Testing for differences in distribution tails to test for differences in 'maximum' lifespan

<p>Abstract</p> <p>Background</p> <p>Investigators are actively testing interventions intended to increase lifespan and wish to test whether the interventions increase maximum lifespan. Based on the fact that one cannot be assured of observing population maximum lifespans in finite samples, in previous work, we constructed and validated several tests of difference in the upper parts of lifespan distributions between a treatment group and a control group by testing whether the probabilities that observations are above some threshold defining 'old' or being in the tail of the survival distribution are equal in the two groups. However, a limitation of these tests is that they do not consider <it>how much </it>above the threshold any particular observation is.</p> <p>Methods</p> <p>In this article we propose new methods which improve upon our previous tests by considering not only whether an observation is above some threshold, but also the magnitudes by which observations exceed the threshold.</p> <p>Results</p> <p>Simulations show that the new methods control type I error rates quite well and that the power of the new methods is usually higher than that of the tests we previously proposed. In illustrative analyses of two real datasets involving rodents, when setting the threshold equal to 110 (100) weeks for the first (second) datasets, the new methods detected differences in 'maximum lifespan' between groups at nominal alpha levels of 0.01 (0.05) for the first (second) datasets and provided more significant results than competitor tests.</p> <p>Conclusion</p> <p>The new methods not only have good performance in controlling the type I error rates but also improve the power compared with the tests we previously proposed.</p

Fibrillation in patients subjected to coronary artery bypass grafting

AbstractObjectiveAtrial fibrillation is the most frequently encountered postoperative arrhythmic complication after coronary artery bypass grafting. Ischemic preconditioning has proved a potent endogenous factor in suppressing ischemia-reperfusion–induced arrhythmias. The protective effect of ischemic preconditioning on atrial fibrillation after coronary artery bypass grafting has not been studied. The purpose of the present study was to investigate whether ischemic preconditioning had an effect on postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting.MethodsEighty-five patients undergoing coronary artery bypass grafting were randomized into ischemic preconditioning and control groups. Holter data from 24-hour electrocardiography were collected 1 day before the operation to the second postoperative day. Atrial fibrillation was registered as positive if any atrial fibrillation event occurred.ResultsThe overall incidence of postoperative atrial fibrillation and sustained atrial fibrillation was 34.1% and 27.1%, respectively. The occurrence of atrial fibrillation was significantly lower in the ischemic preconditioning group (21.4% in patients undergoing ischemic preconditioning and 46.5% in control subjects, P = .015). Preoperative recent unstable angina did not influence the incidence of atrial fibrillation. Patients with atrial fibrillation had longer intensive care unit stays and compromised postoperative hemodynamic outcomes. Binary logistic regression analysis showed that ischemic preconditioning, preoperative mean heart rate, and postoperative pulmonary capillary wedge pressure were the independent predictors of atrial fibrillation.ConclusionsPostcoronary artery bypass grafting atrial fibrillation is associated with more complicated postoperative outcome. Higher preoperative heart rate and postoperative pulmonary capillary wedge pressure were the independent predictors of atrial fibrillation. Recent unstable angina is not related to the occurrence of postcoronary artery bypass grafting atrial fibrillation. Ischemic preconditioning significantly suppresses postcoronary artery bypass grafting atrial fibrillation, suggesting that ischemic preconditioning can be used as an effective prophylactic method for postoperative atrial fibrillation

Progressive Research in the Molecular Mechanisms of Chronic Fluorosis

Long-term excessive intake of fluoride (F) leads to chronic fluorosis, resulting in dental fluorosis and skeletal fluorosis. Chronic exposure to high doses of fluoride can also cause damage to soft tissues, especially when it passes through the blood-brain, blood-testis, and blood-placenta barrier, causing damage to the corresponding tissues. Fluorosis has become a public health problem in some countries or regions around the world. Understanding the pathogenesis of fluorosis is very important. Although the exact mechanism of fluorosis has not been fully elucidated, various mechanisms of fluoride-induced toxicity have been proposed. In this chapter, we will introduce the research progress of the mechanism of fluorosis, focusing on dental fluorosis, skeletal fluorosis, nervous and reproductive system toxicity, and influential factors related to fluoride toxicity (i.e., genetic background, co-exposure with other element). In addition, the application of proteomics and metabolomics in the study of the pathogenesis of fluorosis is also introduced. Currently, there is still no specific treatment for fluorosis. However, since fluorosis is caused by excessive intake of fluoride, avoiding excessive fluoride intake is the critical measure to prevent the disease. In endemic regions, health education and supplement diet with vitamins C, D and E, and calcium and antioxidant compounds are important

