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  • Open Access Croatian
    Authors: 
    Banožić, Marija; Šafranko, Silvija; Bogadi, Dora; Aladić, Krunoslav; Jokić, Stela;
    Country: Croatia

    The peel of the Okitsu variety of mandarin is created as a by-product of the fruit’s growth and processing. The primary goal of this research was to use a unique nonthermal extraction method (high-voltage electric discharge assisted) with green solvent (water) to valorise citrus peel as a valuable raw material. In October 2020, samples (citrus peel) were collected from the farm of Mr. Dalibor Ujević (Opuzen, Hrvatska). Samples were washed, freeze-dried, and sieved before extraction. The effects of extraction process parameters, such as treatment duration (5–15 min), frequency (40–100 Hz), and liquid to solid ratio (200–400 ml g–1) on the extraction yield and content of hesperidin and narirutin were studied. Spectrophotometric methods were used to assess the antiradical activity and total phenolic content of the extracts. Individual phenolic components were identified and quantified using HPLC method. The extraction process parameters were optimised with a commercial softer tool (Design Expert®) using experimental data gathered using the Box-Behnken experimental design. Experiments were conducted as shown in Tables 1 and 2. The extraction yield was ranked from 359.23 to 463.20, the total phenol values ranged from 96.23 to 275.46 mg GAE l–1, DPPH values ranged from 87.08 to 94.93 %. Total phenol content and antiradical activity decreased with increasing extraction time, as shown in Fig. 1. Six phenolic compounds were identified and quantified, predominated by hesperidin and narirutin (Table 3). The regression models for all tested HVED extraction responses were significant (p-value under 0.05) based on the acquired data, and the quality of the models produced was evaluated based on the coefficients of determination (R2) and Lack of Fit value. The obtained R2 values for all models developed were 0.911; 0.844, and 0.845 with a nonsignificant lack of fit, indicating an adequate relationship between input parameters (extraction conditions) and observed variable, in this case, extraction efficiency, hesperidin and narirutin content (Table 4). The obtained data was utilised to create three-dimensional (3D) response surface graphs, as shown in Figs. 2–4. The regression models within this study were predicted by Eqs. (1)–(3). With response surface methodology (RSM), optimal parameters of HVED extraction process were defined, as follows: extraction yield (285.93 ml g–1, 73.38 Hz and 14.84 min), hesperidin content (366.19 ml g–1, 97.56 Hz, and 5.1 min), and narirutin content (200 ml g–1, 70 Hz, and 15 min), as presented in Table 5, together with predicted and experimentally verified values. Konzumacija svježih citrusa, ali i njihova prerada generiraju nusproizvode, kao što su kora, sjemenke, pulpa, kao i otpadne vode. Cilj ovog istraživanja je valorizacija agroindustrijskih nusproizvoda (kore citrusa) kao vrijedne sirovine za ekstrakciju polifenola primjenom inovativne netermalne metode ekstrakcije sa zelenim otapalom (voda). U ekstraktima je kvantificirano i identificirano ukupno šest fenolnih spojeva. Pri tome je promatran utjecaj vremena (od 5 do 15 min), frekvencije (od 40 do 100 Hz) i omjera kapljevito/kruto (od 200 do 400 ml g–1) na efikasnost procesa ekstrakcije (iskorištenje) i udio dominantnih fenolnih spojeva (hesperidina i narirutina). Uz pomoć metode odzivnih površina definirani su optimalni parametri promatranog procesa ekstrakcije za svaki od istraživanih odziva, i to za iskorištenje (285,93 ml g–1, 73,38 Hz i 14,84 min), za hesperidin (366,19 ml g–1, 97,56 Hz i 5,1 min) te za narirutin (200 ml g–1, 70 Hz i 15 min). Ekstrakcija potpomognuta visokonaponskim električnim pražnjenjem (HVED ekstrakcija) pokazala se pogodnom za ekstrakciju fenolnih spojeva, pri čemu je izbjegnuta uporaba organskih otapala.

  • Publication . Other literature type . Article . 2022
    Open Access
    Authors: 
    Štrkalj, Anita; Mesek, Luka; Ocelić Bulatović, Vesna; Glavaš, Zoran;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Metalurški otpad ima velik potencijal za uporabu kao adsorbens za uklanjanje teških metala iz otpadnih voda, ističući se kao mogući jeftini adsorbens. U ovom članku prikazano je adsorpcijsko ponašanje Zn(II) iona na dva kruta metalna otpadna materijala – otpadnoj kalupnoj mješavini (OKM) i otpadnoj anodnoj prašini (AP). Dobiveni rezultati pokazali su da se oba otpadna materijala mogu upotrebljavati kao potencijalni adsorbensi. Anodna prašina ima bolja adsorpcijska svojstva. Ravnotežni podatci za adsorpciju Zn(II) na otpadnim metalurškim materijalima ispitani su Freundlichovim i Langmuirovim izotermnim modelima. Utvrđeno je da je Langmuirov model prikladniji te da se adsorpcija odvija kao kemisorpcija. Metallurgical waste has great potential for use as an adsorbent for the removal of heavy metals from wastewater, standing out as possible low-cost adsorbents. This article presents the adsorption behaviour of Zn(II) ions on two solid metal waste materials – waste mould sand (WMS) and anode dust (AD). The obtained results showed that both waste materials could be used as potential adsorbents. Anode dust has better adsorption properties. The equilibrium data for the adsorption of Zn(II) on waste metallurgical materials were examined by Langmuir and Freundlich’s adsorption isotherm models. It was found that the Langmuir model is more appropriate, and that adsorption takes place as chemisorption.

  • Open Access Croatian
    Authors: 
    Tomislav Domanovac; Marija Vuković Domanovac; Dajana Kučić Grgić; Monika Šabić Runjavec;
    Country: Croatia

    Maintenance of green urban areas, backyards and gardens, as well as food preparation and consumption generate municipal biodegradable waste, i.e., biowaste that must be collected and processed in accordance with environmental protection regulations and waste management objectives of the Republic of Croatia. By determining the composition and amount of municipal waste, the quantities generated in the assumed area were estimated. From the mentioned input data on the amount of biowaste and input process data that are relevant for the implementation of biological treatment of biowaste in aerobic conditions, the necessary equipment and space were dimensioned, taking into account the dynamics of the process and the necessary technological operations. Thus, the operation of machines for shredding and mixing with a capacity of about 50 m3 h–1, aeration and irrigation with a capacity of about 1,000 m3 h–1, screening with a capacity of about 23.2 m3 h–1, as well as manipulation of biowaste and compost was planned. Four bioreactors with a capacity of about 1 421 t y–1 each, fans and other process-measuring equipment were planned. Waste air flow with biodegradation products were purified before released into the atmosphere using a biofilter of about 9 m2 and 1.5 m of filled layer of wood chips, bark, mature compost, and other additives. By composting about 3 641 t y–1 of biowaste, which is approximately the minimum amount of biowaste that a presumed area of about 77 000 inhabitants needs to be processed to meet the waste management objectives of the Republic of Croatia, the estimated production of about 2 575 t y–1 of mature compost would be reduced by about 34.1 %, or volume by about 50.5 %. About 2 174 000 EUR needs to be invested in facilities and equipment, with total operating costs of about 83 EUR/t of input biowaste. Pripremom i konzumiranjem hrane u kućanstvima te održavanjem zelenih javnih površina, okućnica i vrtova nastaje biootpad koji je potrebno odvojeno sakupiti i obraditi u skladu s propisima iz područja zaštite okoliša, odnosno ciljevima gospodarenja otpadom u Republici Hrvatskoj. Na temelju sastava i količine komunalnog otpada procijenjene su godišnje količine biootpada razmatranog područja. Iz ulaznih podataka o količini biootpada te ulaznih procesnih podataka koji su relevantni za provedbu biološke obrade biootpada u aerobnim uvjetima, dimenzionirana je potrebna oprema i prostor uvažavajući dinamiku procesa i potrebne tehnološke operacije. U ovom radu je analizirano pretpostavljeno područje od oko 77 000 stanovnika te je pretpostavljeno da to stanovništvo proizvede oko 3 641 t god–1 biootpada. Biološkom obradom odvojeno sakupljenog biootpada u aerobnim uvjetima koja se provodi na kompostani malog kapaciteta procjenjuje se proizvodnja oko 2 575 t god–1 zrelog komposta, što predstavlja smanjenje ulazne mase biootpada od oko 34,1 %, odnosno volumena za oko 50,5 %. Troškovi izgradnje objekata i nabave opreme procjenjuju se na oko 16 305 000 kn (2 174 000 EUR), a ukupni troškovi rada postrojenja s uračunatom amortizacijom na oko 625 kn/t (83 EUR/t) ulaznog biootpada.

