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PubMed2004

Does support surface coefficient of friction influence postural dynamics and isometric force productions of the upper extremities performed by seated subjects?

The purpose of this study is to determine if increasing the potential risk of slipping on support surface materials decreases postural dynamics and task performance. Seated subjects were asked to exert maximum horizontal two-handed isometric pushes as quickly as possible on a dynamometric bar. Reaction forces exerted at seat (Rxs and Rzs) and footrest (Rxf and Rzf) were measured using force sensors. A dynamometric bar measured horizontal push force (Fx). Global adherence ratio (micro) was calculated. Three support surface materials, characterised by different coefficients of friction, were tested. The same surfaces were placed on the seat and the footrest during a series of pushes. It was shown that the different support surfaces significantly influence Fx, Rxs, Rzs, Rzf and micro maximum values obtained at the end of the push. Even when the instructions given to the subject are to produce a maximum push, the maximum horizontal force applied to the bar differs according to the support surface material. Dynamic postural adjustments are influenced by characteristics of slipperiness of support surfaces. The coefficient of friction contributes an essential element to the program of postural dynamics, which in turn modulates the task performance. During brief isometric pushes, seated subjects have the capacity to control the potential risk of slipping.

Adult↗
PubMed1990

Molecular conformational space analysis using computer graphics: going beyond FRODO.

The molecular graphics program FRODO has been modified to support analytical animation of molecular dynamics trajectories. The enhanced program, mdFRODO, supports all features available in FRODO and is interfaced to GROMOS. A variety of analytical animation modes is included. Extensive coloring and atom selection features are implemented to aid the user in distinguishing features of interest in a set of conformations. Molecular conformational space can be analyzed efficiently and comprehended. Animations may be viewed in stereo, and the animated object can be overlaid with any of the standard FRODO objects. The mdFRODO program is of wide use in molecular dynamics, X-ray crystallography and two-dimensional NMR work. Examples illustrating various aspects of collective motion in protein molecules are given and discussed.

Computer Graphics↗
PubMed2003

Dynamic molecules: molecular dynamics for everyone. An internet-based access to molecular dynamic simulations: basic concepts.

Molecular dynamics is a rapidly developing field of science and has become an established tool for studying the dynamic behavior of biomolecules. Although several high quality programs for performing molecular dynamic simulations are freely available, only well-trained scientists are currently able to make use of the broad scientific potential that molecular dynamic simulations offer to gain insight into structural questions at an atomic level. The "Dynamic Molecules" approach is the first internet portal that provides an interactive access to set up, perform and analyze molecular dynamic simulations. It is completely based on standard web technologies and uses only publicly available software. The aim is to open molecular dynamics techniques to a broader range of users including undergraduate students, teachers and scientists outside the bioinformatics field. The time-limiting factors are the availability of free capacity on the computing server to run the simulations and the time required to transport the history file through the internet for the animation mode. The interactive access mode of the portal is acceptable for animations of molecules having up to about 500 atoms.

Computer Simulation↗
PubMed1999

Comparison of performance with wide dynamic range compression and linear amplification.

This study compared subject performance and preference using a compression-limiting hearing aid set to linear amplification (program 1) and wide dynamic range compression (WDRC, program 2). The frequency responses of the hearing aid were matched to a 65 dB SPL signal and maximum output to a 90 dB SPL signal. Twenty subjects with moderate to moderately severe sensorineural hearing loss were tested. Speech recognition scores and speech reception thresholds were obtained both in quiet and in noise. Subjective preference for WDRC or linear amplification was measured via a paired-comparison procedure on "loudness appropriateness," "clarity," and "pleasantness" to continuous discourse presented in quiet and in noise. Results suggested that WDRC yielded better speech intelligibility in quiet for low-level signals and no difference in speech intelligibility in noise compared to linear amplification. Subjects preferred WDRC for loudness to both high- and low-level signals and for pleasantness to high-level signals.

Adolescent↗
PubMed1993

Structural studies of the 5'-phenazinium-tethered matched and G-A-mismatched DNA duplexes by NMR spectroscopy.

