3,235 research outputs found
Selection of winter cereals for organic agriculture
Productivity in agriculture has more than tripled in developed countries since the 1950s. Beyond the success of plant breeding, the increased use of inorganic fertilizers, application of pesticides, and spread of irrigation also contributed to this success. However, impressive yield increases started to decline in the 1980s because of the lack of sustainability.
One of the most beneficial ways to increase sustainability is organic agriculture. In such systems the prerequisite of successful farming is the availability of crop genotypes that perform well. However, selection of winter cereals for sub-optimal growing conditions is still neglected, and the organic seed market also lacks of information on credibly tested varieties suitable for organic agriculture
Kepler RR Lyrae stars: beyond period doubling
We examined the complete short cadence sample of Kepler RR Lyrae stars to
further investigate the recently discovered dynamical effects such as period
doubling and additional modes. Here we present the findings on four stars. V450
Lyr may be a non-classical double-mode RR Lyrae star pulsating in the
fundamental mode and the second overtone. In three cases we observe the
interaction of three different modes. Since the period ratios are close to
resonant values, we observe quasi-repetiting patterns in the pulsation cycles
in the stars. These findings support the mode-resonance explanations of the
Blazhko effect.Comment: 2 pages, 1 figure. Proceedings of the 301st IAU Symposium, Precision
Asteroseismology, August 2013, Wroc{\l}aw. V2: small corrections to the
wordin
Amplitude Modulation in the ZZ Ceti Star GD 244
Previous studies of GD 244 revealed seven pulsation frequencies (two doublets
and three single periods) in the light variations of the star. The data
obtained at McDonald Observatory between 2003 and 2006, and our additional
measurements in 2006 and 2007 at Konkoly Observatory, allow the investigation
of the long-term pulsational behaviour of GD 244. We found that the 307.1 s
period component of one of the doublets show long-term, periodic amplitude
modulation with a time scale of ~740 days. Possible explanations are that
nonlinear resonant mode coupling is operating among the rotationally split
frequency components, or two modes, unresolved in the yearly data are excited
at ~307.1 s. This is the first time that such long-term periodic amplitude
modulation is published on a ZZ Ceti star.Comment: 4 pages, 2 figures, appeared in ASP Conference Series vol. 493, 2015
(eds.: P. Dufour, P. Bergeron, G. Fontaine, 19th European Workshop on White
Dwarfs, Montreal, Canada
Spin-dependent transmission through a chain of rings: influence of a periodically modulated spin-orbit interaction strength or ring radius
We study ballistic electron transport through a finite chain of quantum
circular rings in the presence of spin-orbit interaction of strength \alpha.
For a single ring the transmission and reflection coefficients are obtained
analytically and from them the conductance for a chain of rings as a function
of \alpha and of the wave vector k of the incident electron. We show that due
to destructive spin interferences the chain can be totaly opaque for certain
ranges of k the width of which depends on the value of \alpha. A periodic
modulation of the strength \alpha or of the ring radius widens up the gaps
considerably and produces a nearly binary conductance output.Comment: 4 pages, 4 figures. Appl. Phys. Lett., in pres
Nonlinear dynamical analysis of the Blazhko effect with the Kepler space telescope: the case of V783 Cyg
We present a detailed nonlinear dynamical investigation of the Blazhko
modulation of the Kepler RR Lyrae star V783 Cyg (KIC 5559631). We used
different techniques to produce modulation curves, including the determination
of amplitude maxima, the O-C diagram and the analytical function method. We
were able to fit the modulation curves with chaotic signals with the global
flow reconstruction method. However, when we investigated the effects of
instrumental and data processing artefacts, we found that the chaotic nature of
the modulation can not be proved because of the technical problems of data
stitching, detrending and sparse sampling. Moreover, we found that a
considerable part of the detected cycle-to-cycle variation of the modulation
may originate from these effects. According to our results, even the
four-year-long, unprecedented Kepler space photometry of V783 Cyg is too short
for a reliable nonlinear dynamical analysis aiming at the detection of chaos
from the Blazhko modulation. We estimate that two other stars could be suitable