  • Open Access
    Authors: 
    Amina Lachenani‬; Mohamed Bentchikou; Mouloud Boumahdi; Salah Hanini; Maamar Laidi;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    U ovom radu predloženo je i primijenjeno šest novih matematičkih modela temeljenih na poluempirijskom proračunu za karakterizaciju procesa sušenja u pećnici kompozita cementne žbuke ojačane celuloznim vlaknima (CMCRCF). Pokusi sušenja provedeni su pri četiri razine temperature sušenja u pećnici (70, 85, 105 i 120 °C) s četiri različita udjela celuloznih vlakana (0, 5, 10 i 20 %). Dobiveni rezultati uspoređeni su s onima dobivenim regresijskom analizom šest najčešće primjenjivanih matematičkih modela sušenja (Newton, Page, Page modified1, Page modified2, Handerson Pabis i Logarithmic) uz šest predloženih modela. Regresijska točnost procesa sušenja procijenjena je koeficijentom determinacije (R2), srednjom kvadratnom pogreškom (MSE), korijenom srednje kvadratne pogreške (RMSE) i srednjom apsolutnom pogreškom (MAE). Primijenjeni su i dodatni kriteriji da bi se osigurala veća valjanost odabranih modela. Dobivene vrijednosti pokazuju dobro slaganje predloženog modela MR9 s eksperimentalnim vrijednostima, što znači da predloženi model može jasno interpretirati eksperimentalne podatke o sušenju i predvidjeti suho stanje CMCRCF-a. In this paper, six novel mathematical models based on semi-empirical calculus are proposed and applied to characterise the oven-drying process of cement mortar composites reinforced with cellulosic fibres (CMCRCFs). The drying experiments were carried out on four levels of oven-drying temperatures (70, 85, 105, and 120 °C), with four different cellulosic fibres content (0, 5, 10, and 20 %). Obtained results were compared to those derived by regression analysis of six most typically used mathematical drying models (Newton, Page, Page modified1, Page modified2, Handerson Pabis, and Logarithmic) in addition to six proposed models. The regression accuracy of the drying process was evaluated by the coefficient of determination (R2), low mean square error (MSE), low root mean squared error (RMSE), and mean absolute error (MAE). Additional criteria were used to ensure more validity of the selected models. The obtained values indicate a highly accurate fit of the proposed model MR9, meaning that the proposed model can clearly interpret the experimental drying data and predict the dry state of CMCRCFs.

  • Publication . Other literature type . Article . 2022
    Open Access English
    Authors: 
    Dornjak, Luka; Ostojić, Karla; Klaser, Teodoro; Urlić, Inga; Rogina, Anamarija;
    Country: Croatia

    Kitozanski nosači su efektivni biološki aktivni materijali sa širokom primjenom u kemiji i medicini. Kitozan je linearni polisaharid, derivat hitina, koji posjeduje dobru biokompatibilnost koja se pripisuje prisustvu funkcionalnih skupina kao što su −OH i −NH2 koje pridonose biorazgradljivim i antibakterijskim svojstvima. U kiselim vodenim otopinama kitozan je polikationske strukturne prirode, koja ima veliku sposobnost stvaranja kompleksa s različitim metalnim ionima i važnim biomolekulama, kao što su DNA, proteini i lipidi. Jedinstvena struktura, kao i uvođenje specifičnih funkcionalnih skupina odgovorni su za antibakterijska svojstva, hemostatsku aktivnost i analgetska svojstva tog biopolimera. Za poboljšanje angiogenih i antimikrobnih svojstava, kitozan se može modificirati borom (boratnim ionima). Cilj ovog rada bio je pripremiti bornom kiselinom modificirane kitozanske nosače, upotrebljavajući bornu kiselinu kao prekursor bora, u svrhu priprave potencijalnih bioaktivnih okosnica za regeneraciju tkiva. Boratni ioni imaju sklonost stvaranja kompleksa s hidroksilnim skupinama, međutim, takve interakcije između funkcionalnih skupina kitozana i bora rezultiraju slabijom učinkovitosti njegove inkapsulacije. Da bi se osigurala bolja ugradnja bora, kitozanski nosači su umreženi genipinom, manje toksičnim umreživalom u odnosu na glutaraldehid koji se obično upotrebljava za pripremu stabilnih materijala čiji se sastav temelji na kitozanu. Stupanj deacetilacije (DD) i koncentracija otopine kitozana kao i koncentracija otapala važni su parametri koji utječu na proces umreživanja. Nadalje, dodatak borne kiseline mogao bi utjecati na proces umreživanja zauzimanjem funkcionalnih skupina kitozana. U ovom radu kitozanski nosači modificirani su bornom kiselinom različite koncentracije, dok su koncentracija otopine kitozana (1,2 w/v), koncentracija genipina (2 % w/w) i koncentracija octene kiseline (0,5 % v/v) bile konstantne. Dobiveni nosači okarakterizirani su pretražnom elektronskom mikroskopijom (SEM), energetski disperzivnom rendgenskom spektroskopijom (EDS), diferencijalnom pretražnom kalorimetrijom (DSC), infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR), dok je citotoksičnost procijenjena kao funkcija koncentracije materijala i vremena izloženosti stanica materijalu. Rezultati su pokazali uspješnu ugradnju bora u umrežene kitozanske nosače, visoko poroznu strukturu i nisku citotoksičnost. Chitosan scaffolds are an effective biologically active material with versatile application in chemistry and medicine. Chitosan is a linear polysaccharide, a derivative of chitin, with great biocompatibility due to the possession of functional groups such as −OH and −NH2, which allow for biodegradability and antibacterial function. Chitosan has a polycation nature allowing complex formation with metal ions and many biomolecules such as DNA, proteins and lipids, while its specific structure and functional groups are responsible for antibacterial, hemostatic, and analgesic properties. To improve its angiogenic and antimicrobial potential, chitosan can be modified by boron (borate ions). The aim of this work was to prepare boric acid modified chitosan scaffolds, using boric acid as a boron precursor, as potential bioactive scaffolds for tissue regeneration. Borate ions tend to form complexes with hydroxyl groups, however, such physical interactions between boron and chitosan functional groups result in poor encapsulation efficiency. To ensure higher boron incorporation, chitosan scaffolds were cross-linked by genipin, a cross linker with lower cytotoxicity in contrast to glutaraldehyde commonly used to prepare stable chitosan-based materials. The degree of deacetylation (DD) and concentration of chitosan solution as well as the concentration of a solvent are important parameters that affect the crosslinking process. Moreover, the addition of boric acid could interfere with the crosslinking process by occupying chitosan functional groups. Here, chitosan scaffolds were modified with different concentrations of boric acid, while the concentrations of chitosan solution (1.2 w/v), genipin (2 % w/w), and acetic acid (0.5 % v/v) were kept constant. Obtained scaffolds were characterised by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), Fourier transformation infrared spectroscopy (FTIR), while cytotoxicity was evaluated as a function of materials concentration and exposure time. The results indicated successful incorporation of boron into cross-linked chitosan scaffolds with highly porous structure and low cytotoxicity.

