Research outputs from Pure / Zinātniskās darbības rezultāti no ZDIS Pure

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Application of Ge nanowire for two-input bistable nanoelectromechanical switch
(2013) Andzane, Jana; Prikulis, Juris; Meija, Raimonds; Kosmaca, Jelena; Biswas, Subhajit; Holmes, Justin D.; Erts, Donats
Recently, several research groups presented bistable two-terminal nanoelectromechanical switches based on individual single-clamped active element. All presented devices had one input electrode. Similar devices having two or more input electrodes have not been yet investigated. In this work we present the two-input bistable controlled nanoelectromechanical switch based on an individual single-clamped Ge nanowire. The switch is realised using in-situ SEM technique and operating due to balancing of electrostatic, adhesion and elastic forces. The operation conditions of the device are investigated and presented. The advantages and drawbacks of the device are discussed.
Autofluorescence imaging of the skin is an objective non-invasive technique for diagnosing pseudoxanthoma elasticum
(2021) Farkas, Klára; Bozsányi, Szabolcs; Plázár, Dóra; Bánvölgyi, András; Fésűs, Luca; Anker, Pálma; Zakariás, Sára; Lihacova, Ilze; Lihachev, Alexey; Lange, Marta; Arányi, Tamás; Wikonkál, Norbert M.; Medvecz, Márta; Kiss, Norbert
Pseudoxanthoma elasticum (PXE) is a rare multisystemic autosomal recessive connective tissue disease. In most cases, skin manifestations of PXE are the first to develop, followed later by severe ocular and cardiovascular complications. In our present study, in addition to dermoscopy, we introduced novel techniques, autofluorescence (AF) and diffuse reflectance (DR) imaging for the assessment of affected skin sites of five PXE patients. PXE-affected skin areas in most skin sites showed a previously observed pattern upon dermoscopic examination. With the novel imaging, PXE-affected skin lesions displayed high AF intensity. During our measurements, significantly higher mean, minimum and maximum AF intensity values were found in areas of PXE-affected skin when compared to uninvolved skin. Conversely, images acquired with the use of 660 and 940 nm illumination showed no mentionable difference. Our results demonstrate that AF imaging may be used in the in vivo diagnostics and quantification of the severity of the skin lesions of PXE patients. In addition, it is a safe, fast and cost-effective diagnostic method. AF imaging may be also used to objectively monitor the efficacy of the possible novel therapeutic approaches of PXE in the future.
Bi2Se3 Nanostructured Thin Films as Perspective Anodes for Aqueous Rechargeable Lithium-Ion Batteries
(2022-10) Lazarenko, Vitalijs; Rublova, Yelyzaveta; Meija, Raimonds; Andzane, Jana; Voikiva, Vanda; Kons, Artis; Sarakovskis, Anatolijs; Viksna, Arturs; Erts, Donats
In recent years, aqueous rechargeable lithium-ion batteries (ARLIBs) have attracted attention as an alternative technology for electrical storage. One of the perspective battery anode materials for application in ARLIBs is Bi2Se3, which has already shown good perspectives in the application of conventional lithium-ion batteries (LIBs) that use organic electrolytes. In this study, the electrochemical properties of Bi2Se3 thin films with two different layers on the electrode surface—the solid electrolyte interphase (SEI) and the Bi2O3 layer—were investigated. The results of this work show that the formation of the SEI layer on the surface of Bi2Se3 thin films ensures high diffusivity of Li+, high electrochemical stability, and high capacity up to 100 cycles, demonstrating the perspectives of Bi2Se3 as anode material for ARLIBs.
