6,557 research outputs found

    From Linked Data to Relevant Data -- Time is the Essence

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    The Semantic Web initiative puts emphasis not primarily on putting data on the Web, but rather on creating links in a way that both humans and machines can explore the Web of data. When such users access the Web, they leave a trail as Web servers maintain a history of requests. Web usage mining approaches have been studied since the beginning of the Web given the log's huge potential for purposes such as resource annotation, personalization, forecasting etc. However, the impact of any such efforts has not really gone beyond generating statistics detailing who, when, and how Web pages maintained by a Web server were visited.Comment: 1st International Workshop on Usage Analysis and the Web of Data (USEWOD2011) in the 20th International World Wide Web Conference (WWW2011), Hyderabad, India, March 28th, 201

    Achievable efficiencies for probabilistically cloning the states

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    We present an example of quantum computational tasks whose performance is enhanced if we distribute quantum information using quantum cloning. Furthermore we give achievable efficiencies for probabilistic cloning the quantum states used in implemented tasks for which cloning provides some enhancement in performance.Comment: 9 pages, 8 figure

    Efficient local behavioral change strategies to reduce the spread of epidemics in networks

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    It has recently become established that the spread of infectious diseases between humans is affected not only by the pathogen itself but also by changes in behavior as the population becomes aware of the epidemic; for example, social distancing. It is also well known that community structure (the existence of relatively densely connected groups of vertices) in contact networks influences the spread of disease. We propose a set of local strategies for social distancing, based on community structure, that can be employed in the event of an epidemic to reduce the epidemic size. Unlike most social distancing methods, ours do not require individuals to know the disease state (infected or susceptible, etc.) of others, and we do not make the unrealistic assumption that the structure of the entire contact network is known. Instead, the recommended behavior change is based only on an individual's local view of the network. Each individual avoids contact with a fraction of his/her contacts, using knowledge of his/her local network to decide which contacts should be avoided. If the behavior change occurs only when an individual becomes ill or aware of the disease, these strategies can substantially reduce epidemic size with a relatively small cost, measured by the number of contacts avoided

    Membrane Assembly of Simple Helix Homo-Oligomers Studied via Molecular Dynamics Simulations

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    This is the publisher's version. Copyright 2007 by Elsevier.The assembly of simple transmembrane helix homo-oligomers is studied by combining a generalized Born implicit membrane model with replica exchange molecular dynamics simulations to sample the conformational space of various oligomerization states and the native oligomeric conformation. Our approach is applied to predict the structures of transmembrane helices of three proteins—glycophorin A, the M2 proton channel, and phospholamban—using only peptide sequence and the native oligomerization state information. In every case, the methodology reproduces native conformations that are in good agreement with available experimental structural data. Thus, our method should be useful in the prediction of native structures of transmembrane domains of other peptides. When we ignore the experimental constraint on the native oligomerization state and attempt de novo prediction of the structure and oligomerization state based only on sequence and simple energetic considerations, we identify the pentamer as the most stable oligomer for phospholamban. However, for the glycophorin A and the M2 proton channels, we tend to predict higher oligomers as more stable. Our studies demonstrate that reliable predictions of the structure of transmembrane helical oligomers can be achieved when the observed oligomerization state is imposed as a constraint, but that further efforts are needed for the de novo prediction of both structure and oligomeric state

    The Role of Solar Wind Hydrogen in Space Weathering: Insights from Laboratory-Irradiated Northwest Africa 12008

