Search Results (1,145)

Oligocarbonate diols (OCD) require tedious and time-consuming synthesis procedures. The most common ones use dimethyl carbonate or alkylene carbonate as starting materials. Considering the preparation of small batches of oligomerols with an atypical structure, this methodology is not convenient. Therefore, we developed a simple way to obtain OCDs and oligo(urethane-carbonate) diols (OUCDs) containing aliphatic, cycloaliphatic, aromatic or oxyethylene units based on commercially available OCDs (ETERNACOLL, UBE). The process was conducted in two stages combining transesterification/transurethanization and polycondensation reactions. It resulted in novel OCDs and OUCDs with an irregular structure. Their composition was characterized using FT-IR, NMR, and MALDI-TOF techniques. The hydroxyl values were determined by potentiometric titration. The numerical average molar masses of the oligomerols ranged from approx. 1000 to 3200 g/mol, making them attractive materials for the preparation of a variety of polyurethane products. Thanks to the presence of carbonate moieties that are resistant to hydrolytic and oxidative degradation, poly(carbonate-urethane)s could find applications as coatings, thermoplastic elastomers, and biomaterials. The influence of the structural variations of the oligomerols on the properties of polyurethanes is now under investigation. Full article

This study takes a further step forward in the analytical treatment of Langmuir–Hinshelwood (LH) kinetics for heterogeneous catalysis by deriving its closed-form solution. Unlike previous studies, we present a general solution that does not impose severe restrictions on the experimental conditions. This solution not only recovers the typical first- and zeroth-order regimes but also enables the simultaneous determination of the reaction rate constant and absorption–desorption equilibrium constant, unlike the traditional approaches to this equation, which needed additional isotherm experiments. The final solution requires a fine mathematical treatment for its numerical implementation, but enhanced approximations of the closed-form solution overcome this problem without losing the main advantage of calculating both constants at the same time. A parameter called “critical time” has been introduced, whose calculation allows us to distinguish quantitatively between kinetic regimes. Finally, the validation of these approximations has been carried out with experiments on zinc oxide and anatase (TiO₂) under different conditions. Anatase experiments undoubtedly show a first-order tendency, regardless the quantity of powder. On the other hand, the degradation regime of the ZnO case cannot be easily ascribed to the zeroth or first order by simple inspection, but the model can mathematically rule out the zeroth order and confirm that it undergoes first-order degradation. Full article

Polylactic acid (PLA) films were directly fluorinated using fluorine gas at room temperature under varying conditions: fluorine concentrations of 190–760 Torr and reaction times of 10–60 min. Some of the fluorinated samples were subsequently dried at 70 °C for 2 d. Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses verified the successful introduction of fluorine and the formation of -CF_x and C=OF groups on the PLA surface after fluorination. The fluorination level initially increased with increasing reaction time or fluorine concentration but then decreased because of the formation and escape of CF₄ gasification. Drying further reduced the surface fluorine content. Both fluorination and drying increased the glass transition temperature of PLA, which was attributed to the increase in surface polarity and crosslinking density of the polymer. Fluorination significantly improved the surface hydrophilicity of PLA, with the water contact angle decreasing from 64.09°to 18.75°. This was due to the formation of a rough, porous surface caused by the introduction of polar fluorine atoms, as observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). However, drying the fluorinated samples increased the water contact angle to 91.46°, resulting in hydrophobicity owing to increased surface crosslinking. This study demonstrates a simple and effective method for tuning the hydrophilic–hydrophobic properties of PLA surfaces using direct fluorination and thermal treatment. Full article

This study examined the auditory and cognitive effects of occupational ultrasonic noise exposure through controlled laboratory experiments simulating workplace conditions. A group of 20 participants aged 18–35 underwent pure-tone audiometry (PTA) in both standard (1–8 kHz) and extended high-frequency (9–16 kHz) ranges before and after exposure to airborne ultrasound emitted by an ultrasonic cleaner. The exposure was conducted at two sound pressure levels: at the current permissible occupational limit and at a level 5 dB below it. The results demonstrated statistically significant temporary threshold shifts (TTS) in hearing sensitivity (bilaterally) at 8 kHz and 16 kHz only at the higher exposure level, with mean shifts reaching 3.8 dB and 5.8 dB, respectively. No significant hearing threshold changes were observed at the reduced exposure level. Additionally, participants completed a battery of Abilitest cognitive tests during exposure. Comparisons with standardized normative data showed that reaction times were approximately 20% longer in simple response tasks and 13% longer in selective attention tasks, suggesting a potential deviation in cognitive performance associated with ultrasonic noise. These findings support the need to reevaluate current occupational exposure limits and highlight the potential health and performance risks associated with airborne ultrasound. Full article