The Biosphere Self-Organization Attractors drive perfect order homeostasis reactions to link bioenergetic with functionally activate oxygen and carbon dioxide molecules
(ICNTC Secretariat, 2021) Kaksis, Āris; Dasdan, Şakar; Department of Human Physiology and Biochemistry
The quantitative studies for oxygen and carbon dioxide functional activity reveal multiply generated Self-Organization Attractors which create and maintain order the homeostasis: water concentration [H2O]=55.3 mol/Liter, pH=7.36, enzyme Carbonic Anhydrase reactivity, air oxygen level 20.95 % O2 [1] , osmolar concentration 0.305 M, ionic strength 0.25 M, temperature 310.15 K degree etc. that make oxygen fire safe and CO2aqua functional active for Life Biochemistry. Air oxygen level 20.95 % O2 [1] dissolute in organism forming arterial concentration [O2aqua] safe for Bioenergetic as Self-Organization Attractor [3] sustaining isooxia. Thermodynamic indicate Biosphere indispensability to reach Self-Organization Attractor values. Destiny is trend to minimum of free energy change in homeostasis. Attractors made functionally active molecules Self-Organize the perfect reactions order in homeostasis. [2,3,4] Deviation from Attractor values disorder the homeostasis. Chaos stop the homeostasis which disappears as extinct from Biosphere.
Body composition and knowledge about a healthy lifestyle of selected combat sport athletes
(2022) Litwiniuk, Artur; Grants, Juris; Boobani, Behnam; Latvian Academy of Sport Education (LASE)
Introduction. Nowadays, the level of physical condition as well as the proper composition of the body gains special importance in terms of proper psychomotor development of children and adolescents. The aim of this research was to obtain knowledge about body tissue composition and selected elements of a healthy lifestyle of combat sports athletes. Materials and methods. The study group consisted of 21 taekwondo athletes. The age of the respondents was 17-18.5 years, training experience M=5.2 years, body height M=175.05 cm and body weight M=71.9. The tool that was used to assess the body composition was the BCA Tanita 545N device and a specially constructed interview questionnaire regarding information on a healthy lifestyle. Results. in the body composition of combat sports athletes, it was found that both partial results and averages are at an adequate level for combat sports athletes to systematic training. Conclusion. It was observed that all individual results of the subjects diagnosed with the BCA Tanita 545 N device are correct and fall within the norms of physically active people, such as people training combat sports. This proves the application of the principles of a healthy lifestyle. We can say that the level of knowledge of taekwondo athletes about a healthy lifestyle is high, because they are able to make a diagnosis, interpret the results and, in the case of values outside the health norm, use a repair algorithm in a professional sense.
Cantilever-enhanced photoacoustic spectroscopy applied in the research of natural and synthetic calcium phosphate
(2017-04-21) Brangule, Agnese; Gross, K. A.; Stepanova, V.; Department of Human Physiology and Biochemistry
This study demonstrates the significant potential of cantilever-enhanced Fourier transform infrared photoacoustic spectroscopy (FTIR PAS) principles. The improved sensitivity and reproducibility of this method presents a potent tool in the study of biomaterials. The article discusses aspects of the application of cantilever-enhanced FTIR PAS in the research of natural and biological calcium phosphate and the statistical evaluation of the FTIR PAS sampling method. The improved constructions of the FTIR PAS accessory reduce limitations of the conventional capacitive microphone and provide a sensitive tool for samples or processes unreachable by more traditional transmittance methods, or ATR sampling technique. The most common and important applications have been discussed in-depth to show the wide range of problems solved by FTIR PAS.
A Case Study on the Development of Math Competence in an Eight-year-old Child with Dyscalculia : Shared Intentionality in Human-Computer Interaction for Online Treatment Via Subitizing
(2022) Danilov, Igor Val.; Mihailova, Sandra; Rīga Stradiņš University
Studies in the field of neuroscience have shown that the neural network responsible for numeracy overlaps with the visual and spatial processing regions. Other studies in psychology also highlighted an association of visual-spatial processing with mathematical competence at the early stages of development. These findings suggest that research on the size of the focal area of attention (consciousness) can contribute to understanding the development of numeracy. In this case study, we verified the hypothesis of developing numeracy in children by training the rapid apperception of a few items called “subitizing.” Shared intentionality promotes cognition from the onset. Therefore, in this study, we investigated this interaction modality to give an eight-year-old girl an insight into expanded apperception of an array in "subitizing" for improving her numerical competence. The child was stimulated to apperceive more objects while performing “subitizing” tasks with the mother. The course of treatment consisted of the four regimes of human-computer interaction based on rapid exposure to several pictures with a few dots. Simultaneously, this human-computer interaction also stimulated shared intentionality in the mother-child dyad for developing the child’s rapid apprehension of these small quantities. The outcome of this intervention was an increase in the size of the focal point of attention (consciousness) and the development of numerical competence, where an association was established between the expanding apperception and the developing numeracy.
