A comprehensive study of a versatile magnetic refrigeration demonstrator

A versatile room temperature reciprocating magnetic refrigeration demonstrator has been designed, built and tested in order to evaluate the influence of different running parameters and to check suitable magnetocaloric materials for cooling at room temperature. A comprehensive study has been done with Gd spheres of 0.2-0.4 mm diameter arranged as a double regenerator with 15 g each. A Halbach Nd2e14B permanent magnet with a slot of 10 mm width has been used to generate the magnetic field with a maximum value of 1.4 T. The heat transfer fluid is a mixture of water and ethylene glycol in a 75-25 percentage. The demonstrator achieves a maximum no-load temperature span close to 20 K, with a regeneration ratio of ¿ = 4.1, and a maximum cooling power Qc=6 W at zero temperature span. COP values have been shown and different thermodynamic AMR cycles have been studied looking for the best parameters

Determinación espectrofotométrica de diacetilo en mantequilla previa formación del complejo diacetil diisonicotin hidrazona-Zr(IV)

A new spectrophotometric method for determination of diacetyl has been developed. This method make use of the abili ty of diacetyl to react with isoniazid forming diacetyl diisonicotin hydrazone. This hydrazone then complexes Zr (IV) at acid pH (1,7) giving rise to a yellow and soluble chelate. The molar absorptivity is 1,7.104 l mol-1 cm-1. Themethodhas been applied tothemeasure of diacetyl in butter.Se ha desarrollado un nuevo método espectrofotométrico para la determinación de diacetilo. Se basa en la formación de diacetildiisonicotin hidrazona por reacción de diacetilo con isoniacida. La hidrazona compleja con Zr (IV) a pH ácido (1,7) formando un quelato amarillo y soluble. La absortividad molar es 1,7.104 l.mol-1 cm-1 a 410 nm. El método ha sido aplicado a la determinación de diacetilo en mantequilla

Determinación espectrofotométrica de diacetilo en mantequilla previa formación del complejo diacetil diisonicotin hidrazona-Zr(IV)

Se ha desarrollado un nuevo método espectrofotométrico para la determinación de diacetilo. Se basa en la formación de diacetildiisonicotin hidrazona por reacción de diacetilo con isoniacida. La hidrazona compleja con Zr (IV) a pH ácido (1,7) formando un quelato amarillo y soluble. La absortividad molar es 1,7.1041.mol·1 cm·1 a 410 nm. El método ha sido aplicado a la determinación de diacetilo en mantequilla.A new spectrophotometric method for determination of diacetyl has been developed. This method make use of the abili ty of diacety 1 to react with isoniazid forming diacetyl diisonicotin hydrazone. This hydrazone then complexes Zr (IV) at acid pH ( 1, 7) giving rise to a yellow and soluble chelate. The molar absorptivity is 1, 7.1041 mol·1 cm·l. Themethodhas been applied tothemeasure of diacetyl in butter

Shedding Light on the Chemical Diversity of Ectopic Calcifications in Kidney Tissues: Diagnostic and Research Aspects

In most industrialized countries, different epidemiologic studies show that chronic renal failure is dramatically increasing. Such major public health problem is a consequence of acquired systemic diseases such as type II diabetes, which is now the first cause for end stage renal failure. Furthermore, lithogenic diseases may also induce intratubular crystallization, which may finally result in end-stage renal failure (ESRF). Up to now, such rare diseases are often misdiagnosed. In this study, based on twenty four biopsies, we show that SR µFTIR (Synchrotron Radiation-µFourier transform infrared) spectroscopy constitutes a significant opportunity to characterize such pathological µcalcifications giving not only their chemical composition but also their spatial distribution in the tissues. This experimental approach offers new opportunities to the clinicians to describe at the cell level the physico-chemical processes leading to the formation of the pathological calcifications which lead to ESRF

Reconocimiento de niveles de razonamiento algebraico en primaria y secundaria

Se propone la realización de un taller para promover en los profesores de primaria y secundaria el desarrollo de conocimientos para discriminar objetos algebraicos y el reconocimiento de distintos niveles de algebrización de la actividad matemática escolar. La actividad práctica a realizar se basa en la resolución de un conjunto de tareas que ponen en juego conocimientos didácticomatemáticos sobre razonamiento algebraico elemental y la puesta en común de las soluciones. La visión ampliada del álgebra escolar que se propone desarrollar tiene en cuenta los procesos de generalización, simbolización, modelización estructural y funcional, así como el cálculo analítico, y permite una articulación coherente entre el pensamiento algebraico en educación primaria y secundaria

