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Biomedical subjects

M A Rowe

Publications and source records attributed to M A Rowe.

14 recordsLinked to original sources
PubMed2001

Experimental demonstration of entanglement-enhanced rotation angle estimation using trapped ions.

We experimentally investigate three methods, utilizing different atomic observables and entangled states, to increase the sensitivity of rotation angle measurements beyond the "standard quantum limit" for nonentangled states. All methods use a form of quantum mechanical "squeezing." In a system of two entangled trapped (9)Be(+) ions we observe a reduction in uncertainty of rotation angle below the standard quantum limit for all three methods including all sources of noise. As an application, we demonstrate an increase in precision of frequency measurement in a Ramsey spectroscopy experiment.

Journal Article↗
PubMed2001

Experimental violation of a Bell's inequality with efficient detection.

Local realism is the idea that objects have definite properties whether or not they are measured, and that measurements of these properties are not affected by events taking place sufficiently far away. Einstein, Podolsky and Rosen used these reasonable assumptions to conclude that quantum mechanics is incomplete. Starting in 1965, Bell and others constructed mathematical inequalities whereby experimental tests could distinguish between quantum mechanics and local realistic theories. Many experiments have since been done that are consistent with quantum mechanics and inconsistent with local realism. But these conclusions remain the subject of considerable interest and debate, and experiments are still being refined to overcome 'loopholes' that might allow a local realistic interpretation. Here we have measured correlations in the classical properties of massive entangled particles (9Be+ ions): these correlations violate a form of Bell's inequality. Our measured value of the appropriate Bell's 'signal' is 2.25 +/- 0.03, whereas a value of 2 is the maximum allowed by local realistic theories of nature. In contrast to previous measurements with massive particles, this violation of Bell's inequality was obtained by use of a complete set of measurements. Moreover, the high detection efficiency of our apparatus eliminates the so-called 'detection' loophole.

Journal Article↗
PubMed2001

A decoherence-free quantum memory using trapped ions.

We demonstrate a decoherence-free quantum memory of one qubit. By encoding the qubit into the decoherence-free subspace (DFS) of a pair of trapped 9Be+ ions, we protect the qubit from environment-induced dephasing that limits the storage time of a qubit composed of a single ion. We measured the storage time under ambient conditions and under interaction with an engineered noisy environment and observed that encoding into the DFS increases the storage time by up to an order of magnitude. The encoding reversibly transfers an arbitrary qubit stored in a single ion to the DFS of two ions.

Journal Article↗
PubMed1998

Optimism, coping and long-term recovery from coronary artery surgery in women.

Optimism, coping strategies, and psychological and functional outcomes were measured in 55 women undergoing coronary artery surgery. Data were collected in-hospital and at 1, 6, and 12 months after surgery. Optimism was related to positive moods and life satisfaction, and inversely related to negative moods. Few relationships were found between optimism and functional ability. Cognitive coping strategies accounted for a mediating effect between optimism and negative mood. Optimists were more likely to accept their situation, and less likely to use escapism. In turn, these coping strategies were inversely related to negative mood and mediated the relationship between optimism and this outcome. Optimism was not related to problem-focused coping strategies; this, these coping strategies cannot explain the relationship between optimism and outcomes.

Adaptation, Psychological↗
PubMed1996

The impact of internal and external resources on functional outcomes in chronic illness.

This study's purpose was to determine if internal and/or external resources could deter negative consequences of physiologic stress in chronic illness. Resource theory was used to test relationships over time among stress (physiologic), distress (functional outcome), and resources (internal-well-being; external-social network). A secondary analysis was done on data from 112 persons with end stage renal disease, collected yearly over 3 years. Physiologic stressors were strongly associated with higher levels of physical dysfunction. Resources were generally unable to reduce deleterious effects of physiologic stress on functional outcomes; functional outcomes were largely determined by preexisting levels of function.

Adult↗
PubMed1996

A comparison of the local anesthetic effects of meperidine, fentanyl, and sufentanil on dorsal root axons.

The local anesthetic effects of opioids have been demonstrated in both clinical and laboratory studies. Clinically, both meperidine and sufentanil can produce segmental sensory anesthesia. However, previous studies of the effects of opioids on nerve conduction have all made use of peripheral nerve preparations and yielded conflicting results. In the present study we describe the local anesthetic effects of phenylpiperidine opioids on individual dorsal root axons, the probable target for intrathecal local anesthetics. Dorsal roots were removed from anesthetized adult male rats and maintained in vitro. Standard single fiber recording techniques were used to isolate activity in the individual axons. Drug exposure was accomplished by perfusing the isolated dorsal root with an artificial cerebrospinal fluid containing the study drug at a clinically relevant concentration. Steady-state drug effects were measured after 15-30 min of exposure and compared to control measurements in the same preparation. Meperidine (705 microM) blocked conduction in 61.5% of 39 myelinated and unmyelinated axons, and significantly reduced conduction velocity in the remaining unblocked axons. These effects were not naloxone reversible. Fentanyl (0.6 microM and 3 microM) and sufentanil (1.04 microM) failed to affect the nerve conduction in any dorsal root axon. The discrepancy between laboratory and clinical observations is discussed. We suggest that the site of conduction block may occur at the proximal end of the dorsal root as it passes through the dorsal root entry zone, an anatomically unique segment of the primary sensory pathway with decreased conduction safety for action potential propagation.

