Characteristics of the 2nd Harmonic ECR Micro Plasma Sources by Using PIC/MCC Simulations

In this paper we have presented our simulation studies of 2.4 GHz microwave plasma production under the electron cyclotron resonance with an idea to expand the plasma generation conditions into the much lower pressure range and much shorter gap length. As the first for this purpose, we have focused on the influences of applied magnetic field, gas pressure and gap length on the breakdown and maintenance of plasmas. Calculations were performed by using a one-dimensional particle-in-cell/Monte Carlo collisions code with three velocity components. The obtained simulation results are in a good agreement with the available experimental data providing an insight into the resonant electron acceleration for ECR condition and the resonant electron confinement for the 2nd harmonic ECR. In addition, analytical expressions for the breakdown voltage and the trapping field have been derived

Study of Multipactor Effect with Applications to Superconductive Radiofrequency Cavities

In this paper a one-dimensional Particle-in-Cell/Monte Carlo collision code has been used in order to study characteristics of multipactors. For multipactor to occur each electron striking the surface must generate more than one secondary on average. The ratio of primary to secondary electrons is given by the secondary emission yield. For this study, calculations were carried out by using Sternglass model that includes energy dependence of the secondary emission yield. The obtained simulation results for the pressure dependence of the breakdown time follow the scaling law. Number of electrons increases in time, while their mean energy decreases. Since secondary electron emission at the cavity surface plays an important role, simulation results, presented here, can help cavity designers predict multipacting issues before fabrication

Three-Dimensional Simulations of the Surface Topography Evolution of Niobium Superconducting Radio Frequency Cavities

This paper contains results of the three-dimensional simulations of the surface topography evolution of the niobium superconducting radio frequency cavities during isotropic and anisotropic etching modes. The initial rough surface is determined from the experimental power spectral density. The simulation results based on the level set method reveal that the time dependence of the root mean square roughness obeys Family-Viscek scaling law. The growth exponential factors beta are determined for both etching modes. Exponential factor for the isotropic etching is 100 times lower than that for the anisotropic etching mode reviling that the isotropic etching is very useful mechanism of the smoothing

Time-resolved SERS study of the oxygen reduction reaction in ionic liquid electrolytes for non-aqueous lithium-oxygen cells

We use the Raman active bands of O2˙− to probe its changing Lewis basicity through its interaction with various ionic liquid electrolytes at the electrode surface.</p

Direct In Situ Raman Spectroscopic Evidence of Oxygen Reduction Reaction Intermediates at High-Index Pt(hkl) Surfaces

The study of the oxygen reduction reaction (ORR) at high-index Pt(hkl) single crystal surfaces has received considerable interest due to their well-ordered, typical atomic structures and superior catalytic activities. However, it is difficult to obtain direct spectral evidence of ORR intermediates during reaction processes, especially at high-index Pt(hkl) surfaces. Herein, in situ Raman spectroscopy has been employed to investigate ORR processes at high-index Pt(hkl) surfaces containing the [011̅] crystal zone—i.e., Pt(211) and Pt(311). Through control and isotope substitution experiments, in situ spectroscopic evidence of OH and OOH intermediates at Pt(211) and Pt(311) surfaces was successfully obtained. After detailed analysis based on the Raman spectra and theoretical simulation, it was deduced that the difference in adsorption of OOH at high-index surfaces has a significant effect on the ORR activity. This research illuminates and deepens the understanding of the ORR mechanism on high-index Pt(hkl) surfaces and provides theoretical guidance for the rational design of high activity ORR catalysts.This work was financially supported by the National Natural Science Foundation of China (21902137, 21925404, 21775127, and 21427813), the Fundamental Research Funds for the Central Universities (20720190044), the China Postdoctoral Science Foundation (2019M652250), and the China Postdoctoral Innovation Talent Support Program (BX20190184). Support from MINECO through project CTQ2016-76221-P (AEI/FEDER, UE) is greatly acknowledged

Background-Free Quantitative Surface Enhanced Raman Spectroscopy Analysis Using Core-Shell Nanoparticles with an Inherent Internal Standard.

