Surfaktanti u okolišu

Surfactants are a diverse group of chemicals that are best known for their wide use in detergents and other cleaning products. After use, residual surfactants are discharged into sewage systems or directly into surface waters, and most of them end up dispersed in different environmental compartments such as soil, water or sediment. The toxic effects of surfactants on various aquatic organisms are well known. In general, surfactants are present in the environment at levels below toxicity and in Croatia below the national limit. Most surfactants are readily biodegradable and their amount is greatly reduced with secondary treatment in wastewater treatment plants. The highest concern is the release of untreated wastewater or wastewater that has undergone primary treatment alone. The discharge of wastewater polluted with massive quantities of surfactants could have serious effects on the ecosystem. Future studies of surfactant toxicities and biodegradation are necessary to withdraw highly toxic and non-biodegradable compounds from commercial use and replace them with more environmentally friendly ones.Surfaktanti ili površinski aktivne tvari raznolika su skupina molekula najpoznatijih po uporabi u sastavu deterdženata i ostalih sredstava za pranje i čišćenje. Nakon uporabe u kućanstvu ili industriji, surfaktanti se ispuštaju u kanalizacijski sustav ili izravno u površinske vode te većina surfaktanata završi raspršena u vodi, sedimentu ili tlu. Toksični utjecaj surfaktanata na vodne organizme dobro je istražen i opisan u literaturi. U većini slučajeva surfaktanti su u okolišu prisutni u koncentracijama nižim od toksične te nižim od maksimalne koncentracije dopuštene hrvatskim zakonskim odredbama. Većina surfaktanata klasifi cirana je kao biološki razgradiva i njihova se koncentracija znatno smanjuje biološkom obradom otpadne vode pa je najveći rizik za okoliš ispuštanje prethodno pročišćene ili nepročišćene otpadne vode. Takva otpadna voda opterećena visokim koncentracijama surfaktanata može nepovoljno utjecati na okoliš. Potrebno je proučavati toksičnost i biološku razgradnju surfaktanata u svrhu uklanjanja visoko štetnih i biološki nerazgradljivih surfaktanata iz komercijalne uporabe te njihovu zamjenu tvarima manje štetnim za okoliš

Microbial Colonization of High Density Polyethylene Garbage Bags

This research aimed to determine the microbial colonization and potential biodegradation of classical high density polyethylene (HDPE) garbage bags in conditions which refl ects its real disposal without preliminary abiotic pretreatment. The HDPE fi lms were buried during 14 weeks in containers with humifi ed soil, activated sludge and its mixture. The colonization of heterotrophic mesophilic aerobic and anaerobic bacteria on the HDPE was monitored. The bacteria and fungi formed biofi lms on the surface of HDPE, but did not have the potential to degrade it since no changes in FTIR spectra of HDPE fi lms were observed. The classical HDPE is primary nontoxic inert material, which is not biodegradable in environmental conditions, what represents a serious ecological problem

Special protection scheme for operation of central Zagreb transmission system

The paper presents a Special Protection Scheme solution for the central Zagreb transmission system. The Central Zagreb transmission system is characterized by a highly meshed network with combined overhead and cable sections and a special operation of the 110 kV cable link between two power plants important for the city’s heat and electricity supply. The Special Protection Scheme is developed using static and dynamic analyses of different network scenarios. Island operation is simulated for a consumption and generation surplus, and an underfrequency load shedding scheme is determined. The Special Protection Scheme architecture is presented with a brief description of the telecommunication infrastructure

Smanjena osjetljivost na dezinficijense bakterije Acinetobacter baumannii u obliku biofilma na staklu i keramici

