993 research outputs found
Spatial synchronization and extinction of species under external forcing
We study the interplay between synchronization and extinction of a species.
Using a general model we show that under a common external forcing, the species
with a quadratic saturation term in the population dynamics first undergoes
spatial synchronization and then extinction, thereby avoiding the rescue
effect. This is because the saturation term reduces the synchronization time
scale but not the extinction time scale. The effect can be observed even when
the external forcing acts only on some locations provided there is a
synchronizing term in the dynamics. Absence of the quadratic saturation term
can help the species to avoid extinction.Comment: 4 pages, 2 figure
Gravitational Baryogenesis: Problems and Possible Resolution
The coupling of baryonic current to the derivative of the curvature scalar,
, inherent to gravitational baryogenesis (GBG), leads to a fourth order
differential equation of motion for instead of the algebraic one of General
Relativity (GR). The fourth-order differential equation is generically
unstable. We consider a possible mechanism of stabilization of GBG by
modification of gravity, introducing an -term into the canonical action of
GR.
It is shown that this mechanism allows for stabilization of GBG with bosonic
and fermionic baryon currents. We have established the region of the model
parameters leading to stabilization of . Still, the standard cosmology would
be noticeably modified.Comment: 11 pages, no figures, presented at International Conference
on Particle Physics and Astrophysics (ICCPA-2022)}. arXiv admin note: text
overlap with arXiv:1808.0857
Generalization of Linearized Gouy-Chapman-Stern Model of Electric Double Layer for Nanostructured and Porous Electrodes: Deterministic and Stochastic Morphology
We generalize linearized Gouy-Chapman-Stern theory of electric double layer
for nanostructured and morphologically disordered electrodes. Equation for
capacitance is obtained using linear Gouy-Chapman (GC) or
Debye-ckel equation for potential near complex
electrode/electrolyte interface. The effect of surface morphology of an
electrode on electric double layer (EDL) is obtained using "multiple scattering
formalism" in surface curvature. The result for capacitance is expressed in
terms of the ratio of Gouy screening length and the local principal radii of
curvature of surface. We also include a contribution of compact layer, which is
significant in overall prediction of capacitance. Our general results are
analyzed in details for two special morphologies of electrodes, i.e.
"nanoporous membrane" and "forest of nanopillars". Variations of local shapes
and global size variations due to residual randomness in morphology are
accounted as curvature fluctuations over a reference shape element.
Particularly, the theory shows that the presence of geometrical fluctuations in
porous systems causes enhanced dependence of capacitance on mean pore sizes and
suppresses the magnitude of capacitance. Theory emphasizes a strong influence
of overall morphology and its disorder on capacitance. Finally, our predictions
are in reasonable agreement with recent experimental measurements on
supercapacitive mesoporous systems
Making On-Demand Routing Efficient with Route-Request Aggregation
In theory, on-demand routing is very attractive for mobile ad hoc networks
(MANET), because it induces signaling only for those destinations for which
there is data traffic. However, in practice, the signaling overhead of existing
on-demand routing protocols becomes excessive as the rate of topology changes
increases due to mobility or other causes. We introduce the first on-demand
routing approach that eliminates the main limitation of on-demand routing by
aggregating route requests (RREQ) for the same destinations. The approach can
be applied to any existing on-demand routing protocol, and we introduce the
Ad-hoc Demand-Aggregated Routing with Adaptation (ADARA) as an example of how
RREQ aggregation can be used. ADARA is compared to AODV and OLSR using
discrete-event simulations, and the results show that aggregating RREQs can
make on-demand routing more efficient than existing proactive or on-demand
routing protocols
myo-Inositol Oxygenase is Required for Responses to Low Energy Conditions in Arabidopsis thaliana
myo-Inositol is a precursor for cell wall components, is used as a backbone of myo-inositol trisphosphate (Ins(1,4,5)P3) and phosphatidylinositol phosphate signaling molecules, and is debated about whether it is also a precursor in an alternate ascorbic acid synthesis pathway. Plants control inositol homeostasis by regulation of key enzymes involved in myo-inositol synthesis and catabolism. Recent transcriptional profiling data indicate up-regulation of the myo-inositol oxygenase (MIOX) genes under conditions in which energy or nutrients are limited. To test whether the MIOX genes are required for responses to low energy, we first examined MIOX2 and MIOX4 gene expression regulation by energy/nutrient conditions. We found that both MIOX2 and MIOX4 expression are suppressed by exogenous glucose addition in the shoot, but not in the root. Both genes were abundantly expressed during low energy/nutrient conditions. Loss-of-function mutants in MIOX genes contain alterations in myo-inositol levels and growth changes in the root. Miox2 mutants can be complemented with a MIOX2:green fluorescent protein fusion. Further we show here that MIOX2 is a cytoplasmic protein, while MIOX4 is present mostly in the cytoplasm, but also occasionally in the nucleus. Together, these data suggest that MIOX catabolism in the shoot may influence root growth responses during low energy/nutrient conditions
Comment on "Mean First Passage Time for Anomalous Diffusion"
We correct a previously erroneous calculation [Phys. Rev. E 62, 6065 (2000)]
of the mean first passage time of a subdiffusive process to reach either end of
a finite interval in one dimension. The mean first passage time is in fact
infinite.Comment: To appear in Phys. Rev.
Chandra Observations of Gas Stripping in the Elliptical Galaxy NGC 4552 in the Virgo Cluster
We use a 54.4 ks Chandra observation to study ram-pressure stripping in
NGC4552 (M89), an elliptical galaxy in the Virgo Cluster. Chandra images in the
0.5-2 keV band show a sharp leading edge in the surface brightness 3.1 kpc
north of the galaxy center, a cool (kT =0.51^{+0.09}_{-0.06} keV) tail with
mean density n_e ~5.4 +/- 1.7 x 10^{-3} cm^{-3} extending ~10 kpc to the south
of the galaxy, and two 3-4 kpc horns of emission extending southward away from
the leading edge. These are all features characteristic of supersonic
ram-pressure stripping of galaxy gas, due to NGC4552's motion through the
surrounding Virgo ICM. Fitting the surface brightness profile and spectra
across the leading edge, we find the galaxy gas inside the edge is cooler (kT =
0.43^{+0.03}_{-0.02} keV) and denser (n_e ~ 0.010 cm^{-3}) than the surrounding
Virgo ICM (kT = 2.2^{+0.7}_{-0.4} keV and n_e = 3.0 +/- 0.3 x 10^{-4} cm^{-3}).
The resulting pressure ratio between the free-streaming ICM and cluster gas at
the stagnation point is ~7.6^{+3.4}_{-2.0} for galaxy gas metallicities of
0.5^{+0.5}_{-0.3} Zsolar, which suggests that NGC4552 is moving supersonically
through the cluster with a velocity v ~ 1680^{+390}_{-220} km/s (Mach
2.2^{+0.5}_{-0.3}) at an angle xi ~ 35 +/- 7 degrees towards us with respect to
the plane of the sky.Comment: 31 pages, 12 figures, ApJ, in press; paper split into 2 parts, Paper
I(sec 1-3) here, added figs and discussion to conform to published version;
Paper II (sec. 4) in astro-ph/060440
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