Quantum anisotropic Heisenberg chains with superlattice structure: a DMRG study

Using the density matrix renormalization group technique, we study spin superlattices composed of a repeated pattern of two spin-1/2 XXZ chains with different anisotropy parameters. The magnetization curve can exhibit two plateaus, a non trivial plateau with the magnetization value given by the relative sizes of the sub-chains and another trivial plateau with zero magnetization. We find good agreement of the value and the width of the plateaus with the analytical results obtained previously. In the gapless regions away from the plateaus, we compare the finite-size spin gap with the predictions based on bosonization and find reasonable agreement. These results confirm the validity of the Tomonaga-Luttinger liquid superlattice description of these systems.Comment: 6 pages, 6 figure

Luttinger liquid superlattices: realization of gapless insulating phases

We investigate Luttinger Liquid superlattices, a periodic structure composed of two kinds of one-dimensional systems of interacting electrons. We calculate several properties of the low-energy sector: the effective charge and spin velocities, the compressibility, various correlation functions, the Landauer conductance and the Drude weight. The low-energy properties are subsumed into effective parameters, much like homogeneous one-dimensional systems. A generic result is the weighted average nature of these parameters, in proportion to the spatial extent of the underlying subunits, pointing to the possibility of ``engineered'' structures. As a specific realization, we consider a one-dimensional Hubbard superlattice, which consists of a periodic arrangement of two long Hubbard chains with different coupling constants and different hopping amplitudes. This system exhibits a rich phase diagram with several phases, both metallic and insulating. We have found that gapless insulating phases are present over a wide range of parameters.Comment: 16 pages, 15 figures, RevTeX

Un Análisis Lingüístico Comparativo del Sistema Fonológico del inglés y el español

This paper analyzes a few significant differences between Spanish and English in relation to phonological patterns. First, a short introduction is given about these two languages, and it is briefly explained in what linguistic aspects they are similar or different. Then, each of these linguistic features is analyzed in detail, clearly establishing the differences existing between Spanish and English. The specific phonological features that are addressed on this academic paper are vowel and consonant phonemes, diphthongs and triphthongs, as well as syllable and sentence stress. Furthermore, several pronunciation difficulties for Spanish speakers are discussed. Finally, some didactic implications are considered so that teachers can help their students of either language learn the second one considering important linguistic features.Este artículo analiza algunas diferencias significativas entre el español y el inglés en relación con los patrones fonológicos. En primer lugar, se hace una breve introducción sobre estos dos idiomas y se explica brevemente en qué aspectos lingüísticos son similares o diferentes. A continuación, se analiza en detalle cada uno de estos rasgos lingüísticos, estableciendo claramente las diferencias existentes entre el español y el inglés. Las características fonológicas específicas que se abordan en este artículo académico son los fonemas vocales y consonantes, diptongos y triptongos, así como el acento de sílabas y oraciones. Además, se discuten varias dificultades de pronunciación para hispanohablantes. Finalmente, se consideran algunas implicaciones didácticas para que los profesores puedan ayudar a sus alumnos de cualquiera de los dos idiomas a aprender el segundo considerando características lingüísticas importantes

A comparative Digital Soil Mapping (DSM) study using a non-supervised clustering analysis and an expert knowledge based model - A case study from Ahuachapán, El Salvador

DSM is the inference of spatial and temporal soil property variations using mathematical models based on quantitative relationships between environmental information and soil measurements. The quality of DSM information depends on the method and environmental covariates used for its estimations. We compared two DSM methods to predict soil properties such as Organic Matter “MO” (%), Sand (%), Clay (%), pH (H2O), Phosphorus (mg/kg), Effective Cationic Exchange Capacity “CICE” (cmol/L), Potassium (cmol/L) and Water Holding Capacity (mm/m) for the department of Ahuachapán in El Salvador to support the activities of the Agriculture Landscape Restoration Initiative (ALRI) in the countr

A comparative Digital Soil Mapping (DSM) study using a non-supervised clustering analysis and an expert knowledge based model - A case study from Ahuachapán, El Salvador

DSM is the inference of spatial and temporal soil property variations using mathematical models based on quantitative relationships between environmental information and soil measurements. The quality of DSM information depends on the method and environmental covariates used for its estimations. We compared two DSM methods to predict soil properties such as Organic Matter “MO” (%), Sand (%), Clay (%), pH (H2O), Phosphorus (mg/kg), Effective Cationic Exchange Capacity “CICE” (cmol/L), Potassium (cmol/L) and Water Holding Capacity (mm/m) for the department of Ahuachapán in El Salvador to support the activities of the Agriculture Landscape Restoration Initiative (ALRI) in the countr