Change in Thermal Metabolic Rate Reaction Norms of Daphnia in Response to Rearing Temperature

Temperature is an important environmental factor that affects the distribution of organisms. It affects the biochemical and physiological processes which are the basis of life. The metabolic cold adaptation (MCA) hypothesis predicts an increase in the metabolic rate of ectotherms from cold environments compared with their more temperate counterparts. This hypothesis is one of the most controversial in ecophysiology. MCA is an example of counter gradient variation, a geographical pattern of genotypes where genetic influences on a trait oppose environmental influences. Environmental gradients are common in nature and are considered to have major effects on intraspecific variation patterns. In this study, I tested the MCA hypothesis at an intraspecific level. As a study model I utilized the water flea, Daphnia magna. These are planktonic crustaceans, common in lakes and ponds, and have a wide geographical and thermal distribution. I tested the MCA hypothesis in a laboratory experiment in which oxygen consumption of water fleas reared at three different temperatures for one year (12 ? 35 generations), were measured at three different experimental temperatures. My results show that the animals from the coldest rearing temperature (10 °C) had the highest metabolism at all three experimental temperatures (10, 17 and 25 °C), compared with animals reared at higher temperatures (17 and 25 °C). Elevated metabolism in animals from cold environment is consistent with the metabolic cold adaptation hypothesis. The present study does however not provide conclusive evidence that clone-specific variation in thermal performance has a genetic basis. Organisms may adjust their thermal reaction norms as a response to the thermal regime in which they live through three mechanisms: acclimation, epigenetic effects and evolution, and these could not be distinguished in experimental design used here

Poređenje metoda za određivanje ostataka bifentrina u fermentisanim uzorcima žita

Efficiency of three different sample preparation methods for GC/MS determination of bifenthrin residues in wheat (Triticum spelta) samples fermented by Lactobacillus plantarum was tested. The first method was based on a methanol:acetone=1:1 extraction folowed by a purification on columns containing mixture of aluminium oxide and activated charcoal slurry-packed and eluted with dichlormethane, the second was based on methanol:acetone=1:1 extraction folowed by the purification on florisil column and elution by ethil acetate:acetone=4:1, while the third tested method was based on a combination of the first two mentioned methods, thus methanol:acetone=1:1 extraction and clean-up throught columns filled with a mixture of aluminum oxide and activated charcoal slurrypacked and eluted with ethil acetate:acetone=4:1. The second method was the most effective for obtaining satisfactory recoveries for bifenthrin in a range of 79-83% for four fortification levels, with good reproducibility i.e. RSD% in a range of 2.2-7.4%. The chosen method was further optimized by assessing the optimum volume of elution solvent used during the clean-up procedures. The highest recovery of 82.1% was obtained after elution with 25 ml of solvent. Overall, two-step extraction with 25 ml of methanol:acetone=1:1 solvent mix for 30 min, followed by clean-up procedure through a glass column with florisil coupled with elution with 25 ml of ethyl acetate: acetone=4:1, allows simple, efficient and reliable GC/MS detection of bifenthrin residues from wheat grain fermented by L. plantarum.Testirane su efikasnosti tri različite metode pripreme uzoraka za određivanje ostataka bifentrina u uzorcima pšenice (Triticum spelta) fermentisane pomoću Lactobacillus plantarum. Prva metoda zasnivala se na metanolsko-acetonskoj (1:1) ekstrakciji i prečišćavanju kroz kolonu punjenu smešom aluminijum-oksida i aktivnog uglja u kombinaciji sa dihlormetanom kao eluentom, druga se zasnivala na metanolsko-acetonskoj (1:1) ekstrakciji i prečišćavanju kroz kolonu punjenu florisilom u kombinaciji sa smešom etil-acetata i acetona (4:1) kao eluentom, dok se treća zasnivala na kombinaciji prve dve, tj. metanolsko-acetonskoj (1:1) ekstrakciji i prečišćavanju kroz kolonu punjenu smešom aluminijum-oksida i aktivnog uglja u kombinaciji sa smešom etil-acetata i acetona (4:1) kao eluentom. Pokazalo se da je druga testirana metoda najefikasnija, pri čemu su dobijeni prinosi bifentrina u opsegu 79-83% za četiri koncentraciona nivoa obogaćivanja, sa RSD% u opsegu 2,2-7,4%. Odabrana metoda je dodatno optimizovana variranjem različitih zapremina korišćenog eluenta. Najveći prinos metode postignut je pri zapremini eluenta od 25 ml. Predložena metoda, bazirana na 30-minutnoj ekstrakciji sa 25 ml smeše metanol:aceton=1:1, prečišćavanju na florisilskoj koloni i eluiranju sa 25 ml smeše etil-acetat:aceton=4:1, pokazala se kao efikasna, jednostavna i pouzdana metoda za određivanje ostataka bifentrina u fermentisanom žitnom supstratu

