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6. Neural stochastic differential equations for particle dispersion in large-eddy simulations of homogeneous isotropic turbulence.

Author

Williams, J., Wolfram, U., and Ozel, A.

Subjects
*STOCHASTIC differential equations, *TURBULENCE, *REYNOLDS number, *TURBULENT flow, *KINETIC energy, *LARGE eddy simulation models
Abstract

In dilute turbulent particle-laden flows, such as atmospheric dispersion of pollutants or virus particles, the dynamics of tracer-like to low inertial particles are significantly altered by the fluctuating motion of the carrier fluid phase. Neglecting the effects of fluid velocity fluctuations on particle dynamics causes poor prediction of particle transport and dispersion. To account for the effects of fluid phase fluctuating velocity on the particle transport, stochastic differential equations coupled with large-eddy simulation are proposed to model the fluid velocity seen by the particle. The drift and diffusion terms in the stochastic differential equation are modeled using neural networks ("neural stochastic differential equations"). The neural networks are trained with direct numerical simulations (DNS) of decaying homogeneous isotropic turbulence at low and moderate Reynolds numbers. The predictability of the proposed models is assessed against DNS results through a priori analyses and a posteriori simulations of decaying homogeneous isotropic turbulence at low-to-high Reynolds numbers. Total particle fluctuating kinetic energy is under-predicted by 40% with no model, compared to the DNS data. In contrast, the proposed model predictions match total particle fluctuating kinetic energy to within 5% of the DNS data for low- to high-inertia particles. For inertial particles, the model matches the variance of uncorrelated particle velocity to within 10% of DNS results, compared to 60%–70% under-prediction with no model. It is concluded that the proposed model is applicable for flow configurations involving tracer and inertial particles, such as transport and dispersion of pollutants or virus particles. [ABSTRACT FROM AUTHOR]

Published
2022
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8. Ongoing and Upcoming Cold-Water Coral Multi Stressor Experiments

Author

Barnhill, K.A., Gutiérrez-Zárate, C. (Cristina), Carreiro-Silva, M. (Marina), Orejas, C. (Covadonga), Veiga, Alfredo, Martins, A., Rakka, M. (María), Movilla-Martín, J. (Juancho), Wolfram, U., Álvarez, M. (Marta), Varela, M.M. (Marta María), Gori, A. (Andrea), Henninge, S., and Roberts, J.M.

Subjects
acidification, CWC multi-stressor experiments, ecophysiology, regeneration, North Atlantic, personnel, global climate change stressors, Cold-water corals (CWC) ecophysiological response, iATLANTIC, financing
Abstract

Comunicación escrita (póster) a Congresos, • Cold-water corals (CWC) form complex 3-D structures that are biodiversity hotspots. However, the knowledge about their ecophysiological response to global change stressors (i.e. warming, acidification, decrease of dissolved oxygen concentration) is still very limited, as well as their possible interactions with local stressors such as the impacts from mining and fishing activities. • Three long-term, multi stressor experiments will explore the combined impact of several environmental and local stressors based on the IPCC projections on different CWC species across the North Atlantic. • Further experiments will include the addition of particles from mining or sediment from trawling activities to all treatments after long-term experiments finish to study the potential physical damage and ecotoxicological effects. • The results from these studies will increase our knowledge on the potential consequences of global change and local stressors and their possible interactions on CWC species and ecosystems that they form. • The results will contribute to support science-based marine spatial planning for the North Atlantic., European Union Commission Horizon 2020 Programa (grant agreement 818123), FEDER ((ACORES-01-0145-FEDER-000140), Ayuntamiento de A Coruña (Spain) and Deep-Sea Biology Society

Published
2021

10. Crumbling Reefs and Cold-Water Coral Habitat Loss in a Future Ocean: Evidence of 'Coralporosis' as an Indicator of Habitat Integrity

Author

Hennige S, Wolfram U, Wickes L, Murray F, Roberts JM, Kamenos NA, Schofield S, Groetsch A, Spiesz EM, Aubin-Tam M-E, and Etnoyer PJ

Abstract

Ocean acidification is a threat to the net growth of tropical and deep-sea coral reefs, due to gradual changes in the balance between reef growth and loss processes. Here we go beyond identification of coral dissolution induced by ocean acidification and identify a mechanism that will lead to a loss of habitat in cold-water coral reef habitats on an ecosystem-scale. To quantify this, we present in situ and year-long laboratory evidence detailing the type of habitat shift that can be expected (in situ evidence), the mechanisms underlying this (in situ and laboratory evidence), and the timescale within which the process begins (laboratory evidence). Through application of engineering principals, we detail how increased porosity in structurally critical sections of coral framework will lead to crumbling of load-bearing material, and a potential collapse and loss of complexity of the larger habitat. Importantly, in situ evidence highlights that cold-water corals can survive beneath the aragonite saturation horizon, but in a fundamentally different way to what is currently considered a biogenic cold-water coral reef, with a loss of the majority of reef habitat. The shift from a habitat with high 3-dimensional complexity provided by both live and dead coral framework, to a habitat restricted primarily to live coral colonies with lower 3-dimensional complexity represents the main threat to cold-water coral reefs of the future and the biodiversity they support. Ocean acidification can cause ecosystem-scale habitat loss for the majority of cold-water coral reefs.

