1. Stability analysis of the singular points and Hopf bifurcations of a tumor growth control modelDániel András Drexler, Ilona Nagy, Valery Romanovski, 2024, izvirni znanstveni članek Opis: We carry out qualitative analysis of a fourth-order tumor growth control model using ordinary differential equations. We show that the system has one positive equilibrium point, and its stability is independent of the feedback gain. Using a Lyapunov function method, we prove that there exist realistic parameter values for which the systems admit limit cycle oscillations due to a supercritical Hopf bifurcation. The time evolution of the state variables is also represented.
Ključne besede: bifurcation, cancer therapy, limit cycle, singular point, tumor therapy, tumor control
Objavljeno v DKUM: 12.08.2024; Ogledov: 73; Prenosov: 5
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2. Advanced technologies in logistics engineering : automated storage systems with shuttles integrated with hoisted carriageTone Lerher, Primož Bencak, 2022, izvirni znanstveni članek Opis: This paper presents automated storage systems with shuttles integrated with hoisted carriage for successful application in intralogistics. The first part of the paper presents classic and advanced AVS/RS along with specific intralogistics automation systems known as AutoStore from Swisslog and Skypod from Exotec. The second part of the paper focuses on an advanced system with shuttle vehicles capable of serving multiple tiers of the storage rack. An analytical model for the shuttle vehicles capable of serving multiple tiers of the storage rack is presented, which is based on (i) the sequences of acceleration, constant velocity and deceleration, and (ii) randomised assignment policy. Based on the presented model, the expected Single Command (SC) and Dual Command (DC) travel (cycle) time as well as the throughput performance of the shuttle vehicles capable of serving several tiers of warehouse, could be calculated. A programme code in MATLAB has been presented for the computation of throughput performances of automated storage systems with shuttles integrated with hoisted carriage capable of serving several tiers of the storage rack.
Ključne besede: analytical and numerical model, automated vehicle-storage and retrieval systems AVS/RS, automated warehouses, cycle time and throughput performance, shuttles integrated with hoisted carriage
Objavljeno v DKUM: 26.06.2024; Ogledov: 162; Prenosov: 7
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3. The role of anaplerotic metabolism of glucose and glutamine in insulin secretion : a model approachVladimir Grubelnik, Jan Zmazek, Marko Gosak, Marko Marhl, 2024, izvirni znanstveni članek Opis: We propose a detailed computational beta cell model that emphasizes the role of anaplerotic metabolism under glucose and glucose-glutamine stimulation. This model goes beyond the traditional focus on mitochondrial oxidative phosphorylation and ATP-sensitive K+ channels, highlighting the predominant generation of ATP from phosphoenolpyruvate in the vicinity of KATP channels. It also underlines the modulatory role of H2O2 as a signaling molecule in the first phase of glucose-stimulated insulin secretion. In the second phase, the model emphasizes the critical role of anaplerotic pathways, activated by glucose stimulation via pyruvate carboxylase and by glutamine via glutamate dehydrogenase. It particularly focuses on the production of NADPH and glutamate as key enhancers of insulin secretion. The predictions of the model are consistent with empirical data, highlighting the complex interplay of metabolic pathways and emphasizing the primary role of glucose and the facilitating role of glutamine in insulin secretion. By delineating these crucial metabolic pathways, the model provides valuable insights into potential therapeutic targets for diabetes.
