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 811 records · Page 45Linked to original sources
PubMed2001

Sexually dimorphic ontogenetic trajectories of frontal sinus cross sections.

In this paper, we analyze a large published data set of cross sections of frontal sinuses of 3 to 11-year-olds (105 males and 87 females) from Central Europe to investigate several issues relating to frontal sinus ontogeny. Despite a large variation in every one year age cohort, we detect no asymmetry of the left average versus the right average frontal sinus lobe cross-sectional areas in the population, neither for males nor for females. The growth rate is shown to be nonuniform and differs between males and females. We demonstrate the use of a sigmoid function interpolation to characterize one aspect of ontogeny, namely, the functional relation between the cross-sectional area of the frontal sinus and the age of the individual. Ontogenetic trajectories of these cross-sectional areas are remarkably well modeled by a sigmoid function (logistic curve) with suitably estimated parameters for development up to an age of 11 years (females) and 9 years (males). However, these developmental curves also reliably predict the average adult cross-sectional area at age 19 (99% for females, 95% for males). Apart from possible inadequacies of the data set, we also discuss the possibility of heterochrony in the ontogenetic trajectory before versus after puberty.

Child↗
PubMed1987

Models of birth trajectories with certain patterns of variations in vital rates.

This article records experiments with a modified version of Lotka's stable population model. The traditional assumption of a set of unchanging net maternity rates as one of the preconditions has been replaced by allowing the rates to vary in certain ways while approaching or varying around a set of underlying constant rates. The integral equation assumes a different form but can be simplified and solved in the same old way. As a result, the birth trajectory does not necessarily attain a stable state. For certain patterns of mathematical functions the trajectory eventually becomes stable while for certain others it shows cyclical fluctuations. The variations in net maternity rates can also be postulated to follow the patterns of some measurable empirical functions which, like the mathematical functions, should be amenable to projections in the future. This information is needed for deriving the long-term solutions in additions to the information about the intrinsic rate of growth which is obtained from the traditional integral equation.

Birth Rate↗
PubMedDate not supplied

[The diversity of reproductive trajectories and institutional interactions].

"This article presents results from research carried out between 1989 and 1991 in a rural region in the state of Morelos [Mexico], beginning from an analysis centered in the interactions between health agents and women.... Using both quantitative and qualitative methodologies, several reproductive trajectories were identified and analyzed, allowing an assessment, on the one hand, of the intensity of women's interactions with health institutions, their community, and their partner and, on the other hand, a characterization of the social trajectories of women as a fundamental factor in their integration with the biomedical system." (SUMMARY IN ENG)

Americas↗
PubMed2002

Academic and health-related trajectories in adolescence: the intersection of gender and athletics.

This study takes a life course approach to adolescent academic and health-related behavior. Researchers have often studied academic achievement and substance use as unrelated, static, and de-contextualized phenomena. Applying latent growth curve modeling to a sample of 2,651 high school freshmen and sophomores in California and Wisconsin (1987-1990), this study treats achievement and substance use as dynamic trajectories, inter-related to each other, and influenced by proximate and structural contexts. In general, achievement is high at the start of high school and then declines. This downward trend is driven by male non-athletes. Substance use is initially low and then increases, with boys driving this increase. Finally, academic and health-related trajectories are most related among athletes, who experience long-term academic consequences from risky health-related behavior. Overall, gender-athletic status can serve as either protective or risk factor, depending on the behavior and the temporal perspective.

Adolescent↗
PubMedDate not supplied

A proposed coast-wide reference monitoring system for evaluating wetland restoration trajectories in Louisiana.

Wetland restoration efforts conducted in Louisiana under the Coastal Wetlands Planning, Protection and Restoration Act require monitoring the effectiveness of individual projects as well as monitoring the cumulative effects of all projects in restoring, creating, enhancing, and protecting the coastal landscape. The effectiveness of the traditional paired-reference monitoring approach in Louisiana has been limited because of difficulty in finding comparable reference sites. A multiple reference approach is proposed that uses aspects of hydrogeomorphic functional assessments and probabilistic sampling. This approach includes a suite of sites that encompass the range of ecological condition for each stratum, with projects placed on a continuum of conditions found for that stratum. Trajectories in reference sites through time are then compared with project trajectories through time. Plant community zonation complicated selection of indicators, strata, and sample size. The approach proposed could serve as a model for evaluating wetland ecosystems.

