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At least 1,243 records · Page 69Linked to original sources
PubMed1980

[Investigations of stability with the fixateur externe during strain of bending. Vertical and eccentric strain during compression of the fracture line and while the distance of support is changed (author's transl)].

The Fixateur externe was investigated under vertical and eccentric load when the fracture line was compressed and the distance of support was changed. Three kinds of mounting were used: R (Fixateur externe as frame), Z (three dimensional Fixateur externe) and Z2S (three dimensional Fixateur externe with two screws according to Schanz). If the distance of outer support was increased, the stability became greatly reduced. A compression increased the stability around the fracture line and on the free end of the system. A compression force of 10 kp at the fracture line yielded the greatest increase in stability. If in case of the methods R and Z, the compression was increased beyond 70 kp, there resulted even an instability, which depended on the distance of support. The most stable method of mounting was the three-dimensional Fixateur externe with two screws according to Schanz. The stability was compared if there was either a defect or a compression at the line of the fracture: there resulted a strikingly increased instability, if the distance of support was increased. The compression made it possible to compensate partly for the loss of stability.

Biomechanical Phenomena↗
PubMed1999

[What is the value of determining walking distance in peripheral arterial occlusive disease on the treadmill and in daily life? Prospective correlation study].

AIM: To investigate the question whether and how walking distances measured under standardized conditions on the treadmill and on the level correlate with the patients walking ability under everyday conditions. PATIENTS AND METHOD: In 49 patients (33 men, 16 women, age 34 to 84 years) with Fontaine Stage II peripheral arterial occlusive disease the pain-free and absolute walking distance on the treadmill were measured under standardized conditions, as also the walking distance on the level at freely selected speed. RESULT: It was found that the pain-free walking distance under everyday conditions was about 2 to 3 times longer than that measured under standardized conditions on the treadmill.

Adult↗
PubMed2005

Accuracy of an electromagnetic tracking device for measuring hip joint kinematics during gait: effects of metallic total hip replacement prosthesis, source-sensor distance and sensor orientation.

The present study sought to investigate the effects of source-sensor distance, sensor orientation and the effects of metallic total hip replacement (THR) prostheses on the accuracy of the 3Space Tracker System (3STS). Using a simulated hip joint, the angles measured by the 3STS with six different source-sensor distances and two source-sensor orientations were recorded. Then the angles measured in the absence and presence of three different THR prostheses were compared. Both source-sensor distance and sensor orientation affects the accuracy of the 3STS. Measurements were only affected by the presence of one type of prosthesis. The 3STS was equally reliable, but less accurate with source-sensor distances of more than 25 cm. The small angular error and insensitivity of this device to the presence of some metallic THR prostheses make it a useful measurement tool for gait studies performed before and after THR surgery.

Arthroplasty, Replacement, Hip↗
PubMed2001

Distance learning in the digital environment.

The expansion of radiology departments and divisions often can not occur in adjacent geographic locations. This leads to a greater separation of staff and residents, as well as workers in similar divisions. This makes traditional teaching difficult in academic institutions. The economic drive forcing many departments to investigate more isolated outpatient imaging centers has further hindered the ability to continue effective academic training at many facilities. The ability to easily share a digital environment across physical distance can greatly enhance the teaching experience, as well as be a valuable tool for consultation and case discussion with referring clinicians. The transition to a filmless environment with picture archiving and communication systems (PACS) can be utilized for distance learning in addition to the clinical arena. It is possible to take advantage of the digital transformation to PACS and case-viewing browser programs to conduct improved interactions with referring clinicians as well as radiologic teaching with relatively minimal hardware and software demands. The integration of web-based teleradiology programs with business networking software can be used for effective distance learning in the digital environment, sufficiently closing the distance on our rapidly expanding departments. This same technology allows for greater interaction with referring clinicians for real-time consultation and enhanced case discussion to entrench a supportive referral base for the radiologic community.

