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Production, Extraction and Characterization of Alginates from Seaweeds
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
Faiez Hentati, Alina V. Ursu, Guillaume Pierre, Cedric Delattre, Bogdan Trica, Slim Abdelkafi, Gholamreza Djelveh, Tanase Dobre, Philippe Michaud
The most important rheological characteristics of polysaccharides are the flow behavior, thixotropy and dynamical viscoelastic properties (Ma et al. 2014). The factors affecting the rheology of alginates are species and structure dependent. Solutions of alginate in water can exhibit oppositional behavior at the same concentrations, i.e. Newtonian or non-Newtonian fluids. Khajouei et al. (2018) stated that solutions of sodium alginate (1.0 to 5.0%, w/v) from Nizimuddinia zanardini exhibited almost Newtonian or very low shear-thinning behavior whereas Ma et al. (2014) found that, above a critical shear rate, solutions of commercial G-rich sodium alginate (1.0 to 3.0%, w/v) exhibited non-Newtonian shear thinning one.
Plasma and Blood Viscosity
Published in Gordon D. O. Lowe, Clinical Blood Rheology, 2019
Sir Isaac Newton, in his Principia of 1686, hypothesized that the shear rate in a fluid was directly proportional to the shear stress, i.e., the viscosity was constant regardless of the flow conditions. Newtonian fluids are thus defined as fluids with constant viscosity despite different shear conditions, provided that temperature is constant. Water, plasma, and serum are Newtonian fluids. In non-Newtonian fluids, viscosity varies with shear conditions, as well as with temperature. Whole blood is non-Newtonian, its viscosity increasing markedly at low shear rates (Figure 2). In non-Newtonian fluids, shear stress and shear rate are not distributed uniformly. However, the viscosity coefficient is calculated as the ratio of overall shear stress to overall shear rate at a given shear rate, as if the fluid were Newtonian: the coefficient is then termed apparent viscosity.5
Blood Flow Mechanics
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
It has been well established that, under low shear stress, blood does not have a constant viscosity (Bureau et al. 1980). Recent studies have shown the importance of accounting for non-Newtonian fluid behavior, even in large vessels under certain conditions. De Vita et al. (2015) showed that the shear rate in the aorta can be low enough to cause aggregation, which could change the blood viscosity. This was attributed to the pulsatile and transitional properties of the blood flow.
Fabrication and analysis of chitosan oligosaccharide based mucoadhesive patch for oromucosal drug delivery
Published in Drug Development and Industrial Pharmacy, 2022
Ashwini Kumar, Ram Kumar Sahu, Shibu Chameettachal, Falguni Pati, Awanish Kumar
Human saliva is a non-Newtonian fluid i.e. its viscosity changes with a change in shear stress. Non-Newtonian fluids are further classified as dilatant and pseudoplastic. Dilatant fluids show an increase in viscosity with an increase in stress while the relation between the viscosity and shear stress is inversely proportional in the case of pseudoplastic fluid. Therefore, human saliva is non-Newtonian pseudoplastic in nature [36]. The viscosity study of our in-house formulated artificial saliva (ASC and ASX with 0.1% CMC and XG respectively) revealed that ASC is showing dilatant behavior while ASX shows pseudoplastic behavior (Figure 3(a and b)). At this stage, we discontinued the ASC solution while we proceeded with ASX. Further, we analyzed the viscosity for ASX with 0.5% w/v XG and ASX with 0.075% w/v XG (Figure 3(c and d)). ASX with 0.075% XG revealed a viscosity pattern like that of human saliva as reported in other publications [37,38]. With the final simulated salivary formulation, the viscosity was measured to be around 4.3 mPa.s at a shear rate of 20/second while it was approximately 2.5 mPa.s at a shear rate of 40/second. At a shear rate of 100/second, the viscosity is recorded to be approximately 2 mPa.s.
Feasibility of developing hospital preparation by semisolid extrusion 3D printing: personalized amlodipine besylate chewable tablets
Published in Pharmaceutical Development and Technology, 2022
Xiaolu Han, Dongzhou Kang, Boshi Liu, Hui Zhang, Zengming Wang, Xiang Gao, Aiping Zheng
Shear thinning is suitable for extruding from the syringe, and the ability to recover quickly after shearing should also be taken into account when evaluating the 3D printing self-supporting ability (Feng et al. 2019). In this study, the viscosities of all the semisolids within shear rate variation were analyzed, as shown in Figure 4. The results showed that all semisolids are non-Newtonian fluids with shear thinning. That is, the flow type wherein viscosity decreases with the increase of shear rate or shear stress is also called pseudoplastic flow, which conforms to the law of pseudoplastic flow (Shastry et al. 2006). The semisolid inside has macromolecule colloid particles composed of huge chain molecules, such as CMC-Na and SSG. At a low flow rate or at rest, because they are entangled with each other, the viscosity is larger, so it appears sticky like the solid. However, when the preparation rate increases, these scattered chain particles will be affected by the shear stress between the flow layers, which reduces their mutual hook, and then they will roll, rotate, and contract into clusters, thus showing shear thinning, which facilitates the process of SSE.
Simulation of non-Newtonian flow of blood in a modified laparoscopic forceps used in minimally invasive surgery
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Md. Abdul Raheem Junaidi, Harsha Sista, Ram Chandra Murthy Kalluri, Y. V. Daseswara Rao, Alla Gopala Krishna Gokhale
In this article, flow analysis of blood (modeled as a non-Newtonian fluid) has been carried out in the alternate design of surgical forceps, and the results are compared with those obtained previously in the case of water (a Newtonian fluid). This new device has functionalities of both dissector forceps and S–I device. The mass flow rates computed using shear-thinning flow models like Carreau and Carreau–Yasuda models, which are used to simulate the blood flow, are found to be almost identical. Compared to the