Influence of Filler Dispersion on Mechanical Behavior with Large-Scale Coarse-Grained Molecular Dynamics Simulation

Filler morphology impact the physical properties of filled rubber. Two large-scale coarse-grained models containing 1,000 filler particles and 20,000,000 polymer beads were created and coarse-grained molecular dynamics simulations based on Kremer-Grest model were carried out in order to investigate a relationship between filler morphology and mechanical behavior. One is an aggregated model including a non-homogeneous filler distribution which is determined by TEM image analysis, and the other is a uniformity arranged model in which filler particles are distributed in lattice pattern. Comparing stress-strain curves of both models under cyclic deformation stretching to Lambda = 2.0, we confirmed that effects of filler morphology observed in experimental results were reproduced qualitatively by our simulations. The effects of filler morphology are differences of mechanical behavior, modulus and hysteresis of the aggregated model are greater than the uniformity arranged model and that remains in subsequent cycles. Analyzing stresses of both models, we found the differences are mainly attributed to filler stress induced during deformation. Fillers are to be contacted with another adjacent filler particle during deformation and filler stress grows when fillers are aggregated. In addition, differences in contact direction of fillers between loading and unloading increase hysteresis of the aggregated model. Breakage of filler aggregate due to the contacts between fillers in the 1st loading causes stress-softening as contact force and area decrease. We focused on changes of length of polymer-paths bridging filler particles and measured those in the uniformity arranged model in order to study a origin of stress which result from polymer chains dynamics. It was found that polymer-paths become longer to adjust the increase of filler-filler distance particularly in the 1st loading, and the change of polymer-paths in subsequent cycles are lesser than the 1st loading. This irreversible change of polymer network causes hysteresis and stress-softening derived from polymer dynamics

Modelling the Microstructure and the Viscoelastic Behaviour of Carbon Black Filled Rubber Materials from 3D Simulations

Volume fraction and spatial repartition of fillers impact the physical properties of rubber. Extended percolating networks of nano-sized fillers significantly modify the macroscopic mechanical properties of rubbers. Random models that describe the multiscale microstructure of rubber and efficient Fourier-based numerical algorithms are combined to predict the material’s mechanical properties. From TEM image analysis, various types of multiscale models were proposed and validated, accounting for the non-homogeneous distribution of fillers: in the present work, aggregates are located outside of an exclusion polymer simulated by two families of random models. The first model generates the exclusion polymer by a Boolean model of spheres. In the second model, the exclusion polymer is a mosaic model built from a Johnson-Mehl tessellation. Here the exclusion polymer and the polymer containing the filler show a similar morphology, contrary to the Boolean model. Aggregates are then described as the intersection of a Boolean model of spheres and of the complementary of the exclusion polymer. Carbon black particles are simulated by a Cox model of spheres in the aggregates. The models rely on a limited number of parameters fitted from experimental covariance and cumulative granulometry. The influence of the model parameters on percolation properties of the models is studied numerically from 3D simulations. Finally, a novel Fourier-based algorithm is proposed to estimate the viscoelastic properties of linear heterogeneous media, in the harmonic regime. The method is compared to analytical results and to a different, time-discretized FFT scheme. As shown in this work, the proposed numerical method is efficient for computing the viscoelastic response of microstructures containing rubbers and fillers

Myocardial deletion of Smad4 using a novel alpha skeletal muscle actin Cre recombinase transgenic mouse causes misalignment of the cardiac outflow tract

S MAD4 acts as the converging point f or T GF β and BMP signaling in heart development. Here, we investigated the role of S MAD4 in heart development usi ng a novel α skeletal muscle actin Cre recombinase (MuCre) transgenic mouse strain. Lineage tracing using MuCre/ROSA26LacZ reporter mice indicated strong Cre-recombinase expression in developing and adult heart and skeletal muscles. In heart development, significant MuCre expression was noted at E11.5 in the atrial, ventricular, outflow tract and atrioventricular canal myocardium, but not in the endocardial cushions. MuCre-driven conditional deletion of Smad4 in mice caused double outlet right ventricle (DORV), ventricular septal defect (VSD), impaired trabeculation and thinning of ventricular myocardium, and mid-gestational embryonic lethality. In conclusion, MuCre mice effectively delete genes in both heart and skeletal muscles, thus enabling the discovery that myocardial Smad4 deletion causes misalignment of the outflow tract and DORV

