Immobilization of alfa-amylase on polyaniline and magnetic particles modified by polyaniline

Циљ ове дисертације био је имобилизација α-амилазе на полианилину и магнетним честицама модификованим полианилином методом адсорпције ради добијања вишефункционалног биокатализаторског система погодног за вишекратну хидролизу скроба. Истраживања у оквиру ове тезе могу се поделити у три дела. У првом делу рада извршена је синтеза и карактеризација честица носача и карактеризација α-амилазe из Bacillus licheniformis ензимског препарата Termamyl. Магнетне честице (MAG) синтетисане су копреципитацијом FeCl3 и FeSO4 у базној средини, а затим обложене полианилинском превлаком (MAG-PANI). Честице полианилина (PANI) синтетисане су хемијски на граници фаза двофазног система вода/хлороформ. Испитане су морфолошке особине, магнетна својства, IR спектри, расподела величине честица и зета потенцијала MAG и MAG-PANI. Показано је да су синтетисани агломерати наночестица MAG и MAG-PANI. Површина магнетних честица униформно је пресвучена полианилином влакнасте структуре. Честице MAG карактерише бимодална, а MAG-PANI тримодална расподела величина честица. У другом делу рада извршена је имобилизација ензима α-амилазе на честицaма MAG, MAG-PANI и PANI. Одређени су оптимални услови имобилизације на MAG-PANI: време, почетна концентрација ензима, рН и температура. Испитивањем кинетичких параметара Km и Vm утврђено је да имобилисана α-амилаза на МАG-PANI показује већи афинитет према супстрату него имобилисана α-амилаза на MAG, а нижи афинитет од слободне α-амилазе. Утврђен је Ленгмиров (Langmuir) модел адсорпције α-амилазе на честицама MAG-PANI. У трећем делу рада испитана је стабилност имобилисане α-амилазе, могућност употребе кроз више циклуса као и оперативна стабилност у проточном биореактору са континуалним и повратним током. Утврђена је рН стабилизација α-амилазе имобилизацијом на MAG честицама и померање температурног оптимума имобилизацијом на MAG-PANI. Имобилисана α-амилаза на MAG-PANI задржала је око 55,5% почетне активности након 9 циклуса коришћења и око 80,3% почетне активности након 50 дана чувања. Време полу-живота биокатализатора при континуалним условима рада било је 6,2 h.The aim of this dissertation is to examine immobilization α-amylase on polyaniline and magnetic particles coated with polyaniline via adsorption in order to obtain a more stable biocatalyst system, with the possibility of repeated use with easy separation from the reaction medium. This thesis can be divided into three parts. In the first part, the synthesis and characterization of the carrier particles was carried out. Magnetic particles (MAG) were synthesized by co-precipitation of FeCl3 and FeSO4 in the base medium. Magnetic particles are coated with a polyaniline (MAG-PANI). Polyaniline particles (PANI) are synthesized chemically at the interface of the water/chloroform system. Morphological, magnetic properties, IR spectrums, particle size distribution and zeta potential of the buffer suspension of the carrier particles were examined. It has been shown that the agglomerates of MAG and MAG-PANI nanoparticles are synthesized. The surface of the magnetic particles is coated uniformly with polyaniline fibrous structure. MAG particles are present in bimodal, and MAG-PANI is a trimodal particle size distribution. In the second part of the work, immobilization of the α-amylase enzymes onto MAG, MAG-PANI and PANI was carried out. The optimal immobilization conditions at MAG-PANI were determined: time, initial concentration of enzymes, pH and temperature. Certain kinetic parameters: Km and Vm immobilized α-amylases show a higher affinity for immobilized α- amylase on MAG-PANI compared to α-amylase immobilized on MAG and lower both of immobilisates than free α-amylase. Langmuir adsorption model of α-amylase was determined for particles MAG-PANI. In the third part of the dissertation, рН, temperature and operational stability of α- amylase immobilized on MAG-PANI particles in recycle packed bed reactor and continuous packed bed reactor without recycling has been studied. Immobilized enzyme particles MAGPANI retained about 55.5% of initial activity after 9 successive use cycles and about 80.3% of initial activity after 50 days. In a bioreactor with a packed bed MAG-PANI-A can be used over several cycles with the increase in the time required for the hydrolysis of the same amount of starch. The half-life of the biocatalyst under continuous working conditions was 6.2 h

