Fuzzy equational logic

Presented is a completeness theorem for fuzzy equational logic with truth values in a complete residuated lattice: Given a fuzzy set Σ of identities and an identity p≈q, the degree to which p≈q syntactically follows (is provable) from Σ equals the degree to which p≈q semantically follows from Σ. Pavelka style generalization of well-known Birkhoff's theorem is therefore established. Received: 15 March 2000 / Revised version: 20 September 2000 Published online: 12 December 2001     

Capillary electrophoresis of boron cluster compounds in aqueous and nonaqueous solvents

The electrophoretic properties of boron cluster compounds were determined in water, methanol and ACN as solvents of the BGE and discussed based on the principles of ion migration. Two types of boron cluster compounds were investigated. One type consisted of derivatives of the nido-7,8-dicarbaundecaborate cluster, the other types are derivatized cobalt bis(dicarbollide) ions (COSANs) whose central cobalt atom is sandwiched by two 7,8-dicarbaundecaborate clusters. The BGE in all solvents was acetate/acetic acid buffer with pH 4.75 in water, 9.7 in methanol and 22.3 in ACN, respectively, at different ionic strength between 5 and 30 mM. The dependence of the mobility on ionic strength could not be explained by the theory of Debye, Hückel and Onsager, but good agreement was found upon considering an ion size parameter. Limiting mobilities were derived by curve fitting, and by the aid of the solvent viscosities the hydrodynamic radii of the analyte anions were calculated. They are between 0.25 and 0.48 nm, and were nearly independent of the solvent. Electrophoresis of the analytes in a BGE consisting of 6 mM perchloric acid in ACN allows the conclusion that the present boron cluster compounds behave as stronger acids than perchloric acid.     

Alkyl glycosides as potential anti-<Emphasis Type="Italic">Candida albicans</Emphasis> growth agents

Candida infections are becoming increasingly prevalent and many clinical isolates are resistant to common azole derivatives treatment. Accordingly, the capacity of a series of 19 alkyl glycosides, mainly mannosides and glucosides but also a cellobioside with aglycone chain-length from C-6 to C-20, to inhibit the growth of laboratory and clinically isolated strains of Candida albicans, was investigated. The study showed that only glycosides with the C-10 and C-12 aglycones were effective growth inhibitors of both types of Candida, strains, whose metabolic activity was also significantly reduced as revealed by an XTT assay.     

Electrophoretic investigation of the boron cluster anion [7-(2'-pyridyl)-nido-7,8-dicarbaundecaborate]- and its protonated zwitterionic product

ACN is a better solvent than methanol for both [NMe(4)] [7-(2'-pyridyl)-nido-7,8-C(2)B(9)H(11)] and its protonated anion. The investigated laboratory preparations of the salt and of its protonated anion are electrophoretically pure solids stable for 2 months at 4 degrees C. At a longer storage, the solid salt is more stable than the solid protonated anion. In the 40:60 v/v water-methanol solvent, decomposition products of the salt anion are detectable after one-week storage of the salt solution at 4 degrees C. The protonated anion does not decompose for almost 1 year in water-organic solutions at 4 degrees C. The exchange of the proton between the protonated anion and the solution is reversible and fast at room temperature. The pH dependence of the mobility of the [7-(2(-pyridyl)-nido-7,8-C(2)B(9)H(11)](-) anion reveals that the basicity of the nitrogen atom in the pyridine ring is not significantly affected by the bonding of the pyridyl group to the nido-7,8-C(2)B(9)H(11) cluster in position 7 and that the proton from the solution is accepted by the nitrogen atom in the 2-pyridyl ring. The UV-spectra of the salt and of its protonated anion indicate that the accepted proton is probably slightly shifted to the open face of the nido-7,8-C(2)B(9)H(11) cluster. The [1](-) is chiral.     

Water-Soluble Polymeric Carbon Nitride Colloidal Nanoparticles for Highly Selective Quasi-Homogeneous Photocatalysis

Heptazine-based polymeric carbon nitrides (PCN) are promising photocatalysts for light-driven redox transformations. However, their activity is hampered by low surface area resulting in low concentration of accessible active sites. Herein, we report a bottom-up preparation of PCN nanoparticles with a narrow size distribution (ca. 10±3 nm), which are fully soluble in water showing no gelation or precipitation over several months. They allow photocatalysis to be carried out under quasi-homogeneous conditions. The superior performance of water-soluble PCN, compared to conventional solid PCN, is shown in photocatalytic H₂O₂ production via reduction of oxygen accompanied by highly selective photooxidation of 4-methoxybenzyl alcohol and benzyl alcohol or lignocellulose-derived feedstock (ethanol, glycerol, glucose). The dissolved photocatalyst can be easily recovered and re-dissolved by simple modulation of the ionic strength of the medium, without any loss of activity and selectivity.     

