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2. Comparison of Neutron Radiation Response of Conventionally Wrought Versus Additive Manufacturing Production Methods in Alloy 625.

Author

O'Donnell, V., He, X., Keya, T., Harvill, G., Andurkar, M., Prorok, B. C., Thompson, S. M., and Gahl, J.

Abstract

A point of study in the characterization of additive manufactured (AM) alloys is whether or not AM microstructure responds to external stimuli differently from conventionally manufactured alloys. Samples of Alloy 625, a nickel-based superalloy of interest, were produced by both additive manufacturing and conventional wrought methods. Samples of differing sizes were subjected to one of two different types of neutron fields during irradiation: fast neutron or reactor-spectrum neutron. Vickers microhardness measurements and transmission electron microscope images were used to analyze the differences between samples before and after they were subjected to the neutron fields. Results showed differing responses between the two fabrication methods. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Comparison of Neutron Radiation Response of Conventionally Wrought Versus Additive Manufacturing Production Methods in Alloy 625

Author

O’Donnell, V., He, X., Keya, T., Harvill, G., Andurkar, M., Prorok, B. C., Thompson, S. M., and Gahl, J.

Abstract

AbstractA point of study in the characterization of additive manufactured (AM) alloys is whether or not AM microstructure responds to external stimuli differently from conventionally manufactured alloys. Samples of Alloy 625, a nickel-based superalloy of interest, were produced by both additive manufacturing and conventional wrought methods. Samples of differing sizes were subjected to one of two different types of neutron fields during irradiation: fast neutron or reactor-spectrum neutron. Vickers microhardness measurements and transmission electron microscope images were used to analyze the differences between samples before and after they were subjected to the neutron fields. Results showed differing responses between the two fabrication methods.

Published
2024
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14. Diagnostic Technique Characterizing Neutron Irradiation Effects on Additively Manufactured Inconel 625 Eliminating the Need for Remote Handling.

Author

O'Donnell, V., Keya, T., Romans, A., Harvill, G., Andurkar, M., Prorok, B. C., Thompson, S. M., and Gahl, J.

Abstract

Experimentally characterizing radioactive materials can be time consuming and expensive. This is mainly due to the size requirements of inspected specimens. Due to the growing interest in using additively manufactured components in next-generation reactors, there is an urgent need to develop new accelerated testing techniques with regard to characterizing radiation damage. This will ensure a more timely certification of the unique material structures inherent to additively manufactured parts. In this study, we investigate a means to reduce the time investment, and thus the human exposure to radioactive specimens in need of experimental characterization. We determine the feasibility of using ultra-small specimens in lieu of much larger specimens to characterize bulk material properties before and after irradiation. Experiments were conducted to investigate this technique and compare it to conventional bulk irradiations and characterization activities. It was found that discernable radiation damage existed in the ultra-small specimens even after relatively short neutron irradiation times. The results also demonstrate decreased radiation hardening in additive manufactured Inconel 625 material relative to its wrought forms. [ABSTRACT FROM AUTHOR]

Published
2023
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19. The New Zealand Southern Alps Experiment

Author

Wratt, D. S., Ridley, R. N., Sinclair, M. R., Larsen, H., Thompson, S. M., Henderson, R., Austin, G. L., Bradley, S. G., Auer, A., Sturman, A. P., Owens, I., Fitzharris, B., Ryan, B. F., and Gayet, J.-F.

Published
1996

20. Diagnostic Technique Characterizing Neutron Irradiation Effects on Additively Manufactured Inconel 625 Eliminating the Need for Remote Handling

Author

O’Donnell, V., Keya, T., Romans, A., Harvill, G., Andurkar, M., Prorok, B. C., Thompson, S. M., and Gahl, J.

