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X-ray stereo microscopy for investigation of dynamics in soils
The presented combination of stereo imaging and elemental mapping with soft X-ray microscopy reveals the spatial arrangement of naturally aqueous colloidal systems, e.g. iron oxides in soil colloid clusters. Changes in the spatial arrangement can be induced by manipulating the sample mounted to the X-ray microscope and thus be investigated directly.
Date:
September 16, 2008
Creator:
Gleber, S.-C.; Sedlmair, J.; Bertilson, M.; von Hofsten, O.; Heim, S.; Guttmann, P. et al.
Object Type:
Article
System:
The UNT Digital Library
Remaining Sites Verification Package for the 100-B-21:2 Subsite (100-B/C Discovery Pipeline DS-100BC-002), Waste Site Reclassification Form 2008-003
The 100-B-21:2 waste site consists of the immediate area of the DS-100BC-02 pipeline. In accordance with this evaluation, the confirmatory and verification sampling results support a reclassification of this site to Interim Closed Out. The results of verification sampling show that residual contaminant concentrations do not preclude any future uses and allow for unrestricted use of shallow zone soils. The results also demonstrate that residual contaminant concentrations are protective of groundwater and the Columbia River.
Date:
June 16, 2008
Creator:
Capron, J. M.
Object Type:
Report
System:
The UNT Digital Library
Remaining Sites Verification Package for the 331 Life Sciences Laboratory Drain Field Septic System, Waste Site Reclassification Form 2008-020
The 331 Life Sciences Laboratory Drain Field (LSLDF) septic system waste site consists of a diversion chamber, two septic tanks, a distribution box, and a drain field. This septic system was designed to receive sanitary waste water, from animal studies conducted in the 331-A and 331-B Buildings, for discharge into the soil column. However, field observations and testing suggest the 331 LSLDF septic system did not receive any discharges. In accordance with this evaluation, the confirmatory sampling results support a reclassification of the 331 LSLDF waste site to No Action. This site does not have a deep zone or other condition that would warrant an institutional control in accordance with the 300-FF-2 ROD under the industrial land use scenario.
Date:
October 16, 2008
Creator:
Capron, J. M.
Object Type:
Report
System:
The UNT Digital Library
Measurement of the Branching Fractions of the Rare Decays B0 to Ds(*)+pi-,B0 to Ds(*)+rho-, and B0 to Ds(*)-K(*)+
The authors report the measurement of the branching fractions of the rare decays B{sup 0} {yields} D{sub s}{sup (*)+} {pi}{sup -}, B{sup 0} {yields} D{sub s}{sup (*)+} {rho}{sup -}, and B{sup 0} {yields} D{sub s}{sup (*)-} K{sup (*)+} in a sample of 381 x 10{sup 6} {Upsilon}(4S) decays into B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring. They present evidence for the decay B{sup 0} {yields} D{sub s}{sup -} K*{sup +} and the vector-vector decays B{sup 0} {yields} D{sub s}{sup *+} {rho}{sup -} and B{sup 0} {yields} D{sub s}{sup *-} K{sup *+}, as well as the first measurement of the vector meson polarization in these decays. They also determine the ratios of the CM-suppressed to CKM-favored amplitudes r(D{sup (*)}{pi}) and r(D{sup (*)}{rho}) in decays B{sup 0} {yields} D{sup (*)}{sup {+-}}{pi}{sup {-+}} and B{sup 0} {yields} D{sup (*)}{sup {+-}}{rho}{sup {-+}}, and comment on the prospects for measuring the Cp observable sin(2{beta} + {gamma}).
