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PubMed1999

Level of automation effects on performance, situation awareness and workload in a dynamic control task.

Various levels of automation (LOA) designating the degree of human operator and computer control were explored within the context of a dynamic control task as a means of improving overall human/machine performance. Automated systems have traditionally been explored as binary function allocations; either the human or the machine is assigned to a given task. More recently, intermediary levels of automation have been discussed as a means of maintaining operator involvement in system performance, leading to improvements in situation awareness and reductions in out-of-the-loop performance problems. A LOA taxonomy applicable to a wide range of psychomotor and cognitive tasks is presented here. The taxonomy comprises various schemes of generic control system function allocations. The functions allocated to a human operator and/or computer included monitoring displays, generating processing options, selecting an 'optimal' option and implementing that option. The impact of the LOA taxonomy was assessed within a dynamic and complex cognitive control task by measuring its effect on human/system performance, situation awareness and workload. Thirty subjects performed simulation trials involving various levels of automation. Several automation failures occurred and out-of-the-loop performance decrements were assessed. Results suggest that, in terms of performance, human operators benefit most from automation of the implementation portion of the task, but only under normal operating conditions; in contrast, removal of the operator from task implementation is detrimental to performance recovery if the automated system fails. Joint human/system option generation significantly degraded performance in comparison to human or automated option generation alone. Lower operator workload and higher situation awareness were observed under automation of the decision making portion of the task (i.e. selection of options), although human/system performance was only slightly improved. The implications of these findings for the design of automated systems are discussed.

Adult↗

PubMed1976

Anaesthesia in patients with phaeochromocytoma.

The authors' technique of balanced neuroleptanaesthesia with droperidol, fentanyl, nitrous oxide, pancuronium and nitroprusside is outlined. It is suggested that this is the anaesthetic method of choice for the surgical removal of catecholamine secreting tumours since it is associated with good operating conditions and an uneventful post-operative period.

Anesthesia, General↗

PubMed1997

A logistic regression model for the decision to perform access surgery.

Access surgery may be recommended to about 80% of patients who present with advanced forms of periodontal disease. In this report, a multivariate logistic regression analysis which incorporated several clinical parameters for each tooth examined, i.e., tooth type, furcation involvement, bleeding on probing, attachment level, probing depth, mobility and BANA test score, was conducted using generalized estimating equations (GEE). This approach identified parameters that were significantly associated at p < 0.05 level with the need for access surgery or extraction for periodontal purposes. The estimated probabilities derived from the GEE model were plotted over the complete spectrum of operating conditions to obtain a receiver-operator characteristic (ROC) curve. At a probability cutpoint of 0.8, the decision threshold for surgery/extraction at the pretreatment examination would have a sensitivity of 76.1% and a specificity of 75.3%. We have taken this 0.8 cut point to look at specific clinical decisions made by our examiners after the patients had received scaling and root planing plus 2 weeks unsupervised usage of systemic antimicrobials. The clinicians' decision was taken as the primary reference standard. The model's estimated decision agreed with the clinicians' decision in 226 of the 284 teeth, for an accuracy of 80%. The specificity was 90% and the sensitivity was 43%.

Algorithms↗

PubMed2003

Outcomes of cataract surgery in Bangladesh: results from a population based nationwide survey.

