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At least 1,225 records · Page 68Linked to original sources
PubMed2005

Positive pressure infusion of therapeutic agents into brain tissues: mathematical and experimental simulations.

Positive pressure infusion is a clinical means of achieving convection-enhanced delivery of therapeutic agents within the tissues of the central nervous system for the treatment of glioblastoma multiforme and other diseases of the brain. We have developed a mathematical model of the technique and an in vitro gelatin surrogate for it, which provide biophysical insights into the performance characteristics of candidate infusion systems and drug delivery protocols. We present a brief overview of the clinical problems that are being addressed, succinctly describe the mathematical and in vitro models used in our laboratories, and highlight some representative results from our studies. A number of references to related work are provided for those seeking further details.

Antineoplastic Agents↗
PubMed2005

[Tendency and mathematical model of relationship of blood ATP content with temperature and time of preservation].

To investigate the relationship of blood ATP content with temperature and time of preservation and to establish its mathematical model, adenosine triphosphate (ATP) concentration was applied as the index of the quality of erythrocytes; systematical study on variation of blood preserved in a series of different temperatures from 4 degrees C to 32 degrees C was performed, and a series of experimental data were obtained. The results showed that when the ATP concentration y = f (d, t, s) in preserved blood was given as the continuous function of the time (d), the temperature (t) and the initiate ATP concentration (s), the model was fitted with the theory of linearity regression in symbolic statistics, and the general mathematical physical equation of the variation of preserved blood quality was deduced. According to the equation, the whole blood in CPDA-1 solution could be efficiently stored for 35, 35, 29, 22, 18, 18, 13, 8, 7, 6, 6, 5, 4, 4 and 3 days in 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 and 32 degrees C, respectively. In conclusion, the general tendency of the variation of preserved blood quality according to the temperature and the time was systematically disclosed for the first time, which would be propitious to estimate the blood quality in various temperatures and to instruct clinical blood transfusion.

Adenosine Triphosphate↗
PubMed2005

Early intervention surveillance strategies (EISS) in dental student clinical performance: a mathematical approach.

Graduating dental practitioners requires the mastery of a number of skills and a significant body of basic information. Dental education is a complex combination of didactic and physical skill learning processes. It is necessary to develop appropriate tools to measure student clinical performance to allow the provision of interventional strategies at the right time targeted at the right individuals. In this study, an approach to early intervention surveillance strategies was developed that is cost-effective, transparent, and robust based on mathematical predictions of student clinical achievements. Using a cohort of students' clinical activity profile, a polynomial pair was developed that represents the predictive function of low and high achieving students. This polynomial pair can then be applied to students to predict their final achievement based on their current status. The polynomial methodology is adaptable to local variation such as access to clinical facilities. The early intervention surveillance strategy developed in this study provides a simple, cost-effective, predictive risk assessment system that relies on data sets already collected in most dental schools and can be completed without the need for significant human intervention. The mathematical approach allows the focusing of educational support towards students that require the assistance, thus augmenting the better use of resources.

Achievement↗
PubMed2005

[Mathematical model in prediction and evaluation of the effects on control measures for schistosomiasis].

OBJECTIVE: To carry out a theoretical research on the rule that a mathematical model may play on predicting and evaluating the control effect of schistosomiasis japonica. METHODS: Earbour's two-host model was used to predict and evaluate the effect of different control measures by computer simulation. Pilot samples in two villages of Shanghai suburb in 1950s were applied for the analysis. RESULTS: When the prevalence was high, synchronous chemotherapy for human and cattle populations quickly reduced the indices of the infection. Mollusciciding provided positive impact on the effect of chemotherapy. Added with the environmental measures for snail control, the basic reproductive rate (BRR) and equilibrium prevalence in human and bovines were sustainably reduced and even reached an interruption of transmission. The effect of chemotherapy could be consolidated by the anti-fecundity vaccine for bovines. Satisfied control effect could also be obtained by chemotherapy in human and bovines combined with behaviour intervention for human and vaccination for bovines without snail control. In areas with lower levels of transmission velocity, BRR and prevalence, the effect of various interventions was better than that obtained in areas with higher levels of the above three infection indices, and the disease control could be easier. Conclusion The Barbour's mathematical model can be used to roughly predict and evaluate the effects of schistosomiasis control measures.

