Search results for "Lene"

Temperature influence on moisture transfer through synthetic films

2000

Abstract Water transfer through films was investigated as a function of the temperature, the physical state of water and the relative humidity (RH) difference. The films were two synthetic packagings: a hydrophobic one, the polyethylene, a hydrophilic one, the cellophane. Some phenomena which could occur at low temperatures were discussed, such as polymer structure change due to mechanical relaxation or network plasticisation and modification of the penetrant diffusion at its melting temperature. But it seems that the comparison of water permeabilities (WPs) with temperature, especially at subzero temperatures, requires the correction of their calculation with the difference of water chemic…

Dynamic evolution of the oscillatory Belousov-Zhabotinsky reaction upon addition of a non-ionic polymer

2006

Abstract The dynamic evolution of the oscillatory Belousov–Zhabotinsky reaction upon addition of increasing amount of the non-ionic polymer polypropylene glycol with molecular weight 425 g mol−1 (PPG-425) was investigated in a stirred-batch reactor by monitoring the Ce(IV) absorbance changes. The oscillatory parameters are significantly altered by the presence of the polymer. The findings obtained in the present work revealed that the PPG-425 is not only more effective, than other polymer previously [R. Lombardo, C. Sbriziolo, M.L. Turco Liveri, K. Pelle, M. Wittmann, Z. Noszticzius, in: J.A. Pojman, Q. Tran-Cong-Miyata (Eds.), Nonlinear Dynamics in Polymeric Systems, American Chemical Soci…

Mechanical properties of injection-molded binary blends of polyethylene with small additions of a liquid-crystalline polymer

2011

The results of the investigation of the mechanical properties of polyethylene (PE) blends with small (<3 wt %) additions of thermotropic liquid-crystalline polymers (LCPs) are reported. PE/LCP compositions with various LCP weight contents were obtained by thermoplastic mixing in a two-stage process. Short-term and long-term mechanical behavior of various PE/LCP compositions were analyzed. Data on the influence of LCP addition on the tensile elastic modulus [or Young's modulus (E)], stress at yield (σY), stress at break (σB), strain at yield, strain at break, and deformation at long-term (1000-h) tensile creep were obtained. The experimental results of the investigation show that even small …

Synthesis and activity of zirconocene catalysts supported on silica-type sol-gel carrier for ethylene polymerization

2001

Synthesis and activity of bis(cyclopentadienyl)zirconium dichloride catalyst supported on unconventional silica-type material obtained in sol-gel process and activated by organoaluminium co-catalyst were studied. The effect of support modification conditions (thermal dehydration and/or modification by organoaluminium compound) and a type of co-catalyst on an activity of the catalytic system in ethylene polymerization and properties of resulting polymers were investigated and compared with results obtained earlier for vanadium catalysts supported on mentioned sol-gel carrier. The most appropriate method of the sol-gel silica-type support preparation is thermal pre-treating (200°C) followed b…

Herbicidally Active Derivatives of Aminomethylenebis-Phosphonic Acid-Mode of Action and Structure - Activity Relationship

1996

Abstract: (N-pyridylamino)methylenebisphosphonates exhibit strong herbicidal activity which may be reversed by supplementation of the growth media with aromatic amino acids. They appeare to be the inhibitors of aromatic amino acids biosynthesis acting as inhibitors of DAHP synthase the first enzyme of shikimate pathway. Over 40 analogues of these acids were synthesized in order to determine the structure-activity relationship.

New amphiphilic conjugates of mono- and bis(carboxy)-PEG(2,000) polymers with lipoamino acids as surface modifiers of colloidal drug carriers

2010

Mode of action of herbicidal derivatives of aminomethylenebisphosphonic acid. Part II. Reversal of herbicidal action by aromatic amino acids

1997

The herbicidal action of N-pyridylaminomethylenebisphosphonic acids is accompanied by an impairment of anthocyanin biosynthesis. This suggests that they might act as inhibitors of some steps in aromatic amino acid biosynthesis. Herbicidal effects were reversed by aromatic amino acids using both bacterial and plant models, a finding that strongly supports this hypothesis. Structural features of these compounds suggest the sixth enzyme in the shikimate pathway 5-enol-pyruvoylshikimate-3-phosphate (EPSP) synthase as a possible target, since a strong structural similarity exists between aminomethylenebisphosphonic acid and an inhibitor of EPSP synthase, the herbicide glyphosate. This is, howeve…

Phytochemical constituents and chemosystematic significance of Pulicaria jaubertii E.Gamal-Eldin (Asteraceae)

2018

Abstract The chemical characterization of methylene chloride/methanol (1:1) extract of the air-dried whole medicinal plant, Pulicaria jaubertii E. Gamal-Eldin, led to isolation and identification of two new hydroquinone compounds; 2-(2-acetoxy propyl), 5-methyl hydroquinone (1) and 2-(2-hydroxy propyl), 5-methyl hydroquinone-4-O-β-D-glucopyranoside (2), four known flavonols (3-6) and 7 known dihydroflavonols (7-13). The structures were established depending upon comprehensive analysis of the NMR, IR and HR/EI-MS data. Herein, compounds 6, and 10-13 were isolated for the first time from this plant. The chemotaxonomic significance of the isolated flavonoids from P. jaubertii comparing with th…

ChemInform Abstract: Comparative Lipase-Catalyzed Hydrolysis of Ethylene Glycol Derived Esters. The 2-Methoxyethyl Ester as a Protective Group in Pep…

2010

FT-IR spectroscopic investigation of bacterial cell envelopes from Zymomonas mobilis which have different surface hydrophobicities

2013

Abstract Changes in the cell envelope composition of bacteria Zymomonas mobilis 113S which resulted in varied cell surface hydrophobicity (CSH) were examined using FT-IR-spectroscopy and conventional methods of biochemical analysis. Significant differences in all analyses were detected between hydrophilic and hydrophobic compounds in the envelopes of Z. mobilis . A significant positive linear relationship ( P Z. mobilis and the ratio of absorbance band intensities assigned to the CH 2 and CH 3 vibrations from lipids as well as the asymmetric and symmetric stretching vibrations of these methylene and methyl groups. Differences were also seen between the ratio of band absorbances arising from…