UV Raman spectroscopy of group IV nanocrystals embedded in a SiO2 matrix

Nanostructures of both Ge nanocrystals formed by thermal oxidation of SiGe layers, and SiGe nanocrystals formed by crystallization of amorphous SiGe nanoparticles deposited by LPCVD have been analyzed by Raman spectroscopy. The nanostructures are formed on a silicon substrate. Raman spectra have been acquired with visible (514.5 nm) and UV (325 nm) excitation lines. When the amount of material is very small, as it has happens in these nanostructures, the visible line is not able to excite the characteristic peaks of the Ge or SiGe in the Raman spectrum; instead the Si second order spectrum of the substrate appears and it can be misinterpreted by attributing it to the Ge–Ge band associated with the nanocrystals. In this work, the use of UV excitation has been demonstrated to enhance the sensitivity respect to the conventional visible excitation, allowing the characteristic peaks of the Ge or SiGe nanocrystals to appear in the spectrum. We attributed this effect to the resonance effects

SOCS1-derived peptide administered by eye drops prevents retinal neuroinflammation and vascular leakage in experimental diabetes

Diabetic retinopathy; Neuroinflammation; Suppressors of cytokine signalingRetinopatía diabética; Neuroinflamación; Supresores de señalizadores de citoquinasRetinopatia diabètica; Neuroinflamació; Supressors de senyalitzadors de citoquinesCurrent treatments for diabetic retinopathy (DR) target late stages when vision has already been significantly affected. Accumulating evidence suggests that neuroinflammation plays a major role in the pathogenesis of DR, resulting in the disruption of the blood-retinal barrier. Suppressors of cytokine signaling (SOCS) are cytokine-inducible proteins that function as a negative feedback loop regulating cytokine responses. On this basis, the aim of the present study was to evaluate the effect of a SOCS1-derived peptide administered by eye drops (2 weeks) on retinal neuroinflammation and early microvascular abnormalities in a db/db mouse model. In brief, we found that SOCS1-derived peptide significantly reduced glial activation and neural apoptosis induced by diabetes, as well as retinal levels of proinflammatory cytokines. Moreover, a significant improvement of electroretinogram parameters was observed, thus revealing a clear impact of the histological findings on global retinal function. Finally, SOCS1-derived peptide prevented the disruption of the blood-retinal barrier. Overall, our results suggest that topical administration of SOCS1-derived peptide is effective in preventing retinal neuroinflammation and early microvascular impairment. These findings could open up a new strategy for the treatment of early stages of DR.This study was supported by grants from the Ministerio de Economia y Competitividad (PI16/00541, SAF2015-63696-R, PI14/00386, PI17/01495 and DTS-2017/00203). Cristina Sola-Adell is a recipient of a Predoctoral Research Grant from MINECO (BES-2013-064944). Joel Sampedro is a recipient of a Predoctoral Research Grant from AGAUR

Si and SixGe1-x NWs studied by Raman spectroscopy

Group IV nanostructures have attracted a great deal of attention because of their potential applications in optoelectronics and nanodevices. Raman spectroscopy has been extensively used to characterize nanostructures since it provides non destructive information about their size, by the adequate modeling of the phonon confinement effect. The Raman spectrum is also sensitive to other factors, as stress and temperature, which can mix with the size effects borrowing the interpretation of the Raman spectrum. We present herein an analysis of the Raman spectra obtained for Si and SiGe nanowires; the influence of the excitation conditions and the heat dissipation media are discussed in order to optimize the experimental conditions for reliable spectra acquisition and interpretation

Identificación ciega de sistemas SIMO con señal de entrada dispersa

We consider the blind identification of FIR channels with a single input and multiple outputs when the input signal is sparse. The problem is equivalent to identifying the mixing matrix for underdetermined blind source separation, but with temporal correlation among the sources. The length of each channel is assumed known, or previously estimated. Exploiting the sparse character of the input signal, the algorithm solves sequentially the three identification problems: estimating the directions of each column of the channel matrix; estimating their L₂-norm; and finding the most likely order of the columns. The performance of the algorithm in additive noise and its computational cost are compared against subspace-based techniques

Raman spectroscopy study of group IV semiconductor nanowires

Group IV nanostructures have attracted a great deal of attention because of their potential applications in optoelectronics and nanodevices. Raman spectroscopy has been extensively used to characterize nanostructures since it provides non destructive information about their size, by the adequate modeling of the phonon confinement effect. However, the Raman spectrum is also sensitive to other factors, as stress and temperature, which can mix with the size effects borrowing the interpretation of the Raman spectrum. We present herein an analysis of the Raman spectra obtained for SiGe nanowires; the influence of the excitation conditions and the heat dissipation media are discussed in order to optimize the experimental conditions for reliable spectra acquisition and interpretation. The interpretation of the data is supported by the calculation of the temperature inside the NWs with different diameters

Investigating the Size and Microstrain Influence in the Magnetic Order/Disorder State of GdCu2 Nanoparticles

