ΦΥΣΙΚΗ Β ΛΥΚΕΙΟΥ ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΥ ΘΕΤΙΚΩΝ ΣΠΟΥΔΩΝ "ΚΑΤΑΣΤΑΤΙΚΗ ΕΞΙΣΩΣΗ ΤΩΝ ΙΔΑΝΙΚΩΝ ΑΕΡΙΩΝ"

ΦΥΣΙΚΗ Β ΛΥΚΕΙΟΥ ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΥ ΘΕΤΙΚΩΝ ΣΠΟΥΔΩΝ "ΚΑΤΑΣΤΑΤΙΚΗ ΕΞΙΣΩΣΗ ΤΩΝ ΙΔΑΝΙΚΩΝ ΑΕΡΙΩΝ"

ΦΥΣΙΚΗ Β ΛΥΚΕΙΟΥ ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΥ ΘΕΤΙΚΩΝ ΣΠΟΥΔΩΝ "ΟΙ ΝΟΜΟΙ ΤΩΝ ΑΕΡΙΩΝ ΚΑΙ Η ΚΥΚΛΙΚΗ ΜΕΤΑΒΟΛΗ"

ΦΥΣΙΚΗ Β ΛΥΚΕΙΟΥ ΠΡΟΣΑΝΑΤΟΛΙΣΜΟΥ ΘΕΤΙΚΩΝ ΣΠΟΥΔΩΝ "ΟΙ ΝΟΜΟΙ ΤΩΝ ΑΕΡΙΩΝ ΚΑΙ Η ΚΥΚΛΙΚΗ ΜΕΤΑΒΟΛΗ"

Raindrop formation in turbulent clouds is observed at long last

22 Nov 2018

Chance of showers: physicists have confirmed the role of turbulence in the creation of raindrops. (Courtesy: iStock/clickhere)

An aeroplane-mounted 3D imaging system has been used to show that turbulence causes water droplets in clouds to cluster together. The long-predicted effect has been confirmed by scientists in the US and Germany who found that droplets group together in clouds in ways that would not be expected if they were randomly distributed. The clustering may have an impact on rainfall, particularly in highly turbulent clouds, but the researchers say more data is needed to confirm this.

Scientists believe that turbulent flows within clouds help droplets cross the size-gap: the turbulent flows cause the mid-size droplets to cluster together, increasing the likelihood of them colliding and merging. “The prevailing theory is that naturally turbulent air motion within the cloud induces cloud particles to have some tendency to cluster,” explains Michael Larsen, a physicist at the College of Charleston in the US.Rain falls when gaseous water vapour in clouds condenses, forming tiny water droplets about 15 µm in diameter that must grow to about 100 µm before they fall as rain. Once the droplets reach around 40 µm in diameter they start to move down through the cloud and collide and merge with other droplets, increasing in size.

Climate impacts will seldom strike singly

22 Nov 2018

Namibia today: before long normally dry places will face drought, heatwave and wildfire. Image by Parsing Eye on Unsplash

By 2100, climate impacts will be felt by everyone and most people will experience at least three simultaneous hazards, inexorably made more hazardous by the build-up of greenhouse gases in the atmosphere.

And they could be the lucky ones: some people could be menaced by six different kinds of warming-related hazard simultaneously.

Camilo Mora of the University of Hawaii at Manoa and 22 colleagues report in Nature Climate Change that they read systematically through 3,280 peer-reviewed papers on the subject of climate change, and compiled a matrix of 467 ways in which 10 major climate hazards – floods, droughts, heat waves, fires and so on – and six aspects of human dependency (health, food, water, etc.) could affect humanity.

They did, they say, identify some positive or neutral effects, but the overwhelming majority of climate impacts would create problems for human communities and their economies.

Human bone growth is a thermodynamic process, reveals 3D printing study

22 Nov 2018

Crystal clear: transmission electron microscope image showing a blob of amorphous calcium phosphate that is beginning to crystallize at the bottom left. (Courtesy: Antiope Lotsari/Chalmers University of Technology)

Important insights into how human bones grow and crystallize on an atomic scale have been made by Martin Andersson and colleagues at Sweden’s Chalmers University of Technology. Inspired by their use of 3D printing to try to mimic bone structures, the team determined that bone development is a thermodynamic process, independent of other biological systems within the body. Their discovery could soon be used to develop treatments for bone-related diseases, and could also aid developments of more advanced prosthetic implants.

