215 research outputs found
Ion acceleration in "dragging field" of a light-pressure-driven piston
We propose a new acceleration scheme that combines shock wave acceleration
(SWA) and light pressure acceleration (LPA). When a thin foil driven by light
pressure of an ultra-intense laser pulse propagates in underdense background
plasma, it serves as a shock-like piston, trapping and reflecting background
protons to ultra-high energies. Unlike in SWA, the piston velocity is not
limited by the Mach number and can be highly relativistic. Background protons
can be trapped and reflected forward by the enormous "dragging field" potential
behind the piston which is not employed in LPA. Our one- and two-dimensional
particle-in-cell simulations and analytical model both show that proton
energies of several tens to hundreds of GeV can be obtained, while the
achievable energy in simple LPA is below 10 GeV.Comment: submitte
Axionlike-particle generation by laser-plasma interaction
Axion, a hypothetical particle that is crucial to quantum chromodynamics and
dark matter theory, has not yet been found in any experiment. With the
improvement of laser technique, much stronger quasi-static electric and
magnetic fields can be created in laboratory using laser-plasma interaction. In
this article, we discuss the feasibility of axion or axionlike-particle's
exploring experiments using planar and cylindrically symmetric laser-plasma
fields as backgrounds while probing with an ultrafast superstrong optical laser
or x-ray free-electron laser with high photon number. Compared to classical
magnet design, the axion source in laser-plasma interaction trades the
accumulating length for the source's interacting strength. Besides, a
structured field in the plasma creates a tunable transverse profile of the
interaction and improves the signal-noise ratio via the mechanisms such as
phase-matching. The mass of axion discussed in this article ranges from 1
\textmu eV to 1 eV. Some simple schemes and estimations of axion production and
probe's polarization rotation are given, which reveals the possibility of
future laser-plasma axion source in laboratory.Comment: 24 pages, 5 figure
N-Myc Downstream-Regulated Gene 2 (NDRG2) as a Novel Tumor Suppressor in Multiple Human Cancers
N-myc downstream-regulated gene 2 (NDRG2) was identified as a novel tumor suppressor gene in regulating the proliferation, differentiation, apoptosis and metastasis of multiple cancer types. Consistent with this finding, we and other groups observed the decreased NDRG2 expression in multiple human cancer cell lines and tumors, including breast cancer, colorectal cancer, and cervical cancer. We identified NDRG2 as a stress sensor for hypoxia, DNA damage stimuli and endoplasmic reticulum stress (ERS). Our recent data showed that NDRG2 could promote the differentiation of colorectal cancer cells. Interestingly, we found that reduced NDRG2 expression was a powerful and independent predictor of poor prognosis of colorectal cancer patients. Furthermore, NDRG2 can inhibit epithelial-mesenchymal transition (EMT) by positively regulating E-cadherin expression. Moreover, NDRG2-deficient mice show spontaneous development of various tumor types, including T-cell lymphomas, providing in vivo evidence that NDRG2 functions as a tumor suppressor gene. We believe that NDRG2 is a novel tumor suppressor and might be a therapeutic target for cancer treatment
Driving positron beam acceleration with coherent transition radiation
Positron acceleration in plasma wakefield faces significant challenges since
the positron beam must be pre-generated and precisely coupled into the
wakefield, and most critically, suffers from defocusing issues. Here we propose
a scheme that utilizes laser-driven electrons to produce, inject and accelerate
positrons in a single set-up. The high-charge electron beam from wakefield
acceleration creates copious electron-positron pairs via the Bethe-Heitler
process, followed by enormous coherent transition radiation due to the
electrons' exiting from the metallic foil. Simulation results show that the
coherent transition radiation field reaches up to 10's GV m-1, which captures
and accelerates the positrons to cut-off energy of 1.5 GeV with energy peak of
500 MeV and energy spread is about 24.3%. An external longitudinal magnetic
field of 30 T is also applied to guide the electrons and positrons during the
acceleration process. This proposed method offers a promising way to obtain GeV
fast positron sources
Transfer of spin to orbital angular momentum in the Bethe-Heitler process
According to the conservation of angular momentum, when a plane-wave
