The role of magnetoplasmons in Casimir force calculations

In this paper we review the role of magneto plasmon polaritons in the Casimir force calculations. By applying an external constant magnetic field a strong optical anisotropy is induced on two parallel slabs reducing the reflectivity and thus the Casimir force. As the external magnetic field increases, the Casimir force decreases. Thus, with an an external magnetic field the Casimir force can be controlled.The calculations are done in the Voigt configuration where the magnetic field is parallel to the slabs. In this configuration the reflection coefficients for TE and TM modes do not show mode conversion.Comment: contribution to QFEXT09, Norman, Oklahoma 200

Three Recent Damaging Earthquakes in Mexico

Seismicity in Mexico is largely influenced by subduction earthquakes that originate along much of its Pacific Coast. These events have recurrently damaged Mexico City but other less frequent earthquakes produced by other sources and mechanisms also contribute to seismic hazard there and have damaged other important cities and towns. In this paper we review, from the point of view of geotechnical engineering, the effects of three of these less frequent events: the Manzanillo earthquake of Octobrer 9, 1995, the Tehuacán Earthquake of June 6, 1999 and the Tecomán Earthquake of January 21, 2003

Pull-in control due to Casimir forces using external magnetic fields

We present a theoretical calculation of the pull-in control in capacitive micro switches actuated by Casimir forces, using external magnetic fields. The external magnetic fields induces an optical anisotropy due to the excitation of magneto plasmons, that reduces the Casimir force. The calculations are performed in the Voigt configuration, and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with increasing magnetic field.Comment: accepted for publication in App. Phys. Let

Ground Movements in Mexico City During Recent Earthquakes

Acceleration records were obtained with a rather dense accelerographic array during three recent earthquakes in Mexico City. Following a purely observational approach, useful information about the nature and characteristics of seismic motions was derived from the analysis of these records. Broad regional studies indicate that the distribution of seismic motions in the city may be affected by directivity effects. From local site studies it is concluded that seismic movements at the base of the compressible clay deposits are fairly uniform and accelerograms recorded in vertical arrays suggest that soil strata in Mexico City respond to seismic movements according to established knowledge

Small oscillations and the Heisenberg Lie algebra

The Adler Kostant Symes [A-K-S] scheme is used to describe mechanical systems for quadratic Hamiltonians of $\mathbb R^{2n}$ on coadjoint orbits of the Heisenberg Lie group. The coadjoint orbits are realized in a solvable Lie algebra $\mathfrak g$ that admits an ad-invariant metric. Its quadratic induces the Hamiltonian on the orbits, whose Hamiltonian system is equivalent to that one on $\mathbb R^{2n}$. This system is a Lax pair equation whose solution can be computed with help of the Adjoint representation. For a certain class of functions, the Poisson commutativity on the coadjoint orbits in $\mathfrak g$ is related to the commutativity of a family of derivations of the 2n+1-dimensional Heisenberg Lie algebra $\mathfrak h_n$. Therefore the complete integrability is related to the existence of an n-dimensional abelian subalgebra of certain derivations in $\mathfrak h_n$. For instance, the motion of n-uncoupled harmonic oscillators near an equilibrium position can be described with this setting.Comment: 17 pages, it contains a theory about small oscillations in terms of the AKS schem

Van der Waals torque induced by external magnetic fields

We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III-IV semiconductors such as $InSb$, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of $InSb$. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of $InSb$ increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropic materials when the magnetic fields is close to 1 T.Comment: to appear in Journal of Applied Physic

Biofertilization of micropropagated Agave tequilana: Effect on plant growth and production of hydrolytic enzymes

Three beneficial bacterial strains [Gluconoacetobacter diazotrophicus (Pal5), the diazotrophs (11B) and Pachaz (008)] and an arbuscular mycorrhizal fungus [Glomus intraradices (AMF)] were evaluated for their ability to enhance plant growth and the production of hydrolytic enzymes in micropropagated Agave tequilana Weber var. Blue. Results show that the growth of the agave plants and the production of hydrolytic enzymes in their roots were influenced by the presence of these microorganisms. AMF + 11B treatment induced the greatest fresh weight, showing significant differences with respect to other combinations. Microscopic analysis showed dense root colonization in the AMF treated plants. Pal 5 treatment produced taller plants, indicating a better plant nitrogen nutrition and possibly phytohormone production by Gluconoacetobacter. Treatment Pachaz 008 presented the highest values of the most important agronomic variables, such as the diameter of the pseudo-stem. On another hand, differential catalytic activities of the enzymes β-glucosidase, cellobiohydrolase and endo-1,4-β-D-glucanase were detected in inoculated roots in comparison to the un-inoculated control . We offer explanations about those results based on nutritional and hormonal relationships between the microorganisms and the agave plantlets, as well as on the microbial mechanism to colonize the agave roots.Key words: Bacterial and mycorrhizal inoculants, Agave plantlets, hydrolytic enzymes