2,905 research outputs found
Measurement of the Integrated Faraday Rotations of BL Lac Objects
We present the results of multi-frequency polarization VLA observations of
radio sources from the complete sample of northern, radio-bright BL Lac objects
compiled by H. Kuhr and G. Schmidt. These were used to determine the integrated
rotation measures of 18 objects, 15 of which had never been measured
previously, which hindered analysis of the intrinsic polarization properties of
objects in the complete sample. These measurements make it possible to correct
the observed orientations of the linear polarizations of these sources for the
effect of Faraday rotation. The most probable origin for Faraday rotation in
these objects is the Galactic interstellar medium. The results presented
complete measurements of the integrated rotation measures for all 34 sources in
the complete sample of BL Lac objects.Comment: 9 pages, 7 figure
Elucidating the Metabolic Regulation of Liver Regeneration
The regenerative capability of liver is well known, and the mechanisms that regulate liver regeneration are extensively studied. Such analyses have defined general principles that govern the hepatic regenerative response and implicated specific extracellular and intracellular signals as regulated during and essential for normal liver regeneration. Nevertheless, the most proximal events that stimulate liver regeneration and the distal signals that terminate this process remain incompletely understood. Recent data suggest that the metabolic response to hepatic insufficiency might be the proximal signal that initiates regenerative hepatocellular proliferation. This review provides an overview of the data in support of a metabolic model of liver regeneration and reflects on the clinical implications and areas for further study suggested by these findings
Potato growing in Iowa as affected by temperature
The white potato is distinctively a cool-season crop. On the average the best yields are secured by planting early in order to get the crop as far along as possible in advance of the high summer temperatures.
The heaviest yields, on the average, were secured from the plantings made shortly after the seasonal rise in temperature crosses the 40° line.
For central Iowa, this period is usually reached during the first half of April.
In a date-of-planting-in-relation-to-yield experiment with late potatoes, covering six years, the results were as follows:
The average of the April plantings was 124.4 bushels per acre and for the June plantings, 76.2 bushels.
The planting dates covered by the last week of April and the first two weeks in May averaged about the same.
The plantings made after the middle of May gave a successive decline in yield.
Between the first and last planting there was a spread of 65.8 bushels per acre.
The minimum vegetative temperature for corn is fully ten degrees above that for potatoes. The general practice of planting late potatoes after corn planting is contrary to the temperature requirements of the two crops, and is regarded as one of the important reasons for the decline in potato yields in Iowa.
In general, the early market is the most profitable. Early planting and early marketing go hand in hand.
The danger from frost injury at harvest time may be largely eliminated by early planting
Polymer desorption under pulling: a novel dichotomic phase transition
We show that the structural properties and phase behavior of a self-avoiding
polymer chain on adhesive substrate, subject to pulling at the chain end, can
be obtained by means of a Grand Canonical Ensemble (GCE) approach. We derive
analytical expressions for the mean length of the basic structural units of
adsorbed polymer, such as loops and tails, in terms of the adhesive potential
and detachment force, and determine values of the universal exponents which
govern their probability distributions. Most notably, the hitherto
controversial value of the critical adsorption exponent is found to
depend essentially on the interaction between different loops. The chain
detachment transition turns out to be of the first order, albeit dichotomic,
i.e., no coexistence of different phase states exists. These novel theoretical
predictions and the suggested phase diagram of the adsorption-desorption
transformation under external pulling force are verified by means of extensive
Monte Carlo simulations.Comment: 10 pages, 4 figure
The effective potential, critical point scaling and the renormalization group
The desirability of evaluating the effective potential in field theories near
a phase transition has been recognized in a number of different areas. We show
that recent Monte Carlo simulations for the probability distribution for the
order parameter in an equilibrium Ising system, when combined with low-order
renormalization group results for an ordinary system, can be used to
extract the effective potential. All scaling features are included in the
process.Comment: REVTEX file, 22 pages, three figures, submitted to Phys. Rev.
Extragalactic Radio Sources and the WMAP Cold Spot
We detect a dip of 20-45% in the surface brightness and number counts of NVSS
sources smoothed to a few degrees at the location of the WMAP cold spot. The
dip has structure on scales of approximately 1-10 degrees. Together with
independent all-sky wavelet analyses, our results suggest that the dip in
extragalactic brightness and number counts and the WMAP cold spot are
physically related, i.e., that the coincidence is neither a statistical anomaly
nor a WMAP foreground correction problem. If the cold spot does originate from
structures at modest redshifts, as we suggest, then there is no remaining need
for non-Gaussian processes at the last scattering surface of the CMB to explain
the cold spot. The late integrated Sachs-Wolfe effect, already seen
statistically for NVSS source counts, can now be seen to operate on a single
region. To create the magnitude and angular size of the WMAP cold spot requires
a ~140 Mpc radius completely empty void at z<=1 along this line of sight. This
is far outside the current expectations of the concordance cosmology, and adds
to the anomalies seen in the CMB.Comment: revised version, ApJ, in pres
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