Monthly Archives: June 2015
must be speeded up 100-fold to help protect the future of life on Earth,
according to an influential group of scientists, astronauts and rock stars.
part in Asteroid Day, an event on Tuesday marked by a series of talks and
debates aimed at raising awareness of the existential threat posed by hurtling
rocks from the heavens.
rock group Queen, added their names to the 100X declaration, which calls for a
rapid acceleration in human efforts to find and track potentially dangerous
asteroids. Other signatories including Peter Gabriel, Richard Dawkins, Brian
Cox and Eileen Collins, the first female commander of Nasa’s space shuttle.
governments to the fact that we are under threat from a meteor strike,” May
told the Guardian. “It’s been made light of, and we’ve seen some great films,
like Bruce Willis saving the day, but it is a very serious threat.”
in 1908 that saw a 40 metre-wide lump of space rock enter the atmosphere over
Tunguska in Siberia at about 33,500 miles per hour. The rock exploded mid-air
and released the energy of a large hydrogen bomb, which flattened 2000 sq km of
atmosphere over London, the blast could destroy much of the capital within the
M25. People in cities as far away as Oxford could be burned by the intense heat
released in the explosion. In Scotland, the same blast would still have the
force to blow peoples’ hats off.
know that of the million or so asteroids that could one day strike Earth, only
about 10,000 are known and tracked. That means we are in the dark about 99% of
the asteroids that have the potential to crash into the planet.
possible for us to do something to reduce that threat,” Lord Rees told the
Earth-crossing asteroids above 50m in diameter, and objects like that impact
Earth about once per century. One could then check their orbits to see if any
are on a collision course with Earth and within 20-30 years have technology to
divert any that are on course,” he added.
Earth every ten million years or so. These can cause destruction on a global
scale. A ten kilometre-wide space rock that crashed into what is now Mexico
triggered a global catastrophe 68 million years ago which brought the reign of
the dinosaurs to an end.
asteroids are more likely to arrive over the oceans. But these can be the worst
impact sites for asteroids of about 300 metres wide. If one landed in the
mid-Atlantic, it would produce a tsunami wave that could devastate cities on
the east coast of the US, and along the coast of Europe.
particular asteroid is going to hit. If we are going to take precautions, we
need to know the orbits of all of these bodies,” Rees said.
are any asteroids which seem to be on course with a high probability of hitting
within the next 50 years. If we knew there was one on course to hit the Earth
in next 50 years, that would focus minds on the technology.”
of the asteroids and other “near earth objects” that are larger than 140m and
come close to Earth’s orbit. The NEOCam mission would use an infra-red camera
to garner information on asteroid size, shape, rotation and composition. A
private mission called Sentinel, which would put an another infra-red telescope
in space, is being led by Ed Lu, a former space shuttle astronaut.
from any asteroids that do turn out to be on a collision course. One strategy
is to crash a massive spacecraft into the asteroid and change its trajectory.
Another option is a “gravity tractor”. In this scenario, a spacecraft flies
alongside an inbound asteroid for long enough that its minuscule gravitational
tug diverts the asteroid enough to pass Earth safely. Both could run into
problems in a real situation, though: if the nudge does not work as expected,
the asteroid may miss one city only to hit another.
is appealing to Hollywood, but less so to many scientists, including May, who
has a PhD in astrophysics.
you have a lot of fragments to deal with then, and it becomes rather random,
but deflecting it one way or another seems to be an option,” he said.
magnitude that would wipe out a major city of the world, and that’s a very big
thing: you’re talking about a human disaster on a vast scale.
all the creatures on the planet, everything which we have built up and might be
proud of. It’s a kind of insurance if you like,” he said.
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is on hand to help out! A range of different molecules are present in stain
removers and detergents to help shift grease and dirt, and they can work in
different ways. This graphic takes a look at how we can categorise different
types of stains, and how the molecules that help remove them work.
|Click to enlarge|
classes: enzymatic, oxidisable, greasy, and particulate. This is really
something of a simplification – in reality, a particular stain will have a
number of components, which may fall into more than one of these categories.
