158 research outputs found
Improved Analytic Solution of Black Hole Superradiance
The approximate solution of the Klein-Gordon equation for a real scalar field
of mass in the geometry of a Kerr black hole obtained by Detweiler
\cite{Detweiler:1980uk} is widely used in the analysis of the stability of
black holes as well as the search of axion-like particles. In this work, we
confirm a missing factor in this solution, which was first identified in
Ref.~\cite{Pani:2012bp}. The corrected result has strange features that put
questions on the power-counting strategy. We solve this problem by adding the
next-to-leading order (NLO) contribution. Compared to the numerical results,
the NLO solution reduces the percentage error of the LO solution by a factor of
2 for all important values of . Especially the percentage error is
in the region of . The NLO solution also
has a compact form and could be used straightforwardly.Comment: 5 pages, 3 figures, Accepted by PR
Next-to-leading-order solution to Kerr-Newman black hole superradiance
The superradiant instabilities of Kerr-Newman black holes with charged or
uncharged massive spin-0 fields are calculated analytically to the
next-to-leading order in the limit of . A missing
factor of in the previous leading-order result is identified. The
next-to-leading order result has a compact form and is in good agreement with
existing numerical calculations. The percentage error increases with ,
from a few percent for to about for .
Massive neutral scalars too heavy to be produced with Kerr black hole
superradiance may exist in the superradiant region of Kerr-Newman black holes.Comment: 11 pages, 5 figures, 2 tables. Matches Physical Review D versio
2,4-Dihydroxy-N′-(3,4,5-trimethoxybenzylidene)benzohydrazide
In the title compound, C17H18N2O6, the molecule is slightly twisted, with a dihedral angle of 18.1 (2)° between the two benzene rings. In the crystal structure, molecules are linked into a network by intermolecular N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds. An intramolecular O—H⋯O hydrogen bond is also present
TaCA: Upgrading Your Visual Foundation Model with Task-agnostic Compatible Adapter
Visual foundation models like CLIP excel in learning feature representations
from extensive datasets through self-supervised methods, demonstrating
remarkable transfer learning and generalization capabilities. A growing number
of applications based on visual foundation models are emerging, including
innovative solutions such as BLIP-2. These applications employ pre-trained CLIP
models as upstream feature extractors and train various downstream modules to
accomplish diverse tasks. In situations involving system upgrades that require
updating the upstream foundation model, it becomes essential to re-train all
downstream modules to adapt to the new foundation model, which is inflexible
and inefficient. In this paper, we introduce a parameter-efficient and
task-agnostic adapter, dubbed TaCA, that facilitates compatibility across
distinct foundation models while ensuring enhanced performance for the new
models. TaCA allows downstream applications to seamlessly integrate
better-performing foundation models without necessitating retraining. We
conduct extensive experimental validation of TaCA using different scales of
models with up to one billion parameters on various tasks such as video-text
retrieval, video recognition, and visual question answering. The results
consistently demonstrate the emergent ability of TaCA on hot-plugging upgrades
for visual foundation models. Codes and models will be available at
https://github.com/TencentARC/TaCA
(Z)-4-[(Ethylamino)(furan-2-yl)methylidene]-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one
In the crystal of the title compound, C17H17N3O2, the molecules exist in the keto–enamine form. The pyrazole ring is oriented at 10.59 (4) and 57.98 (5)° to the phenyl and furyl rings, respectively, and the dihedral angle between phenyl and furyl rings is 73.30 (11)°. An intramolecular N—H⋯O hydrogen bond occurs between imino and carbonyl groups. In the crystal, weak C—H⋯O hydrogen bonds link the molecules into supramolecular chains along the b axis
ViT-Lens: Towards Omni-modal Representations
Though the success of CLIP-based training recipes in vision-language models,
their scalability to more modalities (e.g., 3D, audio, etc.) is limited to
large-scale data, which is expensive or even inapplicable for rare modalities.
In this paper, we present ViT-Lens that facilitates efficient omni-modal
representation learning by perceiving novel modalities with a pretrained ViT
and aligning to a pre-defined space. Specifically, the modality-specific lens
is tuned to project multimodal signals to the shared embedding space, which are
then processed by a strong ViT that carries pre-trained image knowledge. The
encoded multimodal representations are optimized toward aligning with the
modal-independent space, pre-defined by off-the-shelf foundation models. A
well-trained lens with a ViT backbone has the potential to serve as one of
these foundation models, supervising the learning of subsequent modalities.