Abstract

AbstractExperimentally characterizing radioactive materials can be time consuming and expensive. This is mainly due to the size requirements of inspected specimens. Due to the growing interest in using additively manufactured components in next-generation reactors, there is an urgent need to develop new accelerated testing techniques with regard to characterizing radiation damage. This will ensure a more timely certification of the unique material structures inherent to additively manufactured parts. In this study, we investigate a means to reduce the time investment, and thus the human exposure to radioactive specimens in need of experimental characterization. We determine the feasibility of using ultra-small specimens in lieu of much larger specimens to characterize bulk material properties before and after irradiation. Experiments were conducted to investigate this technique and compare it to conventional bulk irradiations and characterization activities. It was found that discernable radiation damage existed in the ultra-small specimens even after relatively short neutron irradiation times. The results also demonstrate decreased radiation hardening in additive manufactured Inconel 625 material relative to its wrought forms.

Published
2023
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23. Making energy metrics relevant to service firms : from energy conservation to energy productivity

Author

Raggio, R. D., Ekman, Peter, Thompson, S. M., Raggio, R. D., Ekman, Peter, and Thompson, S. M.

Abstract

Although energy conservation and reduction in environmental impact are on the international and most national agendas, service firms rarely include energy consumption metrics in their strategic decision-making. One reason for the omission is that for service industries, firm level energy utilization is most commonly measured in kilowatt hours per square meter of office space where changes often related to the space rather than the firm performance. The measure also presents several problems for firms in service industries. First, energy conservation and reduction may be counterproductive for service firms that are growing and require energy to sustain that growth. Second, it may not relate to national and international goals which are often focused on the amount of carbon dioxide produced generating energy than the total amount of energy consumed. Third, it treats energy as a utility rather than a resource in firms’ value creation. Results from a field study focused on service firms in Sweden suggests that focusing on energy productivity overcomes the limitations of existing measures and produces positive results. By conceptualizing energy productivity as output per unit of energy, we create a conservation metric that enables service firms to measure their contributions to energy consumption relative to national economic growth. As a result, energy productivity aligns the interests of service organizations with those of policy makers and conservationists.

Published
2020
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29. American Society of Colon and Rectal Surgeons 91st Annual Convention Podium and Poster abstracts: June 7–12, 1992 San Francisco, CA

