Search

Mathematical models based on partial differential equations (PDEs) can be exploited to handle clinical data with space/time dimensions, e.g. tumor growth challenged by neoadjuvant therapy. A model based on simplified assessment of tumor malignancy and pharmacodynamics efficiency was exercised to discover new metrics of patient prognosis in the OLTRE trial. We tested in a 17-patients cohort affected by early-stage triple negative breast cancer (TNBC) treated with 3 weeks of olaparib, the capability of a PDEs-based reactive–diffusive model of tumor growth to efficiently predict the response to olaparib in terms of SUVmax detected at 18FDG-PET/CT scan, by using specific terms to characterize tumor diffusion and proliferation. Computations were performed with COMSOL Multiphysics. Driving parameters governing the mathematical model were selected with Pearson's correlations. Discrepancies between actual and computed SUVmax values were assessed with Student's t test and Wilcoxon rank sum test. The correlation between post-olaparib true and computed SUVmax was assessed with Pearson's r and Spearman's rho. After defining the proper mathematical assumptions, the nominal drug efficiency (εPD) and tumor malignancy (rc) were computationally evaluated. The former parameter reflected the activity of olaparib on the tumor, while the latter represented the growth rate of metabolic activity as detected by SUVmax. εPD was found to be directly dependent on basal tumor-infiltrating lymphocytes (TILs) and Ki67% and was detectable through proper linear regression functions according to TILs values, while rc was represented by the baseline Ki67-to-TILs ratio. Predicted post-olaparib SUV*max did not significantly differ from original post-olaparib SUVmax in the overall, gBRCA-mutant and gBRCA-wild-type subpopulations (p > 0.05 in all cases), showing strong positive correlation (r = 0.9 and rho = 0.9, p < 0.0001 both). A model of simplified tumor dynamics was exercised to effectively produce an upfront prediction of efficacy of 3-week neoadjuvant olaparib in terms of SUVmax. Prospective evaluation in independent cohorts and correlation of these outcomes with more recognized efficacy endpoints is now warranted for model confirmation and tailoring of escalated/de-escalated therapeutic strategies for early-TNBC patients. [ABSTRACT FROM AUTHOR]

This paper highlights the potential of Sargassum algae, recovered from raw beach seaweed wastes, as a valid source of valuable sodium alginate. Alginate is a biodegradable, highly attractive polysaccharide widely used in food, pharmaceuticals, and biomedicine applications. The aim of this work is to employ a new eco-sustainable and cost-effective extractive method to obtain alginate as a raw material from pollutant organic Sargassum seaweeds. Algae were exposed to microwave pre-treatment under static and dynamic conditions, and three different extractive protocols were followed: (a) conventional, (b) hot water and (c) alkaline method. All samples were characterized by GPC, SEM, FTIR/ATR and TGA. It was found that alginate's best performances were obtained by the microwave dynamic pre-treatment method followed by alkaline extractive protocol. Nevertheless, the microwave pre-treatment of algae allowed the easiest breaking of their cell walls and the following fast releasing of sodium alginate. The authors demonstrated that microwave-enhanced extraction is an effective way to obtain sodium alginate from Sargassum-stranded seaweed waste materials in a cost-effective and eco-sustainable approach. They also assessed their applications as mulching films for agricultural applications. [ABSTRACT FROM AUTHOR]

Drying of bio-substrates such as food can be enhanced when exploiting a variety of simultaneous transport phenomena mechanisms, such as jet impingement and exposure to microwaves. To this end, a laboratory prototype has been exercised to infer on substrate quality departure. Among the various available operating conditions, there are some that address the preservation of color attributes. As an example, emphasis to pulsed exposure to microwaves would result in less spoiled substrates, while colder air would not necessarily lead to optimal processing, and higher flow rates would increase oxidation and color degradation. [ABSTRACT FROM AUTHOR]