The mechanism through which modified oligo-DNA analogues act as antisense repressors at the transcriptional and translational level of gene expression is based on the information content in the nucleotide sequence which is determined by the specific base pairing. The efficiency of such action is largely determined by the stability of the duplex formed between the oligonucleotide reagent and the target sequence and also by the mismatched base pairing, such as G-A, that occurs during replication or recombination. We herein report that the phenazinium (Pzn)-tethered matched duplex p(d(TGTTTGGC)):(Pzn)-p(d(CCAAACA)) (III) (Tm = 50 degrees C) has a much larger stability than the parent matched duplex p(d(TGTTTGGC)):p(d(CCAAACA)) (I) (Tm = 30 degrees C). On the other hand, the Pzn-tethered G-A-mismatched duplex p(d(TGTTTGGC)):(Pzn)-p(d(ACAAACA)) (IV) (Tm = 34 degrees C) is only slightly more stable than its parent mismatched duplex p(d(TGTTTGGC)):p(d(ACAAACA)) (Tm = 25 degrees C). A detailed 500 MHz NMR study and constrained MD refinements of NMR-derived structures have been undertaken for the DNA duplexes (I), (II), (III) and (IV) in order to understand the structural basis of stabilization of Pzn-tethered matched DNA duplex (delta Tm = 20 degrees C) compared to mismatched duplex (delta Tm = 9 degrees C). Assignment of the 1H-NMR (500 MHz) spectra of the duplexes has been carried out by 2D NOESY, HOHAHA and DQF-COSY experiments. The torsion angles have been extracted from the J-coupling constants obtained by simulation of most of the DQF-COSY cross-peaks using program SMART. The solution structure of the duplexes were assessed by an iterative hybride relaxation matrix method (MORASS) combined with NOESY distances and torsion angles restrained molecular dynamics (MD) using program Amber 4.0. The standard Amber 4.0 force-field parameters were used for the oligonucleotide in conjunction with the new parameters for Pzn residue which was obtained by full geometry optimization using ab initio program (3-21G basis set). It has been shown that mismatched G-A bases are in the anti-anti conformation. The mismatched 7G-1A form stable base pairs through inter-strand hydrogen bonds (N7(A)...HN2(G) (1.92 A) with a subtended angle of 176 degrees and N3(G)...HN6(A) (2.01 A) with a subtended angle of 153 degrees (the 'amino-type' hydrogen bond)) and a propeller twist of 36 degrees for 7G-1A residues.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenine↗
PubMed2002

Real-time computer simulations of excitable media: JAVA as a scientific language and as a wrapper for C and FORTRAN programs.

We describe a useful setting for interactive, real-time study of mathematical models of cardiac electrical activity, using implicit and explicit integration schemes implemented in JAVA. These programs are intended as a teaching aid for the study and understanding of general excitable media. Particularly for cardiac cell models and the ionic currents underlying their basic electrical dynamics. Within the programs, excitable media properties such as thresholds and refractoriness and their dependence on parameter values can be analyzed. In addition, the cardiac model applets allow the study of reentrant tachyarrhythmias using premature stimuli and conduction blocks to induce or to terminate reentrant waves of electrical activation in one and two dimensions. The role of some physiological parameters in the transition from tachycardia to fibrillation also can be analyzed by varying the maximum conductances of ion channels associated with a given model in real time during the simulations. These applets are available for download at http://arrhythmia.hofstra.edu or its mirror site http://stardec.ascc.neu.edu/~fenton.

Algorithms↗
PubMed1989

[Programmed laparotomy in the diagnosis and therapy of pathology of the abdominal cavity].

The authors analyse the performance of programmed laparotomy for dynamic visual observation over the condition of the abdominal organs in 3 patients when (as they claimed) laparoscopy would have produced no effect. The article reports on the efficacy of programmed laparotomy conducted by the method suggested by the authors in 15 patients with purulent peritonitis for repeated cleansing of the abdominal cavity.

Abdomen↗
PubMed1997

[Dynamic magnetic resonance of the knee. Considerations on techniques and anatomy with a magnetic resonance system with open magnet].

MRI is currently considered the best technique to study the joints--knee joints in particular. Most studies are performed with the knee straightened out or slightly flexed, which position is mandatory with contemporary MR units. Recently, however, the MR equipment for limb studies and the larger tunnels of total body magnets have permitted partially dynamic knee studies, up to 30-40 degrees flexion; this joint excursion cannot be exceeded. In 1996, Muhle and Niitsu demonstrated that dynamic MRI can be useful to study cruciate ligament injuries, some types of meniscal injuries, all femoropatellar conditions and, mostly, cruciate ligament reconstruction. We used an open magnet MR unit for thorough functional dynamic knee studies, acquiring the images at 0-120 degrees flexion. The open magnet MR unit permits free joint movements. We examined 25 subjects: 10 healthy volunteers and 15 patients with meniscal, capsuloligamentous, femoropatellar or synovial conditions. This technique schedules axial, coronal or sagittal images, according to the diagnostic suspicion, suitably directed with the patient in lateral decubitus and with the knee flexed to maximum joint excursion. Dynamic MR findings are easily transferred to an X-ray film, so that the radiologist can send them to the orthopedist with no need of any videotape or TV take. The current cine MR programs display the dynamic images of the moving joint on an MR monitor, but this option is not yet widely available. The quality of dynamic MR studies is exactly the same as that of conventional images, with a particular emphasis on the small diagnostic details of the injuries. We report our preliminary experience with this technique, indicating some possible clinical applications of dynamic MRI which permits thorough studies of knee flexion-extension.