Author

Lechner, P., Lind, P., Binter, G., Golub, R. W., Kerner, B. A., Wise, Jr., W. E., Meesig, D. M., Hartmann, R. F., Khanduja, K. S., Sayre, J. W., Aguilar, P. S., Guillem, J. G., Forde, K. A., Treat, M. R., Neugut, A. I., O'Toole, K. M., Diamond, B. E., Kewenter, J., Brevinge, H., Haglind, E., Limberg, B., Elles, C. N., Boggs, W. H., Slagle, G. H., Cole, P. A., Coyle, D. J., Smith, L. E., Orkin, B., Saclarides, T. J., Sheridan, W. G., Lowndes, R. H., Young, H. L., Wong, W. D., Rothenberger, D. A., Bartolo, D. C. C., Wexner, S. D., Ger, G. C., Jorge, J. M. N., Lee, E., Nogueras, J. J., Jagelman, D. G., McKenna, K., Koltun, W. A., Bute, B., Lichliter, W., Le, T., Timmcke, A., Gathright, J. B., Mascagni, D., Hojo, K., Moriya, Y., Sugihara, K., Di, G., Zenni, G. C., Abraham, K., Dobrin, P. B., Harford, F. J., Suzuki, K., Gunderson, L., Devine, R. M., Dozois, R. R., Cavaliere, F., Pemberton, J. H., Fazio, V., Cosimelli, M., Beart, R. W., Giannarelli, D., Moran, M., Ramos, A., Rothenberger, D., Goldberg, S., Antonenko, D., Heymen, S., Gulledge, A. D., Jakate, S., Saclarides, T., Heine, J. A., Williams, J. G., VanBergen, E. H., Buie, W. D., Goldberg, S. M., Davies, N., Yates, J., Jenkins, S. A., Taylor, B. A., Bapat, B., Stern, H., Berk, T., Parker, J., Ray, P. N., McLeod, R., Cohen, Z., Rowe, J. K., Zera, R. T., Madoff, R. D., Bubrick, M. P., Roberts, J. C., Johnston, G. R., Fenney, D. A., Farouk, R., Duthie, G. S., McCue, J. L., Phillips, R. K. S., Viamonte, M., Cole, J., Gottesman, L., Solomon, M. J., McLeod, R. S., Kern, K., Jensen, L. L., Lowry, A. C., Vernava, III, A. M., Longo, W. E., Daniel, G. L., Ehrenpreis, E., Stone, J. M., Cosman, B. C., Wolfe, V. A., Nino-Murcia, M., Perkash, I., Marcello, P. W., Roberts, P. L., Schoetz, Jr., D. J., Murray, J. J., Coller, J. A., Veidenheimer, M. C., Keighley, M. R. B., Grobler, S. P., Hosie, K. B., Schmitt, S. L., James, K., Lucas, F., Peck, Donald A., Ferrara, A., Grotz, R. L., Perry, R. E., Hanson, R. B., Lewis, W. G., Holdsworth, P. J., Sagar, P. M., Johnston, D., Perry, T. G., Strong, S. A., Fazio, V. W., Lavery, I. C., Oakley, J. R., Church, J. M., Milsom, J. W., Fozard, J. B. J., Nelson, H., Schneebaum, S., Arnold, M. W., Young, D., LaValle, G. J., Petty, L., Berens, A., Mojizisik, C., Martin, E. W., Hase, K., Shatney, C. H., Trollope, M., Johnson, D., Vierra, M., Deutsch, A. A., Tulchinsky, H., Nudelman, I., Gutman, H., Reiss, R., Taylor, Brian M., Araujo, A., Bleday, R., Jessurun, J., Heine, J., Rosen, Les, Sipe, Paul, Riether, Robert, Stasik, John, Sheets, James, Khubchandani, Indru, Reiter, W., Friedberg, G., Morey, G., Goldstein, E., Williamson, P., Larach, S., Senagore, A. J., Luchtefeld, M. A., MacKeigen, J. M., Mazier, W. P., Wengert, T., Ott, M. T., Bailey, H. R., Hartendorp, P., Dailey, T. H., Church, J. C., Johansen, O. B., Daniel, N., Korst, M., Kuijpers, H. C., Pena, J. P., Christenson, C. E., Balcos, E. G., Lewis, W., Mitchell, C., MacFie, J., Hildebrandt, U., Ecker, K. W., Kraus, J., Schmid, T., Feifel, G., Tjandra, J. J., Scoggin, Steve, Frazee, Richard