74 research outputs found
Hodge ideals and spectrum of isolated hypersurface singularities
We introduce Hodge ideal spectrum for isolated hypersurface singularities to
see the difference between the Hodge ideals and the microlocal -filtration
modulo the Jacobian ideal. Via the Tjurina subspectrum, we can compare the
Hodge ideal spectrum with the Steenbrink spectrum which can be defined by the
microlocal -filtration. As a consequence of a formula of Mustata and Popa,
these two spectra coincide in the weighted homogeneous case. We prove
sufficient conditions for their coincidence and non-coincidence in some
non-weighted-homogeneous cases where the defining function is
semi-weighted-homogeneous or with non-degenerate Newton boundary in most cases.
We also show that the convenience condition can be avoided in a formula of
Zhang for the non-degenerate case, and present an example where the Hodge
ideals are not weakly decreasing even modulo the Jacobian ideal.Comment: 29 page
Spectrum of non-degenerate functions with simplicial Newton polyhedra
We prove a simple formula for the spectrum of non-degenerate functions of 3
variables with simplicial convenient Newton polyhedra (which does not hold in
the non-simplicial case) generalizing a picture of Arnold in the 2 variable
case. Combining this with Steenbrink's conjecture on a refinement of Yomdin's
formula (proved long ago), we can deduce a formula for the spectrum of certain
non-isolated surface singularities with simplicial non-degenerate Newton
boundaries.Comment: 17 page
Disorder-dependent Li diffusion in investigated by machine learning potential
Solid-state electrolytes with argyrodite structures, such as
, have attracted considerable attention due to their
superior safety compared to liquid electrolytes and higher ionic conductivity
than other solid electrolytes. Although experimental efforts have been made to
enhance conductivity by controlling the degree of disorder, the underlying
diffusion mechanism is not yet fully understood. Moreover, existing theoretical
analyses based on ab initio MD simulations have limitations in addressing
various types of disorder at room temperature. In this study, we directly
investigate Li-ion diffusion in at 300 K using
large-scale, long-term MD simulations empowered by machine learning potentials
(MLPs). To ensure the convergence of conductivity values within an error range
of 10%, we employ a 25 ns simulation using a supercell
containing 6500 atoms. The computed Li-ion conductivity, activation energies,
and equilibrium site occupancies align well with experimental observations.
Notably, Li-ion conductivity peaks when Cl ions occupy 25% of the 4c sites,
rather than at 50% where the disorder is maximized. This phenomenon is
explained by the interplay between inter-cage and intra-cage jumps. By
elucidating the key factors affecting Li-ion diffusion in
, this work paves the way for optimizing ionic
conductivity in the argyrodite family.Comment: 34 pages, 6 figure
Achieving Both Ultrahigh Electrical Conductivity and Mechanical Modulus of Carbon Films: Templating-Coalescing Behavior of Single-Walled Carbon Nanotube in Polyacrylonitrile
Promoting the feasibility of carbon films as electrode applications requires sufficient performances in view of both electrical and mechanical properties. Herein, carbon films with ultrahigh electrical conductivity and mechanical modulus are prepared by high temperature carbonization of polyacrylonitrile (PAN)/single-walled carbon nanotube (SWNT) nanocomposites. Achieving both performances is ascribed to remarkable graphitic crystallinity, resulting from the sequential templating???coalescing behavior of concentrated SWNT bundles (B-CNTs). While well-dispersed SWNTs (WD-CNTs) facilitate radial templating according to their tubular geometry, flattened B-CNTs sandwiched between carbonized PAN matrices induce vertical templating, where the former and latter produce concentric and planar crystallizations of the graphitic structure, respectively. After carbonization at 2500 ??C with the remaining WD-CNTs as microstructural defects, the flattened B-CNTs coalesce into graphitic crystals by zipping the surrounding matrix, resulting in high crystallinity with the crystal thicknesses of 27.4 and 39.4 nm for the (002) and (10) planes, respectively. For comparison, the graphene oxide (GO) containing carbon films produce a less-ordered graphitic phase owing to irregular templating, despite the geometrical consistency. Consequently, PAN/B-CNT carbon films exhibit exceptional electrical conductivity (40.7 ?? 104 S m???1) and mechanical modulus (38.2 ?? 6.4 GPa). Thus, controlling the templating???coalescing behavior of SWNTs is the key for improving final performances of carbon films
Identification of a novel human Rad51 variant that promotes DNA strand exchange
