6,492 research outputs found
Predicting coexistence of plants subject to a tolerance-competition trade-off
Ecological trade-offs between species are often invoked to explain species
coexistence in ecological communities. However, few mathematical models have
been proposed for which coexistence conditions can be characterized explicitly
in terms of a trade-off. Here we present a model of a plant community which
allows such a characterization. In the model plant species compete for sites
where each site has a fixed stress condition. Species differ both in stress
tolerance and competitive ability. Stress tolerance is quantified as the
fraction of sites with stress conditions low enough to allow establishment.
Competitive ability is quantified as the propensity to win the competition for
empty sites. We derive the deterministic, discrete-time dynamical system for
the species abundances. We prove the conditions under which plant species can
coexist in a stable equilibrium. We show that the coexistence conditions can be
characterized graphically, clearly illustrating the trade-off between stress
tolerance and competitive ability. We compare our model with a recently
proposed, continuous-time dynamical system for a tolerance-fecundity trade-off
in plant communities, and we show that this model is a special case of the
continuous-time version of our model.Comment: To be published in Journal of Mathematical Biology. 30 pages, 5
figures, 5 appendice
Development of Pratylenchus Coffeae in Biochar Applied Soil, Coffee Roots and Its Effect on Plant Growth
Biochar improve physical, chemical and biological properties of soil. It may also be used as botanical pesticides. The experiment was aimed to determine the effect of biochar on population development of parasitic nematode Pratylenchus coffeae. The experiment was carried out in Nematology Laboratory and in a greenhouse of Indonesian Coffee and Cocoa Research Institute (ICCRI), Jember, Indonesia. The experiment was arranged according to completely randomized design with six treatments of biochar concentrations, i.e. 4%; 3%; 2%; 1%; 0.5% and 0% dry weight of soil. Research results revealed that biochar application of 4.0% was effectively killed 74.5% of P. coffeae, while the lowest mortality level of 37.5% at biochar 0.5% treatment. In the greenhouse trial, application of biochar 4.0% was the most effective in suppressing the population of parasitic nematode in coffee seedlings. Application of biochar was also able to increase the growth and biomass of coffee seedlings
The Hypermasculine and Ubersexual Men in the Harlequin Novels of the 1980s and 2000s
Harlequin novels are so popular that Harlequin romance emerges as a genre. Unlike on the heroines, there are scarcely any studies or works on the heroes, thus, I want to focus my study on the heroes of Harlequin Romance. By analyzing using the Male Sex Role in the 1980s and themes of masculinity in the 2000s, I will prove that there are four types of ideal men in the 1980s Harlequin novels whose characteristics originated from the ideal men in the society at that time, the Hypermasculine men with extreme masculinity and avoidance of any feminine sides. I will also prove that there are three types of ideal men in the 2000s Harlequin novels whose characteristics are in accordance with the Ubersexual men\u27s, the ideal men in the society in 2000s having positive characteristics of traditional manliness with some “feminine“ characteristics. The reason behind these changes is because of the changes in the heroines and the characteristics of men in the society in time and these push for the changes in the heroes. As a publisher, Harlequin\u27s goal is the highest selling rate, thus, they adjust to the market\u27s demand
Eccentricity Evolution for Planets in Gaseous Disks
We investigate the hypothesis that interactions between a giant planet and
the disk from which it forms promote eccentricity growth. These interactions
are concentrated at discrete Lindblad and corotation resonances. Interactions
at principal Lindblad resonances cause the planet's orbit to migrate and open a
gap in the disk if the planet is sufficiently massive. Those at first order
Lindblad and corotation resonances change the planet's orbital eccentricity.
Eccentricity is excited by interactions at external Lindblad resonances which
are located on the opposite side of corotation from the planet, and damped by
co-orbital Lindblad resonances which overlap the planet's orbit. If the planet
clears a gap in the disk, the rate of eccentricity damping by co-orbital
Lindblad resonances is reduced. Density gradients associated with the gap
activate eccentricity damping by corotation resonances at a rate which
initially marginally exceeds that of eccentricity excitation by external
Lindblad resonances. But the corotation torque drives a mass flux which reduces
the density gradient near the resonance. Sufficient partial saturation of
corotation resonances can tip the balance in favor of eccentricity excitation.
A minimal initial eccentricity of a few percent is required to overcome viscous
diffusion which acts to unsaturate corotation resonances by reestablishing the
large scale density gradient. Thus eccentricity growth is a finite amplitude
instability. Formally, interactions at the apsidal resonance, which is a
special kind of co-orbital Lindblad resonance, appears to damp eccentricity
faster than external Lindblad resonances can excite it. However, apsidal waves
have such long wavelengths that they do not propagate in protoplanetary disks.
