13,210 research outputs found
Cost effectiveness analysis of different approaches of screening for familial hypercholesterolaemia
Objectives To assess the cost effectiveness of
strategies to screen for and treat familial
hypercholesterolaemia.
Design Cost effectiveness analysis. A care pathway for
each patient was delineated and the associated
probabilities, benefits, and costs were calculated.
Participants Simulated population aged 16Â54 years
in England and Wales.
Interventions Identification and treatment of patients
with familial hypercholesterolaemia by universal
screening, opportunistic screening in primary care,
screening of people admitted to hospital with
premature myocardial infarction, or tracing family
members of affected patients.
Main outcome measure Cost effectiveness calculated
as cost per life year gained (extension of life
expectancy resulting from intervention) including
estimated costs of screening and treatment.
Results Tracing of family members was the most cost
effective strategy (£3097 (&5066, $4479) per life year
gained) as 2.6 individuals need to be screened to
identify one case at a cost of £133 per case detected. If
the genetic mutation was known within the family
then the cost per life year gained (£4914) was only
slightly increased by genetic confirmation of the
diagnosis. Universal population screening was least
cost effective (£13 029 per life year gained) as 1365
individuals need to be screened at a cost of £9754 per
case detected. For each strategy it was more cost
effective to screen younger people and women.
Targeted strategies were more expensive per person
screened, but the cost per case detected was lower.
Population screening of 16 year olds only was as cost
effective as family tracing (£2777 with a clinical
confirmation).
Conclusions Screening family members of people
with familial hypercholesterolaemia is the most cost
effective option for detecting cases across the whole
population
Determination of the refractive index of organic material from atmospheric aerosol over the visible wavelength range using optical tweezers
Optical trapping combined with Mie spectroscopy is a new technique used to record the refractive index of insoluble organic material extracted from atmospheric aerosol samples over a wide wavelength range. The refractive index of the insoluble organic extracts was shown to follow a Cauchy equation between 460 and 700 nm for organic aerosol extracts collected from urban (London) and remote (Antarctica) locations. Cauchy coefficients for the remote sample were for the Austral summer and gave the Cauchy coefficients of A  =  1.467 and B  =  1000 nm2 with a real refractive index of 1.489 at a wavelength of 589 nm. Cauchy coefficients for the urban samples varied with season, with extracts collected during summer having Cauchy coefficients of A  =  1.465  ±  0.005 and B  =  4625  ±  1200 nm2 with a representative real refractive index of 1.478 at a wavelength of 589 nm, whilst samples extracted during autumn had larger Cauchy coefficients of A  =  1.505 and B  =  600 nm2 with a representative real refractive index of 1.522 at a wavelength of 589 nm. The refractive index of absorbing aerosol was also recorded. The absorption Ångström exponent was determined for woodsmoke and humic acid aerosol extract. Typical values of the Cauchy coefficient for the woodsmoke aerosol extract were A  =  1.541  ±  0.03 and B  =  14 800  ±  2900 nm2, resulting in a real refractive index of 1.584  ±  0.007 at a wavelength of 589 nm and an absorption Ångström exponent of 8.0. The measured values of refractive index compare well with previous monochromatic or very small wavelength range measurements of refractive index. In general, the real component of the refractive index increases from remote to urban to woodsmoke. A one-dimensional radiative-transfer calculation of the top-of-the-atmosphere albedo was applied to model an atmosphere containing a 3 km thick layer of aerosol comprising pure water, pure insoluble organic aerosol, or an aerosol consisting of an aqueous core with an insoluble organic shell. The calculation demonstrated that the top-of-the-atmosphere albedo increases by 0.01 to 0.04 for pure organic particles relative to water particles of the same size and that the top-of-the-atmosphere albedo increases by 0.03 for aqueous core-shell particles as volume fraction of the shell material increases to 25 %
Atomic-scale structure of the SrTiO3(001)-c(6x2) reconstruction: Experiments and first-principles calculations
The c(6x2) is a reconstruction of the SrTiO3(001) surface that is formed
between 1050-1100oC in oxidizing annealing conditions. This work proposes a
model for the atomic structure for the c(6x2) obtained through a combination of
results from transmission electron diffraction, surface x-ray diffraction,
direct methods analysis, computational combinational screening, and density
functional theory. As it is formed at high temperatures, the surface is complex
and can be described as a short-range ordered phase featuring microscopic
domains composed of four main structural motifs. Additionally, non-periodic
TiO2 units are present on the surface. Simulated scanning tunneling microscopy
images based on the electronic structure calculations are consistent with
experimental images
Immersed nano-sized Al dispersoids in an Al matrix; effects on the structural and mechanical properties by Molecular Dynamics simulations
We used molecular dynamics simulations based on a potential model in analogy
to the Tight Binding scheme in the Second Moment Approximation to simulate the
effects of aluminum icosahedral grains (dispersoids) on the structure and the
mechanical properties of an aluminum matrix. First we validated our model by
calculating several thermodynamic properties referring to the bulk Al case and
we found good agreement with available experimental and theoretical data.
