Hrčak - Portal of scientific journals of Croatia
Not a member yet
321498 research outputs found
Sort by
Distribution Influence of Functional Gradient Graphene Reinforced Composites in Solving Differential Equations
No full textTo investigate the effects of different graphene block distribution modes on the vi-bration characteristics of functionally graded graphene-reinforced composite ma-terials, this study first establishes the motion control differential equations based on the Halpin–Tsai micromechanical model and Hamilton’s principle. The non-linear and free vibration behaviors of the materials are also analyzed. The results indicate that different graphene mass fractions and distribution patterns have varying degrees of influence on the resonance characteristics and mechanical properties of functionally graded graphene layer–reinforced composites. Among them, the cross distribution pattern exhibits the most effective vibration suppres-sion under specific conditions. These findings provide a theoretical foundation for the development of lightweight, high-strength materials and contribute to under-standing the inherent relationship between the distribution of graphene blocks and material properties
Enhanced Crop Yield through IoT-Based Soil Monitoring and Machine Learning Analysis for Rice and Sugarcane Cultivation
No full textAgriculture, a cornerstone of global economies, faces persistent challenges in efficient crop monitoring. This study introduces a groundbreaking IoT-based framework, integrated with a novel Deep Ensemble Learning (DEL) technique. The cuurent study objective is to enhance rice and sugarcane yield through monitoring soil parameters precisely. The framework employs an array of sensors, including moisture and pH sensors, to determine key soil properties: moisture content, pH level, Nutrient Retention Capability (NRC), and oxygen content. These parameters are crucial in assessing nutrient availability, Organic Carbon Content (OCC), soil texture, and root health. Data captured by sensors is transmitted via an Arduino kit to the cloud, where it undergoes analysis by advanced deep learning models, namely Bidirectional Long Short-Term Memory (Bi-LSTM). The ensemble of models ensures high accuracy in predicting soil parameter. The farmers acquires the processed data through a mobile application that offers actionable insights and facilitating real-time, automated agricultural interventions. Empirical results from field trials demonstrate a significant enhancement in soil parameter detection and monitoring accuracy.The application enables the IoT and DEL-based system in rice and sugarcane fields that enhances the crop yeild by 97% compared to traditional schemes. The study demonstrates the potential of integrating IoT and machine learning in agriculture paradigm shift towards the precision farming, and sets a new standard for sustainable, efficient agricultural practices
Rootstock Influence on Intra-clonal Variability in Spring Leaf Phenology of Pedunculate Oak (Quercus robur L.)
No full textThis study aimed to investigate the influence of rootstock on intra-clonal variation in spring leaf phenology of pedunculate oak (Quercus robur L.) clones. In the context of clonal seed orchards, phenological synchrony is critical for successful pollination and seed production. While leaf phenology is largely under genetic control, increasing evidence suggests that rootstocks can influence scion phenology.The experiment was conducted at the Brestje nursery using 43 pedunculate oak clones, each represented by three grafted ramets on genetically diverse seedling rootstocks. Phenological monitoring was carried out from 2010 to 2014, and intra-clonal differences in budburst timing (phenophase 3) were analyzed using bootstrap analysis. Additionally, the impact of a late spring frost in 2012 was assessed by comparing the timing of phenophase 4 between frost-damaged and frost-surviving ramets.Results showed that, despite genetic uniformity, there was significant intra-clonal variability in budburst timing. In 2010, as many as 79.1% of clones exhibited a budburst range of ≥3 days between ramets, which can be considered a biologically meaningful threshold. The highest level of phenological synchrony was recorded in 2013. Notably, ramets that flushed later were less susceptible to frost damage, with the greatest observed difference between damaged and undamaged ramets being 21 days.These findings highlight the critical role of rootstock in shaping scion phenology, particularly in the context of optimizing seed production and weather adaptability in clonal seed orchards
The Schizosaccharomyces pombe Glycosyltransferase Gmh5 is a Functional Homologue of the α-1,6-Mannosyltransferase Mnn10 Crucial for N-Glycan Processing
No full textPozadina istraživanja. Glikoziltransferaze predstavljaju veliku i raznoliku skupinu enzima koji kataliziraju prijenos šećernih ostataka na proteine i lipide, čime reguliraju ključne stanične procese, kao što su kontrola kakvoće proteina i biosinteza stanične stijenke. U kvascima su enzimi O-manoziltransferaze i druge glikoziltransferaze presudne za održavanje integriteta stanične stijenke. Iako su funkcije mnogih od tih enzima dobro opisane, uloga nekih, poput Gmh5p, još uvijek nije razjašnjena. Svrha je ovog istraživanja bila rasvijetliti funkciju Gmh5p, prethodno neokarakterizirani enzim iz obitelji glikoziltransferaza GT34, u kontekstu biosinteze proteina i stanične stijenke u kvascu Schizosaccharomyces pombe.