In our bones, new growth is initiated when spherical, disordered blobs of calcium phosphate are sent out from specialized cells to occupy the spaces in between strings of newly-formed collagen. When in place, these spheres transform from amorphous blobs into an orderly, crystalline substance known as apatite (see figure), which gives bone its unique mechanical properties. Exactly how this process plays out on a molecular scale had not been well understood.

Know your boundaries to progress materials science

22 Nov 2018 Anna Demming

A model guide: a technical note in Journal of Physics: Energy provides a guide for researchers to apply the latest tools for modelling energy materials and processes. Credit: Materials Design Group at Imperial College London

“We often focus on the bulk properties of materials for energy applications, such as light absorption for solar cells and ion diffusion rates for batteries, but the reality is that interfaces are critical,” says Aron Walsh, Professor of Materials at Imperial College London in the UK. His comments reflect a trend in energy materials research that is becoming increasingly focused at the boundaries, where one material ends and another begins.

According to Walsh the wealth of useful innovations for optimizing energy materials stemming from interface studies owes more to what is not known about these systems than what is. Identifying unexpected physical behaviour at the junction between compounds can provide insights into what might enhance or restrict the performance of a device.

Cosmic expansion rate remains a mystery despite new measurement

21 Nov 2018

Galaxy far away: an image taken by the Dark Energy Camera. (Courtesy: Fermilab)

A new value for the Hubble constant – the expansion rate of the universe — has been calculated by an international group of astrophysicists. The team used primordial distance scales to study more than 200 supernovae observed by telescopes in Chile and Australia. The new result agrees well with previous values of the constant obtained using a specific model of cosmic expansion, while disagreeing with more direct observations from the nearby universe – so exacerbating a long-running disagreement between cosmologists and astronomers.

The Hubble constant is calculated by looking at distant celestial objects and determining how fast they are moving away from Earth. A plot of the speeds of the objects versus their distance from Earth falls on a straight line, the slope of which is the Hubble constant.

100% renewables? No problems

21 Nov 2018 Dave Elliott

(Courtesy: Shutterstock/FotoIdee)

Australian academics Mark Diesendorf and Ben Elliston have challenged the views of fellow Australian academics Brook and Bradshaw and Heard et al., who criticized studies that claim it will be possible to supply 100% of global power (renewable electricity or “RElec”) or even all global energy needs from renewables. Instead, as I noted in my last post, Diesendorf and Elliston present a strong case for the alternative view — 100% is possible.

It’s hard-hitting stuff, with Diesendorf and Elliston also taking side-swipes at Trainer for dated data and challenging Smil’s view that the transition will be a slow process. They point to the possibility of mass production of low-cost renewable systems that are very different and faster to install than what went before. “Regions with insufficient local RE [renewable energy] resources will in future be able to import RE via transmission line and/or tanker carrying renewable fuels,” they add. A brave new green energy world, somewhat different from the brave new nuclear world that Brook and Bradshaw envisage and not totally incompatible with the “conserver society” that Trainer looks to.

Gender equality – how does medical physics shape up?

21 Nov 2018 Tami Freeman

How does the medical physics profession perform when it comes to gender equality? (Courtesy: iStock/grifare)

Physics has one of the largest gender gaps among all science, technology, engineering and mathematics (STEM) subjects; but within medical physics, the percentage of women is around 40%. So what is medical physics getting right, where could it improve further, and how could these factors be exploited to improve gender equality throughout physics as a whole?

These questions were the subject of a recent event organized by the Institute of Physics’ Medical Physics Group and Women in Physics Group.

Quantum adiabatic and quantum circuit algorithms are equivalent, say physicists

20 Nov 2018 Hamish Johnston

Exactly equivalent: Quantum adiabatic and quantum circuit algorithms should take the same time to run (Courtesy: iStock/Devrimb)

Practical quantum computers could be one step closer thanks to physicists in China, who have published a rigorous proof that “quantum circuit” algorithms can be transformed into algorithms that can be executed at the same running time on adiabatic quantum computers .

A quantum circuit algorithm runs on a quantum computer made up of a sequence of quantum-logic gates. This set-up resembles a conventional computer, which runs algorithms on sequences of classical logic gates. However, fundamental differences between quantum and classical computation mean that certain problems can be solved much more quickly on a quantum computer.

A big challenge for researchers trying to create practical quantum computers is decoherence – the degradation of quantum information caused by interactions with the surrounding environment. This makes it very hard to maintain the quantum nature of information as it is being processed, which is why only very basic quantum computations have been possible so far.