Date:
April 16, 2008
Creator:
Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
Object Type:
Article
System:
The UNT Digital Library
Binary Pseudo-random Grating Standard for Calibration of Surface Profilometers
We suggest and describe the use of a binary pseudo-random (BPR) grating as a standard test surface for measurement of the modulation transfer function (MTF) of interferometric microscopes. Knowledge of the MTF of a microscope is absolutely necessary to convert the measured height distribution of a surface undergoing metrology into an accurate power spectral density (PSD) distribution. For an'ideal' microscope with an MTF function independent of spatial frequency out to the Nyquist frequency of the detector array with zero response at higher spatial frequencies, a BPR grating would produce a flat 1D PSD spectrum, independent of spatial frequency. For a'real' instrument, the MTF is found as the square root of the ratio of the PSD spectrum measured with the BPR grating to the'ideal,' spatial frequency independent, PSD spectrum. We present the results from a measurement of the MTF of MicromapTM-570 interferometric microscope demonstrating a high efficiency for the calibration method.
Date:
January 16, 2008
Creator:
Yashchuk, Valeriy; Yashchuk, Valeriy V.; McKinney, Wayne R. & Takacs, Peter Z.
Object Type:
Article
System:
The UNT Digital Library
Seismic Data for Evaluation of Ground Motion Hazards in Las Vegas in Support of Test Site Readiness Ground Motion
In this report we describe the data sets used to evaluate ground motion hazards in Las Vegas from nuclear tests at the Nevada Test Site. This analysis is presented in Rodgers et al. (2005, 2006) and includes 13 nuclear explosions recorded at the John Blume and Associates network, the Little Skull Mountain earthquake and a temporary deployment of broadband station in Las Vegas. The data are available in SAC format on CD-ROM as an appendix to this report.
Date:
January 16, 2008
Creator:
Rodgers, A
Object Type:
Report
System:
The UNT Digital Library
Search for New Physics Beyond the Standard Model at BaBar
A review of selected recent BaBar results are presented that illustrate the ability of the experiment to search for physics beyond the standard model. The decays B {yields} {tau}{nu} and B {yields} s{gamma} provide constraints on the mass of a charged Higgs. Searches for Lepton Flavour Violation could provide a clear signal for beyond the standard model physics. Babar does not observe any signal for New Physics with the current dataset.
Date:
April 16, 2008
Creator:
Barrett, Matthew & U., /Brunel
Object Type:
Article
System:
The UNT Digital Library
Search for Rare Quark-Annihilation Decays, Charged B Mesons Decaying to Charged D(S) Mesons And Phi Mesons
The authors report on a search for the decay B{sup {+-}} {yields} D{sub s}{sup (*){+-}} {phi} using 212.2 fb{sup -1} of data collected with the BABAR detector at the PEP-II B Factory at the Stanford Linear Accelerator Center between 1999 and 2004. This sample of 234 x 10{sup 6} e{sup +}e{sup -} {yields} {Upsilon}(4S) {yields} B{bar B} events yields no significant signal. They report the Bayesian upper limits {Beta}(B{sup {+-}} {yields} D{sub s}{sup {+-}} {phi}) x {Beta}(D{sub s}{sup {+-}} {yields} {phi}{pi}{sup {+-}}) < 8.6 x 10{sup -8} and {Beta}(B{sup {+-}} {yields} D*{sub s}{sup {+-}}{phi}) x {Beta}(D{sub s}{sup {+-}} {yields} {phi}{pi}{sup {+-}}) < 5.4 x 10{sup -7} at the 90% C.L. Using the latest measurement of {Beta}(D{sub s}{sup {+-}} {yields} {phi}{pi}{sup {+-}}), they report: {Beta}(B{sup {+-}} {yields} D{sub s}{sup {+-}}{phi}) < 1.8 x 10{sup -6} and {Beta}(B{sup {+-}} {yields} D*{sub s}{sup {+-}}{phi}) < 1.1 x 10{sup -5} at the 90% C.L.