A mathematical model predicting Escherichia coli O157:H7 behavior was developed, depending on the applied thermal regimes, using a whole iceberg lettuce as a structured model food. The 3-D, transient model is based on energy and biomass conservation complemented by primary and secondary predictive notations, allowing one to virtualize the combined effect of bacterial growth and migration, under any possible handling and storage conditions. Due to its flexibility and applicability, the model is a suitable tool to virtualize the bacterial contamination in fresh produce, from postharvest to consumer. Realistic cases such as external contamination or pathogen internalization are examined, following model validation. The complex combination of bacterial penetration and population level, for example, is highlighted which depends nonlinearly on bacterial diffusivity and operating temperature. While it is shown that, with variable thermal regimes, the total contamination level is practically equivalent if the cumulative thermal exposures are the same. The proposed procedure can be also applied to other food/microorganism pairs, provided that general data on microbial generation and diffusion are available. [ABSTRACT FROM AUTHOR]

Coupled transfer mechanisms are common in a variety of industrial operations, as in food drying, and their virtualization is becoming indispensable. In this paper one such situation, a rectangular food chunk exposed to heat and mass transfer by a turbulent cross flow of air in a channel (Re ≃ 1·10 4 ), is investigated by modeling the transfer mechanisms (linked each other by evaporation) in conjunction with the inherent flow transport. This formulation is referred to as a conjugate problem. In the present model, the most limiting parameters that commonly are employed in such studies can be disregarded, i.e. the empirical heat and mass transfer coefficients at the auxiliary air/substrate interface: they refer to unrealistical average conditions and unspecified geometry variations. After proper literature evaluation, the solution of a benchmark drying problem is discussed by assessing the conjugate and coupled features of the analytical development, focusing on some transfer phenomena loci on the sample's exposed surface. It is shown that, in case of a finite protrusion with a unitary form factor (height equals streamwise thickness) the average Nusselt number of about 25 (resumed from associated literature) greatly overestimates the one computed based on the model, everywhere along the exposed surface and during process time: varying up to 6 times along the lateral edges and dropping down to an average value of about 6 after less than 2 h of treatment. [ABSTRACT FROM AUTHOR]

This paper is the second of set of two dealing with exposure of moist substrates to electromagnetic energy, while providing localized convection heat and mass transfer. Solution of the comprehensive model lead to the electric distribution in the cavity–substrate ensemble, the velocity distribution in the cavity and around the substrate, and the temperature and residual moisture distributions in the substrate. The model has been successfully validated against the available experimental values, with few temperature degrees of difference, only. It was found that the dielectric loss which dictates the local energy absorption depends inversely on the local temperature, for the devised treatments. For the two extremal treatments, the volume-averaged moisture varies by some 20% only, but in one case hot spots up to 1000 K were induced at the surface, otherwise jet impingement with Reynolds number of 32k allowed to cool off the surface to as low as 300 K. [ABSTRACT FROM AUTHOR]

This paper is the first of set of two dealing with a multidimensional, multiphase and multiphysics model of conjugate and coupled transport phenomena during electromagnetic treatments to moist substrates. Exposure to electromagnetic energy can be controlled and optimized by providing localized convection heat and mass transfer. The model features the stationary Maxwell’s equation, coupled to the transient equations of heat conduction and mass diffusion. Moreover, the stationary Navier–Stokes equations are devised, in conjunction with the energy and mass convective equations, as the dependence on the localized heat and mass convection is accounted for. Energy and vapor transport are applied regardless of the substrate interface, to exploit the advantages of a conjugate formulation. An optimized kinetic formulation is employed to deal with water phase change. Due to the complex interdependence of the various transport phenomena, a computational strategy is set up to solve the model, by means of a finite element code which is run in a cycle of 2 consecutive sweeps, depending on the assumption of the dielectric properties of the substrate. Grid independence tests gave acceptable results for more than 0.5 M elements and more than 5 M degrees of freedom. This paper sets the grounds for the presentation of selected results, reported in Part II. [ABSTRACT FROM AUTHOR]