Eksperimentalni pristup. Proveli smo probir gena prisutnih u više kopija koji suprimiraju uvjetno letalnu mutaciju nmt81-oma2+ u svrhu identifikacije proteina i puteva što kompenziraju smanjenu O-manozilaciju. Enzimska aktivnost Gmh5p je biokemijski okarakterizirana, a njezina funkcionalna sličnost s poznatim manoziltransferazama procijenjena je dodatnim pokusima na kvascu Saccharomyces cerevisiae. Uz to, istražena je N-glikozilacija modelnih supstrata na sojevima mutanata gmh5Δ.
Rezultati i zaključci. Gmh5p je identificirana kao supresor defekata u procesu O-manozilacije. Suprotno predviđanjima, Gmh5p nije pokazala α-1,2-galaktoziltransferaznu aktivnost, nego je iskazala manoziltransferaznu aktivnost. Ekspresija gena gmh5+ u mutantima kvasca S. cerevisiae mnn10Δ obnovila je toleranciju na higromicin gotovo do razine divljeg tipa. Nadalje, N-glikozilacija modelnih supstrata bila je smanjena u mutantima gmh5Δ. Ovi rezultati pokazuju da je manoziltransferaza Gmh5p uključena u produljenje vanjskog lanca N-vezanih glikana, te da djeluje kao homolog Mnn10p.
Novina i znanstveni doprinos. Ovo istraživanje donosi prvu funkcionalnu karakterizaciju Gmh5p kao manoziltransferaze iz obitelji GT34 i potvrđuje njezinu ulogu u biosintezi N-glikana. Naši rezultati proširuju sadašnje razumijevanje raznolikosti i specifičnosti glikoziltransferaza u eukariotima, te naglašavaju njihovu važnost u biologiji stanične stijenke.Research background. Glycosyltransferases represent a large and diverse family of enzymes that catalyze the transfer of sugar residues to proteins and lipids, thereby regulating essential cellular processes such as protein quality control and cell wall biosynthesis. In yeast, protein O-mannosyltransferases and other glycosyltransferases are crucial for maintaining cell wall integrity. While the functions of many of these enzymes are well characterized, the role of some of them, such as Gmh5p, remains unknown. This study aims to elucidate the function of Gmh5p, a previously uncharacterized member of the GT34 glycosyltransferase family, in the context of protein and cell wall biosynthesis in Schizosaccharomyces pombe.
Experimental approach. To identify proteins and pathways compensating for reduced O-mannosylation, we performed a genetic screening for multicopy suppressors in a conditional lethal nmt81-oma2+ mutant background. The enzymatic activity of Gmh5p was biochemically characterized, and its functional homology to known mannosyltransferases was assessed through complementation experiments in Saccharomyces cerevisiae. In addition, the N-glycosylation status of model substrates was analyzed in gmh5Δ mutant strains.
Results and conclusions. Gmh5p was identified as a suppressor of O-mannosylation defects. Contrary to its predicted function, Gmh5p did not exhibit α-1,2-galactosyltransferase activity but instead showed mannosyltransferase activity. Expression of gmh5+ in S. cerevisiae mnn10Δ mutants restored hygromycin tolerance to near wild-type levels. Furthermore, N-glycosylation of model substrates was reduced in gmh5Δ mutants. These results demonstrate that Gmh5p is a mannosyltransferase involved in the outer chain elongation of N-linked glycans and functions as a homologue of Mnn10p.