A WAVE DISCOVERY

A WAVE DISCOVERY

29 Oct 2018

Taken from the October 2018 issue of Physics World, which celebrates 30 years of the world’s best physics magazine. Members of the Institute of Physics can enjoy the full issue via the Physics World app.

James Hough outlines the last 30 years of gravitational-wave astronomy, from building prototype detectors to making a revolutionary discovery

“Gravitational waves, yet to be convincingly detected, promise to open a new astronomical window.” Those are the words I wrote for Physics World in early 1989. Today, with six detections of gravitational waves confirmed over the past three years, I am delighted to see how many of the predictions I made in that article have come to fruition.

Indirect emissions of supply chains skyrocket

20 Nov 2018

(Courtesy: iStock/ermingut)

Besides electricity consumption, the indirect emissions of supply chains are the fastest-rising area of emissions worldwide, according to researchers in the US and Norway.

In the two decades to 2015, such indirect emissions rose by over 80% – nearly double the rise of direct emissions. The non-electrical indirect emissions of the industry sector alone now stand at 32 billion tonnes of carbon dioxide, the study shows.

Edgar Hertwich at Yale University, US, believes his and colleagues’ study exposes “the potential agency different sectors have over supply chain emissions”. The message is to “look at your purchases in addition to your direct energy consumption, to identify opportunities for emission reductions”.

Dust collisions on Earth could shed light on planet formation

17 Nov 2018 Hamish Johnston

On target: time sequence of a glass projectile striking a dust target. (Courtesy: Hiroaki Katsuragi and Jürgen Blum/Phys. Rev. Lett.)

By dropping tiny projectiles into clumps of dust, physicists in Germany and Japan may have uncovered important clues about how dust particles stick together in space to form planets. The work has been carried out by Hiroaki Katsuragi at Nagoya University and Jürgen Blum at the Technical University of Braunschweig, who looked at how a single particle collides with clumps of soft porous dust and also with clumps of hard beads.

The experiments were carried out by dropping a projectile from inside the top of a 1.5 m tall tower held in a vacuum to simulate conditions in space. The projectile, which accelerates under gravity, travels towards a target held in a cup at the bottom of the drop tower. Just before it reaches the target, however, the cup is rapidly removed so that the target material also begins to freefall. But because the projectile is falling much faster than the target, it quickly catches up and collides with the target.

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΔΙΑΣΤΟΛΗ ΤΟΥ ΝΕΡΟΥ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΔΙΑΣΤΟΛΗ ΤΟΥ ΝΕΡΟΥ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ " ΔΙΑΣΤΟΛΗ ΤΩΝ ΥΓΡΩΝ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ " ΔΙΑΣΤΟΛΗ ΤΩΝ ΥΓΡΩΝ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΓΡΑΜΜΙΚΗ ΔΙΑΣΤΟΛΗ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΓΡΑΜΜΙΚΗ ΔΙΑΣΤΟΛΗ"

Kerker scattering locates particles with sub-atomic precision

16 Nov 2018 Belle Dumé

Locating a nanoparticle

Being able to precisely locate individual nanoparticles in a device is no easy task but it is important for many research fields, including nanometrology, medicine and biophysics. A team of scientists in Germany has now taken an important step forward towards this goal with an all-optical technique that works thanks to an effect known as Kerker scattering. The technique can locate nano-objects with a spatial resolution of less than one angstrom, which is the size of an atom.

The Kerker effect is named after Milton Kerker who used light scattering to study aerosols and colloids. Kerker showed that when ordinary, plane-polarized, light scatters from a nanoparticle (that is much smaller than the wavelength of light), highly asymmetric patterns are produced. The effect occurs in particles that respond in a similar way to both magnetic and electric fields and comes about thanks to interactions of the electric and magnetic components of the light beam and the particle.

Kilogram finally redefined as world’s metrologists agree to new formulation for SI units

16 Nov 2018 Michael Banks

Weighty matters: a platinum-iridium kilogram belonging to the US National Institute of standards and Technology. (Courtesy: J.L. Lee/NIST)

Metrologists and policy-makers from 60 countries around the world have unanimously agreed to change the definition of four units of measurement. At a meeting today at the General Conference on Weights and Measures (CGPM) in Versailles, France, delegates voted to redefine the International System of Units (SI), changing the world’s definition of the kilogram, the ampere, the kelvin and the mole. The changes will now come into force on 20 May 2019.

