Pure Form Research Articles

Weber–Maxwell electrodynamics: classical electromagnetism in its most compact and pure form

ABSTRACT Weber–Maxwell electrodynamics is a modernized, compressed, cleansed and, in many respects, advantageous representation of classical electrodynamics that results from the Liénard-Wiechert potentials. In the non-relativistic domain, it is compatible with both Maxwell’s electrodynamics and Weber electrodynamics. It is suitable for all electrical engineering tasks, ranging from electrical machines to radar and high-frequency technologies. Weber–Maxwell electrodynamics also simplifies access to quantum physics and other areas of modern physics, such as optics and atomic physics. Particular advantages of Weber–Maxwell electrodynamics are its simple and fast computability in computer calculations and, as it is based on point charges, in the simulation of plasmas. The latter is particularly important for fusion research. Moreover, Weber–Maxwell electrodynamics is also highly suited to academic and post-primary education, as it allows an easy comprehension of both magnetism and electromagnetic waves. Due to the novelty of Weber–Maxwell electrodynamics, there are currently no articles that summarize its most important aspects. The present article aims to achieve this.

Green and sensitive detection of olopatadine in aqueous humor using a signal-on fluorimetric approach: GREEnness assessment.

Olopatadine (OLP) is widely utilized as an effective antihistaminic drug for alleviating ocular itching associated with allergic conjunctivitis. With its frequent usage in pharmacies, there arises a pressing need for a cost-effective, easily implementable, environmentally sustainable detection method with high sensitivity. This study presents a novel signal-on fluorimetric method for detecting OLP in both its pure form and aqueous humor. The proposed approach depends on enhancing the weak intrinsic fluorescence emission of OLP, achieving a remarkable increase of up to 680% compared to its intrinsic fluorescence. This enhancement is achieved by forming micelles around protonated OLP using an acetate buffer (pH 3.6) and incorporating a solution of sodium dodecyl sulfate (SDS) surfactant. A strong correlation (R = 0.9996) is observed between the concentration of OLP and fluorescence intensities ranging from 1.0 to 100.0 ng mL-1 with a limit of detection of 0.22 ng mL-1. This described method is successfully employed for quantifying OLP in both its powder form and pharmaceutical eye drops. Furthermore, it demonstrates robust performance in determining OLP in artificial aqueous humor with a percentage recovery of 99.05 ± 1.51, with minimal interference from matrix interferents. Moreover, the greenness of the described method was evaluated.

Mixed Endometrioid Clear Cell Carcinoma of the Ovary: A Case Report

Background: Despite the high percentage of pure forms of epithelial ovarian cancers (EOC), mixed epithelial cancer of the ovary is extremely rare and accounts for less than 1% percent of all epithelial ovarian cancers. Because of the low prevalence; there are only a few cases of mixed epithelial cancers published in the literature. This study presents the case of a mixed endometrioid (EC)/clear cell carcinoma (CCC), diagnosed in a woman with a complaint of low back pain and a history of infertility. Case Report: We report the case of a 35-year-old woman who came to our clinic complaining of progressive back pain and a history of infertility. Imaging showed a left ovarian mass that was compatible with malignant tumors. The patient underwent open surgery and a frozen section evaluation of the tumor was done during the operation. The pathology result demonstrated mixed CCC/EC histology in the left ovary. We decided to perform a total abdominal hysterectomy as well as right salpingooophorectomy, omentectomy, bilateral pelvic lymphadenectomy, and para-aortic lymphadenectomy. Adjuvant chemotherapy was administrated postoperatively. Conclusion: Although epithelial cancers account for more than 90% of all ovarian cancers (OC), developing mixed forms of epithelial cancers is extremely rare, and there are little data available in the literature about their presentation and histopathological features. The main purpose of this article was to report a mixed CCC/EC and to discuss different aspects of this rare histologic type of OC. More research is needed to determine metastatic potential as well as the likelihood of recurrence of these unique neoplasms.

