Thermal relaxation of magnetic clusters in amorphous Hf_{57}Fe_{43} alloy

The magnetization processes in binary magnetic/nonmagnetic amorphous alloy Hf_{57}Fe_{43} are investigated by the detailed measurements of magnetic hysteresis loops, temperature dependence of magnetization, relaxation of magnetization and magnetic ac susceptibility, including a nonlinear term. Blocking of magnetic moments at lower temperatures is accompanied with the slow relaxation of magnetization and magnetic hysteresis loops. All of the observed properties are explained with the superparamagnetic behaviour of the single domain magnetic clusters inside the nonmagnetic host, their blocking by the anisotropy barriers and thermal fluctuation over the barriers accompanied by relaxation of magnetization. From magnetic viscosity analysis based on thermal relaxation over the anisotropy barriers it is found out that magnetic clusters occupy the characteristic volume from 25 up to 200 nm3 . The validity of the superparamagnetic model of Hf_{57}Fe_{43} is based on the concentration of iron in the Hf_{100-x}Fe_{43} system that is just below the threshold for the long range magnetic ordering. This work throws more light on magnetic behaviour of other amorphous alloys, too

Nanostructured platinum based catalysts for electrooxidation of small organic molecules prepared by microemulsion method

Pronalazak novih materijala koji bi omogućili komercijalizaciju gorivnih spregova i doprineli smanjenju upotrebe fosilnih goriva u proizvodnji energije je od velikog značaja za razvoj savremenog društva. Zbog toga je broj naučnih radova posvećen ovom problemu u značajnom porastu tokom proteklih godina. Kada je u pitanju oksidacija malih organskih molekula kao potencijalnih goriva za gorivni spreg, pored problema visoke cene platine koja se koristi kao katalizator, prisutan je i problem trovanja površine platine ugljen-monoksidom koji se formira kao intermedijar anodne reakcije. U ovom radu nanočestice platine na ugljeničnom nosaču sintetizovane su mikroemulzionim postupkom. Dodatkom različitih količina aditiva HCl tokom sinteze (od 0 do 35 %) ispitan je uticaj dodatka aditiva na oblik nanočestica. Pri optimalnoj koncentraciji od 25% HCl sintetizovane su nanočestice kubnog oblika. Četiri sintetizovana katalizatora okarakterisana su termogravimetrijskom analizom (TGA), rendgenskom difrakcijom X-zraka (XRD), transmisionom elektronskom mikroskopijom (TEM) i transmisionom elektronskom mikroskopijom visoke rezolucije (HRTEM). Ovim metodama potvrđena je promena oblika nanočestica izazvana dodatkom aditiva, utvrđen je udeo metala u katalizatoru (20%) i određena je veličina čestica, koja raste sa porastom udela aditiva (od 4 do 8 nm prema TEM analizi). Elektrohemijskom karakterizacijom i ispitivanjem reakcija oksidacije mravlje kiseline i metanola na ovim katalizatorima, ustanovljeno je da katalizator sa nanočesticama kubnog oblika, i većim udelom preferencijalno orijentisanih ravni (100) pokazuje bolju aktivnost za ove reakcije od katalizatora Pt sa konvencionalnim kub-oktaedarskim česticama. Razlog tome leži u lakšem uklanjanju adsorbovanog CO sa površine nanočestica sa zastupljenim kubnim oblikom.Development of novel materials that would enable the commercialization of fuel cell technology and contribute to reduction of fossil fuel usage in energy production is of great importance for the progress of modern society. As a result, the number of scientific papers devoted to this problem is in a significant increase over the past years. When it comes to the oxidation of small organic molecules (SOM) as potential fuel for the fuel cells, in addition to the problem of the high price of platinum used as a catalyst, there is a problem of poisoning the platinum surface by carbon-monoxide formed as an intermediate in the anodic reaction. In this research carbon supported platinum nanoparticles were synthesized by a water-in-oil microemulsion synthesis procedure. The effect of HCl as a capping agent on nanoparticle shape was investigated by adding up to 35 % HCl in the water phase of the microemulsion. The optimal HCl amount was found to be 25%, in which case platinum was synthesized in the form of cubic-shaped nanoparticles. Four prepared catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and (high resolution) transmission electron microscopy (HR)TEM. These analyses confirmed the change in particle shape induced by the capping agent. Metal loading in catalyst powder was determined to be close to 20%, and the particle size calculated from TEM data went from 4 to 8 nm, with the increase of the HCl amount used. The electrochemical characterization and the investigation of these samples in the reactions of formic acid and methanol oxidation revealed improved catalytic performance of the sample that predominantly contained cubic-shaped nanoparticles compared to conventional cube-octahedron shaped particles. The reason of the improved activity and stability of this catalyst lies in the facilitated CO removal from the catalyst surface, and thus improved tolerance to surface poisoning

