Valeriano Comincioli | University of Pavia (original) (raw)

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Papers by Valeriano Comincioli

Journal of Mathematical Biology, 1984

A mathematical model of contracting skeletal muscle is studied. The model is composed by an elast... more A mathematical model of contracting skeletal muscle is studied. The model is composed by an elastic element (SE) in series with a contractile dement (CE) that describes the cross bridge kinetics with a formulation derived by that proposed by Eisenberg and Hill (1978). An analytical study of the system of nonlinear partial differential equations of the model allows the existence and the uniqueness of the solution to be proved. A suitable approach to the numerical solution is defined and a series of numerical tests are performed. These tests lead to select an appropriate set of parameters and allow to compare model predictions and experimental observations on frog skeletal muscle.

Engineering Computations, 1986

A numerical solution to the free boundary problem of three‐dimensional transient seepage through ... more A numerical solution to the free boundary problem of three‐dimensional transient seepage through an earth dam with accretion is presented. The numerical model uses a Baiocchi type transformation to extend the unknown solution region to a fixed known region. The initial value problem is then solved by an iterative method of successive over‐relaxation type. A seepage situation of sudden rise of water level on one side of a dam is presented as an example problem. The effects of variation of accretion, effective porosity and hydraulic conductivity are studied.

Journal of Parenteral and Enteral Nutrition, 1981

In spite of the many anthropometric, biohumoral, and immunologic parameters employed in the nutri... more In spite of the many anthropometric, biohumoral, and immunologic parameters employed in the nutritional assessment of hospitalized patients, it is difficult in clinical practice to evaluate accurately the degree and type of malnutrition and to assess the prognostic significance of this determination. The purpose of this study is to evaluate nutritional status of surgical patients by means of cluster analysis in orderr to identify different nutritional patterns and to evaluate their clinical and prognostic significance. Nutritional assessment of 71 surgical patients was carried out at admission, and the sets of data were evaluated by means of cluster analysis. Four clusters with different nutritional patterns were identified. The incidence of clinical variables (type of disease, postoperative sepsis, palliative procedures, mortality at 6 months, etc.) in each cluster was determined in order to evaluate their clinical and prognostic significance. Cluster 1 showed minor variations of the indicators, including most of the controls presented the lowest incidence of sepsis, palliative procedures, and mortality at 6 months. It was then considered as a reference group representative of the normal nutritional condition at our institution. The other three clusters showed major variations of nutritional indicators and represent poorer risk clinical conditions. Sepsis, palliative procedures and mortality rate were significantly more frequent in these clusters (p less than 0.05, p less than 0.001, p less than 0.05). A different distribution in the clusters was recorded in gastrointestinal tract cancers and other neoplasms. Only the incidence of gastrointestinal tract cancers increases progressively in the clusters with poorer prognosis, suggesting that this type of neoplasia is more frequently associated with major changes of nutritional status.

Annali di Matematica Pura ed Applicata, Series 4, 1971

Brain Research, 1980

The content of total thiamine radioactivity in some nervous structures and liver of the rat was d... more The content of total thiamine radioactivity in some nervous structures and liver of the rat was determined in a steady state condition, using [thiazole-2-14C]thiamine as a tracer. The contents were analyzed by a mamillary type compartmental model which enabled us to calculate the influx and efflux fractional rate constants, turnover times, turnover rates and relative accuracy. Total thiamine turnover rates of the central nervous system regions were found to be ordered in the following sequence: cerebellum (0.55 microgram/g.h) greater than medullar and pons greater than spinal cord and hypothalamus greater than midbrain (plus thalamic area) and corpus striatum greater than cerebral cortex (0.16 microgram/g.h). Sciatic nerve turnover rate was 0.58 microgram/g.h. The turnover times were mainly between 5 and 10 h (range 2.4--16.4 h). The influx rate constants could be ordered as follows: cerebellum greater than hypothalamus, pons and medulla greater than corpus striatum, spinal cord, midbrain (plus thalamic area) and sciatic nerve greater than cerebral cortex. The results show in general a good agreement between turnover rate values and brain regional sensitivity to thiamine deficiency, the most vulnerable areas to thiamine depletion being those with the highest turnover rates.

Rendiconti del Seminario Matematico della Università di Padova, 1965

L’accès aux archives de la revue « Rendiconti del Seminario Matematico della Università di Padova... more L’accès aux archives de la revue « Rendiconti del Seminario Matematico della Università di Padova » (http://rendiconti.math.unipd.it/) implique l’accord avec les conditions générales d’utilisation (http://www.numdam.org/legal. php). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright.