Ključne besede: mathematical models, pancreatic beta cell, pyruvate-malate cycle
Objavljeno v DKUM: 06.06.2024; Ogledov: 162; Prenosov: 6
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4. Diversity and content of carotenoids and other pigments in the transition from the green to the red stage of Haematococcus pluvialis microalgae identified by HPLC-DAD and LC-QTOF-MSJaša Veno Grujić, Biljana Todorović, Roman Kranvogl, Terezija Ciringer, Jana Ambrožič-Dolinšek, 2022, izvirni znanstveni članek Opis: H. pluvialis is a unicellular freshwater alga containing many bioactive compounds, especially carotenoids, which are the strongest antioxidants among the pigments. This study evaluates
the composition and content of carotenoids and other pigments in both stages of algae life cycle,
especially in the green vegetative stage, less studied in comparison to the red stage. To determine
the composition and content of carotenoids, a combination of HPLC-DAD and LC-QTOF-MS was
used. The content of carotenoids in the green vegetative stage was significantly lower than in the
red vegetative stage. In the green vegetative stage, 16 different carotenoids and other pigments were
identified. Among the total 8.86 mg g−1 DW of pigments, 5.24 mg g−1 DW or 59% of them were
chlorophyll a with its derivatives, and 3.62 mg g−1 DW or 41% of them were free carotenoids. After
the transition from the green to the red stage, the carotenoid composition was replaced by secondary
carotenoids, astaxanthin and its esters, which predominated in the whole carotenoid composition.
In addition to free astaxanthin, 12 astaxanthin monoesters, 6 diesters and 13 other carotenoids were
determined. The majority of 37.86 mg g−1 DW pigments were monoesters. They represented 82% of
all pigments, and their content was about 5 times higher than both, diesters (5.91 mg g−1 DW or 12%
of all) and free carotenoids (2.4 mg g−1 DW or 6% of all). The results of the study contribute to the
data on the overall pigment composition and content of H. pluvialis algae and provide the basis for
further improvement of cultivation of the H. pluvialis algae.
Ključne besede: antioxidants, astaxanthin, chlorophylls, bioactive compounds, algae, Haematococcus, life cycle, pigment composition, secondary carotenoids
Objavljeno v DKUM: 21.05.2024; Ogledov: 172; Prenosov: 8
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5. Lipotoxicity in a vicious cycle of pancreatic beta cell exhaustionVladimir Grubelnik, Jan Zmazek, Matej Završnik, Marko Marhl, 2022, izvirni znanstveni članek Opis: Hyperlipidemia is a common metabolic disorder in modern society and may precede hyperglycemia and diabetes by several years. Exactly how disorders of lipid and glucose metabolism are related is still a mystery in many respects. We analyze the effects of hyperlipidemia, particularly free fatty acids, on pancreatic beta cells and insulin secretion. We have developed a computational model to quantitatively estimate the effects of specific metabolic pathways on insulin secretion and to assess the effects of short- and long-term exposure of beta cells to elevated concentrations of free fatty acids. We show that the major trigger for insulin secretion is the anaplerotic pathway via the phosphoenolpyruvate cycle, which is affected by free fatty acids via uncoupling protein 2 and proton leak and is particularly destructive in long-term chronic exposure to free fatty acids, leading to increased insulin secretion at low blood glucose and inadequate insulin secretion at high blood glucose. This results in beta cells remaining highly active in the “resting” state at low glucose and being unable to respond to anaplerotic signals at high pyruvate levels, as is the case with high blood glucose. The observed fatty-acid-induced disruption of anaplerotic pathways makes sense in the context of the physiological role of insulin as one of the major anabolic hormones.
Ključne besede: diabetes, insulin secretion, lipids, PEP cycle, uncoupling proteins, mitochondrial dysfunction
Objavljeno v DKUM: 20.05.2024; Ogledov: 133; Prenosov: 4
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6. Hydrogen production, storage and transport for renewable energy and chemicals : An environmental footprint assessmentRobert Hren, Annamaria Vujanović, Yee Van Fan, Damjan Krajnc, Jiri Klemeš, Lidija Čuček, 2023, izvirni znanstveni članek Ključne besede: hydrogen producing technologies, hydrogen storage, hydrogen transport, life cycle assessment, different electricity sources, energy and environmental footprints, eco-benefit and eco-cost, comparative impact assessment
Objavljeno v DKUM: 10.05.2024; Ogledov: 240; Prenosov: 22
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7. A game theoretic approach for plastic life cycle assessmentChunyan Si, Yee Van Fan, Lidija Čuček, Monika Dokl, Petar Varbanov, 2023, izvirni znanstveni članek Opis: Plastic production and its end-of-life management pose a significant environmental footprint. The mitigation strategies of the plastic industry are comparatively attainable than the other hard-to-abate sector. However, the involvement of different stakeholders is needed. The life cycle analysis proposed in this study allocated the environmental footprint to stakeholders based on the game theory concept. It addresses the limitation of previous approaches that do not guarantee the stakeholders from different stages will participate in the initiatives with the lowest net environmental footprint due to the dissatisfaction or imbalance in the allocated unburdening footprint (benefit) and burdening footprint. The applicability of the proposed approach is demonstrated through a plastic recycling case study. An allocation of 82 % of environmental benefit to the producer, 14 % to the manufacturer, and 4 % to the user are suggested to achieve efficiency (lowest external interference) and stable cooperation (participation in recycling). This work serves as an initial assessment in demonstrating the integration of the game theory concept in environmental footprint allocation or Life Cycle Assessment.
