Vibrational anharmonicity of small gold and silver clusters using the VSCF method

We study the vibrational spectra of small neutral gold (Au2–Au10) and silver (Ag2–Au5) clusters using the vibrational self-consistent field method (VSCF) in order to account for anharmonicity. We report harmonic, VSCF, and correlation-corrected VSCF calculations obtained using a vibrational configuration interaction approach (VSCF/VCI). Our implementation of the method is based on an efficient calculation of the potential energy surfaces (PES), using periodic density functional theory (DFT) with a plane-wave pseudopotential basis. In some cases, we use an efficient technique (fast-VSCF) assisted by the Voter–Chen potential in order to get an efficient reduction of the number of pair-couplings between modes. This allows us to efficiently reduce the computing time of 2D-PES without degrading the accuracy. We found that anharmonicity of the gold clusters is very small with maximum rms deviations of about 1 cm−1, although for some particular modes anharmonicity reaches values slightly larger than 2 cm−1. Silver clusters show slightly larger anharmonicity. In both cases, large differences between calculated and experimental vibrational frequencies (when available) stem more likely from the quality of the electronic structure method used than from vibrational anharmonicity. We show that noble gas embedding often affects the vibrational properties of these clusters more than anharmonicity, and discuss our results in the context of experimental studies

The nature and role of the gold-krypton interactions in small neutral gold clusters

© 2015 American Chemical Society. We investigate the nature and role of krypton embedding in small neutral gold clusters. For some of these clusters, we observe a particular site-dependent character of the Kr binding that does not completely follow the criterion of binding at low-coordinated sites, widely accepted for interaction of a noble gas with closed-shell metal systems such as metal surfaces. We aim at understanding the effect of low dimensionality and open-shell electronic structure of the odd-numbered clusters on the noble gas-metal cluster interaction. First, we investigate the role of attractive and repulsive forces, and the frontier molecular orbitals. Second, we investigate the Au-Kr interaction in terms of reactivity and bonding character. We use a reactivity index derived from Fukui formalism, and criteria provided by the electron localization function (ELF), in order to classify the type of bonding. We carry out this study on the minimum energy structures of neutral gold clusters, as obtained using pseudo potential plane-wave density functional theory (DFT). A model is proposed that includes the effect of attractive electrostatic, van der Waals and repulsive forces, together with effects originating from orbital overlap. This satisfactorily explains minimum configurations of the noble gas-gold cluster systems, the site preference of the noble gas atoms, and changes in electronic properties

Recursos lingüísticos de atenuación en el habla de Madrid. Estudio sociopragmático

Desde los inicios del estudio sistemático del discurso, en los años sesenta del siglo XX, hasta la actualidad, hemos llegado a cotas de profundidad en el conocimiento del funcionamiento de la comunicación lingüística difícilmente imaginables en otros tiempos. Hoy en día, la investigación del funcionamiento sociopragmático del discurso se ha convertido en una línea de investigación muy fructífera; sin embargo, aún quedan muchos aspectos que han de ser descritos y explicados de forma detallada, y especialmente si atendemos a Madrid, ciudad irradiadora de norma lingüística, sobre la cual disponemos de escasa información. Este es el caso de la atenuación lingüística, fenómeno variable al que dedicamos las páginas que siguen. El trabajo que aquí presentamos intenta dar cuenta de los tipos y recursos lingüísticos que utilizan mayoritariamente para atenuar los madrileños, a partir de los resultados obtenidos en análisis cualitativos y cuantitativos de materiales recopilados en Madrid mediante entrevistas semidirigidas. Se trata de una investigación sobre la atenuación lingüística que pretende afianzar el estudio de fenómenos discursivos desde un enfoque pragmático y sociolingüístico y que se enmarca en el “Proyecto para el estudio sociolingüístico del español de España y América” (PRESEEA)

An alternative methodology to assess the quality of empirical potentials for small gold clusters

We present a methodology based on local comparisons of potential energy surfaces (PES) in order to assess the quality of empirical potentials. We compare five typical empirical potentials using a criterion that shows which of these potentials resembles better a PES obtained with a high-level electronic structure method. The methodology relies on a many-body expansion in terms of normal coordinates of both the empirical and high-level theory PES. Then we investigate in a systematical way, how the features of the reference high-level theory PES are reproduced by each empirical potential in the vicinity of a given minimum energy structure. We use plane-wave density functional theory (DFT) as a reference, in particular the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional and an ultrasoft Vanderbilt pseudo potential. This study is carried out on neutral gold clusters with up to five atoms

Electrochemistry of proteins at the interface between two immiscible electrolyte solutions

The electrochemistry of proteins at the interface between two immiscible electrolyte solutions (ITIES) is discussed, with detection capabilities based on protein-facilitated anion transfer, and which has enabled protein detection via adsorptive stripping voltammetry. Targeting an enzymatic biomarker has achieved detection at picomolar concentrations, whilst studies into structural aspects of proteins at the ITIES have revealed formation of oligomers (cytochrome c) and unfolded protein (lysozyme) together with alterations to the protein secondary structures

