Optimal Source Parameters Research Articles

Optical variability of the blazar OJ 287 in 2005–2009

Five-year sets of photometric and polarization observations are used to study the variability of the blazar OJ 287. A model with one constant and several variable sources of polarized radiation is considered. Monte-Carlo simulations are used to find the optimal source parameters providing the best agreement between the model and observed relations between the polarization parameters and intensity. The modeling results and four-color photometric data are used to find the spectra of the constant and variable components. Both spectra are power laws, but with different spectral indices. The observed color variability of the object is due to the difference of the color indices of these components and their different contributions to the total observed radiation. It is concluded that the observed variability of the polarization and colors of the blazar OJ 287 in the optical range can be explained with the model used.

Numerical Investigation of Residual Stress in Thick Titanium Alloy Plate Joined with Electron Beam Welding

A finite-element (FE) simulation process integrating three dimensional (3D) with two-dimensional (2D) models is introduced to investigate the residual stress of a thick plate with 50-mm thickness welded by an electron beam. A combined heat source is developed by superimposing a conical volume heat source and a uniform surface heat source to simulate the temperature field of the 2D model with a fine mesh, and then the optimal heat source parameters are employed by the elongated heat source for the 3D simulation without trial simulations. The welding residual stress also is investigated with emphasis on the through-thickness stress for the thick plate. Results show that the agreement between simulation and experiment is good with a reasonable degree of accuracy in respect to the residual stress on the top surface and the weld profile. The through-thickness residual stress of the thick plate induced by electron beam welding is distinctly different from that of the arc welding presented in the references.

SU-GG-T-361: Validation of Dose Calculations with PENFAST (a Fast Monte Carlo Code for TPS in Radiotherapy) Using a Beam Energy Spectrum Reconstructed by a Least Squares Method

Purpose: Conventional treatment planning systems use fast but sometimes not enough accurate numerical calculation methods. Introduction of Monte Carlo (MC) methods allows better accuracy, especially in presence of heterogeneities. Method and Materials: Accuracy on the calculated dose with a MC method depends on the correct description of source parameters: energy spectrum, size or shape of electrons beam. A new method has been developed to determine the energy spectrum of the primary electron beam. It consists in using the least squares (LS) method associated to MC simulation with PENELOPE to reconstruct the spectrum. A phase space file (PSF) is calculated with PENELOPE using these optimized source parameters. This PSF serves as input data for PENFAST to calculate the dose distribution in heterogeneous phantoms (lung and bone). PENFAST is a fast transport algorithm based on PENELOPE and optimized for radiotherapy applications. Depth‐dose and dose profiles calculated with PENFAST are compared to PENELOPE simulations and measurements performed at the LNHB (the French standard laboratory). Both 18 MeV electron beam and 12 MV photon beam generated by a Saturne 43 accelerator are studied. Results: The index gamma test shows that dose distributions simulated with PENELOPE from an energy spectrum reconstructed by LS methods fit the measurements in water much more precisely (3%) than those obtained assuming a gaussian energy spectrum as usual. The dose distributions simulated with PENFAST are also in good agreement with PENELOPE and measurements in the heterogeneous phantoms as well in water. Conclusion: This work demonstrates the ability of the LS method coupled to MC simulations to reconstruct the energy spectrum of a LINAC beam. The good agreement between measurements and MC calculations for depth‐dose curves and dose profiles validates the PENFAST code in heterogeneous configurations.

The Development of Tissue-Engineered Grafts for Reconstructive Cardiothoracic Surgical Applications

Surgical correction of congenital heart defects often requires the use of valves, patches, or conduits to establish anatomic continuity. Homografts, xenografts, or mechanical prosthetic devices are frequently implanted during these surgical procedures. These grafts however lack growth potential, are associated with increased risk of thrombosis and infection and have limited durability, thus increasing the morbidity and mortality of their application in pediatric cardiac surgery. These limitations are being addressed through the development of living, biologic tissue-engineered valves, patches, and conduits. Pilot studies and phase 1 clinical trials are currently underway to evaluate their feasibility, safety, and efficacy. The optimal scaffold, cell source, and conditioning parameters, however, still remain to be determined and are areas of active research.

