We describe a novel theoretical approach to the bimolecular nucleophilic substitution (SN2) reactions that is based on analytical potential energy surfaces (PESs) obtained by fitting a few tens of ...thousands high-level ab initio energy points. These PESs allow computing millions of quasi-classical trajectories thereby providing unprecedented statistical accuracy for SN2 reactions, as well as performing high-dimensional quantum dynamics computations. We developed full-dimensional ab initio PESs for the F– + CH3Y Y = F, Cl, I systems, which describe the direct and indirect, complex-forming Walden-inversion, the frontside attack, and the new double-inversion pathways as well as the proton-transfer channels. Reaction dynamics simulations on the new PESs revealed (a) a novel double-inversion SN2 mechanism, (b) frontside complex formation, (c) the dynamics of proton transfer, (d) vibrational and rotational mode specificity, (e) mode-specific product vibrational distributions, (f) agreement between classical and quantum dynamics, (g) good agreement with measured scattering angle and product internal energy distributions, and (h) significant leaving group effect in accord with experiments.
Medicinal thermal waters consist of a mixture of different organic and inorganic compounds. Traditionally, these waters are only characterized and classified by their inorganic composition; however, ...the bioavailability of the majority of these inorganic compounds is limited. Many authors investigate the organic fractions of thermal waters. These authors propose that these compounds have a potential effect on health. To elucidate the underlying mechanisms, it is crucial to know the composition of the organic fractions. The absorption of these compounds on intact skin or mucosa is notable. Some of them have local anaesthetic effect or affect receptors in the central nervous system. In the knowledge of the chemical composition, we are able to estimate the possible pharmacological effect or might be able to assess possible toxicity risks. In the present article, we aim to review possible health effects of two of the identified organic fractions: benzene and alkylbenzenes and phenolic compounds that might correlate with the therapeutic effect on rheumatological or other diseases.
In the past few years, there has been a significant development in freshwater microplastic research. Pollution has been detected in lakes and rivers of several continents, but the number of papers is ...still marginal compared to the ones investigating marine environments. In this study, we present the first detection of microplastics (MPs) in Central and Eastern European (CEE) surface waters and, globally, the first detection in fish ponds. Samples were taken from different types of fish ponds and natural water bodies along a novel concept down to a particle size of 100 μm, then, after sample preparation, MPs were characterized using an FTIR microscope. 92% of the water samples contained MPs ranging from 3.52 to 32.05 particles/m3. MPs were detected in 69% of the sediment samples ranging from 0.46 to 1.62 particles/kg. Dominant abundance of polypropylene (PP) and polyethylene was shown in water and PP and polystyrene in sediment samples. First results also indicate that fish ponds may act as a deposition area for MPs.
•First detection of microplastics in fish ponds and in Central and Eastern Europe.•New sampling system was developed, collecting particles down to 100 μm.•Concentrations of MPs in pond outlets were always lower compared to the inlets.•Dominance of polyethylene, polypropylene and polystyrene was confirmed by FTIR.•Microplastic concentrations of sediments were much below the international results.
Comparing the scientific output of different researchers applying for a grant is a tedious work. In Hungary, to help reviewers to rapidly rank the scientific productivity of a researcher, a grant ...decision support tool was established and is available at www.scientometrics.org. In the present study, our goal was to assess the impact of this decision support tool on grant review procedures.
The established, publicly available scientometric portal uses four metrics, including the H-index, the yearly citations without self-citations, the number of publications in the last five years, and the number of highly cited publications of a researcher within eleven independent scientific disciplines. Publication-age matched researchers are then ranked and the results are provided to grant reviewers. A questionnaire was completed by reviewers regarding utilization of the scientometric ranking system. The outcome of the grant selection was analyzed by comparing scientometric parameters of applying and funded applicants. We compared three grant allocation rounds before to two grant allocation rounds after the introduction of the portal.
The scientometric decision support tool was introduced in 2020 to assist grant selection in Hungary and all basic research grant applicants (n = 6,662) were screened. The average score of funded proposals compared to submitted proposals increased by 94% after the introduction of the ranking. Correlation between ranking scores and actual grant selection was strong in life and material sciences but some scientific panels had opposite correlation in social sciences and humanities. When comparing selection outcome to H-index across all applicants, both type I and type II errors decreased. All together 540 reviewers provided feedback representing all eleven scientific disciplines and 83.05% of the reviewers (especially younger reviewers) found the ranking useful.
