PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Conditioning, Operant”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63Linked to original sources
PubMed2003

Leakage flow measurements in a bio-centrifugal ventricular assist device model.

The magnetically suspended impeller centrifugal blood pump (MSCBP) has shown its superiority as compared to other artificial hearts. However, it is still plagued by hemolysis and thrombus formation in the clearance gap between the impeller shroud surface and the pump casing. In an early study, a 5 : 1 scaled up model was built in order to measure the radial and tangential velocities at the gap under the operating condition of a flow coefficient (Phi) of 0.04 using a hot wire anemometer. In this study, velocity profiles were obtained at two critical flow coefficients, Phi = 0.078 (fully opened condition) and 0 (fully closed condition), to further the understanding of the flow field in the pump. Similar to the operating condition, the vector plot of the resultant velocity under these two flow coefficients showed that there were no vortices in the gap and a washout mechanism presented at the region around the starting of the splitter plate of the double volute. It was found that the washout mechanism was more obvious in the fully closed condition than in the fully opened condition. This has suggested that with real life operation, the pump could occasionally be operated at a relatively lower flow rate (e.g., under the resting condition of the patient) to obtain a good washout in the gap and thus reduce thrombus formation at the pump casing.

Blood Flow Velocity↗
PubMed1992

Intrauterine pressure and fluid absorption during continuous flow hysteroscopy.

OBJECTIVES: Our objectives were to document the causes of fluid absorption during continuous flow hysteroscopy and to determine under which operative conditions fluid overload may occur. STUDY DESIGN: Fifteen patients underwent operative hysteroscopy with 2% ethanol solution for uterine distention. Absorption of fluid was measured by blood alcohol, sodium, osmolarity, and hematocrit. Intrauterine pressures were measured with an obstetric pressure catheter. RESULTS: Alcohol absorption was noted in one patient during a myoma resection. Two additional patients, not in the study, had fluid absorption after partial perforations of the uterus. Under normal operative conditions there were no changes in sodium, osmolarity, or hematocrit. Intrauterine pressures ranged from 45 to 75 mm Hg. Experimental pressures of greater than 200 mm Hg were not associated with fluid absorption. CONCLUSIONS: Intravasation of fluid may occur through open uterine venous channels with extensive resections and under low pressures in the presence of unrecognized perforations.

Absorption↗
PubMed2003

Analysis of a municipal wastewater treatment plant using a neural network-based pattern analysis.

This paper addresses the problem of how to capture the complex relationships that exist between process variables and to diagnose the dynamic behaviour of a municipal wastewater treatment plant (WTP). Due to the complex biological reaction mechanisms, the highly time-varying, and multivariable aspects of the real WTP, the diagnosis of the WTP are still difficult in practice. The application of intelligent techniques, which can analyse the multi-dimensional process data using a sophisticated visualisation technique, can be useful for analysing and diagnosing the activated-sludge WTP. In this paper, the Kohonen Self-Organising Feature Maps (KSOFM) neural network is applied to analyse the multi-dimensional process data, and to diagnose the inter-relationship of the process variables in a real activated-sludge WTP. By using component planes, some detailed local relationships between the process variables, e.g., responses of the process variables under different operating conditions, as well as the global information is discovered. The operating condition and the inter-relationship among the process variables in the WTP have been diagnosed and extracted by the information obtained from the clustering analysis of the maps. It is concluded that the KSOFM technique provides an effective analysing and diagnosing tool to understand the system behaviour and to extract knowledge contained in multi-dimensional data of a large-scale WTP.

Data Collection↗
PubMed1978

An evaluation of ultraviolet radiation personnel hazards from selected 400-watt high intensity discharge lamps.

A study of selected mercury and multi-vapor lamps, commonly used for working environment illumination, was underta ken to evaluate the scope of the ultraviolet personnel hazards one may expect under various operating conditions of the lamps. Spectral irradiance measurements were made for operating conditions with and without reflector-type luminaires, glass covers on luminaries and outer glass bulbs on the lamps.

Environmental Exposure↗
PubMed2003

Use of a similarity index based on microbial fatty acid (MFA) analysis to monitor biological wastewater treatment systems.