Humans↗
PubMed1997

Accuracies of ancestral amino acid sequences inferred by the parsimony, likelihood, and distance methods.

Information about protein sequences of ancestral organisms is important for identifying critical amino acid substitutions that have caused the functional change of proteins in evolution. Using computer simulation, we studied the accuracy of ancestral amino acids inferred by two currently available methods (maximum-parsimony [MP] and maximum-likelihood [ML] methods) in addition to a distance method, which was newly developed in this paper. All three methods give reliable inference when the divergence of amino acid sequences is low. When the extent of sequence divergence is high, however, the ML and distance methods give more accurate results than the MP method, particularly when the phylogenetic tree includes long branches. The accuracy of inferred ancestral amino acids does not change very much when a few present-day sequences are added or eliminated. When an incorrect model of amino acid substitution is used for the ML and distance methods, the accuracy decreases, but it is still higher than that for the MP method. When the tree topology used is partially incorrect, the accuracy in the correct part of the tree is virtually unaffected. The posterior probability of inferred ancestral amino acids computed by the ML and distance methods is an unbiased estimate of the true probability when a correct substitution model is used but may become an overestimate when a simpler model is used.

Amino Acid Sequence↗
PubMed1997

[Acromio-humeral distance and acromial shape in 3-dimensional computerized tomography reconstruction. Side comparison in supraspinatus outlet syndrome].

Mechanical irritations of the supraspinatus tendon due to a reduction of the subacromial space are considered to be a potential cause of supraspinatus outlet syndrome. The aim of the current study was, therefore, to provide a method of improved measurement of the acromiohumeral distance and the evaluation of the acromial shape. In seven patients aged 50-60 years with unilateral supraspinatus outlet syndrome, imaging with standardized, high-resolution computed tomography (CT) was performed in order to demonstrate the acromion and the subacromial space three-dimensionally. The acromiohumeral distance was measured in three reconstructed frontal sections, and the two sides of each patient were directly compared. The acromial shape was compared with the classification of Bigliani as derived from conventional radiography. Whereas the Constant Score was found to be significantly reduced in the diseased shoulders (p < 0.01), the acromiohumeral distance was not significantly lower in three standardized frontal sections. In five cases the classification of the acromial form from the conventional radiograph was confirmed by 3D CT, whereas in two cases it was shown to be different. Our results suggest that primary or secondary changes of the acromial form can be more accurately evaluated with 3D CT than with conventional radiography. A direct comparison of the two sides in patients with supraspinatus syndrome does not suggest a reduction of acromiohumeral distance in the diseased shoulder.

Female↗
PubMed2001

Dependence of linkage of alleles on their physical distance in natural transformation of Acinetobacter sp. strain ADP1.

The interdependence of genetic linkage in transformation and physical distance was studied in the bacterium Acinetobacter sp. strain ADP1. Transformation experiments were performed using 17 strains containing different mutations within the 21-kb pca-qui-pob gene cluster as recipients for the DNA of one of two strains carrying a mutation causing a temperature-sensitive phenotype. The different phenotypes of the transformants (temperature-sensitive or wild-type-like) were used to evaluate linkage. Combination of the recipient and donor strains resulted in physical distances ranging from 2 bp to 10,533 bp. A logarithmic relationship of decreasing linkage and increasing distance was observed, thus leading to calibration of a system for analysis of physical distance derived from linkage data. Limitations of this application are described here: Certain mutations (3 out of 17 mutations used in this study) are an exception to the observed relationship and result in much lower linkage than expected. Observed DNA sequence repetitions leading to DNA rearrangements may be the cause of this anomaly.

Acinetobacter↗
PubMed2002

Vertical memory-based disconjugate learning for downward saccades at a viewing distance of 70 cm: relation to horizontal vergence and to vertical phoria.

