9,809 research outputs found
Reconstruction of the Primordial Power Spectrum by Direct Inversion
We introduce a new method for reconstructing the primordial power spectrum,
, directly from observations of the Cosmic Microwave Background (CMB). We
employ Singular Value Decomposition (SVD) to invert the radiation perturbation
transfer function. The degeneracy of the multipole to wavenumber
linear mapping is thus reduced. This enables the inversion to be carried out at
each point along a Monte Carlo Markov Chain (MCMC) exploration of the combined
and cosmological parameter space. We present best--fit obtained
with this method along with other cosmological parameters.Comment: 23 pages, 9 figure
Statistical Analysis of the Road Network of India
In this paper we study the Indian Highway Network as a complex network where
the junction points are considered as nodes, and the links are formed by an
existing connection. We explore the topological properties and community
structure of the network. We observe that the Indian Highway Network displays
small world properties and is assortative in nature. We also identify the most
important road-junctions (or cities) in the highway network based on the
betweenness centrality of the node. This could help in identifying the
potential congestion points in the network. Our study is of practical
importance and could provide a novel approach to reduce congestion and improve
the performance of the highway networ
Electronic Properties of Boron and Nitrogen doped graphene: A first principles study
Effect of doping of graphene either by Boron (B), Nitrogen (N) or co-doped by
B and N is studied using density functional theory. Our extensive band
structure and density of states calculations indicate that upon doping by N
(electron doping), the Dirac point in the graphene band structure shifts below
the Fermi level and an energy gap appears at the high symmetric K-point. On the
other hand, by B (hole doping), the Dirac point shifts above the Fermi level
and a gap appears. Upon co-doping of graphene by B and N, the energy gap
between valence and conduction bands appears at Fermi level and the system
behaves as narrow gap semiconductor. Obtained results are found to be in well
agreement with available experimental findings.Comment: 11 pages, 4 figures, 1 table, submitted to J. Nanopart. Re
Structure formation in the presence of dark energy perturbations
We study non-linear structure formation in the presence of dark energy. The
influence of dark energy on the growth of large-scale cosmological structures
is exerted both through its background effect on the expansion rate, and
through its perturbations as well. In order to compute the rate of formation of
massive objects we employ the Spherical Collapse formalism, which we generalize
to include fluids with pressure. We show that the resulting non-linear
evolution equations are identical to the ones obtained in the Pseudo-Newtonian
approach to cosmological perturbations, in the regime where an equation of
state serves to describe both the background pressure relative to density, and
the pressure perturbations relative to the density perturbations as well. We
then consider a wide range of constant and time-dependent equations of state
(including phantom models) parametrized in a standard way, and study their
impact on the non-linear growth of structure. The main effect is the formation
of dark energy structure associated with the dark matter halo: non-phantom
equations of state induce the formation of a dark energy halo, damping the
growth of structures; phantom models, on the other hand, generate dark energy
voids, enhancing structure growth. Finally, we employ the Press-Schechter
formalism to compute how dark energy affects the number of massive objects as a
function of redshift.Comment: 21 pages, 8 figures. Matches published version, with caption of Fig.
6 correcte
The Hubble constant and dark energy from cosmological distance measures
We study how the determination of the Hubble constant from cosmological
distance measures is affected by models of dark energy and vice versa. For this
purpose, constraints on the Hubble constant and dark energy are investigated
using the cosmological observations of cosmic microwave background, baryon
acoustic oscillations and type Ia suprenovae. When one investigates dark
energy, the Hubble constant is often a nuisance parameter, thus it is usually
marginalized over. On the other hand, when one focuses on the Hubble constant,
simple dark energy models such as a cosmological constant and a constant
equation of state are usually assumed. Since we do not know the nature of dark
energy yet, it is interesting to investigate the Hubble constant assuming some
types of dark energy and see to what extent the constraint on the Hubble
constant is affected by the assumption concerning dark energy. We show that the
constraint on the Hubble constant is not affected much by the assumption for
dark energy. We furthermore show that this holds true even if we remove the
assumption that the universe is flat. We also discuss how the prior on the
Hubble constant affects the constraints on dark energy and/or the curvature of
the universe.Comment: 45 pages, 15 figure
Lifetime measurements of Triaxial Strongly Deformed bands in Tm
With the Doppler Shift Attenuation Method, quadrupole transition moments,
, were determined for the two recently proposed Triaxial Strongly Deformed
(TSD) bands in Tm. The measured moments indicate that the
deformation of these bands is larger than that of the yrast, signature
partners. However, the measured values are smaller than those predicted by
theory. This observation appears to be valid for TSD bands in several nuclei of
the regionComment: 8 pages, 5 figures. Submitted to Physical Review
Cosmological constraints combining H(z), CMB shift and SNIa observational data
Recently H(z) data obtained from differential ages of galaxies have been
proposed as a new geometrical probe of dark energy. In this paper we use those
data, combined with other background tests (CMB shift and SNIa data), to
constrain a set of general relativistic dark energy models together with some
other models motivated by extra dimensions. Our analysis rests mostly on
Bayesian statistics, and we conclude that LCDM is at least substantially
favoured, and that braneworld models are less favoured than general
relativistic ones.Comment: 17 pages, 11 figures; improved discussion, new figures, updated to
match published versio
Separation of Oligosaccharides from Lotus Seeds via Medium-pressure Liquid Chromatography Coupled with ELSD and DAD
peer-reviewedLotus seeds were identified by the Ministry of Public Health of China as both food and medicine. One general function of lotus seeds is to improve intestinal health. However, to date, studies evaluating the relationship between bioactive compounds in lotus seeds and the physiological activity of the intestine are limited. In the present study, by using medium pressure liquid chromatography coupled with evaporative light-scattering detector and diode-array detector, five oligosaccharides were isolated and their structures were further characterized by electrospray ionization-mass spectrometry and gas chromatography-mass spectrometry. In vitro testing determined that LOS3-1 and LOS4 elicited relatively good proliferative effects on Lactobacillus delbrueckii subsp. bulgaricus. These results indicated a structure-function relationship between the physiological activity of oligosaccharides in lotus seeds and the number of probiotics applied, thus providing room for improvement of this particular feature. Intestinal probiotics may potentially become a new effective drug target for the regulation of immunity
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