Precision Medicine: Role of Biomarkers in Early Prediction and Diagnosis of Alzheimer’s Disease

Alzheimer’s disease (AD), the most common form of dementia in the aged people, is a chronic and irreversible neurodegenerative disorder. Early prediction, intervention, and objective diagnosis are very critical in AD. In this chapter, we will introduce the current progress in the prediction and diagnosis of AD, including recent development in diagnostic criteria, genetic testing, neuroimaging techniques, and neurochemical assays. Focus will be on some new applied methods with more specific examples, that is, cerebrospinal fluid (CSF) and blood proteins and peptides, which might serve as biomarkers for the diagnosis of AD. We will also discuss biomarker-based diagnostic strategies and their practical application

Improving the physician-patient cardiovascular risk dialogue to improve statin adherence

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to evaluate the effectiveness of a patient education program developed to facilitate statin adherence.</p> <p>Methods</p> <p>A controlled trial was designed to test the effectiveness of a multifaceted patient education program to facilitate statin adherence. The program included a brief, in-office physician counseling kit followed by patient mailings. The primary end point was adherence to filling statin prescriptions during a 120-day period. Patients new to statins enrolled and completed a survey. Data from a national pharmacy claims database were used to track adherence.</p> <p>Results</p> <p>Patients new to statin therapy exposed to a patient counseling and education program achieved a 12.4 higher average number of statin prescription fill days and were 10% more likely to fill prescriptions for at least 120 days (<it>p </it>= .01).</p> <p>Conclusion</p> <p>Brief in-office counseling on cardiovascular risk followed by patient education mailings can be effective in increasing adherence. Physicians found a one-minute counseling tool and pocket guidelines useful in counseling patients.</p

Performance modelling and evaluation of protocols based on formal specifications

Protocol performance issues are important in communication protocol design and network management, especially for those protocols which run in high-speed networking environments. An accurate performance modelling and evaluation approach is necessary to obtain reliable performance estimations and to improve system performance. Using queueing models (QMs) or finite state machines (FSMs) alone is difficult to achieve this goal because many aspects that affect performance are not taken into consideration by the model. This thesis proposes a new performance model called performance extended finite state machine (PEFSM). PEFSM makes use of the strengths of both QM and FSM. A PEFSM is based on an FSM which is extended to include time and probability. Furthermore, the transition time is refined and divided into two parts: the transition wait time and the transition service time. This allows the PEFSMs to integrate message arrival and queueing models which provide useful and essential information necessary for studying real world protocols. PEFSMs are classified into three categories based on the message arrival characteristics: synchronous PEFSMs (SyPEFSMs), asynchronous PEFSMs (AsPEF SMs) and hybrid PEFSMs (HyPEFSMs). While the hybrid model is the most useful and realistic model for communication protocols, the other two models are also presented for completeness, and as a way to explain the hybrid model. A method for computing performance metrics based on SyPEFSMs is given in the thesis. Two types of AsPEFSMs — AsPEFSM-α and AsPEFSM-β — and their performance evaluation methods are also presented. Then a class of HyPEFSM which is a hybrid model of SyPEFSM and AsPEFSM-α is introduced. The proposed performance evaluation method for this class of HyPEFSM is basically the combination of those for SyPEFSMs and AsPEFSM-αs. Our performance mod effing and evaluation approach has been applied to various examples, including the alternating bit protocol and multi-stage interconnection network (MIN). The performance evaluation method for PEFSMs makes use of stochastic pro cess and queueing theory. A new queueing property for an M/G/1. with multiple job classes and an analogous property for AsPEFSM-os have been discovered and proved. As a first step in improving system performance, the thesis defines software performance bottlenecks based on PEFSMs. Two bottleneck identification methods are proposed and tested. This thesis also proposes a testing method called t-test which in most cases is able to obtain the service times of invisible transitions when the protocol implementation under test is given as a black box. Transition service times are important parameters in FSM-based performance models. Studies in the past have usually assumed the transition times to be known a priori without discussing how they may be obtained. Simulations and measurement experiments have been conducted to validate the methodologies proposed in this thesis. The results are quite promising.Science, Faculty ofComputer Science, Department ofGraduat