  • Open Access English
    Authors: 
    Josipa Papac Zjačić; Silvia Morović; Krešimir Košutić; Danijela Ašperger;
    Country: Croatia

    Prisutnost farmaceutika u vodama problematična je iz više aspekata, uglavnom zbog njihove specifične prirode djelovanja u sustavu u kojem se nalaze te pripadajućih fizikalno kemijskih karakteristika koje ih čine postojanim i otpornim na razgradnju. Osim toga, skloni su bioakumulaciji u vodenom okolišu te mogu imati toksičan učinak na žive organizme. Ta grupa onečišćivala redovito je detektirana u konvencionalnim sustavima za obradu otpadnih voda. Uklanjanje farmaceutika iz voda konvencionalnim primarnim i sekundarnim metodama (filtracija, taloženje, biološka obrada) nije zadovoljavajuće, pa se sve više razvijaju i primjenjuju napredni postupci, u koje spadaju membranske i oksidacijske tehnologije. Najveća prednost membranskih tehnologija je njihova visoka razina industrijske primjene uz zadovoljavanje najviših standarda za vode. Napredni oksidacijski postupci karakteristični su po mogućnosti razgradnje složenih onečišćivala do jednostavnijih te mineralizaciji organskih onečišćivala u otpadnim vodama uz malo ili gotovo nikakvo nastajanje sekundarnog otpada. U svrhu daljnjeg poboljšanja njihovih prednosti, ali i otklanjanja nedostataka, te se tehnologije sve češće međusobno nadopunjuju i kombiniraju, što rezultira povećanjem učinkovitosti uklanjanja farmaceutika iz voda i smanjenjem njihove toksičnosti. The presence of pharmaceuticals in the aquatic environment is problematic in many aspects, mainly due to their specific mode of action, and physical and chemical properties that make them highly resistant to degradation. This new group of contaminants is frequently detected in conventional wastewater treatment plants. Removal of pharmaceuticals from water by primary and secondary methods (filtration, sedimentation, biological treatment) is not satisfactory, therefore advanced methods involving membrane and advanced oxidation processes are increasingly being developed. The most significant advantage of membrane technologies is their wide industrial applicability while maintaining the highest water standards. Advanced oxidation processes can effectively decompose complex pollutants into simpler ones, and mineralize organic pollutants in wastewater without generating secondary waste. In order to improve their advantages, but also to eliminate disadvantages, these technologies are increasingly complemented and combined, resulting in higher efficiency in removing pharmaceuticals from water and reducing their toxicity.

  • Open Access Croatian
    Authors: 
    Želimir Kurtanjek;
    Country: Croatia

    Cilj ovog rada je pokazati mogućnosti primijene metodologije umjetne inteligencije i strukturnog kauzalnog modeliranja (engl. Structural Causal Model, SCM) s ciljem postizanja znanstvenog doprinosa utvrđivanjem kauzalne funkcionalne zakonitosti bioloških značajki o abiotičkim parametrima. Temeljna zadaća rada je istražiti model SCM za određivanje zavisnosti koncentracije klorofila o fizikalnim značajkama u području sjevernog Jadrana tijekom razdoblja od 1965. do 2015. godine. Eksperimentalni podatci rezultat su dugotrajnog i ekstenzivnog istraživanja u okviru EU projekta “LTER Northern Adriatic Sea” i dostupni su (putem EU znanstvene politike “Open Science”) u velikoj bazi podataka (engl. Big Data), koja sadrži 10 8687 uzoraka s 43 značajke. Predložen je matematički model Bayesove mreže (engl. Bayes Network, BN) kao usmjereni neciklički graf (engl. Directed Acyclic Graph, DAG). Struktura grafa određena je primjenom testa uvjetne nezavisnosti (Hamilton-Schmidtova Conditional Indepedence test, HSCI) s razinom signifikantnosti α = 0,05. SCM model pokazuje da su neposredni kauzalni utjecaji na koncentraciju klorofila: temperatura, salinitet, pH, dušik, fosfor i silicij. Primijenjena je metodologija d-razdvajanja BN grafa sa svrhom blokiranja interferencije (engl. confounding) za procjenu kauzalne funkcionalne zavisnosti bioloških značajki o abiotičkim parametrima. Funkcije kauzalnosti određene su kao rubne razdiobe (engl. marginal distributions) modeliranjem Bayesovom neuronskom mrežom (engl. Bayes Neural Network, BNN). Najveći neposredni negativni kauzalni učinak na klorofil A (Chlorophyll A) ima temperatura (−0,07 μg klorofila A/°C). Utvrđena je pozitivna kauzalna zavisnost između klorofila-A i otopljenog kisika (0,2 mg otopljenog kisika DO2/μg klorofila A). Također je provedena neparametarska usporedna analiza klorofila A i fizikalnih parametara hrvatskog dijela i podataka za cjelokupni sjeverni Jadran. Medijan koncentracije otopljenog kisika u hrvatskom dijelu Jadrana je 5,8 mg O2/l a u sjevernom je 5,5 mg O2/l, dok je medijan temperature u hrvatskom dijelu T = 14,6 °C u odnosu na T = 15,1 °C za sjeverni Jadran. Medijan broja stanica bičaša (Dinoflagellate) je u hrvatskom dijelu Jadrana 3 stanice/l, u odnosu na cijeli sjeverni Jadran, gdje je on od 5 stanica/l. Značajna je razlika u učestalosti i iznosu visokog broja bičaša. Medijani koncentracija klorofila A ne pokazuju značajnu razliku (0,65 i 0,90 μg l–1), ali u sjevernom Jadranu je znatno veći broj uzoraka koji po iznosu signifikantno odstupaju od normalne razdiobe (engl. outliers or hotspots). Utvrđena je i značajna razlika u razdiobi koncentracije silicija s velikim brojem uzoraka s visokim koncentracijama u zapadnom dijelu Jadrana. Primijenjeni su modeli “šume” stabala odlučivanja (engl. random forest) predikcije bioloških značajki na osnovi abiotičkih veličina. Validacije modela provedene su određivanjem relativne postotne pogreške predikcije primjenom simulacije “novih” podataka peterostrukom podjelom baze podataka. Postignute su sljedeće pogreške modela predikcije: za klorofil (engl. chlorophyll) 6,5 %; feopigment (Pheeopigment) 17,4 %; diatomeje (Diatom) 18,8 %; dinoflagelat (Dinoflagellate) 17,4 %; i kokolitifore (Coccolithoophores) 12,1 %. Za svaki od modela utvrđeni su ključni abiotički faktori za procjenu predikcija. The aim of this work was to show possibilities of applied artificial intelligence methodologies and structural causal modelling (“Structural Causal Model”, SCM) with the object of gaining a scientific level contribution to the determination of functional causal dependencies in complex ecological systems. In this work, applied was SCM for the determination of dependencies of chlorophyll concentration on physical and chemical parameters in the northern Adriatic Sea during the period 1965 to 2015. The experimental data are the outcome of the long-term and extensive investigation as a part of the EU project “LTER Northern Adriatic Sea”, and are freely available within the EU Open Science policy. The data are a “Big Data” base with 108 687 samples and 43 descriptors. Proposed is a mathematical model with Bayes network (BN) as a directed acyclic graph (DAG). The model structure was determined by the Hamilton-Schmidt conditional independence test with a significance level of α = 0.05. The SCM model shows that the direct causal variables for chlorophyll concentration are: temperature, salinity, pH, and concentrations of nitrogen, phosphor, and silica. The BN model was adjusted according to d-separation with the objective to block confounding and contra-causal back door interference. The functions of causal dependencies were determined as the marginal distributions with Bayes network models with a single interior layer for interpolation. The most important causal effect was due to temperature (−0.07 μg chlorophyll A/°C). The model predicted reversed positive causality between chlorophyll concentration and dissolved oxygen (0.2 mg DO2/μg chlorophyll A). Also evaluated was nonparametric comparative analysis of chlorophyll and abiotic parameters between Croatian and northern Adriatic Sea (Slovenia and Italy). The comparison was based on median metrics to avoid the pronounced influence of outliers due to hydrodynamic effects. The median concentration of dissolved oxygen in Croatian Adriatic was 5.8 mg O2/l, while in Slovenian and Italian 5.5 mg O2/l, and the median temperature was T = 14.6 °C compared to T = 15.1 °C. There is a significant difference in the abundance of dinoflagellates in Croatia 3 cell/l, while in Slovenia and Italian 5 cells/l. The difference is more pronounced by the number and values of “hot spots” outliers. The difference between chlorophyll concentrations is not significant (0.65 and 0.90 μg l–1); however, the difference in the distribution of the outliers is significant with more frequent and bigger outliers in Italian and Slovenian Adriatic. Also observed was a significant difference in SiO4 distribution, with higher concentrations in the western Adriatic. The random forest RF decision tree models are applied for the development of the predictive models of biological parameters based on abiotic data. The RF models are validated by 5-fold cross-validation. The models have out-of-box mean relative errors of 6.5 % for chlorophyll, photopigment 17.4 %; diatoms 18.8 %; dinoflagellate 17.4 %; and 12.1 % for coccolithophores. For each predictive model determined are the first five most important predictors accounting for 95 % of importance.

