Magnetic nanoparticles in medicine: methods of determination of heat losses and biodistribution

Magnetna hipertermija je terapeutska metoda za tretiranje tumora. Zasniva se na osobini magnetnih nanočestica da generišu toplotu kada se nađu u promenljivom magnetnom polju. Ako se nalaze u tumorskom tkivu, toplota koju čestice oslobađaju podiže temperaturu tkiva iznad fiziološke vrednosti i izaziva umiranje tumorskih ćelija. Osnovni parametri koji moraju biti poznati pre primene nanočestica su njihova toplotna efikasnost i njihova raspodela po organizmu nakon ubrizgavanja – biodistribucija. Procedura za eksperimentalno određivanje toplote koju oslobode magnetne nanočestice još uvek nije standardizovana, zbog čega postoji problem pouzdanosti merenja. Glavni deo disertacije bavi se kalorimetrijskom metodom, gde se iz porasta temperature medijuma u kom se nalaze nanočestice određuje njihova toplotna efikasnost, kao i pratećim problemima ove metode. Na primeru nanočestica magnetita obloženih PEG surfaktantom pokazano je kako jednostavna teorija, poput Teorije linearnog odgovora, uz uvođenje relaksacionih vremena zavisnih od magnetnog polja može objasniti rezultate dobijene kalorimetrijskim merenjima. Deo disertacije je posvećen merenju dinamičkih histerezisa, kao komplementarnoj metodi merenja gubitaka, i razvoju magnetometra za generisanje promenljivog magnetnog polja u rasponu frekvencija od 50 do 300 kHz, amplitude polja do 0.03 T, sa pratećim detekcionim sistemom kojim se meri dinamički histerezis čestica u ovom polju. Poslednji deo disertacije bavi se određivanjem biodistribucije nanočestica u organima pomoću komplementarnih tehnika. U predloženoj metodi baziranoj na magnetnim merenjima koristi se činjenica da je odziv magnetnih nanočestica u promenljivom magnetnom polju mnogo veći u odnosu na odziv biogenog gvožđa prisutnog u organima.Magnetic hyperthermia is a therapeutic method for treatment of tumors. It is based on magnetic nanoparticles' ability to emit heat if subjected to external AC field. If injected in tumor tissue, the released heat can elevate the temperature of the tumor above critical threshold and cause dying of tumor cells. Two main parameters that must be determined prior to application of nanoparticles are their heat efficacy and distribution in the body. Measurement procedure for determination of released heat is not standardised, because of which the measurements aren't reliable. Large part of the dissertation is dedicated to underlying problems of calorimetry method, where the heat efficacy is determined from temperature change of the sample. The results of investigation on magnetite nanoparticles stabilised with PEG are presented and explained using Linear Response Theory with modified relaxation times. Part of the dissertation is dedicated to dynamic hysteresis measurements as a complementary method for determination of heat losses. Within this part the design and construction of magnetometer for generation of AC fields in the range of frequencies from 50 to 300 kHz and detection of sample's response was presented. The last part of dissertation covers problem of biodistribution determination by complementary techniques. The presented alternative method is based on the fact that magnetic nanoparticles in external magnetic field have significantly larger response than biogen iron present in tissues

Modern methods for design of conventional industrial controllers under constraints on robustness

Предмет истраживања је развој нових метода пројектовања конвенционалних управљачких структура пропорционално-интегрално- диференцијалног типа, са и без редно везаног стабилишућег компензатора. Предложене методе пројектовања су примјенљиве на широкoj класи индустријских процеса: стабилних, интегралних, нестабилних, процеса са временским кашњењем, затим процеса са неминималном фазом, процеса са дистрибуираним параметрима. Посебно су развијене аналитичке формуле подешавања параметара PID/PIDC регулатора за секундарну регулацију фреквенције и снаге размјене у оквиру конвенционалних електроенергетских система.Predmet istraživanja je razvoj novih metoda projektovanja konvencionalnih upravljačkih struktura proporcionalno-integralno- diferencijalnog tipa, sa i bez redno vezanog stabilišućeg kompenzatora. Predložene metode projektovanja su primjenljive na širokoj klasi industrijskih procesa: stabilnih, integralnih, nestabilnih, procesa sa vremenskim kašnjenjem, zatim procesa sa neminimalnom fazom, procesa sa distribuiranim parametrima. Posebno su razvijene analitičke formule podešavanja parametara PID/PIDC regulatora za sekundarnu regulaciju frekvencije i snage razmjene u okviru konvencionalnih elektroenergetskih sistema.The subject of the research is the development of new methods for designing conventional control structures of the proportional-integral-differential type, with and without a series-connected stabilizing compensator. The proposed design methods are applicable to a wide class of industrial processes: stable, integral, unstable, time-delayed processes, processes with non-minimum phase, processes with distributed parameters. Analytical formulas for adjusting the parameters of PID / PIDC controllers for secondary regulation of frequency and power interchange within conventional power systems have been specially developed

Modern methods for design of conventional industrial controllers under constraints on robustness

