المؤلفون: Allieta, Mattia, Marelli, Marcello, Coduri, Mauro, Stefan, Mariana, Ghica, Daniela, Morello, Giorgio, Malara, Francesco, Naldoni, Alberto

مصطلحات موضوعية: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science

الوصف: Understanding the interplay between the structural, chemical and physical properties of nanomaterials is crucial for designing new devices with enhanced performance. In this regards, doping of metal oxides is a general strategy to tune size, morphology, charge, lattice, orbital and spin degrees of freedoms and has been shown to affect nanomaterials properties for photoelectrochemical water splitting, batteries, catalysis, magnetic applications and optics. Here we report the role of lattice small polaron in driving the morphological transition from nearly isotropic to nanowire crystals in Si doped hematite ($\alpha-Fe_2O_3$). Lattice small polaron formation is well evidenced by the increase of hexagonal strain and degree of distortion of $FeO_6$ showing a hyperbolic trend with increasing Si content. Local analysis via pair distribution function highlights an unreported crossover from small to large polarons, which affects the correlation length of the polaronic distortion from short to average scales. Ferromagnetic double exchange interactions between $Fe^{2+}/Fe^{3+}$ species is found to be the driving force of the crossover, constraining the chaining of chemical bonds along the [110] crystallographic direction. This promotes the increase in the reticular density of Fe atoms along the hematite basal plane only, which boosts the anisotropic growth of nanocrystals with more extended [110] facets. Our results show that magnetic and electronic interactions drive preferential crystallographic growth in doped metal oxides, thus providing a new route to design their functional properties.

الوصول الحر: http://arxiv.org/abs/1908.03377Test

المؤلفون: Vlaicu, Ioana D., Stefan, Mariana, Radu, Cristian, Culita, Daniela C., Radu, Dana, Ghica, Daniela

المصدر: Frontiers in Chemistry ; volume 11 ; ISSN 2296-2646

مصطلحات موضوعية: General Chemistry

الوصف: Layered zinc hydroxynitrate (ZHN), with the chemical formula Zn 5 (OH) 8 (NO 3 ) 2 ·2H 2 O, exhibits a range of special properties such as anion-exchange and intercalation capacity, as well as biocompatibility, making it attractive for a large variety of applications in fields from nanotechnology to healthcare and agriculture. In this study nanocrystalline ZHN doped with 1,000 ppm Mn 2+ was prepared by two synthesis methods (coprecipitation and solid state reaction) using similar environment-friendly precursors. The complex morpho-structural [X-ray diffraction, scanning and transmission electron microscopy, textural analysis] and spectroscopic [Fourier transform infrared and electron paramagnetic resonance (EPR)] characterization of the two ZHN nanopowders showed similar crystalline structures with Mn 2+ ions localized in the nanocrystals volume, but with differences in their morphological and textural characteristics, as well as in the doping efficiency. ZHN obtained by coprecipitation consists of larger nanoplatelets with more than two times larger specific surface area and pore volume, as well as a dopant concentration than in the ZHN sample obtained by solid state reaction. The thermal stability and the on-set of the structural phase transformation have been investigated at atomic scale with high accuracy by EPR, using Mn 2+ as paramagnetic probes. The on-set of the ZHN structural phase transformation toward ZnO was observed by EPR to take place at 110°C and 130°C for the samples prepared by coprecipitation and solid state reaction, respectively, evidencing a manganese induced local decrease of the transformation temperature. Our results contribute to the selection of the most appropriate ZHN synthesis method for specific applications and in the development of new green, cost-effective synthesis routes for Mn 2+ doped nano-ZnO.