Date:
January 16, 2008
Creator:
Cunha, J.Adam M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Scale Matters: An Action Plan for Realizing Sector-Wide"Zero-Energy" Performance Goals in Commercial Buildings
It is widely accepted that if the United States is to reduce greenhouse gas emissions it must aggressively address energy end use in the building sector. While there have been some notable but modest successes with mandatory and voluntary programs, there have also been puzzling failures to achieve expected savings. Collectively, these programs have not yet reached the majority of the building stock, nor have they yet routinely produced very large savings in individual buildings. Several trends that have the potential to change this are noteworthy: (1) the growing market interest in 'green buildings' and 'sustainable design', (2) the major professional societies (e.g. AIA, ASHRAE) have more aggressively adopted significant improvements in energy efficiency as strategic goals, e.g. targeting 'zero energy', carbon-neutral buildings by 2030. While this vision is widely accepted as desirable, unless there are significant changes to the way buildings are routinely designed, delivered and operated, zero energy buildings will remain a niche phenomenon rather than a sector-wide reality. Toward that end, a public/private coalition including the Alliance to Save Energy, LBNL, AIA, ASHRAE, USGBC and the World Business Council for Sustainable Development (WBCSD) are developing an 'action plan' for moving the U.S. commercial building sector towards zero …
Date:
June 16, 2008
Creator:
Selkowitz, Stephen; Selkowitz, Stephen; Granderson, Jessica; Haves, Philip; Mathew, Paul & Harris, Jeff
Object Type:
Article
System:
The UNT Digital Library
Merger Histories of Galaxy Halos and Implications for Disk Survival
The authors study the merger histories of galaxy dark matter halos using a high resolution {Lambda}CDM N-body simulation. The merger trees follow {approx} 17,000 halos with masses M{sub 0} = (10{sup 11} - 10{sup 13})h{sup -1}M{sub {circle_dot}} at z = 0 and track accretion events involving objects as small as m {approx_equal} 10{sup 10} h{sup -1}M{sub {circle_dot}}. They find that mass assembly is remarkably self-similar in m/M{sub 0}, and dominated by mergers that are {approx}10% of the final halo mass. While very large mergers, m {approx}> 0.4 M{sub 0}, are quite rare, sizeable accretion events, m {approx} 0.1 M{sub 0}, are common. Over the last {approx} 10 Gyr, an overwhelming majority ({approx} 95%) of Milky Way-sized halos with M{sub 0} = 10{sup 12} h{sup -1}M{sub {circle_dot}} have accreted at least one object with greater total mass than the Milky Way disk (m > 5 x 10{sup 10} h{sup -1}M{sub {circle_dot}}), and approximately 70% have accreted an object with more than twice that mass (m > 10{sup 11} h{sup -1}M{sub {circle_dot}}). The results raise serious concerns about the survival of thin-disk dominated galaxies within the current paradigm for galaxy formation in a {Lambda}CDM universe. in order to achieve a {approx} 70% …
Date:
May 16, 2008
Creator:
Stewart, Kyle R.; Bullock, James S.; Wechsler, Risa H.; Maller, Ariyeh H. & Zentner, Andrew R.
Object Type:
Article
System:
The UNT Digital Library
2007 LDRD ANNUAL REPORT
I am pleased to present the fiscal year 2007 Laboratory Directed Research and Development (LDRD) annual report. This represents the first year that SRNL has been eligible for LDRD participation and our results to date demonstrate we are off to an excellent start. SRNL became a National Laboratory in 2004, and was designated the 'Corporate Laboratory' for the DOE Office of Environmental Management (EM) in 2006. As you will see, we have made great progress since these designations. The LDRD program is one of the tools SRNL is using to enable achievement of our strategic goals for the DOE. The LDRD program allows the laboratory to blend a strong basic science component into our applied technical portfolio. This blending of science with applied technology provides opportunities for our scientists to strengthen our capabilities and delivery. The LDRD program is vital to help SRNL attract and retain leading scientists and engineers who will help build SRNL's future and achieve DOE mission objectives. This program has stimulated our research staff creativity, while realizing benefits from their participation. This investment will yield long term dividends to the DOE in its Environmental Management, Energy, and National Security missions.
