Alpha-coefficient

There was considerable corridor discussion after a presentation by Dr. G. L. Silver, who "got the attention of the audience" by taking plutonium chemists to task concerning (according to him) their erroneous use of a (too) simplified summary equation involving the disproportionation of Pu(IV) and their lack of appreciation of alpha coefficients. Dr. Silver stressed the use of alpha coefficients and equations which explicitly involve acidity, hydrolysis of Pu(IV), and especially the presence of Pu(V), which is too frequently ignored. 

Silver was critical of the lack of use by plutonium chemists of a-coefficients. Assuming that Silver was referring to a-coeffi-cients defined as the fraction of the total concentration of a substance that exists as a particular species, he was wrong to say that plutonium chemists have not used them. Phil Horwitz at ANL has used them. Publications from ORNL have reported them to easily show relative concentrations of plutonium species, and L. M. Toth used such a-coefficients as percent of Pu(IV) polymer in his symposium talk Tuesday. Alpha coefficients are a commonly used, simple concept - certainly since Ringbom s article in the Journal of Chemical Education in 1958."... 

Curves (g), (h) and (i) of Figure 3 show the stability surfaces at pH 3.00. Note that the CLASP-w region for S3 is lower than that for S2. This is the only example of such a trend, in this figure. This is due to the fact that the conditional stability products for the 1 3 complexes are smaller than those for the 1 2 complexes (Table II) because of the enhanced influence of alpha-coefficients (21,22) on reactions of higher stoichiometry. The hydrogen ion concentration at pH 3.00 prevents CLASP-7 conditions from being attained over the range covered in... 

The alpha coefficients method based on simpler algorithms for calculating inter-element influence coefficients. 

All these methods for attenuation or compensation of matrix effects can be optimised by correcting the residual matrix effects using the alpha coefficient method. In this case, the mathematical equation becomes ... 

The addition of a second metal generally poses matrix problems which are resolved by creating numerous cross standards and using the alpha coefficient method to obtain a regression line. 

ABSTRACT A rapid and precise X-ray fluorescence method has been developed for the multielement analysis of gypsum and gypsum products. Gypsum specimens are calcined at IOOO°C and then fused with sodium tetraborate flux into flat and transparent disks. The choice of a suitable flux system for the specimen preparation is critical because of a rapid decomposition of anhydrite. CaSO,. in lithium ba fluxes at temperatures above 95O C. This decomposition causes not only visible imperfections in the didi surface but also alters considerably the concentrations of the major elements, calcium and sulfur. The procedure used for a fast setup of ten element analysis of gypsum on the Philips PW-1400 spectrometer utilizing synthetic standards and off-line calculated alpha coefficients is presented. Calibrations carried out with chemically analyzed specimens and their mixtures are compared lo those performed with synthetic standards prepared by blending pure chemicals and anhydrite into the flux. 

The second part of this paper is devoted to the procedure used for a quick setup of ten element analysis of gypsum and gypsum products on the Philips PW-1400 X-ray fluorescence spectrometer, utilizing alpha coefficients. Calibration data obtained with chemically analyzed specimens and their mixtures are compared with those based on synthetic standards prepared by blending pure chemicals with anhydrite. 

The DeJongh model is similar to the Lachance-Trail model 16), but includes correction for self-absorption effects. The alpha coefficients shown in Table 5 were used as starting values for the straight line regression procedure executed by the PW-1400 software package. 

We would like to thank E>r. Bruce A. Hudgens of the U.S. Gypsum Co. Research Center, IL. for the help with the round-robin analyses of several gypsum specimens and stimulating discussions on the subject. We are also grateful to Dr. Richard Rousseau and Mr. G. R. Lachance of the Canadian Geological Survey in Ottawa, who calculated the alpha coefficients used in the matrix corrections procedure and provided many valuable suggestions. 

Rousseau. R., "A Computer Program for Calculating Alpha-Coefficients," Geological Survey of Canada. Ottawa. Canada. 1980. unpublished. 

Reliability refers to the extent to which measures give consistent or accurate results. The purpose of evaluating the reliability of a QOL instrument is to estimate how much of the variation in a score is real as opposed to random. The two reliability assessment methods discussed most often in the HRQOL literature are internal consistency and test-retest reliability. Internal consistency is an assessment of the performance of items within a scale. It is a function of the number of items and their covariation. Internal consistency is commonly measured using Cronbach s alpha coefficient. Alpha coefficients above 0.90 are recommended for making comparisons between individuals and above 0.70 for comparisons between groups. ... 

They were introduced in 1941 by a Swede, Ido Leden, as the ratio of total molal (or molar) concentration of any basis component to the content of its dissociated form. This coefficient serves a measure of the effect of secondary components and is considered the side reaction coefficient. It is also often called alpha-coefficient or for a case of reactions of complex compounds formation, complexation function. In the presence of secondary components s > 1, in their absence s.= 1. This coefficient substantially simplifies interrelation between the conditional and concentration equilibrium constants... 

Whichever of the alpha correction models are employed, two methods are available for the estimation of the alpha coefficients, namely calculation from first princi-... 

Schwarzenbach also introduced alpha-coefficients, which are related to the extent to which side reactions occur, including the formation of complexes as well as hgand protonation). These coeffi-... 

This study assessed constmct reliability by calculating Cronbach s alpha coefficients. Based on Cuieford (1965), Cronbach s a value higher than 0.7 indicates high reliability, the value between 0.7 and 0.35 represents acceptable reliability, and that below 0.35 means unacceptable reliability. The results of our study demonstrate that aU variables Cronbach s a values exceed 0.7 which represents measuring scales have high reliability and internal consistency. 

The researchers assessed the accuracy and reliability of the questionnaire by examining the content reliability from experts with updates and corrections and the test reliability by finding the discrimination power by using item-total correlation, which measures the performance of SMEs in the discrimination (r) range from 0.329 to 0.731. To test the tools reliability, Cronbach s alpha coefficient was used, and the performance measures of SMEs had alpha coefficients ranging from 0.738 to 0.850. 

The reliability of this construct is satisfactory although relatively low in 2002 the Cronbach alpha coefficient was 0.56 in 2002 and 0.80 in 2005. 

The quantitative data obtained from the LFQ, MSLQ and CSUQ qnestionnaires were in the ordinal scale, for example, 1, 2, 3, 4, 5, 6, 7. In these data types, we can say that 2 is greater than 1 and 3 is greater than 2, but the numbers just represent an order and their specific values have no meaning. For example, the scale can also be represented by the letters a, b, c. .. Therefore, the reliability (internal consistency) of a ordinal data set is measnred by the Ordinal Alpha coefficient, which replaces the Cronbach s Alpha coefficient, often used as a measure of reliability for continuous data [29, 30]... 

In this case as well, the Ordinal Alpha coefficient was calculated to measure the reliabiUty of the data obtained in the four categories, as presented in Table 2. 

If a reagent participating in a side reaction is present at a very low concentration and/or the stability of the formed product is low, the alpha coefficient will be close to unity, and the corresponding side reaction will not contribute significantly to the catalyst destabilization. 

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