1,720,988 research outputs found
H2O2 INDUCES NECROPTOSIS IN MESOANGIOBLAST STEM CELLS
No full textStem cells are used in regenerative medicine, but their therapeutic efficacy is compromised by their huge death during the first days post-transplantation. Indeed, the microenvironment within damaged tissues is hostile for stem cell survival mainly due to oxidative stress. H2O2 may play a relevant role in inducing death of the injected cells. The aim of our study was to determine the mechanism of mesoangioblast (A6) cell death after an H2O2 treatment.
FACS analysis with annV/PI showed that H2O2 induced a dose and time-dependent decrement in A6 viability. We have also found an increase in caspases 8, 9 and 3 activity after the treatment. To assess their involvement in cell death, the pan caspase inhibitor Z-VAD was used. Neither early apoptosis, nor late apoptosis/necrosis, nor necrosis were reduced, suggesting that the cell death induced by H2O2 was caspase-independent. Then, we tested whether H2O2 is responsible for the autophagy activation.To study autophagy we evaluated the expression of specific markers. H2O2 decreased beclin1, Atg5, Atg7 and the ratio LC3II/I, in a dose dependent way. At the same time it increased p62 protein expression indicating an impaired autophagic flux, also confirmed by the increase of pAKT, responsible for the activation of mTOR, a negative regulator of autophagy. According to these data A6 treatment with H2O2 seems to not induce nor apoptosis or autophagy. For this reason we hypothesized the activation of necroptosis, a specific form of caspase-independent, non-apoptotic or necrotic cell death. To confirm whether the observed cell death was due to enhanced necroptosis, the proportion of necrotic cells was determined by annV/PI staining. FACS analysis showed an increase in percentage of both late apoptotic/necrotic and necrotic cells, which were further increased by pretreatment with Z-VAD. To investigate the relationship between physiological autophagy and necroptosis, cells were treated with H2O2 in the presence of the autophagic inhibitor 3MA. AnnV/PI staining showed that the inhibition of autophagy by 3MA significantly enhanced necroptosis in A6 treated cells. Conversely, 3MA had no effect on apoptosis. In conclusion, our data indicate that the cytotoxicity of H2O2 in A6 mainly occurred via the induction of necroptosis, enhanced by both apoptosis and autophagy inhibition
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Distilling Router Data Analysis for Faster and Simpler Dynamic IP Lookup Algorithms
No full textWe consider the problem of fast IP address lookup in the forwarding engines of Internet routers. Many hardware and software solutions available in the literature solve a more general problem on strings, the longest prefix match. These solutions are then specialized on real IPv4/IPv6 addresses to work well on the specific IP lookup problem. We propose to go the other way around. We first analyze over 2400 public snapshots of routing tables collected over five years, discovering what we call the "middle-class effect" of those routes. We then exploit this effect for tailoring a simple solution to the IP lookup scheme, taking advantage of the skewed distribution of Internet addresses in routing tables. Our algorithmic solution is easy to implement in hardware or software as it is tantamount to performing an indirect memory access. Its performance can be bounded tightly in the worst case and has very low memory dependence (e.g., just one memory access to off-chip memory in the hardware implementation). It can quickly handle route announcements and withdrawals on the fly, with a small cost which scales well with the number of routes. Concurrent access is permitted during these updates. Our ideas may be helpful for attaining state-of-art link speed and may contribute to setting up a general framework for designing lookup methods by data analysis
VISTO: VIsual STOryboard for Web Video Browsing
No full textWeb video browsing is rapidly becoming a very popular activity in the Web scenario, causing the production of a concise video content representation a real need. Currently, static video summary techniques can be used to this aim. Unfortunately, they require long processing time and hence all the summaries are produced in advance without any users customization. With an increasing number of videos and with the large users heterogeneousness, this is a burden. In this paper we propose VISTO, a summarization technique that produces customized on-the-fly video storyboards. The mechanism uses a fast clustering algorithm that selects the most representative frames using their HSV color distribution and allows users to select the storyboard length and the processing time. An objective and subjective evaluation shows that the storyboards are produced with good quality and in a time that allows on-the-fly usage
On Using Clustering Algorithms to Produce Video Abstracts for the Web Scenario
No full textA tool to provide an idea of the content of a given video is becoming a need in the current Web scenario, where the presence of videos is increasing day after day. Dynamic summarization techniques can be used to this aim as they set up a video abstract, by selecting and sequencing short video clips extracted from the original video. Needless to say, the selection process is critical. In this paper we focus our attention on clustering algorithms to provide such selection and we investigate the effects of their employment in the web scenario. Clustering algorithms are very effecting in producing static video summary, but few works consider them for video abstract production. For this reason, we set up an experimental scenario where we investigate their performance considering different categories of video, different abstract lengths and different low-level video analysis. Results show that clustering techniques can be useful only for some categories of videos and only if the selection process is based on video scene characteristics. Furthermore, the investigation also shows that to provide a customized service (user can freely decide the abstract time length), only fast clustering algorithm should be used
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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