Reactions occurring at different surface sites on the same nanocatalyst can “communicate” with each other in ways that are very similar to catalytic allostery in enzymes. The new result will help researchers better understand nanoscale catalysis and ultimately develop improved catalysts in the future.
Enzymes are naturally efficient nanoscale catalysts and one of their characteristic features is so-called allostery. Here, reactions at one site affect reactions at another site, typically a few nanometres away, without the reactants directly interacting with each other. Enzymes are not the only nanoscale catalysts, however, and nanoparticles of various materials such as metals or metal oxides, which are the same size as enzymes, can catalyse many chemical transformations on their surfaces. The active sites on these surfaces can be structurally or electronically coupled too.
Researchers led by Peng Chen of Cornell University in the US recently developed a new way to map catalytic reactions on a single catalyst. “For every reaction occurring on a catalyst particle, we now know where it happened and when it happened,” he explains. “I wanted to take this work a step further and find out whether reactions at different places on the same catalyst could ‘talk’ to each other.”
Holes “carry” information
Using spatially and temporally resolved fluorescence imaging of individual catalytic reactions within single nanoscale catalysts (in this case nanoparticles of gold and palladium), Chen and colleagues found that this was indeed the case. They observed that the particles likely “communicate” with each other through the movement of positive charge carriers (holes) over distances of around 102 nm and over times of between 10 to 102 seconds. The researchers also saw that reactions on separate gold nanocatalysts affect each other over even longer distances of many microns. Here the mechanism occurs through diffusion of negatively charged reaction products.
“The inter-particle communication is analogous to the ‘spillover’ effect in heterogeneous catalysis,” says Chen. “Both of the intra-particle and inter-particle effects we saw represent first-of-their kind observations involving individual nanocatalysts and our results provide a new sort of conceptual framework for understanding how a nanoscale catalyst particle works.”
With the World Cup just a few months away, you better start collecting those Panini stickers of football players, managers etc if you want a complete set. But how much would it cost, on average, to collect all the stickers if you don’t swap with friends? There are five stickers in a packet, which costs 80p. There are 682 unique stickers, and don’t forget that you will end up with lots of duplicates. You can check your answer with Cardiff University mathematician Paul Harper, who has used Euler’s constant in his calculations – so he must be right!
Testing someone’s eyes and prescribing glasses is a serious business, so you might think that a leading chain of opticians would have a decent understanding of optics. Not so, claims John Houlihan, who is a physicist at Ireland’s Waterford Institute of Technology. He was in his local branch of Specsavers and suspected that a sales demonstration involving polarized light was trying to pull the wool over his eyes. Not so, says the firm. Conor Pope illuminates both sides of the story in the Irish Times.
A few weeks ago I mentioned the Subatomic Smackdown, which will reach fever pitch today. Physics labs around the world are championing their favourites for the title of “Most Awesome Subatomic Particle”. Today is the big day for voting by the public and you cast your ballot for either the proton, neutron, photon or electron between 9:00-17:00 EDT on Twitter using the hashtag #SubatomicSmackdown. More details here.
NPL is now gearing up for a new challenge, as the UK launches its first high-energy proton therapy facilities. The UK was the site of the world’s first hospital-based proton therapy centre: the low-energy ocular treatment facility at Clatterbridge Cancer Centre, which started treating patients in 1989. Since then, though, the country has lagged behind in establishing a high-energy facility.
Later this year, however, the UK’s National Health Service (NHS) will open its first high-energy proton therapy centre, at The Christie, followed in 2020 by a second facility at UCLH. Both will employ the latest pencil-beam scanning beam delivery. There are also several private centres under development, such as the Rutherford Cancer Centres, which is also aiming to offer proton treatments in 2018.
“Overall, our experience with proton therapy is still much smaller than in the radiotherapy world,” said Richard Amos from University College London, speaking at the recent launch of NPL’s Metrology for Medical Physics Centre (MEMPHYS). “Having a central place like NPL to keep it on track is a great idea – this is why MEMPHYS is so important.”
Absolute dosimetry
One key service offered by NPL is absolute dosimetry of radiotherapy systems. The laboratory has developed graphite calorimeters as primary standards for measuring absorbed dose. These are used to calibrate clinical instruments that hospitals send to NPL, by comparison against the calorimetry results in one of NPL’s well defined linac facilities.
