232 research outputs found
Computer-aided diagnosis of lung nodule using gradient tree boosting and Bayesian optimization
We aimed to evaluate computer-aided diagnosis (CADx) system for lung nodule
classification focusing on (i) usefulness of gradient tree boosting (XGBoost)
and (ii) effectiveness of parameter optimization using Bayesian optimization
(Tree Parzen Estimator, TPE) and random search. 99 lung nodules (62 lung
cancers and 37 benign lung nodules) were included from public databases of CT
images. A variant of local binary pattern was used for calculating feature
vectors. Support vector machine (SVM) or XGBoost was trained using the feature
vectors and their labels. TPE or random search was used for parameter
optimization of SVM and XGBoost. Leave-one-out cross-validation was used for
optimizing and evaluating the performance of our CADx system. Performance was
evaluated using area under the curve (AUC) of receiver operating characteristic
analysis. AUC was calculated 10 times, and its average was obtained. The best
averaged AUC of SVM and XGBoost were 0.850 and 0.896, respectively; both were
obtained using TPE. XGBoost was generally superior to SVM. Optimal parameters
for achieving high AUC were obtained with fewer numbers of trials when using
TPE, compared with random search. In conclusion, XGBoost was better than SVM
for classifying lung nodules. TPE was more efficient than random search for
parameter optimization.Comment: 29 pages, 4 figure
First results on the cluster galaxy population from the Subaru Hyper Suprime-Cam survey. II. Faint end color-magnitude diagrams and radial profiles of red and blue galaxies at
We present a statistical study of the redshift evolution of the cluster
galaxy population over a wide redshift range from 0.1 to 1.1, using
optically-selected CAMIRA clusters from ~deg of the Hyper
Suprime-Cam (HSC) Wide S16A data. Our stacking technique with a statistical
background subtraction reveals color-magnitude diagrams of red-sequence and
blue cluster galaxies down to faint magnitudes of . We find that
the linear relation of red-sequence galaxies in the color-magnitude diagram
extends down to the faintest magnitudes we explore with a small intrinsic
scatter . The scatter does not evolve significantly
with redshift. The stacked color-magnitude diagrams are used to define red and
blue galaxies in clusters for studying their radial number density profiles
without resorting to photometric redshifts of individual galaxies. We find that
red galaxies are significantly more concentrated toward cluster centers and
blue galaxies dominate the outskirt of clusters. We explore the fraction of red
galaxies in clusters as a function of redshift, and find that the red fraction
decreases with increasing distances from cluster centers. The red fraction
exhibits a moderate decrease with increasing redshift. The radial number
density profiles of cluster member galaxies are also used to infer the location
of the steepest slope in the three dimensional galaxy density profiles. For a
fixed threshold in richness, we find little redshift evolution in this
location.Comment: 18pages, 10 figures, accepted as PASJ special issu
Constraining dark matter annihilation with HSC Low Surface Brightness Galaxies
Searches for dark matter annihilation signals have been carried out in a
number of target regions such as the Galactic Center and Milky Way dwarf
spheroidal galaxies (dSphs), among a few others. Here we propose low surface
brightness galaxies (LSBGs) asnovel targets for the indirect detection of dark
matter emission. In particular, LSBGs are known to have very large dark matter
contents and be less contaminated by extragalactic gamma-ray sources (e.g.,
blazars) compared to star forming galaxies. We report on an analysis that uses
eight LSBGs (detected by Subaru Hyper Suprime-Cam survey data) with known
redshifts to conduct a search for gamma-ray emission at the positions of these
new objects in Fermi Large Area Telescope data. We found no excesses of
gamma-ray emission and set constraints on the dark matter annihilation
cross-section. We exclude (at the 95% C.L.) dark matter scenarios predicting a
cross-section higher than 10^-23[cm^3/s] for dark matter particles of mass 10
GeV self-annihilating in the b_b channel. Although this constraint is weaker
than the ones reported in recent studies using other targets, we note that in
the near future, the number of detections of new LSBGs will increase by a few
orders of magnitude. We forecast that with the use of the full catalog of
soon-to-be-detected LSBGs the constraint will reach cross-section sensitivities
of ~ 3*10^-25 [cm^3/s] for dark matter particles with masses less than 10 GeV.Comment: 19 pages, 6 figures, accepted to JCA
One-step synthesis of differently bis-functionalized isoxazoles by cycloaddition of carbamoylnitrile oxide with β-keto esters
A new protocol for synthesizing different functionalized isoxazoles is provided. Carbamoylnitrile oxide generated from nitroisoxazolone underwent inverse electron-demand 1,3-dipolar cycloaddition with 1,3-dicarbonyl compounds in the presence of magnesium acetate that formed magnesium enolatein situ. Although electron-deficient trifluoroacetoacetate did not undergo this cycloaddition under the same conditions, conversion to sodium enolate furnish the corresponding bis-functionalized trifluoromethylisoxazole. The DFT calculations using B3LYP 6-31G+(d,p) also supported the aforementioned reactivity
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High-Sensitivity Rheo-NMR Spectroscopy for Protein Studies
Shear stress can induce structural deformation of proteins, which might result in aggregate formation. Rheo-NMR spectroscopy has the potential to monitor structural changes in proteins under shear stress at the atomic level; however, existing Rheo-NMR methodologies have insufficient sensitivity to probe protein structure and dynamics. Here we present a simple and versatile approach to Rheo-NMR, which maximizes sensitivity by using a spectrometer equipped with a cryogenic probe. As a result, the sensitivity of the instrument ranks highest among the Rheo-NMR spectrometers reported so far. We demonstrate that the newly developed Rheo-NMR instrument can acquire high-quality relaxation data for a protein under shear stress and can trace structural changes in a protein during fibril formation in real time. The described approach will facilitate rheological studies on protein structural deformation, thereby aiding a physical understanding of shear-induced amyloid fibril formation
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