Repository of Faculty of Science
Not a member yet
1747 research outputs found
Sort by
Stochastic climate models
No full textOvaj rad proučava fenomen stohastičke rezonance te njegovu primjenu na modeliranje klimatskih sustava. U uvodu je predstavljen osnovni model energetske ravnoteže (EBM) koji opisuje ravnotežu između dolazne Sunčeve energije i odlazne energije Zemlje. Model uključuje temperaturne varijacije, pri čemu se analiziraju stabilna i nestabilna stacionarna stanja. Iako se spominje mogućnost različitih definicija albeda, u ovom radu albedo je jednostavno modeliran kao funkcija temperature, koristeći linearnu ovisnost. Daljnje simulacije uključuju stohastičke varijacije, s bijelim šumom i periodičnim solarnim forsiranjem, kako bi se prikazali učinci šuma na prijelaz između toplijih i hladnijih klimatskih stanja. Rezultati simulacija potvrđuju da umjerena razina šuma može pojačati slabe, koherentne signale i omogućiti prijelaze između klimatskih stanja, što je ključni element stohastičke rezonance. Rad naglašava važnost uključivanja slučajnih fluktuacija u klimatske modele radi bolje reprezentacije varijabilnosti i potencijalnih klimatskih prijelaza.This paper examines the phenomenon of stochastic resonance and its application to climate system modeling. In the introduction, a basic energy balance model (EBM) describing the balance between incoming solar energy and outgoing terrestrial energy is presented. The model incorporates temperature variations, analyzing both stable and unstable stationary states. Although various definitions of albedo are mentioned, in this work albedo is simply modeled as a function of temperature using a linear relationship. Subsequent simulations include stochastic variations, with white noise and periodic solar forcing, to demonstrate the effects of noise on transitions between warmer and cooler climate states. The simulation results confirm that a moderate level of noise can amplify weak, coherent signals and facilitate transitions between climate states, which is a key aspect of stochastic resonance. This paper emphasizes the importance of incorporating random fluctuations into climate models to better represent variability and potential climate transitions
Pandoraviruses
No full textVirusi su mikroskopske infektivne čestice koje se mogu replicirati isključivo unutar stanica domaćina. Tradicionalno su smatrani jednostavnim entitetima male veličine i ograničenog genetskog sadržaja. Međutim, to shvaćanje se promijenilo nakon otkrića divovskih virusa koji se ističu ne samo fizičkom veličinom, već i kompleksnošću genoma, često većom od one nego kod mnogih prokariotskih organizama. Prvi opisani predstavnik ove skupine bio je Mimivirus (2003.), a kasnije su identificirani i drugi članovi ove skupine, uključujući Pandoravirus, Pithovirus, Mollivirus i Tupanvirus. Unutar ove raznolike skupine, pandoravirusi zauzimaju posebno mjesto zbog svog velikog genoma u kojem velik dio čine geni bez poznatih homologija (orfani) u drugim organizmima, što sugerira postojanje dosad nepoznatih evolucijskih puteva. Ovalnog su oblika i dimenzija oko 1 μm, što ih čini vidljivima svjetlosnim mikroskopom, a njihov genom organiziran je na neobičan način i odudara od klasičnih virusnih genoma. Zbog tih osobitosti, divovski virusi poput pandoravirusa predstavljaju izazov za tradicionalnu definiciju virusa i potiču preispitivanje granice između živih i neživih sustava. Osim toga, potiču nova pitanja o evoluciji, podrijetlu virusa i mogućnosti postojanja još nepoznatih oblika života. U ovom radu su obrađeni pandoravirusi kao jedna od najsloženijih skupina divovskih virusa, s naglaskom na njihovu morfologiju, genomsku strukturu, filogenetski položaj te potencijalni značaj za razumijevanje virusne biologije, evolucije i porijekla kompleksnosti u biosferi.Viruses are microscopic infectious particles that can only replicate in host cells. They were traditionally regarded as simple entities of small size and limited genetic content. However, this understanding changed after the discovery of giant viruses, which are characterised not only by their physical size but also by their genome complexity, which is often greater than that of many prokaryotic organisms. The first member of this group to be described was Mimivirus (2003), and other members of this group were later