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PubMed1995

The orthogonal orientation shift and spatial filtering.

A line abutting two tilted flanks is apparently shifted towards the orientation orthogonal to the flanks and at the same time is reduced in its apparent length. It has been suggested that both effects are caused by band-pass spatial filtering, followed by location of the end points of the line at the peaks in the filtered image. Here implications of the filtering explanation of these effects are explored further. In the first experiment, it was predicted that orientation thresholds (as opposed to biases) would be increased for short line lengths, and would be further increased by abutting bars. The predictions were confirmed. It was shown in experiment 2 that the orientation shift was reduced by a small (4 min arc) gap between target lines and orthogonal flanks. In experiment 3 the threshold elevations and the orientation shift produced by orthogonal and tilted flanks were compared. Last, in experiment 4, the threshold elevations and orientation shift produced by orthogonal and tilted flanks, at different retinal eccentricities varying from 0 to 3.2 deg were compared, and the prediction that the magnitude of the orientation shift would decrease with line length and increase with eccentricity was confirmed. The connection is explored between the orientation shift and the Zöllner illusion, and demonstrations are presented of the Zöllner effect in which target and inducing lines are of opposite contrast on a gray background. It is concluded that the Judd and Zöllner illusions do not depend upon a single mechanism.

Differential Threshold↗
PubMed1998

The analysis of orientation-dependent time costs in visual recognition.

How does the visual system recognise stimuli presented at different orientations? According to the multiple-views hypothesis, misoriented objects are matched to one of several orientation-specific representations of the same objects stored in long-term memory. Much of the evidence for this hypothesis comes from the observation of group mean orientation effects in recognition memory tasks showing that the time taken to identify objects increases as a function of the angular distance between the orientation of the stimulus and its nearest familiar orientation The aim in this paper is to examine the validity of this interpretation of group mean orientation effects. In particular, it is argued that analyses based on group performance averages that appear consistent with the multiple-views hypothesis may, under certain circumstances, obscure a different theoretically relevant underlying pattern of results. This problem is examined by using hypothetical data and through the detailed analysis of the results from an experiment based on a recognition memory task used in several previous studies. Although a pattern of results that is consistent with the multiple-views hypothesis was observed in both the group mean performance and the underlying data, it is argued that the potential limitations of analyses based solely on group performance averages must be considered in future studies that use orientation effects to make inferences about the kinds of shape representations that mediate visual recognition.

Form Perception↗
PubMed1994

Determination of spin-label orientation within the myosin head.

Current methods of analyzing EPR spectra of spin-labeled muscle fibers allow the determination of spin-label orientation within the fiber, rather than the orientation of the myosin head itself. In order to describe the orientational distribution of spin labeled myosin heads within the muscle fibers, the orientation of the spin label within the myosin head must be known. The iodoacetamide label orientation in the myosin head was determined to be (16.8 degrees, 28.3 degrees, 4.2 degrees) or (16.6 degrees, 72.0 degrees, 4.3 degrees). These Eulerian angles were obtained from the analysis of EPR spectra of fibers decorated with labeled myosin heads in the absence of ATP, with the assumption that the head's tilt angle is 40 degrees, as observed in a recent EM study [Pollard, T., Bhandari, D., Maupin, P., Wachsstock, D., Weeds, A. & Zot, H. (1993) Biophys. J. 64, 454-471]. Knowledge of spin-label orientation will allow for quantitative determination of myosin head orientation in the various states of the contractile cycle.

Algorithms↗
PubMed2002

Orientation of bound ligands in mannose-binding proteins. Implications for multivalent ligand recognition.

Mannose-binding proteins (MBPs) are C-type animal lectins that recognize high mannose oligosaccharides on pathogenic cell surfaces. MBPs bind to their carbohydrate ligands by forming a series of Ca(2+) coordination and hydrogen bonds with two hydroxyl groups equivalent to the 3- and 4-OH of mannose. In this work, the determinants of the orientation of sugars bound to rat serum and liver MBPs (MBP-A and MBP-C) have been systematically investigated. The crystal structures of MBP-A soaked with monosaccharides and disaccharides and also the structure of the MBP-A trimer cross-linked by a high mannose asparaginyl oligosaccharide reveal that monosaccharides or alpha1-6-linked mannose bind to MBP-A in one orientation, whereas alpha1-2- or alpha1-3-linked mannose binds in an orientation rotated 180 degrees around a local symmetry axis relating the 3- and 4-OH groups. In contrast, a similar set of ligands all bind to MBP-C in a single orientation. The mutation of MBP-A His(189) to its MBP-C equivalent, valine, causes Man alpha 1-3Man to bind in a mixture of orientations. These data combined with modeling indicate that the residue at this position influences the orientation of bound ligands in MBP. We propose that the control of binding orientation can influence the recognition of multivalent ligands. A lateral association of trimers in the cross-linked crystals may reflect interactions within higher oligomers of MBP-A that are stabilized by multivalent ligands.

