2,608 research outputs found

    Vegetation analysis in the Laramie Basin, Wyoming from ERTS-1 imagery

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    The author has identified the following significant results. The application of ERTS-1 imagery to vegetation mapping and identification was tested and confirmed by field checking. ERTS-1 imagery interpretation and density contour mapping allows definition of minute vegetation features and estimation of vegetative biomass and species composition. Large- and small-scale vegetation maps were constructed for test areas in the Laramie Basin and Laramie mountains of Wyoming. Vegetative features reflecting grazing intensity, moisture availability, changes within the growing season, cutting of hay crops, and plant community constituents in forest and grassland are discussed and illustrated. Theoretical considerations of scattering, sun angle, slope, and instrument aperture upon image and map resolution were investigated. Future suggestions for applications of ERTS-1 data to vegetative analysis are included

    High Speed Phase-Resolved 2-d UBV Photometry of the Crab pulsar

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    We report a phase-resolved photometric and morphological analysis of UBV data of the Crab pulsar obtained with the 2-d TRIFFID high speed optical photometer mounted on the Russian 6m telescope. By being able to accurately isolate the pulsar from the nebular background at an unprecedented temporal resolution (1 \mu s), the various light curve components were accurately fluxed via phase-resolved photometry. Within the UBVUBV range, our datasets are consistent with the existing trends reported elsewhere in the literature. In terms of flux and phase duration, both the peak Full Width Half Maxima and Half Width Half Maxima decrease as a function of photon energy. This is similarly the case for the flux associated with the bridge of emission. Power-law fits to the various light curve components are as follows; \alpha = 0.07 \pm 0.19 (peak 1), \alpha = -0.06 \pm 0.19 (peak 2) and \alpha = -0.44 \pm 0.19 (bridge) - the uncertainty here being dominated by the integrated CCD photometry used to independently reference the TRIFFID data. Temporally, the main peaks are coincident to \le 10 \mu s although an accurate phase lag with respect to the radio main peak is compromised by radio timing uncertainties. The plateau on the Crab's main peak was definitively determined to be \leq 55 \mu s in extent and may decrease as a function of photon energy. There is no evidence for non-stochastic activity over the light curves or within various phase regions, nor is there evidence of anything akin to the giant pulses noted in the radio. Finally, there is no evidence to support the existence of a reported 60 second modulation suggested to be as a consequence of free precession.Comment: 13 pages, 12 figures, accepted for publication in Astronomy & Astrophysic

    Structure and elastic properties of Mg(OH)2_2 from density functional theory

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    The structure, lattice dynamics and mechanical properties of the magnesium hydroxide have been investigated with static density functional theory calculations as well as \it {ab initio} molecular dynamics. The hypothesis of a superstructure existing in the lattice formed by the hydrogen atoms has been tested. The elastic constants of the material have been calculated with static deformations approach and are in fair agreement with the experimental data. The hydrogen subsystem structure exhibits signs of disordered behaviour while maintaining correlations between angular positions of neighbouring atoms. We establish that the essential angular correlations between hydrogen positions are maintained to the temperature of at least 150 K and show that they are well described by a physically motivated probabilistic model. The rotational degree of freedom appears to be decoupled from the lattice directions above 30K

    CATHEDRAL: A Fast and Effective Algorithm to Predict Folds and Domain Boundaries from Multidomain Protein Structures

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    We present CATHEDRAL, an iterative protocol for determining the location of previously observed protein folds in novel multidomain protein structures. CATHEDRAL builds on the features of a fast secondary-structure–based method (using graph theory) to locate known folds within a multidomain context and a residue-based, double-dynamic programming algorithm, which is used to align members of the target fold groups against the query protein structure to identify the closest relative and assign domain boundaries. To increase the fidelity of the assignments, a support vector machine is used to provide an optimal scoring scheme. Once a domain is verified, it is excised, and the search protocol is repeated in an iterative fashion until all recognisable domains have been identified. We have performed an initial benchmark of CATHEDRAL against other publicly available structure comparison methods using a consensus dataset of domains derived from the CATH and SCOP domain classifications. CATHEDRAL shows superior performance in fold recognition and alignment accuracy when compared with many equivalent methods. If a novel multidomain structure contains a known fold, CATHEDRAL will locate it in 90% of cases, with <1% false positives. For nearly 80% of assigned domains in a manually validated test set, the boundaries were correctly delineated within a tolerance of ten residues. For the remaining cases, previously classified domains were very remotely related to the query chain so that embellishments to the core of the fold caused significant differences in domain sizes and manual refinement of the boundaries was necessary. To put this performance in context, a well-established sequence method based on hidden Markov models was only able to detect 65% of domains, with 33% of the subsequent boundaries assigned within ten residues. Since, on average, 50% of newly determined protein structures contain more than one domain unit, and typically 90% or more of these domains are already classified in CATH, CATHEDRAL will considerably facilitate the automation of protein structure classification

