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Results for “trajectory analysis”

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At least 127 records · Page 7Linked to original sources

PubMed2000

Source areas of airborne 7Be and 210Pb measured in Northern Finland.

Daily aerosol samples were collected at Sodankylä, Northern Finland, from July 1995 to June 1997. The filter samples were analyzed for 7Be by semiconductor gamma spectrometry and for 210Pb by alpha counting of the in-grown 210Po. The concentrations were lognormally distributed with median concentrations of 2,500 and 160 muBq m(-3) for 7Be and 210Pb, respectively. The trajectory analysis performed showed that the highest 210Pb activity concentrations were associated with continental air masses originating in Central Russia. High 7Be activity concentrations were found in air masses from Central Russia and, during springtime, also in air masses coming from southwest. The latter cases were attributed to the transfer of stratospheric air masses into the troposphere along the polar front. Slightly elevated 7Be and 210Pb concentrations were found in air masses coming to Sodankyla from northwest between 70th and 80th latitudes. This was attributed to the long-range transport from continental North America.

Air Pollutants, Radioactive↗

PubMed2003

Dynamic probe of dust wakefield interactions using constrained collisions.

The magnitude and the structure of the ion-wakefield potential below a negatively charged dust particle levitated in the plasma-sheath region have been determined. Attractive and repulsive components of the interaction force were extracted from a trajectory analysis of low-energy dust collisions in a well-defined electrostatic potential, which constrained the dynamics of the collisions to be one dimensional. The peak attraction was on the order of 100 fN. The structure of the ion-wakefield-induced attractive potential was significantly different from a screened-Coulomb repulsive potential.

Journal Article↗

PubMed2003

Measurement of attractive interactions produced by the ion wakefield in dusty plasmas using a constrained collision geometry.

Plasma dust particle interactions, charges, and screening lengths are derived from measurements of time-dependent particle positions in a simplified geometry. The magnitude and structure of the ion wakefield potential below a negatively charged dust particle levitated in the plasma sheath region were measured as functions of the pressure and interparticle spacing. Attractive and repulsive components of the interaction force were extracted from a trajectory analysis of low-energy dust collisions between different mass particles in a well-defined electrostatic potential that constrained the dynamics of the collisions to be one-dimensional. Typical peak attractions varied between 60 and 230 fN while the peak particle-particle repulsion was on the order of 60 fN. Random thermal motion of the particles contributed to observable rates for transitions between different equilibrium configurations of vertically separated particles. The influence of nearest- and non-nearest-neighbor interactions on calculated particle parameters is examined using several methods.

Journal Article↗

PubMed2004

Structure of the ion wakefield in dusty plasmas.

The magnitude and structure of the ion wakefield potential below a single negatively charged dust particle levitated in the plasma sheath region were measured using a test particle. Attractive and repulsive components of the interaction force were extracted from a trajectory analysis of low-energy collisions between different mass particles in a well-defined electrostatic potential that constrained the dynamics of the collisions to one dimension. As the vertical spacing between the particles increased, the peak attractive force decreased and the width of the potential increased. For the largest vertical separations measured in this study, the lower particle does not form a vertical pair with the upper particle but rather has an equilibrium position offset from the bottom of the parabolic potential confining well.

Journal Article↗

PubMedDate not supplied

Psychophysical evaluation of in-situ ultrasound visualization.

We present a novel psychophysical method for evaluating ultrasonography based on Real-Time Tomographic Reflection (RTTR), in comparison to Conventional Ultrasound (CUS). The method measures the user's perception of the location of an ultrasound-imaged target independently from assessing the action employed to reach it. Three experiments were conducted with the Sonic Flashlight (SF), an RTTR device, and CUS. The first two experiments determined subjects' perception of target location with a triangulation-by-pointing task. Depth perception with the SF was comparable to direct vision, while CUS caused considerable underestimation of target depth. Binocular depth information in the SF was shown to significantly contribute to its superiority. The third experiment tested subjects in an ultrasound-guided needle insertion task. Because the SF provides visualization of the target at its actual location, subjects performed insertions faster and more accurately by using the SF rather than CUS. Furthermore, the trajectory analysis showed that insertions with the SF generally went directly to the target along the desired path, while CUS often led to a large deviation from the correct path consistent with the observed underestimation of target depth. These findings lend great promise to the use of RTTR-based imaging in clinical practice and provide precise means of assessing efficacy.

Biopsy, Needle↗

PubMed2000

Trp42 rotamers report reduced flexibility when the inhibitor acetyl-pepstatin is bound to HIV-1 protease.

