The spectral method and numerical continuation algorithm for the von Kármán problem with postbuckling behaviour of solutions

In this paper a spectral method and a numerical continuation algorithm for solving eigenvalue problems for the rectangular von Kármán plate with different boundary conditions (simply supported, partially or totally clamped) and physical parameters are introduced. The solution of these problems has a postbuckling behaviour. The spectral method is based on a variational principle (Galerkin’s approach) with a choice of global basis functions which are combinations of trigonometric functions. Convergence results of this method are proved and the rate of convergence is estimated. The discretized nonlinear model is treated by Newton’s iterative scheme and numerical continuation. Branches of eigenfunctions found by the algorithm are traced. Numerical results of solving the problems for polygonal and ferroconcrete plates are presented. Communicated by A. Zhou.     

An experimental and DFT computational study of a novel zerovalent tetracarbonyl tungsten complex of 2-(2′-pyridyl)quinoxaline

Synthesis and characterization of the new complex W(CO)₄(2,2′-pq), (1), where 2,2′-pq = 2-(2′-pyridyl)quinoxaline, is presented. The non-symmetric ligand 2,2′-pq belongs to the general class of quinoxalines, which are natural products yielding a rich coordination chemistry. Complex (1) crystallizes in space group P2_1/n with α = 9.601(6) Å, b = 16.735(11) Å, c = 10.315(8) Å, Z = 4 and V = 1616.0(19) Å³. Although its structure resembles those of W(CO)₄(phen) and W(CO)₄(bpy), some distortions that stem from 2,2′-pq’s asymmetry are present. DFT calculations reveal a ground state consisting of HOMO, HOMO − 1 and HOMO − 2, mainly of metal and carbonyl character, while LUMO is diimine oriented. The bonding scheme of (1) is illustrated after its consideration as been consisted by two fragments, namely W(CO)₄ and 2,2′-pq, acting as a donor and acceptor of electron density, respectively. In that scheme, back-bonding interaction of the main core to 2,2′-pq is mainly related to the mixing of HOMO − 2 from W(CO)₄ moiety with LUMO from 2,2′-pq moiety. The performed TDDFT calculations, not only in the gas phase but also combined with the conductor like polarizable continuum model (CPCM), reveal that the lowest in energy highly solvatochromic transition of (1) can be ascribed as a HOMO − 2 → LUMO transition and it is better described as MLCT/LLCT, underlying the CO → diimine contribution. The solvatochromic behaviour of (1) is anticipated by DFT/CPCM calculations and is probed in detail by absorption and NMR spectroscopy. The correlation of the lowest-energy-band maximum to the dipole moment of the corresponding solvents provides overall good linear fits, while the correlation to the dielectric constant affords good linear patterns only after the segregation of the solvents into groups. The ¹H NMR data of 2,2′-pq and (1) reveal an increase of the solvent influence to the chemical shifts of the diimine ligand after its coordination to the metal and suggest two different types of solvent-effects for the complex and the ligand, respectively. The observed proton shifts of (1) are related with the results of the Mülliken population analysis in solvents of different polarity; the transition from CCl₄ to MeOH seems to signify a charge transfer from the axial COs and the central metal to the equatorial COs and the internal nuclei of 2,2′-pq.     

Novel Foods and Sustainability as Means to Counteract Malnutrition in Madagascar

Although the trends of international reports show an increase in overweight and obesity, even in developing countries, there are still areas of the world, such as Sub-Saharan Africa, strongly affected by undernutrition. Specifically, in Madagascar, the percentage of stunted children under 5 is extremely high. Furthermore, the COVID-19 pandemic is expected to increase the risk of all forms of malnutrition, especially in low-income countries, including Madagascar, with serious intergenerational repercussions. This narrative review aims at investigating eating habits and cooking methods of the Malagasy population, addressing sustainable healthy diets through promotion of novel foods. While novel foods are a recent concept, there are data that describe how they may contribute to counteract food insecurity and malnutrition considering context and place. Efforts to promote native, traditional foods as Moringa oleifera, an indigenous plant in Asia and Africa including Madagascar, rich in protein and micronutrients, as well as edible insects, alternative sustainable source of protein, lipids, iron, and zinc, would provide not only nutritional but also cultural and economic benefits. The potential synergies between food traditions and agroecology have the potential to impact health addressing larger issues of sustainability and food security. Regional, national, and international policies are needed to develop and support one health approach actions.     

Effect of [Fe(CN)6]4- substitutions on the spin-flop transition of a layered nickel phyllosilicate

A 3 to 1 Ni/Si antiferromagnetic layered phyllosilicate, Ni(3)Si(C(3)H(6)NH(3))F(0.65)O(1.9)(OH)(4.45)(CH(3)COO)(1.1)·xH(2)O, was modified with K(4)[Fe(CN)(6)]·3H(2)O. This compound retained its ordering as proved by X-ray diffraction, while infrared spectra revealed the presence of [Fe(CN)(6)](4-) groups and X-ray photoelectron spectroscopy showed that the latter partially substitute the acetate groups. Both the parent and the modified compound are canted antiferromagnets with an anisotropy perpendicular to the layers and show spin-flop transitions. For the parent compound, a single step spin-flop occurs at H = 24 kOe. The modified compound shows increased antiferromagnetic canting and a two-step transition (H(1) = 24 kOe, H(2) = 48 kOe). These results testify to the existence of competing interactions that depend sensitively on the grafted species.     

