1,376 research outputs found
Purification and analytical characterization of an anti- CD4 monoclonal antibody for human therapy
A purification process for the monclonal anti-CD4 antibody MAX.16H5 was developed on an analytical scale using (NH&SO,
precipitation, anion-exchange chromatography on MonoQ or Q-Sepharose, hydrophobic interaction chromatography on phenyl-
Sepharose and gel filtration chromatography on Superdex 200. The purification schedule was scaled up and gram amounts of
MAX.16H5 were produced on corresponding BioPilot columns. Studies of the identity, purity and possible contamination by a
broad range of methods showed that the product was highly purified and free from contaminants such as mouse DNA, viruses,
pyrogens and irritants. Overall, the analytical data confirm that the monoclonal antibody MAX.16H5 prepared by this protocol is
suitable for human therapy
Radiative transfer effects on Doppler measurements as sources of surface effects in sunspot seismology
We show that the use of Doppler shifts of Zeeman sensitive spectral lines to
observe wavesn in sunspots is subject to measurement specific phase shifts
arising from, (i) altered height range of spectral line formation and the
propagating character of p mode waves in penumbrae, and (ii) Zeeman broadening
and splitting. We also show that these phase shifts depend on wave frequencies,
strengths and line of sight inclination of magnetic field, and the polarization
state used for Doppler measurements. We discuss how these phase shifts could
contribute to local helioseismic measurements of 'surface effects' in sunspot
seismology.Comment: 12 pages, 4 figures, Accepted for publication in the Astrophysical
Journal Letter
Cool Companions to White Dwarfs from the 2MASS Second Incremental Data Release
We present near-infrared magnitudes for all white dwarfs (selected from the
catalog of McCook & Sion) contained in the 2 Micron All Sky Survey Second
Incremental Data Release(2MASS 2IDR). We show that the near-IR color-color
diagram is an effective means of identifying candidate binary stars containing
a WD and a low mass main sequence star. The loci of single WDs and WD + red
dwarf binaries occupy distinct regions of the near-IR color-color diagram. We
recovered all known unresolved WD + red dwarf binaries located in the 2IDR sky
coverage, and also identified as many new candidate binaries (47 new candidates
out of 95 total). Using observational near-IR data for WDs and M-L dwarfs, we
have compared a sample of simulated WD + red dwarf binaries with our 2MASS
data. The colors of the simulated binaries are dominated by the low mass
companion through the late-M to early-L spectral types. As the spectral type of
the companion becomes progressively later, however, the colors of unresolved
binaries become progressively bluer. Binaries containing the lowest mass
companions will be difficult to distinguish from single WDs solely on the basis
of their near-IR colors.Comment: 18 pages, including 2 figures, accepted for publication in Ap
Risk analysis of marine activities in the Belgian part of the North Sea (RAMA): final report
RAMA is a 2-year project (04/2004 - 04/2006) executed by two Belgian partners, Ecolas NV (Environmental Consultancy Agency) and the Maritime Institute (University of Ghent), and financed by the SPSD II research program, specific actions, of the Belgian Science Policy (BELPSO). RAMA aims to assess the environmental risks of spills by commercial shipping activities on the Belgian Part of the North Sea. Shipping patterns, transports of dangerous goods, probability of risks and the potential impact of spill incidents (oil & hazardous and noxious substances) will be assessed. The risk analysis within this project studies both the chances of a spill accident happening and the environmental impacts in case of an accident. The valorisation of the RAMA project will result in a thorough analysis of the current status of the shipping at the North Sea in relation to the issue of safety. The scope of the project will however go beyond the mere result of a fundamental risk analysis of the commercial shipping at the North Sea. It is also aiming at the formulation of recommendations to improve the safety level for the environment and at an optimization of response in the framework of the Belgian "North Sea Disaster Plan"
Dynamics and transport properties of heavy fermions: theory
The paramagnetic phase of heavy fermion systems is investigated, using a
non-perturbative local moment approach to the asymmetric periodic Anderson
model within the framework of dynamical mean field theory. The natural focus is
on the strong coupling Kondo-lattice regime wherein single-particle spectra,
scattering rates, dc transport and optics are found to exhibit w/w_L,T/w_L
scaling in terms of a single underlying low-energy coherence scale w_L.