Eco-friendly preparation of nickel cobaltite as an electrode material in sustainable energy storage devices

In this study, urchin and tremella-like NiCo2O4 was synthesised by adopting a facile hydrothermal method using green solvents (water and ethanol). Using different ratios and pure forms of green solvents has a direct impact on materials synthesised. Ethanol based NiCo2O4 (NCO-E) illustrated tremella like microspheres with a specific surface area of 260.8 m2 g−1. The electrochemical performance confirmed that the NCO-E has a maximum specific capacitance of 2271 F g−1 at a current density of 1 A g−1. Further, as-fabricated NCO-E//AC-ASC device delivers a Cs value of 96.6 F g−1 at 1 A g−1 and a cyclic stability of 99.68 % over 5000 cycles. The device exhibited a high energy density of 30.19 Wh kg−1 at a power density of 749.48 W kg−1 and a high power density of 7542.61 W kg−1 at energy density 18.43 Wh kg−1 owing to the working electrode's effective electrochemical usage and excellent ion transfer mechanism.

INFLUENCE OF ULTRAFINE PARTICLES OF SILICON IV OXIDE (SiO2) AND OAK BARK EXTRACT ON BACTERIAL LUMINESCENCE

Background. Phytobiotic additives and ultrafine particles (UFP), especially of metallic nature, are increasingly used in agriculture as fertilizers and components of feed additives. However, there is very little data about the effect of non-metallic UFP. In particular, silicon-containing UFP have shown high efficiency as plant growth stimulators under stress conditions, but whether they can act as antibacterial agents or as protective agents in microbial ecosystems is unknown. Therefore, the aim of the presented work is to evaluate positive and negative reactions of the model luminescent microorganism Escherichia coli K12 TG1 when exposed to suspensions of silicon IV oxide (SiO2) in various concentrations both in pure form and in combination with phytobiotic additive – oak bark extract. Materials and methods. The luminescence intensity of the recombinant strain of Echerichia coli of the natural marine microorganism Photobacterium leiongnathi with cloned luxCDABE-genes under the influence of concentrations (0.5-0.00024 M) of UFP SiO2 and aqueous extract of oak bark (2-1024 multiples) was studied. Results. It was found that UFP in pure form stimulate bacterial luminescence by 252.2 % with respect to the control in the stationary phase of growth at 0.5 mol/L. They also act as protectors of intracellular metabolism, reducing the inhibitory effect of oak bark extract. The latter in pure form suppresses more than 50 % of bacterial luminescence up to 4-fold dilution (12.5 mg/mL), which determines the possibility of its use as an alternative to antibiotic drugs. Conclusion. UFP SiO2 have pronounced protective properties with respect to microbial community.

ChlorTox scale assessment, greenness, and whiteness evaluation of selective spectrophotometric analysis of dimenhydrinate and cinnarizine

Nausea and vomiting are considered common series side effects induced by chemotherapy treatment in cancer patients. This annoying side effect can impair the patient’s compliance to cancer treatment and affect their quality of life. Dimenhydrinate and cinnarizine in combined pharmaceutical dosage form is used to control chemotherapy induced nausea and vomiting in cancer patients. For safety, selective spectrophotometric methods based on novel dual resolution strategies were introduced to estimate dimenhydrinate and cinnarizine in presence of their harmful impurities namely benzophenone and 1- (diphenylmethyl)piperazine, respectively. These methods namely, dual ratio difference (DRD), dual ratio extraction (DRE) and dual absorbance extraction coupled with dual ratio extraction (DAE-DRE) were successfully performed to simultaneously analyze the drug of interests dimenhydrinate and cinnarizine in their pure form, synthetic mixtures and in market dosage form. Linearity ranges were 6.0–60.0 μg/mL and 3.0–30.0 μg/mL for dimenhydrinate and cinnarizine, respectively with good recovery% of Mean ± SD for all the proposed methods 99.82 ± 0.48, 99.79 ± 0.40, 100.14 ± 0.82, 100.03 ± 0.69, respectively. ICH guidelines were adhered in accordance with confirming validation of the proposed methods where fulfilling results were accomplished. Various unified greenness and whiteness assessment tools, such as the chlorTox scale, greenness index via spider chart, AGREE (The Analytical Greenness Metric), green certificate, and the RGB12 algorithm were employed in this research to assess the greenness and sustainability of the introduced UV-spectrophotometric methods in comparison to the reported HPLC method. As a result, these methods hold significant potential for utilization in the quality control department of pharmaceutical companies, contributing to enhanced pharmaceutical product analysis and overall sustainability practices.

