509 research outputs found
Kemunduran dan Kehancuran Kerajaan Mughal
Mughal was one of the Islamic Kingdoms that stay long for about 342 years, starting from Sultan Zahr al-Din Muhammad (1483â1530 A.D) until Sultan Siraj al-Din Bahadur Syah (1837â1858 A.D). There are two prominent factors which caused the Kingdom of Mughal separated each other and faced the decrease, internal and external factors. Internally, the Kingdom of Mughal faced the decrease because of no system and mechanism on power succession, and also the lack leadership integrity of the next generation who descended the former leaders. The hedonism life style also became the main cause of the complicated political situation on the Kingdom. Moreover, the political policy which tends to be more puritanical and ideological also ruined the governmental system. Those internal factors, then, caused weak political control and powerless authority of the Kingdom in front of other kingdoms. As a consequence, many rebellions happened everywhere. It absolutely made the power of the Kingdom one by one belongs to other kingdoms
Flux Expulsion - Field Evolution in Neutron Stars
Models for the evolution of magnetic fields of neutron stars are constructed,
assuming the field is embedded in the proton superconducting core of the star.
The rate of expulsion of the magnetic flux out of the core, or equivalently the
velocity of outward motion of flux-carrying proton-vortices is determined from
a solution of the Magnus equation of motion for these vortices. A force due to
the pinning interaction between the proton-vortices and the neutron-superfluid
vortices is also taken into account in addition to the other more conventional
forces acting on the proton-vortices. Alternative models for the field
evolution are considered based on the different possibilities discussed for the
effective values of the various forces. The coupled spin and magnetic evolution
of single pulsars as well as those processed in low-mass binary systems are
computed, for each of the models. The predicted lifetimes of active pulsars,
field strengths of the very old neutron stars, and distribution of the magnetic
fields versus orbital periods in low-mass binary pulsars are used to test the
adopted field decay models. Contrary to the earlier claims, the buoyancy is
argued to be the dominant driving cause of the flux expulsion, for the single
as well as the binary neutron stars. However, the pinning is also found to play
a crucial role which is necessary to account for the observed low field binary
and millisecond pulsars.Comment: 23 pages, + 7 figures, accepted for publication in Ap
Effect of the Heterogeneity of Metamaterials on Casimir-Lifshitz Interaction
The Casimir-Lifshitz interaction between metamaterials is studied using a
model that takes into account the structural heterogeneity of the dielectric
and magnetic properties of the bodies. A recently developed perturbation theory
for the Casimir-Lifshitz interaction between arbitrary material bodies is
generalized to include non-uniform magnetic permeability profiles, and used to
study the interaction between the magneto-dielectric heterostructures within
the leading order. The metamaterials are modeled as two dimensional arrays of
domains with varying permittivity and permeability. In the case of two
semi-infinite bodies with flat boundaries, the patterned structure of the
material properties is found to cause the normal Casimir-Lifshitz force to
develop an oscillatory behavior when the distance between the two bodies is
comparable to the wavelength of the patterned features in the metamaterials.
The non-uniformity also leads to the emergence of lateral Casimir-Lifshitz
forces, which tend to strengthen as the gap size becomes smaller. Our results
suggest that the recent studies on Casimir-Lifshitz forces between
metamaterials, which have been performed with the aim of examining the
possibility of observing the repulsive force, should be revisited to include
the effect of the patterned structure at the wavelength of several hundred
nanometers that coincides with the relevant gap size in the experiments.Comment: 9 pages, 13 figures. Rewriting equations (10) and (12) and increasing
the size of the lettering/numeral in figure
The elusiveness of old neutron stars
Old neutron stars (ONSs) which have radiated away their internal and
rotational energy may still shine if accreting the interstellar medium. Despite
their large number, only two promising candidates have been detected so far and
rather stringent limits on their observability follow from the analysis of
ROSAT surveys. This contrasts with optimistic theoretical estimates that
predicted a large number of sources in ROSAT fields. We have reconsidered the
issue of ONSs observability, accounting for the spin and magnetic field
evolution over the neutron star lifetime. In the framework of a spin-induced
field decay model, we show that the total number of ONSs which are, at present,
in the accretion stage is reduced by a factor ~5 over previous figures if the
characteristic timescale for crustal current dissipation is ~ 10^8 - 10^9 yr.
This brings theoretical predictions much closer to observational limits. Most
ONSs should be at present in the propeller phase and, if subject to episodic
flaring, they could be observable.Comment: 10 pages Latex, 5 ps figures. To be formatted with the AASTeX
package. Accepted for publication in Ap
A two-parameter random walk with approximate exponential probability distribution
We study a non-Markovian random walk in dimension 1. It depends on two
parameters eps_r and eps_l, the probabilities to go straight on when walking to
the right, respectively to the left. The position x of the walk after n steps
and the number of reversals of direction k are used to estimate eps_r and
eps_l. We calculate the joint probability distribution p_n(x,k) in closed form
and show that, approximately, it belongs to the exponential family.Comment: 12 pages, updated reference to companion paper cond-mat/060126
On the construction of non-Hermitian Hamiltonians with all-real spectra through supersymmetric algorithms
The energy spectra of two different quantum systems are paired through
supersymmetric algorithms. One of the systems is Hermitian and the other is
characterized by a complex-valued potential, both of them with only real
eigenvalues in their spectrum. The superpotential that links these systems is
complex-valued, parameterized by the solutions of the Ermakov equation, and may
be expressed either in nonlinear form or as the logarithmic derivative of a
properly chosen complex-valued function. The non-Hermitian systems can be
constructed to be either parity-time-symmetric or non-parity-time-symmetric.Comment: 9 pages, 2 figures (affiliation institution corrected
Persistent random walk on a one-dimensional lattice with random asymmetric transmittances
We study the persistent random walk of photons on a one-dimensional lattice
of random asymmetric transmittances. Each site is characterized by its
intensity transmittance t (t') for photons moving to the right (left)
direction. Transmittances at different sites are assumed independent,
distributed according to a given probability density Distribution. We use the
effective medium approximation and identify two classes of probability density
distribution of transmittances which lead to the normal diffusion of photons.
