Music discovery on online streaming platforms : the role of consumers’ subjective expertise

Streaming platforms have radically changed the way in which consumers listen to new music, as the process of discovery slowly shifted from an indirect exposure to songs to an increasingly interactive play between users and platforms. Customers are constantly supplied with services offering new releases as well as unexplored artists or genres, that aim at incentivizing and facilitating the consumption and discovery of new contents. The following study aims at investigating the effect of subjective expertise on streaming platforms users’ consumption preferences. It is argued that the potential knowledge offered by a platforms’ service interacts with consumers’ different levels of expertise, affecting willingness to discover new music. Subsequently, the study explores the effect of subjective expertise on two motivational variables, namely, variety seeking and need for uniqueness. In order to test the hypothesis a survey was conducted in which participants were presented with a fake playlist offering two types of potential consumption knowledge (breadth and depth). Participants were randomly assigned to one of the knowledge conditions, as well as a novice or expert condition in which subjective expertise was manipulated. The results showed that novice and expert consumers’ preferences in willingness to discover differ significantly according to the type of consumption knowledge offered by the service. No differences in variety seeking behaviors were found, even though expert consumers appear to be more inclined to seek for uniqueness when listening to music on streaming platforms.As plataformas de streaming mudaram radicalmente a forma como os consumidores ouvem música nova com o processo de descoberta a passar lentamente de uma exposição indireta a canções para uma relação interativa entre utilizadores e plataformas. Aos consumidores são constantemente oferecidos serviços com novos lançamentos bem como artistas e géneros não explorados, que visam incentivar e facilitar o consumo e descoberta de novos conteúdos. Este estudo visa investigar o efeito do conhecimento subjetivo nas preferências de consumo dos utilizadores de plataformas de streaming. É debatido que o conhecimento potencial oferecido por um serviço de uma plataforma interage com os diferentes níveis de conhecimento dos consumidores, afetando o desejo de descobrir música nova. Adicionalmente, este estudo explora o efeito do conhecimento subjetivo em duas variáveis motivacionais, a procura de variedade e a necessidade de singularidade. De forma a testar a hipótese, foi realizado um questionário no qual os inquiridos foram expostos a uma lista de reprodução falsa, oferecendo dois tipos de potencial conhecimento de consumo (amplo e profundo). A cada participante foi atribuído, aleatoriamente, uma das condições de conhecimento bem como a condição de principiante ou especialista, em que o conhecimento subjetivo foi manipulado. Os resultados mostram que que as preferências dos consumidores principiantes e especialistas na vontade de descobrir diferem significativamente de acordo com o tipo de conhecimento de consumo oferecido pelo serviço. Não foram encontradas diferenças no comportamento de procura de variedade, embora os consumidores especialistas mostrem maior desejo de unicidade quando consomem música em plataforma de streaming

Extension of Compact Operators from DF-spaces to C(K) spaces

[EN] It is proved that every compact operator from a DF-space, closed subspace of another DF-space, into the space C(K) of continuous functions on a compact Hausdorff space K can be extended to a compact operator of the total DF-space.The research of the authors was supported by the Coordinación de la Investigación Científica de la UMSNH.Garibay Bonales, F.; Vera Mendoza, R. (2006). Extension of Compact Operators from DF-spaces to C(K) spaces. Applied General Topology. 7(2):165-170. doi:10.4995/agt.2006.1921.SWORD16517072Köthe, G. (1983). Topological Vector Spaces I. Grundlehren der mathematischen Wissenschaften. doi:10.1007/978-3-642-64988-2Johnson, W. B., & Lindenstrauss, J. (2001). Basic Concepts in the Geometry of Banach Spaces. Handbook of the Geometry of Banach Spaces, 1-84. doi:10.1016/s1874-5849(01)80003-6W. B. Johnson and M. Zippin, Extension of operators from weak*-closed subspaces of l1 to C(K), Studia Mathematica 117 (1) (1995), 43–45.Michael, E. (1956). Continuous Selections. I. The Annals of Mathematics, 63(2), 361. doi:10.2307/1969615E. Michael, Some Problems, Open Problems in Topology, Elsevier, Amsterdam, 1990.L. Narici and E. Beckenstein, Topological Vector Spaces, Marcel Dekker, Inc., New York, 1985

Muscle structural assembly and functional consequences.

The relationship between muscle structure and function has been a matter of investigation since the Renaissance period. Extensive use of anatomical dissections and the introduction of the scientific method enabled early scholars to lay the foundations of muscle physiology and biomechanics. Progression of knowledge in these disciplines led to the current understanding that muscle architecture, together with muscle fibre contractile properties, has a major influence on muscle mechanical properties. Recently, advances in laser diffraction, optical microendoscopy and ultrasonography have enabled in vivo investigations into the behaviour of human muscle fascicles and sarcomeres with varying joint angle and muscle contraction intensity. With these technologies it has become possible to identify the length region over which fascicles and sarcomeres develop maximum isometric force in vivo as well as the operating ranges of fascicles and sarcomeres during real-life activities such as walking. Also, greater insights into the remodelling of muscle architecture in response to overloading and unloading, and in ageing, have been obtained by the use of ultrasonography; these have led to the identification of clinical biomarkers of disuse atrophy and sarcopenia. Recent evidence also shows that the pattern of muscle hypertrophy in response to chronic loading is contraction-mode dependent (eccentric versus concentric), as similar gains in muscle mass, but through differing addition of sarcomeres in series and in parallel (as indirectly inferred from changes in fascicle length and pennation angle), have been found. These innovative observations prompted a new set of investigations into the molecular mechanisms regulating this contraction-specific muscle growth