Date:
December 16, 2008
Creator:
French, T
Object Type:
Report
System:
The UNT Digital Library
Net Weight Issue LLNL DOE-STD-3013 Containers
The following position paper will describe DOE-STD-3013 container sets No.L000072 and No.L000076, and how they are compliant with DOE-STD-3013-2004. All masses of accountable nuclear materials are measured on LLNL certified balances maintained under an MC&A Program approved by DOE/NNSA LSO. All accountability balances are recalibrated annually and checked to be within calibration on each day that the balance is used for accountability purposes. A statistical analysis of the historical calibration checks from the last seven years indicates that the full-range Limit of Error (LoE, 95% confidence level) for the balance used to measure the mass of the contents of the above indicated 3013 containers is 0.185 g. If this error envelope, at the 95% confidence level, were to be used to generate an upper-limit to the measured weight of the containers No.L000072 and No.L000076, the error-envelope would extend beyond the 5.0 kg 3013-standard limit on the package contents by less than 0.3 g. However, this is still well within the intended safety bounds of DOE-STD-3013-2004.
Date:
January 16, 2008
Creator:
Wilk, P
Object Type:
Report
System:
The UNT Digital Library
CALCULATION OF DEMONSTRATION BULK VITRIFICATION SYSTEM MELTER INLEAKAGE AND OFF-GAS GENERATION RATE
The River Protection Project (RPP) mission is to safely store, retrieve, treat, immobilize, and dispose of the Hanford Site tank waste. The Demonstration Bulk Vitrification System (DBVS) is a research and development project whose objective is to demonstrate the suitability of Bulk Vitrification treatment technology waste form for disposing of low-activity waste from the Tank Farms. The objective of this calculation is to determine the DBVS melter inleakage and off-gas generation rate based on full scale testing data from 38D. This calculation estimates the DBVS melter in leakage and gas generation rate based on test data. Inleakage is estimated before the melt was initiated, at one point during the melt, and at the end of the melt. Maximum gas generation rate is also estimated.
Date:
April 16, 2008
Creator:
TH, MAY
Object Type:
Report
System:
The UNT Digital Library
The Beta-Neutrino Correlation in Sodium-21 and Other Nuclei
We have measured the mbox beta - nu correlation coefficient,a_beta nu, in 21Na using a laser-trapped sample. We measure the energyspectrum of the recoil nuclei by measuring their time-of-flight incoincidence with the atomic electrons shaken off in beta decay. Highdetectionefficiency of these low-energy electrons allows good countingstatistics, even with low trap density, which suppresses thephotoassociation of molecular sodium, which can cause a large systematicerror. Our measurement, with a 1 percent fractional uncertainty, agreeswith the Standard Model prediction but disagrees with our previousmeasurement which was susceptible to error introduced by molecularsodium. We summarize precise measurements of a_ beta nu and theirconsequences for searches for Beyond Standard Model scalar and tensorcurrent couplings.