Abstract: Biosubstrates drying can be intensified, controlled and optimized, even in blunt shapes, by providing exposure to air jet impingement. In this paper round air jet impingement on cylinder protrusions of a model substrate is investigated, for moderate Reynolds numbers and various geometry arrangements. A comprehensive numerical model, featuring conjugate interface transport (local fluid dynamic effects), multiphase coupling (local surface evaporation) and moisture diffusion notations, is first validated with the corresponding experimental results. Then quantitative distributions of temperature and moisture within the protrusion and along its exposed surface are presented, focussing on the dependence of surface heat and mass transfer on geometry arrangement and fluid dynamic regime. Two values of Reynolds number, two jet heights and two protrusion/jet diameter ratio combinations are investigated. It is pointed out that, within the investigated range of variables, a protrusion/jet diameter ratio equal to 1 allows for flow patterns that foster process enhancement, but at the expenses of treatment uniformity: after 15min of treatment the 10% of protrusion only is still relatively moist, but with a strong internal non-uniformity, whereas with a protrusion/jet diameter ratio equal to 3 the untreated part accounts to the 85%, with a smoother internal distribution. [Copyright &y& Elsevier]

Highlights: [•] Thermostatic sonication of a pectin-containing fluid flow was modeled by CFD. [•] Fluid thickening is inferred upon the motion pattern. [•] Viscosity depends on geometry and two Rayleigh numbers. [•] This tool can be applied to model fluids with tailored functional properties. [ABSTRACT FROM AUTHOR]

Abstract: Mass transfer and related shelf life assessment is an important issue in the beverage industry. Product change due to mass transfer is at stake and, with it, its consumer value and consideration. Carbonation loss takes place at the product/package interface, and to the environment through the package itself. In this paper a joint experimental/computational approach has been exploited: the loss through the polyethylene terephthalate barrier has been computed by means of a multidimensional finite element code, while actual measurements have been carried out to validate the computations. Residual carbonation histories are validated and presented for a variety of thermal regimes and for two different bottles carrying the same capacity. The paper highlights on the combination of bottle weight, initial carbonation and storage temperature, indicating the operational set for the longest shelf life within the explored cases. Lighter bottles can be used with no inference on shelf life, while the carbonic loss depends non-linearly on initial carbonation and temperature increment. The associated concentration maps help infer on the importance of polyethylene terephthalate thickness uniformity. It is then demonstrated that the model carries the flexibility of a general tool, applicable to any carbonated beverage at any storage condition. [Copyright &y& Elsevier]

Abstract: The combination of microwaves exposure with the classical convection heating is seen as a practical solution to improve the uniformity and control of pure microwave heating of moist porous substrates. In the present paper, the complex coupling of electromagnetic exposure and enhanced fluid flow and heat transfer is explored, with an emphasis on the competition of such different mechanisms. To this end, some simple experimental techniques have been adopted to determine the thermal response of a common biological substrate in a microwave/jet-impingement oven prototype (1kW of nominal power), allowing for the local characterization of its electromagnetic and fluid dynamic behavior. A rational approach is proposed by presenting a number of descriptors to help identify the interrelationships for all phenomena at stake, including the total process time (up to 1min), the jet temperature (in the 60–100°C range) and Reynolds number (in the 8000–15000 range). Therefore the effects of microwave exposure and relaxation times, working air velocity and temperature on the substrate''s local temperature rise, are reported and discussed. Even in the explored range of microwave and jet thermization potentials investigated herein, different substrate portions experienced different temperature rises. The proposed configuration and analysis can be used to exercise due control of material conditioning and treatment in a combined microwave/forced convection framework. [Copyright &y& Elsevier]

