Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “trajectory”

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 235 records · Page 13Linked to original sources
PubMedDate not supplied

Comparison of head- and body-velocity trajectories during locomotion among healthy and vestibulopathic subjects.

The optimal strategies for improving locomotor stability in people with vestibulopathy remain unclear. To help identify likely targets for intervention, we sought to determine whether vestibulopathic postural control impairment during locomotor activity was more localized to either the head or the whole body. We used high curvature analysis (HCA) to quantify the smoothness of head- and body-velocity trajectories during repeated stepping in 18 vestibulopathic and 17 healthy subjects. We employed a mixed-model repeated measures analysis of variance to compare differences in head- and body-trajectory HCA scores. Pearson coefficients were used to describe relationships between head- and body-trajectory HCA scores within each group. The results revealed that neither head- nor body-velocity trajectories were relatively more impaired in subjects with vestibulopathy. Importantly, however, the smoothness of head and body trajectories was more strongly related in subjects with vestibulopathy compared with healthy subjects, suggesting that the fundamental motor control impairment produced by vestibulopathy may be related to an abnormal coupling of head and body motion. We discuss implications for locomotor training in patients with vestibulopathy.

Adult↗
PubMed2004

The illness trajectory of end-stage renal disease dialysis patients.

Chronic illness is the number one health problem in the United States. As a consequence, health care professionals have assumed an increasingly important role in helping patients and families manage illness over an extended period of time. Familiarity with the evolution of chronic illness is needed to increase the effectiveness of these efforts. The concept of a trajectory provides a way for clinicians to gain a fuller understanding of the changing nature of chronic illness. The trajectory model has not yet been used to define the experience of end-stage renal disease (ESRD). ESRD is typically viewed as the static end point of chronic renal failure. The new paradigm suggests that the experience of ESRD continues to evolve from the time of diagnosis until death and that it follows a trajectory that can be described. This article represents the first attempt to delineate the ESRD illness trajectory, including the characteristics of each phase relative to the dimensions of life. The significance of the trajectory for clinical practice is discussed as well as the need for further research to validate and refine the model.

Activities of Daily Living↗
PubMed1985

Perceptual information for batting can be extracted throughout a ball's trajectory.

Studies of batters' eye movements have demonstrated that batters do not (or cannot) maintain fixation on the ball throughout its trajectory. In addition, the velocity of a pitched ball, together with the limitations of human reaction time, seems to imply that only the first portions of the ball's trajectory provide information to batters. We prevented nine experienced fast pitch softball players from viewing the ball during the first, middle, or last third of its trajectory and found that seeing the first third of the ball's trajectory is not as critical as had been thought: batters are very good at making do with whichever two-thirds of the ball's trajectory is visible. The results demonstrate the importance of peripheral vision and indicate that batters can extract perceptual information for batting throughout the flight of the ball.

Baseball↗
PubMed2004

Perspective distortion of trajectory forms and perceptual constancy in visual event identification.

Previous studies have shown that people can use the information in trajectory forms to recognize visual events. A trajectory form is composed of the path of motion and the change in speed along that path. In past studies, however, only sensitivity to trajectory forms viewed from a single perspective was examined. The optical components change when an event is viewed from different perspectives, and the projected form of the trajectory is transformed. Does event recognition exhibit constancy despite these changes? In Experiment 1, participants were familiarized with five different trajectory forms viewed from a single perspective. Then the participants had to identify the same events viewed from different perspectives: from the side, at an angle, and entirely in depth. The participants exhibited perceptual constancy. Experiment 2 revealed, however, that both the change in optical components and the perspective transformations affected recognition.

Feedback↗
PubMedDate not supplied

Quantifying ataxia: ideal trajectory analysis--a technical note.

We describe a quantitative method to assess repeated stair stepping stability. In both the mediolateral (ML) and anterioposterior (AP) directions, the trajectory of the subject's center of mass (COM) was compared to an ideal sinusoid. The two identified sinusoids were unique in each direction but coupled. Two dimensionless numbers-the mediolateral instability index (IML) and AP instability index (IAP)-were calculated using the COM trajectory and ideal sinusoids for each subject with larger index values resulting from less stable performance. The COM trajectories of nine nonimpaired controls and six patients diagnosed with unilateral or bilateral vestibular labyrinth hypofunction were analyzed. The average IML and IAP values of labyrinth disorder patients were respectively 127% and 119% greater than those of controls (p<0.014 and 0.006, respectively), indicating that the ideal trajectory analysis distinguishes persons with labyrinth disorder from those without. The COM trajectories also identify movement inefficiencies attributable to vestibulopathy.

Adult↗
PubMed2000

Parents' perceptions of chronic illness trajectories.

