1,121 research outputs found
Protecting Intellectual Capital in the New Century: Are Universities Prepared?
In recent years, intellectual property has become increasingly important to academic institutions throughout the United States. As universities rely more heavily on trademarks and patents for additional revenue, questions arise as to whether these institutions are sufficiently protected by their current intellectual property policies. This iBrief explores the policies promulgated by a variety of academic institutions and assesses whether these universities are adequately protected by their policies
Galaxy gas flows inferred from a detailed, spatially resolved metal budget
We use the most extensive integral field spectroscopic map of a local galaxy,
NGC 628, combined with gas and stellar mass surface density maps, to study the
distribution of metals in this galaxy out to 3 effective radii (). At
each galactocentric distance, we compute the metal budget and thus constrain
the mass of metals lost. We find that in the disc about 50% of the metals have
been lost throughout the lifetime of the galaxy. The fraction of metals lost is
higher in the bulge (70%) and decreases towards the outer disc (). In contrast to studies based on the gas kinematics, which are only
sensitive to ongoing outflow events, our metal budget analysis enables us to
infer the average outflow rate during the galaxy lifetime. By using simple
physically motivated models of chemical evolution we can fit the observed metal
budget at most radii with an average outflow loading factor of order unity,
thus clearly demonstrating the importance of outflows in the evolution of disc
galaxies of this mass range (. The observed
gas phase metallicity is higher than expected from the metal budget and
suggests late-time accretion of enriched gas, likely raining onto the disc from
the metal-enriched halo.FB acknowledges support from the United Kingdom Science and Technology Facilities Council. This work makes use of THINGS (‘The Nearby Galaxy Survey’, Walter et al. 2008), HERACLES (the ‘HERA CO line Extragalactic Survey’, Leroy et al. 2009) and PINGS (the ‘PPAK IFS Nearby Galaxy Survey’, Rosales-Ortega et al. 2010). We acknowledge the contribution from the referee in improving the content and the clarity of the paper. We thank Fiorenzo Vincenzo and Francesca Matteucci for their invaluable help in interpreting the vast literature on chemical abundance modelling and nucleosynthetic yields. We also thank Ying-jie Peng for support and discussion on development of his chemical evolution models. We wish to thank Fabian Rosales-Ortega for kindly sharing the PINGS data on NGC 628 and for his encouragement and feedback on the early stages of this work. We thank Matt Auger for useful discussions and healthy skepticism and the participants to the MPIA summer workshop ‘A 3D view on galaxies evolution: from statistics to physics’ for insightful comments.This is the author accepted manuscript. The final version is available from Oxford University Press via http://dx.doi.org/10.1093/mnras/stv233
PPAR-γ Agonists and Their Effects on IGF-I Receptor Signaling: Implications for Cancer
It is now well established that the development and progression of a variety of human malignancies are associated with dysregulated activity of the insulin-like growth factor (IGF) system. In this regard, promising drugs have been developed to target the IGF-I receptor or its ligands. These therapies are limited by the development of insulin resistance and compensatory hyperinsulinemia, which in turn, may stimulate cancer growth. Novel therapeutic approaches are, therefore, required. Synthetic PPAR-γ agonists, such as thiazolidinediones (TZDs), are drugs universally used as antidiabetic agents in patients with type 2 diabetes. In addition of acting as insulin sensitizers, PPAR-γ agonists mediate in vitro and in vivo pleiotropic anticancer effects. At least some of these effects appear to be linked with the downregulation of the IGF system, which is induced by the cross-talk of PPAR-γ agonists with multiple components of the IGF system signaling. As hyperinsulinemia is an emerging cancer risk factor, the insulin lowering action of PPAR-γ agonists may be expected to be also beneficial to reduce cancer development and/or progression.
