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This paper models a hypothetical Apophis asteroid impact on an chosen deep ocean point on the globe. To assess the potential vulnerabilities of an exposed coast population, the impact effects were assessed as a function of the distance to the asteroid’s impact point as well as altitude for the tsunami case. All the tools and models used are valid and can be implemented for any other point on the Earth’s surface. The impact modelling includes the analysis of cratering formation, generated earthquake, overpressure, ejected material, generated thermal radiation and tsunami, as well as the global geophysical effects of the impact. The vulnerability models entail best, expected, and worst case scenarios, which allows a reasonable range of results. As the impact occurs in the ocean, and if its a great distance away from populated areas, the population is safeguarded from most of the impact effects. The tsunami is undoubtedly the most far-reaching and threatening impact effect from an asteroid impact on the ocean.

Enhancement of luminescence properties to improve and/or control both the absorption and emission of lanthanide (Ln)-activated glasses, ceramics and glass-ceramics, can be achieved with the development of smart photonic systems. Among different possible strategies, a prospective proof of concept for photoluminescence (PL) enhancement based on a one-dimensional photonic crystal (PC) was designed to tailor the up-conversion (UC) emission of Er3+ from a microcavity (MC) with an aluminosilicate glass film co-doped with Er3+/Yb3+ sandwiched between alternating layers of undoped aluminosilicate and TiO2. For the fabrication, the layers of different materials were deposited by sol-gel (SG), in order to mimic the PC structure obtained by simulation for a pre-defined position of the pass band defect (547 nm) within the stop band. An enhancement of up to 13 times of the Er3+ green UC was observed for the MC in comparison with a system without the PC structure.

In order to increase the efficiency of photovoltaic solar cells, photon absorption in an extended range of the solar spectrum is necessary, for example by means of up-conversion (UC) of sub-bandgap photons to minimize transparency losses. While lanthanide (Ln)-doped luminescent layers may be deposited on cell materials to achieve spectral conversion by methods like CVD or PVD, sol-gel (SG) processing is a low-cost technology which may be a good alternative for this purpose. In this work, Ln-doped SG-derived active layers have been deposited by spin-coating onto c-Si substrates for frequency conversion, with particular emphasis on UC, involving host matrices like aluminosilicate glass and titania ceramic doped with the activator/sensitizer pair Er/Yb. White light emitting diodes (WLEDs) based on Ln-doped phosphors still have efficiency limitations, namely because the Stokes shift from UV/blue LED excitation to the emitted lower frequency visible light converts some of the pump energy into heat. However, if white light generation (WLG) is achieved through IR-pumped UC instead, the cost of the LED lamp will be reduced, while the energy loss from Stokes shift can be minimized. SG synthesis of Ln-doped oxide phosphors for UC in WLG has been achieved (Er/Yb and Tm/Er/Yb doping), based on aluminosilicate glass matrices. Photonic crystal-assisted UC emission has also been demonstrated in a Tm/Yb-doped Fabry–Perot microcavity (MC). The different materials have been characterized by XRD, SEM, ellipsometry and photoluminescence (PL) spectroscopies and their light emission has been analyzed with the help of CIE chromaticity diagrams.

As the search continues for novel, cheaper, more sustainable, and environmentally friendly thermoelectric materials in order to expand the range of applications of thermoelectric devices, the tetrahedrite mineral (Cu12Sb4S13) stands out as a potential candidate due to its high abundance, low toxicity, and good thermoelectric performance. Unfortunately, as most current thermoelectric materials achieve zTs above 1.0, ternary tetrahedrite is not a suitable alternative. Still, improvement of its thermoelectric performance has been achieved to zTs ≈ 1 via isovalent doping and composition tuning, but most studies were limited to a single doping element. This project explores the effects of simultaneous doping with nickel and selenium in the thermoelectric properties of tetrahedrite. Simulated properties for different stoichiometric contents of these dopants, as well as the measured thermoelectric properties of the correspondent materials, are reported. One of the samples, Cu11.5Ni0.5Sb4S12.5Se0.5, stands out with a high power factor = 1279.99 µW/m·K2 at 300 K. After estimating the thermal conductivity, a zT = 0.325 at 300 K was obtained for this composition, which is the highest for tetrahedrites for this temperature. However, analysis of the weighted mobility shows the presence of detrimental factors, such as grain boundaries, disorder, or ionized impurity scattering, pointing to the possibility of further improvements.

Harvesting solar energy demands efficient solar cells working over the largest region of the solar spectrum possible. The extension of the wavelength region is viable through the use of frequency converting phosphors. Rare earth (RE) pairs fulfill this criterion and in particular the Erbium/Ytterbium pair allows a good coverage from the near-infrared (NIR) to visible by up conversion (UC) at room temperature. In this study we report the structural and optical properties of aluminosilicate glass films grown by sol-gel (SG) spin-coating deposition technique and co-doped with (Er, Tb)/Yb by ion implantation with different fluences and energy. After implantation, the films were annealed at 1000 °C for 20 min and characterized by scanning electron microscopy (SEM), Rutherford Backscattering (RBS), X-ray diffraction (XRD) and Photoluminescence (PL). The annealing induces a significant redistribution of the RE ions in the films. In particular, the samples implanted with Tb + Yb show a tendency to form a homogeneous distribution over the entire film. In both cases PL shows the cooperative up conversion process.

