On Monday 21 August tens of millions of people will view one of the most remarkable phenomena available on Earth – a total solar eclipse. The shadow created as the Moon blocks out the Sun will sweep across the US in the middle of the day and I’ve been looking forward to it since I learned of it six years ago.
I’m one of the lucky ones – I live in Salem, Oregon, which lies within the eclipse’s 10 km-wide path of totality. Along this path, day will turn dark for about two minutes and the flare of the Sun’s corona will become visible. Birds will roost, crickets will begin to chirp, the temperature will fall about 5 °C, and people will likely gape in awe as humans have no doubt done since our species first began.
The path of totality will cover other prominent places in the US, including Jackson Hole in Wyoming, Kansas City in Missouri, and, last of all, Charleston in South Carolina. More than 12 million people are directly in the path, with 324 million within a 9-hour drive of it.
While all North Americans will see at least a partial eclipse with a minimum 60% blockage, here in Oregon we have a distinct advantage as well as totality – usually clear summer days (our reward for the other eight months of sprinkles, mist, drizzle and rain). The totality shadow – called the eclipse’s “umbra” – first touches land at Oregon’s coast and its edge will move eastward at up to 3900 km/hr. Here in Salem, the Moon will begin to cover the Sun at 9.05 a.m., with totality at 10.18 a.m., lasting one minute and 54 seconds.
The shadow’s path: everyone in North America will experience a partial eclipse. (Courtesy: NASA)
Astronomers say the umbra is the place to be. My sister and her family are coming down from Portland, tenting in my backyard, then after breakfast we’ll go to a park across the street to watch. I bought eclipse glasses months ago; if I have any luck left we’ll get a clear sky.
Oregon officials expect hundreds of thousands of visitors to travel into the state’s path of totality (an Oregon tourist official told me they expect about one million people), likely overwhelming roads, rural towns, cell phone networks, and bathroom facilities. Six helicopters will be on standby to carry first responders above the gridlock. One police official said traffic could be jammed for a week, and Salem has opened its parks to camping with no permit required. I’m glad I can just walk out my front door.
Stay tuned for another blog on the science planned for the eclipse.
Living insects can now be scanned in unprecedented 3D detail without being harmed. The scanning method developed by scientists at Western University in Canada relies on an insect’s ability to survive low-oxygen environments and high-ionizing radiation doses.
Standard methods for looking inside insects involve using dead specimens or killing the bug during the imaging process. “We essentially had snapshots, moments in time, when what we needed were dynamic images of insects’ internal development,” says biologist Joanna Konopka. “We thought, what would happen if we tried to image them live?”
Bug’s life
Konopka therefore teamed up with biophysicist Danny Poinapen to develop a non-invasive technique. Using a steady flow of carbon dioxide, they temporarily immobilized living insects – including Colorado potato beetles and true army worms – for up to seven hours. As the bugs were no longer wiggling around, the team could use X-ray micro-computed tomography (micro-CT) to clearly see the insects’ internal workings in 3D. The bugs were then remobilized and the process repeated again days later, with no effect on the insects’ longevity, behaviour or ability to reproduce.
The live-scan method, presented in BMC Zoology, allowed the team to thoroughly examine how insects develop throughout their lifetime. It could therefore be useful in studying parasites or how insects impact human health.
The ingenious way that mushrooms and certain other fungi fire spores into the atmosphere in order to reproduce has been mimicked by a team of engineers and fungal biologists. These organisms disperse billions or even trillions of spores so that enough land in a suitable environment for them to reproduce. However, the phylum Basidiomycota – which includes all mushrooms and numerous other fungi – has evolved an ingenious dispersal method that uses the energy released by coalescing water droplets to boost the chances of reproduction. By mimicking this “surface-tension catapult” in the lab, the researchers’ work could inspire new approaches to dealing with destructive fungi or lead to artificial methods for dispersing tiny particles.
The basic details of how Basidiomycota launch spores were first worked out in the early 20th century, by the British–Canadian mycologist (fungal biologist) Arthur Henry Reginald Buller. He discovered that in the seconds before launch, the spore secretes chemicals that attract water so that two separate droplets grow on one side of the spore – a spherical “Buller’s droplet” on a small projection at the base, and a larger, flatter “adaxial droplet” higher up.