The aim of this study was to determine the susceptibility of hospital and environmental Acinetobacter baumannii isolate biofilms on ceramics and glass to common disinfectants benzalkonium chloride and chlorhexidine. For this purpose wedeveloped a new method for biofilm cultivation and quantification on ceramics. The biofilm bacteria were more resistant to disinfectants than the planktonic populations, as more than 50 % of the biofilm population and none of the planktonic population survived 5-minute exposure. Furthermore, biofilm populations on ceramic tiles were significantly more resistant than those on glass coverslips, even though the amount of biofilm was practically the same on ceramics and glass. The reason for reduced susceptibility of A. baumannii biofilms on ceramics may be related to surface/disinfection interactions. Our findings suggest that biofilms on ceramic surfaces can be an important source of A. baumannii infection in hospital environmentsVrsta Acinetobacter baumannii prepoznata je kao trenutačno vodeći uzročnik bolničkih infekcija sa smrtnim ishodom. Trajna prisutnost A. baumannii u bolnicama posljedica je ponajviše otpornosti na antibiotike te sposobnosti ove bakterije da stvara biofilm. U radu je testirana osjetljivost biofilma kliničkih i okolišnih izolata vrste A. baumannii na najčešće korištene dezinficijense, benzalkonijev klorid i klorheksidin. Predložena je nova metoda za uzgoj biofilma na keramičkim pločicama te su rezultati uspoređeni s biofilmom koji je nastao na staklu. Bakterije unutar biofilma bile su otporne na dezinficijense; pri koncentraciji dezinficijensa koja je potpuno uništila planktonske bakterije, unutar biofilma preživjelo je više od 50 % populacije, čak i nakon petominutnog izlaganja dezinficijensima. Značajno je opažanje da su bakterije u obliku biofilma na keramici znatno otpornije na dezinficijense od bakterija u obliku biofilma na staklu, iako je brojnost bakterija bila podjednaka. Navedeni rezultati upućuju na zaključak da je međudjelovanje materijala i dezinficijensa važan čimbenik koji određuje učinkovitost dezinfekcije. Sposobnost stvaranja biofilma na keramičkim površinama moguće je ishodište i značajno stanište bakterija A. baumannii u bolničkom okružju

Use of cement for grouting in tufa material

U članku se opisuju mogućnosti primjene mikrocementa pri konsolidacijskom injektiranju. Opisana su istraživanja obavljena na terenu (širi prostor rijeke Plive) i u laboratoriju. Analitički su prikazani rezultati istraživanja stanja prije injektiranja i nakon njega. Zaključeno je da nije moguće injektiranje smjesama na bazi portland cementa, da se uporabom mikrocementa finoće mliva 40 mm postiže djelomična penetracija, a dobri su rezultati uporabom mirkocementa finoće mliva 20 mm.Possibilities of using microcement in consolidation grouting are considered in the paper. On-site investigations (carried out in the wider Pliva river basin) and laboratory testing results are presented. An analytical overview of the situation prior to and after the grouting work is given. The authors have reached the following conclusions: grouting is not possible with mixes based on Portland cement, partial penetration is possible by using microcement with 40 mm grinding fineness, and good results can be obtained when microcement with the grinding fineness of 20 mm is used

Number of Inhabitants of the City of Zagreb during the Period 1857-2011

The aim of this paper is to show migrations and changes in the City of Zagreb since the first official census until today, that is in the period from 1857-2011. Since 1857 when the first official census was conducted which represents the first present-day census until the year 2011, there have been sixteen censuses by means of which we can follow and analyze the number of inhabitants. The first part of the paper analyzes entire migrations of the inhabitants according to official census data whereas the second part analyzes migrations of the current population. Based on scientific analysis, the processing of census and other demographic statistical data and the application of theoretical and empirical literature, this paper also analyzes changes and migrations of the population in the City of Zagreb. The causes and characteristics of these changes are considered and the regional differentiation of the fundamental characteristics of these processes up to the level of settlements is also examined

La calidad de los huevos provenientes de las gallinas ponedoras de la cría libre y en jaula

