5,718 research outputs found
Partial spin freezing in the quasi-two-dimensional La2(Cu,Li)O4
In conventional spin glasses, the magnetic interaction is not strongly
anisotropic and the entire spin system freezes at low temperature. In
La2(Cu,Li)O4, for which the in-plane exchange interaction dominates the
interplane one, only a fraction of spins with antiferromagnetic correlations
extending to neighboring planes become spin-glass. The remaining spins with
only in-plane antiferromagnetic correlations remain spin-liquid at low
temperature. Such a novel partial spin freezing out of a spin-liquid observed
in this cold neutron scattering study is likely due to a delicate balance
between disorder and quantum fluctuations in the quasi-two dimensional S=1/2
Heisenberg system.Comment: 4 pages, 4 figure
Structural Color 3D Printing By Shrinking Photonic Crystals
The rings, spots and stripes found on some butterflies, Pachyrhynchus
weevils, and many chameleons are notable examples of natural organisms
employing photonic crystals to produce colorful patterns. Despite advances in
nanotechnology, we still lack the ability to print arbitrary colors and shapes
in all three dimensions at this microscopic length scale. Commercial nanoscale
3D printers based on two-photon polymerization are incapable of patterning
photonic crystal structures with the requisite ~300 nm lattice constant to
achieve photonic stopbands/ bandgaps in the visible spectrum and generate
colors. Here, we introduce a means to produce 3D-printed photonic crystals with
a 5x reduction in lattice constants (periodicity as small as 280 nm), achieving
sub-100-nm features with a full range of colors. The reliability of this
process enables us to engineer the bandstructures of woodpile photonic crystals
that match experiments, showing that observed colors can be attributed to
either slow light modes or stopbands. With these lattice structures as 3D color
volumetric elements (voxels), we printed 3D microscopic scale objects,
including the first multi-color microscopic model of the Eiffel Tower measuring
only 39-microns tall with a color pixel size of 1.45 microns. The technology to
print 3D structures in color at the microscopic scale promises the direct
patterning and integration of spectrally selective devices, such as photonic
crystal-based color filters, onto free-form optical elements and curved
surfaces
Two Populations of Molecular Clouds in the Antennae Galaxies
Super star clusters --- extremely massive clusters found predominately in
starburst environments --- are essential building blocks in the formation of
galaxies and thought to dominate star formation in the high-redshift universe.
However, the transformation from molecular gas into these ultra-compact star
clusters is not well understood. To study this process, we used the
Submillimeter Array and the Plateau de Bure Interferometer to obtain high
angular resolution (~1.5" or 160 pc) images of the Antennae overlap region in
CO(2--1) to search for the molecular progenitors of the super star clusters. We
resolve the molecular gas distribution into a large number of clouds, extending
the differential cloud mass function down to a 5\sigma completeness limit of
3.8x10^5 M_sun. We identify a distinct break in the mass function around log
M_mol/M_sun ~ 6.5, which separates the molecular clouds into two distinct
populations. The smaller, less massive clouds reside in more quiescent areas in
the region, while the larger, more massive clouds cluster around regions of
intense star formation. A broken power-law fit to the mass function yields
slopes of \alpha = -1.39+/-0.10 and \alpha = -1.44+/-0.14 for the low- and
high-mass cloud population, well-matched to the mass function found for super
star clusters in the Antennae galaxies. We find large velocity gradients and
velocity dispersions at the locations of intense star formation, suggestive of
compressive shocks. It is likely that these environmental factors contribute to
the formation of the observed massive molecular clouds and super star clusters
in the Antennae galaxies.Comment: 20 pages, 13 figures, accepted by Ap
Social Interaction-Aware Dynamical Models and Decision Making for Autonomous Vehicles
Interaction-aware Autonomous Driving (IAAD) is a rapidly growing field of
research that focuses on the development of autonomous vehicles (AVs) that are
capable of interacting safely and efficiently with human road users. This is a
challenging task, as it requires the autonomous vehicle to be able to
understand and predict the behaviour of human road users. In this literature
review, the current state of IAAD research is surveyed in this work. Commencing
with an examination of terminology, attention is drawn to challenges and
existing models employed for modelling the behaviour of drivers and
pedestrians. Next, a comprehensive review is conducted on various techniques
