Teorijski pristupi liderstvu u obrazovanju

In the paper we take into consideration a short review and the analysis of the major theoretical approaches to leadership with the special attention to modern thining about leadership in education. It is determined which approaches represent good basis for planning the activities with the purpose of promoting leadership in schools. The main conclusion of the analysis is that the shown theoretical approaches shed light to different aspects of leadership and that in the theoretical researches and practical considerations it is the integrative approach very often in need. The integrated leadership gives very pragmatic and operative frame for action in the direction of leadership.Polazeći od toga da su u domaćoj literaturi malobrojni pregledni radovi o liderstvu u obrazovanju, u ovom radu napravili smo kratak prikaz i analizu glavnih teorijskih pristupa liderstvu, sa posebnim osvrtom na savremena razmišlja- nja o liderstvu u obrazovanju, kako bismo utvrdili koji pristupi predstavljaju dobru osnovu za planiranje aktivnosti u cilju unapređivanja liderstva u školama. Jednim delom, reč je o pristupima koji se odnose na liderstvo “uopšte”, dok su drugi pristupi (poput transformativnog, pedagoškog i integrisanog liderstva) čvrsto zasnovani na nalazima istraživanja u obrazovanju. Glavni zaključak analize je da prikazani teorijski pristupi osvetljavaju različite aspekte liderstva i da je u teorijskim, istraživačkim i praktičnim razmatranjima često nužno imati integrativni pristup. Upravo zato se u radu posebno ističe značaj integrisanog liderstva kao savremenog pristupa koji, pored toga što je teorijski i empirijski dobro zasnovan, pruža veoma pragmatičan i operativan okvir za delovanje u pravcu razvoja liderstva u školama

On-line blind separation of non-stationary signals

This paper addresses the problem of blind separation of non-stationary signals. We introduce an on-line separating algorithm for estimation of independent source signals using the assumption of non-stationary of sources. As a separating model, we apply a self-organizing neural network with lateral connections, and define a contrast function based on correlation of the network outputs. A separating algorithm for adaptation of the network weights is derived using the state-space model of the network dynamics, and the extended Kalman filter. Simulation results obtained in blind separation of artificial and real-world signals from their artificial mixtures have shown that separating algorithm based on the extended Kalman filter outperforms stochastic gradient based algorithm both in convergence speed and estimation accuracy

Is a Lead Isotope Ratios in Wine Good Marker for Origin Assessment?

Lead isotope ratio pattern (206Pb/207Pb, 208Pb/206Pb, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb) was analyzed in 59 samples of Serbian wine, from four geographical regions. By utilization of powerful inductively coupled plasma mass spectrometry (ICP-QMS), lead isotope ratios were used as unique “fingerprint”, when combined with multivariate methods of analysis (Principal Component Analysis), provided information on the geographical origin of wine. In validation of ICP- QMS method and quantitative analysis, the certified reference material NIST SRM 981 was employed to test the mass-bias correction and thallium isotopes 203Tl and 205Tl (NIST SRM 997) as an internal standard. The obtained results were discussed in correlation with the corresponding values of LIRs of different European and Australian wines. In addition, the impact of anthropogenic Pb from different sources on the total Pb isotopic composition in Serbian wines was analyzed too. On the other side, the obtained values of Pb content were compared with the applicable health safety standards, according to the International Code of Oenological Practices

AIR POLLUTION AS A RISK FACTOR FOR PNEUMONIA

Abstract. Air pollution has been shown to exacerbate respiratory diseases such as pneumonia. The aim of this research was to investigate the relationship between the longterm exposure to air pollution, as a risk factor, and the development of pneumonia in the population. The observed sample consisted of Niš citizens of different age groups who lived in area with high concentrations of air pollutants (investigated group) such as the Square of the October Revolution, as well as the citizens of Niška Banja (control group) which is the zone with the lowest concentration of air pollution. The investigation was carried out in the Public Health Institute in Niš, in the period between 2000 and 2012. A sample of 500 participants from Niš and Niška Banja was split into three age groups: up to 25, between 26 and 50, and above 51. Modified WHO, British MRC and American Thoracis Society questionnaires were run among the investigated and contol population sample group. A significance test was performed using a Mantel-Haenszel chi square (χ2) statistic. This test was used to check for a statistically significant difference between the prevalence of pneumonia between the investigated group and the control group across all age groups. The odds ratio (OR) and relative risk (RR) were determined. The statistical significance between measured concentrations in the air at observed measured spots was determined using the Student's t-test. The highest value of the chi square test was determined in the age group up to 25 (RR = 8,00, OR = 8,87, p0,05.The obtained results prove that the prevalence of pneumonia is significantly higher in the exposed population than in the non-exposed, especially among younger than 25 years old.  Key words: air pollution, pneumoni

