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PubMed2006

Rendezvous-guidance trajectory planning for robotic dynamic obstacle avoidance and interception.

This correspondence presents a novel online trajectory-planning method for the autonomous robotic interception of moving targets in the presence of dynamic obstacles, i.e., position and velocity matching (also referred to as rendezvous). The proposed time-optimal interception method is a hybrid algorithm that augments a novel rendezvous-guidance (RG) technique with the velocity-obstacle approach, for obstacle avoidance, first reported by Fiorini and Shiller. The obstacle-avoidance algorithm itself could not be used in its original form and had to be modified to ensure that the online planned path deviates minimally from the one generated by the RG algorithm. Extensive simulation and experimental analyses, some of which are reported in this correspondence, have clearly demonstrated the tangible time efficiency of the proposed interception method.

Letter↗
PubMed2002

Obstacle avoidance during human walking: transfer of motor skill from one leg to the other.

The aim of this study was to evaluate whether a newly acquired locomotor skill can be transferred to the mirror condition. Subjects were trained to step over an obstacle on a treadmill, the appearance of which was signalled by an acoustic stimulus, while visual information was prevented. Feedback information about foot clearance was provided by acoustic signals. During two successive runs (each consisting of 100 steps over the obstacle) the same leg was leading (i.e. the leg crossing the obstacle first). In the following third run, the leading and trailing legs were changed. During each of the three successive runs the adaptational changes were analysed by recording leg muscle electromyographic (EMG) activity, joint angle trajectories and foot clearance over the obstacle. The training effect gained between the first and second runs and the transfer to the mirror condition (third run) were evaluated. Adaptational changes of all measures, except ankle joint trajectory, could to a significant extent be transferred to the mirror condition. No side-specific differences in the amount of transfer were found, neither from the right to the left side, nor vice versa. These observations are at variance with adaptational changes observed during split-belt walking or one-legged hopping on a treadmill, where no transfer to the mirror condition occurred. It is assumed that this might be due to the specific requirements of the tasks and the leg muscles involved. While in the split-belt and hopping experiments leg extensor muscles are mainly involved, leg flexors predominate in the performance of the present task. It is hypothesised that the learning effects observed in the present experiments are mediated at a higher level (e.g. brainstem) of locomotor control.

Adaptation, Physiological↗
PubMed2003

Cardiac near-field morphology during conduction around a microscopic obstacle--a computer simulation study.

In a recent paper, we described the behavior of the cardiac electric near-field, E, parallel to the tissue surface during continuous conduction. We found that the tip of E describes a vector-loop during depolarization with the peak field, E, pointing opposite to the direction of propagation, phiI(m). Experimentally recorded loop morphologies of E, however, frequently showed significant deviations from the theoretically predicted behavior. We hypothesized that this variety of morphologies might be caused by conduction obstacles at a microscopic size scale. This study examines the influence of obstacles on the morphology of vector loops of E and whether the peak of distorted loops remains a reliable indicator for the direction of propagation. We used a computer model of a sheet of cardiac tissue with a central conduction obstacle immersed in an unbounded volume conductor. We studied the loop morphologies of E and the differences between the intracellularly determined direction of propagation, phiI(m), and the direction of E, phiE. Distortions of the vector loop were morphologically similar to those observed experimentally. Differences between phiI(m) and phiE were less than 18 degrees at all observation sites. The obstacle led to deformations of the loop morphology, particularly during the initial and terminal phases, and to a lesser degree near the instant of E. We concluded that E is a reliable indicator of phiI(m).

Animals↗
PubMed2006

Exploring obstacles to proper timing of prophylactic antibiotics for surgical site infections.

