Search Results (465)

Objectives: The current study aims to investigate the factors associated with the severity of conditions for pediatric cases with postural orthostatic tachycardia syndrome (POTS). Methods: Patients hospitalized and first diagnosed with POTS were retrospectively included and reviewed. The severity of symptoms was evaluated by symptom scores (SSs). Multiple Spearman correlation analyses and multiple linear regression analyses were used to determine factors independently associated with SS. Patients were divided into the mild (SS ≤ P25) and severe (SS ≥ P75) groups to test the distinguishing efficiency of the candidate factors. The efficiency of each independently correlated factor in indicating the condition of children with POTS was assessed by the receiver operating characteristic (ROC) curve. Results: A series of 296 pediatric patients aged 5–17 years suffering from POTS were included. Multiple Spearman correlation analyses and multiple linear regression analyses showed that corrected QT interval dispersion (QTcd) was independently correlated with SS (p < 0.05). QTcd can be used to suggest the severity of POTS symptoms, and the area under the curve (AUC) was 0.986 (95% CI 0.976–0.997). At a threshold of QTcd = 45 ms, the sensitivity and specificity were, respectively, 94.0% and 91.8% for symptom severity indication. Conclusions: In pediatric cases with POTS, QTcd was positively correlated with their symptom severity and exhibited a strong indicative value. A QTcd of 45 ms was a valid cut-off value for indicating symptom severity. Full article

Several experimental studies have shown that clinoptilolite zeolite is a suitable candidate for the adsorption of pharmaceuticals and related compounds. However, there is a significant lack of detailed molecular-level insights regarding how the adsorbed species interact with the zeolite surface. In this work, we employ electronic structure calculations and propose a reliable set of input parameters within the CP2K code in the framework of dispersion-corrected density functional theory (DFT-D) to generate bulk models and study Al and cation distributions. We aim ultimately to investigate the adsorption of emerging contaminants at the clinoptilolite surfaces. Nine different exchange-correlation functionals were tested, and the results suggest that B97-D3 functional is the most robust for this system. Moreover, our results suggest that Na⁺ prefers the presence of Al at T2 and T3 sites but not at T1 sites and prefers being present in channel A and/or channel B. Ca²⁺ tends to favor being present in channel B and favors the presence of Al at T1, T2, and T3 sites. K⁺ prefers the smallest channel C and likes the presence of Al at T1 and T3 sites. Moreover, we found out that the optimization of the basis sets improves the coordination of extra-framework cations like Ca with the framework oxygens. Full article

We investigated the geometry and electronic structure of the oxygen-bridged dicopper complex [Cu^II₂(NH₃)₄O₂]²⁺ and discussed how different DFT methods and basis sets, including dispersion corrections and dielectric media, affect the predicted structure and spin state. Our results showed that pure functionals yielded the closed-shell singlet character, whereas hybrid functionals presented a partial diradical character that coincided with increased spin contamination. Incorporating a polarizable continuum model further enhanced the diradical character and more closely reproduced the measured Cu–Cu distance with a bent Cu₂O₂ core. Analysis of the molecular orbitals and computed absorption spectra revealed how orbitals produce the key transition from ligand-to-metal charge transfer. These findings underscore how environmental effects influence the description of Cu₂O₂ chemistry. Full article

Calculation of second-order derivatives of energy using the DFT method is a valuable approach for the estimation of both the thermodynamical and mechanical properties of organic crystals from the first principles. This type of calculation requires specification of several computational parameters, including the functional, supercell, and method of phonon calculations. Nevertheless, the importance of these parameters is presented in the literature very modestly. In this work, we demonstrate the influence of these computational parameters on the accuracy of calculated second-order derivatives using the practical example of pyrazinamide polymorphs, including the plastically bending α form and the β, γ, and brittle δ form. The effects of the settings used on the resulting enthalpies of the polymorphic modifications of pyrazinamide are compared: supercell setting (primitive cell vs. appropriate supercell) has a much stronger impact than functional (PBE-D3BJ vs. Hamada rev-vdW-DF2) which in turn affects results significantly more than the method for second-order derivative computation (FD vs. DFPT approach). Finally, we propose some suggestions for choosing the right settings for calculating second-order derivatives for molecular crystals. Full article

