591 research outputs found
Sort by
The carboxylic acid derivatives and the synthesis of fragrant esters
No full textDerivati karboksilnih kiselina su organske molekule koje se jednostavnom hidrolizom mogu prevesti u karboksilne kiseline. Svi derivati karboksilnih kiselina sadrže karboksilnu skupinu, osim nitrila koji sadrže nitrilnu skupinu. Derivati karboksilnih kiselina su podijeljeni na kiselinske kloride, anhidride, estere, nitrile i amide. Najreaktivniji derivati karboksilnih kiselina su kiselinski kloridi, a najmanje reaktivni derivati su amidi. Reakcijekojimapodliježu derivati karboksilnih kiselina sureakcijenukleofilneacilnesupstitucije. Nukleofilnom acilnom supstitucijom dolazi do zamijene skupine s nukleofilom. Esteri nastaju posebnom vrstom nukleofilne acilne supstitucije koja se naziva Fischer-ova esterifikacija, to je reakcija karboksilne kiseline i alkohola u prisutnosti jake kiseline kao katalizatora. Esteri su izrazito hlapivi derivati karboksilnih kiselina, intenzivnog mirisa. Zbog svog intenzivnog mirisa estere su lako prepoznatljivi prirodni spojevi, npr. droge poput kokaina hidroliziraju dajući ester intenzivna mirisa, koji se osjeti i u malim količinama. Mnogi esteri daju specifičnu aromu i prepoznatljiv miris voću. Zasluga za aromu vina se pripisuje esterima, koji su nastali pri samoj fermentaciji ili dugim stajanjem vina.Derivatives of carboxylic acids are organic compounds which can be converted into carboxylic acids by simple hydrolysis. All derivatives contain carbonyl group, all except nitrils which contain nitrile group. Derivatives of carboxylic acids are divided on acid chlorides, anhydrides, esters, nitriles and amides. Most reactive derivatives are acid chlorides, and least reactive are amids because they contain bad leaving group. Derivatives of carboxylic acids undergo reaction called nucleophilic acyl substitution. In nucleophilic acyl substitution a good leaving group is substituted by nucleophile. Esters are formed by specific nucleophilic acyl substitution called Fischer esterification, reaction between carboxylic acid and alcohol in presence of strong acid.Ester are extremely volatile with very intense smell. They are easily recognized because of their strong intensive smell, when drugs like cocaine in contact with water a strong smelling ester is formed and it makes it easy to recognisable even in small concentrations. Many esters are responsible for aroma and smell of fruits. Aroma of wine is thanks to presence of esters, which can be formed during fermentation or by aging wine
Chemical warfare agents
No full textKemijsko oružje je izvrstan primjer kako čovjek svoja znanstvena i tehnološka dostignuća može uporabiti protiv društva. U ovom radu opisuje se pojam i podjela smrtonosnih bojnih otrova, temeljne značajke kemijskog oružja, te kemijska i fizikalna svojstva bojnih otrova. Naglasak je stavljen na smrtonosne bojne otrove s njihovim predstavnicima, kako detektirati njihovo djelovanje i poduzeti potrebnu zaštitu, kako osobnu i kolektivnu, tako i zaštitu vode, hrane i okoliša. Pravilan izbor odgovarajuće zaštitne opreme i njena pravilna uporaba mogu biti odlučujući faktor za sposobnost ljudstva da djeluje u kontaminiranom području.Chemical weaponry makes great example how humanity can use scientific and technology achievements against society. In this article, meaning and types of chemical agents and its main differences, as well as its main chemical and physics properties will be explained. Highlights are put on deadly chemical agents and their main types, how to detect them and how to achieve needed personal and group protection, as well as protection of food, water and environment. Right choice of protective gear and actions and its correct usage can be decisive factor for actions in contaminated area
Sonochemical synthesis