BACKGROUND: Surgical site infections remain one of the leading types of nosocomial infections. The administration of prophylactic antibiotics within a specific interval has been shown to reduce the burden of surgical site infections, but adherence to proper timing guidelines remains problematic. This study examined perceived obstacles to the use of evidence-based guidelines for the timely administration of prophylactic antibiotics to prevent surgical site infections. METHODS: 27 semi-structured interviews were conducted with anesthesiologists (n = 12), surgeons (n = 11), and perioperative administrators (n = 4) in two large academic hospitals to elicit their perceptions of the factors that prevent the timely administration of prophylactic antibiotics. Using a grounded theory approach, transcripts were analyzed for recurrent themes. RESULTS: Despite having knowledge of guidelines, participants perceived consistent failure in the proper timing of antibiotic administration. Thematic analysis revealed a number of obstacles to the observance of guidelines including: (1) low priority, (2) inconvenience, (3) workflow, (4) organizational communication, and (5) role perception. Workflow and role perception were the dominant obstacles. CONCLUSION: This study suggests that proper antibiotic timing is thwarted by significant obstacles. The gap between evidence-based guidelines and practice is populated by individual values, professional conflicts, and organizational conflicts which must be addressed in order to achieve optimal practice in this domain. Using group interviews to reveal these factors to team members and managers may be a first step to resolving the gap and reducing surgical site infections.

Anesthesiology↗
PubMedDate not supplied

What visual information is used for navigation around obstacles in a cluttered environment?

The goal of this study was to determine what visual information is used to navigate around barriers in a cluttered terrain. Twelve traffic pylons were arranged randomly in a 4.55 x 3.15 m travel area: there were 20 different arrangements. For each arrangement, individuals (N = 6) were positioned in 1 of 3 locations on the outside border with their eyes closed: on verbal command they were instructed to open their eyes and quickly go to 1 of 2 specified goals (2 vertical posts defining a door) located on one edge of the travel area. The movement of the body was tracked using the OPTOTRAK system, with the IREDS placed on a collar worn by the subjects. Experimental data of travel path chosen were compared with those predicted by models that incorporated different types of visual information to control path trajectory. The 6 models basically use 2 different strategies for route selection: reactive control based on visual input about the obstacle encountered in the line-of-sight travel path (Model # 1) and path planning based on different visual information (Model # 2, 3, 4, 5, and 6). The models that involve path planning are grouped into 2 categories: models 2, 3, 4, and 5 need detailed geometrical configuration of the obstacles to plan a route while model 6 plans a route based on identifying and avoiding a cluster of obstacles in the travel path. Two measures were used to compare model performance with the actual travel path: the difference in area between predicted and actual travel path and the number of trials that accurately predicted the number of turns during travel. The results suggest that route selection is not based on reactive control, but does involve path planning. The model that best predicts the travel paths taken by the individuals uses visual information about cluster of obstacles and identification of safe corridors to plan a route.

Adolescent↗
PubMed2004

Stumbling over obstacles in older adults compared to young adults.

Falls are a major problem in older adults. Many falls occur because of stumbling. The aim of the present study is to investigate stumbling reactions of older adults and to compare them with young adults. While subjects walked on a treadmill, a rigid obstacle unexpectedly obstructed the forward sway of the foot. In general, older adults used the same movement strategies as young adults ("elevating" and "lowering"). The electromyographic responses were categorized according to latencies: short-latency (about 45 ms, RP1), medium-latency (about 80 ms, RP2), and long-latency responses (about 110 ms, RP3; about 160 ms, RP4). Latencies of RP1 responses increased by about 6 ms and of RP2 by 10-19 ms in older adults compared with the young. Amplitudes of RP1 were similar for both age groups, whereas amplitudes of RP2-RP4 could differ. In the early-swing elevating strategy (perturbed foot directly lifted over the obstacle) older adults showed smaller responses in ipsilateral upper-leg muscles (biceps femoris and rectus femoris). This was related to shorter swing durations, more shortened step distances, and more failures in clearing the obstacle. In parallel, RP4 activity in the contralateral biceps femoris was enhanced, possibly pointing to a higher demand for trunk stabilization. In the late-swing lowering strategy (foot placed on the treadmill before clearing the obstacle) older adults showed lower RP2-RP3 responses in most muscles measured. However, kinematic responses were similar to those of the young. It is concluded that the changes in muscular responses in older adults induce a greater risk of falling after tripping, especially in early swing.

Adult↗
PubMedDate not supplied

Parental versus professional perceptions of obstacles to pediatric diabetes care.

