Bioinspired microstructures of chitosan hydrogel provide enhanced wear protection

We describe the fabrication of physical chitosan hydrogels exhibiting a layered structure. This bilayered structure, as shown by SEM and confocal microscopy, is composed of a thin dense superficial zone (SZ), covering a deeper zone (DZ) containing microchannels orientated perpendicularly to the SZ. We show that such structure favors diffusion of macromolecules within the hydrogel matrix up to a critical pressure, σc, above which channels were constricted. Moreover, we found that the SZ provided a higher wear resistance than the DZ which was severely damaged at a pressure equal to the elastic modulus of the gel. The coefficient of friction (CoF) of the SZ remained independent of the applied load with μSZ = 0.38 ± 0.02, while CoF measured at DZ exhibited two regimes: an initial CoF close to the value found on the SZ, and a CoF that decreased to μDZ = 0.18 ± 0.01 at pressures higher than the critical pressure σc. Overall, our results show that internal structuring is a promising avenue in controlling and improving the wear resistance of soft materials such as hydrogels

021: Clopidogrel low response and correlation between the different tests: light transmission aggregometry, VerifyNow-P2Y12 and V ASP

BackgroundClopidogrel low response correlates with poor prognosis after percutaneous coronary intervention (PCI). Many biological tests are currently available to test the clopidogrel response. However, the presence of any correlation between the different tests is today poorly reported.MethodsIn this prospective study, clopidogrel response was assessed in 100 consecutive patients. All patients were tested between 18h and 24h after a600mg clopidogrel loading dose using 3 different tests: light transmission aggregometry with 10μmol ADP (LTA, results expressed as platelet inhibition percentage), VerifyNow-P2Y12 (VN, results expressed as PRU) and vasodilatator stimulated phosphoprotein (VASP, results expressed as IRP). Patients under chronic clopidogrel therapy were excluded.ResultsThe mean platelet inhibition percentage, PRU value and IRP value were 38.5±13% by LTA, 178±89 PRU by VN and 52±21% by VASP. When results were analyzed as continuous variables, there was a good correlation between the different tests: LTA/VN (R2=0,642, p<0,001), LTA/VASP (R2=0,409, p<0,001) and VN/VASP (R2=0,616, p<0,001). However, when results were analyzed as pre-specified cut-off points to define patients as “low or good responders” (according to the literature: 50% for LTA, 235 PRU for VN and 50% IRP for VASP), only 47% of the patients were defined as “good” or “low responders” by the 3 tests. Altogether, 33% of the patients were defined as “low responders” by only 1 test, 20% by 2 tests and only 16% by the 3 tests.ConclusionIf the correlation between the different tests is good when results are analyzed as continuous variables, each individual is rarely (less than 50%) defined as “low or good responder” by all the 3 tests when recognized cut-off values are used. In that way, a sole test might not be sufficient to manage antiplatelet therapy in an individual patient

Impact of initial clinical presentation on clopidogrel low response

SummaryBackgroundLarge interindividual variability exists in clopidogrel response. Clopidogrel low response correlates with poor prognosis after percutaneous coronary intervention. Some authors also suggest intraindividual variability over time.AimTo assess the impact of initial clinical presentation on clopidogrel low response.MethodsIn this prospective study, clopidogrel response was assessed in 100 patients. Fifty patients presenting with acute coronary syndromes (ACS group) were compared with 50 patients with stable coronary artery disease matched 1:1 for age, sex, body mass index and diabetes (stable group). All patients were tested 18–24h after a 600mg loading dose of clopidogrel using the VerifyNow-P2Y12 test (results expressed as platelet reaction units [PRUs]). Patients under chronic clopidogrel therapy or treated with glycoprotein IIb/IIIa inhibitors, bivalirudin or thrombolytics were excluded.ResultsMean age was 61±12 years in each group; 28% of patients in each group were diabetic; mean body mass index was 27.6±5.6kg/m2 in the ACS group and 27.9±5.9kg/m2 in the stable group (p=0.80). Mean PRU values were 197±81 in the ACS group and 159±94 in the stable group (p=0.03). By multivariable analysis, the ACS group was significantly associated with a higher PRU value (p=0.02). There were significantly more clopidogrel low responders (PRU value>230) in the ACS group (38% vs. 18%; p=0.04).ConclusionOur study confirms that initial clinical presentation, especially ACS, is a strong predictor of clopidogrel low response; this suggests that the evolution of coronary artery disease for one patient influences the clopidogrel response over time. These results are in accordance with recent trials showing a benefit for more aggressive antiplatelet therapy in ACS patients

Lubrication and wear protection of micro-structured hydrogels using bioinspired fluids

