Repository of the Faculty of Chemistry and Technology, University of Split
Not a member yet
1086 research outputs found
Sort by
The role of catalase in cell : bachelor thesis
No full textReaktivne kisikove vrste sadrže reaktivan kisik koji proizvode živi organizmi kao rezultat staničnog metabolizma. Obrambeni mehanizam koji sprječava oštećenja uzrokovana reaktivnim kisikovim vrstama predstavljaju antioksidansi koji mogu biti enzimski i neenzimski. Enzimi su proteinske molekule tercijarne ili kvarterne strukture koje imaju katalitičku sposobnost i specifičnost za određene kemijske reakcije. Katalaza je enzim iz skupine oksidoreduktaza, tetramerne je strukture i koristi se u raznim industrijama i medicini. Oksidacijski stres je neravnoteža između ROS-a i antioksidansa. Uzročnik je raznih bolesti i oštećenja molekula (DNA, lipida, proteina). Uzročnici oksidacijskog stresa, ROS, u normalnim količinama ne štete organizmima, ali u visokim koncentracijama dovode do raznih modifikacija molekula. Peroksisomi su specijalizirani organeli za provođenje reakcija oksidacije pomoću molekularnog kisika. Oni generiraju vodikov peroksid koji koriste u oksidacijske svrhe i sadrže katalazu kako bi uništili višak štetnih kisikovih spojeva. Glavna funkcija katalaze je antioksidativna. Katalaza djeluje kao agens u borbi protiv reaktivnih kisikovih spojeva i razgrađuje vodikov peroksid u vodu i kisik, te hidrolizira preko milijun molekula supstrata u sekundi. Cilj rada je ukazati na prisutnost oksidacijskog stresa, čimbenike koji ga uzrokuju i ulogu katalaze u sprječavanju oksidacijskog stresa.Reactive oxygen species contain reactive oxygen produced by living organisms as a result of cellular metabolism. The defence mechanism that prevents damage caused by reactive oxygen species is represented by antioxidants that can be enzymatic and nonenzymatic. Enzymes are protein molecules of tertiary or quaternary structure that have catalytic ability and specificity for certain chemical reactions. Catalase is enzyme from the group of oxidoreductases, it has a tetrameric structure and is use din various industries and medicine. Oxidative stress is an imbalance between ROS and antioxidants. It is the cause of various diseases and damage of molecules (DNA, lipids, proteins). The causes of oxidative stress, ROS, in normal quantities do not harm organisms, but in high concentrations they lead to various modifications of molecules. Peroxisomes are specialized for carrying out oxidation reactions using molecular oxygen, generating hydrogen peroxide and contain catalase to destroy the excess of ROS. The main function of catalase is antioxidant activity. Catalase acts as an agent in the scavenging og reactive oxygen species and decomposes hydrogen peroxide into the water and oxygen. It hydrolises over the million substrates of the molecules per second. The aim of this work is to point out the presence of oxidative stress, the factors that cause it and, conversely, the non-enzymatic and enzymatic antioxidants that can prevent it
Characterization of a dispersed system by laser diffraction : bachelor thesis
No full textDefiniranje stanja grubodisperznog sustava zahtjeva prikaz sastava tog sustava, homogenost mješavine, kao i granulometrijsko stanje disperzne faze. Određivanje veličine i raspodjele veličina čestica često je ključno pri utvrđivanju ishoda proizvodnog procesa, ali i same kvalitete proizvoda. Različite veličine čestica, kao i različite raspodjele veličina tih čestica mogu značajno utjecati na odvijanje određenog procesa tj. na brzinu kemijske reakcije, sve vrste prijenosnih pojava, na stabilnost suspenzije, poroznost sloja i sl. U ovom radu karakterizacija grubodisperznog sustava (kristali boraksa) provedena je dvjema metodama čiji se principi mjerenja značajno razlikuju: prosijavanjem i metodom laserske difrakcije. Jedan od zadataka rada bio je i upućivanje u rad uređaja za lasersku difrakciju Horiba LA-300 pri čemu su istaknute prednosti i nedostaci navedenih metoda.Characterization of a dispersed system requires information on the composition of a system, the homogeneity of the mixture as well as the granulometric properties of the dispersed phase. Key role in determination of the outcome of the production process, but also of the product quality, lies in the analysis of the particle size. Particle size distribution can have a major influence on the chemical reaction rate, all types of transfer phenomena, the suspension stability, the porosity of the layer etc. In this work, characterization of a dispersed system (borax crystals) was performed by two methods, sieving and laser diffraction, whose measurement principles differ significantly. In addition, one of the tasks included was to examine the principle of operation of the measuring instrument - Horiba LA-300 laser diffraction analyzer. In the end, advantages and disadvantages of both methods were discussed in detail
