IDE et risque-pays dans le bassin méditerranéen : quelques enseignements du secteur du Tourisme dans quatre pays.

Évaluation du risque; Tourisme; Investissements étrangers; Egypte; Maroc; Tunisie; Turquie; conditions politiques;

Bernoulli’s principle applied to brain fluids: intracranial pressure does not drive cerebral perfusion or CSF flow

In line with the first law of thermodynamics, Bernoulli's principle states that the total energy in a fluid is the same at all points. We applied Bernoulli's principle to understand the relationship between intracranial pressure (ICP) and intracranial fluids. We analyzed simple fluid physics along a tube to describe the interplay between pressure and velocity. Bernoulli's equation demonstrates that a fluid does not flow along a gradient of pressure or velocity; a fluid flows along a gradient of energy from a high-energy region to a low-energy region. A fluid can even flow against a pressure gradient or a velocity gradient. Pressure and velocity represent part of the total energy. Cerebral blood perfusion is not driven by pressure but by energy: the blood flows from high-energy to lower-energy regions. Hydrocephalus is related to increased cerebrospinal fluid (CSF) resistance (i.e., energy transfer) at various points. Identification of the energy transfer within the CSF circuit is important in understanding and treating CSF-related disorders. Bernoulli's principle is not an abstract concept far from clinical practice. We should be aware that pressure is easy to measure, but it does not induce resumption of fluid flow. Even at the bedside, energy is the key to understanding ICP and fluid dynamics

Identification of the first Rho–GEF inhibitor, TRIPα, which targets the RhoA-specific GEF domain of Trio

AbstractThe Rho–guanine nucleotide exchange factors (Rho–GEFs) remodel the actin cytoskeleton via their Rho–GTPase targets and affect numerous physiological processes such as transformation and cell motility. They are therefore attractive targets to design specific inhibitors that may have therapeutic applications. Trio contains two Rho–GEF domains, GEFD1 and GEFD2, which activate the Rac and RhoA pathways, respectively. Here we have used a genetic screen in yeast to select in vivo peptides coupled to thioredoxin, called aptamers, that could inhibit GEFD2 activity. One aptamer, TRIAPα (TRio Inhibitory APtamer), specifically blocks GEFD2-exchange activity on RhoA in vitro. The corresponding peptide sequence, TRIPα, inhibits TrioGEFD2-mediated activation of RhoA in intact cells and specifically reverts the neurite retraction phenotype induced by TrioGEFD2 in PC12 cells. Thus TRIPα is the first Rho–GEF inhibitor isolated so far, and represents an important step in the design of inhibitors for the expanding family of Rho–GEFs

Neural tracking of visual periodic motion

Periodicity is a fundamental property of biological systems, including human movement systems. Periodic movements support displacements of the body in the environment as well as interactions and communication between individuals. Here, we use electroencephalography (EEG) to investigate the neural tracking of visual periodic motion, and more specifically, the relevance of spatiotemporal information contained at and between their turning points. We compared EEG responses to visual sinusoidal oscillations versus nonlinear Rayleigh oscillations, which are both typical of human movements. These oscillations contain the same spatiotemporal information at their turning points but differ between turning points, with Rayleigh oscillations having an earlier peak velocity, shown to increase an individual's capacity to produce accurately synchronized movements. EEG analyses highlighted the relevance of spatiotemporal information between the turning points by showing that the brain precisely tracks subtle differences in velocity profiles, as indicated by earlier EEG responses for Rayleigh oscillations. The results suggest that the brain is particularly responsive to velocity peaks in visual periodic motion, supporting their role in conveying behaviorally relevant timing information at a neurophysiological level. The results also suggest key functions of neural oscillations in the Alpha and Beta frequency bands, particularly in the right hemisphere. Together, these findings provide insights into the neural mechanisms underpinning the processing of visual periodic motion and the critical role of velocity peaks in enabling proficient visuomotor synchronization

Anti-HIV and immune modulating activities of IND02

International audienc

On the Use of Network Flow Techniques for Assigning Evacuees to Exits

We apply network flow techniques to find good exit selections for evacuees in an emergency evacuation. More precisely, we present two algorithms for computing exit distributions using both classical flows and flows over time which are well known from combinatorial optimization. The performance of these new proposals is compared to a simple shortest path approach and to a best response dynamics approach by using a cellular automaton model

Crystallographic and structural transformations of sedimentary chalcedony in flint upon heat treatment

International audienceThe early occurrence of intentional heat treatment of silica rocks has recently become a key element in the discussion about the cultural modernity of prehistoric populations. Lithic vestiges are the only sources that remain of this process and the understanding of the material's properties and transformations are essential for reconstructing the conditions and parameters applied during heat treatment. Several models of the structural transformations upon heating have been proposed in the current literature. These models are often contradictory and do not account for the most recent structural and mineralogical data on chalcedony. In order to propose a new model, we elaborated an experimental procedure and applied different techniques involving infrared spectroscopy, solid state NMR, X-ray diffraction and electron microscopy. The results show that the major transformation to happen is the loss of silanole (SiOH) and the creation of new Si-O-Si bonds according to the reaction: Si-OH HO-Si -> Si -O-Si + H2O. This reaction starts between 200 degrees C and 300 degrees C and causes an increase in the hardness of the rocks. The maximal annealing temperature and the ramp rate are the functions of the ability of the structure to evacuate newly created H2O and depend on the size of the specimen and the volume of its porosity. These results also show that the annealing duration at maximum temperature can be relatively short (<50 min) for a sufficiently large amount of transformation to be accomplished

Chemical contamination in fish species from rivers in the North of Luxembourg: Potential impact on the Eurasian otter (Lutra lutra).

