The dynamics of a periodically delta-kicked Hamiltonian system moving at low speed (i.e., at speed much less than the speed of light) is studied numerically. In particular, the trajectory of the system predicted by Newtonian mechanics is compared with the trajectory predicted by special relativistic mechanics for the same parameters and initial conditions. We find that the Newtonian trajectory, although close to the relativistic trajectory for some time, eventually disagrees completely with the relativistic trajectory, regardless of the nature (chaotic, nonchaotic) of each trajectory. However, the agreement breaks down very fast if either the Newtonian or relativistic trajectory is chaotic, but very much slower if both the Newtonian and relativistic trajectories are nonchaotic. In the former chaotic case, the difference between the Newtonian and relativistic values for both position and momentum grows, on average, exponentially. In the latter nonchaotic case, the difference grows much slower, for example, linearly on average.
Heralded by the revelation of the double helical structure of the DNA molecule in 1953, the 21st century is aptly designated the biotechnology century. The 20th century of physics, which saw the transformation of silicon into computing magic, was embraced with enthusiasm by virtually every household. However, unlike her predecessor, the same cannot be said about the advancements in biomedicine.
Medical physics is a relatively small community but it spans great geographical distances, usually with a scarcity of experts whose expertise could greatly benefit students entering into the field. In addition there are many software systems for which an interactive education method would be most advantageous.
In recent years there has been a significant economic growth in South East Asia, along with it a concurrent development of medical physics. The status of four countries--Malaysia, Thailand, the Philippines and Indonesia are presented. Medical physicists in these countries have been experiencing the usual problems of lack of recognition, low salaries, and insufficient facilities for education and training opportunities. However the situation has improved recently through the initiative of local enthusiastic medical physicists who have started MS graduate programs in medical physics and begun organizing professional activities to raise the profile of medical physics. The tremendous support and catalytic roles of the American Association of Physicists in Medicine (AAPM) and international organizations such as International Organization for Medical Physics (IOMP), International Atomic Energy Agency (IAEA), World Health Organization (WHO), and International Center for Theoretical Physics (ICTP) have been instrumental in achieving progress. Contributions by these organizations include co-sponsorship of workshops and conferences, travel grants, medical physics libraries programs, and providing experts and educators. The demand for medical physicists is expected to rise in tandem with the increased emphasis on innovative technology for health care, stringent governmental regulation, and acceptance by the medical community of the important role of medical physicists.
The Physics Interviewing Project assists graduate physics departments in evaluating foreign applicants. Supported by some 20 universities, two interviewers, both working scientists, travel abroad and interview students individually for about 1 hour each. Prospective teaching assistants are rated on physics knowledge, problem-solving ability, and English language proficiency. Ratings on all interviewees are sent to all supporting schools and other schools as requested. The Project aids able students from countries that have no physics Ph.D. programs (Indonesia, Malaysia, Thailand) to obtain assistantships and Ph.D.'s abroad, assists in the technological development of those countries, and helps U.S. schools in selecting the most promising foreign candidates. A similar program should be beneficial in other sciences.