There are seven base units of the SI: the second, metre, kilogram, ampere, kelvin, mole and candela. Some have long been based on physical constants. The metre, for example, has been defined since 1983 as the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 seconds. But the four that metrologists today agreed to redefine were previously based on something – i.e. an object, experiment or phenomenon — meaning that its value is not universal.

Quantum tech investments and visiting the Francis Crick Institute

15 Nov 2018 James Dacey

In this episode of Physics World Weekly, Physics World’s general physics editor Hamish Johnston is joined by colleagues to discuss quantum technologies, biomedical research plus the week’s research highlights.

First up in the podcast, industry Editor Margaret Harris speaks about the launch of the €1bn European Quantum Flagship, which she attended at the Hofburg palace in Vienna, Austria. Harris was also at a showcase event in London about the UK’s national quantum technology initiative, which has been allocated extra funding in the government’s recent budget.

The value of sorting graphene flakes from fakes

15 Nov 2018 Anna Demming

Researchers from the NUS Centre for Advanced 2D Materials examining the quality of graphene samples. Credit: National University of Singapore

While theories abound to explain the lag between investment and commercial return in graphene research, a supply chain flooded with samples of graphite masquerading as graphene certainly won’t help. Yet when researchers at the National University of Singapore systematically analysed samples from over 60 suppliers based in America, Asia and Europe, they found most contained less 10% of what the International Standardization Organization defines as graphene, with just one sample containing more than 40% high-quality graphene, as reported in Advanced Materials.

“It is alarming to uncover that producers are labelling black powders as graphene and selling them for top dollar, while in reality, they contain mostly cheap graphite,” says Antonio Castro Neto, Director of the NUS Centre for Advanced 2D Materials, who led the study. “There is a strong need to set up stringent standards for graphene characterization and production to create a healthy and reliable graphene market worldwide.”

Are our water vapour emissions warming the climate?

15 Nov 2018

(Courtesy: USDA)

Plain old H2O: the most abundant and powerful greenhouse gas in the Earth’s atmosphere. Water vapour accounts for around half the present-day greenhouse effect and without it our planet would probably be frozen and lifeless. But should we worry about adding more, given that temperatures are rising? A new study reveals that as long as our water vapour emissions remain close to Earth’s surface, there’s no need to fret.

Most water vapour ends up in the atmosphere naturally, via evaporation from the oceans, but human activities such as irrigation, power plant cooling and flying contribute too. Anthropogenic emissions of water vapour are small compared to ocean evaporation; they’re generally assumed not to be a significant climate forcing agent. Anthropogenic water vapour emissions do, however, make up a sizeable portion of our greenhouse gas emissions. Could they be responsible for more climate change than we thought?

Computing memories

15 Nov 2018 Margaret Harris

Taken from the November 2018 issue of Physics World. Members of the Institute of Physics can enjoy the full issue via the Physics World app.

Margaret Harris reviews The Cryotron Files: the Strange Death of a Pioneering Cold War Computer Scientist by Iain Dey and Douglas Buck

Full of promise: Dudley A Buck developed the cryotron while working at the Massachusetts Institute of Technology. (Courtesy: Peter J Carroll/AP/Shutterstock)

Most children grow up hearing stories about their ancestors. For Douglas Buck, the stories were about his father Dudley – a Cold War-era scientist, computing pioneer and occasional spy who, according to family lore, might have won a Nobel prize if he hadn’t died suddenly aged just 32. Now, nearly 60 years later, Buck has teamed up with a British business journalist, Iain Dey, to write an account of his father’s life. The result is The Cryotron Files – a fascinating tale of military–industrial-complex skulduggery, which, alas, also demonstrates how hard it is to write objectively about members of one’s own family.

The first and most innocuous example of the problem appears in the book’s early chapters. Here, the young Dudley Buck comes across as an all-American, gee-whiz type straight out of a 20th-century Boys’ Own Adventure magazine. His childhood friends, several of whom were interviewed for the book, describe him as inquisitive and hard-working, with a gift for electronics and a fondness for pranks of the jolly, impish, boys-will-be-boys variety. The fact that a few of his pranks were a trifle sadistic (an electrified urinal, anyone?) goes unremarked. In the #MeToo era, it is also disconcerting to read that, as a university student, Buck essentially wiretapped a sorority house for the purpose of seducing its residents (such japes!). But ignore that. The important thing as far as The Cryotron Files is concerned is that Buck was an original thinker who caught the eye of the American military while he was still in high school and was funnelled towards computing during a stint as a Navy cadet.

