4,423 research outputs found
Recommending Items in Social Tagging Systems Using Tag and Time Information
In this work we present a novel item recommendation approach that aims at
improving Collaborative Filtering (CF) in social tagging systems using the
information about tags and time. Our algorithm follows a two-step approach,
where in the first step a potentially interesting candidate item-set is found
using user-based CF and in the second step this candidate item-set is ranked
using item-based CF. Within this ranking step we integrate the information of
tag usage and time using the Base-Level Learning (BLL) equation coming from
human memory theory that is used to determine the reuse-probability of words
and tags using a power-law forgetting function.
As the results of our extensive evaluation conducted on data-sets gathered
from three social tagging systems (BibSonomy, CiteULike and MovieLens) show,
the usage of tag-based and time information via the BLL equation also helps to
improve the ranking and recommendation process of items and thus, can be used
to realize an effective item recommender that outperforms two alternative
algorithms which also exploit time and tag-based information.Comment: 6 pages, 2 tables, 9 figure
Radiation of a circulating quark in strongly coupled N=4 super Yang-Mills theory
The energy density and angular distribution of power radiated by a quark
undergoing circular motion in strongly coupled supersymmetric
Yang-Mills (SYM) theory is computed using gauge/gravity duality. The results
are qualitatively similar to that of synchrotron radiation produced by an
electron in circular motion in classical electrodynamics: At large velocities
the quark emits radiation in a narrow beam along its velocity vector with a
characteristic opening angle and radial thickness
scaling like .Comment: 8 pages, 2 figures - Talk presented by D. Nickel at QCD@Work, June
20-23rd, 2010, Martina Franca, Ital
Synchrotron radiation in strongly coupled conformal field theories
Using gauge/gravity duality, we compute the energy density and angular
distribution of the power radiated by a quark undergoing circular motion in
strongly coupled supersymmetric Yang-Mills (SYM) theory. We
compare the strong coupling results to those at weak coupling, and find the
same angular distribution of radiated power, up to an overall prefactor. In
both regimes, the angular distribution is in fact similar to that of
synchrotron radiation produced by an electron in circular motion in classical
electrodynamics: the quark emits radiation in a narrow beam along its velocity
vector with a characteristic opening angle . To an
observer far away from the quark, the emitted radiation appears as a short
periodic burst, just like the light from a lighthouse does to a ship at sea.
Our strong coupling results are valid for any strongly coupled conformal field
theory with a dual classical gravity description.Comment: 20 pages, 8 figures. v2: published version. v4: factor-of-two error
corrected in the time-averaged angular distribution of the power radiated in
scalars in weak coupling N=4 SYM theory; correcting this error has
interesting ramification
Towards a Framework for Supporting User Satisfaction of Conversational Agents according to the Usability Norm DIN EN ISO 9241-11
The acceptance and use of conversational user interfaces (CUIs) which are for example used in Conversational Agents (CAs) such as Alexa and Siri are crucially dependent on their usability—which is often lacking in practice according to user reviews. Referring to the usability norm DIN EN ISO 9241-11, a usable product, system or service can be used to achieve specified goals with high levels of effectiveness, efficiency, and satisfaction. However, in the case of conversational agents, the bidirectional interaction experience differs from the use of other input devices. We are proposing a conceptual framework for evaluating the design of CAs with regard to the interaction principles as per DIN EN ISO 9241-110. To increase the level of satisfaction in particular, we focus on the new principle of user engagement in order to ensure trust and welfare and specifically self-determination to ensure the success and positive user experience of CUIs
Encased Cantilevers for Ultra-Low-Noise Force Spectroscopy of Proteins and Ligand Receptor Complexes
c-Maf Transcription Factor Regulates ADAMTS-12 Expression in Human Chondrogenic Cells.
ObjectiveADAMTS (a disintegrin and metalloproteinase with thrombospondin type-1 motif) zinc metalloproteinases are important during the synthesis and breakdown of cartilage extracellular matrix. ADAMTS-12 is up-regulated during in vitro chondrogenesis and embryonic limb development; however, the regulation of ADAMTS-12 expression in cartilage remains unknown. The transcription factor c-Maf is a member of Maf family of basic ZIP (bZIP) transcription factors. Expression of c-Maf is highest in hypertrophic chondrocytes during embryonic development and postnatal growth. We hypothesize that c-Maf and ADAMTS-12 are co-expressed during chondrocyte differentiation and that c-Maf regulates ADAMTS-12 expression during chondrogenesis.DesignPromoter analysis and species alignments identified potential c-Maf binding sites in the ADAMTS-12 promoter. c-Maf and ADAMTS-12 co-expression was monitored during chondrogenesis of stem cell pellet cultures. Luciferase expression driven by ADAMTS-12 promoter segments was measured in the presence and absence of c-Maf, and synthetic oligonucleotides were used to confirm specific binding of c-Maf to ADAMTS-12 promoter sequences.ResultsIn vitro chondrogenesis from human mesenchymal stem cells revealed co-expression of ADAMTS-12 and c-Maf during differentiation. Truncation and point mutations of the ADAMTS-12 promoter evaluated in reporter assays localized the response to the proximal 315 bp of the ADAMTS-12 promoter, which contained a predicted c-Maf recognition element (MARE) at position -61. Electorphoretic mobility shift assay confirmed that c-Maf directly interacted with the MARE at position -61.ConclusionsThese data suggest that c-Maf is involved in chondrocyte differentiation and hypertrophy, at least in part, through the regulation of ADAMTS-12 expression at a newly identified MARE in its proximal promoter
Large-scale mass distribution in the Illustris simulation
Observations at low redshifts thus far fail to account for all of the baryons
expected in the Universe according to cosmological constraints. A large
fraction of the baryons presumably resides in a thin and warm-hot medium
between the galaxies, where they are difficult to observe due to their low
densities and high temperatures. Cosmological simulations of structure
formation can be used to verify this picture and provide quantitative
predictions for the distribution of mass in different large-scale structure
components. Here we study the distribution of baryons and dark matter at
different epochs using data from the Illustris simulation. We identify regions
of different dark matter density with the primary constituents of large-scale
structure, allowing us to measure mass and volume of haloes, filaments and
voids. At redshift zero, we find that 49 % of the dark matter and 23 % of the
baryons are within haloes more massive than the resolution limit of M. The filaments of the cosmic web host a further 45 % of the
dark matter and 46 % of the baryons. The remaining 31 % of the baryons reside
in voids. The majority of these baryons have been transported there through
active galactic nuclei feedback. We note that the feedback model of Illustris
is too strong for heavy haloes, therefore it is likely that we are
overestimating this amount. Categorizing the baryons according to their density
and temperature, we find that 17.8 % of them are in a condensed state, 21.6 %
are present as cold, diffuse gas, and 53.9 % are found in the state of a
warm-hot intergalactic medium.Comment: 12 pages, 15 figure
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