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 1,189 records · Page 66Linked to original sources

PubMed1988

Clinical analysis of cerebral abscesses.

42 patients with cerebral abscesses were treated from 1979 until the end of the first six months of 1987 at the Neurosurgical Department of the Faculty of Medicine, Atatürk University, Erzurum, Turkey. The present study aims at studying these patients to determine the factors affecting on prognosis. The patients were studied for the duration of complaints, pre-operational condition, the location of the abscesses, the microorganisms responsible for them, and the techniques of operation applied, by taking their sex and age into consideration. All of the cases were treated operatively. Of these, 18 were treated by excision and 24 were applied drainage, whose percentage was 43 and 57 respectively, 85% of the cases were under 60 years of age. The rate of mortality of the cases with cerebral abscesses was 19%. This rate was between 15% and 37.5% in the cases of several age groups whose complaints lasted less than two months. This rate reached 100% with a sudden increase in the cases who had a duration of complaints over four months. The rate of mortality was 6.2% in the cases with a clear conscious and cooperative ability while it had a significant increase in the patients in pre-coma or coma to go up to 50% and 75% respectively. No correlation was observed between the rate of mortality and the age of the patients but the location and extension of the abscesses had an effect on this rate. The abscesses, covering more than one lobe, had a mortality rate of 31.2%, while the ones with parietal location caused no single death. To conclude, we can say, based on this study, that the age and sex of patients and the operative technique have no effect on the rate of mortality while it is obviously influenced by the duration of the complaints and the pre-operative condition. Consequently, we would like to stress up on early diagnosis and treatment of such cases.

Adolescent↗

PubMed1979

Comparison of tangibly reinforced speech-reception and pure-tone thresholds of mentally retarded children.

Sixteen mentally retarded children who had normal hearing were examined with two tests of auditory sensitivity. One procedure employed a tangibly reinforced operant-conditioning paradigm for pure tones, and the other test was based on a modification of operant conditioning for obtaining speech-reception thresholds. The speech procedure, utilizing an attractive mechanical device in the form of a clown, proved to be effective and efficient for use with retarded children.

Acoustic Stimulation↗

PubMed2005

Effects of nitrous oxide on intraoperative bowel distension.

PURPOSE OF REVIEW: To evaluate evidence and present an objective view on the effect of nitrous oxide on bowel function. RECENT FINDINGS: We determined in a metaanalysis that the chance of having intraoperative bowel distension was increased about two fold in patients receiving nitrous oxide as the anaesthetic carrier gas compared with those receiving nitrogen or oxygen. In a separate logistic regression analysis, we found that the duration of nitrous oxide exposure was a key factor in explaining this difference, as well as the variability of previously published data. In contrast to bowel distension, surgical operating conditions were not hindered by the use of nitrous oxide; however, the number of patients analysed for operating conditions was much less than that for bowel distension data. SUMMARY: Nitrous oxide causes clinically and statistically recognizable bowel distension. This distension, however, does not always exacerbate the surgical conditions, nor does it appear to delay bowel movement or hospital discharge. Although no major problems were noted in bowel functions other than distension, we recommend avoiding nitrous oxide administration during prolonged bowel operations.

Journal Article↗

PubMed2001

Avoiding acetate accumulation in Escherichia coli cultures using feedback control of glucose feeding.

An automated glucose feeding strategy that avoids acetate accumulation in cultivations of Escherichia coli is discussed. We have previously described how a probing technique makes it possible to detect and avoid overflow metabolism using a dissolved oxygen sensor. In this article these ideas are extended with a safety net that guarantees that aerobic conditions are maintained. The method is generally applicable, as no strain-specific information is needed and the only sensor required is a standard dissolved oxygen probe. It also gives the highest feed rate possible with respect to limitations from overflow metabolism and oxygen transfer, thus maximizing bioreactor productivity. The strategy was implemented on three different laboratory-scale platforms and fed-batch cultivations under different operating conditions were performed with three recombinant strains, E. coli K-12 UL635, E. coli BL21(DE3), and E. coli K-12 UL634. In spite of disturbances from antifoam and induction of recombinant protein production, the method reproducibly gave low concentrations of acetate and glucose. The ability to obtain favorable cultivation conditions independently of strain and operating conditions makes the presented strategy a useful tool, especially in situations where it is important to get good results on the first attempt.

