2008
Mar 07 2008
Add yet another way for the government to track you to the list. A University of Utah team led by geochemist Thure E. Cerling and ecologist James R. Ehleringer have shown that the Hydrogen and Oxygen isotopes in human hair correlate with those isotope ratios in local tap water. (doi: 10.1073/pnas.0712228105)
We all expect that a persons diet greatly affects the concentration of certain commonly found isotopes. 13C, 15N, 34S, 40K are all present in our bodies, though in such small quantities that they don’t appear to have a significant effect on our health. Ideally you could measure the concentration of these isotopes, or their relative isotopic ratio, and learn the dietary habits of an individual. By taking into account small differences caused by fractionation events during metabolism and the larger differences in 15N values, the isotopic ratios of 13C, 15N, and 34S provide limited geographic based information about the origins of a food source.
Cerling and Ehleringe, however, chose to look at a more unlikely source for traceable isotopes that turns out to be more useful and easily detectable.
Hydrogen (
2H) and oxygen (
The 2H and 18O values of keratin in human hair should be influenced by a number of factors during synthesis within the hair follicle, including all dietary and atmospheric sources of H and O. Bear in mind, however, that their discussion was limited to the 2H that was not subject to postsynthesis isotopic exchange. Cerling and Ehleringe hypothesized that variations in the nonexchangeable 2H and 18O values in human keratin could provide insights into water and human diet across geographical regions if the hydrogen and/or oxygen isotopes from these sources were recorded in human hair.
After developing a model to account for the difference in the isotopic ratios between drinking water, body water and the actual scalp hair, Cerling and Ehleringer tested the model by attempting to predict the geographic region of origin of individuals based on the isotope composition. They obtained 2H and 18O values in hair sampled from 65 cities in 18 states. Their model which was a function of drinking water, bulk diet, and protein isotope ratios, explained more then 85% of the observed variation and strongly reproduced the relationship of the isotopic composition of hair samples to that of local drinking water.
Plots of the relationships between mean H isotope ratios (Upper) and mean O isotope ratios (Lower) of human scalp hair and tap water for samples randomly acquired in cities representing 18 states across the United States. The lines through the data in each plot represent model-predicted values based on local tap water and a continental supermarket diet.
The really interesting part, though, is this:
Based on the geographical distributions of the isotope ratios of tap waters and the assumption of a “continental supermarket” dietary input, we constructed maps of the expected average H and O isotope ratios in human hair across the contiguous 48 states. Applications of this model and these observations are extensive and include detection of dietary information, reconstruction of historic movements of individuals, and provision of region-of-origin information for unidentified human remains.
So now using a sample of a persons hair, not only can we find out exactly who they are (DNA) we can find out where they are from…as long as they are drinking local tap water.
Feb 28 2008
International Atomic Energy Agency (IAEA) is the only international organization established to regulate and monitor nuclear installation. With 144 member states and the active threat of terrorism, the IAEA suffers from a significant increase in workload with insufficient funding.
In 2002, the Nuclear Security Fund was created in the wake of the 9/11 attack. This plausible effort was deemed ineffective since the fund relies on voluntary funding from its member states, according to an article in Nature. With an inadequate annual budget of 15 million Euro (22.5 million USD), this security fund fails to perform its intended function.
Furthermore, the technology used in detecting nuclear threat needs a complete overhaul. While a vast variety of novel technology are available to detect even a trace amount of hazardous materials, IAEA still utilizes analytical instruments that are “often three decades old and have no available spare parts.” This is not to mention the problem with backlogging samples and even difficulty with obtaining a sample from a potential target. With a mere annual budget of 280 million Euro (406 million USD), the agency does not even have adequate funding to purchase the satellite image needed to search for suspicious targets.
Finally, it is necessary for nuclear operators around the world to form a better network of communication and information sharing. An organized discussion would be effective in developing safe and secure practice. The US Nuclear Threat Initiative is an example of such forum.
Many initiatives and changes are needed to improve and reform the IAEA. None of them comes cheap considering the cutting-edge technology and degree of specificity of this field. However, nuclear security is just as important, if not more applicable, than the next source of security threat. A properly funded regulation agency would be the first step towards building a safer and more open community globally.
For more information, see Nuclear security undervalued, Nature
Feb 19 2008
In recent years, time traveling has been not only a scenario in science fictions and Hollywood blockbusters, but also a scientific possibility due to the rapid developments of quantum theory. Tidbits on the possibility of achieving time traveling has sprouted up in news in the past couple of weeks.
