8,000 research outputs found
The AFLOW Fleet for Materials Discovery
The traditional paradigm for materials discovery has been recently expanded
to incorporate substantial data driven research. With the intent to accelerate
the development and the deployment of new technologies, the AFLOW Fleet for
computational materials design automates high-throughput first principles
calculations, and provides tools for data verification and dissemination for a
broad community of users. AFLOW incorporates different computational modules to
robustly determine thermodynamic stability, electronic band structures,
vibrational dispersions, thermo-mechanical properties and more. The AFLOW data
repository is publicly accessible online at aflow.org, with more than 1.7
million materials entries and a panoply of queryable computed properties. Tools
to programmatically search and process the data, as well as to perform online
machine learning predictions, are also available.Comment: 14 pages, 8 figure
Top Quarks as a Window to String Resonances
We study the discovery potential of string resonances decaying to
final state at the LHC. We point out that top quark pair production is a
promising and an advantageous channel for studying such resonances, due to
their low Standard Model background and unique kinematics. We study the
invariant mass distribution and angular dependence of the top pair production
cross section via exchanges of string resonances. The mass ratios of these
resonances and the unusual angular distribution may help identify their
fundamental properties and distinguish them from other new physics. We find
that string resonances for a string scale below 4 TeV can be detected via the
channel, either from reconstructing the semi-leptonic
decay or recent techniques in identifying highly boosted tops.Comment: 22 pages, 6 figure
Manifestations of Institutional Reform and Resistance to Reform in Ulster Workhouses, Ireland, 1838-1855
Fermionic T-duality in the pp-wave limit
AdS5 X S5 and its pp-wave limit are self-dual under transformations involving
eight fermionic T-dualities, a property which accounts for symmetries seen in
scattering amplitudes in N=4 super-Yang-Mills. Despite strong evidence for
similar symmetries in the amplitudes of three-dimensional N=6 ABJM theory, a
corresponding self-duality in the dual geometry AdS4 X CP3 currently eludes us.
Here, working with the type IIA pp-wave limit of AdS4 X CP3 preserving twenty
four supercharges, we show that the pp-wave is self-dual with respect to eight
commuting fermionic T-dualities and not the six expected. In addition, we show
the same symmetry can be found in a superposition pp-wave and a generic pp-wave
with twenty and sixteen unbroken supersymmetries respectively, strongly
suggesting that self-duality under fermionic T-duality may be a symmetry of all
pp-waves.Comment: 21 pages, typos fixe
Classical and Quantum Solitons in the Symmetric Space Sine-Gordon Theories
We construct the soliton solutions in the symmetric space sine-Gordon
theories. The latter are a series of integrable field theories in
1+1-dimensions which are associated to a symmetric space F/G, and are related
via the Pohlmeyer reduction to theories of strings moving on symmetric spaces.
We show that the solitons are kinks that carry an internal moduli space that
can be identified with a particular co-adjoint orbit of the unbroken subgroup H
of G. Classically the solitons come in a continuous spectrum which encompasses
the perturbative fluctuations of the theory as the kink charge becomes small.
We show that the solitons can be quantized by allowing the collective
coordinates to be time-dependent to yield a form of quantum mechanics on the
co-adjoint orbit. The quantum states correspond to symmetric tensor
representations of the symmetry group H and have the interpretation of a fuzzy
geometric version of the co-adjoint orbit. The quantized finite tower of
soliton states includes the perturbative modes at the base.Comment: 53 pages, additional comments and small errors corrected, final
journal versio
Influence of hospital volume of procedures by year on the risk of revision of total hip and knee arthroplasties: a propensity score-matched cohort study
The volume of total hip (THA) and knee arthroplasties (TKA) performed in a hospital per year could be an influential factor on the revision of these procedures. The aims of this study were: To obtain comparable cohorts in higher- and lower-volume hospitals; and to assess the association between the hospital volume and the incidence of revision. Data from patients undergoing THA and TKA caused by osteoarthritis and recorded in the Catalan Arthroplasty Register (RACat) between January 2005 and December 2016 were used. The main explanatory variable was hospital volume by year (higher/lower). The cut-off point was fixed, based on previous research, at 50 THA and 125 TKA procedures/year. To obtain comparable populations, a propensity-score matching method (1:1) was used. Patient characteristics prior to and after matching were compared. To assess differences by volume, subhazard ratios (SHRs) from competing risks models were obtained. After matching, 13,772 THA and 36,316 TKA patients remained in the study. Prior to matching, in both joints, significant differences in all confounders were observed between volume groups. After matching, none of them remained significant. Both in THA and TKA, a higher risk of revision in higher-volume hospitals was observed (THA SHR: 1.25, 95%CI: 1.02-1.53; and TKA SHR: 1.29, 95%CI: 1.16-1.44). Unlike other contexts, currently in Catalonia, higher-volume hospitals have a greater risk of revision than lower-volume hospitals. Further research could be valuable to define context-dependent measures to reduce the incidence of revision.This article is freely available via Open Access. Click on the Publisher URL to access it from the publisher's site