Published
2020

14. Abstract of the 68th Meeting (Spring Meeting) 6–9 March 1990, Heidelberg

Author

Sakmann, B., Schrader, J., Brenner, B., Murer, H., Boeckh, J., Handwerker, H. O., HonerjÄger, P., Dugas, M., Wang, G., DeLuca, A., Brinkmeier, H., Fakler, B., Pröbstle, T., Rüdel, R., Pohl, J. -A., Meves, H., Kroll, B., Bremer, S., Tümmler, B., Frömter, E., Schwegler, J. S., Steigner, W., Silbernagl, S., Pusch, Michael, Niemann, P., Schmidtmayer, J., Ulbricht, W., Hansen, G., Lönnendonker, U., Neumcke, B., Eickhorn, R., Hornung, D., Antoni, H., Penner, R., Neher, E., Takeshima, H., Nishimura, S., Numa, S., Melzer, W., Feldmeyer, D., Pohl, B., Zöllner, P., Müller, T. H., Swandulla, D., Misgeld, U, Ganitkevich, V. Ya., Isenberg, G., Cavalié, A., Allen, T. J. A., Trautwein, W., Pelzer, Siegried, Shuba, Yaroslav M., Asai, Tatsuya, Trautwein, Wolfgang, Brown, Arthur M., Birnbauner, Lutz, McDonald, Terence F., Pelzer, Dieter, Eckert, R., Hescheler, J., Rosenthal, W., Offermann, S., Krautwurst, D., Schultz, G., Kettenmahn, Helmut, Trotter, J., Verkhratsky, Alexe J N., Savtchenko, Alexej N., Verkhratsky, Alexej N., Schiefer, A., Klöckner, U., Partridge, L. D., SchÄfer, S., Jonas, P., Koh, D. S., Kampe, K., Hermsteiner, M., Vogel, W., Bauer, C. K., Schwarz, J. R., Fink, R. H. A., Wettwer, E., Weik, R., Schlatter, E., Bleich, M., Granitzer, M., Leal, T., Nagel, W., Crabbé, J., Lang, F., Kahn, E., Friedrich, F., Paulmichl, M., Hammerer, M., Maly, K., Grunicke, H., Böhm, T., Nilius, B., Gögelein, H., Dahlem, D., Weiss, H., Waldegger, S., Woell, E., Paulmichl, R., Ruppersberg, J. P., Schröter, K. H., Stocker, M., Pongs, O., Wittka, R., Boheim, G., Lichtinghagen, R, Augustine, C. K., Stühmer, W., Hoppe, Dorothe, Hoppe, D., Zittlau, K. E., Walther, C., Hatt, H., Franke, C., Quasthoff, S., Wischmeyer, E., Jockusch, H., Friedrich, M., Benndorf, K., Bollmann, G., Hirche, Hj., Hollunder-Reese, F., Mohrmann, M., Greger, R., Weber-Schürholz, S., Schürholz, T., Akabas, M., Landry, D., Al-Awqati, Q., Guse, A. H., Gercken, G., Meyerhof, W., Westphale, H. -J., Kerstins, U., Oberleithner, H., Tilmann, M., Kunzelmann, K., Klitsch, T., Siemen, D., Draguhn, A., Verdoorn, T. A., Pritchett, D. B., Seeburg, P. H., Malherbe, P., Möhler, H., Sakmann, B., Hatt H., Dudel, J., Stern, P., Zufall, F., Rosenheimer, J., Smith, D. O., Dörner, R., Ballanyi, K., Schlue, W. -R., Kalthof, B., Pott, L., Busch, C., Konno, T., Stenql, M., Reinhardt, Ch., Kaiser, H., Baumann, R., Wilimzig, M., Eichenlaub, R., Neumann, E., Lessmann, V., Gottmann, K., Dietzel, I. D., Keller, B. U., Yaari, Y., Konnerth, A., Backus, K. H., Giller, T., Knoflach, F., Pflimlin, P., Trübe, G., von Blankenfeld, G., Ymer, S., Sontheimer, H., Ewert, M., Seeburg, P. H., Kettenmann, H., Schneggenburger, R., Paschke, D., Hülser, D. F., Ubl, J., Kolb, H. A., Ströttchen, J., Boheim, S., Wehner, F., Guth, D., Kinne, R. K. H., Hülser, D. F., Polder, H. R., Bödeker, D., Hoppe, Susanne, Höller, H., Hampe, W., Ruf, H., Schulz, I., Dehlinger-Kremer, M., Ozawa, T., Vasilets, L., Schmalzing, G., MÄdefessel, K., Biel, H., Schwarz, W., Burckhardt, B. C., Stallmach, N., MairbÄurl, H., Hoffman, J. F., Schömig, E., Heuner, A., Göbel, B. O., Siffert, W., Butke, A., Hoffmann, G., zu Brickwedde, M. -K. Meyer, Vetter, H., Düsing, R., Rosskopf, D., Osswald, U., Steffgen, J., Koepsell, H., Martens, H., Rübbelke, M., GÄbel, G., Arens, J., Stabel, J., Fischer, Y., Thomas, J., Rose, H., Kammermeier, H., Munsch, Thomas, Deitmer, Joachim W., Engelmann, B., Duhm, J., Deitmer, Joachim W., Gunzel, D., Galler, S., Fischer, H., Clauss, W., Van Driessche, W., Köckerling, A, Schulzke, JD, Sorgenfrei, D, Fromm, M, Simon, B., Ganapathy, V., Leibach, F. H., Burckhardt, G., Krattenmacher, R., Voigt, Rosita, Dietrich, S., Leyssens, A., Zhang, S. L., Weltens, R., Steels, P., Hoffmann, B., Heinz, M., Habura, B., Dörge, A., Rechkemmer, G., von Engelhardt, W., StrauB, O., Wiederholt, M., Margineanu, D. -G., Van Driessche, W., Kreusel, K. M., Fromm, M., Lempart, U., Sorgenfrei, D., Hegel, U., Augustin, A. J., . Goldstein, R., Purucker, E., Lutz, J., Illek, B., Thiele, K -P., Schwealer, JS., Dittmer J., Bauer C., Eckardt, K. -U., Dittmer, J., Neumann, R., Bauer, C., Kurtz, A., Fromm, H., Schulzke, J. D., Clausen, P., Krohn, A., Lüderitz, S., Hierholzer, K., Kersting, U., Woinowski, L., Gro\mann, R., Bin, X. U., Ellendorff, F., Nitschke, R., Fröbe, U., Scholz, H., della Bruna, R., Ehmke, H., Persson, P. B., Seyfarth, M., Kirchheim, H. R., Dietrich, M. S., Parekh, N., Steinhausen, M., Bührle, C. P., Nobiling, R., Ullrich, K. J., Rumrich, G., Klöss, S., Papavassiliou, F., Hoyer, J., Schmitt, C., Jungwirth, A., Ritter, M., Westphale, H. J., Bevan, C., Theiss, C., Denek, Liliana, Schwegler, Johann S., SchÄfer, Roland, Augustin, Albert J., Heidland, August, Nafz, B., Just, A., Steidl, M., Pinggera, G., Gerstberger, R., Schütz, H., Simon, E., Lohrmann, E., Masereel, B., Delarge, J., Lang, H. J., Englert, H. C., Caliebe, D., Mályusz, M., Wrigge, P., Gronow, G., Klause N., Mályusz, M., Zinnert, H., Fagel, H., Jelkmann, W., Weiss, Ch., Augustin, A. J., Keil, R., Schmidt, W., Kröger, C., Brabant, E. G., Hilgendorf, A., Strauch, S., Lane, F., Prick, A., Golenhofen, N., Mildenberger, S., Schwegler, J. S., Flemming, B., Roloff, D., Wronski, T., Drews, G., Debuyser, A., Henquin, J. C., Jackson, M. B., DeRiemer, S. A., Schmid, A., Schnefel, S., Pröfrock, A., Hinsch, K. -D., Milz, J., Lamprecht, G., Seidler, U., Silen, W., Aziz, O., Reschke, W., Fischer, G., De Decker, N., Hayes, T., Coast, G., Van Kerkhove, E., von zur Mühlen, F., Eckstein, F., Hegel, U, Bentzel, CJ, Riecken, EO, Siemer, C., Rothenpieler, P., Smith, E., Lutnicki, K. R., Wróbel, J. T., Ledwożyw, A., PietraŚ, E., Sender, S., Jürgens, Klaus D., Kleinschmidt, T., Werkmeister, F., Kiwull-Schöne, H., Kiwull, P., Vahle, J., Ott, M., Zimmermann, R. E., Elsing, J. G., Million, D., Zillner, P., Thiel, M., Bardenheuer, H., Peter, K., Fandrey, J., Siegers, C. P., Rupp, H., Elimban, V., Dhalla, N. S., Morano, I., Agostini, B., Mühleisen, M., Mommaerts, W. F. H. M., Ono, K., Wussling, M., Schenk, W., Boldt, W., Lipp, P., Schüttler, K., Szymanski, G., Wendt-Gallitelli, M. F., Herzig, J. W., Depersin, H., Grupp, G., Grupp, I., Glitsch, H. G., Pusch, H., Zylka, Ch., Brāndle, M., Jacob, R., Stein, T., Isselhard, W., Sturz, J., Minor, T., Wingenfeld, P., Siegmund, B., Klietz, T., Schwartz, P., Piper, H. M., Linder, Christa, SchÄfer, Stefan, Heusch, Gerd, Becker, B. F., Reinholz, N., Raschke, P., Leipert, B., Gerlach, E., Dierberger, B., Gülch, R. W., Leverkus, M., Mitsuiye, T., Pohl, U., Wang, S. Y., Meyer, R., Haas, H. G., Christmann, H. Ph, Dörner, Th, Hock, D., Hertel, R., Gagelmann, M., Forssmann, W. G., Leijendekker, W. J., Kissling, G., Michel, H., Goetz, A., Freya, M., Fleckenstein-Grün, G., Schipke, Jochen D., Harasawa, Yasuhiko, Sugiura, Seiryo, Alexander, Joe, Burkhoff, Daniel, Kling, L., Müller-Beckmann, B., Schroth, M., Sponer, G., Böhm, E., Strein, K., Dorszewski, A., Arnold, G., Pike, G. K., Bryant, D. J., Roberts, M. L., Fink, R. H., Ross, Ch., Skyschally, A., Schulz, R., Linder, C., Heusch, G., Schipke, J. D., Burkhoff, D., Alexander, J., Gollnick, F., Peter, Kh., Franken-Weyers, R., Borst, M. M., Deussen, A., Pöpping, S., Hose, H., Strotmann, K. H., Lukascek, B., Karnath, T., Güttier, K., Klaus, W., Haverkampf, K., Guhlmann, M., Schmidt-Ott, S., Heuschen, U., Mall, G., Pfitzer, G., Rösch, J., Arner, A., Rüegg, J. C., Kröger, K., Schipke, J. D., ThÄmer, V., Ehring, Thomas, ThÄmer, Volker, Guth, B. D., Schnabel, Ph A., Schmiedl, A., Gebhard, M. M., Richter, J., Bretschneider, H. J., Guth, B. D., Oudiz, R. J., Schnabel, Ph., Richter, J ., Watanabe, H., Spahr, R., Piper, H. M., Obst, O., Mertens, H., Mülsch, A., Busse, R., Lamontagne, D., Herlan, K., Huang, A., Bassenae, E., Mackert, J. R. L., Schilling, L., Parsons, A. A., Wahl, M., Hock, D., Christmann, M. Ph., Thimm, F., Frey, M., Fleckenstein, a. A., Theilen, H., Göbel, U., Kuschinsky, W., Elbert, Th., Tafil-Klawe, M., Rau, H., Lutzenberger, W., Fleckenstein, A., Forst, H., Haller, M., Santjohanser, C., Lauterjung, L., Smieško, Y., Lang, D. J., Johnson, P. C., Schröck, H., Rau H., Elbert T., Geiger B, Lutzenberger W., Koch, G., Koralewski, H. E., Perschel, F. H., Wagner, K., Krüger, U., Albrecht, M., Hohlbach, G., Maassen, N., Foerster, M., Mühling, J., Bari, F., Pleschka, K., Schmidt, H. D., Gro\, H., Loock, W., Stick, C., Diefenbacher, U., Gronewold, D., Tobinsky, M., Walther-Behrends, A., Witzleb, E., Brummermann, M., Reinertsen, R. E., Rogausch, H., Rohn, W. M., Acker, H., Delpiano, M., Dufau, E., Hentschel, J., Heller, H., Schuster, K. -D., Siekmeier, R., Kronenberger, H., Lintl, H., Schiller-Scotland, Ch. F., Gebhart, J., Heyder, J., Meier-Sydow, J., Stahlhofen, W., Mottaghy, K., Geisen, C., Richter, W., Beckman, J., Marek, W., Ulmer, W. T., Thiele, A. E., Raschke, F., Peter, J. H., Hildebrandt, G., Kullmer, T., Kozianka-Burghof, G., Thiele, A. E., Schlaefke, M. E., Gnuschke, H., Schaefer, T., Schaefer, D., Schaefer, C., Bradley, Ronald J., Sterz, Raimund, Peper, Klaus, Benterbusch, R., Kraft, Th., Yu, L. C., Kuhn, H. J., Blankenbach, K., Asmussen, G., Kunze, I., Pieper, K. -S., Steinmetz, J., Schmidt, H., Krippeit-Drews, P., Hübschen, U., Nacimiento, A. C., Günzel, D., Rathmayer, W., Gaunitz, U., Költgen, D., Zachar, E., Soltau, B., De Martino, L., Hasselbach, W., Kössler, F., Lange, P., Küchler, G., Zeugner, C., Van Eyk, J., Hodges, R. S., Lorkovic, H., Clemens, N., Scheid, P., Noack, Th., Deitmer, P., Golenhofen, K., Lammel, E., Welling, Andrea, Felbel, Jochen, Hofmann, Franz, Katoch, S., Watanabe, T., Mandrek, K., Milenov, K., Hammer, K., Rössler, W., Sann, H., Pierau, Fr -K., Nguyen-Duong, H., Schneider, P., Stahl, F., Lepple-Wienhues, A., Korbmacher, C., Haller, H., Gebauer, M., Willner, U., Bialojan, C., Lengsfeld, M., Kyrtatas, V., Dartsch, Peter C., Boels, P. J., Fischer, W., Lenz, T., Thei\, U., Kreye, V. A. W., Ohkubo, T., Kupp, H., Vonderlage, M., Schreiner, V., Dorlöchter, M., Brinkers, M., Irintchev, A., Wernig, A., Langenfeld, B., Finger, W., Wolburg, H., Beer, A., Schwejda, Ch., Scheller, D., Heister, U., Tegtmeier, F., Knöpfel, Thomas, Spuler, Andreas, Grafe, Peter, GÄhwiler, Beat, Bijak, M., Misgeld, U., Müller, W., Rausche, G., Leweke, F M., Bingmann, D., Moraidis, I., Speckmann, E. -J., Madeja, M., Mu\hoff, U., Lehmenkühler, A, Kuhlmann, D., Hans, M., Lux, H. D., StrÄub, H., Waiden, J., Baker, R. E., Grantyn, R., Perouansky, M., Kraszewski, K, Lehmenkühler, Chr, Dodt, H. U., ZieglgÄnsberger, W., Pawelzik, H., ZieglgÄngsberger, W., Mann, K., Wiethölter, H., Albrecht, D., Dreier, J., Ficker, E., Beck, H., Corrette, B J., Dreyer, F., Repp, H., Dreessen, J., Augustine, G. J., Lehmenkühler, A., Büsselberg, D., Heimrich, B., Haas, H. L., Birnstiel, S., Haas, H. L., Schönrock, B., Altrup, U., Reith, H., Speckmann, E. -J., Alzheimer, C., Bruagencate, G. ten, Fruhstorfer, B., Mignot, E., Nishino, S., Dement, W. C., Guilleminault, C., Simon-Oppermann, Christa, Günther, Olaf, Stehle, J., Reuss, S., Seidel, A., Riemann, R., Vollrath, L., Reimer, Susanne, HölIt, Volker, Sonnhof, U., Krupp, J., Claus, H, Hinckel, P., Dick, H. B. H., Hiemke, C., Jussofie, A., Dorn, T., Uhlig, S., Witte, O. W., Bother B., Eiselt M., Witte H., Zwiener ö, Rother M, Eiseit H., Taghavy, A., KrÄtzer, A., Clusmann, H., Heinemann, U., Block, F., Sonatg, K. -H., Falkeristein, M., Hohnsbein, J., Hoormann, J., Frieling, A., Tarkka, I. M., Kullmann, W., Bromm, B., Hirsch, M. Chr, Wissing, H., Braun, H. A., Igelmund, P., Klu\mann, F. W., Ehrenstein, W. H., Yakimoff, N., Mateeff, S., Zeise, M. L., Arriagada, J., Teschemacher, A., ZieglgÄnsberger, W., Pöppelmann, T., Köhling, R., Boerrigter, P., Reith, H., Anders, K., Ohndorf, W., Dermietzel, R., Richter, D. W., Tölle, T. R., Castro-Lopes, J. M., Neuropharmakologie, Klinische, Sandkühler, J., Leah, J. D., Herdegen, T., Zimmermann, M., Vaitl, D., Gnippe, H., Herbert, M. K., Mengel, M. K. C., Kniffki, K. -D., Linke, R., Vahle-Hinz, C., Schenda, J., Matsumura, K., Herdegen, T., fu, Q. -G., Forster, C., Hutchison, W. D., Morton, C. R., Aschoff, J., Wilhelm, Z., Schwarzacher, S. W., Wasserschaff, M, Hörner, M., Kümmel, H., Windhorst, U., Feldman, J. L., Schmid, K., Foutz, A. S., Denavit-Saubié, M., Pak, M. A., Wehling, P., Evans, C., Bandara, G., Awiszus, F., Feistner, H., Heinze, H. -J., Illert, M., Wasserschaff, M., Kleinebeckel, D., Böhmer, G., Schauer, W., Abel, H. -H., Klü\endorf, D., Koepchen, H. P., Jarolimek, W, König, St, Czachurski, J., Seller, H., Meckler, R. L., McLachlan, E. M., Boczek-Funcke, A., HÄbler, H. -J., JÄnig, W., Michaelis, M., Dembowsky, K., Königr, S., Rau, Harald, HÄbler, H. -J., Unger, M., Merker, G., Roth, J., Zeisberger, E., Gao, H., Hunold, M., Kirchner, F., Takano, K., Schulze, K., Pokorski, M., Sakakibara, Y., Masuda, A., Morikawa, T., Ahn, B., Takaishi, S., Paulev, P. -E., Honda, Y., Flügge, G., Fuchs, E., König, S., Eysel, U. Th., Schmidt-Kastner, R., Skrandies, W., Geib, T., Baumann, C., Schmidt, K. -F., Knapp, A. G., Dowling, J. E., Kuba, M., Toyonaga, N., Kubová, Z., Ehrenstein, W. H., Jacobi, P., Schmidt, K. -F., Nöll, G. N., Baumann, Ch., Tabata, M., Martin, Ch., Meissl, H., Knottenberg, Th., Scheibner, H., Zenner, Hans P., Zimmennann, Ulrike, Gitter, Alfred H., Ding, D., Smolders, J. W. T., Klinke, R., Boekhoff, I., Raming, K., Krieger, J., Tareilus, E., Strotinann, J., Breer, H., Schild, D., DeSimone, J. A., Hellwig, S., Gitter, A. H., Plinkert, P. K., Zenner, H. P., Koltzenbwg, M., Pinter, E., SchÄfer, K., Braun, H. A., Necker, R., Hanesch, U., Heppelmann, B., Schmidt, R. F., Mense, S., Hoheisel, U., Steen, K. H., Anton, F., Reek, P. W., Handwerker, H. O., Lewin, G. R., McMahon, S. B., Heyer, G., Hornstein, O. P., Klement, W., Arndt, J. O., Maeerl, W., GrÄmer, G., Schepelmann, K., Me\linger, K., Schaible, H. -G., Treede, R. D., Meyer, R. A., Campbell, J. N., Claus, D., Neundörfer, B., Ernst, R., Tick-Waider, A. M., Bretschneider, F., Peters, R. C., Tennis, P. F. M., Teunis, P. F. M., Hoheisel, D., Scherotzke, R., Bub, A., Manzl, G., Forssmann, W. G., Jessen, C., Nuesslein, B., Schmidt, I., Wetzig, J., Reiser, M., Bregenzer, N., von Baumgarten, R. J., Mohr, E., Krzywanek, H., Warncke, G., Schuchmann, K. -L., Linow, H., Klu\mann, F. H., Redlin, U., Heldmaier, G., Bamler, A, Koller, A., Felber, S., Haid, C., Wicke, K., Raas, E., Xuemin, Wang, Kerning, Chen, Ying, Shi, Hanping, Shi, Warncke, Günther, Voisord, R., Dortsch, P. C., Betz, E., Karbach, U., Walenta, S., Gross, M. W., Mueller-Klieser, W., Vaupel, P., Okunieff, P., Mayer, W. -K., Stohrer, M., Krüger, W., Müller-Klieser, W., Strupp, M., Weial, P., Bostock, H., Piwernetz, K., Renner, R., Grafe, P., Lankers, J., Zangemeister, W., Kunze, K., Tries, S., Heinle, H., Beckerath, N. V., Maier-Rudolph, W., Mehrke, G., Günther, K., Goedel-Meinen, L., Daut, J., Piper, H. M., Kopp, A., Noll, T., Goellner, A., Gerlach, S., Teutsch, H. F., Schienger, K., Schwab, R., Höckel, M., Fotev, Z., Nienhaus, M., Kaczmarczyk, Gabriele, Richter, Dinah, Korte, Gabriele, Förther, J., Reinhardt, H. W., Schreiber, R., Rupp, J., Murphy, G., Fingerle, J., Kloiber, O., Miyazawa, T., Höhn-Berlage, M., Hossmann, K. -A., Schad, H., Heimisch, W., Blasini, R., Haas, F., Mendier, M., Spuler, A., Lehmann-Hom, F., Wolfram, U., Fenske, M., Sachser, N., Weis, Ch., Marktl, W., Kopta, B., Klammer, N., Rudas, B., Pohl, H., Nienartowicz, A., Moll, W., Klempt, M., Blum, S., Bühler, H., Lichtenstein, I., Novak, A., Siebe, H., Hierholzer, K., and Peper, K.

