Le rôle des interfaces dans l’expérience de jeu vidéo : le jeu du ping-pong et son adaptation sur des plateformes numériques

Le succès commercial des jeux vidéo nous montre qu’ils sont devenus une alternative non négligeable en matière de loisir et de divertissement. En observant les tendances, on constate que les concepteurs de jeux vidéo cherchent à transposer ou adapter les loisirs comme la danse, l’interprétation de la musique ou la pratique d’un sport dans le contexte de jeux vidéo (l’univers virtuel) et ceci est devenu encore plus évident depuis l’apparition des nouvelles technologies intégrant le mouvement comme mode d'interaction. En rapport aux activités dont les jeux vidéo s’inspirent, ces tendances entraînent des changements considérables sur l’aspect formel de l’activité ludique et notamment l’interaction. Dans le cas particulier du tennis de table, ou ping-pong dans le langage courant, il semble y avoir des différences en terme de plaisir lors de la pratique de ce loisir de façon traditionnelle ou en mode virtuel dans ses différentes adaptations. Le but de cette recherche est de mettre en évidence les différences entre l’appréciation de l’interaction avec le contrôleur multifonctionnel Wiimote et une raquette traditionnelle de ping-pong et de découvrir les implications sur l’expérience du plaisir de la transposition du jeu ping-pong traditionnel comparé aux adaptations sur la console Wii. Ainsi, en regard du CLASSIC GAME MODEL de Juul (2005) et du modèle THE FOUR FUN KEYS de Lazzaro (2008) nous comparons les deux modes d’interaction, jeu traditionnel avec le jeu virtuel, sur le plan formel du jeu et sur les dimensions du plaisir que chacun procure. Les résultats obtenus par l’observation des tests de jeu et l’entremise des autres outils permettent de souligner le rôle déterminant des interfaces dans l’engagement des joueurs et de montrer les limites des interfaces digitales par rapport à celle des jeux traditionnels.

Análisis cinético de la fase de transición de reacciones enzimáticas tri sustrato que siguen un mecanismo al azar B-C Uni Uni Bi Bi Ping Pong

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Visual Servoing for the Robotenis System: a Strategy for a 3 DOF Parallel Robot to Hit a Ping-Pong Ball

This article describes a new visual servo control and strategies that are used to carry out dynamic tasks by the Robotenis platform. This platform is basically a parallel robot that is equipped with an acquisition and processing system of visual information, its main feature is that it has a completely open architecture control, and planned in order to design, implement, test and compare control strategies and algorithms (visual and actuated joint controllers). Following sections describe a new visual control strategy specially designed to track and intercept objects in 3D space. The results are compared with a controller shown in previous woks, where the end effector of the robot keeps a constant distance from the tracked object. In this work, the controller is specially designed in order to allow changes in the tracking reference. Changes in the tracking reference can be used to grip an object that is under movement, or as in this case, hitting a hanging Ping-Pong ball. Lyapunov stability is taken into account in the controller design.

Mechanism of aminoacylation of tRNA : Influence of spermine on the kinetics of aminoacyl-tRNA synthesis by isoleucyl- and valyl-tRNA synthetases from Mycobacterium smegmatis

Isoleucyl-tRNA synthetase has been purified to homogeneity from Mycobacterium smegmatis. The influence of spermine on the kinetics of valyl-tRNA and isoleucyl-tRNA formation has been investigated by Cleland's method (Cleland, W.W. (1963) Biochim. Biophys. Acta 67, 104–137, 173–187, 188–196). The results suggest that in the presence of spermine and suboptimal concentration of Mg2+, the formation of valyl-tRNA and isoleucyl-tRNA follows a sequential* mechanism. In the presence of an optimal concentration of Mg2+, both valyl-tRNA and isoleucyl-tRNA formation proceeds by a ping-pong mechanism. However, in the presence of spermine and optimal concentrations of Mg2+, valyl-tRNA formation follows the ping-pong mechanism while isoleucyl-tRNA formation follows the sequential mechanism.

Purification and kinetic mechanism of 5,10-metliyienetetrahydrofolate reductase from sheep liver

5,10-Methylenetetrahydrofolate reductase (EC 1.1.1.68) was purified from the cytosolic fraction of sheep liver by (NH4)2 SO4 fractionation, acid precipitation, DEAE-Sephacel chromatography and Blue Sepharose affinity chromatography. The homogeneity of the enzyme was established by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, ultracentrifugation and Ouchterlony immunodiffusion test. The enzyme was a dimer of molecular weight 1,66,000 ± 5,000 with a subunit molecular weight of 87,000 ±5,000. The enzyme showed hyperbolic saturation pattern with 5-methyltetrahydrofolate.K 0.5 values for 5-methyltetrahydrofolate menadione and NADPH were determined to be 132 ΜM, 2.45 ΜM and 16 ΜM. The parallel set of lines in the Lineweaver-Burk plot, when either NADPH or menadione was varied at different fixed concentrations of the other substrate; non-competitive inhibition, when NADPH was varied at different fixed concentrations of NADP; competitive inhibition, when menadione was varied at different fixed concentrations of NADP and the absence of inhibition by NADP at saturating concentration of menadione, clearly established that the kinetic mechanism of the reaction catalyzed by this enzyme was ping-pong.

