Effects Of Different Frequencies Research Articles

Awareness reactions and avoidance responses to sound in juvenile Atlantic salmon, Salmo salar L.

The possibility of using intense sound as a deterrent for juvenile Atlantic salmon (Sulmo salar L.) was studied by recording both physiological awareness reactions in an acoustic tube and behavioural avoidance responses in a pool. The measured awareness reactions consisted of decreased heart rate and breathing movements. Three criteria for the awareness reaction were used to compare the effect of different frequencies between 5 and 150 Hz: (i) threshold for spontaneous awareness reactions relative to the hearing thresholds, (ii) magnitude of the change in heart rate, (iii) degree of habituation to sound. After these criteria the lowest frequencies (5–10 Hz) were most effective in eliciting an awareness reaction from the fish. The responses of freely swimming fish to 10 and 150 Hz sounds were studied in an artificial pool. Juvenile salmon showed avoidance responses to 10 Hz stimulation at intensities 10–15 dB above the threshold for spontaneous awareness reactions measured in the acoustic tube. The 150 Hz sound failed to evoke avoidance responses, even at a level 30 dB above the threshold for spontaneous awareness reactions.

The Association Between Testing Strategies and Performance in College Algebra, Attitude Towards Mathematics, and Attrition Rate

The purposes of the study were: (1) to determine the effects of four testing strategies upon performance in college algebra, attitude towards mathematics, and attrition rate; (2) to determine the effects of two types of frequent testing upon performance, attitude, and attrition rate, (3) to determine the effects of different frequencies of in-class testing upon performance, attitude, and attrition rate; and (4) to draw conclusions which might help in selecting testing methods for college algebra classes.

Home Visiting of Varying Frequency and Child Development

Two studies were made of home visiting and psychosocial stimulation with deprived urban children in Jamaica. The aim was to determine the relative effectiveness of different frequencies of visiting on the children's developmental levels and the feasibility of integrating the model into government primary health care services. Health paraprofessionals supervised by a nurse from a local health center conducted the intervention. In the first study, 152 children aged 6 to 30 months were assigned to groups visited biweekly, monthly, or not at all by area of residence. The biweekly group showed small but significant increases in scores on the Griffiths Mental Development Scales (developmental quotient) and performance subscale compared with the monthly and control groups, whereas no benefit was shown in the Griffiths scores of the monthly group. In the second study, 58 children aged 16 to 30 months from the same neighborhoods were randomly assigned to weekly visited and control groups. The group visited weekly showed marked improvements in the performance and hearing and speech subscales as well as the developmental quotient scores. The results indicate that as the frequency of visiting increases from none through monthly and biweekly to weekly, the benefits increase as well.

Changes in anthelmintic resistance status of Haemonchus contortus and Trichostrongylus colubriformis exposed to different anthelmintic selection pressures in grazing sheep

Changes in anthelmintic resistance status of Haemonchus contortus and Trichostrongylus colubriformis exposed to different anthelmintic selection pressures in grazing sheep. International Journal for Parasitology 19: 99–110. This experiment was designed to study, over a 5-year-period, the effect of different frequencies of treatment with three different anthelmintic groups, namely, benzimidazoles, levamisole and ivermectin, and different frequencies of alternation between them, on existing levels of anthelmintic resistance in the nematode parasites Haemonchus contortus and Trichostrongylus colubriformis of grazing sheep. No evidence of ivermectin resistance emerged, even in suppressively treated groups. Likewise, H. contortus failed to develop resistance to levamisole under a similar selection regimen. Thiabendazole was shown to select positively against levamisole resistance in T. colubriformis resulting in significantly greater susceptibility to this drug than for the natural reversion which occurred in the untreated control. There was no evidence that an anthelmintic treatment combined with a movement of sheep to pastures of low infectivity selected more rapidly for resistance than where the same number of treatments were given to set-stocked sheep. Rotation between anthelmintic groups at yearly intervals appeared to be more beneficial in delaying resistance than rotation of drugs with each treatment.

