Encapsulamento de nanopartículas à base de óxido de ferro com sílica para aplicações biomédicas

Over last decades, a great attention has been devoted to iron oxide-based nanoparticles coated by dielectric organic or inorganic materials for the potential contributions in biomedical applications and microwave absorbers industry. The present Ph.D. study focuses on the fabrication of iron-based oxide nanoparticles and coating the particles within the silica matrix in the form of a core-shell structure exhibiting interesting magnetic and electrical properties for application in the biomedical and microwave technology areas. The combined study of electrical and magnetic properties of the silica-iron oxide composites allowed us to examine the requisites for application in a new generation of the high-efficient microwave absorbents and also for the possibility of hyperthermia and drug delivery agents. In this context, four synthesis methods: sol-gel route, laser floating zone (LFZ), auto-combustion, and Pechini method were employed to prepare the iron oxide-based/silica composites. Several studies, namely, structural, morphological, electrical and magnetic characterizations, were performed on the prepared samples. The utilization of several experimental characterizing techniques not only provide us a comprehensive knowledge of the physical properties of these materials but also look over the future employment of the prepared composites in the biomedical application and the microwave absorbing materials. It was prepared a series of glasses with the composition, xFe2O3-(100-x)SiO2 (x=1, 2, 10, 20 in mol%) by the sol-gel route. The effect of the heat treatment conditions and the Fe/Si ratio on the morphology, electrical and magnetic properties of the glass ceramics were investigated. Fibers with the composition of 10Fe2O3-90SiO2 were processed by LFZ technique. Their morphology, structure, magnetic properties and redox state were studied in function of the pulling rate. An exhautive study on the Raman spectroscopy and the local magnetic microstructure of the fibers were performed to support for a deeper understanding of the magnetic properties of the fibers. A series of manganese ferrite-silica nanocomposites with the composition xMnFe2O4-(100-x)SiO2 (x=100, 20, 15 and 10 in mol%) were prepared by the auto combustion method. The physical parameters obtained from this study showed the great potential of the silica-manganese ferrite nanocomposites for the proposed applications as well other suggested future works. In addition, a preliminary study on the synthesis by the Pechini method and characterization of iron oxide was carried out. The structure, the magnetic properties and the electric conduction mechanism of the prepared iron oxide polycrystallites were investigated leaving open other possible applications industries.Nas últimas décadas grande atenção tem sido dedicada ao estudo de nanopartículas à base de óxido de ferro revestidas por materiais dielétricos orgânicos ou inorgânicos com potencial para aplicações biomédicas e na indústria de absorventes de microondas. O presente trabalho de doutoramento centra-se na fabricação de nanopartículas de óxido de ferro e no seu revestimento com sílica na forma de uma estrutura núcleo-casca com o objectivo de obter propriedades magnéticas e elétricas interessantes para aplicações práticas na área biomédica e na indústria de microondas. O estudo combinado das propriedades elétricas e magnéticas dos compósitos de óxido de ferro-sílica permitiu estudar as características para aplicações em nova geração de absorventes de micro-ondas de alta eficiência e também agentes com possíveis utilizações em hipertermia e libertação de drogas. Neste contexto foram utilizados, quatro métodos de síntese: método de sol-gel, técnica fusão de zona flutuante com laser (LFZ), autocombustão e método de Pechini na preparação dos compósitos à base de óxido de ferro / sílica. Vários estudos como caracterização estrutural, morfológica, elétrica e magnética, foram realizados nas amostras preparadas. A utilização de várias técnicas de caracterização experimental fornece um conhecimento abrangente das propriedades físicas destes materiais e permite perspectivar o possível emprego destes compósitos para aplicações biomédicas e como materiais absorventes de micro-ondas no futuro. Foi preparada a série de vidros xFe2O3- (100-x) SiO2 (x = 1, 2, 10, 20 em mol%) pelo método de rota sol-gel. O efeito das condições de tratamento térmico e da relação Fe / Si na morfologia, propriedades elétricas e magnéticas das cerâmicas vítreas foi investigado. Fibras com a composição 10Fe2O3-90SiO2 foram processadas pela técnica de LFZ. A sua morfologia, estrutura, propriedades magnéticas e estado de redução foram estudadas em função da taxa de extração da preparação das amostras. Foi realizada uma análise exaustiva dos resultados da espectroscopia de Raman e uma pesquisa da microestrutura magnética local para melhor interpretar as características magnéticas das fibras. Uma série de nanocompósitos de silício-ferrite de manganês com a composição xMnFe2O4- (100-x) SiO2 (x = 100, 20, 15 e 10 em % molar) foi preparada pelo método de auto-combustão. Foi realizada investigação das propriedades estruturais, morfológicas, elétricas e magnéticas destas amostras. Os parâmetros físicos obtidos a partir desse estudo mostraram o grande potencial dos nanocompósitos de silício-ferrita de manganês para as aplicações propostas assim como para o trabalho futuro sugerido. Além disso, também foi realizado um estudo preliminar sobre a síntese e caracterização do óxido de ferro pelo método de Pechini.A estrutura, as propriedades magnéticas, o mecanismo de condução elétrica das policristalitas de óxido de ferro preparados foram realizadas deixando em aberto outras possíveis aplicações industriais.Programa Doutoral em Engenharia Físic

