An active index algorithm for the nearest point problem in a polyhedral cone

We consider the problem of finding the nearest point in a polyhedral cone C={x∈R ⁿ :D x≤0} to a given point b∈R ⁿ , where D∈R ^m×n . This problem can be formulated as a convex quadratic programming problem with special structure. We study the structure of this problem and its relationship with the nearest point problem in a pos cone through the concept of polar cones. We then use this relationship to design an efficient algorithm for solving the problem, and carry out computational experiments to evaluate its effectiveness. Our computational results show that our proposed algorithm is more efficient than other existing algorithms for solving this problem.     

Characterization of numerical radius parallelism in $$C^*$$C∗-algebras

Positivity - Let v(x) denote the numerical radius of an element x in a $$C^*$$-algebra $$\mathfrak {A}$$. First, we prove several numerical radius inequalities in $$\mathfrak {A}$$. Particularly,...     

Response of Human Mesenchymal Stem Cells to Patterned and Randomly Oriented Poly(Vinyl Alcohol) Nano-fibrous Scaffolds Surface-Modified with Arg-Gly-Asp (RGD) Ligand

The aim of this study was to obtain a better insight of how nano-fibrous scaffolds can affect human mesenchymal stem cells responses. Therefore, in this study, using electrospinning technique, poly(vinyl alcohol) (PVA) nano-fibers with two different patterns were prepared. In the first structure, PVA nano-fibers were oriented randomly and in the second structure, nano-fibers were electrospun in such a way that a special pattern was obtained. In order to enhance their stability, scaffolds were cross-linked using glutaraldehyde vapor. RGD immobilization was used to improve cell adhesion properties of the scaffolds. SEM micrographs demonstrated that the cell adhesion was effectively enhanced after RGD immobilization and higher cell densities were observed on RGD-modified scaffolds. Randomly oriented nano-fibers showed better cell adhesion compared to patterned structure. Patterned structure also revealed slightly lower cell viability compared to random nano-fibers. Finally, it was assumed that randomly oriented nano-fibers provide a more favorable surface for cells.     

Mesoporous titania photocatalyst: effect of relative humidity and aging on the preparation of mesoporous titania and on its photocatalytic activity performance

Mesoporous TiO₂ has been synthesized by the sol–gel method, using a nonionic triblock copolymer P123 as surfactant template under acidic conditions. The as-prepared samples were characterized by thermogravimetry–differential thermal analysis (TG–DTA), nitrogen absorption–desorption (BET), field emission scanning electron microscopy, and transmission electron microscopy. The photocatalytic activity of the mesoporous TiO₂ was evaluated by degradation of methylene blue under high-intensity UV light irradiation; the amount of methylene blue was measured by UV–visible spectroscopy. TG–DTA analysis revealed that the surfactant had been removed partly in as-synthesized samples. BET analysis proved that all the samples retained mesoporosity with a narrow pore-size distribution (4.5–6.3 nm) and high surface area (103–200 m²/g). All calcined mesoporous TiO₂ had high photocatalytic activity in the photodegradation of methylene blue.     

Mechanisms of Non-Newtonian Polymer Flow Through Porous Media Using Navier–Stokes Approach

This study includes solving non-Newtonian Navier–Stokes equation in three-dimensions (real rock images) and two-dimensions (simplified pore geometries) using the finite-difference method. The purpose of this study is to improve understanding of local phenomena leading to the mobilization of residual oil. This involves local pressure variations for non-Newtonian polymers and compares it with Newtonian fluid behavior. When a higher degree of shear thickening is induced, more flow diversion to side channels perpendicular to the main flow path and larger drag on fluids inside side channels will occur. This is consistent with oil mobilization and lowering of residual oil saturation.     

