1,264 research outputs found

    Calculation of the Z+jet cross section including transverse momenta of initial partons

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    We perform calculations of Z+jet cross-section taking into account the transverse momenta of the initial partons. Transverse Momentum Dependent (TMD) parton densities obtained with the Parton Branching method are used and higher order corrections are included via TMD parton showers in the initial state. The predictions are compared to measurements of forward Z+jet production of the LHCb collaboration at s=7\sqrt{s}=7 TeV. We show that the results obtained in kT-factorization are in good agreement with results obtained from a NLO calculation matched with traditional parton showers. We also demonstrate that in the forward rapidity region, kT-factorization and hybrid factorization predictions agree with each other.Comment: 16 pages, 8 figure

    Fluctuating local moments, itinerant electrons and the magnetocaloric effect: the compositional hypersensitivity of FeRh

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    We describe an ab-initio Disordered Local Moment Theory for materials with quenched static compositional disorder traversing first order magnetic phase transitions. It accounts quantitatively for metamagnetic changes and the magnetocaloric effect. For perfect stoichiometric B2-ordered FeRh, we calculate the transition temperature of the ferromagnetic-antiferromagnetic transition to be Tt=T_t = 495K and a maximum isothermal entropy change in 2 Tesla of ΔS=21.1|\Delta S|= 21.1 J~K1^{-1}~kg1^{-1}. A large (40\%) component of ΔS|\Delta S| is electronic. The transition results from a fine balance of competing electronic effects which is disturbed by small compositional changes - e.g. swapping just 2\% Fe of `defects' onto the Rh sublattice makes TtT_t drop by 290K. This hypersensitivity explains the narrow compositional range of the transition and impurity doping effects.Comment: 11 pages, 4 figure

    Study of non-collinear parton dynamics in the prompt photon photoproduction at HERA

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    We investigate the prompt photon photoproduction at HERA within the framework of kt-factorization QCD approach. Our consideration is based on the off-shell matrix elements for the underlying partonic subprocesses. The unintegrated parton densities in a proton and in a photon are determined using the Kimber-Martin-Ryskin (KMR) prescription. Additionally, we use the CCFM-evolved unintegrated gluon as well as valence and sea quark distributions in a proton. A conservative error analisys is performed. Both inclusive and associated with the hadronic jet production rates are investigated. The theoretical results are compared with the recent experimental data taken by the H1 and ZEUS collaborations. We study also the specific kinematical properties of the photon-jet system which are strongly sensitive to the transverse momentum of incoming partons. Using the KMR scheme, the contribution from the quarks emerging from the earlier steps of the parton evolution is estimated and found to be of 15 - 20 approximately.Comment: 22 pages, 13 figures, 2 tabl

    Relaxation paths for single modes of vibrations in isolated molecules

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    A numerical simulation of vibrational excitation of molecules was devised, and used to excite computational models of common molecules into a prescribed, pure, normal vibration mode in the ground electronic state, with varying, controlable energy content. The redistribution of this energy (either non-chaotic or irreversible IVR) within the isolated, free molecule is then followed in time with a view to determining the coupling strength between modes. This work was triggered by the need to predict the general characters of the infrared spectra to be expected from molecules in interstellar space, after being excited by photon absorption or reaction with a radical. It is found that IVR from a pure normal mode is very "restricted" indeed at energy contents of one mode quantum or so. However, as this is increased, or when the excitation is localized, our approach allows us to isolate, describe and quantify a number of interesting phenomena, known to chemists and in non-linear mechanics, but difficult to demonstrate experimentally: frequency dragging, mode locking or quenching or, still, instability near a potential surface crossing, the first step to generalized chaos as the energy content per mode is increased.Comment: 25 pages, 15 figures; accepted by J. Atom. Phys.

