14 research outputs found

    Promocijas darbs

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    Promocijas darbā pētītas augsnes virskārtas morfoloģiskās īpašības (atbilstoši EHFRB humusa formu klasifikācijai), organisko vielu saturs, padziļināti pētīts augsnes humusvielu sastāvs un ķīmiskās īpašības. Pētījuma rezultāti liecina, ka sausieņu mežos Latvijā organiskajām vielām relatīvi bagātu augšņu (mull humusa formas) telpisko izplatību nosaka glacigēnie un glaciolimniskie nogulumi. Lauksaimniecības zemju apmežošanās procesā organisko vielu uzkrāšanās augsnes virskārtā sākas 30 gadus pēc apmežošanās, augstākā C krāja ir 60 līdz 100 gadus vecu meža zemju augsnēs. Palielināts koku nobiru īpatsvars meža attīstības gaitā augsnē veicina fulvoskābju īpatsvara pieaugumu, kā arī augsnes humīnskābju humifikācijas, aromatizācijas pakāpes un molekulmasas pieaugumu. Atslēgas vārdi: augsne, humusa forma, apmežošanās, organiskais ogleklis, humusvielasThe doctoral thesis presents a research on the topsoil, its morphological properties (according to the EHFRB humus form classification), and organic matter, focusing on the composition and the chemical properties of the soil humic substances. The results indicate that in forests formed on dry mineral soils in Latvia the spatial distribution of soils which are relatively rich in organic matter (mull humus form) is related to glacigenic and glaciolimnic deposits. The afforestation of agricultural lands leads to the accumulation of organic matter in the topsoil which starts 30 years after the establishment of the forest. The highest organic carbon stock can be observed in 60- to 100-year-old forest land soils. An increased amount of woody debris in the process of forest growth produces an increase in the proportion of fulvic acid, humification rate, aromaticity and molecule weight of the soil humic acids. Key words: soil, humus forms, afforestation, organic carbon, humic substancesDarba izstrādāšanai saņemts Eiropas Sociālā fonda projekta “Atbalsts doktora studijām Latvijas Universitātē” Nr. 2009/0138/1DP/1.1.2.1.2/09/IPIA/ VIAA/004 finansiāls atbalsts. Promocijas darbs izstrādāts arī ar ES Sociālā fonda un Latvijas Universitātes snieguma finansējuma projekta “Klimata pārmaiņas un dabas resursu ilgtspējīga izmantošana” (ZD2016/AZ03) finansiālu atbalstu

    Polifunkcionālo kvaternizēto piridina atvasinājumu sintēze un īpašības

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    Advisor: Duburs, Gunārs ; Tirzītis, GunārsLai izveidotu potenciālus gēnu transfekcijas aģentus, kas molekulā vienlaicīgi saturētu vairākas farmakoforas grupas, bija paredzēts mērķtiecīgi sintezēt polifunkcionālus 4-(N-alkilpiridil)-l,4-DHP atvasinājumus, veikt to ķīmisko, fizikoķīmisko un bioloģisko īpašību pārbaudi. Darba pirmajā nodaļā apskatītas šādu savienojumu iegūšanas likumsakarības, kvaternizējot piridilaizvietotāju pie 1,4-DHP cikla. Otrajā nodaļā dots dažu iegūto savienojumu ķīmisko īpašību raksturojums (piridīnija ilīdu veidošanās, ciklopievienošanās reakcijas, oksidēšana). Trešajā nodaļā aplūkotas iegūto savienojumu un dažu fizioloģiski aktīvu 1,4-DHP atvasinājumu bioloģiskās īpašības (inkorporācija dabīgās un modeļmembrānās, gēnu transfekcijas aktivitāte, citotoksicitāte). ABSTRACT: To generate potential gene transfection aģents that could simultaneouslv contain several pharmacophore groups in their molecule the svnthesis of polvfunctional 4-(Nalkylpyridyl)- 1,4-DHP derivatives was carried out. The studies of their chemical, phvsicochemical and biological properties were carried out as well. In the first chapter of the present work the regularities of the svnthesis of such compounds by quaternizing the pyridylsubstituent at the 1,4-DHP cycle are rewiewed. In the second chapter the characterization of the chemical properties (the formation of pyridinium ylides, cycloaddition reactions, oxidation) of some of the synthesized compounds is given. The third chapter is devoted to the biological properties (incorporation into the modei and native membranes, the activity of gene delivery, cytotoxicity) of the synthesized compounds and some physiologically active 1,4-DHP derivatives

