Structural properties of mixed conductor Ba1-xGd1-yLax+yCo2O6-δ.

Ba1-xGd1-yLax+yCo2O6-δ (BGLC) compositions with large compositional ranges of Ba, Gd, and La have been characterised with respect to phase compositions, structure, and thermal and chemical expansion. The results show a system with large compositional flexibility, enabling tuning of functional properties and thermal and chemical expansion. We show anisotropic chemical expansion and detailed refinements of emerging phases as La is substituted for Ba and Gd. The dominating phase is the double perovskite structure Pmmm, which is A-site ordered along the c-axes and with O vacancy ordering along the b-axis in the Ln-layer. Phases emerging when substituting La for Ba are orthorhombic Ba-deficient Pbnm and cubic LaCoO3-based R3̄c. When La is almost completely substituted for Gd, the material can be stabilised in Pmmm, or cubic Pm3̄m, depending on thermal and atmospheric history. We list thermal expansion coefficients for x = 0-0.3, y = 0.2.

Galvanic Deposition of Pt Nanoparticles on Black TiO2 Nanotubes for Hydrogen Evolving Cathodes.

A galvanic deposition method for the in-situ formation of Pt nanoparticles (NPs) on top and inner surfaces of high-aspect-ratio black TiO2 -nanotube electrodes (bTNTs) for true utilization of their total surface area has been developed. Density functional theory calculations indicated that the deposition of Pt NPs was favored on bTNTs with a preferred [004] orientation and a deposition mechanism occurring via oxygen vacancies, where electrons were localized. High-resolution transmission electron microscopy images revealed a graded deposition of Pt NPs with an average diameter of around 2.5 nm along the complete nanotube axis (length/pore diameter of 130 : 1). Hydrogen evolution reaction (HER) studies in acidic electrolytes showed comparable results to bulk Pt (per geometric area) and Pt/C commercial catalysts (per mg of Pt). The presented novel HER cathodes of minimal engineering and low noble metal loadings (µg cm-2 range) achieved low Tafel slopes (30-34 mV dec-1 ) and high stability in acidic conditions. This study provides important insights for the in-situ formation and deposition of NPs in high-aspect-ratio structures for energy applications.

Double Perovskite Cobaltites Integrated in a Monolithic and Noble Metal-Free Photoelectrochemical Device for Efficient Water Splitting.

Water photoelectrolysis has the potential to produce renewable hydrogen fuel, therefore addressing the intermittent nature of sunlight. Herein, a monolithic, photovoltaic (PV)-assisted water electrolysis device of minimal engineering and of low (in the µg range) noble-metal-free catalysts loading is presented for unassisted water splitting in alkaline media. An efficient double perovskite cobaltite catalyst, originally developed for high-temperature proton-conducting ceramic electrolyzers, possesses high activity for the oxygen evolution reaction in alkaline media at room temperatures too. Ba1-xGd1-yLax+yCo2O6-δ (BGLC) is combined with a NiMo cathode, and a solar-to-hydrogen efficiency of 6.6% in 1.0 M NaOH, under 1 sun simulated illumination for 71 h, is demonstrated. This work highlights how readily available earth-abundant materials and established PV methods can achieve high performance and stable and monolithic photoelectrolysis devices with potential for full-scale applications.

Thermochemically stable ceramic composite membranes based on Bi2O3 for oxygen separation with high permeability.

Ceramic oxygen separation membranes can be utilized to reduce CO2 emissions in fossil fuel power generation cycles based on oxy-fuel combustion. State-of-the-art oxygen permeable membranes based on Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) offer high oxygen permeability but suffer from long-term instability, especially in the presence of CO2. In this work, we present a novel ceramic composite membrane consisting of 60 vol% (Bi0.8Tm0.2)2O3-δ (BTM) and 40 vol% (La0.8Sr0.2)0.99MnO3-δ (LSM), which shows not only comparable oxygen permeability to that of BSCF but also outstanding long-term stability. At 900 °C, oxygen fluxes of 1.01 mL min-1 cm-2 and 1.33 mL min-1 cm-2 were obtained for membranes with thicknesses of 1.35 mm and 0.75 mm, respectively. Moreover, significant oxygen fluxes were obtained at temperatures down to 600 °C. A stable operation of the membrane was demonstrated with insignificant changes in the oxygen flux at 750 °C for approx. one month and at 700 °C with 50% CO2 as the sweep gas for more than two weeks.

