Elastic constant measurements of super ionic LiKSO4:Na single crystals

Elastic properties of sodium doped Lithium potassium sulphate, LiK0.9Na0.1SO4, crystal has been studied by ultrasonic Pulse Echo Overlap [PEO] technique and are reported for the first time. The controversy regarding the type of crystal found while growth is performed at 35 °C with equimolar fraction of Li2SO4H2O, K2SO4 and Na2SO4 has been resolved by studying the elastic properties. The importance of this crystal is that it exhibits pyroelectric, ferroelectric and electro optic properties. It is simultaneously ferroelastic and superionic. The elastic properties of LiK0.9Na0.1SO4 crystal are well studied by measuring ultrasonic velocity in the crystal in certain specified crystallographic directions and evaluating the elastic stiffness constants, compliance constants and Poisson’s ratios. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the surface plots of phase velocity, slowness and linear compressibility in a-b and a-c planes.

Biochemical Effects of Anionic, Cationic and Non Ionic Surfactants on a Tropical Teleost Oreochromis Mossambicus(Peters) and a Marine Cyanobacterium Synechocystis Salina Wislouch

The present work is a base line attempt to investigate and assess the toxicities of three surfactants viz. anionic sodium dodecyl sulfate (SDS), non ionic Triton X-1OO (TX-IOO) and cationic cetyl trimethyl ammonium bromide (CTAB). These compounds represent simple members of the often neglected group of aquatic pollutants i.e. the anionic alkyl sulfates, non ionics and the cationics. These compounds are widely used In plastic industry, pesticide/herbicide formulations, detergents, oil spill dispersants, molluscicides etc. The test organisms selected for the present study are the cyanobacterium Synechocystis salina Wislouch representing a primary producer in the marine environment and a fresh water adapted euryhaline teleost Oreochromis mossambicus (peters) at the consumer level of the ecological pyramid. The fish species, though not indigenous to our country, is now found ubiquitously in fresh water systems and estuaries. Also it is highly resistant to pollutants and has been suggested as an indicator of pollution in tropical region .

Local character of magnetic coupling in ionic solids

Magnetic interactions in ionic solids are studied using parameter-free methods designed to provide accurate energy differences associated with quantum states defining the Heisenberg constant J. For a series of ionic solids including KNiF3, K2NiF4, KCuF3, K2CuF4, and high- Tc parent compound La2CuO4, the J experimental value is quantitatively reproduced. This result has fundamental implications because J values have been calculated from a finite cluster model whereas experiments refer to infinite solids. The present study permits us to firmly establish that in these wide-gap insulators, J is determined from strongly local electronic interactions involving two magnetic centers only thus providing an ab initio support to commonly used model Hamiltonians.

Neutral atoms in ionic lattices: Excited states of KCl:Ag(0)

The optical-absorption spectrum of a cationic Ag0 atom in a KCl crystal has been studied theoretically by means of a series of cluster models of increasing size. Excitation energies have been determined by means of a multiconfigurational self-consistent field procedure followed by a second-order perturbation correlation treatment. Moreover results obtained within the density-functional framework are also reported. The calculations confirm the assignment of bands I and IV to transitions of the Ag-5s electron into delocalized states with mainly K-4s,4p character. Bands II and III have been assigned to internal transitions on the Ag atom, which correspond to the atomic Ag-4d to Ag-5s transition. We also determine the lowest charge transfer (CT) excitation energy and confirm the assignment of band VI to such a transition. The study of the variation of the CT excitation energy with the Ag-Cl distance R gives additional support to a large displacement of the Cl ions due to the presence of the Ag0 impurity. Moreover, from the present results, it is predicted that on passing to NaCl:Ag0 the CT onset would be out of the optical range while the 5s-5p transition would undergo a redshift of 0.3 eV. These conclusions, which underline the different character of involved orbitals, are consistent with experimental findings. The existence of a CT transition in the optical range for an atom inside an ionic host is explained by a simple model, which also accounts for the differences with the more common 3d systems. The present study sheds also some light on the R dependence of the s2-sp transitions due to s2 ions like Tl+.

