Efficient Distributed Online Prediction and Stochastic Optimization with Approximate Distributed Averaging

We study distributed methods for online prediction and stochastic optimization. Our approach is iterative: in each round nodes first perform local computations and then communicate in order to aggregate information and synchronize their decision variables. Synchronization is accomplished through the use of a distributed averaging protocol. When an exact distributed averaging protocol is used, it is known that the optimal regret bound of $\mathcal{O}(\sqrt{m})$ can be achieved using the distributed mini-batch algorithm of Dekel et al. (2012), where $m$ is the total number of samples processed across the network. We focus on methods using approximate distributed averaging protocols and show that the optimal regret bound can also be achieved in this setting. In particular, we propose a gossip-based optimization method which achieves the optimal regret bound. The amount of communication required depends on the network topology through the second largest eigenvalue of the transition matrix of a random walk on the network. In the setting of stochastic optimization, the proposed gossip-based approach achieves nearly-linear scaling: the optimization error is guaranteed to be no more than $\epsilon$ after $\mathcal{O}(\frac{1}{n \epsilon^2})$ rounds, each of which involves $\mathcal{O}(\log n)$ gossip iterations, when nodes communicate over a well-connected graph. This scaling law is also observed in numerical experiments on a cluster.Comment: 30 pages, 2 figure

It’s the Youth, Stupid! Greece’s most undervalued asset

Numbers never lie. However the fashion of macroeconomic valuation has a long history of interpreting partially the truth that numbers are intended to resonate. During the last four years, statistical numbers regarding the Greek economy have been interpreted by multiple economists, international investors, and public policy decision makers. Amongst many others, the most popular numbers regurgitated by mass media are the 60% youth unemployment, the 160% debt-to-GDP ratio, the 10% deficit, and the excessive credit default swaps (CDS) spreads widening. These numbers on the country’s current economic state, along with the inverting of the demographic age distribution pyramid, has led traditional methods of macroeconomic growth research to assure investors that the Greek economy has little or negligible growth potential. As a result, the public opinion has come to a consensus: the current Greek youth is a lost generation

A case of nonarteritic anterior ischemic optic neuropathy of a male with family history of the disease after receiving sildenafil

A 51-year-old male was referred to the University Eye Clinic of Ioannina with nonarteritic anterior ischemic optic neuropathy (NAION) 12 hours after receiving sildenafil citrate (Viagra®). Examination for possible risk factors revealed mild hypercholesterolemia. Family history showed that his father had suffered from bilateral NAION. Although a cause-and-effect relationship is difficult to prove, there are reports indicating an association between the use of erectile dysfunction agents and the development of NAION. Physicians might need to investigate the presence of family history of NAION among systemic or vascular predisposing risk factors before prescribing erectile dysfunction drugs

Hotspots und die neue europäische Grenzarchitektur: Zur Ethnographie einer Erfassungsform

Das europäische Asyl- und Grenzregime steckt in einer tiefen systemischen Krise. Diese ist nicht nur im europapolitischen Sinne zu verstehen, sondern auch steuerungspolitisch: Die Instrumente der Migrationskontrolle und -regulation im Mittelmeer und im europäi­schen Binnenraum scheinen tatsächlich beinahe zum Erliegen gekommen sein. Die im Mai 2015 von der Kommission verabschiedete Europäische Migrationsagenda versucht umfassend auf die flüchtlingspolitische Krise zu antworten und ist eine Zusammenstel­lung von Maßnahmen, die zu einer kohärenteren europäischen Migrationspolitik beitragen sollen. Ausgehend von einer kritischen Evaluation der ›Europäischen Migrati­onsagenda‹ und der damit verbundenen Migrations- und Grenzforschung fokussiere ich in meiner Feldforschung zur griechischen Hotspots die Lokalisierung des neuen Dublin- Systems, da seine Effekte sich unmittelbar in aktuellen Grenzkonflikten und Grenzzonen niederschlagen. Grenznahe Hotspots folgen einem Konzept, demgemäß die Agenturen FRONTEX, EASO, EUROPOL und EUROJUST vor Ort an Brennpunkten der Außengrenze untereinander und als ›Migrationsmanagement-Unterstützerteams‹ mit lokalen und nationalen Behörden kollaborieren sollen in Italien und Griechenland. Während die externalisierte Grenzsicherung sowie die Kooperation mit Drittstaaten zu einer Entschleu­nigung und Verschlankung der Ströme der grenzüberschreitenden Mobilität führen sollen, folgt die Strategie der Hotspots der genau entgegengesetzten Bewegung: Die Konzentrati­on unterschiedlicher Kräfte auf einen Punkt soll zu einer Beschleunigung der Verfahren bzw. zu einer schnelleren Sortierung der Ankommenden führen; damit soll erreicht werden, dass die Brennpunkte zu Drehscheiben werden, wo Asylanträge geprüft, Flücht­linge auf andere EU-Länder verteilt, und Menschen ohne Asylgrund bzw. Flüchtende und MigrantInnen mit wenig bis keiner so genannten Bleibeperspektive zügig, konsequent und nahe an der territorialen Grenze abgewiesen und rückgeführt oder abgeschoben werden können. In meinem Vortrag werde ich mittels der Methode der ›ethnographischen Grenzregimeanalyse‹ die ersten Ergebnisse aus meiner Feldforschung zur Implementie­rung des Hotspots-Ansatzes auf Lesbos und Chios präsentieren