    Promocijas darbs

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    Darbā ir izveidota analītiskā pieeja polifenolu savienojumu kvalitatīvai un kvantitatīvai analīzei alkšņu mizās un kviešu salmos. Izmantojot hromatogrāfiskās un spektrofotometriskās metodes veikta diarilheptanoīdu un flavonoīdu-lignīna kompleksu identifikācija un puskvantitatīva noteikšana, dominējošo savienojumu (oregonīna, tricīna-lignīna oligomēru) kvantificēšana. Orientējoties uz bioloģisko aktivitāti veikta attīrīšana, iegūstot tos ar augstu hromatogrāfisko tīrību (≥ 90%, LC-MS). Tie raksturoti kā laboratorijas references materiāli. Kviešu salmu ekstraktu bioloģiskā aktivitāte raksturota ar antioksidanto aktivitāti, bet oregonīnam pierādīta inovatīva labvēlīga ietekme uz reproduktīvo sistēmu. POLIFENOLI, DIARILHEPTANOĪDI, TRICĪNA-LIGNĪNI, IDENTIFIKĀCIJA, KVANTIFICĒŠANA, BIOLOĢISKĀ AKTIVITĀTE, MIZAS, SALMI.An analytical approach for the qualitative and quantitative analysis of polyphenols in alder bark and wheat straw was developed. The chromatographic and spectrophotometric methods were applied for identification and semi quantification of diarylheptanoids and flavonoid-lignins and for quantification of dominant compounds (oregonin, tricin-lignin oligomers). Biological activity guided purification of them was performed, they were obtained with high chromatographic purity (≥ 90%, LC-MS). They were characterized as laboratory reference materials. The biological activity of wheat straw extracts was characterized by antioxidant activity and an innovative beneficial effect of purified oregonin on the reproductive system was demonstrated. POLYPHENOLS, DIARYLHEPTANOIDS, TRICIN-LIGNINS, IDENTIFICATION, QUANTIFICATION BIOLOGICAL ACTIVITY, BARK, STRAW

    Kinetics and mechanism of sodium (Z)-3-(5-chloro-2-((5-chloro-3-(3-sulfonatopropyl) benzothiazol-2(3H)-ylidene)methyl)benzo- thiazol-3-ium-3-yl)propane-1-sulfonate adsorption on gold nanoparticle colloids of different properties and size