Humans↗
PubMedDate not supplied

[Stochastic computer model of cellular microtubule dynamics].

A computer model of the system of microtubules has been developed to study the mechanisms of action of various factors on this system. The model describes the process of polymerization/depolymerization of microtubules as a set of chemical reactions with certain rate constants using a stochastic approach. Microtubules are visualized in the program field, which makes the model visual. The program imitates the dynamics and structure of the system of cellular microtubules with great, reliability. The parameters generated by the model correlate with the corresponding parameters of microtubules in living cells. We are going to develop this approach to modeling microtubules and similar structures to bring them into a better accord with living systems and to study the influence of various factors on these systems.

Computer Simulation↗
PubMed1993

Effects of a 12-week resistive training program in the home using the body bar on dynamic and absolute strength of middle-age women.

Guidelines published by the American College of Sports Medicine indicate that resistive training should be an integral part of an adult fitness program. Most adults will find it difficult to train resistively regularly unless they train in their own homes using simple, inexpensive equipment. The purpose of this study was to examine the extent to which participation in a 12-week resistive training program using the Body Bar, a simple, inexpensive resistive training device, in the home improves dynamic and absolute strength of middle-age women compared to similar women engaged in a walking program. A pretest-midtest-posttest design was employed with subjects randomly assigned to either a resistive (n = 30) or a walking (control) group (n = 30). All subjects were tested on measures of dynamic and absolute strength. Resistive trainers performed significantly better than the controls across the 12-week training period on all strength variables even with statistical control for potential confounders. Number of workouts performed and average intensity of each workout were both significant predictors of strength improvements among the resistive trainers.

Adult↗
PubMed1998

[Continuous quality improvement in anesthesia].

Slow continuous quality improvement (SCQI) in anesthesia is a process that allows identification of problems and their causes. Implementing measures to correct them and continuous monitoring to ensure that the problems have been eliminated are necessary. The basic assumption of CQI is that the employees of an organization are competent and working to the best of their abilities. If problems occur they are the consequences of inadequacies in the process rather that in the individual. The CQI program is a dynamic but gradual system that invokes a slower rate of response in comparison with other quality methods, like quality assurance. Spectacular results following a system change are not to be expected an the ideal is slow and continuous improvement. A SCQI program was adapted by our department in May 1994, according to the recommendations of the American Society of Anesthesiologists. Problem identification was based on 65 clinical indicators, reflecting negative events related to anesthesia. Data were collected using a specially designed computer database. 4 events were identified as crossing previously established thresholds (hypertension, hypotension, hypoxia and inadequate nerve block). Statistical process control was used to establish stability of the system and whether negative events were influenced only by the common causes. The causes responsible for these negative events were identified using specific SCQI tools, such as control-charts, cause-effect diagrams and Pareto diagrams. Hypertension and inadequate nerve block were successfully managed. The implementation of corrective measures for the other events that cross the threshold is still in evolution. This program requires considerable dedication on the part of the staff, and it is hoped that it will improve our clinical performance.

Anesthesia↗
PubMed1980

Automated processing of dynamic properties of intraventricular pressure by computer program and electronic circuit.

A procedure for automatic detection and digital processing of the maximum first derivative of the intraventricular pressure (dp/dtmax), time to dp/dtmax(t - dp/dt) and beat-to-beat intervals have been developed. The procedure integrates simple electronic circuits with a short program using a simple algorithm for the detection of the points of interest. The tasks of differentiating the pressure signal and detecting the onset of contraction were done by electronics, while the tasks of finding the values of dp/dtmax, t - dp/dt, beat-to-beat intervals and all computations needed were done by software. Software/hardware 'trade off' considerations and the accuracy and reliability of the system are discussed.

