2,522 research outputs found
Welfare Reform and Changes in the Economic Well-Being of Children
Since the implementation of the Temporary Assistance for Needy Families program in late-1996, welfare rolls have declined by more than half. This paper explores whether improvements in the economic well-being of children have accompanied this dramatic reduction in welfare participation. Further, we examine the degree to which the success or failure of welfare reform has been shared equally among families of varying educational background. We analyze data from the March Current Population Surveys over the years 1988 through 2001. Specifically, we link data for families with children who are interviewed in adjacent years and determine whether their economic circumstances either improved or deteriorated. We use two alternative approaches to address this general issue: a variety of regression models and a difference-in-differences methodology. These approaches provide consistent answers. In a bivariate framework TANF is associated with higher incomes; but this association becomes insignificant in the presence of business cycle controls. We also determine that children who were poor at an initial time period benefit differently, depending on their parents' educational attainment level. Poor children with parents who do not have a high school degree are significantly worse off in the TANF era, relative to the era prior to welfare reform, than are their more educated counterparts.
Immediate Versus Delayed Feedback on Learning: Do Peopleâs Instincts Really Conflict With Reality?
Researchers have held differing views on the effects of feedback timing for decades. A closer reading of the timing of feedback literature that favored delayed feedback revealed that this conclusion may have been reached prematurely, because the results might have been confounded by the time interval between feedback and a posttest. This study differs from previous feedback timing studies in three distinct ways: First, this study addressed the limitations of previous studies by holding time interval between the feedback (either immediate or delayed) and the posttest constant. Second, this study included various types of knowledge and investigated the interaction between feedback timing and different knowledge types. Third, most studies that investigate the comparative effectiveness of immediate and delayed feedback on written assignments were conducted in the STEM fields, whereas few studies can be found in the second language learning field. Results revealed that the immediate feedback condition significantly outperformed the delayed feedback condition on conceptual knowledge learning, however, no difference between the two conditions was found on situational knowledge learning
Concave Switching in Single and Multihop Networks
Switched queueing networks model wireless networks, input queued switches and
numerous other networked communications systems. For single-hop networks, we
consider a {()-switch policy} which combines the MaxWeight policies
with bandwidth sharing networks -- a further well studied model of Internet
congestion. We prove the maximum stability property for this class of
randomized policies. Thus these policies have the same first order behavior as
the MaxWeight policies. However, for multihop networks some of these
generalized polices address a number of critical weakness of the
MaxWeight/BackPressure policies.
For multihop networks with fixed routing, we consider the Proportional
Scheduler (or (1,log)-policy). In this setting, the BackPressure policy is
maximum stable, but must maintain a queue for every route-destination, which
typically grows rapidly with a network's size. However, this proportionally
fair policy only needs to maintain a queue for each outgoing link, which is
typically bounded in number. As is common with Internet routing, by maintaining
per-link queueing each node only needs to know the next hop for each packet and
not its entire route. Further, in contrast to BackPressure, the Proportional
Scheduler does not compare downstream queue lengths to determine weights, only
local link information is required. This leads to greater potential for
decomposed implementations of the policy. Through a reduction argument and an
entropy argument, we demonstrate that, whilst maintaining substantially less
queueing overhead, the Proportional Scheduler achieves maximum throughput
stability.Comment: 28 page
Developing a context-based bounded centrality approach of street patterns in flooding: a case study of London
Floods affect an average of 21 million people worldwide each year, and their frequency
is expected to increase due to climate warming, population growth, and rapid urbanisation. Previous
research on the robustness of transport networks during floods has mainly used percolation theory.