“We make sure that a patient receiving radiotherapy anywhere in the UK will receive the same radiation dose,” explained Russell Thomas, senior research and clinical scientist at NPL.
While this service ensures excellent consistency for conventional radiotherapy performed in the UK, NPL cannot repeat this model for proton therapy as it does not have an on-site proton therapy system. Previously, the only option for proton beam reference dosimetry was a 60Co-based calibration, which has an uncertainty of about 5-9%. But what’s really needed is the same level of uncertainty achieved for radiotherapy – an accuracy of nearer 2%.
“It’s really important that we can deliver proton therapy as well as we currently deliver standard radiotherapy,” said Rebecca Nutbrown, NPL’s head of metrology for medical physics, noting the importance of end-to-end audits and equipment calibration. “We aim to halve the reference dosimetry uncertainty for proton therapy from the current levels that are based on the international code.”
Proton focus
The nature of proton dose delivery – where the beam deposits most of its energy at a defined distance, within the Bragg peak – makes it of the utmost importance to perform treatments with as high an accuracy as possible. Positional uncertainty due to patient breathing, for example, and anatomical variations such as tumour shrinkage or cavity filling can change the beam range and dramatically degrade the intended dose deposition. “Proton therapy is amazingly conformal, but runs the risk of geometric miss of tumours,” Amos noted.
Much research is currently dedicated to addressing this problem, using emerging in vivo range verification techniques, for example. Meanwhile, proton CT and dual-energy CT are being studied as ways to increase treatment planning accuracy. “Accounting for all uncertainties in proton therapy planning is more complicated than photon planning; and it’s so complicated that not all sites do it the same way,” Amos explained. “Standardizing the way that we account for uncertainties is important.”
To achieve this, NPL is developing a code of practice for proton beam dosimetry, in collaboration with the Institute of Physics and Engineering in Medicine (IPEM). NPL has also established the Proton Physics Research and Implementation Group (PPRIG), with representatives from key stakeholders including The Christie and UCLH.
Another essential task is absolute dosimetry for calibration of the proton beam. With this aim, NPL is developing a primary standard for protons, based on a robust portable graphite calorimeter. This calorimeter has now been transported to proton therapy centres in Liverpool (Clatterbridge), Sicily, Prague and Japan, where it operated successfully in clinical settings.
NPL calorimeters
The proton calorimeter will ultimately provide traceability that is comparable with existing UK dosimetry protocols for conventional X-ray radiotherapy. The improved consistency provided will be of benefit for multi-centre clinical trials. “With more proton centres starting up, we want them all doing the same thing, so we can glean the best knowledge with regard to treating patients,” said Thomas. “This calorimeter will become the UK’s primary standard for protons, but there’s work to do still.”
Looking forward, NPL will play a vital role in the introduction of the UK’s proton therapy centres, including performing absolute and relative dosimetry, and standardization of clinical trials and imaging protocols. NPL-led research will endeavour to understand uncertainties in more depth, as well as investigate radiobiology problems, such as the correlation between LET and RBE. “MEMPHYS is bringing the physical sciences together with the life sciences,” Amos concluded.
Runaway climate change will alter the pattern of ocean productivity and circulation and play perhaps irreversible havoc with fish catches.
Global ocean productivity – the annual bloom of algae and the cornucopia of molluscs, shrimp, krill, squid, fish and marine mammals that depend on this flowering of the blue planet – could be in serious decline by 2300, thanks to climate change.
The harvest from the North Atlantic could fall by almost two thirds. The decline in the Western Pacific could drop by 50%. The overall productivity of the oceans from pole to pole will be at least 20% less.
But the latest study looks not at the immediate consequences of profligate human combustion of fossil fuels, but at the very long-term consequences of turning up the planetary thermometer.
Scientists report in the journal Science that three centuries of continuous rise in carbon dioxide levels in the planet’s atmosphere, as a consequence of fossil fuel combustion, could raise global average temperatures by 9.6°C.
This is ten times the warming already observed. It will change wind patterns, melt almost all the sea ice and increase ocean surface temperatures.
And with this increase in temperature comes change in the growth of phytoplankton, on which ultimately all marine life depends. There will be shifts in ocean circulation that will take nutrients from the surface and deposit them in the deepest waters.
Antarctic waters could become richer in nutrients. But the world’s human population is centred in the northern hemisphere. “Marine ecosystems everywhere to the north will be increasingly starved for nutrients, leading to less primary production by phytoplankton, which form the base of ocean food chains,” said Keith Moore, an earth system scientist at the University of California, Irvine, who led the study.
