12,037 research outputs found
On the Compression of Translation Operator Tensors in FMM-FFT-Accelerated SIE Simulators via Tensor Decompositions
Tensor decomposition methodologies are proposed to reduce the memory
requirement of translation operator tensors arising in the fast multipole
method-fast Fourier transform (FMM-FFT)-accelerated surface integral equation
(SIE) simulators. These methodologies leverage Tucker, hierarchical Tucker
(H-Tucker), and tensor train (TT) decompositions to compress the FFT'ed
translation operator tensors stored in three-dimensional (3D) and
four-dimensional (4D) array formats. Extensive numerical tests are performed to
demonstrate the memory saving achieved by and computational overhead introduced
by these methodologies for different simulation parameters. Numerical results
show that the H-Tucker-based methodology for 4D array format yields the maximum
memory saving while Tucker-based methodology for 3D array format introduces the
minimum computational overhead. For many practical scenarios, all methodologies
yield a significant reduction in the memory requirement of translation operator
tensors while imposing negligible/acceptable computational overhead
Twentieth-century Trends in the Annual Cycle of Temperature across the Northern Hemisphere
The annual cycle of surface air temperature is examined across Northern Hemisphere land areas (north of 25°N) by comparing the results from CRUTS against four reanalysis datasets: two versions of the Twentieth Century Reanalysis (20CR and 20CRC) and two versions of the ERA-CLIM reanalyses (ERA-20C and ERA-20CM). The Modulated Annual Cycle is adaptively derived from an Ensemble Empirical Mode Decomposition (EEMD) filter, and is used to define the phase and amplitude of the annual cycle. The EEMD method does not impose a simple sinusoidal shape of the annual cycle. None of the reanalysis simulations assimilate surface temperature data, but differ in the parameters that are included: both ERA-20C and 20CR assimilate surface pressure data; ERA-20C also includes surface wind data over the oceans; ERA-20CM does not assimilate any of these synoptic data; and none of the reanalyses assimilate land-use data. It is demonstrated that synoptic variability is critical for explaining the trends and variability of the annual cycle of surface temperature across the northern hemisphere. The CMIP5 forcings alone are insufficient to explain the observed trends and decadal-scale variability, particularly with respect to the decline in the amplitude of the annual cycle throughout the twentieth century. The variability in the annual cycle during the latter half of the twentieth century was unusual in the context of the twentieth century, and was most likely related to large-scale atmospheric variability, although uncertainty in the results is greatest before ca. 1930
An Army of Me: Sockpuppets in Online Discussion Communities
In online discussion communities, users can interact and share information
and opinions on a wide variety of topics. However, some users may create
multiple identities, or sockpuppets, and engage in undesired behavior by
deceiving others or manipulating discussions. In this work, we study
sockpuppetry across nine discussion communities, and show that sockpuppets
differ from ordinary users in terms of their posting behavior, linguistic
traits, as well as social network structure. Sockpuppets tend to start fewer
discussions, write shorter posts, use more personal pronouns such as "I", and
have more clustered ego-networks. Further, pairs of sockpuppets controlled by
the same individual are more likely to interact on the same discussion at the
same time than pairs of ordinary users. Our analysis suggests a taxonomy of
deceptive behavior in discussion communities. Pairs of sockpuppets can vary in
their deceptiveness, i.e., whether they pretend to be different users, or their
supportiveness, i.e., if they support arguments of other sockpuppets controlled
by the same user. We apply these findings to a series of prediction tasks,
notably, to identify whether a pair of accounts belongs to the same underlying
user or not. Altogether, this work presents a data-driven view of deception in
online discussion communities and paves the way towards the automatic detection
of sockpuppets.Comment: 26th International World Wide Web conference 2017 (WWW 2017
New methodologies to characterize the effectiveness of the gene transfer mediated by DNA-chitosan nanoparticles
In this work three DNA-chitosan nanoparticle formulations (Np), differing in the
molecular weight (MW; 150 kDa, 400 kDa, and 600 kDa) of the polysaccharide, were prepared
and administered by two different administration routes: the hydrodynamics-based procedure
and the intraduodenal injection. After the hydrodynamic injection, DNA-chitosan nanoparticles
were predominantly accumulated in the liver, where the transgene was expressed during at least
105 days. No signifi cant infl uence of MW was observed on the levels of luciferase expression.
The curves of bioluminescence versus time obtained using the charge-coupled device (CCD)
camera were described and divided in three phases: (i) the initial phase, (ii) the sustained
release step and (iii) the decline phase (promotor inactivation, immunological and physiological
processes). From these curves, which describe the transgene expression profi le, the behavior of
the different formulations as gene delivery systems was characterized. Therefore, the following
parameters such as Cmax (maximum level of detected bioluminescence), AUC (area under the
bioluminescence-time curve) and MET (mean time of the transgene expression) were calculated.
