Author: David Bradley

Fat Gamblers Smoking

The UK government is set to introduce new warning labels on fatty and sugary foods (in the style of the warnings found on packets of cigarettes and other tobacco products.) At the same time it announces that smoking in enclosed public places will be banned within four years and then tells us that it has plans to import Vegas-style super-casinos into the country and to open the pubs 24 hours a day!

What’s going on?

They want us to cut down on fattening food, give up smoking, drink more and take up gambling. Could it be that they’re simply worried that duties on rich foods and cigarettes will plummet in the next five years so they’re shifting the emphasis to booze and gambling to compensate? Your thoughts on that subject are most welcome.

Chemistry of Moores Law

Everyone knows a version of Moore’s Law that states: the number of components on a unit area computer chip will double every 12 months. Empirically, it’s turned out to be every 18 months, but it doesn’t just apply to chip density, but highest hard drive capacity at any given time, CPU speeds, and RAM requirements (the computer hardware and software industries form a self-perpetuating ascending double helix in case you hadn’t noticed). The Chemical Heritage Foundation is marking the fortieth anniversary of Intel co-founder Gordon E Moore’s Law in May next year a celebration of the fact that without an equivalent doubling in chemical savvy none of those advances in computing would have been possible.

Spectral Lines at 40

Spectral Lines is just one of three specialist webzines prepared exclusively for the spectroscopyNOW website by David Bradley Science Writer. In Issue 40 of the spectroscopy news magazine he takes a polarized view of the Big Bang, finds out how spectroscopy could help patients avoid getting the needle, how German scientists are testing atmospheres, and discusses a new approach to finding a compound’s crystal structure without x-rays: spectroscopy news

Green silicon production

Making the electronics industry green

Green silicon electronicsA new electrochemical process for silicon extraction could make large-scale production of this widely used material more environment friendly, according to chemists in China.

Silicon has an essential role in the world of electronics, being familiar in countless components from microelectronic silicon chips and optical fibres to large solar panels. It is also employed in the production of silicones, which are used in everything from bathroom sealant to cosmetic augmentation materials. Silicon even finds a role in alloy production.

Industry generally uses a straightforward reduction method to produce elemental silicon starting with silicon dioxide (SiO2 in the form of quartz). Carbon is the reductant and the process is carried out at 1700 Celsius. Carbon dioxide is the by-product as oxygen is released from the silica. According to Nottingham University’s George Chen currently a Specially Invited Professor in the College of Chemistry and Molecular Science at the Wuhan University in China, this process was used to produce about 4.1 million tonnes of silicon world-wide in 2002, with a corresponding release of 6.5 million tonnes of the greenhouse gas carbon dioxide into the atmosphere.

Chen and his colleagues, Xianbo Jin, Pei Gao, Dihua Wang, and Xiaohong Hu, believe that a more environment friendly approach should be attainable using electrochemical reduction rather than the conventional energy-hungry carbothermal process. “The old-fashioned charcoal technology should be replaced by a more advanced process from the environmentalist viewpoint,” the researchers say.

Electrolytic production of silicon was first carried out as long ago as 1854 by French chemist Etienne Henri Sainte-Claire Deville (1818-1881). A purity level of 99.999% has since been claimed by GM Rao and colleagues using fluorosilicates in a molten fluoride. In the early 1980s, however, results began to suggest that silica would be the ideal raw material, but high temperatures would be needed to make these processes work. The Wuhan researchers have now revealed a new electrochemical technique, which they claim will become viable for the large-scale production of silicon, because it avoids the high energy costs and reduces the carbon dioxide emissions considerably.

For the electrochemical extraction of silicon, Chen and his team took the approach of using silicon dioxide itself as the material for the negative electrode (cathode). They also opted to use molten calcium chloride as the best electrolyte for the job. Calcium chloride is well known as an electrolyte for electrochemical reduction of metal oxides at high temperatures. Sharp-eyed readers will have spotted the potential flaw in their arrangement, however. Silicon dioxide is, of course, an electrical insulator. Nevertheless, the researchers persisted with their idea and found in initial tests that conversion of quartz to elemental silicon does in fact occur at the three-phase boundary between the silicon dioxide, the electrolyte, and the flattened end of the tungsten wire that is used to connect the electrode to the circuit. This provides enough impetus for the electrochemistry to kick in properly as the silica is gradually converted to conducting silicon.

