University of Shefield

United Kingdom

University of Shefield

United Kingdom

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Gade M.,Humboldt University of Berlin | Hall M.,Edge Hill University | Huurdeman H.,University of Amsterdam | Kamps J.,University of Amsterdam | And 4 more authors.
CEUR Workshop Proceedings | Year: 2015

Users looking for books online are confronted with both professional meta-data and user-generated content. The goal of the Interactive Social Book Search Track was to investigate how users used these two sources of information, when looking for books in a leisure context. To this end participants recruited by four teams performed two different tasks using one of two book-search interfaces. Additionally one of the two interfaces also investigated whether user performance can be improved by providing a user-interface that supports multiple search stages.

Sana H.,University of Amsterdam | De Koter A.,University of Amsterdam | De Koter A.,University Utrecht | De Mink S.E.,US Space Telescope Science Institute | And 17 more authors.
Astronomy and Astrophysics | Year: 2013

Context. The Tarantula Nebula in the Large Magellanic Cloud is our closest view of a starburst region and is the ideal environment to investigate important questions regarding the formation, evolution and final fate of the most massive stars. Aims. We analyze the multiplicity properties of the massive O-type star population observed through multi-epoch spectroscopy in the framework of the VLT-FLAMES Tarantula Survey. With 360 O-type stars, this is the largest homogeneous sample of massive stars analyzed to date. Methods. We use multi-epoch spectroscopy and variability analysis to identify spectroscopic binaries. We also use a Monte-Carlo method to correct for observational biases. By modeling simultaneously the observed binary fraction, the distributions of the amplitudes of the radial velocity variations and the distribution of the time scales of these variations, we constrain the intrinsic current binary fraction and period and mass-ratio distributions. Results.We observe a spectroscopic binary fraction of 0:35±0.03, which corresponds to the fraction of objects displaying statistically significant radial velocity variations with an amplitude of at least 20 km s-1.We compute the intrinsic binary fraction to be 0.51±0:04. We adopt power-laws to describe the intrinsic period and mass-ratio distributions: f (log10 P=d) ∼ (log10 P=d)π (with log10 P=d in the range 0.15-3.5) and f (q) ∼ qκ with 0.1 ≤ q = M2=M1 < 1.0. The power-law indexes that best reproduce the observed quantities are π = -0.45 ± 0.30 and κ = -1.0 ± 0.4. The period distribution that we obtain thus favours shorter period systems compared to an Öpik law (π = 0). The mass ratio distribution is slightly skewed towards low mass ratio systems but remains incompatible with a random sampling of a classical mass function (κ = -2.35). The binary fraction seems mostly uniform across the field of view and independent of the spectral types and luminosity classes. The binary fraction in the outer region of the field of view (r > 7.8', i.e. ≈117 pc) and among the O9.7 I/II objects are however significantly lower than expected from statistical fluctuations. The observed and intrinsic binary fractions are also lower for the faintest objects in our sample (Ks > 15.5 mag), which results from observational effects and the fact that our O star sample is not magnitude-limited but is defined by a spectral-type cutoff. We also conclude that magnitude-limited investigations are biased towards larger binary fractions. Conclusions. Using the multiplicity properties of the O stars in the Tarantula region and simple evolutionary considerations, we estimate that over 50% of the current O star population will exchange mass with its companion within a binary system. This shows that binary interaction is greatly affecting the evolution and fate of massive stars, and must be taken into account to correctly interpret unresolved populations of massive stars. © ESO 2013.

