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C H Bennett

Publications and source records attributed to C H Bennett.

At least 19 recordsLinked to original sources
PubMed2001

Remote state preparation.

Quantum teleportation uses prior entanglement and forward classical communication to transmit one instance of an unknown quantum state. Remote state preparation (RSP) has the same goal, but the sender knows classically what state is to be transmitted. We show that the asymptotic classical communication cost of RSP is one bit per qubit--half that of teleportation--and even less when transmitting part of a known entangled state. We explore the tradeoff between entanglement and classical communication required for RSP, and discuss RSP capacities of general quantum channels.

Journal Article↗
PubMed2001

Evidence for inhibitory associations between the unique elements of two compound flavours.

In each of two experiments, rats were pre-exposed to two flavoured solutions, saline-lemon and sucrose-lemon. For group ALT, trials with one solution alternated with trials with the other. Group BLK received all trials with one solution in a block, before any trials with the other. An associative theory suggests that the alternating, but not the blocked, schedule would establish an inhibitory association between sucrose and saline. To provide a retardation test of this inhibition, some animals in each group were then given a single pairing of saline and sucrose, experienced sodium depletion, and were finally tested for their consumption of sucrose. Sodium depletion increased consumption of sucrose more in group BLK than in group ALT. In groups given no saline-sucrose pairing, sodium depletion had only a small effect on sucrose consumption, which was the same in both groups. After multiple pairings of saline and sucrose, sodium depletion had an equally large effect on sucrose consumption in both ALT and BLK groups. These results imply that alternating pre-exposure to two compound solutions does establish an inhibitory association between their unique elements, and thus provide support for an associative theory of perceptual learning.

Animals↗
PubMed2000

Is the context specificity of latent inhibition a sufficient explanation of learned irrelevance?

In three experiments, rats were pre-exposed either to uncorrelated presentations of a light and sucrose pellets (group CS/US) or to equivalent presentations of the light and pellets in separate sessions (control). In Experiment 1, subsequent conditioning to the light proceeded more slowly in group CS/US than in the control group, whether this conditioning was excitatory, with the light signalling the delivery of pellets, or inhibitory, with the light signalling their absence. Bonardi and Hall (1996) have argued that this learned irrelevance effect may be reducible to latent inhibition, which would be stronger in group CS/US because they are both pre-exposed and conditioned to the CS in the presence of traces of previous USs occurring in the same session. This analysis implies that group CS/US should have conditioned more rapidly to the CS than controls on the first trial of each session in Experiment 1, but this did not happen. It also implies that the learned irrelevance effect should be reversed if conditioning trials are given at a rate of one per day. Experiments 2 and 3 found no support for this prediction. We conclude that learned irrelevance effects cannot always be reduced to latent inhibition.

Animals↗
PubMed2000

Process analysis in outpatient knee surgery: effects of regional and general anesthesia on anesthesia-controlled time.

BACKGROUND: The performance of anesthetic procedures before operating room entry (e.g., with either general or regional anesthesia [RA] induction rooms) should decrease anesthesia-controlled time in the operating room. The authors retrospectively studied the associations between anesthesia techniques and anesthesia-controlled time, evaluating one surgeon performing a single procedure over a 3-yr period. The authors hypothesized that, using the anesthesia care team model, RA would be associated with reduced anesthesia-controlled time compared with general anesthesia (GA) alone or combined general-regional anesthesia (GA-RA). METHODS: The authors queried an institutional database for 369 consecutive patients undergoing the same procedure (anterior cruciate ligament reconstruction) performed by one surgeon over a 3-yr period (July 1995 through June 1998). Throughout the period of study, anesthesia staffing consisted of an attending anesthesiologist medically directing two nurse anesthetists in two operating rooms. Anesthesia-controlled time values were compared based on anesthesia techniques (GA, RA, or GA-RA) using one-way analysis of variance, general linear modeling using time-series and seasonal adjustments, and chi-square tests when appropriate. P < 0. 05 was considered significant. RESULTS: RA was associated with the lowest anesthesia-controlled time (11.4 +/- 1.3 min, mean +/- 2 SEM). GA-RA (15.7 +/- 1.0 min) was associated with lower anesthesia-controlled time than GA used alone (20.3 +/- 1.2 min). CONCLUSIONS: When compared with GA without an induction room for outpatients undergoing anterior cruciate ligament reconstruction, RA with an induction room was associated with the lowest anesthesia- controlled time. Managers must weigh the costs and time required for anesthesiologists and additional personnel to place nerve blocks or induce GA preoperatively in such a staffing model.

Adult↗
PubMed1999

Comparison and contrast as a mechanism of perceptual learning?

In a series of flavour aversion experiments, rats received different schedules of pre-exposure to two compound flavours (AX and BX). Discrimination between them was assessed by establishing an aversion to AX and measuring generalization of this aversion to BX. Experiment 1 demonstrated that alternating pre-exposure to AX and BX resulted in less generalization than did blocked exposure, where animals received all exposure to AX before exposure to BX (or vice versa). This difference was not accompanied by any difference in the strength of the aversion conditioned to the common X element. Varying the interval between exposure to AX and BX in the alternating condition from a minute or two to several hours had no effect on generalization. However, Experiments 2 and 3 showed that when the interval between exposure to AX and that to BX was reduced to zero sec, the alternating schedule increased generalization between AX and BX. In this case, the increase in generalization was accompanied by an increase in the strength of the aversion conditioned to X.