Предмет истраживања је развој нових метода пројектовања конвенционалних управљачких структура пропорционално-интегрално- диференцијалног типа, са и без редно везаног стабилишућег компензатора. Предложене методе пројектовања су примјенљиве на широкoj класи индустријских процеса: стабилних, интегралних, нестабилних, процеса са временским кашњењем, затим процеса са неминималном фазом, процеса са дистрибуираним параметрима. Посебно су развијене аналитичке формуле подешавања параметара PID/PIDC регулатора за секундарну регулацију фреквенције и снаге размјене у оквиру конвенционалних електроенергетских система.Predmet istraživanja je razvoj novih metoda projektovanja konvencionalnih upravljačkih struktura proporcionalno-integralno- diferencijalnog tipa, sa i bez redno vezanog stabilišućeg kompenzatora. Predložene metode projektovanja su primjenljive na širokoj klasi industrijskih procesa: stabilnih, integralnih, nestabilnih, procesa sa vremenskim kašnjenjem, zatim procesa sa neminimalnom fazom, procesa sa distribuiranim parametrima. Posebno su razvijene analitičke formule podešavanja parametara PID/PIDC regulatora za sekundarnu regulaciju frekvencije i snage razmjene u okviru konvencionalnih elektroenergetskih sistema.The subject of the research is the development of new methods for designing conventional control structures of the proportional-integral-differential type, with and without a series-connected stabilizing compensator. The proposed design methods are applicable to a wide class of industrial processes: stable, integral, unstable, time-delayed processes, processes with non-minimum phase, processes with distributed parameters. Analytical formulas for adjusting the parameters of PID / PIDC controllers for secondary regulation of frequency and power interchange within conventional power systems have been specially developed

ANALYSIS OF THE INFLUENCE OF DIFFERENT TYPES OF COATINGS ON INCREASING THE WORKING LIFE OF CONSTRUCTIONAL ELEMENTS OF THE VENTILATION MILL AND REDUCING THE WEAR OF WORKING SURFACES

Research presented in this paper analyzed the possibilities of increasing the wear resistance of the ventilation mill parts for coal grinding in power plants, analyzing with multidisciplinary research. The parts of ventilation mill are exposed in very complex working condition (high velocity of particles, presence of sand up 40% and other mineral components). Using the CFD 3D numerical simulation of multiphase flow in grinding mill, is analyzed the speed, concentration and flow angle of mixture around working parts. Analyzing the potential application of wear resistance coating on the working parts ventilation mill have goal to increase remaining working life of working elements. By analyzing the damaged parts of ventilation mill and using the numerical simulation around working elements, are selected wide pallet of wear resistance filer materials for experimental testing. To analyze possibilities to improve surface properties, the wear-resistant coatings were deposited by various technologies: manual metal arc welding, HVOF depositions and plasma welding and also are used filler materials with different chemical compositions. Samples structure is analyzed with SEM-EDS and also by measurement and distribution of hardness in the samples cross-sections. Verification of analyzed result is done by experimental testing, performing simulation of wear in ventilation mill on the samples in sandblasting machines chamber. Medium for simulating wear is quartz sand and the samples are positioned at angle 20 o. Application of this research can increase working life of parts in termoenergetic facilities, reduce the number of possible repairs and extends the period between them. This achieves significant economic effects

Compromised glutathione-dependent redox system of chronically-isolated rats: a harmfull side effect of clozapine

Changes in glutathione (GSH)-related systems are implicated in depressive disorders. Since chronic psychosocial stress contributes to depression, we investigated the effects of 21d of chronic social isolation (CSIS) stress, an animal model of depression, as well as chronic administration of clozapine, an atypical antipsychotic, on GSH content, glutathione peroxidase (GPx) and glutathione reductase (GLR) in the prefrontal cortex of rats. Increased GPx protein expression and its activity in clozapine-treated (controls or chronically-isolated) rats as well as in CSIS group were found. Nonetheless, clozapine administration caused decrease in GSH content but no effects on GLR in controls and CSIS group. Data indicate that CSIS compromises GSH-dependent redox system promoting oxidative stress in rat prefrontal cortex which can’t be protected by clozapine. Moreover, clozapine administration in controls has a harmful side effect on this redox system

Hydroxyapatite/iron oxide nanocomposite prepared by high energy ball milling

Nanocomposites (HAp/iron oxide), made of hydroxyapatite (HAp) and ferrimagnetic iron oxide, were synthesized by high-energy ball milling a mixture consisting of iron oxide nanoparticles and the starting materials used for the HAp synthesis: calcium hydrogen phosphate anhydrous (CaHPO4), and calcium hydroxide (Ca(OH)2). Two HAp/iron oxide samples with the magnetic phase content of 12 and 30 wt.% were prepared and their microstructure, morphology and magnetic properties were analysed by X-ray diffraction and transmission electron microscopy. Furthermore, the measurement of particle size distribution was performed by laser scattering, and temperature/field dependence on magnetization was determined. X-ray diffraction data confirmed the formation of two-phased samples (HAp and spinel iron oxide) without the presence of any other parasite phase. The shape of particles was nearly spherical in both samples, ranging from only a few to several tens of nanometres in diameter. These particles formed agglomerates with the most common value of the number-based particle size distribution of 380 and 310 nm for the sample with 12 and 30 wt.% of iron oxide, respectively. Magnetization data showed that both HAp/iron oxide composites had superparamagnetic behaviour at room temperature. © 2019 University of Novi Sad, Faculty of Technology. All rights reserved

