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PubMed2000

Flexural stress waves responses on human femoral cortical bone.

The response of human femoral cortical bone to lateral impact were investigated both analytically and experimentally. In the analytical part of this investigation the Timoshenko beam theory was used for predicting the propagation of flexural stress waves along the specimens. The final solution was given in integral form and the results were obtained with the aid of a digital computer. In the experimental part of this investigation the employed specimens were obtained by cutting a human femur shaft along its length and the specimens were machined to have a uniform rectangular cross-section. Flexural stress waves in cortical bone were generated by impacting transversely 4.8 mm diameter spherical projectiles, fired from an air gun with the appropriate velocities. Stress waves were detected at two stations (positions) on the beam specimens by means of foil strain gages. These gages were suitably connected with a digital storage oscilloscope to detect the flexural stress waves produced by the lateral impact. Force history was recorded also on a storage oscilloscope by means of a sandwiched quartz crystal arrangement, of high frequency response, placed at the impact point of the specimen. A comparison was made between the corresponding analytical results and experimental data. Significant agreement was observed between them, as shown in the figures of this article.

Biomechanical Phenomena↗
PubMed1986

A computer model of neuronal pathways in the basal ganglia.

Disorders of the basal ganglia and the extrapyramidal motor system exhibit an imbalance of neurotransmitter concentrations in affected neurons. For three synapses with dopamine, acetylcholine, and gamma-amino butyric acid (GABA), mathematical models of synaptic transmission are developed. To describe the kinetics of transmitter substances, compartment analysis is used. Membrane potential behaviour is described by the Hodgkin-Huxley equations with an additional equation accounting for a presynaptic calcium current mediating transmitter release. At the postsynaptic site, activated receptor molecules control the activity of ion channels, eliciting either inhibitory or excitatory postsynaptic potentials. A simple model of the feedback loop connecting the caudate nucleus and the substantia nigra is simulated on a digital computer using the simulation language ACSL. A comparison of the control case with a model of Parkinson's disease shows a shift of eigenvalues towards zero in the diseased state.

Acetylcholine↗
PubMed1965

Application of replica plating and computer analysis for rapid identification of bacteria in some foods. I. Identification scheme.

A method was devised and tested for a quantitative identification of microbial flora in foods. The colonies developing on the initial isolation plates were picked with sterile toothpicks and inoculated on a master plate in prearranged spacing and order. The growth on the master plates was then replicated on a series of solid-agar plates containing differential or selective agents. The characteristic growth and physiological responses of microbial isolates to penicillin, tylosin, vancomycin, streptomycin, chloramphenicol, neomycin, colistin, and to S S Agar, Staphylococcus Medium No. 110, and Potato Dextrose Agar were recorded, together with Gram reaction and cell morphology. This information was then fed into an IBM 1410 digital computer which grouped and analyzed each isolate into 10 microbial genera, or groups, according to the identification key. The identification scheme was established by use of reference culture studies and from the literature. This system was used to analyze the microbial flora in dover sole (Microstomus pacificus) and ground beef. The method described in this article enables one to examine large numbers of microbial isolates with simplicity.

Animals↗
PubMed1980

A computer simulation of physiological factors contributing to hyperventilation and breathlessness in cardiac patients.

A computer model of human respiration is of value for teaching the basic principles of respiratory physiology to students. An extension of this educational use is in the theoretical exploration of the relative importance of individual factors which may be contributing to disordered function in common clinical problems. For example, when a cardiac patient becomes breathless with increase in ventilation during exercise there are alterations in many physiological variables. The influence of their individual contributions on the total ventilation and thence possibly on breathlessness is often difficult to estimate. We present a theoretical analysis using MACPUF, a digital computer simulation of circulation and gas exchange which can be used to extimate the quantitative contribution of relevant physiological variables by altering them singly and in combination. Alterations in dead space, physiological shunt and pulmonary compliance individually produce only small increases in ventilation. Increased neurogenic drive (e.g. from lung reflexes triggered by pulmonary congestion) is a potentially important but very variable factor. A more important influence on ventilation appears when cardiac output is reduced and anaerobic metabolism simulated, causing changes in blood gas tensions and acidaemia which then change ventilation. Any increase in ventilation becomes more significant as a cause of breathlessness when ventilatory capacity is reduced, which in cardiac patients it not infrequently is.

