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Science in Action is hosted by Jon Stewart, produced by me and Ania Lichtarowicz, and is a BBC World Service programme that pulls together the science issues of the week and delivers breaking science news.
New results suggest that insecticide use in the tropics is to blame for the re-emergence of bed-bug infestations.
Exposure to treated bed nets and linens meant that populations of bed-bugs had become resistant to the chemicals used to kill them, researchers said.
The findings could help convince pest controllers to find alternative remedies to deal with the problem.
The results were presented at the American Society of Tropical Medicine and Hygiene’s 60th annual meeting.
Since almost vanishing from homes in industrialised countries in the 1950s, populations of the common bed-bug have become re-established in these regions over the past decade or so.
These mostly nocturnal feeders are difficult to control, not only because they are adept at avoiding detection by crawling into creases of soft furnishing but also because they have developed a resistance to many of the chemicals that have been used to kill them.
Findings presented at the gathering in Philadelphia showed that 90% of 66 populations sampled from 21 US states were resistant to a group of insecticides, known as pyrethroids, commonly used to kill unwanted bugs and flies.
One of the co-authors – evolutionary biologist Warren Booth, from North Caroline State University in Raleigh – explained that the genetic evidence he and his colleagues had collected showed that the bed-bugs infecting households in the US and Canada in the last decade were not domestic bed bugs, but imports.
“If bed-bugs emerged from local refugia, such as poultry farms, you would expect the bed-bugs to be genetically very similar to each other,” explained entomologist and co-author Coby Schal, also from North Carolina State University. “This isn’t what we found.”
In samples collected from across the eastern US, the team discovered populations of bed-bugs that were genetically very diverse.
This suggested that the bugs originated from elsewhere, and relatively recently because the different populations had not had time to interbreed, Dr Schal explained.
He suggested that the source for the new outbreaks was warmer climes, where the creatures would have probably developed a resistance to chemicals.
“The obvious answer is the tropics, where they have used treated bed nets [and] high levels of insecticides on clothing and bedding to protect the military,” Dr Booth told BBC News.
He explained that although bed-bugs were essentially eradicated from industrialised countries in the 1950s, they continued to thrive in Africa and Asia.
“Its very likely that it is from one of these areas where insecticide resistance evolved,” he said.
However, UK-based pest management specialist Clive Boase questioned that hypothesis.
He said bed nets, to protect against mosquito-transmitted malaria and dengue, were only used in parts of Africa that were hot, where the tropical bed-bug (Cimex hemipterus) was found.
But, he added, it was not the tropical bed-bug that was the problem in the US and UK; instead it was their temperate cousin, Cimex lectularius.
Dr Boase explained that comprehensive records showed that infestations of bed-bugs in Europe were less pervasive in the 1970s and 80s, but they were still present.
By continually exposing these populations to insecticides, which came on the market in the late 1970s, these creatures likely developed resistance, he said.
“We don’t have to invoke stories of disease control programmes in Africa; all the evidence here in the UK is that our problem is home-grown.”
Dr Boase wondered that if the US had similar long-term records whether the researchers would have reached a different conclusion.
Evolutionary biologist Richard Naylor from the University of Sheffield agreed: “I am kind of surprised by [their interpretation].
“It doesn’t seem that difficult to develop resistance or lose it; in lab cultures, if you stop exposing [bed-bugs] to pyrethroids it drops out of lab populations very quickly,” he said.
Mr Naylor asked that if the US bed bugs had been exposed to the chemicals elsewhere in the past, “why would they still be resistant?”
Scientists have developed a vaccine that protects mice against a deadly form of the Ebola virus.
First identified in 1976, Ebola fever kills a majority of the people it infects.
The researchers say that this is the first Ebola vaccine to remain viable long-term and can therefore be successfully stockpiled.
The results are reported in the journal Proceedings of National Academy of Sciences.
Ebola is transmitted via bodily fluids, and can become airborne. Sufferers experience nausea, vomiting, internal bleeding and organ failure before they die.
Although few people contract Ebola each year, its effects are so swift and devastating that it is often feared that it could be used against humans in an act of terroism.
All previously developed vaccines have relied on injecting intact, but crippled, viral particles into the body.
Long-term storage tends to damage the virus, paralysing the vaccine’s effectiveness.
The new vaccine contains a synthetic viral protein, which prompts the immune system to better recognise the Ebola virus, and is much more stable when stored long-term.
The vaccine protects 80% of the mice injected with the deadly strain, and survives being “dried down and frozen,” said biotechnologist Charles Arntzen from Arizona State University who was involved in its development.
He said the next step is to try the vaccine on a strain of Ebola that is closer to the one that infects humans.
Scientists have put forward their suggested names for the newest additions to the Periodic Table.
