Resumo É bem conhecido o paralelo exato entre o problema de um jogador que aposta dinheiro iterativamente em um jogo de azar e o de um caminhante aleatório em uma dimensão com uma parede absorvedora. Essa e outras conexões entre finanças e Física motivaram o surgimento, na década de 1990, da área de Econofísica. Como o assunto ainda é pouco conhecido no âmbito de cursos de graduação em Física, vimos primeiramente revisar alguns conceitos básicos relevantes, tais como martingale, derivativo financeiro e opções de ações. Focaremos em opções binárias (OB), que são derivativos financeiros. Os objetivos desse trabalho são: (i) mostrar como funcionam as OB; (ii) simular estocasticamente o comportamento da curva de saldo para diferentes taxas de acertos; (iii) realização de testes de taxa de sucesso do indicador chamado oscilador estocástico em séries temporais de dados financeiros históricos. Esse indicador é muito usado por operadores de OB, portanto é um exemplo ilustrativo ideal. Nossos resultados evidenciam que é difícil a lucratividade consistente, mesmo que se tente recuperar perdas aplicando estratégias baseadas em martingale ou alavancagem “soros”. Tal caracterização empírica dessa dificuldade ajuda a deixar mais claro a imprevisibilidade e o alto grau de complexidade do comportamento visto em mercados financeiros.

Abstract The analogy between the problem of a player who bets money iteratively in a game of chance and a random walker in one dimension with an absorbing boundary is well known. These and other connections between finance and physics motivated the emergence of the field of econophysics in the 1990s. Since the subject matter is still not well known at the level of undergraduate physics programs, here we first review some basic concepts, such as martingales, financial derivatives and stock options. Our objectives are the following: (i) to explain how binary options work; (ii) to simulate stochastically the behavior of the balance sheet curve for different hit rates; (iii) to run tests of the success rates for the stochastic oscillator indicator in financial time series of historical data. This indicator is widely used by binary option traders, so it is an ideal illustrative example. Our results show that it is difficult to obtain consistent profits, even using strategies based on martingales or “Soros” leveraging to recover previous losses. The empirical characterization of this difficulty may help to make clearer the unpredictability and high degree of complexity of the behavior seen in financial markets.

Background and objetive: With the increasing life expectancy in human immunodeficiency virus (HIV) infected patients since the highly active antiretroviral therapy (HAART), other underlying comorbilities such as chronic liver patology, cardiovascular diseases or side effects of treatment may lead to hospitalization. The purpose of this study is to determine the clinical and epidemiological characteristics of these patients. Material and methods: A descriptive-retrospective study. We reviewed the clinical records of patients with HIV infection admitted in our medical departments through a year. Results: There were 125 hospitalizations of 82 patients. 77% were males and 71% had hepatitis C virus (HCV) infection. The median age was 42 years. 64% HIV infection had been acquired by sharing material for intravenous drug use. A 36% were receiving HAART and 51% had AIDS. The respiratory tract patology (32%) and AIDS-defining illnesses (22%) were the most frequent causes of hospitalization, and the main opportunistic disease was tuberculosis (TBC). Ten per cent were admitted in the Intensive Care Unit. Mortality rate was 11% patients/year. Conclusions: Most of the patients were male, drug users and HCV positive, and the admissions to hospital were mostly due to respiratory patology and opportunistic diseases. TBC remains like the most frequent AIDS-defining illness.

Fundamento y objetivo: Con el aumento de la esperanza de vida en pacientes con infección por el virus de la inmunodeficiencia humana (VIH) tras el tratamiento antirretroviral de gran actividad (TARGA), las causas de hospitalización han cambiado. Predominan ahora comorbilidades como la hepatopatía crónica, la patología cardiovascular o los efectos secundarios de los tratamientos. Nuestro objetivo es determinar las características clinicoepidemiológicas actuales de estos pacientes. Material y métodos: Estudio descriptivo y retrospectivo. Revisamos las historias clínicas de los ingresos de pacientes con infección por el VIH hospitalizados en los servicios médicos de nuestro hospital en el transcurso de un año. Resultados: Hubo 125 ingresos de 82 pacientes, un 77% varones y un 71% con infección por el virus de la hepatitis C (VHC). La edad media fue de 42 años. En el 64% la vía de transmisión fue la drogadicción parenteral. Un 36% recibían TARGA y un 51% reunían criterios sida. Los motivos de ingreso más frecuentes fueron la patologia respiratoria (32%) y las enfermedades definitorias de sida (EDS) con un 22%, de las que la tuberculosis (TBC) fue la más frecuente. Un 10% fueron ingresados en la Unidad de Cuidados Intensivos (UCI). La mortalidad fue del 11% pacientes/año. Conclusiones: La mayoría de los pacientes fueron varones, con coinfección por el VHC y usuarios de drogas vía parenteral, siendo las causas de ingreso más frecuentes las patologías respiratorias y las enfermedades oportunistas. La TBC permanece siendo la EDS más frecuente.

Listeria monocytogenes is still a very rare opportunist infection in immunosuppressive patients. The clinical-epidemiological and therapeutic characteristics in 10 patients with infection produced by LM are reported, - four of them had primary bacteriemia, three patients had a meningeal involvement, there were two patients with spontaneous bacterial peritonitis and one suffered from abdominal access. All of the patients had underlying disorders favouring the infection. Sepsis and meningeal syndrome were the most common presenting forms. Ampicilin was the most used antibiotic. The overall mortality was 40%.

La Listeria monocytogenes (LM) continúa siendo una rara infección oportunista en enfermos inmunodeprimidos. Se presentan las características clinicoepidemiológicas y terapéuticas de 10 casos de infección por LM, siendo estas 4 bacteriemias primarias, 3 meningitis, 2 peritonitis bacterianas espontáneas y 1 absceso abdominal. Todos tenían factores predisponentes. Las formas de presentación más frecuentes fueron el cuadro séptico y la meningoencefalitis. El antibiótico más utilizado fue la ampicilina. La mortalidad global fue de un 40%.