8,988 research outputs found
Luffa aegyptiaca (Gourd) Fruit Juice as a Source of Peroxidase
Peroxidases have turned out to be potential biocatalyst for a variety of organic reactions. The research work reported in this communication was done with the objective of finding a convenient rich source of peroxidase which could be used as a biocatalyst for organic synthetic reactions. The studies made have shown that Luffa aegyptiaca (gourd) fruit juice contains peroxidase activity of the order of 180 enzyme unit/mL. The Km values of this peroxidase for the substrates guaiacol and hydrogen peroxide were 2.0 and 0.2 mM, respectively. The pH and temperature optima were 6.5 and 60°C, respectively. Like other peroxidases, it followed double displacement type mechanism. Sodium azide inhibited the enzyme competitively with Ki value of 3.35 mM
Simulations Show that Vortex Flows could Heat the Chromosphere in Solar Plage
The relationship between vortex flows at different spatial scales and their
contribution to the energy balance in the chromosphere is not yet fully
understood. We perform three-dimensional (3D) radiation-magnetohydrodynamic
(MHD) simulations of a unipolar solar plage region at a spatial resolution of
10 km using the MURaM code. We use the swirling-strength criterion that mainly
detects the smallest vortices present in the simulation data. We additionally
degrade our simulation data to smooth-out the smaller vortices, so that also
the vortices at larger spatial scales can be detected. Vortex flows at various
spatial scales are found in our simulation data for different effective spatial
resolutions. We conclude that the observed large vortices are likely clusters
of much smaller ones that are not yet resolved by observations. We show that
the vertical Poynting flux decreases rapidly with reduced effective spatial
resolutions and is predominantly carried by the horizontal plasma motions
rather than vertical flows. Since the small-scale horizontal motions or the
smaller vortices carry most of the energy, the energy transported by vortices
deduced from low resolution data is grossly underestimated. In full resolution
simulation data, the Poynting flux contribution due to vortices is more than
adequate to compensate for the radiative losses in plage, indicating their
importance for chromospheric heating.Comment: 8 pages, 5 figures, accepted in ApJ
Superconductivity at 5.2 K in ZrTe3 polycrystals and the effect of Cu, Ag intercalation
We report the occurrence of superconductivity in polycrystalline samples of
ZrTe3 at 5.2 K temperature at ambient pressure. The superconducting state
coexists with the charge density wave (CDW) phase, which sets in at 63K. The
intercalation of Cu or Ag, does not have any bearing on the superconducting
transition temperature but suppresses the CDW state. The feature of CDW anomaly
in these compounds is clearly seen in the DC magnetization data. Resistivity
data is analysed to estimate the relative loss of carriers and reduction in the
nested Fermi surface area upon CDW formation in the ZrTe3 and the intercalated
compounds.Comment: 5 pages, 8 figure
Determination of Delay in Detonation of a Sandwiched Explosive Impacted by a Shaped Charge Jet
A simple analytical model has been developed to determine delay in detonation of an explosive sandwiched between two metal plates and impacted by a shaped charge jet. The analytical model consists of a relation between detonation delay and depth of jet penetration in a target kept in contact across the explosive sandwich. This relation is derived by expressing depth of jet penetration P as a function of detonation delay Tdx and duration Tw of free passage of the jet through the hole in the top plate of the sandwich. One more relation between Tdx and Tw has been obtained from the theory of expansion of hole produced in a metal plate by jet impact. These two relations have been solved simultaneously to get values of both these parameters as a function of jet penetration. It is proposed that this analytical model can be used in two ways. First, this model can be used to calculate detonation delay by experimental measurement of jet penetration in a target. The detonation delay thus determined can be used to calculate insensitivity constant Aj of an explosive. Second, this model can be used to theoretically calculate jet penetrations obtained by different shaped charge warheads when using a sandwich of explosive with a given insensitivity. Both uses of this analytical model are illustrated using numerical examples
Supercriticality to subcriticality in dynamo transitions
Evidence from numerical simulations suggest that the nature of dynamo
transition changes from supercritical to subcritical as the magnetic Prandtl
number is decreased. To explore this interesting crossover we first use direct
numerical simulations to investigate the hysteresis zone of a subcritical
Taylor-Green dynamo. We establish that a well defined boundary exists in this
hysteresis region which separates dynamo states from the purely hydrodynamic
solution. We then propose simple dynamo models which show similar crossover
from supercritical to subcritical dynamo transition as a function of the
magnetic Prandtl number. Our models show that the change in the nature of
dynamo transition is connected to the stabilizing or de-stabilizing influence
of governing non-linearities.Comment: Version 3 note: Found a sign-error in an equation which propagated
further. Section 4 and Fig. 3,4,5 are updated in Version 3 (final form
Synthesis of novel 3-arylcyclopenta[c]quinolines via acid-induced domino cyclization of 2-arylamino-2-methylthioethenyl 2-arylcyclopropyl ketones
A novel acid-induced domino cyclization of N,S-anilinoacetals of type 3 derived from 2- arylcyclopropyl ketones, is reported which yields a wide range of substituted- and fused- 3- arylcyclopenta[c]quinolines 6 with concomitant formation of a cyclopentane and a quinoline ring
Effect of pressure cycling on Iron: Signatures of an electronic instability and unconventional superconductivity
High pressure electrical resistivity and x-ray diffraction experiments have
been performed on Fe single crystals. The crystallographic investigation
provides direct evidence that in the martensitic
transition at 14 GPa the become the directions. During a pressure cycle, resistivity shows a
broad hysteresis of 6.5 GPa, whereas superconductivity, observed between 13 and
31 GPa, remains unaffected. Upon increasing pressure an electronic instability,
probably a quantum critical point, is observed at around 19 GPa and, close to
this pressure, the superconducting and the isothermal resistivity
(K) attain maximum values. In the superconducting pressure domain,
the exponent of the temperature power law of resistivity and its
prefactor, which mimics , indicate that ferromagnetic fluctuations may
provide the glue for the Cooper pairs, yielding unconventional
superconductivity
The possibility of determining open-cluster parameters from BVRI photometry
In the last decades we witnessed an increase in studies of open clusters of
the Galaxy, especially because of the good determination for a wide range of
values of parameters such as age, distance, reddening, and proper motion. The
reliable determination of the parameters strongly depends on the photometry
available and especially on the U filter, which is used to obtain the color
excess E(B-V) through the color-color diagram (U-B) by (B-V) by fitting a zero
age main-sequence. Owing to the difficulty of performing photometry in the U
band, many authors have tried to obtain E(B-V) without the filter. But because
of the near linearity of the color-color diagrams that use the other bands,
combined with the fact that most fitting procedures are highly subjective (many
done "by eye") the reliability of those results has always been questioned. Our
group has recently developed, a tool that performs isochrone fitting in
open-cluster photometric data with a global optimization algorithm, which
removes the need to visually perform the fits and thus removes most of the
related subjectivity. Here we apply our method to a set of synthetic clusters
and two observed open clusters (Trumpler 1 and Melotte 105) using only
photometry for the BVRI bands. Our results show that, considering the cluster
structural variance caused only by photometric and Poisson sampling errors, our
method is able to recover the synthetic cluster parameters with errors of less
than 10% for a wide range of ages, distances, and reddening, which clearly
demonstrates its potential. The results obtained for Trumpler 1 and Melotte 105
also agree well with previous literature values.Comment: 5 pages, 5 figures, accepted for publication in
Astronomy&Astrophysic
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