When the droplets make contact, they coalesce, with the resulting decrease in surface energy propelling the spore away from the gill at around 1 m/s. The spore is decelerated by viscous drag from the atmosphere, and falls vertically down until it is carried away by air currents. It is important that the sticky spore be launched directly away from the surface because, if it did not get well away, it might re-attach and fail to disperse.
Missing puzzle piece
The energetics of this process were clear, says engineer Chuan-Hua Chen of Duke University in the US. However, he says, it occurs fast – even though Nicholas Money of Miami University and colleagues in 2005 filmed the process at 100,000 frames per second, the dynamics could not be captured, and the process of how the fungus achieves dispersion was unclear.
“There was a big piece of the puzzle missing,” says Chen. “It was like you were building a cannon, and knowing that you could use gunpowder to fire stuff – but you didn’t know where the ball was, so you didn’t know how it was directed.”
Together with two authors of the 2005 paper, his group explored “several different conceptual models over a number of years”, before arriving at one that could explain the phenomenon. Researchers know that, in the seconds before the spore is launched, the structure holding it partially breaks down until it can resist compression but not tension.
Chen and colleagues worked out that the pressure is higher inside Buller’s drop than inside the upper, adaxial drop. So when the two droplets coalesce, the net fluid flow must be upwards. By Newton’s third law, the upward acceleration of the fluid then pushes down on the spore, exerting a compressive force that the structure withstands. However, when the fluid reaches the upper edge of the spore, it needs to be pulled back, which requires a downward force on the fluid, pulling up on the spore and exerting a tensile force the structure could not withstand. The spore would then be pulled directly off the structure.
Model launch
To test this hypothesis, the researchers built a model droplet-launching process, using a polystyrene “spore” hundreds of times larger than a real spore and depositing droplets on one surface with an inkjet printer. The distances and fluid quantities involved were much larger, so the launch process unfolded much more slowly: “We can see the coalescence-induced launching process in fine detail and therefore determine the mechanism by which the spore determines its launching direction,” Chen explains.
Many Basidiomycota fungi are vicious pathogens. “Understanding the details of the launch mechanism may help us either to enhance, or more likely to inhibit, the spore launching mechanism, and therefore to stop the spread of certain pathogens,” says Chen.
Money, who was not involved in the current research, suspects that few researchers will be surprised by the model. “Given the geometry of this situation, if you jump from a pillar, you’re almost bound to go upwards,” he says. Nevertheless, Money sees significant value in the way the model “makes sense of what we know happens in nature” and suspects there may be biomimetic applications: “Because of the supreme efficiency of this method,” he says, “there must be some applications in engineering that can make use of the coalescence of water droplets to move things around.”
A storm complex nearly the size of Earth has been seen in a usually quiet area of Neptune. Ned Molter from the University of California, Berkeley in the US spotted the storm while performing a test run of twilight observing at the W M Keck Observatory in Hawaii.
The storm system appears as a very bright region about 9000 km in length and spans at least 30° in both latitude and longitude. “Seeing a storm this bright at such a low latitude is extremely surprising,” explains Molter. “Normally, this area is really quiet and we only see bright clouds in the mid-latitude bands, so to have such an enormous cloud sitting right at the equator is spectacular.”
An anchored vortex
As on all planets, Neptune’s atmospheric winds vary greatly with latitude. For the storm system to span so many degrees, there therefore has to be something holding it together. A possible explanation is a huge, high-pressure vortex system anchored deep in the planet’s atmosphere. Just like water-vapour-forming clouds on Earth, methane gas on Neptune would cool and condense into clouds as it rises up the vortex.
Alternatively, the bright system could be a huge convective cloud, as seen on other planets such as Saturn. With this scenario, however, Neptune’s storm would likely have smeared out over the course of a week, but Molter observed it getting brighter between 26 June and 2 July.
Drastic dynamics
“This shows that there are extremely drastic changes in the dynamics of Neptune’s atmosphere, and perhaps this is a seasonal weather event that may happen every few decades or so,” says Imke de Pater, also from the University of California, Berkeley.
