scholarly journals Rheological and Rheo-optical Behaviors of Nanocellulose Suspensions Containing Unfibrillated Fibers

2021 ◽  
Author(s):  
Yoshifumi Yamagata ◽  
Shingo Niinobe ◽  
Kotaro Suga ◽  
Keisuke Miyamoto
Keyword(s):  
Structural Changes ◽  
Volume Fraction ◽  
Shape Change ◽  
Flow Direction ◽  
Flow Behavior ◽  
Cellulose Nanofibers ◽  
Plateau Modulus ◽  
Practical Applications ◽  
Entropic Elasticity ◽  
Frequency Sweeps

Abstract Cellulose nanofibers (CNFs) produced by mechanical processing have a more uneven fiber shape, diameter, and length than those produced by chemical processing. Depending on the manufacturing conditions, CNFs containing insufficient fibrillated fibers may be produced. In order to find practical applications for CNFs containing unfibrillated fibers, it is important to understand how to control the rheological behavior of these systems. In this study, we investigated the relationship between the nanosized volume fraction and the rheological behaviors of CNF suspensions containing unfibrillated fibers prepared by a wet refining system (Water Jet System). The macroscopic structural changes in those suspensions under shear flow were also discussed based on rheo-optic measurements. According to the frequency sweeps of the CNF suspensions, it was found that they were elastic-dominated gels, and the elasticity was attributed to the nanofibers. The elastic moduli increased with the volume fraction of the nanofibers, suggesting that the entanglement of the nanofibers was enhanced. The pseudo-plateau modulus Gp' is proportional to the nanofiber volume fraction, with the constant α = 1.5, suggesting that the entropic elasticity is dominant. The viscosity curves of the CNF suspensions showed a shear thinning behavior, in which the viscosity linearly decreased with the increasing shear rate. From the Rheo-SALS measured at the same time, we found that the aggregates of the nanofibers elongated in the flow direction and deformed into an elliptical shape with the applied shearing. The shape change of the aggregates comprised of the nanofibers became more pronounced with the increased nanofiber volume fraction. However, the effect of the shape change of the aggregates was hardly observed on the viscosity curve. We speculate that this is due to the fact that the unnanosized fibers, which exhibit a Newtonian flow, play a significant role in the flow behavior of the CNF suspensions.

Talc Filled Thermoplastic Composites: Melt Rheological Properties

2003 ◽  
Vol 13 (6) ◽  
pp. 297-304 ◽  
Author(s):  
P. Mederic ◽  
M. Moan ◽  
M.-H. Klopffer ◽  
Y. Saint-Gerard
Keyword(s):  
Storage Modulus ◽  
Rheological Behavior ◽  
Volume Fraction ◽  
Flow Direction ◽  
Low Frequency ◽  
Complex Viscosity ◽  
Thermoplastic Composites ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Frequency Sweeps

Abstract The effects of composition and resulting morphology on the rheology of thermoplastics filled with different talc platelets were studied in the 0-22% range of volume fraction, Φ. The sufficiently filled polymer composites exhibit a rheological behavior which significantly differs from the pure polymers used in this work, a linear low density polyethylene, a low density polyethylene and a polyamide 12. The changes in the rheological behavior are influenced by the size, the concentration and the surface treatment of plate-like talc particles. They also depend on the chemical nature and viscous and elastic characteristics of the polymer matrix. In particular, the effect of platelet orientation on the viscoelastic properties of reinforced composites was pointed out. For sufficiently filled systems, a low frequency response indicative of a pseudo solid-like behavior is obtained only during the first frequency sweep. In fact, the low frequency storage modulus, G’, is constant. With repeated frequency sweeps, more platelets were aligned in the flow direction, thus the low frequency storage modulus gradually decreases and becomes dependent on frequency, ω. The low frequency complex viscosity η* also progressively decreases with repeated frequency sweeps. In addition, for these systems, the low shear viscosity η build up in an unbounded manner because of the existence of particle-particle interactions. There are stresses below which there is no flow indicating the existence of yield values. Steady shear elastic properties are also studied, especially in the case of systems showing an apparent yield stress.

