Nitrogen Research Articles

Percutaneous cryoablation in soft tissue tumor management: an educational review

Abstract Background Percutaneous cryoablation (PCA), having shown effectiveness in treating liver, lung, prostate, breast, and kidney tumors, is now gaining attention for the treatment of soft tissue tumors. PCA functions by freezing tissue, which induces ice crystal formation and cell death without damaging collagen structures. Technical considerations include the selection and handling of cryoprobes and cryogenic agents, procedural duration, and choice of image guidance for precision. This review aims to synthesize the mechanisms, applications, and technical aspects of PCA in the treatment of soft tissue tumors. Methods Adhering to PRISMA 2020 guidelines, a review was conducted of studies published prior to March 2024 that investigated PCA of soft tissue tumors. The review focused on technical and procedural aspects of cryoablation, cryobiological principles, cellular and tissue responses to extreme cold, intra- and post-procedure physiological mechanisms during and post-procedure, and main clinical applications. Results PCA is efficient in treating soft tissue tumors, including desmoid tumors, vascular malformations, and abdominal wall endometriosis. Several cryobiological mechanisms are involved, notably ice crystal formation, cellular dehydration, osmotic effects, and the inflammatory response, all of which contribute to its efficacy. Key technical aspects include the choice of cryoprobes, cryogenic agents (argon gas or liquid nitrogen), and the duration and control of freezing/thawing cycles. PCA also frequently outperformed traditional treatments like surgery and radiotherapy in terms of pain reduction, tumor size reduction, and patient outcomes. Moreover, its nerve sideration properties make it effective under local anesthesia. Conclusion Demonstrating substantial pain reduction, tumor size decrease, and high technical success rates, PCA offers a promising and minimally invasive alternative for soft tissue tumor treatment. Critical relevance statement Percutaneous cryoablation provides a minimally invasive, precise alternative for soft tissue tumor management, advancing clinical radiology by offering effective treatment with reduced patient risk and enhanced outcomes through image-guided procedures. Key Points Percutaneous cryoablation (PCA) offers a promising, minimally invasive alternative for managing soft tissue tumors. PCA employs image-guided techniques to accurately target and treat tumors, ensuring high precision and control. PCA preserves structures like collagen, reduces pain, decreases tumor size, and generally enhances patient outcomes. Graphical Abstract

Oxynitrided Ti-6Al-4V Coatings Deposited by Twin Wire Arc Spray for Protection of Aluminum Die-Casting Molds

Abstract Steel molds used for aluminum die-casting often fail due to excessive wear or cracking phenomena associated with the soldering effect in contact with molten aluminum, which leads to the formation of iron-based intermetallic compounds and causes problems in the cast components. One solution is to apply protective coatings whose composition is less reactive with the molten aluminum and improve its hardness, toughness, wear, and corrosion resistance, thus prolonging its service life. This work evaluates the effectiveness of Ti-6Al-4V coatings deposited by twin wire arc spraying in an air or nitrogen atmosphere. Nitrogen was used as the carrier and shielding gas for the in-flight molten particles. Coatings were deposited by varying the stand-off distance, the nitrogen gas pressures, and the substrate temperature. The microstructure of the coatings is interlayered, one porous layer of dendrites and one highly densified layer. The presence of TiN, TiO2, α-Ti, and β-Ti phases was confirmed by different characterization methods. For instance, x-ray photoelectron spectroscopy measurements confirmed the presence of N-Ti, O-Ti, and N-O bonds, with the oxygen/nitrogen/titanium percentage associated with the formation of a non-stoichiometric (Ti, Al, V)NxOy phase. Finally, the reactivity of selected oxynitrided Ti-6Al-4V coating in contact with molten aluminum showed a low reaction rate compared to the coarse reaction layer suffered by the uncoated steel substrates.

