Analytical coupled-wave model for photonic crystal quantum cascade lasers

A coupled-wave model is developed for photonic-crystal quantum cascade lasers. The analytical model provides an efficient analysis of full three-dimensional large-area device structure, and the validity is confirmed via simulations and previous experimental results.Comment: 21 pages and 8 figure

Dynamic responses of non-ballast track structures subjected to high-speed train loads at the welded rail joint

This paper presents a numerical study on the dynamic responses of the non-ballast track structures under the high-speed train load that is excited by the rail irregularity at the welded rail joint. In this study, a multi-body dynamics model with 10 degrees of freedom is built to model a high-speed vehicle and a finite element model is established to simulate the non-ballast track. A mathematical model is also given to characterize the geometry of the local rail irregularity at the welded rail joint. By coupling the high-speed vehicle model and the track model and taking the mathematical model of the welded rail joint as an input, the dynamic responses of the non-ballast track structures under a rail vehicle running at a high speed are simulated and discussed in this paper. The wheel/rail force and the rail and slab vibration acceleration are investigated to demonstrate the significant dynamic effects on the track structures due to the welded rail joint

The K-band properties of Seyfert 2 galaxies

It is well known that the [O {\sc iii}]$\lambda$5007 emission line and hard X-ray(2-10keV) luminosities are good indicators of AGN activities and that the near and mid-infrared emission of AGN originates from re-radiation of dusty clouds heated by the UV/optical radiation from the accretion disk. In this paper we present a study of the near-infrared K-band (2.2$\mu$m) properties for a sample of 65 Seyfert 2 galaxies. By using the AGN/Bulge/Disk decomposition technique, we analyzed the 2MASS K$_{\rm S}$-band images for Seyfert 2 galaxies in order to derive the K$_{\rm S}$- band magnitudes for the central engine, bulge, and disk components. We find that the K$_{\rm S}$-band magnitudes of the central AGN component in Seyfert 2 galaxies are tightly correlated with the [O {\sc iii}]$\lambda$5007 and the hard X-ray luminosities, which suggests that the AGN K-band emission is also an excellent indicator of the nuclear activities at least for Seyfert 2 galaxies. We also confirm the good relation between the central black hole masses and bulge's K-band magnitudes for Seyfert 2s.Comment: 7 pages, 4 figures, accepted for publication in A&

IC 225: a dwarf elliptical galaxy with a peculiar blue core

We present the discovery of a peculiar blue core in the elliptical galaxy IC 225 by using images and spectrum from the Sloan Digital Sky Survey (SDSS). The outer parts of the surface brightness profiles of u-, g-, r-, i- and z-band SDSS images for IC 225 are well fitted with an exponential function. The fitting results show that IC 225 follows the same relations between the magnitude, scale length and central surface brightness for dwarf elliptical galaxies. Its absolute blue magnitude (M_B) is -17.14 mag, all of which suggest that IC 225 is a typical dwarf elliptical galaxy. The g-r color profile indicates a very blue core with a radius of 2 arcseconds, which is also clearly seen in the RGB image made of g-, r- and i-band SDSS images. The SDSS optical spectrum exhibits strong and very narrow nebular emission lines. The metal abundances derived by the standard methods, which are 12+log(O/H) = 8.98, log(N/O) = -0.77 and 12+log(S+/H+) = 6.76, turn out to be significantly higher than that predicted by the well-known luminosity-metallicity relation. After carefully inspecting the central region of IC 225, we find that there are two distinct nuclei, separated by 1.4 arcseconds, the off-nucleated one is even bluer than the nucleus of IC 225. The asymmetric line profiles of higher-order Balmer lines indicate that the emission lines are bluer shifted relative to the absorption lines, suggesting that the line emission arises from the off-center core, whose nature is a metal-rich Hii region. To the best of our knowledge, it is the first high-metallicity Hii region detected in a dwarf elliptical galaxy.Comment: 7 figures, accepted for publication in A

Novel Quasi‐Liquid K‐Na Alloy as a Promising Dendrite‐Free Anode for Rechargeable Potassium Metal Batteries