identified, including Pandoravirus, Pithovirus, Mollivirus and Tupanvirus. Within this diverse group, the pandoraviruses occupy a special position due to their large genome, which consists largely of genes with no known homologies (orphans) in other organisms, suggesting the existence of previously unknown evolutionary pathways. They have an oval shape and are about 1 μm in size, which makes them visible under the light microscope, and their genome is organised in an unusual way and differs from the classical viral genomes. Because of these features, giant viruses such as the pandoraviruses challenge the traditional definition of viruses and prompt a re-examination of the boundary between living and non-living systems. Furthermore, they raise new questions about evolution, the origin of viruses and the possibility of the existence of yet unknown life forms. In this review, pandoraviruses are examined as one of the most complex groups of giant viruses, focusing on their morphology, genomic structure, phylogenetic position and potential significance for understanding virus biology, evolution and the origin of complexity in the biosphere
Representations of finite groups
No full textCilj ovoga rada je predstaviti reprezentacije konačnih grupa. Kao i razumjeti pojmove poput podreprezentacija, ireducibilnosti, karaktera i fundamentalne rezultate koji osim u matematici imaju primjenu u kvantnoj kemiji i fizici.The goal of this work is to present representations of finite groups, with emphasis on the action of the group on vector spaces. As well as to understand concepts such as subrepresentations, irreducibility, character and key structural results that connect group properties with the tools of algebra
CHILDREN'S LEARNING STRATEGIES IN TECHNOLOGY EDUCATION
No full textCilj ovog diplomskog rada bio je istražiti i objasniti strategije učenja koje učenici od 5. do 8. razreda osnovne škole primjenjuju prilikom usvajanja sadržaja iz Tehničke kulture. Poseban naglasak stavljen je na kognitivne i organizacijske strategije, samoregulaciju u učenju te na razvoj i primjenu kritičkog mišljenja tijekom usvajanja tehničkih sadržaja. U istraživanju je sudjelovalo 107 ispitanika, od toga 48 djevojčica i 59 dječaka. Za potrebe ovog istraživanja korištena je Skala strategija učenja preuzeta iz priručnika Motivacija i strategije samoregulacije učenja – teorija, mjerenje i primjena autora Darka Lončarića. Rezultatima istraživanja utvrđeno je da su najčešće korištene strategije, ponavljanje i uvježbavanje (M = 3,87), kontrola tijeka i ishoda učenja (M = 3,85) i organizacija (M = 3,84), dok su strategije poput memoriranja i usmjerenosti na minimalne zahtjeve najmanje korištene. Uočen je i statistički značajan utjecaj razreda i spola: učenici petog razreda češće su koristili sve strategije učenja u odnosu na više razrede, a djevojčice su pokazale višu uporabu metakognitivnih i organizacijskih strategija u odnosu na dječake.
Dobiveni rezultati doprinose boljem razumijevanju procesa učenja u ovom nastavnom području te mogu poslužiti nastavnicima kao smjernice za unaprjeđenje nastavnih metoda i pristupa učenicima.The aim of this thesis was to investigate and explain the learning strategies used by students from 5th to 8th grade of primary school when acquiring content in the subject of Technical Education. Special emphasis was placed on cognitive and organizational strategies, self-regulation in learning, as well as the development and application of critical thinking during the acquisition of technical content. The study included 107 participants, of which 48 were girls and 59 boys. For the purpose of this research, the Learning Strategies Scale was used, adapted from the manual Motivation and Strategies for Self-Regulated Learning – Theory, Measurement and Application by Darko Lončarić. The results showed that the most frequently used strategies were rehearsal and practice (M = 3.87), control of learning process and outcomes (M = 3.85), and organization (M = 3.84), while strategies such as memorization and focus on minimal requirements were the least used. A statistically significant effect of grade and gender was also observed: fifth-grade students used all learning strategies more often than students in higher grades, and girls showed higher use of metacognitive and organizational strategies compared to boys.
