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1.
TLS Detection in Liquid Chromatography, Flow Injection Analysis and Microfluidic Systems for Food Quality Control and Biomedical Diagnostics
Mladen Franko, 2023, predavanje na tuji univerzi

Opis: The basics of thermal lens spectrometry (TLS) and TLS microscopy (TLM) will be explained considering in particular the dependence of the thermal lens signal on the excitation power, thermo-optical properties of the sample, as well as sample flow and photostability of the analyte, with particular focus on the TLS enhancement factor, sensitivity and sample throughput of TLS and TLM measurements. Examples of applications will include most notable achievements of TLS and TLM measurements in liquid chromatography (detection of bilirubin and biliverdin in blood plasma, bilirubin in vascular endothelial cells), flow injection analysis (organophosphate insecticides and allergens in foodstuffs) and microfluidics (high throughput determination of Cr(VI), microcystin, HPV virus antibodies, and biomarkers of acute kidney injury). Before the concluding remarks, recent progress in multi-pass mode-mismatched TLS instrumentation and applications of incoherent light sources will be presented s part of the future outlook for TLS and TLM techniques.
Ključne besede: Spektrometrija TLS, TLM, chromatography, microfluidics, FIA
Objavljeno v RUNG: 14.11.2023; Ogledov: 989; Prenosov: 5
.pdf Celotno besedilo (21,62 MB)

2.
Effects of Photodegradation in TLS Measurements: Troubleshooting and Applications in Photochemistry and Photocatalysis
Mladen Franko, 2023, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)

Opis: Most analytical applications of thermal lens spectrometry (TLS) and related theoretical models consider absorbance of the sample constant during a single excitation by the pump laser beam. For photolabile analytes intensive excitation light can cause photodegradation, which significantly affects the results of TLS measurements. Theoretical models have been developed to account for changes in concentration and consequent changes in absorbance, caused by chemical reactions of different orders. Furthermore, abnormal TLS signal transients were observed for fast photochemical reactions on millisecond time scale, and the contributions of photodegradation as well as molecular diffusion were analyzed in detail. It has also been demonstrated that such effects can be reduced by performing TLS measurements in flowing systems such as in the case of flow injection analysis (FIA) or microfluidics. These findings were utilized to study the kinetics of chemical reactions, processes such as photostability of the soybean oil and thermal stability of biodiesel, or to improve the sensitivity of TLS detection in case of photolabile analytes. Furthermore, in combination with the concept of biomolecular recognition, FIA-TLS was exploited to study the efficiency of photocatalytic degradation of some neurotoxic substances such as organophosphate insecticides and revealed the formation of even more toxic degradation products. High sensitivity of TLS has enabled discrimination between photocatalytic and photosensitization mechanisms in photocatalytic degradation of textile dyes as well as between photodegradation and photocatalysis as will be demonstrated by the results of latest research in this field.
Ključne besede: Spektrometrija TLS, fotolabilnost, CrIVI), fotokataliza, fotorazgradnja
Objavljeno v RUNG: 23.10.2023; Ogledov: 1667; Prenosov: 0
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3.
Recent Progress and Applications of Thermal Lens Spectrometry and Photothermal Beam Deflection Techniques in Chemical Analysis and Materials' Characterization
Mladen Franko, 2023, predavanje na tuji univerzi

Opis: Initially the theoretical background relevant to recent developments of thermal lens spectrometry (TLS) which include TLS detection in liquid chromatography and in microfluidic flow injection analysis (μFIA) and to non-contact and non-destructive characterization of composite materials by beam deflection spectrometry (BDS) is presented. The advantages and basic characteristics of the TLS and BDS techniques are illustrated by presenting applications such as the determination of free bilirubin in endothelial cells by HPLC-TLS, studies of diffusion in Taylor-type microfluidic flows by thermal lens microscopy (TLM), μFIA-TLM detection of microcystin-LR and Cr(VI) in waters, and by the dept profiling of multi-layered coatings of orthopaedic implants. In the main part of the presentation the results of joint MU-UNG research are presented with emphasis on BDS and TLS characterisation of biocomposite materials from cellulose and chitosan or keratin with added Ag nanoparticles, sporopollenin capsules or antibiotics. The focus is on BDS determination of thermal parameters including thermal diffusivity and related properties relevant for medical applications, such as porosity and surface roughness, as well as on the TLS detection of Ag and other nanoparticles applied in studies of nanoparticle leaching from biocomposites.
Ključne besede: Optotermična spektrometrija, TLS, BDS, kemijska analiza, karakterizacija materialov, biokompoziti
Objavljeno v RUNG: 23.10.2023; Ogledov: 935; Prenosov: 2
.pdf Celotno besedilo (25,02 MB)

