The electronic structure and dielectric screening of finite-length armchair carbon nanotubes are studied with both tight-binding and ab initio methods. Good agreement is found in the band gap oscillation patterns and dielectric constants, which validates the tight-binding method as a reliable and fast approach to describe the screening effect of carbon nanotubes. For an illustration, our method is applied to a system consisting of a short (6,6) nanotube filled with six water molecules. Substantial screening of the water dipoles through the nanotube is observed. This polarization effect should have an important influence on the permeation of water and other biomolecules inside carbon nanotubes.
This article presents scientific research on the resistance process forming in
dipteran insects on the example of the housefly (Musca domestica), which occurs
with synthetic pyrethroids, as well as methods to control the occurring resistance.
Houseflies (Musca domestica) are insects of the order Diptera and one of the most
resistant insect species to modern insecticides, and their natural populations may be
insusceptible to all drugs used to control them. Pyrethroids are insecticides that are
synthetic derivatives of natural pyrethrins. They are the most widely used group of
insecticides today, and their use in agriculture is considered to be the most effective
and least toxic in insect control. One of the main disadvantages of pyrethroids is
considered to be insect resistance to modern insecticides. The main content of
the study is the analysis of available scientific data on the resistance occurring in
Dipterans with synthetic pyrethroids, and of the main directions in the control of
such resistance. Scientific research was searched in domestic and foreign sources.
The electronic structure and dielectric screening of finite-length armchair carbon nanotubes are studied with both tight-binding and ab initio methods. Good agreement is found in the band gap oscillation patterns and dielectric constants, which validates the tight-binding method as a reliable and fast approach to describe the screening effect of carbon nanotubes. For an illustration, our method is applied to a system consisting of a short (6,6) nanotube filled with six water molecules. Substantial screening of the water dipoles through the nanotube is observed. This polarization effect should have an important influence on the permeation of water and other biomolecules inside carbon nanotubes.
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