How mobile are dye adsorbates and acetonitrile molecules on the surface of TiO2 nanoparticles? A quasi-elastic neutron scattering study

Motions of molecules adsorbed to surfaces may control the rate of charge transport within monolayers in systems such as dye sensitized solar cells. We used quasi-elastic neutron scattering (QENS) to evaluate the possible dynamics of two small dye moieties, isonicotinic acid (INA) and bis-isonicotinic acid (BINA), attached to TiO2 nanoparticles via carboxylate groups. The scattering data indicate that moieties are immobile and do not rotate around the anchoring groups on timescales between around 10 ps and a few ns (corresponding to the instrumental range). This gives an upper limit for the rate at which conformational fluctuations can assist charge transport between anchored molecules. Our observations suggest that if the conformation of larger dye molecules varies with time, it does so on longer timescales and/or in parts of the molecule which are not directly connected to the anchoring group. The QENS measurements also indicate that several layers of acetonitrile solvent molecules are immobilized at the interface with the TiO2 on the measurement time scale, in reasonable agreement with recent classical molecular dynamics results

A semantic web service-based architecture for the interoperability of e-government services

We propose a semantically-enhanced architecture to address the issues of interoperability and service integration in e-government web information systems. An architecture for a life event portal based on Semantic Web Services (SWS) is described. The architecture includes loosely-coupled modules organized in three distinct layers: User Interaction, Middleware and Web Services. The Middleware provides the semantic infrastructure for ontologies and SWS. In particular a conceptual model for integrating domain knowledge (Life Event Ontology), application knowledge (E-government Ontology) and service description (Service Ontology) is defined. The model has been applied to a use case scenario in e-government and the results of a system prototype have been reported to demonstrate some relevant features of the proposed approach

Productivity Effects on Mexican Manufacturing Employment

We examine the effects of labor productivity and total factor productivity (TFP) on employment across 25 Mexican manufacturing industries from 1984 to 2000. Employing panel data methods, several interesting findings emerge. First, we observe a strong and positive impact of NAFTA on employment. Second, productivity exerts a procyclical, positive effect on employment but this effect becomes smaller after NAFTA. Third, partitions of our sample according to capital-labor intensity suggest that industries which are less capital-intensive were affected negatively on impact by NAFTA but that productivity impacted employment positively after NAFTA. In contrast, more capital-intensive industries display these results in reverse

Productivity Effects on Mexican Manufacturing Employment before and after NAFTA

A vast literature employs vector autoregressions (VAR) methods in order to capture whether innovations in productivity lead to increases or decreases in employment for U.S. manufacturing. Studying 25 Mexican manufacturing industries with annual data from 1984 to 2000, we examine labour productivity (value added per employee) and total factor productivity (TFP) effects on Mexican manufacturing employment. We find that productivity measures vary considerably in Mexico. Making use of panel data methods that control for sector specific effects, the business cycle and real wages, interesting results emerge. First, there are strong positive impacts of TFP (without and with human capital) on manufacturing employment, as well as ambiguous effects of labour productivity on employment. Second, the capital stock effect on employment varies across periods, yielding a positive impact for post-NAFTA and for the overall period. We interpret the latter as evidence that the increase in FDI inflows in the post-NAFTA period has made capital a stronger complement to labour more recently

Microporous polymer particles via phase inversion in microfluidics: impact of non-solvent quality

We investigate the impact of ternary phase behavior on the microstructure of porous polymer particles produced by solvent extraction of polymer solution droplets by a nonsolvent. Microfluidic devices fabricated by frontal photopolymerization are employed to produce monodisperse polymer (P)/solvent (S) droplets suspended in a carrier (C) phase before inducing solvent extraction by precipitation in a nonsolvent (NS) bath. Model systems of sodium poly(styrenesulfonate) (P), water (S), hexadecane (C), and either methyl ethyl ketone (MEK) or ethyl acetate (EA) as NS are selected. Extraction across the liquid–liquid interface results in a decrease in the droplet radius and also an ingress of nonsolvent, leading to droplet phase demixing and coarsening. As the concentration of the polymer-rich phase increases, droplet shrinkage and solvent exchange slow down and eventually cease, resulting in microporous polymer particles (of radius ≃50–200 μm) with a smooth surface. The internal structure of these capsules, with pore sizes of ≃1–100 μm, is found to be controlled by polymer solution thermodynamics and the extraction pathway. The ternary phase diagrams are measured by turbidimetry, and the kinetics of phase separation is estimated by stopped-flow small-angle neutron scattering. The higher solubility of water in MEK results in faster particle-formation kinetics than in EA. Surprisingly, however, the lower polymer miscibility with EA/water results in a deeper quench inside the phase boundary and small phase sizes, thus yielding particles with small pores (of narrow distribution). The effects of droplet size, polymer content, and nonsolvent quality provide comprehensive insight into porous particle and capsule formation by phase inversion, with a range of practical applications