ECONOMIC ANALYSIS OF FRESHWATER FISH PRODUCTION IN THE REPUBLIC OF SERBIA

The authors present the basic characteristics of the fish production in the Republic of Serbia. In the case of the fishpond "OZZ Despotovo", in the municipality of Bačka Palanka, the main economic indicators achieved in the production of freshwater fish (carp, grass carp, silver carp, catfish) are analyzed. The observed production requires very high investment per unit area (€ 4,381.39 ha-1). Despite significant investment, achieved economic results are relatively modest (the contribution margin € 892.15 ha-1; the cost-effectiveness ratio 1.09; the profit rate 8.10%). System support of country in the modernization of existing fishponds and raising the new ones, it can significantly contribute to the improvement of production and economic results in the fish production on the territory of the Republic of Serbia

Uticaj različitih tipova kombajna za ubiranje kamilice na kvalitet ubiranja i visinu dobiti u proizvodnji kamilice

This paper presents the results of three conceptually different types of chamomile harvester and their impact on the quality of the harvested chamomile and profit during the production process. Three working modes of each harvester are considered and values of realized losses and the quality of harvested chamomile are determined. It was found that choosing the type of engaged harvester and its working mode can affect the quality of harvested chamomile, as well as the profit achieved in the entire production process. .U ovom radu su prikazani rezultati istraživanja tri koncepcijski različita tipa kombajna za ubiranje kamilice i njihov uticaj na kvalitet ubrane sirovine i ostvarenu dobit tokom procesa proizvodnje. Posmatrana su tri režima rada svakog od kombajna i utvrđeni su vrednosti ostvarenih gubitaka i kvaliteta ubrane kamilice. Utvrđeno je da se izborom tipa angažovanog kombajna i režima rada može uticati na kvalitet ubrane kamilice, kao i na ostvarenu dobit u celokupnom proizvodnom ciklusu.

Triticum aestivum ir T. durum genetiniai parametrai kokybės technologinėms savybėms Serbijoje

Proteins are important in determining the nutritional value of wheat, and among them gluten determines the baking quality of bread wheat and pasta-making technological properties of wheat. By assessing genetic parameters of wheat quality traits, it is possible to elucidate potential for improvement. The plant material consisted of 30 genotypes of bread and durum wheat of worldwide origin. The trials were sown at three locations in Serbia during two vegetation seasons 2010-2011 and 2011-2012. Protein content, wet gluten content, Zeleny sedimentation volume and deformation energy were determined by near infrared spectrometry. The objectives of this investigation were to assess: i) variability, components of variance, heritability in a broad sense (hb2)expected genetic advance for protein content, wet gluten content, Zeleny sedimentation volume and deformation energy; ii) associations between agronomic characteristics and protein content, wet gluten content, Zeleny sedimentation volume and deformation energy in order to determine indirect selection feasibility. In durum wheat, the highest coefficients of genetic and phenotypic variation (CVg and CVph) were recorded for deformation energy in bread wheat (18% and 18.4%, respectively), whereas the lowest values of 4.1% and 4.6% were shown for protein content. The relation genetic component of variance (σg2)/component of variance due to genotype × environment interaction (σge2) < 1 was observed for protein content (3.2), wet gluten content (2.9) and deformation energy (3.9), and equal to one for Zeleny sedimentation volume, in bread wheat. In durum wheat, σge2/σg2< 1 was detected for protein content (1.4), wet gluten content (1.5), Zeleny sedimentation volume (2.1) and deformation energy (1.4). Considering very high and high hb2 observed for deformation energy and Zeleny sedimentation volume (95.8% and 86.2%, respectively) in bread wheat, coupled with high genetic advance (36.3% and 28.1%, respectively), success from classical breeding can be anticipated. Grain thickness was strongly associated with Zeleny sedimentation volume, and to a lesser extent with protein content, wet gluten content and deformation energy in bread and durum wheat, and along with grain vitreousness in durum wheat, can serve for indirect selection

Razvoj savremenih poljoprivrednih mašina za nove tehnologije ratarske proizvodnje

