939 research outputs found
The haemoproteids of the shrikes of the avian family Laniidae (Passeriformes)
The two haemoproteids parasitizing members of the avian family Laniidae are reviewed. Haemoproteus lanii de Mello, 1937 is re-described and a neohapantotype designated; H. lanii var. nucleophilus Helmy Mohammed, 1958 is considered to be the same as H. lanii and therefore the varietal (= subspecific) designation is suppressed; it is confirmed that H. lanuidae Yakunin, 1976 is declared a nomen nudum; Haemoproteus cublae Peirce, 1984 is re-described
The Subdominant Curvaton
We present a systematic study of the amplitude of the primordial perturbation
in curvaton models with self-interactions, treating both renormalizable and
non-renormalizable interactions. In particular, we consider the possibility
that the curvaton energy density is subdominant at the time of the curvaton
decay. We find that large regions in the parameter space give rise to the
observed amplitude of primordial perturbation even for non-renormalizable
curvaton potentials, for which the curvaton energy density dilutes fast. At the
time of its decay, the curvaton energy density may typically be subdominant by
a relative factor of 10^-3 and still produce the observed perturbation. Field
dynamics turns out to be highly non-trivial, and for non-renormalizable
potentials and certain regions of the parameter space we observe a
non-monotonous relation between the final curvature perturbation and the
initial curvaton value. In those cases, the time evolution of the primordial
perturbation also displays an oscillatory behaviour before the curvaton decay.Comment: Acknowledgments of financial support added, no further change
Initial in vitro evaluations of antibacterial activities of glucosinolate enzymatic hydrolysis products against plant pathogenic bacteria
Aims: The aim of the study was to evaluate the in vitro antibacterial effects of
glucosinolate hydrolysis products (GHP) against plant pathogenic micro-organisms
namely Agrobacterium tumefaciens, Erwinia chrysanthemi, Pseudomonas
cichorii, Pseudomonas tomato, Xanthomonas campestris and Xanthomonas
juglandis.
Methods and Results: Using a disc diffusion assay, seven different doses of 10
GHP were tested against each bacteria. The results showed that the isothiocyanates
were potent antibacterials, whilst the other GHP were much less efficient.
Moreover, the antibacterial effects were dose-dependent, increasing with the
dose applied; 2-phenylethylisothiocyanate and sulforaphane showed the strongest
inhibitory effects. The overall results show a great potential for using the
isothiocyanates as an alternative tool to control undesired bacterial growth in
plants.
Conclusions: Glucosinolate hydrolysis products and more specifically the
isothiocyanates: benzylisothiocyanate, 2-phenylethylisothiocyanate, the isothiocyanate
Mix and sulforaphane, were effective phytochemicals against the in vitro
growth of the phytopathogenic bacteria. The antibacterial activity exhibited by
these phytochemicals reinforces their potential as alternatives to the traditional
chemical control of phytopathogenic bacteria.
Significance and Impact of the Study: This current in vitro study is the first
providing comparative data on GHP as potential control agents for plant
pathogenic bacteria. However, more studies are needed to determine their
possible allelopathic impacts e.g. inhibition of plant growth and negative effects
on beneficial soil bacteria and fungi (mycorrhizae
Running Spectral Index from Inflation with Modulations
We argue that a large negative running spectral index, if confirmed, might
suggest that there are abundant structures in the inflaton potential, which
result in a fairly large (both positive and negative) running of the spectral
index at all scales. It is shown that the center value of the running spectral
index suggested by the recent CMB data can be easily explained by an inflaton
potential with superimposed periodic oscillations. In contrast to cases with
constant running, the perturbation spectrum is enhanced at small scales, due to
the repeated modulations. We mention that such features at small scales may be
seen by 21 cm observations in the future.Comment: 7 pages, 6 figures, v2: published in JCA
Calculations of parity nonconserving s-d transitions in Cs, Fr, Ba II, and Ra II
We have performed ab initio mixed-states and sum-over-states calculations of
parity nonconserving (PNC) electric dipole (E1) transition amplitudes between
s-d electron states of Cs, Fr, Ba II, and Ra II. For the lower states of these
atoms we have also calculated energies, E1 transition amplitudes, and
lifetimes. We have shown that PNC E1 transition amplitudes between s-d states
can be calculated to high accuracy. Contrary to the Cs 6s-7s transition, in
these transitions there are no strong cancelations between different terms in
the sum-over-states approach. In fact, there is one dominating term which
deviates from the sum by less than 20%. This term corresponds to an s-p_{1/2}
weak matrix element, which can be calculated to better than 1%, and a
p_{1/2}-d_{3/2} E1 transition amplitude, which can be measured. Also, the s-d
amplitudes are about four times larger than the corresponding s-s transitions.
