Search results for " Strength"
showing 10 items of 1999 documents
The self-association equilibria of doxorubicin at high concentration and ionic strength characterized by fluorescence spectroscopy and molecular dyna…
2019
Abstract The self-association equilibria of doxorubicin hydrochloride (DX), at high drug and NaCl concentrations, are studied by temperature scan fluorescence spectroscopy, with the support of molecular dynamics (MD) calculations. Even though all anthracyclines show dimerization equilibria, DX only can further associate into long polymeric chains according to DXmon ⇄ DXdim ⇄ DXpol. This is reflected not only in the mechanical properties of DXpol solutions (behaving as thixotropic gels) but also in their spectroscopic behaviour. Fluorescence, in particular, is the technique of election to study this complex set of equilibria. Upon increasing the temperature, DXpol melts into DXdim, which in …
Inspirations for EO polymer design gained from modeling of chromophore poling by Langevin dynamics
2013
One of the possibilities to create organic molecular material for NLO applications are polymers with dispersed NLO active chromophores. These molecules must be acentrically ordered by applying an external electric poling field. The NLO efficiency depends on dipole moment, molecular hyperpolarizabilities, concentration of the chromophores and external poling field strength. Calculating, from first principles, the extent of the alignment and via this NLO efficiency has proven to be challenging. One approach to solve this problem is pure analytic statistical mechanics treatment, what could be enhanced by Monte Carlo ( MC ) statistical mechanical modelling. The chromophore molecules usually hav…
Thermometric study of the dissociation equilibria of the maleinimidodioxime
1982
The values of the dissociation constants of the maleinimidodioxime are potentiometrically determined at various ionic strengths, and extrapolated to zero ionic strength (pK1T=10.41;pk2T=11.60). From these values and from the thermometric titration curves the enthalpies of neutralization (ΔHN1=−21.76,ΔHN2=−23.77 kJ/mol) and the thermodynamic parameters of dissociation of this substance at 25.0 °C are determined (ΔG1θ=59.41,ΔG2θ=66.23,ΔH1θ=34.06,ΔH2θ=32.05 kJ/mol;ΔS1θ=−85.06,ΔS2θ=−114.64 J/(K mol)).
A family of weakest link models for fiber strength distribution
2007
It is well known that the most widely used distribution function for fiber tensile strength, the two-parameter Weibull distribution, does not always adequately describe the experimentally observed fiber strength scatter and the strength dependence on fiber length. To remedy this discrepancy, modifications of the Weibull distribution have been proposed that, while providing a good empirical fit to the strength data, sometimes lack the theoretical appeal of the weakest link models. We derive a family of weakest link models based on the assumption of a two-stage failure process incorporating explicitly the probabilities of flaw initiation and the fiber fracture due to the largest flaw (i.e. th…
Comparative Study of the Mechanical Unfolding Pathways of α- and β-Peptides
2015
Using molecular simulations, we analyze the unfolding pathways of various peptides. We compare the mechanical unfolding of a β-alanine's octamer (β-HAla8) and an α-alanine's decamer (α-Ala10). Using force-probe molecular-dynamics simulations, to induce unfolding, we show that the 3(14)-helix formed by β-HAla8 is mechanically more stable than the α-helix formed by α-Ala10, although both structures are stabilized by six hydrogen bonds. Additionally, computations of the potential of mean force validate this result and show that also the thermal stability of the 3(14)-helix is higher. It is demonstrated that β-HAla8 unfolds in a two-step fashion with a stable intermediate. This is contrasted wi…
Gluon mass generation in the presence of dynamical quarks
2013
We study in detail the impact of dynamical quarks on the gluon mass generation mechanism, in the Landau gauge, for the case of a small number of quark families. As in earlier considerations, we assume that the main bulk of the unquenching corrections to the gluon propagator originates from the fully dressed quark-loop diagram. The nonperturbative evaluation of this diagram provides the key relation that expresses the unquenched gluon propagator as a deviation from its quenched counterpart. This relation is subsequently coupled to the integral equation that controls the momentum evolution of the effective gluon mass, which contains a single adjustable parameter; this constitutes a major impr…
Earth Construction: The Mechanical Properties of Adobe with the Addition of Laponite
2015
The contribution describes testing of compression strength, flexural strength and abrasion resistance of adobe made up of soil, water and sand (AS), soil, water, sand and straw (ASP), soil, water, sand and laponite nanoparticles (ASN). Embodied energy in materials presents an increasingly high percentage of the energy spent in the whole life cycle of a building. The same applies for carbon dioxide (CO2). Therefore, the development of new sustainable construction materi- als with lower embodied energy and lower CO2 emissions is needed. The use in construction of the brick made from soil, water and sand or straw, called adobe, boasts a millenary tradition and in recent years there has been re…
Seismic behavior of exterior RC beam-column joints without code-specified ties in the joint core
2021
Abstract Beam-column joint design for reinforced concrete (RC) buildings is a critical issue for modern earthquake engineering, because for these structural elements, the current codes provide several geometrical constraints and reinforcement provisions, which may be very complex to implement during the construction phase. To investigate how a construction error might influence the joint behavior, two identical full-scale exterior beam-column joints specimens are built, according to Italian Building Code specifications for the high ductility class, but without the required horizontal ties inside the joint panel. This construction error could be plausible because, according to the design dra…
Interaction of ionic compounds with multilamellar liposomes. An electrokinetic model
1998
Abstract We have proposed a theoretical model of interaction of ionic compounds (ionic adsorbate or ionic drugs), with multilamellar-liposomes, by means of their electrokinetic property variation with the ionic compound concentration. In this work, we show the complete development of the model proposed. Its theoretical results have been analysed to study the influence on the zeta-potential value of the following: number of membranes, size, shear-plane situation, critical concentration of formation (ccf), and the ionic compound concentration which annuls the zeta-potential value of the multilamellar-liposomes formed.
Resistance to demineralisation of adjacent enamel and dentine, fluoride release and dentine bond strength of fluoride-containing self-etch adhesive s…
2019
Background The current study aimed to assess the amount of fluoride released from fluoride-containing dental adhesives and its effect on micro-tensile bond strength (µTBS) and on resistance to demineralisation of dentine and enamel. Material and Methods Two fluoride-containing dental adhesives, and a fluoride-free adhesive were used as experimental adhesives. After thermal cycling the µ-TBS of adhesives to dentine and the failure mode were assessed. The fluoride release and cross-sectional microhardness (CSMH) of specimens were measured before and after one day, 7 and 28 days of pH-cycling. The data were analysed using one-way ANOVA, Weibull statistics and repeated measures ANOVA. Results T…