Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “virtual environment”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed2002

Interventional radiology.

PURPOSE OF REVIEW: The capabilities of interventional radiology are developing faster than perhaps any other branch of medicine. Coupled with and fuelled by parallel advances in computer technology, medical physics and developments in endovascular catheter technology, interventional radiologists are innovating not only replacements for open surgeries, but entirely new therapies as well. This has, however, provided a range of new potential complications for the patient and, in contrast to other areas, presents risks for the anesthesiologist as well. RECENT FINDINGS: The techniques involved in interventional radiology have found applications throughout not only medicine but surgery in particular. Here there has been a medicalization of surgical procedures. CT scanning has evolved to the extent that it is now possible to utilize multislice CT scanners, ones with multiple, flat panel digital detectors, to provide real time CT fluoroscopy. Similarly this technology has facilitated the construction of hybrid iMR/X-ray systems, thus enabling dual modality imaging without moving the patient. Another facet of the new breed of iMR systems is their integration in real time with computerized, frameless stereotactic navigation systems. This has enabled the radiological image to keep pace with the changes in anatomy consequent to anesthetic and surgical manipulations. SUMMARY: In the light of these new developments in interventional radiology there is much research to be done. Further developments in imaging and computer processing technology will doubtless make possible the real time integration of anatomical image with metabolic state and functional anatomy. The impact of the hazards of these new techniques on the safety of anesthesia has, however, been the subject of virtually no research. A particularly needy area will be the ergonomics of the delivery of anesthesia care in these new environments.

Journal Article↗
PubMed2002

Bacterial adhesion: seen any good biofilms lately?

The process of surface adhesion and biofilm development is a survival strategy employed by virtually all bacteria and refined over millions of years. This process is designed to anchor microorganisms in a nutritionally advantageous environment and to permit their escape to greener pastures when essential growth factors have been exhausted. Bacterial attachment to a surface can be divided into several distinct phases, including primary and reversible adhesion, secondary and irreversible adhesion, and biofilm formation. Each of these phases is ultimately controlled by the expression of one or more gene products. Ultrastructurally, the mature bacterial biofilm resembles an underwater coral reef containing pyramidal or mushroom-shaped microcolonies of organisms embedded within an extracellular glycocalyx, with channels and cavities to allow the exchange of nutrients and waste. The biofilm protects its inhabitants from predators, dehydration, biocides, and other environmental extremes while regulating population growth and diversity through primitive cell signals. From a physiological standpoint, surface-bound bacteria behave quite differently from their planktonic counterparts. Recognizing that bacteria naturally occur as surface-bound and often polymicrobic communities, the practice of performing antimicrobial susceptibility tests using pure cultures and in a planktonic growth mode should be questioned. That this model does not reflect conditions found in nature might help explain the difficulties encountered in the management and treatment of biomedical implant infections.

Bacterial Adhesion↗
PubMed2002

Evolving concepts of reflux: the ups and downs of the LES.

The common denominator for virtually all episodes of gastroesophageal reflux in health and disease is the loss of the barrier that confines the gastric environment to the stomach. Factors important in the function of the barrier are its pressure, length and position. In early reflux disease, overeating, gastric distention, delayed emptying and aerophagia lead to transient losses of the barrier. A permanent loss results from inflammatory injury to the muscle of the barrier with free flow of gastric juice into the esophageal body and its subsequent injury. Corrective therapy requires augmentation or restoration of barrier function.

Esophageal Diseases↗
PubMed2004

Peptaibol zervamicin IIb structure and dynamics refinement from transhydrogen bond J couplings.