ViT-Lens provides a unified solution for representation learning of increasing
modalities with two appealing benefits: (i) Exploiting the pretrained ViT
across tasks and domains effectively with efficient data regime; (ii) Emergent
downstream capabilities of novel modalities are demonstrated due to the
modality alignment space. We evaluate ViT-Lens in the context of 3D as an
initial verification. In zero-shot 3D classification, ViT-Lens achieves
substantial improvements over previous state-of-the-art, showing 52.0% accuracy
on Objaverse-LVIS, 87.4% on ModelNet40, and 60.6% on ScanObjectNN. Furthermore,
we enable zero-shot 3D question-answering by simply integrating the trained 3D
lens into the InstructBLIP model without any adaptation. We will release the
results of ViT-Lens on more modalities in the near future.Comment: 19 pages, 4 figures and 9 table
NASA-Approved Rotary Bioreactor Enhances Proliferation of Human Epidermal Stem Cells and Supports Formation of 3D Epidermis-Like Structure
The skin is susceptible to different injuries and diseases. One major obstacle in skin tissue engineering is how to develop functional three-dimensional (3D) substitute for damaged skin. Previous studies have proved a 3D dynamic simulated microgravity (SMG) culture system as a “stimulatory” environment for the proliferation and differentiation of stem cells. Here, we employed the NASA-approved rotary bioreactor to investigate the proliferation and differentiation of human epidermal stem cells (hEpSCs). hEpSCs were isolated from children foreskins and enriched by collecting epidermal stem cell colonies. Cytodex-3 micro-carriers and hEpSCs were co-cultured in the rotary bioreactor and 6-well dish for 15 days. The result showed that hEpSCs cultured in rotary bioreactor exhibited enhanced proliferation and viability surpassing those cultured in static conditions. Additionally, immunostaining analysis confirmed higher percentage of ki67 positive cells in rotary bioreactor compared with the static culture. In contrast, comparing with static culture, cells in the rotary bioreactor displayed a low expression of involucrin at day 10. Histological analysis revealed that cells cultured in rotary bioreactor aggregated on the micro-carriers and formed multilayer 3D epidermis structures. In conclusion, our research suggests that NASA-approved rotary bioreactor can support the proliferation of hEpSCs and provide a strategy to form multilayer epidermis structure
Production and Radioprotective Effects of Pyrroloquinoline Quinone
Pyrroloquinoline quinone (PQQ) was produced by fermentation of the Methylovorus sp. MP688 strain and purified by ion-exchange chromatography, crystallization and recrystallization. The yield of PQQ reached approximately 125 mg/L and highly pure PQQ was obtained. To determine the optimum dose of PQQ for radioprotection, three doses (2 mg/kg, 4 mg/kg, 8 mg/kg) of PQQ were orally administrated to the experimental animals subjected to a lethal dose of 8.0 Gy in survival test. Survival of mice in the irradiation + PQQ (4 mg/kg) group was found to be significantly higher in comparison with the irradiation and irradiation + nilestriol (10 mg/kg) groups. The numbers of hematocytes and bone marrow cells were measured for 21 days after sublethal 4 Gy gamma-ray irradiation with per os of 4 mg/kg of PQQ. The recovery of white blood cells, reticulocytes and bone marrow cells in the irradiation + PQQ group was faster than that in the irradiation group. Furthermore, the recovery of bone marrow cell in the irradiation + PQQ group was superior to that in irradiation + nilestriol group. Our results clearly indicate favourable effects on survival under higher lethal radiation doses and the ability of pyrroloquinoline quinine to enhance haemopoietic recovery after sublethal radiation exposure
Natural products in atherosclerosis therapy by targeting PPARs: a review focusing on lipid metabolism and inflammation
Inflammation and dyslipidemia are critical inducing factors of atherosclerosis. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors and control the expression of multiple genes that are involved in lipid metabolism and inflammatory responses. However, synthesized PPAR agonists exhibit contrary therapeutic effects and various side effects in atherosclerosis therapy. Natural products are structural diversity and have a good safety. Recent studies find that natural herbs and compounds exhibit attractive therapeutic effects on atherosclerosis by alleviating hyperlipidemia and inflammation through modulation of PPARs. Importantly, the preparation of natural products generally causes significantly lower environmental pollution compared to that of synthesized chemical compounds. Therefore, it is interesting to discover novel PPAR modulator and develop alternative strategies for atherosclerosis therapy based on natural herbs and compounds. This article reviews recent findings, mainly from the year of 2020 to present, about the roles of natural herbs and compounds in regulation of PPARs and their therapeutic effects on atherosclerosis. This article provides alternative strategies and theoretical basis for atherosclerosis therapy using natural herbs and compounds by targeting PPARs, and offers valuable information for researchers that are interested in developing novel PPAR modulators
Geometry and optics calibration of WFCTA prototype telescopes using star light
The Large High Altitude Air Shower Observatory project is proposed to study
high energy gamma ray astronomy ( 40 GeV-1 PeV ) and cosmic ray physics ( 20
TeV-1 EeV ). The wide field of view Cherenkov telescope array, as a component
of the LHAASO project, will be used to study energy spectrum and compositions
of cosmic ray by measuring the total Cherenkov light generated by air showers
and shower maximum depth. Two prototype telescopes have been in operation since
2008. The pointing accuracy of each telescope is crucial to the direction
reconstruction of the primary particles. On the other hand the primary energy
reconstruction relies on the shape of the Cherenkov image on the camera and the
unrecorded photons due to the imperfect connections between photomultiplier
tubes. UV bright stars are used as point-like objects to calibrate the pointing
and to study the optical properties of the camera, the spot size and the
fractions of unrecorded photons in the insensitive areas of the camera.Comment: 5 pages, 6 figures, submitted to Chinese Physics
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