This paper reports on the optical properties of new organic metal halide material [C6N2H5]3BiCl6. The crystal structure is built up from the packing of distorted [BiCl6]3- octahedra surrounded by organic cation [C6N2H5]+. Unlike the classical metal halide materials in which organic molecules are optically inactive, both organic and inorganic components in this structure are chromospheres. At ambient temperature, photoluminescence measurements show and intense emission in the yellow green region. This emission is believed to be due to π– π* electronic transition within the organic cation [C6N2H5]+. Optical absorption (OA) and photoluminescence (PL) spectra of this compound were analyzed and interpreted by comparison with those of the homologous hybrids on one hand and those of the organic molecules on the other hand. In addition, photoluminescence excitation (PLE) have shown that the intense emission is governed by a resonance energy and charge transfer process in which [BiCl6]3- ions is assumed as a donor and organic cation plays the role of an acceptor. Moreover, photoluminescence study as function of temperature using the Arrhenius model, reveals the behavior a quasi-localized exciton with a binding energy of 73 meV, substantially lower than those found for homologous compounds but it reflects the localized character of the exciton and it may explain the stability of the exciton at ambient temperature.

Transition metal ions are essential micronutrients for all living organisms and play an important role in bone metabolism. In the present study, we investigated the impact of transition metal ions (Cu, Co, Mn, Fe) on the structure and bioactivity of bioactive glasses. The emphasis was laid on understanding their influence on the chemical dissolution behavior of glasses and its impact on their vitro bioactivity, osteoblast proliferation and oxidative stress levels. The structure of glasses was studied by using molecular EXAFS in combination with Raman spectroscopy. The apatite-forming ability of glasses has been investigated by X-ray diffraction, infrared spectroscopy after immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1 and 7 days. A significant effect on the bioactivity was observed with addition of transition metal ions. The cellular responses were observed in vitro on glass powders using human osteosarcoma MG63 cell line. The dose-dependent cytoprotective effect of glasses with respect to the concentration of transition metal ions (Cu, Co, Mn, Fe) released from the glasses is also discussed.

Optically detectable labels and probes are commonly used in bioapplications. Together with the miniaturization of analytical platforms based on microfluidic technology, with tuneable properties, they yield unparalleled opportunities towards faster, cheaper and more efficient biomolecule analysis. This work describes the preparation and testing of uniformly shaded polydimethylsiloxane (PDMS) membranes and microfluidic devices used to enhance or inhibit optical detection of fluorescent labels. The uniformly pigmented black-PDMS nanocomposite mixtures have been prepared by adding a known quantity of black pigment to PDMS, and its optical, spectroscopic and morphological properties have been characterized. The effect of pigment-to-DMS mixing ratio has been investigated by Ultra-Violet/Visible, near infrared and middle infrared spectroscopies; scanning electron microscopy and atomic force microscopy; and contact angle measurements. The results demonstrate that optical and spectroscopic properties of black-PDMS are strongly altered with the progressive inclusion of black pigment while wetting behaviour and morphology are maintained. Surface contact angle decreases more prominently with the decreasing ratio of DMS-to-curing agent than for the inclusion of pigment nanocomposite in the mixture. The ability to tune optical properties of PDMS has been experimentally demonstrated in a Black-PDMS nanocomposite microfluidic chip cast and bonded to glass. The results show double the signal-to-noise in fluorescence images as compared to pure PDMS devices, demonstrating a very promising integrated optical detection strategy for portable microfluidic systems.

A combined strategy to control the release of two drugs, one anti-inflammatory (diclofenac sodium, DCF) and one antibiotic (moxifloxacin hydrochloride, MXF), from a soft contact lens (SCL) material, was assessed. The material was a silicone-based hydrogel, which was modified by molecular imprinting with MXF and coated by the layer-by-layer (LbL) method using natural polyelectrolytes: alginate (ALG), poly- l -lysine (PLL) and hyaluronate (HA), crosslinked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Imprinting was used to increase the amount of MXF loaded and to sustain its release, while the LbL coating acted as a diffusion barrier for DCF and improved the surface properties. The drugs were loaded by soaking in a DCF + MXF dual solution. High hydrostatic pressure (HHP) was successfully applied in the sterilization of the drug-loaded hydrogels. The transmittance, refractive index, wettability and ionic permeability of the hydrogels remained within the required levels for SCLs application. The concentrations of the released DCF and MXF stayed above the IC50 and the MIC (for S. aureus and S. epidermidis) values, for 9 and 10 days, respectively. No ocular irritancy was detected by the HET-CAM test. NIH/3T3 cell viability demonstrated that the drug-loaded hydrogels were not toxic, and cell adhesion was reduced.

The performance of micro/nanoelectromechanical systems (MEMS/NEMS) relies on efficient lubrication. In the present work, new sulfur-based organic salts were tested as additives in a polyethylene glycol to lubricate silicon surfaces used in the manufacture of MEMS/NEMS. Seven salts were tested: 1-butylsulfonic-3-methylimidazolium triflate [(C4SO3H)MIM][TfO], thiamine triflate [Thiamine][TfO]2, 1-ethyl-3-methylimidazolium camphorsulfonate [C2MIM][CSA] [isomers (R) and (S)], 1,3-dimethylpiridinium methylsulfate [C1-3pic][MeSO4], methylimidazolium methanesulfonate [HMIM][MeSO3], and tetramethylguanidine methanesulfonate [TMG][MeSO3]. A nanotribometer was used to determine the friction coefficients using steel spheres as counter bodies. Excellent tribological properties were achieved with the additives containing the anions [MeSO4]− and [MeSO3]−. The films formed on the Si substrates were studied by FTIR, ellipsometry and AFM. A mixed lubrication mechanism was proposed where additive adsorption avoids contact between sliding surfaces. Acknowledgements This research was funded by the projects UID/QUI/00100/2019, UID/QUI/50006/2019, UIDB/00100/2020, UID/NAN/50024/2013, PEst-C/LA0006/2013, and UID/EMS/50022/2019 (LAETA). L. C. Branco and M. C. Donato thank to fnancial support of FCT/MCTES through grants IF/0041/2013/CP1161/CT00 and SFRH/BD/140079/2018, respectively. info:eu-repo/semantics/publishedVersion

