The Anomalous Hall effect in re-entrant AuFe alloys and the real space Berry phase

The Hall effect has been studied in a series of AuFe samples in the re-entrant concentration range, as well as in the spin glass range. The data demonstrate that the degree of canting of the local spins strongly modifies the anomalous Hall effect, in agreement with theoretical predictions associating canting, chirality and a real space Berry phase. The canonical parametrization of the Hall signal for magnetic conductors becomes inappropriate when local spins are canted.Comment: 4 pages, 1 eps figur

The chiral Anomalous Hall effect in re-entrant AuFe alloys

The Hall effect has been studied in a series of AuFe samples in the re-entrant concentration range, as well as in part of the spin glass range. An anomalous Hall contribution linked to the tilting of the local spins can be identified, confirming theoretical predictions of a novel topological Hall term induced when chirality is present. This effect can be understood in terms of Aharonov-Bohm-like intrinsic current loops arising from successive scatterings by canted local spins. The experimental measurements indicate that the chiral signal persists, meaning scattering within the nanoscopic loops remains coherent, up to temperatures of the order of 150 K.Comment: 7 pages, 11 eps figures Published version. Minor change

Análise de Transiçao Resistiva e da irreversibilidade magnètica no superconductor YBACUO texturizado

Os supercondutores de alta temperatura crítica, em especial os granulares, apresentam uma transição resistiva que ocorre em duas etapas: a uma temperatura acima da temperatura crítica de transição Tc0, chamada de supercondutividade intragranular e a uma temperatura mais baixa onde ocorre a supercondutividade em toda a amostra, chamada de supercondutividade intergranular. Em Tc0 ocorre à ativação das ligações fracas e uma ordem de longo alcance é obtida, neste momento, a resistência elétrica é nula em toda amostra. Nos supercondutores de alta temperatura crítica, a linha de irreversibilidade magnética divide o estado misto do plano H-T em duas regiões: reversível e irreversível. Na região reversível todo o transporte elétrico sofre dissipação devido aos efeitos da dinâmica de fluxo magnético no supercondutor. Na região irreversível todo transporte de corrente elétrica é permitido. Em supercondutores granulares, as medidas de irreversibilidade magnética e resistividade nula não dependem das mesmas partes da amostra. Enquanto, a resistência elétrica depende de um arranjo de grãos que atravessam toda a amostra a irreversibilidade depende de clusters de grãos bem acoplados. Devido a isso, as medidas de resistência nula devem estar em pontos abaixo da linha de irreversibilidade magnética. O objetivo deste trabalho é analisar as medidas de transporte elétrico e magnetização e correlacionar às linhas de resistência nula e as linhas de irreversibilidade magnética, em diferentes orientações de campo-corrente, para uma amostra com a adição de 30% da fase Y211 (Y2BaCuO5) e comparar os dados obtidos com uma amostra na qual foram adicionados 17% desta mesma fase.Postprint (published version

Functional behavior of the anomalous magnetic relaxation observed in melt-textured YBa2Cu3O7-δ samples showing the paramagnetic Meissner effect

We have studied the functional behavior of the field-cooled (FC) magnetic relaxation observed in melt-textured YBa2Cu3O7-δ (Y123) samples with 30 wt% of Y2Ba1Cu1O5 (Y211) phase, in order to investigate anomalous paramagnetic moments observed during the experiments. FC magnetic relaxation experiments were performed under controlled conditions, such as cooling rate and temperature. Magnetic fields up to 5T were applied parallel to the ab plane and along the c-axis. Our results are associated with the paramagnetic Meissner effect (PME), characterized by positive moments during FC experiments, and related to the magnetic flux compression into the samples. After different attempts our experimental data could be adequately fitted by an exponential decay function with different relaxation times. We discuss our results suggesting the existence of different and preferential flux dynamics governing the anomalous FC paramagnetic relaxation in different time intervals. This work is one of the first attempts to interpret this controversial effect in a simple analysis of the pinning mechanisms and flux dynamics acting during the time evolution of the magnetic moment. However, the results may be useful to develop models to explain this interesting and still misunderstood feature of the paramagnetic Meissner effect

Phytocannabinoid-dependent mTORC1 regulation is dependent upon inositol polyphosphate multikinase activity

