480 research outputs found
Single deep ultraviolet light emission from boron nitride nanotube film
Light in deep ultraviolet DUV region has a wide range of applications and the demand for finding
DUV light emitting materials at nanoscale is increasingly urgent as they are vital for building
miniaturized optic and optoelectronic devices. We discover that boron nitride nanotubes BNNTs
with a well-crystallized cylindrical multiwall structure and diameters smaller than 10 nm can have
single DUV emission at 225 nm 5.51 eV. The measured BNNTs are grown on substrate in the form
of a thin film. This study suggests that BNNTs may work as nanosized DUV light sources for
various applications. © 20
Absorption Cross Sections of NH_3, NH_2D, NHD_2, and ND_3 in the Spectral Range 140-220 nm and Implications for Planetary Isotopic Fractionation
Cross sections for photoabsorption of NH_3, NH_2D, NHD_2, and ND_3 in the spectral region 140-220 nm were determined at ~298 K using synchrotron radiation. Absorption spectra of NH_2D and NHD_2 were deduced from spectra of mixtures of NH_3 and ND_3, of which the equilibrium concentrations for all four isotopologues obey statistical distributions. Cross sections of NH_2D, NHD_2, and ND_3 are new. Oscillator strengths, an integration of absorption cross sections over the spectral lines, for both A ← X and B ← X systems of NH_3 agree satisfactorily with previous reports; values for NH_2D, NHD_2, and ND_3 agree with quantum chemical predictions. The photolysis of NH_3 provides a major source of reactive hydrogen in the lower stratosphere and upper troposphere of giant planets such as Jupiter. Incorporating the measured photoabsorption cross sections of NH_3 and NH_2D into the Caltech/JPL photochemical diffusive model for the atmosphere of Jupiter, we find that the photolysis efficiency of NH_2D is lower than that of NH_3 by as much as 30%. The D/H ratio in NH_2D/NH_3 for tracing the microphysics in the troposphere of Jupiter is also discussed
Molecular dynamics simulations of thermal evaporation and critical electric field of copper nanotips
Due to the miniaturization of microelectromechanical systems, nanoelectromechanical systems and molecular devices, the problem of vacuum insulation becomes more and more prominent. The nanoscale thermal effects caused by electron emission and electric current Joule heat under high electric fields lead to gasification and migration of material in the device. In this work, a coupled molecular dynamics-electrodynamics method is used to simulate the thermal evaporation of nanotips under high electric field. Moreover, Cu nanotips with different initial geometries and different macroscopic electric fields are modelled. The deformation and damage mechanisms of nanotips under high electric field are discussed. Our simulations show that the aspect ratio of nanotips has a significant influence on the thermal evaporation of nanotips. The thermal runaway occurring in picosecond time-scale plays an important role for the initiation of the vacuum breakdown. An empirical relationship is obtained between the on-set breakdown time and the macroscopic electric field and the geometry of nanotips by analysing the numerical results.Peer reviewe
New advances of DNA methylation in liver fibrosis, with special emphasis on the crosstalk between microRNAs and DNA methylation machinery
AbstractEpigenetics refers to the study of heritable changes in the pattern of gene expression that is controlled by a mechanism specifically not due to changes the primary DNA sequence. Well-known epigenetic mechanisms include DNA methylation, post-translational histone modifications and RNA-based mechanisms including those controlled by small non-coding RNAs (miRNAs). Recent studies have shown that epigenetic modifications orchestrate the hepatic stellate cell (HSC) activation and liver fibrosis. In this review we focus on the aberrant methylation of CpG island promoters of select genes is the prominent epigenetic mechanism to effectively silence gene transcription facilitating HSC activation and liver fibrosis. Furthermore, we also discuss epigenetic dysregulation of tumor-suppressor miRNA genes by promoter DNA methylation and the interaction of DNA methylation with miRNAs involved in the regulation of HSC activation and liver fibrosis. Recent advances in epigenetics alterations in the pathogenesis of liver fibrosis and their possible use as new therapeutic targets and biomarkers
Topological Hall Effect Driven by Short-Range Magnetic Orders in EuZnAs
Short-range (SR) magnetic orders such as magnetic glass orders or
fluctuations in a quantum system usually host exotic states or critical
behaviors. As the long-range (LR) magnetic orders, SR magnetic orders can also
break time-reversal symmetry and drive the non-zero Berry curvature leading to
novel transport properties. In this work, we report that in EuZnAs
compound, besides the LR A-type antiferromagnetic (AF) order, the SR magnetic
order is observed in a wide temperature region. The magnetization measurements
and electron spin resonance (ESR) measurements reveal the ferromagnetic (FM)
correlations for this SR magnetic order which results in an obvious anomalous
Hall effect above the AF transition. Moreover the ESR results reveal that this
FM SR order coexists with LR AF order exhibiting anisotropic magnetic
correlations below the AF transition. The interactions of LR and SR magnetism
evolving with temperature and field can host non-zero spin charility and berry
curvature leading the additional topological Hall contribution even in a
centrosymmetric simple AF system. Our results indicate that EuZnAs is a
fertile platform to investigate exotic magnetic and electronic states.Comment: 6 pages, 4 figure
Curing hemophilia A by NHEJ-mediated ectopic F8 insertion in the mouse
BACKGROUND: Hemophilia A, a bleeding disorder resulting from F8 mutations, can only be cured by gene therapy. A promising strategy is CRISPR-Cas9-mediated precise insertion of F8 in hepatocytes at highly expressed gene loci, such as albumin (Alb). Unfortunately, the precise in vivo integration efficiency of a long insert is very low (~ 0.1%).