Sources and Transformation of Nitrate in Shallow Groundwater in the Three Gorges Reservoir Area: Hydrogeochemistry and Isotopes

Nitrate is among the most widely occurring contaminants in groundwater on a global scale, posing a serious threat to drinking water supplies. With the advancement of urbanization and mountainous agriculture, the nitrate in the groundwater of Wanzhou District in the Three Gorges Reservoir Area has formed a complex combination of pollution sources. To more accurately identify the sources of nitrate in groundwater, this study integrates hydrochemical methods and environmental isotope techniques to analyze the sources and transformation processes in shallow groundwater nitrate under different land-use types. Furthermore, the Bayesian isotope mixing model (MixSAIR) is employed to calculate the contribution rates in various nitrate sources. The results indicate that nitrate is the primary form of inorganic nitrogen in shallow groundwater within the study area, with nitrate concentrations in cultivated groundwater generally higher than those in construction land and forest land. The transformation process of nitrate is predominantly nitrification, with little to no denitrification observed. In cultivated shallow groundwater, nitrate mainly originates from chemical fertilizers (36.3%), sewage and manure (35.4%), and soil organic nitrogen (24.7%); in forested areas, nitrate primarily comes from atmospheric precipitation (35.3%), chemical fertilizers (31.3%), and soil organic nitrogen (22.1%); while in constructed areas, nitrate mainly derives from chemical fertilizers (46.0%) and sewage and manure (32.2%). These results establish a scientific foundation for formulating groundwater pollution control and management strategies in the region and serve as a reference for identifying nitrate sources in groundwater in regions with comparable hydrogeological features and pollution profiles.

Plant organic nitrogen nutrition: costs, benefits, and carbon use efficiency.

Differences in soil mobility and assimilation costs between organic and inorganic nitrogen (N) compounds would hypothetically induce plant phenotypic plasticity to optimize acquisition of, and performance on, the different N forms. Here we evaluated this hypothesis experimentally and theoretically. We grew Arabidopsis in split-root setups combined with stable isotope labelling to study uptake and distribution of carbon (C) and N from l-glutamine (l-gln) and NO3 - and assessed the effect of the N source on biomass partitioning and carbon use efficiency (CUE). Analyses of stable isotopes showed that 40-48% of C acquired from l-gln resided in plants, contributing 7-8% to total C of both shoots and roots. Plants grown on l-gln exhibited increased root mass fraction and root hair length and a significantly lower N uptake rate per unit root biomass but displayed significantly enhanced CUE. Our data suggests that organic N nutrition is linked to a particular phenotype with extensive growth of roots and root hairs that optimizes for uptake of less mobile N forms. Increased CUE and lower N uptake per unit root growth may be key facets linked to the organic N phenotype.

Ag-Catalyzed Cyclization-Intermolecular Sulfinyl Group Transfer Cascade Reactions Enabling Enantioselective Synthesis of 4-Sulfinylisoquinolines.

N-Sulfinylimines derived from ortho-alkynylbenzaldehydes were efficiently converted into the corresponding 4-sulfinylisoquinolines in good to excellent yields. The reaction proceeds via cyclization followed by intermolecular migration of the sulfinyl group from the nitrogen atom to the silver-bound carbon of the resulting cyclized vinylsilver intermediate with the aid of either a counteranion or a nucleophilic species. Moreover, the Ag-catalyzed reaction in the presence of quinidine acetate as a chiral nucleophilic cocatalyst yielded chiral isoquinolines with high enantioselectivities through a dynamic kinetic asymmetric transformation (DYKAT).

The Electron‐Rich Interface Regulated MBene by S‐Bridge Guided to Enhance Nitrogen Fixation under Environmental Conditions

AbstractThe underutilization of active sites limits the performance enhancement of 2D transition metal boride (MBene) in electrocatalytic nitrogen reduction reaction (NRR). Herein, a highly efficient NRR electrocatalyst with S atoms bridging Fe and Mo atoms on the surface of MBene is successfully constructed by using an active site electron optimization strategy, which increases the charge density around the Mo active site and enhances the activation ability of the catalyst to N2 molecules. It is noteworthy that FeS2‐MBene demonstrates a low intrinsic potential for NRR (−0.2 V vs RHE). It is more favorable for the adsorption of nitrogen atoms in comparison to hydrogen atoms, thereby it can effectively inhibit the hydrogen evolution reaction (HER). Under a potential of −0.2 V versus RHE, the ammonia yield rate is 37.13 ± 1.31 µg h−1 mg−1, and the FE is 55.97 ± 2.63%. Density functional theory (DFT) calculations demonstrate that Mo on the surface of MBene serves as a site for the adsorption of N2. The formation of the heterostructure enhances electron transfer, resulting in the Mo active site becoming an electron‐rich state in favor of subsequent hydrogenation steps. This work offers significant insights into the design and utilization of 2D MBene‐based catalysts in NRR.

