104 research outputs found
Laser acceleration of ion beams
We consider methods of charged particle acceleration by means of
high-intensity lasers. As an application we discuss a laser booster for heavy
ion beams provided, e.g. by the Dubna nuclotron. Simple estimates show that a
cascade of crossed laser beams would be necessary to provide additional
acceleration to gold ions of the order of GeV/nucleon.Comment: 4 pages, 4 figures, Talk at the Helmholtz International Summer School
"Dense Matter in heavy Ion Collisions and Astrophysics", August 21 -
September 1, 2006, JINR Dubna, Russia; v2, misprints correcte
"The obesity paradox" in patients with atrial fibrillation according to the results of the REKUR-AF study
To evaluate the effect of excess body weight (EBW) and obesity on the survival of patients with atrial fibrillation (AF) in the REKUR-AF stud
Cuticular wax composition of mature leaves of species and hybrids of the genus Prunus differing in resistance to clasterosporium disease
The interaction of a host plant with pathogen implies an extremely complex process involving the outer waxy layer of the cuticle, cutin, cell membrane, and intracellular structures. However, the initial contact between plants and pathogens takes place in cuticular waxes covering the surface of leaves, stems and fruits. Despite many findings on the role of plant epicuticular waxes, there is a gap in the understanding of the relationship between individual compounds and their functions. The pathogenic fungus Clasterosporium carpohilum (Lev.) Aderh. parasitizes the tissues of many stone fruit trees, damaging leaf and fruit surface. The aim of this work was to find out if the quantity and composition of leaf epicuticular wax could be responsible for the resistance to clasterosporium disease. The study of differences of plants in fungal resistance was carried out on species and hybrids of the genus Prunus from the collection of the Botanical Garden of Oles Honchar Dnipro National University (Dnipro city, Ukraine). The chloroform extracts of epicuticular waxes from the surface of mature leaves were analyzed by gas chromatography connected to mass-spectrometry. GC/MS assay was performed using Shimadzu GCMS-QP 2020 El equipped with capillary column (5% diphenyl/95% dimethyl polysiloxane), and helium as a carrier gas. Mass Spectrum Library 2014 for GSMS was used to identify the separated compounds of the wax extracts. The maximum total wax amount on the adaxial and abaxial leaf surface of hybrid 2 was twice the minimum wax accumulation for hybrid 4. Overall, 20 individual compounds belonging to six hydrocarbon classes were identified. Leaf epicuticular wax composition both in Prunus persica (L.) Batsch and P. dulcis (Mill.) D. A. Webb, and hybrids was dominated by long-chain n-alkanes with even carbon number (77.6–90.9% of total sum). The alkenes’ class was represented only by 17-pentatriacontene detected in the wax of both Prunus species. Octadecanaldehyde was found in epicuticular wax of P. dulcis while absent in wax of the more resistant species P. persica. Prime alcohols 1-tetradecanol and 1-hexacosanol were detected in leaf waxes of hybrid 4 and P. dulcis respectively. The ester class contained seven compounds found in leaf epicuticular waxes of both plant species and all hybrid forms. The identification of phthalic acid esters in leaf wax extracts was unexpected, and the phthalates’ origin is discussed. Strong positive correlation between leaf damage and tetrapentacontane content in epicuticular waxes could presumably be the result of infection-induced metabolism reprogramming in epidermal cells of infected leaves
Three-dimensional writing inside silicon using a 2-µm picosecond fiber laser
International audienc
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
ИЗМЕРЕНИЕ ПАРАМЕТРОВ ПОВЕРХНОСТНЫХ АКУСТИЧЕСКИХ ВОЛН В КРИСТАЛЛАХ ГОЛОГРАФИЧЕСКИМ МЕТОДОМ
