scholarly journals Organogels as nutraceutical carriers: Effect of addition of lecithin, tocopherols, and EPA/DHA on properties of candelilla wax-soybean oil organogels

2021 ◽  
Author(s):  
Nydia E. Buitimea-Cantúa ◽  
Daniel Arellano ◽  
Sergio O. Serna-Saldívar ◽  
Génesis V. Buitimea-Cantúa
Keyword(s):  
Shear Stress ◽  
Soybean Oil ◽  
Organic Liquid ◽  
Visual Appearance ◽  
Color Parameters ◽  
Nutraceutical Compounds ◽  
Lower Shear ◽  
3D Network ◽  
Formation Type ◽  
Candelilla Wax

Organogels are semisolid and 3D systems in which both an organic liquid solvent and other dispersed particles are entrapped. Today there is not much information about the potential of organogels as carriers of lipophilic nutraceuticals. Therefore, in this work, the preparation and characterization of soybean oil-based organogels with candelilla wax (CW) and lecithin, tocopherol, or EPA/DHA were studied. Soybean oil was structured with 0.5, 1.0, 2.0, and 4.0% w/w of CW. In the organogels, the visual appearance, thermal stability, color parameters, microstructure, hardness, and rheological properties were analyzed. Results showed that soybean oil was successfully structured into an array of solid-like organogels varying in concentrations of CW and added nutraceutical compounds. Increasing CW concentration yielded stronger 3D-network gel formation (type 5 or solid organogel). All organogels were stable at 5, 25, and 35°C during the cyclization process. The nutraceuticals affected the color parameters and 3D network structure. Larger crystalline spherulites and a uniform microstructure were observed, especially in organogels formulated with 4.0% w/w of CW and lecithin. In comparison with the control, organogels (4.0% w/w) with tocopherol or EPA/DHA required lower shear stress to flow whereas lecithin required higher shear stress to flow. Texture analysis showed that organogels with nutraceuticals presented higher hardness, this behavior was attributed to the formation of a larger and softer crystal networks. In conclusion, soybean oil-based organogels formulated with lecithin, tocopherol, or EPA/DHA yielded stable organogels with promising properties as nutraceutical carriers.

Vasomotor responses in chronically hyperperfused and hypoperfused rat mesenteric arteries

1998 ◽  
Vol 274 (4) ◽  
pp. H1301-H1307 ◽  
Author(s):  
Fabrice Pourageaud ◽  
Jo G. R. De Mey
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Sodium Nitroprusside ◽  
Arginine Vasopressin ◽  
Side Branch ◽  
Mesenteric Arteries ◽  
Low Flow ◽  
Basal Diameter ◽  
Lower Shear ◽  
Altered Blood

We evaluated the reactivity of small arteries after remodeling induced by elevated or reduced blood flow. In 6-wk-old rats, every other first-order side branch of the superior mesenteric artery was ligated near the bifurcation of second-order branches. Four weeks after surgery, vessels that had been exposed to high flow (HF) or low flow (LF) were isolated and mounted in a pressure myograph at 100 mmHg and were compared with vessels from sham-operated rats (Sham). In HF: 1) basal lumen diameter was increased; 2) sensitivity to norepinephrine, arginine vasopressin, and perivascular nerve stimulation was not modified; 3) maximal constrictor responses (Δ diameter) to these stimuli and 125 mM K+ were increased; and 4) sensitivity and maximal dilator responses to sodium nitroprusside, acetylcholine, and flow were not modified. In LF: 1) basal diameter was reduced; 2) sensitivity to constrictor stimuli was not altered; 3) maximal responses to all vasoconstrictors except arginine vasopressin were reduced; and 4) sensitivity but not maximal dilator responses to sodium nitroprusside and acetylcholine was reduced. During acute flow-induced dilatations, lower shear stress was maintained in HF (48 ± 7 dyn/cm2) than in Sham (63 ± 10 dyn/cm2), but no shear stress regulation was observed in LF. These observations indicate that arterial structural responses to altered blood flow are accompanied by modified reactivity of the arterial smooth muscle, which entails changes in responsiveness to neurogenic and endothelium-dependent stimuli.

scholarly journals RHEOLOGICAL ANALYSIS OF VEGETABLE OILS USED FOR BIODIESEL PRODUCTION IN BRAZIL

2015 ◽  
Vol 14 (2) ◽  
pp. 31 ◽  
Author(s):  
L. E. Silva ◽  
C. A. C. Santos ◽  
J. E. S. Ribeiro ◽  
C. C. Souza ◽  
A. M. S. Sant’Ana
Keyword(s):  
Shear Stress ◽  
Rheological Properties ◽  
Vegetable Oils ◽  
Rheological Behavior ◽  
Apparent Viscosity ◽  
Biodiesel Production ◽  
Viscosity Data ◽  
Concentric Cylinder ◽  
Lower Shear ◽  
Different Temperatures

