Blockchain is an advanced technique to realize smart contracts, various transactions, and P2P crypto-currencies in the e-commerce society. However, the traditional blockchain does not consider a ...mobile environment to design a data offloading of the blockchain such that the blockchain results in high computational cost and huge data propagation delay. In this paper, to remedy the above problem, we propose a scalable blockchain and a task offloading technique based on the neural network of the mobile edge computing scenario. Experimental results show that our approach is very scalable in the mobile scenario.
The shape complexity of a particle confined in the circular quantum well with an external homogeneous perpendicular magnetic field is investigated. First, the Shannon entropy and the averaging ...electron probability density, as well as the shape complexities in the position and momentum spaces for several quantum states, are computed and discussed. The quantum confinement effect on the shape complexity of this system is extensively explored. Then, the influence of the magnetic field on the shape complexities of the particle confined in the circular quantum well is discussed. It is demonstrated that the shape complexity exhibits scaled invariance under the influence of the magnetic field. However, when the radius of the quantum well is fixed, the shape complexity of the given quantum state changes with the magnetic field strength. Results suggest that the shape complexity of a particle confined in the quantum well can be changed by varying both the strength of the magnetic field and the size of the well. This study has some practical applications in quantum information measurement of the confined particle and can guide future researches for the disorder characteristics of confined particle in semiconductor quantum dots.
The ground‐state shape complexity for a particle confined in the magnetic circular quantum well as a function of the radius R. (a) Variation of Sρ and ln <ρ> with R. (b) Variation of Cp with R. (c) Variation of Sρ and ln <ρ> with R. (d) Variation of Cp with R.
Background
High blood pressure (BP) is a common risk factor for cerebral small vessel disease including white matter hyperintensity (WMH). Whether increased BP exacerbates WMH by impacting cerebral ...vascular morphologies remains poorly studied.
Purpose
To determine the relationships among high BP, cerebrovascular morphologies, and WMH in elderly individuals.
Study Type
Cohort.
Subjects
Eight hundred sixty‐three participants (54.2% female) from the Taizhou Imaging Study without clinical evidence of neurologic disorders were included in the analyses.
Field Strength/Sequence
3.0 T; time‐of‐flight magnetic resonance angiography (TOF MRA); T2 fluid‐attenuated inversion recovery (FLAIR); T1 magnetization‐prepared rapid gradient‐echo; gradient echo T2*‐weighted; diffusion tensor imaging; pulsed arterial spin labeling.
Assessment
Cerebrovascular morphologic measurements were quantified based on the TOF MRA images, including vessel density, radius, tortuosity, and branch number. WMH lesion volumes (WMHV) and WMH lesion counts (WMHC) were calculated automatically based on the T2 FLAIR images.
Statistical Tests
Multivariable linear regression analysis and path analysis with a linear single‐mediator model were employed. A P value <0.05 was considered statistically significant.
Results
Higher BP, especially diastolic BP, was significantly correlated with lower cerebrovascular density (β = −104) and lower branch numbers (β = −0.02). Although decreased tortuosity (β = −1.25) and increased radius (β = 93.8) were correlated with BP, no significant relationship of tortuosity (β = −4.6 × 10−4, P = 0.58) or radius (β = 0.03, P = 0.08) with BP in small vessels was found. The proportion of small vessels decreased as BP increased (SBP: β = −6.6 × 10−4; DBP: β = −9.0 × 10−4). Similarly, increased WMHV and WMHC were associated with decreased vessel density (volumes: β = −24, counts: β = −127), decreased tortuosity (volumes: β = −0.08, counts: β = −0.53), and increased radius (volumes: β = 12.6, counts: β = 86.6). Path analyses suggested an association between high BP and WMHs that were mediated by cerebrovascular morphologic changes.
Data Conclusion
Structural alterations of cerebral vessels induced by high BP are correlated with WMH. This result suggested that elevated BP might be one of the pathophysiological mechanisms involving in the co‐occurrence of cerebrovascular alteration and small vessel disease.
Level of Evidence: 1
Technical Efficacy Stage: 1
Purpose
The phase mismatch between odd and even echoes in EPI causes Nyquist ghost artifacts. Existing ghost correction methods often suffer from severe residual artifacts and are ineffective with ...k‐space undersampling data. This study proposed a deep learning–based method (PEC‐DL) to correct phase errors for DWI at 7 Tesla.
