha. Ce sont les régions extrêmes de la pénétration du régime atlantique. Le Haouz – on précise de Marrakech – est l’aboutissement d’une sédimentation continentale dans une gouttière synclinale. Le Tensift est, comme l’Oum-er-Rebia, dans le Tadla, l’artère principale du système hydrographique. Il passe à proximité ..

Spatial accessibility and social inclusion: The impact of Portugal's last health reform

Health policies seek to promote access to health care and should provide appropriate geographical accessibility to each demographical functional group. The dispersal demand of health‐careservices and the provision for such services atfixed locations contribute to the growth of inequality intheir access. Therefore, the optimal distribution of health facilities over the space/area can lead toaccessibility improvements and to the mitigation of the social exclusion of the groups considered mostvulnerable. Requiring for such, the use of planning practices joined with accessibility measures. However,the capacities of Geographic Information Systems in determining and evaluating spatial accessibility inhealth system planning have not yet been fully exploited. This paper focuses on health‐care services planningbased on accessibility measures grounded on the network analysis. The case study hinges on mainlandPortugal. Different scenarios were developed to measure and compare impact on the population'saccessibility. It distinguishes itself from other studies of accessibility measures by integrating network data ina spatial accessibility measure: the enhanced two‐stepfloating catchment area. The convenient location forhealth‐care facilities can increase the accessibility standards of the population and consequently reducethe economic and social costs incurred. Recently, the Portuguese government implemented a reform thataimed to improve, namely, the access and equity in meeting with the most urgent patients. It envisaged,in terms of equity, the allocation of 89 emergency network points that ensured more than 90% of thepopulation be within 30 min from any one point in the network. Consequently, several emergency serviceswere closed, namely, in rural areas. This reform highlighted the need to improve the quality of the emergencycare, accessibility to each care facility, and equity in their access. Hence, accessibility measures becomean efficient decision‐making tool, despite its absence in effective practice planning. According to anapplication of this type of measure, it was possible to verify which levels of accessibility were decreased,including the most disadvantaged people, with a larger time of dislocation of 12 min between 2001 and 2011

Comparing Wireless Traffic Tracking with Regular Traffic Control Systems for the Detection of Congestions in Streets

Detecting congestions on streets is one of the main issues in the area of smart cities. Regular monitoring methods can supply information about the number of vehicles in transit and thus the saturation of the streets, but they are usually expensive and intrusive with respect to the road. In recent years a new trend in traffic detection has arisen, considering the Wireless signals emitted by ‘smart’ on-board devices for counting and tracking vehicles. In this paper, two traffic monitoring methods are compared: detections using a regular Inductive Loop Detector on the road and an own Wireless Tracking System based on Bluetooth detection called Mobywit. The correlation between the day of the week and the hour with the traffic flow in a metropolitan busy street has been analysed. Assuming that our system is not able to defect all the vehicles, but just only subset of them, it is expected a causality between the results obtained using the two methods. This means, that the Bluetooth-based system can detect the same variations in the traffic flow that the regular loop detector, but having two main advantages: the tracking possibilities and a much lower cost.This work has been supported in part by project MOSOS (reference PRY142/14), which has been granted by Fundación Pública Andaluza Centro de Estudios An- daluces in the call `IX Convocatoria de Proyectos de Investigación'. It also has been partially funded by national projects TIN2014-56494-C4-3-P and TEC2015- 68752 (Spanish Ministry of Economy and Competitiveness), PROY-PP2015-06 (Plan Propio 2015 UGR), and project CEI2015-MP-V17 of the Microprojects program 2015 from CEI BioTIC Granada