“By looking at the decline in fish food over time, we can estimate how much our total potential fisheries could be reduced.”
But time is running out: the oceans have yet to respond fully to the greenhouse gases that have already built up in the atmosphere in the last century or so.
“The climate is warming rapidly now, but in the ocean, most of that added heat is still right at the surface. It takes centuries for that heat to work its way into the deeper ocean, changing the circulation and removing the sea ice, which is a big part of this process,” Dr Moore said.
“This is what’s going to happen if we don’t put the brakes on global warming, and it’s pretty catastrophic for the oceans.
“There is still time to avoid most of this warming and get to a stable climate by the end of this century, but in order to do that, we have to aggressively reduce our fossil fuel use and emissions of greenhouse gas pollutants.”
Optical traps provide a valuable non-contact approach for manipulating nanostructures for biological, photonic and material science studies. However heating effects have placed constraints on what laser wavelengths and intensities traps can use, as well as the systems they can manipulate. Researchers in the US, Turkey and Spain have now turned these heating effects to their advantage by demonstrating the versatile manipulation of nanostructures using opto-thermoelectric effects.
Nuisance heating is a recurring theme in nanotechnology where resonances and low-dimensional features can exacerbate milder macroscale effects. Optical tweezers harness the tiny forces exerted by incident light to trap and manipulate nanoparticles, but the inevitable laser heating leads to radiation forces that reduce the trap stability. The situation further deteriorates for trapped metal nanoparticles when the incident light overlaps with a plasmonic resonance, whereby electrons move in response to light collectively, causing enhancements to local fields by several orders of magnitude. To bring these errant heating effects into line Yuebing Zheng and colleagues exploited the different responses of different particles to a thermal gradient.
How it works
Zheng and colleagues demonstrated their thermo-electric nanotweezers on plasmonic silver and gold nanoparticles. They dispersed the particles in a solution of the cationic surfactant, cetyltrimethylammonium chloride (CTAC), so that a positively charged molecular double layer formed at the particle surface. They also coated a porous gold film – which has a plasmonic response at infrared wavelengths – in CTAC and used it as the substrate.
Free CTAC molecules form micellar cations in solution, that were countered by chroide anions. With no incident light the large cations and chloride ions were equally dispersed. When the researchers shone a laser onto the thermoplasmonic substrate, a thermal gradient developed. Both the micellar cations and chloride ions will migrate from hot to cold regions, but the higher molecular mass of the micellar cations leads to an inbalance in the cation and anion distribution causing an electric field in the direction of the nanoparticle.
What it works on
Measurements revealed that the stiffness of the trap exceeded that of optical tweezers by two to three orders of magnitude. Tuning the CTAC concentration further improved the trap stiffness. As well as nanospheres they tested the approach on nanotriangles as well.
They were also able to demonstrate the opto-thermoelectric manipulation of multiple particles into a ring or a triangular shape using a digital micromirror device, a tool that can pixelate incident light switching it on or off for each pixel.
In their report the researchers conclude that “with its low-power and non-invasive operation, diverse options in the trapping wavelength, and generality in size, shape and composition of the trapped nanoparticles, OTENT [opto-thermoelectric nanotweezers] will become a powerful tool in colloid science, life sciences and nanotechnology.”
Nanofabricated ultraflexible electrode arrays that have a cross-sectional area that is much smaller than conventional carbon fibre electrodes could be used to detect action potentials from individual neurons without damaging brain tissue. The devices could allow for high-density electrical recoding of neural activity in the living brain as well as being useful in the field of brain-machine interfacing.
Implanted neural probes are currently the only way to monitor the fast electrophysiological activity of individual neurons. Such probes have also been successfully employed to treat a number of neurological diseases, such as Parkinson’s. And they can be used to establish direct communication between the brain and a man-made interface too.
The problem is that these probes are typically much larger in size than neurons and capillaries (they usually have a cross-sectional area of 103 μm2) and can thus cause significant damage to brain tissue when implanted.
A hundred times smaller cross-sectional area
A team of researchers led by Chong Xie of the University of Texas at Austin has now developed new ultraflexible intracortical probes that are 10 times smaller than conventional carbon fibre electrodes and which have a cross-sectional area that is a hundred times smaller. “This advance is, in our opinion a crucial first step towards high density, full-coverage mapping of neural activity in a sizeable brain region,” says team member and lead author of this study Xiaoling Wei. “It could also prove very useful in the field of brain-machine interfacing.”