Rheology attempts to define a relationship between the stress acting on a given material and the resulting deformation and/or flow that takes place. Thus, the knowledge of rheological properties of fluid materials such as vegetable oils generates auxiliary data that can be used in its storage and application. In this context, the aim of this study was to evaluate the rheological behavior of vegetable oils (cotton, canola, sunflower, corn and soybean) at different temperatures, using four rheological models (Ostwald- de-Waelle, Herschel-Bulkley, Newton and Bingham). The rheological properties were determined using a Thermo Haake rheometer with concentric cylinder geometry. Measurements were taken at 30, 45 and 60 °C by controlling the temperature using a thermostatic bath coupled to the equipment. The software Rheowin Pro Job Manager was used for process control and data record. The rheograms were obtained by measuring the values of shear stress varying the shear rate from 100 to 600 s-1 within 250 seconds. For the analysis of the apparent viscosity at different shear rates was applied simple linear regression until 2nd degree with the aid of SAS (SAS/Stat 9.2) program. The apparent viscosity data were submitted to analysis of variance and the averages were compared by Tukey test at 5% of probability. Higher temperatures of the samples were correlated to lower shear stress values, hence lower values for viscosity and consistency index were obtained, since it is known that the density and viscosity are highly sensitive to temperature and that the increase in temperature results in reduction of viscosity, benefiting the fluid flow. The models of Newton and Ostwald-de-Waelle were chosen to evaluate the rheological behavior of the samples, showing a good fit for the rheological data.

scholarly journals Isolating single cells in a neurosphere assay using inertial microfluidics

Lab on a Chip ◽  
2015 ◽  
Vol 15 (24) ◽  
pp. 4591-4597 ◽  
Author(s):  
S. Shiva P. Nathamgari ◽  
Biqin Dong ◽  
Fan Zhou ◽  
Wonmo Kang ◽  
Juan P. Giraldo-Vela ◽  
...  
Keyword(s):  
Shear Stress ◽  
Stem Cell ◽  
Single Cells ◽  
Inertial Microfluidics ◽  
Stress Regime ◽  
Lower Shear ◽  
Cell Assays ◽  
Neurosphere Assay

We use inertial microfluidics in a novel, lower shear-stress regime to isolate single cells in sphere-forming stem cell assays.

scholarly journals Microcrystalline cellulose effects on the rheology of mixed oleogels structured with candelilla wax and saturated fat

2021 ◽  
Author(s):  
Luz Pérez-Meza ◽  
Miguel Ruiz-Cabrera ◽  
Juan Morales-Rueda ◽  
Jaime Pérez-Martínez
Keyword(s):  
Elastic Modulus ◽  
Soybean Oil ◽  
Microcrystalline Cellulose ◽  
Saturated Fat ◽  
Colloidal Gels ◽  
Crystal Network ◽  
Nucleation Sites ◽  
Hydrogenated Soybean Oil ◽  
Candelilla Wax ◽  
Mechanical Recovery

The structuration processes of mixed oleogels produced with candelilla wax (CW, 0 or 3%), fully hydrogenated soybean oil (FH, 5-15%), and microcrystalline cellulose (MC, 0-9%) were studied to define their rheological effects. During the cooling CW crystals performed as nucleation sites for FH. The elastic modulus (G’) of oleogels with FH and 3% CW were more than two orders of magnitude higher than those produced with 0% CW. Adding MC to the oleogels increased slightly the G’. Independently of the amount of MC, oleogels structured with increasing amounts of FH and 0% CW showed the elastic properties scaling of colloidal gels. This behavior was lost by adding 3% CW, implying that in mixed FH-CW oleogels, the CW crystal network dominated the oleogel rheology. The flow point and the mechanical reversibility of oleogels and commercial butter (CB) was also determined. CB showed flow points at 44 and 59% strain and mechanical reversibility values of 29 and 35% of G’ measured in a pre-shear step. Adding MC to oleogels structured with FH and 0% CW increased their flow point (37.2%) near those of CB. This effect was not produced in mixed FH-3% CW oleogels. The mechanical recovery of oleogels produced with FH, MC, and 0% CW tend to decrease as the FH content increased. CW and MC did not show a simple concentration–effect relationship for the mechanical recovery. Nonetheless, oleogels structured with 3% CW and 10% FH and 6-9% MC showed mechanical recovery (~60%) close to that of CB.

scholarly journals Dynamics of Individual Red Blood Cells Under Shear Flow: A Way to Discriminate Deformability Alterations

