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PubMed2000

Trajectory estimation in schizophrenia.

Two experiments were conducted to investigate the ability of schizophrenia patients to maintain internal representation over time and space. It has been hypothesized that the ability to guide behavior by internal representation, mediated by the dorsolateral prefrontal cortex (DLPFC), is impaired in schizophrenia [e.g. Goldman-Rakic, P.S., 1996. The functional parcellation of dorsolateral prefrontal cortex and the heterogeneous facets of schizophrenia. In: Matthysse, S., Levy, D.L. (Eds.), Psychopathology: Evolution of a New Science. Cambridge University Press, Cambridge]. In Experiment 1, subjects observed a target, which traveled behind an opaque wall during a part of its trajectory. The task was to accurately assess the speed of the target by predicting when the target would re-emerge on the other side of the wall. In Experiment 2, subjects were asked to estimate the spatial trajectory of an established target path when it was partially occluded from view by another object. Schizophrenia patients were impaired in estimating the speed of a moving target and in estimating the spatial trajectory, without showing deficits in the control tasks. These results suggest that schizophrenia patients may not be able to accurately maintain the internal representation of a target over time and space. Such deficits may have deleterious consequences in goal-directed behavior.

Adult↗
PubMed2003

Hemispheric asymmetry for trajectory perception.

Broadly, the right hemisphere is known to be specialized for spatial processing whereas the left hemisphere is known to be specialized for temporal processing. However, it remains unclear how both hemispheres interact when processing spatio-temporal information. This study investigates, from a behavioral point of view, whether spatio-temporal processing involved in trajectory perception generates hemispheric asymmetries. An experimental task requiring the prediction of coincidence between ballistic trajectories and a stationary target was used. Reaction times were analyzed according to various interhemispheric conditions determined by the visual hemifield on which the stimulus was presented and the hand of response. There was shorter reaction time for the left hand than the right hand, and shorter reaction times for the left visual hemifield than the right visual hemifield for both hands. From these findings, it is inferred that there is likely to be right hemisphere specialization for trajectory perception and that this hemispheric asymmetry is independent of handedness.

Adult↗
PubMedDate not supplied

Uncertainty in illness across the HIV/AIDS trajectory.

Uncertainty is a chronic and pervasive source of psychological distress for persons living with HIV. Numerous sources of heightened uncertainty, including complex changing treatments, ambiguous symptom patterns, and fears of ostracizing social response, play a critical role in the experience of HIV-positive persons and are linked with negative perceptions of quality of life and poor psychological adjustment. Currently, research on uncertainty in HIV fails to explicate the uncertainty experience over time. Because the uncertainty of HIV varies over the course of the illness, an explicit consideration of the sources of uncertainty over the HIV illness trajectory is needed to forecast the informational and stress management needs of persons facing uncertainty about HIV illness. A biopsychosocial model developed to characterize the HIV stigma trajectory provides a useful framework modified to depict uncertainty across the HIV illness experience. Uncertainty in four phases of the HIV illness trajectory are differentiated: (a) at risk, (b) diagnosis, (c) latent, and (d) manifest.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Trajectory analysis of winds and vesicular stomatitis in North America, 1982-5.

Outbreaks of vesicular stomatitis, serotype New Jersey, during epidemics in the United States and northern Mexico, 1982-5, were examined by backward trajectories of winds to investigate spread and possible sources. The outbreaks selected for analysis did not involve introduction of disease by infected animals. The findings indicate that wind could have been responsible for carrying infection from northern Mexico to Arizona and New Mexico and thence to Colorado and Utah and on to Wyoming, Idaho and Montana. The results of these analyses are consistent with the findings from T1 RNAse fingerprinting of virus isolates from outbreaks during the epidemics. The arrival of the trajectories was associated with the passage of a front and rain or passage of a front alone or rain alone. At the time of the trajectories temperatures of 10 degrees C and higher were recorded at heights up to 2500-3500 m. Introduction by airborne particles would appear unlikely as it would have required a source of at least 10(5) infectious units per minute per animal. Vesicular stomatitis virus had been isolated from Simulium and Culicoides during the epidemic with amounts of virus from Simulium sufficient to suggest biological transmission. The possibility of Simulium infected with vesicular stomatitis virus being carried downwind to introduce disease is discussed in relation to the behaviour of Simulium and the pathogenesis of vesicular stomatitis in large animals.