Tailoring Upconversion and Morphology of Yb/Eu Doped Y2O3 Nanostructures by Acid Composition Mediation.

The present study reports the production of upconverter nanostructures composed by a yttrium oxide host matrix co-doped with ytterbium and europium, i.e., Y2O3:Yb3+/Eu3+. These nanostructures were formed through the dissociation of yttrium, ytterbium and europium oxides using acetic, hydrochloric and nitric acids, followed by a fast hydrothermal method assisted by microwave irradiation and subsequent calcination process. Structural characterization has been carried out by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM) both coupled with energy dispersive X-ray spectroscopy (EDS). The acid used for dissociation of the primary oxides played a crucial role on the morphology of the nanostructures. The acetic-based nanostructures resulted in nanosheets in the micrometer range, with thickness of around 50 nm, while hydrochloric and nitric resulted in sphere-shaped nanostructures. The produced nanostructures revealed a homogeneous distribution of the doping elements. The thermal behaviour of the materials has been investigated with in situ X-Ray diffraction and differential scanning calorimetry (DSC) experiments. Moreover, the optical band gaps of all materials were determined from diffuse reflectance spectroscopy, and their photoluminescence behaviour has been accessed showing significant differences depending on the acid used, which can directly influence their upconversion performance.

Mineralization of Sialoliths Investigated by Ex Vivo and In Vivo X-ray Computed Tomography.

The fraction of organic matter present affects the fragmentation behavior of sialoliths; thus, pretherapeutic information on the degree of mineralization is relevant for a correct selection of lithotripsy procedures. This work proposes a methodology for in vivo characterization of salivary calculi in the pretherapeutic context. Sialoliths were characterized in detail by X-ray computed microtomography (µCT) in combination with atomic emission spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Correlative analysis of the same specimens was performed by in vivo and ex vivo helical computed tomography (HCT) and ex vivo µCT. The mineral matter in the sialoliths consisted essentially of apatite (89 vol%) and whitlockite (11 vol%) with average density of 1.8 g/cm3. In hydrated conditions, the mineral mass prevailed with 53 ± 13 wt%, whereas the organic matter, with a density of 1.2 g/cm3, occupied 65 ± 10% of the sialoliths' volume. A quantitative relation between sialoliths mineral density and X-ray attenuation is proposed for both HCT and µCT.

Local Response of Sialoliths to Lithotripsy: Cues on Fragmentation Outcome.

Lithotripsy methods show relatively low efficiency in the fragmentation of sialoliths compared with the success rates achieved in the destruction of renal calculi. However, the information available on the mechanical behavior of sialoliths is limited and their apparently tougher response is not fully understood. This work evaluates the hardness and Young's modulus of sialoliths at different scales and analyzes specific damage patterns induced in these calcified structures by ultrasonic vibrations, pneumoballistic impacts, shock waves, and laser ablation. A clear correlation between local mechanical properties and ultrastructure/chemistry has been established: sialoliths are composite materials consisting of hard and soft components of mineralized and organic nature, respectively. Ultrasonic and pneumoballistic reverberations damage preferentially highly mineralized regions, leaving relatively unaffected the surrounding organic matter. In contrast, shock waves leach the organic component and lead to erosion of the overall structure. Laser ablation destroys homogeneously the irradiated zones regardless of the mineralized/organic nature of the underlying ultrastructure; however, damage is less extensive than with mechanical methods. Overall, the present results show that composition and internal structure are key features behind sialoliths' comminution behavior and that the organic matter contributes to reduce the therapeutic efficiency of lithotripsy methods.

Pathogens in Ornamental Waters: A Pilot Study.

In parks, ornamental waters of easy access and populated with animals are quite attractive to children and yet might hide threats to human health. The present work focuses on the microbiota of the ornamental waters of a Lisboa park, characterized during 2015. The results show a dynamic microbiota integrating human pathogens such as Klebsiella pneumoniae, Aeromonas spp. and Enterobacter spp., and also antibiotic resistant bacteria. K. pneumoniae and Aeromonas spp. were present as planktonic and biofilm organized bacteria. In vitro K. pneumoniae and Aeromonas spp. showed an enhanced ability to assemble biofilm at 25 °C than at 37 °C. Bacteria recovered from biofilm samples showed an increased antibiotic resistance compared to the respective planktonic counterparts.

