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Results for “trajectory analysis”

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PubMed2001

Quantifying Population Dynamics Based on Community Structure Fingerprints Extracted from Biosolids Samples.

This paper presents a standardized metric for quantifying the rate change in community structure of complex mixed microbial cultures such as those maintained in biological wastewater treatment systems. Quantifying the stability of microbial community structures is a first step toward more aggressive monitoring and control of biological systems for greater reliability in contaminant removal. Statistical analysis of compositions that uniquely specify the balance of populations of species in a mixed culture sample can be used to specify a biosolids community state as a unique position in an orthogonal coordinate system. Changes in biosolids state are observable as a trajectory within this coordinate space, and the rate of passage along this trajectory relates to the population dynamics. The geometric interpretation and the statistical analysis methods necessary for the proposed calculation methodology are introduced by way of simulated case studies with a simple model system. With the example of this model system, concepts of changing microbial community shape and size are contrasted. The rate change in community structure is defined geometrically in terms of a rate change in relative proportions of the characteristic community shape at constant biomass. A change in biomass is defined as the rate change in the quantity of biosolids at constant shape. The method robustness with respect to random measurement error was also demonstrated using the model system. The potential applications of the approach are presented with experimental data of microbial fatty acid compositions extracted from samples during the operation of bench-scale bioreactors degrading contaminants found in pulp mill wastewater. Scaling the level of population dynamics with a metric that is independent of chemotypic content presents a standard for direct comparisons of community responses between distinct cultures and experiments.

Journal Article↗

PubMed2003

Men's experiences and their resources from cancer diagnosis to recovery.

This study describes the experiences and resources of male cancer patients in Finland during the trajectory of their illness. A semi-structured interview schedule was used to collect data on falling ill with cancer, on periods of treatment (surgery, chemotherapy, radiation therapy), and on convalescence. The participants (n=8), aged 42-64 (mean=53) were interviewed in a clinic setting in connection with a check-up visit. The interviews were tape-recorded and transcribed for qualitative content analysis. The male cancer patients described their experiences through the illness trajectory in terms of suspicions, their encounter with cancer, and the cancer becoming a reality. During treatment, men described their experiences in terms of changes in body image, individual illness experiences, and new social roles. Men's experiences during the convalescence period included physical restoration, anxiety following treatment regimes, reflection, and social roles at transition. The results also indicated that men did not consider their status as a chronic one, but rather as a passing and relatively short stage in their life. Both intra- and extrapersonal resources were described: the former included body image and capacity, self-understanding, social situation, and psychological resources; and the latter wives, children, colleagues, health-care personnel, fellow patients, health-care interventions and society. Extrapersonal resources included informational, emotional, and evaluative support, as well as concrete help.

Adult↗

PubMed1996

Task dynamic and articulatory recovery of lip and velar approximations under model mismatch conditions.

An algorithm for recovering task dynamics and speech articulator movements from speech acoustics was tested under various model mismatch conditions. There was evidence of articulatory compensation to recover tract-variable (constriction) trajectories in speech produced with a lip approximation under sufficiently constrained conditions. However, in more extensive studies of lip and velar approximations, the recovered tract-variable trajectories were also different from those of the data-producing utterance. This phenomenon can occur because the matching criterion in the analysis-by-synthesis procedure is an acoustic criterion and the correspondence between the tract-variable trajectories and the acoustic output is not exact. While there may be some tract-variable compensation to attain a good acoustic match, there is evidence of a correspondence between how well the tract-variable trajectories match and how well the formant frequencies match in particular instances.

Humans↗

PubMed2004

Three-dimensional carpal kinematics of trotting horses.

REASONS FOR PERFORMING STUDY: Descriptions of 3D kinematics assist in understanding joint function and dysfunction, and are an essential step toward 3D inverse dynamic analysis. OBJECTIVES: To measure 3D carpal joint motion during trotting. METHODS: Three-dimensional trajectories of bone-fixed markers on the radius and third metacarpus of the right forelimb of 3 healthy horses were recorded at 120 Hz using a 6-camera analysis system. Joint kinematics were calculated in terms of helical angles between the 2 segments using a spatial attitude method. RESULTS: All horses showed carpal extension and internal rotation of the metacarpus relative to the radius as the carpus assumed the close-packed position. In late stance, the carpus began a cycle of flexion that continued through midswing, accompanied by a small cycle of internal rotation. The direction of abduction/adduction varied between horses. The predominant rotational movement was flexion/extension, which showed a range of motion of 15 +/- 6 degrees in stance and 76 +/- 13 degrees in swing. CONCLUSIONS: Carpal motions were generally similar between horses with the exception of abduction/adduction. POTENTIAL RELEVANCE: Knowledge of carpal joint motion should assist in understanding the pathogenesis of carpal injuries. However, it seems probable that real differences exist between individuals; therefore, further investigations of the effect of conformation on carpal motion should be performed in a much larger population of horses.

