Flow simulations of rectal evacuation: towards a quantitative evaluation from video defaecography.

Mechanistic understanding of anorectal (patho)physiology is missing to improve the medical care of patients suffering from defaecation disorders. Our objective is to show that complex fluid dynamics modelling of video defaecography may open new perspectives in the diagnosis of defaecation disorders. Based on standard X-ray video defaecographies, we developed a bi-dimensional patient-specific simulation of the expulsion of soft materials, the faeces, by the rectum.

Towards an assessment of rectal function by coupling X-ray defecography and fluid mechanical modelling.

Despite the numerous available clinical investi-gation tests, the associated alteration of quality of life and the socio-economic cost, it remains difficult for physicians to identify the pathophysiological origins of defecation disorders and therefore to provide the appropriate clinical care. Based on standardized dynamic X-ray defecography, we developed a 2D patient-specific computational fluid dynamic model of rectal evacuation. X-ray defecography was carried out in a sitting position with a standardized paste whose yield stress matched that of soft human feces.

Biobased nucleation agents for poly-L-(lactic acid) - Effect on crystallization, rheological and mechanical properties.

In the present work, the nucleating aptitude for poly-L-(lactic acid) (PLLA) of several biobased nanoparticles (NPs) with different morphologies and surface properties, including cellulose nanofibrils with and without lignin (LCNFs and CNFs) as well as cellulose, chitin and starch nanocrystals (CNCs, ChNCs and SNCs), was investigated. A single melt-processing step using a small amount of poly(ethylene glycol) (PEG) as carrier for the NPs was adopted to prepare films with the same nanofiller content of 1 wt%. The nucleation efficiency was investigated by differential scanning calorimetry using Avrami's and Lauritzen-Hoffman's secondary nucleation theory.

Twin-screw extrusion for the production of nanocellulose-PVA gels with a high solid content.

Twin-screw extrusion (TSE) is a recent strategy used to prepare nanocelluloses at high solid contents. However, various aspects of the mechanism of disintegration and the role of fiber pretreatment remain to be elucidated. Oxidized cellulose fibers with carboxyl contents between 300 and 700 μmol·g were extruded in the presence of polyvinyl alcohol (PVA) at a 80/20 (w/w) ratio, to produce high-consistency nanocellulose gels at 15 wt% solid content, ready for use in multiple applications.

Honeycomb Organization of Chitin Nanocrystals (ChNCs) in Nanocomposite Films of UV-Cured Waterborne Acrylated Epoxidized Soybean Oil Emulsified with ChNCs.

Stable biobased waterborne Pickering dispersions of acrylated epoxidized soybean oil (AESO) were developed using chitin nanocrystals (ChNCs) as sole emulsifier without any additives. Thin AESO-ChNC nanocomposite films were produced by UV-curing thin-coated layers of the AESO emulsion after water evaporation. The kinetics of photopolymerization were assessed by monitoring the consumption of the AESO acrylate groups by infrared spectroscopy (Fourier transform infrared (FTIR)).

Chitin nanocrystals as Pickering stabilizer for O/W emulsions: Effect of the oil chemical structure on the emulsion properties.

Chitin nanocrystals (ChNCs) produced by hydrochloric acid hydrolysis of chitin were used as stabilizing agent for oil-in-water (O/W) emulsification of soybean oil (SO), acrylated soybean oil (ASO), and epoxidized soybean oil (ESO). The emulsion stability, droplet size, and rheology of the emulsion were found to be significantly affected by the oil chemical structure. Strong interaction between ChNCs and the oil droplets enhanced the stabilizing efficiency of ChNCs through a Pickering effect, resulting in emulsions with low droplet size and long-term stability.

Vinyltriethoxysilane-functionalized starch nanocrystals as Pickering stabilizer in emulsion polymerization of acrylic monomers. Application in nanocomposites and pressure-sensitive adhesives.

Emulsion polymerization provides a sustainable way to produce latex polymers for coatings and adhesives thanks to the use of water as a dispersion medium. This synthesis approach can be even more attractive if synthetic surfactant can be replaced by biobased solid particles as a stabilizer, through what is known as a "Pickering effect". Herein, latex dispersions with solid content up to 35 wt% were successfully produced by emulsion polymerization using starch nanocrystals (SNCs) as a sole stabilizer and HO/citric acid as a redox-initiator.

Cellulose nanofibrils prepared by twin-screw extrusion: Effect of the fiber pretreatment on the fibrillation efficiency.

Twin-screw extrusion (TSE) is a rather recent method to produce cellulose nanofibrils (CNFs) at a high solid content under continuous feeding. Here, never-dried commercial eucalyptus pulp was used as starting material to produce CNFs by TSE after a chemical pretreatment to introduce carboxylic groups via TEMPO-mediated oxidation and carboxymethylation. Five samples with a carboxyl content ranging from 800 to 1300 μmol.

