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Optimised extraction and purification of dual-function cosmetic-grade phycocyanin and allophycocyanin from dried arthrospira platensis biomass using conventional methods /
No full textFeatured Application: This study’s optimised extraction and purification methods provide a cost-effective and scalable approach for producing cosmetic-grade phycobiliproteins from Arthrospira platensis. These methods are particularly suitable for industrial applications in cosmetics, biotechnology, and food industries, where high purity and sustainable processing are essential. Moreover, the framework could be adapted to produce other high-value compounds from microalgae or similar biomasses. Arthospira platensis is a filamentous cyanobacterium considered an important source of phycobiliproteins (PBP), a class of water-soluble pigments with a wide range of applications. Although several extraction and purification techniques of PBP have been reported, there is still a need for strategies that achieve a balance between simplicity, cost-effectiveness, and scalability. To address this need, this study systematically evaluated conventional extraction methods—homogenisation, freeze–thaw cycles, and maceration. Maceration showed the best balance between yield purity and recovery among the tested techniques, and under optimal conditions (three cycles, 2 h/cycle, 0.1 M phosphate buffer), 55.9 mg/g of biomass of phycocyanin (PC) and 24.9 mg/g of biomass of allophycocyanin (APC) with notable antioxidant capacity (Folin-Ciocalteu’s and ABTS●+ assays) were yielded. Among the tested purification techniques, ammonium sulphate fractionation achieved a purity of 2.3 with recoveries of 92.9% and 79.9% for PC and APC, respectively, while purification with 0.5% activated carbon resulted in an extract purity of 2.5 and recoveries of 90.9% (PC) and 87.2% (APC). The suggested procedures could be considered a fast and cost-effective way to obtain cosmetic-grade PBP, thus offering an accessible solution for industries prioritising sustainable and economically viable production pipelines
The impact of temperature on the shear bond strength of conventional multi-step and self-adhesive orthodontic adhesive systems: an in-vitro study /
No full textBACKGROUND: A recurring issue during orthodontic treatment is the detachment of brackets from the tooth surface, which proves problematic for both the patient and the orthodontist. This study aimed to evaluate the impact of various temperatures on the shear bond strength of metal molar tubes, using conventional multi-step and self-adhesive orthodontic adhesive systems. METHODS: A total of 112 extracted human molars were randomly divided into eight groups (n = 14) for bonding tubes with two orthodontic adhesive systems (Transbond XT and GC Ortho Connect) at different temperatures: refrigeration temperature (4 °C), room temperature (20 °C), human body temperature (37 °C), and high temperature (55 °C). The shear bond strength (SBS) test was conducted using a universal testing machine set to a crosshead speed of 0.5 mm/min. The adhesive remnant index (ARI) was used to evaluate the amount of adhesive remnants on the molar surfaces. ARI scores were assessed under Carl Zeiss Stemi 2000-CS stereomicroscope with image recording camera AxioCam Mrc5 at ×10 magnification. The data were analyzed using Student's t-test, parametric analysis of variance (ANOVA), the intra-class correlation coefficient (ICC), the Kruskal-Wallis test, and the chi-square test. RESULTS: Higher mean SBS values were obtained with Transbond XT compared to GC Ortho Connect resin; however, the difference was not statistically significant (p > 0.05). The SBS results were lowest at 20 °C and highest at 55 °C in the Transbond XT group, and lowest at 37 °C and highest at 20 °C in the GC Ortho Connect group with no statistically significant difference (p > 0.05). The distribution of the ARI scores between the two materials showed a statistically significant difference (p = 0.002), with higher ARI scores found in the Transbond XT group. CONCLUSIONS: Pre-heating orthodontic adhesives prior to bonding does not affect the shear bond strength