Zervamicin IIB (Zrv-IIB) is a channel-forming peptaibol antibiotic of fungal origin. The measured transhydrogen bond (3h)J(NC') couplings in methanol solution heaving average value of -0.41 Hz indicate that the stability of the Zrv-IIB helix in this milieu is comparable to the stability of helices in globular proteins. The N-terminus of the peptide forms an alpha-helix, whereas 3(10)-helical hydrogen bonds stabilize the C-terminus. However, two weak transhydrogen bond peaks are observed in a long-range HNCO spectrum for HN Aib(12). Energy calculations using the Empirical Conformation Energy Program for Peptides (ECEPP)/2 force field and the implicit solvent model show that the middle of the peptide helix accommodates a bifurcated hydrogen bond that is simultaneously formed between HN Aib(12) and CO Leu(8) and CO Aib(9). Several lowered (3h)J(NC') on a polar face of the helix correlate with the conformational exchange process observed earlier and imply dynamic distortions of a hydrogen bond pattern with the predominant population of a properly folded helical structure. The refined structure of Zrv-IIB on the basis of the observed hydrogen bond pattern has a small ( approximately 20 degrees ) angle of helix bending that is virtually identical to the angle of bending in dodecylphosphocholine (DPC) micelles, indicating the stability of a hinge region in different environments. NMR parameters ((1)HN chemical shifts and transpeptide bond (1)J(NC') couplings) sensitive to hydrogen bonding along with the solvent accessible surface area of carbonyl oxygens indicate a large polar patch on the convex side of the helix formed by three exposed backbone carbonyls of Aib(7), Aib(9), and Hyp(10) and polar side chains of Hyp(10), Gln(11), and Hyp(13). The unique structural features, high helix stability and the enhanced polar patch, set apart Zrv-IIB from other peptaibols (for example, alamethicin) and possibly underlie its biological and physiological properties.

Hydrogen Bonding↗
PubMedDate not supplied

[Distance learning using internet in the field of bioengineering].

The Leonardo da Vinci training programme supports innovative transnational initiatives for promoting the knowledge, aptitudes and skills necessary for successful integration into working life. Biomedical engineering is an emerging interdisciplinary field that contributes to understand, define and solve problems in biomedical technology within industrial and health service contexts. Paper presents a Leonardo da Vinci pilot-project called Web-based learning and training in the field of biomedical and design engineering (WEBD). This project has started on 2001. The WEBD project proposes to use advanced learning technologies to provide education in the www. Project uses interactive 3D graphics and virtual reality tools. The WEBD distance training permits users to experience and interact with a life-like model or environment, in safety and at convenient times, while providing a degree of control over the simulation that is usually not possible in the real-life situation.

Biomedical Engineering↗
PubMed2002

Temporal bone dissection simulation--an update.

We report on our continued development of a virtual simulation for temporal bone dissection that provides stereoscopic display, haptic feedback, and aural simulation into a straightforward, comprehensive learning environment. The multimodal interface provides a seamless simulation for non-deterministic drilling and cutting of bone in the surgical context, as well as an intuitive interface for the intelligent tutor for learning regional anatomy. We present novel methodologies for integrating multimodal and multiresolution data sets, including extension to functional and structural segmentation. We will present our initial efforts to validate this environment. Through continued iterations, it is our hope that the system will provide a valuable tool for training future otologic surgeons as well as an environment for the quantitative evaluation of surgical skill.

Aged↗
PubMed2006

The surgeon skill set in minimally invasive total knee arthroplasty.

The traditional didactic approach to improving the skill set of surgeons has been shown to have minimal impact. Surgeons, like other adults, learn best by doing, by practicing what they do. and by challenging themselves to take on increasingly difficult scenarios. To be effective, surgical practice requires deconstruction of a procedure into key elements, each of which is repeated until optimal results are achieved before moving on to the next element. Given the multifactorial nature of a procedure such as minimally invasive surgery for total knee arthroplasty, surgeons need to introduce incremental changes into their operating environment to allow for realistic self-assessment during postoperative self-debriefing. One technique, visualization, can be used for virtual practice. In the future, surgical simulators may allow for true virtual practice as well as systematic recording of results. However, psychomotor skills are only one component of surgical success. Intuition and innovation are also key, but these components are more difficult to teach and to learn. The key ingredient to successful practice and ultimate self-improvement in surgery, as in other pursuits in life, is that a person be self-motivated and competitive and have a strong desire to improve coupled with appropriate practice routines that can lead to improvement.

Arthroplasty, Replacement, Knee↗
PubMed2000

The cannabinoid agonist HU 210 modifies rat behavioural responses to novelty and stress.

