Dynamic phenomena in superconducting oxides by ESR

Dynamic electron spin resonance (ESR) measurements compare the paramagnetic and antiferromagnetic (AF) properties of superconducting oxides in the range 4 K to room temperature, at 8 MHz and 9.36 GHz. Two are derivatives of YBa2Cu30 7: 1: Nd(Nd0.05Ba0.95 )2Cu30 7, Te0 =72 K and II: Y0.2Cao.8Sr2[Cu2(Tlo.5Pb0.5 )]07, Te0 =108 K and two are cases where AF ordering dominates the weak superconductivity: III: Nb01.1\u3e 1. 25 ~Teo~ 10 K and IV: La2Ni04.00, 70 K :::: Teo:::: 40 K. At temperatures 298:::: T:::: 64 K, the ESR absorption by I indicates orthorhombic symmetry. The peaks at Ke =2.06, gb =2.13, and Ka =2.24 are identified with the presence of 5% Nd3+( 41912 ) in the Ba layer because the characteristic Cu2+ impurity hyperfine structure is absent and the ESR signal disappears several degrees below Te. Near Te the ESR absorption is reduced by two orders of magnitude. Proximity effects give rise to interference fringes with period r1 ( T) independent of the field B and the rate of sweep dBzldt. ESR is observed below Te because flux penetrates the superconductor. The temperature dependence of r1 leads to an activation energy for the flux motion E0 (1)/R ~ 16 K and Ea (111)/R ~3 K =Te /4. In the superconducting state a coherent flux expulsion response to a change in B. from 500 mT to zero is observed in times T, = 8 to 10 s. The inverse rate of noise spikes due to flux expulsion, when the samples are cooled through Te in a magnetic field, varies from Tnoise=3.5 s for III to 21 s for IV. The microwave absorption spectra identify three temperature regimes: (i) For 3.5 K \u3c T \u3c T m T* \u3c Teo superconducting behavior was confirmed by the energy loss near zero magnetic field and the kinetics of high-field noise due to flux expulsion. Near g =2.00 ESR absorption is observed for all materials. A broad absorption near 50 to 100 mT at 9.36 GHz has been attributed to AF resonance. (ii) T m T* ~ T ~ Te identifies the range where flux motion gives rise to interference fringes in the ESR absorption. (iii) ESR and AF resonance are observed immediately after warming above Tc

Chemical analysis by X-ray spectroscopy near phase transitions in the solid state

The methods discussed in this work show that the types of changes which may be observed, by precise XAS measurements of Absorbance A versus temperature, across a phase transition are: the changes in the relaxation time of the final states due to fluctuations near a phase transition; the detection of the anomalous Bragg condition coupled to phonon modes XAS enhancement that identifies the temperature interval where the phonon modes are active, the symmetry changes which introduce new allowed transitions to finite states below an element edge, near Tc indicate what symmetry changes occur, and the method of XTDAFST0 = XAFS(T) - XAFS(T0), allows the precise measurement of the progressive changes in the Debye-Waller factor versus T near a phase transition, and identify (when no other structural changes occur, except in the vibrational modes of a specific bond) the bond responsible for the transition. The methods have been applied to the superconducting transition in layer cuprates and the metal to insulator transition in NiS2-xSex

The investigation of EPR paramagnetic probe line width and shape temperature dependence in high-temperature superconductors of Bi–Pb–Sr–Ca–Cu–O system

The work is related with the finding out of magnetic phases in strongly anisotropic high-temperature superconductor Bi1,7Pb0,3Sr2Ca2Cu3O10-δ in the temperature region where the superconductor is in the normal state. It was studied the temperature dependence of the paramagnetic probe EPR line width. In the normal state at T\u3eTc near 175 K it was revealed a pick in the temperature dependence of line width. In this region it was observed the time increase of the line width with the characteristic time ~ 17 min. This shows the possibility of magnetic phase formation in this material