Antitumoral action of carvedilol–a repositioning study of the drug incorporated into mesoporous silica MCM-41

We have studied repositioning of carvedilol (an antihypertensive drug) incorporated into MCM-41 mesoporous silica. The repositioning proposes a reduction in the slow pace of discovery of new drugs, as well as toxicological safety and a significant reduction in high research costs, making it an attractive strategy for researchers and large pharmaceutical companies. We obtained MCM-41 bytemplatesynthesis and functionalized it by post-synthesis grafting with aminopropyltriethoxysilane (APTES) only or with folic acid (FA), which gave MCM-41-APTES and MCM-41-APTES-FA, respectively. We characterized the materials by scanning and transmission electron microscopy, zeta potential (ZP) measurements, Fourier transform infrared absorption spectroscopy, x-ray diffractometry, nitrogen gas adsorption, and CHNS elemental analysis. We quantified the percentage of drug that was incorporated into the MCM-41 materials by thermogravimetric analysis and evaluated their cytotoxic activity in non-tumor human lung fibroblasts and the tumor human melanoma and human cervical adenocarcinoma cell lines by XTT salt reduction (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-arboxanilide). The x-ray diffractograms of the MCM-41 materials displayed low-angle peaks in the 2θrange between 2° and 3°, and the materials presented type IV nitrogen adsorption isotherms and H2 hysteresis typical of the MCM-41hexagonal network. The infrared spectra, the charge changes revealed by ZP measurements, and the CHN ratios obtained from elemental analysis showed that MCM-41 was amino-functionalized, and that carvedilol was incorporated into it. MCM-41-APTES incorporated 23.80% carvedilol, whereas MCM-41 and MCM-41-APTES-FA incorporated 18.69% and 12.71% carvedilol, respectively. Incorporated carvedilol was less cytotoxic to tumor and non-tumor cells than the pure drug. Carvedilol repositioning proved favorable and encourages further studies aimed at reducing its cytotoxicity to non-tumor cells. Such studies may allow for larger carvedilol incorporation into drug carriers or motivate the search for a new drug nanocarrier to optimize the carvedilol antitumoral activity.

Structure-mutagenicity relationships on quinoline and indole analogues in the Ames test.

Although the in silico predictive ability of the Ames test results has recently made remarkable progress, there are still some chemical classes for which the predictive ability is not yet sufficient due to a lack of Ames test data. These classes include simple heterocyclic compounds. This study aimed to investigate the mutagenicity and structure-mutagenicity relationships for some heterocycles in the Ames test. In the present study, we selected 12 quinoline analogues containing one or two nitrogen atoms in the naphthalene ring and 12 indole analogues containing one to three nitrogen atoms in the indole ring, without any side moiety. The Ames test was performed with five standard bacterial strains (TA100, TA1535, TA98, TA1537, and WP2uvrA) using the pre-incubation method with and without rat liver S9. Five quinoline and two indole analogues were mutagenic. Among the five quinoline analogues, four were mutagenic in the presence of S9 mix with TA100, whereas cinnoline was mutagenic in the absence of S9 mix with TA1537. Among the two indole analogues, indazole was mutagenic in the presence and absence of S9 mix with WP2uvrA and 4-azaindole was mutagenic in the absence of S9 mix with TA1537. The mechanisms underlying the induction of mutagenesis appear to differ between quinoline and indole analogues. In addition, we performed in silico analysis of the mutagenicity of all these analogues using DEREK Nexus 6.1.1 (Lhasa Limited) and GT_EXPERT from CASE Ultra 1.8.0.5 (MultiCASE Inc.) as knowledge-based models and GT1_BMUT from CASE Ultra 1.8.0.5 (MultiCASE Inc.) as a statistical-based model. The knowledge-based model showed low sensitivity for both the quinoline and indole analogues (DEREK Nexus and GT_EXPERT: 20% for quinolines and 0% for indoles). Conversely, the statistical model showed high sensitivity (100% for both quinolines and indoles) and low specificity (43% for quinolines and 10% for indoles). Based on the Ames test results, we proposed structural alerts noting that quinoline analogues were mutagenic when they had nitrogens in any of the positions 2, 5, 7, or 8 in addition to 1, and indole analogues were mutagenic when they had nitrogens at positions 2 or 4 in addition to 1.

