Riga Technical University
Recent publications
Background: Acute ischemic stroke is one of the leading causes of disability and mortality globally, with increasing incidence in Africa, as the continent is already burdened with infectious diseases. Rapid diagnosis and efficient treatment are crucial, as even a slight delay to reperfuse the brain significantly affects the recovery outcome. Neuroimaging is vital for optimal care and thrombolytic or endovascular therapy in specialised stroke care units. This review aims to discuss the burden of acute ischemic stroke in Africa and how healthcare systems have tried to reduce the incidence and improve outcomes for the disease. Methodology: Data was collected from online databases and medical journal published on PubMed, Ovid MEDLINE, ScienceDirect and Embase bibliographical data. All articles related to acute ischemic stroke in Africa were considered. Results: The medical care for acute ischemic stroke in Africa is far from optimal with little adherence to recommended protocols. There is a lack of public awareness of the disease, imaging infrastructure, personnel, stroke care units and recovery facilities, due to poor funding. Poor knowledge of stroke signs and symptoms results in delay in treatment and poor prognosis. Conclusion: We urge African leaders and private entities to invest in stroke care by building appropriate infrastructures, providing medical equipments, implementing guidelines, and sustainable follow-up systems. Telehealth is a suggested strategy to mitigate the scarcity of health personnel, and international and national efforts to increase treatment affordability should be doubled. Further extensive research on the impact of acute ischemic stroke on the African continent population is encouraged.
The propulsion and acceleration of nanoparticles with light have both fundamental and applied significance across many disciplines. Needle‐free injection of biomedical nano cargoes into living tissues is among the examples. Here a new physical mechanism of laser‐induced particle acceleration is explored, based on abnormal optothermal expansion of mesoporous vaterite cargoes. Vaterite nanoparticles, a metastable form of calcium carbonate, are placed on a substrate, underneath a target phantom, and accelerated toward it with the aid of a short femtosecond laser pulse. Light absorption followed by picosecond‐scale thermal expansion is shown to elevate the particle's center of mass thus causing acceleration. It is shown that a 2 µm size vaterite particle, being illuminated with 0.5 W average power 100 fsec IR laser, is capable to overcome van der Waals attraction and acquire 15m sec ⁻¹ velocity. The demonstrated optothermal laser‐driven needle‐free injection into a phantom layer and Xenopus oocyte in vitro promotes the further development of light‐responsive nanocapsules, which can be equipped with additional optical and biomedical functions for delivery, monitoring, and controllable biomedical dosage to name a few.
Spirulina (Arthrospira spp.) is a blue-green microalga within the phylum Cyanophyta, also known as Cyanobacteria. It has superior nutritional value, clinically proven health benefits, and beneficial interaction in fermentation and preservation processes. Therefore, Spirulina is a functional ingredient and a key ingredient in functional foods for particular dietary use. Nutritional facts show that Spirulina has over 60% of protein, with relatively low fat and sugar contents. The clinical studies have highlighted that health benefits of Spirulina are caused by its high antioxidant activity, especially due to the presence of a unique blue pigment-protein complex—phycocyanin. Contrary to other edible algae, such as Chlorella, Spirulina cell membrane is easy to be digested, and nutrients have high bioavailability. Spirulina as a potential source for vitamin B12 is confirmed. The present chapter discusses some examples of cultivation parameters’ affecting Spirulina’s nutritional value. In addition, the most significant producers, mainly in Asia, with market share of powder, tablets, and capsules, are summarized. Fresh frozen Spirulina is a new, rapidly growing trend in Western countries due to its milder taste. Spirulina-containing products in the market are presented, and many commercial products of snacks, drinks, pasta, and dairy products are given. Studies on Spirulina as a functional ingredient that show its potential to boost fermentation process and prevent pathogen microbe development are summarized.
To select optimal solutions in multicriteria decision-making (MCDM) problems, many practical approaches have been developed. In almost all of these approaches, it is necessary to assess the importance of individual criteria for decision makers. Subjective assessments of importance are transformed into numerical assessments of decision weights by applying appropriate computational procedures. A large number of methods for determining the weights of the criteria have been proposed. These methods differ in their operating principles and in the calculation procedures underlying each method. The paper presents the most well-known methods and provides a brief comparative analysis.
Despite standardisation initiatives, the modern financial landscape continues to be characterised by heterogeneous payment systems. This issue persists even with the emergence of distributed ledger technology in the market. Independent groups of developers are producing their own permissioned blockchain solutions without clear directions for standardisation that could be associated to the lack of a clear position from central banks and regulatory organisations regarding these technologies. The unresolved problem of transaction finality in distributed ledgers adds to the difficulty of reconciling separate distributed platforms. One potential solution is the implementation of cross-chain bridges, which can establish connections between platforms and potentially enable seamless experiences for end users and applications. The paper discusses the advantages and issues associated with these bridges.
