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Effects of semantic cues on mathematical modeling: evidence from word-problem solving and equation construction tasks.

Mathematical solutions to textbook word problems are correlated with semantic relations between the objects described in the problem texts. In particular, division problems usually involve functionally related objects (e.g., tulips-vases) and rarely involve categorically related objects (e.g., tulips-daisies). We examined whether middle school, high school, and college students use object relations when they solve division word problems (WP) or perform the less familiar task of representing verbal statements with algebraic equations (EQ). Both tasks involved multiplicative comparison statements with either categorically or functionally related objects (e.g., "four times as many cupcakes [commuters] as brownies [automobiles]"). Object relations affected the frequency of correct solutions in the WP task but not in the EQ task. In the latter task, object relations did affect the structure of nonalgebraic equation errors. We argue that students use object relations as "semantic cues" when they engage in the sense-making activity of mathematical modeling.

Adolescent↗

Mathematical models of transmission dynamics and control of schistosomiasis.

Mathematical models are potentially valuable aids to a quantitative understanding of schistosome epidemiology and to the design of control programs. A basic theoretical framework is described that is developed to incorporate the impact of acquired immunity, heterogeneous transmission rates, and the effects of control measures. Models that assume that acquired immunity acts to moderate the rate of human infection make predictions consistent with age-intensity data from different human populations. Models incorporating heterogeneous water contact behavior can be applied to suitable field data and used to predict the potential efficacy of targeted chemotherapy or focal molluscicide application. More complex and detailed models can be used in simulation studies to assist with the design of field trials and in the interpretation of data from these trials. These applications of mathematical models suggest several areas requiring further theoretical development and also indicate areas in which adequate field data are still lacking.

Animals↗

Mathematical modeling of the impact of malaria vaccines on the clinical epidemiology and natural history of Plasmodium falciparum malaria: Overview.

We report a major project to develop integrated mathematical models for predicting the epidemiologic and economic effects of malaria vaccines both at the individual and population level. The project has developed models of the within-host dynamics of Plasmodium falciparum that have been fitted to parasite density profiles from malaria therapy patients, and simulations of P. falciparum epidemiology fitted to field malariologic datasets from a large ensemble of settings across Africa. The models provide a unique platform for predicting both the short- and long-term effects of malaria vaccines on the burden of disease, allowing for the temporal dynamics of effects on immunity and transmission. We discuss how the models can be used to obtain robust cost-effectiveness estimates for a wide range of malaria vaccines and vaccination delivery strategies in different eco-epidemiologic settings. This paper outlines for a non-mathematical audience the approach we have taken and its underlying rationale.

Animals↗

New mathematical model for accurate description of absorption kinetics of paracetamol given orally with a high calorie liquid meal.

OBJECTIVE: Gastric emptying (GE) of liquids is quantified as the rate of paracetamol absorption in clinical and research settings (paracetamol method). A conventional 1-compartment model assumes the first-order rate kinetics for paracetamol absorption. This assumption seems improper when paracetamol is coingested with a caloric liquid meal, because the caloric liquid leaves the stomach at a constant rate (zero-order process). Theories based on the 1-compartment model reveal that tmax and Cmax/AUCinfinity accurately reflect the rate of paracetamol absorption, but whether this is also the case when paracetamol is administered with a caloric liquid, has not been investigated. The aims of this study were to propose a new mathematical model for accurately describing absorptive behaviors of paracetamol added to a caloric liquid meal, and, using the model, to clarify the characteristics of tmax and Cmax/AUCinfinity as rate parameters. METHODS: Based on the newly developed model, tamx and Cmax/AUCinfinity were mathematically expressed in terms of GE rates. Subsequently, the characteristics of tmax and Cmax/AUCinfinity were elucidated by simulation works. RESULTS: The simulation study showed that both tamx and Cmax/AUCinfinity could reflect GE rates, tmax was a more sensitive index of GE than Cmax/AUCinfinity and tmax was less reliable than Cmax/AUCinfinity if GE is very rapid. CONCLUSIONS: In the paracetamol method using a caloric liquid test meal, tmax and Cmax/AUCinfinity are suitable for detecting delayed and rapid GE, respectively.

Absorption↗

A mathematical approach to epidemic control.

A mathematical model of an influenza epidemic which occurred in 1961 is suggested. The mathematics imply conclusions on the practical control of similar outbreaks. This is a technique applicable to one general practice.

Disease Outbreaks↗

Mathematical models and their applications in medicine and health.

Mathematical models have great potentialities as regards their utility in different disciplines of medicine and health. This paper attempts to elucidate their uses in the field. A brief mention of some models has also been made. Mathematical models are useful in epidemiologic research, planning and evaluation of preventive and control programmes, clinical trials, measurement of health, cost-benefit analysis, diagnosis of patients and in maximizing effectiveness of operations aimed at attaining specified goals within existing resources.

Health Services Research↗

Bivariate analysis of surgically induced regular astigmatism. Mathematical analysis and graphical display.