Determination of Young's modulus of Sb2S3 nanowires by in situ resonance and bending methods
(2016) Jasulaneca, Liga; Meija, Raimonds; Livshits, Alexander I.; Prikulis, Juris; Biswas, Subhajit; Holmes, Justin D.; Erts, Donats
In this study we address the mechanical properties of Sb2S3 nanowires and determine their Young's modulus using in situ electricfield- induced mechanical resonance and static bending tests on individual Sb2S3 nanowires with cross-sectional areas ranging from 1.1·104 nm2 to 7.8·104 nm2. Mutually orthogonal resonances are observed and their origin explained by asymmetric cross section of nanowires. The results obtained from the two methods are consistent and show that nanowires exhibit Young's moduli comparable to the value for macroscopic material. An increasing trend of measured values of Young's modulus is observed for smaller thickness samples.
Development of methods for analysis of knee articular cartilage degeneration by magnetic resonance imaging data
(2017-03-23) Suponenkovs, Artjoms; Glazs, Aleksandrs; Platkajis, Ardis; Rīga Stradiņš University
The aim of this paper is to describe the new methods for analyzing knee articular cartilage degeneration. The most important aspects regarding research about magnetic resonance imaging, knee joint anatomy, stages of knee osteoarthritis, medical image segmentation and relaxation times calculation. This paper proposes new methods for relaxation times calculation and medical image segmentation. The experimental part describes the most important aspect regarding analysing of articular cartilage relaxation times changing. This part contains experimental results, which show the codependence between relaxation times and organic structure. These experimental results and proposed methods can be helpful for early osteoarthritis diagnostics.
Distribution of Iron Nanoparticles in Arrays of Vertically Aligned Carbon Nanotubes Grown by Chemical Vapor Deposition
(2022-10) Okotrub, Alexander V.; Gorodetskiy, Dmitriy V.; Guselnikov, Artem V.; Kondranova, Anastasiya M.; Bulusheva, Lyubov G.; Korabovska, Mariya; Meija, Raimonds; Erts, Donats
Arrays of aligned carbon nanotubes (CNTs) are anisotropic nanomaterials possessing a high length-to-diameter aspect ratio, channels passing through the array, and mechanical strength along with flexibility. The arrays are produced in one step using aerosol-assisted catalytic chemical vapor deposition (CCVD), where a mixture of carbon and metal sources is fed into the hot zone of the reactor. Metal nanoparticles catalyze the growth of CNTs and, during synthesis, are partially captured into the internal cavity of CNTs. In this work, we considered various stages of multi-walled CNT (MWCNT) growth on silicon substrates from a ferrocene–toluene mixture and estimated the amount of iron in the array. The study showed that although the mixture of precursors supplies evenly to the reactor, the iron content in the upper part of the array is lower and increases toward the substrate. The size of carbon-encapsulated iron-based nanoparticles is 20–30 nm, and, according to X-ray diffraction data, most of them are iron carbide Fe3C. The reasons for the gradient distribution of iron nanoparticles in MWCNT arrays were considered, and the possibilities of controlling their distribution were evaluated.
