843 research outputs found
Electromagnetics from a quasistatic perspective
Quasistatics is introduced so that it fits smoothly into the standard
textbook presentation of electrodynamics. The usual path from statics to
general electrodynamics is rather short and surprisingly simple. A closer look
reveals however that it is not without confusing issues as has been illustrated
by many contributions to this Journal. Quasistatic theory is conceptually
useful by providing an intermediate level in between statics and the full set
of Maxwell's equations. Quasistatics is easier than general electrodynamics and
in some ways more similar to statics. It is however, in terms of interesting
physics and important applications, far richer than statics. Quasistatics is
much used in electromagnetic modeling, an activity that today is possible on a
PC and which also has great pedagogical potential. The use of electromagnetic
simulations in teaching gives additional support for the importance of
quasistatics. This activity may also motivate some change of focus in the
presentation of basic electrodynamics
Comparative Raman Studies of Sr2RuO4, Sr3Ru2O7 and Sr4Ru3O10
The polarized Raman spectra of layered ruthenates of the Srn+1RunO3n+1
(n=1,2,3) Ruddlesden-Popper series were measured between 10 and 300 K. The
phonon spectra of Sr3Ru2O7 and Sr4Ru3O10 confirmed earlier reports for
correlated rotations of neighboring RuO6 octahedra within double or triple
perovskite blocks. The observed Raman lines of Ag or B1g symmetry were assigned
to particular atomic vibrations by considering the Raman modes in simplified
structures with only one double or triple RuO6 layer per unit cell and by
comparison to the predictions of lattice dynamical calculations for the real
Pban and Pbam structures. Along with discrete phonon lines, a continuum
scattering, presumably of electronic origin, is present in the zz, xx and xy,
but not in the x'y' and zx spectra. Its interference with phonons results in
Fano shape for some of the lines in the xx and xy spectra. The temperature
dependencies of phonon parameters of Sr3Ru2O7 exhibit no anomaly between 10 and
300 K where no magnetic transition occurs. In contrast, two B1g lines in the
spectra of Sr4Ru3O10, corresponding to oxygen vibrations modulating the Ru-O-Ru
bond angle, show noticeable hardening with ferromagnetic ordering at 105 K,
thus indicating strong spin-phonon interaction.Comment: 9 pages, 12 figure
Flow graphs: interweaving dynamics and structure
The behavior of complex systems is determined not only by the topological
organization of their interconnections but also by the dynamical processes
taking place among their constituents. A faithful modeling of the dynamics is
essential because different dynamical processes may be affected very
differently by network topology. A full characterization of such systems thus
requires a formalization that encompasses both aspects simultaneously, rather
than relying only on the topological adjacency matrix. To achieve this, we
introduce the concept of flow graphs, namely weighted networks where dynamical
flows are embedded into the link weights. Flow graphs provide an integrated
representation of the structure and dynamics of the system, which can then be
analyzed with standard tools from network theory. Conversely, a structural
network feature of our choice can also be used as the basis for the
construction of a flow graph that will then encompass a dynamics biased by such
a feature. We illustrate the ideas by focusing on the mathematical properties
of generic linear processes on complex networks that can be represented as
biased random walks and also explore their dual consensus dynamics.Comment: 4 pages, 1 figur
Analytical reasoning task reveals limits of social learning in networks
Social learning -by observing and copying others- is a highly successful
cultural mechanism for adaptation, outperforming individual information
acquisition and experience. Here, we investigate social learning in the context
of the uniquely human capacity for reflective, analytical reasoning. A hallmark
of the human mind is our ability to engage analytical reasoning, and suppress
false associative intuitions. Through a set of lab-based network experiments,
we find that social learning fails to propagate this cognitive strategy. When
people make false intuitive conclusions, and are exposed to the analytic output
of their peers, they recognize and adopt this correct output. But they fail to
engage analytical reasoning in similar subsequent tasks. Thus, humans exhibit
an 'unreflective copying bias,' which limits their social learning to the
output, rather than the process, of their peers' reasoning -even when doing so
requires minimal effort and no technical skill. In contrast to much recent work
on observation-based social learning, which emphasizes the propagation of
successful behavior through copying, our findings identify a limit on the power
of social networks in situations that require analytical reasoning
