This paper presents a synthesis of analytical calculations of magnetic parameters (field, force, torque, stiffness) in cylindrical magnets and coils. By using the equivalence between the amperian ...current model and the coulombian model of a magnet, we show that a thin coil or a cylindrical magnet axially magnetized have the same mathematical model. Consequently, we present first the analytical expressions of the magnetic field produced by either a thin coil or a ring permanent magnet whose polarization is axial, thus completing similar calculations already published in the scientific literature. Then, this paper deals with the analytical calculation of the force and the stiffness between thin coils or ring permanent magnets axially magnetized. Such configurations can also be modeled with the same mathematical approach. Finally, this paper presents an analytical model of the mutual inductance between two thin coils in air. Throughout this paper, we emphasize why the equivalence between the coulombian and the amperian current models is useful for studying thin coils or ring permanent magnets. All our analytical expressions are based on elliptic integrals but do not require further numerical treatments. These expressions can be implemented in Mathematica or Matlab and are available online. All our models have been compared to previous analytical and semianalytical models. In addition, these models have been compared to the finite-element method. The computational cost of our analytical model is very low, and we find a very good agreement between our analytical model and the other approaches presented in this paper.
We sought to supplement medical physics textbook knowledge and clinical learning with case-based discussions. To our knowledge, this is the first report on a structured combined applied physics ...curriculum for radiation oncology (RO) and medical physics (MP) trainees. We reviewed our yearly applied physics course given from the years 2016–2021 inclusive. The number of applied physics trainees ranged from 7 to 14 per year (2–9 RO and 3–6 MP residents per year). Each session was taught by a pair of (RO and MP) faculty members. Twenty-nine case-based sessions were given yearly (2016 to 2019). Because of the COVID-19 pandemic restrictions, the course was shortened to 8 case-based sessions in 2020 and 2021. For the years 2016–2021, the mean and median teaching evaluation scores were 4.65 and 5, respectively (range 2–5), where 1 represents worse teaching quality and 5, the best teaching quality. For the year 2021, 2 questions relating to the video virtual format (implemented due to the covid-19 pandemic), revealed consistent high scores with the mean and median responses of 4.14 and 5, respectively (range 1–5). The results from the teaching evaluation scores indicate that the trainees highly valued the teaching sessions and teachers. Our experience indicates that a case-based applied physics course was delivered successfully with continued high teaching evaluation scores. A video virtual platform for an applied physics course could be useful, especially for small programs without a structured applied physics curriculum.
In this paper we present a lucid, easy, and accurate approach for calculation of the mutual inductance between all inclined circular coils with either rectangular cross section or negligible section. ...We use Grover's formula for the mutual inductance between two filamentary circular coils with inclined axes that lie in the same plane. Their centers are either displaced along the axis of one coil or displaced along one axis of the first coil and then displaced sideways in addition. We apply the filament method for coil combinations comprising circular coils of rectangular cross section, thin wall solenoids, thin disk coils (pancakes), and filamentary circular coils. In this approach we clarify how Grover's formulas have to be used for different coil combinations in the filament treatment. Thus, two well-known methods (Grover's formulas and the filament method) can be easily used to calculate the mutual inductance between all inclined circular coils, even though the problem is purely three-dimensional.
Burkholderia pseudomallei causes the potentially fatal disease melioidosis. It is generally accepted that B. pseudomallei is a noncommensal bacterium and that any culture-positive clinical specimen ...denotes disease requiring treatment. Over a 23-year study of melioidosis cases in Darwin, Australia, just one patient from 707 survivors has developed persistent asymptomatic B. pseudomallei carriage. To better understand the mechanisms behind this unique scenario, we performed whole-genome analysis of two strains isolated 139 months apart. During this period, B. pseudomallei underwent several adaptive changes. Of 23 point mutations, 78% were nonsynonymous and 43% were predicted to be deleterious to gene function, demonstrating a strong propensity for positive selection. Notably, a nonsense mutation inactivated the universal stress response sigma factor RpoS, with pleiotropic implications. The genome underwent substantial reduction, with four deletions in chromosome 2 resulting in the loss of 221 genes. The deleted loci included genes involved in secondary metabolism, environmental survival, and pathogenesis. Of 14 indels, 11 occurred in coding regions and 9 resulted in frameshift mutations that dramatically affected predicted gene products. Disproportionately, four indels affected lipopolysaccharide biosynthesis and modification. Finally, we identified a frameshift mutation in both P314 isolates within wcbR, an important component of the capsular polysaccharide I locus, suggesting virulence attenuation early in infection. Our study illustrates a unique clinical case that contrasts a high-consequence infectious agent with a long-term commensal infection and provides further insights into bacterial evolution within the human host.
