A note on representation of lattices by weak congruences

A weak congruence is a symmetric, transitive, and compatible relation. An element u of an algebraic lattice L is ??-suitable if there is an isomorphism ?? from L to the lattice of weak congruences of an algebra such that ??(u) is the diagonal relation. Some conditions implying the ??-suitability of u are presented.     

A Note on Triangular Schemes for Weak Congruences

Some geometrical methods, the so called Triangular Schemes and Principles, are introduced and investigated for weak congruences of algebras. They are analogues of the corresponding notions for congruences. Particular versions of Triangular Schemes are equivalent to weak congruence modularity and to weak congruence distributivity. For algebras in congruence permutable varieties, stronger properties—Triangular Principles—are equivalent to weak congruence modularity and distributivity.     

Pressurized-Liquid Extraction as an Efficient Method for Valorization of Thymus serpyllum Herbal Dust towards Sustainable Production of Antioxidants

The aim of this study was to valorize Thymus serpyllum herbal dust, a particular fraction distinguished as an industrial waste from filter-tea production. Pressurized liquid extraction (PLE) was used with the aim of overcoming certain obstacles of conventional extraction techniques in terms of shortening extraction time, reducing solvent consumption and energy costs, using “green” solvents and obtaining high yield and quality products. In order to optimize PLE of T. serpyllum herbal dust, the preliminary screening of the independent variables in order to define the most influential parameters and their domain was done first. After the screening, the optimization study using the face-centered central composite experimental design (CCD) with response surface methodology (RSM) was implemented. Additionally, taking into account the high awareness of the positive influence of antioxidants on the human health and associating it with high content of polyphenolic compounds in various members of Lamiaceae family, PLE has proven to be a great approach for antioxidants recovery from T. serpyllum herbal dust.     

Seawater zinc/polypyrrole-air cell possessing multifunctional charge-discharge characteristics

An environmentally friendly cell using polypyrrole-air regenerative cathode and zinc as anode is investigated in the 3% sodium chloride solution. The cell can operate in different charge and discharge mode. Polypyrrole can be reoxidized (doped) with chloride anions either by using dissolved oxygen or by an external power supply, e.g., small photovoltaic cell. In that way, after discharge, capacity retaining can be achieved by using seawater as the electrolyte. During low discharge rate, the delicate balance between solid state diffusion-controlled dedoping and chemical oxidation of polypyrrole produced by hydrogen peroxide is achieved, generating stable voltage plateau. The cell is proposed to operate as a power supply for different sensor devices in two modes. In the low discharge mode (10–20 mA g^?1), it can be used for data acquisition, and at the fast discharge mode (up to 2 A g^?1) for collecting data transmission.

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Graphical abstract Charge-discharge curves for different curent densities of Zn|3.5% NaCl(aq)|PPy. Inset: Continuous discharge of the cell under external load of 1 kΩ and constant air supply, during 1-h discharge and 1-h reoxidation charge

     

Mechanism of levulinic acid formation

Based on the intermediates revealed by ¹³C-NMR spectroscopy, the mechanism of levulinic acid ($\text{6}$) formation in acid catalysed hydrolysis of 2-hydroxymethylfurane ($\text{1}$) and 5-hydroxymethylfuran-2-carbaldehyde ($\text{14}$) is proposed.     

Synthesis,structural elucidation,characterization and theoretical DFT study of 1‐(o‐tolyl)biguanidium chloride

The structure of the new salt 1‐(o‐tolyl)biguanidium chloride, C₉H₁₄N₅⁺·Cl^?, has been determined by single‐crystal X‐ray diffraction. The salt crystallizes in the monoclinic space group C2/c. In this structure, the chloride and biguanidium hydrophilic ions are mostly connected to each other via N—H…N and N—H…Cl hydrogen bonds to form layers parallel to the ab plane around y = and y = . The 2‐methylbenzyl groups form layers between these layers around y = 0 and y = , with the methyl group forming C—H…π interactions with the aromatic ring. Intermolecular interactions on the Hirshfeld surface were investigated in terms of contact enrichment and electrostatic energy, and confirm the role of strong hydrogen bonds along with hydrophobic interactions. A correlation between electrostatic energy and contact enrichment is found only for the strongly attractive (N—H…Cl^?) and repulsive contacts. Electrostatic energies between ions reveal that the interacting biguanidium cation pairs are repulsive and that the crystal is maintained by attractive cation…Cl^? dimers. The vibrational absorption bands were identified by IR spectroscopy.     

Eine neue Synthese von (±)-Dihydrorecifeiolid

A New Synthesis of (±)-Dihydrorecifeiolide Ethyl 1-(2′-formylethyl)-2-oxocyclooctane-1-carboxylate ( 2 ) prepared by Michael reaction of ethyl 2-oxocyclooctane-1-carboxylate ( 1 ) was regioselectively methylated at the aldehyde group with (CH₃)₂Ti[OCH(CH₃)₂]₂ to give 3 (Scheme 1). The alcohol 3 was treated with Bu₄NF to give the deethoxycarbonylated product 4 which by distillation gave the bicyclic enol ether 5 . Oxidation (m-chloroperbenzoic acid) of 5 and reduction of the resulting oxolacton 6 yielded the title compound (±)-dihydrorecifeiolide ( 7 ) in an overall yield of nearly 50 %. Methylation of the aldehyde 2 with MeLi gave the ring-enlarged lacton 9 in poor yield (13 %). The deethoxycarbonylation reaction 3 → 4 was studied in more detail (Scheme 3).     

A note on atomistic weak congruence lattices

It is proved that a codistributive element in an atomistic algebraic lattice has a complement, implying that kernels of the related homomorphisms coincide. Some applications to weak congruence lattices of algebras are presented. In particular, necessary and sufficient conditions under which the weak congruence lattice of an algebra is atomistic are given.     

Extraction of Peppermint Essential Oils and Lipophilic Compounds: Assessment of Process Kinetics and Environmental Impacts with Multiple Techniques

Consumers are becoming more mindful of their well-being. Increasing awareness of the many beneficial properties of peppermint essential oil (EO) has significantly increased product sales in recent years. Hydrodistillation (HD), a proven conventional method, and a possible alternative in the form of microwave-assisted hydrodistillation (MWHD) have been used to isolate peppermint EO. Standard Soxhlet and alternatively supercritical fluid (SFE), microwave-assisted, and ultrasound-assisted extraction separated the lipid extracts. The distillations employed various power settings, and the EO yield varied from 0.15 to 0.80%. The estimated environmental impact in terms of electricity consumption and CO₂ emissions suggested that MWHD is an energy efficient way to reduce CO₂ emissions. Different extraction methods and solvent properties affected the lipid extract yield, which ranged from 2.55 to 5.36%. According to the corresponding values of statistical parameters, empiric mathematical models were successfully applied to model the kinetics of MWHD and SFE processes.