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RSC NEWS 8 July 2005 |
Vol 36 : Issue No. 9 |
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Editors - Marilyn Holloway and Sue Riches
As this edition of RSC News goes to print, there is still no word from our jet-setting Academic Secretary. Meanwhile, in my co-editor's capacity I was browsing through some earlier editions and came across this little gem in the April/May 1997 issue under a regular segment headed Overheard in the tea room:
‹‹Would you want to go to Heaven if Ray Withers was standing at the gate?››
CONGRATULATIONS
Congratulations to the following students who will have their PhD degrees conferred at the graduation ceremony next Tuesday, 12 July:
An addition to the Structural Biology Group
Congratulations to Dr Aaron Oakley and his wife Erica on the birth of a second daughter, Marika Leila, on Thursday 30 June.
Item 1
Ethics Test (another Withersism)This test only has one question, but it's a very important one. By giving
an honest answer, you will discover where you stand morally.
The test features an unlikely, completely fictional situation in
which you will have to make a decision.
Remember that your answer needs to be honest, yet spontaneous.
You are in Darwin NT to be specific. There is chaos all around you
caused by a cyclone with severe flooding. This is a flood of biblical
proportions. You are a photojournalist working for a major newspaper,
and you're caught in the middle of this epic disaster. The situation
is nearly hopeless. You're trying to shoot career-making photos. There
are houses and people swirling around you, some disappearing under the
water. Nature is unleashing all of its destructive fury. Suddenly you
see a man floundering in the water. He is fighting for his life,
trying not to be taken down with the debris. You move closer
. . . somehow the man looks familiar. You suddenly realize who it
is. It's John Howard. At the same time you notice that the raging
waters are about to pull him under. You have two options--you can save
the life of "Little Johnny" or you can shoot a dramatic Pulitzer Prize
winning photo, documenting the death of the Australian Prime Minister.
So here's the question, and please give an honest answer:
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Would you select high contrast colour film, or would you go with the classic simplicity of black and white?
Item 2
Scientists Discover New Element
(contributed by Professor Alan Sargeson - author unknown)
The heaviest element known to science was recently discovered by university physicists. The element, tentatively named "Administratium", had no protons or electrons and thus has an atomic number of 0. However, it does have one neutron, 15 assistant neutrons, 70 vice neutrons and 161 assistant vice neutrons. This gives it an atomic mass of 247. These 247 particles are held together in the nucleus by a force that involves the continuous exchange of meson-like particles called "morons".
Since it has no electrons, Administratium is inert. However, it can be detected chemically as it impedes every reaction with which it comes in contact. According to discoverers, a minute amount of Administratium added to one reaction caused it to take over four days to complete. Without the Administratium, the reaction occurs in less than one second.
Administratium has a half life of approximately three years, at which time it does not actually decay, but instead undergoes a reorganization in which assistant neutrons, vice neutrons and assistant vice neutrons exchange places. Studies seem to show that the atomic number actually increases after each reorganization.
Research indicates that Administratium occurs naturally in the atmosphere. It tends to concentrate in certain locations such as government agencies, large corporations, and especially in universities. It can usually be found polluting the best appointed and best maintained buildings.
Scientists warn that Administratium is known to be toxic and recommend plenty of alcoholic fluids followed by bed rest after even low levels of exposure.
Recent Arrivals
A sincere welcome is extended to the following people who have arrived since our last issue:
Following the submission of her thesis, Ms Elizabeth Krenske has taken up a Postdoctoral Fellowship with Dr Michelle Coote's group (room E105, ext. 55411).
Dr Germán Cavigliasso has also joined Dr Coote's group as a Postdoctoral Fellow (room E105, ext. 55411).
Dr Ranganathan Prabhakar has commenced a Postdoctoral Fellowship this week with Dr Edith Sevick's group (room 49, ext. 50388).
Departures
Farewell and best wishes to the following who have left the School since our last issue:
Dr Steffen Gross left the School last week to take up his new position as Head of Laboratory at BASF in Ludwigshafen, Germany.
Dr David Lupton left this week to commence a Postdoctoral Fellowship at Stanford University.
