Search results for "Thermal"
showing 10 items of 3576 documents
Thermal lens spectrometric determination of cerium with oxine
1991
Abstract The spectrophotometric and photothermal (TLS) procedures for cerium determination using 8-hydroxyquinoline (oxine), after extraction into chloroform, are compared. Photothermal measurements are made using a coaxial pump/probe thermal lens spectrometer. The use of high-purity reagents at low concentrations permits a decrease in the TLS blank signal and noise, leading to a limit of detection of 9 × 10−9 M (cerium extract concentration), 40-fold lower than the spectrophotometric value. The dynamic range extended up to 6 × 10−7 M and the relative standard deviation for 5 × 10−7 M cerium was 3.9%.
Responses to Developmental Temperature Fluctuation in Life History Traits of Five Drosophila Species (Diptera: Drosophilidae) from Different Thermal …
2021
Simple Summary Most laboratory experiments on insects to date have been conducted using constant temperature settings. Even when the purpose of the study was to investigate effects of temperature, insects have mostly been kept at different but constant temperatures ignoring natural variation in temperature. Here we investigated effects of simple daily temperature fluctuation (22.5/27.5 °C and 20/30 °C) on some development characteristics in five species of fruit flies (Drosophila) originating from areas with different temperature profiles. We demonstrated how species of the same genus can show substantial differences when developing at fluctuating temperatures not always predictable by deve…
Effect of sisal and hydrothermal ageing on the dielectric behaviour of polylactide/sisal biocomposites
2017
[EN] The dielectric properties of virgin polylactide (PLA) and its reinforced composites with different weight amounts of sisal fibres were assessed at broad temperature (from - 130 degrees C to 130 degrees C) and frequency ranges (from 10(-2)-10(7) Hz), before and after being subjected to accelerated hydrothermal ageing. The synergetic effects of both the loading of sisal and hydrothermal ageing were analysed by means of dielectric relaxation spectra. The relaxation time functions were evaluated by the Havriliak-Negami model, substracting the ohmic contribution of conductivity. The intramolecular and intermolecular relaxations were respectively analysed by means of Arrhenius and Vogel-Fulc…
Thermal studies of sulphonamide derivative complexes
1991
Abstract A thermal study of a new series of acetazolamidate complexes of Co(II), Ni(II) and Cu(II) using the TG, DTG and DTA techniques in flowing air, static air and N 2 atmospheres is described. From the TG-DTG and DTA curves, different thermal behaviours can be observed. Although in all the complexes the processes of dehydration, deammination and pyrolysis can be clearly observed, in some cases they appear as several well-separated steps and, in others, as continuous stages which take place simultaneously. The differences observed between the pyrolytic decomposition in flowing air and in nitrogen are described. In flowing air, metal sulphate is formed from the thiadiazole ring, except fo…
Development of a new peat-based oil sorbent using peat pyrolysis
2013
The growing use and transport of crude oil and oil products has led to increasing numbers of oil spillages of various scales. Oil sorbents have been extensively used for remediation of the consequences of such accidents. The aim of this study is to investigate the possible use of peat and its thermal treatment products for oil sorption. Peat as an oil sorbent has poor buoyancy characteristics, relatively low oil sorption capacity and low hydrophobicity. However, thermal treatment (low-temperature pyrolysis and synthesis of peat-based activated coal) helps to significantly improve its sorptive characteristics. Peat is a potential material for oil sorption because it has such advantages as lo…
Mechanical and thermal behaviour of networks with “flexible” and “rigid” chains
1996
“Rigid-rod” telechelics were synthesized via repetitive Diels-Alder reaction of biscyclohexadienes and bis(1,2,4-triazoline-3,5-diones). The bistriazolinediones were used in slight excess. The rigidity of the building blocks and the molecular weight were varied. Various amounts of these reactive telechelics are used to crosslink cis-1,4-polybutadiene. The mechanical and the thermal properties of these two-component networks were investigated by stress-strain, differential scanning calorimetry and dynamic-mechanical measurements. The occurrence of microphase separation between the “rigid” and the “flexible” components is discussed to explain the properties of these materials.
Thermodynamic approach of supercontinuum generation
2009
International audience; This paper is aimed at providing an overview on recent theoretical and experimental works in which a thermodynamic description of the incoherent regime of supercontinuum generation has been formulated. On the basis of the wave turbulence theory, we show that this highly nonlinear and quasi-continuous-wave regime of supercontinuum generation is characterized by two different phenomena. (i) A process of optical wave thermalization ruled by the four-wave mixing effects: The spectral broadening inherent to supercontinuum generation is shown to result from the natural tendency of the optical field to reach its thermodynamic equilibrium state, i. e., the state of maximum n…
Microscopic Origins of the Anomalous Melting Behavior of Sodium under High Pressure
2012
X-ray diffraction experiments have shown that sodium exhibits a dramatic pressure-induced drop in melting temperature, which extends from 1000 K at ~30 GPa to as low as room temperature at ~120 GPa. Despite significant theoretical effort to understand the anomalous melting, its origins are still debated. In this work, we reconstruct the sodium phase diagram by using an ab initio quality neural-network potential. Furthermore, we demonstrate that the reentrant behavior results from the screening of interionic interactions by conduction electrons, which at high pressure induces a softening in the short-range repulsion.
Electronic structure and transport properties of the Heusler compound Co2TiAl
2009
The properties of the Heusler compound Co2TiAl were investigated in detail by experimental techniques and theoretical methods. X-ray diffraction measurements indicate that as-cast samples of the compound exhibit the L21 structure with a small amount of B2-type disorder. This leads to a reduced saturation magnetization per formula unit of 0.747 μB. The Curie temperature is approximately 120 K. The transport properties are influenced by the change in the electronic structure at the Curie temperature, as revealed experimentally by conductivity, thermal transport and specific heat measurements. Different theoretical models based on ab initio calculations of the electronic structure are used to …
Synthesis of MoO3 Nanostructures and Their Facile Conversion to MoS2 Fullerenes and Nanotubes.
2007
The fast thermolysis of ammonium molybdate leads to a mixture of MoO3 and Mo5.3O14.5(OH)2.8(H2O)1.36 with spherical and rod-like morphologies. The oxide mixture can be converted in quantitative yield to inorganic fullerene-type (IF) MoS2 and MoS2 nanotubes (NT) by H2S reduction using a facile and quick procedure. The products were studied by X-Ray Diffraction (XRD) and by Transmission Electron Microscopy (TEM). TEM analysis reveals that the spherical and rod-like morphology of the oxide precursor is preserved during the H2S treatment.