Search

International audience; Functional nanoporous polymeric materials have been prepared from novel polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer precursors containing a reversible boronate ester junction between both blocks. To this purpose, homopolymers presenting either a boronic acid or a (nitro)catechol end functionality were synthesized. The coupling of each homopolymer presenting complementary chemical functions was successfully achieved under mild conditions and allowed for the generation of the corresponding boronate ester-containing diblock copolymers. Upon orientation of these precursors on silicon wafers via solvent vapor annealing, the resulting films were submitted to PEO etching through selective cleavage of the boronate ester junction under mild acidic conditions. SEM micrographs of the as-obtained thin films revealed the generation of 12 nm-diameter oriented cylindrical nanopores perpendicular to the silicon support surface.

It is common practice for hand surgeons to premix corticosteroids with a local anesthetic and store the mixture in pre-loaded syringes for rapid use during clinic. However, any possible loss of efficacy with this practice has never been studied. The purpose of this study, therefore, is to determine whether premixing betamethasone sodium phosphate/betamethasone acetate (BSP) and lidocaine (L) at different time intervals from injection has diminishing anti-inflammatory effects on chondrocytesHuman articular chondrocytes were partitioned into six groups: two controls and four experimental conditions. The negative control had growth media only. The positive control had growth media and inflammatory cytokines (interleukin-1β and oncostatin M). Experimental conditions were additionally treated with BSP alone or BSP mixed with lidocaine (BSP + L) at the time of treatment (0 hours), or at 4 or 24 hours prior. Relative expressions of inflammatory genes were measured.Relative to the positive control, chondrocytes in all experimental conditions decreased expression of TNF-α, MMP-3, and ADAMTS-4. Chondrocytes exposed to BSP only or BSP + L at 4 hours or 24 hours prior to treatment decreased expression of IL-8. Chondrocytes exposed to BSP only or BSP + L at 0 hours or 4 hours prior to treatment decreased expression of MMP-1. There were no significant differences in expression of IL-6 or MMP-13.Treatment with BSP + L prepared in pre-loaded syringes at varying time intervals up to 24 hours prior to injection does not significantly impact the ability of the mixture to reduce expression of certain key inflammatory mediators

The ability to effectively process large amounts of information in reasonable time will be important for robust deliberative collision avoidance (COLAV) planning algorithms. Failure to do so can lead to collision, and can be compared to lack of proper supervision from officers on watch (OOW). The main contribution in this article is a parallelized implementation of the Probabilistic Scenario-Based Model Predictive Control (PSB-MPC) on a Graphical Processing Unit (GPU) platform which incorporates both dynamic obstacle avoidance and anti-grounding. Simulation results demonstrate that the COLAV planner can produce collision-free trajectories with respect to grounding hazards and nearby vessels at relatively low computational cost, and which also comply to the COLREGS when deemed possible. Corresponding run-time results show that the algorithm utilizing parallel processing performs better than the alternative for increasing numbers of own-ship control behaviours, nearby static and dynamic obstacles, and dynamic obstacle prediction scenarios considered.

International audience; Understanding physical phenomena related to fluid flow transport in plants and especially through wood is still a major challenge for the scientific community. To this end, we have focused our attention on the design of wood-mimicking polymeric architectures through a strategy based on the double porogen templating approach which relies on the use of two distinct types of porogens, namely aligned nylon threads and a porogenic solvent, to produce macro- and nanoporosity levels, respectively. A bio-based phenolic functional monomer, i.e., vanillin methacrylate, was employed to mimic either hard wood or soft wood. Upon free-radical polymerization with a crosslinking agent in the presence of both types of porogenic agents, followed by their removal, biporous materials with anistotropic tubular macropores surrounded by a nanoporous matrix were obtained. They were further fully characterized in terms of porosity and chemical composition via mercury intrusion porosimetry, scanning electron microscopy and X-ray microtomography. It was demonstrated that the two porosity levels could be independently tuned by varying structural parameters. Further, the possibility to chemically modify the pore surface and thus to vary the material surface properties was successfully demonstrated by reductive amination with model compounds via Raman spectroscopy and water contact angle measurements.

