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PubMed2006

Age-related change in executive function: developmental trends and a latent variable analysis.

This study examined the developmental trajectories of three frequently postulated executive function (EF) components, Working Memory, Shifting, and Inhibition of responses, and their relation to performance on standard, but complex, neuropsychological EF tasks, the Wisconsin Card Sorting Task (WCST), and the Tower of London (ToL). Participants in four age groups (7-, 11-, 15-, and 21-year olds) carried out nine basic experimental tasks (three tasks for each EF), the WCST, and the ToL. Analyses were done in two steps: (1) analyses of (co)variance to examine developmental trends in individual EF tasks while correcting for basic processing speed, (2) confirmatory factor analysis to extract latent variables from the nine basic EF tasks, and to explain variance in the performance on WCST and ToL, using these latent variables. Analyses of (co)variance revealed a continuation of EF development into adolescence. Confirmatory factor analysis yielded two common factors: Working Memory and Shifting. However, the variables assumed to tap Inhibition proved unrelated. At a latent level, again correcting for basic processing speed, the development of Shifting was seen to continue into adolescence, while Working Memory continued to develop into young-adulthood. Regression analyses revealed that Working Memory contributed most strongly to WCST performance in all age groups. These results suggest that EF component processes develop at different rates, and that it is important to recognize both the unity and diversity of EF component processes in studying the development of EF.

Adolescent↗

PubMed2001

Concerted motions in copper plastocyanin and azurin: an essential dynamics study.

Essential dynamics analysis of molecular dynamics simulation trajectories (1.1 ns) of two copper containing electron transfer proteins, plastocyanin and azurin, has been performed. The protein essential modes have been analysed in order to identify large concerted motions which could be relevant for the electron transfer function exerted by these proteins. The analysis, conducted for temporal windows of different lengths along the protein trajectories, shows a rapid convergence and indicates that for both the proteins the predominant internal motions occur in a subspace of only a few degrees of freedom. Moreover, it is found that for both the proteins the likely binding sites (i.e. the hydrophobic and negative patches) with the reaction partners move in a concerted fashion with a few structural regions far from the active site. Such results are discussed in connection with the possible involvement of large concerted motions in the recognition and binding interaction with physiological electron transfer partners.

Azurin↗

PubMed1989

Periodic organization of the contractile apparatus in smooth muscle revealed by the motion of dense bodies in single cells.

To study the organization of the contractile apparatus in smooth muscle and its behavior during shortening, the movement of dense bodies in contracting saponin skinned, isolated cells was analyzed from digital images collected at fixed time intervals. These cells were optically lucent so that punctate structures, identified immunocytochemically as dense bodies, were visible in them with the phase contrast microscope. Methods were adapted and developed to track the bodies and to study their relative motion. Analysis of their tracks or trajectories indicated that the bodies did not move passively as cells shortened and that nearby bodies often had similar patterns of motion. Analysis of the relative motion of the bodies indicated that some bodies were structurally linked to one another or constrained so that the distance between them remained relatively constant during contraction. Such bodies tended to fall into laterally oriented, semirigid groups found at approximately 6-microns intervals along the cell axis. Other dense bodies moved rapidly toward one another axially during contraction. Such bodies were often members of separate semirigid groups. This suggests that the semirigid groups of dense bodies in smooth muscle cells may provide a framework for the attachment of the contractile structures to the cytoskeleton and the cell surface and indicates that smooth muscle may be more well-ordered than previously thought. The methods described here for the analysis of the motion of intracellular structures should be directly applicable to the study of motion in other cell types.

Actinin↗

PubMed2003

A methodological note on nonlinear time series analysis: is the open- and closed-loop model of Collins and De Luca (1993) a statistical artifact?

The authors reexamined, theoretically and empirically, the method proposed by J. J. Collins and C. D. De Luca (1993) for the analysis of center-of-pressure trajectories. The main argument in this article is that Collins and De Luca's approach is not adapted to the analysis of bounded time series and leads to statistical artifacts such as underestimation of the diffusion process for long-term intervals. The open- and closed-loop model developed by Collins and De Luca is a direct consequence of those statistical problems. Applying more classical methods, such as rescaled range analysis or detrended fluctuation analysis, the authors show that center-of-pressure trajectories can be modeled as continuous, antipersistent fractional Brownian motion. More specifically, those trajectories behave like 1/f noise, a ubiquitous feature in adaptive biological systems.

Humans↗

PubMed2006

Changes in precipitation chemistry in Lithuania for 1981-2004.

