188 research outputs found
SOLUBILITY OF VEGETABLE CUTICULAR WAXES IN SUPERCRITICAL CO2 ISOTHERMAL CALORIMETRY INVESTIGATIONS
No full textVegetable cuticular waxes have to be separated from the more valuable essential oils in extraction processes carried out with supercritical fluids (namely CO2), allowing a solvent selectivity by modification of temperature and pressure. The solubility of these waxes in supercritical CO2 can be adequately represented by that of solid n-octacosane. The present work shows that isothermal investigations, carried out with a differential flux calorimeter with adequate cells, allow the solubility and solubilization enthalpy of n-octacosane to be determined. The results concern investigations either at constant pressure and variable supercritical CO2 flow-rate, or at zero flow-rate and increasing pressure. The latter conditions allow the solubility-pressure trend to be obtained, in satisfactory agreement with literature data derived from standard dynamic methods
Crystallization of TiO2 Nanotubes by In Situ Heating TEM
Get PDFThe thermally-induced crystallization of anodically grown TiO2 amorphous nanotubes has been studied so far under ambient pressure conditions by techniques such as differential scanning calorimetry and in situ X-ray diffraction, then looking at the overall response of several thousands of nanotubes in a carpet arrangement. Here we report a study of this phenomenon based on an in situ transmission electron microscopy approach that uses a twofold strategy. First, a group of some tens of TiO2 amorphous nanotubes was heated looking at their electron diffraction pattern change versus temperature, in order to determine both the initial temperature of crystallization and the corresponding crystalline phases. Second, the experiment was repeated on groups of few nanotubes, imaging their structural evolution in the direct space by spherical aberration-corrected high resolution transmission electron microscopy. These studies showed that, differently from what happens under ambient pressure conditions, under the microscope’s high vacuum (p < 10−5 Pa) the crystallization of TiO2 amorphous nanotubes starts from local small seeds of rutile and brookite, which then grow up with the increasing temperature. Besides, the crystallization started at different temperatures, namely 450 and 380 °C, when the in situ heating was performed irradiating the sample with electron beam energy of 120 or 300 keV, respectively. This difference is due to atomic knock-on effects induced by the electron beam with diverse energy
SIRIO : Integrated Forest Firesmonitoring, detection and decision supportsystem with low cost commercial sensorssuited for complex orography
Get PDFForest Fires in our society cause a lot of damage, in particular regarding the economic and environmental landscape. In order to monitor a large portion of territory automatically, with a good cost/performances trade-off, it is necessary to develop new early warning systems. We propose a ground-based system with modular architecture, equipped with low cost commercial sensor. The idea is to develop the software able to manage the forest fires monitoring. The technique is based on Static and Dynamic analysis of chromatic changes between images, tailored for our case of study in a large scale monitoring of vegetation and using different sensors to reduce or eliminate the false alarm rate. Concerning the image geo-referencing tool, the present work describes an innovative projective geo-referencing algorithm able to geo-reference complex orography regions using fixed ground station images. Besides, it does not need the collection of Ground Control Points, which is a very hard task in complex orography environments. In order to make a user oriented product and to help the operator during extinguishing activities, a decision support tool has been developed as well. This work presents the results of one year monitoring campaign conducted in cooperation with the Civil Protection Offices in Sanremo (IM), Ital
Evolution of nanomechanical properties and crystallinity of individual titanium dioxide nanotube resonators
Get PDFHerein a complete characterization of single TiO2 nanotube resonator was reported for the first time. The modal vibration response analysis allows a non-invasive indirect evaluation of the mechanical properties of the TiO2 nanotube. The effect of post-grown thermal treatments on nanotube mechanical properties was investigated and carefully correlated to the chemico-physical parameters evolution. The Young's modulus of TiO2 nanotube rises linearly from 57 GPa up to 105 GPa for annealing at 600 °C depending on the compositional and crystallographic evolution of the nanostructure. Considering the growing interest in single nanostructure devices, the reported findings allow a deeper understanding of the properties of individual titanium dioxide nanotubes extrapolated from their standard arrayed architecture
Characterization of aluminum nitride film properties for high signal-to-noise ratio piezoelectric micro-electromechanical system microphones
No full textThe Signal-to-Noise Ratio (SNR) of piezoelectric microphones is significantly dependent on the material properties of the piezoelectric film, namely the piezoelectric coefficient, the dielectric constant, and the dielectric loss. This work presents a metrological approach for the characterization of Aluminum Nitride (AlN) films used as sensing elements in high SNR piezoelectric Micro-Electromechanical System (MEMS) microphones. A dynamic measurement method based on micro-Laser Doppler Vibrometer (LDV) was adopted to evaluate the piezoelectric d33 coefficient of 500 nm thick AlN films deposited by reactive magnetron sputtering over conductive cantilever test samples. The LDV measurement results were also compared against the d33 value determined by a Piezo Evaluation System coupled to a single point laser vibrometer, exploiting the converse piezoelectric effect. The accurate and precise evaluation of the piezoelectric properties, together with the proper mechanical design of the MEMS microphone, is fundamental to provide reliable estimations of the electroacoustic performances, in terms of SNR, dynamic range, and frequency response. Furthermore, a metrological approach for the evaluation of the measurement uncertainty of the piezoelectric coefficient allows predicting its contribution to the uncertainty associated with the electroacoustic characteristics of the MEMS microphone
Low‐Temperature Water‐Assisted Oxidation of Sponge‐Like Zn Nanostructures for Environmental and Energy Harvesting Applications