One-step processing of plasticized starch/cellulose nanofibrils nanocomposites via twin-screw extrusion of starch and cellulose fibers.

Nanocomposites based on thermoplasticized starch filled with cellulose nanofibrils (CNFs) were produced in a single step by twin-screw extrusion of corn starch granules, glycerol as a plasticizer, and oxidized cellulose fibers. The objective was to demonstrate the possibility to produce CNFs in situ during the processing of the nanocomposite when a hydrophilic polymer matrix was used. For comparison purpose, nanocomposites were also prepared by extrusion of a previously prepared CNF suspension, corn starch granules and glycerol.

Hybrid nanocellulose decorated with silver nanoparticles as reinforcing filler with antibacterial properties.

Cellulose (Cel) nanofibrils (CNFs) produced by periodate oxidation of native cellulose fibers were functionalized with silver (Ag) nanoparticles (NPs) using Tollens' reaction. The morphology and chemical composition of the resulting Cel-Aghybrid nanofibrils were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), as well as Fourier-transform infrared (FTIR) and UV-Vis spectroscopies. To check whether the hybridization with Ag affected the reinforcing potential of the CNFs, nanocomposite films based on an acrylic matrix filled with the as-prepared Cel-Ag nanofibrils at different contents were processed by film casting.

Surfactant-free emulsion Pickering polymerization stabilized by aldehyde-functionalized cellulose nanocrystals.

Aldehyde-functionalized cellulose nanocrystals (CN) with two aldehyde contents were produced by periodate oxidation and gentle sonication. The aldehyde-functionalized CNCs were shown to be an effective stabilizer in the Pickering emulsion polymerization of acrylate monomers using potassium persulfate (KPS)/metabisulfite redox initiation system at 50 °C without any added surfactant. The effect of CNC content on the particle size, zeta-potential, colloidal stability and film properties were discussed.

CNFs from twin screw extrusion and high pressure homogenization: A comparative study.

Cellulose nanofibrils (CNFs) from oxidized never dried Eucalyptus pulps have been produced by using twin screw extrusion (TSE) and high pressure homogenizer (HPH), and their properties were compared. CNFs from TSE are produced at 10% solid content and then diluted to 1% for purpose of comparison against HPH. The nanosized fraction (NF) was around 90% for CNFs from HPH compared to 70% when TSE was used.

An experimental model to investigate the biomechanical determinants of pharyngeal mucosa coating during swallowing.

The development of innovative experimental approaches is necessary to gain insights in the complex biomechanics of swallowing. In particular, unraveling the mechanisms of formation of the thin film of bolus coating the pharyngeal mucosa after the ingestion of liquid or semi-liquid food products is an important challenge, with implication in dysphagia treatment and sensory perceptions. The aim here is to propose an original experimental model of swallowing (i) to simulate the peristaltic motions driving the bolus from the oral cavity to the esophagus, (ii) to mimic and vary complex physiological variables of the pharyngeal mucosa (lubrication, deformability and velocity) and (iii) to measure the thickness and the composition of the coatings resulting from bolus flow.

Impact of TEMPO-oxidization strength on the properties of cellulose nanofibril reinforced polyvinyl acetate nanocomposites.

Nanocomposites of polyvinyl acetate (PVAc) reinforced with two different TEMPO-oxidized cellulose nanofibrils (CNF) were prepared by casting/evaporation method. These two sets of CNF, designed as CNF-O-5min (5min of oxidation) and CNF-O-120min (120min of oxidation), are different by their surface charge, geometrical characteristics and crystallinity index. The weight fraction of CNF was changed from 1 to 10wt%.

Ultrasonic assisted production of starch nanoparticles: Structural characterization and mechanism of disintegration.

In this paper, the disintegration of starch (waxy and standard starch) granules into nanosized particles under the sole effect of high power ultrasonication treatment in water/isopropanol is investigated, by using wide methods of analysis. The present work aims at a fully characterization of the starch nanoparticles produced by ultrasonication, in terms of size, morphology and structural properties, and the proposition of a possible mechanism explaining the top-down generation of starch nanoparticles (SNPs) via high intensity ultrasonication. Dynamic light scattering measurements have indicated a leveling of the particle size to about 40nm after 75min of ultrasonication.

Starch nanocrystals and starch nanoparticles from waxy maize as nanoreinforcement: A comparative study.

The morphological, structural and thermal behavior of starch nanocrystals (SNCs) extracted from waxy maize starch through an acid hydrolysis were compared with those of starch nanoparticles (SNPs) obtained through an ultrasound treatment starting from the same waxy maize starch. The SNPs were found to be completely amorphous, slightly smaller and had no surface charge, whereas the SNCs had the expected platelet-like morphology with a negative surface charge introduced as a result of the use of sulphuric acid in the acid hydrolysis step. SNCs also showed better thermal stability than SNPs in the presence of water.

