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PubMed2002

The fractal nature of nature: power laws, ecological complexity and biodiversity.

Underlying the diversity of life and the complexity of ecology is order that reflects the operation of fundamental physical and biological processes. Power laws describe empirical scaling relationships that are emergent quantitative features of biodiversity. These features are patterns of structure or dynamics that are self-similar or fractal-like over many orders of magnitude. Power laws allow extrapolation and prediction over a wide range of scales. Some appear to be universal, occurring in virtually all taxa of organisms and types of environments. They offer clues to underlying mechanisms that powerfully constrain biodiversity. We describe recent progress and future prospects for understanding the mechanisms that generate these power laws, and for explaining the diversity of species and complexity of ecosystems in terms of fundamental principles of physical and biological science.

Ecosystem↗

PubMed2001

Active noise control in a free field with virtual sensors.

The zone of local control around a "virtual energy density sensor" is compared with that offered by an actual energy density sensor, a single microphone, and a virtual microphone. Intended as an introduction to the concept of forward difference prediction and a precursor to evaluating the virtual sensor control algorithms in damped enclosures, this paper investigates an idealized scenario of a single primary sound source in a free-field environment. An analytical model is used to predict the performance of the virtual error sensors and compare their control performance with their physical counterparts. The model is then experimentally validated. The model shows that in general the virtual energy density sensor outperforms the actual energy density sensor, the actual microphone, and the virtual microphone in terms of centering a practically sized zone of local control around an observer who is remotely located from any physical sensors. However, in practice, the virtual sensor algorithms are shown to be sensitive (by varying degrees) to short wavelength spatial pressure variations of the primary and secondary sound fields.

Acoustics↗

PubMedDate not supplied

The importance of distributed broadband networks to academic biomedical research and education programs.

OBJECTIVE: This article highlights the importance of distributed broadband networks as part of the core infrastructure necessary to deliver academic research and education programs. METHOD: The authors review recent developments in the field and present the University of California, Davis, environment as a case study of a future virtual regional academic medical center. RESULTS: Achieving the potential benefits of distributed broadband networks through regional health information organizations will involve considerable collaboration between different academic groups and the development and implementation of standardized technological and business approaches. CONCLUSIONS: Broadband technologies offer a substantial opportunity to improve the way academic education and research programs are delivered.

Biomedical Research↗

PubMed2001

Hopkins Teen Central: Assessment of an internet-based support system for children with cystic fibrosis.

UNLABELLED: Support groups are an important therapeutic intervention for patients with chronic debilitating illnesses. Patients who are difficult to assemble in one physical location may benefit from participating in an electronic support group (ESG). ESGs for adolescents have not been evaluated, although studies have shown a benefit to adult ESGs. Our goals were to create a web-based support service for adolescents with cystic fibrosis (CF) and to qualitatively and quantitatively measure the effects that such a support site could have on patients' relationships with the clinic faculty and staff, access to and interaction with peers with CF, and understanding of CF. METHODS: A highly interactive ESG was developed after discussions with a team of CF specialists and patients. Eighteen of 37 teenagers with CF agreed to use this site. Each patient was asked to assess his or her perceived availability of and comfort with the clinic staff and faculty, perceived support available through peers, knowledge about CF, and perceived usefulness of the Internet as a support tool. RESULTS: Participants logged into the site an average of 4 times each month. Teens who owned home computers accessed the site somewhat more frequently than did teens who were provided with home Internet access for the study. Most activity occurred in those sections of the site that described the participants and that allowed them to socialize. Over one half of the participants e-mailed each other at least once a week, with 77% e-mailing peers at least every other week. There was no significant difference in the participants' scores on a quiz about CF at the beginning and the end of the study; however, there was a significant decrease in perceptions about their knowledge about CF. At the conclusion of the study, participants believed that they had more friends who they could relate to than they did at the beginning of the study. Clinic staff noticed an increase in references to peers among the group who were using the site. In addition, 4 of the teens expressed a desire to get together to meet each other as a result of their interactions on the web site. There was no significant change in perceptions about the perceived availability and comfort with the clinic staff and faculty, support available through peers, knowledge about CF, and the usefulness of the Internet as a support environment. Managing the project was extremely easy, with virtually no technical or procedural issues arising during the study. CONCLUSIONS: Teenagers with a chronic disease will actively participate in an ESG. The social and expressive aspects of their involvement with this support group hold much promise.