4.
Recent progress and applications of thermal lens spectrometry in environmental and bio-medical sensing
Mladen Franko, 2023, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)

Opis: Applications of TLS in environmental and bio-medical sensing, which include determination of iron species and ammonia by TLS and comparison to their microfluidic TLM detection are presented. Advantages of microfluidic FIA-TLM in terms of sensitivity and high sample throughput for determination of microcystin, Cr(VI) and HPV virus are discussed.
Ključne besede: Optotermična spektrometrija TLS, biomedicinska diagnostika, monitoring okolja
Objavljeno v RUNG: 19.10.2023; Ogledov: 1116; Prenosov: 4
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5.
Trajnostni biokompozitni materiali iz naravnih polimerov in njihova neporušna karakterizacija z optotermičnimi tehnikami
Mladen Franko, druga izvedena dela

Opis: Predstavljene so osnove zelene sinteze novih biokompozitnih materialov iz kombinacij celuloze s hitosanom ali keratinom in sporopoleninom ter njihove protimikrobne lastnosti in adsorpcijske sposobnosti za čiščenje vode. Pomembna lastnost biokompozitov z vidika njihove uporabnosti je tudi poroznost, ki jo lahko določamo neporušno in nekontaktno s tehniko optotermičnega odlkona. Ta omogoča določevanje toplotne difuzivnosti materialov ter preko nje poroznosti, kot tudi globinske porazdelitve v material vgrajenih snovi, ki izboljšujejo njegove lastnosti.
Ključne besede: Biokompoziti, celuloza, hitosan, keratin sporopolenin, toplotna difuzivnost, poroznost, optotermična spektrometrija
Objavljeno v RUNG: 11.05.2023; Ogledov: 1729; Prenosov: 0
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6.
Določevanje železa v naravnih vodah s tehniko FIA-TLS
Gaja Tomsič, 2019, magistrsko delo

Opis: Vodni organizmi potrebujejo železo za bistvene metabolne procese. Vendar pa se večina raztopljenega železa v vodi, ki ni vezana na organske molekule ali kompleksirana z anorganskimi ligandi, oksidira v železove ione Fe(III) in tvori oborino Fe(OH)3. Zato je aktivnost biomase na vodni gladini pogosto omejena z razpoložljivostjo raztopljenega železa, ki je lahko nižja od 1 nM. To dejstvo lahko vpliva tudi na širše okolje, saj ima vpliv na hitrost fiksiranja CO2 zaradi fotosinteze avtotrofne biomase. Določanje elementov v sledovih, med katerimi je tudi železo, predstavlja zaradi kompleksnosti naravne vode izziv. Določitev koncentracije železa je v preteklosti zahtevala predhodno koncentracijo vzorca z ekstrakcijo s topilom. V tem delu poročamo o rezultatih spektrometrije s toplotnimi lečami s pretočno injekcijsko analizo, ki ne potrebuje predkoncentracije železa v vzorcu. Koncentracije železa v različnih redoks oblikah smo določali s pretočno injekcijsko analizo (FIA) z uporabo 1,10 - fenantrolina, ki kompleksira železove Fe(II) ione v stabilen kompleks z absorpcijskim maksimumom pri 508 nm. Skupno količino raztopljenega železa (Fe(II) in Fe(III)) smo določili po redukciji Fe(III) iona v Fe(II) z askorbinsko kislino. V sistemu FIA smo za detekcijo uporabili spektrometer s toplotnimi lečami (TLS); tipalni žarek je imel valovno dolžino 633 nm, vzbujevalni pa 450 nm ali 530 nm. Posledica absorpcije svetlobe vzbujevalnega žarka je segrevanje vzorca zaradi neradiacijske relaksacije absorbirane energije. Tvori se toplotna leča (TL). Detekcija temelji na razprševanju tipalnega žarka na TL. Analize vzorcev smo izvajali v »šaržnem« in »on-line« načinu. Z »on-line« konfiguracijo (1,10 - fenantrolin je sestavljal nosilno raztopino za FIA) smo lahko injicirali vzorce brez kakršnekoli predhodne priprave ali dodajanja reagentov, razen askorbinske kisline pri določevanju skupnega železa. V tem magistrskem delu smo primerjali spodnje meje detekcije (LOD) različnih tehnik in pogojev (valovne dolžine laserske svetlobe in koncentracija nosilne raztopine v pretočnem sistemu) s ciljem, da bi dosegli najboljšo občutljivost za železove ione. FIA-TLS je primerna tudi za tehniko standardnega dodatka. Uporabnost in pravilnost FIA-TLS smo preverili z določevanjem koncentracij železa v rečni vodi.
Ključne besede: železove zvrsti, pretočna injekcijska analiza (FIA), spektrometrija s toplotnimi lečami (TLS)
Objavljeno v RUNG: 19.02.2019; Ogledov: 5254; Prenosov: 141
.pdf Celotno besedilo (2,30 MB)