AIM: To evaluate the outcome of cataract surgery in the population of Bangladesh. METHODS: Data were collected by the National Blindness and Low Vision Prevalence Survey of Bangladesh, a cross sectional, nationally representative sample (12 782 subjects) of the population aged >or=30 years. An interview recorded socioeconomic data. Each subject was tested for logMAR visual acuity (VA) of each eye, autorefracted, and then underwent optic disc examination. Those with <6/12 VA on presentation in either eye were retested with their refractive correction, dilated, and examined for anterior and posterior segment disease. In aphakic and pseudophakic subjects the date, location and operating conditions (eye camp/hospital), and type of operation(s) were recorded. RESULTS: 11 624 eligible subjects were examined (90.9% response rate) in the survey. 162 subjects, 77 men and 85 women, had undergone cataract surgery in one or both eyes. 199 (88%) eyes had undergone intracapsular cataract extraction (ICCE), and 22 (10%) extracapsular surgery with intraocular lens (ECCE+IOL); surgical technique(s) in four cases were not identified. Presenting VA for the 226 operated eyes were: 68 eyes (30.1%) were 6/12 or better, 31 (13.7%) <6/12 >or=6/18, 63 (27.9%) 6/18 to 6/60, 8 (3.5%) <6/60 >or=3/60, and 56 (24.8%) <3/60. With "best" refractive correction these values were 114 (50.4%), 31 (13.7%), 51 (22.6%), 5 (2.2%), and 25 (11.1%), respectively. Of the 158 eyes with VA of 6/12 or worse on presentation, 44 (28%) were the result of coincident disease (principally age related macular degeneration), 95 (60%) refractive error (44 of these had uncorrected aphakia), and 19 (12%) operative complications. ICCE was more likely to result in a VA of <6/18 (OR: 4.26, p = 0.01) than ECCE+IOL. Likewise, eye camp surgery was more likely to result in a VA of <6/60 (OR: 1.98, p = 0.04). No significant association was found between time since surgery and VA outcome, nor was there a sex difference for postoperative vision. Literate subjects were significantly less likely to have an outcome of <6/18 (OR: 2.38, p <0.01) or <6/60 (OR: 2.87, p <0.01). Following ICCE (199 eyes), 56 (37%) of the 151 eyes with an aphakic spectacle correction achieved 6/12 or better. Females, eye camp surgeries, illiterate subjects, and rural dwellers were less likely to wear their aphakic correction. The ratio of ICCE:ECCE+IOL has reduced in the past 3 years (3.8:1) compared to >or=4 years before the survey (25:1). Hospital based ECCE+IOL surgeries were associated with a better outcome, yet 36% of these eyes were <6/12 postoperatively, after excluding coincident disease. CONCLUSION: This evaluative research study into cataract surgery outcomes in Bangladesh highlights the need for an improvement in quality and increased quantity of surgery with a more balanced distribution of services.

Adult↗

PubMed1989

Connectionist models of conditioning: A tutorial.

Models containing networks of neuron-like units have become increasingly prominent in the study of both cognitive psychology and artificial intelligence. This article describes the basic features of connectionist models and provides an illustrative application to compound-stimulus effects in respondent conditioning. Connectionist models designed specifically for operant conditioning are not yet widely available, but some current learning algorithms for machine learning indicate that such models are feasible. Conversely, designers for machine learning appear to have recognized the value of behavioral principles in producing adaptive behavior in their creations.

Journal Article↗

PubMed2006

Effect of phosphorus limitation on microbial floc structure and gene expression in activated sludge.

The effect of limiting phosphorus (P) in activated sludge was investigated in laboratory-scale sequencing batch reactors (SBRs). Correlative microscopy revealed that P-limitation (COD:N:P = 100:5:0.05) leads to morphological changes in floc structure and the composition of extracellular polymeric substances (EPS). This was found to be accompanied by expression of quorum-sensing in an acyl homoserine lactone bioassay. Differential gene expression in relation to P-limitation was examined in a global profile using the Affymetrix Escherichia coli antisense genomic microarray. Three separate experiments were conducted where the impact of P-limitation was examined under batch conditions and in SBRs at stable operating conditions and within 3-7 days following a down-shift in P. Significant changes in open reading frames (ORF) and intergenic regions based on the E. coli microarray were observed. Several genes associated with cell structure, including slt, wbbH, fimH, amB, rfaJ and slp were found to be expressed. Quorum regulated genes were also found to be expressed including psiF which is known to be induced by P-starvation (92% confidence level; 1.45 log ratio).

Escherichia coli↗

PubMed2001

Bamboo as an anaerobic medium: effect of filter column height.

Sewage was treated in anaerobic filters filled with rings of bamboo (either whole or cut), and their effectiveness in the reduction of chemical oxygen demand (COD) was monitored along the entire extension of the filter. This efficiency was determined based on the COD reduction in both the brute effluent (COD-T) and that passed through a glass filter (COD-F). The quantity of total suspended solids (TSS) present at various heights in the filter column, measured at approximately 10-cm intervals from the false bottom to the height of the filter outflow (80 cm above) for various hydraulic detention times (HDT). The performance of the system resulted in little variation up to 5 hours of HDT, with the percentage of reduction of COD-T and COD-F being situated in the range of 60-80% and 40-80%, respectively. The first 40 cm of the filter proved to be relatively effective, and no significant differences in performance between whole and cut rings of bamboo were observed. A shock in pH occurring after 562 days of operation provoked an immediate and marked decrease in the performance of the reactors, especially that operating with a HDT of only 2 hours. This latter filter required more time to return to normal operational conditions than did the other reactors operating with longer HDT.

