Оne-dimensional maps of the complex and chaotic oscillations of Bray-Liebhafsky reaction

Cilj disertacije je razvijanje novih metoda obrade i korišćenja 1D mapa u analizi vremenskih serija dinamičkih sistema i njihova primena za razlikovanje različitih tipova dinamike u oscilatornoj reakciji Bray-Liebhafsky. U literaturi se navodi da se uspešnost modeliranja na bazi predloženog modela mehanizma posmatrane reakcije procenjuje na osnovu stepena usaglašenosti simuliranih rezultata sa eksperimentalnim rezultatima. Modeliranje oscilatornih reakcija koje se odigravaju u uslovima udaljenim od termodinamičke ravnoteže je dodatno otežano kompleksnošću ovih reakcija, odnosno činjenicom, da model mehanizma oscilatorne reakcije mora da opiše i brojne dinamičke fenomene karakteristične za nelinerane sisteme: pojavu predoscilatornog perioda, oscilacija, determinističkog haosa, bifurkacija, pobudljivosti oscilatornog sistema i ostale moguće oblike nelinearnosti. U literaturi postoje eksperimentalna i teorijska ispitivanja dinamičkih stanja oscilatorne BL rekacije. Teorijska ispitivanja su zasnovana na numeričkim simulacijama procesa, a na bazi pretpostavljenog modela BL reakcije. To je upravo urađeno u ovoj disertaciji za slučaj procesa u otvorenom-protočnom reaktoru. Rezultati su saglasni sa već postojećima da su dinamička stanja veoma osetljiva na promenu brzine protoka supstanci kroz reaktor, odnosno da se složena dinamička stanja nalaze u veoma uzanom opsegu vrednosti kontrolnog prametra j0, odnosno u uzanom delu koncentracionog faznog prostora. Dinamika složenih reakcionih sistema se može ispitivati na više načina. U literaruti i u disertaciji su opisani postupci: analiza vremenskih serija, analiza atraktora, bifurkaciona analiza, Poenkareovi preseci i jednodimenzione (1D) povratne (iteracione) mape. 1D povratne mape prikazuju dinamičku struktura Poenkareovog preseka preko zavisnost n+1-ve vrednosti posmatrane veličine u tački preseka atraktora od njene n-te vrednosti u prethodnoj tački preseka istog atraktora. Ove mape se relativno retko koriste u literaturi kao metoda za ispitivanje dinamičkih stanja reakcionih sistema, iako je kvalitativno ponašanje 1D mapa veoma korisno da objasni i čak i predvidi različite bifurkacije. U disertaciji se posebno razmatra prednost 1D mapa nad drugim metodama kada je potrebno utvrditi pri kojim protocima se javljaju periodična, a pri kojim...The aim of this Doctoral Dissertation is development of new methods 1D maps using in analysis of time series of dynamical systems and the application thereof to distinguish among different types of dynamics in oscillatory Bray-Liebhafsky reaction. The literature states that the success of the modeling based on the proposed model of the mechanism of the observed reactions, is estimated based on the degree of conformity of simulated results with experimental results. Modeling of oscillatory reactions, taking place under conditions far from thermodynamic equilibrium is further hampered by the complexity of these reactions, and the fact that model oscillatory reaction mechanism must describe a number of dynamic phenomena characteristic of nonlinear systems: the pressence of preoscillatory period, oscillations, deterministic chaos, bifurcation, excitability, oscillatory systems and other possible forms of nonlinearity. The literature records experimental and theoretical study of dynamics of oscillatory BL reactions. Theoretical studies are based on numerical simulations of the reaction process, based on the assumed model of BL reaction. This was exactly done in this dissertation, for the reaction in an open-flow reactor. The results are consistent with the existing ones, confirming dynamic states to be highly sensitive to changes in the flow rate of substances through the reactor, i.e the complex dynamic states range within narrow set of values of the control parameter j0, or in a narrow range of the concentration in phase space. The dynamics of complex reaction systems can be examined in several ways. The reference sources and Dissertation describes procedures: the analysis of time series, attractors analysis, bifurcation analysis, Poincare sections and one-dimensional (1D) (iteration) map. 1D return maps show the dynamic structure of the Poincare-section dependence through n + 1- values of the observed parameter in the attractor cut-point of its n-th value in the preceding cut-point of the same attractor section. These maps are relatively rarely used in the reference sources as a method for testing the dynamic state of the reaction system, although the qualitative behavior of 1D map is very useful in provding explanation, even predicting different bifurcations. The dissertation, ponders especially the advantage of 1D maps over other methods when it is necessary to determine periodical, i.e chaotic dynamic situation, i.e..

