64 research outputs found
Focus on plasma medicine
‘Plasma Healthcare’ is an emerging interdisciplinary research topic
of rapidly growing importance, exploring considerable opportunities at the
interface of plasma physics, chemistry and engineering with life sciences. Some
of the scientific discoveries reported so far have already demonstrated clear
benefits for healthcare in areas of medicine, food safety, environmental hygiene,
and cosmetics. Examples include ongoing studies of prion inactivation, chronic
wound treatment and plasma-mediated cancer therapy. Current research ranges
from basic physical processes, plasma chemical design, to the interaction of
plasmas with (i) eukaryotic (mammalian) cells; (ii) prokaryotic (bacteria) cells,
viruses, spores and fungi; (iii) DNA, lipids, proteins and cell membranes; and
(iv) living human, animal and plant tissues in the presence of biofluids. Of
diverse interests in this new field is the need for hospital disinfection, in particular
with respect to the alarming increase in bacterial resistance to antibiotics, the
concomitant needs in private practices, nursing homes etc, the applications in
personal hygiene—and the enticing possibility to ‘design’ plasmas as possible
pharmaceutical products, employing ionic as well as molecular agents for
medical treatment. The ‘delivery’ of the reactive plasma agents occurs at the
gaseous level, which means that there is no need for a carrier medium and access
to the treatment surface is optimal. This focus issue provides a close look at the
current state of the art in Plasma Medicine with a number of forefront research
articles as well as an introductory review
Levitation of particles in O₂ plasma
Oxygen discharges are scientifically and industrially interesting owing to chemical properties and
physical effects. These latter are mostly due to the presence of negative ions affecting the plasma
boundary in front of the surface to be processed. In this contribution we use particles levitating in the
Oxygen plasma sheath as a diagnostic of the intermediate positions in the sheath between the plasma
and the solid surface. The experimental results for three particle sizes are compared with the theoretical
levitation force obtained by the modelling of the electronegative plasma sheath and the charging of
particles in it.Розряди в кисні представляють науковий і технологічний інтерес завдяки хімічнимвластивостямтафізичним
ефектам. Причиною цього є наявність негативних іонів,
що впливають на границю плазми перед оброблюваною поверхнею. У даній роботі використовуються частинки, які левітують в приелектродному шарі кисневої
плазми як діагностичний засіб для проміжних положень у шарі міжплазмою і твердою поверхнею. Експериментальні результати для трьох розмірів частинок
порівнюються з теоретичною силою левітації, отриманоїза допомогою моделювання плазмового шару в
електронегативному газі та процесу зарядки в ньому
частинок.Разряды в кислороде представляют научный и технологический интерес благодаря химическим свойствам и физическим эффектам. Причиной этого является
наличие отрицательных ионов, воздействующих на границу плазмы перед обрабатываемой поверхностью. В
данной работе используются частицы, левитирующие
в приэлектродном слое кислородной плазмы как диагностическое средство для промежуточных положений
в слое между плазмой и твердой поверхностью. Экспериментальные результаты для трех размеров частиц
сравниваются с теоретической силой левитации, полученной с помощью моделирования плазменного слоя
в электроотрицательном газе и процесса зарядки в нем
частиц
Plasma medicine: an introductory review
This introductory review on plasma health care is intended to
provide the interested reader with a summary of the current status of this
emerging field, its scope, and its broad interdisciplinary approach, ranging
from plasma physics, chemistry and technology, to microbiology, biochemistry,
biophysics, medicine and hygiene. Apart from the basic plasma processes
and the restrictions and requirements set by international health standards,
the review focuses on plasma interaction with prokaryotic cells (bacteria),
eukaryotic cells (mammalian cells), cell membranes, DNA etc. In so doing, some
of the unfamiliar terminology—an unavoidable by-product of interdisciplinary
research—is covered and explained. Plasma health care may provide a fast and
efficient new path for effective hospital (and other public buildings) hygiene—
helping to prevent and contain diseases that are continuously gaining ground
as resistance of pathogens to antibiotics grows. The delivery of medically
active ‘substances’ at the molecular or ionic level is another exciting topic
of research through effects on cell walls (permeabilization), cell excitation
(paracrine action) and the introduction of reactive species into cell cytoplasm.
