Hrčak - Portal of scientific journals of Croatia
Not a member yet
321498 research outputs found
Sort by
Optimiranje sustava za izlaganje rekombinantnih proteina na površini stanica kvasca: uloga UPR-a, ERAD-a i dinamike endoplazmatskog retikuluma
No full textOver the past two decades, the display of various recombinant proteins on the surfaces of microorganisms, particularly yeast, has garnered significant research attention. This method is rapid, simple and cost-effective, combining the biosynthesis and secretion of recombinant proteins with their immobilization on the host cell surface. Proteins synthesized using this technique are transported to the cell surface and incorporated into the cell wall through mild, native processes, avoiding aggressive chemical immobilization methods that often lead to a loss of physiological activity. Surface-displayed proteins are generally more stable and resistant to environmental changes than those in a solution. Depending on the promoter used, cells can continuously renew the recombinant protein on their surface or express it only under certain conditions. Additionally, cells carrying surface-displayed enzymes can be easily separated from the reaction mixture and reused multiple times. These enzymes can also catalyze reactions with substrates that cannot enter the cells, facilitating extracellular synthesis and simplifying product purification. However, the main obstacle to the industrial application of this method is often low efficiency, resulting in limited amounts of displayed protein. The efficiency depends on the processes that the protein undergoes on its way to the cell surface, following the same pathway as native secretory proteins: synthesis in the endoplasmic reticulum (ER), transport to the Golgi, and delivery to the cell surface via transport vesicles. Large amounts of secretory proteins can overload the ER, triggering the unfolded protein response (UPR) and endoplasmic reticulum-associated degradation (ERAD). Despite significant improvements for some proteins, a universal system for all recombinant proteins has yet to be developed. However, the complexity of protein processing and secretion pathways suggests that a single system improving productivity for all recombinant proteins is unlikely. Instead, several optimized systems tailored to specific protein structures may be necessary. This article provides an overview of the processes that recombinant proteins intended for surface display undergo on their way to the cell surface in the endoplasmic reticulum and represent a crucial bottleneck for the successful immobilization of recombinant proteins at the cell surface.Izlaganje različitih rekombinantnih proteina na površini stanica mikroorganizama, posebno kvasca, privuklo je tijekom posljednja dva desetljeća znatnu pozornost istraživača. Ova metoda je brza, jednostavna i isplativa, a kombinira biosintezu i sekreciju rekombinantnih proteina s njihovom imobilizacijom na površini stanice domaćina. Proteini sintetizirani ovom tehnikom transportiraju se na površinu stanice i ugrađuju u staničnu stijenku blagim, nativnim procesima, izbjegavajući agresivne metode kemijske imobilizacije koje često dovode do gubitka fiziološke aktivnosti. Proteini imobilizirani na površini stanice općenito su stabilniji i otporniji na promjene u okolišu od onih u otopini. Ovisno o korištenom promotoru, stanice mogu kontinuirano obnavljati rekombinantni protein na svojoj površini ili ga eksprimirati samo pod određenim uvjetima. Osim toga, stanice koje nose enzime imobilizirane na površini mogu se lako odvojiti od reakcijske smjese i ponovno upotrijebiti više puta. Ovi enzimi također mogu katalizirati reakcije sa supstratima koji ne mogu ući u stanice, olakšavajući izvanstaničnu sintezu i pojednostavljujući pročišćavanje produkta. Međutim, glavna prepreka industrijskoj primjeni ove metode često je mala učinkovitost, što rezultira ograničenim količinama imobiliziranog proteina. Učinkovitost ovisi o procesima koje protein prolazi na putu do površine stanice, slijedeći isti put kao i nativni sekretorni proteini: sintezu u endoplazmatskom retikulumu (ER), transport do Golgijevog aparata i transport na površinu stanice putem vezikula. Velike količine sekretornih proteina mogu preopteretiti ER, pokrećući stanični odgovor na nesmotane i pogrešno smotane proteine (UPR) i degradacijski put povezan s endoplazmatskim retikulumom (ERAD). Unatoč značajnim poboljšanjima za neke proteine, univerzalni sustav za sve rekombinantne proteine još nije razvijen. Međutim, složenost putova obrade i sekrecije proteina sugerira da je jedan sustav koji poboljšava produktivnost svih rekombinantnih proteina malo vjerojatan. Umjesto toga, možda će biti potrebno nekoliko optimiranih sustava prilagođenih specifičnim strukturama proteina. Ovaj rad daje pregled procesa koje rekombinantni proteini namijenjeni za imobilizaciju na površini stanice prolaze na putu do površine stanice u endoplazmatskom retikulumu, čime predstavljaju ključno usko grlo za uspješnu imobilizaciju rekombinantnih proteina na površini stanice
