2,330 research outputs found
Efficient Inflation Estimation
This paper investigates the use of trimmed means as high-frequency estimators of" inflation. The known characteristics of price change distributions, specifically the observation" that they generally exhibit high levels of kurtosis, imply that simple averages of price data are" unlikely to produce efficient estimates of inflation. Trimmed means produce superior estimates" of core inflation,' which we define as a long-run centered moving average of CPI and PPI" inflation. We find that trimming 9% from each tail of the CPI price-change distribution from the tails of the PPI price-change distribution, yields an efficient estimator of core inflation" for these two series, although lesser trims also produce substantial efficiency gains. Historically the optimal trimmed estimators are found to be nearly 23% more efficient (in terms of root-mean-square error) than the standard mean CPI Moreover, the efficient estimators are robust to sample period and to the definition of the" presumed underlying long-run trend in inflation.
Self-organized Beating and Swimming of Internally Driven Filaments
We study a simple two-dimensional model for motion of an elastic filament
subject to internally generated stresses and show that wave-like propagating
shapes which can propel the filament can be induced by a self-organized
mechanism via a dynamic instability. The resulting patterns of motion do not
depend on the microscopic mechanism of the instability but only of the filament
rigidity and hydrodynamic friction. Our results suggest that simplified
systems, consisting only of molecular motors and filaments could be able to
show beating motion and self-propulsion.Comment: 8 pages, 2 figures, REVTe
Implementing a structured education program for children with diabetes: lessons learnt from an integrated process evaluation
There is recognition of an urgent need for clinic-based interventions for young people with type 1 diabetes mellitus that improve glycemic control and quality of life. The Child and Adolescent Structured Competencies Approach to Diabetes Education (CASCADE) is a structured educational group program, using psychological techniques, delivered primarily by diabetes nurses. Composed of four modules, it is designed for children with poor diabetic control and their parents. A mixed methods process evaluation, embedded within a cluster randomized control trial, aimed to assess the feasibility, acceptability, fidelity, and perceived impact of CASCADE
Mean field approximation of two coupled populations of excitable units
The analysis on stability and bifurcations in the macroscopic dynamics
exhibited by the system of two coupled large populations comprised of
stochastic excitable units each is performed by studying an approximate system,
obtained by replacing each population with the corresponding mean-field model.
In the exact system, one has the units within an ensemble communicating via the
time-delayed linear couplings, whereas the inter-ensemble terms involve the
nonlinear time-delayed interaction mediated by the appropriate global
variables. The aim is to demonstrate that the bifurcations affecting the
stability of the stationary state of the original system, governed by a set of
4N stochastic delay-differential equations for the microscopic dynamics, can
accurately be reproduced by a flow containing just four deterministic
delay-differential equations which describe the evolution of the mean-field
based variables. In particular, the considered issues include determining the
parameter domains where the stationary state is stable, the scenarios for the
onset and the time-delay induced suppression of the collective mode, as well as
the parameter domains admitting bistability between the equilibrium and the
oscillatory state. We show how analytically tractable bifurcations occurring in
the approximate model can be used to identify the characteristic mechanisms by
which the stationary state is destabilized under different system
configurations, like those with symmetrical or asymmetrical inter-population
couplings.Comment: 5 figure
Triplicity and Physical Characteristics of Asteroid (216) Kleopatra
To take full advantage of the September 2008 opposition passage of the M-type
asteroid (216) Kleopatra, we have used near-infrared adaptive optics (AO)
imaging with the W.M. Keck II telescope to capture unprecedented high
resolution images of this unusual asteroid. Our AO observations with the W.M.
Keck II telescope, combined with Spitzer/IRS spectroscopic observations and
past stellar occultations, confirm the value of its IRAS radiometric radius of
67.5 km as well as its dog-bone shape suggested by earlier radar observations.
Our Keck AO observations revealed the presence of two small satellites in orbit
about Kleopatra (see Marchis et al., 2008). Accurate measurements of the
satellite orbits over a full month enabled us to determine the total mass of
the system to be 4.64+/-0.02 10^18 Kg. This translates into a bulk density of
3.6 +/-0.4 g/cm3, which implies a macroscopic porosity for Kleopatra of ~
30-50%, typical of a rubble-pile asteroid. From these physical characteristics
we measured its specific angular momentum, very close to that of a spinning
equilibrium dumbbell.Comment: 35 pages, 3 Tables, 9 Figures. In press to Icaru
The Viscous Nonlinear Dynamics of Twist and Writhe
Exploiting the "natural" frame of space curves, we formulate an intrinsic
dynamics of twisted elastic filaments in viscous fluids. A pair of coupled
nonlinear equations describing the temporal evolution of the filament's complex
curvature and twist density embodies the dynamic interplay of twist and writhe.