Air Movements↗
PubMed2005

Patterns of risk and trajectories of preschool problem behaviors: a person-oriented analysis of attachment in context.

A small proportion of children exhibit extreme and persistent conduct problems through childhood. The present study employed the multiple-domain model of Greenberg and colleagues as the framework for person-oriented analyses examining whether parent-child attachment combines with parenting, family ecology, and child characteristics in particular configurations of risk that are linked to this problematic developmental pathway. Using prospective data from a community sample of adolescent mothers and their children, latent variable growth mixture modeling identified a normative trajectory with declining problem behaviors during the preschool period. Consistent with research on early-starter pathways, a distinct group of children featured a higher intercept and a positive slope, indicating an escalation in disruptive behaviors. Attachment security played a role in defining specific risk profiles associated with the probability of exhibiting this problem trajectory. Given particular patterns of risk exposure, secure attachment served a protective function. Avoidant, but not disorganized, attachment was associated with significantly higher likelihood of the disruptive problem trajectory. The results also indicated the general accumulation of risk was detrimental, but the particular configuration of risk made a difference. Overall, the findings suggest early attachment operates in conjunction with personal and contextual risk to distinguish the development of later problem behaviors.

Adolescent↗
PubMed1990

Extraction of the energetics of selected types of motion from molecular dynamics trajectories by filtering.

A novel method for analyzing molecular dynamics trajectories has been developed which enables the study of selected motions and the corresponding energetics. In particular, it is possible to filter out the high-frequency motions and focus on the structural and energetic features of low-frequency collective motions. The trajectories of the properties of interest are Fourier transformed to the frequency domain, a filtering function is applied, and then an inverse transformation back to the time domain yields the filtered trajectory. The method is demonstrated for harmonic fluctuations and conformational transitions of acetamide and N-acetylalanine N-methylamide, as models for peptides and proteins.

Alanine↗
PubMed2005

Effects of wind and air trajectory directions on atmospheric concentrations of persistent organic pollutants near the Great Lakes.

Three different regression models involving air temperature, time, and either wind direction or parametric or nonparametric air trajectory direction were used with concentrations of four representative persistent organic pollutants to quantitate the atmospheric transport of these compounds to the Great Lakes. The local wind and parametric trajectory models predicted an optimal source direction for each compound, whereas the nonparametric trajectory model was based on a hypothesized source region. All three regressions were used to calculate the factor by which the partial pressures of each compound measured at five sampling sites increased when the air came from a particular source direction. Dieldrin, chlordane, polychlorinated biphenyl, and polycyclic aromatic hydrocarbon partial pressures were used with each of these regressions, and the correlation coefficients (r2) were evaluated for each model, for each compound, and for each regression term. In general, with the exception of polycyclic aromatic hydrocarbons at some sites, the explanatory powers of the regressions were not improved by the inclusion of any of these directional terms.

Air Movements↗
PubMed2005

Reaction products with internal energy beyond the kinematic limit result from trajectories far from the minimum energy path: an example from H + HBr --> H2 + Br.

The importance of reactive trajectories straying far from the minimum energy path is demonstrated for the bimolecular reaction H + HBr --> H2(v', j') + Br at 53 kcal/mol collision energy. Product quantum state distributions are measured and calculated using the quasi-classical trajectory technique, and the calculations indicate that highly internally excited H2 products result from indirect reactive trajectories with bent transition states. A general argument is made suggesting that reaction products with internal energy exceeding a kinematic constraint can, in general, be attributed to reactive collisions straying far from the minimum energy path.

Journal Article↗
PubMed2005

Trajectory study of supercollision relaxation in highly vibrationally excited pyrazine and CO2.