Kokošja jaja biološki su visoko vrijedna hrana i ljudski organizam koristi hranjive tvari jajeta u velikom postotku. Cilj je ovoga rada utvrditi kakvoću jaja s obzirom na način držanja kokoši nesilica. Istraživanje je obuhvatilo određivanje kvalitete konzumnih jaja nesilica različite dobi podrijetlom iz slobodnog, podnog i kaveznog uzgoja na ukupno 60 uzoraka. Jaja iz slobodnog uzgoja bila su najteža (mase prosječno 59,35 g) i u odnosu na jaja iz kaveznog (konvencionalnog) sustava imala su veći indeks oblika (75,29 : 74,30) i deblju ljusku (0,44 : 0,43 mm). Količina vode bila je najveća, a količina bjelančevina najmanja u jajima iz slobodnog uzgoja. Jaja su s aspekta njihovih proizvodnih karakteristika i kvalitete u smislu kemijskog sastava bolja u kaveznom u odnosu na slobodno držanje, dok je s aspekta dobrobiti držanje kokoši nesilica bolje u slobodnom uzgoju.Chicken eggs are biologically high value foods and the human organism utilises their nutritional value at a high percentage. The aim of this paper is to determine the influence of poultry housing system on egg quality. The study included the determination of egg quality from egg laying hens of different ages, originating from free, floor and cage systems, to a total of 60 samples. Free range eggs weighed the most (averaging 59,35 g) and in comparison to cage raising system, measuring higher egg index (75,29 : 74,30) and a thicker shell (0,44 : 0,43 mm). The water amount was highest, and the protein amount was lowest in free range eggs. Eggs from the aspect of their production characteristics and quality in terms of chemical composition recorded higher values in conventional cages in comparison to free range, while eggs originating from free range and enriched cage systems recorded higher values from a poultry welfare standpoint.Hühnereier sind biologisch hochwertige Nahrungsmittel, deren Nährstoffe vom menschlichen Körper zu einem hohen Prozentsatz ausgenutzt werden. Ziel dieser Arbeit bestand darin, die Qualität der Eier in Anbetracht der Haltungsweise der Legehühner festzulegen. Die Untersuchung umfasste die Bestimmung der Qualität von Konsumeiern, die von Legehühnern unterschiedlichen Alters aus der Freiland-, Boden- und Käfighaltung stammen, mit insgesamt 60 Probemustern. Die Eier aus der Freilandhaltung waren am schwierigsten (Masse durchschnittlich 59,35 g) und hatten im Vergleich zu den Eiern aus der Käfighaltung (konventionelle Haltung) einen größeren Formindex (75,29 : 74,30) und eine dickere Schale (0,44 : 0,43 mm). Die Freilandeier verfügten über den höchsten Anteil von Wasser und den geringsten Anteil von Proteinen. In Bezug auf die Produktionseigenschaften und die Qualität der chemischen Zusammensetzung schnitten die Eier aus der Käfighaltung besser als die Eier aus der Freilandhaltung ab, während vom Aspekt des Tierwohls die Haltung von Legehühnern in der Freilandhaltung besser ist.Le uova di gallina, dal punto di vista biologico, sono alimenti altamente nutrienti e l’organismo umano utilizza un’alta percentuale delle sostanze nutritive dell’uovo. L’obiettivo di questo studio consiste nell’accertare la qualità dell’uovo di gallina in base alle tecniche d’allevamento delle galline ovaiole. La ricerca ha riguardato l’accertamento della qualità delle uova da tavola di galline ovaiole di diverse età allevate all’aperto, a terra e in gabbie su un totale di 60 campioni. Le uova delle galline ovaiole allevate all’aperto sono risultate avere maggior massa (massa media 59,35 g) e, rispetto alle uova prodotte dalle galline ovaiole allevate in gabbie (sistema convenzionale), sono risultate avere un indice di forma maggiore (75,29 : 74,30) e un guscio più spesso (0,44 : 0,43 mm). Nelle uova prodotte dalle galline ovaiole allevate all’aperto, la quantità d’acqua è risultata maggiore, mentre la quantità di proteine è risultata minore rispetto alle altre uova. Le uova prodotte dalle galline ovaiole allevate in gabbie, sotto l’aspetto delle loro caratteristiche produttive e della loro qualità, hanno quindi una migliore composizione chimica rispetto alle uova prodotte dalle galline ovaiole allevate all’aperto mentre, dal punto di vista del loro benessere, l’allevamento all’aperto è certamente più favorevole per l’animale.Los huevos de gallina son biológicamente el alimento altamente nutritivo y el organismo humano usa los nutrientes de los huevos en un alto porcentaje. El fin de este trabajo fue determinar la calidad de los huevos teniendo en cuenta la manera de criar las gallinas ponedoras. La investigación incluyó la determinación de la calidad de los huevos de consumo de las gallinas ponedoras de diferentes edades provenientes de la cría libre, en suelo y en jaula con 60 muestras en total. Los huevos de cría libre fueron los más pesados (masa promedia de 59,35 g) y en comparación con los huevos de la cría en jaula (convencional) tenían un mayor índice de forma (75,29 : 74,30) y la cáscara más gruesa (0,44 : 0,43 mm). El contenido del agua más alto y el más bajo contenido de las proteínas tenían los huevos de la cría libre. Desde el punto de vista de las características productivas y de la calidad en sentido de su composición química, los huevos de la cría de jaula son mejores que los de la cría libre, mientras desde la perspectiva del bienestar de las gallinas ponedoras la cría libre es mejor

