1,331 research outputs found
Spin motive forces and current fluctuations due to Brownian motion of domain walls
We compute the power spectrum of the noise in the current due to spin motive
forces by a fluctuating domain wall. We find that the power spectrum of the
noise in the current is colored, and depends on the Gilbert damping, the spin
transfer torque parameter , and the domain-wall pinning potential and
magnetic anisotropy. We also determine the average current induced by the
thermally-assisted motion of a domain wall that is driven by an external
magnetic field. Our results suggest that measuring the power spectrum of the
noise in the current in the presence of a domain wall may provide a new method
for characterizing the current-to-domain-wall coupling in the system.Comment: Submitted to "Special issue: Caloritronics" in Solid State
Communication
Spin-transfer mechanism for magnon-drag thermopower
We point out a relation between the dissipative spin-transfer-torque
parameter and the contribution of magnon drag to the thermoelectric
power in conducting ferromagnets. Using this result we estimate in iron
at low temperatures, where magnon drag is believed to be the dominant
contribution to the thermopower. Our results may be used to determine
from magnon-drag-thermopower experiments, or, conversely, to infer the strength
of magnon drag via experiments on spin transfer
Current-driven and field-driven domain walls at nonzero temperature
We present a model for the dynamics of current- and field-driven domain-wall
lines at nonzero temperature. We compute thermally-averaged drift velocities
from the Fokker-Planck equation that describes the nonzero-temperature dynamics
of the domain wall. As special limits of this general description, we describe
rigid domain walls as well as vortex domain walls. In these limits, we
determine also depinning times of the domain wall from an extrinsic pinning
potential. We compare our theory with previous theoretical and experimental
work
Spin motive forces due to magnetic vortices and domain walls
We study spin motive forces, i.e, spin-dependent forces, and voltages induced
by time-dependent magnetization textures, for moving magnetic vortices and
domain walls. First, we consider the voltage generated by a one-dimensional
field-driven domain wall. Next, we perform detailed calculations on
field-driven vortex domain walls. We find that the results for the voltage as a
function of magnetic field differ between the one-dimensional and vortex domain
wall. For the experimentally relevant case of a vortex domain wall, the
dependence of voltage on field around Walker breakdown depends qualitatively on
the ratio of the so-called -parameter to the Gilbert damping constant,
and thus provides a way to determine this ratio experimentally. We also
consider vortices on a magnetic disk in the presence of an AC magnetic field.
In this case, the phase difference between field and voltage on the edge is
determined by the parameter, providing another experimental method to
determine this quantity.Comment: 8 pages, 9 figures, submitted to PR
Exploring how biobanks communicate the possibility of commercial access and its associated benefits and risks in participant documents
Background
Biobanks and biomedical research data repositories collect their samples and associated data from volunteer participants. Their aims are to facilitate biomedical research and improve health, and they are framed in terms of contributing to the public good. Biobank resources may be accessible to researchers with commercial motivations, for example, researchers in pharmaceutical companies who may utilise the data to develop new clinical therapeutics and pharmaceutical drugs. Studies exploring citizen perceptions of public/private interactions associated with large health data repositories/biobanks indicate that there are sensitivities around public/private and/or non-profit/profit relationships and international sample and data sharing. Less work has explored how biobanks communicate their public/private partnerships to the public or to their potential research participants.
Methods
We explored how a biobank’s aims, benefits and risks, and private/public relationships have been framed in public facing recruitment documents (consent forms and participant information sheets).
Results
Biobank documents often communicate their commercial access arrangements but not the detail about what these interactions would entail, and how risks and benefits would be distributed to the public.
Conclusion
We argue that this leads to a polarised discourse between public and private entities and/or activities, and fails to attend to the blurred lines between them. This results in a lack of attention to more important issues such as how risks and benefits in general are distributed to the public. We call for a nuanced approach that can contribute to the much-needed dialogue in this space
Current-induced spin torques in III-V ferromagnetic semiconductors
We formulate a theory of current-induced spin torques in inhomogeneous III-V
ferromagnetic semiconductors. The carrier spin-3/2 and large spin-orbit
interaction, leading to spin non-conservation, introduce significant conceptual
differences from spin torques in ferromagnetic metals. We determine the spin
density in an electric field in the weak momentum scattering regime,
demonstrating that the torque on the magnetization is intimately related to
spin precession under the action of both the spin-orbit interaction and the
exchange field characteristic of ferromagnetism. The spin polarization excited
by the electric field is smaller than in ferromagnetic metals and, due to lack
of angular momentum conservation, cannot be expressed in a simple closed
vectorial form. Remarkably, scalar and spin-dependent scattering do not affect
the result. We use our results to estimate the velocity of current-driven
domain walls.Comment: 10 page
Exploring how biobanks communicate the possibility of commercial access and its associated benefits and risks in participant documents
