1,118 research outputs found
Stereospecific synthesis of endo-6-aryl-2-oxobicyclo [3.3.1]nonanes
Two alternate synthetic routes to endo-6-aryl-2-oxobicyclo 3.3.1 nonan [3a-d] by sterespecific catalytic hydrogenetion of the easily accessible 6-arylbicyclo 3.3.1 nona-3,6-dien-2-ones [2a-d], and regioselective oomologation of endo-2-aryl-6-oxobicycle 3.2.1 octanes [4a-d] are described
Reheating furnace's soaking zone hearth refractories - a rational approach
The technology of steel processing subsequent to ingot casting, follows heating in soaking pit and rolling to form blooms, billets etc. Further reduction is carried out through heating and rolling to yield the final usable products. Reheating furnaces are used in reheating the "Semis" before they are used in secondary-processing
Kinetics of phase transformation in depletion driven colloids
PACS number(s): 82.70.Gg, 82.70.RrWe present results from a detailed numerical study of the kinetics of phase transformations in a model
two-dimensional depletion-driven colloidal system. Transition from a single, dispersed phase to a two-phase
coexistence of monomers and clusters is obtained as the depth of the interaction potential among the colloidal
particles is changed. Increasing the well depth further, fractal clusters are observed in the simulation. These
fractal clusters have a hybrid structure in the sense that they show hexagonal closed-packed crystalline ordering
at short length scales and a ramified fractal nature at larger length scales. For sufficiently deep potential wells,
the diffusion-limited cluster-cluster aggregation model is recovered in terms of the large-scale fractal dimension Df
of the clusters, the kinetic exponent z, and the scaling form of the cluster size distribution. For
shallower well depths inside the two-phase coexistence region, simulation results for the kinetics of cluster
growth are compared with intermediate-stage phase separation in binary mixtures. In the single-phase region,
growth kinetics agree well with a mean-field aggregation-fragmentation model of Sorensen, Zhang, and Taylor.J.J.C. and T.S. acknowledge financial support from the
Spanish MCyT through Grant No. BMF2001-0341-C02-01.
A.C. and C.S.were supported by NASA through Grant No.
NAG 3-2360Peer reviewe
On a kinetic model for a simple market economy
In this paper, we consider a simple kinetic model of economy involving both
exchanges between agents and speculative trading. We show that the kinetic
model admits non trivial quasi-stationary states with power law tails of Pareto
type. In order to do this we consider a suitable asymptotic limit of the model
yielding a Fokker-Planck equation for the distribution of wealth among
individuals. For this equation the stationary state can be easily derived and
shows a Pareto power law tail. Numerical results confirm the previous analysis
Relativistic supernovae have shorter-lived central engines or more extended progenitors: the case of SN\,2012ap
Deep late-time X-ray observations of the relativistic, engine-driven, type Ic
SN2012ap allow us to probe the nearby environment of the explosion and reveal
the unique properties of relativistic SNe. We find that on a local scale of
~0.01 pc the environment was shaped directly by the evolution of the progenitor
star with a pre-explosion mass-loss rate <5x10^-6 Msun yr-1 in line with GRBs
and the other relativistic SN2009bb. Like sub-energetic GRBs, SN2012ap is
characterized by a bright radio emission and evidence for mildly relativistic
ejecta. However, its late time (t~20 days) X-ray emission is ~100 times fainter
than the faintest sub-energetic GRB at the same epoch, with no evidence for
late-time central engine activity. These results support theoretical proposals
that link relativistic SNe like 2009bb and 2012ap with the weakest observed
engine-driven explosions, where the jet barely fails to breakout. Furthermore,
our observations demonstrate that the difference between relativistic SNe and
sub-energetic GRBs is intrinsic and not due to line-of-sight effects. This
phenomenology can either be due to an intrinsically shorter-lived engine or to
a more extended progenitor in relativistic SNe.Comment: Version accepted to ApJ. Significantly broadened discussio
SN 2013ej - A type IIL supernova with weak signs of interaction
We present optical photometric and spectroscopic observations of supernova
2013ej. It is one of the brightest type II supernovae exploded in a nearby
( Mpc) galaxy NGC 628. The light curve characteristics are similar to
type II SNe, but with a relatively shorter ( day) and steeper ( mag (100 d) in V) plateau phase. The SN shows a large drop of
2.4 mag in V band brightness during plateau to nebular transition. The absolute
ultraviolet (UV) light curves are identical to SN 2012aw, showing a similar UV
plateau trend extending up to 85 days. The radioactive Ni mass estimated
from the tail luminosity is M which is significantly lower
than typical type IIP SNe. The characteristics of spectral features and
evolution of line velocities indicate that SN 2013ej is a type II event.
However, light curve characteristics and some spectroscopic features provide
strong support in classifying it as a type IIL event. A detailed SYNOW
modelling of spectra indicates the presence of some high velocity components in
H and H profiles, implying possible ejecta-CSM interaction. The
nebular phase spectrum shows an unusual notch in the H emission which
may indicate bipolar distribution of Ni. Modelling of the bolometric
light curve yields a progenitor mass of M and a radius of R, with a total explosion energy of
erg.Comment: 19 pages, 19 figures, 6 tables. Accepted for publication in Ap
The statistical distribution of money and the rate of money transference
The distribution of money is analysed in connection with the Boltzmann
distribution of energy in the degenerate states of molecules. Plots of the
population density of income distribution for various countries are well
reproduced by a Gamma function, confirming the validity of the statistical
distribution at equilibrium. The equilibrium state is reached through pair wise
money transference processes, independently of the shape of the initial
distribution and also of the detailed nature of the money transactions between
the economic agents.Comment: 15 pages plus 1 table plus 3 figure
A Theoretical Construction of Thin Shell Wormhole from Tidal Charged Black hole
Recently, Dadhich et al [ Phys.Lett.B 487, 1 (2000)] have discovered a black
hole solution localized on a three brane in five dimensional gravity in the
Randall-Sundrum scenario. In this article, we develop a new class of thin shell
wormhole by surgically grafting above two black hole spacetimes. Various
aspects of this thin wormhole are also analyzed.Comment: 14 pages, 6 figures, Accepted in Gen.Rel.Gra
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