The chemical structure of coal is very composite, consisting of a heterogeneous carbonaceous matrix with variable degrees of “turbostratic” order and the inclusion and/or exclusion of mineral matter (ash). The formation of surface oxides on carbon has long been recognized as a key to understanding many chemical and physical properties of carbon materials relevant to their consolidated or emerging applications. The extent and nature of surface oxides can effectively be assessed by high-resolution X-ray photoelectron spectroscopy (XPS), which provides excellent insight into the functional nature of C-O moieties. However, the XPS analysis of ash-bearing carbons may be biased by the interfering effects of inorganics with the most relevant spectral ranges, namely the core levels O_1s and C_1s. The effect of ash components on the spectroscopic characterization of carbon is scrutinized here with reference to a sub-bituminous coal characterized by a fairly large ash content. The coal is subjected to different treatments, including devolatilization, milling, and oxidation. A synthetic carbon (Carboxen) is used as a reference sample for the correct assignment of the carbon–oxygen functionalities in the core-level XPS spectra (C_1s and O_1s) in the absence of mineral matter. On the opposite side, fly ash from an industrial coal boiler is analyzed to investigate the effects of mineral matter. It is shown that the establishment of non-uniform charging of the sample induced by ash provides a key to the interpretation of the XPS spectra of ash-bearing carbon samples. The positive charge on the surface, referred to as the charging effect, brings about a shift of the core-level binding energies towards higher values. Grinding of the samples or partial combustion emphasizes the charging effect. XPS analysis of the fly ash, where carbon is largely consumed and dispersed in the inorganic matter, confirms that charging arises from non-conductive aluminosilicates. These effects may induce remarkable changes in carbon and oxygen peak shapes and need to be accounted for to obtain correct interpretations of the XPS spectra of ash-rich carbonaceous fuels. Full article

Student-centred learning requires a variety of approaches, such as inquiry-based learning and the tackling of authentic and problem-based learning activities, to make the teaching and learning process more meaningful and to encourage students to participate more actively in class. The inquiry approach enables students to investigate solutions to real problems, awakening their need to ask questions, design and conduct research, collect and analyse data, interpret results and present them in a structured way. This study investigates the influence of an inquiry-based science education (IBSE) module on the development of oral and written communication skills among 10th grade students. The study is set in a secondary school context and focuses on a problem-based learning approach centred around gases and dispersions. A total of 111 students participated in this one-group post-assessment qualitative study, where evaluation rubrics were applied to assess students’ written and oral communication, focusing on correctness, clarity and mastery of scientific language. The results showed that the majority of students performed well in both written and oral tasks, demonstrating improved scientific communication skills. This suggests that IBSE, particularly in the context of secondary education, can be an effective approach to fostering students’ abilities to communicate scientific concepts. The study has implications for enhancing pedagogical practices and encourages further research on the long-term effects of IBSE on student learning. Full article

Background: Actinium-225 (²²⁵Ac) has gained interest in nuclear medicine for use in targeted alpha therapy (TAT) for the treatment of cancer. However, the number of suitable chelators for the stable complexation of ²²⁵Ac³⁺ is limited. The promising physical properties of ²²⁵Ac result in an increased demand for the radioisotope that is not matched by its current supply. To expand the possibilities for the development of ²²⁵Ac-based TAT therapeutics, a new hydroxamate-based chelator, DFO*¹², is described. We report the DFT-guided design of dodecadentate DFO*¹² and an efficient and convenient automated solid-phase synthesis for its preparation. To address the limited availability of ²²⁵Ac, a small-scale ²²⁹Th/²²⁵Ac generator was constructed in-house to provide [²²⁵Ac]AcCl₃ for research. Methods: DFT calculations were performed in ORCA 5.0.1 using the BP86 functional with empirical dispersion correction D3 and Becke–Johnson damping (D3BJ). The monomer synthesis over three steps enabled the solid-phase synthesis of DFO*¹². The small-scale ²²⁹Th/²²⁵Ac generator was realized by extracting ²²⁹Th from aged ²³³U material. Radiolabeling of DFO*¹² with ²²⁵Ac was performed in 1 M TRIS pH 8.5 or 1.5 M NaOAc pH 4.5 for 30 min at 37 °C. Results: DFT calculations directed the design of a dodecadentate chelator. The automated synthesis of the chelator DFO*¹² and the development of a small-scale ²²⁹Th/²²⁵Ac generator allowed for the radiolabeling of DFO*¹² with ²²⁵Ac quantitatively at 37 °C within 30 min. The complex [²²⁵Ac]Ac-DFO*¹² indicated good stability in different media for 20 h. Conclusions: The novel hydroxamate-based dodecadentate chelator DFO*¹², together with the developed ²²⁹Th/²²⁵Ac generator, provide new opportunities for ²²⁵Ac research for future radiopharmaceutical development and applications in TAT. Full article