The Q7K/L331/L631 HIV-1 protease mutant was expressed in Escherichia coli and the effect of binding a substrate-analog inhibitor, acetyl-pepstatin, was investigated by fluorescence spectroscopy and molecular dynamics. The dimeric enzyme has four intrinsic tryptophans, located at positions 6 and 42 in each monomer. Fluorescence spectra and acrylamide quenching experiments show two differently accessible Trp populations in the apoenzyme with k(q1) = 6.85 x 10(9) M(-1) s(-1) and k(q2) = 1.88 x 10(9) M(-1) s(-1), that merge into one in the complex with k(q) = 1.78 x 10(9) M(-1) s(-1). 500 ps trajectory analysis of Trp X1/X2 rotameric interconversions suggest a model to account for the observed Trp fluorescence. In the simulations, Trp6/Trp6B rotameric interconversions do not occur on this timescale for both HIV forms. In the apoenzyme simulations, however, both Trp42s and Trp42Bs are flipping between X1/X2 states; in the complexed form, no such interconverions occur. A detailed investigation of the local Trp environments sampled during the molecular dynamics simulation suggests that one of the apoenzyme Trp42B rotameric interconversions would allow indole-quencher contact, such as with nearby Tyr59. This could account for the short lifetime component. The model thus interprets the experimental data on the basis of the conformational fluctuations of Trp42s alone. It suggests that the rotameric interconversions of these Trps, located relatively far from the active site and at the very start of the flap region, becomes restrained when the apoenzyme binds the inhibitor. The model is thus consistent with associating components of the fluorescence decay in HIV-1 protease to ground state conformational heterogeneity.

Acrylamide↗

PubMed2005

Identification of laser generated acoustic waves in the two-dimensional transient response of cylinders.

The published model [Appl. Phys. Lett. 82, 4379-4381 (2003)] for the two-dimensional transient wave propagation in a cylinder is modified to avoid the inherited integration of the numerical inverse scheme. The Fourier series expansion is introduced for one spatial coordinate to resolve the transient response problem: theoretical radial displacements in either the ablation or the thermoelastic regime are obtained with little numerical noise and short computation time. The normal mode expansion method fails to deliver results with the same accuracy. Acoustic waves are fully identified by the ray trajectory analysis. These identified waves are further verified on the experimental results observed with the laser ultrasonic technique.

Journal Article↗

PubMed1975

Conversion of SO2 to sulfur particulate in the Los Angeles atmosphere.

Gas phase and particular phase sulfur have been measured at various locations in the Los Angeles basin to determine atmospheric conversion rates and mechanisms. A new technique was developed for the measurement of particulate sulfur. From measurements of the particulate to gas phase sulfur ratio near the major stationary sources and far downstream and from estimates of travel time determined by air trajectory analysis, it is possible to estimate gas-to-particle conversion rates for sulfur. Such calculations show that automobiles presently contribute a major part of the total sulfur as measured at a receptor site such as Pasadena, while contributing only a small amount to the particulate sulfur loading. The introduction of oxidation catalyst-equipped vehicles may add significantly to the particulate sulfur at downwind receptor sites; predictions of particulate sulfur concentrations near freeways show substantial increases due to such vehicles.

Aerosols↗

PubMed2001

Collision efficiency factor of bubble and particle (alpha bp) in DAF: theory and experimental verification.

The collision efficiency factor of bubble and particle (alpha bp) in dissolved air flotation (DAF) can be calculated theoretically by trajectory analysis, which takes into account both hydrodynamics and interparticle forces. To determine the theoretically optimum particle size for any given bubble size, a collision efficiency diagram for DAF was developed where collision efficiency is contoured on a plane of particle and bubble sizes for different conditions of particle zeta potential. A set of experiments tested the validity of the suggested collision efficiency diagram, and examined whether pretreatment is important and why slight coagulant overdosing and shorter flocculation times are generally preferred in DAF, both current accepted practice. Batch DAF reactors were used and kaolin samples were prepared from jar tests using different alum dosages and flocculation times. The particle size distribution, particle zeta potential, and turbidity removal in each experiment were measured, as were bubble size and zeta potential. The results agreed well with the predictions of the collision efficiency diagram and explained current practices. A collision efficiency diagram identifies the pretreatment goal, i.e., tailoring of the optimum characteristics required of particles (zeta potential and size) under existing operational bubble characteristic.

Air↗

PubMed2004

Fundamental characteristics of bubbles and ramifications for the flotation process.

Flotation processes involve the use of very small bubbles (micro-bubbles) to separate particles from water. The process has become a good alternative to sedimentation, especially where the particles are small or of low density. Although the flotation process commences with a collision between particles and bubbles, most research has been focused only on the characteristics of the particles. In this paper, recent theoretical and experimental research on the characteristics of bubbles is summarized. The effect on the collision efficiency of the size and charge of bubbles is calculated through trajectory analysis. The size and charge of bubbles are measured under different conditions and the ramifications of the results are discussed. The results may lead to a better understanding and optimization of the existing process. In particular, we discuss an idea that a new advanced flotation process might be possible by the modification of the characteristics of the bubble alone or of both bubble and particle.