Novelty and scientific contribution. This study provides the first functional characterization of Gmh5p as a mannosyltransferase of the GT34 family and demonstrates its role in N-glycan biosynthesis. Our findings expand the current understanding of the diversity and specificity of glycosyltransferases in eukaryotes and highlight their importance in cell wall biology
Vascular flora of Kraljevec Forest Park (Zagreb, Croatia)
No full textThe studied Kraljevec Forest Park represents an urban forest complex located in the immediate vicinity of the very center of the city of Zagreb. It is situated in a colline belt zone and floristically belongs to the Epimedio-Carpinetum betuli community. The survey of vascular flora was conducted during the 2023 vegetation season, recording a total of 262 vascular plant taxa, classified into 78 families and 188 genera. The dominant life forms are hemicryptophytes (40.13 %) and geophytes (17.39 %), while the prevailing floristic elements are Eurasian (47.08 %) and European (17.51 %). Alien species constitute 24.05 % of the flora. Moreover, urbanization indices reveal that the proportion of moderately to strongly urbanophobic taxa (35.29 %) is more than twice as high as that of moderately to strongly urbanophilic taxa (14.9 %). Thirteen invasive species were recorded (Juncus tenuis, Acer negundo, Bidens frondosa, Galinsoga ciliata, Solidago gigantea, Impatiens balfourii, Robinia pseudoacacia, Phytolacca americana, Reynoutria japonica, Duchesnea indica, Veronica persica, Ailanthus altissima, and Parthenocissus quinquefolia), along with two potentially naturalised species with invasive potential (Glyceria striata and Rosa multiflora). Seven species are listed under IUCN threat categories: two as Vulnerable (Taxus baccata and Ilex aquifolium) both of which are also strictly protected in Croatia, three as Least Concern (Galanthus nivalis, Poa annua, and Serratula tinctoria), one as Near Threatened (Cyclamen purpurascens), and one as Data Deficient (Aira caryophyllea). The results of this study contribute to the knowledge of the urban flora of Zagreb and support the recommendation for the official designation of Kraljevec Forest Park as a protected area
BENEISH M-SCORE AS FRAUD INDICATOR: COMPARATIVE ANALYSIS FOR CROATIAN AND GERMAN COMPANIES
No full textThe main purpose of this paper is to determine trends and differences in financial statement frauds between Croatian and German observed companies. Fraud in the financial statement was measured using the M-score model and the research period was from 2018 to 2023. The research sample consisted of 29 companies included in the DAX (German stock market index) and 31 companies listed on Croatian stock market in the observed period. According to research results, the M-score can be used as a tool for fraud detection in both observed markets, and different users of financial statements can use this model to detect potential manipulations in financial statements. Results show that, in the whole observed period, most German companies were classified as non-manipulators, and the results were stable throughout the observed period. For the Croatian sample, number of companies classified as non-manipulators is decreasing, while on the other side, number of those classified as probably or likely manipulated is increasing. Such results indicate the existence of certain differences in fraudulent behavior of listed companies in the two observed countries, and that there are more warning signs and red flags of fraudulent behavior detected on a sample of Croatian companies
MEMBERSHIP MODEL AS PART OF RELATIONSHIP MARKETING ON THE EXAMPLE OF FOOTBALL CLUB
No full textUnder increasing competitive pressure in the global market, companies are increasingly implementing relationship marketing strategies to establish long-term and profitable customer relationships. At the same time, the sports industry is experiencing rapid growth, while sports marketing is emerging as a distinct and specialized discipline within the broader field of marketing. Like other market-oriented organizations, sports associations and clubs apply membership models as a key relationship marketing tool to foster long-term, profitable relationships with customers and supporters. This study examines the factors influencing member satisfaction, differences in attitudes and behavior between members and non-members, and the factors affecting members’ identification with the organization. The research was conducted among fans of the Croatian football club Hajduk, including both members and non-members. Data were collected through a questionnaire distributed online and in person. The results indicate that member satisfaction is influenced more strongly by members’ involvement in the club’s operations than by the first team’s on-field performance. Furthermore, members are significantly larger consumers of club products than non-members and demonstrate a higher likelihood of long-term purchasing behavior. The findings also reveal a positive direct relationship between member identification and organizational satisfaction, organizational reputation, frequency of contact with the organization, and satisfaction with the benefits provided to members
