MP Modeling of Glucose-Insulin Interactions in the Intravenous Glucose Tolerance Test

The Intra Venous Glucose Tolerance Test (IVGTT) is an experimental pro- cedure in which a challenge bolus of glucose is administered intra-venously and plasma glucose and insulin concentrations are then frequently sampled. An open problem is to construct a model representing simultaneously the entire control system. In the last three decades, several models appeared in the literature. One of the mostly used one is known as the minimal model, which has been challenged by the dynamical model. However, both the models have not escape from criticisms and drawbacks. In this paper we apply Metabolic P systems theory for developing new physiologically based models of the glucose-insulin system which can be applied to the Intra Venous Glucose Tolerance Test. We considered ten data-sets obtained from literature and for each of them we found an MP model which ts the data and explains the regulations of the dynamics. Finally, further analysis are planned in order to de ne common patterns which explain, in general, the action of the glucose-insulin control system

Linking Bistable Dynamics to Metabolic P Systems

Bistability, or more generally multistability, is an important recurring theme in biological systems. In particular, the discovery of bistability in signal pathways of genetic networks, prompts strong interest in understanding both the design and function of these networks. Therefore, modelling these systems is crucial to understand their behaviors, and also to analyze and identify characteristics that would otherwise be di cult to realize. Although di erent classes of models have been used to study bistable dynamics, there is a lag in the development of models for bistable systems starting from experimental data. This is due to the lack of detailed knowledge of biochemical reactions and kinetic rates. In this work, we propose a procedure to develop, starting from observed dynamics, Metabolic P models for multistable processes. As a case study, a mathematical model of the Schl ogel's dynamics, which represents an example of a chemical reaction system that exhibits bistability, is inferred starting from observed stochastic bistable dynamics. Since, recent experiments indicate that noise plays an important role in the switching of bistable systems, the success of this work suggests that this approach is a very promising one for studying dynamics and role of noise in biological systems, such as, for example, genetic regulatory networks

Experimental estimation of local heat-transfer coefficient in coiled tubes with corrugated wall

The present paper presents the application of an inverse analysis approach to experimental infrared temperature data with the aim of estimating the local convective heat transfer coefficient for forced convection flow in coiled pipe having corrugated wall. The estimation procedure here adopted is based on the solution of the inverse heat conduction problem within the wall domain by adopting the temperature distribution on the external coil wall as input data of the inverse problem: the unwanted noise in filtered out from the infrared temperature maps in order to make feasible the direct calculation of its Laplacian, embedded in the formulation of the inverse heat conduction problem in which the convective heat transfer coefficient is regarded to be unknown. Preliminary results are presented and discussed

Infrared measurements of fluid temperature in a polymeric Pulsating Heat Pipe

Pulsating heat pipes are two-phase passive heat transfer devices partially filled with a working fluid in saturation conditions. During operation, supplying heat to one end of the system (named evaporator) results in a local increase in temperature and pressure, which drives the fluid through a transport section (named adiabatic section) towards the cooled, opposite end (named condenser) for effective heat dissipation. The local thermo-fluid dynamic state of the working fluid is sometimes assessed by means of non-intrusive techniques, such as infrared thermography. In this case, the radiative properties of the systems in the infrared spectrum must be known a priori. Nevertheless, since pulsating heat pipes may be manufactured with different materials, wall thicknesses and channel geometries, the radiative properties of the walls and the confined flow are not always known or assessable by means of the available literature. Hence, the work proposes to design a straightforward calibration procedure for quantitative infrared fluid temperature measurements in a polymeric pulsating heat pipe charged with FC-72 and having unknown radiative properties. The emissivity and transmissivity of the walls and confined fluid are estimated with good accuracy. The results will allow repeatable and reliable fluid temperature measurements in future experimentations on the mentioned device

