Copyright (c) 2009 University of Nebraska - Lincoln All rights reserved. http://digitalcommons.unl.edu/physicskatz Recent documents in Robert Katz Publications en-us Wed, 29 Jul 2009 14:03:42 PDT 3600 http://digitalcommons.unl.edu/physicskatz/204 http://digitalcommons.unl.edu/physicskatz/204 Tue, 28 Jul 2009 10:07:13 PDT According to the theory of Butts and Katz and the new radial dose distribution of Zhang et al., we have calculated inactivation cross sections for the heavy ion bombardment of E. Coli B/r and Bs-1 which w& in agreement with the measurements of Scliafer et made with ions from O to U at energies from 1.5 to 19.5 MeV/u. The data display "thindown", and the decrease in cross section with an increase in stopping power is accompanied by a decrease in energy of a bombarding ion. Following an earlier analysis of heavy ion bombardments of these E. Coli mutants with low atomic number ions at energies neighboring 10 MeV/u by Katz and Zachariah, it can be seen that these bacteria act as 1-hit detectors on the response of these bacteria to ions of lower atomic number and LET where thindown is not exhibited. The analysis of thindown in these bacteria is much clearer than that in the case of mammalian cells because of the relative simplicity of the structure of these bacteria as compared to the complexity of mammalian cell structure. The significance of studying the thindown of E. Coli is to get further understanding of the radiation action in biology. Zhang Chunxiang http://digitalcommons.unl.edu/physicskatz/203 http://digitalcommons.unl.edu/physicskatz/203 Tue, 28 Jul 2009 10:07:12 PDT The validity of a linear extrapolation to lowest fluences of charged particles demands that the transit of a single charged particle through the target volume is capable of inducing the chain of events leading to an observable end-point. This is always the case for one-hit detectors. It is not always the case for biological cells and tissues (Katz and Hofmann 1982). By way of example, Cole ct al. (1980) found that, on average, some 500 electrons pass into the nucleus of a CHO cell for inactivation. Similarly, Warters et al. (1977) found that some 500 tritium decays in the nucleus of a CHO cell are required for observable killing. Robert Katz http://digitalcommons.unl.edu/physicskatz/195 http://digitalcommons.unl.edu/physicskatz/195 Tue, 28 Jul 2009 10:07:02 PDT It has long been suggested that inactivation severely effects the probability of mutation by heavy ions in mammalian cells. Heavy ions have observed cross sections of inactivation that approach and sometimes exceed the geometric size of the cell nucleus in mammalian cells. In the track structure model of Katz the inactivation cross section is found by summing an inactivation probability over all impact parameters from the ion to the sensitive sites within the cell nucleus. The inactivation probability is evaluated using the dose-response of the system to γ-rays and the radial dose of the ions and may be equal to unity at small impact parameters for some ions. We show how the effects of inactivation may be taken into account in the evaluation of the mutation cross sections from heavy ions in the track structure model through correlation of sites for gene mutation and cell inactivation. The model is fit to available data for HPRT mutations in Chinese hamster cells and good agreement is found. The resulting calculations qualitativelv show that mutation cross sections for heavy ions display minima at velocities where inactivation cross sections display maxima. Also, calculations show the high probability of mutation by relativistic heavy ions due to the radial extension of ions track from &rays in agreement with the microlesion concept. The effects of inactivation on mutations rates make it very unlikely that a single parameter such as LET or can be used to specify radiation quality for heavy ion bombardment. Francis Cucinotta http://digitalcommons.unl.edu/physicskatz/194 http://digitalcommons.unl.edu/physicskatz/194 Tue, 28 Jul 2009 10:07:01 PDT The track theory of cell survival after heavy-ion irradiation is based on the probability of survival after a single-particle transit, called ''ion-kill'' (not track core), joined to the cumulative effect of δ rays from adjacent ions in a beam, called ''gamma-kill'' (not penumbra). The model offers a set of equations containing four parameters, E0 and m for the single-hit multitarget statistical model for gamma-kill, and additionally σ0 and κ for ion-kill. A single set of parameters is used to fit a family of survival curves obtained with ions of different LET simultaneously. Robert Katz http://digitalcommons.unl.edu/physicskatz/193 http://digitalcommons.unl.edu/physicskatz/193 Tue, 28 Jul 2009 10:07:00 PDT ''Because the predominant exposure of cells in humans is to single isolated tracks, a critical question is what effects a single track is capable of producing and with what probabilities.'' ''Most of the current biophysical models. . . make the clear prediction that a single track can produce virtually all of the detrimental stochastic effects of interest.'' ''But one model, in particular (the amorphous track model of Katz and coworkers), disagrees fundamentally that a single low LET track has the ability to cause the cellular changes.'' ''This model leads to very dramatic differences in the predicted risk at low