  • Open Access
    Authors: 
    Jeličić, Mario-Livio;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    With the use of fixed-dose drug combinations, the potential risk of non-adherence needs to be minimised, which is particularly important in patients with chronic diseases. The development of such dosage form is a complex process in which an important role is played by testing the physicochemical compatibility of the components intended for the manufacture of the desired product. Various analytical techniques, such as thermoanalytical (DSC, DTA), spectroscopic (FTIR, XRPD) and chromatographic (HPLC), in combination with certain degradation studies, such as forced degradation and isothermal degradation, are often used. In this review, on the example of the development of a fixed-dose combination of 5-aminosalicylate and folic acid, procedures suitable for testing the compatibility of drug components, as well as analytical techniques and various ways of interpretation of results are described. Uvođenjem fiksnih kombinacija lijekova potencijalni rizik od neadherencije nastoji se svesti na najmanju moguću mjeru, što je posebice važno kod pacijenata koji boluju od kroničnih bolesti. Razvoj takvog ljekovitog oblika složen je postupak u kojem važnu ulogu ima ispitivanje fizikalno-kemijske kompatibilnosti sastavnica predviđenih za izradu željenog proizvoda. U svrhu provedbe takvih studija često se primjenjuju različite analitičke tehnike, poput termoanalitičkih (DSC, DTA), spektroskopskih (FTIR, XRPD) te kromatografskih (HPLC) u kombinaciji s određenim studijama razgradnji, poput prisilne razgradnje i izotermalne razgradnje. U ovom radu, na primjeru razvoja fiksne kombinacije 5-aminosalicilata i folne kiseline, bit će opisani postupci prikladni za ispitivanje kompatibilnosti sastavnica lijeka kao i analitičke tehnike te razni načini interpretacije rezultata.

  • Open Access
    Authors: 
    Janda, Rea; Mikulec, Nataša; Andabaka, Damir; Vitale, Ksenija;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Living and working environments are most often closed spaces where it is necessary to provide health protection for family members and employees. Some activities require special protection, especially during a pandemic. The living and working environments can be kept clean and tidy in three ways: by cleaning, disinfecting, and sanitising. This paper presents a review of the literature linking disinfectants, their use, and resistance of microorganisms to disinfectants. In addition, it gives an overview of critical points that have arisen in various testing laboratories in the Republic of Croatia, related to the COVID-19 pandemic, and as a consequence of the lack of guidelines in norms. The literature search was conducted based on the keyword ‘disinfection’ in PubMed, Science Direct, Web of Science, Scopus and Google Scholar databases, and on the CDC and HZJZ websites due to the latest recommendations regarding COVID-19 infections. Results have shown that a norm is a basic document that needs a specific upgrade depending on the type of laboratory and its activities, and it should not be an independent decision of each individual laboratory. Based on the identified needs and problems, state institutions should provide detailed instructions depending on the laboratory activity. Therefore, this situation and the experience gained should be used as a starting point for document development that could be applicable in crisis states generally. In addition, it could be used as a basis for education and training in crisis states. Životni i radni okoliš najčešće su zatvoreni prostori, te je u njima potrebno osigurati zdravstvenu zaštitu ukućana i djelatnika. Neke djelatnosti traže posebnu zaštitu, pogotovo u vrijeme pandemije. Životni i radni okoliš mogu se održavati čistim i urednim na tri načina: čišćenjem, dezinfekcijom i sanitacijom. U ovom radu dan je pregled literature koja povezuje dezinfekcijska sredstva, njihovu uporabu i rezistentnost mikroorganizama na dezinfekcijska sredstva. Također, dan je prikaz kritičnih točki koje su se pojavile u različitim ispitnim laboratorijima u Republici Hrvatskoj vezanih za pandemiju COVID-19, kao posljedica nedostatka naputaka u normama. Pretraživanje literature provedeno je temeljem ključne riječi dezinfekcija u bazama PubMed, Science Direct, Web of Science, Scopus i Google Scholar te na stranicama CDC-a i HZJZ-a zbog najnovijih preporuka vezanih za infekcije COVID-19. Rezultati su pokazali da je Norma osnovni dokument, ali bi za ovakve situacije trebao i specifičnu nadogradnju ovisno o tipu laboratorija i njegovoj djelatnosti kako pojedini laboratoriji ne bi donosili samostalne odluke. Temeljem identificiranih potreba i problema, državne institucije trebale bi dati detaljne upute ovisno o djelatnosti. Stoga, ovu situaciju i stečeno iskustvo treba iskoristiti i izraditi dokumente koji će biti primjenjivi u kriznim situacijama u budućnosti i na temelju kojih je moguće provesti i edukaciju osoblja o ponašanju u kriznim situacijama.

  • Publication . Other literature type . Article . 2022
    Open Access
    Authors: 
    Žužić, Andreja; Macan, Jelena;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Perovskites are investigated as potential working materials in new technologies, such as solid oxide fuel cells, thermochemical energy storage, and magnetic refrigerators. They are interesting due to their application properties, such as electrical conductivity, ferromagnetic properties, and reducibility. Properties of perovskites can be improved by doping and the formation of structural defects. The aim of this work was to investigate the possibility of preparing Sr-doped lanthanum manganite with the chemical formula La0.5Sr0.5MnO3 by coprecipitation procedure, and to analyse the observed phase separation. The material was prepared by coprecipitation procedure in which sources of metal cations (La3+, Sr2+, Mn2+) were dissolved in 0.5 M HNO3. The nitrate solution was added dropwise in 10 wt% NH4HCO3 solution, both solutions being heated to 65 °C. To achieve coprecipitation of all present metal cations, the pH value was maintained at 8 by the addition of aqueous ammonia. The obtained precipitate was filtered and dried to obtain the precursor powder. One part of the prepared powder was calcined at 1200 °C/2 h (sample CL_Sr0.5_p), while the other part was pressed into a tablet and sintered in the same conditions (sample CL_Sr0.5_tab). Even though FTIR and PXRD analyses of the sample CL_Sr0.5_p (Figs. 1A-C) showed the formation of the pure phase, light and dark spots were observed during the SEM analysis of the tablet (CL_Sr0.5_tab) fracture surface (Fig. 2). These spots were analysed by energy-dispersive spectroscopy (EDS). EDS analysis (Table 1) showed that the light spots were SrMnO3 phase, while the dark spots were La0.76Sr0.24MnO3 phase. The tablet was then ground and FTIR and PXRD analyses were conducted. The obtained FTIR results (Figs. 1A and 1B) showed some bands characteristic for the SrMnO3 phase, and low-intensity maxima originating from the SrMnO3 phase were observed on the diffractogram (Fig. 1C) of CL_Sr0.5_tab sample, confirming the existence of separated phase. This was additionally investigated by the Rietveld refinement analysis (Table 1), and it was determined that Sr concentration was 0.24 instead of the targeted 0.5. Therefore, the La0.76Sr0.24MnO3 phase was formed, while the rest of added strontium during the synthesis crystallised in the SrMnO3 phase. Since successful preparation of La0.5Sr0.5MnO3 by hydrothermal synthesis was reported by multiple authors, it can be concluded that the coprecipitation procedure is not suitable for high concentration doping of LaMnO3 due to the separation of Sr into the secondary phase, especially when in tablet form. Perovskiti su tema brojnih znanstvenih istraživanja zbog svojih primjenskih svojstava, kao što su električna vodljivost, feromagnetičnost i reduktivnost. Svojstva perovskita dodatno se mogu poboljšati dopiranjem te formiranjem strukturnih defekata. Cilj ovog rada bio je istražiti mogućnost pripreme stroncijem dopiranog lantanova manganita kemijske formule La0,5Sr0,5MnO3 postupkom koprecipitacije. Dio materijala žaren je na 1200 °C/2h, a dio je prešan u tabletu i sinteriran na istim uvjetima. Iako je rendgenska difrakcijska (PXRD) analiza žarenog praha ukazivala na nastanak čiste faze, morfološkom analizom lomne površine tablete uočene su dvije faze. Energijski razlučujuća rendgenska spektrometrija pokazala je da je svjetlija faza SrMnO3, dok je tamnija La0,76Sr0,24MnO3. Tableta je usitnjena te analizirana PXRD-om. Iako su se maksimumi poklapali sa standardnom rendgenskom karticom faze La0,5Sr0,5MnO3, Rietveldovom metodom utočnjavanja potvrđen je udio Sr od 0,24 i nastanak faze La0,76Sr0,24MnO3. Ostatak stroncija dodanog tijekom sinteze kristalizirao je u SrMnO3 fazu. Time je potvrđeno da je supstitucija moguća do određene mjere nakon koje postoji opasnost od izdvajanje nove faze, pogotovo ako je uzorak pripremljen u obliku tablete.