Acetates↗

PubMed1981

[The bacteria stop system of Meierhans-Weber as room air technical alternative to laminar-air-flow and its air hygienic effectiveness].

Statistics of wound infections demonstrate the linear dependence between postoperative wound infection and the quantity of bacteria in the air of operating theatres. In the most extensive examination series we have made as yet with a special work group of DGOT the quantity of bacteria in the air of non air-conditioned operating theatres and such fitted out with different aircleaning systems was determined. Non air-conditioned operating theatres proved so extremely infected that the risk of wound infection cannot be borne any more in the future. Also air-conditioned systems according to DIN 1946/4 with an average of 190 bacteria/m3 are not sufficiently secure for bone and joint surgery. In Switzerland for such operations a value of 10/m3 at the most is admissible. Such equivalents have been attained only with LAF until today. After extensive air tests the so-called "Keimstop"-system by Meierhans and Weber is to be considered the sole system suitable to supplement air conditioning DIN 1946/4. This combination yields the same effect as the expensive LAF systems.

Air Conditioning↗

PubMed2005

Driver performance modelling and its practical application to railway safety.

This paper reports on the development and main features of a model of driver information processing. The work was conducted on behalf of Network Rail to meet a requirement to understand and manage the driver's interaction with the infrastructure through lineside reminder appliances. The model utilises cognitive theory and modelling techniques to describe driver performance in relation to infrastructure features and operational conditions. The model is capable of predicting the performance time, workload and error consequences of different operational conditions. The utility of the model is demonstrated through reports of its application to the following studies: Research on the effect of line speed on driver interaction with signals and signs. Calculation of minimum reading times for signals. Development of a human factors signals passed at danger (SPAD) hazard checklist, and a method to resolve conflicts between signal sighting solutions. Research on the demands imposed on drivers by European train control system (ETCS) driving in a UK context. The paper also reports on a validation of the model's utility as a tool for assessing cab and infrastructure drivability.

Accidents, Occupational↗

PubMed2007

Relevance of PCDD/PCDF formation for the evaluation of POPs destruction technologies--review on current status and assessment gaps.

One important criterion for assessment of a POPs destruction technology is the potential formation of new POPs and other toxic by-products, in particular whether the highly toxic PCDDs/PCDFs are formed and under which operation conditions their formation is relevant. For incineration processes the formation mechanisms of PCDDs/PCDFs have been investigated thoroughly and strategies and technologies were developed to minimize their formation and emission. A detailed assessment of non-combustion technologies with respect to PCDD/PCDF formation is, however, lacking to date. A comparison of reaction conditions for PCDD/PCDF formation from precursor formation studies and actual applied conditions of a broad range of POPs destruction technologies in the present paper indicates that the operation conditions for a number of destruction technologies have the potential to generate high concentrations of PCDDs/PCDFs if dioxin precursors are present and that also PCDD/PCDF de novo formation can take place. Therefore a strategy and regulations for a more profound assessment and monitoring of the fate of PCDD/PCDF formation and emission is essential for the evaluation of POP destruction technologies and for a sound risk management of POPs. The present paper aims to provide a critical impulse in this respect, discusses the relevant formation pathways with respect to POPs destruction technologies and proposes a basic framework on how evaluations may be performed.

Benzofurans↗

PubMed2005

Theory of peak capacity in gradient elution.

Peak capacity is the best measure of the performance of a gradient separation. In this paper, the theory of peak capacity for the standard operating conditions of reversed-phase and ion-exchange chromatography is outlined. The influence of the operating conditions on the peak capacity of a separation are discussed. Finally, bandspreading phenomena in gradient chromatography are analyzed.

Chemical Phenomena↗

PubMed2003

Ontogeny has a phylogeny: background to adjunctive behaviors in pigeons and budgerigars.

