Subwavelength hole arrays with nanoapertures fabricated by scanning probe nanolithography

Owing to their surface plasmon-based operation, arrays of subwavelength holes show extraordinary electromagnetic transmission and intense field localizations of several orders of magnitude. Thus they were proposed as the basic building blocks for a number of applications utilizing the enhancement of nonlinear optical effects. We designed and simulated nanometer-sized subwavelength holes using an analytical approach. In our experiments we used the scanning probe method for nanolithographic fabrication of subwavelength hole arrays in silver layers sputtered on a positive photoresist substrate. We fabricated ordered nanohole patterns with different shapes, dispositions and proportions. The smallest width was about 60 nm. We characterized the fabricated samples by atomic force microscopy

Prinos krme travno-leguminozne smeše pri različitom vremenu zasnivanja

For comparative testing of the total productivity of mixtures (intercrops) of red clover (Trifolium pratense L.) and Italian ryegrass (Lolium multiflorum L.), a trial was carried out during the 2007-2009 growing seasons at experimental fields of the Institute for Animal Husbandry, Belgrade-Zemun. Intercrops included two red clover varieties (K-17 and Una) and tetraploid Italian ryegrass (K-29t) in different proportional ratios (100:0%, 75:25%, 50:50%, 25:75% and 0:100%). Italian ryegrass sown alone was top-dressed with nitrogen rates of 100 and 200 kg ha-1. Herbage yields and botanical composition were influenced by different sowing times in the first production year. Spring seeded red clover was more persistent and cumulatively yielded, autumn seeded Italian ryegrass produced more dry matter in the mixture than red clover. The trial demonstrates the potential of two red clover cultivars grown either alone or with a suitable Italian ryegrass to achieve and maintain a high output of herbage of good quality in the first production year, with different time of stand establishment. The practical agricultural implications of using ryegrass/clover are discussed.U toku vegetacione sezone 2007-2009 izveden je ogled na eksperimentalnom polju Instituta za stočarstvo, Zemun-Beograd, sa crvenom detelinom i italijanskim ljuljem radi uporednog ispitivanja ukupne proizvodnje biomase smeša. Smeše su uključivale dve sorte crvene deteline (K-17 i Una) i tetraploidnog italijanskog ljulja (K-29t) sa različitim proporcionalnim odnosima (100:0%, 50:50%, 75:25%, 25:75% i 0:100%). Italijanski ljulj sejan u čistom usevu prihranjivan je sa 100 i 200 kg N ha-1. Različito vreme setve uticalo je na prinos krme i botaničku kompoziciju u prvoj proizvodnoj godini. Crvena detelina sejana u proleće bila je otpornija i kumulativno prinosnija, kao i italijanski ljulj sejan u jesen koji je proizveo više suve materije u smeši u odnosu na detelinu. Ogled pokazuje potencijal dve sorte crvene deteline sejane u čistom usevu ili sa italijanskim ljuljem radi dobijanja i održavanja visoke proizvodnje biomase dobrog kvaliteta u prvoj proizvodnoj godini, pri različitom vremenu zasnivanja. Razmatrane su praktične agronomske implikacije korišćenja smeše italijanskog ljulja i crvene deteline

Seasonal variations of microbiological parameters of water quality of the Velika Morava river Serbia

In this study, we investigated the level of sanitary pollution and organic contamination of the Velika Morava River, the largest river in central Serbia. Samples of water for microbiological analysis were collected at 5 sites, monthly, from April 2010 to February 2011. Sanitary analysis, i.e. enumeration of total and fecal coliforms and intestinal enterococci, indicated moderate to critical fecal contamination, while organic load assessment (oligotroph to heterotroph ratio, index of phosphatase activity) revealed the category of moderately polluted water. We also investigated seasonal variations of these groups of bacteria and the factors that could contribute to these differences. Our results showed that the micro- biological quality of the water in the Velika Morava River during different seasons is affected by numerous factors such as unequal loading of wastewaters, solar irradiation, and relations of flow/dilution and rainfall/runoff. [Acknowledgments. This study was financially supported by the Ministry of Education and Science of the Republic of Serbia: projects No 173025, No 177045 and No 043002.

