92,387 research outputs found
Bilateral Differentiation of Color and Morphology in the Larval and Pupal Stages of \u3ci\u3ePapilio Glaucus\u3c/i\u3e (Lepidoptera: Papilionidae)
A sharply delineated, bilateral differentiation of color patterns and morphology were observed in a final (5th) instar larva of a subspecies backcross of a female Papilio glaucus glaucus with a hybrid male (P. g. glaucus x P. g. canadensis). Color and morphological differences were detectable in the pupa as well. In addition, a bilateral size difference was evident in both the pupa and the resulting adult butterfly. Such observations within a single living individual attest to the bilateral independence (also evident in perfect gynandromorphs) and general flexibility of the developmental control in this species of Lepidoptera
Pseudo-rip: Cosmological models intermediate between the cosmological constant and the little rip
If we assume that the cosmic energy density will remain constant or strictly
increase in the future, then the possible fates for the universe can be divided
into four categories based on the time asymptotics of the Hubble parameter
H(t): the cosmological constant, for which H(t) = constant, the big rip, for
which H(t) goes to infinity at finite time, the little rip, for which H(t) goes
to infinity as time goes to infinity, and the pseudo-rip, for which H(t) goes
to a constant as time goes to infinity. Here we examine the last of these
possibilities in more detail. We provide models that exemplify the pseudo-rip,
which is an intermediate case between the cosmological constant and the little
rip. Structure disintegration in the pseudo-rip depends on the model
parameters. We show that pseudo-rip models for which the density and Hubble
parameter increase monotonically can produce an inertial force which does not
increase monotonically, but instead peaks at a particular future time and then
decreases.Comment: 4 pages, 2 figures, title changed to agree with published versio
Aggregation Of Chlorophyll a Probed By Resonance Light Scattering Spectroscopy
We report the resonance light scattering (RLS) spectra of chlorophyll a aggregated in a 9:1 solution of formamide and pH 6.8 phosphate buffer. The aggregate formed after 2 h of mixing, referred to as Chl(469), shows a strong scattering feature at 469 nm (Soret band) and a much weaker feature at 699 nm (Q(y) band). A kinetic investigation confirmed that the aggregation process is cooperative, and also detected one intermediate (Chl(458)) with a strong RLS spectrum but only a weak CD spectrum. We propose that aggregation proceeds via at least three steps: 1) formation of a nucleating species, probably a dimer of chlorophylls; 2) formation of large aggregates with little or no secondary structure (e.g., Chl(458)); and 3) conformational change to form helical aggregate (Chl(469))
Efficient Monte Carlo for high excursions of Gaussian random fields
Our focus is on the design and analysis of efficient Monte Carlo methods for
computing tail probabilities for the suprema of Gaussian random fields, along
with conditional expectations of functionals of the fields given the existence
of excursions above high levels, b. Na\"{i}ve Monte Carlo takes an exponential,
in b, computational cost to estimate these probabilities and conditional
expectations for a prescribed relative accuracy. In contrast, our Monte Carlo
procedures achieve, at worst, polynomial complexity in b, assuming only that
the mean and covariance functions are H\"{o}lder continuous. We also explain
how to fine tune the construction of our procedures in the presence of
additional regularity, such as homogeneity and smoothness, in order to further
improve the efficiency.Comment: Published in at http://dx.doi.org/10.1214/11-AAP792 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Regularity of weak minimizers of the K-energy and applications to properness and K-stability
Let be a compact K\"ahler manifold and the space of
K\"ahler metrics cohomologous to . If a cscK metric exists in , we show that all finite energy minimizers of the extended K-energy are
smooth cscK metrics, partially confirming a conjecture of Y.A. Rubinstein and
the second author. As an immediate application, we obtain that existence of a
cscK metric in implies J-properness of the K-energy, thus
confirming one direction of a conjecture of Tian. Exploiting this properness
result we prove that an ample line bundle admitting a cscK metric in
is -polystable.Comment: v1 Comments welcome v2 New introduction and references added v3 Final
version. Preliminaries section added. Some notation changed. No other change
Thermal performance of a liquid hydrogen tank multilayer insulation system at warm boundary temperatures of 630, 530, and 152 R
The results are presented of a study conducted to obtain experimental heat transfer data on a liquid hydrogen tank insulated with 34 layers of MLI (multilayer insulation) for warm side boundary temperatures of 630, 530, and 150 R. The MLI system consisted of two blankets, each blanket made up of alternate layers of double silk net (16 layers) and double aluminized Mylar radiation shields (15 layers) contained between two cover sheets of Dacron scrim reinforced Mylar. The insulation system was designed for and installed on a 87.6 in diameter liquid hydrogen tank. Nominal layer density of the insulation blankets is 45 layers/in. The insulation system contained penetrations for structural support, plumbing, and electrical wiring that would be representative of a cryogenic spacecraft. The total steady state heat transfer rates into the test tank for shroud temperatures of 630, 530, 152 R were 164.4, 95.8, and 15.9 BTU/hr respectively. The noninsulation heat leaks into the tank (12 fiberglass support struts, tank plumbing, and instrumentation lines) represent between 13 to 17 pct. of the total heat input. The heat input values would translate to liquid H2 losses of 2.3, 1.3, and 0.2 pct/day, with the tank held at atmospheric pressure
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