Cardiac Output↗
PubMed1990

System for mechanical measurements during cardiopulmonary resuscitation in humans.

Effective study of CPR requires measurement of the mechanical properties of the human chest and the resultant vascular pressures. A computer-based mobile data acquisition system was designed and built for this purpose. During manual CPR a short cylindrical module was placed between the rescuer's hands and the patient's chest. This module, which was attached to an easily manipulated position-sensing arm, measured force and acceleration at the sternum. Three-dimensional position and orientation of the module were measured, as well as the component of the applied force which was perpendicular to the sternum. The central venous and aortic pressures were measured by high fidelity pressure transducers. All transducer signals were recorded by digital computer. Real-time feedback of sternal force and displacement, and vascular pressures was provided to the rescue team via chart recordings. An audible signal was produced as an aid in maintaining desired compression rate and duration. The system's mobility permitted rapid implementation at any hospital location. In conclusion, this system was capable of measuring, recording, and displaying multiple physical quantities during manual CPR in humans.

Biomechanical Phenomena↗
PubMed1975

Electric pacing of intact and transected canine small intestine and its computer model.

In 10 conscious, fasted dogs with electrodes chronically implanted on the intestine, current pulses (8 mA, 50 ms) at frequencies the same as, or faster than, that of the natural intestinal pacemaker always entrained pacesetter potentials (PP) along the proximal frequency plateau, but not along the distal frequency gradient. As duodenal PP's were paced faster, the proximal plateau shortened by orad extension of the distal gradient. Entrained PP's propagated orally and aborally. Their velocity slowed caudally while varying inversely with their frequency. After midduodenal transection had reduced the frequency of the natural PP's distal to the cut, pacing entrained PP's in all areas of the bowel and restored the proximal plateau and distal gradient. But no area could be paced faster than before transection. PP's were not propagated across sites of transection. A digital computer model of coupled relaxation oscillators gave similar results. We conclude that the frequency of the natural pacemaker and the declining gradient of maximal driven frequency determine the frequency pattern of the small intestinal PP.

Animals↗
PubMed1978

Semiquantitative 67Ga scanning of lung cancer by scintiscoring: its usefulness in diagnosis of localization, therapeutic effectiveness, radiation pneumo-mediastinitis and recurrence.

Attempts were made to attain a semiquantitative evaluation of therapeutic effectiveness of lung cancer by scintiscoring of the liver as well as the tumor lesion. A relative counting ratio of tumor to liver was computed, and this was found useful: in areas of active tumorous growth, higher ratios were obtained. The ratios returned to the control levels following irradiation with or without an anti-inflammatory regimen including prednine. The technic is simple, and yet invaluable especially when the tumor locates in the mediastinum escaping from radiological detection. Satisfactorily frequent repetition would be competent enough in early diagnosis of developing radiation pneumo-mediastinitis and regrowths in the mediastinum and fibrotic abnormal shadows as well. The principle would be best rewarded by use of a whole-body scanner equipped with a digital computer.

Evaluation Studies as Topic↗
PubMed2005

A concise method of calculating fetal weight percentile.

OBJECTIVE: Assessment of fetal growth used in clinical decision making for managing pregnancies is based on percentiles relative to normal values for gestational age. Most clinicians utilize visual interpolation of look-up tables or graphs, which is neither accurate nor convenient. Calculation of growth percentile by numerical integration formulas requires digital computers with advanced computational capabilities and/or the storage of large data tables. STUDY DESIGN: Using established ultrasound measurement formulas and published fetal weight/gestational age tables, mean weights and standard deviations for gestational ages from 10 to 44 weeks were determined. From this Z-scores were calculated for the gestational ages. Z-scores plotted against 1st through 50th percentiles resulted in a curve. A polynomial equation was derived to fit the curve resulting in an expression for converting the Z-score to percentile: Percentile = 0.0994 * Z score2 - 0.44 * Z score + 0.5026. RESULTS: Comparing calculated values from this equation against standard percentiles from a Z-score to percentile table, all calculated values varied from the table value by < 1 percentile for Z-scores ranging from 0 to 2.33. Values > 2.33 are assigned to the 99th percentile. The equation performed to the goal of calculating percentile to an accuracy of < or = 1 percentile. CONCLUSION: A method whereby the estimated fetal weight can be used to calculate a percentile using two simple equations and only standard math functions allows implementation on a standard personal digital assistant device commonly available for clinical use. This implementation gives the needed accuracy, ease of interpretation, and portability, making it a useful tool in clinical practice.

