129 research outputs found
Tunneling for Dirac Fermions in Constant Magnetic Field
The tunneling effect of two-dimensional Dirac fermions in a constant magnetic
field is studied. This can be done by using the continuity equation at some
points to determine the corresponding reflexion and transmission coefficients.
For this, we consider a system made of graphene as superposition of two
different regions where the second is characterized by an energy gap t'. In
fact, we treat concrete systems to practically give two illustrations: barrier
and diode. For each case, we discuss the transmission in terms of the ratio of
the energy conservation and t'. Moreover, we analyze the resonant tunneling by
introducing a scalar Lorentz potential where it is shown that a total
transmission is possible.Comment: 21 pages, 6 figures, misprints correcte
The influence of humic acids extracted from Chaouia soil on the behavior of transition metal ions and pesticides
   Humic acid (HA) and fulvic acid (FA) exist ubiquitously in environments and have a variety of functional groups, which allow them to complex with metal ions and pesticides. Furthermore, these interactions can not only alter the environmental behavior, but also influence the removal and transportation of those pollutants. The study of the interaction between Cu (II), VO (II) and Mn (II) with HAs provides environmental information on the oxidation states of paramagnetic metals and their mechanisms of binding to humic acids. Electron spin resonance (ESR) study demonstrates that VO (II) and Cu (II) ions are bound with oxygen ligands to HAs, while the Mn (II) complex occurs as [Mn(H2O)6]2+. Additionally, Cu (II) ions are more strongly bound than Mn (II) ions to soil HAs. The effect of the presence of HA on photolysis of Tribenuron-methyl (TRB) and Imazapyr (IMAZ) herbicides in water was studied by irradiation of different mixtures of HA/herbicide (0.5:1 and 1:1 by volume). The obtained results clearly demonstrate that HA substances exhibit a screening effect on the photochemical degradation of the two herbicides. The protective effect of HAs on the TRB and IMAZ degradation could be explained with an inclusion and/or adsorption of the herbicide molecules in the humic matrix
Magnetism of Two Coupled Harmonic Oscillators
The thermodynamical properties of a system of two coupled harmonic
oscillators in the presence of an uniform magnetic field B are investigated.
Using an unitary transformation, we show that the system can be diagonalized in
simple way and then obtain the energy spectrum solutions. These will be used to
determine the thermodynamical potential in terms of different physical
parameters like the coupling parameter \alpha. This allows us to give a
generalization of already significant published work and obtain different
results, those could be used to discuss the magnetism of the system. Different
limiting cases, in terms of \alpha and B, have been discussed. In fact, quantum
corrections to the Landau diamagnetism and orbital paramagnetism are found.Comment: 25 page
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