    Motif affinity and mass spectrometry proteomic approach for the discovery of cellular AMPK targets: identification of mitochondrial fission factor as a new AMPK substrate

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    AMP-activated protein kinase (AMPK) is a key cellular energy sensor and regulator of metabolic homeostasis. Although it is best known for its effects on carbohydrate and lipid metabolism, AMPK is implicated in diverse cellular processes, including mitochondrial biogenesis, autophagy, and cell growth and proliferation. To further our understanding of energy homeostasis through AMPK-dependent processes, the design and application of approaches to identify and characterise novel AMPK substrates are invaluable. Here, we report an affinity proteomicstrategy for the discovery and validation of AMPK targets using an antibody to isolate proteins containing the phospho-AMPK substrate recognition motif from hepatocytes that had been treated with pharmacological AMPK activators. We identified 57 proteins that were uniquely enriched in the activator-treated hepatocytes, but were absent in hepatocytes lacking AMPK. We focused on two candidates, cingulin and mitochondrial fission factor (MFF), and further characterised/validated them as AMPK-dependent targets by immunoblotting with phosphorylation site-specific antibodies. A small-molecule AMPK activator caused transient phosphorylation of endogenous cingulin at S137 in intestinal Caco2 cells. Multiple splice-variants of MFF appear to express in hepatocytes and we identified a common AMPK-dependent phospho-site (S129) in all the 3 predominant variants spanning the mass range and a short variant-specific site (S146). Collectively, our proteomic-based approach using a phospho-AMPK substrate antibody in combination with genetic models and selective AMPK activators will provide a powerful and reliable platform for identifying novel AMPK-dependent cellular targets

    The CCFM Monte Carlo generator CASCADE 2.2.0

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    CASCADE is a full hadron level Monte Carlo event generator for ep, \gamma p and p\bar{p} and pp processes, which uses the CCFM evolution equation for the initial state cascade in a backward evolution approach supplemented with off - shell matrix elements for the hard scattering. A detailed program description is given, with emphasis on parameters the user wants to change and variables which completely specify the generated events

    Determining the 7Li(n,gamma) cross section via Coulomb dissociation of 8Li

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    The applicability of Coulomb dissociation reactions to determine the cross section for the inverse neutron capture reaction was explored using the reaction 8Li(gamma,n)7Li. A 69.5 MeV/nucleon 8Li beam was incident on a Pb target, and the outgoing neutron and 7Li nucleus were measured in coincidence. The deduced (n,gamma) excitation function is consistent with data for the direct capture reaction 7Li(n,gamma)8Li and with low-energy effective field theory calculations.Comment: Accepted for publication in Phys. Rev.

    Evaluation of optical coherence tomography findings in age-related macular degeneration: a reproducibility study of two independent reading centres

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    International audienceBackground/aims : To determine the reproducibility among readers of two independent certified centers, the Vienna Reading Center (VRC) and the University of Wisconsin-Madison Reading Center (UW-FPRC) for OCT images in age-related macular degeneration (AMD). Methods : Fast macular thickness scans and 6 mm cross hair scans were obtained from 100 eyes with all subtypes of AMD using Stratus OCT. Consensus readings were performed by two certified OCT readers of each Reading Center using their grading protocol. Common variables of both grading protocols, such as presence of cystoid spaces, subretinal fluid, vitreomacular traction and retinal pigment epithelial detachment were compared using kappa statistics. In addition, the intraclass correlation coefficient (ICC) was calculated for center point thickness (CPT) of values remeasured manually in the presence of alignment errors. Results : The reproducibility was dependent on the variable measured with a kappa value of 0.81 for the presence of cystoid spaces, 0.78 for the presence of subretinal fluid and 0.795 for the presence of vitreomacular traction. The lowest reproducibility was found for the presence of retinal pigment epithelial detachment with a kappa value of 0.51. The CPT was remeasured in 29 out of 100 scans at both sites with an ICC of the remeasured thicknesses of 0.92. Conclusion : OCT scan data are crucial in monitoring treatment efficacy in AMD clinical trials. For comparison of results obtained by different Reading Centers, the inter-Reading Center reproducibility is essential. Although the reproducibility is generally high, the reliability depends on the selected morphological parameters
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