First order transitions by conduction calorimetry: Application to deuterated potassium dihydrogen phosphate ferroelastic crystal under uniaxial pressure

The specific heat c and the heat power W exchanged by a Deuterated Potassium Dihydrogen Phosphate ferroelectric-ferroelastic crystal have been measured simultaneously for both decreasing and increasing temperature at a low constant rate (0.06 K/h) between 175 and 240 K. The measurements were carried out under controlled uniaxial stresses of 0.3 and 4.5±0.1 bar applied to face (110). At Tt=207.9 K, a first order transition is produced with anomalous specific heat behavior in the interval where the transition heat appears. This anomalous behavior is explained in terms of the temperature variation of the heat power during the transition. During cooling, the transition occurs with coexistence of phases, while during heating it seems that metastable states are reached. Excluding data affected by the transition heat, the specific heat behavior agrees with the predictions of a 2-4-6 Landau potential in the range of 4–15 K below Tt while logarithmic behavior is obtained in the range from Tt to 1 K below Tt. Data obtained under 0.3 and 4.5 bar uniaxial stresses exhibit the same behavior.Dirección General de Investigación Científica y Técnica. Gobierno de España-PB91-60

Quality assessment of sardines during storage by measurement of fluorescent compounds

5 páginas, 2 figuras, 5 tablasSardine alterations during chilled storage (0°C) were investigated by measuring the fluorescence ratio between two excitation/emission maxima (393/463 nm, 327/415 nm) and compared with common quality indices. Sardines were also maintained at 15°C to accelerate all reactions occurring at 0°C. Other quality indices (total volatile base-nitrogen, free fatty acids, formation of conjugated dienes, and thiobarbituric acid values) were determined and the use of the fluorescence ratio (fluorescence shift, δF) was analyzed. A high correlation was found between the δF and the total volatile base-nitrogen (r = 0.93, at 0°C; r = 0.92, at 15°C).Xunta de Galicia (Project XUGA 402 01B93).Peer reviewe

Speaker recognition under stress conditions

Proceeding of: IberSPEECH 2018, 21-23 November 2018, Barcelona, SpainSpeaker recognition systems exhibit a decrease in performance when the input speech is not in optimal circumstances, for example when the user is under emotional or stress conditions. The objective of this paper is measuring the effects of stress on speech to ultimately try to mitigate its consequences on a speaker recognition task. On this paper, we develop a stress-robust speaker identification system using data selection and augmentation by means of the manipulation of the original speech utterances. An extensive experimentation has been carried out for assessing the effectiveness of the proposed techniques. First, we concluded that the best performance is always obtained when naturally stressed samples are included in the training set, and second, when these are not available, their substitution and augmentation with synthetically generated stress-like samples, improves the performance of the system.This work is partially supported by the Spanish Government-MinECo projects TEC2014-53390-P and TEC2017-84395-P