Methods
The acquired k‐space data were divided into 2 independent undersampled datasets according to their readout polarities. Then the proposed PEC‐DL network reconstructed 2 ghost‐free images using the undersampled data without calibration and navigator data. The network was trained with fully sampled images and applied to two‐ and fourfold accelerated data. Healthy volunteers and patients with Moyamoya disease were recruited to validate the efficacy of the PEC‐DL method.
Results
The PEC‐DL method was capable to mitigate the ghost artifacts in DWI in healthy volunteers as well as patients with Moyamoya disease. The fourfold accelerated results showed much less distortion in the lesions of the Moyamoya patient using high b‐value DWI and the corresponding ADC maps. The ghost‐to‐signal ratios were significantly lower in PEC‐DL images compared to conventional linear phase corrections, mini‐entropy, and PEC‐GRAPPA algorithms.
Conclusion
The proposed method can effectively eliminate ghost artifacts for full sampled and up to fourfold accelerated EPI data without calibration and navigator data.
Abstract
The geometric structure of supernova remnants (SNR) provides a clue to unveiling the pre-explosion evolution of their progenitors. Here we present an X-ray study of N103B (0509–68.7), a Type ...Ia SNR in the Large Magellanic Cloud, that is known to be interacting with dense circumstellar matter (CSM). Applying our novel method for feature extraction to deep Chandra observations, we have successfully resolved the CSM, Fe-rich ejecta, and intermediate-mass element (IME) ejecta components, and revealed each of their spatial distributions. Remarkably, the IME ejecta component exhibits a double-ring structure, implying that the SNR expands into an hourglass-shape cavity and thus forms bipolar bubbles of the ejecta. This interpretation is supported by more quantitative spectroscopy that reveals a clear bimodality in the distribution of the ionization state of the IME ejecta. These observational results can be naturally explained if the progenitor binary system had formed a dense CSM torus on the orbital plane prior to the explosion, providing further evidence that the SNR N103B originates from a single-degenerate progenitor.
Abstract
This paper systematically studies the relation between metallicity and mass loss of massive stars. We perform one-dimensional stellar evolution simulations and build a grid of ∼2000 models ...with initial masses ranging between 11 and 60
M
⊙
and absolute metallicities
Z
between 0.00001 and 0.02. Steady-state winds, comprising hot main-sequence winds and cool supergiant winds, are the main drivers of the mass loss of massive stars in our models. We calculate the total mass loss over the stellar lifetime for each model. Our results reveal the existence of a critical metallicity
Z
c
at
Z
∼ 10
−3
, where the mass loss exhibits a dramatic jump. If
Z
>
Z
c
, massive stars tend to evolve into cool supergiants, and a robust cool wind is operational. In contrast, if
Z
<
Z
c
, massive stars usually remain as blue supergiants, wherein the cool wind is not activated and the mass loss is generally weak. Moreover, we calculate the wind feedback in a 10
5
M
⊙
star cluster with the Salpeter initial mass function. The kinetic energy released by winds does not exhibit any significant transition at
Z
c
because the wind velocity of a cool supergiant wind is low and contributes little to the kinetic energy. The effects of critical metallicity provide implications for the fates of metal-poor stars in the early universe.
Abstract
We present low-resolution optical spectra and classifications of 92 blue objects with mid-infrared excesses in the Large Magellanic Cloud. The majority of these objects were selected with ...the criteria of
U
−
B
< 0 and
V
< 17 from the potential young stellar object (YSO) candidates in Gruendl & Chu (GC09), which were identified based on Spitzer Infrared Array Camera and Multiband Imaging Photometer for Spitzer observations in conjunction with optical photometry from the Magellanic Clouds Photometric Survey. Many of the sample objects have ambiguous classifications. We examined the properties of these 92 objects using low-resolution optical spectra obtained with the SOAR 4.1 m Telescope at Cerro Pachon and the Blanco 4 m Telescope at Cerro Tololo Inter-American Observatory, supplemented by available photometric and imaging observations. We estimated the spectral types, temperatures, and luminosities of these objects from the optical to near-IR spectral energy distributions based on the photometric data, and further examined stellar absorption line features in the optical spectra to verify the spectral types. The interstellar/circumstellar environments, assessed from nebular line imaging observations and nebular lines detected in the stellar spectra, further helped constrain the nature of stars. Among these 92 objects, we confirm 42 stars as YSOs, and the remaining 50 objects as protoplanetary nebulae, post-AGB/RGB stars, blue evolved massive stars, stars with dust in vicinity, or uncertain classifications. Our results show that the photometric criteria in GC09 are generally effective in the initial selection of YSO candidates, and the low-resolution spectroscopy combined with environment assessment can be useful to better constrain the classifications and ameliorate most ambiguities.
