Reinforcer Quality and Self-Control

<p>Self-control has been extensively studied using procedures in which subjects chose between two reinforcer alternatives. Traditionally, one of those alternatives delivers a small reinforcer after a short delay (SI), the other, a larger reinforcer after a long delay (LD). Choosing the SI is defined as impulsivity as it requires forfeit of the larger reinforcer; and choosing the LD is termed self-control. Four experiments were conducted to examine behaviour using non-human animal analogues of self-control situations. The subjects used for all four experiments were Norway-hooded rats. Experiment 1 used an SI - LD self-control paradigm to examine the effect of manipulating reinforcer quality on response distribution. Findings were that behaviour became more impulsive as the delay ratio became more extreme and this tendency was more systematic when different quality reinforcers were used for the SI and LD alternatives. Experiments 2 and 3 introduced a novel self-control paradigm designed as an analogue of choice situations in which individuals choose between two competing immediately available reinforcers each associated with a different delayed reinforcer. The procedure used was a concurrent-chains schedule that delivered primary reinforcement in the initial and the terminal links. The initial reinforcers were of equal amount and unequal quality; the terminal reinforcers were of unequal amount and equal quality. An impulsive choice was defined as choosing the alternative that delivered the most-valuable reinforcer in the initial link and the least-valued reinforcer in the terminal link. A self-controlled choice was defined as choosing the alternative that delivered the least-valuable reinforcer in the initial link and the most-valuable reinforcer in the terminal link. The results indicated that behaviour was more self-controlled when the terminal reinforcer quality was ethanol solution and increasing the delay between the initial and terminal links increased subjects' responding on the impulsive choice. Behaviour allocation in Experiment 3 was well described by the Contextual Choice Model (Grace, 1994) when the temporal context scaling parameter (k) was allowed to vary. Subjects that were relatively more impulsive had lower derived k values. The final experiment presented the subjects from Experiment 3 with concurrent variable interval (VI) VI schedules in which one alternative delivered plain-sucrose solution and the other ethanol-sucrose solution. Preference measures obtained from Experiment 4 were negatively correlated with the values obtained for the scaling parameter in Experiment 3, indicating that subjects which were more impulsive in the MN - ML paradigm had a stronger preference for ethanol. In summary, findings indicate that reinforcer quality may change the discriminability of reinforcer alternatives; and the influence of reinforcer quality on response allocation is well described by quantitative models based on the Matching Law.</p>

Reinforcer Quality and Self-Control

<p>Self-control has been extensively studied using procedures in which subjects chose between two reinforcer alternatives. Traditionally, one of those alternatives delivers a small reinforcer after a short delay (SI), the other, a larger reinforcer after a long delay (LD). Choosing the SI is defined as impulsivity as it requires forfeit of the larger reinforcer; and choosing the LD is termed self-control. Four experiments were conducted to examine behaviour using non-human animal analogues of self-control situations. The subjects used for all four experiments were Norway-hooded rats. Experiment 1 used an SI - LD self-control paradigm to examine the effect of manipulating reinforcer quality on response distribution. Findings were that behaviour became more impulsive as the delay ratio became more extreme and this tendency was more systematic when different quality reinforcers were used for the SI and LD alternatives. Experiments 2 and 3 introduced a novel self-control paradigm designed as an analogue of choice situations in which individuals choose between two competing immediately available reinforcers each associated with a different delayed reinforcer. The procedure used was a concurrent-chains schedule that delivered primary reinforcement in the initial and the terminal links. The initial reinforcers were of equal amount and unequal quality; the terminal reinforcers were of unequal amount and equal quality. An impulsive choice was defined as choosing the alternative that delivered the most-valuable reinforcer in the initial link and the least-valued reinforcer in the terminal link. A self-controlled choice was defined as choosing the alternative that delivered the least-valuable reinforcer in the initial link and the most-valuable reinforcer in the terminal link. The results indicated that behaviour was more self-controlled when the terminal reinforcer quality was ethanol solution and increasing the delay between the initial and terminal links increased subjects' responding on the impulsive choice. Behaviour allocation in Experiment 3 was well described by the Contextual Choice Model (Grace, 1994) when the temporal context scaling parameter (k) was allowed to vary. Subjects that were relatively more impulsive had lower derived k values. The final experiment presented the subjects from Experiment 3 with concurrent variable interval (VI) VI schedules in which one alternative delivered plain-sucrose solution and the other ethanol-sucrose solution. Preference measures obtained from Experiment 4 were negatively correlated with the values obtained for the scaling parameter in Experiment 3, indicating that subjects which were more impulsive in the MN - ML paradigm had a stronger preference for ethanol. In summary, findings indicate that reinforcer quality may change the discriminability of reinforcer alternatives; and the influence of reinforcer quality on response allocation is well described by quantitative models based on the Matching Law.</p>

