1,108 research outputs found
Hydroxyapatite promotes superior adhesion and proliferation of telomerase transformed keratocytes in comparison with inert plastic skirt materials used in leading contemporary keratoprostheses
Aim: Published clinical series suggest the osteoodontokeratoprosthesis (OOKP) may have a lower extrusion rate than current synthetic keratoprostheses. The OOKP is anchored in the eye wall by autologous tooth. The authors’ aim was to compare adhesion, proliferation, and morphology for telomerase transformed keratocytes seeded on calcium hydroxyapatite (the principal mineral constituent of tooth) and materials used in the anchoring elements of commercially available synthetic keratoprostheses.
Methods: Test materials were hydroxyapatite, polytetrafluoroethylene (PTFE), polyhydroxyethyl methacrylate (HEMA), and glass (control). Cell adhesion and viability were quantified at 4 hours, 24 hours, and 1 week using a calcein-AM/EthD-1 viability/cytotoxicity assay. Focal contact expression and cytoskeletal organisation were studied at 24 hours by confocal microscopy with immunoflourescent labelling. Further studies of cell morphology were performed using light and scanning electron microscopy.
Results: Live cell counts were significantly greater on hydroxyapatite surfaces at each time point (p<0.04). Dead cell counts were significantly higher for PTFE at 7 days (p<0.002). Β1 integrin expression was highest on hydroxyapatite. Adhesion structures were well expressed in flat, spread out keratocytes on both HA and glass. Keratocytes tended to be thinner and spindle shaped on PTFE. The relatively few keratocytes visible on HEMA test surfaces were rounded and poorly adherent.
Conclusions: Keratocyte adhesion, spreading, and viability on hydroxyapatite test surfaces is superior to that seen on PTFE and HEMA. Improving the initial cell adhesion environment in the skirt element of keratoprostheses may enhance tissue integration and reduce device failure rates
Interaction of 14-3-3 with Signaling Proteins Is Mediated by the Recognition of Phosphoserine
AbstractThe highly conserved and ubiquitously expressed 14-3-3 family of proteins bind to a variety of proteins involved in signal transduction and cell cycle regulation. The nature and specificity of 14-3-3 binding is, however, not known. Here we show that 14-3-3 is a specific phosphoserine-binding protein. Using a panel of phosphorylated peptides based on Raf-1, we have defined the 14-3-3 binding motif and show that most of the known 14-3-3 binding proteins contain the motif. Peptides containing the motif could disrupt 14-3-3 complexes and inhibit maturation of Xenopus laevis oocytes. These results suggest that the interactions of 14-3-3 with signaling proteins are critical for the activation of signaling proteins. Our findings also suggest novel roles for serine/threonine phosphorylation in the assembly of protein–protein complexes
Micro-enterprises: small enough to care?
This report presents findings of an evaluation of micro-enterprises in social care in England, which ran from 2013 to 2015.
Organisations are here classed as micro if they employ five or fewer full-time equivalent staff. The aim of the project was to test the extent to which micro-enterprises deliver services that are personalised, valued, innovative and cost-effective, and how they compare with small, medium and large providers.
Working in three parts of the country, researchers compared 27 organisations providing care and support, of which 17 were micro-enterprises, 2 were small, 4 were medium and 4 were large. The project team interviewed and surveyed 143 people (staff, older people, people with disabilities and carers) who received support from the 27 providers.
The findings presented are relevant to people who use services and their families; social care commissioners; regulators and policy makers at a local and national level; people who provide care services; and social entrepreneurs who are considering setting up micro forms of support.
The research was based at the University of Birmingham. It was funded by the Economic and Social Research Council (ESRC), as part of a project entitled Does Smaller mean Better? Evaluating Micro-enterprises in Adult Social Care (ESRC Standard Grant ES/K002317/1)
Crack propagation and fracture in silicon wafers under thermal stress
The behaviour of microcracks in silicon during thermal annealing has been studied using in situ X-ray diffraction imaging. Initial cracks are produced with an indenter at the edge of a conventional Si wafer, which was heated under temperature gradients to produce thermal stress. At temperatures where Si is still in the brittle regime, the strain may accumulate if a microcrack is pinned. If a critical value is exceeded either a new or a longer crack will be formed, which results with high probability in wafer breakage. The strain reduces most efficiently by forming (hhl) or (hkl) crack planes of high energy instead of the expected low-energy cleavage planes like {111}. Dangerous cracks, which become active during heat treatment and may shatter the whole wafer, can be identified from diffraction images simply by measuring the geometrical dimensions of the strain-related contrast around the crack tip. Once the plastic regime at higher temperature is reached, strain is reduced by generating dislocation loops and slip bands and no wafer breakage occurs. There is only a small temperature window within which crack propagation is possible during rapid annealing
Implications of reflectance measurements on the mechanism for superconductivity in MgB
Recent optical studies in c-axis oriented superconducting MgB films
indicate that the electron-phonon coupling is weak [tu01]. We reinforce this
conclusion by examining the raw reflectance data; its frequency dependence is
incompatible with strong electron-phonon scattering. This is further
