8,648 research outputs found
The Size-Ramsey Number of 3-uniform Tight Paths
Given a hypergraph H, the size-Ramsey number ˆr2(H) is the smallest integer m such that there exists a hypergraph G with m edges with the property that in any colouring of the edges of G with two colours there is a monochromatic copy of H. We prove that the size-Ramsey number of the 3-uniform tight path on n vertices Pn(3) is linear in n, i.e., ˆr2(Pn(3)) = O(n). This answers a question by Dudek, La Fleur, Mubayi, and Rödl for 3-uniform hypergraphs [On the size-Ramsey number of hypergraphs, J. Graph Theory 86 (2016), 417–434], who proved ˆr2(Pn(3)) = O(n3/2 log3/2 n)
Laser-induced charge and spin photocurrents at BiAg surface: a first principles benchmark
Here, we report first principles calculations and analysis of laser-induced
photocurrents at the surface of a prototype Rashba system. By referring to
Keldysh non-equilibrium formalism combined with the Wannier interpolation
scheme we perform first-principles electronic structure calculations of a
prototype BiAg surface alloy, which is a well-known material realization of
the Rashba model. In addition to non-magnetic ground state situation we also
study the case of in-plane magnetized BiAg. We calculate the laser-induced
charge photocurrents for the ferromagnetic case and the laser-induced spin
photocurrents for both the non-magnetic and the ferromagnetic cases. Our
results confirm the emergence of very large in-plane photocurrents as predicted
by the Rashba model. The resulting photocurrents satisfy all the symmetry
restrictions with respect to the light helicity and the magnetization
direction. We provide microscopic insights into the symmetry and magnitude of
the computed currents based on the ab-initio multi-band electronic structure of
the system, and scrutinize the importance of resonant two-band and three-band
transitions for driven currents, thereby establishing a benchmark picture of
photocurrents at Rashba-like surfaces and interfaces. Our work contributes to
the study of the role of the interfacial Rashba spin-orbit interaction as a
mechanism for the generation of in-plane photocurrents, which are of great
interest in the field of ultrafast and terahertz spintronics
Antigenic Change in Human Influenza A(H2N2) Viruses Detected by Using Human Plasma from Aged and Younger Adult Individuals
Sampling constrained probability distributions using Spherical Augmentation
Statistical models with constrained probability distributions are abundant in
machine learning. Some examples include regression models with norm constraints
(e.g., Lasso), probit, many copula models, and latent Dirichlet allocation
(LDA). Bayesian inference involving probability distributions confined to
constrained domains could be quite challenging for commonly used sampling
algorithms. In this paper, we propose a novel augmentation technique that
handles a wide range of constraints by mapping the constrained domain to a
sphere in the augmented space. By moving freely on the surface of this sphere,
sampling algorithms handle constraints implicitly and generate proposals that
remain within boundaries when mapped back to the original space. Our proposed
method, called {Spherical Augmentation}, provides a mathematically natural and
computationally efficient framework for sampling from constrained probability
distributions. We show the advantages of our method over state-of-the-art
sampling algorithms, such as exact Hamiltonian Monte Carlo, using several
examples including truncated Gaussian distributions, Bayesian Lasso, Bayesian
bridge regression, reconstruction of quantized stationary Gaussian process, and
LDA for topic modeling.Comment: 41 pages, 13 figure
Structure of 55Sc and development of the N=34 subshell closure
The low-lying structure of Sc has been investigated using in-beam
-ray spectroscopy with the Be(Ti,Sc+)
one-proton removal and Be(Sc,Sc+)
inelastic-scattering reactions at the RIKEN Radioactive Isotope Beam Factory.
Transitions with energies of 572(4), 695(5), 1539(10), 1730(20), 1854(27),
2091(19), 2452(26), and 3241(39) keV are reported, and a level scheme has been
constructed using coincidence relationships and -ray
relative intensities. The results are compared to large-scale shell-model
calculations in the - model space, which account for positive-parity
states from proton-hole cross-shell excitations, and to it ab initio
shell-model calculations from the in-medium similarity renormalization group
that includes three-nucleon forces explicitly. The results of proton-removal
reaction theory with the eikonal model approach were adopted to aid
identification of positive-parity states in the level scheme; experimental
counterparts of theoretical and states are
suggested from measured decay patterns. The energy of the first
state, which is sensitive to the neutron shell gap at the Fermi surface, was
determined. The result indicates a rapid weakening of the subshell
closure in -shell nuclei at , even when only a single proton occupies
the orbital
Structural evolution in the neutron-rich nuclei 106Zr and 108Zr
The low-lying states in 106Zr and 108Zr have been investigated by means of
{\beta}-{\gamma} and isomer spectroscopy at the RI beam factory, respectively.