scholarly journals Molecular Dynamics Simulation on the Interaction between Palygorskite Coating and Linear Chain Alkane Base Lubricant

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 286
Author(s):  
Jin Zhang ◽  
Lv Yang ◽  
Yue Wang ◽  
Huaichao Wu ◽  
Jiabin Cai ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Structural Changes ◽  
Molecular Diffusion ◽  
Linear Chain ◽  
Interfacial Interaction ◽  
Dynamics Simulation ◽  
Electrostatic Energy ◽  
Experimental Development ◽  
Practical Applications ◽  
Self Diffusion

Molecular dynamics (MD) simulations were conducted to investigate the interactions between a palygorskite coating and linear chain alkanes (dodecane C12, tetradecane C14, hexadecane C16, and octadecane C18), representing base oils in this study. The simulation models were built by placing the alkane molecules on the surface of the palygorskite coating. These systems were annealed and geometrically optimized to obtain the corresponding stable configurations, followed by the analysis of the structural changes occurring during the MD process. The interfacial interaction energies, mean square displacements, and self-diffusion coefficients of the systems were evaluated to characterize the interactions between base lubricant molecules and palygorskite coating. It was found that the alkanes exhibited self-arrangement ability after equilibrium. The interfacial interaction was attractive, and the electrostatic energy was the main component of the binding energy. The chain length of the linear alkanes had a significant impact on the intensity of the interfacial interactions and the molecular diffusion behavior. Moreover, the C12 molecule exhibited higher self-diffusion coefficient values than C14, C16 and C18. Therefore, it could be the best candidate to form an orderliness and stable lubricant film on the surface of the palygorskite coating. The present work provides new insight into the optimization of the structure and composition of coatings and lubricants, which will guide the experimental development of these systems for practical applications.

scholarly journals Lasting effects of prenatal exposure to Cannabis in the retina of the offspring: an experimental study in mice

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Paulo Roberto Arruda Zantut ◽  
Mariana Matera Veras ◽  
Sarah Gomes Menezes Benevenutto ◽  
Angélica Mendonça Vaz Safatle ◽  
Ricardo Augusto Pecora ◽  
...  
Keyword(s):  
Young Adult ◽  
Light Microscopy ◽  
Prenatal Exposure ◽  
Structural Changes ◽  
Volume Fraction ◽  
Clinical Care ◽  
Retinal Layer ◽  
Exposed Population ◽  
The Central Nervous System ◽  
The Impact

Abstract Background Prenatal exposure to Cannabis is a worldwide growing problem. Although retina is part of the central nervous system, the impact of maternal Cannabis use on the retinal development and its postnatal consequences remains unknown. As the prenatal period is potentially sensitive in the normal development of the retina, we hypothesized that recreational use of Cannabis during pregnancy may alter retina structure in the offspring. To test this, we developed a murine model that mimics human exposure in terms of dose and use. Methods Pregnant BalbC mice were exposed daily for 5 min to Cannabis smoke (0.2 g of Cannabis) or filtered air, from gestational day 5 to 18 (N = 10/group). After weaning period, pups were separated and examined weekly. On days 60, 120, 200, and 360 after birth, 10 pups from each group were randomly selected for Spectral Domain Optical Coherence Tomography (SD-OCT) analysis of the retina. All retina layers were measured and inner, outer, and total retina thickness were calculated. Other 37 mice from both groups were sacrificed on days 20, 60, and 360 for retinal stereology (total volume of the retina and volume fraction of each retinal layer) and light microscopy. Means and standard deviations were calculated and MANOVA was performed. Results The retina of animals which mother was exposed to Cannabis during gestation was 17% thinner on day 120 (young adult) than controls (P = 0.003) due to 21% thinning of the outer retina (P = 0.001). The offspring of mice from the exposed group presented thickening of the IS/OS in comparison to controls on day 200 (P < 0.001). In the volumetric analyzes by retinal stereology, the exposed mice presented transitory increase of the IS/OS total volume and volume fraction on day 60 (young adult) compared to controls (P = 0.008 and P = 0.035, respectively). On light microscopy, exposed mice presented thickening of the IS/OS on day 360 (adult) compared to controls (P = 0.03). Conclusion Gestational exposure to Cannabis smoke may cause structural changes in the retina of the offspring that return to normal on mice adulthood. These experimental evidences suggest that children and young adults whose mothers smoked Cannabis during pregnancy may require earlier and more frequent clinical care than the non-exposed population.