Rechargeable potassium metal batteries are promising energy storage devices with potentially high energy density and markedly low cost. However, eliminating dendrite growth and achieving a stable electrode/electrolyte interface are the key challenges to tackle. Herein, a novel "quasi-liquid" potassium-sodium alloy (KNA) anode comprising only 3.5 wt% sodium (KNA-3.5) is reported, which exhibits outstanding electrochemical performance able to be reversibly cycled at 4 mA cm-2 for 2000 h. Moreover, it is demonstrated that adding a small amount of sodium hexafluorophosphate (NaPF6 ) into the potassium bis(fluorosulfonyl)imide electrolyte allows for the formation of the "quasi-liquid" KNA on electrode surface. Comprehensive experimental studies reveal the formation of an unusual metastable KNa2 phase during plating, which is believed to facilitate simultaneous nucleation and suppress the growth of dendrites, thereby improving the electrode's cycle lifetime. The "quasi-liquid" KNA-3.5 anode demonstrates markedly enhanced electrochemical performance in a full cell when pairing with Prussian blue analogs or sodium rhodizonate dibasic as the cathode material, compared to the pristine potassium anode. Importantly, unlike the liquid KNA reported before, the "quasi-liquid" KNA-3.5 exhibits good processability and can be readily shaped into sheet electrodes, showing substantial promise as a dendrite-free anode in rechargeable potassium metal batteries.Z.T. acknowledges the financial support of Maria Curie COFUND fellowship (Grant No. 713640). Z.L. thanks the financial support of China Scholarship Council (Grant No. 201 806 400 066). This project was partly funded by the “Baterias 2030” project through the Mobilizadore Programme by the National Innovation Agency of Portugal (Grant No. POCI-01-0247- FEDER-046109). G.Y. acknowledges the financial support from the Welch Foundation Award F-1861. The authors thank Dr. Artur Martins for his assistance in mechanical property measurement.info:eu-repo/semantics/publishedVersio

ISPTM: an Iterative Search Algorithm for Systematic Identification of Post-translational Modifications from Complex Proteome Mixtures

Identifying protein post-translational modifications (PTMs) from tandem mass spectrometry data of complex proteome mixtures is a highly challenging task. Here we present a new strategy, named iterative search for identifying PTMs (ISPTM), for tackling this challenge. The ISPTM approach consists of a basic search with no variable modification, followed by iterative searches of many PTMs using a small number of them (usually two) in each search. The performance of the ISPTM approach was evaluated on mixtures of 70 synthetic peptides with known modifications, on an 18-protein standard mixture with unknown modifications and on real, complex biological samples of mouse nuclear matrix proteins with unknown modifications. ISPTM revealed that many chemical PTMs were introduced by urea and iodoacetamide during sample preparation and many biological PTMs, including dimethylation of arginine and lysine, were significantly activated by Adriamycin treatment in NM associated proteins. ISPTM increased the MS/MS spectral identification rate substantially, displayed significantly better sensitivity for systematic PTM identification than the conventional all-in-one search approach and offered PTM identification results that were complementary to InsPecT and MODa, both of which are established PTM identification algorithms. In summary, ISPTM is a new and powerful tool for unbiased identification of many different PTMs with high confidence from complex proteome mixtures

Exciton emission of quasi-2D InGaN in GaN matrix grown by molecular beam epitaxy

We investigate the emission from confined excitons in the structure of a single-monolayer-thick quasi-two-dimensional (quasi-2D) Inx Ga1-x N layer inserted in GaN matrix. This quasi-2D InGaN layer was successfully achieved by molecular beam epitaxy (MBE), and an excellent in-plane uniformity in this layer was confirmed by cathodoluminescence mapping study. The carrier dynamics have also been investigated by time-resolved and excitation-power-dependent photoluminescence, proving that the recombination occurs via confined excitons within the ultrathin quasi-2D InGaN layer even at high temperature up to ∼220 K due to the enhanced exciton binding energy. This work indicates that such structure affords an interesting opportunity for developing high-performance photonic devices