Adolescent↗

PubMed2005

The LapSim: a learning environment for both experts and novices.

BACKGROUND: Simulated environments present challenges to both clinical experts and novices in laparoscopic surgery. Experts and novices may have different expectations when confronted with a novel simulated environment. The LapSim is a computer-based virtual reality laparoscopic trainer. Our aim was to analyze the performance of experienced basic laparoscopists and novices during their first exposure to the LapSim Basic Skill set and Dissection module. METHODS: Experienced basic laparoscopists (n=16) were defined as attending surgeons and chief residents who performed >30 laparoscopic cholecystectomies. Novices (n=13) were surgical residents with minimal laparoscopic experience. None of the subjects had used a computer-based laparoscopic simulator in the past. Subjects were given one practice session on the LapSim tutorial and dissection module and were supervised throughout the testing. Instrument motion, completion time, and errors were recorded by the LapSim. A Performance Score (PS) was calculated using the sum of total errors and time to task completion. A Relative Efficiency Score (RES) was calculated using the sum of the path lengths and angular path lengths for each hand expressed as a ratio of the subject's score to the worst score achieved among the subjects. All groups were compared using the Kruskal-Wallis and Mann-Whitney U-test. RESULTS: Novices achieved better PS and/or RES in Instrument Navigation, Suturing, and Dissection (p<0.05). There was no difference in the PS and RES between experts and novices in the remaining skills. CONCLUSION: Novices tended to have better performance compared to the experienced basic laparoscopists during their first exposure to the LapSim Basic Skill set and Dissection module.

Clinical Competence↗

PubMed1997

Outbreak of Salmonella infantis infection in a large animal veterinary teaching hospital.

During the past 11 years, there have been numerous reports of outbreaks of salmonellosis involving horses in veterinary teaching hospitals. Some of these outbreaks have been associated with Salmonella serotypes not commonly associated with infection of horses. Salmonella infantis is among the more common Salmonella serotypes isolated from human beings, and is an important pathogen in the broiler chicken industry. However, it was not commonly isolated from horses or cattle on a national basis between 1993 and 1995. In this report, we describe an outbreak of S infantis infection among large animals, primarily horses, in a veterinary teaching hospital and the control measures that were implemented. Factors that appeared to be key in control of this outbreak in this hospital included providing biosecurity training sessions for hospital personnel, adopting a standard operating procedure manual for biosecurity procedures, installing additional handwashing sinks throughout the facility, painting the interior of the facility with a nontoxic readily cleanable paint, replacing the dirt flooring in 4 stalls with concrete flooring, and removing noncleanable surfaces such as rubber stall mats, wooden hay storage bins, and open grain bins. Our experience with this outbreak suggests that although it is virtually impossible to eliminate Salmonella organisms from the environment, minimizing contamination is possible. Prevention of nosocomial infection must be approached in a multifaceted manner and care must be taken to search out covert sources of contamination, especially if standard intervention procedures do not prevent spread of the disease.

Animals↗

PubMed2005

Development of a data management tool for investigating multivariate space and free will experiences in virtual reality.

