2,705 research outputs found
Analysis of binary spatial data by quasi-likelihood estimating equations
The goal of this paper is to describe the application of quasi-likelihood
estimating equations for spatially correlated binary data. In this paper, a
logistic function is used to model the marginal probability of binary responses
in terms of parameters of interest. With mild assumptions on the correlations,
the Leonov-Shiryaev formula combined with a comparison of characteristic
functions can be used to establish asymptotic normality for linear combinations
of the binary responses. The consistency and asymptotic normality for
quasi-likelihood estimates can then be derived. By modeling spatial correlation
with a variogram, we apply these asymptotic results to test independence of two
spatially correlated binary outcomes and illustrate the concepts with a
well-known example based on data from Lansing Woods. The comparison of
generalized estimating equations and the proposed approach is also discussed.Comment: Published at http://dx.doi.org/10.1214/009053605000000057 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Porous zirconia scaffold modified with mesoporous bioglass coating
Porous yttria-stabilized zirconia (YSZ) has been regarded as a potential candidate for bone substitute as its high mechanical strength. However, porous YSZ bodies are biologically inert to bone tissue. It is therefore necessary to introduce bioactive coatings onto the walls of the porous structures to enhance the bioactivity. In this study, the porous zirconia scaffolds were prepared by infiltration of Acrylonitrile Butadiene Styrene (ABS) scaffolds with 3 mol% yttria stabilized zirconia slurry. After sintering, a method of sol-gel dip coating was involved to make coating layer of mesoporous bioglass (MBGs). The porous zirconia without the coating had high porosities of 60.1% to 63.8%, and most macropores were interconnected with pore sizes of 0.5-0.8mm. The porous zirconia had compressive strengths of 9.07-9.90MPa. Moreover, the average coating thickness was about 7μm. There is no significant change of compressive strength for the porous zirconia with mesoporous biogalss coating. The bone marrow stromal cell (BMSC) proliferation test showed both uncoated and coated zirconia scaffolds have good biocompatibility. The scanning electron microscope (SEM) micrographs and the compositional analysis graphs demonstrated that after testing in the simulated body fluid (SBF) for 7 days, the apatite formation occurred on the coating surface. Thus, porous zirconia-based ceramics were modified with bioactive coating of mesoporous bioglass for potential biomedical applications
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
Functional genomic analysis and neuroanatomical localization of miR-2954, a song-responsive sex-linked microRNA in the zebra finch
Natural experience can cause complex changes in gene expression in brain centers for cognition and perception, but the mechanisms that link perceptual experience and neurogenomic regulation are not understood. MicroRNAs (miRNAs or miRs) have the potential to regulate large gene expression networks, and a previous study showed that a natural perceptual stimulus (hearing the sound of birdsong in zebra finches) triggers rapid changes in expression of several miRs in the auditory forebrain. Here we evaluate the functional potential of one of these, miR-2954, which has been found so far only in birds and is encoded on the Z sex chromosome. Using fluorescence in situ hybridization and immunohistochemistry, we show that miR-2954 is present in subsets of cells in the sexually dimorphic brain regions involved in song production and perception, with notable enrichment in cell nuclei. We then probe its regulatory function by inhibiting its expression in a zebra finch cell line (G266) and measuring effects on endogenous gene expression using Illumina RNA sequencing (RNA-seq). Approximately 1000 different mRNAs change in expression by 1.5-fold or more (adjusted p < 0.01), with increases in some but not all of the targets that had been predicted by Targetscan. The population of RNAs that increase after miR-2954 inhibition is notably enriched for ones involved in the MAP Kinase (MAPK) pathway, whereas the decreasing population is dominated by genes involved in ribosomes and mitochondrial function. Since song stimulation itself triggers a decrease in miR-2954 expression followed by a delayed decrease in genes encoding ribosomal and mitochondrial functions, we suggest that miR-2954 may mediate some of the neurogenomic effects of song habituation
High-resolution 3D shallow crustal structure in Long Beach, California: Application of ambient noise tomography on a dense seismic array
Ambient noise tomography has proven to be effective in resolving shallow earth structure. We applied ambient noise tomography on a dense seismic array in Long Beach, California. The array was composed of more than 5200 stations with an average spacing close to 100 m. Three weeks of passive ambient noise were crosscorrelated between each station pair, which resulted in more than 13.5 million crosscorrelations within the area. Clear fundamental-mode Rayleigh waves were observed between 0.5 and 4 Hz, which were most sensitive to structure above 1-km depth. For each station pair, we applied frequency-time analysis to determine the phase traveltime dispersion, and, for each frequency, we applied eikonal tomography to determine the Rayleigh wave phase velocity map. The eikonal tomography accounted for ray bending by tracking the wavefront and allowed uncertainties to be estimated through statistical analysis. The compilation of phase velocity maps was then used to invert for 3D shear velocity structure. The inverted model showed clear correlation with the known geologic features such as the shallow south–north velocity dichotomy and a deeper fast anomaly associated with the Newport-Inglewood fault zone. Our results can potentially be used to complement traditional active source studies
Getting Real: A Naturalistic Methodology for Using Smartphones to Collect Mediated Communications
This paper contributes an intentionally naturalistic methodology using smartphone logging technology to study communications
in the wild. Smartphone logging can provide tremendous access to communications data from real environments. However,
researchers must consider how it is employed to preserve naturalistic behaviors. Nine considerations are presented to this
end. We also provide a description of a naturalistic logging approach that has been applied successfully to collecting mediated
communications from iPhones. The methodology was designed to intentionally decrease reactivity and resulted in data that were
more accurate than self-reports. Example analyses are also provided to show how data collected can be analyzed to establish
empirical patterns and identify user differences. Smartphone logging technologies offer flexible capabilities to enhance access to
real communications data, but methodologies employing these techniques must be designed appropriately to avoid provoking
naturally occurring behaviors. Functionally, this methodology can be applied to establish empirical patterns and test specific
hypotheses within the field of HCI research. Topically, this methodology can be applied to domains interested in understanding
mediated communications such as mobile content and systems design, teamwork, and social networks
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