Study of Growth Parameters for Single InAs QD Formation on GaAs(001) Patterned Substrates by Local Oxidation Lithography

This work studies the selective nucleation of InAs within nanoholes on GaAs(001) substrates patterned by atomic force microscopy local oxidation. The effects of substrate temperature and As4 overpressure during InAs deposition directly on the patterned substrate (without a GaAs buffer layer) are considered. It is found that when InAs is deposited at substrate temperature of 510 °C under low As4 overpressure, a single InAs quantum dot per nanohole is obtained for a broad range of sizes of pattern motifs. The use of these InAs quantum dots as seed nuclei for vertical stacking of optically active single InAs site-controlled quantum dots is investigated.The authors acknowledge financial support by Spanish MINECO through Grants ENE2012-37804-C02-02 and TEC2011-29120-C05-04. Jesús Herranz acknowledges the JAE program for funds.Peer reviewe

Role of re-growth interface preparation process for spectral line-width reduction of single InAs site-controlled quantum dots

We present growth and optical characterization measurements of single InAs site-controlled quantum dots (SCQDs) grown by molecular beam epitaxy on GaAs (001) patterned substrates by atomic force microscopy oxidation lithography. InAs SCQDs directly grown on the patterned surface were used as a seed layer and strain template for the nucleation of optically active single InAs SCQDs. The preservation of the initial geometry of the engraved pattern motifs after the re-growth interface preparation process, the lack of buffer layer growth prior to InAs seed layer deposition and the development of suitable growth conditions provide us an improvement of the SCQDs' active layer optical properties while retaining a high ratio of single occupation (89%). In this work a fivefold reduction of the average optical line-width from 870 μeV to 156 μeV for InAs SCQDs located 15 nm from the re-growth interface is obtained by increasing the temperature of the initial thermal treatment step of the re-growth interface from 490 °C to 530 °C.The authors thank financial support by Spanish MINECO through grants ENE2012-37804-C02-02 and TEC2011-29120-C05-04. Jesús Herranz acknowledges the JAE program for the funds.Peer reviewe

III-V semiconductor quantum dots for efficient quantum light sources

Comunicación presentada en el 3rd international Workshop Engineering of quantum emitter properties, celebrado en Linz (Austria) el 17 y 18 de diciembre de 2015.Photonic crystal microcavities (PCMs) with embedded quantum dots (QDs) have been shown as excellent test bed systems for experiments in the field of cavity quantum electrodynamics (c-QED) that may open doors to efficient quantum photonic devices for the generation of single-photons, entangled photon pairs and ultra-low threshold lasing. Based on fundamental excitonic emission and on biexciton-exciton recombination cascade, a single QD embedded in a PCM become efficient emitters of single photons or entangled photon pairs provided that both spectral and spatial matching of the optical cavity mode and the optical emission of the single nanostructure occur. Within this approach, we have explored several systems and growth methods with the aim of fabricating QD which fulfil the requirements for an efficient coupling between a single QD and a PCM. We have fabricated QD by molecular beam epitaxy (MBE) using a) droplet epitaxy and b) selective nucleation at nano-holes fabricated by atomic force microscopy local oxidation (AFMLO) lithography. Results will be presented of QD in GaAs/AlGaAs(111)A, InAs/GaAs(001) and InAs/InP (001). With the aim of obtaining coupled QD-PCM, we have followed two procedures: one is based on the fabrication of a PCM around a buried QD whose position and wavelength emission are previously determined; the other approach consists of locating a single QD by using AFMLO, at the maximum of the electric field of a prefabricated PCM. A MBE re-growth procedure has been developed for completing the PCM membrane thickness.Peer Reviewe

Contaminación por ruido y el tráfico vehicular en la frontera de México

Objetivo -determinar la relación entre el nivel de ruido de las principales intersecciones viales y el número de vehículos que transitan sobre ellas. Método - se utilizó un aforador vehicular electrónico no invasivo en periodos de una semana; evaluación del nivel de ruido en intervalos diarios durante la semana completa, utilizando sonómetros integradores tipo I. Resultados - se identificó el tráfico promedio diario anual de 2739 unidades; estimación del nivel de ruido de 77.6 dB para periodos de 12 horas; niveles máximos de 98.5 dB y 58.3 dB como nivel mínimo de ruido. Limitaciones - el desarrollo del trabajo de campo en un periodo menor a un año. Principales hallazgos - el nivel de ruido en la ciudad supera el referente de 65 decibeles, mencionado por la Organización Mundial de la Salud, lo que permite concluir que la ciudad presenta contaminación a causa del ruido derivado del tráfico vehicular