No full textIstraživanja su pokazala da je sonokemijska sinteza (kao posljedica ultrazvučne kavitacije) iznimno učinkovita. Budući da su znanstvenici i industrija počeli tražiti širu primjenu ultrazvučne tehnologije, snaga ultrazvuka proširila se izvan kemijske sinteze. Zbog toga je danas potpuno razumljivo da je primjena ultrazvuka široko zastupljena (na primjer: u fizici, biologiji, kemiji, farmaciji, medicinskoj dijagnostici i kirurgiji, kao i u prehrambenoj i kozmetičkoj industriji). U ovom radu istražene su reakcije hidroksikinolinske kiseline s kationima cinka i kobalta tako što su pripravljene serije otopina hidroksikinolinske kiseline i soli prijelaznih metala u vodi pri određenom pH. Sintetizirani spojevi su okarakterizirani infracrvenom spektroskopijom i termogravimetrijskom analizom. Predložene su strukture spojeva na temelju dobivenih rezultata.Studies have shown that sonochemical synthesis (as effect of ultrasound cavitation) is extremely effective. The power of ultrasound has expanded outside of chemical synthesis since scientists and industry found wider applications for ultrasound technologies. Due to this reason, today it is completely understandable that application of ultrasound is widely represented (for example: in physics, biology, chemistry, pharmacy, medical diagnostics and surgery, as well in the food-processing industry and cosmetic industries). In this experimental work, hydroxyquinolinic acid reactions with zinc(II) and cobalt(II) cations have been explored and studied. Series of hydroxyquinolinic acid and transition metal salts water solutions were prepared within certain pH value in order to obtain metal complexes. Synthesized compounds were characterized by infrared spectroscopy and thermogravimetric analysis. The structures of the compounds are suggested based on the obtained results
Determination of caffeine in tea
No full textKofein je prirodni alkaloid koji se nalazi u biljnim vrstama koje pretežno rastu u tropskim ili suptropskim regijama svijeta. Njegovi glavni izvori su zrna kave i listovi čaja. U ovom radu opisana je izolacija kofeina iz pet vrsta čaja, te su određeni njegovi maseni udjeli u pojedinoj vrsti. Korištena metoda za izolaciju je ekstrakcija na osnovu različite topljivosti između dva otapala, a maseni udjeli kofeina određeni su gravimetrijski. Potom su apsorbancije i masene koncentracije određene pomoću UV-Vis spektroskopije. Rad je podijeljen u nekoliko poglavlja. Iza uvoda slijedi literaturni pregled gdje su ukratko prikazana svojstva kofeina te korištene metode za njegovu izolaciju. Zatim slijedi prikaz dobivenih rezultata a na kraju zaključak i upotrijebljena literatura.Caffeine is a natural alkaloid that is found in plant species that predominantly grow in tropical or subtropical regions of the world. Its main sources are coffee beans and tea leaves. This paper describes the isolation of caffeine from five types of tea, and determination of its mass fraction in each particular species. The method that was used for isolation is the extraction based on the different solubility of the two solvents, and the mass of caffeine is determined gravimetrically. Then absorbance and mass concentration were determined by UV-Vis spectroscopy. The paper is divided into several chapters. Introduction chapter is followed by literature review where the caffeine properties and the methods used for its isolation are briefly resented. Next, is a summary of the results obtained and finally the conclusion and the used literature
Diagnostic aspects of glycosylated hemoglobin - HbA1c
No full textHemoglobin () naziva se "zlatnim standardom" uredne glikemije, izražene u postotcima, ≤ 7%. nastaje procesom glikacije koja obuhvaća reakciju glukoze nakupljene u krvi i eritrocita, te se koristi kao sredstvo praćenja dijagnoze i terapijske ispravnosti kod osoba oboljelih od dijabetesa. Iako se određivanje primjenjuje više od 40 godina, dugo je vremena trebalo da se provede analitička i klinička standardizacija, nađe odgovarajuća referentna metoda i proizvede primarni referentni materijal. Prvotno korištena metodologija bila je precizna ali joj je nedostajala specifičnost. Dugogodišnjim istraživanjima proizveden je referentni materijal, definiran analit te kao referentna metoda postavljen IFCC referentni sustav. Unatoč tomu, referentna metoda imala je previše odstupanja. IFCC-ov referentni sustav snizio bi apsolutne koncentracije , u odnosu na do tada korištene vrijednosti, što bi