scholarly journals Flow responses alteration by geometrical effects of tubercles on plates under the maximal angle of attack

2020 ◽  
pp. 095440622097543
Author(s):  
KS Mu ◽  
ABH Kueh ◽  
PN Shek ◽  
MR Mohd Haniffah ◽  
BC Tan
Keyword(s):  
Flow Direction ◽  
Flow Behavior ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Control Case ◽  
Reattachment Length ◽  
Flow Recirculation ◽  
Pressure Profiles ◽  
Maximal Angle ◽  
Geometrical Effects

Plates with leading-edge tubercles experience beneficially more gradual aerodynamics stalling when entering the post-stall regime. Little is known, however, about the corresponding aquatic flow responses when these tubercles-furnished plates are subjected to the maximal angle of attack, with the flow direction perpendicular to their planar area. Hence, this study presents numerically, by means of the flow behavior solver ANSYS, the flow responses alteration in terms of the geometrical effects of tubercles on plates through changes in amplitudes (5 mm, 10 mm, 15 mm) and wavelengths (50 mm, 100 mm, 150 mm) under the maximal angle of attack in comparison to a control case, i.e., without tubercles. Additional to the commonly examined flow velocity and pressure, characteristics such as wake (area, reattachment length, flow recirculation intensity) and newly defined downstream vortical parameters (area, perimeter, and Feret diameters) for the vortex region have been proposed and assessed. It is found that the drag increases with the tubercle wavelength but corresponds inversely with the tubercle amplitude. By correlating with the best beneficial velocity and pressure profiles, it has been characterized that the optimally performing plate is the one that generates the greatest flow recirculation intensity, wake area, and reattachment length, corresponding to the capability to produce also the highest vortical area, perimeter, and major Feret diameter. Compared to the control case, all plates with tubercles alter beneficially these flow behaviors. In conclusion, plates with tubercles contribute favorably to the flow behaviors under the maximal angle of attack compared to the control case while the newly proposed downstream parameters could serve capably as alternatives in corroborating the flow physics description in future studies.

Gas Carry-Under in GLCC for Separated and Recombined Outlet Configurations

2018 ◽  
Author(s):  
Srinivas Swaroop Kolla ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Volume Fraction ◽  
Swirling Flow ◽  
Control Strategies ◽  
Flow Behavior ◽  
Jet Impingement ◽  
Test Facility ◽  
Experimental Investigations ◽  
Level Control ◽  
Complex Flow ◽  
Control Configuration