We have shown that by using a hybrid mixed-states/sum-over-states approach the
accuracy of the calculations of PNC s-d amplitudes could compete with that of
Cs 6s-7s if p_{1/2}-d_{3/2} E1 amplitudes are measured to high accuracy.Comment: 15 pages, 8 figures, submitted to Phys. Rev.
An accelerated closed universe
We study a model in which a closed universe with dust and quintessence matter
components may look like an accelerated flat Friedmann-Robertson-Walker (FRW)
universe at low redshifts. Several quantities relevant to the model are
expressed in terms of observed density parameters, and
, and of the associated density parameter related
to the quintessence scalar field .Comment: 11 pages. For a festschrift honoring Alberto Garcia. To appear in
Gen. Rel. Gra
The nearly Newtonian regime in Non-Linear Theories of Gravity
The present paper reconsiders the Newtonian limit of models of modified
gravity including higher order terms in the scalar curvature in the
gravitational action. This was studied using the Palatini variational principle
in [Meng X. and Wang P.: Gen. Rel. Grav. {\bf 36}, 1947 (2004)] and
[Dom\'inguez A. E. and Barraco D. E.: Phys. Rev. D {\bf 70}, 043505 (2004)]
with contradicting results. Here a different approach is used, and problems in
the previous attempts are pointed out. It is shown that models with negative
powers of the scalar curvature, like the ones used to explain the present
accelerated expansion, as well as their generalization which include positive
powers, can give the correct Newtonian limit, as long as the coefficients of
these powers are reasonably small. Some consequences of the performed analysis
seem to raise doubts for the way the Newtonian limit was derived in the purely
metric approach of fourth order gravity [Dick R.: Gen. Rel. Grav. {\bf 36}, 217
(2004)]. Finally, we comment on a recent paper [Olmo G. J.: Phys. Rev. D {\bf
72}, 083505 (2005)] in which the problem of the Newtonian limit of both the
purely metric and the Palatini formalism is discussed, using the equivalent
Brans--Dicke theory, and with which our results partly disagree.Comment: typos corrected, replaced to match published versio
Energy-Momentum Tensor of Cosmological Fluctuations during Inflation
We study the renormalized energy-momentum tensor (EMT) of cosmological scalar
fluctuations during the slow-rollover regime for chaotic inflation with a
quadratic potential and find that it is characterized by a negative energy
density which grows during slow-rollover. We also approach the back-reaction
problem as a second-order calculation in perturbation theory finding no
evidence that the back-reaction of cosmological fluctuations is a gauge
artifact. In agreement with the results on the EMT, the average expansion rate
is decreased by the back-reaction of cosmological fluctuations.Comment: 19 pages, no figures.An appendix and references added, conclusions
unchanged, version accepted for publication in PR
Atmospheric Channel Characteristics for Quantum Communication with Continuous Polarization Variables
We investigate the properties of an atmospheric channel for free space
quantum communication with continuous polarization variables. In our
prepare-and-measure setup, coherent polarization states are transmitted through
an atmospheric quantum channel of 100m length on the roof of our institute's
building. The signal states are measured by homodyne detection with the help of
a local oscillator (LO) which propagates in the same spatial mode as the
signal, orthogonally polarized to it. Thus the interference of signal and LO is
excellent and atmospheric fluctuations are autocompensated. The LO also acts as
spatial and spectral filter, which allows for unrestrained daylight operation.
Important characteristics for our system are atmospheric channel influences
that could cause polarization, intensity and position excess noise. Therefore
we study these influences in detail. Our results indicate that the channel is
suitable for our quantum communication system in most weather conditions.Comment: 6 pages, 4 figures, submitted to Applied Physics B following an
invitation for the special issue "Selected Papers Presented at the 2009
Spring Meeting of the Quantum Optics and Photonics Section of the German
Physical Society
Casimir energy-momentum tensor for a brane in de Sitter spacetime
Vacuum expectation values of the energy-momentum tensor for a conformally
coupled scalar field is investigated in de Sitter (dS) spacetime in presence of
a curved brane on which the field obeys the Robin boundary condition with
coordinate dependent coefficients. To generate the corresponding vacuum
densities we use the conformal relation between dS and Rindler spacetimes and
the results previously obtained by one of the authors for the Rindler
counterpart. The resulting energy-momentum tensor is non-diagonal and induces
anisotropic vacuum stresses. The asymptotic behaviour of this tensor is
investigated near the dS horizon and the boundary.Comment: 10 pages, no figur
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