The notion of a small, generic set of chronic illness trajectories that can be independent of specific medical diagnoses, though controversial, has some theoretical, clinical, and qualitative research support. The purpose of this study was to quantitatively describe trajectories among parents of children with a chronic condition. It was hypothesized that factor analysis would confirm 3 trajectories similar to those in the qualitative literature and that parents' perceptions of their child's trajectory would differ significantly from medically based perceptions. A total of 140 parents provided data on their perceptions of the past, present, and future course of the condition of their repeatedly hospitalized child. Fourteen time-related items from the Coping Health Inventory for Parents Questionnaire on Resources and Stress and the Parenting Stress Index were analyzed. Pre- and post-hospitalization factor analyses extracted the same 8 items to construct 3 trajectories: Life Threatening; Declining; and Stable, Optimistic. The views of approximately one third of the parents differed from medically based classifications. Type of nursing care had no bearing on the perceptions of the parents.

Adaptation, Psychological↗
PubMed2002

Monocular motion adaptation affects the perceived trajectory of stereomotion.

Perceived stereomotion trajectory was measured before and after adaptation to lateral motion in the dominant or nondominant eye to assess the relative contributions of 2 cues: changing disparity and interocular velocity difference. Perceived speed for monocular lateral motion and perceived binocular visual direction (BVD) was also assessed. Unlike stereomotion trajectory perception, the BVD of static targets showed an ocular dominance bias, even without adaptation. Adaptation caused equivalent biases in perceived trajectory and monocular motion speed, without significantly affecting perceived BVD. Predictions from monocular motion data closely match trajectory perception data, unlike those from BVD sources. The results suggest that the interocular velocity differences make a significant contribution to stereomotion trajectory perception.

Adaptation, Psychological↗
PubMed2004

Radarsat observations and forecasting of oil slick trajectory movements.

RADARSAT data have a potential role for coastal pollution monitoring. This study presents a new approach to detect and forecast oil slick trajectory movements. The oil slick trajectory movements is based on the tidal current effects and Fay's algorithm for oil slick spreading mechanisms. The oil spill trajectory model contains the integration between Doppler frequency shift model and Lagrangian model. Doppler frequency shift model implemented to simulate tidal current pattern from RADARSAT data while the Lagrangian model used to predict oil spill spreading pattern. The classical Fay's algorithm was implemented with the two models to simulate the oil spill trajectory movements. The study shows that the slick lengths are effected by tidal current V component with maximum velocity of 1.4 m/s. This indicates that oil slick trajectory path is moved towards the north direction. The oil slick parcels are accumulated along the coastline after 48 h. The analysis indicated that tidal current V components were the dominant forcing for oil slick spreading.

Algorithms↗
PubMed2005

Inattention/hyperactivity and aggression from early childhood to adolescence: heterogeneity of trajectories and differential influence of family environment characteristics.

Inattention/hyperactivity and aggressive behavior problems were measured in 335 children from school entry throughout adolescence, at 3-year intervals. Children were participants in a high-risk prospective study of substance use disorders and comorbid problems. A parallel process latent growth model found aggressive behavior decreasing throughout childhood and adolescence, whereas inattentive/hyperactive behavior levels were constant. Growth mixture modeling, in which developmental trajectories are statistically classified, found two classes for inattention/hyperactivity and two for aggressive behavior, resulting in a total of four trajectory classes. Different influences of the family environment predicted development of the two types of behavior problems when the other behavior problem was held constant. Lower emotional support and lower intellectual stimulation by the parents in early childhood predicted membership in the high problem class of inattention/hyperactivity when the trajectory of aggression was held constant. Conversely, conflict and lack of cohesiveness in the family environment predicted membership in a worse developmental trajectory of aggressive behavior when the inattention/hyperactivity trajectories were held constant. The implications of these findings for the development of inattention/hyperactivity and for the development of risk for the emergence of substance use disorders are discussed.

Adolescent↗
PubMed2006

Effects of trajectory wind direction on ion concentration of PM10.

OBJECTIVE: To study the characterization apportionment of main ion concentrations of PM10 under the influence of trajectory wind direction in London. METHODS: PM10 samples from 1 May 1995 to 30 October 1995 of Oxford Street of Central London were collected, the metals and anions of which were measured using atomic absorption spectrometry (AAS) and ion chromatography (IC). Composite trajectories representative of the air mass arriving in London at the same period were calculated based on basic routine back trajectories from the British Atmospheric Data Centre (BADC). RESULTS: Concentration apportionments of main ions were similar when the trajectory was plotted back at 6 h, 12 h, and 24 h, some were obviously different. Mg, Ba, Pb, and Cu had similar peak apportionments at the area 180 degrees-320 degrees, but Zn and Ni at the area of 90 degrees-270 degrees, NO3 and SO4(2-) at the area of 100 degrees-220 degrees. Cl- concentration peak apportionment was at the area of 220 degrees-300 degrees, which showed that Cl- mainly came from the North Sea. CONCLUSION: Trajectory wind direction has important effect on ion concentration apportionment of PM10 in London. The ions have similar concentration peak apportionments or their correlation coefficients are statistically significant.