Parents of children with insulin-dependent diabetes mellitus (IDDM) (n = 38) were surveyed to identify common and difficult obstacles to diabetes care. A list of these obstacles was cross-validated by a second parent sample (n = 47) who rated each item according to how common and difficult each item was for them. The list then was rated by a sample of diabetes professionals (n = 15) to evaluate the extent of agreement between parents and health care professionals regarding the frequency with which these obstacles occur and the difficulty they pose to everyday diabetes care. Professionals disagreed with parents regarding which obstacles were most common and difficult, generally rating problems as significantly more common and difficult (t = 5.20, P = < .001) than did the parents who experienced them. The results of the survey underscore the importance of health care providers evaluating the concerns of the local patient community when developing educational and treatment services for these patients.

Adolescent↗
PubMedDate not supplied

Situational obstacles to adherence for adolescents with diabetes.

Twenty adolescents with insulin-dependent diabetes mellitus were interviewed to obtain samples of problem situations that create obstacles to dietary adherence. The resulting 57 situations were analyzed using a reliable coding system to determine the presence or absence of 28 stimulus features. A hierarchical cluster analysis was used to identify 10 relatively homogeneous categories of obstacles to dietary adherence: being tempted to stop trying; negative emotional eating; facing forbidden foods; peer interpersonal conflict; competing priorities; eating at school; social events and holidays; food cravings; snacking when home, alone, or bored; and social pressure to eat. Diabetes educators should consider an individual's ability to cope with this array of obstacles to adherence when individualizing treatment. Dietary intervention then can be personalized to address specific situational obstacles.

Adolescent↗
PubMed2003

Obstacle training programme for individuals post stroke: feasibility study.

OBJECTIVE: The purposes were threefold: to develop an obstacle ambulation training programme, to recruit and retain individuals post chronic stroke and to assess the effectiveness of the obstacle ambulation training programme. DESIGN: Intervention study; case series; baseline to post-intervention measures and one month follow-up after intervention. SETTING: An outpatient department. SUBJECTS: Five individuals with chronic stroke with mild to moderate functional limitations; convenience sample. INTERVENTIONS: Therapy consisted of twice weekly sessions for four weeks during which subjects walked along a walkway and over obstacles. MAIN OUTCOME MEASURES: Motor Assessment Scale--walking section (MAS--time), Six-minute Walk Test distance, walking velocity, and Medical Outcomes Study-36 Health Status Measurement (SF-36). RESULTS: Significant improvements were seen baseline to post intervention for walking velocity, Six-minute Walk Test, MAS and SF-36 physical function score (p < or = 0.025 for all measures). Most improvements noted at the end of training were retained one month later. The effect sizes ranged from 0.33 to 1.20. CONCLUSIONS: Substantial improvement in ambulation function and disability level were seen as a result of the obstacle training programme for individuals with chronic stroke. Further investigation is warranted.

Adult↗
PubMed2004

Answering physicians' clinical questions: obstacles and potential solutions.

OBJECTIVE: To identify the most frequent obstacles preventing physicians from answering their patient-care questions and the most requested improvements to clinical information resources. DESIGN: Qualitative analysis of questions asked by 48 randomly selected generalist physicians during ambulatory care. MEASUREMENTS: Frequency of reported obstacles to answering patient-care questions and recommendations from physicians for improving clinical information resources. RESULTS: The physicians asked 1,062 questions but pursued answers to only 585 (55%). The most commonly reported obstacle to the pursuit of an answer was the physician's doubt that an answer existed (52 questions, 11%). Among pursued questions, the most common obstacle was the failure of the selected resource to provide an answer (153 questions, 26%). During audiotaped interviews, physicians made 80 recommendations for improving clinical information resources. For example, they requested comprehensive resources that answer questions likely to occur in practice with emphasis on treatment and bottom-line advice. They asked for help in locating information quickly by using lists, tables, bolded subheadings, and algorithms and by avoiding lengthy, uninterrupted prose. CONCLUSION: Physicians do not seek answers to many of their questions, often suspecting a lack of usable information. When they do seek answers, they often cannot find the information they need. Clinical resource developers could use the recommendations made by practicing physicians to provide resources that are more useful for answering clinical questions.

