Rank-Based Analysis of Linear Models Using R

It is well-known that Wilcoxon procedures out perform least squares procedures when the data deviate from normality and/or contain outliers. These procedures can be generalized by introducing weights; yielding so-called weighted Wilcoxon (WW) techniques. In this paper we demonstrate how WW-estimates can be calculated using an L1 regression routine. More importantly, we present a collection of functions that can be used to implement a robust analysis of a linear model based on WW-estimates. For instance, estimation, tests of linear hypotheses, residual analyses, and diagnostics to detect differences in fits for various weighting schemes are discussed. We analyze a regression model, designed experiment, and autoregressive time series model for the sake of illustration. We have chosen to implement the suite of functions using the R statistical software package. Because R is freely available and runs on multiple platforms, WW-estimation and associated inference is now universally accessible.

Rank-Based Analysis of Linear Models Using R

It is well-known that Wilcoxon procedures out perform least squares procedures when the data deviate from normality and/or contain outliers. These procedures can be generalized by introducing weights; yielding so-called weighted Wilcoxon (WW) techniques. In this paper we demonstrate how WW-estimates can be calculated using an L1 regression routine. More importantly, we present a collection of functions that can be used to implement a robust analysis of a linear model based on WW-estimates. For instance, estimation, tests of linear hypotheses, residual analyses, and diagnostics to detect differences in fits for various weighting schemes are discussed. We analyze a regression model, designed experiment, and autoregressive time series model for the sake of illustration. We have chosen to implement the suite of functions using the R statistical software package. Because R is freely available and runs on multiple platforms, WW-estimation and associated inference is now universally accessible

Early and Late Results Following Choledochoduodenostomy and Choledochojejunostomy

Objective —To evaluate the results and complications of choledochoduodenostomy and choledochojejunostomy for benign and malignant disease and to review them in the light of the survival of the underlying disorders

More than fear induction: Toward an understanding of people's motivation to be well-prepared for emergencies in flood prone areas

This article examines the extent and manner to which evaluations of flood-related precautions are affected by an individual's motivation and perception of context. It argues that the relationship between risk perception and flood risk preparedness can be fruitfully specified in terms of vulnerability and efficacy if these concepts are put into the perspective of prevention-focused motivation. This relationship was empirically examined in a risk communication experiment in a delta area of the Netherlands (n = 1,887). Prevention-focused motivation was induced by contextualized risk information. The results showed that prevention-focused individuals were more sensitive to the relevance of potential precautions for satisfying their needs in the context they found themselves in. The needs included, but were not limited to, fear reduction. Due to the heterogeneity of the residents, the evaluations reflected individual differences in the intensity and the selectivity of precautionary processes. Four types of persons could be distinguished according to their evaluation of precautionary measures: a high-scoring minority, two more selective types, and a low-scoring minority. For policymakers and risk communicators it is vital to consider the nature of prevention motivation and the context in which it is likely to be high

Detecting time-fragmented cache attacks against AES using Performance Monitoring Counters

Cache timing attacks use shared caches in multi-core processors as side channels to extract information from victim processes. These attacks are particularly dangerous in cloud infrastructures, in which the deployed countermeasures cause collateral effects in terms of performance loss and increase in energy consumption. We propose to monitor the victim process using an independent monitoring (detector) process, that continuously measures selected Performance Monitoring Counters (PMC) to detect the presence of an attack. Ad-hoc countermeasures can be applied only when such a risky situation arises. In our case, the victim process is the AES encryption algorithm and the attack is performed by means of random encryption requests. We demonstrate that PMCs are a feasible tool to detect the attack and that sampling PMCs at high frequencies is worse than sampling at lower frequencies in terms of detection capabilities, particularly when the attack is fragmented in time to try to be hidden from detection

Trade in the Roman Empire: A Study of the Institutional Framework

The leading question behind this dissertation is: how did trade operate in the Roman Empire under conditions of imperfect government enforcement in private contracting, and of imperfect information? The Roman State, unlike modern states, did not employ the powers at its disposal to enforce private contracts made under the rules of its legal system. Given the lack of government support, information on merchants' reliability and trustworthiness was extremely important in conducting long-distance trade. However, under pre-industrial conditions information could only travel slowly, making it difficult for merchants to assess risk. This dissertation offers a micro-economic model of how these problems were solved in the Roman Empire. It argues that information circulated within networks defined by geographical origin, with the loss of one's reputation or trading position within those networks forming the instrument of enforcement. The discussion consists of three main parts: intra-community trade in the Italian harbor-city of Puteoli; inter-community trade between the provinces and Puteoli, Ostia, and Rome; and finally inter-community trade between Italian merchants and the provinces

Nonbacterial Thrombotic Mitral Valve Endocarditis Presenting as Embolic Stroke in a Young Patient with Lupus and Anti-phospholipid Syndrome

A 37-year-old man on systemic immunosuppression for clinically and biochemically quiescent lupus nephritis, presented with left hemiparesis. Brain MRI was concerning for right sided embolic stroke. Workup was negative for atrial fibrillation, deep venous thrombosis, and heart failure. Transesophageal echocardiogram was remarkable for fixed mitral valve leaflet echodensities. In the absence of bacteremia and systemic signs of infection, and with a history of lupus, small vegetations on atrial and ventricular sides of mitral valve leaflets are suggestive of nonbacterial thrombotic endocarditis. Nonbacterial thrombotic vegetations are composed of fibrin deposits on otherwise-healthy valves. Mainstay of treatment is therapeutic anticoagulation with clinical and echocardiographic surveillance for moderate-severe mitral regurgitation