1,895 research outputs found
Combustion products generating and metering device
Device simulates incipient fire conditions in closely-controlled adjustable manner, to give predetermined degree of intensity at selected locations throughout area, and to verify that detection system will respond. Device can be used with and for cross calibration and experimentation in conjunction with commercially available products of combustion analyzing meters
Combustion products generating and metering device
An apparatus for generating combustion products at a predetermined fixed rate, mixing the combustion products with air to achieve a given concentration, and distributing the resultant mixture to an area or device to be tested is described. The apparatus is comprised of blowers, a holder for the combustion product generating materials (which burn at a predictable and controlled rate), a mixing plenum chamber, and a means for distributing the air combustion product mixture
Preparation and Characterization of Protonated Fumaric Acid
Fumaric acid was reacted with the binary superacidic systems HF/SbF5 and HF/AsF5. The O,O'‐diprotonated [C4H6O4]2+([MF6]–)2 (M = As, Sb) and the O‐monoprotonated [C4H5O4]+[MF6]– (M = As, Sb) species are formed depending on the stoichiometric ratio of the Lewis acid to fumaric acid. The colorless salts were characterized by low‐temperature vibrational spectroscopy. In case of the hexafluoridoantimonates single‐crystal X‐ray structure analyses were carried out. The [C4H6O4]2+([SbF6]–)2 crystallizes in the monoclinic space group C2/c with four formula units per unit cell and [C4H5O4]+[SbF6]– crystallizes in the triclinic space group P1 with one formula unit per unit cell. The protonation of fumaric acid does not cause a notable change of the C=C bond length. The experimental data are discussed together with quantum chemical calculations of the cations [C4H6O4 · 4 HF]2+ and [C4H6O4 · 2 H2CO · 2 HF]2+
Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains
We study the quasiparticle band structure of isolated, infinite HF and HCl
bent (zigzag) chains and examine the effect of the crystal field on the energy
levels of the constituent monomers. The chains are one of the simplest but
realistic models of the corresponding three-dimensional crystalline solids. To
describe the isolated monomers and the chains, we set out from the Hartree-Fock
approximation, harnessing the advanced Green's function methods "local
molecular orbital algebraic diagrammatic construction" (ADC) scheme and "local
crystal orbital ADC" (CO-ADC) in a strict second order approximation, ADC(2,2)
and CO-ADC(2,2), respectively, to account for electron correlations. The
configuration space of the periodic correlation calculations is found to
converge rapidly only requiring nearest-neighbor contributions to be regarded.
Although electron correlations cause a pronounced shift of the quasiparticle
band structure of the chains with respect to the Hartree-Fock result, the
bandwidth essentially remains unaltered in contrast to, e.g., covalently bound
compounds.Comment: 11 pages, 6 figures, 6 tables, RevTeX4, corrected typoe
Fragmentation pathways of nanofractal structures on surface
We present a detailed systematical theoretical analysis of the post-growth
processes occurring in nanofractals grown on surface. For this study we
developed a method which accounts for the internal dynamics of particles in a
fractal. We demonstrate that particle diffusion and detachment controls the
shape of the emerging stable islands on surface. We consider different
scenarios of fractal post-growth relaxation and analyze the time evolution of
the island's morphology. The results of our calculations are compared with
available experimental observations, and experiments in which the post-growth
relaxation of deposited nanostructures can be probed are suggested.Comment: 34 pages, 11 figure
Step-Wise Computational Synthesis of Fullerene C60 derivatives. 1.Fluorinated Fullerenes C60F2k
The reactions of fullerene C60 with atomic fluorine have been studied by
unrestricted broken spin-symmetry Hartree-Fock (UBS HF) approach implemented in
semiempirical codes based on AM1 technique. The calculations were focused on a
sequential addition of fluorine atom to the fullerene cage following indication
of the cage atom highest chemical susceptibility that is calculated at each
step. The effectively-non-paired-electron concept of the fullerene atoms
chemical susceptibility lays the foundation of the suggested computational
synthesis. The obtained results are analyzed from energetic, symmetry, and the
composition abundance viewpoints. A good fitting of the data to experimental
findings proves a creative role of the suggested synthesis methodology.Comment: 33 pages, 11 figures, 2 tables, 2 chart
Dynamical models for sand ripples beneath surface waves
We introduce order parameter models for describing the dynamics of sand
ripple patterns under oscillatory flow. A crucial ingredient of these models is
the mass transport between adjacent ripples, which we obtain from detailed
numerical simulations for a range of ripple sizes. Using this mass transport
function, our models predict the existence of a stable band of wavenumbers
limited by secondary instabilities. Small ripples coarsen in our models and
this process leads to a sharply selected final wavenumber, in agreement with
experimental observations.Comment: 9 pages. Shortened version of previous submissio
Purifying selection in corvids is less efficient on islands
Funding was provided by the European Research Council (ERCStG-336536 FuncSpecGen to J.B.W.W.), the Swedish Research Council Vetenskapsrådet (621-2013-4510 to J.B.W.W.), the Knut and Alice Wallenberg Foundation (to J.B.W.W.), the Lawski foundation (to V.E.K. and J.B.W.W.), the German Research Foundation (KU 3402/1-1 to V.E.K.), the UK’s Biotechnology and Biological Sciences Research Council (BB/G023913/2 to C.R.), and the New Zealand Marsden Fund (to G.R.H.).Theory predicts that deleterious mutations accumulate more readily in small populations. As a consequence, mutation load is expected to be elevated in species where life-history strategies and geographic or historical contingencies reduce the number of reproducing individuals. Yet, few studies have empirically tested this prediction using genome-wide data in a comparative framework. We collected whole-genome sequencing data for 147 individuals across seven crow species (Corvus spp.). For each species, we estimated the distribution of fitness effects of deleterious mutations and compared it with proxies of the effective population size Ne. Island species with comparatively smaller geographic range sizes had a significantly increased mutation load. These results support the view that small populations have an elevated risk of mutational meltdown, which may contribute to the higher extinction rates observed in island species.Publisher PDFPeer reviewe
Continuous symmetry of C60 fullerene and its derivatives
Conventionally, the Ih symmetry of fullerene C60 is accepted which is
supported by numerous calculations. However, this conclusion results from the
consideration of the molecule electron system, of its odd electrons in
particular, in a close-shell approximation without taking the electron spin
into account. Passing to the open-shell approximation has lead to both the
energy and the symmetry lowering up to Ci. Seemingly contradicting to a
high-symmetry pattern of experimental recording, particularly concerning the
molecule electronic spectra, the finding is considered in the current paper
from the continuous symmetry viewpoint. Exploiting both continuous symmetry
measure and continuous symmetry content, was shown that formal Ci symmetry of
the molecule is by 99.99% Ih. A similar continuous symmetry analysis of the
fullerene monoderivatives gives a reasonable explanation of a large variety of
their optical spectra patterns within the framework of the same C1 formal
symmetry exhibiting a strong stability of the C60 skeleton.Comment: 11 pages. 5 figures. 6 table
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