836 research outputs found
Social Ranking Techniques for the Web
The proliferation of social media has the potential for changing the
structure and organization of the web. In the past, scientists have looked at
the web as a large connected component to understand how the topology of
hyperlinks correlates with the quality of information contained in the page and
they proposed techniques to rank information contained in web pages. We argue
that information from web pages and network data on social relationships can be
combined to create a personalized and socially connected web. In this paper, we
look at the web as a composition of two networks, one consisting of information
in web pages and the other of personal data shared on social media web sites.
Together, they allow us to analyze how social media tunnels the flow of
information from person to person and how to use the structure of the social
network to rank, deliver, and organize information specifically for each
individual user. We validate our social ranking concepts through a ranking
experiment conducted on web pages that users shared on Google Buzz and Twitter.Comment: 7 pages, ASONAM 201
Effects of experimental warming and carbon addition on nitrate reduction and respiration in coastal sediments
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 125 (2015): 81-95, doi:10.1007/s10533-015-0113-4.Climate change may have differing effects on microbial processes that control coastal N
availability. We conducted a microcosm experiment to explore effects of warming and carbon
availability on nitrate reduction pathways in marine sediments. Sieved continental shelf
sediments were incubated for 12 weeks under aerated seawater amended with nitrate (~50 ÎŒM),
at winter (4°C) or summer (17°C) temperatures, with or without biweekly particulate organic C
additions. Treatments increased diffusive oxygen consumption as expected, with somewhat
higher effects of C addition compared to warming. Combined warming and C addition had the
strongest effect on nitrate flux across the sediment water interface, with a complete switch early
in the experiment from influx to sustained efflux. Supporting this result, vial incubations with
added 15N-nitrate indicated that C addition stimulated potential rates of dissimilatory nitrate
reduction to ammonium (DNRA), but not denitrification. Overall capacity for both
denitrification and DNRA was reduced in warmed treatments, possibly reflecting C losses due to
increased respiration with warming. Anammox potential rates were much lower than DNRA or
denitrification, and were slightly negatively affected by warming or C addition. Overall, results
indicate that warming and C addition increased ammonium production through remineralization
and possibly DNRA. This stimulated nitrate production through nitrification, but without a
comparable increase in nitrate consumption through denitrification. The response to C of
potential DNRA rates over denitrification, along with a switch to nitrate efflux, raises the
possibility that DNRA is an important and previously overlooked source of internal N cycling in
shelf sediments.This material is based upon work supported by the National Science Foundation by OCE-
0852289 to JJR and OCE-0852263 and OCE-0927400 to AEG, and Rhode Island Sea Grant to
JJR
Similar temperature responses suggest future climate warming will not alter partitioning between denitrification and anammox in temperate marine sediments
Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Global Change Biology 23 (2017): 331-340, doi:10.1111/gcb.13370.Removal of biologically available nitrogen (N) by the microbially mediated processes
denitrification and anaerobic ammonium oxidation (anammox) affects ecosystem N availability.
Although few studies have examined temperature responses of denitrification and anammox,
previous work suggests that denitrification could become more important than anammox in
response to climate warming. To test this hypothesis, we determined whether temperature
responses of denitrification and anammox differed in shelf and estuarine sediments from coastal
Rhode Island over a seasonal cycle. The influence of temperature and organic C availability was
further assessed in a 12-week laboratory microcosm experiment. Temperature responses, as
characterized by thermal optima (Topt) and apparent activation energy (Ea), were determined by
measuring potential rates of denitrification and anammox at 31 discrete temperatures ranging
from 3 to 59°C. With a few exceptions, Topt and Ea of denitrification and anammox did not differ
in Rhode Island sediments over the seasonal cycle. In microcosm sediments, Ea was
somewhat lower for anammox compared to denitrification across all treatments. However,
Topt did not differ between processes, and neither Ea nor Topt changed with warming or carbon
addition. Thus, the two processes behaved similarly in terms of temperature response, and this
response was not influenced by warming. This led us to reject the hypothesis that anammox is
more cold-adapted than denitrification in our study system. Overall, our study suggests that
temperature responses of both processes can be accurately modeled for temperate regions in the
future using a single set of parameters, which are likely not to change over the next century as a
result of predicted climate warming. We further conclude that climate warming will not directly
alter the partitioning of N flow through anammox and denitrification.This material is based upon work supported by the National Science Foundation
under Grant No. OCE-0852289 to JJR and OCE-0852263, OCE-0927400 and OCE1238212 to
AEG, and Rhode Island Sea Grant to JJR.2017-05-2
Fractal Weyl law for quantum fractal eigenstates
The properties of the resonant Gamow states are studied numerically in the
semiclassical limit for the quantum Chirikov standard map with absorption. It
is shown that the number of such states is described by the fractal Weyl law
and their Husimi distributions closely follow the strange repeller set formed
by classical orbits nonescaping in future times. For large matrices the
distribution of escape rates converges to a fixed shape profile characterized
by a spectral gap related to the classical escape rate.Comment: 4 pages, 5 figs, minor modifications, research at
http://www.quantware.ups-tlse.fr
Two-dimensional ranking of Wikipedia articles
The Library of Babel, described by Jorge Luis Borges, stores an enormous
amount of information. The Library exists {\it ab aeterno}. Wikipedia, a free
online encyclopaedia, becomes a modern analogue of such a Library. Information
retrieval and ranking of Wikipedia articles become the challenge of modern
society. While PageRank highlights very well known nodes with many ingoing
links, CheiRank highlights very communicative nodes with many outgoing links.