rezultiralo pomutnjom, kako među zdravstvenim djelatnicima tako i među osobama oboljelim od dijabetesa i njihovim obiteljima. Inzistiranje zdravstvenih stručnjaka za zadržavanjem postojećih metoda potaknulo je projekt "prosječna glikemija". Krajnji cilj projekta bio je ponovno definiranje u smislu podudaranja vrijednosti s koncentracijom glukoze u krvi. Globalna harmonizacija određivanja je izrazito važna za postavljanje pod primarnu zdravstvenu zaštitu, te je upravo taj proces i njegova dijagnostička uloga, kako u svijetu tako i u Hrvatskoj, tema ovoga rada.Hemoglobin () is called "golden standard" of a good glycaemic control expressed in percentage as value ≤ 7%. is formed by the glycation process which includes reaction between glucose and red blood cells and it has been used as a clinical standard of diagnosis and therapeutic suitability for people with diabetes. Although is being used for more than 40 years, it took a long time until analytical and clinical standardization found an appropriate reference method and the primary reference material. The first used methods were precise but it was lacking specificity. Long-term studies produced a reference material, defined analyte and as a specific reference method called IFCC reference system. Despite that, reference method had too many deviations. IFCC's reference system would reduce the absolute levels, compared to a previously used method. It was considered that could cause confusion among professionals along with patients and their families. Medical experts wanted to retain existing methods and it started a project "mean blood glucose". The ultimate project's goal was to redefine in terms of matching the value of the concentration of glucose in the blood. Global harmonization of determining HbA1c is extremely important for setting HbA1c under primary health care and its process and diagnostic role, both worldwide and in Croatia, are the subject of this paper
Role of vitamin D in development of brain and neurodegenerative diseases
No full text3Postoje dva oblika vitamina D, a to su vitamin (ergokalciferol) i vitamin (kolekalciferol). Njihova uloga je regulacija kalcija i fosfatnog metabolizma. Vitamin D se najviše ističe po tome što se uz uobičajeni unos vitamina putem hrane, najviše sintetizira u organizmu endogeno odnosno preko kože. 7-dehidrokolesterol se uz ultraljubičastu Sunčevu svjetlost pretvara u provitamin , koji zatim izomerizira u vitamin D tj. njegov glavni oblik 25(OH) D (25-hidroksikolekalciferol) i to se zbiva u jetri. Dok u bubregu nastaje 1,25 (1,25-dihidroksikolekalciferol) . Metabolizam vitamina D koji je prvotno apsorbiran u crijevima je gotovo isti metabolizmu onog vitamina D koji je apsorbiran u koži. Prosječna potreba za vitaminom D je 600 IU/ dnevno, no to ovisi o dobi i drugim čimbenicima. Neki od razloga nedostatka vitamina D su: nedovoljno izlaganje suncu, korištenje pojedinih antiepileptika, poremećaj metabolizma vitamina D i nedovoljno unošenje vitamina D hranom. Nedavno su otkrivene i uloge vitamina D u razvoju živčanih stanica, te u mnogim neurodegenerativnim bolestima kao što su multipla skleroza, Parkinsonova bolest, Alzheimerova bolest, amiotrofična lateralna skleroza i epilepsija. Kod većine tih bolesti uočen je nedostatak vitamina D, a do sad provedena istraživanja dokazuju da se njegovim povećanim unosom smanjuju neki od simptoma te da vitamin D ima pozitivan učinak kod navedenih bolesti.There are two types of vitamin D, vitamin (ergocalciferol) and vitamin (colecalciferol). Their role is to regulate calcium and phosphate metabolism. Vitamin D mostly stands out for the fact, that together with the usual vitamin intake with food, it is synthesized in the organism through the skin i.e. endogenously. 