Lifeboat Foundation

Most folks probably don’t think of satellites as capable of sinking, but according to the European Space Agency they can and do.

Space news site Space. com reported Thursday that ESA scientists had to raise the Swarm constellation satellites, which measure Earth’s magnetic field, because they were sinking in chaotic space weather.

“In the last five, six years, the satellites were sinking about two and a half kilometers [1.5 miles] a year,” Swarm mission managerAnja Stromme, ESA’s told Space.com. “But since December last year, they have been virtually diving. The sink rate between December and April has been 20 kilometers [12 miles] per year.”

Technique probes dopamine concentrations at the subcellular level.

Special relativity famously dictates that no known object can travel faster than the speed of light in a vacuum – making it unlikely that humans will ever send spacecraft to explore beyond our local area of the Milky Way. However, new research by Erik Lentz at the University of Göttingen suggests there could be a way beyond this limit. The only catch is that his scheme requires vast amounts of energy and so may never actually be able to propel a spacecraft (Class. Quant. Grav. 38 075015).

Lentz proposes that conventional energy sources could arrange the structure of space–time in the form of a soliton – a robust singular wave. This soliton would act like a “warp bubble’”, contracting space in front of it and expanding space behind. Unlike objects within it, space–time itself can bend, expand or warp at any speed. A spacecraft contained in a hyperfast bubble could therefore arrive at its destination faster than light would in normal space without breaking any physical laws.

It had been thought that the only way to produce a warp drive was by generating vast amounts of negative energy – perhaps by using some sort of undiscovered exotic matter or by manipulating dark energy. To get around this problem, Lentz constructed an unexplored geometric structure of space–time to derive a new family of solutions to Einstein’s general relativity equations called positive-energy solitons. Though Lentz’s solitons appear to conform to Einstein’s general theory of relativity and remove the need to create negative energy, space agencies will not be building warp drives any time soon, if ever. Part of the reason is that Lentz’s positive-energy warp drive requires a huge amount of energy. According to Lentz, a 100 m radius spacecraft would require the energy equivalent to “hundreds of times the mass of Jupiter”.

Nanotechnologist and co-founder of the Black in Nanotech initiative, Olivia Geneus. (Courtesy: Alexander Harold) Welcome to this Physics World Nanotechnology Briefing, which showcases the breadth of applications of modern nanotechnology.

Olivia Geneus is one of the growing number of scientists who are developing nanotechnologies for medicine. In an interview, the PhD student at the State University of New York at Buffalo explains how she is developing nanoparticles designed to cross the blood–brain barrier in order to image and destroy brain cancer cells. Geneus also talks about Black in Nanotech Week, which she co-founded, and the need to encourage Black children to consider careers in science.

Ed Lester of the UK’s University of Nottingham knows that there are myriad uses for nanoparticles. In 2007 he founded the company Promethean Particles when he realized industrial users were not able to source nanoparticles in the quantities and quality that they required. In an interview, Lester talks about some of the company’s development projects including nanoparticles for aviation, healthcare and energy.

Researchers in Switzerland and Italy have developed a new method for generating currents of spin-polarized electrons without the need for large external magnetic fields. This could enable the development of devices that are compatible with superconducting electronic components, paving the way for the next generation of highly efficient electronics.

Emerging in the 1980s, “spintronics” is dedicated to creating practical devices that exploit electron spin. Semiconductor-based spintronics systems have garnered particular interest because semiconductors can be integrated within modern-day electronics with the aim of improving the efficiency and storage capacity of devices. But to make useful spintronics devices, researchers must control and detect the spin state of electrons with a high level of accuracy.

One way of controlling electron spin current is a “spin valve”, which usually consists of a non-magnetic material sandwiched between ferromagnetic materials. Electrons in one spin state (say up) can propagate through the device, while spin-down electrons are reflected or scattered away. The result is a “spin polarized current” in which all electrons are either spin-up or all spin-down) – at least in principle.

Next big thing Haifei Zhan and colleagues reckon that carbon nanothreads have a future in energy storage. (Courtesy: Queensland University of Technology) Computational and theoretical studies of diamond-like carbon nanothreads suggest that…

Computational and theoretical studies of diamond-like carbon nanothreads suggest that they could provide an alternative to batteries by storing energy in a strained mechanical system. The team behind the research says that nanothread devices could power electronics and help with the shift towards renewable sources of energy.

The traditional go-to device for energy storage is the electrochemical battery, which predates even the widespread use of electricity. Despite centuries of technological progress and near ubiquitous use, batteries remain prone to the same inefficiencies and hazards as any device based on chemical reactions – sluggish reactions in the cold, the danger of explosion in the heat and the risk of toxic chemical leakages.

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A method of optically selecting and sorting nanoparticles according to their quantum mechanical properties has been developed by researchers in Japan. The method could prove a crucial tool for manufacturing nanostructures for quantum sensing, biological imaging and quantum information technology ( Sci. Adv. 7 eabd9551).

Scientists have several ways of manipulating and positioning tiny objects without touching them. Optical tweezers, for example, use a highly focused laser beam to generate optical forces that hold and move objects in the beam’s trajectory. However, such tweezers struggle to grasp nanoparticles because these tiny objects are much smaller than the wavelength of the laser light used.

Now, a team led by Hajime Ishihara of Osaka University and Keiji Sasaki at Hokkaido University has developed a way of using light to sort nanodiamonds. These are tiny pieces of semiconductor with very useful optoelectronic properties that derive from bulk diamond as well as certain defects such as nitrogen-vacancy (NV) centres.

Takao Someya and colleagues at the University of Tokyo have developed the first artificial-skin patch that does not affect the touch sensitivity of the real skin beneath it. The new ultrathin sensor could be used in applications as diverse as prosthetics and human-machine interfaces.

“A wearable sensor for your fingers has to be extremely thin,” explains Tokyo’s Sunghoon Lee. “But this obviously makes it very fragile and susceptible to damage from rubbing or repeated physical actions.” For this reason most e-skins developed to date been relatively thick and bulky.

In contrast, the sensor developed by the Tokyo team is thin and porous and consists of two layers (Science 370 966). The first layer is an insulating mesh-like network comprising polyurethane fibres around 200–400 nm thick. The second layer is a network of lines that makes up the functional electronic part of the device – a parallel-plate capacitor. This is made of gold on a supporting scaffold of polyvinyl alcohol (PVA), a water-soluble polymer often found in contact lenses. Once this layer has been fabricated, the PVA is washed away to leave only the gold support. The finished pressure sensor is around 13 μ m thick.

An electrochemically powered artificial muscle made from twisted carbon nanotubes contracts more when driven faster thanks to a novel conductive polymer coating. Developed by Ray Baughman of the University of Texas at Dallas in the US and an international team, the device overcomes some of the limitations of previous artificial muscles, and could have applications in robotics, smart textiles and heart pumps.

Carbon nanotubes (CNTs) are rolled-up sheets of carbon with walls as thin as a single atom. When twisted together to form a yarn and placed in an electrolyte bath, CNTs expand and contract in response to electrochemical inputs, much like a natural muscle. In a typical set-up, a potential difference between the yarn and an electrode drives ions from the electrolyte into the yarn, causing the muscle to actuate.

While such CNT muscles are highly energy efficient and extremely strong – they can lift loads up to 100,000 times their own weight – they do have limitations. The main one is that they are bipolar, meaning that the direction of their movement switches whenever the potential drops to zero. This reduces the overall stroke of the actuator. Another drawback is that the muscle’s capacitance decreases when the potential is changed quickly, which also causes the stroke to decrease.