This reading indicates the projection of development of agricultural machines and tools within tractor assemblies that may be used for classic and reduced land cultivation and direct sowing. The reading signifies the synthesis of scientific projection of development of agricultural machines and tools as well as points to advanced production of tractors and attachable units and tools. In addition, the electronic equipment installed in the tractor’s cabin has been also provided for and described as information, since the equipment controls the tractor’s mode of operation and its guidance via satellite.U radu je prikazana prognoza razvoja poljoprivrednih mašina i oruđa u sastavu traktorskih agregata koji mogu da se koriste za klasičnu i redukovanu obradu zemljišta i direktnu setvu. Rad predstavlja sintezu naučne prognoze razvoja poljoprivrednih mašina i oruđa i savremene proizvodnje traktora i priključnih mašina i oruđa. Pored ovoga informativno je opisana elektronska oprema koja je instalirana u kabini traktora preko koje se kontroliše režim rada traktora, kao i mogućnost navođenja rada traktora preko satelita

Istraživanje novog tehničko-tehnološkog rešenja u zasnivanju voćnjaka kombinovanim oruđem rigoler-razrivač u obradi zemljišta

Modern agriculture requires the use of modern technology, with new technical and technological solutions. Basic agro-technical operation in phase of establishing orchards and vineyards that requires large amounts of energy is plowing, for its specificity called rigoling. Trenching phase consumes greatest portion of energy in the processing and preparation of land in general and especially for the establishment of cultural agricultural fruit-grape production. There are more operational technologies, and this paper analyses classical technology, and combined technology using rigoler and plowing tools for soil cultivation. When classic technologies are applied, soil is cut and sectioned, moved and crushed, thus creating loose soil layer. The depth of processed soil is different for different fruit- grape crops, depending on the needs of the root system, as penetration depth and the breadth of development, ranging between 60 and 100 cm. Such technology moves active soil layer to the inactive bottom of the furrow, while inactive soil layer is removed to the surface. This technology has to be defined for different soil types. Combined technical-technological solution using a rigoler with built-in plow enables the achievement of working depth required by the root system, but the inactive soil layer is not moved to the surface of the plowed soil. The lower topsoil layer is only shaken and broken. Work technology combining rigoler and plow in one pass, can significantly increase technological production, while saving significant amounts of energy. This technology should be applied to avoid unnecessary expenditure of energy. .U radu su prikazani rezultati ostvarenih vučnih otpora pri rigolovanju zemljišta sa plugom rigolerom na dubini od 60 cm, 70 cm, 80 cm i 90 cm, kao i vučni otpori rigolera sa dodatnim radnim organom u obliku dleta. Dodatkom dleta, dubina rigolovanja po varijantama rada, povećana je za 10 cm, 15 cm i 20 cm. Dobijeni rezultati pokazuju da na povećanim dubinama rigolovanja, specifičan otpor zemljišta ima nepromenjenu vrednost kao i pri samom rigolovanju. Ovo se postiže time što je odnos povećane dubine rigolovanja veći od povećanog vučnog otpora sa dodatkom dleta. Ekonomičnost upotrebe dleta je do 70 cm rigolovanja i 20 cm dubine rada dleta. Iznad 70 cm rigolovanja primena dleta se ekonomski smanjuje, jer se na toj dubini ispunjava agrotehnički zahtev.