Novel Approach to Mass Tort Class Actions: The Billion Dollar Settlement in the Sulzer Artificial Hip and Knee Litigation: A Symposium
This is a transcript of a two hour symposium which deals with the Sulzer knee and hip replacement class action. A copy of the settlement is included as an appendix. The settlement in the U.S. District Court for the N.D. Ohio was unique and creative approach to resolving a mass tort class action. In a novel move, Sulzer agreed to open its books to an independent review firm to determine how much the firm could pay without going bankrupt. The number was $1 billion. As negotiated by the parties and approved by the court, the final settlement provides compensation for each member of the class based on a variety of factors, such as whether the member has undergone - or is likely to undergo - a revision to replace the defective part. Professor Susan Becker made the introductory remarks. The panel members were all involved in the Sulzer knee and hip replacement class action. R. Eric Kennedy served as lead plaintiffs\u27 counsel. The Honorable Kathleen McDonald O\u27Malley of the U.S. District Court for the Northern District of Ohio presided over the Sulzer class action litigation and settlement. Sidney A. Backstrom and Richard F. Scruggs were the defense counsel. James J. McMonagle served as the Claims Administrator overseeing distribution of the Sulzer class action settlement funds
Novel Approach to Mass Tort Class Actions: The Billion Dollar Settlement in the Sulzer Artificial Hip and Knee Litigation: A Symposium
This is a transcript of a two hour symposium which deals with the Sulzer knee and hip replacement class action. A copy of the settlement is included as an appendix. The settlement in the U.S. District Court for the N.D. Ohio was unique and creative approach to resolving a mass tort class action. In a novel move, Sulzer agreed to open its books to an independent review firm to determine how much the firm could pay without going bankrupt. The number was $1 billion. As negotiated by the parties and approved by the court, the final settlement provides compensation for each member of the class based on a variety of factors, such as whether the member has undergone - or is likely to undergo - a revision to replace the defective part. Professor Susan Becker made the introductory remarks. The panel members were all involved in the Sulzer knee and hip replacement class action. R. Eric Kennedy served as lead plaintiffs\u27 counsel. The Honorable Kathleen McDonald O\u27Malley of the U.S. District Court for the Northern District of Ohio presided over the Sulzer class action litigation and settlement. Sidney A. Backstrom and Richard F. Scruggs were the defense counsel. James J. McMonagle served as the Claims Administrator overseeing distribution of the Sulzer class action settlement funds
An efficient and principled method for detecting communities in networks
A fundamental problem in the analysis of network data is the detection of
network communities, groups of densely interconnected nodes, which may be
overlapping or disjoint. Here we describe a method for finding overlapping
communities based on a principled statistical approach using generative network
models. We show how the method can be implemented using a fast, closed-form
expectation-maximization algorithm that allows us to analyze networks of
millions of nodes in reasonable running times. We test the method both on
real-world networks and on synthetic benchmarks and find that it gives results
competitive with previous methods. We also show that the same approach can be
used to extract nonoverlapping community divisions via a relaxation method, and
demonstrate that the algorithm is competitively fast and accurate for the
nonoverlapping problem.Comment: 14 pages, 5 figures, 1 tabl
Impact of information letters on the reporting rate of adverse drug reactions and the quality of the reports: a randomized controlled study
BACKGROUND: Spontaneous reporting of adverse drug reactions (ADRs) is an important method for pharmacovigilance, but under-reporting and poor quality of reports are major limitations. The aim of this study was to evaluate if repeated one-page ADR information letters affect (i) the reporting rate of ADRs and (ii) the quality of the ADR reports. METHODS: All 151 primary healthcare units in the Region Västra Götaland, Sweden, were randomly allocated (1:1) to an intervention (n = 77) or a control group (n = 74). The intervention consisted of one-page ADR information letters administered at three occasions during 2008 to all physicians and nurses in the intervention units. The number of ADR reports received from the 151 units was registered, as was the quality of the reports, which was defined as high if the ADR was to be reported according to Swedish regulations, that is, if the ADR was (i) serious, (ii) unexpected, and/or (iii) related to the use of new drugs and not labelled as common in the Summary of Product Characteristics. A questionnaire was administered to