The researchers used state-of-the-art electron-beam lithography and photolithography techniques to fabricate nanoelectronic thread (NET-e) probes containing densely packed electrode arrays. They made the devices on 100 mm silicon wafers containing a sacrificial layer of thin nickel. “After releasing the sacrificial layer, we were able to harvest substrate-less small-sized probes with a multilayer layout that markedly reduces their cross-sectional area to the subcellular range,” explains Wei. “One such NTE-e hosted a linear array of electrodes with a cross-sectional profile of 0.8μm × 8 μm, which is the smallest among all reported to our knowledge.”
No damage to brain tissue
One of the probes was designed to function as a multiple tetrode, hosting groups of four closely-spaced electrodes every 100 μm along the thread, he adds. “It was fabricated so that its electrode spacing was smaller than its detection range to allow for ‘spatial oversampling’, which improves spatial resolution of action potential signal recording.”
The researchers tested out their device on a mouse model and found that the electrodes can record action and local field potentials of neurons with high signal-to-noise ratio. “Compared to conventional neural probes, the much-reduced dimensions of our NET-e probes allow us to implant the devices at previously unattainable high densities without damage to brain tissue,” Wei tells nanotechweb.org. “In this work, we could implant the probes to a depth of between 500 and 700 μm in the somatosensory cortex. We also demonstrated implantation at inter-probe distances of 60 μm distances, again without eliciting neuronal death.”
The team, reporting its work in Advanced Science https://doi.org/10.1002/advs.201700625, is now planning to extend its tests to primates. “We also plan to collaborate with other professionals to broaden the use of our probes to other fields, such as monitoring neuronal disease, and in fundamental studies.”
There are close to a billion passenger cars on the road worldwide – a quarter of them use glass made by NSG. Yet while the company seems to specialize in glass – glass that allows heat in but not out; glass that inhibits condensation for display fridges; and even glass that can oxidize organic dirt to form CO2 – as Su Varma, the company’s incubation portfolio manager, told attendees at the Materials Research Exchange 2018 in the UK, they are really selling products that have functional nanoscale coatings on a glass substrate. With the exception of products based on low-iron or ultrathin glass, the real value add is in the coating.
Fabrication matters
NSG’s coatings are largely oxides, such as titanium oxide to catalyse oxidization of organic compounds or doped tin oxide for transparent conductive coatings in which NSG have a leading global position. Key to the company’s success is their fabrication procedures, which include chemical vapour deposition (CVD), physical deposition and sol gel processes. Printing and atomic layer deposition are some of the possible future processes to deposit transparent thin functional films. “The same material but a different process gives a different functionality,” Varma explains.
Forty years of development have gone into the company’s CVD processes. The technique exposes a substrate to different vaporized chemicals that react or decompose forming high quality deposits. Real-time monitoring is in place at NSG to check that the thickness meets the desired specifications. Even just a couple of nanometres out of spec can change the functionality from transparent to reflective, and ultimately customer dissatisfaction. The tight adherence to specifications are met at a formidable fabrication rate with coatings that are around 80 nm thick in total, combining as many as 12 functional layers, produced at rates of 6m × 3.3m in just 45 seconds. “If it’s not on that scale it’s not economic,” says Varma.
The team at Oxford nanoSystems
Starting up
While large companies may rely on a £40 million fabrication plant that can churn out square metres of coatings in seconds, the initial stages of a company’s life cycle will likely have more modest requirements. Current CEO Alex Reip joined Oxford nanoSystems in 2012 at the invitation of an academic acquaintance who alongside an entrepreneur had come up with the idea of setting up a coatings company focused on heat transfer. Bringing Alex on board as science specialist doubled the employee head count to a grand total of two.
The Oxford nanoSystems heat-transfer coating has a dendritic texture to increase the number of bubbles that form thereby increasing heat transfer in liquids by 524%. The company had an unusual beginning, as they won over the support of an Angel investor in the audience at an Oxford business School competition at the outset. As a result, they have been developing the technology and commercializing it simultaneously, as opposed to a lot of start-ups who develop the technology and must then leap “the valley of death” to achieve commercialization. With subsequent funding from innovate UK and others the total investment now exceeds £1,400 000. They plan to double their employee base again to a total of eight in the next 12 months, and they have just applied for further funding to take the company through the next few years after which they hope to be self-sustaining.