Air Pollutants↗
PubMed1991

Shaping the course of a marathon: using the Trajectory Framework for diabetes mellitus.

Persons with either insulin-dependent or non-insulin-dependent diabetes mellitus live with a chronic illness that can have both acute and long-term complications. The therapeutic regimen for glycemic control in diabetes is often complex and is lifelong; it requires special knowledge and skills for both patients and health care providers. In this article, the Corbin and Strauss trajectory framework for chronic illness management is clinically applied to the planning of patient care in two case studies of persons with diabetes. The benefits of using the trajectory framework as a model for care in diabetes include: introduction of the concepts of "locating" the patient on the trajectory and assessing the trajectory projection for both patient and provider, and a more realistic evaluation of incremental change in chronic illness. Two possible barriers to clinical application of the framework for diabetes management are: difficulty in translating the framework for clinical use, and some terminology in the framework that does not seem to describe reimbursable care. The trajectory framework provides a necessary shift in focus to quality of life issues in diabetes management over the lifespan.

Adaptation, Psychological↗
PubMed1979

The physiologic recovery trajectory as the organizing principle for the quantification of hormonometabolic adaptation to surgical stress and severe sepsis.

Preoperative and serial postoperative clinical, cardiovascular, physiologic, and metabolic studies were carried out on 86 patients undergoing coronary artery bypass surgery (CABG); and 48 patients undergoing abdominal general surgical procedures (GSEL). Multivariable statistical analysis of these data showed the patients to be in different physiologic states and to manifest several types of recovery trajectories that could not be discerned on clinical grounds alone. The CABG patients followed one of three types of cardiogenic recovery trajectories. In contrast, GSEL patients show a normal recovery trajectory different from all CABG types. When sepsis develops, and exaggerated stress response (A state) occurs, with increased oxygen consumption and a pattern of amino acids, fat, and glucose breakdown products, which is heightened but similar to the response of nonseptic GSEL patients. With progression of sepsis severity, an unbalanced hyperdynamic recovery trajectory (B state) develops in which a decrease in oxygen consumption is associated with increases in the aromatic amino acids tyrosine, tryptophane, and phenylalanine; and decreases in the branched-chain amino acids, leucine and isoleucine. Triglycerides rise as keto acids fall, but both lactate and pyruvate rise. Glucagon is persistently high, regardless of insulin levels. The quantifiably different physiologic recovery trajectories reflect altered hormone and metabolic states and imply different responses to therapy.

Abdomen↗
PubMed2025

Inferring cell trajectories of spatial transcriptomics via optimal transport analysis.

The integration of cell transcriptomics and spatial position to organize differentiation trajectories remains a challenge. Here, we introduce SpaTrack, which leverages optimal transport to reconcile both gene expression and spatial position from spatial transcriptomics into the transition costs, thereby reconstructing cell differentiation. SpaTrack can construct detailed spatial trajectories that reflect the differentiation topology and trace cell dynamics across multiple samples over temporal intervals. To capture the dynamic drivers of differentiation, SpaTrack models cell fate as a function of expression profiles influenced by transcription factors over time. By applying SpaTrack, we successfully disentangle spatiotemporal trajectories of axolotl telencephalon regeneration and mouse midbrain development. Diverse malignant lineages expanding within a primary tumor are uncovered. One lineage, characterized by upregulated epithelial mesenchymal transition, implants at the metastatic site and subsequently colonizes to form a secondary tumor. Overall, SpaTrack efficiently advances trajectory inference from spatial transcriptomics, providing valuable insights into differentiation processes.

Animals↗
PubMed1999

Simulation of ion trajectories in a quadrupole ion trap: a comparison of three simulation programs

An attempt has been made to compare the performance, design and operation of three simulators, ISIS, ITSIM and SIMION-3D, when applied to the calculation of ion trajectories in a quadrupole ion trap. For the simulation of the trajectory of a single ion in a collision-free system, the calculated spatial trajectory components, kinetic energies and secular frequencies from the three simulators were virtually identical. It is concluded that, despite the various approaches to electrode design, calculation of fields, integration methods and ion generation tactics, there is a remarkable degree of consistency among the products of the simulators when dealing with collision-free conditions. The results of the ion injection simulations under collisional conditions were indicative of the complexity that can be introduced into the simulations with little effort. Random effects such as collisions of ions with He buffer gas and accumulated calculation errors together with the different collision model settings and the different approaches to field calculation are thought to have contributed to the somewhat minor differences in trapping efficiency. SIMION is the simulator of choice for the simulation of ion trajectories in hybrid instruments and in custom-designed assemblies of electrodes; and ITSIM would appear to be the best choice on the basis of computational speed for running multiparticle simulations and user friendliness. Both ISIS and ITSIM are adept at providing detailed information of collision events. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed2000

Off-centered spiral trajectories.