This work reports the effect of different processing parameters on the structural and morphological characteristics of MoSe2 layers grown by chemical vapour deposition (CVD), using MoO3 and Se powders as solid precursors. It shows the strong dependence of the size, shape and thickness of the MoSe2 layers on the processing parameters. The morphology of the samples was investigated by field emission scanning electron microscopy (FESEM) and the thickness of the deposited layers was determined by atomic force microscopy (AFM). Raman and photoluminescence (PL) spectroscopies were used to confirm the high quality of the MoSe2 layers. Surface composition was examined by photoelectron spectroscopy (XPS). Moreover, the MoSe2/SiOx/Si heterojunctions exhibit diode behaviour, with a rectification ratio of 10, measured at ±2.0 V, which is due to the p-i-n heterojunctions formed at the p-Si/SiOx/MoSe2 interface. A photovoltaic effect was observed with a short circuit current density (Jsc), open circuit voltage (VOC) and efficiency of -0.80 mA/cm2, 1.55 V and 0.5%, respectively. These results provide a guide for the preparation of p-i-n heterojunctions based on few-layer MoSe2 with improved photovoltaic response., Tis work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contracts UID/CTM/04540/2019 and UID/FIS/04650/2019. Part of this work was supported by the COST Action MP1406 “Multiscale in modeling and validation for solar photovoltaics (MultiscaleSolar)”. Te authors acknowledge the CERIC-ERIC Consortium for access to experimental facilities and fnancial support under proposal 20182042.

A comprehensive review is presented, regarding the most significant developments and recent progress on one-dimensional (1-D) photonic crystals (PCs) like Bragg mirrors (BMs) and Fabry–Perot microcavities (F–P MCs) based on silica or silicate glass and titania, produced by sol–gel (SG). SG processing, deposition and characterization techniques, including simulations, are described, highlighting their potential for applications in optoelectronic materials and devices. Special emphasis is placed on lanthanide (Ln)-doped 1-D PCs, where the active layer includes elements like Ce, Tb, Er and Yb, corresponding to the defect layer of MC structures. A comparison is also made with similar structures prepared by other methods (e.g. sputtering).

An overview of advances in sol–gel processing methods for phosphors with different possible optical applications will be presented, highlighting examples based on lanthanide-doped materials. Specifically, new emerging applications have been promoted, using spectral conversion phosphors based on down-shifting, down-conversion or quantum-cutting and up-conversion processes. A brief perspective is given in particular on the potential of sol–gel derived lanthanide-doped materials for down-conversion and up-conversion for integration with photovoltaic solar cells in order to reduce the thermalization and transparency problems, which limit their efficiency, as well as their application in other optoelectronic technologies. This chapter shows the potential of sol–gel method to obtain down and up conversion materials based on a variety of compositions such as fluorides, oxides and oxyfluorides with different geometries.

New glasses in the composition 60Sb2O3-(40-x) NaPO3-xWO3 (where x = 0 to 40 mol.%) were prepared using the melt quenching technique. Different physical properties were measured to explain the effect of replacing NaPO3 with WO3. Differential scanning calorimetry (DSC) measurements showed high thermal stability, with Tx-Tg ∼ 100–130 °C. Glass transition temperature, Tg increased with an increasing amount of tungsten oxide. Such increase is also observed for the measurement of density, micro hardness, and the elastic moduli (longitudinal modulus (L), shear modulus (G), bulk modulus (K), and Young's modulus (E)). However, Poissn's ratio remains practically invariant and close to 0.252 confirms the bi-dimensional structure. The insertion of WO3 reduces the optical band gap and increases the refractive index from 1.584 to 1.786 at 486.1 nm where x WO3 is from 0 to 25 (mol.%). Furthermore, the measured optical dispersion changes from low dispersion crown glass to more dispersive flint glass. Following these various results, the glasses studied prove to be potential candidates for optical devices.

A key challenge in second generation solar cell development is to overcome major energy losses and to obtain high efficiency homogeneous films. In order to take advantage of the major portion of the solar spectrum, minimizing transparency losses, the use of frequency converting phosphors is a promising solution. From this viewpoint, the development of up-conversion (UC) materials for improving the light harvesting efficiency is a demanding task. Here, we report a low cost sol-gel (SG) spin-coating deposition technique which allows scalability to deposit SiO2 – Al2O3 and TiO2 films doped with the Erbium/Ytterbium lanthanide pair to obtain functional coatings with efficient near-infrared (NIR) to visible UC photoluminescence (PL) at room temperature. An alternative direct incorporation of the lanthanide ions into the solar cell material was also achieved by ion implantation. Comparison of both methods indicates that, although ion implantation is an accurate and controllable doping method, UC emission is superior at present from the films obtained by solution doping. However, this is the first time, to the best of the authors' knowledge, that UC properties have been studied for the Er/Yb pair in this system by this route. Therefore, the results reported here provide an additional approach for better understanding the doping parameters needed to obtain high PL performance.

