Study Size

MODEL SYSTEMS TO STUDY SIZE EFFECTS IN ELECTROCATALYSIS... 

Synthesis of novel materials with desired and tunable physical and chemical properties continues to draw wide interest. Nanomaterials with a variety of shapes and sizes have been synthesized as they offer numerous possibilities to study size and shape-dependent variations of electronic, optical, and chemical properties. Nanomaterials of a particular element show drastic differences in physical and chemical properties when compared with the bulk state. For example, bulk gold, a metal that is insoluble in water can be made dispersible when it is in the nanoparticle form. There are drastic changes in the optical properties as well. Bulk gold appears yellow in color, but when it is in the nanoparticle form with an average core diameter of 16 nm, it appears wine red. Likewise, the chemistry of gold, such as catalysis, also shows a drastic change when the constituent units are in the nanometer range. 

Using photoelectron detection in a femtochemistry arrangement, we studied size-selected clusters of ionic systems, covering the transition from gas phase to condensed phase dynamics [6]. We investigated the solvent effect on Oj dissociation dynamics, and observed... 

Many of the methods used to extract information related to the structure of macromolecules come from studying the behavior of isolated macromolecules in solution. These techniques are based primarily on the flow behavior in a velocity gradient, the rate of Brownian motion of a particle, or osmotic effects associated with the size of individual molecules. The techniques that have been employed to study size and shape of macromolecules most extensively include viscometry, light scattering, analytical ultracentrifugation, and electron microscopy. 

Experimental Results—Gottschalk and Wartman (loc cit) investigated the properties of a number of magnetite powders. Magnetites from four sources were purified and sized, each size-fraction then being analyzed for FesC>4. Only size-fractions below 100-U. S. mesh were studied. Sizes below 350-mesh were air elutriated by the Roller method. 

It is well known that drugs bind to plasma proteins, particularly to serum albumin and a-acid glycoprotein, and that only the unbound, or free, fraction is responsible for any pharmacological effect. For protein-drug binding studies size-exclusion chromatography in one of three variants—namely, the Hum-mel-Dreyer method (1962), the vacancy peak method (Sebille, et al., 1979), and frontal analysis (Cooper and Wood, 1968)—is the traditional method of... 

Why all the fuss about nanoparticles now As increasing attention in engineering is focused on making smaller and smaller machines, questions about the fundamental processes that govern nanoparticle form, stability, and reactivity emerge. The geoscience community is well equipped to tackle the basic science concepts associated with these questions. However, we have our own reasons to study size-dependent phenomena. 

A major advantage of quantitative data is that the study size required to determine whether or not a clinically important difference exists between two treatments will usually be much less than that needed with qualitative data. The calculation of study size with ordinal data is more problematic, but somewhat more data will usually be needed than with quantitative data but often considerably fewer than with qualitative data. 

Because of its advantage in terms of study size over qualitative data, and usually over ordinal data, it is often attempted to obtain outcome measures in clinical studies on a quantitative scale. Two approaches used in an attempt to achieve this aim are the visual analogue scale (VAS) and summated ratings. ... 

The possibility that the difference might be due to chance is addressed in the design of the study by calculating the appropriate study size to... 

Powers study size and differences between treatments... 

This consideration of study size will deal just with the basic ideas and consider a few simple situations. A comprehensive treatment of this subject can be found in the paper by Lachin. ... 

Predicted confidence intervals for treatment differences Section 7.4.3.2 outlined estimation of treatment differences by calculating a CI for the true difference between the treatments. It is possible to predict how wide such a CI will be when considering the issue of study size. Goodman and Berlin derived a simple equation which enables this calculation to be performed. 

The Goodman and Berlin equation can also be used to determine the required study size to produce a CI of a desired width for the treatment difference. Suppose, for example, that the desired CI is the observed treatment difference 5%.The predicted 95% CI for a study with a power of 95% is the observed difference 0-544 x CID. If 0-544 x CID is to be... 

In conclusion, whatever statistical approach is used, meta-analysis cannot overcome the problems of poor study design, other than that of small study size. A meta-analysis of biased studies, or of a biased sample of all the studies that have been performed, will simply give a biased overall conclusion. 

To develop a process to evaluate the comparative efficiency of FTIH study designs, one must take into account mild adverse events (AEs), dose proportionality, the precision in PK parameter estimates, study duration, and study size. A mild adverse event was chosen because most AEs experienced in FTIH studies are mild (see Section 29.5). A desirable design(s) should be able to appropriately characterize the exposure-AE response curve (for the incidence of a mild AE). 

In principle, using colloids for SERS studies offers a unique opportunity to study size effects. Ideally, one may consider the colloid as a controlled and characterized roughness feature without the surface, while in the usual electrochemical and film work one has a surface with a roughness which is generally not well defined. In practice, however, this goal has not been achieved yet. 

Type of Study Size of Study Finding Reference... 

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