Effect of Femtosecond Laser-Irradiated Titanium Plates on Enhanced Antibacterial Activity and Preservation of Bacteriophage Stability
(2023-07-09) Grase, Liga; Onufrijevs, Pavels; Rezevska, Dace; Racenis, Karlis; Skadins, Ingus; Karosas, Jonas; Gecys, Paulius; Iesalnieks, Mairis; Pludons, Arturs; Kroica, Juta; Raciukaitis, Gediminas; Department of Biology and Microbiology
Titanium (Ti) is widely recognized for its exceptional properties and compatibility with medical applications. In our study, we successfully formed laser-induced periodic surface structures (LIPSS) on Ti plates with a periodicity of 520–740 nm and a height range of 150–250 nm. To investigate the morphology and chemical composition of these surfaces, we employed various techniques, including field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Additionally, we utilized a drop-shape analyzer to determine the wetting properties of the surfaces. To evaluate the antibacterial activity, we followed the ISO 22196:2011 standard, utilizing reference bacterial cultures of Gram-positive Staphylococcus aureus (ATCC 25923) and Gram-negative Escherichia coli (ATCC 25922). The results revealed enhanced antibacterial properties against Staphylococcus aureus by more than 99% and Escherichia coli by more than 80% in comparison with non-irradiated Ti. Furthermore, we conducted experiments using the Escherichia coli bacteriophage T4 (ATCC 11303-B4) and the bacterial host Escherichia coli (ATCC 11303) to investigate the impact of Ti plates on the stability of the bacteriophage. Overall, our findings highlight the potential of LIPSS on Ti plates for achieving enhanced antibacterial activity against common bacterial strains while maintaining the stability of bacteriophages.
Effect of outdoor recreation activity on mental toughness of taekwondo athletes in competition period
(2023-07-10) Boobani, Behnam; Grants, Juris; Boge, Iveta; Glaskova-Kuzmina, Tatjana; Bula-Biteniece, Inta; Jagiello, Wladyslaw; Litwiniuk, Artur; Latvian Academy of Sport Education (LASE)
Background & Study Aim: Taekwondo mixes mental and physical training into a helpful leisure activity. The research focusing on the impact of taekwondo on psychological health, although limited, suggests it is associated with several positive outcomes. These include increased cognitive and affective self-regulation and prosocial behaviour in children and reduced aggressive behaviour in the youth and teenager population. The aim of this study is knowledge about the effect of outdoor recreation activity (walking in nature) on mental toughness components (confidence, control, and constancy) of taekwondo athletes during the competition period. Material & Methods: The participants of this study were 12 Latvian taekwondo athletes, including males (n = 6) and females (n = 6), aged 17-23. The experiment was held four weeks before the International Sweden Taekwondo Competition (2022). The participants had twelve sessions, including 40 minutes of outdoor recreation (walking in nature), in zones 1 and 2 (HR 101-141 bpm). The Sport Mental Toughness Questionnaire (SMTQ) measured the mental toughness components (confidence, constancy, and control). The data was analyzed using the mean, standard deviations, the Shapiro-Wilk test, and paired sample t-test. Results: The outdoor recreation activity (walking in nature) did not significantly affect the component of mental toughness (confidence t (11) = 0.451 as the p-value 0.837 >0.05, for constancy t (11) = −0.233; as the p-value 0.820 >0.05 and control t (11) = 0.117; as the p-value 0.909 >0.05) at the 5% level. Conclusions: Gender disparities exist in the mental toughness components of confidence, constancy, and control among Latvian taekwondo athletes. In particular, male athletes revealed higher average scores in confidence and constancy, with control scores remaining consistent across both male and female athletes. Furthermore, male athletes showed less variability in their confidence and constancy scores when compared to their female counterparts.
EFFECTS OF OUTDOOR ACTIVITY, ELECTRO PHOTONIC IMAGING TECHNIQUE ON STRESS LEVEL AND MENTAL TOUGHNESS ON LATVIAN TAEKWONDO ATHLETES
(2022) Boobani, Behnam; Grants, Juris; Boge, Iveta; Latvian Academy of Sport Education (LASE)
Research investigating sources of stress in athletes has identified physical, social, environmental, general life and secondary (emotional/cognitive/goal oriented) events which cumulatively and interactively contribute to allostatic load. The purpose of this study is 1) to compare measurements made with an Electro Photonic Imaging (EPI) technique before and after an outdoor recreation activity on Taekwondo athletes’ stress level, and 2) to find out the effects of outdoor activity on mental toughness in Taekwondo athletes. Forty Taekwondo athletes who will volunteer to participate in the research (15-19 years old, at least for 2 years have participated in national or international competitions) for 5 weeks walking (3 sessions per week /40 minutes) in the nature, in pre-competition phase will be selected. The current athletes’ stress level and mental toughness will be assessed by Bio-Well pro 2.0 camera and the mental toughness questionnaire (SMTQ). In the procession and analysis of the results MS. Excel software and methods of descriptive statistics will be used. Methods are based on scientific literature review of outdoor activities, questionnaire, and then using statistical analysis. The results and conclusion of the study will be according to the analysis.