Robotic system targets brain tumours with high-intensity ultrasound

15 Nov 2018 Tami Freeman

Gregory Fischer (left) and Christopher Nycz examine a prototype of an MRI-compatible robotic system for treating brain tumours. (Courtesy: Worcester Polytechnic Institute)

An academic–industry partnership has received a five-year, $3.5 million award from the National Institutes of Health to develop a robotic technology for minimally invasive treatment of metastatic brain tumours. The team is creating a robotic system that delivers a needle-based probe into the brain to destroy tumours with high-intensity therapeutic ultrasound. The robot is designed to operate within an MRI scanner to enable real-time treatment guidance.

The researchers, led by principal investigators Gregory Fischer from Worcester Polytechnic Institute (WPI) and Julie Pilitsis from Albany Medical College, are working closely with two corporate partners. Acoustic MedSystems will design and build the ultrasound probe and provide visualization and control software, while GE Global Research will implement thermal imaging to monitor tumour ablation in real time and help integrate the robot with a clinical MRI scanner.

“Thermal ablation has shown potential as an effective treatment, but the available devices for using this therapy have severe limitations and can’t treat all shapes, sizes and locations of tumours,” explains Pilitsis, a professor of neurosurgery. “Our hope is that this integrated robotic system will one day be able to provide all brain tumour patients with a safer, more accurate treatment.”

Controlling magnetism using a proton pump

14 Nov 2018 Belle Dumé

Magneto-ionic switching

Researchers at the Massachusetts Institute of Technology say they have discovered a new way to electrically control magnetism using a gate voltage that could be applied to a wide variety of magnetic materials, including oxides and metals. The “magneto-ionic” technique, which involves reversibly inserting and removing protons into the material structures, could help advance the field of spintronics (a technology that exploits the spin of the electron rather than its electrical charge) for the post CMOS-world.

Complementary metal-oxide semiconductor (CMOS) technologies are reaching the end of their roadmap and scientists are looking for alternatives to silicon microchips. Spintronics devices show promise in this context because they retain their magnetic state even when the power supply is switched off, something that it is not true for silicon memory chips. They also require much less power to operate and generate far less heat than their silicon counterparts.

One of the most important phenomena being studied in spintronics today is spin-orbit coupling, explains MIT Materials

Cracks interact with sound in silicon to create patterns resembling Kelvin wakes

14 Nov 2018 Hamish Johnston

Kelvin wakes: patterns seen in cleaved silicon resemble the wakes made by these boats. (Courtesy: Arpingstone)

Unwanted roughness on cleaved silicon surfaces is created by an acoustic effect that is similar to the “Kelvin wake” that forms behind a slow-moving boat. That is the conclusion of researchers in France, who have studied how a propagating crack in silicon interacts with the sound it emits. The discovery could lead to new ways of controlling the fracture process in materials.

Physicists already know that crack propagation is affected by sound because several studies have shown that the progression of a crack through a material can be altered by the application of sound waves. It is also well-known that cracks produce sound as they move through materials, but exactly how a propagating crack is affected by the sound it emits is not well understood.

new views on units

new views on units

14 Nov 2018 Robert P Crease

Taken from the November 2018 issue of Physics World. Members of the Institute of Physics can enjoy the full issue via the Physics World app.

Robert P Crease explains why philosophers are fascinated by the redefinition of SI units

For scientists, the story of metrology has a simple plot: to ensure that standards keep improving. The pound of Imperial France made way for the platinum Kilogram of the Archives in 1799. In 1889 it in turn was traded for the platinum–iridium International Prototype Kilogram (IPK), which this month is on the verge of being replaced by a definition involving Planck’s constant. Each step has made the kilogram standard more secure, serviceable and stable, allowing more precise and definitive research. The latest development, to tether the definitions of all SI base standards to natural constants, seems to bring a triumphant end to this quest.

Philosophers like me look at such stories with different interests. If scientists study the world, philosophers study how scientists study the world. Philosophy, though, is practised in many ways, in what are referred to as the “analytic”, “pragmatic” and “continental” approaches, each of which focuses on different aspects of science (though in practice philosophers may use more than one of these lenses). Not surprisingly, each approach sees different things in the development of scientific standards. There’s more to metrology, it turns out, than simply producing ever-better measuring tools.