The findings contribute to a better understanding of the learning process within this educational field and can serve as guidelines for teachers in improving instructional methods and approaches to students
Učinak korištenja vlažnih lipidnih filmova, dobivenih fuzijom vezikula, na elektroformaciju divovskih unilamelarnih vezikula s obzirom na različite lipidne sastave i naboj, koncentraciju kolesterola i ionsku snagu otopine
No full textThe long-term aim of this research is to investigate the properties of cholesterol bilayer domains (CBDs). Before starting experimental work, we conducted a detailed literature search and wrote a review article about all membrane models and experimental methods suitable for studying properties of CBD domains. We also described in details their known properties and functions in biological membranes. Our motivation stemmed from the beneficial role of CBDs in protecting the eye lens from cataract development and maintaining its homeostasis. Based on this knowledge we chosen giant unilamellar vesicles (GUVs) as an appropriate model for studying lipid portion of the fiber cell plasma membranes of the eye lens. GUVs are widely used as membrane models in studies of membrane properties, with the electroformation method being the most common approach for their production. However, several factors can affect the success of GUV electroformation. Common challenges include high cholesterol (Chol) concentrations, the use of lipid mixtures containing charged lipids, and solutions with elevated ionic strength. High Chol concentrations pose a particular problem for the traditional electroformation protocol, which involves drying the lipid film by fully evaporating the organic solvent. During this process, anhydrous Chol crystals can form, which do not integrate into the lipid bilayer, resulting in a lower Chol concentration in the vesicle bilayer compared to the original lipid mixture. To address the issue of artifactual Chol demixing, we have modified the electroformation protocol by introducing rapid solvent exchange, ultrasonication, plasma cleaning, and spin-coating techniques for the reproducible production of GUVs from damp lipid films. A high yield of GUVs was achieved for Chol/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) samples with mixing ratios ranging from 0 to 2.5. At Chol/POPC mixing ratios greater than 1,5, where the GUVs may contain Chol bilayer domains (CBDs), a significant decrease in the average GUV diameter is measured. It is about 40% lower compared to that of the pure POPC bilayer. This modified approach not only minimizes Chol demixing but also successfully produces GUVs from lipid mixtures containing charged lipids and ionic solutions as the internal medium. We prepared GUVs from mixtures with up to 60 mol% of the charged lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS) and formed GUVs in low-concentration NaCl solutions.Dugoročni cilj ovog rada je istraživanje svojstava čiste kolesterolove domene. Prije početka
eksperimentalnog rada, istražili smo literaturu te napisali detaljni pregledni članak o različitim
membranskim modelima i eksperimentalnim tehnikama prikladnima za istraživanje tih domena. Sva
poznata svojstva i funkcije čiste kolesterolove domene su opisane. Glavna motivacija za istraživanje su
istraživanje funkcija domene u leći oka, gdje ta domena omogućuje homeostazu stanice i ima zaštitnu
funkciju tijekom razvoja katarakte. Odlučili smo koristiti divovske unilamelarne vezikule (DUV) kao
prikladan model za stanične membrane vlaknastih stanica leće oka. DUV-ovi se koriste kao membranski
modeli za istraživanje osobina bioloških membrana, pri čemu je elektroformacija najčešće primjenjivana
metoda za njihovo formiranje. Međutim, mnogo čimbenika može utjecati na uspjeh elektroformacije DUV-ova. Neki od izazova uključuju upotrebu visoke koncentracije kolesterola, nabijenih lipida i korištenje
otopine s ionskom snagom. Visoke koncentracije kolesterola predstavljaju poseban problem za
tradicionalni protokol, koji uključuje sušenje lipidnog filma. Tijekom ovog procesa mogu se formirati
kolesterolovi kristali koji se ne ugrađuju u vezikulu, što rezultira nižom koncentracijom kolesterola u