Empirical Evidence of Shared Intentionality : Towards Bioengineering Systems Development
(2023) Danilov, Igor Val; Mihailova, Sandra; Komunikācijas fakultāte
This article is the expanded conference paper that reports the results of a psychophysiological research study on shared intentionality conducted in 24 online experiments with 405 subjects (208 recipients and 197 contributor-confederates). In this research, we created a bioengineering system for assessing shared intentionality in human groups by modeling mother-neonate dyad properties in subjects during intellectual testing. In this model, only the mother (contributor-confederate) knows the correct stimulus and shares this knowledge with the neonate (participant-recipient). For modeling mother-neonate dyad properties in subjects, the bioengineering system induces interpersonal dynamics in the subjects by stimulating their interactional synchrony, emotional contagion and neuronal coherence. The system collects data by confronting recipients' performance in "primed" and "unprimed" conditions of confederates. These informed contributors know correct responses only in the "primed" condition and confidently respond on "primed" items. Specifically, in 13 online experiments in mother-child dyads, evidence showed a recipients' performance increase of 48–394%, P-value < 0.001 (62 recipients and 54 confederates) in the “primed” condition of confederates; and in 7 experiments in primary group adults, it showed a performance increase of 143–300%, P-value < 0.002. In experiments in the secondary group, evidence showed a recipients' performance increase only with the UL3 items (a translation of an unfamiliar language, 20 recipients from 41 subjects in experiment No.12). In 3 experiments in 207 secondary group subjects, non-semantic tasks–SL3 (synthetic language) and US3 (two-color unintelligible symbols)–did not stimulate the effect. We also analyzed data confronting the outcome of recipients' performance in the "primed" condition and random value (possible recipients' responses by chance). Comparing the outcomes of these two data collecting methods as well as the sample size of the experiments allow for discussing the research method's validity and reliability. The article also shows four factors' domains that contribute to shared intentionality magnitude.
EVALUATION OF THE EMOTIONAL STATE IN THE OUTDOOR RECREATIONAL ACTIVITIES
(2021) Ulme, Gundega; Boobani, Behnam; Arne, Daina; Grants, Juris; Latvian Academy of Sport Education (LASE)
The aim of the study is to evaluate the emotional state of volunteer participants in outdoor recreational activities (downhill skiing, cycling) by analysing their facial expressions and self-assessments of emotional state before and after the outdoor recreational activities. Twenty-four volunteers (8 women and 16 men with the average age of 38 years old) participated in the study. The emotional state of the participants was assessed by using Sports Emotion Questionnaire (SEQ) and a software "Face Reader 3.0."
Human–robot collaboration trends and safety aspects : A systematic review
(2021-09) Arents, Janis; Abolins, Valters; Judvaitis, Janis; Vismanis, Oskars; Oraby, Aly; Ozols, Kaspars
Smart manufacturing and smart factories depend on automation and robotics, whereas human–robot collaboration (HRC) contributes to increasing the effectiveness and productivity of today’s and future factories. Industrial robots especially in HRC settings can be hazardous if safety is not addressed properly. In this review, we look at the collaboration levels of HRC and what safety actions have been used to address safety. One hundred and ninety-three articles were identified from which, after screening and eligibility stages, 46 articles were used for the extraction stage. Predefined parameters such as: devices, algorithms, collaboration level, safety action, and standards used for HRC were extracted. Despite close human and robot collaboration, 25% of all reviewed studies did not use any safety actions, and more than 50% did not use any standard to address safety issues. This review shows HRC trends and what kind of functionalities are lacking in today’s HRC systems. HRC systems can be a tremendously complex process; therefore, proper safety mechanisms must be addressed at an early stage of development.
