Search results for " glasses"
showing 10 items of 45 documents
Dynamic Phase Diagram of the REM
2019
International audience; By studying the two-time overlap correlation function, we give a comprehensive analysis of the phase diagram of the Random Hopping Dynamics of the Random Energy Model (REM) on time-scales that are exponential in the volume. These results are derived from the convergence properties of the clock process associated to the dynamics and fine properties of the simple random walk in the $n$-dimensional discrete cube.
Structural modifications induced by electron irradiation in SiO2 glass: Local densification measurements
2009
We report a study on the structural modifications induced in amorphous silicon dioxide (a-SiO2) by electron irradiation in the dose range from 1.2?103 to 5?106?kGy. This study has been performed by investigating the properties of the 29Si hyperfine structure of the E '? center by electron paramagnetic resonance (EPR) spectroscopy. Our data suggest that the structural modifications induced by irradiation take place through the nucleation of confined high-defective and densified regions statistically dispersed into the whole volume of the material. In addition, we have estimated that in the high dose limit (D?105?kGy) the degree of densification associated to the local (within the defective r…
Tecnologie e valori dello sguardo. Occhiali e discorsività
2021
What is that very special object in our daily lives that is a pair of spectacles all about? It accompanies us faithfully through every moment of the day, it crouches beside us when we do without, or it is stowed away in a bag, momentarily resting on a shelf. But it is always ready to come back and ride our noses and ears in order to perform its inalienable function to the best of its ability. Function? A notion as pernicious as it is indispensable when dealing with a sure design product such as spectacles. An unfortunate, polysemic, inflated term, problematised in a thousand ways; an intrusive and unwelcome guest, with whom one never ends up coming to terms. One sends him away and finds him…
Several Derivatives of 6-(Tert-Butyl)-4H-Pyran-4-Ylidene Malononitrile with Different Amorphous Phase Promoting Substituents for Light-Amplification …
2019
A series of glassy 6-(tert-butyl)-4H-pyran-4-ylidene malononitrile (DCM) derivatives with covalently attached amorphous state promoting bulky 1,1,1-triphenylmethyl (trityl) moieties through several chemical design approaches have been synthesized and investigated for suitability in organic solid state laser applications. Results showed that the bonding type of such functional groups had a considerable influence on glass structure forming dye thermal properties and a slight influence on their optical properties. Thermal stability up to 346 °C was achieved with glass transitions in the range from 39 to 138 °C. Incorporation of bulky triphenyl substituents via ester groups showed remarkable am…
TL dose reconstruction in watch glasses exposed to photon, electron and proton beams
2010
XANES and EXAFS modelling of configurational disorder in silver borate glasses
2005
The sensitivity of X-ray absorption spectroscopy (XAS) to the local structure around a selected atomic species (symmetry, distances and angles) is commonly exploited to quantitatively describe systems where all the configurations around the absorbing atoms may be approximated by the mean one. However, in many cases of disordered systems a simple description of the local structure with singleconfiguration models cannot be reconciled with experimental spectra. In this paper the necessity to analyse the XAS spectra by considering a multiplicity of atomic structural configurations is demonstrated in the case of silver borate glasses. The local coordination around Ag cations in (Ag2O.nB2O3) glas…
An improved molecular design of obtaining NLO active molecular glasses using triphenyl moieties as amorphous phase formation enhancers
2012
New molecular design of obtaining molecular glasses has been developed by linking triphenylmethyl moieties to chromophore core by flexible C-C bridge. Compounds capable of forming stable amorphous phase with good optical quality have been acquired with increased chemical and thermal sustainability compared to the previously reported design. NLO activity of compounds has been measured after corona discharge polling. Compared to previously synthesized trityloxy fragment containing compounds increase of d 33 coefficient by up to 17 times was achieved for the same chromophore core containing compounds.
E. Leitz palielināmais stikls uz statīva
2020
Raksts par palielināmajiem stikliem, mikroskopiem un optisko instrumentu ražošanas uzņēmumu "Ernst Leitz Wetzlar", kura ražotais vienkāršais sadalīšanas mikroskops nr. 46 atrodas Latvijas Universitātes Muzeja Botānikas un mikoloģijas kolekciju krājumā.
Scanning Tunneling Spectroscope Use in Electrocatalysis Testing
2010
Published version of an article from the journal: Materials (1996-1944). Also available from publisher: http://dx.doi.org/10.3390/ma3063675 The relationship between the electrocatalytic properties of an electrode and its ability to transfer electrons between the electrode and a metallic tip in a scanning tunneling microscope (STM) is investigated. The alkaline oxygen evolution reaction (OER) was used as a test reaction with four different metallic glasses, Ni78Si8B14, Ni70Mo20Si5B5, Ni58Co20Si10B12, and Ni25Co50Si15B10, as electrodes. The electrocatalytic properties of the electrodes were determined. The electrode surfaces were then investigated with an STM. A clear relationship between the…
Properties of EO Active Molecular Glasses Based on Indandione and Azobenzene Chromophores
2012
Continuing previous research of EO active materials we have focused our attention on compounds employing two types of core nonlinear optical (NLO) chromophores – indandione and azobenzene . Coupling of them with bulky triphenyl, pentafluorophenylmethoxy ester, benzyloxy ester molecular fragments, as anti-crystallization agents allows us to obtain amorphous materials for potential NLO applications.