			Home About us Contact

General Limitations (general + limitation)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Internal algorithm variability and among-algorithm discordance in statistical haplotype reconstruction

MOLECULAR ECOLOGY, Issue 8 2009
ZU-SHI HUANG
The potential effectiveness of statistical haplotype inference makes it an area of active exploration over the last decade. There are several complications of statistical inference, including: the same algorithm can produce different solutions for the same data set, which reflects the internal algorithm variability; different algorithms can give different solutions for the same data set, reflecting the discordance among algorithms; and the algorithms per se are unable to evaluate the reliability of the solutions even if they are unique, this being a general limitation of all inference methods. With the aim of increasing the confidence of statistical inference results, consensus strategy appears to be an effective means to deal with these problems. Several authors have explored this with different emphases. Here we discuss two recent studies examining the internal algorithm variability and among-algorithm discordance, respectively, and evaluate the different outcomes of these analyses, in light of Orzack (2009) comment. Until other, better methods are developed, a combination of these two approaches should provide a practical way to increase the confidence of statistical haplotyping results. [source]

Generalization and numerical investigation of QMOM

AICHE JOURNAL, Issue 1 2007
R. Grosch
Abstract A generalized framework is developed for the quadrature method of moments (QMOM), which is a solution method for population balance models. It further evaluates the applicability of this method to industrial suspension crystallization processes. The framework is based on the concepts of generalized moments and coordinate transformations, which have been used already in earlier solution approaches. It is shown how existing approaches to QMOM are derived from the suggested unified framework. Thus, similarities and differences between the various QMOM methods are uncovered. Further, potential error sources involved in the different approaches to QMOM are discussed and assessed by means of a series of test cases. The test cases are selected to be challenging. The error in the QMOM solution is evaluated by comparison to an adaptive, error controlled solution of the population balance. The behavior of a range of different QMOM formulations is analyzed by means of numerical quadrature, dynamic simulation, as well as numerical continuation and bifurcation analysis. As a result of this detailed analysis, some general limitations of the method are detected and guidelines for its application are developed. This article is limited to lumped population balance models with one internal coordinate. © 2006 American Institute of Chemical Engineers AIChE J, 2007 [source]

Dietary fiber, low-molecular-weight food constituents and colo-rectal inflammation in animal models , A review

MOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 10 2009
Dieter Schrenk
Abstract This review provides an overview over studies in experimental animals aimed at elucidating the influence of dietary constituents on colo-rectal inflammation. Human studies as well as in vitro investigations will not be covered. In experimental animals, a variety of chemical treatments and genetic modifications, lead to various types of gut inflammation. In a number of these models, there is good evidence for an anti-inflammatory action of dietary tocopherols, certain polyphenols, and curcumin at relatively high oral doses. It has also been established, that oral application of fats and oils rich in n-3 PUFAs and/or conjugated linoleic acid (CLA) can attenuate certain types of colitis in experimental animal models. While the effect of dietary calcium on experimental colitis is less clear, there are hints indicating that certain high-fiber diets or diets rich in digestion-resistant carbohydrates ("fiber") can attenuate experimental colitis in animals, although contradictory results have been reported. In summary, the anti-inflammatory potency of dietary constituents on colon inflammation in experimental animals seems to be rather limited. The reasons for this lack of activity seem to be manifold including pharmacokinetic limitations and intestinal degradation of the compounds, in particular insufficient local, i. e., intra- or sub-mucosal levels of the effective compounds, and general limitations of animal models. [source]

Digital image analysis of plus disease in retinopathy of prematurity

ACTA OPHTHALMOLOGICA, Issue 4 2009
Tariq Aslam
Abstract. An accurate assessment of retinopathy of prematurity (ROP) is essential in ensuring correct and timely treatment of this potentially blinding condition. Current modes of assessment are based upon clinical grading by expert examination of retinal changes. However, this may be subjective, unreliable and difficult and there has been significant interest in alternative means of measurement. These have been made possible through technological advancements in image capture and analysis as well as progress in clinical research, highlighting the specific importance of plus disease in ROP. Progress in these two fields has highlighted the potential for digital image analysis of plus disease to be used as an objective, reliable and valid measurement of ROP. The potential for clinical and scientific advancement through this method is argued and demonstrated in this article. Along with the potential benefits, there are significant challenges such as in image capture, segmentation, measurement of vessel width and tortuosity; these are also addressed. After discussing and explaining the challenges involved, the research articles addressing digital image analysis of ROP are critically reviewed. Benefits and limitations of the currently published techniques for digital ROP assessment are discussed with particular reference to the validity and reliability of outcome measures. Finally, the general limitations of current methods of analysis are discussed and more diverse potential areas of development are discussed. [source]