Influence of irrigation on leaf water relations and dry matter production in coconut palms

The effect of different frequencies of irrigation on the leaf water relations and dry matter production of the West Coast Tall coconut palms (Cocos nucifera L.) was studied during two growing seasons. Irrigation was applied in amounts of 60 mm at a ratio of irrigation water to cumulative pan evaporation (I/E) of 1.0, 0.75, 0.50 and 0.0. Measurements were made of stomatal resistance, leaf water potential and epicuticular wax content, and vegetative and reproductive dry matter production. Irrigation treatments resulted in a four-to five-fold increase in the soil water deficit at I/E ratios of 0.5 and 0.0 as compared to 1.0. Coconut palms experienced severe moisture stress at an irrigation level of 0.50, resulting in a greater stomatal resistance (111%) and epicuticular wax content (32%) and reduced transpiration rate (10%), leaf water potential (68%), and reproductive dry matter production (22%), compared with well watered palms. Based on the relationship between the soil water deficit and the stomatal resistance, the critical soil water deficit for irrigation scheduling was deduced to be 110 mm. However vegetative dry matter production was reduced at much lower soil water deficits than this value.

Shock-induced modulation of lymphocyte reactivity: Suppression, habituation, and recovery

The present study was designed to evaluate the suppressive effect of different frequencies of signaled-shock presentations on mitogenic reactivity of lymphocytes in Lewis rats, and to assess the recovery of that reactivity at varying times after the shocks. The results showed that the magnitude of decreased reactivity in both the spleen and whole-blood lymphocytes, as determined by mitogenic reactivity to Concanavalin A (Con A), was directly related to the number of shock presentations within a daily session. However, the suppressed reactivity for the spleen cells diminished with repeated sessions of frequent shocks, in contrast to the whole-blood lymphocytes which did not show any habituation. Furthermore, the imposition of different periods of recovery following a single session of frequent shocks showed that the decreased reactivity for the whole-blood lymphocytes extended beyond the immediate period of the shock experience, and took 48 to 96 hours to recover completely. In contrast, the spleen lymphocytes showed complete recovery within 24 hours following the administration of shock. These results establish that the rate of habituation to and recovery from a shock-induced decrease in mitogen reactivity is more rapid for the spleen than whole-blood lymphocytes.

Moderate spanking: Model or deterrent of children's aggression in the family?

Previous research has rarely distinguished among the effects of minimal, moderate, and severe physical punishment on children's antisocial aggression. Using a nationally representative sample, this study compared the effects of different frequencies of physical punishment on children's reported physical aggression against other family members. In addition, the interaction of parental reasoning with physical punishment was examined. All analyses were repeated for preschoolers, preadolescents, and adolescents. The results generally indicated a linear positive association between physical punishment and child aggression. For preadolescent and adolescent aggression toward the parent, however, this association depended upon parental use of reasoning, such that spanking had a minimal effect on aggression for frequent reasoners. The combination of infrequent reasoning and frequent spanking was associated with dramatically increased aggression. The conclusion emphasizes additional unresolved issues about the effects of spanking, particularly the ambiguous direction of causal influence between parent and child.

The Effect of Prolonged Implementation of Cooperative Learning on Social Support Within the Classroom

ABSTRACT This study was conducted to determine whether cooperative learning experiences are related to social support in the classroom. The relationship between cooperative learning and social support, the impact of prolonged implementation of cooperative learning on social support, and the effect of different frequency of cooperative learning experiences on social support in the classroom were investigated. An instrument measuring social support was administered in November and in January to 91 eighth-grade students from a suburban school district in the Midwest. The results indicate that cooperative learning was highly related to social support within the classroom and that the longer and more frequently students engaged in cooperative learning, the greater the social support within the classroom.

Hyperthermia and Inhomogeneous Tissue Effects Using an Annular Phased Array

A regional hyperthermia Annular Phased Array (APA) applicator is described, and examples of its various heating patterns, obtained by scanning the electric fields with a small E-field sensor, are illustrated. Also shown are the effects of different frequencies of an elliptical phantom cylinder having a 1-cm-thick artificial fat wall and the generaf dimensions of the human trunk. These studies show the APA's ability to achieve uniform heating at lower frequencies (below 70 MHz) or to focus central heating at moderately higher frequencies (above 70 MHz). The influence of human anatomical contours in altering heating patterns is discussed using results obtained with a female mannequin having a thin latex shell filled with tissue-equivalent phantom. Field perturbations caused by internaly embedded low-dielectric structures are presented, showing the localized effects of small objects whose surfaces are perpendicular to the electric field.

