650 research outputs found

### Global dynamics in a chemotaxis model describing tumor angiogenesis with/without mitosis in any dimensions

In this work, we study the Neumann initial boundary value problem for a
three-component chemotaxis model in any dimensional bounded and smooth domains;
this model is used to describe the branching of capillary sprouts during
angiogenesis. First, we find three qualitatively simple sufficient conditions
for qualitative global boundedness, and then, we establish two types of global
stability for bounded solutions in qualitative ways. As a consequence of our
findings, the underlying system without chemotaxis and the effect of ECs
mitosis can not give rise to pattern formations. Our findings quantify and
extend significantly previous studies, which are set in lower dimensional
convex domains and are with no qualitative information.Comment: 43 pages, under review in a journa

### Self-Supervised Intensity-Event Stereo Matching

Event cameras are novel bio-inspired vision sensors that output pixel-level
intensity changes in microsecond accuracy with a high dynamic range and low
power consumption. Despite these advantages, event cameras cannot be directly
applied to computational imaging tasks due to the inability to obtain
high-quality intensity and events simultaneously. This paper aims to connect a
standalone event camera and a modern intensity camera so that the applications
can take advantage of both two sensors. We establish this connection through a
multi-modal stereo matching task. We first convert events to a reconstructed
image and extend the existing stereo networks to this multi-modality condition.
We propose a self-supervised method to train the multi-modal stereo network
without using ground truth disparity data. The structure loss calculated on
image gradients is used to enable self-supervised learning on such multi-modal
data. Exploiting the internal stereo constraint between views with different
modalities, we introduce general stereo loss functions, including disparity
cross-consistency loss and internal disparity loss, leading to improved
performance and robustness compared to existing approaches. The experiments
demonstrate the effectiveness of the proposed method, especially the proposed
general stereo loss functions, on both synthetic and real datasets. At last, we
shed light on employing the aligned events and intensity images in downstream
tasks, e.g., video interpolation application.Comment: This paper has been accepted by the Journal of Imaging Science &
Technolog

### Validating quantum-supremacy experiments with exact and fast tensor network contraction

The quantum circuits that declare quantum supremacy, such as Google Sycamore
[Nature \textbf{574}, 505 (2019)], raises a paradox in building reliable result
references. While simulation on traditional computers seems the sole way to
provide reliable verification, the required run time is doomed with an
exponentially-increasing compute complexity. To find a way to validate current
``quantum-supremacy" circuits with more than $50$ qubits, we propose a
simulation method that exploits the ``classical advantage" (the inherent
``store-and-compute" operation mode of von Neumann machines) of current
supercomputers, and computes uncorrelated amplitudes of a random quantum
circuit with an optimal reuse of the intermediate results and a minimal memory
overhead throughout the process. Such a reuse strategy reduces the original
linear scaling of the total compute cost against the number of amplitudes to a
sublinear pattern, with greater reduction for more amplitudes. Based on a
well-optimized implementation of this method on a new-generation Sunway
supercomputer, we directly verify Sycamore by computing three million exact
amplitudes for the experimentally generated bitstrings, obtaining an XEB
fidelity of $0.191\%$ which closely matches the estimated value of $0.224\%$.
Our computation scales up to $41,932,800$ cores with a sustained
single-precision performance of $84.8$ Pflops, which is accomplished within
$8.5$ days. Our method has a far-reaching impact in solving quantum many-body
problems, statistical problems as well as combinatorial optimization problems
where one often needs to contract many tensor networks which share a
significant portion of tensors in common.Comment: 7 pages, 4 figures, comments are welcome

