An Omega-3 That’s Poison for Tumours (Medicine)

In brief:

  • 3D tumours that disintegrate within a few days thanks to the action of a well-known Omega-3 (DHA, found mainly in fish) – this is the exceptional discovery by University of Louvain (UCLouvain) researchers, published in the prestigious scientific journal Cell Metabolism
  • Hungry for fatty acids, tumour cells in acidosis gorge themselves on DHA but are unable to store it correctly and literally poison themselves. The result? They die.
  • What’s so original about the discovery? The result of a collaboration between bioengineers specialising in nutrition and cancer specialists,it creates new possibilities for fighting cancer

Press kit (images, video): https://drive.google.com/drive/folders/1bKVQ_su9q5UmeAkOa5KMPhO9StZBo33U?usp=sharing

So-called “good fatty acids” are essential for human health and much sought after by those who try to eat healthily. Among the Omega-3 fatty acids, DHA or docosahexaenoic acid is crucial to brain function, vision and the regulation of inflammatory phenomena.

In addition to these virtues, DHA is also associated with a reduction in the incidence of cancer. How it works is the subject of a major discovery by a multidisciplinary team of University of Louvain (UCLouvain) researchers, who have just elucidated the biochemical mechanism that allows DHA and other related fatty acids to slow the development of tumours. This is a major advance that has recently been published in the prestigious journal Cell Metabolism.

Key to the discovery: interdisciplinarity

In 2016, Olivier Feron’s UCLouvain team, which specialises in oncology, discovered that cells in an acidic microenvironment (acidosis) within tumours replace glucose with lipids as an energy source in order to multiply. In collaboration with UCLouvain’s Cyril Corbet, Prof. Feron demonstrated in 2020 that these same cells are the most aggressive and acquire the ability to leave the original tumour to generate metastases. Meanwhile, Yvan Larondelle, a professor in the UCLouvain Faculty of Bioengineering, whose team is developing improved dietary lipid sources, proposed to Prof. Feron that they combine their skills in a research project, led by PhD candidate Emeline Dierge, to evaluate the behaviour of tumour cells in the presence of different fatty acids.

Thanks to the support of the Fondation Louvain, the Belgian Cancer Foundation and the Télévie telethon, the team quickly identified that these acidotic tumour cells responded in diametrically opposite ways depending on the fatty acid they were absorbing. Within a few weeks, the results were both impressive and surprising. “We soon found that certain fatty acids stimulated the tumour cells while others killed them,” the researchers explained. DHA literally poisons them.

A fatal overload

The poison acts on tumour cells via a phenomenon called ferroptosis, a type of cell death linked to the peroxidation of certain fatty acids. The greater the amount of unsaturated fatty acids in the cell, the greater the risk of their oxidation. Normally, in the acidic compartment within tumours, cells store these fatty acids in lipid droplets, a kind of bundle in which fatty acids are protected from oxidation. But in the presence of a large amount of DHA, the tumour cell is overwhelmed and cannot store the DHA, which oxidises and leads to cell death. By using a lipid metabolism inhibitor that prevents the formation of lipid droplets, researchers were able to observe that this phenomenon is further amplified, which confirms the identified mechanism and opens the door to combined treatment possibilities.

For their study, UCLouvain researchers used a 3D tumour cell culture system, called spheroidsIn the presence of DHA, spheroids first grow and then implode. The team also administered a DHA-enriched diet to mice with tumours. The result: tumour development was significantly slowed compared to that in mice on a conventional diet.

This UCLouvain study shows the value of DHA in fighting cancer. “For an adult,” the UCLouvain researchers stated, “it’s recommended to consume at least 250 mg of DHA per day. But studies show that our diet provides on average only 50 to 100 mg per day. This is well below the minimum recommended intake.”


