1,027 research outputs found
Synthesis and biodistribution of immunoconjugates of a human IgM and polymeric drug carriers
The synthesis and purification of radiolabelled immunoconjugates, composed of a human IgM monoclonal antibody directed against an intracellular tumour-associated antigen and either poly (alpha-L-glutamic acid) (PGA) or poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG) is described. Coupling of polymers to the antibody was performed through disulfide bond formation involving a single thiol group at the C-terminus of the polymer chain and 2-pyridyldisulfide groups introduced onto the antibody. The antibody was iodinated with 131I before conjugation. The polymers contained tyrosinamide in a low degree of substitution and were radiolabelled with 125I. 125I-labelled PGA and PHEG were found to be stable for at least 3 days in murine and human plasma. The biodistribution in mice of the doubly labelled immunoconjugates was studied and was compared with the pharmacokinetics of the individual components.\ud
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PHEG showed a relatively slow blood clearance, the half-life being approximately 10 h with low uptake in liver, kidneys and spleen. PGA was rapidly cleared from the circulation and was significantly taken up in liver, kidneys and spleen. The biodistribution of both immunoconjugates was indistinguishable from that of the IgM proper, with plasma half-lives of approximately 6 h, indicating that the pharmacokinetic properties of the immunoconjugates are largely determined by the antibody part
Gap Formation by Planets in Turbulent Protostellar Disks
The processes of planet formation and migration depend intimately on the
interaction between planetesimals and the gaseous disks in which they form. The
formation of gaps in the disk can severely limit the mass of the planet and its
migration toward the protostar. We investigate the process of gap formation
through magnetohydrodynamic simulations in which internal stress arises
self-consistently from turbulence generated by the magnetorotational
instability. The simulations investigate three different planetary masses and
two disk temperatures to bracket the tidal (thermal) and viscous gap opening
conditions. The results are in general qualitative agreement with previous
simulations of gap formation, but show significant differences. In the presence
of MHD turbulence, the gaps produced are shallower and asymmetrically wider
than those produced with pure hydrodynamics. The rate of gap formation is also
slowed, with accretion occurring across the developing gap. Viscous
hydrodynamics does not adequately describe the evolution, however, because
planets capable of producing gaps also may be capable of affecting the level
MHD turbulence in different regions of the disk.Comment: accepted by Astrophysical Journal. For associated animations see
http://www.astro.virginia.edu/VITA/papers/planet1
Observations of Binary Stars with the Differential Speckle Survey Instrument. VII. Measures from 2010 September to 2012 February at the WIYN Telescope
We report on speckle observations of binary stars carried out at the WIYN
Telescope over the period from September 2010 through February 2012, providing
relative astrometry for 2521 observations of 883 objects, 856 of which are
double stars and 27 of which are triples. The separations measured span a range
of 0.01 to 1.75 arc seconds. Wavelengths of 562 nm, 692 nm, and 880 nm were
used, and differential photometry at one or more of these wavelengths is
presented in most cases. Sixty-six components were resolved for the first time.
