164 research outputs found
Synthesis of geopolymer from spent FCC: Effect of SiO2/Al2O3 and Na2O/SiO2 molar ratios
This paper assesses the feasibility of using a spent fluid catalytic cracking catalyst (SFCC) as precursor for the production of geopolymers. The mechanical and structural characterization of alkali-activated SFCC binders formulated with different overall (activator + solid precursor) SiO2/Al2O3 and Na2O/SiO2 molar ratios are reported. Formation of an aluminosilicate ‘geopolymer’ gel is observed under all conditions of activation used, along with formation of zeolites. Increased SiO2/Al2O3 induces the formation of geopolymers with reduced mechanical strength, for all the Na2O/SiO2 ratios assessed, which is associated with excess silicate species supplied by the activator. This is least significant at increased alkalinity conditions (higher Na2O/SiO2 ratios), as larger extents of reaction of the spent catalyst are achieved. SiO2/Al2O3 and Na2O/SiO2 ratios of 2.4 and 0.25, respectively, promote the highest compressive strength (67 MPa). This study elucidates the great potential of using SFCC as precursor to produce sustainable ceramic-like materials via alkali-activation
Dynamical locality of the nonminimally coupled scalar field and enlarged algebra of Wick polynomials
We discuss dynamical locality in two locally covariant quantum field
theories, the nonminimally coupled scalar field and the enlarged algebra of
Wick polynomials. We calculate the relative Cauchy evolution of the enlarged
algebra, before demonstrating that dynamical locality holds in the nonminimally
coupled scalar field theory. We also establish dynamical locality in the
enlarged algebra for the minimally coupled massive case and the conformally
coupled massive case.Comment: 39p
I Congreso internacional de la SECAH. Ex officina Hispana. Cádiz Mayo 2011
Acta del I Congreso Internacional de la Sociedad de Estudios de Cerámica antigua en Hispani
Deformations of quantum field theories on spacetimes with Killing vector fields
The recent construction and analysis of deformations of quantum field
theories by warped convolutions is extended to a class of curved spacetimes.
These spacetimes carry a family of wedge-like regions which share the essential
causal properties of the Poincare transforms of the Rindler wedge in Minkowski
space. In the setting of deformed quantum field theories, they play the role of
typical localization regions of quantum fields and observables. As a concrete
example of such a procedure, the deformation of the free Dirac field is
studied.Comment: 35 pages, 3 figure
Electromyography: a simple and accessible tool to assess physical performance and health during hypoxia training. A systematic review
Hypoxia causes reduced partial pressure of oxygen in arterial blood and induces
adaptations in skeletal muscle that may affect individuals’ physical performance and muscular
health. These muscular changes are detectable and quantifiable by electromyography (EMG),
an instrument that assesses electrical activity during active contraction at rest. EMG is a relatively
simple and accessible technique for all patients, one that can show the degree of the sensory and
motor functions because it provides information about the status of the peripheral nerves and muscles.
The main goal of this review is to evaluate the scientific evidence of EMG as an instrument for
monitoring different responses of skeletal muscles subjected to external stimuli such as hypoxia and
physical activity. A structured search was conducted following the Preferred Reporting Items for
Systematic Review and Meta-Analyses (PRISMA) guidelines in Medline/PubMed, Scielo, Google
Scholar, Web of Science, and Cochrane Library Plus. The search included articles published in the last
25 years until May 2020 and was restricted to English- and Spanish-language publications. As such,
investigators identified nine articles that met the search criteria. The results determined that EMG
was able to detect muscle fatigue from changes in the frequency spectrum. When a muscle was
fatigued, high frequency components decreased and low frequency components increased. In other
studies, EMG determined muscle activation increased during exercise by recruiting motor units and
by increasing the intensity of muscle contractions. Finally, it was also possible to calculate the mean
quadriceps quadratic activity used to obtain an image of muscle activation. In conclusion, EMG offers
a suitable tool for monitoring the different skeletal muscle responses and has sufficient sensitivity to
detect hypoxia-induced muscle changes produced by hypoxic stimuli. Moreover, EMG enhances an
extension of physical examination and tests motor-system integrity
Evidencias arqueológicas de desplomes paramentales traumáticos en las Termas Marítimas de Baelo Claudia. Reflexiones arqueosismológicas
