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Background and aims Clinical evidence exists that patients with diabetes are at higher risk for Coronavirus disease 2019 (COVID-19). We investigated the physiological origins of this clinical observation linking diabetes with severity and adverse outcome of COVID-19. Methods Publication mining was applied to reveal common physiological contexts in which diabetes and COVID-19 have been investigated simultaneously. Overall, we have acquired 1,121,078 publications from PubMed in the time span between 01 and 01-2000 and 17-04-2020, and extracted knowledge graphs interconnecting the topics related to diabetes and COVID-19. Results The Data Mining revealed three pathophysiological pathways linking diabetes and COVID-19. The first pathway indicates a higher risk for COVID-19 because of an upregulation of Angiotensin-converting enzyme 2. The other two important physiological links between diabetes and COVID-19 are liver dysfunction and chronic systemic inflammation. A deep network analysis has suggested clinical biomarkers predicting the higher risk: Hypertension, elevated serum Alanine aminotransferase, high Interleukin-6, and low Lymphocytes count. Conclusions The revealed biomarkers can be applied directly in clinical practice. For newly infected patients, the medical history needs to be checked for evidence of a long-term, chronic dysregulation of these biomarkers. In particular, patients with diabetes, but also those with prediabetic state, deserve special attention., Highlights • Three pathophysiological pathways linking diabetes and Coronavirus disease 2019 (COVID-19) were revealed by Data Mining. • Diabetics with upregulated Angiotensin-converting enzyme 2 could be of higher risk for COVID-19. • Liver dysfunction with chronically increased serum Alanine aminotransferase indicates adverse outcome of COVID-19. • Clinical biomarkers for chronic inflammation, in particular Interleukin-6, predict the severity of COVID-19.

Understanding energy consumption patterns in the residential sector is of paramount importance for the design of new energy management strategies that are based on innovative information and communication technologies. Smart metering provides considerable opportunities in this respect and allows for the assessment of household characteristics, behaviors and routines that drive household electricity loads. However, the handling of vast quantities of data delivered by smart metering systems requires advanced data analytics technologies and pattern detection algorithms. For the improvement of load forecasting strategies, a good user aggregation and classification is necessary. In the present paper we address this issue and propose a novel technique for data aggregation that was inspired by network science principles. We operate with a dataset of 1 year hourly measured electricity consumption data of 2201 users. The weekly and annual user load profiles are considered separately. Based on the load time series, we construct functional energy consumption networks and extract the minimum spanning tree. Subgroups with similar consumption curves are then objectively identified by means of a community detection algorithm. The proposed methodology is purely data-driven and facilitates an efficient aggregation of users, reduces heterogeneity, eases the study of the relation with environmental factors such as temperature, and is developed to efficiently handle large datasets in an unbiased manner.

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.

Item banks are generally considered the basis of a new generation of educational measurement. In combination with specialized software, they can facilitate the computerized assembling of multiple pre-equated test forms. However, for advantages of item banks to become fully realized it is important that the item banks store a relatively large number of valid test items. In this paper, we demonstrate how the Rasch model is used for integrating new items into an existing wave optics item bank. First, we identified and applied a set of criteria for selecting 18 linking items from our initial item bank. In order to integrate 12 newly developed items, we combined the 18 linking items with the 12 newly developed ones into one test and administered this test to 106 postinstruction physics students from 4 universities in Slovenia, Croatia, and Bosnia and Herzegovina. It was determined that the 12 new items measure the same construct as items from the initial item bank. In addition, all items exhibited good item fit, item reliability was excellent and person reliability was fair. The ratio of standard deviations of linking item difficulties for the new test and existing item bank amounted to 0.89 and correlation of these difficulties amounted to 0.93 which indicated good linking precision. We could conclude that good linking precision can be obtained if linking items are chosen based on the following set of criteria: number of items, item fit, range and spacing of item difficulties, content representativeness, position in test form and interuniversity DIF contrasts.

Type 2 diabetes mellitus is a complex multifactorial disease of epidemic proportions. It involves genetic and lifestyle factors that lead to dysregulations in hormone secretion and metabolic homeostasis. Accumulating evidence indicates that altered mitochondrial structure, function, and particularly bioenergetics of cells in different tissues have a central role in the pathogenesis of type 2 diabetes mellitus. In the present study, we explore how mitochondrial dysfunction impairs the coupling between metabolism and exocytosis in the pancreatic alpha and beta cells. We demonstrate that reduced mitochondrial ATP production is linked with the observed defects in insulin and glucagon secretion by utilizing computational modeling approach. Specifically, a 30&ndash, 40% reduction in alpha cells&rsquo, mitochondrial function leads to a pathological shift of glucagon secretion, characterized by oversecretion at high glucose concentrations and insufficient secretion in hypoglycemia. In beta cells, the impaired mitochondrial energy metabolism is accompanied by reduced insulin secretion at all glucose levels, but the differences, compared to a normal beta cell, are the most pronounced in hyperglycemia. These findings improve our understanding of metabolic pathways and mitochondrial bioenergetics in the pathology of type 2 diabetes mellitus and might help drive the development of innovative therapies to treat various metabolic diseases.

