Magnon-polaron and Spin-polaron Signatures in the Specific Heat and Electrical Resistivity of La0.6Y0.1Ca0.3MnO3La_{0.6}Y_{0.1}Ca_{0.3}MnO_3 in Zero Magnetic Field, and the Effect of Mn−O−MnMn-O-Mn Bond Environment

$La_{0.6}Y_{0.1}Ca_{0.3}MnO_{3}$, an $ABO_{3}$ perovskite manganite oxide, exhibits a non trivial behavior in the vicinity of the sharp peak found in the resistivity $\rho$ as a function of temperature $T$ in zero magnetic field. The various features seen on $d\rho/dT$ are discussed in terms of competing phase transitions. They are related to the $Mn-O-Mn$ bond environment depending on the content of the $A$ crystallographic site. A Ginzburg-Landau type theory is presented for incorporating concurrent phase transitions. The specific heat $C$ of such a compound is also examined from 50 till 200 K. A log-log analysis indicates different regimes. In the low temperature conducting ferromagnetic phase, a collective magnon signature ($C \simeq T^{3/2}$) is found as for what are called magnon-polaron excitations. A $C \simeq T^{2/3}$ law is found at high temperature and discussed in terms of the fractal dimension of the conducting network of the weakly conducting (so-called insulating) phase and Orbach estimate of the excitation spectral behaviors. The need of considering both independent spin scattering and collective spin scattering is thus emphasized. The report indicates a remarkable agreement for the Fisher-Langer formula, i.e. $C$ $\sim$ $d\rho/dT$ at second order phase transitions. Within the Attfield model, we find an inverse square root relationship between the critical temperature(s) and the total local $Mn-O-Mn$ strain.Comment: 19 pages, 5 figures; to be published in Phys Rev

Degradation of LaMnO{3-y} surface layer in LaMnO{3-y}/ metal interface

We report electrical measurements showing the degradation processes of LaMnO$_{3-y}$ (LaMnO) in LaMnO/normal metal interface in both point contact and planar-type junctions. Immediately after the preparation of the interface, the degradation process was followed by measuring the evolution of the junction resistance versus time. This process is characterized by the appearance of a second maximum in the resistance vs. temperature (R-T) dependence at temperatures lower than the Curie temperature T$_c$, at which the metal-insulator transition occurs in the bulk. These effects are explained in terms of the formation of a depleted interface layer in LaMnO caused by an out-diffusion of oxygen from the manganite surface to the normal metal. This assumption is confirmed by XPS measurement. Similar results on LaSrMnO$_{3-y}$ interfaces are also obtained.Comment: 4 pages, 3 figures, accepted for publication in Appl. Phys. Lett.(2002

Stem Cells for Modeling Human Disease

Human pluripotent stem cells (PSCs) in the form of human embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs) are capable of growing indefinitely in vitro, maintaining their capacity to differentiate into the three primary germ layers: mesoderm, endoderm and ectoderm. Different protocols have been developed to differentiate PSCs into almost any cellular type with different degree of success. This technology has allowed scientists to use patient‐derived iPSCs to study the physiopathology of the disease by analyzing the phenotype of the cells derived from these iPSCs. However, control iPSCs obtained from healthy individuals will always have different genomic environment than patient\u27s iPSCs, making it difficult the interpretation of the cells phenotype. The recent appearance of specific nucleases [zinc‐finger nucleases (ZFNs), the transcription activator‐like effector nucleases (TALENs) and the clustered regularly interspaced short palindromic repeats (CRISPR)] has made it possible to edit the genome of PSCs. We can now generate syngeneic hESCs or iPSCs harboring the desired mutation and comparing the emerging cells with those derived from genetically identical PSCs that will differ only in the mutated gene. In this chapter, we summarize the progress made in this field and discuss the different approaches that have been used recently for the generation of syngeneic human pluripotent cellular models for different pathologies