Uticaj klimatskih uslova na kontaminaciju zrna kukuruza sa aflatoksinom B1 i fumonizinima i njihova združena pojava

Agroecological and climatic conditions in Serbia greatly affected the development of toxigenic fungi and occurrence of mycotoxins in the maize. The presence of fungal toxigenic Aspergillus and Fusarium species and levels of aflatoxin B 1 (AFB 1) and sum of fumonisins B 1 , B 2 and B 3 (FBs) were established in 127 maize kernel samples harvested during 2012 (37 samples) and 2013 (90 samples). The periods of silking and grain filling of the maize in 2012 in comparison to 2013 were characterised with extremely dry spells, with high temperatures and low precipitation sums. The mean incidences of A. flavus and F. verticillioides were 50.4 and 11.7% in 2012 and 18.9 and 33.4% in 2013, respectively. According to the regulations of the World Health Organisation, unacceptable levels of AFB 1 (>20 μg kg-1) and FBs (>2000 μg kg-1) were established in the 30.6 and 24.1% samples of 2012 and 16.7 and 40% maize kernel samples of 2013, respectively. It can be concluded that high temperatures and low precipitation sums in 2012 favoured the development of A. flavus affecting the high level of AFB 1 , in comparison with F. verticillioides and the production of FBs. There was no positive correlation between the incidences of A. flavus and F. verticillioides, while a statistically significant positive correlation has been found between AFB 1 and FBs levels, in both investigated years (2012-2013). This indicates that the mycotoxin production depended more on weather conditions than on the distribution of corresponding toxigenic fungal species.Agroekološki i klimatski uslovi u Srbiji veoma su pogodni za razvoj toksigenih gljiva i njihovih mikotoksina u kukuruzu. Prisustvo toksigenih vrsta gljiva iz rodova Aspergillus i Fusarium, kao i nivoi aflatoksina B1 (AFB1) i ukupnih fumonizina B1, B2 i B3 (FBs) utvrđeni su u 127 uzoraka zrna kukuruza iz berbe tokom 2012 (37 uzoraka) i 2013. godine (90 uzoraka). U fenofazama svilanja i nalivanja zrna kukuruza u 2012. u odnosu na 2013. godinu zapaženi su ekstremno sušni periodi sa visokim temperaturama i niskim količinama padavina. Prosečne vrednosti za učestalost vrsta A. flavus i F. verticillioides bile su 50,4 i 11,7% u 2012., odnosno 18,9 i 33,4% u 2013. godini. Prema pravilniku Svetske zdravstvene organizacije (WHO) nedozvoljeni nivoi AFB1 (>20 µg/kg) i FBs (>2000 µg/kg) utvrđeni su u 30,6% i 24,1% uzoraka u 2012., odnosno u 16,7% i 40% uzoraka u 2013. godini. Na osnovu dobijenih rezultata zaključeno je da su visoke temperature i niske količine padavina u 2012. godini uslovile značajno veću učestalost A. flavus i visoku produkciju AFB1 u poredjenju sa vrstom F. verticillioides i produkcijom FBs. U obe ispitivane godine (2012-2013), između učestalosti A. flavus i F. verticillioides nije ustanovljena pozitivna korelacija, dok je statistički značajna pozitivna korelacija ustanovljena između nivoa AFB1 i FBs. Ovo ukazuje da produkcija mikotoksina je više zavisna od vremenskih uslova u odnosu na distribuciju toksigenih vrsta gljiva

Prognostic factors of mortality in elderly with community acquired pneumonia

Background/Aim. Community acquired pneumonia in elderly has specific clinical aspect and higher mortality in relation to younger patients. According to specific pneumonia severity assessment on admission and its importance in proper prediction of clinical course and outcome, the aim of this study was defining prognostic factors of mortality. Methods. This study included 240 patients aged ≥ 65 years with community acquired pneumonia. On admission, demographic characteristics, underlying diseases, physical symptoms and findings, laboratory values, chest radiography and oxygen blood saturation (SaO2) were analyzed. Multivariate analysis was used to identify characteristic prognostic factors which showed a statistical significance in relation to mortality. Results. Altered mental status, respiratory frequency ≥ 23/min and the presence of bilateral pneumonic infiltrates were defined as the most important prognostic factors of mortality (p < 0.001). These factors displayed 57.89% sensitivity, 100% specificity and 93.33% accuracy. Conclusion. The presence of identified characteristic prognostic factors on admission pointed out an adverse clinical course and outcome of community acquired pneumonia in elderly. Age and sex were not significantly associated with mortality