Elliptic curves associated to a spacelike curve in the Lorentz plane
No full textWe associate an elliptic curve to each point of a natural parametrization of a spacelike naturally parametrized curve in the Lorentz plane. The main tool of our study is the curvature of and the equilateral hyperbola appears as a remarkable example since its elliptic curve is a CM one. Other two elliptic curves are obtained with this approach, the second one corresponding to the adjoint differential equation of the first, which in turn, is associated to a Lorentzian version of the logarithmic spiral
Biorazgradljive PLA/PHBV polimerne mješavine za održivu ambalažu u prehrambenoj industriji
No full textAlmost half of the global production of fossil-based polymers is used for food packaging, and their resistance to biodegradation leads to significant environmental impacts. Polymers synthesised from renewable sources have become crucial for the development of sustainable packaging materials, particularly in the food industry. Biodegradable polymers such as poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) have emerged as promising alternatives to conventional polymers. However, due to the limiting properties of the individual polymers, PLA/PHBV blends have been developed to improve their thermal and barrier performance, and to retain their biodegradability. In this study, the properties of PLA/PHBV polymer blends with varying PLA content were investigated. Thermal properties were analysed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The morphology of the samples was examined by scanning electron microscopy (SEM), while barrier properties were assessed using the Hoffman method. Changes in chemical structure and interactions between PLA and PHBV were studied by Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). Adhesion-related parameters were indirectly evaluated by measuring surface contact angles and test liquids. The results indicate that PLA/PHBV blends with lower PHBV content exhibit better morphological, thermal, mechanical, and barrier properties than blends with higher PHBV content. The obtained properties of the PLA/PHBV blends provide improved functionality while maintaining environmental compatibility, making them promising formulations for the development of sustainable food packaging.Gotovo polovica svjetske proizvodnje polimera na osnovi fosilnih goriva upotrebljava se za ambalažu hrane, a njihova otpornost na biorazgradnju i pretjerana akumulacija dovodi do značajnih negativnih utjecaja na okoliš. Polimeri sintetizirani iz obnovljivih izvora postali su ključni za razvoj održivih ambalažnih materijala, posebice u prehrambenoj industriji. Biorazgradivi polimeri poput poli(mliječne kiseline), PLA i poli(3-hidroksibutirat-co-3-hidroksivalerata), PHBV pokazali su se kao obećavajuće zamjene konvencionalnim polimerima. Međutim, zbog ograničenih svojstava pojedinačnih polimera razvijaju se PLA/PHBV mješavine s ciljem poboljšanja toplinskih i barijernih svojstava uz očuvanje biorazgradljivosti. Stoga, u ovom su radu istražena svojstva polimernih smjesa PLA/PHBV u različitim omjerima. Toplinska svojstva analizirana su diferencijalnom pretražnom kalorimetrijom (DSC) i termogravimetrijskom analizom (TGA). Morfologija uzoraka istražena je pretražnim elektronskim mikroskopom (SEM), a barijerna svojstva metodom po Herfeldu. Promjene u kemijskoj strukturi te kemijske interakcije PLA i PHBV istražene su infracrvenom spektroskopijom s Fourierovom transformacijom s prigušenom totalnom refleksijom (FTIR-ATR). Parametri adhezije indirektno su procijenjeni mjerenjem kontaktnog kuta površine polimera i testnih kapljevina. Dobiveni rezultati pokazuju da polimerne mješavine PLA/PHBV s nižim udjelom PHBV posjeduju poboljšana morfološka, toplinska, mehanička i barijerna svojstva. Dobivena svojstva PLA/PHBV mješavina nude poboljšanu funkcionalnost uz ekološku prihvatljivost, što ih čini perspektivnim formulacijama za razvoj održive prehrambene ambalaže
Phosphatidylethanol in Blood as a Marker of Alcohol Dependence
No full textAim: To establish the cut-off value of phosphatidylethanol (PEth) concentration in the blood for detecting alcohol dependence. Materials and Methods: Using the method of high-performance liquid chromatography - tandem mass spectrometry (HPLC - MS), the concentration of PEth in the blood of 127 alcohol-dependent men undergoing hospital treatment was determined. To assess the diagnostic accuracy and to establish the cut-off values of PEth concentration, a ROC (receiver operating characteristic) analysis was performed. Statistical data processing was carried out using the Statistica 10.0 program. Results: At a cut-off PEth concentration of 495 ng/ ml, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 99 %, 96 %, 98 %, 98 % respectively. Conclusion: The results of the study indicate the high diagnostic reliability of PEth as a biochemical marker of alcohol dependence