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Understanding the effects of siblings on child mortality: evidence from India
Given the intrinsically sequential nature of child birth, timing of a child’s birth has
consequences not only for itself, but also for the older and younger siblings. The paper thus
argues that prior and posterior spacing between consecutive siblings are important measures
of the intensity of competition among siblings for limited parental resources. While the
available estimates of child mortality tend to ignore this simultaneity bias, we use a
correlated recursive model of prior and posterior spacing and child mortality to correct it.
There is evidence that uncorrected estimates underestimate the effects of prior and posterior
spacing on child mortality
Landau level splitting due to graphene superlattices
The Landau level spectrum of graphene superlattices is studied using a
tight-binding approach. We consider non-interacting particles moving on a
hexagonal lattice with an additional one-dimensional superlattice made up of
periodic square potential barriers, which are oriented along the zig-zag or
along the arm-chair directions of graphene. In the presence of a perpendicular
magnetic field, such systems can be described by a set of one-dimensional
tight-binding equations, the Harper equations. The qualitative behavior of the
energy spectrum with respect to the strength of the superlattice potential
depends on the relation between the superlattice period and the magnetic
length. When the potential barriers are oriented along the arm-chair direction
of graphene, we find for strong magnetic fields that the zeroth Landau level of
graphene splits into two well separated sublevels, if the width of the barriers
is smaller than the magnetic length. In this situation, which persists even in
the presence of disorder, a plateau with zero Hall conductivity can be observed
around the Dirac point. This Landau level splitting is a true lattice effect
that cannot be obtained from the generally used continuum Dirac-fermion model.Comment: 12 pages, 9 figure
Metallo-Anti-aromatic Al4Na4 and Al4Na3- compounds: A theoretical investigation
We propose a theoretical investigation in this paper to understand the
bonding and structural properties of neutral Al4Na4 and anion Al4Na3- clusters.
We show that the Al4 species in Al4Na4 and Al4Na3- clusters is a rectangular
planar structure with alternate pi-bonds and hence satisfying the basic
criteria for anti-aromaticity. We prove that the Al4Na4 and Al4Na3- clusters
are metallo-anti-aromatic compounds
Structural, electronic and bonding properties of zeolite Sn-Beta: A periodic density functional theory study
The structural, electronic and the bonding properties of the Sn-BEA are
investigated by using the periodic density functional theory. Each of the 9
different T-sites in the BEA were substituted by the Sn atom and all the 9
geometries were completely optimized using the plane wave basis set in
conjunction with the ultra-soft pseudopotential. On the basis of the structural
and the electronic properties, it has been demonstrated that the substitution
of the Sn atom in the BEA framework is an endothermic process and hence the
incorporation of the Sn in the BEA is limited. The lowest unoccupied molecular
orbitals (LUMO) energies have been used to characterize the Lewis acidity of
each T-site. On the basis of the relative cohesive energy and the LUMO energy,
T2 site is shown to be the most favorable site for the substitution of Sn atom
in the BEA framework.Comment: 17 pages, 5 figures, 2 Table
Formation of rectifier with gold nanoclusters
Gold nanoclusters encapsulated with organic molecules are of great interest
for its possible applications in the fields of molecular electronics, catalysis
and medical science. Here we demonstrate that monolayer and bilayer films of
thiol-capped gold nanoclusters can exhibit diode-like properties provided
controlled spatial asymmetry exist between two tunnel junctions used to connect
a thiol capped gold nanoclusters. Current-voltage characteristics of this
rectifier were obtained from conducting probe atomic force microscopy
measurements and also from conventional two probe resistance measurements.
Systematic x-ray reflectivity and atomic force microscopy measurements were
carried out to characterize the spatial asymmetry introduced by a monolayer of
fatty acid salt gadolinium stearate used to deposit thiol-capped gold
nanocluster molecules on hydrophilic SiO2-Si(001) substrate by Langmuir
Blodgett technique. This information was used to explain prominent
rectification observed in these nano-structured films.Comment: 13 pages, 3 figure
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