In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we
analyze the properties of two-dimensional ranking of all Wikipedia English
articles and show that it gives their reliable classification with rich and
nontrivial features. Detailed studies are done for countries, universities,
personalities, physicists, chess players, Dow-Jones companies and other
categories.Comment: RevTex 9 pages, data, discussion added, more data at
http://www.quantware.ups-tlse.fr/QWLIB/2drankwikipedia
Cross-linguistic study of vocal pathology: perceptual features of spasmodic dysphonia in French-speaking subjects
Clinical characterisation of Spasmodic Dysphonia of the adductor type (SD) in French speakers by Klap and colleagues (1993) appears to differ from that of SD in English. This perceptual analysis aims to describe the phonetic features of French SD. A video of 6 French speakers with SD supplied by Klap and colleagues was analysed for frequency of phonatory breaks, pitch breaks, harshness, creak, breathiness and falsetto voice, rate of production, and quantity of speech output. In contrast to English SD, the French speaking SD patients demonstrated no evidence pitch breaks, but phonatory breaks, harshness and breathiness were prominent features. This verifies the French authorsâ (1993) clinical description. These findings suggest that phonetic properties of a specific language may affect the manifestation of pathology in neurogenic voice disorders
You can't see what you can't see: Experimental evidence for how much relevant information may be missed due to Google's Web search personalisation
The influence of Web search personalisation on professional knowledge work is
an understudied area. Here we investigate how public sector officials
self-assess their dependency on the Google Web search engine, whether they are
aware of the potential impact of algorithmic biases on their ability to
retrieve all relevant information, and how much relevant information may
actually be missed due to Web search personalisation. We find that the majority
of participants in our experimental study are neither aware that there is a
potential problem nor do they have a strategy to mitigate the risk of missing
relevant information when performing online searches. Most significantly, we
provide empirical evidence that up to 20% of relevant information may be missed
due to Web search personalisation. This work has significant implications for
Web research by public sector professionals, who should be provided with
training about the potential algorithmic biases that may affect their judgments
and decision making, as well as clear guidelines how to minimise the risk of
missing relevant information.Comment: paper submitted to the 11th Intl. Conf. on Social Informatics;
revision corrects error in interpretation of parameter Psi/p in RBO resulting
from discrepancy between the documentation of the implementation in R
(https://rdrr.io/bioc/gespeR/man/rbo.html) and the original definition
(https://dl.acm.org/citation.cfm?id=1852106) as per 20/05/201
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Supporting local diversity of habitats and species on farmland: a comparison of three wildlife-friendly schemes
Restoration and maintenance of habitat diversity have been suggested as conservation priorities in farmed landscapes, but how this should be achieved and at what scale are unclear. This study makes a novel comparison of the effectiveness of three wildlife-friendly farming schemes for supporting local habitat diversity and species richness on 12 farms in England.
The schemes were: (i) Conservation Grade (Conservation Grade: a prescriptive, non-organic, biodiversity-focused scheme), (ii) organic agriculture and (iii) a baseline of Entry Level Stewardship (Entry Level Stewardship: a flexible widespread government scheme).
Conservation Grade farms supported a quarter higher habitat diversity at the 100-m radius scale compared to Entry Level Stewardship farms. Conservation Grade and organic farms both supported a fifth higher habitat diversity at the 250-m radius scale compared to Entry Level Stewardship farms. Habitat diversity at the 100-m and 250-m scales significantly predicted species richness of butterflies and plants. Habitat diversity at the 100-m scale also significantly predicted species richness of birds in winter and solitary bees. There were no significant relationships between habitat diversity and species richness for bumblebees or birds in summer.
Butterfly species richness was significantly higher on organic farms (50% higher) and marginally higher on Conservation Grade farms (20% higher), compared with farms in Entry Level Stewardship. Organic farms supported significantly more plant species than Entry Level Stewardship farms (70% higher) but Conservation Grade farms did not (10% higher). There were no significant differences between the three schemes for species richness of bumblebees, solitary bees or birds.
Policy implications. The wildlife-friendly farming schemes which included compulsory changes in management, Conservation Grade and organic, were more effective at increasing local habitat diversity and species richness compared with the less prescriptive Entry Level Stewardship scheme. We recommend that wildlife-friendly farming schemes should aim to enhance and maintain high local habitat diversity, through mechanisms such as option packages, where farmers are required to deliver a combination of several habitats
Existence and stability of viscoelastic shock profiles
We investigate existence and stability of viscoelastic shock profiles for a
class of planar models including the incompressible shear case studied by
Antman and Malek-Madani. We establish that the resulting equations fall into
the class of symmetrizable hyperbolic--parabolic systems, hence spectral
stability implies linearized and nonlinear stability with sharp rates of decay.
The new contributions are treatment of the compressible case, formulation of a
rigorous nonlinear stability theory, including verification of stability of
small-amplitude Lax shocks, and the systematic incorporation in our
investigations of numerical Evans function computations determining stability
of large-amplitude and or nonclassical type shock profiles.Comment: 43 pages, 12 figure
Classical and quantum ergodicity on orbifolds
We extend to orbifolds classical results on quantum ergodicity due to
Shnirelman, Colin de Verdi\`ere and Zelditch, proving that, for any positive,
first-order self-adjoint elliptic pseudodifferential operator P on a compact
orbifold X with positive principal symbol p, ergodicity of the Hamiltonian flow
of p implies quantum ergodicity for the operator P. We also prove ergodicity of
the geodesic flow on a compact Riemannian orbifold of negative sectional
curvature.Comment: 14 page
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