Poly(ethylene oxide) (PEO)/gold nanocomposite hydrogels and suspensions were synthesized by γ-irradiation of PEO and Au3+ aqueous solutions to a dose of 50 kGy under inert atmosphere and without ...addition of 2-propanol, depending on the initial concentration of Au3+ and pH of solutions. The pH of the initial solutions had the major influence on the formation of PEO/Au nanocomposite hydrogels vs. suspensions. The pH and Au3+ initial concentration determined the AuNPs size and suspension stability, as determined by UV-Vis spectroscopy. The neutral pH favored the formation of stable suspensions with the smallest gold nanoparticles (AuNPs), whereas unstable suspensions and bigger nanoparticles (NPs) were obtained at acidic pH and by increasing Au3+ initial concentration. On irradiation at alkaline conditions PEO/AuNPs hydrogels were produced in one-pot synthesis method - by simultaneous crosslinking of PEO chains and reduction/synthesis of Au nanoparticles. Scanning electron microscopy of nanocomposite gels revealed the gold nanoparticles embedded in PEO matrix with homogenous distribution. The thermal and viscoelastic properties of PEO/AuNPs gels depended on the initial Au3+ concentration, that is on amount of AuNPs synthesized inside gels. Lower particle content resulted in gels with generally higher melting and crystallization temperatures as well as higher storage moduli, yield points and flow points than pure PEO gel. The optimal amount were up to 1 wt% Au for obtaining stronger gels, whereas higher amount of NPs, because of NPs agglomeration, lead to deterioration of gel properties and significant weakening of gel.
•γ-irradiation of Au3+/PEO solution produced gold suspension or nanocomposite gels.•Neutral pH favored formation of stable gold suspensions with small NPs.•PEO/AuNPs hydrogels were produced by one-step irradiation procedure at alkaline pH.•Thermal and rheological properties of gels depended on amount of synthesized AuNPs.•Up to 1% Au3+ was optimal amount for incorporating AuNPs and obtaining stronger gels.
In recent decades, precision agriculture and geospatial technologies have made it possible to ensure sustainability in an olive-growing sector. The main goal of this study is the extraction of olive ...tree canopies by comparing two approaches, the first of which is related to geographic object-based analysis (GEOBIA), while the second one is based on the use of vegetation indices (VIs). The research area is a micro-location within the Lun olives garden, on the island of Pag. The unmanned aerial vehicle (UAV) with a multispectral (MS) sensor was used for generating a very high-resolution (VHR) UAVMS model, while another mission was performed to create a VHR digital orthophoto (DOP). When implementing the GEOBIA approach in the extraction of the olive canopy, user-defined parameters and classification algorithms support vector machine (SVM), maximum likelihood classifier (MLC), and random trees classifier (RTC) were evaluated. The RTC algorithm achieved the highest overall accuracy (OA) of 0.7565 and kappa coefficient (KC) of 0.4615. The second approach included five different VIs models (NDVI, NDRE, GNDVI, MCARI2, and RDVI2) which are optimized using the proposed VITO (VI Threshold Optimizer) tool. The NDRE index model was selected as the most accurate one, according to the ROC accuracy measure with a result of 0.888 for the area under curve (AUC).
Multibeam echosounders (MBES) have become a valuable tool for underwater floor mapping. However, MBES data are often loaded with different measurement errors. This study presents a new user-friendly ...and methodological semi-automatic approach of point cloud post-processing error removal. The St. Anthony Channel (Croatia) was selected as the research area because it is regarded as one of the most demanding sea or river passages in the world and it is protected as a significant landscape by the Šibenik-Knin County. The two main objectives of this study, conducted within the Interreg Italy–Croatia PEPSEA project, were to: (a) propose a methodological framework that would enable the easier and user-friendly identification and removal of the errors in MBES data; (b) create a high-resolution integral model (MBES and UAV data) of the St. Anthony Channel for maritime safety and tourism promotion purposes. A hydrographic survey of the channel was carried out using WASSP S3 MBES while UAV photogrammetry was performed using Matrice 210 RTK V2. The proposed semi-automatic post-processing of the MBES acquired point cloud was completed in the Open Source CloudCompare software following five steps in which various point filtering methods were used. The reduction percentage in points after the denoising process was 14.11%. Our results provided: (a) a new user-friendly methodological framework for MBES point filtering; (b) a detailed bathymetric map of the St. Anthony Channel with a spatial resolution of 50 cm; and (c) the first integral (MBES and UAV) high-resolution model of the St. Anthony Channel. The generated models can primarily be used for maritime safety and tourism promotion purposes. In future research, ground-truthing methods (e.g., ROVs) will be used to validate the generated models.