This paper considers the spatial and temporal variability in concentrations of the potentially acidifying ions in precipitation in Lithuania during the 1981-2004 period. Chemical analysis of precipitation included measurements of pH, conductivity, sulfate (SO4(2-)), nitrate (NO3-), chloride (Cl-), ammonium (NH4+), sodium (Na+), potassium (K+), and calcium (Ca2+). Temporal trends in the potentially acidifying ion concentrations in precipitation and wet deposition were evaluated using the non-parametric Mann-Kendall test and Sen's slope estimator. A statistically significant decline was observed in non-sea salt sulfate (nssSO4(2-)) and hydrogen (H+) ions concentrations (82% and 79%, respectively) and wet depositions (88% and 74%, respectively). Temporal trends both in concentration and wet deposition of nitrate and ammonium were not as pronounced as trends in sulfate concentration. Analysis of air mass backward trajectories was applied to reveal the influence of air mass originating in different regions on wet deposition of acidifying species in Lithuania. Sector analysis clearly showed that wet deposition of sulfur and nitrogen in Lithuania is to a large extent anthropogenic and the main source regions of acidifying species contributing to wet deposition in Lithuania are in South and Central Europe.

Acid Rain↗

PubMed2004

A stochastic analysis of a Brownian ratchet model for actin-based motility.

In recent single-particle tracking (SPT) measurements on Listeria monocytogenes motility in cells [Kuo and McGrath (2000)], the actin-based stochastic dynamics of the bacterium movement has been analyzed statistically in terms of the mean-square displacement (MSD) of the trajectory. We present a stochastic analysis of a simplified polymerization Brownian ratchet (BR) model in which motions are limited by the bacterium movement. Analytical results are obtained and statistical data analyses are investigated. It is shown that the MSD of the stochastic bacterium movement is a monotonic quadratic function while the MSD for detrended trajectories is linear. Both the short-time relaxation and the long-time kinetics in terms the mean velocity and effective diffusion constant of the propelled bacterium are obtained from the MSD analysis. The MSD of the gap between actin tip and the bacterium exhibits an oscillatory behavior when there is a large resistant force from the bacterium. For comparison, a continuous diffusion formalism of the BR model with great analytical simplicity is also studied.

Actins↗

PubMed2006

Outcomes in patients undergoing single-trajectory endoscopic third ventriculostomy and endoscopic biopsy for midline tumors presenting with obstructive hydrocephalus.

OBJECT: The primary aim of this study was to evaluate the success of endoscopic third ventriculostomy (ETV) as a treatment for obstructive hydrocephalus secondary to midline tumors (midbrain, pontine, pineal, tectal plate, thalamic, and third ventricular regions). In addition, the study examined the role and value of endoscopic tumor biopsy (ETB) in the management of such cases. All surgical procedures were performed through a single-trajectory approach. METHODS: A retrospective analysis of clinical notes, operation records, and pre- and postventriculostomy neuroimaging data was performed to determine the success or failure and complications of ETV and ETB in 42 patients presenting with tumor-induced obstructive hydrocephalus. Patient data were derived from an endoscopy database initiated in 1998. The study population included 21 female and 21 male patients (mean age 37 years, range 5-77 years). All 42 patients underwent an ETV; 33 of the 42 underwent an ETV and an ETB (single-trajectory). One patient was excluded from the follow-up analysis due to rapid deterioration of his condition from tumor progression. The duration of follow up ranged from 3 to 84 months (mean 32 months). At the last follow up, 11 patients with ETVs had undergone shunt placement and two patients had undergone repeated ETVs, giving a long-term success rate of 68% (28 of 41 cases) for single ETV as a treatment for hydrocephalus at presentation. Statistical analysis revealed no significant relationship (p > 0.92) between tumor location and ETV success or failure. The mean time to ETV failure was 32 weeks. Histological examination of biopsy specimens was non-diagnostic in eight (24%) of the 33 cases in which ETB was performed. Seven of these cases involved pineal region tumors and one involved a tectal plate tumor. There was no death or major morbidity associated with ETV and ETB in this series. CONCLUSIONS: Endoscopic third ventriculostomy is a safe and durable means of controlling hydrocephalus in tumor cases. Its success rate is high--comparable to that reported in aqueduct stenosis cases. Although ETB is probably not as accurate for diagnosis as biopsy with frame-based stereotactic guidance, it is associated with a lower mortality rate and, in the correct clinical setting, may be justifiably attempted as an initial biopsy procedure at the same time as ETV via a single-trajectory approach.

