Jumping Avoidance Research Articles

Nonlinear Frequency Response Analysis and Jump Avoidance Design of Molecular Spring Isolator

AbstractMolecular spring vibration isolation technology has been invented in the recent years but it still needs further development in dynamics theory. A molecular spring isolation (MSI) consists of water and hydrophobic zeolites as working medium, providing high-static-low-dynamic stiffness. The dynamic properties of MSI are thoroughly investigated in this paper. Firstly, the nonlinear dynamic model of a vibration system support by MSI, i.e. the equation of motion, is established. Then the averaging method is employed to estimate the frequency response function (FRF) of the primary resonance. The phase trajectories diagram evolvement of primary resonance is also investigated to analysis the stability of the primary resonance response. From the plot of FRF, it is found that there exists a jump phenomenon induced by nonlinear stiffness, which may have harmful impacts on the equipment which is supposed to be protected from vibrations and shocks. To avoid jump, the FRF is analyzed to find the critical values of system parameters and a jump avoidance criterion is introduced.

Sensitivity analysis of piecewise linear vibration isolator with dual rate spring and damper

Abstract In this paper the exact frequency response of symmetric piecewise linear vibration isolator has been revised and reviewed. The frequency response of the system is calculated and detailed sensitivity analysis is presented. The method of obtaining the exact frequency response of the isolator is based on combining together the liner solutions of different segments within the cycle of motion of the system. In this paper set of graphs for different parameters of the system that illustrates the sensitivity of the system have been provided. The analysis of the impact of parameters of the system on its behavior has been presented. The sensitivity analysis is required to be able to determine the working domain of the parameters. Jump avoidance and peak amplitude minimization are the main aspects of parameter working domain.

NEIMARK BIFURCATIONS OF A GENERALIZED DUFFING–VAN DER POL OSCILLATOR WITH NONLINEAR FRACTIONAL ORDER DAMPING

A generalized Duffing–van der Pol oscillator with nonlinear fractional order damping is introduced and investigated by the residue harmonic homotopy. The cubic displacement involved in fractional operator is used to describe the higher-order viscoelastic behavior of materials and of aerodynamic damping. The residue harmonic balance method is employed to analytically generate higher-order approximations for the steady state responses of an autonomous system. Nonlinear dynamic behaviors of the harmonically forced oscillator are further explored by the harmonic balance method along with the polynomial homotopy continuation technique. A parametric investigation is carried out to analyze the effects of fractional order of damping and the effect of the magnitude of imposed excitation on the system using amplitude-frequency curves. Jump avoidance conditions are addressed. Neimark bifurcations are captured to delineate regions of instability. The existence of even harmonics in the Fourier expansions implies symmetry-breaking bifurcation in certain combinations of system parameters. Numerical simulations are given by comparing with analytical solutions for validation purpose. We find that all Neimark bifurcation points in the response diagram always exist along a straight line.

Discharge Properties of Hippocampal Neurons during Performance of a Jump Avoidance Task

We recorded single hippocampal cells while rats performed a jump avoidance task. In this task, a rat was dropped onto the metal floor of a 33 cm gray wooden cube and was given a mild electric shock if it did not jump up onto the box rim in <15 s. We found that many hippocampal pyramidal cells and most interneurons discharged preferentially at the drop, the jump, or on both events. By simultaneously recording the hippocampal EEG, we found that the discharge of most of the event-related pyramidal cells was modulated by the theta rhythm and moreover that discharge precessed with theta cycles in the same manner seen for pyramidal cells in their role as place cells. The elevations of firing rate at drop and jump were accompanied by increases in theta frequency. We conclude that many of the features of event-related discharge can be interpreted as being equivalent to the activity of place cells with firing fields above the box floor. Nevertheless, there are sufficient differences between expectations from place cells and observed activity to indicate that pyramidal cells may be able to signal events as well as location.