Dielectric heating in industry application of radio frequency and microwaves

Heat is generated in a variety of dielectric or electrical insulating materials when subjected to radio and microwave frequencies. This phenomenon has been successfully exploited for over 40 years by industry in a wide range of applications. Radio frequency (RF) is used for about 90% of all dielectric heating applications, but the more recent development of microwave heating is becoming well established. The place of RF and microwaves in the electromagnetic spectrum and the effects of different frequencies on materials is discussed. Brief details of the various techniques of applying the RF or microwave energy to materials are given. Finally, some typical applications such as welding, baking drying and preheating are discussed.

Acoustic Emission of Fiber Reinforced Plastics

Because most nondestructive test methods are not suitable for use with plastics, and in light of the poor performance record of FRP structures, a practical nondestructive test could be of great value. The paper reports results of a series of tests designed to evaluate the suitability of acoustic emission for testing of FRP structures. In order to characterize FRP, tensile and flexural tests were carried out using various FRP constructions and a range of load levels. In addition, a test of a full-size FRP reactor was undertaken. The tests demonstrate that level of emission, first damage, Kaiser effect, emission during a load hold, amplitude spectrum, and the effect of different frequencies on wave attenuation provide useful information on the structural integrity of FRP. Recommendations for future test work are presented with an assessment of the applicability of acoustic emission for nondestructive testing of FRP structures.

The effect of retinal-image movements on vision. II. Oscillatory movements.

The effect of oscillatory movements imposed on an otherwise stationary image has been studied. Sinusoidal, triangular and square-wave wave­forms were used. Frequencies ( f ) ranged from 0.01 to 30 Hz and peak to peak displacement ( M ) from 0.1 to 13´. The target was usually a dark line, 6´ in diameter, seen in a field of 1000td retinal illuminance. The fraction of time ( V ) for which the target was seen was measured. The results show that movement has two effects: (i) to increase V by causing fluctuations of illuminance in receptors near the boundary and (ii) to decrease V , presumably by blurring the boundary. Effect (ii) can be detected only when effect (i) is small, i. e. for very small values of M or for high values of f . The effect of square-wave movements do not agree with calculations based on the results obtained for sinusoidal waves. Thus the effects of different frequencies do not superpose in a linear way. This is possibly due to the fact that sinusoidal movements produce sinusoidal fluctuations of light only for small movements. The results obtained are compared with the results of an experiment by Yarbus (1960) and also with flicker-fusion experiments. Agreement is as good as may be expected having having regard to differences of experi­mental conditions. The changes in the fraction of pigment bleached in receptors near the boundary due to the movements is calculated and the ratio of the signal to photon-noise is deduced. It is found that for frequencies above 5 Hz, the response to movement is limited by photon-noise. For lower frequencies the response is limited by other processes.

Evaluation of the pain suppressive effect of different frequencies of peripheral electrical stimulation in chronic pain conditions.

The pain suppressive effect of low (2/s) and high (50-100/s) frequency electrical stimulation was studied in 12 patients with severe chronic pain in the back and/or the legs. All patients were subjected to a thorough physical examination before and 2-3 weeks after a series of stimulation sessions. The stimulation was applied via surface electrodes to areas both segmentally related and segmentally unrelated to the regions of chronic pain. Low frequency stimulation induced a partial pain relief in only one patient whereas stimulation with high frequency gave a suppression of pain in seven patients. The effect was short-lasting in most cases and the pain started to increase usually within 30 min. It is concluded that the observed pain suppression is not due to psychological factors but to more basic neurophysiological mechanisms. Augmentation of the effect after repeated stimulation sessions was not observed, neither was there any alteration in the neuro-orthopedic status nor any lasting pain relief in any patient.

Application, Absorption and Translocation of Boron in Oil Palm

SUMMARYThe effects of different frequencies and rates of application of boron fertilizer were studied with regard to uptake of boron by the oil palm. The results indicated that annual or biannual application of this element maintained satisfactory levels in the leaf tissue. Heavy potassium fertilization was found to inhibit boron uptake but nitrogen had no effect.