Spectral content effects study in non-contact resonance ultrasound spectroscopy /
No full textThe application of spread-spectrum signals (arbitrary pulse width and position (APWP) sequences) in air-coupled resonant ultrasound spectroscopy is studied. It was hypothesized that spread-spectrum signal optimization should be based on te signal to noise ratio (SNR). Six APWP signal optimization criteria were proposed for this purpose. Experimental measurements were conducted using a thin polycarbonate sample using two standard spread-spectrum signals, linear and nonlinear frequency modulation, together with six optimized APWP signals. It was found that the performance of APWP signals derived from linear frequency modulation was better. The two best performing optimization criteria are SNR improvement on a linear scale with the SNR as an additional weight and energy improvement on a dB scale. The influence of spectral coverage on measurement errors was evaluated. It was found that it is sufficient to cover the sample resonance peak and the valley. The lowest error rates for density, 3%, and for thickness, 3.5%, were achieved when the upper valley was covered. For velocity, the best result, 5%, was achieved when the lower valley was covered. The lowest error rate for attenuation, 3.8%, was achieved in the case when both valleys were covered. Yet no significant performance degradation was noted when a whole -30 dB passband was covered
Synthesis of novel N-substituted β-amino acid derivatives bearing 2-hydroxyphenyl moieties as promising antimicrobial candidates targeting multidrug-resistant Gram-positive pathogens /
No full textThe increasing prevalence of antimicrobial resistance among ESKAPE group pathogens presents a significant challenge in the healthcare sector, contributing to higher morbidity and mortality rates globally. Thus, it is essential to develop novel antimicrobial agents effective against drug-resistant pathogens. In this study, we report the synthesis and in vitro antimicrobial activity characterization of novel N-substituted β-amino acid derivatives bearing 2-hydroxyphenyl core against multidrug-resistant bacterial pathogens. The synthesized compounds (2-26) exhibited promising antimicrobial activity specifically against Gram-positive bacteria, with minimum inhibitory concentrations (MIC) ranging from 4 to 128 µg/mL. Compounds 9 (R = 4-nitrophenyl), 17 (R = 5-nitro-2-thienyl), 18 (R = 5-nitro-2-furyl), thiosemicarbazide 16, and 26 exhibited the most promising activity against Staphylococcus aureus MRSA USA300 lineage strain TCH-1516, with MIC values between 4 and 16 µg/mL. Compound 26 demonstrated strong antimicrobial activity against both S. aureus TCH-1516 and E. faecalis AR-0781, with the activity comparable to control antibiotics. Furthermore, compound 26 exhibited antifungal activity drug-resistant against Candida albicans AR-0761 (MIC 16 µg/mL). These findings indicate that N-substituted β-amino acid derivatives with a 2-hydroxyphenyl core warrant further investigation as a potential scaffold for the further development of antimicrobial agents based on compound 26 targeting Gram-positive pathogens and drug-resistant C. albicans AR-0761
Novel positioning system for Vantage stereotactical frame enabling accurate and two hands frame placement :
No full textIntroduction. There are 100,000 radiosurgical procedures and around 12,000 DBS implantations carried out worldwide each year using stereotacic frames. 1 Moreover, intracranial lesion biopsies and stereotactic EEG electrode placement also are done by using frame based technique. For optimal stereotactical MRI imaging appropriate frame positioning on the patient’s head is mandatory. The stereotactic frame must be accurately placed on the patient’s head to ensure that the images are aligned correctly with the treatment plan. Incorrect placement can lead to final target coordinates calculation errors. Conventional Leksell G and Vantage frame mounting methods are based on usage of ear bars 2, over-the-head Velcro or mounted bar 3, additional plates for supine placement 4,5 or bite-bars 6. Most of these methods are suitable for Leksell G frame, however not for a Vantage frame® which was presented for clinical use 6 years ago.7