Fluoxetine failed to prevent isolationinduced changes of glutathione-dependent defense in rat hippocampus

Chronic exposure to psychosocial stress is implicated in the pathophysiology of depression. We investigated the effect of 21d of chronic social isolation (CSIS) stress (an animal model of depression) and/or chronic administration of fluoxetine (15 mg/kg/day), an antidepressant, on GSH content, protein expression and activity of glutathione peroxidase (GPx) and glutathione reductase (GLR) in the cytosolic fraction of rat hippocampus. CSIS stress caused reduced GPx and GLR protein expression which was not prevented with fluoxetine treatment. Moreover, fluoxetine administration intensified reduction of these proteins expression. Decreased GSH content, GPx and GLR activity was also found in chronically-isolated animals (vehicle- or fluoxetine treated). Data indicate that fluoxetine not only failed to prevent CSIS-induced changes but itself compromised GSHdependent defense system in control animals

Lazy product discovery in huge configuration spaces

Highly-configurable software systems can have thousands of inter-dependent configuration options across different subsystems. In theresulting configuration space, discovering a valid product configu-ration for some selected options can be complex and error prone.The configuration space can be organized using a feature model,fragmented into smaller interdependent feature models reflectingthe configuration options of each subsystem.We propose a method for lazy product discovery in large frag-mented feature models with interdependent features. We formalizethe method and prove its soundness and completeness. The evalu-ation explores an industrial-size configuration space. The resultsshow that lazy product discovery has significant performance ben-efits compared to standard product discovery, which in contrastto our method requires all fragments to be composed to analyzethe feature model. Furthermore, the method succeeds when moreefficient, heuristics-based engines fail to find a valid configuration

Ultrafast humidity sensor based on liquid phase exfoliated graphene

Humidity sensing is important to a variety of technologies and industries, ranging from environmental and industrial monitoring to medical applications. Although humidity sensors abound, few available solutions are thin, transparent, compatible with large-area sensor production and flexible, and almost none are fast enough to perform human respiration monitoring through breath detection or real-time finger proximity monitoring via skin humidity sensing. This work describes chemiresistive graphene-based humidity sensors produced in few steps with facile liquid phase exfoliation (LPE) followed by Langmuir-Blodgett assembly that enables active areas of practically any size. The graphene sensors provide a unique mix of performance parameters, exhibiting resistance changes up to 10% with varying humidity, linear performance over relative humidity (RH) levels between 8% and 95%, weak response to other constituents of air, flexibility, transparency of nearly 80%, and response times of 30 ms. The fast response to humidity is shown to be useful for respiration monitoring and real-time finger proximity detection, with potential applications in flexible touchless interactive panels.Comment: 18 pages, 13 figure

Synthesis, Surface Modification and Magnetic Properties Analysis of Heat-Generating Cobalt-Substituted Magnetite Nanoparticles

Here, we present the results of the synthesis, surface modification, and properties analysis of magnetite-based nanoparticles, specifically Co0.047Fe2.953O4 (S1) and Co0.086Fe2.914O4 (S2). These nanoparticles were synthesized using the co-precipitation method at 80 ◦C for 2 h. They exhibit a single-phase nature and crystallize in a spinel-type structure (space group Fd3m). Transmission electron microscopy analysis reveals that the particles are quasi-spherical in shape and approximately 11 nm in size. An observed increase in saturation magnetization, coercivity, remanence, and blocking temperature in S2 compared to S1 can be attributed to an increase in magnetocrystalline anisotropy due to the incorporation of Co ions in the crystal lattice of the parent compound (Fe3O4). The heating efficiency of the samples was determined by fitting the Box-Lucas equation to the acquired temperature curves. The calculated Specific Loss Power (SLP) values were 46 W/g and 23 W/g (under HAC = 200 Oe and f = 252 kHz) for S1 and S2, respectively. Additionally, sample S1 was coated with citric acid (Co0.047Fe2.953O4@CA) and poly(acrylic acid) (Co0.047Fe2.953O4@PAA) to obtain stable colloids for further tests for magnetic hyperthermia applications in cancer therapy. Fits of the Box-Lucas equation provided SLP values of 21 W/g and 34 W/g for CA- and PAA-coated samples, respectively. On the other hand, X-ray photoelectron spectroscopy analysis points to the catalytically active centers Fe2+/Fe3+ and Co2+/Co3+ on the particle surface, suggesting possible applications of the samples as heterogeneous self-heating catalysts in advanced oxidation processes under an AC magnetic field