Bifurcations in nonlinear models of fluid-conveying pipes supported at both ends

Stationary bifurcations in several nonlinear models of fluid conveying pipes fixed at both ends are analyzed with the use of Lyapunov-Schmidt reduction and singularity theory. Influence of gravitational force, curvature and vertical elastic support on various properties of bifurcating solutions are investigated. In particular the conditions for occurrence of supercritical and subcritical bifurcations are presented for the models of Holmes, Thurman and Mote, and Paidoussis.Comment: to appear in Journal of Fluids and Structures; 6 figure

The influence of powder particle size on properties of Cu-Al2O3 composites

Inert gas atomized prealloyed copper powder containing 2 wt.% Al (average particle size ≈ 30 μm) and a mixture consisting of copper (average particle sizes ≈ 15 μm and 30 μm) and 4 wt.% of commercial Al2O3 powder particles (average particle size ≈ 0.75 μm) were milled separately in a high-energy planetary ball mill up to 20 h in air. Milling was performed in order to strengthen the copper matrix by grain size refinement and Al2O3 particles. Milling in air of prealloyed copper powder promoted formation of finely dispersed nano-sized Al2O3 particles by internal oxidation. On the other side, composite powders with commercial micro-sized Al2O3 particles were obtained by mechanical alloying. Following milling, powders were treated in hydrogen at 400 0C for 1h in order to eliminate copper oxides formed on their surface during milling. Hot-pressing (800 0C for 3 h in argon at pressure of 35 MPa) was used for compaction of milled powders. Hot-pressed composite compacts processed from 5 and 20 h milled powders were additionally subjected to high temperature exposure (800°C for 1 and 5h in argon) in order to examine their thermal stability. The results were discussed in terms of the effects of different size of starting powders, the grain size refinement and different size of Al2O3 particles on strengthening, thermal stability and electrical conductivity of copper-based composites

DETERMINATION OF CHANGE IN CONTENT OF HEAVY AND RADIOACTIVE METALS IN DRINKING WATER BY AN INDIRECT ANALYSIS METHOD BASED ON SCALE TESTS

In this paper the content of metal in drinking water was determined in two samples, one from 2008 and other from 2010, by the indirect method based on the analysis of scale, which had originally been suggested by Rajkovic and associates. Received results confirmed that drinking water according to the metal content was of constant level (metals are lower than MAC values), but with increased content of U. By the method of fraction extraction it was proved that increased content of U regarded mainly to natural U, and less to U of anthropogenic origin. The increased content of isotope 90Sr was also noticed, probably as the effect of increased presence of alkaline earth metals. The analysis structure of scale by the usage of SEM determined that the dominant form was calcium carbonate of crystal structure of hexagonal shape which corresponded to calcite. By Röentgen diffraction analysis of dust it was determined the content of calcite which contained CaO; MgO; FeO; MnO and CO2 and it belongs to medium manganese calcites. All the analyses done in this paper, confirmed that indirect method of determination of metal content had been reliable and applicable for determination of low concentrations of metals in drinking water

Modulation of the differentiation and function of human monocyte-derived Langerhans cells in vitro