Coordination Chemistry and Spectroscopic Properties of Some Diorganotin(IV) Complexes with S-Donor Schiff Base Ligands

Abstract

Schiff bases S-benzyl- and S-methyl-β-N-(2-hydroxyphenyl)methylene dithiocarbazate (H₂L¹ and H₂L², respectively) and S-benzyl- and S-methyl-β-N-(2-chlorophenyl)methylenedithiocarbazate (HL³ and HL⁴, respectively) were prepared. Then organotin(IV) complexes [SnPh₂(L¹)] (1), [SnMe₂(L¹)] (2), [SnPh₂(L²)] (3), [SnMe₂(L²)] (4), [SnPh₂Cl(L³)] (5), and [SnPh₂Cl(L⁴)] (6) were obtained from the reaction of Schiff bases with SnR₂Cl₂ (R = Ph and Me). The synthesized complexes have been investigated by elemental analysis and IR, ¹H NMR, and ¹¹⁹Sn NMR spectroscopy. Spectroscopic studies show that, in complexes 1–4, the Schiff base acts as a tridentate dianionic ligand and coordinates through the thiol group, imine nitrogen, and phenolic oxygen. The coordination number of tin is five. In complexes 5 and 6, the ligand is monoanionic and unidentate, and coordinated only via the thiol group, and the azomethine nitrogen is not involved in coordination to tin. Therefore the coordination number of tin is four.

GRAPHICAL ABSTRACT      

Study of Interactions Between Sugammadex and Penicillins Using Affinity Capillary Electrophoresis

Sugammadex, a new modified gamma cyclodextrin, reverses the neuromuscular blockage induced by rocuronium by forming a strong complex with this muscle relaxant. To evaluate possible interactions with potentially co-administered drugs, interactions between sugammadex and penicillins were investigated using the affinity capillary electrophoresis method for the first time. Capillary electrophoresis coupled to an ultra violet detector was used as an analytical device for the analysis and detection of cyclodextrin inclusion complexes. Changes in the effective mobility of guest drugs (amoxicillin, ampicillin, oxacillin, dicloxacillin and azlocillin) were correlated with the increasing concentration of host molecules in background electrolyte, and successfully fitted into a non-linear curve equation; assuming 1:1 stoichiometric interaction. The calculated association constants (K _a) were: 383.44, 184.54, 265.34 and 95.06 M^?1 for amoxicillin, ampicillin, oxacillin and dicloxacillin, respectively. No complex formation with sugammadex could be detected for both penicillin G and piperacillin. The difference in the chemical structure of the penicillins, especially in the (R) side chains, is suggested to be responsible for the variety of binding strength between penicillins and sugammadex. The displacement study demonstrated that interactions between sugammadex and co-administered penicillins could reduce the pharmacological effects of both.     

Enantioselectivity Investigation of Short Polar Peptides with Different Positions in the Michael Reaction

This work reports the effectiveness of short polar peptides as asymmetric catalysts in Michael reactions to attain good yields of enantio- and diastereoselective isomers. In a comparison, glutamic acid and histidine produced greater ee and yields when they were applied as the second amino acid in short trimeric peptides. These short polar peptides were found to be efficient organocatalysts for the asymmetric Michael addition reaction in water.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

New and General Nitrogen Heterocycle Synthesis: Use of Heteropoly Acids as a Heterogeneous Recyclable Catalyst

An efficient synthetic method of six- and five-member nitrogen heterocyclic compounds was developed. Nitrogen heterocyclic compounds were prepared by condensation of the β-dicarbonyl compounds with the corresponding β- or γ-amino alcohols, subsequent cyclization, and spontaneous aromatization in the presence of a catalytic amount of Keggin-type heteropoly acids under very mild conditions.     

One-Pot,Three-Component Synthesis of 4H-Pyrans Using Cu(II) Oxymetasilicate

4H-Pyrans are synthesized through one-pot, three-component reaction of benzaldehyde, malononitrile, and ethyl acetoacetate using Cu(II) oxymetasilicate as an efficient, reusable catalyst. The procedure offers advantages in terms of better yields, short reaction times, mild reaction conditions, and reusability of the catalyst.