Iron/titanium oxide nanoparticles with the initial molar ratio FeIII/(FeIII + TiIV) ≤ 0.50 were hydrothermally synthesized at 180 °C in an aqueous ammonia solution (pH ≅ 9.6). The titanium and iron ...precursors were TiCl4 and FeCl3, respectively. The amount of doped iron strongly affected microstructural properties as well as the degree of dispersion of iron in the Fe-Ti-O system. Anatase was the dominant phase in the iron/titanium oxide samples with Fe/(Fe + Ti) ≤ 0.25. The average crystallite size of the anatase phase in iron/titanium oxide samples decreased with the increase of iron doping. The results of precise unit-cell parameters measurement, obtained using Rietveld refinements of the powder diffraction patterns with added silicon indicated that the solid solubility limit of FeIII inside the anatase lattice was ∼8 mol%. The appearance of hematite (α-Fe2O3) sextet in the Mössbauer spectrum in the sample doped with 10 mol% of iron confirmed that the solid solubility limit of FeIII in the TiO2 lattice has been overreached. The relative concentrations of α-Fe2O3 in the samples increased with FeIII doping up to 15 mol% of added FeIII and then, quite unexpectedly, the XRD 104 line and Mössbauer sextet of α-Fe2O3 completely disappeared at 0.20 < Fe/(Fe + Ti) < 0.30. The EELS (electron energy-loss spectroscopy) analysis confirmed that the sample doped with 30 mol% of FeIII contained no hematite. The FeIII in the samples at 0.20 < Fe/(Fe + Ti) < 0.30 segregated not in the form of hematite, but in the form of iron/titanium oxide phase that was poorly crystallized or even amorphous. The α-Fe2O3 again appeared at Fe/(Fe + Ti) = 0.50. The diffuse reflectance spectra were used for band gap energy calculations. The band gap energy of the undoped TiO2 sample was 3.1 eV, whereas the band gap energy of Fe-Ti-O samples doped with up to 10% showed a blue shift (3.2 eV). The significant red shift (from 3.2 to 2.4 eV) was observed in the samples with higher iron content (from 10 to 50 mol%).
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•Iron doped anatase TiO2 was hydrothermally synthesized with up to 50 mol% of FeIII.•Solubility limit of FeIII in anatase lattice was estimated to 8 mol% using XRD.•FeIII that did not dissolve in TiO2 crystal lattice separated as α-Fe2O3 (hematite).•Hematite amount in samples unexpectedly fluctuates with continuous addition of FeIII.•With addition of FeIII band gap increased up to 10 mol% and then steadily decreased.
