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91.
A multi-thermal-lens approach to evaluation of multi-pass probe beam configuration in thermal lens spectrometry
Humberto Cabrera, Leja Goljat, Dorota Korte, Ernesto Marin, Mladen Franko, izvirni znanstveni članek

Opis: In this work, a recently proposed thermal lens instrument based on multi-pass probe beam concept is investigated and described as a multi-thermal-lens equivalent system. A simulation of the photothermal lens signal formation in a multi-thermal-lens equivalent configuration of the system is performed and validated by comparing the experimental signals of single, dual and ten-pass configurations to theoretically calculated values. The theoretically predicted enhancement of the signal is 9 to 10-fold for a weak thermal lens when comparing the ten-pass configuration with the conventional single-pass thermal lens system. Experimentally achieved signal enhancement in the ten-pass system is 8.3 for pure ethanol sample and between 8 and 9 for solutions with different concentrations of the Fe(II) - 1,10-Phenanthroline complex. Additionally, a value of 9.1 was calculated as the ratio of the slopes of the calibration lines obtained using the ten-pass and single-pass configurations. The achieved limit of detection for determination of Fe(II), in the ten-pass configuration, was 0.4 µgL-1, with a relative standard deviation around 4.5%, which compares favorably with previously reported results for TLS determination of Fe(II) in thin samples using low excitation power. For the multi-pass configuration the linear range of measurement is reduced when compared to the single-pass configuration. This is explained by the theoretical analysis of the photothermal signal under multi-pass condition, which shows the important contribution of the nonlinear term in the theoretical expression for the photothermal signal. The ten-pass configuration, which is presented and validated experimentally for the first time, offers important signal enhancement needed in recently developed TLS instruments with tunable, low power excitation sources.
Ključne besede: Thermal lens spectrometry, Photothermal detection, Trace determination, Chemical sensor
Objavljeno v RUNG: 10.12.2019; Ogledov: 3489; Prenosov: 0
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92.
A DNA origami plasmonic sensor with environment-independent read-out
Matjaž Valant, Mattia Fanetti, 2019, izvirni znanstveni članek

Ključne besede: DNA origami, plasmonic sensor, molecular detection, gold nanoparticle
Objavljeno v RUNG: 08.11.2019; Ogledov: 3406; Prenosov: 0
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93.
Increased sensitivity in proton transfer reaction mass spectrometry by incorporation of a radio frequency ion funnel
Shane Barber, Robert S Blake, Iain R. White, Paul S Monks, Fraser Reich, Stephen Mullock, Andrew M Ellis, 2012, izvirni znanstveni članek

Opis: A drift tube capable of simultaneously functioning as an ion funnel is demonstrated in proton transfer reaction mass spectrometry (PTR-MS) for the first time. The ion funnel enables a much higher proportion of ions to exit the drift tube and enter the mass spectrometer than would otherwise be the case. An increase in the detection sensitivity for volatile organic compounds of between 1 and 2 orders of magnitude is delivered, as demonstrated using several compounds. Other aspects of analytical performance explored in this study include the effective E/N (ratio of electric field to number density of the gas) and dynamic range over which the drift tube is operated. The dual-purpose drift tube/ion funnel can be coupled to various types of mass spectrometers to increase the detection sensitivity and may therefore offer considerable benefits in PTR-MS work.
Ključne besede: Analytical performance, Detection sensitivity, Drift tube, Dynamic range, Ion funnels, Proton-transfer reaction mass spectrometry, Volatile organic compounds
Objavljeno v RUNG: 18.07.2019; Ogledov: 3256; Prenosov: 0
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94.
Photothermal lens technique: a comparison between conventional and self-mixing schemes
Humberto Cabrera, Imrana Ashraf, Fatima Matroodi, Evelio E. Ramírez-Miquet, Jehan Akbar, Jose Juan Suárez-Vargas, John Fredy Barrera Ramírez, Dorota Korte, Hanna Budasheva, Joseph J. Niemela, 2019, izvirni znanstveni članek