2022 ◽  
Vol 12 ◽  
Author(s):  
Scott Atwell ◽  
Catherine Badens ◽  
Anne Charrier ◽  
Emmanuèle Helfer ◽  
Annie Viallat
Keyword(s):  
Shear Stress ◽  
Shear Flow ◽  
Red Blood Cells ◽  
Sickle Cell ◽  
Blood Cells ◽  
Center Of Mass ◽  
Shear Plane ◽  
Shear Stresses ◽  
Cell Axis ◽  
Lower Shear

In this work, we compared the dynamics of motion in a linear shear flow of individual red blood cells (RBCs) from healthy and pathological donors (Sickle Cell Disease (SCD) or Sickle Cell-β-thalassemia) and of low and high densities, in a suspending medium of higher viscosity. In these conditions, at lower shear rates, biconcave discocyte-shaped RBCs present an unsteady flip-flopping motion, where the cell axis of symmetry rotates in the shear plane, rocking to and fro between an orbital angle ±ϕ observed when the cell is on its edge. We show that the evolution of ϕ depends solely on RBC density for healthy RBCs, with denser RBCs displaying lower ϕ values than the lighter ones. Typically, at a shear stress of 0.08 Pa, ϕ has values of 82 and 72° for RBCs with average densities of 1.097 and 1.115, respectively. Surprisingly, we show that SCD RBCs display the same ϕ-evolution as healthy RBCs of same density, showing that the flip-flopping behavior is unaffected by the SCD pathology. When the shear stress is increased further (above 0.1 Pa), healthy RBCs start going through a transition to a fluid-like motion, called tank-treading, where the RBC has a quasi-constant orientation relatively to the flow and the membrane rotates around the center of mass of the cell. This transition occurs at higher shear stresses (above 0.2 Pa) for denser cells. This shift toward higher stresses is even more remarkable in the case of SCD RBCs, showing that the transition to the tank-treading regime is highly dependent on the SCD pathology. Indeed, at a shear stress of 0.2 Pa, for RBCs with a density of 1.097, 100% of healthy RBCs have transited to the tank-treading regime vs. less than 50% SCD RBCs. We correlate the observed differences in dynamics to the alterations of RBC mechanical properties with regard to density and SCD pathology reported in the literature. Our results suggest that it might be possible to develop simple non-invasive assays for diagnosis purpose based on the RBC motion in shear flow and relying on this millifluidic approach.

PROPOSED OVAL ST. JUDE MEDICAL VALVE: EFFECT OF HEART RATE

2018 ◽  
Vol 18 (02) ◽  
pp. 1850014 ◽  
Author(s):  
MEHDI JAHANDARDOOST ◽  
LUKE OHLMANN ◽  
GUY FRADET ◽  
HADI MOHAMMADI
Keyword(s):  
Shear Stress ◽  
Heart Valves ◽  
Stress Distributions ◽  
Jude Medical ◽  
Lower Shear ◽  
Wide Range ◽  
Hemodynamic Performance ◽  
Computational Platform ◽  
Oval Shape ◽  
Opening Phase

In this study, the hemodynamic performance of the conventional St. Jude Medical (SJM) valve and our proposed design known as the oval SJM valve are studied and compared. These studies are based on a wide range of physiological heart rates, i.e., 70–130[Formula: see text]bpm, in the opening phase. We designed and developed a precise computational platform to assess the hemodynamics of bileaflet mechanical heart valves for laminar and turbulent regimes. Also, as one of the fundamental changes applied to the conventional SJM vales, the housing is considered oval similar to oval shape of annulus. Results clearly indicate hemodynamic improvements in the proposed design over the SJM valve. The improvements are characterized by lower shear stress and wall shear stress distributions around the valve and leaflets, and lower valve pressure drop compared to that of the conventional SJM model. The proposed design shows potential and merits additional development.

Modulation of adrenergic responses in pressurized resistance arteries by flow

1987 ◽  
Vol 253 (5) ◽  
pp. H1112-H1119 ◽  
Author(s):  
B. Tesfamariam ◽  
W. Halpern
Keyword(s):  
Shear Stress ◽  
Electrical Stimulation ◽  
Mesenteric Arteries ◽  
Shear Stresses ◽  
Resistance Arteries ◽  
Lower Shear ◽  
Dextran Solution ◽  
Uptake And Metabolism ◽  
Similar Flows ◽  
Low Shear

The effects of perfusion on the reactivity of isolated rat resistance mesenteric arteries (200 micron ID) to electrical stimulation and exogenous norepinephrine (NE) were investigated. Diameter constrictions of these arteries that have an intact endothelium in response to the stimuli were significantly greater (P less than 0.05) in the presence than in the absence of flow. Inhibition of NE uptake and metabolism with cocaine, normetanephrine, and pargyline increased constrictor responses to electrical stimulation and NE in the presence and absence of flow, but responses remained larger in the presence of flow. Endothelial cell removal augmented the NE-induced diameter constrictions, which were not different whether or not flow was present. Perfusion at similar flows but a higher shear stress using a dextran solution led to smaller constrictions than obtained at lower shear stress in response to NE. However, NE-induced constrictions at high and low shear stresses were the same after endothelium removal. These observations suggest that NE and elevated levels of shear stress induce the release of relaxing factors from the endothelium, which attenuates direct NE smooth muscle cell constrictor responses.