Analog-Digital Conversion↗
PubMed1992

Controlled mobilization after flexor tendon repair in zone II: a prospective comparison of three methods.

A new controlled-motion program that incorporates dynamic flexion traction to all four digits, a short splint leaving the interphalangeal joints free, and a nighttime extension splint was prospectively compared with a modification of the Kleinert technique and a combination of the modified Kleinert technique and passive movements. Each program was applied to approximately one third of 178 consecutively treated digits with tendon injuries in zone II. The mean total active interphalangeal joint range of motion 6 weeks and 1 year postoperatively was significantly better and extension deficits were significantly less frequent in the digits mobilized with the new program. The postoperative treatment input, in terms of frequency of reviews and time spent in therapy sessions, is not greater than with more traditional controlled-motion programs. Our results indicate that the new program is a safe, reliable, and cost-effective method that produces very good results in a general population.

Exercise Therapy↗
PubMed2003

Oscillatory neural network model of attention focus formation and control.

A new mechanism to control attention focus formation and switching in the model of selective attention is suggested and studied. The model is based on an oscillatory neural network (ONN) with the star-like architecture and phase shifts in connections between oscillators. Attention is modelled as a dynamical mode of partial synchronisation between a particular subgroup of oscillators and the central oscillator (CO). A new theoretical method to study full and partial synchronisation in the system is presented. Equations for the frequency of synchronisation are derived which allow the programming of the dynamical behaviour of the system depending on the parameters. In particular, we show that phase shifts in connections between oscillators provide an efficient mechanism of attention control.

Attention↗
PubMed2001

Dynamic dissociation of visual selection from saccade programming in frontal eye field.

Previous studies of visually responsive neurons in the frontal eye fields have identified a selection process preceding saccades during visual search. The goal of this experiment was to determine whether the selection process corresponds to the selection of a conspicuous stimulus or to preparation of the next saccade. This was accomplished with the use of a novel task, called search-step, in which the target of a singleton visual search array switches location with a distracter on random trials. The target step trials created a condition in which the same stimulus yielded saccades either toward or away from the target. Visually responsive neurons in frontal eye field selected the current location of the conspicuous target even when gaze shifted to the location of a distractor. This dissociation demonstrates that the selection process manifest in visual neurons in the frontal eye field may be an explicit interpretation of the image and not an obligatory saccade command.

Action Potentials↗
PubMedDate not supplied

Group dynamics within long-term continuing education programs.

Nursing educators have responded to the need for continuing education by developing a variety of programs ranging in length from half-day seminars to several months of intensive study. Although books and articles have been written about nurses returning to school for baccalaureate degrees and the ensuing expectations, changes, and needs involved in this process, the literature revealed little information on how students, families, and faculty "live" a long-term continuing education (CE) experience. This article will examine the evolution of students into well-defined groups. The stages of group process, development of norms, assumption of roles within the groups, and factors related to conflicts are discussed. Methods used to reduce conflict and facilitate the movement of the groups to the resolution stage are presented in order to assist instructors involved in long-term CE programs.

Adult↗
PubMed1990

Developing the art of successful clinical supervision in health care programs.

Supervision is a dynamic and ever-changing process. Excellent employees can be trained to be outstanding supervisors if the competencies and skills of the supervisory process are clarified. Supervision is a successful art that can be learned and enhanced if appropriate supervisory skills are identified, taught, and learned. Supervision is too important in developing the future health care work force to be left to chance.

Clinical Competence↗
PubMed1986

Neural dynamics of speech and language coding: developmental programs, perceptual grouping, and competition for short-term memory.

A computational theory of how an observer parses a speech stream into context-sensitive language representations is described. It is shown how temporal lists of events can be chunked into unitized representations, how perceptual groupings of past item sublists can be reorganized due to information carried by newly occurring items, and how item information and temporal order information are bound together into context-sensitive codes. These language units are emergent properties due to intercellular interactions among large numbers of nerve cells. The controlling neural networks can arise through simple rules of neuronal development: random growth of connections along spatial gradients, activity-dependent self-similar cell growth, and competition for conserved synaptic sites. Within these networks, a spatial frequency analysis of temporally evolving activity patterns leads to competitive masking of inappropriate list encodings in short term memory. The neurons obey membrane equations undergoing shunting recurrent on-center off-surround interactions. Several design principles are embodied by the networks, such as the sequence masking principle, the long-term memory invariance principle, and the principle of self-similar growth.

Auditory Pathways↗