441 research outputs found
Frustrated phase separation in two-dimensional charged systems
We study phase separation frustrated by the long-range Coulomb interaction in
two dimensional electronic systems with emphasys in the case of a metallic and
an insulating phase. We find that two-dimensional systems are more prone to
mesoscopic frustrated phase separation than the three dimensional ones.Comment: 15 pages, 11 figure
Impact of Anisotropic Birefringence on Measuring Cosmic Microwave Background Lensing
The power spectrum of cosmic microwave background lensing is a powerful tool
for constraining fundamental physics such as the sum of neutrino masses and the
dark energy equation of state. Current lensing measurements primarily come from
distortions to the microwave background temperature field, but the polarization
lensing signal will dominate upcoming experiments with greater sensitivity.
Cosmic birefringence refers to the rotation of the linear polarization
direction of microwave photons propagating from the last scattering surface to
us, which can be induced by parity-violating physics such as axion-like dark
matter or primordial magnetic fields. We find that, for an upcoming CMB-S4-like
experiment, if there exists the scale-invariant anisotropic birefringence with
an amplitude corresponding to the current upper bound, the measured
lensing power spectrum could be biased by up to a factor of few at small
scales, . We show that the bias scales linearly with the
amplitude of the scale-invariant birefringence spectrum. The signal-to-noise of
the contribution from anisotropic birefringence is larger than unity even if
the birefringence amplitude decreases to of the current upper bound.
Our results indicate that a measurement and characterization of the anisotropic
birefringence is important for lensing analysis in future low-noise
polarization experiments.Comment: 13 pages, 5 figures, to be submitted to PR
Unveiling the green path:How urban openness reduces pollution and paves the way to sustainability
This study investigates the relationship between openness and pollutant emission intensity across 286 Chinese cities from 1990 to 2019, aiming to evaluate the potential environmental benefits of open economy strategies. The findings indicate that enhanced urban openness significantly lowers pollutant emission intensity. To ensure the robustness of our findings, we make an innovative attempt to employ high-speed rail connection and motorway density as instrumental variables to address potential endogeneity issues, corroborating the reliability of the results through various robustness tests. Moreover, we also find the heterogeneous effects of urban openness on pollution emissions, highlighting the moderating influences of trade complexity, urbanization level, and environmental regulatory intensity. Lastly, the study elucidates the mechanisms through which urban openness diminishes pollution emissions, namely fostering green innovation capacity and enhancing public environmental awareness. This research makes theoretical contributions on understanding the nexus between open economies and environmental protection while offering practical insights to inform governmental environmental policy formulation.</p
One-shot ultraspectral imaging with reconfigurable metasurfaces
One-shot spectral imaging that can obtain spectral information from thousands
of different points in space at one time has always been difficult to achieve.
Its realization makes it possible to get spatial real-time dynamic spectral
information, which is extremely important for both fundamental scientific
research and various practical applications. In this study, a one-shot
ultraspectral imaging device fitting thousands of micro-spectrometers (6336
pixels) on a chip no larger than 0.5 cm, is proposed and demonstrated.
Exotic light modulation is achieved by using a unique reconfigurable
metasurface supercell with 158400 metasurface units, which enables 6336
micro-spectrometers with dynamic image-adaptive performances to simultaneously
guarantee the density of spectral pixels and the quality of spectral
reconstruction. Additionally, by constructing a new algorithm based on
compressive sensing, the snapshot device can reconstruct ultraspectral imaging
information (/~0.001) covering a broad (300-nm-wide)
visible spectrum with an ultra-high center-wavelength accuracy of 0.04-nm
standard deviation and spectral resolution of 0.8 nm. This scheme of
reconfigurable metasurfaces makes the device can be directly extended to almost
any commercial camera with different spectral bands to seamlessly switch the
information between image and spectral image, and will open up a new space for
the application of spectral analysis combining with image recognition and
intellisense
Protective Mechanism of Humanin Against Oxidative Stress in Aging-Related Cardiovascular Diseases
Physiological reactive oxygen species (ROS) are important regulators of intercellular signal transduction. Oxidative and antioxidation systems maintain a dynamic balance under physiological conditions. Increases in ROS levels destroy the dynamic balance, leading to oxidative stress damage. Oxidative stress is involved in the pathogenesis of aging-related cardiovascular diseases (ACVD), such as atherosclerosis, myocardial infarction, and heart failure, by contributing to apoptosis, hypertrophy, and fibrosis. Oxidative phosphorylation in mitochondria is the main source of ROS. Increasing evidence demonstrates the relationship between ACVD and humanin (HN), an endogenous peptide encoded by mitochondrial DNA. HN protects cardiomyocytes, endothelial cells, and fibroblasts from oxidative stress, highlighting its protective role in atherosclerosis, ischemia–reperfusion injury, and heart failure. Herein, we reviewed the signaling pathways associated with the HN effects on redox signals, including Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2), chaperone-mediated autophagy (CMA), c-jun NH2 terminal kinase (JNK)/p38 mitogen-activated protein kinase (p38 MAPK), adenosine monophosphate-activated protein kinase (AMPK), and phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)-Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3). Furthermore, we discussed the relationship among HN, redox signaling pathways, and ACVD. Finally, we propose that HN may be a candidate drug for ACVD
Large-scale Kinetic Simulations of Colliding Plasmas within a Hohlraum of Indirect Drive Inertial Confinement Fusions
The National Ignition Facility has recently achieved successful burning
plasma and ignition using the inertial confinement fusion (ICF) approach.
However, there are still many fundamental physics phenomena that are not well
understood, including the kinetic processes in the hohlraum. Shan et al. [Phys.
Rev. Lett, 120, 195001, 2018] utilized the energy spectra of neutrons to
investigate the kinetic colliding plasma in a hohlraum of indirect drive ICF.
However, due to the typical large spatial-temporal scales, this experiment
could not be well simulated by using available codes at that time. Utilizing
our advanced high-order implicit PIC code, LAPINS, we were able to successfully
reproduce the experiment on a large scale of both spatial and temporal
dimensions, in which the original computational scale was increased by
approximately 7 to 8 orders of magnitude. When gold plasmas expand into
deuterium plasmas, a kinetic shock is generated and propagates within deuterium
plasmas. Simulations allow us to observe the entire progression of a strong
shock wave, including its initial formation and steady propagation. Although
both electrons and gold ions are collisional (on a small scale compared to the
shock wave), deuterium ions seem to be collisionless. This is because a
quasi-monoenergetic spectrum of deuterium ions can be generated by reflecting
ions from the shock front, which then leads to the production of neutrons with
unusual broadening due to beam-target nuclear reactions. This work displays an
unprecedented kinetic analysis of an existing experiment, shedding light on the
mechanisms behind shock wave formation. It also serves as a reference for
benchmark simulations of upcoming new simulation codes and may be relevant for
future research on mixtures and entropy increments at plasma interfaces
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