We also estimate detection limits at 0.2 and 1.0 arc seconds for high-quality
observations in cases where no companion was seen, a total of 176 additional
objects. Detection limits vary based on observing conditions and
signal-to-noise ratio, but are approximately 4 magnitudes at 0.2 arc seconds
and 6 magnitudes at 1.0 arc seconds on average. Analyzing the measurement
precision of the data set, we find that the individual separations obtained
have linear measurement uncertainties of approximately 2 mas, and photometry is
uncertain to approximately 0.1 magnitudes in general. This work provides
fundamental, well-calibrated data for future orbit and mass determinations, and
we present three first orbits and total mass estimates of nearby K-dwarf
systems as examples of this potential
The light curve of the semiregular variable L2 Puppis: I. A recent dimming event from dust
The nearby Mira-like variable L2 Pup is shown to be undergoing an
unprecedented dimming episode. The stability of the period rules out intrinsic
changes to the star, leaving dust formation along the line of sight as the most
likely explanation. Episodic dust obscuration events are fairly common in
carbon stars but have not been seen in oxygen-rich stars. We also present a
10-micron spectrum, taken with the Japanese IRTS satellite, showing strong
silicate emission which can be fitted with a detached, thin dust shell,
containing silicates and corundum.Comment: MNRAS (accepted
High-resolution measurement of the time-modulated orbital electron capture and of the decay of hydrogen-like Pm ions
The periodic time modulations, found recently in the two-body orbital
electron-capture (EC) decay of both, hydrogen-like Pr and
Pm ions, with periods near to 7s and amplitudes of about 20%,
were re-investigated for the case of Pm by using a 245 MHz
resonator cavity with a much improved sensitivity and time resolution. We
observed that the exponential EC decay is modulated with a period s, in accordance with a modulation period s as obtained
from simultaneous observations with a capacitive pick-up, employed also in the
previous experiments. The modulation amplitudes amount to and
for the 245 MHz resonator and the capacitive pick-up,
respectively. These new results corroborate for both detectors {\it exactly}
our previous findings of modulation periods near to 7s, though with {\it
distinctly smaller} amplitudes. Also the three-body decays have been
analyzed. For a supposed modulation period near to 7s we found an amplitude , compatible with and in agreement with the preliminary
result of our previous experiment. These observations could
point at weak interaction as origin of the observed 7s-modulation of the EC
decay. Furthermore, the data suggest that interference terms occur in the
two-body EC decay, although the neutrinos are not directly observed.Comment: In memoriam of Prof. Paul Kienle, 9 pages, 1 table, 5 figures Phys.
Lett. B (2013) onlin
Disk Planet Interactions and Early Evolution in Young Planetary Systems
We study and review disk protoplanet interactions using local shearing box
simulations. These suffer the disadvantage of having potential artefacts
arising from periodic boundary conditions but the advantage, when compared to
global simulations, of being able to capture much of the dynamics close to the
protoplanet at high resolution for low computational cost. Cases with and
without self sustained MHD turbulence are considered. The conditions for gap
formation and the transition from type I migration are investigated and found
to depend on whether the single parameter M_p R^3/(M_* H^3), with M_p, M_*, R
and H being the protoplanet mass, the central mass, the orbital radius and the
disk semi-thickness respectively exceeds a number of order unity. We also
investigate the coorbital torques experienced by a moving protoplanet in an
inviscid disk. This is done by demonstrating the equivalence of the problem for
a moving protoplanet to one where the protoplanet is in a fixed orbit which the
disk material flows through radially as a result of the action of an
appropriate external torque. For sustainable coorbital torques to be realized a
quasi steady state must be realized in which the planet migrates through the
disk without accreting significant mass. In that case although there is
sensitivity to computational parameters, in agreement with earlier work by
Masset & Papaloizou (2003) based on global simulations, the coorbital torques
are proportional to the migration speed and result in a positive feedback on
the migration, enhancing it and potentially leading to a runaway. This could
lead to a fast migration for protoplanets in the Saturn mass range in massive
disks and may be relevant to the mass period correlation for extrasolar planets
which gives a preponderance of sub Jovian masses at short orbital period.Comment: To appear in Celestial Mechanics and Dynamical Astronomy (with higher
resolution figures
An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5
Quasars are the most luminous non-transient objects known and as a result
they enable studies of the Universe at the earliest cosmic epochs. Despite
extensive efforts, however, the quasar ULAS J1120+0641 at z=7.09 has remained
the only one known at z>7 for more than half a decade. Here we report
observations of the quasar ULAS J134208.10+092838.61 (hereafter J1342+0928) at
redshift z=7.54. This quasar has a bolometric luminosity of 4e13 times the
luminosity of the Sun and a black hole mass of 8e8 solar masses. The existence
of this supermassive black hole when the Universe was only 690 million years
old---just five percent of its current age---reinforces models of early
black-hole growth that allow black holes with initial masses of more than about
1e4 solar masses or episodic hyper-Eddington accretion. We see strong evidence
of absorption of the spectrum of the quasar redwards of the Lyman alpha
emission line (the Gunn-Peterson damping wing), as would be expected if a
significant amount (more than 10 per cent) of the hydrogen in the intergalactic
medium surrounding J1342+0928 is neutral. We derive a significant fraction of
neutral hydrogen, although the exact fraction depends on the modelling.
