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11.
DOLOČANJE ACETILHOLINESTERAZE V HUMANIH KRVNIH VZORCIH
Tjaša Birsa, 2018, master's thesis

Abstract: V strokovni literaturi zasledimo encim acetilholinesterazo (AChE) v različnih raziskavah s področja okoljevarstva, medicine in veterine. Zmanjšana encimska aktivnost je lahko indikator onesnaženosti okolja z organofosfatnimi in karbamatnimi pesticidi, policikličnimi aromatskimi ogljikovodiki ter težkimi kovinami. Spremembe v encimski aktivnosti AChE pa so tudi biološki označevalec nekaterih nevrodegenerativnih bolezni pri človeku. V človeškem telesu se encim AChE primarno nahaja v živčnem sistemu, najdemo pa ga tudi v krvi, zlasti v membranah eritrocitov. V krvi je v večji meri prisoten tudi encim butirilholinesteraza (BChE), ki ravno tako spada v družino holinesteraz. Naš cilj je bil razviti metodo, ki bi omogočala specifično merjenje encimske aktivnosti AChE v okviru celotnih holinesteraz v krvnem serumu. Za merjenje encimske aktivnosti smo uporabili Ellmanovo metodo. Količino obarvanih produktov reakcije smo določali s spektroskopijo s toplotnimi lečami TLS in z UV-VIS spektrofotometrijo. Z različnimi koncentracijami čistega encima AChE smo najprej določili mejo zaznavnosti obeh metod (LOD). Detekcija s TLS je bila bolj občutljiva, saj je bil LOD 3,13-krat manjši kot pri detekciji z UV-VIS. Potem smo izmerili encimsko aktivnost celotnih holinesteraz AChE in BChE v serumskih vzorcih zdravih ljudi. Izračunana encimska aktivnost holinesteraz se je v analiziranih vzorcih gibala med 3004 mU mL-1 in 5698 mU mL-1. Po dodatku specifičnega inhibitorja BChE se je celotna encimska aktivnost znižala za najmanj 60 %, kar kaže, da večina holinesteraz v krvnem serumu pripada BChE. Preizkusili smo tudi metodo enojne imunske precipitacije, vendar se je le-ta izkazala za neuspešno pri ločevanju posameznih holinesteraz iz serumskih vzorcev. Na podlagi naših rezultatov smo prišli do zaključka, da je za merjenje encimske aktivnosti posameznih holinesteraz AChE in BChE v krvnem serumu najprimernejša uporaba specifičnih inhibitorjev, vendar bi bilo to metodo potrebno še dodatno optimizirati.
Keywords: acetilholinesteraza, krvni serum, nevrodegenerativne bolezni, spektroskopija s toplotnimi lečami, UV-VIS spektrofotometrija, imunska precipitacija.
Published in RUNG: 07.11.2018; Views: 5923; Downloads: 174
.pdf Full text (1,65 MB)

12.
Kako lahko z različnimi vrstami svetlobo opazujemo očem nevidni svet okoli nas
Iztok Arčon, unpublished invited conference lecture

Abstract: Svetloba nam v vsakdanjem žvljenju omogoča, da vidimo in spoznavamo svet okoli nas. Kako zelo je svetloba pomembna za naše življenje opazimo še posebej, če se za nekaj časa znajdemo v popolni temi. In vendar predstavlja vidna svetloba, ki jo lahko zaznajo naše oči, le droben delček v širokem spektru razlčnih vrst svetlobe, ki nam jih ponuja narava. V predavanju si bomo ogledali, kako lahko s svetlobo različnih valovnih dolžin, od infrardeče, preko vidne, ultravijolične in rentgenske svetlobe, opazujemo očem nevidni svet okoli nas. Spomnili se bomo tudi nekaj velikih znastvenih odkritji o svetlobi v zadnjih dvesto letih. Ta osnovna odkritja o lastnostih svetlobe so nam odprla pogled neposredno v svet atomov in danes omogočajo razvoj sodobnih merskih tehnologij na atomski skali. Brez njih si skoraj ne znamo večpredstavljati razvoja novih tehnološko zanimivih materialov in različnih nanotehnologij in različnih raziskav onesnaženja okolja na atomskem nivoju.
Keywords: rentgesnka svetloba, UV, IR, slikanje, mikroskopiranje, rentgenska absorpcijska spektroskopija
Published in RUNG: 01.10.2018; Views: 3383; Downloads: 0
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13.
K-edge absorption spectra of isoelectronic gaseous hydrides: a combination of atomic and molecular channels
Robert Hauko, Jana Padežnik Gomilšek, Alojz Kodre, Iztok Arčon, Giuliana Aquilanti, 2018, published scientific conference contribution abstract