Afterwards, we simulated Al systems containing Al clusters of various sizes. We
found that the structure of the Al matrix is affected by the presence of the
dispersoids resulting in well ordered domains of different symmetries that were
identified using suitable Voronoi analysis. In addition, we found that the
increase of the grain size has negative effect on the mechanical properties of
the nanocomposite as manifested by the lowering of the calculated bulk moduli.
The obtained results are in line with available experimental data.Comment: 15 pages, 8 figures. Submitted to J. Phys: Condens. Matte
Molecular dynamics simulations of lead clusters
Molecular dynamics simulations of nanometer-sized lead clusters have been
performed using the Lim, Ong and Ercolessi glue potential (Surf. Sci. {\bf
269/270}, 1109 (1992)). The binding energies of clusters forming crystalline
(fcc), decahedron and icosahedron structures are compared, showing that fcc
cuboctahedra are the most energetically favoured of these polyhedral model
structures. However, simulations of the freezing of liquid droplets produced a
characteristic form of ``shaved'' icosahedron, in which atoms are absent at the
edges and apexes of the polyhedron. This arrangement is energetically favoured
for 600-4000 atom clusters. Larger clusters favour crystalline structures.
Indeed, simulated freezing of a 6525-atom liquid droplet produced an imperfect
fcc Wulff particle, containing a number of parallel stacking faults. The
effects of temperature on the preferred structure of crystalline clusters below
the melting point have been considered. The implications of these results for
the interpretation of experimental data is discussed.Comment: 11 pages, 18 figues, new section added and one figure added, other
minor changes for publicatio
The role of structural evolution on the quantum conductance behavior of gold nanowires during stretching
Gold nanowires generated by mechanical stretching have been shown to adopt
only three kinds of configurations where their atomic arrangements adjust such
that either the [100], [111] or [110] zone axes lie parallel to the elongation
direction. We have analyzed the relationship between structural rearrangements
and electronic transport behavior during the elongation of Au nanowires for
each of the three possibilities. We have used two independent experiments to
tackle this problem, high resolution transmission high resolution electron
microscopy to observe the atomic structure and a mechanically controlled break
junction to measure the transport properties. We have estimated the conductance
of nanowires using a theoretical method based on the extended H\"uckel theory
that takes into account the atom species and their positions. Aided by these
calculations, we have consistently connected both sets of experimental results
and modeled the evolution process of gold nanowires whose conductance lies
within the first and third conductance quanta. We have also presented evidence
that carbon acts as a contaminant, lowering the conductance of one-atom-thick
wires.Comment: 10 page
Surface-reconstructed Icosahedral Structures for Lead Clusters
We describe a new family of icosahedral structures for lead clusters. In
general, structures in this family contain a Mackay icosahedral core with a
reconstructed two-shell outer-layer. This family includes the anti-Mackay
icosahedra, which have have a Mackay icosahedral core but with most of the
surface atoms in hexagonal close-packed positions. Using a many-body glue
potential for lead, we identify two icosahedral structures in this family which
have the lowest energies of any known structure in the size range from 900 to
15000 lead atoms. We show that these structures are stabilized by a feature of
the many-body glue part of the interatomic potential.Comment: 9 pages, 8 figure
Soil, Snow, Weather, and Sub-Surface Storage Data from a Mountain Catchment in the Rain–Snow Transition Zone
A comprehensive hydroclimatic data set is presented for the 2011 water year to improve understanding of hydrologic processes in the rain-snow transition zone. This type of dataset is extremely rare in scientific literature because of the quality and quantity of soil depth, soil texture, soil moisture, and soil temperature data. Standard meteorological and snow cover data for the entire 2011 water year are included, which include several rain-on-snow events. Surface soil textures and soil depths from 57 points are presented as well as soil texture profiles from 14 points. Meteorological data include continuous hourly shielded, unshielded, and wind corrected precipitation, wind speed, air temperature, relative humidity, dew point temperature, and incoming solar and thermal radiation data. Sub-surface data included are hourly soil moisture data from multiple depths from 7 soil profiles within the catchment, and soil temperatures from multiple depths from 2 soil profiles. Hydrologic response data include hourly stream discharge from the catchment outlet weir, continuous snow depths from one location, intermittent snow depths from 5 locations, and snow depth and density data from ten weekly snow surveys. Though it represents only a single water year, the presentation of both above and below ground hydrologic condition makes it one of the most detailed and complete hydro-climatic datasets from the climatically sensitive rainsnow transition zone for a wide range of modeling and descriptive studies. Data are available at doi:10.1594/PANGAEA.819837
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