Metal oxide nanoparticles as active food packaging components

Replacement of non-degradable food packaging materials with a biodegradable alternative enables reduction of environmental pollution. Metal oxides nanoparticles are good candidates for enhancing and ensuring good mechanical, thermal and barrier properties of biodegradable polymer packaging films. Their incorporation in biodegradable food packaging films has also lead to enhanced antioxidant, antifungal and antibacterial properties of the food packaging and also oxygen barrier properties, UV protection, oxygen and ethylene scavenging resulting in an active food packaging material. The synthesis method has a significant influence on the resulting properties of metal oxide nanoparticles. Green synthesis using plant extracts and extracts of plant bio-waste as reducing and capping agents are one direction for obtaining metal oxide nanoparticles with improved antioxidant and antimicrobial properties. Utilization of bio-waste materials both for metal oxide nanoparticle synthesis and as a source of biopolymers for packaging enables better environmental protection and ensures a circular bioeconomy. In selection of metal oxide nanoparticles suitable for application in active packaging bio-nano-composites special attention needs to be paid to nanoparticle migration and cytotoxic activity in order to produce safe, active and biodegradable food packaging materials for the future

Didehydroroflamycoin pentaene macrolide family from Streptomyces durmitorensis MS405(T): production optimization and antimicrobial activity

AimsThe aim of this study was to improve production of pentaene 32,33-didehydroroflamycoin (DDHR) in Streptomyces durmitorensis MS405 strain to obtain quantities sufficient for in depth analysis of antimicrobial properties. Methods and ResultsThrough classical medium optimization conditions for stable growth, DDHR production within 7days of incubation was established. Yields of 215mgl(-1) were achieved in shake flask experiments in complex medium with mannitol as the primary carbon source. DDHR had poor antibacterial activity with minimal inhibitory concentrations (MIC) of 400gml(-1) for Staphylococcus aureus and Bacillus subtilis, while MIC of 70gml(-1) was determined for Candida albicans. Using flow cytometry and fluorescent microscopy, it was demonstrated that DDHR induced membrane damage in C.albicans followed by cell death. Combination studies with known antifungal nystatin showed that DDHR is a promising agent for the development of novel antimycotic treatments potentially less toxic for human cells. ConclusionsPentaene didehydroroflamycoin has no antibacterial activity but can be further developed for the application in antifungal therapy. Significance and Impact of the StudyThis study is the first report on the stable and production in high yields of a novel pentaene family that acts on Candida cell membranes and can be used in combination with known antifungals. Polyenes are still antifungal antibiotics of choice, and therefore, isolation and production of new lead structures are highly significant

Seasonal variations of microbiological parameters of water quality of the Velika Morava river Serbia

In this study, we investigated the level of sanitary pollution and organic contamination of the Velika Morava River, the largest river in central Serbia. Samples of water for microbiological analysis were collected at 5 sites, monthly, from April 2010 to February 2011. Sanitary analysis, i.e. enumeration of total and fecal coliforms and intestinal enterococci, indicated moderate to critical fecal contamination, while organic load assessment (oligotroph to heterotroph ratio, index of phosphatase activity) revealed the category of moderately polluted water. We also investigated seasonal variations of these groups of bacteria and the factors that could contribute to these differences. Our results showed that the micro- biological quality of the water in the Velika Morava River during different seasons is affected by numerous factors such as unequal loading of wastewaters, solar irradiation, and relations of flow/dilution and rainfall/runoff.Projekat ministarstva br. 173025, br. 177045 i br. 04300

Alginate-derived activated carbon hybridized with NiMn2O4 for use in supercapacitors