Monoliths functionalized with ethylene diamine-derived ligands were synthetized within micro-sized channels as highly permeable catalytic supports for the immobilization of in-situ generated gold nanoparticles. The as-obtained hybrids, essentially differing on the grafted amine-containing ligands were compared, notably regarding the immobilized nanoparticles morphology and their dispersion at the monolith pore surface. Further, such in-capillary hybrid monoliths were successfully applied as flow-through microreactors for the catalytic reduction of nitroaromatic compounds. The general synthetic route for preparing these composite materials consisted in a three-step procedure involving (i) UV-induced polymerization of N-acryloxysuccinimide and ethylene glycol dimethacrylate in toluene, (ii) surface grafting of a series of ethylene diamine derivatives through nucleophilic substitution of N-hydroxysuccinimide leaving groups, and (iii) successive in situ reduction of tetrachloroauric acid to generate monolith-adsorbed gold nanoparticles. The successful synthesis of such hybrid monoliths was ascertained by in-situ Raman spectroscopy, EDX analysis and SEM observations. Microscopy demonstrated the key role of the grafted amine-bearing ligand regarding the morphology, size and surface coverage of the immobilized gold nanoparticles at the monolith pore surface. Monolith-adsorbed gold nanoparticles exhibited good catalytic activities towards the conversion of nitroaromatic compounds into the corresponding amino derivatives in a flow-through process. This study clearly demonstrates the key role of the nature, primary vs. secondary, of the chelating amine in the morphology (shape, size, dispersion) of the supported gold nanoparticles.

In order to determine whether organic production may be a viable option for goat farmers of the lower Mixteca region of Puebla, Mexico, in order to increase sustainability of their farms, we evaluated the extent to which these goat farms fulfill organic standards. Additionally, we revised their level of sustainability by calculating an Organic Livestock Conversion Index (OLCI) using 10 indicators and 36 variables. Information was obtained through two means: direct observation and a questionnaire applied to 119 goat farmers of six municipalities of the region. These goat farms principally consist of creole goats that graze in extensive communal rangelands and grasslands in non-arable lands with xerophytic vegetation, and their principal product is meat of adult goats. The goat farms had a moderate level of OLCI (48.0–53.6%) as well as a moderate level of sustainability (46.0–58%) for the goat farms included in this study). Five indicators showed limited compliance of the goat farms, with organic standards. Five showed a high level of compliance. The greater the OLCI value, the greater the sustainability of the goat farms. Increasing the level of compliance of the goat farms of the lower Mixteca region of Puebla, with the organic standards, which would in turn increase their level of sustainability, would require improving technical, social, environmental, and economic aspects of these farms, as well as co-responsibility in promoting sustainable organic goat farming by the different social actors involved (farmers, researchers, technical advisors, and policymakers).

This work reports the non-covalent functionalization of SWNTs with Fe-porphyrin, Co-porphyrin and Co-phthalocyanine molecules. The functionalized SWNTs were first characterized using Raman and X-ray photoelectron spectroscopies. Observations down to nanoscale resolution were also performed by atomic force microscopy, as well as scanning and transmission electron microscopies. The spectroscopic methods evidenced an electronic interaction between the metal-centered molecules and the SWNTs, ensuring the robustness of the functionalization. High resolution microscopy characterizations reveal that the porphyrin and phthalocyanine molecules are adsorbed on the surface of SWNTs. The electrical characterizations show a weak charge transfer between those grafted molecules and the SWNTs, confirming the electronic interaction between the molecules and the SWNTs. Density functional theory (DFT) supports experimental data and helps understanding the experimental results of selective interaction of metal complexes with one type of semiconducting SWNTs.