Abstract: The fine detail in the x-ray absorption spectra in the energy region of absorption edges provides the insight into the mechanism of inner-shell photoexcitation: in particular in spectra of free atoms or simple molecules, the simplest being gaseous hydrides [1-2]. Measured K edge absorption spectra of hydrides of 3p (PH3, H2S in HCl) and 4p (GeH4, AsH3, H2Se, HBr) elements, and published data of 2p hydrides (CH4, NH3, H2O, HF) as well as SiH4 [3-6] and the noble gases at the end of the isoelectronic series (Ne, Ar, Kr) are compared to the respective calculated spectra, obtained by atomic HF86, GRASP codes [7] and molecular DFT (Density functional theory) ORCA code [8]. For a clearer view of intraatomic processes, the weak and simple structural (XAFS) signal of the molecule is removed from the spectra. Among the spectral features below the continuum limit, those with the lowest energy belong to the transition of the core electron to the lowermost free orbitals with the molecular character. They are, as a rule, wider than the transitions to the higher orbitals with prevailing atomic character. The theoretical description with DFT code without specific adaptations is sufficient for a qualitative picture of the pre-edge structure. The fine structure immediately above the K edge stems from the coexcitation of valence electrons. We have proved that the coexcitations can be explained as a two-step process: the inner-shell photoeffect followed by the shake-up of a valence electron predominantly to a free atomic orbital. This process is markedly different from coexcitations of more tightly bound electrons [9]. In the collection of consecutive and homologous data, analyzed by a common procedure, the reaction channels can be identified with better precision and reliability than in analysis of individual spectra. Our analysis showed that the energies and probabilities of single-electron transitions into the molecular orbitals are strongly affected by the symmetry of the molecule, essentially in the same way in 3p and 4p homologues, but not in 2p homologues with a stronger influence of the core charge. In transitions to atomic orbitals the influence of the molecular field is negligible.
Keywords: hidridi, rentgenska spektroskopija, XAFS
Published in RUNG: 12.09.2018; Views: 3787; Downloads: 0
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14.
K-edge absorption spectra of gaseous hydrides
Alojz Kodre, Robert Hauko, Jana Padežnik Gomilšek, Iztok Arčon, Giuliana Aquilanti, 2018, published scientific conference contribution abstract

Abstract: X-ray absorption spectra in the energy region of absorption edges reveal fine details of the mechanism of inner-shell photoexcitation: in particular in spectra of free atoms or simple molecules, the simplest being gaseous hydrides [1-2]. In a collection of data from consecutive and homologous elements, analyzed by a common procedure, the reaction channels can be identified with better precision and reliability than in analysis of individual spectra. Absorption spectra of the hydrides of 3p elements (PH3, H2S in HCl) were measured at the XAFS beamline of the Elettra synchrotron in Trieste: a new type of adjustable absorption cell for measurement of noxious gases at room temperature and at low photon energies was developed for the purpose. For the analysis, data from an earlier experiment on 4p hydrides (GeH4, AsH3, H2Se, HBr), and published data of 2p hydrides (CH4, NH3, H2O, HF) [3-4] as well as SiH4 and the noble gases concluding the isoelectronic series (Ne, Ar, Kr) were adopted. The spectra are compared to respective calculated spectra, obtained by atomic HF86, GRASP codes and molecular DFT (Density functional theory) ORCA code [5]. Our analysis of the pre-edge structures showed that the energies and probabilities of singleelectron transitions into the lowermost orbitals with the molecular character were strongly affected by the symmetry of the molecule, essentially in the same way in 3p and 4p homologues, but not in 2p homologues with a stronger influence of the core charge. In transitions to higher orbitals with prevailing atomic character the influence of the molecular field is negligible. The fine structure immediately above the K edge stems from the coexcitation of valence electrons. These coexcitations can be explained as a two-step process: the inner-shell photoeffect followed by the shake-up of a valence electron predominantly to a free atomic orbital. The process is markedly different from coexcitations of more tightly bound electrons [3]. The results of relative shake-up probabilities can be compared to results of emission spectroscopies, the probabilities of double excitation to bound states show a correlation with the dissociation probability of the molecule.
Keywords: večelektronske vzbuditve, hidridi, rentgenska absorpcijska spektroskopija
Published in RUNG: 12.09.2018; Views: 4060; Downloads: 0
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15.
Določanje atomske strukture snovi z rentgensko absorpcijsko spektrometrijo s sinhrotronsko svetlobo
Iztok Arčon, invited lecture at foreign university