The quality of spiral images depends on the accuracy of the k-space sampling locations. Although newer gradient systems can provide more accurate gradient waveforms, the sampling positions can be significantly distorted by timing misregistration between data acquisition and gradient systems. Even after the timing of data acquisition is tuned, minor residual errors can still cause shading artifacts which are problematic for quantitative MR applications such as phase-contrast flow quantitation. These timing errors can ideally be corrected by measuring the actual k-space trajectory, but trajectory measurement requires additional data acquisition and scan time. Therefore, off-centered spiral trajectories which are more robust against timing errors are proposed and applied to the phase-contrast method. The new trajectories turn shading artifacts into a slowly varying linear phase in reconstructed images without affecting the magnitude of images.

Artifacts↗
PubMed2006

Impact of Alzheimer's pathology on cognitive trajectories in nondemented elderly.

OBJECTIVE: Some individuals who are asymptomatic for dementia while alive have substantial Alzheimer's disease (AD) neuropathology at autopsy. We investigated whether cognitive trajectories differ between clinically normal elderly individuals with and without AD neuropathology and how they compare with trajectories of clinically impaired individuals before dementia diagnosis. METHODS: Eighty-one elderly participants in the Baltimore Longitudinal Study of Aging (BLSA) were followed prospectively with neurological and neuropsychological assessments before autopsy evaluation at death. Trajectories of cognitive change were estimated for a number of domains using cognitive data before a clinical diagnosis of dementia. RESULTS: Clinically normal elderly individuals with and without AD-type neuropathology have similar cognitive trajectories across different cognitive domains. In contrast, individuals with mild cognitive impairment/AD show steeper rates of longitudinal decline in several aspects of cognition compared with clinically normal elderly individuals regardless of whether the latter have AD neuropathology. Moreover, the cognitive differences between impaired and unimpaired groups can be detected years before a diagnosis of dementia. INTERPRETATION: Clinically normal individuals with and without AD neuropathology do not differ in rates of cognitive decline across a number of cognitive domains. Understanding the factors that protect some individuals with AD pathology from cognitive impairment may contribute to the maintenance of cognitive health in the elderly.

Aged↗
PubMed2002

Trajectorial organisation of cytokeratins within the subapical region of umbrella cells.

The subapical region of umbrella cells in the urinary bladder contains a dense cytokeratin (CK) network. Yet, this network should enable a very intensive traffic of specific fusiform vesicles involved in alterations of the surface area of the apical membrane. Therefore, the cytokeratins should be organised in a way to be both mechanically strong and also passable for fusiform vesicles. The supramolecular organisation of the CKs in the subapical region of umbrella cells in mice was studied by conventional fluorescence, confocal laser microscopy, and TEM. It has been found that the first 150 to 300 nm under the apical membrane is filled with fusiform vesicles and only below that the CK network begins. The CK 7 and CK 20 compose a subapical network, which is created as an array of parallel trajectories pointing to the apical plasma membrane. The network is framed by a strong wall of CK, which is parallely aligned in neighbouring cells. The double labelling of the urothelial-specific membrane proteins, uroplakins, and CKs proved the presence of fusiform vesicles within these trajectories. The measurements proved that the trajectory diameter in the upper half of the network is smaller than in the lower half. The diameters of the trajectories in animals with distended bladders exceeded those in contracted bladders for 70%, which most likely facilitates the transport of fusiform vesicles to the apical membrane. Discovery of the subapical CK network elucidates the until now undescribed supramolecular organisation of CKs in the apical region of urothelial cells.

Animals↗
PubMedDate not supplied

Family caregiver expectations and management of the stroke trajectory.

Less than 20% of stroke survivors enter rehabilitation or long-term care facilities after their stroke. Stroke recovery is extremely variable and the resulting uncertainty places a heavy burden on the survivors' family caregivers. According to the trajectory framework, chronic conditions have a defined course that can be shaped and managed. This grounded theory study, part of a larger research project, explored the expectations of family caregivers of the stroke trajectory and their management strategies. Thirteen family caregivers of stroke patients in a sparsely populated area participated in semi-structured interviews. The caregivers were without ideas about what the recovery of their loved ones would be like and had difficulty making projections about the trajectory. They used several strategies, however, in attempts to manage the stroke trajectory. They constructed a positive recovery, reconstituted family life, maintained family routines, created a safety net, and redoubled self-reliance. The findings have implications for how nurses support family caregivers of stroke survivors.

Attitude to Health↗