6,204 research outputs found
Adapting Visual Question Answering Models for Enhancing Multimodal Community Q&A Platforms
Question categorization and expert retrieval methods have been crucial for
information organization and accessibility in community question & answering
(CQA) platforms. Research in this area, however, has dealt with only the text
modality. With the increasing multimodal nature of web content, we focus on
extending these methods for CQA questions accompanied by images. Specifically,
we leverage the success of representation learning for text and images in the
visual question answering (VQA) domain, and adapt the underlying concept and
architecture for automated category classification and expert retrieval on
image-based questions posted on Yahoo! Chiebukuro, the Japanese counterpart of
Yahoo! Answers.
To the best of our knowledge, this is the first work to tackle the
multimodality challenge in CQA, and to adapt VQA models for tasks on a more
ecologically valid source of visual questions. Our analysis of the differences
between visual QA and community QA data drives our proposal of novel
augmentations of an attention method tailored for CQA, and use of auxiliary
tasks for learning better grounding features. Our final model markedly
outperforms the text-only and VQA model baselines for both tasks of
classification and expert retrieval on real-world multimodal CQA data.Comment: Submitted for review at CIKM 201
Lepton Acceleration in Pulsar Wind Nebulae
Pulsar Wind Nebulae (PWNe) act as calorimeters for the relativistic pair
winds emanating from within the pulsar light cylinder. Their radiative
dissipation in various wavebands is significantly different from that of their
pulsar central engines: the broadband spectra of PWNe possess characteristics
distinct from those of pulsars, thereby demanding a site of lepton acceleration
remote from the pulsar magnetosphere. A principal candidate for this locale is
the pulsar wind termination shock, a putatively highly-oblique,
ultra-relativistic MHD discontinuity. This paper summarizes key characteristics
of relativistic shock acceleration germane to PWNe, using predominantly Monte
Carlo simulation techniques that compare well with semi-analytic solutions of
the diffusion-convection equation. The array of potential spectral indices for
the pair distribution function is explored, defining how these depend
critically on the parameters of the turbulent plasma in the shock environs.
Injection efficiencies into the acceleration process are also addressed.
Informative constraints on the frequency of particle scattering and the level
of field turbulence are identified using the multiwavelength observations of
selected PWNe. These suggest that the termination shock can be comfortably
invoked as a principal injector of energetic leptons into PWNe without
resorting to unrealistic properties for the shock layer turbulence or MHD
structure.Comment: 19 pages, 5 figures, invited review to appear in Proc. of the
inaugural ICREA Workshop on "The High-Energy Emission from Pulsars and their
Systems" (2010), eds. N. Rea and D. Torres, (Springer Astrophysics and Space
Science series
Multivalued SK-contractions with respect to b-generalized pseudodistances
A new class of multivalued non-self-mappings, called SK-contractions with respect to
b-generalized pseudodistances, is introduced and used to investigate the existence of
best proximity points by using an appropriate geometric property. Some new fixed
point results in b-metric spaces are also obtained. Examples are given to support the
usability of our main result
Negative longitudinal magnetoresistance in GaAs quantum wells
Negative longitudinal magnetoresistances (NLMRs) have been recently observed
in a variety of topological materials and often considered to be associated
with Weyl fermions that have a defined chirality. Here we report NLMRs in
non-Weyl GaAs quantum wells. In the absence of a magnetic field the quantum
wells show a transition from semiconducting-like to metallic behaviour with
decreasing temperature. We observed pronounced NLMRs up to 9 Tesla at
temperatures above the transition and weak NLMRs in low magnetic fields at
temperatures close to the transition and below 5 K. The observed NLMRs show
various types of magnetic field behaviour resembling those reported in
topological materials. We attribute them to microscopic disorder and use a
phenomenological three-resistor model to account for their various features.
