Update propagation for peer-to-peer-based massively multi-user virtual environments

Over the last decade Massively Multi-user Virtual Environments (MMVEs) have become an integral part of modern culture and business. Applications for these large-scale virtual environments range from gaming to business and scientific research. Some MMVEs reach a user base in the tens of millions and the total number of users is estimated in the billions. Despite this success, launching an MMVEs is still a risky proposition. This is in large part due to the high cost associated with setting up and maintaining the necessary server infrastructure. One way of reducing the costs of operating MMVEs is to switch their system architecture from the current client/server-based model to one based on peer-to-peer (P2P) technologies. This has the potential to significantly reduce the infrastructure costs of MMVEs, as users bring their own resources into the P2P system and servers are no longer required, thus decreasing expenses and market entry barriers. This thesis describes a scalable and low-latency update propagation system for P2P-based MMVEs. Update propagation refers to the exchange of information about changes in the virtual environment between users and is one of the key components of MMVEs. Thus, the described system represents a key step towards operating MMVEs as fully distributed peer-to-peer systems

Las Academias Correspondientes de la Lengua en la Hispanoamérica del siglo xix

La historia de las Academias americanas en el siglo XIX es una historia de fracaso. Sin embargo, al tener en cuenta la difícil situación política de los países americanos después de la independencia y el gran reto que significaba construir y hacer funcionar los nuevos Estados, no sorprende tanto que las Academias Correspondientes del siglo XIX hayan fracasado, sino que –a pesar de todo– se hayan constituido y hayan funcionado durante algún tiempo. Mientras queda sin duda comprobado que en España se tenía un fuerte interés en la fundación de las Academias, pocas veces se plantea la cuestión de por qué los intelectuales en las repúblicas americanas y también sus gobiernos apoyaron y, finalmente, realizaron el proyecto. La pregunta que se plantea en este ensayo es: ¿qué motivos hubo en los países hispanoamericanos para fundar Academias de la Lengua Correspondientes de la RAE, instituciones que obviamente no solamente iban a defender la norma lingüística tradicional del español de España, sino que además pretendían mantener la hegemonía cultural de España sobre la América independiente? ¿Fue posible crear estas instituciones porque iban conformes a los fundamentos de la construcción de las naciones hispanoamericanas

Offene Lizenzen in den Digitalen Geisteswissenschaften

Bericht über die vom Münchner Zentrum für digitale Geisteswissenschaften organisierten Tagung „Offene Lizenzen in den Digitalen Geisteswissenschaften“ am 27. und 28. April 201

Sex-based differences in clinical and angiographic outcomes in patients with ST-elevation myocardial infarction treated with concomitant use of glycoprotein IIb/IIIa inhibitors

Background: The widespread use of primary coronary intervention (PCI) has significantly improved the prognosis of men presenting with acute coronary syndromes, but the cardiovascular event rate among women has either levelled off or increased. The purpose of the present prospective study was to compare the clinical outcome of women and men presenting with ST-elevation myocardial infarction (STEMI) undergoing primary PCI with concomitant usage of GP IIb/IIIa inhibitors. Methods: Between January 2006 and December 2007, 297 consecutive patients presenting with STEMI were prospectively included in this single center investigation. Overall, 82 (27.6%) women and 215 (72.4%) men were treated by PCI with additional bare metal stent implantation and a GP IIb/IIIa inhibitor. Results: Women were significantly older (65 ± 10 vs 60 ± 12 years, p = 0.04), presented with a smaller reference luminal diameter (2.83 ± 0.51 vs 2.94 ± 0.43, p = 0.03) and had a higher prevalence of hypertension (68% vs 53%, p = 0.025) and obesity (30% vs 18%, p = 0.03). The incidence of major adverse cardiac events (MACE, defined as death, re-myocardial infarction, target lesion revascularization and coronary artery bypass graft) during long-term follow-up was similar in women and men (20% vs 26%, p = 0.29). Age, C-reactive protein, platelet count and cardiogenic shock were identified as independent predictors for MACE, whereas gender was not predictive. Conclusions: In this study, female gender did not emerge as an independent predictor for MACE, but women presenting with STEMI had a higher cardiovascular risk profile; this emphasizes the need for a more extensive therapeutic strategy. Combination therapy with primary PCI and GP IIb/IIIa inhibitors might mitigate gender-related differences in clinical outcomes. (Cardiol J 2010; 17, 6: 580–586

CMR findings in patients with hypertrophic cardiomyopathy and atrial fibrillation

<p>Abstract</p> <p>Objectives</p> <p>We sought to evaluate the relation between atrial fibrillation (AF) and the extent of myocardial scarring together with left ventricular (LV) and atrial parameters assessed by late gadolinium-enhancement (LGE) cardiovascular magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM).</p> <p>Background</p> <p>AF is the most common arrhythmia in HCM. Myocardial scarring is also identified frequently in HCM. However, the impact of myocardial scarring assessed by LGE CMR on the presence of AF has not been evaluated yet.</p> <p>Methods</p> <p>87 HCM patients underwent LGE CMR, echocardiography and regular ECG recordings. LV function, volumes, myocardial thickness, left atrial (LA) volume and the extent of LGE, were assessed using CMR and correlated to AF. Additionally, the presence of diastolic dysfunction and mitral regurgitation were obtained by echocardiography and also correlated to AF.</p> <p>Results</p> <p>Episodes of AF were documented in 37 patients (42%). Indexed LV volumes and mass were comparable between HCM patients with and without AF. However, indexed LA volume was significantly higher in HCM patients with AF than in HCM patients without AF (68 ± 24 ml·m^-2versus 46 ± 18 ml·m^-2, p = 0.0002, respectively). The mean extent of LGE was higher in HCM patients with AF than those without AF (12.4 ± 14.5% versus 6.0 ± 8.6%, p = 0.02). When adjusting for age, gender and LV mass, LGE and indexed LA volume significantly correlated to AF (r = 0.34, p = 0.02 and r = 0.42, p < 0.001 respectively). By echocardiographic examination, LV diastolic dysfunction was evident in 35 (40%) patients. Mitral regurgitation greater than II was observed in 12 patients (14%). Multivariate analysis demonstrated that LA volume and presence of diastolic dysfunction were the only independent determinant of AF in HCM patients (p = 0.006, p = 0.01 respectively). Receiver operating characteristic curve analysis indicated good predictive performance of LA volume and LGE (AUC = 0.74 and 0.64 respectively) with respect to AF.</p> <p>Conclusion</p> <p>HCM patients with AF display significantly more LGE than HCM patients without AF. However, the extent of LGE is inferior to the LA size for predicting AF prevalence. LA dilation is the strongest determinant of AF in HCM patients, and is related to the extent of LGE in the LV, irrespective of LV mass.</p