Shapiro steps in a superconducting film with an antidot lattice

Shapiro voltage steps at voltages V_n=nV_0 (n integer) have been observed in the voltage-current characteristics of a superconducting film with a square lattice of perforating microholes (antidots)in the presence of radiofrequent radiation. These equidistant steps appear at the second matching field H_2 when the flow of the interstitial vortex lattice in the periodic potential created by the antidots and the vortices trapped by them, is in phase with the applied rf frequency. Therefore, the observation of Shapiro steps clearly reveals the presence of mobile intersitial vortices in superconducting films with regular pinning arrays. The interstitial vortices, moved by the driving current, coexist with immobile vortices strongly pinned at the antidots.Comment: 6 pages text, 3 EPS figures, RevTeX, accepted for publication in PRB Rapid Communication

El quiste óseo aneurismático en niños y adolescentes

Desde el año 1981 hasta el año 1996 hemos tratado en nuestro servicio un total de 12 pacientes con diagnóstico de Quiste Óseo Aneurismático (QOA). Esta entidad clínico-patológica continúa hoy teniendo un origen incierto que en la mayoría de las ocasiones no puede reconocerse. Los tratamientos empleados fueron: legrado e injerto óseo en siete casos, resección en bloque en tres casos, y en 2 casos tratamiento expectante. Los resultados del tratamiento quirúrgico fueron satisfactorios en el 75% de los casos, encontrando un 25% de recidivas, que ocurrieron en los pacientes más jóvenes con quistes más agresivos. El tiempo medio de seguimiento fue de 4 años (mínimo 1 - máximo 8). Realizamos en el trabajo, además, una comparación con otros métodos de tratamiento publicados como son la crioterapia intratumoral y la embolizacón arterial selectiva, los cuales encontramos de utilidad relativa ya que requieren una alta especialización y una selección precisa de los casos. También la radioterapia que tiene una utilidad restringida a aquellos casos de inaccesibilidad operatoria.From 1981 to 1996 twelve patients were treated in our orthopaedic department with the diagnosis of Aneurismal Bone Cyst (ABC). This pathologic and clinical entity has an unknown etiology that in the majority of cases it can¿t be elucidated. The threatment was: curettage and bone graft in seven cases; in bloc excision in three cases and expectant in two. Surgical treatment results were satisfactory in 75% of cases, with 25% of local recurrences that took place in younger patients with more aggressive cysts. Mean follow-up was four years (range: 1-8). In this study we make a comparison with other methods of treatment reported like intratumoral criotherapy and selective arterial embolization. We find these methods of relative utility due to their high level of orthopaedist specialization and precise selection of cases. The radiotherapy has restricted application to cases of unresectable tumours

¿Es realmente fiable la evaluación no individualizada en el trabajo cooperativo?

Se presentan y discuten los resultados de una experiencia de trabajo cooperativo empleando la plataforma BSCW en alumnos de la titulación de Maestro de Educación Infantil de la Universidad de Barcelona, con el fin de detectar posibles sesgos de las coevaluaciones y las autoevaluaciones, y para valorar la incidencia que tienen los comportamientos disruptivos en el proceso cooperativo de evaluación. Los resultados muestran que el alumnado es honesto en las calificaciones que otorga, y que los comportamientos disruptivos detectados en los distintos grupos de trabajo cooperativo, causados por una baja ciudadanía de equipo, no tienen una incidencia significativa en las calificaciones otorgadas por el grupo clase. Por tanto, se legitiman las coevaluaciones y las autoevaluaciones como instrumentos fiables de evaluación en un contexto de trabajo cooperativo