Virtual reality (VR) has become mature enough to be successfully used in clinical applications such as exposure therapy, pain distraction, and neuropsychological assessment. However, we now need to go beyond the outcome data from this research and conduct the detailed scientific investigations required to better understand what factors influence why VR works (or doesn't) in these types of clinical applications. This knowledge is required to guide the development of VR applications in the key areas of education, training, and rehabilitation and to further evolve existing VR approaches. One of the primary assets obtained with the use of VR is the ability to simulate the complexity of real world environments, within which human performance can be tested and trained. But this asset comes with a price in terms of the capture, quantification and analysis of large, multivariate and concurrent data sources that reflect the naturalistic behavioral interaction that is afforded in a virtual world. As well, while achieving realism has been a main goal in making convincing VR environments, just what constitutes realism and how much is needed is still an open question situated firmly in the research domain. Just as in real "reality," such factors in virtual reality are complex and multivariate, and the understanding of this complexity presents exceptional challenges to the VR researcher. For certain research questions, good behavioral science often requires consistent delivery of stimuli within tightly controlled lab-based experimental conditions. However, for other important research questions we do not want to constrain naturalistic behavior and limit VR's ability to replicate real world conditions, simply because it is easier to study human performance with traditional lab-based methodologies. By doing so we may compromise the very qualities that comprise VR's unique capacity to mimic the experiences and challenges that exist in everyday life. What is really needed to address scientific questions that require natural exploration of a simulated environment are more usable and robust tools to instrument, organize, and visualize the complex data generated by measurements of participant behaviors within a virtual world. This paper briefly describes the rationale and methodology of an initial study in an ongoing research program that aims to investigate human performance within a virtual environment where unconstrained "free will" exploratory behavior is essential to research questions that involve the relationships between physiology, emotion, and memory. After a discussion of the research protocol and the types of data that were collected, we describe a novel tool that was borne from our need to more efficiently capture, manage, and explore the complex data that was generated in this research. An example of a research participant's annotated display from this data management and visualization tool is then presented. It is our view that this tool provides the capacity to better visualize and understand the complex data relationships that may arise in VR research that investigates naturalistic free will behavior and its impact on other human performance variables.

Activities of Daily Living↗

PubMed2006

Sudden infant death syndrome: selenium administered above dietary needs stabilizes the electrocardiograms of subjects deprived of exercise stimuli to the brain.

The human foetus begins preparation for extrauterine life in the 26th week of gestation. Victims of sudden infant death syndrome (SIDS) were described as having less-intensive reactions to environmental stimuli than their siblings. They were described as less-active physically and more breathless and exhausted during feeding. These foetal-like qualities are similar to the microgravity deconditioning of the space traveller and the autonomic dysfunction of hypokinetic humans. During quiet sleep, a group of near-miss SIDS victims displayed a faster heart-rate and a decreased movement-time, compared to controls. Another group of SIDS victims linked delayed repolarisation and sympathetic overactivity of the nervous system. The excessive Q-T wave intervals, cardiac instability and autonomic dysfunction tended to coincide with the peak incidence of SIDS which is the normal period of autonomic transformation at 2-3 months of age. Sympathetic hyperactivity transforms the subject into an energy-intensive species with an accelerated heartbeat, intensive vasoconstriction and general reactions to a hostile environment. Energy-intensive species (flight-oriented species) were sensitive to selenium (Se) deficiency. Altered mitochondrial structure and defective electron transport of heart mitochondria were features of this syndrome. Runaway excessive sympathetic autonomic activity transforms the subject into an energy-intensive species responsive to selenium. Groups of Se-deficient lambs confined for eight weeks developed abnormal electrocardiograms (ECGs). Groups exercised daily on a treadmill or Se-supplemented groups retained virtually normal ECGs. Foetuses and subjects unreactive to the environment are space travellers lacking parasympathetic stimuli to the brain. Decreased movement-time deprives the brain receptors of the stimulus induced by gravity.

Brain↗

PubMed2004

Online learning of virtual impedance parameters in non-contact impedance control using neural networks.

Impedance control is one of the most effective methods for controlling the interaction between a manipulator and a task environment. In conventional impedance control methods, however, the manipulator cannot be controlled until the end-effector contacts task environments. A noncontact impedance control method has been proposed to resolve such a problem. This method on only can regulate the end-point impedance, but also the virtual impedance that works between the manipulator and the environment by using visual information. This paper proposes a learning method using neural networks to regulate the virtual impedance parameters according to a given task. The validity of the proposed method was verified through computer simulations and experiments with a multijoint robotic manipulator.

Algorithms↗

PubMedDate not supplied

Virtual reality applications in clinical medicine.

