Search results for "Diffusion"
showing 10 items of 1615 documents
Acyclovir Delivery Matrices Based on Poly(Ethylene Glycol)/Chitosan Semi-Interpenetrating Networks
2007
Abstract Chitosan matrix systems have been studied as potential vehicles for the prolonged release of acyclovir (ACV). The influence of chitosan concentration (from 0.83% to 1.67%) on viscoelastic properties of formulations with and without glyoxal was analyzed. For chitosan‐poly(ethylene glycol) 400 formulations loss modulus ( G ″) are greater than storage modulus ( G ′). This corresponds to the characteristic behavior of nonstructured systems. When glyoxal was added to the chitosan‐poly(ethylene glycol) 400 formulations, gelled matrix was obtained (i.e., G ′ is higher than G ″), except for the lowest chitosan concentration. ACV release rates for the both types of systems, with and without…
Representation of solutions and large-time behavior for fully nonlocal diffusion equations
2017
Abstract We study the Cauchy problem for a nonlocal heat equation, which is of fractional order both in space and time. We prove four main theorems: (i) a representation formula for classical solutions, (ii) a quantitative decay rate at which the solution tends to the fundamental solution, (iii) optimal L 2 -decay of mild solutions in all dimensions, (iv) L 2 -decay of weak solutions via energy methods. The first result relies on a delicate analysis of the definition of classical solutions. After proving the representation formula we carefully analyze the integral representation to obtain the quantitative decay rates of (ii). Next we use Fourier analysis techniques to obtain the optimal dec…
The Continued Innovation-Decision Process : A Case Study of Continued Adoption of Robotic Process Automation
2022
Robotic Process Automation (RPA) originally entered the field of information systems as one of those disruptive innovations that will, among other automation solutions, have a profound effect on job descriptions and work itself in near future. One of the sectors that will be revolutionized – and are in fact already changing – are financial and human resource (HR) services, such as accounting, billing, and payroll services. According to statistics, Finnish companies operating on the administrative and support services sector make little use of service robots. Companies that have initially adopted the technology do not necessary reach its full potential. We explore what factors create challen…
Evidence for the Existence of an Effective Interfacial Tension between Miscible Fluids: Isobutyric Acid-Water and 1-Butanol-Water in a Spinning-Drop …
2006
We report definitive evidence for an effective interfacial tension between two types of miscible fluids using spinning-drop tensiometry (SDT). Isobutyric acid (IBA) and water have an upper critical solution temperature (UCST) of 26.3 degrees C. We created a drop of the IBA-rich phase in the water-rich phase below the UCST and then increased the temperature above it. Long after the fluids have reached thermal equilibrium, the drop persists. By plotting the inverse of the drop radius cubed (r(-)(3)) vs the rotation rate squared (omega(2)), we confirmed that an interfacial tension exists and estimated its value. The transition between the miscible fluids remained sharp instead of becoming more…
Serotypes, Antibiotic Resistance, and Class 1 Integrons in Salmonella Isolates from Pediatric Cases of Enteritis in Tehran, Iran
2011
The present study was conducted to investigate serotype distribution, antimicrobial resistance patterns, carriage of class 1 integron, and clonality of Salmonella strains isolated from patients aged 0-12 years in Tehran, Iran, during 2007-2008. A total of 139 Salmonella isolates were studied. Salmonella serotypes Enteritidis, Infantis, and Typhimurium included 84.9% of isolates, Enteritidis accounting for 41.7%. The most prevalent resistances were to doxycycline (64.7%), nalidixic acid (61.2%), tetracycline (51.8%), and streptomycin (42.8%). Fifty-three (38.1%) isolates contained class 1 integron. Eight different gene cassettes were identified, aadA1 being the most frequently encountered. P…
Novel dual-flow perfusion bioreactor for in vitro pre-screening of nanoparticles delivery: design, characterization and testing
2021
An advanced dual-flow perfusion bioreactor with a simple and compact design was developed and evaluated as a potential apparatus to reduce the gap between animal testing and drug administration to human subjects in clinical trials. All the experimental tests were carried out using an ad hoc Poly Lactic Acid (PLLA) scaffold synthesized via Thermally Induced Phase Separation (TIPS). The bioreactor shows a tunable radial flow throughout the microporous matrix of the scaffold. The radial perfusion was quantified both with permeability tests and with a mathematical model, applying a combination of Darcy's Theory, Bernoulli's Equation, and Poiseuille's Law. Finally, a diffusion test allowed to in…
PLLA biodegradable scaffolds for angiogenesis via Diffusion Induced Phase Separation (DIPS)
2008
A critical obstacle in tissue engineering is the inability to maintain large masses of living cells upon transfer from the in vitro culture conditions into the host in vivo. Capillaries, and the vascular system, are required to supply essential nutrients, including oxygen, remove waste products and provide a biochemical communication “highway”. For this reason it is mandatory to manufacture an implantable structure where the process of vessel formation – the angiogenesis – can take place. In this work PLLA scaffolds for vascular tissue engineering were produced by dip-coating via Diffusion Induced Phase Separation (DIPS) technique. The scaffolds, with a vessel-like shape, were obtained by p…
Protein and solvent dynamics of the water-soluble chlorophyll-binding protein (WSCP)
2015
This study presents quasielastic neutron scattering data of the water-soluble chlorophyll-binding protein (WSCP) and the corresponding buffer solution at room temperature. The contributions of protein and buffer solution to the overall scattering are carefully separated. Otherwise, the fast water dynamics dominating the buffer contribution is likely to mask the slow protein dynamics. In the case of WSCP, the protein scattering can be described by two contributions: i) internal protein dynamics represented by a diffusion in a sphere with an average radius of 2.7 u A and ii) global (Brownian) diffusion of the WSCP macromolecule with an upper limit for the translational diffusion coefficient o…
Transport of Mobile Particles in an Immobile Environment: Computer Simulations of Sodium Silicates
2007
Molecular dynamics (MD) simulations of various sodium silicate melts, (Na2O)x(SiO2) with x=2, 3, 20, are presented. In these systems, the mobility of sodium ions is much higher, often by orders of magnitude, than that of the silicon and oxygen atoms forming a tetrahedral network structure. We show that the high mobility of sodium is intimately related to the chemical ordering in sodium silicates. A network of percolating sodium-rich channels is formed in the static structure that serve as diffusion channels for the sodium ions. This channel network is revealed in static structure factors by a prepeak at the wavenumber q=0.95 A-1. Inelastic neutron scattering experiments of sodium silicate m…
Growth of Ice Particles by Accretion and Ice Particle Melting
2010
In Chapter 13, we discussed the growth of snow crystals by vapor diffusion, and in Chapter 14, we described the manner with which snow crystals interact with other snow crystals and with drops. In this chapter, we shalllook closer at the growth of ice particles by the accretion of supercooled drops, at the formation of snow flakes by the collision of snow crystals, and also consider the physics of melting of individual ice particles.