Uvod. Langerhansove ćelije (LĆ) predstavljaju subpopulaciju dendritskih ćelija (DĆ) koja ima ulogu u započinjanju imunskog odgovora na antigene koji su dospeli u epidermis ili sluzokože. DĆ vezuju molekulske obrasce patogena (engl. Pathogen-associated molecular patterns, PAMP) i oštećenih ćelija (engl. Damage-associated molecular patterns, DAMP) pomoću membranskih i citosolnih receptora za prepoznavanje molekulskih obrazaca (engl. Pattern recognition receptors, PRR). Među PRR su najviše proučavani receptori slični Tollu (engl. Toll-like receptors, TLR) i lektinski receptori C-tipa (engl. C-type lectin receptors, CLR). Uspostavljanje kontakta između DĆ i PAMP i DAMP je ključni događaj kojim se povezuju urođena i stečena imunost, što za posledicu ima eradikaciju antigena i nastanak imunološke memorije ili izazivanje periferne tolerancije. Nakon internalizacije i obrade PAMP i DAMP u proinflamacijskom okruženju, DĆ započinju migraciju u T-zavisne zone regionalnih limfnih čvorova u toku koje fenotipski i funkcionalno sazrevaju. Aktivacija CD40 receptora na DĆ nakon vezivanja liganda ovog molekula (CD40L) ispoljenog na površini aktivisanih T-limfocita dovodi do okončanja maturacije DĆ. Tada one postaju potpuno efikasne antigen-prezentujuće ćelije sposobne da polarizuju imunski odgovor CD4+ T-limfocita u Th1 smeru i da indukuju citotoksičnu efektorsku funkciju CD8+ T-limfocita. Konvencionalne DĆ, sa napred navedenim funkcionalnim karakteristikama, su našle primenu u prevenciji i terapiji infektivnih bolesti i maligniteta u obliku DĆ vakcina. Iako je za in vivo ili in vitro sazrevanje DĆ često dovoljna stimulacija samo jednim agonistom TLR ili CLR, fenotipski stabilniji i funkcionalno potentniji imunski odgovor u eksperimentalnim i kliničkim ispitivanjima se najčešće dobija tek kombinovanom primenom njihovih analoga, što je posledica specifične integracije različitih, međusobno nezavisnih, unutarćelijskih signala. Nakon nedavne potvrde da LĆ imaju sposobnost unakrsne prezentacije antigena stvorili su se uslovi da i one postanu kandidati za DĆ vakcine. Do sada nije bilo studija koje su ispitivale načine modulacije fenotipskih i funkcionalnih karakteristika LĆ koji mogu imati potencijalnu ulogu u razvoju maturacijskih protokola neophodnih za terapijsku primenu ovih ćelija...Introduction. Langerhans cells (LCs) represent a subpopulation of dendritic cells (DCs) whose function is to initiate immune responses against the antigens from epidermis and mucoses. DCs bind pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) via membrane and cytosolic pattern recognition receptors (PRRs). The most frequently studied PRRs are Toll-like receptors (TLRs) and C-type lectine receptors (CLRs). Similarly to conventional DCs, the contact established between LC’s PRRs and PAMPs and DAMPs is the key event that links innate and adaptive immunity and leads to eradication of the antigen, initiation of the peripheral tolerance and introduction of the immunological memory. After LCs internalise and process PAMPs and DAMPs in a proinflammatory environment, they start to migrate toward T-dependent regions of the regional lymph nodes and, at the same time, become phenotipically and functionally mature. The activation of the CD40 molecule on LCs with a CD40 ligand (CD40L) expressed on the surface of activated T-lymphocytes brings the maturation of LCs to its end, when they become fully efficient antigen-presenting cells, capable of inducing the Th1 polarisation of CD4+ T-lymphocytes and citotoxic effector functions of CD8+ T-lymphocytes. Conventional DCs with the aforementioned functional characteristics are used in the prevention and therapy of infectious or malignant diseases as DC-vaccines. Although DCs require stimulation with a single TLR or CLR agonist to become mature in vitro and in vivo conditions, phenotipically stable and functionally more potent immune response of these cells in experimental and clinical studies is usually achieved only after combined treatment with analoges of these receptors because of the specific integration of the various, mutually independent, intracellular signals. LCs became candidates for DC-vaccines after recent confirmation that they are capable to cross-present antigens. Until now, there were not any studies that examined the means to modulate phenotypic and functional characteristics of LCs that could have a potential role in the development of maturational protocols necessary for therapeutic application of these cells..