The effect of intracisternal administration of hyaluronidase on the body of cattle

The aim of the research was to determine the magnitude of the irritant effect on breast tissue and the morphobiochemical composition of blood in lactating cows with a single intracisternal administration of hyaluronidase. To do this, 1,280 units of hyaluronidase prepared in 10 ml of 0.9% sodium chloride solution were injected once into the posterior right quarter of the experimental group (n=10). The first heifers of the control group (n = 10) received a saline solution in its pure form. Before and after the administration of the drugs, the electrical conductivity and concentration of somatic cells in milk were determined (by the viscometric method), as well as the morphobiochemical composition of blood was studied. It was found that 12 hours after the introduction of the enzyme, the electrical conductivity of the secretion decreased by 7.6% (P ≤ 0.05), and after the first day it was completely restored to its initial values. The dynamics of the level of somatic cells 6 and 12 hours after the application of hyaluronidase in 40% of animals was characterized by values above 500 thousand / ml, and the average concentration of cells increased by 3 times. After the first and second days, the level of inflammatory reaction cells decreased by 2.0...2.5 times, relative to peak values. After 72 hours, the cell content in the secret decreased by 2.8 times in relation to the values obtained after 6 hours and by 27.7% in relation to the values established a day after the application of hyaluronidase, and did not significantly differ from the indicators before the introduction of the enzyme. The use of the drug did not significantly affect the morphobiochemical parameters of the blood of experimental animals. Thus, a single intracisternal administration of 1280 units of hyaluronidase to lactating cows is accompanied by a slight and short-term irritating effect on udder tissue, which allows further studies of this drug in the pharmacocorrection of breast pathologies.

Analytical method development and validation for simultaneous estimation of Bempedoic acid and Ezetimibe in pure and its pharmaceutical dosage form by RP-HPLC.

A simple, accurate and precise method was developed for the simultaneous estimation of the bempedoic acid and ezetimibe in pure and tablet dosage form. The developed method was validated as per International Conference on Harmonization guidelines. The chromatographic separation was achieved isocratically on a Waters- C18, 250 × 4.6mm, 5μm column. Mobile phase containing K2HPO4-methanol in the ratio 60:40 in buffer at pH 4.3 was pumped through column at a flow rate of 1.0ml/min. The temperature was maintained at 25°C. The optimized wavelength selected was 242 nm. The separation of bempedoic acid and ezetimibe showed retention times of 3.090 and 4.268 min respectively. The RSD values of the bempedoic acid and ezetimibe were 0.34 and 0.08 respectively. The accuracy of method was determined at three levels (50,100 and 150%). The percentage recovery was obtained as 100.0 and 100.0% for bempedoic acid and ezetimibe, respectively. The limits of determination and quantitation obtained from regression equations of bempedoic acid and ezetimibe were 1.065, 3.550 and 0.203, 0.677, respectively. The regression equation of bempedoic acid is y = 20,795x + 24,168, and it is y = 6,885.7x + 11,000 for ezetimibe. The retention times were decreased and the run time was decreased, so that the method developed is simple and economical that can be adopted for regular quality control tests in industry.

