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Search Results: 1 - 10 of 187177 matches for " Michael B. Franklin "
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A Poisson Solver Based on Iterations on a Sylvester System  [PDF]
Michael B. Franklin, Ali Nadim
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.96052
We present an iterative scheme for solving Poisson’s equation in 2D. Using finite differences, we discretize the equation into a Sylvester system, AU +UB = F, involving tridiagonal matrices A and B. The iterations occur on this Sylvester system directly after introducing a deflation-type parameter that enables optimized convergence. Analytical bounds are obtained on the spectral radii of the iteration matrices. Our method is comparable to Successive Over-Relaxation (SOR) and amenable to compact programming via vector/array operations. It can also be implemented within a multigrid framework with considerable improvement in performance as shown herein.
Design of a Neurally Plausible Model of Fear Learning
Franklin B. Krasne,Michael S. Fanselow
Frontiers in Behavioral Neuroscience , 2011, DOI: 10.3389/fnbeh.2011.00041
Abstract: A neurally oriented conceptual and computational model of fear conditioning manifested by freezing behavior (FRAT), which accounts for many aspects of delay and context conditioning, has been constructed. Conditioning and extinction are the result of neuromodulation-controlled LTP at synapses of thalamic, cortical, and hippocampal afferents on principal cells and inhibitory interneurons of lateral and basal amygdala. The phenomena accounted for by the model (and simulated by the computational version) include conditioning, secondary reinforcement, blocking, the immediate shock deficit, extinction, renewal, and a range of empirically valid effects of pre- and post-training ablation or inactivation of hippocampus or amygdala nuclei.
The Effect of Propranolol and Midazolam on the Reconsolidation of a Morphine Place Preference in Chronically Treated Rats
Michael J. F. Robinson,Keith B. J. Franklin
Frontiers in Behavioral Neuroscience , 2011, DOI: 10.3389/fnbeh.2011.00042
Abstract: A stable memory can be disrupted if amnestic treatment is applied in conjunction with memory reactivation. Recent findings in the conditioned place preference (CPP) model suggest that blocking reconsolidation attenuates the ability of environmental cues to induce craving and relapse in drug addicts, but the impact of prior physical dependence has not been described. We examined the effect of post-reactivation amnestic treatment on reconsolidation of a CPP for morphine, in animals na?ve to morphine, under chronic morphine experience or abstinent. Chronic morphine experience was induced by escalating doses of morphine from 10 mg/kg/day (s.c.), and maintained on 30 mg/kg/day during the course of conditioning and reactivation procedures, or conditioning alone. Na?ve and morphine-experienced animals were trained in a three-compartment apparatus by four morphine (5 mg/kg, s.c.) and four saline experiences paired with either of two large conditioning compartments. The memory was then reactivated by a CPP test, and immediately afterward animals received an injection of the beta-adrenergic antagonist propranolol (10 mg/kg, s.c.), the GABAa agonist midazolam (1 mg/kg, i.p.), or saline. Morphine-na?ve rats received only a single reconsolidation-blocking treatment (Experiment 1), while chronic morphine rats were given eight reactivation sessions each followed by amnestic treatment, either before (Experiment 2) or after 10 days of withdrawal (Experiment 3). Propranolol and midazolam disrupted reconsolidation in morphine-na?ve rats, but failed to disrupt the CPP when rats were trained under chronic morphine treatment, even if they were recovered from chronic opiate exposure before reactivation. In fact, propranolol increased the preference for the drug-paired context in animals trained while maintained on chronic morphine. Midazolam had little effect. Morphine experience may produce neurochemical changes which alter memory storage processes and reduce the impact of amnestic treatments on reconsolidation.