OBJECTIVE: The purpose of the study was to develop methods for simultaneous description of astigmatic direction and magnitude on aggregate data, with special reference to refractive surgery. DESIGN: Mathematical analysis of astigmatisms employing bivariate statistical methods. RESULTS: The mean of several astigmatisms is a new astigmatism of specific direction and magnitude, while the confidence region is an area, which may be determined exactly. CONCLUSIONS: Astigmatisms may conveniently be symbolized as an astigmatic direction and magnitude, but are actually composed of refractive powers in the form of polar values. We are operating with two different entities, a net astigmatism and a power vector in the form of polar values. There is an unequivocal point-to-point correlation between these entities. Mathematical conversions can only be performed with polar values, but never by using net astigmatisms. All net astigmatisms must be converted to their appropriate refractive powers and the relevant calculations performed with these entities. The final result, such as an average of several astigmatisms, variances or confidence areas, may be point-to-point reconverted to and symbolized by a net astigmatism. These principles allow for exact description and comparison of surgical methods, but may be employed to describe and analyze any other population of astigmatisms, such as subjective cylinders and spectacle corrections.

Astigmatism↗

Graph-set analysis of hydrogen-bond patterns: some mathematical concepts

To provide a foundation for further theoretical and software development of the application of graph sets to patterns of hydrogen bonding and other intermolecular interactions a number of mathematical concepts and tools are defined, developed and demonstrated. Following a review of the basic definitions and uses of graph sets, the directional properties of hydrogen bonds are now included in the treatment. The concepts of a constructor graph and covalent distance matrix have been developed to aid in the generation of a qualitative descriptor for the straightforward, consistent and ultimately automatic (with appropriate software) definition of patterns. An additional mathematical tool, the arrowed T-labeling, has been developed to deal with situations in which pattern-forming moieties are located on crystallographic special positions. To demonstrate the utility and various features of these concepts they are applied in detail to two particular structures, polymorphic iminodiacetic acid [N-(carboxymethyl)glycine] and trans-tetraamminedinitrocobalt(III) acetate. To facilitate the application and use of graph sets many of these developments have already been incorporated into the software of the Cambridge Structural Database, as described in the accompanying paper.

Journal Article↗

[Prediction of physiological response from mathematical models].

The ability to predict the physiological responses of workers exposed to extreme environmental conditions, has been a challenge to environmental physiologists for more than 3 decades. Therefore, mathematical models have been developed to predict metabolic rate under various levels of work intensity and dynamic changes in body temperature and heart rate. Based on the effect of exercise on the cardiovascular system, a model was developed to predict mean arterial blood pressure as a function of heart rate. Physiological strain could also be estimated on the basis of thermoregulatory and cardiovascular strains. This paper summarizes knowledge accumulated during 25 years of studies in the field of mathematical modeling of physiological parameters. Besides analyzing the logic underlying each model, it explains the scientific approach in developing a model from its early concept to the model's application in the field.

Blood Pressure↗

Mathematical modeling of epidermal growth factor receptor signaling through the phospholipase C pathway: mechanistic insights and predictions for molecular interventions.

Combining engineering analyses and mathematical modeling with intervention and detection methodologies at the molecular level will allow manipulation of intracellular signal transduction pathways, and therefore rational control of functional processes central to medicine and biotechnology. We have formulated a simple mathematical model of a key signaling pathway required for regulated migration of fibroblasts and other cell types: activation of the intracellular enzyme phospholipase C (PLC) mediated by epidermal growth factor receptor (EGFR) and a multitude of other transmembrane receptors. One of the interesting features of this pathway is that the substrate of PLC, the lipid phosphatidylinositol (4,5)-bisphosphate (PIP(2)), is turned over quite rapidly and must be constantly resupplied to the plasma membrane by a known transfer mechanism. The model, which accounts for regulation of PIP(2) concentration, is sufficiently detailed to explain unique quantitative features of recent experimental data. We find that competitive pathways that deplete PIP(2) from the membrane, as well as receptor-mediated enhancement of PIP(2) supply, must be significant for agreement between model and experiment. Importantly, the mechanistic nature of the model also allowed us to predict the efficacy of various molecular intervention strategies, including overexpression of wild-type and variant proteins in the pathway as well as treatment with specific drug inhibitors. For many parameter conditions the intuitive strategy of targeting the enzyme itself is actually predicted to be relatively inefficient, with a novel and potentially useful alternative being disruption of the reactant supply mechanism.

ErbB Receptors↗

[Mathematical modelling and the prognosis of treatment efficacy in papillomavirus infection of the cervix uteri].

In this paper, consideration is given to the problem of mathematical modelling, diagnosis and effects of treatment options on the condition of a patient exposed to papillomavirus infection. The problem is tackled of identifying the most prominent signs of degree of severity of the disease course and of therapy efficiency on the basis of parameters characterizing the immunologic vigor with making use of the covariation matrix eigenvalues algorithm, namely the modelling manifolds algorithm. Such an approach allows the central problem of classification of indices for the immunologic vigor to be settled. A mathematical model as discrimination surface to be used for prediction of results of the treatments administered is constructed.

Algorithms↗

[Continuous flow ventilatory support using a multijet insufflation catheter. Physical, mathematical and clinical prerequisites and principles].