In this study, we investigate the relationship between the progressive lowering of the silicon (Si) anode potential during lithiation and the accompanying crystallization reaction to enable in situ electrochemical detection in Si-based full cells. Si–Li half cells were first analyzed by differential capacity (dQ/dV), revealing a crystallization feature near 0.05 V vs. Li⁺/Li, commonly associated with crystallization to Li₁₅Si₄. In the initial cycle, this signal was obscured by a dominant amorphization peak near 0.1 V; however, once amorphization was completed and the end-of-lithiation potential dropped below ~0.05 V in later cycles, a distinct crystallization peak became clearly resolvable. Under capacity-limited cycling that mimics full-cell operation, degradation-induced lowering of the Si-anode potential led to the appearance of the crystallization signal when the anode potential crossed this threshold. Based on these results, we extended the analysis to LiFePO₄–Si three-electrode full cells and, by reparameterizing dQ/dV as a function of charge time, separated electrode-specific contributions and identified the Si crystallization feature within the full-cell response when N/P ≈ 1. A simple degradation-modeling scenario further showed that in cells initially designed with N/P > 1, loss of anode active material can reduce the effective N/P, drive the Si potential into the crystallization window, and introduce a new peak in the full-cell dQ/dV curve associated with Si crystallization. These combined experimental and modeling results indicate that degradation-driven lowering of the Si-anode potential triggers crystallization and that this process can be detected in full cells via dQ/dV analysis. Practically, the emergence of the Si-crystallization feature provides an in situ marker that the effective N/P has drifted toward unity due to anode-dominated aging and may inform charge cut-off strategies to mitigate further Si-anode degradation. Full article

Antibodies labeled with gold nanoparticles are widely used in analytical systems. Consequently, the choice of methods for producing such conjugates requires a precise determination of the retained reactivity of the antibodies. Existing methods give highly variable results, necessitating new, simple, and accurate approaches. This study demonstrates how a fluorescein (FL) and anti-FL antibody pair can be used to comparatively evaluate conjugation conditions. The method is based on the quenching of fluorescein emission after binding to antibodies, enabling real-time monitoring of interactions in the reaction medium. Using this approach, we compared a series of conjugates of gold nanoparticles (average diameter 24 nm) and anti-FL antibodies that were obtained with antibody concentrations of 5, 10, and 20 μg/mL during the conjugation. The proportion of antibodies that retained their reactivity varied from 11% to 58%. We also estimated the blocking of the conjugates’ surfaces by two widely used reagents, bovine serum albumin and mercapto polyethylene glycol. It was found that the former provides better retention of antigen-binding activity of immobilized antibodies. The difference between these two kinds of preparations is most pronounced—reaching up to a twofold change—at lower antibody densities. Full article