    Роль маркетинга в сфере культуры

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    Сегодня все мы ощущаем завершение очередного этапа развития нашего общества, который выражается в многочисленных кризисах (политическом, экономическом, экологическом и т.д.), что в полной мере отражает художественная культура

    Growth of (110) Diamond using pure Dicarbon

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    We use a density-functional based tight-binding method to study diamond growth steps by depositing dicarbon species onto a hydrogen-free diamond (110) surface. Subsequent C_2 molecules are deposited on an initially clean surface, in the vicinity of a growing adsorbate cluster, and finally, near vacancies just before completion of a full new monolayer. The preferred growth stages arise from C_2n clusters in near ideal lattice positions forming zigzag chains running along the [-110] direction parallel to the surface. The adsorption energies are consistently exothermic by 8--10 eV per C_2, depending on the size of the cluster. The deposition barriers for these processes are in the range of 0.0--0.6 eV. For deposition sites above C_2n clusters the adsorption energies are smaller by 3 eV, but diffusion to more stable positions is feasible. We also perform simulations of the diffusion of C_2 molecules on the surface in the vicinity of existing adsorbate clusters using an augmented Lagrangian penalty method. We find migration barriers in excess of 3 eV on the clean surface, and 0.6--1.0 eV on top of graphene-like adsorbates. The barrier heights and pathways indicate that the growth from gaseous dicarbons proceeds either by direct adsorption onto clean sites or after migration on top of the existing C_2n chains.Comment: 8 Pages, 7 figure

    H2O and the dehydroxylation of phyllosilicates: an infrared spectroscopic study

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    As shown by in situ infrared spectroscopy and analysis of quenched samples, phyllosilicates (muscovite, sericite, pyrophyllite, and talc) under dehydroxylation conditions lack the characteristic bands near 1600 cm–1 (bending) and 5200 cm–1 (combination) of H2O, and they contain virtually no H2O but an abundance of OH. This observation appears to be at variance with the formal description of dehydroxylation in bulk samples as 2(OH) -> H2O + O, whereas it is suggested that hydrogen diffuses in the form of (OH) – or/and H+ in dehydroxylation. The upper limit of H2O in the dehydroxlated bulk is likely to be at the parts per million level in phyllosilicates that contain structural OH ions equivalent to 4–5 wt% H2O. The observations suggest that H2O molecules are probably formed near the surface of the sample

    Unpulsed UBV Optical Emission from the Crab Pulsar

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    Based on observations of the Crab pulsar using the TRIFFID high speed imaging photometer in the UBV bands using the Special Astrophysical Observatory's 6m telescope in the Russian Caucasus, we report the detection of pronounced emission during the so-called `off' phase of emission. Following de-extinction, this unpulsed component of emission is shown to be consistent with a power law with an exponent of alpha = -0.60 +/- 0.37, the uncertainty being dominated by the error associated with the independent CCD photometry used to reference the TRIFFID data. This suggests a steeper power law form than that reported elsewhere in the literature for the total integrated spectrum, which is essentially flat with alpha ~ 0.1, although the difference in this case is only significant at the ~ 2 sigma level. Deeper reference integrated and TRIFFID phase-resolved photometry in these bands in conjunction with further observations in the UV and R region would constrain this fit further.Comment: 26 pages, 2 figures, uses aasms4.sty, accepted for publication in the Astrophysical Journa
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