Circuit modelling by difference equation: Pedagogical advantages and perspectives

Circuit theory is a cornerstone course in electrical engineering and control majors in ordinary universities and colleges throughout the world. This course covers fundamental principles and analysis methods of basic circuits commonly employed in the forthcoming courses. In most electrical programs after the introduction of basic elements of Ohm's and Kirchhoff's current and voltage laws, the dynamic response of the circuits containing capacitors and inductors will be studied. Customarily to solve these circuits, advanced mathematical approaches such as differential equations are used. Under such circumstances, the students are faced with two challenges, solving the differential equations, and understanding the dynamic response of circuits. In order to improve students' understanding, an analysis tool with less mathematical prerequisites should be used for the solutions before embarking on the use of conventional differential equation techniques such as Laplace transform. Hence, we propose a novel approach for these circuit analyses through the application of a discretized version of differential equations which is used in discrete control systems. Although this approach has a well-established background, its exploration uses in the circuit theory course as yet has not been reported. The novelty of the proposed approach not only lies in its intuitive simplicity but also in its contribution to the understanding and visualization of students in the real-time response of linear and non-linear circuits to any desirable input without any mathematical burden. The analysis can be performed by hand or this is also helpful for those who prefer modern education aided by computers. This, in turn, may attract more students to the program. In this paper, the effectiveness of the proposed approach is demonstrated through a set of illustrative examples

The Role of Parental Love in the Mental Health of Children from the Perspective of the Qur’an and Hadith

Parental affection for children is a natural and necessary thing and its role in the mental health of the child is not less than meeting basic needs. Considering the importance of this issue in religious teachings and its great impact from different dimensions on the mental health of children, the purpose of this study is to explain the role of parental love in children's mental health through a descriptive-analytical method and using the Qur’anic verses and hadiths from reliable sources. Through this research, it has been proven that the parental love from the perspective of the Qur’an and Hadith causes motivation, the promotion of moral virtues, socialization, hope, etc. in children and is very effective in their mental health, providing healthy families and consequently leading to a healthy society

Demulsification capabilities of a Microbacterium species for breaking water-in-crude oil emulsions

