The influence of thermal stress on the interface strength of a fibre-reinforced thermoplastic investigated by a novel single fibre technique

The present work focuses on further verification of the hypothesis that the level of apparent IFSS in glass fibre-reinforced thermoplastic composites can be modelled satisfactorily by assuming that the main component of the IFSS is actually due to a combination of thermal residual stress and static friction at the fibre-polymer interface. In order to obtain information on the temperature dependence of glass fibre - polypropylene IFSS we have adapted a thermo-mechanical analyser to enable interfacial microbond testing to be carried out in a well controlled temperature environment. Test results obtained by TMA-microbond testing showed excellent comparability with those obtained by normal microbond testing. The temperature dependence of IFSS of glass fibre - polypropylene was measured in the range from -40°C up to 100°C. The IFSS showed a highly significant inverse dependence on testing temperature

The influence of oxidative-thermal degradation of polypropylene on measured interface strength of glass fibre-polypropylene

It was previously found that thermal-oxidative degradation of the polypropylene could significantly affect the measured interfacial strength of glass fibre reinforced polypropylene (GF-PP) micro-composite. In this work, different approaches have been employed to justify this influence. Hot-stage microscopy was used to establish a degradation profile of PP microdroplets that had different initial dimensions and results revealed that the reduction in droplet dimensions was affected by not only its initial droplet size and but also the presence of the fibre in the droplet. The Young's moduli of PP microdroplets with different heat treatments were examined by using nanoindentation technique and the results showed that there was significant stiffness deterioration in degraded samples and the severity is also related to the droplet size for a given heat treatment. Comparison of adhesion for GF-PP was also made between degraded and non-degraded samples. It shows that non-degraded samples give much higher values for interface strength of GF-PP than degraded ones

Differentiation of silane adsorption onto model E-glass surfaces from mixed solutions of amino and glycidyl silanes

Mixed silanes are often used as coupling agents in sizings for glass fibres. A technique has been developed which enables the preferential adsorption of a particular silane onto a model E-glass from a mixed aqueous silane solution to be probed. It is shown that γ-Aminopropyltriethoxysilane (APS) is preferentially adsorbed over γ-glycidoxypropyltrimethoxysilane (GPS) onto model E-glass fibres. High resolution X-ray photoelectron spectroscopy (XPS) has been employed to investigate the nature of silane deposits. Differentiation between the hydrolysed silane deposit and the model silica-based glass substrate was achieved by Si2p curve fitting. The extent of total silane adsorption onto model E-glass fibres was determined from the intensity of CSiO3 peak. In the case of APS/GPS mixed silanes, the N1s peak intensity provides the concentration of APS in the deposit. By comparing the relative intensities of the components in the Si2p3/2 and Si2p1/2 peaks for SiO4 and CSiO3 with the intensity of the N1s peak an assessment of differential adsorption proved possible

The differential adsorption of silanes from solution onto model E-glass surfaces using high resolution XPS

γ-aminopropyltriethoxysilane (APS), γ-mercaptopropyltrimethoxysilane (MPS) and their mixture have been adsorbed onto acid-treated model E-glass fibres from aqueous solution with different concentrations. High resolution X-ray photoelectron spectroscopy (XPS) has been employed to characterize APS and MPS single silane coatings and the selective adsorption of APS/MPS mixed silane coating. It is found that the Si contribution from the silane can be distinguished from the Si contribution from the acid-treated E-glass fibres by fitting Si2p1/2 and Si2p3/2 peaks with components for CSiO3 and SiO4 environments. The adsorption isotherms of APS and MPS have been obtained by comparing the atomic concentrations of N, S and CSiO3 groups. APS and MPS are equally adsorbed from 0.1% APS/MPS mixed silane solution, however, MPS dominates the deposit on model E-glass fibres to a depth corresponding to the take-off-angle of 45º when it is adsorbed from 0.5% and 1.0% APS/MPS mixed silane solutions

Magneto-optical response of layers of semiconductor quantum dots and nanorings

In this paper a comparative theoretical study was made of the magneto-optical response of square lattices of nanoobjects (dots and rings). Expressions for both the polarizability of the individual objects as their mutual electromagnetic interactions (for a lattice in vacuum) was derived. The quantum-mechanical part of the derivation is based upon the commonly used envelope function approximation. The description is suited to investigate the optical response of these layers in a narrow region near the interband transitions onset, particularly when the contribution of individual level pairs can be separately observed. A remarkable distinction between clearly quantum-mechanical and classical electromagnetic behavior was found in the shape and volume dependence of the polarizability of the dots and rings. This optical response of a single plane of quantum dots and nanorings was explored as a function of frequency, magnetic field, and angle of incidence. Although the reflectance of these layer systems is not very strong, the ellipsometric angles are large. For these isolated dot-ring systems they are of the order of magnitude of degrees. For the ring systems a full oscillation of the optical Bohm-Ahronov effect could be isolated. Layers of dots do not display any remarkable magnetic field dependence. Both type of systems, dots and rings, exhibit an outspoken angular-dependent dichroism of quantum-mechanical origin