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    Micrometeoroid impacts, solar wind plasma interactions, and regolith gardening drive the complicated and nuanced mechanism of space weathering (or optical maturation); a process by which a materials optical properties are changed as a result of chemical and physical alterations at the surface of grains on airless bodies. Reddened slopes, attenuated absorption bands, and an overall reduction in albedo in the visible and near-IR wavelength ranges are primarily the result of native iron nanoparticle (npFe0) production within glassy rims that form from sputtering and vaporization. The sizes and abundance of these particles provide information about the relative surface exposure age of a particular grain. In addition, many studies have indicated that composition greatly affects the rate at which optical maturation occurs. Despite our understanding of how npFe0 affects optical signatures, the relative roles of micrometeoroid bombardment and solar wind interactions remains undetermined. To simulate the early effects of weathering by the solar wind and to determine thresholds for optical change with respect to a given mineral phase, we irradiated a fine-grained lunar basalt with 1 keV H+ to a fluence of 6.4 x 1016 H+ per sq.cm. Surface alterations within four phases have been evaluated using transmission electron microscopy (TEM). We found that for a given fluence of H+, the extent of damage acquired by each grain was dependent on its composition. No npFe(0) was produced in any of the phases evaluated in this study. These results are consistent with many previous studies conducted using ions of similar energy, but they also provide valuable information about the onset of space weathering and the role of the solar wind during the early stages of optical maturation

    Evaporation/boiling heat transfer characteristics in an artery porous structure

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    Nucleate boiling is one of the most efficient and effective heat transfer modes, but is limited by the critical heat flux (CHF). An innovative artery porous structure was proposed in this work to enhance the CHF based on the concept of "phase separation and modulation" by forming individual flow paths for liquid supply and vapor venting while keeping the liquid/vapor interface located in the porous structure. In the experiment, the porous structure was made of sintered copper microparticles, multiple arteries were machined directly on the heated surface, and water was employed as the working fluid. The experimental results were compared with those on a flat surface, and a unique evaporation/boiling curve for the artery porous structure was revealed. The experiment validated the principle proposed here for CHF enhancement, and a maximum heat flux of 416 W/cm2 on a heating area of 0.78 cm2 was achieved without the occurrence of any dryout. Further increase of heat flux was limited only by the design temperature of the electrical heater, and a much higher CHF can be expected. In addition, the effects of pore size, artery depth and contact condition on the evaporation/boiling heat transfer performance in the artery porous structure were also experimentally investigated, which can guide further design optimizations of this novel structure

    Current status and developing recommendations of tailings dam failure

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    This is the final version of the article. Available from Hindawi Publishing Corporation via the DOI in this record.Tailings dam failure accidents with limited emergency response time and huge potential threats, can often lead to heavy casualties and serious financial losses. In recent years, the decreasing trend of tailings dam failure accidents evidences the development of modern technology and safety management. However, the frequency of major tailings dam failure accidents has increased, rather than decreased. The 2015 Samarco Accident in Brazil and the 2014 Mount Polley Accident in Canada, along with their disastrous consequences, once again sounded the alarm for the tailings ponds safety. China is now facing a complicated safety situation, with 8869 tailings ponds all over the country, including 1425 “Overhead Tailings Ponds” which represents the tailings ponds that located within 1 km upstream of residential area, workshops, schools or other important facilities. Based on a large amount of relevant research literatures, focusing on three main aspects of accident prevention and control which include safety monitoring, early-warning and emergency preparation, safety management codes and standards, the current status and frontier progress were reviewed in this paper. Furthermore, the relevant problems in China were discussed and several improvement recommendations were put forward, which could provide a reference for the tailings pond accident prevention theoretical research and technological innovation. The result shows: (1) the safety monitoring standards in China are relatively strict. However, the monitoring instruments are lack of the stability, reliability and practicability. Thus the development of specific devices and new technologies is urgently needed. (2) The current early-warning method is lack of diversity and reliability. And further interdisciplinary application of information technology is becoming the developing trend. (3) The emergency management and decision-making should be based on sufficient scientific proof. However the relevant research is limited by test methods and simulating algorithms. (4) China now has built a complete system of safety management codes and standards. But with shortcomings of safety level classification, life-cycle management, change management process, accident investigation and so on, there is still a long way to go

    The potential for autonomic neuromodulation to reduce perioperative complications and pain: a systematic review and meta-analysis

