87,817 research outputs found
Introduction: Working Stars
No full textThis chapter describes the rationale of the edited collection, connecting it to the Italian research project it stems from. Building on previous theoretical understandings of actorship and on literature on Italian actors, and showcasing the main methods to survey the subject, i.e., performance studies, celebrity studies, and production studies. It shows describes how the subject of Italian contemporary film and media performers is investigated: by looking at the training and the early steps of actors, by following multifaceted careers across different projects, audiences, and media, and by tracing the design of personas and their recognition through press, PR, awards, and social media. Both the agency of actors and the role of intermediaries are highlighted, scrutinizing the background of a changing landscape, with the aim of providing our readership with a thorough account of the individual Italian case histories
The first humans travelling on ice: an energy-saving strategy?
Full text linkEconomy of locomotion is a constant challenge for animals, particularly when related to migrations and travelling. The present study focuses on human locomotion and particularly on the development of ice skating. The aim of our research was to understand whether an environmental feature such as a strong presence of lakes (frozen in winter) could force humans to develop ice skates in order to limit the energy cost of travelling. We hypothesized that the energy-saving principle was a determinant factor in the development of human locomotion on ice. Five healthy adult participants took part in the experiments, during which we recorded the speed (1.2 ± 0.3 m s−1) and metabolic energy cost (4.6 ± 0.9 J kg−1 m−1) associated with travelling on bone skates. Simulations were also performed to demonstrate whether the benefit given by the use of skates was different in the areas where ice skating appears to have evolved originally. The gain reachable by using bone skates could lead to an extremely high energy saving (equal to 10% of the energy needed to survive during the cold season) and differs significantly between the regions considered in the present study. An analysis of the geometrical shape of lakes associated with fractal analysis of their distribution suggests that, in order to better adapt to the severe conditions imposed by the long lasting winters, Finnish populations could benefit more than others from developing this ingenious locomotion tool. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 1–7
Pedaling rate is an important determinant of human oxygen uptake during exercise on the cycle ergometer
Full text linkEstimation of human oxygen uptake (VO₂) during exercise is often used as an alternative when its direct measurement is not feasible. The American College of Sports Medicine (ACSM) suggests estimating human VO₂ during exercise on a cycle ergometer through an equation that considers individual’s body mass and external work rate, but not pedaling rate (PR). We hypothesized that including PR in the ACSM equation would improve its VO₂ prediction accuracy. Ten healthy male participants’ (age 19–48 years) were recruited and their steady-state VO₂ was recorded on a cycle ergometer for 16 combinations of external work rates (0, 50, 100, and 150 W) and PR (50, 70, 90, and 110 revolutions per minute). VO₂ was calculated by means of a new equation, and by the ACSM equation for comparison. Kinematic data were collected by means of an infrared 3-D motion analysis system in order to explore the mechanical determinants of VO₂. Including PR in the ACSM equation improved the accuracy for prediction of sub-maximal VO₂ during exercise (mean bias 1.9 vs. 3.3 mL O₂ kg⁻1 min⁻1 ) but it did not affect the accuracy for prediction of maximal VO₂ (P > 0.05). Confirming the validity of this new equation, the results were replicated for data reported in the literature in 51 participants. We conclude that PR is an important determinant of human VO₂ during cycling exercise, and it should be considered when predicting oxygen consumption
Human locomotion on ice: the evolution of ice-skating energetics through history.
No full textMore than 3000 years ago, peoples living in the cold North European regions started developing tools such as ice skates that allowed them to travel on frozen lakes. We show here which technical and technological changes determined the main steps in the evolution of ice-skating performance over its long history. An in-depth historical research helped identify the skates displaying significantly different features from previous models and that could consequently determine a better performance in terms of speed and energy demand. Five pairs of ice skates were tested, from the bone-skates, dated about 1800 BC, to modern ones. This paper provides evidence for the fact that the metabolic cost of locomotion on ice decreased dramatically through history, the metabolic cost of modern ice-skating being only 25% of that associated with the use of bone-skates. Moreover, for the same metabolic power, nowadays skaters can achieve speeds four times higher than their ancestors could. In the range of speeds considered, the cost of travelling on ice was speed independent for each skate model, as for running. This latter finding, combined with the accepted relationship between time of exhaustion and the sustainable fraction of metabolic power, gives the opportunity to estimate the maximum skating speed according to the distance travelled. Ice skates were probably the first human powered locomotion tools to take the maximum advantage from the biomechanical properties of the muscular system: even when travelling at relatively high speeds, the skating movement pattern required muscles to shorten slowly so that they could also develop a considerable amount of force
A common perceptual parameter for stair climbing for children, young and old adults.
