16168 research outputs found
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Modeling and evaluation of customizable immobilization masks for precision radiotherapy /
No full textAccurate immobilization is critical in head and neck (H&N) radiotherapy to ensure precise dose delivery while minimizing irradiation of surrounding healthy tissues. However, conventional thermoplastic masks cannot secure 100% replicas of the patient’s surface and are often limited by mechanical weakness, patient discomfort, and workflow inefficiencies. Recently, the best replicas of the patient’s face have been obtained by exploring personal CT or MRI scans of patients that are used for manufacturing of immobilization masks. This study aimed to design and evaluate customizable immobilization masks using acrylonitrile butadiene styrene (ABS)-based composites reinforced with bismuth oxide (Bi2O3) and to compare their mechanical performance against commercial thermoplastic masks. ABS and ABS/Bi2O3 composite filaments (5, 10, and 20 wt%) were fabricated and characterized by tensile testing. A patient-specific virtual mask was modeled and subjected to finite element analysis (FEA) under clinically relevant loading scenarios, including neck flexion and lateral bending. Results were benchmarked against two commercial thermoplastic masks. ABS and ABS-based composites exhibited significantly higher stiffness (1.7–2.5 GPa) and yield strength (20–25 MPa) compared to commercial thermoplastics (0.25–0.3 GPa, ~7 MPa; p < 0.001). FEA simulations revealed markedly reduced displacement in ABS masks (1–5 mm at 2 mm thickness; <1 mm at 4 mm thickness) relative to commercial masks, which exceeded 20 mm under lateral load. Hybrid configurations with reinforced edges further optimized rigidity while limiting material usage. Customized ABS-based immobilization masks outperform conventional thermoplastics in mechanical stability and displacement control, with the potential to reduce planning margins and improve patient comfort. In addition, ABS-based masks can be recycled, and Bi2O3-filled composites can be reused for printing new immobilization masks, thus contributing to a reduced amount of plastic waste. These findings support their promise as next-generation immobilization devices for precision radiotherapy, warranting further clinical validation, workflow integration and sustainable implementation within a circular economy
Calibration-free shoulder kinematics using single and dual asynchronous RGB-D cameras /
No full textThis study experimentally evaluates whether shoulder joint kinematics can be accurately reconstructed using calibration free asynchronous RGB-D cameras under rehabilitation relevant conditions. We present a markerless framework that jointly learns temporal alignment, geometric consistency, and pose reconstruction using continuous-time modeling based on Neural Ordinary Differential Equations and implicit representations, eliminating the need for hardware synchronization or manual camera calibration. The system was validated in a controlled laboratory setting against a BTS Smart-DX optical motion capture reference during five clinically relevant shoulder movements. Performance was assessed for single- and dual-camera configurations. The dual-camera setup achieved a mean joint position error of 15.4 ± 2.8 mm with low temporal jitter (5.9 ± 0.7 mm), while the single-camera configuration showed reduced accuracy and higher sensitivity to occlusion. The results demonstrate that calibration-free asynchronous RGB-D systems can provide feasible shoulder kinematics, with a clear accuracy–complexity trade-off between single-and dual-camera deployments
Shortcut to highly π-extended optoelectronic systems based on the dibenzothiophene core /
No full textThe Scholl reaction stands as a versatile tool to synthetize multiple π-extended systems via intramolecular C-C oxidative couplings. A prime example is the expansion of dibenzothiophene to polycyclic butterfly-shaped heterocycles, which claim key characteristics in diverse optoelectronic applications. Herein we describe a protocol from commercial tetrabromothiophene based on sequential one-pot Suzuki-Miyaura reactions followed by the Scholl reaction. This strategy permits rapid access to complex constructions fusing up to 11 rings in just two steps and improved yields. The proposed πextensions successfully reduced the HOMO energy levels in the solid state to align with the gold work function (5.1 eV), while offering tunable photophysical properties. Remarkably, phenanthrene as scaffold endowed the core with a hole mobility value of 7 × 10 -5 cm 2 V -1 s -1 in OTFTs and excellent air-stability, with a shelf lifetime exceeding one year. Moreover, the inclusion of sulfurated units unlocked room temperature phosphorescence under oxygen-free conditions, a highly sought-after characteristic in metal-and halogen-free constructions. Their RTP quantum yields when introduced into a Zeonex matrix are as high as 14%, with oxygen-sensitive photoluminiscence that goes from deep-blue to yellow-orange.Altogether, this strategy holds great potential and versatility in developing adaptable materials for multiple functionalities
From pixels to predictions: integrating machine learning and digital image correlation for damage identification in engineering materials /
No full textDamage assessment in engineering materials is essential for structural reliability and safety. While traditional imaging techniques and Digital Image Correlation (DIC) provide valuable insights into deformation and crack evolution, they often require significant manual effort and suffer from accuracy limitations under complex loading conditions. Recent advances in Artificial Intelligence (AI), particularly Machine Learning (ML) and Deep Learning (DL), have enabled the development of automated, high-resolution, and near real-time damage assessment techniques. This paper reviews methods that integrate ML with DIC to assess damage in composites, metals, and other engineering materials. We compare conventional ML models with modern DL architectures, discuss key challenges, and propose future research directions. The findings demonstrate that coupling DIC with ML significantly improves the accuracy, speed, and reliability of damage identification in engineering materials
Imidazole-2-thione derivatives as new selective anticancer agents with anti-metastatic properties: synthesis and pharmacological evaluation /
