591 research outputs found
Sort by
Synthesis of lithium-nickel-based complex oxides for energy storage
No full textSloženi metalni oksidi jedni su od najistraživanijih vrsta spojeva zbog svojih raznolikih svojstava i primjene, posebno u današnje vrijeme kada postoje sve veći zahtjevi za inovativnim materijalima sa širokim spektrom svojstava. Ovim radom istraživane su optimalne količine litijevih iona dopiranih u sustav niklova oksida, s ciljem nastanka različitih kristalnih struktura Li-Ni-O sustava. Svi spojevi sintetizirani su modificiranom citratnom sol-gel sintezom uz provođenje kalcinacije u struji zraka, pri temperaturama od 600°C i 700°C. Nastali produkti detaljno su okarakterizirani pomoću nekoliko analitičkih metoda: rentgenske difrakcije na prahu (PXRD), termogravimetrijske analize s razlikovnom pretražnom kalorimetrijom (TGA/DSC) te analize specifične površine Brunauer-Emmett-Teller metodom (BET) i poroznosti teorijom funkcionala gustoće (DFT).Complex metal oxides are one of the most investigated types of compounds due to their diverse properties and applications, especially nowadays when there are increasing demands for innovative materials with a wide range of properties. This work presents the fundamental research of the optimal amounts of lithium ions doped into the nickel oxide system, with the aim of producing different single-phase Li-Ni-O systems. All compounds were synthesized by a modified citrate sol-gel synthesis with calcination in a stream of air, at temperatures of 600°C and 700°C. The products were characterized in detail using several analytical methods such as: powder X-ray diffraction (PXRD), thermogravimetric analysis with differential scanning calorimetry (TGA/DSC), specific surface area analysis using the Brunauer-Emmett-Teller method (BET) and porosity analysis using the density functional theory method (DFT)
Synthesis of new imidazolium ionic liquids
No full textU ovome diplomskom radu provedene su reakcije kvaternizacije imidazola, 2-fenilimidazola i 4-metilimidazola s alkil-halogenidom pri čemu je alkilni lanac (R) sadržavao 18 ugljikovih atoma, a za halogenid (X) uzet je bromid. Reakcije su se odvijale u bazičnim uvjetima uz acetonitril kao otapalo, u zatvorenoj inertnoj atmosferi dušika pri 100°C. Nakon reakcije kvaternizacije, dobiveni produkti korišteni su kao polazni spojevi za drugi korak u sintezi ionskih tekućina, točnije u reakcijama metateza. Ove reakcije provodile su se u zatvorenom sustavu pri sobnoj temperaturi i uz upotrebu odgovarajućih otapala. Uspješno je sintetizirano trinaest spojeva, od kojih su dva kvaterne amonijeve soli na bazi imidazola te 11 ionskih tekućina. Navedeni spojevi su karakterizirani infracrvenom spektroskopijom (IR) te masenom spektrometrijom (MS).In this thesis, quaternization reactions of imidazole, 2-phenylimidazole, and 4-methylimidazole were carried out. The compounds were quaternized with an alkyl halide which contained an 18 carbon atom alkyl chain (R) and bromide as the halide (X). The reactions were performed under basic conditions with acetonitrile as the solvent, under a closed inert nitrogen atmosphere at 100° C. After the quaternization, the obtained products were used as starting compounds for the second step in the synthesis of ionic liquids, more precisely in metathesis reactions. These reactions were carried out in a closed system at room temperature and with appropriate solvents. In the end, thirteen compounds were successfully synthesized: two imidazole-based quaternary ammonium salts and eleven ionic liquids. All obtained compounds have been characterized by infrared spectroscopy (IR) and mass spectrometry (MS)
The application of cranberry fruit, Vaccinium sp. L., as acid-base indicator