Deep neural networks are widely used in computer vision for image classification, segmentation and generation. They are also often criticised as “black boxes” because their decision-making process is often not interpretable by humans. However, learning explainable representations that explicitly disentangle the underlying mechanisms that structure observational data is still a challenge. To further explore the latent space and achieve generic processing, we propose a pipeline for discovering the explainable directions in the latent space of generative models. Since the latent space contains semantically meaningful directions and can be explained, we propose a pipeline to fully resolve the representation of the latent space. It consists of a Dirichlet encoder, conditional deterministic diffusion, a group-swap and a latent traversal module. We believe that this study provides an insight into the advancement of research explaining the disentanglement of neural networks in the community.
The sensational Covid-19 and the pandemic have profoundly changed many areas and enterprises. For many entrepreneurs, it was a huge challenge to revolutionize their logistics and be able to switch over to online payment and remote delivery of goods and services in an extremely short time. The article reviews the work of logistics and supply chains both before and after Сovid-19, the article introduces FinTech and the possible interaction of FinTech to improve the work of logistics and supply chains. This work aims to research the synergy of financial technologies and logistics. For this purpose, it is necessary to analyze the situation in the supply chain and FinTech sphere after the pandemic.
This article presents a novel approach aimed at minimizing state desynchronization faults between two networked applications. The approach addresses the challenge of working with a legacy application that solely supports a synchronous HTTP API and cannot undergo modifications. To tackle this limitation, an algorithm leveraging statistical data on service response time and a Markov transition matrix has been developed. The algorithm strategically sends commit messages during optimal network conditions, while ping messages provide valuable insights into the network state.Laboratory experiments were conducted to evaluate the effectiveness of the proposed approach. The results showcased a significant 72% reduction in desynchronization errors, with an average ping/commit message ratio of 2.2.
Considering the documented health benefits of bacterial exopolysaccharides (EPSs), specifically of bacterial levan (BL), including its intrinsic antimicrobial activity against certain pathogenic species, the current study concentrated on the development of active pharmaceutical ingredients (APIs) in the form of colloid systems (CoSs) containing silver nanoparticles (AgNPs) employing in-house biosynthesized BL as a reducing and capping agent. The established protocol of fermentation conditions implicating two species of lactic acid bacteria (LAB), i.e., Streptococcus salivarius K12 and Leuconostoc mesenteroides DSM 20343, ensured a yield of up to 25.7 and 13.7 g L −1 of BL within 72 h, respectively. An analytical approach accomplished by Fourier-transform infrared (FT-IR) spectroscopy allowed for the verification of structural features attributed to biosynthesized BL. Furthermore , scanning electron microscopy (SEM) revealed the crystalline morphology of biosynthesized BL with a smooth and glossy surface and highly porous structure. Molecular weight (M w) estimated by multi-detector size-exclusion chromatography (SEC) indicated that BL biosynthesized using S. salivarius K12 has an impressively high M w , corresponding to 15.435 × 10 4 kilodaltons (kDa). In turn, BL isolated from L. mesenteroides DSM 20343 was found to have an M w of only 26.6 kDa. Polydispersity index estimation (PD = M w /M n) of produced BL displayed a monodispersed molecule isolated from S. salivarius K12, corresponding to 1.08, while this was 2.17 for L. mesenteroides DSM 20343 isolate. The presence of fructose as the main backbone and, to a lesser extent, glucose and galactose as side chain molecules in EPS hydrolysates was supported by HPLC-RID detection. In producing CoS-BL@AgNPs within green biosynthesis, the presence of nanostructured objects with a size distribution from 12.67 ± 5.56 nm to 46.97 ± 20.23 was confirmed by SEM and energy-dispersive X-ray spectroscopy (EDX). The prominent inhibitory potency of elaborated CoS-BL@AgNPs against both reference test cultures, i.e., Pseudomonas aeruginosa, Escherichia coli, Enterobacter aerogenes, and Staphylococcus aureus and those of clinical origin with multi-drug resistance (MDR), was confirmed by disc and well diffusion tests and supported by the values of the minimum inhibitory and bactericidal concentrations. CoS-BL@AgNPs can be treated as APIs suitable for designing new antimicrobial agents and modifying therapies in controlling MDR pathogens.