Date:
January 16, 2008
Creator:
Vetter, Paul A.; Abo-Shaeer, Jamil; Freedman, Stuart J. & Maruyama, Reina
Object Type:
Article
System:
The UNT Digital Library
A Summary of Recent Experimental Research on Ion Energy and Charge States of Pulsed Vacuum Arcs
The paper reviews the results of vacuum arc experimental investigations made collaboratively by research groups from Berkeley and Tomsk over the last two years, i.e. since the last ISDEIV in 2006. Vacuum arc plasma of various metals was produced in pulses of a few hundred microseconds duration, and the research focussed on three topics: (i) the energy distribution functions for different ion charge states, (ii) the temporal development of the ion charge state distribution, and (iii) the evolution of the mean directed ion velocities during plasma expansion. A combined quadruple mass-to-charge and energy ana-lyzer (EQP by HIDEN Ltd) and a time-of-flight spectrometer were employed. Cross-checking data by those complimen-tary techniques helped to avoid possible pitfalls in interpre-tation. It was found that the ion energy distribution func-tions in the plasma were independent of the ion charge state, which implies that the energy distribution on a substrate are not equal to due to acceleration in the substrate's sheath. In pulsed arc mode, the individual ion charge states fractions showed changes leading to a decrease of the mean charge state toward a steady-state value. This decrease can be re-duced by lower arc current, higher pulse repetition rate and reduced length of the discharge …
Date:
June 16, 2008
Creator:
Oks, Efim M.; Yushkov, Georgy Yu. & Anders, Andre
Object Type:
Article
System:
The UNT Digital Library
CH-TRU Waste Content Codes
The CH-TRU Waste Content Codes (CH-TRUCON) document describes the inventory of the U.S. Department of Energy (DOE) CH-TRU waste within the transportation parameters specified by the Contact-Handled Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC). The CH-TRAMPAC defines the allowable payload for the Transuranic Package Transporter-II (TRUPACT-II) and HalfPACT packagings. This document is a catalog of TRUPACT-II and HalfPACT authorized contents and a description of the methods utilized to demonstrate compliance with the CH-TRAMPAC. A summary of currently approved content codes by site is presented in Table 1. The CH-TRAMPAC describes "shipping categories" that are assigned to each payload container. Multiple shipping categories may be assigned to a single content code. A summary of approved content codes and corresponding shipping categories is provided in Table 2, which consists of Tables 2A, 2B, and 2C. Table 2A provides a summary of approved content codes and corresponding shipping categories for the "General Case," which reflects the assumption of a 60-day shipping period as described in the CH-TRAMPAC and Appendix 3.4 of the CH-TRU Payload Appendices. For shipments to be completed within an approximately 1,000-mile radius, a shorter shipping period of 20 days is applicable as described in the CH-TRAMPAC and Appendix 3.5 …
Date:
January 16, 2008
Creator:
Westinghouse TRU Solutions LLC
Object Type:
Report
System:
The UNT Digital Library
Fundamental Problems of Neutron Physics at the Spallation Neutron Source at the ORNL
We propose to provide theoretical support for the experimental program in fundamental neutron physics at the SNS. This includes the study of neutron properties, neutron beta-decay, parity violation effects and time reversal violation effects. The main purpose of the proposed research is to work on theoretical problems related to experiments which have a high priority at the SNS. Therefore, we will make a complete analysis of beta-decay process including calculations of radiative corrections and recoil corrections for angular correlations for polarized neutron decay, with an accuracy better that is supposed to be achieved in the planning experiments. Based on the results of the calculations, we will provide analysis of sensitivity of angular correlations to be able to search for the possible extensions of the Standard model. Also we will help to plan other experiments to address significant problems of modern physics and will work on their theoretical support.
