19,311 research outputs found
Why Have Poorer Neighbourhoods Stagnated Economically, While the Richer have Flourished? Neighbourhood Income Inequality in Canadian Cities
Higher income neighbourhoods in Canada’s eight largest cities flourished economically during the past quarter century, while lower income communities stagnated. This paper identifies some of the underlying processes that led to this outcome. Increasing family income inequality drove much of the rise in neighbourhood inequality. Increased spatial economic segregation, the increasing tendency of “like to live nearby likeâ€, also played a role. In the end, the differential economic outcomes between richer and poorer neighbourhoods originated in the labour market, or in family formation patterns. Changes in investment, pension income, or government transfers played a very minor role. But it was not unemployment that differentiated the richer from poorer neighbourhoods. Rather, it was the type of job found, particularly the annual earnings generated. The end result has been little improvement in economic resources in poor neighbourhoods during a period of substantial economic growth, and a rise in neighbourhood income inequality.Inequality, Neighbourhood, Poverty
Scaling Relations for Galaxies Prior to Reionization
The first galaxies in the Universe are the building blocks of all observed
galaxies. We present scaling relations for galaxies forming at redshifts when reionization is just beginning. We utilize the ``Rarepeak'
cosmological radiation hydrodynamics simulation that captures the complete star
formation history in over 3,300 galaxies, starting with massive Population III
stars that form in dark matter halos as small as ~. We make
various correlations between the bulk halo quantities, such as virial, gas, and
stellar masses and metallicities and their respective accretion rates,
quantifying a variety of properties of the first galaxies up to halo masses of
. Galaxy formation is not solely relegated to atomic cooling
halos with virial temperatures greater than K, where we find a dichotomy
in galaxy properties between halos above and below this critical mass scale.
Halos below the atomic cooling limit have a stellar mass -- halo mass
relationship .
We find a non-monotonic relationship between metallicity and halo mass for the
smallest galaxies. Their initial star formation events enrich the interstellar
medium and subsequent star formation to a median of and
, respectively, in halos of total mass that
is then diluted by metal-poor inflows, well beyond Population III
pre-enrichment levels of . The scaling relations presented
here can be employed in models of reionization, galaxy formation and chemical
evolution in order to consider these galaxies forming prior to reionization.Comment: 10 pages, 10 figures. Accepted to Ap
Imaging Neuroinflammation – from Bench to Bedside
Neuroinflammation plays a central role in a variety of neurological diseases, including stroke, multiple sclerosis, Alzheimer’s disease, and malignant CNS neoplasms, among many other. Different cell types and molecular mediators participate in a cascade of events in the brain that is ultimately aimed at control, regeneration and repair, but leads to damage of brain tissue under pathological conditions. Non-invasive molecular imaging of key players in the inflammation cascade holds promise for identification and quantification of the disease process before it is too late for effective therapeutic intervention. In this review, we focus on molecular imaging techniques that target inflammatory cells and molecules that are of interest in neuroinflammation, especially those with high translational potential. Over the past decade, a plethora of molecular imaging agents have been developed and tested in animal models of (neuro)inflammation, and a few have been translated from bench to bedside. The most promising imaging techniques to visualize neuroinflammation include MRI, positron emission tomography (PET), single photon emission computed tomography (SPECT), and optical imaging methods. These techniques enable us to image adhesion molecules to visualize endothelial cell activation, assess leukocyte functions such as oxidative stress, granule release, and phagocytosis, and label a variety of inflammatory cells for cell tracking experiments. In addition, several cell types and their activation can be specifically targeted in vivo, and consequences of neuroinflammation such as neuronal death and demyelination can be quantified. As we continue to make progress in utilizing molecular imaging technology to study and understand neuroinflammation, increasing efforts and investment should be made to bring more of these novel imaging agents from the “bench to bedside.
Transport in Molecular Junctions with Different Metallic Contacts
Ab initio calculations of phenyl dithiol connected to Au, Ag, Pd, and Pt
electrodes are performed using non-equilibrium Green's functions and density
functional theory. For each metal, the properties of the molecular junction are
considered both in equilibrium and under bias. In particular, we consider in
detail charge transfer, changes in the electrostatic potential, and their
subsequent effects on the IV curves through the junctions. Gold is typically
used in molecular junctions because it forms strong chemical bonds with sulfur.
