85 research outputs found
Modelling the fluid phase behaviour of aqueous mixtures of multifunctional alkanolamines and carbon dioxide using transferable parameters with the SAFT-VR approach
Cooee bitumen. II. Stability of linear asphaltene nanoaggregates
Asphaltene and smaller aromatic molecules tend to form linear nanoaggregates
in bitumen.Over the years bitumen undergoes chemical aging and during this
process, the size of the nanoaggregate increases. This increase is associated
with an increase in viscosity and brittleness of the bitumen, eventually
leading to road deterioration. This paper focuses on understanding the
mechanisms behind nanoaggregate size and stability. We used molecular dynamics
simulations to quantify the probability of having a nanoaggregate of a given
size in the stationary regime. To model this complicated behavior, we chose
first to consider the simple case where only asphaltene molecules are counted
in a nanoaggregate. We used a master equation approach and a related
statistical mechanics model. The linear asphaltene nanoaggregates behave as a
rigid linear chain. The most complicated case where all aromatic molecules are
counted in a nanoaggregate is then discussed. The linear aggregates where all
aromatic molecules are counted seem to behave as a flexible linear chain.Comment: 31 pages, 9 figure
Diurnal variation of atmospheric Maxwell current over the low-latitude continental station, Tirunelveli, India (8.7°N, 77.8°E)
The global atmospheric electrical circuit and climate
Evidence is emerging for physical links among clouds, global temperatures, the global atmospheric electrical circuit and cosmic ray ionisation. The global circuit extends throughout the atmosphere from the planetary surface to the lower layers of the ionosphere. Cosmic rays are the principal source of atmospheric ions away from the continental boundary layer: the ions formed permit a vertical conduction current to flow in the fair weather part of the global circuit. Through the (inverse) solar modulation of cosmic rays, the resulting columnar ionisation changes may allow the global circuit to convey a solar influence to meteorological phenomena of the lower atmosphere. Electrical effects on non-thunderstorm clouds have been proposed to occur via the ion-assisted formation of ultra-fine aerosol, which can grow to sizes able to act as cloud condensation nuclei, or through the increased ice nucleation capability of charged aerosols. Even small atmospheric electrical modulations on the aerosol size distribution can affect cloud properties and modify the radiative balance of the atmosphere, through changes communicated globally by the atmospheric electrical circuit. Despite a long history of work in related areas of geophysics, the direct and inverse relationships between the global circuit and global climate remain largely quantitatively unexplored. From reviewing atmospheric electrical measurements made over two centuries and possible paleoclimate proxies, global atmospheric electrical circuit variability should be expected on many timescale
Constraining the electric charges of some astronomical bodies in Reissner-Nordstrom spacetimes and generic r^-2-type power-law potentials from orbital motions
We put model-independent, dynamical constraints on the net electric charge Q
of some astronomical and astrophysical objects by assuming that their exterior
spacetimes are described by the Reissner-Nordstroem metric, which induces an
additional potential U_RN \propto Q^2 r^-2. Our results extend to other
hypothetical power-law interactions inducing extra-potentials U_pert = r^-2 as
well (abridged).Comment: LaTex2e, 16 pages, 3 figures, no tables, 128 references. Version
matching the one at press in General Relativity and Gravitation (GRG). arXiv
admin note: substantial text overlap with arXiv:1112.351
Changes in concentration and size distribution of aerosols during fog over the south Indian Ocean
Calculation of liquid-liquid equilibrium of aqueous two-phase systems using a chemical-theory-based excess Gibbs energy model
Charakterisierung nichtperiodischer Feinraster fuer das Offsetverfahren
SIGLEAvailable from TIB Hannover: RO 7846(32108) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekArbeitsgemeinschaft Industrieller Forschungsvereinigungen e.V., Koeln (Germany); Bundesministerium fuer Wirtschaft, Bonn (Germany)DEGerman
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