Published
1990
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16. Die Waldtiere Ruprecht halfen, damit er zu Weihnachten wieder gesund wurde. : Weihnachtsgeschichte

Author

Wolfram U. Kirsch and Wolfram U. Kirsch

Abstract

In der Vorlesegeschichte zur Weihnachtszeit stehen die Waldtiere im verschneiten Märchenwald vor der Tatsache, dass ihre Futterstelle, die sonst von Ruprecht, dem Weihnachtsmann, täglich aufgefüllt wird, leer ist. Als ihn eine Krankheit ans Bett fesselt, organisieren alle gemeinsam Medizin, die dem Weihnachtsmann gegeben wird, um seine Vorbereitungen für das Fest zu treffen. Zur selben Zeit sorgen sich die kaputten Spielsachen, wie es der kranke Weihnachtsmann schaffen will, sie zu reparieren, damit sie es pünktlich unter den Christbaum schaffen. Im letzten Teil starten die Waldtiere eine Hilfsaktion für den Koalabären Phu, weil der Ruprecht bei der Abfahrt am Heiligen Abend aus seiner Manteltasche die kleine Puppe verlor, die vom Rehkitz Wally mit seiner Mutter Adele weinend neben der Schlittenspur gefunden wird. Alle Tiere helfen Phu, der dann auch kurz vor der Bescherung, in einer Luftgondel von Schwänen gezogen, bis zum Haus der Puppenmutti kommt. Aber kurz nach der Bescherung gibt es Tränen. Zum Schluss sind alle.....

Published
2018

17. Commissioning of a Versa HDTM linear accelerator for three commercial treatment planning systems.

Author

Laub, Wolfram U., Merz, Brandon, and Kishore, Monica

Subjects
LINEAR accelerators, VOLUMETRIC-modulated arc therapy, PHOTON beams, MODEL validation, RADIOTHERAPY
Abstract

In a mixed‐vendor radiation oncology environment, it is advantageous if the department's treatment planning system (TPS) supports the linear accelerators of different vendors. In this publication beam data collection and modeling for the Versa HD linear accelerator in Monaco, Pinnacle, and Eclipse are discussed. In each TPS static field, Intensity‐Modulated Radiation Therapy (IMRT) step and shoot, and Volumetric‐Modulated Arc Therapy (VMAT) plans for flattened and flattening‐filter free photon beams of all available energies were evaluated for field sizes >3 × 3. To compare passing rates, identical beam model validation plans were calculated in each TPS. Eclipse, Monaco, and Pinnacle beam models passed validation measurements in homogeneous materials for a variety of treatment fields, including static, IMRT, and VMAT. In the case of Eclipse, the "dosimetric leaf gap" parameter was found to be critical for passing rates of VMAT plans. The source size parameter plays an important role as well for small fields. In the case of Pinnacle the multileaf collimator offset table needed to be optimized for better VMAT QA results. Each of the investigated treatment planning systems met the criteria to be used clinically in conjunction with Elekta Versa HD linear accelerators. It can be of great advantage to have the option to operate a TPS and linear accelerator from different vendors, as decisions surrounding linear accelerator or TPS purchases are very complicated and not just limited to technical considerations. [ABSTRACT FROM AUTHOR]

Published
2021
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18. A generalized anisotropic quadric yield criterion and its application to bone tissue at multiple length scales

Author

Schwiedrzik, J., Wolfram, U., Zysset, P., Schwiedrzik, J., Wolfram, U., and Zysset, P.