Theoretically, says the team, the reaction should eat its way through the entire silica electrode. However, the researchers found that in practice only a small area around the tungsten plate is in fact converted. They explain this in terms of the physical characteristics of the electrolytic melt – it simply cannot penetrate sufficiently deeply into the newly formed silicon layer on the surface of the silica electrode. This has the inhibiting effect of preventing further formation of the three-phase boundary and so the electrochemical reaction grinds to a halt.

Determined to make the process work though, Chen and his co-workers have now found a practical solution. Instead of using a solid quartz electrode, they have switched this for silicon dioxide powder that has been pressed into thin pellets and then sintered. The resulting electrode is, of course, then porous enough to allow the electrolytic melt to penetrate more deeply into the material of the electrode. Indeed, the particles, just a few micrometers across, are much more effectively converted to silicon powder by the electrolysis process than in the solid silica electrode. The use of X-ray diffraction provided the researchers with assurance of the purity of the silicon they were producing.

In terms of industrial application, high purity, low-energy, and reduced carbon dioxide emissions will all be rather desirable properties of the new silicon-production process. Moreover, as bulk quartz would not be practicable for industrial production, the discovery that silica powder, which is far more readily available, works with this degree of success is much more likely to be make the process attractive to silicon manufacturers.

In addition, the researchers discovered that by mixing the quartz powder with other metal-oxide powders it is possible to directly produce fine-tuned alloys using their electrochemical reduction method. Fine powders of oxides can be prepared easily and mixed uniformly, the researchers explain, so that the electroreduction of such mixtures leads to an alloy, the composition of which is precisely controlled. They have successfully produced Si-Fe and Si-Cr alloy powders with a particle size of 2-3 mm in this way.

Despite the long history of silica electrolysis dating back to the mid-nineteenth century, Chen and his colleagues have demonstrated, for the first time, that porous pellets of silica powder or mixtures with other metal oxide powders can be electroreduced to pure silicon or its alloy in molten calcium chloride. Their cyclic voltammetry studies revealed that electroreduction can proceed very quickly indeed, although perhaps at higher current densities than would be viable on the industrial scale. Nevertheless, the CV studies will provide developers with a fundamental reference against which to match the design of a true industrial process for the mass production of silicon powder by electrolysis. Usefully, as reduction depth and time follow an approximate logarithmic law, this can be used to select for a particular particle size too adding to the versatility of the process.

At the time of writing, the team was optimising their electrolysis process.

Further reading

Electrochemical Preparation of Silicon and Its Alloys from Solid Oxides in Molten Calcium Chloride. Xianbo Jin, Pei Gao, Dihua Wang, Xiaohong Hu, and George Z. Chen. Angew. Chem. Int. Ed. 2004, 43, 733-736

Women in Science – Cracks in the Glass Ceiling?

Women often just don’t get it – recognition or high-ranking positions, that is. Vertical segregation is the trendy sociological term, but while the proportion of female graduates in many scientific disciplines has shot up, the proportion of women reaching the top is still low. In most European countries women occupy fewer than one in ten top slots in science faculties.

Mookambeswaran ‘Viji’ Vijayalakshmi is head of a bioengineering laboratory at the Compeigne University of Technology in France. Recently, she became the first winner from France since 1985 of the ‘International Excellency Award’ in the field of affinity technology and biological recognition. Viji, however, is aggrieved that her University failed to communicate the news to the media positively. ‘They did not want to mention my name or my identity as head of this lab,’ she says, ‘nor even to mention the research field…the local press was not even present during the award ceremony.’ Is this a case of unwitting discrimination?

So, what is going on? Haven’t those tough old glass ceilings long since been smashed and piled up in scrapheaps along with that other structural blunder, asbestos? Seemingly not.

According to Nicole Dewandre head of the European Commission’s ‘Women and Science’ Sector there are several factors that underlie the slower progress of women’s careers in science. Surveys, she has pointed out, consistently show that women scientists more often follow their partners than the converse when a job change is in the offing and women are also more commonly forced to compromise their careers in order to balance the issue of child-bearing and child-rearing. While efforts are made by some establishments to assist with relocation through bridging finance and job offers for partners, the so-called received wisdom is that women follow their men. ‘When women go into the workforce, they almost never have the kind of support that men enjoy – their husbands have lives and careers,’ says Nancy Cox, who is researching the genetic basis of diabetes at UChicago. ‘Fewer men have that kind of support either, but there are still some that do, and that it’s difficult to break standards set in a different time.’