for similar analysis in the Kepler sample and in the future TESS and PLATO may
provide additional candidates.Comment: 9 pages, 12 figures, accepted for publication in MNRA
On the interchange of alternating-amplitude pulsation cycles
We characterized the time intervals between the interchanges of the
alternating high- and low-amplitude extrema of three RV Tauri and three RR
Lyrae stars.Comment: 2 pages, Proceedings of the 301st IAU Symposium, Precision
Asteroseismology, August 201
Cytomolecular identification of individual wheat-wheat chromosome arm associations in wheat-rye hybrids
Chromosome pairing in the meiotic metaphase I of wheatrye
hybrids has been characterized by sequential genomic
and fluorescent in situ hybridization allowing not only the
discrimination of wheat and rye chromosomes, but also the
identification of the individual wheat and rye chromosome
arms involved in the chromosome associations. The majority
of associations (93.8%) were observed between the wheat
chromosomes. The largest number of wheat-wheat chromosome
associations (53%) was detected between the A and D
genomes, while the frequency of B-D and A-B associations
was significantly lower (32 and 8%, respectively). Among the
A-D chromosome associations, pairing between the 3AL and
3DL arms was observed with the highest frequency, while
the most frequent of all the chromosome associations (0.113/
cell) was found to be the 3DS-3BS. Differences in the pairing
frequency of the individual chromosome arms of wheat-rye
hybrids have been discussed in relation to the homoeologous
relationships between the constituent genomes of
hexaploid wheat
Long time-scale behavior of the Blazhko effect from rectified Kepler data
In order to benefit from the 4-year unprecedented precision of the Kepler
data, we extracted light curves from the pixel photometric data of the Kepler
space telescope for 15 Blazhko RR Lyrae stars. For collecting all the flux from
a given target as accurately as possible, we defined tailor-made apertures for
each star and quarter. In some cases the aperture finding process yielded
sub-optimal result, because some flux have been lost even if the aperture
contains all available pixels around the star. This fact stresses the
importance of those methods that rely on the whole light curve instead of
focusing on the extrema (O-C diagrams and other amplitude independent methods).
We carried out detailed Fourier analysis of the light curves and the amplitude
independent O-C diagram. We found 12 (80%) multiperiodically modulated stars in
our sample. This ratio is much higher than previously found. Resonant coupling
between radial modes, a recent theory to explain of the Blazhko effect, allows
single, multiperiodic or even chaotic modulations. Among the stars with two
modulations we found three stars (V355 Lyr, V366 Lyr and V450 Lyr) where one of
the periods dominate in amplitude modulation, but the other period has larger
frequency modulation amplitude. The ratio between the primary and secondary
modulation periods is almost always very close to ratios of small integer
numbers. It may indicate the effect of undiscovered resonances. Furthermore, we
detected the excitation of the second radial overtone mode for three
stars where this feature was formerly unknown. Our data set comprises the
longest continuous, most precise observations of Blazhko RR Lyrae stars ever
published. These data which is made publicly available will be unprecedented
for years to come.Comment: 19 pages, 17 figures, accepted for publication in Astrophys. J.
Suppl. Rectified data are here: http://www.konkoly.hu/KIK/data.htm
Time evolution in the Morse potential using supersymmetry: dissociation of the NO molecule
We present an algebraic method for treating molecular vibrations in the Morse
potential perturbed by an external laser field. By the help of a complete and
normalizable basis we transform the Schr\"{o}dinger equation into a system of
coupled ordinary differential equations. We apply our method to calculate the
dissociation probability of the NO molecule excited by chirped laser pulses.
The dependence of the molecular dipole-moment on the interatomic separation is
determined by a quantum-chemical method, and the corresponding transition
dipole moments are given by approximate analytic expressions. These turn out to
be very small between neighboring stationary states around the vibrational
quantum number , therefore we propose to use additional pulses in order
to skip this trapping state, and to obtain a reasonable dissociation
probability.Comment: 4 pages, 3 figure
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