Amphoteric SnO2 nanoparticles via pH-controlled continuous flow solvothermal synthesis

Amphoteric oxides can be challenging to produce in phase pure form due to their sensitivity to the pH of the reaction mixture. The high-pressure, high-temperature reaction conditions of hydrothermal processes make the pH difficult to control. Here we report a simple approach to obtain nanoparticles of amphoteric oxides, where cheap metal nitrate precursors are reacted in alcohol (2-propanol) water mixtures (25 vol%:75 vol%) to maintain a neutral pH under solvothermal conditions. Phase pure SnO2 nanoparticles were synthesized in a continuous flow solvothermal reactor at 250 °C, 300 °C, 350 °C and 400 °C with sizes ranging from 3 nm to 7 nm. The nanoparticles were characterized using powder X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, 119Sn MAS NMR spectroscopy, Brunauer-Emmett-Teller nitrogen adsorption, UV–VIS, and as anode material in CR2032 Li-ion battery cells. To demonstrate generality, amphoteric oxides ZnO, Bi2O3, Cr2O3 and γ-AlOOH were also synthesized.

Simultaneous Determination of Pyridoxine HCl, Isoniazid, Trimethoprim and Sulfamethoxazole by Double Divisor Ratio Spectra Derivative Spectroscopic Method

Tuberculosis could be regarded as a serious and enduring menace to global health. A significant hurdle in tuberculosis treatment lies in drug resistance, including the emergence of multiple drug resistance. A regulatory agency has recently endorsed the fixed-dose combination of pyridoxine HCl, isoniazid, trimethoprim, and sulfamethoxazole as a robust therapy for cases of tuberculosis resistant to multiple drugs. Therefore, a successful attempt was made to develop and validate a novel spectroscopic method, i.e., double deviation ratio spectra derivative spectroscopic method, for the simultaneous determination of pyridoxine HCl, Isoniazid, trimethoprim, and sulfamethoxazole in their pure form. The optimized divisor concentration in the developed method was found to be a mixture of 6 μg/mL of sulfamethoxazole and 16 μg/mL of pyridoxine HCl for the determination of isoniazid and trimethoprim in the same quaternary mixture. Similarly, the optimized divisor concentration for the determination of sulfamethoxazole and pyridoxine HCl was found to be a mixture of isoniazid and trimethoprim with concentrations of 10 and 12 μg/mL, respectively. With the developed method, the linearity for pyridoxine HCl, isoniazid, trimethoprim, and sulfamethoxazole was found to be in the range of 8 to 40 μg/mL, 10 to 30 μg/mL, 12 to 36 μg/mL, and 4 to 12 μg/mL, respectively. The results of the accuracy study, in terms of percentage recovery, were found to be 99.92 ± 0.978, 100.04 ± 1.731, 99.87 ± 1.811, and 98.83 ± 0.922 for the simultaneous determination of pyridoxine HCl, isoniazid, trimethoprim, and sulfamethoxazole, respectively, using the developed method. The developed method has been successfully validated as per the ICH guidelines.

Plasma-Activated Tap Water with Oxidative Potential Has an Inactivating Effect on Microbiological Contaminants in Aqueous Suspensions.

Plasma-activated water (PAW) generated from tap water has gained attention as a disinfectant when used directly in its pure form. Little is known about the application of PAW for bacterial inactivation in aqueous environments because its use in fluids results in dilutions. We investigated the effect of PAW in aqueous suspensions simulating such dilutions, and we focused on the minimal addition of PAW volumes to bacterial aqueous suspensions still resulting in high inactivation rates. The antimicrobial effect was highly dependent on the activation of PAW. An increase in activation power from 90 to 100 W resulted in a greater microbial reduction with an identical 10 min activation time. The susceptibility to PAW dilutions was analyzed in detail regarding nine Gram-negative species out of Enterobacterales and other waterborne microorganisms as well as four Gram-positive species present in two different matrices, in saline and in tap water, at high concentrations simulating massive contamination situations. For this purpose, the PAW activation setting of 90 W and 30 min was defined in order to be able to differentiate the limitations of inactivation in individual bacterial species. The Gram-negatives in saline demonstrated susceptibility when one volume unit of PAW was added. However, twice the PAW volume was necessary for inactivation when bacteria were present in tap water. Gram-positive microorganisms were more robust, indicated by prolonged contact times before inactivation. Our results indicate that PAW can be used for bacterial decontamination processes in aqueous environments when added in surplus. Optimized activation settings such as electric power to generate PAW and the contact times to the samples increase the effect of the inactivation a wide range of bacteria, regardless of their resistance profiles.

