Beneath three antique bell jars in a Paris vault lies a silvery metal cylinder, made in 1879, which weighs exactly one kilogramme and is the world’s official unit of mass. Forty identical replicas sit in national laboratories across the globe, as the basis of international standardisation of weights. The kilo is the only unit in the International System of Units (SI) system still defined directly by a material object rather than a fundamental property of nature. For example, the second is measured officially by the frequency of radiation emitted by a caesium atom under precisely defined conditions, while the metre is based on the speed of light in a vacuum.
Unfortunately, however, the kilo held by the Bureau International des Poids et Mesures in Paris (and its official replicas around the world) turn out not to represent an eternal and unvarying standard. Although they were made from an alloy of platinum and iridium, a material designed by 19th-century scientists to combine hardness with extreme resistance to corrosion, recent measurements show that the masses of the various cylinders are slowly changing, as a result of physical and chemical changes on the surface.
Most are gradually putting on weight. “We’re only talking about a very small change – less than 100 micrograms,” says Peter Cumpson, metrology professor at Newcastle University. “But mass is such a fundamental unit that even this very small change is significant and the impact of a slight variation on a global scale is huge.”
The Newcastle lab is using the technique of X-ray photoelectron spectroscopy (XPS) to analyse the surface reactions and discover how best to remove contamination without harming the underlying metal. Their results appear in the journal Metrologia.
Most of the dirt is carbonaceous material formed from the hydrocarbons present even in filtered laboratory air. Some come from natural sources such as the terpenes emitted by coniferous forests, some are man-made such as vehicle and industrial emissions.
This layer, with strong cross-linking between carbon atoms, is hard to remove. The traditional way is to apply an organic solvent to a chamois leather cloth, rub gently and then steam-clean. But Cumpson and his colleague Naoko Sano have come up with a better method. “What we have done at Newcastle is effectively give these surfaces a suntan,” he says. “By exposing the surface to a mixture of ultraviolet light and ozone, we can remove the carbonaceous contamination and potentially bring prototype kilograms back to their ideal weight.”
Although the search for a definition of the unit in terms of fundamental physics is progressing, the metal cylinders will have to serve as the standard for a while. So metrologists will welcome a reliable way to remove unwanted weight.
Recognise, destroy: cells that help fight cancer
A popular approach in cancer research is to boost the immune system so that it works better at recognising and destroying tumour cells. There are different ways of doing this, and one showing promise is in early clinical trials with Adaptimmune, an Oxford-based biotech company.
Adaptimmune uses genetic engineering to soup up the patient’s own T-cells – white blood cells that play a central role in the immune attack on pathogens and other intruders. T-cells, extracted from the patient, are given extra copies of “receptors” that recognise and attach to specific proteins (called NY-ESO-1 and LAGE-1) that occur on the surface of cancer cells. The genetically engineered T-cells are then infused back into the patient.
The first clinical trial of the technology is taking place in 26 people with multiple myeloma, a blood cancer based in the bone marrow that is usually incurable. Results in the initial 13 subjects are encouraging, with 10 showing “a very good response” and the other three “some response”, says James Noble, Adaptimmune’s CEO.
Before anyone gets too excited, however, some other experimental cancer treatments have given amazing results in early trials, which turned out to be less wonderful when used on larger numbers of patients.
Many new drugs are tested in placebo-controlled trials: participants are allocated at random to receive either the drug or a dummy treatment, without them or the researchers knowing who is getting what.
This is not practical or ethical with such an elaborate procedure as Adaptimmune’s genetically modified cell therapy, so its clinical trials will continue to be “open-label”.
If the procedure works as well as the company hopes, this may not matter. Its “affinity-enhanced T-cell receptors” will only be worth using if they are very effective, because the procedure is complex and costly, and such high efficacy should show up convincingly even in small trials.
History’s earliest carpenters? Farmers
Stone Age farmers in central Europe were remarkably skilful carpenters long before the invention of metal tools, German archaeologists have discovered. The evidence comes from wooden water wells, more than 7,000 years old, which were excavated from four sites in eastern Germany where the timbers were preserved in waterlogged ground.
“Our results … contradict the common belief that metal was necessary for complex timber constructions,” Willy Tegel and colleagues from the University of Freiburg report in the journal PLOS ONE. “Early Neolithic craftsmanship now suggests that the first farmers were also the first carpenters.”
The study shows that Neolithic farmers felled mature oak trees up to a metre in diameter with adzes – tools with a stone blade tied to a wooden handle. In an adze the blade is set at a right angle to the tool’s shaft, unlike an axe in which the blade is in line with the shaft.
The oak logs were first split in half by hammering in wooden wedges with a wooden maul and then cut to length by a combination of adzes and burning charcoal. Further fire and adze work cut them into boards ready for construction. Tool marks on the timbers show that the prehistoric carpenters used adzes with ground stone blades to make the tenon joints that hold together the well’s wooden frame.
How your phone can help you out of a jam
Mobile phone data can provide transport planners with better information about road traffic flow than any other source, according to US research.
Marta González and colleagues at Massachusetts Institute of Technology carried out what they said was the first large-scale traffic study that tracked travel using anonymised mobile phone data. A motorist’s location can be deduced from the radio “cells” with which the phone communicates.
Using three weeks of data from two metropolitan areas, Boston and San Francisco, the researchers found that changing people’s driving patterns – for example, by improving public transport or upgrading roads – would have much more impact in some neighbourhoods than others. The results appear in the journal Scientific Reports.
Cancelling or delaying the trips of 1 per cent of drivers across a whole urban area would reduce congestion delays by 3 per cent. But if 1 per cent of trips were cancelled in particular places – such as Lowell (MA), or San Jose (CA) – all drivers in the area would benefit by 14 to 18 per cent.
The new methodology requires only three types of input – population density, topological information about a road network and mobile phone data – so it could be used almost anywhere.
“In many cities in the developing world, traffic congestion is a major problem and travel surveys don’t exist,” González says. “So the detailed methodology we developed for using cellphone data to characterise road network use could help ... control congestion and allow planners to create road networks that fit a population’s needs.”