Benchmarking Croatian airports: A data-driven approach through DEA window analysis
No full textThis study benchmarks the efficiency of seven certified international airports in Croatia using Data Envelopment Analysis (DEA) with a window framework under variable returns to scale, explicitly addressing the challenge of a small number of decision-making units through dynamic window specification. Efficiency scores were calculated across overlapping three-year periods from 2019-2023, allowing performance dynamics to be captured during both crisis and recovery phases. The results reveal substantial heterogeneity across airports. Osijek Airport emerged as the most consistently efficient, outperforming larger hubs such as Zagreb and Split, while Zadar and Rijeka demonstrated notable efficiency improvements over time. In contrast, Dubrovnik Airport recorded persistently low efficiency despite traffic recovery, suggesting structural cost rigidity and seasonal vulnerability. These findings highlight the operational resilience of smaller regional airports and signal performance constraints among major hubs. By integrating traffic trends with efficiency outcomes, the study shows that rising passenger volumes alone do not ensure improved economic performance. The results provide a timely, evidence-based framework for airport managers and policymakers to enhance strategic planning, improve resource allocation, and strengthen the financial sustainability and competitiveness of Croatia’s air transport sector
Preliminarno ispitivanje različitih low-cost organskih i anorganskih materijala za sorpciju karbendazima – prednosti, nedostaci i značaj pH vrijednosti
No full textCarbendazim, a widely used fungicide, is frequently detected in agricultural runoff and in surface and groundwater, raising environmental and public health concerns. The efficient removal of carbendazim from water sources remains a significant challenge, especially at different pH conditions. This study evaluates the sorption performance of several organic and inorganic materials for the removal of carbendazim (≈1mgl−) from aqueous solutions across a pH range of 3–6. A series of batch experiments was conducted using fruit-processing by-products (olive, cherry, and sour cherry pits) and various zeolite samples (natural zeolite clinoptilolite and its modified forms enriched with sodium, iron or sulphur). The results showed that only sodium-rich natural zeolite and sour cherry pits achieved notable removal efficiencies. Sodium-rich natural zeolite exhibited maximum performance of up to 99.0% at pHo=3.02, while sour cherry pits achieved 58.4 % efficiency at pHo=5.81. The findings demonstrate that both sorbent type and solution pH are key factors affecting carbendazim removal. These findings provide a basis for the development of optimised, pH-sensitive sorption-based treatment strategies for pesticide-contaminated waters using environmentally friendly and readily available materials.Karbendazim, široko upotrebljavan fungicid, često se detektira u površinskim i podzemnim vodama diljem svijeta, uzrokujući zabrinutost za okoliš i zdravlje ljudi. Učinkovito uklanjanje karbendazima iz vode predstavlja velik izazov, posebice pri različitim pH uvjetima. Ovo istraživanje procjenjuje sorpcijsku sposobnost nekoliko organskih i anorganskih materijala za uklanjanje karbendazima iz vodene otopine (≈1mgl−) pri različitim pH vrijednostima u području od 3 do 6. Šaržni eksperimenti provedeni su na nusproizvodima prerade voća (košticama maslina, trešanja i višanja) i različitim uzorcima zeolita (prirodnim zeolitom klinoptilolit te njegovim modificiranim oblicima – obogaćenim natrijem, željezom i sumporom). Rezultati su pokazali zadovoljavajuće učinke uklanjanja jedino na natrijem obogaćenom prirodnom zeolitu te na košticama višanja. Natrijem obogaćen prirodni zeolit postigao je maksimalnu učinkovitost uklanjanja od čak 99,0% pri pHo=3,02, dok su koštice višanja bile 58,4% učinkovite pri pHo=5,81. Ovim istraživanjem utvrđeno je da su i vrsta sorbenta i pH uvjeti ključni faktori koji utječu na uklanjanje karbendazima, a dobiveni rezultati mogu poslužiti kao temelj za razvoj i optimizaciju metoda obrade voda onečišćenih pesticidima uporabom ekološki prihvatljivih i lako dostupnih materijala
Ispitivanje učinkovitosti C-EcoForHome kompostera za obradu biootpada u zatvorenim prostorima odgojno-obrazovnih ustanova
