920,217 research outputs found
Spectral Entropies as Information-Theoretic Tools for Complex Network Comparison
No full textAny physical system can be viewed from the perspective that information is implicitly represented in its state. However, the quantification of this information when it comes to complex networks has remained largely elusive. In this work, we use techniques inspired by quantum statistical mechanics to define an entropy measure for complex networks and to develop a set of information-theoretic tools, based on network spectral properties, such as Rényi q entropy, generalized Kullback-Leibler and Jensen-Shannon divergences, the latter allowing us to define a natural distance measure between complex networks. First, we show that by minimizing the Kullback-Leibler divergence between an observed network and a parametric network model, inference of model parameter(s) by means of maximum-likelihood estimation can be achieved and model selection can be performed with appropriate information criteria. Second, we show that the information-theoretic metric quantifies the distance between pairs of networks and we can use it, for instance, to cluster the layers of a multilayer system. By applying this framework to networks corresponding to sites of the human microbiome, we perform hierarchical cluster analysis and recover with high accuracy existing community-based associations. Our results imply that spectral-based statistical inference in complex networks results in demonstrably superior performance as well as a conceptual backbone, filling a gap towards a network information theory
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Characterization of NGF, trkA NGFR and p75 NTR Expression In Retina From Mice Lacking Reelin Glycoprotein.
No full textPurpose: Reelin is expressed in the retina as well as in injured cornea, in concert with several growth factors such as NGF. Reelin absence leads to abnormal retinal development (including migration, differentiation and plasticity) and loss of rod Bipolar cells (RBPs). The aim of this study was to assess whether NGF pathway is affected in reeler mice, by analyzing NGF and trkANGFR-p75NTR expression in all retinal cells.
Methods: Reeler-L7-EGFP were obtained from B6C3Fe-a/a-rl X C57/BL6J that were backcrossed to N[8] generation. C57/BL6J and L7-EGFP strains were used as controls. Eyes were obtained from anaesthetised mice on postnatal day 21 and processed for NGF, trkANGFR and p75NTR analysis. Reeler status was verified by genotyping. Confocal images were acquired and mean fluorescence intensities were recorded for statistical analysis. Real time PCR was carried out to evaluate differences in molecular expression. Green fluorescent protein (GFP) was used to identify RBPs in both reeler (rl/rl) and wild type (+/+) retinas.
Results: Retinas from both rl/rl and +/+ mice showed specific GFP fluorescence localized in the dendrites, soma and axon terminals of RBPs. The typical appearance of RBPs populating the inner neuronal layer was affected in rl/rl as compared to +/+ mice. A reduced dendrite length and number of synapses were detected in RBPs populating rl/rl retina, as compared to +/+ retina. A selective increase of p75NTR expression was observed in most of RBPs, some Retinal Ganglion Cells (RGCs) and amacrine cells, as compared to +/+, and validated by real time PCR. trkANGFR expression was found slightly decreased. p75NTR/trkANGFR ratio was markedly increased, indicating a selective shift to p75NTR expression in the retina of reeler mice. Most rl/rl RGCs showed a specific NGF immunoreactivity, in comparison to +/+.
Conclusions: Our study shows a decrease in dendritic length and a selective p75NTR over-expression in RBPs, which might be interpreted as a tentative of cell rescue. The selective NGFover-expression in RGC close-to RBP and amacrine cells might be consistent with this hypothesis. From these studies, Reeler mice appear to be a good model for exploring the cross-talk between NGF and Reelin in development/maintenance of a normal retinal function. The complete characterization of NGF pathway in reeler mice might provide further information on RBP and RGC cross-talk during normal and pathological conditions
Changes in Bcl2; Bax; JNK, P65 and Smad 7 Genes in Conjunctival Myofibroblasts Exposed to NGF.
No full textPurpose: Nerve Growth Factor (NGF) might be involved in both healing and fibrotic process occurring in conjunctiva as a result of pathological conditions. We previously described the profibrogenic effect of NGF on conjunctival Fibroblasts, partially mediated by the release of Transforming Growth Factor-β1 (TGFβ1). The aim of this study was to quantify and compare caspase, cJun, p65-NFkB and smad7 expression and/or activation in NGF and TGFβ1 exposed myoFBs.
Methods: Human conjunctival Fibroblast (Innoprot.com) were expanded and TGFβ1-induced myofibroblast (myoFBs) were developed according to a stabilize setting. Serum-starved myoFBs were exposed to single/repeated increasing doses of NGF (0-200ng/mL) or TGFβ1 (10ng/mL) for 15min and 1, 3, 5, 24, 48 and 72 hrs. MTS and HO342 staining were performed. Pellets were analysed for Bcl2, Bax, smad7 and caspase3 by real-time PCR, FACS and confocal analysis. Both dosing and timing exposure results were statistically compared.
Results: NGF effects on myoFBs are strongly dependent on expression ratio of trkANGFR/p75NTR. TGFβ1 by itself does not trigger significant p75NTR expression, retaining a high trkANGFR/p75NTR ratio. Further exposure to NGF shifted trkANGFR/p75NTR ratio in favour to p75NTR expression, with maximum effect at chronic NGF treatment. NGF triggered Bax expression, without affecting significantly Bcl2 expression. Smad7 was up-regulated in those myoFBs treated with NGF (p<.05). By contrary, TGFβ1 inhibited the pro-apoptotic activities and downregulated Bax expression (p<.05). Phosporylation of cJun and p65-NFkB translocation were detected as later as at chronic 100ng/mL NGF exposure.