Adolescent↗

PubMed2001

Culture and schizophrenia: a cross-ethnic growth curve analysis.

This study examined the longitudinal trajectory of a sociocentric construct among African-Americans, Latinos, and nonminorities. Participants were 163 individuals diagnosed with schizophrenia who were admitted to community-based psychosocial programs. Previous research had established empathy and social competence as sociocentric cultural mediators of a benign symptom profile for ethnic minorities. Data on sociocentric indicators were collected every 6 months for over 3 years. Growth curve methodology was used to examine the empathy and social competence outcomes over time and across ethnic groups. The results revealed a dynamic course for both sociocentric mediators. However, the dynamic growth curve for empathy was related to ethnicity; for social competence it was not. Empathy levels for African-Americans decreased and then attenuated, whereas empathy levels for Latinos decreased over the entire study. Nonminorities showed very little change overall. The nature of sociocentric phenomena is dynamic and complex. These qualities can apparently be cultivated or diminished over time.

Adult↗

PubMed2002

Fractal analysis of Daphnia motion for acute toxicity bioassay.

To quantify individual behavioral responses to toxic chemicals, the swimming motion of individual Daphnia magna was continuously monitored using a motion analysis system. The fractal dimension was introduced to compare the straightness or complexity of the swimming trajectory before and after exposure to toxic chemicals. Analysis indicated that the swimming trajectory of individual Daphnia has a fractal structure. The basal fractal dimension in the control medium was 1.35+/-0.01 (n = 50 Daphnia). Exposure to CuSO(4) (10 microg/L), organophosphorus (Dichlorvos; 10 microg/L), and carbamate (Propoxur; 500 microg/L) pesticide caused a significant increase in the fractal dimension with a latency of 60 min, reaching a maximal level of 2.26+/-0.34, 2.43+/-0.19, and 2.51+/-0.21, respectively, after a 120-min exposure. The magnitude of the change in the fractal dimension was related to the toxic chemical concentration and the exposure time. Threshold concentrations determined at 60 min of exposure were 10 microg/L for CuSO(4), 5 microg/L for Dichlorvos, and 500 microg/L for Propoxur. The toxicity index (EC(50)) values after 120 min of exposure were 6.31 microg/L, 7.64 microg/L, and 466 microg/L for CuSO(4), Dichlorvos, and Propoxur, respectively. Thus, the fractal dimension seems useful for analyzing and comparing complex trails, such as swimming trajectories, which could be used as the endpoint for an acute bioassay.

Animals↗

PubMed1986

Geometrical principal component analysis of planar-segments of the three-channel Lissajous' trajectory of human auditory brain stem evoked potentials.

Three-Channel Lissajous' Trajectories (3CLTs) of Auditory Brain Stem Evoked Potentials (ABEP) were obtained from 15 normal humans. Planar-segments of 3CLT were identified and the orientations of the first two geometrical principal components, which interact to produce the planar-segments, were calculated. Each principal component's orientation in voltage space was quantified by its coefficients (A, B and C). Intersubject variability of these orientations was comparable to the variability of plane orientations. The principal components of planar-segments can indicate the type of generator activity that is involved in the formation of planar-segments. The results of this analysis indicate that planarity of each 3CLT component is produced by the interaction of simultaneous multiple generators, or by a single synchronous generator which changes its orientation. The coefficients of these principal components may complement plane coefficients as quantitative indices of 3CLT of ABEP.

Adult↗

PubMed1998

Reversible inactivation of monkey superior colliculus. I. Curvature of saccadic trajectory.

The neurons in the intermediate layers of the monkey superior colliculus (SC) that discharge before saccadic eye movements can be divided into at least two types, burst and buildup neurons, and the differences in their characteristics are compatible with different functional contributions of the two cell types. It has been suggested that a spread of activity across the population of the buildup neurons during saccade generation may contribute to the control of saccadic eye movements. The influence of any such spread should be on both the horizontal and vertical components of the saccade because the map of the movement fields on the SC is a two-dimensional one; it should affect the trajectory of saccade. The present experiments used muscimol injections to inactivate areas within the SC to determine the functional contribution of such a spread of activity on the trajectory of the saccades. The analysis concentrated on saccades made to areas of the visual field that should be affected primarily by alteration of buildup neuron activity. Muscimol injections produced saccades with altered trajectories; they became consistently curved after the injection, and successive saccades to the same targets had similar curvatures. The curved saccades showed changes in their direction and speed at the very beginning of the saccade, and for those saccades that reached the target, the direction of the saccade was altered near the end to compensate for the initially incorrect direction. Postinjection saccades had lower peak speeds, longer durations, and longer latencies for initiation. The changes in saccadic trajectories resulting from muscimol injections, along with the previous observations on changes in speed of saccades with such injections, indicate that the SC is involved in influencing the eye position during the saccade as well as at the end of the saccade. The changes in trajectory when injections were made more rostral in the SC than the most active burst neurons also are consistent with a contribution of the buildup neurons to the control of the eye trajectory. The results do not, however, support the hypothesis that the buildup neurons in the SC act as a spatial integrator.

