32,496 research outputs found
Modeling of secondary organic aerosol yields from laboratory chamber data
Laboratory chamber data serve as the basis for constraining models of secondary organic aerosol (SOA) formation. Current models fall into three categories: empirical two-product (Odum), product-specific, and volatility basis set. The product-specific and volatility basis set models are applied here to represent laboratory data on the ozonolysis of α-pinene under dry, dark, and low-NOx conditions in the presence of ammonium sulfate seed aerosol. Using five major identified products, the model is fit to the chamber data. From the optimal fitting, SOA oxygen-to-carbon (O/C) and hydrogen-to-carbon (H/C) ratios are modeled. The discrepancy between measured H/C ratios and those based on the oxidation products used in the model fitting suggests the potential importance of particle-phase reactions. Data fitting is also carried out using the volatility basis set, wherein oxidation products are parsed into volatility bins. The product-specific model is most likely hindered by lack of explicit inclusion of particle-phase accretion compounds. While prospects for identification of the majority of SOA products for major volatile organic compounds (VOCs) classes remain promising, for the near future empirical product or volatility basis set models remain the approaches of choice
A study of inner zone electron data and their comparison with trapped radiation models
A summary and intercomparison of recent inner radiation zone electron data are presented. The morphology of the inner radiation zone is described and the data compared with the current generation of inner zone trapped electron models. An analytic representation of the inner zone equatorial pitch angle distribution is presented. This model was based upon data from eight satellites and was used to reduce all data to the form of equatorial flux. Although no Starfish-free high energy electron measurements were available from the inner portion of the inner radiation zone, it was found that the AE-6 model provided a good description of the present solar maximum environment
Monte Carlo simulations of bosonic reaction-diffusion systems
An efficient Monte Carlo simulation method for bosonic reaction-diffusion
systems which are mainly used in the renormalization group (RG) study is
proposed. Using this method, one dimensional bosonic single species
annihilation model is studied and, in turn, the results are compared with RG
calculations. The numerical data are consistent with RG predictions. As a
second application, a bosonic variant of the pair contact process with
diffusion (PCPD) is simulated and shown to share the critical behavior with the
PCPD. The invariance under the Galilean transformation of this boson model is
also checked and discussion about the invariance in conjunction with other
models are in order.Comment: Publishe
Wormholes in String Theory
A wormhole is constructed by cutting and joining two spacetimes satisfying
the low energy string equations with a dilaton field. In spacetimes described
by the "string metric" the dilaton energy-momentum tensor need not satisfy the
weak or dominant energy conditions. In the cases considered here the dilaton
field violates these energy conditions and is the source of the exotic matter
required to maintain the wormhole. There is also a surface stress-energy, that
must be produced by additional matter, where the spacetimes are joined. It is
shown that wormholes can be constructed for which this additional matter
satisfies the weak and dominant energy conditions, so that it could be a form
of "normal" matter. Charged dilaton wormholes with a coupling between the
dilaton and the electromagnetic field that is more general than in string
theory are also briefly discussed.Comment: 9 pages, LaTex, submitted to Phys. Rev.
Assessment Of Co2 Emission Mitigation For A Brazilian Oil Refinery
Currently the oil refining sector is responsible for approximately 5% of the total Brazilian energy related CO2 emissions. Possibilities to reduce CO2 emissions and related costs at the largest Brazilian refinery have been estimated. The abatement costs related to energy saving options are negative, meaning that feasibility exists without specific income due to emission reductions. The assessment shows that short-term mitigation options, i.e., fuel substitution and energy efficiency measures, could reduce CO2 emissions by 6% of the total current refinery emissions. It is further shown that carbon capture and storage offers the greatest potential for more significant emission reductions in the longer term (up to 43%), but costs in the range of 64 to162 US$/t CO2, depending on the CO2 emission source (regenerators of FCC units or hydrogen production units) and the CO2 capture technology considered (oxyfuel combustion or post-combustion). Effects of uncertainties in key parameters on abatement costs are also evaluated via sensitivity analysis.334835850Universidade Estadual de Campinas (UNICAMP)11th Latin American Symposium on Anaerobic Digestion (DAAL)2014Havana, CUB
Electroweak quark-lepton symmetry and weak topological-charge confinement in the Standard Model with Dirac neutrinos
The standard electroweak model with Dirac neutrinos is extended by way of the
principles of electroweak quark-lepton symmetry and weak topological-charge
confinement to account for quark-lepton charge relations which, if not
accidental, are indicative of charge structures. A mixing in quarks and leptons
of underlying integer local charges with integer weak topological charges
associated with an additive group Z_3, fixed by the anomaly cancellation
requirement, is discussed. It is found that the electroweak difference between
topological quarks and leptons is the nonequivalence between the topological
vacua of their weak field configurations, produced by a four-instanton which
carries the topological charge, induces the universal fractional piece of
charge distinguishing quarks from leptons, and breaks the underlying symmetry.
The constituent quarks of the standard model appear as coming from topological
quarks, via the weak four-instanton event. Dual transitions occur for leptons.
It is shown that several other fundamental problems left open in the standard
electroweak model with Dirac neutrinos are solved: the one-to-one
correspondence between quark and lepton flavors, the existence of three
generations, the conservation and ungauging of B-L, the electric charge
quantization, and the confinement of fractional electric charges.Comment: 23 pages, 1 figure, uses IJMPA.cl
Forced Symmetry Breaking from SO(3) to SO(2) for Rotating Waves on the Sphere
We consider a small SO(2)-equivariant perturbation of a reaction-diffusion
system on the sphere, which is equivariant with respect to the group SO(3) of
all rigid rotations. We consider a normally hyperbolic SO(3)-group orbit of a
rotating wave on the sphere that persists to a normally hyperbolic
SO(2)-invariant manifold . We investigate the effects of this
forced symmetry breaking by studying the perturbed dynamics induced on
by the above reaction-diffusion system. We prove that depending
on the frequency vectors of the rotating waves that form the relative
equilibrium SO(3)u_{0}, these rotating waves will give SO(2)-orbits of rotating
waves or SO(2)-orbits of modulated rotating waves (if some transversality
conditions hold). The orbital stability of these solutions is established as
well. Our main tools are the orbit space reduction, Poincare map and implicit
function theorem
Suppression of superconductivity in nanowires by bulk superconductors
Transport measurements were made on a system consisting of a zinc nanowire
array sandwiched between two bulk superconducting electrodes (Sn or In). It was
found that the superconductivity of Zn nanowires of 40 nm diameter is
suppressed either completely or partially by the superconducting electrodes.
When the electrodes are driven into their normal state by a magnetic field, the
nanowires switch back to their superconducting state. This phenomenon is
significantly weakened when one of the two superconducting electrodes is
replaced by a normal metal. The phenomenon is not seen in wires with diameters
equal to and thicker than 70 nm.Comment: 4 pages, 5 figure
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