Impulsive Reaction Research Articles

Global μ-stability of impulsive reaction–diffusion neural networks with unbounded time-varying delays and bounded continuously distributed delays

This paper investigates the global μ-stability for impulsive cellular neural networks with reaction–diffusion terms and mixed delays, where mixed delays consist of unbounded time-varying delays and bounded continuously distributed delays. The model under consideration is more general than those investigated in most existing literature. By establishing a novel Lyapunov–Krasovskii functional and employing the delay differential inequality with impulsive initial conditions, boundary conditions and LMI, we obtain two concise and sufficient conditions ensuring global μ-stability of the impulsive reaction–diffusion cellular neural networks with mixed delays. The newly obtained criteria are concerned with the reaction–diffusion coefficients and the regional feature. However, they are independent of boundaries of variable time delays. Several corollaries are also presented. Finally, three concrete numerical examples are given to demonstrate the effectiveness and superiority of our main results.

Spreading speed and traveling wave solutions in impulsive reaction–diffusion models

In this paper, we study a certain kind of impulsive reaction–diffusion equation models. With the methods of Lewis and Li (2012) and others, we provide an explicit formula for the spreading speed in terms of model parameters, and show that the spreading speed can be characterized as the slowest speed of a class of traveling wave solutions. Some applications are presented to show that our results essentially include and generalize some existing ones.

On the impulsive dynamics of M-blocks

This paper is concerned with the motion of a cubic rigid body (cube) with a rotor, caused by a sudden brake of the rotor, which imparts its angular momentum to the body. This produces an impulsive reaction of the support, leading to a jump or rolling from one face to another. Such dynamics was demonstrated by researchers from Massachusetts Institute of Technology at the IEEE/RSJ International Conference on Intelligent Robots and Systems in Tokio in November 2013. The robot, called by them M-block, is 4 cm in size and uses an internal flywheel mechanism rotating at 20 000 rev/min. Initially the cube rests on a horizontal plane. When the brake is set, the relative rotation slows down, and its energy is imparted to the case. The subsequent motion is illustrated in a clip [13]. Here the general approach to the analysis of dynamics of M-cube is proposed, including equations of impulsive motion and methods of their solution. Some particular cases are studied in details.

Permanence and periodic solutions for an impulsive reaction–diffusion food-chain system with ratio-dependent functional response

An impulsive reaction–diffusion periodic food-chain system with ratio-dependent functional response is investigated in the present paper. Sufficient conditions for the ultimate boundedness and permanence of the food-chain system are established based on the comparison theory of differential equation and upper and lower solution method. By constructing appropriate auxiliary function, the conditions for the existence of a unique globally stable positive periodic solution are also obtained. Some numerical examples are presented to verify our results. A discussion is given in the end of the paper.

La violence de la rage en clinique institutionnelle

In institution, the teams have difficulties to cope with the violent demonstrations of the rage. The analysis of the rage in its intersubjective dimension brings a comprehensive model to their containing work. The rage replies to an attempt of differentiation of the subject, according to the process of the destruction of the primary object: 1) The rage has been theoretically defined by Kohut as an impulsive reaction facing a narcissistic injury. The need of the other becomes inside its own movement with the model of the “destruction of the object”, extracted by Roussillon from the works of Winnicott on “the use of an object”; 2) Four vignettes put to the test this hypothesis. These clinical interventions come from the analysis of practices or the supervision of team (psychiatry services, home of handicapped adults or children, foster home); 3) Finally, the analysis shows that the rage is linked with the psychic envelope's dynamic. The rage appears in very different structures in psychopathology. It is as an explosive movement which jumbles the borders or the psychic envelopes. Its different forms are concomitant to the variations of the subject–object differentiation according to pathologies (autism, psychosis, borderline pathologies). It is an attempt of repeated differentiation of the psychic envelops or spaces between the subject and his objects. So, in institution, its transformation depends on the recognition of its origin (the “ruthless love” in primitive relations) by the containing function of the team.

