Twisted molecule forms M?bius band to order
Polish researchers have made an aromatic molecule whose conjugated
An aromatic compound has an almost flat ring system with a cloud of electron density above and below the ring. This is the classic H?ckel topology, with a clear distinction between upper and lower parts of the electron cloud.
If the ring system holds a half-twist, then what had been the upper and lower electron density clouds merge to form a single continuous surface. This alternative M?bius topology is named after the M?bius strip (a band with a 180? twist and only one surface).
The expanded porphyrin reported in Angewandte Chemie can switch topologies thanks to two phenylene rings, which stack either flat or perpendicular depending on temperature and solvent. If flat, the compound looks green in solution and the
’Some concern’ on bisphenol A
A federal US panel of scientists found ’some concern’ that bisphenol A (BPA), a component of many plastics, may pose risks to children’s brain development at typical human exposure levels. But there’s negligible concern that BPA could cause reproductive effects.
The findings of the Centre for the Evaluation of Risks to Human Reproduction (CERHR) were more moderate than those of 38 independent scientists writing in Reproductive Toxicology a week earlier. They’d warned that BPA exposure in the womb could cause cancer and severely affect development, since these effects have been seen in animal studies at doses close to human exposure levels.
The CERHR panel didn’t consider all of these studies, dismissing those that administered BPA by injection as not relevant to humans.
In March, the panel’s preliminary report was revealed to have been drafted by a consulting firm with industry ties. That company was quickly fired by officials at the National Toxicology Program, who will now peruse the CERHR’s recommendations before any final declaration on whether BPA is toxic to humans.
EU science gets funding agreement
The European Science Foundation (ESF) has agreed a
The budget could be stretched by
Ceramic straws that filter oxygen from air have been developed by scientists at the University of Newcastle, UK. The idea is to help burn fossil fuels in pure oxygen, rather than air. This is both more efficient and produces a cleaner stream of carbon dioxide, easier to separate for later storage.
Pure oxygen is normally produced by liquefying air, but this cryogenic process is relatively expensive. Ceramic membranes would be a much cheaper option. The hollow fibres of a material containing lanthanum, tin, cobalt and iron, allow only oxygen ions to seep through them; so a gas streaming through the middle of the millimetre-wide, five metre long, fibres would burn in pure oxygen.
The US Department of Energy has been developing prototype membrane-based oxygen separators for several years, but hasn’t divulged details of
Spot the structure
A software tool which converts pictures of chemical structures into computer-readable format promises to solve the most tedious problem plaguing chemical bibliographers.
For years, the images contained in old scientific journals and patents have had to be redrawn digitally and entered manually into databases, so that computers can search them. Germany’s Fraunhofer Institute for Algorithms and Scientific Computing (SCAI) says it has developed software, chemoCR, that automates this process.
But SCAI’s claim to have achieved a world first is disputed by other structure-recognition software developers. Peter Johnson, a chemist at the University of Leeds, UK, who helped develop the Chemical Literature Data Extraction (CLiDE) software, told Chemistry World he would welcome a head-to-head comparison with any other system.
The US Environmental Protection Agency (EPA)’s ToxCast program - which aims to build computer models that can predict chemicals’ environmental toxicity - was launched in August.
The EPA released a list of 340 candidate chemicals, including pesticides, phthalates and fluorochemicals, which have already undergone traditional animal-based toxicology. It will put them through a battery of computerised bioassays developed by the pharmaceutical industry, before comparing the two sets of data to create its own screening computer model for potential health risks (in animals, at first).
EPA regulators hope to eventually use this model on untested compounds, so that only the risky ones need progress to traditional animal-based safety checks.
The program’s launch complements an earlier US National Research Council report concluding that alternatives to animals are the future of toxicology (Chemistry World, August 2007, p12).
Chemist and double Nobel laureate Linus Pauling extolled the virtues of vitamin C, claiming it was beneficial against cancer, atherosclerosis, and the common cold. Now a large review of placebo-controlled trials has concluded, as many scientists believe, that vitamin C is not much use as a cold-cure.
The Cochrane Database of Systematic Reviews gathered together data from thirty trials involving over 11,000 participants, testing the effect of ingesting at least 200 milligrams a day of vitamin C (the recommended daily allowance is 75-90 milligrams). The extra dose didn’t significantly shorten or weaken colds in the normal population, researchers concluded.
But a subset of six trials on people under extreme physical stress - including marathon runners and soldiers exercising in sub-arctic conditions - suggested vitamin C did cut their chance of developing colds. And even when taken in enormous doses (more than one gram a day), vitamin C seemed to do little harm.
US science gets competitive
The US Congress has approved legislation authorising $33.6 billion (?16.8 billion) over the next three years for federal science R&D, and science and maths education.
The America Competes Act supports doubling funding at the Department of Energy’s (DOE) Office of Science and the National Science Foundation within seven years, and at the National Institute of Standards & Technology within ten years. It also a
uthorises programs to improve the quality of science and maths teachers.
The so-called ’competitiveness’ legislation, signed by president Bush on 9 August, remedies the deficits noted in the 2005 National Academies’ report, ’Rising above the gathering storm’, which suggested that the US was losing ground on other countries in maths and science education.
An isotope of hydrogen with one proton and six neutrons has been fleetingly created in an experiment at the national heavy ion accelerator (GANIL) facility in France. H-7 has a lifetime of less than 10-21 seconds, researchers reported in Physical Review Letters.
H-7, the heaviest hydrogen isotope ever made, was created by smashing a beam of helium-8 ions into carbon-12 nuclei. Occasionally, a helium ion transferred a proton to a carbon nucleus, leaving behind H-7, which almost immediately fell apart to tritium (H-3) and four separate neutrons. Its presence was deduced by measurements on the trajectory of the N-13 also created.
H-8 and H-9 might be spotted by the same kind of trick, the researchers said.