Some bacterial pathogens establish long-term infections that are difficult or impossible to eradicate with current treatments. Rapid advances in genome sequencing technologies provide a powerful tool for understanding bacterial persistence within the human host. Burkholderia pseudomallei is considered a highly pathogenic bacterium because infection is commonly fatal. Here, we document within-host evolution of B. pseudomallei in a unique case of human infection with ongoing chronic carriage. Genomic comparison of isolates obtained 139 months (11.5 years) apart showed a strong signal of adaptation within the human host, including inactivation of virulence and immunogenic factors, and deletion of pathways involved in environmental survival. Two global regulatory genes were mutated in the 139-month isolate, indicating extensive regulatory changes favoring bacterial persistence. Our study provides insights into B. pseudomallei pathogenesis and, more broadly, identifies parallel evolutionary mechanisms that underlie chronic persistence of all bacterial pathogens.
Atosiban, an oxytocin/vasopressin receptor antagonist, is used to decrease preterm uterine activity. The risk of preterm delivery is undoubtedly associated with stress, but potential side effects of ...atosiban on neuroendocrine functions and stress-related pathways are mostly unknown. These studies were designed to test the hypothesis that the chronic treatment of rats with atosiban modulates neuroendocrine functions under stress conditions. Male rats were treated (osmotic minipumps) with atosiban (600 μg/kg per day) or vehicle and were restrained for 120 min/day for 14 days. All animals were treated with a marker of cell proliferation 5-bromo-2-deoxyuridine. Anxiety-like behavior was measured using an elevated plus-maze. Treatment with atosiban failed to modify plasma concentrations of the stress hormones ACTH and corticosterone, but led to a rise in circulating copeptin. Atosiban increased prolactin levels in the non-stressed group. Oxytocin receptor mRNA levels were increased in rats exposed to stress. Treatment with atosiban, in both control and stressed animals, resulted in a decrease in oxytocin receptor gene expression in the hypothalamus. No changes were observed in vasopressin receptor 1A and 1B gene expression. The decrease in hippocampal cell proliferation induced by stress exposure was not modified by atosiban treatment. This study provides the first data, to our knowledge, revealing the effect of atosiban on gene expression of oxytocin receptors in the brain. Atosiban-induced enhancement of plasma copeptin indicates an elevation in vasopressinergic tone with potential influence on water–electrolyte balance.
In this paper, we present analytic-numerical expressions for the calculation of the mutual inductance of two axisymmetric circular coils with rectangular cross section in air. This original and new ...method may seem complicated but it is explicit, accurate, and fast, even though all expressions are obtained by the complete elliptic integrals of the first and second kind, Heuman's lambda function, and three terms that must be solved numerically. We confirm the validity of this approach by comparing it with other approaches (filament method and previously published data). We also compare the accuracy and the computational cost of this approach and that of the filament method. All results obtained by the various approaches are in excellent agreement
We present new and fast procedures for calculating magnetic forces between thin coaxial circular coaxial coils in air. The results are expressed in semianalytical form in terms of the complete ...elliptical integrals of the first and second kind, Heuman's Lambda function, and a term that must be solved numerically. These expressions are accurate and simple to use for several practical applications. We also describe a comparative method based on the filament technique. We discuss the computational cost and the accuracy of two methods and compare them with already published data. Results obtained by our two approaches are in excellent agreement with each other. They can be used in industrial electromagnetic applications such as electrodynamic levitation systems, linear induction launchers, linear actuators, and coil guns.
Objective: Phenytoin is an antiepileptic drug that has been shown to reduce some neurotoxic effects of glutamate in states when glutamate neurotransmission is increased, such as neurodegeneration and ...stress. In the present study, we tested the hypothesis that treatment with phenytoin prevents stress-induced alterations in the production of new cells in the hippocampus and in the heart.
Methods: Adult male Wistar rats were exposed to repeated hypokinesis (restraint, 2 hours daily) and were treated with phenytoin (20 mg/kg/day, s.c.) or vehicle for 8 days. On the 7th day, all animals were treated with 5-bromo-2'-deoxyuridine (BrdU), a marker of cell proliferation.
Results: The treatment with phenytoin under both control and stress conditions resulted in an inhibitory effect on cell proliferation, which was more evident in the heart than in the hippocampus. Repeated treatment with phenytoin led to adrenal gland hypertrophy as well as to a marginal increase in plasma renin activity. Basal and stress-induced concentrations of adrenal steroids were unchanged by phenytoin administration.
Discussion: Treatment with the glutamate release inhibiting drug phenytoin did not prevent negative consequences of repeated stress exposure on cell proliferation in Wistar rats. Treatment with phenytoin even deepened stress-induced reduction of cell proliferation in the heart. It cannot be excluded that the phenytoin-induced increase in plasma renin activity observed in the present study may occur during therapeutic use of phenytoin and contribute to its adverse effects.
PDF
