Cs adsorption on Si(001) surface: ab initio study

First-principles calculations using density functional theory based on norm-conserving pseudopotentials have been performed to investigate the Cs adsorption on the Si(001) surface for 0.5 and 1 ML coverages. We found that the saturation coverage corresponds to 1 ML adsorption with two Cs atoms occupying the double layer model sites. While the 0.5 ML covered surface is of metallic nature, we found that 1 ML of Cs adsorption corresponds to saturation coverage and leads to a semiconducting surface. The results for the electronic behavior and surface work function suggest that adsorption of Cs takes place via polarized covalent bonding.Comment: 8 pages, 7 figure

Deslizamientos naturales y comunidades pionera de ecosistemas montanos al occidente del parque nacional podocarpus (ecuador)

El Parque Nacional Podocarpus (PNP), ubicado al sur del Ecuador, ocupa una posición climatológica clave con respecto a la deflexión de Huancabamba aledaña a esta área hacia el sur, que ocasiona una barrera natural de distribución de especies y por otro lado este aislamiento biogeográfíco ha originado especiación florística en algunas especies. La geografía accidentada de esta región, sumada a la escasa capa vegetal y precipitaciones que superan los 6000 mm en los páramos, ocasiona impactos severos en los flancos orientales y occidentales de la baja Cordillera Oriental que no sobrepasa los 3700 m, en sus límites altitudinales más altos. Es aquí donde existe una dinámica alta de deslizamientos, los mismos que si bien afectan la diversidad vegetal, también son considerados un motor generador de continuos procesos de regeneración. Se establecieron 138 parcelas, distribuidas a o largo de un gradiente latitudinal y altitudinal, de 1 x 5m al occidente del PNP, encontrándose 218 especies representantes de 180 géneros y 51 familias; el piso altitudinal de mayor diversidad está a los 2700 m. El análisis TWINSPAN separó nueve comunidades vegetales, mientras que el análisis multivariado CANOCO, determinó que las características edafológicas influyen en la composición de la vegetación, mientras que la altitud y la pendiente no establecen notable diferencia

Temperature Sensitive Nanocapsule of Complex Structural Form for Methane Storage

The processes of methane adsorption, storage and desorption by the nanocapsule are investigated with molecular-dynamic modeling method. The specific nanocapsule shape defines its functioning uniqueness: methane is adsorbed under 40 MPa and at normal temperature with further blocking of methane molecules the K@C601+ endohedral complex in the nanocapsule by external electric field, the storage is performed under normal external conditions, and methane desorption is performed at 350 K. The methane content in the nanocapsule during storage reaches 11.09 mass%. The nanocapsule consists of tree parts: storage chamber, junction and blocking chamber. The storage chamber comprises the nanotube (20,20). The blocking chamber is a short nanotube (20,20) with three holes. The junction consists of the nanotube (10,10) and nanotube (8,8); moreover, the nanotube (8,8) is connected with the storage chamber and nanotube (10,10) with the blocking chamber. The blocking chamber is opened and closed by the transfer of the K@C601+ endohedral complex under electrostatic field action

Negative affect moderates the effect of social rejection on frontal and anterior cingulate cortex activation in borderline personality disorder

Patients with borderline personality disorder (BPD) have a heightened sensitivity to social exclusion. Experimental manipulations have produced inconsistent findings and suggested that baseline negative affect (NA) might influence the experience of exclusion. We administered a standardized social exclusion protocol (Cyberball paradigm) in BPD (n = 39) and age-matched and sex-matched healthy controls (n = 29) to investigate the association of NA on social exclusion and activation in brain regions previously implicated in this paradigm. Compared with controls, patients with BPD showed higher activation during social exclusion in the anterior cingulate cortex (ACC), the medial prefrontal cortex (mPFC), and in the right precuneus. Prescan NA ratings were associated with higher brain activation in the ACC and mPFC over all conditions, and post hoc t tests revealed that differences between the groups were only significant when controlling for NA. Brain activation during exclusion was correlated with NA separately for each group. Only BPD patients showed a significant association of NA and exclusion related precuneus activation (r = .52 p = .001). Additionally, BPD patients experienced less feelings of belonging compared with a healthy control (HC) group during inclusion and exclusion, although they estimated their ball possessions significantly higher than did the HC. These findings suggest that baseline NA has a crucial impact on Cyberball-related brain activation. The results underscore the importance of considering levels of NA in social exclusion protocols for participants high in this trait