A bacterium strain belonging to Microbacterium sp., isolated from oily sludge samples of Siri Island in the south of Iran, produced a strong, thermo stable microbial demulsifier (Yx/s=0.663, Yp/s=0.204, productivity=0.185 g L-1 h-1) on glucose as a sole carbon source supplemented with yeast extract. The optimum values of temperature, inoculum concentration, pH and culture age for microbial demulsifier production were 25°C, 108 CFU mL-1, 7 and 24 h, respectively. The maximum demulsification activity and the half-life value (t1/2) of culture broth measured for a water-in-crude oil (W/CO) emulsion were 96.4% and 36 h at 80°C in flask. The demulsifier was purified to homogeneity using cold ethanol. For 4.33 mg mL-1 of partially purified microbial demulsifier, the half-life value for the W/CO model emulsion was 3 h.Keywords: Biopolymer, demulsification, Microbacterium, demulsifier, petroleum emulsion, water-in-crude oilAfrican Journal of Biotechnology Vol. 12(16), pp. 2019-202

Synthesis and characterization of core-shell Fe3O4-gold-chitosan nanostructure

<p>Abstract</p> <p>Background</p> <p>Fe₃O₄-gold-chitosan core-shell nanostructure can be used in biotechnological and biomedical applications such as magnetic bioseparation, water and wastewater treatment, biodetection and bioimaging, drug delivery, and cancer treatment.</p> <p>Results</p> <p>Magnetite nanoparticles with an average size of 9.8 nm in diameter were synthesized using the chemical co-precipitation method. A gold-coated Fe₃O₄monotonous core-shell nanostructure was produced with an average size of 15 nm in diameter by glucose reduction of Au³⁺which is then stabilized with a chitosan cross linked by formaldehyde. The results of analyses with X-ray diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) indicated that the nanoparticles were regularly shaped, and agglomerate-free, with a narrow size distribution.</p> <p>Conclusions</p> <p>A rapid, mild method for synthesizing Fe₃O₄-gold nanoparticles using chitosan was investigated. A magnetic core-shell-chitosan nanocomposite, including both the supermagnetic properties of iron oxide and the optical characteristics of colloidal gold nanoparticles, was synthesized.</p

Critical Ignition Conditions of Structural Materials by Cylindrical Firebrands

Smoldering firebrands (embers) are a major cause of ignition and eventual structural damage during wildfires at the wildland-urban interface (WUI). These small pieces of wood can loft several kilometers ahead of the main flame front and ignitespot fires directly on structural elements such as decks. In this research, dense structural materials such as wood and engineered wood will be studied with a focus on capturing the critical thermal conditions necessary for ignition. Unique to this study will be a configuration where whole piles of firebrands are placed on the recipient material, emulating observations from WUI fires. In order to design appropriate fire safety standards at the WUI and, someday, to model the propagation of these fires, the conditions leading to ignition of common WUI materials by piles of lofted firebrands must be quantified. Firebrands were modeled using small cylindrical wooden dowels which were ignited and placed in a small-scale wind tunnel. Two tests were performed for each loading condition of firebrands, one studying ignition of wooden structural elements such as decking and marine-grade plywood and another measuring temperatures and heat fluxes over an inert piece of ceramic insulation. A single-point water-cooled heat flux gauge was used for time-resolved measurements of heat flux at the center of the inert setup surrounded by thin-skin calorimeters and K-type thermocouples which allowed for a spatial characterization of heating. The wind speed was the main quantity of interest changed during the test to determine the effects of wind speed on the heat flux released from the glowing dowels to recipient fuels. The results showed a drastic increase in heating from piles of firebrands vs. individual brands. The piles also produced higher heat fluxes under increasing winds. This is due, for the most part, to higher surface temperatures resulting from increased surface oxidation under higher wind speeds. Both smoldering and flaming ignition of wood was found to be similarly dependent on wind speed. Larger piles also produced higher peak heat fluxes at the center of the pile, highlighting the role of re-radiation within the pile influencing heat fluxes to recipient fuels. Critical heat flux and firebrand loading conditions required to achieve smoldering and flaming ignition of structural materialsused in the WUI are determined by comparing tests with inert and flammable fuels. These critical conditions can be used to model the propagation of WUI fires over structural elements to design appropriate fire safety standards at the WUI. A non-dimensional relationship incorporating fuel type, geometry, and ambient conditions is also proposed to describe the results