vezikuli nego u izvornoj smjesi lipida. Kako bismo se riješili problemom izlučivanja kolesterola,
modificirali smo protokol elektroformacije korištenjem različitih metoda kao što su: brza izmjene otapala,
sonikacija, čišćenje elektrode plazmom i brzo razmazivanje. Modificirani elektroformacijski protokol
omogućuje reproducibilnu proizvodnju DUV-ova za različite omjere kolesterola i 1-palmitnska-2-
oleoinska-sn-glicero-3-fosfokolina (POPC) od 0 do 2.5, uz minimiziranje izlučivanja kolesterola. Za
omjere kolesterol/POPC veće od 1.5 izmjeren je pad drastični promjera DUV-ova. Promjer se smanjio oko
40% u usporedbi s čistom POPC membranom. Osim formiranja DUV-ova s visokom koncentracijom
kolesterola, uspješno smo formirali DUV-ove koristeći nabijene lipide (1-palmitoil-2-oleoil-sn-glicero-3-
fosfo-L-serin, POPS) i ionske otopine s niskom koncentracijom NaCl-a
Struktura, biološka aktivnost i mehanizam djelovanja novosintetiziranih kvaternih amonijevih spojeva
No full textThis thesis investigates the development of novel quaternary ammonium compounds (QACs) with the aim of addressing the growing concerns regarding bacterial resistance and environmental impacts associated with conventional QACs. The research focusses on two different QAC series: traditional derivatives based on pyridine-4-aldoxime and biodegradable "soft" variants derived from 3-substituted quinuclidine. While the structural modifications of the traditional QACs resulted in potent antiviral properties, their antibacterial efficacy was impaired, possibly due to an increased polarity of the backbone that hinders electrostatic interactions with the bacterial membrane. Consequently, the polarity of the amide bond in the "soft" QAC variants was diminished by the addition of long hydrocarbon chains in its extension, resulting in compounds with a dual mechanism of action, lower toxicity and an improved biodegradability profile. In addition, the research emphasizes the importance of fine-tuning the hydrophobic/hydrophilic ratio, as demonstrated by the example of 3-aminoquinuclidine derived QACs in which the amino functional group mimics bis-QAC by protonation under physiological conditions. These derivatives showed potent bactericidal activity against a variety of bacterial strains, including the ability to disrupt biofilm formation and induce bacterial cell death by destabilization of the membrane and generation of the reactive oxygen species. Taken together, the obtained results and the established structure-activity relationships provide valuable insights for the rational design and synthesis of next-generation QACs with improved efficacy, biosafety profile and potential therapeutic applications.Ova doktorska disertacija rezultirala je razvojem novih kvaternih amonijevih spojeva (QAC) s ciljem rješavanja rastućeg problema razvoja bakterijske rezistencije te negativnog ekološkog učinka uzrokovanog konvencionalnim QAC derivatima. Istraživanje se fokusira na dvije različite QAC serije: tradicionalne derivate temeljene na piridinijevom-4-aldoksimu i biorazgradive "meke" varijante 3-supstituiranog kinuklidina. Dok su strukturne modifikacije tradicionalnih QAC rezultirale snažnim antivirusnim svojstvima, isti su pokazali smanjenu antibakterijsku učinkovitost, koju je moguće pripisati povećanoj polarnosti okosnice što može ometati povoljne elektrostatske interakcije s bakterijskom membranom. Posljedično, polarnost amidne veze u "mekim" QAC varijantama smanjena je dodatkom dugih alkilnih lanaca u njenom produžetku, što je rezultiralo spojevima s dvostrukim mehanizmom djelovanja, nižom toksičnošću i poboljšanim profilom biorazgradivosti. Osim toga, istraživanje naglašava važnost optimalnog podešavanja omjera hidrofobno/hidrofilno, a isto je pokazano na primjeru QAC deriviranih na okosnici 3-aminokinuklidina u kojima protonirana amino skupima pruža mogućnost oponašanja bis-QAC. Ovi derivati su pokazali snažnu baktericidnu aktivnost, uključujući sposobnost inhibicije stvaranja biofilma i induciranja smrti bakterijske stanice destabilizacijom membrane i generiranjem reaktivnih vrsta kisika. Rezultati ovog istraživanja, zajedno sa zaključcima utjecaja strukture na aktivnost, omogućuju daljnji racionalan dizajn i sintezu novih QAC varijanti s poboljšanom učinkovitošću, biosigurnosnim profilom i potencijalnom terapeutskom primjenom