Gas Carry-Under (GCU) is one of the undesirable phenomena that exists in the GLCC©1 even within the Operational Envelope (OPEN) for liquid carry-over. Few studies that are available on GLCC© GCU have been carried out when the GLCC© is operated in a metering loop configuration characterized by recombined outlets. In such configurations the gas and the liquid outlets of the GLCC are recombined downstream which acts as passive level control. However, studies have shown that the GLCC© OPEN increases significantly when active control strategies are employed. There has not been a systematic study aimed at analyzing the effect of control on the GCU in the GLCC. This study compares the previously published GLCC GCU swirling flow mechanism under recombination outlet configuration with data taken under the separated outlet configuration (control configuration). Experimental investigations for GCU are conducted in a state-of-the-art test facility for air-water and air-oil flow incorporating pressure and level control configurations. The experiments are carried out using a 3″ diameter GLCC© equipped with 3 sequential trap sections to measure simultaneously the Gas Volume Fraction (GVF) and gas evolution in the lower part of the GLCC. Also, gas trap sections are installed in the liquid leg of the GLCC© to measure simultaneously the overall GCU. The liquid level was controlled at 6″ below the GLCC© inlet for all experiments using various control strategies. Tangential wall jet impingement is the cause for entrainment of gas, thereby leading to GCU. 3 different flow mechanisms have been identified in the lower part of the GLCC and have significant effect on the GCU. Viscosity and surface tension are observed to affect the GCU. The extensive acquired data shed light on the complex flow behavior in the lower part of the GLCC© and its effect on the GCU of the GLCC©.

scholarly journals Injectable and Gellable Chitosan Formulations Filled with Cellulose Nanofibers for Intervertebral Disc Tissue Engineering

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1202 ◽  
Author(s):  
Ingo Doench ◽  
Maria Torres-Ramos ◽  
Alexandra Montembault ◽  
Paula Nunes de Oliveira ◽  
Celia Halimi ◽  
...  
Keyword(s):  
Intervertebral Disc ◽  
Rheological Behavior ◽  
Biomedical Application ◽  
Flow Behavior ◽  
Cellulose Nanofibers ◽  
Nanofibrillated Cellulose ◽  
The Body ◽  
Mechanical Reinforcement ◽  
Invasive Approach

The development of non-cellularized injectable suspensions of viscous chitosan (CHI) solutions (1.7–3.3% (w/w)), filled with cellulose nanofibers (CNF) (0.02–0.6% (w/w)) of the type nanofibrillated cellulose, was proposed for viscosupplementation of the intervertebral disc nucleus pulposus tissue. The achievement of CNF/CHI formulations which can gel in situ at the disc injection site constitutes a minimally-invasive approach to restore damaged/degenerated discs. We studied physico-chemical aspects of the sol and gel states of the CNF/CHI formulations, including the rheological behavior in relation to injectability (sol state) and fiber mechanical reinforcement (gel state). CNF-CHI interactions could be evidenced by a double flow behavior due to the relaxation of the CHI polymer chains and those interacting with the CNFs. At high shear rates resembling the injection conditions with needles commonly used in surgical treatments, both the reference CHI viscous solutions and those filled with CNFs exhibited similar rheological behavior. The neutralization of the flowing and weakly acidic CNF/CHI suspensions yielded composite hydrogels in which the nanofibers reinforced the CHI matrix. We performed evaluations in relation to the biomedical application, such as the effect of the intradiscal injection of the CNF/CHI formulation in pig and rabbit spine models on disc biomechanics. We showed that the injectable formulations became hydrogels in situ after intradiscal gelation, due to CHI neutralization occurring in contact with the body fluids. No leakage of the injectate through the injection canal was observed and the gelled formulation restored the disc height and loss of mechanical properties, which is commonly related to disc degeneration.

The ellipsoidal form of clasts with practical applications to fabric and size analyses of fluvial gravels

1980 ◽  
Vol 17 (12) ◽  
pp. 1725-1739 ◽  
Author(s):  
Emlyn H. Koster ◽  
Brian R. Rust ◽  
Don J. Gendzwill
Keyword(s):  
Statistical Analysis ◽  
Flow Direction ◽  
Probability Distributions ◽  
Size Analysis ◽  
Shape Variation ◽  
Practical Applications ◽  
Flow Interactions ◽  
Typical Range ◽  
Plane Area ◽  
Key Parameter

