David Bradley – Page 305

What are Significant Figures?

By definition the use of significant figures in measurement and value is a form of rounding. They represent the the number of digits in a number, beginning at the first non-zero digit and including any trailing zeros. For instance, 0.005746180 has 7 significant figures. All 7 of those digits are significant, if someone were measuring a distance, volume, time period or whatever and they included all those numbers as well as that final zero, you would assume that they had measured the value to seven significant figures. The next number after the final digit would not be reliable and so is not included.

Understanding the application of significant figures is crucial in science and engineering, especially when converting between units, litres to fluid ounces for instance, pounds to kilograms, or feet to metres. Often conversion factors of the kind cited and used at online conversion sites are quoted with long strings after the decimal point. These represent (usually) the level of accuracy the standard measurements are known. However, if you measure the distance from A to B with a tape measure marked in inches, the best degree of accuracy you will obtain will be down to a quart or possibly an eighth of an inch.

Your error will then be + or – a sixteenth or thereabouts. If the value you obtain is 46 and three eighths inches, and the gradations on your tape only go down to eighths then you cannot know for certain any smaller a fraction. That figure would be 46.375 inches. Five significant figures. But, you might round that to three significant figures, 46.4 to accommodate measuring errors.

Now, you want to know what that inch measurement is in centimetres, so you go to your online converter and get the conversion factor. 1 cm is equal to 0.393700787 inches. That’s quite a few digits to tap into your calculator. But, wait! We’ve got nine significant figures in that conversion factor, that’s way about the three we’re looking at in our actual measurement, so we need to round it to the same level of precision. Our conversion factor would be 0.394. 46.4 inches is therefore divided by this factor to give the value in centimetres, 117.766497….

Again, the calculator can fool us into believing we’ve gained some extra accuracy. Remember, we began with only three sig figs, so we should end up with only three sig figs in our converted value. our measured value of 46.4 inches should therefore be 118 centimetres, rounded to 3 sig figs.

One thing you should always remember about doing calculations on measurements. If you have a bunch of different values to different levels of accuracy then you must use the number of significant figures in the value with the least number of sig figs to start with. So if you’re doing an acceleration calculation, for instance, and you have velocity as 1.56 m/s, distance as 12.45 m and time as 82 seconds, then the least reliable value of the three is the time. That’s only cited to two SFs so you have to round your final answer to two SFs too, once you’ve done the calculation.

Intute Spotlight for February

Keypad lock The latest physical science news from David Bradley can also be found on the intute portal under the Spotlight. This month:

Shedding light on a molecular lock

Logic at the molecular scale has been exploited to build a keypad lock that “opens” only when the correct sequence of inputs is applied. Researchers at the Weizmann Institute of Science in Israel explain how they have harnessed the principles of molecular Boolean logic to create a nanoscale keypad lock…one you’re going to need very small fingers to key.

Anthropogenic volcanic activity

The first scientific report into the causes and impact of Lusi, the Indonesian mud volcano located in Eastern Java that erupted on 29th May 2006 in the middle of a rice paddy, has now been published. The results provide a damning indictment of the cause of this eruption, laying the blame most likely at the feet of natural gas explorers.

Demonic chemistry

In 1867, Scottish physicist James Clerk Maxwell devised a thought experiment that would help scientists find ways of breaking the law. The second law of thermodynamics, that is. The second law of thermodynamics tells us that heat cannot pass from a hotter object to a colder one. David Bradley talked to David Leigh who has devised a molecule that almost plays a demonic role.

Read the February issue of Intute Spotlight online now.

NearIR Nightly

Organic light-emitting diodes (OLEDs) are finding applications in a whole range of devices now not least because of their flexibility, in both the physical and viability sense, and their high energy efficiency. Until recently, however, OLED research was focused on visible emission. Now, US scientists have developed a near infra-red OLED, a NIR OLED. They reckon an NIR OLED could be used in future night-vision devices. NIR OLEDs might also one day find use in small-scale, portable NIR spectrometers or lab-on-a-chip systems for medical and environmental analysis, or potentially chemical and bio weapons detection.

Mark Thompson of the University of Southern California and colleagues at Princeton University, Steve Forrest’s group at the University of Michigan, and Julie Brown’s team at Universal Display Corporation have used a phosphorescent platinum-porphyrin complex as a doping agent to create the new class of NIR OLED.

You can read the full story in my SpectroscopyNOW column this week.

If anyone gets the allusion in this post title, drop me a line.

Viagra and steroids

Viagra stanozolol structure Sciencebase reader Toar Winter emailed with a rather intriguing question.

Baseball star Rafael Palmeiro tested positive for anabolic steroids in August 2005 after telling the US Congress he had never taken such drugs before and was banned for ten days. He still insists he did not take steroids, or that if he did they were ingested through unprescribed supplements that contained stanozolol, the actual substance for which he tested positive.

Stanozolol is an old steroid and a test for its illegal use in sport has been used successfully for many years. It would actually make little sense for any sportsperson to cheat using this particular drug as it is detected so easily. This is especially true given the plethora of alternative, including human growth hormon (HGH) for which current testing methods are not quite so efficient.