proposed for interaction modelling, encompassing cognitive methods, machine
learning approaches, and game-theoretic methods. The conclusion is reached
through a discussion of potential advantages and risks associated with IAAD,
along with the illumination of pivotal research inquiries necessitating future
exploration
Developmental changes in the role of different metalinguistic awareness skills in Chinese reading acquisition from preschool to third grade
Copyright @ 2014 Wei et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and source are credited.The present study investigated the relationship between Chinese reading skills and metalinguistic awareness skills such as phonological, morphological, and orthographic awareness for 101 Preschool, 94 Grade-1, 98 Grade-2, and 98 Grade-3 children from two primary schools in Mainland China. The aim of the study was to examine how each of these metalinguistic awareness skills would exert their influence on the success of reading in Chinese with age. The results showed that all three metalinguistic awareness skills significantly predicted reading success. It further revealed that orthographic awareness played a dominant role in the early stages of reading acquisition, and its influence decreased with age, while the opposite was true for the contribution of morphological awareness. The results were in stark contrast with studies in English, where phonological awareness is typically shown as the single most potent metalinguistic awareness factor in literacy acquisition. In order to account for the current data, a three-stage model of reading acquisition in Chinese is discussed.National Natural Science Foundation of China and Knowledge Innovation Program of the
Chinese Academy of Sciences
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Cathelicidin preserves intestinal barrier function in polymicrobial sepsis.
ObjectivesThe intestinal epithelium compartmentalizes the sterile bloodstream and the commensal bacteria in the gut. Accumulating evidence suggests that this barrier is impaired in sepsis, aggravating systemic inflammation. Previous studies reported that cathelicidin is differentially expressed in various tissues in sepsis. However, its role in sepsis-induced intestinal barrier dysfunction has not been investigated.DesignTo examine the role of cathelicidin in polymicrobial sepsis, cathelicidin wild-(Cnlp+/+) and knockout (Cnlp-/-) mice underwent cecal-ligation and puncture (CLP) followed by the assessment of septic mortality and morbidity as well as histological, biochemical, immunological, and transcriptomic analyses in the ileal tissues. We also evaluated the prophylactic and therapeutic efficacies of vitamin D3 (an inducer of endogenous cathelicidin) in the CLP-induced murine polymicrobial sepsis model.ResultsThe ileal expression of cathelicidin was increased by three-fold after CLP, peaking at 4 h. Knockout of Cnlp significantly increased 7-day mortality and was associated with a higher murine sepsis score. Alcian-blue staining revealed a reduced number of mucin-positive goblet cells, accompanied by reduced mucin expression. Increased number of apoptotic cells and cleavage of caspase-3 were observed. Cnlp deletion increased intestinal permeability to 4kD fluorescein-labeled dextran and reduced the expression of tight junction proteins claudin-1 and occludin. Notably, circulating bacterial DNA load increased more than two-fold. Transcriptome analysis revealed upregulation of cytokine/inflammatory pathway. Depletion of Cnlp induced more M1 macrophages and neutrophils compared with the wild-type mice after CLP. Mice pre-treated with cholecalciferol (an inactive form of vitamin D3) or treated with 1alpha, 25-dihydroxyvitamin D3 (an active form of VD3) had decreased 7-day mortality and significantly less severe symptoms. Intriguingly, the administration of cholecalciferol after CLP led to worsened 7-day mortality and the associated symptoms.ConclusionsEndogenous cathelicidin promotes intestinal barrier integrity accompanied by modulating the infiltration of neutrophils and macrophages in polymicrobial sepsis. Our data suggested that 1alpha, 25-dihydroxyvitamin D3 but not cholecalciferol is a potential therapeutic agent for treating sepsis
A Non-Abelian Self-Dual Gauge Theory in 5+1 Dimensions
We construct a non-Abelian gauge theory of chiral 2-forms (self-dual gauge
fields) in 6 dimensions with a spatial direction compactified on a circle of
radius R. It has the following two properties. (1) It reduces to the Yang-Mills
theory in 5 dimensions for small R. (2) It is equivalent to the
Lorentz-invariant theory of Abelian chiral 2-forms when the gauge group is
Abelian. Previous no-go theorems prohibiting non-Abelian deformations of the
chiral 2-form gauge theory are circumvented by introducing nonlocality along
the compactified dimension.Comment: 23 pages, reference adde
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