Bacteria, Anaerobic↗

PubMed2002

[Stability of the two-stage SBR system treating dyeing wastewater during a long-term operation].

The stability of the two-stage SBR system treating dyeing wastewater was investigated during a 120-cycle continuous operation. The system was fed with influent of low dye concentration and high dye concentration. The results showed that the two-stage SBR system was adaptable to the change of influent quality and operation conditions during the long-term operation. It could efficiently remove the pollutants in the wastewater, the average dyestuff and COD removal rates were 81% to 92.5% and 89.4% to 93.1% respectively for low and high influent loading, and could produce continuous good quality effluent. In the two-stage SBR system, the anaerobic sludge had the characteristics of high activity and strong pollutant degradation ability, and the aerobic sludge existed in the form of aggregate structure, which helped stabilize the effluent quality.

Aerobiosis↗

PubMed2006

Formaldehyde uptake by Methylobacterium sp. MF1 and Acidomonas methanolica MB 58 with the different formaldehyde assimilation pathways.

Methylobacterium sp. MF1 (an obligate methylotrophic bacterium isolated newly by the authors) and Acidomonas methanolica MB58 (a facultative methylotrophic bacterium) uptake formaldehyde similarly. It was found that the former assimilated formaldehyde via the serine pathway whereas the latter did so via the ribulose-monophosphate pathway from the measurement of the key enzyme activities in each assimilation pathway. That is, hydroxy pyruvate reductase was detected in only the above-mentioned MF1 strain, but hexulose phosphate synthase (HPS) was not. The efficiencies of formaldehyde consumption by both strains under a continuous chemostat cultivation in the steady state were almost the same in spite of their different assimilation pathways. That is, the consumption efficiencies of the MF strain and the MB58 strain were ca. 1.2 g/L/d and ca. 1.8 g/L/d, respectively, under the experimental conditions. In the future, optimal continuous operating conditions will be investigated.

Formaldehyde↗

PubMed1982

Decreased resistance to extinction in ob/ob mice following operant training.

Inconsistent results have emerged from past studies in which operant conditioning paradigms were used to assess the hunger motivation of genetically obese mice relative to that of normal mice. Methodological considerations indicated the need to examine operant performance to a criterion, rather than performance during time-based sessions, and then to focus upon response differences in resistance to extinction. Therefore, genetically obese (ob/ob) mice and normal littermates were trained successfully to bar-press for 100 food rewards on either a CRF or a FR-10 schedule of reinforcement. Extinction behavior was then examined over 9 daily 1-hr sessions. While obese and normal mice evidenced similar patterns of learning, or response discrimination for food rewards, they evidenced different levels of hunger motivation during extinction conditions. Obese mice displayed a greater reduction in responding across extinction sessions, or less resistance to extinction, than normal mice following training on both schedules of reinforcement. These findings suggest that ob/ob mice exhibit lower levels of hunger motivation than normal littermates.

Animals↗

PubMed1976

[Conditioning of the avoidance to the contact call in the red face lovebird (Agapornis roseicollis, Aves, Psittacidae)].

Two experiments were run on 10 lovebirds to test the reinforcing effect of the social call in an operant conditioning task. In the first experiment, the reinforced behavior (perching) which provoked the occurence of the call decreased. In the second experiment, where the same behavior stopped the continuous emission of the call, the behavior increased. This behavior may results from an avoidance to the call recorded from a lovebird which do not belong to the group of our experimental birds.

Animals↗

PubMed1969

Visual reinforcement of nonnutritive sucking in human infants.

High-amplitude sucking was studied as a conditioned operant response reinforced by visual feedback in 4-and 12-month infants. Typicalresponse acquisition and extinction effects were obtained. With the 12-month infants the conditioned sucking rates were influenced by amounts of redundancy in the visual reinforcers.

Conditioning, Operant↗

PubMed2006

Neurofeedback treatment of epilepsy: from basic rationale to practical application.