The widespread assumption that most water-worn gravel clasts approximate ellipsoids is confirmed by a statistical analysis of available data. The analysis demonstrates a Gaussian distribution of V/Ve ratios, centred on unit ratio, where V is clast volume and Ve the volume of a symmetric ellipsoid with equivalent triaxial dimensions. For internally isotropic and unbroken clasts, ellipsoidal form evolves as the rounding due to abrasion reaches its final stages. There appears to be no other major control on the tendency towards ellipsoidal geometry. The ellipsoidal tendency assists the interpretation of fluvial gravel deposits, which depends greatly on accurate description of clast size and fabric.Firstly, it facilitates calculation of Ap, the plane area projected upstream by clasts, a key parameter in bed–flow interactions such as preferred fabric. Formulae are derived to calculate Ap for ellipsoidal clasts with any configuration relative to flow direction. Viewing fabric in terms of the Ap variable supports and explains earlier conclusions concerning the controls on variability of imbrication angle.Secondly, an investigation of the relative merits of six size measures as descriptors of areal trends and predictors of nominal diameter, dn, concludes that (abc)1/3(the formula for dn of an ellipsoid) is superior. Other measures, namely, a, b, c, (a + c)/2, and (a + b + c)/3, are all subject to error in proportion to the degree of shape variation. Also, since downstream fining is typically accompanied by a changing proportion of oblate, bladed, prolate, and equant forms, dn is subject to inconsistent levels of under- or overestimation. The commonly used b dimension is endorsed as an acceptable predictor of dn, but a severely overestimates dn and should be abandoned. Information on errors in size analysis is presented as nomograms in the form of contoured c/b versus b/a plots and as probability distributions based on the typical range of shape variation in fluvial gravel.

Effects of Inclination Angle of Ribs on the Flow Behavior in Rectangular Ducts

2004 ◽  
Vol 126 (4) ◽  
pp. 692-699 ◽  
Author(s):  
Xiufang Gao ◽  
Bengt Sunde´n
Keyword(s):  
Velocity Component ◽  
Flow Direction ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Fluid Flows ◽  
Streamwise Velocity ◽  
Flow Structures ◽  
Local Flow ◽  
Flow Motion ◽  
Streamwise Velocity Component

The flow behavior in rib-roughened ducts is influenced by the inclination of ribs and the effect is investigated in the present study by Particle Image Velocimetry (PIV). The local flow structures between two adjacent ribs were measured. The Reynolds number was fixed at 5800. The flow field description was based on the PIV results in planes both parallel and perpendicular to the ribbed walls at various locations. The rib angle to the main flow direction was varied as 30 deg, 45 deg, 60 deg and 90 deg. The ribs induce three dimensional flow fields. The flow separation and reattachment between adjacent ribs are clearly observed. In addition, the inclined ribs are found to alter the spanwise distribution of the streamwise velocity component. The streamwise velocity component has its highest values at the upstream end of the ribs, and decreases continuously to its lowest values at the downstream end. Strong secondary flow motion occurs over the entire duct cross section for the inclined ribs. The flow structures between two consecutive ribs show that the fluid flows along the ribs from one end of the ribs to the other end, and then turns back at the transverse center. Downwash and upwash flows are observed at the upstream end and downstream end of the ribs, respectively.

Abstract 14309: A Novel Fibroblast Activation Inhibitor, NM922, Attenuates Maladaptive Fibrotic Remodeling to Preserve Cardiac Function Following the Onset of Heart Failure

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Jessica M Bradley ◽  
Craig M Ziblich ◽  
Kazi N Islam ◽  
Amanda M Rushing ◽  
David J Polhemus ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Function ◽  
Structural Changes ◽  
Volume Fraction ◽  
Left Ventricular ◽  
Normal Fibroblast ◽  
Wall Thickening ◽  
Cellular Mechanisms ◽  
Collagen Formation ◽  
Failing Heart

