Monthly Archives: October 2016

The Chemistry of Pumpkins

We eat them, we carve them, but do we really know what’s
behind them? Here, we look at the chemistry of pumpkins.

Source: http://ift.tt/2eC5JZy

Pumpkins are grown all around the world for a variety of
reasons ranging from agricultural purposes (such as animal feed) to commercial
and ornamental sales. Of the seven continents, only Antarctica is unable to
produce pumpkins; the biggest international producers of pumpkins include the
United States, Canada, Mexico, India, and China. The traditional American
pumpkin used for jack-o-lanterns is the Connecticut Field variety.
As one of the most popular crops in the United States, 1.5
billion pounds (680,000,000 kilograms or 680,000 tonnes) of pumpkins are
produced each year. The top pumpkin-producing states include Illinois, Indiana,
Ohio, Pennsylvania, and California.

Pumpkins are a warm-weather crop that is usually planted in
early July. The specific conditions necessary for growing pumpkins require that
soil temperatures three inches (7.6 cm) deep are at least 60 °F (15.5 °C) and
soil that holds water well. Pumpkin crops may suffer if there is a lack of water
or because of cold temperatures (in this case, below 65 °F (18.3 °C); frost can
be detrimental), and sandy soil with poor water retention or poorly drained
soils that become waterlogged after heavy rain. Pumpkins are, however, rather
hardy, and even if many leaves and portions of the vine are removed or damaged,
the plant can very quickly re-grow secondary vines to replace what was removed.

Pumpkins produce both a male and female flower; honeybees
play a significant role in fertilization. Pumpkins have historically been
pollinated by the native squash bee Peponapis pruinosa, but this bee has
declined, probably at least in part to pesticide sensitivity, and today most
commercial plantings are pollinated by honeybees. One hive per acre (4,000 m²
per hive) is recommended by the U.S. Department of Agriculture. If there are
inadequate bees for pollination, gardeners often have to hand pollinate.
Inadequately pollinated pumpkins usually start growing but abort before full
development.

“Giant pumpkins” are a large squash (within the
group of common squash Cucurbita maxima) that can exceed 1 ton (2,000 pounds)
in weight. The variety arose from the large squash of Chile after 1500 A.D
through the efforts of botanical societies and enthusiast farmers.

Such germplasm is commercially provocative, and in 1986 the
United States extended protection for the giant squash. This protection was
limited to small specimens of a very specific parameters, being a weight of 175
pounds, oblong shape, etc. In 2004, the restriction expired except for the
requirement of indefinite use of the pseudonym “Dill’s Atlantic
Giant” for squash fitting the specific parameters or the seeds thereof.

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The Chemistry of Pumpkins

We eat them, we carve them, but do we really know what’s
behind them? Here, we look at the chemistry of pumpkins.

Source: http://ift.tt/2eC5JZy

Pumpkins are grown all around the world for a variety of
reasons ranging from agricultural purposes (such as animal feed) to commercial
and ornamental sales. Of the seven continents, only Antarctica is unable to
produce pumpkins; the biggest international producers of pumpkins include the
United States, Canada, Mexico, India, and China. The traditional American
pumpkin used for jack-o-lanterns is the Connecticut Field variety.
As one of the most popular crops in the United States, 1.5
billion pounds (680,000,000 kilograms or 680,000 tonnes) of pumpkins are
produced each year. The top pumpkin-producing states include Illinois, Indiana,
Ohio, Pennsylvania, and California.

Pumpkins are a warm-weather crop that is usually planted in
early July. The specific conditions necessary for growing pumpkins require that
soil temperatures three inches (7.6 cm) deep are at least 60 °F (15.5 °C) and
soil that holds water well. Pumpkin crops may suffer if there is a lack of water
or because of cold temperatures (in this case, below 65 °F (18.3 °C); frost can
be detrimental), and sandy soil with poor water retention or poorly drained
soils that become waterlogged after heavy rain. Pumpkins are, however, rather
hardy, and even if many leaves and portions of the vine are removed or damaged,
the plant can very quickly re-grow secondary vines to replace what was removed.

Pumpkins produce both a male and female flower; honeybees
play a significant role in fertilization. Pumpkins have historically been
pollinated by the native squash bee Peponapis pruinosa, but this bee has
declined, probably at least in part to pesticide sensitivity, and today most
commercial plantings are pollinated by honeybees. One hive per acre (4,000 m²
per hive) is recommended by the U.S. Department of Agriculture. If there are
inadequate bees for pollination, gardeners often have to hand pollinate.
Inadequately pollinated pumpkins usually start growing but abort before full
development.

“Giant pumpkins” are a large squash (within the
group of common squash Cucurbita maxima) that can exceed 1 ton (2,000 pounds)
in weight. The variety arose from the large squash of Chile after 1500 A.D
through the efforts of botanical societies and enthusiast farmers.