Animals↗

PubMed1996

TRAJAN: a tool for analyzing trajectories from molecular simulations.

Molecular dynamics simulations of biological systems are notoriously difficult to analyze because of the complexity of the information that contain. We describe a new method for analyzing trajectories from simulations in order to extract important features of the motion. The trajectory of each atom is partitioned into conformation wells, in each of which its motion is assumed to be predominantly harmonic oscillation around an average position. Thus each atom moves anharmonically through a sequence of wells during the trajectory. The movement of atoms between wells, their ellipsoids of motion within each well, and correlations in the motion of atoms are quantified and can be visualized with molecular graphics. The TRAJAN analysis procedure is applicable to trajectories from equilibrium and nonequilibrium simulations and is not restricted to molecular dynamics simulations. Its application is demonstrated for a range of model systems.

Algorithms↗

PubMed2006

Classical trajectory simulations of photoionization dynamics of tryptophan: intramolecular energy flow, hydrogen-transfer processes and conformational transitions.

One-photon and two-photon ionization dynamics of tryptophan is studied by classical trajectory simulations using the semiempirical parametric method number 3 (PM3) potential surface in "on the fly" calculations. The tryptophan conformer is assumed to be in the vibrational ground state prior to ionization. Initial conditions for the trajectories are weighted according to the Wigner distribution function computed for that state. Vertical ionization in the spirit of the classical Franck-Condon principle is assumed. For the two-photon ionization process the ionization is assumed to go resonantively through the first excited state. Most trajectories are computed, and the analysis is carried out for the first 10 ps. A range of interesting effects are observed. The main findings are as follows: (1) Multiple conformational transitions are observed in most of the trajectories within the ultrafast duration of 10 ps. (2) Hydrogen transfer from the carboxyl group to the amino group and back has been observed. A zwitterion is formed as a transient state. (3) Two new isomers are formed during the dynamics, which have apparently not been previously observed. (4) Fast energy flow between the ring modes and the amino acid backbone is observed for both one- and two-photon ionization. However, the effective vibrational temperatures only approach the same value after 90 ps. The conformation transition dynamics, the proton-transfer processes and the vibrational energy flow are discussed and analyzed.

Computer Simulation↗

PubMed1995

Superimposed Image Analysis System (SIAS) software: a new approach to sperm motility assessment.

OBJECTIVE: To apply Superimposed Image Analysis System (SIAS) software (Delta Sistemi, Rome, Italy) to the objective analysis of sperm motility. DESIGN: To test a new procedure for sperm motility assessment based on image superimposition. RESULTS: The system can superimpose six sequential frames onto a monitor producing a final image with a motion effect similar to the multiple exposure photography method, but bypassing the film processing stage. Viewing the final image of a complete series of six superimposed frames allows the evaluation of the percentage of motile spermatozoa and their kinetic characteristics. Compared with multiple exposure photography, SIAS has the following main advantages: [1] the procedure is quick; [2] projecting the first frame alone allows the easy evaluation of sperm concentration; and [3] the system allows quick and easy analysis and measurement of each sperm trajectory frame by frame, thus avoiding misleading interpretations because of crossing sperm trajectories, collisions, and overlapping of motile spermatoza with round cells or immotile spermatozoa. CONCLUSIONS: Superimposed image analysis is a new approach to sperm motility assessment. It seems to be useful particularly in selected situations, such as oligozoospermia or in cases of increased round cell concentration. In these situations, SIAS can even serve as a support or an alternative to the computer-aided sperm analysis system widely used for objective sperm analysis.

Humans↗

PubMed2006

Crime, prostitution, drugs, and malingered insanity: female offenders' resistant strategies to abuse and domination.