This reduces eccentricity damping by the apsidal resonance to a modest level.Comment: Submitted to Ap
Broad-band Modeling of GRB Afterglows
Observations of GRB afterglows ranging from radio to X-ray frequencies
generate large data sets. Careful analysis of these broad-band data can give us
insight into the nature of the GRB progenitor population by yielding such
information like the total energy of the burst, the geometry of the fireball
and the type of environment into which the GRB explodes. We illustrate, by
example, how global, self-consistent fits are a robust approach for
characterizing the afterglow emission. This approach allows a relatively simple
comparison of different models and a way to determine the strengths and
weaknesses of these models, since all are treated self-consistently. Here we
quantify the main differences between the broad-band, self-consistent approach
and the traditional approach, using GRB000301C and GRB970508 as test cases.Comment: Appears in "Gamma-Ray Bursts in the Afterglow Era" proceedings of the
Roma 2000 GRB Workshop; 3 pages; 2 figure
Jets in GRBs: Tests and Predictions for the Structured Jet Model
The two leading interpretations of achromatic breaks that are observed in the
light curves of GRBs afterglow are (i) the manifestation of the edge of a jet,
which has a roughly uniform energy profile and a sharp edge and (ii) a line of
sight effect in jets with a variable energy profile. The first scenario
requires the inner engine to produce a jet with a different opening angle each
explosion, while the latter requires a standard engine. The physical structure
of the jet is a crucial factor in understanding GRB progenitors, and therefore
discriminating the two jet scenarios is particularly relevant. In the
structured jet case, specific predictions can be made for the distribution of
observed break angles , while that distribution is
arbitrary in the first scenario. We derive the theoretical distribution for the
structured jet model. Specifically, we predict the most common angle to be
about 0.12 rad, in rough agreement with the sample. If this agreement would
hold as the sample size increases, it would strengthen the case for the
standard jet hypothesis. We show that a prediction of this model is that the
average viewing angle is an increasing function of the survey sensitivity, and
in particular that a mission like {\em Swift} will find the typical viewing
angle to be about 0.3 rad. The local event rate predicted by this model is
Gpc yr.Comment: 14 pages, 3 figures; accepted to Ap
Recovery Among People with Mental Illness (PMI) as Perceived by the Caregivers in Islamic Boarding School (IBS) in Indonesia
Background: Mental hospitals as places to rehabilitation people with mental illness(PMI) in Indonesia are limited in numbers and do not meet with the number of PMI.The society may contribute in facilitating recovery and rehabilitation place for PMI including Islamic boarding school. Some Islamic boarding schools provide rehabilitation for PMI to help with recovery process. Recovery is an important aspect to assess the success of PMI rehabilitation. Nevertheless, there has been no study on Islamic boarding school\u27s caregivers\u27 perception on PMI recovery.Purpose: This study aims to explore recovery perception of caregivers treating PMI in Islamic boarding school and factors affecting recovery.Methods: Data are acquired from 19 caregivers from three Islamic boarding schools providing rehabilitation for PMI with Focus Group Discussion (FGD). The data analyzed using descriptive analysis.Result: Having a good communication is a recovery criterion that is mentioned themost by caregivers. There are three biggest factors affecting recovery based on the caregivers such as prayers or religion followed by social support from family and environment and also doing activities.Conclusion: The results may depict the PMI recovery so that the health care providers can provide interventions that can support the recovery process in PMI
The prompt energy release of gamma-ray bursts using a cosmological k-correction
The fluences of gamma-ray bursts (GRBs) are measured with a variety of
instruments in different detector energy ranges. A detailed comparison of the
implied energy releases of the GRB sample requires, then, an accurate
accounting of this diversity in fluence measurements which properly corrects
for the redshifting of GRB spectra. Here, we develop a methodology to
``k-correct'' the implied prompt energy release of a GRB to a fixed co-moving
bandpass. This allows us to homogenize the prompt energy release of 17
cosmological GRBs (using published redshifts, fluences, and spectra) to two
common co-moving bandpasses: 20-2000 keV and 0.1 keV-10 MeV (``bolometric'').
While the overall distribution of GRB energy releases does not change
significantly by using a k-correction, we show that uncorrected energy
estimates systematically undercounts the bolometric energy by ~5% to 600%,
depending on the particular GRB. We find that the median bolometric
isotropic-equivalent prompt energy release is 2.2 x 10^{53} erg with an r.m.s.
scatter of 0.80 dex. The typical estimated uncertainty on a given k-corrected
energy measurement is ~20%.Comment: Accepted to the Astronomical Journal. 21 pages (LaTeX) and 4 figure
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