974 research outputs found
Assessment of changes in plasticity and mechanical properties of polystyrene fatty acid-based neem seed oil blends
Communication In Physical Sciences 2019, 4(1): 17-22
Authors: Salihu, Takuma. Mamza, Paul .A.P and Siaka, Abdulfatai. A.
In order to assess changes in plasticity and mechanical properties of polystyrene fatty acidbased neem seed oil blends, the value added product was developed. The effect of loading on the mechanical and thermal properties of polystyrene and the nature of interaction in the blend were investigated. Neem seed oil was epoxidised at 60oC and at a pressure of 1 atm for 5 hours. Fouriertransform infrared (FTIR) spectroscopy was used to identify the unsaturation and epoxy group in the neem oil and in the epoxidised neem oil. The infrared spectrum indicated that the absorption band at 3012 cm-1 was absent in the blend and that a new band was formed at 943 cm-1, which supported epoxidation. The mechanical performance of the various composites (95/5, 85/15, 75/25, 65/35, 45/55, and 35/65) were tested using tensiometer. Comparison of mechanical properties such as elongation at break, tensile strength and tensile modulus revealed apparent compatibility domain for 95/5 polystyrene/epoxidized neem seed oil (8.70±0.08, 24.40±0.02 and 37.0±1.0. Viscosity measurements revealed that miscibility occurs between the compositions 95/5, 85/15, 45/55 and 35/65 while phase inversion and phase separation occur in the 65/35 and 75/25 blends, indicating immiscibility and incompatibility
Explosions inside Ejecta and Most Luminous Supernovae
The extremely luminous supernova SN2006gy is explained in the same way as
other SNIIn events: light is produced by a radiative shock propagating in a
dense circumstellar envelope formed by a previous weak explosion. The problems
in the theory and observations of multiple-explosion SNe IIn are briefly
reviewed.Comment: 9 pages, 6 figures, LateX aipproc.cls. A bit more details and color
added to Fig.3. The 10th International Symposium on Origin of Matter and
Evolution of Galaxies (OMEG07), Sapporo, Japan, December 200
Energy Spectra of Quantum Turbulence: Large-scale Simulation and Modeling
In simulation of quantum turbulence within the Gross-Pitaevskii
equation we demonstrate that the large scale motions have a classical
Kolmogorov-1941 energy spectrum E(k) ~ k^{-5/3}, followed by an energy
accumulation with E(k) ~ const at k about the reciprocal mean intervortex
distance. This behavior was predicted by the L'vov-Nazarenko-Rudenko bottleneck
model of gradual eddy-wave crossover [J. Low Temp. Phys. 153, 140-161 (2008)],
further developed in the paper.Comment: (re)submitted to PRB: 5.5 pages, 4 figure
Field-induced phase transitions in a Kondo insulator
We study the magnetic-field effect on a Kondo insulator by exploiting the
periodic Anderson model with the Zeeman term. The analysis using dynamical mean
field theory combined with quantum Monte Carlo simulations determines the
detailed phase diagram at finite temperatures. At low temperatures, the
magnetic field drives the Kondo insulator to a transverse antiferromagnetic
phase, which further enters a polarized metallic phase at higher fields. The
antiferromagnetic transition temperature takes a maximum when the Zeeman
energy is nearly equal to the quasi-particle gap. In the paramagnetic phase
above , we find that the electron mass gets largest around the field where
the quasi-particle gap is closed. It is also shown that the induced moment of
conduction electrons changes its direction from antiparallel to parallel to the
field.Comment: 7 pages, 6 figure
Local instability signatures in ALMA observations of dense gas in NGC7469
We present an unprecedented measurement of the disc stability and local
instability scales in the luminous infrared Seyfert 1 host, NGC7469, based on
ALMA observations of dense gas tracers and with a synthesized beam of 165 x 132
pc. While we confirm that non-circular motions are not significant in
redistributing the dense interstellar gas in this galaxy, we find compelling
evidence that the dense gas is a suitable tracer for studying the origin of its
intensely high-mass star forming ring-like structure. Our derived disc
stability parameter accounts for a thick disc structure and its value falls
below unity at the radii in which intense star formation is found. Furthermore,
we derive the characteristic instability scale and find a striking agreement
between our measured scale of ~ 180 pc, and the typical sizes of individual
complexes of young and massive star clusters seen in high-resolution images.Comment: Accepted for publication in ApJ Letter
Self-Consistent MHD Modeling of a Coronal Mass Ejection, Coronal Dimming, and a Giant Cusp-Shaped Arcade Formation