Robust Control Design for Laser Cavity Squeezing in Quantum Optical Systems

Quantum control theory is a rapidly evolving research field, which has developed over the last three decades. Quantum optics has practical importance in quantum technology and provides a promising means of implementing quantum information and computing device. In quantum control, it is difficult to acquire information about quantum states without destroying them since microscopic quantum systems have many unique characteristics such as entanglement and coherence which do not occur in classical mechanical system. Therefore, the Lyapunov-based control methodology is used to first construct an artificial closed-loop controller and then an open-loop law is derived by simulation of the artificial closed-loop system. This work considers the stabilization of laser cavity as the main integral part of quantum optical systems through squeezing the output beam of the cavity. As a comprehensive example of this type of system, quantum optomechanical sensors are investigated. To this end, a nonlinear model of quantum optomechanical sensors is first extended incorporating various noises. Then, linear quadratic Gaussian (LQG) control method is used to tackle the problem of mode-squeezing in optomechanical sensors. Coherent feedback quantum control is synthesized by incorporating both shot noise and back-action noise to attenuate the output noise well below the shot noise level (Two waves are said to be coherent if they have a constant relative phase). In the second phase of this work, due to entanglement of the system with critical uncertainties and technical limitations such as laser noise and detector imprecision, robust H [infinity] method is employed for the robust stabilization and robust performance of the system in practice. In H [infinity] methods, a control designer expresses the control problem as a mathematical optimization problem and then finds the controller that solves this. The effectiveness of the proposed control strategy in squeezing the cavity output beam is demonstrated by simulation

Determine the relationship between resistin levels and Metabolic Syndrome components

Background and aims: Metabolic Syndrome is a collection of risk factors which increase the risk of cardiovascular disease and type II Diabetes. The aim of this study was to determine the relationship between resistin levels and Metabolic Syndrome components. Methods: This case control study was conducted on a subgroup of patients referred to the clinic of Isfahan Cardiovascular Research Center. Serum sample from 76 person (38 healthy individuals and 38 patients with metabolic syndrome) were analyzed by Eliza for resistin enzyme-linked immunosorbent assay. Association between serum resistin and levels of triglycerides(TG), total cholesterol (TC), LDL-C, HDL-C, fasting blood sugar (FBS), waist circumference, body mass index and systolic and diastolic blood pressure was determined. Results: Serum levels of total cholesterol, triglycerides, fasting blood sugar and LDL cholesterol was significantly(P0.05). Conclusion: Serum resistin levels are higher in people with metabolic syndrome than in healthy individuals end can be considered for the early detection and severity of this syndrome in the future

An artificial neural network approach for revealing market competitors' behavior

For an electricity market player, obtaining a holistic viewpoint from the behavior of competitors is essential to determine its optimal bidding strategy. This paper proposes a novel approach for modeling and revealing the competitor's behavior from perspective of an intended player (IP). To this end, from perspective of IP, we define an Equivalent Rival (ER) whose behavior in the electricity market reflects the aggregation of behaviors of all individual competitors. It is assumed that IP and its ER participate in an equivalent market which its outcomes are approximately equal to those of the real market. The revealing procedure is designed as a two-stage Artificial Neural Network-based approach to estimate and predict the bids of ER after each run of the real market. Predicted bids of ER are used for the bidding strategy of IP. The proposed approach has been examined on two different case studies. In the first case study the aggregate supply curve of a market with 12 players has been obtained using the proposed approach and the result has been compared with a Bayesian inference approach. In the second case study a six-player electricity market is considered. The competitors' behavior has been revealed from perspective of an intended player using proposed approach and an optimal bidding strategy based on the proposed approach has been constructed. The results have been compared with those of a fuzzy Q-learning based optimal bidding strategy. The superiority of the proposed method in both case studies has been shown.fi=vertaisarvioitu|en=peerReviewed