Frequency Response and Jump Avoidance in a Nonlinear Passive Engine Mount

This paper explores a model for a nonlinear one-degree of freedom passive vibration isolator system, known as a smart engine mount. Nonlinearities are employed to analyze and possibly improve the behavior of the optimal linear mount. Nonlinear damping and stiffness rates of the isolator have interacting effects on the dynamic behavior of the mount. The frequency response of the system is obtained using the averaging perturbation method, and a parametric analysis shows that the effect of nonlinear stiffness rate on frequency response is opposite to that of the nonlinear damping rate. Stability of the steady state periodic response has also been analyzed. Jump avoidance criteria are introduced, and the conditions for jump avoidance are studied. Closed form solutions for the absolute acceleration and relative displacement frequency responses are derived, since they are essential to use of the RMS optimization method.

Effects of duration of feedback on signaled avoidance

Two experiments were carried out to study vertical jumping avoidance learning in rats. In particular, we examined the effects of the duration of a feedback stimulus and of the interval between the end of the feedback stimulus and the start of the next trial on acquisition and extinction of avoidance. In Experiment 1, the duration of feedback was manipulated while intertriai interval (feedback plus no-feedback) was held constant. Animals with feedback lasting more than 1 sec needed fewer trials to reach the acquisition criteria than did animals with no feedback or with 1-sec feedback. No differences were observed in extinction. In Experiment 2, the durations of both feedback and no-feedback were manipulated. Animals without feedback needed more trials to reach the acquisition criterion than did animals with feedback, but the performance of the feedback animals did not differ as a function of feedback duration, no-feedback duration, or total intertrial interval. Again, no differences were observed in extinction. These results indicate that the presentation of feedback improves the acquisition of vertical jumping avoidance, but that this effect is independent of the temporal characteristics of feedback.

VERTICAL JUMPING AND SIGNALED AVOIDANCE

This paper reports an experiment intended to demonstrate that the vertical jumping response can be learned using a signaled-avoidance technique. A photoelectric cell system was used to record the response. Twenty female rats, divided equally into two groups, were exposed to intertrial intervals of either 15 or 40 s. Subjects had to achieve three successive criteria of acquisition: 3, 5, and 10 consecutive avoidance responses. Results showed that both groups learned the avoidance response, requiring increasingly larger numbers of trials as the acquisition criteria increased. No significant effect of intertrial interval was observed.

Hyperprolactinaemia alleviates behavioral alterations of rats with hereditary hypothalamic diabetes insipidus (Brattleboro strain)

Male rats homozygous for hereditary hypothalamic diabetes insipidus (HO) and their heterozygous (HE) and normal (NO) variants (Brattleboro rats) were made hyperprolactinaemic by homografting two adenopituitaries under the kidney capsule. The high water intake and urine output of homozygous diabetic sham-operated rats (sham-HO) were similar to those of homografted HO animals. Also, hyperprolactinaemia failed to change the water intake and urine output of HE and NO rats, as compared to those of heterozygous (sham-HE) and normal (sham-NO) sham-operated animals. Compared to sham-HE and sham-NO animals, sham-HO rats showed a slow acquisition of active avoidance responses, a facilitated extinction of a pole jumping avoidance behavior and a reduced retention of a passive avoidance response. However, an improved performance of acquisition and retention behaviors up to the level of sham-HEs and sham-NOs was observed in homografted HO rats. Hyperprolactinaemia resulted in a reduced responsiveness to electrical footshock in HO, HE and NO animals, and in facilitated acquisition of active avoidance responses in HE and NO rats, but it failed to affect avoidance extinction and retention in the latter variants. These results suggest that the behavioral alterations shown by homozygous diabetes insipidus rats are alleviated by hyperprolactinaemia although high levels of plasma prolactin do not interfere with the mechanisms regulating water intake and urine output. In addition, hyperprolactinaemia affects the behavior of heterozygous and normal variants of Brattleboro strain but in a selective way.