Animals↗
PubMed1996

Facilitation and retardation of flavour aversion conditioning following prior exposure to the CS.

Two sets of experiments on flavour aversion conditioning in rats examined the effects of the following factors: the nature of the flavour serving as the conditioned stimulus (CS), which was either a compound of monsodium glutamate, sucrose and quinine, or an elemental flavour, either sucrose or dilute acid; the amount of the CS rats consumed on a single conditioning trial-4 ml or 1 ml; and whether rats had been pre-exposed to the CS before this conditioning trial. There were three main findings. First, conditioning to an elemental CS was unaffected by the amount consumed on the conditioning trial, but conditioning to 1 ml of the compound CS was poorer than to 4 ml. Second, pre-exposure produced a latent inhibition effect if the CS was an elemental flavour, or if rats were allowed to drink 4 ml of the compound solution on their conditioning trial. But, third, pre-exposure facilitated conditioning in rats given only 1 ml of the compound solution as their CS.

Animals↗
PubMed1995

Learned irrelevance is not the sum of exposure to CS and US.

In three experiments hungry rats received appetitive conditioning trials with a light that signalled the delivery of sucrose solution. In Experiment 1, prior exposure to uncorrelated presentations of the conditioned stimulus (CS) and unconditioned stimulus (US) retarded conditioning significantly more than did prior exposure to the CS alone. In Experiments 2 and 3, groups exposed to uncorrelated presentations of the CS and US within the same session conditioned significantly more slowly than groups given separate sessions of exposure to the CS followed by sessions of exposure to the US (or vice versa). Some part of the learned irrelevance effect depends on exposure to a zero correlation between the CS and US, perhaps because this promotes learning that the CS predicts no change in the probability of the US.

Animals↗
PubMed1994

Reduced generalization following preexposure: latent inhibition of common elements or a difference in familiarity?

Rats injected with lithium chloride after drinking a saline-lemon solution also reduced their consumption of saline-lemon and sucrose-lemon, but a single prior exposure to sucrose-lemon decreased the generalized aversion. Experiment 1 showed that this decrease in the aversion to sucrose-lemon could not be explained by a decrease either in the aversion conditioned to saline-lemon or in neophobia to sucrose-lemon. Experiment 2 ruled out the possibility that generalization between saline-lemon and sucrose-lemon was based on shared novelty. Experiment 3 showed that generalization between the two solutions was related to the strength of the aversion to the lemon flavor they shared in common and that prior exposure to sucrose-lemon reduced generalization by causing latent inhibition of this common element.

Animals↗
PubMed1991

Perceptual learning in flavour aversion conditioning.

In each of four experiments, rats drank a solution of saline or of lemon and saline shortly before receiving an injection of lithium chloride, and the generalization of the resulting aversion to sucrose or to lemon and sucrose was measured. There was little generalization from saline alone to sucrose alone, and prior exposure to the two solutions had no effect on their discriminability. An aversion conditioned to lemon-saline, however, did generalize to lemon-sucrose, and the extent of this generalization was substantially reduced by prior exposure to the two compound solutions. This perceptual learning effect was partly, but not entirely, attributable to the latent inhibition of the common element, lemon, produced by exposure to the two compounds: animals pre-exposed to lemon alone discriminated between lemon-saline and lemon-sucrose better than animals pre-exposed to saline and sucrose alone; but exposure to the three elements in isolation was not as effective as exposure to the two compound solutions in enhancing their discriminability. The final experiment established that one critical feature of compound pre-exposure is that it involves experience of saline and sucrose in the presence of the same common element. According to an associative theory of perceptual learning, this would result in the establishment of inhibitory associations between saline and sucrose, thus reducing generalization between the two compound solutions.

Animals↗
PubMed1990

Time-dependent changes in cardiovascular regulation caused by chronic tobacco smoke exposure.

The purpose of this study was to determine whether chronic tobacco smoke exposure for less than 2 mo alters cardiovascular regulation. One group of male Sprague-Dawley rats was administered tobacco smoke from low-nicotine cigarettes (group A, 1 mg/cigarette) for 4-6 wk, while a second group (B) served as a sham control by receiving only puffs of room air. Reflex adjustments in mean arterial blood pressure (MAP) after bilateral common carotid occlusion (BCCO) were compared between the two groups. In the anesthetized control state, no significant difference existed for the cardiovascular parameters measured in the two groups. However, MAP increases after BCCO were significantly greater in the smoke-treated animals (P less than 0.05) compared with the sham-treated group. At 10, 20, 30, and 40 s after BCCO, MAP increases above preocclusion values were 66, 45, 42, and 38% for group A and 35, 26, 24, and 22% for group B, respectively. Additionally, the time required to reach maximum MAP after BCCO was significantly less (P less than 0.05) for the smoke-treated vs. sham-treated animals (8.5 +/- 0.2s for group A, 11.2 +/- 0.3s for group B). MAP changes during BCCO were significantly different (P less than 0.05) between the treatment groups after cervical vagotomy. It is concluded that chronic tobacco smoke exposure in experimental animals for periods as short as 4-6 wk alters the reflex regulation of the cardiovascular system.