Adicción y factores determinantes en el uso problemático del Internet, en una muestra de jóvenes universitarios

El estudio tiene como objetivo conocer la probabilidad de presentar adicción y los factores determinantes sobre el uso problemático del internet en estudiantes universitarios en la ciudad de H. Matamoros, Tamaulipas. Metodología: La población fue de 1,125 estudiantes y una muestra de 323, en una universidad pública, el instrumento utilizado fue el “Cuestionario de Uso Problemático de Internet” (CUPI) con un Alfa de Cronbach de 0.966, el diseño de estudio fue descriptivo, transversal. Resultados: se encontró que el factor de determinante “Anticipación” fue el que presento una mayor probabilidad de presentarse, y los de menor fueron “Pérdida de Control” y  “Reconocimiento de Falta de Control.

Genomics And Susceptibility Profiles Of Extensively Drug-resistant Pseudomonas Aeruginosa Isolates From Spain

This study assessed the molecular epidemiology, resistance mechanisms, and susceptibility profiles of a collection of 150 extensively drug-resistant (XDR) Pseudomonas aeruginosa clinical isolates obtained from a 2015 Spanish multicenter study, with a particular focus on resistome analysis in relation to ceftolozane-tazobactam susceptibility. Broth microdilution MICs revealed that nearly all (> 95%) of the isolates were nonsusceptible to piperacillin-tazobactam, ceftazidime, cefepime, aztreonam, imipenem, meropenem, and ciprofloxacin. Most of them were also resistant to tobramycin (77%), whereas nonsusceptibility rates were lower for ceftolozane-tazobactam (31%), amikacin (7%), and colistin (2%). Pulsed-field gel electrophoresis-multilocus sequence typing (PFGE-MLST) analysis revealed that nearly all of the isolates belonged to previously described high-risk clones. Sequence type 175 (ST175) was detected in all 9 participating hospitals and accounted for 68% (n = 101) of the XDR isolates, distantly followed by ST244 (n = 16), ST253 (n = 12), ST235 (n = 8), and ST111 (n = 2), which were detected only in 1 to 2 hospitals. Through phenotypic and molecular methods, the presence of horizontally acquired carbapenemases was detected in 21% of the isolates, mostly VIM (17%) and GES enzymes (4%). At least two representative isolates from each clone and hospital (n = 44) were fully sequenced on an illumina MiSeq. Classical mutational mechanisms, such as those leading to the overexpression of the beta-lactamase AmpC or efflux pumps, OprD inactivation, and/or quinolone resistance-determining regions (QRDR) mutations, were confirmed in most isolates and correlated well with the resistance phenotypes in the absence of horizontally acquired determinants. Ceftolozane-tazobactam resistance was not detected in carbapenemase-negative isolates, in agreement with sequencing data showing the absence of ampC mutations. The unique set of mutations responsible for the XDR phenotype of ST175 clone documented 7 years earlier were found to be conserved, denoting the long-term persistence of this specific XDR lineage in Spanish hospitals. Finally, other potentially relevant mutations were evidenced, including those in penicillin-binding protein 3 (PBP3), which is involved in beta-lactam (including ceftolozane-tazobactam) resistance, and FusA1, which is linked to aminoglycoside resistance

EstuPlan: Methodology for the development of creativity in the resolution of scientific and social problems

[EN] Creative thinking is necessary to generate novel ideas and solve problems. "EstuPlan" is a methodology in which knowledge and creativity converge for the resolution of scientific problems with social projection. It is a training programme that integrates teachers, laboratory technicians and PhD students, master and undergraduate students which form working groups for the development of projects. Projects have a broad and essential scope and projection in terms of environmental problems, sustainable use of natural resources, food, health, biotechnology or biomedicine. The results show the success of this significant learning methodology using tools to develop creativity in responding to scientific and social demand for problem-solving to transfer academic knowledge to different professional environments. Bioplastics, Second Life of Coffee, LimBio, Algae oils, Ecomers, Caring for the life of your crop and Hate to Deforestate are currently being developed.Astudillo Calderón, S.; De Díez De La Torre, L.; García Companys, M.; Ortega Pérez, N.; Rodríguez Martínez, V.; Alzahrani, S.; Alonso Valenzuela, R.... (2019). EstuPlan: Methodology for the development of creativity in the resolution of scientific and social problems. En HEAD'19. 5th International Conference on Higher Education Advances. Editorial Universitat Politècnica de València. 711-717. https://doi.org/10.4995/HEAD19.2019.9205OCS71171