Mr Darragh O'Neill has left to take up a Postdoctoral Fellowship at the University of Mainz in Germany.
Cayzer, T.N., Paddon-Row, M.N., Moran, D., Payne, A.D., Sherburn, M.S., Turner, P. Intramolecular Diels-Alder reactions of ester-linked 1,3,8-nonatrienes. J. Org. Chem. (2005), 70(14), 5561-5570. http://dx.doi.org/10.1021/jo0505829
Kim, H.K., Liu, J.-W., Carr, P.D., Ollis, D.L. Following directed evolution with crystallography: structural changes observed in changing the substrate specificity of dienelactone hydrolase. Acta Crystallogr., Sect. D (2005), 61(7), 920-931. http://dx.doi.org/10.1107/S0907444905009042
Wood, G.P.F., Moran, D., Jacob, R., Radom, L. Bond dissociation energies and radical stabilization energies associated with model peptide-backbone radicals. J. Phys. Chem. A (2005), 109(28), 6318-6325. http://dx.doi.org/10.1021/jp051860a
For a good many years in the 1980s I was editor of the RSC News. It was a thankless task then, as it is now, and the hardest part of all was eliciting contributions from staff and students. In my day the RSC News came out once a month and the big challenge was to get someone to write a lead article. What usually happened was that I ended up writing them myself. This particular article (from the August 1986 edition) was written in the aftermath of the major catastrophe that occurred in April of the same year at the nuclear power plant in Chernobyl, USSR (as it was then). I've resurrected the article, as I thought the subject would be topical given the current debate in some political quarters - Mr Carr, the NSW Premier, for instance - to reconsider nuclear power as a way of combating greenhouse gases. Furthermore, just recently, France has been awarded an internationally funded project to set up and run an experimental hydrogen fusion plant, which if successful, will produce energy, but not unwanted radioactive bi-products in the nuclear process (save for the radiated containment equipment itself). Following on from my article is one that takes a more rational look at the circumstances surrounding the Chernobyl incident. It is written by the President of the Australasian Radiation Protection Society and appeared in the Society's Journal in the August 2000 edition.
I shall expect a rigorous debate on this subject, with plenty of blood on the tea room floor.
GRAPPLING WITH GRAYS
by Lee Welling
What does it all mean?
After the nuclear faux pas at Chernobyl in the USSR in 1986, there appeared many learned articles by many learned men about the effects, or possible effects, of the escaping radiation. We were warned we would be bombarded with Becquerels, covered in Curies and saturated with Sieverts. But as with all intangibles, units of radiation can be meaningless to all but those in The Know. To confuse things even further, those units which some of us may have got used to have been superseded. So if you're worried that you may be getting a dose of 2,000 microSieverts per year, read on.
Radioactivity is the spontaneous decay of unstable nuclei and this is usually accompanied by the emission of charged particles or photons. Broadly, these are α and β- particles, and γ photons. These particles and photons are very energetic and can interact with matter causing ionization. α particles have a double charge and a relatively large mass and when they pass through matter they lose energy rapidly, leaving short, densely ionized trails. β- particles have a lower mass than α particles and only have a single unit charge. They are less densely ionizing and are more easily deflected by molecules, leaving erratic trails when they pass through matter. γ photons are uncharged, have zero rest mass, and although they leave long trails through matter, they interact with molecules infrequently.
Before 1980, the basic measure of radiation was the Curie (Ci), but now the Becquerel (Bq) has taken over. 1 Bq = 1 radioactive disintegration per second. (1 Ci = 3.7 x1010 Bq). And if you think it's essential to know it, for a million Becquerels you can have one Rutherford.
After Chernobyl, the vagaries of atmospheric conditions meant that the radioactive cloud was spread far and wide. Precipitation brought the radiation to ground and there it entered the food chain. British milk had up to 300 Bq per litre of radioactive iodine, which is much lower than the 2,000 Bq per litre considered dangerous. However, this figure is misleading, as it gives no indication of the dose for biological systems.
