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At least 559 records · Page 31Linked to original sources
PubMed2005

Influence of operating conditions on the ammonia electro-oxidation rate in wastewaters from power plants (ELONITA technique).

Power plants, like many other industries, are confronted with the need to reduce the nitrogen content of their wastewaters. Indirect electro-oxidation, through hypochlorite formation, is a possible answer to an ammonia-nitrogen problem, through converting it into gaseous nitrogen. Several parameters affect the ammonia oxidation rate: current density, chloride concentration and the presence of oxygen-containing anions, mainly SO(4)(2-), CO(3)(2-) and PO(4)(3-). pH values between 5.5 and 10 have been found to have no effect on the ammonia oxidation rate. However, at higher pH values (above 11), the oxidation slows down and chlorate ions appear. A model can be fitted from the experiments to predict the ammonia oxidation rate based on four main parameters: pH, current density, sulfate concentration and chloride concentration. The average difference between the predicted oxidation rates and the experimental measures is only 6.5%. This model confirms that the optimal operating conditions are a high chloride concentration (7 gl(-1)), no sulfate and a high current density (1200 Am(-2)).

Ammonia↗
PubMed2002

Optimization of operating conditions in a high-shear mixer using dem model: determination of optimal fill level.

For the purpose of evaluating optimal fill level of starting materials in a high-shear mixer, discrete element method (DEM) simulation was conducted to visualize kinetic status between particles. The simulation results obtained by changing fill levels were used to determine solid fraction of particles, particle velocity, particle velocity vector, and kinetic energy and discuss the flow pattern. Optimal fill level was obtained from the information on these matters. It was pointed out that understanding the kinetic energy between particles in an agitating vessel was effective in determining the optimal fill level. Granulation experiment was conducted to validate the optimal fill level obtained by the simulation, confirming the good agreement between these two results. It was pointed out that determination of kinetic energy between particles through the simulation was effective in obtaining an index of the kinetic status of particles. Further, it was confirmed that the simulation could provide more information than conventional granulation experiments could provide and also helpful in optimizing the operating conditions.

Drug Compounding↗
PubMed2006

Does cerebral monitoring improve ophthalmic surgical operating conditions during propofol-induced sedation?

Sudden movements from over-sedation during ophthalmic surgery can be detrimental to the eye. Bispectral index (BIS) and middle-latency auditory-evoked potentials (Alaris AEP index, AAI) were reported to be accurate indicators for the level of sedation and loss of consciousness. We assessed these monitors during sedation with special emphasis on preventing over-sedation. One-hundred patients scheduled for elective eye surgery were sedated with target-controlled propofol infusion and randomly allocated to BIS-guided, AAI-guided, BIS/AAI-guided, or clinically guided groups (n = 25 each). The initial target concentration was 0.5 microg x mL(-1) in patients >70 yr and 1.0 microg x mL(-1) in all other patients. The concentration was increased every 3 min by 0.1 or 0.2 microg x mL(-1), respectively until the patient had reached a BIS value of 75 (range 70-90) or an AAI of 40 (range 35-60). The surgeon who was blinded to group allocation assessed treatment quality after the procedure. Sedation was converted into general anesthesia in four patients because of excessive head movements. BIS was out of range 7% of the time vs 58% for AAI. No significant differences in treatment quality were observed among the four groups. We conclude that propofol sedation, guided by BIS or AAI monitoring, did not enhance ophthalmic surgical operating conditions over sedation guided by clinical observation only.

Adolescent↗
PubMed1968

Operant conditioning of eye movement in the monkey (Macaca nemestrina).

With the horizontal electrooculographic potential as the operant, four monkeys (Macaca nemestrina) were conditioned to move their eyes at high and low rates by initial use of fixed-ratio schedules of reinforcement, followed by a changeover to multiple schedules of fixed-ratio reinforcement and discriminated differential reinforcement of low rate. These differences in rate of eye movement were not observed in a control animal given the same patterns of discriminative stimuli and deliveries of the reinforcing agent independent of its eye movements.

Animals↗
PubMed2005

Influence of operational conditions on the performance of a mesh filter activated sludge process.

Recently, a new type of wastewater treatment system became the focus of scientific research, the mesh filter activated sludge system. It is a modification of the membrane bioreactor where a membrane filtration process serves to separate the sludge from the purified effluent. The difference is that a mesh filter is used instead of the membrane. Due to the much larger pore size of the mesh, the effluent is not of the same excellent quality as with membrane bioreactors. Nevertheless, it still resembles the quality of the now most widely used standard treatment system, where settling tanks are used to retain the activated sludge. At the same time, the new system features all the other advantages of membrane bioreactors including elevated sludge concentrations resulting in decreased volumina of basins and complete substitution of the settling tank. Therefore, this process presents a potential future alternative where a small footprint of the plant is required. However, so far only a few preliminary studies on this innovative process type have been done. In this paper, the effects of suspended solids concentration, flux rate as well as aeration rate on the effluent quality are discussed. Furthermore, the characteristic of the sludge floc was identified as a factor of vital importance. Therefore, another influencing parameter, the food to microorganism (F/M) ratio, which is known to have a significant effect on floc characteristics, was studied. The main result demonstrated that the process was very effective under most of the operation conditions. The suspended solids concentration in the effluent was below 12 mg l(-1), the average COD in the effluent was between 24 and 45 mg l(-1) and the BOD(5) was lower than 5 mg l(-1). High flux rates of up to 150 l m(-2)h(-1) were also achieved.