In the context of an escalating energy crisis, the burgeoning prevalence of remote work, and challenging climatic conditions, ensuring optimal indoor air quality (IAQ) has emerged as a pressing concern. This pilot study rigorously investigates the complex interplay between biological, chemical, and physical parameters that characterize IAQ, focusing specifically on university classrooms during active teaching sessions. Employing a comprehensive array of instrumentation – such as SAS SUPER ISO 100 for microbiological sampling, Aranet4 for monitoring relative humidity, temperature, and CO 2 concentration, and PCE-PCO 1 and PCE-RSCM 16 for particulate matter (PM2.5 and PM10) quantification—the study spanned a duration of three days in November 2022 and covered classrooms of varying dimensions, both reliant on natural ventilation. An extensive collection of 52 microbiological samples were obtained and cultured on specialized growth media to differentiate between various classes of airborne microorganisms. Concurrently, the pilot study meticulously recorded students’ activity patterns, along with the temporal dynamics of window openings and closures. The colony-forming units per cubic meter (CFU/m ³ ) fluctuated between 174 and 934 CFU/m ³ , with fungi constituting the majority. Furthermore, the CFU/m ³ for fungi cultivated on Sabouraud Dextrose Agar ranged from 24 to 610 CFU/m ³ , whereas bacteria cultured on Trypticase Soy Agar and Mannitol Salt Agar exhibited ranges of 42–476 CFU/m ³ and 42–254 CFU/m ³ , respectively. Contrasting these findings with extant guidelines that recommend microbiological contamination not exceeding 500 CFU/m ³ highlights significant IAQ concerns. Thermal assessments revealed that the smaller classroom surpassed the acceptable indoor temperature threshold of 25 °C within an average duration of 50 minutes, while the larger classroom remained compliant. Notably, the highest CO 2 concentrations recorded over the three-day period were alarmingly high: 2689 ppm, 1970 ppm, and 2131 ppm on the first, second, and third days, respectively. A 25-minute ventilation intervention was sufficient to reduce CO 2 levels to 499 ppm, although existing literature stipulates that CO 2 concentrations should not surpass 1000 ppm. Importantly, the pilot study highlighted the rapid increasing of PM2.5 and PM10 concentrations in crowded instructional settings, averaging 400 μg/m ³ and 35 μg/m ³ , respectively. This underscores the necessity for a continuous air ventilation and purification mechanism during classroom activities. Despite these pivotal findings, the study identifies a glaring absence of standardized regulations or guidelines pertaining to maximum acceptable concentrations of particulate matter and microbial CFU in public indoor environments, indicating a critical area requiring immediate policy intervention.
Urban growth needs large cities, and the current emphasis on landscape preservation makes using underground spaces an opportunity and a significant necessity. However, underground construction techniques significantly impact the sustainability of the built environment, including infrastructure systems and their entire supply chains. Nowadays, there is a shortage of quantitative methodologies to assess and measure the sustainability of construction and underground building processes towards the three sustainable pillars, i.e. environmental, social, and economic. Thus, this study aims to cover this gap by explaining how to appropriately incorporate sustainability goals into geotechnical projects to address measure-driven strategies and eco-design-based solutions. This study illustrates a novel methodology based on the Life Cycle Thinking approach, with an emphasis on geotechnical ground improvement techniques. The proposed method incorporates the concept of the EU Taxonomy, following the EU Green Deal, with the Envision framework to guide decision-makers toward a more sustainable, resilient, and equitable infrastructure design. The proposed method will incorporate a cradle-to-site Life Cycle Assessment perspective, improving the quantitative estimation of the environmental performance of construction processes and providing guidelines to systematically assess the sustainability of geotechnical infrastructures.
In this study a problematic of logistics service provider selection is discussed. Traditional decision-making techniques are functionally limited and must be adjusted. Modern approach must be based on contemporary tools and information. The aim of this study is to develop a modern, industry-oriented decision-making model for selection of strategic logistics service providers. Main tasks of this study include: to perform critical analysis and comparison of multiple-criteria decision-making methods; to adapt decision-making framework for specific needs of selection of third-party logistics service providers; to collect and analyze industry data related to procurement projects; to develop modern decision-making model for selection of logistics service providers; to perform practical application of developed decision-making model based on collected industry data. The key novelties of this study are developed methodology for collection of industry data for decision-making process, developed hybrid decision-making model for selection of third-party logistics service provider, as well as application of the model. As the result, there is developed decision-making model for selection of 3PL service providers that includes 6 steps.
