Interpretation of the Pattern in Rate Ratios Across Strata

The pattern in the ratio of disease rates over strata is a summary statistic used to describe the changing risk of disease in one group relative to another. While patterns of the ratios of disease rates over strata appear to correspond to specific changes in disease rates, plots of the disease rates over strata seem to contradict the information yielded by the ratios. For example, if disease rates from populations A and B have identical rates of decline (parallel lines), the difference in the rates (A - B) at each strata remains constant, while the ratio of the rates (AIB) increases over strata. Through simple algebraic manipulation, one can show that the pattern of the rate ratio is a function of the rate difference relative to the endemic disease rate. Thus, rather than describing the behavior of the disease rates, ratio patterns reflect the importance of exposure relative to the disease rate in the unexposed population

Postsynaptic α1-Adrenergic vasoconstriction is impaired in young patients with vasovagal syncope and is corrected by nitric oxide synthase inhibition

BACKGROUND: Syncope is a sudden transient loss of consciousness and postural tone with spontaneous recovery; the most common form is vasovagal syncope (VVS). During VVS, gravitational pooling excessively reduces central blood volume and cardiac output. In VVS, as in hemorrhage, impaired adrenergic vasoconstriction and venoconstriction result in hypotension. We hypothesized that impaired adrenergic responsiveness because of excess nitric oxide can be reversed by reducing nitric oxide. METHODS AND RESULTS: We recorded cardiopulmonary dynamics in supine syncope patients and healthy volunteers (aged 15-27 years) challenged with a dose-response using the α1-agonist phenylephrine (PE), with and without the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine, monoacetate salt (L-NMMA). Systolic and diastolic pressures among control and VVS were the same, although they increased after L-NMMA and saline+PE (volume and pressor control for L-NMMA). Heart rate was significantly reduced by L-NMMA (P<0.05) for control and VVS compared with baseline, but there was no significant difference in heart rate between L-NMMA and saline+PE. Cardiac output and splanchnic blood flow were reduced by L-NMMA for control and VVS (P<0.05) compared with baseline, while total peripheral resistance increased (P<0.05). PE dose-response for splanchnic flow and resistance were blunted for VVS compared with control after saline+PE, but enhanced after L-NMMA (P<0.001). Postsynaptic α1-adrenergic vasoconstrictive impairment was greatest in the splanchnic vasculature, and splanchnic blood flow was unaffected by PE. Forearm and calf α1-adrenergic vasoconstriction were unimpaired in VVS and unaffected by L-NMMA. CONCLUSIONS: Impaired postsynaptic α1-adrenergic vasoconstriction in young adults with VVS can be corrected by nitric oxide synthase inhibition, demonstrated with our use of L-NMMA

The HIM glocal metric and kernel for network comparison and classification

Due to the ever rising importance of the network paradigm across several areas of science, comparing and classifying graphs represent essential steps in the networks analysis of complex systems. Both tasks have been recently tackled via quite different strategies, even tailored ad-hoc for the investigated problem. Here we deal with both operations by introducing the Hamming-Ipsen-Mikhailov (HIM) distance, a novel metric to quantitatively measure the difference between two graphs sharing the same vertices. The new measure combines the local Hamming distance and the global spectral Ipsen-Mikhailov distance so to overcome the drawbacks affecting the two components separately. Building then the HIM kernel function derived from the HIM distance it is possible to move from network comparison to network classification via the Support Vector Machine (SVM) algorithm. Applications of HIM distance and HIM kernel in computational biology and social networks science demonstrate the effectiveness of the proposed functions as a general purpose solution.Comment: Frontiers of Network Analysis: Methods, Models, and Applications - NIPS 2013 Worksho

Construção de aparato experimental para controle de sistemas térmicos com atraso de transporte

Trabalho de Conclusão Curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2017.Em processos de controle industriais, o fenômeno de transporte de calor está presente e saber identifica-lo para obter um modelo matemático é importante para o desenvolvimento de um projeto de controle dinâmico. Assim, este trabalho aborda o contexto da criação, desenvolvimento, identificação, modelagem e controle de um aparto experimental para controle de sistemas térmicos com atraso no transporte. Foi construída uma planta de controle com um tubo metálico de dois metros de comprimento onde o ar aquecimento por uma resistência elétrica passa em seu interior. A eletrônica envolvida na construção do aparato envolve o uso de TRIAC, para o controle da resistência elétrica, de uma ponte H, para a amplificação do sinal PWM para um motor DC e do microcontrolador Atmega 328 do Arduino Uno para fazer a interface entre a planta de controle e um computador. No computador, os sinais de acionamento eram gerados pelo software MATLAB em conjunto com as leituras dos sensores. No mesmo software foram feitas as análises gráficas dos resultados obtidos, a identificação do modelo matemático no domínio da frequência e a criação do controlador PID. Para isso, usamos toolbox que o MATLAB disponibiliza especificamente para projetos de controle dinâmico. Foi projetado um controlador do tipo PID (Proporcional – Integrador – Derivador) em série com o modelo do sistema. Foi feita uma realimentação com ganho unitário negativo para o fechamento da malha de controle.In industrial control processes, the phenomenon of heat transport is present and knowing how to identify it to obtain a mathematical model is important for the development of a dynamic control project. Thus, this work addresses the context of the creation, development, identification, modeling and control of an experimental unit for the control of thermal systems with delay in transportation. A control plant was built with a metal tube with two meters long where air heating by an electric resistance passes inside. The electronics involved in the construction of the apparatus involves the use of TRIAC, for the control of electrical resistance, an H-bridge, for the amplification of the PWM signal for a DC motor and the Atmega 328 microcontroller of the Arduino Uno to interface the plant and a computer. On the computer, the drive signals were generated by the MATLAB software in conjunction with the sensor readings. In the same software, the graphical analysis of the results obtained, the identification of the mathematical model in the frequency domain and the creation of the PID controller were made. For this, we use a toolbox that MATLAB makes available specifically for dynamic control projects. A PID-type controller has been designed in series with the system model. A negative feedback gain was obtained for the control loop closure