A smooth coated Dachshund, Border Terrier, Jack Russell Terrier Mix and Yorkshire Terrier in an undated photo. (Edouard Cadieu via The New York Times)A nano-sensor much like the human nose

The human sensor coordinates signals sent by thousands of sensory neurons to detect smells. The sensor, in this case, is a silicon chip which consists of nickel oxide nanoparticles acting as the neurons. When a chemical touches the surface of the oxide, it responds electrically; the response varies because each chemical has its own signature.

The sensor detects the response and, in turn, helps identify the chemical. Patricia Morris, professor of Chemistry at Ohio State University, with doctoral student Elvin Beach, had to first find a simple and easy way of making nanoparticles of nickel oxide.

The nanoparticles would give the sensor a large surface area to quickly capture and identify a wide variety of chemical molecules. The team subjected nickel oxide to a pressure of 225°C. In less than 24 hours, they obtained nanoparticles which were then washed in a common solvent called methyl ethyl ketone. “You mix everything together in a pressure vessel, pop it in the oven, rinse it off and it’s ready to use,” said Beach.

The team then applied a thin coating of the nickel oxide nanoparticles onto the surface of a silicon chip. The details of the synthesis are in a recent issue of Materials Chemistry and Physics.

Each nickel oxide nanoparticle measures about 50 atoms across. The researchers claim a one-gramme batch of nanoparticles costs about US $5 (Rs 240) to make; one sensor carries only four nanogrammes of material, so the chips are cheap to make. These sensors can provide a low cost method for air quality monitoring. But the researchers are yet to use them in the field.

Down To Earth Feature Service

How does the dog get its coat?

How did the dog get its coat? Kipling never pondered that question; he was more concerned with how the leopard got its spots, among other things, but scientists have. And the answer, they report in Science, lies in just three genes.

Edouard Cadieu and Elaine A Ostrander of the National Human Genome Research Institute, part of the National Institutes of Health, and colleagues looked at the genetic differences within single breeds that have more than one coat type. Purebred dogs are particularly suited for this kind of study, Ostrander said, because they have been selectively bred to segregate traits.

There are long- and short-haired dachshunds, for example.

The researchers then used that information to look at a large dataset of genetic information from about 900 dogs representing 80 breeds. They were able to identify mutations at specific points, or loci, on three genes linked to fur length, curliness and growth pattern (bushy eyebrows, beards and other features that dog breeders refer to as furnishings).

Then they looked at these three loci, on the genes of another 662 dogs representing 108 breeds, from fluffy Old English sheepdogs to short-haired pugs.  They found that the presence of the mutations or not, in various combinations, accounted for the variation in coat in 95 per cent of the breeds.

Only a few breeds, including Afghan hounds, have coats that can’t be explained by these genes.  There’s a certain elegance to the findings, Ostrander said. “We look at so much of the complexity in the world around us and say, Oh gosh, the underlying genetics must be so complicated,” she said. “But we’re beginning to feel that in fact nature is simple.”
The eventual goal, Ostrander said, is to use the same kind of sampling and comparison techniques to uncover how genetic variations combine to cause human diseases.

Henry Fountain
NYT News Service