Relevance of Dielectric Properties in Microwave Assisted Processes

Microwaves are electromagnetic radiation with wavelength ranging from 1 mm to 1 m in free space with a frequency from 300 GHz to 300 MHz, respectively. International agreements regulate the use of the different parts of the spectrum; the frequencies 915 MHz and 2.45 GHz are the most common among those dedicated to power applications for industrial, scientific and medical purposes (Metaxas & Meredith, 1983). Although microwaves have been firstly adopted for communications scope, an increasing attention to microwave heating applications has been gained since after World War II (Meredith, 1998; Chan & Reader, 2002). Reasons for this growing interest can be found in the peculiar mechanism for energy transfer: during microwave heating, energy is delivered directly to materials through molecular interactions with electromagnetic field via conversion of electrical field energy into thermal energy. This can allow unique benefits, such as high efficiency of energy conversion and shorter processing times, thus reductions in manufacturing costs thanks to energy saving. Moreover, other effects have been pointed out, such as the possibility to induce new structural properties to irradiated materials (development of new materials) and to apply novel strategies in chemical syntheses (green techniques). Crucial parameters in microwave heating are the dielectric properties of matter; they express the energy coupling of a material with electromagnetic microwave field and, thus, the heating feasibility (Metaxas & Meredith, 1983; Schubert & Regier 1995; Tang et al., 2002). On the bases of dielectric properties, microwave devices (applicators) can be adopted in heating operations and optimized working protocols can be used. This chapter is divided into four sections dealing with: i. fundamentals of microwave heating and relevance of dielectric properties of materials; ii. different techniques used in dielectric properties measurements of materials (test fixtures characteristics, technique applicability, advantages and disadvantages); iii. application of the open-ended coaxial-probe method in dielectric properties measurements of food, pharmaceutical ingredients, living materials, to understand specific heating phenomenology and, thus, to optimize thermal treatments / to define safety limits of exposition; iv. basics of heat and mass transfer modeling in microwave assisted processes

Image sequence inpainting: Towards numerical software for detection and removal of local missing data via motion estimation

AbstractFilm restoration aims to remove or reduce various types of film and video defects in order to provide visual enhancements of image sequences. The automatic treatment of these defects is a challenge. Restoration is still performed by hand even if by using numerical techniques for retouching. This is a very intensive activity and great improvements, both in quality and in speed, can be obtained by using automatic or semiautomatic software.This paper surveys the overall computational steps needed for the development of effective software tools to be actually used in a concrete application. In particular, here we focus on recovery and reconstruction of a particular local random defect of old black-and-white films, commonly referred to as “blotch”. We start from the characterization of the degradation model both for detecting and for restoring the defect and deal with such inverse and ill-posed problem through edge preserving regularization. We employ a spatio-temporal interpolation for blotch removal where the initial approximation is given by interpolating along the motion trajectory data belonging to adjacent frames. Finally, we describe the numerical algorithm and some experimental results

Molecular regulation of vascular endothelial growth factor expression in the retinal pigment epithelium

Purpose: Vascular endothelial growth factor (VEGF) plays an important role in homeostasis and diseases of the retinal pigment epithelium (RPE), choriocapillaris, and, most notably, age-related macular degeneration (AMD). Although much is known about VEGF regulation in pathologies, little is known about the control of VEGF expression under normal conditions. VEGF expression has been previously shown to be regulated in coordination with cell differentiation in the muscle and kidney. We therefore tested the hypothesis that VEGF in the adult RPE would similarly be regulated in conjunction with differentiation. Methods: A human retinal pigment epithelium cell line (ARPE-19), a line of immortalized human RPE cells, was used for all experiments. RPE cells were polarized in culture for 4 weeks on laminin-coated Transwells. Levels of VEGF mRNA and protein were determined with real-time PCR and enzyme-linked immunosorbent assay, respectively. VEGF-luciferase reporter constructs were used to identify regions of the VEGF promoter that control VEGF expression in the RPE. Microphthalmia-associated transcription factor (MITF)-Tfe transcription factors were blocked using either a pan MITF-Tfe dominant negative or specific small interfering RNA (siRNA). Results: VEGF mRNA and protein secretion increased over time in the RPE cells cultured on Transwells, with protein secretion occurring in a polarized fashion primarily toward the basolateral side. Overexpression of a dominant negative that targets the MITF-Tfe family resulted in a 50% reduction in VEGF expression. The role of the MITF-Tfe family in VEGF regulation in the RPE was corroborated in studies with the VEGF-luciferase reporter constructs, where deletion of the distal VEGF promoter region containing putative binding sites for the MITF-Tfe family resulted in a 50% reduction in VEGF promoter activity. siRNA knockdown of the MITF-Tfe family individually, and in combination, revealed that downregulation of Tfe3 resulted in reduced VEGF expression. Conclusions: Our results indicate that Tfe3, in conjunction with other MITF-Tfe members, regulates VEGF expression in the RPE and are consistent with the hypothesis that VEGF expression in RPE cells is regulated as part of their differentiation

