2,055 research outputs found
A novel concept for the manufacture of individual sapphire-metallic hip joint endoprostheses.
At the present time, artificial joints made with metallic, ceramic, metal-polymeric or ceramicpolymeric
friction pairs substituting for the natural biomechanic articulations "head of the hip
joint-acetabulum" are widely used for endoprosthetic operations on hip joints. Experience
gained in the course of more than 2000 operations has shown that along with the
advantageous properties of modern endoprosthetic constructions made of metal, ceramics
and polymers, they have certain drawbacks. Among them are insufficient biological inertness
and susceptibility to excessive wear of the friction pair components. In addition, as a result of
wear of the hinge friction pair, toxic and oncologically dangerous products of degradation
accumulate in the different organs and tissues. This in turn results in severe complications and
demands correspondingly complicated corrective intervention, often leading to worse
disability than that which the original operation was designed to cure. The aim of the study
reported here was the development and clinical validation of a highly effective and long-lived
hip joint endoprosthesis with a sapphire head whose wear capacity is superior to all others.
The endoprosthesis consists of a metallic pedicle, a dismountable articulation (metallic necklayer
of supramolecular polyethylene-sapphire head) and an acetabular cup. The endoprostheses
with the sapphire head proved themselves positively in clinical trials and are
considered to be highly promising for future applications
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Associated reading skills in children with a history of Specific Language Impairment (SLI)
A large cohort of 200 eleven-year-old children with Specific Language Impairment (SLI) were assessed on basic reading accuracy and on reading comprehension as well as language tasks. Reading skills were examined descriptively and in relation to early language and literacy factors. Using stepwise regression analyses in which age and nonverbal IQ were controlled for, it was found that a single word reading measure taken at 7 years was unsurprisingly a strong predictor of the two different types of reading ability. However, even with this measure included, a receptive syntax task (TROG) entered when reading accuracy score was the DV. Furthermore, a test of expressive syntax/narrative and a receptive syntax task completed at 7 years entered into the model for word reading accuracy. When early reading accuracy was excluded from the analyses, early phonological skills also entered as a predictor of both reading accuracy and comprehension at 11 years. The group of children with a history of SLI were then divided into those with no literacy difficulties at 11 and those with some persisting literacy impairment. Using stepwise logistic regression, and again controlling for IQ and age, 7 years receptive syntax score (but not tests of phonology, expressive vocabulary or expressive syntax/narrative) entered as a positive predictor of membership of the ‘no literacy problems’ group regardless of whether early reading accuracy was controlled for in step one. The findings are discussed in relation to the overlap of SLI and dyslexia and the long term sequelae of language impairment
Adsorption of colloidal particles in the presence of external field
We present a new class of sequential adsorption models in which the adsorbing
particles reach the surface following an inclined direction (shadow models).
Capillary electrophoresis, adsorption in the presence of a shear or on an
inclined substrate are physical manifestations of these models. Numerical
simulations are carried out to show how the new adsorption mechanisms are
responsible for the formation of more ordered adsorbed layers and have
important implications in the kinetics, in particular modifying the jamming
limit.Comment: LaTex file, 3 figures available upon request, to appear in
Phys.Rev.Let
Coarsening dynamics of adsorption processes with diffusional relaxation
We investigate the late coarsening stages of one dimensional adsorption
processes with diffusional relaxation. The nonequilibrium domain size
distribution is studied by means of the field theory associated to the
stochastic evolution. An exact asymptotic solution satisfying dynamical scaling
is given for cluster sizes smaller than the average domain length. Our results
are supported and compared with Monte Carlo simulations.Comment: 5 pages, 1 Postscript figur
Secondary gamma-ray production in a coded aperture mask
The application of the coded aperture mask to high energy gamma-ray astronomy will provide the capability of locating a cosmic gamma-ray point source with a precision of a few arc-minutes above 20 MeV. Recent tests using a mask in conjunction with drift chamber detectors have shown that the expected point spread function is achieved over an acceptance cone of 25 deg. A telescope employing this technique differs from a conventional telescope only in that the presence of the mask modifies the radiation field in the vicinity of the detection plane. In addition to reducing the primary photon flux incident on the detector by absorption in the mask elements, the mask will also be a secondary radiator of gamma-rays. The various background components in a CAMTRAC (Coded Aperture Mask Track Chamber) telescope are considered. Monte-Carlo calculations are compared with recent measurements obtained using a prototype instrument in a tagged photon beam line
Operating characteristics of a prototype high energy gamma-ray telescope
The field of gamma-ray astronomy in the energy range from ten to several hundred MeV is severely limited by the angular resolution that can be achieved by present instruments. The identification of some of the point sources found by the COS-B mission and the resolution of detailed structure existing in those sources may depend on the development of a new class of instrument. The coded aperture mask telescope, used successfully at X-ray energies hold the promise of being such an instrument. A prototype coded aperture telescope was operated in a tagged photon beam ranging in energy from 23 to 123 MeV. The purpose of the experiment was to demonstrate the feasibility of operating a coded aperture mask telescope in this energy region. Some preliminary results and conclusions drawn from some of the data resulting from this experiment are presented
Shaping electron wave functions in a carbon nanotube with a parallel magnetic field
A magnetic field, through its vector potential, usually causes measurable
changes in the electron wave function only in the direction transverse to the
field. Here we demonstrate experimentally and theoretically that in carbon
nanotube quantum dots, combining cylindrical topology and bipartite hexagonal
lattice, a magnetic field along the nanotube axis impacts also the longitudinal
profile of the electronic states. With the high (up to 17T) magnetic fields in
our experiment the wave functions can be tuned all the way from "half-wave
resonator" shape, with nodes at both ends, to "quarter-wave resonator" shape,
with an antinode at one end. This in turn causes a distinct dependence of the
conductance on the magnetic field. Our results demonstrate a new strategy for
the control of wave functions using magnetic fields in quantum systems with
nontrivial lattice and topology.Comment: 5 figure
Model of correlated sequential adsorption of colloidal particles
We present results of a new model of sequential adsorption in which the
adsorbing particles are correlated with the particles attached to the
substrate. The strength of the correlations is measured by a tunable parameter
. The model interpolates between free ballistic adsorption in the limit
and a strongly correlated phase, appearing for
and characterized by the emergence of highly ordered structures. The phenomenon
is manifested through the analysis of several magnitudes, as the jamming limit
and the particle-particle correlation function. The effect of correlations in
one dimension manifests in the increased tendency to particle chaining in the
substrate. In two dimensions the correlations induce a percolation transition,
in which a spanning cluster of connected particles appears at a certain
critical value . Our study could be applicable to more general
situations in which the coupling between correlations and disorder is relevant,
as for example, in the presence of strong interparticle interactions.Comment: 6 pages, 8 EPS figures. Phys. Rev. E (in press
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