1,876 research outputs found
Promoting cold-start items in recommender systems
As one of major challenges, cold-start problem plagues nearly all recommender
systems. In particular, new items will be overlooked, impeding the development
of new products online. Given limited resources, how to utilize the knowledge
of recommender systems and design efficient marketing strategy for new items is
extremely important. In this paper, we convert this ticklish issue into a clear
mathematical problem based on a bipartite network representation. Under the
most widely used algorithm in real e-commerce recommender systems, so-called
the item-based collaborative filtering, we show that to simply push new items
to active users is not a good strategy. To our surprise, experiments on real
recommender systems indicate that to connect new items with some less active
users will statistically yield better performance, namely these new items will
have more chance to appear in other users' recommendation lists. Further
analysis suggests that the disassortative nature of recommender systems
contributes to such observation. In a word, getting in-depth understanding on
recommender systems could pave the way for the owners to popularize their
cold-start products with low costs.Comment: 6 pages, 6 figure
Depositional model for mixed carbonate-clastic sediments in the Middle Cambrian Lower Zhangxia Formation, Xiaweidian, North China
In order to make accurate decisions in interpreting depositional environments of sedimentary rocks, a multi-proxy approach is best employed. In the Middle Cambrian Lower Zhangxia Formation exposed at Xiaweidian in the Northern China, lack of this form of approach puts doubts on the various models (e.g. carbonate ramp and isolated platform) proposed by previous workers. In this study, we integrated field outcrop investigation with laboratory examinations of thin sections with light and electron microscopies to further understand sedimentary environments of the Lower Zhangxia Formation. Dominant rock types of this formation include oolitic limestone, muddy limestone, flat-pebble limestone and calcareous mudstone. Evidence from ooid features and lime-mud content of oolitic limestones suggests their deposition in an environment with intermittent high energy level. The muddy limestones were formed on a restricted platform with lower wave energy, which is supported by the existence of pyrites in a reducing environment and the input of terrestrial clays from neighboring clastic environments. The flat-pebble limestones were formed by storm reworking of early deposits on restricted platform below a fair-weather wave base, due to their composition and clast features. Mudstones with occurrences of terrestrial silts could be associated with clastic shallow marine adjacent to the restricted platform. A mixed carbonate-clastic depositional model is suggested for this formation and can be used as model for other researchers working in the North China.Cited as: Zhang, X., Pang, X., Jin, Z., Hu, T., Toyin, A., Wang, K. Depositional model for mixed carbonate-clastic sediments in the Middle Cambrian Lower Zhangxia Formation, Xiaweidian, North China. Advances in Geo-Energy Research, 2020, 4(1): 29-42, doi: 10.26804/ager.2020.01.0
Empirical study on clique-degree distribution of networks
The community structure and motif-modular-network hierarchy are of great
importance for understanding the relationship between structures and functions.
In this paper, we investigate the distribution of clique-degree, which is an
extension of degree and can be used to measure the density of cliques in
networks. The empirical studies indicate the extensive existence of power-law
clique-degree distributions in various real networks, and the power-law
exponent decreases with the increasing of clique size.Comment: 9 figures, 4 page
Rapid detection of sacbrood virus (SBV) by one-step reverse transcription loop-mediated isothermal amplification assay
<p>Abstract</p> <p>Background</p> <p><it>Sacbrood virus </it>(SBV) primarily infects honeybee broods, and in order to deal with the problem cost effective detection methods are required.</p> <p>Findings</p> <p>A one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for the rapid identification of SBV. The data demonstrated that, in a simple water bath, SBV RNA could be detected as early as 20 min at 65°C, and a positive amplification reaction was visible to the naked eye due to a color change brought on by the addition of nucleic acid stain SYBR Green.</p> <p>Conclusions</p> <p>The current study presents a method for the rapid and simple detection of SBV by RT-LAMP with high sensitivity and analytic specificity.</p
Vortex Dynamics in Rotating Rayleigh-B\'enard Convection
We investigate the spatial distribution and dynamics of the vortices in
rotating Rayleigh-B\'enard convection in a reduced Rayleigh-number range
. Under slow rotations (), the
vortices are randomly distributed. The size-distribution of the Voronoi cells
of the vortex centers is well described by the standard distribution.
In this flow regime the vortices exhibit Brownian-type horizontal motion. The
probability density functions of the vortex displacements are, however,
non-Gaussian at short time scales. At modest rotating rates
() the centrifugal force leads to radial
vortex motions, i.e., warm cyclones (cold anticyclones) moving towards (outward
from) the rotation axis. The mean-square-displacements of the vortices increase
faster than linearly at large time. This super-diffusive behavior can be
satisfactorily explained by a Langevin model incorporating the centrifugal
force. In the rapidly rotating regime () the
vortices are densely distributed, with the size-distribution of their Voronoi
cells differing significantly from the standard distribution. The
hydrodynamic interaction of neighboring vortices results in formation of vortex
clusters. Inside clusters the correlation of the vortex velocity fluctuations
is scale free, with the correlation length being approximately of the
cluster length. We examine the influence of cluster forming on the dynamics of
individual vortex. Within clusters, cyclones exhibit inverse-centrifugal motion
as they submit to the motion of strong anticyclones, while the velocity for
outward motion of the anticyclones is increased. Our analysis show that the
mobility of isolated vortices, scaled by their vorticity strength, is a simple
power function of the Froude number
Molecular Docking of Potential Inhibitors for Influenza H7N9
As a new strain of virus emerged in 2013, avian influenza A (H7N9) virus is a threat to the public health, due to its high lethality and pathogenicity. Furthermore, H7N9 has already generated various mutations such as neuraminidase R294K mutation which could make the anti-influenza oseltamivir less effective or ineffective. In this regard, it is urgent to develop new effective anti-H7N9 drug. In this study, we used the general H7N9 neuraminidase and oseltamivir-resistant influenza virus neuraminidase as the acceptors and employed the small molecules including quercetin, chlorogenic acid, baicalein, and oleanolic acid as the donors to perform the molecular docking for exploring the binding abilities between these small molecules and neuraminidase. The results showed that quercetin, chlorogenic acid, oleanolic acid, and baicalein present oseltamivir-comparable high binding potentials with neuraminidase. Further analyses showed that R294K mutation in neuraminidase could remarkably decrease the binding energies for oseltamivir, while other small molecules showed stable binding abilities with mutated neuraminidase. Taken together, the molecular docking studies identified four potential inhibitors for neuraminidase of H7N9, which might be effective for the drug-resistant mutants
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