Great efforts have been made in the last few years to increase the energy efficiency of solar cells. Among several factors which influence their performance, the light harvesting efficiency is the most relevant factor. In order to reduce the transparency losses of sub-bandgap solar photons, especially for wide gap solar cell materials, the development of up-conversion (UC) coatings to transform near infrared (NIR) light into short-wavelength visible photons is clearly a suitable approach. In spite of recent advances, the development of UC materials involves techniques which are generally not cost effective. This work will primarily focus on the evaluation of UC luminescence in aluminosilicate glass phosphors co-doped with the Tb3+/Yb3+ ion pair and synthesized by sol-gel (SG), a technique which is especially adequate to the deposition of films. The optimization of dopant concentrations has also been investigated, together with the structural, morphological and UC emission study of the coatings obtained. Lastly, a potential demonstrator has been developed in the form of a 1-D photonic crystal (PC) microcavity, in order to integrate the spectral conversion function into a more complex but more efficient structure.

The spectral mismatch between incident solar photons and the bandgap of crystalline silicon in solar cells results in major energy losses. Photons with energies lower than the bandgap are lost due to transparency, while those with energies above the bandgap value will be absorbed, generating electron-hole pairs, but consuming only the energy Eg, with the excess being lost as heat through thermalization. Despite intensive research to obtain efficient down-conversion (DC) materials for frequency shifting layers in c-Si cells, their development so far involves techniques which are not cost effective. Taking this into account, aluminosilicate phosphors co-doped with the Tb3+/Yb3+ ion pair have been synthesized by sol-gel (SG) processing, a low cost technique which allows scalability and is especially useful to obtain films. The molar composition 90 SiO2-10 AlO1.5 was chosen as host to investigate if DC based on the Tb3+/Yb3+ pair leads to efficient quantum cutting in such material. We demonstrate the potential of this approach to obtain near infrared DC emission in aluminosilicate matrix with a conversion efficiency of up to 158%, with potential to improve the performance of low bandgap photovoltaic solar cells.

A favourable electronic structure, together with a high abundance of pyrite (FeS2) in the Earth's crust, make this sulfide a promising material for thermoelectric applications. However, the experimental work published to date underlines a challenging scenario, with FeS2 presenting systematically small power factors. Knowing that sulfur vacancies are a key aspect for controlling the electronic transport properties of FeS2, this work focuses on the preparation of pyrite by hot-pressing and entails a careful characterization of its microstructure, chemical composition, thermal stability, and electrical transport properties. Dense pellets (>90% of the theoretical density) were obtained, consisting mostly of pyrite with trace amounts of Fe7S8. Different hot-pressing conditions led to similar chemical compositions, with no significant lattice distortions. Pyrite proved to be thermally stable up to 400 °C under an inert atmosphere. Analysis of the electronic band structure and density of states by density functional theory implies a p-type semiconductivity. However, measurements of Seebeck coefficient indicated n-type semiconductivity for pyrite produced by this experimental procedure. The highest power factor measured in this work, 0.23 μW K−2 m−1, is still far from what can be considered a promising value for thermoelectric materials, but different ways of improving it are discussed.

The trivalent Sm 3+ ion doped tellurium-antimony-tungsten oxides based glasses were prepared by conventional melt quenching and pressing method. Spectroscopic characterizations such as optical absorption, photoluminescence and decay profile measurements were performed on the glasses. Judd-Ofelt theory is used to evaluate the oscillator strengths and the three phenomenological intensity parameters (Ω λ , λ = 2, 4, 6) of the glasses. The photoluminescence spectra recorded under 479 nm excitation exhibited the emission bands at 562, 598, 645 and 708 nm corresponding to the transitions 4 G 5/2 → 6 H J ( J = 5/2, 7/2, 9/2, 11/2) respectively. Using J-O parameters (Ω λ ) various important radiative parameters viz., transition probabilities, emission cross-sections, branching ratios of various emission bands were evaluated. Decay profiles were recorded to find the lifetime of the 4 G 5/2 excited level and the obtained life time values are observed to decrease with an increase of Sm 3+ ion concentration; such decrease is attributed due to clustering of Sm 3+ ions which may cause luminescence quenching.

Yb-doped YAG single crystal is commonly used as the active material in high power lasers. Sol–gel processing is a possible alternative to prepare a similar active polycrystalline ceramic at lower cost. This work describes the preparation of YAG matrix ceramics by sol–gel with a continuous replacement of Y3+ by Yb3+ in the YAG structure. X-ray diffraction showed that the cubic YAG phase was obtained for all Yb doping levels. Structural characterization by infrared and Raman spectroscopies followed the replacement of Y by Yb. Finally, Yb3+ photoluminescence spectra were recorded, together with lifetime measurements, which yielded values in the range of 0.5–0.9 ms. Using Er co-doping as an internal standard, the absolute intensities of the Yb3+ photoluminescence peaks were compared and the optimum Yb concentration for maximum photoluminescence efficiency was determined at ~50 mol% Yb. Based on the photoluminescence efficiency and the lifetime values, a figure of merit for laser operation was maximum for the 40 mol% Yb concentration.

