2,238 research outputs found
Entwicklung eines Inkubationssystems fĂŒr ein inverses Mikroskop zur Langzeitbeobachtung von Zellkulturen in gekammerten ObjekttrĂ€gern
Trifunctional bispecific antibodies open up new immunological possibilities in tumour treatment. Prior to clinical application, comprehensive investigations using animal models and in vitro examinations need to be done. To investigate long-term interactions between Various immunologically active blood cells and individual tumour cells in the presence of antibodies, we developed an incubation system for experimental cell cultures on an inverted microscope. The system consists of a perspex box with a central moisture chamber with integrated water reservoir, external air circulation heating, and a CO2 supply. The sterile cell cultures are located in the wells of a slide positioned within a depression in the water reservoir. The newly developed incubation system enables continuous observation over the long term of experiments under optimal cell cultures conditions in combination with modern video techniques
The effect of induced forelimb lameness on thoracolumbar kinematics during treadmill locomotion
Reasons for performing study: Lameness has often been suggested to result in altered movement of the back, but there are no detailed studies describing such a relationship in quantitative terms. Objectives: To quantify the effect of induced subtle forelimb lameness on thoracolumbar kinematics in the horse. Methods: Kinematics of 6 riding horses was measured at walk and at trot on a treadmill before and after the induction of reversible forelimb lameness grade 2 (AAEP scale 1-5). Ground reaction forces (GRF) for individual limbs were calculated from kinematics. Results: The horses significantly unloaded the painful limb by 11.5% at trot, while unloading at walk was not significant. The overall flexion-extension range of back motion decreased on average by 0.2° at walk and increased by 3.3° at trot (P<0.05). Changes in angular motion patterns of vertebral joints were noted only at trot, with an increase in flexion of 0.9° at T10 (i.e. angle between T6, T10 and T13) during the stance phase of the sound diagonal and an increase in extension of the thoracolumbar area during stance of the lame diagonal (0.7° at T13, 0.8° at T17, 0.5° at L1, 0.4° at L3 and 0.3° at L5) (P<0.05). Lameness further caused a lateral bending of the cranial thoracic vertebral column towards the lame side (1.3° at T10 and 0.9° at T13) (P<0.05) during stance of the lame diagonal. Conclusions: Both range of motion and vertebral angular motion patterns are affected by subtle forelimb lameness. At walk, the effect is minimal, at trot the horses increased the vertebral range of motion and changed the pattern of thoracolumbar motion in the sagittal and horizontal planes, presumably in an attempt to move the centre of gravity away from the lame side and reduce the force on the affected limb. Potential relevance: Subtle forelimb lameness affects thoracolumbar kinematics. Future studies should aim at elucidating whether the altered movement patterns lead to back and/or neck dysfunction in the case of chronic lameness
X-ray constraints on the fraction of obscured AGN at high accretion luminosities
The wide-area XMM-XXL X-ray survey is used to explore the fraction of
obscured AGN at high accretion luminosities, , and out to redshift . The sample covers an area
of about and provides constraints on the space density of
powerful AGN over a wide range of neutral hydrogen column densities extending
beyond the Compton-thick limit, . The fraction
of obscured Compton-thin () AGN is estimated
to be for luminosities
independent of redshift. For less luminous sources the fraction of obscured
Compton-thin AGN increases from at to at
. Studies that select AGN in the infrared via template fits to the
observed Spectral Energy Distribution of extragalactic sources estimate space
densities at high accretion luminosities consistent with the XMM-XXL
constraints. There is no evidence for a large population of AGN (e.g. heavily
obscured) identified in the infrared and missed at X-ray wavelengths. We
further explore the mid-infrared colours of XMM-XXL AGN as a function of
accretion luminosity, column density and redshift. The fraction of XMM-XXL
sources that lie within the mid-infrared colour wedges defined in the
literature to select AGN is primarily a function of redshift. This fraction
increases from about 20-30% at z=0.25 to about 50-70% at .Comment: MNRAS accepte
The Effect of Coherent Structures on Stochastic Acceleration in MHD Turbulence
We investigate the influence of coherent structures on particle acceleration
in the strongly turbulent solar corona. By randomizing the Fourier phases of a
pseudo-spectral simulation of isotropic MHD turbulence (Re ), and
tracing collisionless test protons in both the exact-MHD and phase-randomized
fields, it is found that the phase correlations enhance the acceleration
efficiency during the first adiabatic stage of the acceleration process. The
underlying physical mechanism is identified as the dynamical MHD alignment of
the magnetic field with the electric current, which favours parallel
(resistive) electric fields responsible for initial injection. Conversely, the
alignment of the magnetic field with the bulk velocity weakens the acceleration
by convective electric fields - \bfu \times \bfb at a non-adiabatic stage of
the acceleration process. We point out that non-physical parallel electric
fields in random-phase turbulence proxies lead to artificial acceleration, and
that the dynamical MHD alignment can be taken into account on the level of the
joint two-point function of the magnetic and electric fields, and is therefore
amenable to Fokker-Planck descriptions of stochastic acceleration.Comment: accepted for publication in Ap
The X-ray luminosity function of Active Galactic Nuclei in the redshift interval z=3-5
We combine deep X-ray survey data from the Chandra observatory and the
wide-area/shallow XMM-XXL field to estimate the AGN X-ray luminosity function
in the redshift range z=3-5. The sample consists of nearly 340 sources with
either photometric (212) or spectroscopic (128) redshift in the above range.