Surface enhanced Raman spectroscopy (SERS) is an ultrasensitive label-free analytical technique that can provide unique chemical and structural fingerprint information. However, gaining reliable quantitative analysis with SERS remains a huge challenge because of poor reproducibility and the instability of nanostructured SERS active surfaces. Herein, an effective strategy of coating Au nanoparticles (NPs) with ultrathin and uniform Prussian blue (PB) shell (Au@PB NPs) was developed for quantitative detection of dopamine (DA) concentrations in blood serum and crystal violet (CV) contaminants in lake water. The only intense PB Raman signal at 2155 cm-1 served as an ideal and interference-free internal standard (IS) for correcting fluctuations in the Raman intensities of analytes. Also, the stability of Au@PB NPs was investigated, exhibiting good functionality in strong acid solutions and thermal stability at 100 °C. This work demonstrates a convenient and fast quantitative SERS technique for detecting analyte concentrations in complex systems and has a great number of potential applications for use in analytical chemistry

In situ Spectroscopic Insight into the Origin of the Enhanced Performance of Bimetallic Nanocatalysts towards the Oxygen Reduction Reaction (ORR).

It is vital to understand the oxygen reduction reaction (ORR) mechanism at the molecular level for the rational design and synthesis of high activity fuel-cell catalysts. Surface enhanced Raman spectroscopy (SERS) is a powerful technique capable of detecting the bond vibrations of surface species in the low wavenumber range, however, using it to probe practical nanocatalysts remains extremely challenging. Herein, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was used to investigate ORR processes on the surface of bimetallic Pt3 Co nanocatalyst structures. Direct spectroscopic evidence of *OOH suggests that ORR undergoes an associative mechanism on Pt3 Co in both acidic and basic environments. Density functional theory (DFT) calculations show that the weak *O adsorption arise from electronic effect on the Pt3 Co surface accounts for enhanced ORR activity. This work shows SHINERS is a promising technique for the real-time observation of catalytic processes

Difficulties in establishing a timely diagnosis of pulmonary artery sarcoma misdiagnosed as chronic thrombo-embolic pulmonary disease: a case report

<p>Abstract</p> <p>Introduction</p> <p>Pulmonary artery sarcomas are rare neoplasms that are often confused with chronic thrombo-embolic disease, as both can have similar clinical and imaging presentation.</p> <p>Case presentation</p> <p>In this report, we present a case of a 50-year-old man initially diagnosed with chronic thrombo-embolic pulmonary disease, but who was later found to have pulmonary artery sarcoma with poor survival prognosis. We review the clinical and imaging characteristics of the two diseases and discuss the difficulties in establishing a timely diagnosis.</p> <p>Conclusion</p> <p>Similar clinical features and imaging presentation of pulmonary artery sarcoma and chronic thrombo-embolic pulmonary disease make definitive diagnosis difficult. This case report also illustrates and emphasizes that in any case with no predisposition factors for embolism, no evidence of deep venous thrombosis and pulmonary emboli, and inadequate relief of symptoms with anticoagulation, an alternative diagnosis of pulmonary artery sarcoma should be considered. If pulmonary artery sarcoma is diagnosed late in the course of the disease, there is usually a poor survival outcome.</p

Eigenmodes of finite length silicon-on-insulator microring resonator arrays

In this paper the eigenmodes of finite length microring resonator arrays have been systematically studied, both analytically using temporal coupled mode theory (CMT), and numerically using two-dimensional finite element method (FEM). The method for obtaining the values of parameters appearing in simplified CMT model using results of FEM calculations is presented. Calculations were carried out by COMSOL FEM packages for a wide range of distances between the rings. The obtained results reveal that the rotational degeneracy is preserved for a wide range of interrings distances. It is shown how the eigenvalue spectrum depends on the number of cavities in the system. The differences for the cases of odd and even numbers of rings, and its implications on actual applications, are discussed in details. The central branch appearing in odd-number arrays plays significant role for the delay-lines and optical buffering applications. Based on the first order perturbation theory, an analytical expressions for the eigenfrequencies of arbitrary (finite) length linear array of microring resonators are derived. The analytical expressions describing eigenfrequencies are useful for determining positions of the maxima in transfer characteristics in microring arrays with external buses

A Simulation Framework for the Ion Transport in Spiral Inflectors

Here, we present some results of the simulations of the transport of an H- ion beam bunch through the spiral inflector of the VINCY cyclotron. Calculations of the electric field were performed using a finite-element method, whereas the trajectories of the particles in the bunch were tracked by solving Newton-Lorentz equations of motion with direct Coulomb interaction between particles included