Ključne besede: plastic production, environmental footprint, life cycle
Objavljeno v DKUM: 18.04.2024; Ogledov: 155; Prenosov: 4
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8. Organizational maturity and sustainability orientation influence on DMS life cycle : case analysisSandra Jordan, Simona Sternad Zabukovšek, 2023, izvirni znanstveni članek Opis: The topic of the article addresses the management of the document management system (DMS), which represents one of the important steps for organizations to speed up the implementation of business processes, achieve better control over documents, and ensure safer operations. When implementing and using DMS, the importance of the organization’s maturity shall not be forgotten, as it gives the organization a framework to evaluate and improve the overall effectiveness and efficiency of the organization’s DMS, which can contribute to better decision-making and increased productivity. On the other hand, sustainable-oriented organizations are likely to show interest in choosing, implementing, and using DMS. In the article, the impact of an organization’s maturity and the role of sustainability on the DMS lifecycle are researched. Results are presented based on a case analysis of Company X. Supporting the case analysis, structured interviews with the project leader on the clients’ and the project leader on the providers’ side have been performed, which shall give a deeper insight into DMS implementation and the importance of sustainability and organizational maturity, resulting in more successful DMS implementation and use.
Ključne besede: document management system (DMS), DMS life cycle, maturity model, sustainability, case analysis
Objavljeno v DKUM: 09.04.2024; Ogledov: 167; Prenosov: 8
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10. LCF behaviour of high strength aluminium alloys AA 6110A and AA 6086Jernej Klemenc, Srečko Glodež, Matej Steinacher, Franc Zupanič, 2023, izvirni znanstveni članek Opis: The proposed research presents the comprehensive investigation of the Low Cycle Fatigue (LCF) behaviour of two high-strength aluminium alloys of series AA 6xxx: the conventional alloy AA 6110A and the newly developed alloy AA 6086. Both alloys were characterised in the as-cast condition after homogenisation, extrusion, and T6 heat treatment.
The quasi-static strength and hardness of the aluminium alloy AA 6086 were found to be significantly higher if compared to the AA 6110A alloys, while the ductility was a little bit smaller. The LCF tests showed that the AA 6086 alloy is more suitable for the high-cycle fatigue regime. On the other hand, the engineering advantage of the AA 6110A alloy is only for low-cycle fatigue applications if less than 100 loading cycles are expected in the service life of the analysed structure. The fatigue cracks formed predominantly on the α-AlMnSi intermetallic particles in both alloys, and, during LCF tests, exhibited small crack propagation. The area of the fatigue crack growth was much smaller than the area of the forced fracture. At smaller amplitude strains the fatigue striations were present at the fracture surface, while, at higher amplitude strains, they were not present. The obtained experimental results represent a good basis for engineering design applications of the analysed alloys AA 6086 and AA 6110A.
Ključne besede: aluminijeve zlitine, malociklično utrujanje, eksperimentalno testiranje, fraktografija, aluminium alloys, low cycle fatigue, experimental testing, fractography
Objavljeno v DKUM: 29.03.2024; Ogledov: 197; Prenosov: 13
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