6,636 research outputs found
Diffraction Analysis of 2-D Pupil Mapping for High-Contrast Imaging
Pupil-mapping is a technique whereby a uniformly-illuminated input pupil,
such as from starlight, can be mapped into a non-uniformly illuminated exit
pupil, such that the image formed from this pupil will have suppressed
sidelobes, many orders of magnitude weaker than classical Airy ring
intensities. Pupil mapping is therefore a candidate technique for coronagraphic
imaging of extrasolar planets around nearby stars. Unlike most other
high-contrast imaging techniques, pupil mapping is lossless and preserves the
full angular resolution of the collecting telescope. So, it could possibly give
the highest signal-to-noise ratio of any proposed single-telescope system for
detecting extrasolar planets. Prior analyses based on pupil-to-pupil
ray-tracing indicate that a planet fainter than 10^{-10} times its parent star,
and as close as about 2 lambda/D, should be detectable. In this paper, we
describe the results of careful diffraction analysis of pupil mapping systems.
These results reveal a serious unresolved issue. Namely, high-contrast pupil
mappings distribute light from very near the edge of the first pupil to a broad
area of the second pupil and this dramatically amplifies diffraction-based edge
effects resulting in a limiting attainable contrast of about 10^{-5}. We hope
that by identifying this problem others will provide a solution.Comment: 23 pages, 13 figures, also posted to
http://www.orfe.princeton.edu/~rvdb/tex/piaaFresnel/ms.pd
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Stimulation of bone growth with thrombin peptide derivatives
Disclosed is a method of stimulating bone growth at a site in a subject in need of osteoinduction. The method comprises the step of administering a therapeutically effective amount of an agonist of the non-proteolytically activated thrombin receptor to the site.Board of Regents, University of Texas Syste
Free-vibration characteristics and correlation of a space station split-blanket solar array
Two methods for studying the free-vibration characteristics of a large split-blanket solar array in a zero-g cantilevered configuration are presented. The zero-g configuration corrresponds to an on-orbit configuration of the Space Station solar array. The first method applies the equations of continuum mechanics to determine the natural frequencies of the array; the second uses the finite element method program, MSC/NASTRAN. The stiffness matrix from the NASTRAN solution was found to be erroneously grounded. The results from the two methods are compared. It is concluded that the grounding does not seriously compromise the solution to the elastic modes of the solar array. However, the correct rigid body modes need to be included to obtain the correct dynamic model
Chemical Abundance Study of One Red Giant Star in NGC 5694 : A Globular Cluster with Dwarf Spheroidals' Chemical Signature?
We report the abundance analysis of one red giant branch star in the
metal-poor outer halo globular cluster NGC 5694. We obtain [Fe/H] = -1.93,
based on the ionized lines, and our metallicity measurement is in good
agreement with previous estimates. We find that [Ca+Ti/2Fe] and [Cu/Fe] of NGC
5694 are about 0.3 -- 0.4 dex lower than other globular clusters with similar
metallicities, but similar to some LMC clusters and stars in some dwarf
spheroidal galaxies. Differences persist, however, in the abundances of neutron
capture elements. The unique chemical abundance pattern and the large
Galactocentric distance (30 kpc) and radial velocity (-138.6 +/- 1.0 km/sec)
indicate that NGC 5694 had an extragalactic origin.Comment: ApJL accepte
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'Abandoned by Medicine'? A qualitative study of women's experiences with lymphoedema secondary to cancer, and the implications for care
Background: Lymphoedema secondary to cancer is a relatively neglected and under-researched condition. Few studies report people's experiences of care and treatment provision when living with the condition. Current practice focuses on the physical treatment yet psychosocial needs often remain unmet. A previous study examining the patient perspective identified the theme of being ‘abandoned by medicine’. Perceived lack of support may result in a delayed adaptation and acceptance of this long-term condition and can significantly impact on psychological well-being. We explore this emerging theme alongside others in order to provide a guide to action for improvements for patient benefit.
Aim: The central aim was to explore women's views of their care and treatment following a diagnosis with lymphoedema secondary to cancer. This forms part of a larger study aimed at assessing appropriate screening tools to measure psychosocial distress.