The combination of deep and shallow survey fields provides a luminosity
baseline of three orders of magnitude, Lx(2-10keV)~1e43-1e46erg/s at z>3. We
follow a Bayesian approach to determine the binned AGN space density and
explore their evolution in a model-independent way. Our methodology accounts
for Poisson errors in the determination of X-ray fluxes and uncertainties in
photometric redshift estimates. We demonstrate that the latter is essential for
unbiased measurement of space densities. We find that the AGN X-ray luminosity
function evolves strongly between the redshift intervals z=3-4 and z=4-5. There
is also suggestive evidence that the amplitude of this evolution is luminosity
dependent. The space density of AGN with Lx<1e45erg/s drops by a factor of 5
between the redshift intervals above, while the evolution of brighter AGN
appears to be milder. Comparison of our X-ray luminosity function with that of
UV/optical selected QSOs at similar redshifts shows broad agreement at bright
luminosities, Lx>1e45erg/s. The faint-end slope of UV/optical luminosity
functions however, is steeper than for X-ray selected AGN. This implies that
the type-I AGN fraction increases with decreasing luminosity at z>3, opposite
to trends established at lower redshift. We also assess the significance of AGN
in keeping the hydrogen ionised at high redshift. Our X-ray luminosity function
yields ionising photon rate densities that are insufficient to keep the
Universe ionised at redshift z>4. A source of uncertainty in this calculation
is the escape fraction of UV photons for X-ray selected AGN.Comment: MNRAS accepte
Instantaneous Normal Mode analysis of liquid HF
We present an Instantaneous Normal Modes analysis of liquid HF aimed to
clarify the origin of peculiar dynamical properties which are supposed to stem
from the arrangement of molecules in linear hydrogen-bonded network. The
present study shows that this approach is an unique tool for the understanding
of the spectral features revealed in the analysis of both single molecule and
collective quantities. For the system under investigation we demonstrate the
relevance of hydrogen-bonding ``stretching'' and fast librational motion in the
interpretation of these features.Comment: REVTeX, 7 pages, 5 eps figures included. Minor changes in the text
and in a figure. Accepted for publication in Phys. Rev. Let
Three-Dimensional MHD Simulation of FTEs Produced by Merging at an Isolated Point in a Sheared Magnetic Field Configuration
We present predictions for the evolution of FTEs generated by localized bursts of reconnection on a planar magnetopause that separates a magnetosheath region of high densities and weak magnetic field from a magnetospheric region of low densities and strong magnetic field. The magnetic fields present a shear angle of 105 degrees. Reconnection forms a pair of FTEs each crossing the magnetopause in the field reversal region and bulging into the magnetosphere and magnetosheath. At their initial stage they can be characterized as flux tubes since the newly reconnected magnetic field lines are not twisted. Reconnection launches Alfvenic perturbations that propagate along the FTEs generating high-speed jets, which move the pair of FTEs in opposite directions. As the FTE moves, it displaces the ambient magnetic field and plasma producing bipolar magnetic field and plasma velocity signatures normal to the nominal magnetopause in the regions surrounding the FTE. The combination of the ambient plasma with the FTE flows generates a vortical velocity pattern around the reconnected field lines. During its evolution the FTE evolves to a flux rope configuration due to the twist of the magnetic field lines. The alfvenic perturbations propagate faster along the part of the FTE bulging into the magnetosphere than in the magnetosheath, and due to the differences between the plasma and magnetic field properties the perturbations have slightly different signatures in the two regions. As a consequence, the FTEs have different signatures depending on whether the satellite encounters the part bulging into the magnetosphere or into the magnetosheath
Saddles in the energy landscape probed by supercooled liquids
We numerically investigate the supercooled dynamics of two simple model
liquids exploiting the partition of the multi-dimension configuration space in
basins of attraction of the stationary points (inherent saddles) of the
potential energy surface. We find that the inherent saddles order and potential
energy are well defined functions of the temperature T. Moreover, decreasing T,
the saddle order vanishes at the same temperature (T_MCT) where the inverse
diffusivity appears to diverge as a power law. This allows a topological
interpretation of T_MCT: it marks the transition from a dynamics between basins
of saddles (T>T_MCT) to a dynamics between basins of minima (T<T_MCT).Comment: 4 pages, 3 figures, to be published on PR
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