an efficient and simple procedure for the synthesis of 1,8-dioxo-octahydroxanthenes from the aromatic aldehydes and 5,5-dimethylcyclohexane-1,3-dione (dimedone) in the presence of boric acid [bo3h3 or b(oh)3] as an inexpensive and reusable catalyst is described. the salient features of this methodology are: the elimination of corrosive liquid acids, high yields, simple methodology, short reacti...

Item test analysis is an aid to identify items that need to be eliminated from an assessment. An automatic elimination procedure based on item statistics, therefore, could help to increase the quality of a test in an objective manner. This was investigated by studying the effect of a standardized elimination procedure on the test results of a second-year course over a period of 6 successive yea...

It is well known that the solution of the equality constrained least squares (LSE) problem minBx=d ‖b−Ax‖2 is the limit of the solution of the unconstrained weighted least squares problem min x ∥∥ [ μd b ] − [ μB A ] x ∥∥ 2 as the weight μ tends to infinity, assuming that [B A ] has full rank. We derive a method for the LSE problem by applying Householder QR factorization with column pivoting t...

Aim. To identify the predictors of compliance to gluten free diet in children with celiac disease. Methods. 134 children in the study group were assessed for dietary compliance followed by a questionnaire based interview. Psychosocial parameters were assessed by standard Pediatric Symptom Checklist (PSC). Dietary compliant and noncompliant groups were compared and assessed for factors affecting...

Prognostic models based on survival data frequently make use of the Cox proportional hazards model. Developing reliable Cox models with few events relative to the number of predictors can be challenging, even in low-dimensional datasets, with a much larger number of observations than variables. In such a setting we examined the performance of methods used to estimate a Cox model, including (i) ...

Neurodegenerative diseases are frequently associated with structural changes in the brain. Magnetic resonance imaging (MRI) scans can show these variations and therefore can be used as a supportive feature for a number of neurodegenerative diseases. The hippocampus has been known to be a biomarker for Alzheimer disease and other neurological and psychiatric diseases. However, it requires accura...

A method was developed to accurately predict the risk of injuries in industrial jobs based on datasets not meeting the assumptions of parametric statistical tools, or being incomplete. Previous research used a backward-elimination process for feedforward neural network (FNN) input variable selection. Simulated annealing (SA) was used as a local search method in conjunction with a conjugate-grad...

Muntinga JH, Schuil HA. Effects of automatic item eliminations based on item test analysis. Adv Physiol Educ 31: 247–252, 2007; doi:10.1152/advan.00019.2007.—Item test analysis is an aid to identify items that need to be eliminated from an assessment. An automatic elimination procedure based on item statistics, therefore, could help to increase the quality of a test in an objective manner. This...

If is the computed solution to a tridiagonal system Ax b obtained by Gaussian elimination, what is the "best" bound available for the error x and how can it be computed efficiently? This question is answered using backward error analysis, perturbation theory, and properties of the LU factorization of A. For three practically important classes of tridiagonal matrix, those that are symmetric posi...

We present a model of roundoff error analysis that combines simplicity with predictive power. Though not considering all sources of roundoff within an algorithm, the model is related to a recursive roundoff error analysis and therefore is capable of correctly predicting stability or instability of an algorithm. By means of nontrivial examples, such as the componentwise backward stability analys...