Amino Acid Sequence↗
PubMedDate not supplied

Respiratory consequences of exposure to wood dust and formaldehyde of workers manufacturing oriented strand board.

A cross-sectional study was performed at a plant in which 99 workers were employed in the manufacture of oriented strand board. This group was compared with 165 unexposed workers from the petroleum industry. Both groups were assessed, using a questionnaire, spirometry, and skin prick tests to common environmental antigens. Environmental studies showed a low dust level of 0.27 mg/m3, consisting of particles of a mass median aerodynamic equivalent diameter of 2.5 microns. There were variable concentrations of formaldehyde, up to 0.27 ppm. A significant difference between the oriented strand board workers and oil field workers was noted for the forced expiratory volume in 1 s/forced vital capacity ratio, without significant differences in either the forced expiratory volume in 1 s or the forced vital capacity. Oriented strand board workers who were current smokers were three times as likely to have a forced expiratory volume in 1 s/forced vital capacity ratio of less than 75% of that found in the currently smoking oil field workers. Significant reductions in forced expiratory volume in 1 s (p = .044) and forced vital capacity (p = .022) in oriented strand board workers were noted across the work shift. The oriented strand board workers complained of self-reported asthma and of lower respiratory tract symptoms significantly more frequently than did oil workers for all of the symptoms examined. The prevalence of atopy was not different in the two groups. Lung function was significantly better in oriented strand board workers who had no symptoms, compared with oriented strand board workers who were symptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Are the Orientations of the Head and Arm Related During Pointing Movements?

The head, eye, and shoulder are each free to rotate around three mutually orthogonal axes. These three degrees of freedom allow a given gaze or pointing direction of the eye, head, or arm to be obtained in many different possible orientations. Unlike translations in three dimensions, three-dimensional (3-D) rotations are noncommutative. Therefore, the orientation of a rigid body following sequential rotations about two different axes depends on the order of the rotations. In this article, we demonstrate that only two degrees of freedom are used during orienting movements of the head and pointing movements of the arm. This provides a unique orientation of head and arm for each gaze or pointing direction despite the noncommutativity of three-dimensional rotations. This observation is in itself not new. We found, however, that (a) the two-dimensional lquot;rotation surface,rquot; which describes the orientation of the head for all gaze directions, is curved, unlike the analogous flat plane for the eye. (b) The rotation surface for the head is curved differently than that for the arm. This result argues against the hypothesis that the orientations of head and arm are directly coupled during pointing. It also implies that the orientation of the eye in space during gaze shifts of the eye and head is not uniquely determined for a given direction of gaze. This finding argues against a perceptual basis for the reduction of rotational degrees of freedom.

Journal Article↗
PubMed2002

Analysis of performance in orienteering with treadmill tests and physiological field tests using a differential global positioning system.

The aim of this study was to determine the physiological responses to orienteering by examining the interrelationships between the information provided by a differential global positioning system (dGPS) about an orienteer's route, speed and orienteering mistakes, portable metabolic gas analyser data during orienteering and data from incremental treadmill tests. Ten male orienteers completed a treadmill threshold test and a field test; the latter was performed on a 4.3 km course on mixed terrain with nine checkpoints. The anaerobic threshold, threshold of decompensated metabolic acidosis, respiratory exchange ratio, onset of blood lactate accumulation and peak oxygen uptake (VO2peak) were determined from the treadmill test. Time to complete the course, total distance covered, mean speed, distance and timing of orienteering mistakes, mean oxygen uptake, mean relative heart rate, mean respiratory exchange ratio and mean running economy were computed from the dGPS data and metabolic gas analyser data. Correlation analyses showed a relationship between a high anaerobic threshold and few orienteering mistakes (r = - 0.64, P < 0.05). A high threshold of decompensated metabolic acidosis and VO2peak were related to a fast overall time (r = -0.70 to -0.72, P < 0.05) and high running speed (r = 0.64 to 0.79, P < 0.05 and P < 0.01, respectively), and were thus the best predictors of performance.

Adult↗
PubMed2003

Heart rate responses of male orienteers aged 21-67 years during competition.