In light of these evidences, TZDs or other PPAR-γ agonists may be exploited in those tumors “addicted” to the IGF signaling and/or in tumors occurring in hyperinsulinemic patients
Supergiant Fast X-ray Transients uncovered by the EXTraS project: flares reveal the development of magnetospheric instability in accreting neutron stars
The low luminosity, X-ray flaring activity, of the sub-class of high mass
X-ray binaries called Supergiant Fast X-ray Transients, has been investigated
using XMM-Newton public observations, taking advantage of the products made
publicly available by the EXTraS project. One of the goals of EXTraS was to
extract from the XMM-Newton public archive information on the aperiodic
variability of all sources observed in the soft X-ray range with EPIC (0.2-12
keV). Adopting a Bayesian block decomposition of the X-ray light curves of a
sample of SFXTs, we picked out 144 X-ray flares, covering a large range of soft
X-ray luminosities (1e32-1e36 erg/s). We measured temporal quantities, like the
rise time to and the decay time from the peak of the flares, their duration and
the time interval between adjacent flares. We also estimated the peak
luminosity, average accretion rate and energy release in the flares. The
observed soft X-ray properties of low-luminosity flaring activity from SFXTs is
in qualitative agreement with what is expected by the application of the
Rayleigh-Taylor instability model in accreting plasma near the neutron star
magnetosphere. In the case of rapidly rotating neutron stars, sporadic
accretion from temporary discs cannot be excluded.Comment: Accepted for publication in MNRAS (accepted 2019 May 1; received 2019
April 30; in original form 2019 February 25). 22 pages, 16 figures, 3 tables
Widespread star formation inside galactic outflows
Several models have predicted that stars could form inside galactic outflows
and that this would be a new major mode of galaxy evolution. Observations of
galactic outflows have revealed that they host large amounts of dense and
clumpy molecular gas, which provide conditions suitable for star formation. We
have investigated the properties of the outflows in a large sample of galaxies
by exploiting the integral field spectroscopic data of the large MaNGA-SDSS4
galaxy survey. We find that star formation occurs inside at least half of the
galactic outflows in our sample. We also show that even if star formation is
prominent inside many other galactic outflows, this may have not been revealed
as the diagnostics are easily dominated by the presence of even faint AGN and
shocks. If very massive outflows typical of distant galaxies and quasars follow
the same scaling relations observed locally, then the star formation inside
high-z outflows can be up to several 100 Msun/yr and could contribute
substantially to the early formation of the spheroidal component of galaxies.
Star formation in outflows can also potentially contribute to establishing the
scaling relations between black holes and their host spheroids. Moreover,
supernovae exploding on large orbits can chemically enrich in-situ and heat the
circumgalactic and intergalactic medium. Finally, young stars ejected on large
orbits may also contribute to the reionization of the Universe
Nitrogen and oxygen abundances in the Local Universe
We present chemical evolution models aimed at reproducing the observed (N/O)
vs. (O/H) abundance pattern of star forming galaxies in the Local Universe. We
derive gas-phase abundances from SDSS spectroscopy and a complementary sample
of low-metallicity dwarf galaxies, making use of a consistent set of abundance
calibrations. This collection of data clearly confirms the existence of a
plateau in the (N/O) ratio at very low metallicity, followed by an increase of
this ratio up to high values as the metallicity increases. This trend can be
interpreted as due to two main sources of nitrogen in galaxies: i) massive
stars, which produce small amounts of pure primary nitrogen and are responsible
for the (N/O) ratio in the low metallicity plateau; ii) low- and
intermediate-mass stars, which produce both secondary and primary nitrogen and
enrich the interstellar medium with a time delay relative to massive stars, and
cause the increase of the (N/O) ratio. We find that the length of the
low-metallicity plateau is almost solely determined by the star formation
efficiency, which regulates the rate of oxygen production by massive stars. We
show that, to reproduce the high observed (N/O) ratios at high (O/H), as well
as the right slope of the (N/O) vs. (O/H) curve, a differential galactic wind -
where oxygen is assumed to be lost more easily than nitrogen - is necessary. No
existing set of stellar yields can reproduce the observed trend without