A disturbing study in 1997 funded by the Swedish Medical Research Council by microbiologist Christine WennerÃ¥s and immunologist Agnes Wold (Nature, 387, 341) uncovered that there is a strong gender bias in the way research funds are doled out. ‘The system is revealed as being riddled with prejudice…’ the authors claimed. It became apparent that women needed to be at least twice as productive to reap the rewards. The revelation has prompted greater interest in the issues. An inspired EC conference in April 1998 determined that beyond the need to be fair to women, the promotion of women in science is crucial to European society as a whole. The EC has now set itself a 40% target for female participation in its Fifth Framework research program and the pressure is on to ensure women are fairly represented and represent fairly the program’s expert committees. Currently, however, only 15% of applications are from women although the Sixth Framework rather optimistically expects to achieve 50% women participants.

Nancy Lane a cell biologist at the University of Cambridge believes women represent a ‘huge untapped economic potential’. She says as few as 3-4% of UK professors in any branch of science, engineering or technological disciplines are women while the number of women Fellows within the hallowed halls of the Royal Society and the Institute of Biology are, astoundingly, well below 10%. ‘Things are being done,’ she says, ‘but the culture takes a long time to change and many obstacles relating to the ‘old boy network’ still remain.’ Various initiatives are in place, such as the Women’s SET Unit at the Office of Science & Technology, a UK government department. Lane and colleagues are now establishing a Code of Practice for laboratories.

Statistics from the UK’s Royal Society of Chemistry reveal that the percentage of female graduates is higher in chemistry than in physics and mathematics but is lower than in biology. Non-science subjects, such as French and English, still beat the sciences by a wide margin. The female to male ratio of undergraduates in the biological sciences is roughly 50:50. The percentage of females achieving higher degrees in chemistry is smaller than at first degree but it is increasing. US government statistics reflect something similar for the sciences in general, showing that women are approaching half of science and engineering bachelor’s degree recipients having been steadily increasing since the 1980s.

But degrees don’t always facilitate career progression. We are still seeing a strong gender bias. The first full female chemistry professor in the UK, Judith Howard of Durham University, only took her chair in 1991. In chemistry, there were a mere 0.8% females. Extrapolations see no parity between male and female professors existing before the year 2120!

So, where are the women in the upper echelons of science? There are a few famous names admittedly but women seem to remain footsoldiers or else leave the ranks altogether when faced with a lack of professorships available to them. There is a well-worn argument that science, with its goal-oriented attitudes and methodology is a more masculine than feminine pursuit. Women are said to be more interested in finding ways to reach a solution and in learning from the experience whereas men tend to gain more from getting the results and disseminating them in order to gain peer recognition. But, this argument relies on the archaic white-coated male stereotype. ‘I don’t think the problems women face in science and academia are so different from the problems they face in trying to move into the upper echelons anywhere else,’ says Cox.

Some commentators believe it will take more than conferences and proposals to eradicate inherent and ancient sex discrimination in society. According to Anthony Engwirda of Griffith University, Brisbane, Australia, the underlying reason that there are so few women in positions of power is purely historical. ‘When a woman, her mother and her grandmother have no memory of personal discrimination then we could justify a belief about the integration of equal rights,’ he says. The duration and prevalence of an idea might hint at the difficulty in revoking it but, adds Engwirda, ‘changes to society are difficult and take time, the right of a woman to equality must become a pervasive global idea for several generations before the concept becomes self-perpetuating.’

Lane emphasises that women have been waiting for more than a decade to see a gradual filtering of women up through the system. It has not yet happened. Some argue that women are excluded from male lobbies, so have to work harder to get what they need, something certainly confirmed by the 1997 Swedish report. Viji recounts a half-serious comment she heard from a colleague – ”Decisions are so often made in the ‘washrooms’ among men that women can do nothing but be excluded from participating in the decision making process.” Cox adds that, ‘Women scientists are often underestimated because we are more social,’ she says, ‘which can make it harder to recognize that you are serious.’

‘Time will tell if the huge number of women in biological sciences as students now will rise to populate academic positions higher than assistant professor,’ affirms Karen Cone, a geneticist and molecular biologist at the University of Missouri-Columbia and joint owner of the WiS net discussion group. ‘We still have a long way to go, and the prospects for the “harder science” fields of chemistry, engineering, math and physics have a steeper climb because the number of women choosing to enter these fields at the college level is incredibly low.’