No full textImidazole scaffolds are attractive in drug design for bioactivity and synthetic accessibility. We developed S-substituted imidazole-2-thione derivatives, focusing on compound 24, which showed potent cytotoxicity against lung, cervical, and colorectal cancer cells with submicromolar IC50 and selectivity over fibroblasts. Mechanistic analyses revealed G1 arrest, caspase-dependent apoptosis, and p-γH2AX accumulation. Importantly, compound 24 strongly inhibited A-549 cell migration and invasion in both 2D and 3D assays, correlating with downregulation of MMP-2, MMP-9, and hTERT. In vitro enzyme assays further confirmed that compound 24 directly inhibits MMP-9 activity. In vivo, 24 suppressed tumour growth and vasculotropic spread in the CA M model without detectable toxicity. Docking and dynamics simulations confirmed stable binding to MMP-2 and MMP-9 active sites. These results identify compound 24 as a promising anticancer agent with both cytotoxic and anti-metastatic properties, supporting its further preclinical investigation
Quality and chemical safety of wheat bread enriched with untreated, milled, and Lactiplantibacillus plantarum fermented red lentils (Lens culinaris L.) /
No full textThis study investigated the effects of untreated, milled, and fermented with Lactiplantibacillus plantarum No. 122 red lentils (Lens culinaris L.) on the quality and safety parameters of wheat bread (WB). The quantity (5, 10, 15, 20 and 25 %) and type of lentils added significantly influenced WB specific volume. Bread with 10 % of fermented non-milled (FNM) and 15 % of fermented milled (FM) lentils exhibited lower porosity (average, 52.4 %), while the highest total titratable acidity (1.12°N) was observed in bread enriched with 25 % of (FM) lentils. Enrichment with red lentils increased acrylamide levels in most breads to 14–44 μg/kg. A moderate correlation (−0.415–0.449) was found between acrylamide levels and certain VOCs of WB. Breads containing 10 and 15 % (FM) and (FNM) lentils showed overall acceptability scores (average, 4.1) similar to control bread. In conclusion, adding 5 % of non-fermented/fermented lentils to WB allowed for high acceptability without increasing acrylamide concentrations
Optimal shape design of cantilever structure thickness for vibration strain distribution maximization /
No full textEnergy harvesting systems face performance limitations, and existing optimizations are not always sufficient; this study addresses these gaps by enhancing piezoelectric energy systems. To improve the performance of piezoelectric energy harvesting systems, an optimization methodology is developed in this study. Since the mechanical strain distribution directly affects energy conversion efficiency, this issue is addressed through optimization of the thickness geometry of a common cantilever-type harvester elastic substrate element via a state-space gradient projection method combined with design sensitivity analysis. The gradient projection method is implemented in MATLAB R2024b software to determine the optimal elastic substrate design, after which the optimized design is simulated in COMSOL 6.3 Multiphysics for strain analysis in a transient study. The optimized cantilever designs are produced by 3D printing using a photopolymer and experimentally validated using piezo sensors and laser measurements for dynamic analysis. Theoretically compared with traditional uniform beams, the optimized cantilever designs maximize strain along the upper layer of the elastic substrate element, leading to a substantial increase in the energy conversion efficiency. This maximization is validated by experimental measurements showing a significant increase in strain in the elastic substrate (approximately 30% at the first eigenfrequency and 70% at the second). The correlation between the experimentally obtained data and the simulation results validates the optimization results. Deviation between the results did not exceed 3% and indicates that cantilever-type energy harvesters with optimized thickness profiles outperform traditional rectangular beams in energy conversion efficiency
Factors determining burnout among middle and lower-level managers in manufacturing companies.
No full textBurnout is a state of an employee arising from long-term and uncontrollable stress in the work environment, which is manifested by a lack of energy and strength, mental detachment and a reduced sense of professional achievement. Although burnout is often associated with supporting professions, the relevance of this work is also obvious for middle and lower-level managers in the manufacturing sector, who are affected by intense demands, role conflicts and limited resources; effective burnout management allows maintaining the competence, motivation and sustainability of the organization's activities. The object of the study is the factors determining the burnout among middle and lower-level managers in manufacturing companies. The aim of the study is to reveal the factors determining the burnout among middle and lower-level managers in manufacturing companies. The results of the study showed that middle and lower-level managers are characterized by an average level of all three burnout dimensions (emotional exhaustion, depersonalization and reduced perception of personal achievements). Although the expression of all three burnout dimensions is at an average level, a significant proportion of managers are at high risk. A high level of emotional exhaustion was found in 26.6 percent of managers, a low perception of personal achievements (corresponding to a high risk of burnout) – 32.5 percent, and a high level of depersonalization – as many as 40.4 percent of respondents, which indicates that emotional detachment is the most pronounced risk of burnout in this group. Sociodemographic characteristics do not significantly affect burnout, while organizational factors and personal motivation together explain a large part of the variation in burnout (the general model explained about 55.5 percent of the total burnout rate). A more detailed analysis revealed that emotional exhaustion is most strongly promoted by workload and emotional labor, and its risk is reduced by strong motivation; depersonalization is mainly determined by workload and role conflict; a reduced perception of personal achievements is determined by low personal motivation
The impact of leadership styles on employee work engagement and innovative work behavior across different generations.