Determination of the degree of disintegration of polylactide under simulated composting conditions in a laboratory - scale test : bachelor thesis
No full textU ovom radu istraživana je biorazgradnja polilaktida (PLA) u uvjetima kompostiranja. Kao kompost je korišten simulirani kruti otpad koji se sastoji od piljevine, zečje hrane, vrtnog komposta, kukuruznog škroba, saharoze, ulja kukuruznih klica i uree prema međunarodnoj normi ISO 20200:2004(E). U svrhu postizanja potrebnog stupnja vlage dodana je i destilirana voda. Komadići PLA su stavljeni u tako pripremljen kompost u sušionik na 60 dana pri temperaturi 58±2 °C. Povremeno je nadomještena isparena voda. Nakon 60 dana može se zaključiti da je PLA biorazgradljiv u zadanim uvjetima kompostiranja.In this work polylactide (PLA) biodegradation under composting conditions has been researched. For the composting simulated solid waste composed of sawdust, rabbit-feed, ripe compost, corn starch, saccharose, cornseed oil and urea according to the international standard ISO 20200:2004(E) was used. Appropriate moisture content was achieved using distilled water. PLA pieces were placed in the compost and then in a air – circulation oven for 60 days at 58±2 °C. Distilled water was added. Occasionally, evaporated water was compensate. It can be concluded that, after 60 days, PLA is biodegradable under the composting conditions
Testing the response of membranes made of FePO4 : Ag2S : PTFE = 1 : 4 : 5 and FePO4 : Ag2S : PTFE = 1 : 5 : 6 at pH = 1 and pH = 1,5 : bachelor thesis
No full textCilj ovog završnog rada je ispitivanje odziva ionsko-selektivnih membrana na Fe 3+ ione pri pH=1 i pH=1,5. Postupak pripreme i ispitivanje ovih elektroda je jednostavan, relativno jeftin, praktičan i brz te se danas vrlo često koriste. Selektivnost metode je povećana promjenom pH otopine uzorka. Membrane koje su se koristile tijekom rada slijedećeg su sastava: MEMBRANA 4 : FePO 4 :Ag 2 S:PTFE= 1:4:5 MEMBRANA 5 : FePO 4 :Ag 2 S:PTFE= 1:5:6 Membrane su ispitivane metodom slijednog razrjeđenja pri čemu se koristila otopina željezovog(III) klorida. Metodom slijednog razrjeđenja se mjerio potencijal koji ovisi o smanjenju koncentracije Fe 3+ iona i vrijeme odziva. Mjerenja su se ponavljala tri puta. Rezultati su prikazani grafički.The base of this bachelor thesis is testing the responses of membranes on Fe 3+ ions at pH=1 and pH=1,5. The preparation and testing procedures for these electrodes are simple, relatively inexpensive, practical and fast and are nowadays very commonly used. The selectivity of the method is increased by changing the pH of the sample solution The membranes that were used were made of: MEMBRANE 1 : FePO 4 :Ag 2 S:PTFE=1:4:5 MEMBRANE 2: FePO 4 :Ag 2 S:PTFE=1:5:6 The membranes were examined by sequential dilution method using a solution of ferric chloride. The sequential dilution method measured the potential, which depends on the decrease of Fe 3+ ion concentration and response time. The measurements were repeated three times. The results are presented graphically
Analysis of the biowaste composting process : diploma thesis
No full textKompostiranje je tehnološki proces gospodarenja otpadom kojim se pomoću mikroorganizama u aerobnim uvjetima obrađuje i stabilizira biološki razgradivi otpad te prevodi u kompost. Stoga je prepoznat kao ekološki prihvatljiv način zbrinjavanja biootpada. U ovom radu praćen je proces kompostiranja biootpada u rotacijskom komposteru valjkastog oblika (zatvoreni sustav) i otvorenoj posudi (otvoreni sustav). Biootpad je prikupljen u studentskoj menzi Kampus u okviru Studentskog centra Sveučilišta u Splitu. Tijekom kompostiranja u oba sustava su praćeni parametri: temperatura, sadržaj suhe i hlapive tvari, sadržaj vlage, ugljika, dušika, pH, električna vodljivost te C/N omjer. Uspoređene su vrijednosti mjerenih parametara u otvorenom i zatvorenom sustavu. Rezultati promjene sadržaja organske tvari su obrađeni prema kinetičkom modelu prvog reda. Dobivena su dobra slaganja eksperimentalnih rezultata s modelom, a brzina razgradnje organske tvari je veća pri kompostiranju