1,882 research outputs found

    Multi-black rings and the phase diagram of higher-dimensional black holes

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    Configurations of multiple concentric black rings play an important role in determining the pattern of branchings, connections and mergers between different phases of higher-dimensional black holes. We examine them using both approximate and (in five dimensions) exact methods. By identifying the role of the different scales in the system, we argue that it is possible to have multiple black ring configurations in which all the rings have equal temperature and angular velocity. This allows us to correct and improve in a simple, natural manner, an earlier proposal for the phase diagram of singly-rotating black holes in D6D\geq 6.Comment: 14 pages, 2 figure

    The problematic backreaction of SUSY-breaking branes

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    In this paper we investigate the localisation of SUSY-breaking branes which, in the smeared approximation, support specific non-BPS vacua. We show, for a wide class of boundary conditions, that there is no flux vacuum when the branes are described by a genuine delta-function. Even more, we find that the smeared solution is the unique solution with a regular brane profile. Our setup consists of a non-BPS AdS_7 solution in massive IIA supergravity with smeared anti-D6-branes and fluxes T-dual to ISD fluxes in IIB supergravity.Comment: 27 pages, Latex2e, 5 figure

    Using genetic algorithms to generate test sequences for complex timed systems

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    The generation of test data for state based specifications is a computationally expensive process. This problem is magnified if we consider that time con- straints have to be taken into account to govern the transitions of the studied system. The main goal of this paper is to introduce a complete methodology, sup- ported by tools, that addresses this issue by represent- ing the test data generation problem as an optimisa- tion problem. We use heuristics to generate test cases. In order to assess the suitability of our approach we consider two different case studies: a communication protocol and the scientific application BIPS3D. We give details concerning how the test case generation problem can be presented as a search problem and automated. Genetic algorithms (GAs) and random search are used to generate test data and evaluate the approach. GAs outperform random search and seem to scale well as the problem size increases. It is worth to mention that we use a very simple fitness function that can be eas- ily adapted to be used with other evolutionary search techniques

    Enzyme‐assisted aqueous extraction of Kalahari melon seed oil: optimization using response surface methodology

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    Enzymatic extraction of oil from Kalahari melon seeds was investigated and evaluated by response surface methodology (RSM). Two commercial protease enzyme products were used separately: Neutrase® 0.8 L and Flavourzyme® 1000 L from Novozymes (Bagsvaerd, Denmark). RSM was applied to model and optimize the reaction conditions namely concentration of enzyme (20–50 g kg−1 of seed mass), initial pH of mixture (pH 5–9), incubation temperature (40–60 °C), and incubation time (12–36 h). Well fitting models were successfully established for both enzymes: Neutrase 0.8 L (R 2 = 0.9410) and Flavourzyme 1000 L (R 2 = 0.9574) through multiple linear regressions with backward elimination. Incubation time was the most significant reaction factor on oil yield for both enzymes. The optimal conditions for Neutrase 0.8 L were: an enzyme concentration of 25 g kg−1, an initial pH of 7, a temperature at 58 °C and an incubation time of 31 h with constant shaking at 100 rpm. Centrifuging the mixture at 8,000g for 20 min separated the oil with a recovery of 68.58 ± 3.39%. The optimal conditions for Flavourzyme 1000 L were enzyme concentration of 21 g kg−1, initial pH of 6, temperature at 50 °C and incubation time of 36 h. These optimum conditions yielded a 71.55 ± 1.28% oil recovery

    Lorentz violation, Gravity, Dissipation and Holography

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    We reconsider Lorentz Violation (LV) at the fundamental level. We show that Lorentz Violation is intimately connected with gravity and that LV couplings in QFT must always be fields in a gravitational sector. Diffeomorphism invariance must be intact and the LV couplings transform as tensors under coordinate/frame changes. Therefore searching for LV is one of the most sensitive ways of looking for new physics, either new interactions or modifications of known ones. Energy dissipation/Cerenkov radiation is shown to be a generic feature of LV in QFT. A general computation is done in strongly coupled theories with gravity duals. It is shown that in scale invariant regimes, the energy dissipation rate depends non-triviallly on two characteristic exponents, the Lifshitz exponent and the hyperscaling violation exponent.Comment: LateX, 51 pages, 9 figures. (v2) References and comments added. Misprints correcte

    Definitive and adjuvant radiotherapy for sinonasal squamous cell carcinomas: a single institutional experience