strengthened by analysis of the real part of the conductivity, and by the
temperature dependence of the effective Drude scattering rate. Using a
realistic electron-phonon spectral shape [kong01], we find , in agreement with Tu et al. [tu01]. To the extent that
, this disagrees sharply with model
calculations [kong01,kortus01,an01], and is far too low to provide the means
for K. A simple model is constructed with coupling to a high
frequency excitation, which is consistent with both the low frequency optical
data and the high .Comment: 4 pages, 4 figure
Molecular transport and flow past hard and soft surfaces: Computer simulation of model systems
The properties of polymer liquids on hard and soft substrates are
investigated by molecular dynamics simulation of a coarse-grained bead-spring
model and dynamic single-chain-in-mean-field (SCMF) simulations of a soft,
coarse-grained polymer model. Hard, corrugated substrates are modelled by an
FCC Lennard-Jones solid while polymer brushes are investigated as a
prototypical example of a soft, deformable surface. From the molecular
simulation we extract the coarse-grained parameters that characterise the
equilibrium and flow properties of the liquid in contact with the substrate:
the surface and interface tensions, and the parameters of the hydrodynamic
boundary condition. The so-determined parameters enter a continuum description
like the Stokes equation or the lubrication approximation.Comment: 41 pages, 13 figure
Frequency dependent relaxation rate in the superconducting YBa2Cu3O{6+delta}
The submillimeter-wave 3 cm{-1} < nu < 35 cm{-1} complex conductivity of the
reduced YBa2Cu3O{6+delta} film (Tc=56.5 K) was investigated for temperatures 4
K < T < 300 K and compared to the properties of the same film in the optimally
doped state. The frequency dependence of the effective quasiparticle scattering
rate 1/tau*(nu) was extracted from the spectra. 1/tau*(nu) is shown to be
frequency independent at low frequencies and high temperatures. A gradual
change to 1/tau*~nu^{1.5} law is observed as temperature decreases. In order to
explain the observed temperature dependence of the low frequency spectral
weight above Tc, the quasiparticle effective mass is supposed to be temperature
dependent for T>Tc.Comment: 4 pages, 4 figure
The nature of the Galactic Center source IRS 13 revealed by high spatial resolution in the infrared
High spatial resolution observations in the 1 to 3.5 micron region of the
Galactic Center source known historically as IRS 13 are presented. They include
ground-based adaptive optics images in the H, Kp (2.12/0.4 micron) and L bands,
NICMOS data in filters between 1.1 and 2.2 micron, and integral field
spectroscopic data from BEAR, an Imaging FTS, in the HeI 2.06 micron and the
Br line regions. Analysis of all these data provides a completely new
picture of the main component, IRS 13E, which appears as a cluster of seven
individual stars within a projected diameter of ~0.5'' (0.02 pc). The brightest
sources, 13E1, 13E2, 13E3 (a binary), and 13E4, are all massive stars, 13E1 a
blue object, with no detected emission line while 13E2 and 13E4 are high-mass
emission line stars. 13E2 is at the WR stage and 13E4 a massive O-type star.
13E3A and B are extremely red objects, proposed as other examples of dusty WR
stars. All these sources have a common westward proper motion. 13E5, is a red
source similar to 13E3A/B. This concentration of comoving massive hot stars,
IRS 13E, is proposed as the remaining core of a massive star cluster, which
could harbor an intermediate-mass black hole (IMBH) of ~1300 M_sol. This
detection plays in favor of a scenario in which the helium stars and the other
hot stars in the central pc originate from the stripping of a massive cluster
formed several tens of pc from the center. The detection of a discrete X-ray
emission (Baganoff et al. 2003) at the IRS~13 position is examined in this
context.Comment: 14 pages, 6 figures (3 in color), LaTeX2e, accepted in A&
Metallicity of solar-type stars with debris discs and planets
Around 16% of the solar-like stars in our neighbourhood show IR-excesses due
to debris discs and a fraction of them are known to host planets. We aim to
determine in a homogeneous way the metallicity of a sample of stars with known
debris discs and planets. Our analysis includes the calculation of the
fundamental stellar parameters by applying the iron ionisation equilibrium
conditions to several isolated Fe I and Fe II lines. The metallicity
distributions of the different stellar samples suggest that there is a
transition toward higher metallicities from stars with neither debris discs nor
planets to stars hosting giant planets. Stars with debris discs and stars with
neither debris nor planets follow a similar metallicity distribution, although
the distribution of the first ones might be shifted towards higher
metallicities. Stars with debris discs and planets have the same metallicity
behaviour as stars hosting planets, irrespective of whether the planets are
low-mass or gas giants. In the case of debris discs and giant planets, the
planets are usually cool, -semimajor axis larger than 0.1 AU. The data also
suggest that stars with debris discs and cool giant planets tend to have a low
dust luminosity, and are among the less luminous debris discs known. We also
find evidence of an anticorrelation between the luminosity of the dust and the
planet eccentricity. Our data show that the presence of planets, not the debris
disc, correlates with the stellar metallicity. The results confirm that
core-accretion models represent suitable scenarios for debris disc and planet
formation. Dynamical instabilities produced by eccentric giant planets could
explain the suggested dust luminosity trends observed for stars with debris
discs and planets.Comment: Accepted for publication by A&A, 17 pages, 10 figure
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