4,063 research outputs found
A survey of parallel algorithms for fractal image compression
This paper presents a short survey of the key research work that has been undertaken in the application of parallel algorithms for Fractal image compression. The interest in fractal image compression techniques stems from their ability to achieve high compression ratios whilst maintaining a very high quality in the reconstructed image. The main drawback of this compression method is the very high computational cost that is associated with the encoding phase. Consequently, there has been significant interest in exploiting parallel computing architectures in order to speed up this phase, whilst still maintaining the advantageous features of the approach. This paper presents a brief introduction to fractal image compression, including the iterated function system theory upon
which it is based, and then reviews the different techniques that have been, and can be, applied in order to parallelize the compression algorithm
The North Wyke Farm Platform: Field Survey Data
The North Wyke Farm Platform (NWFP) was established in 2010 to study and improve grassland livestock production at the farm-scale. The NWFP uses a combination of environmental sensors, routine field and lab-based measurements, and detailed management records to monitor livestock and crop production, emissions to water, emissions to air, soil health, and biodiversity. The rich NWFP datasets help researchers to evaluate the effectiveness of different grassland (and arable) farming systems, which in turn, contributes to the development of sustainable, resilient and net zero land management strategies. This document serves as a user guide to the sub-catchment high-resolution (within-field) and low-resolution (field-level) surveys collected on the NWFP. Most surveys are site-wide across all the NWFP fields, while some are specific to a given triplet or small group of NWFP catchments. Low resolution surveys are site wide and are carried out quarterly and routinely as a management tool. This document is associated with other dedicated user guides that detail the design, establishment and development of the NWFP, field events, and the quality control process of datasets
Impact of Scottish vocational qualifications on residential child care : have they fulfilled the promise?
This article will present findings from a doctoral study exploring the impact of 'SVQ Care: Promoting Independence (level III)' within children's homes. The study focuses on the extent to which SVQs enhance practice and their function within a 'learning society'. A total of 30 staff were selected from seven children's homes in two different local authority social work departments in Scotland. Each member of staff was interviewed on four separate occasions over a period of 9 months. Interviews were structured using a combination of repertory grids and questions. Particular focus was given to the assessment process, the extent to which SVQs enhance practice and the learning experiences of staff. The findings suggest that there are considerable deficiencies both in terms of the SVQ format and the way in which children's homes are structured for the assessment of competence. Rather than address the history of failure within residential care, it appears that SVQs have enabled the status quo to be maintained whilst creating an 'illusion' of change within a learning society
The European Court of Human Rights and the Hague Child Abduction Convention:prioritising return or reflection?
Nonlinear electron transport in normally pinched-off quantum wire
Nonlinear electron transport in normally pinched-off quantum wires was
studied. The wires were fabricated from AlGaAs/GaAs heterostructures with
high-mobility two-dimensional electron gas by electron beam lithography and
following wet etching. At certain critical source-drain voltage the samples
exhibited a step rise of the conductance. The differential conductance of the
open wires was noticeably lower than e^2/h as far as only part of the
source-drain voltage dropped between source contact and saddle-point of the
potential relief along the wire. The latter limited the electron flow injected
to the wire. At high enough source-drain voltages the decrease of the
differential conductance due to the real space transfer of electrons from the
wire in GaAs to the doped AlGaAs layer was found. In this regime the sign of
differential magnetoconductance was changed with reversing the direction of the
current in the wire or the magnetic field, whet the magnetic field lies in the
heterostructure plane and is directed perpendicular to the current. The
dependence of the differential conductance on the magnetic field and its
direction indicated that the real space transfer events were mainly mediated by
the interface scattering.Comment: LaTeX 2e (epl.cls) 6 pages, 3 figure