RESULTS: We report that the use of a double-cut donor leads to a 10- to 20-fold increase in liver editing efficiency, thereby completely reconstituting serum F8 activity in a mouse model of hemophilia A after hydrodynamic injection of Cas9-sgAlb and B domain-deleted (BDD) F8 donor plasmids. We find that the integration of a double-cut donor at the Alb locus in mouse liver is mainly through non-homologous end joining (NHEJ)-mediated knock-in. We then target BDDF8 to multiple sites on introns 11 and 13 and find that NHEJ-mediated insertion of BDDF8 restores hemostasis. Finally, using 3 AAV8 vectors to deliver genome editing components, including Cas9, sgRNA, and BDDF8 donor, we observe the same therapeutic effects. A follow-up of 100 mice over 1 year shows no adverse effects.
CONCLUSIONS: These findings lay the foundation for curing hemophilia A by NHEJ knock-in of BDDF8 at Alb introns after AAV-mediated delivery of editing components
MLPerf Inference Benchmark
Machine-learning (ML) hardware and software system demand is burgeoning.
Driven by ML applications, the number of different ML inference systems has
exploded. Over 100 organizations are building ML inference chips, and the
systems that incorporate existing models span at least three orders of
magnitude in power consumption and five orders of magnitude in performance;
they range from embedded devices to data-center solutions. Fueling the hardware
are a dozen or more software frameworks and libraries. The myriad combinations
of ML hardware and ML software make assessing ML-system performance in an
architecture-neutral, representative, and reproducible manner challenging.
There is a clear need for industry-wide standard ML benchmarking and evaluation
criteria. MLPerf Inference answers that call. In this paper, we present our
benchmarking method for evaluating ML inference systems. Driven by more than 30
organizations as well as more than 200 ML engineers and practitioners, MLPerf
prescribes a set of rules and best practices to ensure comparability across
systems with wildly differing architectures. The first call for submissions
garnered more than 600 reproducible inference-performance measurements from 14
organizations, representing over 30 systems that showcase a wide range of
capabilities. The submissions attest to the benchmark's flexibility and
adaptability.Comment: ISCA 202
Substantial transition to clean household energy mix in rural China
The household energy mix has significant impacts on human health and climate, as it contributes greatly to many health- and climate-relevant air pollutants. Compared to the well-established urban energy statistical system, the rural household energy statistical system is incomplete and is often associated with high biases. Via a nationwide investigation, this study revealed high contributions to energy supply from coal and biomass fuels in the rural household energy sector, while electricity comprised ∼20%. Stacking (the use of multiple sources of energy) is significant, and the average number of energy types was 2.8 per household. Compared to 2012, the consumption of biomass and coals in 2017 decreased by 45% and 12%, respectively, while the gas consumption amount increased by 204%. Increased gas and decreased coal consumptions were mainly in cooking, while decreased biomass was in both cooking (41%) and heating (59%). The time-sharing fraction of electricity and gases (E&G) for daily cooking grew, reaching 69% in 2017, but for space heating, traditional solid fuels were still dominant, with the national average shared fraction of E&G being only 20%. The non-uniform spatial distribution and the non-linear increase in the fraction of E&G indicated challenges to achieving universal access to modern cooking energy by 2030, particularly in less-developed rural and mountainous areas. In some non-typical heating zones, the increased share of E&G for heating was significant and largely driven by income growth, but in typical heating zones, the time-sharing fraction was <5% and was not significantly increased, except in areas with policy intervention. The intervention policy not only led to dramatic increases in the clean energy fraction for heating but also accelerated the clean cooking transition. Higher income, higher education, younger age, less energy/stove stacking and smaller family size positively impacted the clean energy transition
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