The Synergistic Optimization of Rice Yield, Quality, and Profit by the Combined Application of Organic and Inorganic Nitrogen Fertilizers

The replacement of urea with polymer-coated urea (PCU) fertilizer and the application of organic fertilizers (OFs) are effective strategies for reducing N loss in farmland and preventing soil degradation. However, limited research has been conducted on the synergistic effects of OF combined with inorganic N fertilizer, particularly PCU, on rice yield, quality, and profit. To address this issue, a two-year field experiment was conducted involving five fertilization treatments: no nitrogen fertilizer (0N), urea applied at the full local rate of 270 kg N ha−1 (CK), PCU at a reduced rate of 240 kg N ha−1 (T1), a combination of 70% PCU and 30% urea at 240 kg N ha−1 (T2), and T2 supplemented with 4500 kg ha−1 of OF (T3). The results showed that, compared with CK, the T1 treatment improved the appearance quality and taste value but slightly reduced the other quality indices. In contrast, the T2 and T3 treatments enhanced the grain yield, especially for T3, with an advantage in the tiller number, shoot dry weight, and leaf area index, which promoted the panicle number, filled grain, and grain weight, thereby significantly increasing the yield. The T2 improved the processing, appearance, and taste qualities by reducing the protein content, increasing the amylose content and gel consistency, and optimizing the starch viscosity characteristics (increasing the peak viscosity and breakdown while reducing the setback and consistency), with the addition of OF (T3) further expanding the benefits. Furthermore, the nutritional quality was also enhanced by optimizing the protein components and increasing the protein yield. Although the agricultural inputs in the T2 and T3 treatments were higher, the profit from the increased grain yield could cover these inputs, thereby maintaining profit with T3 or increasing profit with T2. In summary, the combined application of PCU with urea and OF can synergistically improve the rice yield, quality, and profit.

Impact of nano cerium oxide addition with pyrolysis waste plastic oil on combustion, performance and emission characteristics of CRDI diesel engine

Abstract This investigation examined the effect of incorporating cerium oxide (CeO2) nanoparticle into diesel and waste plastic oil (WPO) blends on the combustion, performance and emission characteristics of the diesel engine. The WPO was extracted from low density polyethylene using plastic pyrolysis. The blending of diesel and WPO with combination of D70:WPO30 and D50:WPO50 was prepared to evaluate the engine operation. Additionally, the spherical sized CeO2 with 50 mg/L and 100 mg/L was added with this blend. The various blends named as Diesel, D-WPO30, D-WPO30+Ce50, D-WPO30+Ce100, D-WPO50, D-WPO50+Ce50 and D-WPO50+Ce100 were used in this investigation to operate the engine under various load conditions. The experiment was performed using water cooled common rail direct injection (CRDI) diesel engine with prepared D-WPO blend. Different characteristics such as In-cylinder pressure (CP), heat release rate (HRR), ignition delay time (IDT), brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and exhaust gas temperature (EGT), carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx) and smoke opacity emission are studied with respect to the effect of different blends and applied load used. It was observed that increasing of CeO2 nanoparticles in blend improved the overall performance and emission of the engine. Form the results, D-WPO30+Ce100 blend showed enhanced brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and exhaust has temperature (EGT) are 28.2%, 3% and 465oC respectively. Similarly, reduced emission of CO, NOx, HC and smoke opacity was observed in the CeO2 added blends particularly at 100 mg/L. It was concluded that among all blends prepared, the D70:WPO30 with 100 mg/L of CeO2 showed improved combustion, performance and emission characteristics in proposed diesel engine.