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.

Background: The pathogenesis of type 2 diabetes mellitus is complex and still unclear in some details. The main feature of diabetes mellitus is high serum glucose, and the question arises of whether there are other statistically observable dysregulations in laboratory measurements before the state of hyperglycemia becomes severe. In the present study, we aim to examine glucose and lipid profiles in the context of age, sex, medication use, and mortality. Methods: We conducted an observational study by analyzing laboratory data from 506,083 anonymized laboratory tests from 63,606 different patients performed by a regional laboratory in Slovenia between 2008 and 2019. Laboratory data-based results were evaluated in the context of medication use and mortality. The medication use database contains anonymized records of 1,632,441 patients from 2013 to 2018, and mortality data were obtained for the entire Slovenian population. Results: We show that the highest percentage of the population with elevated glucose levels occurs approximately 20 years later than the highest percentage with lipid dysregulation. Remarkably, two distinct inflection points were observed in these laboratory results. The first inflection point occurs at ages 55 to 59 years, corresponding to the greatest increase in medication use, and the second coincides with the sharp increase in mortality at ages 75 to 79 years. Conclusions: Our results suggest that medications and mortality are important factors affecting population statistics and must be considered when studying metabolic disorders such as dyslipidemia and hyperglycemia using laboratory data.

Words are the building blocks of human communication. They are arranged in sentences in a non-trivial and universal way, which implies the existence of fundamental organizational principles that have shaped language development. One of the fundamental examples is the Zipf's law, which says that the frequency of word occurrence is roughly an inverse power-law function of its rank. In our article, we study the structure and complexity of texts in Slovene belles-lettres, with an emphasis on evaluating the differences in the texts for different age groups. We show that the co-occurrence connectivity of words forms a complex and heterogeneous network that is characterized by an efficient transfer of information. Moreover, we show that with the increasing age of readers, the length of texts, the average length of words, different combinations of phrases and the complexity of social interactions between literary characters, also all increase. Conversely, the fraction of unique words decreases. We also show that the word co-occurrence networks for older age groups are less modular and exhibit a higher level of small-worldness, and that the Zipf's exponent as a measure for the linguistic complexity is more negative, than for younger age groups. Taken together, we demonstrate that network theory enables an in-depth theoretical exploration of Slovene belles-lettres, with clear distinctions in statistical properties between different age groups, thus bridging art and exact sciences in a mutually rewarding way.

The determination of properties of nonlinear dynamics from recorded time series offers fascinating insights into everyday phenomena that can be explored in the lab as well as in physics classrooms. A noteworthy challenge thereby is the distinction between multirhythmic signals, i.e., time series with many but still a finite number of harmonic frequencies, and deterministically chaotic signals. Especially if the signals are relatively short and decaying in intensity, both can have very similar continuous Fourier transforms. We show that stringed instruments offer easily accessible waveforms that can be studied with methods of nonlinear time series analysis to demonstrate that even highly multirhythmic signals can be robustly distinguished from deterministic chaos. In particular, we study the transition from sounds to chords by means of recordings of picked guitar strings, showing how the increasing complexity of the waveforms is still in fact periodic although it might seem chaotic. The treatment is instructive in terms of identifying common pitfalls that are associated with declaring deterministic chaos in observed data, and since it relies on readily available resources, it seems particularly well suited for the classroom on nonlinear dynamics and time series analysis.

We study theoretically and computationally the behavior of the classical and quantum parametrically periodically driven linear oscillator. As a basic paradigm of such a Floquet system we consider the case of the harmonic oscillation of the oscillator frequency, which is convenient to handle theoretically and computationally, while keeping the general features. We derive an explicit analytic formula for the quantum propagator in terms of the classical propagator. Using this, we derive the explicit exact formula for the evolution of the expectation value of the energy starting from an arbitrary normalizable initial state. In the case of the starting pure stationary eigenstate the evolution is exactly the same as for the classical microcanonical ensemble of initial conditions of the same starting energy. We perform a rather complete computational analysis of the system's behavior inside the instability regions (lacunae), where the energy of the oscillator increases exponentially, as well as in the stability regions, and in particular in the vicinity of the (in)stability borders. We confirm also numerically with absolute certainty that the borders of (in)stability regions classically and quantally coincide exactly, in accordance with the theory, which is an important check of the numerical accuracy of computations, and we find a number of important empirical results, especially an equation of the elliptic type describing the rate of exponential energy growth inside the lacunae in terms of other systems' quantities. We believe that our approach and findings are of generic linear type, i.e., applicable in most such linear Floquet systems, and we present a strong motivation for a general theory, classically and quantally.

