4,838 research outputs found
Tau functions as Widom constants
We define a tau function for a generic Riemann-Hilbert problem posed on a
union of non-intersecting smooth closed curves with jump matrices analytic in
their neighborhood. The tau function depends on parameters of the jumps and is
expressed as the Fredholm determinant of an integral operator with block
integrable kernel constructed in terms of elementary parametrices. Its
logarithmic derivatives with respect to parameters are given by contour
integrals involving these parametrices and the solution of the Riemann-Hilbert
problem. In the case of one circle, the tau function coincides with Widom's
determinant arising in the asymptotics of block Toeplitz matrices. Our
construction gives the Jimbo-Miwa-Ueno tau function for Riemann-Hilbert
problems of isomonodromic origin (Painlev\'e VI, V, III, Garnier system, etc)
and the Sato-Segal-Wilson tau function for integrable hierarchies such as
Gelfand-Dickey and Drinfeld-Sokolov.Comment: 26 pages, 6 figure
Near-Infrared Photometry of the Star Clusters in the Dwarf Irregular Galaxy IC 5152
We present JHK-band near-infrared photometry of star clusters in the dwarf
irregular galaxy IC 5152. After excluding possible foreground stars, a number
of candidate star clusters are identified in the near-infrared images of IC
5152, which include young populations. Especially, five young star clusters are
identified in the (J-H, H-K) two color diagram and the total extinction values
toward these clusters are estimated to be A_V =2 - 6 from the comparison with
the theoretical values given by the Leitherer et al. (1999)'s theoretical star
cluster model.Comment: Accepted by the Journal of the Korean Astronomical Society, 2006
December issue (Vol. 39, No. 4
Feature Re-calibration based Multiple Instance Learning for Whole Slide Image Classification
Whole slide image (WSI) classification is a fundamental task for the
diagnosis and treatment of diseases; but, curation of accurate labels is
time-consuming and limits the application of fully-supervised methods. To
address this, multiple instance learning (MIL) is a popular method that poses
classification as a weakly supervised learning task with slide-level labels
only. While current MIL methods apply variants of the attention mechanism to
re-weight instance features with stronger models, scant attention is paid to
the properties of the data distribution. In this work, we propose to
re-calibrate the distribution of a WSI bag (instances) by using the statistics
of the max-instance (critical) feature. We assume that in binary MIL, positive
bags have larger feature magnitudes than negatives, thus we can enforce the
model to maximize the discrepancy between bags with a metric feature loss that
models positive bags as out-of-distribution. To achieve this, unlike existing
MIL methods that use single-batch training modes, we propose balanced-batch
sampling to effectively use the feature loss i.e., (+/-) bags simultaneously.
Further, we employ a position encoding module (PEM) to model
spatial/morphological information, and perform pooling by multi-head
self-attention (PSMA) with a Transformer encoder. Experimental results on
existing benchmark datasets show our approach is effective and improves over
state-of-the-art MIL methods.Comment: MICCAI 202
SOLiDzipper: A High Speed Encoding Method for the Next-Generation Sequencing Data
Background Next-generation sequencing (NGS) methods pose computational challenges of handling large volumes of data. Although cloud computing offers a potential solution to these challenges, transferring a large data set across the internet is the biggest obstacle, which may be overcome by efficient encoding methods. When encoding is used to facilitate data transfer to the cloud, the time factor is equally as important as the encoding efficiency. Moreover, to take advantage of parallel processing in cloud computing, a parallel technique to decode and split compressed data in the cloud is essential. Hence in this review, we present SOLiDzipper, a new encoding method for NGS data. Methods The basic strategy of SOLiDzipper is to divide and encode. NGS data files contain both the sequence and non-sequence information whose encoding efficiencies are different. In SOLiDzipper, encoded data are stored in binary data block that does not contain the characteristic information of a specific sequence platform, which means that data can be decoded according to a desired platform even in cases of Illumina, Solexa or Roche 454 data. Results The main calculation time using Crossbow was 173 minutes when 40 EC2 nodes were involved. In that case, an analysis preparation time of 464 minutes is required to encode data in the latest DNA compression method like G-SQZ and transmit it on a 183 Mbit/s bandwidth. However, it takes 194 minutes to encode and transmit data with SOLiDzipper under the same bandwidth conditions. These results indicate that the entire processing time can be reduced according to the encoding methods used, under the same network bandwidth conditions. Considering the limited network bandwidth, high-speed, high-efficiency encoding methods such as SOLiDzipper can make a significant contribution to higher productivity in labs seeking to take advantage of the cloud as an alternative to local computing. Availability http://szipper.dinfree.com . Academic/non-profit: Binary available for direct download at no cost. For-profit: Submit request for for-profit license from the web-site
