152 research outputs found
Investigation of various factors on the germination of chia seeds sprouts (Salvia hispanica L.)
ArticleSalvia hispanica L. is capable to produce a large amount of green matter, which can be
used as a source of biologically active substances. The purpose of this research was to select the
optimal factors for the chia seed sprouts (Salvia hispanica L.) germination. Dark variety chia
seeds (100 grains/sample) were investigated. The most significant factors for the process of
sprouting were selected as the study factors, such as the water mass fraction, the temperature and
the light exposure for seed germination. The output parameters of the experiment were seed
germination energy, germination of seeds, speed of germination and seedling vigor. It was
revealed that the mass fraction of added water had the greatest influence on the growing process
of chia seed sprouts. The optimal amount of water for producing the chia seed sprouts was in the
average of 4 mL/sample. As a result, it was noted that an insufficient or excessive amount of
water had a negative effect on the chia seed sprouts germination. The optimum temperature for
germination of chia seed sprouts was 25 °C. The optimal light factor was also determined; in
particular light exposure peaks occur in the red spectrum with a wavelength of 660 nm and a blue
spectrum with a wavelength of 450 nm
Ground state properties of the 2D disordered Hubbard model
We study the ground state of the two-dimensional (2D) disordered Hubbard
model by means of the projector quantum Monte Carlo (PQMC) method. This
approach allows us to investigate the ground state properties of this model for
lattice sizes up to , at quarter filling, for a broad range of
interaction and disorder strengths. Our results show that the ground state of
this system of spin-1/2 fermions remains localised in the presence of the
short-ranged Hubbard interaction.Comment: 7 pages, 9 figure
Transition to an Insulating Phase Induced by Attractive Interactions in the Disordered Three-Dimensional Hubbard Model
We study numerically the interplay of disorder and attractive interactions
for spin-1/2 fermions in the three-dimensional Hubbard model. The results
obtained by projector quantum Monte Carlo simulations show that at moderate
disorder, increasing the attractive interaction leads to a transition from
delocalized superconducting states to the insulating phase of localized pairs.
This transition takes place well within the metallic phase of the
single-particle Anderson model.Comment: revtex, 4 pages, 3 figure
Analysis of the nature of the and decays
We study interference patterns in the and reactions. Taking into account the interference, we fit the
experimental data and show that the background reaction does not distort the
spectrum in the decay everywhere over the
energy region and does not distort the spectrum in the decay
in the wide region of the system
invariant mass, MeV, or when the photon energy is less than
300 MeV. We discuss the details of the scalar meson production in the radiative
decays and note that there are reasonable arguments in favor of the one-loop
mechanism and . We
discuss also distinctions between the four-quark, molecular, and two-quark
models and argue that the Novosibirsk data give evidence in favor of the
four-quark nature of the scalar and mesons.Comment: 15 pages, 7 figures, title is changed, a few clarifying remarks are
added, accepted for publication in Physical Review
Particle creation, classicality and related issues in quantum field theory: II. Examples from field theory
We adopt the general formalism, which was developed in Paper I
(arXiv:0708.1233) to analyze the evolution of a quantized time-dependent
oscillator, to address several questions in the context of quantum field theory
in time dependent external backgrounds. In particular, we study the question of
emergence of classicality in terms of the phase space evolution and its
relation to particle production, and clarify some conceptual issues. We
consider a quantized scalar field evolving in a constant electric field and in
FRW spacetimes which illustrate the two extreme cases of late time adiabatic
and highly non-adiabatic evolution. Using the time-dependent generalizations of
various quantities like particle number density, effective Lagrangian etc.
introduced in Paper I, we contrast the evolution in these two limits bringing
out key differences between the Schwinger effect and evolution in the de Sitter
background. Further, our examples suggest that the notion of classicality is
multifaceted and any one single criterion may not have universal applicability.
