167 research outputs found
Humus forms as a synthetic parameter for ecological investigations. Some examples in the Ligurian Alps (North-Western Italy)
In the Ligurian Alps, a wide range of site conditions that influence soil development and may affect humus variability is present. In this work, we wanted to evaluate the potentialities of humus forms as a synthetic indicator of both chemical properties of the humic episola and site conditions in the upper Tanaro Valley (NW Italy). Vegetation affected the C/N ratio of the least transformed organic horizons, but the effect disappeared in mineral ones, where soil pH was related to the parent material. All terrestrial humus forms were found in the area and their distribution well reflected the interactions between vegetation, lithology, elevation that shaped soil properties and affected the degradability of litter and its actual degradation by microorganisms and soil fauna. Humus forms were thus able to capture the ecological conditions, integrating the information provided by soil classifications
One-Parameter Homothetic Motion in the Hyperbolic Plane and Euler-Savary Formula
In \cite{Mul} one-parameter planar motion was first introduced and the
relations between absolute, relative, sliding velocities (and accelerations) in
the Euclidean plane were obtained. Moreover, the relations
between the Complex velocities one-parameter motion in the Complex plane were
provided by \cite{Mul}. One-parameter planar homothetic motion was defined in
the Complex plane, \cite{Kur}. In this paper, analogous to homothetic motion in
the Complex plane given by \cite{Kur}, one-parameter planar homothetic motion
is defined in the Hyperbolic plane. Some characteristic properties about the
velocity vectors, the acceleration vectors and the pole curves are given.
Moreover, in the case of homothetic scale identically equal to 1, the
results given in \cite{Yuc} are obtained as a special case. In addition, three
hyperbolic planes, of which two are moving and the other one is fixed, are
taken into consideration and a canonical relative system for one-parameter
planar hyperbolic homothetic motion is defined. Euler-Savary formula, which
gives the relationship between the curvatures of trajectory curves, is obtained
with the help of this relative system
Donar, un cambio de vida: comprender la experiencia de familiares que aceptaron la donación de órganos
Indexación: Web of Science; Scielo.Background: Most organ donors are already death. Therefore family members become an essential link in the final decision for organ donation. Aim: To get acquainted about the life lessons of people who accepted donating an organ of a deceased family member. Material and Methods: Qualitative research, in depth interviews to eight families that accepted donating an organ of a deceased family member. The interviews were analyzed using the method proposed by Streubert et al and modified by Rivera. Results: The life lessons are described in six comprehensive categories. The painful experience changed towards the feeling that the loved one remains alive. This sensation generated a sense of pride in family members and sensitized them towards the painful experience of other people. Therefore, a desire to help and improve as humans beings was awakened. Conclusions: A compassionate approach towards families donating organs with improve organ donation and humanize the process.
Key words: Family; Social values; Tissue and organ procurement
Arbuscular Mycorrhizal Symbiosis Limits Foliar Transcriptional Responses to Viral Infection and Favors Long-Term Virus Accumulation
Tomato (Solanum lycopersicum) can establish symbiotic interactions with arbuscular mycorrhizal (AM) fungi, and can be infected by several pathogenic viruses. Here, we investigated the impact of mycorrhization by the fungus Glomus mosseae on the Tomato spotted wilt virus (TSWV) infection of tomato plants by transcriptomic and hormones level analyses. In TSWV-infected mycorrhizal plants, the AM fungus root colonization limited virus-induced changes in gene expression in the aerial parts. The virus-responsive upregulated genes, no longer induced in infected mycorrhizal plants, were mainly involved in defense responses and hormone signaling, while the virus-responsive downregulated genes, no longer repressed in mycorrhizal plants, were involved in primary metabolism. The presence of the AM fungus limits, in a salicylic acid-independent manner, the accumulation of abscissic acid observed in response to viral infection. At the time of the molecular analysis, no differences in virus concentration or symptom severity were detected between mycorrhizal and nonmycorrhizal plants. However, in a longer period, increase in virus titer and delay in the appearance of recovery were observed in mycorrhizal plants, thus indicating that the plant's reaction to TSWV infection is attenuated by mycorrhization. </jats:p
Inter-individual differences in foraging tactics of a colonial raptor : consistency, weather effects, and fitness correlates
Background: Consistent inter-individual differences in behavioural phenotypes may entail differences in energy efficiency and expenditure, with different fitness payoffs. In colonial-breeding species, inter-individual differences in foraging behaviour may evolve to reduce resource use overlap among conspecifics exploiting shared foraging areas. Furthermore, individual differences in foraging behaviour may covary with individual characteristics, such as sex or physiological conditions.