We present a mathematical model of the energy-driven metabolic switch for glucagon and insulin secretion from pancreatic alpha and beta cells, respectively. The energy status related to hormone secretion is studied for various glucose concentrations. Additionally, the physiological response is studied with regards to the presence of other metabolites, particularly the free-fatty acids. At low glucose, the ATP production in alpha cells is high due to free-fatty acids oxidation in mitochondria, which enables glucagon secretion. When the glucose concentration is elevated above the threshold value, the glucagon secretion is switched off due to the contribution of glycolytic ATP production, representing an "anaerobic switch". On the other hand, during hypoglycemia, the ATP production in beta cells is low, reflecting a "waiting state" for glucose as the main metabolite. When glucose is elevated above the threshold value, the oxidative fate of glucose in mitochondria is the main source of energy required for effective insulin secretion, i.e. the "aerobic switch". Our results show the importance of well-regulated and fine-tuned energetic processes in pancreatic alpha and beta cells required for efficient hormone secretion and hence effective blood glucose regulation. These energetic processes have to be appropriately switched on and off based on the sensing of different metabolites by alpha and beta cells. Our computational results indicate that disturbances in cell energetics (e.g. mitochondrial dysfunction), and dysfunctional metabolite sensing and distribution throughout the cell might be related to pathologies such as metabolic syndrome and diabetes.

Experimental work in the research of astronomical phenomena is often difficult or even impossible because of long-lasting processes or too distant objects and correspondingly too expensive equipment. In this paper, we present an example of observation of the Moon, which is our nearest astronomic object and therefore does not require professional astronomic equipment for observation. We focus on the observation of craters on the Moon, determining their lateral size and depth on the basis of photographs and simple calculations. The fieldwork with students of junior grade school education was performed within the framework of the optional subject Astronomy. An analysis of the results of the students’ experimental work, as well as of curricula on various levels of education, led us to conclusion that this kind of experimental work is suitable for incorporation in secondary school physics education. With some mathematical simplifications, however, the treatment of the topic can also be appropriate in primary school. Such experimental work enables students to gain specific natural science and mathematical competences that are also required for the study of other natural phenomena.

Despite difficulties understanding the dynamics of complex systems only simple dynamical systems without feedback connections have been taught in secondary school physics. Consequently, students do not have opportunities to develop intuition of temporal development of systems, whose dynamics are conditioned by the influence of feedback processes. We present a research study on students' understanding of temporal development of simple dynamical systems. Students participating in the study were attending the final two years of a technical secondary school (gimnazija) program. Based on written equations for the rate of change of some quantity students had to qualitatively determine dynamical development. The study confirmed the initial hypotheses with regard to poor knowledge in the area of dynamical systems, irrelevant of year in secondary school or final grade in physics or mathematics. The results showed that most students understood the development of linear systems without feedback and based on equations, students were able to forecast the dynamical development of changing quantities. Issues arose in understanding systems with feedback connections that influence the nonlinear dynamical development of changing quantity. Especially with negative feedback connections that provide stabilization of changing quantities. The reason could be that in most of the cases they turned towards linear dynamical development of changing quantities. Frequently, they incorrectly concluded that the temporal development of changing quantities is the same to temporal development of current, which determines the state of quantity. As a response in overcoming such issues, we recommend a geometrical consideration of one-dimensional dynamical systems.

In Slovene educational curriculum the subject Environmental education is taught from the first to the third level of primary school (pupils age between seven and nine). The goal of this subject is not merely acquiring basic facts about the world around us; it is rather more important for students to gain specific and general competences for lifelong learning. Competences consist of different kinds of knowledge, skills and abilities, as well as personality attributes (character, behaviour, convictions, etc.). They can be trained only by appropriate didactic methods which force students activity. Teachers must themselves possess required competences in order to guide children in right direction. Therefore, the need for frequent thorough training of teachers often appears. Here we discuss in particular e-learning materials for the 3rd grade Environmental education developed within our national project two years ago. Digital literacy is needed among other teacher's competences when using e-materials in school. We will also focus on a list of generic competences tightly connected with the natural sciences.