So, back to Winter’s question. First, he points out that Palmeiro’s only advertising sponsor is Viagra, then asks whether or not it could be Viagra that produced a “false positive” for the steroid. After all, there is certainly some overlap between the effects and side effects of viagra and certain steroids. Winter, wants to know whether or not Pfizer in developing Viagra initially altered the structure of stanozolol slightly to produce a ‘different’ drug with similar or more directed effects.

As far as I know this is not the case. Pfizer was developing a drug for angina and high blood pressure in the late 1980s when it discovered that male volunteers in its clinical trials were seeing a rather outstanding side-effect of the drug. They’d actually based their leads on a known, but unmarketed, allergy drug Zaprinast, which inhibits the enzyme phosphodiesterase. The rest is history. This compound is not related to stanozolol as far as I know. If any readers can affirm otherwise, please leave a comment or email me.

Winter’s line of reasoning, however, is intriguing nonetheless. “Think about it,” he says, “not many athletes in today’s world are of the age where Viagra is needed, so drug testing probably wouldn’t detect many offenders.

It’s an intriguing idea, but I don’t think Winter’s theory stands up to close scrutiny. If it did, wouldn’t it be ironic that many of those same (elder) Congressmen pointing the finger at Palmeiro would have also shown positive in the same test?

Meanwhile, in other news, Pfizer has lost its battle to name the Chinese brand Viagra, “Wei Ge” (according to http://www.chinacourt.org/). The phrase is commonly used in China, where copycat generics out sell the real thing, but Guangzhou Welman, a Chinese ED drug maker already registered this name and the courts have said it should be allowed to retain the rights to it. I’m sure at least one regular reader of the Sciencebase blog will be able to tell us the origin of that name…

How to Sneeze

How to sneeze Kleenex is out, disposable arm bands are not yet de rigeur, so what’s the alternative when you just have to sneeze or cough? Use your sleeve, that’s what. It’s the most effective way to reduce the spread of cold and flu viruses. Coughing into the open air without covering your mouth simply releases a myriad of viral and bacterial particles into the air around you. If there’s no one else around that’s not so bad, but just picture those droplets of spittle and snot flying in the video we’re going to show you here and you’ll think again.

Perhaps worse than open-air sneezing is inappropriate Kleenex use. If you don’t cover your nose and mouth properly then you might as well not bother. Coughing or sneezing into your hand is worse still. Germs will contaminate your hands, you touch a door knob or handle food and those germs get transferred to the next person who touches said objects. The video, which comes from the Maine Medical Association suggests your sleeve is the way forward. Cough or sneeze on to your sleeve and the germs will simply dry out and die.

It’s not just a matter of avoiding the sniffles, if we’re heading for a major viral epidemic from bird flu or something worse then the advice in this video could save lives. Listen to what the panel of experts – Polly Morph, Graham Stain, Blood Hagar – have to say. There’s a useful science fair project that can help you answer the question, “Does covering your mouth stop germs spreading?” and if you’re after more advice on how to avoid colds and flu check out the Sciencebase FAQ on the subject.

For advice on how to stop a sneeze, check out this site.

H5N1 in the UK

UK government vets have confirmed infection with the H5N1 strain of avian influenza in 2600 turkeys that died on a Suffolk farm owned by the Bernard Matthews company. The 159,000 turkey flock will have to be culled with all the risks that entails to prevent the disease spreading further.

According to a statement from the European Commission a protection zone of 3 km radius and a 10 km surveillance zone will be established around Holton, a village about 25 km south-west of Lowestoft.

This is the first time H5N1 has been identified in the UK on a commercial property. A previous outbreak of avian influenza was H7 that required a cull of 50000 fowl to be culled.

There are fifteen known variants of avian influenza. The most virulent, and usually fatal in birds, are H5 and H7 strains. There are then nine variants of the H5 strain and the type of most concern because of the risk to human health is H5N1. While H5N1 can be fatal in humans it has not yet mutated into a form that can be transmitted from person to person.

According to virologist John Oxford of the Queen Mary College, University of London, “I don’t think it has made any difference as a threat to the human population.”

Meanwhile, Channelnewsasia.com today reports yet another outbreak of H5N1 in Japan, the fourth this year.

Negative refraction

Light at the end of the tunnel “Can visible light ever be manipulated so that it bends the wrong way?” asks Katharine Sanderson in Nature. She suggests that successfully reversing light by making a negative refraction material could open up the possibility of some rather futuristic devices, such as microscope lenses that can resolve objects smaller than the wavelength of light or the much-desired invisibility cloak.

Sanderson reveals that Jennifer Dionne and Henri Lezec, working in Harry Atwater’s group at Caltech have made a material with a negative refractive index for visible light. The findings were announced at Nanometa 2007 in Seefeld, Austria, but are yet to be peer-reviewed for publication.

The only caveat is that Dionne and Lezec have only demonstrated the effect with a two-dimensional system. Does that count as true negative refraction, asks Sanderson? She quotes Atwater as explaining the options of upgrading to 3D: “Atwater envisages stacking a dense array of waveguides on end: “We have not done this yet, but at least this work illustrates the inherent possibility of doing so.”