u otvorenoj posudi, u odnosu na rotacijski komposter.Composting is a technological process of waste management which use microorganisms under aerobic conditions to treat and stabilize biodegradable waste and translate it to compost. Therefore, it is recognized as an environmentally friendly way of biowaste management. In this paper, the process of biowaste composting in a cylindrical rotary composter (closed system) and an open container (open system) was monitored. Biowaste was collected in the Campus student canteen within the Student Center of the University of Split. During composting in both systems, the following parameters were monitored: temperature, dry and volatile matter content, moisture content, carbon and nitrogen content, pH, electrical conductivity and C/N ratio. The values of measured parameters in the open and closed system were compared. The experimental results of organic matter content during composting process were tested according to the first order kinetic model. Good agreement of the experimental results with the model was obtained. The rate of organic matter decomposition was higher when composting in an open vessel, compared to a rotary composter
Determination of initial and final setting time of cement CEM I (Ultimo) according to HRN EN 196-3:2016 and conductometric method : bachelor thesis
No full textU ovom radu odreĊivano je vrijeme poĉetka i kraja vezivanja cementa CEM I (Ultimo) pomoću Vicatova aparata i konduktometrijskom metodom. Korišteni cement komercijalni je proizvod tvornice „Cemex“ iz Kaštel Sućurca i to je portlandski cement s udjelom 95 – 100 % klinkera. Najprije je odreĊena normalna konzistencija cementne paste Vicatovim aparatom prema HRN EN 196-3:2016. OdreĊeni vodocementni omjer koji zadovoljava normalnu konzistenciju cementne paste je V/C NK = 0,275. Za cementne paste pripremljene uz V/C = 0,275, 0,285 i 0,50 odreĊeno je vrijeme poĉetka i kraja vezivanja Vicatovim aparatom te poĉetak vezivanja elektrokemijskom metodom odreĊivanjem specifiĉne elektriĉne provodnosti. Maksimalna vrijednost specifiĉne elektriĉne provodnosti odgovara poĉetku vezivanja. Podatci su obraĊeni i prikazani tabelarno i grafiĉki te su usporeĊeni s obzirom na vodocementni omjer i metode odreĊivanja.In this work, the start and the end of CEM I (Ultimo) cement setting time was determined using a Vicat apparatus and the conductometric method. The used cement is a commercial product of the cement plant "Cemex" from Kaštel Sućurac and it is a Portland cement with a share of 95 – 100 % clinker. First, the normal consistency of the cement paste was determined with a Vicat apparatus according to HRN EN 196-3:2016. The specific water-cement ratio that satisfies the normal consistency of the cement paste is V/C NK = 0.275. For cement pastes prepared with V/C = 0.275, 0.285 and 0.50, the start and the end of setting time was determined with a Vicat apparatus and the start of setting time with the electrochemical method by determining the specific electrical conductivity. The maximum value of specific electrical conductivity corresponds to the beginning of setting time. The data were processed and presented in tables and graphs and compared with respect to water- cement ratio and determination methods
Water removal from biodisel using natural zeolite : graduate thesis
No full textOtpadno jestivo ulje iz domaćinstva podvrgnuto je procesu transesterifikacije metanolom, uz KOH kao katalizator, u svrhu dobivanja biodizela. Cilj rada je provjeriti mogućnost uklanjanja vode iz biodizela, zaostale nakon ispiranja, pomoću zeolita klinoptilolita. Upotrijebljen je klinoptilolit različite veličine čestica (10 i 50 mikrona) i mase u rasponu od 0,5 do 2 grama. Određene su fizikalno – kemijske karakteristike otpadnog jestivog ulja: udio vlage, kinematička viskoznost, gustoća, kiselinski i peroksidni broj i fizikalno- kemijske karaktristike biodizela: gustoća, kinematička viskoznost te plamište. Rezultati pokazuju da se količina ostatne vode u biodizelu smanjuje povećanjem mase klinoptilolita korištenog za sušenje, ali nedovoljno da bi se zadovoljila norma o kvaliteti biodizela (ASTM D6751). Povećanjem mase klinoptilolita do četiri puta, ne uočava se proporcionalno snižavanje udjela vlage, ali pri većim udjelima klinoptilolit čestica većih dimenzija ima bolju sposobnost apsorpcije vode.Waste edible household oil was subjected to a methanol transesterification process, with KOH as a catalyst, for the purpose of obtaining biodiesel. The aim of