452 research outputs found
Microwave Properties of Ba(0.6)K(0.4)BiO(3) Crystals
We report on field-induced variations of the microwave surface resistance at
9.6 GHz of Ba(0.6)K(0.4)BiO(3) crystals. Energy losses have been investigated
as a function of the static magnetic field in the range of temperatures 4.2 K -
Tc. By analyzing the experimental results in the framework of the Coffey and
Clem model we determine the temperature dependence of the first-penetration
field, upper critical field and depinning frequency. The results show that the
pinning energy of this bismuthate superconductor is weaker than those of
cuprates.Comment: 6 pages, 8 embedded figure
The Effect of Condensed Tannins in Lotus spp. on the Lesser Migratory Grasshopper
Hatchling grasshoppers (Melanoplus sanguinipes Fab.) fed one accession of field grown big trefoil (Lotus uliginosis Schkuhr) containing a tannin content of 56 mg. g-1 FW, had a significantly lower mean weight than hatchlings fed field grown Lotus species and accessions with lower tannin content. Adult female grasshoppers fed L. uliginosis foliage with 32.3 mg.g-1 FW tannin also ate more feed and had a 2-fold higher gut trypsin and chymotrypsin activity than adults fed low tannin L. corniculatus foliage (0.13 mg.g-1 FW tannin). In more controlled experiments, growth at 20o C or 30o C was used to increase tannin in rooted cuttings of L. uliginosis to concentrations ranging from 7 to 195 mg.g-1 FW. Hatchling weight decreased as a function of dietary tannin concentration when fed these clones. Both hatchling weight and survival were affected when hatchlings were fed pelleted wheat seedlings supplemented with purified L. uliginosis tannin preparations
Health research systems in change: the case of ‘Push the Pace’ in the National Institute for Health Research
Background
Those running well-organised health research systems are likely to be alert for ways in which they might increase the quality of the services they provide and address any problems identified. This is important because the efficiency of the research system can have a major impact on how long it takes for new treatments to be developed and reach patients. This opinion piece reflects on the experience and learning of the United Kingdom-based National Institute for Health Research (NIHR) when it implemented continuous improvement activity to improve its processes.
Discussion
This paper describes the structure and work of the NIHR and why, despite is successes as a health research system and ongoing local continuous improvement, it believed in the value of an organisation-wide continuous improvement activity. It did this by implementing an approach called ‘Push the Pace’. Initially, the organisation focused on reducing the amount of time it took for research to transition from an early concept to evidence that changes lives. This scrutiny enabled the NIHR to realise further areas of improvement it could make – additional goals were increased transparency, process simplification, and improved customer and stakeholder experience. We discuss our experience of Push the Pace with reference to literature on continuous improvement.
Conclusion
Continuous improvement is a cycle, an activity that is done constantly and over time, rather than an act or linear activity (such as Push the Pace). We believe that the work of Push the Pace has initiated a strong commitment to a culture of continuous improvement in the NIHR. This is significant because culture change is widely recognised as immensely challenging, particularly in such a large and distributed organisation. However, our biggest challenge will be to enable all staff and stakeholders of the NIHR to participate in the continuous improvement cycle
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Evaluating GPS Receiver Robustness to Ionospheric Scintillation
A method for testing GPS receivers for ionospheric
scintillation robustness has been implemented using a
GPS signal simulator and a statistical model that captures
the characteristics of scintillation relevant to receiver
performance. This technique will help GNSS equipment
manufacturers and users prepare for the approaching solar
maximum by enabling repeatable receiver performance
tests under realistic scintillation conditions. Ionospheric
scintillation can impair the performance of phase tracking
loops in GNSS receivers by introducing deep amplitude
fades and abrupt phase changes in a signal. A statistical
model has been developed that accurately recreates these
effects by shaping the complex spectrum rather than
treating phase and amplitude individually. Generated
scintillation histories have been incorporated into the
output of a GPS signal simulator so that any compatible
receiver can be evaluated without modification. Such a
hardware-in-the-loop approach provides a controlled test
environment and the ability to characterize receiver
performance statistically by running many experiments.