Adult↗
PubMed2001

Bipedal locomotion by the normally quadrupedal Japanese monkey, M. Fuscata: strategies for obstacle clearance and recovery from stumbling.

This study explored how the normally quadrupedal Japanese monkey adjusts to treadmill perturbations, when trained to walk bipedally. The monkey was required to use the left hindlimb to clear an obstacle that was fixed on the left side of a treadmill belt. The monkey either cleared the obstacle (CL: cleared locomotion), or stumbled over it (SL: stumbled locomotion). For CL, it changed its left hind limb's kinematics according to the obstacle's height and position relative to the left foot. In SL, the monkey used a "defensive posture", which included a rapid lowering of the right foot and forelimb movements, to stabilize the perturbed posture and thereby prevent falling. Then, with powerful extensions of its lower limb joints, the monkey raised its center-of-mass to the appropriate level for continuation of normal bipedal walking. The results show that M. Fuscata recruited both anticipatory and reactive neural mechanisms to accommodate to the obstacle.

Animals↗
PubMed2002

The effect of creatine monohydrate supplementation on obstacle course and multiple bench press performance.

Dietary creatine (Cr) supplementation has been shown to enhance muscular strength and endurance. This study determined the effects of Cr supplementation on performance of military training tasks. Two groups (Cr and placebo [Pl]) of 13 male soldiers each performed 3 consecutive military obstacle course runs ( approximately 3 minutes over 7 obstacles with a 2-minute rest between runs) followed by a rifle marksmanship task on 3 occasions (T(1), T(2), and T(3)), each separated by 5 days. They also completed a bench press protocol (5 sets to failure at 70% of 1 repetition maximum) and answered the Profile of Mood States questionnaire during each test session. Testing was done 3 times. No supplementation was given before T(1). Supplementation was provided using sports bars, with both groups receiving Pl bars between T(1) and T(2), whereas from T(2) to T(3) the Cr group consumed 24 g per day of Cr monohydrate in sports bars and the Pl group consumed an equal amount (kilocalories) of Pl sports bars. Creatine usage resulted in a significant (14%) increase in total bench press repetitions (p </= 0.05), but no difference between groups in obstacle course run times for the 3 runs from T(2) to T(3). Marksmanship or mood was not affected by Cr supplementation. An increase of 1.4 kg in body mass (p </= 0.005) and a 0.5% decrease in percent body fat (p </= 0.05) were observed after Cr ingestion. Creatine supplementation over 5 days improved performance during a controlled strength test but did not significantly improve military obstacle course performance.

Adult↗
PubMed2005

Developmental changes in the response to obstacles during prehension.

Adults are proficient at reaching to grasp objects of interest in a cluttered workspace. The issue of concern, obstacle avoidance, was studied in 3 groups of young children aged 11-12, 9-10, and 7-8 years (n=6 in each) and in 6 adults aged 18-24 years. Adults slowed their movements and decreased their maximum grip aperture when an obstacle was positioned close to a target object (the effect declined as the distance between target and obstacle increased). The children showed the same pattern, but the magnitude of the effect was quite different. In contrast to the adults, the obstacle continued to have a large effect when it was some distance from the target (and provided no physical obstruction to movement).

Adolescent↗
PubMed2005

Providing end-of-life care to patients: critical care nurses' perceived obstacles and supportive behaviors.

BACKGROUND: Critical care nurses care for dying patients daily. The process of dying in an intensive care unit is complicated, and research on specific obstacles that impede delivery of end-of-life care and/or supportive behaviors that help in delivery of end-of-life care is limited. OBJECTIVE: To measure critical care nurses' perceptions of the intensity and frequency of occurrence of (1) obstacles to providing end-of-life care and (2) supportive behaviors that help in providing end-of-life care in the intensive care unit. METHODS: An experimental, posttest-only, control-group design was used. A national, geographically dispersed, random sample of members of the American Association of Critical-Care Nurses was surveyed. RESULTS: The response rate was 61.3%, 864 usable responses from 1409 eligible respondents. The highest scoring obstacles were frequent telephone calls from patients' family members for information, patients' families who did not understand the term lifesaving measures, and physicians disagreeing about the direction of a dying patient's care. The highest scoring supportive behaviors were allowing patients' family members adequate time alone with patients after death, providing peaceful and dignified bedside scenes after death, and teaching patients' families how to act around a dying patient. CONCLUSIONS: The biggest obstacles to appropriate end-of-life care in the intensive care unit are behaviors of patients' families that remove nurses from caring for patients, behaviors that prolong patients' suffering or cause patients pain, and physicians' disagreement about the plan of care.