This research aims to specify critical urban sustainability issues by mining unstructured text data derived from the C40 city datasets of the Carbon Disclosure Project. The current study identifies ...underlying topical issues exhibited by text corpora, enables creation of smarter data visualizations, and forms useful profiles. Four underlying topical areas are examined: economic opportunities, climate risks, incentives to reduce greenhouse gas emissions, and emissions reduction activities. For each area, we built text data visualization profiles. Developing these text data visualization profiles enables greater attention to be paid to the list of topical issues shown in the profiles. Given the number of discovered topic issues, we generate an urban sustainability activity index and use it to identify which cities were detailing their actions toward becoming more sustainable cities. The city officials and municipal planners of either C40 or non‐C40 cities worldwide can benchmark this study and put the process of text data visualization at the center of their process of generating citywide sustainable development.
Non-covalent functionalization was used to functionalize graphene nanosheets (GNSs) through π–π stacking of pyrene molecules with a functional segmented polymer chain, which results in a remarkable ...improvement in the thermal conductivity of GNS-filled polymer composites. The functional segmented poly(glycidyl methacrylate) containing localized pyrene groups (Py-PGMA) was prepared by atom transfer radical polymerization, and Py-PGMA was characterized by nuclear magnetic resonance spectroscopy. Raman spectra, X-ray photoelectron spectroscopy and thermogravimetric analysis reveal the characteristics of Py-PGMA–GNS. Differential scanning calorimetry indicated that the functional groups on Py-PGMA–GNSs can generate covalent bonds with the epoxy matrix, and further form a cross-linked structure in Py-PGMA–GNS/epoxy composites. The Py-PGMA on the GNS surface not only plays an important role to facilitate a homogeneous dispersion in the polymer matrix but also improves the GNS–polymer interaction, which results in a high contact area. Consequently, the thermal conductivity of integrated Py-PGMA–GNS/epoxy composites exhibited a remarkable improvement and is much higher than epoxy reinforced by multi-walled carbon nanotubes or GNSs. The thermal conductivity of 4
phr Py-PGMA–GNS/epoxy has about 20% (higher than that of pristine GNS/epoxy) and 267% (higher than pristine MWCNT/epoxy).
Abstract
The supernova remnant (SNR) 30 Dor B is associated with the H
ii
region ionized by the OB association LH99. The complex interstellar environment has made it difficult to study the physical ...structure of this SNR. We have used Hubble Space Telescope H
α
images to identify SNR shocks and deep Chandra X-ray observations to detect faint diffuse emission. We find that 30 Dor B hosts three zones with very different X-ray surface brightnesses and nebular kinematics that are characteristic of SNRs in different interstellar environments and/or evolutionary stages. The ASKAP 888 MHz map of 30 Dor B shows counterparts to all X-ray emission features except the faint halo. The ASKAP 888 and 1420 MHz observations are used to produce a spectral index map, but its interpretation is complicated by the background thermal emission and the pulsar PSR J0537−6910's flat spectral index. The stellar population in the vicinity of 30 Dor B indicates a continuous star formation in the past 8–10 Myr. The observed very massive stars in LH99 cannot be coeval with the progenitor of 30 Dor B’s pulsar. Adopting the pulsar’s spin-down timescale, 5000 yr, as the age of the SNR, the X-ray shell would be expanding at ∼4000 km s
−1
and the post-shock temperature would be 1–2 orders of magnitude higher than that indicated by the X-ray spectra. Thus, the bright central region of 30 Dor B and the X-ray shell requires two separate SN events, and the faint diffuse X-ray halo perhaps other older SN events.
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