7-dehydrocholesterol is turned into provitamin by the action of ultraviolet sunlight and is then isomerized into vitamin D i.e. its main form 25(OH) D (25-hydroxycholecalciferol). Those reactions occur in the liver while 1,25 (1,25-dihydroxycholecalciferol) is generated in kidneys. Metabolism of vitamin D absorbed in the colon is almost the same as the metabolism of the one that is absorbed through skin. The average need for vitamin D is 600 IU per day although this depends on the age and other factors. Some of the reasons for the lack of vitamin D are: insufficient exposure to the sun, usage of some antiepileptics, disturbance of vitamin D metabolism and insufficient intake of vitamin D with food. Recently, the role of vitamin D in the development of nervous cells as well as in many neurodegenerative diseases like multiple sclerosis, Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis and epilepsy, has been discovered. In most of these diseases a lack of vitamin D has been reported, and novel studies prove that the increased intake of vitamin D diminishes some of the symptoms and has a positive impact on the aforementioned diseases
Adsorption of hidrophilically modified silicones on oxide nanoparticles
No full textCilj i svrha ovog diplomskog rada je ispitati adsorpciju hidrofilno modificiranih silikona male molarne mase na oksidnim nanočesticama () i provjeriti kako adsorbirani silikoni utječu na svojstva i stabilnost suspenzija. Korišteni su hidrofilno modificirani silikoni proizvođača Elkay® Silicones i Xiameter® Dow Corning, te uzorci nanočestica proizvođača EPRUI Nanoparticles. Za karakterizaciju uzoraka silikona korištene su nuklearna magnetska rezonancija (NMR) i FT-IR spektroskopija. Morfologija nanočestica i ZnO ispitivana je pomoću pretražnog elektronskog mikroskopa (SEM). Za određivanje veličine čestica i mjerenje zeta potencijala korištena je akustična spektroskopija. Koncentracije silikona prije i nakon adsorpcije (početna i konačna koncentracija) određene su TOC analizom. Određivanjem kinetike adsorpcije silikona ustanovljeno je da do potpune adsorpcije dolazi unutar 5-10 minuta. Za daljnja ispitivanja (određivanje adsorpcijskih izotermi) odabrano vrijeme miješanja je 20 minuta. Dobivena adsorpcijska izoterma za uzorak OFX-0193 ima oblik Langmuirove izoterme, a za uzorak OFX-5330 oblik tipične adsorpcijske izoterme karakteristične za polimere, tzv. "High affinity" izoterma. Rezultati ispitivanja akustične spektroskopije pokazuju da silikoni pospješuju raspršenost suspenzija. U metodičkom dijelu rada obrađena je nastavna jedinica "Plastične mase" u obliku blok sata s ciljem upoznavanja građe i svojstava plastičnih masa, te upotrebom u svakodnevnom životu.The aim and purpose of this work is to investigate the adsorption of hydrophilically modified silicones of small molecular weight on oxide nanoparticles () and to verify that adsorbed silicones affect the nanoparticles suspension properties and stability. The hydrophilically modified silicones from two different manufactures, Elkay® Silicones and Xiameter® Dow Corning were used, and nanoparticles of EPRUI Nanoparticles, were used. For characterization of silicon samples, nuclear magnetic resonance (NMR) and FT-IR spectroscopy were used. The morphology of nanoparticles and ZnO was investigated by scanning electron microscopy (SEM). Acoustic spectroscopy was used to determine the particle size and the measurement of the zeta potential. Silicone concentrations before and after adsorption (initial and final concentration) were determined by TOC analysis. Determination of silicone adsorption kinetics show revealed the maximum adsorption (adsorption plateau) after 5-10 minutes. For further testing (determination of adsorption isotherms), the mixing time selected is 20 minutes. The obtained adsorption isotherm for the OFX-0193 sample has the form of Langmuir isotherm, and for the OFX-5330 sample a typical polymer adsorption isotherm, so-called "High affinity" isotherm. The results of the acoustic spectroscopy showed that silicones enhance the dispersion of the suspension. The methodical part of work, the "Plastic Masses" teaching unit was elaborated in the form of a block hour in order to get acquainted with the material and properties of plastic masses and their use in everyday life
Influence of inert electrolyte on electrochemical properties of quercetin