Rad51 plays a key role in the repair of DNA double-strand breaks through homologous recombination, which is the central process in the maintenance of genomic integrity. Five paralogs of the human Rad51 gene (hRad51) have been identified to date, including hRad51B, hRad51C, hRad51D, Xrcc2 and Xrcc3. In searches of additional hRad51 paralogs, we identified a novel hRad51 variant that lacked the sequence corresponding to exon 9 (hRad51-Īex9). The expected amino acid sequence of hRad51-Īex9 showed a frame-shift at codon 259, which resulted in a truncated C-terminus. RT-PCR analysis revealed that both hRad51 and hRad51-Īex9 were prominently expressed in the testis, but that there were subtle differences in tissue specificity. The hRad51-Īex9 protein was detected as a 31-kDa protein in the testis and localized at the nucleus. In addition, the hRad51-Īex9 protein showed a DNA-strand exchange activity comparable to that of hRad51. Taken together, these results indicate that hRad51-Īex9 promotes homologous pairing and DNA strand exchange in the nucleus, suggesting that alternative pathways in hRad51- or hRad51-Īex9-dependent manners exist for DNA recombination and repair
MicroRNA-150 modulates intracellular Ca2+ levels in naĆÆve CD8+ T cells by targeting TMEM20
Regulation of intracellular Ca2+ signaling is a major determinant of CD8+ T cell responsiveness, but the mechanisms underlying this regulation of Ca2+ levels, especially in naĆÆve CD8+ T cells, are not fully defined. Here, we showed that microRNA-150 (miR-150) controls intracellular Ca2+ levels in naĆÆve CD8+ T cells required for activation by suppressing TMEM20, a negative regulator of Ca2+ extrusion. miR-150 deficiency increased TMEM20 expression, which resulted in increased intracellular Ca2+ levels in naĆÆve CD8+ T cells. The subsequent increase in Ca2+ levels induced expression of anergy-inducing genes, such as Cbl-b, Egr2, and p27, through activation of NFAT1, as well as reduced cell proliferation, cytokine production, and the antitumor activity of CD8+ T cells upon antigenic stimulation. The anergy-promoting molecular milieu and function induced by miR-150 deficiency were rescued by reinstatement of miR-150. Additionally, knockdown of TMEM20 in miR-150-deficient naĆÆve CD8+ T cells reduced intracellular Ca2+ levels. Our findings revealed that miR-150 play essential roles in controlling intracellular Ca2+ level and activation in naĆÆve CD8+ T cells, which suggest a mechanism to overcome anergy induction by the regulation of intracellular Ca2+ levels115Ysciescopu
Prestack depth migration using straight ray technique(SRT)
Kirchhoff prestack depth migration requires an elaborate book-keeping effort and a massive
IO process to construct Kirchhoff hyperbolas. In order to avoid the complexity of the programming
code and the massive IO process, we propose a straight ray technique (SRT) for traveltimi
calculations in Kirchhoff migration. Since all the rays are straight in. polar coordinates for the 2D
velocity model,or in sphericalc oordinatesf or the 3D velocity model, traveltimesc an be simply
computed along a straight ray for a given source-receiver configuration,without suffering from
shadow zones and caustics, and used directly for building Kirchhoff hyperbolas. In this way, we
clrcumvent the substantial IO process required for reading traveltimes on a disk and save
computationals torage.N umerical examplesd emonstrateth at SRT computest raveltimesi ntermediate
between first-arrival traveltimes and the most energetic arrival traveltimes, resulting in better images
than the first arrival traveltimes for the 2D IFP Marmousi data. With the implementation of SRT
for 2D Kirchhoff migration, we successfully extend our SRT to 3D Kirchhoff misration for the
SECiEAGE salr dome data.This work was financially supported by the National Laboratory Project
of the Ministry of Science and Technology, Brain Korea 21 Project of the
Ministry of Education, grant No. R05-2000-00003 from the Basic Research
Program of the Korea Science & Engineering Foundation, and grant No.
PM10300 from the Korea Ocean Research & Development Institute
Microcantilever-integrated photonic circuits for broadband laser beam scanning
Laser beam scanning is central to many applications, including displays,
microscopy, three-dimensional mapping, and quantum information. Reducing the
scanners to microchip form factors has spurred the development of
very-large-scale photonic integrated circuits of optical phased arrays and
focal plane switched arrays. An outstanding challenge remains to simultaneously
achieve a compact footprint, broad wavelength operation, and low power
consumption. Here, we introduce a laser beam scanner that meets these
requirements. Using microcantilevers embedded with silicon nitride nanophotonic
circuitry, we demonstrate broadband, one- and two-dimensional steering of light
with wavelengths from 410 nm to 700 nm. The microcantilevers have ultracompact
~0.1 mm areas, consume ~31 to 46 mW of power, are simple to control, and
emit a single light beam. The microcantilevers are monolithically integrated in
an active photonic platform on 200-mm silicon wafers. The
microcantilever-integrated photonic circuits miniaturize and simplify light
projectors to enable versatile, power-efficient, and broadband laser scanner
microchips
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