Absolute polarimetric calibration of the retardance of a liquid crystal on silicon microdisplay

The phase-shift exhibited by liquid crystal on silicon devices (LCoS) depends on the voltage applied and the illumination wavelength. Most of the LCoS used in the labs are digitally addressed using a binary pulse width modulated signal. Usually, these devices are characterized for a very small range of the available binary voltage values and for specific wavelengths. In this work, we consider a commercial parallel-aligned liquid crystal on silicon device (PA-LCoS) in which the binary voltages are accessible through the software of the vendor. We perform a complete averaged Stokes polarimetric characterization of the device where we are able to obtain the absolute unwrapped retardance values for a wide range of voltage parameters and across the visible spectrum. This provides a practical approach to evaluate the whole range of phase modulation possibilities, and to analyze some issues related with the physics of the device.Funded by the “Generalitat Valenciana” (Spain) (IDIFEDER/2021/014, cofunded by EU through FEDER Programme; and PROMETEO/2021/006), “Ministerio de Ciencia e Innovación” (Spain) (PID2021-123124OB-I00, PID2019-106601RB-I00). ARS-M thanks the “Generalitat Valenciana” for the grant (GRISOLIAP/2021/106)

Diseño de un cuestionario para evaluar conocimientos didáctico-matemáticos sobre razonamiento algebraico elemental

La promoció del pensament algebraic en alumnes de primària requereix implementar accions formatives específiques per als professors, la qual cosa al seu torn implica elaborar instruments d'avaluació de l'estat dels seus coneixements didàctic - matemàtics sobre el tema. En aquest treball presentem resultats de l'estudi realitzat per a la construcció d'un qüestionari d'avaluació dels coneixements didàctic - matemàtics d'estudiants de magisteri sobre raonament algebraic elemental. Descrivim les categories de coneixements algebraics tingudes en compte (estructures, funcions i modelització) i les categories de coneixements didàctics (facetes epistèmica, cognitiva, instruccional i ecològica). Així mateix es descriuen i analitzen les tasques incloses en el qüestionari informant de la validesa de contingut del mateix.Promoting algebraic thinking in elementary school pupils requires implementing specific training activities for teachers, which in turn involves developing tools to assess their didactic-mathematical knowledge about this subject. In this paper we present results of a study aimed to build a questionnaire for assessing the didactic-mathematic knowledge of prospective primary teachers on elementary algebraic reasoning. We describe the categories of algebraic knowledge (structures, functions and modeling), as well as the categories of didactical knowledge (epistemic, cognitive, instructional and ecological facets) taken into account. We also describe and analyze the tasks included in the questionnaire reporting its content validity.La promoción del pensamiento algebraico en alumnos de primaria requiere implementar acciones formativas específicas para los profesores, lo que a su vez implica elaborar instrumentos de evaluación del estado de sus conocimientos didáctico - matemáticos sobre el tema. En este trabajo presentamos resultados del estudio realizado para la construcción de un cuestionario de evaluación de los conocimientos didáctico - matemáticos de estudiantes de magisterio sobre razonamiento algebraico elemental. Describimos las categorías de conocimientos algebraicos tenidas en cuenta (estructuras, funciones y modelización) y las categorías de conocimientos didácticos (facetas epistémica, cognitiva, instruccional y ecológica). Así mismo se describen y analizan las tareas incluidas en el cuestionario informando de la validez de contenido del mismo

Parameter analysis for LCoS devices as a function of the voltage and wavelength

A model describing the parameter and wavelength dependencies not only of retardance, but also its flicker in liquid-crystal-on-silicon spatial light modulators (LCoS SLMs), is presented. We provide results for different digital addressing sequences producing different levels of flicker.Work funded by Generalitat Valenciana (Spain) (PROMETEO/2021/006, IDIFEDER/2021/014, cofunded by European Union through the FEDER Programme GV/2019/021); and Universidad de Alicante (Spain), projects GRE17-06 and UATALENTO 18-10