Bioreactors↗
PubMed1966

Operant conditioning of a small-scale muscle response.

Six naive male subjects were reinforced for responses in the 20-30 microvolt range, and two each for those in 10-20 and 30-40 microvolt ranges. Records were taken of 15 min of "settling down," 15 min of initial operant level responding, 30 min of conditioning, and 45 min of extinction, 30 min with light present and 15 min without. The results were: (1) small-scale muscle potentials from the thenar eminence, in the 10-20, 20-30, and 30-40 microvolt ranges, were conditioned, using pointer movement as the reinforcement; (2) the response rate in adjacent ranges of greater and lesser amplitude also increased during such conditioning and decreased during the subsequent extinction; (3) during conditioning the frequency of response distribution shifted toward the reinforced range; (4) subjects were unaware of the reinforced response; (5) observing a noncontingent moving pointer increased the response rate in the 20-30 microvolt range, but did not lead to conditioning.

Adult↗
PubMedDate not supplied

Effects of ageing and long-term operant conditioning on behavior and presynaptic cholinergic and dopaminergic neuronal mechanisms in rats.

Presynaptic events in the brain, such as neurotransmitter synthesis and release, may change during ageing or by performance of an operant behavior. Therefore, we measured the acetylcholine synthesis and release, and the dopamine release in brain tissue from different groups of rats. Male Sprague-Dawley rats, 4-5 or 16-17 months old, were housed individually under identical conditions; one group of the older rats was maintained under an operant conflict procedure for 8 months. Striatal and cerebral cortex slices were preincubated with [3H]dopamine and [3H]choline, respectively, superfused and stimulated electrically. Different Ca++ concentrations were used and, in [3H]dopamine experiments, 0.1 mumol/l of apomorphine was added. Hippocampal slices were incubated with [3H]choline, and 3H-uptake and [3H]acetylcholine synthesis were measured. Gross behavior was not different between the groups as regards duration of exploration, defecation rate or spontaneous motility. Uptake of [3H]choline and synthesis of [3H]acetylcholine tended to be lower in the aged rats but did not differ significantly in the groups. The [3H]dopamine release was significantly reduced by 20% in aged rats as compared to young or aged, trained rats. The effect of changes in Ca++ concentrations and the response to apomorphine on the release of [3H]dopamine were similar in all groups, indicating a lack of age-related changes of the N-type Ca++ channels and presynaptic D-2 receptors. Thus, ageing coincided with an impaired striatal dopamine release which was prevented by the operant conditioning.

Acetylcholine↗
PubMed1975

An electronic activity integrator for operant conditioning of patterns of neural and muscular activity.

An activity integrator circuit designed to detect and operantly reinforce patterns of neural and muscular activity is described. An integrator voltage proportional to the weighted sum of multiple input signals reaches a threshold level when the requisite response pattern is emitted. A variety of response patterns may be differentially reinforced, depending on the nature of the integrated signals.

Animals↗
PubMed2004

Recent advances in operant conditioning technology: a versatile and affordable computerized touchscreen system.

We report the construction of a new operant chamber that incorporates modern computer, touchscreen, and display technologies. An LCD display was housed in the front wall of a lightweight Plexiglas chamber. An Apple eMac computer was used to present visual stimuli on the monitor and to control other chamber events. Responses to the stimuli were recorded using a transparent resistive-type touchscreen that overlaid the monitor. The resulting system is simple and inexpensive to construct but powerful and flexible enough to explore a broad range of issues in animal learning and behavior.

Animals↗
PubMed1977

Combination operant conditioning--liquid nitrogen immersion chamber for studying neurotransmitter systems and behavior.

Studies of neurochemical events associated with behavior require a method of tissue fixation that is rapid and does not itself produce neurochemical changes. An apparatus is described that permits immediate immersion of an unrestrained behaving animal into liquid nitrogen. This method of tissue fixation has the greatest versatility for studying multiple neurotransmitter systems. In addition to the measurement of neurotransmitter content and turnover, investigation of neurotransmitter receptors, enriched nerve ending fractions and enzyme activities are possible. The operant conditioning-liquid nitrogen immersion chamber described here can be used for studying these neurotransmitter systems as they relate to animal's responding on operant schedules of reinforcement.

Animals↗
PubMed2002

The effect of amiloride on operantly conditioned performance in an NaCl taste detection task and NaCl preference in C57BL/6J mice.