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    Primenom više eksperimentalnih metoda (TEM, UV-Vis spektrofotometrija, fluorescentna spektroskopija, FTIR, DLS, merenja zeta potencijala) ispitane su nanočestice zlata različitih svojstava i veličina sa adsorbovanim boratnim (C6 i C9,5) i citratnim (C17 i C30) jonima na površini, u odsustvu i prisustvu TC boje (natrijum-(Z)-3- (5-hlor-2-((5-hlor-3-(3-sulfonatopropil)benzotiazol-2(3H)-iliden)metil)benzotiazol-3- ium-3-il)propan-1-sulfonata) u vodenoj sredini, i potvrđena je adsorpcija TC na površini ovih nanočestica. Merenje fluorescencije agregata čestica-boja, korigovane za efekat unutrašnjeg filtera, je ukazalo da nanočestice zlata, u zavisnosti od koncentracije, gase fluorescenciju TC boje. Nađeno je da je ovaj proces kvantitativno povezan sa stepenom pokrivenosti površine nanočestica zlata molekulima TC boje. Pritom je efikasnost gašenja rasla sa povećanjem veličine čestica, pri čemu je koncentracija nanočestica zlata u rastvoru održavana konstantnom. Uz pretpostavku da je maksimalno gašenje fluorescencije TC boje ograničeno na potpunu monoslojnu pokrivenost površine nanočestica TC bojom (zavisno od orijentacije boje), eksperimentalno dobijene vrednosti koncentracije nanočestica C17 i C30 potrebne za potpuno gašenje fluorescencije TC boje su bile niže od teorijski izračunatih, dok su za gašenje fluorecencije TC boje pri konstantnoj koncentraciji nanočestica dobijene više eksperimentalne vrednosti u poređenju sa teorijski izračunatim, iz čega je zaključeno da je najverovatnija orijentacija molekula TC boje na površini ovih nanočestica kosa. S druge strane, u slučaju nanočestica C6 i C9,5 teorijski dobijene vrednosti za koncentraciju TC boje potrebnu da pokrije površinu nanočestice i da fluorescencija boje bude potpuno ugašena, u slučaju sve tri orijentacije, su niže u poređenju sa dobijenim eksperimentalnim vrednostima. Koncentracija nanočestica C9,5, potrebna da bi došlo do potpunog gašenja fluorescencije TC boje, po vrednosti najpribližnije odgovara vertikalnoj orijentaciji boje duž kraće strane, dok je u slučaju C6 eksperimentalno dobijen rezultat dosta niži od teorijski izračunatih vrednosti za sve tri moguće orijentacije boje, iz čega je zaključeno da je na površini ovih nanočestica boja smeštena u više od jednog sloja. Iz eksperimenata u kojima je ispitivano gašenja fluorescencije, izračunate su i konstante ravnoteže za proces adsorpcije TC na površini svih ispitivanih nanočestica...The borate (C6 and C9,5) and citrate (C17 and C30) capped gold nanoparticles of different average core sizes and properties, were characterized by transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and zeta potential measurements, in the absence and presence of cyanine dye, sodium (Z)-3-(5-chloro-2-((5-chloro-3-(3-sulfonatopropyl) benzothiazol-2(3H)- ylidene)methyl)benzothiazol-3-ium-3-yl)propane-1-sulfonate (TC) in water conditions, and the obtained results confirmed that TC was adsorbed on the surface of these nanoparticles. The measurements of fluorescence of the particle–dye assembly, corrected for inner filter effects, clearly indicated that the fluorescence of TC was quenched by gold nanoparticles on the concentration dependent manner. This process was found to be quantitatively related to the surface coverage of the Au nanoparticle by TC dye molecules. Significant increase of quenching efficiency was noticed when nanoparticle size increased, keeping the concentration of nanoparticles of different size constant. The experimental results of fluorescence quenching were compared with those obtained by theoretical calculations, in which we assumed that the maximum quenching of TC dye fluorescence was restricted to full monolayer coverage of TC on the nanoparticle surface. In case of C17 and C30 nanoparticles, the experimentally obtained values for nanoparticle concentration needed to completely quench TC dye fluorescence were lower than the calculated ones, while higher experimental values in comparision with calculated ones of quenched TC dye at constant nanoparticle concentration were obtained. These findings leaded to the conclusion that the most probable orientation of TC dye molecules on the surface of these nanoparticle was slanted. On the other hand, in case of C6 and C9,5 nanoparticles, the obtained calculated values for TC concentration needed to cover the nanoparticle surface and be completely quenched, for all three possible orientations of TC dye, were lower in comparision with the experimental values. The experimentally obtained value of C9,5 concentration needed to completely quench TC dye fluorescence most closely corresponds to vertical TC dye orientation along the short side, while the experimentally obtained results in case of C6 nanoparticles were much lower than theoretically calculated values for all three possible TC dye orientations. These findings indicated that on the surface of C6 nanoparticles the dye was accommodated in more than one layer. In addition, from the fluorescence quenching experiments, the equilibrium constants for the sorption of TC on the surface of all mentioned nanoparticles were calculated..

    Latvijas Vēstures Institūta Žurnāls. 2018, Nr. 2 (107) 

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    Žurnāls sagatavots LU Akadēmiskās attīstības projekta “Zinātniskā periodiskā izdevuma “Latvijas Vēstures Institūta Žurnāls” sagatavošana un izdošana 2018. gadā” (vad. Guntis Zemītis) ietvaro

    Latvijas Universitātes 2010.gada publiskais pārskats

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    Pārskatā ir dota pamatinformācija par Latvijas Universitāti un zinātniskās darbības pārskats. Pārskata sagatavošanā izmantoti dati no LU fakultāšu, zinātnisko institūtu, studiju centru un LU aģentūru iesniegtajiem pārskatiem, LUIS, kā arī LU administratīvo un akadēmisko struktūrvienību sagatavotie materiāli
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