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    BACKGROUND: Autonomic dysfunction promotes organ injury after major surgery through numerous pathological mechanisms. Vagal withdrawal is a key feature of autonomic dysfunction, and it may increase the severity of pain. We systematically evaluated studies that examined whether vagal neuromodulation can reduce perioperative complications and pain. METHODS: Two independent reviewers searched PubMed, EMBASE, and the Cochrane Register of Controlled Clinical Trials for studies of vagal neuromodulation in humans. Risk of bias was assessed; I2 index quantified heterogeneity. Primary outcomes were organ dysfunction (assessed by measures of cognition, cardiovascular function, and inflammation) and pain. Secondary outcomes were autonomic measures. Standardised mean difference (SMD) using the inverse variance random-effects model with 95% confidence interval (CI) summarised effect sizes for continuous outcomes. RESULTS: From 1258 records, 166 full-text articles were retrieved, of which 31 studies involving patients (n=721) or volunteers (n=679) met the inclusion criteria. Six studies involved interventional cardiology or surgical patients. Indirect stimulation modalities (auricular [n=23] or cervical transcutaneous [n=5]) were most common. Vagal neuromodulation reduced pain (n=10 studies; SMD=2.29 [95% CI, 1.08-3.50]; P=0.0002; I2=97%) and inflammation (n=6 studies; SMD=1.31 [0.45-2.18]; P=0.003; I2=91%), and improved cognition (n=11 studies; SMD=1.74 [0.96-2.52]; P<0.0001; I2=94%) and cardiovascular function (n=6 studies; SMD=3.28 [1.96-4.59]; P<0.00001; I2=96%). Five of six studies demonstrated autonomic changes after vagal neuromodulation by measuring heart rate variability, muscle sympathetic nerve activity, or both. CONCLUSIONS: Indirect vagal neuromodulation improves physiological measures associated with limiting organ dysfunction, although studies are of low quality, are susceptible to bias and lack specific focus on perioperative patients

    An Exact Characterization of the Generalization Error for the Gibbs Algorithm

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    Various approaches have been developed to upper bound the generalization error of a supervised learning algorithm. However, existing bounds are often loose and lack of guarantees. As a result, they may fail to characterize the exact generalization ability of a learning algorithm.Our main contribution is an exact characterization of the expected generalization error of the well-known Gibbs algorithm (a.k.a. Gibbs posterior) using symmetrized KL information between the input training samples and the output hypothesis. Our result can be applied to tighten existing expected generalization error and PAC-Bayesian bounds. Our approach is versatile, as it also characterizes the generalization error of the Gibbs algorithm with data-dependent regularizer and that of the Gibbs algorithm in the asymptotic regime, where it converges to the empirical risk minimization algorithm. Of particular relevance, our results highlight the role the symmetrized KL information plays in controlling the generalization error of the Gibbs algorithm

    Monovalent counterion distributions at highly charged water interfaces: Proton-transfer and Poisson-Boltzmann theory

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    Surface sensitive synchrotron-X-ray scattering studies reveal the distributions of monovalent ions next to highly charged interfaces. A lipid phosphate (dihexadecyl hydrogen-phosphate) was spread as a monolayer at the air-water interface, containing CsI at various concentrations. Using anomalous reflectivity off and at the L3L_3 Cs+^+ resonance, we provide, for the first time, spatial counterion distributions (Cs+^+) next to the negatively charged interface over a wide range of ionic concentrations. We argue that at low salt concentrations and for pure water the enhanced concentration of hydroniums H3_3O+^+ at the interface leads to proton-transfer back to the phosphate group by a high contact-potential, whereas high salt concentrations lower the contact-potential resulting in proton-release and increased surface charge-density. The experimental ionic distributions are in excellent agreement with a renormalized-surface-charge Poisson-Boltzmann theory without fitting parameters or additional assumptions
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