BACKGROUND AND PURPOSE: Cannabidiol (CBD) has been shown to differentially regulate the mechanistic target of rapamycin complex 1 (mTORC1) in preclinical models of disease, where it reduces activity in models of epilepsies and cancer and increases it in models of multiple sclerosis (MS) and psychosis. Here, we investigate the effects of phytocannabinoids on mTORC1 and define a molecular mechanism. EXPERIMENTAL APPROACH: A novel mechanism for phytocannabinoids was identified using the tractable model system, Dictyostelium discoideum. Using mouse embryonic fibroblasts, we further validate this new mechanism of action. We demonstrate clinical relevance using cells derived from healthy individuals and from people with MS (pwMS). KEY RESULTS: Both CBD and the more abundant cannabigerol (CBG) enhance mTORC1 activity in D. discoideum. We identify a mechanism for this effect involving inositol polyphosphate multikinase (IPMK), where elevated IPMK expression reverses the response to phytocannabinoids, decreasing mTORC1 activity upon treatment, providing new insight on phytocannabinoids' actions. We further validated this mechanism using mouse embryonic fibroblasts. Clinical relevance of this effect was shown in primary human peripheral blood mononuclear cells, where CBD and CBG treatment increased mTORC1 activity in cells derived from healthy individuals and decreased mTORC1 activity in cells derived from pwMS. CONCLUSION AND IMPLICATIONS: Our findings suggest that both CBD and the abundant CBG differentially regulate mTORC1 signalling through a mechanism dependent on the activity of the upstream IPMK signalling pathway, with potential relevance to the treatment of mTOR-related disorders, including MS

Caracterización mecánica a escala picométrica de YBa1.75Sr0.25Cu3O7-d monocristalino mediante la técnica de autoflujo

Se implementa un método para indentar superficies rígidas a niveles nanométricos utilizando un microscopio de fuerzas atómicas (Atomic Force Microscopy-AFM), empleando el modo de espectroscopia de fuerzas (Force Spectroscopy-FS), el cual nos permite generar un movimiento vertical de la punta sin producir fuerzas laterales. Uno de los factores más críticos durante este estudio ha sido caracterizar la máxima fuerza aplicada por el AFM la cual no produce deformación remanente, esto se ha obtenido a partir del factor de sensitividad de la palanca del AFM, así como de la correcta determinación del radio de curvatura (r) de la punta antes y después de la indentación. A partir de las curvas de fuerzapenetración (F vs. he) obtenidas a 200 nN de carga aplicada, y utilizando un modelo de contacto Hertziano, se ha podido determinar el módulo de Young (E) del material cuando se encuentra sometido a un campo de deformación totalmente elástico.Postprint (published version

COPPADIS-2015 (COhort of Patients with PArkinson's DIsease in Spain, 2015), a global--clinical evaluations, serum biomarkers, genetic studies and neuroimaging--prospective, multicenter, non-interventional, long-term study on Parkinson's disease progressio

Background: Parkinson?s disease (PD) is a progressive neurodegenerative disorder causing motor and non-motor symptoms that can affect independence, social adjustment and the quality of life (QoL) of both patients and caregivers. Studies designed to find diagnostic and/or progression biomarkers of PD are needed. We describe here the study protocol of COPPADIS-2015 (COhort of Patients with PArkinson?s DIsease in Spain, 2015), an integral PD project based on four aspects/concepts: 1) PD as a global disease (motor and non-motor symptoms); 2) QoL and caregiver issues; 3) Biomarkers; 4) Disease progression.Methods/design: Observational, descriptive, non-interventional, 5-year follow-up, national (Spain), multicenter (45 centers from 15 autonomous communities), evaluation study. Specific goals: (1) detailed study (clinical evaluations, serum biomarkers, genetic studies and neuroimaging) of a population of PD patients from different areas of Spain, (2) comparison with a control group and (3) follow-up for 5 years. COPPADIS-2015 has been specifically designed to assess 17 proposed objectives. Study population: approximately 800 non-dementia PD patients, 600 principal caregivers and 400 control subjects. Study evaluations: (1) baseline includes motor assessment (e.g., Unified Parkinson?s Disease Rating Scale part III), non-motor symptoms (e.g., Non-Motor Symptoms Scale), cognition (e.g., Parkinson?s Disease Cognitive Rating Scale), mood and neuropsychiatric symptoms (e.g., Neuropsychiatric Inventory), disability, QoL (e.g., 39-item Parkinson?s disease Quality of Life Questionnaire Summary-Index) and caregiver status (e.g., Zarit Caregiver Burden Inventory); (2) follow-up includes annual (patients) or biannual (caregivers and controls) evaluations. Serum biomarkers (S-100b protein, TNF-?, IL-1, IL-2, IL-6, vitamin B12, methylmalonic acid, homocysteine, uric acid, C-reactive protein, ferritin, iron) and brain MRI (volumetry, tractography and MTAi [Medial Temporal Atrophy Index]), at baseline and at the end of follow-up, and genetic studies (DNA and RNA) at baseline will be performed in a subgroup of subjects (300 PD patients and 100 control subjects). Study periods: (1) recruitment period, from November, 2015 to February, 2017 (basal assessment); (2) follow-up period, 5 years; (3) closing date of clinical follow-up, May, 2022. Funding: Public/Private. Discussion: COPPADIS-2015 is a challenging initiative. This project will provide important information on the natural history of PD and the value of various biomarkers