Somatic cell counts in bulk milk and their importance for milk processing

Bulk tank milk somatic cell counts are the indicator of the mammary gland health in the dairy herds and may be regarded as an indirect measure of milk quality. Elevated somatic cell counts are correlated with changes in milk composition The aim of this study was to assess the somatic cell counts that significantly affect the quality of milk and dairy products. We examined the somatic cell counts in bulk tank milk samples from 38 farms during the period of 6 months, from December to the May of the next year. The flow cytometry, Fossomatic was used for determination of somatic cell counts. In the same samples content of total proteins and lactose was determined by Milcoscan. Our results showed that average values for bulk tank milk samples were 273,605/ml from morning milking and 292,895/ml from evening milking. The average values for total proteins content from morning and evening milking are 3,31 and 3,34%, respectively. The average values for lactose content from morning and evening milking are 4,56 and 4,63%, respectively. The highest somatic cell count (516,000/ml) was detected in bulk tank milk sample from evening milk in the Winter and the lowest content of lactose was 4,46%. Our results showed that obtained values for bulk tank milk somatic cell counts did not significantly affected the content of total proteins and lactose

The (theta, wheel)-free graphs Part II: Structure theorem

A hole in a graph is a chordless cycle of length at least 4. A theta is a graph formed by three paths between the same pair of distinct vertices so that the union of any two of the paths induces a hole. A wheel is a graph formed by a hole and a node that has at least 3 neighbors in the hole. In this paper we obtain a decomposition theorem for the class of graphs that do not contain an induced subgraph isomorphic to a theta or a wheel, i.e. the class of (theta, wheel)-free graphs. The decomposition theorem uses clique cutsets and 2-joins. Clique cutsets are vertex cutsets that work really well in decomposition based algorithms, but are unfortunately not general enough to decompose more complex hereditary graph classes. A 2-join is an edge cutset that appeared in decomposition theorems of several complex classes, such as perfect graphs, even-hole-free graphs and others. In these decomposition theorems 2-joins are used together with vertex cutsets that are more general than clique cutsets, such as star cutsets and their generalizations (which are much harder to use in algorithms). This is a first example of a decomposition theorem that uses just the combination of clique cutsets and 2-joins. This has several consequences. First, we can easily transform our decomposition theorem into a complete structure theorem for (theta, wheel)-free graphs, i.e. we show how every (theta, wheel)-free graph can be built starting from basic graphs that can be explicitly constructed, and gluing them together by prescribed composition operations; and all graphs built this way are (theta, wheel)-free. Such structure theorems are very rare for hereditary graph classes, only a few examples are known. Secondly, we obtain an (n⁴m)-time decomposition based recognition algorithm for (theta, wheel)-free graphs. Finally, in Parts III and IV of this series, we give further applications of our decomposition theorem

The (theta, wheel)-free graphs Part IV: Induced paths and cycles

A hole in a graph is a chordless cycle of length at least 4. A theta is a graph formed by three internally vertex-disjoint paths of length at least 2 between the same pair of distinct vertices. A wheel is a graph formed by a hole and a node that has at least 3 neighbors in the hole. In this series of papers we study the class of graphs that do not contain as an induced subgraph a theta nor a wheel. In Part II of the series we prove a decomposition theorem for this class, that uses clique cutsets and 2-joins. In this paper we use this decomposition theorem to solve several problems related to finding induced paths and cycles in our class