Flame-weeding in maize and soybean

Prva naučna istraživanja u Srbiji na temu primene plamena u suzbijanju korova u redu useva započeta su 2010. godine u Institutu za ratarstvo i povrtarstvo iz Novog Sada. Mašina za primenu plamena je napravljena u Srbiji od domaćih komponenti modifikacijom četvororednog kultivatora. Dodavanjem dva rezervoara po 35 kg propana, gasnih instalacija i dva plamenika bočno na svaki red, dobijena je funkcionalna mašina koja plamenom suzbija korove koji su u početnim fazama razvoja i nalaze se u redu useva, a između redova ih suzbija kultivacijom. Rastuće doze propana 20–100 kg ha-1 primenjene su u kukuruzu (3, 5 i 7 listova) i soji (1, 3 i 5 trolista), bez prisustva korova, kako bi se ispitala tolerantnost gajene biljke na plamen. Za ispitivanje efikasnosti suzbijanja korova, primenjeno je 16 tretmana. Primena plamena je kombinovana sa primenom drljače sa opružnim zupcima i međurednog kultivatora. Efekti na korove i gajene biljke upoređivani su sa kontrolom sa i bez uklanjanja korova. Na osnovu izmerenih temperatura na različitim visinama, utvrđeno je da je unakrsna pozicija plamenika pod uglom od 45o najbolja sa aspekta oštećenja gajene biljke i efikasnosti na ponikle korove. Kukuruz bolje toleriše plamen od soje i generalno je tolerantan na plamen u svim fazama razvoja. Pravovremenom primenom 40 kg ha-1 propana dobija se visoka efikasnost u suzbijanju širokolisnih korova, dok su travni korovi nešto tolerantniji, pa je potrebno tretman ponoviti i kombinovati sa drugim mehaničkim merama suzbijanja korova. U obe godine ispitivanja, najveći prinos kukuruza 6,02 i 7,10 t ha-1 je ostvaren tretmanom dva puta 40 kg ha-1 propana u fazama 3 i 7 listova kukuruza. Kod soje najveći prinos 2,11 i 3,56 t/ha ostvaren je kod tretmana sa drljačom sa opružnim zupcima u fazama prostih listova i 1. trolista, a u 3. trolistu primenjeno 30 kg ha-1 propana. Bruto marže sa preporučenim tretmanima iznose 30.302 i 58.674 din. ha-1 za kukuruz, odnosno 300.784 i 375.583 din. ha-1 za soju

Changes of biomechanical variables of the stroke under influence of rowing 2000m with maximum speed on rowing ergometer