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  • Open Access Croatian
    Authors: 
    Banožić, Marija; Šafranko, Silvija; Bogadi, Dora; Aladić, Krunoslav; Jokić, Stela;
    Country: Croatia

    The peel of the Okitsu variety of mandarin is created as a by-product of the fruit’s growth and processing. The primary goal of this research was to use a unique nonthermal extraction method (high-voltage electric discharge assisted) with green solvent (water) to valorise citrus peel as a valuable raw material. In October 2020, samples (citrus peel) were collected from the farm of Mr. Dalibor Ujević (Opuzen, Hrvatska). Samples were washed, freeze-dried, and sieved before extraction. The effects of extraction process parameters, such as treatment duration (5–15 min), frequency (40–100 Hz), and liquid to solid ratio (200–400 ml g–1) on the extraction yield and content of hesperidin and narirutin were studied. Spectrophotometric methods were used to assess the antiradical activity and total phenolic content of the extracts. Individual phenolic components were identified and quantified using HPLC method. The extraction process parameters were optimised with a commercial softer tool (Design Expert®) using experimental data gathered using the Box-Behnken experimental design. Experiments were conducted as shown in Tables 1 and 2. The extraction yield was ranked from 359.23 to 463.20, the total phenol values ranged from 96.23 to 275.46 mg GAE l–1, DPPH values ranged from 87.08 to 94.93 %. Total phenol content and antiradical activity decreased with increasing extraction time, as shown in Fig. 1. Six phenolic compounds were identified and quantified, predominated by hesperidin and narirutin (Table 3). The regression models for all tested HVED extraction responses were significant (p-value under 0.05) based on the acquired data, and the quality of the models produced was evaluated based on the coefficients of determination (R2) and Lack of Fit value. The obtained R2 values for all models developed were 0.911; 0.844, and 0.845 with a nonsignificant lack of fit, indicating an adequate relationship between input parameters (extraction conditions) and observed variable, in this case, extraction efficiency, hesperidin and narirutin content (Table 4). The obtained data was utilised to create three-dimensional (3D) response surface graphs, as shown in Figs. 2–4. The regression models within this study were predicted by Eqs. (1)–(3). With response surface methodology (RSM), optimal parameters of HVED extraction process were defined, as follows: extraction yield (285.93 ml g–1, 73.38 Hz and 14.84 min), hesperidin content (366.19 ml g–1, 97.56 Hz, and 5.1 min), and narirutin content (200 ml g–1, 70 Hz, and 15 min), as presented in Table 5, together with predicted and experimentally verified values. Konzumacija svježih citrusa, ali i njihova prerada generiraju nusproizvode, kao što su kora, sjemenke, pulpa, kao i otpadne vode. Cilj ovog istraživanja je valorizacija agroindustrijskih nusproizvoda (kore citrusa) kao vrijedne sirovine za ekstrakciju polifenola primjenom inovativne netermalne metode ekstrakcije sa zelenim otapalom (voda). U ekstraktima je kvantificirano i identificirano ukupno šest fenolnih spojeva. Pri tome je promatran utjecaj vremena (od 5 do 15 min), frekvencije (od 40 do 100 Hz) i omjera kapljevito/kruto (od 200 do 400 ml g–1) na efikasnost procesa ekstrakcije (iskorištenje) i udio dominantnih fenolnih spojeva (hesperidina i narirutina). Uz pomoć metode odzivnih površina definirani su optimalni parametri promatranog procesa ekstrakcije za svaki od istraživanih odziva, i to za iskorištenje (285,93 ml g–1, 73,38 Hz i 14,84 min), za hesperidin (366,19 ml g–1, 97,56 Hz i 5,1 min) te za narirutin (200 ml g–1, 70 Hz i 15 min). Ekstrakcija potpomognuta visokonaponskim električnim pražnjenjem (HVED ekstrakcija) pokazala se pogodnom za ekstrakciju fenolnih spojeva, pri čemu je izbjegnuta uporaba organskih otapala.

  • Publication . Other literature type . Article . 2022
    Open Access
    Authors: 
    Štrkalj, Anita; Mesek, Luka; Ocelić Bulatović, Vesna; Glavaš, Zoran;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Metalurški otpad ima velik potencijal za uporabu kao adsorbens za uklanjanje teških metala iz otpadnih voda, ističući se kao mogući jeftini adsorbens. U ovom članku prikazano je adsorpcijsko ponašanje Zn(II) iona na dva kruta metalna otpadna materijala – otpadnoj kalupnoj mješavini (OKM) i otpadnoj anodnoj prašini (AP). Dobiveni rezultati pokazali su da se oba otpadna materijala mogu upotrebljavati kao potencijalni adsorbensi. Anodna prašina ima bolja adsorpcijska svojstva. Ravnotežni podatci za adsorpciju Zn(II) na otpadnim metalurškim materijalima ispitani su Freundlichovim i Langmuirovim izotermnim modelima. Utvrđeno je da je Langmuirov model prikladniji te da se adsorpcija odvija kao kemisorpcija. Metallurgical waste has great potential for use as an adsorbent for the removal of heavy metals from wastewater, standing out as possible low-cost adsorbents. This article presents the adsorption behaviour of Zn(II) ions on two solid metal waste materials – waste mould sand (WMS) and anode dust (AD). The obtained results showed that both waste materials could be used as potential adsorbents. Anode dust has better adsorption properties. The equilibrium data for the adsorption of Zn(II) on waste metallurgical materials were examined by Langmuir and Freundlich’s adsorption isotherm models. It was found that the Langmuir model is more appropriate, and that adsorption takes place as chemisorption.

  • Open Access Croatian
    Authors: 
    Tomislav Domanovac; Marija Vuković Domanovac; Dajana Kučić Grgić; Monika Šabić Runjavec;
    Country: Croatia

    Maintenance of green urban areas, backyards and gardens, as well as food preparation and consumption generate municipal biodegradable waste, i.e., biowaste that must be collected and processed in accordance with environmental protection regulations and waste management objectives of the Republic of Croatia. By determining the composition and amount of municipal waste, the quantities generated in the assumed area were estimated. From the mentioned input data on the amount of biowaste and input process data that are relevant for the implementation of biological treatment of biowaste in aerobic conditions, the necessary equipment and space were dimensioned, taking into account the dynamics of the process and the necessary technological operations. Thus, the operation of machines for shredding and mixing with a capacity of about 50 m3 h–1, aeration and irrigation with a capacity of about 1,000 m3 h–1, screening with a capacity of about 23.2 m3 h–1, as well as manipulation of biowaste and compost was planned. Four bioreactors with a capacity of about 1 421 t y–1 each, fans and other process-measuring equipment were planned. Waste air flow with biodegradation products were purified before released into the atmosphere using a biofilter of about 9 m2 and 1.5 m of filled layer of wood chips, bark, mature compost, and other additives. By composting about 3 641 t y–1 of biowaste, which is approximately the minimum amount of biowaste that a presumed area of about 77 000 inhabitants needs to be processed to meet the waste management objectives of the Republic of Croatia, the estimated production of about 2 575 t y–1 of mature compost would be reduced by about 34.1 %, or volume by about 50.5 %. About 2 174 000 EUR needs to be invested in facilities and equipment, with total operating costs of about 83 EUR/t of input biowaste. Pripremom i konzumiranjem hrane u kućanstvima te održavanjem zelenih javnih površina, okućnica i vrtova nastaje biootpad koji je potrebno odvojeno sakupiti i obraditi u skladu s propisima iz područja zaštite okoliša, odnosno ciljevima gospodarenja otpadom u Republici Hrvatskoj. Na temelju sastava i količine komunalnog otpada procijenjene su godišnje količine biootpada razmatranog područja. Iz ulaznih podataka o količini biootpada te ulaznih procesnih podataka koji su relevantni za provedbu biološke obrade biootpada u aerobnim uvjetima, dimenzionirana je potrebna oprema i prostor uvažavajući dinamiku procesa i potrebne tehnološke operacije. U ovom radu je analizirano pretpostavljeno područje od oko 77 000 stanovnika te je pretpostavljeno da to stanovništvo proizvede oko 3 641 t god–1 biootpada. Biološkom obradom odvojeno sakupljenog biootpada u aerobnim uvjetima koja se provodi na kompostani malog kapaciteta procjenjuje se proizvodnja oko 2 575 t god–1 zrelog komposta, što predstavlja smanjenje ulazne mase biootpada od oko 34,1 %, odnosno volumena za oko 50,5 %. Troškovi izgradnje objekata i nabave opreme procjenjuju se na oko 16 305 000 kn (2 174 000 EUR), a ukupni troškovi rada postrojenja s uračunatom amortizacijom na oko 625 kn/t (83 EUR/t) ulaznog biootpada.