Abstract: Zakaj so velike evropske države pripravljene investirati ogromna sredstva v izgradnjo in delovanje sinhrotronov? Gre za izjemno svetle vire ultravijolične in rentgenske svetlobe, ki so v zadnjih dveh ali treh desetletjih postali nepogrešljivo orodje pri analizi snovi na atomskem oziroma molekularnem nivoju. Razvoja in sinteze novih materialov z želenimi lastnostmi si ne moremo predstavljati brez sodobnih preiskovalnih metod, ki temeljijo na sinhrotronski svetlobi. V predavanju bo predstavljen princip delovanja in primeri uporabe ene od rentgenskih metod s sinhrotronsko svetlobo – rentgensko absorpcijsko spektroskopijo, s katero lahko določamo atomsko oz. molekularno strukturo snovi v vseh agregatnih stanjih. Za take raziskave so danes zanimivi predvsem različni nanostrukturni materiali, kot so katalizatorji, katodni materiali za Li-ionske in Li-žveplove baterije, tanke zaščitne plasti, in drugi, pri katerih atomska struktura določa njihove funkcionalne lastnosti. Na predavanju bodo izpostavljeni v prvi vrsti primeri in-operando karakterizacije z metodama XANES in EXAFS ki omogoča zelo natančno in neposredno spremljanje postopnih sprememb valence kovinskih kationov in njihove lokalne atomske strukture v nanozrnih v katodnem materialu med polnjenjem in praznjenjem baterije, ali kovinskih kationov na površini nanostrukturnega (foto)katalitskega materiala med samo katalitsko reakcijo. Sodobni sinhrotronski viri rentgenske svetlobe pa omogočajo tudi uporabo kombinacije rentgenske absorpcijske spektroskopije z rentgenskimi mikroskopskimi metodami, z ločljivostjo do nekaj deset nanometrov. Na predavanju bodo predstavljeni primeri mikro-XANES in EXAFS analize lokalizacije in vezave toksičnih kovinskih kationov na sub-celičnem nivoju v različnih tkivih rastlin, s čimer lahko ključno prispevamo k razumevanju mehanizmov zajemanja, transporta, akumulacije in kompleksacije kovinskih kationov na sub-celičnem nivoju v različnih tkivih rastlin, ki te polutante (hiper)akumulirajo, in jih s tem prenašajo v prehranjevalno verigo, s čimer je ogroženo zdravje ljudi.
Keywords: rentgenska absorpcijska spektroskopija, XANES, EXAFS, strukturna analiza, sinhrotronska svetloba
Published in RUNG: 01.06.2018; Views: 4186; Downloads: 0
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16.
Hemichrome Determination by Thermal Lensing with Polyethylene Glycols for Signal Enhancement in Aqueous Solutions
Viktoriya Galimova, Mladen Franko, Mikhail Proskurnin, Mingqiang Liu, 2018, original scientific article

Abstract: The thermal lens technique is proposed for the determination of total hemoglobin in the form of reversible hemichrome. The conditions were optimized (concentration of sodium dodecyl sulfate, 2 mM) to attain the maximum sensitivity with the use of polyethylene glycols as signal enhancers. For polyethylene glycols with molecular weights 1500–35000 Da in a concentration range of 5–15% w/w (5–25 mM), the influence on thermal lens signal enhancement was estimated. It is shown that the use of 5% w/w polyethylene glycol 2000 provides the maximum increase in the thermal lens enhancement factor (by 40%) in comparison with unmodified aqueous solutions. The detection limit of iron(II) tris(1,10-phenanthrolinate) as a model system is 60 nM. Under these conditions, the thermal lens detection limit of hemichrome is 10 nM, which shows a 15-fold enhancement compared to spectro- photometry. Modification of the medium with polyethylene glycols decreases the limit of detection of hemichrome determination by 15% in comparison with unmodified aqueous solutions due to better reproducibility for the range of concentrations from 0.02 to 0.9 μM.
Keywords: Hemoglobin, hemikrom, optotermična spektroskopija, etilenglikol, spektrometrija s toplotnimi lečami
Published in RUNG: 16.04.2018; Views: 4027; Downloads: 0
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17.
Swift X-ray detection and VLT/FORS2 spectroscopy of the nuclear transient Gaia17cmd/AT2017har
Nada Ihanec, 2017, other component parts

Keywords: tranzienti, Gaia, Swift, spektroskopija
Published in RUNG: 31.01.2018; Views: 3520; Downloads: 0
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18.
Gaia Alert Spectroscopy with SPRAT at the Liverpool Telescope
Andreja Gomboc, Iain Steele, Robert S. Piascik, 2016, published scientific conference contribution abstract

Keywords: teleskopi, spektroskopija, satelit Gaia
Published in RUNG: 02.03.2017; Views: 4766; Downloads: 1
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19.
Extinction curves of GRB environment with the X-shooter
Andreja Gomboc, Jure Japelj, Stefano Covino, 2016, published scientific conference contribution

Keywords: izbruhi sevanja gama, spektroskopija, galaksije
Published in RUNG: 01.03.2017; Views: 3600; Downloads: 1
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20.
Spectroscopic Classification of MASTER OT J222817.90-145657.4 as a dwarf nova outburst
Andreja Gomboc, 2016, other component parts

Keywords: robotski teleskop, spektroskopija, astronomska opazovanja
Published in RUNG: 12.10.2016; Views: 3818; Downloads: 0
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