C., Ambroze, Jr., W. L., Nezhat, C., Pennington, E., Nezhat, F., Stolfi, V. M., Thorson, A. G., Falk, P. M., Fitzgibbons, Jr, R. J., Luukkonen, P., Järvinen, H. J., James, E., Paty, P. B., Enker, W. E., Cohen, A. M., Lauwers, G. Y., Saad, R., Birnbaum, E., DeVos, W., Fry, R., Kodner, I., Fleshman, J., Cali, R. L., Pitsch, R. M., Blatchford, G. J., Christensen, M. A., Schroeder, T. K., Easley, K. A., Ellis, C. N., Cheape, J. D., Hull, T. L., Salanga, V., Kokoszka, Joseph, Andrianopoulos, Georgia, Nelson, Richard, Abcarian, Herand, Kumar, D., Benson, M. J., Roberts, J., Martin, J. E., Swash, M., Wingate, D. L., Williams, N. S., Orkin, B. A., Emsellem, H., Dent, John, Tissaw, M. A., Shafik, A., Abel, M. E., Chiu, Y. S. Y., Russell, T. R., Volpe, P. A., Casillas, G. L., Mashas, W. E., Eastman, D. A., Grace, R. H., Anderson, J. M., Hacker, K., Heryer, J., Conner, W., Rubin, R., Eisenstat, T., Salvati, E., Oliver, G., Duberman, E., Simmang, C. L., Fry, R. D., Kodner, I. J., Fleshman, J. W., Corman, M. L., Galandiuk, S., Weiner, G. J., Kahn, D., Mitchell, E., Abdel-Nabi, H., Block, G. E., Mannella, E., Tedesco, M., Anza, M., Civalleri, D., Di Tora, P., Capussotti, L., Morandi, G. B., Tirelli, C., Da Pian, P. P., Cortesi, E., Ruggeri, E., Fitzgerald, S. D., Davis, Faith, Bowen, Phyllis, Sutter, Eileen, Kikendall, Walter, McGannon, E., Brantley, P. A., Czyrko, C., Falardeau, C., Trepashko, Don, Skosey, John, Michelassi, F., Staniunas, R. J., Vignati, P. V., Beck, D. E., Karulf, R., Roettger, R., Braidt, J., Ruoff, K., Ackroyd, F., Shellito, P., Goh, H. S., Lin, L. W., Edwards, E., Farmer, J., Walters, C. A., Hyman, N. H., Hebert, J. C., Richman, Irving M., Staren, E. D., Sessions, S. C., Scoma, R. S., Clements, B., Smink, Jr., R. D., Arai, K., Sugita, A., Yamazaki, Y., Harada, H., Fukushima, T., Armstrong, D. N., Ballantyne, G. H., Sillin, L. F., Davie, R. J., Harding, L. K., Birch, N. J., Yamanouchi, T., Bayer, I., Mitmaker, B., Gordon, P. H., Wang, E., Kynaston, H., Edelstein, P. S., Thompson, S. M., Davies, R. J., Farmer, K. C. R., Oliver, S. E., Spigelman, A. D., Bennett, P., O'Kelly, T. J., Brading, A. F., Mortensen, N. J., Paul, P., McGannon, E. M., Huth, P., Hull-Boiner, S., Pezim, M. E., Johnson, H. W., Gillespie, K. D., Willard, P., Owen, D. A., Ramsey, P. S., Leu, S. Y., Hsu, H., Al-Humadi, Adil H., Eisman, E., Tries, J., Gupta, N. C., Frick, M. P., Boman, B. M., Franceschi, D., Eckhauser, M. L., Pritchard, T., Konsten, J., Baeten, C. G. M. I., Havenith, M. G., Soeters, P. B., Lau, P. W. K., Lorentz, T. G., Wong, J., and The III In-CYT-103 Immunoscintigraphy Study Group

