2d Finite-Element Calculation of Superconducting Magnets Applying a Reduced Vector Potential Formulation

The program package ROXIE has been developed at CERN for the design and optimization of the coil geometries for the superconducting magnets for the Large Hadron Collider, LHC. It has recently been extended, in a close collaboration with the University of Graz, to the calculation of iron induced effects applying a reduced vector potential formulation. The method allows accurate computation of the multipole errors in the magnets and allows the distinction between the effects resulting from the coil geometry and the yoke geometry

Quantifying trading behavior in financial markets using Google Trends

Crises in financial markets affect humans worldwide. Detailed market data on trading decisions reflect some of the complex human behavior that has led to these crises. We suggest that massive new data sources resulting from human interaction with the Internet may offer a new perspective on the behavior of market participants in periods of large market movements. By analyzing changes in Google query volumes for search terms related to finance, we find patterns that may be interpreted as “early warning signs” of stock market moves. Our results illustrate the potential that combining extensive behavioral data sets offers for a better understanding of collective human behavior

Quantifying the behavior of stock correlations under market stress

Understanding correlations in complex systems is crucial in the face of turbulence, such as the ongoing financial crisis. However, in complex systems, such as financial systems, correlations are not constant but instead vary in time. Here we address the question of quantifying state-dependent correlations in stock markets. Reliable estimates of correlations are absolutely necessary to protect a portfolio. We analyze 72 years of daily closing prices of the 30 stocks forming the Dow Jones Industrial Average (DJIA). We find the striking result that the average correlation among these stocks scales linearly with market stress reflected by normalized DJIA index returns on various time scales. Consequently, the diversification effect which should protect a portfolio melts away in times of market losses, just when it would most urgently be needed. Our empirical analysis is consistent with the interesting possibility that one could anticipate diversification breakdowns, guiding the design of protected portfolios

Microscopic theory of the coupling of intrinsic Josephson oscillations and phonons

A microscopic theory for the coupling of intrinsic Josephson oscillations and dispersive phonon branches in layered superconductors is developed. Thereby the effect of phonons on the electronic c-axis transport enters through an effective longitudinal dielectric function. This coupling provides an explanation of recently observed subgap resonances in the $I_{dc}$-$V_{dc}$- curve of anisotropic cuprate superconductors forming a stack of short Josephson junctions. Due to the finite dispersion these resonances can appear at van-Hove-singularities of both optical and acoustical phonon branches, explaining low-voltage structures in the I-V-characteristic, which are not understood in phonon models without dispersion. In long junctions the dispersion of collective electron-phonon modes parallel to the layers is investigated.Comment: 4 pages, 3 figures, 1 table, espcrc2.sty, invited contribution to "Materials and Mechanisms of Superconductivity and High Temperature Superconductors VI - M2S-HTSC-VI", Houston, Texas, 20-25 Feb 2000, to appear in Physica

Search strategies of Wikipedia readers

The quest for information is one of the most common activity of human beings. Despite the the impressive progress of search engines, not to miss the needed piece of information could be still very tough, as well as to acquire specific competences and knowledge by shaping and following the proper learning paths. Indeed, the need to find sensible paths in information networks is one of the biggest challenges of our societies and, to effectively address it, it is important to investigate the strategies adopted by human users to cope with the cognitive bottleneck of finding their way in a growing sea of information. Here we focus on the case of Wikipedia and investigate a recently released dataset about users’ click on the English Wikipedia, namely the English Wikipedia Clickstream. We perform a semantically charged analysis to uncover the general patterns followed by information seekers in the multi-dimensional space of Wikipedia topics/categories. We discover the existence of well defined strategies in which users tend to start from very general, i.e., semantically broad, pages and progressively narrow down the scope of their navigation, while keeping a growing semantic coherence. This is unlike strategies associated to tasks with predefined search goals, namely the case of the Wikispeedia game. In this case users first move from the ‘particular’ to the ‘universal’ before focusing down again to the required target. The clear picture offered here represents a very important stepping stone towards a better design of information networks and recommendation strategies, as well as the construction of radically new learning paths

