22,508 research outputs found
Feature and Region Selection for Visual Learning
Visual learning problems such as object classification and action recognition
are typically approached using extensions of the popular bag-of-words (BoW)
model. Despite its great success, it is unclear what visual features the BoW
model is learning: Which regions in the image or video are used to discriminate
among classes? Which are the most discriminative visual words? Answering these
questions is fundamental for understanding existing BoW models and inspiring
better models for visual recognition.
To answer these questions, this paper presents a method for feature selection
and region selection in the visual BoW model. This allows for an intermediate
visualization of the features and regions that are important for visual
learning. The main idea is to assign latent weights to the features or regions,
and jointly optimize these latent variables with the parameters of a classifier
(e.g., support vector machine). There are four main benefits of our approach:
(1) Our approach accommodates non-linear additive kernels such as the popular
and intersection kernel; (2) our approach is able to handle both
regions in images and spatio-temporal regions in videos in a unified way; (3)
the feature selection problem is convex, and both problems can be solved using
a scalable reduced gradient method; (4) we point out strong connections with
multiple kernel learning and multiple instance learning approaches.
Experimental results in the PASCAL VOC 2007, MSR Action Dataset II and YouTube
illustrate the benefits of our approach
The spontaneous emergence of ordered phases in crumpled sheets
X-ray tomography is performed to acquire 3D images of crumpled aluminum
foils. We develop an algorithm to trace out the labyrinthian paths in the three
perpendicular cross sections of the data matrices. The tangent-tangent
correlation function along each path is found to decay exponentially with an
effective persistence length that shortens as the crumpled ball becomes more
compact. In the mean time, we observed ordered domains near the crust, similar
to the lamellae phase mixed by the amorphous portion in lyotropic liquid
crystals. The size and density of these domains grow with further compaction,
and their orientation favors either perpendicular or parallel to the radial
direction. Ordering is also identified near the core with an arbitrary
orientation, exemplary of the spontaneous symmetry breaking
Line tension and structure of smectic liquid crystal multilayers at the air-water interface
At the air/water interface, 4,-8-alkyl[1,1,-biphenyl]-4-carbonitrile (8CB)
domains with different thicknesses coexist in the same Langmuir film, as
multiple bilayers on a monolayer. The edge dislocation at the domain boundary
leads to line tension, which determines the domain shape and dynamics. By
observing the domain relaxation process starting from small distortions, we
find that the line tension is linearly dependent on the thickness difference
between the coexisting phases in the film. Comparisons with theoretical
treatments in the literature suggest that the edge dislocation at the boundary
locates near the center of the film, which means that the 8CB multilayers are
almost symmetric with respect to the air/water interface.Comment: 21 pages, 6 figure
The vitellogenesis-inhibiting hormone (SpVIH) of the crab Scylla paramamosain is not likely to have a vitellogenesis-inhibiting function in the ovary
The function and molecular characterization of the previously reported crab (Scylla paramamosain) vitellogenesis inhibiting hormone SpVIH is still unclear. In this experiment, SpVIH’s bioinformatic and functional characterizations were analyzed. Sequence analysis showed SpVIH was clustered with several type II MIH/GIHs of the Brachyura. The expression of SpVIH in the eyestalk was low in the early ovarian developmental stage I and increased with the advancement of ovary maturation. Interestingly, the SpVIH transcript was still at a high level in the ovary of females at the middle to late maturation stage. SpVIH’s function was studied according to the expression of vitellogenin (Vg) and vitellogenin receptor (VgR) in the ovary and hepatopancreas after incubation with SpVIH-dsRNA and recombinant SpVIH protein (rSpVIH). In vitro assay results indicated that rSpVIH has a significant stimulative effect on the expression of Vg in the hepatopancreas in the middle stage of vitellogenesis and in the ovary of each vitellogenesis stage. However, SpVIH-dsRNA has no significant effect on the expression of Vg when SpVIH-dsRNA is introduced to the ovary and hepatopancreas at the early, middle, and late stages of vitellogenesis. Furthermore, the co-incubation experiment result indicated that the eyestalk consists of factor(s) that can significantly up-regulate the expression of Vg in the ovary, with a further combination of dsVIH and eyestalk under incubation, the significant increase of Vg-mRNA expression levels were also found in the ovary of four ovarian development stages of S. paramamosain. Contrary to the previous reports, SpVIH does not possess a vitellogenesis-inhibiting function but can promote vitellogenesis in the ovary and hepatopancreas
Discovery of Balmer Broad Absorption Lines in the Quasar LBQS 1206+1052
We report the discovery of Balmer broad absorption lines (BALs) in the quasar
LBQS 1206+1052 and present a detailed analysis of the peculiar absorption line
spectrum. Besides Mg II doublet, BALs are also
detected in He I* multiplet at \AA arising
from metastable helium level, and in H and H from excited
hydrogen H I* level, which are rarely seen in quasar spectra. We identify
two components in the BAL troughs of 2000 km s width: One
component shows an identical profile in H I*, \hei* and \mgii with its centroid
blueshifted by km\ s. The other component is
detected in \hei* and \mgii with km s. We
estimate the column densities of H I*, He I*, and Mg II, and compare them with
possible level population mechanisms. Our results favor the scenario that the
Balmer BALs originate in a partially ionized region with a column density of
