Woolly hair nevus: case report and review of literature

Woolly hair nevus consists of a patch of curly and hypopigmented hair that is restricted to an area of the scalp. It is usually benign but it can be associated with other systemic findings. Trichoscopy and dermoscopy may be useful when analyzing this entity. The authors describe a case of woolly hair nevus in a 5-year-old boy and present a review of the literature of woolly hair nevus, including classification, histopathology, associated systemic findings, and the recent described genetic mutations

Statistics, distillation, and ordering emergence in a two-dimensional stochastic model of particles in counterflowing streams

In this paper, we proposed a stochastic model which describes two species of particles moving in counterflow. The model generalizes the theoretical framework describing the transport in random systems since particles can work as mobile obstacles, whereas particles of one species move in opposite direction to the particles of the other species, or they can work as fixed obstacles remaining in their places during the time evolution. We conducted a detailed study about the statistics concerning the crossing time of particles, as well as the effects of the lateral transitions on the time required to the system reaches a state of complete geographic separation of species. The spatial effects of jamming were also studied by looking into the deformation of the concentration of particles in the two-dimensional corridor. Finally, we observed in our study the formation of patterns of lanes which reach the steady state regardless the initial conditions used for the evolution. A similar result is also observed in real experiments involving charged colloids motion and simulations of pedestrian dynamics based on Langevin equations, when periodic boundary conditions are considered (particles counterflow in a ring symmetry). The results obtained through Monte Carlo numerical simulations and numerical integrations are in good agreement with each other. However, differently from previous studies, the dynamics considered in this work is not Newton-based, and therefore, even artificial situations of self-propelled objects should be studied in this first-principle modeling.Comment: 27 pages, 13 figure

On the semi-dynamical reflection equation: solutions and structure matrices

Explicit solutions of the non-constant semi-dynamical reflection equation are constructed, together with suitable parametrizations of their structure matrices. Considering the semi-dynamical reflection equation with rational non-constant Arutyunov-Chekhov-Frolov structure matrices, and a specific meromorphic ansatz, it is found that only two sets of the previously found constant solutions are extendible to the non-constant case. In order to simplify future constructions of spin-chain Hamiltonians, a parametrization procedure is applied explicitly to all elements of the semi-dynamical reflection equation available. Interesting expressions for `twists' and R-matrices entering the parametrization procedure are found. In particular, some expressions for the R-matrices seem to appear here for the first time. In addition, a new set of consistent structure matrices for the semi-dynamical reflection equation is obtained.Comment: typos corrected and some comments adde

Pressure and Deformation Measurement with Piezoresistive Sensors

This dissertation shows us the processes to develop a sensor capable of measuring deformations of surfaces. The work englobes the processes of production and assemblage of the transducers, the electronics boards to read the signals from the transducers and, finally, the development of algorithms used to transform the signal of the sensor in readable information either for humans and other computers. The work starts with the study of the production and assemblage methods of the transducers. In this part, we used the screen printing technique to print the different layers of the transducer. After obtaining the printed transducer, we tested it, measuring only the main characteristics, as the variation of resistance with pressure. This gave us important information to proceed with the dimensioning of the measurement chain. The second part of this project, was focused in the design of the measurement chain. For this work, we projected a device that can adapt automatically to different values of sensors’ resistance. Because the transducers tested in this project have a hysteretic behavior, a mathematical model used to model the magnetic hysteresis was adapted to be used with piezoresistive sensors. This work meets the initial goal which was building a complete data acquisition system for a printed piezoresistive sensor. The proposed mathematical algorithm to model the resistance of piezoresistive sensors opens doors for future projects.Esta dissertação vem mostrar o processo completo para o desenvolvimento de um sensor capaz de medir deformações de superfícies. O trabalho passa assim pelos processos de produção e montagem dos transdutores, pelos circuitos eletrónicos desenhados para fazer as leituras do transdutor e finalmente pelos algoritmos utilizados para transformar o sinal do sensor numa informação que pode ser interpretada por humanos ou por outras máquinas. Desta forma, o trabalho inicia-se por um estudo dos métodos de produção e montagem dos transdutores. No final optou-se pela técnica de screen printing para produzir os transdutores e os elétrodos. Quanto ao método de montagem, optou-se por fazer uma sobreposição das camadas impressas. Após termos o transdutor impresso conseguimos testá-lo e assim obter informações como a variação da resistência. Estes são parâmetros muito importantes para o dimensionamento da cadeia de medida, que foi o segundo passo deste trabalho. Foi desenhada uma cadeia de medida capaz de fazer a leitura de diferentes sensores ao mesmo tempo. Este circuito é também capaz de se adaptar a diferentes sensores automaticamente. Como os sensores testados neste projeto apresentaram histerese, para contornar esta situação, um modelo de aproximação utilizado com materiais magnéticos foi adaptado para os sensores piezoresistivos. O trabalho cumpre o objetivo proposto no início deste projeto que era construir um sistema completo de aquisição de dados de um sensor piezoresistivo impresso. No final foi introduzido a adaptação do algoritmo que abre portas para futuros trabalhos

Nonequilibrium scaling explorations on a 2D Z(5)-symmetric model

We have investigated the dynamic critical behavior of the two-dimensional Z(5)-symmetric spin model by using short-time Monte Carlo (MC) simulations. We have obtained estimates of some critical points in its rich phase diagram and included, among the usual critical lines the study of first-order (weak) transition by looking into the order-disorder phase transition. Besides, we also investigated the soft-disorder phase transition by considering empiric methods. A study of the behavior of $\beta /\nu z$ along the self-dual critical line has been performed and special attention has been devoted to the critical bifurcation point, or FZ (Fateev-Zamolodchikov) point. Firstly, by using a refinement method and taking into account simulations out-of-equilibrium, we were able to localize parameters of this point. In a second part of our study, we turned our attention to the behavior of the model at the early stage of its time evolution in order to find the dynamic critical exponent z as well as the static critical exponents $\beta$ and $$ of the FZ-point on square lattices. The values of the static critical exponents and parameters are in good agreement with the exact results, and the dynamic critical exponent $z\approx 2.28$ very close of the 4-state Potts model ($z\approx 2.29$).Comment: 11 pages, 7 figure