2,588 research outputs found
Distance Measures for Dynamic Citation Networks
Acyclic digraphs arise in many natural and artificial processes. Among the
broader set, dynamic citation networks represent a substantively important form
of acyclic digraphs. For example, the study of such networks includes the
spread of ideas through academic citations, the spread of innovation through
patent citations, and the development of precedent in common law systems. The
specific dynamics that produce such acyclic digraphs not only differentiate
them from other classes of graphs, but also provide guidance for the
development of meaningful distance measures. In this article, we develop and
apply our sink distance measure together with the single-linkage hierarchical
clustering algorithm to both a two-dimensional directed preferential attachment
model as well as empirical data drawn from the first quarter century of
decisions of the United States Supreme Court. Despite applying the simplest
combination of distance measures and clustering algorithms, analysis reveals
that more accurate and more interpretable clusterings are produced by this
scheme.Comment: 7 pages, 5 figures. Revision: Added application to the network of the
first quarter-century of Supreme Court citations. Revision 2: Significantly
expanded, includes application on random model as wel
Evaluation of two lyophilized molecular assays to rapidly detect foot-and-mouth disease virus directly from clinical samples in field settings
Accurate, timely diagnosis is essential for the control, monitoring and eradication of footâandâmouth disease (FMD). Clinical samples from suspect cases are normally tested at reference laboratories. However, transport of samples to these centralized facilities can be a lengthy process that can impose delays on critical decision making. These concerns have motivated work to evaluate simpleâtoâuse technologies, including molecularâbased diagnostic platforms, that can be deployed closer to suspect cases of FMD. In this context, FMD virus (FMDV)âspecific reverse transcription loopâmediated isothermal amplification (RTâLAMP) and realâtime RTâPCR (rRTâPCR) assays, compatible with simple sample preparation methods and in situ visualization, have been developed which share equivalent analytical sensitivity with laboratoryâbased rRTâPCR. However, the lack of robust âreadyâtoâuse kitsâ that utilize stabilized reagents limits the deployment of these tests into field settings. To address this gap, this study describes the performance of lyophilized rRTâPCR and RTâLAMP assays to detect FMDV. Both of these assays are compatible with the use of fluorescence to monitor amplification in realâtime, and for the RTâLAMP assays end point detection could also be achieved using molecular lateral flow devices. Lyophilization of reagents did not adversely affect the performance of the assays. Importantly, when these assays were deployed into challenging laboratory and field settings within East Africa they proved to be reliable in their ability to detect FMDV in a range of clinical samples from acutely infected as well as convalescent cattle. These data support the use of highly sensitive molecular assays into field settings for simple and rapid detection of FMDV
A long-term follow-up study investigating health-related quality of life and resource use in survivors of severe sepsis: comparison of recombinant human activated protein C with standard care
ISICSoo: a class for the calculation of ionization cross sections from ECPSSR and PWBA theory
ISICS, originally a C language program for calculating K-, L- and M-shell
ionization and X-ray production cross sections from ECPSSR and PWBA theory, has
been reengineered into a C++ language class, named ISICSoo. The new software
design enables the use of ISICS functionality in other software systems. The
code, originally developed for Microsoft Windows operating systems, has been
ported to Linux and Mac OS platforms to facilitate its use in a wider
scientific environment. The reengineered software also includes some fixes to
the original implementation, which ensure more robust computational results and
a review of some physics parameters used in the computation. The paper
describes the software design and the modifications to the implementation with
respect to the previous version; it also documents the test process and
provides some indications about the software performance.Comment: Preprint submitted to Computer Physics Communication
Magnetoconductivity of quantum wires with elastic and inelastic scattering
We use a Boltzmann equation to determine the magnetoconductivity of quantum
wires. The presence of a confining potential in addition to the magnetic field
removes the degeneracy of the Landau levels and allows one to associate a group
velocity with each single-particle state. The distribution function describing
the occupation of these single-particle states satisfies a Boltzmann equation,
which may be solved exactly in the case of impurity scattering. In the case
where the electrons scatter against both phonons and impurities we solve
numerically - and in certain limits analytically - the integral equation for