Understanding Neptune’s atmosphere is becoming increasingly important with regards to exoplanets, as the majority resemble the ice giant. Molter and de Pater hope to investigate the storm system further with more twilight observation runs at the Keck Observatory.
Smaller, potentially cheaper sources of high-intensity protons could become reality thanks to a novel type of fixed-field alternating-gradient (FFAG) accelerator designed by a physicist in the UK. FFAGs were first developed in the 1950s but have only recently come to the fore as a result of improved magnet and computing technology. The new design should be able to reach higher energies than existing devices and might prove well suited to transmuting radioactive waste, among other things.
Whereas particle accelerators operate at the highest possible energies to search for new particles, other machines are designed to yield very high intensities (albeit at fairly high energies). Synchrotrons, for example, use electromagnets to accelerate charged particles in a closed loop. To stop the particles drifting outwards as they speed up, these devices have magnets whose fields are ramped up in line with the particles’ increasing energy. But as the magnetic field changes with time, a synchrotron cannot simultaneously hold particles with different energies, thereby limiting its intensity.
Cyclotrons, meanwhile, do not suffer from this shortcoming, using magnets with a fixed field that allow high particle currents. Unfortunately, the particles in a cyclotron trace out ever larger orbits as they speed up, meaning that the device’s energy is limited by the strength and size of the magnets. While synchrotrons can produce beams of protons with several gigaelectronvolts or even teraelectronvolts in the case of the Large Hadron Collider at CERN, cyclotrons usually cannot manage more than a few hundred megaelectronvolts.
Best of both worlds
An FFAG, in principle, can combine the best of both worlds by using magnetic fields that vary in space rather than in time. Its magnets are designed so that their field strength increases sharply towards the edge of the machine, which keeps the orbits of faster-moving particles confined within a moderate radius. An FFAG can also operate quickly because its magnets do not have to ramp up and down. The result: beams of particles with high energies and high intensities.
Unfortunately, in practice FFAGs are hard to build. Their space-varying fields require that the accelerated particles be confined both horizontally and vertically as they travel in a circle. This can be done using two types of “radial” magnet shaped like slices of cake, which alternately focus and defocus particles in the horizontal plane while simultaneously defocusing and focusing them vertically. But the use of defocusing magnets pushes the particle orbits further out than they would otherwise be. At high energies, this would make FFAGs significantly larger, and more expensive, than synchrotrons.
An alternative option is for FFAGs to confine particles using spiral-shaped magnets. The idea here is that the bulk of each magnet focuses particles horizontally while its spiral edge defocuses them without pushing them out – and vice-versa for the vertical focusing. However, high energies require very tight spirals, which are hard to make.
Soften demands
In the latest work, Shinji Machida at the Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory near Oxford lays out the design of what he calls a DF-spiral FFAG that incorporates both radial and spiral elements. In other words, it uses focusing and defocusing magnets, both of which have a spiral shape. This allows Machida to soften the demanding requirements of machines that use just one or the other – reducing the circumference compared to a purely radial device, and the “spiral angle” compared to a purely spiral one.
In particular, he calculates that the circumference of a 1.2 GeV proton machine could be roughly halved by adding a 45° spiral to the edge of its focusing and defocusing magnets.
Roger Barlow of the University of Huddersfield in the UK describes the research as “an important development” in the quest for GeV-energy, high-intensity proton accelerators, arguing that the design “has obvious cost and space advantages”. But he says that developing suitably shaped coils to provide the magnetic fields for such a device will be challenging.
Also enthusiastic is Ken Peach of the University of Oxford, who says that the new design would require smaller and fewer magnets than “non-scaling FFAGs”, which themselves simplify magnet design by varying the field roughly linearly with radial distance. (In contrast, scaling FFAGs, including Machida’s, rely on a power-law variation.)
Potential limits
Carol Johnstone of Fermilab in the US, on the other hand, remains to be convinced. She agrees that a DF-spiral machine would be smaller than other scaling FFAGs, but says it would nonetheless remain larger than non-scaling devices. It would also be unable to generate continuous beams, she maintains, which would limit its intensity.
Machida and colleagues are currently planning a prototype high-intensity device, probably, he says, based on the DF-spiral design. Requiring prior R&D on magnets, radio-frequency systems and beam diagnostics, the idea, he says, is to show the device’s “superiority to the accelerator community in a convincing way”.
