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PubMed2004

Elastic scattering and light transport in three-dimensional collagen gel constructs: a mathematical model and computer simulation approach.

A mathematical modeling approach for elastic scattering and light propagation is presented, which can be used to obtain the scattering coefficient, the index of refraction, and the distribution of the collagen fibrils in a gel. Collagen fibrils can be realistically represented by small cylindrical particles. The analysis of the scattering of light by such particles provides the scattering coefficient. Light transport in multilayered tissues has been modeled and the collagen fibrils scattering coefficient has been considered as main input parameters. Assuming that a gel is composed of fibrils with the same diameter, it is possible to obtain all the input parameters of the model and, therefore, a simulated spectrum. This can be repeated for several diameters. Considering a gel composed of fibrils with different diameters, it is possible to obtain a best-fitting simulated spectrum as a weighted sum (least-square-error based) of the spectra corresponding to several fibril diameters, and, therefore, obtain an estimate of the percentages of fibrils of each diameter in the gel. Moreover, the scattering coefficient and refractive index, which are also provided by the model, are relevant parameters as they relate to tissue properties in their own right.

Algorithms↗
PubMed1983

The combinatorial distance geometry method for the calculation of molecular conformation. I. A new approach to an old problem.

A new approach to the long-standing local minimum problem of molecular energy minimization is proposed. The approach relies upon a field of computer mathematics known as combinatorial optimization, together with methods of conformational analysis derived from distance geometry. The advantages over the usual numerical techniques of optimization are, first, that the algorithms derived are globally convergent, and second, that the mathematical problems involved are well-posed and suitable for study within the modern theory of computational complexity. In this paper we introduce the approach, and describe a computer program based on it.

Computers↗
PubMed2005

RF tumour ablation: computer simulation and mathematical modelling of the effects of electrical and thermal conductivity.

This study determined the effects of thermal conductivity on RF ablation tissue heating using mathematical modelling and computer simulations of RF heating coupled to thermal transport. Computer simulation of the Bio-Heat equation coupled with temperature-dependent solutions for RF electric fields (ETherm) was used to generate temperature profiles 2 cm away from a 3 cm internally-cooled electrode. Multiple conditions of clinically relevant electrical conductivities (0.07-12 S m-1) and 'tumour' radius (5-30 mm) at a given background electrical conductivity (0.12 S m-1) were studied. Temperature response surfaces were plotted for six thermal conductivities, ranging from 0.3-2 W m-1 degrees C (the range of anticipated clinical and experimental systems). A temperature response surface was obtained for each thermal conductivity at 25 electrical conductivities and 17 radii (n=425 temperature data points). The simulated temperature response was fit to a mathematical model derived from prior phantom data. This mathematical model is of the form (T=a+bRc exp(dR) s(f) exp(g)(s)) for RF generator-energy dependent situations and (T=h+k exp(mR)+n?exp(p)(s)) for RF generator-current limited situations, where T is the temperature (degrees C) 2 cm from the electrode and a, b, c, d, f, g, h, k, m, n and p are fitting parameters. For each of the thermal conductivity temperature profiles generated, the mathematical model fit the response surface to an r2 of 0.97-0.99. Parameters a, b, c, d, f, k and m were highly correlated to thermal conductivity (r2=0.96-0.99). The monotonic progression of fitting parameters permitted their mathematical expression using simple functions. Additionally, the effect of thermal conductivity simplified the above equation to the extent that g, h, n and p were found to be invariant. Thus, representation of the temperature response surface could be accurately expressed as a function of electrical conductivity, radius and thermal conductivity. As a result, the non-linear temperature response of RF induced heating can be adequately expressed mathematically as a function of electrical conductivity, radius and thermal conductivity. Hence, thermal conductivity accounts for some of the previously unexplained variance. Furthermore, the addition of this variable into the mathematical model substantially simplifies the equations and, as such, it is expected that this will permit improved prediction of RF ablation induced temperatures in clinical practice.

Catheter Ablation↗
PubMed1982

[Bases, technic and expressiveness of computer tomography. Indications and efficiency].