Patogenost izolata Aspergillus spp. poreklom iz Srbije

Species of the genus Aspergillus, section Flavi are facultative plant pathogens with the capability to contaminate primary agricultural products in the field, at harvest, in warehouses, and during processing. Infection is done through silk or injuries on maize ears. The objective of this study was to test pathogenicity of 25 A. parasiticus isolates on barley leaves. A parasiticus was isolated from maize kernels collected from 22 locations in Serbia during 2013-2015. Inoculation of the first barley leaf was done by the spore suspension of the fungus A. parasiticus. The spot sizes were statistically compared and this comparison showed that the isolate MRIZP 3930 was the least virulent. The isolate MRIZP 3819 was the most virulent seven days after inoculation and together with the isolate MRIZP 4265 was classified into the most aggressive group rated as 5. Pathogenicity was confirmed in all isolates.Vrste roda Aspergillus sekcije Flavi su fakultativní biljni patogeni, čija se sposobnost ogleda u kontaminaciji primarnih poljoprivrednih proizvoda u polju, tokom berbe, u skladištu i tokom procesa prerade. Infekcija se obavlja preko svile ili oštećenja na klipu kukuruza. Cilj ovog rada bio je da se oceni patogenost 25 izolata A. parasiticus na listovima ječma. Kulture A. parasiticus su izolovane iz uzoraka zrna kukuruza koji su prikupljani sa 22 lokaliteta u Srbiji u periodu 2013-2015. godina. Inokulacija prvog lista ječma izvršena je pomoću suspenzije spora gljive A. parasiticus. Statističkim poređenjem dobijenih vrednosti veličina pega, pokazano je da je najmanje virulentan izolat MRIZP 3930. Izolat MRIZP 3819 se izvojio kao najvirulentniji posle 7 dana inokulacije, a zajedno s izolatom MRIZP 4265 je svrstan u najagresivniju grupu koja je kategorisana ocenom 5. Svi ispitivani izolati su potvrdili patogenost

Fumonizin B1 u zrnu kukuruza, pšenice i ječma u Srbiji

A wide variety of commodities in the world have been analyzed for fumonisins contamination. However, they have mostly been reported in maize and maize-based foods and feeds. Just a few scientific researches were conducted to obtain results on natural contamination of wheat and barley with these mycotoxins. This survey was conducted to evaluate fumonisin B1 contamination in maize, wheat and barley grain in Serbia. A total of 203 maize, 180 wheat and 120 barley samples were obtained from different local warehouses between October 2007 and June 2009. Concentration of FB1 were analysed with the Enzyme-Linked Immunosorbent Assay (ELISA). Positive results were found in 70.7%, 60.6% and 34.1%, in the maize, wheat and barley samples, respectively. FB 1 concentration varied from 750 to 4900 μg kg-1, and the mean levels recorded were: 1225.7 kg-1 in maize; 852.7 μg kg-1 in wheat; and 768.2 μg kg-1 in barley. The mycotoxin contamination of cereals was affected by factors such as origin resistance, droughtstress, and insect damage and differed between the years of investigation The results obtained in this survey revealed that FB1 is frequent contaminant of cereal grains in Serbia. Considering that these products are consumed in large amounts either directly or as components of foods and feeds, the levels of contamination reported herein indicate a potential threat to animal and public health.Širok spektar proizvoda u svetu je analiziran na kontaminaciju fumonizinima. Međutim, prisustvo ovog mikotoksina uglavnom je zabeleženo u zrnu kukuruza i hrani na bazi kukuruza. Malo je istraživanja o prirodnoj kontaminaciji pšenice i ječma fumonizinima. Cilj ovog istraživanja bio je da se ispita kontaminacija fumonizinom B1 zrna kukuruza, pšenice i ječma u Srbiji. Ukupan broj od 203 uzoraka zrna kukuruza, 180 uzoraka zrna pšenice i 120 uzoraka zrna ječma sakupljenih u različitim lokalitetima Srbije u periodu oktobar 2007. - jun 2009. godine. Koncentracija FB1 u zrnu žita je analizirana ELISA testom. FB1 je utvrđen u 72% uzoraka zrna kukuruza, 60,6% uzoraka zrna pšenice i 34,1% uzoraka zrna ječma. Koncentracija ovog mikotoksina je varirala od 750 do 4900 μg kg-1, sa srednjim vrednostima: 1225,7 kg-1 u kukuruzu; 852,7 μg kg-1 u pšenici; i 768,2 μg kg-1 u ječmu. Kontaminacija zrna sa FB1 je varirala u zavisnosti od mnogih faktora, kao što je otpornost biljke, stres suše, povrede od insekata i razlikovala se u ispitivanim godinama. Rezultati ovog istraživanja ukazali su da je FB1 značajan kontaminant zrna žita u Srbiji. S obzirom da se ovi proizvodi koriste u velikim količinama, bilo kao hrana za ljude, bilo kao hrana za životinje, utvrđeni stepen kontaminacije ukazuje na visok potencijalni rizik po javno zdravlje