Behavioral effects of the β-endorphin fragment 2–9

The non-opiate β-endorphin (βE) fragment des-Tyr-α-endorphin (βE 2–16) delays extinction of pole jumping avoidance behavior and potentiates apomorphine-induced stereotyped sniffing. Structure-activity relationship studies revealed that the active moiety mediating these psycho-stimulant effects resides in the sequence βE 2–9. The interaction between βE 2–9 and apomorphine was also present following intrastriatal injection of both substances. These data provide evidence for a selective interference of the fragment βE 2–9 with brain mechanisms, which can be distinghuised from the opiate-and neuroleptic-like activity of β-endorphin fragments. This further demonstrates the importance of β-enndorphin and its fragments for modulation of behavioral processes.

Jump avoidance acquisition and locomotor behavior in rats with the hippocampal theta rhythm disrupted

It has previously been shown that medial fornical lesions can selectively disrupt the hippocampal theta rhythm in rats, whereas the major hippocampal input and output systems remain functionally intact. However, selective theta disruption did not affect the performance of well-trained jump avoidance responses that are usually accompanied by clear theta waves. Therefore, the main purpose of the present study was to investigate whether theta activity proves necessary for the acquisition of the jump task. In addition, it appeared of interest to test the potential effects of theta disruption on open-field behavior, since medial septal lesions that most likely destroy theta have been reported to cause decreased locomotor activity in the open field. The present results show that the occurrence of theta activity is not necessary for avoidance acquisition or normal open-field behavior. These findings give further support to the notion that the theta rhythm may be a correlate of internal hippocampal processes rather than of some overt behavior.

Behavioral effects of intraventricularly administered vasopressin and vasopressin fragments

Vasopressin is involved in memory processes. A single subcutaneous injection of arginine-8-vasopressin (AVP) increases resistance to extinction of a pole jumping avoidance response. This effect can also be achieved after a single intraventricular administration of much lower amounts than after systemic injection. The covalent ring of AVP, pressinamide (PA), is also highly active following intraventricular administration while the C-terminal part prolyl-arginyl-glycinamide (PAG) is less active. These results indicate that the covalent ring of vasopressin contains the essential requirements for the behavioral effect of this neurohormone. A second activity site however may be present in the C-terminal portion of the molecule.

Dorsal hippocampus: A site of action of neuropeptides on avoidance behavior?

Vasopressin and ACTH 4–10 induce a dose dependent long-term, respectively short-term inhibition of extinction of a pole jumping avoidance response in animals with sham lesions in the antero-dorsal hippocampus. Small lesions, causing a restricted damage in this area of the brain, partly inhibit the behavioral effect of vasopressin. Extensive lesions in the antero-dorsal hippocampus completely prevent the inhibitory effects of vasopressin and of ACTH 4–10 on extinction of the avoidance response. The extensive lesions in the dorsal hippocampus complex do not interfere with the rate of extinction, but acquisition of the response is retarded. These observations do not allow the conclusion that the hippocampal complex is the locus of action of neuropeptides in relation to avoidance behavior; it is more likely that this brain region is but one site of behavioral action of these hormones, and that the limbic system needs to be intact to permit the neuropeptides to exert their behavioral effects.

Interhemispheric transfer of extinction of the active avoidance reaction in rats.

Cortical spreading depression (CSD) was employed in rats to study the lateralization of extinction of a jumping avoidance reaction. Under unilateral CSD, 181 nonreinforced trials were needed to extinguish the avoidance reaction acquired in three 100-trial sessions of intact-brain training. During a second extinction session, either with the same or with the contralateral hemisphere depressed, the mean number of trials to the extinction criterion (9/10) was 39 (n = 12) or 186 (n = 15), respectively. Five extinction trials performed with the brain intact 1 hr before extinction with contralateral CSD decreased the number of trials to extinction of 98 (n = 11). Thus, extinction of active avoidance can be lateralized and interhemispherically transferred in the same way as acquisition of this habit.