The goal of this study was to examine vertical disconjugate learning based on memorization of vertical disparity at a viewing distance of 70 cm; such a distance is common in many visual ergonomic conditions, including car driving. For a period of 15 min, eight subjects made downward saccades to a memorized target. The target was rendered disparate with the use of a magnifier placed in front of one eye. Learning occurred in only four of the subjects: saccades became disconjugate and the disconjugacy was retained when the target was not disparate. These observations extend a prior study dealing with a longer distance (1 m) and indicate that such learning is subject dependent for both viewing distances. Importantly, the present study shows, for the first time, that vertical disconjugate learning is related to two other phenomena: (a) the horizontal vergence present during vertical saccades and (b) the degree of vertical phoria normal subjects exhibit.

Adolescent↗
PubMed2005

Humans use continuous visual feedback from the hand to control both the direction and distance of pointing movements.

Vision of the hand during reaching provides dynamic feedback that can be used to control movement. We investigated the relative contributions of feedback about the direction and distance of the hand relative to a target. Subjects made pointing movements in a 3-D virtual environment, in which a small sphere provided dynamic visual feedback about the position of their unseen fingertip. On a subset of trials, the position of the virtual fingertip was smoothly shifted by 2 cm during movement, either (1) in the direction of movement, which would require adjustments to the distance moved, or (2) orthogonal to the direction of movement, which would require adjustments to the direction moved. Despite not noticing the perturbations, subjects adjusted their movements to compensate for both types of visual shifts. Corrective responses to direction perturbations were observed within 117 ms, and response latencies were invariant to movement speed and perturbation onset time. Initial corrections to distance perturbations were smaller and appeared after longer delays of 130-200 ms, and both the speed and magnitude of responses were reduced for early onset perturbations. Simulations of a feedback control model that optimally integrates visual information over time show that the results can be explained by differences in the sensory noise levels in the visual dimensions relevant for direction and distance control.

Adaptation, Physiological↗
PubMed2001

Vertical gaze angle as a distance cue for programming reaching: insights from visual form agnosia II (of III).

It has been shown that a patient with visual form agnosia (DF) relies predominantly on vergence information when gauging target distance in an open-loop pointing task. This finding suggested that the programming of prehension might be severely disrupted if DF viewed target objects through ophthalmic prisms. An initial experiment showed that this prediction was not upheld; DF was able to programme reasonably accurate movements to objects located on a tabletop despite large changes in vergence angle. A second experiment, however, showed that placing the target objects at eye height whilst manipulating vergence angle caused gross disruption to prehension, with DF mis-programming the reach component in a predictable manner. Notably, the evidence for DF's reliance on vergence distance information was obtained in a task where the targets were viewed at eye height. These experiments indicate that DF uses vertical gaze angle to gauge target distance in normal prehension and suggest that this extra-retinal cue may be a useful source of distance information for the human nervous system, especially where pictorial cues are impoverished.

Agnosia↗
PubMed2005

The effect of tumour type and distance on activation in the motor cortex.

