8,781 research outputs found
Non-implementation of Rational Expectations as a Perfect Bayesian Equilibrium
We show that a rational expectations equilibrium need not be incentive compatible, need not be implementable as a perfect Bayesian equilibrium and may not be fully Pareto optimal, unless the utility functions are state independent. A comparison of rational expectations equilibria with core concepts is also provided.Differential information economy, Rational expectations equilibrium, Implementation, Game trees, Private core
Design: the quintessential business transaction
The fundamental structures that underpin business activities must evolve and change in order to equip companies to thrive in a market whose characteristics are increasing competition and instability. The incremental advances in applied computing technology and business methodologies which focus on improving one aspect of company operations ignore the need for an underlying structure and model through which to engage any and all functions in a consistent and integrated fashion. Indeed, many exacerbate the problem through closed architectures, isolationist views of entity data storage and rigid methodologies imposed on the company that employs them.
The Product Model proposed fulfils that role. It is a model of the processes and entities that a company uses to conduct its business, at all levels and across all departments. Two other concepts are exposed: product model data and the design history record. Product model data are the values of instances of product model entities and relations, created to represent a particular design, artefact or object. The design history record captures the data and functions used in a transaction and the order and context in which they are used.
To exercise these concepts, a software suite was written, the Glasgow Utility for Integrated Design, Guide. It supports the definition of a proud model and its subsequent use in the creation of product model data. Each interaction with the system is recorded, thus capturing the design history record, which can subsequently be processes to various advantageous ends. The major such uses are for re-use of part information in other designs and the extraction of design best practice with which to augment the company's design methodology. It is a comprehensive record, since all business processes are supported by, and can be transacted through Guide.
Guide has been used to validate the adequacy of the product model and has established many benefits through its use. Applications in many spheres are possible; engineering has been the primary focus for exemplars and case studies. The development was carried out under the scrutiny of constant validation and testing in live situations with several industrial partners. Guide is built on industry standard tools and uses relational database technology to store frame-based representations of entities, methods and relationships.
The design of project plans is carried out on the same platform used to support the project itself; the design data are not dissociated from the project controlling mechanism. Resources, including staff, are engaged according to requirements and audit mechanisms allow for constant re-evaluation of the project development. Control and communication mechanisms support applications in an extended enterprise environment and the distribution of resources that this entails
Effects of magnesium treatment in a model of internal capsule lesion in spontaneously hypertensive rats
<p><b>Background and Purpose:</b> The study aim was to assess the effects of magnesium sulfate (MgSO4) administration on white matter damage in vivo in spontaneously hypertensive rats.</p>
<p><b>Methods:</b> The left internal capsule was lesioned by a local injection of endothelin-1 (ET-1; 200 pmol) in adult spontaneously hypertensive rats. MgSO4 was administered (300 mg/kg SC) 30 minutes before injection of ET-1, plus 200 mg/kg every hour thereafter for 4 hours. Infarct size was measured by T2-weighted magnetic resonance imaging (day 2) and histology (day 11), and functional recovery was assessed on days 3 and 10 by the cylinder and walking-ladder tests.</p>
<p><b>Results:</b> ET-1 application induced a small, localized lesion within the internal capsule. Despite reducing blood pressure, MgSO4 did not significantly influence infarct volume (by magnetic resonance imaging: median, 2.1 mm3; interquartile range, 1.3 to 3.8, vs 1.6 mm3 and 1.2 to 2.1, for the vehicle-treated group; by histology: 0.3 mm3 and 0.2 to 0.9 vs 0.3 mm3 and 0.2 to 0.5, respectively). Significant forelimb and hindlimb motor deficits were evident in the vehicle-treated group as late as day 10. These impairments were significantly ameliorated by MgSO4 in both cylinder (left forelimb use, P<0.01 and both-forelimb use, P<0.03 vs vehicle) and walking-ladder (right hindlimb score, P<0.02 vs vehicle) tests.</p>
<p><b>Conclusions:</b> ET-1–induced internal capsule ischemia in spontaneously hypertensive rats represents a good model of lacunar infarct with small lesion size, minimal adverse effects, and a measurable motor deficit. Despite inducing mild hypotension, MgSO4 did not significantly influence infarct size but reduced motor deficits, supporting its potential utility for the treatment of lacunar infarct.</p>
Early recurrent ischemic stroke complicating intravenous thrombolysis for stroke: incidence and association with atrial fibrillation
<p><b>Background and Purpose:</b> Mechanisms of early neurologic deterioration after treatment with intravenous, recombinant, tissue-type plasminogen activator (IV rt-PA) include symptomatic intracerebral hemorrhage (SICH) and early recurrent ischemic stroke. We observed a number of cases of acute deterioration due to recurrent ischemic events.</p>
<p><b>Methods:</b> We undertook a single-center, retrospective analysis of consecutive acute stroke patients treated with IV rt-PA between January 2006 and December 2008 to define the incidence of early neurologic deterioration (>= 4-point drop on the National Institutes of Health Stroke Scale within 72 hours) and its mechanism. Deterioration was attributed to SICH when associated with a PH1 or PH2 hemorrhage on postdeterioration computed tomography scans, to recurrent ischemic stroke when there was clinical and radiologic evidence of a new territorial infarction or new vessel occlusion, and otherwise to evolution of the incident stroke.</p>
<p><b>Results:</b> Of 228 consecutive IV rt-PA-treated patients, 34 (15%) developed early neurologic deterioration, 18 (8%) secondary to incident strokes 10 (4.4%) due to SICH, and 6 (2.6%) due to early recurrent ischemic events, which were significantly associated with atrial fibrillation (present in 5 of 6 patients; 4 paroxysmal, 1 permanent). In 4 patients, sudden clinical deterioration developed during or shortly after IV rt-PA infusion, and in 2, deterioration developed 3 days later. All died 2 days to 2 weeks later. The single case without atrial fibrillation had a recurrent, contralateral, middle cerebral artery stroke during IV rt-PA infusion and multiple high-signal emboli detected by transcranial Doppler. Early recurrent ischemic stroke accounted for 5 of 12 (42%) cases of early neurologic deterioration in patients with atrial fibrillation.</p>
<p><b>Conclusion:</b> In this single-center series, the incidence of early recurrent ischemic stroke after IV rt-PA was 2.6% and was associated with previous atrial fibrillation.</p>
- …