Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble

As the number of spins in an ensemble is reduced, the statistical uctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer- scale ensembles of nuclear spins in a KPF6 sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble

Work-life interferences in the early academic career stages: The case of precarious researchers in Italy

This paper addresses the topic of work–life interferences in academic contexts. More specifically, it focuses on early career researchers in the Italian university system. The total availability required from those who work in the research sector is leading to significant transformations of the temporalities of work, especially among the new generation of researchers, whose condition is characterized by a higher degree of instability and uncertainty. Which are the experiences of the early career researchers in an academic context constituted by a growing competition for permanent positions and, as a consequence, by a greatly increased pressure? Which are the main gender differences? In what elements do Science, Technology, Engineering and Mathematics disciplines differ from Social Sciences and Humanities? The collected narratives reveal how the ongoing process of precarization is affecting both the everyday working activities and the private and family lives of early career researchers, with important consequences also on their future prospects

Karyotype and Nuclear DNA Content of Six Species of <i>Astragalus</i> (Leguminosae)

Karyological characteristics of six Argentinian Astragalus species are reported: A. crucksh-anksii (2n=28), A. illinii (2n=28), A. neuquenensis (2n=28), A. moyanoi (2n=28), A. pehuenches (2n=22) and A. palenae var. grandiflora (2n=26). The x=13 and 14 species have bimodal complements but differ in chromosome morphology and asymmetry indices. All species have a single pair of chromosomes with satellites located on the long arms. A. pehuenches (2n=22, x=11) has a more symmetrical karyotype and a pair of SAT chromosomes with a satellite located on the short arms. Among the species with 2n=28, A. moyanoi has significantly greater DNA content than the rest. The species with the lowest chromosome number, A. pehuenches, has the highest DNA content. The members of species with 2n=28 studied in the present work are similar in both vegetative and reproductive morphology.Facultad de Ciencias Agrarias y ForestalesComisión de Investigaciones Científicas de la provincia de Buenos Aire

Spin dynamics in electrochemically charged CdSe quantum dots

We use time-resolved Faraday rotation to measure coherent spin dynamics in colloidal CdSe quantum dots charged in an electrochemical cell at room temperature. Filling of the 1Se electron level is demonstrated by the bleaching of the 1Se-1S3/2 absorption peak. One of the two Lande g-factors observed in uncharged quantum dots disappears upon filling of the 1Se electron state. The transverse spin coherence time, which is over 1 ns and is limited by inhomogeneous dephasing, also appears to increase with charging voltage. The amplitude of the spin precession signal peaks near the half-filling potential. Its evolution at charging potentials without any observable bleaching of the 1Se-1S3/2 transition suggests that the spin dynamics are influenced by low-energy surface states.Comment: 4 pages, 4 figure

Quantum dot opto-mechanics in a fully self-assembled nanowire

We show that fully self-assembled optically-active quantum dots (QDs) embedded in MBE-grown GaAs/AlGaAs core-shell nanowires (NWs) are coupled to the NW mechanical motion. Oscillations of the NW modulate the QD emission energy in a broad range exceeding 14 meV. Furthermore, this opto-mechanical interaction enables the dynamical tuning of two neighboring QDs into resonance, possibly allowing for emitter-emitter coupling. Both the QDs and the coupling mechanism -- material strain -- are intrinsic to the NW structure and do not depend on any functionalization or external field. Such systems open up the prospect of using QDs to probe and control the mechanical state of a NW, or conversely of making a quantum non-demolition readout of a QD state through a position measurement.Comment: 20 pages, 6 figure

Multi-Class Learning: Simplex Coding And Relaxation Error

We study multi-category classification in the framework of computational learning theory. We show how a relaxation approach, which is commonly used in binary classification, can be generalized to the multi-class setting. We propose a vector coding, namely the simplex coding, that allows to introduce a new notion of multi-class margin and cast multi-category classification into a vector valued regression problem. The analysis of the relaxation error be quantified and the binary case is recovered as a special case of our theory. From a computational point of view we can show that using the simplex coding we can design regularized learning algorithms for multi-category classification that can be trained at a complexity which is independent to the number of classes

Utilization of morphological and AFLP molecular markers in the identification of native and cultivated germplasm of Elymus scabrifolius (Poaceae)

Elymus scabrifolius es una gramínea perenne nativa de Sudamérica con gran potencial como recurso forrajero para ambientes con limitantes edáficas. En el presente trabajo se analizó la utilización de caracteres morfológicos y marcadores moleculares AFLP para la identificación genotípica de seis accesiones, un cultivar comercial y siete híbridos artificiales de esta especie. Ambos tipos de marcadores permitieron diferenciar a los materiales analizados en los respectivos dendrogramas, aunque las relaciones entre materiales variaron según el tipo de marcador. El Análisis de Componentes Principales permitió identificar las variables más relevantes para la diferenciación morfológica. Los híbridos se diferenciaron morfológicamente de ambos parentales, excepto un híbrido que se agrupó con su material paterno. Aunque en el análisis de los marcadores AFLP los híbridos se agruparon con uno de sus parentales, se pudo corroborar su origen híbrido mediante el registro de bandas paternas y polimórficas entre parentales. Se concluye que las metodologías empleadas para caracterizar los materiales analizados de E. scabrifolius serían de gran utilidad para el manejo eficiente de colecciones de germoplasma como así también para su utilización en programas de mejoramiento genético.Elymus scabrifolius is a South American perennial grass exhibiting great potential as a forage resource, especially for environments with edaphic limitations. In the present work we use morphological traits and AFLP molecular markers to genotypically identify six E. scabrifolius accessions, one commercial cultivar and seven artificial hybrids of this species. Both types of marker systems resulted in an accurate differentiation of the interrogated E. scabrifolius germplasm in the dendrograms. Moreover, relationships between the tested germplasm tend to vary according to the type of marker system used. Principal Component Analysis was used to identify the traits that best described the morphological variation. The morphological study revealed that almost all hybrids were different from their parents, with exception of one hybrid that was clustered with their own male parent. In the AFLP marker analysis, all the hybrids were clustered with one of their own parents. However, hybrid origin of those individuals was verified by the presence of paternal bands and polymorphic bands. In conclusion, the use of different methodologies to characterize and analyze E. scabrifolius materials has the potential to become of great benefit for the efficient management of germplasm collections and also for their utilization in breeding programs.Fil: Tomas, Pablo A.. Universidad Nacional del Litoral. Facultad de Ciencias Agrarias. Cátedra de Mejoramiento Vegetal y Animal.Fil: Gottlieb, Alexandra M.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución.Fil: Schrauf, Gustavo E.. Universidad de Buenos Aires. Facultad de AgronomíaFil: Poggio, Lidia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución