Monte Carlo and analytical calculation of lateral deflection of proton beams in homogeneous targets

Proton radiation therapy is a precise form of radiation therapy, but the avoidance of damage to critical normal tissues and the prevention of geographical tumor misses require accurate knowledge of the dose delivered to the patient and the verification of his position demand a precise imaging technique. In proton therapy facilities, the X-ray Computed Tomography (xCT) is the preferred technique for the planning treatment of patients. This situation has been changing nowadays with the development of proton accelerators for health care and the increase in the number of treated patients. In fact, protons could be more efficient than xCT for this task. One essential difficulty in pCT image reconstruction systems came from the scattering of the protons inside the target due to the numerous small-angle deflections by nuclear Coulomb fields. The purpose of this study is the comparison of an analytical formulation for the determination of beam lateral deflection, based on Moli��re's theory and Rutherford scattering with Monte Carlo calculations by SRIM 2008 and MCNPX codes. �� 2010 American Institute of Physics.

Monte Carlo simulation applied in total reflection X-ray fluorescence: Preliminary results

The X-ray Fluorescence (XRF) analysis is a technique for the qualitative and quantitative determination of chemical constituents in a sample. This method is based on detection of the characteristic radiation intensities emitted by the elements of the sample, when properly excited. A variant of this technique is the Total Reflection X-ray Fluorescence (TXRF) that utilizes electromagnetic radiation as excitation source. In total reflection of X-ray, the angle of refraction of the incident beam tends to zero and the refracted beam is tangent to the sample support interface. Thus, there is a minimum angle of incidence at which no refracted beam exists and all incident radiation undergoes total reflection. In this study, we evaluated the influence of the energy variation of the beam of incident x-rays, using the MCNPX code (Monte Carlo NParticle) based on Monte Carlo method. �� 2013 AIP Publishing LLC.

Estudo de percola����o de clusters de Monte Carlo para o modelo de Ising bidimensional

P��s-gradua����o em F��sica - IFT

Estudo de Monte Carlo da produ����o de nova resson��ncia neutra decaindo em dois b��sons vetoriais no experimento CMS

P��s-gradua����o em F��sica - IFT

Teoria qu��ntica do campo escalar real com autoacoplamento qu��rtico - simula����es de Monte Carlo na rede com um algoritmo worm

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Estudo de solvatocromismo em l��quidos moleculares org��nicos via m��todo seq��encial Monte Carlo/Mec��nica Qu��ntica

Utilizou-se o m��todo seq��encial Monte Carlo / Mec��nica Qu��ntica para obterem-se os desvios de solvatocromismo e os momentos de dipolo dos sistemas de mol��culas org��nicas: Uracil em meio aquoso, -Caroteno em ��cido Ol��ico, ��cido Ricinol��ico em metanol e em Etanol e ��cido Ol��ico em metanol e em Etanol. As otimiza����es das geometrias e as distribui����es de cargas foram obtidas atrav��s da Teoria do Funcional Densidade com o funcional B3LYP e os conjuntos de fun����es de base 6-31G(d) para todas as mol��culas exceto para a ��gua e Uracil, as quais, foram utilizadas o conjunto de fun����es de base 6-311++G(d,p). No tratamento cl��ssico, Monte Carlo, aplicou-se o algoritmo Metrop��lis atrav��s do programa DICE. A separa����o de configura����es estatisticamente relevantes para os c��lculos das propriedades m��dias foi implementada com a utiliza����o da fun����o de auto-correla����o calculada para cada sistema. A fun����o de distribui����o radial dos l��quidos moleculares foi utilizada para a separa����o da primeira camada de solvata����o, a qual, estabelece a principal intera����o entre soluto-solvente. As configura����es relevantes da primeira camada de solvata����o de cada sistema foram submetidas a c��lculos qu��nticos a n��vel semi-emp��rico com o m��todo ZINDO/S-CI. Os espectros de absor����o foram obtidos para os solutos em fase gasosa e para os sistemas de l��quidos moleculares comentados. Os momentos de dipolo el��trico dos mesmos tamb��m foram obtidos. Todas as bandas dos espectros de absor����o dos sistemas tiveram um desvio para o azul, exceto a segunda banda do sistema de Beta-Caroteno em ��cido Ol��ico que apresentou um desvio para o vermelho. Os resultados encontrados apresentam-se em excelente concord��ncia com os valores experimentais encontrados na literatura. Todos os sistemas tiveram aumento no momento de dipolo el��trico devido ��s mol��culas dos solventes serem mol��culas polares. Os sistemas de ��cidos graxos em ��lcoois apresentaram resultados muito semelhantes, ou seja, os ��cidos graxos mencionados possuem comportamentos espectrosc��picos semelhantes submetidos aos mesmos solventes. As simula����es atrav��s do m��todo seq��encial Monte Carlo / Mec��nica Qu��ntica estudadas demonstraram que a metodologia �� eficaz para a obten����o das propriedades espectrosc��picas dos l��quidos moleculares analisados.

Investiga����o da din��mica sequ��ncial Monte Carlo/Mec��nica Qu��ntica para sitemas moleculares org��nicos

O principal objetivo deste trabalho �� investigar te��ricamente as propriedades eletr��nicas e ��ticas de compostos org��nicos em ambiente l��quido. A compreens��o das intera����es em sistemas l��quidos �� muito importante para a descri����o de fen��menos em muitas partes da ci��ncia, como F��sica, Qu��mica, Biologia e Materiais, bem como no desenvolvimento de materiais ��ticos. As flutua����es t��rmicas fazem que inumaram das configura����es para os l��quidos possam ser gerados. Esta �� a raz��o do comportamento estat��stico observado em sistemas l��quidos. Considerando estas dificuldades, o tratamento sequencial Monte Carlo / Mec��nica Qu��ntica (SMC/QM) �� usado neste trabalho. Neste procedimento, a estrutura l��quida �� gerada primeiramente por simula����es cl��ssicas de MC e mais tarde, somente a parte mais importante do sistema �� tratada com mec��nica qu��ntica. Usando o procedimento acima, os propriedades do quantum o pirazine dimethyl do thiene Methyl da laranja (MO) e do O 2,3-dimetil tieno[3,4-b] pirazina (DTP) foram investigados. O MO �� um conhecido indicador de pH e pode ser encontrado sob circunst��ncias b��sicas e acidas. Suas geometrias de m��nima energia foram obtidas mediante a Teoria do Funcional da Densidade pelo funcional B3LYP, sendo o sistema descrito pelas bases de Pople com uma fun����o de polariza����o (6-31G*). Para obter as propriedades m��dias dos observaveis, c��lculos de qu��mica qu��ntica foram executados dentro da aproxima����o semi-emp��rica de INDO/S-CI. Com respeito ao espectro de absor����o, os dados experimentais existentes na literatura cient��fica reportam a exist��ncia de uma larga banda localizada na regi��o de baixas energias, mais precisamente entre 400 e 600 nm. Nossos resultados te��ricos para a forma alcalina mostram uma transi����o intensa transi����o �� ��� ��* aproximadamente �� 432.4 �� 0.03 nm e, sob condi����es ��cidas, esta transi����o aparece aproximadamente �� 507.4 �� 0.12, 496.4 �� 0.28 ou 545.3 �� 0.10 nm, dependendo da estrutura, mostrando bom acordo com resultados experimentais. O DTP �� um sistema particular usado na produ����o de pol��meros de baixo gap. Suas propriedades el��tricas e ��ticas foram obtidas atrav��s de um novo procedimento conhecido por Configura����o Eletrost��tica M��dia do Solvent (ASEC). O procedimento ASEC inclui mol��culas do solvente como cargas pontuais e permite o obten����o das quantidades qu��nticas executando somente poucos c��lculos de mec��nica qu��ntica. Para o DTP, usando a teoria das perturba����es de segunda ordem M��ller-Plesset (MP2) e o conjunto de bases aug-cc-pVDZ, a converg��ncia do momento de dipolo foi alcan��ada com apenas quatro c��lculos de mec��nica qu��ntica �� 1.16 D, apresentando um aumento de 42% quando comparado ao dipolo isolado. O polarizabilidade corresponde �� outra caracter��stica el��trica que p��de ser medida. Considerando o mesmo n��vel empregado ao c��lculo do dipolo, o valor m��dio 132.7 a30 foi observado. A regi��o de mais baixas da energias do espectro de absorption foi investigada tamb��m atrav�� de procedimento de ASEC usando ambos as aproxima����es, semi-emp��rico e DFT. Esta regi��o de absor����o �� motivo de conclus��es contradit��rias com rela����o �� natureza das transi����es n ��� ��* e �� ��� ��*. Nossos resultados mostram que realmente que essas excita����es s��o realmente observadas simultanemente podendo sobrep��r-se. Como exemplo, nossos resultados para DFT, encontrados usando o funcional B3LYP nos mostra que estas transi����es aparecem aproximadamente �� 360.6 e 351.1 nm.

C��lculo das fun����es de anisotropia e radial de dose para braquiterapia com semente de 192Ir em diferentes materiais de interesse em radiologia com o aux��lio do programa baseado no m��todo de Monte Carlo MCNPX

The brachytherapy braquiterapia is an x-ray modality radiotherapy in which stamped or halfstamped radioactive sources in format of seeds are used, wires or to one short distance, in contact or implanted to the fabric to be treated. All the treatment modalities require a previous planning. The formalism recommended for calculation of dose was considered by the AAPM for the first TG-43 Report. In it distributions of dose of isolated seeds measured and calculated by Monte Carlo method in water instead of with models half-empiricists. In this work we in accordance with present some preliminary results of the calculation of functions of radial anisotropy and of dose in the distance for seed of 192Ir, wide used in brachytherapy treatments of high tax of dose (HDR), with the aid of the program based on the Monte Carlo method MCNPX v2.50 (Mount Carlo N ParticleeXtended). The materials chosen in the simulation beyond water, had been MS20 and estriado muscle

A simula����o de Monte Carlo como instrumento fundamental para a an��lise de viabilidade econ��mica: a implementa����o de uma fundi����o de ferro em uma empresa metal��rgica

In uncertainly economic scenarios, an economic feasibility analysis must be done to accept a project based on investment criteria, such as NPV and IRR, mainly because the shareholders tend to invest their budget in a project if it has a great chance to return their investments. The studied company outsources all of its foundry services, what makes it very dependent of its suppliers, because the products have a lower quality level, long delivery periods and high prices. Therefore, this work will analyze the project of building an iron-casting foundry to decrease the dependence of its suppliers. In order to develop this research, all needed data related to the construction of the foundry and sales were collected to create deterministic and probabilistic (Monte Carlo Simulation) cash flows using MsExcel�� and Oracle's Crystal Ball�� software. As a result, the project was found to be risky by the NPV and IRR in the case of this new production line supplying only the internal needs. However, when the company offers its services to the foundry market, the project turns to be feasible

Uso do m��todo de Monte Carlo para simula����o e detec����o do espectro de raios-X gerado com feixes de el��trons em alvo de Molibd��nio, utilizando o Geant4

The huge demand for procedures involving ionizing radiation promotes the need for safe methods of experimentation considering the danger of their biological e ects with consequent risk to humans. Brazilian's legislation prohibits experiments involving this type of radiation in humans through Decree 453 of Ministry of Health with determines that such procedures comply with the principles of justi cation, optimization and dose limitation. In this line, concurrently with the advancement of available computer processing power, computing simulations have become relevant in those situations where experimental procedures are too cost or impractical. The Monte Carlo method, created along the Manhattan Project duringWorldWar II, is a powerful strategy to simulations in computational physics. In medical physics, this technique has been extensively used with applications in diagnostics and cancer treatment. The objective of this work is to simulate the production and detection of X-rays for the energy range of diagnostic radiology, for molybdenum target, using the Geant4 toolkit. X-ray tubes with this kind of target material are used in diagnostic radiology, speci cally in mammography, one of the most used techniques for screening of breast cancer in women. During the simulations, we used di erent models for bremsstrahlung available in physical models for low energy, in situations already covered by the literature in earlier versions of Geant4. Our results show that although the physical situations seems qualitatively adequate, quantitative comparisons to available analytical data shows aws in the code of Geant4 Low Energy source

Estudo do m��todo Monte Carlo e sua aplica����o no modelo SIR

In this work we present a discussion and the results of the simulation of disease spread using the Monte Carlo method. The dissemination model is the SIR model and presents as main characteristic the disease evolution among individuals of the population subdivided into three groups: susceptible (S), infected (I) and recovered (R). The technique used is based on the introduction of transition probabilities S-> I and I->R to do the spread of the disease, they are governed by a Poisson distribution. The simulation of the spread of disease was based on the randomness introduced, taking into account two basic parameters of the model, the power of infection and average time of the disease. Considering appropriate values of these parameters, the results are presented graphically and analysis of these results gives information on a group of individuals react to the changes of these parameters and what are the chances of a disease becoming a pandemic

Application of reverse Monte Carlo simulations to diatomic molecules. Part 1. Noncomplete radial distribution functions

The reverse Monte Carlo (RMC) method generates sets of points in space which yield radial distribution functions (RDFS) that approximate those of the system of interest. Such sets of configurations should, in principle, be sufficient to determine the structural properties of the system. In this work we apply the RMC technique to fluids of hard diatomic molecules. The experimental RDFs of the hard-dimer fluid were generated by the conventional MC method and used as input in the RMC simulations. Our results indicate that the RMC method is only satisfactory in determining the local structure of the fluid studied by means of only mono-variable RDF. Also we suggest that the use of multi-variable RDFs would improve the technique significantly. However, the accuracy of the method turned out to be very sensitive to the variance of the input experimental RDF. �� 1995.

Using the Ferrenberg-Swendsen Monte Carlo method for nonuniversal exponents

We use the method of Monte Carlo evolution in the coupling constant space of Ferrenberg and Swendsen to evaluate the nonuniversal exponent ��* associated to a linear defect in a 2d Ising model. �� 1989.

Simula����o de Monte Carlo: de modelos de spin �� teoria de campos na rede

P��s-gradua����o em F��sica - IFT