Uređenje, korišćenje i zaštita poljoprivrednog zemljišta opštine UB

The Ub municipality is located in the north-east end of the Podrinjsko-Kolubarski region. The total area of the Ub municipality is 45670 ha or 456.7 km2. The agricultural area takes 35471.55 ha or, approximately, 77.67% of the municipality’s territory. Cultivable agricultural land takes 32955.18 ha, or 71.16%, which is distinguished by relatively large amounts of arable areas, where fields and gardens take 29470.05 ha, or 89.42% of the cultivable areas, which is an indicator that the most common activity in the Ub municipality is grain cultivation (corn and wheat). Fruit-gardens and wineyards take an area of 1953.55 ha, or 4.65%. Meadows are on an area of 5.93%. Soils of the Ub municipality, according to existing data, are distinguished by unfavorable physical and mechanical characteristics, with needs for repairs by means of different types of soil reclamation techniques. Analysis of the usable structure of the agricultural lands shows that the estates are small, and the average area of a demesne is 3.4 ha per household. The average parcel size is 0.40 ha per each cultivated crop. There are no commasative areas and no arranged irrigation and drainage systems, according to data gathered by the Regional Unit of Ub, inclusive 31st of April, 2007. Possible positive results of arrangement, exploitation and protections of the agricultural land of the Ub municipality are many, of which the most important are: Switching from a traditional extensive agricultural production to an intense agricultural production; Increase of the number of registered and educated agriculturists, organizing of the business connecting of family households; agricultural products in compliance with high quality and safety standards; a skilled and developed consultative and informative agricultural service, which monitors agriculturist’s work; intensified sustainable development of the rural regions with the development of organic production; a reduced negative trend of the country-side to city migration; a created consciousness about the need for the protection of the environment from harmful effects of the agricultural production.Opština Ub se nalazi na severoistočnim delu Podrinjsko - Kolubarskog regiona. Ukupna površina opštine Ub je 45670 ha ili 456,7 km2. Poljoprivredne površine zauzimaju 35.471,55 ha ili, približno 77,67% teritorije opštine. Obradivog poljoprivrednog zemljišta ima 32955,18 ha ili 72,16%, koje se odlikuje relativno visokom zastupljenošću oraničnih površina, gde njive i vrtovi zauzimaju 29470,05 ha ili 89,42% obradivih površina, što ukazuje da je najzastupljenija delatnost u opštini Ub, ipak gajenje žitarica (kukuruz, pšenica). Voćnjaci i vinogradi su na površini od 1953,55 ha ili 4,65%. Livade se nalaze na površini 5,93%. Zemljišta opštine Ub prema postojećim podacima, odlikuju nepovoljne fizičko-mehaničke osobine, sa velikim potrebama za popravku sa primenom različitih pedo-meliorativnih mera. Analiza upotrebne strukture poljoprivrednog zemljišta daje karakteristike da su zemljišni posedi malih površina, gde je prosečna veličina poseda 3,4 ha po domaćinstvu. Prosečna veličina parcele je 0,40 ha po gajenoj poljoprivrednoj kulturi. Nema komasacionih površina, kao ni uređenih sistema za navodnjavanje i odvodnjavanje, prema podacima Područne jedinice Ub, zaključno sa 31. aprilom. 2007. godine. Mogući pozitivni rezultati uređenja, korišćenja i zaštite poljoprivrednog zemljišta Opštine Ub su mnogobrojni, od kojih su najvažniji: Prelazak sa tradicionalne ekstenzivne poljoprivredne proizvodnje, na intenzivnu poljoprivrednu proizvodnju; povećanje broja registrovanih i edukovanih poljoprivrednika, organizovanje odgovarajućih načina poslovnog povezivanja porodičnih gazdinstava; poljoprivredni proizvodi u skladu sa visokim standardima kvaliteta i bezbednosti; stručna i razvijena savetodavna i informaciona poljoprivredna služba koja prati rad poljoprivrednika; intenziviran održivi razvoj sela sa razvojem organske poljoprivredne proizvodnje; usporen negativni trend migracije selo - grad; i stvorena svest o potrebi zaštite životne sredine od štetnih efekata poljoprivredne proizvodnje

Alkyl polyglucoside vs. ethoxylated surfactant-based microemulsions as vehicles for two poorly water-soluble drugs: physicochemical characterization and in vivo skin performance

Two types of biocompatible surfactants were evaluated for their capability to formulate skin-friendly/non-irritant microemulsions as vehicles for two poorly water-soluble model drugs differing in properties and concentrations: alkyl polyglucosides (decyl glucoside and caprylyl/capryl glucoside) and ethoxylated surfactants (glycereth-7-caprylate/caprate and polysorbate 80). Phase behavior, structural inversion and microemulsion solubilization potential for sertaconazole nitrate and adapalene were found to be highly dependent on the surfactants structure and HLB value. Performed characterization (polarized light microscopy, pH, electrical conductivity, rheological, FTIR and DSC measurements) indicated a formulation containing glycereth-7-caprylate/caprate as suitable for incorporation of both drugs, whereas alkyl polyglucoside-based systems did not exhibit satisfying solubilization capacity for sertaconazole nitrate. Further, monitored parameters were strongly affected by sertaconazole nitrate incorporation, while they remained almost unchanged in adapalene-loaded vehicles. In addition, results of the in vivo skin performance study supported acceptable tolerability for all investigated formulations, suggesting selected microemulsions as promising carriers worth exploring further for effective skin delivery of model drugs