MetaboliQs project targets breakthrough in cardiac metabolic MRI

14 Nov 2018

© 

AuntMinnieEurope.com

Two of Europe’s leading research groups in hyperpolarized and cardiovascular MRI — ETH Zurich in Switzerland and the Technical University of Munich in Germany — have joined MetaboliQs, the project funded by the European Union (EU) that is due to continue until the end of 2021.

The project is part of Quantum Flagship, which has received funding from the EU’s Horizon 2020 research and innovation program. The other partners are the Fraunhofer Institute for Applied Solid State Physics (IAF), Bruker BioSpin and NVision Imaging Technologies (all from Germany), Element Six (the UK-based supplier of synthetic diamonds) and the Hebrew University of Jerusalem in Israel.

“This initiative intends to place Europe at the forefront of the second quantum revolution, which is now unfolding worldwide.

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΘΕΡΜΙΚΗ ΣΥΣΤΟΛΗ ΚΑΙ ΔΙΑΣΤΟΛΗ-ΓΡΑΜΜΙΚΗ ΔΙΑΣΤΟΛΗ - ΕΠΙΦΑΝΕΙΑΚΗ ΔΙΑΣΤΟΛΗ ΚΑΙ ΚΥΒΙΚΗ ΔΙΑΣΤΟΛΗ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΘΕΡΜΙΚΗ ΣΥΣΤΟΛΗ ΚΑΙ ΔΙΑΣΤΟΛΗ-ΓΡΑΜΜΙΚΗ ΔΙΑΣΤΟΛΗ - ΕΠΙΦΑΝΕΙΑΚΗ ΔΙΑΣΤΟΛΗ ΚΑΙ ΚΥΒΙΚΗ ΔΙΑΣΤΟΛΗ"

Optical micromirrors reveal the secrets of cell membranes

13 Nov 2018 Sponsored by Mad City Labs

Janice L Robertson with Rahul Chadda (middle), Kacey Mersch (right), and the team's TIRF microscope

Progress in understanding the lipid bilayer – an ingenious two-molecule thick oily barrier that protects all living cells, including our own – has been dramatic over the past 100 years. But there are still puzzles to be solved. In particular, biologists are keen to discover more about the mysterious proteins that exist inside the lipid bilayer. These chains of amino acids assemble into folded structures that change the behaviour of the cell membrane – allowing, for example, the selective passage of salts and sugars in and out of a micro-organism.

In fact, cell membranes are home to a variety of proteins that are essential for life to proceed, including channels, transporters, pumps, and receptors. These forms are relatively well known, but what isn’t understood is how these membrane proteins, which are oily themselves, navigate the oily lipid bilayer to go about their work.

Flood models validated in Africa

13 Nov 2018

Point where the rivers Niger and Benue meet in Lokoja (by Ayobami Macaulay - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=59830510)

Flood models tested in the first collective validation captured between 52 and 97% of flooded areas for two flood events and three areas in Nigeria and Mozambique. This result was “better than expected”, according to the research team.

“These models have shown a level of performance that allows them to be used for large-scale questions, like identifying the regions of highest flood risk globally,” says Mark Bernhofen of the University of Leeds, UK. “The majority of the models performed fairly well.”

In the decade leading up to 2015, floods killed an estimated 157,000 people worldwide, and affected 2.3 billion in total. As climate changes, the number of people exposed to river flooding over the next three decades is likely to rise by over 30%.

Encrypted quantum keys sent a record-breaking 421 km in optical fibre

13 Nov 2018

Key to success: noise reduction has allowed quantum keys to be transmitted 421 km over an optical fibre. (Courtesy: iStock/ktsimage)

Encrypted quantum keys have been sent across a record-breaking 421 km of optical fibre at the fastest data rate ever achieved for long-distance transmission. Alberto Boaron and colleagues at University of Geneva and ID Quantique in Switzerland and Corning in the US achieved this feat by modifying the detectors used for quantum key distribution (QKD) to minimize noise. Their experiment represents a significant advance in the secure exchange of quantum information.

QKD uses the laws of quantum mechanics to ensure that an eavesdropper cannot intercept a cryptography key without alerting the sender and recipient.