Virtual reality, the use of computational methods to present users with a multimedia environment that simulates reality, is becoming a practical, affordable technology for the teaching and practice of clinical medicine. Although limited-fidelity virtual reality systems have been used in medical education for decades, modern, high-fidelity virtual reality systems have practical applications in areas ranging from psychiatry to surgical planning and telemedicine. Factors that limit widespread use of virtual reality in medicine include a lack of standards for the re-purposing and sharing of system components and the resultant low return on investment from custom systems. The standards issue is being addressed by economic incentives from organizations such as the U.S. military, which requires computer-based educational materials, including simulations, to be interoperable. Similarly, the low return on investment is becoming less of a factor in clinical scenarios in which virtual reality systems offer physicians and their patients experiences that are impossible or impractical to gain elsewhere.

Clinical Medicine↗

PubMed2006

Quantitative analysis of accuracy of an inertial/acoustic 6DOF tracking system in motion.

An increasing number of neuroscience experiments are using virtual reality to provide a more immersive and less artificial experimental environment. This is particularly useful to navigation and three-dimensional scene perception experiments. Such experiments require accurate real-time tracking of the observer's head in order to render the virtual scene. Here, we present data on the accuracy of a commonly used six degrees of freedom tracker (Intersense IS900) when it is moved in ways typical of virtual reality applications. We compared the reported location of the tracker with its location computed by an optical tracking method. When the tracker was stationary, the root mean square error in spatial accuracy was 0.64 mm. However, we found that errors increased over ten-fold (up to 17 mm) when the tracker moved at speeds common in virtual reality applications. We demonstrate that the errors we report here are predominantly due to inaccuracies of the IS900 system rather than the optical tracking against which it was compared.

Acceleration↗

PubMed1996

A pilot study of fieldwork rotations vs. year long placements for social work students in a public hospital.

A comparison of two types of fieldwork was undertaken with 26 social work students in a large urban hospital. The first group was assigned to a traditional, year long placement. The second group was assigned to three successive placements of approximately 10 weeks each. The impact of these two types of placement on students' general sense of self-efficacy, self-efficacy regarding specific hospital social work activities and perceptions of the work environment, was assessed. Initial results suggest that both groups produce virtually no change in students' general sense of self-efficacy, yet produce positive changes in students' self-efficacy regarding hospital social work. In addition, results suggest that the fieldwork rotation used in the second group may produce somewhat more positive views of the work environment.

Attitude of Health Personnel↗

PubMed1998

Single-clone and mixed-clone infections versus host environment in Crithidia bombi infecting bumblebees.

Current theories assume that adaptive parasite evolution explains variation in the level of virulence and parasite success. In particular, mixed-genotype infections by parasites should generally be more virulent, and faster multiplying strains more successful, either because fixed strategies have evolved or because parasites facultatively alter virulence in response to co-infecting competitors. We compared several measures of parasite success and virulence between single-clone and mixed-clone infections of 2 strains of the trypanosome Crithidia bombi in its bumblebee host, Bombus terrestris. Contrary to expectation, we could not find differences between single-clone and mixed-clone infections in parasite prevalence, infection success, duration and clearance rate. However, a clearly significant effect of colony on infection intensity was present, and the colony effect emerged in virtually all other measures. We thus conclude that host environment as defined by the family (colony) genotype and thus host heterogeneity are more important in determining parasite virulence than the parasite characteristics. This does not invalidate modern theories of parasite evolution but suggests that variation in both hosts and parasites must be taken into account in more detail.

Animals↗

PubMedDate not supplied

The reemergence of the hospital-based laboratory.

The Reference Laboratory Alliance (RLA) in Pittsburgh is an example of multiple hospital laboratories integrated for the purpose of delivering competitive outpatient laboratory services in a managed-care environment. Developed in 1994, the RLA model includes a "virtual" core laboratory (comprising four tertiary care centers of excellence) and a distributed network of more than 30 community hospitals. Linked through information systems, logistics, and an extensive committee structure, the RLA is capable of delivering a "seamless" service to the region's managed-care organizations. In its first full year of operation, the RLA is expected to shift between $12 and $15 million worth of laboratory activity back into the community's hospitals. Through its pathology component, the RLA is now actively engaged in redefining the role of the clinical laboratory in the managed-care environment.

Community Networks↗

PubMed2005

Tackling childhood obesity: diet, physical activity or lifestyle change?