Prisustvo toksigenih vrsta gljiva i mikotoksina u stočnoj hrani u Republici Srbiji

Climatic conditions and growing of grain on large areas in Republic of Serbia are suitable for development of numerous toxigenic species, such as Fusarium spp., Aspergillus spp. and Penicillium spp., and resulting from this is frequent incidence of animal feed contamination by their toxic products. In Republic of Serbia, the most frequent fungi determined in animal feed are those from Fusarium genus, as well as their mycotoxins. Of Fusarium species the most frequent one is F. graminearum, and of toxins zearalenon, in maize or wheat grains, which are the main raw material in production of animal feeds. Development of this fungi and bio-synthesis of zearalenon most often depend on period of rains in the third decade of May when wheat is in the blossoming phenostage or on ample precipitation and low temperatures at the end of summer or beginning of autumn during sensitive pheno-stage of maize growing. Aflatoxins are rarely isolated in Republic of Serbia, but there are conditions for their increased presence in imported feed components. Natural occurrence of ochratoxin A is more frequent than incidence of aflatoxins in climatic conditions of Republic of Serbia. Presence of mycotoxins produced by species of genera Fusarium, Aspergillus and Penicillium indicates potential risk of incidence of mycotoxicosis, especially in younger animal categories. For the purpose of protection of health of animals, realization of profit and high productivity in livestock production, it is necessary to explain factors which can cause animal intoxication, and to identify toxins and develop methodology for assessment of the potential toxicity of animal feed.Klimatski uslovi i gajenje žita na velikim površinama u Republici Srbiji pogoduju razvoju brojnih toksigenih vrsta, kao što su Fusarium spp., Aspergillus spp. i Penicillium spp., i kao rezultat toga je i česta kontaminacija hrane za životinje njihovim toksičnim produktima. U Republici Srbiji su u hrani za životinje najčešće utvrđene gljive iz roda Fusarium, kao i njihovi mikotoksini. Od Fusarium vrsta najčešća je F. graminearum, a od toksina zearalenon, bilo u zrnu kukuruza ili pšenice koje su najčešće sirovine za stočnu hranu. Razvoj ove gljive i biosinteza zearalenona najčešće zavise od kišnog perioda u trećoj dekadi maja kada je pšenica u fenofazi cvetanja ili od obilnih padavina i niskih temperatura pri kraju leta i početkom jeseni kada je osetljiva fenofaza kukuruza. Aflatoksini su retko izolovani u Republici Srbiji, ali postoje uslovi za veće prisustvo prilikom uvoza komponenti hrane za životinje. Prirodna pojava ohratoksina A je češća od pojave aflatoksina u klimatskim uslovima Srbije. Prisustvo mikotoksina koje produkuju vrste roda Fusarium, Aspergillus i Penicillium ukazuje na potencijalni rizik od pojave mikotoksikoza, posebno za mlađe kategorije životinja. U cilju zaštite zdravlja životinja, ostvarivanja dobiti i visoke produktivnosti u stočarskoj proizvodnji, postoji potreba da se objasne faktori koji mogu prouzrokovati intoksikaciju životinja, kao i da se toksini identifikuju i razvije metodologija za ocenu potencijalne toksičnosti hrane za životinje

