752 research outputs found
Effects of electrode surface roughness on motional heating of trapped ions
Electric field noise is a major source of motional heating in trapped ion
quantum computation. While the influence of trap electrode geometries on
electric field noise has been studied in patch potential and surface adsorbate
models, only smooth surfaces are accounted for by current theory. The effects
of roughness, a ubiquitous feature of surface electrodes, are poorly
understood. We investigate its impact on electric field noise by deriving a
rough-surface Green's function and evaluating its effects on adsorbate-surface
binding energies. At cryogenic temperatures, heating rate contributions from
adsorbates are predicted to exhibit an exponential sensitivity to local surface
curvature, leading to either a large net enhancement or suppression over smooth
surfaces. For typical experimental parameters, orders-of-magnitude variations
in total heating rates can occur depending on the spatial distribution of
absorbates. Through careful engineering of electrode surface profiles, our
results suggests that heating rates can be tuned over orders of magnitudes.Comment: 12 pages, 5 figure
Continuing Use of SNS Games for the Growth of Social Network Services
By using Social Network Services (SNSs) as platforms, game developers have gathered a huge user base, and the entertainment these games provide has further enlarged the SNS user base. However, there are signs that this symbiotic growth is slowing down. We developed a model and tested 14 hypotheses. Our main findings are: Although SNSs are “social,” “social norms” do not have much impact on the intention to use the games continually. Although users generally are not addicted to SNS games, the creation of addiction is an effective way to achieve continuance
Childhood tuberculosis in southern Taiwan, with emphasis on central nervous system complications
Background/PurposeChildhood tuberculosis (TB) continues to be a major public health problem in Taiwan. Taiwan remains a highly endemic area despite neonatal Bacillus Calmette–Guérin (BCG) vaccination and the availability of anti-TB therapy. The presentation is highly variable and it is often difficult to make an accurate diagnosis. This study was designed to evaluate the demographic, clinical, and laboratory findings and outcomes of TB in children with emphasis on central nervous system (CNS) complications.MethodsThe medical records of 80 children diagnosed with TB at a medical center in southern Taiwan over the past 24 years (1988–2012) were reviewed.ResultsAmong them, 48.8% (39/80) had pulmonary TB, 27.5% (22/80) had isolated extrapulmonary TB, and 23.7% (19/80) had disseminated TB. Most infected cases were aged either < 4 years or > 12 years. TB contact history was found in 42.5% (34/80) cases. Fourteen (17.5%) of the cases had CNS involvement. The most common presentations were fever (85.7%), signs of increased intracranial pressure (71.4%), drowsiness (64.3%), and focal neurological signs (57.1%). The major radiological findings were tuberculoma (50%), basilar enhancement (41.6%), infarction (41.6%), hydrocephalus (16.6%), and transverse myelitis (16.6%). The case fatality of CNS TB was 14.3% and 21.4% had neurologic sequelae.ConclusionFindings suggest that positive exposure history and suspicious clinical presentations are important clues for further confirmatory laboratory and image studies in childhood TB. CNS TB usually presented as part of disseminated TB in children. Early diagnosis and treatment may lead to favorable outcomes in CNS TB
ImGeoNet: Image-induced Geometry-aware Voxel Representation for Multi-view 3D Object Detection
We propose ImGeoNet, a multi-view image-based 3D object detection framework
that models a 3D space by an image-induced geometry-aware voxel representation.