Animals coping with operant conditioning tasks often show behaviors that are not recorded by keys, levers and similar response transducers. Nevertheless, these adjunctive behaviors should not be disposed of by classifying them as incidental. Often they are found to be at least partially influenced by the experimentally programmed contingencies, and under certain conditions they can in turn influence conditioned behaviors. Here we describe the occurrence and characteristics of two such behaviors, stimulus grasping in operantly key-pecking pigeons and intra-delay stereotypies in a delayed matching-to-sample task with budgerigars. It is argued that for a proper account of these behaviors it is necessary to refer to a behavioral systems approach that appeals to longer ranging ontogenetic and phylogenetic histories than is usually considered in the psychological literature. The gaping towards on-key stimuli by pigeons is attributed to the hypothesis that operantly conditioned key-pecks probably relate to a grasp-pecking response that is normally executed towards non-edible items covering food. The intra-delay behaviors shown by the budgerigars are assumed to have originated from stress-induced displacement responses that adventitiously came under the influence of differential reinforcement contingencies. Finally, we discuss what kinds of evidence are needed to put these hypothetical explanations on a more certain footing.

Journal Article↗

PubMed2001

Preparation and characterization of spray-dried oxidized cellulose microparticles.

The goal of this study was to investigate the feasibility of spray drying to produce microparticles of oxidized cellulose (OC), a biocompatible and bioresorbable polymer. OCs containing 7, 13, and 20 wt% carboxylic groups were converted into stable aqueous dispersions and then spray dried using a Yamoto G-32 spray dryer equipped with a standard fluid nozzle with an orifice of 406 microm. The following operating conditions were investigated: inlet temperature 140, 170, and 190 degrees C; feed rate 3, 6, and 9 mL/min; and atomization airpressure 0.5, 1, and 1.5 kg f/cm2. The amounts of OC used in feed were 1, 2.5, and 5%. OC microparticles produced under these conditions were shrunken spheres, ranging in size between 0.98+/-0.47 and 2.05+/-0.98 microm. The different operating conditions used had no significant effect on the size and shape of particles. The use of a water-soluble plasticizer (glycerin, polyethylene glycol 400, or polyethylene glycol 6000) in the dispersion yielded microparticles with a good sphericity and a smooth surface morphology, whereas no change in the shape or size of microparticles was noted with water-insoluble plasticizers, Triacetin and dibutyl phthalate. Powder X-ray diffraction and Fourier transform infrared spectral analyses of spray-dried microparticles showed no change in the solid-state structure of OC. In conclusion, results show that OC can be converted into stable aqueous dispersions and used to produce microparticles by spray drying.

Capsules↗

PubMed2001

On the phase-space dynamics of systems of spiking neurons. II: formal analysis.

We begin with a brief review of the abstract dynamical system that models systems of biological neurons, introduced in the original article. We then analyze the dynamics of the system. Formal analysis of local properties of flows reveals contraction, expansion, and folding in different sections of the phase-space. The criterion for the system, set up to model a typical neocortical column, to be sensitive to initial conditions is identified. Based on physiological parameters, we then deduce that periodic orbits in the region of the phase-space corresponding to normal operational conditions in the neocortex are almost surely (with probability 1) unstable, those in the region corresponding to seizure-like conditions are almost surely stable, and trajectories in the region corresponding to normal operational conditions are almost surely sensitive to initial conditions. Next, we present a procedure that isolates all basic sets, complex sets, and attractors incrementally. Based on the two sets of results, we conclude that chaotic attractors that are potentially anisotropic play a central role in the dynamics of such systems. Finally, we examine the impact of this result on the computational nature of neocortical neuronal systems.

Action Potentials↗

PubMed2006

Photocatalytic degradation of Reactive Red 22 in aqueous solution by UV-LED radiation.

