Spin-polarized current oscillations in diluted magnetic semiconductor multiple quantum wells

We study the spin and charge dynamics of electrons in n-doped II--VI semiconductor multiple quantum wells when one or more quantum wells are doped with Mn. The interplay between strongly nonlinear inter-well charge transport and the large tunable spin-splitting induced by exchange interactions with spin-polarized Mn ions produces interesting new spin dependent features. The tunneling current between quantum wells can be strongly spin polarized and, under certain conditions, can develop self sustained oscillations under a finite dc voltage. The spin polarization oscillates in both magnetic and nonmagnetic quantum wells and the time average in magnetic wells can differ from its zero-voltage value. Our numerical simulations demonstrate that the amplitude of the spin polarization oscillations depends on the distribution of magnetic wells within the sample. We discuss how the spin polarized current and the spin polarization of the quantum wells can be tailored experimentally.Comment: 5 pages, 5 figures; to be published in Phys. Rev.

POSICIÓN COMPETITIVA Y MODELO PRODUCTIVO EN EL PERÚ

In the world competitiveness framework, the performance of Peru goes toward a worrying deterioration. Even more, when the construction of new forces to revert the process is not becoming visible, maintaininganeconomicmodeland, therefore, a productive model that does not guarantee the production and export of products with high aggregate value, to the extent that we continue depending on the natural resources. For purpose of analysis, the last reports of the World Economic Forum (WEF) on the competitiveness index and the evolution of the country, regional and world economy have been taken into consideration.En el marco de la competitividad mundial, el desempeño del Perú tiende hacia un deterioro preocupante, más aún, cuando no se vislumbran la construcción de nuevas fuerzas para revertir el proceso, manteniendo un modelo económico y, por lo tanto, un modelo productivo que, en la medida que sigamos dependiendo de los recursos naturales, no garantiza la producción y exportación de productos con alto valor agregado. Para el análisis, se han tomado en consideración los últimos informes del World Economic Forum (WEF) sobre los índices de competitividad, la evolución de la economía mundial, regional y del país

Caracterización estructural del sistema de producción de alpacas (Vicugna pacos) en Huancavelica, Perú

El objetivo fue identificar los factores que ocasionan bajos resultados de explotación en el sistema de producción de alpacas del departamento de Huancavelica, en función del componente estructural, realizando un muestreo aleatorio estratificado con afijación proporcional. Se visitó 224 unidades productivas con alpacas (UPA) de más de 100 cabezas, analizando 40 variables, encontrando una dimensión media de 133,3 ha y 143,8 cabezas. El empadre es estacional de enero a marzo (37%) y continuo todo el año (63%), sin registros reproductivos idóneos (70%). La hembra entra al primer empadre a los 22,6 meses en que su peso promedio bordea los 40 kg dentro de una relación de 11,3 hembras/macho, con alimentación a base de pastos naturales (100%) mediante pastoreo continuo (96%) y diferido (4%). La carga animal es 0,8 UA/ha/año (p>0,05). El descarte de machos y hembras se realiza a los 8,8±1,0 años (p≤0,05) y 7,9±0,7 años (p≤0,05), respectivamente. El tratamiento en salud animal se realiza en el 97% de las UPA, frente a una tasa de natalidad del 57,3±2,7 % y peso al nacimiento 7,8±1,0 kg; tasa de mortalidad de 5,6% en adultos y de 33,6% en crías. Los factores que ocasionan bajos resultados de explotación son: infraestructura inadecuada, instalaciones de manejo deficientes, ineficaz planificación de la reproducción, suplementación deficiente e ineficientes programas en salud animal.Por pare

Dogs Detecting COVID-19 From Sweat and Saliva of Positive People : A Field Experience in Mexico

