Superconductivity and Microwaves

Superconductivity conforms to a quantum, thermal, and electrodynamic set of physical phenomena of great interest by themselves. They have, also, the potential to be one clean energy source that technology is looking for. Superconductors do not allow static magnetic fields to penetrate them below a critical field, that is, Meissner effect. However, microwave magnetic fields do penetrate them already, and their energy is readily absorbed by the superconductor. High-temperature, perovskite superconductors do absorb microwave energy the most due to the presence of unpaired electron spins, fluxoid dynamics, and quasiparticle motion. We describe the fundamental physics of the interaction of the superconductors with microwaves. Experimental techniques to measure microwave absorption are presented. Experimental setups for absorption of energy are described in terms of the central quantity, Q. The measurements are analyzed in terms of irreversible energy exchange processes. The knowledge gained can inform the design of superconducting devices operating in microwave environments

Electromagnetism of Microwave Heating

Detailed electrodynamic descriptions of the fundamental workings of microwave heating devices are presented. We stress that all results come from Maxwell equations and the boundary conditions (BC). We analyze one by one the principal components of a microwave heater; the cooking chamber, the waveguide, and the microwave sources, either klystron or magnetron. The boundary conditions at the walls of the resonant cavity and at the interface air/surface of the food are given and show how relevant the BC are to understand how the microwaves penetrate the nonconducting, electric polarizable specimen. We mention the application of microwaving waste plastics to obtain a good H2 quantity that could be used as a clean energy source for other machines. We obtained trapped stationary microwaves in the resonant cavity and traveling waves in the waveguides. We show 3D plots of the mathematical solutions and agree quite well with experimental measurements of hot/cold patterns. Simulations for cylindrical cavities are shown. The radiation processes in klystrons and magnetrons are described with some detail in terms of the accelerated electrons and their trajectories. These fields are sent to the waveguides and feed the cooking chamber. Whence, we understand how a meal or waste plastic, or an industrial sample is microwave heated

The Electric Fields of Lightning Clouds in Atmospheres of Different Properties

In this work, we concentrate on the electric fields produced by any distribution or structure of electric charges in clouds, these quantities are, for the most part, unknowns, and still we extract valuable information from their vectorial properties and working within close distances, especially on the structures that produce pronounced sinks/sources with large divergences of E → and focusing on observation points close to them. We introduce the concept of “at the verge of discharge electric field,” Ę → produced by two specific charge configurations. We detail the role the dielectric character of the cloud plays in allowing/not allowing discharge. We profile the conditions to be met by Ę → to appear and to be sustained for at least a few milliseconds. One objective of this work is to calculate some relevant quantities for a typical thundercloud modeled just at the verge of discharging. A simple electrified cloud model containing many of the features widely reported in the literature is constructed and described with some detail. The charge structures possible are delineated and the electric fields produced described. A few basic calculations are carried out for a thought experiment, moving charges around, we calculate some velocities and accelerations and analyze what we learn from it

Sinapsis glutamatérgicas, análisis de factores que propician neurotoxicidad y enfermedades psicológicas

Las sinapsis glutamatérgicas (S-Glu) son las excitado-ras universales del cerebro. De ellas depende una acti-vidad intensa y/o orquestada de varias redes neurona-les. Cuando la difusión de glutamato (D-Glu) se ve perturbada, esta actividad neuronal puede alterarse y dar paso a alguna patología (Alzheimer, epilepsia, etc.). Nos interesa construir un modelo simple de cómo pueden, físicamente, alterarse estas sinapsis (S), con respecto al flujo del neurotransmisor Glu. Se modela una sinapsis S-Glu como un cilindro uniforme de radio c y altura 50 nm. Las distintas condiciones biológicas que operan en una S-Glu se traducen a condiciones físicas y geométricas con parámetros cuantitativos concretos

The Interaction of Microwaves with Materials of Different Properties

Electromagnetic radiation, such as microwaves, are all the time reflected, transmitted, and/or absorbed by any kind of matter, glasses, conductors, water, ferrites, and so forth. Magnetic materials absorb greatly microwaves. The more magnetic, the more microwaves are absorbed. The aim of this chapter is to present the fundamental physics of the absorption of microwave power (energy per unit time) by ferrimagnetic and ferromagnetic matter in the nano and micro size scale. The magnetic moments and their collective modes are the basic microscopic absorbers under in-resonance and out-of-resonance conditions. Experimental setups and measurement techniques are described. The profiles of microwave absorption are described and connected to the micromagnetic environment that elicits such absorption. Section by section and the overall microwave power absorption profiles are related to the micromagnetic structures. Emphasis is made on nano- and micromagnets. These interactions of microwaves with nano- and micromagnets serve to infer microscopic magnetic information

