1. Synchronization in simplicial complexes of memristive Rulkov neuronsMahtab Mehrabbeik, Sajad Jafari, Matjaž Perc, 2023, original scientific article Abstract: Simplicial complexes are mathematical constructions that describe higher-order interactions within the interconnecting elements of a network. Such higher-order interactions become increasingly significant in neuronal networks since biological backgrounds and previous outcomes back them. In light of this, the current research explores a higher-order network of the memristive Rulkov model. To that end, the master stability functions are used to evaluate the synchronization of a network with pure pairwise hybrid (electrical and chemical) synapses alongside a network with two-node electrical and multi-node chemical connections. The findings provide good insight into the impact of incorporating higher-order interaction in a network. Compared to two-node chemical synapses, higher-order interactions adjust the synchronization patterns to lower multi-node chemical coupling parameter values. Furthermore, the effect of altering higher-order coupling parameter value on the dynamics of neurons in the synchronization state is researched. It is also shown how increasing network size can enhance synchronization by lowering the value of coupling parameters whereby synchronization occurs. Except for complete synchronization, cluster synchronization is detected for higher electrical coupling strength values wherein the neurons are out of the completed synchronization state.
Keywords: simplicial complex, higher-order network, memristive Rulkov, synchronization, cluster synchronization
Published in DKUM: 11.09.2024; Views: 2; Downloads: 0
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2. Self-organization in Slovenian public spendingJelena Joksimović, Matjaž Perc, Zoran Levnajić, 2023, original scientific article Abstract: Private businesses are often entrusted with public contracts, wherein public money is allocated to a private company. This process raises concerns about transparency, even in the most developed democracies. But are there any regularities guiding this process? Do all private companies benefit equally from the state budgets? Here, we tackle these questions focusing on the case of Slovenia, which keeps excellent records of this kind of public spending. We examine a dataset detailing every transfer of public money to the private sector from January 2003 to May 2020. During this time, Slovenia has conducted business with no less than 248 989 private companies. We find that the cumulative distribution of money received per company can be reasonably well explained by a power-law or lognormal fit. We also show evidence for the first-mover advantage, and determine that companies receive new funding in a way that is roughly linear over time. These results indicate that, despite all human factors involved, Slovenian public spending is at least to some extent regulated by emergent self-organizing principles.
Keywords: complex system, self-organization, Slovenia, public funds
Published in DKUM: 11.09.2024; Views: 1; Downloads: 0
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3. Sinteza magnetno zeolitnega nanokompozitaMelissa Sterniša, 2024, master's thesis Abstract: Magistrsko delo zajema sinteze magnetnih nanodelcev in sinteze magnetno zeolitnih nanokompozitov. Magnetni nanodelci so bili sintetizirani z metodo koprecipitacije oz. s soobarjalno metodo in mikrovalovno metodo. Magnetno zeolitni nankompoziti so nastali z naknadno sintezo in sočasno sintezo. Dobljeni produkti so bili okarakterizirani s Fourierjevo transformirano infrardečo spektroskopijo na oslabljen totalni odboj (ATR-FTIR), termogravimetrično analizo (TGA), dinamičnim sipanjem svetlobe (DLS), Brunauer-Emmett-Tellerjevo metodo (BET), vrstičnim elektronskim mikroskopom (SEM) in rentgensko praškovno difrakcijo (RTG). Rezultati karakterizacijskih metod so pokazali, da je bila uspešnejša sinteza magnetno zeolitnega nanokompozita z naknadno sintezo tako pri soobarjalnih magnetnih nanodelcih kot tudi pri mikrovalovnih. Sintetizirani magnetni nanodelci in nanokompoziti so bili nato še uporabljeni za odstranjevanje mikro in nanoplastike iz vode. Odstranjevanje je potekalo s pomočjo ultrazvočne kopeli in posedanjem na magnetu iz modelne raztopine polietilena. UV/VIS spektroskopija je pokazala, da je bilo najuspešnejše odstranjevanje z magnetnimi nanodelci sintetiziranimi s soobarjalno sintezo.
Keywords: Magnetni nanodelci, zeolit, magnetno zeolitni nanokompozit, mikro in nanoplastika
Published in DKUM: 11.09.2024; Views: 7; Downloads: 0
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4. Korozijske lastnosti cirkonija v umetni slini z dodatkom organskih in ortofosforne kislineLaura Kobe Stožinič, 2024, undergraduate thesis Abstract: Zaradi vse pogostejše uporabe cirkonijevih implantatov, je bil namen diplomske naloge raziskati korozijske lastnosti cirkonija v umetni slini z dodatkom organskih in ortofosforne kisline.