If the names are accepted, element 114 will become Flerovium (Fl) in honour of the physicist Georgiy Flerov.
While element 116 will become Livermorium (Lv), after the Californian laboratory where it was discovered.
The table’s governing body will officially endorse the names in five month’s time, 10 years after the elements were discovered.
The newest elements were among a handful of elements put forward for inclusion in the table in recent years.
They were accredited in June this year after a three year review by the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP).
The other putative heavy elements, 113, 115, and 118, are still under review.
Scientists at Lawrence Livermore National Laboratory (LLNL), in collaboration with a team at the Flerov Laboratory of Nuclear Reactions in Dubna, Russia, discovered the newest additions to the periodic table by smashing calcium ions into the element curium to create element 116, which quickly decays to element 114.
The teams also created element 114 separately by replacing curium with a plutonium target.
IUPAC will officially accept the proposed names after giving the public time to comment on the discoverers’ choice.
Scientists are set to begin a six-week mission to explore the Indian Ocean’s underwater mountains.
Aboard the UK research vessel the RRS James Cook, the team will study animals thousands of metres below the surface.
This year a report in the journal Marine Policy found that deep sea trawling is one of the most damaging forms of fishing.
The expedition will help scientists to better understand the threats to this environment.
The mission, led by the International Union for Conservation of Nature (IUCN), is the second to visit the seamounts along the South-West Indian Ocean Ridge; the first set out in November 2009.
Seamounts are underwater mountains which rise to at least 1,000 metres above the sea floor.
“Because of their interactions with underwater currents, the biodiversity that develops around them is remarkably rich,” explained Aurelie Spadone, IUCN’s marine programme officer and a member of the team.
“They attract a great diversity of species and act as a type of ‘bed and breakfast’ for deep-sea predators such as sharks, which often feed on seamount communities,” she added.
The catch of deep-sea species has increased seven-fold since the mid-1960s, as stocks of shallower waters plummet and the fishing industry took to exploiting deeper waters.
Industrial fishing at depth, which generally relies on trawling the ocean’s bottom with huge weighted nets, has a huge impact on seafloor ecosystems, say researchers.
Carl Gustaf Lundin, director of IUCN’s Global Marine and Polar Programme explained that very little was known about the species associated with seamounts.
“Many of them grow and reproduce slowly, which makes them particularly vulnerable to overexploitation,” he said.
“Deep-sea bottom fisheries, including bottom trawling, can damage seamount habitats and negatively impact fish stocks. It can also irreversibly damage cold water corals, sponges and other animals.”
Alex Rogers of the University of Oxford and chief scientist on board RRS James Cook said: “We’re hoping that this expedition will help us better understand this unique marine life and assess the threats it faces.
Diet has shaped human jaw bones; a result that could help explain why many people suffer with overcrowded teeth.
The study has shown that jaws grew shorter and broader as humans took on a more pastoral lifestyle.
Before this, developing mandibles were probably strengthened to give hunter-gatherers greater bite force.
The results were published in the Proceedings of the National Academy of Sciences.
“This is a fascinating study which challenges the common perception that there has been little recent change in the morphology of humans,” said anthropologist Jay Stock from the University of Cambridge.
Many scientists have suggested that the range of skull shapes that exist within our species is the result of exposure to different climates, while others have argued that chance played more of a role in creating the diversity we see in people’s profiles.
The new data, collected from over 300 skulls, across 11 populations, shows that jaws shortened and widened as humans moved from hunting and gathering to a more sedentary way of life.
The link between jaw morphology and diet held true irrespective of where people came from in the world, explained anthropologist Noreen von Cramon-Taubadel from the University of Kent.
It would be tempting to conclude that this is evidence for concurrent evolutionary change – where jaw bones have evolve to be shorter and broader multiple, independent times, she told BBC News.
But the sole author of the paper suggested that the changes in human skulls are more likely driven by the decreasing bite forces required to chew the processed foods eaten once humans switch to growing different types of cereals, milking and herding animals about 10,000 years ago.
“As you are growing up… the amount that you are chewing, and the pressure that your chewing muscles and bone [are] under, will affect the way that the lower jaw is growing,” explained Dr von Cramon-Taubadel.
She thinks that the shorter jaws of farmers meant that they have less space for their teeth relative to hunter-gatherers, whose jaws are longer.
“I have had four of my pre-molars pulled and that is the only reason that my teeth fit in my mouth,” said Dr von Cramon-Taubadel.
Ever since that time, she has wondered why so many people suffer with teeth-crowding.
“I think that’s the reason why this result resonates with people,” she said.
Dr Stock added: “[The finding] is particularly important in that it demonstrates that variation that we find in the modern human skeletal system is not solely driven by population history and genetics.”
These results fit with previous evidence of both a reduction in tooth and body size as humans moved to a more pastoral way of life.