ReqNet and ReqSim: A Network and Semantic Similarity Dataset of Requirements from the Tree Structure of System Requirement Specifications

Abstract Systems are developed as a solution to the problem space defined by their requirements. The requirements are acquired during the elicitation process. The creative nature of the elicitation process, proprietary nature of requirements, the need of extensive preprocessing and the diverse techniques for analysis restricts the development of a requirement dataset. There exists no standard method to create a requirement dataset. Thus, we devise a semi-formal method to create a multi-purpose requirement dataset that harnesses human knowledge in the system requirement specification documents (SyRSDs) to facilitate the deployment of modern computing algorithms. Our dataset has three forms. (1) ReqList, a list of requirements from 86 distinct systems with their document structure in pure text form. The 12701 requirements are ready to leverage natural language processing techniques and unsupervised machine learning techniques. (2) ReqNet, a large network of requirements consisting of 17375 nodes to deploy graph-theoretic algorithms for requirement engineering. ReqNet portrays small-world network characteristics with an average distance of 9.5619 links. (3) ReqSim, a dataset consisting of 10933 pairs of requirements annotated with their similarity scores. ReqSim enables sentence-level supervised learning tasks to exploit the semantics of requirements. The similarity scores are coherent with human knowledge. Our dataset is grounded by the tree structure of SyRSDs. We devise a method to extract a tree from the SyRSDs. The tree structure resonates with the hierarchical nature of the requirement allocation process. The ReqList, ReqNet and ReqSim dataset is available at https://github.com/ChandanKSahu/ReqList_ReqNet_ReqSim.

In-depth metabolite characterization of seaweed-based plant biostimulants: Insights into bioactive components

Biostimulants derived from Kappaphycus alvarezii are renowned for sustainable agricultural enhancement, yet the exploration of numerous other tropical algae remains uncharted. This study aimed to unravel the metabolite diversity, bioactivities, and potential plant biostimulant properties of extracts derived from Kappaphycus alvarezii (KAE), Gracilaria debilis (GDE), and Sargassum cinctum (SCE). Two-year field trials showcased a significant boost in maize grain yields, indicating the biostimulant potential of each extract.Application of 7.5 % seaweed extract concentration substantially increased grain yields by 32 %, 29 %, and 31 % over the control for KAE, GDE, and SCE in the first-year trial and by 31 %, 28 %, and 32 % in the second year. Even a lower concentration of 2.5 % resulted in an increase in grain yield over the control. High-resolution chromatographic techniques coupled with tandem mass spectrometry (MS/MS) revealed 198, 202, and 191 compounds in KAE, GDE, and SCE, respectively. GC–MS profiling further unveiled 23, 21, and 12 metabolites, respectively. The extracts from red and brown seaweeds harbored distinct metabolites with low similarities to each other. These extracts contained a spectrum of compounds, including glycerol, glycine, valine, ellagic acid, cromakalim, genistein, 1,4-β-d-glucan, polyamines, n1-acetylspermine, mannose, propionic acid, benzoic acid, glycine, coumaric acid, hydroxycinnamic acids, and resveratrol. These compounds, known for their potent bio-stimulatory properties in various crops when applied exogenously in pure forms. This study transcends the conventional understanding of seaweed extract efficacy by shedding light on lesser-known metabolites which might have potential biostimulant roles. In contrast to the well-established components traditionally associated with seaweed extracts, this exploration highlights the need to test the biological activities of several other overlooked compounds spanning diverse classes.