The authors present theoretical principles of a new ventilatory support continuous flow ventilatory support (CFVS) with multijet insufflation catheter (MIC). Theoretical part of the presented work reasons the need of this type of ventilatory support and explains basic mathematical and physiologic principles of described mechanical ventilation method and reveals the advantages of continuous flow ventilatory support with multijet insufflation catheter in comparison with terminal eye catheter. Physical and mathematical analysis on a model of lungs in static and dynamic conditions revealed that the difference in the value of maximal inspiratory pressure is significantly higher in the system with terminal eye catheter and confirmed that the CFVS application with multijet insufflation catheter is connected with minimal risk of barotrauma by gas flow up to 20-26 l/min. The paper concludes that continuous flow ventilatory support with multijet insufflation catheter is more efficient with the possibility of significantly higher gas flow application than with terminal eye catheter and without the risk of pressure rise in the airways and without rise of breathing work. (Fig. 10, Ref. 11.)

Humans↗

[Principles in construction of mathematical model for neonatal corpse cooling studies].

The process of cooling of the body of a dead human was studied with consideration for the anatomical characteristics of adult and newborn human corpses. The body was simulated as a homogeneous elongated rotation ellipsoid and mathematical model was developed as function of relationship between body temperature and time. After appropriate characteristics in the mathematical model were established, cooling processes and effects of various factors on this process were analyzed for the final ellipsoid. The model suggests the possibility of amendments for environmental temperature and body parameters.

Body Temperature↗

Application of mathematical tools to improve the design and operation of activated sludge plants. Case study: the new WWTP of Galindo-Bilbao. Part I: Optimum design.

This paper presents a mathematical formulation for the optimum design of a new activated sludge WWTP. The WWTP optimum design problem has been formulated as a Mathematical Programming problem, which is solved through a nonlinear optimisation method. The plant model has been based on the ASM1. The minimum volume of the biological reactors and the minimum total cost (including construction and exploitation costs) have been considered as optimisation criteria. Some practical results are also included, using as a case study the design of the second stage of the Galindo-Bilbao WWTP.

Algorithms↗

A comparison of overall mathematical models of the cardiovascular system for simulating response to orthostatic stresses.

Although numerous mathematical models of the cardiovascular system (CVS) have appeared in the literature only a few of them are models of the entire system with detailed representation of the heart, the vasculature, and the control elements. Like all models of biological systems, these models vary in complexity, and most of them are stimulus- specific. Their ability to simulate with acceptable accuracy either responses over a wide range of the stimulus or responses to stimuli of similar kind has not been reported. In this paper, three mathematical models of the CVS are examined in terms of their response to different orthostatic stresses, namely, lower body negative pressure (LBNP), head-up tilt, and blood loss. The short-term orthostatic responses of the models are compared to available experimental data. The models are: (i) Croston and Fitzjerrell's for study of LBNP and head-up tilt response, (ii) Jaron et al.'s for study of +Gz response, and (iii) Pullen's for simulation of response to blood loss. We will henceforth refer to these models by the letters C, J, and P, respectively.

Hemorrhage↗

[Regular changes in histogram forms in physical measurements and mathematical modeling].

A study of macroscopic fluctuations for objects separated by large distances confirmed the conclusion drawn earlier that, if the objects being measured are in different time zones, the increase in the probability of occurrence of histograms of similar form corresponds to the difference in the local time at the points of measurement. It was also found that, upon realization of pseudo-random sequences of numbers in mathematical generators, sequences of histograms very similar to those in real physical series can be realized. This suggests the presence of previously unknown regularities, both physical and mathematical, in sequences traditionally considered as absolutely random.

Alpha Particles↗

[Mathematical model of the infection process in diphtheria for determining the therapeutic dose of antitoxic anti-diphtheria serum].

It is known that administration of horse serum against diphtheria toxin can cause autoimmune and allergic complications. Therefore it is important for improvement of serotherapy to develop methods of prediction of disease course and quantity of diphtheria toxin and antitoxic antibodies in a serum. We have developed the mathematical model of diphtheria infection, which consists of six differential equations describing dynamics of diphtheria toxin and antitoxic antibodies in a serum, quantity of infection agent and macrophages in a site of inflammation. This mathematical model allows to predict the course of infectious process, the level of diphtheria toxin and antitoxic antibodies in the sera of people with diphtheria and to calculate the individual therapeutic dose of antitoxic serum for each patient.

Diphtheria↗

[Physiological analysis of a mathematical model for predicting somatic eigenstates under combined stresses].

Objective. To put a mathematical model for predicting human somatic eigenstates (HS) into practical engineering design of countermeasures against combined stresses (hypoxia, heat, noise and vibration) in an aircraft cabin, and confirm the model from the human physiological viewpoint. Method. Published works on these 4 stresses were employed to verify the main and interactive effects which had been previously proved mathematically. Result. The main effects of 4 stresses and the significant interactive effects of 2 from 4 stresses agreed with the published experiments in single or in the same combination of these stresses. Conclusion. The model is reasonable in human physiological consideration and has been adopted in engineering design.

Adaptation, Physiological↗