Couto N.,University of Manchester | Couto N.,University of Shefield | Malys N.,University of Manchester | Malys N.,University of Warwick | And 3 more authors.
Journal of Proteome Research | Year: 2013

Glutathione reductase (Glr1) is a low abundance protein involved in defense mechanisms against reactive oxygen species. Expressed on cytosolic ribosomes, the same gene, GLR1, uses alternative start codons to generate two forms of Glr1. Translation from the first AUG codon generates the mitochondrial form incorporating a presequence necessary for import; translation from the second AUG codon yields the cytosolic counterpart. Proteomic strategies were used to analyze the N-terminal sequences and the turnover of Saccharomyces cerevisiae Glr1. The N-terminus of cytosolic Glr1 was found normally to be N-acetylserine. When a Glr1-overproducing strain was employed, unprocessed mitochondrial Glr-1 with N-terminal acetylmethionine also accumulated in the cytosol. The processed mitochondrial Glr1 was surprisingly found to have three alternative N-termini, none of them acetylated. Mitochondrial Glr1 was turned over faster than the cytosolic form by a factor of about 2, consistent with the importance of redox homeostasis in the mitochondria. These experiments also allowed us to estimate the extent of "leaky scanning" in the synthesis of Glr1. Surprisingly, the second AUG appears to be responsible for most of the cellular Glr1. This is the first report of protein turnover measurements of a low-abundance protein distributed in different compartments of a eukaryotic cell. © 2013 American Chemical Society.

Han L.,University College London | Hipwell J.H.,University College London | Tanner C.,ETH Zurich | Taylor Z.,University of Shefield | And 4 more authors.
Physics in Medicine and Biology | Year: 2012

Physically realistic simulations for large breast deformation are of great interest for many medical applications such as cancer diagnosis, image registration, surgical planning and image-guided surgery. To support fast, large deformation simulations of breasts in clinical settings, we proposed a patient-specific biomechanical modelling framework for breasts, based on an open-source graphics processing unit-based, explicit, dynamic, nonlinear finite element (FE) solver. A semi-automatic segmentation method for tissue classification, integrated with a fully automated FE mesh generation approach, was implemented for quick patient-specific FE model generation. To solve the difficulty in determining material parameters of soft tissues in vivo for FE simulations, a novel method for breast modelling, with a simultaneous material model parameter optimization for soft tissues in vivo, was also proposed. The optimized deformation prediction was obtained through iteratively updating material model parameters to maximize the image similarity between the FE-predicted MR image and the experimentally acquired MR image of a breast. The proposed method was validated and tested by simulating and analysing breast deformation experiments under plate compression. Its prediction accuracy was evaluated by calculating landmark displacement errors. The results showed that both the heterogeneity and the anisotropy of soft tissues were essential in predicting large breast deformations under plate compression. As a generalized method, the proposed process can be used for fast deformation analyses of soft tissues in medical image analyses and surgical simulations. © 2012 Institute of Physics and Engineering in Medicine.

Sudholt D.,University of Shefield
GECCO 2015 - Companion Publication of the 2015 Genetic and Evolutionary Computation Conference | Year: 2015

Insight into probabilistic models underlying ACO and PSO. How design choices and parameters affect (bounds on) running times. How simple ACO algorithms optimize unimodal functions and plateaus. Results for ACO in combinatorial optimization. First analyses of basic PSO algorithms in discrete and continuous spaces.

Guttmann W.,University of Ulm | Struth G.,University of Shefield | Weber T.,University of Cambridge
CEUR Workshop Proceedings | Year: 2011

We have implemented a repository of algebraic structures and theorems in the theorem proving environment Isabelle/HOL. It covers variants of Kleene algebras and relation algebras with many of their models. Most theorems have been obtained by automated theorem proving within Isabelle. Main purposes of the repository are the engineering of algebraic theories for computing systems and their application in formal program development. This paper describes the present state of the repository, illustrates its potential by a theory engineering and a program verification example, and discusses the most important directions for future work.

