1,858 research outputs found
Abundance determination from global emission-line SDSS spectra: exploring objects with high N/O ratios
We have compared the oxygen and nitrogen abundances derived from global
emission-line SDSS spectra of galaxies using (1) the Te method and (2) two
recent strong line calibrations: the ON and NS calibrations. Using the Te
method, anomously high N/O abundances ratios have been found in some SDSS
galaxies. To investigate this, we have Monte Carlo simulated the global spectra
of composite nebulae by a mix of spectra of individual components, based on
spectra of well-studied HII regions in nearby galaxies. We found that the Te
method results in an underestimated oxygen abundance (and hence in an
overestimated nitrogen-to-oxygen ratio) if HII regions with different physical
properties contribute to the global spectrum of composite nebulae. This effect
is somewhat similar to the small-scale temperature fluctuations in HII regions
discussed by Peimbert. Our work thus suggests that the high Te-based N/O
abundances ratios found in SDSS galaxies may not be real. However, such an
effect is not expected to be present in dwarf galaxies since they have
generally an uniform chemical composition. The ON and NS calibrations give O
and N abundances in composite nebulae which agree with the mean
luminosity-weighted abundances of their components to within 0.2 dex.Comment: 12 pages, 9 figures, accepted for publication in MNRA
Supernovae data and perturbative deviation from homogeneity
We show that a spherically symmetric perturbation of a dust dominated
FRW universe in the Newtonian gauge can lead to an apparent
acceleration of standard candles and provide a fit to the magnitude-redshift
relation inferred from the supernovae data, while the perturbation in the
gravitational potential remains small at all scales. We also demonstrate that
the supernovae data does not necessarily imply the presence of some additional
non-perturbative contribution by showing that any Lemaitre-Tolman-Bondi model
fitting the supernovae data (with appropriate initial conditions) will be
equivalent to a perturbed FRW spacetime along the past light cone.Comment: 8 pages, 3 figures; v2: 1 figure added, references added/updated,
minor modifications and clarifications, matches published versio
Probing the interiors of the ice giants: Shock compression of water to 700 GPa and 3.8 g/ccm
Recently there has been tremendous increase in the number of identified
extra-solar planetary systems. Our understanding of their formation is tied to
exoplanet internal structure models, which rely upon equations of state of
light elements and compounds like water. Here we present shock compression data
for water with unprecedented accuracy that shows water equations of state
commonly used in planetary modeling significantly overestimate the
compressibility at conditions relevant to planetary interiors. Furthermore, we
show its behavior at these conditions, including reflectivity and isentropic
response, is well described by a recent first-principles based equation of
state. These findings advocate this water model be used as the standard for
modeling Neptune, Uranus, and "hot Neptune" exoplanets, and should improve our
understanding of these types of planets.Comment: Accepted to Phys. Rev. Lett.; supplementary material attached
including 2 figures and 2 tables; to view attachments, please download and
extract the gzipped tar source file listed under "Other formats
Back-reaction and effective acceleration in generic LTB dust models
We provide a thorough examination of the conditions for the existence of
back-reaction and an "effective" acceleration (in the context of Buchert's
averaging formalism) in regular generic spherically symmetric
Lemaitre-Tolman-Bondi (LTB) dust models. By considering arbitrary spherical
comoving domains, we verify rigorously the fulfillment of these conditions
expressed in terms of suitable scalar variables that are evaluated at the
boundary of every domain. Effective deceleration necessarily occurs in all
domains in: (a) the asymptotic radial range of models converging to a FLRW
background, (b) the asymptotic time range of non-vacuum hyperbolic models, (c)
LTB self-similar solutions and (d) near a simultaneous big bang. Accelerating
domains are proven to exist in the following scenarios: (i) central vacuum
regions, (ii) central (non-vacuum) density voids, (iii) the intermediate radial
range of models converging to a FLRW background, (iv) the asymptotic radial
range of models converging to a Minkowski vacuum and (v) domains near and/or
intersecting a non-simultaneous big bang. All these scenarios occur in
hyperbolic models with negative averaged and local spatial curvature, though
scenarios (iv) and (v) are also possible in low density regions of a class of
elliptic models in which local spatial curvature is negative but its average is
positive. Rough numerical estimates between -0.003 and -0.5 were found for the
effective deceleration parameter. While the existence of accelerating domains
cannot be ruled out in models converging to an Einstein de Sitter background
and in domains undergoing gravitational collapse, the conditions for this are
very restrictive. The results obtained may provide important theoretical clues
on the effects of back-reaction and averaging in more general non-spherical
models.Comment: Final version accepted for publication in Classical and Quantum
Gravity. 47 pages in IOP LaTeX macros, 12 pdf figure
Quantifying Thermal‐Imager Effectiveness for Detecting Bird Nests on Farms
We conducted a designed experiment to test whether having a thermal‐imaging camera available affected researchers’ nest detection rates when searching for bird nests in cropland and grassland habitat in an agricultural landscape of Iowa, USA, in 2016. With known active nests present, naïve observers searched for nests with and without a thermal imager available. We did not find a difference in detection probabilities, although only a large difference would have been detectable with our sample size. Extraneous heat signatures from reflected solar radiation and dense vegetation were key factors limiting the usefulness of thermal imagers for locating nests
Feeling controlled or being in control? Apps for self-management among older people with neurological disability
Purpose: The aim of this paper was to describe how people living with a neurological disability such as multiple sclerosis, Parkinson’s disease and stroke reason regarding using apps to facilitate self-management in everyday life.