Reference: Emeline Dierge, Elena Debock, Céline Guilbaud, Cyril Corbet, Eric Mignolet, Louise Mignard, Estelle Bastien, Chantal Dessy, Yvan Larondelle, Olivier Feron, Peroxidation of n-3 and n-6 polyunsaturated fatty acids in the acidic tumor environment leads to ferroptosis-mediated anticancer effects, Cell Metabolism, 2021, , ISSN 1550-4131, https://doi.org/10.1016/j.cmet.2021.05.016. (https://www.sciencedirect.com/science/article/pii/S1550413121002333)


Provided by UC Louvain

ALICE Finds That Charm Hadronisation Differs At The LHC (Physics)

New measurements by the ALICE collaboration show that the way charm quarks form hadrons in proton-proton collisions differs significantly from expectations based on electron collider measurements.

Quarks are among the elementary particles of the Standard Model of Particle Physics. Besides up and down quarks, which are the basic building blocks of ordinary matter in the Universe, four other quark flavours exist and are also abundantly produced in collisions at particle accelerators like the CERN Large Hadron Collider. Quarks are not observed in isolation due to a fundamental aspect of the strong interaction, known as colour charge confinement. Confinement requires particles that carry the charge of the strong interaction, called colour, to form states that are colour-neutral. This in turn forces quarks to undergo a process of hadronisation, i.e. to form hadrons, which are composite particles mostly made of a quark and an antiquark (mesons) or of three quarks (baryons). The only exception is the heaviest quark, the top, which decays before it has time to hadronise.

Fraction of charm quarks that hadronise to form each species of mesons (quark-antiquark) or baryons (three quarks). The ALICE measurements in proton-proton collisions show a larger fraction of baryons than those at colliders using electron beams. (Image: CERN)

At particle accelerators, quarks with a large mass, such as the charm quark, are produced only in the initial interactions between the colliding particles. Depending on the type of beam used, these can be electron-positron, electron-proton or proton-proton collisions (as at the LHC). The subsequent hadronisation of charm quarks into mesons (D0, D+, Ds) or baryons (𝛬c, 𝛯c, …) occurs on a long space-time scale and was considered to be universal – that is, independent of the species of the colliding particles – until the recent findings by the ALICE collaboration.

The large data samples collected during Run 2 of the LHC allowed ALICE to count the vast majority of charm quarks produced in the proton-proton collisions by reconstructing the decays of all charm meson species and of the most abundant charm baryons (𝛬c and 𝛯c). The charm quarks were found to form baryons almost 40% of the time, which is four times more often than what was expected based on measurements previously made at colliders with electron beams (e+e and ep in the figure below).

These measurements show that the process of colour-charge confinement and hadron formation is still a poorly understood aspect of the strong interaction. Current theoretical explanations of baryon enhancement include the combination of multiple quarks produced in proton-proton collisions and new mechanisms in the neutralisation of the colour charge. Additional measurements during the next run of the LHC will allow these theories to be scrutinised and further our knowledge of the strong interaction.

Read more in the article by ALICE and on the ALICE website.

Featured image: A view of the ALICE experiment during the installation of new components. (Image: CERN)


Reference: ALICE Collaboration, “Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC”, Arxiv, 2021. https://arxiv.org/abs/2105.06335


Provided by CERN

RECOVERY Trial Finds Aspirin Does Not Improve Survival for Patients Hospitalised With COVID-19 (Medicine)

The RECOVERY trial was established as a randomised clinical trial to test a range of potential treatments for patients hospitalised with COVID-19.

Patients with COVID-19 are at increased risk of blood clots forming in their blood vessels, particularly in the lungs. Between November 2020 and March 2021, the RECOVERY trial included nearly 15,000 patients hospitalised with COVID-19 in an assessment of the effects of aspirin, which is widely used to reduce blood clotting in other diseases.

A total of 7351 patients were randomised to aspirin 150 mg once daily and compared with 7541 patients randomised to usual care alone. There was no evidence that aspirin treatment reduced mortality. There was no significant difference in the primary endpoint of 28-day mortality (17% aspirin vs. 17% usual care; rate ratio 0.96 [95% confidence interval 0.89-1.04]; p=0.35). The results were consistent in all pre-specified subgroups of patients.