Conservation of Natural Resources↗
PubMed2002

Trajectories of gender role orientations in adolescence and early adulthood: a prospective study of the mental health effects of masculinity and femininity.

Adolescence is the segment of the life course when gender differences in mental health emerge and gender becomes a more salient factor shaping orientations toward oneself and views of one's place in the social world. This study uses mixture modeling, to identify trajectories of masculinity and femininity between ages 12 and 25, and OLS regression, to examine the effects of those trajectories on mental health in young adulthood (measured as depressive symptoms and alcohol problems at age 25). Four waves of prospective data from the Rutgers Health and Human Development Project are used; respondents (n = 447) are age 12 at Wave 1 (1979-81), 15 at Wave 2 (1982-84), 18 at Wave 3 (1985-87), and 25 at Wave 4 (1992-94). Results indicate that having relatively high and increasing levels of masculinity over adolescence decreases depressive symptoms in early adulthood for both males and females. Reflecting the privileging of males over females, the findings suggest that masculinity, but not femininity, is a central axis on which advantages and disadvantages across some dimensions of mental health accumulate over adolescence.

Adolescent↗
PubMed1996

Eye movement modifies motion trajectory of a moving target.

Smooth pursuit eye movements have strong modulating effects on perceived motion both temporally and spatially. Abrupt changes in the direction of a target cause non-veridical perceived velocity and trajectory pattern when a visual cues appear with the moving target. In addition, this condition of non-veridical velocity and trajectory perception increases no visual cues are presented. Non-veridical perception was also connected with target velocity: the more difficult the eye pursuit, the more frequent was the non-veridical perception.

Acceleration↗
PubMed2004

An adoption study of a clinical reminder system in ambulatory care using a developmental trajectory approach.

In this study, we assess 41 medical residents' acceptance and adoption of a clinical reminder system for chronic disease and preventive care management in the ambulatory care environment using a novel developmental trajectory approach. This group-based, semi-parametric statistical modeling method identifies distinct groups, following distinct usage trajectories, among those who recorded use of the reminder system within an evaluation period of 10 months. We trace system use within these groups over time using computer-generated logs and user satisfaction surveys. Our preliminary analysis of this small sample of users delineates three categories of users. Feedback from these categories of users is being used to re-engineer the application and adapt it better to their workflow and functionality requirements. Despite the small sample size in this particular study, we conclude that this methodology has considerable promise to provide new insights into system usability and adoption issues that may benefit clinical decision support systems as well as information systems more generally.

Ambulatory Care↗
PubMedDate not supplied

[Dynamics and variability of early morphogenesis in the loach according to observations of individual developmental trajectories].

The dynamics and variability of quantitative morphological characters (morphological variables), which undergo changes upon epiboly, were studied by means of vital observations and measurements of developing loach (Misgurnus fossilis L.) embryos within equal time intervals. None of morphological variables, which characterize the dynamics of blastoderm shape, had monotonous dependence on time. In each individual embryo, the intervals of changes in morphological variables in the "normal" direction corresponding to the change of their mean values during the normal course of epiboly alternated with arrests, as well as with the changes of morphological variables in the reverse direction. The dynamics of morphological variables in time, which reflect the sequence of morphological states of the same embryo, and those of individual variations (variations of morphological states of different embryos on the same temporal section) had identical structure. This suggests instability of individual trajectories of morphogenesis or, strictly speaking, their actual absence. It was shown for the first time on the basis of analysis of individual trajectories of morphogenesis that its dynamics corresponded to so-called "determined chaos", which was previously discussed only as a theoretical possibility. The data obtained suggest that upon approach to the equatorial area of the embryo, the blastoderm marginal zone was elongated in the longitudinal direction and contracted across the axis of its movement. As a result, a positive feedback arises between the cooperated cell movement and the change of shape of the surface, over which the cells move. This leads, due to unstable radial symmetry of this movement, to the formation of embryonic shield.

Animals↗
PubMed2005

[Identification process in hemodialysis patients: impact of the technique on the life trajectory].