However, even in our most conservative analysis we find a fraction of more than
0.33 (0.11) at 68 per cent (95 per cent) probability, indicating that we are
probing well within the reionization epoch of the Universe.Comment: Updated to match the final journal versio
Electronic detection of charged particle effects in a Penning trap
We present a thorough analysis of the electronic detection of charged
particles, confined in a Penning trap, via image charges induced in the trap
electrodes. Trapping of charged particles in an electrode structure leads to
frequency shifts, which are due to image charge and space charge effects. These
effects are of importance for Penning trap experiments which involve high
charge densities or require high precision in the motional frequencies. Our
analysis of image charges shows that only (higher order) odd powers of the
particle displacement lead to induced charge differences, giving rise to a
signal. This implies that, besides the centre-of-mass frequency of a trapped
particle cloud, also higher order individual particle frequencies induce a
signal, which can be picked up by an electronic detection circuit attached to
the trap electrodes. We also derive analytic expressions for the image charge
and space charge induced frequency shifts and perform simulations of space
charge effects. In relation to this, we discuss the consequences of the shifted
particle frequencies for resistive cooling of the particle motion.Comment: 16 pages, 4 figure
End-diastolic wall thickness as a predictor of recovery of function in myocardial hibernation Relation to rest-redistribution Tl-201 tomography and dobutamine stress echocardiography
AbstractOBJECTIVESThe study assessed whether end-diastolic wall thickness (EDWT), measured with echocardiography, is an important marker of myocardial viability in patients with suspected myocardial hibernation, and it compared this index to currently established diagnostic modalities of dobutamine stress echocardiography (DSE) and rest-redistribution thallium-201 (Tl-201) scintigraphy.BACKGROUNDBecause myocardial necrosis is associated with myocardial thinning, preserved EDWT may provide a simple index of myocardial viability that is readily available from the resting echocardiogram.METHODSAccordingly, 45 patients with stable coronary artery disease and ventricular dysfunction underwent rest 2D echocardiograms, DSE and rest-redistribution Tl-201 tomography before revascularization and a repeat resting echocardiogram â„2 months later.RESULTSGlobal wall motion score index decreased from 2.38 ± 0.73 to 1.94 ± 0.82 after revascularization (p < 0.001). Thirty-eight percent of severely dysfunctional segments recovered resting function. Compared to segments without recovery of resting function, those with recovery had greater EDWT (0.94 ± 0.18 cm vs. 0.67 ± 0.22 cm, p †0.0001) and a higher Tl-201 uptake (78 ± 13% vs. 59 ± 21%; p < 0.0001). An EDWT >0.6 cm had a sensitivity of 94% and specificity of 48% for recovery of function. Similarly, a Tl-201 maximal uptake of â„60% had a sensitivity of 91% and specificity of 50%. Receiver operating characteristic curves for prediction of recovery of regional and global function were similar for EDWT and maximum Tl-201 uptake. Combination of EDWT and any contractile reserve during DSE for recovery of regional function improved the specificity to 77% without a significant loss in sensitivity (88%).CONCLUSIONSEnd-diastolic wall thickness is an important marker of myocardial viability in patients with suspected hibernation, and it can predict recovery of function similar to Tl-201 scintigraphy. Importantly, a simple measurement of EDWT â€0.6 cm virtually excludes the potential for recovery of function and is a valuable adjunct to DSE in the assessment of myocardial viability
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