The karst landscapes of the Mediterranean are regarded as some of the most vulnerable, fragile, and complex systems in the world. They hold a particularly interesting group of small islands with a ...distinctive, recognizable landscape. The Republic of Croatia (HR), which has one of the most indented coasts in the world, is particularly known for them. In this paper, we analyzed the spatio-temporal changes (STCs) in the landscape of Ošljak Island, the smallest inhabited island in HR. Landuse/landcover change (LUCC) analysis has been conducted from 1944 to 2021. The methodology included the acquisition of multi-temporal data, data harmonization, production of landuse/landcover (LU/LC) maps, selection of optimal environmental indicators (EIs), and simulation modeling. In total, eleven comparable LU/LC models have been produced, with moderate accuracy. STCs have been quantified using the nine EIs. The dominant processes that influenced the changes in the Ošljak landscape have been identified. The results have shown that, in recent decades, Ošljak has undergone a landscape transformation which was manifested through (a) pronounced expansion of Aleppo pine; (b) deagrarianization, which led to secondary succession; and (c) urban sprawl, which led to the transformation of the functional landscape. The most significant of the detected changes is the afforestation of the Aleppo pine. Namely, in a 77-year span, the Aleppo pine has expanded intensively to an area of 11.736 ha, created a simulation model for 2025, and pointed to the possibility of the continued expansion of Aleppo pine. Specific guidelines for the management of this new transformed landscape have been proposed. This research provides a user-friendly methodological framework that can efficiently monitor LUCCs of a smaller area in the case when geospatial data are scarce and satellite imagery of coarser resolution cannot be used. Moreover, it gives an insight into the availability and quality of multi-temporal data for the HR.
Iron(III) chloride deaerated alkaline aqueous colloidal solutions in the presence of 2-propanol and DEAE-dextran (diethylaminoethyl-dextran hydrochloride) were γ-irradiated with doses of 36 and ...130 kGy. The dose rates were ~7 and ~31 kGy h−1. The extremely stable aqueous suspension of substoichiometric Fe2.83O4 magnetite nanoparticles ~4.7 nm in size were formed at a dose rate of ~7 kGy h−1 and at a dose of 36 kGy. At a dose of 130 kGy the anisotropic δ-FeOOH magnetic discs with a diameter of ~256 nm and thickness of ~40 nm were formed. Each disc has a substructure consisting of approximately eighteen laterally stacked thin nanodiscs of about 2.2 nm in thickness. At a higher dose rate of ~31 kGy h−1and at a dose of 36 kGy, XRD revealed the presence of highly substoichiometric Fe2.75O4 magnetite, whereas TEM analysis revealed the presence of ~4.3 nm magnetite nanoparticles along with rod-shaped γ-Fe2O3 nanoparticles. The values of isomer shift in Mössbauer spectra of about 0.33 mm s−1 showed that all Fe(II) in substoichiometric magnetites oxidized to Fe(III) one month after synthesis. At high dose and dose rate, the rolled rod-like δ-FeOOH magnetic nanoparticles were formed having the diffraction patterns with streaks, which are characteristic of tubular structures. The magnetic measurements showed exceptional intrinsic room-temperature magnetic properties of both δ-FeOOH nanostructures with the Curie temperature above 300 K. In order to ascertain the formation of Fe(II) intermediate products prior to their oxidation, γ-irradiated samples were isolated by admixing glycerol. The amounts of Fe(II) in glycerol-isolated solid samples were determined using Mössbauer spectroscopy. Carbonate Green Rust I GR(CO32−) and Fe(OH)2 intermediate phases were confirmed by XRD and Mössbauer spectroscopy. The amounts of Fe2+ in the acidified solutions containing dissolved γ-irradiation ferrous products were determined using the potassium permanganate titration. The amounts of Fe2+ were 68.9% and 96.1% at doses of 36 and 130 kGy, respectively. Thus, at a dose of 130 kGy the radiolytically generated Fe(OH)2, after coming in contact with oxygen and CO2 from the air, topotactically oxidized to GR(CO32−) and further to δ-FeOOH without any structural changes. The lower dose rate (~7 kGy h−1) favored the δ-FeOOH nanodisc morphology, whereas the higher dose rate (~31 kGy h−1) favored the formation of tubular rod-like δ-FeOOH nanoparticles.
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•γ-Irradiation can reduce Fe(III) up to Fe(OH)2 in the presence of DEAE-dextran.•The intermediate phases Fe(OH)2 and GR(CO32−) were captured by admixing glycerol.•Magnetite NPs 4.7 nm in size formed at dose rate of 7 kGy h−1 and at a dose of 36 kGy.•At a dose of 130 kGy the δ-FeOOH nanodiscs or δ-FeOOH tubular rod-like NPs formed.•Synthesized δ-FeOOH has unique magnetic properties with Curie temperature above 300 K.