The haemodialysis is a palliative technical treatment relatively recent which makes it possible insufficient renal to continue to live. Those indefinitely follow in weekly time three meetings of extra-renal purification as long as they are not transplanted. Within the framework of the research task realized for obtaining the licence and the diploma of framework of health, I was interested in the trajectory of life and the identity of these patients by questioning the processes which lead it to be qualified by its treatment and becoming one "haemodialysis". I chose a step of sociological investigation of nature by leading a comparative analysis between two centres of haemodialysis. The trajectory of the patient is defined by a process in stages: the initial shock precedes the adaptation by the sick person and supports the emergence of a profane knowledge which will be or not recognized by the professionals of dialysis according to centres'. The technique structure also the identity process of the patients, process marked by signs of entry in the deviating career and/or stigmatization, which take part to build in return a singular identity, i.e. defined by a deficit of specific identity. This deficit could explain the request for training and the emergence of a technical skill among certain patients, whereas they attend heavy centres of haemodialysis. The recognition of the patient as an actor of the process of care as well as looking after redefines the place of the nurses who can find a benefit for their professional identity there.

Adaptation, Psychological↗
PubMed2005

Perspective: Sign epistasis and genetic constraint on evolutionary trajectories.

Epistasis for fitness means that the selective effect of a mutation is conditional on the genetic background in which it appears. Although epistasis is widely observed in nature, our understanding of its consequences for evolution by natural selection remains incomplete. In particular, much attention focuses only on its influence on the instantaneous rate of changes in frequency of selected alleles via epistatic contribution to the additive genetic variance for fitness. Thus, in this framework epistasis only has evolutionary importance if the interacting loci are simultaneously segregating in the population. However, the selective accessibility of mutational trajectories to high fitness genotypes may depend on the genetic background in which novel mutations appear, and this effect is independent of population polymorphism at other loci. Here we explore this second influence of epistasis on evolution by natural selection. We show that it is the consequence of a particular form of epistasis, which we designate sign epistasis. Sign epistasis means that the sign of the fitness effect of a mutation is under epistatic control; thus, such a mutation is beneficial on some genetic backgrounds and deleterious on others. Recent experimental innovations in microbial systems now permit assessment of the fitness effects of individual mutations on multiple genetic backgrounds. We review this literature and identify many examples of sign epistasis, and we suggest that the implications of these results may generalize to other organisms. These theoretical and empirical considerations imply that strong genetic constraint on the selective accessibility of trajectories to high fitness genotypes may exist and suggest specific areas of investigation for future research.

Biological Evolution↗
PubMedDate not supplied

Characteristics and trajectories of treatment foster care youth.

Using cross-sectional analyses in conjunction with dynamic modeling (hierarchical linear modeling), the authors profiled 119 treatment foster care youth and constructed behavioral change trajectories for a subset of 97 children. Children generally showed improvements in internalizing and critical pathology problem domains but remained the same on measures of externalizing behaviors and total problem score. The number of previous out-of-home placements was positively associated with increased levels of psychiatric symptomatology and served as the most robust predictor for modeling treatment response trajectories across problem domains. Placement instability places the well-being of children at heightened risk, therefore, accurate assessment of child need and risk in relation to caregiver capacities is critical.

Adolescent↗
PubMed1992

Trajectories of functional impairment in later life.

Functional impairment trajectories in late adulthood over a decade are characterized using the Longitudinal Retirement History Study (LRHS) data set. Non-linear patterns of age-related increase in impairment are documented with longitudinal data. Subsets of panelists from the initial large, nationally representative probability sample of employed males and unmarried employed females (N = 11,000) also exhibit differential non-linear trajectories of impairment by sex, income, and educational attainment. Concurrent analysis of the relationship over a decade among sex, SES, and functional impairment suggests that in health research, both sex and SES are broad proxy variables whose usefulness for understanding health outcomes and for policy analysis would be enhanced by the specification of components.

Activities of Daily Living↗
PubMedDate not supplied

Pediatric hospital dying trajectories: what we learned and can share.