Immobilised humic substances as low-cost sorbents for emerging contaminants
(2021-04-01) Ansone-Bertina, Linda; Upska, Karina; Dobkevica, Linda; Kviesis, Jorens; Meija, Raimonds; Klavins, Maris; Department of Physics
Environmental pollution with contaminants of emerging concern (CECs) is a worldwide problem that is receiving increasing attention. Although these substances have been released in the aquatic environment for a long time, wastewater treatment plants are still incapable of removing emerging contaminants completely. Consequently, trace metals, metalloids and pharmaceuticals, as well as surfactant leftovers, are often found in environmental samples. Environmentally friendly and cost-effective sorbents such as humic substances can be used for purification if their sorption properties are increased by immobilization. To our knowledge, immobilized humic substances have not been widely studied as sorbents up to now. In this study, humic substances were immobilized to obtain low-cost sorbents. The chosen methods for characterization of the obtained sorbents showed successful immobilization. Traditional pollutants, such as Cr(III) (a metal), As(V) (a metalloid) and chlorpromazine (a pharmaceutical), were used as representative contaminants. Sorption experiments were conducted using the batch system, and sorption was also studied based on the sorbent dosage, initial concentration of the studied element or substance, solution pH and sorption time. The results show that all the obtained immobilized humic substances in this study can be used as sorbents to remove contaminants from water. At the same time, from these humic substances, only those immobilized using iron compounds are suitable for the removal of arsenic.
Macro model of the injury of brain functional regions
(2020-11-25) Minejeva, O.; Markovics, Z.; Zdanovskis, N.
A lot of studies are related to brain activity. Researchers are trying to structure all available information with a purpose to analyse and predict different diseases, their mechanism. One of the methods that can be easily used in the medical sphere is topological modelling. It allows displaying any diagnosis or process in the form of a graph. This form is convenient and considered to analyse the causal-consequence links between graph nodes representing symptoms, different states of the body, etc. This article focusses at the process of building a stroke topological model that gathers knowledge of how stroke can hurt certain brain functional regions, and what consequences can cause the damage to these regions. The model is formed in 2 steps, increasing its level of detailing, i.e. by specifying brain regions.
Mixing divalent ionic liquids : effects of charge and side-chains
(2021-02-28) Bakis, Eduards; van den Bruinhorst, Adriaan; Pison, Laure; Palazzo, Ivan; Chang, Thomas; Kjellberg, Marianne; Weber, Cameron C.; Costa Gomes, Margarida; Welton, Tom
We have prepared novel divalent ionic liquids (ILs) based on the bis(trifluoromethylsulfonyl)imide anion where two charged imidazolium groups in the cations are either directly bound to each other or linked by a single atom. We assessed the influence of the side-chain functionality and divalency on their physical properties and on the thermodynamics of mixing. The results indicate that shortening the spacer of a divalent IL reduces its thermal stability and increases its viscosity. Mixtures of divalent and monovalent ILs show small but significant deviations from ideality upon mixing. These deviations appear to depend primarily on the (mis)match of the nature and length of the cation side-chain. The non-ideality imposed by mixing ILs with different side-chains appears to be enhanced by the increase in formal charge of the cations in the mixture.
Nanomechanics of individual aerographite tetrapods
(2017-04-12) Meija, Raimonds; Signetti, Stefano; Schuchardt, Arnim; Meurisch, Kerstin; Smazna, Daria; Mecklenburg, Matthias; Schulte, Karl; Erts, Donats; Lupan, Oleg; Fiedler, Bodo; Mishra, Yogendra Kumar; Adelung, Rainer; Pugno, Nicola M.
Carbon-based three-dimensional aerographite networks, built from interconnected hollow tubular tetrapods of multilayer graphene, are ultra-lightweight materials recently discovered and ideal for advanced multifunctional applications. In order to predict the bulk mechanical behaviour of networks it is very important to understand the mechanics of their individual building blocks. Here we characterize the mechanical response of single aerographite tetrapods via in situ scanning electron and atomic force microscopy measurements. To understand the acquired results, which show that the overall behaviour of the tetrapod is governed by the buckling of the central joint, a mechanical nonlinear model was developed, introducing the concept of the buckling hinge. Finite element method simulations elucidate the governing buckling phenomena. The results are then generalized for tetrapods of different size-scales and shapes. These basic findings will permit better understanding of the mechanical response of the related networks and the design of similar aerogels based on graphene and other two-dimensional materials.

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