A general-purpose approach to computer-aided dynamic analysis of a flexible helicopter

A general purpose mathematical formulation is described for dynamic analysis of a helicopter consisting of flexible and/or rigid bodies that undergo large translations and rotations. Rigid body and elastic sets of generalized coordinates are used. The rigid body coordinates define the location and the orientation of a body coordinate frame (global frame) with respect to an inertial frame. The elastic coordinates are introduced using a finite element approach in order to model flexible components. The compatibility conditions between two adjacent elements in a flexible body are imposed using a Boolean matrix, whereas the compatibility conditions between two adjacent bodies are imposed using the Lagrange multiplier approach. Since the form of the constraint equations depends upon the type of kinematic joint and involves only the generalized coordinates of the two participating elements, then a library of constraint elements can be developed to impose the kinematic constraint in an automated fashion. For the body constraints, the Lagrange multipliers yield the reaction forces and torques of the bodies at the joints. The virtual work approach is used to derive the equations of motion, which are a system of differential and algebraic equations that are highly nonlinear. The formulation presented is general and is compared with hard-wired formulations commonly used in helicopter analysis

Pycnogenol: a nutraceutical for venous health

Recent studies utilizing highly sophisticated methodology and techniques were able to provide a new insight into the molecular mechanism of the biological activity of various botanical extracts. The present review provides an update of the multifaceted biological profile of the nutraceutical Pycnogenol® in venous health, using a target oriented approach in light of pathophysiology of chronic venous insufficiency. Pycnogenol is French maritime pine bark extract produced by extraction of the outer bark of Pinus pinaster Ait. Subsp. atlantica. Pycnogenol has strong antioxidant profile proven by in vitro and in vivo studies in animals and further confirmed in clinical trials. Its strong antioxidant profile, vasodilator activity, antithrombotic effect and its collagen stabilizing property make it a unique health product. It reduces edema of legs and lowers chances of developing deep venous thrombosis and skin ulceration. These properties further qualify Pycnogenol to be a useful food supplement for venous health particularly in chronic venous insufficiency. Developing new combination products using synergistic approaches are the future trends of research and development to prove efficacy in conditions which involves oxidative stress, inflammation, endothelial dysfunction, thrombogenesis, and ulceration.Biomedical Reviews 2008; 19: 33-43

The nutraceutical Pycnogenol: its role in cardiovascular health and blood glucose control

Pycnogenol® (a registered trademark of Horphag Research Ltd.) is French maritime pine bark extract of the outer bark of Pinus pinaster Ait. Subsp. atlantica. Its specificationsaredescr ibedinthe USP 28-Dietary supplements. Pycnogenol has strong antioxidant profile proven by in vitro and in vivo studies and further confirmed in clinica ltrials. Its strong antioxidant profile, vasodilator activity, antithrombotic effect and collagen stabilizing property make it a unique health product. In humans, Pycnogenol has been shown to lower blood pressure in mild to moderate hypertensive individuals and blood glucose levels in diabetics. In this review the diverse biological effects of Pycnogenol are presented and discussed using a target-oriented approach, in health and disease conditions like edema, inflammation, chronic venous insufficiency, deep vein thrombosis, diabetes, diabetic retinopathy, and hypertension. The future trends are the continuous efforts proving its efficacy inconditions which involves oxidative stress and inflammation. Recent preliminary study utilizing "high throughput" methodology and nutrigenomics approach are able to provide a new insight into the molecular mechanism of the biological activity of this botanical sourced nutraceutical.Biomedical Reviews 2005; 16: 49-57

World-Class high quality mathematics education for all K-12 American Students

In September 1989, the United States’ Governors Conference in Charlottesville, Virginia set an ambitious goal by declaring that “By the year 2000, United States students will be first in the world in mathematics and science achievements”. However, recent results of the ‘Programme for International Student Achievement’ and ‘Trends in International Mathematics and Science Study’ indicate that the United States students’ achievements in mathematics are far below world class standards. This paper seeks to discuss issues in an international context related to the goal of creating world-class high quality mathematics education for all K-12 American students. In particular, the author also shares his reflections and depicts lessons from Singapore’s success story in mathematics education

A statistical approach to persistent homology

Assume that a finite set of points is randomly sampled from a subspace of a metric space. Recent advances in computational topology have provided several approaches to recovering the geometric and topological properties of the underlying space. In this paper we take a statistical approach to this problem. We assume that the data is randomly sampled from an unknown probability distribution. We define two filtered complexes with which we can calculate the persistent homology of a probability distribution. Using statistical estimators for samples from certain families of distributions, we show that we can recover the persistent homology of the underlying distribution.Comment: 30 pages, 2 figures, minor changes, to appear in Homology, Homotopy and Application