COMPARATIVE CHARACTERISTICS OF THE TERMINAL LINK OF GLYCOLYSIS IN THE MUSCLES OF ADULT ANIMALS AND THEIR OFFSPRING

The organism of sexually mature individuals differs significantly from the organism of immature individuals in a number of anatomical, physiological and biochemical parameters. The aim of the work was to investigate the state of the terminal link of glycolysis in the muscles of sexually mature animals and their offspring. The isoenzyme spectrum of LDH in the myocardium of sexually mature animals is characterized by a high content of LDH1 and LDH2 isozymes rapidly migrating to the anode. The isoenzyme spectrum of LDH in skeletal muscles of mature animals is represented mainly by the LDH 5.A feature of the isozyme spectrum of LDH in the tissues of rat pups is that the content of LDH1 and LDH2 is significantly reduced in the myocardium. Their number is 1.2 and 1.13 times, respectively, less than in sexually mature animals. Against this background, the content of LDH3 increases slightly, the content of LDH4 exceeds twice, and that of LDH5 is more than 6 times the indicators of sexually mature animals. In skeletal muscles of rat pups, the dominant content of LDH5 and LDH4 increases and this occurs due to a decrease in the activity of LDH3 (more than 1.5 times), LDH2 (more than 2.3 times) and LDH1 (2.2 times) compared with sexually mature animals. The data obtained indicate that in the myocardium and skeletal muscles of rat pups there is a greater percentage of isoenzymes formed from M-subunits functioning under anaerobic conditions, and with age, as a result of epigenetic transformations, the content of H-subunits increases.

A Parallel Manipulator with Planar Configurable Platform and Three End-Effectors

This work reports on the kinematic analysis of a planar parallel manipulator endowed with a configurable platform assembled with six terminal links serially connected by means of revolute joints. This topology allows the robot manipulator to dispose of three relative degrees of freedom owing to the mobility of an internal closed-loop chain. Therefore, the proposed robot manipulator can admit three end-effectors. The forward displacement analysis of the configurable planar parallel manipulator is easily achieved based on unknown coordinates denoting the pose of each terminal link. Thereafter, the analysis leads to twelve quadratic equations which are numerically solved by means of the Newton homotopy method. Furthermore, a closed-form solution is available for the inverse position analysis. On the contrary, the instantaneous kinematics of the robot manipulator is investigated by means of the theory of screws. Numerical examples are included with the purpose to illustrate the method of kinematic analysis.

Effect of the coordinate frame on high-order expansion of serial-chain displacement

An algorithmic differentiation technique gives a simpler, faster power series expansion of the finite displacement of a closed-loop linkage. It accomplishes this by using a higher order than what has been implemented by complicated prior formulas for kinematic derivatives. In this expansion, the joint rates and axis lines generate the instantaneous screw of each link. Constraining the terminal link to have a zero instantaneous screw satisfies closure. In order to maintain closure over a finite displacement, it is necessary to track the spatial trajectory of each joint axis line, which in turn is directed by the instantaneous screw of a link to which it is attached. Prior algorithms express these screws in a common ground-referenced coordinate frame. Motivated by the kinematics solver portion of the recursive Newton–Euler algorithm, an alternative formulation uses sparse matrices to update the instantaneous screw between successive link-local frames. The recursive Newton–Euler algorithm, however, conducts the expansion to only second order, where this paper shows local coordinate frames that are only instantaneously aligned with their respective links give identical expressions to those in frames that move with the links. Moving frames, however, require about 40% of the operations of the global-frame formulation in the asymptotic limit. Both incrementally translated (Java) and statically compiled (C++) software implementations offer more modest performance gains; execution profiling shows reasons in order of importance (1) balance of calculation tasks when below the asymptotic limit, (2) Java array bounds checking, and (3) hardware acceleration of loops.

Kinematic and Potential Energy Analysis of Self-Adaptive Robotic Legs

This paper presents how the kinematic and potential energy analysis of self-adaptive robotic legs can help to improve their performances with respect to their ability to overcome obstacles and the required actuation torque to do so. Self-adaptive leg mechanisms, inspired by the underactuated linkages used in grasping, generally rely on a single degree of freedom (DOF) to generate a trajectory at its endpoint that is appropriate for walking applications. When colliding with an unexpected obstacle, a second DOF in the leg automatically engages and creates a motion allowing the leg to overcome said obstacle. Since this behavior is obtained mechanically, with no sensor or control, these robotic legs are referred to as self-adaptive. In this paper, the conditions for the passive adaptation to obstacles are first briefly recalled. Then, the range of obstacles for which this adaptation is possible is determined through the analysis, using potential energy, of the mechanism workspace and it is shown how the results are connected to its kinematics. In particular, the influence of the shape of the terminal link of the leg is discussed with two compared examples. Finally, practical designs and especially the relative advantages of various locking mechanisms, required to improve stability during the support phase of the leg trajectory, are discussed.

Generalized Jacobian Analysis of Parallel Manipulators With Multiple End-Effectors

This paper presents a methodology for the Jacobian analysis of parallel manipulators with multiple end-effectors (PMxE). The end-effector velocity state of a PMxE is described by one twist of a principal end-effector with respect to the base and a set of relative twists of the remaining end-effectors with respect to the principal end-effector The twist of each terminal link with respect to the principal end-effector is then expressed as a linear function of the relative twists, which enables an extension of the generalized Jacobian analysis to PMxE. The presented methodology is detailed for parallel manipulators with two end-effectors, where a planar 6-RRR manipulator with a 2-RRR internal closed-loop is used as an example.

Modeling Method for Mechanism Configuration of the Articulated Industrial Robot

Modeling method for mechanism configuration of the articulated industrial robot is proposed. Each link of mechanism configuration is modeled by a type of variable coordinate system based on UG system. The variable coordinate system is changed with a type of variable kinematical parameter of the links. Thus the position and direction vector of terminal link by reference to frame at any time can be obtained by using inquiry command in UG system. The typical modeling example of the FANUC articulated industrial robot which possesses 6 rotation freedoms in space is as shown in figure. It is appearance that the Modeling method by this way is simple and the modeling result of the articulated industrial robot is visual, believable and reliable.