Linear response functions for a vibrational configuration interaction state

Linear response functions are implemented for a vibrational configuration interaction state allowing accurate analytical calculations of pure vibrational contributions to dynamical polarizabilities. Sample calculations are presented for the pure vibrational contributions to the polarizabilities of water and formaldehyde. We discuss the convergence of the results with respect to various details of the vibrational wave function description as well as the potential and property surfaces. We also analyze the frequency dependence of the linear response function and the effect of accounting phenomenologically for the finite lifetime of the excited vibrational states. Finally, we compare the analytical response approach to a sum-over-states approach

The role of fungi and bacteria on the organic matter decomposition process in streams: interaction and relevance in biofilms

L'objectiu d'aquest estudi és el d'investigar sobre l'ús de matèria orgànica per part dels fongs i bacteris que colonitzen diferents substrats bentònics en rius Mediterranis i analitzar l'efecte dels factors ambientals i antròpics sobre l'estabilitat estructural i funcional de les comunitats del biofilm. La metodologia emprada en aquest estudi consisteix en: i) anàlisi de la biomassa bacteriana i fúngica, ii) anàlisi de la composició de les comunitats bentòniques (identificació d'hifomicets aquàtics i anàlisi del 16S rDNA bacterià), i iii) anàlisi de l'activitat enzimàtica extracel·lular relacionada amb el reciclatge de matèria orgànica en rius.

A comparison of social interaction between groups of multiply handicapped and hearing-impaired children

This paper reviews a study to determine the differences between multiply handicapped and deaf children in social interactions.

The slow cortical evoked potential: cross modality interaction of auditory, vibro-tactile and shock stimuli

This paper discusses a study that collected cortical evoked responses when stimuli of different modalities were presented.

Las relaciones comerciales de América Latina: integraciones económicas regionales y análisis de la proliferación de acuerdos con los EE.UU. (Tema Central)

El objetivo del presente artículo es hacer una reflexión acerca de la nueva geografía comercial de América Latina, relativa a los acuerdos celebrados con los EE.UU. Frente a las incertidumbres en el ámbito regional y multilateral, hoy existe un cierto predominio de un tercer movimiento en las relaciones económicas internacionales, esto es, la proliferación de tratados bilaterales. Aunque estos tratados asuman diferentes contenidos y obligaciones, en general tienen compromisos más rígidos para los países en desarrollo en América Latina, que las obligaciones firmadas en foros de negociación subjetivamente más amplios (como es el caso de la OMC).

Aspectos relevantes del estado actual de las negociaciones del Tratado de Libre Comercio entre Ecuador y EE.UU. (Tema Central)

El artículo, centrándose en el sector agrícola ecuatoriano, hace una descripción del estado en que se encuentran las negociaciones del Tratado de Libre Comercio entre Estados Unidos y Ecuador. De acuerdo con el autor, en el sector agrícola, manejado como tema sensible y relevante por parte de los negociadores ecuatorianos, el ritmo de negociación ha sido desgastante para la parte ecuatoriana debido, entre otras razones, a la inflexibilidad mostrada hasta el momento por parte de los negociadores norteamericanos. Igualmente plantea y analiza dos escenarios factibles una vez concluidas las rondas de negociación: que el Ecuador decida poner un freno al proceso de negociación o que el proceso negociador continúe y las condiciones actuales se flexibilicen, especialmente por parte de los EE.UU. para facilitar la firma del Tratado.

La seguridad nacional de EE. UU. en el nuevo orden global: de la vinculación y expansión a la seguridad patria y el antiterrorismo (Tema Central)

El artículo describe y compara las estrategias de seguridad nacional de Estados Unidos de las administraciones de Bill Clinton y George Bush. Trata de clarificar la forma en que se concibe el espacio nacional estadounidense, mundial y global dentro de estas estrategias.

Relaciones bilaterales entre el Ecuador y EE. UU. durante las décadas de los años ochenta y noventa (Artículos Varios)

Este artículo desarrolla un análisis comparativo de las relaciones bilaterales entre el Ecuador y Estados Unidos, durante los gobiernos de Osvaldo Hurtado, León Febres Cordero, Rodrigo Borja, Sixto Durán Ballén, Abdalá Bucaram, Fabián Alarcón y Jamil Mahuad. El autor encuentra puntos coincidentes y de diferencia en cada una de las administraciones, con respecto a las temáticas prioritarias sobre las que se han desarrollado las relaciones bilaterales: democracia, Derechos Humanos, drogas, deuda externa, comercio y el conflicto bélico Ecuador-Perú.

