176 research outputs found
Nonconcave penalized likelihood with a diverging number of parameters
A class of variable selection procedures for parametric models via nonconcave
penalized likelihood was proposed by Fan and Li to simultaneously estimate
parameters and select important variables. They demonstrated that this class of
procedures has an oracle property when the number of parameters is finite.
However, in most model selection problems the number of parameters should be
large and grow with the sample size. In this paper some asymptotic properties
of the nonconcave penalized likelihood are established for situations in which
the number of parameters tends to \infty as the sample size increases.
Under regularity conditions we have established an oracle property and the
asymptotic normality of the penalized likelihood estimators. Furthermore, the
consistency of the sandwich formula of the covariance matrix is demonstrated.
Nonconcave penalized likelihood ratio statistics are discussed, and their
asymptotic distributions under the null hypothesis are obtained by imposing
some mild conditions on the penalty functions
Monodisperse core/shell and other complex structured nanocrystals and methods of preparing the same
Provides new compositions containing nearly monodisperse colloidal core/shell semiconductor nanocrystals with high photoluminescence quantum yields (PL QY), as well as other complex structured semiconductor nanocrystals. This invention also provides new synthetic methods for preparing these nanocrystals, and new devices comprising these compositions. In addition to core/shell semiconductor nanocrystals, this patent also provides complex semiconductor nanostructures, quantum shells, quantum wells, doped nanocrystals, and other multiple-shelled semiconductor nanocrystals
Generalized Category Discovery in Semantic Segmentation
This paper explores a novel setting called Generalized Category Discovery in
Semantic Segmentation (GCDSS), aiming to segment unlabeled images given prior
knowledge from a labeled set of base classes. The unlabeled images contain
pixels of the base class or novel class. In contrast to Novel Category
Discovery in Semantic Segmentation (NCDSS), there is no prerequisite for prior
knowledge mandating the existence of at least one novel class in each unlabeled
image. Besides, we broaden the segmentation scope beyond foreground objects to
include the entire image. Existing NCDSS methods rely on the aforementioned
priors, making them challenging to truly apply in real-world situations. We
propose a straightforward yet effective framework that reinterprets the GCDSS
challenge as a task of mask classification. Additionally, we construct a
baseline method and introduce the Neighborhood Relations-Guided Mask Clustering
Algorithm (NeRG-MaskCA) for mask categorization to address the fragmentation in
semantic representation. A benchmark dataset, Cityscapes-GCD, derived from the
Cityscapes dataset, is established to evaluate the GCDSS framework. Our method
demonstrates the feasibility of the GCDSS problem and the potential for
discovering and segmenting novel object classes in unlabeled images. We employ
the generated pseudo-labels from our approach as ground truth to supervise the
training of other models, thereby enabling them with the ability to segment
novel classes. It paves the way for further research in generalized category
discovery, broadening the horizons of semantic segmentation and its
applications. For details, please visit https://github.com/JethroPeng/GCDS
Phosphatidic acid counteracts S-RNase signaling in pollen by stabilizing the actin cytoskeleton
S-RNase is the female determinant of self-incompatibility (SI) in pear (Pyrus bretschneideri). After translocation to the pollen tube, S-RNase degrades rRNA and induces pollen tube death in an S-haplotype-specific manner. In this study, we found that the actin cytoskeleton is a target of P. bretschneideri S-RNase (PbrS-RNase) and uncovered a mechanism that involves phosphatidic acid (PA) and protects the pollen tube from PbrS-RNase cytotoxicity. PbrS-RNase interacts directly with PbrActin1 in an S-haplotype-independent manner, causing the actin cytoskeleton to depolymerize and promoting programmed cell death in the self-incompatible pollen tube. Pro-156 of PbrS-RNase is essential for the PbrS-RNase-PbrActin1 interaction, and the actin cytoskeleton-depolymerizing function of PbrS-RNase does not require its RNase activity. PbrS-RNase cytotoxicity enhances the expression of phospholipase D (PbrPLDδ1), resulting in increased PA levels in the incompatible pollen tube. PbrPLDδ1-derived PA initially prevents depolymerization of the actin cytoskeleton elicited by PbrS-RNase and delays the SI signaling that leads to pollen tube death. This work provides insights into the orchestration of the S-RNase-based SI response, in which increased PA levels initially play a protective role in incompatible pollen, until sustained PbrS-RNase activity reaches the point of no return and pollen tube growth ceases
Monodisperse core/shell and other complex structured nanocrystals and methods of preparing the same
This invention provides new compositions containing nearly monodisperse colloidal core/shell semiconductor nanocrystals with high photoluminescence quantum yields, as well as other complex structured semiconductor nanocrystals. It also provides new synthetic methods for preparing these nanocrystals, and new devices comprising these compositions. In addition to core/shell semiconductor nanocrystals, it also provides complex semiconductor nanostructures, quantum shells, quantum wells, doped nanocrystals, and other multiple-shelled semiconductor nanocrystals