We performed magnetohydrodynamic simulation of coronal mass ejections (CMEs)
and associated giant arcade formations, and the results suggested new
interpretations of observations of CMEs. We performed two cases of the
simulation: with and without heat conduction. Comparing between the results of
the two cases, we found that reconnection rate in the conductive case is a
little higher than that in the adiabatic case and the temperature of the loop
top is consistent with the theoretical value predicted by the Yokoyama-Shibata
scaling law. The dynamical properties such as velocity and magnetic fields are
similar in the two cases, whereas thermal properties such as temperature and
density are very different.In both cases, slow shocks associated with magnetic
reconnectionpropagate from the reconnection region along the magnetic field
lines around the flux rope, and the shock fronts form spiral patterns. Just
outside the slow shocks, the plasma density decreased a great deal. The soft
X-ray images synthesized from the numerical results are compared with the soft
X-ray images of a giant arcade observed with the Soft X-ray Telescope aboard
{\it Yohkoh}, it is confirmed that the effect of heat conduction is significant
for the detailed comparison between simulation and observation. The comparison
between synthesized and observed soft X-ray images provides new interpretations
of various features associated with CMEs and giant arcades.Comment: 39 pages, 18 figures. Accepted for publication in the Astrophysical
Journal. The PDF file with high resplution figures can be downloaded from
http://www.kwasan.kyoto-u.ac.jp/~shiota/study/ApJ62426.preprint.pdf
ALMA follows streaming of dense gas down to 40 pc from the supermassive black hole in NGC1097
We present a kinematic analysis of the dense molecular gas in the central 200
parsecs of the nearby galaxy NGC1097, based on Cycle 0 observations with the
Atacama Large Millimeter/sub-millimeter Array (ALMA). We use the HCN(4-3) line
to trace the densest interstellar molecular gas, and quantify its kinematics,
and estimate an inflow rate for the molecular gas. We find a striking
similarity between the ALMA kinematic data and the analytic spiral inflow model
that we have previously constructed based on ionized gas velocity fields on
larger scales. We are able to follow dense gas streaming down to 40 pc distance
from the supermassive black hole in this Seyfert 1 galaxy. In order to fulfill
marginal stability, we deduce that the dense gas is confined to a very thin
disc, and we derive a dense gas inflow rate of 0.09 Msun/yr at 40 pc radius.
Combined with previous values from the Ha and CO gas, we calculate a combined
molecular and ionized gas inflow rate of 0.2 Msun/yr at 40 pc distance from the
central supermassive black hole of NGC1097.Comment: Accepted for Publication in the ApJ Letter
Adjuvant Antitumor Immunity Contributes to the Overall Antitumor Effect of Pegylated Liposomal Doxorubicin (Doxil®) in C26 Tumor-Bearing Immunocompetent Mice
Doxorubicin (DXR) has been reported to have direct cytotoxicity against cancer cells and indirect immunotoxicity by modulation of host antitumor immunity. Hence, it may prevent cancer progression by a dual mechanism. Doxil®, a formulation of DXR encapsulated in polyethylene glycol modified (PEGylated) liposomes, is the most widely used of the clinically approved liposomal anticancer drugs. However, the effect of Doxil® on host antitumor immunity is not well understood. In this study, Doxil® efficiently suppressed tumor growth in immunocompetent mice bearing C26 murine colorectal carcinomas, but not in T cell-deficient nude mice, indicating a contribution of T cells to the overall antitumor effect of Doxil®. In immunocompetent mice, Doxil® increased major histocompatibility complex (MHC-1) levels in C26 tumors, which may be an indicator of increased immunogenicity of tumor cells, and potentially amplified tumor immunogenicity by decreasing immunosuppressive cells such as regulatory T cells, tumor-associated microphages and myeloid-derived suppressor cells that collectively suppress T cell-mediated antitumor responses. This suggests that encapsulation of DXR into PEGylated liposomes increased the therapeutic efficacy of DXR though effects on host antitumor immunogenicity in addition to direct cytotoxic effects on tumor cells. This report describes the role of host antitumor immunity in the overall therapeutic effects of Doxil®. Manipulating pharmacokinetics and biodistribution of chemotherapeutic agents with immunomodulatory properties may increase their therapeutic efficacies by amplifying host antitumor immunity in addition to direct cytotoxic effects on tumor cells
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