This approach offers the possibility of studying and comparing transgene expression kinetics
among a wide variety of gene delivery systems. Finally, the intraduodenal administration of
naked DNA permitted the gene transfer in a dose dependent manner quantifi able with the CCD
camera within 3 days. Nevertheless, the same administration procedure of the three formulations
did not improve the levels of transgene expression obtained with naked DNA. This fact could
be explained by the rapid physiological turn-over of enterocytes and by the ability of chitosan
nanoparticles to control the DNA release
Restudy on Dark Matter Time-Evolution in the Littlest Higgs model with T-parity
Following previous study, in the Littlest Higgs model (LHM), the heavy photon
is supposed to be a possible dark matter candidate and its relic abundance of
the heavy photon is estimated in terms of the Boltzman-Lee-Weinberg
time-evolution equation. The effects of the T-parity violation is also
considered. Our calculations show that when Higgs mass taken to be 300
GeV and don't consider T-parity violation, only two narrow ranges
GeV and GeV are tolerable with the
current astrophysical observation and if GeV, there must at
least exist another species of heavy particle contributing to the cold dark
matter. As long as the T-parity can be violated, the heavy photon can decay
into regular standard model particles and would affect the dark matter
abundance in the universe, we discuss the constraint on the T-parity violation
parameter based on the present data. Direct detection prospects are also
discussed in some detail.Comment: 13 pages, 11 figures include
Antitumor effect of allogenic fibroblasts engineered to express Fas ligand (FasL)
Fas ligand is a type II transmembrane protein which can induce apoptosis in Fas-expressing cells. Recent reports indicate that expression of FasL in transplanted cells may cause graft rejection and, on the other hand, tumor cells may lose their tumorigenicity when they are engineered to express FasL. These effects could be related to recruitment of neutrophils by FasL with activation of their cytotoxic machinery. In this study we investigated the antitumor effect of allogenic fibroblasts engineered to express FasL. Fibroblasts engineered to express FasL (PA317/FasL) did not exert toxic effects on transformed liver cell line (BNL) or colon cancer cell line (CT26) in vitro, but they could abrogate their tumorigenicity in vivo. Histological examination of the site of implantation of BNL cells mixed with PA317/FasL revealed massive infiltration of polymorphonuclear neutrophils and mononuclear cells. A specific immune protective effect was observed in animals primed with a mixture of BNL or CT26 and PA317/FasL cells. Rechallenge with tumor cells 14 or 100 days after priming resulted in protection of 100 or 50% of animals, respectively. This protective effect was due to CD8+ cells since depletion of CD8+ led to tumor formation. In addition, treatment of pre-established BNL tumors with a subcutaneous injection of BNL and PA317/FasL cell mixture at a distant site caused significant inhibition of tumor growth. These data demonstrate that allogenic cells engineered with FasL are able to abolish tumor growth and induce specific protective immunity when they are mixed with neoplastic cells
SWIFT: Scalable Wasserstein Factorization for Sparse Nonnegative Tensors
Existing tensor factorization methods assume that the input tensor follows
some specific distribution (i.e. Poisson, Bernoulli, and Gaussian), and solve
the factorization by minimizing some empirical loss functions defined based on
the corresponding distribution. However, it suffers from several drawbacks: 1)
In reality, the underlying distributions are complicated and unknown, making it
infeasible to be approximated by a simple distribution. 2) The correlation
across dimensions of the input tensor is not well utilized, leading to
sub-optimal performance. Although heuristics were proposed to incorporate such
correlation as side information under Gaussian distribution, they can not
easily be generalized to other distributions. Thus, a more principled way of
utilizing the correlation in tensor factorization models is still an open
challenge. Without assuming any explicit distribution, we formulate the tensor
factorization as an optimal transport problem with Wasserstein distance, which
can handle non-negative inputs.
We introduce SWIFT, which minimizes the Wasserstein distance that measures
the distance between the input tensor and that of the reconstruction. In
particular, we define the N-th order tensor Wasserstein loss for the widely
used tensor CP factorization and derive the optimization algorithm that
minimizes it. By leveraging sparsity structure and different equivalent
formulations for optimizing computational efficiency, SWIFT is as scalable as
other well-known CP algorithms. Using the factor matrices as features, SWIFT
achieves up to 9.65% and 11.31% relative improvement over baselines for
downstream prediction tasks. Under the noisy conditions, SWIFT achieves up to
15% and 17% relative improvements over the best competitors for the prediction
tasks.Comment: Accepted by AAAI-2
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