Bounds for separating hash families

This paper aims to present new upper bounds on the size of separating hash families. These bounds improve previously known bounds for separating hash families.     

N,N'-dipyridoxyl Schiff bases: synthesis, experimental and theoretical characterization

Three N,N'-dipyridoxyl Schiff bases (L1, L2 and L3) have been newly synthesized and characterized by IR, (1)H NMR, mass spectrometry and elemental analysis. Their optimized geometries together with the theoretical assignment of the vibrational frequencies and the (1)H NMR chemical shifts of them have been computed by using density functional theory (DFT) method. In the optimized structures of the Schiff bases, two pyridine rings are not in a same plane; however the substitutions are essentially in the same plane with the pyridine rings. Also, the benzene ring(s) in the bridge region is (are) not in the same plane with the pyridine rings and azomethine moieties. In all the species, engagement in intramolecular-hydrogen bonds causes to weakness of the phenolic O-H bonds. Consistency between the theoretical results and experimental evidence confirms suitability of the optimized geometries for the synthesized Schiff bases.     

On the centrality of vertices of molecular graphs

For acyclic systems the center of a graph has been known to be either a single vertex of two adjacent vertices, that is, an edge. It has not been quite clear how to extend the concept of graph center to polycyclic systems. Several approaches to the graph center of molecular graphs of polycyclic graphs have been proposed in the literature. In most cases alternative approaches, however, while being apparently equally plausible, gave the same results for many molecules, but occasionally they differ in their characterization of molecular center. In order to reduce the number of vertices that would qualify as forming the center of the graph, a hierarchy of rules have been considered in the search for graph centers. We reconsidered the problem of “the center of a graph” by using a novel concept of graph theory, the vertex “weights,” defined by counting the number of pairs of vertices at the same distance from the vertex considered. This approach gives often the same results for graph centers of acyclic graphs as the standard definition of graph center based on vertex eccentricities. However, in some cases when two nonequivalent vertices have been found as graph center, the novel approach can discriminate between the two. The same approach applies to cyclic graphs without additional rules to locate the vertex or vertices forming the center of polycyclic graphs, vertices referred to as central vertices of a graph. In addition, the novel vertex “weights,” in the case of acyclic, cyclic, and polycyclic graphs can be interpreted as vertex centralities, a measure for how close or distant vertices are from the center or central vertices of the graph. Besides illustrating the centralities of a number of smaller polycyclic graphs, we also report on several acyclic graphs showing the same centrality values of their vertices. © 2013 Wiley Periodicals, Inc.     

Carbon black nanoparticles film electrode prepared by using substrate-induced deposition approach

A new type of carbon film electrode, composed of a thin layer of tightly packed carbon black (CB) nanoparticles deposited onto a gelatin-covered indium tin oxide/glass support using the surface-induced deposition (SID) approach, is presented. Some parameters of the novel SID method were optimized and the surface image and functionalization of the investigated carbon black film electrode (CBFE) was inspected by employing scanning electron microscopy and infrared spectroscopy. A cyclic voltammetry (CV) study was conducted in which the electron-transfer kinetics and CBFE interfacial characteristics were evaluated employing several selected reference redox systems, such as [Ru(NH₃)₆]^3+/2+, [Fe(CN)₆]^3−/4− and Fe^3+/2+ in aqueous, and ferrocene/ferrocenium in acetonitrile media. CV recordings were also performed in order to compare the electrochemical behavior of the CBFE with that of some well-known and established bare carbon-based electrodes. In order to confirm the validity of the CB film preparation method, the electroanalytical performance of the proposed CBFE was examined by carrying out linear sweep voltammetry of ascorbic acid (AA), anodic stripping square-wave voltammetry of Cu(II) in acidic medium, and amperometric measurements of hydrogen peroxide under flow injection conditions. The sensing characteristics of the novel carbon film electrode, demonstrated in this preliminary study, comprise: (i) a wide working potential window ranging from +1.0 to −1.3 V (depending on the solution pH), (ii) a wide applicable pH range (at least from 2 to 12), (iii) low voltammetric background (<5 μA cm⁻²), (iv) a satisfactory linear voltammetric and amperometric response (r² > 0.99) to various analytes, (v) good reproducibility (for example, r.s.d. of 2% in amperometric detection of H₂O₂ and r.s.d. of 8.5% for electrode-to-electrode CV runs), and (vi) stable and fast current response (at least 100 CV runs with negligible change in CV response). The main advantages of the proposed CBFE originate from the unique CB film formation procedure that enables fast, simple, inexpensive and non-toxic CBFE preparation, which can find application in advanced electrochemical devices and is suitable for mass production.     

