University of Kentucky

About: University of Kentucky is a education organization based out in Lexington, Kentucky, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 43933 authors who have published 92195 publications receiving 3256087 citations. The organization is also known as: UK.

Costs and limits of phenotypic plasticity.

Abstract: The costs and limits of phenotypic plasticity are thought to have important ecological and evolutionary consequences, yet they are not as well understood as the benefits of plasticity. At least nine ideas exist regarding how plasticity may be costly or limited, but these have rarely been discussed together. The most commonly discussed cost is that of maintaining the sensory and regulatory machinery needed for plasticity, which may require energy and material expenses. A frequently considered limit to the benefit of plasticity is that the environmental cues guiding plastic development can be unreliable. Such costs and limits have recently been included in theoretical models and, perhaps more importantly, relevant empirical studies now have emerged. Despite the current interest in costs and limits of plasticity, several lines of reasoning suggest that they might be difficult to demonstrate.

New Evidence on Measuring Financial Constraints: Moving Beyond the KZ Index

Abstract: We collect detailed qualitative information from financial filings to categorize financial constraints for a random sample of firms from 1995 to 2004. Using this categorization, we estimate ordered logit models predicting constraints as a function of different quantitative factors. Our findings cast serious doubt on the validity of the KZ index as a measure of financial constraints, while offering mixed evidence on the validity of other common measures of constraints. We find that firm size and age are particularly useful predictors of financial constraint levels, and we propose a measure of financial constraints that is based solely on these firm characteristics.

Assessment of mindfulness by self-report: the Kentucky inventory of mindfulness skills.

Abstract: A self-report inventory for the assessment of mindfulness skills was developed, and its psychometric characteristics and relationships with other constructs were examined. Participants included thr...

Synapse loss in frontal cortex biopsies in Alzheimer's disease: Correlation with cognitive severity

Abstract: Ultrastructural studies of biopsied cortical tissue from the right frontal lobe of 8 patients with mild to moderate Alzheimer's disease (AD) revealed that the number of synapses in lamina III of Brodmann's area 9 was significantly decreased when compared with the number in age-matched control brains (n = 9; postmortem time, less than 13 hours). Further decline in synaptic number was seen in age-matched autopsied AD specimens. In the AD brains there was significant enlargement of the mean apposition length, which correlated with degree of synapse loss; as synapse density declined, synapse size increased. The enlargement of synapses, coupled with the decrease in synaptic number, allowed the total synaptic contact area per unit volume to remain stable in the patients who underwent biopsy. In autopsied subjects who had AD, there was no further enlargement of mean synaptic contact area. There was a significant correlation between synapse counts and scores on the Mini-Mental State examination in the patients who underwent biopsy. Lower mental status scores were associated with greater loss of synapses. Choline acetyltransferase activity was significantly decreased in the biopsied group and declined further in the autopsied specimens of AD. There was no relationship between choline acetyltransferase activity and scores on the Mini-Mental State examination or synapse number. There is evidence of neural plasticity in the AD neuropil; synaptic contact size increased in patients who had biopsy and possibly compensated for the numerical loss of synapses. But by end stage of the disease, the ability of the cortex to compensate was exceeded and both synapse number and synaptic contact area declined.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial Least Squares for Discrimination

Abstract: Partial least squares (PLS) was not originally designed as a tool for statistical discrimination. In spite of this, applied scientists routinely use PLS for classification and there is substantial empirical evidence to suggest that it performs well in that role. The interesting question is: why can a procedure that is principally designed for overdetermined regression problems locate and emphasize group structure? Using PLS in this manner has heurestic support owing to the relationship between PLS and canonical correlation analysis (CCA) and the relationship, in turn, between CCA and linear discriminant analysis (LDA). This paper replaces the heuristics with a formal statistical explanation. As a consequence, it will become clear that PLS is to be preferred over PCA when discrimination is the goal and dimension reduction is needed. Copyright © 2003 John Wiley & Sons, Ltd.