  • Open Access
    Authors: 
    Amina Lachenani‬; Mohamed Bentchikou; Mouloud Boumahdi; Salah Hanini; Maamar Laidi;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    U ovom radu predloženo je i primijenjeno šest novih matematičkih modela temeljenih na poluempirijskom proračunu za karakterizaciju procesa sušenja u pećnici kompozita cementne žbuke ojačane celuloznim vlaknima (CMCRCF). Pokusi sušenja provedeni su pri četiri razine temperature sušenja u pećnici (70, 85, 105 i 120 °C) s četiri različita udjela celuloznih vlakana (0, 5, 10 i 20 %). Dobiveni rezultati uspoređeni su s onima dobivenim regresijskom analizom šest najčešće primjenjivanih matematičkih modela sušenja (Newton, Page, Page modified1, Page modified2, Handerson Pabis i Logarithmic) uz šest predloženih modela. Regresijska točnost procesa sušenja procijenjena je koeficijentom determinacije (R2), srednjom kvadratnom pogreškom (MSE), korijenom srednje kvadratne pogreške (RMSE) i srednjom apsolutnom pogreškom (MAE). Primijenjeni su i dodatni kriteriji da bi se osigurala veća valjanost odabranih modela. Dobivene vrijednosti pokazuju dobro slaganje predloženog modela MR9 s eksperimentalnim vrijednostima, što znači da predloženi model može jasno interpretirati eksperimentalne podatke o sušenju i predvidjeti suho stanje CMCRCF-a. In this paper, six novel mathematical models based on semi-empirical calculus are proposed and applied to characterise the oven-drying process of cement mortar composites reinforced with cellulosic fibres (CMCRCFs). The drying experiments were carried out on four levels of oven-drying temperatures (70, 85, 105, and 120 °C), with four different cellulosic fibres content (0, 5, 10, and 20 %). Obtained results were compared to those derived by regression analysis of six most typically used mathematical drying models (Newton, Page, Page modified1, Page modified2, Handerson Pabis, and Logarithmic) in addition to six proposed models. The regression accuracy of the drying process was evaluated by the coefficient of determination (R2), low mean square error (MSE), low root mean squared error (RMSE), and mean absolute error (MAE). Additional criteria were used to ensure more validity of the selected models. The obtained values indicate a highly accurate fit of the proposed model MR9, meaning that the proposed model can clearly interpret the experimental drying data and predict the dry state of CMCRCFs.

  • Publication . Other literature type . Article . 2022
    Open Access English
    Authors: 
    Dornjak, Luka; Ostojić, Karla; Klaser, Teodoro; Urlić, Inga; Rogina, Anamarija;
    Country: Croatia

    Kitozanski nosači su efektivni biološki aktivni materijali sa širokom primjenom u kemiji i medicini. Kitozan je linearni polisaharid, derivat hitina, koji posjeduje dobru biokompatibilnost koja se pripisuje prisustvu funkcionalnih skupina kao što su −OH i −NH2 koje pridonose biorazgradljivim i antibakterijskim svojstvima. U kiselim vodenim otopinama kitozan je polikationske strukturne prirode, koja ima veliku sposobnost stvaranja kompleksa s različitim metalnim ionima i važnim biomolekulama, kao što su DNA, proteini i lipidi. Jedinstvena struktura, kao i uvođenje specifičnih funkcionalnih skupina odgovorni su za antibakterijska svojstva, hemostatsku aktivnost i analgetska svojstva tog biopolimera. Za poboljšanje angiogenih i antimikrobnih svojstava, kitozan se može modificirati borom (boratnim ionima). Cilj ovog rada bio je pripremiti bornom kiselinom modificirane kitozanske nosače, upotrebljavajući bornu kiselinu kao prekursor bora, u svrhu priprave potencijalnih bioaktivnih okosnica za regeneraciju tkiva. Boratni ioni imaju sklonost stvaranja kompleksa s hidroksilnim skupinama, međutim, takve interakcije između funkcionalnih skupina kitozana i bora rezultiraju slabijom učinkovitosti njegove inkapsulacije. Da bi se osigurala bolja ugradnja bora, kitozanski nosači su umreženi genipinom, manje toksičnim umreživalom u odnosu na glutaraldehid koji se obično upotrebljava za pripremu stabilnih materijala čiji se sastav temelji na kitozanu. Stupanj deacetilacije (DD) i koncentracija otopine kitozana kao i koncentracija otapala važni su parametri koji utječu na proces umreživanja. Nadalje, dodatak borne kiseline mogao bi utjecati na proces umreživanja zauzimanjem funkcionalnih skupina kitozana. U ovom radu kitozanski nosači modificirani su bornom kiselinom različite koncentracije, dok su koncentracija otopine kitozana (1,2 w/v), koncentracija genipina (2 % w/w) i koncentracija octene kiseline (0,5 % v/v) bile konstantne. Dobiveni nosači okarakterizirani su pretražnom elektronskom mikroskopijom (SEM), energetski disperzivnom rendgenskom spektroskopijom (EDS), diferencijalnom pretražnom kalorimetrijom (DSC), infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR), dok je citotoksičnost procijenjena kao funkcija koncentracije materijala i vremena izloženosti stanica materijalu. Rezultati su pokazali uspješnu ugradnju bora u umrežene kitozanske nosače, visoko poroznu strukturu i nisku citotoksičnost. Chitosan scaffolds are an effective biologically active material with versatile application in chemistry and medicine. Chitosan is a linear polysaccharide, a derivative of chitin, with great biocompatibility due to the possession of functional groups such as −OH and −NH2, which allow for biodegradability and antibacterial function. Chitosan has a polycation nature allowing complex formation with metal ions and many biomolecules such as DNA, proteins and lipids, while its specific structure and functional groups are responsible for antibacterial, hemostatic, and analgesic properties. To improve its angiogenic and antimicrobial potential, chitosan can be modified by boron (borate ions). The aim of this work was to prepare boric acid modified chitosan scaffolds, using boric acid as a boron precursor, as potential bioactive scaffolds for tissue regeneration. Borate ions tend to form complexes with hydroxyl groups, however, such physical interactions between boron and chitosan functional groups result in poor encapsulation efficiency. To ensure higher boron incorporation, chitosan scaffolds were cross-linked by genipin, a cross linker with lower cytotoxicity in contrast to glutaraldehyde commonly used to prepare stable chitosan-based materials. The degree of deacetylation (DD) and concentration of chitosan solution as well as the concentration of a solvent are important parameters that affect the crosslinking process. Moreover, the addition of boric acid could interfere with the crosslinking process by occupying chitosan functional groups. Here, chitosan scaffolds were modified with different concentrations of boric acid, while the concentrations of chitosan solution (1.2 w/v), genipin (2 % w/w), and acetic acid (0.5 % v/v) were kept constant. Obtained scaffolds were characterised by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), Fourier transformation infrared spectroscopy (FTIR), while cytotoxicity was evaluated as a function of materials concentration and exposure time. The results indicated successful incorporation of boron into cross-linked chitosan scaffolds with highly porous structure and low cytotoxicity.

