1,620 research outputs found

    ACT2 Project: Measuring Energy Savings

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    Pacific Gas and Electric Company has initiated a major demonstration project to test the hypothesis that substantial energy efficiency improvements can be achieved in customer facilities at costs competitive with supply. This paper describes the initial pilot site design, focusing on how energy savings will be tracked and measured. The specific objective of the Advanced Customer Technology Test (ACT^2) for Maximum Energy Efficiency project is to provide scientific field test information, for use by PG&E and its customers, on the maximum energy savings possible, at or below projected competitive costs, by using modern high-efficiency end-use technologies in integrated packages acceptable to the customer. The project is a demand side demonstration analogous to a supply side demonstration, where near commercial advanced technologies are field-tested to determine actual economic and technical performance. PG&E has chosen a "Learn by Doing" approach in the development of the project design, technology design methods, and measurement and monitoring techniques. The project planning is being done in parallel to a "pilot demonstration", with the hope that our planning will be responsive to lessons learned in pilot demonstration. A design to maximize energy efficiency at the pilot demonstration site has been selected, and an energy monitoring system is being designed. The paper describes the pilot site design, the proposed monitoring system and the data processing and analysis system which will be used to collect and analyze the data

    Hadronic vacuum polarization contribution to the anomalous magnetic moments of leptons from first principles

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    We compute the leading, strong-interaction contribution to the anomalous magnetic moment of the electron, muon and tau using lattice quantum chromodynamics (QCD) simulations. Calculations include the effects of uu, dd, ss and cc quarks and are performed directly at the physical values of the quark masses and in volumes of linear extent larger than 6 fm6\,\mathrm{fm}. All connected and disconnected Wick contractions are calculated. Continuum limits are carried out using six lattice spacings. We obtain aeLO−HVP=189.3(2.6)(5.6)×10−14a_e^\mathrm{LO-HVP}=189.3(2.6)(5.6)\times 10^{-14}, aμLO−HVP=711.1(7.5)(17.4)×10−10a_\mu^\mathrm{LO-HVP}=711.1(7.5)(17.4)\times 10^{-10} and aτLO−HVP=341.0(0.8)(3.2)×10−8a_\tau^\mathrm{LO-HVP}=341.0(0.8)(3.2)\times 10^{-8}, where the first error is statistical and the second is systematic.Comment: 17 pages, 8 figures (in 13 PDF files), RevTeX 4.1. Minor changes to results and to text. References updated. Matches version published in Physical Review Letter

    Yin and Yang: CCN3 inhibits the pro-fibrotic effects of CCN2

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    Fibrotic disease is a significant cause of mortality. CCN2 (connective tissue growth factor [CTGF]), a member of the CCN family of matricellular proteins, plays a significant role in driving the fibrogenic effects of cytokines such as transforming growth factor β (TGFβ). It has been proposed that other members of the CCN family can either promote or antagonize the action of CCN2, depending on the context. A recent elegant study published by Bruce Riser and colleagues (Am J Pathol. 174:1725–34, 2009) illustrates that CCN3 (nov) antagonizes the fibrogenic effects of CCN2. This paper, the subject of this commentary, raises the intriguing possibility that CCN3 may be used as a novel anti-fibrotic therapy

    Ab initio calculation of the neutron-proton mass difference

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    The existence and stability of atoms rely on the fact that neutrons are more massive than protons. The measured mass difference is only 0.14% of the average of the two masses. A slightly smaller or larger value would have led to a dramatically different universe. Here, we show that this difference results from the competition between electromagnetic and mass isospin breaking effects. We performed lattice quantum-chromodynamics and quantum-electrodynamics computations with four nondegenerate Wilson fermion flavors and computed the neutron-proton mass-splitting with an accuracy of 300 kilo-electron volts, which is greater than 0 by 5 standard deviations. We also determine the splittings in the Sigma, Xi, D, and Xi(cc) isospin multiplets, exceeding in some cases the precision of experimental measurements