International audience; In this study, we have investigated the use of silver cation as nucleating agent in germanotellurite glass matrix of compositions (100−x) [70TeO2–10GeO2–10Nb2O5–10K2O]–xAg2O (x=0-6 mol%), in order to promote bulk crystallization. Density measurements, differential scanning calorimetry, X-ray diffraction, UV-Vis, and Raman spectroscopies have been performed to study the crystallization process. We have observed bulk crystallization of a unique noncentrosymmetric phase, K[Nb1/3Te2/3]2O4.8, which has been investigated for its second-order optical activity. Transparent to translucent glass-ceramics have been successfully tailored under thermal treatment and second harmonic generation signals were recorded on the glass-ceramic samples as a function of their synthesis procedure. It is suggested that the second-order optical properties observed are strongly related to the organization of crystallites within phase-separated domains.

The present paper regards the development of functional microcapsules (MCs), containing encapsulated glycerol, to act as sustainable solid curing agents for one-component polyurethane (PU) foams. They consist of silica-based MCs with an aminosilane surface treatment, obtained through sol–gel processing technique. These MCs are intended to burst and release their content only at the spraying process, in order to promote an accelerated curing of the PU foam. The superficial amino groups react with the isocyanate groups present in the PU pre-polymer, producing polyurea moieties on the MCs’ surface, which prevents the leaching of encapsulated glycerol inside the PU aerosol can. This enables the long shelf life of the product, required for commercial application. The amino-silica MCs exhibit a perfect spherical shape, without significant leaching, in opposition to silica-based MCs and led to a significant increase in the curing rate of the PU foam. The study involved various characterization techniques, such as scanning electron microscopy, Fourier transformed infrared spectroscopy, thermogravimetric analyses, leaching and curing speed evaluation.

AC Popa,1,2 GE Stan,1 MA Husanu,1 I Mercioniu,1 LF Santos,3 HR Fernandes,4 JMF Ferreira4 1National Institute of Materials Physics, Măgurele, 2Army Centre for Medical Research, Bucharest, Romania; 3Centro de Química Estrutural, Instituto Superior Técnico (CQE-IST), University of Lisbon, Lisbon, 4Department of Materials and Ceramics Engineering, Centre for Research in Ceramics and Composite Materials (CICECO), University of Aveiro, Aveiro, Portugal Abstract: Synthetic physiological fluids are currently used as a first in vitro bioactivity assessment for bone grafts. Our understanding about the interactions taking place at the fluid–implant interface has evolved remarkably during the last decade, and does not comply with the traditional International Organization for Standardization/final draft International Standard 23317 protocol in purely inorganic simulated body fluid. The advances in our knowledge point to the need of a true paradigm shift toward testing physiological fluids with enhanced biomimicry and a better understanding of the materials’ structure-dissolution behavior. This will contribute to “upgrade” our vision of entire cascades of events taking place at the implant surfaces upon immersion in the testing media or after implantation. Starting from an osteoinductive bioglass composition with the ability to alleviate the oxidative stress, thin bioglass films with different degrees of polymerization were deposited onto titanium substrates. Their bio­mineralization activity in simulated body fluid and in a series of new inorganic–organic media with increasing biomimicry that more closely simulated the human intercellular environment was compared. A comprehensive range of advanced characterization tools (scanning electron microscopy; grazing-incidence X-ray diffraction; Fourier-transform infrared, micro-Raman, energy-dispersive, X-ray photoelectron, and surface-enhanced laser desorption/ionization time-of-flight mass spectroscopies; and cytocompatibility assays using mesenchymal stem cells) were used. The information gathered is very useful to biologists, biophysicists, clinicians, and material scientists with special interest in teaching and research. By combining all the analyses, we propose herein a step forward toward establishing an improved unified protocol for testing the bioactivity of implant materials. Keywords: biomaterials, bioglass, in vitro biomimetic assays, proteins

The objective is to emphasize on the environmental and organizational pressure, namely, the pressure and fatigue induced in aircraft professionals. Safety is the main driver of aviation; environmental and organizational conditions, including extended working hours, have a negative impact on the performance of aircraft maintenance professionals and on aircraft safety. Just as aircraft crews and air traffic controllers have their work schedules highly monitored by aviation regulators; but regulators do not monitor the work schedules of professionals and they are subject to extended working timetables required by aeronautic players. The authors, through an international survey aimed at aeronautical professionals, demonstrate that errors are linked to stress, pressure and fatigue, environmental and organizational. This work also intends to demonstrate the need for regulators to monitor the work schedules of aircraft professionals to avoid that extended working hours having a negative impact on aircraft safety. The authors give the possible diagnostics and recommendations, which can be used to help the aeronautical players and aircraft maintenance staffs to create a safety culture and a decision and validation matrix of the aircraft maintenance.

Although cataract surgery is considered a safe procedure, post-surgery complications such as endophthalmitis and ocular inflammation, may occur. To prevent this, antibiotics and anti-inflammatories are prescribed in the form of eye drops during the post-operatory period, but they lead to a low drug bioavailability in target tissues. The objective of this work is to develop an intraocular lens (IOL) material to deliver simultaneously one antibiotic, moxifloxacin (MXF), and one anti-inflammatory, diclofenac (DFN), in therapeutic concentrations to prevent both complications. The IOL material was modified through the incorporation of functional monomers, as well as molecular imprinting with both drugs using the same functional monomers, namely acrylic acid (AA), methacrylic acid (MAA), 4-vinylpiridine (4-VP) and a combination of MAA + 4-VP. The best results were obtained with MAA. Molecular imprinting did not influence the drug release, except with AA. Application of a mathematical model predicted that the released MXF and DFN concentrations would stay above the pre-determined MIC of S. aureus and S. epidermidis and the minimum values of IC50 of COX-1 and COX-2, for 9 and 14 days, respectively. Antibacterial tests showed that the released antibiotic remained active. The physical properties of the drug-loaded MAA-hydrogel remained adequate. The developed system proved to be non-irritant and non-cytotoxic.

