Search results for " atom"
showing 10 items of 1526 documents
Svina noteikšanas iespējas asinīs ar instrumentālajām analīzes metodēm, izmantojot dažādus paraugu sagatavošanas veidus
2017
Svina noteikšanas iespējas asinīs ar instrumentālajām analīzes metodēm, izmantojot dažādus paraugu sagatavošanas veidus. Ribkinska L., darba vadītājas Dr. med. Inese Mārtiņsone un Dr. Chem. Agnese Osīte. Maģistra darbs, 45 lappuses, 18 attēli, 12 tabulas, 45 literatūras avoti, 18 pielikumi. Latviešu valodā. Maģistra darbā ir apkopota literatūra par instrumentālajām analīzes metodēm (ETAAS un ICP-MS), paraugu sagatavošanas metodēm un svina toksisko iedarbību uz cilvēka veselību. Eksperimentālajā daļā veikta svina masas koncentrācijas noteikšana asinīs, izmantojot dažādus paraugu sagatavošanas veidus. Paraugu sagatavošanas metodēm veikta to salīdzināšana, kā arī rezultātu pareizības kontrolei…
The gas-phase chemiionization reaction between samarium and oxygen atoms: A theoretical study
2004
The Sm + O chemiionization reaction has been investigated theoretically using a method that allows for correlation and relativistic effects. Potential energy curves have been calculated for several electronic states of SmO and SmO+. Comparison with available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemiionization reaction Sm + O is proposed. The importance of spin–orbit coupling in the excited states of SmO, in allowing this chemiionization reaction to take place, has been revealed by these calculations. This paper shows the metal-plus-oxidant chemiionization reaction.
From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials
2014
In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters a…
4-(3H)-quinazolinones N-3 substituted with a five membered heterocycle: A promising scaffold towards bioactive molecules
2020
Abstract The quinazolinone nucleus represents, among the class of fused heterocycles, a very important scaffold to obtain molecules with biological activities. A review of literature revealed how such kind of fused heterocycles, coming from natural or synthetic source, are associated with a wide range of biological activities. This review is mainly directed towards the 4-(3H)-quinazolinones N-3 substituted with a five membered heterocycle in which all the possible combinations of nitrogen, sulfur and oxygen atoms are present.
Fast apparent oscillations of fundamental constants
2019
Precision spectroscopy of atoms and molecules allows one to search for and to put stringent limits on the variation of fundamental constants. These experiments are typically interpreted in terms of variations of the fine structure constant $\alpha$ and the electron to proton mass ratio $\mu=m_e/m_p$. Atomic spectroscopy is usually less sensitive to other fundamental constants, unless the hyperfine structure of atomic levels is studied. However, the number of possible dimensionless constants increases when we allow for fast variations of the constants, where "fast" is determined by the time scale of the response of the studied species or experimental apparatus used. In this case, the relevan…
<title>Scanning probe microscopy of nanocrystalline iridium oxide thin films</title>
2003
Structural investigations of nanocrystalline iridium oxide thin films, prepared by dc magnetron sputtering technique were performed by scanning probe microscopy (SPM). SPM studies, using both atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), indicate that the thin films are composed of grains with a size of about 20-50 nm. Fine crystallinity and small RMS microroughness of the films, being well below 2 nm, make iridium oxide thin films promising candidates for nanolithographic applications. The possibility to perform nanolithograhpic processes at a scale of less than 150 nm was successfully examined in AFM and STM modes.© (2003) COPYRIGHT SPIE--The International Societ…
Tunable Polarons in Bose-Einstein Condensates
2017
A toolbox for the quantum simulation of polarons in ultracold atoms is presented. Motivated by the impressive experimental advances in the area of ultracold atomic mixtures, we theoretically study the problem of ultracold atomic impurities immersed in a Bose-Einstein condensate mixture (BEC). The coupling between impurity and BEC gives rise to the formation of polarons whose mutual interaction can be effectively tuned using an external laser driving a quasi-resonant Raman transition between the BEC components. Our scheme allows one to change the effective interactions between polarons in different sites from attractive to zero. This is achieved by simply changing the intensity and the frequ…
Temperature and Isotopic Mass Dependence of the Direct Band Gap in Semiconductors: LCAO Calculations
2000
Novel bioactive bromopyrrole alkaloids from the Mediterranean sponge Axinella verrucosa
2005
The Mediterranean sponge Axinella verrucosa has been investigated for its alkaloid composition and has been found to produce a complex mixture of bromopyrrole alkaloids. Along with the previously isolated compounds 5-18, four novel alkaloids of this class, compounds 1-4, have been isolated, and their structures established through spectroscopic methods. Compounds 1-4 were found to display neuroprotective activity against the agonists serotonin and glutamate in vitro.