Patients allocated to aspirin had a slightly shorter duration of hospitalisation (median 8 days vs. 9 days) and a higher proportion were discharged from hospital alive within 28 days (75% vs. 74%; rate ratio 1·06; 95% CI 1·02-1·10; p=0·0062). Among those not on invasive mechanical ventilation at baseline, there was no significant difference in the proportion who progressed to invasive mechanical ventilation or death (21% vs. 22%; risk ratio 0·96; 95% CI 0·90-1·03; p=0·23). For every 1000 patients treated with aspirin, approximately 6 more patients experienced a major bleeding event and approximately 6 fewer experienced a thromboembolic (clotting) event.

Peter Horby, Professor of Emerging Infectious Diseases in the Nuffield Department of Medicine, University of Oxford, and Joint Chief Investigator for the RECOVERY trial, said, ‘The data show that in patients hospitalised with COVID-19, aspirin was not associated with reductions in 28-day mortality or in the risk of progressing to invasive mechanical ventilation or death. Although aspirin was associated with a small increase in the likelihood of being discharged alive this does not seem to be sufficient to justify its widespread use for patients hospitalised with COVID-19.’

Martin Landray, Professor of Medicine and Epidemiology at the Nuffield Department of Population Health, University of Oxford, and Joint Chief Investigator, said, ‘There has been a strong suggestion that blood clotting may be responsible for deteriorating lung function and death in patients with severe COVID-19. Aspirin is inexpensive and widely used in other diseases to reduce the risk of blood clots so it is disappointing that it did not have a major impact for these patients. This is why large randomised trials are so important – to establish which treatments work and which do not.

‘As ever, we are enormously grateful to the thousands of medical staff and patients who have contributed to the RECOVERY trial, helping to find better treatments for patients all around the world.’

The results of this evaluation of aspirin will be published shortly on medRxiv and have been submitted to a leading peer-reviewed medical journal.

Featured image: First patients enrolled in new clinical trial of possible COVID-19 treatments. Credit: Shutterstock


Provided by University of Oxford

Scientists Make DNA Breakthrough Which Could Identify Why Some People Are More Affected by Covid-19 (Biology)

Scientists from the MRC Weatherall Institute of Molecular Medicine at Oxford University have developed a method that allows them to see, with far greater accuracy, how DNA forms large scale structures within a cell nucleus.

This breakthrough will improve understanding of how differences in DNA sequences can lead to increased risks of developing many different diseases.

The method, which is around 1000 times more accurate than existing techniques, enables scientists to measure the contacts between different pieces of DNA, which are a million base pairs apart to the nearest base pair. This is the equivalent of being able to measure contacts in the DNA fibre that are 1km apart to the nearest millimetre.

Put another way, if each letter of DNA was the size of a brick, each cell would contain roughly the number of bricks in a city (6 billion). Scientists are now able to work out which bricks are next to each other, and see the fine details of how DNA forms structures inside cells, when previously they could only see the DNA “architecture” on the scale of small buildings.

Associate Professor James Davies, the MRC clinician scientist at the Radcliffe Department of Medicine who led the research, explains, ‘This technique has real potential to make a significant impact on human health. For example, at the moment we know that there is a genetic variant which doubles the risk of being severely affected by COVID-19. However, we do not know how the genetic variant makes people more vulnerable to COVID-19.

‘This new breakthrough is helping us to work out how this causes severe COVID and which genes are involved. This is important because we know that drugs which are developed to targets with this type of genetic evidence have double the chance of making it past early stage clinical trials. The team is now using the technique to make the genetic identification and hopes to report on results in coming weeks.’

The technology has been licensed to the University of Oxford spinout company, Nucleome Therapeutics funded by Oxford Sciences Innovation. The company is using these 3D genome approaches to identify new drug targets by working out how variation in the genetic code causes common diseases such as rheumatoid arthritis and multiple sclerosis.

Featured image: How blood cell genetic variations impact on common diseases. Image credit: Shutterstock


Provided by University of Oxford

Green light for European Space Agency mission to Venus (Astronomy)

With the EnVision mission, Europe flies to discover the Earth’s twin planet. On board the probe, an Italian instrument that sees the involvement of the Italian Space Agency and the responsibility of the University of Trento

Oxford University scientists will play a leading role in a new mission to study the geology and atmosphere of Venus, our neighbouring planet, helping determine whether it was once habitable – and why Earth became the only known planet that can sustain life.

