SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Many different varieties of modeling coexist in theoretical neuroscience. Here, we consider the positive and negative implications, for theories of schizophrenia, of a crucial distinction between computational and mathematical modeling.
The mathematical basis and methodology for determining the effective atomic number and electron density of a tissue are presented. Cranial computed tomography (CT) scanning is performed at two different energy levels, both with and without contrast enhancement. The histology of 15 brain tumors has been correlated with the effective atomic number and electron density of the tumor, with parameters of the linear attenuation coefficient, and with statistical values of the CT numbers. The most useful value in separating gliomas from meningiomas from metastases appears to be the percentage change of effective atomic number following contrast enhancement.
Theoretical considerations of metal complex formation in aqueous solutions were used to develop a computer program (CHELATE) to calculate all equilibrium species (free metal ions, metal complexes, etc.) in any user-defined system, such as xylem fluid. Mass-balance equations were established to describe each free metal ion and each free ligand concentration as a function of solution pH, total metal or total ligand, hydrogen-association constants, and the stability constants of known metal complexes. A default data base can be altered by the user to define any desired system covered by the stored equilibrium data. The program can currently handle nine metal ions, 35 ligands, and 500 complex species. The validity of the program was confirmed by using experimental test systems in which free-metal ion activity measurements were made with ion-selective electrodes.Program CHELATE was used to calculate the distribution of six metals in 0- to 1-hour exudate from soybean (Glycine max L. Merr.) and tomato (Lycopersicon esculentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. The results indicated that Fe is bound by citric acid, and Cu is bound by several amino acids in the normal-Zn exudate. Most of the Cu in soybean exudate is bound to asparagine and histidine. In tomato, Cu is bound to histidine, glutamine, and asparagine. Zinc, Mn, Ca, and Mg are bound primarily by citric acid and malic acid in both species; the per cent bound for these metals is lower than that for Fe and Cu. Zinc phytotoxicity caused equilibrium concentration shifts and resulted in the formation of several additional metal complexes not found in the normal-Zn exudate.
A new, very fast, yet accurate program, MGSEED, has been developed that computes steady-state temperatures from the three-dimensional bioheat transfer equation due to heating by a ferromagnetic seed. Seeds have a self-regulating power absorption characteristic such that their temperatures remain within a few degrees of their Curie transition point. The code is also very flexible, being able to model a seed of any orientation embedded in a tissue domain that can be inhomogeneous with respect to blood perfusion or thermal conductivity. MGSEED uses multigrid (or multilevel) programming techniques as well as a finite volume discretization that exploits knowledge of the approximate shape of the temperature solution very near to a seed. These techniques allow the code to sample the seed very coarsely, requiring only one or two nodes to cross the seed. With these coarse samplings MGSEED calculated very accurate temperatures in under 3 min of CPU time on a Sun Sparcstation 2. The accuracy of MGSEED is demonstrated at different levels of perfusion by comparing its solution in a perpendicular plane that bisects the seed with the known analytical solution. The speed of MGSEED is compared to other methods of solution and it is found that MGSEED performs 14 times faster than successive over relaxation and conjugate gradient methods, and 2.5 times faster than a preconditioned (modified block incomplete Cholesky) conjugate gradient method. It is concluded that the techniques for discretization and solution incorporated into MGSEED can greatly improve the flexibility and speed of hyperthermia treatment planning, which could ultimately lead to an increased level of control over treatment outcome.
Computational algorithms that mimic the response of the basilar membrane must be capable of reproducing a range of complex features that are characteristic of the animal observations. These include complex input output functions that are nonlinear near the site's best frequency, but linear elsewhere. This nonlinearity is critical when using the output of the algorithm as the input to models of inner hair cell function and subsequent auditory-nerve models of low- and high-spontaneous rate fibers. We present an algorithm that uses two processing units operating in parallel: one linear and the other compressively nonlinear. The output from the algorithm is the sum of the outputs of the linear and nonlinear processing units. Input to the algorithm is stapes motion and output represents basilar membrane motion. The algorithm is evaluated against published chinchilla and guinea pig observations of basilar membrane and Reissner's membrane motion made using laser velocimetry. The algorithm simulates both quantitatively and qualitatively, differences in input/output functions among three different sites along the cochlear partition. It also simulates quantitatively and qualitatively a range of phenomena including isovelocity functions, phase response, two-tone suppression, impulse response, and distortion products. The algorithm is potentially suitable for development as a bank of filters, for use in more comprehensive models of the peripheral auditory system.
Here's a review of a computer program, The Resident's Friend, designed to assist interns and residents in the extremely time-consuming tasks of detail management and record-keeping.
In continuation of the program of data recording presented earlier a computer program for analysis and calculation of a data base which consists of the results of dental examination of children is introduced. The presented possibilities of data processing are fitted to the general reports in dentistry of children. They are recommended in solving the problems of a simple and modern data processing in this special field of dentistry.
The main elements of the computer system used in medical practice are discussed. Typical application possibilities of microcomputers in perinatal medicine are described.
Issuing from the metabolic changes under perioperative conditions the problems and the significance of a subtile perioperative management of the metabolism in diabetics with labile metabolism and coronary disease are described. The device-technical components and the function of a computer-assisted regulation and advisory system (Glucon) for the support of the perioperative management of blood glucose and for the parenteral glucose supply in diabetics during large operative interventions. When the system was applied for several days under submaximal metabolization of glucose nearly normoglycaemia conditions could be achieved. The system is proposed as alternative to the conventional perioperative blood glucose management for diabetics with labile metabolism and coronary diseases in large operations.
The authors discuss basic problems of analogue - digital transmission focused on practical questions with regard to the application of medical technique in combination with a computer. They discuss the different parts of the digital-measurement chain, different methods of signal transmission and finally also practical applications.
1. The relationship between tolerated nitrogen oversaturation and ambient pressure is practically linear. 2. Tissues with short half-times have a higher tolerance than tissues with long half-times. 3. The human body can be regarded as consisting of 16 compartments with half-times from 4 to 635 minutes for nitrogen and from 1.5 to 240 minutes for helium. 4. The coefficients for calculation of minimal tolerated ambient pressure for a given PN2 in the tissue can be deduced directly from the half-times for nitrogen. 5. The results of 573 simulated air dives and 544 real dives in mountain lakes are in accordance with the computed limits of tolerance. 6. The ZH-L16 system is applicable to all exposures with air or oxygen-nitrogen mixtures. 7. Adaptation to breathing of oxy-helium or trimix is simple.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.