1,299 research outputs found
An hourglass model for the flare of HST-1 in M87
To explain the multi-wavelength light curves (from radio to X-ray) of HST-1
in the M87 jet, we propose an hourglass model that is a modified two-zone
system of Tavecchio & Ghisellini (hereafter TG08): a slow hourglass-shaped or
Laval nozzle-shaped layer connected by two revolving exponential surfaces
surrounding a fast spine, through which plasma blobs flow. Based on the
conservation of magnetic flux, the magnetic field changes along the axis of the
hourglass. We adopt the result of TG08---the high-energy emission from GeV to
TeV can be produced through inverse Compton by the two-zone system, and the
photons from radio to X-ray are mainly radiated by the fast inner zone system.
Here, we only discuss the light curves of the fast inner blob from radio to
X-ray. When a compressible blob travels down the axis of the first bulb in the
hourglass, because of magnetic flux conservation, its cross section experiences
an adiabatic compression process, which results in particle acceleration and
the brightening of HST-1. When the blob moves into the second bulb of the
hourglass, because of magnetic flux conservation, the dimming of the knot
occurs along with an adiabatic expansion of its cross section. A similar broken
exponential function could fit the TeV peaks in M87, which may imply a
correlation between the TeV flares of M87 and the light curves from radio to
X-ray in HST-1. The Very Large Array (VLA) 22 GHz radio light curve of HST-1
verifies our prediction based on the model fit to the main peak of the VLA 15
GHz radio light curve.Comment: 14 pages, 2 figures, accepted for publication in A
Three-state coherent control using narrowband and passband sequences
In this work, we propose a comprehensive design for narrowband and passband
composite pulse sequences by involving the dynamics of all states in the
three-state system. The design is quite universal as all pulse parameters can
be freely employed to modify the coefficients of error terms. Two modulation
techniques, the strength and phase modulations, are used to achieve arbitrary
population transfer with a desired excitation profile, while the system keeps
minimal leakage to the third state. Furthermore, the current sequences are
capable of tolerating inaccurate waveforms, detunings errors, and work well
when rotating wave approximation is not strictly justified. Therefore, this
work provides versatile adaptability for shaping various excitation profiles in
both narrowband and passband sequences.Comment: 28 pages, 9 figure
Image Synthesis with Disentangled Attributes for Chest X-Ray Nodule Augmentation and Detection
Lung nodule detection in chest X-ray (CXR) images is common to early
screening of lung cancers. Deep-learning-based Computer-Assisted Diagnosis
(CAD) systems can support radiologists for nodule screening in CXR. However, it
requires large-scale and diverse medical data with high-quality annotations to
train such robust and accurate CADs. To alleviate the limited availability of
such datasets, lung nodule synthesis methods are proposed for the sake of data
augmentation. Nevertheless, previous methods lack the ability to generate
nodules that are realistic with the size attribute desired by the detector. To
address this issue, we introduce a novel lung nodule synthesis framework in
this paper, which decomposes nodule attributes into three main aspects
including shape, size, and texture, respectively. A GAN-based Shape Generator
firstly models nodule shapes by generating diverse shape masks. The following
Size Modulation then enables quantitative control on the diameters of the
generated nodule shapes in pixel-level granularity. A coarse-to-fine gated
convolutional Texture Generator finally synthesizes visually plausible nodule
textures conditioned on the modulated shape masks. Moreover, we propose to
synthesize nodule CXR images by controlling the disentangled nodule attributes
for data augmentation, in order to better compensate for the nodules that are
easily missed in the detection task. Our experiments demonstrate the enhanced
image quality, diversity, and controllability of the proposed lung nodule
synthesis framework. We also validate the effectiveness of our data
augmentation on greatly improving nodule detection performance
The swimming behavior of the aquatic larva of Neoneuromus ignobilis (Megaloptera: Corydalidae: Corydalinae).
In order to explore the pattern and significance of swimming, through photos and videos we observed and recorded the swimming behavior of the aquatic larvae of Megaloptera in detail for the first time using the endemic Chinese species Neoneuromus ignobilis Navas, 1932 as the test insect, which were collected from the Dadu River and reared in nature-simulated environments. Four swimming postures are recognized and described herein in detail, i. e., vertical, parallel, back and side swimming, and these postures were used by the larvae disproportionately, with a frequency of 89.08%, 5. 49%, 4. 40% and 0. 61% , respectively. The swimming larvae tend to pose their body into an S-shape, with various degree of sinuation. By changing the directions of the head and tail, they can easily rise up or sink and change swimming postures. The propulsion was generated by the wriggling of the body while the legs were mostly held close to the body. Larvae of different instars varied greatly in swimming ability, the 6th ins tar larvae being the best and most active swimmer compared to the 2nd and final instars. The larvae may also employ complex defense behaviors not often known from relatively ancient insect groups, like chemical defense as secretion from the end of abdomen
Angiogenesis and Vasculogenesis at 7-Day of Reperfused Acute Myocardial Infarction
Objectives 
This study is to investigate the angiogenesis and vasculogenesis at the first week of reperfused acute myocardial infarction (AMI).
Methods 
16 of mini-swines (20 to 30 Kg) were randomly assigned to the sham-operated group and the AMI group. The acute myocardial infarction and reperfusion model was created and the pig tail catheter was performed to monitor hemodynamics before left anterior descending coronary artery (LAD) occlusion, 90 min of LAD occlusion and 120 min of LAD reperfusion. Pathologic myocardial tissue was collected at 7-day of LAD reperfusion and further assessed by immunochemistry, dual immunochemistry, in-situ hybridization, real-time quantitative polymerase chain reaction and western blot. 
Results 
The infarcted area had higher FLK1 mRNA expression than sham-operated area and the normal area (all P<0.05), and the infarcted and marginal areas showed higher CD146 protein expression than the sham-operated area (all P<0.05), but the microvessel density (CD31 positive expression of microvessels/HP) was not significantly different between the infarcted area and the sham-operated area (8.92±3.05 vs 6.43±1.54) at 7-day of reperfused acute myocardial infarction (P>0.05). 
Conclusions 
FLK1 and CD146 expression significantly increase in the infarcted and marginal areas, and the microvessel density is not significantly different between the infarcted area and the sham-operated area, suggesting that angiogenesis and vasculogenesis in the infarcted area appear to high frequency of increase in 7-day of reperfused myocardial infarction. 

- …