Search results for "OEL"

Lokanu oglekļa nanocaurulīšu-metālu halkogenīdu hibrīdstruktūru sintēze un īpašības

2021

Darbā ir veikti pētījumi par lokanu oglekļa nanocaurulīšu tīklojumu, oglekļa nanocaurulīšu-metālu halkogenīdu hibrīdstruktūru un to nanokompozītu ar nevadošiem polimēriem termoelektrisko īpašību izmaiņām materiālu lieces iespaidā. Bakalaura darba ietvaros tika sagatavoti lokani oglekļa nanocaurulīšu tīklu un oglekļa nanocaurulīšu-antimona telurīda/ oglekļa nanocaurulīšu-bismuta selenīda hibrīdstruktūru paraugi ar dažādu hibrīdstruktūru sadalījumu parauga tilpumā, kā arī tie tika iemaisīti vai iekapsulēti nevadoša polimēra matricā. Tika pētīta šo paraugu termoelektrisko īpašību (pretestības un Zēbeka koeficienta) atkarība no to liekuma rādiusa, un analizēti iegūtie rezultāti. Šāda tipa parau…

Mikrozaļumu ķīmiskais sastāvs atkarībā no fotoperioda audzēšanas laikā

2020

Literatūras apskatā ir aprakstīts augu ķīmiskais sastāvs un gaismas ietekme uz to. Apkopotas paraugu sagatavošanas un analīzes metodes. Darbā ir veikta četru dažādu ģiņšu mikrozaļumu diedzēšana pie 4, 8 un 12 stundu ilgiem fotoperiodiem. Spektrometriski ir noteikta kopējā hlorofila un karotenoīdu koncentrācija, kopējā polifenolu koncentrācija un antiradikālā aktivitāte augos. Noteica mikroelementu un makroelementu sastāvu augos ar ICP-MS metodi. Noteica brīvo aminoskābju koncentrāciju augos ar HPLC-MS metodi. Iegūtie dati salīdzināti savā starpā, kā arī tika salīdzināts ķīmiskais sastāvs atkarībā no fotoperioda.

Study of the electronic and atomic structure of thermally treated SrTiO3(110) surfaces

2003

The electronic structure of heated SrTiO3(110) surfaces was investigated with metastable impact electron spectroscopy and ultraviolet photoelectron spectroscopy (He(I). Scanning tunnelling microscopy and atomic force microscopy (AFM) were used to study the topology of the surface. The crystals were heated up to 1000 °C under reducing conditions in ultrahigh vacuum or under oxidizing conditions in synthetic air for 1 h, respectively. Under both conditions microfacetting of the surface is observed. The experimental results are compared with ab initio Hartree-Fock calculations, also presented here, carried out for both ideal and reconstructed SrTiO 3(110) surfaces. The results give direct evid…

Posterior cordotomy in bilateral vocal cord paralysis using monopolar microelectrodes and radiofrequency in 18 patient

2017

<title>Ion and electron trapping: release and relaxation processes in fluoride crystals</title>

2001

The thermally stimulated relaxation (TSR) processes in CaF2, BaF2 and LiBaF3 crystals (X-ray irradiated at LNT or RT) have been investigated by means of the ionic conductivity, thermally stimulated (TS) ionic depolarization current (TSDC), TS current (TSC), TS luminescence (TSL) and thermal bleaching techniques. The ionic TSDC measurements evidence that under DC field fluorides accumulate large ionic space-charge (thermoelectric state is formed) as a result of the migrating anion interstitial and/or vacancy capture on defects. In the ionic conductivity region (290 - 650 K) the thermoelectric state anneals, and several wide and overlapping anionic TSDC peaks are detected. The ionic TSDC stag…

Light-induced transmission nonlinearities in gallium selenide

1999

The intensity of a He–Ne laser (633 nm, 5 mW) transmitted by different GaSe samples is observed to change in correlation with a Nd-yttrium–aluminum–garnet laser pulse (532 nm, 7.8 ns, 3 mJ) which excites them. Such time response has been attributed to a nonlinear optical effect, i.e., a decrease in the refractive index due to the exciton screening by the photogenerated carriers. A calculation of the absorption coefficient and refractive index at different carrier concentrations has led to a reconstruction of transmittance transients which fully agree with the experimental data at different incident intensities and temperatures. Chantal.Ferrer@uv.es ; Jaqueline.Bouvier@uv.es ; Miguel.Andres@…

Absorption kinetics and swelling stresses in hydrothermally aged epoxies investigated by photoelastic image analysis

2015

Abstract The present work proposes an experimental optical methodology able to measure the transient swelling stresses induced by the water uptake ageing of polymers. In particular, the work describes the implementation of a Photoelastic technique to quantify internal stresses arising during the hydrothermal ageing of cast epoxy samples. The material investigated is a model DGEBA/DDS epoxy system. Curing and post-curing cycles have been optimised in order to obtain a fully cured, high T g , and completely stress free initial condition. Rectangular beam samples were then left in a hydrothermal bath at 90 °C, and regularly monitored by gravimetric and photoelastic analyses. The quantitative e…

Electronic structure of p-type ultraviolet-transparent conducting CuScO2 films

2008

Abstract We investigate the electronic structure of CuScO 2 thin films grown on sapphire and mica substrates by pulsed laser deposition. X-ray diffraction and microanalysis confirm that the films have the expected delafossite crystal structure and stoichiometric proportions. The electronic structure is investigated by means of X-ray and ultraviolet photoelectron spectroscopy. Electronic states in the range 0–1350 eV are identified, making reference to theoretical density-of-states calculations up to 80 eV. Photoelectron spectra near the Fermi energy confirm the p-character of the films. Optical absorption spectroscopy shows that the films are transparent up to 3.7 eV and exhibit an intense …

Pd–M/C (M = Pd, Cu, Pt) Electrocatalysts for Oxygen Reduction Reaction in Alkaline Medium: Correlating the Electronic Structure with Activity

2017

The increasing global needs for clean and renewable energy have fostered the design of new and highly efficient materials for fuel cells applications. In this work, Pd-M (M = Pd, Cu, Pt) and Pt nanoparticles were prepared by a green synthesis method. The carbon-supported nanoparticles were evaluated as electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium. A comprehensive electronic and structural characterization of these materials was achieved using X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Their electrochemical properties were investigated by cyclic voltammetry, while the…

Fabrication and characterization of vacuum deposited fluorescein thin films

2011

Simple vacuum evaporation technique for deposition of dyes on various solid surfaces has been developed. The method is compatible with conventional solvent-free nanofabrication processing enabling fabrication of nanoscale optoelectronic devices. Thin films of fluorescein were deposited on glass, fluorine-tin-oxide (FTO) coated glass with and without atomically layer deposited (ALD) nanocrystalline 20 nm thick anatase TiO2 coating. Surface topology, absorption and emission spectra of the films depends on their thickness and the material of supporting substrate. On a smooth glass surface the dye initially formes islands before merging into a uniform layer after 5 to 10 monolayers. On FTO cove…