Different types The term LGBT+ covers wide spectra of gender and sexual identities. (Courtesy: iStock/RobinOlimb)
Scientists are often driven by a need to classify the world around them. Physics can equip us with a broad range of concepts and analyses that ought, in principle, to make us open minded not just in terms of science but in our day-to-day lives too. Nevertheless, many physicists who identify as LGBT+ still face challenges based on their identity.
Gender and sexuality are no longer defined the moment a person is born or by the way they may look, and despite some presumptions, the two need not be correlated in any way. Today, the concepts of being lesbian, gay, bisexual and transgender are not onlyin the public consciousness but also increasingly accepted as a part of the norm, meaning that now is an exciting time to be openly exploring one’s own identity.
Less familiar are terms encompassed by the ‘+’ in LGBT+, which highlights the ever growing list of identities coming to prominence, including asexual, aromantic, pansexual, agender, non-binary and demisexual. As we come across more and more identities, it is clear that gender and sexuality, which one may assume are discretely quantized groups, instead lie in spectra on which different people place themselves and indeed may move across throughout their lives.
There is an analogy with the electromagnetic spectrum, which was built from the discovery of different forms of light such as visible, infrared and X-rays. These categories exist because of their construction within man-made boundaries as opposed to any physical boundaries, but we always know the spectrum is continuous. Likewise, with sexual or gender identity, the categories – gay, straight, male, female and so on – are in place for convenience and because of their historical foundations. In reality, a spectrum works as a much better model, but is often overlooked because most people tend to place themselves at one end or the other of these spectra. Coincidentally, the visible region ties in very neatly with the rainbow pride flag, a key symbol of the LGBT+ community.
A survey published in March 2016 by the American Physical Society – LGBT Climate in Physics – provides some insight into the current condition for LGBT+ physicists (see May 2016 p11). Notably, 20% of respondents stated that they had experienced exclusionary behaviour based on sexual/gender identity in the previous year, with about half having come “out” in the workplace. Somewhat alarmingly, 40% agreed with the statement that “Employees are expected to not act too gay,” demonstrating a culture that is far from entirely inclusive.
A fluid concept
Regrettably, several factors prevent a thorough analysis of the current opinions of LGBT+ scientists. Surveys, anonymous or otherwise, cannot account for those who remain firmly “in the closet” or who may feel unable to voice their actual opinions for fear of being “outed”. Furthermore, sexuality and gender identity are not necessarily static, but can be in flux throughout an individual’s life, meaning that these surveys may present only a snapshot of one moment in time.
It is no real secret that science, technology, engineering and mathematics (STEM) subjects are largely a straight, male-dominated environment. Few LGBT+ figureheads exist, and those who do are often remembered solely for their contributions to science rather than as a person. More recently, incidents where noticeboards for an LGBT+ group at the CERN particle-physics lab were vandalized shows a shocking lack of tolerance from some of the most brilliant minds in the field (see March 2016 pp31–36).
Larger companies and universities often have mandatory diversity training courses that bring these issues to prominence, but particularly in the STEM workplace, LGBT+ people feel under-represented and unable to bring their complete selves to work. Some would argue that your identity as a physicist should not affect your work since any fundamental physical concept will not be changed by the person investigating it. But we are not machine-like in our labour. If someone who is transgender uses the bathroom of the gender they identify with, say, and is regularly met with hesitant or even aggressive glances from colleagues, it will quickly have a negative impact on their work.
Inevitably there will be opposition to the idea of sexuality and gender as individual spectra. Indeed, as scientists it is to our advantage to be scrupulous with new ideas and to harbour a healthy level of scepticism. This is relatively harmless when a physical concept is being explored, but when this is being applied to the identity of an individual, much more is at stake.
If a heterosexual, cisgender (someone who identifies as the same gender they were assigned at birth) physicist were to claim that an asexual-panromantic-trans-man was statistically so rare that they probably did not exist, they would be denying an entire group of people their identity. If one person from this group comes forward and falsifies this theory, some scientists might claim that this person must be “confused” or “going through a phase”, as is so often presumed by those whose identity lies comfortably in the majority.