The Effects of Different Frequencies of Response Frames in Programmed Instruction

Most linearly sequenced programmed instructional materials are patterned after the model formulated by Skinner (1958). This model essentially consists of a fixed sequence of small frames, each requiring a constructed response by the learner. Programmed instruction (PI) of this nature is based upon extrapolations of laboratory operant learning studies and it is generally assumed that the principles operating in such laboratory studies are also operating in PI. A key assumption of such materials is that feedback provided to the learner following overt responses reinforces the learning of the content. The validity of this assumption, however, lacks empirical verification. While knowledge of results in PI has been regarded as generally reinforcing (e.g., Skinner, 1968), it cannot be unequivocally stated that such feedback will reinforce the learner's acquisition of content. Briggs, et al (1962) report a study in which students who read frames without overtly responding (hence, no feedback) have superior test scores and time-efficiency over those who overtly responded. Licklider (1962) reports that highly motivated students found scores and comments unimportant in a CAI study, while the less motivated stu-

The Effects of Different Frequencies of Response Frames in Programmed Instruction

The Effects of Different Frequencies of Response Frames in Programmed Instruction

Effect of different frequencies of vibration on pain-threshold detection

Radiant-heat pain threshold judgments were obtained from human subjects while the stimulated region was simultaneously vibrated with one of three vibration frequencies. Threshold detection of pain was found to be a function of the frequency of applied vibration. The results are interpreted in terms of a current theory of pain reception.

Control of Hippocampal Output by Afferent Volley Frequency

This chapter discusses the control of hippocampal output by afferent volley frequency. One of the crucial factors determining the ouput from a neuronal system is the frequency of the input stimulation. The aim of the present investigation has been to study the effect of a relatively shortlasting tetanic stimulation on the efficiency of certain excitatory synapses in the hippocampus. Further, possible correlations between neurophysiological responses and processes of learning have been sought This affects both the electrical and, most likely, the behavioural responses to stimulation of various brain structures. All investigators studying the responses of hippocampal pyramidal neurones are familiar with the great increase, or decrease, down to the level of extinction, of the responses that may occur in different circumstances. In cats and rabbits, anaesthetized with nembutal or urethane and chloralose, the effect of different frequencies of stimulation on synaptic transmission in the hippocampus was studied. Repetitive stimulation led to the development of large negative waves with population spikes superimposed. The evoked potentials could increase by a factor of several hundred.

Cortical and subcortical patterns of response to afferent vagal stimulation

Cortical and subcortical patterns of activity were studied upon electrical stimulation of the cut central end of the cervical vagus nerve in acutely prepared adult cats. The effects of different frequencies and voltages of afferent vagal stimulation were studied while the duration of the stimulus pulses was kept constant (0.75 msec). High-frequency (> 70/sec) low voltage (< 3v) stimulation resulted in the induction of cortical EEG synchronization, while all other combinations of frequency and voltage gave rise to cortical activation. Subcortical structures responded in a manner consistent with the cortical observations. The cerebral cortex and thalamic nuclei responded to synchronogenic vagal afferent stimulus parameters only after an initial latent period, while the hippocampus responded immediately. All responses were bilaterally equivalent and could be induced by either vagus nerve. Severance of both sympathetic trunks and vagi and transection of the neuraxis at the spinomedullary junction indicated that the central responses were neurogenic in origin. These and other studies presently in progress offer convincing evidence that the different cortical responses (synchronization or desynchronization) observed by various investigators from stimulation of the central end of the cervical vagus nerve result from the differential stimulation of specific afferent fiber systems within that nerve.

THE EFFECTS OF MUIRBURNING MOLINIA‐DOMINANT COMMUNITIES

The effect of muirburn (that is, periodic burning of rough land) on Molinia caerulea dominant communities of south‐east Scotland has been studied. The weight of burnable litter has been assessed at 1809 lb dry matter/acre and the chemical composition of this DM as SFA 0·64%, P2O5 0·23%, CaO 0·13%, MgO 0·05%, and K2O 0·19%. Data are also given on the chemical composition of Molinia leaf from both burnt and unburnt areas. The effect of burning, of raking off the litter and of manurial applications on the growth of Molinia and on the botanical composition of the sward is reported, as is the effect of different frequencies of burning. The agronomic value of muirburning is discussed. In the opinion of the authors the practice of muirburning Molinia is not be to recommended unless the burned areas are closely grazed.