Orienteering is a sport in which it is common for most participants to be aged over 40 years, but research into the demands of the sport has focused almost exclusively on elite participants aged 21-35 years. The aim of the present study was to examine the heart rate responses of older male orienteers. Thirty-nine competitive male orienteers were divided into three groups: group 1 (international competitive standard, n = 11, age 21-67 years), group 2 (national competitive standard, n = 15, age 24-66 years) and group 3 (club competitive standard, n = 13, age 23-60 years). Each participant had his heart rate monitored during two orienteering races of contrasting technical difficulty. The results were analysed using analysis of covariance, with age as a covariate, and Pearson product-moment correlation coefficients to determine whether age was related to the observed heart rate responses. The groups did not differ in their peak (175 +/- 12 beats x min(-1), P = 0.643) or mean (159 +/- 13 beats x min(-1), P = 0.171) heart rates during the races. There was a decline of 6 beats x min(-1) x decade(-1) (P = 0.001) for peak heart rate and 5 beats x min(-1) x decade(-1) (P < 0.001) for mean heart rate. Mean heart rates were 86 +/- 6% of the participants' maximal heart rates and were not associated with age. The orienteers in group 1 displayed a lower (P < 0.005) within-race standard deviation in heart rate (6 +/- 2 beats x min(-1)) than those in groups 2 and 3 (10 +/- 3 and 10 +/- 4 beats x min(-1), respectively). In conclusion, the mean heart rates indicated that all three groups of orienteers ran at a relative high intensity and the international competitive standard orienteers displayed a less variable heart rate, which may have been related to fewer instances of slowing down to relocate and being able to navigate while running at relatively high speeds.

Adult↗
PubMed2003

Predicting motivational regulations in physical education: the interplay between dispositional goal orientations, motivational climate and perceived competence.

In this study, we examined the main and interactive effects of students' goal orientations, perceived competence and perceptions of the motivational climate on the motivational styles advanced by self-determination theory. The participants were 328 British secondary school students aged 13.6 +/- 0.6 years (mean +/- s). Moderated hierarchical regression analyses revealed task orientation, perceived competence and perceptions of a mastery climate to be positive predictors of self-determined styles of motivation. Perceived competence in physical education was negatively associated with amotivation. Significant interaction effects for mastery climate x task orientation and for ego orientation x perceived competence emerged. The results indicate that: (1) for students endorsing a high task orientation, the perception that the class climate was high in mastery cues was associated with increased intrinsic motivation; and (2) for students high in ego orientation, the belief that one was competent increased, while perceptions of incompetence attenuated intrinsic motivation. Additionally, a three-way interaction between ego orientation, performance climate and perceived competence emerged. In light of achievement goal and self-determination frameworks, we propose that studying the potential interplay between both individual and situational goal perspectives and the moderating effect of perceived competence may further enhance our understanding of motivation in physical education.

Adolescent↗
PubMed1999

Economy in track runners and orienteers during path and terrain running.

The aims of the present study were to assess running economy in track runners and orienteers and to identify the factors responsible for any differences. The participants were 11 orienteers and 10 track runners of similar age, body mass, maximal oxygen uptake and training background. However, the orienteers included heavy terrain running in their daily training, whereas the track runners ran almost entirely on the roads and tracks. Maximal oxygen uptake and running economy were calculated during horizontal path running and during cross-country running in rough terrain with steep hills, using a telemetric system (K2, Cosmed, Italy). Running economy during path running was 217+/-12 and 212+/-14 ml x kg(-1) x km(-1) (mean +/- s) in the orienteers and the track runners, respectively. Running economy was impaired by 41-52% in heavy terrain (P < 0.05), and was less pronounced in the orienteers than in the track runners (88+/-18 vs 109+/-26 ml x kg(-1) x km(-1); P < 0.05). In conclusion, the better running economy of orienteers when changing from horizontal path to heavy terrain running could be an innate ability, or it could be speculated that specific training may improve running economy, indicating the importance of specific training for orienteers.

Adult↗
PubMed2005

Coping strategies, social support, life orientation and health-related quality of life following traumatic brain injury.