UNLABELLED: The present day, almost worldwide, fattening of children is widely attributed to both excessive energy intake and reduced physical activity. However, treatments which only focus on reducing energy intakes and increasing energy expenditures rarely show long-term success. The family attitudes and environments which contribute to energy imbalance and the development of obesity are virtually unchanged by many treatment programmes. We need to learn more about the nurture of those children who retain normal fatness although enveloped by obesity-promoting environments. CONCLUSION: Better understanding of these children's lifestyles could lead to significant community-directed initiatives to promote normal childhood nutrition and growth even within affluent modem society.

Child↗

PubMed2004

Increasing face validity of a vascular interventional training system.

BACKGROUND: Many aspects of medical training take place on real patients in a live environment thus incurring risk. Apart from the obvious risks to patients there is the issue of X-ray exposure to both staff and trainees. Image quality used during interventional procedures is low to ensure minimum X-ray radiation dose. A virtual interventional system may be used to simulate the interventional cardiology training environment therefore reducing overall risk. The purpose of this project was to determine the appropriate image quality settings on a virtual training system to accurately simulate interventional cardiology and increase the face validity of the overall system. METHODS: Real image data was obtained from patients undergoing diagnostic interventional cardiology examinations in the Royal Victoria Hospital, Belfast. The images were obtained during catheter placement and contrast enhancement around the region of the heart. The diagnostic views were left anterior oblique, right anterior oblique, left lateral, caudal and the spider view. These five views were simulated on a virtual interventional training system (VIST, Mentice Medical Simulation AB, Sweden) by adjusting x-ray tube and table position at 20 different image quality settings. Signal to noise ratio and image contrast were measured for each of these views using soft tissue and vertebra. The results from the real image data and the VIST image data were compared. Calibration curves were compiled to determine the appropriate VIST image quality setting for each procedure. RESULTS: Average SNR ranged from 2.94 to 74.0 and IC ranged from 0.009 to 0.61 on the real image data. This indicates the very wide range of image quality encountered in interventional cardiology. Calibration curves for each view with the corresponding range of real patient image quality were produced. These calibration curves enabled the appropriate VIST image quality setting to be determined and therefore simulate the real examination image quality as closely as possible. CONCLUSIONS: The VIST system has been calibrated in terms of image quality for interventional cardiology examinations. This has increased the face validity of the system.

Cardiology↗

PubMed2003

Caring for people in the 'virtual ward': the practical ramifications for acute nursing work.

This paper discusses an aspect of data analysis arising from an ethnographic study of acute mental health nursing conducted in an inner city psychiatric unit. The data were collected in the form of field notes. These were made during and following episodes of participant observation on one acute ward and on a psychiatric intensive care unit over a period of 20 months. Acute wards have been subject to continuing criticism as both sites of care and treatment for mentally ill people and of nursing work. However, the practical operations of this social world remain largely unexamined. It is argued that without this understanding, mundane work methods will always be regarded as an impediment to work that is regarded as 'therapeutic' and therefore, of importance. The focus will be on phenomena named the 'virtual ward'. The research has demonstrated that the boundaries of nurses' responsibility reach far beyond the ward's spatial environment, both physically and communicatively. The complexity of the work that takes place within the virtual ward and the skills required for its successful completion are taken for granted, but are also a practical source of frustration. Anonymized examples from the practice site studied are used to illuminate the discussion. Working within the virtual ward is part of the messy reality of nurses' work. It is argued that understanding and respecting this reality is necessary if we are to be seriously and consistently ambitious about practice development.

Acute Disease↗

PubMed1998

A comparative analysis of integrating visual representations with haptic displays.

As further advances in visual display technologies and force feedback devices are integrated in virtual systems, questions remain: What level of reality does the system provide to the user? Is the environment convincing enough to engage the user and to maximize transfer? Are the visual and haptic displays fully integrated to provide seamless operation in the simulated environment? Does the system provide not only the ability to navigate through a simulated environment, but also realistic interaction with instrumentation and structures? We report on our advances in developing a virtual simulation system for training in functional endoscopic sinus surgery (FESS). Specifically, we will present work on subject trials exploring the realism provided by integrated visual and haptic displays, and compare and contrast surface vs. volume representation for presenting realistic models of the anatomy for surgical interaction.

Computer Simulation↗