Even if we feel that we may have more impartial judgement as scientists given our skills for analysing and presenting data, social, political and religious concepts of sexuality and gender in such circumstances inevitably come into play. Crucially, people cannot be viewed as data. Despite the fact we may like to fully understand every aspect governing gender identity and sexual orientation, whether this is rooted in biology, psychology or something else altogether, it seems unlikely to me that we can possibly create a single system to successfully categorize a planet full of different people.
Our priorities lie not in finding an answer, but in amplifying the conversation about tolerance and openness to new or unfamiliar concepts. After all, is this not the mindset we already use in learning and exploring physics?
It’s Mars Curiosity’s 5th birthday tomorrow! The NASA rover touched down on 5 August 2012 and has been exploring the red planet ever since. It has travelled more than 10 miles, studied more than 600 vertical feet of rock and even proved that Mars was once habitable. While a Mars birthday party for Curiosity would be a lonely affair, researchers at NASA Goddard Space Flight Center have programmed the rover to sing “Happy birthday” to itself using its Sample Analysis at Mars (SAM) instrument. To introduce ground samples into the rover, SAM resonates through a range of frequencies, so the researchers programmed the instrument to run through the frequencies of the celebratory song.
The fastest rotating fluid ever seen has been created by an international team of physicists working on the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in the US. The record-breaking vortices are quark–gluon plasmas (QGPs), which are made by smashing gold ions together at energies up to 200 GeV.
QGPs can be thought of as tiny versions of the universe shortly after the Big Bang – and studying their rotation could provide insight into both the early universe and the strong force that binds quarks together.
A QGP is created in a high-energy collision when the quarks and gluons that make up protons and neutrons become de-confined and create a hot, dense fluid-like state of matter. These collisions are rarely perfectly head on, so the resulting QGP can be left spinning with extremely high angular momentum.
Intrinsic spins
The rotation of the QGP cannot be measured directly and instead physicists working on the STAR detector at RHIC look at hadrons that are emitted from the QGP as it rotates. The intrinsic spins of these particles tend to be aligned with the angular rotation of the QGP, so the challenge becomes how to measure their intrinsic spins. Fortunately one of these hadrons – the Lambda; hyperon – decays rapidly to a proton and a pion – and the proton tends to be emitted along the direction of the Λ hyperon’s intrinsic spin.
The team tracks the proton and pion as they travel through the STAR detector. Because the two particles have opposite electrical charge, they are deflected in opposite directions by the detector’s electric and magnetic fields. The result is a distinct set of tracks that can be traced back to the Λ hyperon (see figure).
Faster than superfluid helium
By studying the intrinsic spin of the ejected Λ hyperons, the team worked out that the QGPs spin at a rate of about 1022 rotations per second. This makes them the fastest fluid vortex ever observed. Their speed is many orders of magnitude faster than a tornado, Jupiter’s red spot and even the previous record holder – vortices in superfluid helium that have been clocked at 107 rotations per second.
Studying QGPs should provide important information about the state of the universe shortly after the Big Bang, when the cosmos was itself a plasma of quarks and gluons. After a short while, this primordial QGP cooled to form the familiar hadrons (protons and neutrons) that comprise most matter today – and physicists are very interested in knowing exactly how this phase transition occurs. By studying the rotational properties of QGPs made here on Earth, physicists should gain important insight into the collective properties of QGPs that drove this transition.
Magnetic measurements
STAR physicists are also looking forward to using Λ hyperon measurements to study the extremely strong magnetic fields that are expected to exist in a QGP, because these fields affect how particles are ejected from the QGP.
The strongest evidence to date for an exoplanet stratosphere has been identified by scientists using NASA’s Hubble Space Telescope. Spectra of WASP-121b’s atmosphere are the first to show the resolved signature of hot-water molecules for a planet outside the solar system.
A planet’s stratosphere is a layer of atmosphere where temperatures increase with altitude. For example, Earth’s stratosphere contains ozone gas that traps ultraviolet radiation from the Sun, raising the temperature within the layer. Meanwhile, on Jupiter and Saturn’s moon, Titan, methane is behind the temperature increase.
