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217 results on '"Burkhart, R."'

1. Radon Decays and Their Implications for Elementary Particle Physics

Author

Scarlett, C., Fischbach, E., Freeman, B., Coy, J. J., Edwards, P., Burkhart, R., Piatibratova, O., Monsue, T., Egoh, A., Mwibanda, L., and Alsayegh, A.

Subjects
Nuclear Experiment, High Energy Physics - Phenomenology, Nuclear Theory
Abstract

This paper presents a new analysis of the observations of radon decay in an enclosed environment by the Geological Survey of Israel (GSI) between 2007 and 2012 [4]; for a more complete list of experiments performed by GSI on radon see also references [1-3]. The data exhibit a large peak around local noon followed by an abrupt drop, and by a second peak around 6PM local time. Additionally, there is also a very low amplitude peak occurring before daybreak. The salient features of the GSI radon decay data can be modeled as arising from a change in the radon decay rate, rather than due to the changes in the local concentration of radon (N0). Such a model may provide a clue to long theorized axionic, dark matter, interactions. Finally, new experimentation is suggested that can distinguish between changes in N0 versus changes in decay rate. Should a follow-up experiment show an effect similar to that seen in GSI, this could have significant implications for elementary particle physics.

Published
2022

3. Dynamics of Serum CA19-9 in Patients Undergoing Pancreatic Cancer Resection.

Author

Floortje van Oosten, A., Groot, Vincent P., Dorland, Galina, Burkhart, R. A., Wolfgang, Christopher L., van Santvoort, Hjalmar C., Jin He, Quintus Molenaar, I., and Daamen, Lois A.

Abstract

Background: Carbohydrate antigen (CA) 19-9 is an established perioperative prognostic biomarker for pancreatic ductal adenocarcinoma (PDAC). However, it is unclear how CA19-9 monitoring should be used during postoperative surveillance to detect recurrence and to guide the initiation of recurrence-focused therapy. Objective: This study aimed to elucidate the value of CA19-9 as a diagnostic biomarker for disease recurrence in patients who underwent PDAC resection. Methods: Serum CA19-9 levels at diagnosis, after surgery, and during postoperative follow-up were analyzed in patients who underwent PDAC resection. All patients with at least two postoperative follow-up CA19-9 measurements before recurrence were included. Patients deemed to be nonsecretors of CA19-9 were excluded. The relative increase in post-operative CA19-9 was calculated for each patient by dividing the maximum postoperative CA19-9 value by the first postoperative value. Receiver operating characteristic analysis was performed to identify the optimal threshold for the relative increase in CA19-9 levels to identify recurrence in the training set using Youden's index. The performance of this cutoff was validated in a test set by calculating the area under the curve (AUC) and was compared to the performance of the optimal cutoff for postoperative CA19-9 measurements as a continuous value. In addition, sensitivity, specificity, and predictive values were assessed. Results: In total, 271 patients were included, of whom 208 (77%) developed recurrence. Receiver operating characteristic analysis demonstrated that a relative increase in postoperative serum CA19-9 of 2.6x was predictive of recurrence, with 58% sensitivity, 83% specificity, 95% positive predictive value, and 28% negative predictive value. The AUC for a 2.6x relative increase in the CA19-9 level was 0.719 in the training set and 0.663 in the test set. The AUC of postoperative CA19-9 as a continuous value (optimal threshold, 52) was 0.671 in the training set. In the training set, the detection of a 2.6-fold increase in CA19-9 preceded the detection of recurrence by a mean difference of 7months (P<0.001) and in the test set by 10months (P<0.001). Conclusions: A relative increase in the postoperative serum CA19-9 level of 2.6-fold is a stronger predictive marker for recurrence than a continuous CA19-9 cutoff. A relative CA19-9 increase can precede the detection of recurrence on imaging for up to 7 to 10 months. Therefore, CA19-9 dynamics can be used as a biomarker to guide the initiation of recurrence-focused treatment. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Impact of Liver Disease and Parenchymal Changes on Patterns of Liver Recurrence in Patients with Resected PDAC: A New Insight into the Biological Behavior of This Lethal Disease

