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Search Results: 1 - 10 of 191922 matches for " Ines D. Steenbuck "
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Homeostatic structural plasticity increases the efficiency of small-world networks
Markus Butz,Ines D. Steenbuck,Arjen van Ooyen
Frontiers in Synaptic Neuroscience , 2014, DOI: 10.3389/fnsyn.2014.00007
Abstract: In networks with small-world topology, which are characterized by a high clustering coefficient and a short characteristic path length, information can be transmitted efficiently and at relatively low costs. The brain is composed of small-world networks, and evolution may have optimized brain connectivity for efficient information processing. Despite many studies on the impact of topology on information processing in neuronal networks, little is known about the development of network topology and the emergence of efficient small-world networks. We investigated how a simple growth process that favors short-range connections over long-range connections in combination with a synapse formation rule that generates homeostasis in post-synaptic firing rates shapes neuronal network topology. Interestingly, we found that small-world networks benefited from homeostasis by an increase in efficiency, defined as the averaged inverse of the shortest paths through the network. Efficiency particularly increased as small-world networks approached the desired level of electrical activity. Ultimately, homeostatic small-world networks became almost as efficient as random networks. The increase in efficiency was caused by the emergent property of the homeostatic growth process that neurons started forming more long-range connections, albeit at a low rate, when their electrical activity was close to the homeostatic set-point. Although global network topology continued to change when neuronal activities were around the homeostatic equilibrium, the small-world property of the network was maintained over the entire course of development. Our results may help understand how complex systems such as the brain could set up an efficient network topology in a self-organizing manner. Insights from our work may also lead to novel techniques for constructing large-scale neuronal networks by self-organization.
Homeostatic structural plasticity can account for topology changes following deafferentation and focal stroke
Markus Butz,Ines D. Steenbuck,Arjen van Ooyen
Frontiers in Neuroanatomy , 2014, DOI: 10.3389/fnana.2014.00115
Abstract: After brain lesions caused by tumors or stroke, or after lasting loss of input (deafferentation), inter- and intra-regional brain networks respond with complex changes in topology. Not only areas directly affected by the lesion but also regions remote from the lesion may alter their connectivity—a phenomenon known as diaschisis. Changes in network topology after brain lesions can lead to cognitive decline and increasing functional disability. However, the principles governing changes in network topology are poorly understood. Here, we investigated whether homeostatic structural plasticity can account for changes in network topology after deafferentation and brain lesions. Homeostatic structural plasticity postulates that neurons aim to maintain a desired level of electrical activity by deleting synapses when neuronal activity is too high and by providing new synaptic contacts when activity is too low. Using our Model of Structural Plasticity, we explored how local changes in connectivity induced by a focal loss of input affected global network topology. In accordance with experimental and clinical data, we found that after partial deafferentation, the network as a whole became more random, although it maintained its small-world topology, while deafferentated neurons increased their betweenness centrality as they rewired and returned to the homeostatic range of activity. Furthermore, deafferentated neurons increased their global but decreased their local efficiency and got longer tailed degree distributions, indicating the emergence of hub neurons. Together, our results suggest that homeostatic structural plasticity may be an important driving force for lesion-induced network reorganization and that the increase in betweenness centrality of deafferentated areas may hold as a biomarker for brain repair.
Hiperplasia Suprarrenal de Iniciación Tardia Late-Onset Adrenal Hyperplasia (CAH)
Ronald Youlton R,Maria Ines Sims D
Revista chilena de pediatría , 1985,
Driver study oriented to the vegetation spectral library creation
Nico Bonora,Ines Marinosci,Manuela D’Amen,Valter Sambucini
Italian Journal of Remote Sensing , 2008,
Abstract: By utilising the Italian component of the Image & Corine Land Cover 2000 project (I&CLC2000) it has been proposed the creation of a database containing vegetation spectral signature, by using Landsat 7 ETM+ images acquired during the summer of 1999-2001 and covering the whole Italian territory, in order to contribute on the improving of the land cover/use classification processes. The initial project structure foresees both the spectral and statistical results analysis of beechwood land cover (CLC2000 class). For the spectral analysis it has been utilised the vector layer retailed from the CLC2000 and applied on the Landsat images. The statistical analysis on the selected areas has been effectuated by non-parametric test (Kruskal-Wallis ANOVA). In order to implement the spectral dataset of land vegetation component, this study aims at the chestnut analysis (CLC2000 class), by using the same methodology previously applied to the beachwood.
Detection of Spin Correlations in Optical Lattices by Light Scattering
Ines de Vega,J. Ignacio Cirac,D. Porras
Physics , 2007, DOI: 10.1103/PhysRevA.77.051804
Abstract: We show that spin correlations of atoms in an optical lattice can be reconstructed by coupling the system to the light, and by measuring correlations between the emitted photons. This principle is the basis for a method to characterize states in quantum computation and simulation with optical lattices. As examples, we study the detection of spin correlations in a quantum magnetic phase, and the characterization of cluster states.