OBJECTIVE: To study coping strategies, social support and life orientation in patients following moderate and severe traumatic brain injury (TBI) in relation to health-related quality of life. SUBJECTS: Eighty-five patients with moderate or severe TBI and 68 control persons. METHODS: Estonian versions of the COPE-D test, the Brief Social Support Questionnaire, the Life Orientation Test and the RAND-36 questionnaire. RESULTS: Persons with TBI reported using task-oriented and social/emotional support strategies less often and avoidance-oriented strategies more often than control persons (p < 0.05). The social support network, satisfaction with it and optimism as life orientation were lower in the patient group (p < 0.05). Task-oriented coping styles, satisfaction with social support and optimistic life orientation were associated with the majority of the domains of health-related quality of life and resuming work after TBI. CONCLUSIONS: To achieve effective rehabilitation and to enhance patients' well-being, it is important to improve the quality and amount of social support network, as well as to support patients' adequate coping efforts for promoting an active lifestyle.

Adaptation, Psychological↗
PubMed1991

The relationship of task and ego orientation to sportsmanship attitudes and the perceived legitimacy of injurious acts.

Nicholls's theory of achievement motivation (1989) assumes one's goal orientation in an achievement activity is consistent with one's views concerning what is acceptable behavior in that setting. The purpose of this study was to determine the relationship of a task and ego goal orientation (i.e., the tendency to focus on personal mastery or beating others, respectively) to sportsmanship attitudes and perceptions of the legitimacy of aggressive acts by testing this assumption in the context of interscholastic sport. Fifty-six male and 67 female high school basketball players completed a three-part questionnaire assessing (a) individual differences in goal orientation, (b) approval of "unsportsmanlike play/cheating," "strategic play," and "sportsmanship behaviors," and (c) subjective ratings of the legitimacy of intentionally injurious behaviors. All measures were basketball-specific. Results indicated a low task orientation and high ego orientation corresponded to an endorsement of unsportsmanlike play/cheating. Ego orientation positively related to the rating of aggressive acts as more legitimate. Gender differences in goal orientation, sportsmanship attitudes, and legitimacy ratings were observed.

Achievement↗
PubMed2004

Individual differences of action orientation for risktaking in sports.

The goal of this article is to explain empirical risk-taking behavior in sports from an individual cognitive modeling perspective. A basketball task was used in which participants viewed four video options that varied in the degree of associated risk. The participants were independently classified by scores on the Questionnaire for Assessing Prospective Action Orientation and State Orientation in Success, Failure, and Planning Situations as action-oriented or state-oriented decision makers. The results of the experiment show that action-oriented players shoot faster and more often to the basket and that state-oriented players prefer to pass to a playmaker more often. Four versions of a computational model of decision making, Decision Field Theory, were compared to evaluate whether behavioral differences depend on the focus of attention, the initial preferences, threshold values, or an approach-avoidance interpretation of the task. Different starting preferences explained individual choices and decision times most accurately. Risk taking in basketball shooting behavior can be best explained by different preferences for starting values for risky and safe options caused by different levels of action orientation.

Adult↗
PubMed1992

Role of astral microtubules and actin in spindle orientation and migration in the budding yeast, Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, before the onset of anaphase, the spindle apparatus is always positioned with one spindle pole at, or through, the neck between the mother cell and the growing bud. This spindle orientation enables proper chromosome segregation to occur during anaphase, allowing one replicated genome to be segregated into the bud and the other to remain in the mother cell. In this study, we synchronized a population of cells before the onset of anaphase such that > 90% of the cells in the population had spindles with the correct orientation, and then disrupted specific cytoskeletal elements using temperature-sensitive mutations. Disruption of either the astral microtubules or actin function resulted in improper spindle orientation in approximately 40-50% of the cells. When cells with disrupted astral microtubules or actin function entered into anaphase, there was a 100-200-fold increase in the frequency of binucleated cell bodies. Thus, the maintenance of proper spindle orientation by these cytoskeletal elements was essential for proper chromosome segregation. These data are consistent with the model that proper spindle orientation is maintained by directly or indirectly tethering the astral microtubules to the actin cytoskeleton. After nuclear migration, but before anaphase, bulk chromosome movement occurs within the nucleus apparently because the chromosomes are attached to a mobile spindle. The frequency and magnitude of bulk chromosome movement is greatly diminished by disruption of the astral microtubules but not by disruption of the nonkinetochore spindle microtubules. These results suggest that astral microtubules are not only important for spindle orientation before anaphase, but they also mediate force on the spindle, generating spindle displacement and in turn chromosome movement. Potential roles for this force in spindle assembly and orientation are discussed.

Actins↗
PubMed1999

The role of actin in spindle orientation changes during the Saccharomyces cerevisiae cell cycle.