Tailor‐Made Buffer Materials: Advancing Uniformity and Stability in Perovskite Solar Cells

AbstractAlong with the growing popularity of the p‐i‐n structure, bathocuproine (BCP) is increasingly recognized as a crucial buffer layer between the electron transport layer and electrode with the role of mitigating Schottky contact and enhancing performance. However, the chemical structure and role of its functional groups have not been thoroughly elucidated. This study introduces a novel modification of BCP in perovskite solar cells (PSCs) by altering functional groups to optimize their geometrical molecular structures and electronic properties. The substitution of aromatic phenyl and p‐tolyl groups to 2,9‐position on the BCP is highly effective in increasing the planarity of the conjugated backbone and protecting the reactive nitrogen atoms of the phenanthroline core, thereby improving charge transport and device stability. Experimental analyses, including electrostatic force microscopy, impedance spectroscopy, and photoluminescence, reveal that the modified BCP significantly enhances charge transport, reduces recombination losses, and markedly improves the structural stability of PSCs, leading to prolonged device lifetimes. The findings highlight the potential of structurally optimized BCP derivatives as a critical component in advancing high‐efficiency and durable PSCs.

Optimization of Superconducting Niobium Nitride Thin Films via High-Power Impulse Magnetron Sputtering

Abstract We report a systematic comparison of niobium nitride thin films deposited on oxidized silicon substrates by reactive DC magnetron sputtering and reactive high-power impulse magnetron sputtering (HiPIMS). After determining the nitrogen gas concentration that produces the highest superconducting critical temperature for each process, we characterize the dependence of the critical temperature on film thickness. The optimal nitrogen concentration is higher for HiPIMS than for DC sputtering, and HiPIMS produces higher critical temperatures for all thicknesses studied. We attribute this to the HiPIMS process enabling the films to get closer to optimal stoichiometry before beginning to form a hexagonal crystal phase that reduces the critical temperature, along with the extra kinetic energy in the HiPIMS process improving crystallinity. We also study the ability to increase the critical temperature of the HiPIMS films through the use of an aluminum nitride buffer layer and substrate heating.

Synthesis, Corrosion Inhibition, In Silico ADME, DFT, and Antibacterial Activity of Pyridine‐Based Schiff Base and Its Cu (II) Complex

ABSTRACTHerein, we report the synthesis of an (E)‐N‐(pyridine‐3‐ylmethylene)pyridine‐2‐amine Schiff base (ENppa) and its Cu (II) complex (Cu‐ENppa) using 2‐aminopyridine (2APy) and pyridine‐3‐carbaldehyde (P3C). This study aimed to investigate the ADMET profiles, electronic features, antibacterial and anticorrosion activities of the synthesized ligand, and its Cu (II) complex. The compounds were characterized using various techniques, including CHN analysis, FT‐IR, 1H and 13C NMR, MALDI‐TOF MS, ICP‐MS, SEM, TGA/DTA, UV–visible spectroscopy, and powder X‐ray diffraction (PXRD). The Cu (II) ion exhibited tetrahedral geometry in the complex by coordinating with two nitrogen atoms, one from an imine group and the other from a pyridine ring. UV–visible spectroscopy and magnetic moment data also supported this geometry. TGA/DTA revealed three stages of decomposition at 141°C°C–255°C, 255°C°C–367°C, and 549°C°C–659°C, with CuO as the final residue. PXRD analysis identified ENppa and Cu‐ENppa as nanocrystallites, with crystallinities of 82% and 49%, respectively. Both compounds were highly effective in inhibiting mild steel corrosion in acidic media, with inhibition efficiencies of 97% and 98%, respective for Cu‐ENppa and ENppa. They also exhibited favorable ADME profiles, indicating potential as drug candidates for in silico ADME studies. The antibacterial activity results demonstrated promising efficacy, with Cu‐ENppa showing higher activity than ENppa.

A distinctive bound exciton line induced by electron-beam irradiation and subsequent annealing of an unintentionally doped GaN layer

Abstract An undefined bound exciton line (UDX) with a photon energy 0.6 meV lower than the Si-donor bound exciton line was observed by photoluminescence in GaN layers annealed at 1100 °C after electron beam (EB) irradiation at an energy of 137–2000 keV. The UDX was not observed in samples not subjected to EB irradiation or annealing but was found in a sample annealed after EB irradiation at an energy of 137 keV, where only nitrogen atoms are displaced in GaN. The origin of the UDX was presumably formed by a thermal reaction of defects containing nitrogen-displacement-related defects.