Experiments were performed on groups of rats after acute and sub-chronic treatment (once daily for 9 days) with the cannabinoid agonist HU 210 (25-100 microg kg(-1), i.p.) as well as 24 h and 7 days after the last drug injection. The animals underwent three behavioural tests in novel environments. In the observation cages (Test 1), rat locomotor activity was found to be dose-dependently reduced after acute and sub-chronic treatment at all doses and virtually unchanged during abstinence; grooming was potently inhibited by acute treatment but potentiated by the sub-chronic one at doses of 50 and 100 microg kg(-1), the effect of the higher dose persisting after 24 h and 7 days abstinence. Vocalization in animals in response to a tactile stimulus was highest after HU 210 at 100 microg kg(-1) in all experimental modes except after 7 days abstinence. In the X-maze (Test 2), sub-chronic HU 210 dose- dependently enhanced rat natural aversion for open arms, and this behaviour persisted during abstinence after the highest dose. Grooming in the X-maze was completely absent in rats acutely injected with HU 210 but potentiated in those sub-chronically treated or abstinent. In the swimming test (Test 3) rats sub-chronically treated at 50 and 100 pg kg(-1) displayed relevant wall-hugging and the same occurred 24 h after last injection. On the whole, our results are indicative of an anxiogenic-like effect of sub-chronic HU 210 at high doses and reflect the persistence of enhanced emotional response to novel environments when the treatment is discontinued.

Animals↗
PubMed1993

The role of nematophagous fungi in the biological control of nematode parasites of livestock.

The control of nematode parasites of livestock is presently based entirely on anthelmintic treatment and grazing management. On their own, these methods are not sustainable because parasites invariably develop resistance to anthelmintics and because of increasing public concern about chemical residues in livestock products and the environment. Although alternative, non-chemotherapeutic control strategies, such as vaccines and genetic selection for resistance are the focus of considerable research activity worldwide, biological control of nematode parasites has been virtually ignored. The little work that has been done is restricted largely to western Europe and involves virtually just one fungal species, namely Arthrobotrys oligospora. More recent studies indicate other known nematophagous fungal species are more efficient predators of infective larvae in sheep faeces than A. oligospora, and others have a greater capacity to survive passage through the gastrointestinal tract of ruminants. These findings plus the relatively sparse numbers of microbial competitors in the fresh faecal environment, compared with the plant rhizosphere where biological control of plant parasites is proving a particularly intractable problem, engenders optimism that the biological control of animal parasitic nematodes may become a practical reality. Such control will never be a substitute for chemotherapy, where the primary purpose is worm removal from the host, but should be incorporated together with other options into integrated pest management systems to provide sustainable nematode control of livestock into the twenty-first century.

Animals↗
PubMed2005

Emotion understanding from the perspective of autonomous robots research.

In this paper, I discuss some of the contributions that modeling emotions in autonomous robots can make towards understanding human emotions-'as sited in the brain' and as used in our interactions with the environment-and emotions in general. Such contributions are linked, on the one hand, to the potential use of such robotic models as tools and 'virtual laboratories' to test and explore systematically theories and models of human emotions, and on the other hand to a modeling approach that fosters conceptual clarification and operationalization of the relevant aspects of theoretical notions and models. As illustrated by an overview of recent advances in the field, this area is still in its infancy. However, the work carried out already shows that we share many conceptual problems and interests with other disciplines in the affective sciences and that sound progress necessitates multidisciplinary efforts.

Adaptation, Psychological↗
PubMed2003

The virtual microscope.

We present the design and implementation of the Virtual Microscope, a software system employing a client/server architecture to provide a realistic emulation of a high power light microscope. The system provides a form of completely digital telepathology, allowing simultaneous access to archived digital slide images by multiple clients. The main problem the system targets is storing and processing the extremely large quantities of data required to represent a collection of slides. The Virtual Microscope client software runs on the end user's PC or workstation, while database software for storing, retrieving and processing the microscope image data runs on a parallel computer or on a set of workstations at one or more potentially remote sites. We have designed and implemented two versions of the data server software. One implementation is a customization of a database system framework that is optimized for a tightly coupled parallel machine with attached local disks. The second implementation is component-based, and has been designed to accommodate access to and processing of data in a distributed, heterogeneous environment. We also have developed caching client software, implemented in Java, to achieve good response time and portability across different computer platforms. The performance results presented show that the Virtual Microscope systems scales well, so that many clients can be adequately serviced by an appropriately configured data server.