evaluate if the ADR information letter had reached the intended recipient. RESULTS: Before the intervention, no significant differences in reporting rate or number of high quality reports could be detected between the randomization groups. In 2008, 79 reports were sent from 37 intervention units and 52 reports from 30 control units (mean number of reports per unit ± standard deviation: 1.0 ± 2.5 vs. 0.7 ± 1.2, P = 0.34). The number of high quality reports was higher in intervention units than in control units (37 vs. 15 reports, 0.5 ± 0.9 vs. 0.2 ± 0.6, P = 0.048). According to the returned questionnaires (n = 1,292, response rate 57%), more persons in the intervention than in the control group had received (29% vs. 19%, P < 0.0001) and read (31% vs. 26%, P < 0.0001) an ADR information letter. CONCLUSIONS: This study suggests that repeated ADR information letters to physicians and nurses do not increase the ADR reporting rate, but may increase the number of high quality reports
Impact of information letters on the reporting rate of adverse drug reactions and the quality of the reports: a randomized controlled study
BACKGROUND: Spontaneous reporting of adverse drug reactions (ADRs) is an important method for pharmacovigilance, but under-reporting and poor quality of reports are major limitations. The aim of this study was to evaluate if repeated one-page ADR information letters affect (i) the reporting rate of ADRs and (ii) the quality of the ADR reports. METHODS: All 151 primary healthcare units in the Region Västra Götaland, Sweden, were randomly allocated (1:1) to an intervention (n = 77) or a control group (n = 74). The intervention consisted of one-page ADR information letters administered at three occasions during 2008 to all physicians and nurses in the intervention units. The number of ADR reports received from the 151 units was registered, as was the quality of the reports, which was defined as high if the ADR was to be reported according to Swedish regulations, that is, if the ADR was (i) serious, (ii) unexpected, and/or (iii) related to the use of new drugs and not labelled as common in the Summary of Product Characteristics. A questionnaire was administered to evaluate if the ADR information letter had reached the intended recipient. RESULTS: Before the intervention, no significant differences in reporting rate or number of high quality reports could be detected between the randomization groups. In 2008, 79 reports were sent from 37 intervention units and 52 reports from 30 control units (mean number of reports per unit ± standard deviation: 1.0 ± 2.5 vs. 0.7 ± 1.2, P = 0.34). The number of high quality reports was higher in intervention units than in control units (37 vs. 15 reports, 0.5 ± 0.9 vs. 0.2 ± 0.6, P = 0.048). According to the returned questionnaires (n = 1,292, response rate 57%), more persons in the intervention than in the control group had received (29% vs. 19%, P < 0.0001) and read (31% vs. 26%, P < 0.0001) an ADR information letter. CONCLUSIONS: This study suggests that repeated ADR information letters to physicians and nurses do not increase the ADR reporting rate, but may increase the number of high quality reports
Using citizen science to identify Australia’s least known birds and inform conservation action
Citizen science is a popular approach to biodiversity surveying, whereby data that are collected by volunteer naturalists may help analysts to understand the distribution and abundance of wild organisms. In Australia, birdwatchers have contributed to two major citizen science programs, eBird (run by the Cornell Lab of Ornithology) and Birdata (run by Birdlife Australia), which collectively hold more than 42 million records of wild birds from across the country. However, these records are not evenly distributed across space, time, or taxonomy, with particularly significant variation in the number of records of each species in these datasets. In this paper, we explore this variation and seek to determine which Australian bird species are least known as determined by rates of citizen science survey detections. We achieve this by comparing the rates of survey effort and species detection across each Australian bird species? range, assigning all 581 species to one of the four groups depending on their rates of survey effort and species observation. We classify 56 species into a group considered the most poorly recorded despite extensive survey effort, with Coxen?s Fig Parrot Cyclopsitta coxeni, Letter-winged Kite Elanus scriptus, Night Parrot Pezoporus occidentalis, Buff-breasted Buttonquail Turnix olivii and Red-chested Buttonquail Turnix pyrrhothorax having the very lowest numbers of records. Our analyses provide a framework to identify species that are poorly represented in citizen science datasets. We explore the reasons behind why they may be poorly represented and suggest ways in which targeted approaches may be able to help fill in the gaps.Publisher PDFPeer reviewe
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