For example, the peaking of the phase space Wigner distribution on the
classical trajectory \emph{alone} does not imply transition to classical
behavior. An analysis of the behavior of the \emph{classicality parameter},
which was introduced in Paper I, leads to the conclusion that strong particle
production is necessary for the quantum state to become highly correlated in
phase space at late times.Comment: RevTeX 4; 27 pages; 18 figures; second of a series of two papers, the
first being arXiv:0708.1233 [gr-qc]; high resolution figures available from
the authors on reques
Dark Energy and Gravity
I review the problem of dark energy focusing on the cosmological constant as
the candidate and discuss its implications for the nature of gravity. Part 1
briefly overviews the currently popular `concordance cosmology' and summarises
the evidence for dark energy. It also provides the observational and
theoretical arguments in favour of the cosmological constant as the candidate
and emphasises why no other approach really solves the conceptual problems
usually attributed to the cosmological constant. Part 2 describes some of the
approaches to understand the nature of the cosmological constant and attempts
to extract the key ingredients which must be present in any viable solution. I
argue that (i)the cosmological constant problem cannot be satisfactorily solved
until gravitational action is made invariant under the shift of the matter
lagrangian by a constant and (ii) this cannot happen if the metric is the
dynamical variable. Hence the cosmological constant problem essentially has to
do with our (mis)understanding of the nature of gravity. Part 3 discusses an
alternative perspective on gravity in which the action is explicitly invariant
under the above transformation. Extremizing this action leads to an equation
determining the background geometry which gives Einstein's theory at the lowest
order with Lanczos-Lovelock type corrections. (Condensed abstract).Comment: Invited Review for a special Gen.Rel.Grav. issue on Dark Energy,
edited by G.F.R.Ellis, R.Maartens and H.Nicolai; revtex; 22 pages; 2 figure
Dynamical complexity in the C.elegans neural network
We model the neuronal circuit of the C.elegans soil worm in terms of a Hindmarsh-Rose system of ordinary differential equa- tions, dividing its circuit into six communities which are determined via the Walktrap and Louvain methods. Using the numerical solution of these equations, we analyze important measures of dynamical com- plexity, namely synchronicity, the largest Lyapunov exponent, and the ?AR auto-regressive integrated information theory measure. We show that ?AR provides a useful measure of the information contained in the C.elegans brain dynamic network. Our analysis reveals that the C.elegans brain dynamic network generates more information than the sum of its constituent parts, and that attains higher levels of integrated information for couplings for which either all its communities are highly synchronized, or there is a mixed state of highly synchronized and de- synchronized communities
Dalitz plot analysis of e+ e- --> pi0 pi0 gamma events at SQRT(s) ~ M(phi) with the KLOE detector
We have studied the Dalitz plot of the e+ e- --> pi0 pi0 gamma events
collected at SQRT(s) ~ M(phi) with the KLOE detector. In the dipion invariant
mass (Mpp) region below 700 MeV, the process under study is dominated by the
non-resonant process e+ e- --> omega pi0 with omega --> pi0 gamma whereas, for
higher Mpp values, the radiative phi decay to the f0(980) is the dominant
mechanism. Different theoretical models are used to fit the Dalitz plot, taking
also into account a possible contribution of the sigma(600). For each model, we
extract the f0(980) mass and its coupling to pipi, KKbar and to the phi.Comment: 21 pages, 15 figures, 5 tables, submitted to European Physics Journal
Magnetic Field Generation in Stars
Enormous progress has been made on observing stellar magnetism in stars from
the main sequence through to compact objects. Recent data have thrown into
sharper relief the vexed question of the origin of stellar magnetic fields,
which remains one of the main unanswered questions in astrophysics. In this
chapter we review recent work in this area of research. In particular, we look
at the fossil field hypothesis which links magnetism in compact stars to
magnetism in main sequence and pre-main sequence stars and we consider why its
feasibility has now been questioned particularly in the context of highly
magnetic white dwarfs. We also review the fossil versus dynamo debate in the
context of neutron stars and the roles played by key physical processes such as
buoyancy, helicity, and superfluid turbulence,in the generation and stability
of neutron star fields.
Independent information on the internal magnetic field of neutron stars will
come from future gravitational wave detections. Thus we maybe at the dawn of a
new era of exciting discoveries in compact star magnetism driven by the opening
of a new, non-electromagnetic observational window.
We also review recent advances in the theory and computation of
magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo
theory. These advances offer insight into the action of stellar dynamos as well
as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field
generation in stars to appear in Space Science Reviews, Springe
The Leiden MEMS Tribometer: Real Time Dynamic Friction Loop Measurements With an On-Chip Tribometer
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