A torsion pendulum having masses with -loZ2 and -10" polarized electrons is used to search for an anomalous spin interaction of macroscopic range. Competition from magnetic forces is reduced by using Dy-Fe masses (which exhibit orbital compensation of the electron intrinsic spin), combined with light magnetic shielding, so that the sensitivity is better than one-tenth of a percent of the gravitational force. Fluctuations set the overall experimental limit at about 8 times this level. Interpretation of our null result sets limits on electron spin interactions and on moments which are not of electromagnetic origin. In terms of a standard dipole-dipole form the result is (1.6+6.9)X l o 1 * of the interaction strength between the magnetic moments of the electrons. Comparisons are made with theoretical predictions for very light exchange particles. 42 977-
Very small implanted permanent magnets guided by large electromagnetic coils have been proposed previously as a method for delivering hyperthermia to or guiding catheters through brain tissue. This procedure is termed "magnetic stereotaxis." Early efforts employed a single coil on a movable boom, a design that proved logistically difficult to use on human patients. The present work deals instead with a design where several stationary coils are employed to develop a force on the implanted magnet. The coil current-to-force relationship is developed for this type of machine, and several optimal solutions for realizing an arbitrary static force are presented for various constraints on the orientation of the implanted permanent magnet. Costs of the different solutions are compared in several examples using a mathematical model based on the Magnetic Stereotaxis System (MSS) developed by Stereotaxis, Inc.,
The torsion pendulum is not only a mainstay instrument in the world of precision measurement and gravitational physics, but is important in electrical science, biophysics, petrology, metallurgy, and various other fields of endeavor. Whether used in the ‘‘static’’ (deflection) mode, the ‘‘dynamic’’ (oscillating) mode, or in some more complex configuration, instrumentation of this kind enables one to isolate and measure weak effects that would otherwise be difficult if not impossible to observe against the background gravitational field of the earth. In this review, we present a brief history of fiber-suspended apparatus and assess the fundamental limits of performance of the dumbbell pendulum. We then inventory the different versions of such systems presently used by gravitational physicists and discuss the various interrogation techniques used to monitor the movement of the suspended test mass. Next, we tabulate some of the applications for torsion instruments outside of gravitational physics, and close with a few comments on the direction of research in this area.
The noncontact magnetic manipulation of probe masses within the body is an area of research that has received substantial attention from the medical physics community, especially during the past three decades. The therapeutic and diagnostic possibilities arising from such technology include site-specific drug delivery within the central nervous system, advancement of techniques for navigation and selective catheterization of vessels within the cardiovascular and cerebrovascular systems, and the nonsurgical exploration of the alimentary and respiratory tracts. In this review, we examine the physical principles underlying in vivo magnetic manipulation systems, and catalog the various types of instrumentation used for such purposes to date. Thereafter, we evaluate the different methods of image-based localization used to identify the position of the probe within the body. Finally, we appraise an emerging technology known as nonlinear magnetic stereotaxis, a technique that permits minimally invasive access to difficult-to-approach parts of the brain. We close the review with a few comments on the directions for future work within this field.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.