Suppression of electron spin decoherence of the diamond NV center by a transverse magnetic field

We demonstrate that the spin decoherence of nitrogen vacancy (NV) centers in diamond can be suppressed by a transverse magnetic field if the electron spin bath is the primary decoherence source. The NV spin coherence, created in "a decoherence-free subspace" is protected by the transverse component of the zero-field splitting, increasing the spin-coherence time about twofold. The decoherence due to the electron spin bath is also suppressed at magnetic fields stronger than ~25 gauss when applied parallel to the NV symmetry axis. Our method can be used to extend the spin-coherence time of similar spin systems for applications in quantum computing, field sensing, and other metrologies.Comment: 20 pages, 4 figure

Hippocampal Memory Recovery After Acute Stress: A Behavioral, Morphological and Molecular Study

Indexación: Scopus.Laboratory of Neuroplasticity and Neurogenetics, Department of Biochemistry and Molecular Biology, Faculty of Chemistry and Pharmaceutical Sciences, Universidad de Chile, Santiago, Chile, 2Laboratorio Farmacología del Comportamiento, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile, 3Department of Kinesiology, Faculty of Health Sciences, Universidad Católica del Maule, Talca, Chile, 4Facultad de Psicología, Universidad de Talca, Talca, Chile, 5Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile, 6Escuela de Química y Farmacia, Facultad de Medicina, Universidad Andres Bello, Santiago, Chile.This study was supported by the following grants: Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT) 1120528 (JLF), Fondo Central de Investigación, Universidad de Chile ENL025/16 (JLF).Several studies have shown that a single exposure to stress may improve or impair learning and memory processes, depending on the timing in which the stress event occurs with relation to the acquisition phase. However, to date there is no information about the molecular changes that occur at the synapse during the stress-induced memory modification and after a recovery period. In particular, there are no studies that have evaluated—at the same time—the temporality of stress and stress recovery period in hippocampal short-term memory and the effects on dendritic spine morphology, along with variations in N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits. The aim of our study was to take a multidimensional approach to investigate concomitant behavioral, morphological and molecular changes induced by a single restraint stress exposure (2.5 h) and a recovery period of 6 and 24 h in rats. We found that acute stress elicited a reduced preference to explore an object placed in a novel position (a hippocampal-dependent task). These changes were accompanied by increased activity of LIM kinase I (LIMK; an actin-remodeling protein) and increased levels of NR2A subunits of NMDA receptors. After 6 h of recovery from stress, rats showed similar preference to explore an object placed in a novel or familiar position, but density of immature spines increased in secondary CA1 apical dendrites, along with a transient rise in GluA2 AMPA receptor subunits. After 24 h of recovery from stress, the animals showed a preference to explore an object placed in a novel position, which was accompanied by a normalization of NMDA and AMPA receptor subunits to control values. Our data suggest that acute stress produces reversible molecular and behavioral changes 24 h after stress, allowing a full reestablishment of hippocampal-related memory. Further studies need to be conducted to deepen our understanding of these changes and their reciprocal interactions.Adaptive stress responses are a promising avenue to develop interventions aiming at restoring hippocampal function impaired by repetitive stress exposure. © 2018 Aguayo, Tejos-Bravo, Díaz-Véliz, Pacheco, García-Rojo, Corrales, Olave, Aliaga, Ulloa, Avalos, Román-Albasini, Rojas and Fiedler.https://www.frontiersin.org/articles/10.3389/fnmol.2018.00283/ful

Kinetics of Particles Adsorption Processes Driven by Diffusion

The kinetics of the deposition of colloidal particles onto a solid surface is analytically studied. We take into account both the diffusion of particles from the bulk as well as the geometrical aspects of the layer of adsorbed particles. We derive the first kinetic equation for the coverage of the surface (a generalized Langmuir equation) whose predictions are in agreement with recent simulation results where diffusion of particles from the bulk is explicitly considered.Comment: 4 page

PLoS One

Estimating and selecting risk factors with extremely low prevalences of exposure for a binary outcome is a challenge because classical standard techniques, markedly logistic regression, often fail to provide meaningful results in such settings. While penalized regression methods are widely used in high-dimensional settings, we were able to show their usefulness in low-dimensional settings as well. Specifically, we demonstrate that Firth correction, ridge, the lasso and boosting all improve the estimation for low-prevalence risk factors. While the methods themselves are well-established, comparison studies are needed to assess their potential benefits in this context. This is done here using the dataset of a large unmatched case-control study from France (2005-2008) about the relationship between prescription medicines and road traffic accidents and an accompanying simulation study. Results show that the estimation of risk factors with prevalences below 0.1% can be drastically improved by using Firth correction and boosting in particular, especially for ultra-low prevalences. When a moderate number of low prevalence exposures is available, we recommend the use of penalized techniques

Degradación del almidón mediante la amilasa salival

Palabras clave: experiencias de química; materiales y reactivos caseros; demostraciones de química.Starch degradation by salivary amylaseKeywords: chemistry experiments; home materials and reagents; chemical demonstrations

Cómo construir un espectroscopio casero con un CD

Palabras clave: espectroscopía; red de difracción; ciencia recreativaHow to build a homemade spectroscope with a CDKeywords: spectroscopy; diffraction grating; recreational scienc

Experiencias divertidas de electroquímica casera

La química, dentro de la cual se incluye la electroquímica, es una materia que los estudiantes suelen ver como complicada, aburrida, carente de interés y que, además requiere de material de laboratorio sofisticado y reactivos químicos inaccesibles. Nada más lejos de la realidad, tal y como se pondrá de manifiesto en este trabajo, donde se proponen varias experiencias sencillas usando sustancias baratas, la mayoría de las cuales pueden encontrarse en un supermercado, y utensilios de cocina. Estas experiencias permiten abordar la electroquímica de una forma amena y divertida, despertando el interés de los alumnos por la química, en general, y por la electroquímica, en particular.Palabras clave: Experiencias de química; electroquímica; materiales y reactivos caseros; demostraciones de químicaEntertaining experiments of home electrochemistryChemistry, and electrochemistry, whose study is included within chemistry, is a subject that students usually think difficult, boring, without interest and moreover that requires sophisticated laboratory material and expensive and strange chemicals, not a bit of it, as it will be stated in this work, where several simple experiments are proposed using cheap chemicals that mostly can be found in supermarkets, and kitchen utensils. These experiments permit to deal with electrochemistry in a nice and entertaining way, arousing the interest of the students by the chemistry.Keywords: Chemistry experiments; electrochemistry; home materials and reagents; chemical demonstrations

Convierta cobre en plata y en oro

Palabras clave: demostraciones de química; reacciones redox: materiales y reactivos caseros.Turn copper into silver and into goldKeywords: chemical demonstrations; redox reactions; home materials and reagents