Spin-dependent beating patterns in thermoelectric properties: Filtering the carriers of the heat flux in a Kondo adatom system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento de tratamentos térmicos visando ganhos magnéticos em aços com ultra baixa concentração de carbono

The relationship between the microstructure and the magnetic properties of soft magnetic materials, have been studied by different researchers who seek to employ electrical systems, increasing their life span and reduce their energy consumption. Following this same line the Brazilian Synchrotron Light Laboratory developed a new synchrotron light source, the Sirius, where magnetic materials with high magnetic permeability values are being studied for use in accelerator dipoles. The low carbon steel is a ferromagnetic material that has a great relationship between cost and magnetic permeability. Aiming to raise the values of permeability of the material, heat treatments were done and evaluated the magnetic properties, microstructure and mechanical properties to correlate them. It was noted that the thermal annealing were the most effective, and the annealing performed with a small time threshold, which only phenomenon observed was the primary recrystallisation, was the most elevated values of magnetic permeability of the material, due to the average grain size ideal achieved. The heat treatments do not guide the magnetic domains of the material and not influence the mechanical properties of the material due to lack of carbon in the microstructure. The annealing treatments were shown to be an alternative to raising the values of the magnetic permeability of the material and facilitate the implementation of ultra low carbon steel in the dipoles of Sirius

Radioterapia com elétrons

Radiotherapy is a field of medical physics, which has been going through a scientific and technological advancement, it is extreme important the professionals that work in this area continuous their study to improve the quality of service provided. For it, they should know the physical principles related as well their employment in radiotherapy. The electrons have been using in therapy of superficial tumors, because they show rapid decrease of dose in depth, they don’t expose the deeper tissues to radiation. The electron therapy has replaced the surface therapy with x-ray and mold brachytherapy, and nowadays, it represents 10 to 15% of radiotherapy treatments. This study brings the definition of physical parameters used in the dosimetry of electron beam, describes the tests for quality control of linear accelerator with a electrons beam, as well the activities realized in the Radiotherapy Division, of Hospital de Clinicas, in the Universidade Estadual of Campinas, in the Clinac 2100C machine

Efeitos de campos elétrico e magnético em um sistema dissipativo pulsante

The main idea of this work is to understand and analyze the dynamical aspects of the motion of a particle moving in the annular billiard, which corresponds to two circles of radius R and r (rFermi acceleration indeed. However, in presence of the electric field, to same values, the magnetic one together can improve this referred process, obtaining greater energy values to the same number of iterations. These results are applied to the concentric case, that was reported did not haven any significant energy gain on the free particle motion

Controle de qualidade em radioterapia: dosimetria de fótons em acelerador linear – Mevatron MXT

The treatment of a tumor with ionizing radiation is an ongoing process with well differentiated stages. These ones include the tumor diagnosis and location, the decision on the treatment strategy, the absorbed dose planning and calculation, the treatment administration, the absorbed dose verification and the evaluation of results in short and long terms. The quality of a radiotherapy procedure is closely linked to factors that may be classified as clinical, such as the diagnosis, the tumor location, the treatment strategy chosen and the continuous treatment reassessment; dosimetric or physical, such as the uncertainty in the dose calculation, its optimization and verification, the suitability of the equipment to provide a radiation beam consistent with the treatment planning; finally, others which are related to the practical application of radiotherapy treatment and the handling of the patient. In order to analyze the radiotherapy quality, one should realize that the three aspects (medical, physical or dosimetric and practical application) should be considered in a combined way. This means that numerous actions of the radiotherapists, medical physicists and technicians in radiotherapy should be held jointly and their knowledge level will significantly affect the treatment quality. In this study, the main physical parameters used in dosimetry are defined as well as determined experimentally for a linear accelerator Mevatron - MXT. With this, it is intended to provide recommendations for the physical aspects of Quality Assurance (QA) in the radiotherapy treatments, and these will usually be applied by professionals in Medical Physics. In addition to these instructions, it is recommended that additional texts are prepared to address in detail the clinical aspects of the treatments QA

Uma avaliação do uso do NCRP 151 na realidade brasileira

Medical Physics is an interdisciplinary field that applies concepts and laws of physics in medical practices. Currently, one of its main applications is the use of ionizing radiation in the treatment of oncological diseases. Due to its wide use and highly dangerous, many of radioprotection procedures should be adopted with the objective of protecting human beings from harmful effects of radiation. Thus, you can better enjoy the benefits that the practice can offer. The methodology proposed by the National Council on Radiation Protection 151 (NCRP 151), relates technical information necessary to Structural Shielding Design and Evaluation for Megavoltage X- and Gamma- Ray Radiotherapy Facilities. However, many parameters used to calculate the shield are based on estimates only, and it is an international standard that may not be adequate to the Brazilian reality. Thus, the central idea of this study is the collection of data from the routine of the Radiotherapy Service of the Real e Benemérita Associação Portuguesa de Beneficência, in particular equipment cobalt therapy Theratron 780 (Atomic Energy of Canada Ltd.) and the linear accelerator Varian Clinac 2100C for measurement of workload, number of patients, fields, and dose factors to determine the best use of barrier protection. Furthermore, this work features a profile of radiotherapy treatments carried out closer to the Brazilian reality

Sistema de Acelerador Linear Comercial para Radioterapia

This paper presents a study about the operation of the major system’s components of a linear particle acclerator (Linac). It addresses the components mainly responsible for the formation of the beam, through the inclusion of several block diagrams showing the details of the structure. Among the systems discussed may be mentioned the system modulator, automatic frequency control, dosimetry and auxiliary systems. The main objective is the dissemination of basic technology applied in linear accelerators and create literature about this subject in national language. Despite the high complexity and large number of devices that comprise a linear accelerator, it has been developed an easy to understand text that adresses the most relevant issues to the operation of the linear accelerator from the point of view of electrical engineering

Sistema de cálculo computacional da unidade monitora para feixes de elétrons em radioterapia

In radiation theraphy with electron beam, the electrons are produced in linear accelerators, and energy the most used have between 4MeV and 20MeV. Generally, the treatments are done for superficial injuries, because the low penetration of these particles. In this work a system for calculation of monitor units (U.M.) for cases of treatments with electron beam was developed. The Excel program of Microsoft was used and is easily found in the operational system of the personal microcomputers. In the Excel has been inserted the pertinent data of the linear accelerator of Varian, model 2100C, used in the Service of radiation theraphy of the Hospital of the Clinics of the College of Medicine of the UNESP of Botucatu. For some values of the physical parameters, such as: factors field and factors calibration, not supplied in the tests of acceptance of the machine, still proceeded calculations from interpolation and extrapolation. The mathematical formulas for automatic search of these and others factors used in the calculations of the determination of the U.M had been developed in agreement available routines in Excel. For this the functions had been used the function IF (that it imposes search condition) and the PROCH (that looks a value in a column from determined line), beyond the basic functions of addition, multiplication and division. It is intended to optimize the routine of the Services of radiation theraphy that perform through eletrontheraphy procedures, speeding the calculations and minimizing the occurrence of errors and uncertainties deriving of the maken a mistake manipulation of the parameters gotten in tables of data of electron beams

Temperature-induced spontaneous time-reversal symmetry breaking on the honeycomb lattice

Phase transitions involving spontaneous time-reversal symmetry breaking are studied on the honeycomb lattice at finite hole doping with next-nearest-neighbor repulsion. We derive an exact expression for the mean-field equation of state in closed form, valid at temperatures much less than the Fermi energy. Contrary to standard expectations, we find that thermally induced intraband particle-hole excitations can create and stabilize a uniform metallic phase with broken time-reversal symmetry as the temperature is raised in a region where the ground state is a trivial metal.