When measuring the effects on the human body a more important quantity is the amount of energy absorbed by the body as radiation interacts with it. The unit of dose is the Gray (Gy). 1 Gy of radiation deposits 1 Joule of energy per kg of material through which it is passing. (Of course, if you were from the old school your 1 Gy would be worth 100 rads). To give some indication of the relationship between dose and radiation, a person working 1 metre away from an unshielded 60Co source of activity 109 Bq, would receive a dose of approximately 10 mGy every hour (this is well above the acceptable limit).
Measuring the dose in Gy, though, does not discriminate between different types of radiation. The density of ionization as well as the amount produces biological effects within the irradiated subject. As mentioned earlier α particles are more densely ionizing than β particles, which are more densely ionizing than γ photons. For this reason, the Sievert (Sv) was devised which measures the unit equivalent dose. An equivalent dose in Sv is defined as: dose in Gy multiplied by the quality factor (see Table 1).
Table 1
| Type of Radiation | Quality Factor |
| X and γ rays, β- particles (Emax < 30 KeV) | 1.0 |
| β particles (Emax < 30 KeV) | 1.7 |
| α particles | 10.0 |
| Ions heavier than4He2+ | 20.0 |
It can be seen that the more densely ionizing α particles are considerably more damaging than β- particles or γ photons, even though the latter two are more energetic. γ rays are usually considered more damaging because they are so penetrating and hard to shield against.
The older unit for equivalent radiation dose was the rem (Roentgen equivalent man) where 1 rem produces the same biological effect as 1 Roentgen of X-rays or 8 billion Bq per kg. (1 rem = 0.01 Sv.)
For purposes of radiation protection, standards are usually given in terms of annual dose equivalent limits, and are measured in Sieverts. For whole body exposures, the annual limit for radiation workers is 50,000 μSv. This is most reassuring for the average world citizen as their annual effective dose equivalent is 2,000 μSv. This has the same effective cancer risk as smoking one cigarette every ten days. However, you are advised not to smoke if visiting Cornwall in the UK, as the native granite there is considerably more radioactive than normal.
August 4 2000 PRESS RELEASE
THE MYTHS OF CHERNOBYL
One of the most widespread myths of recent times is that the Chernobyl nuclear reactor accident in 1986 caused many thousands of extra cancer deaths in neighbouring regions, and that public health has been severely affected by exposure to radiation.
According to the latest report of the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) neither of these beliefs is true. UNSCEAR recently approved its UNSCEAR 2000 report and a review of its contents was presented at the International Radiation Protection Association Congress in Hiroshima in May. The report is expected to be published shortly.
Apart from the early fatalities in rescue workers who responded to the accident, the main health effect is an increased risk of non-fatal thyroid cancer in children. About 1800 cases of thyroid cancer have been diagnosed in those who were children at the time of the accident. This increased risk is linked to exposure to iodine-131, a radionuclide with a half-life of 8 days, which was a major component of the fission products released from the reactor. However, UNSCEAR reports no evidence of any other health effects attributable to radiation exposures. In particular, there has been no evidence of increases in cancer incidence or mortality. The risk of leukaemia, one of the main concerns due to its short latency period (5-10 years after radiation exposure in adults), is also not elevated in the exposed groups, including the recovery workers who received some of the highest exposures.
The accident on April 26 1986 in reactor 4 of the Chernobyl nuclear power plant caused the deaths of 30 power plant employees and firemen within a few days or weeks (including 28 deaths that were due to acute radiation exposure). Later on, during 1986-87, about 240 000 recovery workers were called on to take part in clean-up activities at the plant and within the 30-km exclusion zone established around the reactor. The remediation activities continued until 1990 and ultimately involved about 600 000 people.
In addition, about 116 000 people were evacuated from areas surrounding the reactor in 1986, because of large-scale radioactive releases of radioactive materials into the atmosphere. After 1986, about 220 000 people were relocated in what are now the three independent republics of the former Soviet Union: Belarus, the Russian Federation, and Ukraine. Wide areas of the three republics were contaminated and trace levels of released radionuclides were measurable in all countries of the Northern Hemisphere. The radiation exposures arising from the accident were due initially to iodine-131 and short-lived radionuclides, and subsequently to radiocaesiums from both external radiation and the consumption of foods.
