Mikrobiološki aspekti primene informacionih sistema u monitoringu akumulacija i jezera

Procena povezanosti uticaja koji neki fizički, hemijski ili biološki parametri imaju na određenu bakterijsku zajednicu ili obrnuto, je kako fundamentalna u boljem razumevanju samih bakterijskih zajednica, tako i praktična u praćenju, predviđanju i unapređenju stanja kvaliteta voda. Bakterijske zajednice imaju veliki značaj u funkcionisanju akvatičnih ekosistema i određivanju njihovog kvaliteta. Na osnovu te činjenice, postojećih podataka iz ranijih naučnih i standardnih hidrobioloških istraživanja, odabrane su tri akumulacije u Srbiji koje se razlikuju po morfometrijskim osobinama, trofičkom statusu i dominantnoj zajednici bakterija. Na njima su primenjeni novi, savremeni alati informacionih tehnologija i korišćene metode DM, nove za ovu oblast istraživanja, sa ciljem da se utvrde: - stepen zavisnosti i veličina uticaja bakterijskih zajednica međusobno; - stepen zavisnosti i veličina uticaja relevantnih fizičkih, hemijskih i bioloških parametara na stanje i dinamiku različitih bakterijskih zajednica i vrsta; - predviđanje stanja na osnovu dobijenih rezultata; - najefikasnije metode za racionalizaciju i povećanje efikasnosti limnoloških istraživanja u Srbiji, uspostavi adekvatan monitoring i doprinese održivom upravljanju akumulacijama i jezerim

Great horsetail (Equisetum telmateia Ehrh.)

This paper deals with the antioxidant and antimicrobial activity, total phenolic content and concentrations of flavonoids of Equisetum telmateia extracts. Total phenolic content was determined with Folin-Ciocalteu reagent and it ranged between 129.0 to 262.7 mg GA/g. The concentration of flavonoids in various extracts of E. telmateia was determined using spectrophotometric method with aluminum chloride and obtained results varied from 112.6 to 199.8 mg RU/g. Antioxidant activity was monitored spectrophotometrically and expressed in terms of IC50 (μg/ml), and its values ranged from 33.4 to 982.2 μg/ml. The highest phenolic content, concentrations of flavonoids and capacity to neutralize DPPH radicals were found in the acetone extract. In vitro antimicrobial activity was determined using microdilution method. Minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) were also determined. Testing was performed on 22 microorganisms, including 15 strains of bacteria (standard and clinical strains) and 7 species of fungi. There were statistically significant differences in activity between the extracts of E. telmateia. Different effects were noticed against the bacteria and the methanol extract appeared to be most efficient. All the extracts showed significant antibacterial activity against G+ bacteria and weak to moderate activity against other microorganisms

Variability and bimodal distribution of size in uninuclear microspores of Aesculus flava Marshall

Projekat ministarstva br. 14302

Mechanical features of copper coatings electrodeposited by the pulsating current (PC) regime on Si(111) substrate

Mechanical features of the Cu coatings produced by the pulsating current (PC) regime on Si(111) substrate have been investigated. The Cu coatings were electrodeposited by varying duty cycle (15−50 %) and keeping the current density amplitude constant (100 mA cm−2), and by keeping duty cycle constant (50 %) but varying the current density amplitude value (80−120 mA cm−2). The scanning electron microscopy (SEM) and optical microscopy (OM) techniques showed that morphology of the coatings changed with increasing the duty cycle from those with large and well defined grains to uniform and compact fine-grained coatings. The Vickers microindentation technique was used for an examination of hardness applying the Chen-Gao (C-G) composite hardness model and indentation creep features of the Cu coatings. The obtained values of hardness for the Cu coatings on Si(111) in the 0.9069−1.5079 GPa range indicated the successful implementation of the C-G model for this "soft film on hard substrate" composite system. The obtained stress exponents ranging from 2.79 to 5.29 indicated that creep mechanism changed from grain boundary sliding to both dislocation climbs and dislocation creep with decreasing duty cycle values. The maximum hardness and minimum stress exponent was obtained for the fine-grained Cu coating produced with a duty cycle of 50 % and the current density amplitude of 100 mA cm-2, indicating that its plastic deformation during microindentation was primarily caused by grain boundary sliding. Optimization of process formation and mechanical features of the Cu coatings was made using Response Surface Methodology (RSM), and error of 3.2 % showed a good agreement between predicted and measured values