Diastereodivergent Synthesis of A-Ring Lactones Derived from Cholesterol and Diosgenin: A Convenient Solution for an Old Problem – NMR and X-ray Characterization

AbstractA convenient protocol for the synthesis of A-ring lactones derived from cholesterol was developed. A lactone reduction–lactol separation–reoxidation sequence, applied to the inseparable mixture of diastereomeric lactones, allows the production of multigram amounts of each lactone in pure form. The same sequence applied to A-ring lactones derived from diosgenin produced similar results. A detailed NMR characterization of all the obtained lactones is also provided. X-ray diffraction corroborated the structure of the obtained compounds.

Exploring the electrocatalytic performance of silicene and single atom doped silicene for HER, OER and ORR activity using density functional theory

The transition towards hydrogen energy is paramount due to its potential to mitigate environmental pollution caused by fossil fuels. The greener and cleaner way of producing and utilizing hydrogen is through water electrolysis and hydrogen fuel cell where the sluggish reaction kinetics bottlenecks the widescale implementation. Hence, in this study, density functional theory (DFT) is utilized to study the HER, OER and ORR performance of pristine and doped silicene sheets where the dopants (B, C, N, Al and P) are introduced as single atom. The thermodynamical stability for pristine and doped sheets are confirmed with ADMP study and the cohesive energy for all the sheets are found to be around -4.2 eV per atom which validates their stability. The hydrogen evolution reaction (HER) performance of all the sheets is studied and the N doped silicene exhibits better catalytic property with a lowest overpotential of 70 mV and the C doped silicene shown good HER performance with an overpotential of 180 mV. In case of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), the pristine silicene is found to behave better in the ORR performance while the C doped silicene has the lowest overpotential compared with the other sheets. The variation in the catalytic performance is studied with the reactivity parameters which implies that the nucleophilic nature of the material enhances the HER performance. Furthermore, the results suggest that C doped silicene can be utilized as a bifunctional catalyst for the HER and OER performance. This study suggests that the silicene in the pure form as well as with dopant can be a good electrocatalyst for the water splitting and fuel cell application.

Carbon-based Flame Retardants for Polymers: A Bottom-up Review.

This state-of-the-art review is geared toward elucidating the molecular understanding of the carbon-based flame-retardant mechanisms for polymers via holistic characterization combining detailed analytical assessments and computational material science. The use of carbon-based flame retardants, which include graphite, graphene, carbon nanotubes (CNTs), carbon dots (CDs), and fullerenes, in their pure and functionalized forms are initially reviewed to evaluate their flame retardancy performance and to determine their elevation of the flammability resistance on various types of polymers. The early transition metal carbides such as MXenes, regarded as next-generation carbon-based flame retardants, are discussed with respect to their superior flame retardancy and multifunctional applications. At the core of this review is the utilization of cutting-edge molecular dynamics (MD) simulations which sets a precedence of an alternative bottom-up approach to fill the knowledge gap through insights into the thermal resisting process of the carbon-based flame retardants, such as the formation of carbonaceous char and intermediate chemical reactions offered by the unique carbon bonding arrangements and microscopic in-situ architectures. Combining MD simulations with detailed experimental assessments and characterization, a more targeted development as well as a systematic material synthesis framework can be realized for the future development of advanced flame-retardant polymers.

Synthesis and Inclusion Properties of a β-Cyclodextrin Heptaphosphoramidate.

In this study, we report a novel per-6-substituted β-cyclodextrin (4) featuring seven phosphoramidate moieties as an innovative host for inclusion. This structurally well-defined host has remarkable water solubility and was isolated in pure form. Analytical techniques such as NMR and ITC were used to probe the molecular interactions with different drug molecules. Our investigations revealed that host 4 can form 2:1 inclusion complexes with various drugs. Further studies showed that the inclusions of drugs by β-CD host (4) are mostly enthalpy driven, highlighting the potential roles played by the phosphoramidate functionalities of the host. Comparatively, a per-O2, O3-acetylated analog (6) of compound 4 was also obtained, which also shows unusual water solubility but diminished inclusion capability.

