Search results for "element"
showing 10 items of 13601 documents
H-He collision-induced satellite in the Lyman alpha profile of DBA white dwarf stars
2020
The spectra of helium-dominated white dwarf stars with hydrogen in their atmosphere present a distinctive broad feature centered around 1160~\AA\/ in the blue wing of the Lyman-$\alpha$ line. It is extremely apparent in WD 1425+540 recently observed with HST COS. With new theoretical line profiles based on ab initio atomic interaction potentials we show that this feature is a signature of a collision-induced satellite due to an asymptotically forbidden transition. This quasi-molecular spectral satellite is crucial to understanding the asymmetrical shape of Lyman-$\alpha$ seen in this and other white dwarf spectra. Our previous work predicting this absorption feature was limited by molecular…
Relief of microRNA-Mediated Translational Repression in Human Cells Subjected to Stress
2006
SummaryIn metazoans, most microRNAs imperfectly base-pair with the 3′ untranslated region (3′UTR) of target mRNAs and prevent protein accumulation by either repressing translation or inducing mRNA degradation. Examples of specific mRNAs undergoing microRNA-mediated repression are numerous, but whether the repression is a reversible process remains largely unknown. Here we show that cationic amino acid transporter 1 (CAT-1) mRNA and reporters bearing its 3′UTR can be relieved from the microRNA miR-122-induced inhibition in human hepatocarcinoma cells subjected to different stress conditions. The derepression of CAT-1 mRNA is accompanied by its release from cytoplasmic processing bodies and i…
Augsnes piesārņojuma ar smagajiem metāliskajiem elementiem izvērtējums dzelzceļa apkārtnē
2018
Augsnes piesārņojuma ar smagajiem metāliskajiem elementiem izvērtējums dzelzceļa apkārtnē. Jansons Ā., zinātniskais vadītājs Dr. chem., doc. Osīte A. Bakalaura darbs, 52 lappuses, 21 attēls, 7 tabulas, 25 literatūras avoti, 5 pielikumi. Latviešu valodā. Darba ietvaros ir veikta smago metālisko elementu – dzelzs, mangāna, vara, cinka, niķeļa un svina jonu kvantitatīvā analīze augsnes paraugos, kas ievākti Torņakalna, Jāņavārtu, Dārziņu un Kūdras dzelzceļa staciju apkārtnē – blakus stacijai (vilcienu bremzēšanas ceļa sākumā) un atstatus no tās. Vispirms tika veikta ievākto augsnes paraugu sagatavošana mineralizācijai (žāvēšana, homogenizēšana, sijāšana). Augsnes paraugu matricas sagraušana ti…
Lauksaimniecības augsnes ķīmiskā sastāva izvērtējums pēc dažādu mēslošanas līdzekļu iestrādes
2015
Darbā analizēti augsnes un zālaugu paraugi uz vieglo stabilo izotopu attiecību masspektrometriju, sadarbojoties ar Latvijas Valsts mežzinātnes institūtu „Silava”. Paraugi iegūti no Viduslatvijas, Skrīveriem. Augsnes paraugiem noteikts augsnes pH, cinks, mangāns, varš, svins, niķelis, kadmijs un kobalta saturs. Iegūtie rezultāti tika izvērtēti.
Metālisko elementu saturs augsnē Liepājas Ziemeļu Fortu teritorijā
2019
Metālisko elementu saturs augsnē Liepājas Ziemeļu fortu teritorijā. Butkus D., darba vadītāja Mg. chem., lektore Balcerbule Z. Bakalaura darbs, 45 lappuses, 21 attēls, 18 tabulas, 32 literatūras avoti, 4 pielikumi. Latviešu valodā. Darbā ir veikta metālisko elementu analīze Ziemeļu fortu teritorijā ņemtajos augsnes paraugos. Augsnes izvilkumi gatavoti HNO3 šķīdumos, veikta arī mineralizācija ar mikroviļņu enerģiju. Elementu koncentrācijas tika noteiktas ar liesmas atomabsorbciometrijas un ICP – MS metodēm. Iegūtie rezultāti tika salīdzināti ar LR MK augsnes un grunts kvalitātes normatīviem un literatūrā pieejamiem datiem.
Lāzerinducētās sagraušanas spektroskopijas un enerģijas dispersīvās rengenfluoriscences metožu pielietojums zāļu tēju paraugu pētījumos
2022
Lāzerinducētās sagraušanas spektroskopijas un enerģijas dispersīvās rengenfluoriscences metožu pielietojums zāļu tēju paraugu pētījumos. Černiševs R.., darba vadītāji Mg.chem. Bērtiņš M., Dr.sc.ing. Brangule A. Bakalaura darbs, 39 lappuses, 16 attēli, 13 tabulas, 28 literatūras avoti. Latviešu valodā. Darbā tika veikta zinātniskās literatūras izpēte un apkopojums par spektroskopijas metodēm, ko var izmantot ķīmisko elementu kvalitatīvo un kvantitatīvo noteikšanai. Praktiskajā daļā tika veikta zāļu tēju analīze izmantojot rentgenfluoriscences spektroskopiju un lāzerinducētās sagraušanas spektroskopijas metodēm.
Ab Initio Study on the Mechanism of the Reactions of the Nitrate Radical with Haloalkenes: 1,2-Dichloroethene, 1,1-Dichloroethene, Trichloroethene, …
2000
A general mechanism for the reactions of the NO3 radical with 1,2-dichloroethene, 1,1-dichloroethene, trichloroethene, and tetrachloroethene is proposed from ab initio DFT calculations. The calculated mechanism shows three main parallel reaction pathways. For the systems where the two carbon atoms are differently substituted, the study includes both the attacks with Markownikoff and contra-Markownikoff orientation. The first reaction pathway leads to the formation of an epoxide along with the NO2 radical, the second one to the formation of carbonyl compounds, and the third one leads, through the cleavage of the C−C bond, to the formation of carbonyl compounds with a lower number of carbon a…
Kurzweil-Henstock type integral on zero-dimensional group and some of its application
2008
A Kurzweil-Henstock type integral on a zero-dimensional abelian group is used to recover by generalized Fourier formulas the coefficients of the series with respect to the characters of such groups, in the compact case, and to obtain an inversion formula for multiplicative integral transforms, in the locally compact case.
Carbon and nitrogen stable isotope ratios of soils and grasses as indicators of soil characteristics and biological taxa
2019
Abstract The use of stable isotope techniques can assist in understanding interactions of plants with various abiotic and biotic processes. In the research, we focused on carbon (C) and nitrogen (N) isotopes because they are the most important resources influencing plant function and the biogeochemical cycles. The 13C/12C and 15N/14N ratios in plants and in soils and the relationships between these ratios and biological and environmental factors of widely distributed native C3 plants (couch grass, plantain and yarrow) collected from two sites in St. Petersburg, Russia were studied. The soil characteristics of the sites were rather different. This had a significant effect on the isotope rati…
Not So Much Societal: The Catholic Church in Poland as a Veto Player
2021
George Tsebelis distinguished two forms of veto players’ actions: institutional and partisan. In a democracy, the Church is not able to play either role because it is not an element of the state’s institutional structure. This was the source for Simon Fink’s proposal to look at the Church as a societal veto player (VP). The case of Poland shows, however, that such an approach becomes inadequate in numerous situations. The Church’s influence on political parties, and particularly the state’s institutions, may be exerted outside society. Performed on the basis of the existing literature and political debates conducted since 1989, the analysis of the social and political reality of Poland all…