Thin sums matroids and duality

Building on the recent axiomatisation of infinite matroids with duality, we present a theory of representability for infinite matroids. This notion of representability allows for infinite sums, and is preserved under duality.     

A nanostructure-based electrochemical sensor for square wave voltammetric determination of N-acetylcysteine in pharmaceutical and biological samples

Ionics - In this study, a carbon paste electrode (CPE) was chemically modified with Pt/carbon nanotubes (CNTs) nanocomposite and 8,9-dihydroxy-7-methyl-12H-benzothiazolo [2,3-b] quinazolin-12-one...     

Pyridine-2,6-Dicarboxylic Acid (Dipic): Crystal Structure from Co-Crystal to a Mixed Ligand Nickel(II) Complex

Abstract  

Pyridine-2,6-dicarboxylic acid (dipic) was used for the synthesis of a co-crystal with 1,10-phenanthroline-5,6-dione (phen-dione) and a nickel(II) complex. The co-crystal dipic·phen-dione·4H₂O (1) has been synthesized and studied by X-ray crystallography. The structure is stabilized with hydrogen bonds between dipic, H₂O and phen-dione. It is surprising that there is no direct hydrogen bonding between phen-dione and dipic and yet the molecules co-crystallize in aqueous solution. A new complex of nickel(II), [Ni(phen)(dipic)(H₂O)]·4H₂O (2), (where phen = 1,10-phenanthroline) has been synthesized and characterized by elemental and thermogravimetric analyses, FT-IR, UV–Vis and ¹H-NMR spectroscopy. The structure of (2) has been studied by X-ray crystallography. The coordination around Ni(II) is a distorted octahedron. The crystal packing shows that the dimensionality of (2) is enlarged to 3D, through hydrogen bonds and π–π interactions. Cyclic voltammetry of (2) shows that the Ni(II/I) couple is irreversible.     

Comparative studies of mercapto thiadiazoles self-assembled on gold nanoparticle as ionophores for Cu(II) carbon paste sensors

Comparative studies of the potentiometric behavior of three mercapto compounds [2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol] (MTMP), [5-(2-methoxy benzylidene amino)-1,3,4-thiadiazole-2-thiol] (MBYT) and [5-(pyridin-2-ylmethyleneamino)-1,3,4-thiadiazole-2-thiol] (PYTT) self-assembled on gold nanoparticles (GNPs) as ionophores in carbon paste electrodes (CPEs) have been made. These mercapto thiadiazole compounds were self-assembled onto gold nanoparticles and then incorporated within carbon paste electrode. The self-assembled ionophores exhibit a high selectivity for copper ion (Cu²⁺), in which the sulfur and nitrogen atoms in their structure play a role as the effective coordination donor site for the copper ion. These carbon paste electrodes were applied as indicator electrodes for potentiometric determination of copper ions. The sensor based on PYTT exhibits the working concentration range of 4.0 × 10⁻⁹ to 7.0 × 10⁻² M and a Nernstian slope of 28.7 ± 0.3 mV decade⁻¹ of copper activity. The detection limit of electrode was 1.0 × 10⁻⁹ M and potential response was pH independent across the range of 3.0-6.5. It exhibited a quick response time of <5 s and could be used for a period of 45 days. The ion selectivity of this electrode for Cu²⁺ was over 10⁴ times that for other metal cations. The application of prepared sensors has been demonstrated for the determination of copper ions in spiked water and natural water samples.     

Self-modeling curve resolution techniques applied to comparative analysis of volatile components of Iranian saffron from different regions

Volatile components of saffron from different regions of Iran were extracted by ultrasonic-assisted solvent extraction (USE) and were analyzed by gas chromatography-mass spectrometry (GC-MS). Self-modeling curve resolution (SMCR) was proposed for resolving the co-eluted GC-MS peak clusters into pure chromatograms and mass spectra. Multivariate curve resolution-objective function minimization (MCR-FMIN) and multivariate curve resolution-alternating least square (MCR-ALS) were successfully used for this purpose. The accuracy of the qualitative and quantitative results was improved considerably using SMCR techniques. Comparison of the results of saffron from different regions of Iran showed that their volatile components are different from chemical components and relative percentages points of view. Safranal is the main component of all samples. In addition, 4-hydroxy-2,6,6-trimethyl-1-cyclohexene-1-carboxaldehyde (HTCC), 2(5H)-furanone, 2,4,4-trimethyl-3-carboxaldehyde-5-hydroxy-2,5-cyclohexadien-1-one and 2(3H)-furanone, dihydro-4-hydroxy were common in all samples with high percentages. The results proved that combining of SMCR techniques with USE-GC-MS produces a powerful tool for the analysis of the complex samples.     

Polymer-based electrospray device with multiple nozzles to minimize end effect phenomenon

In this paper, “end effect”, which represents the deflection of meniscus of boundary nozzles in an array due to asymmetric electric field and repulsive forces between adjacent nozzles, is experimentally investigated and a polymer-based electrospray device is fabricated and tested to minimize the end effect. For the electrically conductive nozzles of electrospray, the end effect could be reduced by dummy nozzles, through which no liquid is supplied, mounted at the boundary of the array. However, the polymer-based electrospray device can eliminate the end effect without using the dummy dry nozzles due to dielectric characteristic. A novel multiple nozzles of Polymethyl Methacrylate (PMMA)-based electrospray device was successfully fabricated and evaluated for reducing the end effect, showing no deflection of menisci through the boundary nozzles. And ten nozzles device was fabricated and observed to eject liquid jet simultaneously. The electrical current of the spray issued from the nozzles of the polymer-based electrospray device is measured with respect to flow rate and shows a good agreement with the scaling law.     

Experimental investigation for enhanced ferrofluid heat transfer under magnetic field effect

This paper reports an experimental work on the convective heat transfer of ferrofluid flowing through a heated copper tube in the laminar regime in the presence of magnetic field. Significant enhancement on the heat transfer of ferrofluid by applying various orders of magnetic field is observed in this experiment. Also in this experiment, the effect of magnetic nanoparticles concentrations and magnet position have been investigated. The main reason for the enhancement of heat transfer coefficient could be caused due to remarkable changes in thermophysical properties of ferrofluid under the influence of applied magnetic field.