Abstract

Nonlinear computational analysis of materials showing elasto-plasticity or damage relies on knowledge of their yield behavior and strengths under complex stress states. In this work, a generalized anisotropic quadric yield criterion is proposed that is homogeneous of degree one and takes a convex quadric shape with a smooth transition from ellipsoidal to cylindrical or conical surfaces. If in the case of material identification, the shape of the yield function is not known a priori, a minimization using the quadric criterion will result in the optimal shape among the convex quadrics. The convexity limits of the criterion and the transition points between the different shapes are identified. Several special cases of the criterion for distinct material symmetries such as isotropy, cubic symmetry, fabric-based orthotropy and general orthotropy are presented and discussed. The generality of the formulation is demonstrated by showing its degeneration to several classical yield surfaces like the von Mises, Drucker-Prager, Tsai-Wu, Liu, generalized Hill and classical Hill criteria under appropriate conditions. Applicability of the formulation for micromechanical analyses was shown by transformation of a criterion for porous cohesive-frictional materials by Maghous et al. In order to demonstrate the advantages of the generalized formulation, bone is chosen as an example material, since it features yield envelopes with different shapes depending on the considered length scale. A fabric- and density-based quadric criterion for the description of homogenized material behavior of trabecular bone is identified from uniaxial, multiaxial and torsional experimental data. Also, a fabric- and density-based Tsai-Wu yield criterion for homogenized trabecular bone from in silico data is converted to an equivalent quadric criterion by introduction of a transformation of the interaction parameters. Finally, a quadric yield criterion for lamellar bone at the microscale is identified from a

Published
2018

19. Deine Kraft, um zu leben

Author

Wolfram U. Kirsch and Wolfram U. Kirsch

Abstract

Diese Geschichte basiert auf Erlebnissen und Erfahrungen mit der schrecklichsten Geißel der Menschheit, dem Krebs. Den jeweils Betroffenen soll diese Erfahrung helfen, die Angst der Hilflosigkeit zu überwinden und Mut machen, den steinigen Weg mit allen Höhen und Tiefen zu gehen, um weiterzuleben. Keiner sollte alleinstehen, es gibt immer jemanden, der DIR zur Seite steht.DU schaffst das, weil DU das willst. Zusammen mit DEINER Familie und Betroffenen zu kämpfen. DU musst das nur WOLLEN. Diese Last lässt sich zusammen BESSER tragen.

Published
2017

20. Inselspuren

Author

Wolfram U. Kirsch and Wolfram U. Kirsch

Abstract

Die Geschichte der Jugend, die ihr Glück sucht, ist so alt wie die Menschheit. In jeder Zeit steht diese Suche unter einem anderen Stern.In dieser Erzählung sind die Geschichten und Erlebnisse von jungen Leuten beschrieben. Ihre Wünsche und ihre Sehnsüchte, ihre Liebe und der Mut zur Veränderung von eingefahrenen Gewohnheiten.Auf einer Insel in der Ostsee, die ein Mekka junger Leute ist, treffen sich Jahr für Jahr Gleichgesinnte und leben dort ihren Traum vom Glück und der Freiheit, so zu leben und zu lieben, wie sie das wollen. In dieser Zeit nehmen und leben sie ihre Freiheit und lernen, damit umzugehen.Jedes Jahr werden es mehr, die ihre Erfahrungen austauschen, und sie werden verstanden. Unsere hier beschriebenen jungen Leute kommen aus den unterschiedlichsten Elternhäusern, die ihre eigenen Auffassungen haben.Nach dem Sommer hinterlassen jedenfalls alle ihre Spuren auf der Insel.

Published
2017

21. Circumferential or sectored beam arrangements for stereotactic body radiation therapy (SBRT) of primary lung tumors: Effect on target and normal-structure dose-volume metrics

Author

James A. Tanyi, Lu Z. Meng, Martin Fuss, Nathan M. Matsunaga, Robert F. Arao, Kelly M.P. Carson, Yiyi Chen, Wolfram U. Laub, Charles L. McCracken, Catherine M. Kato, Mara Rosenberg, and Emily J. Doss

Subjects
Male, Lung Neoplasms, Stereotactic body radiation therapy, medicine.medical_treatment, Radiosurgery, Beam (nautical), Carcinoma, Non-Small-Cell Lung, medicine, Humans, Radiology, Nuclear Medicine and imaging, Esophagus, Lung cancer, Aged, Aged, 80 and over, Monitor unit, Lung, Radiological and Ultrasound Technology, business.industry, Radiotherapy Planning, Computer-Assisted, Middle Aged, medicine.disease, Radiation therapy, medicine.anatomical_structure, Oncology, Female, Radiotherapy, Intensity-Modulated, Nuclear medicine, business
Abstract

To compare 2 beam arrangements, sectored (beam entry over ipsilateral hemithorax) vs circumferential (beam entry over both ipsilateral and contralateral lungs), for static-gantry intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) delivery techniques with respect to target and organs-at-risk (OAR) dose-volume metrics, as well as treatment delivery efficiency. Data from 60 consecutive patients treated using stereotactic body radiation therapy (SBRT) for primary non-small-cell lung cancer (NSCLC) formed the basis of this study. Four treatment plans were generated per data set: IMRT/VMAT plans using sectored (-s) and circumferential (-c) configurations. The prescribed dose (PD) was 60Gy in 5 fractions to 95% of the planning target volume (PTV) (maximum PTV dose ~ 150% PD) for a 6-MV photon beam. Plan conformality, R50 (ratio of volume circumscribed by the 50% isodose line and the PTV), and D2cm (Dmax at a distance ≥2cm beyond the PTV) were evaluated. For lungs, mean doses (mean lung dose [MLD]) and percent V30/V20/V10/V5Gy were assessed. Spinal cord and esophagus Dmax and D5/D50 were computed. Chest wall (CW) Dmax and absolute V30/V20/V10/V5Gy were reported. Sectored SBRT planning resulted in significant decrease in contralateral MLD and V10/V5Gy, as well as contralateral CW Dmax and V10/V5Gy (all p < 0.001). Nominal reductions of Dmax and D5/D50 for the spinal cord with sectored planning did not reach statistical significance for static-gantry IMRT, although VMAT metrics did show a statistically significant decrease (all p < 0.001). The respective measures for esophageal doses were significantly lower with sectored planning (p < 0.001). Despite comparable dose conformality, irrespective of planning configuration, R50 significantly improved with IMRT-s/VMAT-c (p < 0.001/p = 0.008), whereas D2cm significantly improved with VMAT-c (p < 0.001). Plan delivery efficiency improved with sectored technique (p < 0.001); mean monitor unit (MU)/cGy of PD decreased from 5.8 ± 1.9 vs 5.3 ± 1.7 (IMRT) and 2.7 ± 0.4 vs 2.4 ± 0.3 (VMAT). The sectored configuration achieves unambiguous dosimetric advantages over circumferential arrangement in terms of esophageal, contralateral CW, and contralateral lung sparing, in addition to being more efficient at delivery.

Published
2013

22. Characterizing microcrack orientation distribution functions in osteonal bone samples

Author

Wolfram, U., Schwiedrzik, J., Mirzaali, M., Bürki, A., Varga, P., Olivier, Cécile, Peyrin, F., Zysset, P., Institute for Surgical Technology and Biomechanics [Bern] (ISTB), University of Bern, School of Engineering and Physical Science, Institute for Mechanical, Process and Energy Engineering, Heriot-Watt University [Edinburgh] (HWU), Swiss Federal Laboratories for Materials Science and Technology [Thun] (EMPA), AO Research institute Davos (ARI), AO Foundation, European Synchrotron Radiation Facility (ESRF), Imagerie Tomographique et Radiothérapie, Centre de Recherche en Acquisition et Traitement de l'Image pour la Santé (CREATIS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Hospices Civils de Lyon (HCL)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Hospices Civils de Lyon (HCL)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Microcrack segmentation, Synchrotron radiation, X-ray phase micro-tomography, Microdamage, [SDV.IB.IMA]Life Sciences [q-bio]/Bioengineering/Imaging, Cortical bone, 570 Life sciences, biology, Orientation distribution functions, 610 Medicine & health, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing
Abstract