The highest radiation doses arising from the accident were received by approximately 600 emergency workers and plant operators who were on the plant site during the night of the accident. Acute radiation sickness was experienced by 134 of these workers. The recovery operation workers, subsequently called upon to decontaminate the reactor site and roads, and to build the sarcophagus and a town for reactor personnel, received generally much lower doses. The average recorded doses decreased from about 170 millisievert (mSv) for those employed in 1986, to 130 mSv in 1987, and much lower values in subsequent years. (A lifetime dose from natural background radiation is typically 100 to 200 mSv, but is significantly greater in some parts of the world.)
Within a few weeks of the accident more than 100 000 persons were evacuated from the most contaminated areas of Ukraine and Belarus. While the thyroid doses, largely from ingestion of iodine-131, were significant, particularly in infants, doses to organs other than the thyroid were much smaller with effective doses (excluding the thyroid) of about 40 mSv in Belarus and 30 mSv in Ukraine. The thyroid cancer cases which arose were, regrettably, largely avoidable. No significant measures were taken at the time to reduce exposures by distributing stable iodine or by restricting the consumption of milk and fresh leafy vegetables in the vicinity of Chernobyl. If such countermeasures had been instituted, as in Poland, it is likely that the incidence of thyroid cancer would have been much reduced.
Many of the persons evacuated from the more contaminated areas after 1986 would, if they had remained, have received doses of not more than about 2 mSv per year, and in many cases the relocation of these people was unnecessary on radiological grounds. These relocations served mainly to heighten anxiety, and concerns and misconceptions about the dangers of radiation. Natural background radiation dose rates are normally in the range 2-10 mSv/y. The International Commission on Radiological Protection has issued new guidance on dose levels at which intervention should be considered and has proposed 10 mSv/y as a generic reference level below which intervention is not likely to be justifiable.
Apart from the radiation-associated thyroid cancers among those exposed in childhood, the only group that received doses high enough to possibly incur statistically detectable risks is the recovery operation workers. Among the emergency response workers there is a particular group of about 100 individuals who survived relatively high doses of radiation in the immediate, acute, phase of the accident and are currently experiencing health impairments as a consequence of their original injuries. Studies of this group will probably contribute to scientific knowledge on late effects of ionising radiation.
The UNSCEAR report notes that, of papers available to date regarding the estimation of health effects resulting from the Chernobyl accident, many suffer from methodological weaknesses such as inadequate diagnoses and classification of diseases, selection of inadequate control groups, or inadequate estimation of radiation doses. It concludes that, apart from the substantial increase in thyroid cancer after childhood exposure -
The risk of leukaemia, one of the most sensitive indicators of
radiation exposure, has not been found to be elevated even in the
recovery operation workers or in children. In spite of claims of
cancers, genetic effects and many other disorders, including
statements by health and other officials in the countries concerned,
there is no scientific proof of an increase in malignant or
non-malignant disorders, somatic or mental, that is related to
ionising radiation (except for thyroid cancers in children). The
additional annual doses to residents in the contaminated zones are
generally well within the normal range of variation of natural
background radiation doses.
It must be concluded that reports of health effects caused by radiation have been greatly exaggerated. A particular example is that of the groups of children from around Chernobyl who visited other countries after the accident or who were filmed in hospitals following chemotherapy. These were widely reported to have been suffering sickness due to radiation. Many of the children appeared to be in poor health. However, with the possible exception of any thyroid cancer cases among them there is no evidence that their illnesses were caused by radioactive emissions from the damaged reactor.
NOTE FOR EDITORS
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was established in 1955 to advise the General Assembly of the United Nations on the sources and biological effects of ionising radiation. Its main objective is to assess radiation exposures and the possible consequences for human health. The Committee's publications form the scientific basis on which international and national agencies develop appropriate radiation protection standards for workers, patients and the general public.
Dr A C McEwan
President
Australasian Radiation Protection Society
Please contact the ARPS
Secretariat for more information.