Fetal Weight↗
PubMed1982

The pharmacokinetics of nomifensine. Comparison of pharmacokinetics and pharmacodynamics using computer pharmaco-EEG.

Pharmacokinetics and pharmacodynamics of nomifensine infusions as compared with oral preparations were investigated in a double-blind place-controlled crossover study in 10 healthy normal volunteers. They received randomized in weekly intervals 75 mg nomifensine and placebo intravenously as well as placebo, 75 and 150 mg nomifensine orally. Blood samples, quantitative EEG evaluations, psychometric tests, blood pressure, pulse rate and side effects were obtained and monitored at the hours 0, 1, 2, 4, 6 and 8. Nomifensine serum levels were determined by a radioimmunoassay; peak levels occurred within the first 2 h, the elimination half-life was around 2 h, both results indicating fast absorption and elimination. While the evaluation of the total nomifensine demonstrated almost identical bioavailability of the oral and intravenous form, free nomifensine levels after 75 mg i.v. were more similar to those after 150 mg than 75 mg p.o. Digital computer period analysis of the EEG confirmed nomifensine as a drug with a significant effect on the CNS as compared with placebo, showing in fact an antidepressant 'pharmaco-EEG profile' similar to desipramine. Evaluation of dose-effect curves demonstrated that 75 mg i.v. was the most effective drug, being closer to 150 than 75 mg p.o. The latter oral dosage could be discriminated from placebo only in certain variables at certain times. Concerning time-effect, nomifensine was most effective around the 6th hour post-drug, which was similar to the psychometric findings, thus showing a considerable delay compared to the peak serum concentration. Relating pharmacodynamic findings to pharmacokinetic results it became evident that free nomifensine may be of far greater importance for the drugs encephalotropic and psychotropic properties than the total unconjugated and conjugated nomifensine--thus justifying the development of a parenteral preparation. Finally, the relationship of blood levels and CNS effects was found to have a characteristic 'hysteresis loop' shape suggesting a delay of pharmacodynamic effects as opposed to the serum concentrations. This delay may be due to a slowly formed active metabolite, the drug acting on deep compartment receptors or both.

Adult↗
PubMed1975

Monitoring respiratory function by computer in ICU. Preliminary work.

The structure of the respiratory monitoring system under construction in Brussels University Hospitals is described. It is modular and hierarchized. It is based on the observation of the lung mechanics, of the flows of inspired and expired gases and of continuous blood measurements in patients artificially ventilated. Respiratory monitoring may be confined to the continuous observation of the natural evolution of a large number of parameters and the extraction of the most possible information with the aid of automatic calculations effected in real time. The authors propose to add deliberate and controlled aggressions of the pulmonary system in order to observe its dynamic behavior. Practical function tests are described. They lead to the calculation of functional residual capacity, continuous distribution of tidal volume, and pulmonary capillary blood flow. These tests can be performed automatically by using a new electronic unit built in our laboratory. It enables a digital computer to control the functioning of a commercially available ventilator.

Belgium↗
PubMed1977

A computer program for the analysis of controllability, observability and structural identifiability of biological compartmental systems.

A computer program to check structural identifiability of biological compartmental systems, that is the priori possibility of estamating all unknown system parameters through a multi input-multi output tracer experiment is presented. The procedure, as based only on the adopted compartmental structure and the chosen input-output experiment, is independent of the numerical values of the parameters: therefore the program can be usefully employed before parameter estimation algorithms, to assure that all the unknown parameters evidenced in the model can be estimated from the experimental data. After a short review on compartmental models, controllability observability and structural identifiability are defined and techniques to check them are provided. The digital computer implementation of the whole procedure is discussed in detail. Some typical program runs regarding the application to biological systems are given.

Computers↗
PubMed2000

Proposed abdominal sonographic staging to predict severity of liver diseases: analysis with peritoneoscopy and histology.

