191 research outputs found
N-body simulation for self-gravitating collisional systems with a new SIMD instruction set extension to the x86 architecture, Advanced Vector eXtensions
We present a high-performance N-body code for self-gravitating collisional
systems accelerated with the aid of a new SIMD instruction set extension of the
x86 architecture: Advanced Vector eXtensions (AVX), an enhanced version of the
Streaming SIMD Extensions (SSE). With one processor core of Intel Core i7-2600
processor (8 MB cache and 3.40 GHz) based on Sandy Bridge micro-architecture,
we implemented a fourth-order Hermite scheme with individual timestep scheme
(Makino and Aarseth, 1992), and achieved the performance of 20 giga floating
point number operations per second (GFLOPS) for double-precision accuracy,
which is two times and five times higher than that of the previously developed
code implemented with the SSE instructions (Nitadori et al., 2006b), and that
of a code implemented without any explicit use of SIMD instructions with the
same processor core, respectively. We have parallelized the code by using
so-called NINJA scheme (Nitadori et al., 2006a), and achieved 90 GFLOPS for a
system containing more than N = 8192 particles with 8 MPI processes on four
cores. We expect to achieve about 10 tera FLOPS (TFLOPS) for a self-gravitating
collisional system with N 105 on massively parallel systems with at most 800
cores with Sandy Bridge micro-architecture. This performance will be comparable
to that of Graphic Processing Unit (GPU) cluster systems, such as the one with
about 200 Tesla C1070 GPUs (Spurzem et al., 2010). This paper offers an
alternative to collisional N-body simulations with GRAPEs and GPUs.Comment: 14 pages, 9 figures, 3 tables, accepted for publication in New
Astronomy. The code is publicly available at
http://code.google.com/p/phantom-grape
Seismic Wavefield Reconstruction based on Compressed Sensing using Data-Driven Reduced-Order Model
A seismic wavefield reconstruction framework based on compressed sensing
using the data-driven reduced-order model (ROM) is proposed and its
characteristics are investigated through numerical experiments. The data-driven
ROM is generated from the dataset of the wavefield using the singular value
decomposition. The spatially continuous seismic wavefield is reconstructed from
the sparse and discrete observation and the data-driven ROM. The observation
sites used for reconstruction are effectively selected by the sensor
optimization method for linear inverse problems based on a greedy algorithm.
The proposed framework was applied to simulation data of theoretical waveform
with the subsurface structure of the horizontally-stratified three layers. The
validity of the proposed method was confirmed by the reconstruction based on
the noise-free observation. Since the ROM of the wavefield is used as prior
information, the reconstruction error is reduced to an approximately lower
error bound of the present framework, even though the number of sensors used
for reconstruction is limited and randomly selected. In addition, the
reconstruction error obtained by the proposed framework is much smaller than
that obtained by the Gaussian process regression. For the numerical experiment
with noise-contaminated observation, the reconstructed wavefield is degraded
due to the observation noise, but the reconstruction error obtained by the
present framework with all available observation sites is close to a lower
error bound, even though the reconstructed wavefield using the Gaussian process
regression is fully collapsed. Although the reconstruction error is larger than
that obtained using all observation sites, the number of observation sites used
for reconstruction can be reduced while minimizing the deterioration and
scatter of the reconstructed data by combining it with the sensor optimization
method
Observation Site Selection for Physical Model Parameter Estimation toward Process-Driven Seismic Wavefield Reconstruction
The seismic data not only acquired by seismometers but also acquired by
vibrometers installed in buildings and infrastructure and accelerometers
installed in smartphones will be certainly utilized for seismic research in the
near future. Since it is impractical to utilize all the seismic big data in
terms of the computational cost, methods which can select observation sites
depending on the purpose are indispensable. We propose an observation site
selection method for the accurate reconstruction of the seismic wavefield by
process-driven approaches. The proposed method selects observation sites
suitable for accurately estimating physical model parameters such as subsurface
structures and source information to be input into a numerical simulation of
the seismic wavefield. The seismic wavefield is reconstructed by the numerical
simulation using the parameters estimated based on the observed signals at only
observation sites selected by the proposed method. The observation site
selection in the proposed method is based on the sensitivity of each
observation site candidate to the physical model parameters; the matrix
corresponding to the sensitivity is constructed by approximately calculating
the derivatives based on the simulations, and then, observation sites are
selected by evaluating the quantity of the sensitivity matrix based on the
D-optimality criterion proposed in the optimal design of experiments. In the
present study, physical knowledge on the sensitivity to the parameters such as
seismic velocity, layer thickness, and hypocenter location was obtained by
investigating the characteristics of the sensitivity matrix. Furthermore, the
effectiveness of the proposed method was shown by verifying the accuracy of
seismic wavefield reconstruction using the observation sites selected by the
proposed method.Comment: Preprint submitted to Geophysical Journal International on
8-June-202
Structural Analysis of the Glycosylated Intact HIV-1 gp120-b12 Antibody Complex Using Hydroxyl Radical Protein Footprinting