Lee P.J.,University of Liverpool | Lee P.J.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Kang J.,University of Shefield
Acta Acustica united with Acustica | Year: 2015

Street geometry is one of main issues on urban design which influence sound environment as well as urban climate in a street canyon. A parametric study was performed in order to investigate the influence of height-to-width ratio (H/W) on sound fields in urban streets in terms of sound pressure level (SPL), reverberation time (T30), and early decay time (EDT). A computer simulation technique based on a hybrid method combining ray tracing and image source modeling was adopted, and an omnidirectional sound source was used. Four typical idealized urban streets were modeled, with street widths of 6 m, 13 m, 20 m, and 27 m, respectively. The H/W ratio was then changed in seven steps with varying building heights while the widths of streets were fixed. Comparisons with experimental studies showed that the computer simulation models produce reliable results for SPL and T30. It was found that the variation of SPL was afected by the H/W ratio only for narrow urban streets, and the T30 and EDT increased with an increase in the H/W ratio for both narrow and wide streets. It was also observed that the T30 decreased with increasing scattering coeficients, and the EDT significantly increased as scattering coeficients increased for H/W of 3 and 6. A line source representing road trafic noise was found to produce diferent tendencies in SPL and EDT, showing that SPL and EDT were relatively constant along the length. © S. Hirzel Verlag • EAA.

Vere J.,University of Shefield | Joshi R.,University of Shefield
The International journal of oral & maxillofacial implants | Year: 2012

PURPOSE: The aim of this systematic review was to assess the methodologic and statistical quality of prospective case series of treatment interventions of dental implant surgery and prosthodontics published between 2004 and 2008.MATERIALS AND METHODS: Prospective case series were identified following detailed searches of the Medline, EMBASE, and CINAHL databases. Identified studies were independently assessed by two nonblinded reviewers for 10 key methodologic and statistical domains. Information was collected using a customized data collection sheet.RESULTS: The initial search yielded 1,484 studies. Following application of inclusion criteria, 31 prospective case series reports that did not present the same patient material were identified for this review. Interexaminer agreement was assessed for all domains (median kappa score, 0.84). All disagreements were resolved by discussion. The source of funding was unclear in 20 studies (65%). Treatment protocol was adequately described in 21 studies (68%), and eligibility criteria were adequately reported in 24 studies (77%). Only two studies (6.5%) tested the intraexaminer/interexaminer reliability of at least one outcome of interest. Inferential statistical analysis was presented in 21 studies. However, this analysis was only considered appropriate in 12 studies (57%). Confidence intervals were reported in four studies (13%).CONCLUSIONS: Prospective case series of treatment interventions of dental implant surgery and Prosthodontics are poorly analyzed and rarely test the reliability of outcome measures. These particular studies have limited external validity and appear to provide little unbiased evidence to support clinical decision-making.

Mazumdar S.,University of Shefield | Zhang Z.,University of Shefield
CEUR Workshop Proceedings | Year: 2016

This paper describes an extension of the TableMiner+ sys- tem, an open source Semantic Table Interpretation system that annotates Web tables using Linked Data in an effective and efficient approach. It adds a graphical user interface to TableMiner+, to facilitate the visualization and correction of automatically generated annotations. This makes TableMiner+ an ideal tool for the semi-automatic creation of high-quality semantic annotations on tabular data, which facilitates the publication of Linked Data on the Web.

Caicedo-Nunez C.H.,University of Southampton | Veres S.M.,University of Shefield
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2013

Problems dealing with coordination of autonomous vehicles usually assume that the agents share a universal orientation in their local reference frames. Although the sensing requirements to satisfy this assumption can sometimes be low, they cannot always be guaranteed. The basic problem of frame alingment is studied here, in the absence of orientation sensors, by exploiting the notions of rigidity, visibility and communication graphs. First the relationship is examined between geometric rigidity of a formation and the agents' ability to agree on a shared orientation to their local frames. Our main results are then formulated in terms of visibility and communication graphs using cyclic graph coverage. Cases when only distances are measurable are also investigated, in which case the motion capabilities of the agents need to be exploited to resolve ambiguity caused by symmetry. © 2013 IFAC.

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