No full textModern organizations operate in a dynamic, multigenerational work environment in which, as the employee engagement crisis grows and the need for innovation increases, the ability to adapt leadership style to the characteristics of different generations becomes increasingly important. Transformational and transactional leadership are widely analysed as models explaining how leaders shape employee motivation, emotional attachment to the organization, and the tendency to create and implement innovations (Bass & Riggio, 2006; Jensen et al., 2016). In this study, employee engagement is understood as an energetic, meaningful, and deeply work–related state (Schaufeli & Bakker, 2004), and innovative behaviour as a set of actions from exploring opportunities and generating ideas to defending them and implementing them in practice (De Jong & Den Hartog, 2010). At the same time, differences in values and work expectations across generations are considered, influencing how employees respond to leadership and the work environment (Twenge ir kt., 2010; Lyons & Kuron, 2014). The object of the study is the influence of managers’ leadership styles on work engagement and innovative work behaviour among employees of different generations. The aim of the research is to examine how transformational and transactional leadership are related to work engagement and innovativeness across generations. To achieve the aim, four objectives were formulated: to analyse leadership styles and the concepts of generations, employee engagement, and innovative behaviour, to prepare the research methodology, and, after an empirical study, to provide practical recommendations for organizations. To achieve the aim, a quantitative study was conducted – a survey of 306 employees in Lithuania. Data were analysed using descriptive statistics, correlation, and regression analysis. The results showed that respondents generally evaluated managers’ leadership behaviour, their own work engagement, and innovativeness positively – five–point scale, scores exceeded the midpoint. Regression analysis revealed that leadership styles explain almost half of the variation in employee work engagement, with transformational leadership as the strongest factor. Innovative work behaviour was most strongly linked to transactional leadership incentives. Generational analysis revealed different leadership effects. For Baby Boomer and Generation X employees, transformational leadership was important – it was consistently associated with higher engagement and, in the case of Generation X, more frequent innovative behaviour. For Generation Y, the most favourable situation is when transformational leadership is combined with material and non–material incentives. Generation Z appeared more contradictory: transformational leadership was associated with engagement, but transactional elements – especially sanctions, reduced engagement while being linked to higher innovativeness, and engagement and innovative behaviour were negatively related
Assessment of the impact of labour force migration on the Lithuanian labour market.
No full textIn this final master’s project, we evaluate the impact of emigration, immigration, and return migration on Lithuania’s labour market indicators – employment level, unemployment rate, average wages, and labour productivity. The assessment covers the period from 2008 to 2024. Drawing on academic literature, the project discusses migration-related issues and their effects on the labour market, identifies the causes of labour force migration, conducts statistical data analysis, reviews migration trends between 2008 and 2024, performs a macro-level econometric study to assess the impact of migration on the labour market, and provides recommendations. The review of scientific literature shows that there is no unified conclusion. Some researchers identify positive effects, others – negative consequences. This diversity of findings is believed to result from the dynamic nature of migration processes and the fact that research outcomes depend on the country studied and the specific aspect of migration being analysed. Based on publicly available statistical data, this study examines the impact of labour force migration on Lithuania’s labour market. The dependent variables used in the analysis include unemployment, employment, average wages, and labour productivity, while the independent variables are emigration, immigration, and return migration. The study consists of two stages: the first involves statistical and graphical analysis, which forms the basis for generating hypotheses; the second includes econometric analysis, such as correlation analysis, the Granger causality test, and the development of OLS and ARDL regression models. According to the results, the hypotheses are confirmed or rejected. The findings of the econometric analysis show that only emigration has a clear effect on the labour market. A one percentage point increase in emigration reduces the employment level by 2,74 percentage points, while the unemployment rate decreases by 3,17 percentage points. Immigration also demonstrates an effect: a one percentage point increase in immigration raises labour productivity by 0,11 percentage points and average wages by 0,02 percentage points. However, return migration has no statistically significant impact on any of the labour market indicators. To gain a more comprehensive understanding of migration’s impact on Lithuania’s labour market, it is necessary to analyse not only macroeconomic indicators but also sectoral, occupational, and regional levels. Migration may have meaningful effects on specific labour market groups even when macro-level indicators do not reveal such relationships. Therefore, future research could incorporate more detailed microeconomic and regional analyses to determine the true impact of migration on Lithuania’s labour market