Multiphase zinc and magnesium mono-substituted calcium phosphates derived from cuttlefish bone : A multifunctional biomaterials

Biomimetic calcium phosphate (CaP) systems mono-substituted with zinc (Zn2+) and magnesium (Mg2+) ions were prepared from a biogenic source (cuttlefish bone) by wet precipitation method. The results revealed that the as-prepared powders were composed of calcium-deficient carbonated hydroxyapatite (HAp), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP), while the heat-treated powders consisted of HAp, α-tricalcium phosphate (α-TCP), and β-tricalcium phosphate (β-TCP). In addition to Zn2+ and Mg2+ ions, the presence of CO32−, Sr2+ and Na + ions was detected with elemental analysis, which can be attributed to the use of cuttlefish bone as a natural precursor of Ca2+ ions. The data obtained by XRD study demonstrated the decrease in lattice parameters in the OCP and β-TCP phases for Zn-substitution and Mg-substitution in the HAp, OCP, and β-TCP phases. Zn2+ occupies the Ca(1,3,4,6,7,8) sites in OCP and Ca(1,2,3,4) sites in β-TCP, while Mg2+ occupies the Ca(2) sites in HAp and the Ca(4,5) sites in β-TCP. Phase transformation study under simulated physiological conditions for 7 days showed the transformation of OCP and ACP into the thermodynamically more stable HAp. Characterization of the zeta-potential showed positively charged populations for all prepared CaP powders, while all samples showed high bovine serum albumin adsorption capacity. The culture of human embryonic kidney cells showed that the prepared CaPs are non-cytotoxic and that viability of the cells increases during the culture period. All powders obtained showed antibacterial activity towards Gram-negative Escherichia coli and low antibacterial effect against Gram-positive Staphylococcus aureus, as determined by viability analysis during 48 h. Inhibition zone analysis and observation of the morphology after 24 h showed no antibacterial properties.publishedVersionPeer reviewe

Bending moment curvature relationship as an indicator of seismic resistance of older bridge piers

U seizmički aktivnim područjima poželjno je projektirati mostove duktilnog ponašanja. Veliki se broj postojećih mostova, projektiranih prema danas zastarjelim normama, a koje nisu nudile smjernice za oblikovanje elemenata za duktilno ponašanje, nalaze se u seizmički aktivnim područjima. Nepoznata je razina duktilnosti koju ti mostovi posjeduju. U ovome se radu razmatra jedan od bitnih pokazatelja seizmičke otpornosti starijih mostova sa stupovima u kojima je ugrađena glatka armatura – krivulja ovisnosti momenta savijanja i zakrivljenosti, M- krivulja. Uspoređeni su rezultati analitičkog, eksperimentalnog i numeričkog pristupa u određivanju krivulje te su doneseni zaključci o utjecaju proklizavanja glatke armature.In seismic areas, it is recommended to design bridges characterized by ductile behaviour. A large number of existing bridges designed according to outdated standards, without guidelines for ductile behaviour detailing, can be found in seismically active areas. The level of ductility exhibited by these bridges is unknown. A crucial seismic performance indicator for older bridges with piers containing round reinforcing bars, i.e. the bending moment-curvature curve (M- curve), is considered in this paper. The results of analytical, experimental and numerical approaches for determining the M- curve are compared, and conclusions on the effect of round reinforcement slippage are presented