When he joined the company, Reip had just finished a PhD on nanophosphors for fingerprint detection. Although some of the basic chemistry was similar, moving into a new field of research meant there was a lot of knowledge to pick up. “The heat transfer field of research is vast,” says Reip. But Reip suggests in some ways this was the easy part. “Moving from research to commercializing something was the bigger leap.”
Applications of Oxford nanoSystems coatings range from low cost and large quantities in sectors such as air-conditioning, to electronics and space technology where costs are high and the volume is low. “We started on boilers but spreading our scope makes failure much less likely,” says Reip. “Being a small company makes it easier to change tack.”
Yet commercializing for different industries presents its own challenges to meet the different requirements, and Oxford nanoSystems has also had to contend with market inertia in some areas. “The AC market doesn’t change much so you need to prove more for take up,” says Reip. That said new markets are emerging, which may be easier to penetrate, such as the rise in electric vehicles where cooling battery coatings may be crucial.
Regulatory market changes
Changes in regulations can also influence the market for coatings. Indestructible specializes in protective paints, largely for applications in the aerospace industry. So far their products have incorporated nanomaterials, particularly for paints to protect regions exposed to high temperatures, and as Managing Director Brian Norton, whose father founded the company, points out nanomaterials have been used for decades, carbon black being one example.
However the latest evaluation by the International Agency for Research on Cancer (IARC) evaluation is that, “Carbon black is possibly carcinogenic to humans (Group 2B)”. In addition exposure to carbon black can irritate people’s airways. EU regulations for nanomaterials in general are currently under development and although Indestructible is still looking into the possible attractions of exploiting graphene in its paints, pending regulatory restrictions have made the use of nanomaterials less appealing to the company on the whole.
Necessity is the mother of invention
Regulatory inhibitions are already under contention in some fields. Throughout the second half of the twentieth century fluorocarbons, particularly long eight-atom-chain fluorocarbons (C8 PFCs) were the back bone of the non-wetting coatings sector. Until recently, the efficacy of C8 PFCs had drawn attention away from the hazardous emissions they break down into: PFOS and PFOA, which are not only carcinogenic but also persistent and bioaccumulative. “We can detect increased values of these substances in watercourses and even in the breast milk of US mothers,” stated a recent release by the specialists in ultra-thin coatings, Nano-Care Deutschland AG.
Founded in 2000 as a spin-off from the Leibniz Institute for New Materials (INM), Nano-Care produces coatings for textiles, building construction and non-absorbing surfaces. A key achievement recently was the launch of the Nanoflex F-Bond system in February 2018. As legal restrictions have tightened up on the use of C8 PFCs a lot of companies have resorted to using more comparatively less pernicious C6 PFCs. However, use of any PFCs is still cause for concern for organizations like GreenPeace, who are campaigning for their complete elimination, and as C6 PFCs are less effective than their longer chain counterparts, larger quantities are needed.
“The great challenge for us has been to retain existing high standards of oil repellency – whilst eliminating long-chain fluorination,” says Oliver Sonntag, CEO of Nano-Care, and relative of Bernhard Sonntag who founded the company. The company has already developed fluorine-free durable water-repelling coatings in their “Intelligent Hybrid” range, using chemicals that have a silicon dioxide backbone. However as Sonntag points out some applications need a textile coating that repels not just water but alcohol and oil as well. “Our particular focus is on military, work-wear and health sectors, which have to satisfy especially high-performance requirements and currently have only temporary permission to use C8 technologies. Their elimination – particularly outside the European Union – is an important step towards achieving “ecological sustainability” in the textile industry.”
As part of the Intelligent Hybrid range, the Nanoflex F-Bond system reduces to a minimum both the chain length and the quantity of PFCs required to achieve C8 performance with short-chain C6 technology. It combines the silicon dioxide backbone with a modified C6 polymer and process additives, thereby achieving dewetting performance at level 8 on polyester and 7 on cotton according to ISO 14419. It has also been certified with the Eco Passport standard 100 by Oeko-Tex.
The company is currently working towards C4 technology with the ultimate aim of eliminating PFCs altogether. Nano-Care sees a market potential amounting to the hundreds of millions of Euros with their Intelligent Hybrid technology. Based in Saarwellingen with subsidiaries in the UK and Mexico, the company is currently expanding and reorganizing its corporate structure to include a new Textile Effects’ department. It currently has 70 employees and customers in 65 countries.
