5,628 research outputs found
Electron-Angular-Distribution Reshaping in Quantum Radiation-Dominated Regime
Dynamics of an electron beam head-on colliding with an ultraintense focused
ultrashort circularly-polarized laser pulse are investigated in the quantum
radiation-dominated regime. Generally, the ponderomotive force of the laser
fields may deflect the electrons transversely, to form a ring structure on the
cross-section of the electron beam. However, we find that when the Lorentz
factor of the electron is approximately one order of magnitude larger
than the invariant laser field parameter , the stochastic nature of the
photon emission leads to electron aggregation abnormally inwards to the
propagation axis of the laser pulse. Consequently, the electron angular
distribution after the interaction exhibits a peak structure in the beam
propagation direction, which is apparently distinguished from the
"ring"-structure of the distribution in the classical regime, and therefore,
can be recognized as a proof of the fundamental quantum stochastic nature of
radiation. The stochasticity signature is robust with respect to the laser and
electron parameters and observable with current experimental techniques
A Novel FastICA Method for the Reference-based Contrast Functions
This paper deals with the efficient optimization problem of Cumulant-based contrast criteria in the Blind Source Separation (BSS) framework, in which sources are retrieved by maximizing the Kurtosis contrast function. Combined with the recently proposed reference-based contrast schemes, a new fast fixed-point (FastICA) algorithm is proposed for the case of linear and instantaneous mixture. Due to its quadratic dependence on the number of searched parameters, the main advantage of this new method consists in the significant decrement of computational speed, which is particularly striking with large number of samples. The method is essentially similar to the classical algorithm based on the Kurtosis contrast function, but differs in the fact that the reference-based idea is utilized. The validity of this new method was demonstrated by simulations
Enzymes and genes involved in the betalain biosynthesis in higher plants
Betalains, a class of water-soluble nitrogen-containing pigments, replace anthocyanins and serve the analogous functions in 13 families of the order, caryophyllales. They modulate the attractive appearance of plants and protect them against destructive oxidative damage. Their antioxidant roles, radicalscavenging properties in human health and their potential uses in food and pharmaceutical industries have made significant progress achieved in the detection, purification, quantification, structure elucidation of betalains, and in particular in the understanding of biosynthetic pathways of the pigments,the enzymes and their genes involved in the pathways. In this paper, major progress in betalain biosynthesis and the enzymes and genes involved in the biosynthetic pathways in higher plant are reviewed, and the perspectives discussed
An Efficient Algorithm by Kurtosis Maximization in Reference-Based Framework
This paper deals with the optimization of kurtosis for complex-valued signals in the independent component analysis (ICA) framework, where source signals are linearly and instantaneously mixed. Inspired by the recently proposed reference-based contrast schemes, a similar contrast function is put forward, based on which a new fast fixed-point (FastICA) algorithm is proposed. The new optimization method is similar in spirit to the former classical kurtosis-based FastICA algorithm but differs in the fact that it is much more efficient than the latter in terms of computational speed, which is significantly striking with large number of samples. The performance of this new algorithm is confirmed through computer simulations
Abnormal neurofilament inclusions and segregations in dorsal root ganglia of a Charcot-Marie-Tooth type 2E mouse model
Charcot-Marie-Tooth (CMT) disease or hereditary motor and sensory neuropathy is the most prevalent inherited peripheral neuropathy and is associated with over 90 causative genes. Mutations in neurofilament light polypeptide gene, NEFL cause CMT2E, an axonal form of CMT that results in abnormal structures and/or functions of peripheral axons in spinal cord motor neurons and dorsal root ganglion neurons. We have previously generated and characterized a knock-in mouse model of CMT2E with the N98S mutation in Nefl that presented with multiple inclusions in spinal cord neurons. In this report, we conduct immunofluorescence studies of cultured dorsal root ganglia (DRG) from NeflN98S/+ mice, and show that inclusions found in DRG neurites can occur in embryonic stages. Ultrastructural analyses reveal that the inclusions are disordered neurofilaments packed in high density, segregated from other organelles. Immunochemical studies show decreased NFL protein levels in DRG, cerebellum and spinal cord in NeflN98S/+ mice, and total NFL protein pool is shifted toward the triton-insoluble fraction. Our findings reveal the nature of the inclusions in NeflN98S/+ mice, provide useful information to understand mechanisms of CMT2E disease, and identify DRG from NeflN98S/+ mice as a useful cell line model for therapeutic discoveries
A two-part mixed-effects model for analyzing clustered time-to-event data with clumping at zero
In longitudinal epidemiological studies consisting of a baseline stage and a follow-up stage, observations at the baseline stage may contain a countable proportion of negative responses. The time-to-event outcomes of those observations corresponding to negative responses at baseline can be denoted as zeros, which are excluded from standard survival analysis. Consequently, some important information on these subjects is therefore lost in the analysis. Furthermore, subjects are often clustered within hospitals, communities or health service centers, resulting in correlated observations. The framework of the two-part model has been developed and utilized widely to analyze semi-continuous data or count data with excess zeros, but its application to clustered time-to-event data with clumping at zero remains sparse.This study was partially supported by China Scholarship Council (Grant NO: 201406240008)
General theory of decoy-state quantum cryptography with source errors
The existing theory of decoy-state quantum cryptography assumes the exact
control of each states from Alice's source. Such exact control is impossible in
practice. We develop the theory of decoy-state method so that it is
unconditionally secure even there are state errors of sources, if the range of
a few parameters in the states are known. This theory simplifies the practical
implementation of the decoy-state quantum key distribution because the
unconditional security can be achieved with a slightly shortened final key,
even though the small errors of pulses are not corrected.Comment: Our results can be used securely for any source of diagonal states,
including the Plug-&-Play protocol with whatever error pattern, if we know
the ranges of errors of a few parameter
Demonstration of the First 4H-SiC EUV Detector with Large Detection Area
Ultraviolet (UV) and Extreme Ultraviolet (EUV) detectors are very attractive in astronomy, photolithography and biochemical applications. For EUV applications, most of the semiconductor detectors based on PN or PIN structures suffer from the very short penetration depth. Most of the carries are absorbed at the surface and recombined there due to the high surface recombination before reach the depletion region, resulting very low quantum efficiency. On the other hand, for Schottky structures, the active region starts from the surface and carriers generated from the surface can be efficiently collected. 4H-Sic has a bandgap of 3.26eV and is immune to visible light background noise. Also, 4H-Sic detectors usually have very good radiation hardness and very low noise, which is very important for space applications where the signal is very weak. The E W photodiodes presented in this paper are based on Schottky structures. Platinum (Pt) and Nickel (Ni) are selected as the Schottky contact metals, which have the highest electron work functions (5.65eV and 5.15eV, respectively) among all the known metals on 4H-Sic
Density-functional fidelity approach to quantum phase transitions
We propose a new approach to quantum phase transitions in terms of the
density-functional fidelity, which measures the similarity between density
distributions of two ground states in parameter space. The key feature of the
approach, as we will show, is that the density-functional fidelity can be
measured easily in experiments. Both the validity and versatility of the
approach are checked by the Lipkin-Meshkov-Glick model and the one-dimensional
Hubbard model.Comment: 4 pages, 2 figures, submitted to Chin. Phys. Let
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