ContextMolecular tests are useful in detecting COVID-19, but they are expensive in developing countries. COVID-19-sniffing dogs are an alternative due to their reported sensitivity (>80%) and specificity (>90%). However, most of the published evidence is experimental, and there is a need to determine the performance of the dogs in field conditions. Hence, we aimed to test the sensitivity and specificity of COVID-19-sniffing dogs in the field. MethodsWe trained four dogs with sweat and three dogs with saliva of COVID-19-positive patients, respectively, for 4.5 months. The samples were obtained from a health center in Hermosillo, Sonora, with the restriction to spend 5 min per patient. We calculated sensitivity, specificity, and their 95% confidence intervals (CI). ResultsTwo sweat-sniffing dogs reached 76 and 80% sensitivity, with the 95% CI not overlapping the random value of 50%, and 75 and 88% specificity, with the 95% CI not overlapping the 50% value. The 95% CI of the sensitivity and specificity of the other two sweat dogs overlapped the 50% value. Two saliva-sniffing dogs had 70 and 78% sensitivity, and the 95% CI of their sensitivity and specificity did not overlap the 50% value. The 95% CI of the third dog's sensitivity and specificity overlapped the 50% value. ConclusionFour of the six dogs were able to detect positive samples of patients with COVID-19, with sensitivity and specificity values significantly different from random in the field. We considered the performance of the dogs promising because it is reasonable to expect that with gauze exposed for a longer time to sweat and saliva of people with COVID-19, their detection capacity would improve. The target is to reach the sensitivity range requested by the World Health Organization for the performance of an antigen test (>= 80% sensitivity, >= 97% specificity). If so, dogs could become important allies for the control of the COVID-19 pandemic, especially in developing countries.Peer reviewe

Boletín NUESTRA AMÉRICA XXI - Desafíos y alternativas, num.36, Octubre 2019

Una excelente iniciativa del Grupo de Trabajo Crisis y economía mundial, coordinado por María Josefina Morales y Gabriela Roffinelli

Active tectonics on a volcanic island by using fractal and structural techniques (Deception Island, West Antarctica)

En este trabajo se obtiene el campo de esfuerzo y deformación activo en la isla volcánica de Decepción, en la Antártida Occidental. Para ello, se han aplicado tres técnicas estructurales diferentes: (1) medida de planos de falla con vector de deslizamiento, (2) estudio de la geometría fractal de la distribución espacial de lineamientos en la isla, interpretados a partir de imágenes satélite y MDT de alta resolución y (3) cartografía y geometría de la caldera volcánica. El campo de deformación obtenido es de tipo extensional con dos orientaciones ortogonales para el máximo acortamiento horizontal (ey), NE-SO y NO-SE. El campo de esfuerzos obtenido mediante el análisis fractal y de la geometría de la caldera volcánica se define a partir de SHMAX según NE-SO.The tectonic field on Deception Island (South Shetlands, West Antarctica) is determined from structural and fractal analyses. Three different analyses are applied to the study of the strain and stress fields into the area: (1) field measurements of faults (strain analysis), (2) fractal geometry of the spatial distribution of lineaments and (3) the caldera plan shape (stress analysis). In this work, the identified strain field is extensional with the maximum horizontal shortening trending NE-SW and NW-SE. The fractal technique applied to the spatial distribution of lineaments indicates a stress field with SHMAX oriented NE-SW. The elliptical caldera of Deception Island, determined from field mapping, satellite imagery and vents and fissure eruptions, has an elongate shape and a stress field with SHMAX trending NE-SW as well.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEMinisterio de Ciencia e Innovación (MICINN)pu

MYC activation impairs cell-intrinsic IFNγ signaling and confers resistance to anti-PD1/PD-L1 therapy in lung cancer

Elucidating the adaptive mechanisms that prevent host immune response in cancer will help predict efficacy of anti-programmed death-1 (PD1)/L1 therapies. Here, we study the cell-intrinsic response of lung cancer (LC) to interferon-y (IFNy), a cytokine that promotes immunoresponse and modulates programmed death-ligand 1 (PD-L1) levels. We report complete refractoriness to IFNy in a subset of LCs as a result of JAK2 or IFNGR1 inactivation. A submaximal response affects another subset that shows constitutive low levels of IFNy-stimulated genes (IySGs) coupled with decreased H3K27ac (histone 3 acetylation at lysine 27) depo-sition and promoter hypermethylation and reduced IFN regulatory factor 1 (IRF1) recruitment to the DNA on IFNy stimulation. Most of these are neuroendocrine small cell LCs (SCLCs) with oncogenic MYC/MYCL1/ MYCN. The oncogenic activation of MYC in SCLC cells downregulates JAK2 and impairs IySGs stimulation by IFNy. MYC amplification tends to associate with a worse response to anti-PD1/L1 therapies. Hence alterations affecting the JAK/STAT pathway and MYC activation prevent stimulation by IFNy and may predict anti-PD1/L1 efficacy in LC

