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At least 73 records · Page 4Linked to original sources
PubMed1990

Pharmacokinetics of 2,4,5-T in mice as a function of dose and gestational status.

A pharmacokinetic study was conducted in CD-1 mice with the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) as a function of dose (15, 30, 60, and 90 mg/kg, iv) and gestational status (nonpregnant, day 6, 10, 13, and 17 of gestation, and postpartum). Analysis for 2,4,5-T and its metabolites was based on an electron-capture gas-liquid chromatographic method. Pharmacokinetic stimulation of the blood, urine, and feces data from each mouse was performed on an analog-digital hybrid computer system based on a two-compartment model with parallel, first-order elimination kinetics. Data analysis demonstrated dose-independent kinetics for most pharmacokinetic parameters but a gestational status-dependence. There was a tendency, as indicated by an increase in the biologic half-life and AUC and decrease in clearance and total percent recovery, for pregnant animals to eliminate 2,4,5-T more slowly as gestation progressed, resulting in potentially increasing fetal exposure during the later stages of pregnancy.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1969

Flow through a collapsible tube. Experimental analysis and mathematical model.

Flow through thin-wall axisymmetric tubes has long been of interest to physiologists. Analysis is complicated by the fact that such tubes will collapse when the transmural pressure (internal minus external pressure) is near zero. Because of the absence of any body of related knowledge in other sciences or engineering, previous workers have directed their efforts towards experimental studies of flow in collapsible tubes. More recently, some attention has been given towards analytical studies. Results of an extensive series of experiments show that the significant system parameter is transmural pressure. The cross-sectional area of the tube depends upon the transmural pressure, and changes in cross-section in turn affect the flow geometry. Based on experimental studies, a lumped parameter system model is proposed for the collapsible tube. The mathematical model is simulated on a hybrid computer. Experimental data were used to define the functional relationship between cross-sectional area and transmural pressure as well as the relation between the energy loss coefficient and cross-sectional area. Computer results confirm the validity of the model for both steady and transient flow conditions.

Computers, Hybrid↗
PubMed1979

Appropriate nitroxoline dosage regimen design.

Clinically used dosage regimen of nitroxoline, three times 100 mg daily, was proved to be inappropriate because the successfulness of medical treatment was rarely sufficient. Nitroxoline, used as urinary antiseptic, exhibits its antibacterial activity in concentrations higher than 6 mg/l, as demonstrated in many "in vitro" experiments. This work deals with the most appropriate nitroxoline dosage form as well as with the optimal dosage regimen design. The data were obtained by the aid of the suitable pharmacokinetic model and multiple dosing simulation on analog-hybrid computer EAI 580. From the several studied alternatives two usable dosage forms with the necessary dose and corresponding dosage interval were selected.

Anti-Infective Agents, Urinary↗
PubMed1982

Model analysis of the frequency of neuronal action potentials in the case of Gaussian input stochastic processes.

The authors describe the effects of changes in excitatory and inhibitory synapse weight on the number of spikes generated in the presence of constant absolute refractory phase and threshold level values. Input stochastic processes with Gaussian distributions were presumed. The problem was resolved in a hybrid computer model of stochastic neuronal activity. The results are given in the form of "e-curves", "i-curves" and gradient fields. It was shown that, in a set of paired values of the two weights, zones could be found in which the number of generated spikes depended mainly on just one of them. It was also shown that, in a given neurone with a fixed synapse morphology, the effect of the individual synapses on the number of generated spikes altered with changes in input stochastic processes to the synapses.

Action Potentials↗
PubMed1998

Incorporation of a set enumeration trees-based classifier into a hybrid computer-assisted diagnosis scheme for mass detection.