Synthesis, experimental and theoretical characterization of tetra dentate N,N'-dipyridoxyl (1,3-propylenediamine) salen ligand and its Co(III) complex

The new tetra dentate dianionic H2PS (N,N'-dipyridoxyl (1,3-propylenediamine)) Schiff-base ligand and its octahedral Co(III) salen complex [Co(PS)(H2O)(CH3OH)]+CH3COO(-) were synthesized, where coordinating atoms of H2PS (N,N,O(-),O(-)) occupied equatorial positions with H2O and CH3OH as axial ligands. The nature of the H2PS and its complex were determined by elemental and spectrochemical (IR, UV-vis, 1H NMR and Mass) analysis. Also, the fully optimized geometries and vibrational frequencies of them together with the 1H NMR chemical shifts of H2PS have been calculated using density functional theory (B3LYP) method. Obtained structural parameters are in good agreement with the experimental data reported for similar compounds. The calculated and experimental results confirmed the suggested structures for the ligand and complex.     

Synthesis and characterization of (Mo72Fe30)-coated large hexagonal gibbsite gamma-Al(OH)3 platelets

The polyoxometalates or POMs (clusters comprising at least two metal and many oxygen atoms) have recently gained significant interest owing to their versatile architecture and especially their catalytic activities. Due to their high catalytic activity but low surface area, there is always a demand for making high surface area POMs. This work demonstrates the attachment of the anionic (Mo72Fe30) POMs to gibbsite nanoplatelets with a residual positive charge to form large surface area composites. The resulting composite reported here has been characterized using cryo-TEM imaging, EDX/STEM (elemental) analysis, ATR-IR spectroscopy, SAXS, electrophoretic mobility determination and XRD. The composite reported here could find application in catalysis.     

Antinociceptive and anti-inflammatory activities of the essential oil of Nepeta crispa Willd. in experimental rat models

This study was conducted to evaluate the antinociceptive and anti-inflammatory activities of the essential oil of Nepeta crispa. The study was done using the tail-flick and formalin test pain models and the paw oedema model of inflammation. Male Wistar rats were used as the animal model. The essential oil dose-dependently produced analgesia in the acute pain models, including the tail-flick (p?相似文献   

Determination of selenium species in plant leaves by HPLC-UV-HG-AFS

The purpose of this work was the development of a method for the determination of Se compounds in leaves of plants. Water-soluble Se compounds were extracted from samples by water. Enzymatic hydrolysis with the non-specific enzyme protease XIV was used for the release of Se compounds bound to proteins. Separation of Se species was made by ion exchange chromatography, using an anion exchange column for Se^IV, Se^VI and selenomethionine (SeMet), and a cation exchange column for selenomethylselenocysteine (SeMeSeCys) and selenocystine (SeCys₂). Columns were connected “on line” to a hydride generation atomic fluorescence spectrometer (HG-AFS) using a UV lamp between the separation and detection system. The repeatability of the results obtained by the developed method was under 15% (R.S.D.) for all Se species; the detection limit was 2-10 ng Se/g of supernatant. The accuracy was checked by comparison with some literature data for reference materials since there were no suitable certified reference materials available. The method was used for the determination of Se compounds in chicory (Cichorium intybus L.) leaves from plants which were cultivated aeroponically with elevated concentrations of Na₂SeO₄ for different periods. Se accumulated efficiently in chicory leaves; up to 480 μg/g after 41 days of exposure, mostly (64%) as Se^VI, i.e. in the form of Se added. Beside inorganic Se, in the extracts from enzyme hydrolysis we also found SeMet (4.2-8.4%) and SeMeSeCys (<DL−0.7%). Some unidentified peaks were also observed in the chromatograms of plant extracts.     

Synthesis,characterization and crystal structures of dinuclear macrocyclic Schiff base copper(I) complexes bearing different bridges

Utilizing a new 20-membered macrocyclic Schiff base ligand with two coordination sites formed from the [2+2] condensation of 1,3-diaminopropane and benzene-1,3-dicarboxaldehyde in the presence of CuX (X = Cl⁻, Br⁻, I⁻) salts, air-stable dicopper(I) complexes were synthesized in acetonitrile, intramolecularly linked via two halide groups, and characterized by different physico-chemical techniques. The single crystal X-ray diffraction technique indicates these complexes consist of two N₂X₂ donor sets that have distorted tetrahedral coordination environments around the copper(I) ions. In these halogen-bridged binuclear Cu₂LX₂ systems the Cu?Cu separation can be controlled, as this distance is reduced on increasing the halide size and hence the X?X repulsion, with the rigidity of the macrocycle playing a significant role.