Estimating the stability of microbial community structures may be useful in advanced biological wastewater treatment system design and operation. In this research, a monitoring method using fatty acid profiles was evaluated for detecting changes in microbial community structures. For the evaluation, the operating parameters such as pH, organic loading, and chlorine addition were varied in two identical laboratory scale conventional activated sludge systems. A similarity index based on microbial fatty acid analysis was used to express the stability of microbial community structures in the systems. Experiments using a model microbial community showed that microbial compositions changed daily even under constant operating conditions and that the rate of change increased under dynamic operating conditions. Substrate changes brought about a relatively large change in a microbial community structure, eventually resulting in a very different microbial community. After only 7 days following a substrate change in a lab-scale bioreactor, the biomass exhibited only 45% similarity to the original structure. The analysis of microbial fatty acids conveys additional information, in that it could be used for the calculation of biomass concentrations in a wastewater treatment system if microbial fatty acid analyses are executed on a routine basis as a monitoring tool for biological wastewater treatment systems. The total fatty acid concentrations were about 0.61% of the biomass concentration as mixed liquor volatile suspended solid concentrations in this research.

Bacteria↗
PubMedDate not supplied

Immediate and delayed voluntary ethanol effects on motor performance, learning and inhibition in rats.

The effects of prolonged voluntary ethanol consumption on psychomotor performance, operant conditioning and inhibition were examined in adult male Wistar rats. Animals were food deprived and alcohol or control solution was available 1 h/day during 15 days, with free water for the rest of the day. Then, rats were tested in a two-bottle paradigm (solution and water available) for 1 h/day during 19 days, and subjects were tested daily for psychomotor performance and operant conditioning immediately or 6 h after (delayed) the solution access. Psychomotor performance was tested in an 80 degrees -inclined screen. Successive conditioning phases were: free shaping (FS), continuous reinforcement (CRF), operant extinction (EXT), successive discrimination (DIS) and two-stimuli test (TST). Alcohol consumption deteriorated psychomotor performance and improved the animal's ability to learn simple associations between stimuli and responses (free shaping and extinction), in immediate and delayed groups. Finally, alcohol deteriorated behavioral inhibition (DIS and TST) tested immediately after drinking. Taken together, results suggest that prolonged voluntary ethanol intake could induce permanent psychomotor impairment and associative learning facilitation, and also an impairment of the inhibition related to the intoxication state.

Alcohol Drinking↗
PubMed1973

Conditioning and post-hospital generalization of nondelusional responses in a chronic psychotic patient.

An operant conditioning approach was successful in getting a chronic psychotic patient to give factual answers to direct questions that had previously elicited only delusional responses. Multiple baseline and reversal controls established that the changes were due to the experimental procedure. The subject was a female patient classified as paranoid schizophrenic who had persisted in giving bizarre responses to direct questions regarding her identity, age, and personal history during 26 yr of hospitalization. She was discharged after factual answers to these questions had been obtained, but operant conditioning trials were continued in the community to promote generalization. Two follow-up interviews were conducted 36 and 52 days after discharge to evaluate generalization. No generalization was found in the first interview, but the second gave evidence of some generalization.

Journal Article↗
PubMed1981

The effects of pimozide during pairing on the transfer of classical conditioning to an operant discrimination.

Transfer of classical conditioning to operant learning was demonstrated by showing enhanced acquisition of an operant discrimination in a group of rats (n = 6) previously exposed to pairings of the discriminative stimulus with food as compared to control animals (n = 6). A group (n = 6) that received the classical conditioning sessions while under the influence of the neuroleptic, pimozide (1.0 mg/kg, IP) also showed enhanced acquisition of the discrimination when tested while undrugged but their performance was intermediate between that of the other groups for the first seven sessions. For the remaining sessions, the two groups that had received classical conditioning did not differ from each other and both groups discriminated better than the controls. These data may indicate a role for dopaminergic neurons in the mechanism by which the effects of classical conditioning influence operant responding.

Animals↗
PubMed2003

Continuous in vitro evolution of ribozymes that operate under conditions of extreme pH.

Continuous in vitro evolution methods were used to study the behavior of an evolving population of RNA ligase ribozymes in response to selection pressures involving conditions of extreme pH. The starting population consisted of randomized variants of a ribozyme that had been optimized for activity at pH 8.5. The ribozymes were subjected to repeated rounds of selective amplification under progressively more acidic or more alkaline conditions. The two final evolved populations of ribozymes were able to operate at either pH 5.8 or pH 9.8, respectively. Representative individuals from the two final populations were isolated and characterized. The low-pH ribozyme exhibited a 10-fold increase in catalytic rate at pH 5.8 compared to the starting molecule. The high-pH ribozyme retained its structural integrity and activity at pH 9.8, whereas the starting molecule was denatured under this condition. These findings demonstrate that a population of functional macromolecules can adapt to stringent environmental conditions through the acquisition of relatively few mutations. The results establish continuous in vitro evolution as a useful model system for exploring the evolution of enzymatic function in extreme environments.