The scientometric decision support tool can save time and increase transparency of grant review processes. The majority of reviewers found the ranking-based scientometric analysis useful when assessing the publication performance of an applicant.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Despite its importance in chemistry, the microscopic dynamics of bimolecular nucleophilic substitution (SN2) reactions is still not completely elucidated. In this publication, the dynamics of a ...prototypical SN2 reaction (F– + CH3Cl → CH3F + Cl–) is investigated using a high-dimensional quantum mechanical model on an accurate potential energy surface (PES) and further analyzed by quasi-classical trajectories on the same PES. While the indirect mechanism dominates at low collision energies, the direct mechanism makes a significant contribution. The reactivity is found to depend on the specific reactant vibrational mode excitation. The mode specificity, which is more prevalent in the direct reaction, is rationalized by a transition-state-based model.
A high-performance liquid chromatographic method was developed for the simultaneous determination of the related substances-three potential synthesis-related chemical impurities and the distomer-of ...escitalopram. The separation capacity of seven different polysaccharide-type chiral columns, including three amylose-based (Lux Amylose-1, Lux i-Amylose-1, Lux Amylose-2) and four cellulose-based columns (Lux Cellulose-1, Lux Cellulose-2, Lux Cellulose-3, and Lux Cellulose-4) were screened in the polar organic and reversed-phase modes. Lux Cellulose-1, based on cellulose tris(3,5-dimethylphenylcarbamate) as the chiral selector with an acetonitrile-water mixture containing 0.1% diethylamine was identified as the most promising separation system. Using the "one factor at a time" optimization approach, the effect of column temperature, flow rate, and mobile phase constituents on separation performance was evaluated, and the critical resolution values were determined. A U-shaped retention pattern was obtained when plotting the retention factors of the citalopram enantiomers versus the water content of the binary mobile phases on the Lux Cellulose-1 column. A thermodynamic analysis revealed enthalpy-driven enantioseparation in both the polar organic and reversed-phase modes. For further method optimizations, an L9 orthogonal array table was employed. Using the optimized parameters (Lux Cellulose-1 column with 0.1% (
/
) diethylamine in water/acetonitrile 55/45 (
/
); 0.8 mL/min flow rate at 25 °C), baseline separations were achieved between all compounds. Our newly developed HPLC method was validated according to the ICH guidelines and its application was tested with a commercially available pharmaceutical formulation. The method proved to be suitable for routine quality control of related substances and the enantiomeric purity of escitalopram.
•The microstructure of the NanoShuttle™-PL was characterized with TEM, STEM and MFM and Raman spectroscopy.•A lognormal particle size distribution was found, and the clustering of the magnetic ...nanoparticles was observed.•The VSM measurements have shown a marked difference for the liquid and dried out samples.
Magnetic nanoparticles have several promising biomedical applications. One example is the magnetic nanoparticle-based hyperthermia, where the magnetic nanoparticles absorbed by the tumor cells are subjected to alternating magnetic field to generate local heating. Other applications rely on the effect of static magnetic fields to collect or rearrange cells, which are covered with magnetic nanoparticle containing substrates. In both cases, the effect of clustering largely modifies the magnetic properties of these materials. In the present study, we have examined the commercially available multicomponent material, NanoShuttle™-PL (Greiner Bio-One) particles composed of gold, iron oxide and poly-L-lysine, which are used for the creation of levitated 3D cell cultures. While this material is often used for cell culture studies, there is no available data on its magnetic and structural properties. The aim of the study was to understand the magnetic properties of this composite material based on the characterisation of the size distribution and clustering of the magnetic nanoparticles. We have performed RAMAN, AFM/MFM measurements and SEM/STEM investigation of the composite material. Magnetic properties were investigated with a vibrating sample magnetometer (VSM) both in the liquid state and in the surface extracted form.
In this study, a deep transfer learning model was developed using ResNet-101 architecture to diagnose double roller bearing defects. Vibration data were collected for three different load scenarios, ...including conditions without load, and for five different rotational speeds, ranging from 500 to 2500 RPM. Significantly, the speed condition of 2500 RPM has not previously been investigated, therefore offering a potential avenue for future investigations. This study offers a thorough examination of bearing conditions using multidirectional vibration data collected from accelerometers positioned in both vertical and horizontal orientations. In addition to transfer learning using ResNet-101, four additional models (VGG-16, VGG19, ResNet-18, and ResNet-50) were trained. Transfer learning using ResNet-101 consistently achieved the highest accuracy in all scenarios, with accuracy rates ranging from 90.78% to 99%. Scattergram Filter Bank 1 was used as the image input for training as a preprocessing method to enhance feature extraction. Research has effectively applied transfer learning to improve fault diagnosis accuracy, especially in limited data scenarios. This shows the capability of the method to differentiate between normal and faulty bearing conditions using signal-to-image transformation, emphasizing the potential of transfer learning to augment diagnostic performance in scenarios with limited training data.
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