It is not so long ago that society created a stifling atmosphere for women aspiring to engage in scientific research. Collaborations with male colleagues were almost a necessity for women’s research to be heard. The astronomer Caroline Herschel relied on her brothers William and John to disseminate her research results. While archetypal role model Marie Curie received the Physics Nobel apparently on the insistence of her husband Pierre who would not accept it alone. Mme. Curie, of course, won the Chemistry prize in her own right after her husband’s death.

Society frowned on women in science – taunts of ‘unladylike behavior’, ‘immodesty’ and worse were bandied about, according to physicist Gina Hamilton – a staff astronomer at the University of Southern Maine – writing in Physics World recently – the goading still goes on, albeit the language is more ‘modern’. Hamilton adds that while various efforts have been launched, in the US and elsewhere, to increase the number of women studying university science these ‘well-meaning attempts are often frustrated by the reality of the numbers game’. In the more mathematically inclined physics and astronomy, there are simply not enough women with the right skills, who are interested in entering the field.

It is not all doom and gloom. At the Southwest Foundation for Biomedical Research, a non-profit private research institute, the departmental chair of virology and a leading scientist in the department are both women. These are prestigious positions considering there are only four such labs in the country she says.

Bioinformatician Fiona Brinkman of UBC, Vancouver, believes she has benefited from having female role models, however, ‘My PhD supervisor was a woman, and was head of a section of the Canadian Laboratory Centre for Disease Control and a Pan-American Health Organization project, before taking a University Chair,’ she says. She also reveals that her mother was a technician in a scientific field. ‘I believe without really realizing it, I have chosen to be around suitable role models,’ she says.

Hazel Moncrieff meanwhile working in the labs of Bristol-Myers Squibb in England is also more positive about the issue. ‘I have not been put off applying for jobs since the jobs I would be looking for would require technical qualifications which are equal irrespective of gender.’ She adds that within her company most people are BSc/PhD qualified and she does not sense any obvious gender bias. Women, she says, are well represented in management although maybe not at the director level. ‘I don’t think this is due to a direct gender bias but is rather attributable to a wider issue of not affording flexibility to workers.’

Isolated examples are not enough, things may truly have moved on little since the Herschel’s day. Perhaps it is all about mobilization. Maybe action plans will create integration, but nothing substitutes for the involvement of women scientists. All the initiatives, committees, proposals and schemes in the world only make sense and deliver results if women are involved and make their voice heard.

This article originally appeared in BioMedNet’s HMSBeagle in my regular Adapt or Die column.

Chemical Structure Drawing Software

“I made this drawing in less than five minutes, but it took me sixty years to be able to do that”

— Pierre-Auguste Renoir (1841-1919)

Sketchbook Chemistry – Chemists think in pictures, structures are all. It comes as no surprise that chemical-drawing packages are among the most popular software components available. Indeed, ACD/Labs own ChemSketch had, at the time of writing, reached its 341,320th download in less than six years since the launch of the freeware version. So, what makes chemical sketching such a valuable tool for chemists and others whose research touches on this underpinning science? David Bradley reports on the views of ChemSketch users.

“I saw a colleague using ChemSketch, and became amazed by its simplicity,” Barbaros Akkurt of the Turkish Chemical Society told us. Carlos Franco PhD of the Department of Chemistry at the National Pedagogical University of Colombia echoes the sentiment, saying that ChemSketch is “an excellent free software package that users can apply either in the classroom or in their chemical research.” Clyde Metz of the Department of Chemistry and Biochemistry at the College of Charleston came across ChemSketch at an American Chemical Society meeting via a demo disc in action. “As new versions were released, I kept up to date.” Metz has an academic site license for the department so that his students can use the structure building features for copying over to lab reports, papers, etc.

It is easy to see why ACD/Labs has such a rapidly growing number of followers for its ChemSketch program. With the freeware version 5.0 of ChemSketch, users can draw molecules freehand, build their structures from a wide range of ready to use templates or import various standard chemical structure formats and modify them to their own needs. For instance, it is possible to import and export ChemDraw, ISIS Sketch, MDL molfile, and SMILES strings. ACD/Labs describes the process as “click and draw molecules” with ions, stereo-bonds, text, polygons, arrows, etc., all readily available. Once a molecule is complete, users can automatically calculate molecular weight and formula, display estimates of density, refractive index, molar volume, and many other useful parameters.

