1,848 research outputs found
Photo-reduced route of polyaniline nanofiber synthesis with embedded silver nanoparticles
AbstractThis work presents a method on the preparation and performance of four silver (Ag) concentrations in polyaniline (PANI) and polyvinyl alcohol (PVA) nanocomposite blend (PNPAg). The synthesis of Ag nanoparticles is first performed by photo reduction and then aniline is polymerized in Ag-PVA matrix. Morphological analysis by SEM and TEM reveals formation of nanoparticles with diameter 30–70nm. Nanocomposites with lower Ag concentrations have highly aligned PNPAg nanofibers of diameter 50–80nm and agglomeration for the one with higher concentrations. In addition, FTIR spectra show a systematic change in its characteristic peaks with increase in Ag contents. The crystallinity study depicts the tetragonal crystal structure of metallic nanocomposites having same particle sizes as obtained in SEM and TEM. In order to explore the possible applications of these nanocomposites in electronic industry, their electrical properties are investigated. The in-plane I-V characteristics indicate a transition of polymer nanocomposites from non-ohmic to ohmic material with increase of Ag content. The room temperature electrical conductivities are found to be in the range of 4.74×10−4 to 3.96×10−2S/m with no major difference in activation energy for all nanocomposites
Comment on "On Mach's critique of Newton and Copernicus"
Hartman and Nissim-Sabat have argued that Mach's idea of the relativity of
rotational motion suffers from internal inconsistencies and leads to a
contradiction that there cannot be a stationary bucket in a rotating universe.
They also claimed that non-inertial electromagnetic and stellar aberration
observations can distinguish between a rotating and a stationary universe,
whereas according to Mach there cannot be any observable way to distinguish
these two cases. We contest these objections.Comment: Six pages, to appear in AJ
Photo-reduced route of polyaniline nanofiber synthesis with embedded silver nanoparticles
This work presents a method on the preparation and performance of four silver (Ag) concentrations in polyaniline (PANI) and polyvinyl alcohol (PVA) nanocomposite blend (PNPAg). The synthesis of Ag nanoparticles is first performed by photo reduction and then aniline is polymerized in Ag-PVA matrix. Morphological analysis by SEM and TEM reveals formation of nanoparticles with diameter 30–70 nm. Nanocomposites with lower Ag concentrations have highly aligned PNPAg nanofibers of diameter 50–80 nm and agglomeration for the one with higher concentrations. In addition, FTIR spectra show a systematic change in its characteristic peaks with increase in Ag contents. The crystallinity study depicts the tetragonal crystal structure of metallic nanocomposites having same particle sizes as obtained in SEM and TEM. In order to explore the possible applications of these nanocomposites in electronic industry, their electrical properties are investigated. The in-plane I-V characteristics indicate a transition of polymer nanocomposites from non-ohmic to ohmic material with increase of Ag content. The room temperature electrical conductivities are found to be in the range of 4.74 × 10−4 to 3.96 × 10−2 S/m with no major difference in activation energy for all nanocomposites.The authors express their deep sense of gratitude to SAIF, Department of Instrumentation & USIC, Gauhati University, India, for XRD data collection.Scopu
Gravitational lensing by a charged black hole of string theory
We study gravitational lensing by the
Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) charged black hole of
heterotic string theory and obtain the angular position and magnification of
the relativistic images. Modeling the supermassive central object of the galaxy
as a GMGHS black hole, we estimate the numerical values of different
strong-lensing parameters. We find that there is no significant string effect
present in the lensing observables in the strong-gravity scenario.Comment: 6 page
Strong field gravitational lensing in scalar tensor theories
Strong field gravitational lensing in the Brans-Dicke theory has been
studied. The deflection angle for photons passing very close to the photon
sphere is estimated for the static spherically symmetric space-time of the
theory and the position and magnification of the relativistic images are
obtained. Modeling the super massive central object of the galaxy by the
Brans-Dicke space-time, numerical values of different strong lensing observable