  • Open Access English
    Authors: 
    Josipa Papac Zjačić; Silvia Morović; Krešimir Košutić; Danijela Ašperger;
    Country: Croatia

    Prisutnost farmaceutika u vodama problematična je iz više aspekata, uglavnom zbog njihove specifične prirode djelovanja u sustavu u kojem se nalaze te pripadajućih fizikalno kemijskih karakteristika koje ih čine postojanim i otpornim na razgradnju. Osim toga, skloni su bioakumulaciji u vodenom okolišu te mogu imati toksičan učinak na žive organizme. Ta grupa onečišćivala redovito je detektirana u konvencionalnim sustavima za obradu otpadnih voda. Uklanjanje farmaceutika iz voda konvencionalnim primarnim i sekundarnim metodama (filtracija, taloženje, biološka obrada) nije zadovoljavajuće, pa se sve više razvijaju i primjenjuju napredni postupci, u koje spadaju membranske i oksidacijske tehnologije. Najveća prednost membranskih tehnologija je njihova visoka razina industrijske primjene uz zadovoljavanje najviših standarda za vode. Napredni oksidacijski postupci karakteristični su po mogućnosti razgradnje složenih onečišćivala do jednostavnijih te mineralizaciji organskih onečišćivala u otpadnim vodama uz malo ili gotovo nikakvo nastajanje sekundarnog otpada. U svrhu daljnjeg poboljšanja njihovih prednosti, ali i otklanjanja nedostataka, te se tehnologije sve češće međusobno nadopunjuju i kombiniraju, što rezultira povećanjem učinkovitosti uklanjanja farmaceutika iz voda i smanjenjem njihove toksičnosti. The presence of pharmaceuticals in the aquatic environment is problematic in many aspects, mainly due to their specific mode of action, and physical and chemical properties that make them highly resistant to degradation. This new group of contaminants is frequently detected in conventional wastewater treatment plants. Removal of pharmaceuticals from water by primary and secondary methods (filtration, sedimentation, biological treatment) is not satisfactory, therefore advanced methods involving membrane and advanced oxidation processes are increasingly being developed. The most significant advantage of membrane technologies is their wide industrial applicability while maintaining the highest water standards. Advanced oxidation processes can effectively decompose complex pollutants into simpler ones, and mineralize organic pollutants in wastewater without generating secondary waste. In order to improve their advantages, but also to eliminate disadvantages, these technologies are increasingly complemented and combined, resulting in higher efficiency in removing pharmaceuticals from water and reducing their toxicity.

  • Open Access Croatian
    Authors: 
    Želimir Kurtanjek;
    Country: Croatia

    Cilj ovog rada je pokazati mogućnosti primijene metodologije umjetne inteligencije i strukturnog kauzalnog modeliranja (engl. Structural Causal Model, SCM) s ciljem postizanja znanstvenog doprinosa utvrđivanjem kauzalne funkcionalne zakonitosti bioloških značajki o abiotičkim parametrima. Temeljna zadaća rada je istražiti model SCM za određivanje zavisnosti koncentracije klorofila o fizikalnim značajkama u području sjevernog Jadrana tijekom razdoblja od 1965. do 2015. godine. Eksperimentalni podatci rezultat su dugotrajnog i ekstenzivnog istraživanja u okviru EU projekta “LTER Northern Adriatic Sea” i dostupni su (putem EU znanstvene politike “Open Science”) u velikoj bazi podataka (engl. Big Data), koja sadrži 10 8687 uzoraka s 43 značajke. Predložen je matematički model Bayesove mreže (engl. Bayes Network, BN) kao usmjereni neciklički graf (engl. Directed Acyclic Graph, DAG). Struktura grafa određena je primjenom testa uvjetne nezavisnosti (Hamilton-Schmidtova Conditional Indepedence test, HSCI) s razinom signifikantnosti α = 0,05. SCM model pokazuje da su neposredni kauzalni utjecaji na koncentraciju klorofila: temperatura, salinitet, pH, dušik, fosfor i silicij. Primijenjena je metodologija d-razdvajanja BN grafa sa svrhom blokiranja interferencije (engl. confounding) za procjenu kauzalne funkcionalne zavisnosti bioloških značajki o abiotičkim parametrima. Funkcije kauzalnosti određene su kao rubne razdiobe (engl. marginal distributions) modeliranjem Bayesovom neuronskom mrežom (engl. Bayes Neural Network, BNN). Najveći neposredni negativni kauzalni učinak na klorofil A (Chlorophyll A) ima temperatura (−0,07 μg klorofila A/°C). Utvrđena je pozitivna kauzalna zavisnost između klorofila-A i otopljenog kisika (0,2 mg otopljenog kisika DO2/μg klorofila A). Također je provedena neparametarska usporedna analiza klorofila A i fizikalnih parametara hrvatskog dijela i podataka za cjelokupni sjeverni Jadran. Medijan koncentracije otopljenog kisika u hrvatskom dijelu Jadrana je 5,8 mg O2/l a u sjevernom je 5,5 mg O2/l, dok je medijan temperature u hrvatskom dijelu T = 14,6 °C u odnosu na T = 15,1 °C za sjeverni Jadran. Medijan broja stanica bičaša (Dinoflagellate) je u hrvatskom dijelu Jadrana 3 stanice/l, u odnosu na cijeli sjeverni Jadran, gdje je on od 5 stanica/l. Značajna je razlika u učestalosti i iznosu visokog broja bičaša. Medijani koncentracija klorofila A ne pokazuju značajnu razliku (0,65 i 0,90 μg l–1), ali u sjevernom Jadranu je znatno veći broj uzoraka koji po iznosu signifikantno odstupaju od normalne razdiobe (engl. outliers or hotspots). Utvrđena je i značajna razlika u razdiobi koncentracije silicija s velikim brojem uzoraka s visokim koncentracijama u zapadnom dijelu Jadrana. Primijenjeni su modeli “šume” stabala odlučivanja (engl. random forest) predikcije bioloških značajki na osnovi abiotičkih veličina. Validacije modela provedene su određivanjem relativne postotne pogreške predikcije primjenom simulacije “novih” podataka peterostrukom podjelom baze podataka. Postignute su sljedeće pogreške modela predikcije: za klorofil (engl. chlorophyll) 6,5 %; feopigment (Pheeopigment) 17,4 %; diatomeje (Diatom) 18,8 %; dinoflagelat (Dinoflagellate) 17,4 %; i kokolitifore (Coccolithoophores) 12,1 %. Za svaki od modela utvrđeni su ključni abiotički faktori za procjenu predikcija. The aim of this work was to show possibilities of applied artificial intelligence methodologies and structural causal modelling (“Structural Causal Model”, SCM) with the object of gaining a scientific level contribution to the determination of functional causal dependencies in complex ecological systems. In this work, applied was SCM for the determination of dependencies of chlorophyll concentration on physical and chemical parameters in the northern Adriatic Sea during the period 1965 to 2015. The experimental data are the outcome of the long-term and extensive investigation as a part of the EU project “LTER Northern Adriatic Sea”, and are freely available within the EU Open Science policy. The data are a “Big Data” base with 108 687 samples and 43 descriptors. Proposed is a mathematical model with Bayes network (BN) as a directed acyclic graph (DAG). The model structure was determined by the Hamilton-Schmidt conditional independence test with a significance level of α = 0.05. The SCM model shows that the direct causal variables for chlorophyll concentration are: temperature, salinity, pH, and concentrations of nitrogen, phosphor, and silica. The BN model was adjusted according to d-separation with the objective to block confounding and contra-causal back door interference. The functions of causal dependencies were determined as the marginal distributions with Bayes network models with a single interior layer for interpolation. The most important causal effect was due to temperature (−0.07 μg chlorophyll A/°C). The model predicted reversed positive causality between chlorophyll concentration and dissolved oxygen (0.2 mg DO2/μg chlorophyll A). Also evaluated was nonparametric comparative analysis of chlorophyll and abiotic parameters between Croatian and northern Adriatic Sea (Slovenia and Italy). The comparison was based on median metrics to avoid the pronounced influence of outliers due to hydrodynamic effects. The median concentration of dissolved oxygen in Croatian Adriatic was 5.8 mg O2/l, while in Slovenian and Italian 5.5 mg O2/l, and the median temperature was T = 14.6 °C compared to T = 15.1 °C. There is a significant difference in the abundance of dinoflagellates in Croatia 3 cell/l, while in Slovenia and Italian 5 cells/l. The difference is more pronounced by the number and values of “hot spots” outliers. The difference between chlorophyll concentrations is not significant (0.65 and 0.90 μg l–1); however, the difference in the distribution of the outliers is significant with more frequent and bigger outliers in Italian and Slovenian Adriatic. Also observed was a significant difference in SiO4 distribution, with higher concentrations in the western Adriatic. The random forest RF decision tree models are applied for the development of the predictive models of biological parameters based on abiotic data. The RF models are validated by 5-fold cross-validation. The models have out-of-box mean relative errors of 6.5 % for chlorophyll, photopigment 17.4 %; diatoms 18.8 %; dinoflagellate 17.4 %; and 12.1 % for coccolithophores. For each predictive model determined are the first five most important predictors accounting for 95 % of importance.