Base Sequence↗
PubMed2003

Investigation of the direct hydride generation nebulizer for the determination of arsenic, antimony and selenium in inductively coupled plasma optical emission spectrometry.

A direct hydride generation nebulizer (DHGN) was explored for introduction of the sample in inductively coupled plasma-optical emission spectrometry (ICP-OES) using radially viewed mode. This simple hydride generation system was constructed in our laboratory and requires similar plasma operating conditions to conventional nebulizer-spray-chamber arrangements. This work was focused on the optimization of the operating conditions for hydride generation and evaluation of the main analytical figures of merit for the determination of As, Sb and Se. The excitation conditions of the ICP-OES instrument operated with the DHGN were also explored. Results showed that the analytical performance of the new system for the determination of As, Sb and Se was superior to that of conventional nebulization systems. The DHGN also enabled the determination of elements that do not form volatile hydrides, but with less sensitivity than conventional nebulization systems. Evaluation of the plasma robustness showed that gases generated in hydride generation do not significantly affects the plasma discharge. Similar to conventional hydride generation techniques, analysis with DHGN was susceptible to non-spectroscopic interferences produced by transition metals. Finally, the utility of the DHGN in practical ICP-OES studies was demonstrated in the determination of trace elements in an oyster tissue standard reference material.

Animals↗
PubMed1980

Assessment of waste anaesthetic gas scavenging systems under simulated conditions of operation.

A critical assessment of available waste anaesthetic gas scavenging devices was made by simulating the worst theatre conditions as well as ideal conditions. Only one of the scavenging devices tested proved to be unacceptable. However, the critical nature of suction flow rates was revealed and the ineffectiveness of air conditioning in the absence of adequate scavenging was highlighted.

Air Conditioning↗
PubMed2003

Comparison of two combined bioelectrochemical and sulfur autotrophic denitrification processes for drinking water treatment.

Two combined bioelectrochemical and sulfur autotrophic denitrification (CBSAD) processes for the treatment of nitrate contaminated drinking water were studied in this article, the main difference between the two processes was whether the limestone was packed in the reactor. In these processes, the sulfur denitrification was carried out in the lower part (Sulfur Part) of the reactors while the bioelectrochemical hydrogen denitrification in the upper part (Bioelectrochemical Part). Sulfur Part of one reactor was packed with elemental sulfur and limestone while no limestone was packed in Sulfur Part of the other, the former reactor is referred to as RSL and the latter as RS. The denitrification results of the two reactors were compared under different conditions, from which it can be concluded that the minimum current of RSL was about 2 mA higher than that of RS. However, at the same hydraulic retention time (HRT) and minimum current, the nitrate removal of both reactors was higher than 90% while no nitrite was accumulated in the effluent. Ca2+ concentration in Sulfur Part effluent of RSL was increased because of the packed limestone, which led to the requirement of Ca2+ removal in Bioelectrochemical Part. The effluent sulfate concentration of RSL was higher than that of RS. When current was lower than 3 mA, the effluent pH value of RSL was about 0.6 higher than that of RS. However, the effluent pH of two parts of both reactors was about neutral under optimum operation conditions. The optimum operation condition of RSL was 1.9-4h HRT under 1.5-14 mA minimum current, while that of RSL was 1.9-5 h under 3-16.5 mA. The effluent quality of RS was better than that of RSL.

Bioreactors↗
PubMed1976

Simulation studies of learning in an informon network.

A single informon reproduces classical conditioning to compound stimuli under a wide range of conditions during reinforcement and non-reinforcement; it also reproduces simple operant conditioning. A network of 210 informons with 8400 simultaneouslly varying pathways has been simulated; it can learn to recognize handprinted numerals. The networks studied must be more richly interconnected before they can reproduce more detailed behaviour of animals.

Animals↗
PubMed2001

Pollutants in incineration flue gas.

Previous studies have shown that pollutants from incineration include heavy metals, organic compounds, particulate and acid gas. However, most studies on a single pollutant, it is rare for a study to concentrate on all possible pollutants and the relations between these pollutants under various incineration conditions. The objective of this work was to experimentally study the effect of different operating conditions on the pollutants emitted during incineration and the relations between these pollutants. The operating conditions of the experiments included the temperature of the combustion chamber and the species of organics. The findings indicated that the concentration of hydrogen chloride (HCl) in the presence of polyvinyl chloride (PVC) was higher than that of sodium chloride (NaCl). Regardless of what Cl-containing feedstock was added, the concentration of chromium (Cr) was constant. When organic chloride was added, Cr was the main metallic element which influenced the formation of polycyclic aromatic hydrocarbons (PAHs). On the other hand, when inorganic chloride (NaCl) was added, lead (Pb) was the major element.

