5,989 research outputs found
Neutrino decay as a possible interpretation to the MiniBooNE observation with unparticle scenario
In a new measurement on neutrino oscillation , the
MiniBooNE Collaboration observes an excess of electron-like events at low
energy and the phenomenon may demand an explanation which obviously is beyond
the oscillation picuture. We propose that heavier neutrino decaying
into a lighter one via the transition process
where denotes any light products, could be a natural mechanism. The
theoretical model we employ here is the unparticle scenario established by
Georgi. We have studied two particular modes \nu_\mu\to \nu_e+\Un and
. Unfortunately, the number coming out from
the computation is too small to explain the observation. Moreover, our results
are consistent with the cosmology constraint on the neutrino lifetime and the
theoretical estimation made by other groups, therefore we can conclude that
even though neutrino decay seems plausible in this case, it indeed cannot be
the source of the peak at lower energy observed by the MiniBooNE collaboration
and there should be other mechanisms responsible for the phenomenon.Comment: 14 pages, conclusions are changed; published version for EPJ
Estimation of Incident Photosynthetically Active Radiation From Moderate Resolution Imaging Spectrometer Data
Incident photosynthetically active radiation (PAR) is a key variable needed by almost all terrestrial ecosystem models. Unfortunately, the current incident PAR products estimated from remotely sensed data at spatial and temporal resolutions are not sufficient for carbon cycle modeling and various applications. In this study, the authors develop a new method based on the look-up table approach for estimating instantaneous incident PAR from the polar-orbiting Moderate Resolution Imaging Spectrometer (MODIS) data. Since the top-of-atmosphere (TOA) radiance depends on both surface reflectance and atmospheric properties that largely determine the incident PAR, our first step is to estimate surface reflectance. The approach assumes known aerosol properties for the observations with minimum blue reflectance from a temporal window of each pixel. Their inverted surface reflectance is then interpolated to determine the surface reflectance of other observations. The second step is to calculate PAR by matching the computed TOA reflectance from the look-up table with the TOA values of the satellite observations. Both the direct and diffuse PAR components, as well as the total shortwave radiation, are determined in exactly the same fashion. The calculation of a daily average PAR value from one or two instantaneous PAR values is also explored. Ground measurements from seven FLUXNET sites are used for validating the algorithm. The results indicate that this approach can produce reasonable PAR product at 1 km resolution and is suitable for global applications, although more quantitative validation activities are still needed
The Extreme Small Scales: Do Satellite Galaxies Trace Dark Matter?
We investigate the radial distribution of galaxies within their host dark
matter halos by modeling their small-scale clustering, as measured in the Sloan
Digital Sky Survey. Specifically, we model the Jiang et al. (2011) measurements
of the galaxy two-point correlation function down to very small projected
separations (10 < r < 400 kpc/h), in a wide range of luminosity threshold
samples (absolute r-band magnitudes of -18 up to -23). We use a halo occupation
distribution (HOD) framework with free parameters that specify both the number
and spatial distribution of galaxies within their host dark matter halos. We
assume that the first galaxy in each halo lives at the halo center and that
additional satellite galaxies follow a radial density profile similar to the
dark matter Navarro-Frenk-White (NFW) profile, except that the concentration
and inner slope are allowed to vary. We find that in low luminosity samples,
satellite galaxies have radial profiles that are consistent with NFW. M_r < -20
and brighter satellite galaxies have radial profiles with significantly steeper
inner slopes than NFW (we find inner logarithmic slopes ranging from -1.6 to
-2.1, as opposed to -1 for NFW). We define a useful metric of concentration,
M_(1/10), which is the fraction of satellite galaxies (or mass) that are
enclosed within one tenth of the virial radius of a halo. We find that M_(1/10)
for low luminosity satellite galaxies agrees with NFW, whereas for luminous
galaxies it is 2.5-4 times higher, demonstrating that these galaxies are
substantially more centrally concentrated within their dark matter halos than
the dark matter itself. Our results therefore suggest that the processes that
govern the spatial distribution of galaxies, once they have merged into larger
halos, must be luminosity dependent, such that luminous galaxies become poor
tracers of the underlying dark matter.Comment: 12 pages, 6 figures, Accepted to Ap
CDKG1 protein kinase is essential for synapsis and male meiosis at high ambient temperature in Arabidopsis thaliana
The Arabidopsis cyclin-dependent kinase G (CDKG) gene defines a clade of cyclin-dependent protein kinases related to CDK10 and CDK11, as well as to the enigmatic Ph1-related kinases that are implicated in controlling homeologous chromosome pairing in wheat. Here we demonstrate that the CDKG1/CYCLINL complex is essential for synapsis and recombination during male meiosis. A transfer-DNA insertional mutation in the cdkg1 gene leads to a temperature-sensitive failure of meiosis in late Zygotene/Pachytene that is associated with defective formation of the synaptonemal complex, reduced bivalent formation and crossing over, and aneuploid gametes. An aphenotypic insertion in the cyclin L gene, a cognate cyclin for CDKG, strongly enhances the phenotype of cdkg1–1 mutants, indicating that this cdk–cyclin complex is essential for male meiosis. Since CYCLINL, CDKG, and their mammalian homologs have been previously shown to affect mRNA processing, particularly alternative splicing, our observations also suggest a mechanism to explain the widespread phenomenon of thermal sensitivity in male meiosis
MER 2023: Multi-label Learning, Modality Robustness, and Semi-Supervised Learning
Over the past few decades, multimodal emotion recognition has made remarkable
progress with the development of deep learning. However, existing technologies
are difficult to meet the demand for practical applications. To improve the
robustness, we launch a Multimodal Emotion Recognition Challenge (MER 2023) to
motivate global researchers to build innovative technologies that can further
accelerate and foster research. For this year's challenge, we present three
distinct sub-challenges: (1) MER-MULTI, in which participants recognize both
discrete and dimensional emotions; (2) MER-NOISE, in which noise is added to
test videos for modality robustness evaluation; (3) MER-SEMI, which provides
large amounts of unlabeled samples for semi-supervised learning. In this paper,
we test a variety of multimodal features and provide a competitive baseline for
each sub-challenge. Our system achieves 77.57% on the F1 score and 0.82 on the
mean squared error (MSE) for MER-MULTI, 69.82% on the F1 score and 1.12 on MSE
for MER-NOISE, and 86.75% on the F1 score for MER-SEMI, respectively. Baseline
code is available at https://github.com/zeroQiaoba/MER2023-Baseline
Learning Shape Priors for Robust Cardiac MR Segmentation from Multi-view Images
© 2019, Springer Nature Switzerland AG. Cardiac MR image segmentation is essential for the morphological and functional analysis of the heart. Inspired by how experienced clinicians assess the cardiac morphology and function across multiple standard views (i.e. long- and short-axis views), we propose a novel approach which learns anatomical shape priors across different 2D standard views and leverages these priors to segment the left ventricular (LV) myocardium from short-axis MR image stacks. The proposed segmentation method has the advantage of being a 2D network but at the same time incorporates spatial context from multiple, complementary views that span a 3D space. Our method achieves accurate and robust segmentation of the myocardium across different short-axis slices (from apex to base), outperforming baseline models (e.g. 2D U-Net, 3D U-Net) while achieving higher data efficiency. Compared to the 2D U-Net, the proposed method reduces the mean Hausdorff distance (mm) from 3.24 to 2.49 on the apical slices, from 2.34 to 2.09 on the middle slices and from 3.62 to 2.76 on the basal slices on the test set, when only 10% of the training data was used
- …