Signal detection in pathological skin picking. Findings from non – clinical sample

Aim of the studyThe present study investigated the role of general impulsivity in pathological skin picking (PSP).Subject or material and methodsThree groups of participants: university students who pick their skin and experience distress and/or functional impairment caused by picking (n = 27), students who pick their skin but do not experience distress and/or functional impairment caused by picking (n = 19), and students without history of skin picking (n = 43) were administered the task based on the search for the emotionally neutral signal hidden among distractors. It was predicted that individuals suffering from PSP should present an impulsive reaction style, i.e. they should search for the signal faster than individuals without history of PSP and should react to irrelevant stimuli rather than missing the correct reaction.ResultsParticipants with severe picking performed as quickly and correctly as controls, thus not revealing an impulsive reaction pattern. Students with milder forms of picking reacted more slowly than the others gradually diminishing their performance as the task was extended.DiscussionIndividuals with severe PSP symptoms are not characterized by general impulsiveness defined as a tendency to react quickly and carelessly. Skin picking behaviors of different severity may be associated with different signal detection patterns.ConclusionsThe results of the current study indicate that skin picking is not a homogeneous condition. They also provide that skin picking behavior in ‘severe’ pickers and non – ‘severe’ ones may have different underlying psychological mechanisms.

Spreading Speed, Traveling Waves, and Minimal Domain Size in Impulsive Reaction–Diffusion Models

How growth, mortality, and dispersal in a species affect the species' spread and persistence constitutes a central problem in spatial ecology. We propose impulsive reaction-diffusion equation models for species with distinct reproductive and dispersal stages. These models can describe a seasonal birth pulse plus nonlinear mortality and dispersal throughout the year. Alternatively, they can describe seasonal harvesting, plus nonlinear birth and mortality as well as dispersal throughout the year. The population dynamics in the seasonal pulse is described by a discrete map that gives the density of the population at the end of a pulse as a possibly nonmonotone function of the density of the population at the beginning of the pulse. The dynamics in the dispersal stage is governed by a nonlinear reaction-diffusion equation in a bounded or unbounded domain. We develop a spatially explicit theoretical framework that links species vital rates (mortality or fecundity) and dispersal characteristics with species' spreading speeds, traveling wave speeds, as well as minimal domain size for species persistence. We provide an explicit formula for the spreading speed in terms of model parameters, and show that the spreading speed can be characterized as the slowest speed of a class of traveling wave solutions. We also give an explicit formula for the minimal domain size using model parameters. Our results show how the diffusion coefficient, and the combination of discrete- and continuous-time growth and mortality determine the spread and persistence dynamics of the population in a wide variety of ecological scenarios. Numerical simulations are presented to demonstrate the theoretical results.

Reducing self-control by weakening belief in free will

Believing in free will may arise from a biological need for control. People induced to disbelieve in free will show impulsive and antisocial tendencies, suggesting a reduction of the willingness to exert self-control. We investigated whether undermining free will affects two aspects of self-control: intentional inhibition and perceived self-control. We exposed participants either to anti-free will or to neutral messages. The two groups (no-free will and control) then performed a task that required self-control to inhibit a prepotent response. No-free will participants showed less intentional inhibitions than controls, suggesting a reduction of self-control. We assessed perceived self-control by asking participants whether the response resulted from a deliberate intention or from an impulsive reaction. Perceived self-control was lower in the no-free will group than in control group. Our findings show that undermining free will can degrade self-control and provide insights into how disbelieving in free will leads to antisocial tendencies.

Exponential stability of impulsive stochastic fuzzy reaction–diffusion Cohen–Grossberg neural networks with mixed delays

The problem of mean square exponential stability for a class of impulsive stochastic fuzzy Cohen–Grossberg networks with mixed delays and reaction–diffusion terms is investigated in this paper. By using the properties of “M-cone”, eigenspace of the spectral radius of nonnegative matrices, Lyapunov functional, Itô's formula and inequality techniques, several sufficient conditions guaranteeing the mean square exponential stability of its equilibrium solution are obtained. These results extend and improve the earlier publications. Two examples are presented to illustrate the effectiveness and efficiency of the results.

Psychogenic Skin Excoriations: Diagnostic Criteria, Semiological Analysis and Psychiatric Profiles

Psychogenic excoriations are also called neurotic excoriations, dermatillomania or skin picking syndrome. We proposed diagnostic criteria and then performed a study of the psychiatric profiles of outpatients with psychogenic excoriations and the circumstancesaround the creation of these excoriations. Although the results must be interpreted with caution because the study was performed with only 10 patients, interesting data is provided about the onset of psychogenic excoriations, the behaviour of picking, and comorbidity. Common or specific characteristics were identified according to type of case. The majority of patients associated first excoriations with personal problems. Four patients reported abuse in childhood or adolescence. This study confirms that skin picking is an impulsive reaction and does not belong to the obsessive-compulsive disorders: impulsivity is defined by ineffective or failing control resulting in uninhibited behaviour.

