2,033 research outputs found
The chemokine receptor CCR5 plays a role in post-traumatic cartilage loss in mice, but does not affect synovium and bone
SummaryObjectiveCâC chemokine receptor type 5 (CCR5) has been implicated in rheumatoid arthritis and several inflammatory diseases, where its blockade resulted in reduced joint destruction. However, its role in modulating cartilage and bone changes in post-traumatic osteoarthritis (OA) has not yet been investigated. In this study, we investigated changes in articular cartilage, synovium and bone in a post-traumatic OA model using CCR5-deficient (CCR5â/â) mice.MethodDestabilization of the medial meniscus (DMM) was performed on the right knee of 10-week old CCR5â/â and C57BL/6J wild-type (WT) mice to induce post-traumatic OA. The contralateral left knee served as sham-operated control. Knee joints were analyzed at 4-, 8- and 12-weeks after surgery to evaluate cartilage degeneration and synovitis by histology, and bone changes via micro-CT.ResultsOur findings showed that CCR5â/â mice exhibited significantly less cartilage degeneration than WT mice at 8- and 12-weeks post-surgery. CCR5â/â mice showed some altered bone parameters 18- and 22-weeks of age, but body size and weight were not affected. The effect of CCR5-ablation was insignificant at all time points post-surgery for synovitis and for bone parameters such as bone volume/total volume, connectivity density index (CDI), structure model index (SMI), subchondral bone plate thickness, and trabecular bone number, thickness and spacing.ConclusionThese findings suggest that CCR5â/â mice developed less cartilage degeneration, which may indicate a potential protective role of CCR5-ablation in cartilage homeostasis. There were no differences in bone or synovial response to surgery suggesting that CCR5 functions primarily in cartilage during the development of post-traumatic OA
Continuous measurements of greenhouse gases and atmospheric oxygen at the Namib Desert atmospheric observatory
A new coastal background site has been established for observations of greenhouse gases (GHGs) in the central Namib Desert at Gobabeb, Namibia. The location of the site was chosen to provide observations for a data-poor region in the global sampling network for GHGs. Semi-automated continuous measurements of carbon dioxide, methane, nitrous oxide, carbon monoxide, atmospheric oxygen, and basic meteorology are made at a height of 21 m a.g.l., 50 km from the coast at the northern border of the Namib Sand Sea. Atmospheric oxygen is measured with a differential fuel cell analyzer (DFCA). Carbon dioxide and methane are measured with an early-model cavity ring-down spectrometer (CRDS); nitrous oxide and carbon monoxide are measured with an off-axis integrated cavity output spectrometer (OA-ICOS). Instrument-specific water corrections are employed for both the CRDS and OA-ICOS instruments in lieu of drying. The performance and measurement uncertainties are discussed in detail. As the station is located in a remote desert environment, there are some particular challenges, namely fine dust, high diurnal temperature variability, and minimal infrastructure. The gas handling system and calibration scheme were tailored to best fit the conditions of the site. The CRDS and DFCA provide data of acceptable quality when base requirements for operation are met, specifically adequate temperature control in the laboratory and regular supply of electricity. In the case of the OA-ICOS instrument, performance is significantly improved through the implementation of a drift correction through frequent measurements of a reference cylinder
Quantum corrections to the mass of the supersymmetric vortex
We calculate quantum corrections to the mass of the vortex in N=2
supersymmetric abelian Higgs model in (2+1) dimensions. We put the system in a
box and apply the zeta function regularization. The boundary conditions
inevitably violate a part of the supersymmetries. Remaining supersymmetry is
however enough to ensure isospectrality of relevant operators in bosonic and
fermionic sectors. A non-zero correction to the mass of the vortex comes from
finite renormalization of couplings.Comment: Latex, 18 pp; v2 reference added; v3 minor change
Factsheet: onderzoek Leeratelier Maatwerk & Regie
The politics and administration of institutional chang
The response function of a sphere in a viscoelastic two-fluid medium
In order to address basic questions of importance to microrheology, we study
the dynamics of a rigid sphere embedded in a model viscoelastic medium
consisting of an elastic network permeated by a viscous fluid. We calculate the
complete response of a single bead in this medium to an external force and
compare the result to the commonly-accepted, generalized Stokes-Einstein
relation (GSER). We find that our response function is well approximated by the
GSER only within a particular frequency range determined by the material