Animals↗

PubMed2005

Information entropy analysis of discrete aiming movements.

Information entropy and mutual information were investigated in discrete movement aiming tasks over a wide range of spatial (20-160 mm) and temporal (250-1250 ms) constraints. Information entropy was calculated using two distinct analyses: (1) with no assumption on the nature of the data distribution; and (2) assuming the data have a normal distribution. The two analyses showed different results in the estimate of entropy that also changed as a function of task goals, indicating that the movement trajectory data were not from a normal distribution. It was also found that the information entropy of the discrete aiming movements was lower than the task defined indices of difficulty (ID) that were selected for the congruence with Fitts' law. Mutual information between time points of the trajectory was strongly influenced by the average movement velocity and the acceleration/deceleration segments of the movement. The entropy analysis revealed structure to the variability of the movement trajectory and outcome that has been masked by the traditional distributional analyses of discrete aiming movements.

Adult↗

PubMedDate not supplied

Development and validation of the Hogan Grief Reaction Checklist.

The purpose of this article is to provide data on a recently developed instrument to measure the multidimensional nature of the bereavement process. In contrast to widely used grief instruments that have been developed using rational methods of instrument construction, the Hogan Grief Reaction Checklist (HGRC) was developed empirically from data collected from bereaved adults who had experienced the death of a loved one. Factor analysis of the HGRC revealed 6 factors in the normal trajectory of the grieving process: Despair, Panic Behavior, Blame and Anger, Detachment, Disorganization, and Personal Growth. Additional data are provided that support reliability and validity of the HGRC as well as its ability to discriminate variability in the grieving process as a function of cause of death and time lapsed since death. Empirical support is also provided for Personal Growth as an integral component of the bereavement process. The article concludes by considering the substantive as well as psychometric findings of this research for such issues as traumatic grief, anticipatory grief, change in the bereaved person's self-schema, and spiritual and existential growth.

Adult↗

PubMed1991

Control of the cryosurgical process in nonideal materials.

A study of a controlled cryosurgical process is presented. This study is based on the energy equations describing the probe response and the phase change occurring in the medium. First-order nonlinear differential equations (state equations) are obtained by applying the integral-solution method. In order to obtain maximal cell destruction, it is desired to control a specific cooling rate at the solid-liquid interface. This cooling rate defines the desired trajectories of the state variables through the state equations. In order to satisfy the cooling rate condition on the freezing front, a closed-loop is designed to control the probe temperature program. A simple analysis of the system stability employed linearization at several points along the desired trajectories. Ranges of stability were obtained for a system containing a proportional-integral controller. It was demonstrated that these stability ranges depend mainly on the selected sampling time of the discrete control loop and that the phase-change process does not significantly affect the stability results. A complete study of the nonlinear equations was performed by a computer simulation program which enables the selection of the final values of the controller parameters, in order to minimize the error and to ensure stability. In addition, the simulation program gives information about the effects of the A/D and D/A converters accuracy on the performance of the control loop. An A/D converter accuracy of 12 bits was found necessary in order to reduce the oscillations in probe temperature to acceptable values. The simulation also yields a complete calculated temperature field in the tissue during the controlled process. From these simulated results it can be seen that oscillations of +/- 0.5 degrees C in the desired probe temperature do not significantly affect the desired cooling rate at the freezing front. An initial overshoot of 1.5 degrees C in the desired probe temperature was obtained both experimentally and theoretically from the simulation. When this initial overshoot occurs at the beginning of the freezing process, it causes an error in freezing front velocity and consequently in ice-front position. From the numerical simulation, it can be deduced that the cooling rate obtained at the front deviates from the desired value by approximately 1%. The probe-temperature error increases at two instants: a) during the super-cooling effect and the subsequent sudden crystallization, and b) when the probe temperature is below -80 degrees C and unstable boiling of the cooling medium causes oscillations.

Cryosurgery↗

PubMed2003

Automated segmentation and analysis of vascular structures in magnetic resonance angiographic images.

The accurate assessment of the presence and extent of vascular disease, and planning of vascular interventions based on MRA requires the determination of vessel dimensions. The current standard is based on measuring vessel diameters on maximum intensity projections (MIPs) using calipers. In order to increase the accuracy and reproducibility of the method, automated analysis of the 3D MR data is required. A novel method for automatically determining the trajectory of the vessel of interest, the luminal boundaries, and subsequent the vessel dimensions is presented. The automated segmentation in 3D uses deformable models, combined with knowledge of the acquisition protocol. The trajectory determination was tested on 20 in vivo studies of the abdomen and legs. In 93% the detected trajectory followed the vessel. The luminal boundary detection was validated on contrast-enhanced (CE) MRA images of five stenotic phantoms. The results from the automated analysis correlated very well with the true diameters of the phantoms used in the in vitro study (r = 0.999, P < 0.001). MRA and x-ray angiography (XA) of the phantoms also correlated well (r = 0.895, P < 0.001). The average unsigned difference between the MRA and XA measurements was 0.08 +/- 0.05 mm. In conclusion, the automated approach allows the accurate assessment of vessel dimensions in MRA images.