the distribution function, and determine the conductivity as a function of
temperature and magnetic field. The magnetoconductivity exhibits a maximum at a
temperature, which depends on the relative strength of the impurity and
electron-phonon scattering, and shows oscillations when the Fermi energy or the
magnetic field is varied.Comment: 21 pages (revtex 3.0), 5 postscript figures available upon request at
[email protected] or [email protected]
Switching the stereochemical outcome of 6-endo-trig cyclizations; Synthesis of 2,6-Cis-6-substituted 4-oxopipecolic acids
A base-mediated 6-endo-trig cyclization of
readily accessible enone-derived α-amino acids has been
developed for the direct synthesis of novel 2,6-cis-6-
substituted-4-oxo-L-pipecolic acids. A range of aliphatic and
aryl side chains were tolerated by this mild procedure to give
the target compounds in good overall yields. Molecular
modeling of the 6-endo-trig cyclization allowed some insight as
to how these compounds were formed, with the enolate
intermediate generated via an equilibrium process, followed by irreversible tautomerization/neutralization providing the driving force for product formation. Stereoselective reduction and deprotection of the resulting 2,6-cis-6-substituted 4-oxo-L-pipecolic acids to the corresponding 4-hydroxy-L-pipecolic acids was also performed
Spatiotemporal distribution of the seismicity along the Mid-Atlantic Ridge north of the Azores from hydroacoustic data: Insights into seismogenic processes in a ridge-hot spot context
The seismicity of the North Atlantic was monitored from May 2002 to September 2003 by the 'SIRENA array' of autonomous hydrophones. The hydroacoustic signals provide a unique data set documenting numerous low-magnitude earthquakes along the section of the Mid-Atlantic Ridge (MAR) located in a ridge-hot spot interaction context. During the experiment, 1696 events were detected along the MAR axis between 40 degrees N and 51 degrees N, with a magnitude of completeness level of m(b) approximate to 2.4. Inside the array, location errors are in the order of 2 km, and errors in the origin time are less than 1 s. From this catalog, 15 clusters were detected. The distribution of source level (SL) versus time within each cluster is used to discriminate clusters occurring in a tectonic context from those attributed to non-tectonic (i.e. volcanic or hydrothermal) processes. The location of tectonic and non-tectonic sequences correlates well with regions with positive and negative Mantle Bouguer Anomalies (MBAs), indicating the presence of thinner/colder and thicker/warmer crust respectively. At the scale of the entire array, both the complete and declustered catalogs derived from the hydroacoustic signals show an increase of the seismicity rate from the Azores up to 43 degrees 30'N suggesting a diminishing influence of the Azores hot spot on the ridge-axis temperature, and well correlated with a similar increase in the along-axis MBAs. The comparison of the MAR seismicity with the Residual MBA (RMBA) at different scales leads us to think that the low-magnitude seismicity rates are directly related to along-axis variations in lithosphere rheology and temperatures.info:eu-repo/semantics/publishedVersio
Carbon clusters near the crossover to fullerene stability
The thermodynamic stability of structural isomers of ,
, and , including
fullerenes, is studied using density functional and quantum Monte Carlo
methods. The energetic ordering of the different isomers depends sensitively on
the treatment of electron correlation. Fixed-node diffusion quantum Monte Carlo
calculations predict that a isomer is the smallest stable
graphitic fragment and that the smallest stable fullerenes are the
and clusters with and
symmetry, respectively. These results support proposals that a
solid could be synthesized by cluster deposition.Comment: 4 pages, includes 4 figures. For additional graphics, online paper
and related information see http://www.tcm.phy.cam.ac.uk/~prck
Metallo-cryptophane cages from cis-linked and trans-linked strategies.
Data supporting study of Pd(II) metallo-cage species from cyclotriguaiacylene derived ligands
24 New Citizen Science Light Curves of WASP-12b and Updated Ephemeris by Combining with ETD and ExoClock Datasets
NASA citizen scientists from all over the world have used EXOplanet Transit
Interpretation Code (EXOTIC) to reduce 71 sets of time-series images of WASP-12
taken by the 6-inch telescope operated by the Centre of Astrophysics | Harvard
& Smithsonian MicroObservatory. Of these sets, 24 result in clean Transit light
curves of the WASP-12b which are uploaded to the NASA Exoplanet Watch website.
We use priors from the NASA Exoplanet Archive to calculate the ephemeris of the
planet and combine it with ETD (Exoplanet Transit Database) and ExoClock
observations. Combining the Exoplanet Watch, ETD, and Exoclock datasets gives
an updated ephemeris for the WASP-12b system of 2454508.97872 +/- 0.00003 with
an orbital period of 1.0914196 +/- 1.7325322e-08 days which can be used to
inform future space telescope observations
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