Opis: This work focuses on assessing the analytical capabilities of a new photothermal lens method based on the self-mixing effect to reliably measure metallic traces in water-ethanol solutions. We compare it with the conventional thermal lens scheme, considering the low detection limit and versatility. A theoretical model is presented to describe the laser power variations as a function of the photothermal parameters of the analyzed sample. The experimental results demonstrate that the laser intensity variations, induced by the external optical feedback, are governed by the photothermal lens effect. Measurements of Fe(II)-1,10-phenanthroline in water–ethanol solutions show a favourable correspondence and agreement with the theory. The low detection limits obtained by the two analytic techniques also agree very well. Nevertheless, our instrument presents advantages regarding compactness and simplicity, suggesting that this platform could be potentially useful as a robust analytical tool for metallic trace detection. In addition, calibration of the method is performed by measuring the so-called self-mixing constant.
Ključne besede: thermal lens, photothermal spectroscopy, self-mixing effect, trace detection
Objavljeno v RUNG: 05.04.2019; Ogledov: 3700; Prenosov: 0
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95.
96.
Recombinant nanobodies as cheap and customizable reagents for unicellular algae detection
Elisa Mazzega, Ario De Marco, Marina Cabrini, Alfred Beran, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: At the present, the identification of planktonic species in coastal water mainly relies on light microscopy observations. This kind of analyses is performed by highly trained personnel, requires lab equipment and long processing time. High-throughput and easy-to-perform methods are instead highly needed for routine costal and ballast water monitoring. Immuno-reagents are widely employed in the medical field for routine diagnostics, where they provide the necessary sensitivity and specificity, as for example for cancer subtype characterization. Reagents of similar grade are so far not widely available for both diagnostics and basic research of microalgae. We describe the first successful isolation of a single-domain antibody (nanobody or VHH) from a pre-immune library, its engineering into application-ready reagents, and its inexpensive production as recombinant fusion protein. Alexandrium minutum was chosen as a model organism to test the feasibility of the procedure. The procedure foresees the panning of a pre-immune phage library of VHHs that was used for in vitro selection against directly the target cells. Monoclonal nanobodies specific for A. minutum cells were identified and optimized for recombinant production as fusion with fluorescent proteins in bacterial hosts. Such fluorescently-tagged VHHs were validated by immunofluorescence and cytofluorimetry for their selectivity by testing unicellular algal species that can be found in the same environment of A. minutum. Two nanobodies were found to be highly specific for the target cells, were able to bind also cysts of A. minutum and they gave no cross-reaction, even for a not-toxic strain of the closely related A. tamutum. Different tags can be then fused to the selected nanobodies and used instead of the fluorescent proteins to obtain a reagent immediately applicable to further techniques, such as cell Enzyme Linked Immuno Sorbent Assay (ELISA) or biosensor surface functionalization. The newly produced reagents can be applied for direct whole-cell detection in seawater, bypassing the need of cell processing required for DNA or RNA diagnostics, and can be used for both alive and fixed cells, guaranteeing the possibility to check old samples and to perform confirmatory morphological studies.
Ključne besede: Nanobodies, toxic algae, detection, recombinant reagent, naive library, phage display
Objavljeno v RUNG: 21.12.2018; Ogledov: 3880; Prenosov: 0
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97.
Nanobodies as convenient reagents for multiple biotechnological applications
Ario De Marco, predavanje na tuji univerzi

Ključne besede: biomarker detection, immunocapture, nanobodies
Objavljeno v RUNG: 17.09.2018; Ogledov: 3217; Prenosov: 0
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98.
99.
Search for Physics beyond the Standard Model with the CRESST Experiment
2017, magistrsko delo

Opis: In spite of the successes of observational astro- and particle physics and cosmology very much of the universe remains unknown. The Standard Model of particle physics is a theory describing the electromagnetic, weak, and strong nuclear interactions, as well as classifying all the subatomic particles known. But there is overwhelming evidence, that all the known particles, the ordinary (baryonic) matter, the building blocks of planets, stars and ourselves, only make up about 4.9% of the energy content of the universe. The standard model of cosmology (CDM) indicates that the total mass-energy of the universe contains beside the 4.9% ordinary matter two other components: 26.8% dark matter and 68.3% dark energy. The accelerating expansion of the Universe is the result of the effect of the dark energy with its most simple form given by a cosmological constant in Einstein's Equation. Dark matter is an unidentified type of matter that is not accounted for by dark energy and neutrinos and is generally believed to be a non-relativistic, charge neutral and non-baryonic new form of matter. Although dark matter has not been directly observed yet, its existence and properties are inferred from its gravitational effects such as the motions of visible matter, gravitational lensing, its influence on the universe's large-scale structure, and its effects in the cosmic microwave background. Thus the search for Dark Matter is the search for physics beyond the standard model. Although the nature of dark matter is yet unknown, its presence is crucial to understanding the future of the universe. The CRESST experiment is searching for direct evidence in the form of a nuclear recoil induced on a scintillating CaWO4 crystal by a dark matter particle, and is installed and taking data underground at Laboratory Nazionali del Gran Sasso (LNGS) in Italy. While both, dark energy and dark matter, have not been detected directly, a class of dark matter particles that interact only via gravity and the weak force, referred to asWeakly Interacting Massive Particles (WIMPs), has been established as the leading candidate among the dark matter community. For this thesis a special model of dark matter was studied, namely the dark photon. This thesis provides a detailed description of the calculation of the 90% upper limit on the dark photon kinetic mixing based on data from the second phase of the CRESST experiment. The analysis was carried out in a frequentist approach based on the (unbinned) maximum-likelihood method and likelihood ratios. To make a statement about the calculated result and its quality, the used algorithm had to be tested, what was done with Monte Carlo simulations (pseudo data).
Ključne besede: astro physics, particle physics, cosmology, universe, Standard Model of particle physics, standard model of cosmology, matter, ordinary matter, dark matter, dark energy, accelerating expansion of the Universe, non-baryonic, new form of matter, gravitational lensing, cosmic microwave background, search for physics beyond the standard model, CRESST experiment, direct detection, CaWO4 crystal, underground laboratory, Laboratory Nazionali del Gran Sasso, Weakly Interacting Massive Particles, WIMP, dark photon, 90% upper limit, upper limit, kinetic mixing, frequentist approach, unbinned, maximum likelihood
Objavljeno v RUNG: 13.10.2017; Ogledov: 4828; Prenosov: 0
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100.
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