Large-Scale Forest Modeling: Deducing Stand Density from Inventory Data
Oskar Franklin,Elena Moltchanova,Florian Kraxner,Rupert Seidl,Hannes B?ttcher,Dimitry Rokityiansky,Michael Obersteiner
International Journal of Forestry Research , 2012, DOI: 10.1155/2012/934974
Abstract: While effects of thinning and natural disturbances on stand density play a central role for forest growth, their representation in large-scale studies is restricted by both model and data availability. Here a forest growth model was combined with a newly developed generic thinning model to estimate stand density and site productivity based on widely available inventory data (tree species, age class, volume, and increment). The combined model successfully coupled biomass, increment, and stand closure (=stand density/self-thinning limited stand density), as indicated by cross-validation against European-wide inventory data. The improvement in model performance attained by including variable stand closure among age cohorts compared to a fixed closure suggests that stand closure is an important parameter for accurate forest growth modeling also at large scales. 1. Introduction A common challenge in large-scale forest planning is to find an optimal balance among different land use management options, such as forest carbon sequestration, timber production, and other forest-based services. In such an analysis, regional-to-national and even continental-scale computationally efficient modeling of potential effects of forestry activities and disturbances on these services is necessary. These effects depend on many factors of which forest productivity, stand density, and characteristics of management, such as thinning and rotation length, are particularly important [1, 2]. In addition, stand density and thinning are important in relation to other forestry topics, such as carbon sequestration in forests [3], biodiversity [4], sensitivity to wind damage [5], sensitivity to insect damage [6], and fire risk [7]. Stand density and thinning have received considerable attention in forest research, and a large body of knowledge has been accumulated on the effects of thinning on physiology and productivity from the leaf to the stand level [8]. However, despite the central role of thinning in forestry, large-scale (continental) forest scenario analysis tools hardly incorporate state-of-the-art knowledge of thinning and stand density effects [9–11]. A reason for not including these effects in large-scale analyses may be the site and species-specific nature of most stand-scale stand density models. The stand scale models are often limited in their generality and require input data that limits their applicability over large scales where coherent data are scarce. Stand and individual-based thinning models relying on empirical findings of growth and yield studies, such as the
Diabetes-Induced Superoxide Anion and Breakdown of the Blood-Retinal Barrier: Role of the VEGF/uPAR Pathway
Azza B. El-Remessy, Telina Franklin, Nagla Ghaley, Jinling Yang, Michael W. Brands, Ruth B. Caldwell, Mohamed Ali Behzadian
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0071868
Abstract: Diabetes-induced breakdown of the blood-retinal barrier (BRB) has been linked to hyperglycemia-induced expression of vascular endothelial growth factor (VEGF) and is likely mediated by an increase in oxidative stress. We have shown that VEGF increases permeability of retinal endothelial cells (REC) by inducing expression of urokinase plasminogen activator receptor (uPAR). The purpose of this study was to define the role of superoxide anion in VEGF/uPAR expression and BRB breakdown in diabetes. Studies were performed in streptozotocin diabetic rats and mice and high glucose (HG) treated REC. The superoxide dismutase (SOD) mimetic tempol blocked diabetes-induced permeability and uPAR expression in rats and the cell permeable SOD inhibited HG-induced expression of uPAR and VEGF in REC. Inhibiting VEGFR blocked HG-induced expression of VEGF and uPAR and GSK-3β phosphorylation in REC. HG caused β-catenin translocation from the plasma membrane into the cytosol and nucleus. Treatment with HG-conditioned media increased REC paracellular permeability that was blocked by anti-uPA or anti-uPAR antibodies. Moreover, deletion of uPAR blocked diabetes-induced BRB breakdown and activation of MMP-9 in mice. Together, these data indicate that diabetes-induced oxidative stress triggers BRB breakdown by a mechanism involving uPAR expression through VEGF-induced activation of the GSK3β/β-catenin signaling pathway.
An Ontology for Comparative Cognition: A Functional Approach
Stan Franklin,Michael Ferkin
Comparative Cognition & Behavior Reviews , 2006,
Abstract: The authors introduce an ontology for the study of how animals think, as well as a comprehensive model of human and animal cognition utilizing the ontology. The IDA (Intelligent Distribution Agent) model of cognition, a computational and conceptual model derived from a working software agent, is described within the framework of the ontology. The model is built on functional needs of animals, relating it to the existing literature. The article provides testable hypotheses and a sample a model of decision-making processes in voles. The article closes with a brief comparison of the IDA model to other computational models of cognition, and a discussion of the strengths and weaknesses of the ontology and the model.