The soon to be available Large Hadron Collider (LHC, pictured above) of CERN utilizes several superconducting magnets (kept at just 1.9 K) to guide charged particles to a desired projectile. Scheduled to be in operation by May of this year, it is the largest and highest energy particle accelerator in the world.[1] Using the LHC, a special run is scheduled for April 2008 in attempt to recreate the Big Bang.
By colliding charged particles at high velocity, researchers hope to reproduce the first billionth second after the Big Bang. By successfully doing so, this exercise would further validate the theory–some claim as the origin of life–since the Nobel win of Professor George Smoot in 2007.
However, the public hype of the launch of LHC isn’t all for the recreation of the mysterious Big Bang. Much of its attention is the possibility of creating a time machine as a side product of this exercise. As mathematicians Irina Aref’eva and Igor Volovich of Moscow’s Steklov Mathematical Institute pointed out, Einstein’s theory of general relativity suggests that particle collisions at such high energy level would distort the space-time fabric surrounding it. This distortion can create a wormhole, or “time tunnel,” allowing time traveling.[2] A related interview with Irina Aref’eva is available on YouTube.
Such claim sounds little more than a scene out of some scifi movie; and many in the scientific community agrees. Most remains skeptical of the production and application of the man-made wormhole. Surely, arguments like the lack of “time travelers” from the future still echo every time machine idea is brought up. Since what will happen inside the particle accelerator is still largely unknown, its secondary consequences also remain unpredictable.
Noel
Feb 07 2008
Earlier this month, the American Physics Society updated their Online Archive to include all the Physical Review articles as far back as 1893. While we celebrate for the time saved from making photocopies of old, dusty volumes in the back room of the library, this new addition is also good news for literature-surfing enthusiasts. Among the sea of findings is a pair of articles, published in 1939 by Hans Bethe of Cornell University that eventually earned him the Nobel Prize of Physics.
In these papers, Bethe proposed two possible fusion reaction mechanisms that enables stellar energy production. They are as follows:
p + p –> 2H
2H + p –> 3He
This helium-3 nucleus further reacts, resulting in helium-4. A second reaction chain was named the C-N-O cycle. This mechanism uses a small amount of carbon, interacting with nitrogen and oxygen intermediates to produce He nuclei from ejected protons as an end product.
While later experiments confirmed the validity of both of his mechanism proposals, he was incorrect in predicting the reaction prevalent in solar energy production. Bethe concluded that C-N-O cycle is the dominant mechanism by the estimated temperature on the sun at that time, which was an over approximation. Both of Bethe’s proposed mechanisms are accepted in the current astrophysics community, with proton-proton fusion as the main source of solar energy.
This pair of articles marked the beginning of many stellar physics discoveries to come. More detail on Bethe’s theory is available in the new APS online archive!
For more information: Landmarks: What Makes the Star Shine?
Noel
Jan 18 2008
In this week’s issue of Nature magazine Arnold et al. have published an intriguing reactive complex of the notoriously stable uranyl dication [UO2]+ that cleaves C-Si bonds and yields a functionalized U=O bond. This was accomplished by first encapsulating the UO2 into a cyclic macrocycle, followed by the addition of the metal (either iron or zinc bound to the inner U=O bond) with a silylamide base. The major product is shown in the figure below.
Reprinted by permission from Macmillan Publishers Ltd: Nature, advance online publication, 17 January 2008 (doi:10.1038/nature06467)
A solution to the problem of determining the presence of the postulated intermediate might simply be to take mass specs along the course of the reaction; as one described prep takes 42 hours. In the end, this work literally builds the scaffold for future chemists to begin functionalizing uranyl. Although, no mention is given how to un-encapsulate the newly derivatized uranium. 
Note 1: Link to article — Reduction and selective oxo group silylation of the uranyl dication
Mitch
Jan 15 2008
The discovery of a new isotope of Bohrium, by Nelson et al., was published yesterday in PRL. In total, 8 events of 260Bh were reported. Unfortunately, the new isotope is not long-lived enough to be of practical chemical interest. A summary of the decay properties is summarized in the Nuclear Trading Card format shown below.
The yellow color signifies the observation that it decays by alpha emission 100% of the time. Fortunately the nuclide decays into 256Db, which is long-lived enough for chemistry, and the results taken with this paper and others updates the known decay properties of Dubnium-256. The updated trading card is below.