No full textIndoor biowaste treatment using small-scale composters has proven effective for processing organic waste and recovering valuable resources. This study evaluated the performance of the handmade C-EcoForHome composter, supplemented with an inoculant, in processing biowaste generated at five educational institutions in Split. During the biowaste treatment, key parameters were monitored, including temperature, compost heap height, moisture content, dry and volatile matter, carbon and nitrogen content, pH, and electrical conductivity. The collected leachates were analysed for volume, pH, electrical conductivity, and turbidity. Pre-composts were subsequently matured in two soil types, where the same physicochemical parameters were assessed to evaluate further stabilisation. Fourier-transform infrared (FTIR) spectroscopy was used to evaluate compositional changes in the biowaste resulting from composting conditions, and to analyse the produced water-dominated leachates. The results showed that the C-EcoForHome composter effectively processed biowaste in institutional settings, producing stable pre-composts with only minor variations compared to the initial substrate composition. Anaerobic fermentation caused acidification, ion release, and partial stabilisation of organic matter, while soil maturation further contributed to drying and consolidation. Indoor small-scale biowaste treatment represents a sustainable, low-maintenance solution for biowaste management, producing nutrient-rich pre-compost suitable for soil amendment.Obrada biootpada u zatvorenom prostoru (engl. indoor biowaste treatment) uporabom malih kompostera pokazuje se učinkovitom metodom za obradu organskog otpada i povrat resursa. U ovom je radu ispitana učinkovitost ručno izrađenog C-EcoForHome kompostera, obogaćenog inokulantom, u obradi biootpada nastalog u pet odgojno-obrazovnih ustanova u Splitu. Tijekom obrade biootpada praćeni su ključni parametri, uključujući temperaturu, visinu kompostne hrpe, maseni udio vlage, suhe i hlapljive tvari, sadržaj ugljika i dušika, pH vrijednost te električnu vodljivost. Prikupljenoj procjednoj vodi analiziran je volumen, pH vrijednost, električna vodljivost i mutnoća. Prekomposti su potom dozrijevali u dvjema vrstama tla, pri čemu su isti fizikalno-kemijski parametri ponovno ispitani radi praćenja dodatne stabilizacije. FTIR spektroskopijom provedena je analiza promjene sastava biootpada zbog utjecaja kompostiranja te analiza nastalih procjednih voda u kojima dominira voda. Rezultati su pokazali da C-EcoForHome komposter učinkovito obrađuje biootpad u odgojno-obrazovnim ustanovama proizvodeći stabilne prekomposte s minimalnim varijacijama u odnosu na početni sastav biootpada. Anaerobna fermentacija dovela je do acidifikacije, otpuštanja iona i djelomične stabilizacije organske tvari, dok je dozrijevanje u tlu dodatno pridonijelo sušenju i konsolidaciji materijala. “Indoor” obrada biootpada u malom mjerilu omogućuje održivo, ekonomski prihvatljivo rješenje za upravljanje biootpadom proizvodeći hranjivi prekompost prikladan za poboljšanje tla
The Role of Psychologists in Working with Crisis Negotiators
No full textAim: Crisis negotiation is one of the extremely effective police tools for resolving crisis interventions peacefully, i.e., without the use of force. This paper will try to clarify the role of psychologists in working with crisis negotiators, depending on the different areas of work of negotiators to which psychologists can contribute. Materials and Methods: Psychologists have been involved in this type of police activity since the very beginning of crisis negotiations in the world. Many police organizations across the globe have psychologists in their negotiation units. Communication techniques are only some of the skills of crisis negotiators, and existing methods are based on different psychological models and concepts. Conclusion: The entire negotiation process involves various steps and phases and, among other things, is imbued with numerous principles and legalities of the psychological profession
National recommendations of the Working Group for Postanalytics of the Croatian Society of Medical Biochemistry and Laboratory Medicine: Quality indicators of the postanalytical phase
No full textConsidering the concept of quality as a degree of excellence, the term quality of laboratory work tells us how excellent our results are in all areas of laboratory work. Therefore, quality indicators have been introduced with the aim of monitoring and measuring quality. Quality indicators describe the efficiency of the laboratory process in the form of a numerical value, providing objective evidence of the conformity of the specified laboratory process with respect to predefined criteria. The Working Group for Postanalytics of the Croatian Society of Medical Biochemistry and Laboratory Medicine has decided to describe the necessary steps in designing and monitoring quality indicators, with an emphasis on the quality of the postanalytical and post-postanalytical phase. The main purpose of these recommendations is to facilitate the incorporation of quality indicators into laboratories’ daily routines. Laboratories in the Republic of Croatia are recommended to monitor three quality indicators in the postanalytical phase of laboratory work: turnaround time, withdrawn or retracted laboratory test reports, and notification of critical results. Additionally, two indicators are recommended in the post-postanalytical phase: monitoring issuance of laboratory test reports and monitoring user satisfaction. Harmonising acceptable performance limits and monitoring of the most commonly used quality indicators opens up the possibility of comparisons between laboratories and a uniform quality of laboratory services throughout the healthcare system