Uticaj sadržaja organske materije i gline u zemljištu na adsorpciju pesticida

The effect of organic matter and clay content on the adsorption of atrazine, acetochlor, clomazone, pendimethalin and oxyfluorfen in soil samples was studied. In order to determine whether and to what degree different soil properties affect the process of determination of selected pesticides, three soils with different clay and organic matter contents were used. An optimized liquid-solid extraction procedure followed by SPME measurement was applied to analyse the selected pesticides in soil samples. Detection and quantification were done by gas chromatography-mass spectrometry (GC/MS). Relative standard deviation (RSD) values for multiple analyses of soil samples fortified at 30 μg/kg of each pesticide were below 19%. Limits of detection (LODs) for all compounds studied were less than 2 μg/ kg. The results indicate that soils with different physico-chemical properties have different effects on the adsorption of most pesticides, especially at higher concentration levels.Proučavan je uticaj sadržaja organske materije i gline u uzorcima zemljišta na procese adsorpcije atrazina, acetohlora, klomazona, pendimetalina i oksifluorfena. U cilju utvrđivanja da li i u kojoj meri različite zemljišne karakteristike utiču na adsorpciju proučavanih pesticida, a time i na njihovo određivanje, izabrana su tri zemljišta sa različitim sadržajem organske materije i gline. Za određivanje pomenutih pesticide u uzorcima zemljišta korišćena je optimizovana tečno-čvrsta ekstrakciona procedura u kombinaciji sa metodom mikroekstrakcije u čvrstoj fazi (SPME). Detekcija i kvantifikacija analita je vršena gasno-masenim spektrometrom (GC/MS). Vrednosti relativnih standardnih devijacija (RSDs) višestruko ponovljenog merenja uzorka obogaćenog do 30 μg/kg svakog pesticida su ispod 19%. Granice detekcije (LODs) za sve pesticide i zemljišta uključena u ispitivanje su bila ispod 2 μg/kg. Rezultati ukazuju da zemljišta različitih fizičko-hemijskih karakteristika imaju različit uticaj na sorpciju za većinu proučavanih jedinjenja, što je naročito izraženo kod većih koncentracija

Određivanje atrazina, acetohlora, klomazona, pendimetalina i oksifluorfena u zemljištu metodom mikroekstrakcije u čvrstoj fazi

A solid phase microextraction (SPME) method for simultaneous determination of atrazine, acetochlor, clomazone, pendimethalin and oxyfluorfen in soil samples was developed. The method is based on a combination of conventional liquid-solid procedure and a following SPME determination of the selected pesticides. Initially, various microextraction conditions, such as the fibre type, desorption temperature and time, extraction time and NaCl content, were investigated and optimized. Then, extraction efficiencies of several solvents (water, hexane, acetonitrile, acetone and methanol) and the optimum number of extraction steps within the sample preparation step were optimized. According to the results obtained in these two sets of experiments, two successive extractions with methanol as the extraction solvent were the optimal sample preparation procedure, while the following conditions were found to be most efficient for SPME measurements: 100 μm PDMS fibre, desorption for 7 min at 2700C, 30 min extraction time and 5% NaCl content (w/v). Detection and quantification were done by gas chromatography-mass spectrometry (GC/MS). Relative standard deviation (RSD) values for multiple analysis of soil samples fortified at 30 μg/kg of each pesticide were below 19%. Limits of detection (LOD) for all the compounds studied were less than 2 μg/kg.Za istovremeno određivanje atrazina, acetohlora, klomazona, pendimetalina i oksifluorfena u zemljištu ustanovljena je metoda mikroekstrakcije u čvrstoj fazi (SPME). Metoda je zasnovana na kombinaciji klasične tečno-čvrste pripreme uzorka i SPME određivanja. Izvršena je optimizacija najvažnijih mikroekstrakcionih parametara, kao što su izbor ekstrakcionog vlakna, desorpciona temperatura i vreme, ekstrakciono vreme i sadržaj natrijumhlorida (NaCl). Ispitivani su, takođe, ekstrakciona efikasnost različitih rastvarača (voda, heksan, acetonitril, aceton i metanol), kao i optimalan broj ekstrakcionih koraka u toku pripreme uzoraka zemljišta. Na osnovu rezultata dobijenih iz ova dva seta eksperimenata izabrani su sledeći radni uslovi: dve sukcesivne ekstrakcije sa metanolom kao ekstrakcionim rastvaračem u stupnju pripreme uzorka, dok su za mikroekstrakcione uslove uzeti: 100 μm PDMS vlakno, desorpcija u trajanju od 7 min na 270ºC, ekstrakciono vreme – 30 min, uz dodatak NaCl (5%, w/v). Detekcija i kvantifikacija analita je vršena gasno-masenim spektrometrom (GC/MS). Vrednosti relativnih standardnih devijacija (RSDs) višestruko ponovljenog merenja uzorka obogaćenog do 30 μg/kg svakog pesticida su ispod 19%. Granice detekcije (LODs) za sve pesticide uključene u ispitivanje su ispod 2 μg/kg