“I’ve encountered no difficulties in getting used to the software,” says Akkurt. He adds that the best feature of the package is its 3D optimization, although the IUPAC naming facility comes a close second. “The IUPAC naming service is very nice,” he adds, “as many other programs cannot recognize a number of special organic radicals.” Akkurt goes on to explain how ChemSketch has helped him greatly in quickly processing elemental analysis data for various organic compounds as well as producing their IUPAC names. “ChemSketch allows me to produce reliable structures quickly,” he says, “I don’t use nor need to run any other program.” Interestingly, while he uses the ChemSketch Draw mode mainly for chemistry-related sketches, he has also found it amenable to creating non-chemistry structures, such as organization trees too.

The freeware version also includes the tautomers module, dozens of templates, the 3D viewer program and one of the most interesting features, the Name Freeware Add-On, which allows users to convert a structure into an IUPAC name for their molecule. For users who opt for the full version, ChemSketch includes the ACD/Dictionary module, which contains more than 125,000 systematic and non-systematic names of structures and so can speed up the structure-drawing process considerably.

There are many specialist users too. “I first saw ChemSketch at a meeting of the American Society for Mass Spectrometry,” says David Powell, Director of Spectroscopic Services in the Department of Chemistry, University of Florida at Gainesville, where a number of groups use ChemSketch. “I found ChemSketch a little easier to learn so the learning curve was faster,” says Powell, “ACD/Labs also gave us the ability to import a structure directly into our sample submission form for mass spectrometry, working with us to set up a macro in ChemSketch to do this.” Powell is also enthusiastic about one of the program’s specialist features which can be purchased as an add-on, “I really like the MS Fragmenter routine,” he told us, “which allows prediction of fragment masses and structures, this is very useful for interpreting unknown mass spectra.”

Another specialist user is forensic toxicologist Chip Walls, Technical Director of the Department of Pathology at the University of Miami. He first saw a favorable review on the Web about chemical drawing programs that did a nice comparison. “I downloaded the free version of ChemSketch and found it much easier to use,” he said. He was so impressed, he bought the full version with the dictionary. “With each revision I grow more attached to the ease of use and the ever expanding dictionary,” he added. The many more import and export features and the dictionary are major advantages over other packages and keep Walls coming back for more. “I use the structures in my procedures and in talks I have to present,” he explained, “I export the drawings in windows metafile format (WMF) and can insert them as a picture in just about any application. You can change color of the structure easily making it a snap to insert into PowerPoint slides with colored backgrounds.” He adds that the WMF is small, fast to load and easy to keep within a presentation. “Of course, you can also insert the ChemSketch file and link to it to keep it up to date with any changes,” he adds.

Some users do not take to ChemSketch immediately, Tamas Gunda of the University of Debrecen in Hungary, for instance, gave the program a quick try after finding it on the Internet. It was only later when he did a probing review of chemical drawing applications that he began to see its advantages over other packages. “The freeware version contains more features than other free chemical drawing applications,” he says, and although every application has its strong and weak sides, one of the big pros of ChemSketch is in making poster-sized drawings. Gunda adds, “In my experience, ChemSketch is best for joining chemistry and other pictures together for direct printing or transferring to a general drawing package in Windows Meta Format.”

Metz adds that the free 3D viewer is also a rather attractive feature, “I realize that this is the front-end for other programs which we don’t have, but it is for student use and works fine,” he explains. Indeed, ChemSketch has become an integral part of the curriculum for the College’s NCSI/CCCE workshops to show and let people work with it. “For what is in the free version of ChemSketch/3D Viewer, it is done well,” adds Metz, “and for someone with no funding, it is a way to introduce a little molecular modeling and visualization into an undergraduate course.”

Funding levels are an important consideration for many users. Franco admitted that finances are a main driver in choosing software in a country where resources are limited: “The primary advantage over other similar packages is that the free version of ChemSketch is fully functional in all its options.” That said, Franco points out that all users can view models in 3D dimensions, with animation or from different perspectives. “The ChemSketch drawing tool is an easy way to make presentations, make templates and export images to a word processor, for instance.”

“As a teacher of 16-18 years olds,” adds British educator Steve Lewis, “I was looking for a quick means of producing simple structures. The initial attraction of ChemSketch was the freeware version!”

