Authors:B. Pacewska, M. Nowacka, I. Wilińska, W. Kubissa, and V. Antonovich
England in years 1973–1974) CACs are applied to structural concrete much less often than Portland cements [ 1 – 3 ]. The deterioration of strength is related with a process of conversion of aluminate hydrates. In case of CACs the nature of hydration
Authors:M. Sajewicz, M. Gontarska, D. Kronenbach, and T. Kowalska
In previous studies we focused our attention on the in-vitro oscillatory chiral conversion of selected profens and amino acids when dissolved in low-molecular-weight solvents. The results obtained encouraged us to check other propionic acid derivatives of biological importance and we therefore decided to investigate the tendency of l-(+)-lactic acid to undergo an analogous process of spontaneous oscillatory in-vitro chiral conversion. As far as we are aware, this type of investigation on lactic acid has not previously been conducted. In our studies, we used solutions of l-(+)-lactic acid in three different mixed solvents, ethanol-water, ethanol-glacial acetic acid, and ethanol-basic buffer (pH 9), in the volume proportion 7:3. The investigations were conducted by thinlayer chromatography (TLC) and polarimetry. The results obtained by TLC gave evidence of the spontaneous oscillatory chiral conversion of l-(+)-lactic acid solution. From TLC results alone it is hardly possible to judge whether this process commences in solution before chromatography, catalyzed by the solid-liquid interface of the TLC plate, or commences immediately on dissolution of the acid and occurs continuously without interruption, both outside and inside the chromatographic system. It is easy to believe that the highly active surface of the silica gel adsorbent acts as a catalyst of chiral conversion. From long-term polarimetric studies it was concluded that l-(+)-lactic acid also undergoes oscillatory chiral conversion in the bulk liquid phase at ambient temperature, i.e. outside the TLC system, although the rate is much lower than in TLC and the racemic mixture is obtained after approximately one month only. In TLC racemization is practically complete within one chromatographic run.
Marchand (1960; 1969) presents a unique analysis of back-formation (e.g.,
) as a combination of zero-derivation (
) and clipping (
). This paper will take a closer look at his analysis and argue that its revised version, which uses the notion of conversion rather than zero-derivation, is superior to the mainstream analyses of back-formation. Citing a lot of instances of back-formed verbs, we will show that back-formation does not necessarily delete an affix (e.g.,
), and that it is semantically parallel not to affixation (e.g.,
) but to conversion (e.g.,
). Almost all the preceding analyses fail to deal with these facts, for they are based on the assumption that back-formation deletes a (supposed) affix, or it is the reverse of affixation. Our new analysis, on the other hand, is free from this traditional assumption and can account for various properties of back-formation, including the above two, in terms of general characteristics of conversion and clipping.
Authors:A. Maciejowska, A. Godziek, M. Sajewicz, and T. Kowalska
This study is devoted to the thin-layer chromatographic demonstration of spontaneous chiral conversion of l-hydroxyproline (l-Hyp) to d-hydroxyproline (d-Hyp), and to its spontaneous peptidization, when dissolved in 70% aqueous methanol and stored at room temperature in a stoppered glass vessel. The adopted enantioseparation conditions were the same ones, as employed earlier for a successful enantioseparation of l- and d-proline. To this effect, we used microcrystalline cellulose as stationary phase and a quaternary mixture composed of 2-butanol:pyridine:glacial acetic acid:water (30:20:4:24, v/v) as mobile phase. Structural difference between proline and hydroxyproline consists in the presence of one hydroxyl group per molecule of the latter amino acid, which makes the respective enantioseparation a more difficult task. Consequently, the obtained separation effect was not a complete (i.e., a baseline) resolution of the two Hyp antimers yet a sufficient enough proof of the appearance of d-Hyp, apparently due to spontaneous chiral conversion taking place in the course of the l-Hyp solution storage and ageing period. The condensation products were discovered both in the fresh and the aged l-Hyp solution, yet in the aged sample, the condensation product yields were considerably higher than in the freshly prepared one (as convincingly demonstrated by mass spectrometry). Demonstration of the condensation products was performed with the aid of thin-layer chromatography (TLC), liquid chromatography-mass spectrometry (LC-MS), and thin-layer chromatography-mass spectrometry (TLC-MS).
Authors:M. Rasul Jan, Farah Jabeen, Jasmin Shah, and Fazal Mabood
An environment friendly method, thermal catalytic pyrolysis of used isobutyl isoprene rubber was investigated. In this method,
the used inner butyl tube rubbers were catalytically pyrolyzed into valuable hydrocarbons and carbon black. In this method,
the tube rubber was pyrolyzed both thermally (with out catalyst) and catalytically in a batch reactor under atmospheric pressure.
The effect of temperature, the amount of catalyst, and the reaction time on the yields of the pyrolyzed products were investigated.
Char yield decreased with increase of pyrolysis temperature while total gas and liquid yields increased. The liquid fraction
was obtained with boiling point up to 478 K. At optimum conditions, the liquid product was collected and analyzed for different
fuel properties. Typical analysis of the used isobutyl isoprene rubber oil for both the cases of parent and refluxed oil has
been performed. Phenols and carbonyls were quantitatively determined by spectrophotometric methods using folin-denis and phenyl
hydrazine reagents, respectively. The distillation data showed that ~100% of oil has boiling point <473 K which is the boiling
point for 80% of distilled product in commercial kerosene. Its specific gravity, viscosity, freezing point, Cetane number,
and diesel index were also within the limits of kerosene.
/min, isothermally at 250 °C for 5 min, cooling to 60 °C.
After calculating the mass balance, the main functions describing the process were determined: the selectivity to the epoxide compound in relation to the allylic compound consumed and the conversion of
Authors:Zoltán Kovács, Juraj Števek, Miroslav Fikar, and Peter Czermak
fructosyltransferase (FTase). The reaction is commonly performed at high initial sucrose concentration (over 300 gL −1 ) in order to shift enzyme activity from hydrolysis of sucrose towards transfructosylation. The conversion is a complex process that involves a series
Authors:Andrzej Mianowski, Zbigniew Robak, Martyna Tomaszewicz, and Sławomir Stelmach
, represented by the level of conversion. By using the Arrhenius equation, the following expression can be derived [ 10 – 19 ]:
Solving Eq. 5 for the condition τ = 0, α s = 0 gives the typical first-order kinetic relationship:
The other form of the
Authors:Lech Nowicki, Anna Antecka, Tomasz Bedyk, Paweł Stolarek, and Stanisław Ledakowicz
agriculture utilization and the waste disposal sites. However, there is a wide range of other uses for sludge, which exploit its energy, namely the thermal processes. The thermal and chemical processes of sewage sludge conversion consist of pyrolysis