Transient free convection in open-ended vertical channels

Abstract. The aim of the present work is to investigate the heat transfer for laminar natural convection of a fully developed flow in a chimney consisting of two parallel vertical plates with open ends, occurring due to a sudden change in temperature of one of the plates. The momentum conservation equation was analytically solved by applying the Laplace transform technique and the Green’s function method, resulting in the evaluation of the velocity field with a very low computational effort. The proposed analytical solution was adopted to assess the effect of the Prandtl number on the fluid behaviour of the flow. The results revealed that the steady-state velocity distribution is reached when the Fourier number became comparable with the Prandtl number, except for low values of the Prandtl number

An analytical approach to the cooling of a flat plate

Abstract. The present work deals with the cooling of a flat plate having an initial non-homogeneous temperature distribution, which undergoes a sudden temperature drop at its surfaces. Hence, starting from an arbitrary steady-state temperature distribution, the two surfaces of the slab are suddenly cooled down to the value 0, resulting in a strong perturbation of the initial temperature distribution. A general analytical solution is provided by adopting the variable separation technique to the Fourier equation in transient conditions, thus obtaining a general solution in terms of a very fast converging series, which includes a definite integral of the initial steady-state distribution. Common engineering applications are investigated and the related results, obtained thanks to an extremely low computational effort, are presented and discussed

MP Modelling of Glucose-Insulin Interactions in the Intravenous Glucose Tolerance Test

The Intravenous Glucose Tolerance Test is an experimental procedure used to study the glucose-insulin en- docrine regulatory system. An open problem is to construct a model representing simultaneously the entire regulative mechanism. In the past three decades, several models have appeared, but they have not escaped criticisms and drawbacks. In this paper, the authors apply the Metabolic P systems theory for developing new physiologically based models of the glucose-insulin system, which can be applied to the IVGTT. Ten data- sets obtained from literature were considered and an MP model was found for each, which fits the data and explains the regulations of the dynamics. Finally, each model is analysed to define a common pattern which explains, in general, the action of the glucose-insulin control system

Experimental investigation on the convective heat transfer enhancement for highly viscous fluids in helical coiled corrugated tubes

Abstract. In the present analysis, the forced convective heat transfer in smooth and corrugated helical coiled tubes was experimentally studied in the Reynolds and Dean number ranges 50÷1200 and 12÷295 respectively, by adopting Ethylene Glycol as working fluid. The primary aim of the investigation is to study the combined effect of the wall curvature and of the wall corrugation in the thermal entrance region for highly viscous fluids. Two coiled tubes with a curvature ratio of about 0.06, one with smooth wall and the other with spirally corrugated wall, were investigated under the uniform heat flux boundary condition. The main conclusion is that in the Reynolds number range analyzed, both curvature and corrugation enhance the heat transfer. For Dean number values lower than about 120 the wall curvature effect prevails, and the heat transfer enhancement reflects Nusselt numbers that are approximately 2-3 times higher than the straight smooth section. For greater Dean number values, the wall corrugation instead prevails. In fact the corrugated coiled tube reaches Nusselt number values which are up to 8 times higher than the ones expected for the smooth straight tube. The smooth coiled tube shows instead thermal performances at maximum 3.6 times over the straight section

NONINTRUSIVE DETERMINATION OF LOCAL HEAT TRANSFER COEFFICIENT IN PIPES UNDER THE INVERSE HEAT CONDUCTION PROBLEM APPROACH

Most of passive techniques for heat transfer enhancement (e.g. rough surfaces, swirl-flow devices and coiled tubes) origins an irregular distribution of the heat transfer coefficient at the fluid wall-interface along the wall perimeter. This irregular distribution could be critical in some industrial applications but most of the available research papers presents the results only in terms of Nusselt number averaged along the wall circumference, due to the practical difficulty of locally measuring heat flux on internal wall surface of a pipe. Placing probes in a pipe is usually unfeasible because of the perturbation effects of the probes on the observed phenomenon, the geometric inaccessibility of the surface, or because of the fluid in the pipe that may destroy the sensors. The application of inverse heat conduction problem solution techniques overcomes these limitations because this approach enables to estimate the local convective heat transfer coefficient starting from the temperature distribution acquired on the external wall surface. In this work different estimation techniques were compared considering a particular problem of passive heat transfer enhancement: estimating the local convective heat transfer coefficient in coiled tubes. The comparison was performed both by synthetic and experimental data