Animals↗
PubMed2006

A mathematical model for constituent ratios of energy expenditure in human.

In order to assess the constituent ratios of energy expenditure in human, the deductive process of establishing a mathematical model for assessing the constituent ratios of the three major nutrients in energy expenditure in human was described in this paper. Total oxygen consumption, total carbon dioxide output and total nitrogen (urine nitrogen + skin nitrogen) excretion are related to the oxidation of the three major nutrients and the physiological combustion values of the three nutrients are already known. Based on these measurable and known parameters, the mathematical model established by the authors will help understand the characteristics of the tested individual's energy expenditure.

Carbon Dioxide↗
PubMed2006

Using mathematical models to assess sediment stability.

The application of mathematical models to a sediment stability study is presented, with an emphasis on using models as a component of an effort to develop, refine, and potentially validate a conceptual site model (CSM) for sediment transport at a study site. The utility of mathematical models is discussed, in which the modeling framework consists of linked hydrodynamic, sediment transport, and contaminant fate and transport models. Benefits and drawbacks of empirically based mechanistic models are presented. An approach for integrating modeling analyses into the development, refinement and validation of a CSM is provided. This approach focuses on a phased study that combines modeling and data-based analyses to test hypotheses related to the CSM and sediment stability. Uncertainty in modeling results is a primary concern in sediment stability studies, and issues related to model uncertainty are discussed. Finally, communication of modeling results to stakeholders is addressed.

Environmental Pollutants↗
PubMed2006

The pier abutment: a review of the literature and a suggested mathematical model.

Many clinicians consider the prosthetic restoration of missing posterior teeth by means of a 5-unit fixed partial denture with a pier abutment a non-favorable situation. The present article assesses the validity of the pier abutment by means of a critical review of the literature and mathematical analysis of the forces generated within a fixed partial denture of this design. Few studies are available, and none substantiate the theory that the pier abutment serves as a fulcrum. A mathematical model suggests that debonding may occur in the anterior abutment, but not due to the teetering of the fixed partial denture around the pier abutment.

Algorithms↗
PubMed2006

Tumor growth parameters of in-vivo human breast carcinoma: a proposed mathematical model for tumor growth kinetics.

Many mathematical models have been proposed to study tumor growth parameters in vivo. Nevertheless most of the medical models have given variable results even when experimental conditions are exactly the same. There are multiple factors that are capable of affecting tumor growth that should be taken into account when proposing a mathematical model for tumor growth in vivo. We discuss here own proposed model for tumor growth kinetics utilizing a modified Gompertz function that better responds to the growth characteristic of in "vivo" tumors.

Breast Neoplasms↗
PubMed2006

[The effects of noise on NIR analysis and related mathematic pretreatments and models].

The feasibility of using a relatively high noise NIR spectrometer for analysis was examined by using maize powder samples. The results showed that with four-time averaged NIR spectrum data without more pretreatments, PLS mathematic models and CAU-NIR software, the relative high noise scan NIR spectrometer could be used to get satisfied prediction results compared with other low noise NIR spectrometers. The prediction coefficient could reach 98% and the CV (variation coefficient) was 6.2%. It was proved that when the S/N of NIR spectrometer was lower than 10(5), it still could be used for quantity analysis with the help of some mathematic pretreatments and models.

Models, Theoretical↗
PubMedDate not supplied

[Mathematical modeling of cardiovascular system in patients with hemorrhage and hypothermia].

