78 research outputs found
The Results of Breeding Perennial Grasses: The Evaluation of Developed \u3cem\u3eDactylis glomerata\u3c/em\u3e Hybrids
Perennial grasses are high yielding, pest resistant and less demanding in terms of soil (Peeters, 2008), they are the most important source of roughage. Each species has certain valuable features that make it unique among others and which are desirable to be highlighted for ensuring high productivity, good forage quality, plasticity, strength of various stress conditions, as well as winter hardiness, which is particularly important characteristic of northern latitudes. It is the main task of breeders, as far as possible to combine all the aforesaid properties into one breed. In order to create such a universal variety the breeders of perennial grasses carry out hybridisation outside the borders of one species. At present the work with Festulolium hybrids is important in order to combine the modesty, hardiness and perennity of fescue with high forage quality characteristic of ryegrass in one variety.
At the Latvia University of Agriculture Research Institute of Agriculture (LLU RIA) in Skriveri the breeding work of perennial grasses has been performed for a long time and during the period of 35 years several varieties of species widely used in forage production have been created, including Phleum pratense, Lolium perenne, Festuca pratensis, and Festulolium hybrids
Two-dimensional tetramer-cuprate Na5RbCu4(AsO4)4Cl2: phase transitions and AFMorder as seen by 87Rb NMR
We report the Rb nuclear magnetic resonance (NMR) results in a recently
synthesized Na5RbCu4(AsO4)Cl2. This complex novel two-dimensional (2D) cuprate
is an unique magnetic material, which contains layers of coupled Cu4O4
tetramers. In zero applied magnetic field, it orders antiferromagnetically via
a second-order low-entropy phase transition at TN = 15(1) K. We characterise
the ordered state by 87Rb NMR, and suggest for it a noncollinear rather than
collinear arrangement of spins. We discuss the properties of Rb nuclear site
and point out the new structural phase transition(s) around 74 K and 110 K.Comment: 2 pages, 2 figures, Proceedings of SCES'05, Vienna 200
Hybrid adiabatic quantum computing for tomographic image reconstruction -- opportunities and limitations
Our goal is to reconstruct tomographic images with few measurements and a low
signal-to-noise ratio. In clinical imaging, this helps to improve patient
comfort and reduce radiation exposure. As quantum computing advances, we
propose to use an adiabatic quantum computer and associated hybrid methods to
solve the reconstruction problem. Tomographic reconstruction is an ill-posed
inverse problem. We test our reconstruction technique for image size, noise
content, and underdetermination of the measured projection data. We then
present the reconstructed binary and integer-valued images of up to 32 by 32
pixels. The demonstrated method competes with traditional reconstruction
algorithms and is superior in terms of robustness to noise and reconstructions
from few projections. We postulate that hybrid quantum computing will soon
reach maturity for real applications in tomographic reconstruction. Finally, we
point out the current limitations regarding the problem size and
interpretability of the algorithm
Anomalous specific heat in high-density QED and QCD
Long-range quasi-static gauge-boson interactions lead to anomalous
(non-Fermi-liquid) behavior of the specific heat in the low-temperature limit
of an electron or quark gas with a leading term. We obtain
perturbative results beyond the leading log approximation and find that
dynamical screening gives rise to a low-temperature series involving also
anomalous fractional powers . We determine their coefficients in
perturbation theory up to and including order and compare with exact
numerical results obtained in the large- limit of QED and QCD.Comment: REVTEX4, 6 pages, 2 figures; v2: minor improvements, references
added; v3: factor of 2 error in the T^(7/3) coefficient corrected and plots
update
Quark-Gluon Plasma Fireball
Lattice-QCD results provide an opportunity to model, and extrapolate to
finite baryon density, the properties of the quark-gluon plasma (QGP). Upon
fixing the scale of the thermal coupling constant and vacuum energy to the
lattice data, the properties of resulting QGP equations of state (EoS) are
developed. We show that the physical properties of the dense matter fireball
formed in heavy ion collision experiments at CERN-SPS are well described by the
QGP-EoS we presented. We also estimate the properties of the fireball formed in
early stages of nuclear collision, and argue that QGP formation must be
expected down to 40A GeV in central Pb--Pb interactions.Comment: 10 pages, 9 postscript figures, 1 table, uses revtex, V3: introduced
difference between n_f and n_s; fireball restframe energy corrected,
references added. Publisched version in press Phys. Rev.
Chemical equilibration and thermal dilepton production from the quark gluon plasma at finite baryon density
The chemical equilibration of a highly unsaturated quark-gluon plasma has
been studied at finite baryon density. It is found that in the presence of
small amount of baryon density, the chemical equilibration for gluon becomes
slower and the temperature decreases less steeply as compared to the baryon
free plasma. As a result, the space time integrated yield of dilepton is
enhanced if the initial temperature of the plasma is held fixed. Even at a
fixed initial energy density, the suppression of the dilepton yields at higher
baryo-chemical potential is compensated, to a large extent, by the slow cooling
of the plasma.Comment: Latex, 19 pages, 8 postscript figures. To appear in Phys. Rev.
A first order transition and parity violation in a color superconductor
In cold, dense quark matter, quarks of different flavor can form Cooper pairs
which are anti-triplets under color and have total spin J=0. The transition to
a phase where strange quarks condense with either up or down quarks is driven
first order by the Coleman-Weinberg mechanism. At densities sufficiently high
to (effectively) restore the axial U(1) symmetry, then relative to the ordinary
vacuum, the condensation of up with down quarks (effectively) breaks parity
spontaneously.Comment: 4 pages, ReVTeX, final versio
Effect of baryon density on parton production, chemical equilibration and thermal photon emission from quark gluon plasma
The effect of baryon density on parton production processes of
and is studied
using full phase space distribution function and also with inclusion of quantum
statistics i.e. Pauli blocking and Bose enhancement factors, in the case of
both saturated and unsaturated quark gluon plasma. The rate for the process is found to be much less as compared to the most
commonly used factorized result obtained on the basis of classical
approximation. This discrepancy, which is found both at zero as well as at
finite baryon densities, however, is not due to the lack of quantum statistics
in the classical approximation, rather due to the use of Fermi-Dirac and
Bose-Einstein distribution functions for partons instead of Boltzmann
distribution which is appropriate under such approximation. Interestingly, the
rates of parton production are found to be insensitive to the baryo-chemical
potential particularly when the plasma is unsaturated although the process of
chemical equilibration strongly depends on it. The thermal photon yields, have
been calculated specifically from unsaturated plasma at finite baryon density.
The exact results obtained numerically are found to be in close agreement with
the analytic expression derived using factorized distribution functions
appropriate for unsaturated plasma. Further, it is shown that in the case of
unsaturated plasma, the thermal photon production is enhanced with increasing
baryon density both at fixed temperature and fixed energy density of the quark
gluon plasma.Comment: Latex, 24 pages, 6 postscript figures. Submitted to Phys. Rev.
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