An assessment of contact and laser-based scanning of rock particles for railway ballast

Performance of traditional railway structure depends significantly on the behaviour of its support layers, particularly the ballast. This layer’s rock particles are selected to ensure high mechanical strength, but traffic and mechanical maintenance break and wear the particles. Consequently, the layer incurs permanent deformations that degrade its strength and increase deformability and permeability. Particle physical characteristics, in particular those related to size and shape, influence their fragmentation and wear and must be studied accordingly. In addition, structural numerical models that represent individual particles, such as the discrete element method, have been increasingly used to model the infrastructure and therefore detailed geometrical characterization in the form of 3D digital models of the particles are necessary. This work contributes to this goal by investigating a contact-based cost-effective method that digitizes particle form and allows the determination of their geometric parameters. This method is described, compared with well-established laser scanning technique and then applied to study degradation of particles in Los Angeles and microDeval fragmentation tests.info:eu-repo/semantics/publishedVersio

Luminescent and Scintillating Properties of Lanthanum Fluoride Nanocrystals in Response to Gamma/Neutron Irradiation: Codoping with Ce Activator, Yb Wavelength Shifter, and Gd Neutron Captor

A novel concept for detection and spectroscopy of gamma rays, and detection of thermal neutrons based on codoped lanthanum fluoride nanocrystals containing gadolinium is presented.The trends of colloidal synthesis of the mentioned material, LaF3 co-doped with Ce as the activator, Yb as the wavelength-shifter and Gd as the neutron captor, is reported. Nanocrystals of the mentioned material were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), optical absorption, and photoluminescence spectroscopy. Gamma detection and its potential spectroscopy feature have been confirmed. The neutron detection capability has been confirmed by experiments performed using a 252Cf neutron source.Comment: 5 figures, 16 page

Genomic Evolution of Two Acinetobacter baumannii Clinical Strains from ST-2 Clones Isolated in 2000 and 2010 (ST-2_clon_2000 and ST-2_clon_2010)

Acinetobacter baumannii is a successful nosocomial pathogen due to its ability to persist in hospital environments by acquiring mobile elements such as transposons, plasmids, and phages. In this study, we compared two genomes of A. baumannii clinical strains isolated in 2000 (ST-2_clon_2000) and 2010 (ST-2_clon_2010) from GenBank project PRJNA308422

Clival chordomas: The endoscopic transnasal transsphenoidal approach

Os cordomas da base do crânio são tumores raros, localmente destrutivos, que constituem um desafio cirúrgico pela proximidade a estruturas neurovasculares vitais e ao elevado potencial de recidiva. Os autores descrevem o caso de uma mulher de 45 anos, com quadro de cefaleias, anisocória e diplopia, com cinco meses de evolução, cujos exames complementares de diagnóstico revelaram uma volumosa lesão expansiva dos 2/3 superiores do clivus, com preenchimento do seio esfenoidal, destruição selar e extensão para ambos os seios cavernosos. Procedeu-se a excisão da lesão, após biopsia diagnóstica compatível com cordoma, por abordagem endoscópica endonasal transesfenoidal (EET), guiada por neuronavegação. Com 3 meses de seguimento, a doente encontra-se clinicamente bem e a ressonância magnética revela eventual resíduo tumoral no seio cavernoso direito. A cirurgia EET constitui uma alternativa minimamente invasiva na abordagem de lesões expansivas da base do crânio, possibilitando, em casos seleccionados, resultados similares e com menor morbilidade, relativamente às técnicas cirúrgicas clássicas.info:eu-repo/semantics/publishedVersio

Fock quantization of a scalar field with time dependent mass on the three-sphere: unitarity and uniqueness

We study the Fock description of a quantum free field on the three-sphere with a mass that depends explicitly on time, also interpretable as an explicitly time dependent quadratic potential. We show that, under quite mild restrictions on the time dependence of the mass, the specific Fock representation of the canonical commutation relations which is naturally associated with a massless free field provides a unitary dynamics even when the time varying mass is present. Moreover, we demonstrate that this Fock representation is the only acceptable one, up to unitary equivalence, if the vacuum has to be SO(4)-invariant (i.e., invariant under the symmetries of the field equation) and the dynamics is required to be unitary. In particular, the analysis and uniqueness of the quantization can be applied to the treatment of cosmological perturbations around Friedmann-Robertson-Walker spacetimes with the spatial topology of the three-sphere, like e.g. for gravitational waves (tensor perturbations). In addition, we analyze the extension of our results to free fields with a time dependent mass defined on other compact spatial manifolds. We prove the uniqueness of the Fock representation in the case of a two-sphere as well, and discuss the case of a three-torus.Comment: 30 page