Metabolic and Stress Responses in Senegalese Soles (Solea senegalensis Kaup) Fed Tryptophan Supplements: E ects of Concentration and Feeding Period

The objective of this study was to assess the impact of di erent dietary Trp concentrations on the stress and metabolism response of juvenile Senegalese soles (Solea senegalensis). Fish (38.1 1.9 g) were fed di erent Trp-enriched feeds (0%, 1% and 2% Trp added) for two and eight days, and later exposed to air stress for three min. Samples were taken pre- and 1 h post-stress (condition). Plasma cortisol, lactate, glucose and proteins were significantly a ected by the sampling time, showing higher values at 1 h post-stress. Trp concentration in food also had significant e ects on lactate and glucose levels. However, the feeding period did not a ect these parameters. Post-stress values were higher than in the pre-stress condition for every plasma parameter, except for lactate in two days and 1% Trp treatment. Nevertheless, cortisol, glucose and lactate did not vary significantly between pre- and post-stress samplings in fish fed the 1% Trp-enriched diet for two days. The lack of variability in cortisol response was also due to the high pre-stress value, significantly superior to pre-stress control. The exposure time to Trp feeding did not significantly a ect any enzyme activity; however, Trp added and condition influenced protein-related enzyme activities. In spite of decreasing stress markers, Trp-enriched diets altered the protein metabolism

Identification and characterisation of putative drug binding sites in human ATP-binding cassette B5 (ABCB5) transporter.

The human ATP-binding cassette B5 (ABCB5) transporter, a member of the ABC transporter superfamily, is linked to chemoresistance in tumour cells by drug effluxion. However, little is known about its structure and drug-binding sites. In this study, we generated an atomistic model of the full-length human ABCB5 transporter with the highest quality using the X-ray crystal structure of mouse ABCB1 (Pgp1), a close homologue of ABCB5 and a well-studied member of the ABC family. Molecular dynamics simulations were used to validate the atomistic model of ABCB5 and characterise its structural properties in model cell membranes. Molecular docking simulations of known ABCB5 substrates such as taxanes, anthracyclines, camptothecin and etoposide were then used to identify at least three putative binding sites for chemotherapeutic drugs transported by ABCB5. The location of these three binding sites is predicted to overlap with the corresponding binding sites in Pgp1. These findings will serve as the basis for future in vitro studies to validate the nature of the identified substrate-binding sites in the full-length ABCB5 transporter

Reproduction of the wedge sole (Dicologoglossa cuneata Moreau) in captivity: spawning parameters and influence of the natural temperature

In this work, the wedge sole (Dciologoglossa cuneata) spawning under natural thermocycle has been studied. The spawning parameters were similar to those of other flatfish in captivity, the relative fecundity being very high (1.7&plusmn;0.1 &middot;106 eggs Kg female-1 per spawning season). The percentage of floating eggs decreased in parallel to the time and was directly related to egg diameter, daily relative fecundity and fertilization rate. Nevertheless, the hatching rate variations were not correlated to any other spawning parameter. The temperature range during the spawning season was very wide (11-21 &ordm;C) though the largest spawns occurred between 12 and 16 &ordm;C . The natural temperature cycle influenced wedge sole egg production, the winter temperature minimum indicating the onset of spawning, but the variations in the reproductive season did not appear to affect the daily egg production. Future research should focus on the photoperiod and its interaction with temperature as key factor for spawning. This work was supported by Interreg Project 0251_ECOAQUA_5_E, financed by the EDRF (European Regional Development Fund). www.juntadeandalucia.es/agriculturaypesca/ifapa/ecoaqua.. &nbsp;El presente trabajo trata del estudio de las puestas de la aced&iacute;a (Dicologoglossa cuneata) en cautividad bajo condiciones naturales de temperatura. Los par&aacute;metros de puesta fueron similares a los de otros peces planos en cautividad, siendo la fecundidad relativa muy alta (1.7&plusmn;0.1 &middot;106 huevos Kg hembra-1 por estaci&oacute;n reproductora). El porcentaje de huevos flotantes disminuy&oacute; paralelamente con el tiempo y fue directamente proporcional al di&aacute;metro de huevos, fecundidad relativa diaria y tasa de fecundaci&oacute;n. Sin embargo, las variaciones de la tasa de eclosi&oacute;n no estuvieron correlacionadas con ning&uacute;n par&aacute;metro de puesta. El rango de temperatura durante la estaci&oacute;n de puesta fue muy amplio (11-21 &ordm;C), aunque las mayores puestas tuvieron lugar entre 12 y 16 &ordm;C. El ciclo natural de temperatura tuvo efectos sobre la producci&oacute;n de huevos de aced&iacute;a, con los m&iacute;nimos invernales indicando el comienzo de la puesta, aunque las variaciones dentro de la estaci&oacute;n de puesta no pareci&oacute; afectar a la producci&oacute;n diaria de huevos. Este trabajo fue apoyado por el proyecto Interreg 0251_ECOAQUA_5_E , financiado por el FEDER (Fondo Europeo de Desarrollo Regional).www.juntadeandalucia.es/agriculturaypesca/ifapa/ecoaqua.</p