Surface-state electron dynamics in noble metals

Theoretical investigations of surface-state electron dynamics in noble metals are reported. The dynamically screened interaction is computed, within many-body theory, by going beyond a free-electron description of the metal surface. Calculations of the inelastic linewidth of Shockley surface-state electrons and holes in these materials are also presented. While the linewidth of excited holes at the surface-state band edge (${\bf k}_\parallel=0$) is dominated by a two-dimensional decay channel, within the surface-state band itself, our calculations indicate that major contributions to the electron-electron interaction of surface-state electrons above the Fermi level come from the underlying bulk electrons.Comment: 17 pages, 7 figures, to appear in Prog. Surf. Sc

Self-energy of image states on copper surfaces

We report extensive calculations of the imaginary part of the electron self-energy in the vicinity of the (100) and (111) surfaces of Cu. The quasiparticle self-energy is computed by going beyond a free-electron description of the metal surface, either within the GW approximation of many-body theory or with inclusion, within the GW$\Gamma$ approximation, of short-range exchange-correlation effects. Calculations of the decay rate of the first three image states on Cu(100) and the first image state on Cu(111) are also reported, and the impact of both band structure and many-body effects on the electron relaxation process is discussed.Comment: 8 pages, 5 figures, to appear in Phys. Rev.

Encapsulación de lacasa en alginato: comparación entre extrusión asistida y no asistida para producción a gran escala

ResumenSe estudió el efecto de la extrusión asistida y no asistida para la producción a gran escala sobre el tamaño, forma y desempeño bioquímico de capsulas de lacasa-alginato. Las capsulas se formularon usando una concentración de alginato al 1.0% y 3.0% (m/v) y se prepararon por un método de extrusión-goteo. Los resultados mostraron que la técnica de extrusión afecta el tamaño de las capsulas y su distribución de tamaño, pero no afecta su forma. La caracterización bioquímica mostro un comportamiento similar entre ambos métodos de extrusión. Sin embargo, las capsulas no asistidas presentaron mayor variabilidad en su actividad enzimática y menor estabilidad en el tiempo. Los resultados muestran que con el método de extrusión, material particulado altamente homogéneo mejora bioprocesos facilitando el control de etapas de temperatura y pH, por lo tanto, un método asistido presenta varias ventajas para la producción de material particulado de lacasa en grandes cantidades. AbstractThe effect of assisted and not-assisted extrusion for large scale production on size, shape and biochemical performance of the laccase-alginate beads was studied. The alginate beads were formulated using 1.0% and 3.0% (w/v) alginate concentrations and were prepared by an extrusion-dripping method. Results showed that the extruding technique affects the beads size and size distribution but not the beads shape. The biochemical characterization showed a similar performance for both extruding methods. However, not-assisted beads presented higher enzymatic activity variability and lower stability in time. Results shown that in extrusion method, bioprocesses are improved by highly homogeneous particulate material easing temperature or pH controlled steps, then, an assisted method presents several benefits for producing laccase particulate material at large quantities

An Assessment of Students’ Satisfaction in Higher Education

Student’s Satisfaction (SS) with a particular subject may impact the learning process, being the figure of attentiveness of the utmost importance over time, and also a very difficult undertaking to accomplish. To go forward with such exercise, a workable methodology for problem solving had to be built and tested. It is based on a thermodynamic approach to Knowledge Representation and Reasoning, which is the ultimate goal of SS assessment when working on a particular topic

A Soft Computing Approach to Quality Evaluation of General Chemistry Learning in Higher Education

In contemporary societies higher education must shape individuals able to solve problems in a workable and simpler manner and, therefore, a multidisciplinary view of the problems, with insights in disciplines like psychology, mathematics or computer science becomes mandatory. Undeniably, the great challenge for teachers is to provide a comprehensive training in General Chemistry with high standards of quality, and aiming not only at the promotion of the student’s academic success, but also at the understanding of the competences/skills required to their future doings. Thus, this work will be focused on the development of an intelligent system to assess the Quality-of-General-Chemistry-Learning, based on factors related with subject, teachers and students

Micromixers for Wastewater Treatment and Their Life Cycle Assessment (LCA)

The use of micromixers and catalytically active nanocomposites can be an attractive alternative for the treatment of wastewaters from the textile industry, due to their high activity, low consumption of such nanocomposites, short reaction times and the possibility to work under continuous operation. In this study, 6 different designs of micromixers were modeled and evaluated for the treatment of wastewaters. Velocity profiles, pressure drops, and flows were analyzed and compared for the different devices under the same mixing conditions. In addition, Life cycle assessment (LCA) methodology was applied to determine their performance in terms of environmental impact. Considering the high environmental impact of water sources contaminated by dyes from the textile industry, it becomes critically important to determine when the proposed micromixers are a suitable alternative for their remediation. The LCA and operational efficiency studies results shown here provide a route for the design of novel wastewater treatment systems by coupling low-cost and high-performance micromixers

Methemoglobinemia presenting in a circumcised baby following application of prilocaine: a case report

<p>Abstract</p> <p>Introduction</p> <p>Local anesthesia with prilocaine has become a routine part of ambulatory circumcision procedures. Methemoglobinemia is a rare but potentially lethal complication of local anesthetics.</p> <p>Case presentation</p> <p>We report the case of a 40-day-old Turkish boy who presented with cyanosis after receiving local anesthesia with prilocaine. His methemoglobin level revealed severe methemoglobinemia (methemoglobin = 44%). His cyanosis resolved after intravenous administration of methylene blue.</p> <p>Conclusion</p> <p>Although the association between prilocaine use and methemoglobinemia has generally restricted the use of prilocaine in babies, it is still widely used in ambulatory procedures, especially during circumcision in the neonatal period. Prilocaine should not be used in babies who are less than 3 months old because of the risk of methemoglobinemia; other local anesthetics may be used for this age group. Furthermore, general anesthesia by mask ventilation may be favored for babies less than 3 months of age instead of local anesthetics.</p