In the aviation sector, human factors are the primary cause of safety incidents. Intelligent prediction systems, which are capable of evaluating human state and managing risk, have been developed over the years to identify and prevent human factors. However, the lack of large useful labelled data has often been a drawback to the development of these systems. This study presents a methodology to identify and classify human factor categories from aviation incident reports. For feature extraction, a text pre-processing and Natural Language Processing (NLP) pipeline is developed. For data modelling, semi-supervised Label Spreading (LS) and supervised Support Vector Machine (SVM) techniques are considered. Random search and Bayesian optimization methods are applied for hyper-parameter analysis and the improvement of model performance, as measured by the Micro F1 score. The best predictive models achieved a Micro F1 score of 0.900, 0.779, and 0.875, for each level of the taxonomic framework, respectively. The results of the proposed method indicate that favourable predicting performances can be achieved for the classification of human factors based on text data. Notwithstanding, a larger data set would be recommended in future research.

Contact lenses may act as drug release platforms for the treatment of ocular infections, but there is still the need for extending their typical release periods and enhancing ocular bioavailability. The present study aimed to develop a molecularly imprinted silicone-based hydrogel to be used in the manufacturing of contact lenses that can be loaded efficiently and be able to release the antibiotic moxifloxacin hydrochloride (MXF) in a sustained way. A set of hydrogels was prepared by the molecular imprinting method using acrylic acid (AA) as the functional monomer for the specific recognition of MXF. The modified hydrogels loaded a higher amount of MXF, which was released for a longer time. In vitro experiments, using a microfluidic cell to mimic the ocular surface fluid turnover, showed that the imprinted hydrogel TRIS(300)-I prepared with the highest content in AA led to MXF concentrations in the release medium which were effective against S. aureus and S. epidermidis for about 2 weeks. Furthermore, some important properties such as water uptake, wettability, transmittance, ionic permeability, and Young´s modulus of the modified hydrogel remained within the range of values recommended for contact lenses. No cytotoxicity and no potential ocular irritancy effect were detected. Such hydrogel seems to be a promising alternative to the current options for the treatment of ocular infections.

Tellurite based ternary glasses with compositions TSW: 75TeO 2 –xSb 2 O 3 –(25−x)WO 3 where x = 5, 10, 15, 20 mol% were prepared by conventional melt quenching and pressing method. The prepared samples were investigated by X-ray diffraction (XRD), Differential thermal analysis (DTA), UV-VIS absorption spectroscopy, Raman and Fourier transform-infrared (FTIR) spectroscopies. XRD patterns recorded at room temperature confirm the amorphous nature of the glasses. Thermal properties such as glass transition temperature (T g ) and thermal stability of the glasses were determined from the differential thermal analysis curves. The absorption edge of the glasses shifts towards lower wavelength with increasing antimony oxide content in the glass indicating the increase of rigidity of the glass. FTIR and Raman spectra of the glasses showed the existence of WO 4 , WO 6 , TeO 4 , TeO 3 , TeO 3+1 and SbO 3 structural units in the glass network. The gradual increase of antimony oxide content in the glass matrix causes the transformation of TeO 4 structural units to TeO 3 or TeO 3+1 . Energy band gaps (E g ) and Urbach energies (ΔE) of the glasses were obtained by using the optical absorption spectral data. Density, molar volume, oxygen molar volume and oxygen packing density (OPD) of the glass samples were calculated to evaluate the physical and structural properties of the glasses.

Urban metabolism provides a characterization of anthropogenic material flows in urban systemsand should contribute to identify the economic activities that were involved on their supply andtransformation. Typically, its quantification requires data that is not easily available in differentgeographies. This paper makes use of a methodology based on monetary input–output tables andinternational trade statistics that might be easily replicable to many metropolitan areas in theworld, and which is intended to provide a first rough estimation of urban material flows.The paper discusses the results obtained for four metropolitan areas (Lisbon, Paris, Seoul–Incheonand Shanghai), assessing the material requirements of these economies. The urban areas arecompared in terms of the quantity and the type of material input, destination of materials withinthe economy and their distribution among economic activities. The results showed that whileLisbon is the most diverse urban area in terms of the consumption of material types, it is also theurban area with the least diversified manufacturing sector.The application of this methodology to several urban areas and across multiple years enables theassessment of the technological and economic evolution of those regions

Cu 2 SnS 3 (CTS) and Cu 2 Sn 0.83 Ge 0.17 S 3 (CTGS) compounds were successfully prepared by a powder technology using a combination of mechanical alloying (MA) and spark plasma sintering (SPS). Structural, compositional and optical properties were studied. A true alloy with composition similar to the starting constituents was formed after 2 h of MA at 400 rpm. Subsequently, SPS was performed at 600 °C for 5 min under a pressure of 50 MPa. The Cu/(Sn + Ge) composition ratios of the MA and SPS materials, determined by wavelength dispersive X-ray spectroscopy, are in the range of 1.84–1.94. Rietveld refinements of the powder X-ray diffraction data show a good agreement with the monoclinic crystal structure already for the MA materials. No structural changes were observed after SPS. Raman measurements coincide with XRD results in the identification of the characteristic peaks from phonon vibrational modes of monoclinic CTS phase. Band gaps between 1.24 eV and 1.34 eV were determined by diffuse reflectance for the mechanically alloyed and sintered samples.

