1,721,049 research outputs found
Space Rider Observer Cube - SROC: a CubeSat mission for proximity operations demonstration
No full textNormal Values and Patterns of Normality and Physiological Variability of Mitral and Tricuspid Inflow Pulsed Doppler in Healthy Children
No full textBackground: While mitral (MV) and tricuspid valve (TV) pulsed Doppler velocities and derived gradients are commonly evaluated, data on normal pediatric values are limited. This study aimed to evaluate the normal values and physiological variability for MV and TV Doppler velocities and derived gradients in a large cohort of prospectively enrolled healthy children. Methods: The echocardiographic measurements included pulsed Doppler MV and TV E and A velocities, E deceleration times (EDT), maximal and mean gradients, and velocity time integral (VTI). Results: A total of 544 healthy subjects (median age 6.4 years, range 1 day–17.68 years) were included. MV and TV E velocity, E/A ratio, and E and A wave duration increased, while A velocity decreased with age (p < 0.001). Along with an increase in VTI, there occurred a progressive increase in maximum velocity and gradients and a decrease in mean velocities and gradients. E/A inversions were common, especially at the TV in neonates and infants. For MV, inversion in either one, two, or three consecutive beats occurred in 51.9% of neonates and 18.3% of infants, while it was rare at older ages (all p < 0.001). For TV, inversions in three consecutive beats occurred in 71.4% of neonates, while inversions in only one or two beats were more common in infants (27.3%). For TV, inversion in one or more beats, however, was not infrequent at all ages. Conclusions: We report normal values and patterns of normality and physiological variability for MV and TV inflow Doppler from a large population of healthy children
Particle Size in SRM Plume: Assessment of Collection Method
Full text linkThe present work aims at giving an overview of the current experimental activity status of an intrusive technique for particles capturing in supersonic-high temperature flows for the use in solid rocket motors plume. The innovative technique was conceived in the EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) framework, an initiative financed by the European Space Agency aiming at the characterization of the alumina exiting from rocket nozzles in terms of size, temperature, and spatial distribution. This kind of information are of paramount importance for the environmental impact assessment of space launch activity. Experimental tests are still ongoing and the present paper discusses some of the
critical aspects, solutions, and open questions arising during the hot fire testing of this innovative intrusive
technique
Particle Size in Solid Rocket Motor Plume: New Experimental Method
Full text linkSolid propellant rocket boosters release metal oxide particulate in the atmosphere, as a result of the combustion of the aluminum powder contained in the energetic material. The characterization of these particles is still an open question regarding the environmental impact of space launch activities. For this reason an innovative collection technique was conceived in the frame of the EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) project, an activity financed by the European Space Agency. The method consists in an intrusive probe capable of quenching and capturing
the particles exiting from the nozzle, thus enabling size measurement, chemical characterization, and morphology observation. This paper presents an overview of the activity and reports some preliminary results obtained from the initial particle size characterization
Experiments for Collection and Characterization of Particles Exiting from Solid Propellant Rocket Nozzles
Full text linkMetals in solid propellants are used to improve specific impulse and increment the energy density. Their combustion generates condensed products that move along the motor chamber and are expelled through the nozzle. The discharge of liquid or solid particles across the gas
dynamic nozzle of large boosters is not only a matter of specific impulse loss. Recent climatological studies are addressing possible short and long term environmental effects that may be attributed to space launch activity by large launchers. In this respect, the knowledge of plume
content and, specifically, of physical, chemical, and morphological properties of the exhausted particulate is needed. In the frame of the EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) project, an activity financed by the European Space Agency, the Space
Propulsion Laboratory (SPLab) of Politecnico di Milano developed a collection method and an analysis protocol for the characterization of the particles contained in the rocket plume. The collection is performed by an intrusive probe capable of capturing the particles directly from the nozzle exit and quenching them. The post-collection protocol enables size measurement, chemical characterization, and morphology observation. In this paper an overview of the collection and analysis activity is presented, along with the final results that were achieved by analyzing the plume of different rocket motors
Lung Ultrasound Findings in Healthy Children and in Those Who Had Recent, Not Severe COVID-19 Infection
No full textLung ultrasound (LUS) is gaining consensus as a non-invasive diagnostic imaging method for the evaluation of pulmonary disease in children
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
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