Date:
July 16, 2008
Creator:
Gudkov, Vladimir
Object Type:
Report
System:
The UNT Digital Library
Managing Carbon Regulatory Risk in Utility Resource Planning:Current Practices in the Western United States
Concerns about global climate change have substantially increased the likelihood that future policy will seek to minimize carbon dioxide emissions. Assuch, even today, electric utilities are making resource planning and investment decisions that consider the possible implications of these future carbon regulations. In this article, we examine the manner in which utilities assess the financial risks associated with future carbon regulations within their long-term resource plans. We base our analysis on a review of the most recent resource plans filed by fifteen electric utilities in the Western United States. Virtually all of these utilities made some effort to quantitatively evaluate the potential cost of future carbon regulations when analyzing alternate supply- and demand-side resource options for meeting customer load. Even without Federal climate regulation in the U.S., the prospect of that regulation is already having an impact on utility decision-making and resource choices. That said, the methods and assumptions used by utilities to analyze carbon regulatory risk, and the impact of that analysis on their choice of a particular resource strategy, vary considerably, revealing a number of opportunities for analytic improvement. Though our review focuses on a subset of U.S. electric utilities, this work holds implications for all electric utilities …
Date:
May 16, 2008
Creator:
Barbose, Galen; Wiser, Ryan; Phadke, Amol & Goldman, Charles
Object Type:
Article
System:
The UNT Digital Library
Geochemical Characterization of Chromate Contamination in the 100 Area Vadose Zone at the Hanford Site
The major objectives of the proposed study were to: 1.) determine the leaching characteristics of hexavalent chromium [Cr(VI)] from contaminated sediments collected from 100 Area spill sites; 2.) elucidate possible Cr(VI) mineral and/or chemical associations that may be responsible for Cr(VI) retention in the Hanford Site 100 Areas through the use of i.) macroscopic leaching studies and ii.) microscale characterization of contaminated sediments; and 3.) provide information to construct a conceptual model of Cr(VI) geochemistry in the Hanford 100 Area vadose zone. In addressing these objectives, additional benefits accrued were: (1) a fuller understanding of Cr(VI) entrained in the vadose zone that will that can be utilized in modeling potential Cr(VI) source terms, and (2) accelerating the Columbia River 100 Area corridor cleanup by providing valuable information to develop remedial action based on a fundamental understanding of Cr(VI) vadose zone geochemistry. A series of macroscopic column experiments were conducted with contaminated and uncontaminated sediments to study Cr(VI) desorption patterns in aged and freshly contaminated sediments, evaluate the transport characteristics of dichromate liquid retrieved from old pipelines of the 100 Area; and estimate the effect of strongly reducing liquid on the reduction and transport of Cr(VI). Column experiments used the < …
Date:
July 16, 2008
Creator:
Dresel, P. Evan; Qafoku, Nikolla; McKinley, James P.; Fruchter, Jonathan S.; Ainsworth, Calvin C.; Liu, Chongxuan et al.
Object Type:
Report
System:
The UNT Digital Library
Validation of DNA probes for molecular cytogenetics by mapping onto immobilized circular DNA
Fluorescence in situ hybridization (FISH) is a sensitive and rapid procedure to detect gene rearrangements in tumor cells using non-isotopically labeled DNA probes. Large insert recombinant DNA clones such as bacterial artificial chromosome (BAC) or P1/PAC clones have established themselves in recent years as preferred starting material for probe preparations due to their low rates of chimerism and ease of use. However, when developing probes for the quantitative analysis of rearrangements involving genomic intervals of less than 100kb, careful probe selection and characterization are of paramount importance. We describe a sensitive approach to quality control probe clones suspected of carrying deletions or for measuring clone overlap with near kilobase resolution. The method takes advantage of the fact that P1/PAC/BAC's can be isolated as circular DNA molecules, stretched out on glass slides and fine-mapped by multicolor hybridization with smaller probe molecules. Two examples demonstrate the application of this technique: mapping of a gene-specific {approx}6kb plasmid onto an unusually small, {approx}55kb circular P1 molecule and the determination of the extent of overlap between P1 molecules homologous to the human NF-?B2 locus. The relatively simple method presented here does not require specialized equipment and may thus find widespread applications in DNA probe preparation …
Date:
December 16, 2008
Creator:
Greulich-Bode, Karin; Wang, Mei; Rhein, Andreas; Weier, Jingly & Weier, Heinz-Ulli
Object Type:
Article
System:
The UNT Digital Library
Preliminary Estimation of Isotopic Inventories of 2000 Mwt Abr (Revision 1).
