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At least 1,711 records · Page 95Linked to original sources
PubMed2006

Engineering entrainment and adaptation in limit cycle systems : From biological inspiration to applications in robotics.

Periodic behavior is key to life and is observed in multiple instances and at multiple time scales in our metabolism, our natural environment, and our engineered environment. A natural way of modeling or generating periodic behavior is done by using oscillators, i.e., dynamical systems that exhibit limit cycle behavior. While there is extensive literature on methods to analyze such dynamical systems, much less work has been done on methods to synthesize an oscillator to exhibit some specific desired characteristics. The goal of this article is twofold: (1) to provide a framework for characterizing and designing oscillators and (2) to review how classes of well-known oscillators can be understood and related to this framework. The basis of the framework is to characterize oscillators in terms of their fundamental temporal and spatial behavior and in terms of properties that these two behaviors can be designed to exhibit. This focus on fundamental properties is important because it allows us to systematically compare a large variety of oscillators that might at first sight appear very different from each other. We identify several specifications that are useful for design, such as frequency-locking behavior, phase-locking behavior, and specific output signal shape. We also identify two classes of design methods by which these specifications can be met, namely offline methods and online methods. By relating these specifications to our framework and by presenting several examples of how oscillators have been designed in the literature, this article provides a useful methodology and toolbox for designing oscillators for a wide range of purposes. In particular, the focus on synthesis of limit cycle dynamical systems should be useful both for engineering and for computational modeling of physical or biological phenomena.

Adaptation, Biological↗
PubMed2002

Robotics.

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Endoscopy↗
PubMed2001

Evaluation of telesurgical (robotic) NISSEN fundoplication.

BACKGROUND: The laparoscopic surgical approach has proven its benefit for the patient. There are however several shortcomings, which have triggered considerable research for improvement. One improvement may be the introduction of telesurgery by the interposition of a computer interface between surgeon and patient. MATERIAL AND METHODS: A prospective randomized study was conducted in an advanced laparoscopic procedure, Nissen fundoplication. The control group underwent the conventional laparoscopic approach, while the investigational group underwent the telesurgical approach. RESULTS: Feasibility was 100%. The procedure was more time consuming in the Telesurgical group, at all stages of the operation. Mortality was nil and morbidity was comparable in both groups. CONCLUSION: The telesurgical approach is feasible in advanced laparoscopic procedures like Nissen fundoplication. At the present time there is however no obvious added benefit from this new technique.

Adolescent↗
PubMed2003

Laparoscopic and robotic surgical training in urology.

The most important change in urology during the past decade was the development of minimally invasive surgery, particularly laparoscopy. However, the main drawback of laparoscopy is a steep learning curve, which results from the significant changes in the surgical environment. Although laparoscopy can provide important advantages for the patient, including decreased length of hospitalization, decreased analgesic requirement, and a shortened postoperative convalescence, one concern has been whether laparoscopic techniques should be learned solely in the operating room. For example, sports, music, and aviation are practiced before an actual performance is ever undertaken. In this review, the advantages and limitations of all available training modalities in minimally invasive surgery are described. Testing basic laparoscopic skills on inanimate models, becoming familiar with the principles of dissection and hemostasis on living animals, and studying surgical anatomy on cadavers should be considered as indispensable and complementary elements for laparoscopic training in the future. In addition, telementoring with the help of modern image processing and virtual reality eventually may become the basis of tomorrow's surgical instruction.

Clinical Competence↗
PubMedDate not supplied

Effects of low doses of cholinesterase inhibitors on behavioral performance of robot-tested marmosets.

To investigate at which dose levels undesirable effects started, behavioural performance and several physiological parameters were measured in marmosets (Callithrix jacchus) after soman (1.75 and 3.5 micrograms/kg), sarin (3 and 6 micrograms/kg), physostigmine (10 and 20 micrograms/kg), and pyridostigmine (200 and 400 micrograms/kg). Effects on performance were investigated with a discrete-trial, two-choice visual discrimination task and a hand-eye coordination task. The former test appeared more sensitive to disruption than the hand-eye coordination task. "Motor speed" was not disrupted by any of the four compounds. However, "choice time" as well as "no attempts" increased and were clearly more disturbed by soman and physostigmine than by sarin and pyridostigmine. All effects had disappeared after 24 h. Except for a small effect of sarin on heart rate and blood pressure, none of the cholinesterase (ChE) inhibitors affected a number of physiological parameters at behavioural effective does that caused a profound ChE inhibition in blood. Take together, these results strongly suggest that both soman and physostigmine may interfere with higher CNS functions at low dose levels. These effects may go undetected because physical signs are absent.