Mizrahi female offenders have been described as passive victims propelled into crime, prostitution, and drug abuse as a result of traumatic childhood and life course experiences. This qualitative study adopts a postmodern critical orientation and Foucault's bottom-up microsocial analysis of power to examine the trajectories of resistance of 8 female offenders who break the silence to tell their life story. Analysis of narratives, informal conversations, and more focused, in-depth interviews with these women allow the deconstruction of the stereotype of the passive and helpless female offender. Using the sensitizing concepts of control, agency, and resistant efforts and letting the data speak, this research reconstructs female offending as a hidden script of resistance against intolerable socioeconomic deprivation and extreme forms of abuse.

Adult↗

PubMed2004

Balance control during an arm raising movement in bipedal stance: which biomechanical factor is controlled?

In order to obtain new insight into the control of balance during arm raising movements in bipedal stance, we performed a biomechanical analysis of kinematics and dynamical aspects of arm raising movements by combining experimental work, large-scale models of the body, and techniques simulating human behavior. A comparison between experimental and simulated joint kinematics showed that the minimum torque change model yielded realistic trajectories. We then performed an analysis based on computer simulations. Since keeping the center of pressure (CoP) and the projection of the center of mass (CoM) inside the support area is essential for equilibrium, we modeled an arm raising movement where displacement of one or the other variable is limited. For this optimization model, the effects of adding equilibrium constraints on movement trajectories were investigated. The results show that: (a) the choice of the regulated variable influences the strategy adopted by the system and (b) the system was not able to regulate the CoM for very fast movements without compromising its balance. Consequently, we suggest that the system is able to maintain balance while raising the arm by only controlling the CoP. This may be done mainly by using hip mechanisms and controlling net ankle torque.

Adult↗

PubMed2004

Intelligent on-line fault tolerant control for unanticipated catastrophic failures.

As dynamic systems become increasingly complex, experience rapidly changing environments, and encounter a greater variety of unexpected component failures, solving the control problems of such systems is a grand challenge for control engineers. Traditional control design techniques are not adequate to cope with these systems, which may suffer from unanticipated dynamic failures. In this research work, we investigate the on-line fault tolerant control problem and propose an intelligent on-line control strategy to handle the desired trajectories tracking problem for systems suffering from various unanticipated catastrophic faults. Through theoretical analysis, the sufficient condition of system stability has been derived and two different on-line control laws have been developed. The approach of the proposed intelligent control strategy is to continuously monitor the system performance and identify what the system's current state is by using a fault detection method based upon our best knowledge of the nominal system and nominal controller. Once a fault is detected, the proposed intelligent controller will adjust its control signal to compensate for the unknown system failure dynamics by using an artificial neural network as an on-line estimator to approximate the unexpected and unknown failure dynamics. The first control law is derived directly from the Lyapunov stability theory, while the second control law is derived based upon the discrete-time sliding mode control technique. Both control laws have been implemented in a variety of failure scenarios to validate the proposed intelligent control scheme. The simulation results, including a three-tank benchmark problem, comply with theoretical analysis and demonstrate a significant improvement in trajectory following performance based upon the proposed intelligent control strategy.

Artificial Intelligence↗

PubMed2003

Computational study on the origin of the stereoselectivity for the photochemical denitrogenation of diazabicycloheptene.

The origin of the inversion stereoselectivity of housane formation via photochemical nitrogen extrusion of diazabicycloheptene (DBH) has been investigated using reaction path computations and multireference second-order perturbation theory within a CASPT2//CASSCF scheme. We show that the primary photoproduct of the reaction is an exo-axial conformer of the diazenyl diradical ((1) DZ) which displays a cyclopenta-1,3-diyl moiety with a Cs-like structure. (1) DZ is selectively generated via decay at a linear-axial conical intersection, and it is located in a shallow region of the ground state potential energy surface that provides access to five different reaction pathways. Reaction path analysis (including probing with classical trajectories) indicates that production of inverted housane can only occur via impulsive population of an axial-to-equatorial pathway, and it is thus inconsistent with thermal equilibration of the primary (1) DZ conformer. Similarly, according to the same analysis, the decrease of inversion stereoselectivity and even the retention (stereochemical memory effect) observed for suitably substituted DBHs are explained by dynamics effects where the axial-to-equatorial impulsive motion is restrained by the inertia and/or steric hindrance of the substituents. These results shade light on the poorly understood mechanisms that allow a photochemical reaction, in which a large amount of energy is deposited in the reactant by photon absorption, to show a high degree of stereoselectivity.

Journal Article↗