    Lattice Computation of the Nucleon Scalar Quark Contents at the Physical Point

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    We present a QCD calculation of the u, d, and s scalar quark contents of nucleons based on 47 lattice ensembles with Nf=2+1 dynamical sea quarks, 5 lattice spacings down to 0.054 fm, lattice sizes up to 6 fm, and pion masses down to 120 MeV. Using the Feynman-Hellmann theorem, we obtain fNud=0.0405(40)(35) and fNs=0.113(45)(40), which translates into σπN=38(3)(3)  MeV, σsN=105(41)(37)  MeV, and yN=0.20(8)(8) for the sigma terms and the related ratio, where the first errors are statistical and the second errors are systematic. Using isospin relations, we also compute the individual up and down quark contents of the proton and neutron (results in the main text)

    Deformation change in light iridium nuclei from laser spectroscopy

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    Laser spectroscopy measurements have been performed on neutron-deficient and stable Ir isotopes using the COMPLIS experimental setup installed at ISOLDE-CERN. The radioactive Ir atoms were obtained from successive decays of a mass-separated Hg beam deposited onto a carbon substrate after deceleration to 1kV and subsequently laser desorbed. A three-color, two-step resonant scheme was used to selectively ionize the desorbed Ir atoms. The hyperfine structure (HFS) and isotope shift (IS) of the first transition of the ionization path 5d^{7}6s ^{2}^{4}F_{9/2} \to 5d^{7}6s6p ^{6}F_{11/2} at 351.5nm were measured for 182−189^{182-189}Ir, 186Irm^{186}Ir^{m} and the stable 191,193^{191,193}Ir. The nuclear magnetic moments μI and the spectroscopic quadrupole moments Qs were obtained from the HFS spectra and the change of the mean square charge radii from the IS measurements. The sign of μI was experimentally determined for the first time for the masses 182≤A≤189 and the isomeric state 186Irm^{186}Ir^ m . The spectroscopic quadrupole moments of 182^{182}Ir and 183^{183}Ir were measured also for the first time. A large mean square charge radius change between 187^{187}Ir and 186Irg^{186}Ir^g and between 186Irm^{186}Ir^m and 186Irg^{186}Ir ^g was observed corresponding to a sudden increase in deformation: from β2 ≃ + 0.16 for the heavier group A = 193, 191, 189, 187 and 186m to β2 ≥ + 0.2 for the lighter group A = 186g, 185, 184, 183 and 182. These results were analyzed in the framework of a microscopic treatment of an axial rotor plus one or two quasiparticle(s). This sudden deformation change is associated with a change in the proton state that describes the odd-nuclei ground state or that participates in the coupling with the neutron in the odd-odd nuclei. This state is identified with the π3/2+[402] orbital for the heavier group and with the π1/2-[541] orbital stemming from the 1h _9/2 spherical subshell for the lighter group. That last state seems to affect strongly the observed values of the nuclear moments

    Charmonium from Statistical Hadronization of Heavy Quarks -- a Probe for Deconfinement in the Quark-Gluon Plasma

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    We review the statistical hadronization picture for charmonium production in ultra-relativistic nuclear collisions. Our starting point is a brief reminder of the status of the thermal model description of hadron production at high energy. Within this framework an excellent account is achieved of all data for hadrons built of (u,d,s) valence quarks using temperature, baryo-chemical potential and volume as thermal parameters. The large charm quark mass brings in a new (non-thermal) scale which is explicitely taken into account by fixing the total number of charm quarks produced in the collision. Emphasis is placed on the description of the physical basis for the resulting statistical hadronization model. We discuss the evidence for statistical hadronization of charmonia by analysis of recent data from the SPS and RHIC accelerators. Furthermore we discuss an extension of this model towards lower beam energies and develop arguments about the prospects to observe medium modifications of open and hidden charm hadrons. With the imminent start of the LHC accelerator at CERN, exciting prospects for charmonium production studies at the very high energy frontier come into reach. We present arguments that, at such energies, charmonium production becomes a fingerprint of deconfinement: even if no charmonia survive in the quark-gluon plasma, statistical hadronization at the QCD phase boundary of the many tens of charm quarks expected in a single central Pb-Pb collision could lead to an enhanced, rather than suppressed production probability when compared to results for nucleon-nucleon reactions scaled by the number of hard collisions in the Pb-Pb system.Comment: review article, 27 pages, Landoldt review volume "Relativistic Heavy Ion Physics", Reinhard Stock, edito
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