Published
1992
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30. Percutaneous MR Imaging-Guided Laser Ablation and Cryoablation for the Treatment of Pediatric and Adult Symptomatic Peripheral Soft Tissue Vascular Anomalies.

Author

Augustine, Matthew Robert, Thompson, Scott M., Powell, Garret M., Koepsel, Erica Knavel, Adamo, Daniel A., Bendel, Emily C., Anderson, Katelyn R., Bjarnason, Haraldur, Tollefson, Megha, Woodrum, David A., Augustine, M R, Thompson, S M, Powell, G M, Knavel, E, Adamo, D A, Bendel, E C, Anderson, K R, Bjarnason, H, Tollefson, M, and Woodrum, D A

Abstract

Purpose: To evaluate the safety and effectiveness of percutaneous magnetic resonance (MR) imaging-guided laser ablation and cryoablation for the treatment of symptomatic soft tissue vascular anomalies (VAs) of the trunk and extremities.Materials and Methods: An institutional review board-approved retrospective review was undertaken of all pediatric and adult patients who underwent MR imaging-guided and monitored laser ablation and/or cryoablation for the treatment of symptomatic peripheral soft tissue VA. Preablation and postablation MR imaging was independently reviewed. Pain scores on the visual analog scale (0 to 10) and self-reported subjective symptomatic improvement were assessed. Change in VA size and pain scores were compared using a paired t test.Results: Thirty patients (24 females; age, 10-75 years) with 34 VAs were treated for moderate to severe pain (n = 27) or swelling/mass effect (n = 3) with 60 total ablation sessions. The baseline maximum VA diameter was 9.5 cm ± 8.6. At baseline, all VAs (100%) demonstrated variable T2-weighted signal hyperintensity and enhancement. The baseline pain score was 6.4 ± 1.6. Clinical follow-up was available for 23 patients. At a mean follow-up time of 12.2 months ± 10.1, 19 of 20 (95%) patients treated for pain and 2 of 3 (67%) patients treated for swelling/mass effect reported partial or complete symptomatic relief. There was a significant decrease in the postablation pain scores (-5.7 ± 1.0, P < .001) and maximum VA size (-2.3 cm ± 2.7, P = .004), with >50% reduction in VA T2 signal (59%) and enhancement (73%). Nine of 30 (30%) patients experienced minor complications.Conclusions: MR imaging-guided and monitored percutaneous laser ablation and cryoablation appear to be safe and effective for the treatment of symptomatic peripheral soft tissue VAs. [ABSTRACT FROM AUTHOR]

Published
2021
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31. Dynamic Harris current sheet thickness from Cluster current density and plasma measurements

Author

Thompson, S. M, Kivelson, M. G, Khurana, K. K, McPherron, R. L, Weygand, J. M, Balogh, A, Reme, H, and Kistler, L. M

Subjects
Geophysics
Abstract

We use the first accurate measurements of current densities in the plasma sheet to calculate the half-thickness and position of the current sheet as a function of time. Our technique assumes a Harris current sheet model, which is parameterized by lobe magnetic field B(o), current sheet half-thickness h, and current sheet position z(sub o). Cluster measurements of magnetic field, current density, and plasma pressure are used to infer the three parameters as a function of time. We find that most long timescale (6-12 hours) current sheet crossings observed by Cluster cannot be described by a static Harris current sheet with a single set of parameters B(sub o), h, and z(sub o). Noting the presence of high-frequency fluctuations that appear to be superimposed on lower frequency variations, we average over running 6-min intervals and use the smoothed data to infer the parameters h(t) and z(sub o)(t), constrained by the pressure balance lobe magnetic field B(sub o)(t). Whereas this approach has been used in previous studies, the spatial gnuhen& now provided by the Cluster magnetometers were unavailable or not well constrained in earlier studies. We place the calculated hdf&cknessa in a magnetospheric context by examining the change in thickness with substorm phase for three case study events and 21 events in a superposed epoch analysis. We find that the inferred half-thickness in many cases reflects the nominal changes experienced by the plasma sheet during substorms (i.e., thinning during growth phase, thickening following substorm onset). We conclude with an analysis of the relative contribution of (Delta)B(sub z)/(Delta)X to the cross-tail current density during substorms. We find that (Delta)B(sub z)/(Delta)X can contribute a significant portion of the cross-tail c m n t around substorm onset.

Published
2005

32. Plasma sheet turbulence observed by Cluster II

Author

Weygand, James M, Kivelson, M. G, Khurana, K. K, Schwarzl, H. K, Thompson, S. M, McPherron, R. L, Balogh, A, Kistler, L. M, Goldstein, M. L, and Borovsky, J

Subjects
Geophysics
Abstract

Cluster fluxgate magnetometer (FGM) and ion spectrometer (CIS) data are employed to analyze magnetic field fluctuations within the plasma sheet during passages through the magnetotail region in the summers of 2001 and 2002 and, in particular, to look for characteristics of magnetohydrodynamic (MHD) turbulence. Power spectral indices determined from power spectral density functions are on average larger than Kolmogorov's theoretical value for fluid turbulence as well as Kraichnan's theoretical value for MHD plasma turbulence. Probability distribution functions of the magnetic fluctuations show a scaling law over a large range of temporal scales with non-Gaussian distributions at small dissipative scales and inertial scales and more Gaussian distribution at large driving scales. Furthermore, a multifractal analysis of the magnetic field components shows scaling behavior in the inertial range of the fluctuations from about 20 s to 13 min for moments through the fifth order. Both the scaling behavior of the probability distribution functions and the multifractal structure function suggest that intermittent turbulence is present within the plasma sheet. The unique multispacecraft aspect and fortuitous spacecraft spacing allow us to examine the turbulent eddy scale sizes. Dynamic autocorrelation and cross correlation analysis of the magnetic field components allow us to determine that eddy scale sizes fit within the plasma sheet. These results suggest that magnetic field turbulence is occurring within the plasma sheet resulting in turbulent energy dissipation.