The isotopic inventories of a 2000 MWt Advanced Burner Reactor (ABR) core have been estimated to support the ABR accident analysis to be reported in the Appendix D of the Programmatic Environmental Impact Statement (PEIS). Based on the Super-PRISM design, a preliminary core design of 2000 MWt ABR was developed to achieve a one-year cycle length with 3-batch fuel management scheme. For a bounding estimation of transuranics (TRU) inventory, a low TRU conversion ratio ({approx}0.3) was targeted to increase the TRU enrichment. By changing the fuel compositions, isotopic inventories of mass and radioactivity were evaluated for four different core configurations: recycled metal fuel core, recycled oxide fuel core, startup metal fuel core, and startup oxide fuel core. For recycled cores, the TRU recovered from ABR spent fuel was used as the primary TRU feed, and the TRU recovered from 10-year cooled light water reactor spent fuel was used as the makeup TRU feed. For startup cores, weapons-grade plutonium was used as TRU feed without recycling ABR spent fuel. It was also assumed that a whole batch of discharged fuel assemblies is stored in the in-vessel storage for an entire irradiation cycle. For both metal and oxide fuel cores, the estimated …
Date:
June 16, 2008
Creator:
Kim, T. K. & Yang, W. S.
Object Type:
Report
System:
The UNT Digital Library
Direct drive heavy-ion-beam inertial fusion at high coupling efficiency
Issues with coupling efficiency, beam illumination symmetry, and Rayleigh-Taylor instability are discussed for spherical heavy-ion-beam-driven targets with and without hohlraums. Efficient coupling of heavy-ion beams to compress direct-drive inertial fusion targets without hohlraums is found to require ion range increasing several-fold during the drive pulse. One-dimensional implosion calculations using the LASNEX inertial confinement fusion target physics code shows the ion range increasing fourfold during the drive pulse to keep ion energy deposition following closely behind the imploding ablation front, resulting in high coupling efficiencies (shell kinetic energy/incident beam energy of 16% to 18%). Ways to increase beam ion range while mitigating Rayleigh-Taylor instabilities are discussed for future work.
Date:
May 16, 2008
Creator:
Logan, B. G.; Perkins, L. J. & Barnard, J. J.
Object Type:
Article
System:
The UNT Digital Library
Analytical analysis of longitudinal space charge effects for a bunched beam with radial dependence
The longitudinal space-charge (LSC) force can be a major cause of the microbunching instability in the linac for an x-ray free-electron laser. In this paper, the LSC-induced beam modulation is studied using an integral equation approach that takes into account the transverse (radial) variation of the LSC field for both the coasting-beam limit and a bunched beam. Variation of the beam energy and the transverse beam size is also incorporated. We discuss the validity of this approach and compare it with other analytical analyses as well as numerical simulations.
Date:
June 16, 2008
Creator:
Wu, Juhao; Huang, Zhirong & Emma, Paul
Object Type:
Article
System:
The UNT Digital Library
Post-Treatment Hemodynamics of a Basilar Aneurysm and Bifurcation
Aneurysm re-growth and rupture can sometimes unexpectedly occur following treatment procedures that were initially considered to be successful at the time of treatment and post-operative angiography. In some cases, this can be attributed to surgical clip slippage or endovascular coil compaction. However, there are other cases in which the treatment devices function properly. In these instances, the subsequent complications are due to other factors, perhaps one of which is the post-treatment hemodynamic stress. To investigate whether or not a treatment procedure can subject the parent artery to harmful hemodynamic stresses, computational fluid dynamics simulations are performed on a patient-specific basilar aneurysm and bifurcation before and after a virtual endovascular treatment. The simulations demonstrate that the treatment procedure produces a substantial increase in the wall shear stress. Analysis of the post-treatment flow field indicates that the increase in wall shear stress is due to the impingement of the basilar artery flow upon the aneurysm filling material and to the close proximity of a vortex tube to the artery wall. Calculation of the time-averaged wall shear stress shows that there is a region of the artery exposed to a level of wall shear stress that can cause severe damage to endothelial cells. …
Date:
January 16, 2008
Creator:
Ortega, J; Hartman, J; Rodriguez, J & Maitland, D
Object Type:
Article
System:
The UNT Digital Library