Representations in matematics education: an onto-semiotic approach

Research in didactics of mathematics has shown the importance that representations have in teaching and learning processes as well as the complexity of factors related to them. Particularly, one of the central open questions that the use of representations poses is the nature and diversity of objects that carry out the role of representation and of the objects represented. The objective of this article is to show how the notion of semiotic function and mathematics ontology elaborated by the ontosemiotic approach of mathematics knowledge, enables us to face such a problem, by generalizing the notion of representation and by integrating different theoretical notions used to describe mathematics cognition

On Communication Protocols that Compute Almost Privately

A traditionally desired goal when designing auction mechanisms is incentive compatibility, i.e., ensuring that bidders fare best by truthfully reporting their preferences. A complementary goal, which has, thus far, received significantly less attention, is to preserve privacy, i.e., to ensure that bidders reveal no more information than necessary. We further investigate and generalize the approximate privacy model for two-party communication recently introduced by Feigenbaum et al.[8]. We explore the privacy properties of a natural class of communication protocols that we refer to as "dissection protocols". Dissection protocols include, among others, the bisection auction in [9,10] and the bisection protocol for the millionaires problem in [8]. Informally, in a dissection protocol the communicating parties are restricted to answering simple questions of the form "Is your input between the values \alpha and \beta (under a predefined order over the possible inputs)?". We prove that for a large class of functions, called tiling functions, which include the 2nd-price Vickrey auction, there always exists a dissection protocol that provides a constant average-case privacy approximation ratio for uniform or "almost uniform" probability distributions over inputs. To establish this result we present an interesting connection between the approximate privacy framework and basic concepts in computational geometry. We show that such a good privacy approximation ratio for tiling functions does not, in general, exist in the worst case. We also discuss extensions of the basic setup to more than two parties and to non-tiling functions, and provide calculations of privacy approximation ratios for two functions of interest.Comment: to appear in Theoretical Computer Science (series A

Controlled Release of Drugs fromMicroparticles Produced by Ultrasonic Assisted Atomization Based on Biocompatible Polymers

Microencapsulation of active molecules in biocompatible polymers is a matter of great interest in pharmaceutical sciences. Ultrasonic assisted atomization as a new technique to produce microencapsulated systems seems to offer several advantages (low level of mechanical stress in materials, reduced energy request, reduced apparatuses size) with respect to more conventional techniques. In this work, fine drug-loaded particles were produced by ionic reticulation of droplets obtained by ultrasonic atomization of biopolymers solutions. The particles were then characterized in terms of morphology and drug release kinetics. Data were used to estimate the PNMS (Polymeric Network Mesh-Size) with the aims of clarifying its role in controlled drug release, and analyzing its relationships with material and process parameters. For materials and operative conditions investigated, the calculated PNMS was found consistent with a fast release of drugs of small molecular size

Thermal and Acoustic Numerical Simulation of Foams for Constructions

Cellular foams are widely employed as insulation materials, both thermal and acoustic, often in competition with traditional fibrous insulation material, e.g., rock wool. As for the acoustic and thermal properties, several models have been developed to predict acoustic properties of poroelastic materials, but they are usually applied to fibrous layers or polyurethane foams, whereas their application to new materials like complex cellular foams has not been assessed due to the different cell microstructures. There is a very strong interest both in industrial and academic in developing novel insulation materials; accordingly, the possibility of ideally designing the cellular foam microstructure to achieve desired acoustic performances appears a highly attractive target. The paper will first discuss the state-of-the-art acoustic and thermal models and their application to cellular foam materials. Then a novel sustainable alginate-based foam material will be analyzed as a case study, by focusing the aspects related to their microstructure and acoustic properties. For the derivation of an acoustic model, the determination of the parameters of Johnson-Champoux-Allard (JCA) acoustic model (tortuosity, viscous characteristic length, thermal characteristic length, porosity, and flow resistivity) was performed using five different forecasting methods, including traditional analytical model for fibrous materials as well as inverse procedure