3,916 research outputs found
Query Expansion for Survey Question Retrieval in the Social Sciences
In recent years, the importance of research data and the need to archive and
to share it in the scientific community have increased enormously. This
introduces a whole new set of challenges for digital libraries. In the social
sciences typical research data sets consist of surveys and questionnaires. In
this paper we focus on the use case of social science survey question reuse and
on mechanisms to support users in the query formulation for data sets. We
describe and evaluate thesaurus- and co-occurrence-based approaches for query
expansion to improve retrieval quality in digital libraries and research data
archives. The challenge here is to translate the information need and the
underlying sociological phenomena into proper queries. As we can show retrieval
quality can be improved by adding related terms to the queries. In a direct
comparison automatically expanded queries using extracted co-occurring terms
can provide better results than queries manually reformulated by a domain
expert and better results than a keyword-based BM25 baseline.Comment: to appear in Proceedings of 19th International Conference on Theory
and Practice of Digital Libraries 2015 (TPDL 2015
The β6/β7 region of the Hsp70 substrate-binding domain mediates heat-shock response and prion propagation.
Hsp70 is a highly conserved chaperone that in addition to providing essential cellular functions and aiding in cell survival following exposure to a variety of stresses is also a key modulator of prion propagation. Hsp70 is composed of a nucleotide-binding domain (NBD) and substrate-binding domain (SBD). The key functions of Hsp70 are tightly regulated through an allosteric communication network that coordinates ATPase activity with substrate-binding activity. How Hsp70 conformational changes relate to functional change that results in heat shock and prion-related phenotypes is poorly understood. Here, we utilised the yeast [PSI +] system, coupled with SBD-targeted mutagenesis, to investigate how allosteric changes within key structural regions of the Hsp70 SBD result in functional changes in the protein that translate to phenotypic defects in prion propagation and ability to grow at elevated temperatures. We find that variants mutated within the β6 and β7 region of the SBD are defective in prion propagation and heat-shock phenotypes, due to conformational changes within the SBD. Structural analysis of the mutants identifies a potential NBD:SBD interface and key residues that may play important roles in signal transduction between domains. As a consequence of disrupting the β6/β7 region and the SBD overall, Hsp70 exhibits a variety of functional changes including dysregulation of ATPase activity, reduction in ability to refold proteins and changes to interaction affinity with specific co-chaperones and protein substrates. Our findings relate specific structural changes in Hsp70 to specific changes in functional properties that underpin important phenotypic changes in vivo. A thorough understanding of the molecular mechanisms of Hsp70 regulation and how specific modifications result in phenotypic change is essential for the development of new drugs targeting Hsp70 for therapeutic purposes
Using satellites to monitor Severn Bridge structure, UK
The Severn Bridge is a large UK suspension bridge. In 2010, a series of field surveys was commissioned to monitor the magnitude and frequencies of the bridgeâs movements, through attaching nine dual-frequency survey grade global navigation satellite system receivers on the bridge and two reference satellite receivers adjacent to the structure. The satellite antenna locations and configuration allow the movements of the north cable to be analysed at four locations, as well as the differential movements of the two suspension cables to each other. In addition, this configuration allows the movements of the tops of the towers to be compared to the cablesâ movements, as well as with each other. All in all, this allowed the relative movements of the various locations on the bridgeâs suspension cables and tower tops to be compared to each other, at a rate of up to 20âHz. Overall, some 3 days of raw code and carrier phase satellite data were gathered. During these sessions, normal traffic loading was experienced. This paper describes the survey, presents a selection of the key results and draws conclusions about the effective use of satellite positioning systems to enhance structural health monitoring.The Highways Agency, Severn River Crossing plc and Mott MacDonal
Adaptive Evolutionary Clustering
In many practical applications of clustering, the objects to be clustered
evolve over time, and a clustering result is desired at each time step. In such
applications, evolutionary clustering typically outperforms traditional static
clustering by producing clustering results that reflect long-term trends while
being robust to short-term variations. Several evolutionary clustering
algorithms have recently been proposed, often by adding a temporal smoothness
penalty to the cost function of a static clustering method. In this paper, we
introduce a different approach to evolutionary clustering by accurately
tracking the time-varying proximities between objects followed by static
clustering. We present an evolutionary clustering framework that adaptively
estimates the optimal smoothing parameter using shrinkage estimation, a
statistical approach that improves a naive estimate using additional
information. The proposed framework can be used to extend a variety of static
clustering algorithms, including hierarchical, k-means, and spectral
clustering, into evolutionary clustering algorithms. Experiments on synthetic
and real data sets indicate that the proposed framework outperforms static
clustering and existing evolutionary clustering algorithms in many scenarios.Comment: To appear in Data Mining and Knowledge Discovery, MATLAB toolbox
available at http://tbayes.eecs.umich.edu/xukevin/affec
Edge Label Placement in Layered Graph Drawing
Many visual languages based on node-link diagrams use edge labels. We describe different strategies of placing edge labels in the context of the layered approach to graph drawing and investigate ways of encoding edge direction in labels. We evaluate the label placement strategies based on both common aesthetic criteria and a controlled experiment. We find that placing labels on their edge can lead to more compact diagrams. Also, placing labels with additional arrows indicating edge direction can help users navigate in large diagrams and is generally preferred by participants of our experiment, outperforming other ways of indicating edge direction
Magnetic Catalysis and Quantum Hall Ferromagnetism in Weakly Coupled Graphene
We study the realization in a model of graphene of the phenomenon whereby the
tendency of gauge-field mediated interactions to break chiral symmetry
spontaneously is greatly enhanced in an external magnetic field. We prove that,
in the weak coupling limit, and where the electron-electron interaction
satisfies certain mild conditions, the ground state of charge neutral graphene
in an external magnetic field is a quantum Hall ferromagnet which spontaneously
breaks the emergent U(4) symmetry to U(2)XU(2).