Transition metal oxides (TMOs) are promising materials because of their specific properties enabling their application in energy solutions, such as their pseudocapacitive behavior enabling utilization as electrode materials in supercapacitors. Activated carbon is a material well known as an electric double layer capacitor (EDLC). Bringing together the two different capacitor materials- TMOs as pseudocapacitors and carbon materials as EDL capacitors is the goal for generating future generation supercapacitors. Nickel manganite is a material of interest because of various oxidation states of manganese which provide its reactivity in oxidoreduction reactions, enhancing the pseudocapacitive behavior. Herein, we synthesized nano-sized nickel manganite by a sol-gel combustion synthesis process using glycine as fuel and subsequent calcination process. The structure and morphology of synthesized material was investigated via XRD, FESEM, and FTIR spectroscopy. Specific surface area and was determined from measured nitrogen desorption/desorption isotherms. Activated carbon was obtained by pyrolytic carbonization of alginate hydrogel in nitrogen atmosphere and activation with KOH. The material was combined with synthesized NiMn2O4 nanopowder and tested as supercapacitor electrode. The second alternative was incorporating NiMn2O4 powder into alginate hydrogel, followed by pyrolysis in nitrogen atmosphere to obtain a NiMn2O4 -activated carbon composite. The obtained materials were electrochemically characterized with cyclic voltammetry (LV) and galvanostatic chronopotentiometry to get galvanostatic charge-discharge curves. We calculated high specific capacitance values ranging to several hundred F/g, showing our hybrid material is a promising electrode in a supercapacitor system

Humidity sensing properties of nanocrystalline pseudobrookite (Fe2TiO5) based thick films

Pseudobrookite based nanopowder was obtained by solid state synthesis of starting hematite and anatase nanopowders in the weight ratio 55:45. Structural and morphological properties were analyzed using X-ray diffraction (XRD), BET, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) confirming the formation of nanocrystalline pseudobrookite. The obtained powder was mixed with a binder (ethyl cellulose), dispersant (alpha-terpinol) and adhesion agents (acetic acid and distilled water) to obtain a thick film paste. It was screen printed on alumina substrate with interdigitated PdAg electrodes and fired at 600 degrees C for 30 min. Formation of a porous nanocrystalline thick film structure was shown using Scanning electron microscopy (SEM), while Hall measurements enabled determination of carrier mobility. Change of impedance response in the frequency range 42 Hz-1 MHz with humidity was analyzed at room temperature (25 degrees C) and 50 degrees C in the relative humidity range 30-90% and 40-90%, respectively. At 42 Hz, and room temperature the impedance reduced similar to 28 times, while at 50 degrees C it reduced similar to 147 times in the relative humidity range 40-90%. The sensor showed rapid response (16 s) and relatively low hysteresis (8.39% at 25 degrees C and 2.64% at 50 degrees C) showing that this is a promising material for application in humidity sensing

ACTIVATION OF DOMESTIC ALUMINA AND TESTING OF POSSIBILITIES FOR APPLICATION IN SOME MINERAL BASE OILS RAFINATION

Mineral base oils are extracted from oil fractions of naphta that has boiling point of over 350 °C, and contain different kinds of carbohydrates and hetero-compunds. Removal of unwanted compunds from mineral base oils in domestic rafineries is made by rafination of imported commercial clays. For ther eventual replacement there has been conducted a testing of various domestic adsorbens. In this paper, examples of natural alumina from the vicinity of Sipovo are previously activated with sulphuric acid, and then used for rafination of naphtenic and hydrocracked base oil in laboratory conditions. Emerged changes on mineral base oils are followed by corresponding standardised methods. Results of testing showed that, by refining the given base oils with activated alumina, one can achieve good results and therefore further explorations shoud be continued, because of their commercial application in semi-industry and industry condition

Nickel manganite-carbonized alginate composite for use as energy storage electrodes

Nickel-manganite is a versatile material used in many technology applications. One of the established uses is as a supercapacitor electrode. The advantage of this type of material is the abundance of required metals, compared to noble metals, the synthesis methods' simplicity, and high redox activity. Metal-oxide battery materials are usually combined with activated carbon to enhance the specific surface area and add to energy storage capacity via surface charge accumulation. In the current work, nickel manganite was synthesized via the sol-gel combustion synthesis method with glycine as fuel and nitrate ions as oxidizers. The post-combustion amorphous powder was calcined at temperatures between 300 and 800 °C. Powders were structurally characterized. Obtained materials were tested as energy storage electrodes in a three-electrode cell setup in 6 M KOH aqueous solution as electrolyte. Methods embedded in electrochemical characterization were cyclic voltammetry (CV), electric impedance spectroscopy (EIS) and constant current chronopotentiometry at different current densities to obtain galvanostatic charge-discharge (GCD) curves. Results show considerable charge storage activity, which can be ascribed to oxido reduction reactions of manganese ions and charge accumulation on the surface of the activated carbon