Polyaniline thin films in sensors for detection of toxic welding vapors

In this paper the possibilities of applying sensors based on filters with surface acoustic waves (SAW) for the detection of harmful products in welding processes are analyzed. This review discusses the sensing mechanism and configurations of the sensors. The principles of SAW sensors are considered with special emphasis on the application of conducting polyaniline nanocomposites as sensitive thin layers in sensors for the detection of CO, NO2, and COCl2. The literature suggests the use of In2O3 as a dopant for CO and NO2 detection sensors, and ethylenediamine and phenylenediamine in COCl2 sensors. The paper presents original results of modeling of sensors that are designed for detection of CO and NO2 for which there are experimental data in the literature. The results obtained based on this model are in excellent agreement with results from the literature, which shows the validity of modeling. Based on the developed modeling methods, calculations were done for sensors for the detection of these gases in which the structure was the surface of quartz. From these modeling results it can be concluded that the use of the quartz substrate provides better sensitivity. In addition, the quartz sensors are thermally stable.U radu su analizirane mogućnosti primene senzora u čijoj osnovi se nalaze filtri sa površinskim akustičkim talasom (PAT), za detekciju štetnih produkata u procesu zavarivanja. Objašnjeni su principi rada PAT senzora sa posebnim osvrtom na primenu elektroprovodnih polianilinskih nanokompozitnih materijala – polianilin/In2O3 i etilendiamin i fenilendiamin polianilinskih nanokompozita kao osetljivih tankih slojeva za detekciju CO, NO2 i COCl2. Prikazan je deo originalnih rezultata modelovanja PAT senzora koji su namenjeni detekciji pomenutih gasova. Rezultati dobijeni na bazi sopstvenog modela poređeni su sa rezultatima iz literature. Pokazano je da se ovim na činom modelovanja može uspešno odrediti koncentracija štetnih gasova u okruženju

Determination of air and hydrofoil pressure coefficient by laser doppler anemometry

Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp) was experimentally determined by Laser Doppler Anemometry (LDA) measurements. Two models were tested: model of airplane G4 (Super Galeb) and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles

Turbulence recognition in free convective flow by thermal-video post-processing in the case of a thermal power plant mill

This paper presents a study of a free convection flow around the walls of a ventilation mill of the Thermal Power Plant "Kostolac B", Kostolac, Serbia. A combined method consists of thermography and software post-processing, PATS. The PATS is specially developed for recognition of turbulence zones by the custom processing of large input data sets from thermal videos. The calculations determine maximum temperature fluctuation i.e. peak-to-peak fluctuation at every spot during the recording time. Three thermal videos of the walls were analyzed. Maximum temperature fluctuation occurred in the zones close to the obstacles, which are thus recognized as one of the main sources of turbulence. Besides, PATS has recognized fine camera oscillations and mechanical movements of a flexible material near the dozer wall. The detected zones of turbulence correspond to the previous studies and to the theory. The method shows good potential in the field of free convective flow research through the improvement of testing efficiency and cost savings. State-of-the-art thermograph cameras and updated software are recommended

Wear resistance improvement of thermal plant fan mill impact plates based on numerical flow simulation

Numerical simulation of 3D multiphase flow is performed to determine the velocity field in the fan mill. The mixture model of the Euler-Euler approach is used. Recirculating gas is a primary phase that carries granular phases including the coal powder and sand. The latter causes heavy wear of mill impact plates. The optimal form of hardfacing geometry and technology has an impact both on velocity magnitude and direction of flow in such a way as to reduce plate wear. This paper presents results of surface modification (based on numerical simulation), implemented on impact plates of the fan mill in the Kostolac B power plant in Serbia. Fishbone hardfacing is made in order to increase the lifetime of impact plates and extend the period between overhauls of fan mills. The experimental tests of fishbone surfacing plates, in exploitation conditions, show that the applied modification, hardfacing technologies and coating materials, give expected results. The application of this hardfacing in the form of a fishbone is simpler, faster and more economical compared to complete overlaying and honeycomb impact plate surfacing. The relative weight loss of base plate after an 1440-hour period of exploitation is 8%, while the weight losses for the hard-faced plate is below 7%