LEAD, MERCURY AND ARSENIC CONTENT IN SPICES: BLACK, WHITE AND GREEN PEPPER, BLACK CUMIN AND GINGER

In order to evaluate the safety of selected commercial spices brands, concentration of lead, mercury and arsenic, as well as  moisture and mineral contents were analyzed in samples of dried black and white pepper powders, black, white and green peppercorns, black cumin seeds and ginger powder. Lead (Pb), mercury (Hg) and arsenic (As) concentrations in spice samples purchased from local markets in Belgrade were determined, after a microwave digestion of the samples, by atomic absorption spectrometry (AAS), using the graphite furnace AAS technique (Pb), cold vapor AAS technique (Hg) and hydride generation AAS technique (As). Trace levels of Pb, Hg and As in the selected dried spices samples were in the range 0.10 ppm - 0.79 ppm, 0.01 ppm - 0.10 ppm and 0.01 ppm - 0.51 ppm, respectively. The maximum Pb concentration was determined in the sample of ginger and it was 0.79 ppm, the maximum concentration of Hg was 0.10 ppm, determined in green peppercorns samples, while the maximum concentration of As in powdered black pepper sample was 0.51 ppm. The moisture and mineral contents in the different analyzed spices were in the range 1.70-13.10% and 3.40-6.50%, respectively. According to the obtained results, the concentrations of the analyzed toxic elements, as well as the moisture and mineral content in selected spices, were below the maximum permissible limits declared by the national legislations deemed safe for human consumption.SADRŽAJ OLOVA, ŽIVE I ARSENA U ZAČINIMA: CRNI, BELI I ZELENI BIBER, CRNI KIM I ĐUMBIRU ovom radu, u cilju utvrđivanja bezbednosti odabranih komercijalnih začina, analizirane su koncentracije teških metala, kao i sadržaj vlage i ukupnih mineralnih materija, u uzorcima sušenog crnog i belog bibera u prahu, crnog, belog i zelenog bibera u zrnu, semena crnog kima i đumbira u prahu. Koncentracije olova (Pb), žive (Hg) i arsena (As) u uzorcima začina iz lokalnih prodavnica u Beogradu, određene su nakon mikrotalasne digestije atomskom apsorcionom spektrometrijom (AAS), primenom tehnike grafitne peći (Pb), tehnike hladne pare (Hg) i hidridne tehnike (As). Određene koncentracije Pb, Hg i As u uzorcima sušenih začina su u opsegu 0,10 ppm - 0,79 ppm, 0,01 ppm - 0,10 ppm i 0,01 ppm - 0,51 ppm, redom. Maksimalna koncentracija Pb od 0,79 ppm određena je u uzorku đumbira, maksimalna koncentracija Hg od 0,10 ppm u uzorcima zelenog bibera u zrnu, dok je maksimalna koncentracija As određena u uzorku crnog bibera u prahu i iznosila je 0,51 ppm. U uzorcima ispitivanih začina sadržaj vlage i mineralnih materija je u opsegu 1,70-13,10% i 3,40-6,50%, redom. Dobijeni rezultati pokazuju da su koncentracije ispitivanih teških metala, kao i sadržaj vlage i mineralnih materija ispod maksimalno dozvoljenih vrednosti propisanih zakonskom regulativom Republike Srbije, kao i da su ispitivani uzorci crnog, belog i zelenog bibera u prahu i zrnu, crnog kima u zrnu i đumbira u prahu propisanog kvaliteta u ovom smislu.HIGHLIGHTSCommercially formulated anti-dandruff shampoos contain zinc pyrithione (ZPT) as an active ingredient that has antifungal, antibacterial and anti-seborrheic effects;In ZPT, pyrithione (PT) forms a complex with a zinc ion in the 2 : 1 ratio;Determination of ZPT concentration in commercial anti-dandruff shampoos by differential pulse polarography was based on an electrochemical reduction of zinc ions in ammoniacal buffer at pH 10.2;Surface active ingredients (anionic and amphoteric) and micro-components in the shampoos did not exert a polarographic interference for the determination of zinc and did not affect the determination of the content of ZPT active ingredient;This simple and sensitive differential pulse polarography method is suitable for a routine and rapid control of the active ingredient content, as well as for the quality control of anti-dandruff shampoos

