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P&R Labpak - Everything for your laboratory
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Tuesday, 30 June 2015

Search for deadly asteroids must be accelerated to protect Earth, say experts

The search for deadly asteroids that could slam into Earth 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.

The call for action comes as experts around the world take 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.

Lord Rees, the astronomer royal, and Brian May, from the 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.

“The aim is to ramp up public awareness and the awareness of 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.”

Asteroid Day falls on the anniversary of an asteroid strike 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 conifer forest.

Were an asteroid of the same size to slam into the 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.

From observations with ground-based telescopes, researchers 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.

“They are clearly a threat and for the first time it is possible for us to do something to reduce that threat,” Lord Rees told the Guardian.

“It is now feasible to do a survey of all the potentially 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.

Huge asteroids several kilometres across are expected to hit 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.

Since most of the Earth’s surface is covered by water, 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.

“We know the rough numbers, we just don’t know when a 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.

“The first thing is to do the survey to find out if there 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.”

One mission, proposed by Nasa, aims to catalogue two thirds 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.

Scientists are actively looking at ways to protect Earth 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.

The option to lob nuclear warheads at an incoming asteroid is appealing to Hollywood, but less so to many scientists, including May, who has a PhD in astrophysics.

“Blowing it up is probably not the greatest option, because 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.

“It’s absolutely possible there’s something out there of the 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.

“This is about saving us all. All the people on the planet, 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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Tuesday, 23 June 2015

Stain Removal - How Does it Work?

We’ve all struggled to get stains out of clothes – but do you understand the science behind this? Most stains are removed by dissolving them with a solvent. But which one do you use? Two factors should help you to decide this:

  • The agent that is causing the stain
  • The material that has been stained

Different solvents will dissolve different stains, however some solvents not only dissolve the stain, but also dissolve the material that is stained as well – something that you don’t want to happen! 

Click to enlarge

Stains can be roughly grouped into a few categories:

Enzymatic stains, such as blood, human sweat and grass stains, are mainly made up of proteins and can therefore be combatted by enzymes in stain remover formulations, such as proteases, lipases and amylases.

Oxidisable stains, like tea, coffee and red wine, which can be broken down by bleaching agents, like hydrogen peroxide.

Greasy stains, which can be attacked by lipase enzymes and surfactants. Compound Chemicals describes these as most commonly being "‘long carbon chain compounds with a charged water-soluble ‘head’ and an oil-soluble ‘tail’ (which) remove oil and grease by forming structures called ‘micelles’ around them.”

Particulate stains, such as soil stains, can be removed by ‘builders’ compounds, which remove positive metal ions from the water and help soften it, in turn removing calcium ions which often bind stains to fabrics.

So, next time you regret that wine spillage or try to take that grass stain out of a football shirt, you’ll know what’s going on behind that brightly coloured stain remover – the science of stains! 

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Tuesday, 16 June 2015

The Real Reason Sweet Tastes Sweet

You might think that the sweet taste of fruit is all down to those natural sugars. Think again, says Veronique Greenwood.

We tend to think of sugar as the supreme ruler of the 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.

But Linda Bartoshuk, a University of Florida taste scientist 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 you taste.

Now, this is a different phenomenon than the old trick of 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.

In the case of Bartoshuk and company's recent work, however, it isn't the complex overtones of flavour they are talking about. This is more fundamental. It's the sweetness itself.

Bartoshuk says that the idea that volatile compounds 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.

The team had analysed the make-up of 152 heirloom varieties 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 taste characteristics.

Bartoshuk still remembers the moment when she was sitting in 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 volatiles.

Moreover, the volatiles seemed to account for why panellists 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?
They've also investigated blueberries and strawberries, 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 doubled it.

And it wasn't that an aroma of strawberries, or cherry 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.

What is going here? Researchers are still investigating how 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 enhancement”.

While researchers continue to investigate the causes of this 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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Friday, 12 June 2015

The Chemistry of Stinging Nettles

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. 

Urtica dioica herb has been used in the traditional Austrian 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. 

Nettle is used in shampoo to control dandruff and is said to make hair more glossy, which is why some farmers include a handful of nettles with cattle feed. 

Nettle root extracts have been extensively studied in human 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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