cm for an electron density of cm via Ly resonant scattering pumping. The harsh
conditions needed may help to explain the rarity of Balmer absorption line
systems in quasar spectra. With an -band PSF magnitude of 16.50, LBQS
1206+1052 is the brightest Balmer-BAL quasar ever reported. Its high brightness
and unique spectral properties make LBQS 1206+1052 a promising candidate for
follow-up high-resolution spectroscopy, multi-band observations, and long-term
monitoring.Comment: 16 pages,4 figure
Accurate Group Delay Measurement for Radial Velocity Instruments Using the Dispersed Fixed Delay Interferometer Method
The dispersed fixed-delay Intereferometer (DFDI) method is attractive for its
low cost, compact size, and multiobject capability in precision radial-velocity
(RV) measurements. The phase shift of fringes of stellar absorption lines is
measured and then converted to an RV shift via an important parameter,
phase-to-velocity scale (PV scale), determined by the group delay (GD) of a
fixed-delay interferometer. Two methods of GD measurement using a DFDI Doppler
instrument are presented in this article: (1) GD measurement using white-light
combs gen- erated by the fixed-delay interferometer and (2) GD calibration
using an RV reference star. These two methods provide adequate precision of GD
measurement and calibration, given the current RV precision achieved by a DFDI
Doppler instrument. They can potentially be used to measure GD of an
fixed-delay interferometer for submeter- precision Doppler measurement with a
DFDI instrument. Advantages and limitations of each method are discussed in
detail. The two methods can serve as standard procedures of PV-scale
calibration for DFDI instruments and cross- checks for each other.Comment: 19 pages, 7 figures, 3 tables, accepted by PAS
Effects of Fertilization on Porewater Nutrients, Greenhouse-gas Emissions and Rice Productivity in a Subtropical Paddy Field
Suitable fertilization is crucial for the sustainability of rice production and for the potential mitigation of global warming. The effects of fertilization on porewater nutrients and greenhouse-gas fluxes in cropland, however, remain poorly known. We studied the effects of no fertilization (control), standard fertilization and double fertilization on the concentrations of porewater nutrients, greenhouse-gas fluxes and emissions, and rice yield in a subtropical paddy in southeastern China. Double fertilization increased dissolved NH4+ in porewater. Mean CO2 and CH4 emissions were 13.5% and 7.4%, and 20.4% and 39.5% higher for the standard and double fertilizations, respectively, than the control. N2O depositions in soils were 61% and 101% higher for the standard and double fertilizations, respectively, than the control. The total global warming potentials (GWPs) for all emissions were 14.1% and 10.8% higher for the standard and double fertilizations, respectively than the control, with increasing contribution of CH4 with fertilization and a CO2 contribution > 85%. The total GWPs per unit yield were significantly higher for the standard and double fertilizations than the control by 7.3% and 10.9%, respectively. The two levels of fertilization did not significantly increase rice yield. Prior long-term fertilization in the paddy (about 20 years with annual doses of 95 kg N ha−1, 70 kg P2O5 ha−1 and 70 kg K2O ha−1) might have prevented these fertilizations from increasing the yield. However, fertilizations increased greenhouse-gas emissions. This situation is common in paddy fields in subtropical China, suggesting a saturation of soil nutrients and the necessity to review current fertilization management. These areas likely suffer from unnecessary nutrient leaching and excessive greenhouse-gas emissions. These results provide a scientific basis for continued research to identify an easy and optimal fertilization management solution
Modeling acute toxicity of metal mixtures to wheat (Triticum aestivum L.) using the biotic ligand model-based toxic units method
The combined toxic effects of copper (Cu) and cobalt (Co) were predicted using the biotic ligand model (BLM) for different concentrations of magnesium (Mg2+) and pH levels, with parameters derived from Cu-only and Co-only toxicity data. The BLM-based toxic unit (TU) approach was used for prediction. Higher activities of Mg2+ linearly increased the EC50 of Cu and Co, supporting the concept of competitive binding of Mg2+ and metal ions in toxic action. The effects of pH on Cu and Co toxicity were related not only to free Cu2+ and Co2+ activity, respectively, but also to inorganic metal complexes. Stability constants for the binding of Cu2+, CuHCO3 +, CuCO3(aq), CuOH+, Mg2+, Co2+, CoHCO3+ and Mg2+ with biotic ligands were logK(CuBL) 5.87, logK(CuHCO3BL) 5.67, logK(CuCO3BL) 5.44, logK(CuOHBL) 5.07, logK(MgBL) 2.93, logK(CoBL) 4.72, logK(CoHCO3BL) 5.81 and logKMgBL 3.84, respectively. The combinations of Cu and Co showed additive effects under different conditions. When compared with the FIAM-based TU model (root mean square error [RMSE = 16.31, R-2 = 0.84]), the BLM-based TU model fitted the observed effects better (RMSE = 6.70, R-2 = 0.97). The present study supports the BLM principles, which indicate that metal speciation and major cations competition need to be accounted for when predicting toxicity of both single metals and mixtures of metals
PaGeFinder: quantitative identification of spatiotemporal pattern genes
Summary: Pattern Gene Finder (PaGeFinder) is a web-based server for on-line detection of gene expression patterns from serial transcriptomic data generated by high-throughput technologies like microarray or next-generation sequencing. Three particular parameters, the specificity measure, the dispersion measure and the contribution measure, were introduced and implemented in PaGeFinder to help quantitative and interactive identification of pattern genes like housekeeping genes, specific (selective) genes and repressed genes. Besides the on-line computation service, the PaGeFinder also provides downloadable Java programs for local detection of gene expression patterns
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