Van Gogh painting revealed 

Researchers have revealed, in unprecedented detail, an early van Gogh masterpiece hidden beneath one of the Dutch artist's later works. About a third of van Gogh's paintings are believed to cover his own earlier efforts. 

Now, the first use of a new non-invasive x-ray technique has allowed researchers to recreate, in colour, a hidden portrait of a peasant woman underneath the van Gogh painting Grasgond (Patch of Grass)  , completed in 1887. A vague shadow of a face lurking under the painting's surface had previously been spotted using x-rays and infrared reflectography. But in the new technique, based on synchrotron radiation induced x-ray fluorescence spectroscopy, the measured x-ray fluorescence is specific to each chemical element. This allows different atoms and their associated paint pigments (such as the flesh colours, yellow/white antimony and red mercury) to be charted individually. Sadly, the approach might not be useful for all works of art, says Katherine Higget, head of science at the British Museum. 'Nevertheless,' she told Chemistry World  , 'this is a hugely exciting development.' 
Joris Dik at Delft University of Technology and colleagues published their research in Analytical Chemistry  (DOI: 10.1021/ac800965g). 

Perchlorate on Mars

Early chemical analyses from Nasa's Phoenix lander, on the northern plains of Mars, have, surprisingly, detected perchlorate (ClO₄^-) salts in the planet's soil. The ion is an oxidant - and on Earth, known as a contaminant in drinking water and an ingredient in rocket fuel. It adds to the ice and various salts already found in Mars' alkaline soil (see  Chemistry World  , August 2008, p9).  
Whether the ion is widespread on Mars is not yet known; nor have the wet chemistry perchlorate findings been confirmed by other chemical detectors, such as Phoenix's thermal gas emission analyser (TEGA).  
But researchers say that the possible presence of perchlorate on Mars has little bearing on whether the planet might support life. 

Closer to invisibility 

In another advance towards cloaking devices that might render objects invisible (see  Chemistry World  , December 2006, p7; May 2007, p31), US researchers have created three-dimensional materials that can bend back visible-wavelength light. The metamaterials also work over a broad range of wavelengths, unlike previous efforts.  
Xiang Zhang and co-workers from the University of California at Berkeley published two types of structures. In Nature  (DOI: 10.1038/nature07247) they report alternate stacks of silver and magnesium fluoride milled into a fishnet structure; and in  Science  (DOI: 10.1126/science.1157566), silver nanowires interspersed in aluminium oxide. The close patterning of both these materials' components gives them their light-bending properties. They may find first use in optics applications, such as sophisticated lenses. 

Exercise in a pill

A US research team has developed drugs that boost endurance in mice - apparently mimicking the effects of exercise. The researchers, led by Ronald Evans from the Salk Institute in La Jolla, California, report in  Cell  (DOI: 10.1016/j.cell.2008.06.051) that mice on training regimes could run longer and farther if dosed with the drug GW1516; while mice taking another experimental drug, AICAR, gained endurance even without the training.  
Both molecules boost genes and biochemical events similar to those previously found to be triggered by exercise - such as activating enzymes that keep cells burning fats and sugars even when energy levels are low. The drugs are currently in unrelated clinical trials but aren't approved for use in humans. Though Evans says plenty more research is needed to develop an 'exercise pill', his team has already developed a test to spot athletes who might be using the compounds. 

Renewables rumpus

The US Environmental Protection Agency (EPA) has denied the state of Texas' request to halve until 2010 the national target for producing renewable fuels. Texas governor Rick Parry argued that ethanol production was driving up the price of corn.  
The EPA - which has taken since April to make its decision - found no evidence to suggest that the renewable fuels standard (RFS) would damage the Texan economy in this time. Under the RFS, 9 billion gallons of renewable fuels (such as ethanol and biodiesel) must be blended into the national fuel supply this year.  
Meanwhile, 80 per cent of the UK's biofuels fail to meet environmental standards, according to the first monthly report from the UK government's renewable fuels agency (RFA). The main problem is tracing where the fuel comes from or how sustainably it is produced. 

Hot chillies evolved to kill fungi

The capsaicinoid chemicals that make chilli peppers 'hot' are produced to help kill fungal invaders, according to US researchers.
Joshua Tewksbury and coworkers from the University of Washington, Seattle, tracked chilli plants across Bolivia. The plants, which differ genetically in capsaicinoid production levels, are susceptible to a fungus that attacks through holes created by a foraging bug. The researchers found that more pungent peppers were less vulnerable to fungal attack, and backed up their research with laboratory experiments using artificial fruit loaded with capsaicinoids. 

The capsaicinoids are just one example of the various pungent, bitter, or toxic chemicals found in many types of fruits, and it's a popular hypothesis that plants evolved these to ward off unwanted predators like microbes (while still allowing animals or birds to eat fruit and spread seeds). The intuitive idea hadn't been backed up by solid evidence before, says Tewksbury, publishing in Proceedings of the National Academy of Sciences  (DOI: 10.1073/pnas.0802691105). 

Vitamin C cancer hope 

Injecting vitamin C (ascorbate) into the bloodstream might help to treat cancer - in mice at least - suggests research published in  Proceedings of the National Academy of Sciences  (DOI: 10.1073.pnas.0804226105).  
Mark Levine and colleagues from the National Institutes of Health in Maryland, US, injected human cancer cells into mice, and found that vitamin C injections halved the rate of tumour growth. They suggest that this is because very high levels of ascorbate in the bloodstream - not attainable by oral ingestion - produce hydrogen peroxide which kills cancer cells. Preliminary trials to test injections in cancer patients are underway. Taking vitamin C orally has no effect, two trials in 1985 showed. 

Chemical fingerprints 

Analysis of fingerprints lifted directly from a crime scene can reveal not only a standard identification pattern, but also minute traces of any potentially incriminating compound, say US scientists. The research, published in  Science  (DOI: 10.1126/science.1157199), is another offshoot of desorption electrospray ionisation (Desi) mass spectrometry, which sprays charged droplets onto a surface, ionising molecules and drawing them into a mass spectrometer for analysis (see  Chemistry World  , August 2006, p46).  
Researchers at Purdue University, who unveiled Desi in 2004, imaged from fingerprints molecules such as cocaine and the explosive RDX, with resolution sufficient to create compound-specific patterns - something that might also be useful to resolve smudged prints. 

Phthalates ban 

The US Congress has passed a bill with a provision banning certain phthalate plasticisers in children's toys and consumer products. Di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP) and benzyl butyl phthalate (BBP) are permanently banned in objects used by children under 12, while diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and di- n  -octyl phthalate (DNOP) have an interim ban pending safety studies. Similar phthalate restrictions already exist in the EU.  

No AS chemistry for terror suspect 

An Iraqi terrorism suspect who had been training as a doctor in his home country has been denied permission to take UK AS-level courses in chemistry and human biology. High Court judge Stephen Silber ruled that he could gain expertise that might further terrorist activities.  
RSC chief executive Richard Pike said the ruling made a scapegoat of chemistry: 'There is nothing in [AS-level chemistry] that can be said to be a special tool for terrorist activities, ... [or that] cannot be found easily on the web and through other means.'