Such germplasm is commercially provocative, and in 1986 the
United States extended protection for the giant squash. This protection was
limited to small specimens of a very specific parameters, being a weight of 175
pounds, oblong shape, etc. In 2004, the restriction expired except for the
requirement of indefinite use of the pseudonym “Dill’s Atlantic
Giant” for squash fitting the specific parameters or the seeds thereof.

Source: 





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On this day in science history: Jupiter orbiter Galileo launched

In 1989, the Galileo space
orbiter was released from the STS 34 flight of the Atlantis orbiter. Then the
orbiter’s inertial upper stage rocket pushed it into a course through the inner
solar system. The craft gained speed from gravity assists in encounters with
Venus and Earth before heading outward to Jupiter. During its six year journey
to Jupiter, Galileo’s instruments made interplanetary studies, using its dust
detector, magnetometer, and various plasma and particles detectors. It also
made close-up studies of two asteroids, Gaspra and Ida in the asteroid belt.
The Galileo orbiter’s primary mission was to study Jupiter, its satellites, and
its magnetosphere for two years. It released an atmospheric probe into
Jupiter’s atmosphere on 7 Dec 1995.

Jupiter and its shrunken great red spot. By NASA, ESA, and A. Simon (Goddard Space Flight Center) [Public domain], via Wikimedia Commons

Jupiter’s mass is 2.5 times that
of all the other planets in the Solar System combined—this is so massive that
its barycenter with the Sun lies above the Sun’s surface at 1.068 solar radii
from the Sun’s center. Jupiter is much larger than Earth and considerably less
dense: its volume is that of about 1,321 Earths, but it is only 318 times as
massive. Jupiter’s radius is about 1/10 the radius of the Sun, and its mass is
0.001 times the mass of the Sun, so the densities of the two bodies are
similar. A “Jupiter mass” (MJ or MJup) is often used as a unit to
describe masses of other objects, particularly extrasolar planets and brown
dwarfs. So, for example, the extrasolar planet HD 209458 b has a mass of 0.69
MJ, while Kappa Andromedae b has a mass of 12.8 MJ.

Theoretical models indicate that
if Jupiter had much more mass than it does at present, it would shrink. For
small changes in mass, the radius would not change appreciably, and above about
500 M⊕
(1.6 Jupiter masses) the interior would become so much more compressed under
the increased pressure that its volume would decrease despite the increasing
amount of matter. As a result, Jupiter is thought to have about as large a
diameter as a planet of its composition and evolutionary history can achieve.
The process of further shrinkage with increasing mass would continue until
appreciable stellar ignition is achieved as in high-mass brown dwarfs having
around 50 Jupiter masses.


Although Jupiter would need to be
about 75 times as massive to fuse hydrogen and become a star, the smallest red
dwarf is only about 30 percent larger in radius than Jupiter. Despite this,
Jupiter still radiates more heat than it receives from the Sun; the amount of
heat produced inside it is similar to the total solar radiation it receives. This
additional heat is generated by the Kelvin–Helmholtz mechanism through
contraction. This process causes Jupiter to shrink by about 2 cm each year.
 When it was first formed, Jupiter was much
hotter and was about twice its current diameter.

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Methane muted: How did early Earth stay warm?

For at least a billion years of the distant past, planet
Earth should have been frozen over but wasn’t. Scientists thought they knew
why, but a new modeling study from the Alternative Earths team of the NASA
Astrobiology Institute has fired the lead actor in that long-accepted scenario.

Humans worry about greenhouse gases, but between 1.8 billion
and 800 million years ago, microscopic ocean dwellers really needed them. The
sun was 10 to 15 percent dimmer than it is today – too weak to warm the planet
on its own. Earth required a potent mix of heat-trapping gases to keep the
oceans liquid and livable.

For decades, atmospheric scientists cast methane in the
leading role. The thinking was that methane, with 34 times the heat-trapping
capacity of carbon dioxide, could have reigned supreme for most of the first
3.5 billion years of Earth history, when oxygen was absent initially and little
more than a whiff later on. (Nowadays oxygen is one-fifth of the air we
breathe, and it destroys methane in a matter of years.)

Full structural formula of the methane molecule
“A proper accounting of biogeochemical cycles in the
oceans reveals that methane has a much more powerful foe than oxygen,”
said Stephanie Olson, a graduate student at the University of California,
Riverside, a member of the Alternative Earths team and lead author of the new
study published September 26 in the Proceedings of the National Academy of
Sciences. “You can’t get significant methane out of the ocean once there
is sulfate.”

Sulfate wasn’t a factor until oxygen appeared in the
atmosphere and triggered oxidative weathering of rocks on land. The breakdown
of minerals such as pyrite produces sulfate, which then flows down rivers to
the oceans. Less oxygen means less sulfate, but even 1 percent of the modern
abundance is sufficient to kill methane, Olson said.