Assessment of future Technology Education teachers on teaching self-efficacy
No full textCilj diplomskog rada bio je ispitati razinu nastavničke samoefikasnosti budućih učitelja Tehničke kulture te analizirati kako različiti čimbenici, poput spola, godine studija i smjera studija, utječu na njihovu percepciju profesionalne spremnosti. U istraživanju je sudjelovalo N= 65 ispitanika (n=49 studentica i n=16 studenta) nastavničkih studija Prirodoslovno-matematičkog fakulteta u Splitu. Podaci su prikupljeni pomoću Norveške skale samoefikasnosti (NTSES), koja obuhvaća šest dimenzija nastavne kompetencije: poučavanje, prilagodba individualnim potrebama učenika, motivacija učenika, disciplina, suradnja te suočavanje s promjenama. Rezultati su pokazali da studenti izražavaju najveću sigurnost u području poučavanja, dok se najmanje sigurnima osjećaju pri prilagodbi nastave učenicima s različitim potrebama. Spol i godina studija nisu pokazali statistički značajne razlike u percepciji samoefikasnosti. Ovo istraživanje pomaže u boljem razumijevanju čimbenika koji utječu na profesionalnu samoefikasnost budućih nastavnika. Rezultati pokazuju da je važno poboljšati pripremu nastavnika kroz više prakse, mentorstva, kako bi studenti razvili snažnu profesionalnu samouvjerenost. Povećanje osjećaja kompetentnosti i spremnosti za suočavanje s izazovima obrazovanja ključno je za podizanje kvalitete nastave i izgradnju učinkovitog obrazovnog sustava.The aim of this work was to study the level of teaching self-efficacy of future teachers of Technology Education and to analyze how different factors, such as gender, year of study and field of study, affect their perception of professional readiness. The research involved N= 65 respondents (n=49 female students and n=16 male students) of teacher education at the Faculty of Science and Mathematics in Split. Data were collected using the Norwegian Self-Efficacy Scale (NTSES), which includes six dimensions of teaching competence: teaching, adapting to individual student needs, student motivation, discipline, collaboration and coping with change. The results showed that students expressed the highest level of confidence in the area of teaching, while they felt the least confident when adapting teaching to students with different needs. Gender and year of study did not show statistically significant differences in the perception of self-efficacy. This research helps to better understand the factors that influence the professional self-efficacy of future teachers. The results show that it is important to improve teacher preparation through more practice, mentoring, so that students develop strong professional self-confidence. Increasing the sense of competence and readiness to face the challenges of education is crucial for raising the quality of teaching and building an effective education system
Spontaneous Symmetry Breaking in the Higgs Mechanism
No full textOvaj rad bavi se matematičkim formalizmom za dobivanje mase bozona pomoću principa spontanog loma simetrije, tj. Higgsovog mehanizma. Pošto je rad preglednog tipa, naglasak je stavljen na matematičku teoriju koja se koristi u čestičnoj fizici, primarno na teoriju grupa i polja. Izvod loma simetrije za lagrangian elektroslabog sektora Standardnog modela detaljno je izveden, uz primjere loma i drugih simetrija.Work in this thesis provides mathematical formalism for obtaining masses of bosons via principle of spontaneous symmetry breaking, i.e. the Higgs mechanism. Since thesis is primarily written as a review of existing research, accent has been given to theoretical framework used in particle physics, mainly group and field theories. Derivation of symmetry breaking for electroweak part of Lagrangian has been done in detail, together with examples of the same principle applied to other symmetries
VOLATILE COMPOUNDS OF THE SPECIES Veronica agrestis L. (Plantaginaceae) ISOLATED FROM PLANTS FROM NATURAL AND CULTIVATED HABITAT AND THEIR ANTIOXIDATION POTENTIAL