Keeping the industry in good health
Besides regulating against health hazards, the coatings industry stands to benefit from a general increase in standards and digitization according to the Surface Engineering and Coatings (SEAC) report. As Allan Matthews, from the BP International Centre for Advanced Materials told delegates at Materials Research Exchange 2018, £140 billion of goods in the UK economy alone would not work without coatings. Yet he added that in the view of the Royce Institute – the UK National Centre for Research and Innovation of Advanced Materials – coatings is the one sector where the data falls short. With the main hub at Manchester University, the Royce Institute was set up as part of plans for a “northern power house” in the UK under former UK Chancellor of the Exchequer George Osbourne.
The Royce is currently working with partners to implement findings and recommendations from the SEAC report such as improving process coatings modelling; developing state-of-the-art facilities; driving digitization; and improving characterization, analysis, testing and evaluation. It is hoped that focussing on these areas will ensure that businesses in coatings are not just match fit, but reach their full economic potential on the global stage.
A distant galaxy apparently devoid of dark matter has been discovered by astronomers in the US, Canada and Germany. Paradoxically, they believe their finding could strengthen the case for dark matter as the source of the universe’s “missing mass” – because alternative theories that modify gravity should apply to all galaxies. Other researchers, however, remain unconvinced.
The idea that the universe might largely comprise “dark bodies” dates back to a talk given in 1884 by Lord Kelvin. In the 1930s, astrophysicists such as Fritz Zwicky realized the dynamics of galaxy clusters implied they contained far more mass than was visible to telescopes – mass that is now known as dark matter. More precise, observational evidence from Vera Rubin and colleagues was presented in 1980. Most astronomers now accept that only around 15% of the matter in the universe is “normal”, but the nature of the remainder remains largely mysterious.
Some astrophysicists, however, remain unconvinced. Pointing to several observations that dark matter struggles to explain, together with the fact that no one has yet identified dark matter, they argue that the underlying problem lies in the failure of current theories of gravity to correctly predict the large-scale dynamics of galaxies. Astrophysicist Pavel Kroupa of the University of Bonn in Germany, argued in 2012 that, if the dark-matter model were correct, there should be some “tidal dwarf galaxies” that, owing to having formed in a different way from other galaxies, did not contain dark matter. The absence of such galaxies would suggest that the dark-matter model is deficient.
Strange appearance
Pieter van Dokkum of Yale University and colleagues believe that their galaxy could fit the bill as a tidal dwarf devoid of dark matter. When studying the elliptical galaxy group NGC 1052 – around 63 million light-years from the Milky Way – with the Dragonfly Telephoto Array, which van Dokkum and a colleague built in New Mexico in 2013, the researchers noticed that a surrounding dwarf galaxy called NGC1052-DF2 looked very different in its Dragonfly images and in the Sloan Digital Sky Survey. “To try and find out what was going on, we applied for time on the Keck telescope and also took some images from the Hubble Space Telescope,” says van Dokkum.
Using the data, the researchers measured the brightnesses and rotation speeds of various clusters of stars within the galaxy. The researchers used the surface brightness fluctuation method, in which variation in the brightness of pixels arising from fluctuations in the specific number of stars’ light each pixel receives allows astronomers to calculate the brightness of single stars, and thereby to estimate the distance of the dwarf galaxy. Upon reaching the conclusion that it was indeed associated with NGC 1052 rather than sitting far in the foreground, they used measurements of the galaxy’s apparent luminosity, compared with its “true” luminosity, to estimate that the dwarf galaxy contained about 1.1×108 solar masses of stars.
Finally, they used the motions of the stars to calculate the amount of dark matter needed to explain the cluster motions observed. To their surprise, their results were consistent with there being no dark matter in the galaxy at all. The researchers suggest three possible formation scenarios for their surprising result. One is that they are observing a tidal dwarf galaxy that formed from normal matter that was liberated when much larger galaxies interact with each other. However, under all scenarios they conclude: “NGC1052–DF2 demonstrates that dark matter is not always coupled with baryonic matter on galactic scales.”
Stimulus to investigate
Kroupa is unconvinced, however: he notes that the dwarf galaxy appears extremely exotic, containing a number of unusually bright globular clusters (star clusters) but apparently no dimmer ones. “If the object is shifted toward the observer,” he says, “the gravitating mass will remain about the same, but the globular clusters and the galaxy become less luminous. So, the globular clusters can be brought into agreement with known globular clusters, the galaxy is less luminous for the same gravitating mass, and voila, we have dark matter in the object, which now is not exotic.”