No full textIn this paper we examine whether a common perceptual parameter is available for guiding old adults, young adults and children in climbing the highest stair mountable in a bipedal fashion. Previous works have shown that the ratio between the height of the stair and the hip height was the body-scaled invariance adopted as information for selecting the highest stair by young adults [Journal of Experimental Psychology: Human Perception and Performance 10 (1984) 683-703] but not by older adults [Journal of Experimental Psychology: Human Perception and Performance 3 (1992) 691-697]. Indeed, for older adults additional bio-mechanical parameters needed to be added to the model due to their decrease in leg strength and flexibility.Up to now, no perceptual invariant has been identified yet for determining the relevant information used for guiding the stair climbing action for normal healthy people. We propose a new parameter as the angle defined by the ratio between the height of the stair and the distance taken from the feet to the top edge of the stair before the initiation of the movement. We show that this angle is the same for children, young adults and older adults despite the different kinematics of the motion, the anthropometrics and the skill ability exhibit by the participants. In summary we show that even when the climbability judgments, based on the simple ratio leg length-stair height, are influenced by differences in age, participants use a common perceptual variable when they are coordinating their stair climbing action
Pd-Catalyzed Synthesis of Heterocycles from Nitro Compounds using Liquid CO Sources
No full textCatalytic carbonylation processes represent a key synthetic tool for the preparation of bulk and fine chemicals. Furthermore, the CO molecule can be even employed as a stoichiometric reductant towards many functional groups. In particular, the transition-metal catalysed reductive cyclization of substituted aromatic nitro compounds allows for the synthesis of a large variety of N-containing heterocycles. However, from a laboratory-scale point of view, the use of pressurized CO requires the installation of expensive safety measures and high-pressure equipments. A solution to this problem is represented by the use of molecules capable of releasing an equivalent CO in situ. Among the various alternatives, formate esters (both alkyl and aryl) are the most promising one given their relative low cost, availability and functional group tolerance. Herein, we reported the use of formate esters as effective CO surrogates in the Pd-catalyzed reductive cyclization of substituted nitro compounds for the synthesis of heterocycles. Key for the success was the use of phenyl formate that, under optimal conditions, enable the synthesis of substituted indoles with excellent selectivities, while performing the reactions in an economical pressure tube without the need for autoclaves and/or a CO gas line. In addition, mechanistic investigations of the formate activation were performed in order to discriminate between a base-mediated and a metal-catalyzed process
Paleo-biomechanics and paleo-energetics of cross-country skiing and ice skating (3200 BC to date)
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Reductive cyclization of nitro compounds using CO surrogates: formate esters at work
No full textCatalytic reductive cyclization of substituted aromatic nitro compounds represents a valuable approach for the synthesis of N-containing heterocycles. Using gaseous CO as the reductant is possible to selectively transform the nitro group into much more reactive intermediates (such as nitroso compounds) that can further undergo inter or intra-molecular amination reactions.1 Nevertheless, CO is a highly toxic molecule whose handling requires the installation of expensive safety measures and high-pressure equipments. In order to overcome this issue, we developed a synthetic protocol in which formate esters (both alkyl and aryl) are employed as CO sources, thus avoiding the use of pressurized gas.2 In particular phenyl formate was found to be an excellent CO surrogate enabling the preparation of various substituted indoles by Pd-catalyzed reductive cyclization of ortho-nitrostyrenes with excellent selectivities. Notably, the transformation proceeds more efficiently than the corresponding reaction carried out under gaseous CO conditions. In addition, preliminary investigations devoted to the clarification of the reaction mechanism are presented
Indole synthesis by reductive cyclization of ortho-nitrostyrenes: formate ester as CO surrogates
No full textThe palladium catalyzed reductive cyclization of substituted ortho-nitrostyrenes is a powerful method for the synthesis of indoles. The reaction proceeds using CO as the reductant [1]. However CO is a highly toxic gas and its use implies the installation of expensive safety measures and high-pressure equipments. Therefore carbonylation reactions using non-gaseous CO precursors are highly desirable [2].
For our purpose we chose formate esters as the CO sources due their commercial availability and low cost. Thus, we developed a one-pot two-catalysts system composed of Ru3(CO)12 and [Pd(Phen)2][BF4]2 for the decarbonylation and the reductive cyclization step respectively. As the result various 2,6-substituted indoles were synthesized in good yields using a cheap and safe CO source [3]
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