Conclusions: Together these findings suggest that NGF triggers apoptosis selectively in p75NTR-bearing myoFBs, mainly due to a selective p75NTR-dependent p65 translocation and JNK activation. The molecular mechanism behind this effect may also involve a deregulation of TGFβ1 signaling, as NGF exposure resulted also in Smad7 gene expression, a component of the TGFβ1 pathway with inhibitory activities
Flow Cytometry Approach to Study NGF and p75 in Retinal Cells from Reeler mice
No full textAbstract
Purpose:Reeler mice appear to be a good model for exploring the cross-talk between NGF and Reelin in development/maintenance of a physiological retinal function. Therefore, we sought to characterize NGF and trkANGFR/p75NTR expression in retinal cells from Reeler-L7-EGFPreln-/- transgenic mice (E-Reeler, n=2) and C57BL/6J-L7-EGFPreln+/+ transgenic mice (E-control, n=7), both expressing EGFP positivity in Rod Bipolar Cells (RBC).
Methods:Retinas were dissected from not pooled whole eyes. Single cell were obtained by DispaseII and/or Trypsin digestion, in the presence of DNAseI, equilibrated in HBSS-EDTA and fixed in 1% PFA. Cells were probed with specific antibodies (NGF, p75NTR and trkANGFR) and at least 10000 cells were acquired/analysed by flow cytometry, according to the MACSquant technology. Apoptosis was also estimated by AnnexinV.
Results:Both treatments were successful to obtain single cells from dissected retinas, albeit trypsin allowed a better side-scatter definition/resolution of population. Three main cell populations were separated according to physical parameters: RBC/retinal ganglion cell (RGC), accessory cells (Muller, Amacrine, Horizontal) and photoreceptor. A slight expression of Annexin V was detected (2.9%). EGFP was detected only in RBC (9%). NGF and p75NTR were expressed mainly in RBC/RGC and faintly in accessories cells, while trkANGFR was weakly expressed by RBC and RGC. Both NGF and p75NTR were increased in GFP-positive RBC and RGC, from E-Reeler as compared to E-control.
Conclusions:From our studies, single cells can be enzymatic dissociated from unpooled retinas. The isolation method and the selective NGF/p75NTR increase in GFP-bearing RBC and RGC may provide a good experimental system for studying NGF-reelin cross-talk in these cells
Nutritional strategies to counteract the loss of muscle mass and function characteristic of senescent muscle.
No full textDuring aging, multifactorial events such as activation of inflammatory pathways and mitochondrial dysfunction lead to the onset of sarcopenia, which is characterized by a gradual loss of muscle protein component. It is well known that changes in the quantity and the quality of dietary proteins, as well as the intake of specific amino acids or antioxidants supplementation, counteract some physiopathological processes related to the progression of the loss of muscle mass and may have beneficial effects in improving the anabolic response of muscle in the elderly. The aim of this research is to delay and hopefully prevent, in a mouse experimental model, the loss of muscle mass and functional capacity of aged muscle by dietary supplementation of micronutrients intake. To this purpose we evaluated whether a protein diet rich in arginine and/or taurine, already known to down-regulate the release of inflammatory cytokines in dystrophic muscles (1, 2), modulates the activation of catabolic processes leading to loss of muscle mass characteristic of aged muscle. To this purpose, adult mice were subjected to intraperitoneal injections of taurine, arginine or both, all days for 2 months. The tibialis anterior muscles (TA) were then damaged by cardiotoxin injection. Our results demonstrate that injured TA muscles of mice which received both aminoacids show enhanced regeneration response as demonstrated by the presence of central nucleated fibers, less amount of inflammatory cells and fibrosis, if compared to the control. Moreover the high expression of the inflammation marker, NF-kB, in injured muscle of control mice strongly decreases in taurine + arginine injected mice. These results suggest a role of taurine and arginine in the down-regulation of inflammation and the enhancement of regeneration in skeletal muscle
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Ground State Spin Calculus
No full textWe present an intuitive compositional theory from which one is able to predict and also to control the ground state manifold (and higher energy excitations) of interacting spin systems governed by variants of tunable Ising models, hence giving precise control over the apriori additive structure of Hamiltonian composition. This compositional theory is given in terms of string diagrams: these results were made possible by mapping a variant of the Boolean F2-calculus onto spins and synthesizing modern ideas appearing in Category Theory, Coalgebras, Classical Network Theory and Graphical Calculus. Specifically, we present an algebraic method which allows one to explicitly engineer several energy levels including the low-energy subspace of interacting spin systems. We call this new framework: Ground State Spin Calculus, and in the first instance, the theory requires interactions of up to third order (3- body). By introducing ancillary qubits, we present a novel approach allowing k-body interactions to be captured exactly using only two-body Hamiltonians [Biamonte, Phys. Rev. A 77(5), 052331 (2008)]. Our reduction method has no dependence on perturbation theory or the associated large spectral gap and allows for problem instance solutions to be embedded into the ground energy state of Ising spin systems. This could have important applications for future technology as adiabatic quantum evolution might be used to place such a computational system into it’s ground state
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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