A 2-response operant taste discrimination procedure, modified to assess taste sensitivity in water-restricted C57BL/6J mice, revealed a detection threshold of 0.065 M sodium chloride. Amiloride increased the threshold by approximately 1 log10 unit. These results are the first to demonstrate the necessity of the amiloride-sensitive taste transduction pathway in the normal detection of low concentrations of sodium chloride in mice and provide a functional context in which to evaluate electrophysiological findings. Two-bottle preference tests performed with these mice and additional naive mice revealed only marginal, if any, effects of amiloride on salt intake behavior, highlighting the importance of considering the relative attributes and limitations of different behavioral assays of taste function.

Amiloride↗
PubMed2004

Operant conditioning in the Ts65Dn mouse: learning.

Ts65Dn and littermate controls were trained to respond (nose-poke) under operant schedules of reinforcement. A small difference was observed in the initial operant training of the Ts65Dn mouse that disappeared with training under a fixed-ratio 15 schedule of milk presentation. No difference was observed in a position reversal task in which mice initially trained to respond upon one photocell had to learn to respond on a previously inactive photocell. Under an incremental repeated acquisition of behavioral chains schedule, no difference was observed when one or two responses were required to complete the sequence. However, when three or four responses were required to complete the sequence, a marked deficit was observed in the Ts65Dn mice. These results show that both Ts65Dn and littermate controls can be trained to respond under operant schedules of reinforcement, but that Ts65Dn mice have a learning deficit that is correlated with task difficulty.

Animals↗
PubMed1987

Performance of large groups of chicks using operant conditioning to control the thermal environment.

In four trials, 408, 320, 160, and 400 chicks were housed on litter in pens 1.8 x 2.4 m. Eight pens were used for each trial. For the first 6 days the environmental temperature was maintained at 28 C; on Day 7 the temperature was reduced to 16 C. Four pens were equipped with microswitches; the remaining four pens were each heated by two infrared lamps in constant operation. When chicks struck the microswitch, infrared lamps were turned on for 1 min during the learning phase when chicks were being conditioned to the experimental setup and 4 min during the experimental phase during which data were collected for analysis. Feed intake, gain, and mortality were recorded. Trials 1 and 2 were concluded at 28 days and Trials 3 and 4 concluded at 21 days. At the conclusion of the trials protein, fat, and water content of the birds were determined. Additional analysis for ash content was performed for Trials 1 and 2 only. No significant differences (P greater than .05) in gain, feed conversion, body composition, and mortality rate were found between treatments. Chicks provided with continuous heat were exposed to three times as much supplemental heat as operant conditioned groups yet feed efficiency was unaffected.

Animals↗
PubMedDate not supplied

Operant conditioning of pontine gigantocellular units.

In order to investigate the behavioral role of pontine gigantocellular field (FTG) units, we have operantly reinforced discharge in these cells in unrestrained cats using lateral hypothalamic stimulation as the reinforcing stimulus. Cats readily learned to increase discharge rate in reinforced FTG cells relative to simultaneously recorded, non-reinforced control cells. Increased FTG discharge was associated with elevated levels of motor activity and often with stereotyped movements. Our results are compatible with the hypothesis that FTG unit discharge is related to specific movements.

Animals↗
PubMed2004

Effects of quinpirole on operant conditioning: perseveration of behavioral components.

Quinpirole (QNP) is reported to elicit repetitive spontaneous behaviors as well as reduce extinction of operant responses. To determine whether these effects represent perseveration of learned behaviors, behavioral components were examined during the acquisition and extinction of operant responses. Rats, receiving either 0, 0.08, or 0.60 mg/kg QNP were trained to nose poke to receive water. The lower dose interfered with acquisition, but once learned, behavioral characteristics were normal. The higher dose produced excessive time in the drinking well when water was delivered. When water was withheld, the control and 0.08 mg/kg dose groups altered their behavior by initially increasing nose poke duration, followed by a progressive extinction of the operant response. The higher dose group, however, did not modify the characteristics of their behaviors, but continued to perform the behavioral sequence in the absence of reward. These effects are not ascribable to generalized locomotor activation in that response rates during reinforced responses, as well as at the beginning of the extinction phase, did not differ significantly across treatment groups. These results indicate that perseveration effects of QNP are not accountable by general behavioral arousal, nor are specific to extinction. Instead, these effects appear to reflect reduced adaptability of learned behavioral patterns to changes in reinforcement contingencies.

Analysis of Variance↗
PubMed1979

Operant conditioning of infant monkeys (Macaca fascicularis) for toxicity testing.

A technique has been developed that allows infant monkeys to perform on an operant schedule as soon as they are able to self-feed. Behavior is shaped in small increments through a series of operants; sensory and motor systems as well as performance on schedules using intermittent reinforcement may be tested as early as 3-4 weeks of age. This is accomplished by exposing the infant to the operant situation almost continuously, and allowing the infant to feed only by operantly responding. Infants exposed to lead post-natally differed from controls in pattern of fixed ratio responding, "activity" as measured by pattern of responding over the course of the session, and on a two-choice form discrimination reversal learning set paradigm. This technique allows rapid accumulation of large amounts of data without experimenter intervention.

Animals↗