Dynamics/transport on all relevant (w,T)-scales are encompassed, from the
low-energy behaviour characteristic of the lattice coherent Fermi liquid,
through incoherent effective single-impurity physics likewise found to arise in
the universal scaling regime, to non-universal high-energy scales; and which
description in turn enables viable quantitative comparison to experiment.Comment: 27 pages, 12 figure
Ferromagnetic Kondo-Lattice Model
We present a many-body approach to the electronic and magnetic properties of
the (multiband) Kondo-lattice model with ferromagnetic interband exchange. The
coupling between itinerant conduction electrons and localized magnetic moments
leads, on the one hand, to a distinct temperature-dependence of the electronic
quasiparticle spectrum and, on the other hand, to magnetic properties, as
e.~g.the Curie temperature T_C or the magnon dispersion, which are strongly
influenced by the band electron selfenergy and therewith in particular by the
carrier density. We present results for the single-band Kondo-lattice model in
terms of quasiparticle densities of states and quasiparticle band structures
and demonstrate the density-dependence of the self-consistently derived Curie
temperature. The transition from weak-coupling (RKKY) to strong-coupling
(double exchange) behaviour is worked out.
The multiband model is combined with a tight-binding-LMTO bandstructure
calculation to describe real magnetic materials. As an example we present
results for the archetypal ferromagnetic local-moment systems EuO and EuS. The
proposed method avoids the double counting of relevant interactions and takes
into account the correct symmetry of atomic orbitals.Comment: 15 pages, 10 figure
Frequency and damping of hydrodynamic modes in a trapped Bose-condensed gas
Recently it was shown that the Landau-Khalatnikov two-fluid hydrodynamics
describes the collision-dominated region of a trapped Bose condensate
interacting with a thermal cloud. We use these equations to discuss the low
frequency hydrodynamic collective modes in a trapped Bose gas at finite
temperatures. We derive a variational expressions based on these equations for
both the frequency and damping of collective modes. A new feature is our use of
frequency-dependent transport coefficients, which produce a natural cutoff by
eliminating the collisionless low-density tail of the thermal cloud. Above the
superfluid transition, our expression for the damping in trapped inhomogeneous
gases is analogous to the result first obtained by Landau and Lifshitz for
uniform classical fluids. We also use the moment method to discuss the
crossover from the collisionless to the hydrodynamic region. Recent data for
the monopole-quadrupole mode in the hydrodynamic region of a trapped gas of
metastable He is discussed. We also present calculations for the damping of
the analogous monopole-quadrupole condensate mode in the superfluid
phase.Comment: 22 pages, 10 figures, submitted to Physical Review
q-Deformed Superalgebras
The article deals with q-analogs of the three- and four-dimensional Euclidean
superalgebra and the Poincare superalgebra.Comment: 38 pages, LateX, no figures, corrected typo
Spitzer Space Telescope observations of magnetic cataclysmic variables: possibilities for the presence of dust in polars
We present Spitzer Space Telescope photometry of six short-period polars, EF
Eri, V347 Pav, VV Pup, V834 Cen, GG Leo, and MR Ser. We have combined the
Spitzer Infrared Array Camera (3.6 -8.0 microns) data with the 2MASS J, H, K_s
photometry to construct the spectral energy distributions of these systems from
the near- to mid-IR (1.235 - 8 microns). We find that five out of the six
polars have flux densities in the mid-IR that are substantially in excess of
the values expected from the stellar components alone. We have modeled the
observed SEDs with a combination of contributions from the white dwarf,
secondary star, and either cyclotron emission or a cool, circumbinary dust disk
to fill in the long-wavelength excess. We find that a circumbinary dust disk is
the most likely cause of the 8 micron excess in all cases, but we have been
unable to rule out the specific (but unlikely) case of completely optically
thin cyclotron emission as the source of the observed 8 micron flux density.
While both model components can generate enough flux at 8 microns, neither dust
nor cyclotron emission alone can match the excess above the stellar components
at all wavelengths. A model combining both cyclotron and dust contributions,
possibly with some accretion-generated flux in the near-IR, is probably
required, but our observed SEDs are not sufficiently well-sampled to constrain
such a complicated model. If the 8 micron flux density is caused by the
presence of a circumbinary dust disk, then our estimates of the masses of these
disks are many orders of magnitude below the mass required to affect CV
evolution.Comment: 58 pages, 14 figures, ApJ accepte
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