Electric fields, charging of surfaces, current flows etc can also affect tissue in
a controlled way. The field is young and hopes are high. It is fitting to cover
the beginnings in New Journal of Physics, since it is the physics (and nonequilibrium
chemistry) of room temperature atmospheric pressure plasmas that
have made this development of plasma health care possible
Rotational kinetics of absorbing dust grains in neutral gas
We study the rotational and translational kinetics of massive particulates
(dust grains) absorbing the ambient gas. Equations for microscopic phase
densities are deduced resulting in the Fokker-Planck equation for the dust
component. It is shown that although there is no stationary distribution, the
translational and rotational temperatures of dust tend to certain values, which
differ from the temperature of the ambient gas. The influence of the inner
structure of grains on rotational kinetics is also discussed.Comment: REVTEX4, 20 pages, 2 figure
26Al in the local interstellar medium
We estimate the 1.8 MeV luminosity of the Sco-Cen association due to
radioactive decay of 26Al to (4-15) 10e-5 ph cm**-2 s**-1. We propose a low
surface brightness, limb brightened bubble for the 1.8 MeV intensity
distribution. The detectibility of this distribution with existing gamma-ray
telescopes is discussed.Comment: 4 pages, LaTeX, lamuphys macro, to be published in "Lecture Notes in
Physics
Fokker-Planck Equation for Boltzmann-type and Active Particles: transfer probability approach
Fokker-Planck equation with the velocity-dependent coefficients is considered
for various isotropic systems on the basis of probability transition (PT)
approach. This method provides the self-consistent and universal description of
friction and diffusion for Brownian particles. Renormalization of the friction
coefficient is shown to occur for two dimensional (2-D) and three dimensional
(3-D) cases, due to the tensorial character of diffusion. The specific forms of
PT are calculated for the Boltzmann-type of collisions and for the
absorption-type of collisions (the later are typical for dusty plasmas and some
other systems). Validity of the Einstein's relation for the Boltzmann-type
collisions is analyzed for the velocity-dependent friction and diffusion
coefficients. For the Boltzmann-type collisions in the region of very high
grain velocity as well as it is always for non-Boltzmann collisions, such as,
e.g., absorption collisions, the Einstein relation is violated, although some
other relations (determined by the structure of PT) can exist. The generalized
friction force is investigated in dusty plasma in the framework of the PT
approach. The relation between this force, negative collecting friction force
and scattering and collecting drag forces is established.+AFwAXA- The concept
of probability transition is used to describe motion of active particles in an
ambient medium. On basis of the physical arguments the PT for a simple model of
the active particle is constructed and the coefficients of the relevant
Fokker-Planck equation are found. The stationary solution of this equation is
typical for the simplest self-organized molecular machines.+AFwAXA- PACS
number(s): 52.27.Lw, 52.20.Hv, 52.25.Fi, 82.70.-yComment: 18 page
Interstellar Dust Inside and Outside the Heliosphere
In the early 1990s, after its Jupiter flyby, the Ulysses spacecraft
identified interstellar dust in the solar system. Since then the in-situ dust
detector on board Ulysses continuously monitored interstellar grains with
masses up to 10e-13 kg, penetrating deep into the solar system. While Ulysses
measured the interstellar dust stream at high ecliptic latitudes between 3 and
5 AU, interstellar impactors were also measured with the in-situ dust detectors
on board Cassini, Galileo and Helios, covering a heliocentric distance range
between 0.3 and 3 AU in the ecliptic plane. The interstellar dust stream in the
inner solar system is altered by the solar radiation pressure force,
gravitational focussing and interaction of charged grains with the time varying
interplanetary magnetic field. The grains act as tracers of the physical
conditions in the local interstellar cloud (LIC). Our in-situ measurements
imply the existence of a population of 'big' interstellar grains (up to 10e-13
kg) and a gas-to-dust-mass ratio in the LIC which is a factor of > 2 larger
than the one derived from astronomical observations, indicating a concentration
of interstellar dust in the very local interstellar medium. Until 2004, the
interstellar dust flow direction measured by Ulysses was close to the mean apex
of the Sun's motion through the LIC, while in 2005, the data showed a 30 deg
shift, the reason of which is presently unknown. We review the results from
spacecraft-based in-situ interstellar dust measurements in the solar system and
their implications for the physical and chemical state of the LIC.Comment: 10 pages, 2 b/w figures, 1 colour figure; submitted to Space Science
Review
Long-range attraction between particles in dusty plasma and partial surface tension of dusty phase boundary
Effective potential of a charged dusty particle moving in homogeneous plasma
has a negative part that provides attraction between similarly charged dusty
particles. A depth of this potential well is great enough to ensure both
stability of crystal structure of dusty plasma and sizable value of surface
tension of a boundary surface of dusty region. The latter depends on the
orientation of the surface relative to the counter-ion flow, namely, it is
maximal and positive for the surface normal to the flow and minimal and
negative for the surface along the flow. For the most cases of dusty plasma in
a gas discharge, a value of the first of them is more than sufficient to ensure
stability of lenticular dusty phase void oriented across the counter-ion flow.Comment: LATEX, REVTEX4, 7 pages, 6 figure
Galileo dust data from the jovian system: 2000 to 2003
The Galileo spacecraft was orbiting Jupiter between Dec 1995 and Sep 2003.