are estimated. It is found that against the expectation there is no significant
scalar field effect in the strong field observable lensing parameters. This
observation raises question on the potentiality of the strong field lensing to
discriminate different gravitational theories.Comment: 20 pages, accepted in Class. Quantum Grav., final versio
Drosophila Argonaute-1 is critical for transcriptional cosuppression and heterochromatin formation
Argonaute-1 (Ago-1) plays a crucial role in gene regulation and genome stability via biogenesis of small non-coding RNAs. Two “Argonaute” family genes, piwi and Ago-2 in Drosophila are involved in multiple silencing mechanisms in the nucleus, transgene cosuppression, long-distant chromosome interaction, nuclear organization and heterochromatin formation. To investigate whether Ago-1 also plays a similar role, we have generated a series of Ago-1 mutations by excising P element, inserted in the Ago-1 promoter (Ago-1k08121). AGO-1 protein is distributed uniformly in the nucleus and cytosol in early embryos but accumulated predominantly in the cytoplasm during the gastrulation stage. Repeat induced silencing produced by the mini-white (mw) array and transcriptional cosuppression of non-homologous transgenes Adh-w/w-Adh was disrupted by Ago-1 mutation. These effects of Ago-1 are distict from its role in microRNA processing because Dicer-1, a critical enzyme for miRNA biogenesis, has no role on the above silencing. Reduction of AGO-1 protein dislodged the POLYCOMB, EZ (enhancer of zeste) and H3me3K27 binding at the cosuppressed Adh-w transgene insertion sites suggesting its role in Polycomb dependent cosuppression. An overall reduction of methylated histone H3me2K9 and H3me3K27 from the polytene nuclei precisely from the mw promoters was also found that leads to concomitant changes in the chromatin structure. These results suggest a prominent role of Ago-1 in chromatin organization and transgene silencing and demonstrate a critical link between transcriptional transgene cosuppression, heterochromatin formation and chromatin organization. We propose Drosophila Ago-1 as a multifunctional RNAi component that interconnects at least two unrelated events, chromatin organization in the nucleus and microRNA processing in the cytoplasm, which may be extended to the other systems
Relativistic Electromagnetic Mass Models: Charged Dust Distribution in Higher Dimensions
Electromagnetic mass models are proved to exist in higher dimensional theory
of general relativity corresponding to charged dust distribution. Along with
the general proof a specific example is also sited as a supporting candidate.Comment: Latex, 7 pages. Accepted in Astrophysics and Space Scienc
Possible observation sequences of Brans-Dicke wormholes
The purpose of this study is to investigate observational features of
Brans-Dicke wormholes in a case if they exist in our Universe. The energy flux
from accretion onto a Brans-Dicke wormhole and the so-called "maximum impact
parameter" are studied (the last one might allow to observe light sources
through a wormhole throat). The computed values were compared with the
corresponding ones for GR-wormholes and Schwarzschild black holes. We shown
that Brans-Dicke wormholes are quasi-Schwarzschild objects and should differ
from GR wormholes by about one order of magnitude in the accretion energy flux.Comment: 5 pages, 6 figure
On Traversable Lorentzian Wormholes in the Vacuum Low Energy Effective String Theory in Einstein and Jordan Frames
Three new classes (II-IV) of solutions of the vacuum low energy effective
string theory in four dimensions are derived. Wormhole solutions are
investigated in those solutions including the class I case both in the Einstein
and in the Jordan (string) frame. It turns out that, of the eight classes of
solutions investigated (four in the Einstein frame and four in the
corresponding string frame), massive Lorentzian traversable wormholes exist in
five classes. Nontrivial massless limit exists only in class I Einstein frame
solution while none at all exists in the string frame. An investigation of test
scalar charge motion in the class I solution in the two frames is carried out
by using the Plebanski-Sawicki theorem. A curious consequence is that the
motion around the extremal zero (Keplerian) mass configuration leads, as a
result of scalar-scalar interaction, to a new hypothetical "mass" that confines
test scalar charges in bound orbits, but does not interact with neutral test
particles.Comment: 18 page
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