While some users rely on the more advanced features, others, including Lewis, have relatively unsophisticated needs for their chemical-drawing software. ChemSketch, he says, meets these well, “ChemSketch itself is not unsophisticated, rather, it’s designed well enough that I can use it to my advantage without being overwhelmed by too much functionality intended for more advanced purposes.” Having said that, he adds that he is “very impressed by the 3D viewer facilities,” which he uses for school ‘open’ event displays.

ChemSketch is downloaded from the ACD/Labs website at a rate of about 300 copies every day and every single country in the world has downloaded it at least once! At the time of writing, the Top 5 countries by number of downloads were USA (>67,000), Germany (>23,000), Canada (>15,000), United Kingdom (>14,000), and China (>11,000). There have even been almost 200 downloads from users in the Vatican City State domain! There are thousands of others in many different countries from the Philippines to Puerto Rico via Antarctica showing just how chemistry brings nations together.

ChemSketch users also have the ability to interact with the software itself through the freeware Programming Language for the Freeware ChemSketch (http://www.acdlabs.com/products/chem_dsn_lab/chembasic/). More than 15,000 users have downloaded the language, which forms the basis of the popular ACD/Goodies. ACD/Labs updates these user contributions to the program store regularly. (http://www.acdlabs.com/products/chem_dsn_lab/goodies.html).

ACD/Labs remains at the cutting edge of structure drawing and visualization including the first structure drawing applet (freeware version at http://www.acdlabs.com/download/sda.html) and recent PDA-based tools (http://www.acdlabs.com/products/chem_dsn_lab/chemsketch/chempalm/). Site licenses of the commercial version of ACD/ChemSketch v5.0 are currently being donated to any interested academic institution (http://www.acdlabs.com/educators/chsk_licenses.html).

This article was originally commissioned as a promotional feature article by ACD/Labs, creators of ChemSketch and Reactive Reports. – ChemSketch – Elemental Discoveries – 08/04

New Spin on Electronics

At the borders between physics, chemistry, materials science and electrical engineering, is where some of the most exciting technological developments take place. Think polymer light-emitting diodes, porous silicon explosives and now spintronics.

Denis Greig and Robert Cywinski at Leeds University are working with colleagues at the Universities of Salford and York to grow ultra-thin magnetic films on semiconducting materials and to characterise their surface chemistry. Spotting dead layers with no magnetism in the surface atomic layers of such material composites will be important in controlling the spin properties of the material in the bulk.

Oxide magnets such as CrO2La1-xCaxMnO3, Fe3O4 and the Heusler alloy NiMnSb are being developed by Lesley Cohen (http://www.ph.ic.ac.uk/staffcv/cohen.htm) and Tony Stradling (http://www.ph.ic.ac.uk/staffcv/stradling.htm) of Imperial College with European Union funding. They reckon these materials will make excellent sources of spin-polarized currents. They are trying to grow such “half metallic ferromagnets” on high-quality semiconductor layers, such as indium arsenide. The ultimate aim being to fabricate to fabricate spin transistors and highly sensitive magnetic sensors.

“A huge effort is being generated world wide in this area,” explains Stradling. This is mainly driven by the putative link between spintronics and quantum computing, which once researchers get it to work will provide much faster information processing than is presently possible. Much of the spintronics work is going on in many UK physics departments, such as Bath, Bristol, Cambridge, Glasgow, Heriot-Watt, Nottingham, Oxford, St Andrews, Salford, Southampton, and York.

Such efforts are at the centre of worldwide multidisciplinary efforts to add another dimension of control to electronics and bring us into the realm of spintronic devices. Physicists are still just learning how to control the spins of electrons to allow them to align them on the fly in materials being created to exploit their properties in new computers, sensors, and other devices. Materials designed to exploit the spin of the electron are beginning to emerge. The only spintronic device which is presently being used in real systems though is the two-terminal GMR type of sensor . But, spintronics has potential in fields as diverse as position and motion sensors for robots, fuel-handling systems for vehicles and chemical plants, military guidance systems, and even the next generation of keyhole surgery techniques.

The mobile phone hanging on your belt, the motherboard in your PC, or the amplifier in your portable MP3 player all use charge carriers to transport information in semiconductor materials such as silicon. But, charge is not the only intrinsic property of the electron, in common with certain other sub-atomic particles, the electron also has spin.