Demystifying Synergistic Multifunctional Electrocatalysis of N-Doped Graphene/WS2 Heterostructure with Single-Atom Catalysts for Water Splitting and Fuel Cells.

As the demand for sustainable energy continues to rise, electrocatalysis has become increasingly prominent in the advancement of clean energy technologies. By scrutinizing the material to function as a multifunctional catalyst, the effectiveness of energy conversion processes is significantly enhanced. This study focuses on harnessing graphene/WS2 van der Waals heterostructures for overall water splitting and fuel cell applications, using transition metals (TMs) from Sc-Zn as single-atom catalysts (SACs). Additionally, the research explores the synergistic effect of nitrogen doping combined with SACs to modify the material into multifunctional catalysts. The stability of all TMs as SACs in the vdW heterostructure (TM@GW) and nitrogen-doped TM@GW (TM@NGW) is validated with negative cohesive and formation energies, and thermodynamic stability is also corroborated with ab initio molecular dynamics (AIMD) analysis at both 300 and 500 K for 5 ps. The observed electrocatalytic performance of TM@GW and TM@NGW depicts that the Ni@NGW system exhibits trifunctional property with the lowest overpotentials {ηHER; ηOER; ηORR = 0.21; 0.42; 0.27 V}. Additionally, the Cr@NGW material displays bifunctional catalytic activity for the OER and ORR, with overpotentials of 0.53 and 0.37 V, respectively. The synergistic effect between N doping and SACs is further studied with the d, p band centers and density of states calculations. Furthermore, the scaling relation between the adsorption of intermediates and reaction kinetics is studied, which validates the coaction of N and SACs in the TM@NGW heterostructure. This study demonstrates that the inclusion of SACs and nitrogen atoms in the GW heterostructure significantly enhances the catalytic performance by approximately 26%, effectively transforming the system into a multifunctional catalyst. These findings emphasize the role of SACs in vdW heterostructures and N doping effects, providing valuable insights to guide the design of advanced catalysts for water splitting and fuel cell applications.

Preparation, Purification, and Hydrophilization of Magnetic-Carbon Nanofibers

This study aims to synthesize, purify, and modify magnetic carbon nanofibers (Mag-CNF) into hydrophilic carbon material. The synthesis method was carried out by chemical vapor deposition (CVD) using the catalyst from Incolloy at 800°C with argon, nitrogen, hydrogen, and acetylene gases. The purification of Mag-CNF was then conducted by dissolving Mag-CNF with toluene and ethanol, followed by vacuum annealing. The hydrophilization of Mag-CNF was further performed by adding amine groups via reacting Mag-CNF with ethylene diamine, NaNO2, and H2SO4. The successfully prepared Mag-CNF has characteristics of tubular tube bundles consisting of carbon nanofibers with an average diameter of 100-120 nm. The X-ray diffraction (XRD) profile shows the characteristics of carbon, iron, iron oxide, and iron carbide. The Raman spectra show the existence of D, G, and G' bands corresponding to the characteristics of carbon nanomaterials. The magnetic property characterization using a vibration sample magnetometer (VSM) shows the synthesized product as ferrimagnetic materials. The modification results show the addition of hydrophilic groups to Mag-CNF, such as O–H and N–H groups, as analyzed in Fourier Transform Infrared (FTIR) spectra. The successful hydrophilization was also visually confirmed using a dispersion test in water, showing that Mag-CNF has better dispersion after surface modification.