Holographic interferometry allows visualizing SAW on the entire specimen surface simultaneously and measuring wave characteristics directly. A special method of SAW characteristics measurements by digital holographic interferometry was developed. The use of a picosecond laser allowed registering high frequency SAW two−exposure interferograms, and optical magnification of the CCD input image was used to increase spatial resolution.As a result we reach a sensitivity and resolution of visu-alization and SAW characteristics measurements that significantly exceeded the commonly known limitations of standard holographic methods. Разработана специализированная методика применения цифровой голографической интерферометрии для измерения параметров поверхностных акустических волн (ПАВ). При этом для обеспечения возможности регистрации двухэкспозиционных интерферограмм высокочастотных ПАВ в качестве источника излучения использовали пикосекундный импульсный лазер, а для повышения пространственного разрешения системы применяли увеличение изображения, поступающего на вход ПЗС−матрицы регистрирующей камеры. Достигнуты чувствительность и разрешающая способность, позволяющие проводить визуализацию и измерение параметров ПАВ, значение которых лежат далеко за пределами возможностей стандартных методов голографической интерферометрии
Orientation of Vortices in a Superconducting Thin-Film: Quantitative Comparison of Spin-Polarized Neutron Reflectivity and Magnetization
We present a quantitative comparison of the magnetization measured by
spin-polarized neutron reflectivity (SPNR) and DC magnetometry on a 1370 \AA\
-thick Nb superconducting film. As a function of magnetic field applied in the
film plane, SPNR exhibits reversible behavior whereas the DC magnetization
shows substantial hysteresis. The difference between these measurements is
attributed to a rotation of vortex magnetic field out of the film plane as the
applied field is reduced. Since SPNR measures only the magnetization parallel
to the film plane whereas DC magnetization is strongly influenced by the
perpendicular component of magnetization when there is a slight sample tilt,
combining the two techniques allows one to distinguish two components of
magnetization in a thin film.Comment: 12 pages, 8 figures, It will be printed in PRB, Oct. 200
Wigner symmetry in the limit of large scattering lengths
We note that in the limit where the NN 1S0 and 3S1 scattering lengths,
a^(1S0) and a^(3S1), go to infinity, the leading terms in the effective field
theory for strong NN interactions are invariant under Wigner's SU(4)
spin-isospin symmetry. This explains why the leading effects of radiation pions
on the S-wave NN scattering amplitudes vanish as a^(1S0) and a^(3S1) go to
infinity. The implications of Wigner symmetry for NN to NN axion and gamma d to
n p are also considered.Comment: 4 pages, 2 figs, minor typos and discussion regarding the number of
three body operators correcte
The neutron and its role in cosmology and particle physics
Experiments with cold and ultracold neutrons have reached a level of
precision such that problems far beyond the scale of the present Standard Model
of particle physics become accessible to experimental investigation. Due to the
close links between particle physics and cosmology, these studies also permit a
deep look into the very first instances of our universe. First addressed in
this article, both in theory and experiment, is the problem of baryogenesis ...
The question how baryogenesis could have happened is open to experimental
tests, and it turns out that this problem can be curbed by the very stringent
limits on an electric dipole moment of the neutron, a quantity that also has
deep implications for particle physics. Then we discuss the recent spectacular
observation of neutron quantization in the earth's gravitational field and of
resonance transitions between such gravitational energy states. These
measurements, together with new evaluations of neutron scattering data, set new
constraints on deviations from Newton's gravitational law at the picometer
scale. Such deviations are predicted in modern theories with extra-dimensions
that propose unification of the Planck scale with the scale of the Standard
Model ... Another main topic is the weak-interaction parameters in various
fields of physics and astrophysics that must all be derived from measured
neutron decay data. Up to now, about 10 different neutron decay observables
have been measured, much more than needed in the electroweak Standard Model.
This allows various precise tests for new physics beyond the Standard Model,
competing with or surpassing similar tests at high-energy. The review ends with
a discussion of neutron and nuclear data required in the synthesis of the
elements during the "first three minutes" and later on in stellar
nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic
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