Heavy metal tolerance and removal efficiency of the Rhodotorula mucilaginosa and Saccharomyces boulardii planktonic cells and biofilm

The impact of heavy metals, cadmium (Cd2+), zinc (Zn2+) and nickel (Ni2+) on planktonic cells and biofilm of Rhodotorula mucilaginosa and Saccharomyces boulardii was examined. The metal tolerance testing was performed by MBECTM-HTP assay. The minimum inhibitory concentration (MICp) and minimum lethal concentration (MLCp) were determined as well as the minimum biofilm eradication concentration (MBEC). Biofilm was more tolerant on the presence of heavy metals than the planktonic cells. The planktonic cells of R. mucilaginosa were tolerant to high concentrations of Cd2+, Zn2+ and Ni2+, while the planktonic cells of S. boulardii tolerated Zn2+, exclusively. The R. mucilaginosa biofilm was tolerant to all of the tested metal concentrations and the obtained results were confirmed by fluorescence microscopy. S. boulardii did not show ability of biofilm formation. Metal removal efficiency of the R. mucilaginosa planktonic cells and biofilm were also tested. The R. mucilaginosa biofilm showed higher efficiency in metals removing compared to the planktonic cells. Until now, the heavy metal tolerance and the removal efficiency (Cd2+, Zn2+ and Ni2+) analyzes were performed solely on planktonic cells of Rhodotorula species. In this study, we investigated the metal removal efficiency of R. mucilaginosa planktonic cells and biofilm and compared the obtained results

Influence of intensity of ultrasound on morphology and hardness of copper coatings obtained by electrodeposition

The influence of various intensities of ultrasound applied for the electrolyte stirring on morphological and mechanical characteristics of electrolytically produced copper coatings has been investigated. The copper coatings produced by the galvanostatic regime of the electrodeposition from the basic sulphate electrolyte and the electrolyte with added levelling/brightening additives at the low temperature were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques (surface morphology and topography, respectively) and by Vickers microindentation (hardness). The roughness of coatings increased with the increasing intensity of ultrasound, indicating that morphology of the coatings worsened with the enhanced application of ultrasonic waves. This is attributed to the strong effect of ultrasound on hydrodynamic conditions in the near-electrode layer, which is manifested by the increase of share of the activation control in the mixed activation-diffusion control of electrodeposition with increasing the intensity of ultrasound. The concept of "effective overpotential" originally proposed to explain a change of surface morphology in the conditions of vigorous hydrogen evolution is also applicable for a change of morphology of Cu coatings under the imposed effect of ultrasonic waves. Hardness analysis of the coatings showed that an intensity of applied ultrasound did not have any significant effect on the hardness, especially for the Cu coatings produced from the basic sulphate electrolyte

Одређивање апсолутне тврдоће електролитички добијених превлака бакра применом Chicot-Lesage композитног модела тврдоће