The spin of an electron is not like the spin of a pool ball though. Rotate a pool ball through 360 degrees and you get it back to where you started. If you can see the “8” and you rotate that ball 360 degrees you will see it come around again. If an electron could be marked in some way, you would have to rotate it through 720 degrees before you saw the marker again. It takes two full turns for an electron to “spin” once. This bizarre quantum property is not at all far-fetched, one just has to remember that an electron is not a tiny pool ball, but a sub-atomic entity closer to a notional Möbius strip than a sphere. Anyway, I digress. Electron spin, can be up or down, and this property will be used to develop spintronic devices that are smaller, more versatile and more robust than any conventional microelectronic circuit.

It is the alignment of electron spin that gives rise to the bulk magnetic properties of a metal such as iron or cobalt. If the bulk of the electrons in a piece of iron are either up or down then the iron is magnetised. The magnetic state of an iron particle can be written and read – viz. magnetic data storage, from tape to disk. The state is represented by the orientation of the iron’s magnetic moment.

But, rather than looking at the properties of chunks of iron, what if we consider the more subtle effects seen with a sandwich of very thin layers of material – the outside layers might be cobalt or another magnetic material while the innards would be non-magnetic. The magnetic layers have their electrons either all up or all down as usual. But, because of the thinness of the layers electrons with the same spin can pass through the non-magnetic layer while those of opposite spin are deflected, or scattered back. Because of this the sandwich acts as a filter for either up or down electrons depending on the nature of the magnetic layers.

At this level one begins to see a much stronger effect – the “giant magnetoresistance” (GMR) effect, which relies on this filtering of electron spins across the layers. The effect, an increase in resistance due to the presence of a magnetic field, is 200 times greater than seen with common magnetoresistance and provides the basis of the read head in multi-gigabyte computer hard disks pioneered by IBM.

It is of course possible to change the orientation of the spins of the electrons in each layer so that they can be made the same or opposite, in this way the number of electrons that are scattered back can be changed. A device that functions in this way has been referred to as a spin valve because it can be used to inhibit or open up current flow. Any device acting as a valve can be considered a switch, and a switch to a computer designer means logical unit or memory bit. Simply flipping the orientation of spin in one layer changes the spin valve from a 0 setting to a 1 setting and so forms the basis of a new magnetic version of random access memory (RAM). Importantly, MRAM is non-volatile. Switch off the power on your computer now and you’ll lose everything in memory. Not so with MRAM, what is written to memory stays there until it is deliberately wiped. Some observers caution that while this is true in that it has indeed been proposed it has yet to be shown that GMR RAM chips are a viable technology; remember magnetic bubble memory? No?

Quite.

However, we already have GMR read heads – to read high density media – although increasing data density is still a major aim of IBM and other manufacturers, while developments in the preparative methods of insulating metal oxide layers and other materials are making for rapid progress in MRAM. Other devices are beginning to emerge with the development of controllable spin transistors and the like as magnetic semiconductors and other oxides are designed with greater magnetoresistance and spintronics effects. The silicon age is not quite passé, it will be with us a long while yet, but there is a new spin on electronics.

Elemental Discoveries – The history of the chemical elements

The history of the chemical elements – An elemental chronology compiled by David Bradley back in 2004

Ancient Times – gold, silver copper iron lead tin mercury sulfur carbon
Time of the Alchemists – arsenic, antimony
13th Century India – zinc
1669 phosphorus
1737 cobalt (~1735)
1741 platinum (1735)
1751 nickel
1753 bismuth
1755 magnesium (1775)
1766 hydrogen
1772 nitrogen
1774 oxygen, chlorine, manganese
1778 molybdenum
1782 tellurium
1783 tungsten
1789 uranium (1841)
1789 zirconium
1793 strontium (1808)
1794 yttrium
1797 titanium (1791)
1797 chromium
1798 beryllium

1801 vanadium, niobium
1802 tantalum
1803 cerium, rhodium, palladium, osmium, iridium
1807 potassium, sodium
1808 calcium, barium
1811 iodine
1817 lithium, cadmium, selenium
1823 silicon (1824)
1825 aluminum/aluminium (1827)
1826 bromine
1828 thorium
beryllium
1839 lanthanum
1843 terbium, erbium
1844 ruthenium
1860 caesium/cesium (rubidium)
1861 rubidium, thallium
1863 indium
1868 helium, boron
1875 gallium
1878 ytterbium
1879 thulium, scandium (1878), holmium (1878), samarium
1880 gadolinium
1885 praseodymium, neodymium
1886 germanium, fluorine (1866), dysprosium
1894 argon
1898 neon, krypton, xenon, radon, polonium,
1899 actinium

