3,180 research outputs found
Neural Ideal Point Estimation Network
Understanding politics is challenging because the politics take the influence
from everything. Even we limit ourselves to the political context in the
legislative processes; we need a better understanding of latent factors, such
as legislators, bills, their ideal points, and their relations. From the
modeling perspective, this is difficult 1) because these observations lie in a
high dimension that requires learning on low dimensional representations, and
2) because these observations require complex probabilistic modeling with
latent variables to reflect the causalities. This paper presents a new model to
reflect and understand this political setting, NIPEN, including factors
mentioned above in the legislation. We propose two versions of NIPEN: one is a
hybrid model of deep learning and probabilistic graphical model, and the other
model is a neural tensor model. Our result indicates that NIPEN successfully
learns the manifold of the legislative bill texts, and NIPEN utilizes the
learned low-dimensional latent variables to increase the prediction performance
of legislators' votings. Additionally, by virtue of being a domain-rich
probabilistic model, NIPEN shows the hidden strength of the legislators' trust
network and their various characteristics on casting votes
Structural and Correlation Effects in the Itinerant Insulating Antiferromagnetic Perovskite NaOsO3
The orthorhombic perovskite NaOsO3 undergoes a continuous metal-insulator
transition (MIT), accompanied by antiferromagnetic (AFM) order at T_N=410 K,
suggested to be an example of the rare Slater (itinerant) MIT. We study this
system using ab initio and related methods, focusing on the origin and nature
of magnetic ordering and the MIT. The rotation and tilting of OsO6 octahedra in
the GdFeO3 structure result in moderate narrowing the band width of the t_{2g}
manifold, but sufficient to induce flattening of bands and AFM order within the
local spin density approximation (LSDA), where it remains metallic but with a
deep pseudogap. Including on-site Coulomb repulsion U, at U_c ~2 eV a MIT
occurs only in the AFM state. Effects of spin-orbit coupling (SOC) on the band
structure seem minor as expected for a half-filled shell, but SOC
doubles the critical value U_c necessary to open a gap and also leads to large
magnetocrystalline energy differences in spite of normal orbital moments no
greater than 0.1. Our results are consistent with a Slater MIT driven by
magnetic order, induced by a combination of structurally-induced band narrowing
and moderate Coulomb repulsion, with SOC necessary for a full picture. Strong
p-d hybridization reduces the moment, and when bootstrapped by the reduced
Hund's rule coupling (proportional to the moment) gives a calculated moment of
~1 , consistent with the observed moment and only a third of the formal
value. We raise and discuss one important question: since this AFM
ordering is at q=0 (in the 20 atom cell) where nesting is a moot issue, what is
the microscopic driving force for ordering and the accompanying MIT?Comment: 9 page
Putative cell adhesion membrane protein Vstm5 regulates neuronal morphology and migration in the central nervous system
During brain development, dynamic changes in neuronal membranes perform critical roles in neuronal morphogenesis and migration to create functional neural circuits. Among the proteins that induce membrane dynamics, cell adhesion molecules are important in neuronal membrane plasticity. Here, we report that V-set and transmembrane domain-containing protein 5 (Vstm5), a cell-adhesion-like molecule belonging to the Ig superfamily, was found in mouse brain. Knock-down of Vstm5 in cultured hippocampal neurons markedly reduced the complexity of dendritic structures, as well as the number of dendritic filopodia. Vstm5 also regulates neuronal morphology by promoting dendritic protrusions that later develop into dendritic spines. Using electroporationin utero, we found that Vstm5 overexpression delayed neuronal migration and induced multiple branches in leading processes during corticogenesis. These results indicate that Vstm5 is a new cell-adhesion-like molecule and is critically involved in synaptogenesis and corticogenesis by promoting neuronal membrane dynamics.SIGNIFICANCE STATEMENTNeuronal migration and morphogenesis play critical roles in brain development and function. In this study, we demonstrate for the first time that V-set and transmembrane domain-containing protein 5 (Vstm5), a putative cell adhesion membrane protein, modulates both the position and complexity of central neurons by altering their membrane morphology and dynamics. Vstm5 is also one of the target genes responsible for variations in patient responses to treatments for major depressive disorder. Our results provide the first evidence that Vstm5 is a novel factor involved in the modulation of the neuronal membrane and a critical element in normal neural circuit formation during mammalian brain development.</jats:p
Searching for MgII absorbers in and around galaxy clusters
To study environmental effects on the circumgalactic medium (CGM), we use the
samples of redMaPPer galaxy clusters, background quasars and cluster galaxies
from the SDSS. With ~82 000 quasar spectra, we detect 197 MgII absorbers in and
around the clusters. The detection rate per quasar is 2.70.7 times higher
inside the clusters than outside the clusters, indicating that MgII absorbers
are relatively abundant in clusters. However, when considering the galaxy
number density, the absorber-to-galaxy ratio is rather low inside the clusters.
If we assume that MgII absorbers are mainly contributed by the CGM of massive
star-forming galaxies, a typical halo size of cluster galaxies is smaller than
that of field galaxies by 3010 per cent. This finding supports that galaxy
haloes can be truncated by interaction with the host cluster.Comment: 11 pages, 12 figures. To appear in MNRA
Blending-NeRF: Text-Driven Localized Editing in Neural Radiance Fields
Text-driven localized editing of 3D objects is particularly difficult as
locally mixing the original 3D object with the intended new object and style
effects without distorting the object's form is not a straightforward process.