الإتاحة: https://doi.org/10.3389/fchem.2023.1154219Test

المؤلفون: Mihalcea, Catalina G., Stefan, Mariana, Ghica, Corneliu, Florea, Ovidiu G., Stanoiu, Adelina, Simion, Cristian E., Somacescu, Simona, Ghica, Daniela

المصدر: Applied Surface Science ; volume 651, page 159252 ; ISSN 0169-4332

مصطلحات موضوعية: Surfaces, Coatings and Films, Condensed Matter Physics, Surfaces and Interfaces, General Physics and Astronomy, General Chemistry

الإتاحة: https://doi.org/10.1016/j.apsusc.2023.159252Test
https://api.elsevier.com/content/article/PII:S016943322302932X?httpAccept=text/xmlTest
https://api.elsevier.com/content/article/PII:S016943322302932X?httpAccept=text/plainTest

المؤلفون: Andronic, Luminita, Ghica, Daniela, Stefan, Mariana, Mihalcea, Catalina Gabriela, Vlaicu, Aurel-Mihai, Karazhanov, Smagul

المصدر: 17 ; 12 ; Nanomaterials ; 15

الوصف: publishedVersion

وصف الملف: application/pdf

العلاقة: Norges forskningsråd: 300107; Nanomaterials. 2022, 12 (15), .; urn:issn:2079-4991; https://hdl.handle.net/11250/3026618Test; https://doi.org/10.3390/nano12152563Test; cristin:2046339

الإتاحة: https://doi.org/10.3390/nano12152563Test
https://hdl.handle.net/11250/3026618Test

المؤلفون: Bondár, István, Šindelářová, Tereza, Ghica, Daniela, Mitterbauer, Ulrike, Liashchuk, Alexander, Baše, Jiří, Chum, Jaroslav, Czanik, Csenge, Ionescu, Constantin, Neagoe, Cristian, Pásztor, Marcell, Pichon, Alexis Le

المساهمون: National Research, Development and Innovation Fund

المصدر: Geophysical Journal International ; volume 230, issue 1, page 565-579 ; ISSN 0956-540X 1365-246X

مصطلحات موضوعية: Geochemistry and Petrology, Geophysics

الوصف: SUMMARY The Central and Eastern European Infrasound Network (CEEIN) has been established in 2018 with the collaboration of four research institutes, the Zentralanstalt für Meteorologie and Geodynamik (ZAMG), Vienna, Austria; the Institute of Atmospheric Physics of the Czech Academy of Sciences (CAS IAP), Prague, Czech Republic; the Research Centre for Astronomy and Earth Sciences of the Eötvös Loránd Research Network (ELKH CSFK), Budapest, Hungary; and the National Institute for Earth Physics (NIEP), Magurele, Romania. The Main Centre of Special Monitoring National Center for Control and Testing of Space Facilities, State Agency of Ukraine joined CEEIN in 2019. We show how the CEEIN infrasound arrays improve the detection capability of the European infrasound network and discuss coherent noise sources observed at CEEIN stations. We present the first CEEIN bulletin (2017–2020) of infrasound-only and seismo-acoustic events and using ground truth events, we demonstrate how adding infrasound observations to seismic data in the location algorithm improves location accuracy.

الإتاحة: https://doi.org/10.1093/gji/ggac066Test
https://academic.oup.com/gji/article-pdf/230/1/565/43177469/ggac066.pdfTest

المؤلفون: Šindelářová, Tereza, de Carlo, Marine, Czanik, Csenge, Ghica, Daniela, Kozubek, Michal, Podolská, Kateřina, Baše, Jiří, Chum, Jaroslav, Mitterbauer, Ulrike

المساهمون: Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)

المصدر: Journal of Atmospheric and Solar-Terrestrial Physics ; https://hal-insu.archives-ouvertes.fr/insu-03683263Test ; Journal of Atmospheric and Solar-Terrestrial Physics, 2021, 217, ⟨10.1016/j.jastp.2021.105603⟩

مصطلحات موضوعية: Microbaroms, Post-tropical storm, Microbarom source modelling, Microbarom propagation modelling, [SDU]Sciences of the Universe [physics]