Published
2005

34. Cluster observations of quasi-periodic impulsive signatures in the dayside northern lobe: High-latitude flux transfer events?

Author

Thompson, S. M, Kivelson, M. G, Khurana, K. K, Balogh, A, Reme, H, Fazakerley, A. N, and Kistler, L. M

Subjects
Geophysics
Abstract

We report on a series of quasi-periodic reversals in GSM B(sub Z) observed by the four Cluster spacecraft in the northern dayside lobe poleward of the cusp on 23 February 2001. During an interval of about 35 min, multiple reversals (negative to positive) in B(sub Z) of approximately 1-min duration with an approximate 8-min recurrence time were observed. The individual structures do not resemble low-latitude flux transfer events (FTE) [Russell and Elphic, 1979] but the 8-min recurrence frequency suggests that intermittent reconnection may be occurring .Measurements (appropriately lagged) of the solar wind at ACE show that the IMF was southward-oriented with a strong B(sub X) and that a modest dynamic pressure increased as the events started. The multi-point observations afforded by the Cluster spacecraft were used to infer the motion (direction and speed) of the observed magnetic field reversals. The associated currents were also calculated and they are consistent with the spatial confinement of the observed magnetic field reversals. We propose that the observed reversals are due to flux tubes reconnecting with closed field lines on the dayside. Ancillary data from the Cluster Ion Spectrometry (CIS) and Plasma Electron And Current Experiment (PEACE) instruments were used to develop a physical picture of the reversals.

Published
2004

37. First Reports of Diaporthe kongii, D. masirevicii, and D. ueckerae Associated with Stem and Peg Dieback on Peanut in Australia

Author

Thompson, S. M., Grams, R. A., Neate, S. M., Shivas, R. G., Ryley, M. J., Tan, Y. P., Aitken, E. A. B., Wright, G. C., O’Connor, D. J., Thompson, S. M., Grams, R. A., Neate, S. M., Shivas, R. G., Ryley, M. J., Tan, Y. P., Aitken, E. A. B., Wright, G. C., and O’Connor, D. J.

Abstract

In July 2016, peanuts (Arachis hypogaea L. cvs. Holt, Kairi) with symptoms of stem and peg dieback were collected from Kingaroy, Childers, and Bundaberg regions in Queensland, Australia. Pycnidia of Diaporthe spp. were visible in brown lesions on stems and on live and shriveled pegs. Affected tissues were surface sterilized in 1% v/v NaOCl for 3 min, rinsed with sterile distilled water, incubated on water agar with 100 µg/ml streptomycin sulfate at 23 to 25°C under ambient light. After 1 to 14 days, conidia were streaked onto potato dextrose agar with 100 µg/ml streptomycin sulfate (PDAS) and incubated as above. After 24 h, single germinating conidia were transferred to PDAS. Mycelial DNA was extracted from 80 single conidial isolates using the Bioline Isolate II Genomic DNA extraction kit. Primers for the internal transcribed spacer region (ITS) and partial region of the translation elongation factor 1-alpha (TEF) were as described in Thompson et al. (2015). Both ITS and TEF loci were amplified with Biolabs Hot Start Taq 2x Master Mix Enzyme. PCR products were purified using Bioline Sure Clean Plus and sequenced by Macrogen Incorporated (Seoul, Korea) with the amplification primers. Sequences were assembled with Geneious v.9.1. Species morphological descriptions are in Thompson et al. 2011, 2015, and Gao et al. 2016. Using BLAST sequence analysis and culture morphology, species were identified as D. kongii (four isolates), D. masirevicii (42), D. ueckerae (syn. D. miriciae) (27), or Diaporthe sp. (seven) (Gao et al. 2016; Thompson et al. 2011, 2015). A representative isolate of D. kongii (BRIP 64964d), D. masirevicii (BRIP 64786a), and D. ueckerae (BRIP 64785a) was deposited into the Queensland Plant Pathology Herbarium (Brisbane, Australia) and was used for pathogenicity testing. To verify pathogenicity, early podfill peanut plants (cv. Taabinga) grown at 21 to 25°C day, 14 to 18°C night, were stem slit inoculated (Thompson et al. 2011), using three plants per iso