Tribological study of FeCuCrgraphite alloy and cast iron railway brake shoes

[EN] A new class of materials is being installed in railway brake blocks to substitute classic cast iron in order to reduce the rolling noise produced by the roughness of the tread-wheel surface. The tribological properties of cast iron and Fe-Cu-Cr-graphite sintered alloy brake shoes were analyzed. Kinetic friction coefficient (mu) and wear were monitored by means of a pin-on-disc technique. The sintered alloy brake showed an increase in mu at higher braking velocities while the cast iron brake exhibited a decrease in mu. Wear was greater on the sintered alloy, explained by its low shear strength which decreased due to its low thermal conductivity. The roughness produced by the sintered brake shoes in wheel-tread surface was 10 times lower than that produced by cast iron. (c) 2009 Elsevier B.V. All rights reserved.Ferrer Giménez, C.; Pascual Guillamón, M.; Busquets Mataix, DJ.; Rayón, E. (2010). Tribological study of FeCuCrgraphite alloy and cast iron railway brake shoes. Wear. 268(5):784-789. doi:10.1016/j.wear.2009.12.014S784789268

Analysis of the perception of conflict and its positive resolution in university students

This research aimed to analyze the perception of conflict in universities and the ways of dealing with it in relation to the 17 Sustainable Development Goals of the United Nations. The research was developed from a quantitative approach in three universities in two European countries: the University of Murcia and Complutense University of Madrid (Spain) and University of Minho (Portugal). The sample consisted of 247 university students and the technique used was an ad hoc survey administered online. Among the main research results we can highlight that (a) the perception of conflict is mostly negative; (b) there are predictive variables in the positive view of conflict; and (c) university students clearly identify the peaceful resolution of conflicts with some of the Sustainable Development Goals. The main conclusions are that conflict is inherent to any organization and the university must be sensitive to the conflicts that occur within it. It is therefore necessary to create intra-university mediation services as a conflict resolution resource for the entire university community. Training and a positive view of conflict favors the construction of a citizenry capable of dialogue and of resolving the conflicts that arise in their adult life.This research work is the result of the Eramus+ LIMEdiat− Licence Européenne en Médiation pour l’Inclusion Sociale (European Degree in Mediation for Social Inclusion) project -2020-1-FR01-KA203-079934, with the participation of the University of Minho (Portugal), the University of Murcia (Spain), Conservatoire National des Arts et Métiers (CNAM) (France), and the Universitat Degli Studi di Cagliari (Italy). The total budget of the research project was 304,066 €

Uniqueness of the Fock quantization of fields with unitary dynamics in nonstationary spacetimes

The Fock quantization of fields propagating in cosmological spacetimes is not uniquely determined because of several reasons. Apart from the ambiguity in the choice of the quantum representation of the canonical commutation relations, there also exists certain freedom in the choice of field: one can scale it arbitrarily absorbing background functions, which are spatially homogeneous but depend on time. Each nontrivial scaling turns out into a different dynamics and, in general, into an inequivalent quantum field theory. In this work we analyze this freedom at the quantum level for a scalar field in a nonstationary, homogeneous spacetime whose spatial sections have $S^3$ topology. A scaling of the configuration variable is introduced as part of a linear, time dependent canonical transformation in phase space. In this context, we prove in full detail a uniqueness result about the Fock quantization requiring that the dynamics be unitary and the spatial symmetries of the field equations have a natural unitary implementation. The main conclusion is that, with those requirements, only one particular canonical transformation is allowed, and thus only one choice of field-momentum pair (up to irrelevant constant scalings). This complements another previous uniqueness result for scalar fields with a time varying mass on $S^3$, which selects a specific equivalence class of Fock representations of the canonical commutation relations under the conditions of a unitary evolution and the invariance of the vacuum under the background symmetries. In total, the combination of these two different statements of uniqueness picks up a unique Fock quantization for the system. We also extend our proof of uniqueness to other compact topologies and spacetime dimensions.Comment: 12 page

[The Importance of Early Referral in Pediatric Acute Liver Failure]

INTRODUCTION: Acute liver failure is a rare disorder associated to high morbidity and mortality despite survival improvement through liver transplantation. The importance of a multidisciplinary approach and early referral to a pediatric liver transplantation center were important conclusions of a national meeting in 2008, from which resulted an actuation consensus. OBJECTIVES: To characterize acute liver failure admissions in a Pediatric Intensive Care Unit of the portuguese pediatric livertransplantation center. To compare results before (A) and after (B) 2008. MATERIAL AND METHODS: Observational, retrospective study during a 20 year period (1994-2014). INCLUSION CRITERIA: age < 18 years old and acute liver failure (INR ≥ 2 without vitamin K response and hepatocellular necrosis). Children with previous liver disease were excluded. RESULTS: Fifty children were included, with median age of 24.5 months. The most common etiology under 2 years old was metabolic (34.6%) and above that age was infectious (29.2%). Forty six percent were submitted to liver transplantation and 78% of them survived. Overall mortality was 34%. Median referral time was 7 days in period A (n = 35) and 2 days in period B (n = 15; p = 0.006). Pediatric risk of mortality's median was 14.7 in period A and 6.5 in B (p = 0.019). Mortality was 37% vs 26% in periods A and B, respectively (p = 0.474). DISCUSSION AND CONCLUSIONS: Overall mortality was similar to the observed in other European centers. Liver transplantation is in fact the most effective therapeutic option. After 2008, there was a reduction in referral time and cases severity on admission; however, mortality has not reduced so far.info:eu-repo/semantics/publishedVersio