Osnovna raztopina, ki je služila kot agresivni medij, je bila umetna slina v prisotnosti najpogostejših kislin, ki jih vnašamo v ustno votlino s hrano in pijačo. Kisline, ki smo jih glede na priporočene dnevne vnose dodajali umetni slini, so bile različne organske: vinska, jabolčna in mlečna ter ortofosforna kislina.
Eksperimentalni del smo izvedli z gravimetrično metodo, pri temperaturi 37 °C, kar je optimalna telesna temperatura človeka in pri atmosferskem tlaku 101,3 kPa, na ta način smo se čim bolj približali pogojem v ustni votlini. Pred samim postopkom gravimetrije smo pripravili raztopino umetne sline s preračunanimi količinami organskih in ortofosforne kisline. Sam postopek gravimetrije je vključeval naslednje korake: vzorce, ki smo jih termostatirali smo predhodno ustrezno pripravili, kar je zajemalo postopke brušenja, poliranja, razmastitve, ultrazvočnega čiščenja in sušenja s komprimiranim zrakom. Tako pripravljene vzorce smo stehtali in termostatirali v raztopinah 24, 48, 72 in 96 h. Po pretečenem času smo korodirane vzorce ponovno ustrezno očistili in stehtali. Na podlagi spremembe mase vzorca pred in po izpostavitvi raztopini smo izračunali korozijsko hitrost. Tako smo ugotovili, katera kislina povzroča največje korodiranje cirkonija oziroma v kateri kislini je cirkonij najbolj odporen in tvori stabilen pasivni film. Z vrstičnim elektronskim mikroskopiranjem smo posneli površine nekaterih vzorcev.
Po 24, 48, 72 in 96 urni pasivaciji, so rezultati pokazali, da na spološno cirkonij tvori najbolj stabilen pasivni film v raztopini umetne sline z dodatkom jabolčne kisline. Najmanj odporen je v raztopini umetne sline z dodatkom mlečne kisline do 48 ur pasivacije, po 48 urah pa korozijske hitrosti cirkonija v raztopini umetne sline z dodatkom mlečne kisline padajo, medtem, ko v raztopini umetne sline z dodatkom vinske kisline naraščajo. Izračunane korozijske hitrosti so v splošnem nizke, kar pomeni, da je cirkonij v kovinski obliki glede korozije primeren material za medicinske vsadke.
Keywords: cirkonij, umetna slina, dentalni implantati, korozija, organske kisline, ortofosforna kislina
Published in DKUM: 10.09.2024; Views: 20; Downloads: 4
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5. Statistically significant features improve binary and multiple motor imagery task predictions from EEGsMurside Degirmenci, Yilmaz Kemal Yuce, Matjaž Perc, Yalcin Isler, 2023, original scientific article Abstract: In recent studies, in the field of Brain-Computer Interface (BCI), researchers have
focused on Motor Imagery tasks. Motor Imagery-based electroencephalogram
(EEG) signals provide the interaction and communication between the paralyzed
patients and the outside world for moving and controlling external devices
such as wheelchair and moving cursors. However, current approaches in the
Motor Imagery-BCI system design require.
Keywords: brain-computer interfaces, electroencephalogram, feature selection, machine learning, task classification
Published in DKUM: 10.09.2024; Views: 9; Downloads: 0
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6. Modelling of dysregulated glucagon secretion in type 2 diabetes by considering mitochondrial alterations in pancreatic ▫$\alpha$▫-cellsVladimir Grubelnik, Rene Markovič, Saška Lipovšek Delakorda, Gerd Leitinger, Marko Gosak, Jurij Dolenšek, Ismael Valladolid-Acebes, Per-Olof Berggren, Andraž Stožer, Matjaž Perc, Marko Marhl, 2020, original scientific article Abstract: Type 2 diabetes mellitus (T2DM) has been associated with insulin resistance and the failure of β-cells to produce and secrete enough insulin as the disease progresses. However, clinical treatments based solely on insulin secretion and action have had limited success. The focus is therefore shifting towards α-cells, in particular to the dysregulated secretion of glucagon. Our qualitative electron-microscopy-based observations gave an indication that mitochondria in α-cells are altered in Western-diet-induced T2DM. In particular, α-cells extracted from mouse pancreatic tissue showed a lower density of mitochondria, a less expressed matrix and a lower number of
cristae. These deformities in mitochondrial ultrastructure imply a decreased efficiency in mitochondrial ATP production, which prompted us to theoretically explore and clarify one of the most challenging problems associated with T2DM, namely the lack of glucagon secretion in hypoglycaemia and its oversecretion at high blood glucose concentrations. To this purpose, we constructed a novel computational model that links α-cell metabolism with their electrical activity and glucagon secretion. Our results show that defective mitochondrial metabolism in α-cells can
account for dysregulated glucagon secretion in T2DM, thus improving our understanding of T2DM pathophysiology and indicating possibilities for new clinical treatments.
