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1.
Izbrana poglavja iz naravoslovnih znanosti - fizika
Borut Krajnc, Marko Žigart, Marjeta Capl, Vladimir Grubelnik, Marko Marhl, 2021, drugo učno gradivo

Opis: Navodila laboratorijskega dela pri predmetu Izbrana poglavja iz naravoslovnih znanosti – fizika je plod večletnega soustvarjanja in dograjevanja naravoslovnih vsebin različnih avtorjev. Glavni namen je ponuditi strnjeno in pregledno gradivo s področja fizikalnih laboratorijskih vaj za študentke in študente Razrednega pouka Pedagoške fakultete Univerze v Mariboru. Gradivo je razdeljeno na 13 vsebinskih enot, ki pokrivajo vsa pomembna fizikalna področja od merjenj do astronomije. Vsaka enota je razčlenjena z navodili za izvedbo številnih fizikalnih poskusov, ki so neposredno uporabni pri naravoslovnih vsebinah na razredni stopnji v osnovni šoli. Izbrani so tisti poskusi, ki so poučni in zanimivi, hkrati pa izvedljivi z osnovnošolsko eksperimentalno opremo.
Ključne besede: Učno gradivo, fizika, laboratorijske vaje
Objavljeno: 27.02.2021; Ogledov: 188; Prenosov: 14
URL Povezava na celotno besedilo
Gradivo ima več datotek! Več...
; Gradivo je zbirka in zajema 1 gradivo!

2.
Rekonstrukcija funkcionalnih mrež iz dinamike pankreasnih celic beta
Jakob Murko, 2019, magistrsko delo

Opis: V magistrskem delu obravnavamo funkcionalno povezanost celic beta. Te celice se nahajajo v Langerhansovih otočkih v trebušni slinavki in so ključne pri uravnavanju koncentracije glukoze v krvi, saj ob povečani ravni glukoze v organizmu izločajo hormon inzulin. V prvi fazi dela dinamiko električno vzdraženih celic beta simuliramo z modelom, v drugi fazi pa se osredotočimo na analizo eksperimentalno izmerjene dinamike znotrajceličnega kalcija. Za opis dinamike posameznih celic uporabimo fenomenološki model, t.i. iterativno mapo Rulkova. Posamezne Rulkove oscilatorje med seboj povežemo v mrežo, s čimer simuliramo funkcijo presledkovnih stikov, s katerimi so povezane celice beta v realnem tkivu. Da bi naš večcelični model čimbolj približali realnemu obnašanju, vpeljemo tudi naključno in prostorsko definirano heterogenost celic. Na podlagi podatkov aktivnosti celic iz simulacij določimo funkcionalno povezanost le-teh. Predstavimo dve metodi določitve funkcionalne mreže, to je korelacijsko in metodo pseudo-inverza kovariance. Analiza simuliranih podatkov pokaže, da sta obe metodi zanesljivi, zato jih preizkusimo tudi na eksperimentalno pridobljenih podatkih, in sicer na in situ meritvah kalcijeve aktivnosti v svežih tkivnih rezinah mišje trebušne slinavke. Ugotovimo, da sta si funkcionalna mreža na podlagi simulacijskih in eksperimentalnih podatkov podobni, kar nam kaže na natančno obnašanje modela. Z analizo obeh funkcionalnih mrež ustvarjenih na podlagi eksperimentalnih podatkov lahko vsaj delno sklepamo na strukturo povezav presledkovnih stikov v opazovani plasti Langerhansovega otočka. Pomembna je tudi ugotovitev, da v funkcionalni mreži celic beta opazimo celice z nadpovprečnim številom povezav, tudi daljnosežnih, kar je v skladu z ugotovitvami preteklih raziskav.
Ključne besede: celice beta, Langerhansov otoček, funkcionalna mreža, Rulkov model, celična heterogenost, korelacijski koeficient, pseudo-inverz kovariance.
Objavljeno: 05.11.2019; Ogledov: 405; Prenosov: 41
.pdf Celotno besedilo (3,34 MB)