Author

Javed, A., primary, Baig, E., additional, Habib, J., additional, Correa, C., additional, Lafaro, K., additional, Greer, J., additional, Burkhart, R., additional, Burns, W., additional, Cohen, S., additional, Fishman, E., additional, Cameron, J., additional, He, J., additional, Weiss, M., additional, and Wolfgang, C., additional

Published
2022
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10. Not all point mutations are the same: A multi-institutional study of KRAS in Colorectal Liver Metastases

Author

Buettner, S., primary, Margonis, G., additional, Andreatos, N., additional, Wagner, D., additional, Amini, N., additional, Sasaki, K., additional, Wang, J., additional, Kamphues, C., additional, Morioka, D., additional, Loes, I.M., additional, Imai, K., additional, He, J., additional, Pawlik, T., additional, Kaczirek, K., additional, Lønning, P Eystein, additional, Burkhart, R., additional, Endo, I., additional, Baba, H., additional, Mischinger, H.J., additional, Aucejo, F., additional, Poultsides, G., additional, Kreis, M., additional, Wolfgang, C., additional, and Weiss, M., additional

Published
2020
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11. Persistent Circulating Tumor Cells At One Year After Oncologic Resection Of Pancreatic Cancer Predict Recurrence

Author

Wolfgang, C.L., primary, Ding, D., additional, Hasanain, A., additional, Oosten, F.V., additional, Gemenetzis, G., additional, Groot, V., additional, Tenior, J., additional, Javed, A.A., additional, Wright, M., additional, Yu, J., additional, Cameron, J., additional, Weiss, M., additional, Burns, W.R., additional, Burkhart, R., additional, Zheng, L., additional, and He, J., additional

Published
2020
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14. The Prognostic Value of Varying Definitions of Positive Resection Margin in Patients with Colorectal Cancer Liver Metastases

Author

Wang, J. Margonis, G.A. Amini, N. Andreatos, N. Yuan, C. Damaskos, C. Antoniou, E. Garmpis, N. Buettner, S. Barbon, C. Deshwar, A. He, J. Burkhart, R. Pawlik, T.M. Wolfgang, C.L. Weiss, M.J.

Abstract

Background: Varying definitions of resection margin clearance are currently employed among patients with colorectal cancer liver metastases (CRLM). Specifically, a microscopically positive margin (R1) has alternatively been equated with an involved margin (margin width = 0 mm) or a margin width < 1 mm. Consequently, patients with a margin width of 0–1 mm (sub-mm) are inconsistently classified in either the R0 or R1 categories, thus obscuring the prognostic implications of sub-mm margins. Methods: Six hundred thirty-three patients who underwent resection of CRLM were identified. Both R1 definitions were alternatively employed and multivariable analysis was used to determine the predictive power of each definition, as well as the prognostic implications of a sub-mm margin. Results: Five hundred thirty-nine (85.2%) patients had a margin width ≥ 1 mm, 42 had a sub-mm margin width, and 52 had an involved margin (0 mm). A margin width ≥ 1 mm was associated with improved survival vs. a sub-mm margin (65 vs. 36 months; P = 0.03) or an involved margin (65 vs. 33 months; P < 0.001). No significant difference in survival was detected between patients with involved vs. sub-mm margins (P = 0.31). A sub-mm margin and an involved margin were both independent predictors of worse OS (HR 1.66, 1.04–2.67; P = 0.04, and HR 2.14, 1.46–3.16; P < 0.001, respectively) in multivariable analysis. Importantly, after combining the two definitions, patients with either an involved margin or a sub-mm margin were associated with worse OS in multivariable analysis (HR 1.94, 1.41–2.65; P < 0.001). Conclusions: Patients with involved or sub-mm margins demonstrated a similar inferior OS vs. patients with a margin width > 1 mm. Consequently, a uniform definition of R1 as a margin width < 1 mm should perhaps be employed by future studies. © 2018, The Society for Surgery of the Alimentary Tract.