Abdomen↗

PubMed1983

Quantitative gait evaluation of hip diseases using principal component analysis.

The measurement of five gait parameters, namely, joint angular displacement of lower extremities, floor reaction forces, trajectory for a point of force application, temporal factor and distance factor has been performed with ease and high speed using mini-computer on-line real-time processing. Gait data of 211 patients with hip diseases was normalized, quantified and summarized by the principal component analysis. A 'gait evaluation plane' was formed according to the results obtained by the principal component analysis. The gait evaluation using the plane was compared with clinical conditions of patients, and it was evident that this system can evaluate the recovery of the gait by treatment.

Biomechanical Phenomena↗

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↗

PubMed2003

Adolescent alcohol-use trajectories in the transition from high school.

A cohort of 3300 students from high schools across Victoria, Australia, were surveyed regarding their patterns of alcohol consumption from mid-1993 to 1995. The first wave of data was collected halfway through the students' final year of school (year 12). Students were then resurveyed 3 months following school completion and on two subsequent occasions, each separated by 6-month intervals. Analysis of the four waves of data indicated that five longitudinal patterns (trajectories) characterized temporal trends in male and female alcohol use through the transition from high school. Stable non-use trajectories were evident for 17% of males and 16% of females. Trajectories of less than weekly use characterized 45% of females and 46% of males, and showed little tendency to escalate toward harmful use. Among those using alcohol on a weekly or more frequent basis in high school, with few exceptions, use continued with at least the same frequency, but the quantity of alcohol consumed tended to escalate over time toward harmful levels. Overall, findings indicate that patterns of alcohol use tend to be stable over time, and more frequent alcohol use during the final year of high school tends to precede potentially harmful alcohol use following high school. Encouraging those high school students who consume alcohol once per week or more often to use alcohol on a less than weekly basis may be a valuable yet neglected harm minimization strategy.

Adolescent↗

PubMed2002

Bullet trajectory predicts the need for damage control: an artificial neural network model.

BACKGROUND: Effective use of damage control in trauma hinges on an early decision to use it. Bullet trajectory has never been studied as a marker for damage control. We hypothesize that this decision can be predicted by an artificial neural network (ANN) model based on the bullet trajectory and the patient's blood pressure. METHODS: A multilayer perceptron ANN predictive model was developed from a data set of 312 patients with single abdominal gunshot injuries. Input variables were the bullet path, trajectory patterns, and admission systolic pressure. The output variable was either a damage control laparotomy or intraoperative death. The best performing ANN was implemented on prospectively collected data from 34 patients. RESULTS: The model achieved a correct classification rate of 0.96 and area under the receiver operating characteristic curve of 0.94. External validation showed the model to have a sensitivity of 88% and specificity of 96%. Model implementation on the prospectively collected data had a correct classification rate of 0.91. Sensitivity analysis showed that systolic pressure, bullet path across the midline, and trajectory involving the right upper quadrant were the three most important input variables. CONCLUSION: Bullet trajectory is an important, hitherto unrecognized, factor that should be incorporated into the decision to use damage control.

Abdominal Injuries↗

PubMed1989

Time-based changes in fibroblast three-dimensional locomotory characteristics and phenotypes.

Three-dimensional locomotory trajectories have been determined for an embryonic fibroblast population and also for these cells after a 20-day period in tissue culture (C-20 cells). Differences in locomotory characteristics between these two cell populations are reported. Applying factor analysis to the distribution of angle changes between vectors in a cell's trajectory reveals the possibility that different locomotory phenotypes exist. Of the three phenotypes detected in the embryonic population only one continues in the C-20 population while a new phenotype appears in the latter. These results document changes in locomotory characteristics and phenotypes in an embryonic population with time.

Animals↗

PubMed1995

Automatic identification of discrete substates in proteins: singular value decomposition analysis of time-averaged crystallographic refinements.

The singular value decomposition (SVD) provides a method for decomposing a molecular dynamics trajectory into fundamental modes of atomic motion. The right singular vectors are projections of the protein conformations onto these modes showing the protein motion in a generalized low-dimensional basis. Statistical analysis of the right singular vectors can be used to classify discrete configurational substates in the protein. The configuration space portraits formed from the right singular vectors can also be used to visualize complex high-dimensional motion and to examine the extent of configuration space sampling by the simulation.