### Manipulation of ionized impurity scattering for achieving high thermoelectric performance in n-type Mg

Achieving higher carrier mobility plays a pivotal role for obtaining potentially high thermoelectric performance. In principle, the carrier mobility is governed by the band structure as well as by the carrier scattering mechanism. Here, we demonstrate that by manipulating the carrier scattering mechanism in n-type Mg[subscript 3]Sb[subscript 2 ]-based materials, a substantial improvement in carrier mobility, and hence the power factor, can be achieved. In this work, Fe, Co, Hf, and Ta are doped on the Mg site of Mg[subscript 3.2]Sb[subscript 1.5]Bi[subscript 0.49]Te [subscript 0.01], where the ionized impurity scattering crosses over to mixed ionized impurity and acoustic phonon scattering. A significant improvement in Hall mobility from âˆ¼16 to âˆ¼81 cm 2 Â·V[superscript âˆ’1]Â·s[superscript âˆ’ 1] is obtained, thus leading to a notably enhanced power factor of âˆ¼13 Î¼WÂ·cm [superscript âˆ’1]Â·K [superscript âˆ’2] from âˆ¼5 Î¼WÂ·cm[superscript âˆ’1]Â·K[superscript âˆ’2]. A simultaneous reduction in thermal conductivity is also achieved. Collectively, a figure of merit (ZT) of âˆ¼1.7 is obtained at 773 K in Mg[subscript 3.1]Co[subscript 0.1]Sb[subscript 1.5]Bi[subscript 0.49]Te [subscript 0.01]. The concept of manipulating the carrier scattering mechanism to improve the mobility should also be applicable to other material systems. Keywords: thermoelectric; carrier scattering mechanism; ionized impurity scattering; n-type; Mg[subscript 3]Sb[subscript 2]; defect

### Chemical Tuning of Fibers Drawn from Extensible Hyaluronic Acid Networks

Â© 2020 American Chemical Society. Polymer fibers with specific chemical and mechanical properties are key components of many biomaterials used for regenerative medicine and drug delivery. Here, we develop a bioinspired, low-energy process to produce mechanically tunable biopolymer fibers drawn from aqueous solutions. Hyaluronic acid (HA) forms dynamic cross-links with branched polyethylene glycol polymers end-functionalized with boronic acids of varied structure to produce extensible polymer networks. This dynamic fiber precursor (DFP) is directly drawn by pultrusion into HA fibers that display high aspect ratios, ranging from 4 to 20 Î¼m in diameter and up to âˆ¼10 m in length. Dynamic rheology measurements of the DFP and tensile testing of the resulting fibers reveal design considerations to tune the propensity for fiber formation and fiber mechanical properties, including the effect of polymer structure and concentration on elastic modulus, tensile strength, and ultimate strain. The materials' humidity-responsive contractile behavior, a unique property of spider silks rarely observed in synthetic materials, highlights possibilities for further biomimetic and stimulus-responsive fiber applications. This work demonstrates that chemical modification of dynamic interactions can be used to tune the mechanical properties of pultrusion-based fibers and their precursors.Leona M. and Harry B. Helmsley Charitable Trust (Grant 2017PG-T1D027)NIH (Grants F32DK118785, K99EB025254 and PDF-2015-90-A-N)National Cancer Institute (Grant P30-CA14051

### A Measurement of Psi(2S) Resonance Parameters

Cross sections for e+e- to hadons, pi+pi- J/Psi, and mu+mu- have been
measured in the vicinity of the Psi(2S) resonance using the BESII detector
operated at the BEPC. The Psi(2S) total width; partial widths to hadrons,
pi+pi- J/Psi, muons; and corresponding branching fractions have been determined
to be Gamma(total)= (264+-27) keV; Gamma(hadron)= (258+-26) keV, Gamma(mu)=
(2.44+-0.21) keV, and Gamma(pi+pi- J/Psi)= (85+-8.7) keV; and Br(hadron)=
(97.79+-0.15)%, Br(pi+pi- J/Psi)= (32+-1.4)%, Br(mu)= (0.93+-0.08)%,
respectively.Comment: 8 pages, 6 figure

### Measurements of the Mass and Full-Width of the $\eta_c$ Meson

In a sample of 58 million $J/\psi$ events collected with the BES II detector,
the process J/$\psi\to\gamma\eta_c$ is observed in five different decay
channels: $\gamma K^+K^-\pi^+\pi^-$, $\gamma\pi^+\pi^-\pi^+\pi^-$, $\gamma
K^\pm K^0_S \pi^\mp$ (with $K^0_S\to\pi^+\pi^-$), $\gamma \phi\phi$ (with
$\phi\to K^+K^-$) and $\gamma p\bar{p}$. From a combined fit of all five
channels, we determine the mass and full-width of $\eta_c$ to be
$m_{\eta_c}=2977.5\pm1.0 ({stat.})\pm1.2 ({syst.})$ MeV/$c^2$ and
$\Gamma_{\eta_c} = 17.0\pm3.7 ({stat.})\pm7.4 ({syst.})$ MeV/$c^2$.Comment: 9 pages, 2 figures and 4 table. Submitted to Phys. Lett.

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