Exact Solution of a Electron System Combining Two Different t-J Models

A new strongly correlated electron model is presented. This is formed by two types of sites: one where double occupancy is forbidden, as in the t-J model, and the other where double occupancy is allowed but vacancy is not allowed, as an inverse t-J model. The Hamiltonian shows nearest and next-to-nearest neighbour interactions and it is solved by means of a modified algebraic nested Bethe Ansatz. The number of sites where vacancy is not allowed, may be treated as a new parameter if the model is looked at as a t-J model with impurities. The ground and excited states are described in the thermodynamic limit.Comment: Some corrections and references added. To be published in J. Phys.

Excitations and S-matrix for su(3) spin chain combining 3{3} and ${3^{*}}

The associated Hamiltonian for a su(3) spin chain combining ${3}$ and ${3^{*}}$ representations is calculated. The ansatz equations for this chain are obtained and solved in the thermodynamic limit, and the ground state and excitations are described. Thus, relations between the number of roots and the number of holes in each level have been found . The excited states are characterized by means of these quantum numbers. Finally, the exact S matrix for a state with two holes is found.Comment: 17 pages, plaintex, harvmac (to be published in J. of Phys. A

Integrability of a t-J model with impurities

A t-J model for correlated electrons with impurities is proposed. The impurities are introduced in such a way that integrability of the model in one dimension is not violated. The algebraic Bethe ansatz solution of the model is also given and it is shown that the Bethe states are highest weight states with respect to the supersymmetry algebra gl(2/1)Comment: 14 page

Integrable su(3) spin chain combining different representations

The general expression for the local matrix $t(\theta)$ of a quantum chain with the site space in any representation of su(3) is obtained. This is made by generalizing $t(\theta)$ from the fundamental representation and imposing the fulfillment of the Yang-Baxter equation. Then, a non-homogeneous spin chain combining different representations of su(3) is solved by developing a method inspired in the nested Bethe ansatz. The solution for the eigenvalues of the trace of the monodromy matrix is given as two coupled Bethe equations. A conjecture about the solution of a chain with the site states in different representations of su(n) is presented. The thermodynamic limit of the ground state is calculated.Comment: PlainTex harvmac, 30 pages, 7 figures, to appear in Journal of Physics

Observation of Sulfate Aerosols and SO₂ From the Sarychev Volcanic Eruption Using Data From the Atmospheric Chemistry Experiment (ACE)

[1] Infrared spectra measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on the SCISAT satellite were used to analyze the Sarychev volcanic aerosol after the eruption in June 2009. Evidence of the Sarychev eruptions was first detected in July 2009 from enhanced SO2 concentrations and atmospheric extinction. By February 2010, the atmosphere had returned to pre-Sarychev conditions. In July 2009, the volcanic plume was found between 8.5 km and 17.5 km in altitude at mid- and high latitudes (55°N–70°N). The first SO2 and sulfate aerosol retrievals carried out using the infrared solar occultation spectra recorded with the ACE-FTS are presented here. The size distribution parameters, the aerosol volume slant column and the composition of the sulfate aerosol were obtained by using a least squares algorithm. The maximum volume slant column of the aerosols was found to be 850 μm3 cm−3 km, which results in an approximate aerosol loading of 3 μm3 cm−3. One month after the eruption, the composition of the aerosols providing the best-fit is a 75% sulfuric acid-water solution with an effective radius (Reff) of 0.1–0.3 μm

Characterization of silicon thin overlayers on rutile \ce{TiO2} (110)-(1x1)

Silicon thin films for coverages ($\theta$) between 0.3 and 3 monolayers have been grown on rutile \ce{TiO2}(110)-(1x1) at room temperature and studied by x-ray and ultra-violet photoelectron spectroscopies, Auger electron spectroscopy, and low energy electron diffraction (LEED). A clear evidence of a strong \ce{Si}/\ce{TiO2} interaction consistent with the high affinity of O for Si has been found. The Ti cations on the substrate are reduced, while the Si film is oxidized, yielding \ce{SiO2} and a mixture of silicon suboxides. Neutral Si atoms are observed at a coverage of 3 monolayers. At the interface region we observe the formation of cross-linking Ti-O-Si bonds. The thin Si overlayer strongly attenuates the $(1 \times 1)$ LEED pattern from the substrate. Finally, thermal annealing results in the improvement of the \ce{SiO2} stoichiometry, but the surface order is not recovered. Using ab-initio density functional theory we have obtained optimum geometrical configurations and corresponding density of states for 1/3 \le \theta \le 1$monolayers of Si adsorbed on the$1 \times 1$ two-dimensional unit cell

Efficacy of standard and low drift nozzles for insecticide applications against Aonidiella aurantii (Maskell) in citrus

Drift is especially critical when spraying fruit, vine and citrus orchards where pesticides are intensively used. In this context, cone low drift nozzles (LDN) intended for spraying tree crops, have been evaluated relating to cone standard nozzles (STN) in laboratory and deciduous fruit orchards (Van de Zande et al. 2012); (Planas et al., 2013)