Boiling metal
WASP-121b is a “hot Jupiter” – a gas giant with 1.2 times the mass of Jupiter and 1.9 times the radius and a much higher temperature. Located about 900 light-years away, it orbits the star WASP-121 in just 1.3 days, and the planet’s close proximity to the star means the top of its atmosphere reaches 2500 °C – so hot that some metals can boil.
While previous research has found possible signs of stratospheres on other exoplanets, the evidence of water on WASP-121b is the best to date. Thomas Evans from the University of Exeter in the UK and colleagues identified the water because it has a very distinct and predictable interaction with light, depending on its temperature. If there is cool water at the top of the atmosphere, the molecules will prevent certain wavelengths of light (typically infrared due to heating) from escaping the planet. On the other hand, if the water is hot, the molecules will “glow” at the same infrared wavelength. “When we pointed Hubble at WASP-121b,” says Evans, “we saw glowing water molecules, implying that the planet has a strong stratosphere.”
Unknown gaseous cause
The temperature change within stratospheres of solar-system planets is typically around 56 °C, but on WASP-121b the temperature rises by 560 °C. The researchers do not know what chemicals are causing this rise in temperature, but possible candidates include vanadium oxide and titanium oxide because they are gaseous under such high temperatures and are commonly seen in brown-dwarf stars, which have similarities to some exoplanets.
“This result is exciting because it shows that a common trait of most of the atmospheres in our solar system – a warm stratosphere – also can be found in exoplanet atmospheres,” says team member Mark Marley at NASA’s Ames Research Center in the US. “We can now compare processes in exoplanet atmospheres with the same processes that happen under different sets of conditions in our own solar system.”
Scientists have improved cancer treatments in recent years by combining radiation therapy with immunotherapy. Now, researchers in the US and China have engineered nanoparticles to improve outcomes further. The nanoparticles capture tumour-derived proteins at the treatment site, providing a kick to the immune system and enabling it to detect and respond to cancer cells elsewhere in the body.
On its own, radiation therapy works by damaging cancer cells’ DNA, killing them and preventing them from propagating their defective genetic material. Immune cells arriving at the tumour site after irradiation use mutated proteins released by the dying cells to coach other immune cells into recognising and fighting cancer elsewhere. This phenomenon is known as the abscopal effect, and it results in tumour shrinkage even outside of the sites targeted with radiation therapy. Immunotherapy drugs known as checkpoint inhibitors are given alongside radiation therapy to help the body’s immune system marshal its attack on cancerous cells.
Writing in Nature Nanotechnology, a group comprising scientists at the University of North Carolina, Duke University Medical Center and Memorial Sloan-Kettering Cancer in the US, and Xuzhou Medical University in China, outline how antigen-capturing nanoparticles (AC-NPs) can enhance the abscopal effect by attaching themselves to tumour-derived protein antigens (TDPAs). The increase in immune response is thought to result from the size of the nanoparticles, which make the TDPAs much more attractive to the immune system. When TDPAs are bound to nanoparticles, the body mistakes them for something foreign such a virus, and responds more aggressively.
The researchers
Starting with nanoparticles made from PGLA, a biocompatible and biodegradable polymer, the researchers prepared several formulations of AC-NPs by surface modification. Different coatings were attached to the AC-NPs through a number of mechanisms, and the group found that the surface chemistry determined the diversity and composition of the proteins captured.
The attachment of TDPAs to AC-NPs was shown to translate to a more robust activation of T-lymphocytes (T-cells), which play a central role in cell immunity. This increased therapeutic effect led to improved survival when tested in mice. The scientists found that 20% of the mice had a complete response rate when treated with the nanoparticles alongside radiation therapy, compared to none of those mice that received radiation therapy alone. Additionally, when the nanoparticle-treated mice were re-injected with cancerous cells three months after treatment, the mice rejected the cells, demonstrating that the treatment strategy outlined induces a durable response, increasing immunity to the tumours long-term.
Traditional methods of immunotherapy focus on administering one or several chosen antigens. The researchers believe that the limited success of this approach could be due to its failure to take into account diversity in tumour cells. The novel method outlined here is more promising as the immune system is exposed to a wide variety of TDPAs in a patient-specific manner. This offers opportunities for the future in precise and personalized medicines when treating patients suffering from extensive cancers.
