1,721,033 research outputs found
Effects of hypoxia on the cytotoxicity mediated by tumor necrosis factor-alpha
No full textWe investigated whether hypoxia (2% O-2, similar to 14 mm Hg partial pressure) in comparison to O-2 atmospheric pressure (20.9% O-2, similar to 140 mm Hg) can affect the cytotoxic effects of tumor necrosis factor-alpha (TNF) on the murine cell line L929. Under hypoxic conditions, L929 cells were significantly less inhibited by TNF treatment, even in the presence of actinomycin D. Moreover, under hypoxic conditions, TNF cytotoxicity was significantly inhibited by glutathione, which has been shown to protect cells against oxidative damage induced by various agents. On the other hand, under aerobic conditions treatment with other antioxidant agents and active species oxygen scavengers, as superoxide dismutase and catalase, did not markedly affect the cytotoxicity of TNF. Since hypoxia occurs normally in most solid tumors, these results are interesting because they suggest a disadvantageous inhibition of the cytotoxic effects of TNF in vivo in hypoxic tissues and confirm that oxygen-dependent metabolic processes or free radicals are required to exert TNF-induced cytotoxicity
A weather forecast-based control for the improvement of PCM enhanced radiant floors
Full text linkSignificant energy savings and thermal comfort improvement related to radiant floor systems may not be achieved when underfloor heating/cooling is adopted in lightweight building envelopes. Phase change materials (PCMs) are suitable candidates for providing the necessary thermal inertia with a minimum effect on the construction technology. Impacting variables like internal heat gains, weather conditions and dynamic energy price require the adoption of advanced control strategies to ensure and maximise the energy benefits of PCMs. Despite the potential of model predictive control using weather prediction data has been widely examined by the literature, there is a lack of studies experimentally analysing their implementation in PCM enhanced radiant floor systems. Within the H2020 European project IDEAS the integration of PCMs in a radiant floor system was examined by the University of Ferrara through numerical and experimental investigation. A first prototype was then installed in a small experimental building characterised by a low thermal capacity. Analysis of the monitoring data for the heating period showed that solar radiation strongly impacts on the lightweight building envelope in a short time. Without suitable control, the contribution of PCM that slowly reduced its heat flux during its transition, together with solar heat gains, resulted in an excessive increase in indoor air temperature, wasting the PCM energy saving potential. The aim of the study is the evaluation of a control strategy to improve the management of PCM enhanced radiant floor systems in relation to forthcoming weather conditions in lightweight buildings. The control routine was implemented in the corresponding dynamic energy model in TRNSYS. Results estimated achievable energy saving equal to about 4% and 8% on the heating and the cooling energy demand respectively
Study on thermal performance of a PCM enhanced hydronic radiant floor heating system
No full textRadiant floor systems enhanced with Phase Change Materials (PCMs) could achieve significant energy savings while improving the thermal comfort of occupants in lightweight buildings. Effective integration of PCMs typically requires customised solutions based on a comprehensive analysis due to their complex nature. The objective of the present study is the experimental and numerical investigation of a hydronic radiant floor heating system integrated with macroencapsulated PCM. Experimental tests were carried out on a laboratory-scale by the University of Ferrara, Italy, within the H2020 European project IDEAS. A 2D model was then implemented in COMSOL Multiphysics and calibrated in steady as well as in transient state according to the experimental tests. The behaviour of the system, including temperature distribution and heat flux, were analysed under different conditions. The impact of using dry and wet sand, as well as the effect of the position of PCM – above or under heating pipes – on thermal performance, were investigated. Results showed that the use of high thermal conduction in mortar increases much faster the overall performance of the PCM integrated underfloor heating system. Furthermore, the coupling technology with PCM containers installed under piping significantly enhances the positive effect of wet sand
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
Experimental data and simulations of performance and thermal comfort in a patient room equipped with radiant ceiling panels
Full text linkHospitals require the highest energy demands in non-residential buildings. They provide healthcare 24/7/365 and, at the same time, they ensure indoor air quality, thermal comfort and sterility. However, several studies reveal that high indoor temperatures and low relative humidity (RH) are often perceived in patient rooms during the heating season, suggesting an important energy saving potential. Against this background, radiant ceiling panel (RCP) systems result to be one of the most appropriate solutions as they allow to achieve significant energy savings while providing the highest level of thermal and acoustic comfort, as well as of infection control. In the present study the microclimatic survey of a patient room at Maggiore Hospital in Bologna, Italy, equipped with an air conditioning system integrated with RCP, has reported occupant thermal discomfort. Experimental data were used to calibrate a building model and dynamic building energy simulations were carried out to analyse indoor air temperature, relative humidity, predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) indexes under different inlet air temperatures, to identify the best design conditions for energy efficiency and thermal comfort improvement. It was found that the highest advantages can be obtained when neutral air is supplied
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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