In this case the red signifies an ~30% electron capture branch. We hope you enjoy the announcement of a new member to the Bohrium family, and have fun with your new nuclear trading card.
Note 1: Link to article: Lightest Isotope of Bh Produced via the 209Bi(52Cr, n)260Bh Reaction
Mitch
Dec 13 2007
Earlier this week a paper by L. Soderholm et al. in Angewandte Chemie may have solved the great plutonium polymer mystery. Plutonium polymer is the ubiquitous noun often spoken by plutonium chemists in regards to the un-extractable ill-defined hydrous oxides of plutonium that will form in any solution of aqueous plutonium lying about the bench top. Often plutonium polymerization can be inhibited by storing aqueous plutonium solutions at high acid concentrations. It was thought to form from a series of olation reactions:
Plutonium Olation Reaction: Pu—OH + Pu—OH2 —> Pu—OH—Pu + H2O
This old hypothesis is put to rest with the isolation of Li14(H2O)n[Pu38O56Cl54(H2O)8]. This occurred after repeated anion-exchange with an acidified alkaline peroxide solution of plutonium, that then crystallized in the presence of aqueous LiCl. This type of workup is common for samples containing plutonium polymer. The crystal is reported to have the same intracluster packing and structural topology as bulk PuO2. The crystal structure of the [Pu38O54(H2O)8]40+ is shown below.
The Plutonium is in green, oxygen from the oxide in red, and oxygen from water in blue. With this and other evidence of well defined Pu—O clusters and the lack of hard evidence for oxyhydroxides they expect plutonium to condensate through an oxolation reaction.
Plutonium Oxolation Reaction: 2Pu—OH —> Pu—O—Pu + H2O
The one caveat with this work is that it was performed with the more stable plutonuium-242 (t1/2=3.7 x 105 y) and not the typical reactor plutonium-239 (t1/2=2.4 x 104 y). Perhaps in the presence of the >10x more radioactive Pu-239 the nanoclusters would become either too structurally damaged to resolve nice crystalline structures, or more chemically reactive towards hydrous oxide formation or oxyhydroxide formation. Regardless, this work may still lead to better methods of extracting plutonium out of the nuclear fuel cycle and represents a nice resolution to the nebulous plutonium polymer conundrum.
Link to Paper: http://dx.doi.org/10.1002/anie.200704420
Mitch
Nov 19 2007
Baumann et al. have recently reported the discovery of three new isotopes 40Mg, 42Al, and 43Al. The discovery is notable for producing an isotope that neither the finite range droplet model (FRDM) nor the Hartree-Fock-Bogoliubov (HFB-8) predicted should be bound.
Of the 3 isotopes, the discovery of 42Al is an unexpected surprise and thusly the most fascinating. As we all know from undergraduate nuclear chemistry the Weizsäcker’s formula contains a pairing term (d) approximately equal to 34*A-3/4 MeV. The term increases the binding energy for an even number of protons (Z) and neutrons (N), decreases it for an odd Z and N, and of course is zero for an odd atomic number (A). 42Al contains 13-protons and 29-neutrons, lies on the extreme neutron-rich side, and thus was not predicted to exist in a bound state.
Theory can be seen to be in contradiction from experimental data as seen below.
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| Reprinted by permission from Macmillan Publishers Ltd: Nature 449, 1022 - 1024 (25 Oct 2007). |
To the immediate left of the 43Al dot is the collection of 42Al events. The 43Al event had a probability of ~2 x 10-3 of arising from the Al-42 cluster of events.
The tantalizing conclusion of this work is that the neutron-drip line may reside further than even the next generation nuclear facilities could explore for Z>12.
Link to article: http://dx.doi.org/10.1038/nature06213
Mitch
Nov 18 2007
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Mitch André Garcia: Mitch is a chemist at Berkeley trying to finish his PhD, one day… (read postings)  |
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Maz Ali: Maz is a chemist/physicist at Berkeley trying to finish his B.Sc., one day…  |
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Noel Chang: Noel is a chemist at Berkeley trying to finish Mitch’s PhD, one day…  |
Nov 17 2007
Welcome to the DNCT’s blog experiment exploring new methods in communicating scientific nuclear knowledge. The goal is to have DNCT members discuss interesting nuclear literature, discuss research questions, and participate more actively with each other.
If you are a DNCT member and would like to be a part of the DNCT blogging team please register for an account here: Login and send an email to mitch-at-berkeley-d0t-edu expressing your interest. Other wise feel free to post comments.
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Mitch
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