8,051 research outputs found
SphereFed: Hyperspherical Federated Learning
Federated Learning aims at training a global model from multiple
decentralized devices (i.e. clients) without exchanging their private local
data. A key challenge is the handling of non-i.i.d. (independent identically
distributed) data across multiple clients that may induce disparities of their
local features. We introduce the Hyperspherical Federated Learning (SphereFed)
framework to address the non-i.i.d. issue by constraining learned
representations of data points to be on a unit hypersphere shared by clients.
Specifically, all clients learn their local representations by minimizing the
loss with respect to a fixed classifier whose weights span the unit
hypersphere. After federated training in improving the global model, this
classifier is further calibrated with a closed-form solution by minimizing a
mean squared loss. We show that the calibration solution can be computed
efficiently and distributedly without direct access of local data. Extensive
experiments indicate that our SphereFed approach is able to improve the
accuracy of multiple existing federated learning algorithms by a considerable
margin (up to 6% on challenging datasets) with enhanced computation and
communication efficiency across datasets and model architectures.Comment: European Conference on Computer Vision 202
Parity Violation in Neutrino Transport and the Origin of Pulsar Kicks
In proto-neutron stars with strong magnetic fields, the neutrino-nucleon
scattering/absorption cross sections depend on the direction of neutrino
momentum with respect to the magnetic field axis, a manifestation of parity
violation in weak interactions. We study the deleptonization and thermal
cooling (via neutrino emission) of proto-neutron stars in the presence of such
asymmetric neutrino opacities. Significant asymmetry in neutrino emission is
obtained due to multiple neutrino-nucleon scatterings. For an ordered magnetic
field threading the neutron star interior, the fractional asymmetry in neutrino
emission is about , corresponding to a pulsar kick velocity
of about km/s for a total radiated neutrino energy of
erg.Comment: AASTeX, 10 pages including 2 ps figures; ApJ Letter in press (March
10, 1998). Shortened to agree with the published versio
Orbit- and Atom-Resolved Spin Textures of Intrinsic, Extrinsic and Hybridized Dirac Cone States
Combining first-principles calculations and spin- and angle-resolved
photoemission spectroscopy measurements, we identify the helical spin textures
for three different Dirac cone states in the interfaced systems of a 2D
topological insulator (TI) of Bi(111) bilayer and a 3D TI Bi2Se3 or Bi2Te3. The
spin texture is found to be the same for the intrinsic Dirac cone of Bi2Se3 or
Bi2Te3 surface state, the extrinsic Dirac cone of Bi bilayer state induced by
Rashba effect, and the hybridized Dirac cone between the former two states.
Further orbit- and atom-resolved analysis shows that s and pz orbits have a
clockwise (counterclockwise) spin rotation tangent to the iso-energy contour of
upper (lower) Dirac cone, while px and py orbits have an additional radial spin
component. The Dirac cone states may reside on different atomic layers, but
have the same spin texture. Our results suggest that the unique spin texture of
Dirac cone states is a signature property of spin-orbit coupling, independent
of topology
Transplantation of Ciliary Neurotrophic Factor-Expressing Adult Oligodendrocyte Precursor Cells Promotes Remyelination and Functional Recovery after SpinalCord Injury
Demyelination contributes to the dysfunction after traumatic spinal cord injury (SCI). We explored whether the combination of neurotrophic factors and transplantation of adult rat spinal cord oligodendrocyte precursor cells (OPCs) could enhance remyelination and functional recovery after SCI. Ciliary neurotrophic factor (CNTF) was the most effective neurotrophic factor to promote oligodendrocyte (OL) differentiation and survival of OPCs in vitro. OPCs were infected with retroviruses expressing enhanced green fluorescent protein (EGFP) or CNTF and transplanted into the contused adult thoracic spinal cord 9 d after injury. Seven weeks after transplantation, the grafted OPCs survived and integrated into the injured spinal cord. The survival of grafted CNTF-OPCs increased fourfold compared with EGFP-OPCs. The grafted OPCs differentiated into adenomatus polyposis coli (APC+) OLs, and CNTF significantly increased the percentage of APC+ OLs from grafted OPCs. Immunofluorescent and immunoelectron microscopic analyses showed that the grafted OPCs formed central myelin sheaths around the axons in the injured spinal cord. The number of OL-remyelinated axons in ventrolateral funiculus (VLF) or lateral funiculus (LF) at the injured epicenter was significantly increased in animals that received CNTF-OPC grafts compared with all other groups. Importantly, 75% of rats receiving CNTF-OPC grafts recovered transcranial magnetic motor-evoked potential and magnetic interenlargement reflex responses, indicating that conduction through the demyelinated axons in VLF or LF, respectively, was partially restored. More importantly, recovery of hindlimb locomotor function was significantly enhanced in animals receiving grafts of CNTF-OPCs. Thus, combined treatment with OPC grafts expressing CNTF can enhance remyelination and facilitate functional recovery after traumatic SCI
Human influence on the record-breaking cold event in January of 2016 in Eastern China
Anthropogenic influences are estimated to have reduced the likelihood of an extreme cold event in midwinter with the intensity equal to or stronger than the record of 2016 in eastern China by about twoâthirds
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Efficient distribution of carbon emissions reduction targets at the city level: A case of Yangtze River Delta region
The Chinese central government has released detailed carbon emissions abatement targets at the provincial level, but provides no specific emissions reduction targets at the city level. Most provincial governments simply allocate carbon emissions reduction tasks to their cities based on the GDP of their cities. Allocation approaches, however, should emphasize the most effective distribution to reach overall targets that reflect actual reduction capacities of cities. This paper proposes an allocation method at the city level by combining a data envelop analysis method, an entropy weight method and a clustering analysis method using the Yangtze River Delta region as a case study. Results of our analysis indicate that cities with higher carbon emissions abatement potentials, financial abilities, a larger number of above-scaled industrial enterprises and higher GDP are better positioned to reduce carbon emissions and should be assigned proportionately higher reduction targets. The merits and policy implications of the proposed approach are discussed in comparison to simply using GDP to allocate emission reduction targets
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