Air Pollutants↗
PubMed1998

[Use of the laryngeal mask in oral and dental surgery].

OBJECTIVE: The suitability of the laryngeal mask (LM) for anesthesia in oral and dental surgery of the face was investigated considering in particular the risks of aspiration and dislocation. We also examined acceptability to the surgeon. METHODS: In a prospective study, a total of 105 patients (ASA I-III) was included. Provided with flexible LMs, patients were operated upon the third molars (n = 64), around the dentoalveolar area (n = 32) and extraorally (n = 9). The number of placing efforts, preoperative leakage pressure, cuff pressure and complications occurring during the course of anesthesia were recorded. After the operation, the procedure was compared to endotracheal anesthesia (ETA) by the surgeon. A retrospective study comparing LM with ETA was performed on 1395 patients examining the time in between two operations, the period from the end of operation to the beginning of control of vital signs in the recovery room, and the time spent in the recovery room. The number of patients necessitating a change of anesthesia from LM to ETA was recorded. RESULTS: In 33 patients (31%), intraoperative leakage due to dislocation was observed. 33 patients (31%) had obstruction of the airway. Only when leakage occurred together with obstruction of the airway, SaO2 fell below 94% (n = 11). This was seen in particular during exposure of the wisdom teeth. In 2 of these cases, SaO2 decreased below 70 or 34% respectively. Aspiration of blood, gastric juice or dental and bone fragments was not observed. In one case, ETA became necessary. 19 patients complained of local pains (cough, sore throat, dysphagia). Operative conditions for the surgeon were comparable to oral ETA in 79% of the cases. The time in between two operations decreased about 35%, the period from the end of operation until first control of vital signs in the recovery room was reduced of about 41%, and the time spent in the recovery room decreased by 37% when compared to ETA. Out of 1111 anesthesias performed with the LM, 17 had to be exchanged for ETA. CONCLUSION: Leakage due to dislocation of the LM and airway obstruction only leads to a relevant risk of SaO2 to drop if both components occur simultaneously. With increasing experience and close cooperation between surgeon and anesthesiologist, they may be almost completely avoided so that even exposure of the lower, wisdorri teeth will seldom iiecessiiate the LM to be replaced by ETA. In relation to the tongue depressor, cuff pressure should be kept at low levels in order to obtain better flexibility of the LM. The LM provides sufficient protection against aspiration of intraoperative fluid in the pharynx. Acceptability to the surgeon is high because of good operative conditions and shortened periods in between two operations when compared to ETA. Improved protective reflex responses after the operation and its advantages when used in patients with tightness of the jaw make the LM a suitable instrument for anesthesia in oral and dental surgery.

Adult↗
PubMed2006

Operant responding for conditioned and unconditioned reinforcers in rats is differentially enhanced by the primary reinforcing and reinforcement-enhancing effects of nicotine.

RATIONALE: Nicotine self-administration in rats is modest when response-contingent nicotine infusions are delivered alone (primary reinforcement) but robust when nicotine infusions are combined with a mildly reinforcing non-pharmacological stimulus. Furthermore, response-independent (non-contingent) nicotine administration also elevates responding for that same non-pharmacological stimulus, suggesting that in addition to primary reinforcement, nicotine can enhance the incentive value of other reinforcers. OBJECTIVES: In this study, we tested the hypothesis that the reinforcement-enhancing effects of non-contingent nicotine are more dependent on the reinforcing strength of the non-pharmacological stimulus than are the effects of contingent nicotine. MATERIALS AND METHODS: A weakly reinforcing light-tone stimulus was established as a conditioned reinforcer by repeated pairings with sucrose for some rats, or by delivery in an explicitly unpaired design with sucrose to other rats. Subsequently, both groups lever pressed for the stimulus with contingent nicotine, non-contingent nicotine (0.06 mg kg(-1) per infusion, freebase), or non-contingent saline, according to fixed ratio and progressive ratio reinforcement schedules. RESULTS: Compared to sucrose-unpaired training, repeated association with sucrose established the light-tone stimulus as a robust conditioned reinforcer. Contingent and non-contingent nicotine equally elevated responding for this conditioned stimulus. Conversely, for the less reinforcing (sucrose-unpaired) stimulus contingent nicotine more effectively elevated behavior compared to non-contingent nicotine. CONCLUSIONS: The reinforcement-enhancing effect of nicotine increases behavior controlled by both conditioned and unconditioned reinforcers; however, for less salient stimuli associative processes derived from the primary reinforcing effects of contingent nicotine may also be important. These data suggest that nicotine present in tobacco may differentially modulate stimulus-driven behavior in smokers.

Animals↗