It also helps explain why studies of captive primates have shown that animals tend to have more problems with teeth misalignment than wild individuals.
Further evidence comes from experimental studies that show that hyraxes – rotund, short-tailed rabbit-like creatures – have smaller jaws when fed on soft food compared to those fed on their normal diet.
Global temperatures could be less sensitive to changing atmospheric carbon dioxide (CO2) levels than previously thought, a study suggests.
The researchers said people should still expect to see “drastic changes” in climate worldwide, but that the risk was a little less imminent.
The results are published in Science.
The study is the latest to derive a value for “climate sensitivity” – the temperature rise for a doubling of CO2 concentrations – from palaeontology.
Previous studies have produced a mean value around 3C; but the new analysis concludes it is somewhat lower, around 2.3C.
More accurate analyses of climate sensitivity from historical data should allow for development of more accurate climate models that forecast the future.
The new analysis uses palaeoclimate data going back to the latter stages of the most recent Ice Age, 21,000 years ago, and a computer model.
Lead author Andreas Schmittner from Oregon State University, US, explained that by looking at how surface temperatures changed during a period when humans were having no impact on global temperatures, his team showed that it had not been as cold as previous estimates had suggested.
“This implies that the effect of CO2 on climate is less than previously thought,” he explained.
The researchers suggest that this finding can reduce uncertainty in future climate projections, though they do still give a range rather than a precise value.
The new models predict that given a doubling in CO2 levels from pre-industrial levels, the Earth’s surface temperatures will rise by 1.7C to 2.6C (3.1F to 4.7F), with a mean value of 2.3C.
That is a much tighter range than the one produced by the Intergovernmental Panel on Climate Change’s (IPCC) 2007 report, which suggested a rise of 2.0-4.5C, with a mean of about 3C.
The authors stress the results do not mean that the threat from human-induced climate change should be treated any less seriously, explained palaeoclimatologist Antoni Rosell-Mele from the Autonomous University of Barcelona, a member of the team that came up with the new estimates.
But it does mean that to induce large-scale warming of the planet, leading to widespread catastrophic consequences, we would have to increase CO2 more than we are going to do in the near future, he said.
“But we don’t want that to happen at any time, right?” he remarked
“At least, given that no one is doing very much around the planet [about] mitigating CO2 emissions, we have a bit more time.”
Whether these results mean that the global temperatures would be less responsive to falling CO2, if emissions do fall, is unclear.
“I don’t think we know that, to be honest,” remarked Dr Rosell-Mele.
Gabriele Hegerl from the University of Edinburgh is cautious about the result in her perspective piece published in the same issue of Science.
She says that this is just one particular climate model, and “future work with a range of models would serve to strengthen the result”.
Climatologist Andrey Ganopolski from the Potsdam Institute for Climate Impact Research, Germany, went further, saying he would not make such a strong conclusion based on this data.
“The results of this paper are the result of the analysis of [a] cold climate during the glacial maximum (the most recent ice age),” he told BBC News.
“There is evidence that the relationship between CO2 and surface temperatures is likely to be different [during] very cold periods than warmer [periods].”
Scientists, he said, would therefore prefer to analyse periods of the Earth’s history that are much warmer than now when making projections about future temperatures.
However, although good data exists for the last million years, temperatures during this time have been either similar to present, or colder.
“One should be very careful about using cold climates to [construct] the future,” he added.
Scientists have found the best evidence yet for water just beneath the surface of Jupiter’s icy moon, Europa.
Analysis of the moon’s surface suggests plumes of warmer water well up beneath its icy shell, melting and fracturing the outer layers.
The results, published in the journal Nature, predict that small lakes exist only 3km below the crust.
Any liquid water could represent a potential habitat for life.
From models of magnetic forces, and images of its surface, scientists have long suspected that a giant ocean, roughly 160km (100 miles) deep, lies somewhere between 10-30km beneath the ice crust.
Many astrobiologists have dreamed of following in the footsteps of Arthur C Clarke’s fictional character David Bowman, who, in the novel Odyssey Two, discovers aquatic life-forms in the deep Europan sea.
But punching holes through the moon’s thick, icy outer layers has always seemed untenable.
The discovery of shallow liquid water by an American team makes a space mission to recover water from the moon much more plausible.
The presence of shallow lakes also means that surface waters are probably vigorously mixing with deeper water.The icy eddies could transfer nutrients between the surface water and the ocean’s depths.
“That could make Europa and its ocean more habitable,” said lead author Britney Schmidt from the University of Texas at Austin, US, who analysed images collect by the Galileo spacecraft launched in 1989.
Glaciologists have been studying the surface of Europa for many years, trying to work out what formed its scarred, fractured surface.
By looking at Antarctica, where we see similar [features] – glaciers, ice shelves – we can infer something about the processes that are happening on Europa, said glaciologist Martin Siegert from the University of Edinburgh.
