Search results for "Modulus"

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…

Microstructural manipulation of electrospun scaffolds for specific bending stiffness for heart valve tissue engineering

2012

Biodegradable thermoplastic elastomers are attractive for application in cardiovascular tissue construct development due to their amenability to a wide range of physical property tuning. For heart valve leaflets, while low flexural stiffness is a key design feature, control of this parameter has been largely neglected in the scaffold literature where electrospinning is being utilized. This study evaluated the effect of processing variables and secondary fiber populations on the microstructure, tensile and bending mechanics of electrospun biodegradable polyurethane scaffolds for heart valve tissue engineering. Scaffolds were fabricated from poly(ester urethane) urea (PEUU) and the deposition…

Integration of PCL and PLA in a monolithic porous scaffold for interface tissue engineering.

2016

A novel bi-layered multiphasic scaffold (BLS) have been fabricated for the first time by combining melt mixing, compression molding and particulate leaching. One layer has been composed by polylactic acid (PLA) presenting pore size in the range of 90-110µm while the other layer has been made of polycaprolactone (PCL) with pores ranging from 5 to 40µm. The different chemo-physical properties of the two biopolymers combined with the tunable pore architecture permitted to realize monolithic functionally graded scaffolds engineered to be potentially used for interface tissues regenerations. BLS have been characterized from a morphological and a mechanical point of view. In particular, mechanica…

Experimental Survey on Dry Asphalt Rubber Concrete for Sub-ballast Layers

2012

The railway traffic through a town or near built-up areas causes heavy effects such as noise and vibration on surroundings. In order to minimize the level of these impacts the railway companies with researchers and practitioners seek suitable solutions especially in the field of the rail-track because the main source of the ground borne vibrations and noise is the bad wheel-track contact. In particular, a big effort is addressed to new materials with high mechanical and environmental performance that can be utilized within the sub-ballast layer. This paper presents the results of an experimental survey on the potential application of Dry Asphalt Rubber Concrete (DARC) in sub-ballast layers …

Do we understand the solid-like elastic properties of confined liquids?

2021

Recently, in polymeric liquids, unexpected solid-like shear elasticity has been discovered, which gave rise to a controversial discussion about its origin (1⇓–3). The observed solid-like shear modulus G depends strongly on the distance L between the plates of the rheometer according to a power law G ∝ L − p with a nonuniversal exponent ranging between p = 2 and p = 3 . Zaccone and Trachenko (4) have published an article in which they claim to explain these findings by a nonaffine contribution to the liquid shear modulus. The latter is represented as Δ G ∝ − ∑ λ = L , T 1 V … [↵][1]1To whom correspondence may be addressed. Email: giancarlo.ruocco{at}roma1.infn.it. [1]: #xref-corresp-1-1

Heterogeneous shear elasticity of glasses: the origin of the boson peak

2013

The local elasticity of glasses is known to be inhomogeneous on a microscopic scale compared to that of crystalline materials. Their vibrational spectrum strongly deviates from that expected from Debye's elasticity theory: The density of states deviates from Debye's law, the sound velocity shows a negative dispersion in the boson-peak frequency regime and there is a strong increase of the sound attenuation near the boson-peak frequency. By comparing a mean-field theory of shear-elastic heterogeneity with a large-scale simulation of a soft-sphere glass we demonstrate that the observed anomalies in glasses are caused by elastic heterogeneity. By observing that the macroscopic bulk modulus is …

Confined Crystals on Substrates: Order and Fluctuations in Between One and Two Dimensions

2010

The effect of lateral confinement on a crystal of point particles in d = 2 dimensions in a strip geometry is studied by Monte Carlo simulations and using phe- nomenological theoretical concepts. Physically, such systems confined in long strips of width D can be realized via colloidal particles at the air-water interface, or by adsorbed monolayers at suitably nanopatterned substrates, etc. As a generic model, we choose a repulsive interparticle potential decaying with the twelfth inverse power of distance. This system has been well studied in the bulk as a model for two- dimensional melting. The state of the system is found to depend very sensitively on the boundary conditions providing the …

Effective charges along the melting line of colloidal crystals

2006

The shear modulus G of charged colloidal crystals was measured at several constant particle densities n and varying salt concentrations c up to the melting salt concentration cM using torsional resonance spectroscopy. Far from the phase boundary the samples are polycrystalline and the shear modulus stays roughly constant as a function of c. Upon approaching the melting transition an increasing amount of wall based crystal material is formed surrounding a shrinking polycrystalline core and G drops nearly linearly. When the transition is complete G again stays constant. The morphologic transitions may be scaled upon a single master curve. For the polycrystalline morphology, the elastic data a…

Publisher's Note: "Thermodynamic formalism for transport coefficients with an application to the shear modulus and shear viscosity" [J. Chem. Phys. 1…

2017

Qualitative characterisation of effective interactions of charged spheres on different levels of organisation using Alexander’s renormalised charge a…

2005

Abstract Effective interactions are conveniently determined from experimental or numerical data by fitting a Debye–Huckel potential with an effective charge Z ∗ and an effective electrolyte concentration c ∗ as free parameters. In this contribution we numerically solved the Poisson–Boltzmann equation to obtain the so-called renormalised charge Z PBC ∗ . For sufficiently large bare charge Z one finds a saturation of Z ∗ which scales as Z ∗ = A a / λ B , where a is the particle radius, λ B the Bjerrum length and A a proportionality factor of order (8–10). The saturation value increases with increased total micro-ion concentration and shows a shallow minimum as a function of packing fraction. …