International audience; Prefailure microdamage in bone tissue is considered to be the most detrimental factor in defining its strength and toughness with respect to age and disease. To understand the influence of microcracks on bone mechanics it is necessary to assess their morphology and three-dimensional distribution. This requirement reaches beyond classic histology and stereology, and methods to obtain such information are currently missing. Therefore, the aim of the study was to develop a methodology that allows to characterize three-dimensional microcrack distributions in bulk bone samples.Four dumbbell-shaped specimens of human cortical bone of a 77-year-old female donor were loaded beyond yield in either tension, compression or torsion (one control). Subsequently, synchrotron radiation micro-computed tomography (SRμCT) was used to obtain phase-contrast images of the damaged samples. A microcrack segmentation algorithm was developed and used to segment microcrack families for which microcrack orientation distribution functions were determined.Distinct microcrack families were observed for each load case that resulted in distinct orientation distribution functions. Microcracks had median areas of approximately 4.7 inline imagem2, 33.3 inline imagem2 and 64.0 inline imagem2 for tension, compression and torsion. Verifying the segmentation algorithm against a manually segmented ground truth showed good results when comparing the microcrack orientation distribution functions. A size dependence was noted when investigating the orientation distribution functions with respect to the size of the volume of interest used for their determination. Furthermore, a scale separation between tensile, compressive and torsional microcracks was noticeable. Visual comparison to classic histology indicated that microcrack families were successfully distinguished.We propose a methodology to analyse three-dimensional microcrack distributions in overloaded cortical bone. Such information could improve our understanding of bone microdamage and its impact on bone failure in relation to tissue age and disease.Lay descriptionPrefailure microdamage in bone tissue is considered to be the most detrimental factor in defining its strength and toughness with respect to age and disease. To understand the influence of microcracks on bone mechanics it is necessary to assess their morphology and three-dimensional distribution. This requirement reaches beyond classic histology and stereology, and methods to obtain such information are currently missing.

Published
2016
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24. Depolarization-induced retrograde synaptic inhibition in the mouse cerebellar cortex is mediated by 2-arachidonoylglycerol

Author

Vincenzo Di Marzo, Michal J. Urbanski, Ilka Freiman, Aitziber Mendiguren, Tiziana Bisogno, Bela Szabo, and Wolfram U. Baer

Subjects
medicine.medical_specialty, Diacylglycerol lipase, biology, Physiology, 2-Arachidonoylglycerol, Anandamide, Endocannabinoid system, Rhc80267, Cell biology, Monoacylglycerol lipase, chemistry.chemical_compound, Endocrinology, nervous system, chemistry, Fatty acid amide hydrolase, Cerebellar cortex, Internal medicine, biology.protein, medicine, lipids (amino acids, peptides, and proteins)
Abstract

Endocannabinoids acting on CB1 cannabinoid receptors are involved in short- and long-term depression of synaptic transmission. The aim of the present study was to determine which endocannabinoid, anandamide or 2-arachidonoylglycerol (2-AG), is involved in depolarization-induced suppression of inhibition (DSI) in the cerebellar cortex, which is the most widely studied form of short-term depression. Depolarization of Purkinje cells in the mouse cerebellum led to an increase in intracellular calcium concentration and to suppression of the inhibitory input to these neurons (i.e. DSI occurred). Orlistat and RHC80267, two blockers of sn-1-diacylglycerol lipase, the enzyme catalysing 2-AG formation, abolished DSI by acting downstream of calcium influx. In contrast, DSI occurred also in the presence of a phospholipase C inhibitor. Intact operation of the calcium-dependent messengers calmodulin and Ca2+–calmodulin-dependent protein kinase II were necessary for DSI. DSI was potentiated by an inhibitor of the main 2-AG-degrading enzyme, monoacylglycerol lipase. Interference with the anandamide metabolizing enzyme, fatty acid amide hydrolase, did not modify DSI. Thus, three kinds of observations identified 2-AG as the endocannabinoid involved in DSI in the mouse cerebellum: DSI was abolished by diacylglycerol lipase inhibitors; DSI was potentiated by a monoglyceride lipase inhibitor; and DSI was not changed by an inhibitor of fatty acid amide hydrolase. Further experiments indicated that 2-AG is the endocannabinoid mediating short-term retrograde signalling also at other synapses: orlistat abolished DSI in the rat cerebellum, DSI in the mouse substantia nigra pars reticulata and depolarization-induced suppression of excitation in the mouse cerebellum.

Published
2006

25. The volume effect of detectors in the dosimetry of small fields used in IMRT

Author

Tony Wong and Wolfram U Laub

Subjects
Quality Control, Film Dosimetry, Physics::Instrumentation and Detectors, Transducers, Physics::Medical Physics, Dose profile, Models, Biological, Sensitivity and Specificity, Optics, Dosimetry, Computer Simulation, Radiometry, Image resolution, Physics, Scintillation, business.industry, Radiotherapy Planning, Computer-Assisted, Detector, Reproducibility of Results, Isocenter, Radiotherapy Dosage, General Medicine, Equipment Failure Analysis, Ionization chamber, Radiotherapy, Conformal, business, Intensity modulation
Abstract

In this study we investigate the effect of detector size in the dosimetry of small fields and steep dose gradients with a particular emphasis on IMRT measurements. Comparisons of calculated and measured cross-profiles and absolute dose values of IMRT treatment plans are presented. As a consequence of the finite size of the detector that was used for the commissioning of the IMRT tool, local discrepancies of more than 10% are found between calculated cross-profiles of intensity modulated beams and intensity modulated profiles measured with film. Absolute dose measurements of intensity modulated fields with a 0.6 cm3 Farmer chamber show significant differences of more than 6% between calculated and measured dose values at the isocenter of an IMRT treatment plan. Differences of not more than 2% are found in the same experiment for dose values measured with a 0.015 cm3 pinpoint ion chamber. A method to correct for the spatial response of finite-sized detectors and to obtain the "real" penumbra width of cross-profiles from measurements is introduced. Output factor measurements are performed with different detectors and are presented as a function of detector size for a 1 x 1 cm2 field. Because of its high spatial resolution and water equivalence, a diamond detector is found to be suitable as an alternative to other detectors used for small field dosimetry as there are photographic and photochromic film, TLDs, or water-equivalent scintillation detectors.

Published
2003

26. Validation of composite finite elements efficiently simulating elasticity of trabecular bone

Author

Schwen, L.O., Wolfram, U., and Publica

Abstract

Patient-specific analyses of the mechanical properties of bones become increasingly important for the management of patients with osteoporosis. The potential of composite finite elements (CFEs), a novel FE technique, to assess the apparent stiffness of vertebral trabecular bone is investigated in this study. Segmented volumes of cylindrical specimens of trabecular bone are compared to measured volumes. Elasticity under uniaxial loading conditions is simulated; apparent stiffnesses are compared to experimentally determined values. Computational efficiency is assessed and recommendations for simulation parameters are given. Validating apparent uniaxial stiffnesses results in concordance correlation coefficients 0.69 < r c < 0.92 for resolutions finer than 168 mm, and an average error of 5.8% between experimental and numerical results at 24 mm resolution. As an application, the code was used to compute local, macroscopic stiffness tensors for the trabecular structure of a lumbar vertebra. The presented technique allows for computing stiffness using smooth FE meshes at resolutions that are well achievable in peripheral high resolution quantitative CT. Therefore, CFEs could be a valuable tool for the patient-specific assessment of bone stiffness.

