Authors:B. Meena, R. Radhajeyalakshmi, P. Vidhyasekaran, and R. Velazhahan
Swain, T. and Hillis, W. E. (1959): The phenolic constituents of Prunus domestica. I. The quantitative analysis of phenolic constitutents. J. Sci. Food Agric. 10, 63-68.
The phenolic constituents of Prunus domestica. I. The
This study furnished results on the enzymatic detection of phenolic compounds by means of a miniaturized heat-flow calorimeter
(IC-calorimeter). Two enzymes were used: tyrosinase and peroxidase. Additionally to the investigations with the IC-calorimeter,
measurements were carried out with a classical reaction calorimeter (LKB 8700) for the very slow reactions with tyrosinase.
By way of contrast, the reactions with peroxidase are fast and seem more suitable for sensor application. The detection limit
for the investigated phenolic compounds is of the order of 1 mmol l−1 .
Authors:G. Vázquez, F. López-Suevos, J. González-Alvarez, and G. Antorrena
Phenol-urea-formaldehyde-tannin (PUFT) adhesives have been prepared by copolymerization at room temperature of pine bark tannins
with phenol-urea-formaldehyde (PUF) prepolymers prepared under varying operating conditions. Differential scanning calorimetry
(DSC) and dynamic mechanical analysis (DMA) have been used to analyse the curing of prepolymers and adhesives. DSC curves
were obtained at three different heating rates and, by means of the Model Free Kinetics isoconversional method, chemical conversion
vs. time at a given temperature was obtained. Mechanical conversion was calculated from DMA storage modulus data for those
adhesives which gave the best results for plywood and MDF boards.
Authors:O. Nikulicheva, L. Pokrovskiy, A. Krysin, V. Fadeeva, and V. Logvinenko
The present paper deals with thermal decomposition of some spatially hindered phenols, which are in the industry as stabilizers
in synthetic materials used. The investigated stabilizers are separated to two groups in respect to mechanism of decomposition
(group I and II). This assumption was confirmed by chromatomass-spectrometric investigations. It allows a stabilizer for forming
a plastic with variety properties to choose.
Authors:O. Nikulicheva, V. Fadeeva, and V. Logvinenko
This paper reports a linear relationship between kinetic characteristics from the Arrhenius equation describing a decomposition
process found when studying the kinetics of thermolysis of spatially hindered phenols. This relationship between the coefficients
is known in the literature as a 'compensation effect'. The existence of the compensation effect permits some conclusions concerning
the decomposition mechanism and thermal characteristics of the compounds under investigation.
Authors:A. Durak, I. Kowalska, and U. Gawlik-Dziki
Phenolic compounds have began to attract the interest of researchers, because they show promise of being powerful antioxidants that can protect the human body from free radicals, the formation of which is
Ionizing radiation, such as gamma-rays and electron-beams, has been applied to modify toxicity of refractory pollutants and
industrial wastewaters, however, very few studies reported the cause of toxicity changes by radiation treatment. In this work,
degradation of phenol and chlorophenols (5·10−4M) by gamma-ray treatment and consequent toxicity changes were evaluated. Toxicity of 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol
(2,4,6-TCP) was gradually decreased with increasing absorbed dose of gamma-radiation. However, in the case of phenol and monochlorophenols
(2-, 3-, and 4-CPs), toxicity was dramatically increased particularly, for a dose of as low as 1 kGy. Hydroquinone, benzoquinone,
catechol, chlorohydroquinone, and 4-chlorocatechol were identified to be main by-products of gamma-ray treatment. From the
solid phase extraction (SPE) fractionation study, toxicity-causing by-products were found to be hydroquinone, benzoquinone,
chlorohydroquinone, and/or 4-chlorocatechol.
], polyaniline [ 20 , 21 ] and polyvinyl alcohol [ 22 ] modified TiO 2 showed photocatalytic activity in the degradation of methyl orange, phenol, and so on.
Unlike these recently reported insoluble homopolymers such as polypyrrole [ 18 ], polythiophene
The gun system of the M1 series tank rides on a pair of self-aligning spherical bearings that allows the elevation and depression
of the cannon. Because these bearings are encapsulated within the rotor housing, periodic lubrication or maintenance is impossible.
To overcome this problem self-lubricating bearings were incorporated into the system. There are two basic liner designs, molded
and fabric. Molded liners are produced by applying a formulation of teflon and typically asbestos into a phenolic resin, which
is applied to the bearing surface, then cured. Fabric liners utilize a woven fabric bonded to the bearing surface, then teflon
which is mixed into phenolic resin is applied to the bearing surface and cured.
Initial studies of the existing bearing liner were completed to determine the liner composition and establish a baseline or
standard to compare thermal and mechanical properties with potential vendors. DSC revealed an average teflon content of 39.53%,
which varied significantly throughout the liner. TG analysis showed an asbestos concentration of 12.22%. The remainder of
the liner was phenolic resin. Physical testing of the bearing from −20 to 120‡C under normal loading conditions demonstrated
excellent thermal stability with little wear.
Bearings from each vendor were tested and compared to the standard properties of the baseline bearing. Some properties were
difficult to compare or insignificant due to the design differences between molded and fabric liners. The testing program
resulted in the qualification of two bearings, which met or exceeded the established standards. Both of these bearings were
designed with fabric liners.
Authors:Petar M. Ristivojević and Gertrud E. Morlock
The quality of three types of beer (dark, light and non-alcoholic) was assessed using high-performance thin-layer chromatography (HPTLC) combined with high-resolution mass spectrometry and chemometrics. An HPTLC separation of the polar beer components in the ethyl acetate extract was developed. The polar components were detected either by the in situ 2,2-diphenyl-1-pic-rylhydrazyl (DPPH*) assay or by derivatization with the Neu’s reagent, followed by the PEG solution. This directly allowed the visual comparison and evaluation of the phenolic/flavonoid or radical scavenging (antioxidative) beer profile. Although the three types of beer showed a very similar chemical HPTLC pattern, the signal intensities were different. Detected by the Neu's reagent, the dark beer extracts contained a high amount of phenolic compounds, and the light beer extracts showed a moderate content, while the non-alcoholic beer extracts had the lowest phenolic content. The HPTLC-DPPH* assay confirmed the higher radical scavenging activity of dark beer extracts, if compared to light and non-alcoholic beer extracts. The most active bands with regard to the radical scavenging property were identified to be desdimethyl-octahydro-iso-cohumulone and iso-n/ad-humulone. The use of pattern recognition techniques showed a clear differentiation between dark and non-alcoholic beer extracts, while light beer extracts did overlap with both beer types. This HPTLC screening allowed the (1) direct comparison of beer samples/types via classification and pattern recognition, (2) the assessment of the beer quality with regard to its antioxidative potential, and (3) the reference to single components.