Published
2018

40. Evidence for electrical spin tunnel injection into silicon.

Author

Dennis, C. L., Gregg, J. F., Ensell, G. J., and Thompson, S. M.

Subjects
QUANTUM tunneling, ELECTRON transport, MAGNETIC fields, POLARIZATION (Electricity), SEMICONDUCTORS
Abstract

Electrical spin injection into silicon was studied in a ferromagnet/insulator/silicon/insulator/ferromagnet structure, where the insulator is Si3N4. Si3N4 barriers conduct by hopping conduction at low voltages, but switch to Fowler-Nordheim tunneling at high voltages. In the Fowler-Nordheim tunneling regime a magnetic field dependence of the output current consistent with spin dependent transport through the silicon is observed; in the hopping conduction regime reduced magnetic field dependence of the output current is observed. This voltage dependence of the magnetic sensitivity strongly supports the existence of spin injection into silicon. After correction for Lorentz magnetoresistance, the magnitude of this signal is 4.1%±0.5% (12%±5%) for p-type (n-type) Si. [ABSTRACT FROM AUTHOR]

Published
2006
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41. Photovoltage detection of x-ray absorption and magnetic circular dichroism spectra of magnetic films grown on semiconductors.

Author

Mallett, J. J., Dudzik, E., Schwarzacher, W., Thompson, S. M., Tsang, H. K., and van der Laan, G.

Subjects
MAGNETIC films, SEMICONDUCTORS, X-rays, DICHROISM
Abstract

We describe a measurement technique for x-ray absorption spectroscopy, in which the sample is used as the detector. Co L[sub 2,3] absorption spectra were taken from cobalt films grown on n-GaAs by measuring the photovoltage generated by the x rays transmitted across the rectifying metalsemiconductor contact. After correcting the effects of signal saturation good agreement was obtained with spectra acquired using the conventional total electron yield method. X-ray magnetic circular dichroism measurements using the method gave values for the spin moment of cobalt between 1.48 and 1.89 µ[sub B]/atom, compared to the value in the literature of 1.55 ·[sub B]/atom for the bulk. An anomalously high average value of 0.39 ·[sub B]/atom was found for the orbital moment and attributed to the presence of oxide in the films. [ABSTRACT FROM AUTHOR]

Published
2003
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50. The liquid–vapor interface of simple polar fluids. II. Computer simulation.

Author

Eggebrecht, J., Thompson, S. M., and Gubbins, K. E.

Subjects
*MOLECULAR dynamics, *DISTRIBUTION (Probability theory), *TEMPERATURE, *PERTURBATION theory
Abstract

The molecular dynamics method is used to study the liquid–vapor interface of the Stockmayer fluid. We compare our results for the singlet density-orientation distribution function and surface tension with the predictions of integral equation and perturbation theory. We find that at low temperature and high moment conditions, dipolar orientations in the interfacial region parallel to the surface are more probable. The pressure tensor, mean squared force, and mean squared torque are also determined as functions of position with respect to the interface. Directional anisotropy in the mobility of particles in the vicinity of the surface is found by decomposing the mean squared displacements into components parallel and perpendicular to the interfacial plane. [ABSTRACT FROM AUTHOR]

Published
1987
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