Published
2014

27. Intensity modulated irradiation of a thorax phantom: comparisons between measurements, Monte Carlo calculations and pencil beam calculations

Author

Annemarie Bakai, Fridtjof Nüsslin, and Wolfram U Laub

Subjects
Physics, Radiological and Ultrasound Technology, Phantoms, Imaging, business.industry, Radiotherapy Planning, Computer-Assisted, Physics::Medical Physics, Monte Carlo method, Dose-Response Relationship, Radiation, Thoracic Neoplasms, Thorax, Radiation, Imaging phantom, Intensity (physics), Optics, Humans, Dosimetry, Radiology, Nuclear Medicine and imaging, Radiotherapy, Conformal, business, Particle beam, Monte Carlo Method, Intensity modulation, Beam (structure)
Abstract

The present study investigates the application of compensators for the intensity modulated irradiation of a thorax phantom. Measurements are compared with Monte Carlo and standard pencil beam algorithm dose calculations. Compensators were manufactured to produce the intensity profiles that were generated from the scientific version of the KonRad IMRT treatment-planning system for a given treatment plan. The comparison of dose distributions calculated with a pencil beam algorithm, with the Monte Carlo code EGS4 and with measurements is presented. By measurements in a water phantom it is demonstrated that the method used to manufacture the compensators reproduces the intensity profiles in a suitable manner. Monte Carlo simulations in a water phantom show that the accelerator head model used for simulations is sufficient. No significant overestimations of dose values inside the target volume by the pencil beam algorithm are found in the thorax phantom. An overestimation of dose values in lung by the pencil beam algorithm is also not found. Expected dose calculation errors of the pencil beam algorithm are suppressed, because the dose to the low density region lung is reduced by the use of a non-coplanar beam arrangement and by intensity modulation.

Published
2001

28. Compensators for IMRT – An Investigation in Quality Assorance1

Author

Annemarie Bakai, Fridtjof Nüsslin, and Wolfram U Laub

Subjects
medicine.medical_specialty, Radiological and Ultrasound Technology, Computer science, business.industry, Biophysics, Planning target volume, Dose distribution, Imaging phantom, Dose homogeneity, Control theory, Ionization chamber, medicine, Radiology, Nuclear Medicine and imaging, Medical physics, Intensity modulated radiotherapy, business, Quality assurance, Beam (structure)
Abstract

Intensity modulated radiotherapy (IMRT) allows dose distributions which adequately consider organs at risk (OAR) and dose homogeneity to the target volume. This is practically reached by conforming the beam profiles to the shape of the planning target volume (PTV), by shaping the fluence with multileaf collimators (MLC) or compensators. Though compensator production is time consuming and seems less convenient than the use of MLC, compensators offer much easier quality assurance. In this study the effects of certain simplifications of compensator production were studied. Compensators were produced and ionization chamber measurements in a water phantom and film measurements in a solid phantom were performed to verify the compensators. The results of the measurements were compared to the fluence distributions given by the planning system. The measurements were meant to show how realistic the investigated simplifications were, and to reveal a suitable and reliable testing method for compensators. Monte-Carlo calculations employing the EGS 4 Code were further performed to support the measurements.

Published
2001

29. Monte Carlo dose computation for IMRT optimization*

Author

Markus Alber, Wolfram U Laub, M Birkner, and Fridtjof Nüsslin

Subjects
Lung Neoplasms, Quantitative Biology::Tissues and Organs, Computation, Physics::Medical Physics, Monte Carlo method, Optics, Humans, Dosimetry, Radiology, Nuclear Medicine and imaging, Radiometry, Head and neck, Physics, Sequence, Radiological and Ultrasound Technology, business.industry, Radiotherapy Planning, Computer-Assisted, Dose-Response Relationship, Radiation, Intensity (physics), Head and Neck Neoplasms, Modulation, Radiotherapy, Conformal, business, Monte Carlo Method, Intensity modulation, Algorithm, Algorithms
Abstract

A method which combines the accuracy of Monte Carlo dose calculation with a finite size pencil-beam based intensity modulation optimization is presented. The pencil-beam algorithm is employed to compute the fluence element updates for a converging sequence of Monte Carlo dose distributions. The combination is shown to improve results over the pencil-beam based optimization in a lung tumour case and a head and neck case. Inhomogeneity effects like a broader penumbra and dose build-up regions can be compensated for by intensity modulation.

Published
2000

30. Experimental investigation of a fast Monte Carlo photon beam dose calculation algorithm

Author

Bernd Huber, Matthias Fippel, Fridtjof Nüsslin, and Wolfram U Laub

Subjects
Physics, Photons, Photon, Radiological and Ultrasound Technology, Phantoms, Imaging, Radiotherapy Planning, Computer-Assisted, Physics::Medical Physics, Monte Carlo method, Water, Computational physics, Experimental uncertainty analysis, Personal computer, Polystyrenes, Dosimetry, Radiology, Nuclear Medicine and imaging, Variance reduction, Particle Accelerators, Monte Carlo Method, Algorithms, Simulation, Beam (structure), Monte Carlo algorithm
Abstract

An experimental verification of the recently developed XVMC code, a fast Monte Carlo algorithm to calculate dose distributions of photon beams in treatment planning, is presented. The treatment head is modelled by a point source with energy distribution (primary photons) and an additional head scatter contribution. Utility software is presented, allowing the determination of the parameters for this model using a single measured depth dose curve in water. The simple beam model is considered to be a starting point for more complex models being planned for future versions of the code. This paper is mainly focused on the influence of the different techniques on variance reduction and material property determination for dose distributions. It is demonstrated that XVMC and the simple beam model reproduce measured (by a diamond detector) relative dose distributions with an accuracy of better than +/-2% in various homogeneous and inhomogeneous phantoms. Furthermore, relative dose distributions in solid state phantoms have been measured by film. Also for these cases, measured and calculated dose distributions agree within experimental uncertainty. The short calculation time (depending on voxel resolution, statistical accuracy, field size and energy, a span of 1 min to 1 h using a present-day personal computer) and an interface to a commercial planning system will allow the implementation of the code for routine treatment planning of clinical electron and photon beams.

Published
1999

31. A diamond detector in the dosimetry of high-energy electron and photon beams

Author

Theodor W. Kaulich, Wolfram U Laub, and Fridtjof Nüsslin

Subjects
Physics, Photons, Photon, Radiological and Ultrasound Technology, Physics::Instrumentation and Detectors, business.industry, Detector, Diamond, Dose-Response Relationship, Radiation, Electrons, Electron, Models, Theoretical, engineering.material, Particle detector, Optics, Ionization chamber, engineering, Cathode ray, Dosimetry, Radiology, Nuclear Medicine and imaging, Radiometry, business
Abstract

A diamond detector type 60003 (PTW Freiburg) was examined for the purpose of dosimetry with 4-20 MeV electron beams and 4-25 MV photon beams. Results were compared with those obtained by using a Markus chamber for electron beams and an ionization chamber for photon beams. Dose distributions were measured in a water phantom with the detector connected to a Unidos electrometer (PTW Freiburg). After a pre-irradiation of about 5 Gy the diamond detector shows a stability in response which is better than that of an ionization chamber. The current of the diamond detector was measured under variation of photon beam dose rate between 0.1 and 7 Gy min(-1). Different FSDs were chosen. Furthermore the pulse repetition frequency and the depth of the detector were changed. The electron beam dose rate was varied between 0.23 and 4.6 Gy min(-1) by changing the pulse-repetition frequency. The response shows no energy dependence within the covered photon-beam energy range. Between 4 MeV and 18 MeV electron beam energy it shows only a small energy dependence of about 2%, as expected from theory. For smaller electron energies the response increases significantly and an influence of the contact material used for the diamond detector can be surmised. A slight sublinearity of the current and dose rate was found. Detector current and dose rate are related by the expression i alpha Ddelta, where i is the detector current, D is the dose rate and delta is a correction factor of approximately 0.963. Depth-dose curves of photon beams, measured with the diamond detector, show a slight overestimation compared with measurements with the ionization chamber. This overestimation is compensated for by the above correction term. The superior spatial resolution of the diamond detector leads to minor deviations between depth-dose curves of electron beams measured with a Markus chamber and a diamond detector.