Komparacija metoda za utvrđivanje toksigenog potencijala Aspergillus parasiticus Speare i Aspergillus flavus Link izolovanih sa kukuruza

Maize is considered one of the most susceptible crops to mycotoxins worldwide. Compared to other mycotoxins, the greatest attention has been paid to aflatoxins, due to their potential carcinogenicity and due to significant and longstanding problems they can cause in humans and animals. A. flavus and A. parasiticus produce aflatoxins in many economically significant crops in both fields and storages. Because of the potential aflatoxin contamination of maize grain, the toxigenic potential of A. flavus and A. parasiticus isolates, originating from Serbia, was tested in the present study. Furthermore, various applied methods for detection of these mycotoxins were compared in the study. Cultural, serological and analytical methods for the detection of mycotoxins were compared in the course of the experiment by the direct extraction of aflatoxins from the nutrient medium. The cultural methods for the detection of aflatoxin production were applied to 20 isolates of A. flavus (MRIZP Af18-20) and A. parasiticus (MRIZP Ap1-17). These methods are based on the yellow pigment formation in mycelia and nutrition media, occurrence of fluorescence on PDA (potato dextrose agar), agar containing β-cyclodextrine (CD-PDA), as well as on the red pigment formation after adding ammonium hydroxide to the existing medium. The ELISA was used to check quantitative and qualitative analyses of total aflatoxins (B1, B2, G1, G2) while the HPLC method was applied to establish ability of isolates to synthesize aflatoxins B1, B2, G1, G2. The yellow pigment formation, fluorescence and colony color changes of isolates into red, as a proof of toxigenicity of isolates, were confirmed in all cases by ELISA. A high potential of total aflatoxin production was determined in the majority of observed isolates. The ability of A. parasiticus isolates to synthesize aflatoxins G1 and G2 was confirmed by the HPLC method. This was essential for a better understanding of the key role of the suitability of cultural methods for preliminary evaluation of a large number of isolates. Our goal was to employ rapid biochemical approaches to prevent aflatoxin contamination of crops, and to reduce human and animal exposure to foodborne mycotoxins.Kukuruz se širom sveta smatra jednim od useva najpodložnijih za kontaminaciju mikotoksinima. Aflatoksinima se, u poređenju s drugim mikotoksinima, pridaje najveća pažnja zbog njihove potencijalne kancerogenosti, značajnih i dugoročnih problema koje izazivaju kod ljudi i životinja. Vrste A. flavus i A. parasiticus mogu produkovati aflatoksine kod mnogih ekonomski značajnih kultura u poljima i skladištima. Zbog potencijalne kontaminacije zrna kukuruza aflatoksinima u ovom radu je ispitan toksigeni potencijal izolata upravo ove dve vrste poreklom iz Srbije i upoređene su različite metode detekcije ovih mikotoksina. Tokom eksperimenta upoređene su odgajivačke, serološke i analitičke metode detekcije mikotoksina, direktnom ekstrakcijom aflatoksina iz hranljive podloge. Istraživanja su bazirana na primeni odgajivačke metode za određivanje produkcije aflatoksina kod 20 izolata A. parasiticus (MRIZP Ap1-17) i A. flavus (MRIZP Af18-20) poreklom iz Srbije. Odgajivačke metode su bile zasnovane na formiranju žutog pigmenta u miceliji i hranljivoj podlozi, na pojavi fluorescencije na PDA (krompir dekstrozni agar) i podlozi koja sadrzi β-ciklodekstrin (CD-PDA), kao i na obrazovanju crvenog pigmenta u podlozi nakon dodavanja amonijum hidroksida. ELISA test je korišćen za proveru kvantitativnih i kvalitativnih sadržaja ukupnih aflatoksina B1, B2, G1 i G 2, dok je HPLC metodom utvrđena koncentracija pojedinačnih aflatoksina B1, B2, G1 i G2. Obrazovanje žutog pigmenta, fluorescencija i promena boje kolonije izolata u crvenu, kao dokaz toksigenosti izolata, potvrđena je u svim slučajevima i ELISA testom. Kod većine izolata ustanovljen je visok potencijal produkcije ukupnih aflatoksina. HPLC metodom potvrđena je i sposobnost sinteze aflatoksina G1 i G2 od strane izolata A. parasiticus. Cilj eksperimenta bio je da se ispita efikasnost upotrebe brzih testova za detekciju aflatoksina, kako bi se sprečila kontaminacija useva i izloženost ljudi i životinja afla-toksinima