O- and N-alkylated diketopyrrolopyrrole derivatives

The alkylation of 3-phenyl-6-(2-thienyl)pyrrolo[3,4-c]pyrrole-1,4-dione with 1-bromo-2-ethylhexane was performed. Besides the expected N,N′-dialkylated product, both possible N,O-dialkyl derivatives were isolated and identified for the first time. The position of the alkyl substituents in all three dialkylated isomers was determined by 2D ¹H and ¹³C NMR spectroscopy.     

Alkaloids from some amaryllidaceae species and their cholinesterase activity

Alkaloid extracts of four Amaryllidaceae species were studied with respect to their acetylcholinesterase and butyrylcholinesterase inhibitory activity and alkaloid patterns. Twenty-one alkaloids were determined by GC/MS, and seventeen of them identified from their mass spectra and retention times. The GC/MS analysis of the alkaloid extract of Nerine filamentosa is the first phytochemical investigation of this species. Promising erythrocytic acetylcholinesterase inhibitory activity was demonstrated by the alkaloid extracts of Narcissus poeticus var recurvus, Nerine filifolia and N. filamentosa (IC(50,HuAChE) = 6.0 +/- 0.1 microg/mL; IC(50,HuAChE) = 18.5 +/- 0.8 microg/mL, IC(50,HuAChE) = 21.6 +/- 1.1 microg/mL). The most potent inhibitory activity against serum butyrylcholinesterase was shown by extracts of Sternbergia lutea and Nerinefilamentosa (IC(50,HuBuChE) = 3.7 +/- 0.1 microg/mL; IC(50.HuBuChE) = 13.0 +/- 0.7 microg/mL).     

Determination of seventeen polar/thermolabile pesticides in apples and apricots by liquid chromatography/mass spectrometry

A simple liquid chromatography/mass spectrometry (LC/MS) approach for the determination of widely used representatives of polar/thermolabile pesticides in fruits was developed and validated. The group of pesticides comprised benzimidazoles and azoles (carbendazim, thiabendazole, imazalil, propiconazole, prochloraz, epoxiconazole, flusilazole, tebuconazole, bitertanol); N-methylcarbamates (carbaryl, carbofuran, methiocarb); and phenylureas and benzoylphenylureas (linuron, diflubenzuron, triflumuron, teflubenzuron, flufenoxuron). Matrixes (apple, apricot) were extracted with acetonitrile and crude extracts were cleaned up by solid-phase extraction (SPE) using either mixed cation exchange or hydrophilic lipophilic balance cartridges. LC separation of pesticides was performed on a reversed-phase column, Discovery C18. Electrospray ionization and ion trap MS/MS detection were applied. For most pesticides, overall recoveries ranged from 75 to 122%, and repeatability (as relative standard deviation) from 5 repetitive determinations of recovery ranged from 3 to 21%. Carbofuran was the only compound for which recovery was not satisfactory due to its loss in the SPE cleanup step. Limits of detection were 0.1-3 microg/kg for benzimidazole and azole fungicides and carbamate insecticides. For urea insecticides, detection limits were slightly higher (3-10 microg/kg).     

Synthesis of alpha-amino acids via asymmetric phase transfer-catalyzed alkylation of achiral nickel(II) complexes of glycine-derived Schiff bases

Achiral, diamagnetic Ni(II) complexes 1 and 3 have been synthesized from Ni(II) salts and the Schiff bases, generated from glycine and PBP (7) and PBA (11), respectively, in MeONa/MeOH solutions. The requisite carbonyl-derivatizing agents pyridine-2-carboxylic acid(2-benzoyl-phenyl)-amide 7 (PBP) and pyridine-2-carboxylic acid(2-formyl-phenyl)-amide 11 (PBA) were readily prepared from picolinic acid and o-aminobenzophenone or picolinic acid and methyl o-anthranilate, respectively. The structure of 1 was established by X-ray crystallography. Complexes 1 and 3 were found to undergo C-alkylation with alkyl halides under PTC conditions in the presence of beta-naphthol or benzyltriethylammonium bromide as catalysts to give mono- and bis-alkylated products, respectively. Decomposition of the complexes with aqueous HCl under mild conditions gave the required amino acids, and PBP and PBA were recovered. Alkylation of 1 with highly reactive alkyl halides, carried out under the PTC conditions in the presence of 10% mol of (S)- or (R)-2-hydroxy-2'-amino-1,1'-binaphthyl 31a (NOBIN) and/or its N-acyl derivatives and by (S)- or (R)-2-hydroxy-8'-amino-1,1'-binaphthyl 32a (iso-NOBIN) and its N-acyl derivatives, respectively, gave rise to alpha-amino acids with high enantioselectivities (90-98.5% ee) in good-to-excellent chemical yields at room temperature within several minutes. An unusually large positive nonlinear effect was observed in these reactions. The Michael addition of acrylic derivatives 37 to 1 was conducted under similar conditions with up to 96% ee. The (1)H NMR and IR spectra of a mixture of the sodium salt of NOBIN and 1 indicated formation of a complex between the two components. Implications of the association and self-association of NOBIN for the observed sense of asymmetric induction and nonlinear effects are discussed.