Knockdown resistance (kdr)-like mutations in the voltage-gated sodium channel of a malaria vector Anopheles stephensi and PCR assays for their detection

<p>Abstract</p> <p>Background</p> <p>Knockdown resistance (<it>kdr</it>) in insects, resulting from mutation(s) in the voltage-gated sodium channel (vgsc) gene is one of the mechanisms of resistance against DDT and pyrethroid-group of insecticides. The most common mutation(s) associated with knockdown resistance in insects, including anophelines, has been reported to be present at residue Leu1014 in the IIS6 transmembrane segment of the vgsc gene. This study reports the presence of two alternative <it>kdr</it>-like mutations, L1014S and L1014F, at this residue in a major malaria vector <it>Anopheles stephensi </it>and describes new PCR assays for their detection.</p> <p>Methods</p> <p>Part of the vgsc (IIS4-S5 linker-to-IIS6 transmembrane segment) of <it>An. stephensi </it>collected from Alwar (Rajasthan, India) was PCR-amplified from genomic DNA, sequenced and analysed for the presence of deduced amino acid substitution(s).</p> <p>Results</p> <p>Analysis of DNA sequences revealed the presence of two alternative non-synonymous point mutations at L1014 residue in the IIS6 transmembrane segment of vgsc, i.e., T>C mutation on the second position and A>T mutation on the third position of the codon, leading to Leu (TTA)-to-Ser (TCA) and -Phe (TTT) amino acid substitutions, respectively. Polymerase chain reaction (PCR) assays were developed for identification of each of these two point mutations. Genotyping of <it>An. stephensi </it>mosquitoes from Alwar by PCR assays revealed the presence of both mutations, with a high frequency of L1014S. The PCR assays developed for detection of the <it>kdr </it>mutations were specific as confirmed by DNA sequencing of PCR-genotyped samples.</p> <p>Conclusions</p> <p>Two alternative <it>kdr-</it>like mutations, L1014S and L1014F, were detected in <it>An. stephensi </it>with a high allelic frequency of L1014S. The occurrence of L1014S is being reported for the first time in <it>An. stephensi</it>. Two specific PCR assays were developed for detection of two <it>kdr</it>-like mutations in <it>An. stephensi</it>.</p

Higher fine-scale genetic structure in peripheral than in core populations of a long-lived and mixed-mating conifer - eastern white cedar (Thuja occidentalis L.)

<p>Abstract</p> <p>Background</p> <p>Fine-scale or spatial genetic structure (SGS) is one of the key genetic characteristics of plant populations. Several evolutionary and ecological processes and population characteristics influence the level of SGS within plant populations. Higher fine-scale genetic structure may be expected in peripheral than core populations of long-lived forest trees, owing to the differences in the magnitude of operating evolutionary and ecological forces such as gene flow, genetic drift, effective population size and founder effects. We addressed this question using eastern white cedar (<it>Thuja occidentalis</it>) as a model species for declining to endangered long-lived tree species with mixed-mating system.</p> <p>Results</p> <p>We determined the SGS in two core and two peripheral populations of eastern white cedar from its Maritime Canadian eastern range using six nuclear microsatellite DNA markers. Significant SGS ranging from 15 m to 75 m distance classes was observed in the four studied populations. An analysis of combined four populations revealed significant positive SGS up to the 45 m distance class. The mean positive significant SGS observed in the peripheral populations was up to six times (up to 90 m) of that observed in the core populations (15 m). Spatial autocorrelation coefficients and correlograms of single and sub-sets of populations were statistically significant. The extent of within-population SGS was significantly negatively correlated with all genetic diversity parameters. Significant heterogeneity of within-population SGS was observed for 0-15 m and 61-90 m between core and peripheral populations. Average <it>Sp</it>, and gene flow distances were higher in peripheral (<it>Sp </it>= 0.023, σ_g= 135 m) than in core (<it>Sp </it>= 0.014, σ_g= 109 m) populations. However, the mean neighborhood size was higher in the core (<it>Nb </it>= 82) than in the peripheral (<it>Nb </it>= 48) populations.</p> <p>Conclusion</p> <p>Eastern white cedar populations have significant fine-scale genetic structure at short distances. Peripheral populations have several-folds higher within-population fine-scale genetic structure than core populations. Anthropogenic disturbances and population fragmentation presumably have significant effects on fine-scale genetic structure in eastern white cedar. Core populations have higher neighborhood size than peripheral populations, whereas gene flow distances are higher in peripheral than in core populations. The results of our study contribute to the knowledge of poorly-understood spatial genetic structure of core versus peripheral populations in plants. As well, the information is of significance for conservation of genetic resources of eastern white cedar and perhaps of other long-lived forest trees with mixed-mating system.</p