Bio-based polyurethane reinforced with cellulose nanofibers: a comprehensive investigation on the effect of interface.

Novel bio-based polyurethane (PU) nanocomposites composed of cellulose nanofiller extracted from the rachis of date palm tree and polycaprolactone (PCL) diol based PU were prepared by casting/evaporation. Two types of nanofiber were used: cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs). The mechanical and thermal properties of the nanocomposite films were studied by DMA, DSC, and tensile tests and the morphology was investigated by SEM.

Starch nanocrystal stabilized Pickering emulsion polymerization for nanocomposites with improved performance.

Latex/starch nanocrystal (SNC) nanocomposite dispersions were successfully synthesized via a one-step surfactant-free Pickering emulsion polymerization route using SNC as the sole stabilizer. The effect of the SNC content, initiator type and comonomer on the particle size, colloidal stability, and film properties were investigated. Both HCl and H2SO4-hydrolysed starch nanocrystals, each bearing different surface charges, were used as Pickering emulsion stabilizing nanoparticles.

Electric field alignment of nanofibrillated cellulose (NFC) in silicone oil: impact on electrical properties.

This work aims to study how the magnitude, frequency, and duration of an AC electric field affect the orientation of two kinds of nanofibrillated cellulose (NFC) dispersed in silicone oil that differ by their surface charge density and aspect ratio. In both cases, the electric field alignment occurs in two steps: first, the NFC makes a gyratory motion oriented by the electric field; second, NFC interacts with itself to form chains parallel to the electric field lines. It was also observed that NFC chains become thicker and longer when the duration of application of the electric field is increased.

Control of size and viscoelastic properties of nanofibrillated cellulose from palm tree by varying the TEMPO-mediated oxidation time.

The main objective of the present study was to control and optimize the preparation of nanofibrillated cellulose (NFC) from the date palm tree by monitoring the oxidation time (degree of oxidation) of the pristine cellulose and the number of cycles through the homogenizer. The oxidation was monitored by TEMPO (1-oxo-2,2,6,6-tétraméthylpipyridine 1-oxyle) mediated oxidation. Evidence of the successful isolation of NFC was given by FE-SEM observation revealing fibrils with a width in the range 20-30nm, depending of the oxidation time.

Starch nanoparticles formation via high power ultrasonication.

Nano-sized starch particles (NSP) were prepared from starch granules using a purely physical method of high-intensity ultrasonication. Particle size distribution, Field Effect Scanning Electron Microscopy (FE-SEM), Raman spectroscopy, and Wide-Angle X-ray Diffraction (WAXD) were used to characterize the morphology and crystal structure of the ensuing nanoparticles. The results revealed that ultrasound treatment of the starch suspension in water and at low temperature for 75 min results in the formation of starch nanoparticles between 30 and 100 nm in size.

Synthesis and characterization of cellulose whiskers/polymer nanocomposite dispersion by mini-emulsion polymerization.

Stable film-forming nanocomposite particles with diameters ranging from 120 to 300 nm, based on polybutylmethacrylate (PBMA) and cellulose whiskers in water dispersions, were successfully synthesized in one step through mini-emulsion polymerization. The nanocomposite dispersion with a solid content of 25 wt.% and up to 5 wt.

A biomechanical model of swallowing for understanding the influence of saliva and food bolus viscosity on flavor release.

After swallowing a liquid or a semi-liquid food product, a thin film responsible for the dynamic profile of aroma release coats the pharyngeal mucosa. The objective of the present article was to understand and quantify physical mechanisms explaining pharyngeal mucosa coating. An elastohydrodynamic model of swallowing was developed for Newtonian liquids that focused on the most occluded region of the pharyngeal peristaltic wave.

A lubrication analysis of pharyngeal peristalsis: application to flavour release.

After eating a liquid or a semi-liquid food product, a thin film responsible for the dynamic profile of aroma release coats the pharyngeal mucosa. The aim of this article was to analyse the fluid mechanics of pharyngeal peristalsis and to develop a simple biomechanical model in order to understand the role of saliva and food bolus viscosity on the coating of pharyngeal mucosa. We began by analysing the physiology and the biomechanics of swallowing in order to determine relevant model assumptions.

The initial single yeast cell adhesion on glass via optical trapping and Derjaguin-Landau-Verwey-Overbeek predictions.

We used an optical tweezer to investigate the adhesion of yeast Saccharomyces cerevisiae onto a glass substrate at the initial contact. Micromanipulation of free-living objects with single-beam gradient optical trap enabled to highlight mechanisms involved in this initial contact. As a function of the ionic strength and with a displacement parallel to the glass surface, the yeast adheres following different successive ways: (i) Slipping and rolling at 1.