this work is to check the possibility of removing water from biodiesel, left after rinsing, using clinoptilolite zeolite. Clinoptilolite of different particle sizes (10 and 50 microns) and weights ranging from 0.5 to 2 grams were used. Physico-chemical characteristics of waste edible oil were determined: moisture content, kinematic viscosity, density, acid and peroxide number and physico-chemical characteristics of biodiesel: density, kinematic viscosity and flash point. The results show that the amount of residual water in biodiesel decreases with increasing mass of clinoptilolite used for drying, but not enough to meet the biodiesel quality norm (ASTM D6751). By increasing the mass of clinoptilolite up to four times, no proportional decrease in the moisture content is observed, but at higher proportions clinoptilolite particles of larger dimensions have a better ability to absorb water
Implementation of food safety system in the production of semi-hard cheeses : bachelor thesis
No full textHrvarski sabor je 29. lipnja 2013. proglasio Zakon o higijeni hrane i mikrobiološkim kriterijima za hranu (NN 81/2013) čime je implementacija HACCP sustava u sve objekte koji posluju s hranom postala zakonska obaveza . Uvođenjem HACCP sustava svi subjekti u poslovanju hranom, osim primarne proizvodnje, su dužni provoditi sve korake HACCP sustava koji spriječavaju moguće opasnosti , odnosno svode ih u zakonske okvire, identificiraju kritične kont rolne t očke te osiguravaju zdravstvenu ispravnost hrane. Za ispravnu provedbu HACCP plana, potrebno je sastaviti tim stručnih ljudi među kojima su tehnolozi, inženjeri, mikrobiolozi , a uz to svi zaposlenici u subjektu koji posluje hranom moraju biti adekvatno obučeni i posvećeni ispravnoj provedbi HACCP sustava. U ovom radu analiziran je tehnološkog procesa proizvodnje polutvdih sireva tvrtke Puđa d.o.o. Izrađen je dijagram toka proizvodnje polutvrdih sireva, provedena analiza opasnosti, određene kritične kontrolne točke, kritične granice. Navedene su i popravne radnje u slučaju nesukladnosti, k ao i sva potrebna dokumentacija koja obuhvaća HACCP sustav.On 29 June 2013, the Croatian Parliament passed the Act on Food Hygiene and Microbiological Criteria for Food (NN 81/2013), making the implementation of the HACCP system in all food business facilities a legal obligation. With the introduction of the HACCP system, all food business operators, except for primary production, are obliged to implement all steps of the HACCP system that prevent possible hazards, reduce them to legal frameworks, identify critical control points and ensure food safety. For the proper implementation of the HACCP, it is necessary to assemble a team of experts including technologists, engineers, microbiologists, and in addition, all employees in the food business must be adequately trained, and committed to the proper implementation of the HACCP system. In this paper, the technological process of production of semi- hard cheeses of the company Puđa d.o.o. was analyzed. A flow diagram of the production of semi-hard cheeses was make; a hazard analysis carried out, defined critical control points and critical limits. Corrective actions in case of non-compliance are also listed, as well as all necessary documentation covering the HACCP syste
The effect of different extraction methods and parameters on the phenolic profile and antioxidant activity of common juniper (Juniperus communis L.) : diploma thesis
No full textBorovica (Juniperus communis L.) je zimzeleni, bodljikavi grm iz porodice čempresovki (Cupressaceae) koja raste na području Europe, Azije, Sjeverne Afrike i Sjeverne Amerike. Od davnina se koristi u tradicionalnoj medicini, a u zadnje vrijeme je sve češće predmet brojnih istraživanja zbog dobrog kemijskog sastava i biološke aktivnosti. U ovom radu ispitana je primjena različitih metoda ekstrakcije (ultrazvučna-UZV i mikrovalna-MAE), kao i otapala (voda i 50%-tni etanol), na prinos ukupnih fenola u ekstraktima crvenih i zelenih plodova borovice te iglica borovice. Udio ukupnih fenola određen je spektrofotometrijskom Folin-Ciocalteu metodom. U cilju ispitivanja antioksidacijske aktivnosti korištene su tri metode: FRAP (engl.Ferric-reducing antioxidant power), ORAC (engl.Oxygen radical absorbing capacity) i DPPH (engl.2,2,-Diphenyl-1-picrylhydrazyl assay). Svi ispitivani uzorci pokazuju izrazito dobru antioksidacijsku aktivnost i bogat udio ukupnih fenola. Kao najbolje ekstrakcijsko otapalo pokazao se etanol jer su etanolni ekstrakti