A Systematic Review and Meta-Analysis of the Sustainable Impact of Sewage Sludge Application on Soil Organic Matter and Nutrient Content

The increasing scarcity of natural resources makes the linear production model unsustainable, highlighting the need for more sustainable practices under the umbrella of circular economic principles. Sewage sludge emerges as a promising solution to provide soil organic matter (SOM) and nutrients. This meta-analysis evaluated the impacts of three levels of sludge application (low, medium, and high) on organic matter (OM), nitrogen (N), phosphorus (P), copper (Cu), and zinc (Zn) contents, considering different areas and experimental conditions worldwide. The analysis included 37 studies and 355 comparisons, after screening 7625 records, following the 2020 PRISMA protocol. The effects of sludge concentrations, continents, and types of experiment (field or greenhouse) were evaluated. Sewage sludge application significantly increased OM, N, Cu, and Zn levels, mainly at medium and high rates. The largest effects were observed in greenhouses, suggesting variation by location and environment. Moderators explained a part of the variation in the results, but the residual heterogeneity test revealed that there is still unexplained variability.

Fe‐Catalyzed α‐C(sp3)−H Amination of N‐Heterocycles

AbstractNitrogen‐heterocycles are privileged structures in both marketed drugs and natural products. On the other hand, C−H amination reactions furnish unconventional and straightforward approaches for the construction of C−N bonds. Yet, most of the known methods rely on precious metal catalysts. Herein we report a site‐selective intermolecular C(sp3)−H amination of N‐heterocycles, catalyzed by inexpensive FeCl2, which allows the functionalization of a wide range of pharmaceutically relevant cyclic amines. The C−H amination occurs site‐selectively in α‐position to the nitrogen atom, even when weaker C−H bonds are present, and furnishes Troc‐protected aminals or amidines. The method employs the N‐heterocycle as limiting reagent and is applicable to the late‐stage functionalization of complex molecules. Its synthetic potential was further illustrated through the derivatization of α‐aminated products and the application to a concise total synthesis of the reported structure for senobtusin. Mechanistic studies allowed to propose a plausible reaction mechanism involving a turnover‐limiting Fe‐nitrene generation followed by fast H atom transfer and radical rebound.

Antibacterial Activity and Antifungal Activity of Monomeric Alkaloids

Scientists are becoming alarmed by the rise in drug-resistant bacterial and fungal strains, which makes it more costly, time-consuming, and difficult to create new antimicrobials from unique chemical entities. Chemicals with pharmacological qualities, such as antibacterial and antifungal elements, can be found in plants. Alkaloids are a class of chemical compounds found in nature that mostly consist of basic nitrogen atoms. Biomedical science relies heavily on alkaloid compounds. Based on 241 papers published in peer-reviewed scientific publications within the last ten years (2014–2024), we examined 248 natural or synthesized monomeric alkaloids that have antifungal and antibacterial activity against Gram-positive and Gram-negative microorganisms. Based on their chemical structure, the chosen alkaloids were divided into four groups: polyamine alkaloids, alkaloids with nitrogen in the side chain, alkaloids with nitrogen heterocycles, and pseudoalkaloids. With MIC values of less than 1 µg/mL, compounds 91, 124, 125, 136–138, 163, 164, 191, 193, 195, 205 and 206 shown strong antibacterial activity. However, with MIC values of below 1 µg/mL, compounds 124, 125, 163, 164, 207, and 224 demonstrated strong antifungal activity. Given the rise in antibiotic resistance, these alkaloids are highly significant in regard to their potential to create novel antimicrobial drugs.

The Influence of Coaxial Ultrasound on the Droplet Transfer of High Nitrogen Steel GMAW Process

The nitrogen bubble bursting phenomenon during the welding process of high nitrogen steel (HNS) can lead to unstable droplet transfer and welding process, reducing the quality of weld formation. In this study, a novel approach, ultrasonic-assisted gas metal arc welding (U-GMAW), is proposed to suppress the escape of nitrogen gas during droplet transfer. This study investigates the influence of ultrasound on the metal transfer process during two distinct metal transfer modes: short-circuiting and droplet transfer. Ultrasound has a significant effect on the welding process; as ultrasonic power increases, both the arc length and droplet size decrease, while the droplet transfer frequency increases and the electrical signal stabilizes. Under the experimental conditions of this study, ultrasound has the most effective improvement on the metal transfer behavior when the ultrasonic power reaches 2 kW. Ultrasound enhances the stability of the droplet transfer process, making U-GMAW an effective and novel approach for controlling the droplet transfer behavior of high nitrogen steel.