Investigation of the differentiation of kinetic models

The differentiation of known kinetic models in appropriately chosen coordinate systems has been investigated. A new method of defining the control of chemical reaction rate has been presented, the suggested method being based on the use of known kinetic model equations. It consists in comparing the respective model courses with the experimental. For isothermal conditions, the model curves, f(α) vs. α, are compared with the experimental DTG vs. TG. For conditions of linear temperature increase, however, model courses of the type (1/f(α) (df(α)/dα) vs. α and corresponding experimental curves {[(DDTG/DTG²)—(Eγ/RT²)](1/DTG)} vs. TG are used for comparison: such visual comparison allows a rapid estimation of the closeness of experimental results and predicted models. This method was verified with positive results with experimental material under isothermal conditions (for the thermal decomposition of PbSO₄ and for the oxidation of copper in air) and for conditions of linear temperature increase (for the oxidation of copper in air).     

Determination of cefotaxime and desacetylcefotaxime in cerebrospinal fluid by solid-phase extraction and high-performance liquid chromatography

A microfluidic analytical system for the separation and detection of organic peroxides, based on a microchip capillary electrophoresis device with an integrated amperometric detector, was developed. The new microsystem relies on the reductive detection of both organic acid peroxides and hydroperoxides at -700 mV (vs. Ag wire/AgCl). Factors influencing the separation and detection processes were examined and optimized. The integrated microsystem offers rapid measurements (within 130 s) of these organic-peroxide compounds, down to micromolar levels. A highly stable response for repetitive injections (RSD 0.35-3.12%; n = 12) reflects the negligible electrode passivation. Such a "lab-on-a-chip" device should be attractive for on-site analysis of organic peroxides, as desired for environmental screening and industrial monitoring.     

I[NI4] · NH3, ein neues Derivat des Iodstickstoffs

I[NI₄] · NH₃, a New Derivate of Nitrogen Triiodide The former unknown compound I[NI₄] · NH₃ can be prepared in a closed vessel in the presence of a trace of water from nitrogen triiodide NI₃ · NH₃. It crystallizes hexagonal in the space group P6₃mc with a = 842.5 pm, c = 876.5 pm and Z = 2 formula units. Three corners of a nearly regular tetrahedron (d(N–I) = 219.0, 223.6 pm) are connected by trigonal-pyramidal coordinated iodine atoms with d(I–I) = 308.8 pm to puckered layers stacked in the direction of the c-axis. The molecule NH₃ fills the space between the iodine layers. It is coordinated to that iodine atom of the NI₄-tetrahedron which is not involved in the iodine net. Some chemical properties of the compound are reported.     

RP-LC for Determination of Plastochromanol, Tocotrienols and Tocopherols in Plant Oils

An isocratic high performance liquid chromatographic method, with the application of C₁₈ and C₃₀ reverse-phase column and fluorescence detection, is described for the analysis of plastochromanol, tocotrienols and tocopherols in plant seed oils. The solvent systems have been optimized to obtain high resolution for all tocochromanols and relatively short analysis time. The use of reverse-phase columns for plastochromanol analysis, previously not reported, enables very sensitive and selective detection of plastochromanol which under the described separation conditions did not interfere with tocochromanols or any other compounds. The sample extraction method is fast, simple and highly efficient. The obtained results show that plastochromanol was present in most of the investigated seed oils. Its level was the highest in flax (17–30 mg/100 g oil), rape (8.5–9), camelina (4.3), peanut (1.95), corn (1.69) and grape (1.31) seed oils. Its level in the other investigated oils was below 1 mg/100 g oil, and only in sesame and coconut oils it was not detected. Tocotrienols were found in most of the oils but their content was usually very low (<<1 mg/100 g oil) with the exception of grape, milk thistle and corn oils where it reached >1 mg/100 g oil. Tocopherol content and isomer composition was within the earlier reported literature values for the investigated oils.     

Azo and azoxythiacrown ethers: synthesis and properties

A series of 16- and 18-membered azo- and azoxythiacrown ethers have been synthesized by reductive macrocyclization of the respective bis(nitrophenoxy)oxaalkanes. The aromatic residues located in the polyether region of the molecule were introduced to macrocyclic skeletons and their affinities toward different groups of metal cations in ion-selective electrodes were described. X-ray structures for one dinitropodand and one azoxybenzothiacrown exhibiting strong π–π and π–H interactions have been found.     

Hardy’s Inequality for Laguerre Expansions of Hermite Type

Journal of Fourier Analysis and Applications - Hardy’s inequality for Laguerre expansions of Hermite type with the index $$\alpha \in (\{-1/2\}\cup [1/2,\infty ))^d$$ is proved in the...     

Physical and Sensory Properties of Japanese Quince Chips Obtained by Osmotic Dehydration in Fruit Juice Concentrates and Hybrid Drying

Japanese quince has high health value, but due to its taste and texture, it is difficult to eat raw. The use of innovative drying methods to produce dried snack foods from these fruits may be of interest to producers and consumers. The physicochemical and sensory properties of 3 mm slices of Japanese quince fruit (with skin, without seeds) obtained by osmotic pre-treatment in chokeberry and apple juice concentrates, and with the use of convection (convective drying, C-D), freeze-drying (F-D), and convection-microwave-vacuum drying (hybrid) are assessed. The methods of drying osmo-dehydrated slices do not affect the dry matter content. In most dried quince, the water activity is 0.40 or lower. Pre-osmotic dehydration and drying have a significant impact on the mechanical and acoustic properties of quince chips. Sensory attractive chips emit loud acoustic emission (AE) during the breaking test. Chips that are osmo-dehydrated in a mixture of chokeberry juice concentrate and sucrose and dried by a hybrid method are attractive. They have a dark red color given by chokeberry concentrate and a slight sweet (with a slight sour-bitter) taste. The sensory evaluation was useful for determining the quality of the chips in terms of their texture (crispness) tested by mechanical methods. Their sensory ratings (overall desirability as weight of color, taste, crispness, and flavor) are high and similar (from 3.8 to 4.1). The use of innovative drying methods with pre-osmotic treatment allows obtaining dried material with properties comparable to those obtained by the F-D method, but in a much shorter time, i.e., with lower energy and using a simple method.     

Emission Characteristics of the D.C., 100 kHz and 13.5 MHz Hollow Cathode Discharges

Hollow cathode discharges in argon at various pressures and currents have been studied by optical emission spectroscopy. The cathodes were made of copper, bronze and brass. The discharges were supplied by direct, 100 kHz and 13.5 MHz currents. Atomic and ionic spectra of plasma gas and elements of cathode materials and molecular bands of ZnH and PN formed due chemical reactions between plasma components have been excited and measured. Relations between emission intensities, excitation temperatures and discharge conditions have been analysed and discussed.