Functional MRI has been widely used to identify the eloquent cortex in neurosurgical/radiosurgical planning and treatment of CNS neoplasms and malformations. In this study we examined the effect of CNS tumours on the blood oxygenation level-dependent (BOLD) activation maps in the primary and supplementary motor cortex. A total of 33 tumour patients and five healthy right-handed adults were enrolled in the study. Patients were divided into four groups based on tumour type and distance from primary motor cortex: (1) intra-axial, near, (2) extra-axial, near, (3) intra-axial, far and (4) extra-axial, far. The intra-axial groups consisted of patients with astrocytomas, glioblastomas and metastatic tumours of mixed histology; all the extra-axial tumours were meningiomas. The motor task was a bilateral, self-paced, finger-tapping paradigm. Anatomical and functional data were acquired with a 1.5 T GE Echospeed scanner. Maps of the motor areas were derived from the BOLD images, using SPM99 software. For each subject we first determined the activation volume in the primary motor area and the supplementary motor area (SMA) and then calculated the percentage difference between the hemispheres. Two factors influenced the activation volumes: tumour type (P<0.04) and distance from the eloquent cortex (P<0.06). Patients in group 1 (intra-axial, near) had the smallest activation area in the primary motor cortex, the greatest percentage difference in the activation volume between the hemispheres, and the largest activation volume in the SMA. Patients in group 4 (extra-axial, far) had the largest activation volume in the primary motor cortex, the least percentage difference in volume between the hemispheres, and the smallest activation volume in the SMA. There was no significant change in the volume of the SMA in any group, compared with controls, suggesting that, although there is a gradual decrease in SMA volume with distance from the primary motor area, the effect on motor reorganisation is minimal. All the tumour patients showed a net loss in total activation volumes (both hemispheres plus SMA) compared with controls. The effect of the tumours on interhemispheric volume differences was: group 1>group 3>group 2>group 4. Within the intra-axial tumours, there was no significant effect of tumour type on the results. We conclude that BOLD-imaged activation volume is affected at least by the interplay of two factors: tumour type and distance from the motor cortex. Further, all tumours may be expected to cause some loss of activation volumes in motor areas. We suggest that, with proper precautions and planning, BOLD functional magnetic resonance imaging (fMRI) maps can be useful in minimising damage to the functional areas.

Adult↗
PubMed2005

Energy cost of swimming of elite long-distance swimmers.

The aim of this study was: (1) to assess the energy cost of swimming (C(s), kJ km(-1)) in a group of male (n = 5) and female (n = 5) elite swimmers specialised in long-distance competitions; (2) to evaluate the possible effect of a 2-km trial on the absolute value of C(s). C(s) was assessed during three consecutive 400-m trials covered in a 50-m pool at increasing speeds (v1, v2, v3). After these experiments the subjects swam a 2-km trial at the 10-km race speed (v2km) after which the three 400-m trials were repeated at the same speed as before (v5 = v1, v6 = v2, v7 = v3). C(s) was calculated by dividing the net oxygen uptake at steady state VO2ss by the corresponding average speed (v, m s(-1)). VO2ss was estimated by using back extrapolation technique from breath-to-breath VO2 recorded during the first 30 s of recovery after each test. C(s) increased (from 0.69 kJ m(-1) to 1.27 kJ m(-1)) as a function of v (from 1.29 m s(-1) to 1.50 m s(-1)), its values being comparable to those measured in elite short distance swimmers at similar speeds. In both groups of subjects the speed maintained during the 2-km trial (v2km) was on the average only 1.2% faster than of v2 and v6 (P>0.05), whereas C(s) assessed at the end of the 2-km trial (v2km) turned out to be 21 +/- 26% larger than that assessed at v2 and v6 (P<0.05); the average stroke frequency (SF, cycles min(-1)) during the 2-km trial turned to be about 6% (P<0.05) faster than that assessed at v2 and v6. At v5, C(s) turned out to be 19 +/- 9% (P<0.05) and 22 +/- 27% (0.1 < P = 0.05) larger than at v1 in male and female subjects (respectively). SF was significantly faster (P<0.05, in male subjects) and the distance per stroke (Ds = v/SF) significantly shorter (P<0.05) in female subjects at v5 and v6 than at v1 and v2. These data suggest that the increase of C(s) found after the 2-km trial was likely related to a decrease in propelling efficiency, since the latter is related to the distance per stroke.

Adult↗
PubMed2006

Distance of walking in childhood and femoral bone density in perimenopausal women.