Olson and her Alternative Earths coauthors, Chris Reinhard,
an assistant professor of earth and atmospheric sciences at Georgia Tech
University, and Timothy Lyons, a distinguished professor of biogeochemistry at
UC Riverside, assert that during the billion years they assessed, sulfate in
the ocean limited atmospheric methane to only 1 to 10 parts per million – a
tiny fraction of the copious 300 parts per million touted by some previous
models.

The fatal flaw of those past climate models and their
predictions for atmospheric composition, Olson said, is that they ignore what
happens in the oceans, where most methane originates as specialized bacteria
decompose organic matter.

Seawater sulfate is a problem for methane in two ways:
Sulfate destroys methane directly, which limits how much of the gas can escape
the oceans and accumulate in the atmosphere. Sulfate also limits the production
of methane. Life can extract more energy by reducing sulfate than it can by
making methane, so sulfate consumption dominates over methane production in
nearly all marine environments.

The numerical model used in this study calculated sulfate
reduction, methane production, and a broad array of other biogeochemical cycles
in the ocean for the billion years between 1.8 billion and 800 million years
ago. This model, which divides the ocean into nearly 15,000 three-dimensional
regions and calculates the cycles for each region, is by far the highest resolution
model ever applied to the ancient Earth. By comparison, other biogeochemical
models divide the entire ocean into a two-dimensional grid of no more than five
regions.

“Free oxygen [O2] in the atmosphere is required to form
a protective layer of ozone [O3], which can shield methane from photochemical
destruction,” Reinhard said. When the researchers ran their model with the
lower oxygen estimates, the ozone shield never formed, leaving the modest puffs
of methane that escaped the oceans at the mercy of destructive photochemistry.

With methane demoted, scientists face a serious new
challenge to determine the greenhouse cocktail that explains our planet’s
climate and life story, including a billion years devoid of glaciers, Lyons
said. Knowing the right combination other warming agents, such as water vapor,
nitrous oxide, and carbon dioxide, will also help us assess habitability of the
hundreds of billions of other Earth-like planets estimated to reside in our
galaxy.

“If we detect methane on an exoplanet, it is one of our
best candidates as a biosignature, and methane dominates many conversations in
the search for life on Mars,” Lyons said. “Yet methane almost
certainly would not have been detected by an alien civilization looking at our
planet a billion years ago – despite the likelihood of its biological
production over most of Earth history.”

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The chemistry behind the aroma of coffee

The Aroma of Coffee (Compound Interest
What is it about that delicious smell of coffee? Or, more specifically, what lies behind it? The graphic above takes a look at a selection of the chemical compounds behind this aroma. 

So that’s the chemistry, but what about the biology of coffee?

Several species of shrub of the genus Coffea produce the
berries from which coffee is extracted. The two main species commercially
cultivated are Coffea canephora (predominantly a form known as ‘robusta’) and
C. arabica. C. arabica, the most highly regarded species, is native to the
southwestern highlands of Ethiopia and the Boma Plateau in southeastern Sudan
and possibly Mount Marsabit in northern Kenya. C. canephora is native to western
and central Subsaharan Africa, from Guinea to Uganda and southern Sudan. Less
popular species are C. liberica, C. stenophylla, C. mauritiana, and C.
racemosa.

All coffee plants are classified in the large family
Rubiaceae. They are evergreen shrubs or trees that may grow 5 m (15 ft) tall
when unpruned. The leaves are dark green and glossy, usually 10–15 cm (4–6 in)
long and 6 cm (2.4 in) wide, simple, entire, and opposite. Petioles of opposite
leaves fuse at base to form interpetiolar stipules, characteristic of
Rubiaceae. The flowers are axillary, and clusters of fragrant white flowers
bloom simultaneously. Gynoecium consists of inferior ovary, also characteristic
of Rubiaceae. The flowers are followed by oval berries of about 1.5 cm (0.6
in). When immature they are green, and they ripen to yellow, then crimson,
before turning black on drying. Each berry usually contains two seeds, but
5–10% of the berries have only one; these are called peaberries. 

Arabica
berries ripen in six to eight months, while robusta take nine to eleven months.

Coffea arabica is predominantly self-pollinating, and as a
result the seedlings are generally uniform and vary little from their parents.
In contrast, Coffea canephora, and C. liberica are self-incompatible and
require outcrossing. This means that useful forms and hybrids must be
propagated vegetatively. Cuttings, grafting, and budding are the usual methods
of vegetative propagation. On the other hand, there is great scope for
experimentation in search of potential new strains.

In 2016, Oregon State University entomologist George Poinar,
Jr. announced the discovery of a new plant species that’s a 45-million-year-old
relative of coffee found in amber. Named Strychnos electri, after the Greek word
for amber (electron), the flowers represent the first-ever fossils of an
asterid, which is a family of flowering plants that not only later gave us
coffee, but also sunflowers, peppers, potatoes, mint — and deadly poisons.

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