Multiple plasmon resonances in naturally-occurring multiwall nanotubes: infrared spectra of chrysotile asbestos

Chrysotile asbestos is formed by densely packed bundles of multiwall hollow nanotubes. Each wall in the nanotubes is a cylindrically wrapped layer of $Mg_3 Si_2 O_5 (OH)_4$. We show by experiment and theory that the infrared spectrum of chrysotile presents multiple plasmon resonances in the Si-O stretching bands. These collective charge excitations are universal features of the nanotubes that are obtained by cylindrically wrapping an anisotropic material. The multiple plasmons can be observed if the width of the resonances is sufficiently small as in chrysotile.Comment: 4 pages, 5 figures. Revtex4 compuscript. Misprint in Eq.(6) correcte

Tracking Cooper Pairs in a Cuprate Superconductor by Ultrafast Angle-Resolved Photoemission

In high-temperature superconductivity, the process that leads to the formation of Cooper pairs, the fundamental charge carriers in any superconductor, remains mysterious. We use a femtosecond laser pump pulse to perturb superconducting Bi2Sr2CaCu2O8+{\delta}, and study subsequent dynamics using time- and angle-resolved photoemission and infrared reflectivity probes. Gap and quasiparticle population dynamics reveal marked dependencies on both excitation density and crystal momentum. Close to the d-wave nodes, the superconducting gap is sensitive to the pump intensity and Cooper pairs recombine slowly. Far from the nodes pumping affects the gap only weakly and recombination processes are faster. These results demonstrate a new window into the dynamical processes that govern quasiparticle recombination and gap formation in cuprates.Comment: 22 pages, 9 figure

Angular hadron correlations probing the early medium evolution

Hard processes are a well calibrated probe to study heavy-ion collisions. However, the information to be gained from the nuclear suppression factor R_AA is limited, hene one has to study more differential observables to do medium tomography. The angular correlations of hadrons associated with a hard trigger appear suitable as they show a rich pattern when going from low p_T to high p_T. Of prime interest is the fate of away side partons with an in-medium pathlength O(several fm). At high p_T the correlations become dominated by the punchtrough of the away side parton with subsequent fragmentation. We discuss what information about the medium density can be gained from the data.Comment: Talk given at the 19th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2006 (QM 2006), Shanghai, China, 14-20 Nov 200

Relative Feed Values for High Fiber Corn and Conventional Corn Silage for Growing Steers

The relative feed value of a corn variety developed for the primary purpose of corn silage production was evaluated using a 70-d steer growing trial. The high fiber corn (CSV1) and conventional corn (CSV2) varieties were planted in adjacent plots and harvested at approximately 30% DM. Silage varieties were stored in separate bunker silos and allowed to ferment for 52 d. CSVl yielded 5.4 T/acre while CSV2 yielded 4.7 T/acre (DM basis). Variety affected (P\u3c.001) NDF (43.3% vs 38.6%), ADF (24.1% vs 20.2%), lignin (5.7% vs 4.6%), starch (18.69% vs 30.18%) and CP content (7.37% vs 6.89%) of CSVl and CSV2, respectively. IVDMD was not, different (P\u3e. 10) between varieties. One hundred sixty steers were divided into light (516 ± 7.1 Ib.) and heavy (595 ± 9.7 Ib.) BW groups. Steers within those groups were stratified by BW into 10 pens, and pens were randomly assigned to one of two corn silage variety treatments. Steers that were consuming CSV2 tended to gain faster (P\u3c. 10) and were more efficient (P\u3c .05). CSV2 had a greater (P\u3c.05) caloric density than CSV1, as predicted by three prediction methods. Net energy values predicted using NIR were significantly (P=.05) lower than energy values predicted by proximate analysis or by steer performance. This trial demonstrates the need for multiple selection criteria when choosing a corn variety for corn silage production. CSVl yielded 1593 Ib. of beef per acre compared to 1417 Ib. of beef per acre yielded by CSV2 when evaluating varieties on a field-to-feedbunk basis

Impact of observational uncertainties on universal scaling of MHD turbulence

Scaling exponents are the central quantitative prediction of theories of turbulence and in-situ satellite observations of the high Reynolds number solar wind flow have provided an extensive testbed of these. We propose a general, instrument independent method to estimate the uncertainty of velocity field fluctuations. We obtain the systematic shift that this uncertainty introduces into the observed spectral exponent. This shift is essential for the correct interpretation of observed scaling exponents. It is sufficient to explain the contradiction between spectral features of the Elsasser fields observed in the solar wind with both theoretical models and numerical simulations of Magnetohydrodynamic turbulence

Quark Matter 2006: high-pT and jets

An overview of new experimental results on high-\pT{} particle production and jets in heavy ion collisions from the Quark Matter 2006 conference is presented.Comment: Presented at Quark Matter 200

Mach Cones in Quark Gluon Plasma

The experimental azimuthal dihadron distributions at RHIC show a double peak structure in the away side ($\Delta \phi = \pi \pm 1.2$ rad.) for intermediate $p_t$ particles. A variety of models have appeared trying to describe this modification. We will review most of them, with special emphasis in the Conical Flow scenario in which the observed shape is a consequence of the emission of sound by a supersonic high momentum particle propagating in the Quark Gluon Plasma.Comment: 8 pages, 3 figures, Invited plenary talk given at the 19th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2006 (QM 2006), Shanghai, China, 14-20 Nov 200