1,721,024 research outputs found
Heat transfer and pressure drops in micro-tubes for ground and space applications
Get PDFThe aim of the research is to compare and understand the bubble dynamics, heat transfer mechanism and pressure drops in subcooled flow boiling, at both, microgravity and normal gravity conditions. Nowadays, there are few studies on this topic, nevertheless the possible applications are many, from the spatial usage to microelectronics cooling. Micro-exchangers are the next generation of cooling systems useful for both terrestrial and space applications where weight and dimensions are important. Flow boiling is the best way to reach high heat fluxes. Micro-tubes, thanks to their dimension, can be used in a wide range of microgravity systems i.e. satellites for communications, thermal management for the International Space Station, cooling of hi-power electronic devices, nuclear space reactors, etc. To develop and design thermal systems for small applications, it is necessary to achieve a detailed understanding of all flow boiling aspects, also under low gravity conditions, at low pressure and at high thermal fluxes. A deepen analysis of available correlations in the literature has been performed and a comprehensive comparison with experimental data provided by two ENEA facilities (MICROBO and BOEMIA) has been carried out. The analysis considers 17 micro-channel correlations, 5 macro-channels and 2 models to calculate heat transfer. Instead, 5 correlations were chosen to calculate saturated boiling pressure drops and 3 for subcooled boiling. As most of data are in subcooled boiling, its effect on prediction is discussed and a model is proposed to calculate vapor quality in the channel. Moreover, a new methodology to calculate pressure drops has been developed and discussed
Coronary Drainage In the Octopus-vulgaris Systemic Heart
No full textThe vascular architecture of the coronary system of the systemic heart of the octopus (Octopus vulgaris) has been studied by means of both the corrosion-cast method and scanning electron microscopy. It is shown that the Octopus systemic heart myocardium is supplied through a very rich capillary network, the complexity of which probably reflects the complex organization of the ventricular wall. Drainage occurs by way of a classic venous system that originates from this capillary network. Morphological evidences are reported indicating that the coronary bed communicates directly with the ventricular lumen. In the isolated perfused systemic heart, the flow through this system is related directly to cardiac contractility. In an in situ preparation of the systemic heart, where for the first time simultaneous records have been obtained, ventricular pressure, coronary vein pressure, and coronary flow appear to be time related. It is suggested that in Octopus the venous coronary flow is not dependent on the systemic arterial pressure, as in the vertebrate heart, but it is directly dependent on intraventricular pressure
The Heart of the Icefish - Bioconstruction and Adaptation
No full textThe Channichthyidae or ''icefish'' represent an intriguing example of extreme adaptation to the stable low temperature and high oxygen content of the Antarctic waters. The lack of respiratory pigments (hemoglobin and myoglobin) in these teleosts is associated with relatively low oxygen consumption and relevant. cardio-circulatory adjustments which include large blood volume, increased relative heart weight (cardiomegaly), and very high cardiac output. The heart has the ability to displace large systolic volumes at a low rate and relatively low pressure, with large ventricular fillings (high ventricular compliance), whereas it is incapable effacing increased afterloads. These functional aspects of mechanical flexibility and restrictions of the cardiac pump have been tentatively related to some constructional aspects of the icefish cardiomegaly, particularly, at the whole ventricular level, to the trabeculate type of myo-architecture, and, at the subcellular level, to the conflict in space economy between the exceptionally high mitochondrial densities and the consequent severe reduction in myofibrillar volume. On the basis of this morphodynamic approach, we suggest that the icefish may illustrate how a certain feature (i.e., an architectural cardiac design) common to the suborder and to most teleosts, and apparently with ''irrelevant'' properties, can become useful for a specialized purpose (i.e., volume pump design); and how, in contrast, the internal machinery construction. because of structural and ultrastructural constraints, may pre;ent these stenothermal sedentary teleosts from conquering niches requiring more active locomotory habits
Modificazioni indotte dall'aloperidolo sul comportamento attentivo del ratto.
No full textAim of present research was to analyze effects of haloperidol, a dopamine D2 receptor antagonist, on focused attention, in the rat. Results suggest that haloperidol might influence specific neural mechanisms involved inn the regulation of attentive behavior likely by affecting sensory-gating dopamine-dependent processes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
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