A Calculation Method of X-Ray Emitted Intensity in Multi-Layer Films by Monte Carlo Simulation

A calculation method of X-ray emitted intensity in multi-layer films is proposed in this paper. The method is based on the work developed by us: (1) a simplified physical model of electron scattering and Monte Carlo evaluations in a single medium and in multi-layer media and (2) the theories and the formulae for excitation, absorption and fluorescence of characteristic X-rays. The intensity ratio of X-rays for the known thickness films, Au/Cu/Si and Cr/Ni/Si, were calculated at 20, 25 and 30 keV. Calculated results are compared with experimental values of electron microprobe analysis for the multi-layer film specimens, and the correspondence is excellent. The work lays foundations for X-ray quantitative microanalysis of multi-layer specimens

An Analytical Method of Determining Thickness of Multi-Layer Films with Electron Microprobe

In the previous work we have developed a series of theoretical corrections for calculating the emitted X-ray intensity in multi-layer films. By the use of these theories, along with careful experimental operation of the electron probe microanalysis (EPMA) and Monte Carlo iteration calculation, the thickness of each layer in multi-layer films can be determined. To test the reliability of this method, the multi-layer film specimens Au/Cu/Si, Cu/Au/Si and Ag/Cr/Si of known thicknesses were analyzed at 20, 25, 30 and 35 keV. The percentage relative errors between the thicknesses determined using the correction procedures and those measured using nuclear backscattering are less than 10%, the average value of the errors is 4.6%. The method may be extended to the calculations of determining element concentrations for the multi-layer specimens of known thicknesses

A Calculation Method for Quantitative X-Ray Microanalysis for Microparticle Specimens by Monte Carlo Simulation

A calculation method for quantitative X-ray microanalysis (QXMA) for microparticle specimens of a compound with various shapes is proposed in this paper. On the basis of a simplified physical model, the scattering of electrons in particles is calculated by Monte Carlo simulation. We have derived a series of evaluation formulae of the absorption and fluorescence of characteristic X-rays for the particles with regular shapes. With the use of these theories, along with an iteration calculation, compositions of microparticle specimens can be obtained from the measured X-ray intensity ratios. In order to examine the reliability of the method, a large number of electron probe experiments and analysis calculations were carried out for the microparticle specimens of a variety of geometric shapes, dimensions and compositions. Agreement of calculated concentrations using our method with known compositions of the analyzed particle specimens is fairly good. In practical work, calculation formulae for particle specimens with irregular shapes can be replaced by those of particles with approximate regular shapes

A Theory and Monte Carlo Calculation on Low Energy Electron Scattering in Solids

Low energy electron scattering (LEES) courses in solids are described by using a strict theory and direct simulation method proposed in this paper: we have improved Pendry\u27s method based on the partial wave expansion, which can be applied to calculate the elastic scattering between an electron and atoms. The contributions of shell electrons, conductive electrons and plasma excitations are considered in the calculation of the inelastic scattering; electron scattering and cascade process of secondary electrons are simulated by Monte Carlo method. The secondary electron yields, the energy spectra curve and the backscattering electron coefficients for Cu were evaluated at the various energies, the theoretical results are in agreement with the Koshikawa\u27s experiments

Nanodiamond-Gutta Percha Composite Biomaterials for Root Canal Therapy.

Root canal therapy (RCT) represents a standard of treatment that addresses infected pulp tissue in teeth and protects against future infection. RCT involves removing dental pulp comprising blood vessels and nerve tissue, decontaminating residually infected tissue through biomechanical instrumentation, and root canal obturation using a filler material to replace the space that was previously composed of dental pulp. Gutta percha (GP) is typically used as the filler material, as it is malleable, inert, and biocompatible. While filling the root canal space with GP is the standard of care for endodontic therapies, it has exhibited limitations including leakage, root canal reinfection, and poor mechanical properties. To address these challenges, clinicians have explored the use of alternative root filling materials other than GP. Among the classes of materials that are being explored as novel endodontic therapy platforms, nanodiamonds (NDs) may offer unique advantages due to their favorable properties, particularly for dental applications. These include versatile faceted surface chemistry, biocompatibility, and their role in improving mechanical properties, among others. This study developed a ND-embedded GP (NDGP) that was functionalized with amoxicillin, a broad-spectrum antibiotic commonly used for endodontic infection. Comprehensive materials characterization confirmed improved mechanical properties of NDGP over unmodified GP. In addition, digital radiography and microcomputed tomography imaging demonstrated that obturation of root canals with NDGP could be achieved using clinically relevant techniques. Furthermore, bacterial growth inhibition assays confirmed drug functionality of NDGP functionalized with amoxicillin. This study demonstrates a promising path toward NDGP implementation in future endodontic therapy for improved treatment outcomes

