Search results for " composition"
showing 10 items of 1437 documents
The effects of water absorption and salt fog exposure on agglomerated cork compressive response
2022
The replacement of synthetic foams with agglomerated cork in sandwich composites can meet the increasing environmental concerns. Its peculiar morphology and chemical composition lead to outstanding dimensional recovery that endorsed a broad investigation of its compressive behavior. The knowledge of neat material response is fundamental to obtain a reliable design dataset, but it is necessary to consider all the environmental factors (water, moisture and sunlight) that significantly modify material mechanical properties. In view of this, the present work investigates the effect of distilled and seawater absorption and salt fog exposure on the compressive behavior of two agglomerated corks w…
NuSTAR and NICER reveal IGR J17591-2342 as a new accreting millisecond X-ray pulsar
2018
We report the discovery by the Nuclear Spectroscopic Telescope Array (NuSTAR) and the Neutron Star Interior Composition Explorer (NICER) of the accreting millisecond X-ray pulsar IGR J17591-2342. Coherent X-ray pulsations around 527.4 Hz (1.9 ms) with a clear Doppler modulation were detected. This implies an orbital period of ∼8.8 h and a projected semi-major axis of ∼1.23 lt-s. With the binary mass function, we estimate a minimum companion mass of 0.42 M, obtained assuming a neutron star mass of 1.4[subscript ⊙] and an inclination angle lower than 60°, as suggested by the absence of eclipses or dips in the light curve of the source. The broad-band energy spectrum, obtained by combining NuS…
Timing of the accreting millisecond pulsar IGR J17591-2342: evidence of spin-down during accretion
2020
We report on the phase-coherent timing analysis of the accreting millisecond X-ray pulsar IGR J17591-2342, using Neutron Star Interior Composition Explorer (NICER) data taken during the outburst of the source between 2018 August 15 and 2018 October 17. We obtain an updated orbital solution of the binary system. We investigate the evolution of the neutron star spin frequency during the outburst, reporting a refined estimate of the spin frequency and the first estimate of the spin frequency derivative ($\dot{\nu} \sim -7\times 10^{-14}$ Hz s$^{-1}$), confirmed independently from the modelling of the fundamental frequency and its first harmonic. We further investigate the evolution of the X-ra…
Metabolic shift of polyphosphate-accumulating organisms with different levels of polyphosphate storage
2012
Previous studies have shown that polyphosphate-accumulating organisms (PAOs) are able to behave as glycogen-accumulating organisms (GAOs) under different conditions. In this study we investigated the behavior of a culture enriched with Accumulibacter at different levels of polyphosphate (poly-P) storage. The results of stoichiometric ratios Gly degraded/HAc uptake, PHB synthesized/HAc uptake, PHV synthesized/HAc uptake and P release/HAc uptake confirmed a metabolic shift from PAO metabolism to GAO metabolism: PAOs with high poly-P content used the poly-P to obtain adenosine tri-phosphate (ATP), and glycogen (Gly) to obtain nicotinamide adenine dinucleotide (NADH) and some ATP. In a test whe…
Ferro-pedrizite, NaLi2(Fe2+ 2Al2Li)Si8O22(OH)2, a new amphibole-supergroup mineral from the Sutlug pegmatite, Tyva Republic, Russia
2015
Ferro-pedrizite, a new amphibole-supergroup mineral was discovered in the Sutlug pegmatite occurrence situated in the Targi River Basin, Tyva Republic, Eastern Sibera, Russia. The associated minerals are quartz, albite, microcline, spodumene, cassiterite, beryl, columbite-(Mn), fergusonite-β-(Y), fluorapatite, schorl, trilithionite and fluorite. Ferro-pedrizite forms dark grey-blue to violet-blue acicular and long prismatic crystals up to 2 × 5 × 50 mm and their aggregates. D meas = 3.16(1) g/cm3 (by hydrostatic weighing), 3.13(1) g/cm3 (by flotation in heavy liquids); D calc = 3.135 g/cm3. Ferro-pedrizite is optically biaxial (−), α = 1.614(3), β = 1.638(3), γ = 1.653(3), 2 V meas = 75(5)°…
Preparation and characterization of octadecyl acrylate monoliths for capillary electrochromatography by photochemical, thermal, and chemical initiati…
2013
Monolithic stationary phases based on octadecyl acrylate for CEC using different initiating systems (UV irradiation, thermal, and chemical initiation) in the presence of lauroyl peroxide as initiator were synthesized. For each initiation mode, the influence of the porogenic solvent composition on both the morphological and electrochromatographic properties of the resulting monoliths was investigated. Under optimal conditions, excellent efficiencies for the photochemically and chemically polymerized monoliths (minimum plate heights of 6.9–10.7 and 6.5–12.6 μm, respectively) were achieved. Thermally initiated columns gave lower efficiency values, permeabilities, and longer analysis times comp…
Chemical initiation for butyl and lauryl acrylate monolithic columns for CEC.
2009
Butyl acrylate (BA)- and lauryl acrylate (LA)-based monolithic stationary phases for CEC were synthesized, using a redox system as initiator of polymerization. BA monoliths were initiated with ammonium peroxodisulfate, whereas LA columns were obtained with lauroyl peroxide as initiator. In both cases, TEMED was used to activate the process. The influence of porogenic solvent composition on both morphological and electrochromatographic properties of the resulting monoliths was investigated. Excellent efficiencies (minimum plate heights of 4.2-6.3 microm for BA columns and 2.6-5.3 microm for LA stationary phases, for a PAHs mixture) were achieved. The capability of separation of both types of…
Generalized effective stress concept for saturated active clays
2021
Experimental evidence shows that changes in pore-water chemistry can significantly affect the mechanical behavior of saturated active clays. Despite this evidence, how the chemical composition of the pore water can be considered in effective stress definition is questionable. This paper develops the concept of generalized effective stress for active clays. To this end, physicochemical studies on water–clay mineral interactions are used to clearly define the different types of ions and water present in an active clay. In particular, the presence of both movable and non-movable ions within the liquid water is highlighted. Taking this into account, thermodynamic and geochemistry principles ar…
Caracterización mineralógica de materias primas cerámicas por métodos cuantitativos de difracción de rayos x
2002
[ES] El objetivo de este trabajo es la caracterización de fases minerales presentes en materias primas utilizadas en la industria cerámica. Para ello se utilizan dos métodos cuantitativos basados en la difracción de rayos X, el método de Rietveld y un método sin estándar. Los resultados obtenidos por difracción rayos X de estos materiales policristalinos se comparan con los correspondientes análisis químicos y la composición normativa calculada. La precisión y reproducibilidad de los resultados obtenidos, en concordancia con los del análisis químico, son una de las más importantes ventajas de la difractometría cuantitativa que facilitan su utilización en la industria cerámica en el control …
Radiation protection in non-ionizing and ionizing body composition assessment procedures
2020
Body composition assessment (BCA) represents a valid instrument to evaluate nutritional status through the quantification of lean and fat tissue, in healthy subjects and sick patients. According to the clinical indication, body composition (BC) can be assessed by different modalities. To better analyze radiation risks for patients involved, BCA procedures can be divided into two main groups: the first based on the use of ionizing radiation (IR), involving dual energy X-ray absorptiometry (DXA) and computed tomography (CT), and others based on non-ionizing radiation (NIR) [magnetic resonance imaging (MRI)]. Ultrasound (US) techniques using mechanical waves represent a separate group. The pur…