Monodisperse core/shell and other complex structured nanocrystals and methods of preparing the same
Provides new compositions containing nearly monodisperse colloidal core/shell semiconductor nanocrystals with high photoluminescence quantum yields (PL QY), as well as other complex structured semiconductor nanocrystals. New synthetic methods for preparing these nanocrystals, and new devices comprising these compositions are also provided. In addition to core/shell semiconductor nanocrystals, this patent application also provides complex semiconductor nanostructures, quantum shells, quantum wells, doped nanocrystals, and other multiple-shelled semiconductor nanocrystals
Monodisperse core/shell and other complex structured nanocrystals and methods of preparing the same
This invention provides new compositions containing nearly monodisperse colloidal core/shell semiconductor nanocrystals with high photoluminescence quantum yields, as well as other complex structured semiconductor nanocrystals. It also provides new synthetic methods for preparing these nanocrystals, and new devices comprising these compositions. In addition to core/shell semiconductor nanocrystals, it also provides complex semiconductor nanostructures, quantum shells, quantum wells, doped nanocrystals, and other multiple-shelled semiconductor nanocrystals
Joint optimization of bitrate selection and beamforming for holographic video cooperative streaming in VLC systems
Holographic video streaming requires ultrahigh channel capacity, which might not be achieved by the existing radio frequency-based wireless networks. To address this challenge, we propose a holographic video cooperative streaming framework by integrating coordinated multipoint transmission and beamforming technologies in visible light communication (VLC) systems. This framework enables simultaneous video streaming with an ultrahigh data rate for multiple users in the VLC system, resulting in a more efficient and effective streaming process. By mathematically modeling the streaming framework, we formulate a joint bitrate selection and beamforming problem, aiming to maximize the average video quality experienced by all users. The problem is a non-convex mixed-integer problem and is NP-hard in general. We propose an algorithm with polynomial time complexity for the problem using an alternative optimization technique along with an appropriate rounding operation. Numerical results demonstrate the superiority of the proposed joint bitrate selection and beamforming solution over baselines
Direct Conversion of Mouse Astrocytes Into Neural Progenitor Cells and Specific Lineages of Neurons
Background: Cell replacement therapy has been envisioned as a promising treatment for neurodegenerative diseases. Due to the ethical concerns of ESCs-derived neural progenitor cells (NPCs) and tumorigenic potential of iPSCs, reprogramming of somatic cells directly into multipotent NPCs has emerged as a preferred approach for cell transplantation.
Methods: Mouse astrocytes were reprogrammed into NPCs by the overexpression of transcription factors (TFs) Foxg1, Sox2, and Brn2. The generation of subtypes of neurons was directed by the force expression of cell-type specific TFs Lhx8 or Foxa2/Lmx1a.
Results: Astrocyte-derived induced NPCs (AiNPCs) share high similarities, including the expression of NPC-specific genes, DNA methylation patterns, the ability to proliferate and differentiate, with the wild type NPCs. The AiNPCs are committed to the forebrain identity and predominantly differentiated into glutamatergic and GABAergic neuronal subtypes. Interestingly, additional overexpression of TFs Lhx8 and Foxa2/Lmx1a in AiNPCs promoted cholinergic and dopaminergic neuronal differentiation, respectively.
Conclusions: Our studies suggest that astrocytes can be converted into AiNPCs and lineage-committed AiNPCs can acquire differentiation potential of other lineages through forced expression of specific TFs. Understanding the impact of the TF sets on the reprogramming and differentiation into specific lineages of neurons will provide valuable strategies for astrocyte-based cell therapy in neurodegenerative diseases
Solenoid-free current drive via ECRH in EXL-50 spherical torus plasmas
As a new spherical tokamak (ST) designed to simplify engineering requirements
of a possible future fusion power source, the EXL-50 experiment features a low
aspect ratio (A) vacuum vessel (VV), encircling a central post assembly
containing the toroidal field coil conductors without a central solenoid.
Multiple electron cyclotron resonance heating (ECRH) resonances are located
within the VV to improve current drive effectiveness. Copious energetic
electrons are produced and measured with hard X-ray detectors, carry the bulk
of the plasma current ranging from 50kA to 150kA, which is maintained for more
than 1s duration. It is observed that over one Ampere current can be maintained
per Watt of ECRH power issued from the 28-GHz gyrotrons. The plasma current
reaches Ip>80kA for high density (>5e18me-2) discharge with 150kW ECHR heating.
An analysis was carried out combining reconstructed multi-fluid equilibrium,
guiding-center orbits of energetic electrons, and resonant heating mechanisms.
It is verified that in EXL-50 a broadly distributed current of energetic
electrons creates smaller closed magnetic-flux surfaces of low aspect ratio
that in turn confine the thermal plasma electrons and ions and participate in
maintaining the equilibrium force-balance
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