Monte Carlo simulations confirm our predictions.Comment: 7 pages, submitted to Phys. Rev.
Experimental Measurement of the Berry Curvature from Anomalous Transport
Geometrical properties of energy bands underlie fascinating phenomena in a
wide-range of systems, including solid-state materials, ultracold gases and
photonics. Most famously, local geometrical characteristics like the Berry
curvature can be related to global topological invariants such as those
classifying quantum Hall states or topological insulators. Regardless of the
band topology, however, any non-zero Berry curvature can have important
consequences, such as in the semi-classical evolution of a wave packet. Here,
we experimentally demonstrate for the first time that wave packet dynamics can
be used to directly map out the Berry curvature. To this end, we use optical
pulses in two coupled fibre loops to study the discrete time-evolution of a
wave packet in a 1D geometrical "charge" pump, where the Berry curvature leads
to an anomalous displacement of the wave packet under pumping. This is both the
first direct observation of Berry curvature effects in an optical system, and,
more generally, the proof-of-principle demonstration that semi-classical
dynamics can serve as a high-resolution tool for mapping out geometrical
properties
Worldwide evaluations of quinoa: preliminary results from post International Year of Quinoa FAO projects in nine countries
Chenopodium quinoa Willd, a high quality grain crop, is resistant to abiotic stresses (drought, cold, and salt) and offers an optimal source of protein. Quinoa represents a symbol of crop genetic diversity across the Andean region. In recent years, this crop has undergone a major expansion outside its countries of origin. The activities carried out within the framework of the International Year of Quinoa provided a great contribution to raise awareness on the multiple benefits of quinoa as well as to its wider cultivation at the global level. FAO is actively involved in promoting and evaluating the cultivation of quinoa in 26 countries outside the Andean region with the aim to strengthen food and nutrition security. The main goal of this research is to evaluate the adaptability of selected quinoa genotypes under different environments outside the Andean region. This paper presents the preliminary results from nine countries. Field evaluations were conducted during 2013/2014 and 2014/2015 in Asia (Kyrgyzstan and Tajikistan), and the Near East and North African countries (Algeria, Egypt, Iraq, Iran, Lebanon, Mauritania, and Yemen). In each country, the trials were carried out in different locations that globally represent the diversity of 19 agrarian systems under different agro-ecological conditions. Twenty-one genotypes of quinoa were tested using the same experimental protocol in all locations consisting in a randomized complete block design (RCBD) with three replicates. Some genotypes showed higher yields and the Q18 and Q12 landraces displayed greater adaptation than others to new environmental conditions. The Q21 and Q26 landraces were evaluated with stable and satisfactory levels of yield (>1 t.haâ1) in each of the different trial sites. This production stability is of considerable importance especially under climate change uncertainty. While these results suggest that this Andean crop is able to grow in many different environments, social, and cultural considerations remain crucial regarding its possible introduction as a staple food in new cropping systems around the world
The characteristics of millisecond pulsar emission: I. Spectra, pulse shapes and the beaming fraction
We have monitored a large sample of millisecond pulsars using the 100-m
Effelsberg radio telescope in order to compare their radio emission properties
to the slowly rotating population. With some notable exceptions, our findings
suggest that the two groups of objects share many common properties. A
comparison of the spectral indices between samples of normal and millisecond
pulsars demonstrates that millisecond pulsar spectra are not significantly
different from those of normal pulsars. There is evidence, however, that
millisecond pulsars are slightly less luminous and less efficient radio
emitters compared to normal pulsars. We confirm recent suggestions that a
diversity exists among the luminosities of millisecond pulsars with the
isolated millisecond pulsars being less luminous than the binary millisecond
pulsars. There are indications that old millisecond pulsars exhibit somewhat
flatter spectra than the presumably younger ones. We present evidence that
millisecond pulsar profiles are only marginally more complex than those found
among the normal pulsar population. Moreover, the development of the profiles
with frequency is rather slow, suggesting very compact magnetospheres. The
profile development seems to anti-correlate with the companion mass and the
spin period, again suggesting that the amount of mass transfer in a binary
system might directly influence the emission properties. The angular radius of
radio beams of millisecond pulsars does not follow the scaling predicted from a
canonical pulsar model which is applicable for normal pulsars. Instead they are
systematically smaller. The smaller inferred luminosity and narrower emission
beams will need to be considered in future calculations of the birth-rate of
the Galactic population.Comment: 40 pages, 14 figures, accepted for publication in Ap
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