Targeting multi-drug-resistant ESKAPE pathogens: antibacterial, antioxidant, cytotoxicity, and metabolic profiling of selected Cameroonian plants /
No full textDifferent parts of Allanblackia floribunda, Calotropis procera, Hymenocardia acida, Irvingia gabonensis, Newbouldia laevis , and Xylopia acutiflora have been used traditionally across different parts of Cameroon to overcome infectious diseases, especially pneumonia. Hence, this study investigated the antibacterial potential of six Cameroonian medicinal plants against selected ESKAPE pathogens ( Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa) as well as Streptococcus pneumoniae
Influence of Al2O3 additive on the synthesis kinetics of 1.13 nm tobermorite, and its crystallinity and morphology /
No full textOne of the effective types of heat-resistant insulating products with an operating temperature of 1050 °C is made from calcium silicates or their hydrates. These materials are made from synthetic xonotlite and 1.13 nm tobermorite. Various wastes and by-products from other industries can be used for the synthesis of the latter compound. However, such raw materials often contain various impurities, especially Al-containing compounds, which strongly influence the kinetics of 1.13 nm tobermorite formation and its properties. Using XRD, DSC, TG, and SEM/EDX methods, it was found that at the beginning of the hydrothermal synthesis, the Al2O3 additive promotes the formation of 1.13 nm tobermorite; however, it later begins to inhibit the recrystallization of semi-crystalline C-S-H(I)-type calcium silicate hydrate and pure, high-crystallinity 1.13 nm tobermorite is more easily formed in mixtures without the aluminum additive. Aluminum oxide also influence the morphology of 1.13 nm tobermorite. When hydrothermally curing the CaO-SiO2 mixture, long, thin fibers (needles) are formed within 24 h. Later, they thicken and form rectangular parallelepiped crystals. After adding alumina, the product produced by 24 h synthesis is dominated by agglomerates, the surface of which is partially covered with crystal plates. By extending the synthesis duration, amorphous aggregates are absent and the crystal shape becomes increasingly square
Selective sorption of gold ions from iron-rich solutions using a dual-phase interpolymer system /
No full textThis study investigates the selective sorption of gold(I) ions from binary gold-iron solutions using the interpolymer system Amberlite IR120:AV-17-8. The system leverages remote interactions between cationic and anionic resins to enhance gold selectivity. Amberlite IR120 (H+ form) and AV-17-8 (OH- form) were evaluated at molar ratios of 6:0, 5:1, 4:2, 3:3, 2:4, 1:5, and 0:6. Sorption characteristics were analyzed using gravimetry, inductively coupled plasma optical emission spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The optimized 4:2 ratio exhibited the highest gold selectivity, achieving 96.26% sorption after 48 hours, while iron sorption remained at 42.33%. In contrast, Amberlite IR120 (6:0) showed negligible sorption (~3%), whereas AV-17-8 (0:6) reached 91.9% for gold and 92.33% for iron. Desorption with 9% thiourea and 2% sulfuric acid yielded 92.28% gold recovery and 46.44% iron recovery at the 4:2 ratio, which correlates with the high sorption efficiency. Based on calculations per mole of anion exchanger, the highest gold sorption was 18.45 mg/L at a 5:1 ratio, 301% higher than the 4.60 mg/L at a 0:6 ratio and gold desorption peaked at 15.4 mg/L at a 5:1 ratio, 266.67% higher than the 4.20 mg/L at a 0:6. These findings demonstrate that optimizing cation-anion ratios significantly enhances gold recovery. The system's efficiency is attributed to remote interactions and enhanced ion exchange, as analyzed using Pearson’s Hard and Soft Acids and Bases theory
Factors determining the career dynamics of novice teachers.