In the budding yeast Saccharomyces cerevisiae, the mitotic spindle must align along the mother-bud axis to accurately partition the sister chromatids into daughter cells. Previous studies showed that spindle orientation required both astral microtubules and the actin cytoskeleton. We now report that maintenance of correct spindle orientation does not depend on F-actin during G2/M phase of the cell cycle. Depolymerization of F-actin using Latrunculin-A did not perturb spindle orientation after this stage. Even an early step in spindle orientation, the migration of the spindle pole body (SPB), became actin-independent if it was delayed until late in the cell cycle. Early in the cell cycle, both SPB migration and spindle orientation were very sensitive to perturbation of F-actin. Selective disruption of actin cables using a conditional tropomyosin double-mutant also led to defects in spindle orientation, even though cortical actin patches were still polarized. This suggests that actin cables are important for either guiding astral microtubules into the bud or anchoring them in the bud. In addition, F-actin was required early in the cell cycle for the development of the actin-independent spindle orientation capability later in the cell cycle. Finally, neither SPB migration nor the switch from actin-dependent to actin-independent spindle behavior required B-type cyclins.

Actins↗
PubMed1969

Chromosome micromanipulation. 3. Spindle fiber tension and the reorientation of mal-oriented chromosomes.

Kinetochore reorientation is the critical process ensuring normal chromosome distribution. Reorientation has been studied in living grasshopper spermatocytes, in which bivalents with both chromosomes oriented to the same pole (unipolar orientation) occur but are unstable: sooner or later one chromosome reorients, the stable, bipolar orientation results, and normal anaphase segregation to opposite poles follows. One possible source of stability in bipolar orientations is the normal spindle forces toward opposite poles, which slightly stretch the bivalent. This tension is lacking in unipolar orientations because all the chromosomal spindle fibers and spindle forces are directed toward one pole. The possible role of tension has been tested directly by micromanipulation of bivalents in unipolar orientation to artificially create the missing tension. Without exception, such bivalents never reorient before the tension is released; a total time "under tension" of over 5 hr has been accumulated in experiments on eight bivalents in eight cells. In control experiments these same bivalents reoriented from a unipolar orientation within 16 min, on the average, in the absence of tension. Controlled reorientation and chromosome segregation can be explained from the results of these and related experiments.

Animals↗
PubMed1972

The orientation of rhodopsin and other pigments in dry films.

When rhodopsin in a gelatin film is dried, the rhodopsin chromophores orient primarily in the plane of the film. When the film is wetted, the chromophores disorient. These changes are reversible. When rhodopsin in a wet film. is bleached in the presence of hydroxylamine and redried, the retinal oxime which results is oriented more perpendicularly to the plane of the film. These orientations in dry gelatin films resemble those in the disc membranes of rod outer segments. A variety of other proteins are similarly oriented in dry gelatin films: methemoglobin, cytochrome c, phycocyanin. Films of methemoglobin and cytochrome c display prominently the high Soret band near 410 nm when measured with unpolarized light passing through the face of the fim, but display no Soret band at all with light passing through the edge of the film. All of these orientations imply a large asymmetry of the protein micelles, perhaps conferred upon them by linear polymerization in the course of drying. Such asymmetry can be demonstrated directly with rhodopsin. A wet paste of rhodopsin-digitonin micelles, sheared between glass slides, becomes highly oriented, the rhodopsin chromophores lining up in the direction of shear, the retinal oxime produced by bleaching orienting more perpendicularly to the shear.

Acetates↗
PubMed2003

Optimization of beam orientations and beam weights for conformal radiotherapy using mixed integer programming.

An algorithm for optimizing beam orientations and beam weights for conformal radiotherapy has been developed. The algorithm models the optimization of beam orientations and beam weights as a problem of mixed integer linear programming (MILP), and optimizes the beam orientations and beam weights simultaneously. The application process of the algorithm has four steps: (a) prepare a pool of beam orientation candidates with the consideration of avoiding any patient-gantry collision and avoiding direct irradiation of organs at risk with quite low tolerances (e.g., eyes). (b) Represent each beam orientation candidate with a binary variable, and each beam weight with a continuous variable. (c) Set up an optimization problem according to dose prescriptions and the maximum allowed number of beam orientations. (d) Solve the optimization problem with a ready-to-use MILP solver. After optimization, the candidates with unity binary variables remain in the final beam configuration. The performance of the algorithm was tested with clinical cases. Compared with standard treatment plans, the beam-orientation-optimized plans had better dose distributions in terms of target coverage and avoidance of critical structures. The optimization processes took less than 1 h on a PC with a Pentium IV 2.4 GHz processor.

Algorithms↗