15,329 research outputs found
Preferences for Prenatal Tests for Cystic Fibrosis: A Discrete Choice Experiment to Compare the Views of Adult Patients, Carriers of Cystic Fibrosis and Health Professionals
As new technologies enable the development of non-invasive prenatal diagnosis (NIPD) for cystic fibrosis (CF), research examining stakeholder views is essential for the preparation of implementation strategies. Here, we compare the views of potential service users with those of health professionals who provide counselling for prenatal tests. A questionnaire incorporating a discrete choice experiment examined preferences for key attributes of NIPD and explored views on NIPD for CF. Adult patients (n = 92) and carriers of CF (n = 50) were recruited from one children’s and one adult NHS specialist CF centre. Health professionals (n = 70) were recruited via an e-mail invitation to relevant professional bodies. The key attribute affecting service user testing preferences was no miscarriage risk, while for health professionals, accuracy and early testing were important. The uptake of NIPD by service users was predicted to be high and includes couples that would currently decline invasive testing. Many service users (47%) and health professionals (55.2%) thought the availability of NIPD for CF would increase the pressure to undergo prenatal testing. Most service users (68.5%) thought NIPD for CF should be offered to all pregnant women, whereas more health professionals (68.2%) thought NIPD should be reserved for known carrier couples. The implications for clinical practice are discussed
Distributed lag models for hydrological data
The distributed lag model (DLM), used most prominently in air pollution studies, finds application
wherever the effect of a covariate is delayed and distributed through time. We explore the use of modified formulations
of DLMs to provide flexible varying-coeficient models with smoothness constraints, applicable in any setting in which
lagged covariates are regressed on a time-dependent response. The models are applied to simulated flow and rainfall
data and to flow data from a Scottish mountain river, with particular emphasis on approximating the relationship
between environmental covariates and flow regimes in order to detect the influence of unobserved processes. It was
found that under certain rainfall conditions some of the variability in the influence of rainfall on flow arises through
a complex interaction between antecedent ground wetness and the time-delay in rainfall. The models are able to
identify subtle changes in rainfall response, particularly in the location of peak influence in the lag structure and offer
a computationally attractive approach for fitting DLMs
Spectroscopy of drums and quantum billiards: perturbative and non-perturbative results
We develop powerful numerical and analytical techniques for the solution of
the Helmholtz equation on general domains. We prove two theorems: the first
theorem provides an exact formula for the ground state of an arbirtrary
membrane, while the second theorem generalizes this result to any excited state
of the membrane. We also develop a systematic perturbative scheme which can be
used to study the small deformations of a membrane of circular or square
shapes. We discuss several applications, obtaining numerical and analytical
results.Comment: 29 pages, 12 figures, 7 tabl
The Standard Model Fermion Spectrum From Complex Projective spaces
It is shown that the quarks and leptons of the standard model, including a
right-handed neutrino, can be obtained by gauging the holonomy groups of
complex projective spaces of complex dimensions two and three. The spectrum
emerges as chiral zero modes of the Dirac operator coupled to gauge fields and
the demonstration involves an index theorem analysis on a general complex
projective space in the presence of topologically non-trivial SU(n)xU(1) gauge
fields. The construction may have applications in type IIA string theory and
non-commutative geometry.Comment: 13 pages. Typset using LaTeX and JHEP3 style files. Minor typos
correcte
Topological Constraints on the Charge Distributions for the Thomson Problem
The method of Morse theory is used to analyze the distributions of unit
charges interacting through a repulsive force and constrained to move on the
surface of a sphere -- the Thomson problem. We find that, due to topological
reasons, the system may organize itself in the form of pentagonal structures.
This gives a qualitative account for the interesting ``pentagonal buttons''
discovered in recent numerical work.Comment: 10 pages; dedicated to Rafael Sorkin on his 60th birthda
A view from the watershed
International audiencePapers by H. L. Penman, H. C. Pereira, J. E. Nash and M. Nixon presented at a one-day Symposium to mark the opening of the Institute of Hydrology's new building in 1973 and reprinted from Institute of Hydrology Report No. 20
Relaxation of strained silicon on Si0.5Ge0.5 virtual substrates
Strain relaxation has been studied in tensile strained silicon layers grown on Si0.5Ge0.5 virtual substrates, for layers many times the critical thickness, using high resolution x-ray diffraction. Layers up to 30 nm thick were found to relax less than 2% by the glide of preexisting 60° dislocations. Relaxation is limited because many of these dislocations dissociate into extended stacking faults that impede the dislocation glide. For thicker layers, nucleated microtwins were observed, which significantly increased relaxation to 14%. All these tensile strained layers are found to be much more stable than layers with comparable compressive strain
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