2,838 research outputs found
The modification of the renal carcinogenicity of dimethylnitrosamine by actinomycin D and a protein deficient diet.
The effect of a single treatment with 30 mg dimethylnitrosamine (DMN) and 6 mug actinomycin D (ACT), given at different time intervals (ACT application to DMN, 2 h before, simultaneously, 5, 9 or 48 h later), was tested in female Sprague-Dawley rats in relation to renal carcinogenesis; additionally, the animals were fed either a normal or a protein deficient diet. The ACT treatment did not significantly modify either the kidney tumour incidence or the survival time in the different groups fed a normal diet. Nevertheless, there are indications that additional ACT application may shorten the latency period for DMN induced renal neoplasms or, when administered 5 h later than DMN, a slightly decreased and delayed tumour induction can be assumed. In groups fed a protein deficient diet, a significantly higher percentage of kidney tumour bearing animals as well as a shortened latency period were found when compared with the DMN group on normal diet, but these differences were independent of the additional ACT treatment 9 h later than DMN and were due to the protein deprivation. Morphologically, the tumours were of epithelial and mesenchymal type with a clear preponderance of the former type. Biochemical and morphological aspects are discussed
Basic principles of postgrowth annealing of CdTe:Cl ingot to obtain semi-insulating crystals
The process of annealing of a CdTe:Cl ingot during its cooling after growth
was studied. The annealing was performed in two stages: a high-temperature
stage, with an approximate equality of chlorine and cadmium vacancy
concentrations established at the thermodynamic equilibrium between the crystal
and vapors of volatile components, and a low-temperature stage, with charged
defects interacting to form neutral associations. The chlorine concentrations
necessary to obtain semi-insulating crystals were determined for various ingot
cooling rates in the high temperature stage. The dependence of the chlorine
concentration [Cl+Te] in the ingot on the temperature of annealing in the
high-temperature stage was found. The carrier lifetimes and drift mobilities
were obtained in relation to the temperature and cadmium vapor pressure in the
postgrowth annealing of the ingot.Comment: 6 pages, 6 figure
Democratization in a passive dendritic tree : an analytical investigation
One way to achieve amplification of distal synaptic inputs on a dendritic tree is to scale the amplitude and/or duration of the synaptic conductance with its distance from the soma. This is an example of what is often referred to as âdendritic democracyâ. Although well studied experimentally, to date this phenomenon has not been thoroughly explored from a mathematical perspective. In this paper we adopt a passive model of a dendritic tree with distributed excitatory synaptic conductances and analyze a number of key measures of democracy. In particular, via moment methods we derive laws for the transport, from synapse to soma, of strength, characteristic time, and dispersion. These laws lead immediately to synaptic scalings that overcome attenuation with distance. We follow this with a Neumann approximation of Greenâs representation that readily produces the synaptic scaling that democratizes the peak somatic voltage response. Results are obtained for both idealized geometries and for the more realistic geometry of a rat CA1 pyramidal cell. For each measure of democratization we produce and contrast the synaptic scaling associated with treating the synapse as either a conductance change or a current injection. We find that our respective scalings agree up to a critical distance from the soma and we reveal how this critical distance decreases with decreasing branch radius
Pediatric Transplantation in the United States, 1995â2004
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72899/1/j.1600-6143.2006.01271.x.pd
Mass-Selection and the Evolution of the Morphology-Density Relation from z=0.8 to z=0
We examined the morphology-density relations for galaxy samples selected by
luminosity and by mass in each of five massive X-ray clusters from z=0.023 to
0.83 for 674 spectroscopically-confirmed members. Rest-frame optical colors and
visual morphologies were obtained primarily from Hubble Space Telescope images.
Morphology-density relations (MDR) are derived in each cluster from a complete,
luminosity-selected sample of 452 galaxies with a magnitude limit M_V <
M^{*}_{V} + 1. The change in the early-type fraction with redshift matches
previous work for massive clusters of galaxies. We performed a similar
analysis, deriving MDRs for complete, mass-selected samples of 441 galaxies
with a mass-limit of 10^{10.6} M_{\sun}. Our mass limit includes faint objects,
the equivalent of =~1 mag below L^{*} for the red cluster galaxies, and
encompasses =~70% of the stellar mass in cluster galaxies. The MDRs in the
mass-selected sample at densities of Sigma > 50 galaxies Mpc^{-2} are similar
to those in the luminosity-selected sample but show larger early-type
fractions. However, the trend with redshift in the fraction of elliptical and
S0 galaxies with masses > 10^{10.6} M_{\sun} differs significantly between the
mass- and luminosity-selected samples. The clear trend seen in the early-type
fraction from z=0 to z=~ 0.8 is not found in mass-selected samples. The
early-type galaxy fraction changes much less, and is consistent with being
constant at 92% +/- 4% at \Sigma> 500 galaxies Mpc^{-2} and 83 +/- 3% at 50 <
\Sigma < 500 galaxies Mpc^{-2}. This suggests that galaxies of mass lower than
> 10^{10.6} M_{\sun} play a significant role in the evolution of the early-type
fraction in luminosity-selected samples. (Abstract abridged)Comment: 18 pages in emulate ApJ format, with 10 color figures, Accepted to
ApJ. Version updated to reflect published version, includes new references
and a correction to table
A candidate redshift z ~ 10 galaxy and rapid changes in that population at an age of 500 Myr
Searches for very-high-redshift galaxies over the past decade have yielded a
large sample of more than 6,000 galaxies existing just 900-2,000 million years
(Myr) after the Big Bang (redshifts 6 > z > 3; ref. 1). The Hubble Ultra Deep
Field (HUDF09) data have yielded the first reliable detections of z ~ 8
galaxies that, together with reports of a gamma-ray burst at z ~ 8.2 (refs 10,
11), constitute the earliest objects reliably reported to date. Observations of
z ~ 7-8 galaxies suggest substantial star formation at z > 9-10. Here we use
the full two-year HUDF09 data to conduct an ultra-deep search for z ~ 10
galaxies in the heart of the reionization epoch, only 500 Myr after the Big
Bang. Not only do we find one possible z ~ 10 galaxy candidate, but we show
that, regardless of source detections, the star formation rate density is much
smaller (~10%) at this time than it is just ~200 Myr later at z ~ 8. This
demonstrates how rapid galaxy build-up was at z ~ 10, as galaxies increased in
both luminosity density and volume density from z ~ 8 to z ~ 10. The 100-200
Myr before z ~ 10 is clearly a crucial phase in the assembly of the earliest
galaxies.Comment: 41 pages, 14 figures, 2 tables, Nature, in pres
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