Factorizations of Km,n into Spanning Trees

 We establish necessary and sufficient conditions for the existence of a spanning tree factorization of the complete bipartite graph K _m,n. Received: September 1, 1997 Revised: June 29, 1998     

The synthesis of metal-free octaazaphthalocyanine derivatives containing bulky phenoxy substituents to prevent self-association

Octaazaphthalocyanines with eight phenoxy groups in the peripheral sites are prepared for the first time using the simple synthetic procedure of heating their pyrazine-2,3-dicarbonitrile precursor in quinoline. This process avoids transetherification, which has hindered previous attempts at preparing metal-free octaazaphthalocyanines. Metal-containing derivatives were also prepared by adding the appropriate metal salt to the reaction mixture. Bulky iso-propyl or phenyl groups at the 2,6-positions of the phenoxy substituents prevent self-association of the octaazaphthalocyanine cores even in the solid state.     

FT-IR spectroscopy of carbon dioxide in CR-39 and SR-90 track detectors irradiated with ions and gamma-rays at different energies and fluences

Two types of polymeric track detectors CR-39 and SR-90 were irradiated with protons, alpha particles, heavy ions and gamma-rays at different energies and fluences. After irradiation these detectors were analyzed with an FT-IR spectrometer of Jasco type 5300 in transmission and ATR modes. We have found that CO₂ is produced not only by irradiation but also by polymerization. The amount of CO₂ in the detector material is closely related to the latent track formation.     

Determination of Z/β for strange quark matter candidates with CR-39 track detector

In order to confirm the existence of strange quark matter (SQM) in cosmic rays, a series of international balloon flights with a hybrid system combining active counters and passive detectors was conducted under the collaboration between Japan and Italy. In this report, the methodology of how to detect SQM with the hybrid system and how to determine Z/β with CR-39 track detectors are presented.     

Effect of TiCl4‐based TiO2 compact and blocking layers on efficiency of dye‐sensitized solar cells

The effect of the number and arrangement of TiO₂‐based photoanode layers on the efficiency of dye‐sensitized solar cells (DSSCs) was investigated. Compact, mesoporous, and blocking layers of TiO₂ were prepared to form monolayer, bilayer, and trilayer photoanodes. Compact and blocking TiO₂ layers were prepared using dip‐coating technique, whereas the doctor‐blade method was employed to prepare TiO₂ paste layers using nanoparticles prepared by the sol–gel method. The crystalline structure of photoanodes was characterized by X‐ray diffraction (XRD) measurements and their morphology and thickness were characterized by the scanning electron microscopy (SEM) technique. The photovoltaic performance of constructed DSSC devices was investigated and the optimum arrangement was identified and explained in terms of dye loading enhancement and recombination reduction at the fluorine‐doped tin oxide (FTO)/electrolyte interface.     

Evaluating the Effect of four Hosting Ionophores on the Performance of Anion Selective Potentiometric Sensor

A systematically designed practical approach was carried out for the optimization of an anion selective electrode for the determination of an anionic laxative, docusate sodium (DS). The PVC membrane composition and the sensor assembly were systematically optimized. Different sensors were fabricated using tetradodecylammonium bromide (TDAB), tridodecylmethylammonium bromide, tetraheptylammonium bromide as ion exchangers. The effect of ionophore was evaluated using four different host‐guest ionophores, namely; calix[8]arene, β‐cylodextrin, hydroxypropyl‐β‐cylodextrin and carboxymethyl‐β‐cylodextrin to reach the optimum membrane composition. Sensors were constructed in both liquid membrane and solid contact sensor‐assemblies. The slope, linear range, LOQ and response time for each sensor was calculated to assess their performance characteristics. Best Nernstian slope of ?61.38 mV/decade and lowest quantification limit of 7.62×10^?7 M was achieved by the sensor containing TDAB as ion exchanger and Calix[8]arene as ionophore in the PVC matrix using the gold wire solid contact sensor assembly. Electrode selectivity was assured in the presence of DS potential degradation product, common interfering ions and industrial excipients of tablet and gel formulations. Validation was carried out regarding the ICH validation parameters.     

Telescoped,Divergent, Chemoselective C1 and C1‐C1 Homologation of Imine Surrogates: Access to Quaternary Chloro‐ and Halomethyl‐Trifluoromethyl Aziridines

A conceptually novel, high‐yielding, mono‐ or bis‐homologation was realized with lithium halocarbenoids and enables the one‐step, fully chemocontrolled assembly of a new class of quaternary trifluoromethyl aziridines. Trifluoroacetimidoyl chlorides (TFAICs) act as convenient electrophilic platforms, enabling the addition of either one or two homologating elements by simply controlling the stoichiometry of the process. Mechanistic studies highlighted that the homologation event, carried out with two different carbenoids (LiCH₂Cl and LiCH₂F), leads to fluoromethyl analogues in which the first nucleophile is employed for constructing the cycle and the second for decorating the resulting molecular architecture.     

Development of a Reversed-Phase High-Performance Thin-Layer Chromatography Method for the Simultaneous Determination of Trigonelline and Diosgenin Biomarkers in Trigonella foenum-graecum L. Seeds Grown in Variable Environment

JPC – Journal of Planar Chromatography – Modern TLC - We have recently reported on the effect of the environmental conditions on the quantity of diosgenin. Attempts for the simultaneous...