SAŽETAK: Istraživanje je realizovano na uzorku od 73 veslača iz šest veslačkih klubova iz Srbije, prosečne starosti 16 ± 2godine, prosečne telesne mase 74 ± 10kg i prosečne telesne visine 184 ± 8cm. Za prikupljanje podataka korišćen je veslački ergometar „Concept II –d“. Za merenje varijabli zaveslaja korišćen je instrument „FITROROWER“ firme „WEBA SPORT“, a za obradu podataka program „SOFTWARE EXPERT“. Praćeno je 18 biomehaničkih varijabli zaveslaja: ukupno vreme na 2000m (s), ukupan broj zaveslaja na 2000m (zav), prolazno vreme na 100m (s), brzina na veslačkom ergometru (m/s), trajanje aktivne faze (s), trajanje pasivne faze (s), ritam (%), frekvencija zaveslaja (zav/min), trajanje zaveslaja (s), pređeni put rukohvata (cm), prosečna brzina rukohvata (m/s), prosečna sila zaveslaja (N), maksimalna sila (N), gradijent sile (s), odnos prosečne i maksimalne sile (%), odnos prosečne sile sa telesnom masom veslača (%), prosečna snaga (W), izvršeni rad (J). Pored razlika apsolutnih vrednosti, zabeležene su i razlike u varijabilnosti varijabli zaveslaja, kao i korelacije između samih varijabli kod različitih takmičarskih kategorija i nivoa kvaliteta veslača. Maksimalnu brzinu na veslačkom ergometru kao krajnji cilj, moguće je ostvariti na različite načine, sa različitim uticajem i doprinosom pojedinih varijabli zaveslaja. Moguće je definisati redosled stabilizacije uticaja određenih varijabli zaveslaja u doprinosu ostvarivanja visokih vrednosti brzine. Definisani modeli predstavljaju stanja i odnose između testiranih grupa veslača u Srbiji za vreme prelaznog perioda, sa ograničenom moći uopštavanja. Pri zadavanju načina ostvarenja brzine, (većeg ili manjeg uticaja pojedinih biomehaničkih varijabli zaveslaja) kod svakog pojedinog veslača na treningu i takmičenju treba uzeti u obzir njegove specifičnosti u smislu funkcionalnih, motoričkih i tehničko – taktičkih sposobnosti. Pri definisanju zadataka za pojedine treninge potrebno je biti posebno oprezan kod kadeta i juniora, gde pojavne oblike retardanata treba tretirati strpljivo, poštujući specifična pravila i ritam njihovog razvoja sportskog rezultata, ne odbacujući ih. Greške u veslačkoj tehnici moguće je definisati i po udelu određenih biomehaničkih varijabli zaveslaja u ostvarivanju prosečne brzine. Veslanje pri visokim vrednostima tempa, na 2000m maksimalnom brzinom na veslačkom ergometru, definiše sve takmičarske kategorije i nivoe kvaliteta veslača, kao izrazito homogene skupove po skoro svim biomehaničkim varijablama zaveslaja.Research was done on a sample of 73 rowers from 6 serbian rowing clubs, of average age 16 ± 2 years, average weight 74 ± 10kg, and average height 184 ± 8cm. Rowing machine „Concept II-d“ was used for gathering basic data. Stroke variables in real time was measured by „FITROROWER“ instrument „WEBA SPORT“, and they were processed on programe „SOFTWARE EXPERT“. Eighteen biomechanical variables of the stroke were measured: overall time on 2000m (s), overall number of the strokes for 2000m, lap times on 100m (s), speed on rowing ergometer (m/s), drive time (s), recovery time (s), rhythm (%), frequency (stroke/min), duration of the stroke (s), length of the handle movement (cm), average handle velocity (m/s), average force (N), force peak (N), time to force peak (s), average force and maximum force ratio (%), average force and rowers weight ratio (%), average power (W) and performed work (J). Diferences of absolute values, variability and corelation between stroke variables were defined between different competition catogories and quality level of rowers. Maximum speed on rowing ergometer as a main goal, is possible to achive on different ways, with different influence and contribution of specified variables of the stroke. It is possible to define order of stabilization on specified variables contribution of high speed. Defined models describe conditions and relations between tested groups of rowers in Serbia, during transition training period, with limited power of conclusion. During defining ways of achieving speed (higher or lower influence of some biomechanical variables) for every individual rower on training and competition, specific functional, motorical and techniqual-tactical capabilities, must be take into the consideration. During defining training tasks for rowers under 16 and juniors, special caution must be in power, where defined retardants must be treated with patience, and respect of their slower rhythm of sport result development, whithout rejection. Errors in rowing technique could be define also with influence specific stroke variables on achieving average speed. High frequency during rowing 2000m, defines extremly homogenous sets for all competition categories and quality level of rowers almost for all variables of the stroke

DETERMINATION THE QUALITY OF DRINKING WATER BY INDIRECT METHOD ON SCALE TEST

Investigation of the composition of elements in drinking water, from water network of Belgrade city, with indirect method. This method is based on the scale that is made with precipitation from the water during heating, indicated presence of alkali and alkaline earth elements to a greater extent and heavy metals which is quite expected. Somewhat unexpectedly the presence of some elements, whose presence leads to a greater amount isn’t desirable, because they have the cumulative effect (Hg, Pb, Ni, As ), which indicates that these are areas of developed industrial production. The water from which was formed scale found a greater presence of Fe, Cu, and Mn. Scale testing determined the presence of radioactive elements U and Sr in drinking water. Based on X-ray diffraction analysis of the composition of the sample is composed of a mixture Mg calcite and aragonite. Multidisciplinary approach to the analysis of the scale is defining the new original indirect method of determining the quality of drinking water, so far not recorded in the literature