Dyons in Nonabelian Born-Infeld Theory

We analyze a nonabelian extension of Born--Infeld action for the SU(2) group. In the class of spherically symmetric solutions we find that, besides the Gal'tsov--Kerner glueballs, only the analytic dyons have finite energy. The presented analytic and numerical investigation excludes the existence of pure magnetic monopoles of 't Hooft--Polyakov type.Comment: 12 pages, 3 figure

Magnetotunnelling in resonant tunnelling structures with spin-orbit interaction

Magnetotunnelling spectroscopy of resonant tunnelling structures provides information on the nature of the two-dimensional electron gas in the well. We describe a model based on nonequilibrium Green's functions that allows for a comprehensive study of the density of states, tunnelling currents and current spin polarization. The investigated effects include the electron-phonon interaction, interface roughness scattering, Zeeman effect and the Rashba spin-orbit interaction. A qualitative agreement with experimental data is found regarding the satellite peaks. The spin polarization is predicted to be larger than ten percent for magnetic fields above 2 Tesla and having a structure even at the satellite peaks. The Rashba effect is confirmed to be observable as a beating pattern in the density of states but found to be too small to affect the tunnelling current.Comment: 31 pages, 11 figure

REMOTE SENSING ROLE IN ENVIRONMENTAL STRESS ANALYSIS: ЕАST SERBIA WILDFIRES CASE STUDY (2007–2017)

Wildfire has been one of the most dangerous environmental stressors nowadays. It is an important disturbance where ecosystem biomass is burned and where organisms are damaged or killed by fire. Therefore, the detecting and monitoring of this stressor are of great importance. During last decades, extensive forest fires have spread in Southern Europe, and they are registered in Serbia as well. During year 2007, several significant fires were registered in Stara Planina and Svrljiške Planine Mountains. The aims of this study were to detect land cover changes for the studied site from 2007–2017, to focus on monitoring the area affected by the wildfire, and to analyse the environment response to stressor. The study area is situated in East Serbia, partially covering the Mountains Stara Planina (western part) and Svrljiške planine (eastern part). The remote sensing techniques were used in the analysis and main satellite data were obtained via USGS Earth Explorer application. Six different classes were selected: Water, Forest, Pastures, Artificial area, Agriculture, and Bare soil. Results showed significant changes in two classes, Forest, and Pastures — the forest spread for more than 20% at the expense of pasture, which decreased more than 23%

Information-Theoretic Analysis of Cardio-Respiratory Interactions in Heart Failure Patients: Effects of Arrhythmias and Cardiac Resynchronization Therapy

The properties of cardio-respiratory coupling (CRC) are affected by various pathological conditions related to the cardiovascular and/or respiratory systems. In heart failure, one of the most common cardiac pathological conditions, the degree of CRC changes primarily depend on the type of heart-rhythm alterations. In this work, we investigated CRC in heart-failure patients, applying measures from information theory, i.e., Granger Causality (GC), Transfer Entropy (TE) and Cross Entropy (CE), to quantify the directed coupling and causality between cardiac (RR interval) and respiratory (Resp) time series. Patients were divided into three groups depending on their heart rhythm (sinus rhythm and presence of low/high number of ventricular extrasystoles) and were studied also after cardiac resynchronization therapy (CRT), distinguishing responders and non-responders to the therapy. The information-theoretic analysis of bidirectional cardio-respiratory interactions in HF patients revealed the strong effect of nonlinear components in the RR (high number of ventricular extrasystoles) and in the Resp time series (respiratory sinus arrhythmia) as well as in their causal interactions. We showed that GC as a linear model measure is not sensitive to both nonlinear components and only model free measures as TE and CE may quantify them. CRT responders mainly exhibit unchanged asymmetry in the TE values, with statistically significant dominance of the information flow from Resp to RR over the opposite flow from RR to Resp, before and after CRT. In non-responders this asymmetry was statistically significant only after CRT. Our results indicate that the success of CRT is related to corresponding information transfer between the cardiac and respiratory signal quantified at baseline measurements, which could contribute to a better selection of patients for this type of therapy