It expands the range of possible test conditions beyond
those available during field testing. The method is simple
to implement, and its value has been demonstrated by a
variety of tests applied to four different receivers.Aerospace Engineering and Engineering Mechanic
Retention of Two-Band Superconductivity in Highly Carbon-Doped MgB2
Tunneling data on MgB_{1.8}C_{0.2} show a reduction in the energy gap of the
pi-bands by a factor of two from undoped MgB2 that is consistent with the Tc
reduction, but inconsistent with the expectations of the dirty limit.
Dirty-limit theory for undoped MgB2 predicts a single gap about three times
larger than measured and a reduced Tc comparable to that measured. Our
heavily-doped samples exhibit a uniform dispersion of C suggestive of
significantly enhanced scattering, and we conclude that the retention of
two-band superconductivity in these samples is caused by a selective
suppression of interband scattering.Comment: 4 pages, 4 figures; added one figure, added one reference, minor
changes to the text, manuscript accepted for publication as a Phys. Rev. B
Rapid Communicatio
Evolution of the local superconducting density of states in ErRhB close to the ferromagnetic transition
We present local tunneling spectroscopy experiments in the superconducting
and ferromagnetic phases of the reentrant superconductor ErRhB. The
tunneling conductance curves jump from showing normal to superconducting
features within a few mK close to the ferromagnetic transition temperature,
with a clear hysteretic behavior. Within the ferromagnetic phase, we do not
detect any superconducting correlations. Within the superconducting phase we
find a peculiar V-shaped density of states at low energies, which is produced
by the magnetically modulated phase that coexists with superconductivity just
before ferromagnetism sets in.Comment: 5 pages, 4 figure
Semi-automated creation of accurate FEM meshes of heritage masonry walls from point cloud data
The structural analysis of buildings requires accurate spatial models. Additionally, pathologies such
as settlement-induced damages are paramount in the assessment of heritage assets. This spatial information is
used as a basis for Finite Element Method (FEM) meshes to evaluate the stability of the structure. Traditional
data acquisition approaches rely on manual measurements which are labor intensive and error prone. Therefore,
major simplifications are made to document structures efficiently. The goal of this research is to provide faster
and more accurate procedures to capture the spatial information required by a FEM.
This paper presents a semi-automated approach to create accurate models of complex heritage buildings for the
purpose of structural analysis. By employing non-destructive techniques such as terrestrial laser scanning and
photogrammetry, a complex mesh of the structure is created. Also, a methodology is proposed to capture crack
information. A stepwise approach is elaborated to illustrate how the spatial information is adapted towards a
FEM mesh. The results show a significant difference between the geometry our model and a traditional wire-
frame model. Not only does accurate modelling result in deviating loads, it also affects the behavior of the
object. Through the proposed approach, experts can develop highly accurate FEM meshes to assess the stability
of the structure up to as-built conditionsPostprint (published version
Field Dependence of Electronic Specific Heat in Two-Band Superconductors
The vortex structure is studied in light of MgB theoretically based on a
two-band superconducting model by means of Bogoliubov-de Gennes framework. The
field dependence of the electronic specific heat coefficient is
focused. The exponent in is shown to
become smaller by adjusting the gap ratio of the two gaps on the major and
minor bands. The observed extremely small value could be
explained reasonably well in this two-band model with the gap ratio .Comment: 5 pages, 4 figures, to be published in J. Phys. Soc. Jp
An iron-sulfur cluster in the family 4 uracil-DNA glycosylases
The 25-kDa Family 4 uracil-DNA glycosylase (UDG) from Pyrobaculum aerophilum has been expressed and purified in large quantities for structural analysis. In the process we observed it to be colored and subsequently found that it contained iron. Here we demonstrate that P. aerophilum UDG has an iron-sulfur center with the EPR characteristics typical of a 4Fe4S high potential iron protein. Interestingly, it does not share any sequence similarity with the classic iron-sulfur proteins, although four cysteines (which are strongly conserved in the thermophilic members of Family 4 UDGs) may represent the metal coordinating residues. The conservation of these residues in other members of the family suggest that 4Fe4S clusters are a common feature. Although 4Fe4S clusters have been observed previously in Nth/MutY DNA repair enzymes, this is the first observation of such a feature in the UDG structural superfamily. Similar to the Nth/MutY enzymes, the Family 4 UDG centers probably play a structural rather than a catalytic role
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