Nanoestruturas bidimensionais de MoSe2: de triângulos a fractais

Tese de mestrado integrado, Engenharia Física, Universidade de Lisboa, Faculdade de Ciências, 2021The semiconductor transition metal dichalcogenides (TMDs) are materials, with chemical formula MX2, where M represents the transition metal (M: Mo, W) and X the chalcogen (X: S, Se, Te). These materials have been studied intensively in recent years due to the appearance of attractive physical, chemical and electronic properties when they reach the monolayer thickness, such as high electronic mobility and direct band gap between 1 and 2 eV. This value is comparable to that of silicon, which makes them promising candidates for the development of new electronic and optoelectronic devices. The morphology of the monolayers influences the performance of these compounds. For instance, the triangular shape in domains of high lateral dimension is desirable for electronic applications, while a morphology with a high number of active sites favors the use of TMDs in catalytic applications such as the hydrogen evolution reaction (HER). Within the TMDs, MoSe2 has attracted a lot of interest, because in addition to being a semiconductor material, it also has a high optical absorption. The chemical vapor deposition (CVD) technique has proved to be the preferred MoSe2 synthesis methodology, because it provides better control over experimental parameters and a higher yield at a lower cost. However, the height of the MoSe2 monolayers belongs to the nanometric scale and during the synthesis of MoSe2 by CVD there is competition between lateral and vertical growth. For this reason, an in¬depth study of the most relevant experimental synthesis parameters is necessary, in addition to the temperature profile of the furnace, which guarantees the maintenance of the monolayers growth temperature. Currently, the growth mechanisms of MoSe2 monolayers are not fully understood and the optimization of the system is far from being achieved, which would ensure the quality and reproducibility of the results. In this work, the influence of the total flow rate of argon and hydrogen, the partial flow of hydrogen, the growth time, the ratio of the precursor masses and the geometry and position of the substrate were investigated, based on several characterization techniques such as optical microscopy, scanning electron microscopy (SEM), energy¬dispersive X¬ray spectroscopy (EDS), atomic force microscopy (AFM) and Raman spectroscopy. Triangles and hexagons with high lateral dimension were obtained for gas flow rates between 50 and 80 sccm. The largest approximately equilateral triangle was about 40 µm in lateral size, synthesized with ≈ 0.6 g of selenium and ≈ 0.08 g of MoO3, a total gas flow rate of 70 sccm, a relative percentage of hydrogen of 12.50% and a growth time of 15 minutes. The highest average lateral size obtained was 5.30 µm for the same masses and the same total flow rate, but for a relative hydrogen percentage of 17.50% and a growth time of 10 minutes. For a high flow rate (ϕ =200 sccm) morphological transitions occur, resulting in fractal nanostructures that can be irregular or dendritic, depending on the mass ratio of the precursors. The correlation between experimental parameters and morphological results provides greater control over lateral size, nucleation density and thickness at the nanometer scale. Therefore, future step would be the characterization of the monolayers by photoluminescence in order to determine their optical band gap and evaluate their crystalline quality.Os dicalcogenetos de metais de transição (TMDs) semicondutores são materiais com fórmula química MX2, em que M representa o metal de transição (M: Mo, W) e X o calcogénio (X: S, Se, Te). Estes materiais têm sido estudados intensivamente nos últimos anos devido ao aparecimento de atrativas propriedades físicas, químicas e eletrónicas quando atingem a espessura de monocamada, tais como elevada mobilidade eletrónica e hiato de energia direto entre 1 e 2 eV, comparável ao do silício, o que os tornam candidatos perfeitos para o desenvolvimento de novos dispositivos eletrónicos e optoeletrónicos. A morfologia das monocamadas influencia o desempenho destes compostos. Por exemplo, a forma triangular em domínios de elevada dimensão lateral é desejável para aplicações eletrónicas, enquanto uma morfologia com um elevado número de locais ativos favorece a utilização dos TMDs em aplicações catalíticas como a reação de evolução do hidrogénio (HER). Dentro dos TMDs, o MoSe2 suscitou bastante interesse porque, para além de ser um material semicondutor, apresenta uma elevada absorção óptica. A técnica de deposição química em fase vapor (CVD) tem¬se revelado a metodologia de síntese de MoSe2 mais favorável, porque proporciona um melhor controlo nos parâmetros experimentais e um rendimento mais elevado a um menor custo. Porém, a espessura das monocamadas de MoSe2 situa¬se na escala nanométrica e, durante a síntese de MoSe2 por CVD, ocorre a competição entre o crescimento lateral e vertical. Por este motivo é necessário um estudo aprofundado dos parâmetros experimentais de síntese mais relevantes para além do perfil de temperatura do forno utilizado que garante a manutenção da temperatura dos precursores durante o crescimento das monocamadas. Atualmente, os mecanismos de crescimento das monocamadas de MoSe2 não são totalmente compreendidos e a optimização do sistema encontra¬se longe de ser alcançada, o que permitiria assegurar a qualidade e a reprodutibilidade dos resultados. Neste trabalho foi investigada a influência do fluxo total de árgon e hidrogénio, do fluxo parcial de hidrogénio, do tempo de crescimento, da razão das massas dos precursores e da geometria e posição do substrato, fundamentada em diversas técnicas de caraterização como microscopia óptica, microscopia eletrónica de varrimento (SEM), espetroscopia de raios X por dispersão em energia (EDS), microscopia de força atómica (AFM) e espetroscopia Raman. Triângulos e hexágonos de elevada dimensão lateral foram obtidos para fluxos entre 50 e 80 sccm. O maior triângulo aproximadamente equilátero possuía cerca de 40 µm de aresta, sintetizado com ≈ 0,6 g de selénio e ≈ 0,08 g de MoO3, um fluxo total de 70 sccm, uma percentagem relativa de hidrogénio de 12,50% e um tempo de crescimento de 15 minutos. O tamanho lateral médio mais elevado obtido foi de 5,30 µm para as mesmas massas e o mesmo fluxo total, mas para uma percentagem relativa de hidrogénio de 17,50% e um tempo de crescimento de 10 minutos. Para um fluxo elevado (ϕ =200 sccm) ocorrem transições morfológicas surgindo nanoestruturas fratais que podem ser irregulares ou dendríticas, conforme a razão da massa dos precursores. O encadeamento entre os parâmetros experimentais e os resultados morfológicos fornece um maior controlo no tamanho lateral, na densidade de nucleação e na espessura à escala nanométrica. Por conseguinte, a etapa futura seria a caraterização das monocamadas por fotoluminescência de forma a determinar o hiato de energia e avaliar a qualidade cristalina

Spark Plasma Sintered Zirconia Ceramic Composites with Graphene-Based Nanostructures

The addition of graphene-based nanostructures (GBNs) can improve the inherent fragility of ceramics and provide them with improved electrical and thermal conductivities. However, both the starting material (ceramic matrix and GBNs) and the processing/sintering approach are crucial for the final composite microstructure and properties. This work focuses on the influence of the content and dimensions of the GBN filler (10 and 20 vol%; 3 and ~150 layers), the powder-processing conditions (dry versus wet), and the homogenization method (ultrasound sonication versus high-energy planetary ball milling) on GBN/tetragonal zirconia (3YTZP) composites. The microstructure and electrical properties of the spark plasma sintered (SPS) composites were quantified and analyzed. The highest microstructural homogeneity with an isotropic microstructure was achieved by composites prepared with thicker GBNs milled in dry conditions. A high content (20 vol%) of few-layered graphene as a filler maximizes the electrical conductivity of the composites, although it hinders their densification.Ministerio de Economía y Competitividad MAT2015-67889-P

