A Family of Finite-Temperature Electronic Phase Transitions in Graphene Multilayers

Suspended Bernal-stacked graphene multilayers up to an unexpectedly large thickness exhibit a broken-symmetry ground state, whose origin remains to be understood. Here we show that a finite-temperature second order phase transition occurs in multilayers whose critical temperature Tc increases from 12 K in bilayers to 100 K in heptalayers. A comparison of the data to a phenomenological model inspired by a mean field approach suggests that the transition is associated with the appearance of a self-consistent valley- and spin-dependent staggered potential changing sign from one layer to the next, appearing at Tc and increasing upon cooling. The systematic evolution with thickness of several measured quantities imposes constraints on any microscopic theory aiming to analyze the nature of electronic correlations in this system

Electron-hole collision limited transport in charge-neutral bilayer graphene

Ballistic transport occurs whenever electrons propagate without collisions deflecting their trajectory. It is normally observed in conductors with a negligible concentration of impurities, at low temperature, to avoid electron-phonon scattering. Here, we use suspended bilayer graphene devices to reveal a new regime, in which ballistic transport is not limited by scattering with phonons or impurities, but by electron-hole collisions. The phenomenon manifests itself in a negative four-terminal resistance that becomes visible when the density of holes (electrons) is suppressed by gate-shifting the Fermi level in the conduction (valence) band, above the thermal energy. For smaller densities transport is diffusive, and the measured conductivity is reproduced quantitatively, with no fitting parameters, by including electron-hole scattering as the only process causing velocity relaxation. Experiments on a trilayer device show that the phenomenon is robust and that transport at charge neutrality is governed by the same physics. Our results provide a textbook illustration of a transport regime that had not been observed previously and clarify the nature of conduction through charge-neutral graphene under conditions in which carrier density inhomogeneity is immaterial. They also demonstrate that transport can be limited by a fully electronic mechanism, originating from the same microscopic processes that govern the physics of Dirac-like plasmas.Comment: Submitte

La sostenibilidad social de la agricultura intensiva almeriense: una mirada desde la organización social del trabajo

Este artículo tiene como principal objetivo explicar la organización social del trabajo en el modelo de producción hortofrutícola almeriense desde una perspectiva de sostenibilidad social. Para ello, parte de una noción compleja de trabajo que contempla sus dimensiones socioculturales, las relaciones sociales de clase, interétnicas y de sexo-género sobre las que se configura y el modo en que se halla arraigado en el conjunto de instituciones sociales. Como primera hipótesis se plantea que existe una contradicción entre el papel central que ocupa el trabajo de las mujeres y las personas inmigrantes para la continuidad del modelo, y la tendencia a minusvalorarlo. La segunda hipótesis mantiene que la organización del trabajo se estructura sobre un conjunto de insostenibilidades sociales que ponen en jaque las condiciones de trabajo y la vida de quienes lo realizan. El texto se basa en una metodología cualitativa apoyada en las técnicas de la entrevista y la observación participante.This article approaches the social organization of labour in Almería’s fruit and vegetable farming from the viewpoint of social sustainability. The article is grounded on a complex notion of labour, involving sociocultural dimensions as well as class, ethnic, and sex-gender social relationships, and taking into account the way in which labour is rooted into social institutions as a whole. Our first hypothesis suggests that a contradiction exists between the major role that labour plays in the continuity of farming among women and immigrants, on the one hand, and the tendency to undervalue these forms of work, on the other. Our second hypothesis is that labour organization is structured upon a set of socially unsustainable factors, which put workers’ labour and life conditions at stake. The text is based on a qualitative analysis, supported by interviewing and participant observation techniques

The social sustainability of intensive agriculture in Almería (Spain): a view from the social organization of labour

[ES] Este artículo tiene como principal objetivo explicar la organización social del trabajo en el modelo de producción hortofrutícola almeriense desde una perspectiva de sostenibilidad social. Para ello, parte de una noción compleja de trabajo que contempla sus dimensiones socioculturales, las relaciones sociales de clase, interétnicas y de sexo-género sobre las que se configura y el modo en que se halla arraigado en el conjunto de instituciones sociales. Como primera hipótesis se plantea que existe una contradicción entre el papel central que ocupa el trabajo de las mujeres y las personas inmigrantes para la continuidad del modelo, y la tendencia a minusvalorarlo. La segunda hipótesis mantiene que la organización del trabajo se estructura sobre un conjunto de insostenibilidades sociales que ponen en jaque las condiciones de trabajo y la vida de quienes lo realizan. El texto se basa en una metodología cualitativa apoyada en las técnicas de la entrevista y la observación participante.[EN] This article approaches the social organization of labour in Almería’s fruit and vegetable farming from the viewpoint of social sustainability. The article is grounded on a complex notion of labour, involving sociocultural dimensions as well as class, ethnic, and sex-gender social relationships, and taking into account the way in which labour is rooted into social institutions as a whole. Our first hypothesis suggests that a contradiction exists between the major role that labour plays in the continuity of farming among women and immigrants, on the one hand, and the tendency to undervalue these forms of work, on the other. Our second hypothesis is that labour organization is structured upon a set of socially unsustainable factors, which put workers’ labour and life conditions at stake. The text is based on a qualitative analysis, supported by interviewing and participant observation techniques.S

Validation of the MC-GPU Monte Carlo code against the PENELOPE/penEasy code system and benchmarking against experimental conditions for typical radiation qualities and setups in interventional radiology and cardiology