Keywords: diabetes, pancreatic alpha cells, glucagon, mitochondrial dysfunction, free fatty acid
Published in DKUM: 03.09.2024; Views: 39; Downloads: 2
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7. Informacijska varnost v avtonomnih hotelih : diplomsko delo visokošolskega študijskega programa Informacijska varnostMatjaž Hriberšek, 2024, undergraduate thesis Abstract: V diplomskem delu sem želel raziskati kakšna je izkušnja uporabnika pametnega hotela in kakšno je zaupanje v hotelske storitve v takšnih hotelih, da bo varovalo informacije strank. Cilj je preučiti, kako sodobna digitalna tehnologija spreminja hotelirstvo in v kolikšni meri posega v posameznikovo zasebnost. Glede na to, da so pametni hoteli v zadnjih par letih prišli na tržišče, ogromno ljudi niti ne ve, da takšni hoteli obstajajo oz. še niso bivali v njem. V teoretičnem delu sem za lažje razumevanje razložil nekaj pojmov kot so informacijska varnost, pametni hotel. Nato sem predstavil kakšno tehnologijo lahko najdemo v pametnih hotelih. Omenil sem internet stvari, ki je eden od glavnih razlogov, da so se pametni hoteli sploh razvili. Varnost in zasebnost gostov je zelo problematičen del nudenja storitev v pametnih hotelih. Tu je je treba zelo paziti in skrbeti za pametne naprave, ki so na voljo gostu v hotelu ali v sami sobi. V zadnjem delu pa sem se dotaknil še osebnih podatkov in informacijske varnosti v samih hotelih. Zaupanje gosta v hotel, da bo varoval osebne podatke gostov je zelo pomembna naloga hotelskih organizacij. Gost namreč pričakuje, da bo organizacija skrbela za informacijsko varnost in odpravljala napake, ki bi jih sami zaznali, še predno pride do kakšnih resnejših incidentov. Pri raziskovalnem delu je bila z deskriptivno metodo preučena pretežno tuja literatura. V metodološkem delu naloge pa sem s pomočjo anketnega vprašalnika v elektronski obliki iskal odgovore na zastavljene hipoteze. Na podlagi zbranih informacij so se potrdile zastavljene hipoteze.
Keywords: informacijska varnost, pametni hoteli, zasebnost, diplomske naloge
Published in DKUM: 29.08.2024; Views: 105; Downloads: 17
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8. Characterization of germanium nanoparticles from arylgermanium trihydridesPhilipp Schmid, Brigitte Koppelhuber-Bitschnau, Matjaž Finšgar, Ilse Letofsky-Papst, Johannes Rattenberger, Robert Saf, 2024, original scientific article Keywords: nanoparticles, germanium, optical properties, electronic properties
Published in DKUM: 29.08.2024; Views: 67; Downloads: 2
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9. Study of V[sub]2CT[sub]x-MXene Based Immunosensor for Sensitive Label-Free Impedimetric Detection of SARS-CoV-2 Spike ProteinNikola Tasić, Ivan Konjević, Alnilan Cristina Barros Lobato, Dino Metarapi, Matjaž Finšgar, Filipa M. Oliveira, Zdeněk Sofer, Rui Gusmão, Xueji Zhang, Samo B. Hočevar, 2024, original scientific article Abstract: Rapid and reliable immunosensing is undoubtedly one of the priorities in the efficient management and combat against a pandemic, as society has experienced with the SARS-CoV-2 outbreak; simple and cost-effective sensing strategies are at the forefront of these efforts. In this regard, 2D-layered MXenes hold great potential for electrochemical biosensing due to their attractive physicochemical properties. Herein, we present a V$_2$CT$_x$ MXene-based sensing layer as an integral part of a label-free immunosensor for sensitive and selective detection of the SARS-CoV-2 spike protein. The sensor was fabricated on a supporting screen-printed carbon electrode using Nafion as an immobilizing agent for MXene and glutaraldehyde, the latter enabling effective binding of protein A for further site-oriented immobilization of anti-SARS-CoV-2 antibodies. A thorough structural analysis of the sensor architecture was carried out, and several key parameters affecting the fabrication and analytical performance of the immunosensor were investigated and optimized. The immunosensor showed excellent electroanalytical performance in combination with an impedimetric approach and exhibited a low detection limit of only 45 fM SARS-CoV-2 spike protein. Its practical applicability was successfully demonstrated by measuring the spike protein in a spiked artificial nasopharyngeal fluid sample.
Keywords: imunosenzorji, polprevodniške nanostrukture, proteini, spike protein, immunosensors, SARS-CoV-2, V2CTxMXene
Published in DKUM: 29.08.2024; Views: 41; Downloads: 1
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