X-Shooter Medium Resolution Brown Dwarfs Library

} We obtain medium-resolution spectra in the optical (550-1000 nm, R̃5400) and the near-infrared (1000-2500 nm, R̃3300) using the Wideband ultraviolet-infrared single target spectrograph (X-Shooter) at the Very Large Telescope (VLT). Our sample is compound of 22 brown dwarfs binary candidates with spectral types between L1 and T7. We aim to empirically confirm or refute the binarity of our candidates, comparing them to spectral templates and to other brown dwarfs in a color-magnitude diagram, for targets that have published parallaxes. } We use X-shooter at the VLT to obtain medium resolution spectra of the targets. We develop a slightly different analysis depending of the type of binaries we search for. To find L plus T brown dwarf binaries candidates, we comput spectral indices to select L-brown dwarfs plus T-brown dwarf binaries, and then we compare them to single and composite template spectra. To find potential L plus L or T plus T brown dwarf binaries, we first simulate their spectra creating synthetic binaries using combination of single template spectra. Then we compare them to our set of spectral libraries and composite of them to test if our method is able to find these binaries. } Using spectral indices, we select four possible candidates to be combination of L plus T brown dwarfs: SIMP 0136 662+0933473, 2MASSI J0423485-041403 (T0, known binary), DENIS-P J0255.0-4700 and 2MASS J13411160-3052505 We compare these candidates to single brown dwarf template spectra and combinations of them, and we select the best matches. All candidates beside SIMP 0136 662+0933473 have decent matches to composite of two single template spectra. DENIS-P J0255.0-4700 have also good agreements to several late L and early T single template spectra. To find L plus L or T plus T brown dwarfs candidates, test the comparison to templates method use before to find L plus T brown dwarf binaries. The test consist on finding synthetic L plus L and T plus T binaries by comparing with spectral templates. We conclude that we cannot find L plus L and T plus T binaries using comparing to single and composite spectral templates, because the main difference between different L or T spectral types is just the spectral energy distribution.} Optical and near infrared spectra report in this paper will serve as templates for future studies in any of these wavelengths. In the near future, Gaia satellite will release high precision parallaxes of more than one billion of objects in the Milky Way, including hundred of brown dwarfs. These parallaxes will allow us to detect the overluminosity of brown dwarf binaries.} <P /

The 1970’s volcanic eruption at Deception Island (West-Antarctica) and fault-related activity: the Maria’s Fault

Este trabajo analiza la formación de un escarpe de falla asociado a la erupción freatomagmática que ocurrió en 1970 en la Isla Decepción (Antártida Occidental). El hecho de tener información de fotografías aéreas previas a su desarrollo (1968) y una imagen de satélite de alta resolución (2003) permite establecer la formación de dicho escarpe, la evolución de la red de drenaje y la presencia de terrazas fluviales levantadas. A partir de esta información, llevamos a cabo una campaña de campo durante el verano austral de 2007, con el fin de realizar una serie de trincheras a lo largo del escarpe. De toda la información expuesta, se constata un movimiento de componente inverso a lo largo de la falla con 1 km de ruptura superficial y 20 cm de salto, afectando a los depósitos piroclásticos de la erupción de 1970. Tres modelos podrían explicar dicha actividad: (1) Terremoto inverso de tamaño pequeño-moderado (5<M<6) posterior a la erupción de 1970, (2) Reactivación de una falla previa asociada a la inyección o migración de un dique somero durante el proceso eruptivo y (3) Actividad asísmica de tipo creep a lo largo del plano de falla post terremoto.This work addresses the presence of a superficial rupture fault scarp in relationship with the phreatomagmatic eruption occurred in 1970 at Deception Island, West Antarctica. We have analysed aerial photographs (1968) previous to the eruption and contemporaneous high resolution satellite image (Quickbird, 2003). This information was relevant to establish the scarp morphology, fluvial network variations and uplifted fluvial terraces. Accordingly and during the austral summer of 2007, we carried out a field survey with the purpose to perform several paleoseismic trenches across the fault scarp. This analysis showed a reverse fault movement through 1 km of superficial rupture with 20 cm of vertical throw. This activity affected to the pyroclastic volcano sedimentary sequence of the 1970’s eruption. We propose three models that could explain this activity: (1) Reverse small-moderate earthquake (5<M<6) triggered by the 1970`s eruption, (2) Reactivation of a previous fault as a consequence of dike injection and/or magma migration in relationship with the eruptive process and (3) Aseismic fault creep activity post-earthquake.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEMinisterio de Educación y Ciencia (MEC)pu