Classical trajectory calculations were performed to simulate state-resolved energy transfer experiments of highly vibrationally excited pyrazine (E(vib) = 37,900 cm(-1)) and CO(2), which were conducted using a high-resolution transient infrared absorption spectrometer. The goal here is to use classical trajectories to simulate the supercollision energy transfer pathway wherein large amounts of energy are transferred in single collisions in order to compare with experimental results. In the trajectory calculations, Newton's laws of motion are used for the molecular motion, isolated molecules are treated as collections of harmonic oscillators, and intermolecular potentials are formed by pairwise Lennard-Jones potentials. The calculations qualitatively reproduce the observed energy partitioning in the scattered CO(2) molecules and show that the relative partitioning between bath rotation and translation is dependent on the moment of inertia of the bath molecule. The simulations show that the low-frequency modes of the vibrationally excited pyrazine contribute most to the strong collisions. The majority of collisions lead to small DeltaE values and primarily involve single encounters between the energy donor and acceptor. The large DeltaE exchanges result from both single impulsive encounters and chattering collisions that involve multiple encounters.

Journal Article↗
PubMed2006

Quantum trajectory dynamics in arbitrary coordinates.

The quantum trajectory approach is generalized to arbitrary coordinate systems, including curvilinear coordinates. This allows one to perform an approximate quantum trajectory propagation, which scales favorably with system size, in the same framework as standard quantum wave packet dynamics. The trajectory formulation is implemented in Jacobi coordinates for a nonrotating triatomic molecule. Wave packet reaction probabilities are computed for the O(3P) + H2 --> OH + H reaction using the approximate quantum potential. The latter is defined by the nonclassical component of the momentum operator expanded in terms of linear and exponential functions. Unlike earlier implementations with linear functions, the introduction of the exponential function provides an accurate description of asymptotic dynamics for this system and gives good agreement of approximate reaction probabilities with accurate quantum calculations.

Journal Article↗
PubMed2006

Trajectory approach to the mode-selected photodissociation of CS2.

Through the study of photodissociation events in the CS(2) molecule that originate in various selected vibrational modes, but terminate in the same final predissociation state, we looked for the evidence that photodissociation processes can depend on the initial conditions. Such dependence would not occur within RRKM theory, because of its statistical assumptions. The experimental results were compared with trajectory calculations in normal mode coordinates, in which initial conditions were given in terms of coordinates and momenta. We have found that the photodissociation rate for events originating in the combination nu(1), nu(2) mode is higher than that for events from the pure nu(2) mode, and shows a large variation along the vibrational progression. The experimental observations agree with the trajectory calculations. In addition, the trajectory calculations predict that photodissociation events initiated at small values of the vibrational coordinates result in larger dissociation rates at low excess energy above the dissociation limit, while events from large values of the coordinates result in larger dissociation rates at high excess energies.

Journal Article↗
PubMed1999

The nature and predictors of the trajectory of change in marital quality for husbands and wives over the first 10 years of marriage.

Four parameters of the trajectory of change in marital quality (initial status as well as linear, quadratic, and cubic patterns of change) were estimated for husbands and wives over the first 10 years of marriage (n = 522 couples at Year 1 and 93 couples at Year 10). Both husbands and wives started their trajectories of change at fairly high levels of marital quality and showed a cubic pattern of change such that marital quality declined fairly rapidly in the early years of marriage, stabilized, and then declined again. Whereas individual-differences variables predicted the initial status of the trajectory, husbands and wives living with only their biological children showed a steeper decline in marital quality than husbands and wives living without children or stepchildren.

Adult↗
PubMed2002

The optic trajectory is not a lot of use if you want to catch the ball.

According to linear optic trajectory (LOT) theory, fielders use the direction of curvature of theoptic trajectory to control the way they run to intercept the ball. Data presented by D. M. Shaffer and M. K. McBeath (2002) as support for LOT theory show that the optic trajectory of balls that will fall behind the fielder provide the cue that LOT theory predicts would send the fielder running forward, not backward. In this article, the authors show that watching these balls would provide the fielder with the cue that the optic acceleration cancellation (OAC) theory of interception predicts would send the fielder running backward. It appears that the fielders studied by Shaffer and McBeath were following the cue predicted by OAC theory, not that predicted by LOT theory.

Cues↗
PubMed2003

Academic growth curve trajectories from 1st grade to 12th grade: effects of multiple social risk factors and preschool child factors.