Desorption Electrospray Ionization (DESI) Analysis of Tryptic Digests/Peptides

INTRODUCTIONThe analytical utility of desorption electrospray ionization (DESI) is such that it can be applied to qualitative proteomics research in the same way as matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) methods, although little work has yet been reported in this regard. Because DESI is a surface analysis technique and easily automated, it can be implemented for high-throughput applications, which include the analysis of chromatographic fractions of digested proteins. The analysis of tryptic peptides follows the same protocols as in typical MALDI or ESI methods, except that the mixture is spotted directly onto an insulating surface, allowed to dry, and analyzed directly without adding matrix compounds (as in the case of MALDI methods). The spectral characteristics are similar to those of ESI in that both singly and multiply charged analyte ions are detected. Spectra are highly similar to electrospray spectra of tryptic digests with regard to the overwhelming presence of multiply charged ions of peptides. DESI-mass spectrometry (DESI-MS) is an emerging technique with great promise, but its application range is still being investigated. Therefore, the protocol for DESI-MS analysis of tryptic digests/peptides presented here provides general procedures used for the applications that have been investigated so far. Optimal ion source parameters and surface types may vary, depending on the application.

Desorption Electrospray Ionization (DESI) Analysis of Intact Proteins/Oligopeptides

INTRODUCTIONDesorption electrospray ionization (DESI) is amenable to the study of intact proteins in complex mixtures, including blood or other biological media. Intact proteins can be desorbed and ionized from the surface under gentle (soft) conditions to produce compact conformations of the protein. A procedure for DESI analysis of intact proteins and oligopeptides using mass spectrometry (MS) is described here. DESI-MS is an emerging technique with great promise, but its application range is still being investigated. Therefore, the protocol presented here provides general procedures used for the applications that have been investigated so far. Optimal ion source parameters and surface types may vary depending on the application.

In Situ Desorption Electrospray Ionization (DESI) Analysis of Tissue Sections

INTRODUCTIONDesorption electrospray ionization (DESI) allows in situ analysis of biological tissues. The analysis of less abundant protein constituents within a tissue sample often requires the removal of lipid species prior to analysis, similar to the situation with matrix-assisted laser desorption/ionization (MALDI). After removal of lipid constituents, the tissue can be treated with protease to degrade proteins present in the tissue. The tryptic products can be investigated directly from the tissue using DESI. The spectra obtained feature ions of tryptic fragments from abundant proteins present in the tissue sample. The digestion is usually not complete; hence, the presence of missed cleavage sites is typical in the peptides detected. The signal is more stable for longer times than in the case of deposited samples, so the recording of mass spectrometry (MS)/MS data is simple in this case. DESI-MS is an emerging technique with great promise, but its application range is still being investigated. Therefore, the protocol for DESI-MS analysis of tissue sections presented here provides general procedures used for the applications that have been investigated so far. Optimal ion source parameters and surface types may vary depending on the application.

InSAR constraints on the source parameters of the 2001 Bhuj earthquake

We present InSAR results of the coseismic displacement field for the January 2001 Bhuj earthquake. Using InSAR data along multiple tracks, we determine the optimal source parameters of the earthquake. The deformation pattern is first modeled assuming uniform slip on an elastic dislocation. A grid search is used to constrain the source location and finiteness assuming a strike, rake, and dip consistent with seismic studies. An inversion for the distributed slip places oblique reverse slip at depth with strike‐slip motion resolved at shallower depths. The estimated size of the event is Mw 7.6. Results also suggest that the postseismic response is minimal.