Droplet microfluidics enables high-throughput, compartmentalized reactions using minimal reagent volumes, but most implementations rely on precision-fabricated chips and external pumping systems that limit portability and accessibility. Here, we present a handheld vibrational droplet generator that repurposes a consumer electric toothbrush and a modified disposable pipette tip to produce nearly monodisperse water-in-oil droplets without microfluidic channels or syringe pumps. The device is powered by the toothbrush’s built-in motor and controlled by a simple 3D-printed adapter and adjustable counterweight that tune the vibration amplitude transmitted to the pipette tip. By varying the aperture of the pipette tip, droplets with diameters from ~100–300 µm were generated at rates of ~100 droplets s⁻¹. Image analysis revealed narrow size distributions with coefficients of variation below 5% in typical operating conditions. We further demonstrate proof-of-concept applications in digital loop-mediated isothermal amplification (LAMP) and microbiological colony-forming unit (CFU) assays. A commercial feline parvovirus (FPV) kit manufactured by Beyotime Biotechnology Co., Ltd. (Shanghai, China), three template concentrations yielded emulsified reaction droplets that remained stable at 65 °C for 45 min and produced distinct fractions of fluorescent-positive droplets, allowing estimation of template concentration via a Poisson model. In a second set of experiments, the device was used as a droplet-based spreader to dispense diluted Escherichia coli suspensions onto LB agar plates, achieving uniform colony distributions across the plate at different dilution factors. The proposed handheld vibrational generator is inexpensive, easy to assemble from off-the-shelf components, and minimizes dead volume and cross-contamination because only the pipette tip contacts the sample. Although the current prototype still exhibits device-to-device variability and moving droplets in open containers complicate real-time imaging, these results indicate that toothbrush-based vibrational actuation can provide a practical and scalable route toward “lab-in-hand” droplet assays in resource-limited or educational settings. Full article

Background/Objectives: Beyond respiratory problems, COVID-19 can cause a variety of symptoms, such as neurological disorders caused by biological and psychological factors. Brain fog (BF), a post-illness cognitive impairment that many patients report, can be evaluated with reaction time (RT) testing. Response latency is measured by RT, which can be either simple (sRT) or complex (cRT). This study focuses on how COVID-19 affects cognitive function, with particular attention on RT changes, BF prevalence, and implications for daily life. Methods: The study included 599 participants from Bosnia and Herzegovina, Croatia and Serbia. RT was measured using PsyToolkit and participants completed a COVID-19-associated BF questionnaire. Participants who experienced BF after their latest COVID-19 infection rated its severity using a visual analogue scale (VAS). Additional clinical data were obtained from medical records. Results: BF was reported by 40% of participants post-COVID-19. Men reported it less frequently but found it more disruptive. RT progressively declined post-infection, reaching peak impairment at 15 weeks, following recovery, with RT normalizing by six months. Conclusions: COVID-19 is linked to temporary RT impairment, peaking at 15 weeks post-infection and resolving by six months, independent of BF presence. This study emphasizes the need for a biopsychosocial approach to BF management. Easily available RT assessments should be incorporated into routine clinical practice. Full article

Caffeine is widely used to enhance cognitive performance, but its efficacy may vary with the administration route and circadian timing. This study compared the acute effects of caffeine capsule ingestion and caffeine mouth rinsing on cognitive performance across morning, midday, and evening sessions in well-trained, adolescent male volleyball players. Twenty-four athletes completed three randomized, double-blind, crossover trials involving a caffeine capsule (3 mg·kg⁻¹), a caffeine mouth rinse of the same dose (expectorated), and a placebo. Cognitive performance was assessed using simple and choice reaction time tests and the Stroop task, alongside a side-effects questionnaire. Both caffeine forms improved performance versus the placebo, with the greatest enhancements occurring at midday and moderate benefits evident in the morning. Capsule ingestion produced the most consistent improvements across reaction speed and executive control, whereas mouth rinsing elicited smaller, task-dependent effects, particularly at midday. No consistent or practically relevant benefits were observed for either caffeine condition in the evening, when cognitive performance was naturally highest. Side effects were mild and infrequent, with occasional headaches after capsule ingestion. These findings indicate that caffeine capsules most effectively enhance cognitive performance when baseline alertness is suboptimal, while caffeine mouth rinsing represents a practical ingestion-free alternative with moderate efficacy. Full article