Abstract: Jet impingement can be successfully and efficiently employed in drying or dehydration of moist substrates, like food slices or plates, among other applications. With this intensification technique, a great deal of the available water is removed by applying heat under controlled conditions, but excessive or nonuniform local drying may cause local deterioration (i.e. in case of foods, the eating quality, the nutritional value, the mechanical consistence and so forth). In this paper the thermal, water activity and moisture depletion histories have been measured in a food substrate, due to localized heating by a turbulent air jet impingement, to infer on the inherent driving forces and transport phenomena. It is evident that strong non-uniformity may exist in the substrate so that a local analysis as the reported one is necessary to help reach optimal processing. [ABSTRACT FROM AUTHOR]

Abstract: Fluid food products, in the agri-food industry, are commonly subject to thermal treatments to ensure their safety and quality characteristics. Therefore, these treatments must be accurately selected and monitored to avoid over-processing, as consumer safety and product acceptability must be preserved. In this work, thermal processing is predicted locally by modeling and visualizing selected bio-indicators (bacteria and vitamins). A sample sterilization of citrus juice is scrutinized through a multidimensional numerical analysis for fluid flow, heat transfer and bio-indicator kinetics and transport, by including proper biochemical evolutive notations. Direct steam injection is used as the thermal carrier, so complete two-phase notations are included. Good agreement has been reached, with the available experimental benchmark data. Process performance is evaluated by inferring on survived microbial and native vitamin patterns, and the relative importance of kinetics over macroscopic transport is discussed. [Copyright &y& Elsevier]

Abstract: Microwave treatment has been gaining increasing recognitions in the food industry and household frameworks alike. Better energy and finishing efficiencies can be obtained by adding an additional transport mechanism, such as forced air convection heating. In this work, transient distributions of temperature and moisture during the combined treatment is analyzed by a full computational fluid dynamics model, coupled with custom moisture diffusion and evaporation notations. Non-linear, interdependent transfer phenomena equations are discussed, and the multi-physics effects are emphasized. Realistic transfer exchanges are inherently considered by using a conjugate approach and no resort to empirical, averaged heat and mass transfer coefficients is made. A validation with the experimental results from the available literature has been brought forth, for potato disks drying by either pure convection, pure MW exposure or both mechanisms combined. The effect of process time and working air velocity on the local temperature distributions are finally presented. [Copyright &y& Elsevier]

Abstract: Thermal treatment of fluid foods represents a major unit operation in the food industry, to ensure the product''s safety and quality features. But during the thermal treatments of such sensible fluids in common plate heat exchangers, food constituents such as proteins can be thermally damaged and precipitated to form fouling that greatly affect the treatment efficiency and alter the product''s desired features. Computational Fluid Dynamics simulations can then be successfully exploited, bringing forth temperature and velocity information that yield for deposit distributions when coupled to biochemical notations for thermal denaturation of fluid constituents. The present work exploits such modeling for a single-channel heat exchanger during pasteurization of milk. The model enforces a conjugate system of differential equations to a heat exchanger''s corrugated plate to combine flow, heat transfer and local transport of β-lactoglobulin. A preliminary computation has been performed that could be applied to geometry optimization (different corrugation shape and orientation) and for a variety of biochemically evolutive products. [Copyright &y& Elsevier]

Mathematical modeling constitutes an emerging area of oncological research aiming to predict spatial and temporal evolution of tumors, by describing many different phenomena which occur at different scales. Among these, modeling at the macroscopic scale has a great potential of application, when diagnostic imaging evaluation is used to identify the metabolic tumor volume undergoing proliferation. With breast carcinoma one of the most common cancer occurrences, the personal involvement for the patient and the cost for the national health system vary considerably with the adopted treatment. When a neoadjuvant (volume reducing) drug therapy is a direct option, the choice of drug may dictate the physical burden and the surgical strategy for subsequent lumpectomy/mastectomy. This paper employs a mass transfer modeling approach in order to gain deeper insight into breast carcinoma proliferation and therapy at the tissue scale. The aim is to develop a predictive, quantitative method for each given patient. Model flexibility is demonstrated, to facilitate model replication for large patient cohorts. The proposed procedure may serve as a basis for a decision support system for surgeons and towards personalized treatment optimization of breast tumors. [ABSTRACT FROM AUTHOR]