Sobre el pensamiento científico de Albert Einstein

Albert Einstein (AE) theories attract the attention and curiosity of the general public, children, students, teachers and scientists. Today, we can inquire into his writings and letters about his scientific thinking. In 1952, in a letter to his friend M. Solovine, explains again, based on a simple, yet substantial diagram, his “epistemology creed”. This work focus on the description of AE scientific thought. His diagram includes: Axioms (A); Propositions (S); and Sensorial Experience E). We give two examples in which the diagram applies: Maxwell electromagnetic theory and his own Special Relativity theory. We also apply it to Oparin’s theory of the origin of life. In this case the diagram remains incomplete, which is consistent with the fact that nowadays there is not a convincing theory of the origin of life. This, AE, epistemology creed has a great importance to inform students, teachers and scientists of how AE visualized an axiomatic, or a first principles, theory.Las teorías de Albert Einstein (AE) atraen la atención y curiosidad del público en general, niños, estudiantes, profesores y científicos. Hoy podemos indagar en sus escritos y cartas el pensamiento científico de A. Einstein. En 1952 en una carta a su amigo M. Solovine, vuelve a explicar en base a un diagrama sencillo y substancioso, su credo epistemológico. Este trabajo está centrado en la descripción del pensamiento científico de Albert Einstein. Su diagrama incluye: Axiomas (A), Proposiciones (S) y la Experiencia sensorial (E). Proporcionamos dos ejemplos donde aplica el esquema: la teoría electromagnética de Maxwell y su propia teoría de la Relatividad Especial. También lo aplicamos a la Teoría de Oparin sobre el origen de la vida. Aquí el diagrama queda incompleto, lo cual es consistente con el hecho de que al día de hoy no existe una teoría convincente del origen de la vida. Dicho esquema es de gran importancia para informar a estudiantes, profesores y científicos de como Einstein visualizaba una teoría axiomática o de primeros principios

Spectroscopic and Kinetic Characterization of Peroxidase-Like π-Cation Radical Pinch-Porphyrin-Iron(III) Reaction Intermediate Models of Peroxidase Enzymes

The spectroscopic and kinetic characterization of two intermediates from the H2O2 oxidation of three dimethyl ester [(proto), (meso), (deuteroporphyrinato) (picdien)]Fe(III) complexes ([FePPPic], [FeMPPic] and [FeDPPic], respectively) pinch-porphyrin peroxidase enzyme models, with s = 5/2 and 3/2 Fe(III) quantum mixed spin (qms) ground states is described herein. The kinetic study by UV/Vis at λmax = 465 nm showed two different types of kinetics during the oxidation process in the guaiacol test for peroxidases (1–3 + guaiacol + H2O2 → oxidation guaiacol products). The first intermediate was observed during the first 24 s of the reaction. When the reaction conditions were changed to higher concentration of pinch-porphyrins and hydrogen peroxide only one type of kinetics was observed. Next, the reaction was performed only between pinch-porphyrins-Fe(III) and H2O2, resulting in only two types of kinetics that were developed during the first 0–4 s. After this time a self-oxidation process was observed. Our hypotheses state that the formation of the π-cation radicals, reaction intermediates of the pinch-porphyrin-Fe(III) family with the ligand picdien [N,N’-bis-pyridin-2-ylmethyl-propane-1,3-diamine], occurred with unique kinetics that are different from the overall process and was involved in the oxidation pathway. UV-Vis, 1H-NMR and ESR spectra confirmed the formation of such intermediates. The results in this paper highlight the link between different spectroscopic techniques that positively depict the kinetic traits of artificial compounds with enzyme-like activity

Tetramer Compound of Manganese Ions with Mixed Valence [Mn^II Mn^III Mn^IV] and Its Spatial, Electronic, Magnetic, and Theoretical Studies

Using different spectroscopic techniques and computational calculations, we describe the structural and electromagnetic relationship that causes many interesting phenomena within a novel coordination compound with mixed valence manganese (II, III and IV) in its crystal and powder state. The novel compound [MnII MnIII MnIV(HL)2(H2L)2(H2O)4](NO3)2(H2O) 1 was obtained with the Schiff base (E)-2-((2-hydroxybenzylidene)amine)-2-(hydroximethyl)propane-1,3-diol, (H4L), and Mn(NO3)2.4H2O. The coordination reaction was promoted by the deprotonation of the ligand by the soft base triethylamine. The paper’s main contribution is the integration of the experimental and computational studies to explain the interesting magnetic behavior that the mixed valence manganese multimetallic core shows. The results presented herein, which are rarely found for Mn(II), (III) and (IV) complexes, will contribute to the understanding of the magnetic communication generated by the valence electrons and its repercussion in the local geometry and in the overall crystalline structure

Catalytic Activity of Cytochrome P-450 using NADP+ Reduced by an Anionic Hydride Organosiloxane

Abstract Cytochrome P-450 (P450) catalyzes a wide variety of chemical reactions; however, its use for in vitro assays has several limitations, the most striking one is the use of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) coenzyme. In this work, the P450 activity using NADP+ reduced by an anionic organosiloxane, commonly named silica hydride, was evaluated. The results showed that the reduction of NADP+with silica hydride was concentration- and time-dependent. P-450 activity was maintained when NADP+ and silica hydride were added during the reaction; however, it was lower than when commercial NADPH was employed. This is due to the ability of silica hydride to reduce P450 iron atom as corroborated by the electronic paramagnetic resonance (EPR). Furthermore, this compound possibly chelates FeII because, in its presence, the P450 affinity for aniline diminishes. However, the P450 activity was the best when NADP+ was reduced by silica hydride before the former was added to the reaction. Therefore, this system could be apt for studying biotransformation reactions