Hadron structure from lattice quantum chromodynamics

This is a review of hadron structure physics from lattice QCD. Throughout this report, we place emphasis on the contribution of lattice results to our understanding of a number of fundamental physics questions related to, e.g., the origin and distribution of the charge, magnetization, momentum and spin of hadrons. Following an introduction to some of the most important hadron structure observables, we summarize the methods and techniques employed for their calculation in lattice QCD. We briefly discuss the status of relevant chiral perturbation theory calculations needed for controlled extrapolations of the lattice results to the physical point. In the main part of this report, we give an overview of lattice calculations on hadron form factors, moments of (generalized) parton distributions, moments of hadron distribution amplitudes, and other important hadron structure observables. Whenever applicable, we compare with results from experiment and phenomenology, taking into account systematic uncertainties in the lattice computations. Finally, we discuss promising results based on new approaches, ideas and techniques, and close with remarks on future perspectives of the field.Comment: 189 pages, to be published in Physics Report

Neurovascular unit dysfunction with blood-brain barrier hyperpermeability contributes to major depressive disorder: a review of clinical and experimental evidence

About one-third of people with major depressive disorder (MDD) fail at least two antidepressant drug trials at 1 year. Together with clinical and experimental evidence indicating that the pathophysiology of MDD is multifactorial, this observation underscores the importance of elucidating mechanisms beyond monoaminergic dysregulation that can contribute to the genesis and persistence of MDD. Oxidative stress and neuroinflammation are mechanistically linked to the presence of neurovascular dysfunction with blood-brain barrier (BBB) hyperpermeability in selected neurological disorders, such as stroke, epilepsy, multiple sclerosis, traumatic brain injury, and Alzheimer’s disease. In contrast to other major psychiatric disorders, MDD is frequently comorbid with such neurological disorders and constitutes an independent risk factor for morbidity and mortality in disorders characterized by vascular endothelial dysfunction (cardiovascular disease and diabetes mellitus). Oxidative stress and neuroinflammation are implicated in the neurobiology of MDD. More recent evidence links neurovascular dysfunction with BBB hyperpermeability to MDD without neurological comorbidity. We review this emerging literature and present a theoretical integration between these abnormalities to those involving oxidative stress and neuroinflammation in MDD. We discuss our hypothesis that alterations in endothelial nitric oxide levels and endothelial nitric oxide synthase uncoupling are central mechanistic links in this regard. Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to the pathophysiology of MDD may help to identify novel therapeutic and preventative approaches

O limiar de esforço percebido (LEP) corresponde à potência crítica e a um indicador de máximo estado estável de consumo de oxigěnio

The perceived exertion has been a target of several investigations, many times with association with objective physiological indicators in exercise. Recently, the identification of the perceived exertion threshold (PET) was proposed in the water running, which presented no difference in relation to the critical velocity. Theoretically, both parameters would be indicators of the maximum steady state of variables such as V̇O2 and blood lactate. The objective of this work was to verify the coincidence between PET, critical power (PCrit) and an indicator of maximum V̇O2 steady state (PCrit') in cycle ergometer. Eight male participants were submitted to progressive effort test in order to determine V̇O2peak (46.7 ± 8.5 ml/kg/min) and to four rectangular tests until exhaustion for the estimation of the critical power model parameters, PET and PCrit'. The hyperbolic relation between mechanical power and time spent for the V̇O2peak to be reached in each test was used for the PCrit' estimation, considered as the asymptote in the power axis, and the portion of the anaerobic work capacity (CTAnaer) depleted up to the establishment of the V̇O2peak (CTAnaer'). In order to identify PET, the straight lines angular coefficients of the perceived exertion in time (ordinate) and the powers used (abscissa) were adjusted to a linear function that provided a point in the power axis in which the perceived exertion would be kept indefinitely stable. The parameters PCrit and CTAnaer were estimated by means of the power-time non-linear equation. In order to compare the estimations of PET, PCrit and PCrit', the analysis of variance ANOVA for repeated measurements was employed, and the associations were established through the Pearson correlation. CTAnaer and CTAnaer' were compared through the t test. PET (180 W ± 61 W), PCrit (174 W ± 43 W) and PCrit' (176 W ± 48 W) were not significantly different and the correlations were of 0.92-0.98. CTAnaer' (14,080 ± 5,219 J) was lower than CTAnaer (22,093 ± 9,042 J). One concludes that the PET predicts the intensity of PCrit and PCrit' with accuracy