Get PDFAbstract In this work, the oxidation of sponge‐like nanostructured Zn films exploiting their interaction with water in liquid and vapor phases is investigated. By simply exposing the sputtered porous metal layers to a water vapor atmosphere or incubating them in water at different temperatures, the full conversion to ZnO is obtained. Depending on the kind of treatment, the oxidized ZnO layers exhibit different morphologies and physico‐chemical properties. When in combination with low heating of the surface, a better crystallinity and the growth of hexagonal nanocrystals (nanoprisms and nanoflowers) from the nanobranched Zn structure is observed, preserving the sponge‐like morphology of the starting material. Good photocatalytic activities for the degradation of an organic dye are measured under simulated sunlight irradiation. The piezoelectric and semiconducting response of the oxidized ZnO layers is also examined, revealing appealing performance in both cases and envisaging their use as nanogenerators and photoanode material in dye‐sensitized solar cells. The multifunctional properties of the oxidized ZnO film are discussed in terms of the selected water oxidation approach that tune the corresponding morphology and crystallinity. The low‐temperature oxidation approaches here proposed allow the fabrication of flexible semiconductive ZnO films highly desirable in different fields of nanoelectronics
Dissipative Dynamics of Polymer Phononic Materials
Get PDFPhononic materials are artificial composites with unprecedented abilities to control acoustic waves in solids. Their performance is mainly governed by their architecture, determining frequency ranges in which wave propagation is inhibited. However, the dynamics of phononic materials also depends on the mechanical and material properties of their constituents. In the case of viscoelastic constituents, such as most polymers, it is challenging to correctly predict the actual dynamic behavior of real phononic structures. Existing studies on this topic either lack experimental evidence or are limited to specific materials and architectures in restricted frequency ranges. A general framework is developed and employed to characterize the dynamics of polymer phononic materials with different architectures made of both thermoset and thermoplastic polymers, presenting qualitatively different viscoelastic behaviors. Through a comparison of experimental results with numerical predictions, the reliability of commonly used elastic and viscoelastic material models is evaluated in broad frequency ranges. Correlations between viscous effects and the two main band-gap formation mechanisms in phononic materials are revealed, and experimentally verified guidelines on how to correctly predict their dissipative response are proposed in a computationally efficient way. Overall, this work provides comprehensive guidelines for the extension of phononics modeling to applications involving dissipative viscoelastic materials
Electrocatalytic Activity and Durability of Pt-Decorated Non-Covalently Functionalized Graphitic Structures
No full textCarbon graphitic structures that differ in morphology, graphiticity and specific surface area were used as support for platinum for Oxygen Reduction Reaction (ORR) in low temperature fuel cells. Graphitic supports were first non-covalently functionalized with pyrene carboxylic acid (PCA) and, subsequently, platinum nanoparticles were nucleated on the surface following procedures found in previous studies. Non-covalent functionalization has been proven to be advantageous because it allows for a better control of particle size and monodispersity, it prevents particle agglomeration since particles are bonded to the surface, and it does not affect the chemical and physical resistance of the support. Synthesized electrocatalysts were characterized by electrochemical half-cell studies, in order to evaluate the Electrochemically Active Surface Area (ECSA), ORR activity, and durability to potential cycling and corrosion resistance.ChemE/Chemical EngineeringApplied Science
Characterization of an incipient granulosa cell tumour in a Holstein cow: Steroid hormone receptors and coregulators expression
No full textThe objective of this study was to describe a case of a granulosa cell tumour (GCT) of incipient formation and to characterize it by its immunohistochemical pattern and hormonal profile. The case presented corresponds to a 7-year-old Holstein cow without reproductive disorders. No alterations were observed at rectal palpation, neither in the ultrasonography nor in the hormonal profile. A GCT concomitant with normal follicular development was diagnosed. Through a panel of immunohistochemical markers, a highly differentiated pattern could be determined in the GCT, which preserves the expression of steroid receptors (ESR1, ESR2 and PR) typical of granulosa cells, but does not express the enzymes for the synthesis of androgens (CYP17A1) and oestrogens (CYP19A1). In addition, the expression of co-regulators of steroid hormone receptors and neuroendocrine markers was described for the first time in a GCT in cattle. These results increase the information about GCTs in cattle before the ovarian function is compromised.Fil: Belotti, Eduardo Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Sacco, Sofía Clara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Stassi, Antonela Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Notaro, Ulises Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Angeli, Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Etchevers, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Chiaraviglio, Juan Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Ortega, Hugo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Salvetti, Natalia Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentin
Crystallization of TiO2 Nanotubes by In Situ Heating TEM
No full textThe thermally-induced crystallization of anodically grown TiO2 amorphous nanotubes has been studied so far under ambient pressure conditions by techniques such as differential scanning calorimetry and in situ X-ray diffraction, then looking at the overall response of several thousands of nanotubes in a carpet arrangement. Here we report a study of this phenomenon based on an in situ transmission electron microscopy approach that uses a twofold strategy. First, a group of some tens of TiO2 amorphous nanotubes was heated looking at their electron diffraction pattern change versus temperature, in order to determine both the initial temperature of crystallization and the corresponding crystalline phases. Second, the experiment was repeated on groups of few nanotubes, imaging their structural evolution in the direct space by spherical aberration-corrected high resolution transmission electron microscopy. These studies showed that, differently from what happens under ambient pressure conditions, under the microscope’s high vacuum (p < 10−5 Pa) the crystallization of TiO2 amorphous nanotubes starts from local small seeds of rutile and brookite, which then grow up with the increasing temperature. Besides, the crystallization started at different temperatures, namely 450 and 380 °C, when the in situ heating was performed irradiating the sample with electron beam energy of 120 or 300 keV, respectively. This difference is due to atomic knock-on effects induced by the electron beam with diverse energy.The authors acknowledge financial support from the KAUST baseline funding of Andrea Falqui
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