Two-dimensional turbulent wakes

1967 ◽  
Vol 30 (3) ◽  
pp. 547-560 ◽  
Author(s):  
Ian S. Gartshore
Keyword(s):  
Shear Stress ◽  
Stress Reduction ◽  
Shear Stresses ◽  
Pressure Gradients ◽  
Two Dimensional ◽  
Stress Distributions ◽  
Mean Velocity ◽  
Lower Shear ◽  
Turbulent Wakes ◽  
Velocity Scale

The equations of mean motion indicate that two-dimensional turbulent wakes, when subjected to appropriately tailored adverse pressure gradients, can be self-preserving. An experimental examination of two nearly self-preserving wakes is reported here. Mean velocity, longitudinal and lateral turbulence intensity, inter-mittency and shear stress distributions have been measured and are compared with Townsend's data from the small-deficit undistorted wake. In comparison with the undistorted case, the present wakes have slightly lower turbulent intensities and significantly lower shear stresses, all quantities being non-dimensionalized by a local velocity scale taken as the maximum mean velocity deficit. A consideration of the reasons for the shear stress reduction leads to an expression from which the shear stresses in any symmetrical free equilibrium shear flow can be found. This relationship is used to calculate the rate of growth in the measured wakes, with reasonable success.

Effect of Plastic Flattening on the Shearing Response of Metal Asperities: A Dislocation Dynamics Analysis

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
Fengwei Sun ◽  
Erik Van der Giessen ◽  
Lucia Nicola
Keyword(s):  
Shear Stress ◽  
Contact Area ◽  
Dislocation Dynamics ◽  
Dynamics Analysis ◽  
Rectangular Shape ◽  
Lower Shear ◽  
Discrete Dislocation ◽  
Plastic Shearing ◽  
Edge Dislocations

Discrete dislocation (DD) plasticity simulations are carried out to investigate the effect of flattening and shearing of surface asperities. The asperities are chosen to have a rectangular shape to keep the contact area constant. Plasticity is simulated by nucleation, motion, and annihilation of edge dislocations. The results show that plastic flattening of large asperities facilitates subsequent plastic shearing, since it provides dislocations available to glide at lower shear stress than the nucleation strength. The effect of plastic flattening disappears for small asperities, which are harder to be sheared than the large ones, independently of preloading. An effect of asperity spacing is observed with closely spaced asperities being easier to plastically shear than isolated asperities. This effect fades when asperities are very protruding, and therefore plasticity is confined inside the asperities.

The influence of fluid shear and AlCl3 on the material properties of Pseudomonas aeruginosa PAO1 and Desulfovibrio sp. EX265 biofilms

2001 ◽  
Vol 43 (6) ◽  
pp. 113-120 ◽  
Author(s):  
P. Stoodley ◽  
A. Jacobsen ◽  
B. C. Dunsmore ◽  
B. Purevdorj ◽  
S. Wilson ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Shear Stress ◽  
Material Properties ◽  
Extracellular Polysaccharide ◽  
Relative Strength ◽  
Aluminium Chloride ◽  
Shear Stresses ◽  
Fluid Shear ◽  
Pseudomonas Aeruginosa Pao1 ◽  
Lower Shear

An understanding of the material properties of biofilms is important when describing how biofilms physically interact with their environment. In this study, aerobic biofilms of Pseudomonas aeruginosa PAO1 and anaerobic sulfate-reducing bacteria (SRB) biofilms of Desulfovibrio sp. EX265 were grown under different fluid shear stresses (τg) in a chemostat recycle loop. Individual biofilm microcolonies were deformed by varying the fluid wall shear stress (τw). The deformation was quantified in terms of strain (ε), and the relative strength of the biofilms was assessed using an apparent elastic coefficient (Eapp) and residual strain (εr) after three cycles of deformation. Aluminium chloride (AlCl3) was then added to both sets of biofilm and the tests repeated. Biofilms grown under higher shear were more rigid and had a greater yield shear stress than those grown under lower shear. The addition of AlCl3 resulted in a significant increase in Eapp and also increased the yield point. We conclude that the strength of the biofilm is in part dependent on the shear under which the biofilm was grown and that the material properties of the biofilm may be manipulated through cation cross-linking of the extracellular polysaccharide (EPS) slime matrix.

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