Mathematical modeling is the most expedient method for studying the response of human cardiovascular system to a combined effect of several external factors, in particular, hemorrhage and hypothermia. A complex mathematical model integrating models of the functional systems of human body and the physiological effects of disturbing factors can be used to study the combined effect of external factors. It allows the response of human body to various combinations of external effects of different intensities to be assessed with high accuracy. In addition, the model makes it possible to prognosticate the dynamics of changes in the cardiovascular system parameters from their initial variation. This facilitates prediction of the development of patient's state.

Cardiovascular System↗
PubMedDate not supplied

[Determination of the parameters for producing a biobinder from wood: a mathematical modeling of the transformation of lignocellulose substrate by the fungus Panus tigrinus].

A biochemical scheme for the transformation of wood lignocellulose during enzymatic hydrolysis of polysaccharides and lignin destruction in reactions involving free radicals was developed, and a corresponding mathematical model was constructed. Processing (fermentation) of wood particles by the fungus Panus tigrinus in a submerged culture for producing a biobinder of wood composites--woodchip boards and fiber-boards--is considered. The mathematical model was used to study the technological parameters that influence the production of enzymes and fungal biomass and the level of free radical accumulation in the substrate, i.e., the factors determining the production of the biobinder. The optimal values of these parameters were determined, namely: the specific surface of wood particles, amounting to 2000 cm2/g; processing time of 56 h; and an initial concentration of 3.0 g/l of fungal biomass in the submerged culture.

Cellulose↗
PubMed1991

[New electronic-mathematical method for measuring the condylar center of rotation].

Until today, not all methodical details and problems concerning the exact and reproducible determination of the condylar hinge axis have been solved yet. All familiar mechanical-manual and electronically supported methods as well as computer methods of some electronical recording systems have their limitations and are partly incorrect up to now. The reason for this lies mainly in the theoretical respectively mathematical approach towards these methods. With the aim of determining a point of minimal translatory movement ("steady point") during the rotatory opening movement in the TMJ condyle, a mathematical method is presented, which calculates the 3D coordinates of the condylar rotation centers automatically, i.e. without manual manipulation of the recording system. Contrary to conventional methods, this new technique is very precise and relatively less sensitive towards superimposed translatory movements.

Dental Articulators↗
PubMed1991

The influence of transport parameters and enzyme kinetics of the fibrinolytic system on thrombolysis: mathematical modelling of two idealised cases.

Experimental data obtained by magnetic resonance imaging and photographing clot dissolution in vitro have shown that whole blood clots dissolve almost two orders of magnitude faster when urokinase is introduced into the clot by pressure induced permeation than when its access is limited to diffusion. In view of these findings, two mathematical models have been developed that quantitatively link the enzymatic and transport properties of the fibrinolytic system to the velocity of thrombolysis. Without a pressure gradient across the thrombus, the plasminogen activator molecules diffuse into the thrombus through the blood-thrombus boundary plane. The blood-thrombus boundary slowly moves inwards due to thrombolysis that is spatially restricted to a relatively narrow zone. The velocity of thrombolysis is primarily limited by the diffusion constants of the plasminogen activator and plasmin. In contrast, when plasminogen activator is rapidly distributed along the thrombus by pressure induced bulk flow, lysis occurs at each segment of the thrombus after a lag period that is due to plasmin activation and sufficient fibrin degradation. The lag time is determined primarily by the catalytical properties of the plasminogen activator and plasmin. The mathematical models with the observations of the clot boundaries during lysis permit the characterization of plasmin action on the fibrin network.

Biological Transport↗
PubMed1991

[A mathematical simulation model of the AIDS pandemic].

In this work the mathematical model of the spread of AIDS pandemic over 5 regions of the world are presented. With the values of all parameters corresponding to the initial dynamics of the process the prognosis obtained with the use of this model is highly unfavorable. The program of mathematical modeling, developed in this investigation, may help in the evaluation of the effectiveness of different measures aimed at the liquidation of the epidemic process and in their correction, as well as in the choice of the optimum strategy of AIDS control.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Three-dimensional SPECT simulations of a complex three-dimensional mathematical brain model and measurements of the three-dimensional physical brain phantom.

