479 research outputs found
Direct electronic measurement of the spin Hall effect
The generation, manipulation and detection of spin-polarized electrons in
nanostructures define the main challenges of spin-based electronics[1]. Amongst
the different approaches for spin generation and manipulation, spin-orbit
coupling, which couples the spin of an electron to its momentum, is attracting
considerable interest. In a spin-orbit-coupled system, a nonzero spin-current
is predicted in a direction perpendicular to the applied electric field, giving
rise to a "spin Hall effect"[2-4]. Consistent with this effect,
electrically-induced spin polarization was recently detected by optical
techniques at the edges of a semiconductor channel[5] and in two-dimensional
electron gases in semiconductor heterostructures[6,7]. Here we report
electrical measurements of the spin-Hall effect in a diffusive metallic
conductor, using a ferromagnetic electrode in combination with a tunnel barrier
to inject a spin-polarized current. In our devices, we observe an induced
voltage that results exclusively from the conversion of the injected spin
current into charge imbalance through the spin Hall effect. Such a voltage is
proportional to the component of the injected spins that is perpendicular to
the plane defined by the spin current direction and the voltage probes. These
experiments reveal opportunities for efficient spin detection without the need
for magnetic materials, which could lead to useful spintronics devices that
integrate information processing and data storage.Comment: 5 pages, 4 figures. Accepted for publication in Nature (pending
format approval
The effect of Lycium Barbarum on spinal cord injury, particularly its relationship with M1 and M2 macrophage in rats
BACKGROUND: Our past researches suggested that L. barbarum exhibits direct neuroprotective and immune regulatory effects on the central nervous system, which are highly related to the events involved in the spinal cord injury, but not yet been investigated. Immune responses play an important role in the development of the pathology after secondary injury, particularly the M1 and M2 types of macrophage, on which special emphasis was laid in this study. METHODS: In our previous studies L. barbarum was administrated orally from 7 days before the injury to ensure a stabilized concentration in the blood. For clinical application, L. barbarum can only be administered after the injury. Therefore, both pre-injury and post-injury administration protocols were compared. In vivo and in vitro studies were conducted and analyzed immunohistochemically, including Western blotting. RESULTS: The lesion size in the pre-treated group was much larger than that in the post-treated group. To explain this difference, we first studied the effect of L. barbarum on astrocytes, which forms the glial scar encircling the lesion. L. barbarum did not significantly affect the astrocytes. Then we studied the effect of L. barbarum on microglia/macrophages, particularly the M1 and M2 polarization. After spinal cord injury, the deleterious M1 cells dominant the early period, whereas the beneficial M2 cells dominate later. We found that in the pre-treated group L. barbarum significantly enhanced the expression of M1 cells and suppressed that of M2 cells, while in the post-treated group LBP markedly promoted the activity of M2 cells. This explained the difference between the pre- and post-treated groups. CONCLUSIONS: Lycium barbarum has been wildly accepted to have beneficial effects in various central nervous system diseases. Our finding of deleterious effect of LBP administered at early period of spinal cord injury, indicates that its application should be avoided. The substantial beneficial effect of LBP when administered at later stage has an important impact for clinical application
Social disorganization and history of child sexual abuse against girls in sub-Saharan Africa : a multilevel analysis
Background:
Child sexual abuse (CSA) is a considerable public health problem. Less focus has been paid to the role of community level factors associated with CSA. The aim of this study was to examine the association between neighbourhood-level measures of social disorganization and CSA.
Methods:
We applied multiple multilevel logistic regression analysis on Demographic and Health Survey data for 6,351 adolescents from six countries in sub-Saharan Africa between 2006 and 2008.
Results:
The percentage of adolescents that had experienced CSA ranged from 1.04% to 5.84%. There was a significant variation in the odds of reporting CSA across the communities, suggesting 18% of the variation in CSA could be attributed to community level factors. Respondents currently employed were more likely to have reported CSA than those who were unemployed (odds ratio [OR] = 2.05, 95% confidence interval [CI] 1.48 to 2.83). Respondents from communities with a high family disruption rate were 57% more likely to have reported CSA (OR=1.57, 95% CI 1.14 to 2.16).
Conclusion:
We found that exposure to CSA was associated with high community level of family disruption, thus suggesting that neighbourhoods may indeed have significant important effects on exposure to CSA. Further studies are needed to explore pathways that connect the individual and neighbourhood levels, that is, means through which deleterious neighbourhood effects are transmitted to individuals
Spin Seebeck insulator
Thermoelectric generation is an essential function of future energy-saving
technologies. However, this generation has been an exclusive feature of
electric conductors, a situation which inflicts a heavy toll on its
application; a conduction electron often becomes a nuisance in thermal design
of devices. Here we report electric-voltage generation from heat flowing in an
insulator. We reveal that, despite the absence of conduction electrons, a
magnetic insulator LaY2Fe5O12 converts a heat flow into spin voltage. Attached
Pt films transform this spin voltage into electric voltage by the inverse spin
Hall effect. The experimental results require us to introduce thermally
activated interface spin exchange between LaY2Fe5O12 and Pt. Our findings
extend the range of potential materials for thermoelectric applications and
provide a crucial piece of information for understanding the physics of the
spin Seebeck effect.Comment: 19 pages, 5 figures (including supplementary information
Use of clinical chromosomal microarray in Chinese patients with autism spectrum disorder—implications of a copy number variation involving DPP10
published_or_final_versio
Spin-injection Hall effect in a planar photovoltaic cell
Successful incorporation of the spin degree of freedom in semiconductor
technology requires the development of a new paradigm allowing for a scalable,
non-destructive electrical detection of the spin-polarization of injected
charge carriers as they propagate along the semiconducting channel. In this
paper we report the observation of a spin-injection Hall effect (SIHE) which
exploits the quantum-relativistic nature of spin-charge transport and which
meets all these key requirements on the spin detection. The two-dimensional
electron-hole gas photo-voltaic cell we designed to observe the SIHE allows us
to develop a quantitative microscopic theory of the phenomenon and to
demonstrate its direct application in optoelectronics. We report an
experimental realization of a non-magnetic spin-photovoltaic effect via the
SIHE, rendering our device an electrical polarimeter which directly converts
the degree of circular polarization of light to a voltage signal.Comment: 14 pages, 4 figure
All-linear time reversal by a dynamic artificial crystal
The time reversal of pulsed signals or propagating wave packets has long been recognized to have profound scientific and technological significance. Until now, all experimentally verified time-reversal mechanisms have been reliant upon nonlinear phenomena such as four-wave mixing. In this paper, we report the experimental realization of all-linear time reversal. The time-reversal mechanism we propose is based on the dynamic control of an artificial crystal structure, and is demonstrated in a spin-wave system using a dynamic magnonic crystal. The crystal is switched from an homogeneous state to one in which its properties vary with spatial period a, while a propagating wave packet is inside. As a result, a linear coupling between wave components with wave vectors k≈π/a and k′=k−2ππ/a≈−π/a is produced, which leads to spectral inversion, and thus to the formation of a time-reversed wave packet. The reversal mechanism is entirely general and so applicable to artificial crystal systems of any physical nature
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