Strong Correlations Produce the Curie-Weiss Phase of Nax_{x}CoO2_2

Within the t-J model we study several experimentally accessible properties of the 2D-triangular lattice system Na$_x$CoO$_2$, using a numerically exact canonical ensemble study of 12 to 18 site triangular toroidal clusters as well as the icosahedron. Focusing on the doping regime of $x\sim0.7$, we study the temperature dependent chemical potential, specific heat, magnetic susceptibility and the dynamic Hall coefficient $R_H(T,\omega)$ as well as the magnetic field dependent thermopower. We find a crossover between two phases near $x \sim 0.75$ in susceptibility and field suppression of the thermopower arising from strong correlations. An interesting connection is found between the temperature dependence of the diamagnetic susceptibility and the Hall-coefficient. We predict a large thermopower enhancement, arising from {\em transport corrections} to the Heikes-Mott formula, in a model situation where the sign of hopping is reversed from that applicable to Na$_x$CoO$_2$.Comment: 5 pages, 4 figure

Finite temperature properties of the triangular lattice t-J model, applications to Nax_xCoO2_2

We present a finite temperature ($T$) study of the t-J model on the two-dimensional triangular lattice for the negative hopping $t$, as relevant for the electron-doped Na$_x$CoO$_2$ (NCO). To understand several aspects of this system, we study the $T$-dependent chemical potential, specific heat, magnetic susceptibility, and the dynamic Hall-coefficient across the entire doping range. We show systematically, how this simplest model for strongly correlated electrons describes a crossover as function of doping ($x$) from a Pauli-like weakly spin-correlated metal close to the band-limit (density $n=2$) to the Curie-Weiss metallic phase ($1.5<n<1.75$) with pronounced anti-ferromagnetic (AFM) correlations at low temperatures and Curie-Weiss type behavior in the high-temperature regime. Upon further reduction of the doping, a new energy scale, dominated by spin-interactions ($J$) emerges (apparent both in specific heat and susceptibility) and we identify an effective interaction $J_{eff}(x)$, valid across the entire doping range. This is distinct from Anderson's formula, as we choose here $t<0$, hence the opposite sign of the usual Nagaoka-ferromagnetic situation. This expression includes the subtle effect of weak kinetic AFM - as encountered in the infinitely correlated situation ($U=\infty$). By explicit computation of the Kubo-formulae, we address the question of practical relevance of the high-frequency expression for the Hall coefficient $R_H^*$. We hope to clarify some open questions concerning the applicability of the t-J model to real experimental situations through this study

Open and Hidden Charm Production in dAA Collisions at RHIC and LHC

We discuss aspects of open and hidden charm production in deuterium-nucleus collisions at RHIC and LHC energies. We describe calculations of the total $c \bar c$ cross section and the charm quark transverse momentum distributions. We next explain how shadowing and moderate nuclear absorption can explain the PHENIX $J/\psi$ dAu/$pp$ ratios and predict the combined effect of shadowing and absorption in 6.2 TeV d+Pb collisions.Comment: 6 pages, 4 figures, European Physics Journal conference proceedings style files included, in proceedings of Hard Probes, 2004 Ericeira, Portuga

Ecological Studies of Wolves on Isle Royale Annual Report 2020-2021

Annual Report 2020-2021https://digitalcommons.mtu.edu/wolf-annualreports/1000/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 2019-2020

Annual Report 2019-2020https://digitalcommons.mtu.edu/wolf-annualreports/1001/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 2018-2019

Annual Report 2018-2019https://digitalcommons.mtu.edu/wolf-annualreports/1002/thumbnail.jp

Ecological Studies of Wolves on Isle Royale Annual Report 2021-2022

Annual Report 2021-2022https://digitalcommons.mtu.edu/wolf-annualreports/1063/thumbnail.jp

Swimming Wolves, Canis lupus, Attack a Swimming Moose, Alces alces

In August 2008 at a small pond on Isle Royale, Michigan, we saw three Wolves (Canis lupus) run towards and leap at or onto a cow Moose (Alces alces) standing at the shore's edge in water ca. 1.7 m deep. The Moose swam out into the pond with the Wolves swimming in pursuit while attempting, with occasional success, to climb on the back of the Moose. The chase eventually moved out of our view, but a week later we found a Wolf-eaten cow on the pond's shoreline where we estimated it might have been killed. The animal was ca. 14-yr old with arthritic lesions in the pelvic region. This is apparently the first published report of swimming Wolves attacking and killing a swimming Moose, the kill likely having been made as the Moose emerged from the pond. Remains of a second kill in that pond were found shortly thereafter