5,716 research outputs found

    Method of Joining Graphite Fibers to a Substrate

    Get PDF
    A method of assembling a metallic-graphite structure includes forming a wetted graphite subassembly by arranging one or more layers of graphite fiber material including a plurality of graphite fibers and applying a layer of metallization material to ends of the plurality of graphite fibers. At least one metallic substrate is secured to the wetted graphite subassembly via the layer of metallization material

    Correlations of the elements of the neutrino mass matrix

    Full text link
    Assuming Majorana nature of neutrinos, we re-investigate, in the light of the recent measurement of the reactor mixing angle, the allowed ranges for the absolute values of the elements of the neutrino mass matrix in the basis where the charged-lepton mass matrix is diagonal. Apart from the derivation of upper and lower bounds on the values of the matrix elements, we also study their correlations. Moreover, we analyse the sensitivity of bounds and correlations to the global fit results of the neutrino oscillation parameters which are available in the literature.Comment: 37 pages, 146 figures, minor corrections, 17 additional figures, version for publication in JHE

    Immobilization of Clover-trapped White-tailed Deer, Odocoileus virginianus, with Medetomidine and Ketamine, and Antagonism with Atipamezole

    Get PDF
    We evaluated the effectiveness of immobilizing Clover-trapped White-tailed Deer (Odocoileus virginanus) with medetomidine hydrochloride (HCl) and ketamine HCl during winter and summer by monitoring immobilization intervals and vital signs. In winter, we captured deer in Clover traps in 1 4-ha research enclosure for relocation to another on-site enclosure (n = 5). In summer, we captured free-ranging deer in Clover traps to attach radio-collars (n = 4). We administered an estimated 0.055 mg/kg medetomidine HCl and 2.5 mg/kg ketamine HCl to adult (> 1.5 years of age) deer and 0.06 mg/kg medetomidine HCl and 2.5 mg/kg ketamine HCl to subadult (< 1.5 years of age) deer. We used an intramuscular injection of atipamezole HCl as the antagonist at a rate of 0.275 mg/kg for adults and 0.3 mg/kg for subadults > 30 minutes post-induction. Mean induction time in winter was 11.2 minutes (SE = 2.5, range = 5.4 - 24.2) and 6.5 minutes (SE = 0.8, range = 6.2 - 7.5) in summer. After atipamezole HCl injection, the mean time to walking was 17.1 minutes (SE = 3.5, range = 7.5 - 41.5 minutes) in winter and 11.3 minutes (SE = 3.8, range = 4.7 - 13.5) in summer. Rectal temperature was relatively constant throughout immobilization; however rectal temperatures of 5 deer (n = 3 in winter; n = 2 in summer) exceeded 40oC, a sign of hyperthermia. Respiration rate and pulse rate peaked at about 20 minutes post-medetomidine HCl and ketamine HCl injection, then generally declined thereafter. No mortalities were observed in our study. Medetomidine HCl and ketamine HCl doses for Clover-trapped White-tailed Deer provided satisfactory induction times, sufficient level of anesthesia for short-distance relocation or radio-collar attachment, and were effectively reversed with an IM injection of atipamezole HCl

    A simple inert model solves the little hierarchy problem and provides a dark matter candidate

    Full text link
    We discuss a minimal extension to the standard model in which two singlet scalar states that only interacts with the Higgs boson is added. Their masses and interaction strengths are fixed by the two requirements of canceling the one-loop quadratic corrections to the Higgs boson mass and providing a viable dark matter candidate. Direct detection of the lightest of these new states in nuclear scattering experiments is possible with a cross section within reach of future experiments.Comment: Finite corrections included. Model modified. Conclusion unchange

    Coupling carbon allocation with leaf and root phenology predicts tree-grass partitioning along a savanna rainfall gradient

    Get PDF
    © Author(s) 2016. The relative complexity of the mechanisms underlying savanna ecosystem dynamics, in comparison to other biomes such as temperate and tropical forests, challenges the representation of such dynamics in ecosystem and Earth system models. A realistic representation of processes governing carbon allocation and phenology for the two defining elements of savanna vegetation (namely trees and grasses) may be a key to understanding variations in tree-grass partitioning in time and space across the savanna biome worldwide. Here we present a new approach for modelling coupled phenology and carbon allocation, applied to competing tree and grass plant functional types. The approach accounts for a temporal shift between assimilation and growth, mediated by a labile carbohydrate store. This is combined with a method to maximize long-term net primary production (NPP) by optimally partitioning plant growth between fine roots and (leaves + stem). The computational efficiency of the analytic method used here allows it to be uniquely and readily applied at regional scale, as required, for example, within the framework of a global biogeochemical model. We demonstrate the approach by encoding it in a new simple carbon-water cycle model that we call HAVANA (Hydrology and Vegetation-dynamics Algorithm for Northern Australia), coupled to the existing POP (Population Orders Physiology) model for tree demography and disturbance-mediated heterogeneity. HAVANA-POP is calibrated using monthly remotely sensed fraction of absorbed photosynthetically active radiation (fPAR) and eddy-covariance-based estimates of carbon and water fluxes at five tower sites along the North Australian Tropical Transect (NATT), which is characterized by large gradients in rainfall and wildfire disturbance. The calibrated model replicates observed gradients of fPAR, tree leaf area index, basal area, and foliage projective cover along the NATT. The model behaviour emerges from complex feedbacks between the plant physiology and vegetation dynamics, mediated by shifting above- versus below-ground resources, and not from imposed hypotheses about the controls on tree-grass co-existence. Results support the hypothesis that resource limitation is a stronger determinant of tree cover than disturbance in Australian savannas

