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The theory of kinetic effects on resistive wall mode stability in tokamaks

Tokamak fusion plasmas benefit from high pressures but are then susceptible to modes of instability. These magnetohydrodynamic (MHD) modes are macroscopic distortions of the plasma, but certain collective motions of individual particles can provide stabilizing effects opposing them. The presence of a resistive wall slows the mode growth, converting a kink to a resistive wall mode (RWM). A kinetic MHD model includes Maxwell’s equations, ideal MHD constraints, and kinetic effects included through the pressure tensor, calculated with the perturbed drift-kinetic distribution function of the particles. The kinetic stabilizing effects on the RWM arise through resonances between the plasma rotation and particle drift motions: precession, bounce, and transit. A match between particle motions and the mode allows efficient transfer of energy that would otherwise drive the growth of the mode, thus damping the growth. The first approach to calculating RWM stability is to write a set of equations for the complex mode frequency in terms of known quantities and then to solve the system. The “energy principle” approach, which has the advantage of clarity in distinguishing the various stabilizing and destabilizing effects, is to change the force balance equation into an equation in terms of changes of kinetic and potential energies, and then to write a dispersion relation for the mode frequency in terms of those quantities. These methods have been used in various benchmarked codes to calculate kinetic effects on RWM stability. The theory has illuminated the important roles of plasma rotation, energetic particles, and collisions in RWM stability.

Visualizing multiple sclerosis with a new MRI procedure

Multiple sclerosis (MS) is a neurological disease that usually leads to permanent disabilities. It affects about 2.9 million people worldwide, and about 15,000 in Switzerland alone. One key feature of the disease is that it causes the patient’s own immune system to attack and destroy the myelin sheaths in the central nervous system.

These protective sheaths insulate the nerve fibers, much like the plastic coating around a copper wire. Myelin sheaths ensure that electrical impulses travel quickly and efficiently from nerve cell to nerve cell. If they are damaged or become thinner, this can lead to irreversible visual, speech and coordination disorders.

So far, however, it hasn’t been possible to visualize the myelin sheaths well enough to reliably diagnose and treat MS. Now researchers at ETH Zurich, led by Markus Weiger and Emily Baadsvik from the Institute for Biomedical Engineering, have developed a new magnetic resonance imaging (MRI) procedure that maps the condition of the myelin sheaths more accurately than was previously possible. The researchers successfully tested the procedure on healthy people for the first time.

Immunomodulatory Therapy Outperforms Steroids in Multifocal Choroiditis Patients with Choroidal Neovascularization

Multifocal Choroiditis (MFC) patients with inflammatory choroidal neovascularization (iCNV) face challenges in visual and treatment outcomes. A recently published study delves into the effectiveness of Immunomodulatory Therapy (IMT) compared to an approach using steroids as needed, shedding light on visual and treatment outcomes. This study was published in the American Journal of Ophthalmology by Matteo Airaldi and colleagues.

Low-frequency Ultrasound can Improve Oxygen Saturation in blood

Research conducted by a team of scientists from Kaunas universities, Lithuania, revealed that low-frequency ultrasound influences blood parameters. The findings suggest that ultrasound’s effect on haemoglobin can improve oxygen’s transfer from the lungs to bodily tissues.

The research was undertaken on 300 blood samples collected from 42 pulmonary patients. The samples were exposed to six different low-frequency ultrasound modes at the Institute of Mechatronics of Kaunas University of Technology (KTU).

The changes in 20 blood parameters were registered using the blood analysing equipment at the Lithuanian University of Health Sciences (LSMU) laboratories. For the prediction of ultrasound exposure, artificial intelligence, i.e. analysis of variance (ANOVA), non-parametric Kruskal-Wallis method and machine learning algorithms were applied. The calculations were made at the KTU Artificial Intelligence Centre.

Salad in Space? New Research says it’s Not a Healthy Choice

It’s been more than three years since the National Aeronautics and Space Administration made space-grown lettuce an item on the menu for astronauts aboard the International Space Station. Alongside their space diet staples of flour tortillas and powdered coffee, astronauts can munch on a salad, grown from control chambers aboard the ISS that account for the ideal temperature, amount of water and light that plants need to mature.

But there is a problem. The International Space Station has a lot of pathogenic bacteria and fungi. Many of these disease-causing microbes at the ISS are very aggressive and can easily colonize the tissue of lettuce and other plants. Once people eat lettuce that’s been overrun by E. coli or Salmonella, they can get sick.

With billions of dollars poured into space exploration each year by NASA and private companies like SpaceX, some researchers are concerned that a foodborne illness outbreak aboard the International Space Station could derail a mission.

It’s time to admit that genes are not the blueprint for life

Ball is not alone in calling for a drastic rethink of how scientists discuss biology. There has been a flurry of publications in this vein in the past year, written by me and others2–4. All outline reasons to redefine what genes do. All highlight the physiological processes by which organisms control their genomes. And all argue that agency and purpose are definitive characteristics of life that have been overlooked in conventional, gene-centric views of biology.

This burst of activity represents a frustrated thought that “it is time to become impatient with the old view”, as Ball says. Genetics alone cannot help us to understand and treat many of the diseases that cause the biggest health-care burdens, such as schizophrenia, cardiovascular diseases and cancer. These conditions are physiological at their core, the author points out — despite having genetic components, they are nonetheless caused by cellular processes going awry. Those holistic processes are what we must understand, if we are to find cures.

Ultimately, Ball concludes that “we are at the beginning of a profound rethinking of how life works”. In my view, beginning is the key word here. Scientists must take care not to substitute an old set of dogmas with a new one. It’s time to stop pretending that, give or take a few bits and pieces, we know how life works. Instead, we must let our ideas evolve as more discoveries are made in the coming decades. Sitting in uncertainty, while working to make those discoveries, will be biology’s great task for the twenty-first century.