3,161 research outputs found
Molecular Phylogeny of Chinese Thuidiaceae with emphasis on Thuidium and Pelekium
We present molecular phylogenetic investigation of Thuidiaceae, especially on
Thudium and Pelekium. Three chloroplast sequences (trnL-F, rps4, and atpB-rbcL)
and one nuclear sequence (ITS) were analyzed. Data partitions were analyzed
separately and in combination by employing MP (maximum parsimony) and Bayesian
methods. The influence of data conflict in combined analyses was further
explored by two methods: the incongruence length difference (ILD) test and the
partition addition bootstrap alteration approach (PABA). Based on the results,
ITS 1& 2 had crucial effect in phylogenetic reconstruction in this study, and
more chloroplast sequences should be combinated into the analyses since their
stability for reconstructing within genus of pleurocarpous mosses. We supported
that Helodiaceae including Actinothuidium, Bryochenea, and Helodium still
attributed to Thuidiaceae, and the monophyletic Thuidiaceae s. lat. should also
include several genera (or species) from Leskeaceae such as Haplocladium and
Leskea. In the Thuidiaceae, Thuidium and Pelekium were resolved as two
monophyletic groups separately. The results from molecular phylogeny were
supported by the crucial morphological characters in Thuidiaceae s. lat.,
Thuidium and Pelekium.Comment: 20 pages, 4 tables, 3 figure
Charge Transfer and Functionalization of Monolayer InSe by Physisorption of Small Molecules for Gas Sensing
First-principles calculations are performed to investigate the effects of the
adsorption of gas molecules (CO, NO, NO2, H2S, N2, H2O, O2, NH3 and H2) on the
electronic properties of atomically thin indium selenium (InSe). Our study
shows that the lone-pair states of Se are located at the top of the valence
band of InSe and close to the Fermi energy level, implying its high sensitivity
to external adsorbates. Among these gas molecules, H2 and H2S are strong
donors, NO, NO2, H2O and NH3 are effective acceptors, while CO and N2 exhibit
negligible charge transfer. The O2 molecule has very limited oxidizing ability
and a relatively weak interaction with InSe which is comparable to the N2
adsorption. A clear band gap narrowing is found for the H2S, NO2, and NH3
adsorbed systems whereas a Fermi level shifting to the conduction band is
observed upon a moderate uptake of H2 molecules. Our analysis suggests several
interesting applications of InSe: 1) Due to the different interaction behaviors
with these external molecules, InSe can be used for gas sensing applications;
2) By monitoring the adsorption/desorption behavior of these gas molecules, the
population of hole states in InSe due to photon stimulation or defect
production can be quantitatively estimated; and 3) It is promising for novel
electronic and optoelectronic applications since the adsorption-induced in-gap
states and strong charge transfer are able to change the content and polarity
of charged carriers and lead to different optical properties
Polarity Reversed Robust Carrier Mobility in Monolayer MoS2 Nanoribbons
Using first-principles calculations and deformation potential theory, we
investigate the intrinsic carrier mobility ({\mu}) of monolayer MoS2 sheet and
nanoribbons. In contrast to the dramatic three orders of magnitude of
deterioration of {\mu} in graphene upon forming nanoribbons, the magnitude of
{\mu} in armchair MoS2 nanoribbons is comparable to that in monolayer MoS2
sheet, albeit oscillating with width. Surprisingly, a room-temperature
transport polarity reversal is observed with {\mu} of hole (h) and electron (e)
being 200.52 (h) and 72.16 (e) cm2V-1s-1 in sheet, and 49.72 (h) and 190.89 (e)
cm2V-1s-1 in 4 nm-wide nanoribbon. The robust magnitudes of {\mu} and polarity
reversal are attributable to the different characteristics of edge states
inherent in MoS2 nanoribbons. Our study suggests that width-reduction together
with edge engineering provide a promising route for improving the transport
properties of MoS2 nanostructures
Optical Transient Object Classification in Wide Field Small Aperture Telescopes with Neural Networks
Wide field small aperture telescopes are working horses for fast sky
surveying. Transient discovery is one of their main tasks. Classification of
candidate transient images between real sources and artifacts with high
accuracy is an important step for transient discovery. In this paper, we
propose two transient classification methods based on neural networks. The
first method uses the convolutional neural network without pooling layers to
classify transient images with low sampling rate. The second method assumes
transient images as one dimensional signals and is based on recurrent neural
networks with long short term memory and leaky ReLu activation function in each
detection layer. Testing with real observation data, we find that although
these two methods can both achieve more than 94% classification accuracy, they
have different classification properties for different targets. Based on this
result, we propose to use the ensemble learning method to further increase the
classification accuracy to more than 97%.Comment: 13 pages, 10 figures. Accepted by AJ and all the code can be
downloaded from aojp.lamost.org. Comments welcom
Predicting the Popularity of Online Videos via Deep Neural Networks
Predicting the popularity of online videos is important for video streaming
content providers. This is a challenging problem because of the following two
reasons. First, the problem is both "wide" and "deep". That is, it not only
depends on a wide range of features, but also be highly non-linear and complex.
