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From Modeling Nanoparticle–Membrane Interactions toward Nanotoxicology
Published in Agnieszka Gajewicz, Tomasz Puzyn, Computational Nanotoxicology, 2019
Karandeep Singh, Qingfen Yu, Sabyasachi Dasgupta, Gerhard Gompper, Thorsten Auth
For penetration, generic models for lipid-bilayer membranes to study nanoparticle penetration and insertion can be based on self-consistent field theory for membranes [16, 24] or on a director field of the lipid molecules [19, 25]. For membrane wrapping, computer simulations that discretize a continuum membrane model are most appropriate because they provide the possibility to study wrapping for a wide variety of nanoparticle shapes [8, 26]. In meshless membrane models the scale of the discretization is comparable with the membrane thickness [23], whereas in triangulated membrane models single vertices can represent thousands of lipids [4, 27, 28]. Table 5.1 summarizes the main characteristics of chemically specific and continuum models, as well as the parameter regimes where these models are applicable.
Desalination
Published in Frank R. Spellman, Hydraulic Fracturing Wastewater, 2017
The plate-and-frame configuration is one of the earliest membrane models developed. As shown in Figure 7.9, plate-and-frame modules use flat sheet membranes that are layered between spacers and supports. The supports also form a flow channel for the permeate water. The feed water flows across the flat sheets and from one layer to the next. Because of the very low surface area-to-volume ratio, the plate-and-frame configuration is considered inefficient and is therefore seldom used in drinking water applications. Recent innovations have increased the packing densities for new designs of plate-and-frame modules. Maintenance on plate-and-frame modules is possible due to the nature of their assembly. They offer high recoveries with their long feed channels and are used to treat feed streams that often cause fouling problems. Advanced designs of plate-and-frame modules capable of operating at up to 25% dissolved solids and operating pressures up to 4500 psia (pounds per square in absolute) have been placed in operation in Germany (Tiwari et al., 2004). This development opens new opportunities for the use of reverse osmosis for concentration of metal-finishing wastewaters.
Biological Systems and Biomimetics
Published in Efstathios E. Michaelides, Clayton T. Crowe, John D. Schwarzkopf, Multiphase Flow Handbook, 2016
Efstathios E. Michaelides, Clayton T. Crowe, John D. Schwarzkopf
ere are several ways to simulate blood ows containing many RBCs. One of the standard methods is using the boundary element method (BEM) for Stokes ow. As mentioned, the presence of blood cells becomes important in the microcirculation, where the ow Reynolds number is very small. So, the Stokes ow assumption is applicable in many situations. e other approach to simulate extra-large number of RBCs is by the lattice Boltzmann method. Both methods and simulated results are explained in detail in the book by Pozrikidis (2010). In coupled methods for a uid and elastic membrane typi ed by the immersed boundary (IB) method (Peskin, 1972, 2002), the Lagrangian description is employed for the membrane motion, whereas the Eulerian description is employed for the uid. However, there is an open question for the numerical stability in a long time run without any numerical stabilization. For that reason, rather than using the Lagrangian particles, eld variables to identify the membrane interface are introduced and utilized for interaction between the uid and membrane on the Eulerian mesh. Cottet and Maitre (2006) introduced the level-set function to identify the interface; in addition, the membrane stretching or variation of the surface area was obtained from the information of the level-set function. As a result, the membrane force was successfully obtained on the Eulerian mesh without using the interfacial material points. However, since the constitutive law of the membrane elasticity is limited to a model that only involves a variation of the surface area, it has not been applied yet to more general membrane models that depend on the principal strains.
Apparent molar volume, compressibility, and spectroscopic studies of ionic surfactants in aqueous solutions of antibiotic gemifloxacin
Published in Journal of Dispersion Science and Technology, 2023
Muhammad Sohail, Hafiz Muhammad Abd ur Rahman, Muhammad Nadeem Asghar, Saadia Shoukat
Various pseudo-membrane models, like hybrid membrane systems, liposomes, bicelles, bilayers, and micellar systems, have been designed to envisage the geometry, dynamics, and biophysical interactions of membranes.[9] Surfactant micelles with small sizes (∼10-80 nm), narrow size distribution, high curvature, spherical shape, and surface properties show excellent topological resemblances with biological membranes compared to other alternative models.[10] Moreover, they have wide applications as drug delivery vehicles in pharmaceutical products. More precisely, micelles can solubilize hydrophobic drugs, transport them to the action site, lessen their administration frequency, reduce their degradation, customize their pharmacokinetic profile, and improve their therapeutic index and bioavailability.[11] It is also observed that drugs may lower the CMC (critical micelle concentration) of the surfactants, which improve the stability of the drug in the blood.[12]
Spectroscopic, conductivity and voltammetric investigations of interaction of sulfamethoxazole alone and in combination with trimethoprim with self-assembled structures
Published in Journal of Dispersion Science and Technology, 2022
Muhammad Nadeem Asghar, Iqra Bisma, Muhammad Sohail, Asad Muhammad Khan, Hafiz Muhammad Abd Ur Rahman, Iram Nadeem
Micellar systems are used as pseudo-membrane models, as well as drug carriers in numerous drug delivery and drug targeting systems.[6,7] The former situation exploits the resemblance of the structure of micelles with cellular membranes which are considered to be very much dynamic in nature. All the time a number of different transport processes are taking place across these barriers. Moreover, the structural versatility and compositional complexity render it very difficult to explore any drug-membrane interaction in vivo. Micelles being chemical mimics of these membranes provide excellent pseudo-membrane models to make such studies possible in in vitro conditions. Moreover, all types of drug molecules, depending upon their polarity, can interact and find their loci onto or into the micelles. This is possible due to an anisotropic distribution of water within micellar architecture which creates a polarity gradient starting from very polar head group region (facing bulk aqueous environment) to almost completely hydrophobic interior or core and ensures drug-micellar interaction. Consequently, very non-polar drug molecules occupy the lipophilic core while the polar ones develop electrostatic associations at the head group region.[8,9] The drugs with intermediate polarity prefer to reside somewhere in the palisade region. Thus, prior to use a surfactant in pharmaceutical formulation and as a drug carrier, the study of drug-surfactant interaction can be used to have an insight into the elucidation of the interactions of drugs with biological membranes as well as to help design tailored drug delivery systems.