Online reference book for biological topics
Ines Chyla
Genome Biology , 2000, DOI: 10.1186/gb-2000-1-1-reports207
Abstract: Navigating around the site is very easy. A link at the bottom of every page returns the visitor to the 'welcome' page. Each alphabetized index/glossary page has an alphabetical listing, at its top, which can be used to search for the next term or item. There is also a 'frames' version, which has a permanent clickable alphabet at the top of each page.The site is updated regularly, and most recently on 17 October 1999.The 'how to navigate' section on the 'welcome' page explains how the site is structured and how it can best be navigated. It even introduces browser functions that can be used to search the site.External links to expand on the information given here would be useful.Cornell University provides a site devoted to The logic of molecular approaches to biological problems.Kimball's biology pagesThe logic of molecular approaches to biological problems
How to design experiments logically
Ines Chyla
Genome Biology , 2000, DOI: 10.1186/gb-2000-1-1-reports209
Abstract: All pages have a menu at the top, making navigation around the site relatively easy. The pages are very long though, and within pages (except the homepage) there are no 'back to the top' links. Links that are accompanied by an asterisk lead to the appropriate alphabetical section of the dictionary, but not to the relevant entry itself. Also, there are a few internal page links that do not work.The site was last updated 25 November 1997.There is extensive linking to and from the dictionary across the site and this enables visitors to read the topics in any order.Individual pages are too long.A third layer of pages to cut down on length would be useful. Repair of the misdirected internal links would also make the long pages easier to navigate.Kimball's biology pages provide a comprehensive online biology reference book.The logic of molecular approaches to biological problemsKimball's biology pages
Ribozymes as tools for the analysis of gene function
Ines Chyla
Genome Biology , 2000, DOI: 10.1186/gb-2000-1-1-reports208
Abstract: It is relatively easy to navigate through the site as it consists of only three pages. There are, however, no 'back to...' links so the back button of the browser has to be used instead. The external links for the software program described do not work, and neither do some of the links to cited literature. None of the small images within the text displayed, but the links to the larger versions of the images all worked.The site was last updated 30 April 1997.This is the best comprehensive information on ribozymes available on-line, and is supported by explanatory graphics.Apart from the lack of updates, there is no real site structure and many links are broken. Some of the graphics are too large to be printed without becoming truncated.The site needs a thorough update to repair the broken links, especially the external ones. It would also benefit from the addition of links to other important papers on the subject, and a general update to include recent developments.The determinants of ribozyme and antisense activity in the cell
Trends in Productive Years of Life Lost to Premature Mortality Due to Coronary Heart Disease
Lessa, Ines;
Arquivos Brasileiros de Cardiologia , 2002, DOI: 10.1590/S0066-782X2002001500007
Abstract: objective: to estimate the number of productive years of life lost to premature death due to coronary heart disease in brazil and to report their trends over a 20-year period. methods: the brazilian ministry of health raw database on death due to coronary heart disease from 1979-1998 was used. the productive years of life lost to premature death were estimated using 20 and 59 years of age as the cut points for the productive years, replacing the potential years of 1 and 70 of the original formula. a descriptive analysis was provided with adjustments, means, proportions, ratios, percentages of increase or reduction, and mobile means. results: a 35.8% increase in death for males and 51.3% for females was observed, +43.3% being the relative difference for females. the annual means of the productive years of life prematurely lost were analyzed in 140,865 males and 58,559 females, with the differential ratio between the age groups ranging from 2.3 to 2.5. the annual means were less favorable for males. within each group (intragroup), the ratios decreased with the increase in age, and the age means at the time of death remained constant. the raw tendencies decreased in the 20- to 29-year age group and increased in the 40- to 59-year age group for females and the 40- to 49-year age group for males. when adjusted, the raw tendencies decreased. conclusion: the 43.3% increase in the number of female deaths as compared with that of males and the ascending tendency in the productive years of life lost in the 40- to 59-year age group point to the influence of unfavorable changes in female lifestyles and suggest a deficiency in programs for prevention and control of risk factors and in their treatment in both sexes.
Medical care and deaths due to coronary artery disease in Brazil, 1980-1999
Lessa, Ines;
Arquivos Brasileiros de Cardiologia , 2003, DOI: 10.1590/S0066-782X2003001200001
Abstract: objective: to estimate the frequency of medical care preceding deaths due to coronary artery diseases (cad) in different brazilian regions and capitals and to describe trends in medical care from 1980 to 1999. methods: information on medical care preceding deaths due to coronary artery diseases/acute myocardial infarction in adults > 20 years from 1980 to 1999 was collected in the datasus, the databank of the brazilian health ministry. sex, states, and capitals selected for 1999 were analyzed in the study. medical care was stratified as follows: with, without, and ignored medical care. the descriptive analysis comprised frequencies, ratios of frequency, test for proportions, and increments or reductions in frequencies. results: acute myocardial infarction (ami) represented 75 to 85% of the cad in the period; the frequency of deaths with medical care ranged from 48.9 to 63%, and that of ignored medical care ranged from 27.2 to 41.5%. the frequency of other cad with medical care ranged from 56 to 76%. the frequency of deaths preceded by medical care decreased by 17.8%, and that with ignored medical care increased by 36.5% (rf=2). the values for the other cad were -20.2% and +64.6% (rf=44.4). deaths preceded by medical care were more frequent in females at all ages and in all brazilian regions. conclusion: the results show a high frequency of sudden death and suggest errors in diagnosis or codification and overestimation of the statistics about mortality. validation of the death certificate diagnosis and frequent surveillance are required.
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