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Abstract: Polluted urban environment enhances dissolution of patina and underlying bronze material of recent and historical bronze sculptures exposed outdoors. In this work, two bronze statues, situated in one of the most polluted Croatian cities, were examined in order to characterize composition of patina and its electrochemical stability. The composition of patina on several positions on each sculpture was determined by EDS, Raman spectroscopy, and FTIR measurements. Electrochemical impedance spectroscopy measurements were conducted in order to evaluate the corrosion stability of both patina and underlying bronze. Results obtained in this work show that the two examined bronze sculptures were covered with patina layer that was mainly composed of copper sulfides and sulphates, which is in accordance with the high concentrations of H2S and SO2 in the atmosphere. However, the variations in the appearance of FTIR and Raman spectra revealed that the amount of each species differed from spot to spot, as well as the fact that other compounds, such as carbonates, were present at some areas. This difference in patina composition was reflected in electrochemical behavior as observed by electrochemical impedance spectroscopy.
Keywords: bronze, corrosion, spectroscopy, FTIR, Raman, EIS, open access
Published in DiRROS: 16.05.2023; Views: 304; Downloads: 179
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Abstract: Understanding tumors and their micro-environment are essential for successfuland accurate disease diagnosis. Tissuephysiology and morphology are altered intumors compared to healthy tissues, andthere is a need to monitor tumors and their surrounding tissues, includingblood vessels, non-invasively. This preliminary study utilizes a multimodaloptical imaging system combining hyperspectral imaging (HSI) and three-dimensional (3D) optical profilometry (OP) to capture hyperspectral imagesand surface shapes of subcutaneously grown murine tumor models. Hyper-spectral images are corrected with 3D OP data and analyzed using the inverse-adding doubling (IAD) method to extract tissue properties such as melaninvolume fraction and oxygenation. Blood vessels are segmented using theB-COSFIRE algorithm from oxygenation maps. From 3D OP data, tumor vol-umes are calculated and compared to manual measurements using a verniercaliper. Results show that tumors can be distinguished from healthy tissuebased on most extracted tissue parameters (p<0:05). Furthermore, blood oxy-genation is 50% higher within the blood vessels than in the surrounding tissue,and tumor volumes calculated using 3D OP agree within 26% with manualmeasurements using a vernier caliper. Results suggest that combining HSI andOP could provide relevant quantitative information about tumors and improvethe disease diagnosis.
Keywords: medical physics, hyperspectral imaging, diffuse reflectance spectroscopy, blood vessels, tumors
Published in DiRROS: 08.09.2022; Views: 574; Downloads: 196
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Abstract: Measurements of carbon dioxide and their stable isotopes are propulsive research tool in ecology and environmental science as they can give us insight into carbon cycle. They are widely used to investigate both natural and anthropogenic carbon sources in the atmosphere, hydrosphere and geosphere, as well as the exchange between these reservoirs. In this paper, we provide a basic overview of two different analytical measurement techniques, isotope ratio mass spectrometry (IRMS) and laser-absorption spectroscopy (LAS) which have been developed and utilized for monitoring of CO2 isotopologues in ecosystem. We present the basics for each technique, however with the emphasis on LAS measurement technique we are targeting readers who are not familiar with this topic. A major objective of this paper is to illustrate the current value and future potential of various analytical instruments in a wide range of applications deployed in the terrestrial ecosystem. Finally, we draw a conclusion from recent research campaigns by presenting a decision tree to better understand and choose a correct application combination for a selected scale of ecosystem.
Keywords: Isotope ratio mass spectrometry, laser-absorption spectroscopy, CO2 isotopologues, terrestrial ecosystem, decision tree, spectroscopic databases
Published in DiRROS: 18.02.2020; Views: 1781; Downloads: 792
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Abstract: The renin-angiotensin-aldosterone system (RAAS) plays a key role in the regulation of blood pressure. Renin is the rate limiting enzyme of the RAAS and aliskiren is a highly potent and selective inhibitor of the human renin. Renin is known to be active both in the circulating blood stream as well as locally, when bound to the (pro)-renin receptor ((P)RR). In this study we have investigated a possible mechanism of action of aliskiren, in which its accumulation in the plasma membrane is considered as an essential step for effective inhibition. Aliskiren's interactions with model membranes (cholesterol rich and poor) have been investigated by applying different complementary techniques: differential scanning calorimetry (DSC), Raman spectroscopy, magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and small- and wide-angle X-ray scattering (SAXS and WAXS). In addition, in silico molecular dynamics (MD) calculations were applied for further confirmation of the experimental data. Aliskiren's thermal effects on the pre- and main transition of dipalmitoyl-phosphatidylcholine (DPPC) membranes as well as its topographical position in the bilayer show striking similarities to those of angiotens.in II type 1 receptor (AT1R) antagonists. Moreover, at higher cholesterol concentrations aliskiren gets expelled from the membrane just as it has been recently demonstrated for the angiotensin receptor blocker (ARB) losartan. Thus, we propose that both the AT1R and the (P)RR-bound renin active sites can be efficiently blocked by membrane-bound ARBs and aliskiren when cholesterol rich membrane rafts/caveolae are formed in the vicinity of the receptors.
Keywords: aliskiren, renin, PRR, DPPC bilayers, raman spectroscopy, solid state NMR spectroscopy, SAXS and WAXS, MD simulations
Published in DiRROS: 26.01.2015; Views: 4355; Downloads: 314
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