Action Potentials↗
PubMed1996

Differential nerve block. Direct measurements on individual myelinated and unmyelinated dorsal root axons.

BACKGROUND: Clinically, differential block is manifested by the loss of small fiber mediated sensation (e.g., temperature) two or more dermatomes beyond the sensory limit for large fiber mediated sensations. These observations support the belief that sensitivity to local anesthetics is inversely proportional to axon diameter. This study reports the first measurements of differential sensitivity to lidocaine in individual myelinated and unmyelinated mammalian dorsal root axons. METHODS: Lumbar dorsal roots and vagus nerves were isolated from anesthetized adult rats and maintained in vitro in a perfusion/recording chamber at 37 +/- 0.3 degrees C. Using single fiber techniques, evoked action potentials in individual myelinated and unmyelinated axons were digitized and recorded for subsequent analysis. Axons were exposed to lidocaine at 150, 260, or 520 microM. Sensitivity to local anesthetic was assessed by measuring the incidence of conduction block and the magnitude of conduction velocity slowing under steady-state conditions. RESULTS: Data were obtained from 77 dorsal root axons and 41 vagal axons. The estimated steady-state EC50 lidocaine concentration for myelinated dorsal root axons (232 microM) was comparable to that for unmyelinated axons (228 microM). Similarly, the incidence of conduction block was not significantly different among dorsal root axon groups. However, unmyelinated dorsal root axons were significantly less sensitive to the conduction velocity slowing effect of lidocaine than their myelinated counterparts (P < 0.01). The incidence of conduction block in short (mean length 13.5 mm) dorsal root axons was not significantly different from that in long (mean length 22.4 mm) axons. Compared with dorsal root axons, the estimated EC50s for vagal myelinated and unmyelinated axons (345 and 285 microM, respectively), while lower were not significantly different. However, the incidence of conduction block at 260 microM lidocaine was significantly lower (16.7% vs. 56.7%; P < 0.05) in vagal myelinated axons. CONCLUSIONS: Although no difference in sensitivity to the conduction blocking effects of lidocaine could be demonstrated among dorsal root axons, myelinated axons were more sensitive to the conduction velocity slowing effects of lidocaine. This differential effect cannot explain clinical observations of differential nerve block. Differential sensory block with lidocaine may depend on factors (e.g., physiologic function) related only indirectly to individual axon conduction velocity (diameter).

Anesthetics, Local↗
PubMedDate not supplied

Long-term chest wall discomfort in women after coronary artery bypass grafting.

OBJECTIVE: The purpose of the study was to determine the occurrence of long-term chest wall discomfort in women after coronary artery bypass grafting. DESIGN: Prospective repeated-measures design. SETTING: Posthospitalization. SAMPLE: Fifty-one women who had undergone coronary artery bypass grafting. Data were collected at 12 and 18 months by self-report and data collection instruments. INSTRUMENTS: Life Orientation Test, Satisfaction with Life Scale, Profile of Mood States, Sickness Impact Profile, interview schedule, and discomfort scale 0 to 10. RESULTS: Women who had an internal mammary artery graft had significantly (p = 0.003) more discomfort. Most discomforts were intermittent and did not interfere with daily activities. However, the feelings of numbness and itchiness tended to be continuous.

Activities of Daily Living↗
PubMedDate not supplied

Concerns and risk factor modification in women during the year after coronary artery surgery.

BACKGROUND: Future plans or return to a usual lifestyle has been shown to be of concern to persons recovering from coronary artery surgery. However it is not clear whether early concerns remain stable or evolve over time. OBJECTIVE: To examine women's concerns about having coronary artery surgery and living with coronary artery disease after surgery over time. METHODS: Concerns and risk factor modification strategies were measured in 55 women at 1, 6, and 12 months after coronary artery surgery. The Carr and Powers Stressor Scale and an investigator-developed interview were used. RESULTS: Women's primary concerns shifted over the year from surgical recovery to living with coronary heart disease. At 1 month after surgery, issues related to future plans, such as progress in recovery and resuming lifestyle, were rated as causing the most concern. Concern about diet was the highest rated concern 1 year after surgery. More than half of the women reported exercising more, and approximately three fourths reported eating a better diet 1 year after surgery. CONCLUSIONS: The findings demonstrate that women are concerned about diet and exercise, and many women attempt to change their behavior. Capitalizing on women's concerns about living with coronary artery disease may help address risk factors. However, specialized interventions may be needed that focus on women who are not concerned about and/or not engaged in risk reduction behaviors.

Adult↗
PubMedDate not supplied

Antecedents, descriptions and consequences of wandering in cognitively-impaired adults and the Safe Return (SR) program.

Unattended wandering is a major problem in cognitively impaired (CI) individuals and can result in those individuals becoming lost in the community. The purpose of this study was to identify important characteristics of unattended wandering and important prevention strategies. Data were compiledfrom registration files and missing and discovery reports collected through the Safe Return (SR) program. These data were analyzed to determine where individuals were found, who found them, from what setting they left, what mode of transportation they used, and what circumstances surrounded the unattended wandering. The study highlights the unpredictable and varied nature of unattended wandering. Recommendations are provided for communities to develop strategies to minimize unattended wandering and to determine effective methods of locating CI individuals when they become lost.

Adult↗