Influence of hydroxycinnamic acids on the oxy-radical generated iodide/hydrogen peroxide reaction system

The influence of hydroxycinnamic acids (HCA): caffeic acid, chlorogenic acid, and p-coumaric acid, on the potassium iodide/hydrogen peroxide system was investigated. A linear correlation between absorption maximum of triiodide (I3 -) at 351 nm and HCA concentration was found. In the presence of HCA, reaction yield of I3 - was found to increase in following order p-cumaric < chlorogenic ≤ caffeic acid. This is attributing to their oxyradical scavenging activity. Results obtained in this study have showed correlation between antioxidant activities of HCA and their ability to enhanced I3 - production

The examination of ZnMnO4 in an aqueous solution of ZnCl2 and Mn(NO3)2

This work yields in the examination of potentially cathode material for aqueous Zn-ion batters. LiMn2O4, which is used in commercial organic Li-ion batteries is replaced with ZnMn2O4 in this work. Due to the presence of Mn3+ ions, the dissolution of them occurs in electrolyte decomposing to Mn4+ and Mn2+. To overcome this issue, 1 ml of 1M Mn(NO3)2 aqueous solution was added into 10 ml of aqueous solution of ZnCl2 to achieve an equilibrium between Mn2+ ions in the material and ones in an electrolyte. The results obtained showed that a higher capacity was obtained when 1 ml of 1M Mn(NO3)2 was added into 10 ml of aqueous solution of ZnCl2

The synthesis and characterization of ZnMn2O4 in an aqueous solution of ZnCl2

This work provides the synthesis and characterization of ZnMn2O4 that may be a potential replacement for the hazardous cathode materials used in commercial Li-ion batteries, as well as the examination of its electrochemical properties in an aqueous solution of ZnCl2. Due to the fact that commercial Li-ion batteries contain toxic and flammable electrolyte, there is a need for their replacement with less harmful substance

The comparison of electrochemical properties of ZnMn2O4 and ZnCr0.15Mn1.85O4 in an aqueous solution of ZnCl2

As commercial Li-ion batteries are chiefly composed of a toxic and flammable electrolyte, as well as that Li itself is also toxic and not economical for widespread use due to its rare metal nature, the aim of this work is to create an aqueous Zn-ion battery that contains the same cathode material as used in Li-ion batteries. The materials ZnMn2O4 and ZnCr0.15Mn1.85O4 were synthesized through glycine nitrate combustion. The initial material ZnMn2O4 was doped with Cr3+ in order to diminish Jan-Teller distortion which prevents of Zn2+ ions to fully intercalate into their original sites of crystal lattice. The materials were characterized by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM), while the electrochemical properties were examined through cyclic voltammetry in aqueous solutions of ZnCl2. The capacities obtained for the cyclic voltamogrammes recorded at 10 mVs-1 and 50 mVs-1 showed that cathode capacities for ZnMn2O4 amounted to be 12.4 mAhg-1 for 10 mVs-1, as well as 4.8 mAhg-1 for 50 mVs-1. The ZnCr0.15Mn1.85O4 demonstrated 45.3 mAhg-1 for 10 mVs-1, as well as 12.6 mAhg-1 for 50 mVs-1. The results obtained for the capacities of the original and doped material indicate that doping with Cr2+ partly diminishes the Jan Teller effect and facilitates the intercalation of Zn2+ ions

ZnMn2O4 as a cathode material in an aqueous solution of ZnCl2 and Mn(NO3)2 for Zn-ion batteries