Falsely decreased triglyceride concentration in a patient with acute pancreatitis due to insufficient configuration of alarm rules
No full textAcute pancreatitis is a potentially life-threatening complication of severe hypertriglyceridemia. The accurate measurement of triglyceride concentration is essential for diagnosis and therapeutic monitoring. This article presents a case of acute hypertriglyceridemia pancreatitis in which the patient’s triglyceride concentration appeared to drop rapidly from 128.04 mmol/L to 1.53 mmol/L within 12 hours of admission. Subsequent retesting revealed an actual triglyceride value of 88.92 mmol/L. This case underscores a critical and underreported preanalytical challenge: the failure of the analyzer to trigger “> Kin” warnings despite clear abnormalities in the reaction kinetics curve, leading to clinically significant underestimation. To mitigate such errors, we propose a novel strategy that integrates automated lipemic index-based predilution protocols with enhanced alarm configurations, including the introduction of a “>Abs” alert, adjustment of prozone detection parameters, and the implementation of correlation checks between lipemic indices and triglyceride values within the laboratory information system. These practical interventions, which can be adopted in clinical laboratories, represent a proactive approach to prevent erroneous reporting and enhance diagnostic reliability. This report highlights the necessity for increased vigilance among laboratory professionals when discordance occurs between high lipemic indices and unexpectedly low triglyceride results, suggesting possible kinetic anomalies
Solution to the single parametric linear programming problems via simplex-based algorithms: handling the uncertainties in costs, left or right-hand sides
No full textParametric programming is one of the notable approaches to expressing the uncertainties encountered in real life. Many studies express the parameters of the objective function and right-hand side parametrically, but only a few include the parametric coefficient matrix of the constraints. This paper examines the feasibility and optimality conditions of the simplex table and proposes a simplex-based algorithm (dual-simplex, generalized-simplex, or primal-simplex). In the solution process, each case is considered independently through the mathematical analysis of simplex multipliers. Distinct numerical examples illustrate each case to demonstrate the algorithm’s implementation
Analysis of the Black and White Image Recording of the Converted RGB Photographic Image
No full textA digital camera is generally used for digital recording of photographic images in the RGB system. When such a multicoloured photographic image is converted to black and white using the standard Grayscale conversion in Adobe Photoshop, the colour information, expressed as R, G and B channel values, is lost. This paper analyses the darkening caused by different conversions of the RGB record of a photographic image to a black and white image record. The conversions were performed on three photos, with 10 random colours separated for each photo before conversion. After conversion, the L parameter, which indicates the brightness value, was analysed. The changes in the L parameter due to different methods of photo conversion from multicolour to black and white, such as desaturation, extraction of the R channel, extraction of the G channel and extraction of the B channel, were also analysed
Fuelling Logistics from Refinery to Retail: Case Study of the Romanian Oil Supply Chain
No full textThe purpose of this paper was to examine how EU sanctions on Russia impacted Romania and how its refineries managed to continue operating with alternative suppliers. Production performance dynamics and their share in total output of refined petroleum products in the last 5 years (2019-2023) are analyzed using descriptive statistics. Own empirical research is used to study the supply chains of the Petrobrazi, Petrotel and Petromidia refineries and provide an overview of their role on the domestic fuel market by mapping out their fuel storage locations and network of filling stations. Findings underpin the importance of an interconnected infrastructure network (pipelines, railways and ports) and using it to its full extent to balance out onshore and offshore imports, as well as downstream deliveries. Study replicability is affected by the limited extent to which the collected data can be revealed, whilst future research can study sustainability of non-Russian oil sourcing alternatives