Second, multiple competitors may be involved. In this paper, we propose a
general prediction model using the multi-task learning (MTL) module and the
relation network (RN) module, where MTL can reduce over-fitting and RN can
model the relations of multiple competitors. Experimental results show that our
proposed approach significantly increases the accuracy on predicting the total
view counts of TV series with RN and MTL modules
Comment on "Quantum Key Distribution with Classical Bob"
In this comment, we present a frequency-shift attack on "quantum key
distribution with classical Bob". This practical attack should also be
considered in other two-way quantum key distribution protocols.Comment: In this comment, we present a frequency-shift attack on "quantum key
distribution with classical Bob". This practical attack should also be
considered in other two-way quantum key distribution protocol
Quantum thermal transport in stanene
By way of the non-equilibrium Green's function simulations and analytical
expressions, the quantum thermal conductance of stanene is studied. We find
that, due to the existence of Dirac fermion in stanene, the ratio of electron
thermal conductance and electric conductance becomes a
chemical-potential-dependent quantity, violating the Wiedemann-Franz law. This
finding is applicable to any two-dimensional (2D) materials that possess
massless Dirac fermions. In strong contrast to the negligible electronic
contribution in graphene, surprisingly, the electrons and phonons in stanene
carry a comparable heat current. The unusual behaviours in stanene widen our
knowledge of quantum thermal transport in 2D materials
Model Slicing for Supporting Complex Analytics with Elastic Inference Cost and Resource Constraints
Deep learning models have been used to support analytics beyond simple
aggregation, where deeper and wider models have been shown to yield great
results. These models consume a huge amount of memory and computational
operations. However, most of the large-scale industrial applications are often
computational budget constrained. In practice, the peak workload of inference
service could be 10x higher than the average cases, with the presence of
unpredictable extreme cases. Lots of computational resources could be wasted
during off-peak hours and the system may crash when the workload exceeds system
capacity. How to support deep learning services with dynamic workload
cost-efficiently remains a challenging problem. In this paper, we address the
challenge with a general and novel training scheme called model slicing, which
enables deep learning models to provide predictions within the prescribed
computational resource budget dynamically. Model slicing could be viewed as an
elastic computation solution without requiring more computational resources.
Succinctly, each layer in the model is divided into groups of contiguous block
of basic components (i.e. neurons in dense layers and channels in convolutional
layers), and then partially ordered relation is introduced to these groups by
enforcing that groups participated in each forward pass always starts from the
first group to the dynamically-determined rightmost group. Trained by
dynamically indexing the rightmost group with a single parameter slice rate,
the network is engendered to build up group-wise and residual representation.
Then during inference, a sub-model with fewer groups can be readily deployed
for efficiency whose computation is roughly quadratic to the width controlled
by the slice rate. Extensive experiments show that models trained with model
slicing can effectively support on-demand workload with elastic inference cost.Comment: 14 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1706.02093 by other author
Scale-dependent CMB power asymmetry from primordial speed of sound and a generalized N formalism
We explore a plausible mechanism that the hemispherical power asymmetry in
the CMB is produced by the spatial variation of the primordial sound speed
parameter. We suggest that in a generalized approach of the
formalism the local e-folding number may depend on some other primordial
parameters besides the initial values of inflaton. Here the
formalism is extended by considering the effects of a spatially varying sound
speed parameter caused by a super-Hubble perturbation of a light field. Using
this generalized formalism, we systematically calculate the
asymmetric primordial spectrum in the model of multi-speed inflation by taking
into account the constraints of primordial non-Gaussianities. We further
discuss specific model constraints, and the corresponding asymmetry amplitudes
are found to be scale-dependent, which can accommodate current observations of
the power asymmetry at different length scales.Comment: 14 pages, 2 figures, several references added, version published in
JCA
Direction dependent thermal conductivity of monolayer phosphorene: parameterization of Stillinger-Weber potential and molecular dynamics study
A Stillinger-Weber interatomic potential is parameterized for phosphorene. It
well reproduces the crystal structure, cohesive energy and phonon dispersion
predicted by first-principles calculations. The thermal conductivity of
phosphorene is further explored by equilibrium molecular dynamics simulations
adopting the optimal set of potential parameters. At room temperature, the
intrinsic thermal conductivities along zigzag and armchair directions are about
152.7 and 33.0 W/mK, respectively, with a large anisotropy ratio of five. The
remarkably directional dependence of thermal conductivity in phosphorene,
consistent with previous reports, is mainly due to the strong anisotropy of
phonon group velocities, and weak anisotropy of phonon lifetimes as revealed by
lattice dynamics calculations. Moreover, the effective phonon mean free paths
at zigzag and armchair directions are about 141.4 and 43.4nm, respectively.Comment: accepted by J. Appl. Phy
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