We report the fabrication and the use of a bioinspired synovial fluid acting as a lubricant fluid and anti-wear agent at soft and porous chitosan hydrogel tribopairs. This synthetic synovial fluid is composed of sodium hyaluronate (HA) and a bottle-brush polymer (BB) having a polycationic attachment group and polyzwitterionic pendant chains. 2.5 %w/w chitosan hydrogel plugs are organized in a bilayered structure exposing a thin and dense superficial zone (SZ), covering a porous deep zone (DZ) and exhibiting microchannels perpendicularly aligned to the SZ. Using a low-load tribometer, the addition of HA lubricating solution at the hydrogel-hydrogel rubbing contact drastically decreased the coefficient of friction (CoF) from μ = 0.20 ± 0.01 to μ = 0.04 ± 0.01 on the DZ configuration and from μ = 0.31 ± 0.01 to μ = 0.08 ± 0.01 on the SZ surface when increasing HA concentration from 0 to 1000 μg/mL and its molecular mass from 10 to 1500 kDa, similar to what was found when using BB polymer alone. When combining the BB polymer and the 1500 kDa HA, the CoF remained stable at μ = 0.04 ± 0.01 for both studied contact configurations, highlighting the synergistic interaction of the two macromolecules. Hydrogel wear was characterized by assessing the final gel surface roughness by the means of an interferometer. Increasing HA concentration and molecular weight plus the addition of BB polymer lead to a dramatic surface wear protection with a final gel surface roughness of the hydrogels similar to the untested gels. In brief, BB polymer in combination with high molecular weight HA is a potential lubricating fluid as well as a wear resistant agent for soft materials lubrication and wear protection

Intermolecular interactions between Bottlebrush Polymers boost the protection of surfaces against frictional wear

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of materials, copyright American Chemical Society after peer review and technical editing by the publisher."Polymers exhibiting the bottlebrush (BB) architecture have excellent lubricating properties. However, to motivate their use in real life systems, they must also protect surfaces against frictional damage. In this article, we synthesized a library of polyzwiterrionic bottlebrush polymers of different architectures to explore the effect of intermolecular interactions on their conformation at interfaces and their tribological properties. Using the surface forces apparatus, we show that increasing the number of adhesive blocks on the BB polymers does not impact the friction coefficient on mica surfaces, μ, which remained close to μ = 0.02 but drastically increased the threshold pressure, P*, at which wear initiates from P* = 0.4 ± 0.1 up to 8.0 ± 0.8 MPa. In mixtures of high molecular weight hyaluronic acid and BB polymers, a synergistic interaction between polymers occurred, leading to a significant increase in P*, independently of the BB polymer tested and even reaching superprotection for strongly interacting polymers (up to P* > 14 MPa). Overall, these results show that strong intermolecular interaction between BB polymers and high molecular weight linear polymers is a promising strategy to create highly protective lubricants

Advanced rotorcraft aeromechanics studies in the French-German SHANEL project

The present paper gives an overview of the SHANEL research project (partly supported by the French DGAC and the German BMWA) which was started at the end of 2006 between the German and French Aerospace Research Centres DLR and ONERA, the University of Stuttgart and the two national helicopter manufacturers, Eurocopter and Eurocopter Germany. This program represents the continuation of the binational CHANCE project, involving the same partners. The objective of the project is to enhance and further validate the CFD tools: the structured multi-block elsA software of Onera and the unstructured TAU code of DLR, for computing the aerodynamics of the complete trimmed helicopter, accounting for the blade elasticity by coupling with blade dynamics and structural mechanics tools. A coupling activity between the FLOWer code of DLR and the HOST tool of Eurocopter is also completed to achieve the free flight trim of a complete helicopter. In this program particular attention is being given to wake conservation, to the modelling of elaborated complex shapes such as rotor hubs and consequently to interactional phenomena, with the global objective of improving the prediction of helicopter performance and noise. Rotorcraft noise prediction chains were rationalized, enhanced and compared. The validation activity of the flow solvers elsA and TAU is progressing from the CHANCE results and is now focussing on more complex problems such as the simulation of a rotating rotor head mounted on its fuselage, of a complete helicopter in steady mode through the use of actuator discs and engine boundary conditions, the time-accurate simulation of a complete trimmed helicopter in forward-flight, and the numerical simulation of Blade Vortex Interactions. All along the research program the updated versions of the CFD and acoustic codes are systematically delivered to industry. This approach, also followed during the former CHANCE project, is chosen to speed up the transfer of capabilities to industry and check early enough that the products meet the expectations for applicability in the industrial environment of Eurocopter

Etude épidémiologique sur la santé bucco-dentaire de la personne âgée en EHPAD

CLERMONT FD-BCIU Odontol. (631132226) / SudocPARIS-BIUM (751062103) / SudocCLERMONT FD-BCIU-Santé (631132104) / SudocSudocFranceF

Droit administratif et Convention européenne des droits de l'homme

International audienc

Droit administratif et Convention européenne des droits de l'homme

International audienc

Droit administratif et Convention européenne des droits de l'homme

International audienc