3.
Vesoljski turizem v resničnosti in v znanstveni fantastiki
Matic Jelenovec, 2018, diplomsko delo/naloga

Opis: Vesoljski turizem postaja v današnjem času vse bolj priljubljen, saj se izvaja vse več raziskav in v zvezi s tem je vse več povpraševanja. Turistična potovanja v vesolje so se pred nekaj desetletji zdela še nemogoča, a danes je popolnoma drugače. Vse več je špekulacij in načrtovanj, kako se bo v naslednjih letih potovalo v vesolje. Glavni akterji pri načrtovanju le-tega so zdaj že svetovno znane zasebne organizacije za vesoljski turizem, ki že vrsto let načrtujejo, da bi izvedle prvo potovanje v vesolje, kar bi na tem področju predstavljalo prelomnico. Zaradi vse večje priljubljenosti omenjene vrste turizma nas je zanimalo, kako bodo vesoljska potovanja izgledala v prihodnosti in predvsem, kako bo to potekalo v praksi. Prav tako nas je zanimalo, ali tudi Slovenija prispeva k razvoju vesoljskega turizma, ter ali obstajajo turistični produkti, povezani z vesoljskim turizmom, tudi na slovenskih tleh. Analiza podatkov je pokazala, da vesoljski turizem iz leta v leto napreduje, kot tudi tehnologija za potovanje v vesolje. Prav tako smo spoznali, da je v Sloveniji še veliko prostora za promocijo vesoljskega turizma in za ustvarjanje turističnih produktov, povezanih s to vrsto v turizma.
Ključne besede: vesoljski turizem, potovanje v vesolje, organizacije za vesoljski turizem, turistični produkti, tehnologija za potovanje v vesolje
Objavljeno: 29.11.2018; Ogledov: 515; Prenosov: 106
.pdf Celotno besedilo (1,82 MB)

4.
Analiza lastnosti jezika kot kompleksnega dinamičnega sistema na primerih slovenskih besedil
Maja Sokolovič, 2018, magistrsko delo

Opis: V magistrskem delu smo se osredotočili na področje, ki je v našem prostoru še precej neraziskano, to je dinamika in kompleksnost sistemov. Odločili smo se za obravnavo jezika s statističnega vidika. Namen raziskave je bil ugotoviti, ali v slovenskih besedilih zastopanost besed glede na njihovo pogostost sledi potenčno padajoči funkciji ter kako se skozi posamezna vzgojno-izobraževalna obdobja spreminja kompleksnost besedil. Z analizo slovenskih besedil smo raziskali pogostost besed glede na njihovo pojavljanje v besedilu ter pogostost pojavljanja besed glede na njihov rang in dolžino. Posebno pozornost smo namenili tudi literarnim osebam in njihovi prepletenosti v besedilu. S pomočjo programskega jezika Python in programov OriginPro 8.5 ter Gephi smo analizirali, kako so si v teh lastnostih medsebojno podobna besedila, primerna za posamezno vzgojno-izobraževalno obdobje, ter izpostavili razlike in podobnosti besedil med vzgojno-izobraževalnimi obdobji. Ugotovili smo, da so si besedila znotraj ene starostne skupine za posamezno vzgojno-izobraževalno obdobje zelo podobna. Smo pa na podlagi pridobljenih rezultatov prav tako ugotovili, da obstajajo precejšnje razlike v strukturi besedil med starostnimi skupinami. V magistrskem delu smo tako predstavili orodje, ki bi lahko v prihodnje učiteljem zagotavljalo enostavnejšo in bolj učinkovito določanje literarnih besedil, primernih za branje v določeni starostni skupini.
Ključne besede: jezik, kompleksni sistemi, Zipfov zakon, zastopanost besed, samoorganizacija
Objavljeno: 11.04.2018; Ogledov: 823; Prenosov: 78
.pdf Celotno besedilo (1,45 MB)