Published
2018

15. Evaluation of a Novel Absorbable Radiopaque Hydrogel in Patients Undergoing Image-Guided Radiotherapy (IGRT) for Borderline Resectable and Locally Advanced Pancreatic Adenocarcinoma

Author

Rao, A.D., primary, Shin, E.J., additional, Meyer, J.J., additional, Thompson, E., additional, Fu, W., additional, Hu, C., additional, Fishman, E., additional, Weiss, M., additional, Wolfgang, C., additional, Burkhart, R., additional, He, J., additional, Kerdsirichariat, T., additional, Herman, J.M., additional, Ding, K., additional, and Narang, A., additional

Published
2019
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16. Not all point mutations are the same: A multi-institutional study of KRAS in colorectal liver metastases

Author

Margonis, G.A., primary, Buettner, S., additional, Andreatos, N., additional, Wagner, D., additional, Sasaki, K., additional, Wang, J., additional, Kamphues, C., additional, Morioka, D., additional, Løes, I.M., additional, Imai, K., additional, He, J., additional, Pawlik, T.M., additional, Kaczirek, K., additional, Lønning, P.E., additional, Burkhart, R., additional, Endo, I., additional, Baba, H., additional, Mischinger, H.J., additional, Aucejo, F.N., additional, Poultsides, G., additional, Kreis, M.E., additional, Wolfgang, C.L., additional, and Weiss, M.J., additional

Published
2019
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21. SU‐E‐T‐131: Artificial Neural Networks Applied to Overall Survival Prediction for Patients with Periampullary Carcinoma

Author

Gong, Y, primary, Yu, J, additional, Yeung, V, additional, Palmer, J, additional, Yu, Y, additional, Lu, B, additional, Babinsky, L, additional, Burkhart, R, additional, Leiby, B, additional, Siow, V, additional, Lavu, H, additional, Rosato, E, additional, Winter, J, additional, Lewis, N, additional, Sama, A, additional, Mitchell, E, additional, Anne, P, additional, Hurwitz, M, additional, Yeo, C, additional, Bar‐Ad, V, additional, and Xiao, Y, additional

Published
2015
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27. TRANAIR - A computer code for transonic analyses of arbitrary configurations

Author

Samant, S. S, Bussoletti, J. E, Johnson, F. T, Burkhart, R. H, Everson, B. L, Melvin, R. G, Young, D. P, Erickson, L. L, and Madson, M. D

Subjects
Aerodynamics
Abstract

Attention is given to a new approach to solving full potential equations about arbitrary configurations. Numerical algorithms from such fields as finite elements, preconditioned Krylov subspace methods, discrete Fourier analysis, and integral equations are combined to take advantage of the size and speed of current and emerging supercomputers. On the basis of this appraoch, a robust, efficient and easy to use computer code referred to as TRANAIR has been developed for transonic analysis of complex geometries.

Published
1987

28. A new approach to the solution of boundary value problems involving complex configurations

Author

Rubbert, P. E, Bussoletti, J. E, Johnson, F. T, Sidwell, K. W, Rowe, W. S, Samant, S. S, Sengupta, G, Weatherill, W. H, Burkhart, R. H, and Woo, A. C

Subjects
Numerical Analysis
Abstract

A new approach for solving certain types of boundary value problems about complex configurations is presented. Numerical algorithms from such diverse fields as finite elements, preconditioned Krylov subspace methods, discrete Fourier analysis, and integral equations are combined to take advantage of the memory, speed and architecture of current and emerging supercomputers. Although the approach has application to many branches of computational physics, the present effort is concentrated in areas of Computational Fluid Dynamics (CFD) such as steady nonlinear aerodynamics, time harmonic unsteady aerodynamics, and aeroacoustics. The most significant attribute of the approach is that it can handle truly arbitrary boundary geometries and eliminates the difficult task of generating surface fitted grids.

Published
1986

29. Numerical simulations of a transverse indirect circulation and low-level jet in the exit region of an upper-level jet

Author

Brill, K. F, Uccellini, L. W, Burkhart, R. P, Warner, T. T, and Anthes, R. A

Subjects
Meteorology And Climatology
Abstract

A numerical study was performed of a severe weather event (tornado) which occurred on May 10, 1973 in the Ohio region. The situation was modeled with a primitive equation mesoscale dynamic formulation. Account was taken of precipitation, the planetary boundary layer parameters as bulk quantities, the vertical pressure gradient, and lateral boundary conditions based on radiosonde data. Two 12-hr simulations, adiabatic and nondivergent, respectively, were analyzed for relationships between upper and lower level jets. In the adiabatic formulation, a transverse circulation with a low level jet formed at the exit region of the upper level jet. The nondivergent situation led to similar, but weaker, phenomena. Both forms suggest that indirect circulation in the exit zone of an upper level jet is strongly influenced by the initial structure of the jet.