A new isomer with a half-life of 620\pm150 ns has been identified in 108Zr. For
the sequence of even-even Zr isotopes, the excitation energies of the first 2+
states reach a minimum at N = 64 and gradually increase as the neutron number
increases up to N = 68, suggesting a deformed sub-shell closure at N = 64. The
deformed ground state of 108Zr indicates that a spherical sub-shell gap
predicted at N = 70 is not large enough to change the ground state of 108Zr to
the spherical shape. The possibility of a tetrahedral shape isomer in 108Zr is
also discussed.Comment: 10 pages, 3 figures, Accepted for publication in Phys. Rev. Let
Integration of GOCI and AHI Yonsei aerosol optical depth products during the 2016 KORUS-AQ and 2018 EMeRGe campaigns
The Yonsei Aerosol Retrieval (YAER) algorithm for the Geostationary Ocean Color Imager (GOCI) retrieves aerosol optical properties only over dark surfaces, so it is important to mask pixels with bright surfaces. The Advanced Himawari Imager (AHI) is equipped with three shortwave-infrared and nine infrared channels, which is advantageous for bright-pixel masking. In addition, multiple visible and near-infrared channels provide a great advantage in aerosol property retrieval from the AHI and GOCI. By applying the YAER algorithm to 10 min AHI or 1 h GOCI data at 6km x 6km resolution, diurnal variations and aerosol transport can be observed, which has not previously been possible from low-Earth-orbit satellites. This study attempted to estimate the optimal aerosol optical depth (AOD) for East Asia by data fusion, taking into account satellite retrieval uncertainty. The data fusion involved two steps: (1) analysis of error characteristics of each retrieved result with respect to the ground-based Aerosol Robotic Network (AERONET), as well as bias correction based on normalized difference vegetation indexes, and (2) compilation of the fused product using ensemble-mean and maximum-likelihood estimation (MLE) methods. Fused results show a better statistics in terms of fraction within the expected error, correlation coefficient, root-mean-square error (RMSE), and median bias error than the retrieved result for each product. If the RMSE and mean AOD bias values used for MLE fusion are correct, the MLE fused products show better accuracy, but the ensemble-mean products can still be useful as MLE
EVpedia: a community web portal for extracellular vesicles research
MOTIVATION: Extracellular vesicles (EVs) are spherical bilayered proteolipids, harboring various bioactive molecules. Due to the complexity of the vesicular nomenclatures and components, online searches for EV-related publications and vesicular components are currently challenging. RESULTS: We present an improved version of EVpedia, a public database for EVs research. This community web portal contains a database of publications and vesicular components, identification of orthologous vesicular components, bioinformatic tools and a personalized function. EVpedia includes 6879 publications, 172 080 vesicular components from 263 high-throughput datasets, and has been accessed more than 65 000 times from more than 750 cities. In addition, about 350 members from 73 international research groups have participated in developing EVpedia. This free web-based database might serve as a useful resource to stimulate the emerging field of EV research. Availability and implementation: The web site was implemented in PHP, Java, MySQL and Apache, and is freely available at http://evpedia.info. CONTACT: [email protected]
Regularizing effect and local existence for non-cutoff Boltzmann equation
The Boltzmann equation without Grad's angular cutoff assumption is believed
to have regularizing effect on the solution because of the non-integrable
angular singularity of the cross-section. However, even though so far this has
been justified satisfactorily for the spatially homogeneous Boltzmann equation,
it is still basically unsolved for the spatially inhomogeneous Boltzmann
equation. In this paper, by sharpening the coercivity and upper bound estimates
for the collision operator, establishing the hypo-ellipticity of the Boltzmann
operator based on a generalized version of the uncertainty principle, and
analyzing the commutators between the collision operator and some weighted
pseudo differential operators, we prove the regularizing effect in all (time,
space and velocity) variables on solutions when some mild regularity is imposed
on these solutions. For completeness, we also show that when the initial data
has this mild regularity and Maxwellian type decay in velocity variable, there
exists a unique local solution with the same regularity, so that this solution
enjoys the regularity for positive time
Examining Organizational Response and Employee Coping Behaviors amid the COVID-19 Pandemic
Using the crisis in context theory (CCT) as an ecological framework to understanding human behaviors, the study examined organizational responses and individual employee coping behaviors to mitigate the impact of the COVID-19 pandemic. Drawing from the perspectives of psychology, organization development, and management, the research examined dependent and independent organization and self-initiated actions that employees deemed helpful in coping with the effects of the crisis. Qualitative data were gathered through online survey from 216 employees in the Philippines, a developing country whose major cities were on community quarantine to minimize the spread of the pandemic. The study identified organizational actions or responses to help employees adapt to the COVID-19 crisis. These are: 1) flexible work arrangements, 2) mental health and well-being programs, 3) physical health and safety measures, 4) financial support, 5) provision of material resources, and 6) communication of short and long term plans. Findings also surfaced coping strategies at the individual employee level and how these relate to organizational initiatives. Seven themes emerged from the data- 1) task-focused coping, 2) stress management, 3) social coping, 4) cognitive strategies, 5) learning and development activities, 6) faith-oriented coping, and 7) maladaptive strategies. The analysis highlighted the interrelatedness of organizational responses and employee actions (e.g. how individual task/social coping behaviors were enabled by the company\u27s flexible work arrangements and provision of technological resources amidst physical distancing). Insights from the findings may orient organizational efforts to mitigate the impact of the pandemic as well as encourage and support positive employee coping behaviors
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