Kuopio osteoporosis risk factor and prevention (OSTPRE) study is a population-based study from Eastern Finland. At baseline in 1989-91, bone densitometry of lumbar spine and femoral neck as assessed by DXA was carried out on women aged 48-58 (n = 3,222). In 1993, menarcheal age and health habits during adolescence were inquired from a postal inquiry. In 1996, a random sample of 254 women who had been premenopausal at baseline was interviewed over phone. They were asked how many kilometers per day they had walked to school and back, in each grade of primary school. The study sample (N = 185) was formed by excluding women with menarcheal age of >14 or <11 years. Women with any reported HRT history were also excluded. The mean age of the study sample was 50.7 (1.63) years, weight 70.8 (13.1) kg, height 161.5 (5.0) cm, and mean walking distance to and fro from the school at ages from 9 to 11 years was 2.7 (1.7) km. In regression analysis, the walking distance was associated with femoral BMD (r = 0.18, P = 0.015). After adjusting for baseline age, weight and height, this association persisted (P = 0.025). When walking distance was categorized as I = 0-0.549 km, II = 0.55-1.99 km, III = 2.0-4.99 and IV = 5.0 km and more, the respective means for femoral BMDs were 0.92, 0.97, 0.98 and 1.01 g/cm(2). Statistical significance persisted after adjusting for height, weight, age, grip strength, calcium intake, smoking, place of residence, use of contraceptive pills, physical load of work and baseline physical activity (P = 0.032). A 10 year follow-up revealed no changes in bone loss rate between the groups and femoral BMD benefits persisted (repeated measures analysis = NS). Walking distance was not associated with spinal bone density. Even though walking is a low impact activity, walking before menarche may have a moderate but long-lasting positive effect on femoral peak bone density. Lack of walking and similar low impact physical activities during peak growth years may have a negative effect on peak bone mass formation.

Aging↗
PubMed2005

Predatory search algorithm with restriction of solution distance.

A variety of methods and algorithms have been developed to solve NP-Hard problems in recent decades. In this paper, we are concerned with a relatively new algorithm based on animal behavioral adaptability and evolutionary computation, namely predatory search. When first introduced, the algorithm was implemented with restrictions based on solution cost as a simplification of distance adopted by search-intensive predators. Our research concentrates on exploring the possibility of using distance to restrict search area. Based on the research of Boese et al. (1994), we propose a type of predatory search algorithm restricted by solution distance (particularly bond distance), and compare it with the original algorithm based on three benchmark traveling salesman problems. The results indicate that both algorithms are suitable for solving the traveling salesman problems, while our proposed algorithm either outperforms or at least matches its predecessor with respect to both the running time and the quality of solutions. In addition, further experiments suggest that there exists a certain relationship between the two algorithms.

Algorithms↗
PubMed2004

Seed dispersal by white-tailed deer: implications for long-distance dispersal, invasion, and migration of plants in eastern North America.

For many plant species in eastern North America, short observed seed dispersal distances (ranging up to a few tens of meters) fail to explain rapid rates of invasion and migration. This discrepancy points to a substantial gap in our knowledge of the mechanisms by which seeds are dispersed long distances. We investigated the potential for white-tailed deer ( Odocoileus virginianus Zimm.), the dominant large herbivore in much of eastern North America, to disperse seeds via endozoochory. This is the first comprehensive study of seed dispersal by white-tailed deer, despite a vast body of research on other aspects of their ecology. More than 70 plant species germinated from deer feces collected over a 1-year period in central New York State, USA. Viable seeds included native and alien herbs, shrubs, and trees, including several invasive introduced species, from the full range of habitat types in the local flora. A mean of >30 seeds germinated per fecal pellet group, and seeds were dispersed during all months of the year. A wide variety of presumed dispersal modes were represented (endo- and exozoochory, wind, ballistic, ant, and unassisted). The majority were species with small-seeded fruits having no obvious adaptations for dispersal, underscoring the difficulty of inferring dispersal ability from diaspore morphology. Due to their broad diet, wide-ranging movements, and relatively long gut retention times, white-tailed deer have tremendous potential for effecting long-distance seed dispersal via ingestion and defecation. We conclude that white-tailed deer represent a significant and previously unappreciated vector of seed dispersal across the North American landscape, probably contributing an important long-distance component to the seed shadows of hundreds of plant species, and providing a mechanism to help explain rapid rates of plant migration.

Animals↗
PubMed2005

Do distances among host patches and host density affect the distribution of a specialist parasitoid?