polarized photon splits into a pair of electron-positron under the influence of
the Coulomb field, the spin angular momentum (SAM) of the photon is converted
into the angular momentum of the leptons. We investigate this process (the
Bethe-Heitler process) by describing the final electron and positron with
twisted states and find that the SAM of the incident photon is not only
converted into SAM of the produced pair, but also into their orbital angular
momentum (OAM), which has not been considered previously. The average OAM
gained by the leptons surpasses the average SAM, while their orientations
coincide. Both properties depend on the energy and open angle of the emitted
leptons. The demonstrated spin-orbit transfer shown in the Bethe-Heitler
process may exist in a large group of QED scattering processes
Endoplasmic reticulum stress in innate immune cells -Â a significant contribution to non-alcoholic fatty liver disease
Liver disease and its complications affect millions of people worldwide. NAFLD (non-alcoholic fatty liver disease) is the liver disease associated with metabolic dysfunction and consists of four stages: steatosis with or without mild inflammation (NAFLD), non-alcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. With increased necroinflammation and progression of liver fibrosis, NAFLD may progress to cirrhosis or even hepatocellular carcinoma. Although the underlying mechanisms have not been clearly elucidated in detail, what is clear is that complex immune responses are involved in the pathogenesis of NASH, activation of the innate immune system is critically involved in triggering and amplifying hepatic inflammation and fibrosis in NAFLD/NASH. Additionally, disruption of endoplasmic reticulum (ER) homeostasis in cells, also known as ER stress, triggers the unfolded protein response (UPR) which has been shown to be involved to inflammation and apoptosis. To further develop the prevention and treatment of NAFLD/NASH, it is imperative to clarify the relationship between NAFLD/NASH and innate immune cells and ER stress. As such, this review focuses on innate immune cells and their ER stress in the occurrence of NAFLD and the progression of cirrhosis
Single-Shot Top-Down Proteomics with Capillary Zone Electrophoresis-Electrospray Ionization-Tandem Mass Spectrometry for Identification of Nearly 600 Escherichia coli Proteoforms
Capillary zone electrophoresis-electrospray ionization-tandem mass spectrometry (CZE-ESI-MS/MS) has been recognized as an invaluable platform for top-down proteomics. However, the scale of top-down proteomics using CZE-MS/MS is still limited due to the low loading capacity and narrow separation window of CZE. In this work, for the first time we systematically evaluated the dynamic pH junction method for focusing of intact proteins during CZE-MS. The optimized dynamic pH junction-based CZE-MS/MS approached a 1 μL loading capacity, 90 min separation window, and high peak capacity (∼280) for characterization of an Escherichia coli proteome. The results represent the largest loading capacity and the highest peak capacity of CZE for top-down characterization of complex proteomes. Single-shot CZE-MS/MS identified about 2800 proteoform-spectrum matches, nearly 600 proteoforms, and 200 proteins from the Escherichia coli proteome with spectrum-level false discovery rate (FDR) less than 1%. The number of identified proteoforms in this work is over three times higher than that in previous single-shot CZE-MS/MS studies. Truncations, N-terminal methionine excision, signal peptide removal, and some post-translational modifications including oxidation and acetylation were detected
Generation of Ultra-intense Gamma-ray Train by QED Harmonics
When laser intensity exceeds 10^22W/cm^2, photons with energy above MeV can
be generated from high-order harmonics process in the laser-plasma interaction.
We find that under such laser intensity, QED effect plays a dominating role in
the radiation pattern. Contrast to the gas and relativistic HHG processes, both
the occurrence and energy of gamma-ray emission produced by QED harmonics are
random and QED harmonics are usually not coherent, while the property of high
intensity and ultra-short duration is conserved. Our simulation shows that the
period of gamma-ray train is half of the laser period and the peak intensity is
1.4e22W/cm^2. This new harmonic production with QED effects are crucial to
light-matter interaction in strong field and can be verified in experiments by
10PW laser facilities in the near future.Comment: 12 pages, 4 figure
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