7.
Hemichrome Determination by Thermal Lensing with Polyethylene Glycols for Signal Enhancement in Aqueous Solutions
Viktoriya Galimova, Mladen Franko, Mikhail Proskurnin, Mingqiang Liu, 2018, izvirni znanstveni članek

Opis: 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.
Ključne besede: Hemoglobin, hemikrom, optotermična spektroskopija, etilenglikol, spektrometrija s toplotnimi lečami
Objavljeno v RUNG: 16.04.2018; Ogledov: 4428; Prenosov: 0
Gradivo ima več datotek! Več...

8.
Priprava in izvedba preizkušanja v okviru razvoja novega drsnega obroča : Diplomsko delo
Simon Majnik, 2018, diplomsko delo

Opis: Razvoj na področju avtomobilske industrije in transporta je v zadnjem desetletju usmerjen predvsem v zamenjavo pogonskega agregata, torej motorja z notranjim izgorevanjem, z okolju prijaznejšimi elektromotorji. Uporaba elektrike kot vira energije pa zahteva ustrezne rešitve prenosa elektrike, za kar skrbijo drsni obroči. Tudi drsni obroči morajo za ustrezno opravljanje svoje funkcije prenosa elektrike med gibanjem izpolnjevati materialne, trdnostne in funkcionalne zahteve. Vsebina diplomske naloge je tako vezana na opis delovanja drsnih obročev in preučitev zahtev kupca o potrebnih lastnostih na novo razvitega drsnega obroča za pogon električnega osebnega avtomobila. Na podlagi teh zahtev je potrebno nato definirati in izvesti preizkuse lastnosti, s katerimi zagotovimo izpolnjevanje zahtev izdelka. Namen diplomskega dela je bil predstaviti teoretične osnove delovanja in izvedb drsnih obročev, opisati preizkuse lastnosti in funkcionalnosti drsnih obročev ter predstaviti rezultate preizkušanja na novo razvitega drsnega obroča vključno z alternativno tehnologijo tesnjenja kontaktne žice. V diplomskem delu so tako predstavljeni rezultati preizkusov tesnosti žice z uporabo različnih materialov žice in s primerjavo različnih tehnologij tesnjenja žice ter rezultati preizkušanja tesnosti po izpostavljenosti agresivnim medijem. V drugem delu so prestavljeni rezultati preizkušanja zvarov na zvarjencih, ki so sestavni del drsnega obroča, z uporabo dveh različnih testnih metod. Rezultati diplomskega dela kažejo, da je nova tehnologija izdelave tesnil iz tesnilne mase primerna za uporabo v primeru drsnih obročev, medtem ko na mestu zvara električnih kontaktov najboljšo trdnost, določeno z dvema različnima testnima metodama, dosežemo z uporabo spajkalne paste in časa varilnega pulza 125 ms.
Ključne besede: Drsni obroč, električni kontakti, test tesnosti, masna spektrometrija, uporovno varjenje, o-tesnilo, x-tesnilo
Objavljeno v RUNG: 26.02.2018; Ogledov: 4831; Prenosov: 258
.pdf Celotno besedilo (2,00 MB)

9.
10.
Applications of Thermal Lens Microscopy in Microfluidic Systems
Mladen Franko, 2016, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje)