الوصف: International audience ; The Central and Eastern European Infrasound Network (CEEIN) detects significant irregularities in microbarom arrivals between 15 and October 18, 2017. The processes driving the irregular microbarom arrivals are searched in the microbarom source region in the North Atlantic and in the stratospheric waveguide. Generation of microbaroms is simulated using ocean WAVEWATCHIII wave-action model and an updated source theory which combines the effects of both finite depth ocean and source directivity. Signal propagation in a uniform range independent atmosphere is considered. In the studied time interval, a dominant moving microbarom source occurs at the tail of the post-tropical storm Ophelia. The storm Ophelia provides an opportunity to study the development of an intense microbarom source on the open ocean and particularly in coastal waters. Discrepancies between observations and modelling results are identified and discussed. This study shows that the state-of-the-art wave-action models are underestimated in coastal areas during storms which can pose a problem for civil security in coastal areas. The capability of the CEEIN stations to monitor microbaroms is proved. Measurement biases and uncertainties associated with the configurations of the CEEIN stations and current limitations of the processing method are discussed and improvements are suggested.

العلاقة: insu-03683263; https://hal-insu.archives-ouvertes.fr/insu-03683263Test; https://hal-insu.archives-ouvertes.fr/insu-03683263/documentTest; https://hal-insu.archives-ouvertes.fr/insu-03683263/file/82426.pdfTest; BIBCODE: 2021JASTP.21705603S

الإتاحة: https://doi.org/10.1016/j.jastp.2021.105603Test
https://hal-insu.archives-ouvertes.fr/insu-03683263Test
https://hal-insu.archives-ouvertes.fr/insu-03683263/documentTest
https://hal-insu.archives-ouvertes.fr/insu-03683263/file/82426.pdfTest

المؤلفون: Dinescu, Raluca, Borleanu, Felix, Poiata, Natalia, Popa, Mihaela, Radulian, Mircea, Chircea, Andreea, Munteanu, Ioan, Ghica, Daniela

المصدر: XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

الوصف: The seismicity of the South Western part of Romania is linked to tectonic deformation being the result of the dextral movements at the contact between the Carpathians Orogen and Moesian Platform. The most notable active faults in this region are the Oravita-Moldova Noua Fault and Cerna-Jiu Fault. The crustal structure of this region was investigated through classical and modern techniques such as refraction and reflection profiling, seismic tomography, joint inversion of dispersion curves, and receiver functions. Targu-Jiu region was characterized before 2023 by sporadic small to moderate earthquakes. A well-investigated seismic sequence was produced in 2011-2012. The recent double-shock occurred in the area in February 2023 (5.2 and 5.7 ML) and was followed by more than 700 aftershocks. In order to estimate an improved 1-D velocity model for this active region, we extracted from the Romanian earthquake bulletins 170 events, recorded by Romanian Seismic Network. The events were selected based on the following criteria: a minimum of 20 recorded phases for each individual earthquake, the RMS location of less than 1 second, and a maximum azimuthal gap of 180 degrees. The region's velocity model and station corrections were accurately determined by minimizing the misfit between the model predictions and arrival times. The VELEST algorithm was run on the selected data, using P and S-wave travel times and the initial velocity models for generating new improved velocity models. We noticed a reduction of up to 40% in RMS location errors for all resulting velocity models.
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::b86297345d4a87570d6457ac432d16afTest
https://gfzpublic.gfz-potsdam.de/pubman/item/item_5020354Test

المؤلفون: Dinescu, Raluca, Popa, Mihaela, Radulian, Mircea, Vanciu-Rau, Adina, Chircea, Andreea, Ghica, Daniela

المصدر: XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

الوصف: The seismicity of Romania is characterized by seismic events with magnitudes between 1 ≤ Mw ≤ 7.9 (the largest earthquake produced in Vrancea in 1802) and depths from crustal to intermediate-depth domains. The Vrancea source generates a few significant earthquakes (magnitudes above 7.0) per century. The instrumental period of recording seismic activity in Romania started in 1888 when one of the first seismic stations from Europe was installed in Bucharest, at the Seismic Observatory from Cutitul de Argint. The seismicity recorded before the instrumental period is mostly based on macroseismic observations and early seismic instrumentation. Once the instrumental recording started to operate, over one million paper seismograms had been collected in the National Institute for Earth Physics archive. The archive includes records on smoked and photographic paper and ink recordings since 1900. The analog paper recordings are affected by continuous degradation which is followed by loss of data over time. Since the paper recordings are strongly affected by the passage of time and the storage conditions, currently, work is being done on the inventory of the existing seismograms, their evaluation, and scanning.
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::e8e65dc17f9462b0743b63563667a775Test
https://gfzpublic.gfz-potsdam.de/pubman/item/item_5020355Test