The Application of Cathodoluminescence (CL) for the Characterization of Blue Pigments

The combined application of Cathodoluminescence (CL) with Scanning Electron Microscopy (SEM) on paintings and painted surfaces has the potential to identify both organic and inorganic pigments on a micrometre or even nanometre scale. Additionally, the combination with Energy-Dispersive Spectrometry (EDS) allows for a more holistic, elemental, and mineralogical characterization of pigments. In addressing the need for the creation of a robust, open access database of characteristic CL spectra of pigments, a large project has been undertaken, focusing primarily on common organic and inorganic pigments. The present paper focuses on the CL characterization of 10 significant blue pigments in pure powder form: cerulean blue, Egyptian blue, Han blue, indigo, lapis lazuli, Maya blue, phthalo blue, vivianite, ultramarine blue, and zirconium blue. The CL spectra present characteristic bands for most of the pigments, allowing their secure identification, especially when combining the results with the EDS analyses. The effect of binding media and of the mixture of different pigments was also studied, via the analysis of mixtures of pigments with oil painted over canvas. Overall, both the binding medium and the mixture of pigments do not appear to create significant differences in the occurring spectra, thus allowing the identification of individual pigments. EDS and RAMAN spectra are included in order to facilitate comparison with other databases.

Iron Oxyhydroxide Transformation in a Flooded Rice Paddy Field and the Effect of Adsorbed Phosphate.

The mobility and bioavailability of phosphate in paddy soils are closely coupled to redox-driven Fe-mineral dynamics. However, the role of phosphate during Fe-mineral dissolution and transformations in soils remains unclear. Here, we investigated the transformations of ferrihydrite and lepidocrocite and the effects of phosphate pre-adsorbed to ferrihydrite during a 16-week field incubation in a flooded sandy rice paddy soil in Thailand. For the deployment of the synthetic Fe-minerals in the soil, the minerals were contained in mesh bags either in pure form or after mixing with soil material. In the latter case, the Fe-minerals were labeled with 57Fe to allow the tracing of minerals in the soil matrix with 57Fe Mössbauer spectroscopy. Porewater geochemical conditions were monitored, and changes in the Fe-mineral composition were analyzed using 57Fe Mössbauer spectroscopy and/or X-ray diffraction analysis. Reductive dissolution of ferrihydrite and lepidocrocite played a minor role in the pure mineral mesh bags, while in the 57Fe-mineral-soil mixes more than half of the minerals was dissolved. The pure ferrihydrite was transformed largely to goethite (82-85%), while ferrihydrite mixed with soil only resulted in 32% of all remaining 57Fe present as goethite after 16 weeks. In contrast, lepidocrocite was only transformed to 12% goethite when not mixed with soil, but 31% of all remaining 57Fe was found in goethite when it was mixed with soil. Adsorbed phosphate strongly hindered ferrihydrite transformation to other minerals, regardless of whether it was mixed with soil. Our results clearly demonstrate the influence of the complex soil matrix on Fe-mineral transformations in soils under field conditions and how phosphate can impact Fe oxyhydroxide dynamics under Fe reducing soil conditions.

Influence of heterochirality on the structure, dynamics, biological properties of cyclic(PFPF) tetrapeptides obtained by solvent-free ball mill mechanosynthesis

Cyclic tetrapeptides c(Pro-Phe-Pro-Phe) obtained by the mechanosynthetic method using a ball mill were isolated in a pure stereochemical form as a homochiral system (all L-amino acids, sample A) and as a heterochiral system with D configuration at one of the stereogenic centers of Phe (sample B). The structure and stereochemistry of both samples were determined by X-ray diffraction studies of single crystals. In DMSO and acetonitrile, sample A exists as an equimolar mixture of two conformers, while only one is monitored for sample B. The conformational space and energetic preferences for possible conformers were calculated using DFT methods. The distinctly different conformational flexibility of the two samples was experimentally proven by Variable Temperature (VT) and 2D EXSY NMR measurements. Both samples were docked to histone deacetylase HDAC8. Cytotoxic studies proved that none of the tested cyclic peptide is toxic.