181 research outputs found
Study of outgoing longwave radiation anomalies associated with Haiti earthquake
The paper presents an analysis by using the methods of Eddy field calculation mean and wavelet maxima to detect seismic anomalies within the outgoing longwave radiation (OLR) data based on time and space. The distinguishing feature of the method of Eddy field calculation mean is that we can calculate "the total sum of the difference value" of "the measured value" between adjacent points, which could highlight the singularity within data. The identified singularities are further validated by wavelet maxima, which using wavelet transformations as data mining tools by computing the maxima that can be used to identify obvious anomalies within OLR data. The two methods has been applied to carry out a comparative analysis of OLR data associated with the earthquake recently occurred in Haiti on 12 January 2010. Combining with the tectonic explanation of spatial and temporal continuity of the abnormal phenomena, the analyzed results have indicated a number of singularities associated with the possible seismic anomalies of the earthquake and from the comparative experiments and analyses by using the two methods, which follow the same time and space, we conclude that the singularities observed from 19 to 24 December 2009 could be the earthquake precursor of Haiti earthquake
Correlated Hybrid Fluctuations from Inflation with Thermal Dissipation
We investigate the primordial scalar perturbations in the thermal dissipative
inflation where the radiation component (thermal bath) persists and the density
fluctuations are thermally originated. The perturbation generated in this model
is hybrid, i.e. it consists of both adiabatic and isocurvature components. We
calculate the fractional power ratio () and the correlation coefficient
() between the adiabatic and the isocurvature perturbations at the
commencing of the radiation regime. Since the adiabatic/isocurvature
decomposition of hybrid perturbations generally is gauge-dependent at
super-horizon scales when there is substantial energy exchange between the
inflaton and the thermal bath, we carefully perform a proper decomposition of
the perturbations. We find that the adiabatic and the isocurvature
perturbations are correlated, even though the fluctuations of the radiation
component is considered uncorrelated with that of the inflaton. We also show
that both and depend mainly on the ratio between the
dissipation coefficient and the Hubble parameter during inflation.
The correlation is positive () for strong dissipation cases
where , and is negative for weak dissipation instances where
. Moreover, and in this model are not
independent of each other. The predicted relation between and
is consistent with the WMAP observation. Other testable predictions are also
discussed.Comment: 18 pages using revtex4, accepted for publication in PR
Effects of dark sectors' mutual interaction on the growth of structures
We present a general formalism to study the growth of dark matter
perturbations when dark energy perturbations and interactions between dark
sectors are present. We show that dynamical stability of the growth of
structure depends on the type of coupling between dark sectors. By taking the
appropriate coupling to ensure the stable growth of structure, we observe that
the effect of the dark sectors' interaction overwhelms that of dark energy
perturbation on the growth function of dark matter perturbation. Due to the
influence of the interaction, the growth index can differ from the value
without interaction by an amount within the observational sensibility, which
provides a possibility to disclose the interaction between dark sectors through
future observations on the growth of large structure.Comment: 15 pages, 4 figures, revised version, to appear in JCA
The influence of gene expression time delays on Gierer-Meinhardt pattern formation systems
There are numerous examples of morphogen gradients controlling long range signalling in developmental and cellular systems. The prospect of two such interacting morphogens instigating long range self-organisation in biological systems via a Turing bifurcation has been explored, postulated, or implicated in the context of numerous developmental processes. However, modelling investigations of cellular systems typically neglect the influence of gene expression on such dynamics, even though transcription and translation are observed to be important in morphogenetic systems. In particular, the influence of gene expression on a large class of Turing bifurcation models, namely those with pure kinetics such as the GiererâMeinhardt system, is unexplored. Our investigations demonstrate that the behaviour of the GiererâMeinhardt model profoundly changes on the inclusion of gene expression dynamics and is sensitive to the sub-cellular details of gene expression. Features such as concentration blow up, morphogen oscillations and radical sensitivities to the duration of gene expression are observed and, at best, severely restrict the possible parameter spaces for feasible biological behaviour. These results also indicate that the behaviour of Turing pattern formation systems on the inclusion of gene expression time delays may provide a means of distinguishing between possible forms of interaction kinetics. Finally, this study also emphasises that sub-cellular and gene expression dynamics should not be simply neglected in models of long range biological pattern formation via morphogens
Cosmic coincidence problem and variable constants of physics
The standard model of cosmology is investigated using time dependent
cosmological constant and Newton's gravitational constant . The
total energy content is described by the modified Chaplygin gas equation of
state. It is found that the time dependent constants coupled with the modified
Chaplygin gas interpolate between the earlier matter to the later dark energy
dominated phase of the universe. We also achieve a convergence of parameter
, with minute fluctuations, showing an evolving . Thus our
model fairly alleviates the cosmic coincidence problem which demands
