10,504 research outputs found
An interaction Lagrangian for two spin 1/2 elementary Dirac particles
The kinematical formalism for describing spinning particles developped by the
author is based upon the idea that an elementary particle is a physical system
with no excited states. It can be annihilated by the interaction with its
antiparticle but, if not destroyed, its internal structure can never be
modified. All possible states of the particle are just kinematical
modifications of any one of them. The kinematical state space of the
variational formalism of an elementary particle is necessarily a homogeneous
space of the kinematical group of spacetime symmetries. By assuming Poincare
invariance we have already described a model of a classical spinning particle
which satisfies Dirac's equation when quantized. We have recently shown that
the spacetime symmetry group of this Dirac particle is larger than the Poincare
group. It also contains spacetime dilations and local rotations. In this work
we obtain an interaction Lagrangian for two Dirac particles, which is invariant
under this enlarged spacetime group. It describes a short- and long-range
interaction such that when averaged, to supress the spin content of the
particles, describes the instantaneous Coulomb interaction between them. As an
application, we analyse the interaction between two spinning particles, and
show that it is possible the existence of metastable bound states for two
particles of the same charge, when the spins are parallel and provided some
initial conditions are fulfilled. The possibility of formation of bound pairs
is due to the zitterbewegung spin structure of the particles because when the
spin is neglected, the bound states vanish
Sorption of apolar pesticides by units of benzoic acid propyl ester in cyclic phosphazene
Indexación: Scopus.The effects of temperature, pH and agitation time (equilibrium) on the adsorption process of different pesticides on N3P3(OC6H4COOCH2CH2CH3)6 was studied. With optimal conditions experimental, the adsorption isotherms have been realized with through Langmuir and Freundlich models. Pesticides are compounds used mainly in agriculture to control various species (plants, insects, worms, fungi). Due to their physicochemical properties, they can remain for a long time in the application sites, bioaccumulating and moving between environmental compartments which generate various environmental problems. The results obtained showed a physisorption mechanism for the fve pesticides studied, with higher sorption for: azinphos methyl (93,5 mg kg-1), carbaryl (290.5 mg kg-1) and carbofuran (580.5 mg kg-1) at 20 ° C, according to the models used. © 2018 Sociedad Chilena de Quimica. All rights reserved.https://scielo.conicyt.cl/pdf/jcchems/v62n4/0717-9324-jcchems-62-04-3783.pd
The dynamical equation of the spinning electron
We obtain by invariance arguments the relativistic and non-relativistic
invariant dynamical equations of a classical model of a spinning electron. We
apply the formalism to a particular classical model which satisfies Dirac's
equation when quantised. It is shown that the dynamics can be described in
terms of the evolution of the point charge which satisfies a fourth order
differential equation or, alternatively, as a system of second order
differential equations by describing the evolution of both the center of mass
and center of charge of the particle. As an application of the found dynamical
equations, the Coulomb interaction between two spinning electrons is
considered. We find from the classical viewpoint that these spinning electrons
can form bound states under suitable initial conditions. Since the classical
Coulomb interaction of two spinless point electrons does not allow for the
existence of bound states, it is the spin structure that gives rise to new
physical phenomena not described in the spinless case. Perhaps the paper may be
interesting from the mathematical point of view but not from the point of view
of physics.Comment: Latex2e, 14 pages, 5 figure
FERROCENYL ALKYLAMMONIUM N-SUBSTITUTED POLYPYRROLE CONTAINING Pt AND Pd AND ITS APPLICATION ON ELECTROANALYSIS OF ARSENITE
Indexación: Web of Science; Scopus; Scielo.Arsenic occurs in a variety of forms and oxidation states and is a very toxic element. The main inorganic arsenic species present in natural waters are arsenate (oxidation state V) and arsenite ions (oxidation state III). Arsenite is more toxic and mobile than arsenate. Therefore, it is important the development of new materials for analysis and control of these toxic species.
This research proves that polymer-metal composite electrode materials synthesized by incorporation of Pt-0 and Pd-0 nanoparticles into a poly(pyrrole-ferrocenyl alkylammonium) matrix present electrocatalytic properties towards the oxidation of arsenite to arsenate.
The polymer films displayed a stable electrochemical response in aqueous solution. However, when the polymer film modified electrode were transferred to aqueous solution in presence of arsenite anions, the CV curves for polymer films were deeply modified by the decrease in the electroactivity of the film. It can be concluded that the cationic polymer films present a strong affinity toward arsenite anions. The composite films containing Pt-0 or Pd-0 showed catalytic activity towards oxidation of As(III) to As(V) due to the presence of metal catalyst particles into the polymer films.http://ref.scielo.org/dgdvx
Towards understanding the design of dual-modal MR/fluorescent probes to sense zinc ions
A series of gadolinium complexes were synthesised in order to test the design of dual-modal probes that display a change in fluorescence or relaxivity response upon binding of zinc. A dansyl-DO3ATA gadolinium complex [GdL1] displayed an increase and a slight blue-shift in fluorescence in the presence of zinc; however, a decrease in relaxation rate was observed. Consequently, the ability of the well-known zinc chelator, BPEN, was assessed for relaxivity response when conjugated to the gadolinium chelate. The success of this probe [GdL2], lead to the inclusion of the same zinc-probing moiety alongside a longer wavelength emitting fluorophore, rhodamine [GdL3], to arrive at the final iteration of these first generation dual-modal zinc-sensing probes. The compounds give insight into the design protocols required for the successful imaging of zinc ions
- …