13,118 research outputs found

### Observation of the dielectric-waveguide mode of light propagation in p-n junctions

Theoretical considerations of the propagation of electromagnetic energy near a p-n junction (1) show that the âsandwichâ formed by having a depletion layer bounded by the p and n regions can act as a dielectric waveguide. (1,2

### Application of XFaster power spectrum and likelihood estimator to Planck

We develop the XFaster Cosmic Microwave Background (CMB) temperature and
polarization anisotropy power spectrum and likelihood technique for the Planck
CMB satellite mission. We give an overview of this estimator and its current
implementation and present the results of applying this algorithm to simulated
Planck data. We show that it can accurately extract the power spectrum of
Planck data for the high-l multipoles range. We compare the XFaster
approximation for the likelihood to other high-l likelihood approximations such
as Gaussian and Offset Lognormal and a low-l pixel-based likelihood. We show
that the XFaster likelihood is not only accurate at high-l, but also performs
well at moderately low multipoles. We also present results for cosmological
parameter Markov Chain Monte Carlo estimation with the XFaster likelihood. As
long as the low-l polarization and temperature power are properly accounted
for, e.g., by adding an adequate low-l likelihood ingredient, the input
parameters are recovered to a high level of accuracy.Comment: 25 pages, 20 figures, updated to reflect published version: slightly
extended account of XFaster technique, added improved plots and minor
corrections. Accepted for publication in MNRA

### Signal-to-Noise Eigenmode Analysis of the Two-Year COBE Maps

To test a theory of cosmic microwave background fluctuations, it is natural
to expand an anisotropy map in an uncorrelated basis of linear combinations of
pixel amplitudes --- statistically-independent for both the noise and the
signal. These $S/N$-eigenmodes are indispensible for rapid Bayesian analyses of
anisotropy experiments, applied here to the recently-released two-year COBE
{\it dmr} maps and the {\it firs} map. A 2-parameter model with an overall
band-power and a spectral tilt $\nu_{\Delta T}$ describes well inflation-based
theories. The band-powers for {\it all} the {\it dmr} $53,90,31$ $a$+$b$ GHz
and {\it firs} 170 GHz maps agree, $\{(1.1\pm 0.1)\times 10^{-5}\}^{1/2}$, and
are largely independent of tilt and degree of (sharp) $S/N$-filtering. Further,
after optimal $S/N$-filtering, the {\it dmr} maps reveal the same
tilt-independent large scale features and correlation function. The unfiltered
{\it dmr} $53$ $a$+$b$ index $\nu_{\Delta T}+1$ is $1.4\pm 0.4$; increasing the
$S/N$-filtering gives a broad region at (1.0--1.2)$\pm$0.5, a jump to
(1.4--1.6)$\pm$0.5, then a drop to 0.8, the higher values clearly seen to be
driven by $S/N$-power spectrum data points that do not fit single-tilt models.
These indices are nicely compatible with inflation values ($\sim$0.8--1.2), but
not overwhelmingly so.Comment: submitted to Phys.Rev.Letters, 4 pages, uuencoded compressed
PostScript; also bdmr2.ps.Z, via anonymous ftp to ftp.cita.utoronto.ca, cd to
/pub/dick/yukawa; CITA-94-2

### In Nightingale's footsteps: A qualitative analysis of the impact of leadership development within the clinical learning environment

Aim
To identify and describe the impact areas of a newly developed leadership development programme focussed on positioning leaders to improve the student experience of the clinical learning environment.
Background
There is a need to consider extending traditional ways of developing leaders within the clinical learning in order to accommodate an increased number of students and ensure their learning experience is fulfilling and developmental. The Florence Nightingale Foundation implemented a bespoke leadership development programme within the clinical learning environment. Identifying the areas of impact will help to inform organisational decision making regarding the benefits of encouraging and supporting emerging leaders to undertake this type of programme.
Method
For this qualitative descriptive study, eight health care professionals who took part in a bespoke leadership development programme were interviewed individually and then collectively. The Florence Nightingale Foundation fellowship/scholarship programme is examined to determine impact.
Results
Two key themes were described in relation to impact of the programme. These were âPersonal Developmentâ and âProfessional Impactâ. The two key themes comprised several subthemes. The notion of time and space to think was subsumed within each theme.
Conclusion
Data highlights that the Florence Nightingale Foundation programme had a distinct impact on participants by transforming thinking and increasing self-confidence to enable changes to make improvements both within their organisations and at national level.
Implications for Nursing Management
Health care managers must continue to invest in building leadership capacity and capability through programmes that can help position individuals to realize their potential to positively influence health outcomes and wider society

