23,214 research outputs found
Earliest tea as evidence for one branch of the Silk Road across the Tibetan Plateau.
Phytoliths and biomolecular components extracted from ancient plant remains from Chang'an (Xi'an, the city where the Silk Road begins) and Ngari (Ali) in western Tibet, China, show that the tea was grown 2100 years ago to cater for the drinking habits of the Western Han Dynasty (207BCE-9CE), and then carried toward central Asia by ca.200CE, several hundred years earlier than previously recorded. The earliest physical evidence of tea from both the Chang'an and Ngari regions suggests that a branch of the Silk Road across the Tibetan Plateau, was established by the second to third century CE
Identification of an intraocular microbiota
The current dogma in ophthalmology and vision research presumes the intraocular environment to be sterile. However, recent evidence of intestinal bacterial translocation into the bloodstream and many other internal organs including the eyes, found in healthy and diseased animal models, suggests that the intraocular cavity may also be inhabited by a microbial community. Here, we tested intraocular samples from over 1000 human eyes. Using quantitative PCR, negative staining transmission electron microscopy, direct culture, and high-throughput sequencing technologies, we demonstrated the presence of intraocular bacteria. The possibility that the microbiome from these low-biomass communities could be a contamination from other tissues and reagents was carefully evaluated and excluded. We also provide preliminary evidence that a disease-specific microbial signature characterized the intraocular environment of patients with age-related macular degeneration and glaucoma, suggesting that either spontaneous or pathogenic bacterial translocation may be associated with these common sight-threatening conditions. Furthermore, we revealed the presence of an intraocular microbiome in normal eyes from non-human mammals and demonstrated that this varied across species (rat, rabbit, pig, and macaque) and was established after birth. These findings represent the first-ever evidence of intraocular microbiota in humans
NODIS: Neural Ordinary Differential Scene Understanding
Semantic image understanding is a challenging topic in computer vision. It
requires to detect all objects in an image, but also to identify all the
relations between them. Detected objects, their labels and the discovered
relations can be used to construct a scene graph which provides an abstract
semantic interpretation of an image. In previous works, relations were
identified by solving an assignment problem formulated as Mixed-Integer Linear
Programs. In this work, we interpret that formulation as Ordinary Differential
Equation (ODE). The proposed architecture performs scene graph inference by
solving a neural variant of an ODE by end-to-end learning. It achieves
state-of-the-art results on all three benchmark tasks: scene graph generation
(SGGen), classification (SGCls) and visual relationship detection (PredCls) on
Visual Genome benchmark
Enhancement of Friction between Carbon Nanotubes: An Efficient Strategy to Strengthen Fibers
Interfacial friction plays a crucial role in the mechanical properties of
carbon nanotube based fibers, composites, and devices. Here we use molecular
dynamics simulation to investigate the pressure effect on the friction within
carbon nanotube bundles. It reveals that the intertube frictional force can be
increased by a factor of 1.5 ~ 4, depending on tube chirality and radius, when
all tubes collapse above a critical pressure and when the bundle remains
collapsed with unloading down to atmospheric pressure. Furthermore, the overall
cross-sectional area also decreases significantly for the collapsed structure,
making the bundle stronger. Our study suggests a new and efficient way to
reinforce nanotube fibers, possibly stronger than carbon fibers, for usage at
ambient conditions.Comment: revtex, 5 pages, accepted by ACS Nano 10 Dec 200
Gate-Voltage Control of Chemical Potential and Weak Anti-localization in Bismuth Selenide
We report that BiSe thin films can be epitaxially grown on
SrTiO substrates, which allow for very large tunablity in carrier density
with a back-gate. The observed low field magnetoconductivity due to weak
anti-localization (WAL) has a very weak gate-voltage dependence unless the
electron density is reduced to very low values. Such a transition in WAL is
correlated with unusual changes in longitudinal and Hall resistivities. Our
results suggest much suppressed bulk conductivity at large negative
gate-voltages and a possible role of surface states in the WAL phenomena. This
work may pave a way for realizing three-dimensional topological insulators at
ambient conditions.Comment: 5 pages, 4 figures
Lanthanum distribution and dielectric properties of intergrowth Bi₅ˍₓLaₓTiNbWO₁₅ ferroelectrics
Bi₅ˍₓLaₓTiNbWO₁₅ (x=0–1.50)ceramics prepared by conventional solid-state reaction were studied using x-ray diffraction(XRD),dielectric spectroscopy and Raman scattering techniques. The XRD analysis implied that single-phase intergrowth bismuth layered perovskite structure was obtained for all the samples and when x=0.75, the Bi³⁺ in (Bi₂O₂)²⁺ layer begins to be substituted by La³⁺. The dielectric spectra showed that, when Bi³⁺ in (Bi₂O₂)²⁺ is substituted, the Curie temperature becomes diffusive and the dielectricpermittivity at room temperature is increased in a wide frequency range. Especially when x=1.50, the dielectricpermittivity reaches its maximum of 270, nearly two times larger than that of the La3+ undoped sample. The Raman scattering experiments evidenced further that Bi³⁺ in (Bi₂O₂)²⁺ is substituted when x⩾0.75 and revealed the orthorhombic distortion of the octahedra is responsible for the increase of the dielectricpermittivity at x⩾1.25.This work was supported by the Ministry of Science and
Technology of China through 973-Project under Grant No.
2002CB613307
Distribution of Spectral Lags in Gamma Ray Bursts
Using the data acquired in the Time To Spill (TTS) mode for long gamma-ray
bursts (GRBs) collected by the Burst and Transient Source Experiment on board
the Compton Gamma Ray Observatory (BATSE/CGRO), we have carefully measured
spectral lags in time between the low (25-55 keV) and high (110-320 keV) energy
bands of individual pulses contained in 64 multi-peak GRBs. We find that the
temporal lead by higher-energy gamma-ray photons (i.e., positive lags) is the
norm in this selected sample set of long GRBs. While relatively few in number,
some pulses of several long GRBs do show negative lags. This distribution of
spectral lags in long GRBs is in contrast to that in short GRBs. This apparent
difference poses challenges and constraints on the physical mechanism(s) of
producing long and short GRBs. The relation between the pulse peak count rates
and the spectral lags is also examined. Observationally, there seems to be no
clear evidence for systematic spectral lag-luminosity connection for pulses
within a given long GRB.Comment: 20 pages, 4 figure
Barnyard grasses were processed with rice around 10000 years ago
Rice (Oryza sativa) is regarded as the only grass that was selected for cultivation and eventual domestication in the Yangtze basin of China. Although both macro-fossils and micro-fossils of rice have been recovered from the Early Neolithic site of Shangshan, dating to more than 10,000 years before present (BP), we report evidence of phytolith and starch microfossils taken from stone tools, both for grinding and cutting, and cultural layers, that indicating barnyard grass (Echinochloa spp.) was a major subsistence resource, alongside smaller quantities of acorn starches (Lithocarpus/Quercus sensu lato) and water chestnuts (Trapa). This evidence suggests that early managed wetland environments were initially harvested for multiple grain species including barnyard grasses as well as rice, and indicate that the emergence of rice as the favoured cultivated grass and ultimately the key domesticate of the Yangtze basin was a protracted process
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