2,6‐Dicarboxypyridinium Fluorochromate: A Mild and Efficient Reagent for Oxidative Deprotection of Oximes,Phenylhydrazones, and Semicarbazones to Their Corresponding Carbonyl Compounds under Solvent‐Free Conditions

2,6‐Dicarboxypyridinium fluorochromate as a new, rapid, and efficient reagent was prepared and used for the oxidative deprotection of oximes, phenylhydrazones, and semicarbazones to their carbonyl analogues under solvent‐free conditions at room temperature.     

Oxygen atom-induced D2 and D2O desorption on D/Si(1 1 1) surfaces

We studied reaction of oxygen atoms with D-terminated Si(1 1 1) surfaces from a desorption point of view. As the D (1 ML)/Si(1 1 1) surface was exposed to O atoms D₂ and D₂O molecules were found to desorb from the surface. The desorption kinetics of D₂ and D₂O molecules exhibited a feature characterized with a quick rate jump at the very beginning of O exposure, which was followed by a gradual increase with a delayed maximum and then by an exponential decrease. The O-induced D₂ desorption spectra as a function of T_s appeared to be very similar to the H-induced D₂ desorption spectrum from the D/Si(1 1 1) surfaces. Possible mechanisms for the O-induced desorption reactions were discussed.     

A simple in situ visual and tristimulus colorimetric method for the determination of trace arsenic in environmental water after its collection on a mercury(II)-impregnated paper.

A simple in situ visual and tristimulus colorimetric method for the determination of trace arsenic in environmental water after collecting arsenic on a test paper impregnated with mercury(II) bromide and rosaniline chloride by its reduction aeration has been developed. The color development on the test paper is based on the formations of AsH(HgBr)2 (yellow) and/or As(HgBr)3 (brownish yellow) by a reaction between mercury(II) bromide and arsine (AsH3), which is produced through the reduction of As(III) (arsenite ion) and/or As(V) (arsenate ion) in a sample solution. To a sample solution, potassium iodide, tin(II) chloride, zinc sand and 4 ml of 6 M hydrochloric acid solution were added successively. The liberated arsine was collected on the test paper. The yellow or brownish-yellow color intensity on the test paper was measured by a tristimulus colorimeter and also by a visual method. The established method is applicable to the determination of arsenic in environmental water sample such as river, brackish, and seawater types.     

Hertz problem for a rigid punch moving across the surface of a semi-infinite elastic solid

The elastodynamic problem of a rigid punch moving at a constant sub-Rayleigh speed across the surface of an elastic half-space is investigated in the present paper. The unknown contact region is determined as part of solution from the unilateral or Signorini conditions. Numerical results are plotted showing how the eccentricity of the contact ellipse changes with the punch speed. Some asymptotic properties of the solution for the case where the punch speed is comparable with the Rayleigh wave speed are explored in details.     

Kinetic spectrophotometric determination of famotidine in commercial dosage forms.

A simple kinetic spectrophotometric method is described for the determination of famotidine. The method is based on the oxidation of the drug with alkaline potassium permanganate. The reaction is followed spectrometrically by measuring the rate of change of the absorbance at 610 nm. The initial-rate and fixed-time (at 12 min) methods are adopted for determining the drug concentration. The calibration graphs are linear in the ranges of 2-10 microg mL(-1) and 1-8 microg mL(-1) using the initial-rate and fixed-time methods, respectively. The method has been applied to the determination of famotidine in tablet formulations. The obtained results are compared statistically with those given by a reference spectrophotometric method.     

Mathematical analysis of impulsive fractional differential inclusion of pantograph type

In this article, we formulate fractional differential inclusion of pantograph type (IFDIP), incorporating impulsive behavior of the solution. The boundary conditions taken into account are nonlocal in nature. We will consider the convex problem and prove the Filippov–Wazewski-type theorem. Moreover, existence of solution, uniqueness of a solution, and the topological properties of the solution's set will be examined for the problem under consideration. In the second part, the study will be confined to the second-order impulsive fractional differential equation of pantograph type. For certain geometric characteristics of the solution's set, Aronszajn–Browder–Gupta-type results will be explored for the newly introduced differential equation. Also, it will prove the existence of solution for the first-order fractional differential equation of pantograph type having impulsive behavior of the solution.     

A new triterpenoid from roots of Laportea crenulata and its antifungal activity

A new triterpenoid 2alpha,3beta,21beta,23,28-penta hydroxyl 12-oleanene and two known compounds were isolated from the roots of Laportea crenulata Gaud. The structures of all compounds were elucidated on the basis of various spectroscopic data. The two known compounds beta-sitosterol and beta-sitosterol 3-beta-D-glucopyranoside are also the first report of isolation from this plant. The antifungal activity of new triterpenoid was studied against Aspergillus flavus, Aspergillus niger, Candida albicans, and Rhizopus aurizae, and compared with the activity of nystatin (30 microg disc(-1)). This compound has shown moderate activity against tested fungi.     

Synthesis, characterization, and photoinduced electron transfer in functionalized single wall carbon nanohorns

Single-wall carbon nanohorns (SWNHs) are a new class of material that is closely related to single-wall carbon nanotubes. Here, we describe the synthesis and characterization of a series of SWNHs functionalized with ethylene glycol chains and porphyrins. Functionalization of carbon nanohorns has been achieved using two different synthetic protocols: (1) direct attack of a free amino group on the nanohorn sidewalls (nucleophilic addition) and (2) amidation reaction of the carboxylic functions in oxidized nanohorns. The nanohorn derivatives have been characterized by a combination of several techniques, and the electronic properties of the porphyrin/nanohorn assemblies (SWNH/H2P) have been investigated by electrochemistry, spectroelectrochemistry, and a series of steady-state and time-resolved spectroscopy. The cyclic voltammetry curve of nanohorn/porphyrin conjugate 6 showed a continuum of faradic and pseudocapacitive behavior, which is associated with multiple-electron transfers to and from the SWNHs. Superimposed on such a pseudocapacitive current, the curve also displays three discrete reduction peaks at -2.26, -2.57, and -2.84 V and an oxidation peak at 1.12 V (all attributed to the porphyrin moiety). Steady-state and time-resolved fluorescence demonstrated a quenching of the fluorescence of the porphyrin in SWNH/H2P conjugates 5 and 6 compared to the reference free base porphyrin. Transient absorption spectra permitted the electron-transfer process between the porphyrins and the carbon nanostructures to be highlighted.