at present time.Comment: 27 pages, 15 figure
Suppressing CMB Quadrupole with a Bounce from Contracting Phase to Inflation
Recent released WMAP data show a low value of quadrupole in the CMB
temperature fluctuations, which confirms the early observations by COBE. In
this paper, a scenario, in which a contracting phase is followed by an
inflationary phase, is constructed. We calculate the perturbation spectrum and
show that this scenario can provide a reasonable explanation for lower CMB
anisotropies on large angular scales.Comment: 5 pages, 3 figure
Aberrant behaviours of reaction diffusion self-organisation models on growing domains in the presence of gene expression time delays
Turingâs pattern formation mechanism exhibits sensitivity to the details of the initial conditions suggesting that, in isolation, it cannot robustly generate pattern within noisy biological environments. Nonetheless, secondary aspects of developmental self-organisation, such as a growing domain, have been shown to ameliorate this aberrant model behaviour. Furthermore, while in-situ hybridisation reveals the presence of gene expression in developmental processes, the influence of such dynamics on Turingâs model has received limited attention. Here, we novelly focus on the GiererâMeinhardt reaction diffusion system considering delays due the time taken for gene expression, while incorporating a number of different domain growth profiles to further explore the influence and interplay of domain growth and gene expression on Turingâs mechanism. We find extensive pathological model behaviour, exhibiting one or more of the following: temporal oscillations with no spatial structure, a failure of the Turing instability and an extreme sensitivity to the initial conditions, the growth profile and the duration of gene expression. This deviant behaviour is even more severe than observed in previous studies of Schnakenberg kinetics on exponentially growing domains in the presence of gene expression (Gaffney and Monk in Bull. Math. Biol. 68:99â130, 2006). Our results emphasise that gene expression dynamics induce unrealistic behaviour in Turingâs model for multiple choices of kinetics and thus such aberrant modelling predictions are likely to be generic. They also highlight that domain growth can no longer ameliorate the excessive sensitivity of Turingâs mechanism in the presence of gene expression time delays. The above, extensive, pathologies suggest that, in the presence of gene expression, Turingâs mechanism would generally require a novel and extensive secondary mechanism to control reaction diffusion patterning
Evolution and Flare Activity of Delta-Sunspots in Cycle 23
The emergence and magnetic evolution of solar active regions (ARs) of
beta-gamma-delta type, which are known to be highly flare-productive, were
studied with the SOHO/MDI data in Cycle 23. We selected 31 ARs that can be
observed from their birth phase, as unbiased samples for our study. From the
analysis of the magnetic topology (twist and writhe), we obtained the following
results. i) Emerging beta-gamma-delta ARs can be classified into three
topological types as "quasi-beta", "writhed" and "top-to-top". ii) Among them,
the "writhed" and "top-to-top" types tend to show high flare activity. iii) As
the signs of twist and writhe agree with each other in most cases of the
"writhed" type (12 cases out of 13), we propose a magnetic model in which the
emerging flux regions in a beta-gamma-delta AR are not separated but united as
a single structure below the solar surface. iv) Almost all the "writhed"-type
ARs have downward knotted structures in the mid portion of the magnetic flux
tube. This, we believe, is the essential property of beta-gamma-delta ARs. v)
The flare activity of beta-gamma-delta ARs is highly correlated not only with
the sunspot area but also with the magnetic complexity. vi) We suggest that
there is a possible scaling-law between the flare index and the maximum umbral
area
Inflation, cold dark matter, and the central density problem
A problem with high central densities in dark halos has arisen in the context
of LCDM cosmologies with scale-invariant initial power spectra. Although n=1 is
often justified by appealing to the inflation scenario, inflationary models
with mild deviations from scale-invariance are not uncommon and models with
significant running of the spectral index are plausible. Even mild deviations
from scale-invariance can be important because halo collapse times and
densities depend on the relative amount of small-scale power. We choose several
popular models of inflation and work out the ramifications for galaxy central
densities. For each model, we calculate its COBE-normalized power spectrum and
deduce the implied halo densities using a semi-analytic method calibrated
against N-body simulations. We compare our predictions to a sample of dark
matter-dominated galaxies using a non-parametric measure of the density. While
standard n=1, LCDM halos are overdense by a factor of 6, several of our example
inflation+CDM models predict halo densities well within the range preferred by
observations. We also show how the presence of massive (0.5 eV) neutrinos may
help to alleviate the central density problem even with n=1. We conclude that
galaxy central densities may not be as problematic for the CDM paradigm as is
sometimes assumed: rather than telling us something about the nature of the
dark matter, galaxy rotation curves may be telling us something about inflation
and/or neutrinos. An important test of this idea will be an eventual consensus
on the value of sigma_8, the rms overdensity on the scale 8 h^-1 Mpc. Our
successful models have values of sigma_8 approximately 0.75, which is within
the range of recent determinations. Finally, models with n>1 (or sigma_8 > 1)
are highly disfavored.Comment: 13 pages, 6 figures. Minor changes made to reflect referee's
Comments, error in Eq. (18) corrected, references updated and corrected,
conclusions unchanged. Version accepted for publication in Phys. Rev. D,
scheduled for 15 August 200
Large-scale power in the CMB and new physics: An analysis using Bayesian model comparison
Published versio
- âŠ