We argue that, due to a residual CP symmetry, the quantum Hall ferromagnet
order parameter is given exactly by the leading order in perturbation theory.
On the other hand, the chiral condensate which is the order parameter for
chiral symmetry breaking generically obtains contributions at all orders. We
compute the leading correction to the chiral condensate. We argue that the
ensuing fermion spectrum resembles that of massive fermions with a vanishing
U(4)-valued chemical potential. We discuss the realization of parity and charge
conjugation symmetries and argue that, in the context of our model, the charge
neutral quantum Hall state in graphene is a bulk insulator, with vanishing
longitudinal conductivity due to a charge gap and Hall conductivity vanishing
due to a residual discrete particle-hole symmetry.Comment: 35 page
Tracing magnetism and pairing in FeTe-based systems
In order to examine the interplay between magnetism and superconductivity, we
monitor the non- superconducting chalcogenide FeTe and follow its transitions
under insertion of oxygen, doping with Se and vacancies of Fe using
spin-polarized band structure methods (LSDA with GGA) starting from the
collinear and bicollinear magnetic arrangements. We use a supercell of Fe8Te8
as our starting point so that it can capture local changes in magnetic moments.
The calculated values of magnetic moments agree well with available
experimental data while oxygen insertions lead to significant changes in the
bicollinear or collinear magnetic moments. The total energies of these systems
indicate that the collinear-derived structure is the more favorable one prior
to a possible superconducting transition. Using a 8-site Betts-cluster-based
lattice and the Hubbard model, we show why this structure favors electron or
hole pairing and provides clues to a common understanding of charge and spin
pairing in the cuprates, pnictides and chalcogenides
Comets, historical records and vedic literature
A verse in book I of Rigveda mentions a cosmic tree with rope-like aerial
roots held up in the sky. Such an imagery might have ensued from the appearance
of a comet having `tree stem' like tail, with branched out portions resembling
aerial roots. Interestingly enough, a comet referred to as `heavenly tree' was
seen in 162 BC, as reported by old Chinese records. Because of weak surface
gravity, cometary appendages may possibly assume strange shapes depending on
factors like rotation, structure and composition of the comet as well as solar
wind pattern. Varahamihira and Ballala Sena listed several comets having
strange forms as reported originally by ancient seers such as Parashara,
Vriddha Garga, Narada and Garga.
Mahabharata speaks of a mortal king Nahusha who ruled the heavens when Indra,
king of gods, went into hiding. Nahusha became luminous and egoistic after
absorbing radiance from gods and seers. When he kicked Agastya (southern star
Canopus), the latter cursed him to become a serpent and fall from the sky. We
posit arguments to surmise that this Mahabharata lore is a mythical recounting
of a cometary event wherein a comet crossed Ursa Major, moved southwards with
an elongated tail in the direction of Canopus and eventually went out of sight.
In order to check whether such a conjecture is feasible, a preliminary list of
comets (that could have or did come close to Canopus) drawn from various
historical records is presented and discussed.Comment: This work was presented in the International Conference on Oriental
Astronomy held at IISER, Pune (India) during November, 201
The Effect of Adenosine A2A Receptor Antagonists on Hydroxyl Radical, Dopamine, and Glutamate in the Striatum of Rats with Altered Function of VMAT2
It has been shown that a decreased vesicular monoamine transporter (VMAT2) function and the disruption of dopamine (DA) storage is an early contributor to oxidative damage of dopamine neurons in Parkinsonâs disease (PD). In our previous study, we demonstrated that adenosine A2A receptor antagonists suppressed oxidative stress in 6-hydroxydopamine-treated rats suggesting that this effect may account for neuroprotective properties of drugs. In the present study, rats were injected with reserpine (10 mg/kg sc) and 18 h later the effect of the adenosine A2A receptor antagonists 8-(3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on extracellular DA, glutamate and hydroxyl radical formation was studied in the rat striatum using in vivo microdialysis. By disrupting VMAT2 function, reserpine depleted DA stores, and increased glutamate and hydroxyl radical levels in the rat striatum. CSC (1 mg/kg) but not ZM 241385 (3 mg/kg) increased extracellular DA level and production of hydroxyl radical in reserpinised rats. Both antagonists decreased the reserpine-induced increase in extracellular glutamate. l-3,4-Dihydroxyphenylalanine (L-DOPA) (25 mg/kg) significantly enhanced extracellular DA, had no effect on reserpine-induced hydroxyl radical production and decreased extracellular glutamate concentration. CSC but not ZM 241385 given jointly with L-DOPA increased the effect of L-DOPA on extracellular DA and augmented the reserpine-induced hydroxyl radical production. CSC and ZM 241385 did not influence extracellular glutamate level, which was decreased by L-DOPA. It seems that by decreasing the MAO-dependent DA metabolism rate, CSC raised cytosolic DA and by DA autoxidation, it induced hydroxyl radical overproduction. Thus, the methylxanthine A2A receptor antagonists bearing properties of MAO-B inhibitor, like CSC, may cause a risk of oxidative stress resulting from dysfunctional DA storage mechanism in early PD
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