Wavelet transform and wavelet bases [11, 16] were originally conceived as a powerful tool for sig... more Wavelet transform and wavelet bases [11, 16] were originally conceived as a powerful tool for signal and image processing. More recently, wavelet analysis has been applied to the numerical solution of partial di erential equations arising in various areas of engineering and physics. In particular, with wavelets based methods one can realize an e ective multiscale analysis of functions and operators [6]. Within this framework it is possible to build suitable preconditioners for a given problem as well as consider new fast and higher order adaptive algorithms by using wavelet bases [9]. This kind of methods has been studied both from the theoretical and the computational point of view. As to applications to steady state problems, a wavelet-Galerkin approach was considered in [5], collocation-wavelet methods were introduced in [2], the boundary element framework was studied in [20], preconditioning in [7], and fast operator compression in [10]. For time dependent problems, noteworthy c...

Annali dell'Università di Ferrara. Sezione 7: Scienze matematiche

Biomathematics and Related Computational Problems, 1988

An overview of the results obtained from the collaboration of mathematicians and physiologists in... more An overview of the results obtained from the collaboration of mathematicians and physiologists in mathematical simulation of muscle contraction is presented. Next a mathematical model taking into account the heterogeneity of the muscle, is presented. A mathematical analysis of the model is given along with a numerical approach and some physiological implications.

Nonlinear Analysis: Theory, Methods & Applications, 1983

Communications in Numerical Methods in Engineering, 2000

Computer Methods in Applied Mechanics and Engineering, 1976

A free boundary problem related to the stationary flow in a porous medium in which the capillary ... more A free boundary problem related to the stationary flow in a porous medium in which the capillary fringe is taken account of is analyzed and solved numerically. In particular two different numerical methods are applied. With the first method by means of a suitable transformation the solution of the problem is equivalent to the search for the minimum of a quadratic functional on a fixed domain. The second method applies a classical idea and determines the free boundary by means of successive approximations. The results of the two methods are compared with each other and with those obtained by means of an analogous model and found to be in good agreement. The first method, which is a new one, is better justified on a theoretical level and moreover is more convenient with regard to the pro~amming effort and the execution time needed to carry it out on a computer.

Brain Research, 1984

Different steps of the metabolism of thiamine (T), thiamine mono-(TMP), pyro-(TPP) and triphospha... more Different steps of the metabolism of thiamine (T), thiamine mono-(TMP), pyro-(TPP) and triphosphate ('Iq'P) in the cerebellum, brainstem, cerebral cortex and the sciatic nerve were evaluated in the rat in vivo. The radioactivity of T and its phosphoesters was determined at fixed time intervals (0.5-240 h) after an intraperitoneal injection of [14C]T (30/.tg: 1.25 ~Ci), under steady state conditions. The dynamics of thiamine compounds was evaluated using a compartmental mathematical model that allowed the fractional rate constants (FRC), turnover rates (TR) and turnover times to be calculated. The phosphorylation of T to TPP and the dephosphorylations of TPP to TMP and TMP to T could be estimated in all the structures investigated. Their turnover rates were found to be ordered in the sequence: cerebellum > brainstem > cerebral cortex > sciatic nerve. The transphosphorylation of TPP to TTP was so small that it could not be determined in a reliable way. Regional differences were found both in the rate and in the composition of T and TMP mixture released from nervous structures. The shortest turnover time of TPP was found in the cerebellum, while the sciatic nerve exhibited the fastest renewal of T and TMP. In all the structures investigated TPP had a rather short turnover time, suggesting that its function might be associated to a rapid conversion into chemically different forms. The possible relationships between the rates of turnover of T compounds are the sensitivity of the nervous structures to T deficiency are discussed.

We describe here a possible approach to the formation of choice in a society by methods borrowed ... more We describe here a possible approach to the formation of choice in a society by methods borrowed from the kinetic theory of rarefied gases. It is shown that the evolution of the continuous density of opinions obeys a linear Boltzmann equation where the background density represents the fixed distribution of possible choices. The binary interactions between individuals are in general non-local, and take into account both the compromise propensity and the self-thinking. In particular regimes, the linear Boltzmann equation is well described by a Fokker-Planck type equation, for which in some cases the steady states (distribution of choices) can be obtained in analytical form. This Fokker-Planck type equation generalizes analogous one obtained by mean field approximation of the voter model in [27]. Numerical examples illustrate the influence of different model parameters in the description both of the shape of the distribution of choices, and in its mean value.

Applied Numerical Mathematics, 2000

We describe an adaptive algorithm for solving one-dimensional system of nonlinear partial differe... more We describe an adaptive algorithm for solving one-dimensional system of nonlinear partial differential equations. Different strategies are considered for the discretization in time while a multiscale collocation method is applied for the discretization in space. In particular we look at the so called Rothe method which is based on first time then space discretization. Numerical experiments are presented for a