Surgery and COVID-19: Balancing the nosocomial risk a french academic center experience during the epidemic peak
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Clinical pattern of ocular toxoplasmosis treated in a referral centre in Serbia
Purpose To analyze the clinical pattern of ocular toxoplasmosis (OT) in a referral centre in Serbia. Patients and methods The medical records of consecutive patients admitted for OT to the single referral centre for uveitis in Serbia between 2006 and 2010 were retrospectively analyzed. OT was diagnosed on the basis of typical fundus lesions and positive serology for Toxoplasma. Results In a total of 457 uveitis patients, OT was the third leading cause, with 59 patients (12.9%). Most OT cases (73%) were monocular. An active primary retinal lesion was observed in 36% and recurrent OT in 64% patients. Localization of lesions was central/paracentral (44%), juxtapapillar (27%), peripheral (19%), and multifocal (10%). Other ocular manifestations of inflammation included vitritis (44%), anterior uveitis (19%), and retinal vasculitis (10%). Complications included choroidal neovascularization in two and exudative retinal detachment with cataract, glaucoma, and cystoid macular oedema in one patient each. The detection of Toxoplasma-specific IgM antibodies in a single patient indicates a low rate of OT concomitant with acute infection. After treatment, the mean best-corrected visual acuity (BCVA) increased significantly. However, 14 (24%) patients ended up legally blind in the affected eye, of which 2 (3%) with bilateral blindness, all with a very poor BCVA (0.047 +/- 0.055) at presentation. Visual impairment and treatment outcome were both associated with central localization of lesions (P lt 0.0001 and P = 0.006, respectively). Conclusion OT is a significant cause of posterior uveitis in Serbia. Patients should be aware of the recurring nature of OT and react immediately if symptoms occur. Eye (2012) 26, 723-728; doi: 10.1038/eye.2012.20; published online 24 February 201
Type IIB supergravity solutions with AdS5 from Abelian and non-Abelian T dualities
We present a large class of new backgrounds that are solutions of type IIB
supergravity with a warped AdS factor, non-trivial axion-dilaton,
-field and three-form Ramond-Ramond flux but yet have no five-form flux. We
obtain these solutions and many of their variations by judiciously applying
non-Abelian and Abelian T-dualities, as well as coordinate shifts to
AdS IIB supergravity solutions with . We address a number of issues pertaining to charge quantization in
the context of non-Abelian T-duality. We comment on some properties of the
expected dual super conformal field theories by studying their CFT central
charge holographically. We also use the structure of the supergravity Page
charges, central charges and some probe branes to infer aspects of the dual
super conformal field theories.Comment: 71 pages, one table. v2: References added, some normalizations
corrected, results unchange
3-D Ultrastructure of O. tauri: Electron Cryotomography of an Entire Eukaryotic Cell
The hallmark of eukaryotic cells is their segregation of key biological functions into discrete, membrane-bound organelles. Creating accurate models of their ultrastructural complexity has been difficult in part because of the limited resolution of light microscopy and the artifact-prone nature of conventional electron microscopy. Here we explored the potential of the emerging technology electron cryotomography to produce three-dimensional images of an entire eukaryotic cell in a near-native state. Ostreococcus tauri was chosen as the specimen because as a unicellular picoplankton with just one copy of each organelle, it is the smallest known eukaryote and was therefore likely to yield the highest resolution images. Whole cells were imaged at various stages of the cell cycle, yielding 3-D reconstructions of complete chloroplasts, mitochondria, endoplasmic reticula, Golgi bodies, peroxisomes, microtubules, and putative ribosome distributions in-situ. Surprisingly, the nucleus was seen to open long before mitosis, and while one microtubule (or two in some predivisional cells) was consistently present, no mitotic spindle was ever observed, prompting speculation that a single microtubule might be sufficient to segregate multiple chromosomes
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