Silves Castle is located in the Algarve, South of Portugal. Archaeological excavations provided numerous remains of the Islamic presence in this area from the 8th to the 13th c., which could be traced back to the Ommiad, Caliphal, Taifa, Almoravid and Almohad periods. The spectroscopic study of the ceramics, enabled us to discuss their provenance and production techniques. A clear difference in the diffraction patterns of the sherds from the Ommiad period (8th to 9th c.), and the Caliphal period (10th–11th c.) was observed, pointing to imported ceramics in both groups, the latter most likely from Medinat al-Zahra. The origin of the Ommiad ceramics still remains controversial. The samples from the Taifa kingdoms (11th c. period) were characterized as Lisbon productions. The blue and white ceramics studied here (12th–13th c.) are most probably the first samples showing the use of cobalt blue onto a white tin oxide layer made in Portugal.

Cenospheres are one of the most desired byproducts of coal combustion process nowadays. They are small hollow spheres with roughly 10–1000 μm in diameter and constitute about 1–2% of the fly ash obtained from the coal combustion processes. Because of their specific properties, namely their low density and high mechanical strength, cenospheres are an important subject of coal fired power plants. In this study, several fly ash samples from a coal-fired power plant located in Poland were analyzed in terms of fly ash composition, cenosphere content and its relation with glass formation principles and combustion conditions. The cenosphere samples, with different size, color and shape, were characterized, chemically and structurally, in order to establish the conditions that favor their formation. For this purpose, cenospheres have been collected and characterized by techniques such as SEM, EDS, XRD, XRF and Raman spectroscopy. Results indicate that cenospheres from coal combustion are constituted by aluminosilicate glasses with some crystalline phases like quartz, mullite and calcite. The high alumina content – roughly 25–27 wt.% – is responsible for the high mechanical strength, while density of most cenospheres is lower than 1 g/cm 3 . Regarding the formation process, there are correlations between the amount of cenospheres and the sodium and calcium content, in the different fly ash samples.

A series of Yb-doped glass films has been prepared by sol–gel processing within the SiO2–Al2O3–P2O5–Yb2O3 system with doping levels up to 30 mol% Yb on a cation basis, with a thickness up to ~36 μm. The refractive indices at 633 nm, measured by spectroscopic ellipsometry, varied between 1.457 and 1.577, depending on the composition. Infrared (IR) and Raman spectroscopies were used to establish the main structural features of the different compositions, which included the presence of mixed Si–O–Al bonds evidenced by a IR peak at 940 cm−1, as well as P=O bonds revealed by a Raman peak at 1326 cm−1. The photoluminescence spectrum of Yb3+ ions was dominated by peaks at 987 and 1020 nm, with a lifetime between ~0.5–1.0 ms.

A layer-by-layer (LbL) coating was designed using ionic polysaccharides (chitosan, sodium alginate, sodium hyaluronate) and genipin (crosslinker), to sustain the release of diclofenac sodium salt (DCF) from soft contact lens (SCL) materials. The coating was hydrophilic, biocompatible, non-toxic, reduced bacterial growth and had minor effects on the physical properties of the material, such as wettability, ionic permeability, refractive index and transmittance, which remained within the recommended values for SCLs. The coating was applied on a silicone-based hydrogel and on commercial SofLens and Purevision SCLs. The coating attenuated the initial drug burst and extended the therapeutic period for, at least, two weeks. Relevantly, the problems of sterilizing drug loaded SCLs coated with biopolymers, using classic methods that involve high temperature or radiation, were successfully solved through high hydrostatic pressure (HHP) sterilization.

In this study we investigated the possibility of using polyelectrolytes with antibacterial properties to form layer-by-layer (LbL) coatings on contact lens materials with the objective of controlling the release of ophthalmic drugs, while minimizing bacterial growth. A silicone-based hydrogel recently proposed by our group was chosen as a drug releasing soft contact lens (SCL) material and three drugs were tested: moxifloxacin hydrochloride (MXF), chlorhexidine diacetate monohydrate (CHX), and diclofenac sodium salt (DIC). Employed coatings involved combinations of sodium alginate (ALG), chitosan (CHI), sodium hyaluronate (HA) and polylysine hydrobromide (PLL), using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) as a cross-linking agent. Controlled release of DIC was achieved using two double layers of the following combinations: ALG/PLL (EDC), HA (EDC)/CHI and HA/PLL (EDC) + Drug. Furthermore, the physical properties of the coated lens material were kept, or even improved, and bacterial growth was reduced. In contrast, these coatings did not retard the release of MXF and CHX. The specificity of the barrier effect of these LbL films for DIC may be attributed to the formation of reversible interactions between DIC and the polyelectrolyte chains. A top layer of HA was needed to reduce the interaction with tear proteins. The in vivo efficacy of a contact lens coated with ALG/PLL (EDC)//HA and loaded with DIC was predicted using a simplified mathematical model to estimate the drug concentration in the tear fluid. The period of time during which the estimated concentration of DIC remained above the half-maximum inhibitory concentrations for the active enzymes in the process of inflammation, was at least double that obtained with the uncoated sample.

