Search results for "Synthetic materials"
showing 8 items of 8 documents
Experimental evidence for two different precursors of Eγ′ centers in silica
2004
Abstract Electron paramagnetic resonance measurements of concentration and line shape of E γ ′ centers induced by γ ray irradiation are presented for natural and synthetic commercial silica with different OH contents. Synthetic materials with OH content >200 ppm by weight show one line shape for all investigated doses. In contrast, the other materials show a different line shape at low irradiation doses. Differences are also observed in the concentration growth of the E γ ′ centers in synthetic wet materials and in the other materials. The results are interpreted as evidence of two E γ ′ centers distinguishable by their line shape and having different precursors.
On the hygrothermal behavior of coconuts fiber insulators on green roofs.
2020
Coconut fibre insulators, represent an insulating material considered as “exotic”, which clashes with the doubts of his thermo-hygrometric behavior, in particular, in the case of covering technology such as green roofs, a technological solution adopted in the case of sustainable buildings or nearly zero energy building. Green roofs represent a valid constructive solution with high thermal performances, adopted in existing and new buildings. The purpose of the research regards the study of the thermo-hygrometric behavior of the concrete and Cross-Laminated Timber (CLT) slabs, insulated with coconut fibre-boards (CF) such as alternative synthetic insulators, referred to 10 different green roo…
Hackmanite—The Natural Glow-in-the-Dark Material
2020
“Glow-in-the-dark” materials are known to practically everyone who has ever traveled by airplane or cruise ship, since they are commonly used for self-lit emergency exit signs. The green afterglow, persistent luminescence (PeL), is obtained from divalent europium doped to a synthetic strontium aluminate, but there are also some natural minerals capable of afterglow. One such mineral is hackmanite, the afterglow of which has never been thoroughly investigated, even if its synthetic versions can compete with some of the best commercially available synthetic PeL materials. Here we combine experimental and computational data to show that the white PeL of natural hackmanite is generated and cont…
Gellan gum-based delivery systems of therapeutic agents and cells.
2020
The purpose of this review is to make a summary of high quality research trends using gellan gum (GG) as a polymeric constituent for the design of innovative drug delivery systems and devices for biomedical applications, such as cell therapy and regenerative medicine. The use of gellan gum is described both in its native form and as chemically functionalized derivatives or physically mixed with natural or synthetic materials. Starting from a systematic study of recent research works, the main properties of the native polysaccharide have been highlighted and therefore some improvements have been focused thanks to the design of chemically functionalized derivatives and the use of composite ma…
Dependence of polytetrafluoroethylene reflectance on thickness at visible and ultraviolet wavelengths in air
2020
[EN] Polytetrafluoroethylene (PTFE) is an excellent diffuse reflector widely used in light collection systems for particle physics experiments. However, the reflectance of PTFE is a function of its thickness. In this work, we investigate this dependence in air for light of wavelengths 260 nm and 450 nm using two complementary methods. We find that PTFE reflectance for thicknesses from 5 mm to 10 mm ranges from 92.5% to 94.5% at 450 nm, and from 90.0% to 92.0% at 260 nm We also see that the reflectance of PIFE of a given thickness can vary by as much as 2.7% within the same piece of material. Finally, we show that placing a specular reflector behind the PTFE can recover the loss of reflectan…
Measurement of inclusive neutral current pi(0) production on carbon in a few-GeV neutrino beam
2010
The SciBooNE Collaboration reports inclusive neutral current neutral pion production by a muon neutrino beam on a polystyrene target (C8H8). We obtain (7.7 +/- 0.5(stat) +/- 0.5(sys)) X 10(-2) as the ratio of the neutral current neutral pion production to total charged current cross section; the mean energy of neutrinos producing detected neutral pions is 1.1 GeV. The result agrees with the Rein-Sehgal model implemented in our neutrino interaction simulation program with nuclear effects. The spectrum shape of the pi(0) momentum and angle agree with the model. We also measure the ratio of the neutral current coherent pion production to total charged current cross section to be (0.7 +/- 0.4) …
Large Scale Fractionation of Macromolecules
2004
Access to sufficiently large amounts of material with adequate molecular and chemical uniformity from polydisperse natural products or synthetic materials has been a long-standing challenge to polymer scientists. We have developed a broadly applicable preparative fractionation method consisting of a special kind of continuous extraction removing the easier soluble components from the initial product. It is rendered possible by the use of spinning nozzles throught which a concentrated polymer solution is pressed into a liquid of tailored thermodynamic quality. The initially produced jets of the source phase disintegrate rapidly into minute droplets of typically 50 μm diameter. This efficient…
Mechanical performance of thermoplastic matrix natural-fibre composites
2008
Publisher Summary Natural-Fibre Composites (NFCs) are being considered as high-tech materials meant to replace conventional composites in high-performance applications. There are a number of advantages that natural fibres can offer compared with synthetic materials. Thermoplastic natural-fibre composites can be classified by the polymer used as a matrix as well as by the type of the fibre reinforcing the polymer. Currently, the main areas of application of thermoplastic NFCs are packaging, transportation and building industries. The packaging industry requires materials that possess specific properties, but that can also be easily discarded after use. This chapter discusses the mechanical p…