Accelerated increase in the Arctic tropospheric warming events surpassing stratospheric warming events during winter

In January 2016, a robust reversal of the Arctic Oscillation (AO) took place associated with a rapid tropospheric warming in the Arctic region; this was followed by the occurrence of a classic sudden stratospheric warming in March-April. The succession of these two distinct Arctic warming events provides a stimulating opportunity to examine their characteristics in terms of similarities and differences. Historical cases of these two types of Arctic warming were identified and validated based upon tropical linkages with the Madden-Julian Oscillation and El Niño as well as those documented in previous studies. Our results indicate a recent and accelerated increase in the tropospheric warming type versus a flat trend in stratospheric warming type. The relatively shorter duration and rapid transition of tropospheric warming events suggest a link to the documented increase in midlatitude weather extremes during boreal winter. Forced simulations with an atmospheric general circulation model suggest that the reduced Arctic sea ice contributes to the observed increase in the tropospheric warming events and associated impact on the anomalously cold Siberia

Pulsed Wave Doppler Ultrasound Is Useful to Assess Vasomotor Response in Patients with Multiple System Atrophy and Well Correlated with Tilt Table Study

The study aim was to assess sympathetic vasomotor response (SVR) by using pulsed wave Doppler (PWD) ultrasound in patients with multiple system atrophy (MSA) and correlate with the tilt table study. We recruited 18 male patients and 10 healthy men as controls. The SVR of the radial artery was evaluated by PWD, using inspiratory cough as a provocative maneuver. The response to head-up tilt was studied by a tilt table with simultaneous heart rate and blood pressure recording. The hemodynamic variables were compared between groups, and were examined by correlation analysis. Regarding SVR, MSA patients exhibited a prolonged latency and less heart rate acceleration following inspiratory cough. Compared with the tilt table test, the elevation of heart rate upon SVR was positively correlated to the increase of heart rate after head-up tilt. The correlation analysis indicated that the magnitude of blood pressure drop from supine to upright was positively associated with the SVR latency but negatively correlated with the heart rate changes upon SVR. The present study demonstrated that blunted heart rate response might explain MSA's vulnerability to postural challenge. PWD may be used to predict cardiovascular response to orthostatic stress upon head-up tilt in MSA patients

Substrate Specificity and Plasticity of FERM-Containing Protein Tyrosine Phosphatases

SummaryEpidermal growth factor receptor (EGFR) pathway substrate 15 (Eps15) is a newly identified substrate for protein tyrosine phosphatase N3 (PTPN3), which belongs to the FERM-containing PTP subfamily comprising five members including PTPN3, N4, N13, N14, and N21. We solved the crystal structures of the PTPN3-Eps15 phosphopeptide complex and found that His812 of PTPN3 and Pro850 of Eps15 are responsible for the specific interaction between them. We defined the critical role of the additional residue Tyr676 of PTPN3, which is replaced by Ile939 in PTPN14, in recognition of tyrosine phosphorylated Eps15. The WPD loop necessary for catalysis is present in all members but not PTPN21. We identified that Glu instead of Asp in the WPE loop contributes to the catalytic incapability of PTPN21 due to an extended distance beyond protonation targeting a phosphotyrosine substrate. Together with in vivo validations, our results provide novel insights into the substrate specificity and plasticity of FERM-containing PTPs

Multi-user video streaming using unequal error protection network coding in wireless networks

In this paper, we investigate a multi-user video streaming system applying unequal error protection (UEP) network coding (NC) for simultaneous real-time exchange of scalable video streams among multiple users. We focus on a simple wireless scenario where users exchange encoded data packets over a common central network node (e.g., a base station or an access point) that aims to capture the fundamental system behaviour. Our goal is to present analytical tools that provide both the decoding probability analysis and the expected delay guarantees for different importance layers of scalable video streams. Using the proposed tools, we offer a simple framework for design and analysis of UEP NC based multi-user video streaming systems and provide examples of system design for video conferencing scenario in broadband wireless cellular networks