Metoda tečno-čvrste ekstrakcije za određivanje pesticida u uzorcima zemljišta

A multiresidue method for simultaneous determination of four pesticides (diazinon, acetochlor, aldrine and carbofuran) belonging to different pesticide groups, extracted from soil samples, is described. The method presented is based on liquid-solid extraction (LSE) and determination of pesticides, i.e. the pesticides were extracted by methanol- acetone mixture, purified on florisil column and eluted by ethyl acetate-acetone mixture. Optimization of the main parameters affecting the LSE procedure, such as the choice of purification sorbent, as well as the elution solvent and its volume, were investigated in details and optimized. Also, validation of the proposed method was done. Gas chromatography-mass spectrometry (GC-MS) was used for detection and quantification of the pesticides studied. Relative standard deviation (RSD) and recovery values for multiple analysis of soil samples fortified with 30 μg/kg of each pesticide were below 8% and higher than 89%, respectively. Limits of detection (LOD) for all the compounds studied were less than 4 μg/kg.U radu je prikazana metoda tečno-čvrste ekstrakcije (LSE) za istovremeno određivanje pesticida (diazinon, acetohlor, aldrin i karbofuran) u zemljištu, koji na osnovu svoje strukture pripadaju različitim hemijskim grupama. Metoda se zasniva na metanolsko-acetonskoj ekstrakciji uzoraka zemljišta, koja je praćena prečišćavanjem na florisilu i eluiranju sa smešom etil-acetata i acetona. Izvršena je optimizacija glavnih eksperimentalnih parametara koji mogu da utiču na efikasnost LSE metode, kao što su izbor sorbenta za prečišćavanje zemljišnog ekstrakta pesticida, izbor adekvatnog eluenta i njegove optimalne zapremine. Takođe, izvršena je i validacija optimizovane metode. Detekcija i kvantifikacija ispitivanih pesticida su izvršeni metodom gasno-masene spektrometrije (GC-MS). Vrednosti relativnih standardnih devijacija (RSD) i prinosa određivanja pesticida u uzorcima zemljišta obogaćenim do koncentracija od 30 μg/kg svakog jedinjenja su ispod 8%, odnosno iznad 89%, respektivno, dok su granice detekcije (LOD) niže od 4 μg/kg

Reducing sheet resistance of self-assembled transparent graphene films by defect patching and doping with UV/ozone treatment

Liquid phase exfoliation followed by Langmuir-Blodgett self-assembly (LBSA) is a promising method for scalable production of thin graphene films for transparent conductor applications. However, monolayer assembly into thin films often induces a high density of defects, resulting in a large sheet resistance that hinders practical use. We introduce UV/ozone as a novel photochemical treatment that reduces sheet resistance of LBSA graphene threefold, while preserving the high optical transparency. The effect of such treatment on our films is opposite to the effect it has on mechanically exfoliated or CVD films, where UV/ozone creates additional defects in the graphene plane, increasing sheet resistance. Raman scattering shows that exposure to UV/ozone reduces the defect density in LBSA graphene, where edges are the dominant defect type. FTIR spectroscopy indicates binding of oxygen to the graphene lattice during exposure to ozone. In addition, work function measurements reveal that the treatment dopes the LBSA film, making it more conductive. Such defect patching paired with doping leads to an accessible way of improving the transparent conductor performance of LBSA graphene, making solutionprocessed thin films a candidate for industrial use

Osetljivost kukuruza, suncokreta i ječma na rezidualno delovanje klomazona u zemljištu

Sensitivity of maize, sunflower and barley to clomazone residues in loamy soil was assessed in the study using bioassay. Clomazone was applied at a series of concentrations from 0.12 to 12 mg a.i./kg of soil. After 14 days, morphological (shoot height, fresh and dry weight) and physiological (content of carotenoids, chlorophyll a and chlorophyll b) parameters were measured. The results showed that morphological parameters are not valid indicators of clomazone sensitivity. Based on the results showing inhibition of the physiological parameters, I50 values were calculated and used to estimate the difference in sensitivity between the species tested. Sunflower was the most sensitive species, while the difference in sensitivity between maize and barley was not significant. Nomenclature: clomazone (2-(2-chlorbenzyl)-4,4-dimethyl-1,2-oxazolidin-3-one), maize (Zea mays L.), sunflower (Helianthus annuus L.), barley (Hordeum vulgare L.)U radu je ispitivana osetljivost kukuruza, suncokreta i ječma na rezidualno delovanje klomazona u zemljištu tipa ilovače, metodom biotesta. Klomazon je primenjen u seriji koncentracija 0,12-12 mg a.s./kg zemljišta. Nakon 14 dana rasta biljaka mereni su morfološki (visina, sveža i suva masa izdanka) i fiziološki parametri (sadržaj karotenoida, hlorofila a i hlorofila b). Konstatovano je da morfološki parametri nisu pouzdano merilo osetljivosti na klomazon. Prema ostvarenim procentima inhibicije za merene fiziološke parametre izračunate su vrednosti I50, a na osnovu njih utvrđene su razlike u osetljivosti ispitivanih biljnih vrsta. Najosetljiviji je bio suncokret, dok se kukuruz i ječam nisu međusobno značajno razlikovali