Objective: This study evaluates the short-term cardiovascular effects of guanfacine treatment in children and adolescents with attention deficit/hyperactivity disorder (ADHD). The treatment’s impact on novel electrocardiographic parameters was also investigated. Methods: In a retrospective study conducted between January 2023 and June 2024, 37 patients aged 6–18 years with ADHD underwent baseline and follow-up cardiac evaluations including electrocardiography (ECG) and blood pressure measurements. Novel ECG markers (QRS-T angle, QT dispersion, QTc dispersion, Tp-e interval, Tp-e dispersion, Tp-e/QT ratio, and Tp-e/QTc ratio) were analyzed alongside standard parameters such as heart rate, QT, and corrected QT (QTc) intervals. Guanfacine was initiated at 1 mg and titrated weekly until an optimal clinical response was achieved. Results: Guanfacine treatment led to a significant reduction in heart rate (−12.3 bpm; p < 0.001) and P wave axis (−12.3°; p = 0.038) and an increase in QT interval (+16.8 ms; p = 0.014). However, no significant changes were observed in blood pressure, QTc duration, or the novel ECG parameters. Importantly, the absence of any changes in these advanced markers supports the cardiovascular safety of guanfacine. Two patients experienced side effects (bradycardia and hypotension), leading to treatment discontinuation. ANCOVA analysis indicated that the duration between ECG evaluations significantly influenced the QT interval changes, emphasizing the importance of timing when monitoring cardiovascular effects. Conclusions: Guanfacine demonstrated minor, statistically significant effects on the selected cardiac parameters without clinically meaningful changes to or adverse impacts on the novel ECG markers investigated. As extended-release guanfacine has only been available in Türkiye for the management of ADHD for approximately two years, studies evaluating its clinical efficacy and side effects are critical for clinicians working in this field. Full article

Given the significant impact of air pollution on global health, the continuous and precise monitoring of air quality in all populated environments is crucial. Unfortunately, even in the most developed economies, current air quality monitoring networks are largely inadequate. The high cost of monitoring stations has been identified as a key barrier to widespread coverage, making cost-effective air quality monitoring devices a potential game changer. However, the accuracy of the measurements obtained from low-cost sensors is affected by many factors, including gas cross-sensitivity, environmental conditions, and production inconsistencies. Fortunately, machine learning models can capture complex interdependent relationships in sensor responses and thus can enhance their readings and sensor accuracy. After gathering measurements from cost-effective air pollution monitoring devices placed alongside a reference station, the data were used to train such models. Assessments of their performance showed that models tailored to individual sensor units greatly improved measurement accuracy, boosting their correlation with reference-grade instruments by up to 10%. Nonetheless, this research also revealed that inconsistencies in the performance of similar sensor units can prevent the creation of a unified correction model for a given sensor type. Full article

Modulation format identification (MFI) is one of the most critical functions embedded in digital coherent receivers in elastic optical networks (EONs). In view of inherent amplitude and phase characteristics of received signals, different modulation formats exhibit a set of notable features in the polar coordinate system, based on which an MFI scheme incorporating the Gaussian weighted k-nearest neighbors (KNN) algorithm was proposed to identify polarization division multiplexed (PDM)-QPSK/-16QAM/-32QAM/-64QAM/-128QAM signals. The performance of the proposed scheme was numerically verified in 28GBaud coherent optical communication systems. The numerical simulation results show that, to achieve 100% correct identification rates for all of the five modulation formats, the required minimum optical signal-to-noise ratios (OSNRs) were less than their relevant thresholds corresponding to the 20% forward error correction (FEC). The tolerable ranges of the residual chromatic dispersion (CD) for QPSK, 16QAM, 32QAM, 64QAM, and 128QAM were −1920 ps/nm~1920 ps/nm, −720 ps/nm~360 ps/nm, −1200 ps/nm~1680 ps/nm, −600 ps/nm~360 ps/nm, and −600 ps/nm~480 ps/nm, respectively. Meanwhile, the results demonstrate the maximum tolerable differential-group delay (DGD) for the QPSK, 16QAM, 32QAM, 64QAM, and 128QAM signals were 34 ps, 16 ps, 20 ps, 6 ps, and 1.2 ps, respectively. In addition, the simulated results also show that the proposed MFI scheme is robust against the fiber nonlinearities, even if the launch power is increased to 4 dBm. Full article

Background: Radiomics has become a valuable tool in medical imaging, but its clinical use is limited by data variability and a lack of reproducibility between centers. This study aims to assess the differences between two scanners and provide guidance on image acquisition methods to reduce variations between images obtained from different centers. Methods: This study utilized medical images obtained in two different imaging centers, with two different 3T MRI scanners. For each scanner, 3D T2 FLAIR sequences were acquired in two forms: the raw and the clinical practice images typically used in diagnostic workflows. The differences between images were analyzed regarding resolution, SNR, CNR, and radiomic features. To facilitate comparison, bias field correction was applied, and the data were standardized to the same scale using Z-score normalization. Descriptive and inferential statistical methods were used to analyze the data. Results: The results show that there are significant differences between centers. Filtering and zero-padding significantly influence the resolution, SNR, CNR values, and radiomics features. Applying Z-score normalization has resolved variations in features sensitive to scale differences, but features reflecting dispersion and extreme values remain significantly different between scanners. Some feature differences may be resolved by analyzing the raw images in both centers. Conclusions: Variations arise due to different acquisition parameters and the differing quality and sensitivity of the equipment. In multi-center studies, acquiring raw images and then applying standardized post-processing methods across all images can enhance the robustness of results. This approach minimizes technical differences, and preserves the integrity of the information, reflecting a more accurate representation of reality and contributing to more reliable and reproducible findings. Full article

