Thin-layer chromatographic determination of catecholamines, 5-hydroxytryptamine, and their metabolites in biological samples: a review

A review of methodology for separation, detection, and quantitative determination of catecholamines, 5-hydroxytryptamine, and their acidic metabolites in biological tissue and fluids by thin-layer chromatography is presented. Selected procedures, including fluorometric scanning densitometry for catecholamine acetyl derivatives and color scanning densitometry for acids, are described.     

Growth Kinetics of Potassium-Dihydrogen Phosphate Crystals in Solution

Growth rate data of (101) faces of KDP crystals as a function of the relative supersaturation of the solution are analyzed on the basis of BURTON , CABRERA and FRANK surface-diffusion model applied to the growth from solution. The characteristic constants in the BCF function are determined for 50°C. Approximate values of the free activation energies for dehydration, desorption, surface diffusion and entering the kinks from the surface are calculated. The experimental data previously obtained by MULLIN and AMATAVIVADHANA and by BELOUET are also discussed.     

Oscillation of Functions in the Hölder Class

Potential Analysis - We study the size of the set of points where the α-divided difference of a function in the Hölder class Λα is bounded below by a fixed positive constant....     

Synthesis and conjugation of a triiodohydroxylamine for the preparation of highly X‐ray opaque poly(ε‐caprolactone) materials

To address a need for highly X‐ray opaque biodegradable materials, a series of poly(ε‐caprolactone) derivatives were prepared using oxime post‐polymerization modification to conjugate two different iodinated hydroxylamines. These materials were synthesized with up to 32 wt. % iodine content and demonstrated improved X‐ray contrast relative to both the ketone precursors and previously reported monoiodinated materials. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 787–793     

Mass spectrometry characterisation of fatty acids from metabolically engineered soybean seeds

Improving the quality and performance of soybean oil as biodiesel depends on the chemical composition of its fatty acids and requires an increase in monounsaturated acids and a reduction in polyunsaturated acids. Despite its current use as a source of biofuel, soybean oil contains an average of 25 % oleic acid and 13 % palmitic acid, which negatively impacts its oxidative stability and freezing point, causing a high rate of nitrogen oxide emission. Gas chromatography and ion mobility mass spectrometry were conducted on soybean fatty acids from metabolically engineered seed extracts to determine the nature of the structural oleic and palmitic acids. The soybean genes FAD2-1 and FatB were placed under the control of the 35SCaMV constitutive promoter, introduced to soybean embryonic axes by particle bombardment and down-regulated using RNA interference technology. Results indicate that the metabolically engineered plants exhibited a significant increase in oleic acid (up to 94.58 %) and a reduction in palmitic acid (to <3 %) in their seed oil content. No structural differences were observed between the fatty acids of the transgenic and non-transgenic oil extracts.

Singular Polynomials of Generalized Kasteleyn Matrices

Kasteleyn counted the number of domino tilings of a rectangle by considering a mutation of the adjacency matrix: a Kasteleyn matrix K. In this paper we present a generalization of Kasteleyn matrices and a combinatorial interpretation for the coefficients of the characteristic polynomial of KK* (which we call the singular polynomial), where K is a generalized Kasteleyn matrix for a planar bipartite graph. We also present a q-version of these ideas and a few results concerning tilings of special regions such as rectangles.     

Modelling magnetic polarisation J50 by different methods

Two different methods for modelling the angular behaviour of magnetic polarisation at 5000 A/m (J₅₀) of electrical steels were evaluated and compared. Both methods are based upon crystallographic texture data. The texture of non-oriented electrical steels with silicon content ranging from 0.11 to 3%Si was determined by X-ray diffraction. In the first method, J₅₀ was correlated to the calculated value of the average anisotropy energy in each direction, using texture data. In the second method, the first three coefficients of the spherical harmonic series of the ODF and two experimental points were used to estimate the angular variation of J₅₀. The first method allows the estimation of J₅₀ for samples with different textures and Si contents using only the texture data, with no need of magnetic measurement, and this is advantageous, because texture data can be acquired with less than 2 g of material. The second method may give better adjust in some situations but besides the texture data, it requests magnetic measurements in at least two directions, for example, rolling and transverse directions.     

Effect of deformation and annealing on the microstructure and magnetic properties of grain-oriented electrical steels

The effect of plastic deformation and subsequent annealing on the magnetic properties and microstructure of a grain-oriented (GO) electrical steel has been studied. True strain (ε) from 0.002 to 0.23 was applied by rolling in two directions, rolling (RD) and transverse (TD). The deterioration of power losses varies according to the direction of deformation. Annealing the strained material—at 800 °C/2 h—leads to a recrystallization and restored magnetic properties. The main components of annealed-textures are around 15–35° from those of deformed-textures for both RD and TD. Rolling along {1 1 0} 〈0 0 1〉 direction leads to the development of deformation twins.     

Recent trends on the implementation of reticular materials in column-centered separations

Advances in the development of column-based analytical separations are strongly linked to the development of novel materials. Stationary phases for chromatographic separation are usually based on silica and polymer materials. Nevertheless, recent advances have been made using porous crystalline reticular materials, such as metal-organic frameworks and covalent organic frameworks. However, the direct packing of these materials is often limited due to their small crystal size and nonspherical shape. In this review, recent strategies to incorporate porous crystalline materials as stationary phases for liquid-phase separations are covered. Moreover, we discuss the potential future directions in their development and integration into suitable supports for analytical applications. Finally, we discuss the main challenges to be solved to take full advantage of these materials as stationary phases for analytical separations.