Spatiotemporal Patterns and Predictability of Cyberattacks

Y.C.L. was supported by Air Force Office of Scientific Research (AFOSR) under grant no. FA9550-10-1-0083 and Army Research Office (ARO) under grant no. W911NF-14-1-0504. S.X. was supported by Army Research Office (ARO) under grant no. W911NF-13-1-0141. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Radiative transitions of the helium atom in highly magnetized neutron star atmospheres

Recent observations of thermally emitting isolated neutron stars revealed spectral features that could be interpreted as radiative transitions of He in a magnetized neutron star atmosphere. We present Hartree-Fock calculations of the polarization-dependent photoionization cross sections of the He atom in strong magnetic fields ranging from 10^12 G to 10^14 G. Convenient fitting formulae for the cross sections are given as well as related oscillator strengths for various bound-bound transitions. The effects of finite nucleus mass on the radiative absorption cross sections are examined using perturbation theory.Comment: 14 pages, 7 figures. Minor changes. MNRAS in pres

Human African trypanosomiasis : the current situation in endemic regions and the risks for non-endemic regions from imported cases

Human African trypanosomiasis (HAT) is caused by Trypanosoma brucei gambiense and T. b. rhodesiense and caused devastating epidemics during the 20th century. Due to effective control programs implemented in the last two decades, the number of reported cases has fallen to a historically low level. Although fewer than 977 cases were reported in 2018 in endemic countries, HAT is still a public health problem in endemic regions until it is completely eliminated. In addition, almost 150 confirmed HAT cases were reported in non-endemic countries in the last three decades. The majority of non-endemic HAT cases were reported in Europe, United States and South Africa, due to historical alliances, economic links or geographic proximity to disease endemic countries. Furthermore, with the implementation of the “Belt and Road” project, sporadic imported HAT cases have been reported in China as a warning sign of tropical diseases prevention. In this paper, we explore and interpret the data on HAT incidence and find no positive correlation between the number of HAT cases from endemic and non-endemic countries.This data will provide useful information for better understanding the imported cases of HAT globally in the post-elimination phase

The secondary Bjerknes force between two oscillating bubbles in Kelvin-Voigt-type viscoelastic fluids driven by harmonic ultrasonic pressure

The interaction between two small bubbles experiencing transient cavitation in a nonlinear Kelvin-Voigt fluid is investigated. The time-delay effect in the interaction is incorporated in the coupled Keller-Miksis model. The refined model predicts that bubbles with radii smaller than 2μm will be repelled by large bubbles, in contrast to predictions from previous models. The matching pressure needed to obtain same level of transient cavitation in different Kelvin-Voigt fluids is shown to depend mainly on the shear modulus and is insensitive to other parameters, which makes it a useful parameter to correlate the results. When the radii of the bubbles fall between 4μm and 6μm, the secondary Bjerknes force obtained with matching pressures shows only weak dependence on the shear modulus. For the pressure amplitudes investigated, equilibrium distances can be found between two bubbles when the equilibrium radius of one of the bubbles is in a narrow range around 2 μm. The equilibrium distance decreases when the shear modulus is increased. A simple relation between the two quantities is established

Engineering d-band center of FeN<inf>4</inf> moieties for efficient oxygen reduction reaction electrocatalysts

Atomically-dispersed FeN4 moieties are emerging as low-cost electrocatalysts for oxygen reduction reaction (ORR), which can be applied in fuel cells and metal-air batteries. Whereas, the unsatisfactory position of the d-band center from the metal sites offered by FeN4 affects the adsorption-desorption behaviors of oxygenated intermediates, further impeding the improvement of their ORR performances. Herein, we report a well-designed diatomic Fe/Zn-CNHC catalyst on a microporous hollow support. This strategy drives the position of the d-band center of Fe upward, thus making FeN4 active sites more favorable and stable during the ORR kinetic processes. The material exhibits an excellent ORR activity with a half-wave potential of 0.91 V and excellent stability (insignificant attenuation after 5,000 cycles), surpassing commercial Pt/C and many other single-atom catalysts. DFT calculations further indicate that the tuning effect of Zn on the d-orbital electron distribution of Fe facilitates the stretching and cleavage of Fe-O, thus accelerating the rate-determining step. This work presents a simple strategy to fabricate well-defined diatomic coordination in single-atom ORR electrocatalysts and inspires future research on developing new syntheses to control the coordination of single-atom electrocatalysts

Surface response of spherical core-shell structured nanoparticle by optically induced elastic oscillations of soft shell against hard core

The optically induced oscillatory response of a spherical two-component, shell-core structured, nanoparticle by nodeless elastic vibrations of soft peripheral shell against hard and dynamically immobile inner core is considered. The eigenfrequencies of the even-parity, spheroidal and odd-parity torsional vibrational modes trapped in the finite-depth shell are obtained which are of practical interest for modal specification of individual resonances in spectra of resonant scattering of long wavelength electromagnetic waves by ultrafine particles.Comment: Surface Review and Letters (World Scientific) Year: 2009 Vol: 16 Issue: 1 (February 2009) Page: 5 - 1