ENHANCING PRODUCTION THROUGH OPTIMISATION OF DPPH AND RADICAL SCAVENGING ACTIVITY OF GRAPE SEED EXTRACTS

Polyphenols are important for their pharmacological activity and positive contribution to cellular processes within the body. They have the capacity to protect against oxidation of High Density Lipids (HDL) and, thus help the body to retain HDL, while removing the problematic Low Density Lipids (LDL). Polyphenols also possess anti-ulcer, anti-carcinogenic and anti-mutagenic activities. The objective of this study was to evaluate the effect of temperature and grain size of grape seed on the efficiency of extraction of polyphenols from grape seed, using the compressed hot water and solvent extraction techniques. Polyphenols were extracted from milled (<0.5 mm) and whole grape seed, using compressed hot water (high temperature and high pressure) and solvents (Acetone, Methanol and Ethanol). The total polyphenol content and DPPH radical scavenging activity of the extracts were determined using spectrometer and the active compounds identified using HPLC. Total polyphenol content increased with extraction temperature, but decreased at 200 \ub0C. The difference in polyphenol extracts from the milled and whole seed decreased with increase in temperature, but was more evident at 135 \ub0C. The 2 hour extracts showed relatively higher values than those for 1 hour, with the lowest difference occurring at 165 \ub0C and the highest at 180 \ub0C. Solvent extracts from whole seeds were very low compared with the milled seeds, with acetone showing the highest value of 105 mg g-1 dry matter for polyphenol content and 110 mg g-1 of dry matter for DPPH radical scavenging activity. Methanol had the lowest value (78 mg g-1 dry matter) for polyphenol extracts and 80 mg g-1 for the DPPH radical scavenging activity. The main extract compounds were gallic acid, catechin and epicatechin.Les polyph\ue9nols sont importants eu \ue9gard \ue0 leur activit\ue9 pharmacologique et leur contribution positive aux processus cellulaires dans le corps. Ils sont dou\ue9s d\u2019une capacit\ue9 protective contre l\u2019oxydation des Lipides \ue0 Densit\ue9 Elev\ue9e (HDL) et, ainsi aident le corps \ue0 maintenir le HDL, tout en \ue9liminant les probl\ue9matiques Lipides \ue0 Basse Densit\ue9. Les polyph\ue9nols poss\ue8dent aussi des activit\ue9s anti-ulc\ue8res, anticarcinog\ue8nes et antimutag\ue8nes. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer les effets de la temp\ue9rature et taille des grains de raisin sur l\u2019efficacit\ue9 de l\u2019extraction des polyph\ue9nols des grains de raisin, utilisant une eau chaude compress\ue9e et des techniques d\u2019extraction au solvant. Les polyphenols \ue9taient extraits des grains entiers de raisin et des grains moulus (<0.5 mm) \ue0 l\u2019aide d\u2019une eau chaude compress\ue9e (temp\ue9rature \ue9lev\ue9e et haute pression) et des solvants (Ac\ue9tone, M\ue9thanol et Ethanol). La concentration totale des polyph\ue9nols et l\u2019activit\ue9 d\u2019absoption du radical DPPH des extraits \ue9taient d\ue9termin\ue9s \ue0 l\u2019aide du spectrophotom\ue8tre et les compos\ue9s actifs identifi\ue9s par HPLC. La concentration totale des polyph\ue9nols a augment\ue9 avec la temp\ue9rature d\u2019extraction, mais a diminu\ue9 \ue0 200 \ub0C. La diff\ue9rence dans les extraits de polyph\ue9nol des grains moulus et entiers a diminu\ue9 avec l\u2019augmentation de la temperature, mais \ue9tait plus \ue9vidente \ue0 135 \ub0C. Les extraits de deux heures ont montr\ue9 des valeurs relativement plus \ue9lev\ue9es que ceux d\u2019une heure, avec les diff\ue9rences les plus faibles apparaissant \ue0 165 \ub0C et les plus \ue9lev\ue9es \ue0 180 \ub0C. Les extraits de graines enti\ue8res aux solvants \ue9taient de faible quantit\ue9 en comparaison avec ceux des grains moulus, les valeurs les plus \ue9lev\ue9es \ue9tant de 105 mg g-1 de mati\ue8re s\ue8che de polyph\ue9nol et 110 mg g-1 de mati\ue8re s\ue8che d\u2019absorption du radical DPPH obtenues en utilisant l\u2019ac\ue9tone comme solvant. Les extraits obtenus au m\ue9thanol comme solvant \ue9taient encore en plus faible quantit\ue9 avec 78 mg-1 de la mati\ue8re s\ue8che pour les extraits du polyph\ue9nol et 80 mg g-1 pour l\u2019activit\ue9 d\u2019absorption du DPPH. Les principaux compos\ue9s de ces extraits \ue9taient des acides galliques, des cat\ue9chines et des epicat\ue9chines

