144 research outputs found
Neurofibromin knockdown in glioma cell lines is associated with changes in cytokine and chemokine secretion in vitro.
The neurofibromin-1 tumor suppressor gene (NF1) is altered in approximately 20% of sporadic glioblastoma (GBM) cases. NF1 deficient GBM frequently shows a mesenchymal gene expression signature, suggesting a relationship between NF1 status and the tumor microenvironment. To identify changes in the production of secreted cytokines/chemokines in NF1 deficient glioma, we applied cytokine arrays to conditioned media from a panel of three GBM cell lines after siRNA-mediated NF1 knockdown. We identified increased secretion of platelet-derived growth factor AA (PDGF-AA), chitinase-3-like protein 1 (CHI3L1), interleukin-8 (IL-8), and endoglin (ENG) in different subsets of these cell lines. Secretion was associated with induction of the corresponding messenger RNA, suggesting a mechanism involving transcriptional upregulation. By contrast, in non-transformed immortalized normal human astrocytes, PDGF-AA secretion was increased upon NF1 knockdown, while secreted CHI3L1, ENG, and IL-8 were reduced or unchanged. Analysis of The Cancer Genome Atlas confirmed a relationship between glioma NF1 status and ENG and CHI3L1 in tumor samples. Overall, this study identifies candidate changes in secreted proteins from NF1 deficient glioma cells that could influence the tumor microenvironment, and suggests a direct link between NF1 loss and increased tumor cell production of CHI3L1 and endoglin, two factors implicated in mesenchymal identity in glioblastoma
Designing an effective student evaluation of teaching (SET) questionnaire for cadaveric dissection
Recent changes in curriculum have seen a curtailment in the time devoted to the teaching of gross anatomy, one of the most integral components of medical education. This has resulted in the reduction, and in some cases the elimination of cadaveric dissection, most significantly due to the huge amount of resources involved in conducting a cadaveric dissection program. Nevertheless, cadaveric dissection still comprises a significant part of the time devoted to the teaching of gross anatomy. Hence it is of paramount importance that maximum benefit be derived from cadaveric dissections since it offers unique advantages, most significant being the appreciation of the three-dimensional concepts of body organization. The key part of effective anatomy teaching using cadaveric dissection is having the best instructors for this task. While student evaluation of teaching (SET) questionnaires have been used to evaluate instructor proficiency in lecture classes, there is no SET questionnaire that has been specifically designed for the assessment of instructors involved in cadaveric dissection. The aim of this article is to design a questionnaire specifically for the evaluation of the competency of instructors involved in cadaveric dissection, and reinforce the arguments for the continued use of cadaveric dissection in the teaching of anatomy.
Multi-photon signal in supersymmetry comprising non-pointing photon(s) at the LHC
We study a distinct supersymmetric signal of multi-photons in association
with jets and missing transverse energy. At least one of these photons has the
origin in displaced vertex, thus delayed and non-pointing. We consider a
supersymmetric scenario in which the gravitino is the lightest supersymmetric
particle (LSP) (with a mass ) and the lightest neutralino is the
next-to-lightest supersymmetric particle (NLSP). The NLSP decays dominantly
into a photon and a gravitino within the detector with a decay length ranging
from 50-100 cm. In addition, we assume that the
second lightest neutralino and the lightest neutralino are nearly degenerate
and this leads to a prompt radiative decay of the next-to-lightest neutralino
into a photon and a lightest neutralino with a large branching ratio. Such
degenerate neutralinos can be realised in various representations of the
, , and Grand Unified Theories (GUTs). The non-pointing
photons can be reconstructed at the electromagnetic calorimeter of the ATLAS
inner-detector, which have been designed with good timing and directional
resolution. We find that with a centre-of-mass energy at an
integrated luminosity of 100 one may see evidence of hundreds of
tri-photon events and a few four-photons events at the LHC, in addition to
several thousands di-photon events. We also predict the event rates even at the
early phase of LHC run.Comment: 10 pages; 6 figure
Resonant Leptogenesis with nonholomorphic R-Parity violation and LHC Phenomenology
In R-parity violating supersymmetric models both leptogenesis and the correct
neutrino masses are hard to achieve together. The presence of certain soft
nonholomorphic R-parity violating terms helps to resolve this problem. We
consider a scenario where the lightest and the second-lightest neutralino are
nearly degenerate in mass and enough CP-asymmetry can be produced through
resonant leptogenesis. In this model, the lighter chargino and the lightest
