Performance analysis using timed Petri Nets

Petri Nets have been successfully used to model and evaluate the performance of distributed systems. Several researchers have extended the basic Petri Net model to include time, and have demonstrated that restricted classes of Petri Nets can be analyzed efficiently. Unfortunately, the restrictions prohibit the techniques from being applied to many interesting systems, e.g. communication protocols. This paper proposes a version of timed Petri Nets which accurately models communication protocols, and which can be analyzed using Timed Reachability Graphs. Procedures for constructing and analyzing these graphs are presented. The analysis is shown to be applicable to a larger class of Timed Petri Nets than previously thought. The model and the analysis technique are demonstrated using a simple communication protocol

Media and the Shooter Bias: Investigating the Relationship Between Implicit Racial Biases and News Coverage

Abstract Past research has suggested that the media is likely to depict Black individuals in a more negative and/or threatening manner than White individuals (Dixon & Linz, 2000; Sommers et al., 2006). Additionally, past research investigating the effect of race on the decision to shoot or not shoot in a simple shooter videogame suggests that people are both faster and more accurate when deciding to shoot armed Black targets and when deciding to not shoot unarmed White targets (Correll et al., 2002). This phenomenon is known as shooter bias. This study investigated the effect of media exposure, specifically exposure to an online news article, on an individual’s shooter bias. Participants read an article depicting either a Black or White individual committing a crime directly before completing a shooter game. Contrary to past research, results revealed no main effects of race or item (gun vs. no gun) on reaction time. However, a race x item interaction was observed for reaction time, as was an item x condition interaction for inaccuracy. Participants were faster to react to targets if the target was Black and held a random object. They were also more inaccurate in their decisions while playing the game if they had read the media article with the White criminal and the target was holding a random object. Results revealed a main effect of item for both shooting and not shooting, such that participants were more likely to shoot armed targets and more likely to not shoot unarmed targets. A main effect of condition on participant’s likelihood to not shoot targets was also observed, such that participants who read the article with the White criminal were less likely to shoot targets while playing the shooter game. Neither explicit attitudes towards racial minorities nor explicit ratings of fear experienced while reading the media article correlated with reaction times

Response and Recovery of the Comanche Carbonate Platform Surrounding Multiple Cretaceous Oceanic Anoxic Events, Northern Gulf of Mexico

The ubiquity of carbonate platforms throughout the Cretaceous Period is recognized as a product of high eustatic sea-level and a distinct climatic optimum induced by rapid sea-floor spreading and elevated levels of atmospheric carbon-dioxide. Notably, a series of global oceanic anoxic events (OAEs) punctuate this time-interval and mark periods of significantly reduced free oxygen in the world's oceans. The best records of these events are often from one-dimensional shelf or basin sections where only abrupt shifts between oxygenated carbonates and anoxic shales are recorded. The Comanche Platform of central Texas provides a unique opportunity to study these events within a well-constrained stratigraphic framework in which their up-dip and down-dip sedimentologic effects can be observed and the recovery of the platform to equilibrium states can be timed and understood. Stable isotope data from whole cores in middle Hauterivian through lower Campanian mixed carbonate-siliciclastic strata are used to construct a 52-myr carbon isotope reference profile for the northern Gulf of Mexico. Correlation of this composite curve to numerous global reference profiles permits identification of several anoxic events and allows their impact on platform architecture and fades distribution to be documented. Oceanic anoxic events la, 1b, 1d, and 2 occurred immediately before, after, or during shale deposition in the Pine Island Member, Bexar Member, Del Rio Formation, and Eagle Ford Group, respectively. Oceanic anoxic event 3 corresponds to deposition of the Austin Chalk Group. Platform drowning on three occasions more closely coincided with globally recognized anoxic sub-events such as the Fallot, Albian-Cenomanian, and Mid-Cenomanian events. This illustrates that the specific anoxic event most affecting a given carbonate platform varied globally as a function of regional oceanographic circumstances. Using chemo- and sequence-stratigraphic observations, a four-stage model is proposed to describe the changing fades patterns, fauna, sedimentation accumulation rates, platform architectures, and relative sea-level trends of transgressive-regressive composite sequences that developed in response to global carbon-cycle perturbations. The four phases of platform evolution include the equilibrium, crisis, anoxic, and recovery stages. The equilibrium stage is characterized by progradational shelf geometries and coralrudist phototrophic faunal assemblages. Similar phototrophic fauna typify the crisis stage; however, incipient biocalcification crises of this phase led to retrogradational shelf morphologies, transgressive facies patterns, and increased clay mineral proportions. Anoxic stages of the Comanche Platform were coincident with back-ground deposition of organic-rich shale on drowned shelves and heterotrophic fauna dominated by oysters or coccolithophorids. Eustatic peaks of this stage were of moderate amplitude (similar to 30 m), yet relative sea-level rises were greatly enhanced by reduced sedimentation rates. In the recovery stage, heterotrophic carbonate factories re-established at the shoreline as progradational ramp systems and sediment accumulation rates slowly increased as dysoxia diminished. Full recovery to equilibrium conditions may or may not have followed. Geochemical and stratigraphic trends present in the four stages are consistent with increased volcanism along mid-ocean ridges and in large-igneous provinces as primary drivers of Cretaceous OAEs and the resulting transgressive-regressive composite sequences. (C) 2014 Elsevier Ltd. All rights reserved.BHP-BillitonReservoir Characterization Research Laboratory, the Bureau of Economic GeologyJackson School of Geosciences at the University of Texas at AustinBureau of Economic Geolog