Efikasnost različitih metoda za određivanje ostataka organofosfata u fermentisanim uzorcima žita

In the present work, the efficiencies of three different sample preparation methods for GC/ MS determination of pirimiphos-methyl and chlorpyrifos-methyl residues in wheat (Triticum spelta) samples fermented by Lactobacillus plantarum were compared. All three methods were based on methanol:acetone=1:1 extraction, while further purification of the obtained samples was altered. First purification was through a column containing a mixture of aluminium oxide and activated charcoal slurry-packed and eluted with dichlormethane, the second was purification on a florisil column slurry-packed and eluted with ethyl acetate:acetone=4:1, while the third was based on a combination of the former two methods, i.e. clean-up through columns filled with a mixture of aluminum oxide and activated charcoal slurry-packed and eluted with ethyl acetate:acetone=4:1. The second method was found the most effective for obtaining satisfactory recoveries at four fortification levels. For pirimiphos-methyl, recoveries were in the range of 91.3-96.0% and had good reproducibility, i.e. RSD ranging from 2.2-4.1%, while the corresponding range for chlorpyrifos-methyl was 81.6-88.2%, and the RSD range 2.5-5.4%. The chosen method was further optimized in order to establish the optimum volume of elution solvent used during the clean-up procedures. The highest recoveries of 93.7±3.5% for pirimiphos- methyl and 85.3±2.5% for chlorpyrifos-methyl were obtained after elution with 25 ml volume of solvent. Considering all, simple, efficient and reliable GC/MS detection of pirimiphosmethyl and chlorpyrifos-methyl residues in wheat grain substrate altered by fermentation with L. plantarum was achieved by the two-steps extraction with 25 ml of methanol:acetone=1:1 solvent mix for 30 min, followed by a clean-up procedure through a glass column with florisil coupled with elution by 25 ml of ethyl acetate:acetone=4:1.Poređene su efikasnosti tri različite metode pripreme uzoraka za određivanje ostataka pirimifos-metila i hlorpirifos-metila u uzorcima pšenice (Triticum spelta) fermentisane sa Lactobacillus plantarum. Sve tri metode zasnivale su se na metanolsko-acetonskoj (1:1) ekstrakciji dok su se procedure prečišćavanja dobijenih ekstrakata razlikovale. Prva metoda bila je prečišćavanje kroz kolonu punjenu smešom aluminijum-oksida i aktivnog uglja u kombinaciji sa dihlormetanom kao eluentom, druga prečišćavanje kroz kolonu punjenu florisilom u kombinaciji sa smešom etil-acetata i acetona (4:1) kao eluentom, dok se treća zasnivala na kombinaciji prve dve, tj. prečišćavanju kroz kolonu punjenu smešom aluminijum-oksida i aktivnog uglja u kombinaciji sa smešom etil-acetata i acetona (4:1) kao eluentom. Druga testirana metoda pokazala se kao najefikasnija, pri čemu su dobijeni prinosi pirimifos-metila u opsegu 91,3-96,0% za četiri koncentraciona nivoa obogaćivanja, sa RSD% u opsegu 2,2-4,1%, dok su za hlorpirifos-metil ovi prinosi bili u opsegu 81,6-88,2% sa RSD% u opsegu 2,5-5,4%. Odabrana metoda je dodatno optimizovana variranjem različitih zapremina korišćenog eluenta. Najveći prinos metode za oba ispitivana pesticida postignut je pri zapremini eluenta od 25 ml (93,7±3.5% za pirimifos-metil i 85,3±2,5% za hlorpirifos-metil). Predložena metoda, bazirana na 30-minutnoj ekstrakciji sa 25 ml smeše metanol:aceton=1:1, prečišćavanju na florisilskoj koloni i eluiranju sa 25 ml smeše etilacetat: aceton=4:1, pokazala se kao efikasna, jednostavna i pouzdana metoda za određivanje ostataka ispitivanih organofosfata u fermentisanom žitnom supstratu