3 research outputs found
Pea (Pisum sativum) genes involved in symbiosis with nitrogen-fixing bacteria.1.Analysis of the expression of the early nodulin gene ENOD12 using the polymerase chain-reaction
The polymerase chain reaction (PCR) was used to detect the transcription products of the early nodulin gene in the pea. Single-stranded DNA copies were prepared using a primer corresponding to the terminal part of a previously sequenced cDNA clone and a total RNA isolate. The presence of amplification products was detected using Southern hybridization. Expression of the ENOD12 gene was found to occur at the earliest developmental stages of the symbiosis between the pea and nitrogenfixing bacteria, and occurred in root hair cell. Transcription activation required sufficient levels of activity of a limited number of symbiotic bacterial genes, namely nodDABC and nodE. Expression of ENOD12 was inducible by a soluble component excreted into the medium by activated bacteria, and by inhibitors of soluble hormone (auxins) transport. The ENOD12 gene was shown to lack introns
Unexpected Effects of Activator Molecules’ Polarity on the Electroreological Activity of Titanium Dioxide Nanopowders
Titanium
dioxide nanoparticles, obtained using the sol–gel
method and modified with organic solvents, such as acetone, acetonitrile,
benzene, diethyl ether, dimethyl sulfoxide, toluene, and chloroform,
were used as the filler of polydimethylsiloxane-based electrorheological
fluids. The effect of electric field strength on the shear stress
and yield stress of electrorheological fluids was investigated, as
well as the spectra of their dielectric relaxation in the frequency
range from 25 to 10<sup>6</sup> Hz. Modification of titanium dioxide
by polar molecules was found to enhance the electrorheological effect,
as compared with unmodified TiO<sub>2</sub>, in accordance with the
widely accepted concept of polar molecule dominated electrorheological
effect (PM-ER). The most unexpected result of this study was an increase
in the electrorheological effect during the application of nonpolar
solvents with zero or near-zero dipole moments as the modifiers. It
is suggested that nonpolar solvents, besides providing additional
polarization effects at the filler particles interface, alter the
internal pressure in the gaps between the particles. As a result,
the filler particles are attracted to one another, leading to an increase
in their aggregation and the formation of a network of bonds between
the particles through liquid bridge contacts. Such changes in the
electrorheological fluid structure result in a significant increase
in the mechanical strength of the structures that arise when an electric
field is applied, and an increase in the observed electrorheological
effect in comparison with the unmodified titanium dioxide