He concludes that “it’s a very stimulating paper, but I think that, given the importance of this type of argument, the exciting part is that maybe we can take this as a stimulus to investigate the surface brightness fluctuation method a bit more.” If the dwarf galaxy is associated with NGC 1052, however, he says the researchers need to calculate whether the external field effect – a non-linear effect in modified Newtonian dynamics (the main competitor to dark matter) – could explain the observations.
Dennis Zaritsky of the University of Arizona – whose observations of the Bullet Cluster are often cited as unambiguous proof of dark matter – is also sceptical. His own doubts, however, concern not the distance and luminosity measurements but the dynamical ones. “We’re now in this strange situation where the extraordinary claim is that something does not have dark matter rather than that it does,” he explains: “It’s an intriguing object and it’s worth pointing it out so that more work is done on it, but I think we’re not quite there yet.”
In this video, we take you inside the atmospheric boundary layer wind tunnel at TU Eindhoven in the Netherlands, which officially opened in December 2017. Part of the university’s department of the built environment, the facility is designed to examine the effects of wind on buildings, traffic and other urban infrastructures. Bert Blocken, TU Eindhoven’s chair of building physics, demonstrates the facility with a model of Bahrain’s iconic World Trade Center, which has three wind turbines fixed between the two halves of the building along horizontal axes. An admirer of the building, Blocken explains how it could have generated even more electricity with a few design tweaks.
With a test section of 27 m and wind speeds up to 33 m/s, the facility will also be used by athletes and sports equipment manufacturers, particularly cyclists. A keen cyclist himself, Blocken has previously published a study on the advantage gained by cyclists of having a motorbike behind them.
The US must improve its ability to measure and monitor methane emissions from human activity. That is the main conclusion of a new report – Improving Characterization of Anthropogenic Methane Emissions in the United States – by the National Academies of Sciences, Engineering, and Medicine that says better data on methane could help decisions related to climate, economics and human health.
Methane is a greenhouse gas that is now present in the atmosphere at just under 1900 parts per billion (ppb) – a huge jump from around 700 ppb at pre-industrial levels. While there is much more carbon dioxide in the atmosphere than methane, it has a greater warming impact per molecule because of methane’s high-vibrational absorption of energy. While methane stays active in the atmosphere for about a decade, additional contributions from human activity have resulted in it being too abundant for the hydroxyl radical – the atmosphere’s naturally-occurring scrubber – to completely wash it out.
It is time for us to take that impact seriously and take the responsibility that comes from that impact
Geochemist James White from the University of Colorado Boulder
Methane released from human activities accounts for 60% of US methane emissions while natural processes, such as wetland microbial activity, cause the rest. While the US Greenhouse Gas Inventory keeps track of larger atmospheric methane measurements it does not offer adequate data on possible sources of methane. “What we don’t have today is a fully developed surface inventory that we could use to really benefit our understanding of methane and benefit our ability to track and learn from the concentrations in the atmosphere,” says geochemist James White from the University of Colorado Boulder, who chaired the 14-strong committee that wrote the report.
Serious impact
The report lays out a programme for better characterizing and identifying sources of anthropogenic methane, especially from the US’s biggest emitters – the livestock, oil and gas, landfill and manure industries. While coal mines are also significant, the report states that their methane output is reasonably well known. To do this, the report calls for enhanced large-scale aerial observations by satellites as well as detailing different sectors’ methane patterns, for example, describing livestock methane releases that vary with feed or other practices across agricultural areas.
Committee member Fiji George, an environment and energy engineer with Southwest Energy in Texas, notes that the report proposes measuring methane across the US with a 10 x 10 km grid. “What we are calling for is a coordinated effort to monitor methane,” says White. “The rationale behind it is not a methane rationale. We are the major agent of change on the planet. It is time for us to take that impact seriously and take the responsibility that comes from that impact.”
Given that methane is short-lived, the report says there is an opportunity to impact global temperatures. Reducing methane along with black carbon could help to reduce temperature increases by up to 0.5 degrees centigrade by 2050. This would be a significant contribution to the Paris Accord’s goal of restricting temperature increases to 1.5 to 2.0 degrees Celsius relative to pre-industrial times.