The objective of this study was to establish the kinetic of gasification reactions involved in chemical looping gasification (CLG) using pelletized biomass as solid fuel. However, significant limitations have been found in obtaining such kinetics using a traditional methodology from a large number of tests in a thermogravimetric analyzer (TGA) for pelleted biomass. A novel methodology is presented in this article, namely: (i) the determination of the intrinsic gasification rate for several biomasses; (ii) the determination of the gasification rate of pelletized biomass under selected operating conditions; (iii) the development and validation of a reaction model for pelletized biomass considering the determined intrinsic kinetics and gas diffusion in the biomass particles; and (iv) obtaining an apparent kinetics from data calculated with the developed model, which will be easy to implement in the modeling of gasifiers. To evaluate the applicability of this methodology, it was demonstrated with three different types of biomasses: pine forest residue (PFR), industrial wood pellets (IWP), and wheat straw pellets (WSP). The intrinsic kinetics was derived from tests with powdered char under several operating conditions: reacting temperature (1073–1223 K), concentration of gasifying agent (10–40 vol.% H₂O or CO₂), and concentration of gasification product (0–40 vol.% H₂ or CO). The evolution of the char conversion with the reacting time was predicted using a model involving three different regimes: (I) deactivation at the beginning; (II) uniform progress in the main middle part following a n-order model; and (III) catalytic activation as complete conversion is approached. The second regime was included for all biomasses, being 1, 0.4, and zero-order for WSP, IWP, and PFR, respectively. However, the third regime was observed for PFR and IWP, and the first regime only for IWP. The intrinsic kinetics was successfully used in a theoretical model to properly predict the gasification rate of pelletized biomass, and, eventually, to determine an apparent gasification kinetics as simple as possible in order to be easily implemented in future gasifier modeling works. Full article

Water pollution from textile effluents poses serious environmental risks, particularly due to persistent anionic dyes such as Reactive Black 5 (RB5). This study demonstrates that simple deposition of Y₂O₃ onto commercially available, biobased TiO₂ (bTiO₂) significantly enhances photocatalytic degradation efficiency under simulated sunlight, suppressing rapid recombination of electron–hole pairs. Addressing a key research gap, the proposed method replaces expensive nanoscale precursors and complex synthesis routes typically used for Y₂O₃/TiO₂ systems with a low-cost, straightforward approach involving weak complexation and co-precipitation. The resulting Y₂O₃-bTiO₂ composite was characterized using FTIR, XRD, SEM, EDX, TEM, XPS, and UV-DRS techniques, confirming efficient incorporation of Y₂O₃ on the TiO₂ surface. Photocatalytic experiments revealed that nanoparticles calcined at 700 °C achieved complete RB5 degradation within 60 min—reducing the reaction time by half compared to undoped bTiO₂. Systematic studies of initial dye concentration, catalyst loading, and irradiation time confirmed that the degradation followed pseudo-first-order kinetics with a rate constant of 0.064 min⁻¹ (R² = 0.98). Calculated quantum yields corroborated the reduced electron–hole recombination induced by Y₂O₃ deposition. These findings highlight the novelty and practicality of the developed Y₂O₃-bTiO₂ photocatalyst as an efficient, affordable, and environmentally sustainable material for the degradation of industrial dyes. Full article

Current gene-based PCR diagnostics involving reverse-transcription polymerase chain reaction (RT-PCR) require at least several hours, expensive tools, and complicated sample collection methods to obtain results. A test for detecting volatile organic compounds (VOCs) in exhaled breath is advantageous as a simple, non-invasive, and fast screening method. In this study, a VOC detection system of array sensors was applied for the classification of breath control and COVID-19 virus infection. The ability to classify VOCs in the breath with COVID-19 virus infection has been studied with two metal-oxide (MOX) gas sensor arrays, commercially available sensors, and in-house sensors. The dataset of gas response signals from the array-type semiconductive gas sensors of the VOC detection system was analyzed using machine learning; principal component analysis (PCA) was used as a dimensionality-reduction method, and random forest (RF) and a convolutional neural network (CNN) were used as classification methods for the VOC concentration patterns in each breath. For the RF model, the accuracy results for the classification by two gas sensor arrays was 0.917 and this was improved by CO₂ calibration to 0.967, and the feature importance analysis revealed the importance of specific gas sensors. For the CNN, an input layer of a transformed gray-scale image with the shape of 12 data points × 8 sensors was used, and its accuracy reached 100% within a relatively small number of epochs, demonstrating a short training time, which is beneficial for breath detectors or e-nose devices. Full article