P-146 - Impulsiveness in pathological skin picking. the evidence from the signal detection task

Introduction Pathological skin picking is a repetitive picking of the skin that leads to tissue damages and to significant distress. One of the most important aspects of skin picking is inability to inhibit one's notorious behavior; however, very few studies have examined whether the general impulsiveness underlies this disorder. Objectives The aim of the current study was to investigate whether the PSP sufferers exhibit a tendency to be more reactive in general and represent the impulsive reaction style characterized by faster response and incorrection rely on the tendency to react to irrelevant stimuli rather than missing the correct reaction. Method 30 students suffering from pathological skin picking and 30 healthy controls were administered the Moron Clock Test which allows to examine the basic mechanisms of information selection. The participants’ task was to search for, among the various distractors, the one predefined icon as quickly and as correctly as possible. Results The individuals with pathological skin picking did not differ from healthy controls neither in the speed of signal detection nor in the number of ‘false - alarms’ being made; however, skin picking sufferers demonstrated the pattern of signal detection which seems to be characteristic of individuals with high level of anxiety. At the very beginning of the task they performed slowly and carelessly but gradually improved their performance when the task became more familiar to them. Conclusions The results demonstrate that individuals with pathological skin picking do not show an impulsive reaction style.

Determining the internal reactions due to permanent constraints acting on ideal impulsive systems

A method to determine the impulsive reaction exerted by an internal bilateral constraint acting on a system colliding with an external unilateral ideal constraint is presented. The method has its rationale on the superposition principle and is based on the results of Geometric Impulsive Mechanics for ideal systems. It can be applied to systems subject to both positional and kinetic permanent constraints colliding with both positional and kinetic instantaneous constraints. Applications of the method to physically meaningful examples are presented and discussed.

Dynamics of impulsive reaction–diffusion predator–prey system with Holling type III functional response

An impulsive reaction–diffusion periodic predator–prey system with Holling type III functional response is investigated in the present paper. Sufficient conditions for the ultimate boundedness and permanence of the predator–prey system are established based on the upper and lower solution method and comparison theory of differential equation. By constructing an appropriate auxiliary function, the conditions for the existence of a unique globally stable positive periodic solution are also obtained. Some numerical examples are presented to verify our results. A discussion is given at the end.

Psychopathology and weapon choice: A study of 103 perpetrators of homicide or attempted homicide

The aim of this study was to ascertain if a relationship between weapon choice and psychopathology existed. The perpetrators (103) were evaluated at the Department of Criminology and Forensic Psychiatry of the University of Bari in southern Italy. Psychiatric examination and psycho-diagnostic tests were administered for each of the perpetrators and a database was subsequently formulated. The results showed a significant correlation between some types of mental disorder and weapon choice. A strong correlation was found between delusional disorders and the use of sharp weapons, whereas depressive disorders were more strongly associated with asphyxia. Organic disorders were found to be highly correlated with the use of blunt instruments. In cases where the homicide was the result of an impulsive reaction, the use of sharp weapons was most often observed.

A gravitational impulse model predicts collision impulse and mechanical work during a step-to-step transition

The simplest walking model, which assumes an instantaneous collision with negligible gravity effect, is limited in its representation of the collision mechanics of human gaits because the actual step-to-step transition occurs over a finite duration of time with finite impulsive ground reaction forces (GRFs) that have the same order of magnitude as the gravitational force. In this study, we propose a new collision model that includes the contribution of the gravitational impulse to the momentum change of the center of mass (COM) during a step-to-step transition. To validate the model, we measured the GRFs of six subjects’ over-ground walking at five different gait speeds and calculated the collision impulses and mechanical work. The data showed a significant contribution of the gravitational impulse to the momentum change during collision. To compensate for the gravity, the magnitudes of collision impulse and COM work were estimated to be much greater than in previous predictions. Consistent with the model prediction, push-off propulsion fully compensated for the collision loss, implying the step-to-step transition occurred in an energetically optimal manner. The new model predicted a moderate change in the collision mechanics with gait speed, which seems to be physiologically achievable. The gravitational collision model enables us to better understand collision dynamics during a step-to-step transition.

Uniform attractors for impulsive reaction–diffusion equations

The goal of this paper is to consider the long time behavior of solutions of reaction–diffusion equations with impulsive effects at fixed moment of time. Under a new class of impulse function, we prove the existence of uniform attractors in the spaces L 2 ( Ω ) , H 0 1 ( Ω ) , L p ( Ω ) and L 2 p - 2 ( Ω ) , respectively.