The Galileo dust detector monitored the jovian dust environment between about 2
and 370 R_J (jovian radius R_J = 71492 km). We present data from the Galileo
dust instrument for the period January 2000 to September 2003. We report on the
data of 5389 particles measured between 2000 and the end of the mission in
2003. The majority of the 21250 particles for which the full set of measured
impact parameters (impact time, impact direction, charge rise times, charge
amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in
radius), most of them originating from Jupiter's innermost Galilean moon Io.
Their impact rates frequently exceeded 10 min^-1. Surprisingly large impact
rates up to 100 min^-1 occurred in Aug/Sep 2000 when Galileo was at about 280
R_J from Jupiter. This peak in dust emission appears to coincide with strong
changes in the release of neutral gas from the Io torus. Strong variability in
the Io dust flux was measured on timescales of days to weeks, indicating large
variations in the dust release from Io or the Io torus or both on such short
timescales. Galileo has detected a large number of bigger micron-sized
particles mostly in the region between the Galilean moons. A surprisingly large
number of such bigger grains was measured in March 2003 within a 4-day interval
when Galileo was outside Jupiter's magnetosphere at approximately 350 R_J
jovicentric distance. Two passages of Jupiter's gossamer rings in 2002 and 2003
provided the first actual comparison of in-situ dust data from a planetary ring
with the results inferred from inverting optical images.Comment: 59 pages, 13 figures, 6 tables, submitted to Planetary and Space
Scienc
One year of Galileo dust data from the Jovian system: 1996
The dust detector system onboard Galileo records dust impacts in circumjovian
space since the spacecraft has been injected into a bound orbit about Jupiter
in December 1995. This is the sixth in a series of papers dedicated to
presenting Galileo and Ulysses dust data. We present data from the Galileo dust
instrument for the period January to December 1996 when the spacecraft
completed four orbits about Jupiter (G1, G2, C3 and E4). Data were obtained as
high resolution realtime science data or recorded data during a time period of
100 days, or via memory read-outs during the remaining times. Because the data
transmission rate of the spacecraft is very low, the complete data set (i. e.
all parameters measured by the instrument during impact of a dust particle) for
only 2% (5353) of all particles detected could be transmitted to Earth; the
other particles were only counted. Together with the data for 2883 particles
detected during Galileo's interplanetary cruise and published earlier, complete
data of 8236 particles detected by the Galileo dust instrument from 1989 to
1996 are now available. The majority of particles detected are tiny grains
(about 10 nm in radius) originating from Jupiter's innermost Galilean moon Io.
These grains have been detected throughout the Jovian system and the highest
impact rates exceeded . A small number of grains has been
detected in the close vicinity of the Galilean moons Europa, Ganymede and
Callisto which belong to impact-generated dust clouds formed by (mostly
submicrometer sized) ejecta from the surfaces of the moons (Kr\"uger et al.,
Nature, 399, 558, 1999). Impacts of submicrometer to micrometer sized grains
have been detected thoughout the Jovian system and especially in the region
between the Galilean moons.Comment: accepted for Planetary and Space Science, 33 pages, 6 tables, 10
figure
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