Opis: Detection in microfluidic systems requires highly sensitive analytical methods, because of the very short optical interaction length, which is usually in the range of 100 μm or shorter. Furthermore, the amounts of analytes in detection volumes are extremely small (femto- or attomoles). Thermal lens spectrometry and particularly thermal lens microscopy (TLM) appear as techniques of choice for detection in microfluidic and lab-on-a-chip systems, since they enable measurements of absorbance’s or absorbance changes as low as 10-7. In addition to ultra-high sensitivity, TLM offers high spatial resolution (≈1 μm) and sufficient temporal resolution (ms range), which is required for studies of processes in microfluidic systems. Recent development of TLM theory and instrumentation lead to experimental confirmations of the effects of microfluidic flows on the TLM signal, which affects the sensitivity. On the other hand, these observations have enabled optimization of TLM instruments [1]. As a result of these advancements, applications of TLM were extended from simple laminar flows [2], to highly complex systems such as Tylor-type flows, where TLM detection provided data for description of diffusion processes in n-octane/methanol binary liquid systems [3]. The major streamline of TLM applications was however focused on the development of vanguard analytical systems [4], which are needed in various fields of chemical analysis, including food safety and quality control, environmental monitoring as well as biomedical research and diagnostics. Such systems are used as sample screening systems (sample filters or selectors) when the information is needed quickly to make immediate decisions in relation to the analytical problem. They provide simplicity (e.g. little or no sample pre-treatment), low cost, rapid and reliable response, and frequently give just binary responses. However, their major weakness is low metrological quality of results. Therefore, uncertainties of up to 5–15% are usually accepted as a toll for rapidity and simplicity, which are essential even though in contradiction with conventional analytical concepts. With the objective of developing new vanguard analytical systems, a relevant goal is to exploit the advantages offered by microfluidic lab-on-a-chip systems on one hand, and TLM detection on the other. In such combinations, the FIA approach simplifies sample handling (e.g. volume measurements) and transport to the detector, while microfluidic lab-on-a-chip technology can facilitate and speed up processes including colorimetric reactions, antigen–antibody or enzyme–substrate interactions in bioanalytical systems, and even extraction and preconcentration steps by introducing continuous flow processing and micro unit operations in chemical analysis [2]. High sensitivity of TLM in such systems offers low limits of detection, which also contribute to low uncertainties that are typically below 10%. An important advantage of microfluidic systems lies in the fact that small dimensions of such systems, which consist of capillaries and micro reactors with dimensions about 10 to 100 μm, significantly reduce the molecular diffusion time, which is inversely proportional to the second power of distance. For example, the time required for completion of an ELISA immunoassay for NGAL a biomarker of acute kidney failure was reduced from four hours to only 30 mins. [5, 6] when transferring the assay into a microfluidic system, while maintaining or even improving the sensitivity. Even more evident improvement in sample throughput (reduction of analysis time from 10 hours to 30 minutes) was achieved for determination of antibodies for human papilloma virus (anti L1 HPV 16) in blood plasma, after immobilizing adequate pseudovirions as antigens on magnetic nanobeads [6]. Other health-related applications include detection of toxins, such as microcystin, or carcinogenic substances such as Cr(VI), which offers improved limits of detection as compared to spectrophotometry as well as sample throughput, which can reach 20 samples/min. [7]. [1] M. Liu and M. Franko, Crit. Rev. Anal. Chem. 44, 328-353 (2014). [2] T. Kitamori, M. Tokeshi, A. Hibara, and K. Sato, Anal. Chem. 76, 52A-60A (2004). [3] M. Lubej, U. Novak, M. Liu, M. Martelanc, M. Franko and I. Plazl, Lab Chip (2015) DOI:10.1039/c4lc01460j. [4] M. Valcárcel and B. Lendl. Trends Anal. Chem. 23, 527-534 (2004). [5] T. Radovanović, M. Liu, P. Likar, M. Klemenc and M. Franko, Int. J. Thermophys. (2014) DOI:10.1007/s10765-014-1699-9. [6] T. Radovanović, Dissertation, University of Nova Gorica (2016). [7] M. Franko, M. Liu, A. Boškin, A. Delneri, and M.A. Proskurnin, Anal. Sci. 32, 23-30 (2016).
Ključne besede: Spektrometrija TLM, mikrofluidni sistemi, biomarkerji, alergeni, pesticidi, acetilholinesteraza
Objavljeno v RUNG: 07.11.2016; Ogledov: 5921; Prenosov: 42
.pdf Celotno besedilo (42,25 MB)

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