Objetividade da medida do limiar ventilatório

Vários critérios têm sido utilizados na detecção do limiar ventilatório (LV). Três dos mais empregados são: (1) aumento do equivalente ventilatório de O2 (VE/VO2), (2) quebra da linearidade do aumento da ventilação-minuto (VE) e, (3) quebra da linearidade da relação entre os aumentos do VCO2 e VO2 (V-slope). O objetivo deste estudo foi verificar a objetividade da medida do LV, assim como verificar a consistência intra-avaliador do LV a partir dos diferentes critérios. Foram avaliados 16 homens jovens fisicamente ativos. Estes foram submetidos a teste de esforço progressivo até exaustão voluntária em cicloergômetro. O LV foi identificado independentemente por três avaliadores mediante os critérios (1), (2) e (3). A concordância inter-avaliadores no que se refere à aplicação dos diferentes critérios foi relativamente baixa (entre 18,0 a 62,5%) em praticamente todos os casos, sendo que a concordância em torno do critério (1) foi superior em comparação aos outros. Houve alta consistência intra-avaliador na determinação do LV, evidenciado pela ausência de diferenças entre critérios. Ao considerar a mediana dos resultados apresentados pelos três avaliadores, foram obtidos, em média, 132,5 ± 30 W para o critério (1), 135,0 ± 33,1 W para o critério (2), e 135,0 ± 36,1 W para o critério (3), sem diferenças significantes entre os critérios (p > 0,05). A correlação intra-classe entre todos os pares de critérios foi igual a 0,94. Em conclusão, o critério (1) parece ser o mais objetivo, e a adoção da mediana entre as estimativas dos avaliadores parece eliminar o problema do viés intra-avaliador

Oxygen uptake kinetics during supra-maximal exercise: Mathematical modelling

http://dx.doi.org/10.5007/1980-0037.2008v10n1p43 Precise estimation of oxygen uptake kinetics parameters is essential to understand its control and/or limit uptake mechanisms. The purpose of the present study was to characterize the oxygen uptake kinetics responses during supramaximal cycle ergometer exercise using two modeling techniques. Eleven male subjects (age = 25.4 ± 4.9 years, height = 177.0 ± 4.0 cm, mass = 77.1 ± 11.3 kg, VO2max = 40.3 ± 6.3 mL.kg-1.min-1) performed a series of square- have exercise transitions to exhaustion at intensities equivalent to 100, 113, 133 and 153% of VO2max. The time constant of the primary component was estimated with an exponential and semi-logarithmic model, comparisons were made using repeated measures ANOVA and the Tukey post hoc tests, with statistical signifi cance accepted when p<0.05. In order to calculate the time constant by the semi-logarithmic model it is necessary to estimate oxygen demand, which was performed by means of a regression procedure. The exponential model resulted in lower values for the time constant (35.1 ± 8.0s; 32.5 ± 7.4s; 29.6 ± 11.3s; 25.3 ± 7.5s) compared to the semi-logarithmic model (107.9 ± 27.1s; 104.5 ± 24.3s; 114.1 ± 30.4s; 125.3 ± 24.9s) at all intensities. The observation of this confl icting oxygen uptake kinetics behavior depending upon which mathematical model is applied suggests that physiological inferences on the basis of parameters obtained during supra-maximal exercise should be made with caution