Abdominal sonography is a routinely used noninvasive modality for screening and treatment of liver diseases. We attempted to establish a morphological sonographic staging to predict the severity of liver diseases with their consequent analysis with morphological staging of peritoneoscopy and histology. In all, 136 patients were enrolled for the final confirmation of disease state by peritoneoscopy and histology preceded by abdominal sonography. All patients were categorized from stage 0 to stage 5, depending on a proposed criterion of sonographic features based on surface pattern of liver and the appearance of internal echogenic bands relating to the irregularity of the liver texture. A digitized computer quantitation of histogram-based standard deviation (SD) values from different stages of sonographic images was analyzed, and their values were justified by correlation with the definite appearance of an internal echogenic band. The association of different sonographic stages with disease progression was also demonstrated by their relation with peritoneoscopy and histology. In all patients, the different sonographic staging results were significantly correlated with hepatic surface features of peritoneoscopic staging (r = 0.939, P < 0.0001) graded from stage 0 to stage 5 and were also correlated with biopsy-proven staging of fibrosis (r = 0.739, P < 0.0001). The greater SD values of histogram-based echo levels, as analyzed from digitized sonographic images of 90 patients, were associated with the appearance of internal echogenic bands (P < 0.0001). Furthermore, the corresponding SDS were significantly correlated with the qualitative staging of sonographic features (r = 0.781, P < 0.0001), peritoneoscopy (r = 0.786, P < 0.0001) and histology (r = 0.779, P < 0.0001). We concluded that our proposed sonographic staging is well correlated with peritoneoscopic and histological staging of liver diseases, with only a small discrepancy, and can be used clinically to demonstrate the ongoing severity of liver diseases.

Abdomen↗
PubMedDate not supplied

The information revolution: opportunities and pitfalls for patients and providers.

The Information Revolution is changing everything in our world. Although this era is developing and evolving, some have described networks, globalization, diffusion of power away from professionals, and information overload as direct results of the Information Revolution. These megatrends are affecting every person and every organization in the world, and this article examines them to see how they might affect medicine and the delivery of health care in the millennium. What is truly significant about the changes brought about by the creation of cyberspace is that through computers, digitized information can be inexpensively and quickly transmitted anywhere in the world. Many of the traditional ethical and professional standards of medicine are feeling the strain of being applied to the strange, unfamiliar world-cyberconsultations and other virtual medical applications are explored. Physicians who understand this revolution will have a far better chance of controlling their destinies--and more importantly, aiding their patients in the quest for good health.

Attitude to Computers↗
PubMed1982

Computer simulation for studying calcium dependent abnormalities in firing mechanism of molluscan neurones.

Computer modelling technique is proposed to assist in physiological research on invertebrate neuronal membranes. The firing mechanism of a single patch of invertebrate neuronal membrane has been studied in dependence on maximum Ca++ conductance. The calculations are based on modification of Hodgkin-Huxley's data completed by a straight line approximation between experimental points of the kinetic parameters of Ca++ current and early transient potassium current. The time course of conductance changes is assumed to be proportional to m2h for Ca++ current. Three distinct potassium currents are involved into the model, viz. transient potassium current, delayed potassium current and Ca++-dependent potassium current. The modified Euler method run on a digital computer has been used for numerical integration of kinetic equations. Significant effects of Ca++ conductance on spike broadening, plateau development and spike afterhyperpolarization are represented. In the range of small Ca++ conductance an infinite spontaneous activity can be triggered by a short (suprathreshold) current pulse which may be considered a model of pacemaker activity. Plateau development resulting from potassium blocking or decreasing potassium equilibrium is facilitated by Ca++ conductance in the range of greater Ca++ conductance. The effects of voltage sensitivity of the coupling coefficient describing the current of Ca++-dependent K+ channels were studied and compared to the voltage independent case. The coupling coefficient seems to be a crucial factor in broadening the range of Ca++ conductance responsible for pacemaker activity. For greater values of Ca++ conductance, a decrease of the coupling coefficient leads to a transition from prolonged bursting to interruption of burst activity by burst-afterhyperpolarization. The blocking effect of 4-aminopyridine on fast outward current has been studied by the model which has a practical significance considering that aminopyridine is known as a convulsive agent. We suppose that it is reasonable to study the convulsive effects of aminopyridine by the model based on the kinetics of the isolated neuronal membrane. The model may help in understanding the ionic background underlying abnormal network activity during epileptic discharges of mammalian neurones.

