Search results for "Ethylene"

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…

Improvement of biphasic polymerization by application of binary ionic liquid mixture

2013

Abstract The mixture of two ionic liquids, 1- n -butyl-3-methylimidazolium and 1-(2-phenylethyl)-3-methylimidazolium chloroaluminates, [C 4 -mim][AlCl 4 ] and [PhC 2 -mim][AlCl 4 ], were applied as a medium to immobilize the Cp 2 TiCl 2 titanocene catalyst for biphasic ionic liquid/hexane ethylene polymerization. The system makes possible to perform the reaction at lower temperatures, below the melting temperature of the aralkyl ionic liquid. A better separation of the ionic liquid phase was observed and an easier mass transfer of the polymer product from the ionic liquid to the hexane phase was obtained. The polyethylene reveals bimodal distribution of molecular weight. It is characterized…

Hydrophilic and hydrophobic copolymers of a polyasparthylhydrazide bearing positive charges as vector for gene therapy

2008

BACKGROUND: The design of polymeric vectors for gene delivery provided with specific properties is one of the most critical aspects for a successful gene therapy. These polymers should be biocompatible as well as able to carry efficiently DNA to target tissues and to transfect it into cells. RESULTS: The formation of complexes of poly[(α,β-asparthylhydrazide)–poly(ethylene glycol)] and poly[(α,β-asparthylhydrazide)–hexadecylamine] copolymers functionalised with glycidyltrimethylammonium chloride (PAHy–PEG-GTA and PAHy–C16-GTA, respectively) with DNA was studied. The effects of the introduction of hydrophilic (PEG) or hydrophobic (C16) moieties on the chains of PAHy–GTA copolymers, such as t…