Radical scavenging and antimicrobial activity of essential oil and extracts of Echinophora sibthorpiana Guss. from Macedonia

This study was undertaken to determine the antioxidant and antimicrobial effect of essential oil and extracts of Echinophora sibthorpiana Guss. (fam. Apiaceae) collected in Macedonia. The chemical composition of E. sibthorpiana essential oil was characterized by the presence of methyl eugenol (60.40%), p-cymene (11.18%) and α-phellandrene (10.23%). The free radical scavenging activity of extracts and essential oil was evaluated by DPPH and ABTS assays. The aqueous extract of aerial parts exhibited the strongest scavenging activity (IC50=1.67 mg/ml); results of the ABTS test showed that the most effective was the ethanol extract of aerial parts (1.11 mg vit. C/g). The essential oil showed stronger antioxidant activity compared to hydroxyanisole, ascorbic acid and quercetin that were used in the DPPH and ABTS tests, respectively. The total phenolic and flavonoid concentrations in the extracts ranged between 38.65-60.72 mg GA/g, and 3.15-19.00 mg Qu/g, respectively. The antimicrobial properties of the extracts and essential oil were investigated using a micro-well dilution technique against human pathogenic strains. The results were comparable with the effects of the positive controls, streptomycin and fluconazole. These findings indicate that E. sibthorpiana extracts and oil can be used in preventive treatments and as an alternative for synthetic preservatives. [Projekat Ministarstva nauke Republike Srbije, br. 173029 i br. 173021

Chemical composition and antifungal activity of Salvia sclarea (Lamiaceae) essential oil

Clary sage (Salvia sclarea L.) is native to Southern Europe and is cultivated worldwide. The essential oil of clary sage was analyzed as a potential antifungal agent. The main compounds in the oil were linalyl acetate (52.83%) and linalool (18.18%). Food poisoning agents, spoilage fungi, and plant and animal pathogens were among the tested fungal species. The microdilution method was used to establish minimal inhibitory concentrations (MIC) and minimal fungicidal concentrations (MFC). The commercial antimycotic bifonazole was used as a control. A concentration of 25 μl/ml showed fungicidal activity against Aspergillus, Penicillium, and Fusarium species and Trichoderma viride. For the species Mucor mucedo and Aspergillus viride, the MFC was 15μl/ml; for Candida albicans, it was 10 μl/ml, as in the case of bifonazole. Fungistatic and fungicidal activities of the oil against Cladosporium cladosporioides and Trichophyton menthagrophytes were recorded at concentrations of 2.5 μl/ml and 5 μl/ml. The most sensitive micromycetes were Cladosporium fulvum, Alternaria alternata, Phomopsis helianthi, and Phoma macdonaldii, where a concentration of 2.5 μl/ml was lethal.Šarlahna žalfija (Salvia sclarea L.) je kao samonikla vrsta rasprostranjena u Južnoj Evropi, a kultivisana širom sveta. U radu je analizirano etarsko ulje ove vrste i utvrđivana njegova antifungalna aktivnost. Glavne komponente etarskog ulja su linalil acetat (52.83%) i linalol (18.18%). Kao test organizmi korišćene su gljivice koje izazivaju kvarenje hrane, kao i patogeni biljaka i životinja. Korišćenjem mikrodilucione metode određivane su minimalne inhibitorne (MIC) i minimalne fungicidne koncentracije (MFC). Komercijalni antimikotik bifonazol je korišćen kao kontrola. U koncentraciji od 25 µl/ml ulje je delovalo fungicidno na vrste rodova Aspergillus, Penicillium i Fusarium i vrstu Trichoderma viride. Za vrste Mucor mucedo i Aspergillus viride MFC je bila 15 µl/ml, i 10 µl/ml za C. albicans, slično kao za bifonazol. Potpuno zaustavljanje rasta micelija Cladosporium cladosporioides i Trichophyton menthagrophytes je postignuto pri koncentracijama 2.5 µl/ml i 5 µl/ml. Najosetljivije mikromicete bile su Cladosporium fulvum, Alternaria alternata, Phomopsis helianthi i Phoma macdonaldii, za koje je letalna koncentracija bila 2.5 µl/ml.Projekat ministarstva br. 143041 i 14304