Air↗

PubMed1991

Possible introduction of epizootic hemorrhagic disease of deer virus (serotype 2) and bluetongue virus (serotype 11) into British Columbia in 1987 and 1988 by infected Culicoides carried on the wind.

Outbreaks of epizootic hemorrhagic disease of deer and of bluetongue began in British Columbia in August and October 1987 respectively and recrudescence of infection by both viruses was detected the following year in August. Weather records for up to 18 days before the initial outbreaks of disease, isolation of virus or seroconversion were examined to determine if the viruses could have been introduced by infected Culicoides carried on the wind. Data on temperature, rainfall, wind speed and direction and pressure together with backward trajectory analysis showed that there were suitable winds which could have introduced Culicoides infected with epizootic hemorrhagic disease of deer virus on 13 August 1987 (14 days before disease was observed), Culicoides infected with bluetongue virus on 1 October 1987 (7 days before virus was isolated and 13 days before disease in sheep) and Culicoides infected with bluetongue or epizootic hemorrhagic disease of deer viruses on 20 July 1988 (15 days before seroconversion was detected). The arrival on 13 August 1987 coincided with the passage of a cold front and rain and that on 1 October 1987 with a fall in temperature and calm winds. The source of the Culicoides before arrival could have been the Okanogan Valley as far south as the junction of the Okanogan and Columbia rivers in Washington, USA. Flight would have been at temperatures of 12.6 degrees C or higher and at heights up to 1.5 km.

Animals↗

PubMed2006

Chemical characteristics of aerosol particles (PM2.5) at a site of Horqin Sand-land in northeast China.

The objective of this study was to characterize the mass concentration and chemical composition of aerosol particles (PM2.5) collected at Tongliao (Inner Mongolia Autonomous Region, China), a site in Horqin Sand-land in northeast China. During spring 2005, the mass concentration for PM2.5 was (126 +/- 71)microg/m3 in average. Five dust storm events were monitored with higher concentration of (255 +/- 77)microg/m3 in average than the non dusty days of (106 +/- 44)microg/m3. Concentrations for 20 elements were obtained by the PIXE method. Mass concentrations of Al, Mg, Si, K, Ca, Ti, Mn, and V, which increased with the PM2.5 concentration, were higher than the pollution elements (S, Cl, Zn, Ar, Se, Br, and Pb). Enrichment factor relative to crust material was also calculated, which showed dust trace elements were mainly from earth upper crust and pollution elements were dominated the anthropogenic aerosols. The Si/Al, Ca/Al, and Fe/Al ratios in PM2.5 samples at Tongliao were 4.07, 0.94, and 0.82, respectively, which were remarkably different with those on other source regions, such as "Western desert source region", "North desert source region" and central Asia source. Air mass back-trajectory analysis identified three kinds of general pathways were associated with the aerosol particle transport to Tongliao, but have the similar elemental ratios, implying that elemental signatures for dust aerosol from Horqin Sand-land were different with other regions.

Air Pollutants↗

PubMed1979

Temperature dependence on the passive and dynamic electrical parameters of muscle cells.

Measurements of the temperature dependence in the range from 10 C to 30 C on the passive and dynamic electrical properties of single frog muscle cell following Arrhenius relation have been made. The propagated responses (V-t) and conduction velocity theta were analyzed following the H-H propagated cable equation. The ionic current-membrane potential relationship (I-t) was calculated from the phase-plane trajectory analysis (V-V) of the action potential curve (V-t). All the rate and time constants of the excitation and propagation processes kr, kNa, kK, tau Na, tau K, the negative conductance (-gNa) and the ionic conductances gNa, gK, influencing the evolution of the curves (V-t), (V-V) and (I-V) are correlated. The magnitudes of the resting (Vr) and action potential amplitude (Vs), the excitation potential (V*), the negative after potential (Vn), and the sodium equilibrium potential (VNa); the magnitudes of the maximum rate of rise and fall of the spike (V+) and (V-) and those corresponding to the inward INa and outward IK ionic currents, were analyzed. Two general classes of findings were obtained. One group of action potential parameters theta, V+, V-, Vn, kr, kNa, kK, tau Na, tau K, -gNa, gNa, gK, INa and IK is strongly temperature dependent with Q 10 S approximately 2 and energy of activation E approximately 10 kcal/mole. The other group of parameters, Gm (passive conductance), Cm (capacitance), tau, Vr, V*, Vs, and VNa are slightly temperature dependent, with Q10's lower than 1.4. This study contributes deeply to the analysis of temperature effects on the electrical cell responses to adequate stimuli. This temperature dependence analysis was designed to detect possible "masked" actions of microwave radiation on cell membrane functions.