Room temperature synthesis of Cu2O nanospheres: optical properties and thermal behavior.

The present work reports a simple and easy wet chemistry synthesis of cuprous oxide (Cu2O) nanospheres at room temperature without surfactants and using different precursors. Structural characterization was carried out by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy coupled with focused ion beam and energy-dispersive X-ray spectroscopy. The optical band gaps were determined from diffuse reflectance spectroscopy. The photoluminescence behavior of the as-synthesized nanospheres showed significant differences depending on the precursors used. The Cu2O nanospheres were constituted by aggregates of nanocrystals, in which an on/off emission behavior of each individual nanocrystal was identified during transmission electron microscopy observations. The thermal behavior of the Cu2O nanospheres was investigated with in situ X-ray diffraction and differential scanning calorimetry experiments. Remarkable structural differences were observed for the nanospheres annealed in air, which turned into hollow spherical structures surrounded by outsized nanocrystals.

Conduta cirúrgica em terceiro molar incluso com geminação / Surgical conduct for impacted third molar with gemination

Este trabalho objetiva apresentar o relato de paciente, sexo feminino, 29 anos de idade que compareceu para exodontia do elemento 38 parcialmente erupcionado. Na radiografia panorâmica observa-se o 38 associado a elemento dentário extranumerário, que se estende do rebordo a bem próximo a basilar, ultrapassando os limites do canal mandibular. Na tomografia cone beam observa-se coroa com diâmetro mesiodistal comproporções elevadas, sendo uma coroa dentária, uma câmara pulpar ampliada e três raízes, compatível com geminação. Duas das raízes estavam acima do canal mandibular e uma abaixo. A conduta cirúrgica proposta foi remoção da coroa e das raízes superiores e sepultamento da inferior, para evitar fratura mandibular e parestesia. Realizou-se acesso, osteotomia para exposição da coroa dentária até a região das furcas, seguida odontosecção para separação da coroa das raízes, clivagem e remoção da coroa. Na remoção do fragmento coronário observa--se presença da raiz mais profunda aderida a coroa, não sendo possível realizar clivagem total. As raízes superiores ao canal foram removidas sem maiores problemas. O alvéolo foi curetado, o retalho reposicionado na sua posição, seguido de sutura. Ressalta-se a importância da solicitação de exames de imagem e do planejamento de modo a evitar possíveis complicações no ato cirúrgico.

This paper reports the case of a 29-year-old female patient who visited the dental clinic for the extraction of partially eruption tooth 38. The panoramic radiograph revealed that tooth 38 was associated with an extranumerary tooth extending from the rim to near the basal lamina, surpassing the limits of the mandibular canal. Cone-beam tomography revealed a dental crown with a large mesio-distal diameter, large pulp chamber and three roots, compatible with gemination. Two of the rootswere above the mandibular canal and one was below. The proposedsurgical conduct was the removal of the crown and upper roots and burying of the lower root to avoid mandibular fracture and paresthesia. The region was accessed and osteotomy was performed to expose the dental crown to the furcation region, followed by sectioning for the separation of the crown from the roots, cleavage and removal of the crown. During this procedure, it was noted that the deepest root was adhered to the crown and complete cleavage was not possible. The roots above the canal were removed without incident. The alveolus was curetted and the flap was repositioned and sutured. This case underscores the importance of imaging exams and adequate planning toavoid possible complications during the act of surgery.

Uniform arrays of ZnO 1D nanostructures grown on Al:ZnO seeds layers by hydrothermal method.

In obtaining uniform array of ZnO 1D nanostructures, especially using solution based methods, the thickness and the morphology of the epitaxial seeds layer are very important. The paper presents the effect of the thickness and the morphology of the Al:ZnO seeds layer on the morphology and properties of ZnO nanowires array grown by hydrothermal method. Compact and vertically aligned ZnO 1D nanostructures were obtained. Concentration of 0.02 M of zinc nitrate was found to be optimal for growing nanowires with diameters up to 50 nm and lengths between 1.5 and 2.5 microns. Using 0.04 M solution, nanorods with diameter between 50 and 100 nm were obtained. The correlation between the crystal structure and optical properties of ZnO nanowires is discussed. From electrical measurements on single nanowire, resistivity value of 9 x 10(-2) omega cm was obtained. The I-V curves of single ZnO NWs show quasi diode characteristic when an e-beam is irradiating the NWs, and a typical semiconductive behaviour when the e-beam is turned off.