Rigorous characterization of oxygen vacancies in ionic oxides

Charged and neutral oxygen vacancies in the bulk and on perfect and defective surfaces of MgO are characterized as quantum-mechanical subsystems chemically bonded to the host lattice and containing most of the charge left by the removed oxygens. Attractors of the electron density appear inside the vacancy, a necessary condition for the existence of a subsystem according to the atoms in molecules theory. The analysis of the electron localization function also shows attractors at the vacancy sites, which are associated to a localization basin shared with the valence domain of the nearest oxygens. This polyatomic superanion exhibits chemical trends guided by the formal charge and the coordination of the vacancy. The topological approach is shown to be essential to understand and predict the nature and chemical reactivity of these objects. There is not a vacancy but a coreless pseudoanion that behaves as an activated host oxygen.

Ionic-covalent transition in titanium oxides

The nature of the chemical bond in three titanium oxides of different crystal structure and different formal oxidation state has been studied by means of the ab initio cluster-model approach. The covalent and ionic contributions to the bond have been measured from different theoretical techniques. All the analysis is consistent with an increasing of covalence in the TiO, Ti2O3, and TiO2 series as expected from chemical intuition. Moreover, the use of the ab initio cluster-model approach combined with different theoretical techniques has permitted us to quantify the degree of ionic character, showing that while TiO can approximately be described as an ionic compound, TiO2 is better viewed as a rather covalent oxide.

Atomic and ionic radii of superheavy elements

Atomic and ionic radii are presented for the elements E104-E120 and E156-E172. It is shown that a number of effects correlated with the large relativistic contraction of orbitals with low angular momentum leads to smaller atoms for higher atomic numbers. It is expected that Cs is the largest atom in nature.

Evaluating Greek primary school textbooks used to teach students with learning disabilities

Evaluaci??n de los libros de texto de Educaci??n Primaria griegos utilizados en la ense??anza de los estudiantes con dificultades de aprendizaje. La evaluaci??n de los libros de texto en cuanto a su cumplimiento de las normas basadas en la evidencia de dise??o instruccional, y en cuanto a su idoneidad para acomodar las diversas necesidades educativas de los diversos grupos de la poblaci??n escolar, se considera un medio importante de mejorar la calidad de los servicios educativos incluyendo a estudiantes con discapacidades de aprendizaje. En el presente trabajo, se explican los resultados de las evaluaciones de los libros de texto de Lengua y Matem??ticas que se utilizan en los tres primeros grados de la escuela griega primaria para ense??ar a los estudiantes con y sin dificultades de aprendizaje. La evaluaci??n se bas?? en los siguientes criterios: claridad de objetivos de instrucci??n, el examen de conocimientos previos, explicitaci??n de las explicaciones de instrucci??n, la suficiencia de los ejemplos de ense??anza, la introducci??n de conceptos adicionales y capacidades, la adecuaci??n de la pr??ctica guiada, la eficacia de la pr??ctica independiente, y la adecuaci??n de los conocimientos. Seg??n los resultados, los libros de texto no cumplen en cuatro de los ocho criterios revisados, en concreto los criterios de la claridad de los objetivos de instrucci??n, la explicitud de las explicaciones de instrucci??n, la introducci??n de conceptos adicionales y habilidades, y la conveniencia de revisar los conocimientos. Bas??ndose en estos resultados, el punto de vista puede considerarse que los libros de texto evaluados presentan considerables deficiencias e insuficiencias, lo que exige la aplicaci??n de modificaciones sustanciales en varios par??metros de dise??o de la instrucci??n cuando se utilizan para ense??ar a los estudiantes con dificultades de aprendizaje. Se discuten los efectos de estas deficiencias.