No full textBrusnicom, Vaccinium sp. L, se naziva nekoliko vrsta grmolikih biljaka koje pripadaju porodici vrijesova, Ericaceae. Ove biljke su raširene po sjevernoj hemisferi, a poznate su po svojim sjajnim crvenim plodovima. Plodovi su bogati raznim vitaminima i mineralima te su zastupljeni u raznim prehrambenim proizvodima. Boja ploda govori da se u plodu nalaze spojevi koji bi pri pojedinoj pH vrijednosti mogli dati drugačiju boju, stoga bi plodovi brusnice mogli poslužiti u pripremi prirodnih kiselo-baznih indikatora. U radu su pomoću svježih plodova brusnice i odabranih otapala (metanol, etanol, aceton, hladna i vruća voda) pripremljene otopine indikatora. Cilj ovog rada je bio utvrditi bolje otapalo za pripremu indikatora te ispitati njihovu trajnost. Indikatori su se pokazali dugotrajnima, a osim toga imaju i niz drugih prednosti (niska cijena, jednostavna nabava, jednostavna i brza priprema, manja opasnost, manje ili nimalo otpada). Na temelju ovih rezultata, može se uvidjeti da se ovakvi indikatori mogu upotrebljavati u školstvu - u nastavi kemije.Cranberry, Vaccinium sp. L, refers to several species of shrub plants belonging to the heath family, Ericaceae. These plants are spread throughout the northern hemisphere and are known for their shiny red fruits. The fruits are rich in various vitamins and minerals, and are present in various food products. The colour of the fruit indicates that there are compounds in the fruit that could give a different colour at a certain pH value, so cranberry fruit could be used in the preparation of natural acid-base indicators. In this thesis, indicator solutions were prepared using fresh cranberry fruit and selected solvents (methanol, ethanol, acetone, cold and hot water). The aim was to determine a better solvent for the preparation of indicators and to test their durability. Indicators have proven to be long lasting; and also have a number of other advantages (low cost, simple supply, simple and easy preparation, safe, little or no waste). Based on these results, it is observed that such indicators can be used in education - in chemistry classes
Electrochemical characterization ond determination of vitamin E
No full textU ovom radu su ispitivana elektrokemijska svojstva α-tokoferola, uporabom cikličke i diferencijalne pulsne voltametrije. Cilj rada bio je ispitati topljivost α-tokoferola u različitim otapalima, utjecaj pH, brzine polarizacije i koncentracije na njegova oksido-redukcijska svojstva, istražiti moguću adsorpciju α-tokoferola na površinu radne elektrode te odrediti α-tokoferol u realnim uzorcima pomoću HPLC metode. Prilikom ispitivanja topljivosti α-tokoferola najbolja se pokazala smjesa etanola i vode u omjeru 70:30. U cikličkom voltamogramu α-tokoferola uočen je anodni strujni vrh pri potencijalu, Ep,a = 0,175 V koji se odnosi na ireverzibilnu oksidaciju α-tokoferola. Utvrđeno je da je oksidacija α-tokoferola difuzijski kontroliran proces jer je dobivena linearna ovisnost struje oksidacijskog strujnog vrha (Ip,a) o drugom korijenu brzine polarizacije elektrode ( 1/2) te je nagib pravca log Ip,a vs log iznosio oko 0,5. U diferencijalnom pulsnom voltamogramu α-tokoferola je također detektiran jedan oksidacijski strujni vrh pri potencijalu, Ep,a = 0,070 V, koji je linearno rastao s povećanjem masene koncentracije α-tokoferola u koncentracijskom području od 0,43 mg dm-3 do 70,41 mg dm-3. Tekućinskom kromatografijom visoke djelotvornosti ispitivan je sadržaj α-tokoferola u realnim uzorcima te stabilnost otopina i najbolji omjer suhe tvari i smjese za ekstrakciju. Za ekstrakciju α-tokoferola iz praškastog dodatka prehrani kao najbolji omjer utvrđen je 1:1,25, dok je za peršin i kelj najbolji omjer bio 1:50. Da bi se utvrdila ponovljivost mjerenja napravljena su tri uzorka ekstrakta peršina u omjeru 1:50, uzorci su ostavljeni 1h na tamnom i zatim pripremljeni na isti način kao i prethodni. Svaki uzorak injektiran je dva puta Srednja vrijednost rezultata mjerenja za prvo injektiranje je 0,833 mg/100g, dok za drugo injektiranje srednja vrijednost iznosi 0,823 mg/100g. Standardna devijacija rezultata dobivenih za prvo injektiranje iznosi 0,020, a za drugo 0,019. Relativno standardno odstupanje za rezultate dobivene za prvo injektiranje je 2,425%, a za drugo 2,299%. Interval pouzdanosti