RATIONALE AND OBJECTIVES: The authors evaluated whether a hybrid classifier of two independent computer-aided diagnosis (CAD) schemes, the set enumeration (SE) trees approach and an artificial neural network (ANN), could improve the detection of masses on digitized mammograms. The potential benefits resulting from the interpretability of the SE trees model was also explored. MATERIALS AND METHODS: Two hundred thirty verified mass regions and 230 negative but suspicious regions were randomly selected from 618 digitized mammograms. Each region was represented by a 24-parameter feature vector. These features were used as input data for the SE trees and ANN-based schemes. After the positive and negative regions were randomly segmented into five exclusive partitions, a fivefold cross-validation method was applied to evaluate and compare the performance of the SE trees, ANN, and hybrid system in the identification of masses. RESULTS: The performance of the SE trees approach was comparable to that of the ANN. The average area under the receiver operating characteristic (ROC) curves for all five partitions was 0.88 (standard deviation, 0.04). Owing to the relatively low correlation between the region-based results of the SE trees and ANN methods, the hybrid classifier yielded a significantly improved performance, with an area under the ROC curve of 0.94 (standard deviation, 0.02; P < .05). CONCLUSION: The hybrid CAD scheme significantly improved performance. The amenability of the SE trees models to interpretation may aid in the assessment of the importance of specific features.

Artificial Intelligence↗
PubMed2001

Extraction of all coefficients of coupled-mode equations for natural, single-phase, unidirectional SAW transducers from dispersion characteristics computed by hybrid finite element method.

A numerical method is presented for determining all of the coefficients of coupled-mode equations for natural, single-phase, unidirectional SAW transducers (NSP-UDTs). Substituting numerical results computed by the hybrid finite element method for infinite NSPUDTs with shorted and open electric ports into several relations derived from the coupled-mode theory, we can determine all of the coefficients. Specifically, the edge frequencies of a stop-band and the static capacitances yield the self-coupling coefficients and the amplitudes of mutual-coupling and transduction coefficients, and the electric potential standing wave on the substrate surface, which can be derived from the projection of the standing wave distributions of particle displacements and electric potential in the whole substrate onto the set of those predicted by the coupled-mode theory, yields the phases of mutual-coupling and transduction coefficients. NSPUDTs on ST-25 degrees X quartz, Y-51.25 degrees Z LiTaO3, and 50 degrees Y-25 degrees X La3Ga5SiO14 substrates are investigated. Our results agree well with the earlier experimental ones.

Journal Article↗
PubMed2006

A randomized, controlled, prospective study validating the acquisition of percutaneous renal collecting system access skills using a computer based hybrid virtual reality surgical simulator: phase I.

PURPOSE: The need to develop new methods of surgical training combined with advances in computing has led to the development of sophisticated virtual reality surgical simulators. The PERC Mentortrade mark is designed to train the user in percutaneous renal collecting system access puncture. We evaluated and established face, content and construct validation of the simulator in this task. MATERIALS AND METHODS: A total of 63 trainees underwent baseline testing on the simulator, consisting of percutaneous renal puncture followed by the introduction of a guidewire into the collecting system. Subjects were then randomized to an intervention arm, in which they underwent 2, 30-minute training sessions on the simulator, and a control arm, in which no further training was given, followed by repeat testing. Performance was assessed using a global rating scale and by virtual reality derived parameters. RESULTS: There were no significant differences between the 2 groups with respect to baseline measures. Subjects who underwent training with the simulator demonstrated significant improvement in objective and subjective parameters compared to their baseline performance and compared to the untrained control group. Spearman rank correlations demonstrated a significant relationship between multiple parameters of the objective and subjective data. CONCLUSIONS: Training on the simulator improves virtual reality skills. It may allow trainees to develop the basic skills necessary to perform percutaneous renal collecting system access. Face and content validity were demonstrated and construct validity was supported by establishing convergent validity.

Computer Simulation↗
PubMed2004

Energy intensity of computer manufacturing: hybrid assessment combining process and economic input-output methods.

