30 research outputs found
Non-linear dynamo waves in an incompressible medium when the turbulence dissipative coefficients depend on temperature
Microbial synthesis of silver nanoparticles by streptomyces glaucus and spirulina platensis
Microbial synthesis of nanoparticles has a potential to develop simple, costeffective
and eco-friendly methods for production of technologically important
materials. In this study, for the first time a novelactinomycete strain Streptomyces glaucus71
MD isolated from a soy rhizosphere in Georgiais for the first time extensively
characterized and utilized for the synthesis of silver nanoparticles. Scanning Electron
Microscope (SEM) allowed observing extracellular synthesis of nanoparticles, which
has many advantages from the point of view of applications. Production of silver nanoparticles
proceeded extracellularlywith the participation of another microorganism, bluegreen
microalgae Spirulinaplatensis (S. platensis). In this study it is shown that the
production rate of the nanoparticles depends not only on the initial concentration of
AgNO3 but also varies with time in a nonmonotonic way. SEM study of silver nanoparticles
remaining on the surface of microalgae revealed that after 1 day of exposure to 1
mM AgNO3 nanoparticles were arranged as long aggregates along S. platensiscells
strongly damaged by silver ions. However, after 5 days of exposure to silver S. platensiscells
looked completely recovered and the nanoparticles were distributed more uniformly
on the surface of the cells.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2067
The spark-associated soliton model for pulsar radio emission
We propose a new, self-consistent theory of coherent pulsar radio emission
based on the non-stationary sparking model of Ruderman & Sutherland (1975),
modified by Gil & Sendyk (2000) in the accompanying Paper I. According to these
authors, the polar cap is populated as densely as possible by a number of
sparks with a characteristic perpendicular dimension D approximately equal to
the polar gap height scale h, separated from each other also by about h. Each
spark reappears in approximately the same place on the polar cap for a time
scale much longer than its life-time and delivers to the open magnetosphere a
sequence of electron-positron clouds which flow orderly along a flux tube of
dipolar magnetic field lines. The overlapping of particles with different
momenta from consecutive clouds leads to effective two-stream instability,
which triggers electrostatic Langmuir waves at the altitudes of about 50
stellar radii. The electrostatic oscillations are modulationally unstable and
their nonlinear evolution results in formation of ``bunch-like'' charged
solitons. A characteristic soliton length along magnetic field lines is about
30 cm, so they are capable of emitting coherent curvature radiation at radio
wavelengths. The net soliton charge is about 10^21 fundamental charges,
contained within a volume of about 10^14 cm^3. For a typical pulsar, there are
about 10^5 solitons associated with each of about 25 sparks operating on the
polar cap at any instant. One soliton moving relativisticaly along dipolar
field lines with a Lorentz factor of the order of 100 generates a power of
about 10^21 erg/s by means of curvature radiation. Then the total power of a
typical radio pulsar can be estimated as being about 10^(27-28) erg/s.Comment: 27 pages, 5 figures, accepted by Ap
MERCURY ADSORPTION BY ARTHOBACTER GLOBIFORMIS AND SPIRULINA PLATENSIS
Abstract. The increasing contamination of soil, sediment, and water with heavy metals by natural and industrial processes is a worldwide problem. Many bacteria and microalgae have demonstrated ability to absorb toxic elements. To study mercury biosorption by bacteria Arthrobacter globiformis and microalga Spirulina platensis neutron activation analysis (NAA) was applied. The process of mercury biosorption by these media was described by Freundlich and Langmuir-Freundlich Model. Both microorganisms showed a great potential to be used as biosorbing agents for mercury removal from the environment
Non-linear dynamo waves in an incompressible medium when the turbulence dissipative coefficients depend on temperature
Non-linear α-ω; dynamo
waves existing in an incompressible medium with the turbulence dissipative
coefficients depending on temperature are studied in this paper. We investigate
of α-ω solar non-linear dynamo waves when only the first
harmonics of magnetic induction components are included. If we ignore the second
harmonics in the non-linear equation, the turbulent magnetic diffusion
coefficient increases together with the temperature, the coefficient of
turbulent viscosity decreases, and for an interval of time the value of dynamo
number is greater than 1. In these conditions a stationary solution of the
non-linear equation for the dynamo wave's amplitude exists; meaning that the
magnetic field is sufficiently excited. The amplitude of the dynamo waves
oscillates and becomes stationary. Using these results we can explain the
existence of Maunder's minimum