Animals↗
PubMed1989

Cardiovascular responses to alpha adrenergic agents in chronically-exercised spontaneously hypertensive rats.

The influence of treadmill exercise training on cardiovascular regulation was investigated in spontaneously hypertensive rats (SHR) of Okamoto strain during their 8th to 18th week of life. Non-exercising age-matched SHR and Wistar-Kyoto (WKY) rats served as cage controls. Resting systolic blood pressure (SBP), heart rate (HR) and weight changes were measured in the three groups during the training period. At the completion of the training period (week 18), the trained SHR had SBP values of 164 +/- 4 mm Hg and HR values of 388 +/- 8 beats per minute, which were significantly less than (P less than 0.05) those values recorded for the control SHR (SBP = 186 +/- 3 mm Hg; HR = 422 +/- 11 bpm). The influence of exercise on baroreceptor regulation of HR was evaluated in anesthetized animals from all three groups. Phenylephrine-induced increases in mean arterial blood pressure (MAP) produced significantly greater (P less than 0.05) reflex decreases in HR in the trained SHR versus the sedentary SHR. No significant difference in baroreflex sensitivity values were noted between the WKY and trained SHR. Additionally, norepinephrine infusion produced significantly smaller (P less than 0.05) pressor responses in trained versus sedentary SHR. We conclude that exercise training significantly reduces resting SBP and HR while modifying the baroreceptor regulation of HR and cardiovascular responses to adrenergic agents in the SHR.

Animals↗
PubMed1986

Kit systems for identifying gram negative aerobic bacilli: report of the Welsh Standing Specialist Advisory Working Group in Microbiology.

Under the auspices of the Welsh Standing Specialist Advisory Working Group in Microbiology (WMG) 10 clinical microbiology laboratories in Wales undertook a collaborative study to assess 10 commercial kits for the identification of aerobic Gram negative bacilli. In excess of 1000 such strains were examined in parallel with each kit system. Accuracy, reproducibility of accuracy, and reproducibility alone were assessed, together with the cost effectiveness of the kits used. A ranking order of kit performance based on the above variables was drawn up.

Bacteriological Techniques↗
PubMed1984

Effects of chronic tobacco smoke exposure on arterial blood pressure regulation.

The purpose of this study was to determine the effects of long-term consumption of tobacco smoke on arterial blood pressure regulation. Male Sprague-Dawley rats were administered tobacco smoke for 6-8 mo. Two groups of animals (A and B) received tobacco smoke containing different levels of nicotine (group A: high nicotine, 4 mg/cigarette; group B: low nicotine, 1 mg/cigarette), while a third group (C) served as a sham control by receiving only puffs of room air. Reflex adjustments in mean arterial blood pressure (MAP), heart rate (HR), lower body blood flow, and lower body vascular resistance were compared between the three groups. In the anesthetized control state, no significant difference existed for the cardiovascular parameters measured in the three groups. However, perturbating the cardiovascular system by reducing central blood volume via a 60 degrees head-up tilt elicited less of a fall in MAP in the two smoke groups compared with the sham group. Percent decreases in MAP follow: group A, 23%; group B, 22%; and group C, 48%. Increasing MAP with phenylephrine elicited a significantly greater (P less than 0.05) reduction in HR in groups A and B (smoke treated) compared with group C (sham treated). Finally, varying carotid sinus pressure elicited significantly greater (P less than 0.01) changes in MAP in the smoke-treated animals (A and B) compared with the sham group (C). It is concluded that chronic tobacco smoke administration to laboratory rats increases the sensitivity of the reflex control of the cardiovascular system.

Animals↗
PubMed1979

Dissipation-error tradeoff in proofreading.

Chemical proofreading systems, of the kind believed responsible for the extremely high fidelity of DNA replication, achieve minimum error probability (equal to the product of the error probabilities of the writing and proofreading stages) only in the limit of infinite energy dissipation. However, a considerable degree of proofreading can be obtained in less strongly driven systems, dissipation only 0.1-1 kT/step.

Chemical Phenomena↗
PubMedDate not supplied

Current trends in anterior cruciate ligament reconstruction. Part II. Operative procedures and clinical correlations.

Surgical management of the anterior cruciate ligament-deficient knee has evolved from primary repair to extracapsular augmentation to anterior cruciate ligament reconstruction using biologic tissue grafts. The technique of anterior cruciate ligament reconstruction has improved over the last few decades with the aid of knowledge gained from basic science and clinical research. The biology and biomechanics of anterior cruciate ligament reconstruction were analyzed in the previously published first part of this article. In this second part, current operative concepts of anterior cruciate ligament reconstruction as well as clinical correlations are discussed. The latest information regarding anterior cruciate ligament reconstruction is presented with a goal of demonstrating the correlation between the application of basic science knowledge and the improvement of clinical outcomes.

Anterior Cruciate Ligament↗