Economic Foundations of Cost Effective Analysis

In order to address several controversies in the application of cost-effectiveness analysis, we investigate the principles underlying the technique and discuss the implications for the evaluation of medical interventions. Using a standard von Neumann-Morgenstern utility framework, we show how a cost-effectiveness criterion can be derived to guide resource allocation decisions. We investigate its relation to age, gender, income level, and risk aversion. Cost-effectiveness analysis can be a useful and powerful tool for resource allocation decisions, but in the presence of heterogeneous preferences and personal characteristics, a cost-effectiveness criterion that is applied at the population level is unlikely to yield pareto-optimal resource allocations.

Affective, Behavioral, and Social-Cognitive Dysregulation as Mechanisms for Sexual Abuse Revictimization

Using a sample of 1,117 female college students, this study examined emotional, behavioral, and social-cognitive mechanisms of sexual abuse revictimization. It was hypothesized that numbing, alexithymia, alcohol problems, mistrust, and adult attachment dimensions would mediate the relationship between childhood sexual abuse (CSA) and adult sexual abuse (ASA). Aside from the close adult attachment dimension, the results indicated that all of the hypothesized mediators were associated with CSA. However, only alcohol problems and mistrust met the necessary conditions of mediation. The results with respect to mistrust are especially unique in that it is one of the first empirical demonstrations of a social-cognitive mechanism for sexual abuse revictimization. Thus, these results enhance our understanding of interpersonal mediators of the relationship between CSA and ASA and provide a new direction for future research

Do medical images aid understanding and recall of medical information? An experimental study comparing the experience of viewing no image, a 2D medical image and a 3D medical image alongside a diagnosis

Objective: This study compared the experience of viewing 3D medical images, 2D medical images and no image presented alongside a diagnosis. Methods: We conducted two laboratory experiments, each with 126 healthy participants. Participants heard three diagnoses; one accompanied by 3D medical images, one accompanied by 2D medical images and one with no image. Participants completed a questionnaire after each diagnosis rating their experience. In Experiment 2, half of the participants were informed that image interpretation can be susceptible to errors. Results: Participants preferred to view 3D images alongside a diagnosis (p < .001) and reported greater understanding (p < .001), perceived accuracy (p < .001) and increased trust (p < .001) when the diagnosis was accompanied by an image compared to no image. There was no significant difference in trust between participants who were informed of errors within image interpretation and those who were not. Conclusion: When presented alongside a diagnosis, medical images may aid patient understanding, recall and trust in medical information. Practical Considerations: Medical images may be a powerful resource for patients that could be utilised by clinicians during consultations

A qualitative study exploring the experience of viewing three‐dimensional medical images during an orthopaedic outpatient consultation from the perspective of patients, health care professionals, and lay representatives

Rationale, aims and objectives Three‐dimensional (3D) medical images are shown to patients during clinical consultations about certain health conditions. However, little is known about patients' experience of viewing them. The aim of this qualitative study was to explore the impact of sharing 3D medical images with patients during a clinical consultation about hip surgery, from the perspective of patients, health care professionals, and lay representatives. Method Interviews were conducted with 14 patients who were shown their own 3D medical images during their clinical consultation and four health care professionals conducting consultations within one orthopaedic outpatient clinic. In addition to interviews, 31 lay representatives participated in six focus groups. The focus groups aimed to gain a broader understanding of the advantages and concerns of showing patients their medical images and to compare 3D and two‐dimensional (2D) medical images. Interviews and focus groups were audio‐recorded, transcribed verbatim, and analysed using thematic analysis. Results Three themes were developed from the data: (a) the truthful image, (b) the empowering image, and (c) the unhelpful image. Focus group participants' preference for 3D or 2D images varied between conditions and groups, suggesting that the experience of viewing images may differ between individuals and conditions. Conclusions When shown to patients during an orthopaedic clinical consultation, 3D medical images may be an empowering resource. However, in this study, patients and focus group participants perceived medical images as factual and believed they could provide evidence of a diagnoses. This perception could result in overreliance in imaging tests or disregard for other forms of information