Computer Graphics↗
PubMed2004

Design and preparation of a particle dynamics space flight experiment, SHIVA.

This paper describes the flight experiment, supporting ground science, and the design rationale for a project on spaceflight holography investigation in a virtual apparatus (SHIVA). SHIVA is a fundamental study of particle dynamics in fluids in microgravity. Gravitation effects and steady Stokes drag often dominate the equations of motion of a particle in a fluid and consequently microgravity provides an ideal environment in which to study the other forces, such as the pressure and viscous drag and especially the Basset history force. We have developed diagnostic recording methods using holography to save all of the particle field optical characteristics, essentially allowing the experiment to be transferred from space back to Earth in what we call the "virtual apparatus" for microgravity experiments on Earth. We can quantify precisely the three-dimensional motion of sets of particles, allowing us to test and apply new analytic solutions developed by members of the team. In addition to employing microgravity to augment the fundamental study of these forces, the resulting data will allow us to quantify and understand the ISS environment with great accuracy. This paper shows how we used both experiment and theory to identify and resolve critical issues and to produce an optimal experimental design that exploits microgravity for the study. We examined the response of particles of specific gravity from 0.1 to 20, with radii from 0.2 to 2 mm, to fluid oscillation at frequencies up to 80 Hz with amplitudes up to 200 microns. To observe some of the interesting effects predicted by the new solutions requires the precise location of the position of a particle in three dimensions. To this end we have developed digital holography algorithms that enable particle position location to a small fraction of a pixel in a CCD array. The spaceflight system will record holograms both on film and electronically. The electronic holograms can be downlinked providing real-time data, essentially acting like a remote window into the ISS experimental chamber. Ground experiments have provided input to a flight system design that can meet the requirements for a successful experiment on ISS. Moreover the ground experiments have provided a definitive, quantitative observation of the Basset history force over a wide range of conditions. Results of the ground experiments, the flight experiment design, preliminary flight hardware design, and data analysis procedures are reported.

Acceleration↗
PubMedDate not supplied

"In silico" design of new uranyl extractants based on phosphoryl-containing podands: QSPR studies, generation and screening of virtual combinatorial library, and experimental tests.

This paper is devoted to computer-aided design of new extractants of the uranyl cation involving three main steps: (i) a QSPR study, (ii) generation and screening of a virtual combinatorial library, and (iii) synthesis of several predicted compounds and their experimental extraction studies. First, we performed a QSPR modeling of the distribution coefficient (logD) of uranyl extracted by phosphoryl-containing podands from water to 1,2-dichloroethane. Two different approaches were used: one based on classical structural and physicochemical descriptors (implemented in the CODESSA PRO program) and another one based on fragment descriptors (implemented in the TRAIL program). Three statistically significant models obtained with TRAIL involve as descriptors either sequences of atoms and bonds or atoms with their close environment (augmented atoms). The best models of CODESSA PRO include its own molecular descriptors as well as fragment descriptors obtained with TRAIL. At the second step, a virtual combinatorial library of 2024 podands has been generated with the CombiLib program, followed by the assessment of logD values using developed QSPR models. At the third step, eight of these hypothetical compounds were synthesized and tested experimentally. Comparison with experiment shows that developed QSPR models successfully predict logD values for 7 of 8 compounds from that "blind test" set.

Journal Article↗
PubMed1985

Biofeedback vs. video games: effects on impulsivity, locus of control and self-concept with incarcerated juveniles.

Research has found hyperactivity, poor impulse control, impaired sustained attention and low self-concept to be behavioral deficits common to juvenile delinquents. Limited opportunities for exercising self-control while incarcerated may encourage helplessness. If biofeedback training enhances self-regulation skills, then perhaps these behaviors can be taught in confinement. A sample of 12 felonious juvenile residents (aged 15-18) from a highly restricted environment were assigned randomly to a biofeedback or video game group and trained for 10 half-hour sessions. Results indicated virtually no significant differences between biofeedback and video game training. However, pre and post differences for both groups combined demonstrated significant gains in impulsivity, EMG, and self-concept. Both groups rated themselves equally on self-control ability, regardless of training. Further comparisons between other institutionalized residents (N = 14) and staff counselors (N = 10) as non-treatment controls were made. On each measure, both training groups improved consistently and became more like their less restricted counterparts.