4-Aminopyridine↗
PubMedDate not supplied

Computer-assisted design of surface coils used in magnetic resonance imaging. II. Rotational discrimination nonlinear regression analysis and the design of surface coils.

For a number of reasons, it is desirable to fabricate coils which, for a known current, shall produce predetermined values of the magnetic field intensity at a number of points within a nuclear magnetic resonance imager. The calculation of the magnetic field intensity at a set of points involves the integration of the Biot-Savart equation for all components of the segments of conductor which make up the coil. This process in itself is a rather formidable task. When this process is parameterized in terms of coil diameter, coil spacing, etc. the problem is to determine the values of these parameters to match values of magnetic field intensities which are desired. The problem thereby increases in complexity to the point where, by ordinary methods, the problem becomes intractable. A generalized solution technique has been developed on a digital computer to implement the rotational discrimination nonlinear regression techniques of Faris, Law and Letcher to find the best solution to this problem. The problem is posed by integrating the Biot-Savart equation. This produces algebraic expressions for incorporation into the optimization program which is executed on a computer in a conversational mode. This technique was employed to specify the dimensions of a rectangular surface coil for the investigation of the whole human spine.

Equipment Design↗
PubMed1968

Computation of impulse conduction in myelinated fibers; theoretical basis of the velocity-diameter relation.

For myelinated fibers, it is experimentally well established that spike conduction velocity is proportional to fiber diameter. However no really satisfactory theoretical treatment has been proposed. To treat this problem a theoretical axon was described consisting of lengths of passive leaky cable (internode) regularly interrupted by short isopotential patches of excitable membrane (node). The nodal membrane was assumed to obey the Frankenhaeuser-Huxley equations. The explicit diameter dependencies of the various parameters were incorporated into the equations. The fiber diameter to axon diameter ratio was taken to be constant, and the internode length was taken to be proportional to the fiber diameter. Both these conditions reflect the situation that exists in real, experimental fibers. Dimensional analysis shows that these anatomical conditions are equivalent to Rushton's (1951) assumption of corresponding states. Hence, conduction velocity will be proportional to fiber diameter, in complete agreement with the experimental findings. Digital computer solutions of these equations were made in order to compute a set of actual velocities. Computations made with constant internode length or constant myelin thickness (i.e., nonconstant fiber diameter to axon diameter ratio) did not show linearity of the velocity-diameter relation.

Action Potentials↗
PubMed1987

Normal and abnormal temporomandibular joints: quantitative evaluation of inferior joint space arthrography.

Arthrography has been shown to provide important diagnostic information in patients with temporomandibular joint (TMJ) dysfunction. In this study, 60 arthrograms on totally asymptomatic patients and 64 arthrograms on symptomatic patients were evaluated. Quantitative evaluation of inferior joint space arthrography was performed with the help of a computer digitizing morphometry program. Results indicate a significant difference in the areas of the anterior and posterior recesses between normal and abnormal joints in the closed-mouth position. Differences between the 2 groups also exist in linear measurements of the anterior recess. This data further defines important diagnostic criteria in the arthrographic evaluation of both the normal and abnormal TMJ.

Adolescent↗
PubMed1977

Dialysis continuous process for ammonium-lactate fermentation of whey: mathematical model and computer simulation.

A mathematical model was developed to describe a dialysis process for the continuous fermentation of whey lactose to lactic acid, with neutralization to a constant pH by ammonia. In the process, whey of a relatively high concentration is fed into the fermentor circuit at a relatively low rate so that the residual concentration of lactose is low. The fermentor effluent contains ammonium lactate, bacterial cells, and residual whey solids and could be used as a nitrogen-enriched feedstuff for ruminant animals. Only water is fed into the dialysate circuit at a relatively high rate. The dialysate effluent contains purified ammonium lactate and could be converted to lactic acid and ammonium sulfate for industry. The fermentation was specifically modeled as a set of equations representing material balances and rate relationships in the two circuits. Dialysis continuous fermentations, in general, were modeled by combining these equations and by using dimensionless parameters. The generalized model was then solved for the steady state and used to simulate the specific fermentation on a digital computer. The results showed the effects of various material and operational and kinetic parameters on the process and predicted that it could be operated efficiently.

Journal Article↗