davali veći udio fenola i bolju antioksidacijsku aktivnost u odnosu na vodu. Uspoređujući UZV i MAE ekstrakciju može se zaključiti da je MAE bolji izbor jer većinom daje bolje rezultate za kraće vrijeme provedbe ekstrakcije. Rezultati dobiveni FRAP, ORAC i DPPH metodama ukazuju da MAE etanolni ekstrakt iglice borovice pokazuje najjaču antioksidacijsku aktivnost što je u korelaciji sa sadržajem ukupnih fenola,slijede ekstrakti zelene borovice i na kraju kao ekstrakti s najslabijom antioksidacijskom aktivnošću i najmanjom količinom fenola pokazali su se ekstrakti crvene borovice.Juniperus communis is an evergreen, prickly bush from the cypress family (Cupressaceae) that grows in Europe, Asia, North Africa and North America. It has been used in traditional medicine since ancient times, and recently it has been the subject of numerous researches due to its good chemical composition and biological activity. In this paper, the application ultrasound (UZV) and microwave (MAE) assisted extraction, as well as two solvents (water and 50% ethanol), on the yield of total phenols in extracts of red and green common juniper fruits and leafs was investigated. The proportion of total phenols was determined by the Folin-Ciocalte spectrophotometric method. In order to test antioxidant activity, three methods were used: FRAP (Ferric-reducing antioxidant power), ORAC (Oxygen radical absorbing capacity) and DPPH (2,2, -Diphenyl-1-picrylhydrazyl assay). All tested samples show extremely good antioxidant activity and a rich content of total phenols. Ethanol proved to be the best extraction solvent because ethanol extracts gave a higher phenol content and better antioxidant activity compared to water. Comparing UZV and MAE extraction, MAE has shown to be a better choice as it gives better results for a shorter extraction time. The results obtained by FRAP, ORAC and DPPH methods indicated that MAE ethanolic extract of common juniper leafs shows the strongest antioxidant activity, which correlates with the content of total phenols, followed by extracts of green berries and finally red berries as extracts with the weakest antioxidant activity and the least amount of total phenols
Determination of iron corrosion in acidic chloride media by electrochemical methods : bachelor thesis
No full textCilj ovog rada je bio ispitati korozivno djelovanje kisele kloridne otopine na uzorak željeza elektrokemijskom metodom ekstrapolacije Tafelovih pravaca i metodom određivanja polarizacijskog otpora (Rp). Ispitivanja su provedena u tri kiselo kloridne otopine, međusobno različitih koncetracija HCl (0,1 M, 0,01 M i 0,0001 M) uz konstantnu količinu klorida (30 g NaCl/L otopine). S obje metode najveća struja korozije dobivena je u otopini s najvišom koncentracijom H + iona (otopina s 0,1 M HCl), koja opada porastom pH vrijednosti otopine. Vrijednosti polarizacijskog otpora (R p ) određenih iz rezultata dobivenih polarizacijom željeza u užem području potencijala i onih dobivenih metodom elektrokemijske impendancijske spektroskopije (EIS) su pokazale dobro slaganje i da porastom pH dolazi do povećanja polarizacijskog otpora. Povećanjem pH vrijednosti otopine mijenjaju se vrijednosti kako anodnog tako i katodnog Tafelovog nagiba što upućuje na promjenu mehanizma korozije, vjerojatno izazvane sve jačim utjecajem otopljenog O 2 , kao dodatnog depolarizatora.The aim of this study was to examine the corrosive effect of an acidic chloride solution on an iron sample by two different methods: method of Tafel extrapolation and method of determining the polarization resistance (Rp). The tests were performed in three acidic chloride solutions, with different concentrations of HCl (0.1 M, 0.01 M and 0.0001 M) and constant amount of chloride (30 g NaCl/L solution). With both methods, the highest corrosion current was obtained in solution with the highest concentration of H + ions (0.1 M HCl). It was also shown that corrosion current decreases with the increase of pH. Values of polarization resistance (Rp) determined from the results obtained by polarization of iron in the narrow potential range and those obtained by electrochemical impendance spectroscopy (EIS) showed good agreement and that an increase in pH leads to an increase in polarization resistance. Increasing the pH of the solution changes the values of both anodic and cathodic Tafel slopes, which indicates a change in the corrosion mechanism, probably caused by the increasing influence of dissolved O 2 as an additional depolarizer