Methods: A mixed-methods approach was used for the main study. Here we report the qualitative component, derived from in-depth semi-structured interviews conducted in the homes of the participants (n = 14) and focus group discussions (n = 15). In addition, qualitative comments from questionnaire data from a large-scale postal survey are included (n = 104).
Findings: Participants identified considerable deficiencies in health care workers’ knowledge and awareness of lymphoedema, which subsequently impacted on the patients’ needs for information, support and understanding. Access to appropriate treatment was patchy and problems were identified with the process of obtaining compression garments, massage and other sources of help. Although lymphoedema is a long-term disfiguring condition, and much is known about how this impacts on patients’ emotional well-being, little attention was paid by health professionals to potential psychosocial consequences. In essence women had to become experts of their own condition and cope as best as they could. We provide recommendations to improve service delivery and address these unmet needs
Synthetic Mudscapes: Human Interventions in Deltaic Land Building
In order to defend infrastructure, economy, and settlement in Southeast Louisiana, we must construct new land to
mitigate increasing risk. Links between urban environments and economic drivers have constrained the dynamic delta
landscape for generations, now threatening to undermine the ecological fitness of the entire region. Static methods of
measuring, controlling, and valuing land fail in an environment that is constantly in flux; change and indeterminacy are
denied by traditional inhabitation.
Multiple land building practices reintroduce deltaic fluctuation and strategic deposition of fertile material to form the
foundations of a multi-layered defence strategy. Manufactured marshlands reduce exposure to storm surge further
inland. Virtual monitoring and communication networks inform design decisions and land use becomes determined
by its ecological health. Mudscapes at the threshold of land and water place new value on former wastelands. The
social, economic, and ecological evolution of the region are defended by an expanded web of growing land
Fundamental parameters of RR Lyrae stars from multicolour photometry and Kurucz atmospheric models -- II. Adaptation to double-mode stars
Our photometric-hydrodynamic method is generalized to determine fundamental
parameters of multiperiodic radially pulsating stars. We report 302 UBV(RI)_C
Johnson-Kron-Cousins observations of GSC 4868-0831. Using these and published
photometric data of V372 Ser, their metallicity, reddening, distance, mass,
radius, equilibrium luminosity, effective temperature are determined. The
results underline the necessity of using multicolour photometry including an
ultraviolet band to classify properly subgroups of RR Lyrae stars: our U
observations could reveal that GSC 4868-0831 is a subgiant star pulsating in
two radial modes, V372 Ser is a giant star with size and mass of an RRd star.Comment: 10 pages, 4 figures, 5 tables. Accepted for publication in Monthly
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Computational lens for the near field
A method is presented to reconstruct the structure of a scattering object from data acquired with a photon scanning tunneling microscope. The data may be understood to form a Gabor type near-field hologram and are obtained at a distance from the sample where the field is defocused and normally uninterpretable. Object structure is obtained by the solution of the inverse scattering problem within the accuracy of a perturbative, two-dimensional model of the object
Reactions to uncertainty and the accuracy of diagnostic mammography.
BackgroundReactions to uncertainty in clinical medicine can affect decision making.ObjectiveTo assess the extent to which radiologists' reactions to uncertainty influence diagnostic mammography interpretation.DesignCross-sectional responses to a mailed survey assessed reactions to uncertainty using a well-validated instrument. Responses were linked to radiologists' diagnostic mammography interpretive performance obtained from three regional mammography registries.ParticipantsOne hundred thirty-two radiologists from New Hampshire, Colorado, and Washington.MeasurementMean scores and either standard errors or confidence intervals were used to assess physicians' reactions to uncertainty. Multivariable logistic regression models were fit via generalized estimating equations to assess the impact of uncertainty on diagnostic mammography interpretive performance while adjusting for potential confounders.ResultsWhen examining radiologists' interpretation of additional diagnostic mammograms (those after screening mammograms that detected abnormalities), a 5-point increase in the reactions to uncertainty score was associated with a 17% higher odds of having a positive mammogram given cancer was diagnosed during follow-up (sensitivity), a 6% lower odds of a negative mammogram given no cancer (specificity), a 4% lower odds (not significant) of a cancer diagnosis given a positive mammogram (positive predictive value [PPV]), and a 5% higher odds of having a positive mammogram (abnormal interpretation).ConclusionMammograms interpreted by radiologists who have more discomfort with uncertainty have higher likelihood of being recalled
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