Photoelectrochemical water splitting (PEC-WS) provides a sustainable route to transform solar energy into hydrogen; however, its overall efficiency is constrained by the inherently slow kinetics of the oxygen evolution reaction. Bismuth vanadate (BiVO₄) is considered an attractive visible-light-responsive photoanode due to its suitable band gap (~2.4 eV) and chemical stability; however, its efficiency is restricted by limited charge transport and significant charge carrier recombination. To overcome these limitations, BiVO₄–MoS₂ (BVO–MS) heterostructures were synthesized through a simple in situ hydrothermal approach, ensuring robust interfacial coupling and uniform dispersion of MS nanosheets over BVO dendritic surfaces. This intimate contact promotes rapid charge transfer and improved light-harvesting capability. Structural and spectroscopic analyses confirmed the formation of monoclinic BVO with uniformly integrated amorphous MS. The optimized BVO–MS10 electrode delivered a photocurrent density of 4.72 mA cm⁻² at 0.6 V vs. SCE, approximately 5.3 times higher than pristine BVO, and achieved an applied bias photon-to-current efficiency of 0.49%. Mott–Schottky analysis revealed a distinct negative shift in the flat-band potential for BVO–MS10, indicative of an upward movement of its conduction band and the establishment of a strong internal electric field that enhances charge separation and interfacial electron transport. These synergistic effects collectively endow the in situ engineered BVO–MS heterostructure with superior PEC water oxidation performance and highlight its promise for efficient solar-driven hydrogen generation. Full article

Physical fitness and psychomotor performance can play a crucial role in decision-making ability, reaction time, and movement time among female handball players at different age levels. Our study aimed to compare the physical fitness performance and psychomotor abilities among trained young female handball players from different age groups (U14 vs. U16). The study group included 61 female handball players (U14 = 26; $13.2\pm 0.8$) and U16 = 35; $15.1\pm 0.8$). The Mann–Whitney U test was conducted to compare the performance of physical fitness and psychomotor abilities between groups (U14 and U16). Afterward, the Pearson product-moment correlation was used to explore the relationship between physical fitness and psychomotor abilities performance among all participants. Results showed that zig-zag with the ball (s) had a significant correlation with movement time (ms) in the Spatial Attention Test (SPANT) (r = 0.30). The plate tapping test (s) emerged as a strong indicator of psychomotor speed (ms), showing significant correlations with a range of variables, including Simple Reaction Time Test (SIRT) movement time (r = 0.48), Choice Reaction Time Test (CHORT) movement time (r = 0.57), Hand–Eye Coordination Test (HECOR) reaction time (r = –0.48), HECOR movement time (r = 0.69), SPANT reaction time (r = 0.63), and SPANT movement time (r = 0.52). These findings have implications for the development of trained young female handball players. Training programs may benefit from age-specific emphasis, focusing more on fundamental coordination and reaction-based exercises in younger athletes and progressively incorporating cognitively demanding drills for older adolescents. Full article

CRISPR/Cas12a systems coupled with lateral flow tests (LFTs) are a promising route to rapid, instrument-free nucleic acid diagnostics due to conversion target recognition into a simple visual readout via cleavage of dual-labeled single-stranded DNA reporters. However, the conventional CRISPR/Cas12a–LFT system is constructed in a format where the intact reporter should block nanoparticle conjugate migration and can produce false-positive signals and shows strong dependence on component stoichiometry and kinetics. Here, we present the first combined experimental and theoretical analysis quantifying these limitations and defining practical solutions. The experimental evaluation included 480 variants of LFT configuration with reporters differing in the concentration of interacting components and the kinetic conditions of the interactions. The most influential factor leading to 100% false-positive results was insufficient interaction time between the components; pre-incubation of the conjugate with the reporter for 5 min eliminated these artifacts. Theoretical analysis of the LFT kinetics based on a mathematical model confirmed kinetic constraints at interaction times below a few minutes, which affect the detectable signal. Reporter concentration and conjugate architecture represented the second major factors: lowering reporter concentration to 20 nM and using smaller gold nanoparticles with multivalent fluorescent reporters markedly improved sensitivity. The difference in sensitivity between various LFT configurations exceeded 50-fold. The combination of identified strategies eliminated false-positive reactions and enabled the detection of up to 20 pM of DNA target (the hisZ gene of Erwinia amylovora, a bacterial phytopathogen). The strategies reported here are general and readily transferable to other DNA targets and CRISPR/Cas12a amplification-free diagnostics. Full article