Osteochondral (OC) disorders such as osteoarthritis (OA) damage joint cartilage and subchondral bone tissue. To understand the disease, facilitate drug screening, and advance therapeutic development, in vitro models of OC tissue are essential. This study aims to create a bioprinted OC miniature construct that replicates the cartilage and bone compartments. For this purpose, two hydrogels were selected: one composed of gelatin methacrylate (GelMA) blended with nanosized hydroxyapatite (nHAp) and the other consisting of tyramine-modified hyaluronic acid (THA) to mimic bone and cartilage tissue, respectively. We characterized these hydrogels using rheological testing and assessed their cytotoxicity with live-dead assays. Subsequently, human osteoblasts (hOBs) were encapsulated in GelMA-nHAp, while micropellet chondrocytes were incorporated into THA hydrogels for bioprinting the osteochondral construct. After one week of culture, successful OC tissue generation was confirmed through RT-PCR and histology. Notably, GelMA/nHAp hydrogels exhibited a significantly higher storage modulus (G′) compared to GelMA alone. Rheological temperature sweeps and printing tests determined an optimal printing temperature of 20 °C, which remained unaffected by the addition of nHAp. Cell encapsulation did not alter the storage modulus, as demonstrated by amplitude sweep tests, in either GelMA/nHAp or THA hydrogels. Cell viability assays using Ca-AM and EthD-1 staining revealed high cell viability in both GelMA/nHAp and THA hydrogels. Furthermore, RT-PCR and histological analysis confirmed the maintenance of osteogenic and chondrogenic properties in GelMA/nHAp and THA hydrogels, respectively. In conclusion, we have developed GelMA-nHAp and THA hydrogels to simulate bone and cartilage components, optimized 3D printing parameters, and ensured cell viability for bioprinting OC constructs.
Background: Unsupervised sports activities could cause traumas, about 70% of them are those of the low extremities. To avoid traumas, the athlete should be aware of dangerous forces acting within low extremity joints. Research in gait analysis indicated that plantar pressure alteration rate correlates with the gait pace. Thus, the changes in plantar pressure should correlate with the accelerations of extremities, and with the forces, acting in the joints. Smart socks provide a budget solution for the measurement of plantar pressure. Objective: To estimate the correlation between the plantar pressure, measured using smart socks, and forces, acting in the joints of the lower extremities. Methods: The research is case study based. The volunteer performed a set of squats. The arbitrary plantar pressure-related data were obtained using originally developed smart socks with embedded knitted pressure sensors. Simultaneously, the lower extremity motion data were recorded using two inertial measurement units, attached to the tight and the ankle, from which the forces acted in the knee joint were estimated. The simplest possible model of knee joint mechanics was used to estimate force. Results: The estimates of the plantar pressure and knee joint forces demonstrate a strong correlation (r= 0.75, P< 0.001). The established linear regression equation enables the calculation of the knee joint force with an uncertainty of 22% using the plantar pressure estimate. The accuracy of the classification of the joint force as excessive, i.e., being more than 90% of the maximal force, was 82%. Conclusion: The results demonstrate the feasibility of the smart socks for the estimation of the forces in the knee joints. Smart socks therefore could be used to develop excessive joint force alert devices, that could replace less convenient inertial sensors.
In response to rising concerns over the environmental and human health ramifications of polymers derived from petroleum, particularly in the food packaging industry, research has pivoted towards more sustainable materials. Poly(butylene succinate) (PBS), selected as the polymer matrix, stands out as one of the most promising bio-based and biodegradable polymers suitable for film blowing and lamination. A layered spray-coating technique was employed to apply 1, 5, 10, and 20 layers of nanofibrillated cellulose (NFC) between blown PBS films, creating a three-layer laminate structure. NFC sourced from minimally processed hemp stalk waste highlights the potential for minimizing environmental impact. The water vapor transmission rate (WVTR) of these films, a critical parameter for food packaging, was assessed in a controlled environment at 38 °C and 90% relative humidity over a period of two months. The integration of a single NFC layer, constituting 0.35% of the composite’s weight, was observed to significantly reduce the WVTR by up to 5.5-fold. It was noted that higher NFC layer counts above 10 reduced the adhesion within the laminate layers. Morphological assessments showed that the number of structural defects increased with a higher count of NFC layers. As the count of NFC layers increased, the optical transparency of the laminates dropped from approximately 65% to 25% in the visible light spectrum. Notably, by weight percent, NFC proved to be an effective barrier even without chemical modification. The developed laminates stand out as a viable, green option for food packaging, offering a sustainable and renewable solution.
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3,347 members
Talis Juhna
  • Institute of Heat, Gas, and Water Technology & Head of Water Research and Environmetal Biotehnology Laboratory
Sabīne Upnere
  • Faculty of Mechanical Engineering, Transport and Aeronautics
Dmitry Pikulin
  • Faculty of Electronics and Telecommunications (FET)
Gundars Mezinskis
  • Institute of Materials and Surface Enginering
Maris Knite
  • Institute of Technical Physics, Faculty of Materials Science and Applied Chemistry
Riga, Latvia