The treatment of epilepsy through operant conditioning of the sensorimotor rhythm electroencephalogram has a 35-year history. Neurophysiological studies have shown that this phasic oscillation reflects an inhibitory state of the sensorimotor system. Operant learning of sensory motor rhythm production results in an upregulation of excitation thresholds within the thalamocortical sensory and motor circuitry, which in turn is associated with reduced susceptibility to seizures. The clinical benefits derived from this neurofeedback training protocol, particularly in patients that are nonresponsive to pharmacotherapy, have been documented in many independent laboratories. Recent advances in computer technology have resulted in the availability of relatively inexpensive high-quality equipment for the application of neurofeedback therapy, thus presenting a viable and promising treatment alternative to the interested clinician.

Animals↗

PubMed1997

[Intravenous sedation in implantology].

Local or block anesthesia can be used satisfactorily in many implant procedures. However, when advanced implant techniques or pre-prosthetic reconstruction surgery of the maxillofacial bones are required, local or regional anesthesia is insufficient. The "day-hospital" concept is a rational approach which meets the requirements for anesthesia and deep sedation with criteria for patient safety and comfort while guaranteeing optimal operating conditions. Intravenous sedation, both "conscious" and "deep" sedation, is a very well adapted form of anesthesia for implant recipients. Local or block anesthesia is enhanced or reinforced prior to surgery by the intravenous administration of a sedative and anxiolytic agent (single-drug concept), such as a benzodiazepine, associated or not with a morphinomimetic agent and an antihistaminic substance (multiple-drug concept). The main goal is to maintain spontaneous respiration while obtaining postoperative amnesia of the entire procedure. Mandatory use of a pulse oximeter has greatly contributed to improved safety of intravenous sedation, essentially indicated for operations not lasting more than 2 and a half hours in patients in good general health (scoring 1 or 2 in the American Society of Anesthesiology (ASA) classification) and with a low risk of postoperative complications. This concept requires an adapted technical facility. The operating theatre should have all the equipment necessary for cardiovascular, neurological and respiratory emergency care. The postoperative recovery room should also be equipped with cardiovascular monitoring devices and be able to accommodate an intensive care unit. Under these strict rules, short duration surgical procedures (< 150') can be performed : 1) with the best conditions of medical safety, 2) with improved operating conditions for the implant surgeon (the patient responds immediately to vocal orders when necessary) while asepsis is maintained as easily as with general anesthesia, 3) with better conditions for postoperative care and patient comfort (the anesthetist is continuously present). 4) better psychological conditions for the patient who will be discharged the same day, 5) with total amnesia of the entire surgical procedure, 6) elimination of a usually disproportionately long hospitalization. Day hospitalization also helps contain health care costs by cutting out the need for overnight care and accommodation. We underline the safety of current intravenous sedation techniques and present two series of data related to the use of this technique by an anesthetist and an operating surgeon in a day hospital from 1986 to 1995.

Ambulatory Surgical Procedures↗

PubMed1991

Conditioning and long-term memory in three-month-old infants with Down syndrome.

The learning and memory of twenty 3-month-old infants with Down syndrome was compared with that of 20 infants without handicaps using an operant conditioning task known as mobile conjugate reinforcement. The infants were trained for 2 days to produce movement in an overhead crib mobile by kicking and were reexposed to this task a week later. Both groups successfully acquired the contingency and displayed reliable long-term retention. In addition, the conditioning and retention-test performance of the two groups of infants did not differ.

Arousal↗

PubMed2005

In-air thermal imaging comparison of Legacy AdvanTec, Millennium, and Sovereign WhiteStar phacoemulsification systems.