Dynamical behaviors of impulsive reaction–diffusion Cohen–Grossberg neural network with delays

In this paper, an impulsive reaction–diffusion Cohen–Grossberg neural network with delays and Neumann boundary condition is considered. By utilizing Poincaré inequality, constructing suitable Lyapunov functional method, some new sufficient conditions are obtained to ensure the global exponential stability of the equilibrium point. The obtained sufficient conditions depend on the reaction–diffusion terms. A comparison between our results and the previous results shows that diffusion terms can be used to exponentially stabilize some reaction–diffusion neural networks with delays and the previous results have been improved.

Stability criteria for impulsive reaction–diffusion Cohen–Grossberg neural networks with time-varying delays

This paper studies impulsive reaction–diffusion Cohen–Grossberg neural networks with time-varying delays and Neumann boundary conditions. By employing the topological degree theory, delay differential inequality with impulses, linear matrix inequality (LMI) and Poincaré inequality, a set of sufficient conditions are derived to ensure the existence, uniqueness and global exponential stability of the equilibrium point. These global exponential stability conditions depend on the reaction–diffusion term. A comparison between our results and the previous results shows that our results establish a new set of stability criteria for reaction–diffusion neural networks and have improved the previous results.

Increasing pre-activation of the quadriceps muscle protects the anterior cruciate ligament during the landing phase of a jump: An in vitro simulation

We hypothesize that application of an unopposed quadriceps force coupled with an impulsive ground reaction force may induce anterior cruciate ligament (ACL) injury. This situation is similar to landing from a jump if only the quadriceps muscle is active; an unlikely but presumably dangerous circumstance. The purpose of this study was to test our hypothesis using in vitro simulation of jump landing. A jump-landing simulator was utilized. Nine cadaveric knees were tested at an initial flexion angle of 20°. Each ACL was instrumented with a differential variable reluctance transducer (DVRT). Quadriceps pre-activation forces (QPFs) ranging from 25 N to 700 N were applied to each knee, followed by an impulsive ground reaction force produced by a carriage-mounted drop weight (7 kg) that impulsively drove the ankle upward. ACL strain was monitored before landing due to application of QPF (pre-activation strain) and at landing due to application of the ground reaction force (landing strain). No ACLs were injured. Pre-activation strains exhibited a positive correlation with QPF ( r = 0.674, p < 0.001) while landing strains showed a negative correlation ( r = − 0.235, p = 0.032). Total ACL strain (pre-activation + landing strain) showed no correlation with QPF ( r = 0.023, p = 0.428). Our findings indicate that elevated QPF increases pre-activation strain but reduces the landing strain and is therefore protective post-landing. Overall, there is a complete lack of correlation between “total” ACL strain and QPF suggesting that the total strain in the ACL is independent of the QPF under the simulated conditions.

Dynamics of the Reaction of O(3P) Atoms with Alkylthiol Self-assembled Monolayers

We have studied the dynamics of the reactions of O((3)P) atoms with alkylthiol self-assembled monolayers (SAMs). Superthermal O((3)P) atoms, with a fairly broad distribution of laboratory-frame kinetic energies (mean = 16 kJ mol(-1), fwhm = 26 kJ mol(-1)), were generated by 355 nm photolysis of NO(2) introduced at a low pressure above the SAM surface. Nascent OH v' = 0 products were detected by laser-induced fluorescence. SAMs of two different alkyl chain lengths, C(6) and C(18), were studied. The existence of SAM layers, and their robustness under our experimental conditions during the relevant measurement period, were confirmed by scanning-tunneling microscopy (STM). Reaction at the SAM surface was verified as the authentic source of the hydroxyl radicals using a perdeuterated C(6)D(13)-SAM sample. The OH appearance profiles as a function of photolysis-probe delay, and the rotational-state distributions at their peaks, were compared with those of liquid squalane (C(30)H(62), 2,6,10,15,19,23-hexamethyltetracosane). The reactivity of the SAMs and of squalane was found to be comparable. We conclude that the O((3)P) atoms must be able to access the more reactive secondary hydrogen atoms along the alkyl chains of the SAMs. We find no perceptible differences in reactivity or product energy disposal between the two SAM chain lengths. Both produce a substantial fraction of the OH with relatively high velocities, which must result from direct, impulsive reaction. There is also a slower component, with velocities consistent with a thermal, trapping-desorption mechanism. The proportion of this component appears to be lower for SAMs than for squalane. This would be compatible with the expected greater smoothness of the SAM surface at the molecular scale. We find little evidence for significant rotational excitation of the OH products, although the details of any correlation between translational and rotational energy release require further investigation. We compare our results with the limited available prior theoretical modeling of O((3)P) + SAM systems.