Contamination levels of PCBs, and of the heavy metals cadmium (Cd), lead (Pb) and mercury (Hg) were analyzed in four fish species from seven rivers in the North of Luxembourg. During August and September 2007, 85 samples of fish were collected belonging to four species: the stone loach (Barbatula barbatula, n = 12 pools), the chub (Squalius cephalus, n = 36), the barbel (Barbus barbus, n = 23) and eel (Anguilla anguilla, n = 14). The concentration of seven indicator PCBs (P7PCBs) reached a mean of 39 ng g 1 and varied between 4.0 and 346.2 ng g 1 (wet wt) depending on the site and species. Fish collected at Wal- lendorf on the Our River and sites on the Wiltz and the Clerve rivers showed the highest concentrations for PCBs. In comparison with 1994, PCB levels in fish decreased strongly during the last decade in these rivers. Lead was detected at low levels (0–181.4 ng g 1 wet wt). Mercury concentrations ranged between 10.3 and 534.5ngg 1 (wet wt) exceeding maximum tolerable levels for human consumption of 500 ng g 1 in two fish out of 85. Chubs and eels from the Sûre River were the most contaminated by mer- cury. Cadmium levels varied between 4.0 and 103.9 ng g 1 (wet wt). In addition to mercury in fish, cad- mium was the most problematic pollutant on the Our, the Wiltz, the Clerve and the Troine Rivers, because values found in 20% of fish exceeded the threshold of about 10–50 ng g 1 (wet wt) recommended for human health. The total PCB level predicted to accumulate in livers from otter potentially feeding on these fish based on a previously published mathematical model is 37.7 lg g 1 (lipid wt), which is between a proposed ‘‘safe level” and a ‘‘critical level” for otters. Rivers in the North of Luxembourg are thus to some extent polluted, and the establishment of otter populations could be affected by current levels of contamination.Peer reviewe

Probing vulnerability of the gp41 C-terminal heptad repeat as target for miniprotein HIV inhibitors

One of the therapeutic strategies in HIV neutralization is blocking membrane fusion. In this process, tight interaction between the N-terminal and C-terminal heptad-repeat (NHR and CHR) regions of gp41 is essential to promote membranes apposition and merging. We have previously developed single-chain proteins (named covNHR) that accurately mimic the complete gp41 NHR region in its trimeric conformation. They tightly bind CHR-derived peptides and show a potent and broad HIV inhibitory activity in vitro. However, the extremely high binding affinity (sub-picomolar) is not in consonance with their inhibitory activity (nanomolar), likely due to partial or temporal accessibility of their target in the virus. Here, we have designed and characterized two single-chain covNHR miniproteins each encompassing one of the two halves of the NHR region and containing two of the four sub-pockets of the NHR crevice. The two miniproteins fold as trimeric helical bundles as expected but while the C-terminal covNHR (covNHR-C) miniprotein is highly stable, the N-terminal counterpart (covNHR-N) shows only marginal stability that could be improved by engineering an internal disulfide bond. Both miniproteins bind their respective complementary CHR peptides with moderate (micromolar) affinity. Moreover, the covNHR-N miniproteins can access their target in the context of trimeric native envelope proteins and show significant inhibitory activity for several HIV pseudoviruses. In contrast, covNHR-C cannot bind its target sequence and neither inhibits HIV, indicating a higher vulnerability of C-terminal part of CHR. These results may guide the development of novel HIV inhibitors targeting the gp41 CHR region.Spanish Ministry of Economy and Competitiveness (grant: BIO2016-76640-R), ANRS and the Vaccine Research Institute for the Investissements d'Avenir program to C.M. and by the European Fund for Research and Development from the European Union.Departamento de Química Física, Facultad de Ciencias, Universidad de Granada. Grupo FQM-171 "Biofísica y Biotecnología Molecular

State selective measurements of HCI produced by strong ultrashort laser clusters interaction

International audienceWe have performed studies of keV x-ray production from (Ar)n , (Kr)n and (Xe)n rare gas clusters (with n between 104 and 106 atoms/cluster) submitted to intense (~10^18 W/cm2) infrared (790 nm) laser pulses. We have determined the photon energies and the absolute photon emission yields as a function of several physical parameters governing the interaction : size and atomic number of the clusters, peak intensity of the laser. Up to 10^6 3 keV photons per pulse at a moderate (10^15/cm3) atomic density have been observed. High resolution spectroscopy studies in the case of (Ar)n clusters have also been performed, giving unambiguous evidence of highly charged (up to heliumlike) ions with K vacancies production. The results obtained indicate that X-rays are emitted before cluster explosion on a subpicosecond time scale, and shed some light on the mechanisms involved in the first stage of the production of the nanoplasma induced from each cluster