Charge-Transfer Excitations in the Model Superconductor HgBa2_2CuO4+δ_{\bf 4+\delta}

We report a Cu $K$-edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa$_2$CuO$_{4+\delta}$ at optimal doping ($T_{\rm c} = 96.5$ K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly-dispersive ($< 0.5$ eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a charge-transfer pseudogap deep in the superconducting phase. Quite generally, our data demonstrate the importance of exploring the incident photon energy dependence of the RIXS cross section.Comment: 5 pages, 3 figure

Where and Why Do Coastal Retrogressive Thaw Slumps Develop?

Retrogressive thaw slumps (RTSs) are among the most active landforms in the Arctic; their number has increased tremendously over the past decades. While processes initiating discrete RTSs are well defined, little research has been done on a regional scale to reveal the major terrain controls on their development. Our research provides new insights into the dynamics of coastal RTSs. We reveal the main geomorphic factors determining the development of RTSs along a 238 km coastal segment of the Yukon Coastal Plain, Canada. We 1) show the current extent of RTSs, 2) ascertain the factors controlling their activity and initiation, and 3) explain the differences in density and coverage of RTSs. We mapped and classified the RTSs based on high-resolution satellite images acquired in 2011. We derived the terrain characteristics for each RTS and highlighted the main terrain controls over their development using univariate regression trees. We tested the response variables (RTSs activity, initiation, density and coverage) against 16 environmental variables. We detected 287 coastal RTSs in the study area. Both the activity and the initiation of the RTSs were influenced by coastal geomorphology: active RTSs and new RTSs occurred primarily on terrain with slope angles greater than 3.9° and 5.9°, respectively. The density and coverage of RTSs within each coastal segment were constrained by the volume and thickness of massive ice bodies. Coastal erosion appears to have only an indirect effect on the development of RTSs by maintaining the best conditions for RTSs to reactivate

Unraveling the Nature of Charge Excitations in La2_2CuO4_4 with Momentum-Resolved Cu KK-edge Resonant Inelastic X-ray Scattering

Results of model calculations using exact diagonalization reveal the orbital character of states associated with different Raman loss peaks in Cu $K$-edge resonant inelastic X-ray scattering (RIXS) from La$_{2}$CuO$_{4}$. The model includes electronic orbitals necessary to highlight non-local Zhang-Rice singlet, charge transfer and $d$-$d$ excitations, as well as states with apical oxygen 2$p_z$ character. The dispersion of these excitations is discussed with prospects for resonant final state wave-function mapping. A good agreement with experiments emphasizes the substantial multi-orbital character of RIXS profiles in the energy transfer range 1-6 eV.Comment: Original: 4.5 pages. Replaced: 4 pages and 4 figures with updated content and reference

Soil weathering rates in 21 catchments of the Canadian Shield

Soil mineral weathering represents an essential source of nutrient base cation (Ca, Mg and K) for forest growth in addition to provide a buffering power against precipitation acidity for soils and surface waters. Weathering rates of base cations were obtained for 21 catchments located within the temperate and the boreal forest of the Canadian Shield with the geochemical model PROFILE. Weathering rates ranged from 0.58 to 4.46 kmol&lt;sub&gt;c&lt;/sub&gt; ha&lt;sup&gt;−1&lt;/sup&gt; yr&lt;sup&gt;−1&lt;/sup&gt; and their spatial variation within the studied area was mostly in agreement with spatial variations in soil mineralogy. Weathering rates of Ca and Mg were significantly correlated (&lt;i&gt;r&lt;/i&gt; = 0.80 and 0.64) with their respective lake concentrations. Weathering rates of K and Na did not correlate with lake concentrations of K and Na. The modeled weathering rates for each catchment were also compared with estimations of net catchment exportations. The result show that modeled weathering rates of Ca were not significantly different than the net catchment exportations while modeled weathering rates of Mg were higher by 51%. Larger differences were observed for K and Na weathering rates that were significantly different than net catchment exportations being 6.9 and 2.2 times higher than net exportations, respectively. The results for K were expected given its high reactivity with biotic compartments and suggest that most of the K produced by weathering reactions was retained within soil catchments and/or above ground biomass. This explanation does not apply to Na, however, which is a conservative element in forest ecosystems because of the insignificant needs of Na for soil microorganisms and above ground vegetations. It raises concern about the liability of the PROFILE model to provide reliable values of Na weathering rates. Overall, we concluded that the PROFILE model is powerful enough to reproduce spatial geographical gradients in weathering rates for relatively large areas as well as adequately predict absolute weathering rates values for the sum of base cations, Ca and Mg

Applying dissipative dynamical systems to pseudorandom number generation: Equidistribution property and statistical independence of bits at distances up to logarithm of mesh size

The behavior of a family of dissipative dynamical systems representing transformations of two-dimensional torus is studied on a discrete lattice and compared with that of conservative hyperbolic automorphisms of the torus. Applying dissipative dynamical systems to generation of pseudorandom numbers is shown to be advantageous and equidistribution of probabilities for the sequences of bits can be achieved. A new algorithm for generating uniform pseudorandom numbers is proposed. The theory of the generator, which includes proofs of periodic properties and of statistical independence of bits at distances up to logarithm of mesh size, is presented. Extensive statistical testing using available test packages demonstrates excellent results, while the speed of the generator is comparable to other modern generators.Comment: 6 pages, 3 figures, 3 table

Recent Progress in the Management of Retroperitoneal Sarcoma

Retroperitoneal sarcomas (RPS) are rare tumours that typically present late and carry a poor prognosis even following grossly complete resection. In an attempt to improve the outlook for patients with RPS, sarcoma specialists have employed various adjuvant therapies, including extermal beam radiation, intraoperative radiation, brachyradiation and systemic chemotherapy. This article reviews the presentation and prognosis of RPS, and focuses on the results of new treatment strategies compared with conventional management

[Colored solutions of Yang-Baxter equation from representations of U_{q}gl(2)]

We study the Hopf algebra structure and the highest weight representation of a multiparameter version of $U_{q}gl(2)$. The commutation relations as well as other Hopf algebra maps are explicitly given. We show that the multiparameter universal ${\cal R}$ matrix can be constructed directly as a quantum double intertwiner, without using Reshetikhin's transformation. An interesting feature automatically appears in the representation theory: it can be divided into two types, one for generic $q$, the other for $q$ being a root of unity. When applying the representation theory to the multiparameter universal ${\cal R}$ matrix, the so called standard and nonstandard colored solutions $R(\mu,\nu; {\mu}', {\nu}')$ of the Yang-Baxter equation is obtained.Comment: [14]pages, latex, no figure

Fermion contribution to the static quantities of arbitrarily charged vector bosons

We present an analysis of the one-loop contribution from left- and right-handed fermions to the static electromagnetic properties of an arbitrarily charged no self-conjugate vector boson $V$. Particular emphasis is given to the case of a no self-conjugate neutral boson $V^0$. Regardless the electric charge of the $V$ boson, a fermionic loop can induce the two CP-even form factors but only one CP-odd. As a result the corresponding electric dipole moment is directly proportional to the magnetic quadrupole moment. The CP-odd form factor might be severely suppressed since it requires the presence of both left- and right-handed fermions. The behavior of the form factors is analyzed for several scenarios of the fermion masses in the context of the decoupling theorem.Comment: 12 pages, 3 figures, submitted to Journal of Physics