For example, a stain from something like a tomato pasta sauce would have a
coloured, oxidisable component, but would probably also be a little greasy. As
such, stain removers tend to be a mixture of all of the agents we’ll discuss,
to tackle these multi-component stains.
which are both largely the result of proteins. Enzymes in stain remover
formulations can be used to break these down. Specifically, proteases will
break down proteins by breaking the larger molecules into smaller, soluble
chunks. Human sweat stains can also be removed by proteases. Other molecules
that can be broken down by enzymes include fats, broken down by lipases, and
starch, broken down by amylases.
stain category. These include stains like tea and coffee, as well as red wine.
Throwing white wine on a red wine stain won’t help at all – but throwing a
bleach-based stain remover on it might. These stain removers contain bleaching
agents, commonly hydrogen peroxide, which breaks down colour-causing sections
of chemical structures, removing the appearance of the stain. The hydrogen
peroxide is usually present in the form of sodium percarbonate, which releases hydrogen
peroxide when combined with water.
quite as well at removing stains below 40˚C. Not a problem if you’re washing at
or above that temperature, but if you’re washing lower, or just wanting to use
your stain remover on carpet or furnishings, the hydrogen peroxide is going to
need some help. It gets this in the form of the addition of
tetraacetylethylenediamine, or TAED for short. TAED reacts with hydrogen
peroxide to produce peracetic acid, an even stronger bleaching agent than
they are primarily removed by the use of surfactants. These are commonly long
carbon chain compounds with a charged water-soluble ‘head’ and an oil-soluble
‘tail’. Generally, they’ll appear listed as either ‘cationic surfactants’,
‘anionic surfactants’, and ‘nonionic surfactants’ on the stain remover bottle.
These simply refers to the charge (or lack of) on the molecule’s ‘head’. A
cationic surfactant has a positive charge, an anionic surfactant a negative
charge, and a nonionic surfactant has no charge.
structures called ‘micelles’ around them. The oil-soluble parts of the molecule
dissolve in the oil or grease, forming a spherical structure around the oil
droplet. The water-soluble parts of the surfactant molecule are then sticking
outwards, meaning that the micelles are able to dissolve in water, allowing the
greasy stain to be washed away.
‘builders’ are used. These compounds primarily help to soften the water during
washes by removing positive metal ions (mainly calcium and magnesium ions) from
the water. They are also very helpful in removing soil stains from clothes, as
these stains are often bound to fabrics by calcium ion bridging. Removing the
calcium ions therefore helps remove the dirt.
as a builder, but due to concerns about its excessive release into the
environment (it can cause eutrophication) many companies have now replaced it
with other agents. Some of these can include sodium carbonate,
polycarboxylates, and also zeolites. Zeolites are crystalline aluminium silicates,
inorganic structures with pores that can incorporate calcium and magnesium
ions. They also possess a number of other advantages over other builders, such
as inhibiting dye transfer during washes. Generally, builders also increase the
cleaning action of other chemicals in the detergent, by preventing cations
interfering with other charged molecules, such as surfactants. They can
additionally help prevent the redeposition of dirt onto fabrics once it has
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those natural sugars. Think again, says Veronique Greenwood.
sensation of sweetness. If an orange tastes sweet, it’s because of the sugars
it contains hit the sweet receptors in your taste buds. The same, it’s fair to
say, should ring true for any other fruit, from blueberries to tomatoes.
interviewed for this column before, and her colleagues think there is a
different explanation. They’ve found that the chemicals responsible for a large
chunk of the perception of sweetness in fruit are ones you smell – not the ones
plugging your nose while you eat a jelly bean and finding you can’t identify
its flavour. If you haven’t done this, try it – it’s a marvellous glimpse into
how much of flavour isn’t about the tongue. At first all you can taste is
sweet, but when you open your nose, the sensation of strawberry or root beer or
whatever the specific flavour is washes over you.
it isn’t the complex overtones of flavour they are talking about. This is more
fundamental. It’s the sweetness itself.
emanating from fruit could be linked to sweetness was being discussed in the
1970s. But the effects of individual volatiles were very small, and the amounts
of each chemical in the fruit were small as well. “I knew that the issue
existed, but I didn’t think anything hot had been done on it, and I was right,”
Bartoshuk says. A few years ago, however, while she and colleagues were working
on a study attempting to dissect exactly which molecules are responsible for
what you experience while eating a tomato, she found something surprising.