doses. . . '' ''Because of the very major implications this would have if true, there may be strong grounds for critical evaluation of the model'' (1). Robert Katz http://digitalcommons.unl.edu/physicskatz/192 http://digitalcommons.unl.edu/physicskatz/192 Thu, 04 Dec 2008 07:58:28 PST Measured cross sections after heavy ion bombardment, for both single and double strand breaks of SV-40 virus in EO buffer (which emphasizes indirect effects), are consistent with the theory of Butts and Katz for 1-hit detectors. Robert Katz http://digitalcommons.unl.edu/physicskatz/191 http://digitalcommons.unl.edu/physicskatz/191 Tue, 02 Dec 2008 10:26:54 PST The delta-ray theory of track structure, applied earlier to such 1-or-more hit detection systems as the inactivation of dry enzymes and viruses, the NaI(Tl) scintillation counter, and nuclear emulsion, is extended to the silver activated phosphate glass dosimeter, the LiF thermoluminescent dosimeter, the creation of free radicals in solid biological substances, solid and liquid organic scintillators, and the ferrous sulfate (Fricke) dosimeter. The response of these systems to both gamma-rays and heavy ions is characterized by two parameters: 1) Dγ37, the dose of gamma-rays at which 37% of the sensitive elements remain unaffected by the radiation, and 2) a0, the physical radius (or the exciton diffusion length, or the range of short-range order) of the sensitive element. The decline of detector response with increase in the stopping power of the bombarding ion, and the non-linearity of the detector response are characteristic properties of 1-hit detectors, and are most pronounced for the most sensitive detectors. Explicit information about the cross-sectional area of the sensitive target cannot be gained from measurement of the activation cross-section as a function of the stopping power of the incident ion, for there is no saturation cross-section for 1-hit detectors. Since parameters describing the incident ion and those describing the detector are not separable variables, the response of a detector cannot be described through a product of two factors, one containing only ion parameters and representing "radiation quality," and the other containing only detector parameters and representing " detector quality." Robert Katz http://digitalcommons.unl.edu/physicskatz/190 http://digitalcommons.unl.edu/physicskatz/190 Tue, 02 Dec 2008 10:17:43 PST An earlier representation of the radial distribution of dose about the path of a heavy ion in liquid water is modified and extended to include silicon, lithium fluoride, sodium iodide, and silicon dioxide. Robert Katz http://digitalcommons.unl.edu/physicskatz/189 http://digitalcommons.unl.edu/physicskatz/189 Tue, 02 Dec 2008 10:08:54 PST A formula for the OER in a mixed field of neutrons and gamma rays (Hall, 1972a; 1972b) is given .... Our results, calculated from track structure theory (Katz and Sharma, 1973) and secondary particle-energy spectra in tissue from these neutrons (Caswell and Coyne, 1973; Dennis, 1972) are within 5 per cent of the values of Omix found from the Hall formula, when that formula is supplied with calculated values of Rn, On, and Oγ, at appropriate survival levels. Our calculations suggest that the Hall formula may be used with confidence for neutrons of different energies and for pions. Robert Katz http://digitalcommons.unl.edu/physicskatz/188 http://digitalcommons.unl.edu/physicskatz/188 Wed, 12 Nov 2008 10:33:14 PST This book is intended for students of science and engineering; it aims to develop both an understanding of the important concepts of physics and some analytical skill in the solutions of problems. The mathematical level of the book is such that it may be used by students who are taking a course in calculus concurrently. The notations and methods of the calculus are introduced early in the text, beginning with the concept of a derivative in the discussion of motion, and are then extended to more complex problems as the student progresses both in physics and in mathematics. Vector algebra is, of course, also used. The vector notation is introduced at the beginning of the text in treating displacements; it is then extended to include the use of the dot product and cross product of two vectors, and the resolution of a vector into components with the aid of unit vectors. These vector methods are used extensively in the sections on Mechanics and Electricity. The method of exposition and the division of the subject matter into six parts--Mechanics, Heat, Wave Motion and Sound, Electricity and Magnetism, Optics, and Atomics and Nucleonics--follow closely those of the senior author's Fundamentals of Physics, now in its third edition. However, the treatment of much of the material is entirely new, as are over two hundred of the figures. The problems at the end of each chapter are graded in difficulty, and many illustrative examples are provided in the text both to clarify concepts and to guide the student in the analytical approach to the solutions of problems. Included among these problems are some involving selected derivations and some requiring the use of calculus. Answers to odd-numbered problems are given in the Appendix, and a booklet containing all the answers is available to the instructor and may be distributed to his students if he so desires. Complete work is 927 pages; pdf file is 39 Mbytes. Henry Semat