Wpływ ondansetronu na parametry hemodynamiczne matki podczas znieczulenia podpajęczynówkowego do cięcia cesarskiego – badanie randomizowane, przeprowadzone metodą podwójnie ślepej próby

Objective: verification of a hypothesis assuming that 5-HT3 receptor blockade by intravenous administration of ondansetron reduces the incidence of hypotension and bradycardia in patients undergoing spinal anaesthesia for Caesarean section. Material and methods: The study design was approved by the Bioethics Committee and included 72 patients undergoing elective Caesarean section, randomly assigned to ondansetron group (group O) or placebo group (group P). Finally, group O encompassed 35 patients administered ondansetron 8 mg i.v. dissolved in 10ml 0.9% NaCl whereas group P consisted of 34 patients receiving 0.9% NaCl 10 mg. Systolic and diastolic pressures were measured every 2 minutes since the onset of anaesthesia. Heart rate (HR) was monitored continuously. The criterion of hypotension requiring ephedrine was a decrease in systolic pressure by 20% compared to its baseline value or a decrease in systolic pressure below 90 mm Hg. The criterion of bradycardia was a decrease in HR below 60/min. Results: Hypotension was observed in 14 group O patients (39%) and in 15 group P patients (44%); the difference was not statistically significant. Bradycardia was noted in 1 group O patient (3%) and in 2 group P patients (6%); the difference was not statistically significant. Conclusion: A hypothesis assuming a reduction in pressure following subarachnoid anaesthesia for Caesarean section after the administration of 8 mg of ondansetron was not confirmed.Cel pracy: weryfikacja hipotezy zakładającej, że blokada receptorów 5-HT3 poprzez dożylne podanie ondansetronu redukuje częstość występowania hipotensji i bradykardii u pacjentek znieczulanych podpajęczynówkowo do cięcia cesarskiego. Materiał i metodyka: Plan badań uzyskał zgodę komisji bioetycznej. Do badania zakwalifikowano 72 pacjentki poddawane planowemu cięciu cesarskiemu, losowo przydzielając je do grupy ondansetronu (grupa O) lub grupy placebo (grupa P). Ostatecznie grupa O liczyła 36 pacjentek, którym przed znieczuleniem podano dożylnie 8 mg ondansetronu rozcieńczonego w 10 ml 0,9% NaCl, grupa P liczyła 34 pacjentki, które otrzymały 10 ml 0,9% NaCl. Pomiaru skurczowego i rozkurczowego ciśnienia tętniczego krwi dokonywano co 2 minuty od momentu znieczulenia. Częstość akcji serca (HR) monitorowana była w sposób ciągły. Za kryterium hipotensji wymagającej podania efedryny przyjęto spadek ciśnienia skurczowego o 20% w porównaniu z ciśnieniem wyjściowym lub spadek ciśnienia skurczowego poniżej 90 mm Hg. Za kryterium bradykardii przyjęto spadek akcji serca poniżej 60/min. Wyniki: Hipotensję zanotowano u 14 pacjentek w grupie O (39%) i u 15 pacjentek w grupie P (44%) co nie stanowiło statystycznie istotnej różnicy. Bradykardię zanotowano u 1 pacjentki w grupie O (3%) i u 2 pacjentek w grupie P (6%) co nie stanowiło statystycznie istotnej różnicy. Wnioski: Nie potwierdzono przyjętej hipotezy zakładającej redukcję spadku ciśnienia po znieczuleniu podpajęczynówkowym do cięcia cesarskiego po podaniu 8 mg Ondansetronu

Information sharing promotes prosocial behaviour

More often than not, bad decisions are bad regardless of where and when they are made. Information sharing might thus be utilized to mitigate them. Here we show that sharing information about strategy choice between players residing on two different networks reinforces the evolution of cooperation. In evolutionary games, the strategy reflects the action of each individual that warrants the highest utility in a competitive setting. We therefore assume that identical strategies on the two networks reinforce themselves by lessening their propensity to change. Besides network reciprocity working in favour of cooperation on each individual network, we observe the spontaneous emergence of correlated behaviour between the two networks, which further deters defection. If information is shared not just between individuals but also between groups, the positive effect is even stronger, and this despite the fact that information sharing is implemented without any assumptions with regard to content