These are used to illustrate a novel nonlinear phenomenon: ``geometric
untwisting" of open filaments, whereby twisting strains relax through a
transient writhing instability without performing axial rotation. This may
explain certain experimentally observed motions of fibers of the bacterium B.
subtilis [N.H. Mendelson, et al., J. Bacteriol. 177, 7060 (1995)].Comment: 9 pages, 4 figure
A pilot project to increase health literacy among youth from seasonal farmworker families in rural eastern North Carolina: a qualitative exploration of implementation and impact
Objective
There are substantial health inequalities for seasonal agricultural workers and their families in the United States. One identified inequality is in health literacy. The authors explored the implementation and impact of connecting youth from seasonal farmworker families who participated in a leadership and college pipeline program with Internet access by providing a tablet with a paid cellular data plan and university library–based health literacy training.
Methods
With the support of a National Network of Libraries of Medicine Health Information Outreach Award, we conducted a qualitative, utilization-focused evaluation by conducting semi-structured interviews from December 2017 through February 2018 with middle and high school age participants in the program (n=10). After parental consent and youth assent, we recorded interviews with participants at program activity locations or in their homes. We then utilized inductive thematic analysis with 2 primary coders.
Results
We identified four themes: (1) having access to the Internet can be transformative, (2) access resulted in increased knowledge of and interest in one’s own and others’ health, (3) “Google� is the norm, and (4) participant training increased self-efficacy to determine credible sources and resources.
Conclusion
Providing Internet access and iPads was possible to implement and resulted in increased utilization of health information. The combination of Internet access with training on information literacy was a key factor in achieving these positive outcomes. The findings suggest the importance of ensuring equitable access to the Internet in efforts to improve educational and health outcomes for seasonal farmworkers and their families
Bifurcations, Chaos, Controlling and Synchronization of Certain Nonlinear Oscillators
In this set of lectures, we review briefly some of the recent developments in
the study of the chaotic dynamics of nonlinear oscillators, particularly of
damped and driven type. By taking a representative set of examples such as the
Duffing, Bonhoeffer-van der Pol and MLC circuit oscillators, we briefly explain
the various bifurcations and chaos phenomena associated with these systems. We
use numerical and analytical as well as analogue simulation methods to study
these systems. Then we point out how controlling of chaotic motions can be
effected by algorithmic procedures requiring minimal perturbations. Finally we
briefly discuss how synchronization of identically evolving chaotic systems can
be achieved and how they can be used in secure communications.Comment: 31 pages (24 figures) LaTeX. To appear Springer Lecture Notes in
Physics Please Lakshmanan for figures (e-mail: [email protected]
The multi-faceted Type II-L supernova 2014G from pre-maximum to nebular phase
We present multi-band ultraviolet, optical, and near-infrared photometry,
along with visual-wavelength spectroscopy, of supernova (SN) 2014G in the
nearby galaxy NGC 3448 (25 Mpc). The early-phase spectra show strong emission
lines of the high ionisation species He II/N IV/C IV during the first 2-3 d
after explosion, traces of a metal-rich CSM probably due to pre-explosion mass
loss events. These disappear by day 9 and the spectral evolution then continues
matching that of normal Type II SNe. The post-maximum light curve declines at a
rate typical of Type II-L class. The extensive photometric coverage tracks the
drop from the photospheric stage and constrains the radioactive tail, with a
steeper decline rate than that expected from the Co decay if
-rays are fully trapped by the ejecta. We report the appearance of an
unusual feature on the blue-side of H after 100 d, which evolves to
appear as a flat spectral feature linking H and the O I doublet. This
may be due to interaction of the ejecta with a strongly asymmetric, and
possibly bipolar CSM. Finally, we report two deep spectra at ~190 and 340 d
after explosion, the latter being arguably one of the latest spectra for a Type
II-L SN. By modelling the spectral region around the Ca II, we find a
supersolar Ni/Fe production. The strength of the O I 6300,6363
doublet, compared with synthetic nebular spectra, suggests a progenitor with a
zero-age main-sequence mass between 15 and 19 M.Comment: 24 pages, 14 figure
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