1,821 research outputs found
Melanism as a potential thermal benefit in eastern fox squirrels (Sciurus niger)
Melanistic fox squirrels (Sciurus niger) have expanded westward and increased in frequency in the Omaha, Nebraska, and Council Bluffs, Iowa, metropolitan areas. The selective advantage of melanism is currently unknown, but thermal advantages have been hypothesized, especially in winter. No difference in metabolic response curves were measured between melanistic (black) and rufus (orange) fox squirrels. When exposed to sunny skies, both melanistic and rufus squirrels had higher surface (skin and fur) temperature as ambient temperatures increased. Melanistic squirrel surface temperatures did not differ when squirrels were exposed to sunny or cloudy skies. However, rufus individuals showed significantly lower increases in surface temperatures when under cloudy skies. During fall months, rufus individuals were about 1.5 times more active throughout the day than melanistic individuals. However, in winter, melanistic fox squirrels were approximately 30% more active in the mornings (before 13:00) compared to rufus squirrels. Pre-winter body condition was higher in melanistic (25.5 ± 1.8 g/cm) compared to rufus (20.30 ± 3.6 g/cm) fox squirrels; however, there were no significant differences between melanistic (22.8 ± 1.4 g/cm) and rufus (23.9 ± 0.8 g/cm) fox squirrel post-winter body condition. The results of this study indicate that melanistic fox squirrels may have a slight winter thermal advantage over rufus fox squirrels by maintaining higher skin temperatures
On Second-Order Cone Functions
We consider the second-order cone function (SOCF) defined by . Every SOCF is concave.
We give necessary and sufficient conditions for strict concavity of . The
parameters and are not
uniquely determined. We show that every SOCF can be written in the form . We give necessary and
sufficient conditions for the parameters , , , , and
to be uniquely determined. We also give necessary and sufficient
conditions for to be bounded above.Comment: 21 pages, 5 figure
A Pre-Protostellar Core in L1551. II. State of Dynamical and Chemical Evolution
Both analytic and numerical radiative transfer models applied to high
spectral resolution CS and N2H+ data give insight into the evolutionary state
of L1551 MC. This recently discovered pre-protostellar core in L1551 appears to
be in the early stages of dynamical evolution. Line-of-sight infall velocities
of >0.1km/s are needed in the outer regions of L1551 MC to adequately fit the
data. This translates to an accretion rate of ~ 1e-6 Msun/yr, uncertain to
within a factor of 5 owing to unknown geometry. The observed dynamics are not
due to spherically symmetric gravitational collapse and are not consistent with
the standard model of low-mass star formation. The widespread, fairly uniform
CS line asymmetries are more consistent with planar infall. There is modest
evidence for chemical depletion in the radial profiles of CS and C18O
suggesting that L1551 MC is also chemically young. The models are not very
sensitive to chemical evolution. L1551 MC lies within a quiescent region of
L1551 and is evidence for continued star formation in this evolved cloud.Comment: 27 pages, 7 figures, ApJ accepte
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