Entropy of the Schwarzschild-de Sitter Black Hole due to arbitrary spin fields in different Coordinates

By using the Newman-Penrose formalism and the improved thin-layer ``brick wall'' approach, the statistical-mechanical entropies of the Schwarzschild-de Sitter black hole arising from quantum massless arbitrary spin fields are studied in the Painlev\'e and Lemaitre coordinates. Although the metrics in both the Painlev\'e and the Lemaitre coordinates do not obviously possess the singularities as that in the Schwarzschild-like coordinate, we find that, for arbitrary spin fields, the entropies in the Painlev\'e and Lemaitre coordinates are exactly equivalent to that in the Schwarzschild-like coordinate.Comment: 14 pages, no figure, to be published in JHE

The signal of Z±(4430)Z^\pm(4430) in nucleon-antinucleon scattering

We study the production of $Z^\pm(4430)$ at a nucleon-antinucleon scattering experiment. Considering the PANDA experiment to be an ideal platform to explore the production of the charmonium and charmonim-like states, we suggest the forthcoming PANDA experiment to pay attention to the production of $Z^\pm(4430)$.Comment: 6 pages, 15 figures. Published version in EPJ

Low-temperature anomalous specific heat without tunneling modes: a simulation for a-Si with voids

Using empirical potential molecular dynamics we compute dynamical matrix eigenvalues and eigenvectors for a 4096 atom model of amorphous silicon and a set of models with voids of different size based on it. This information is then employed to study the localization properties of the low-energy vibrational states, calculate the specific heat C(T) and examine the low-temperature properties of our models usually attributed to the presence of tunneling states in amorphous silicon. The results of our calculations for C(T) and "excess specific heat bulge" in the C(T)/T^3 vs. T graph for voidless a-Si appear to be in good agreement with experiment; moreover our investigation shows that the presence of localized low-energy excitations in the vibrational spectrum of our models with voids strongly manifests itself as a sharp peak in C(T)/T^3 dependence at T < 3K. To our knowledge this is the first numerical simulation that provides adequate agreement with experiment for the very low-temperature properties of specific heat in disordered systems within the limits of harmonic approximation.Comment: 5 pages with 2 ps figures, submitted to PR

Possible mechanism of efferent arteriole (Ef-Art) tubuloglomerular feedback

Adenosine triphosphate (ATP) is liberated from macula densa cells in response to increased tubular NaCl delivery. However, it is not known whether ATP from the macula densa is broken down to adenosine, or whether this adenosine mediates efferent arteriole (Ef-Art) tubuloglomerular feedback (TGF). We hypothesized that increased macula densa Ca2+, release of ATP and degradation of ATP to adenosine are necessary for Ef-Art TGF. Rabbit Ef-Arts and adherent tubular segments (with the macula densa) were simultaneously microperfused in vitro while changing the NaCl concentration at the macula densa. The Ef-Art was perfused orthograde through the end of the afferent arteriole (Af-Art). In Ef-Arts preconstricted with norepinephrine (NE), increasing NaCl concentration from 10 to 80mM at the macula densa dilated Ef-Arts from 7.5±0.7 to 11.1±0.3μm. Buffering increases in macula densa Ca2+ with the cell-permeant Ca2+ chelator BAPTA-AM diminished Ef-Art TGF from 3.1±0.3 to 0.1±0.2μm. Blocking adenosine formation by adding α-β-methyleneadenosine 5′-diphosphate (MADP) blocked Ef-Art TGF from 2.9±0.5 to 0.1±0.2μm. Increasing luminal NaCl at the macula densa from 10 to 45mM caused a moderate Ef-Art TGF response, 1.3±0.1μm. It was potentiated to 4.0±0.3μm by adding hexokinase, which enhances conversion of ATP into adenosine. Our data show that in vitro changes in macula densa Ca2+ and ATP release are necessary for Ef-Art TGF. ATP is broken down to form adenosine, which mediates signal transmission of Ef-Art TGF