  • Open Access
    Authors: 
    Jeličić, Mario-Livio;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    With the use of fixed-dose drug combinations, the potential risk of non-adherence needs to be minimised, which is particularly important in patients with chronic diseases. The development of such dosage form is a complex process in which an important role is played by testing the physicochemical compatibility of the components intended for the manufacture of the desired product. Various analytical techniques, such as thermoanalytical (DSC, DTA), spectroscopic (FTIR, XRPD) and chromatographic (HPLC), in combination with certain degradation studies, such as forced degradation and isothermal degradation, are often used. In this review, on the example of the development of a fixed-dose combination of 5-aminosalicylate and folic acid, procedures suitable for testing the compatibility of drug components, as well as analytical techniques and various ways of interpretation of results are described. Uvođenjem fiksnih kombinacija lijekova potencijalni rizik od neadherencije nastoji se svesti na najmanju moguću mjeru, što je posebice važno kod pacijenata koji boluju od kroničnih bolesti. Razvoj takvog ljekovitog oblika složen je postupak u kojem važnu ulogu ima ispitivanje fizikalno-kemijske kompatibilnosti sastavnica predviđenih za izradu željenog proizvoda. U svrhu provedbe takvih studija često se primjenjuju različite analitičke tehnike, poput termoanalitičkih (DSC, DTA), spektroskopskih (FTIR, XRPD) te kromatografskih (HPLC) u kombinaciji s određenim studijama razgradnji, poput prisilne razgradnje i izotermalne razgradnje. U ovom radu, na primjeru razvoja fiksne kombinacije 5-aminosalicilata i folne kiseline, bit će opisani postupci prikladni za ispitivanje kompatibilnosti sastavnica lijeka kao i analitičke tehnike te razni načini interpretacije rezultata.

  • Open Access
    Authors: 
    Janda, Rea; Mikulec, Nataša; Andabaka, Damir; Vitale, Ksenija;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Living and working environments are most often closed spaces where it is necessary to provide health protection for family members and employees. Some activities require special protection, especially during a pandemic. The living and working environments can be kept clean and tidy in three ways: by cleaning, disinfecting, and sanitising. This paper presents a review of the literature linking disinfectants, their use, and resistance of microorganisms to disinfectants. In addition, it gives an overview of critical points that have arisen in various testing laboratories in the Republic of Croatia, related to the COVID-19 pandemic, and as a consequence of the lack of guidelines in norms. The literature search was conducted based on the keyword ‘disinfection’ in PubMed, Science Direct, Web of Science, Scopus and Google Scholar databases, and on the CDC and HZJZ websites due to the latest recommendations regarding COVID-19 infections. Results have shown that a norm is a basic document that needs a specific upgrade depending on the type of laboratory and its activities, and it should not be an independent decision of each individual laboratory. Based on the identified needs and problems, state institutions should provide detailed instructions depending on the laboratory activity. Therefore, this situation and the experience gained should be used as a starting point for document development that could be applicable in crisis states generally. In addition, it could be used as a basis for education and training in crisis states. Životni i radni okoliš najčešće su zatvoreni prostori, te je u njima potrebno osigurati zdravstvenu zaštitu ukućana i djelatnika. Neke djelatnosti traže posebnu zaštitu, pogotovo u vrijeme pandemije. Životni i radni okoliš mogu se održavati čistim i urednim na tri načina: čišćenjem, dezinfekcijom i sanitacijom. U ovom radu dan je pregled literature koja povezuje dezinfekcijska sredstva, njihovu uporabu i rezistentnost mikroorganizama na dezinfekcijska sredstva. Također, dan je prikaz kritičnih točki koje su se pojavile u različitim ispitnim laboratorijima u Republici Hrvatskoj vezanih za pandemiju COVID-19, kao posljedica nedostatka naputaka u normama. Pretraživanje literature provedeno je temeljem ključne riječi dezinfekcija u bazama PubMed, Science Direct, Web of Science, Scopus i Google Scholar te na stranicama CDC-a i HZJZ-a zbog najnovijih preporuka vezanih za infekcije COVID-19. Rezultati su pokazali da je Norma osnovni dokument, ali bi za ovakve situacije trebao i specifičnu nadogradnju ovisno o tipu laboratorija i njegovoj djelatnosti kako pojedini laboratoriji ne bi donosili samostalne odluke. Temeljem identificiranih potreba i problema, državne institucije trebale bi dati detaljne upute ovisno o djelatnosti. Stoga, ovu situaciju i stečeno iskustvo treba iskoristiti i izraditi dokumente koji će biti primjenjivi u kriznim situacijama u budućnosti i na temelju kojih je moguće provesti i edukaciju osoblja o ponašanju u kriznim situacijama.

  • Publication . Other literature type . Article . 2022
    Open Access
    Authors: 
    Žužić, Andreja; Macan, Jelena;
    Publisher: Croatian Society of Chemical Engineers/HDKI
    Country: Croatia

    Perovskites are investigated as potential working materials in new technologies, such as solid oxide fuel cells, thermochemical energy storage, and magnetic refrigerators. They are interesting due to their application properties, such as electrical conductivity, ferromagnetic properties, and reducibility. Properties of perovskites can be improved by doping and the formation of structural defects. The aim of this work was to investigate the possibility of preparing Sr-doped lanthanum manganite with the chemical formula La0.5Sr0.5MnO3 by coprecipitation procedure, and to analyse the observed phase separation. The material was prepared by coprecipitation procedure in which sources of metal cations (La3+, Sr2+, Mn2+) were dissolved in 0.5 M HNO3. The nitrate solution was added dropwise in 10 wt% NH4HCO3 solution, both solutions being heated to 65 °C. To achieve coprecipitation of all present metal cations, the pH value was maintained at 8 by the addition of aqueous ammonia. The obtained precipitate was filtered and dried to obtain the precursor powder. One part of the prepared powder was calcined at 1200 °C/2 h (sample CL_Sr0.5_p), while the other part was pressed into a tablet and sintered in the same conditions (sample CL_Sr0.5_tab). Even though FTIR and PXRD analyses of the sample CL_Sr0.5_p (Figs. 1A-C) showed the formation of the pure phase, light and dark spots were observed during the SEM analysis of the tablet (CL_Sr0.5_tab) fracture surface (Fig. 2). These spots were analysed by energy-dispersive spectroscopy (EDS). EDS analysis (Table 1) showed that the light spots were SrMnO3 phase, while the dark spots were La0.76Sr0.24MnO3 phase. The tablet was then ground and FTIR and PXRD analyses were conducted. The obtained FTIR results (Figs. 1A and 1B) showed some bands characteristic for the SrMnO3 phase, and low-intensity maxima originating from the SrMnO3 phase were observed on the diffractogram (Fig. 1C) of CL_Sr0.5_tab sample, confirming the existence of separated phase. This was additionally investigated by the Rietveld refinement analysis (Table 1), and it was determined that Sr concentration was 0.24 instead of the targeted 0.5. Therefore, the La0.76Sr0.24MnO3 phase was formed, while the rest of added strontium during the synthesis crystallised in the SrMnO3 phase. Since successful preparation of La0.5Sr0.5MnO3 by hydrothermal synthesis was reported by multiple authors, it can be concluded that the coprecipitation procedure is not suitable for high concentration doping of LaMnO3 due to the separation of Sr into the secondary phase, especially when in tablet form. Perovskiti su tema brojnih znanstvenih istraživanja zbog svojih primjenskih svojstava, kao što su električna vodljivost, feromagnetičnost i reduktivnost. Svojstva perovskita dodatno se mogu poboljšati dopiranjem te formiranjem strukturnih defekata. Cilj ovog rada bio je istražiti mogućnost pripreme stroncijem dopiranog lantanova manganita kemijske formule La0,5Sr0,5MnO3 postupkom koprecipitacije. Dio materijala žaren je na 1200 °C/2h, a dio je prešan u tabletu i sinteriran na istim uvjetima. Iako je rendgenska difrakcijska (PXRD) analiza žarenog praha ukazivala na nastanak čiste faze, morfološkom analizom lomne površine tablete uočene su dvije faze. Energijski razlučujuća rendgenska spektrometrija pokazala je da je svjetlija faza SrMnO3, dok je tamnija La0,76Sr0,24MnO3. Tableta je usitnjena te analizirana PXRD-om. Iako su se maksimumi poklapali sa standardnom rendgenskom karticom faze La0,5Sr0,5MnO3, Rietveldovom metodom utočnjavanja potvrđen je udio Sr od 0,24 i nastanak faze La0,76Sr0,24MnO3. Ostatak stroncija dodanog tijekom sinteze kristalizirao je u SrMnO3 fazu. Time je potvrđeno da je supstitucija moguća do određene mjere nakon koje postoji opasnost od izdvajanje nove faze, pogotovo ako je uzorak pripremljen u obliku tablete.

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