Geographic Variation in Wood Properties of Pinus Tecunumanii

Wood properties of Pinus tecunumanii were studied on 108 trees collected from four different departments of Guatemala (Baja Verapaz, Zacapa, Totonicapán, and El Quiché). Unextracted and extracted specific gravities were calculated from 108 Cores (one per tree) of 4.5 mm diameter. The specific gravity varied from 0.51 to 0.56 with a weak decreasing trend from east to west. Most of the extractives were found in the core segment closest to the pith. Tracheid measurements were recorded on 11-mm cores from Baja Verapaz and Zacapa with tracheid length, cell-wall thickness, lumen width, and tracheid diameter being recorded. With the exception of tracheid length, all the measured cell characteristics showed highly statistical differences between locations and among trees. Most of the variation was within and between trees. Tracheid diameter and lumen width were highly correlated. The wood of the Tecun Umán pine showed extreme variability, especially in tracheid dimensions. Overall, however, the wood of this species is quite usable for both solid wood and pulp products

The spin state transition in LaCoO3_{3}; revising a revision

Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-$L_{2,3}$ edge we reveal that the spin state transition in LaCoO$_{3}$ can be well described by a low-spin ground state and a triply-degenerate high-spin first excited state. From the temperature dependence of the spectral lineshapes we find that LaCoO$_{3}$ at finite temperatures is an inhomogeneous mixed-spin-state system. Crucial is that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low-/intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance and inelastic neutron data

Evidence for orbital ordering in LaCoO3

We present powder and single crystal X-ray diffraction data as evidence for a monoclinic distortion in the low spin (S=0) and intermediate spin state (S=1) of LaCoO3. The alternation of short and long bonds in the ab plane indicates the presence of eg orbital ordering induced by a cooperative Jahn-Teller distortion. We observe an increase of the Jahn-Teller distortion with temperature in agreement with a thermally activated behavior of the Co3+ ions from a low-spin ground state to an intermediate-spin excited state.Comment: Accepted to Phys. Rev.

Looking at Vector Space and Language Models for IR using Density Matrices

In this work, we conduct a joint analysis of both Vector Space and Language Models for IR using the mathematical framework of Quantum Theory. We shed light on how both models allocate the space of density matrices. A density matrix is shown to be a general representational tool capable of leveraging capabilities of both VSM and LM representations thus paving the way for a new generation of retrieval models. We analyze the possible implications suggested by our findings.Comment: In Proceedings of Quantum Interaction 201

Geologische Untersuchungen an Sedimenten des indisch-pakistanischen Kontinentalrandes (Arabischs Meer)

From the R./V. "Meteor" and the Pakistan F./V. "Machhera" sediments from the Indian-Pakistan continental margin habe been investigated in order to delineate the facies distribution of the recent deposits. One of the several objectives of this study was to find out how far the suspended matter of the Indus River is being transported into the Arabian Sea. A close genetic relationship was recognised between the oceanographic conditions of the water masses (chemistry and currents) and the characteristics of the sediments. The activity of the monsoons is reflected by the rhythmic lamination of the sediments of the upper continental slope. The suspended matter from the Indus River can be traced far into the Arabian Sea. The clay minerals show the following tendenciey from litoral to abyssal regions and from the top ot the cores downward: detrital clay minerals (chlorite, muscovite, illite) - degraded clay minerals (montmorillonite, mixed-layer minerals) - "re-formational" minerals (illite). The biostratigraphic investigations of the sedimentds combined with several C14-dates results in sedimentation rates from >50 cm/1000 years at the upper continental slope decreasing to about 1 cm/1000 years inhe faunal composition proves the existende of a climatic optimum during part of the Holocene. The geochemical investigation of the recent pore fluids demonstrates that their composition very soon assumes the characteristics of fossil inerstitial waters (cf. V. Marchig, in this vol.). The results will be published in Meteor-Forschungsergebnisse, Reihe C

Specific heat and magnetization study on single crystals of a frustrated, quasi one-dimensional oxide: Ca3Co2O6

Specific heat and magnetization measurements have been carried out under a range of magnetic fields on single crystals of Ca3Co2O6. This compound is composed of Ising magnetic chains that are arranged on a triangular lattice. The intrachain and interchain couplings are ferromagnetic and antiferromagnetic, respectively. This situation gives rise to geometrical frustration, that bears some similarity to the classical problem of a two-dimensional Ising triangular antiferromagnet. This paper reports on the ordering process at low-T and the possibility of one-dimensional features at high-T.Comment: 7 pages, 6 figures, accepted for publication in PR

Leaf-level physiology in four subalpine plants in tephra-impacted forests during drought

Ecological impacts of climate change in the Pacific Northwest may hinge on acclimation to drier summers, highlighting the importance of plant physiological studies in forests. Evaluating dominant forest plant species under old-growth and managed forest conditions is similarly important as timber harvest might change microclimates and alter drought effects on plants. We examined water potential and gas exchange rates of four dominant plant species in understories of subalpine forests of the Pacific Northwest region of the United States during 2015 - a year with drought conditions representative of future climate projections. We examined two conifer species (Abies amabilis Douglas ex J. Forbes and Tsuga heterophylla (Raf.) Sarg.) and two huckleberry species (Vaccinium membranaceum Douglas ex Torr. and Vaccinium ovalifolium Sm.) in old-growth and formerly clear-cut forests at two elevations. Contrary to expectations, we found no evidence of hydraulic stress, and there were no significant differences between old-growth and clear-cut stands, consistent with an edaphic buffering effect in this volcanic landscape. Variation in stem elongation rates among years also indicated the lack of a strong drought response in 2015. Water potential, photosynthesis, and stomatal conductance varied among species and among elevations. In combination, our results help constrain expected physiological activity of understory species in subalpine forests and emphasize the importance of the edaphic context (e.g., tephra deposits) in framing expectations for the responses to drought

Electronic States in Two-Dimensional Triangular Cobalt Oxides: Role of Electronic Correlation

We obtain the electronic states and structures of two-dimensional cobalt oxides, Na$_{x}$CoO$_{2}$ (x=0, 0.35, 0.5 and 0.75) by utilizing the full-potential linear muffin-tin orbitals (FP-LMTO) methods, from which some essential electronic interaction parameters are estimated: the bare on-site Coulomb interaction of cobalt U$_{dd}$=7.5 eV renormalizes to 5 eV for x=0.35, the $pd$ hybridizations t$_{pd\sigma}$ and t$_{pd\pi}$ are -1.40 and 0.70 eV, respectively. The density of states at E$_{F}$ decreases from 6-7 states/eV in the local density approximation (LDA) to about 1.0 states/eV in the LDA+U scheme. The role of the intercalation of water molecules and the microscopic mechanism of the superconductivity in Na$_{0.35}$CoO$_{2}$$\cdot$mH$_{2}$O is discussed.Comment: minor errors correcte