Efectos en los mercados financieros internacionales de la derogatoria en 1999 de la Ley Glass Steagall de los EE.UU. (Tema Central)

Actualmente la profunda crisis del sistema financiero internacional, similar a la que vivió Estados Unidos en los años treinta, es el punto más importante de discusión en todo el mundo. Por ello, se consideró importante realizar un análisis de la Ley Glass Steagall Act, promulgada en el año 1933, justamente como una salida a la crisis financiera estadounidense, de aquella época, precisando cuáles son sus principales características, y sobre todo los efectos que su derogatoria (en 1999) trajo consigo en el sistema financiero mundial, pues como veremos, para muchos la actual crisis es producto de la inadecuada mezcla de regulación y libertad que se produjo con la promulgación de la Ley Gramm Leach Bliley Act, mediante la cual los bancos comerciales empezaron a incursionar en operaciones bursátiles, actividades que anteriormente estaban vetadas, y por tanto existían garantías suficientes para los depositantes.

Improving computer interaction for older people - studying mouse clicks

Interactions using a standard computer mouse can be particularly difficult for novice and older adult users. Tasks that involve positioning the mouse over a target and double-clicking to initiate some action can be a real challenge for many users. Hence, this paper describes a study that investigates the double-click interactions of older and younger adults and presents data that can help inform the development of methods of assistance. Twelve older adults (mean age = 63.9 years) and 12 younger adults (mean age = 20.8 years) performed click and double-click target selections with a computer mouse. Initial results show that older users make approximately twice as many errors as younger users when attempting double-clicks. For both age groups, the largest proportion of errors was due to difficulties with keeping the cursor steady between button presses. Compared with younger adults, older adults experienced more difficulties with performing two button presses within a required time interval. Understanding these interactions better is a step towards improving accessibility, and may provide some suggestions for future directions of research in this area.

How does a weakened Atlantic thermohaline circulation lead to an intensification of the ENSO-south Asian summer monsoon interaction?

This study investigates the change of the El Niño–Southern Oscillation (ENSO)-South Asian summer monsoon interaction in response to a weakened Atlantic thermohaline circulation (THC) by applying an additional freshwater flux into the North Atlantic. The simulated results indicate that the weakened THC leads to intensified ENSO-South Asian summer monsoon relationship and enhanced South Asian summer monsoon interannual variability. Furthermore, it is suggested that this intensification of the ENSO-monsoon relationship is likely due to the enhanced ENSO variability induced by the weakened THC. This study indicates that the low frequency fluctuation of Atlantic SSTs might have an influence on South Asian summer monsoon interannual variability and the ENSO-monsoon interaction, and suggests a nonlocal mechanism for the observed decadal-multidecadal modulation of ENSO-monsoon relationship.

Examining the interaction of growing crops with local climate using a coupled crop-climate model

This paper examines to what extent crops and their environment should be viewed as a coupled system. Crop impact assessments currently use climate model output offline to drive process-based crop models. However, in regions where local climate is sensitive to land surface conditions more consistent assessments may be produced with the crop model embedded within the land surface scheme of the climate model. Using a recently developed coupled crop–climate model, the sensitivity of local climate, in particular climate variability, to climatically forced variations in crop growth throughout the tropics is examined by comparing climates simulated with dynamic and prescribed seasonal growth of croplands. Interannual variations in land surface properties associated with variations in crop growth and development were found to have significant impacts on near-surface fluxes and climate; for example, growing season temperature variability was increased by up to 40% by the inclusion of dynamic crops. The impact was greatest in dry years where the response of crop growth to soil moisture deficits enhanced the associated warming via a reduction in evaporation. Parts of the Sahel, India, Brazil, and southern Africa were identified where local climate variability is sensitive to variations in crop growth, and where crop yield is sensitive to variations in surface temperature. Therefore, offline seasonal forecasting methodologies in these regions may underestimate crop yield variability. The inclusion of dynamic crops also altered the mean climate of the humid tropics, highlighting the importance of including dynamical vegetation within climate models.

Surface wave processes in air-sea interaction

We review briefly recent progress on understanding the role of surface waves on the marine atmospheric boundary layer and the ocean mixed layer and give a global perspective on these processes by analysing ERA-40 data. Ocean surface waves interact with the marine atmospheric boundary layer in two broad regimes: (i) the conventional wind-driven wave regime, when fast winds blow over slower moving waves, and (ii) a wave-driven wind regime when long wavelength swell propagates under low winds, and generates a wave-driven jet in the lower part of the marine boundary layer. Analysis of ERA-40 data indicates that the wave-driven wind regime is as prevalent as the conventional wind-driven regime. Ocean surface waves also change profoundly mixing in the ocean mixed layer through generation of Langmuir circulation. Results from large-eddy simulation are used here to develop a scaling for the resulting Langmuir turbulence, which is a necessary step in developing a parametrization of the process. ERA-40 data is then used to show that the Langmuir regime is the predominant regime over much of the global ocean, providing a compelling motivation for parameterising this process in ocean general circulation models.