Dominating Clasp of the Financial Sector Revealed by Partial Correlation Analysis of the Stock Market

What are the dominant stocks which drive the correlations present among stocks traded in a stock market? Can a correlation analysis provide an answer to this question? In the past, correlation based networks have been proposed as a tool to uncover the underlying backbone of the market. Correlation based networks represent the stocks and their relationships, which are then investigated using different network theory methodologies. Here we introduce a new concept to tackle the above question—the partial correlation network. Partial correlation is a measure of how the correlation between two variables, e.g., stock returns, is affected by a third variable. By using it we define a proxy of stock influence, which is then used to construct partial correlation networks. The empirical part of this study is performed on a specific financial system, namely the set of 300 highly capitalized stocks traded at the New York Stock Exchange, in the time period 2001–2003. By constructing the partial correlation network, unlike the case of standard correlation based networks, we find that stocks belonging to the financial sector and, in particular, to the investment services sub-sector, are the most influential stocks affecting the correlation profile of the system. Using a moving window analysis, we find that the strong influence of the financial stocks is conserved across time for the investigated trading period. Our findings shed a new light on the underlying mechanisms and driving forces controlling the correlation profile observed in a financial market

Separating Probability and Reversal Learning in a Novel Probabilistic Reversal Learning Task for Mice

The exploration/exploitation tradeoff – pursuing a known reward vs. sampling from lesser known options in the hope of finding a better payoff – is a fundamental aspect of learning and decision making. In humans, this has been studied using multi-armed bandit tasks. The same processes have also been studied using simplified probabilistic reversal learning (PRL) tasks with binary choices. Our investigations suggest that protocols previously used to explore PRL in mice may prove beyond their cognitive capacities, with animals performing at a no-better-than-chance level. We sought a novel probabilistic learning task to improve behavioral responding in mice, whilst allowing the investigation of the exploration/exploitation tradeoff in decision making. To achieve this, we developed a two-lever operant chamber task with levers corresponding to different probabilities (high/low) of receiving a saccharin reward, reversing the reward contingencies associated with levers once animals reached a threshold of 80% responding at the high rewarding lever. We found that, unlike in existing PRL tasks, mice are able to learn and behave near optimally with 80% high/20% low reward probabilities. Altering the reward contingencies towards equality showed that some mice displayed preference for the high rewarding lever with probabilities as close as 60% high/40% low. Additionally, we show that animal choice behavior can be effectively modelled using reinforcement learning (RL) models incorporating learning rates for positive and negative prediction error, a perseveration parameter, and a noise parameter. This new decision task, coupled with RL analyses, advances access to investigate the neuroscience of the exploration/exploitation tradeoff in decision making

Tratamento da síndrome da apnéia e hipopnéia obstrutiva do sono com aparelhos intrabucais Treatment of obstructive sleep apnea and hipoapnea syndrome with oral appliances

A síndrome da apnéia e hipopnéia obstrutiva do sono (SAHOS) é um distúrbio que atinge cerca de 4% da população adulta e que, além dos problemas sociais associados ao ronco e à sonolência diurna excessiva, é preocupante pelos quadros de hipertensão pulmonar e insuficiência cardíaca que pode desencadear. REVISÃO E DISCUSÃO: Através de uma revisão de literatura discutiu-se o uso de aparelhos intrabucais para o tratamento dessa patologia, destacando-se a eficácia e as limitações dessa terapia, os principais sintomas clínicos, os principais efeitos colaterais oclusais, o grau de colaboração e o índice de satisfação dos pacientes. CONCLUSÕES: Concluiu-se que a terapia com aparelhos intrabucais deve ser a de primeira escolha para o tratamento de SAHOS de média a moderada, sendo o desconforto dentário, articular e muscular, a hipersalivação e a xerostomia os sintomas clínicos mais freqüentes, com efeitos colaterais oclusais leves que normalmente não geram incômodos aos pacientes, com bom grau de colaboração e alto índice de satisfação.<br>Obstructive sleep apnea and hipoapnea syndrome (OSAHS) is a disorder that affects about 4% of the adult population, and besides the social problems associated to snoring and extreme day time sleepiness, it is preoccupying since it may cause pulmonary hypertension and cardiac failure. REVIEW AND DISCUSSION: Through a literature review, we discuss the use of oral appliances to treat this condition, in regards of therapy effectiveness and limitations, main clinical symptoms, major occlusal side effects, rate of improvement and patient satisfaction. CONCLUSIONS: We concluded that the use of oral appliances should be a first choice treatment for mild to moderate OSAHS, being dental, joint and muscular discomforts, hypersalivation and xerostomia, the most frequent clinical symptoms, with light occlusal side effects that normally do not bother the patients, with a good degree of improvement and high satisfaction index

Prehospital fibrinolysis with dual antiplatelet therapy in ST-elevation acute myocardial infarction: a substudy of the randomized double blind CLARITY-TIMI 28 trial.

Contains fulltext : 52227.pdf (publisher's version ) (Closed access)BACKGROUND: Fibrinolytic therapy for acute ST-elevation myocardial infarction (STEMI) is frequently limited by delays in administration and by incomplete reperfusion or reocclusion of the infarct-related artery. Intensified prehospital management of STEMI may shorten time to treatment and improve outcomes. METHODS: We carried out a prospective substudy in 11 ambulance systems in 216 of the 3,491 patients with STEMI who were enrolled in the CLARITY-TIMI 28 trial. They were randomized in the ambulance to clopidogrel (n = 109) or placebo (n = 107) along with fibrinolysis, aspirin, and heparin. The primary endpoint was the composite of an occluded infarct-related artery (TIMI flow grade 0 or 1), or death or recurrent myocardial infarction before angiography. RESULTS: All patients received a fibrin-specific lytic and the baseline characteristics in both groups were comparable. The incidence of the primary endpoint was 16.5% in the clopidogrel-treated and 27.1% in the placebo patients (adj OR 0.62, 95% CI 0.31-1.21, p = 0.16), an effect that was consistent with the effects seen in the in-hospital patients in the main CLARITY-TIMI 28 trial. Prehospital clopidogrel therapy reduced the incidence of an occluded infarct-related artery on the predischarge angiogram (11.8% vs. 22.3%, adj OR 0.52, 95% CI 0.24-1.13, p = 0.10). The 30-day incidence of cardiovascular death, recurrent MI or recurrent myocardial ischemia requiring urgent revascularization was 12.8% vs. 14.0% (adj OR 1.07, 95% CI 0.48-2.39, p = 0.87). Early TIMI major bleeding occurred in no clopidogrel patients compared with two placebo patients (1.9%). CONCLUSIONS: Addition of clopidogrel to medical reperfusion of STEMI with fibrinolysis, heparin, and aspirin before reaching the hospital is feasible in medically equipped ambulances without an apparent increase in bleeding. Furthermore, prehospital clopidogrel tended to show better early coronary patency compared to placebo, a result consistent with that observed in patients randomized in-hospital in the CLARITY-TIMI 28 trial