A profile-/emittance monitor at the Frankfurt 14 GHz ECRIS

A beam profile-/emittance monitor has been developed and tested at the Frankfurt 14 GHz electron cyclotron resonance ion source. It consists of a standard moving slit system in combination with a new type of profile monitor that can easily be integrated into the diagnose boxes of the existing beam line. Utilizing the standard Faraday cup measurements of the beam diagnosis, the system is permanently integrated into the beam line. This is in contrast to the device used so far, which always demanded for a major reconfiguration of the existing beam line, merely for the case of emittance measurements. This device(s) will be introduced at certain diagnose boxes of the beam transport system to meet the increased need of an improved characterization of the beam quality during normal operation as well as for optimizing source parameters. It is also an important input for transport calculations of new beam lines. Such calculations are necessary to control the matching of the beam emittance to the acceptance of the variable-energy radio frequency quadrupole postaccelerator.

Optimization of Discharge Parameters for a Flat-Type Radio-Frequency Glow Discharge Source Coupled to a Quadrupole Mass Spectrometer System

A radio-frequency (rf)-powered glow discharge (GD) atomization/ionization source for nominally flat sample types (>6 mm o.d.) has been designed and coupled to a commercial GD mass spectrometer system, the VG GloQuad. This source was evaluated and optimized for conducting as well as nonconducting samples. A parametric study has been conducted on this rf-GDMS system with respect to discharge power, Ar flow (cell pressure), limiting orifice plate (anode) diameter, and ion sampling distance. Analytical characteristics under the optimized source parameters—including stabilization times (5 min for conducting samples, 60 min for nonconducting samples); repeatability (overall internal <2% RSD, overall external <8% RSD employing ion beam ratios); quantification; and detection limits—were evaluated for both conducting and nonconducting samples.

Earthquake source parameter determination using genetic algorithms

Determination of earthquake source parameters is a non‐linear and multi‐dimensional problem in which trade‐off problems between the parameters can be significant and complicated. Accordingly global optimization is desirable to find the best fit parameters in a large model parameter space. We apply Genetic Algorithms (GA) to search for optimal source parameters in a multiparameter space. Results show that the GA method can rapidly explore a large multiparameter model space and find optimal solutions for the source parameters with a relatively small number of function evaluations. Results with the data of the 1988 Nepal‐India border earthquake indicate that GA determined source parameters better explain the observed waveforms.

Inversion of geodetic data. II. Optimal model of conjugate fault system for the 1927 Tango earthquake.

Parmanent changes in displacement due to the 1927 Tango earthquake (M=7.5) are analyzed by using the method of "geodetic data inversion" developed in a previous paper (Part I; MATSU'URA, 1977), and a set of optimal source parameters is obtained for a system of conjugate faults, the Gomura and the Yamada.Deformation fields are modelled by a multiple-fault system composed of several dimensional faults in an elastic half-space, and the optimization of model parameters is accomplished through a process of successive iteration of inversions for 85 triangulation and 25 levelling data around the seismic faults.The optimal fault parameters obtained are D (dislocation)=3.7m, δ(dipangle)=64°E, λ(slip direction)=-8°, L(length)=33km, W(width)=19km, d(depth)=0.4km and θ(strike of fault)=N24°W for the Gomura fault, and D=1.8m, δ=58°N, λ=120°, L=15km, W=9km, d=0.2km and θ=N77°E for the Yamada fault, where the slip direction is measured counterclockwise from horizon on the fault plane. These results indicate that the two seismic faults constitute a system of conjugate faults caused by a single stress system of NW-SE compression.A computer program for the geodetic data inversion is completed, by which a set of optimal source parameters of seismic and aseismic events can be obtained from the observed static displacement data.

The determination of uranium in rocks by inductively coupled plasma-optical emission spectrometry

A method for the determination of uranium in rock samples by emission spectrometry is presented. The rock is dissolved and the uranium content determined by nebulizing the solution into an inductively coupled-plasma optical excitation source. Various spectral lines were investigated. The uranium emission at 378.28 nm -was chosen because of its relative freedom from matrix element spectral interferences. For this emission, a practical detection limit of 0.1 p.p.m. in solution was achieved by optimizing source parameters (power, flow-rate, observation height). Results are compared with those obtained by a number of other techniques.