1,495 research outputs found

    Ethyl α-​phenylhydrazono-​2-​furanpropionate

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    The title compd. is orthorhombic, space group Pca21, with a 11.115(1)​, b 8.170(1)​, and c 15.341(1) Å; Z = 4 for dm = 1.290 and dc = 1.293. The structure was solved by direct methods and refined to an R of 0.041 for 1033 reflections. At. coordinates are given. The structure conforms to the non-​H-​bonded α form. The hydrazine moiety is planar with sp2 hybridization at the N and neighboring atoms. Intermol. N-​H...O hydrogen bonds link the mols. into chains along a

    Measurement of the elastic tensor of SmScO3 and NdSc03 using resonant ultrasound spectroscopy with ab initio calculations

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    The complete elastic tensors of SmScO3 and NdScO3 were measured using resonant ultrasound spectroscopy (RUS) in combination with ab-initio calculations. Measurement of the elastic tensor of these recently synthesized single crystal RE scandates is essential for understanding dynamic lattice applications including phonon confinement, strain induced thin film growth and superlattice construction. On average, the experimental elastic constants differed by less than 5% of the theoretical values, further validating the accuracy of modern ab-initio calculations as a means of estimating the initial elastic constants used in RUS measurements

    HESFIRE: a global fire model to explore the role of anthropogenic and weather drivers

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    Vegetation fires are a major driver of ecosystem dynamics and greenhouse gas emissions. Anticipating potential changes in fire activity and their impacts relies first on a realistic model of fire activity (e.g., fire incidence and interannual variability) and second on a model accounting for fire impacts (e.g., mortality and emissions). In this paper, we focus on our understanding of fire activity and describe a new fire model, HESFIRE (Human–Earth System FIRE), which integrates the influence of weather, vegetation characteristics, and human activities on fires in a stand-alone framework. It was developed with a particular emphasis on allowing fires to spread over consecutive days given their major contribution to burned areas in many ecosystems. A subset of the model parameters was calibrated through an optimization procedure using observation data to enhance our knowledge of regional drivers of fire activity and improve the performance of the model on a global scale. Modeled fire activity showed reasonable agreement with observations of burned area, fire seasonality, and interannual variability in many regions, including for spatial and temporal domains not included in the optimization procedure. Significant discrepancies are investigated, most notably regarding fires in boreal regions and in xeric ecosystems and also fire size distribution. The sensitivity of fire activity to model parameters is analyzed to explore the dominance of specific drivers across regions and ecosystems. The characteristics of HESFIRE and the outcome of its evaluation provide insights into the influence of anthropogenic activities and weather, and their interactions, on fire activityinfo:eu-repo/semantics/publishedVersio

    Global fire activity patterns (1996-2006) and climatic influence: an analysis using World Fire Atlas

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    Vegetation fires have been acknowledged as an environmental process of global scale, which affects the chemical composition of the troposphere, and has profound ecological and climatic impacts. However, considerable uncertainty remains, especially concerning intra and inter-annual variability of fire incidence. The main goals of our globalscale study were to characterise spatial-temporal patterns of fire activity, to identify broad geographical areas with similar vegetation fire dynamics, and to analyse the relationship between fire activity and the El Ni˜no-Southern Oscillation. This study relies on 10 years (mid 1996–mid 2006) of screened European Space Agency World Fire Atlas (WFA) data, obtained from Along Track Scanning Radiometer (ATSR) and Advanced ATSR (AATSR) imagery. Empirical Orthogonal Function analysis was used to reduce the dimensionality of the dataset. Regions of homogeneous fire dynamics were identified with cluster analysis, and interpreted based on their eco-climatic characteristics. The impact of 1997–1998 El Ni˜no is clearly dominant over the study period, causing increased fire activity in a variety of regions and ecosystems, with variable timing. Overall, this study provides the first global decadal assessment of spatialtemporal fire variability and confirms the usefulness of the screened WFA for global fire ecoclimatology researc

    Configuration mixing in 188^{188}Pb : band structure and electromagnetic properties

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    In the present paper, we carry out a detailed analysis of the presence and mixing of various families of collective bands in 188^{188}Pb. Making use of the interacting boson model, we construct a particular intermediate basis that can be associated with the unperturbed bands used in more phenomenological studies. We use the E2 decay to construct a set of collective bands and discuss in detail the B(E2)-values. We also perform an analysis of these theoretical results (Q, B(E2)) to deduce an intrinsic quadrupole moment and the associated quadrupole deformation parameter, using an axially deformed rotor model.Comment: submitted to pr

    Passive scalar convection in 2D long-range delta-correlated velocity field: Exact results

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    The letter presents new field-theoretical approach to 2D passive scalar problem. The Gaussian form of the distribution for the Lyapunov exponent is derived and its parameters are found explicitly.Comment: 11 pages, RevTex 3.0, IFUM-94/455/January-F

    Equilibrium states of the pressure function for products of matrices

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    Let {Mi}i=1ℓ\{M_i\}_{i=1}^\ell be a non-trivial family of d×dd\times d complex matrices, in the sense that for any n∈Nn\in \N, there exists i1...in∈{1,...,ℓ}ni_1... i_n\in \{1,..., \ell\}^n such that Mi1...Min≠0M_{i_1}... M_{i_n}\neq {\bf 0}. Let P ⁣:(0,∞)→RP \colon (0,\infty)\to \R be the pressure function of {Mi}i=1ℓ\{M_i\}_{i=1}^\ell. We show that for each q>0q>0, there are at most dd ergodic qq-equilibrium states of PP, and each of them satisfies certain Gibbs property.Comment: 12 pages. To appear in DCD

    Novel anisotropy in the superconducting gap structure of Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} probed by quasiparticle heat transport

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    Since the nature of pairing interactions is manifested in the superconducting gap symmetry, the exact gap structure, particularly any deviation from the simple d_{x^2-y^2} symmetry, would help elucidating the pairing mechanism in high-T_c cuprates. Anisotropic heat transport measurement in Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} (Bi-2212) reveals that the quasiparticle populations are different for the two nodal directions and thus the gap structure must be uniquely anisotropic, suggesting that pairing is governed by interactions with a rather complicated anisotropy. Intriguingly, it is found that the "plateau" in the magnetic-field dependence of the thermal conductivity is observed only in the b-axis transport.Comment: 4 pages, 5 figures, accepted for publication in Phys. Rev. Let
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