metode je za prvo injektiranje uzorka ±0,023, a za drugo 0,021.In this paper, the electrochemical properties of α-tocopherol were investigated by using cyclic and differential pulse voltammetry. The aim of the work was to examine the solubility of α-tocopherol in different solvents, the influence of pH, scan rate and concentration on its oxido-reduction properties, to investigate the possible adsorption of α-tocopherol on the surface of the working electrode, and to determine α-tocopherol in real samples using the HPLC method. When testing the solubility of α-tocopherol, the mixture of ethanol and water in a ratio of 70:30 proved to be the best. In the cyclic voltammogram of α-tocopherol, an anodic peak current was observed at the potential, Ep,a = 0,175 V, which corresponds to the irreversible oxidation of α-tocopherol. It was determined that the oxidation of α-tocopherol is a diffusion-controlled process, because a linear dependence of the oxidation peak current (Ip,a) vs the square root of scan rate ( 1/2) was obtained, and the slope of the line log Ip,a vs log was around 0,5. One oxidation peak current was also detected in the differential pulse voltammogram of α-tocopherol at the potential, Ep,a = 0,070 V, which increased linearly with the increase of mass concentration of α-tocopherol in the concentration range from 0,43 mg dm-3 to 70,41 mg dm-3. The content of α-tocopherol in real samples, the solutions stability, and the best ratio of dry matter to the extraction mixture were examined by high-performance liquid chromatography. For the extraction of α-tocopherol from the powdered food supplement, the best ratio was 1:1,25, while for parsley and kale the best ratio was 1:50. In order to determine the repeatability of the measurements, three samples of parsley extract were made in a ratio of 1:50, the samples were left for 1 hour in the dark and then prepared in the same way as the previous one. Each sample was injected twice. The mean value of the measurement results for the first injection is 0,833 mg/100g, while for the second injection the mean value is 0,823 mg/100g. The standard deviation of the results obtained for the first injection is 0,020, and for the second 0,019. The relative standard deviation for the results obtained for the first injection is 2,425% and for the second injection 2,299%. The confidence interval of the method is ±0.023 for the first injection of the sample, and 0,021 for the second
Study of the application of selected representatives of the orchid family as acid-base indicator
No full textRod Phalaenopsis jedan je od najrasprostranjenijih i najduže cvjetajućih rodova porodice Orchidaceae. Osim lijepog izgleda, latice ovoga cvijeta možda bi mogle poslužiti i kao pH indikatori. Određivanje pH vrijednosti provodi se pomoću opće poznatih konvencionalnih kiselo-baznih indikatora, ali u istu svrhu mogu se koristiti i neki biljni materijali. To je moguće zbog prisutnosti raznih pigmenata, poput antocijanina i karotenoida, koji mijenjaju boju ovisno o pH vrijednosti. Cilj ovog rada bio je ispitati mogućnost primjene cvijeta odabranih predstavnika porodice Orchidaceae kao kiselo-baznog indikatora. U tu svrhu korištene su svježe latice Phalaenopsis orhideja u kombinaciji s različitim otapalima (voda, aceton, etanol i metanol). Istraživanjem je utvrđeno da se većina ispitanih latica Phalaenopsis orhideja može koristiti kao alternativni kiselo-bazni indikator. Neki od ispitanih uzoraka dali su dobre rezultate samo u bazičnom mediju, a neki u cijelom pH spektru.The genus Phalaenopsis is one of the most widespread and longest flowering genera of the Orchidaceae family. In addition to their beauty, the petals of this flower could be used as pH indicators. The determination of pH is carried out using commonly known conventional acid-base indicators, but some plant materials may also be used for the same purpose. This is possible due to the presence of various pigments, such as anthocyanins and carotenoids, that change colour depending on the pH value. The aim of this work was to investigate the possibility of using flowers of selected representatives of the Orchidaceae family as an acid-base indicator. For this purpose, fresh Phalaenopsis orchid petals were used in combination with different solvents (water, acetone, ethanol and methanol). The research found that most of the examined Phalaenopsis orchid petals can be used as an alternative acid-base indicator. Some give good result only in the alkaline medium, and some in the entire pH spectrum