A series of GdCu 22 nanoparticles with controlled sizes ranging from 7 nm to 40 nm has been produced via high-energy inert-gas ball milling. Rietveld refinements on the X-ray diffraction measurements ensure that the bulk crystalline ImmaImma structure is retained within the nanoparticles, thanks to the employed low milling times ranging from t = 0.5 to t = 5 h. The analysis of the magnetic measurements shows a crossover from Superantiferromagnetism (SAF) to a Super Spin Glass state as the size decreases at NP size of ?D???D?? 18 nm. The microstrain contribution, which is always kept below 1%, together with the increasing surface-to-core ratio of the magnetic moments, trigger the magnetic disorder. Additionally, an extra contribution to the magnetic disorder is revealed within the SAF state, as the oscillating RKKY indirect exchange achieves to couple with the aforementioned contribution that emerges from the size reduction. The combination of both sources of disorder leads to a maximised frustration for ?D???D?? 25 nm sized NPs.This work has been supported by MAT2017-83631-C3-R. EMJ thanks the “Beca Concepción Arenal” BDNS: 406333 granted by the Gobierno de Cantabria and the Universidad de Cantabri

Exploring the Different Degrees of Magnetic Disorder in TbxR1−xCu2 Nanoparticle Alloys

Recently, potential technological interest has been revealed for the production of magnetocaloric alloys using Rare-Earth intermetallics. In this work, three series of TbxR1−xCu2 (R ≡ Gd, La, Y) alloys have been produced in bulk and nanoparticle sizes via arc melting and high energy ball milling. Rietveld refinements of the X-ray and Neutron diffraction patterns indicate that the crystalline structure in all alloys is consistent with TbCu2 orthorhombic Imma bulk crystalline structure. The analyses of the DC-magnetisation (MDC) and AC-susceptibility (χAC) show that three distinct degrees of disorder have been achieved by the combination of both the Tb3+ replacement (dilution) and the nanoscaling. These disordered states are characterised by transitions which are evident to MDC, χAC and specific heat. There exists an evolution from the most ordered Superantiferromagnetic arrangement of the Tb0.5La0.5Cu2 NPs with Néel temperature, TN∼ 27 K, and freezing temperature, Tf∼ 7 K, to the less ordered weakly interacting Superparamagnetism of the Tb0.1Y0.9Cu2 nanoparticles (TN absent, and TB∼ 3 K). The Super Spin Glass Tb0.5Gd0.5Cu2 nanoparticles (TN absent, and Tf∼ 20 K) are considered an intermediate disposition in between those two extremes, according to their enhanced random-bond contribution to frustration.This work has been supported by the Spanish MAT2017-83631-C3-R grant. E.M.J.’s work was supported by “Beca de Colaboración”, BDNS: 311327 granted by Ministerio de Educación, Cultura y Deporte and “Beca Concepción Arenal” BDNS: 406333 granted by the Gobierno de Cantabria and the Universidad de Cantabria. MRF work was supported by FPI (BES-2012-058722)

Plan de Acción Tutorial para nuevos estudiantes de la Facultad de Economía y Empresa

Memoria ID-010. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2021-2022

Pauta de observación de la enseñanza de las matemáticas en Educación Secundaria en España (POEMat.ES)

POEMat.ES es una pauta de observación de las prácticas de enseñanza de profesores de matemáticas de Educación Secundaria grabadas en vídeo. Este instrumento permite recoger información sobre las acciones de los profesores de matemáticas en el aula desde 3 dimensiones diferentes, organizadas a su vez en 17 subdimensiones. Cada subdimensión se puede valorar en cuatro niveles de desempeño que describen características concretas de las acciones realizadas por el profesor observadas en un fragmento de vídeo. POEMat.ES ha sido desarrollada con el objetivo inicial de ofrecer una visión equilibrada y multidimensional de la enseñanza de las matemáticas en Educación Secundaria en el contexto español

Twitter as a Tool for Teaching and Communicating Microbiology: The #microMOOCSEM Initiative

Online social networks are increasingly used by the population on a daily basis. They are considered a powerful tool for science communication and their potential as educational tools is emerging. However, their usefulness in academic practice is still a matter of debate. Here, we present the results of our pioneering experience teaching a full Basic Microbiology course via Twitter (#microMOOCSEM), consisting of 28 lessons of 40-45 minutes duration each, at a tweet per minute rate during 10 weeks. Lessons were prepared by 30 different lecturers, covering most basic areas in Microbiology and some monographic topics of general interest (malaria, HIV, tuberculosis, etc.). Data analysis on the impact and acceptance of the course were largely affirmative, promoting a 330% enhancement in the followers and a >350-fold increase of the number of visits per month to the Twitter account of the host institution, the Spanish Society for Microbiology. Almost one third of the course followers were located overseas. Our study indicates that Massive Online Open Courses (MOOC) via Twitter are highly dynamic, interactive, and accessible to great audiences, providing a valuable tool for social learning and communicating science. This strategy attracts the interest of students towards particular topics in the field, efficiently complementing customary academic activities, especially in multidisciplinary areas like Microbiology.Versión del edito