Adolescent↗
PubMed2005

Applications of variable-angle sample spinning experiments to the measurement of scaled residual dipolar couplings and 15N CSA in soluble proteins.

NMR spectra of ubiquitin in the presence of bicelles at a concentration of 32% w/v have been recorded at 700 MHz under sample spinning conditions at the magic angle (54.7 degrees ) and at an angle of 45.5 degrees . At the magic angle, the 1H-15N HSQC spectrum of ubiquitin in bicelles is virtually indistinguishable from the one recorded on the protein in solution. Spinning the sample at the magic angle creates an isotropic environment with no preferred bicelle orientations, thus allowing the determination of scalar coupling constants. For an angle of rotation of 45.5 degrees , the bicelles orient with their normal perpendicular to the spinning axis leading to the observation of strong residual dipolar couplings and chemical shift variations of the 15N resonances.

Anisotropy↗
PubMed1999

Virtual reality training in laparoscopic surgery: a preliminary assessment of minimally invasive surgical trainer virtual reality (MIST VR).

BACKGROUND: The "fulcrum effect" of the body wall on surgical instrument manipulation is a major hurdle for novice endoscopic surgeons. Virtual reality training has not previously been evaluated as a means to overcome this problem. MATERIALS AND METHODS: 16 participants with no experience of endoscopy were required to make multiple defined incisions under laparoscopic laboratory conditions within 2-minute periods. Half of the subjects were randomized to receive initial training on the Minimally Invasive Surgical Trainer, Virtual Reality (MIST VR) computer programme. RESULTS: Participants with MIST VR training made significantly more correct incisions (P = 0.0001) than the control group on test trial 1, and even after extended practice by both groups (P = 0.0001). They were also significantly more likely to actively use both hands to perform the endoscopic evaluation task (P = 0.01). CONCLUSIONS: Virtual reality training represents a potential, viable solution for junior endoscopists, for overcoming the "fulcrum effect", in a replicable, safe learning environment which allows objective and reliable quantification of skill levels by trainers.

Adult↗
PubMed2006

Patient-specific bronchoscopy visualization through BRDF estimation and disocclusion correction.

This paper presents an image-based method for virtual bronchoscope with photo-realistic rendering. The technique is based on recovering bidirectional reflectance distribution function (BRDF) parameters in an environment where the choice of viewing positions, directions, and illumination conditions are restricted. Video images of bronchoscopy examinations are combined with patient-specific three-dimensional (3-D) computed tomography data through two-dimensional (2-D)/3-D registration and shading model parameters are then recovered by exploiting the restricted lighting configurations imposed by the bronchoscope. With the proposed technique, the recovered BRDF is used to predict the expected shading intensity, allowing a texture map independent of lighting conditions to be extracted from each video frame. To correct for disocclusion artefacts, statistical texture synthesis was used to recreate the missing areas. New views not present in the original bronchoscopy video are rendered by evaluating the BRDF with different viewing and illumination parameters. This allows free navigation of the acquired 3-D model with enhanced photo-realism. To assess the practical value of the proposed technique, a detailed visual scoring that involves both real and rendered bronchoscope images is conducted.

Algorithms↗
PubMed1992

Living in hospital and hostel: the pattern of interactions of people with learning difficulties.

This study compared interactions between the staff and residents living in hospital wards and in community-based hostels. Twenty-four people with moderate to severe learning difficulties participated in this study. Interactions were categorized according to who was the initiator and recipient, their purpose, attitude of the recipient, duration, and place. It was found that the hospital and hotel residents had virtually no interactions with people outwith the establishment in which they lived. The hostel appeared to offer the residents a sociable environment with more interpersonal interactions and more positive attitudes towards the interactants than the hospital. Interactions in both kinds of setting were very short, thus giving residents little chance to develop communicative skills. It is suggested that a more personal approach, such as joint activities between residents and staff, and living in small groups in ordinary housing, should be the first priorities in the effort to improve the pattern of social interactions of people with moderate to severe learning difficulties.

Activities of Daily Living↗