Durante los años 2011 a 2013 se han localizado, identificado y excavado parcialmente los restos de un nuevo complejo termal en la ciudad hispanorromana de Baelo Claudia (Tarifa, Cádiz), situado en el suburbium occidental de la ciudad, junto a la línea de costa. Denominadas Termas Marítimas, construidas en la primera mitad del s. II d.C. y abandonadas en época de Diocleciano/Constantino han sido excavadas estratigráficamente con detalle, habiéndose detectado la existencia de fases anteriores (que se remontan al s. II a.C.) y una continuidad de uso del ambiente en época tardorromana y moderna, vinculada con la explotación de los recursos marinos. Especialmente singular ha sido la constatación del desplome traumático de parte de los paramentos de las habitaciones del edificio en dos momentos concretos: por un lado en la Antigüedad Tardía (500 d.C. circa), ya que una unidad muraria de una de las habitaciones (H-3), anexa a la natatio, se localizó completamente derrumbada sobre el suelo, conexionada; y por otro, el desplome del muro oeste de la natatio y el oriental de la cisterna, estructuras de más de seis metros de longitud y cuatro de altura mínima conservada, desplomadas sobre los niveles de abandono del asentamiento en época bajomedieval o moderna (ss. XIV-XV d.C.). Se trata en ambas ocasiones de colapsos estructurales no habituales en circunstancias normales en los procesos de sedimentación arqueológica, por lo que es muy probable que su desplome se pueda vincular con eventos sísmicos u otras causas naturales similare
Threading through Macrocycles Enhances the Performance of Carbon Nanotubes as Polymer Fillers
Mindfulness-based program for anxiety and depression treatment in healthcare professionals: A pilot randomized controlled trial
In primary health care, the work environment can cause high levels of anxiety and depression, triggering relevant expert and individual change. Mindfulness-Based Stress Reduction (MBSR) programs reduce signs of anxiety and depression. The purpose of this sub-analysis of the total project, was to equate the effectiveness of the standard MBSR curriculum with the abbreviated version in minimizing anxiety and depression. This randomized controlled clinical trial enrolled 112 mentors and resident specialists from Family and Community Medicine and Nurses (FCMN), distributed across six teaching units (TU) of the Spanish National Health System (SNHS). Experimental group participants received a MBRS training (abbreviated/standard). Depression and anxiety levels were measured with the Goldberg Anxiety and Depression Scale (GADS) at three different time periods during the analysis: before (pre-test) and after (post-test) participation, as well as 3 months after the completion of intervention. Taking into account the pre-test scores as the covariate, an adjusted analysis of covariance (ANCOVA) showed significant depletion in anxiety and depression in general (F (2.91) = 4.488; p = 0.014; ¿2 = 0.090) and depression in particular (F (2, 91) = 6.653; p = 0.002; ¿2 = 0.128 at the post-test visit, maintaining their effects for 3 months (F (2.79) = 3.031; p = 0.050; ¿2 = 0.071—F (2.79) = 2.874; p = 0.049; ¿2 = 0.068, respectively), which is associated with the use of a standard training program. The abbreviated training program did not have a significant effect on the level of anxiety and depression. The standard MBSR training program had a positive effect on anxiety and depression and promotes long-lasting effects in tutors and resident practitioners. New research is needed to demonstrate the effectiveness of abbreviated versions of training programs. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
Theoretical characterisation of nanofluids based on metallic nanoparticles and organic oils
Equilibrium molecular dynamics simulation was used to model a nanofluid system composed of Cu nanoparticles and organic oils as base fluid (eutectic mixture of diphenyl oxide and biphenyl). The base fluid selected was an experimental fluid used as High Temperature-Heat Transfer Fluid in Concentrating Solar Power (CSP) plants. Thermodynamic properties as heat capacity and thermal conductivity were calculated and the results were compared with experimental data available. The comparison of some properties obtained from our simulated nanofluid system with experimental data let us to validate the model. The analysis of the Radial Function Distributions (RDFs) and the inspection of the Spatial Distribution Functions (SDFs) indicate the important role that plays the metal-oxygen interaction in the system. Dynamic properties as the diffusion coefficients of base fluid and nanofluid were computed according to Einstein relation by computing the mean square displacement (MSD).Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
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