PURPOSE: To compare the temperature profiles of 3 popular phacoemulsification units (Alcon Legacy AdvanTec, Bausch & Lomb Millennium, and AMO Sovereign WhiteStar) under similar operating conditions in air. SETTING: Jules Stein Eye Institute and the Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA. METHODS: Phacoemulsification probes from the 3 units were placed side by side in air and imaged in the infrared region using model P60 ThermaCAM (Flir Systems). The highest temperature produced by each probe was measured 10 seconds and 30 seconds after power application. Testing was performed under conditions that might produce a corneal burn during cataract surgery. Irrigation flow was set at the low rate of 1 cc/min to simulate a tight incision. Aspiration flow was set at 0 cc/min to simulate occlusion of the needle lumen. Wound compression was simulated in some tests by suspending 22.6 g weights by rubber bands from the silicone sleeves. Manufacturers' specific and identical silicone sleeves were used to evaluate possible variations in thermal conductivity. The AdvanTec Legacy and Millennium were operated in pulse mode at 15 Hertz; 50% duty cycle; and 10%, 30%, and 50% power. The Sovereign WhiteStar was operated in both C/F (56 Hz, 33% duty cycle) and C/L (33 Hz, 20% duty cycle) modes at the same console power settings. Temperature profiles were determined at a variety of power settings with each system operating in continuous and pulse mode. RESULTS: Under all experimental conditions (at 10%, 30%, and 50% powers; with and without external weights suspended from the phacoemulsification probes; with manufacturers' and identical silicone sleeves; and in continuous and pulse modes), the Millennium and the Sovereign WhiteStar generated higher temperatures than the Legacy AdvanTec. CONCLUSIONS: Under controlled operating conditions in air and under a variety of power, load, and duty-cycle settings, the Millennium and the Sovereign WhiteStar, operating in both pulse and continuous modes, generated higher peak temperatures than the Legacy AdvanTec.

Air↗

PubMed1979

Aversive conditioning of elevations in total peripheral resistance in dogs.

Operant conditioning experiments were performed with 12 chronically instrumented dogs to which aversive stimulation was presented whenever total peripheral resistance (mean pressure/cardiac output) decreased acutely below a criterion level. Initial experiments in which aversive stimulation occurred whenever total peripheral resistance decreased below mean base-line levels resulted in sustained decreases in total peripheral resistance, accompanied by elevations in heart rate, cardiac output, and arterial pressure. Subsequent experiments showed, however, that if aversive stimulation occurred only following large-magnitude decreases in resistance (30% below base-line levels), a progressive cardiovascular response pattern emerged during daily sessions of 5--16 h. This cardiovascular pattern included progressive elevations in resistance (10--50%), accompanied by progressive decreases or no change in heart rate and cardiac output and moderate increases in arterial (up to 20 mmHg) and pulse pressure. These within-session cardiovascular changes were accompanied by sustained inhibition of overt behavioral acitivity and progressive inhibition in respiratory activity. Implications of these observation for behavioral regulation of circulatory function are discussed.

Animals↗

PubMed2005

The mGluR5 antagonist MPEP decreases operant ethanol self-administration during maintenance and after repeated alcohol deprivations in alcohol-preferring (P) rats.

RATIONALE: Recent research indicates that blockade of mGluR5 modifies the reinforcing properties of ethanol. OBJECTIVES: The present studies examined the effects of mGluR5 receptor blockade in a genetic model of high ethanol intake, the alcohol-preferring (P) rat, on the maintenance of operant ethanol self-administration. In addition, we determined the effect of 2-methyl-6-(phenylethyl)-pyridine (MPEP) on the repeated alcohol deprivation effect. METHODS: Twelve male (P) rats were trained in experimental sessions to self-administer 10% w/v ethanol via a sucrose-fading procedure. After the establishment of operant ethanol self-administration, subjects were treated with various metabotropic glutamate receptor (mGluR) subtype antagonists immediately prior to experimental sessions: the mGluR5 antagonist MPEP (1, 3, and 10 mg/kg); the mGluR2--3 antagonist LY-341495 (1, 3, and 10 mg/kg); and the mGluR1 antagonist CPCCOEt (1, 3, and 10 mg/kg). After determining the role of mGluR5 in the maintenance of operant ethanol self-administration, we examined the role of this receptor in relapse following repeated periods of alcohol deprivation by depriving subjects of ethanol exposure for three 2-week deprivation periods. RESULTS: The mGluR5 antagonist MPEP dose-dependently decreased operant ethanol self-administration. In addition, rats that received saline immediately prior to repeated alcohol deprivation sessions self-administered ethanol at increasing levels that were above those achieved in the last operant-conditioning session prior to the initial 2-week deprivation period. This repeated alcohol deprivation effect was prevented in subjects pretreated with MPEP (10 mg/kg). CONCLUSIONS: These findings suggest that mGluR5 receptors may modulate both the maintenance of operant ethanol self-administration and abstinence-induced increases in ethanol intake.

Alcohol Drinking↗