A deep wide-field sub-mm survey of the Carina Nebula complex
The Great Nebula in Carina is a superb location in which to study the physics
of violent massive star-formation and the resulting feedback effects, including
cloud dispersal and triggered star-formation. In order to reveal the cold dusty
clouds in the Carina Nebula complex, we used the Large APEX Bolometer Camera
LABOCA at the APEX telescope to map a 1.25 deg x 1.25 deg (= 50 x 50 pc^2)
region at 870 micrometer. From a comparison to Halpha images we infer that
about 6% of the 870 micrometer flux in the observed area is likely free-free
emission from the HII region, while about 94% of the flux is very likely
thermal dust emission. The total (dust + gas) mass of all clouds for which our
map is sensitive is ~ 60 000 Msun, in good agreement with the mass of the
compact clouds in this region derived from 13CO line observations. We generally
find good agreement in the cloud morphology seen at 870 micrometer and the
Spitzer 8 micrometer emission maps, but also identify a prominent infrared dark
cloud. Finally, we construct a radiative transfer model for the Carina Nebula
complex that reproduces the observed integrated spectral energy distribution
reasonably well. Our analysis suggests a total gas + dust mass of about 200000
Msun in the investigated area; most of this material is in the form of
molecular clouds, but a widely distributed component of (partly) atomic gas,
containing up to ~ 50% of the total mass, may also be present. Currently, only
some 10% of the gas is in sufficiently dense clouds to be immediately available
for future star formation, but this fraction may increase with time owing to
the ongoing compression of the strongly irradiated clouds and the expected
shockwaves of the imminent supernova explosions.Comment: Accepted for publication in Astronomy & Astrophysics; high-quality
pre-prints can be obtained from
http://www.usm.uni-muenchen.de/people/preibisch/publications.htm
Genetic evidence for different adiposity phenotypes and their opposing influence on ectopic fat and risk of cardiometabolic disease
To understand the causal role of adiposity and ectopic fat in type 2 diabetes and cardiometabolic diseases, we aimed to identify two clusters of adiposity genetic variants, one with ‘adverse’ metabolic effects (UFA) and the other with, paradoxically, ‘favourable’ metabolic effects (FA). We performed a multivariate genome-wide association study using body fat percentage and metabolic biomarkers from UK Biobank and identified 38 UFA and 36 FA variants. Adiposity-increasing alleles were associated with an adverse metabolic profile, higher risk of disease, higher CRP, higher fat in subcutaneous and visceral adipose tissue, liver and pancreas for UFA; and a favourable metabolic profile, lower risk of disease, higher CRP, higher subcutaneous adipose tissue but lower liver fat for FA. We detected no sexual dimorphism. The Mendelian randomization studies provided evidence for risk-increasing effect of UFA and protective effect of FA on type 2 diabetes, heart disease, hypertension, stroke, non-alcoholic fatty liver disease and polycystic ovary syndrome. FA is distinct from UFA by its association with lower liver fat, and protection from cardiometabolic diseases; it was not associated with visceral or pancreatic fat. Understanding the difference in FA and UFA may lead to new insights in preventing, predicting and treating of cardiometabolic diseases
Optimization of a high work function solution processed vanadium oxide hole-extracting layer for small molecule and polymer organic photovoltaic cells
We report a method of fabricating a high work function, solution processable vanadium oxide (V2Ox(sol)) hole-extracting layer. The atmospheric processing conditions of film preparation have a critical influence on the electronic structure and stoichiometry of the V2Ox(sol), with a direct impact on organic photovoltaic (OPV) cell performance. Combined Kelvin probe (KP) and ultraviolet photoemission spectroscopy (UPS) measurements reveal a high work function, n-type character for the thin films, analogous to previously reported thermally evaporated transition metal oxides. Additional states within the band gap of V2Ox(sol) are observed in the UPS spectra and are demonstrated using X-ray photoelectron spectroscopy (XPS) to be due to the substoichiometric nature of V2Ox(sol). The optimized V2Ox(sol) layer performance is compared directly to bare indium–tin oxide (ITO), poly(ethyleneoxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and thermally evaporated molybdenum oxide (MoOx) interfaces in both small molecule/fullerene and polymer/fullerene structures. OPV cells incorporating V2Ox(sol) are reported to achieve favorable initial cell performance and cell stability attributes
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