Spaceflight and ageing: reflecting on Caenorhabditis elegans in space

The prospect of space travel continues to capture the imagination. Several competing companies are now promising flights for the general population. Previously, it was recognized that many of the physiological changes that occur with spaceflight are similar to those seen with normal ageing. This led to the notion that spaceflight can be used as a model of accelerated ageing and raised concerns about the safety of individuals engaging in space travel. Paradoxically, however, space travel has been recently shown to be beneficial to some aspects of muscle health in the tiny worm Caenorhabditis elegans. C. elegans is a commonly used laboratory animal for studying ageing. C. elegans displays age-related decline of some biological processes observed in ageing humans, and about 35% of C. elegans' genes have human homologs. Space flown worms were found to have decreased expression of a number of genes that increase lifespan when expressed at lower levels. These changes were accompanied by decreased accumulation of toxic protein aggregates in ageing worms' muscles. Thus, in addition to spaceflight producing physiological changes that are similar to accelerated ageing, it also appears to produce some changes similar to delayed ageing. Here, we put forward the hypothesis that in addition to the previously well-appreciated mechanotransduction changes, neural and endocrine signals are altered in response to spaceflight and that these may have both negative (e.g. less muscle protein) and some positive consequences (e.g. healthier muscles), at least for invertebrates, with respect to health in space. Given that changes in circulating hormones are well documented with age and in astronauts, our view is that further research into the relationship between metabolic control, ageing, and adaptation to the environment should be productive in advancing our understanding of the physiology of both spaceflight and ageing

Muscle thickness correlates to muscle cross sectional area in the assessment of strength training induced hypertrophy

Aim: Muscle thickness (MT) measured by ultrasound has been used to estimate cross-sectional area (measured by CT and MRI) at a single time-point. We tested whether MT could be used as a valid marker of MRI determined muscle anatomical cross-sectional area (ACSA) and volume changes following resistance training (RT). Methods: Nine healthy, young, male volunteers (24±2 y.o., BMI 24.1±2.8 kg/m2) had vastus lateralis (VL) muscle volume (VOL) and ACSA mid (at 50% of femur length, FL) assessed by MRI, and VL MT measured by ultrasound at 50% FL. Measurements were taken at baseline and after 12 weeks of isokinetic RT. Differences between baseline and post-training were assessed by Student’s paired t-test. The relationships between MRI and ultrasound measurements were tested by Pearson’s correlation. Results: After RT, MT increased by 7.5±6.1% (p0.05). Conclusions: These data support evidence that MT is a reliable index of muscle ACSAmid and VOL at a single time-point. MT changes following RT are associated with parallel changes in muscle ACSAmid but not with the changes in VOL, highlighting the impact of RT on regional hypertrophy

Heavy ions light flashes and brain functions: recent observations at accelerators and in spaceflight

Interactions between ionizing radiation in space and brain functions, and the related risk assessments, are among the major concerns when programming long permanence in space, especially when outside the protective shield of the Earth's magnetosphere. The light flashes (LF) observed by astronauts in space, mostly when dark adapted, are an example of these interactions; investigations in space and on the ground showed that these effects can originate with the action of ionizing radiation in the eye. Recent findings from ALTEA, an interdisciplinary and multiapproach program devoted to the study of different aspects of the radiation?brain functions interaction, are presented in this paper. These include: (i) study of radiation passing through the astronauts' eyes in the International Space Station (?20?ions?min?1, excluding H and fast and very slow He), measured in conjunction with reporting of the perception of LF; (ii) preliminary electrophysiological evidence of these events in astronauts and in patients during heavy ion therapy; and (iii) in vitro results showing the radiation driven activation of rhodopsin at the start of the phototransduction cascade in the process of vision. These results are in agreement with our previous work on mice. A brief but complete summary of the earlier works is also reported to permit a discussion of the results

An easy-to-use function to assess deep space radiation in human brains

Health risks from radiation exposure in space are an important factor for astronauts' safety as they venture on long-duration missions to the Moon or Mars. It is important to assess the radiation level inside the human brain to evaluate the possible hazardous effects on the central nervous system especially during solar energetic particle (SEP) events. We use a realistic model of the head/brain structure and calculate the radiation deposit therein by realistic SEP events, also under various shielding scenarios. We then determine the relation between the radiation dose deposited in different parts of the brain and the properties of the SEP events and obtain some simple and ready-to-use functions which can be used to quickly and reliably forecast the event dose in the brain. Such a novel tool can be used from fast nowcasting of the consequences of SEP events to optimization of shielding systems and other mitigation strategies of astronauts in space