Ispitivanje interakcije rubinskog lasera sa staklom

This paper presents the results of the ruby laser light interaction with glass surface. The investigation was conducted in order to determine the maximum density of laser light energy (λ = 694.3 nm, t = 30ns) that can be safely applied in different laser systems used in nondestructive testing methods (NDT). The process of irradiation took place in atmospheric conditions. The results show that interaction of laser beams with glass materials is a complex phenomenon. It depends on many factors and it is associated with localized formation of plasma, heating of the material that leads to melting and transient stresses causing mechanical damages. The zones of laser light interactions were investigated by scanning electron microscope (SEM) with energy-dispersal unit for the analysis of X-ray (EDX). The results obtained by SEM and EDX analysis show that the maximum allowable energy density is 5 J/cm2 for ruby laser light.У овом раду је приказан део резултата истраживања која се односе на проучавање интеракције светлости рубинског ласера и површине стакла. Циљ испитивања је одређивање максималне густине енергије ласерске светлости (λ = 694.3 nm, t = 30ns), која може безбедно да се користи у различитим ласерским системима за испитивање без разарања (ИБР). Озрачавање стаклених узорака је вршено у атмосферским условима. Резултати показују да је интеракција ласерске светлости са стаклом веома комплексан феномен. Резултати интеракције зависе од више фактора и повезани су са формирањем локалне плазме и грејањем материјала које доводи до топљења и напрезања што причињава механичка оштећења. Зоне интеракције ласерске светлости са површином стакла су испитивани скенирајућим електронским микроскопом (SEM) и енергодисперзивним детектором рендгенских зрака (EDX). Резултати добијени SEM и EDX анализом показују да је DE = 5·J/cm2 максимално дозвољена енергија за безбедан рад оптичких система који користе рубински ласер

Laser cleaning of corrosion, efficient and environmentally friendly method

In recent years, lasers have been used more and more in different areas of human life, science, industry, medicine, military, agriculture, and show business, protection of environmental and culturalheritage objects, in the arts and so on. Laser technology has some advantages in many areas over classical methods. This paper presents the results of laser application for cleaning corrosion of metal objects, cooper and brass. The first sample was oxidised cooper plate and the second ashtray made of brass. Nd: YAG laser was used as a source of radiation to clean surface corrosion deposits. Removal of layers from the surface occurs through the process of laser ablation. Three wavelengths were used with different fluences. The cleaning results, i.e. the morphological and chemical changes were investigated by optical microscopy, XRF analysis and colorimetry. The obtained results show that lasers are efficient corrosion cleaning and environmentally friendly method

Probiotic potential of Lactobacillus fermentum G-4 originating from the meconium of newborns

The present study was dedicated to determining probiotic potential of a human isolate G-4, originated from meconium. The isolate was identified using morphological, physiological and biochemical assays and molecular method based on 16S rRNA gene sequencing. In order to evaluate its probiotic properties in vitro tests were performed: the survival in simulated gastrointestinal conditions, adhesion to hexadecane, and antimicrobial activity. Safety aspects of the isolate were examined by testing toxicity, gastrointestinal tolerance and bacterial translocation in vivo, as well as hemolytic activity in vitro. The isolate G-4, identified as Lactobacillus fermentum, showed viability in artificial gastric and intestinal juice (low degree of cell viability reduction for 0.69 and 1.30 logCFU mL(-1) units, respectively), moderate adhesion to hexadecane (39 +/- 2.1 %), and antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serotype Abony and Clostridium sporogenes, due to production of lactic acid (9.80 g L-1). No signs of toxicity, bacterial translocation, hemolytic activity, were observed

Laser cleaning of varnish from bog oak surface

The removal of varnish is a very challenging task in the conservation of wooden artifacts. The results of experiments performed to investigate the suitability of lasers for cleaning aged varnish from bog oak wood (ebony) are presented in this paper. Optimal laser parameters for safe and efficient varnish ablation were determined in order to preserve the integrity of the original wooden substrate during the cleaning process. The ablation threshold for varnish and wood damage threshold was examined using Nd:YAG laser (1064, 532 and 355 nm) emitting pulses of nanosecond (8 ns) duration. Results of induced varnish removal and other morphological alterations to the wood surface were investigated by optical microscopy and colorimetry