Let’s hope so, I really fancy one of those invisibility cloaks.

A Good Delusion

Evolutionary biologist Richard Dawkins continues to wow them Stateside with his book The God Delusion. Recently, he appeared on Stephen Colbert’s show to discuss the fundamantal differences between a rational scientific perspective of the universe and the nature of reality and the irrational viewpoint Colbert supports.

Dawkins, with good humour, attempts to argue his corner with Colbert who stubbornly insists that invoking God provides a much simpler explanation of the universe and man’s place in it than a Big Bang and Darwinian evolution. Dawkins points out that, “You get to complex like a human being by slow gradual degrees, and that’s the only ultimate explanation that will work. You can’t just suddenly magical complex things like God into existence,” he adds.

Life is not due to random chance, that’s the one thing it isn’t, because Darwinian natural selection is the exact opposite of random chance, it’s a highly non-random process, Dawkins further explains, “The big thing that everybody misunderstands about Darwinism is that it’s not an accident, it’s too complex to be an accident.”

Egg in a Bottle

Egg in a bottle Ever fancied squeezing an egg into a bottle? No? Well, it’s a kind of perennial physics demonstration that science teachers the world over love to do. I could simply describe how to do it and the results you might expect, but that would be no fun at all. Instead, I spent a good ten minutes scanning videos on the net where individuals attempted to carry out this experiment, some of them more successfully than others. Most handling naked flames and solvents (methylated spirits and the like) in a non-laboratory setting with absolutely no safety equipment (not even goggles) in sight.

More importantly though, most of these experimenters managed to get most of the egg in the bottle, but usually the egg split and simply splurted into the bottle rather than squeezing through the neck and plopping into the bottle intact.

In this video, the “researchers” succeeded in getting a nice squeeze and plop (far better even than the Brainiac team in their attempt).

The key to their success is apparently using a bottle with a nice wide neck. Most of the other videos try to use a beer bottle or something similar which constricts the egg as it squeezes through the opening and splits it.

So, how does it work? What mysterious force is pulling the egg into the bottle? Well, the answer is there is no mystery it is simply air pressure pushing down on the egg. But, wait a minute, what’s the burning paper got to do with air pressure?

Okay, here’s the short of it. Dropping a burning spill (or burning piece of paper into a bottle) and the air in the bottle will quickly expand and a small volume escapes. When the hard-boiled egg (with the shell removed) is placed into the opening, the spill goes out, the remaining gas cools and contracts and the greater outside air pressure pushes the moist flexible egg into the hole nicely.

If you use a nice moist egg and a bottle with a wide enough neck you’ll get a nice squeeze and plop. Anyone who has a use for a hard-boiled egg covered in burnt paper stuck in a bottle is welcome to contact us at Sciencebase with their ideas. Additionally, if you know how to get the egg out again without breaking the bottle leave us you thoughts in the comment form.

Bottled seaside air

Seaside Beach Huts Bottled seaside air! It almost sounds like a scam from the Victorian era when the bracing “ozone” of fresh air at the British seaside was said to cure all kinds of ailments and led to a boom in seaside resorts and continues to ebb and flow.

But, it’s not a scam. Researchers at the University of East Anglia have been plucking bacteria from the North Norfolk coast at a little village called Stiffkey (pronounced Stoo-Kee) and fermenting them to reproduce the marshy smell of the seaside in the laboratory.

Andrew Johnston and his team isolated the bacterium from the mud at Stiffkey saltmarsh and have identified the single gene responsible for the emission of the strong-smelling gas, dimethyl sulfide (DMS).

“On bracing childhood visits to the seaside we were always told to “breathe in that ozone, it’s good for you’,” said Prof Johnston. “But we were misled, twice over,” he adds, “First, that distinctive smell is not ozone [a highly toxic allotrope of oxygen], it is dimethyl sulfide. And secondly, inhaling it is not necessarily good for you.”

DMS is a little known but important gas. Across the world’s oceans, seas and coasts, tens of millions of tonnes are released by microbes that live near plankton and marine plants, including seaweeds and some salt-marsh plants. The gas plays an important role in the formation of cloud cover over the oceans, with major effects on climate.

Intriguingly, DMS acts as a homing scent for seabirds, almost like the odour of Brussels sprouts at a festive dinner table – it helps birds sniff out food in the lonely oceans, even at astonishingly low concentrations. Understanding the role of microbes in producing this key chemical is important in understanding a whole range of ecosystems.

The discovery adds to the diverse list of Stiffkey’s claims to fame. The small coastal village is renowned for its ‘Stewkey Blue’ cockles and was also the home of Henry Williamson, author of “Tarka the Otter”. It’s also known for its infamous rector, Reverend Harold Davidson, who was defrocked in 1932 after allegedly “cavorting with” London prostitutes. The pronunciation of the village’s name itself is even controversial with the older locals preferring the archaic Stoo-Kee, while the incomers often prefer the posher sounding and phonetic Stiff-Key. (Incidentally, my photograph of beachhuts at the head of this article was taken along the coast at Wells-next-the-Sea.