Diverse settings, diagnoses, and time constraints challenge a small hospital's ability to provide comprehensive care to all dying children and their families. Children who died at a regional hospital in southeast Georgia were studied to document the circumstances under which they died and the palliative and end-of-life care provided. The most common causes of death were injury and circulatory events. At the time of death, 56% of the children studied were in the care of the Emergency Department. Seventy-two percent were previously healthy children; 78% were hospitalized for less than 24 hours prior to death. Based on previous medical history and length of final hospitalization, four hospital dying trajectories were defined. Hospital dying trajectories provide a basis for planning comprehensive hospital pediatric palliative and end-of-life care program by identifying the settings, time limitations, and key personnel.

Adolescent↗
PubMed2006

An experimental manipulation of life-history trajectories and resistance to oxidative stress.

Optimal investment into life-history traits depends on the environmental conditions that organisms are likely to experience during their life. Evolutionary theory tells us that optimal investment in reproduction versus maintenance is likely to shape the pattern of age-associated decline in performance, also known as aging. The currency that is traded against different vital functions is, however, still debated. Here, we took advantage of a phenotypic manipulation of individual quality in early life to explore (1) long-term consequences on life-history trajectories, and (2) the possible physiological mechanism underlying the life-history adjustments. We manipulated phenotypic quality of a cohort of captive zebra finches (Taeniopygia guttata) by assigning breeding pairs to either an enlarged or a reduced brood. Nestlings raised in enlarged broods were in poorer condition than nestlings raised in reduced broods. Interestingly, the effect of environmental conditions experienced during early life extended to the age at first reproduction. Birds from enlarged broods delayed reproduction. Birds that delayed reproduction produced less offspring but lived longer, although neither fecundity nor longevity were directly affected by the experimental brood size. Using the framework of the life-table response experiment modeling, we also explored the effect of early environmental condition on population growth rate and aging. Birds raised in reduced broods tended to have a higher population growth rate, and a steeper decrease of reproductive value with age than birds reared in enlarged broods. Metabolic resources necessary to fight off the damaging effect of reactive oxygen species (ROS) could be the mechanism underlying the observed results, as (1) birds that engaged in a higher number of breeding events had a weaker red blood cell resistance to oxidative stress, (2) red blood cell resistance to oxidative stress predicted short-term mortality (but not longevity), and (3) was related with a parabolic function to age. Overall, these results highlight that early condition can have long-term effects on life-history trajectories by affecting key life-history traits such as age at first reproduction, and suggest that the trade-off between reproduction and self-maintenance might be mediated by the cumulative deleterious effect of ROS.

Aging↗
PubMed1991

A nursing model for chronic illness management based upon the Trajectory Framework.

The trajectory framework developed by Strauss and associates provides a conceptual basis for developing a nursing model that gives direction for practice, teaching, and research in the area of chronic illness. This paper presents an overview of the trajectory framework and shows how it can be used to generate such a nursing model.

Adaptation, Psychological↗
PubMed1991

Applying the chronic illness Trajectory Model to HIV/AIDS.

The Corbin and Strauss chronic illness trajectory model is particularly helpful in explaining the different phases of HIV (Human Immunodeficiency Virus) disease, since this infectious process is characterized by both phases and subphases. The model is not particularly helpful in identifying when the illness trajectory begins, since the model starts with the onset of symptoms, and HIV disease is characterized by a long, symptomless phase. The importance of politics and economics is also underestimated when applying this model to HIV disease. While this model presupposes the existence of support systems as being significant others, HIV disease is unique in that whole family systems may be eliminated by this infectious process, i.e., the typical pattern of HIV disease in the 1990s is that of a father dying from AIDS, a mother sick with HIV disease, one or more siblings infected, and one or more siblings coping with tremendous losses at a very young age.

Adult↗
PubMed1991

Chronic mental illness: the timeless trajectory.

Mental illness encompasses many dimensions. While the etiology of most major disorders remains unclear, their devastating effects are readily apparent. The substantive and practical value of the trajectory model of chronic illness is examined in relation to the characteristics of major mental disorders. Two clinical vignettes illustrating the timeless trajectory of chronic mental illness are analyzed with reference to the model's components. The potential utility of this model for revitalizing research and practice in psychiatric-mental health nursing is discussed.

Adult↗