Polyelectrolytes (PEs) bearing easily derivatizable functions for possible post-modification under mild conditions can find a broad range of applications in various fields. The present paper describes the successful controlled side-chain allylation of two types of PEs: polyamine-based polycations, i.e. poly(allylamine hydrochloride) (PAH) and branched polyethyleneimine (PEI), and strong polyanions, i.e. poly(sodium vinyl sulfonate) (PVS) and poly(sodium 4-styrene sulfonate) (PSS). PSS has been largely investigated in the literature, while PVS is much less commonly explored. The allylation of each type presents its own drawback, i.e. heterogeneous reaction in the case of strong polyanions and instability of partially protonated allylated polyamine products. Nevertheless, all encountered difficulties could be solved and thoroughly elucidated by different experimental tests. This partial allyl-functionalization does not affect the electrolytic properties of the newly allylated PEs, as evidenced by the effective construction of two series of polyelectrolyte multilayer (PEM) films, namely PEI-ene (PSS-ene/PAH-ene)4 and PEI-ene (PVS-ene/PAH-ene)4, the latter being one of the rare examples developed in the literature. The presence of allyl groups on the PE side-chains allows for the stabilization of the resulting PEM films via thiol-ene photo-crosslinking in the presence of a water-soluble dithiol crosslinker. In order to fix permanently the resulting crosslinked PEM films on substrates, the covalent crosslinking occurs not only between different C=C bonds on PE layers but also with those present on substrates preliminarily functionalized with allyl groups via sulfur–gold chemistry. The robustness of both resulting crosslinked PEM films under strongly basic solution (pH 14) is validated by Quartz Crystal Microbalance (QCM) measurements. The versatility and effectiveness of the present approach is expected to find potential applications in different scientific and technological fields.

Nanoporous materials with 3-D interconnected channels and large surface areas have been known to be technologically useful for a wide spectrum of applications, particularly in the fields of energy storage and conversion, supported catalysis and separation technology. For the first time, we herein report upon an original approach to elaborate nanoporous polymers, especially thermosets, with bicontinuous morphology. The versatility of this strategy stems from the possibility of using nanoporous gold (np-Au) as a template to replicate any polymeric material. Depending on the solubility behavior of the polymer, the infiltration solution used in the step of pore filling is different, i.e. a preformed polystyrene (PS) solution or pure liquid dicyanate monomers followed by in-situ polymerization in the case of thermosetting polycyanurate (PCN). After selective and quantitative dissolution of the np-Au template in a KI/I2 solution, the resulting np-PS or np-PCN, respectively, takes the inverse morphology of np-Au, as evidenced by SEM and Fourier transform analysis. Both np-PS and np-PCN frameworks present well-defined nanostructures with a homogeneous size distribution over the entire volume of the processed samples. This new pathway is very promising not only because of its versatility in terms of polymer diversity but also for the possibility of precisely tuning the nanostructure size of the resulting nanoporous polymers.

A versatile approach towards porous polystyrene-based frameworks functionalized with triazolyl moieties is reported. These porous materials were prepared from poly( D , L -lactic acid)-block-poly(styrene-stat-4-azidomethylstyrene) (PLA-b-P(S-stat-4-AMS)) diblock copolymer precursors. Upon macroscopic orientation and subsequent alkaline hydrolysis of the PLA block, such triazolyl-containing porous polystyrenes were produced. Experimentally, a PLA macroinitiator was synthesized by ring-opening polymerization (ROP) of D , l -lactide using a heterobifunctional initiator. The prepared macroinitiator containing a terminal tertiary α-bromo ester group allowed for further ATRP statistical copolymerization of styrene and 4-azidomethylstyrene, affording the second block, i.e. the P(S-stat-4-AMS) block. The styrene to 4-azidomethylstyrene molar ratio was tuned to obtain various compositions of the hydrophobic block. PLA macroinitiators and corresponding PLA-b-P(S-stat-4-AMS) diblock copolymers were fully characterized by size exclusion chromatography (SEC), 1H and 13C nuclear magnetic resonance (NMR), Fourier Transform Infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). Functionalization of PLA-b-P(S-stat-4-AMS) diblock copolymers with p-tolylacetylene or 2-methyl-3-butyn-2-ol was carried out via copper-catalyzed azide-alkyne cycloaddition (CuAAC), yielding triazole ring in high yields (>90%). Finally, the porous structure of such functional polystyrene frameworks was examined by scanning electron microscopy (SEM).

