3,487 research outputs found
Room temperature self-assembly of mixed nanoparticles into complex material systems and devices
The ability to manufacture nanomaterials with complex and structured
composition using otherwise incompatible materials increasingly underpins the
next generation of technologies. This is translating into growing efforts
integrating a wider range of materials onto key technology platforms1 - in
photonics, one such platform is silica, a passive, low loss and robust medium
crucial for efficient optical transport2. Active functionalisation, either
through added gain or nonlinearity, is mostly possible through the integration
of active materials3, 4. The high temperatures used in manufacturing of silica
waveguides, unfortunately, make it impossible to presently integrate many
organic and inorganic species critical to achieving this extended
functionality. Here, we demonstrate the fabrication of novel waveguides and
devices made up of complex silica based materials using the self-assembly of
nanoparticles. In particular, the room temperature fabrication of silica
microwires integrated with organic dyes (Rhodamine B) and single photon
emitting nanodiamonds is presented.Comment: Key words: nanotechnology, nanoparticles, self-assembly, quantum
science, singel photon emitters, telecommunications, sensing, new materials,
integration of incompatible materials, silica, glass, breakthrough scienc
A questionnaire to identify patellofemoral pain in the community: an exploration of measurement properties
Background
Community-based studies of patellofemoral pain (PFP) need a questionnaire tool that discriminates between those with and those without the condition. To overcome these issues, we have designed a self-report questionnaire which aims to identify people with PFP in the community.
Methods
Study designs: comparative study and cross-sectional study.
Study population: comparative study: PFP patients, soft-tissue injury patients and adults without knee problems. Cross-sectional study: adults attending a science festival.
Intervention: comparative study participants completed the questionnaire at baseline and two weeks later. Cross-sectional study participants completed the questionnaire once.
The optimal scoring system and threshold was explored using receiver operating characteristic curves, test-retest reliability using Cohenâs kappa and measurement error using Bland-Altman plots and standard error of measurement. Known-group validity was explored by comparing PFP prevalence between genders and age groups.
Results
Eighty-four participants were recruited to the comparative study. The receiver operating characteristic curves suggested limiting the questionnaire to the clinical features and knee pain map sections (AUC 0.97 95 % CI 0.94 to 1.00). This combination had high sensitivity and specificity (over 90 %). Measurement error was less than the mean difference between the groups. Testâretest reliability estimates suggest good agreement (Nâ=â51, kâ=â0.74, 95 % CI 0.52â0.91). The cross-sectional study (Nâ=â110) showed expected differences between genders and age groups but these were not statistically significant.
Conclusion
A shortened version of the questionnaire, based on clinical features and a knee pain map, has good measurement properties. Further work is needed to validate the questionnaire in community samples
The potential of ground gravity measurements to validate GRACE data
New satellite missions are returning high precision, time-varying, satellite measurements of the Earthâs gravity field. The GRACE mission is now in its calibration/- validation phase and first results of the gravity field solutions are imminent. We consider here the possibility of external validation using data from the superconducting gravimeters in the European sub-array of the Global Geodynamics Project (GGP) as âground truthâ for comparison with GRACE. This is a pilot study in which we use 14 months of 1-hour data from the beginning of GGP (1 July 1997) to 30 August 1998, when the Potsdam instrument was relocated to South Africa. There are 7 stations clustered in west central Europe, and one station, Metsahovi in Finland. We remove local tides, polar motion, local and global air pressure, and instrument drift and then decimate to 6-hour samples. We see large variations in the time series of 5â10<i>”</i>gal between even some neighboring stations, but there are also common features that correlate well over the 427-day period. The 8 stations are used to interpolate a minimum curvature (gridded) surface that extends over the geographical region. This surface shows time and spatial coherency at the level of 2â 4<i>”</i>gal over the first half of the data and 1â2<i>”</i>gal over the latter half. The mean value of the surface clearly shows a rise in European gravity of about 3”gal over the first 150 days and a fairly constant value for the rest of the data. The accuracy of this mean is estimated at 1<i>”</i>gal, which compares favorably with GRACE predictions for wavelengths of 500 km or less. Preliminary studies of hydrology loading over Western Europe shows the difficulty of correlating the local hydrology, which can be highly variable, with large-scale gravity variations.<br><br><b>Key words. </b>GRACE, satellite gravity, superconducting gravimeter, GGP, ground trut
Who the hell was that? Stories, bodies and actions in the world