Kinetics of enzymatic synthesis of geranyl butyrate by transesterification in various supercritical fluids

The transesterification of methyl butyrate, ethyl butyrate and butyl butyrate to geranyl butyrate was investigated in supercritical carbon dioxide. The effect of chain length of the butyrate on the rate of transesterification was investigated. The initial rates followed the trend: ethyl butyrate < butyl butyrate < methyl butyrate. The transesterification of butyl butyrate to geranyl butyrate in various supercritical fluids such as ethylene, methane, ethane was also examined. The initial rate of transesterification of butyl butyrate in different supercritical fluids followed the order: ScCO2 < ScC2H6 < ScC2H4 < ScCH4. The highest initial rate was obtained in supercritical methane and the reasons for this observation were proposed. The Ping-Pong Bi-Bi model with inhibition by both acid and alcohol was used to model the experimental data and determine the kinetics of the reaction. (C) 2010 Elsevier B.V. All rights reserved.

Effect of Chain Length of Alcohol on the Lipase-Catalyzed Esterification of Propionic Acid in Supercritical Carbon Dioxide

The esterification of propionic acid was investigated using three different alcohols, namely, isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol. The variation of conversion with time for the synthesis of isoamyl propionate was investigated in the presence of five enzymes. Novozym 435 showed the highest activity, and this was used as the enzyme for investigating the various parameters that influence the esterification reaction. The Ping-Pong Bi-Bi model with inhibition by both acid and alcohol was used to model the experimental data and determine the kinetics of the esterification reaction.

Synthesis of biodiesel in supercritical alcohols and supercritical carbon dioxide

Biodiesel was synthesized in supercritical fluids by two routes: non-catalytically in supercritical alcohols and by enzyme catalysis in supercritical carbon dioxide. Two oils, sesame oil and mustard oil, and two alcohols, methanol and ethanol, were used for the synthesis. Complete conversion was observed for synthesis in supercritical alcohols whereas only a maximum of 70% conversion was observed for the enzymatic synthesis in supercritical carbon dioxide. For the synthesis in supercritical alcohols, the activation energies and pseudo-first order rate constants were determined. For the reactions in supercritical carbon dioxide, a mechanism based on ping pong bi-bi was proposed and the kinetic parameters were determined. (C) 2009 Elsevier Ltd. All rights reserved.

Conformational basis for substrate recognition and regulation of catalytic activity in Staphylococcus aureus nucleoside di-phosphate kinase

Nucleoside diphosphate kinases (NDK) are characterized by high catalytic turnover rates and diverse substrate specificity. These features make this enzyme an effective activator of a pro-drug an application that has been actively pursued for a variety of therapeutic strategies. The catalytic mechanism of this enzyme is governed by a conserved histidine that coordinates a magnesium ion at the active site. Despite substantial structural and biochemical information on NDK, the mechanistic feature of the phospho-transfer that leads to auto-phosphorylation remains unclear. While the role of the histidine residue is well documented, the other active site residues, in particular the conserved serine remains poorly characterized. Studies on some homologues suggest no role for the serine residue at the active site, while others suggest a crucial role for this serine in the regulation and quaternary association of this enzyme in some species. Here we report the biochemical features of the Staphylococcus aureus NDK and the mutant enzymes. We also describe the crystal structures of the apo-NDK, as a transition state mimic with vanadate and in complex with different nucleotide substrates. These structures formed the basis for molecular dynamics simulations to understand the broad substrate specificity of this enzyme and the role of active site residues in the phospho-transfer mechanism and oligomerization. Put together, these data suggest that concerted changes in the conformation of specific residues facilitate the stabilization of nucleotide complexes thereby enabling the steps involved in the ping-pong reaction mechanism without large changes to the overall structure of this enzyme. (C) 2011 Elsevier B.V. All rights reserved.