No full textU ovom su radu ispitivana elektrokemijska svojstva kvercetina (3,3',4',5,7-pentahidroksiflavona) u tri različita inertna elektrolita: kalijevom kloridu, natrijevom kloridu i litijevom kloridu. Elektroanalitička metoda korištena u ovom radu je diferencijalna pulsna voltametrija gdje se mjeri struja u elektrokemijskoj ćeliji. Ova metoda je korištena jer dobiveni voltamogrami pokazuju oksidacijske strujne vrhove čija je visina proporcionalna koncentraciji kvercetina u ispitivanoj otopini. Najbolji kalibracijski dijagram je dobiven u otopini s kalijevim kloridom kao inertnim elektrolitom, pa je za određivanje nepoznate koncentracije kvercetina u ekstraktu kore jabuke Zimnjare korišten taj kalibracijski dijagram. Određena koncentracija kvercetina u ekstraktu iznosi 4,19∙ mol .In this work, electrochemical properties of quercetin (3,3',4',5,7-pentahydroxy-flavone) in three different inert electrolytes: potassium chloride, sodium chloride and lithium chloride were studied. Electroanalytical method used in this work is differential pulse voltammetry where current in the electrochemical cellwas measured. This method was used because in the obtained voltammograms oxidation peaks which height is proportional to the concentration of quercetin in solution were shown. The best calibration diagram was obtained in solution with potassium chloride as inert electrolyte, so this calibration diagram was used for determination of quercetin concentration in an apple peel extract of Zimnjara. The concentration of quercetin in extract was 4,19∙ mol
Spectroscopic and thermal characterization of cobalt complex compounds with dipicolinic acid derivatives
No full textU ovom radu predstavljena je priprava kompleksnih spojeva kobalta uz korištenje dvije vrste liganada. Derivat dipikolinske kiseline upotrijebljen je kao glavni prekursor za sintezu i koordinaciju kompleksnih spojeva s kobaltovim kationom, dok su diaminski ligandi korišteni za povezivanje s centralnim metalom. Priprava se odvijala na temperaturi od 30°C, uz dodavanje metanola kao otapala. Nakon ukupno pet izvedenih sinteza, reakcijskim produktima ispitane su spektroskopske i termalne značajke korištenjem infracrvene spektroskopije i termogravimetrijske analize. Svrha sinteza kobaltovih kompleksnih spojeva jest predvidjeti njihovu koordinaciju i strukturu.This research paper presents the preparation of cobalt complex compounds using two types of ligands. Dipicolinic acid derivative was used as the main precursor for the synthesis and coordination of complex compounds with cobalt cation, whereas diamin ligands were used for chemical bonding with central metal. The preparation was performed at temperature of 30°C, with the addition of methanol as a solvent. After a total of five syntheses, spectroscopic and thermal features were determined for the reaction products by means of infrared spectroscopy and thermogravimetric analysis. The purpose of the synthesis of cobalt complex compounds is to predict their coordination and structure
Mechanisms of antimicrobial resistance in bacteria
No full textAntibiotici su jedni od najuspješnijih lijekova diljem svijeta, ali njihova učestala upotreba dovela je do razvitka rezistencije koja ugrožava liječenje raznih bolesti. Kada nastupi rezistencija, primijenjena količina antibiotika nije dovoljna za suzbijanje bakterija. One mogu biti prirodno otporne ili rezistenciju mogu steći naknadno. Bakterije su razvile mnogobrojne mehanizme otpornosti što je dovelo do povećanja stope smrtnosti i morbiditeta. Brzim širenjem rezistencije kod bakterija i nedovoljnim razvitkom novih antibiotika moglo bi doći do znatno velike krize u liječenju raznovrsnih bolesti.Antibiotics are among the most potent drugs around the world. However, their frequent use has also led to the development of resistance that endangers the treatment of various diseases. When resistance occurs, the amount of antibiotic that is applied is not sufficient to eliminate the bacteria. This resistance can be primary or it can be acquired later. Bacteria have developed several mechanisms of resistance that have led to the increase in mortality and morbidity rates. Rapid expansion of bacterial resistance and insufficient development of new antibiotics could lead to a major crisis in the treatment of various diseases