To address this issue, we propose a novel NeRF-based model, Blending-NeRF,
which consists of two NeRF networks: pretrained NeRF and editable NeRF.
Additionally, we introduce new blending operations that allow Blending-NeRF to
properly edit target regions which are localized by text. By using a pretrained
vision-language aligned model, CLIP, we guide Blending-NeRF to add new objects
with varying colors and densities, modify textures, and remove parts of the
original object. Our extensive experiments demonstrate that Blending-NeRF
produces naturally and locally edited 3D objects from various text prompts. Our
project page is available at https://seokhunchoi.github.io/Blending-NeRF/Comment: Accepted to ICCV 2023. The first two authors contributed equally to
this wor
Adversarial Dropout for Recurrent Neural Networks
Successful application processing sequential data, such as text and speech,
requires an improved generalization performance of recurrent neural networks
(RNNs). Dropout techniques for RNNs were introduced to respond to these
demands, but we conjecture that the dropout on RNNs could have been improved by
adopting the adversarial concept. This paper investigates ways to improve the
dropout for RNNs by utilizing intentionally generated dropout masks.
Specifically, the guided dropout used in this research is called as adversarial
dropout, which adversarially disconnects neurons that are dominantly used to
predict correct targets over time. Our analysis showed that our regularizer,
which consists of a gap between the original and the reconfigured RNNs, was the
upper bound of the gap between the training and the inference phases of the
random dropout. We demonstrated that minimizing our regularizer improved the
effectiveness of the dropout for RNNs on sequential MNIST tasks,
semi-supervised text classification tasks, and language modeling tasks.Comment: published in AAAI1
Treatment of Spontaneous Cervical Spinal Subdural Hematoma with Methylprednisolone Pulse Therapy
We report herein a case of hyperacute onset of spontaneous cervical spinal subdural hematoma treated with methylprednisolone pulse therapy that showed good results. A 57-year-old man was admitted for posterior neck pain and paraparesis which occurred an hour ago. MRI revealed a ventral subdural hematoma distributed from the level of C1 down to T3, compressing the spinal cord. Conservative management with methylprednisolone pulse therapy was administered considering the patient's poor general condition. Although emergent surgical decompression is necessary in most cases of spinal subdural hematoma, conservative management with steroid therapy could be effective
Quasi-particle scattering and protected nature of topological states in a parent topological insulator BiSe
We report on angle resolved photoemission spectroscopic studies on a parent
topological insulator (TI), BiSe. The line width of the spectral
function (inverse of the quasi-particle lifetime) of the topological metallic
(TM) states shows an anomalous behavior. This behavior can be reasonably
accounted for by assuming decay of the quasi-particles predominantly into bulk
electronic states through electron-electron interaction and defect scattering.
Studies on aged surfaces reveal that topological metallic states are very much
unaffected by the potentials created by adsorbed atoms or molecules on the
surface, indicating that topological states could be indeed protected against
weak perturbations.Comment: accepted for publication in Phys. Rev. B(R
Angle-tolerant linear variable color filter based on a tapered etalon
We propose and fabricate a linear variable color filter (LVCF) that possesses an enhanced angular tolerance in conjunction with a wide linear filtering range (LFR) by taking advantage of an Ag-TiO2-Ag configuration. The TiO2 cavity is tapered in thickness along the device so that the resonance wavelength can be continuously tuned according to the position. In addition, the metal-dielectric-metal structure is overlaid with a pre-designed graded anti-reflection coating in SiO2 to complete the etalon, thereby maximizing the transmission efficiency across the entire device. The tapered dielectric layers in the proposed filter were
fabricated via glancing angle deposition without the help of any mask or moving parts. The center wavelength was scanned from 410 nm to 566 nm, resulting in an LFR of 156 nm, and the overall spectra exhibited an approximate peak transmission of 40% and spectral
bandwidth of 68 nm. The angular tolerance was as large as 45°, incurring a fractional wavelength shift below 4.2%. The resonance wavelength was verified to be linearly dependent on the position, providing a linearity beyond 99%. The proposed LVCF will thus
be actively utilized in a portable micro-spectrometer and spectral scanning device.National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (No. 2016R1A2B2010170); ARC Future Fellowship FT110100853
GaAs droplet quantum dots with nanometer-thin capping layer for plasmonic applications
We report on the growth and optical characterisation of droplet GaAs quantum
dots with extremely-thin (11 nm) capping layers. To achieve such result, an
internal thermal heating step is introduced during the growth and its role in
the morphological properties of the quantum dots obtained is investigated via
scanning electron and atomic force microscopy. Photoluminescence measurements
at cryogenic temperatures show optically stable, sharp and bright emission from
single quantum dots, at near-infrared wavelengths. Given the quality of their
optical properties and the proximity to the surface, such emitters are ideal
candidates for the investigation of near field effects, like the coupling to
plasmonic modes, in order to strongly control the directionality of the
emission and/or the spontaneous emission rate, crucial parameters for quantum
photonic applications.Comment: 1 pages, 3 figure
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