Material and methods: A qualitative research approach with a focus group methodology was used. The sample comprised 16 participants, 11 men and 5 women, with an average age of 64 years (ranging from 51–80 years). Six participants were diagnosed with multiple sclerosis, six with Parkinson’s disease and four with stroke. Data were analyzed using thematic analysis, which is a method for identifying, analyzing and reporting patterns.
Results: The results formed two themes. The first theme “using apps to have control of my health” comprises two subthemes; “monitor and take responsibility for a healthy lifestyle” and “compensate to facilitate everyday life”. The second theme “using the app as a tool and means for communication” also comprised two subthemes; “dare to trust the app” and “feeling safe when sharing information with health care professionals”.
Conclusions: The use of apps put increased responsibility on the person and had the possibility to make them more involved in their own care. The use of an app can facilitate a healthy lifestyle and help to monitor disease-specific symptoms. In order to be able to use apps for communication with the health care sector legislation and safety issues need to be considered.
Implications for rehabilitation
Apps can be used for self-management if they are safe and can be trusted.
People with neurological disabilities want to be involved in their healthcare and needs to be addressed by health care professionals.
The use of apps grasp over a wide variety of areas this is something that may be considered in health care and something that can be addressed by interdisciplinary approaches.
Ordinary health-oriented apps and disease-specific apps were used differently and for different purposes
An Improved High Order Finite Difference Method for Non-conforming Grid Interfaces for the Wave Equation
This paper presents an extension of a recently developed high order finite difference method for the wave equation on a grid with non-conforming interfaces. The stability proof of the existing methods relies on the interpolation operators being norm-contracting, which is satisfied by the second and fourth order operators, but not by the sixth order operator. We construct new penalty terms to impose interface conditions such that the stability proof does not require the norm-contracting condition. As a consequence, the sixth order accurate scheme is also provably stable. Numerical experiments demonstrate the improved stability and accuracy property
Advancing oral medicine through informatics and information technology: a proposed framework and strategy.
The implementation of information technology in healthcare is a significant focus for many nations around the world. However, information technology support for clinical care, research and education in oral medicine is currently poorly developed. This situation hampers our ability to transform oral medicine into a 'learning healthcare discipline' in which the divide between clinical practice and research is diminished and, ultimately, eliminated. This paper reviews the needs of and requirements for information technology support of oral medicine and proposes an agenda designed to meet those needs. For oral medicine, this agenda includes analyzing and reviewing current clinical and documentation practices, working toward progressively standardizing clinical data, and helping define requirements for oral medicine systems. IT professionals can contribute by conducting baseline studies about the use of electronic systems, helping develop controlled vocabularies and ontologies, and designing, implementing, and evaluating novel systems centered on the needs of clinicians, researchers and educators. Successfully advancing IT support for oral medicine will require close coordination and collaboration among oral medicine professionals, information technology professionals, system vendors, and funding agencies. If current barriers and obstacles are overcome, practice and research in oral medicine stand ready to derive significant benefits from the application of information technology
Would You Choose to be Happy? Tradeoffs Between Happiness and the Other Dimensions of Life in a Large Population Survey
A large literature documents the correlates and causes of subjective well-being, or happiness. But few studies have investigated whether people choose happiness. Is happiness all that people want from life, or are they willing to sacrifice it for other attributes, such as income and health? Tackling this question has largely been the preserve of philosophers. In this article, we find out just how much happiness matters to ordinary citizens. Our sample consists of nearly 13,000 members of the UK and US general populations. We ask them to choose between, and make judgments over, lives that are high (or low) in different types of happiness and low (or high) in income, physical health, family, career success, or education. We find that people by and large choose the life that is highest in happiness but health is by far the most important other concern, with considerable numbers of people choosing to be healthy rather than happy. We discuss some possible reasons for this preference
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