Evidence of multiple sorption modes in layered double hydroxides using Mo as structural probe

Layered double hydroxides (LDHs) have been considered as effective phases for the remediation of aquatic environments, to remove anionic contaminants mainly through anion exchange mechanisms. Here, a combination of batch isotherm experiments and X-ray techniques was used to examine molybdate (MoO ) sorption mechanisms on CaAl LDHs with increasing loadings of molybdate. Advanced modeling of aqueous data shows that the sorption isotherm can be interpreted by three retention mechanisms, including two types of edge sites complexes, interlayer anion exchange, and CaMoO precipitation. Meanwhile, Mo geometry evolves from tetrahedral to octahedral on the edge, and back to tetrahedral coordination at higher Mo loadings, indicated by Mo K-edge X-ray absorption spectra. Moreover, an anion exchange process on both CaAl LDHs was followed by in situ time-resolved synchrotron-based X-ray diffraction, remarkably agreeing with the sorption isotherm. This detailed molecular view shows that different uptake mechanisms - edge sorption, interfacial dissolution-reprecipitation - are at play and control anion uptake under environmentally relevant conditions, which is contrast to the classical view of anion exchange as the primary retention mechanism. This work puts all these mechanisms in perspective, offering a new insight into the complex interplay of anion uptake mechanisms by LDH phases, by using changes in Mo geometry as powerful molecular-scale probe.This work has been supported by a grant from Labex OSUG@2020 (Investissements d’avenir - ANR10 LABX56). B.M., A.F.-M., L.C., S.G. and F.C. thank the NEEDS program from the CNRS for funding support. B.M. also thanks the financial support from the China Scholarship Council (CSC)

Hedgehog signal activation in oesophageal cancer patients undergoing neoadjuvant chemoradiotherapy

The zinc finger protein glioma-associated oncogene homologue 1 (Gli-1) is a critical component of the Hedgehog (Hh) signalling pathway, which is essential for morphogenesis and stem-cell renewal, and is dysregulated in many cancer types. As data were not available on the role of Gli-1 expression in oesophageal cancer progression, we analysed whether it could be used to predict disease progression and prognosis in oesophageal cancer patients undergoing neoadjuvant chemoradiotherapy (CRT). Among 69 patients with histologically confirmed oesophageal squamous cell carcinomas (ESCCs), 25 showed a pathological complete response after preoperative CRT. Overall survival (OS) was significantly associated with lymph-node metastasis, distant metastasis, and CRT, and was further correlated with the absence of both Gli-1 nuclear expression and residual tumour. All patients with Gli-1 nuclear expression (10.1%) had distant or lymph-node metastasis, and six out of seven died within 13 months. Furthermore, patients with Gli-1 nuclear-positive cancers showed significantly poorer prognoses than those without (disease-free survival: mean DFS time 250 vs 1738 months, 2-year DFS 0 vs 54.9%, P=0.009; OS: mean OS time 386 vs 1742 months, 2-year OS 16.7 vs 54.9%, P=0.001). Our study provides the first evidence that Gli-1 nuclear expression is a strong and independent predictor of early relapse and poor prognosis in ESCC after CRT. These findings suggest that Hh signal activation might promote cancer regrowth and progression after CRT