BACKGROUND: Biobanks and biomedical research data repositories collect their samples and associated data from volunteer participants. Their aims are to facilitate biomedical research and improve health, and they are framed in terms of contributing to the public good. Biobank resources may be accessible to researchers with commercial motivations, for example, researchers in pharmaceutical companies who may utilise the data to develop new clinical therapeutics and pharmaceutical drugs. Studies exploring citizen perceptions of public/private interactions associated with large health data repositories/biobanks indicate that there are sensitivities around public/private and/or non-profit/profit relationships and international sample and data sharing. Less work has explored how biobanks communicate their public/private partnerships to the public or to their potential research participants. METHODS: We explored how a biobank's aims, benefits and risks, and private/public relationships have been framed in public facing recruitment documents (consent forms and participant information sheets). RESULTS: Biobank documents often communicate their commercial access arrangements but not the detail about what these interactions would entail, and how risks and benefits would be distributed to the public. CONCLUSION: We argue that this leads to a polarised discourse between public and private entities and/or activities, and fails to attend to the blurred lines between them. This results in a lack of attention to more important issues such as how risks and benefits in general are distributed to the public. We call for a nuanced approach that can contribute to the much-needed dialogue in this space
A Randomized Controlled Trial Comparing two Cognitive-Behavioral Programs for Adolescent Girls with Subclinical Depression: A School-Based Program (Op Volle Kracht) and a Computerized Program (SPARX)
Limited research has indicated the effectiveness of the school-based Cognitive Behavioral Therapy (CBT) prevention program ‘Op Volle Kracht (OVK)’ and the computerized CBT program ‘SPARX’ in decreasing depressive symptoms. Therefore, a randomized controlled trial of the effectiveness of OVK and SPARX was conducted among Dutch female adolescents (n = 208, mean age = 13.35) with elevated depressive symptoms. Participants were randomly assigned to one of four conditions: OVK only (n = 50), SPARX only (n = 51), OVK and SPARX combined (n = 56) and a monitoring control condition (n = 51). Participants in the first three conditions received OVK lessons and/or the SPARX game. Depressive symptoms were assessed before interventions started, weekly during the interventions, and immediately after the interventions ended, with follow-up assessments at 3, 6 and 12 months. Intention to treat results showed that depressive symptoms decreased in all conditions (F(12, 1853.03) = 14.62, p < .001), with no difference in depressive symptoms between conditions. Thus, all conditions, including the monitoring control condition, were equally effective in reducing depressive symptoms. Possible explanations for the decrease of depressive symptoms in all conditions are discussed and suggestions for future research are provided. Dutch Trial Register: NTR3737
Geoquímica y sistemática isotópica de rocas metamórficas del Paleozoico inferior. Noroeste de Argentina y Norte de Chile (21°-27° S)
Más del 95% de los afloramientos del basamento metamórfico del Paleozoico inferior en el Noroeste de A rgentina y Norte de Chile están compuestos por rocas félsicas. Los contenidos de elementos mayores, trazas y las composiciones isotópicas de Pb, Rb-Sr y Sm-Nd son típicos de las rocas que conforman la corteza superior. Las edades modelos Sm-Nd de las rocas estudiadas son de ca 1.8 Ga. Estas rocas han sido afectadas por un evento principal de metamorfismo del Paleozoico temprano (ca. 500 Ma).
Se considera que el reciclado de la corteza, con un importante evento de metamorfismo durante el Paleozoico temprano, es el proceso dominante en la generación de muchos de los magmas con composiciones graníticas originados desde el Paleozoico temprano hasta el Reciente.
Las espesas secuencias sedimentarias ordovícicas son derivadas también de esa misma corteza en común. Los xenolitos félsicos de la corteza inferior extraídos por el magmatismo perteneciente al sistema del Rift Salta, son muy similares composicionalmente al basamento del Paleozoico inferior. Se estima que la composición de la corteza desde la parte superior hasta la inferior sería principalmente félsica.
Las rocas máficas tienen muy poco volumen y forman principalmente diques. Sus edades modelos Sm-Nd revelan dos grupos, uno con edades de ca 1.8 Ga y otro con edades de ca £ 1.0 Ga No ha sido posible realizar una interpretación ajustada del ambiente geodinámico en donde se ha desarrollado este magmatismo básico.Felsic rocks comprise more than 95% of the outcropping Early Paleozoic metamorphic basement. Their major and trace element contents and Pb, Rb-Sr and Sm-Nd isotope compositions are typical for upper crustal rocks. Sm-Nd model ages are ca 1.8 Ga. The principal ages of high-grade metamorphism is Early Paleozoic (ca 500 Ma).
Recycling of this crust is the dominating process in the formation of granitoid magmatic rocks from Early Paleozoic to Recent. Ordovician sediments are also derivates of this crust. Felsic lower crustal xenoliths from the Salta Rift system are compositionally very similar compared to the early Paleozoic basement. The crustal composition from top to the bottom seems mainly felsic.
Early Paleozoic mafic rocks are of minor volume and form mainly dikes. Their Sm-Nd model ages reveal two groups; one with ages of ca 1.8 Ga another with ages of £ 1.0 Ga. A meaningful interpretation of their geodynamic setting is not possible
Fluctuations of current-driven domain walls in the non-adiabatic regime
We outline a general framework to determine the effect of non-equilibrium
fluctuations on driven collective coordinates, and apply it to a current-driven
domain wall in a nanocontact. In this case the collective coordinates are the
domain-wall position and its chirality, that give rise to momentum transfer and
spin transfer, respectively. We determine the current-induced fluctuations
corresponding to these processes and show that at small frequencies they can be
incorporated by two separate effective temperatures. As an application, the
average time to depin the domain wall is calculated and found to be lowered by
current-induced fluctuations. It is shown that current-induced fluctuations
play an important role for narrow domain walls, especially at low temperatures.Comment: More computations, explanations, and results include
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