neutralino are highly degenerate. We have relatively lighter gauginos which can
be produced at the LHC leading to heavily ionizing charged tracks. At the same
time this model can also generate the correct neutrino mass scale. Thus our
scenario is phenomenologically rich and testable at colliders.Comment: 17 pages, 7 figures, Numerical results are improved and new plots are
added, Journal version. arXiv admin note: text overlap with
arXiv:hep-ph/0006173 by other author
Geometric phases and Wannier functions of Bloch electrons in 1-dimension
We present a formal expression for Wannier functions of composite bands of
1-D Bloch electrons in terms of parallel-transported Bloch functions and their
non-Abelian geometric phases. Spatial decay properties of these Wannier
functions are studied in the case of simple bands of 1-D model insulator and
metal. Within first-principles density functional theory, we illustrate the
formalism through the construction of Wannier functions of polyethylene and
polyacetylene.Comment: 4 pages, 4 figure
Search and analysis of giant radio galaxies with associated nuclei (SAGAN) -- I : New sample and multi-wavelength studies
We present the first results of a project called SAGAN, which is dedicated
solely to the studies of relatively rare megaparsec-scale radio galaxies in the
Universe, called giant radio galaxies (GRGs). We have identified 162 new GRGs
primarily from the NVSS with sizes ranging from ~0.71 Mpc to 2.82 Mpc in the
redshift range of ~0.03 - 0.95, of which 23 are hosted by quasars (giant radio
quasars, GRQs). As part of the project SAGAN, we have created a database of all
known GRGs, the GRG catalogue, from the literature (including our new sample);
it includes 820 sources. For the first time, we present the multi-wavelength
properties of the largest sample of GRGs. Our results establish that the
distributions of the radio spectral index and the black hole mass of GRGs do
not differ from the corresponding distributions of normal-sized radio galaxies
(RGs). However, GRGs have a lower Eddington ratio (ER) than RGs. Using the
mid-infrared data, we classified GRGs in terms of their accretion mode: either
a high-power radiatively efficient high-excitation state, or a radiatively
inefficient low-excitation state. We find that GRGs in high-excitation state
statistically have larger sizes, stronger radio power, jet kinetic power, and
higher ER than those in low-excitation state. Our analysis reveals a strong
correlation between the ER and the scaled jet kinetic power, which suggests a
disc-jet coupling. Our environmental study reveals that ~10% of all GRGs may
reside at the centres of galaxy clusters, in a denser galactic environment,
while the majority appears to reside in a sparse environment. We find that the
probability of BCG as a GRG is quite low. We present new results for GRGs that
range from black hole mass to large-scale environment properties. We discuss
their formation and growth scenarios, highlighting the key physical factors
that cause them to reach their gigantic size. Abridged.Comment: Accepted for publication in Astronomy & Astrophysics. 14 figures, 7
tables and 7 montages. Comments are welcome. "SAGAN Project website
https://sites.google.com/site/anantasakyatta/sagan
SAGAN -- III: New insights into giant radio quasars
Giant radio quasars (GRQs) are radio-loud active galactic nuclei (AGNs),
propelling megaparsec-scale jets. In order to understand GRQs and their
properties, we have compiled all known GRQs ("the GRQ catalogue"), and a subset
of small (size <700 kpc) radio quasars (SRQs) from the literature. In this
process, we have found 10 new FR-II GRQs, in the redshift range of 0.66 < z <
1.72, which we include in the GRQ catalogue. Using the above samples, we have
carried out a systematic comparative study of GRQs and SRQs, using optical and
radio data. Our results show that the GRQs and SRQs statistically have similar
spectral index and black hole mass distributions. However, SRQs have higher
radio core power, core dominance factor, total radio power, jet kinetic power
and Eddington ratio compared to GRQs. On the other hand, when compared to giant
radio galaxies (GRGs), GRQs have higher black hole mass and Eddington ratio.
The high core dominance factor of SRQs is an indicator of them lying closer to
the line of sight than GRQs. We also find a correlation of the accretion disc
luminosity with the radio core and jet power of GRQs, which provides evidence
for disc-jet coupling. Lastly, we find the distributions of Eddington ratios of
GRGs and GRQs to be bi-modal, similar to that found in small radio galaxies
(SRGs) and SRQs, which indicate that size is not strongly dependent on the
accretion state. Using all of these, we provide a basic model for the growth of
SRQs to GRQs.Comment: Accepted for publication in Astronomy & Astrophysics. 9 figures, and
2 tables. This is the third paper in the series. Comments are welcome. "SAGAN
Project website this http https://sites.google.com/site/anantasakyatta/sagan
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