Study of the application of common yew fruit, Taxus baccata L., as acid-base indicator
No full textPomoću pH vrijednosti možemo opisati kemijske uvjete u otopini i odrediti točku ekvivalencije. Osim toga, mjerenje pH vrijednosti koristi se i izvan kemijskog laboratorija, primjerice u svrhu poboljšanja kvalitete ljudskog zdravlja možemo provjeriti i kontrolirati pH vrijednost tla, vode ili hrane. U kemiji su najzastupljeniji konvencionalni kiselo-bazni indikatori, a sve se više radi na razvoju prirodnih kiselo-baznih indikatora. Tako pripremljeni indikatori sadrže biljne pigmente koji mijenjaju boju ovisno o pH vrijednosti sredine u kojoj se nalaze. Cilj ovog rada bio je ispitati potencijal primjene bobica šumske tise (Taxus baccata L.) kao kiselo-baznog indikatora u kombinaciji s odabranim otapalima (voda, metanol, etanol i aceton). Naime, bobice šumske tise izrazito su crvene boje i sadrže polifenole i karotenoide, što upućuje na moguću upotrebu kao kiselo-bazni indikator. Rezultati ispitivanja pokazali su vizualno najdojmljivije rezultate pri pH = 14, a aceton se pokazao kao najpogodnije otapalo za pripremu ovih indikatora.Using the pH value, we can describe chemical conditions in solution and determine the equivalence point. pH value measurement is also used outside of chemical laboratory, for example in order to improve the quality of health, we can check and control the pH value of soil, water or food. Conventional acid-base indicators are the ones most commonly used in chemistry, but there is a lot of effort being put in the development of natural acid-base indicators. Indicators prepared in this way contain plant pigments that change colour depending on the pH value their environment. The aim of this work was to examine the potential of yew berries (Taxus baccata L.) as acid-base indicators in combination with selected solvents (water, methanol, ethanol and acetone). Yew berries are bright red and contain polyphenols and carotenoids, which points to their potential use as acid-base indicators. Obtained results showed visually most impressive results at pH = 14, and acetone showed to be the most suitable solvent for preparation of these indicators
Traditional uses, bioactive composition, pharmacology and toxicology of herbs from Thymus genus
No full textLjekovito bilje i njegove aktivne komponente uvelike doprinose boljitku ovje anstva. Ve ina biljaka porodice Lamiaceae ljekovite su biljke koje zbog bioaktivnih komponenti koristimo u borbi protiv gljivica, virusa, bakterija i raznih upala. Rod Thymus, koji je lan porodice Lamiaceae, sastoji se od oko 250 predstavnika, a neki od najpoznatijih su maj ina dubica, timijan, lavanda, bosiljak, ru~marin i dr. Izuzev svoje ljekovitosti, ove biljke se odlikuju i aromati nob u zbog ega se esto koriste kao za ini. Jedan od predstavnika roda Thymus je timijan, Thymus vulgaris L., koji se nabiroko koristi u narodnoj medicini, prehrani i pripremi ljekovitih preparata. Iako ljekovito bilje ima niz aktivnih komponenata, eteri no ulje se isti e najve im udjelom bioaktivnih sastojaka. U slu aju biljaka roda Thymus, aktivni sastojci eteri nog ulja s najizra~enijim djelovanjem pripadaju klasi terpenoida, a to su timol i karvakrol. Stoga terapeutski potencijal timijana ovisi o sadr~aju timola i karvakrola, ali i drugih bioaktivnih spojeva, kao bto su flavonoidi, saponini i flavoni, dok eteri no ulje pokazuje antibakterijski, antisepti ni, antifungalni i antioksidacijski u inak. Stoga timijan i drugo bilje roda