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The majority of soil nitrogen is closely associated with soil organic matter, the cleavage of high molecular weight organic N such as protein to smaller soluble compounds (e.g amino acids) is a key step in the terrestrial N cycle. Therefore, as amino acids occupy a central position in understanding the N biogeochemical cycling processes and ecosystem functions, using natural abundance level isotopic information of amino acids or the heavier isotope 15N as a tracer helps advance the knowledge of soil fertility and its biological mechanism. Currently isotope pool dilution approach and compound-specific isotope analysis (CSIA) approaches have been successful established to measure amino acid in soils. However, both of them need large sample requirements and labor-consuming isolation procedures for the isotope analysis of amino acids. In this study, a novel distillation-chemical conversion N2O approach based on the 15N analysis by the oxidation of amino groups to NO2- and further reduction to N2O was described, followed by PreCon isotope ratio mass spectrometry (PreCon-IRMS). Sample preparation was carried out by our self-developed device-automatic micro-nitrogen conversion N2O generating device, allowing either helium (He) purging of gas or liquid charging from a range of suitable, airtight bottles. The reaction conditions for the N2O production were explored and optimized, including the hypobromite concentration, NaOH concentration, and amino acid mixtures concentration. The nitrogen stable isotope abundance in standard solutions of amino acid mixtures with different concentrations and 15N abundance, as well as the nitrogen stable isotope abundance of free amino acids in tested soil were analyzed by using the newly developed pretreatment method combined with the PreCon-IRMS system. The results showed that the developed method coupled IRMS analytical system was able to measure the 15N abundance in all standard solutions and soil extracts with good precision of 0.2%-08% (CV

The sustainable development of novel photo/electrocatalytic CO2/N2 fixation for chemical synthesis is predicated on reliable, accurate, and rapid detection methods. The directness, specificity, and simultaneity in detecting multiple molecules of the 1H nuclear magnetic resonance (1H‐NMR) technique have aroused increasing interest in photo/electrocatalysis. Thus far, two data processing means have been developed for the precise 1H‐NMR data processing: peak integral and peak height methods. However, few detailed studies offer a clear steer for choosing data processing methods for the concerned products in photo/electrocatalysis, especially the guidelines under the conditions of baseline distortions induced by water suppression. Herein, the feasible practices are restudied to quantify classical products in photo/electrocatalytic CO2/N2 fixation. On the basis of experimental results, 1H‐NMR data processing methods (peak integral and peak height methods) are found to convey different applicability for the different low‐concentration products, while introducing water suppression in the 1H‐NMR tests. The essential reason can be attributed to the baseline distortions caused by the water suppression, which arouses differentiated deviation of peaks with different peak widths. With this in mind, an accessible quantification criterion is provided to avoid superfluous input of time or cost in precise 1H‐NMR detection of low‐concentration products. [ABSTRACT FROM AUTHOR]

Consider Dirichlet problems of Laplace's equation in a bounded simply‐connected domain S$$ S $$, and use the null field equation (NFE) of Green's representation formulation, where the source nodes Q$$ Q $$ are located on a pseudo‐boundary ΓR$$ {\Gamma}_R $$ outside S$$ S $$ but not close to its boundary Γ(=∂S)$$ \Gamma \kern0.3em \left(=\partial S\right) $$. Simple algorithms are proposed in this article by using the central rule for the NFE, and the normal derivatives uν$$ {u}_{\nu } $$ of the solutions on the boundary Γ(=∂S)$$ \Gamma \kern0.3em \left(=\partial S\right) $$ can be easily obtained. These algorithms are called the discrete null field equation method (DNFEM) because the collocation equations are, indeed, the direct discrete form of the NFE. The bounds of the condition number are like those by the method of fundamental solutions (MFS) yielding the exponential growth as the number of unknowns increases. One trouble of the DNFEM is the near singularity of integrations for the solutions in boundary layers in Green's representation formulation. The traditional BEM also suffers from the same trouble. To deal with the near singularity, quadrature by expansions and the sinh transformation are often used. To handle this trouble, however, we develop two kinds of new techniques: (I) the interpolation techniques by Taylor's formulas with piecewise q$$ q $$‐degree polynomials and the Fourier series, and (II) the mini‐rules of integrals, such as the mini‐Simpson's and the mini‐Gaussian rules. Error analysis is made for technique I to achieve optimal convergence rates. Numerical experiments are carried out for disk domains to support the theoretical analysis made. The numerical performance of the DNFEM is excellent for disk domains to compete with the MFS. The errors with O(10−4)$$ O\left(1{0}^{-4}\right) $$ can be obtained by combination algorithms, which are satisfactory for most engineering problems. In summary, the new simple DNFEM is based on the NFE, which is different from the boundary element method (BEM). The theoretical basis in error and stability has been established in this article. One trouble in seeking the numerical solutions in boundary layers has been handled well; this is also an important contribution to the BEM. Besides, numerical experiments are encouraging. Hence the DNFEM is promising, and it may become a new boundary method for scientific/engineering computing. [ABSTRACT FROM AUTHOR]

The complex [Pb(phen)(4-NB)(CH3COO)] of lead(II) was prepared and characterized by means of elemental analysis, FT-IR, and single crystal X-ray analysis, where phen = 1,10-phenanthroline, 4-NB = 4-nitrobenzoate. The single crystal X-ray analysis indicates that the complex is a monomeric species, including two carboxylate ligands, and adopts a hemidirected structure. It is further extended by intermolecular C−H⋯O hydrogen bonds, π–π interactions and secondary Pb⋯O interactions to form two-dimensional supramolecular architecture.

Interest in the development of eco-friendly, sustainable, and convenient bio-based coatings to enhance flame retardancy and antibacterial properties in cotton fabrics is growing. In this work, chitosan was protonated at its amino groups using a method with a high atom economy using an equimolar amount of amino trimethylene phosphonic acid (ATMP), resulting in the fabrication of a single-component chitosan-based multifunctional coating (ATMP-CS), thereby avoiding any additional neutralization or purification steps. Cotton fabrics coated with various loads of ATMP-CS were prepared through a padding–drying–curing process. The morphology, thermal stability, mechanical properties, antibacterial properties, flame-retardant behavior, and flame-retardant mechanism of these fabrics were investigated. The coating exhibited excellent film-forming properties, and it imparted a uniform protective layer onto the surfaces of the cotton fabrics. When the load capacity reached 11.5%, the coated fabrics achieved a limiting oxygen index of 29.7% and successfully passed the VFT test. Moreover, the ATMP-CS coating demonstrated antibacterial rates against Escherichia coli and Staphylococcus aureus reaching 95.1% and 99.9%, respectively. This work presents a straightforward and gentle approach to fabricating colorless, environmentally friendly, and highly efficient fabric coatings that have potential applications in promoting the use of bio-based materials. [ABSTRACT FROM AUTHOR]