Stereoscopic spherical panoramas

[EN] The advances in the field of digital imaging have expanded the horizons of panoramic photography, thanks to the development of stitching software, with which several images can be joined in a wide field of view panoramic image. The panoramas produced by stitching software can reach a field of view of 360 degrees horizontally and 180 degrees vertically, in case of a spherical panorama. This kind of panorama has a great potential representing the architecture, so it could be interesting to add a new dimension applying the stereoscopic vision foundations. Therefore, the article focusses these issues in order to provide an affordable photographic technique to capture spherical panoramas analyzing also their compatibility with the latest immersive display systems[ES] Los avances en el campo de la imagen digital nos han permitido ampliar los horizontes de la fotografía panorámica, gracias a la aparición de software de stitching o cosido de imágenes, con los que se pueden unir varias fotografías para formar una imagen panorámica de amplio campo visual. Las imágenes producidas mediante el software de stitching pueden llegar a abarcar un campo visual de 360º en horizontal y 180º en vertical, formando un panorama esférico. Este tipo de panorama tiene una gran potencial para la representación arquitectónica, por lo que resultaría interesante añadir una nueva dimensión aplicando los fundamentos de la visión estereoscópica. Por ello, en el artículo se estudia esta problemática con el fin de aportar una metodología asequible de captura fotográfica de panoramas esféricos estereoscópicos, además de analizar su compatibilidad con los últimos sistemas de visualización inmersivaCabezos-Bernal, PM.; Cisneros Vivó, J. (2016). Panoramas esféricos estereoscópicos. EGA. Revista de Expresión Gráfica Arquitectónica. 21(28):70-81. doi:10.4995/ega.2016.6264.SWORD7081212

Advanced displays and natural user interfaces to support learning

[EN] Advanced displays and Natural User Interfaces (NUI) are a very suitable combination for developing systems to provide an enhanced and richer user experience. This combination can be appropriate in several fields and has not been extensively exploited. One of the fields that this combination is especially suitable for is education. Nowadays, children are growing up playing with computer games, using mobile devices, and other technological devices. New learning methods that use these new technologies can help in the learning process. In this paper, two new methods that use advanced displays and NUI for learning about a period of history are presented. One of the methods is an autostereoscopic system that lets children see themselves as a background in the game and renders the elements in 3D without the need for special glasses; the second method is a frontal projection system that projects the image on a table in 2D and works similarly to a touch table. The Microsoft Kinect© is used in both systems for the interaction. A comparative study to check different aspects was carried out. A total of 128 children from 7 to 11 years old participated in the study. From the results, we observed that the different characteristics of the systems did not influence the children s acquired knowledge, engagement, or satisfaction. There were statistically significant differences for depth perception and presence in which the autostereoscopic system was scored higher. However, of the two systems, the children considered the frontal projection to be easier to use. We would like to highlight that the scores for the two systems and for all the questions were very high. These results suggest that games of this kind (advanced displays and NUI) could be appropriate educational games and that autostereoscopy is a technology to exploit in their development.This work was funded by the Spanish Ministry of Science and Innovation through the APRENDRA project (TIN2009-14319-C02-01).Martín San José, JF.; Juan, M.; Mollá Vayá, RP.; Vivó Hernando, RA. (2017). Advanced displays and natural user interfaces to support learning. Interactive Learning Environments. https://doi.org/10.1080/10494820.2015.1090455

Stereoscopy in Descriptive Geometry books

[EN] This article summarizes the research carried out by collecting the books, related to Descriptive Geometry, that have employed stereoscopy as a way to improve the knowledge of the represented forms. It has been possible to collect 19 books, published between 1912 and 2007, which have been analyzed and compared. Many of them have been acquired through international dealers, as they are a rarity. The article focuses on the oldest and most interesting ones, highlighting their most relevant aspects. To display the stereoscopic figures conveniently, It has been necessary to carry out a thorough process of digital optimization, in order to adapt the colors of inks to a single visualization system with conventional red/cyan glasses. Finally, the results of the full analysis will be shown.[ES] Este artículo sintetiza la investigación llevada a cabo a partir de la recopilación de los libros relacionados con la Geometría Descriptiva, que han utilizado la estereoscopia para ampliar el conocimiento de las formas geométricas representadas. Se han podido recopilar 19 obras, publicadas entre 1912 y 2007, que han sido analizadas y comparadas. Muchas de ellas han tenido que ser adquiridas a través de anticuarios internacionales, pues constituyen toda una rareza. Aquí se muestran las más antiguas e interesantes, destacando los aspectos más relevantes de cada una de ellas. Para mostrar convenientemente sus figuras estereoscópicas, ha sido necesario realizar un profundo trabajo de edición digital, con el fin de uniformizar las tintas, adaptándolas a un único sistema de visualización con gafas convencionales de filtros rojo/cian. Finalmente se muestran los resultados del análisis completo con todos los libros encontradosCabezos Bernal, PM.; Cisneros Vivó, JJ. (2015). La estereoscopia en los libros de geometría descriptiva. EGA. Revista de Expresión Gráfica Arquitectónica. 20(26):242-255. doi:10.4995/ega.2015.4058.SWORD242255202