Animals↗
PubMed2005

Development of a high-throughput robotic fluorescence-based assay for HsEg5 inhibitor screening.

HsEg5 has microtubule-activated ATPase activity and plays essential roles in bipolar spindle formation. Because HsEg5 is validated as an attractive cancer target, in vitro biochemical assays have been developed for identifying compounds with high inhibitory activity. Several compounds, including quinazoline ring-containing compounds, have been identified and are currently in clinical trials. Although considerable progress has been made during recent years, limitations of HsEg5 in vitro screening assays still reside in two main aspects. First, colorimetric-based assays exhibit relatively low sensitivity and limited dynamic range that are unable to accurately measure compounds with nanomolar potencies. Second, current fluorescence assays are relatively low throughput without "mix and read" homogeneous features. In this study, we describe a sensitive fluorescence-based assay for HsEg5-specific inhibitors. By coupling several enzymes' activities, the release of ADP was measured quantitatively through red fluorescent resorufin. The Km for ATP hydrolysis in this assay was calculated as 23 microM. The known HsEg5 inhibitors CK0106023 and CK0238273 gave IC50 values of 9.8 and 30.6 nM, respectively. Our fluorescence assay has a 20-fold increase in sensitivity with broader dynamic range when compared with a colorimetric assay. We further automated this assay for high-throughput screening with a Z' factor of 0.8.

Adenosine Diphosphate↗
PubMed2005

Video and robotic-assisted minimally invasive mitral valve surgery: a comparison of the Port-Access and transthoracic clamp techniques.

BACKGROUND: In order to assess different surgical techniques for video-assisted minimally invasive mitral valve surgery, a retrospective study was undertaken comparing the Port-Access system (Cardiovations, Ethicon Inc, Somerville, NJ) and the transthoracic clamp technique. METHODS: In 120 patients mitral valve surgery was performed through a small right minithoracotomy using either the Port-Access endovascular cardiopulmonary bypass system (Port-Access, n = 60) or the transthoracic clamp technique (MICRO, n = 60). Mean patient age was 61.5 +/- 10.5 years (81 patients with isolated mitral valve insufficiency, 39 patients with combined mitral valve disease). RESULTS: Eighty-one (67.5%) patients underwent mitral valve repair and 39 (32.5%) patients had valve replacement. Mean time of surgery was 4.5 +/- 3.5 and 4.1 +/- 3.2 hours (p = 0.07), aortic cross-clamp time 89 +/- 69 and 78 +/- 65 minutes (p = 0.08), mean intensive care unit stay 1.5 +/- 2.1 and 1.6 +/- 2.5 days (p = ns), and hospital stay 9.0 +/- 10.5 and 9.2 +/- 9.7 days (p = ns) in the Port-Access and MICRO groups, respectively. In the Port-Access group, there were 6 reexplorations for bleeding, one perforation of the right ventricle with the endopulmonary vent, and 2 reconstructions of the femoral artery necessary after femoral cannulation, compared to one reexploration for bleeding in the MICRO group. There was only one minor paravalvular leak after replacement and 2 cases of residual greater than or equal to grade II mitral valve regurgitation after mitral valve repair in the Port-Access group, necessitating reoperation. In both groups, there was no mortality, no cerebrovascular accident, no aortic dissection, and no conversion to sternotomy. CONCLUSIONS: Minimally invasive mitral valve surgery has become a standard approach for isolated mitral valve operations at our institution. The MICRO technique tends to shorten the time of surgery and aortic cross-clamping and reduces perioperative costs by simplifying the operative procedure.

Cardiopulmonary Bypass↗
PubMed2005

Evolutionary pressures and a stable world for animals and robots: a commentary on Merker.

In his article on The Liabilities of Mobility, asserts that "Consciousness presents us with a stable arena for our actions-the world ..." and argues for this property as providing evolutionary pressure for the evolution of consciousness. In this commentary, I will explore the implications of Merker's ideas for consciousness in artificial agents as well as animals, and also meet some possible objections to his evolutionary pressure claim.

Animals↗
PubMedDate not supplied

Surgical robotics.

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Humans↗