Photocatalytic processes using TiO(2) as a catalyst have attracted extensive attention for decomposition of organic contaminants. The determination of optimum reactor design and operational conditions are the major concerns for the development and potential application of the photocatalytic process. Various photoreactor types, photocatalyst arrangements, light sources, and operation conditions were reported. This study was focused on the application of the ultraviolet light emitting diode (UV-LED) as the UV light source for the photocatalytic decomposition of Reactive Red 22 (RR 22). The temporal behavior of the photocatalytic decomposition of RR 22 in aqueous solution by the UV-LED/TiO(2) with a rectangular planar fixed-film reactor operated in a recirculation mode was studied under various conditions including initial dye concentration, periodic illumination, light intensity, and arrangements of TiO(2) coating. The decomposition of RR 22 in aqueous solution by TiO(2) photocatalytic processes with the UV-LED was found to be technically feasible with a high TiO(2) coated weight (1.135g) and low pH value (pH 2). A Langmuir-Hinshelwood-type kinetic equation was adequate for modeling the photocatalytic decomposition of RR 22 by the UV-LED/TiO(2) photocatalytic processes. The experimental results indicated that the photonic efficiency with periodic illumination was much higher than those with continuous illumination. The photonic efficiencies with the quartz-liquid-catalyst (QLC) arrangement were higher than those with the quartz-catalyst-liquid (QCL) arrangement for experiments conducted at lower applied light intensity; however, the photonic efficiencies for these two arrangements were nearly identical for experiments conducted at higher light intensities.

Catalysis↗

PubMed2004

Estimating exposure to chemical contaminants in drinking water.

A model is developed that predicts exposure and absorbed dose for chemical contaminants in household drinking water via three pathways: inhalation, direct and indirect ingestion, and dermal penetration. Extensive probability distributions for building characteristics, activity and water use patterns, operating conditions of water devices, and physiological characteristics of the general population are developed. The impacts of different operating conditions on mass transfer coefficients for the shower, bath, washing machine, dishwasher, and faucet are established. Dichlorobromomethane, inorganic lead, and endosulfan, three compounds associated with adverse birth outcomes that have significantly different chemical properties, are selected for analysis. The primary exposure pathways for dichlorobromomethane are inhalation (62%) and ingestion (27%). Seventy percent of total exposure to endosulfan comes from ingestion, and 18% from dermal sorption with the remaining 12% due to inhalation. Virtually all (99.9%) of the exposure to lead occurs via ingestion. A nested Monte Carlo analysis shows that natural variability contributes significantly more (a factor of 10) toward total uncertainty than knowledge uncertainty (a factor of 1.5). Better identification of certain critical input variables (ventilation rate in the shower and bathroom, ingestion rate, the boiling water mass transfer coefficient, and skin permeability) is required.

Adsorption↗

PubMed1992

Risk factors responsible for patients' falls.

The study determined intrinsic factors which contributed to the falls of adults hospitalized in a general hospital during 1987-88. Two hundred and fourteen patients were studied in two groups. Group A consisted of 108 patients who fell during their hospitalization and control Group B consisted of 106 patients with the same characteristics also hospitalized during the same period who did not fall. Of the 23 variables which have been analyzed by the multivariate logistic regression method, seven present statistically significant incidence and increased risk of patients' falls: (1) gender: the number of accidents occurring among male patients was higher than that among females (p = 0.0022); (2) age: the majority of accidents occurred in the 65 greater than or equal to years old age group (p = 0.00426); (3) general pathological conditions: mostly patients with cardiac problems (p = 0.0062); (4) neoplasms (p = 0.0334); (5) anaemias (p = 0.0128); (6) post-operative conditions (p = 0.0063); and the taking of hypnotic/tranquilizer drugs (p = 0.0486). Other significant findings were: the highest incidence of falls occurred during the first 4 days of the patients' admission to hospital and most during the early morning hours (5-6 am). Injuries incurred were bruises (32.4%), minor injuries (24%), major injuries (16.7%) and fractures (10.2%). The high correlation between patients' falls and (1) specific diseases, namely neoplasms, anaemias, cardiac and post-operative conditions and (2) the taking of hypnotic/tranquilizer drugs are risk factors in relation to patients' falls in general hospitals.

Accidental Falls↗

PubMed2000

Treatment of hazardous sorbents generated from the adsorption of heavy metals during incineration.

