Atomic resolution imaging of electrode surfaces in solutions containing reversible redox species

Procedures are described for insulating metal scanning tunneling microscope (STM) tips with either glass or polymer coatings. In solutions containing 0.10 M of a reversible redox couple, Fe(CN) - 3/-46 , the faradaic limiting current to polymer coated tips was 200–500 pA and that for glass coated tips was <10 pA. For polymer insulated tips, steady-state currents of 10–100 pA were observed at tip-sample displacements less than 0.3 µm. The suppression of faradaic current achieved by these coating procedures enabled the collection of the first atomic resolution STM images of highly ordered pyrolytic graphite electrodes in contact with redox-active electrolytes. Preliminary data for the in situ electrochemical characterization of these tips are also discussed

Design of a scanning tunneling microscope for electrochemical applications

A design for a scanning tunneling microscope that is well suited for electrochemical investigations is presented. The construction of the microscope ensures that only the tunneling tip and the sample participate in electrochemical reactions. The design also allows rapid replacement of the tip or sample, and enables facile introduction of auxiliary electrodes for use in electrochemical experiments. The microscope utilizes stepper motor driven approach mechanics in order to achieve fully remote operation and to allow reproducible coarse control of tip/sample spacings for electrochemical experiments. Highly ordered pyrolytic graphite images at atomic resolution in air and aqueous solutions can be obtained with this microscope

Predictable forward performance processes : infrequent evaluation and applications to human‐machine interactions

We study discrete‐time predictable forward processes when trading times do not coincide with performance evaluation times in a binomial tree model for the financial market. The key step in the construction of these processes is to solve a linear functional equation of higher order associated with the inverse problem driving the evolution of the predictable forward process. We provide sufficient conditions for the existence and uniqueness and an explicit construction of the predictable forward process under these conditions. Furthermore, we find that these processes are inherently myopic in the sense that optimal strategies do not make use of future model parameters even if these are known. Finally, we argue that predictable forward preferences are a viable framework to model human‐machine interactions occurring in automated trading or robo‐advising. For both applications, we determine an optimal interaction schedule of a human agent interacting infrequently with a machine that is in charge of trading

Effect of density of state on isotope effect exponent of two-band superconductors

The exact formula of Tc's equation and the isotope effect exponent of two-band s-wave superconductors in weak-coupling limit are derived by considering the influence of two kinds of density of state : constant and van Hove singularity. The pairing interaction in each band consisted of 2 parts : the electron-phonon interaction and non-electron-phonon interaction are included in our model. We find that the interband interaction of electron-phonon show more effect on isotope exponent than the intraband interaction and the isotope effect exponent with constant density of state can fit to an experimental data,MgB2, and high-Tc superconductors, better than van Hove singularity density of state.Comment: 11 pages. accepted in Physica

Descripción del crecimiento de ovinos criollos (Ovis aries) en dos poblaciones de Córdoba, Colombia

Objective. Evaluate the model that best described the growth in sheep creole in the Department of Cordoba. Materials and methods. Weights of 55 Criollos sheep were used to select the model that best fit the data. Brody, Logistic, Gompertz and Von Bertalanffy models were evaluated. The parameters of the models were estimated using the NLIN procedure of SAS. The selection of the curve that best described the growth was done considering the Aikaike Information Criterion (AIC), the Bayesian Information Criterion (BIC), the Determination Coefficient (R2), and the Percentage of Convergent Curves (CCP). For the model that best described the growth curve, the percentage of maturity at 4 (M4) and 6 (M6) months of age and age at 75 (AM75) and 95% (AM95) at maturity was estimated. Results. The Brody model presented the best fit. Sex effect was significant (p≤0.05) for β2, M4, M6, EM75 and EM95. While the Farm effect had only a significant effect (p≤0.05) for β2. Conclusions. The Brody model best described growth of the studied sheep populations, its estimated values for maturity and age at maturity were low. Objetivo. Determinar curvas de crecimiento en ovinos Criollos en dos poblaciones del Departamento de Córdoba. Materiales y métodos. Se utilizaron registros de pesos de 55 ovinos Criollos para seleccionar el modelo que mejor se ajustara a los datos. Los modelos evaluados fueron Brody, Logístico, Gompertz y Von Bertalanffy. Los parámetros de los modelos fueron estimados por medio del procedimiento NLIN de SAS. La selección de la curva que mejor describió el crecimiento se realizó considerando el Criterio de Información Aikaike (AIC), el Criterio de Información Bayesiana (BIC), el Coeficiente de Determinación (R2) y el Porcentaje de Curvas Convergentes (PCC). Para el modelo que mejor describió la curva de crecimiento se estimó el porcentaje de madurez a los 4 (M4) y 6 (M6) meses de edad y edad al 75 (EM75) y 95% (EM95) de madurez. Resultados. El modelo de Brody fue el que presentó mejor ajuste. El efecto sexo fue significativo (p≤0.05) para β2, M4, M6, EM75 y EM95, mientras que el efecto finca solo presentó efecto significativo (p≤0.05) para β2. Conclusiones. El modelo de Brody fue el que mejor describió el crecimiento en las poblaciones ovinas estudiadas, siendo los valores estimados para porcentaje de madurez y edad a la madurez bajos

The Role of Endoscopic Ultrasound in the Diagnosis and Management of Primary Gastric Lymphoma

Endoscopic ultrasound (EUS) is considered a valuable diagnostic tool during the workup of malignant gastric lesions, including primary gastric lymphomas (PGL). Although endoscopy combined with multiple biopsies remains essential in the establishment of PGL diagnosis, EUS utilization in locoregional disease staging has been well documented in the literature. Data also support the possible role of EUS in prediction of response to first-line treatment, that is, Helicobacter pylori eradication. However, its application in the posttreatment setting remains problematic, since concordance rates between endosonography and histology findings during follow-up seem to vary substantially. The aim of the present review is to summarize all available data regarding the role of EUS in the management of PGL