Background: Cardiac fibroblasts are critical mediators of fibrotic remodeling in the failing heart. These maladaptive structural changes can worsen cardiac function accelerating the progression to decompensated heart failure (HF). We investigated the effects of a novel inhibitor of the conversion of normal fibroblast to the myofibroblast phenotype in the setting of pressure overload induced HF. Methods: Male C57BL/6J mice (10 wks) were subjected to transverse aortic constriction (TAC; 27 g needle) and NM922 (NovoMedix, LLC50 mg/kg/d i.p.) or VEH (DMSO + HS-15) was administered daily starting at 6 wks post TAC. Echocardiography was assessed at baseline and for 16 wks post TAC. At the 16 wk endpoint, mice were sacrificed and hearts were collected for biochemical and molecular assessment. Results: NM922 significantly attenuated TAC-induced left ventricular (LV) dilation at 16 wks post TAC (LVEDD: 3.5 ± 0.1 vs. 4.5 ± 0.2 mm, p < 0.01; LVESD: 2.5 ± 0.2 vs. 3.8 ± 0.3 mm, p < 0.01) compared to VEH. NM922 treated mice displayed reduced wall thickening (LVPWd: 1.0 ± 0.03 vs. 1.2 ± 0.05 mm; p < 0.05) at 10 wks post TAC compared to VEH. LV ejection fraction (LVEF) was preserved in NM922 treated mice at 8-16 wks post TAC compared to VEH (*p < 0.05; **p < 0.001) compared to VEH. Treatment with NM922 resulted in reductions in heart (8.5 ± 0.5 vs. 12.0 ± 0.9 mg/mm; p < 0.01) and lung (8.2 ± 0.3 vs. 11.5 ± 0.6 mg/mm; p < 0.0001) weights compared to VEH. Picrosirius Red staining revealed that NM922 reduced cardiac interstitial collagen volume fraction by 50% (p < 0.05 vs. VEH). Circulating BNP levels trended toward lower (p = 0.08) in the NM922 mice when compared to VEH. Conclusion: Chronic treatment with NM922 following the onset of cardiac hypertrophy and HF resulted in attenuated myocardial collagen formation and adverse remodeling with preservation of LVEF. Future studies are aimed at further elucidation of the molecular and cellular mechanisms by which this novel agent protects the failing heart.

scholarly journals Phosphorylated cellulose nanofibers exhibit exceptional capacity for uranium capture

Cellulose ◽  
2020 ◽  
Vol 27 (18) ◽  
pp. 10719-10732
Author(s):  
Janika Lehtonen ◽  
Jukka Hassinen ◽  
Avula Anil Kumar ◽  
Leena-Sisko Johansson ◽  
Roni Mäenpää ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Structural Changes ◽  
Cellulose Nanofibers ◽  
Aqueous Media ◽  
Isotherm Models ◽  
Batch Adsorption ◽  
Maximum Adsorption Capacity ◽  
Electron Microscopies ◽  
Network Scanning ◽  
Aqueous Matrices

AbstractWe investigate the adsorption of hexavalent uranium, U(VI), on phosphorylated cellulose nanofibers (PHO-CNF) and compare the results with those for native and TEMPO-oxidized nanocelluloses. Batch adsorption experiments in aqueous media show that PHO-CNF is highly efficient in removing U(VI) in the pH range between 3 and 6. Gelling of nanofiber hydrogels is observed at U(VI) concentration of 500 mg/L. Structural changes in the nanofiber network (scanning and transmission electron microscopies) and the surface chemical composition (X-ray photoelectron spectroscopy) gave insights on the mechanism of adsorption. The results from batch adsorption experiments are fitted to Langmuir, Freundlich, and Sips isotherm models, which indicate a maximum adsorption capacity of 1550 mg/g, the highest value reported so far for any bioadsorbent. Compared to other metals (Zn, Mn, and Cu) and typical ions present in natural aqueous matrices the phosphorylated nanofibers are shown to be remarkably selective to U(VI). The results suggest a solution for the capture of uranium, which is of interest given its health and toxic impacts when present in aqueous matrices.

Sign in / Sign up

Export Citation Format

Share Document