This study examined the main and interactive effects of multiple social risk factors and the preschool child factors of IQ and mental health on students' academic trajectories from 1st grade to 12th grade. A multiple risk score summarizing 10 environmental risk factors was calculated at 4 years of age for 145 families. Hierarchical linear modeling showed that high-risk students had lower grades and more absences from 1st grade to 12th grade than did low-risk students. Significant interactions between risk and child factors for students' grade point average (GPA) revealed that child factors had significant effects only for low-risk students. Higher IQ and better mental health improved the GPA trajectories of low-risk children but did not influence the GPA trajectories of high-risk children.

Adaptation, Psychological↗
PubMed2006

Depression, self-esteem, and anger in emerging adulthood: seven-year trajectories.

This study used a school-based community sample (N=920) to examine trajectories of depressive symptoms, self-esteem, and expressed anger in the critical years of emerging adulthood (ages 18-25). Using data from 5 waves, the authors discovered that multilevel models indicated that, on average, depressive symptoms and expressed anger declined, whereas self-esteem increased. Between-persons predictors of variability in trajectories included gender (gender gaps in depressive symptoms and self-esteem narrowed), parents' education, and conflict with parents (depressive symptoms and expressed anger improved fastest in participants with highly educated parents and in those with higher conflict). Across time, increases in social support and marriage were associated with increased psychological well-being, whereas longer periods of unemployment were connected with higher depression and lower self-esteem. Emerging adulthood is a time of improving psychological well-being, but individual trajectories depend on specific individual and family characteristics as well as role changes.

Adolescent↗
PubMed2004

Heterogeneity in youth symptom trajectories following psychiatric crisis: predictors and placement outcome.

The authors examined heterogeneity in symptom trajectories among youths following psychiatric crises as well as the psychosocial correlates and placement outcomes associated with identified trajectories. Using semiparametric mixture modeling with 156 youths approved for psychiatric hospitalization, the authors identified 5 trajectories based on symptoms over the 16 months following crisis: high improved, high unimproved, borderline improved, borderline unimproved, and subclinical. Membership in unimproved symptom groups was associated with less suicidality, younger age, more youth hopelessness, and more caregiver empowerment. Improved symptom group membership predicted long-term decreases in days in out-of-home placements. More important, and in contrast with general impressions from the existing literature, findings suggest that a substantive proportion of youths with serious emotional disturbance sustain high levels of symptomatology following intensive mental health services.

Adolescent↗
PubMed2004

Psychological and physical adjustment to breast cancer over 4 years: identifying distinct trajectories of change.

The goal of this study was to identify distinct trajectories of adjustment to breast cancer over 4 years as well as to distinguish among the different trajectories. The mental and physical functioning of 287 women with breast cancer who remained alive and disease free through 4 years of follow-up were examined. The majority of women showed slight and steady improvement in functioning with time, but subgroups of women were identified who showed marked improvement and marked deteriorations over time. Age successfully distinguished different trajectories of physical functioning. Indices of personal resources (i.e., self-image, optimism, perceived control) and social resources (i.e., social support) successfully distinguished different courses of mental and physical functioning.

Adaptation, Physiological↗
PubMed2005

Similarities and differences of longitudinal phenotypes across alternate indices of alcohol involvement: a methodologic comparison of trajectory approaches.

Extant developmental research distinguishing young adults who moderate versus persist in alcohol consumption has not consistently evaluated the domain of alcohol involvement being modeled, making it difficult to compare findings across studies. In the present study, the authors characterized the developmental course of 5 indices of alcohol involvement using a prospective (6-wave) sample of 377 young adults (Year 1 age = 18.52 years; 55% female; 51% with family history of alcoholism) over 11 years. Growth mixture models were applied to each measure. Despite similarity in trajectory shape, predicted prevalences varied, and the consistency of trajectory classifications across alternate indices revealed low agreement. Correlates of drinking course, however, were somewhat robust across alcohol index. The finding that trajectories are conditional on the specific indices used suggests that it may be hazardous to generalize across alternate indices of alcohol involvement.

Alcoholism↗