International audience; Esters of 2-bromo-2-methylpropanoate of poly(oxyalkylene) polymers such as poly(ethylene glycol) or α-methyl poly(ethylene glycol) were prepared in high yields and characterized by spectroscopic and chromatographic methods (NMR, FT-IR, mass spectroscopy and SEC). The halogen chain-end group in the poly(oxyalkylene) bromine-terminated esters were characterized by MALDI-TOF MS. The effect of the solvents (methanol or tetrahydrofuran) and the cationic agents such as silver trifluoroacetate (AgTFA), silver trifluoromethanesulfonate (AgTFS) and sodium trifluoroacetate (NaTFA) on the mass spectra was studied. Analysis of the mass spectra demonstrated that the analyte was transformed to unsaturated (elimination), alkoxy or hydroxyl end groups (substitution) molecules when silver cationic agents were used, these results were also supported by 1H NMR study. When sodium salt was used as a cationic agent, well-defined bromine-terminated macromolecules were successfully determined through MALDI-TOF MS. Well characterized esters of 2-bromo-2-methylpropanoate of poly(oxyalkylene) polymers could be used as ATRP macroinitiators for the synthesis of a variety of polymeric architectures of interest as drug delivery bioconjugates.

International audience; Doubly porous polymeric materials were prepared from 2-hydroxyethyl methacrylate (HEMA) through the double porogen templating approach. One such approach required the use of a macroporogenic agent, i.e., NaCl particles, and a porogenic solvent. To this purpose, sieved NaCl particles of different size ranges were used (125–200 μm, 200–250 μm, and 250–400 μm), either sintered through Spark Plasma Sintering or non-fused, in conjunction with a porogenic solvent, i.e., isopropanol. After removal of both porogens, the resulting biporous scaffolds were finely characterized in terms of porosity by scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and nitrogen sorption porosimetry. All the obtained results indicated higher porosity ratios and specific surface areas for doubly porous materials prepared from SPS-mediated sintering of macroparticles, thus demonstrating the crucial role of macroporogen packing on the resulting porosity features. Indeed, a higher compaction of NaCl particles generated fewer interstitial voids between adjacent inorganic particles and thus afforded a higher porosity (87% porosity ratio) in the resulting porous material as compared to the corresponding analogue prepared from non-sintered NaCl particles (80% porosity ratio). A complementary 3-D imaging of the microstructure by means of laboratory X-ray computed microtomography (μCT) but also synchrotron μCT analysis qualitatively confirmed these findings. The macroporogen size was also considered to be a crucial parameter regarding the porosity features, as increasing macroporogen sizes were notably associated with increasing porosity ratios. Finally, swelling of those mono- and biporous materials was investigated. The interconnection in the higher porosity level was notably evaluated, and it was observed that the water uptake of biporous PHEMA scaffolds comprising an interconnected higher porosity level can be as high as ~ 2500%.

International audience; Thermally stable nanoporous polymer films have been created as promising materials for membrane technologies. Thermosetting Cyanate Ester Resins (CERs) and linear polyurethane (LPU) were combined by stepwise thermal curing, and the films of resulting hybrid polymers were irradiated with α-particles followed by chemical etching. Well-defined highly regular nanoporous structures were developed in the films as evidenced by using SEM. No significant changes in chemical structure of the polymer systems obtained after α-irradiation were observed by FTIR spectroscopy measurements. The polymer films obtained on the basis of hybrid networks with the CER/LPU composition equal to 90/10 wt.% had quite narrow pore diameter distribution with average pore diameters around 12 nm. DSC and TGA measurements showed that the thermal characteristics of the nanoporous films were sufficiently high (Тg ~ 167 °C to ~199 °C, Тd5% ~ 293-359 o C, and Тd max ~ 429-457 o C). The CER/LPU nanoporous thermosetting materials demonstrated effective gas transport properties tested with gases, such as О2, СО2, N2, and СН4. The combination of an additional sensitization step using -rays and longer time of chemical etching improved the properties of the nanoporous systems developed. Such materials open the way to numerous applications, for example, as ultrafiltration membranes for advanced technologies, especially under extreme conditions.

