Search results for "Mass fraction"

Elastic Modulus and Thermal Conductivity of Thiolene/TiO2 Nanocomposites

2017

Metal oxide based polymer nanocomposites find diverse applications as functional materials, and in particular thiol-ene/TiO2 nanocomposites are promising candidates for dental restorative materials. The important mechanical and thermal properties of the nanocomposites, however, are still not well understood. In this study, the elastic modulus and thermal conductivity of thiol-ene/TiO2 nanocomposite thin films with varying weight fractions of TiO2 nanoparticles are investigated by using Brillouin light scattering spectroscopy and 3ω measurements, respectively. As the TiO2 weight fraction increases from 0 to 90%, the effective elastic longitudinal modulus of the films increases from 6.2 to 37…

Electrical conductivity properties of expanded graphite-polycarbonatediol polyurethane composites

2014

Conductive polymer composites of segmented polycarbonatediol polyurethane and expanded graphite (EG) have been synthesized with different amounts of EG conductive filler (from 0 to 50 wt%). SEM, X-ray diffraction measurements, Fourier transform infrared and Raman spectroscopies demonstrated a homogeneous dispersion of the EG filler in the matrix. The dielectric permittivity of the composites showed an insulator to conductor percolation transition with increase in EG content. Significant changes in the dielectric permittivity take place when the weight fraction of EG is in the range 20–30 wt%. Special attention has been paid to the dependence of the conductivity on frequency, temperature and…

SAXS/WAXS study of the annealing process in quenched samples of isotactic poly(propylene)

1999

The structural rearrangement in samples of quenched isotactic poly(propylene) (iPP) submitted to different annealing treatments has been studied using simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) at the synchrotron radiation source of DESY, Hamburg. From a quantitative analysis of the WAXS profiles the values of the α-monoclinic, mesomorphic, and amorphous mass fractions coexisting in the material were determined. It is demonstrated that the SAXS patterns were characterized by two different long-period values that are attributed to α- and mesomorphic periodicity, respectively. The related α- and mesomorphic volume phase fractions, calculated from the analysis of the SAXS …

Light Scattering as an Easy Tool to Measure Vesicles Weight Concentration

2020

Over the last few decades, liposomes have emerged as promising drug delivery systems and effective membrane models for studying biophysical and biological processes. For all applications, knowing their concentration after preparation is crucial. Thus, the development of methods for easily controlling vesicles concentration would be of great utility. A new assay is presented here, based on a suitable analysis of light scattering intensity from liposome dispersions. The method, tested for extrusion preparations, is precise, easy, fast, non-destructive and uses a tiny amount of sample. Furthermore, the scattering intensity can be measured indifferently at different angles, or even by using the…

Phase equilibria and interfacial tension between coexisting phases for the system water/2-propanol/poly(acrylic acid)

1995

The cloud point curve, tie-lines and interfacial tensions were measured for solutions of 50 mol-% neutralized (counter-ion Na ○+ ) poly(acrylic acid) (molar mass M w = 9 700 g/mol; polydispersity index M w /M n = 2,0) in the mixed solvent water/2-propanol at 30°C. Due to the non-uniformity of the polymer, the end-points of the tie-lines are not situated on the cloud-point curve. The interfacial tension σ, determined by means of the spinning drop method, increases in sigmoidal manner with R tl , the length of the tie-line, expressed in terms of weight fractions. An evaluation of these data in a double-logarithmic plot of σ.M -0,5 versus R tl yields a critical exponent of 4,23 as compared wit…

Preparation of pH sensitive poly(vinilydenefluoride) porous membranes by grafting of acrylic acid assisted by supercritical carbon dioxide

2012

Free radical grafting of acrylic acid (AA) on poly(vinilydenefluoride) (PVDF) porous membranes was studied at 65°C using supercritical carbon dioxide (scCO 2) as a solvent and delivery agent. The process was initiated by the thermal decomposition of benzoylperoxide (BPO). Spectroscopic analyses confirmed the presence of poly(AA) chains linked to treated membranes. The mass fraction of grafted AA increased with grafting time and BPO concentration while it decreased when the density of the fluid phase was enhanced. A not-monotonic trend was obtained when the effect of the initial AA concentration was studied. The grafting process was accompanied by a reduction of the crystallinity of the PVDF…

Determination of trace amounts of β tegafur in commercial α tegafur by powder X-ray diffractometric analysis.

2011

Abstract Objectives The main objective of this work was to develop a suitable analytical technique for determining trace amounts of the thermodynamically stable solid form in bulk samples of metastable form, to a sensitivity of 0.005%–1.0%. Tegafur (5-fluoro-1-(tetrahydro-2-furyl)-uracil) α and β crystalline forms were used as a model for this problem. Methods The trace content of the thermodynamically stable β polymorphic form in tegafur samples was increased by promoting phase transition from the bulk of thermodynamically metastable α form to β form, and achieving sufficient β form content for a quantitative powder X-ray diffractometry (PXRD) analysis. The phase transition was stimulated …

OUP accepted manuscript

2019

Following Cui et al. 2018 (hereafter Paper I) on the classification of large-scale environments (LSE) at z = 0, we push our analysis to higher redshifts and study the evolution of LSE and the baryon distributions in them. Our aim is to investigate how baryons affect the LSE as a function of redshift. In agreement with Paper I, the baryon models have negligible effect on the LSE over all investigated redshifts. We further validate the conclusion obtained in Paper I that the gas web is an unbiased tracer of total matter -- even better at high redshifts. By separating the gas mainly by temperature, we find that about 40 per cent of gas is in the so-called warm-hot intergalactic medium (WHIM). …

Dark Matter Fraction in Lens Galaxies: New Estimates from Microlensing

2014

We present a joint estimate of the stellar/dark matter mass fraction in lens galaxies and the average size of the accretion disk of lensed quasars from microlensing measurements of 27 quasar image pairs seen through 19 lens galaxies. The Bayesian estimate for the fraction of the surface mass density in the form of stars is $\alpha=0.21\pm0.14$ near the Einstein radius of the lenses ($\sim 1 - 2$ effective radii). The estimate for the average accretion disk size is $R_{1/2}=7.9^{+3.8}_{-2.6}\sqrt{M/0.3M_\sun}$ light days. The fraction of mass in stars at these radii is significantly larger than previous estimates from microlensing studies assuming quasars were point-like. The corresponding l…

2013

Abstract. As part of the CLACE-6 campaign we performed size-resolved CCN measurements for a~supersaturation range of S = 0.079 % to 0.66% at the high-alpine research station Jungfraujoch, Switzerland, in March~2007. The derived effective hygroscopicity parameter κ describing the influence of particle composition on CCN activity was on average 0.23–0.30 for Aitken (50–100 nm) and 0.32–0.43 for accumulation mode particles (100–200 nm). The campaign average value of κ = 0.3 is similar to the average value of κ for other continental locations. When air masses came from southeasterly directions crossing the Po Valley in Italy, particles were much more hygroscopic (κ ≈ 0.42) due to…