The total energy and fossil fuels used in producing a desktop computer with 17-in. CRT monitor are estimated at 6400 megajoules (MJ) and 260 kg, respectively. This indicates that computer manufacturing is energy intensive: the ratio of fossil fuel use to product weight is 11, an order of magnitude larger than the factor of 1-2 for many other manufactured goods. This high energy intensity of manufacturing, combined with rapid turnover in computers, results in an annual life cycle energy burden that is surprisingly high: about 2600 MJ per year, 1.3 times that of a refrigerator. In contrast with many home appliances, life cycle energy use of a computer is dominated by production (81%) as opposed to operation (19%). Extension of usable lifespan (e.g. by reselling or upgrading) is thus a promising approach to mitigating energy impacts as well as other environmental burdens associated with manufacturing and disposal.

Computers↗
PubMed2000

Web-based continuing medical education (I): field test of a hybrid computer-mediated instructional delivery system.

BACKGROUND: The Internet and the World Wide Web (the Web) present exciting new possibilities for distributing educational materials at a distance and facilitating collaborative learning among geographically isolated physicians. This article provides a brief overview of the Web as an instructional delivery platform and discusses its strengths and weaknesses as a potential medium for enhancing distance learning opportunities for rural and remote physicians. It also describes an innovative hybrid instructional delivery model that was field tested by the Telemedicine Centre to determine its efficiency and effectiveness for providing Web-based instruction. A hybrid model merges the Web and CD-ROMs (compact disk read-only memory) to use several of the more valuable instructional components of Web-based education (i.e., multimedia, interactive forms, hypermedia, and computer-mediated communications). The results of the field test indicate that the hybrid delivery model was an efficient means for delivering computer-mediated continuing medical education instruction on dermatologic office procedures to a group of rural physicians in low telecommunication bandwidth regions.

CD-ROM↗
PubMed2006

Breast tumor malignancy modelling using evolutionary neural logic networks.

The present work proposes a computer assisted methodology for the effective modelling of the diagnostic decision for breast tumor malignancy. The suggested approach is based on innovative hybrid computational intelligence algorithms properly applied in related cytological data contained in past medical records. The experimental data used in this study were gathered in the early 1990s in the University of Wisconsin, based in post diagnostic cytological observations performed by expert medical staff. Data were properly encoded in a computer database and accordingly, various alternative modelling techniques were applied on them, in an attempt to form diagnostic models. Previous methods included standard optimisation techniques, as well as artificial intelligence approaches, in a way that a variety of related publications exists in modern literature on the subject. In this report, a hybrid computational intelligence approach is suggested, which effectively combines modern mathematical logic principles, neural computation and genetic programming in an effective manner. The approach proves promising either in terms of diagnostic accuracy and generalization capabilities, or in terms of comprehensibility and practical importance for the related medical staff.

Artificial Intelligence↗
PubMed1997

Hybrid ultrasonic computed tomography.

Ultrasonic computed tomography can provide valuable information on tissue properties. However, the large number of projections required to obtain a high-resolution image renders it impractical for routine clinical use. B-scan imaging, on the other hand is very rapid, but mainly provides information on tissue morphology. An algorithm which fuses information from a compound B-scan image and a limited view speed of sound (SOS) tomographic reconstruction of an object is presented here. The algorithm is iterative and is based on the two-dimensional Taylor series expansion. The algorithm diminishes artifacts caused by tomographic reconstruction from too few projections and produces an image which depicts both tissue morphology and acoustic properties (SOS). Consequently, quantitative images can be acquired in a much shorter time than required by conventional tomography. This method may potentially find application in ultrasonic breast screening.

Algorithms↗
PubMed2000

Hybrid computer-guided and minimally open surgery: anterior lumbar interbody fusion and translaminar screw fixation.

Less invasiveness is the way forward for spinal surgery. Minimal disruption of tissue, preservation of muscle function, and restoration of normal spinal alignment are still the goals of most surgical procedures. An anterior lumbar fusion technique using a less invasive procedure with the addition of translaminar screws is described. The autograft is harvested from the vertebral body, thus avoiding the morbidity associated with an iliac crest bone graft. The operative steps for the procedure are described.

Bone Screws↗