Introduction: Interventional procedures are associated with potentially high radiation doses to the skin. The 2013/59/EURATOM Directive establishes that the equipment used for interventional radiology must have a device or a feature informing the practitioner of relevant parameters for assessing patient dose at the end of the procedure. Monte Carlo codes of radiation transport are considered to be one of the most reliable tools available to assess doses. However, they are usually too time consuming for use in clinical practice. This work presents the validation of the fast Monte Carlo code MC-GPU for application in interventional radiology. Methodologies: MC-GPU calculations were compared against the well-validated Monte Carlo simulation code PENELOPE/penEasy by simulating the organ dose distribution in a voxelized anthropomorphic phantom. In a second phase, the code was compared against thermoluminescent measurements performed on slab phantoms, both in a calibration laboratory and at a hospital. Results: The results obtained from the two simulation codes show very good agreement, differences in the output were within 1%, whereas the calculation time on the MC-GPU was 2500 times shorter. Comparison with measurements is of the order of 10%, within the associated uncertainty. Conclusions: It has been verified that MC-GPU provides good estimates of the dose when compared to PENELOPE program. It is also shown that it presents very good performance when assessing organ doses in very short times, less than one minute, in real clinical set-ups. Future steps would be to simulate complex procedures with several projections.Peer ReviewedObjectius de Desenvolupament Sostenible::3 - Salut i BenestarPostprint (published version

Probing magnetism in exfoliated VI3 layers with magnetotransport

We perform magnetotransport experiments on exfoliated multilayers of $\rm{VI_3}$, a 2D magnetic semiconductor reported to exhibit Ising ferromagnetism both in bulk and 2D form. Measurements of the magnetoconductance performed on field-effect transistors and tunnel barriers consistently show that the Curie temperature is $T_C~=~57~K$ (significantly larger than in the bulk; $T_C^{\rm bulk}~=~50~K$), irrespective of thickness (between 7 and 20~nm), in agreement with recent magneto-optical experiments. Measurements on tunnel barriers allow magnetism to be probed down to temperatures much lower than $T_C$. They show that below $T~\simeq~40$ K the magnetoconductance in a perpendicular magnetic field becomes negative, and that a pronounced hysteresis appears when the field is applied parallel to the planes. These phenomena, which have no observable counterpart in magneto-optical measurements, indicate an evolution of the magnetic state that deviates from that expected from a simple Ising ferromagnet. We attribute the effect to the large in-plane component of the magnetization, which we suggest to point in different directions in different $\rm{VI_3}$ layers. Our results provide new information about magnetism in exfoliated $\rm{VI_3}$ crystals and illustrate the complementarity of magnetotransport and magneto-optical measurements to probe the state of atomically thin 2D magnets.Comment: 10 pages, 5 figure

Cognitive Reserve as a Protective Factor of Mental Health in Middle-Aged Adults Affected by Chronic Pain

Chronic pain is associated with worse mental health and cognitive impairment, which can be a cause or a consequence of brain structure and function alterations, e.g., maladaptive plasticity, antinociceptive system dysregulation. Cognitive reserve reflects the effectiveness of the internal connections of the brain and it has been shown to be a protective factor in brain damage, slowing cognitive aging or reducing the risk of mental health disorders. The current study explored the impact of chronic pain on psychosocial factors, mental health, and cognition. Furthermore, we aimed to examine the role of cognitive reserve in the relationship between mental health and chronic pain clinical characteristics in middle-aged adults. The study group consisted of 477 volunteers from the Barcelona Brain Health Initiative who completed online surveys on pain, mental health, cognitive reserve, and psychosocial factors (sleep and quality of life). We described the differences in sociodemographic data, psychosocial factors, mental health, and self-perceived cognitive impairment, and neuropsychological assessment, between participants reporting pain compared with those without pain, as well as the main characteristics of the chronic pain group. Finally, to study the role of cognitive reserve in the modulation of the relationship between chronic pain and mental health, we compared variables between subgroups of participants with high/low pain intensity and cognitive reserve. The results showed that chronic pain was reported by 45.5% of middle-aged adults. Our results revealed that participants with chronic pain were older and had worse health status than people without pain. The presence of chronic pain affected working memory, mental health, and daily life activities. Moreover, cognitive reserve moderated the influence of pain intensity on mental health, resulting in less mental health affection in people suffering from high pain intensity with high cognitive reserve. In conclusion, the construct of the cognitive reserve could explain differential susceptibility between chronic pain and its mental health association and be a powerful tool in chronic pain assessment and treatment, principally due to its modifiable nature

Growth hormone remodels the 3D-structure of the mitochondria of inflammatory macrophages and promotes metabolic reprogramming

IntroductionMacrophages are a heterogeneous population of innate immune cells that support tissue homeostasis through their involvement in tissue development and repair, and pathogen defense. Emerging data reveal that metabolism may control macrophage polarization and function and, conversely, phenotypic polarization may drive metabolic reprogramming.MethodsHere we use biochemical analysis, correlative cryogenic fluorescence microscopy and cryo-focused ion-beam scanning electron microscopy.ResultsWe demonstrate that growth hormone (GH) reprograms inflammatory GM-CSF-primed monocyte-derived macrophages (GM-MØ) by functioning as a metabolic modulator. We found that exogenous treatment of GM-MØ with recombinant human GH reduced glycolysis and lactate production to levels similar to those found in anti-inflammatory M-MØ. Moreover, GH treatment of GM-MØ augmented mitochondrial volume and altered mitochondrial dynamics, including the remodeling of the inner membrane to increase the density of cristae.ConclusionsOur data demonstrate that GH likely serves a modulatory role in the metabolism of inflammatory macrophages and suggest that metabolic reprogramming of macrophages should be considered as a new target to intervene in inflammatory diseases