Carbon use efficiency variability from MODIS data

[EN] Carbon use efficiency (CUE) describes how efficiently plants incorporate the carbon fixed during photosynthesis into biomass gain and can be calculated as the ratio between net primary production (NPP) and gross primary production (GPP). In this work, annual CUE has been obtained from annual GPP and NPP MODIS products for the peninsular Spain study area throughout eight years. CUE is spatially and temporally analyzed in terms of the vegetation type and annual precipitation and annual average air temperature. Results show that dense vegetation areas with moderate to high levels of precipitation present lower CUE values, whereas more arid areas present the highest CUE values. However, the temperature effect on the spatial variation of CUE is not well characterized. On the other hand, inter-annual variations of CUE of different ecosystems are discussed in terms of inter-annual variations of temperature and precipitation. It is shown that CUE exhibited a positive correlation with precipitation and a negative correlation with temperature in most ecosystems. Thus, CUE decreases when the ecosystem conditions change towards aridity.[ES] La eficiencia en el uso de carbono (CUE) cuantifica el incremento de la biomasa de las plantas a partir del carbono que fijan a través de su actividad fotosintética. En este trabajo se analiza la variación de la CUE anual (estimada a partir del cociente entre los productos de producción primaria neta, NPP, y producción primaria bruta, GPP, anuales de MODIS) en función del tipo de vegetación y de las variables meteorológicas temperatura del aire y precipitación, a lo largo de ocho años en la España peninsular. Los valores más bajos de CUE se encuentran en zonas de vegetación densa con niveles de precipitación de moderada a elevada (superior a 1000 mm/año), mientras que los valores más altos se localizan en zonas más áridas (con precipitación por debajo de 800 mm/año). La influencia de la temperatura es menos marcada. Cuando se analizan las variaciones interanuales de la CUE se observa que, para la mayor parte de los ecosistemas, un incremento de la precipitación produce un incremento de su CUE, mientras que un incremento de la temperatura la disminuye. En este caso, además, la influencia de la temperatura es más significativa desde un punto de vista estadístico. Es decir, para un ecosistema en particular, la CUE disminuye cuando se intensifi-can las condiciones de aridez.Este trabajo ha sido subvencionado, en parte, por los proyectos ERMES (FP7/2007-2013) y ESCENARIOS (MINECO/FEDER, CGL2016-75239-R). Agradecemos a AEMet, y muy especialmente al Dr. J. Tamayo, la cesión de los datos meteorológicos. Los productos MODIS se descargaron utilizando la herramienta online Data Pool, que es cortesía de NASA EOSDIS Land Processes Distributed Active Archive Center (LP DAAC), USGS/Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota, [https://lpdaac.usgs.gov/data_access]. Finalmente, les damos las gracias a los revisores, cuyas sugerencias han contribuido a mejorar el manuscrito.Cañizares, M.; Moreno, A.; Sánchez-Ruiz, S.; Gilabert, M. (2017). Variabilidad de la eficiencia en el uso del carbono a partir de datos MODIS. Revista de Teledetección. (48):1-12. https://doi.org/10.4995/raet.2017.70441124

Estimation of the charge carrier localization length from Gaussian fluctuations in the magneto-thermopower of La_{0.6}Y_{0.1}Ca_{0.3}MnO_3

The magneto-thermoelectric power (TEP) $\Delta S(T,H)$ of perovskite type manganise oxide $La_{0.6}Y_{0.1}Ca_{0.3}MnO_3$ is found to exhibit a sharp peak at some temperature $T^{*}=170K$. By approximating the true shape of the measured magneto-TEP in the vicinity of $T^{*}$ by a linear triangle of the form $\Delta S(T,H)\simeq S_p(H)\pm B^{\pm}(H)(T^{*}-T)$, we observe that $B ^{-}(H)\simeq 2B ^{+}(H)$. We adopt the electron localization scenario and introduce a Ginzburg-Landau (GL) type theory which incorporates the two concurrent phase transitions, viz., the paramagnetic-ferromagnetic transition at the Curie point $T_C$ and the "metal-insulator" (M-I) transition at $T_{MI}$. The latter is characterized by the divergence of the field-dependent charge carrier localization length $\xi (T,H)$ at some characteristic field $H_0$. Calculating the average and fluctuation contributions to the total magnetization and the transport entropy related magneto-TEP $\Delta S(T,H)$ within the GL theory, we obtain a simple relationship between $T^{*}$ and the above two critical temperatures ($T_{C}$ and $T_{MI}$). The observed slope ratio $B ^{-}(H)/B ^{+}(H)$ is found to be governed by the competition between the electron-spin exchange $JS$ and the induced magnetic energy $M_sH_0$. The comparison of our data with the model predictions produce $T_{C}=195K$, $JS=40meV$, $M_0=0.4M_s$, $\xi_0=10\AA$, and $n_e/n_i=2/3$ for the estimates of the Curie temperature, the exchange coupling constant, the critical magnetization, the localization length, and the free-to-localized carrier number density ratio, respectively.Comment: 6 pages (REVTEX), 2 PS figures (epsf.sty); submitted to Phys.Rev.