Fire in the Whole World

Fires account for a significant part of
the interannual variability of the atmospheric
concentrations of many
important trace gases like CO2 and
CH4, but the relative contribution of
emissions from different global regions
is very uncertain. In a study using
satellite and atmospheric data,
biogeochemical modeling, and an inverse
analysis of atmospheric CO
anomalies, van der Werf et al. (p.
73) analyzed how fires across different
regions contributed to global
trace gas variability between 1998
and 2001. Unusually high fire emissions
from Southeast Asia accounted for most of the global signals.
Contributions from Central America, northern boreal regions,
and South America that were underestimated previously
were also important sources.

Breaking Down the Stride

The energetic costs of running and the underlying physiological
mechanisms have been studied for decades. However, relating the
energetics to underlying mechanics has relied on “black-box” approaches.
In an experimental study of guinea fowl, Marsh et al. (p.
80; see the Perspective by Heglund) used blood flow to the muscles
as a measure of how the energy is distributed. Contrary to previous
predictions, the energy used by muscles that swing the upper limbs
was not negligible—it was about a third of the amount used by the
lower limbs that transmit force to the ground.

Mix and Fix Damaged DNA

Double-stand breaks (DSBs) in DNA can lead to tumorigenic
chromosomal translocations, but it is not clear how the broken
ends find each other. Are the different sites in the DNA in contact
before the breakage occurs (“contact-first” model) or are the
two different broken ends mobile in the nucleus (“breakage-first”
model)? By exposing cells to particles,
Aten et al. generated linear
tracks of DSBs through cell nuclei.
DSB-containing chromosomes were
mobile within the nucleus, as predicted
by the “breakage-first” model. In
some cells, the broken ends formed
large clusters, which brought many
DSBs in close proximity with one another
for potential repair.

A Home in the Milky Way

What fraction of
stars in our Galaxy
might play host
to planets that
can support multicellular
life?
Lineweaver et al.
calculate
the probable extent
of hospitable
space for complex life in the Galaxy, called the Galactic
habitable zone (GHZ). Their criteria include distance
from deadly supernovae, enough heavy elements to
form terrestrial planets, and enough time for life to
evolve. Based on these criteria, the GHZ is an annular
region between 7 to 9 kiloparsecs from the Galactic center
and contains about 10% of the Milky Way stars with
ages between 4 to 8 billion years old.

Now You See Them

Self-assembly of small molecules
can create objects with a wide variety
of morphologies on the
nanometer-to-micrometer scale.
Yan et al. (p. 65) have used hyperbranched
polymers that have both
hydrophilic and hydrophobic domains
to create hollow tubes that are millimeters in width and
centimeters long. The tubes form when the polymer is stirred into
acetone. Electron microscopy analysis of the tube walls indicates
that alternating lamellae form in which the hydrophobic domains
are amorphous and the hydrophilic ones are ordered. These tubes
are robust and can likely be tailored by derivatizing the side walls.

A Winter’s Trail

Before migrating into North America, early humans first moved into
Arctic Siberia and adapted to its harsh environment. The few oldest
sites have been dated to at most about 15,000 years ago or so,
which was after the major Northern Hemisphere ice sheets had begun
to recede. Pitulko et al. now report a series of
radiocarbon ages and artifacts
found in a terrace along the Yana
River (just south of its mouth into
the Arctic Ocean, in central Siberia)
that date to 27,000 radiocarbon
years ago (about 30,000 calendar
years). Artifacts include an ivory
foreshaft from the horn of a rhinoceros,
two others made from
mammoth tusk, and several hundred
stone points and flakes.

Dolphin gets help nursing her calf

BALTIMORE, Maryland (AP) -- A two-month old dolphin calf at the National Aquarium is being nursed by three females, the aquarium announced.

Jade is the calf's mother, but Chesapeake and Shiloh are helping Jade with her motherly duties.

While it is known that female bottlenose dolphins can spontaneously produce milk if a calf is present, the practice is not well documented and aquarium staff are carefully watching the process.
The unnamed male calf was born to a dolphin named Jade, who is being helped in her nursing duties by the mother-daughter team of Chesapeake and Shiloh, the aquarium said in a statement issued Tuesday to announce the birth.
Aquarium officials are compiling a list of possible names for the calf, which appears to be thriving.
The three-foot-long, 36-pound calf is nursing regularly, swimming more on its own and has begun to interact with the trainers and toys, the aquarium said.
Dolphin calves are fragile and not easily handled during their first two to three months of life, and trainers at the aquarium are leaving the nursing duties to its mother and her helpers.

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