In this study, a novel procedure, based on application of the Chicot–Lesage (C–L) composite hardness model, was proposed for the determination of an absolute hardness of electrolytically produced copper coatings. The Cu coatings were electrodeposited on the Si(111) substrate by the pulsating current (PC) regime with a variation of the following parameters: the pause duration, the current density amplitude and the coating thickness. The topography of produced coatings was characterized by atomic force microscope (AFM), while a hardness of the coatings was examined by Vickers microindentation test. Applying the C–L model, the critical relative indentation depth (RID)c of 0.14 was determined, which is independent of all examined parameters of the PC regime. This RID value separated the area in which the composite hardness of the Cu coating corresponded to its absolute hardness (RID <0.14) from the area in which the application of the C–L model was necessary for a determination of the absolute coating hardness (RID ≥ 0.14). The obtained value was in a good agreement with the value already published in the literature.Предложен je нови поступак заснован на примени Chicot–Lesage (C–L) композитног модела тврдоће за одређивање апсолутне тврдоће електролитички добијених превлака бакра. Превлаке бакра су електрохемијски исталожене на силицијуму (111) оријентације режимом пулсирајуће струје варирањем следећих параметара: трајање паузе, амплитудна густина струје и дебљина превлаке. Топографија произведених превлака је окарактерисана микроскопијом атомских сила, док је тврдоћа превлака испитивана Викерсовим тестом утискивања. Применом C–L композитног модела тврдоће, одређена је критична релативна дубина утискивања (RID), од 0,14, која је независна од свих испитиваних параметара режима пулсирајуће струје. Ова вредност раздваја област у којој композитна тврдоћа превлаке може да се изједначи са њеном апсолутном тврдоћом (RID << 0,14) од области у којој је неопходно применити C–L модел за одређивање апсолутне тврдоће превлаке (RID ≥ 0,14). Добијена вредност RID показује добро слагање са вредностима публикованим у литератури

Morphology, structure and hardness of electrolytically produced copper coatings

Poster presented at: 4th International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, June, 30th-July, 02nd, Sarajevo, Bosnia and HerzegovinaAbstract: [https://cer.ihtm.bg.ac.rs/handle/123456789/5213

Effect of concentration pigment particles on microstructure of the metal matrix copper composite coatings

This research focuses on the synthesis and characterization of composite coatings via electrochemical route with co-deposition pigments. For that reason, the effect of adding yellow green phosphorescent pigment on microstructural evaluation of the Cu/pigment composite systems has been investigated.Second International Conference on Electron Microscopy of Nanostructures ELMINA 2022, August 22nd-26th, 2022, Belgrade, Serbia

Influence of parameters of the pulsating current (PC) regime on morphological, structural and hardness characteristics of copper coatings electrodeposited on Si(111)

Electrodeposition of Cu was performed on Si(111) by the pulsating current (PC) regime in the range of the average current densities (jav) between 15 and 70 mA cm-2 . The selected values of the average current densities were attained by varying either pause duration (tp: 28.3, 15, 7.5 and 5 ms, i.e. jav: 15, 25, 40 and 50 mA cm-2 for the constant values of deposition pulse of 5 ms and current density amplitude (jA) of 100 mA cm-2) or amplitude of the current density (jA: 120 and 140 mA cm-2 , i.e. jav: 60 and 70 mA cm-2 for the constant values of deposition pulse of 5 ms and pause duration of 5 ms). Morphological and structural characteristics of the obtained coatings were examined by scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD), respectively. With increasing the average current density, morphologes of the coatings changed from those with large and well defined crystal grains obtained at jav of 15 mA cm-2 (the dominant effect of activation control) to fine-grained obtained at jav of 50 mA cm-2 (the mixed activation-diffusion control) and those with globules when diffusion becomes a dominant process (jav = 70 mA cm-2). The minimum roughness showed the Cu coating obtained at jav of 50 mA cm-2 . Simultaneously, crystal structure changed from the strong (220) to the strong (111) preferred orientation with increasing average current density. The change of surface morphology was discussed by the effect of applied parameters of the PC regime on the type of electrodeposition control, while change in crystal orientation of produced coatings was explained by various rates of growth on various crystal planes. Hardness analysis of the produced coatings was performed by application of the Chicot-Lesage (C-L) composite hardness model. By application of this model, the relative indentation depth (RID; where RID = h/d; h is an indentation depth, and d is a thickness of coating) of 0.14 was established as the limiting value separating the area of the absolute hardness of the Cu coatings (RID < 0.14) from the area in which application of the C-L model is necessary for a determination of the absolute hardness of coatings (RID > 0.14). For RID < 0.14, the measured composite hardness corresponded to the absolute hardness of the coating