A quantum theory for the excitation spectrum of a rectangular Andreev billiard

We consider a N - S box system consisting of a rectangular conductor coupled to a superconductor. The Green functions are constructed by solving the Bogoliubov-de Gennes equations at each side of the interface, with the pairing potential described by a step-like function. Taking into account the mismatch in the Fermi wave number and the effective masses of the normal metal - superconductor and the tunnel barrier at the interface, we use the quantum section method in order to find the exact energy Green function yielding accurate computed eigenvalues and the density of states. Furthermore, this procedure allow us to analyze in detail the nontrivial semiclassical limit and examine the range of applicability of the Bohr-Sommerfeld quantization method.

Constraining the absolute neutrino mass scale and Majorana CP violating phases by future 0νββ decay experiments

Assuming that neutrinos are Majorana particles, in a three-generation framework, current and future neutrino oscillation experiments can determine six out of the nine parameters which fully describe the structure of the neutrino mass matrix. We try to clarify the interplay among the remaining parameters, the absolute neutrino mass scale and two CP violating Majorana phases, and how they can be accessed by future neutrinoless double beta (0vυββ) decay experiments, for the normal as well as for the inverted order of the neutrino mass spectrum. Assuming the oscillation parameters to be in the range presently allowed by atmospheric, solar, reactor, and accelerator neutrino experiments, we quantitatively estimate the bounds on m 0, the lightest neutrino mass, that can be inferred if the next generation 0υββ decay experiments can probe the effective Majorana mass (m ee) down to ∼1 meV. In this context we conclude that in the case that neutrinos are Majorana particles, (a) if m 0≳300 meV, i.e., within the range directly attainable by future laboratory experiments as well as astrophysical observations, then m ee≳30 meV must be observed, (b) if m 0 ≤ 300 meV, results from future 0υββ decay experiments combined with stringent bounds on the neutrino oscillation parameters, especially the solar ones, will place much stronger limits on the allowed values of m 0 than these direct experiments. For instance, if a positive signal is observed around m ee = 10 meV, we estimate 3≲m 0/meV≲65 at 95% C.L.; on the other hand, if no signal is observed down to m ee = 10 meV, then m 0≲55 meV at 95% C.L.

Nuclear magnetic relaxation for the spin-degenerate Anderson model

A renormalization-group calculation of the temperature-dependent nuclear spin relaxation rate for a magnetic impurity in a metallic host is reported. The calculation follows a simplified procedure, which produces accurate rates in the low-temperature Fermi-liquid regime, although yielding only qualitatively reliable results at higher temperatures. In all cases considered, as the temperature T diminishes, the rates peak before decaying linearly to zero in the Fermi-liquid range. For T → 0, the results agree very well with Shiba's expression relating the low-temperature coefficient of the relaxation rate to the squared zero-temperature susceptibility. In the Kondo limit, the enhanced susceptibility associated with the Kondo resonance produces a very sharp peak in the relaxation rate near the Kondo temperature. © 1991.

Estudo do fenômeno de decaimento de energia média do Bilhar Stadium dependente do tempo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Termodinâmica do modelo Bouncer: um gás unidimensional simplificado

Pós-graduação em Física - IGCE

A theoretical analysis of Sb5+ incorporation in highly doped SnO2 matrix

We have used the periodic quantum-mechanical method with density functional theory at the B3LYP hybrid functional level in order to study the doping of SnO2 with pentavalent Sb5+. The 72-atom 2x3x2 supercell SnO2 (Sn24O48) was employed in the calculations. For the SnO2:4%Sb , one atom of Sn was replaced by one Sb atom. For the SnO2:8%Sb, two atoms of Sn were replaced by two Sb atoms. The Sb doping leads to an enhancement in the electrical conductivity of this material, because these ions substitute Sn4+ in the SnO2 matrix, leading to an electronic density rise in the conduction band, due to the donor-like behavior of the doping atom. This result shows that the bandgap magnitude depends on the doping concentration, because the energy value found for SnO2:4%Sb was 2.8eV whereas for SnO2:8%Sb it was 2.7eV. It was also verified that the difference between the Fermi level and the bottom of the conduction band is directly related to the doping concentration. - See more at: http://www.eurekaselect.com/117255/article#sthash.Z5ezhCQD.dpuf