The developments of reconstruction mathematics, computer technology and X-ray detectors were prerequisite to the invention of computer tomography. Essential progress was made leading to the development of the currently used third and fourth generation scanners. The use of CT has greatly influenced diagnostic imaging and therapy planning. The main advantages of CT are the demonstration of the third dimension, the differentiation of very minor density differences and non-invasiveness. In spite of the high costs of CT equipment and maintenance, an overall reduction of cost was achieved by decreasing the number of diagnostic procedures and reducing the time between the beginning of illness and therapy.

Humans↗
PubMed1997

[Diagnosis of normal pressure hydrocephalus. A calculation model for determining intracranial pressure-dependent resistance and compliance].

Computer-aided analysis of the results of the intrathecal infusion test using our mathematical computation leads to simplification of this investigation, and therefore normal pressure hydrocephalus is more easily diagnosed. Simultaneous measurement of resistance and compliance during a single investigation allows the exertion of the patients to be minimized. In contrast to classic methods it is not necessary that the ICP reaches a plateau. Our mathematical method diverges with the description of a pressure-dependent slope of the function for the resistance from the static examination models. For that we are able to take the non-linearity of the cerebrospinal fluid resorption into consideration. The intrathecal infusion tests is a reliable diagnostic method for measuring resistance and compliance in patients suspected of having normal pressure hydrocephalus.

Cerebral Ventricles↗
PubMedDate not supplied

An introduction to simulation and visualization of biological systems at multiple scales: a summer training program for interdisciplinary research.

Advances in biomedical research require a new generation of researchers having a strong background in both the life and physical sciences and a knowledge of computational, mathematical, and engineering tools for tackling biological problems. The NIH-NSF Bioengineering and Bioinformatics Summer Institute at the University of Pittsburgh (BBSI @ Pitt; www.ccbb.pitt.edu/bbsi) is a multi-institutional 10-week summer program hosted by the University of Pittsburgh, Duquesne University, the Pittsburgh Supercomputing Center, and Carnegie Mellon University, and is one of nine Institutes throughout the nation currently participating in the NIH-NSF program. Each BBSI focuses on a different area; the BBSI @ Pitt, entitled "Simulation and Computer Visualization of Biological Systems at Multiple Scales", focuses on computational and mathematical approaches to understanding the complex machinery of molecular-to-cellular systems at three levels, namely, molecular, subcellular (microphysiological), and cellular. We present here an overview of the BBSI @ Pitt, the objectives and focus of the program, and a description of the didactic training activities that distinguish it from other traditional summer research programs. Furthermore, we also report several challenges that have been identified in implementing such an interdisciplinary program that brings together students from diverse academic programs for a limited period of time. These challenges notwithstanding, presenting an integrative view of molecular-to-system analytical models has introduced these students to the field of computational biology and has allowed them to make an informed decision regarding their future career prospects.

Computational Biology↗
PubMed2003

Will the digital computer transform classical mathematics?

Mathematics and machines have influenced each other for millennia. The advent of the digital computer introduced a powerfully new element that promises to transform the relation between them. This paper outlines the thesis that the effect of the digital computer on mathematics, already widespread, is likely to be radical and far-reaching. To articulate this claim, an abstract model of doing mathematics is introduced based on a triad of actors of which one, the 'agent', corresponds to the function performed by the computer. The model is used to frame two sorts of transformation. The first is pragmatic and involves the alterations and progressive colonization of the content and methods of enquiry of various mathematical fields brought about by digital methods. The second is conceptual and concerns a fundamental antagonism between the infinity enshrined in classical mathematics and physics (continuity, real numbers, asymptotic definitions) and the inherently real and material limit of processes associated with digital computation. An example which lies in the intersection of classical mathematics and computer science, the P=NP problem, is analysed in the light of this latter issue.

Artificial Intelligence↗
PubMed1993

Physical exertion and immediate mental performance of sixth-grade children.