Thymus imaju veliki zna aj kao funkcionalna hrana i potencijal primjene u lije enju raznih stanja. Cilj ovoga rada je dati kratki pregled tradicionalne uporabe, bioaktivnih spojeva, farmakologije i toksikologije bilja iz roda Thymus.Medicinal plants and their active components greatly contribute to the well-being of mankind. Most of the plants of the Lamiaceae family are medicinal plants that, due to their bioactive components, we use in the fight against fungi, viruses, bacteria and various inflammations. The genus Thymus, a member of the Lamiaceae family, consists of approximately 250 representatives, and some of the most famous are thyme, lavender, basil, rosemary, etc. Apart from their healing properties, they are also characterized by their aromaticity, which is why they are often used as spices. Thyme, Thymus vulgaris L., a plant from the Thyme genus, is widely used in traditional medicine, diet and medicinal preparations producion. Although medicinal plants have many active components, essential oil stands out due to the highest content of bioactive ingredients. In the case of Thymus genus, the active ingredients of the essential oil with the most pronounced effect belong to the class of terpenoids, namely thymol and carvacrol. Hence, thyme therapeutic effect depends on the content of thymol and carvacrol, and also other bioacive compunds such as flavonoids, saponins and flavons, while the etheric oil has antibacterial, antiseptic, antifungal and antioxidative effect. Hence, thyme and other members of Thymus genus have a great importance as functional food and potential in treatment of various conditions. The aim of this thesis is to give a brief overview of the traditional use, bioactive compounds, pharmacology and toxicology of herbs from the Thymus genus
Traditional uses, bioactive composition, pharmacotolgy and toxicology of selected representatives from Capsicum genus
No full textRod Capsicum obuhvaća četrdeset i dvije vrste paprike od kojih je pet udomaćeno i primjenjivano za razne svrhe. Koriste se za spremanje jela, zimnica, začina, dodataka prehrani te lijekova. Jedan od najpoznatijih proizvoda od paprike su ljuti umaci cijelog raspona ljutine. Ostaci paprika stari više od 9 tisuća godina su nađeni u Južnoj Americi gdje su ih domoroci uzgajali te koristili na slične načine kao što se koriste danas. Najistraživija i najrasprostranjenija vrsta roda je Capsicum annuum L. koja se uzgaja diljem Sredozemlja, Afrike, Azije, SAD-a te Srednje i Južne Amerike. U većini klima je jednogodišnja biljka te joj otuda i latinski naziv, iako je biljka višegodišnja. Sve paprike sadrže vitamin C, A i B6 te flavonoide i karotenoide. Ljute sorte također sadrže kapsaicinoide odgovorne za ljutost po kojoj su poznate. Vitamin C i A, flavonoidi i karotenoidi su antioksidansi te imaju brojne pozitivne učinke na zdravlje. Osim toga, flavonoidi imaju i protuupalna, protukancerogena i protumutagena svojstva, kao i kapsaicinoidi. U rijetkim slučajevima su se pokazali kao promotori raka jer pojačavaju djelovanje kancerogena. Kapsaicin pak predstavlja opasnost nakon izlaganja spreju za samoobranu, sa štetnim učincima na sluznicu oka, nosa i usta, kao i na dišne puteve.Genus Capsicum refers to forty-two species of peppers, five of which are domesticated and used in various ways. They are used for making dishes, preserves, spices, supplements and medicine. One of the most famous products are pepper hot sauces made with a varying degree of spiciness. Over 9 thousand years old leftover of peppers have been found in South America, where they were cultivated by the natives and used in the same way as today. The most researched and widespread specie is Capsicum annuum L., which is grown all throughout Mediterranean, Africa, Asia, USA, Middle and South America. In most climates it's an annual plant, hence its Latin name, although the plant is perennial. All peppers contain vitamin C, A, B6, flavonoids and carotenoids. Hot peppers also contain capsaicinoids, responsible for their spiciness. Vitamin C and A, flavonoids and carotenoids are antioxidants and have numerous positive effects on health. Flavonoids also show anti-inflammatory, anti-carcinogenic and antimutagenic properties, similar as capsaicinoids. In rare cases, they have been shown as cancer promotors due to enhancing cancerogenic compound effects. Capsaicin becomes harmful after exposure to self-defence pepper sprays, with harmful effects on the eye, nose and mouth mucosa as well as on the airways
