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Blood in flow. Basic concepts
Published in Annie Viallat, Manouk Abkarian, Dynamics of Blood Cell Suspensions in Microflows, 2019
Etienne Loiseau, Annie Viallat, Manouk Abkarian
Red blood cells (RBCs) represent more than 90% of the cells in blood. The volume fraction in whole blood of RBCs ranges between 40% and 50%. They are responsible for transporting oxygen from the lung to the tissues, and carbon dioxide from tissues to the lung. In humans, RBCs are biconcave disk-shaped, with a diameter of ∼7.5μm and and a thickness of ∼2.5μm. Mature RBCs do not contain a nucleus at odds with many other species as will be discussed in Chapter 12. Human RBCs membrane is a double shell. The outer shell is a lipid bilayer and the inner shell is a 2D spectrin cytoskeleton. Specific membrane proteins bind the two layers together. RBCs are filled with a solution of hemoglobin, the key protein used in oxygen transport. RBCs have an average life span of 120 days. Old or damaged RBCs are eliminated in the liver and spleen, and new ones are produced in the bone marrow. Red blood cells are specifically studied in Chapters 3, 5, 4, 6 and 12.
Dispersions of Rigid Nonspherical Particles
Published in Rajinder Pal, Rheology of Particulate Dispersions and Composites, 2006
Suspensions of nonspherical (anisometric) rigid particles in liquids are ubiquitous in many industries, such as printing and papermaking, petroleum, polymer, aerospace, bioengineering, construction, ceramics, coal, magnetic media, pharmaceutical, and food [1–10]. Slurries of nonspherical particles (such as calcium carbonate, kaolin clay, titanium dioxide, talc) and water are widely used in the paper-coating process. Clay particles used in drilling muds are nonspherical in shape; the particles of bentonite and hectorite clays are platelike, whereas the particles of attapulgite and sepiolite clays are rod shaped. Platelike particles of mica, aluminum, magnesium hydroxide, and talc are commonly used as fillers/reinforcing agents in plastics to enhance stiffness [5]. Many polymeric composites are manufactured from suspensions of rodlike fibers in polymer melts. Fibers of rayon, vinylon, glass, nylon, and carbon materials are often utilized [8]. The solid propellants commonly used in aerospace propulsion are prepared from dispersion of nonspherical solid particles (oxidizer particles) in a rubbery matrix. Blood is a suspension of red blood cells (erythrocytes), white blood cells (leukocytes), and platelets in plasma [11]. Red blood cells are biconcave disks about 8 μm in diameter and 1 μm in thickness at the center. White blood cells are generally spherical with a mean diameter of about 7 μm. Platelets are irregularly oval or spherical bodies without any nucleus. Suspensions of acicular (needle or cigar shaped) magnetic particles are commonly used in the manufacture of digital tapes and magnetic recording media [6]. Molten chocolate is a suspension of solid nonspherical particles (mostly sugar granules and crushed cocoa beans) in cocoa butter [4]. Other examples of suspensions of nonspherical particles include suspensions of mineral pigments, cement, concrete, coal, starch, and insoluble drugs.
Curvatures of smectic liquid crystals and their applications
Published in Journal of Information Display, 2018
Curvatures of soft matters are of interest for both fundamental scientific research and a number of potential applications. Common examples of curvatures are found in cell membranes, organelles, proteins, block copolymers, and liquid crystals (LCs) [1–7]. Curvatures of soft matters are varied depending on intermolecular interactions and stimuli-responsive characteristics [8–13]. Generally, a curvature can be described by its mean curvature H and Gaussian curvature K, which are given by two principal radii of curvature, R1 and R2, as shown in Figure 1. Thus, curved surfaces of differential geometries in soft matters allow us to define the topological features and symmetry, and understand structural functions for practical applications. For example, the biconcave disc-like shape of a red blood cell, consisting of a phospholipid bilayer and the underlying two-dimensional network of spectrin molecules, plays a crucial role for the fast gas exchange between hemoglobin and the surrounding medium, enabling flexible migration into various vessels including capillary vessels of smaller size than the red blood cells [14]. Block copolymers are another example, being a material frequently used in the fabrication and engineering of nanostructures. These can show a variety of curvatures such as spheres, cylinders, and lamella are gyroids depending on the volume fraction of each block, which can be used in patterning applications [15–22].