MRI-guided cryoablation safely freezes tumours in the spine

13 Nov 2018

The AMIGO operating suite (viewed through the PET scanner) contains a PET/CT, a 3T MRI system and a fluoroscopy arm. (Courtesy: Brigham and Women's Hospital)

Treatment of epidural tumours located in the spinal canal can be highly challenging, due to the risk of causing irreversible damage. To address this challenge, a medical team at Brigham and Women’s Hospital and Dana Farber Cancer Institute have performed a study showing that MRI-guided cryoablation is feasible for treating such epidural tumours. After cryoablation, both patients in the study experienced successful decompression of the tumour away from the spinal cord, regrowth of previously eroded bone around the spinal canal, and reduction or elimination of the risk of becoming paralysed by the cancer (Am. J. Roentgenol. 10.2214/AJR.18.19951).

When a tumour compresses the spinal cord, previous options treatment included spinal decompression, a surgical procedure to relieve pressure, spinal decompression and radiotherapy, stereotactic radiosurgery, or laser interstitial thermal therapy. Each of these treatments, however, is associated with serious risks. Some patients are unsuitable candidates for surgery, and some who undergo it may not recover rapidly, delaying radiotherapy. Radiation dose delivery may be limited by the tumour’s proximity to the spinal cord, therefore reducing the effectiveness of radiotherapy. And ablative techniques such as laser interstitial thermal therapy may cause permanent neural burn injury.

Live Barcelona event shows hybrid imaging’s vast potential

12 Nov 2018

© AuntMinnieEurope.com

PET/MRI is set to shake up tumour biology imaging and is already proving to be a useful algorithm development tool in machine learning, delegates were told at the Conference on Hybrid Imaging Live (CHILI), held in Barcelona, Spain, on 26 October.

Speaking at the conference, Thomas Beyer, president of the European Society for Hybrid, Molecular and Translation Imaging (ESHIMT), highlighted the advantages of PET/MRI in the medical field and pointed to where its future shone brightest. He underlined his opinion that PET/MRI was less of a modality in clinical routine and more of a noninvasive tumour phenotyping machine.

“The clinical utility of PET/MR is challenged by PET/CT, which has excelled in oncology for whole-body staging. PET/MR took a long time and a lot of effort to develop but in oncology yields no superior diagnostic benefits to PET/CT, and its exams are lengthier,” Beyer told AuntMinnieEurope.com ahead of the event.PET/CT has excelled in oncology for whole-body staging. (Courtesy: Thomas Beyer)

“Instead, PET/MR’s strengths lie in its ‘fifty shades of grey’ soft-tissue contrast, meaning that it can be used locally and regionally for better tumour phenotyping, local staging, and to assay tissue density biomarkers. In addition, the adoption of MR navigators can help compensate for involuntary patient motion, thus, improving the quality and accuracy of the adjoined PET information,” he added.

Beyer’s talk focused on the following four main points:

PET/MRI is a technical revolution that has led to medical evolution.

The benefit over standalone PET is in the conscious choice of CT and MR protocols and in the adoption of CT- and MR-driven correction schemes of PET.

PET/MRI is an expensive deblurring machine for PET data.

PET/MRI is a promising tumour-phenotyping tool.

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΘΕΡΜΙΔΟΜΕΤΡΙΑ ΚΑΙ ΘΕΡΜΙΔΟΜΕΤΡΑ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΘΕΡΜΙΔΟΜΕΤΡΙΑ ΚΑΙ ΘΕΡΜΙΔΟΜΕΤΡΑ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΤΥΠΟΙ ΘΕΡΜΙΔΟΜΕΤΡΩΝ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "ΤΥΠΟΙ ΘΕΡΜΙΔΟΜΕΤΡΩΝ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "Ο ΝΟΜΟΣ ΤΗΣ ΘΕΡΙΔΟΜΕΤΡΙΑΣ"

ΦΥΣΙΚΗ Β ΓΥΜΝΑΣΙΟΥ "Ο ΝΟΜΟΣ ΤΗΣ ΘΕΡΙΔΟΜΕΤΡΙΑΣ"

Ocean warming may be faster than thought

10 Nov 2018

Warming seas melt Arctic ice – and the warmth is rising. Image: By NASA, via Wikimedia Commons

The seas are getting hotter – and researchers have thought again about just how much faster ocean warming is happening. They believe that in the last 25 years the oceans have absorbed at least 60% more heat than previous global estimates by the UN’s Intergovernmental Panel on Climate Change (IPCC) had considered.

And they calculate this heat as the equivalent to 150 times the annual human electricity generation in any one year.