Methods: We investigated individual differences in foraging tactics of a colonial raptor, the lesser kestrel (Falco naumanni). We tracked foraging trips of breeding individuals using miniaturized biologgers. We classified behaviours from GPS data and identified tactics at the foraging trip level by cluster analysis. We then estimated energy expenditure associated to each tactic from tri-axial accelerometer data.
Results: We obtained 489 foraging trips by 36 individuals. Two clusters of trips were identified, one (SF) characterized by more static foraging behaviour and the other (DF) by more dynamic foraging behaviour, with a higher proportion of flying activity and a higher energy expenditure compared to SF. Lesser kestrels showed consistent inter-individual differences in foraging tactics across weather condition gradients, favouring DF trips as solar radiation and crosswind intensity increased. DF trips were more frequent during the nestling-rearing than during the egg incubation stage. Nestlings whose tracked parent was more prone to perform DF trips experienced higher daily mass increase, irrespective of nestling feeding rates.
Conclusions: Our study provided evidence that breeding lesser kestrels flexibly adopted different foraging tactics according to contingent weather landscapes, with birds showing consistent inter-individual differences in the tendency to adopt a given tactic. The positive correlation between the tendency to perform more energy-demanding DF trips and nestling growth suggests that individual differences in foraging behaviour may play a role in maintaining key life-history trade-offs between reproduction and self-maintenance
Landscape statistics of the low autocorrelated binary string problem
The statistical properties of the energy landscape of the low autocorrelated
binary string problem (LABSP) are studied numerically and compared with those
of several classic disordered models. Using two global measures of landscape
structure which have been introduced in the Simulated Annealing literature,
namely, depth and difficulty, we find that the landscape of LABSP, except
perhaps for a very large degeneracy of the local minima energies, is
qualitatively similar to some well-known landscapes such as that of the
mean-field 2-spin glass model. Furthermore, we consider a mean-field
approximation to the pure model proposed by Bouchaud and Mezard (1994, J.
Physique I France 4 1109) and show both analytically and numerically that it
describes extremely well the statistical properties of LABSP
Last passage percolation and traveling fronts
We consider a system of N particles with a stochastic dynamics introduced by
Brunet and Derrida. The particles can be interpreted as last passage times in
directed percolation on {1,...,N} of mean-field type. The particles remain
grouped and move like a traveling wave, subject to discretization and driven by
a random noise. As N increases, we obtain estimates for the speed of the front
and its profile, for different laws of the driving noise. The Gumbel
distribution plays a central role for the particle jumps, and we show that the
scaling limit is a L\'evy process in this case. The case of bounded jumps
yields a completely different behavior
A second order differential equation for the relativistic description of electrons and photons
A new relativistic description of quantum electrodynamics is presented.
Guideline of the theory is the Klein-Gordon equation, which is reformulated to
consider spin effects. This is achieved by a representation of relativistic
vectors with a space-time algebra made up of Pauli matrices and hyperbolic
numbers. The algebra is used to construct the differential operator of the
electron as well as the photon wave equation. The properties of free electron
and photon states related to this wave equation are investigated. Interactions
are introduced as usual with the minimal substitution of the momentum
operators. It can be shown that the new wave equation is equivalent to the
quadratic form of the Dirac equation. Furthermore, the Maxwell equations can be
derived from the corresponding wave equation for photons.Comment: Reverted preprint to initial version of 1999. Most of the content has
been published under the new title "Relativistic quantum physics with
hyperbolic numbers". However, interesting parts like the second quantization
of fermion fields within a Klein-Gordon theory, which is only possible with
the help of hyperbolic or bicomplex numbers, dropped out of the revised
versio
Grafting vigour is associated with DNA de-methylation in eggplant.
In horticulture, grafting is a popular technique used to combine positive traits from two different plants. This is achieved by joining the plant top part (scion) onto a rootstock which contains the stem and roots. Rootstocks can provide resistance to stress and increase plant production, but despite their wide use, the biological mechanisms driving rootstock-induced alterations of the scion phenotype remain largely unknown. Given that epigenetics plays a relevant role during distance signalling in plants, we studied the genome-wide DNA methylation changes induced in eggplant (Solanum melongena) scion using two interspecific rootstocks to increase vigour. We found that vigour was associated with a change in scion gene expression and a genome-wide hypomethylation in the CHH context. Interestingly, this hypomethylation correlated with the downregulation of younger and potentially more active long terminal repeat retrotransposable elements (LTR-TEs), suggesting that graft-induced epigenetic modifications are associated with both physiological and molecular phenotypes in grafted plants. Our results indicate that the enhanced vigour induced by heterografting in eggplant is associated with epigenetic modifications, as also observed in some heterotic hybrids
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