Bias potential

Certainly, the same arguments apply for chemical redox catalysis , but as discussed above, thinner films may be effective in this case. Hence, it will be reasonable to work with modified electrodes having a large effective area instead of thick films, i.e. three-dimensional, porous or fibrous electrodes. The notorious problem with current/potential distribution in such electrodes may be overcome by the potential bias given by selective redox catalysts. Some approaches in this direction are described in the next section. 

The second procedure is different from the previous one in several aspects. First, the metallic substrate employed is Au, which does not show a remarkable dissolution under the experimental conditions chosen, so that no faradaic processes are involved at either the substrate or the tip. Second, the tip is polarized negatively with respect to the surface. Third, the potential bias between the tip and the substrate must be extremely small (e.g., -2 mV) otherwise, no nanocavity formation is observed. Fourth, the potential of the substrate must be in a region where reconstruction of the Au(lll) surface occurs. Thus, when the bias potential is stepped from a significant positive value (typically, 200 mV) to a small negative value and kept there for a period of several seconds, individual pits of about 40 nm result, with a depth of two to four atomic layers. According to the authors, this nanostructuring procedure is initiated by an important electronic (but not mechanical) contact between tip and substrate. As a consequence of this interaction, and stimulated by an enhanced local reconstruction of the surface, some Au atoms are mobilized from the Au surface to the tip, where they are adhered. When the tip is pulled out of the surface, a pit with a mound beside it is left on the surface. The formation of the connecting neck between the tip and surface is similar to the TILMD technique described above but with a different hnal result a hole instead of a cluster on the surface (Chi et al., 2000). 

We will use ANOVA to evaluate potential bias in reported results inherent in the analytical methods themselves, or due to the operators (i.e., location of laboratory) performing the methods. For the next series of articles all computations were completed using MathCad Worksheets [4] written by the authors. The objectives of this next set of articles is to determine the precision, accuracy, and bias due to choice of analytical... 

The scanning tunneling microscope (STM) is an excellent device to obtain topographic images of an electrode surface [1], The principal part of this apparatus is a metal tip with a very fine point (see Fig. 15.1), which can be moved in all three directions of space with the aid of piezoelectric crystals. All but the very end of the tip is insulated from the solution in order to avoid tip currents due to unwanted electrochemical reactions. The tip is brought very close, up to a few Angstroms, to the electrode surface. When a potential bias AF, usually of the order... 

Space charge layers and contact potential for efficient charge carrier separation can be achieved with proper semiconductor structure in several ways. When possible semiconductor structures are considered, the charge separation can be attained in an active mode, i.e., by the use of a potential bias in a photoelectrochem-ical cell, or in a passive mode, i.e., with the use of proper contact between different phases. 

It must be noted that for a randomly oriented tracer in solution, the polarization measurement may not provide a zero value as one would expect, due to potential bias... 

A double-blind control is also an essential element of drug studies. Double-blind means that neither experimenter nor subject knows who is receiving the active treatment or the placebo. Again, this is to eliminate potential bias from both parties. Otherwise, experimenters could unwittingly influence the outcome of the study by subtly treating subjects differently. 

A slightly more structured approach uses AVhat-If Analysis,(i) which involves the team asking What if questions that usually concern equipment failures, human errors, or external occurrences. Some examples are What if the procedure was wrong What if the steps were performed out of order The questions can be generic in nature or highly specific to the process or activity where the incident occurred. Sometimes these questions are preprepared by one or two individuals, which may also potentially bias the discussion. 

The use of weekly paclitaxel (45 mg/m2) and carboplatin (100 mg/m2) has been reported (135,136). This combination as used to treat 62 patients with stage III and IV squamous cell carcinoma of the head and neck concurrently with radical radiotherapy lead to a clinical complete response rate of 75 % both at the primary and in the neck with a median survival of 33 mo (135). The authors report a retrospective comparison to similar patients treated with concurrent carboplatin alone or concurrent carboplatin and bleomycin and show on multivariate analysis that complete response and treatment with paclitaxel were predictive for survival (136). This result while encouraging is retrospective in nature and is subject to potential bias. 

Fourth, due to ethical obligations that arise when patients are enrolled in trials, outcomes detected in trials may be treated more aggressively than they would be in usual care. In trials, it is likely that physicians will treat all detected treatable clinical outcomes. In usual care, physicians may treat only those outcomes that in their judgment are clinically relevant. This potential bias would tend to increase the costs of care observed in the trial compared to usual care. 

These omissions will not cause bias only under some circumstances. In particular, subjects in each of the treatment groups should receive equal scrutiny for protocol violations and all such violators should be excluded, in relation to the first point. For the second and third points, the fact that patients do not take study medication or do not provide any post-baseline data should be unrelated to the treatments to which such subjects were assigned. Any potential bias arising from these exclusions should be fully investigated. 

The internal validity. There should be no indications of a potential bias... 

A critical methodological issue for a proper meta-analysis is the choice of studies. It is important that all studies meet reasonable criteria otherwise, a potential bias is introduced. We chose only those studies that had an appropriate control group, which provided a standard by which a drug s effects could be measured. By contrast, there have been meta-analyses of multiple studies on psychotherapy, all done without comparison groups or with invalid comparison groups. Combining the... 

Disclosure of financial arrangements and steps to minimize the potential bias on the study of interest. 

PCI was performed using standard techniques (6,30). All 100 patients received one or more identical close cell-stent design. The same stent design was used in order to avoid potential bias with stent selection in both groups. All patients received 325 mg/day of aspirin indefinitely and clopidogrel as a loading dose of 300 mg on the day of the procedure and 75 mg/day thereafter for one month. Statins were given to all patients indefinitely. 

The application of human data in risk assessment for children has been detailed in a number of publications (USEPA, 1991 Richter-Reichhelm et al., 2002 IPCS, 2005 Kimmel et al., 2006). In general, the risk assessor should evaluate each human study for its power and potential bias. The power of the study is the study s ability to detect an effect. It is dependent on the size of the study population, the frequency of the effect or the exposure in the population, and the level of risk to be identified. The greater the population size and the effect or exposure frequency, the greater the power of the study. In studies of low power, it is generally not possible to establish the lack of an association between an exposure and an effect, and even positive findings may be difficult to support. Metaanalysis, which combines populations from different studies, may increase the power of the overall database, but the potential for the combination of dissimilar populations must be considered in any risk assessment. 

Data are most appropriate to use when there is a close match between the needs of the assessment and the characteristics, methods and assumptions underlying the data. Assessment of appropriateness is an important first step towards ensuring accuracy of the data, the second of the hallmarks we discuss (see next section). At worst, when data are completely inappropriate, they should not be used. However, in cases when the match is not as close as desired, clear documentation at least allows for an appraisal of the potential bias and/or uncertainty introduced by utilization of the data. 

The electrochemistry of silicon is highly important as a tool for surface treatment and the formation of porous silicon. Under the reverse bias (anodic for n-type, cathodic for p-type) of silicon immersed in an electrolyte, a space charge layer is formed near the electrode surface, in which the concentration of the charge carriers differs from that of the bulk material. The width of this space charge layer depends on the type and density of dopants in the material and the potential bias. 

Predetermined reasons for removing patients from therapy should be described along with follow-up procedures. If decisions about evaluability are made after blinding is broken, this should be noted and any potential bias discussed. 

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