“Imagine if the ocean was only 30 feet (10m) deep,” said Laure Resplandy, a researcher at the Princeton Environment Institute in the US. “Our data show that it would have warmed by 6.5°C every decade since 1991. In comparison, the estimate of the last IPCC assessment report would correspond to a warming of only 4°C every decade.”

Benchtop cosmology exploits solid-state systems

10 Nov 2018 Anna Demming

Benchtop cosmology: Solid state research reveals analogues of cosmological phenomena. Credit: iStock angelinast

The kind of dynamos thought to be behind the huge magnetic fields found in stars and galaxies, may also exist in Weyl semimetals, materials more common to a solid-state laboratory. Why does this matter? As Belle Dumé points out, the presence of dynamos capable of generating and sustaining a magnetic field in readily available metal systems could provide a handy lab-sized model for what researchers Victor Galitski, Mehdi Kargarian, and Sergey Syzranov describe as the “beautiful astrophysical phenomenon, first proposed by Larmor in 1919.”

Wily Weyls

While a Weyl metal may be found in more manageable proportions than a star or a galaxy, these materials are not without their own brand of exoticism. Electronic excitations in these crystals take the form of charge carrying Weyl fermions – massless chiral quasiparticles.

The discovery of Weyl points is not only the smoking gun to a scientific mystery

Hermann Weyl predicted their existence in his solution of the Dirac equation, and they have contributed to some of the keystones in fundamental physics – quantum field theory and the standard model. Crucial but elusive, Weyl fermions were not observed for more than 85 years, when two separate reports of them appeared. In 2015 M. Zahid Hasan at Princeton University in the US and colleagues in the US, China, Taiwan and Singapore reported experimental observations of a Weyl metal in TaAs single crystals. Elswhere Marin Soljačić and colleagues at Massachusetts Institute of Technology in the US and Zhejiang University in China spotted evidence for Weyl fermions in a a “double-gyroid” photonic crystal. “The discovery of Weyl points is not only the smoking gun to a scientific mystery,” said Soljačić, adding, “it paves the way to absolutely new photonic phenomena and applications.”

Just a few months later researchers at ETH Zurich in Switzerland, Princeton University in the US and the Chinese Academy of Sciences extended the family of Weyl semimetals with their predictions of a new type of Weyl semimetals. When solving the Dirac equations Weyl had conscientiously maintained Lorentz symmetry, an important invariance principle for particle physicists. For condensed matter researchers Lorentz symmetry is not such an issue and by generalizing the Dirac equation Alexey A. Soluyanov and colleagues revealed the type II Weyl semimetal.

More recently studies of the type-II Weyl semimetal phase of MoTe2 solicited yet more interest. Jian-Hao Chen and colleagues at Peking University, Collaborative Innovation Center of Quantum Matter and Tsinghua University in China observed resistivity jumps that indicated the Barkhausen effect. More than just a useful way of characterizing ferroelectric and ferromagnetic materials, the Barkhausen effect is a stochastic process that shows universality – “the observation that a wide range of macroscopic systems behave in much the same way, even if the systems have different microscopic components” as Hamish Johnston explains in his coverage of no less than three Nature reports of universal behaviour in systems far from equilibrium.READ MORE

Astrophysical dynamo could appear in Weyl metal

Weyl you’re not alone

Given their recent track record, perhaps the possibility of gaining insights from Weyl semimetals as to the origins of magnetism in vast astrophysical objects is less of a surprise. However they are not the only systems to have provided convenient solid-state analogues for probing cosmological phenomena. In July Dumé also reported theoretical calculations by a team in Canada, the US, UK and Israel revealing a quantum hologram in a graphene flake that faithfully reproduces some of the signature characteristics of a black hole.

“In recent years, physicists have gleaned important new insights into these questions through the study of the SYK [Sachdev-Ye-Kitaev] model,” explained lead researcher Marcel Franz of the University of British Columbia in Canada. “This model is an illustration of a type of ‘holographic duality’ in which a lower-dimensional system can be represented by a higher dimensional one. In our calculations, the former is N graphene electrons in (0+1) dimensions and the latter the dilation gravity of a black hole in (1+1) dimensional anti-de Sitter (AdS2) space.”

The graphene flake must meet certain requirements: it must have an irregular boundary because of the random structure of electron-electron interactions in the SYK model they use, and it is subjected to an intense magnetic field. Nonetheless it is straightforward to fabricate and far easier to handle than a black hole.

Anna Demming is materials editor of Physics World