المؤلفون: Popescu, Traian, Matei, Christien Oktaviani, Vlaicu, Ioana Dorina, Tivig, Ioan, Kuncser, Andrei Cristian, Stefan, Mariana, Ghica, Daniela, Miclea, Luminita Claudia, Savopol, Tudor, Culita, Daniela Cristina, Moisescu, Mihaela Georgeta

المصدر: Scientific Reports ; volume 10, issue 1 ; ISSN 2045-2322

مصطلحات موضوعية: Multidisciplinary

الوصف: The present study concerns the in vitro oxidative stress responses of non-malignant murine cells exposed to surfactant-tailored ZnO nanoparticles (NPs) with distinct morphologies and different levels of manganese doping. Two series of Mn-doped ZnO NPs were obtained by coprecipitation synthesis method, in the presence of either polyvinylpyrrolidone (PVP) or sodium hexametaphosphate (SHMTP). The samples were investigated by powder X-ray Diffraction, Transmission Electron Microscopy, Fourier-Transform Infrared and Electron Paramagnetic Resonance spectroscopic methods, and N 2 adsorption–desorption analysis. The observed surfactant-dependent effects concerned: i) particle size and morphology; ii) Mn-doping level; iii) specific surface area and porosity. The relationship between the surfactant dependent characteristics of the Mn-doped ZnO NPs and their in vitro toxicity was assessed by studying the cell viability, intracellular reactive oxygen species (ROS) generation, and DNA fragmentation in NIH3T3 fibroblast cells. The results indicated a positive correlation between the specific surface area and the magnitude of the induced toxicological effects and suggested that Mn-doping exerted a protective effect on cells by diminishing the pro-oxidative action associated with the increase in the specific BET area. The obtained results support the possibility to modulate the in vitro toxicity of ZnO nanomaterials by surfactant-controlled Mn-doping.

الإتاحة: https://doi.org/10.1038/s41598-020-74816-0Test
https://www.nature.com/articles/s41598-020-74816-0.pdfTest
https://www.nature.com/articles/s41598-020-74816-0Test

المؤلفون: Ghica, Daniela, Vlaicu, Ioana D., Stefan, Mariana, Maraloiu, Valentin A., Joita, Alexandra C., Ghica, Corneliu

المصدر: Scientific Reports ; volume 9, issue 1 ; ISSN 2045-2322

مصطلحات موضوعية: Multidisciplinary

الوصف: The synthesis of semiconductor nanocrystals with controlled doping is highly challenging, as often a significant part of the doping ions are found segregated at nanocrystals surface, even forming secondary phases, rather than incorporated in the core. We have investigated the dopant distribution dynamics under slight changes in the preparation procedure of nanocrystalline ZnO doped with manganese in low concentration by electron paramagnetic resonance spectroscopy, paying attention to the formation of transient secondary phases and their transformation into doped ZnO. The acidification of the starting solution in the co-precipitation synthesis from nitrate precursors lead to the decrease of the Mn 2+ ions concentration in the core of the ZnO nanocrystals and their accumulation in minority phases, until ~79% of the Mn 2+ ions were localized in a thin disordered shell of zinc hydroxynitrate (ZHN). A lower synthesis temperature resulted in polycrystalline Mn-doped ZHN. Under isochronal annealing up to 250 °C the bulk ZHN and the minority phases from the ZnO samples decomposed into ZnO. The Mn 2+ ions distribution in the annealed nanocrystals was significantly altered, varying from a uniform volume distribution to a preferential localization in the outer layers of the nanocrystals. Our results provide a synthesis strategy for tailoring the dopant distribution in ZnO nanocrystals for applications ranging from surface based to ones involving core properties.

الإتاحة: https://doi.org/10.1038/s41598-019-43388-zTest
https://www.nature.com/articles/s41598-019-43388-z.pdfTest
https://www.nature.com/articles/s41598-019-43388-zTest