Dynamic surface activity of phenylalanine glycerol-ether surfactant solutions measured by a differential maximum bubble pressure tensiometer

A refined differential maximum bubble pressure tensiometer was used for measuring the dynamic surface tension at various concentrations of a nonconventional surfactant, a member of a new homologous series of phenylalanine glycerol-ether amphiphiles, with 10 carbon atoms to the hydrophobic alkyl chain (C(10)-PhGE). The effective bubble formation frequency for the examined surfactant concentrations was varied from 2 bubbles per second to 1 bubble per 20 s. The variation of equilibrium surface tension with concentration as well as the critical micelle concentration were determined by a Wilhelmy plate technique. Comparisons between dynamic and equilibrium surface tension values demonstrate that, under the employed surface deformation rates, the equilibrium surface tension is a misleading indicator of surface activity. This is also supported by simple surface rheology considerations. Results based on a diffusion-controlled kinetic analysis provide further evidence on the strong dependence of surface activity on the particular time scale of deformation.     

pH‐responsive photoluminescence properties of a water‐soluble copolymer containing quinoline groups in aqueous solution

The synthesis of a water‐soluble copolymer containing quinoline groups, P(DMAM‐co‐SDPQ), through free radical copolymerization of N,N‐dimethylacrylamide, DMAM, with 2,4‐diphenyl‐6‐(4‐vinylphenyl)quinoline, SDPQ, is presented and the optical properties of the final product are investigated in aqueous solution as a function of pH. It is found that the emission peak of SDPQ is red‐shifted from 411 to 484 nm with decreasing pH, due to the protonation of quinoline groups at low pH, suggesting that this copolymer may function as a luminescent pH‐indicator. Moreover, the copolymer exhibits the characteristics of a luminescent pH‐detector within the pH range 2 < pH < 4, as in this pH region the ratio of the emission intensity at 411 nm over that at 484 nm changes linearly in a logarithmic scale with the pH of the solution. Finally, the formation of less polar quinoline clusters in the aqueous P(DMAM‐co‐SDPQ) solution upon increasing pH was detected through Nile red probing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2078–2083, 2010     

A dynamic wicking technique for determining the effective pore radius of pregelatinized starch sheets

A dynamic wicking technique is employed for the first time for the determination of the effective mean pore radius of a thin-layer porous food: drum dried pregelatinized starch sheets. The technique consists of measuring the penetration rate of various n-alkanes in the porous matrix of the starch sheets and using this data to calculate the effective pore radius via the Washburn equation. Pore sizes in the order of a few nanometers have been determined in the starch sheets depending on the drum dryer’s operating variables (drum rotation speed, steam pressure and starch feed concentration). The conditions for the application of the technique in porous foods are discussed as compared to the conditions for single capillaries and inorganic porous material measured in other studies.     

The crystal structure of the inclusion complex of cyclomaltoheptaose (β-cyclodextrin) with 3,5-dimethylbenzoic acid

The crystal of theCD-3,5-dimethylbenzoic acid inclusion complex is triclinicP1 witha=15.707(3),b=15.694(3),c=15.999(3) Å, =101.502(5),=101.557(5), =103.805(4)°,V=3624 ų, andZ=1. Two crystallographically independentCD molecules form a dimer by means of hydrogen bonds between secondary hydroxyl groups in which disordered guest molecules in six orientations are accommodated. In two of them the guest molecules are situated at the dimer interface, their carboxyl groups interacting with the carboxyl groups of two other guest orientations that are found on either side of the monomer cavity. In the two last orientations the guest molecules enter the monomer cavities in an opposite sense with the carboxyl groups protruding from the primary side and are stabilized by cyclodextrin hydroxyl groups. A dense water network is formed in the interdimer space consisted of 18.2 water molecules distributed over 24 sites. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82175 (61 pages).Dedicated to Professor József Szejtli.     

Advances in molecular techniques for the detection and quantification of genetically modified organisms

Progress in genetic engineering has led to the introduction of genetically modified organisms (GMOs) whose genomes have been altered by the integration of a novel sequence conferring a new trait. To allow consumers an informed choice, many countries require food products to be labeled if the GMO content exceeds a certain threshold. Consequently, the development of analytical methods for GMO screening and quantification is of great interest. Exponential amplification by the polymerase chain reaction (PCR) remains a central step in molecular methods of GMO detection and quantification. In order to meet the challenge posed by the continuously increasing number of GMOs, various multiplex assays have been developed for the simultaneous amplification and/or detection of several GMOs. Classical agarose gel electrophoresis is being replaced by capillary electrophoresis (CE) systems, including CE chips, for the rapid and automatable separation of amplified fragments. Microtiter well-based hybridization assays allow high-throughput analysis of many samples in a single plate. Microarrays have been introduced in GMO screening as a technique for the simultaneous multianalyte detection of amplified sequences. Various types of biosensors, including surface plasmon resonance sensors, quartz crystal microbalance piezoelectric sensors, thin-film optical sensors, dry-reagent dipstick-type sensors and electrochemical sensors were introduced in GMO screening because they offer simplicity and lower cost. GMO quantification is performed by real-time PCR (rt-QPCR) and competitive PCR. New endogenous reference genes have been validated. rt-QPCR is the most widely used approach. Multiplexing is another trend in this field. Strategies for high-throughput multiplex competitive quantitative PCR have been reported.