Tow New Species of Ceratopogonidae (Diptera)
Franklin B. Lewis
Psyche , 1956, DOI: 10.1155/1956/39053
Library usage patterns in the electronic information environment. Electronic journals, Use studies, Libraries, Medical libraries
B. Franklin,T. Plum
Information Research: an international electronic journal , 2004,
Abstract: This paper examines the methodology and results from Web-based surveys of more than 15,000 networked electronic services users in the United States between July 1998 and June 2003 at four academic health sciences libraries and two large main campus libraries serving a variety of disciplines. A statistically valid methodology for administering simultaneous Web-based and print-based surveys using the random moments sampling technique is discussed and implemented. Results from the Web-based surveys showed that at the four academic health sciences libraries, there were approximately four remote networked electronic services users for each in-house user. This ratio was even higher for faculty, staff, and research fellows at the academic health sciences libraries, where more than five remote users for each in-house user were recorded. At the two main libraries, there were approximately 1.3 remote users for each in-house user of electronic information. Sponsored research (grant funded research) accounted for approximately 32% of the networked electronic services activity at the health sciences libraries and 16% at the main campus libraries. Sponsored researchers at the health sciences libraries appeared to use networked electronic services most intensively from on-campus, but not from in the library. The purpose of use for networked electronic resources by patrons within the library is different from the purpose of use of those resources by patrons using the resources remotely. The implications of these results on how librarians reach decisions about networked electronic resources and services are discussed.
El Ni o and Multidecadal Climate Change: A Global Perspective
Franklin B Schwing
Investigaciones Marinas , 2002,
Guías para la localización de metales preciosos en ofiolitas colombianas. Informe de avance proyecto Cyted XIII.1. Ofiolitas: características mineralógicas y petrográficas del yacimiento de...
Franklin Ortiz B.
DYNA , 2004,
Abstract: En desarrollo de un programa iberoamericano de investigación aprobado por el CYTED, red Metales Preciosos, cuyo objetivo es establecer guías de exploración que permitan localizar depósitos de Metales Preciosos, MP, (Au, Ag, Platinoides) en Ofiolitas y en el cual participa el CIMEX y el ICNE, se ha acumulado información geológica, bibliográfica, de campo y laboratorio, que permite mostrar la importancia metalogénica que para Colombia tienen estos complejos de rocas máficas y ultramáficas. Algunos resultados preliminares muestran que la sola existencia de Metales Preciosos (MP) en algunas áreas del país, en unidades litológicas de las secuencias ofiolíticas tanto de su ambiente primario como secundario, justifica el que las entidades involucradas en la industria minera colombiana den una mirada hacia este ambiente geológico. Ejemplos de yacimientos en explotación, de ambiente primario y secundario, donde el oro y la plata son elementos de interés económico son el yacimiento de la mina El Roble (Sulfuros masivos) y el de Cerro Matoso (Lateritas) y por lo cual, especialmente del segundo, donde aún no se ha definido su posibilidad, se indican algunas particularidades y características geológicas que pueden servir de guías de exploración para estimar su verdadero potencial minero y para la eventual búsqueda en otras áreas del territorio donde se tengan cuerpos similares. De la explotación minera que por más de 14 a os se ha realizado en el yacimiento de níquel de Cerro Matoso, se tiene hoy acumulado una abundante información acerca de las características geológicas y mineralógicas del yacimiento. A pesar de ello, aún se desconocen aspectos relevantes acerca de su origen y el potencial en otros elementos de interés económico. En este trabajo se hace una síntesis sobre los diversos materiales constitutivos de la mineralización, su distribución, características petrográficas, mineralógicas y su composición química. En términos generales y de acuerdo con la terminología empleada rutinariamente en la mina, la columna del regolito laterítico del yacimiento está constituida, del techo hacia la base, por los siguientes materiales: Canga, laterita, saprolito café, saprolito verde, peridotita saprolitizada y peridotita. Sin embargo, es necesario evitar confusiones y ser cuidadoso con el uso de esta terminología en razón de que hay materiales que no encajan en tales términos. Se indican los materiales, sus características químicas y/o mineralógicas, y los nuevos minerales determinados (Chamosita, metales preciosos, etc.) dadas la gran importancia que tienen por sus im
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