Abstract: A model describing the heat and mass transfer involved in food drying is presented. The aim is to determine the effect of air temperature on the performance of the drying process applied to fresh-cut vegetable slices, but other effects can be easily incorporated in the model. The model allows to disregard one of the most limiting parameters in such modeling, i.e. the average heat and mass transfer coefficients at the food/drying substrate interface, which are generally taken from the literature. Such assumptions are limiting in the sense that they are referred to average transfer conditions and general geometries. The presented model relies upon a finite-element solution of time-dependent differential equations for simultaneous and conjugate heat and moisture transfer in a two-dimensional domain, without any inference in such empiricism. A special formulation for drying kinetic of the substrate is also exploited, and a treatment of the dependence of the properties upon the residual moisture content is included. After proper validation with the available experimental measurements, the numerical solution is discussed by presenting each involved field variables, emphasizing on the conjugate nature of the drying process. Due to its flexibility and generality, the model can be used in common industrial driers’ optimization, even in the assumption of a laminar flow field. [Copyright &y& Elsevier]

Abstract: Jet impingement is commonly used to attain high local heat exchange coefficients in several industrial frameworks. Both cooling and heating air jets can be used, where precise and rapid thermal control is required. This paper focuses on the air impingement cooling of cylindrical foods, the use of which has been devised and analyzed numerically during the initial stage of cooling/chilling operations. Results include the temperature distributions within the food and at its surface, as well as the associated flow field due to the jet–food interaction. Results have also been compared with available literature data and with classical heat transfer solutions. The local, time-dependent Nusselt number distribution in jet impingement cooling has been shown to be strongly dependent upon the conjugate effect, i.e. the heat transfer rate is altered by the conduction in the food, which is neglected in the associated studies available so far. Slowest Cooling Zones (SCZs) have also been found to lie off-center, depending upon the given thermal boundary conditions. The knowledge of transient temperature distributions within the processed food and related local heat transfer is important in cold treatment of foods, in order to achieve the desired system performance in the most efficient manner. [Copyright &y& Elsevier]

Simulation of tumor evolution at the macroscopic, tissue scale can be applied to cancer treatment optimization. This paper aims to gain deeper insight into the dynamics of tumor growth at this scale and to develop predictive, quantitative mathematical models which can be used as a decision tool supporting oncologists and surgeons. This preliminary model describes tumor progression as mass transfer governed by partial differential equations, incorporating a multi-species logistic growth/decay law to account for the production of necrosis and the interaction with therapy. The set of governing equations is integrated by a commercial platform of Finite Element Method. After a validation study with literature data on a hepatocellular carcinoma, a sensitivity analysis was conducted by including the driving source terms (growth rates, drug efficiency and its delivery/availability). Results suggest that, in the first two months of therapy, tumor volume progress is related nonlinearly so that a mere 10% of stronger/weaker cancer malignancy lead to doubling/halving the tumor volume, the increment of drug efficiency by 25% lead to a 60% decrease of the volume, while a smaller efficiency by 25% lead to a sudden run-away of the disease. Finally, the optimal administration pattern for chemoembolization was found with a 4-points therapy delivery on the same side with respect to the Region of Interest. [ABSTRACT FROM AUTHOR]

