1,853 research outputs found
WHEN SHOULD RANDOM EFFECTS BE INCLUDED IN ESTIMABLE FUNCTIONS AND WHEN THEY SHOULD NOT?
In the mixed model, the behavior of linear functions of the fixed and random effects is examined. It is found that inclusion of certain functions of random effects can lead to estimators which are equivalent to those under a fixed effects model and are inconsistent with the inherent structure of the mixed model. Three examples are presented which illustrate the behavior of linear functions of the fixed and random effects. These functions represent the broad, narrow and intermediate inference spaces as introduced by McLean, Sanders and Stroup (1991). Which random effects should be included in the model is discussed. Random effects representing experimental error units are candidates for inclusion in estimable functions. Inclusion of experimental unit effects in estimable functions can lead to misleading results
Exploring the Factors Associated with Online Financial and Performance Disclosure in Nonprofits
Informed by theories of technological innovation, this paper develops and empirically tests a web disclosure adoption model. In order to test the model, a questionnaire was administered to a sample of 775 organizations in an eight-county regional area in the Northeastern United States. Results reveal that Chief Executive Officer (CEO) and organizational characteristics are related to web disclosure adoption. Specifically, there is more disclosure of performance information online when the CEO believes that the web is useful for promoting transparency and accountability when the organization views the web as a communication or strategic tool, when more employees have technical expertise, and when the board of directors is more supportive of web technology. We found more web disclosure of financial information when the organization possesses the technological readiness for web disclosure. This paper contributes to research by identifying the main factors that facilitate web disclosure adoption in nonprofit contexts
Population Structure and Conservation Genetics of the Oregon Spotted Frog, Rana Pretiosa
The Oregon spotted frog (Rana pretiosa) is one of the most threatened amphibians in the Pacific Northwest. Here we analyzed data from 13 microsatellite loci and 298 bp of mitochondrial DNA in frogs collected from 23 of the remaining R. pretiosa populations in order to (1) assess levels of genetic diversity within populations of R. pretiosa, (2) identify the major genetic groups in the species, (3) estimate levels of genetic differentiation and gene flow among populations within each major group, and (4) compare the pattern of differentiation among R. pretiosa populations with that among populations of R. cascadae, a non-endangered congener that also occurs in Oregon and Washington. There is a strong, hierarchical genetic structure in R. pretiosa. That structure includes six major genetic groups, one of which is represented by a single remaining population. R. pretiosa populations have low genetic diversity (average He = 0.31) compared to R. cascadae (average He = 0.54) and to other ranid frogs. Genetic subdivision among populations is much higher in R. pretiosa than in R. cascadae, particularly over the largest geographic distances (hundreds of kilometers). A joint analysis of migration rates among populations and of effective sizes within populations (using MIGRATE) suggests that both species have extremely low migration rates, and that R. pretiosa have slightly smaller effective sizes. However, the slight difference in effective sizes between species appears insufficient to explain the large difference in genetic diversity and in large-scale genetic structure. We therefore hypothesize that low connectivity among the more widely-spaced R. pretiosa populations (owing to their patchier habitat), is the main cause of their lower genetic diversity and higher among-population differentiation. Conservation recommendations for R. pretiosa include maintaining habitat connectivity to facilitate gene flow among populations that are still potentially connected, and either expanding habitat or founding additional \u27backup\u27 populations to maintain diversity in the isolated populations. We recommend that special consideration be given to conservation of the Camas Prairie population in Northern Oregon. It is the most geographically isolated population, has the lowest genetic diversity (He = 0.14) and appears to be the only remaining representative of a major genetic group that is now almost extinct. Finally, because the six major groups within R. pretiosa are strongly differentiated, occupy different habitat types, and are geographically separate, they should be recognized as evolutionarily significant units for purposes of conservation planning
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Improved resolution and signal-to-noise ratio in laser-ultrasonics by SAFT processing.
Laser-ultrasonics is an emerging nondestructive technique using lasers for the generation and detection of ultrasound which presents numerous advantages for industrial inspection. In this paper, the problem of detection by laser-ultrasonics of small defects within a material is addressed. Experimental results obtained with laser-ultrasonics are processed using the Synthetic Aperture Focusing Technique (SAFT), yielding improved flaw detectability and spatial resolution. Experiments have been performed on an aluminum sample with a contoured back surface and two flat-bottom holes. Practical interest of coupling SAFT to laser-ultrasonics is also discussed
A balanced complex chromosomal rearrangement (BCCR) in a family with reproductive failure
Balanced complex chromosomal rearrangements are very rare events in the human population. Translocations involving three or more chromosomes frequently lead to a severe reproductive impairment secondary to meiotic disturbance in males and to chromosomal imbalance in gametes of females. We report a new familial case of complex chromosome anomaly involving chromosomes 13, 14 and 22. Cytogenetic investigations showed a complex chromosomal chromosome rearrangement involving: (i) a Robertsonian translocation between chromosomes 13 and 14; and (ii) a reciprocal translocation between the long arms of chromosome 14 and the long arm of chromosome 22. The aetiology of the translocation was characterized by conventional fluorescence inâsitu hybridization (FISH) studies and routine Râ and Gâbanding (RTBG and GBTG) combined with α and ÎČ satellite centromeric FISH probes. Predicted configuration of the hexavalent at pachytene stage of meiosis was used to consider the modes of segregation; only two configurations resulted in a normal or balanced gamete karyotype. Reproductive management and genetic counselling are discusse
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