Greek grime.

Con esta serie se quiere dar a conocer los hábitos higiénicos de las sociedades antiguas. En este caso, vemos cómo los antiguos griegos se esforzaban por mantener su limpieza corporal, rascandose la mugre y extendiendo después grasa. Los atletas solo llevaban sobre su cuerpo aceite de oliva y las señoras, se emborrachaban con los abundantes aceites perfumados sobre sus cuerpos. Conoce, también los truculentos detalles de la vida cotidiana, putrefacta de plagas y de chisporroteantes sacrificios.

Un método realmente nuevo. Reading Greek.

Se pone de manifiesto un nuevo método para la lectura del griego antiguo denominado Reading Greek. Que la enseñanza del griego antiguo se haya visto reducido a prácticamente un solo curso de enseñanza, ha sido motivo de queja, a la que no se ha dado respuesta. De ahí que los profesionales de la enseñanza de esta materia se hayan propuesto nuevos métodos para ser más eficaces en su aprovechamiento de este escaso tiempo. Por un lado la gramática se ha dosificado con reglas sintácticas entremezcladas. Aún así no parece claro que el alumno al final del curso esté en las adecuadas condiciones de poder afrontar con un mínimo de garantías la lectura de un texto. Pero La Joint Association of Classical Teachers, tras diez largos años de trabajo ha elaborado un método denominado Reading greek, es decir, leyendo Griego, de gran eficacia. Se propone que lo mejor desde el principio mismo es introducir en los textos al alumno y éstos de una manera gradual en cuanto a adaptación del original, y con un bagaje de vocabulario que va aumentando progresivamente, al igual que la gramática al uso, que más que estudiarla tras cada unidad, resulta más bien la síntesis de la misma. En cuanto a la descripción detallada del método se señala que consta de dos volúmenes, siendo el primero el que contiene tos textos y el segundo, la gramática, el vocabulario y los ejercicios. El tiempo requerido para la puesta en práctica del método son treinta y siete semanas, que viene a coincidir con el curso académico. La materia se distribuye por secciones, dentro de siete apartados o capítulos que enfocan diversos aspectos del mundo heleno. Cada sección dentro de estos apartados viene configurada por cuatro o cinco unidades. Para terminar se realizan dos precisiones sobre la eficacia del método: en primer lugar se le considera de gran utilidad y eficacia para la docencia; y en segundo, el orden de palabras, que acostumbra ya desde el primer texto, a ese hipérbaton tan sorprendente para los que se inician.

A word study unit on Latin and Greek prefixes, roots and derivations

This paper contains an outline of study for hearing impaired children to learn language through the study of Latin and Greek roots, derivatives and prefixes.

The Greek debt trap: an escape plan. Bruegel Policy Contribution 2012/19, 7 November 2012

Without corrective measures, Greek public debt will exceed 190 percent of GDP, instead of peaking at the anyway too-high target ratio of 167 percent of GDP of the March 2012 financial assistance programme. The rise is largely due to a negative feedback loop between high public debt and the collapse in GDP, and endangers Greek membership of the euro area. But a Greek exit would have devastating impacts both inside and outside Greece. A small reduction in the interest rate on bilateral loans, the exchange of European Central Bank holdings, buy-back of privately-held debt, and frontloading of some privatisation receipts are unlikely to be sufficient. A credible resolution should involve the reduction of the official lending rate to zero until 2020, an extension of the maturity of all official lending, and indexing the notional amount of all official loans to Greek GDP. Thereby, the debt ratio would fall below 100 percent of GDP by 2020, and if the economy deteriorates further, there will not be a need for new arrangements. But if growth is better than expected, official creditors will also benefit. In exchange for such help, the fiscal sovereignty of Greece should be curtailed further. An extended privatisation plan and future budget surpluses may be used to pay back the debt relief. The Greek fiscal tragedy highlights the need for a formal debt restructuring mechanism