No full textVeronica agrestis L. biljna je vrsta koja pripada porodici Plantaginaceae. Cilj ovog istraživanja bio je usporediti sastav i antioksidativni potencijal eteričnih ulja i hidrosola dobivenih iz biljaka s prirodnog staništa te iz uzgoja. Eterična ulja i hidrosoli izolirani su mikrovalnom ekstrakcijom, a hlapljivi spojevi identificirani su GC-MS analizom. U eteričnom ulju biljke s prirodnog staništa prevladavaju heksadekanska kiselina, fitol i heksahidrofarnezil aceton, dok su u hidrosolu najzastupljeniji spojevi heksahidrofarnezil aceton, β-jonon i metil eugenol. U eteričnom ulju biljke iz uzgoja spojevi s najvećim udjelom su heksahidrofarnezil aceton, heksadekanska kiselina i (E)-β-damascenon, a u hidrosolu iste biljke to su α-tujen, (E)-β-damascenon i benzaldehid. Antioksidativna aktivnost određena je ORAC metodom. Eterično ulje biljke s prirodnog staništa pokazalo je značajno veću antioksidativnu aktivnost u odnosu na eterično ulje biljke iz uzgoja, dok su hidrosoli pokazali približno jednaku aktivnost.Veronica agrestis L. is a plant species belonging to the Plantaginaceae family. The aim of this study was to compare the composition and antioxidant potential of essential oils (EO) and hydrosols obtained from plants growing in a natural and a cultivated habitat. The essential oils and hydrosols were isolated by microwave-assisted extraction, and the volatile compounds were identified by GC-MS analysis. Hexadecanoic acid, phytol and hexahydrofarnesyl acetone dominated in the EO of the wild plant, while hexahydrofarnesyl acetone, β-ionone and methyl eugenol were most abundant in the hydrosol. In the EO of the cultivated plant, the major compounds were hexahydrofarnesyl acetone, hexadecanoic acid, and (E)-β-damascenone, while in the hydrosol of the same plant, the predominant compounds were α-thujene, (E)-β-damascenone and benzaldehyde. The antioxidant activity was determined using the ORAC method. The EO of the plant from a natural habitat showed a significantly higher antioxidant activity than the EO extracted from the cultivated plant, while the hydrosols showed approximately the same activity
THE IMPACT OF SOCIAL NETWORKS ON ACADEMIC ACHIEVEMENT IN PRIMARY AND SECONDARY SCHOOLS IN SINJ
No full textZbog sve veće prisutnosti društvenih mreža u životima učenika, cilj ovog rada bio je ispitati njihove stavove o utjecaju društvenih mreža na školski uspjeh i emocionalno funkcioniranje. Istraživanje je provedeno na uzorku od N=205 učenika viših razreda osnovne škole (n=135) i prvog razreda srednje škole (n=70). U svrhu istraživanja korišten je anketni upitnik koji je sadržavao tri subskale: navike korištenja društvenih mreža, školski uspjeh i motivaciju te emocionalne i psihološke reakcije. Rezultati pokazuju da većina učenika svakodnevno koristi društvene mreže putem pametnih telefona, najčešće radi komunikacije i zabave. Učenici osnovne škole češće izražavaju zabrinutost zbog negativnog utjecaja društvenih mreža na vrijeme za učenje, dok učenice u većoj mjeri ističu smetnje u koncentraciji i razinu stresa. Zaključak je da društvene mreže imaju kompleksan utjecaj na učenike, a njihovi obrazovni i emocionalni učinci ovise o individualnim razlikama i podršci iz okoline.The aim of this study was to examine students’ perceptions of the impact of social media use on their academic achievement and emotional functioning. The research was conducted on a sample of N=205 students, including n=135 upper primary school students and n=70 first-year secondary school students. A questionnaire was used in the study, comprising three subscales: habits of social media use, academic achievement and motivation, and emotional and psychological reactions. The results indicated that the majority of students use social media daily via smartphones, primarily for communication and entertainment purposes. Primary school students more frequently perceive a negative impact of social media on the time available for studying, while female students report greater difficulties with concentration and higher levels of stress. It was concluded that social media have a complex and multifaceted impact on students, with educational and emotional effects depending on individual differences and the support of their environment