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

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

Mechanistic investigations of nanometer-scale lithography at liquid-covered graphite surfaces

Pulse-induced nanometer-scale lithography has been performed on graphite surfaces that were in contact with pure water or other organic liquids. Very reproducible control over the pit diameter was observed in aqueous solutions, and a well-defined voltage threshold (4.0±0.2 V) was also apparent. Near the threshold voltage, 7 Å diameter×2 Å high protrusions were formed, while larger initial pulse voltages resulted in pits of diameter>~20 Å

Single-Wall Carbon Nanotube Anodes for Lithium Cells

In recent experiments, highly purified batches of single-wall carbon nanotubes (SWCNTs) have shown promise as superior alternatives to the graphitic carbon-black anode materials heretofore used in rechargeable thin-film lithium power cells. The basic idea underlying the experiments is that relative to a given mass of graphitic carbon-black anode material, an equal mass of SWCNTs can be expected to have greater lithium-storage and charge/discharge capacities. The reason for this expectation is that whereas the microstructure and nanostructure of a graphitic carbon black is such as to make most of the interior of the material inaccessible for intercalation of lithium, a batch of SWCNTs can be made to have a much more open microstructure and nanostructure, such that most of the interior of the material is accessible for intercalation of lithium. Moreover, the greater accessibility of SWCNT structures can be expected to translate to greater mobilities for ion-exchange processes and, hence, an ability to sustain greater charge and discharge current densities

Translation directionality and translator anxiety : evidence from eye movements in L1-L2 translation

While considerable research on the impact of anxiety on second language learning has been carried out in international contexts, the impact of anxiety on the translator’s undertaking L2 translation, a sort of anxiety arising from the translation directionality, as well as the structure of cognitive mechanism for translational anxiety, remain under-explored. Adopting the eye-tracking and key-logging approach to data collection, this study implemented an eye-tracking experiment with EFL learners at a Chinese university to probe into how the participants responded to L1 and L2 translation-tasks and the mechanism involved in these processes. It is found that translation directionality does have a great impact on the processing of translation, which causes the change of cognitive load and then leads to the change of levels in translator anxiety. The finding further confirms the key premises of the Processing Proficiency Model and the Revised Hierarchical Model with attendant implications for translation processes

Lithium-enhanced radioactive iodine ablation of hyperthyroid patients

Objective: The objective of this study was to compare the effect of adjuvant lithium therapy on the efficacy of radioactive iodine therapy in hyperthyroidism.Methods: This was a prospective simple randomised comparative, experimental cohort study of hyperthyroid patients for radioactive iodine (RAI) ablation therapy. A total of 163 of the 185 hyperthyroid patients recruited completed the study. Cure was defined by achievement of euthyroidism or hypothyroidism.Results: From of total of 163 patients, 75 received RAI alone and 88 received RAI with lithium. Those who received RAI with adjuvant lithium showed a higher cure rate (78.4%) compared with those who received RAI only (68.1%) (p = 0.002). At one month post RAI therapy, 27.4% of patients who received RAI with adjuvant therapy were cured. This finding showed a trend of being significant compared with just 14.5% cure rate in the group of patients who received RAI alone (p = 0.08). This is an indication of a faster cure rate for patients receiving RAI with lithium. Difference in mean T4 concentration at three months between RAI only (17.67 pmol/l) and RAI with lithium (11.55 pmol/l) was significant with a small size effect (U = 2328.5, Z = –2.700, p = 0.007, r = 0.01). A significant drop in T4 concentrations was observed between the baseline and one-month visit with small effect size (p = 0.001, r = 0.287) in patients who received both RAI and lithium.Conclusion: Adjuvant lithium therapy increases the efficacy of radioactive iodine treatment in hyperthyroidism by increasing overall cure rate and also shortening the time to cure.Keywords: hyperthyroidism, lithium, radioactive iodine ablation, thyroid stimulating hormone, thyroxin

Real-Time Spectroscopic Ellipsometry for Flux Calibrations in Multi-Source Co-Evaporation of Thin Films: Application to Rate Variations in CuInSe₂ Deposition

Flux calibrations in multi-source thermal co-evaporation of thin films have been developed based on real-time spectroscopic ellipsometry (RTSE) measurements. This methodology has been applied to fabricate CuInSe2 (CIS) thin film photovoltaic (PV) absorbers, as an illustrative example, and their properties as functions of deposition rate have been studied. In this example, multiple Cu layers are deposited step-wise onto the same Si wafer substrate at different Cu evaporation source temperatures (TCu). Multiple In2Se3 layers are deposited similarly at different In source temperatures (TIn). Using RTSE, the Cu and In2Se3 deposition rates are determined as functions of TCu and TIn. These rates, denoted Reff, are measured in terms of effective thickness which is the volume per planar substrate area and accounts for surface roughness variations with deposition time. By assuming that all incident metal atoms are incorporated into the films and that the atomic concentrations in the deposited material components are the same as in single crystals, initial estimates of the Cu and In atom fluxes can be made versus TCu and TIn. Applying these estimates to the co-evaporation of a set of CIS films from individual Cu, In, and Se sources, atomic concentration corrections can be assigned to the Cu and In2Se3 calibration films. The corrections enable generation of a novel calibration diagram predicting the atomic ratio y = [Cu]/[In] and rate Reff within the TCu-TIn plane. Using this diagram, optimization of the CIS properties as a PV absorber can be achieved versus both y and Reff