We have developed a three-dimensional computer simulation of SPECT imaging. We have applied the simulation procedure to the realistic mathematical Hoffman three-dimensional brain model to generate the projection data (in the absence of attenuation, scatter, or noise) of both a parallel-hole and a multidetector SPECT system with point-focusing collimators. The simulated projection data were then reconstructed using standard software. The projection data resulting from the distribution of grey matter alone, or grey and white matter, were simulated. The results of these simulations indicate the existence of significant qualitative and quantitative artifacts in reconstructed human brain images. For example, the reconstructed values for grey matter along a cortical circumferential profile in a transverse slice through the basal ganglia varied by a factor of 2.40 (parallel-hole) and 2.99 (point-focusing), although the original grey matter values were identical in all cortical regions in the model. We have compared the simulated reconstructed images with those obtained by imaging the physical three-dimensional Hoffman brain phantom, which was constructed based upon the same set of data from which the mathematical three-dimensional Hoffman brain model was derived. Although the simulation did not include all of the degrading factors present in the physical imaging, the two images were in good agreement, indicating the applicability of the simulation to a realistic situation and the importance of the detector resolution effect.

Artifacts↗
PubMedDate not supplied

[Statistico-mathematical appraisal of the length of the pretherapeutic interval in the prognosis of tubercular meningitis in children].

The data obtained concerning the two main parameters for the prognosis of tuberculous meningitis: onset-admission interval, assessed anamnestically and electtoencephalogram performed on admission, were processed mathematically by computer. The EEG is a more reliable parameter for assessing the gravity of the lesions on admission that the anammestic data regarding the onset, at a signficance threshold of 10.48% as against 5.23%. For 11.3 days there was a close correspondence between the two parameters, after which the onset-admission variable became aleatory, the only objective index of gravity being the EEG. Statistico-mathematical processing increases the objectivity and precision of the prognosis.

Adolescent↗
PubMed1991

Evaluation of a mathematical algorithm for analysis of platelet volume distributions provided by Coulter hematological analyzers.

The human platelet volume distribution has been shown log-normal. Coulter Counter S-Plus models, as well as JT and STKS models, give mean platelet volume and platelet distribution width parameters. A computerized mathematical method, working with an IBM-XT microcomputer, was designed to calculate median and modal volumes, as well as the percentage of platelets smaller or larger than operator definable volume thresholds, on the basis of mean platelet volume and platelet distribution width. Preliminary experiments defined that the optimal stability of results was obtained in the range 2-6 hours after the blood collection; further experiments demonstrated that the results of the mathematical analysis were reproducible and accurate, by comparison to data obtained from a channel analysis in all samples, even including macroplatelets and/or microplatelets. It was thus shown that Coulter counters working with a curve fitting process may provide a complete analysis of platelet distribution curves, which could be extensively used for studying pathological conditions involving changes in platelet parameters.

Algorithms↗
PubMed1990

[Evolution and prognosis in patients with liver cirrhosis. II. A multifactorial analysis using a stepped regression mathematical model].

The multivariant approach offers best possibilities for assessment of liver function. The role of the different clinical, clinico-laboratory and combined clinical and clinicochemical indices in the prognosis of liver cirrhosis was studied in patient in ambulatory conditions. A step regressive mathematical model with the help of the program 2R of the statistical package BMDP was used. The regression of the clinical indices by 5 steps of the mathematical model showed that of greatest importance for the survival are the following indices: ascites, months since its onset, collaterals, anorexia and vascular nevi. By 4 steps of the regressive model of the clinico-chemical indices the following indices were chosen: prothrombin time, albumin, total bilirubin, cholesterol and alkaline phosphatase. The regression of the combined clinical and clinico-chemical indices pointed out as basic factors 3 clinical indices (ascites, months since its onset, collaterals) and 3 clinico-chemical indices related to the disturbed liver function (prothrombin time, total bilirubin, albumin).

Adult↗