A Flexible Piezoelectric Energy Harvester-Based Single-Layer WS2 Nanometer 2D Material for Self-Powered Sensors
A piezoelectric sensor is a typical self-powered sensor. With the advantages of a high sensitivity, high frequency band, high signal-to-noise ratio, simple structure, light weight, and reliable operation, it has gradually been applied to the field of smart wearable devices. Here, we first report a flexible piezoelectric sensor (FPS) based on tungsten disulfide (WS2) monolayers that generate electricity when subjected to human movement. The generator maximum voltage was 2.26 V, and the produced energy was 55.45 μJ of the electrical charge on the capacitor (capacity: 220 μF) when applying periodic pressing by 13 kg. The generator demonstrated here can meet the requirements of human motion energy because it generates an average voltage of 7.74 V (a knee), 8.7 V (a sole), and 4.58 V (an elbow) when used on a running human (weight: 75 kg). Output voltages embody distinct patterns for different human parts, the movement-recognition capability of the cellphone application. This generator is quite promising for smart sensors in human–machine interaction detecting personal movement
Red supergiant stars in IC 1613 and metallicity-dependent mixing length in the evolutionary model
We report a spectroscopic study on red supergiant stars (RSGs) in the
irregular dwarf galaxy IC 1613 in the Local Group. We derive the effective
temperatures () and metallicities of 14 RSGs by synthetic
spectral fitting to the spectra observed with the MMIRS instrument on the MMT
telescope for a wavelength range from 1.16 m to 1.23 m. A weak
bimodal distribution of the RSG metallicity centered on the [Fe/H]= is
found, which is slightly lower than or comparable to that of the Small
Magellanic Cloud (SMC). There is no evidence for spatial segregation between
the metal rich ([Fe/H]) and poor ([Fe/H]) RSGs throughout the
galaxy. The mean effective temperature of our RSG sample in IC 1613 is higher
by about 250 K than that of the SMC. However, no correlation between
and metallicity within our RSG sample is found. We calibrate
the convective mixing length () by comparing stellar
evolutionary tracks with the RSG positions on the HR diagram, finding that
models with can best reproduce the
effective temperatures of the RSGs in IC 1613 for both Schwarzschild and Ledoux
convection criteria. This result supports our previous study that a metallicity
dependent mixing length is needed to explain the RSG temperatures observed in
the Local Group, but we find that this dependency becomes relatively weak for
RSGs having a metallicity equal to or less than the SMC metallicity.Comment: 15 pages, 7 figures, accepted in Ap
Monitoring of multi-frequency polarization of gamma-ray bright AGNs
We started two observing programs with the Korean VLBI Network (KVN)
monitoring changes in the flux density and polarization of relativistic jets in
gamma-ray bright AGNs simultaneously at 22, 43, 86, 129 GHz. One is a
single-dish weekly-observing program in dual polarization with KVN 21-m
diameter radio telescopes beginning in 2011 May. The other is a VLBI
monthly-observing program with the three-element VLBI network at an angular
resolution range of 1.0--9.2 mas beginning in 2012 December. The monitoring
observations aim to study correlation of variability in gamma-ray with that in
radio flux density and polarization of relativistic jets when they flare up.
These observations enable us to study the origin of the gamma-ray flares of
AGNs.Comment: 4 pages, 4 figures, Proceedings of the conference "The innermost
regions of relativistic jets and their magnetic fields", Granada, Spai
The cortical activation pattern by a rehabilitation robotic hand: a functional NIRS study
Introduction: Clarification of the relationship between external stimuli and brain response has been an important topic in neuroscience and brain rehabilitation. In the current study, using functional near infrared spectroscopy (fNIRS), we attempted to investigate cortical activation patterns generated during execution of a rehabilitation robotic hand. Methods: Ten normal subjects were recruited for this study. Passive movements of the right fingers were performed using a rehabilitation robotic hand at a frequency of 0.5 Hz. We measured values of oxy-hemoglobin (HbO), deoxy-hemoglobin (HbR) and total-hemoglobin (HbT) in five regions of interest: the primary sensory-motor cortex (SM1), hand somatotopy of the contralateral SM1, supplementary motor area (SMA), premotor cortex (PMC), and prefrontal cortex (PFC). Results: HbO and HbT values indicated significant activation in the left SM1, left SMA, left PMC, and left PFC during execution of the rehabilitation robotic hand (uncorrected, p < 0.01). By contrast, HbR value indicated significant activation only in the hand somatotopic area of the left SM1 (uncorrected, p < 0.01). Conclusions: Our results appear to indicate that execution of the rehabilitation robotic hand could induce cortical activation. © 2014 Chang, Lee, Gu, Lee, Jin, Yeo, Seo and Jang.1
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