Currently, the demand for environmental sustainability options in the construction industry is increasing, especially those related to the correct use of water. The aim of this work is to study different sustainable alternatives that minimize the use of water in cured hydraulic concrete, analyzing the effect of curing on hydration, microstructure, and compressive strength of hydraulic concrete exposed to different curing techniques: Manual Curing, Standard Curing, Vinipel, and Uncured. An experimental study was conducted using 180 cylindrical hydraulic concrete specimens, which were compression-tested at 7, 28, and 56 days. A Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer analysis was carried out to examine the microstructural and compositional changes under the different curing techniques. The results indicate that the Vinipel technique is the best alternative, showing a compressive strength of 35 MPa after 56 days of curing. In general, Vinipel > Standard Curing > Manual Curing > Uncured is the order of strength from highest to lowest. The formation of hydration products was observed in all curing techniques. The presence of ettringite, complementing by abundant portlandite in Vinipel, shows the dominance of an important product in the strength of concrete. The best strength capacity under load and the lowest percentages of vacuum are likely to be favorable for the durability of the processes. Full article

This paper presents the results of the analysis of the redistribution of cesium-137 (¹³⁷Cs) in the bottom sediments of beaver ponds in two small rivers in the forest-steppe north of the Volga Upland, which is one of the most contaminated areas of the Middle Volga region (European Russia) with artificial radionuclides. This study is based on fieldwork materials, laboratory analyses of the specific radioactivity of ¹³⁷Cs in soil and bottom sediment samples, their granulometric composition, and the content of organic matter in them. The obtained results indicate a significant decrease in the specific activity of ¹³⁷Cs in the direction from near-water-divide surface soils (on average, 54 Bq/kg) to the bottom sediments of beaver ponds of the studied rivers (on average, no more than 6 Bq/kg). A weak (statistically insignificant) tendency towards a decrease in the specific activity of ¹³⁷Cs in the bottom sediments of beaver ponds downstream of rivers was also revealed. With this detected trend, no statistically significant relationship was found between changes in ¹³⁷Cs and changes in the granulometric composition of bottom sediments. However, a relatively good relationship was identified with changes in the content of total organic matter. The stage-by-stage accumulation of sediment thickness in one of the beaver ponds was revealed, with the highest concentration of ¹³⁷Cs in the layer with the highest content of finely dispersed fractions and organic matter. The obtained results indicate that for a correct quantitative assessment of the migration of pollutants (including radioactive ones) in floodplain-channel systems, it is necessary to consider beaver structures (primarily ponds), which act as zones of their intensive accumulation. Full article

In marine remote sensing, underwater images play an indispensable role in ocean exploration, owing to their richness in information and intuitiveness. However, underwater images often encounter issues such as color shifts, loss of detail, and reduced clarity, leading to the decline of image quality. Therefore, it is critical to study precise and efficient methods for assessing underwater image quality. A no-reference multi-space feature fusion and entropy-based metrics for underwater image quality assessment (MFEM-UIQA) are proposed in this paper. Considering the color shifts of underwater images, the chrominance difference map is created from the chrominance space and statistical features are extracted. Moreover, considering the information representation capability of entropy, entropy-based multi-channel mutual information features are extracted to further characterize chrominance features. For the luminance space features, contrast features from luminance images based on gamma correction and luminance uniformity features are extracted. In addition, logarithmic Gabor filtering is applied to the luminance space images for subband decomposition and entropy-based mutual information of subbands is captured. Furthermore, underwater image noise features, multi-channel dispersion information, and visibility features are extracted to jointly represent the perceptual features. The experiments demonstrate that the proposed MFEM-UIQA surpasses the state-of-the-art methods. Full article

The Split-Hopkinson pressure bar (SHPB) test is a commonly accepted experiment to investigate the material behavior under high strain rates. Due to the low impedance of soft materials, here, the test has to be performed with plastic bars instead of metal bars. Such plastic bars have a certain viscosity and require a correction of the measured signals to account for the attenuation and dispersion of the transmitted waves. This paper presents a signal correction method based on a spectral decomposition of the strain-wave signals using Fast Fourier Transform and additional applied strain gauges in the experimental setup. The concept can be used to adapt the pulses and to concurrently validate the measurement method, which supports the evaluation of the experiment. Our investigation is carried out with a Split-Hopkinson pressure bar setup of PMMA bars and silicon-like specimens produced by the 3D printing process of digital light processing. Full article