The emission of heavy metals during waste incineration can be effectively reduced through the practice of employing non-toxic sorbents. These sorbents can react with toxic metals at high temperatures and create metal binding between them by various physical and chemical mechanisms. After the adsorption process, the used sorbents, which contain heavy metals, need to be desorbed to reduce their potential environmental hazards or provide reusable sorbents for economical aspect. The sorbent's adsorption efficiency is affected by different operating conditions and waste elemental compositions during incineration, which, in turn, affect their desorption characteristics. However, the effects of operating condition and waste elemental composition on the stability of heavy metals in the sorbents and the desorption efficiencies have been little studied. This study investigates the desorption characteristics of heavy metals (Cr, Pb, Cu, and Cd) from the hazardous sorbents with different extracting reagents (H(2)O, HCl, EDTA, and Na(2)S(2)O(5)). The hazardous sorbents were generated under different adsorption time and various input waste elemental compositions during incineration process.

Adsorption↗

PubMed2003

Dissociation of visual associative and motor learning in Drosophila at the flight simulator.

Ever since operant conditioning was studied experimentally, the relationship between associative learning and possible motor learning has become controversial. Although motor learning and its underlying neural substrates have been extensively studied in mammals, it is still poorly understood in invertebrates. The visual discriminative avoidance paradigm of Drosophila at the flight simulator has been widely used to study the flies' visual associative learning and related functions, but it has not been used to study the motor learning process. In this study, newly-designed data analysis was employed to examine the flies' solitary behavioural variable that was recorded at the flight simulator-yaw torque. Analysis was conducted to explore torque distributions of both wild-type and mutant flies in conditioning, with the following results: (1) Wild-type Canton-S flies had motor learning performance in conditioning, which was proved by modifications of the animal's behavioural mode in conditioning. (2) Repetition of training improved the motor learning performance of wild-type Canton-S flies. (3) Although mutant dunce(1) flies were defective in visual associative learning, they showed essentially normal motor learning performance in terms of yaw torque distribution in conditioning. Finally, we tentatively proposed that both visual associative learning and motor learning were involved in the visual operant conditioning of Drosophila at the flight simulator, that the two learning forms could be dissociated and they might have different neural bases.

Journal Article↗

PubMed2002

Topical versus retrobulbar anesthesia for combined phacotrabeculectomy: prospective randomized study.

PURPOSE: To compare the safety and efficacy of topical and retrobulbar anesthesia for combined phacotrabeculectomy. SETTING: Tertiary-care university hospital ambulatory surgical center. METHODS: In this prospective study, 40 consecutive patients having combined phacotrabeculectomy were randomized to receive topical (n = 20) or retrobulbar (n = 20) anesthesia. Operating conditions, patient comfort, and surgical outcome were evaluated. RESULTS: There was no significant between-group difference in operating conditions (P =.56), pain during (P =.41) or after (P =.23) surgery, or supplemental anesthesia required (P =.49). Few patients in either group were bothered by tissue manipulation or the microscope light, although more patients in the topical group were slightly bothered by touch sensation (P =.05). Chemosis, subconjunctival hemorrhage, and eyelid hematoma were seen almost exclusively in the retrobulbar group (P <.05). Inadvertent eye movement was present more frequently in the topical group (P =.04), although this did not pose a problem to the surgeon. CONCLUSION: Topical anesthesia is a safe and effective alternative to retrobulbar anesthesia for combined phacotrabeculectomy.

Administration, Topical↗

PubMed1999

Learning, memory and a respiratory central pattern generator.

In an attempt to elucidate the causal mechanisms underlying learning and memory we have developed a model system, aerial respiration in the pond snail Lymnaea stagnalis. A three-neuron central pattern generator (CPG) whose sufficiency and necessity have been demonstrated mediates this behaviour. Aerial respiration, while an important homeostatic behaviour, is inhibited by the activation of the whole body withdrawal response that the animal uses to protect itself. We found that it was possible to operantly condition snails not to perform aerial respiration in a situation, a hypoxic environment, where aerial respiration should predominate. Operant conditioning was achieved by eliciting the pneumostome withdrawal response, part of the whole body withdrawal response, each time the animal attempted to open its pneumostome to breathe. Yoked control animals did not demonstrate an alteration in breathing behaviour. Subsequently we determined neural correlates of this associative behaviour and found that neuronal changes are distributed throughout the CPG. This preparation may afford us the opportunity to determine the casual neuronal changes that underlie learning and memory of associative conditioning.

Animals↗