The Alchemist Newsletter: April 25, 2013

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Graphene, the monolayer all-carbon supermaterial has been touted as stronger than steel, having marvelous electro-optical properties and having the potential to revolutionize engineering, computing and electronics. But, not so fast, Rice University theoretical physicist Boris Yakobson and his colleagues in China. Writing in the journal Nano Letters, the team says that less-than-perfect sheets of the material have an unexpected weakness that apparently makes them only half as strong as predicted. The team has calculated that flaws in the otherwise endless "chicken wire" array of hexagons, that allows seven-membered carbon rings to appear, inevitably occur at grain boundaries in graphene and so under tension, polycrystalline graphene is expected to break under lower loads than the pristine material would. Yakobson explains that, "If you need a patch of graphene for mechanical performance, you’d better go for perfect monocrystals or graphene with rather small domains that reduce the stress concentration."

Researchers find unexpected weakness in graphene sheets

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Fit an insect larva out with a nano-spacesuit made from the detergent Tween-20 and it can survive the journey into the deep vacuum, not of space, but of the scanning electron microscope. The discovery by Takahiko Hariyama, of Hamamatsu University, and colleagues could pave the way for detailed microscopic imaging of living organisms. SEM usually kills cells and organisms, but the Japanese team initially discovered that an extra cellular substance that coats larva was being cross-linked by the electron beam to form a natural polymer spacesuit that protects the grubs. The fruit fly larva could thus survive for up to an hour as long as they were exposed to the electron beam early in the process. In the vacuum chamber with the electron beam switched off they die within minutes. The natural material is amphiphilic, so the team tested several synthetic materials that might allow them to mimic the effect of the natural protection with other organisms. Tween-20 gives a dipped organism an extra half an hour of life in the SEM, the team reports.

Polymer ‘nano-suit’ protects insects from vacuum

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Robert Turesky of the Wadsworth Center at the New York State Department of Public Health and colleagues have developed a mass spectrometry technique that identifies and quantifies chemical signatures of carcinogen exposure in preserved biopsy and tissue samples from cancer patients. The research could allow toxicologists to preserved samples from the last few decades to determine whether or not exposure to certain toxic chemicals might be linked to specific forms of the disease. Snippets of medical samples are usually preserved with formaldehyde and paraffin wax, which had precluded subsequent chemical analysis until now. He has now shown that a banned compound from some herbal medicines, aristolochic acid, known to react with adenosine nucleotides to form DNA adducts can be identified and quantified at the same time in a preserved tissue sample.

Seeking Carcinogen-Linked DNA In Tissue Samples

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Dwayne Miller of the University of Toronto, Canada, and colleagues have recorded atomic motions in real time at the transition state of a reaction using an ultra-bright electron source. "Electrons interact with atoms 1 million times stronger than X-rays and can be produced with a table-top instrument to efficiently produce enormous, effective brightness for viewing atomic motions," explains Miller. "It’s the first look at how chemistry and biology involve just a few key motions for even the most complex systems," he says. "There is an enormous reduction in complexity at the defining point, the transition state region, which makes chemical processes transferrable from one type of molecule to another."

Scientists produce best image yet of atoms moving in real time

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Anssi Vähätalo of the University of Jyväskylä in Finland and colleagues have demonstrated that a smaller proportion of "black carbon" created during combustion will remain in the soil than was previously estimated. The finding could have implications for modeling the potential for climate change mitigation of burying the waste product of slash-and-burn and controlled burning of fields. The burning of organic matter creates 40–250 million tons of black carbon every year through incomplete combustion of organic matter. Advocates of burying such waste, an approach to carbon sequestration, had assumed that black carbon would remain locked away in the soil for millennia. This, the work by Vähätalo and colleagues suggests, is not the case, and that sampling of world rivers suggests that 27 million tons of black carbon per year will reach the oceans. The results prove that the proportion of water soluble black carbon may be as much as 40 per cent of black carbon created annually, the team says.

"Black carbon" flowing from soil to oceans

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American biochemist Christopher T. Walsh of Harvard University is to be the 2013 recipient of the 5 000 Euro (about $6500) Inhoffen Medal. The award recognizes his work on the response of bacteria to chemical stresses, such as mercury antibiotics and so-called suicide inhibitors. His work has implications for circumventing bacterial drug resistance and developing novel biotransformation tools for organic synthesis that exploit bacterial enzymes. The prize, which is funded by the Friends of the Helmholtz Centre for Infection Research (HZI), is awarded on the occasion of the public Inhoffen Lecture, an event co-hosted by the HZI and the Technische Universität (TU) Braunschweig.

American biochemist to receive this year's Inhoffen Medal

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