Adult↗
PubMed1990

Problems, obstacles, and complications of limb lengthening by the Ilizarov technique.

Difficulties that occur during limb lengthening were subclassified into problems, obstacles, and complications. Problems represented difficulties that required no operative intervention to resolve, while obstacles represented difficulties that required an operative intervention. All intraoperative injuries were considered true complications, and all problems during limb lengthening that were not resolved before the end of treatment were considered true complications. The difficulties that occurred during limb lengthening include muscle contractures, joint luxation, axial deviation, neurologic injury, vascular injury, premature consolidation, delayed consolidation, nonunion, pin site problems, and hardware failure. Late complications are those of loss of length, late bowing, and refracture. Joint stiffness may also be a permanent residual complication. Pain and difficulty sleeping are other problems that arise during limb lengthening, especially in the more extensive cases. Forty-six patients had 60 limb segments lengthened between 1.0 and 16.0 cm, with a mean of 5.6 cm. The average treatment time was approximately one month per centimeter for single-level lengthenings with no deformity and 1.2 months per centimeter with deformity correction. The lengthening index for double-level lengthening was 0.57 month per centimeter with no deformity and 0.90 month per centimeter with correction of deformity. In adults, the lengthening index was 1.7 months per centimeter for single-level and 1.1 months per centimeter for double-level lengthening. There were 35 problems that had to be resolved in the outpatient clinic. There were 11 obstacles that required additional operative intervention to resolve. There were 27 true complications, of which 17 were considered minor and ten were considered major complications. Of the major complications, three interfered with achieving the original goals of treatment. All three required further operative intervention to achieve the original goal. These were nonunion in one and late bowing in two. Despite these problems, obstacles, and complications, the original goals of surgery were achieved in 57 of the 60 limb segments treated. Patient satisfaction was achieved in 94% of 46 cases.

Adult↗
PubMed1991

Obstacles and advocacy in children's mental health services: managing the Medicaid maze.

Of federal programs available, Medicaid offers the greatest potential for serving children's mental health needs. Obstacles to children receiving services through Medicaid are largely determined by a state's policy of regulating services. State policies affect the delivery of mental health services for children in two ways: first, by determining which services to make available, and second, by specifying the conditions of access to those services. Accordingly, this article focuses on obstacles within states' policies that prevent effective utilization of services by children. Specifically, states' choices of eligibility criteria, services, and the procedural obstacles present within payment options are examined. Suggestions for future research are made.

Adolescent↗
PubMed1993

Effects of high frequency stimulation on cardiac tissue with an inexcitable obstacle.

We study numerically the effects of high-frequency stimulation in excitable cardiac tissue with an inexcitable obstacle using a Fitz-Hugh Nagumo type model. We show that if the frequency of stimulation is sufficiently high and the size of the inexcitable obstacle is sufficiently large, then a re-entrant pattern can be initiated. We also show that with overdrive stimulation a re-entrant pattern can be removed provided there are no obstacles at which new re-entrant patterns are created.

Animals↗
PubMed1994

Obstacles on the road towards a neuroscientific theory of mind.

In the efforts to establish neuroscientific theories of the mind, one should distinguish between conceptual and scientific obstacles. The conceptual obstacles comprise, for example, various dualist-materialist philosophical positions, emergentism, failure to distinguish between models and non-models, lack of ontological commitment, and the constraints of language. The scientific obstacles comprise, for example, the lack of methods to describe the behaviour of neuron networks and their properties, the difficulties of establishing transition rules between micro-networks and macro-networks, the difficulties in working with non-Pavlovian paradigms and imposing information processing constraints and informational requirements on brain processes.

Animals↗