In this paper we compare the cascade mechanisms of signal amplification in biological and electrical engineering systems, and show that they share the capacity to considerably amplify signals, and respond to signal changes both quickly and completely, which effectively preserves the form of the input signal. For biological systems, these characteristics are crucial for efficient and reliable cellular signaling. We show that this highly-efficient biological mechanism of signal amplification that has naturally evolved is mathematically fully equivalent with some man-developed amplifiers, which indicates parallels between biological evolution and successful technology development.

The narrowing of a falling stream of liquid is a well-known demonstration of the equation of continuity. We consider the behavior of the bottom of a falling liquid stream where the stream ceases to narrow, and swells and forms droplets. Drop formation is demonstrated by detailed photos of experiments. A simple mathematical description of the observations is given, including the key processes responsible for drop formation.

In a mathematical model for simple calcium oscillations [Biophys. Chem. 71 (1998) 125], it has been shown that mitochondria play an important role in the maintenance of constant amplitudes of cytosolic Ca 2+ oscillations. Simple plausible rate laws for Ca 2+ fluxes across the inner mitochondrial membrane have been used in this model. Here we show that it is possible to use the same rate laws as a plug-in element in other existing mathematical models and obtain the same effect on amplitude regulation. This result appears to be universal, independent of the type of model and the type of Ca 2+ oscillations. We demonstrate this on two models for spiking Ca 2+ oscillations [J. Biol. Chem. 266 (1991) 11068; Cell Calcium 14 (1993) 311] and on two recent models for bursting Ca 2+ oscillations; one of them being a receptor-operated model [Biophys. J. 79 (2000) 1188] and the other one being a store-operated model [BioSystems 57 (2000) 75].

We use a Landau-de Gennes model to study the effect of static external electric fields on the director and layer structure and switching in surface stabilized smectic-C cells with uniform chevron structure. We consider uniform switching of the whole cell and find the threshold electric field needed to switch the director from one stable state to the other stable state. The effect of temperature and cell thickness on the value of the threshold electric field is studied. We also find the switching time as a function of the strength of the applied electric field and study the director and layer structure during the switch.

In this paper we compare the cascade mechanisms of signal amplification in biological and electrical engineering systems, and show that they share the capacity to considerably amplify signals, and respond to signal changes both quickly and completely, which effectively preserves the form of the input signal. For biological systems, these characteristics are crucial for efficient and reliable cellular signaling. We show that this highly-efficient biological mechanism of signal amplification that has naturally evolved is mathematically fully equivalent with some man-developed amplifiers, which indicates parallels between biological evolution and successful technology development.

In biological signal transduction pathways intermediates are often oscillatory and need to be converted into smooth output signals at the end. We show by mathematical modelling that protein kinase cascades enable converting oscillatory signals into sharp stationary step-like outputs. The importance of this result is demonstrated for the switch-like protein activation by calcium oscillations, which is of biological importance for regulating different cellular processes. In addition, we found that protein kinase cascades cause memory effects in the protein activation, which might be of a physiological advantage since a smaller amount of calcium transported in the cell is required for an effective activation of cellular processes.

We study numerically the quantum mechanics of a point particle in the one-dimensional potential box, whose boundary oscillates periodically according to the sawtooth driving law. We perform very accurate numerical calculations over up to about 500 periods. Unlike in smooth driving, this system admits classical Fermi acceleration, because the Kolmogorov–Arnold–Moser theorem does not apply, and surprisingly also admits quantum Fermi acceleration, but only in the extremely narrow resonant gaps located at the values of the driving parameter that corresponds to either one-photon transitions or multi-photon transitions. In the gaps the energy of the particle increases indefinitely, quadratically with time, as predicted by our quite general two-level theory derived for general periodic quantum systems, whilst outside the gaps it oscillates and displays beatings with long or very long periods which are theoretically unexplained, but very well and clearly manifested.

The electrostatic pendulum, also known as the electrostatic ping-pong, is an exciting experiment in school as well as in undergraduate education. We can easily demonstrate how the frequency of the electrostatic pendulum depends on the voltage across the capacitor. In this paper, we develop a simple mathematical model describing the dynamics of this experiment. In a step-wise manner, we introduce the external forces influencing the dynamics of the electrostatic pendulum. First, we take into account the electric force only. Then, we add air resistance and the non-elasticity of ball collisions with the capacitor plates. The model predictions show that the non-elastic collisions have greater effect on the pendulum dynamics than air resistance; in particular, this is true for higher frequencies of the pendulum. For lower frequencies, however, gravity is of crucial importance. The mathematical model is implemented in a graphic-oriented computer program, which gives the possibility of using this theoretical analysis also at the secondary school level.