5.
Critical and supercritical spatiotemporal calcium dynamics in beta cells
Marko Gosak, Andraž Stožer, Rene Markovič, Jurij Dolenšek, Matjaž Perc, Marjan Rupnik, Marko Marhl, 2017, izvirni znanstveni članek

Opis: A coordinated functioning of beta cells within pancreatic islets is mediated by oscillatory membrane depolarization and subsequent changes in cytoplasmic calcium concentration. While gap junctions allow for intraislet information exchange, beta cells within islets form complex syncytia that are intrinsically nonlinear and highly heterogeneous. To study spatiotemporal calcium dynamics within these syncytia, we make use of computational modeling and confocal high-speed functional multicellular imaging. We show that model predictions are in good agreement with experimental data, especially if a high degree of heterogeneity in the intercellular coupling term is assumed. In particular, during the first few minutes after stimulation, the probability distribution of calcium wave sizes is characterized by a power law, thus indicating critical behavior. After this period, the dynamics changes qualitatively such that the number of global intercellular calcium events increases to the point where the behavior becomes supercritical. To better mimic normal in vivo conditions, we compare the described behavior during supraphysiological non-oscillatory stimulation with the behavior during exposure to a slightly lower and oscillatory glucose challenge. In the case of this protocol, we observe only critical behavior in both experiment and model. Our results indicate that the loss of oscillatory changes, along with the rise in plasma glucose observed in diabetes, could be associated with a switch to supercritical calcium dynamics and loss of beta cell functionality.
Ključne besede: beta cells, islets of Langerhans, self-organized criticality, intercellular dynamics, calcium waves, glucose oscillations, computational model, confocal calcium imaging
Objavljeno: 23.01.2018; Ogledov: 707; Prenosov: 294
.pdf Celotno besedilo (3,43 MB)
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6.
Progressive glucose stimulation of islet beta cells reveals a transition from segregated to integrated modular functional connectivity patterns
Rene Markovič, Andraž Stožer, Marko Gosak, Jurij Dolenšek, Marko Marhl, Marjan Rupnik, 2015, izvirni znanstveni članek

Opis: Collective beta cell activity in islets of Langerhans is critical for the supply of insulin within an organism. Even though individual beta cells are intrinsically heterogeneous, the presence of intercellular coupling mechanisms ensures coordinated activity and a well-regulated exocytosis of insulin. In order to get a detailed insight into the functional organization of the syncytium, we applied advanced analytical tools from the realm of complex network theory to uncover the functional connectivity pattern among cells composing the intact islet. The procedure is based on the determination of correlations between long temporal traces obtained from confocal functional multicellular calcium imaging of beta cells stimulated in a stepwise manner with a range of physiological glucose concentrations. Our results revealed that the extracted connectivity networks are sparse for low glucose concentrations, whereas for higher stimulatory levels they become more densely connected. Most importantly, for all ranges of glucose concentration beta cells within the islets form locally clustered functional sub-compartments, thereby indicating that their collective activity profiles exhibit a modular nature. Moreover, we show that the observed non-linear functional relationship between different network metrics and glucose concentration represents a well-balanced setup that parallels physiological insulin release.
Ključne besede: endocrinology, computational biophysics, calcium signalling, biological physics
Objavljeno: 23.06.2017; Ogledov: 682; Prenosov: 237
.pdf Celotno besedilo (957,14 KB)
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7.
The analysis of intracellular and intercellular calcium signaling in human anterior lens capsule epithelial cells with regard to different types and stages of the cataract
Marko Gosak, Rene Markovič, Aleš Fajmut, Marko Marhl, Marko Hawlina, Sofija Andjelić, 2015, izvirni znanstveni članek