Structural insights into the role of Bacillus subtilis YwfH (BacG) in tetrahydrotyrosine synthesis

The synthesis of the dipeptide antibiotic bacilysin involves the sequential action of multiple enzymes in the bac operon. YwfH (also referred to as BacG) catalyzes the stereoselective reduction of dihydro-hydroxyphenylpyruvate (H2HPP) to tetrahydro-hydroxyphenylpyruvate (H4HPP) in this biosynthetic pathway. YwfH is an NADPH-dependent reductase that facilitates the conjugate addition of a hydride at the C4 olefin terminus of H2HPP. Here, the structure of YwfH is described at three conformational steps: the apo form, an apo-like conformation and the NADPH complex. YwfH is structurally similar to other characterized short-chain dehydrogenase/reductases despite having marginal sequence similarity. The structures of YwfH in different conformational states provide a rationale for the ping-pong reaction mechanism. The identification and role of the residues in the catalytic tetrad (Lys113Tyr117Ser155Asn158) in proton transfer were examined by mutational analysis. Together, the structures and biochemical features revealed synchronized conformational changes that facilitate cofactor specificity and catalysis of H4HPP formation en route to tetrahydrotyrosine synthesis.

An 8-to-1 bit 1-MS/s SAR ADC With VGA and Integrated Data Compression for Neural Recording

Low power consumption per channel and data rate minimization are two key challenges which need to be addressed in future generations of neural recording systems (NRS). Power consumption can be reduced by avoiding unnecessary processing whereas data rate is greatly decreased by sending spike time-stamps along with spike features as opposed to raw digitized data. Dynamic range in NRS can vary with time due to change in electrode-neuron distance or background noise, which demands adaptability. An analog-to-digital converter (ADC) is one of the most important blocks in a NRS. This paper presents an 8-bit SAR ADC in 0.13-mu m CMOS technology along with input and reference buffer. A novel energy efficient digital-to-analog converter switching scheme is proposed, which consumes 37% less energy than the present state-of-the-art. The use of a ping-pong input sampling scheme is emphasized for multichannel input to alleviate the bandwidth requirement of the input buffer. To reduce the data rate, the A/D process is only enabled through the in-built background noise rejection logic to ensure that the noise is not processed. The ADC resolution can be adjusted from 8 to 1 bit in 1-bit step based on the input dynamic range. The ADC consumes 8.8 mu W from 1 V supply at 1 MS/s speed. It achieves effective number of bits of 7.7 bits and FoM of 42.3 fJ/conversion-step.

Dense, efficient chip-to-chip communication at the extremes of computing

The scalability of CMOS technology has driven computation into a diverse range of applications across the power consumption, performance and size spectra. Communication is a necessary adjunct to computation, and whether this is to push data from node-to-node in a high-performance computing cluster or from the receiver of wireless link to a neural stimulator in a biomedical implant, interconnect can take up a significant portion of the overall system power budget. Although a single interconnect methodology cannot address such a broad range of systems efficiently, there are a number of key design concepts that enable good interconnect design in the age of highly-scaled CMOS: an emphasis on highly-digital approaches to solving ‘analog’ problems, hardware sharing between links as well as between different functions (such as equalization and synchronization) in the same link, and adaptive hardware that changes its operating parameters to mitigate not only variation in the fabrication of the link, but also link conditions that change over time. These concepts are demonstrated through the use of two design examples, at the extremes of the power and performance spectra.

A novel all-digital clock and data recovery technique for high-performance, high density interconnect has been developed. Two independently adjustable clock phases are generated from a delay line calibrated to 2 UI. One clock phase is placed in the middle of the eye to recover the data, while the other is swept across the delay line. The samples produced by the two clocks are compared to generate eye information, which is used to determine the best phase for data recovery. The functions of the two clocks are swapped after the data phase is updated; this ping-pong action allows an infinite delay range without the use of a PLL or DLL. The scheme's generalized sampling and retiming architecture is used in a sharing technique that saves power and area in high-density interconnect. The eye information generated is also useful for tuning an adaptive equalizer, circumventing the need for dedicated adaptation hardware.

On the other side of the performance/power spectra, a capacitive proximity interconnect has been developed to support 3D integration of biomedical implants. In order to integrate more functionality while staying within size limits, implant electronics can be embedded onto a foldable parylene (‘origami’) substrate. Many of the ICs in an origami implant will be placed face-to-face with each other, so wireless proximity interconnect can be used to increase communication density while decreasing implant size, as well as facilitate a modular approach to implant design, where pre-fabricated parylene-and-IC modules are assembled together on-demand to make custom implants. Such an interconnect needs to be able to sense and adapt to changes in alignment. The proposed array uses a TDC-like structure to realize both communication and alignment sensing within the same set of plates, increasing communication density and eliminating the need to infer link quality from a separate alignment block. In order to distinguish the communication plates from the nearby ground plane, a stimulus is applied to the transmitter plate, which is rectified at the receiver to bias a delay generation block. This delay is in turn converted into a digital word using a TDC, providing alignment information.