Computer Simulation↗

PubMed1999

Dynamics of multilayer networks in the vicinity of temporary minima.

A dynamical system model is derived for a single-output, two-layer neural network, which learns according to the back-propagation algorithm. Particular emphasis is placed on the analysis of the occurrence of temporary minima. The Jacobian matrix of the system is derived, whose eigenvalues characterize the evolution of learning. Temporary minima correspond to critical points of the phase plane trajectories, and the bifurcation of the Jacobian matrix eigenvalues signifies their abandonment. Following this analysis, we show that the employment of constrained optimization methods can decrease the time spent in the vicinity of this type of minima. A number of numerical results illustrates the analytical conclusions.

Journal Article↗

PubMed2001

Free energy component analysis for drug design: a case study of HIV-1 protease-inhibitor binding.

A theoretically rigorous and computationally tractable methodology for the prediction of the free energies of binding of protein-ligand complexes is presented. The method formulated involves developing molecular dynamics trajectories of the enzyme, the inhibitor, and the complex, followed by a free energy component analysis that conveys information on the physicochemical forces driving the protein-ligand complex formation and enables an elucidation of drug design principles for a given receptor from a thermodynamic perspective. The complexes of HIV-1 protease with two peptidomimetic inhibitors were taken as illustrative cases. Four-nanosecond-level all-atom molecular dynamics simulations using explicit solvent without any restraints were carried out on the protease-inhibitor complexes and the free proteases, and the trajectories were analyzed via a thermodynamic cycle to calculate the binding free energies. The computed free energies were seen to be in good accord with the reported data. It was noted that the net van der Waals and hydrophobic contributions were favorable to binding while the net electrostatics, entropies, and adaptation expense were unfavorable in these protease-inhibitor complexes. The hydrogen bond between the CH2OH group of the inhibitor at the scissile position and the catalytic aspartate was found to be favorable to binding. Various implicit solvent models were also considered and their shortcomings discussed. In addition, some plausible modifications to the inhibitor residues were attempted, which led to better binding affinities. The generality of the method and the transferability of the protocol with essentially no changes to any other protein-ligand system are emphasized.

Algorithms↗

PubMed2004

Feature selection of stabilometric parameters based on principal component analysis.

This study addresses the challenge of identifying the features of the Centre of pressure (COP) trajectory that are most sensitive to postural performance, with the aim of avoiding redundancy and allowing a straightforward interpretation of the results. Postural sway in 50 young, healthy subjects was measured by a force platform. Thirty-seven stabilometric parameters were computed from the one-dimensional and two-dimensional COP time series. After normalisation to the relevant biomechanical factors, by means of multiple regression models, a feature selection process was performed based on principal component analysis. Results suggest that COP two-dimensional time series can be primarily characterised by four parameters, describing the size of the COP path over the support surface; the principal sway direction; and the shape and bandwidth of the power spectral density plot. COP one-dimensional time series (antero-posterior (AP) and medio-lateral (ML)) can be characterised by six parameters describing COP dispersion along the AP direction; mean velocity along the ML and AP directions; the contrast between ML and AP regulatory activity; and two parameters describing the spectral characteristics of the COP along the AP direction. On the basis of the results obtained, some guidelines are suggested for the choice of stabilometric parameters to use, with the aim of promoting standardisation in quantitative posturography.

Adult↗

PubMed2005

ExoMars alternative escape trajectories with Soyuz/Fregat.

The objectives of ExoMars are to inject an orbiter around Mars and to land a rover on the surface to look for possible traces of life. During the first stages of the feasibility analysis, the mass margin of the orbiter was very small for a direct transfer in the Soyuz/Fregat scenario. An analysis of the combined use of lunar swing-bys and the Sun gravity gradient is performed with WESBOT in order to obtain alternative trajectories for injecting higher mass into Mars transfer. WESBOT is a GMV tool to find WSB transfers to the Moon and to design escape trajectories by performing several swing-bys with the Moon and the Earth. The weak stability boundary has been successfully used for lunar transfers (Hiten, SMART-1). For escape trajectories from the Earth, the potential mass gains depend on the escape direction and the departure date to make a series of gravity assists with the help of the Sun gravity gradient to save DeltaV. Several strategies are studied depending on the number and order of swing-bys. The departing conditions (date and orbit) are optimized but the arrival date to Mars is maintained because of mission requirements. For each type of strategy, a systematic search of initial guess trajectories is performed. The initial guess trajectory is made up of patched conics arcs and multiple shooting arcs when necessary. The optimal trajectories for the various scenarios are presented and show different morphologies. An analysis in terms of applicability to the ExoMars mission is included.

Journal Article↗