Published
1999

32. XVMC – Schnelle Monte-Carlo-Dosisberechnung für die Bestrahlungsplanung bei Photonenstrahlung

Author

Fridtjof Nüsslin, B. Huber, Matthias Fippel, and Wolfram U Laub

Subjects
Gynecology, Physics, medicine.medical_specialty, Radiological and Ultrasound Technology, Biophysics, medicine, Photon beams, Radiology, Nuclear Medicine and imaging
Abstract

Zusammenfassung Es wurde ein neuer Monte-Carlo-Algorithmus (MC) fur die Berechnung von Dosisverteilungen von Photonen-strahlung in der Strahlentherapie entwickelt, welcher um den Faktor 15 bis 20 schneller ist als EGS4/PRESTA. Damit kann ein Standard-Bestrahlungsplan auf einem einfachen Personalcomputer (450MHz. Pentium II) in etwa 20 Minuten mit dem MC-Verfahren berechnet werden. Das neue Modell basiert auf der schnellen Elektronentrans-portroutine des Voxel-Monte-Carlo-Codes (VMC) fur Elektronenstrahlung. Der Photonentransport wurde durch exponentielle Schwachung, Ray-Tracing und die Photonenwirkungsquerschnitte (Compton-Streuung, Paarproduktion) berucksichtigt. Die notigen Materialeigenschaften (Brems- und Streuvermogen der Elektronen, Elektronendichte, Schwachungskoeffizienten) werden direkt aus einer vorgegebenen Dichteverteilung bestimmt. Der Strahler-kopf wird entweder durch eine Punktquelle mit Energieverteilung (Primarphotonen) einschlieslich eines Streuanteils oder durch eine Phasenraumdatei, die mit dem MC-Code BEAM generiert wurde, modelliert. XVMC wurde mit EGS4 und Messungen verglichen. Ein Hilfsprogramm zur Generierung der Strahlparameter sowie eine Schnittstelle zu kommerziellen Planungssystemen wird in naher Zukunft die Nutzung des Codes fur die Bestrahlungsplanung in der klinischen Routine ermoglichen.

Published
1999

35. Inverse treatment planning for radiation therapy based on fast Monte Carlo dose calculation

Author

Fridtjof Nüsslin, Matthias Fippel, Wolfram U Laub, Markus Alber, Iwan Kawrakow, and M. Birkner

Subjects
Physics, Radiation therapy, Parallel simulation, Dose calculation, medicine.medical_treatment, Monte Carlo method, medicine, Dose distribution, Fluence, Intensity (heat transfer), Computational physics, Inverse treatment planning
Abstract

An inverse treatment planning system based on fast Monte Carlo (MC) dose calculation is presented. It allows optimisation of intensity modulated dose distributions in 15 to 60 minutes on present day personal computers. If a multi-processor machine is available, parallel simulation of particle histories is also possible, leading to further calculation time reductions. The optimisation process is divided into two stages. The first stage results in fluence profiles based on pencil beam (PB) dose calculation. The second stage starts with MC verification and post-optimisation of the PB dose and fluence distributions.

Published
2009

36. Depolarization-induced retrograde synaptic inhibition in the mouse cerebellar cortex is mediated by 2-arachidonoylglycerol

Author

Bela, Szabo, Michal J, Urbanski, Tiziana, Bisogno, Vincenzo, Di Marzo, Aitziber, Mendiguren, Wolfram U, Baer, and Ilka, Freiman

Subjects
Neurotransmitter Agents, Polyunsaturated Alkamides, Neural Inhibition, Arachidonic Acids, Synaptic Transmission, Glycerides, Membrane Potentials, Cerebellar Cortex, Mice, Purkinje Cells, nervous system, Interneurons, Animals, lipids (amino acids, peptides, and proteins), Cells, Cultured, Endocannabinoids, Neuroscience
Abstract

Endocannabinoids acting on CB(1) cannabinoid receptors are involved in short- and long-term depression of synaptic transmission. The aim of the present study was to determine which endocannabinoid, anandamide or 2-arachidonoylglycerol (2-AG), is involved in depolarization-induced suppression of inhibition (DSI) in the cerebellar cortex, which is the most widely studied form of short-term depression. Depolarization of Purkinje cells in the mouse cerebellum led to an increase in intracellular calcium concentration and to suppression of the inhibitory input to these neurons (i.e. DSI occurred). Orlistat and RHC80267, two blockers of sn-1-diacylglycerol lipase, the enzyme catalysing 2-AG formation, abolished DSI by acting downstream of calcium influx. In contrast, DSI occurred also in the presence of a phospholipase C inhibitor. Intact operation of the calcium-dependent messengers calmodulin and Ca(2+)-calmodulin-dependent protein kinase II were necessary for DSI. DSI was potentiated by an inhibitor of the main 2-AG-degrading enzyme, monoacylglycerol lipase. Interference with the anandamide metabolizing enzyme, fatty acid amide hydrolase, did not modify DSI. Thus, three kinds of observations identified 2-AG as the endocannabinoid involved in DSI in the mouse cerebellum: DSI was abolished by diacylglycerol lipase inhibitors; DSI was potentiated by a monoglyceride lipase inhibitor; and DSI was not changed by an inhibitor of fatty acid amide hydrolase. Further experiments indicated that 2-AG is the endocannabinoid mediating short-term retrograde signalling also at other synapses: orlistat abolished DSI in the rat cerebellum, DSI in the mouse substantia nigra pars reticulata and depolarization-induced suppression of excitation in the mouse cerebellum.

Published
2006

38. Comparison of TG-43 dose calculations to pinpoint ion chamber and diamond detector measurements

Author

Wolfram U Laub

Subjects
Quality Control, Materials science, Dose calculation, medicine.medical_treatment, Brachytherapy, Sensitivity and Specificity, Optics, Germany, medicine, Radiology, Nuclear Medicine and imaging, Radiometry, Diamond detector, Task group, Radiological and Ultrasound Technology, business.industry, Radiotherapy Planning, Computer-Assisted, Detector, A diamond, Radiotherapy Dosage, Iridium Radioisotopes, United States, Equipment Failure Analysis, Formalism (philosophy of mathematics), Ionization chamber, Diamond, business, Nuclear medicine
Abstract

Brachytherapy is an area of radiation therapy where the availability of high-resolution detectors with a low energy-dependence is of great importance. The suitability of two detectors is investigated in this study. Measurements in the proximity of an Ir-192 source were performed with a diamond detector type 60003 and a pinpoint chamber type 31006 (both PTW-Freiburg). For comparison, dose values were calculated with the dose calculation formalism recommended by the task group 43 (Nath et al 1995 Med. Phys. 22 209-34).

Published
2003

40. IMRT with Monte Carlo dose computation: what is the benefit?

Author

Markus Alber, Wolfram U Laub, Fridtjof Nüsslin, and M Birkner

Subjects
Physics, Radiation transport, Computation, Monte Carlo method, Degrees of freedom (statistics), Low density, Computational physics, Small field
Abstract

Monte Carlo simulations arguably offer the most readily explorable route to computing radiation transport in complex geometries and inhomogeneous media. With IMRT, not only the dose computation in the patient poses problems, but also the predominantly small field sizes and the modulation devices in the accelerator head. However, IMRT also offers abundant degrees of freedom to compensate for the dose loss due to lateral electron transport at low density surfaces by adjustments to the primary fluence.

Published
2000

41. Hyperion — An integrated IMRT planning tool

Author

M. Birkner, Fridtjof Nüsslin, M. Alber, and Wolfram U Laub

Subjects
Software, Risk analysis (engineering), Computer science, Process (engineering), Feature (computer vision), business.industry, Imrt planning, business
Abstract

The IMRT planning process poses problems beyond conventional planning, and as yet not all confounding factors have been fully understood or countermeasures devised. It may thus be argued that the most prominent feature of IMRT software is its capacity for development.

Published
2000

44. Energy and dose rate dependence of a diamond detector in the dosimetry of 4-25 MV photon beams

Author

Theodor W. Kaulich, Wolfram U Laub, and Fridtjof Nüsslin

Subjects
medicine.medical_specialty, Photons, Photon, Materials science, Dosimeter, Radiotherapy, business.industry, Detector, Diamond, Radiotherapy Dosage, General Medicine, engineering.material, Models, Theoretical, Linear particle accelerator, Optics, medicine, engineering, Photon beams, Dosimetry, Humans, Medical physics, Particle Accelerators, business, Energy (signal processing)
Published
1997

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