Opis: In this work we investigated how modifications of the Ca2+ homeostasis in anterior lens epithelial cells (LECs) are associated with different types of cataract (cortical or nuclear) and how the progression of the cataract (mild or moderate) affects the Ca2+ signaling. We systematically analyzed different aspects of intra- and inter-cellular Ca2+ signaling in the human LECs, which are attached to surgically isolated lens capsule (LC), obtained during cataract surgery. We monitored the temporal and spatial changes in intracellular Ca2+ concentration after stimulation with acetylcholine by means of Fura-2 fluorescence captured with an inverted microscope. In our analysis we compared the features of Ca2+ signals in individual cells, synchronized activations, spatio-temporal grouping and the nature of intercellular communication between LECs. The latter was assessed by using the methodologies of the complex network theory. Our results point out that at the level of individual cells there are no significant differences when comparing the features of the signals with regard either to the type or the stage of the cataract. On the other hand, noticeable differences are observed at the multicellular level, despite inter-capsule variability. LCs associated with more developed cataracts were found to exhibit a slower collective response to stimulation, a less pronounced spatio-temporal clustering of LECs with similar signaling characteristics. The reconstructed intercellular networks were found to be sparser and more segregated than in LCs associated with mild cataracts. Moreover, we show that spontaneously active LECs often operate in localized groups with quite well aligned Ca2+ activity. The presence of spontaneous activity was also found to affect the stimulated Ca2+ responses of individual cells. Our findings indicate that the cataract progression entails the impairment of intercellular signaling thereby suggesting the functional importance of altered Ca2+ signaling of LECs in cataractogenesis.
Ključne besede: intracellular calcium signaling, anterior lens, epithelial cells, cataract
Objavljeno: 19.06.2017; Ogledov: 672; Prenosov: 329
.pdf Celotno besedilo (1,45 MB)
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8.
Planar cell polarity genes frizzled4 and frizzled6 exert patterning influence on arterial vessel morphogenesis
Rene Markovič, Julien Peltan, Marko Gosak, Denis Horvat, Borut Žalik, Benjamin Seguy, Remi Chauvel, Gregoire Malandain, Thierry Couffinhal, Cécile Dupláa, Marko Marhl, Etienne Roux, izvirni znanstveni članek

Opis: Quantitative analysis of the vascular network anatomy is critical for the understanding of the vasculature structure and function. In this study, we have combined microcomputed tomography (microCT) and computational analysis to provide quantitative three-dimensional geometrical and topological characterization of the normal kidney vasculature, and to investigate how 2 core genes of the Wnt/planar cell polarity, Frizzled4 and Frizzled6, affect vascular network morphogenesis. Experiments were performed on frizzled4 (Fzd4-/-) and frizzled6 (Fzd6-/-) deleted mice and littermate controls (WT) perfused with a contrast medium after euthanasia and exsanguination. The kidneys were scanned with a high-resolution (16 μm) microCT imaging system, followed by 3D reconstruction of the arterial vasculature. Computational treatment includes decomposition of 3D networks based on Diameter-Defined Strahler Order (DDSO). We have calculated quantitative (i) Global scale parameters, such as the volume of the vasculature and its fractal dimension (ii) Structural parameters depending on the DDSO hierarchical levels such as hierarchical ordering, diameter, length and branching angles of the vessel segments, and (iii) Functional parameters such as estimated resistance to blood flow alongside the vascular tree and average density of terminal arterioles. In normal kidneys, fractal dimension was 2.07±0.11 (n = 7), and was significantly lower in Fzd4-/- (1.71±0.04; n = 4), and Fzd6-/- (1.54±0.09; n = 3) kidneys. The DDSO number was 5 in WT and Fzd4-/-, and only 4 in Fzd6-/-. Scaling characteristics such as diameter and length of vessel segments were altered in mutants, whereas bifurcation angles were not different from WT. Fzd4 and Fzd6 deletion increased vessel resistance, calculated using the Hagen-Poiseuille equation, for each DDSO, and decreased the density and the homogeneity of the distal vessel segments. Our results show that our methodology is suitable for 3D quantitative characterization of vascular networks, and that Fzd4 and Fzd6 genes have a deep patterning effect on arterial vessel morphogenesis that may determine its functional efficiency.
Ključne besede: cell polarity, vascular network, metrics, quantitative analyses
Objavljeno: 19.06.2017; Ogledov: 604; Prenosov: 303
.pdf Celotno besedilo (2,56 MB)
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9.
Modeling the seasonal adaptation of circadian clocks by changes in the network structure of the suprachiasmatic nucleus
Christian Bodenstein, Marko Gosak, Stefan Schuster, Marko Marhl, Matjaž Perc, 2012, izvirni znanstveni članek

