Empirical Interpolation Decomposition

The Kantorovich metric provides a way of measuring the distance between two Borel probability measures on a metric space. This metric has a broad range of applications from bioinformatics to image processing, and is commonly linked to the optimal transport problem in computer science (Deng and Du in Electron. Notes Theor. Comput. Sci. 253: 73–82, 2009; Villani in Optimal Transport: Old and New, Grundlehren der mathematischen Wissenschaften, vol. 338, 2009). Noteworthy to this paper will be the role of the Kantorovich metric in the study of iterated function systems, which are families of contractive mappings on a complete metric space. When the underlying metric space is compact, it is well known that the space of Borel probability measures on this metric space, equipped with the Kantorovich metric, constitutes a compact, and thus complete metric space. In previous work, we generalized the Kantorovich metric to operator-valued measures for a compact underlying metric space, and applied this generalized metric to the setting of iterated function systems (Davison in Acta Appl. Math., 2014, https://doi.org/10.1007/s10440-014-9976-y; Generalizing the Kantorovich Metric to Projection-Valued Measures: With an Application to Iterated Function Systems, 2015; Acta Appl. Math., 2018, https://doi.org/10.1007/s10440-018-0161-6). We note that the work of P. Jorgensen, K. Shuman, and K. Kornelson provided the framework for our application to this setting (Jorgensen in Adv. Appl. Math. 34(3):561–590, 2005; Jorgenson et al. in J. Math. Phys. 48(8):083511, 2007; Jorgensen in Operator Theory, Operator Algebras, and Applications, Contemp. Math., vol. 414, pp. 13–26, 2006). The situation when the underlying metric space is complete, but not necessarily compact, has been studied by A. Kravchenko (Sib. Math. J. 47(1), 68–76, 2006). In this paper, we extend the results of Kravchenko to the generalized Kantorovich metric on operator-valued measures.

     

Synthesis,characterization and antibacterial activity of palladium(II) bromide complexes of thioamides; X-ray structure of [Pd(tetramethylthiourea)<Subscript>4</Subscript>]Br<Subscript>2</Subscript>

Palladium(II) bromide complexes of thioamides having the general formulae [PdL₂Br₂] and [PdL₄]Br₂ where L = Thiourea (Tu), Methylthiourea (Metu), Dimethylthiourea (Dmtu), Tetramethylthiourea (Tmtu), Imidazolidine-2-thione (Imt), Mercaptopyridine (Mpy), Mercaptopyrimidine (Mpm) and Thionicotinamide (Tna) were prepared by reacting K₂[PdCl₄] with KBr and the corresponding thioamides. The complexes were characterized by elemental analysis, IR and NMR spectroscopy, and one of them, [Pd(Tmtu)₄]Br₂ (1) by X-ray crystallography. The crystal structure of 1 shows a square-planar coordination environment around the Pd(II) atoms with the average cis and trans S–Pd–S bond angles of 90.0° and 180.0°, respectively. The synthesized complexes were screened for antibacterial effects, and the results showed that the complexes exhibit significant activities against both gram positive and gram negative bacteria.     

Ensemble of a subset of <Emphasis Type="Italic">k</Emphasis>NN classifiers

Combining multiple classifiers, known as ensemble methods, can give substantial improvement in prediction performance of learning algorithms especially in the presence of non-informative features in the data sets. We propose an ensemble of subset of kNN classifiers, ESkNN, for classification task in two steps. Firstly, we choose classifiers based upon their individual performance using the out-of-sample accuracy. The selected classifiers are then combined sequentially starting from the best model and assessed for collective performance on a validation data set. We use bench mark data sets with their original and some added non-informative features for the evaluation of our method. The results are compared with usual kNN, bagged kNN, random kNN, multiple feature subset method, random forest and support vector machines. Our experimental comparisons on benchmark classification problems and simulated data sets reveal that the proposed ensemble gives better classification performance than the usual kNN and its ensembles, and performs comparable to random forest and support vector machines.     

Xanthine oxidase inhibiting flavonol glycoside from Amberboa ramosa

A new flavonol glycoside (1) has been isolated from the ethyl acetate soluble fraction of Amberboa ramosa and assigned the structure 5,7,4'-trihydroxy-3,8-dimethoxylflavone 5-O-beta-D-gluco-pyranoside (1). In addition, 6,4'-dihydroxy-3,5,7-trimethoxyflavone (2), 5,7-dihydroxy-4'-methoxyflavone (3) and (23R)-5alpha-cycloart-24-ene-3beta,21,23-triol (4) have also been reported for the first time from this species. The structures were deduced on the basis of 1D and 2D NMR techniques. The compounds 1-3 displayed weak to moderate inhibition against the xanthine oxidase enzyme.     