This article explores a two-way relationship between stories and the experiential actions of bodies in the world. Through an autoethnographic approach, the article presents a series of interlinked story fragments in an effort to show and evoke a feel for the ways in which stories, bodies, and actions influence and shape each other over time. It offers some reflections on the experiences the stories portray from the perspective of a social constructionist conception of narrative theory and suggest that while stories exert a powerful influence on the actions of our bodies, our bodies intrude on or âtalk backâ to this process because bodies have an existence beyond stories
Improved peroxide biosensor based on Horseradish Peroxidase/Carbon Nanotube on a thiol-modified gold electrode
A new 3-dimensional (3D) network of crosslinked Horseradish Peroxidase/Carbon Nanotube (HRP/CNT) on a thiol-modified Au surface has been described in order to build up the effective electrical wiring of the enzyme units with the electrode. The synthesized 3D HRP/CNT network has been characterized with cyclic voltammetry and amperometry which results the establishment of direct electron transfer between the redox active unit of HRP and the Au surface. Electrochemical measurements reveal that the high biological activity and stability is exhibited by the immobilized HRP and a quasi-reversible redox peak of the redox centre of HRP was observed at about â0.355 and â0.275 V vs. Ag/AgCl. The electron transfer rate constant, KS and electron transfer co-efficient α were found as 0.57 sâ1 and 0.42, respectively. Excellent electrocatalytic activity for the reduction of H2O2 was exhibited by the developed biosensor. The proposed biosensor modified with HRP/CNT 3D network displays a broader linear range and a lower detection limit for H2O2 determination. The linear range is from 1.0 Ă 10â7 to 1.2 Ă 10â4 M with a detection limit of 2.2.0 Ă 10â8 M at 3 Ï. The MichaeliesâMenten constant Kapp M value is estimated to be 0.19 mM. Moreover, this biosensor exhibits very high sensitivity, good reproducibility and long-time stability
The Effect of Crystallization on the Pulsations of White Dwarf Stars
We consider the pulsational properties of white dwarf star models with
temperatures appropriate for the ZZ Ceti instability strip and with masses
large enough that they should be substantially crystallized. Our work is
motivated by the existence of a potentially crystallized DAV, BPM 37093, and
the expectation that digital surveys in progress will yield many more such
massive pulsators.
A crystallized core makes possible a new class of oscillations, the torsional
modes, although we expect these modes to couple at most weakly to any motions
in the fluid and therefore to remain unobservable. The p-modes should be
affected at the level of a few percent in period, but are unlikely to be
present with observable amplitudes in crystallizing white dwarfs any more than
they are in the other ZZ Ceti's. Most relevant to the observed light variations
in white dwarfs are the g-modes. We find that the kinetic energy of these modes
is effectively excluded from the crystallized cores of our models. As
increasing crystallization pushes these modes farther out from the center, the
mean period spacing between radial overtones increases substantially with the
crystallized mass fraction. In addition, the degree and structure of mode
trapping is affected. The fact that some periods are strongly affected by
changes in the crystallized mass fraction while others are not suggests that we
may be able to disentangle the effects of crystallization from those due to
different surface layer masses.Comment: 18 pages, 5 figures, accepted on 1999 July 2 for publication in the
Astrophysical Journa
Structural lubricity: Role of dimension and symmetry
When two chemically passivated solids are brought into contact, interfacial
interactions between the solids compete with intrabulk elastic forces. The
relative importance of these interactions, which are length-scale dependent,
will be estimated using scaling arguments. If elastic interactions dominate on
all length scales, solids will move as essentially rigid objects. This would
imply superlow kinetic friction in UHV, provided wear was absent. The results
of the scaling study depend on the symmetry of the surfaces and the
dimensionalities of interface and solids. Some examples are discussed
explicitly such as contacts between disordered three-dimensional solids and
linear bearings realized from multiwall carbon nanotubes.Comment: 7 pages, 1 figur
Quantitative Models and Implicit Complexity
We give new proofs of soundness (all representable functions on base types
lies in certain complexity classes) for Elementary Affine Logic, LFPL (a
language for polytime computation close to realistic functional programming
introduced by one of us), Light Affine Logic and Soft Affine Logic. The proofs
are based on a common semantical framework which is merely instantiated in four
different ways. The framework consists of an innovative modification of
realizability which allows us to use resource-bounded computations as realisers
as opposed to including all Turing computable functions as is usually the case
in realizability constructions. For example, all realisers in the model for
LFPL are polynomially bounded computations whence soundness holds by
construction of the model. The work then lies in being able to interpret all
the required constructs in the model. While being the first entirely semantical
proof of polytime soundness for light logi cs, our proof also provides a
notable simplification of the original already semantical proof of polytime
soundness for LFPL. A new result made possible by the semantic framework is the
addition of polymorphism and a modality to LFPL thus allowing for an internal
definition of inductive datatypes.Comment: 29 page
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