Human responses to cold and hypoxia: Implications for mountaineers

This thesis is a compilation of 5 different projects. A brief summary for each project is presented below. A Comparison of a Bubble-Wrap Bag and a Mountain Rescue Casualty Bag In a Cold Windy Environment: Reports from Norwegian mountain rescue teams suggest that one layer of bubble-wrap (BW) around a casualty requiring evacuation is useful in preventing loss of body heat. The aim of this study was to compare a BW bag against a previously evaluated casualty bag (CB) currently in use by some Scottish mountain rescue teams. Factors Affecting a Climber's Ability to Ascend Mont Blanc: The aim of the study was to determine the factors affecting a climber's ability to ascend Mont Blanc (4807m) using a number of variables collected at the Gouter Hut (3817m) before and after an attempted ascent on the Mont Blanc summit. Performance at Altitude and Angiotensin Converting Enzyme Genotype: The 'insertion' (I) rather than 'deletion' (D) variant of the human Angiotensin Converting Enzyme (ACE) gene is associated with both lower tissue ACE activity and enhanced performance at high altitude. The aim of the study was to examine whether the onset of acute mountain sickness (AMS), and further performance on reaching the summit of Mont Blanc are influenced by the ACE I/D polymorphism. The Effect of ACE Genotype and Hypoxic Ventilatory Response On Arterial Oxygen Saturation and other Physiological Measurements During a Staged Ascent to 5000m: The aims of this study were to consider the role of the ACE genotype on daily SaO2, HR and AMS during gradual ascent to altitude (5000m). Furthermore, the speed of Hypoxic Ventilatory Response, measured during rest at sea level, was used to predict the daily physiological responses of SaO2, HR, and AMS, while any ACE genotype related differences on HVR were considered. ACE Genotype and Mount Everest: The angiotensin converting enzyme gene has been previously associated with elite mountaineering status. We sought such an advantage in a prospective study of those attempting the ascent of the highest mountain on earth, Mount Everest (8850m). There were no genotype differences in those who succeeded vs. those who failed, p=0.56. Although suggesting that ACE genotype may have little influence upon mountaineering success, these data may be misinterpreted by the use of supplementary oxygen (in all those summiting). Finally, it may be that ACE genotype influences success more when acclimatisation time has been limited. Further investigations are required. (Abstract shortened by ProQuest.)

Psychophysical Load During the Multistage Marathon des Sables: A Case Study

Introduction: This study investigated the impact of the multistage ultra-marathon event ‘‘Marathon des Sables’’ (MdS) performed in the Sahara Desert on the psychophysical capacity of an athlete. Methods: We collected and analyzed environmental, physiological, and behavioral data from a 39-year-old athlete who participated in the MdS. Specifically, we collected environmental temperature (Tenv), upper inguinal skin temperature (Tsk), heart rate, and running speed data. Also, we recorded blood glucose and lactate, thermal comfort, total body water, perceived exertion, and cognitive function at the start, middle, and the end of each race stage. Results: We found significant detrimental impacts on the health and wellbeing of the monitored athlete. The monitored athlete suffered a multi-toe injury during the 3rd stage of MdS. Furthermore, the Tsk (32.6 ¡ 2.6°C) fluctuated considerably between day and night, as the lowest value presented was 29.8°C while the highest was 40.4°C. The Tsk tended to be higher both when the Tenv was higher and when daily running distance was longer. Finally, the athlete’s cognitive and athletic performances tended to be higher when his blood glucose (118.33 ± 19.20mg/dl) levels were higher. Conclusion: The health and wellbeing parameters of the monitored athlete were significantly impacted during the MdS

Human Factors As A Parameter For Improving Interface Usability And User Satisfaction

The endeavour to optimize HCI should integrate a wide array of user characteristics that have an effect throughout users’ interactions with a system. Human factors such as cognitive traits and current state, from a psychological point of view, are undoubtedly significant in the shaping of the perceived and objective quality of interactions with a system. The research that is presented in this paper focuses on identifying human factors that relate to users’ performance in Web applications that involve information processing, and a framework of personalization rules that are expected to increase users’ performance is depicted. The empirical results that are presented are derived from environments both learning and commercial; in the case of e-learning personalization was beneficial, while the interaction with a commercial site needs to be further investigated due to the implicit character of information processing in the Web