Search results for "crystals"

Upper tropospheric water vapour and its interaction with cirrus clouds as seen from IAGOS long-term routine in-situ observations

2017

IAGOS (In-service Aircraft for a Global Observing System) performs long-term routinein situobservations of atmospheric chemical composition (O3, CO, NOx, NOy, CO2, CH4), water vapour, aerosols, clouds, and temperature on a global scale by operating compact instruments on board of passenger aircraft. The unique characteristics of the IAGOS data set originate from the global scale sampling on air traffic routes with similar instrumentation such that the observations are truly comparable and well suited for atmospheric research on a statistical basis. Here, we present the analysis of 15 months of simultaneous observations of relative humidity with respect to ice (RHice) and ice crystal number …

Tropical tropopause ice clouds: a dynamic approach to the mystery of low crystal numbers

2012

Abstract. The occurrence of high, persistent ice supersaturation inside and outside cold cirrus in the tropical tropopause layer (TTL) remains an enigma that is intensely debated as the "ice supersaturation puzzle". However, it was recently confirmed that observed supersaturations are consistent with very low ice crystal concentrations, which is incompatible with the idea that homogeneous freezing is the major method of ice formation in the TTL. Thus, the tropical tropopause "ice supersaturation puzzle" has become an "ice nucleation puzzle". To explain the low ice crystal concentrations, a number of mainly heterogeneous freezing methods have been proposed. Here, we reproduce in situ measure…

Ion-Track Template Synthesis and Characterization of ZnSeO3 Nanocrystals

2022

A.I.P. thanks the Institute of Solid-State Physics, University of Latvia. ISSP UL as the Center of Excellence is supported through the Framework Program for European universities. The work was carried out within the framework of the grant AP05134367 of the Ministry Funding: The work was carried out within the framework of the grant AP05134367 of the Ministry of education and Science Science of of the Republic Republic of Kazakhstan.

Di- and Tricationic Organic Salts: an Overview of Their Properties and Applications

2014

During recent years growing interest has been devoted to the synthesis and applications of polycationic organic salts. Among them, di- and tricationic organic salts can be considered the natural evolution of monocationic ones. These last have given rise to the large class of ionic liquids. In the cases of di- and tricationic organic salts, the potential to change their structural features simply by varying the properties either of the charged heads or of the spacers separating them provides the opportunity to obtain materials suitable for different applications. This review article highlights recent progress in the study of the properties of di- and tricationic organic salts, as well as in …

Ionic liquid crystals based on 3-perfluoalkyl-1,2,4-triazol-4-ium salts

2016

Liquid-crystalline ionic liquids (LC-ILs) are a class of organic materials that of great current interest: they are defined as organic salts that possess the properties of two interesting kinds of material – ionic liquids (ILs) and liquid crystals (LCs). LC-ILs combine many interesting features of ILs (e.g. low volatility and the ability to dissolve solutes with a range of polarities) as well as many attractive properties of LCs (e.g. their intrinsic order and anisotropy). This provides unique opportunities that can be exploited in many different fields, for example their use as solvents for extraction processes as well as electrolytes for batteries, fuel cells, and dye-sensitised solar cel…

Oxadiazolyl-pyridinium based organic salts

2011

Etenzamīda kokristāli ar karbonskābēm: saderības ar palīgvielām noteikšana

2017

Darbā noteikta etenzamīda–fumārskābes un etenzamīda–4-hidroksibenzoskābes kokristālu saderība ar dažādām palīgvielām. Kokristālu saderība ar palīgvielām tika noteikta, izmantojot diferenciālās skenējošās kalorimetrijas, pulvera rentgendifraktometrijas un Furjē transformācijas infrasarkanās spektrometrijas analīzes metodes.

Time resolved confocal luminescence investigations on reverse proton exchange Nd : LiNbO3 channel waveguides

2009

In this work we report on the time and spatial resolved fluorescence of Neodymium ions in LiNbO(3) channel waveguides fabricated by Reverse Proton Exchange. The analysis of the fluorescence decay curves obtained with a sub-micrometric resolution has evidenced the presence of a relevant fluorescence quenching inside the channel waveguide. From the comparison between diffusion simulations and the spatial dependence of the (4)F(3/2) fluorescence decay rate we have concluded that the observed fluorescence quenching can be unequivocally related to the presence of H+ ions in the LiNbO(3) lattice. Nevertheless, it turns out that Reverse Proton Exchange guarantees a fluorescence quenching level sig…

Radiācijas defektu pētījumi ar EPR metodi LiBaF3 kristālā

2004

Izpētīts ar rentgenu istabas temperatūrā apstarotā L i B a F 3 kristālā radīta defekta EPR spektrs. EPR spektrs sastāv no apmēram 35 ekvidistantām līnijām. Defekts ir nestabils Jienas gaismā, bet tumsā sabrūk dažu stundu laikā. Šīs līnijas magnētiskā lauka orientācijā mralēli [111] kristāla asij atrodas vienādos attālumos (ar soli 0,9 mT) ar intensitāšu sadalījumu tuvu binomiālajam. EPR spektru var aprakstīt kā nesapārota spina S = 1/2 hiper- >īkstruktūras (liss) mijiedarbību ar divām ekvivalentu kaimiņu kodolu spinu grupām: 2 Li kodoliem pirmajā grupā un 8 F kodoliem otrajā grupā. Šāds modelis atbilst F-tipa centram elektrons atrodas fluora vakancē) LiBaF3 kristālā. Līniju intensitāšu stip…

Light harvesting with Ge quantum dots embedded in SiO2 and Si3N4

2014

Cataloged from PDF version of article. Germanium quantum dots (QDs) embedded in SiO2 or in Si3N4 have been studied for light harvesting purposes. SiGeO or SiGeN thin films, produced by plasma enhanced chemical vapor deposition, have been annealed up to 850 degrees C to induce Ge QD precipitation in Si based matrices. By varying the Ge content, the QD diameter can be tuned in the 3-9 nm range in the SiO2 matrix, or in the 1-2 nm range in the Si3N4 matrix, as measured by transmission electron microscopy. Thus, Si3N4 matrix hosts Ge QDs at higher density and more closely spaced than SiO2 matrix. Raman spectroscopy revealed a higher threshold for amorphous-to-crystalline transition for Ge QDs e…