Determination of molecular and crystal structure of Schiff bases with quinazoline
No full textSupstituirani imin, dušični analog ketona ili aldehida gdje je karbonilna (C=O) skupina nadomještena iminskom (C=N) skupinom, dvostrukom vezom ugljika i dušika, naziva se Schiffova baza. Reakcija gdje se aminobenzojeve kiseline i dialdehidi mogu upotrebljavati kao reaktanti, reverzibilna je reakcija te se naziva sinteza Schiffove baze. Dva primarna faktora nadziru efikasnost navedene reakcije te imaju značajan učinak na iskorištenje. Neophodni su blago kiseli uvjeti pri čemu može doći do nestanka vode što znači da koncentracija kiseline ne smije biti povećana (pH između 3 i 5), u protivnom, ukoliko je otopina previše kisela, doći će do protoniranja amina što će inhibirati prvi stupanj odnosno reakcija se neće moći nastaviti. Heterociklički spojevi koji su načinjeni od spojenog pirimidinskog i benzenskog prstena nazivaju se kinazolini. Svojstva supstituiranih derivata kinazolina uvelike ovise o prirodi samog supstituenta. U ovom diplomskom radu kristalizirane su tri Schiffove baze s kinazolinskim supstituentom te im je određena molekulska i kristalna građa.A substituted imine, a nitrogen analog of a ketone or aldehyde where the carbonyl ( C=O) group is replaced by an imine (C=N) group, a carbon-nitrogen double bond is called a Schiff base. The reaction where aminobenzoic acids and dialdehydes can be used as reactants is a reversible reaction it is called Schiff base synthesis. Two primary factors control the efficiency of the above reactions and have a significant effect on utilization. Slightly acidic conditions are necessary, where water can disappear, which means that the acid concetration must not be increased ( pH between 3 and 5), otherwise, if the solution is too acidic, the protonation of the amine will occur, which will inhibit the first stage and the reaction will not be able to continue. Heterocyclic compounds that are made from a fused pyrimidine and benzene ring are called quinazolines. The properties of substituted quinazoline derivatives largely depend on the nature of the substituent itself. In this thesis, three Schiff bases with a quinazoline substituent were crystallized and their crystal and molecular structures were determined
Molecular mechanisms of tumor cell growth
No full textTumor se odnosi na bilo koju neobičnu izbočinu, kvržicu ili masu koja se javlja na ili unutar tijela. Dijeli se prema različitoj klasifikaciji, a tu spadaju: klinička klasifikacija, morfološka klasifikacija, histogenetska i etiološka klasifikacija. Genetske promjene igraju važnu ulogu u razvoju tumora. Tumori se formiraju kada normalne stanice u tijelu steknu genetske mutacije koje mijenjaju njihovu prirodnu kontrolu rasta te se podijele. Za širenje tumora odgovorne su angiogeneza i metastaze koje omogućuju tumorskim stanicama ulazak u krvotok te ulazak u različita tkiva i stanice u cijelom tijelu.A tumor refers to any unusual growth, lump, or mass that occurs on or inside the body. It is divided according to different classifications, which include: clinical classification, morphological classification, histogenetic and etiological classification. Genetic changes play a pivotal role in tumor development. Tumors form when normal cells in the body acquire genetic mutations that alter their natural control of growth and division. Angiogenesis and metastasis are responsible for tumor spread, which enable tumor cells to enter the bloodstream and enter various tissues and cells throughout the body