Marine litter is a growing threat to the marine environment. Mapping of marine litter is becoming increasingly important to detect its potential hotspots and prevent their spread. In this paper, the ...applicability of the multibeam echo sounder (MBES) WASSP S3 and remotely operated underwater vehicle (ROV) Chasing M2 was tested in the detection and mapping of marine litter on the seafloor within the wider area of the St. Ante Channel (Šibenik, Croatia). Also, the precision assessment of WASSP S3 was tested at different cruising speeds. Results have shown that Chasing M2 can be used effectively for the initial detection of marine debris in shallow waters. However, if the underwater navigation and positioning system and auxiliary measurement scales are not used, the ROV has limited capabilities in deriving morphometric parameters of marine litter on the seafloor. This was determined by comparing the 3D model of a tire which was derived using video photogrammetry captured with ROV and the 3D model of a tire which was produced using a hand-held 3D scanner. Furthermore, the results have shown the WASSP S3 is not suitable for identifying marine litter smaller than 1 m at depths up to 10 m. The MBES WASSP S3 can detect marine litter that has a minimum area of 100 * 100 cm and a height of around 40 cm at depths up to 10 m. The results pointed to the need for caution when choosing an adequate sensor to detect and map marine litter on the seafloor. In addition, MBES interval measurements have shown that WASSP S3 precision is in the centimeter range (<10 cm) at different cruising speeds. The obtained results have helped to establish the guidelines for the integrated use of MBES, ROV, and UAV in the detection of marine litter on the seafloor.
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Developed GIS automated multicriteria analysis (GAMA) method presented in this article allows automation and simplification of multicriteria GIS decision analysis (GIS-MCDA) ...susceptibility modelling. Traditional GIS-MCDA susceptibility modelling still represents time and labor demanding process, whose success is highly influenced by the user's experience and knowledge. In order to make overall GIS-MCDA susceptibility modelling process more straightforward and practical, GAMA method is designed as easy to use three step process, which allows automation of following GIS-MCDA steps: (1) standardization of criteria, (2) criteria grouping and weight assignment and (3) susceptibility model aggregation. GAMA method is developed within ArcGIS 10.4 ModelBuilder application, as a toolset that can be easily shared and incorporated within default ESRI’s ArcGIS toolbox. GAMA was successfully applied for gully erosion susceptibility modelling on example of Pag island, Croatia, whose results are published in separate article. Since GAMA method is applicable to various GIS-MCDA susceptibility modelling purposes we are encouraging its future use and therefore open-source GAMA method toolset can be acquired for research purposes (htps://gal.unizd.hr).
•GAMA method simplifies overall GIS-MCDA susceptibility modelling process.•GAMA allows automated standardization, grouping, weight coefficient assignment and aggregation of GIS-MCDA’s criteria.•GAMA method has broad application in various different GIS-MCDA susceptibility modelling purposes.
The main objective of this paper was to discuss applications of GIS based multi-criteria decision analysis (GIS MCDA) and Analytical Hierarchy Process (AHP). These two techniques were applied in ...order to assist preparation of the Tourism Management Plan, depicting the most suitable zones for ecotourism development in Dikgathlong Dam Lease Area (DDLA) as one of the largest resources of potable water in Botswana. The MCDA was based on geo-morphometric, hydrologic, landscape and community indicators and criteria which emanated from expert's opinions, intensive field survey and literature review. In addition the AHP has helped to calculate individual criteria weights and to point the degree of suitability zones classified as highly suitable, moderately suitable, marginally suitable and not suitable for ecotourism. After performing both processes and establishing broad management zones it has been found that the Sustainable Development Scenario is the most appropriate option as the future ecotourism development proposal. This research provides new methodology that can be incorporated into future tourism policies and management strategies.
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