Structure and growth of sialoliths: computed microtomography and electron microscopy investigation of 30 specimens.

Theories have been put forward on the etiology of sialoliths; however, a comprehensive understanding of their growth mechanisms is lacking. In an attempt to fill this gap, the current study has evaluated the internal architecture and growth patterns of a set of 30 independent specimens of sialoliths characterized at different scales by computed microtomography and electron microscopy. Tomography reconstructions showed cores in most of the sialoliths. The cores were surrounded by concentric or irregular patterns with variable degrees of mineralization. Regardless of the patterns, at finer scales the sialoliths consisted of banded and globular structures. The distribution of precipitates in the banded structures is compatible with a Liesegang-Ostwald phenomenon. On the other hand, the globular structures appear to arise from surface tension effects and to develop self-similar features as a result of a viscous fingering process. Electron diffraction patterns demonstrated that Ca- and P-based electrolytes crystallize in a structure close to that of hydroxyapatite. The organic matter contained sulfur with apparent origin from sulfated components of secretory material. These results cast new light on the mechanisms involved in the formation of sialoliths.

Exploring the contribution of mycobacteria characteristics in their interaction with human macrophages.

Tuberculosis (TB) is a major health problem. The emergence of multidrug resistant (MDR) Mycobacterium tuberculosis (Mtb) isolates confounds treatment strategies. In Portugal, cases of MDR-TB are reported annually with an increased incidence noted in Lisbon. The majority of these MDR-TB cases are due to closely related mycobacteria known collectively as the Lisboa family and Q1 cluster. Genetic determinants linked to drug resistance have been exhaustively studied resulting in the identification of family and cluster specific mutations. Nevertheless, little is known about other factors involved in development of mycobacteria drug resistance. Here, we complement genetic analysis with the study of morphological and structural features of the Lisboa family and Q1 cluster isolates by using scanning and transmission electron microscopy. This analysis allowed the identification of structural differences, such as cell envelope thickness, between Mtb clinical isolates that are correlated with antibiotic resistance. The infection of human monocyte derived macrophages allowed us to document the relative selective advantage of the Lisboa family isolates over other circulating Mtb isolates.

Electron diffraction of ThMn12/Th2Zn17-type structures in the Nd-Fe-Ti system.

Nd:11Fe:Ti alloys prepared by arc melting followed by splat quenching and annealing have been investigated by electron microscopy. The as-cast microstructure evidenced an α-Fe(Ti) --> NdFe11Ti --> Nd2(Fe,Ti)17 solidification sequence compatible with a cascade of peritectic reactions. The Nd2(Fe,Ti)17 phase was not detected in the microstructure of the splat-quenched materials, but after annealing the ternary compound grains consisted of a mixture of ThMn12-type and Th2Zn17-type structures exhibiting a consistent (020)1:12//(003)2:17 and [100]1:12//[110]2:17, orientation relation, with the invariant plane sitting at (022)1:12//(333)2:17. A series of 3D microdiffraction experiments carried out on grains presenting a random distribution of planar defects has been used to map the reciprocal space of the intergrown phases.

Regional bond strength to lateral walls in class I and II ceramic inlays luted with four resin cements and glass-ionomer luting agent.