He explained that the new study tells us how upwelling of warmer water causes melting of surface ice, forming cracks.
“You get freezing [water] between the cracks… so you end up with the existing ice cemented in with new ice.”
“The underside then freezes again, which causes the uplifting; its pretty neat,” Dr Siegert told BBC News.
The US and Europe are working on missions to Europa, and Jupiter’s other moons, which they hope to launch either late this decade or early in the 2020s.
Europa was discovered – together with three other satellites of Jupiter – by Italian astronomer Galileo Galilei in January 1610.
The icy moon is 350 million miles from Earth, and is one of 64 Jovian satellites.
In the 1990s, Nasa’s Galileo probe sent pictures back of its surface.
Europa has a small metal core (light blue, centre), surrounded by a large layer of rock (orange).
The surface is thought to consist of an ocean of liquid water (blue) covered by a thick layer of ice (beige).
New research has found that radioactive material in parts of north-eastern Japan exceeds levels considered safe for farming.
The findings provide the first comprehensive estimates of contamination across Japan following the nuclear accident in 2011.
Food production is likely to be affected, the researchers say.
The results are reported in the Proceedings of National Academy of Sciences(PNAS) journal.
In the wake of the accident at Japan’s Fukushima nuclear power plant, radioactive isotopes were blown over Japan and its coastal waters.
Fears that agricultural land would be contaminated prompted research into whether Japanese vegetables and meat were safe to eat.
An early study suggested that harvests contained levels of radiation well under the safety limit for human consumption.
Now, an international team of researchers suggests this result deserves a second look.
To estimate contamination levels, Teppei Yasunari, from the Universities Space Research Association in the US state of Maryland, and his colleagues, took measurements of the radioactive element caesium-137 in soil and grass from all but one of Japan’s 47 regions and combined these results with simulations based on weather patterns following the meltdown.
Caesium-137 lingers in the environment for decades, and so is more of a concern than other radioactive elements released in the cloud of steam when the reactors’ cooling systems failed, leading to explosions.
The team found that the area of eastern Fukushima had levels of the radioactive element that exceeded official government limits for arable land.Under Japanese Food Sanitation Law, 5,000 becquerel per kg (Bq/kg) of caesium is considered the safe limit in soil (caesium-137 makes up about half of total radioactive caesium, and therefore its safe limit is 2,500 Bq/kg).
The researchers estimate that caesium-137 levels close to the nuclear plant were eight times the safety limit, while neighbouring regions were just under this cut off; the rest of Japan was well below (averaging about 25 Bq/kg) the safety limit.
Relatively low contamination levels in western Japan could be explained by mountain ranges sheltering those regions from the dispersal of radioactive material, the authors said.
Food production in the most contaminated regions, the researchers write, is likely to be “severely impaired”, and that Fukishima’s neighbouring regions, such as, Iwate, Miyagi, Yamagata, Niigata, Tochigi, Ibaraki, and Chiba are likely to also be affected.
“Some neighbouring prefectures… are partially close to the limit under our upper bound estimate and, therefore, local-scale exceedance is likely given the strong spatial variability of [caesium-137] deposition,” the researchers explained in PNAS.
They urge the Japanese government to carry out a more thorough assessment of radioactive contamination across Japan before considering future decontamination plans.
A second study, published in the same edition of PNAS, collected over a hundred soil samples from within 70km of the Fukishima plant, and found similarly high caesium-137 levels across the Fukishima prefecture, and its neighbouring regions.
Radioecologist Nick Beresford from Centre of Ecology and Hydrology in Lancaster explained that once in soil, caesium will become bound to mineral components, which limits its uptake into plants.
However, this process depends on the soil type. “Caesium stays mobile for longer in organic soils, hence why England and Wales still have some post-Chernobyl restrictions in upland areas,” he told BBC News.
Ploughing, and some fertilisers can help farmers reduce plants’ uptake of the dangerous elements, and binding agents can be added to animal feed to reduce their uptake from the gut, he added.
New figures on background radiation levels recorded 60km northwest of the Daiichi power plant have also been released this week by Japanese physicist Tsuneo Konayashi from Fukushima Medical University.
Dr Konayashi saw an initial spike reaching over nine times the usual levels hours after the explosions at the plant; five months later levels have dropped to one and a half times those expected.
He continues to monitor radiation levels and distribute his data around campus.
Becquerels and Sieverts
A becquerel (Bq), named after French physicist Henri Becquerel, is a measure of radioactivity
A quantity of radioactive material has an activity of 1Bq if one nucleus decays per second – and 1kBq if 1,000 nuclei decay per second
A sievert (Sv) is a measure of radiation absorbed by a person, named after Swedish medical physicist Rolf Sievert