Our results showcase a new contribution of microscopic disorder in the
occurrence of novel phenomena. They may stimulate further work on tuning
electronic properties via disorder/defect nano-engineering
Optical Monitoring of BL Lacertae Object S5 0716+714 with a Novel Multi-Peak Interference Filter
We at first introduce a novel photometric system, which consists of a Schmidt
telescope, an objective prism, a CCD camera, and, especially, a multi-peak
interference filter. The multi-peak interference filter enables light in multi
passbands to pass through it simultaneously. The light in different passbands
is differentially refracted by the objective prism and is focused on the CCD
separately, so we have multi "images" for each object on the CCD frames. This
system enables us to monitor blazars exactly simultaneously in multi wavebands
on a single telescope, and to accurately trace the color change during the
variation. We used this novel system to monitor the BL Lacertae object S5
0716+714 during 2006 January and February and achieved a very high temporal
resolution. The object was very bright and very active during this period. Two
strong flares were observed, with variation amplitudes of about 0.8 and 0.6
mags in the band, respectively. Strong bluer-when-brighter correlations
were found for both internight and intranight variations. No apparent time lag
was observed between the - and -band variations, and the observed
bluer-when-brighter chromatism may be mainly attributed to the larger variation
amplitude at shorter wavelength. In addition to the bluer-when-brighter trend,
the object also showed a bluer color when it was more active. The observed
variability and its color behaviors are consistent with the shock-in-jet model.Comment: 30 pages, 22 figures, accepted by A
Cross-optical-beam nonlinear photoacoustic microscopy
We present a photoacoustic microscopy (PAM) technique with an optical sectioning capability. By combining crossoptical- beam illumination with nonlinear PAM, an axial resolution of 8.7 μm was measured, demonstrating a fourfold improvement over the acoustically determined value. Compared to methods relying on high-frequency ultrasound transducers to improve the axial resolution, our approach offers a greater working distance and a higher signal-to-noise ratio
Accelerating Bayesian hierarchical clustering of time series data with a randomised algorithm
We live in an era of abundant data. This has necessitated the development of new and innovative statistical algorithms to get the most from experimental data. For example, faster algorithms make practical the analysis of larger genomic data sets, allowing us to extend the utility of cutting-edge statistical methods. We present a randomised algorithm that accelerates the clustering of time series data using the Bayesian Hierarchical Clustering (BHC) statistical method. BHC is a general method for clustering any discretely sampled time series data. In this paper we focus on a particular application to microarray gene expression data. We define and analyse the randomised algorithm, before presenting results on both synthetic and real biological data sets. We show that the randomised algorithm leads to substantial gains in speed with minimal loss in clustering quality. The randomised time series BHC algorithm is available as part of the R package BHC, which is available for download from Bioconductor (version 2.10 and above) via http://bioconductor.org/packages/2.10/bioc/html/BHC.html. We have also made available a set of R scripts which can be used to reproduce the analyses carried out in this paper. These are available from the following URL. https://sites.google.com/site/randomisedbhc/
Ultrasonic transducer-guided electrochemical impedance spectroscopy to assess lipid-laden plaques
Plaque rupture causes acute coronary syndromes and stroke. Intraplaque oxidized low density lipoprotein (oxLDL) is metabolically unstable and prone to induce rupture. We designed an intravascular ultrasound (IVUS)-guided electrochemical impedance spectroscopy (EIS) sensor to enhance the detection reproducibility of oxLDL-laden plaques. The flexible 2-point micro-electrode array for EIS was affixed to an inflatable balloon anchored onto a co-axial double layer catheter (outer diameter = 2 mm). The mechanically scanning-driven IVUS transducer (45 MHz) was deployed through the inner catheter (diameter = 1.3 mm) to the acoustic impedance matched-imaging window. Water filled the inner catheter to match acoustic impedance and air was pumped between the inner and outer catheters to inflate the balloon. The integrated EIS and IVUS sensor was deployed into the ex vivo aortas dissected from the fat-fed New Zealand White (NZW) rabbits (n = 3 for fat-fed, n = 5 normal diet). IVUS imaging was able to guide the 2-point electrode to align with the plaque for EIS measurement upon balloon inflation. IVUS-guided EIS signal demonstrated reduced variability and increased reproducibility (p < 0.0001 for magnitude, p < 0.05 for phase at <15 kHz) as compared to EIS sensor alone (p < 0.07 for impedance, p < 0.4 for phase at <15 kHz). Thus, we enhanced topographic and EIS detection of oxLDL-laden plaques via a catheter-based integrated sensor design to enhance clinical assessment for unstable plaque
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