assuming differential galactic winds. Finally, considering the current best set
of stellar yields, a bottom-heavy initial mass function is favoured to
reproduce the data.FV thanks the Cavendish Astrophysics Group at the University of Cambridge for kindly supporting his visit during 2014 September. FB acknowledges funding from the United Kingdom Science and Technology Facilities Council (STFC). RM acknowledges funding from the United Kingdom STFC through grant ST/M001172/1. FM acknowledges financial support from PRIN-MIUR 2010-2011 project ‘The Chemical and Dynamical Evolution of the Milky Way and Local Group Galaxies’, prot. 2010LY5N2T.This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/mnras/stw53
A candidate optical counterpart to the middle-aged gamma-ray pulsar PSR J1741-2054
We carried out deep optical observations of the middle-aged -ray
pulsar PSR J1741-2054 with the Very Large Telescope (VLT). We identified two
objects, of magnitudes and , at positions
consistent with the very accurate Chandra coordinates of the pulsar, the
faintest of which is more likely to be its counterpart. From the VLT images we
also detected the known bow-shock nebula around PSR J1741-2054. The nebula is
displaced by \sim 0\farcs9 (at the confidence level) with respect
to its position measured in archival data, showing that the shock propagates in
the interstellar medium consistently with the pulsar proper motion. Finally, we
could not find evidence of large-scale extended optical emission associated
with the pulsar wind nebula detected by Chandra, down to a surface brightness
limit of magnitudes arcsec. Future observations are needed
to confirm the optical identification of PSR J1741-2054 and characterise the
spectrum of its counterpart.Comment: 8 pages, 3 figures, Astrophysical Journal, in pres
Discovery of periodic dips in the brightest hard X-ray source of M31 with EXTraS
We performed a search for eclipsing and dipping sources in the archive of the
EXTraS project - a systematic characterization of the temporal behaviour of
XMM-Newton point sources. We discovered dips in the X-ray light curve of 3XMM
J004232.1+411314, which has been recently associated with the hard X-ray source
dominating the emission of M31. A systematic analysis of XMM-Newton
observations revealed 13 dips in 40 observations (total exposure time 0.8
Ms). Among them, four observations show two dips, separated by 4.01 hr.
Dip depths and durations are variable. The dips occur only during
low-luminosity states (L erg s), while the
source reaches L erg s. We propose this
system to be a new dipping Low-Mass X-ray Binary in M31 seen at high
inclination (60-80), the observed dipping periodicity is
the orbital period of the system. A blue HST source within the Chandra error
circle is the most likely optical counterpart of the accretion disk. The high
luminosity of the system makes it the most luminous dipper known to date.Comment: 11 pages, 2 figures, 5 tables, accepted for publication in ApJ
Multi-wavelength observations of 3FGL J2039.6-5618: a candidate redback millisecond pulsar
We present multi-wavelength observations of the unassociated gamma-ray source
3FGL J2039.6-5618 detected by the Fermi Large Area Telescope. The source
gamma-ray properties suggest that it is a pulsar, most likely a millisecond
pulsar, for which neither radio nor -ray pulsations have been detected
yet. We observed 3FGL J2039.6-5618 with XMM-Newton and discovered several
candidate X-ray counterparts within/close to the gamma-ray error box. The
brightest of these X-ray sources is variable with a period of 0.22450.0081
d. Its X-ray spectrum can be described by a power law with photon index
, and hydrogen column density cm, which gives an unabsorbed 0.3--10 keV X-ray flux of erg cm s. Observations with the Gamma-Ray Burst
Optical/Near-Infrared Detector (GROND) discovered an optical counterpart to
this X-ray source, with a time-average magnitude . The counterpart
features a flux modulation with a period of 0.227480.00043 d that
coincides, within the errors, with that of the X-ray source, confirming the
association based on the positional coincidence. We interpret the observed
X-ray/optical periodicity as the orbital period of a close binary system where
one of the two members is a neutron star. The light curve profile of the
companion star, with two asymmetric peaks, suggests that the optical emission
comes from two regions at different temperatures on its tidally-distorted
surface. Based upon its X-ray and optical properties, we consider this source
as the most likely X-ray counterpart to 3FGL J2039.6-5618, which we propose to
be a new redback system.Comment: 35 pages, 8 figures, accepted for publication on Astrophysical
Journa
- …