Search results for "quantitative"
showing 10 items of 2409 documents
Simulations of the cultured granule neuron excitability
2003
Abstract We have developed a biophysical model of a cultured rat cerebellar granule neuron and simulated its excitability under different experimental conditions. The basic excitability properties of such a small neuron; the specific action potential waveforms, the overall firing patterns induced by current stimulations, and the linear frequency-current relation, are the main model constraints. Simulations show that for a one-compartmental granule neuron model, the constraints are met using six voltage- and time-dependent ion channel types and calcium dynamics linked to BK Ca ion channel function. This kind of model of a single neuron forms a solid basis for building the increasingly more c…
Quantification of GABA(A) receptor subunit mRNAs by non-radioisotopic competitive RT-PCR utilizing plate-based EIA methodology.
2000
We developed a non-radioisotopic quantitative competitive RT-PCR method for the measurement of gamma-aminobutyric acid (GABA) type A receptor subunit mRNA levels. The specificity of the method was optimized by the use of four subunit-specific oligonucleotides in the sequential steps: reverse transcription, polymerase chain reaction (PCR), and detection. The biotinylated PCR products were bound on streptavidin-coated microtiter plates allowing detection of the products using dinitrophenyl (DNP)-labeled probes and anti-DNP alkaline phosphatase conjugate. The method was set up for the six major cerebellar GABA(A) receptor subunits: alpha1; alpha6; beta2; beta3; gamma2 and delta. The method is …
On localization of moving objects in the visual system of cats.
1980
In cortical areas direction-specific receptive fields occur systematically. Direction specifity is based on unsymmetric coupling of neurons. Such a coupling allows an exact localization of moved stimuli. For this task, the asymmetry in the time domain is compensated for by a spatial asymmetry.
Computational identification of chemical compounds with potential anti-Chagas activity using a classification tree
2021
Chagas disease is endemic to 21 Latin American countries and is a great public health problem in that region. Current chemotherapy remains unsatisfactory; consequently the need to search for new drugs persists. Here we present a new approach to identify novel compounds with potential anti-chagasic action. A large dataset of 584 compounds, obtained from the Drugs for Neglected Diseases initiative, was selected to develop the computational model. Dragon software was used to calculate the molecular descriptors and WEKA software to obtain the classification tree. The best model shows accuracy greater than 93.4% for the training set; the tree was also validated using a 10-fold cross-validation p…
Application of molecular topology in the prediction of new compounds with anti-trypanosomal cytotoxic activity
2021
La enfermedad de Chagas es una antropozoonosis parasitaria de transmisión mayoritariamente vectorial. Si bien afecta principalmente a América, constituye una de las mayores enfermedades desatendidas a nivel mundial. Solamente dos fármacos con un alto grado de toxicidad se encuentran disponibles para su tratamiento, por lo que es preciso aunar esfuerzos en pos del desarrollo de nuevas drogas antitripanosomales eficaces y con escasos efectos adversos. En este estudio, se aplicó la topología molecular para el desarrollo de un modelo QSAR capaz de predecir la actividad citotóxica antitripanosomal de un grupo de 39 compuestos. El modelo desarrollado mediante análisis lineal discriminante permiti…
The Community Structure of the Global Corporate Network
2013
We investigate the community structure of the global ownership network of transnational corporations. We find a pronounced organization in communities that cannot be explained by randomness. Despite the global character of this network, communities reflect first of all the geographical location of firms, while the industrial sector plays only a marginal role. We also analyze the network in which the nodes are the communities and the links are obtained by aggregating the links among firms belonging to pairs of communities. We analyze the network centrality of the top 50 communities and we provide the first quantitative assessment of the financial sector role in connecting the global economy.
World Influence of Infectious Diseases from Wikipedia Network Analysis
2019
AbstractWe consider the network of 5 416 537 articles of English Wikipedia extracted in 2017. Using the recent reduced Google matrix (REGOMAX) method we construct the reduced network of 230 articles (nodes) of infectious diseases and 195 articles of world countries. This method generates the reduced directed network between all 425 nodes taking into account all direct and indirect links with pathways via the huge global network. PageRank and CheiRank algorithms are used to determine the most influential diseases with the top PageRank diseases being Tuberculosis, HIV/AIDS and Malaria. From the reduced Google matrix we determine the sensitivity of world countries to specific diseases integrat…
Contagion in Bitcoin Networks
2019
12 pages, 6 figures. Paper accepted in 2nd Workshop on Blockchain and Smart Contract Technologies (BSCT 2019), workshop satellite of 22nd International Conference on Business Information Systems (BIS 2019); International audience; We construct the Google matrices of bitcoin transactions for all year quarters during the period of January 11, 2009 till April 10, 2013. During the last quarters the network size contains about 6 million users (nodes) with about 150 million transactions. From PageRank and CheiRank probabilities, analogous to trade import and export, we determine the dimensionless trade balance of each user and model the contagion propagation on the network assuming that a user go…
Computer simulation of bottle-brush polymers with flexible backbone: good solvent versus theta solvent conditions.
2011
By Molecular Dynamics simulation of a coarse-grained bead-spring type model for a cylindrical molecular brush with a backbone chain of $N_b$ effective monomers to which with grafting density $\sigma$ side chains with $N$ effective monomers are tethered, several characteristic length scales are studied for variable solvent quality. Side chain lengths are in the range $5 \le N \le 40$, backbone chain lengths are in the range $50 \le N_b \le 200$, and we perform a comparison to results for the bond fluctuation model on the simple cubic lattice (for which much longer chains are accessible, $N_b \le 1027$, and which corresponds to an athermal, very good, solvent). We obtain linear dimensions of …
Exploring Chemical Reactivity in Enzyme Catalyzed Processes Using QM/MM Methods: An Application to Dihydrofolate Reductase
2015
Enzymes are the catalysts used by living organisms to accelerate chemical processes under physiological conditions. In this chapter, we illustrate the current view about the origin of their extraordinary rate enhancement based on molecular simulations and, in particular, on methods based on the combination of Quantum Mechanics and Molecular Mechanics potentials which provide a solution to treat the chemical reactivity of these large and complex molecular systems. Computational studies on Dihydrofolate Reductase have been selected as a conductor wire to present the evolution and difficulties to model chemical reactivity in enzymes. The results discussed here show that experimental observatio…