• Shape memory alloys are exploited to cast morphing appendices, to improve car's handling and fuel consumption rate. • A numerical simulation solving for thermo-fluid-structure interactions in turbulent air flow was implemented. • Variable space and a new dimensionless number were proposed for the thermally activated aerodynamics appendix. In the framework of vehicle aerodynamics, new integrated systems can be developed based on shape memory metal alloys (SMAs) capability to perform surface morphing. Such systems can be exploited to create appendices containing active composites that change shape in response to variable thermal inputs, in relation to the desired aerodynamic behavior. The purpose of these systems is to offer benefits in terms of vehicle's performance and fuel consumption rate. Even the design of the simplest geometry appendix, a finite horizontal plate aligned with a turbulent air flow, is nevertheless affected by three intertwined and nonlinear phenomena - namely the solid/fluid/thermal interactions. In order to approach the definition of appropriate design parameters, the space of operating variables must be explored by devising a numerical simulation encompassing the equation of structural motion and the energy and Reynolds Averaged Navier Stokes equations, complemented by a viable turbulence model. In this paper, a fully-coupled model encompassing all phenomena involved is tested by implementing a sensitivity analysis for a thermally activated morphing surface. Temperature, stress and velocity distributions are presented and discussed for a given geometry case. A new metrics leading to aerodynamic lift calculations is then proposed and demonstrated, that will simplify the preliminary design procedures. [ABSTRACT FROM AUTHOR]

New heating technologies are constantly being developed worldwide, specially the electrical ones that take advantage of renewable energy. In this paper, the Basic Cell of Energy Transference (BCET) is proposed as an innovative fluid heater, carrying a microwave-fed heat transfer plate for thermal contact. A fully-dimensional thermo-fluid analysis was implemented and validated to determine the key design parameters and operation features for heat transfer to temperature-sensitive working fluids. Circulation patterns were observed, when using certain fluids, in turn causing strong temperature non-uniformities. As fluid treatment in the heater relies on the thermal contact at its active plate, the model was used to ascertain the undesired excess/lack temperature range for quality/safety treatments, with reference to a final effective process temperature. Therefore, a geometry optimization by means of internal baffles was carried out which ensured variation to fluid pattern and more uniform active plate temperature. In a base case, the new design allowed to limit the uncontrolled temperature excess by almost 30%, while favouring the pressure drop reduction across the flow device by more than 10%. [ABSTRACT FROM AUTHOR]

Mathematical modeling constitutes an emerging area of oncological research aiming to predict spatial and temporal evolution of tumors, by describing many different phenomena, which occur at different scales. Among these, modeling at the macroscopic scale has an interesting potential of application, when applied in a framework where actual diagnostic imaging is used to identify the metabolic tumor volume undergoing proliferation. Diffuse large B-cell lymphoma (DLBCL) is a cancer of B cells, a type of lymphocyte that is responsible for producing antibodies. The most common form of Non-Hodgkin lymphoma among adults, DLBCL can arise in any part of the body and may play a very aggressive malignancy. This paper aims to enforce a mass transfer modeling approach in order to gain deeper insight into the dynamics of tumor growth at the tissue scale and to develop a predictive, quantitative method for each patient at hand. A cohort of 18 patients has been successfully enrolled to validate the model. Results confirm that tumor proliferation, at the macroscopic scale, scores many nonlinear features, and show that the proposed model could be used by oncologists as a decision support tool towards personalized treatment optimization of solid tumors. [ABSTRACT FROM AUTHOR]

Abstract: It is nowadays well known that heating, which is carried out to improve the hygienic, sensory and nutritional properties of foods, can be also responsible for the development of acrylamide. Acrylamide levels between a few ppb and in excess of 1000ppb have been found in many heated foods. As acrylamide is classified as a probable human carcinogen, the knowledge of critical processing variables leading to its formation is needed to ensure safety requirements. In this work, acrylamide formation during deep-frying of potato samples is analyzed in space and time through a joint HPLC-MS/MS measurement and a computational fluid dynamics simulation. Such an approach allowed to describe the thermal and physico-chemical history of processed potatoes to bring forth their complete and validated multidimensional distributions of acrylamide concentrations during deep-frying. The effect of a number of operational parameters have been scrutinized to make the simulation results closer to the industrial settings. [Copyright &y& Elsevier]