    Large θ13ν\theta_{13}^\nu and Unified Description of Quark and Lepton Mixing Matrices

    Full text link
    We present a revised version of the so-called "yukawaon model", which was proposed for the purpose of a unified description of the lepton mixing matrix UPMNSU_{PMNS} and the quark mixing matrix VCKMV_{CKM}. It is assumed from a phenomenological point of view that the neutrino Dirac mass matrix MDM_D is given with a somewhat different structure from the charged lepton mass matrix MeM_e, although MD=MeM_D=M_e was assumed in the previous model. As a result, the revised model predicts a reasonable value sin22θ130.07\sin^2 2\theta_{13} \sim 0.07 with keeping successful results for other parameters in UPMNSU_{PMNS} as well as VCKMV_{CKM} and quark and lepton mass ratios.Comment: 13 pages, 3 figures, version accepted by EPJ

    BˉXsγ\bar{B}\to X_s \gamma in the Two Higgs Doublet Model up to Next-to-Next-to-Leading Order in QCD

    Get PDF
    We compute three-loop matching corrections to the Wilson coefficients C7C_7 and C8C_8 in the Two Higgs Doublet Model by applying expansions for small, intermediate and large charged Higgs boson masses. The results are used to evaluate the branching ratio of BˉXsγ\bar{B}\to X_s \gamma to next-to-next-to leading order accuracy, and to determine an updated lower limit on the charged Higgs boson mass. We find \mhplus \ge 380 GeV at 95% confidence level when the recently completed BABAR data analysis is taken into account. Our results for the charged Higgs contribution to the branching ratio exhibit considerably weaker sensitivity to the matching scale μ0\mu_0, as compared to previous calculations.Comment: 20 pages, 15 figures; v2: minor modifications, matches published version in JHE

    Coupling carbon allocation with leaf and root phenology predicts tree-grass partitioning along a savanna rainfall gradient

    Full text link
    Abstract. The relative complexity of the mechanisms underlying savanna ecosystem dynamics, in comparison to other biomes such as temperate and tropical forests, challenges the representation of such dynamics in ecosystem and Earth system models. A realistic representation of processes governing carbon allocation and phenology for the two defining elements of savanna vegetation (namely trees and grasses) may be a key to understanding variations in tree/grass partitioning in time and space across the savanna biome worldwide. Here we present a new approach for modelling coupled phenology and carbon allocation, applied to competing tree and grass plant functional types. The approach accounts for a temporal shift between assimilation and growth, mediated by a labile carbohydrate store. This is combined with a method to maximise long-term net primary production (NPP) by optimally partitioning plant growth between fine roots and (leaves + stem). The computational efficiency of the analytic method used here allows it to be uniquely and readily applied at regional scale, as required, for example, within the framework of a global biogeochemical model. We demonstrate the approach by encoding it in a new simple carbon/water cycle model that we call HAVANA (Hydrology and Vegetation-dynamics Algorithm for Northern Australia), coupled to the existing POP (Population Orders Physiology) model for tree demography and disturbance-mediated heterogeneity. HAVANA-POP is calibrated using monthly remotely-sensed fraction of absorbed photosynthetically active radiation (fPAR) and eddy-covariance-based estimates of carbon and water fluxes at 5 tower sites along the Northern Australian Tropical Transect (NATT), which is characterized by large gradients in rainfall and wildfire disturbance. The calibrated model replicates observed gradients of fPAR, tree leaf area index, basal area and foliage projective cover along the NATT. The model behaviour emerges from complex feed-backs between the plant physiology and vegetation dynamics, mediated by shifting above- vs. below-ground resources, and not from imposed hypotheses about the controls on tree/grass co-existence. Results support the hypothesis that resource limitation is a stronger determinant of tree cover than disturbance in Australian savannas. </jats:p

    Origins of Mass

    Get PDF
    Newtonian mechanics posited mass as a primary quality of matter, incapable of further elucidation. We now see Newtonian mass as an emergent property. Most of the mass of standard matter, by far, arises dynamically, from back-reaction of the color gluon fields of quantum chromodynamics (QCD). The equations for massless particles support extra symmetries - specifically scale, chiral, and gauge symmetries. The consistency of the standard model relies on a high degree of underlying gauge and chiral symmetry, so the observed non-zero masses of many elementary particles (WW and ZZ bosons, quarks, and leptons) requires spontaneous symmetry breaking. Superconductivity is a prototype for spontaneous symmetry breaking and for mass-generation, since photons acquire mass inside superconductors. A conceptually similar but more intricate form of all-pervasive (i.e. cosmic) superconductivity, in the context of the electroweak standard model, gives us a successful, economical account of WW and ZZ boson masses. It also allows a phenomenologically successful, though profligate, accommodation of quark and lepton masses. The new cosmic superconductivity, when implemented in a straightforward, minimal way, suggests the existence of a remarkable new particle, the so-called Higgs particle. The mass of the Higgs particle itself is not explained in the theory, but appears as a free parameter. Earlier results suggested, and recent observations at the Large Hadron Collider (LHC) may indicate, the actual existence of the Higgs particle, with mass mH125m_H \approx 125 GeV. In addition to consolidating our understanding of the origin of mass, a Higgs particle with mH125m_H \approx 125 GeV could provide an important clue to the future, as it is consistent with expectations from supersymmetry.Comment: Invited review for the Central European Journal of Physics. This is the supplement to my 2011 Solvay Conference talk promised there. It is adapted from an invited talk given at the Atlanta APS meeting, April 2012. 33 pages, 6 figures. v2: Added update section bringing in the CERN discovery announcemen
    corecore