Unlike previous methods which aggregate 2D features into 3D voxels without
considering geometry, ImGeoNet learns to induce geometry from multi-view images
to alleviate the confusion arising from voxels of free space, and during the
inference phase, only images from multiple views are required. Besides, a
powerful pre-trained 2D feature extractor can be leveraged by our
representation, leading to a more robust performance. To evaluate the
effectiveness of ImGeoNet, we conduct quantitative and qualitative experiments
on three indoor datasets, namely ARKitScenes, ScanNetV2, and ScanNet200. The
results demonstrate that ImGeoNet outperforms the current state-of-the-art
multi-view image-based method, ImVoxelNet, on all three datasets in terms of
detection accuracy. In addition, ImGeoNet shows great data efficiency by
achieving results comparable to ImVoxelNet with 100 views while utilizing only
40 views. Furthermore, our studies indicate that our proposed image-induced
geometry-aware representation can enable image-based methods to attain superior
detection accuracy than the seminal point cloud-based method, VoteNet, in two
practical scenarios: (1) scenarios where point clouds are sparse and noisy,
such as in ARKitScenes, and (2) scenarios involve diverse object classes,
particularly classes of small objects, as in the case in ScanNet200.Comment: ICCV'23; project page: https://ttaoretw.github.io/imgeonet
UNIT project: Universe -body simulations for the Investigation of Theoretical models from galaxy surveys
We present the UNIT -body cosmological simulations project, designed to
provide precise predictions for nonlinear statistics of the galaxy
distribution. We focus on characterizing statistics relevant to emission line
and luminous red galaxies in the current and upcoming generation of galaxy
surveys. We use a suite of precise particle mesh simulations (FastPM) as well
as with full -body calculations with a mass resolution of M to investigate the recently suggested
technique of Angulo & Pontzen 2016 to suppress the variance of cosmological
simulations We study redshift space distortions, cosmic voids, higher order
statistics from down to . We find that both two- and three-point
statistics are unbiased. Over the scales of interest for baryon acoustic
oscillations and redshift-space distortions, we find that the variance is
greatly reduced in the two-point statistics and in the cross correlation
between halos and cosmic voids, but is not reduced significantly for the
three-point statistics. We demonstrate that the accuracy of the two-point
correlation function for a galaxy survey with effective volume of 20
(Gpc) is improved by about a factor of 40, indicating that two
pairs of simulations with a volume of 1 (Gpc) lead to the
equivalent variance of 150 such simulations. The -body simulations
presented here thus provide an effective survey volume of about seven times the
effective survey volume of DESI or Euclid. The data from this project,
including dark matter fields, halo catalogues, and their clustering statistics,
are publicly available at http://www.unitsims.org.Comment: 12 pages, 9 figures. This version matches the one accepted by MNRAS.
The data from this project are publicly available at: http://www.unitsims.or
New fermions on the line in topological symmorphic metals
Topological metals and semimetals (TMs) have recently drawn significant
interest. These materials give rise to condensed matter realizations of many
important concepts in high-energy physics, leading to wide-ranging protected
properties in transport and spectroscopic experiments. The most studied TMs,
i.e., Weyl and Dirac semimetals, feature quasiparticles that are direct
analogues of the textbook elementary particles. Moreover, the TMs known so far
can be characterized based on the dimensionality of the band crossing. While
Weyl and Dirac semimetals feature zero-dimensional points, the band crossing of
nodal-line semimetals forms a one-dimensional closed loop. In this paper, we
identify a TM which breaks the above paradigms. Firstly, the TM features
triply-degenerate band crossing in a symmorphic lattice, hence realizing
emergent fermionic quasiparticles not present in quantum field theory.
Secondly, the band crossing is neither 0D nor 1D. Instead, it consists of two
isolated triply-degenerate nodes interconnected by multi-segments of lines with
two-fold degeneracy. We present materials candidates. We further show that
triplydegenerate band crossings in symmorphic crystals give rise to a Landau
level spectrum distinct from the known TMs, suggesting novel magneto-transport
responses. Our results open the door for realizing new topological phenomena
and fermions including transport anomalies and spectroscopic responses in
metallic crystals with nontrivial topology beyond the Weyl/Dirac paradigm.Comment: 24 pages, 4 figures, and 1 tabl
Benthic Fluxes of Dissolved Organic Carbon from Gas Hydrate Sediments in the Northern South China Sea
Hydrocarbon vents have recently been reported to contribute considerable amounts of dissolved organic carbon (DOC) to the oceans. Many such hydrocarbon vents widely exist in the northern South China Sea (NSCS). To investigate if these hydrocarbon vent sites release DOC, we used a real-time video multiple-corer to collect bottom seawater and surface sediments at vent sites. We analyzed concentrations of DOC in these samples and estimated DOC fluxes. Elevated DOC concentrations in the porewaters were found at some sites suggesting that DOC may come from these hydrocarbon vents. Benthic fluxes of DOC from these sediments were 28 to 1264 µmol m−2 d−1 (on average ~321 µmol m−2 d−1 which are several times higher than most DOC fluxes in coastal and continental margin sediments. The results demonstrate that the real-time video multiple-corer can precisely collect samples at vent sites. The estimated benthic DOC flux from the methane venting sites (8.6 x 106 mol y-1, is 24% of the DOC discharge from the Pearl River to the South China Sea, indicating that these sediments make an important contribution to the DOC in deep waters
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