However, giant component size of disrupted networks cannot capture the entire networkâs
information and, more importantly, does not reflect the local reality. To address this issue, this study
introduces a novel approach to bounded context-based centrality to extract the local impact of
disruption. In particular, we propose embedding travel behaviour into the road network to calculate
bounded centrality and develop new measures characterising the size of connected components
during flooding. Our analysis can identify critical road segments during floods by comparing the
decreasing trend and dispersibility of component sizes on road networks. To demonstrate the
feasibility of these approaches, a case study of London's transport infrastructure that integrates road
networks with relevant urban contexts was developed. This approach is beneficial for practical risk
management, helping decision-makers allocate resources efficiently in space and time
Characterization of the lncRNA transcriptome in mESC-derived motor neurons: Implications for FUS-ALS
Long non-coding RNAs (lncRNAs) are currently recognized as crucial players in nervous system development,
function and pathology. In Amyotrophic Lateral Sclerosis (ALS), identification of causative mutations in FUS
and TDP-43 or hexanucleotide repeat expansion in C9ORF72 point to the essential role of aberrant RNA metabolism
in neurodegeneration. In this study, by taking advantage of an in vitro differentiation system generating
mouse motor neurons (MNs) from embryonic stem cells, we identified and characterized the long non-coding
transcriptome of MNs. Moreover, by using mutant mouse MNs carrying the equivalent of one of the most severe
ALS-associated FUS alleles (P517L), we identified lncRNAs affected by this mutation. Comparative analysis with
humanMNs derived in vitro frominduced pluripotent stemcells indicated that candidate lncRNAs are conserved
between mouse and human. Our work provides a global view of the long non-coding transcriptome of MN, as a
prerequisite toward the comprehension of the still poorly characterized non-coding side ofMNphysiopatholog
Inferring neutron star properties with continuous gravitational waves
Detection of continuous gravitational waves from rapidly-spinning neutron
stars opens up the possibility of examining their internal physics. We develop
a framework that leverages a future continuous gravitational wave detection to
infer a neutron star's moment of inertia, equatorial ellipticity, and the
component of the magnetic dipole moment perpendicular to its rotation axis. We
assume that the neutron star loses rotational kinetic energy through both
gravitational wave and electromagnetic radiation, and that the distance to the
neutron star can be measured, but do not assume electromagnetic pulsations are
observable or a particular neutron star equation of state. We use the Fisher
information matrix and Monte Carlo simulations to estimate errors in the
inferred parameters, assuming a population of gravitational-wave-emitting
neutron stars consistent with the typical parameter domains of continuous
gravitational wave searches. After an observation time of one year, the
inferred errors for many neutron stars are limited chiefly by the error in the
distance to the star. The techniques developed here will be useful if
continuous gravitational waves are detected from a radio, X-ray, or gamma-ray
pulsar, or else from a compact object with known distance, such as a supernova
remnant.Comment: 10 pages, 4 figures. To be published in MNRA
A Regulatory Circuitry Between Gria2, miR-409, and miR-495 Is Affected by ALS FUS Mutation in ESC-Derived Motor Neurons
Mutations in fused in sarcoma (FUS) cause amyotrophic lateral sclerosis (ALS). FUS is a multifunctional protein involved in the
biogenesis and activity of several types of RNAs, and its role in the pathogenesis of ALS may involve both direct effects of
disease-associated mutations through gain- and loss-of-function mechanisms and indirect effects due to the cross talk between
different classes of FUS-dependent RNAs. To explore how FUS mutations impinge on motor neuron-specific RNA-based
circuitries, we performed transcriptome profiling of small and long RNAs of motor neurons (MNs) derived from mouse
embryonic stem cells carrying a FUS-P517L knock-in mutation, which is equivalent to human FUS-P525L, associated with a
severe and juvenile-onset form of ALS. Combining ontological, predictive and molecular analyses, we found an inverse correlation
between several classes of deregulated miRNAs and their corresponding mRNA targets in both homozygous and heterozygous
P517L MNs. We validated a circuitry in which the upregulation of miR-409-3p and miR-495-3p, belonging to a brainspecific
miRNA subcluster implicated in several neurodevelopmental disorders, produced the downregulation of Gria2, a subunit
of the glutamate αâaminoâ3âhydroxyâ5âmethyl-4-isoxazole propionic acid (AMPA) receptor with a significant role in excitatory
neurotransmission. Moreover, we found that FUS was involved in mediating such miRNA repression. Gria2 alteration has been
proposed to be implicated in MN degeneration, through disturbance of Ca2+ homeostasis, which triggers a cascade of damaging
âexcitotoxicâ events. The molecular cross talk identified highlights a role for FUS in excitotoxicity and in miRNA-dependent
regulation of Gria2. This circuitry also proved to be deregulated in heterozygosity, which matches the human condition perfectly
Microwave-to-optical conversion using lithium niobate thin-film acoustic resonators
Acoustic or mechanical resonators have emerged as a promising means to mediate efficient microwave-to-optical conversion. Here, we demonstrate conversion of microwaves up to 4.5 GHz in frequency to 1500 nm wavelength light using optomechanical interactions on suspended thin-film lithium niobate. Our method uses an interdigital transducer that drives a freestanding 100 ÎŒm-long thin-film acoustic resonator to modulate light traveling in a MachâZehnder interferometer or racetrack cavity. The strong microwave-to-acoustic coupling offered by the transducer in conjunction with the strong photoelastic, piezoelectric, and electro-optic effects of lithium niobate allows us to achieve a half-wave voltage of VÏ = 4.6 V and VÏ = 0.77 V for the MachâZehnder interferometer and racetrack resonator, respectively. The acousto-optic racetrack cavity exhibits an optomechanical single-photon coupling strength of 1.1 kHz. To highlight the versatility of our system, we also demonstrate a microwave photonic link with unitary gain, which refers to a 0 dB microwave power transmission over an optical channel. Our integrated nanophotonic platform, which leverages the compelling properties of lithium niobate, could help enable efficient conversion between microwave and optical fields
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