parameters of both the bead and the network. We then discuss the relevance of
this result to recent experiments. Finally we discuss the approximations made
in our solution of the response function by comparing our results to the exact
solution for the response function of a bead in a viscous (Newtonian) fluid.Comment: 12 pages, 2 figure
A Single Laser System for Ground-State Cooling of 25-Mg+
We present a single solid-state laser system to cool, coherently manipulate
and detect Mg ions. Coherent manipulation is accomplished by
coupling two hyperfine ground state levels using a pair of far-detuned Raman
laser beams. Resonant light for Doppler cooling and detection is derived from
the same laser source by means of an electro-optic modulator, generating a
sideband which is resonant with the atomic transition. We demonstrate
ground-state cooling of one of the vibrational modes of the ion in the trap
using resolved-sideband cooling. The cooling performance is studied and
discussed by observing the temporal evolution of Raman-stimulated sideband
transitions. The setup is a major simplification over existing state-of-the-art
systems, typically involving up to three separate laser sources
Particle-Like Description in Quintessential Cosmology
Assuming equation of state for quintessential matter: , we
analyse dynamical behaviour of the scale factor in FRW cosmologies. It is shown
that its dynamics is formally equivalent to that of a classical particle under
the action of 1D potential . It is shown that Hamiltonian method can be
easily implemented to obtain a classification of all cosmological solutions in
the phase space as well as in the configurational space. Examples taken from
modern cosmology illustrate the effectiveness of the presented approach.
Advantages of representing dynamics as a 1D Hamiltonian flow, in the analysis
of acceleration and horizon problems, are presented. The inverse problem of
reconstructing the Hamiltonian dynamics (i.e. potential function) from the
luminosity distance function for supernovae is also considered.Comment: 35 pages, 26 figures, RevTeX4, some applications of our treatment to
investigation of quintessence models were adde
Macromolecular theory of solvation and structure in mixtures of colloids and polymers
The structural and thermodynamic properties of mixtures of colloidal spheres
and non-adsorbing polymer chains are studied within a novel general
two-component macromolecular liquid state approach applicable for all size
asymmetry ratios. The dilute limits, when one of the components is at infinite
dilution but the other concentrated, are presented and compared to field theory
and models which replace polymer coils with spheres. Whereas the derived
analytical results compare well, qualitatively and quantitatively, with
mean-field scaling laws where available, important differences from ``effective
sphere'' approaches are found for large polymer sizes or semi-dilute
concentrations.Comment: 23 pages, 10 figure
Inflation with a constant ratio of scalar and tensor perturbation amplitudes
The single scalar field inflationary models that lead to scalar and tensor
perturbation spectra with amplitudes varying in direct proportion to one
another are reconstructed by solving the Stewart-Lyth inverse problem to
next-to-leading order in the slow-roll approximation.
The potentials asymptote at high energies to an exponential form,
corresponding to power law inflation, but diverge from this model at low
energies, indicating that power law inflation is a repellor in this case. This
feature implies that a fine-tuning of initial conditions is required if such
models are to reproduce the observations. The required initial conditions might
be set through the eternal inflation mechanism.
If this is the case, it will imply that the spectral indices must be nearly
constant, making the underlying model observationally indistinguishable from
power law inflation.Comment: 20 pages, 7 figures. Major changes to the Introduction following
referee's comments. One figure added. Some other minor changes. No conclusion
was modifie
Cosmology with a long range repulsive force
We consider a class of cosmological models in which the universe is filled
with a (non-electric) charge density that repels itself by means of a force
carried by a vector boson with a tiny mass. When the vector's mass depends upon
other fields, the repulsive interaction gives rise to an electromagnetic
barrier which prevents these fields from driving the mass to zero. This can
modify the cosmology dramatically. We present a very simple realization of this
idea in which the vector's mass arises from a scalar field. The electromagnetic
barrier prevents this field from rolling down its potential and thereby leads
to accelerated expansion.Comment: 15 pages, 8 figures, LaTeX (version accepted for publication in PRD).
3 new figures, extended discussion of observational consequence
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