Glycoprotein gp120 is a surface antigen and virulence factor of human immunodeficiency virus 1. Broadly neutralizing antibodies (bNAbs) that react to gp120 from a variety of HIV isolates offer hope for the development of broadly effective immunogens for vaccination purposes, if the interactions between gp120 and bNAbs can be understood. From a structural perspective, gp120 is a particularly difficult system because of its size, the presence of multiple flexible regions, and the large amount of glycosylation, all of which are important in gp120-bNAb interactions. Here, the interaction of full-length, glycosylated gp120 with bNAb b12 is probed using high-resolution hydroxyl radical protein footprinting (HR-HRPF) by fast photochemical oxidation of proteins. HR-HRPF allows for the measurement of changes in the average solvent accessible surface area of multiple amino acids without the need for measures that might alter the protein conformation, such as mutagenesis. HR-HRPF of the gp120-b12 complex coupled with computational modeling shows a novel extensive interaction of the V1/V2 domain, probably with the light chain of b12. Our data also reveal HR-HRPF protection in the C3 domain caused by interaction of the N330 glycan with the b12 light chain. In addition to providing information about the interactions of full-length, glycosylated gp120 with b12, this work serves as a template for the structural interrogation of full-length glycosylated gp120 with other bNAbs to better characterize the interactions that drive the broad specificity of the bNAb
Droplet digital PCR assay provides intrahepatic HBV cccDNA quantification tool for clinical application
The persistence of covalently closed circular DNA (cccDNA) poses a major obstacle to curing chronic hepatitis B (CHB). Here, we used droplet digital PCR (ddPCR) for cccDNA quantitation. The cccDNA-specific ddPCR showed high accuracy with the dynamic range of cccDNA detection from 101 to 105 copies/assay. The ddPCR had higher sensitivity, specificity and precisely than qPCR. The results of ddPCR correlated closely with serum HB core-related antigen and HB surface antigen (HBsAg) in 24 HBV-infected human-liver-chimeric mice (PXB-mice). We demonstrated that in 2 PXB-mice after entecavir treatment, the total cccDNA content did not change during liver repopulation, although the cccDNA content per hepatocyte was reduced after the treatment. In the 6 patients with HBV-related hepatocellular carcinoma, ddPCR detected cccDNA in both tumor and non-tumor tissues. In 13 HBeAg-negative CHB patients with pegylated interferon alpha-2a, cccDNA contents from paired biopsies were more significantly reduced in virological response (VR) than in non-VR at week 48 (p = 0.0051). Interestingly, cccDNA levels were the lowest in VR with HBsAg clearance but remained detectable after the treatment. Collectively, ddPCR revealed that cccDNA content is stable during hepatocyte proliferation and persists at quantifiable levels, even after serum HBsAg clearance
Real-time In Situ Electron Spin Resonance Measurements on Fungal Spores of Penicillium digitatum during Exposure of Oxygen Plasmas
We report the kinetic analysis of free radicals on fungal spores of
Penicillium digitatum interacted with atomic oxygen generated plasma electric
discharge using real time in situ electron spin resonance (ESR) measurements.
We have obtained information that the ESR signal from the spores was observed
and preliminarily assignable to semiquinone radical with a g-value of around
2.004 and a line width of approximately 5G. The decay of the signal is possibly
linked to the inactivation of the fungal spore. The real-time in situ ESR has
proven to be a useful method to elucidate plasma-induced surface reactions on
biological specimens.Comment: 11 pages, 5 figure
FcɛRI-mediated mast cell degranulation requires calcium-independent microtubule-dependent translocation of granules to the plasma membrane
The aggregation of high affinity IgE receptors (Fcɛ receptor I [FcɛRI]) on mast cells is potent stimulus for the release of inflammatory and allergic mediators from cytoplasmic granules. However, the molecular mechanism of degranulation has not yet been established. It is still unclear how FcɛRI-mediated signal transduction ultimately regulates the reorganization of the cytoskeleton and how these events lead to degranulation. Here, we show that FcɛRI stimulation triggers the formation of microtubules in a manner independent of calcium. Drugs affecting microtubule dynamics effectively suppressed the FcɛRI-mediated translocation of granules to the plasma membrane and degranulation. Furthermore, the translocation of granules to the plasma membrane occurred in a calcium-independent manner, but the release of mediators and granule–plasma membrane fusion were completely dependent on calcium. Thus, the degranulation process can be dissected into two events: the calcium-independent microtubule-dependent translocation of granules to the plasma membrane and calcium-dependent membrane fusion and exocytosis. Finally, we show that the Fyn/Gab2/RhoA (but not Lyn/SLP-76) signaling pathway plays a critical role in the calcium-independent microtubule-dependent pathway
Honeycomb-Layered Oxides With Silver Atom Bilayers and Emergence of Non-Abelian SU(2) Interactions
Honeycomb-layered oxides with monovalent or divalent, monolayered cationic lattices generally exhibit myriad crystalline features encompassing rich electrochemistry, geometries, and disorders, which particularly places them as attractive material candidates for next-generation energy storage applications. Herein, global honeycomb-layered oxide compositions, Ag2M2TeO6 ((Formula presented.).) exhibiting (Formula presented.) atom bilayers with sub-valent states within Ag-rich crystalline domains of Ag6M2TeO6 and (Formula presented.) -deficient domains of (Formula presented.) ((Formula presented.)). The (Formula presented.) -rich material characterized by aberration-corrected transmission electron microscopy reveals local atomic structural disorders characterized by aperiodic stacking and incoherency in the bilayer arrangement of (Formula presented.) atoms. Meanwhile, the global material not only displays high ionic conductivity but also manifests oxygen-hole electrochemistry during silver-ion extraction. Within the (Formula presented.) -rich domains, the bilayered structure, argentophilic interactions therein and the expected (Formula presented.) sub-valent states ((Formula presented.), etc.) are theoretically understood via spontaneous symmetry breaking of SU(2)
7 U(1) gauge symmetry interactions amongst 3 degenerate mass-less chiral fermion states, justified by electron occupancy of silver (Formula presented.) and 5s orbitals on a bifurcated honeycomb lattice. This implies that bilayered frameworks have research applications that go beyond the confines of energy storage
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