PURPOSE: To investigate regional shear bond strength to lateral walls of ceramic inlays in occlusal and occlusoproximal cavities using etch-and-rinse and self-adhesive resin cements and a glass-ionomer luting agent. MATERIALS AND METHODS: IPS e.max Press ceramic inlays were made in 50 Class I and 50 Class II standardized cavities in intact extracted human molars and divided into 5 luting agent subgroups (n = 10): Variolink II (VL); Multilink Sprint (MLS); Multilink Automix (MLA); RelyX Unicem (RLX), and Ketac Cem Aplicap (KC). Inlays were pre-etched with IPS Ceramic etching gel for 60s. After 48 h, two disks of ca 1.0 mm thickness, one of superficial and the other of deep dentin, were push-out tested in a universal testing machine at a crosshead speed of 1.0 mm/min. The mode of failure was determined under a stereomicroscope at 20X. Data were analyzed with one way ANOVA, and Scheffé's test was used for post-hoc comparisons (α = 0.05). RESULTS: There were no significant differences in shear bond strength between Class I and Class II cavities for the dual-curing system in light-curing mode (VL=MLS=RLX), except that RLX demonstrated greater bond strength to deep dentin in Class II cavities. Bond strength values were significantly higher on deep than on superficial dentin. KC showed the worst result. Failures were mixed (adhesive/cohesive) for the resin luting cements and solely adhesive (cement/ceramic) for the glass-ionomer luting agent. CONCLUSION: Dual-curing etch-and-rinse or self-etching self-adhesive resin luting cements achieved greater bond strength when light curing was applied, with no differences between Class I and Class II cavities but higher values for deep vs superficial dentin. The weakest adhesion was obtained with glass-ionomer luting agent in both cavity types.

One-pot synthesis of triangular gold nanoplates allowing broad and fine tuning of edge length.

A photocatalytic approach was used to synthesize triangular nanoplates in aqueous solution. The synthesis is based on the reduction of a gold salt using a tin(iv) porphyrin as photocatalyst, cetyltrimethylammonium bromide (CTAB) as a stabilizing agent, and triethanolamine (TEA) as the final electron donor. The average edge length of the triangular nanoplates can be easily changed in the range 45-250 nm by varying the concentration of photocatalyst, and fine-tuning of the average edge length is achieved by varying the concentration of CTAB. Study of the mechanism of formation of the nanoplates by UV-vis and by transmission electron microscopy (TEM) shows that there is a first stage where formation of 5 nm seeds takes place, further growth is probably by fusion and by direct reduction of gold onto the preformed nanoparticles. The nanoparticles formed during the photocatalytic reduction of the gold precursor show an irregular shape that evolves to regular triangular nanoplates after ripening in solution for 24 h.

New insights into the use of magnetic force microscopy to discriminate between magnetic and nonmagnetic nanoparticles.

Magnetic force microscopy (MFM) is a very powerful technique, which can potentially be used to detect and localize the magnetic fields arising from nanoscopic magnetic domains, such as magnetic nanoparticles. However, in order to achieve this, we must be able to use MFM to discriminate between magnetic forces arising from the magnetic nanoparticles and nonmagnetic forces from other particles and sample features. Unfortunately, MFM can show a significant response even for nonmagnetic nanoparticles, giving rise to potentially misleading results. The literature to date lacks evidence for MFM detection of magnetic nanoparticles with nonmagnetic nanoparticles as a control. In this work, we studied magnetite particles of two sizes and with a silica shell, and compared them to nonmagnetic metallic and silica nanoparticles. We found that even on conducting, grounded substrates, significant electrostatic interaction between atomic force microscopy probes and nanoparticles can be detected, causing nonmagnetic signals that might be mistaken for a true MFM response. Nevertheless, we show that MFM can be used to discriminate between magnetic and nonmagnetic nanoparticles by using an electromagnetic shielding technique or by analysis of the phase shift data. On the basis of our experimental evidence we propose a methodology that enables MFM to be reliably used to study unknown samples containing magnetic nanoparticles, and correctly interpret the data obtained.

On the structural diversity of sialoliths.

Sialoliths from parotid and submaxillar glands have been characterized. Fractured and polished surfaces revealed an intrinsic structural diversity across the calculi sections. In general, the calculi presented highly mineralized amorphous-looking cores surrounded by concentric alternating mineralized and organic layers. The thickness of these layers decreased from the outer regions toward the center of the sialolith, illustrating a sequence of growth stages. Nevertheless, a significant variability could be detected among the specimens. In some cases, the calculi displayed multiple cores and lacked concentric laminated structures. In other instances, the specimens exhibited extensive regions of globular structures. In these cases, the globule diameter decreased across the radius toward the center of the sialoliths, and the globular structures tended to reorganize, forming bright and dark laminated layers surrounding the core. The participation of globular structures in the layer formation process points to morphogenetic mechanisms not previously described.