Phase coexistence in highly deuterated ferroelectric triglycine selenate: Landau description

The phase transition in a 90% deuterated sample of TGSe has been investigated by calorimetric and dielectric measurements. As a consequence of the presence of an internal crack in the sample, the transition takes place in two stages separated by an interval where the paraelectric and the ferroelectric phases coexist without latent heat contribution. From the latent heat, the specific heat excess and the Curie law for the dielectric constant, it is shown that the transition follows a 2-4-6 Landau potential, whose coefficients are determined. This potential describes completely all the data, including those corresponding to the coexistence interval.Dirección General de Investigación Científica y Técnica (DGICYT) FIS2005-0244

Successful restoration of corneal surface integrity with a tissue-engineered allogeneic implant in severe keratitis patients

Objectives: Corneal diseases are among the main causes of blindness, with approximately 4.6 and 23 million patients worldwide suffering from bilateral and unilateral corneal blindness, respectively. The standard treatment for severe corneal diseases is corneal transplantation. However, relevant disadvantages, particularly in high-risk conditions, have focused the attention on the search for alternatives. Methods: We report interim findings of a phase I-II clinical study evaluating the safety and preliminary efficacy of a tissue-engineered corneal substitute composed of a nanostructured fibrin-agarose biocompatible scaffold combined with allogeneic corneal epithelial and stromal cells (NANOULCOR). 5 subjects (5 eyes) suffering from trophic corneal ulcers refractory to conventional treatments, who combined stromal degradation or fibrosis and limbal stem cell deficiency, were included and treated with this allogeneic anterior corneal substitute. Results: The implant completely covered the corneal surface, and ocular surface inflammation decreased following surgery. Only four adverse reactions were registered, and none of them were severe. No detachment, ulcer relapse nor surgical re-interventions were registered after 2 years of follow-up. No signs of graft rejection, local infection or corneal neovascularization were observed either. Efficacy was measured as a significant postoperative improvement in terms of the eye complication grading scales. Anterior segment optical coherence tomography images revealed a more homogeneous and stable ocular surface, with complete scaffold degradation occurring within 3–12 weeks after surgery. Conclusions: Our findings suggest that the surgical application of this allogeneic anterior human corneal substitute is feasible and safe, showing partial efficacy in the restoration of the corneal surface.Biobank of the Andalusian Public Health Syste

Optimizing the homogenization technique for graphene nanoplatelet/yttria tetragonal zirconia composites: Influence on the microstructure and the electrical conductivity

3 mol% yttria tetragonal zirconia polycrystalline (3YTZP) ceramic composite powders with 10 vol% nominal content of graphene nanoplatelets (GNPs) were prepared using four different homogenization routines: dispersion of the powder mixture by ultrasonication in isopropyl alcohol, homogenization in a high-energy planetary ball mill in wet or dry conditions after ultrasonication, and milling of the powders in a high-energy planetary ball mill in dry conditions. A significant effect of the homogenization routine on the powders particle size distribution was revealed by laser granulometry and Raman spectroscopy. Highly densified composites were obtained after spark plasma sintering (SPS) and remarkable differences on the GNP size, shape and distribution throughout the ceramic matrix and also in the electrical conductivity were observed in the four different composites. The composite with the best performance in terms of electrical conductivity was the one prepared after planetary ball milling of the powders in dry conditions as a consequence of the reduced dimensions of the GNPs and their excellent distribution throughout the ceramic matrix.Ministerio de Economía y Competitividad MAT2015-67889-

Promoting higher added value to a finfish species rejected to sea

332 páginas.-- José Ramón Fuertes ... et al.This project aimed to the development of the research and the technology necessary to promote higher added value to fishing activity. This is to be achieved by obtaining profit from a finfish species (“Rockcod”, Patagonotothen spp.) not known to consumers and currently discarded by the EU fishing fleet operating in the South West Atlantic, in order to supply the EU seafood industry with a good quality raw material for human food manufacturing. Use of this species, caught as a by-catch in the existing fisheries targeting hakes and cephalopods, should also increase the profitability of the fleet, contribute to maintaining employment and help to counterbalance the negative effects of fishing activity and discards in the ecosystem. The main scientific-technological objectives and expected achievements were the following: - Description of the fisheries - Improved knowledge of the biology of the species - Biomass assessment - Estimation of catches and discards - Analysis of the spatial and temporal distribution of the resource. Fishery forecasting and testing - Sensorial, Microbiological, Nutritional and Biochemical Evaluation of Rock cod - Development of the technical modifications on board commercial vessels - Development of new processed products from frozen Rock codContract number Q5CR-2002-71709Peer reviewe