Memory and Transfer of Information

Memory and Transfer of Information

The Parafascicular Area as the Site of Action of ACTH Analogs on Avoidance Behavior

Publisher Summary This chapter talks about the parafascicular area as the site of action of adrenocorticotropic hormone (ACTH) analogs on avoidance behavior. The present experiments indicate that an intact parafascicular area is essential for the effect of ACTH analogs on extinction of conditioned avoidance behavior in contrast to that of vasopressin and analogs. The influence, however, of ACTH analogs on the parafascicular nuclei is unknown and is, therefore, the subject of further experiments. The pituitary-adrenal system is involved in acquisition and extinction of conditioned avoidance behavior ACTH and peptides related to ACTH (MSH, ACTH 1-10 and ACTH 4-10 induce a short lasting inhibition of extinction of a shuttle box or pole jumping avoidance response. Lesions in the parafascicular nuclei result in a poor avoidance performance in a pole jumping avoidance test. The results reported in the present chapter are in agreement with those obtained by Bohus and de Wied, who showed that bilateral lesions of the parafascicular nuclei block the inhibitory effects of long acting α-MSH preparations on extinction of a shuttle box avoidance response.

Behavioural evaluation of peptides related to scotophobin

A synthetic pentadecapeptide, desacetylscotophobin analogue (DS 1-15), which differs from the natural product in terms of activity and in structure, has been tested in various behavioural tests. To determine the active core of DS 1–15, two other peptides corresponding to the residues 8–15 of the parent molecule (ZS 8–15 and HS 8–15) were tested in the same behavioural situations. These three peptides given in a single subcutaneous injection of 5 μg delayed extinction of a pole jumping avoidance response in an equipotent manner for approximately 7 days. In a passive avoidance situation, in which latency to enter a dark box was measured after animals had experienced mild shock 24 hr previously, avoidance latency was increased for several days following a single subcutaneous injection of 5 μg DS 1–15 and HS 8–15, while ZS 8-15 was much less active. None of these peptides affected passive avoidance latency in rats which had no previous shock experience in the dark box. Peptides were virtually inactive in a light-dark preference test and in an open field test. It is suggested that discrepancies in data with scotophobin and analogues as reported in the literature could well be the result of differences in aversive stimulation to which animals might have been unintentionally exposed.

Effects of intracerebral implantation of corticosteroids on extinction of an avoidance response in rats

Abstract Intracerebral implantation of dexamethasone phosphate facilitated the rate of extinction of a pole jumping avoidance response when implanted into various areas in the median and posterior thalamus and in the ventriculus lateralis. Corticosterone, the rat's natural corticosteroid, also facilitated extinction of the avoidance response, but mainly if implanted in or near the nucleus parafascicularis. Implantations of either dexamethasone phosphate or corticosterone in other areas like hippocampus, nucleus septi lateralis, nucleus caudatus putamen, nucleus interstitialis striae terminalis and nucleus ventralis thalami did not result in a modification of the extinction rate.

Acquisition of a jumping avoidance response in hamsters

Hamsters were found to readily acquire a jumping avoidance response, but showed no differential performance as a result of differences in shock intensity or intertrial interval. The performance of rats in an earlier experiment was superior to that of the hamsters in our study.

The inhibitory effect of ACTH 1–10 on extinction of a conditioned avoidance response: Its independence of thyroid function

The effect of the ACTH analogue ACTH 1–10 was studied on the rate of extinction of a pole jumping avoidance response in thyroidectomized rats with or without replacement therapy with 1-thyroxin. ACTH 1–10 appeared to delay the rate of extinction of the CAR in thyroidectomized rats in a similar way as in sham-operated animals. ACTH 1–10 was also active in thyroidectomized rats treated with thyroxin. The thyroxin treatment itself also caused a significant delay in the rate of extinction of the CAR. These results indicate that the inhibitory effect of ACTH analogues on the rate of extinction of the CAR is not mediated by the thyroid gland.