Primena metode atomske apsorpcione spektrofotometrije (AAS) za određivanje sadržaja teških metala u fosfogipsu

Phosphogypsum is formed as a by-product in the process of 'green' phosphoric acid production. This is done in the so called 'wet process' by the action of sulphuric acid on raw phosphate at low temperature ( lt 100 °C). Despite the same molecular formula and marked similarity with natural gypsum, phosphogypsum contains more than 50 impurities, and this is directly connected with the type of phosphate used in the production cycle. The aim of this paper was to consider the possibility of using phosphogypsum for amelioration of solonetz soil, bearing in mind its content of heavy metals, which are rather toxic for human organism and which can be transferred from soil to various plants used in human nutrition. On the other hand, there are very few data in the literature about the determination of heavy metals in phosphogypsum. The content of heavy metals in phosphogypsum was determined by atomic absorption spectrophotometry because this method has broad application in ana­lytical practice due to its high sensitivity, selectivity and precision. The results of the investigation indicate the following average content of heavy metals (in ppm): Fe-785, Pb-45, Zn-45, Cd-7, Mn-8, Co-10, Ni-20 and Cu-17. For the investigation of the effect of phosphogypsum on solonetz soil the following points were taken into consideration: maximum recommended dose of phosphogypsum (7 t/ha) for the amelioration of solonetz soil and the weight of soil layer (from 0 to 20 cm) having an area of 1 ha. The results obtained indicate that the amounts of heavy metals that are introduced into the soil with 7 t/ha of phosphogypsum are in the range from 0.035 to 0.8% of their maximum permissible content for arable soils. This means that only long-term application of phosphogypsum would introduce significant amounts of these elements into the soil.Procesom dobijanja 'zelene' fosforne kiseline tzv. 'mokrim postupkom', dejstvom sumporne kiseline na sirovi fosfat na niskoj temperaturi ( lt 100 °C) kao nus-proizvod nastaje - fosfogips (sa faktorom 5:1, u odnosu na H3PO4). Uprkos istoj molekulskoj formuli i izraženoj sličnosti sa prirodnim gipsom, fosfogips sadrži preko 50 vrsta nečistoća, što je u direktnoj vezi sa vrstom fosfata koji je korišćen u proizvodnom ciklusu. Cilj rada bio je razmatranje mogućnosti primene fosfogipsa za melioraciju soloneca, sa aspekta sadržaja teških metala, koji su izuzetno toksični i kumulativni za čovekov organizam, a iz zemljišta prelaze u biljke, kojima se čovek hrani. Sa druge strane, u literaturi se nalaze veoma oskudni podaci o ispitivanju sadržaja teških metala u fosfogipsu. Sadržaj teških metala u fosfogipsu određivan je metodom atomske apsorpcione spektrofotometrije (AAS), budući da je to metoda koja je našla veliku primenu u praksi usled visoke osetljivosti, selektivnosti i preciznosti. Rezultati ispitivanja su pokazali sledeći sadržaj teških metala (u ppm): Fe-785, Pb-45, Zn-45, Cd-7, Mn-8, Co-10, Ni-20, Cu-17. Za ispitivanje uticaja primene fosfogipsa za melioraciju soloneca, uzeta je u obzir preporučena maksimalna norma za gipsovanje soloneca od 7 t/ha zemljišta i težina sloja debljine od 0 do 20 cm a površine 1 ha. Dobijeni rezultati su pokazali da se preporučenom maksimalnom normom za gipsovanje soloneca fosfogipsom unosi po 1 ha zemljišta od 0,035 do 0,8% od maksimalno dozvoljenog sadržaja teških metala - MDK vrednosti, što znači da bi tek višegodišnjom upotrebom fosfogipsa došlo do unošenja značajnijih količina ovih elemenata u zemljište. Kako se proces melioracije soloneca najčešće vrši u intervalu od 5 do 6 godina, unošenje teških metala bilo bi u zanemarljivoj količini i bez uticaja na životnu sredinu