1901 europium (1890)
1907 lutetium
1917 protactinium (1913)
1923 hafnium
1925 rhenium
1937 technetium
1939 francium
1940 astatine, neptunium (plutonium)
1941 plutonium (1940)
1944 curium
1945 americium (1944), promethium
1949 berkelium
1950 californium
1952 einsteinium
1953 fermium (1952)
1955 mendelevium
1958 nobelium
1961 lawrencium
1964 rutherfordium
1970 dubnium (1967)
1974 seaborgium
1976 bohrium (1975)
1982 meitnerium
1984 hassium
1994 darmstadtium, unununium
1996 ununbium
1999 ununquadium

2004 ununtrium, ununpentium – read about the discoveries of the most recent chemical elements.

For a list complete with details of the discoveries try the Wikipedia entry or the About site, there are discrepancies between the two, however (see bracketed entries above) and I’d say the only definitive elemental data online is provided by Mark Winter’s WebElements.

Fat thin

Reader John Sime of Zylepsis brought this latest bite to our attention. Mark Pereira of the Children’s Hospital, Boston has highlighted three risk factors for obesity and type 2 diabetes. Watching television and consuming fast food increase the risk in whites, he found, while eating breakfast reduced the risk in white and black men, but not black women. Apparently, “fast food emphasizes primordial preferences for salt and fat… this may promote overeating”. But, why should black women not benefit from breakfast in the way that white and black men do…? Very strange.

Poisonous Zebra Mussels

poisonous zebra mussel

Inland lakes in Michigan that have been invaded by zebra mussels, an exotic species that has plagued bodies of water in several states since the 1980s, have higher levels of algae that produce a toxin that can be harmful to humans and animals, according to a Michigan State University researcher.

In a paper published in the recent issue of Limnology and Oceanography, Orlando ‘Ace’ Sarnelle, an associate professor in MSU’s Department of Fisheries and Wildlife, and colleagues report that lakes that are home to zebra mussels have, on average, three times higher levels of a species of blue-green algae known as Microcystis.

Those same lakes also have about two times higher levels of microcystins, a toxin produced by the algae.

‘If these blooms of blue-green algae are a common side effect of zebra mussel invasion, then hard-fought gains in the restoration of water quality may be undone,’ Sarnelle said. ‘Right now, it appears that the numbers of blooms in Michigan have been increasing and appear to be correlated with the spread of zebra mussels.’

Initially, water samples were taken from nearly 100 inland lakes in Michigan’s Lower Peninsula, ranging from Benzie County in the northwest to Oakland County in the southeast, that had established zebra mussel populations.

Follow-up experiments by Sarnelle and colleagues in west Michigan’s Gull Lake showed that zebra mussels are indeed the cause of the increase in toxic algae.

There have been documented cases in which animals, including cattle and dogs, died after drinking water with high levels of microcystins. The toxin is also believed to be responsible for liver damage in humans.

Surprisingly, zebra mussels seem to have no effect on the amount of blue-green algae in lakes with high levels of phosphorus, a nutrient that builds up in lakes and other bodies of water as a result of erosion, farm run-off and human waste.

In contrast, zebra mussels cause an increase in toxic Microcystis in lakes with low to moderate levels of phosphorus, anywhere between 10 and 25 micrograms per liter. Such lakes are not normally expected to have very many blue-green algae, Sarnelle said.

‘Our data suggest that zebra mussels promote Microcystis at low to medium phosphorus levels — not at very low or very high phosphorus levels,’ he said. ‘However, we’re still not sure why this happens.’

Zebra mussels have been causing problems in the Great Lakes since the late 1980s. For example, in Lake Erie, Sarnelle said, increased incidence of blue-green algae blooms have been reported since the establishment of zebra mussels.

‘Similarly, data from the Bay of Quinte in Lake Ontario show a dramatic increase in the biomass of Microcystis after zebra mussel establishment,’ he said. ‘In addition, toxic algal blooms in Saginaw Bay and Lake Erie are disturbing because they come after many years of expensive reductions in nutrient loading to improve water quality.’

Zebra mussels, which are native to the Caspian Sea region of Asia, were first discovered in Lake St. Clair in 1988. It’s believed they were transported to the Great Lakes via ballast water from a transoceanic vessel.

Since then, they have spread to all of the Great Lakes, as well as many other U.S. and Canadian inland lakes and rivers.