The intent of this investigation was to examine the potential influence of varying durations of physical exertion at different times of the day on immediate mathematical performance by 120 sixth-grade boys and girls. Subjects were assigned to two control and two treatment groups (Solomon Four-group Design), with treated subjects administered physical exertion (paced walking at controlled moderate intensity) for durations of 20, 30, and 40 min. at three different times of the school day [8:30 a.m., 11:50 a.m. (before lunch), 2:20 p.m.] over 3 weeks. After each exertion session, subjects were immediately administered a 90-sec. mathematical computation test. Analysis indicated no significant differences in mathematical performance at any duration in the morning, but scores were significantly higher at 11:50 a.m. and 2:20 p.m. at 30- and 40-min. durations in comparison to the 20-min. duration. There were no differences by gender of subject.

Arousal↗
PubMed1976

Screening random asymptomatic women under 50 by annual mammographies: does it make sense?

The effectiveness of screening random asymptomatic women for breast cancer using mammography has been analyzed using a new mathematical-computer technology. The technology is based on a general mathematical theory of screening recently developed by Blumenson combined with a mathematical model for breast cancer developed by Blumenson and Bross over the past decade. The technology makes it relatively simple to try alternative strategies for age at onset of screening, screening interval, etc. and to calculate the relative effectiveness of the strategy. When the benefits of alternative strategies with periodic screening beginning at different ages were compared with the increasing risk of iatrogenic disease from multiple exposure to low levels of radiation, it was concluded that screening of asymptomatic women should begin no earlier than age 50.

Age Factors↗
PubMed1991

A deterministic computer simulation model of life-cycle lamb and wool production.

A deterministic mathematical computer model was developed to simulate effects on life-cycle efficiency of lamb and wool production from genetic improvement of performance traits under alternative management systems. Genetic input parameters can be varied for age at puberty, length of anestrus, fertility, precocity of fertility, number born, milk yield, mortality, growth rate, body fat, and wool growth. Management options include mating systems, lambing intervals, feeding levels, creep feeding, weaning age, marketing age or weight, and culling policy. Simulated growth of animals is linear from birth to inflection point, then slows asymptotically to specified mature empty BW and fat content when nutrition is not limiting. The ME intake requirement to maintain normal condition is calculated daily or weekly for maintenance, protein and fat deposition, wool growth, gestation, and lactation. Simulated feed intake is the minimum of availability, DM physical limit, or ME physiological limit. Tissue catabolism occurs when intake is below the requirement for essential functions. Mortality increases when BW is depressed. Equations developed for calculations of biological functions were validated with published and unpublished experimental data. Lifetime totals are accumulated for TDN, DM, and protein intake and for market lamb equivalent output values of empty body or carcass lean and wool from both lambs and ewes. These measures of efficiency for combinations of genetic, management, and marketing variables can provide the relative economic weighting of traits needed to derive optimal criteria for genetic selection among and within breeds under defined industry production systems.

Animals↗
PubMed1990

A computer designed graph for administration of atracurium by i.v. infusion.

A bi-exponential mathematical computer model was used to develop a guidance graph for atracurium infusions. The model permitted variation in infusion rates, in pharmacokinetic parameters and in "effect" thresholds. Systematic experiments revealed a relationship between the rate of recovery from a fixed bolus loading dose and the most appropriate initial infusion rate. This relationship was expressed as a guidance graph or "ready reckoner". The quality of guidance was assessed in 50 anaesthetics, given consecutively. In 39 patients optimal myoneural block for surgery was maintained for the duration of the infusion without adjustments or supplementary bolus doses. The mean operating time was 92 min and the mean duration of infusion was 59 min.

Adult↗
PubMed1984

An arterial blood gas interpretation program for hand-held computers.

Because of its portability, the hand-held computer can be easily used at the bedside to perform mathematical computations and assist with patient care decision making. This paper describes applications software for arterial blood gas interpretation with the hand-held computer. From the arterial blood gas values entered, the program calculates the arterial/alveolar PO2 ratio (a/A PO2), provides an interpretation of oxygenation, a/A PO2, ventilation, and acid-base status, and makes suggestions for therapy. This program can be used for the individualized bedside teaching of students and others with limited experience in arterial blood gas interpretation.

Blood Gas Analysis↗
PubMed1998

A system for the objective screening of dysphonia and the possibilities for its application in exposed workers.

