Search results for "fields"
showing 10 items of 575 documents
Lack of mutagenic and co-mutagenic effects of magnetic fields during magnetic resonance imaging
2001
Mutagenic and co-mutagenic effects of static, pulsed bipolar gradient, and high-frequency magnetic fields, as well as combinations of them, were examined using the Ames test. The Ames test using Salmonella typhimurium bacteria, wild-type strain RTA, preincubation assay, without metabolic activation, was performed. All combinations of magnetic fields were tested with and without co-exposure to N-methyl-N′-nitro-N-nitrosoguanidine and benzo[a]pyrene-4,5-oxide, ethylene oxide, carboplatin, or cisplatin. As expected, chemical mutagens caused a clear-cut increase of the revertants in the Ames test. However, neither the static fields nor a combination of a static magnetic field with the time-vary…
Moving across the static magnetic field of a 1.5 T MRI scanner: Analysing compliance with Directive 2013/35/EU
2018
Abstract Does the exposure of magnetic resonance imaging personnel to static magnetic fields fully comply with Directive 2013/35/EU? Despite the obligation to satisfy this question, a general answer cannot be provided, nor are final satisfying good practices methods for exposure assessment currently available. In order to contribute to fix this problem, three different 1.5 T scanners are analysed and – by a new theoretical insight – a positive answer is provided.
Experimental and Modeling Analyses of Human Motion Across the Static Magnetic Field of an MRI Scanner
2021
It is established that human movements in the vicinity of a permanent static magnetic field, such as those in magnetic resonance imaging (MRI) scanners induce electric fields in the human body; this raises potential severe risks of health to radiographers and cleaners exposed routinely to these fields in MRI rooms. The relevant directives and parameters, however, are based on theoretical models, and accurate studies on the simulation of the effects based on human movement data obtained in real conditions are still lacking. Two radiographers and one cleaner, familiar with MRI room activities and these directives, were gait analyzed during the execution of routine job motor tasks at different…
Poisson-Nijenhuis structures and the Vinogradov bracket
1994
We express the compatibility conditions that a Poisson bivector and a Nijenhuis tensor must fulfil in order to be a Poisson-Nijenhuis structure by means of a graded Lie bracket. This bracket is a generalization of Schouten and Frolicher-Nijenhuis graded Lie brackets defined on multivector fields and on vector valued differential forms respectively.
Improved Upper Limit on the Neutrino Mass from a Direct Kinematic Method by KATRIN
2019
We report on the neutrino mass measurement result from the first four-week science run of the Karlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. A fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 keV gives an effective neutrino mass square value of (−1.0−1.1+0.9) eV2. From this, we derive an upper limit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincides with the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurements by almost a …
On the number of limit cycles which appear by perturbation of separatrix loop of planar vector fields
1986
Consider a fami ly of vector fCelds x~ on the plane. This fami ly depends on a parameter ~ ~ /R A, for some A ~ /~, and is supposed to be 0 ~ in (m,~) 6 /i~ 2X /~A. Suppose that for ~ = O, the vector f i e l d X o has a separatrix loop. This means that X o has an hyperbol ic saddle point s o and that one of the stable separatr ix of 8 o coincides with one of the unstable one. The union of th is curve and s o is the loop ?. A return map is defined on one side of r .
Interference of left and right cerebellar rTMS with procedural learning.
2004
Abstract Increasing evidence suggests cerebellar involvement in procedural learning. To further analyze its role and to assess whether it has a lateralized influence, in the present study we used a repetitive transcranial magnetic stimulation interference approach in a group of normal subjects performing a serial reaction time task. We studied 36 normal volunteers: 13 subjects underwent repetitive transcranial magnetic stimulation on the left cerebellum and performed the task with the right (6 subjects) or left (7 subjects) hand; 10 subjects underwent repetitive transcranial magnetic stimulation on the right cerebellum and performed the task with the hand ipsilateral (5 subjects) or contral…
The role of the dorsolateral prefrontal cortex in implicit procedural learning.
1996
We studied the role of the dorsolateral prefrontal cortex in procedural learning. Normal subjects completed several blocks of a serial reaction time task using only one hand without or with concurrent non-invasive repetitive transcranial magnetic stimulation. To disrupt their function transiently, stimulation was applied at low intensity over the supplementary motor area or over the dorsolateral prefrontal cortex contralateral or ipsilateral to the hand used for the test. Stimulation to the contralateral dorsolateral prefrontal cortex markedly impaired procedural implicit learning, as documented by the lack of significant change in response times during the task. Stimulation over the other …
Josephson-junction-based axion detection through resonant activation
2022
We discuss the resonant activation phenomenon on a Josephson junction due to the coupling of the Josephson system with axions. We show how such an effect can be exploited for axion detection. A nonmonotonic behavior, with a minimum, of the mean switching time from the superconducting to the resistive state versus the ratio of the axion energy and the Josephson plasma energy is found. We demonstrate how variations in switching times make it possible to detect the presence of the axion field. An experimental protocol for observing axions through their coupling with a Josephson system is proposed.
Orbital Evolution of an Accreting Millisecond Pulsar: Witnessing the Banquet of a Hidden Black Widow?
2007
We have performed a timing analysis of all the four X-ray outbursts from the accreting millisecond pulsar SAX J1808.4-3658 observed so far by the PCA on board RXTE. For each of the outbursts we derived the best-fit value of the time of ascending node passage. We find that these times follow a parabolic trend, which gives an orbital period derivative $\dot P_{\rm orb} = (3.40 \pm 0.18) \times 10^{-12}$ s/s, and a refined estimate of the orbital period, $P_{\rm orb} = 7249.156499 \pm 1.8 \times 10^{-5}$ s (reference epoch $T_0 = 50914.8099$ MJD). This derivative is positive, suggesting a degenerate or fully convective companion star, but is more than one order of magnitude higher than what is…