University of Alberta

About: University of Alberta is a education organization based out in Edmonton, Alberta, Canada. It is known for research contribution in the topics: Population & Health care. The organization has 65403 authors who have published 154847 publications receiving 5358338 citations. The organization is also known as: Ualberta & UAlberta.

Simultaneous seismic data denoising and reconstruction via multichannel singular spectrum analysis

Abstract: We present a rank reduction algorithm that permits simultaneous reconstruction and random noise attenuation of seismic records. We based our technique on multichannel singular spectrum analysis (MSSA). The technique entails organizing spatial data at a given temporal frequency into a block Hankel matrix that in ideal conditions is a matrix of rank k , where k is the number of plane waves in the window of analysis. Additive noise and missing samples will increase the rank of the block Hankel matrix of the data. Consequently, rank reduction is proposed as a means to attenuate noise and recover missing traces. We present an iterative algorithm that resembles seismic data reconstruction with the method of projection onto convex sets. In addition, we propose to adopt a randomized singular value decomposition to accelerate the rank reduction stage of the algorithm. We apply MSSA reconstruction to synthetic examples and a field data set. Synthetic examples were used to assess the performance of the method in two...

Common Principles of Motor Control in Vertebrates and Invertebrates

Abstract: Comparative neurobiology has proven to be a powerful discipline for elucidating the principles that describe the evolution, development, and functioning of the nervous system (Arb as et a11991; Cohen & Strumwasser 1985; Heiligenberg 1991). Studies on invertebrates have contributed sub­ stantially to establishing many of these principles. Some noteworthy ex­ amples are the mechanisms that establish the diversity of potassium chan­ nels (Jan & Jan 1990; MacKinnon 1991), the ionic mechanisms that generate action potentials (Hodgkin & Huxley 1952), and the cellular and molecular events that underlie learning and memory (Carew & Sahley 1986; Hawkins & Kandel 1990). The analysis of more complex integrative processes has also benefited from studies of invertebrate nervous systems. One example is the influence that the finding of lateral inhibition in the eye of Limulus (Hartline et al 1956) had on our understanding of sensory processing in more complex systems. Another is the profound effect that the analysis of rhythmic motor systems in invertebrates has had on inves­ tigations on rhythmic pattern generating networks in vertebrates (Getting 1988; Grillner 1981; Grillner & Wallen 1985). More recently, the utility of analyzing the action of neuromodulator� on the functioning of neuronal

Role of the ACE2/Angiotensin 1-7 Axis of the Renin-Angiotensin System in Heart Failure.

Abstract: Heart failure (HF) remains the most common cause of death and disability, and a major economic burden, in industrialized nations. Physiological, pharmacological, and clinical studies have demonstrated that activation of the renin-angiotensin system is a key mediator of HF progression. Angiotensin-converting enzyme 2 (ACE2), a homolog of ACE, is a monocarboxypeptidase that converts angiotensin II into angiotensin 1-7 (Ang 1-7) which, by virtue of its actions on the Mas receptor, opposes the molecular and cellular effects of angiotensin II. ACE2 is widely expressed in cardiomyocytes, cardiofibroblasts, and coronary endothelial cells. Recent preclinical translational studies confirmed a critical counter-regulatory role of ACE2/Ang 1-7 axis on the activated renin-angiotensin system that results in HF with preserved ejection fraction. Although loss of ACE2 enhances susceptibility to HF, increasing ACE2 level prevents and reverses the HF phenotype. ACE2 and Ang 1-7 have emerged as a key protective pathway against HF with reduced and preserved ejection fraction. Recombinant human ACE2 has been tested in phase I and II clinical trials without adverse effects while lowering and increasing plasma angiotensin II and Ang 1-7 levels, respectively. This review discusses the transcriptional and post-transcriptional regulation of ACE2 and the role of the ACE2/Ang 1-7 axis in cardiac physiology and in the pathophysiology of HF. The pharmacological and therapeutic potential of enhancing ACE2/Ang 1-7 action as a novel therapy for HF is highlighted.

MetPA: a web-based metabolomics tool for pathway analysis and visualization

Abstract: Summary: MetPA (Metabolomics Pathway Analysis) is a user-friendly, web-based tool dedicated to the analysis and visualization of metabolomic data within the biological context of metabolic pathways. MetPA combines several advanced pathway enrichment analysis procedures along with the analysis of pathway topological characteristics to help identify the most relevant metabolic pathways involved in a given metabolomic study. The results are presented in a Google-map style network visualization system that supports intuitive and interactive data exploration through point-and-click, dragging and lossless zooming. Additional features include a comprehensive compound library for metabolite name conversion, automatic generation of analysis report, as well as the implementation of various univariate statistical procedures that can be accessed when users click on any metabolite node on a pathway map. MetPA currently enables analysis and visualization of 874 metabolic pathways, covering 11 common model organisms. Availability: Freely available at http://metpa.metabolomics.ca Contact: david.wishart@ualberta.ca.