This paper is on the study of the Dynamics of a Gyrostat Satellite on a Circular Orbit, and the achievement of the analytical expressions which describes the bifurcation of equilibria. The attitude control of modern spacecraft's is essential to fulfil its missions. Every time that is necessary to point a camera or a scientific instrument the space platform must be perfectly balanced and stabilized. When a space platform loses its ability to be balanced and stabilized, which might be due to several factors, loses also its ability to carry out its mission. One approach to achieve such conditions is using Gyrostat configuration.

The oldest kilns producing tin glaze wares discovered in the region of Lisbon were located in the south shore of Tagus river at Santo Antonio da Charneca (SAC) and Mata da Machada (MM). Firing this type of pottery from the fourth quarter of the 15th century to mid-16th century, they were located about 20 km away from central Lisbon. Many other examples of ceramics produced in Lisbon workshops from that period are also known and exist in museums or archaeological collections, in spite of the fact that only one kiln dated from that period was found in Lisbon until now. Therefore, the spectroscopic characterization of ceramics found in Lisbon archaeological contexts (attributed to Lisbon workshops) – and also from SAC or MM – was needed and was performed here. Sherds representative of these faience production centres in the Lisbon region dated from the 16th/17th centuries were studied with the use of non-invasive spectroscopies, namely micro-Raman, Ground State Diffuse Reflectance Absorption (GSDR) and X-ray fluorescence emission (XRF). X-ray diffraction (XRD) experiments were also performed. Also clays were collected both in the North and South shores of the river Tagus, as much as possible from the same clay sources as used in the initial workshops. The obtained results evidence a clear similarity in the pastes of the pottery of the Lisbon region, quartz, gehlenite and diopside (or augite) being the major components. Clays are from Miocene origin, but differences between the ceramic pastes were detected pointing to the use of several clay sources. The spectroscopic trend exhibited at SAC and MM pottery is remarkably different, quartz being the major component of those pastes, and clays are from Pliocene origin.

We study the dynamics of the rotational motion of a gyrostat satellite moving in the central Newtonian force field along a circular orbit. We propose a method for determining the equilibrium attitudes (equilibrium orientations) of a gyrostat satellite in the orbital coordinate system for given values of the gyrostatic moment vector and principal central moments of inertia, and obtain their existence conditions. For each equilibrium orientation, sufficient conditions for stability are obtained using a generalized energy integral such as a Lyapunov function. We conduct a detailed numerical analysis of domains where the stability conditions for equilibrium attitudes are satisfied depending on four dimensionless parameters of the problem. It is shown that the number of equilibrium attitudes of a gyrostat satellite for which the sufficient conditions of stability are satisfied in the general case varies from four to two with an increase in the magnitude of a gyrostatic moment. The results obtained in this paper can be used for constructing gravitational systems of control over the orientation of the Earth’s artificial satellites.

Glass samples in the GeO2·SiO2·Nb2O5·K2O system, with different K2O/Nb2O5 ratios, were prepared, and glass–ceramics were obtained by controlled crystallization. Characterization included density measurements (Archimedes’ method), differential thermal analysis, X-ray diffraction (XRD), and Raman and UV–Visible spectroscopies. Crystal volume fractions were estimated from density measurements, while XRD was used to estimate the crystal size, by the Scherrer formula. XRD and Raman data showed that a K2O/Nb2O5 ratio of 1 promoted the formation of the crystalline phase K3.8Nb5Ge3O20.4 and transparent glass–ceramics could be obtained with a crystalline fraction of 79 % and an average crystal size of 19 nm, while a K2O/Nb2O5 ratio of 2 promoted the formation of KNbO3 crystalline phase, and a translucent glass–ceramic was obtained with a crystalline fraction of 27 % and a crystal size of 14 nm. The Maker fringe method was used to compare the second-harmonic generation efficiency of the glass–ceramics with a Y-cut quartz reference.

A new class of glass-ceramic nanocomposite systems with a uniform distribution of SnO2 nanocrystals dispersed within an amorphous silica phase is fabricated in the form of thin films by using sol–gel processing. In this work, experiments with (100-x)SiO2-xSnO2 nanocomposite thin films with (x = 25 and 30 mol%) doped with Er3+ ions (concentrations of 0.5, 1 and 2 mol%) are presented. The focus has been both to determine the effect of rare-earth doping on the growth of SnO2 nanocrystals as well as the distribution of the Er3+ ions within the ceramic structure. Vibrational spectroscopic assessments have proven the glass-ceramic nature of the samples. EXAFS and photoluminescence spectra show that the rare-earth ions exist in both amorphous and crystalline phases. Moreover an energy transfer from SnO2 nanocrystals to erbium ions on excitation at 351 nm is demonstrated.

A ytterbium doped active material for thin-disk laser was developed based on aluminosilicate and phosphosilicate glass matrices containing up to 30 mol% YbO1.5. Thick films and bulk samples were prepared by sol-gel processing. The structural nature of the base material was assessed by X-ray diffraction and Raman spectroscopy and the film morphology was evidenced by scanning electron microscopy. The photoluminescence (PL) properties of different compositions, including emission spectra and lifetimes, were also studied. Er3+ was used as an internal reference to compare the intensities of the Yb3+ PL peaks at ~ 1020 nm. The Yb3+ PL lifetimes were found to vary between 1.0 and 0.5 ms when the Yb concentration increased from 3 to 30 mol%. Based on a figure of merit, the best active material selected was the aluminosilicate glass composition 71 SiO2-14 AlO1.5-15 YbO1.5 (in mol%). An active disk, ~ 36 μm thick, consisting of a Bragg mirror, an aluminosilicate layer doped with 15 mol% Yb and an anti-reflective coating, was fabricated.