563 research outputs found
Improved spatial resolution of the sodium distribution on Mercury
The distribution of sodium emission over the surface of Mercury is non-uniform, and changes over time. These non-uniformities and time-dependent changes give clues to the processes that produce the sodium. However, observations of the distribution of sodium on Mercury are hampered by the bad seeing that accompanies the need to observe either in daytime, or at extremely large air masses in twilight. In an effort to improve this situation, we have developed an image stabilizer utilizing a piezoelectric driven tip-tilt correction mirror for daytime spectral imaging of Mercury. The system is a modification of one that was originally developed for solar observations at the McMath-Pierce solar telescope. Use of image stabilization results in a noticeable improvement in spatial resolution of our Mercury sodium images. A series of sodium images taken over an eight-day period show changes in which an emission peak in high southern latitudes disappears, and is replaced by an emission peak at high northern latitudes. Further systematic observations and improvements are planned for the image stabilizer system, as well as experimental observations with a low-order adaptive optics system incorporating a commercially available 37-actuator deformable mirror
Mode structure and ray dynamics of a parabolic dome microcavity
We consider the wave and ray dynamics of the electromagnetic field in a
parabolic dome microcavity. The structure of the fundamental s-wave involves a
main lobe in which the electromagnetic field is confined around the focal point
in an effective volume of the order of a cubic wavelength, while the modes with
finite angular momentum have a structure that avoids the focal area and have
correspondingly larger effective volume. The ray dynamics indicates that the
fundamental s-wave is robust with respect to small geometrical deformations of
the cavity, while the higher order modes are associated with ray chaos and
short-lived. We discuss the incidence of these results on the modification of
the spontaneous emission dynamics of an emitter placed in such a parabolic dome
microcavity.Comment: 50 pages, 17 figure
Metastable Random Field Ising model with exchange enhancement: a simple model for Exchange Bias
We present a simple model that allows hysteresis loops with exchange bias to
be reproduced. The model is a modification of the T=0 random field Ising model
driven by an external field and with synchronous local relaxation dynamics. The
main novelty of the model is that a certain fraction f of the exchange
constants between neighbouring spins is enhanced to a very large value J_E. The
model allows the dependence of the exchange bias and other properties of the
hysteresis loops to be analyzed as a function of the parameters of the model:
the fraction f of enhanced bonds, the amount of the enhancement J_E and the
amount of disorder which is controlled by the width sigma of the Gaussian
distribution of the random fields.Comment: 8 pages, 11 figure
Women, men and coronary heart disease: a review of the qualitative literature
Aim. This paper presents a review of the qualitative literature which examines the experiences of patients with coronary heart disease. The paper also assesses whether the experiences of both female and male patients are reflected in the literature and summarizes key themes.
Background. Understanding patients' experiences of their illness is important for coronary heart disease prevention and education. Qualitative methods are particularly suited to eliciting patients' detailed understandings and perceptions of illness. As much previous research has been 'gender neutral', this review pays particular attention to gender.
Methods. Published papers from 60 qualitative studies were identified for the review through searches in MEDLINE, EMBASE, CINAHL, PREMEDLINE, PsychINFO, Social Sciences Citation Index and Web of Science using keywords related to coronary heart disease.
Findings. Early qualitative studies of patients with coronary heart disease were conducted almost exclusively with men, and tended to generalize from 'male' experience to 'human' experience. By the late 1990s this pattern had changed, with the majority of studies including women and many being conducted with solely female samples. However, many studies that include both male and female coronary heart disease patients still do not have a specific gender focus. Key themes in the literature include interpreting symptoms and seeking help, belief about coronary 'candidates' and relationships with health professionals. The influence of social roles is important: many female patients have difficulties reconciling family responsibilities and medical advice, while male patients worry about being absent from work.
Conclusions. There is a need for studies that compare the experiences of men and women. There is also an urgent need for work that takes masculinity and gender roles into account when exploring the experiences of men with coronary heart disease
Search for the exotic Resonance in 340GeV/c -Nucleus Interactions
We report on a high statistics search for the resonance in
-nucleus collisions at 340GeV/c. No evidence for this resonance is
found in our data sample which contains 676000 candidates above
background. For the decay channel and the
kinematic range 0.150.9 we find a 3 upper limit for the
production cross section of 3.1 and 3.5 b per nucleon for reactions with
carbon and copper, respectively.Comment: 5 pages, 4 figures, modification of ref. 43 and 4
The Impact of Sexual Abuse in Patients Undergoing Colonoscopy
Development and application of statistical models for medical scientific researc
Have we seen the geneticisation of society? Expectations and evidence
Abby Lippman’s geneticization thesis, of the early 1990s, argued and anticipated that with
the rise of genetics, increasing areas of social and health related activities would come to be
understood and defined in genetic terms leading to major changes in society, medicine and
health care. We review the considerable literature on geneticization and consider how the
concept stands both theoretically and empirically across scientific, clinical, popular and lay
discourse and practice. Social science scholarship indicates that relatively little of the original
claim of the geneticization thesis has been realised, highlighting the development of more
complex and dynamic accounts of disease in scientific discourse and the complexity of
relationships between bioscientific, clinical and lay understandings. This scholarship
represents a shift in social science understandings of the processes of sociotechnical change,
which have moved from rather simplistic linear models to an appreciation of disease
categories as multiply understood. Despite these shifts, we argue that a genetic imaginary
persists, which plays a performative role in driving investments in new gene-based
developments. Understanding the enduring power of this genetic imaginary and its
consequences remains a key task for the social sciences, one which treats ongoing genetic
expectations and predictions in a sceptical yet open way
Reconsidering the Heritability of Intelligence in Adulthood: Taking Assortative Mating and Cultural Transmission into Account
Heritability estimates of general intelligence in adulthood generally range from 75 to 85%, with all heritability due to additive genetic influences, while genetic dominance and shared environmental factors are absent, or too small to be detected. These estimates are derived from studies based on the classical twin design and are based on the assumption of random mating. Yet, considerable positive assortative mating has been reported for general intelligence. Unmodeled assortative mating may lead to biased estimates of the relative magnitude of genetic and environmental factors. To investigate the effects of assortative mating on the estimates of the variance components of intelligence, we employed an extended twin-family design. Psychometric IQ data were available for adult monozygotic and dizygotic twins, their siblings, the partners of the twins and siblings, and either the parents or the adult offspring of the twins and siblings (N = 1314). Two underlying processes of assortment were considered: phenotypic assortment and social homogamy. The phenotypic assortment model was slightly preferred over the social homogamy model, suggesting that assortment for intelligence is mostly due to a selection of mates on similarity in intelligence. Under the preferred phenotypic assortment model, the variance of intelligence in adulthood was not only due to non-shared environmental (18%) and additive genetic factors (44%) but also to non-additive genetic factors (27%) and phenotypic assortment (11%).This non-additive nature of genetic influences on intelligence needs to be accommodated in future GWAS studies for intelligence
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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