Development and Validation of a Stability-Indicating High-Performance Thin-Layer Chromatographic Method for Determination of Pyridostigmine Bromide in the Presence of Its Alkaline-Induced Degradation Product

JPC – Journal of Planar Chromatography – Modern TLC - A validated, sensitive, and highly selective stability-indicating high-performance thin-layer chromatographic (HPTLC) method has...     

Sampling theory for Sturm–Liouville problem with boundary and transmission conditions containing an eigenparameter

In this paper, we derive the sampling theorem associated with a Sturm–Liouville problem which has two points of discontinuity and contains an eigenparameter in a boundary condition and also two transmission conditions. We establish briefly spectral properties of the problem, and then, we prove the sampling theorem associated with the problem.     

A 1,1‐Carboboration Route to Bora‐Nazarov Systems

Hydroboration of the conjugated enynes 1 a and 1 b with Piers’ borane [HB(C₆F₅)₂] gave the respective dienylboranes trans‐ 2 c and trans‐ 2 d . Their photolysis resulted in the formation of the dihydroborole products 3 c and 3 d . Both were converted to their pyridine adducts 5 c and 5 d , respectively. Compounds 3 c and 5 c,d were characterized by X‐ray diffraction. The reaction of the bis(enynyl)boranes 6 a and 6 b with B(C₆F₅)₃ resulted in the formation of the dihydroboroles 7 a and 7 b , respectively. This reaction is thought to proceed by 1,1‐carboboration of one of the enynyl substituents at boron to generate the dienylborane intermediates 8 a / 8 b , followed by thermally induced bora‐Nazarov ring‐closure and subsequent stabilizing 1,2‐pentafluorophenyl group migration from boron to carbon. Compound 7 a was characterized by X‐ray diffraction and solid‐state ¹¹B NMR spectroscopy.     

Preparation of (99m)Tc labeled vitamin C (ascorbic acid) and biodistribution in rats

The aim of this study was to label ascorbic acid with (99m)Tc and to investigate its radiopharmaceutical potential in rats. Ascorbic acid was labeled with (99m)Tc using the stannous chloride method. The radiochemical purity of [(99m)Tc]ascorbic acid ((99m)Tc-AA) was determined by RTLC, paper electrophoresis, and RHPLC methods. The labeling yield was found to be 93+/-5.0%. The maximum labeling yield of (99m)Tc-AA was determined at pH 5 and 25 degrees C. The biodistribution studies related to (99m)Tc-AA were done in male albino Wistar rats. (99m)Tc-AA, which has a specific activity of 13.02 GBq/mmol, was administered into the tail vein of the rats. The rats were sacrificed at 15, 30, 60, and 120 min after the injection by heart puncture under ether anaesthesia. The organs were weighed after removal. Their activities were counted using a Cd(Te) detector equipped with a RAD 501 count system. The %ID/g (% of injected dose per gram of tissue weight) in each organ and in blood was calculated. Maximum uptake of (99m)Tc-AA was observed in prostate and kidneys at the 60th min. (99m)Tc-AA may be a promising radiopharmaceutical for the imaging of prostate and kidneys.     

Using digital stories to reduce misconceptions and mistakes about fractions: an action study

The aim of this study is to determine the mistakes and misconceptions about fractions of the fourth-grade students in a primary school and to eliminate these mistakes and misconceptions through digital stories. The study has been conducted with a total of 25 students in the fourth-grade of a private primary school in Turkey. An action research method based on qualitative research approach has been used in the study. In the preparation of activities related to digital stories, the mistakes and misconceptions that students have regarding fractions are taken into account. As a data collection tool, the Determination of Misconceptions Form consisting of 30 open ended questions about the fractions prepared by the researchers and the observation notes taken during the implementation process have been used. In addition, semi-structured interviews have been conducted to identify views of teachers and students about activities designed with digital stories. The implementation has been carried out for 5 weeks. Qualitative data analysis techniques have been used in analysing the data. As a result of the research, it has emerged that teaching implementations designed with digital stories have eliminated the mistakes and misconceptions that a large majority of students have about fractions. Most of the students who had a limited perception about the concept of fraction before implementation have fully perceived the definition of fractions after the activities designed with digital stories. Likewise, most of the students who incorrectly modelled the operations with fractions before the implementation, have been able to use the correct model for the operations with fractions after the-implementation fractions. When opinions about the activities designed with digital stories have been examined, it has been found that most students’ express positive opinions on digital story use in lessons and found digital stories fun, instructive and constructive.     

The Existence of Solutions for a Nonlinear First-Order Differential Equation Involving the Riemann–Liouville Fractional-Order and Nonlocal Condition

In this paper, we study necessary conditions for the existence and uniqueness of continuous solution for a nonlocal boundary value problem with nonlinear term involving Riemann–Liouville fractional derivative. Our results are based on Schauder fixed point theorem and the Banach contraction principle fixed point theorem. Examples illustrating the obtained results are also presented.     

Substitution reactions of thorium(IV) acetate to synthesize nano-sized carboxylate complexes

Some mixed-ligand thorium(IV) complexes with the general formula [Th(OOCCH₃)_4?nL_n] (L = anions of myristic, palmitic or stearic acid and n = 1–4) have been synthesized by the stepwise substitution of acetate ions of thorium(IV) acetate with straight chain carboxylic acids in toluene under reflux. The complexes were characterized by elemental analyses, spectral (electronic, infrared, NMR and powder XRD) studies, electrical conductance and magnetic susceptibility measurements. Doubly and triply bridged coordination modes of the ligands were established by their infrared spectra and nano-size of the complexes by powder XRD. Room temperature magnetic susceptibility measurements revealed diamagnetic nature of the complexes. Electronic absorption spectra of the complexes showed π → π*, n → π* and charge transfer transitions. Molar conductance values indicated the complex to be non-electrolytes. These are a new type of mixed-ligand thorium(IV) complexes for which a nano-sized, oxygen bridged polymeric structure has been established on the basis of physico-chemical studies.     

The high-mass component (>m/z 10 000) of coal tar pitch by matrix-assisted laser desorption/ionisation mass spectrometry and size-exclusion chromatography

The size-exclusion chromatography (SEC) of acetone-soluble, pyridine-soluble and pyridine-insoluble fractions of a coal tar pitch indicates a bimodal distribution in each fraction. The proportion of high-mass material excluded from the SEC column porosity increases with solvent polarity. The polymer calibration of SEC shows the mass range of the small molecules to be from approximately 100 u to approximately 6000 u, with the mass range of the large excluded molecules above 200 000 u and up to several million u. In contrast, matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) shows a similar low-mass range of ion abundances (< m/z 6000), but with a smaller range of high-mass ion abundances, from approximately m/z 10 000 to 100 000. The large molecules may have three-dimensional structures to allow molecules of relatively low mass to behave as if they are of large size in SEC. Laser desorption mass spectrometry of the acetone- and pyridine-soluble fractions produced molecular ions of polycyclic aromatics that can be related to the known compositions from gas chromatography (GC) mass spectrometry. The experimental conditions used to generate the bimodal distribution by MALDI-MS involve reducing the ion signal intensities to avoid overload of the detector and enable detection of the high-mass ions, by reducing the high-mass detector voltage (i.e. sensitivity) and increasing the laser power.