Modern computers and their implementation have enabled the development of software based on mathematical computations, which analyse the parameters of voice signals in real time, as well as in the spectral and capstral domains. A software system written on the basis of specific methods and algorithms for pathological voice analysis allows the evaluation of: to D; PPQ, APQ, D S, D DISS, HNR, DH and GQ. The system was tested (using the vowel "a") on 900 workers at the Neftochim and Devnya chemical refineries in Bulgaria, exposed to irritating gases (NOx, SOx, etc.). The analysis of the studied parameters of the voice signal "a" showed significant changes in 137 workers, diagnosed after routine otolaryngological examination as the following laryngeal pathology: 101 workers suffered from chronic laryngitis, 31 from inflammatory-reactive formations on the vocal folds and five from laryngeal carcinoma. The non-invasive microcomputer system for the quantitative analysis of hoarseness enabled the scanning of laryngeal pathology in large populations of workers exposed to irritating gases in the chemical industry.

Chemical Industry↗
PubMed2003

[Scientometrics and bibliometrics of biomedical engineering periodicals and papers].

This investigation was made to reveal the current status, research trend and research level of biomedical engineering in Chinese mainland by means of scientometrics and to assess the quality of the four domestic publications by bibliometrics. We identified all articles of four related publications by searching Chinese and foreign databases from 1997 to 2001. All articles collected or cited by these databases were searched and statistically analyzed for finding out the relevant distributions, including databases, years, authors, institutions, subject headings and subheadings. The source of sustentation funds and the related articles were analyzed too. The results showed that two journals were cited by two foreign databases and five Chinese databases simultaneously. The output of Journal of Biomedical Engineering was the highest. Its quantity of original papers cited by EI, CA and the totality of papers sponsored by funds were higher than those of the others, but the quantity and percentage per year of biomedical articles cited by EI were decreased in all. Inland core authors and institutions had come into being in the field of biomedical engineering. Their research topics were mainly concentrated on ten subject headings which included biocompatible materials, computer-assisted signal processing, electrocardiography, computer-assisted image processing, biomechanics, algorithms, electroencephalography, automatic data processing, mechanical stress, hemodynamics, mathematical computing, microcomputers, theoretical models, etc. The main subheadings were concentrated on instrumentation, physiopathology, diagnosis, therapy, ultrasonography, physiology, analysis, surgery, pathology, method, etc.

Authorship↗
PubMed1995

A new three-dimensional treatment algorithm for complex surfaces: applications in surgery.

PURPOSE: Recent advances in computer technology enable automatic reconstruction of surface models using digitized contour lines and three-dimensional (3D) representation on a graphic terminal. This work was aimed at obtaining 3D reconstructions of facial bones to help guide oral surgery and complex dental implantology procedures. MATERIAL AND METHODS: The starting point was a computed tomographic examination. The limits of the cortical bone were automatically outlined and then digitized using a special computer program. The resulting data were then compiled for computer-aided design (CAD) purposes, and a virtual 3D model of the bone was mathematically computed. This model was next transferred to a computer program that piloted a CAD/computer-aided manufacture (CAM) machine that guided a laser stereolithography process. RESULTS: The early results of the use of 3D images, as well as solid models, for clinical and surgical purposes, indicate a high degree of reliability in morphologic diagnosis, determining the surgical procedure, and establishing the subsequent prognosis.

Algorithms↗
PubMed1999

The cell as the smallest DNA-based molecular computer.

The pioneering work of Adleman (1994) demonstrated that DNA molecules in test tubes can be manipulated to perform a certain type of mathematical computation. This has stimulated a theoretical interest in the possibility of constructing DNA-based molecular computers. To gauge the practicality of realizing such microscopic computers, it was thought necessary to learn as much as possible from the biology of the living cell--presently the only known DNA-based molecular computer in existence. Here the recently developed theoretical model of the living cell (the Bhopalator) and its associated theories (e.g. cell language), principles, laws and concepts (e.g. conformons, IDS's) are briefly reviewed and summarized in the form of a set of five laws of 'molecular semiotics' (synonyms include 'microsemiotics', 'cellular semiotics', or 'cytosemiotics') the study of signs mediating measurement, computation, and communication on the cellular and molecular levels. Hopefully, these laws will find practical applications in designing DNA-based computing systems.

Animals↗