Opis: The dynamics of circadian rhythms needs to be adapted to day length changes between summer and winter. It has been observed experimentally, however, that the dynamics of individual neurons of the suprachiasmatic nucleus (SCN) does not change as the seasons change. Rather, the seasonal adaptation of the circadian clock is hypothesized to be a consequence of changes in the intercellular dynamics, which leads to a phase distribution of electrical activity of SCN neurons that is narrower in winter and broader during summer. Yet to understand this complex intercellular dynamics, a more thorough understanding of the impact of the network structure formed by the SCN neurons is needed. To that effect, we propose a mathematical model for the dynamics of the SCN neuronal architecture in which the structure of the network plays a pivotal role. Using our model we show that the fraction of long-range cell-to-cell connections and the seasonal changes in the daily rhythms may be tightly related. In particular, simulations of the proposed mathematical model indicate that the fraction of long-range connections between the cells adjusts the phase distribution and consequently the length of the behavioral activity as follows: dense long-range connections during winter lead to a narrow activity phase, while rare long-range connections during summer lead to a broad activity phase. Our model is also able to account for the experimental observations indicating a larger light-induced phase-shift of the circadian clock during winter, which we show to be a consequence of higher synchronization between neurons. Our model thus provides evidence that the variations in the seasonal dynamics of circadian clocks can in part also be understood and regulated by the plasticity of the SCN network structure.
Ključne besede: circadian rhythms, neuronal networks, small world, structures
Objavljeno: 16.06.2017; Ogledov: 592; Prenosov: 266
.pdf Celotno besedilo (1005,71 KB)
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10.
Functional connectivity in islets of Langerhans from mouse pancreas tissue slices
Andraž Stožer, Marko Gosak, Jurij Dolenšek, Matjaž Perc, Marko Marhl, Marjan Rupnik, Dean Korošak, 2013, izvirni znanstveni članek

Opis: We propose a network representation of electrically coupled beta cells in islets of Langerhans. Beta cells are functionally connected on the basis of correlations between calcium dynamics of individual cells, obtained by means of confocal laser-scanning calcium imaging in islets from acute mouse pancreastissue slices. Obtained functional networks are analyzed in the light of known structural and physiological properties of islets. Focusing on the temporal evolution of the network under stimulation with glucose, we show thatthe dynamics are more correlated under stimulation than under non-stimulated conditions and that the highest overall correlation, largely independent of Euclidean distances between cells, is observed in the activation and deactivation phases when cells are driven by the external stimulus. Moreover, we find that the range of interactions in networks during activity shows a clear dependence on the Euclidean distance, lending support to previous observations that beta cells are synchronized via calcium waves spreading throughout islets. Most interestingly, the functional connectivity patterns between beta cells exhibit small-world properties, suggesting that beta cells do not form a homogeneous geometric network but are connected in a functionally more efficient way. Presented results provide support for the existing knowledge of beta cell physiology from a network perspective and shedimportant new light on the functional organization of beta cell syncitia whose structural topology is probably not as trivial as believed so far.
Ključne besede: islets of Langerhans, mouse pancreas
Objavljeno: 16.06.2017; Ogledov: 800; Prenosov: 323
.pdf Celotno besedilo (798,57 KB)
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