Materials Literature
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Although it is widely known to textile scientists that when yarn twist exceeds the optimal level, yam strength will decline due to the so-called obliquity effect, the exact physical mechanism behind this obliquity effect is still unknown. It is therefore our objective to investigate this issue. We adopt a special tech…
Abstract Several species of freshwater green algae belonging to the order Zygnematales (Spirogyra crassa (Ktz.) Czurda, S. longata (Vauch.) Ktz., and Mougeotia viridis (Ktz.) Wittr.) were found to have a specific composition of the volatile fraction, which confirms an earlier proposal for the existence of two groups i…
Luminescent Si nanocrystals formed in SiO 2 layers were irradiated with electrons and He + ions with energies of 400 and 25–130 keV, respectively. The effects of irradiation and subsequent annealing at 600–1000°C were studied by the methods of photoluminescence and electron microscopy. After irradiation with low doses…
Molecular dynamics simulations of alumina containing silicate glasses have been performed in order to determine the influence of that ion on the final properties of the glasses. In particular, short- and mid-range structures were analyzed in terms of the distribution of non bridging oxygen, bridging oxygen, three brid…
Thermoplastic copolyimide synthesised from 3,3′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxydianiline, and 1,3-phenylenediamine were success fully coated onto carbon fibres by electrochemical deposition and subsequently impregnated with polymerisable reaction mixtures of PMR-15 thermosetting polyimide. Carb…
Molecular assemblies of meso-pyridylporphyrins and zinc(II) 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine held through axial coordination are reported. Their formation has been revealed by 1H NMR spectroscopy and photophysical measurements.
The possibility of using CVD diamond films as dosimeters in radiotherapy applications has been tested in both off-line and on-line configurations. The thermoluminescent and thermally stimulated current responses after 20 MeV electron and 22 MeV proton irradiation have been studied as a function of the dose up to 10 Gy…
Temperature dependence of the deformation behavior of Mg-alloy single crystals containing 0.5 at.%Dy or Zn is investigated by compression tests at various test temperatures ranging from 77 K to 473 K. The basal slip operates and the CRSS increases with decreasing temperature at the temperature range lower than room te…
Direct-template synthesis and purification of a new phase of the triple-decker bismuth(III) phthalocyanine Bi2(Pc)3, prepared from bismuth acetate and phthalonitrile, are described. X-ray analysis shows a triple-decker molecular structure involving three phthalocyanine rings and two bismuth atoms that are 3.838(9) Å a…
Discrete and monodisperse submicron crystals of silicalite-1 with a mean size of 0.3 μ m were synthesized from clear crystallization solutions. The effects of silica content, alkalinity of batch and the nature of silica source on the product yield, crystal morphology and particle size distribution were investigated. T…
The freshwater zones of the Warri/Forcados Estuaries contain a rich and diverse flora of tropical desmids, which compare favourably and show strong affinities with desmids from other parts of Africa, tropical South America, Southeast Asia, tropical Australia and the Indian sub-continent. In this study, ninety (90) tax…
Two mesogenic homologous series, 2-[4-(4-n-alkoxybenzoyloxy)-2-methylphenylazo]-naphthalenes (I) and 2-[4-(4-n-alkoxybenzoyloxy)-3-methylphenylazo]naphthalenes (II) with a lateral methyl group have been synthesized. Both series are purely nematogenic. The mesomorphic properties of both series are compared with each ot…
Chromium-doped silica-based optical fibres emit infrared fluorescence at 77 K near 1250 nm (500 nm band-width) under 860−980 nm excitation. Visible and near-infrared absorption spectra of fibres were analysed using the Tanabe-Sugano formalism. It is shown that although the fibre core is codoped with only 1 mol% of alu…
Ground-state properties and phonon dispersion curves of a classical linear-chain model describing a crystal with an incommensurate phase are studied. This model is the DIFFOUR (discrete frustrated ${\ensuremath{\varphi}}^{4})$ model with an extra fourth-order term added to it. The incommensurability in these models ma…
The optical spectra of bis(phenethylimido)perylene (PhPTCD) are discussed. Surface-pressure area isotherms of floating Langmuir monomolecular layers have been obtained, and Langmuir-Blodgett (LB) molecular monolayers of the material have been fabricated on silver island substrates for surface-enhanced vibrational stud…
Pb2+ is a low cost activator which can provide strong absorption of UV and an efficient conversion to longer wavelengths. Considering that aluminate hosts are used in some lamp phosphors, Pb2+ luminescence in these hosts is studied. This paper reports results on the luminescence of Pb2+ in aluminates. It was found tha…
The temperature dependences of the dielectric constant ε of sodium niobate single crystals NaNbO 3 and sodium niobate-based (Na,Li)NbO 3 and (Na,K)NbO 3 solid solutions with low content of the second component have been studied. A weak anomaly observed in ε( T ) indicates a new phase transition in the vicinity of 150°…
Two different cubic phases in pure (Ia3d cubic space group) and mixed (Im3m cubic space group) thermotropic carboxylic acids are observed by optical microscopy. In unpolarized light, the presence of the cubic phases is identified unambiguously by the observation of facetted single crystals with highly symmetrical shap…
In the production of MDF, wet resinated fibre must be dried to its target moisture content, normally 9 to 11%, before compaction into a board by hot pressing. Fibre drying can be interpreted as an incorporated process involving gas-solid two phase-flow, inter-component transfer, and heat and mass transfer within the f…
The kinetics of photobleaching of zinc(II) tetra-t-butyltetrabenzoporphyrin 1, zinc(II) 13,17-diethyl-12,18-dimethyl-5-azadibenzo[b,g]porphyrin 2 and zinc(II) tetra-t-butylphthalocyanine 3 are studied. In methanol containing ca 0.1% pyridine, complex 1 undergoes photoaggregation, 2 is relatively photostable, while 3 u…