On analytical solutions of f(R) modified gravity theories in FLRW cosmologies

A novel analytical method for f(R) modified theories without matter in Friedmann-Lemaitre-Robertson-Walker spacetimes is introduced. The equation of motion for the scale factor in terms of cosmic time is reduced to the equation for the evolution of the Ricci scalar R with the Hubble parameter H. The solution of equation of motion for actions of the form of power law in Ricci scalar R, is presented with a detailed elaboration of the action quadratic in R. The reverse use of the introduced method is exemplified in finding functional forms f(R) which lead to specified scale factor functions. The analytical solutions are corroborated by numerical calculations with excellent agreement. Possible further applications to the phases of inflationary expansion and late-time acceleration as well as f(R) theories with radiation are outlined.Comment: 16 pages, 6 figures. v2: minor changes, references added. v3: minor changes, more references added. v4: version to appear in IJMPD. v5: DOI and journal reference adde

Modeling and applications of Quantum Cascade in external magnetic field

The rapidly emerging field of nano-optoelectronics is based on the understanding and control of intersubband transitions in nano-dimensional systems. One of the most striking outcomes of intersubband transitions engineering is the quantum cascade laser (QCL) – an efficient and reliable unipolar semiconductor laser source [1], with the possibility to operate from the mid-infrared (MIR) to the THz range of frequencies. These powerful devices are particularly appreciated for such wide scope of operating wavelengths which can be achieved by using the same heterostructure combination, but changing the design of the active region, i.e. ‘tailoring’ the layers’ widths and composition. This renders QCLs suitable for numerous applications, including free-space communications, medical diagnostics and in particular, chemical sensing and monitoring [2]. In the MIR part of the spectrum, QCLs are of great interest for gas sensing and monitoring. We explore the possibilities of using advanced tools for global optimization, namely the genetic algorithm, to obtain structural parameters of gain-maximized QCL emitting at specified wavelengths, suitable for detection of pollutant gasses, such as SO2, HNO3, CH4 and NH3, in the ambient air. Then we introduce a strong external magnetic field perpendicular to the epitaxial layers, to fine tune the laser output properties [2]. This magnetic field alters the electron energy spectrum by splitting the continuous energy subbands into discrete Landau levels whose arrangement influences the magnitude of the optical gain. In addition, strong effects of band nonparabolicity result in subtle changes in the lasing wavelength at magnetic fields which maximize the gain, thus allowing us to explore the prospects of multi-wavelength emission of the given structure. THz frequencies belong to the quite under-utilized part of the electromagnetic spectrum, despite their significant application potential. This is mostly due to the lack of coherent solid-state THz sources. The so called „THz gap“ falls between two frequency ranges that have been well developed, the microwave and millimeter-wave frequency range. THz QCLs are great candidates to fill in this gap [3]. We have analyzed two structures lasing in this region (both of them reported in the literature, but not studied under the influence of an external magnetic field), the three- and four-well (per period) based structures that operate at 3.9THz and 1.9THz, respectively, implemented in GaAs/Al0.15Ga0.85As. Numerical results are presented for magnetic field values from 1.5 T up to 20 T, while the band nonparabolicity is carefully accounted for. Because of their high output gain, QCLs are suitable to be used as active media in metamaterial unit cells, thus enabling evasion of metallic inclusions present in conventional metamaterials [4]. We analyze a quantum cascade structure lasing at 4.6THz, placed under the influence of a strong magnetic field. We first solve the full system of rate equations for all the relevant Landau levels, and obtain the necessary information about the carrier distribution among the levels, after which we are able to evaluate the permittivity component along the growth direction of the structure, as well as the range of frequencies at which the structure exhibits negative refraction for a predefined total electron sheet density.V International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 and the Second international workshop "Control of light and matter waves propagation and localization in photonic lattices" : PHOTONICA2015 : book of abstracts; August 24-28, 2015; Belgrad