Influence of differences between sample and mobile phase viscosities on the shape of chromatographic elution profiles

The injection of samples whose viscosities are appreciably different from íhat of the motile phase can result in highly distorted elution profiles, showing severai maxima. The distortions are produced at the rear of the band when the viscosity of the sample solvent is higher than that of the motile phase. It is shown that the distortion of the peaks produced on injecting arbutin in columns of aminopropyl silica, using water as mobile phase and mixtures of 2-propanol and water as the sample solvent, grows in importance when the sample size increases, when the viscosity of the sample solvent increases and when the flow rate is decreased On the other side distortions at the band front are observed when arbutin dissolved in water or in acetonitrile + water mixtures is injected in a 2-propanol-water (50:50) mobile phase of higher viscosity. These trends are coincident with the predictions of a hydrodynamic instability criterion postulated several years ago and up to now almost entirely ignored in chromatography, except in relation with size exclusión chromatography

Trust and privacy in distributed work groups

Proceedings of the 2nd International Workshop on Social Computing, Behavioral Modeling and PredictionTrust plays an important role in both group cooperation and economic exchange. As new technologies emerge for communication and exchange, established mechanisms of trust are disrupted or distorted, which can lead to the breakdown of cooperation or to increasing fraud in exchange. This paper examines whether and how personal privacy information about members of distributed work groups influences individuals' cooperation and privacy behavior in the group. Specifically, we examine whether people use others' privacy settings as signals of trustworthiness that affect group cooperation. In addition, we examine how individual privacy preferences relate to trustworthy behavior. Understanding how people interact with others in online settings, in particular when they have limited information, has important implications for geographically distributed groups enabled through new information technologies. In addition, understanding how people might use information gleaned from technology usage, such as personal privacy settings, particularly in the absence of other information, has implications for understanding many potential situations that arise in pervasively networked environments.Preprin

Current methods of soccer match analysis

Ha sido realizada una revisión de 86 artículos, con el objetivo de analizar a través de los estudios más recientes los beneficios y limitaciones de los nuevos sistemas para el análisis del futbolista durante el partido, debido a que las mayores exigencias en el rendimiento del fútbol moderno está obligando a replantearse cuáles son sus demandas físicas, así como los modelos de planificación y los métodos de entrenamiento tradicionales. Los resultados muestran que el vídeo análisis asistido por ordenador para la codificación de los patrones de movimiento y la tecnología GPS se presentan como herramientas de gran utilidad para conocer mejor la carga física del jugador, mientras que el diseño observacional facilita la evaluación del comportamiento técnico-táctico del futbolista y el equipo. Como conclusión podemos decir que hemos observado sin embargo una metodología diferente entre las opciones comerciales disponibles y una tecnología ubicada todavía en una etapa inicial de desarrolloA review of 86 references has been made, in order to analyze through the most recent studies the benefits and limitations of the new systems for the analysis of soccer player during the match, due to the fact that the greater performance requirements of modern soccer is forcing to review his physical demands, as well as planning models and traditional training methods. The results show that the computer-aided video analysis for coding movement patterns and the GPS technology are presented as very useful tools for a better understanding of the players physical load, whereas the observational design facilitates assessment of the technical-tactical behavior of the soccer player and the team. In conclusion we can say that we have however observed a different methodology among the available commercial options and a technology still placed at an initial stage of development

From policy to pedagogy: widening the discourse and practice of the learning society in the European Union

This paper explores the policy turn of the learning society, and how the academic world is responding to new social and political demands. It highlights some of the criticisms levelled at the learning society, as well as the voices of support. The paper also showcases the European Language Portfolio and the Transferable Skills project as two examples of good practice. Cet article examine le tournant de la politique de la socie´te´ du savoir ainsi que la re´ponse du monde intellectuel face aux nouvelles exigences sociales et politiques. Il met en lumie`re certaines des critiques souleve´es par la socie´te´ du savoir ainsi que par les voix favorables. L’article s’appuie sur deux exemples pratiques, a` savoir le Portfolio Europe´en des Langues et le Project des Compe´tences Transmissibles

Foundation and empire : a critique of Hardt and Negri

In this article, Thompson complements recent critiques of Hardt and Negri's Empire (see Finn Bowring in Capital and Class, no. 83) using the tools of labour process theory to critique the political economy of Empire, and to note its unfortunate similarities to conventional theories of the knowledge economy

Social media, protest cultures and political subjectivities of the Arab spring

This article draws on phenomenological perspectives to present a case against resisting the objectification of cultures of protest and dissent. The generative, self-organizing properties of protest cultures, especially as mobilized through social media, are frequently argued to elude both authoritarian political structures and academic discourse, leading to new political subjectivities or ‘imaginaries’. Stemming from a normative commitment not to over-determine such nascent subjectivities, this view has taken on a heightened resonance in relation to the recent popular uprisings in the Middle East and North Africa. The article argues that this view is based on an invalid assumption that authentic political subjectivities and cultures naturally emerge from an absence of constraint, whether political, journalistic or academic. The valorisation of amorphousness in protest cultures and social media enables affective and political projection, but overlooks politics in its institutional, professional and procedural forms

Thermodynamic consideration of the retention mechanism in a poly(perfluoroalkyl ether) gas chromatographic stationary phase used in packed columns

Retention voluntes of fifteen hydrocarbons were measured in columns containing several concentrations of a commercial poly(perfluoroalkyl ether), Fomblin Y HVAC 140/13, as the stationary phase. Two different type ofpacking were studied: one ofthem employed pre-silylated Chromosorb P AW DMCS as the solid support, and the other type wasprepared by coating the stationary phase on Chromosorb P AW and silylating on-column. On-column silylated columns showed unequivocal symptoms of partial deactivation; retention volumes changed regularly with the contení of stationary phase in pre-silylated columns. Analysis of retention in pre-silylated columns indicates that a mixed mechanism (partition and adsorption on the gas-liquid interface) is operative. Systems hydrocarbon + perfluorocompound show pronounced positive deviations from the ideal behaviour that can be attributed to repulsión between the hydrocarbon and the perfluorocompund segments

Concurrent solution and adsorption of hydrocarbons in gas chromatographic columns packed with different loadings of 3- methylsydnone on chromosorb P

Thermodynamic properties of solution in 3-methylsydnone (3MS) and of adsorption at the nitrogen/3MS interface were gas chromatographically measured for a graup of fifteen hydrocarbons at infinite dilution conditions. Retention voluntes were measured at five temperatures within the range 37-52°C in six columns containing different loadings of 3MS on Chromosorb P AW. Partition and adsorption coejficients were calculated and from their temperature dependence the corresponding enthalpies were obtained, although with considerable error; infinite dilution activity coejficients of the hydrocarbons in the bulk and in the surface phases demonstrated an strong correlation. Bulk activity coefficients in 3MS were very much smaller than those previously measured for the same solutes in formamide (FA) and in ethyleneglycol (EG), and were also smaller than what could be predicted on account of 3MS cohesive energy density as estimated from the quotient a/v13 (cr. surface tensión; v: molar volume). There was not such a large difference between the surface activity coefficients in the three solvents; furthermore, the quotients (surface activity coefficient/bulk activity coefficient) for a given solute in 3MS were twice as large as in FA and about three times larger than in EG. These results make evident the difficulties inherent in the prediction of surface phase properties from those in the bulk, and casi doubts on the pertinency of employing the surface tensión to compare cohesive energy densities of polar solvents with important Chemical dijferences