No full textIn recent years, the Lithuanian education system has faced a pressing challenge: the instability of novice teachers' careers and the growing shortage of teaching staff. While new professionals do enter the education sector, many of them leave the profession quickly due to work-related stress, unfavourable working conditions, lack of support, and an underdeveloped sense of professional identity (Lebedytė-Mečionienė, 2022; Lander, 2022; Daly et al., 2023). This situation poses a serious threat to the quality and continuity of education and underscores the need for a more thorough analysis of the factors influencing beginning teachers’ decisions to remain in or leave the profession. The aim of this research is to identify the internal and external factors that shape the career dynamics of novice teachers. The theoretical framework is grounded in Bronfenbrenner’s (1996) ecological systems theory, which emphasizes the influence of various systemic levels (micro-, meso-, exo-, macro-, and chronosystems) on professional development (Sadownik, 2023; Kairienė et al., 2022), along with contemporary career development theories (Super, 1990; Savickas, 2005, 2018), which highlight the importance of adaptability, meaning-making, and self-reflection in career construction (Urbanavičiūtė, 2021; Paužuolienė & Laskytė, 2019). The empirical part of the study included a qualitative research design based on semi-structured interviews with ten novice primary school teachers from various regions of Lithuania. The interview guide was developed in accordance with the theoretical framework, which categorized career factors into internal (e.g., professional identity, emotional well-being, motivation, self-reflection) and external (e.g., administrative support, workplace climate, mentoring, education policy) career factors. Using content analysis, key categories and subcategories were identified, reflecting the respondents’ lived experiences and the dynamics behind their career-related decisions. The results revealed that strong internal motivation, a sense of professional meaning, emotional well-being, and a reflective approach to teaching are significant factors encouraging teachers to remain in the profession (Didžiulienė, 2023; Skaalvik & Skaalvik, 2021). At the same time, a supportive work environment—including collegial relationships, empowering leadership, and a clear educational policy—emerged as critical external factors influencing commitment (Day & Gu, 2010; Mockler, 2022; Ben-Amram & Davidovich, 2024). Nevertheless, unstable education reforms, excessive workloads, and societal uncertainty may undermine commitment and generate doubts about continuing to work in schools. The novelty of this research lies in its integrative approach, which connects three levels of internal factors—value-based motivation, emotional self-regulation, and professional reflection—with contextual external dimensions such as organizational culture, professional support, and education policy. The findings may serve as a valuable resource for policymakers, school leaders, and teacher education institutions in developing sustainable and empowering environments for early-career teachers
Synthesis and investigation of the properties of pyrido[2,3-b]pyrazine-based electroactive compounds for organic light emitting diodes.
No full textFour electroactive compounds containing pyrido[2,3-b]pyrazine acceptor fragments were synthesised. Their properties-structure dependence, and potential applications were investigated. Due to their favourable properties for optoelectronic applications, carbazole and phenothiazine were chosen as electron–donating fragments. The compounds were synthesised using the Buchwald–Hartwig cross–coupling reaction. The structures of the final compounds were confirmed by 13C and 1H nuclear magnetic resonance and FTIR, while molecular weights were determined by MS. Thermogravimetric analysis showed that all compounds are thermally stable, and their decomposition temperatures were determined. The 5 % weight loss temperatures of the compounds with one carbazole or phenothiazine fragment are 345 and 329 °C, respectively, and 434 °C for the compounds with two donor fragments. All compounds were found to be morphologically stable by differential scanning calorimetry. The compound containing two phenothiazine fragments and both compounds containing one carbazole or one phenothiazine fragment exhibited only glass transition (at 134, 89, and 82 °C, respectively). The product containing two carbazole fragments showed glass (155 °C), melting (310 °C), and crystallisation (249 °C) transitions. By analysis via an optical profilometer, it was confirmed that all compounds were capable of forming amorphous layers with a low surface roughness. The ionisation potentials of the compounds, determined by cyclic voltammetry and photoemission yield spectroscopy in air (5,31–5,54 eV and 5,25–5,55 eV, respectively), are compatible with the typical values of other OLED layers. All compounds are electrochemically stable. Monosubstituted compounds exhibit reversible oxidation, while disubstituted ones show quasi–reversible oxidation. UV–Vis spectroscopy showed that the toluene solutions of compounds absorb light up to 500 nm and thin films up to 650 nm. The emission maxima of the toluene solutions (468–652 nm) and thin films (505–663 nm) of compounds were determined via fluorescence spectroscopy. The toluene solutions emit blue to red light, while the films emit green to red light. Temperature-dependent emission analysis and the calculated singlet–triplet energy gaps (0,16–0,38 eV) confirmed that the compounds exhibit thermally activated delayed fluorescence. Based on the evaluated properties, it was concluded that all compounds are suitable for use in the emissive layer of OLEDs. Upon constructing OLEDs, a high external quantum efficiency (18 %) was achieved. A technological scheme was also developed for 10,10'-(pyrido[2,3-b]pyrazine-2,3-diylbis(4,1-phenylene))bis(10Hphenothiazine)