The effect of spatial habitat structure and patchiness may differ among species within a multi-trophic system. Theoretical models predict that species at higher trophic levels are more negatively affected by fragmentation than are their hosts or preys. The absence or presence of the higher trophic level, in turn, can affect the population dynamics of lower levels and even the stability of the trophic system as a whole. The present study examines different effects of spatial habitat structure with two field experiments, using as model system the parasitoid Cotesia popularis which is a specialist larval parasitoid of the herbivore Tyria jacobaeae. One experiment examines the colonisation rate of the parasitoid and the percentage parasitism at distances occurring on a natural scale; the other experiment examines the dispersal rate and the percentage parasitism in relation to the density of the herbivore and its host plant. C. popularis was able to reach artificial host populations at distances up to the largest distance created (at least 80 m from the nearest source population). Also, the percentage parasitism did not differ among the distances. The density experiment showed that the total number of herbivores parasitised was higher in patches with a high density of hosts, regardless of the density of the host plant. The percentage parasitism, however, was not related to the density of the host. The density of the host plant did have a (marginally) significant effect on the percentage parasitism, probably indicating that the parasitoid uses the host plant of the herbivore as a cue to find the herbivore itself. In conclusion, the parasitoid was not affected by the spatial habitat structure on spatial scales that are typical of local patches.

Animals↗
PubMed2004

Bone assessment of female long-distance runners.

The objective of the present study was to investigate the effects of long-distance training on the bones in different growth stages by evaluating the bones of female high school athletes and female adult athletes who engage in long-distance training. Thirteen female high school athletes (aged 15-17 years) and 7 female adult athletes (aged 21-25 years) were enrolled in the present study. Bone mineral density (BMD) and bone mineral content (BMC) were measured using dual X-ray absorptiometry (DXA). Cortical bone status was also evaluated by measuring the tibial speed of sound (t-SOS). The bone metabolic status was evaluated by osteocalcin (OC) and tartrate-resistant acid phosphatase (TRAP). OC ( P < 0.01) and lumbar BMD ( P < 0.05) were significantly higher in high school athletes who were in the modeling period than in the adult athletes. Leg BMD ( P < 0.01) and t-SOS ( P < 0.05) were significantly higher in adult athletes who were in the remodeling period than in high school athletes. When lumbar BMD and leg BMD were compared according to menstrual conditions, the high school athletes with regular menstruation showed a significantly higher level of bone density than those having irregular or absent menstruation. These results indicate that the effect of long-distance training on bone metabolism is influenced strongly by sex hormones during late puberty. We concluded that the effect of long-distance training on bone metabolism in the female high school athletes (i.e., during puberty) was different from that in the adult athletes.

Acid Phosphatase↗
PubMed2006

Patchy distribution fields: sampling distance unit of an interleaved survey and reconstruction adequacy.

A mathematical model was used to examine the effects of choosing various units of sampling distance of an interleaved (two-pass) acoustic survey on the adequacy of reconstructing patchy distribution fields. The model simulates fish or plankton patches (or gaps) of different shapes and spatial orientations, and an interleaved survey by parallel or zigzag transects, along which a unit of sampling distance is set. The efficiency of a survey is determined by the adequacy of a reconstructed field to that originally generated, which is evaluated by calculating their correlations (r). Regarding immovable fields, the experiments conducted indicate that a patchy field can be reconstructed properly (r2 > 0.70) if the distance between transects D < (1.5-2.0)R and the unit of sampling distance d < (1.5- 2.0)R(p). As, for regular surveys d < (1.0-1.5)R(p), it may be concluded that interleaved surveys are more efficient than regular ones because of the factor studied. In regard to movable fields, a comparison of the results of interleaved surveys with those of regular surveys directly indicates that the former may ensure a more adequate field reconstruction than the latter do. This fact confirms the previous conclusion that an interleaved survey is expedient in cases where there is no preference regarding the position of a vessel for further work.

Acoustics↗