We find however that Pt and Pd make better electrical contacts than Au. The
zero-bias conductance is found to be greatest for Pt, followed by Pd, Au, and
then Ag
The bandmerged Planck Early Release Compact Source Catalogue: Probing sub-structure in the molecular gas at high Galactic latitude
The Planck Early Release Compact Source Catalogue (ERCSC) includes nine lists
of highly reliable sources, individually extracted at each of the nine Planck
frequency channels. To facilitate the study of the Planck sources, especially
their spectral behaviour across the radio/infrared frequencies, we provide a
"bandmerged" catalogue of the ERCSC sources. This catalogue consists of 15191
entries, with 79 sources detected in all nine frequency channels of Planck and
6818 sources detected in only one channel. We describe the bandmerging
algorithm, including the various steps used to disentangle sources in confused
regions. The multi-frequency matching allows us to develop spectral energy
distributions of sources between 30 and 857 GHz, in particular across the 100
GHz band, where the energetically important CO J=1->0 line enters the Planck
bandpass. We find ~3-5sigma evidence for contribution to the 100 GHz intensity
from foreground CO along the line of sight to 147 sources with |b|>30 deg. The
median excess contribution is 4.5+/-0.9 percent of their measured 100 GHz flux
density which cannot be explained by calibration or beam uncertainties. This
translates to 0.5+/-0.1 K km s^{-1} of CO which must be clumped on the scale of
the Planck 100 GHz beam, i.e., ~10 arcmin. If this is due to a population of
low mass (~15 Msun) molecular gas clumps, the total mass in these clumps may be
more than 2000 Msun. Further, high-spatial-resolution, ground-based
observations of the high-latitude sky will help shed light on the origin of
this diffuse, clumpy CO emission.Comment: 15 pages, 15 figures, MNRAS in pres
MgB2 tunnel junctions and 19 K low-noise dc superconducting quantum interference devices
Point contact junctions made from two pieces of MgB2 can be adjusted to
exhibit either superconductor-insulator-superconductor (SIS) or
superconductor-normal metal-superconductor (SNS) current-voltage
characteristics. The SIS characteristics are in good agreement with the
standard tunneling model for s-wave superconductors, and yield an energy gap of
(2.02 +/- 0.08) meV. The SNS characteristics are in good agreement with the
predictions of the resistively-shunted junction model. DC Superconducting
QUantum Interference Devices made from two SNS junctions yield magnetic field
noise as low as 35 fT/Hz^{1/2} at 19 K.Comment: 4 pages, 4 figure
A Fixed-Point Algorithm for the AC Power Flow Problem
This paper presents an algorithm that solves the AC power flow problem for
balanced, three-phase transmission systems at steady state. The algorithm
extends the "fixed-point power flow" algorithm in the literature to include
transmission losses, phase-shifting transformers, and a distributed slack bus
model. The algorithm is derived by vectorizing the component-wise AC power flow
equations and manipulating them into a novel equivalent fixed-point form.
Preliminary theoretical results guaranteeing convergence are reported for the
case of a two-bus power system. We validate the algorithm through extensive
simulations on test systems of various sizes under different loading levels,
and compare its convergence behavior against those of classic power flow
algorithms.Comment: Submitted to American Control Conference 202
Using MOOCs to Promote Digital Accessibility and Universal Design, the MOOCAP Experience
The recently completed Massive Open Online Course for Accessibility Partnership project (MOOCAP), had the twin aims of establishing a strategic partnership around the promotion of Universal Design and Accessibility for ICT professionals and of developing a suite of Open Educational resources (OERs) in this domain. MOOCAP\u27s eight university partners from Germany, Norway, Greece, Ireland, the UK and Austria have a significant history in developing and providing courses in the domains of Universal Design and Accessibility, as well as leading research and advocacy roles within Europe. The MOOCAP project consisted of two phases: the development of an introductory MOOC on Digital Accessibility and the delivery of set of online courses with more in-depth and focused learning topics. During the lifetime of the project over 10,000 students signed up for these courses. This paper reflects on the challenges of creating and delivering MOOCs, especially in topics around Digital Accessibility and Universal Design. It considers the outcomes, impacts and legacies of the project. Based on our experiences of integrating these materials into our courses and on feedback and project evaluations, this paper will assess the potential of MOOCs to promote Universal Design for ICT and other professionals, while pointing up the possible trials and opportunities of such activities
Attraction Between Like-Charged Walls: Short-Ranged Simulations Using Local Molecular Field Theory
Effective attraction between like-charged walls mediated by counterions is
studied using local molecular field (LMF) theory. Monte Carlo simulations of
the "mimic system'' given by LMF theory, with short-ranged "Coulomb core"
interactions in an effective single particle potential incorporating a
mean-field average of the long-ranged Coulomb interactions, provide a direct
test of the theory, and are in excellent agreement with more complex
simulations of the full Coulomb system by Moreira and Netz [Eur. Phys. J. E 8,
33 (2002)]. A simple, generally-applicable criterion to determine the
consistency parameter sigma_{min} needed for accurate use of the LMF theory is
presented
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