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    Background: The aim of this study was to evaluate the disease outcomes of patients treated with definitive and adjuvant radiotherapy for squamous cell carcinomas of the nasal cavity and paranasal sinuses in a single institution. Methods: Between 2007–2012 patients were retrospectively identified from electronic databases who had undergone surgery and adjuvant radiotherapy or definitive radiotherapy for sinonasal squamous cell carcinomas with curative intent. Results: Fourty three patients with sinonasal squamous cell carcinoma were identified (22 nasal cavity, 21 paranasal sinuses). 31/43 (72 %) had T3 or T4 disease; nodal stage was N0 in 38, N1 in 4, Na/b in 0 and N2c in 1 patient. Median age was 67 years (range 41–86). 18 (42 %) received definitive and 25 (58 %) adjuvant radiotherapy. Radiotherapy was delivered using either conventional radiotherapy (n = 39) or intensity modulated radiotherapy (n = 4). Elective neck radiotherapy was delivered to two patients. Chemotherapy was delivered to 6/43 (14 %) of patients. Two-year local control, regional control, distant metastases free survival, progression free survival, cause specific survival and overall survival were 81 %, 90 %, 95 %, 71 %, 84 % and 80 % respectively. There was no significant difference in outcome comparing patients who underwent surgery and adjuvant radiotherapy with patients receiving definitive radiotherapy (2 year locoregional disease free survival 75 % and 70 % respectively, p = 0.98). Pooly differentiated tumours were significantly associated with inferior disease outcomes. Local, regional, combined local and regional, and distant failure occurred in 7 (16 %), 3 (7 %), 1 (2 %) and 2 (5 %) of patients; all 3 regional recurrences were in patients with nasal cavity squamous cell carcinomas who had not undergone elective neck treatment. Conclusions: Definitive or adjuvant radiotherapy provides an effective treatment for sinonasal malignancies. The main pattern of failure remains local, suggesting the need for investigation of intensified local therapy. Whilst remaining uncommon, the cases of regional failure mean that the merits of elective lymph node treatment should be considered on an individual basis

    Stationary Black Holes: Uniqueness and Beyond

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    The spectrum of known black-hole solutions to the stationary Einstein equations has been steadily increasing, sometimes in unexpected ways. In particular, it has turned out that not all black-hole-equilibrium configurations are characterized by their mass, angular momentum and global charges. Moreover, the high degree of symmetry displayed by vacuum and electro-vacuum black-hole spacetimes ceases to exist in self-gravitating non-linear field theories. This text aims to review some developments in the subject and to discuss them in light of the uniqueness theorem for the Einstein-Maxwell system.Comment: Major update of the original version by Markus Heusler from 1998. Piotr T. Chru\'sciel and Jo\~ao Lopes Costa succeeded to this review's authorship. Significantly restructured and updated all sections; changes are too numerous to be usefully described here. The number of references increased from 186 to 32

    Metabolomics demonstrates divergent responses of two Eucalyptus species to water stress

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    Past studies of water stress in Eucalyptus spp. generally highlighted the role of fewer than five “important” metabolites, whereas recent metabolomic studies on other genera have shown tens of compounds are affected. There are currently no metabolite profiling data for responses of stress-tolerant species to water stress. We used GC–MS metabolite profiling to examine the response of leaf metabolites to a long (2 month) and severe (Ψpredawn < −2 MPa) water stress in two species of the perennial tree genus Eucalyptus (the mesic Eucalyptus pauciflora and the semi-arid Eucalyptus dumosa). Polar metabolites in leaves were analysed by GC–MS and inorganic ions by capillary electrophoresis. Pressure–volume curves and metabolite measurements showed that water stress led to more negative osmotic potential and increased total osmotically active solutes in leaves of both species. Water stress affected around 30–40% of measured metabolites in E. dumosa and 10–15% in E. pauciflora. There were many metabolites that were affected in E. dumosa but not E. pauciflora, and some that had opposite responses in the two species. For example, in E. dumosa there were increases in five acyclic sugar alcohols and four low-abundance carbohydrates that were unaffected by water stress in E. pauciflora. Re-watering increased osmotic potential and decreased total osmotically active solutes in E. pauciflora, whereas in E. dumosa re-watering led to further decreases in osmotic potential and increases in total osmotically active solutes. This experiment has added several extra dimensions to previous targeted analyses of water stress responses in Eucalyptus, and highlights that even species that are closely related (e.g. congeners) may respond differently to water stress and re-waterin

    A hippocampal Cdk5 pathway regulates extinction of contextual fear

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    Treatment of emotional disorders involves the promotion of extinction processes, which are defined as the learned reduction of fear. The molecular mechanisms underlying extinction have only begun to be elucidated. By employing genetic and pharmacological approaches in mice, we show here that extinction requires downregulation of Rac-1 and cyclin-dependent kinase 5 (Cdk5), and upregulation of p21 activated kinase-1 (PAK-1) activity. This is physiologically achieved by a Rac-1–dependent relocation of the Cdk5 activator p35 from the membrane to the cytosol and dissociation of p35 from PAK-1. Moreover, our data suggest that Cdk5/p35 activity prevents extinction in part by inhibition of PAK-1 activity in a Rac-1–dependent manner. We propose that extinction of contextual fear is regulated by counteracting components of a molecular pathway involving Rac-1, Cdk5 and PAK-1. Our data suggest that this pathway could provide a suitable target for therapeutic treatment of emotional disorders.National Institutes of Health (U.S.) (Grant NS051874)Alexander von Humboldt-Stiftung (German Research Foundation Fellowship)European Neuroscience Institute Goettinge

    Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

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    Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente
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