### Power Spectrum of Primordial Inhomogeneity Determined from the 4-Year COBE DMR Sky Maps

Fourier analysis and power spectrum estimation of the cosmic microwave
background anisotropy on an incompletely sampled sky developed by Gorski (1994)
has been applied to the high-latitude portion of the 4-year COBE DMR 31.5, 53
and 90 GHz sky maps. Likelihood analysis using newly constructed Galaxy cuts
(extended beyond |b| = 20deg to excise the known foreground emission) and
simultaneously correcting for the faint high latitude galactic foreground
emission is conducted on the DMR sky maps pixelized in both ecliptic and
galactic coordinates. The Bayesian power spectrum estimation from the
foreground corrected 4-year COBE DMR data renders n ~ 1.2 +/- 0.3, and
Q_{rms-PS} ~ 15.3^{+3.7}_{-2.8} microK (projections of the two-parameter
likelihood). These results are consistent with the Harrison-Zel'dovich n=1
model of amplitude Q_{rms-PS} ~ 18 microK detected with significance exceeding
14sigma (dQ/Q < 0.07). (A small power spectrum amplitude drop below the
published 2-year results is predominantly due to the application of the new,
extended Galaxy cuts.)Comment: 9 pages of text in LaTeX, 1 postscript Table, 4 postscript figures (2
color plates), submitted to The Astrophysical Journal (Letters

### Power Spectrum Estimators For Large CMB Datasets

Forthcoming high-resolution observations of the Cosmic Microwave Background
(CMB) radiation will generate datasets many orders of magnitude larger than
have been obtained to date. The size and complexity of such datasets presents a
very serious challenge to analysing them with existing or anticipated
computers. Here we present an investigation of the currently favored algorithm
for obtaining the power spectrum from a sky-temperature map --- the quadratic
estimator. We show that, whilst improving on direct evaluation of the
likelihood function, current implementations still inherently scale as the
equivalent of the cube of the number of pixels or worse, and demonstrate the
critical importance of choosing the right implementation for a particular
dataset.Comment: 8 pages LATEX, no figures, corrected misaligned columns in table

### Exactly solvable model of A + A \to 0 reactions on a heterogeneous catalytic chain

We present an exact solution describing equilibrium properties of the
catalytically-activated A + A \to 0 reaction taking place on a one-dimensional
lattice, where some of the sites possess special "catalytic" properties. The A
particles undergo continuous exchanges with the vapor phase; two neighboring
adsorbed As react when at least one of them resides on a catalytic site (CS).
We consider three situations for the CS distribution: regular, annealed random
and quenched random. For all three CS distribution types, we derive exact
results for the disorder-averaged pressure and present exact asymptotic
expressions for the particles' mean density. The model studied here furnishes
another example of a 1D Ising-type system with random multi-site interactions
which admits an exact solution.Comment: 7 pages, 3 Figures, appearing in Europhysics Letter

### 2-Point Correlations in the COBE DMR 4-Year Anisotropy Maps

The 2-point temperature correlation function is evaluated from the 4-year
COBE DMR microwave anisotropy maps. We examine the 2-point function, which is
the Legendre transform of the angular power spectrum, and show that the data
are statistically consistent from channel to channel and frequency to
frequency. The most likely quadrupole normalization is computed for a
scale-invariant power-law spectrum of CMB anisotropy, using a variety of data
combinations. For a given data set, the normalization inferred from the 2-point
data is consistent with that inferred by other methods. The smallest and
largest normalization deduced from any data combination are 16.4 and 19.6 uK
respectively, with a value ~18 uK generally preferred.Comment: Sumbitted to ApJ Letter

### Current cosmological constraints from a 10 parameter CMB analysis

We compute the constraints on a ``standard'' 10 parameter cold dark matter
(CDM) model from the most recent CMB and data and other observations, exploring
30 million discrete models and two continuous parameters. Our parameters are
the densities of CDM, baryons, neutrinos, vacuum energy and curvature, the
reionization optical depth, and the normalization and tilt for both scalar and
tensor fluctuations.
Our strongest constraints are on spatial curvature, -0.24 < Omega_k < 0.38,
and CDM density, h^2 Omega_cdm <0.3, both at 95%. Including SN 1a constraints
gives a positive cosmological constant at high significance.
We explore the robustness of our results to various assumptions. We find that
three different data subsets give qualitatively consistent constraints. Some of
the technical issues that have the largest impact are the inclusion of
calibration errors, closed models, gravity waves, reionization, nucleosynthesis
constraints and 10-dimensional likelihood interpolation.Comment: Replaced to match published ApJ version. More details added. 13 ApJ
pages. CMB movies and color figs at
http://www.hep.upenn.edu/~max/10par_frames.html or from [email protected]

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