International audience

Poly-4-hydroxybutyrate (P4HB) is a biopolymer produced by Escherichia coli K12 bacteria. P4HB is fully resorbed in vivo by 18-24 months post-implantation. The aim of this study is to evaluate P4HB in the rabbit abdomen and vagina to determine that the biomechanical and histological properties are similar to the standard polypropylene mesh. Our hypothesis is that the histological and biomechanical properties of a fully absorbable graft will be similar to a lightweight polypropylene (PP) mesh when implanted in rabbit vagina and abdomen.Sixteen (n = 16) female New Zealand White (retired breeder) rabbits were equally divided between two time points (3 and 9 months). A total of 17 rabbits were used owing to one death secondary to suspected cardiomyopathy. P4HB scaffold and PP mesh were subcutaneously and peri-vaginally implanted into the rabbit abdomen and vagina respectively. All rabbits had both posterior and anterior vaginal implants, and half of the rabbits had four abdominal implants in addition to the vaginal implants. The abdominal implants were 4.5 cm long × 1.5 cm wide whereas the vaginal implants were 1.5 cm long × 0.5 cm wide. At 3 and 9 months, gross necropsy was performed and samples were obtained, sectioned, stained and evaluated via histological analysis. Specimens were assessed for host inflammatory response, neovascularization, elastin content, and collagen deposition/maturation. Specimens were also biomechanically evaluated via uniaxial tensile test to determine the stiffness, ultimate tensile strength and load at ultimate tensile strength of the device/tissue composite.No abdominal mesh exposures were noted. A comparable number of asymptomatic partial vaginal exposures were observed at 3 months (P4HB: n = 3; PP: n = 2) and 9 months (P4HB: n = 3; PP: n = 2) respectively. Histological analysis of specimens showed comparable results in the P4HB and PP groups at 3 and 9 months post-implantation. Although no acute inflammation was seen, chronic inflammation was demonstrated in all specimens. Elastic fibers were present in the 3-month vaginal PP and P4HB specimens, but were not seen again. There was an increase in type I/III collagen noted over time. Biomechanical evaluation of the vaginal mesh tissue complex showed ultimate tensile strength was not significantly different between P4HB and PP groups at 3 (P = 0.625) and 9 months (P = 0.250) respectively.P4HB scaffold may represent a fully absorbable alternative to permanent mesh for pelvic organ prolapse (POP) repair.

International audience; In this paper we provide a FFT algorithm to compute the effective permeability of doubly porous solids constituted of two populations of pores which are different in size. The paper focuses on the resolution of the fluid flow at the intermediate scale, that of the macropores, that requires the resolution of the coupled Darcy/Stokes problem. The permeability associated with the first population of cavities is assumed to be known. A two-field FFT based iterative scheme is derived to compute the solution of the Darcy/Stokes problem. The principle is to reformulate the problem by considering a unique Brinkman equation with different coefficients for the Darcy and the Stokes regions. As a first application, we determine the macroscopic permeability of a porous solid containing circular macropores. The results are compared to analytic expressions and simplified modeling which use an equivalent Darcy medium in place of the macropores. Next, we apply the FFT method to a bi-porous polymer. The computations are performed on 2D and 3D cells extracted from X-ray computed microtomography.

Background: At the present, agricultural production systems need to produce more food, in the shortest possible time, and at the same time conserve natural resources. Among the initiatives that have been implemented, agrosilvopastoral systems are a viable strategy with regard to extensive livestock. Objective: We characterize the historical trajectory as well as technical and socioeconomic indicators of cattle raising using extensive and agrosilvopastoral practices in the municipality of Pijijiapan, Chiapas, Mexico. Methodology: Information was obtained through in-depth interviews with key informants, documentary review, semi-structured interviews, and direct observation in 35 livestock production units (LPU). Qualitative information was organized chronologically and presented in a descriptive, narrative manner. Quantitative data were analyzed using a K-means cluster analysis according to a Livestock Agroecosystem Services Index (ISAGAN according to its Spanish initials) of the LPU. Information was examined using analysis of variance and a non-parametric Kruskal-Wallis test in order to identify differences among clusters. Results: Three important stages were identified in the historical trajectory: i) a colonial, pre-livestock raising period with little anthropic intervention, prior to 1900; ii) a period of productive development of livestock raising, from 1900 to 1955, and iii) a period of expansion of extensive livestock raising, beginning in 1955, with significant environmental impacts. More recently, agrosilvopastoral management has been presented as a sustainable alternative to extensive livestock raising. Implications: Livestock raising based on grazing is characterized by a tree gradient, a low level of technological development, low use of external inputs, and holistic diversified resource use. Conclusion: Of 26 technical and socioeconomic indicators evaluated, technical advisory was the only one which varied (p< 0.05) among clusters; upon increasing the values of this indicator, ISAGAN also increased.