Published
1985
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30. Low-level circulations induced by an upper-level jet in a fine mesh numerical model

Author

Burkhart, R. P and Anthes, R. A

Subjects
Meteorology And Climatology
Abstract

Attention is given to varying the initial conditions in the Penn State three-dimensional numerical model in the development of the low-level jet over the Ohio Valley during the 10 May 1973 severe weather event. The results of two forecasts are summarized: (1) the control forecast which interpolated the National Meteorological Center's operational analysis to the mesoscale model grid; and (2) modifying the control forecast by inserting artificial soundings and surface observations. Enhancements are made on the basis of subsynoptic scale analyses by Uccellini and surface data. The results indicate that the low-level jet was in part induced by pressure changes associated with deceleration and horizontal divergence of air in the exit region of the upper-level jet. The enhancement of the initial moisture field using surface reports of clouds and precipitation has a substantial effect on precipitation.

Published
1981

43. Some Photophysical Properties of Electronically Excited Phenyldibenzophosphole in Rigid Polymer Matrices

Author

Ganguly, T. and Burkhart, R. D.

Abstract

Phenyldibenzophosphole (PDP), present as a dopant in polymer matrices, has been subjected to photoexcitation by 308 nm excimer laser pulses. Both polystyrene (PS) and poly(butyl methacrylate) (PBuMA) have been used as hosts. Luminescence spectra and transient absorption spectra and their respective temporal behavior have been recorded for samples varying in PDP content from 2 to 15% by weight. The time regime from several tens of nanoseconds to seconds was investigated. Phosphorescence decays examined at 15 K yield a lifetime component in the microsecond domain as well as a very long-lived component on the order of seconds. In addition to the phosphorescence spectrum, with origin at 427 nm, a shorter wavelength component with origin near 350 nm is found. In polymer hosts a band at 395 nm is also observed. This latter is assigned to delayed excimer fluorescence while the 350 nm component is delayed monomeric fluorescence. Similarly, an emission at 500 nm is found which grows relative to the main phosphorescence peak at 470 nm with increasing solute concentration. This band is assigned to an excited state van der Waals complex. Transient triplet absorption decays were very well represented by a rate equation for concurrent first- and second-order kinetics. Similar first-order rate constants were found both in PS and PBuMA. The second-order component is believed to be due to triplet−triplet annihilation. Phosphorescence decays yield first-order rate constants in excellent agreement with those obtained by transient absorption. All aspects of the photophysics are strongly influenced by the dramatic non-homogeneity of the solute distribution.

Published
1997

44. Triplet Energy Migration in Poly(4-methacryloylbenzophenone-co-methyl methacrylate) Films:  Temperature Dependence and Chromophore Concentration Dependence

Author

Tsuchida, A., Yamamoto, M., Liebe, W. R., Burkhart, R. D., and Tsubakiyama, K.

Abstract

Transient decays of triplet−triplet (TT) absorption of excited triplet benzophenone (BP) chromophore in poly(4-methacryloylbenzophenone-co-methyl methacrylate) (BPX, X is the mol % of BP, X = 1−100) films were studied by laser photolysis with a kinetic scheme involving a TT annihilation in a wide temperature range (20−240 K). The rate constant of the TT annihilation was analyzed by a diffusion model of the BP triplet state. The calculated diffusion coefficient (D) increased greatly with the increase of temperature and BP concentration in the BPX sample from 1 × 10-11 cm2 s-1 (20 K, X = 1) to 5 × 10-7 cm2 s-1 (240 K, X = 100). The steep increase in D was observed at the average BP distance less than 1.2 nm and above ca. 150 K. This temperature corresponds to Tγ of poly(methyl methacrylate), α-methyl rotation.

Published
1996

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