Exploring Amantadine Derivatives as Urease Inhibitors: Molecular Docking and Structure–Activity Relationship (SAR) Studies

This article describes the design and synthesis of a series of novel amantadine-thiourea conjugates (3a–j) as Jack bean urease inhibitors. The synthesized hybrids were assayed for their in vitro urease inhibition. Accordingly, N-(adamantan-1-ylcarbamothioyl)octanamide (3j) possessing a 7-carbon alkyl chain showed excellent activity with IC₅₀ value 0.0085 ± 0.0011 µM indicating that the long alkyl chain plays a vital role in enzyme inhibition. Whilst N-(adamantan-1-ylcarbamothioyl)-2-chlorobenzamide (3g) possessing a 2-chlorophenyl substitution was the next most efficient compound belonging to the aryl series with IC₅₀ value of 0.0087 ± 0.001 µM. The kinetic mechanism analyzed by Lineweaver–Burk plots revealed the non-competitive mode of inhibition for compound 3j. Moreover, in silico molecular docking against target protein (PDBID 4H9M) indicated that most of the synthesized compounds exhibit good binding affinity with protein. The compound 3j forms two hydrogen bonds with amino acid residue VAL391 having a binding distance of 1.858 Å and 2.240 Å. The interaction of 3j with amino acid residue located outside the catalytic site showed its non-competitive mode of inhibition. Based upon these results, it is anticipated that compound 3j may serve as a lead structure for the design of more potent urease inhibitors.     

Synthesis and antimicrobial activity of new functionalized derivatives of [1,2,4]triazolo[4,3‐a]pyrimidin‐5(1H)‐one

New functionalized 1,7‐diaryl‐6‐cyano‐1,2,4‐triazolo[4,3‐a]pyrimidin‐5(1H)‐one derivatives ( 5a–j ) were synthesized via reaction of 5‐cyano‐6‐phenyl‐2‐thiouracil 1 with the respective hydrazonoyl halides 2a–j and their biological activity was evaluated. The mechanism and the regioselectivity of the studied reactions are discussed. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:393–398, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20311     

Application of a thiourea‐containing task‐specific ionic liquid for the solid‐phase extraction cleanup of lead ions from red lipstick,pine leaves,and water samples

Here, task‐specific ionic liquid solid‐phase extraction is proposed for the first time. In this approach, a thiourea‐functionalized ionic liquid is immobilized on the solid sorbent, multiwalled carbon nanotubes. These modified nanotubes packed into a solid‐phase extraction column are used for the selective extraction and preconcentration of ultra‐trace amounts of lead(II) from aqueous samples prior to electrothermal atomic absorption spectroscopy determination. The thiourea functional groups act as chelating agents for lead ions retaining them and so, give the selectivity to the sorbent. Elution of the retained ions can be performed using an acidic thiourea solution. The effects of experimental parameters including pH of the aqueous solution, type and amount of eluent, and the flow rates of sample and eluent solutions on the separation efficiency are investigated. The linear dependence of absorbance of lead on its concentration in the initial solution is in the range of 0.5–40.0 ng/mL with the detection limit of 0.13 ng/mL (3s_b/m, n = 10). The proposed method is applicable to the analysis of red lipstick, pine leaves, and water samples for their lead contents.     

LC-MS/MS method for the simultaneous quantification of artesunate and its metabolites dihydroartemisinin and dihydroartemisinin glucuronide in human plasma

Artesunate (AS), a hemisuccinate derivative of artemisinin, is readily soluble in water and can easily be used in formulations for parenteral treatment of severe malaria. AS is rapidly hydrolyzed to the active metabolite dihydroartemisinin (DHA) and primarily eliminated by biliary excretion after glucuronidation. To investigate systematically the AS metabolism and pharmacokinetics, a novel liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of AS and its metabolites DHA and DHA glucuronide (DHAG) in human plasma samples was developed. Compared to previous methods, our method includes for the first time the quantification of the glucuronide metabolite using a newly synthesized stable isotope-labeled analogue as internal standard. Sample preparation was performed with only 50 μL plasma by high-throughput solid-phase extraction in the 96-well plate format. Separation of the analytes was achieved on a Poroshell 120 EC-C₁₈ column (50*2.1 mm, 2.7 μm, Agilent Technologies, Waldbronn, Germany). The method was validated according to FDA guidelines. Calibration curves were linear over the entire range from 1 to 2,500 nM (0.4–961.1 ng/mL), 165 to 16,500 nM (46.9–4,691.8 ng/mL), and 4 to 10,000 nM (1.8–4,604.7 ng/mL) for AS, DHA, and DHAG, respectively. Intra- and interbatch accuracy, determined as a deviation between nominal and measured values, ranged from ?5.7 to 3.5 % and from 2.7 to 5.8 %, respectively. The assay variability ranged from 1.5 to 10.9 % for intra- and interbatch approaches. All analytes showed extraction recoveries above 85 %. The method was successfully applied to plasma samples from patients under AS treatment.