of tomato, recording the levels of glucose, fructose, fruit acids, and 28
volatiles. At the same time, over the course of three years, they organised 13
panels of taste-testers to sample more than 66 of these varieties, rating each
according to how much they liked it, its sweetness, its sourness, and other
her office with this mountain of data one afternoon and ran a test, out of
curiosity, to see which compounds contributed most to sweetness. She was
expecting the answer to be sugar, and it certainly was key, but “I about fell
out of my chair,” she says. Also significantly contributing were seven
had reported some tomato varieties to taste sweeter than others that had far
more sugar. The team tested a variety called Yellow Jelly Bean, for instance,
and another called Matina. The Yellow Jelly Bean has 4.5g of glucose and
fructose in 100 millilitres of fruit and rated about a 13 on a scale used for
perceived sweetness. The Matina has just under 4g but rated a whopping 25. The
major biochemical difference between the two was that the Matina had at least
twice as much of each of the seven volatiles as the Yellow Jelly Bean did. When
the team isolated those volatiles from a tomato and added them to sugar water,
its perceived sweetness jumped.
|How sweet can a tomato be?|
among other fruits. Strawberries have much less sugar than blueberries but are
consistently rated much sweeter. Bartoshuk and colleagues suggest that this is
because strawberries have so many more volatiles – something like 30 – than
blueberries, which have “maybe three”, Bartoshuk estimates. They found that
adding strawberry volatiles to sugar water boosted perceived sweetness even
more than the tomato volatiles did, and adding volatiles from both together
tomatoes, was wafting up off the water. The volatiles weren’t concentrated
enough to float up and hit the nose. (Which is a good thing – one of the volatiles
in tomatoes is isovaleric acid, which, on its own, smells like stinky cheese.)
The more sugar there is, the less the volatiles contribute to sweetness. But
the effect gets stronger, somehow, when greater numbers of volatiles are
involved: even volatiles that aren’t present in large amounts still seem to
contribute to the sensation.
and why the brain is blending this information. It’s known that the signals
coming from smell receptors activated by volatiles from the back of the mouth
are shunted to the same part of the brain that handles taste, rather than being
bundled with signals from the nose itself. Bartoshuk says. Though she is not a
neuroscientist herself, she suggests that “in the brain, when you have
volatiles affecting some of the same cells as taste, it integrates the message.
And part of the integrating, for certain volatiles and certain tastes, is
strange effect, we can daydream about the possibilities. Could you make fresh
lemonade with less sugar if you tossed in a cocktail of volatiles? Possibly,
Bartoshuk says, if you added many of them. She is also curious about the idea
of breeding a fruit that’s as sweet as it can possibly be. Could plant breeders
analyse volatiles and select for strains that maximise this volatile effect?
Bartoshuk thinks so.
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Stinging nettles are a type of plant which have defensive hairs. Their stings hurt a lot. Stinging nettles can be found in all of America except Hawaii. They can also be found in most of Europe and in Asia. Nettles sting because the hairs on it contains poison. If nettles are heated the poison disappears, making it edible.
|Click to enlarge|
The excellent Compound Interest site once again shows us how something that has happened to most of us actually works. The chemistry of stinging nettles and what can be done to counter act them.
Nettles have long been used for medicinal purposes. Nettle leaf is a herb that has a long tradition of use as an
adjuvant remedy in the treatment of arthritis in Germany. Nettle leaf extract
contains active compounds that reduce TNF-α and other inflammatory
cytokines. It has been demonstrated that nettle leaf lowers TNF-α
levels by potently inhibiting the genetic transcription factor that activates
TNF-α and IL-1B in the synovial tissue that lines the joint.
medicine internally (as tea or fresh leaves) for treatment of disorders of the
kidneys and urinary tract, gastrointestinal tract, locomotor system, skin,
cardio-vascular system, hemorrhage, flu, rheumatism and gout.
make hair more glossy, which is why some farmers include a handful of nettles
with cattle feed.
clinical trials as a treatment for symptoms of benign prostatic hyperplasia
(BPH). These extracts have been shown to help relieve symptoms compared to
placebo both by themselves and when combined with other herbal medicines.
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