2,721 research outputs found

    Study and teaching of the Italian language in the British Isles

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    Ad Lucem: QED parton distribution functions in the MMHT framework

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    We present the MMHT2015qed PDF set, resulting from the inclusion of QED corrections to the existing set of MMHT Parton Distribution Functions (PDFs), and which contain the photon PDF of the proton. Adopting an input distribution from the LUXqed formulation, we discuss our methods of including QED effects for the full, coupled DGLAP evolution of all partons with QED at O(α) , O(ααS) , O(α2) . While we find consistency for the photon PDF of the proton with other recent sets, building on this we also present a set of QED corrected neutron PDFs and provide the photon PDF separated into its elastic and inelastic contributions. The effect of QED corrections on the other partons and the fit quality is investigated, and the sources of uncertainty for the photon are outlined. Finally we explore the phenomenological implications of this set, giving the partonic luminosities for both the elastic and inelastic contributions to the photon and the effect of our photon PDF on fits to high mass Drell–Yan production, including the photon-initiated channel

    Charm and beauty quark masses in the MMHT2014 global PDF analysis

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    We investigate the variation in the MMHT2014 PDFs when we allow the heavy-quark masses mcmc and mbmb to vary away from their default values. We make PDF sets available in steps of Δmc=0.05 GeVΔmc=0.05 GeV and Δmb=0.25 GeVΔmb=0.25 GeV , and present the variation in the PDFs and in the predictions. We examine the comparison to the HERA data on charm and beauty structure functions and note that in each case the heavy-quark data, and the inclusive data, have a slight preference for lower masses than our default values. We provide PDF sets with three and four active quark flavours, as well as the standard value of five flavours. We use the pole mass definition of the quark masses, as in the default MMHT2014 analysis, but briefly comment on the MS¯¯¯¯¯¯¯MS¯ definition

    MMHT PDFs: Updates and Outlook

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    We present the latest results of studies within the MMHT PDF framework. We discuss the impact of the most recent ATLAS 7 TeV jet data, demonstrating that while a good fit can be achieved for individual jet rapidity bins, it is not possible to achieve a good description of the data when all bins are fitted. We examine the role that the experimental correlated systematic uncertainties play in this, and demonstrate that by simply decorrelating no more than two sources of error between rapidity bins, a remarkably improved description of the data can be achieved. We then study the impact of NNLO corrections, showing that a mild decrease in the fit quality is produced. We also present the results of including new LHC W, Z, W + c and tt¯ data on the MMHT14 PDF set, showing that a marked decrease in the s + ¯s uncertainty is in particular achieved. Finally, some discussion of the latest work towards the inclusion of the photon PDF within the MMHT framework is presented

    Estimation of Buttiker-Landauer traversal time based on the visibility of transmission current

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    We present a proposal for the estimation of B\"uttiker-Landauer traversal time based on the visibility of transmission current. We analyze the tunneling phenomena with a time-dependent potential and obtain the time-dependent transmission current. We found that the visibility is directly connected to the traversal time. Furthermore, this result is valid not only for rectangular potential barrier but also for general form of potential to which the WKB approximation is applicable . We compared these results with the numerical values obtained from the simulation of Nelson's quantum mechanics. Both of them fit together and it shows our method is very effective to measure experimentally the traversal time.Comment: 12 pages, REVTeX, including 7 eps figure

    Preeclampsia is associated with compromized maternal synthesis of long chain polyunsaturated fatty acids leading to offspring deficiency

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    Obesity and excessive lipolysis are implicated in preeclampsia (PE). Intrauterine growth restriction is associated with low maternal body mass index and decreased lipolysis. Our aim was to assess how maternal and offspring fatty acid metabolism is altered in mothers in the third trimester of pregnancy with PE (n=62) or intrauterine growth restriction (n=23) compared with healthy pregnancies (n=164). Markers of lipid metabolism and erythrocyte fatty acid concentrations were measured. Maternal adipose tissue fatty acid composition and mRNA expression of adipose tissue fatty acid–metabolizing enzymes and placental fatty acid transporters were compared. Mothers with PE had higher plasma triglyceride (21%, P<0.001) and nonesterified fatty acid (50%, P<0.001) concentrations than controls. Concentrations of major n−6 and n−3 long-chain polyunsaturated fatty acids in erythrocytes were 23% to 60% lower (all P<0.005) in PE and intrauterine growth restriction mothers and offspring compared with controls. Subcutaneous adipose tissue Δ−5 and Δ−6 desaturase and very long-chain fatty acid elongase mRNA expression was lower in PE than controls (respectively, mean [SD] control 3.38 [2.96] versus PE 1.83 [1.91], P=0.030; 3.33 [2.25] versus 1.03 [0.96], P<0.001; 0.40 [0.81] versus 0.00 [0.00], P=0.038 expression relative to control gene [square root]). Low maternal and fetal long-chain polyunsaturated fatty acid concentrations in PE may be the result of decreased maternal synthesis

    Spectroscopic Investigation of the Activation of a Chromium-Pyrrolyl Ethene Trimerization Catalyst

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    1-Hexene is an important α-olefin for polyethylene production and is produced from ethene. Recent developments in the α-olefin industry have led to the successful commercialization of ethene trimerization catalysts. An important industrially applied ethene trimerization system uses a mixture of chromium 2-ethylhexanoate, AlEt3, AlEt2Cl, and 2,5-dimethylpyrrole (DMP). Here, we have studied the activation of this system using catalytic and spectroscopic experiments (XAS, EPR, and UV–vis) under conditions employed in industry. First, chromium 2-ethylhexanoate was prepared and characterized to be [Cr3O­(RCO2)6(H2O)3]­Cl. Next, the activation of chromium 2-ethylhexanoate with AlEt3, AlEt2Cl, and DMP was studied, showing immediate reduction (<5 ms) of the trinuclear Cr­(III) carboxylate and formation of a neutral polynuclear Cr­(II) carboxylate complex. Over time, this Cr­(II) carboxylate complex is partially converted into a chloro-bridged dinuclear Cr­(II) pyrrolyl complex. In cyclohexane, small quantities of an unknown Cr­(I) complex (∼1% after 1 h) are observed, while in toluene, the quantity of Cr­(I) is much higher (∼23% after 1 h). This is due to the formation of cationic bis­(tolyl)­Cr­(I) complexes, which likely leads to the observed inferior performance using toluene as the reaction solvent. Catalytic studies allow us to exclude some of the observed Cr­(I) and Cr­(II) complexes as the active species in this catalytic system. Using this combination of techniques, we have been able to structurally characterize complexes of this selective Cr-catalyzed trimerization system under conditions which are employed in industry

    Energy prices in Europe. Evidence of persistence across markets

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    This paper deals with the behavior of energy price changes and how their shocks exert an impact on suppliers and consumers in different markets. For this purpose, a fractional integration model is used to evaluate the persistence and mean reversion in prices across the major European markets (Germany, France, Italy, UK, Spain). We compare the results with other major players as the US and Japan, to understand, first, if the European behavior is different, and second, if geopolitical shocks that are affecting this market are expected to be permanent. Empirical results show evidence of mean reversion properties in European prices, though some minor differences arise from market to market that apparently, are not associated with the energy generation strategies followed by each country. Thus, it will likely be expected following the current energy shocks the series will recover due to natural market forces, without the need for additional policies
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