Due to Li-ion batteries having become the main power source of most portable electronic devices, their waste has also become a significant environmental problem. To find batteries that would be environmentally friendly, this work examines Zn-ion batteries in an aqueous solution of ZnCl2. The ZnMnO4 was synthesized by glycine nitrate combustion of Zn(NO3)2, Mn(NO3)2 and glycine as a chelating agent [1]. The structure of the material obtained was characterized by X-ray powder diffraction (XRPD) showing a spinel structure; the morphology was characterized by scanning electron microscopy (SEM) showing that nano-particles were obtained. The electrochemical characterization was done by cyclic voltammetry in an aqueous solution of ZnCl2. The mixture pasted on the glossy carbon electrode was prepared by mixing the cathode material, graphite and polyvinyl diene difluoride (PVDF) in a ratio 85:10:5 [2]. Due to the low discharge capacity obtained of ~14 mAh g-1 for 5 mV s-1, further examination was done by adding 1 ml of 1M Mn(NO3)2 into 10ml of a saturated aqueous solution of ZnCl2. After adding the Mn(NO3)2 , the discharge capacity increased from ~14 mAh g-1 to ~65 mAh g-1 at the same polarization rate, making this additive a promising one for aqueous Zn-ion batteries. Further investigation needs to be directed to adding the same additive in larger amounts compared to 1ml to the same volume of the electrolyte. The results obtained suggest the aqueous Zn-ion battery described in this work to be a potentially promising “green” battery that may replace harmful commercial organic Li-ion batteries

Indigo carmine determining by UV/VIS spectrometric and the kinetic method using Briggs-Rauscher oscillator: two methods comparison

Indigo carmine (InC) is broadly used blue dye in different industrial area. This work aims to obtain analytical curves for determination of InC in aqueous solutions. For such as purposes, two methods were used: UV/VIS spectrophotometry and the kinetic method based on Briggs- Rauscher (BR) oscillatory reaction, and compared in terms of methods sensitivity which expressed as limit of detection (LOD) and limit of quantification (LOQ). To the best authors' knowledge, as candidate for proposed analytical method, the BR oscillatory reaction was applied for the first time to InC quantification. The results obtained show that kinetic method using BR oscillatory reaction has a quite lower LOD and LOQ making this method more acceptable to determine an unknown concentration of InC dissolved in water, compared to UV/Vis spectrophotometric method

The Synthesis of ZnMn2O4 by Glycine Nitrate Combustion and an Examination of Its Electrochemical Properties in Aqueous Solutions of ZnCl2 and NaNO3

To research potential replacements for LiMn2O4, this work carries out a synthesis of ZnMn2O4 (ZMO) through the glycine-nitrate combustion. XRPD validates its phase characterization; electron microscopy confirmed the presence of single phase ZMO in the form of curvy and rod-shaped sub-micron sized particles at an average of 113 nm. This work is novel for its electrochemical measurements of ZMO as a cathodic material for alkali-ion batteries, performed by cyclic voltammetry in aqueous solutions of ZnCl2 and NaNO3 ranging from 5 to 100 mV s–1 polarization rates, yielding stable capacities for both electrolytes. The highest capacities were obtained for the polarization speed of 5 mV s–1 for both electrolytes. Their cathode capacities were 11.3 and 27.2 mA h g–1 for ZnCl2 and NaNO3, respectively. Concerning Na-ions batteries, the surface storage is the deciding factor due to the adsorption of Na+ ions on the λ-MnO2 phase. Unlike Znions, Na+ ions cannot intercalate into the spinel structured materials

Enhancement of the electrocatalytic activity of Ni electrode for hydrogen evolution by electrodeposited V and Co on its surface

Enhancement of the electrocatalytic effect of Ni electrode for hydrogen evolution reaction (HER) by co-electrodeposited V and Co at metallic Ni (Ni-V-Co) was studied by using quasi-potentiostatic polarization technique from 1 M KOH at 25 ºC. The obtained exchange current density for HER with Ni-V-Co electrode, (5.5x10-4 Acm-2), is about two orders of magnitude higher than for metallic Ni electrode. The results suggested the existence of the synergetic effect of V and Co deposit on the catalytic activity of Ni electrode for HER. By using X-ray fluorescence (XRF) analysis the presence of Co and V at metallic Ni support was proved.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200