825 research outputs found
Citation Flows in the Zones of Influence of Scientific
Domestic citation to papers from the same country and the greater citation impact of documents involving international collaboration are two phenomena that have been extensively studied and contrasted. Here, however, we showthat it is not somuch a national bias,but that papers have a greater impact on their immediate environments, an impact that is diluted as that environment grows. For this reason, the greatest biases are observed in countries
with a limited production. Papers that involve international collaboration have a greater impact in general, on the one hand, because they have multiple “immediate
environments,” and on the other because of their greater quality or prestige. In short, one can say that science knows no frontiers. Certainly there is a greater impact
on the authors’ immediate environment, but this does not necessarily have to coincide with their national environments, which fade in importance as the collaborative
environment expands
Whistler Waves Driven by Anisotropic Strahl Velocity Distributions: Cluster Observations
Observed properties of the strahl using high resolution 3D electron velocity distribution data obtained from the Cluster/PEACE experiment are used to investigate its linear stability. An automated method to isolate the strahl is used to allow its moments to be computed independent of the solar wind core+halo. Results show that the strahl can have a high temperature anisotropy (T(perpindicular)/T(parallell) approximately > 2). This anisotropy is shown to be an important free energy source for the excitation of high frequency whistler waves. The analysis suggests that the resultant whistler waves are strong enough to regulate the electron velocity distributions in the solar wind through pitch-angle scatterin
Citation Flows in the Zones of Influence of Scientific
Domestic citation to papers from the same country and the greater citation impact of documents involving international collaboration are two phenomena that have been extensively studied and contrasted. Here, however, we showthat it is not somuch a national bias,but that papers have a greater impact on their immediate environments, an impact that is diluted as that environment grows. For this reason, the greatest biases are observed in countries
with a limited production. Papers that involve international collaboration have a greater impact in general, on the one hand, because they have multiple “immediate
environments,” and on the other because of their greater quality or prestige. In short, one can say that science knows no frontiers. Certainly there is a greater impact
on the authors’ immediate environment, but this does not necessarily have to coincide with their national environments, which fade in importance as the collaborative
environment expands
Tracking the momentum flux of a CME and quantifying its influence on geomagnetically induced currents at Earth
We investigate a CME propagating towards Earth on 29 March 2011. This event
is specifically chosen for its predominately northward directed magnetic field,
so that the influence from the momentum flux onto Earth can be isolated. We
focus our study on understanding how a small Earth-directed segment propagates.
Mass images are created from the white-light cameras onboard STEREO which are
also converted into mass height-time maps (mass J-maps). The mass tracks on
these J-maps correspond to the sheath region between the CME and its associated
shock front as detected by in situ measurements at L1. A time-series of mass
measurements from the STEREO COR-2A instrument are made along the Earth
propagation direction. Qualitatively, this mass time-series shows a remarkable
resemblance to the L1 in situ density series. The in situ measurements are used
as inputs into a 3D magnetospheric space weather simulation from CCMC. These
simulations display a sudden compression of the magnetosphere from the large
momentum flux at the leading edge of the CME and predictions are made for the
time-derivative of the magnetic field (dB/dt) on the ground. The predicted
dB/dt were then compared with observations from specific equatorially-located
ground stations and show notable similarity. This study of the momentum of a
CME from the Sun down to its influence on magnetic ground stations on Earth is
presented as preliminary proof of concept, such that future attempts may try to
use remote sensing to create density and velocity time-series as inputs to
magnetospheric simulations.Comment: Accepted for publication 8th March 2013. Submitted 18th Dec 2012. 19
Pages, 10 figures, 2 Appendice
The 1989 and 2015 outbursts of V404 Cygni: a global study of wind-related optical features
The black hole transient V404 Cygni exhibited a bright outburst in June 2015
that was intensively followed over a wide range of wavelengths. Our team
obtained high time resolution optical spectroscopy (~90 s), which included a
detailed coverage of the most active phase of the event. We present a database
consisting of 651 optical spectra obtained during this event, that we combine
with 58 spectra gathered during the fainter December 2015 sequel outburst, as
well as with 57 spectra from the 1989 event. We previously reported the
discovery of wind-related features (P-Cygni and broad-wing line profiles)
during both 2015 outbursts. Here, we build diagnostic diagrams that enable us
to study the evolution of typical emission line parameters, such as line fluxes
and equivalent widths, and develop a technique to systematically detect outflow
signatures. We find that these are present throughout the outburst, even at
very low optical fluxes, and that both types of outflow features are observed
simultaneously in some spectra, confirming the idea of a common origin. We also
show that the nebular phases depict loop patterns in many diagnostic diagrams,
while P-Cygni profiles are highly variable on time-scales of minutes. The
comparison between the three outbursts reveals that the spectra obtained during
June and December 2015 share many similarities, while those from 1989 exhibit
narrower emission lines and lower wind terminal velocities. The diagnostic
diagrams presented in this work have been produced using standard measurement
techniques and thus may be applied to other active low-mass X-ray binaries.Comment: Accepted for publication in MNRAS. 23 pages paper, plus a 9 pages
appendix with extra tables and figures. 18 figures are included in the paper
and 8 in the appendi
Gout Activity Score has predictive validity and is sensitive to change: results from the Nottingham Gout Treatment Trial (Phase II)
Objectives: To examine the predictive validity of the Gout Activity Score (GAS), its’ correlation with the Gout Impact Scale (GIS), and their sensitivity to change.Methods: Data from a clinical trial in which participants with ≥1 gout flare in the previous year were recruited from primary-care, and randomized to nurse-led or continuing usual care were used in this study. GAS and GIS were calculated as described, with higher scores indicating worse disease activity and quality of life respectively. Correlation between GAS and GIS was examined using Spearman’s correlation. Standardized response means (SRMs) were calculated to assess sensitivity to change. The association between GAS at baseline and number of flares in the next 12 months was evaluated using Poisson regression. Data analyses were performed using STATA version 14, with p [less than] 0.05 being statistically significant.Results: There was low positive correlation between GAS and gout concern overall, and unmet treatment need subscales of GIS (r = 0.34-0.45). Female sex associated independently with fewer gout flares, while increasing GAS, body mass index, and age associated independently with frequent flares. Of all the outcome measures examined, GAS was the most responsive to change (SRMs 0.89 to -0.53). Of the GIS domains, the gout concern overall domain had the best sensitivity to change (SRMs 1.06 to 0.01).Conclusion: GAS is sensitive to change, has predictive validity, and, correlates with relevant domains of GIS such as gout concern overall. Additional independent validation of GAS is required before it can be adopted in clinical practice
Topical Issue in Solar Physics: Flux-rope Structure of Coronal Mass Ejections Preface
This Topical Issue of Solar Physics, devoted to the study of flux-rope
structure in coronal mass ejections (CMEs), is based on two Coordinated Data
Analysis Workshops (CDAWs) held in 2010 (20 - 23 September in Dan Diego,
California, USA) and 2011 (September 5-9 in Alcala, Spain). The primary purpose
of the CDAWs was to address the question: Do all CMEs have flux rope structure?
There are 18 papers om this topical issue, including this preface.Comment: 4 page
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