Action Potentials↗

PubMedDate not supplied

[Magnetic susceptibility and magnetic capture of cells].

A phenomenon of magnetic capture of human erythrocytes and lymphocytes in paramagnetic and diamagnetic modes of motion near a transversely magnetized wire has been investigated. The values of magnetic susceptibility of numerous individual erythrocytes containing hemoglobin in various forms and lymphocytes were determined using a trajectory analysis. The distribution histograms of erythrocytes in various states and lymphocytes of magnetic susceptibility have been constructed. This histogram for lymphocytes cannot exclude magnetic identification of these cells. The method of determination of physiological concentration of methemoglobin in erythrocytes based on the distribution histogram has been suggested.

Erythrocytes↗

PubMed1997

500 picosecond molecular dynamics simulation of amphiphilic polypeptide Ac(LKKL)4 NHEt with 1,2 di-mysristoyl-sn-glycero-3-phosphorylcholine (DMPC) molecules.

Molecular dynamics (MD) simulation of the interaction between amphiphilic polypeptide Ac(LKKL)4NHEt and 4 DMPC (1,2 di-mysristoyl-sn-glycero-3-phosphorylcholine) molecules has been carried out at 310 K for 500 picoseconds (ps) using AMBER 4.0. Interaction energy and a number of conformational parameters are calculated for the subaveraged coordinates, using P-CURVES 3.1 and our MD trajectory analysis program ANALMD. No significant change in DMPC headgroup conformation was observed. However, the mobility of P atoms was found to be restricted. The chains were quite flexible and their flexibility increased towards the ends. They interacted amongst themselves. The polypeptide remained predominantly in alpha-helical conformation. Leu1 and Lys2 at the N terminus and Leu13 to Leu16 at C terminus assumed non helical conformation and were quite flexible. Average interaction energy between the polypeptide and DMPC molecules was found to be -151.828 kcal*mol-1. The main contributory factor was electrostatic interaction of Lys NH3+ groups with the DMPC phosphates. On an average one Lys chain interacted with 1.5 DMPC molecules. Central region of the polypeptide had better contact with DMPC molecules. A model for the fusogenic properties of the polypeptide is presented on the basis of MD results.

Amino Acid Sequence↗

PubMed1994

Improved automatized recording of masticatory reflexes through analysis of effort trajectory during biofeedback.

Tap and sound evoked inhibitory motor reflexes within masseteric EMG were studied by means of a new technique that uses real time analysis of the trajectory followed during voluntary occlusal effort, controlled through visual biofeedback, in order to stimulate on exactly the same activity background. This technique uses a two computers system, doing parallel processing to support data acquisition, video indication, calculus of the pursued trajectory and evaluation of it. Stimuli were automatically delivered when the effort's trajectory fulfilled a set of conditions. Denomination of reflexigram (RFXG) is proposed to the cumulative, rectified and filtered EMG's series so recorded. Normal morphologies of RFXG were established on a 90 normal patients group. Clear clinical correlations were also found within two groups: 30 bruxists and 50 with temporomandibular joint dysfunction.

Acoustic Stimulation↗

PubMed2005

A wavelet approach for the analysis of folding trajectory of protein Trp-cage.

Understanding how protein folds into a functional native structure is arguably one of the most challenging problems remaining in computational biology. Currently, the protein folding mechanism is often characterized by calculating the free energy landscape in terms of various reaction coordinates such as the fraction of native contacts, the radius of gyration, the RMS deviation from the native and so on. In this paper, we present a wavelet approach towards understanding the global state changes during protein folding. The approach is based on the wavelet analysis on the trajectories of various reaction coordinates to identify the significant intermediate states or structural motifs in the folding process. We demonstrate through an example protein Trp-cage that this approach extracts crucial information about protein folding intermediate states as well as the time correlation among these states. Furthermore, the current approach reveals a meaningful structural pattern that had been overlooked in previous works, which provides a better understanding of the folding mechanism as well as the limitation of the current force fields.

Algorithms↗

PubMedDate not supplied

[Analysis of the trajectory of care of a cohort of 280 depressive patients. Initial results].

This work presents an analysis instrument and the first results obtained while applying it to 280 depressive patients compared to 496 non-depressive patients who were followed during a 4 year period. The treatment follow-up permits us to present the chronological "history" of the patient's contacts with different services and to establish a classification. One of the interests, for the clinician, consists in specifying the best therapeutical approach possible. A more detailed study should allow us to relate certain patterns with diagnostic subcategories and to determine if the high proportion of short patterns corresponds to the "successful" treatments or to the dropouts.

Adult↗