Researchers from the University of Oxford, Royal Holloway, University of London and Imperial College London will make key contributions to the mission, called EnVision, which has been selected as the fifth Medium Class mission in the European Space Agency’s (ESA) Cosmic Vision programme. With ESA mission costs of €610 million, EnVision aims to investigate Venus by researching past and present volcanic activity and tracking the key volcanic gases that sustain its clouds and hostile environment.

Understanding the evolution of Venus

Working with European and American scientists, the UK team will compare geologic and atmospheric processes to those on Earth and other planets and aim to discover more about how interactions between its interior, surface and atmosphere have shaped its evolution.

Venus is the most Earth-like planet in size, composition and distance to our Sun.  When they initially formed, Earth and Venus were probably once quite similar, with oceans of molten rock and thick atmospheres of carbon dioxide and steam. But Earth evolved to become the habitable planet we enjoy today; Venus may or may not have had a habitable phase with liquid water oceans before developing a runaway greenhouse effect which today cooks its surface to an inhospitable 450 degrees Centigrade. The EnVision mission has been designed to study how geological activity throughout time has driven the evolution of Venus’ climate and habitability.

Exciting scientific insights

I have been working towards getting ESA to choose a Venus mission for over 15 years now, including balloons, probes and landers and we have been developing this orbiter proposal since 2009

Dr Colin Wilson, Senior Research Fellow at Oxford’s Department of Physics and a Deputy Lead Scientist of the mission comments: ‘It is great news that we will be getting back to Venus. The selection of this mission, along with the two Venus missions seelcted by NASA last week, shows the widespread recognition of how important Venus is in understanding how Earthlike planets evolve to be the way they are.

‘I have been working towards getting ESA to choose a Venus mission for over 15 years now, including balloons, probes and landers and we have been developing this orbiter proposal since 2009. Today’s announcement comes as a great reward for the huge efforts put in over this time by the whole team of scientists and engineers who have brought us this far. The real work lies ahead of us, of course, in getting the mission realised and to the launchpad; I’m then really looking forward the exciting scientific insights it will yield!

The real work lies ahead of us, of course, in getting the mission realised and to the launchpad; I’m then really looking forward the exciting scientific insights it will yield!

‘Oxford has a long history in Venus exploration: Professor Fred Taylor led an instrument which went to Venus in 1978, and was one of the proposers of ESA’s Venus Express mission which orbited Venus from 2006-2014. It is fantastic to be able to carry on this legacy. This Venus mission is relevant to a wide range of planetary research being carried out across the University from terrestrial exoplanet research in the Department of Physics to planetary formation and interior research at the Department of Earth Sciences.’

The EnVision orbiter is expected to launch in 2031-2032. It will take 15 months to reach Venus, where it will take a further 16 months of aerobraking to get into its low circular orbit. Once this stage is achieved, the satellite will start its 4-year scientific study.

For more information, visit www.envisionvenus.eu

Featured image: EnVision: Understanding why Earth’s closest neighbor is so different – Copyright: NASA / JAXA / ISAS / DARTS / Damia Bouic / VR2Planets


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Provided by University of Oxford

Reduce Emissions? The Answer in the Stars (Planetary Science)

What do Titan’s atmosphere and the combustion engines of our cars have in common? The production of particular molecules, polyclic aromatic hydrocarbons – including benzene – are the basis of many environmental pollutants. The exact mechanism of formation of these molecules, in space and in motors, was for the first time reproduced in the laboratory and could prove decisive for the production of cleaner motors. The results in Science Advances

On the occasion of Earth Day 2021 – celebrated last April 22 – the Nobel laureates have launched an appeal to the world leaders of the Climate Summit : leave fossil fuels underground. Stop the expansion of coal, oil and gas, the main culprits of the climate catastrophe we are already witnessing. The first step is to raise awareness and empower governments so that investments are increasingly dedicated to renewable energy.

“Together, we must listen to science and face the moment,” said US President Biden on that occasion. Governments and scientists, then. A relationship that is not always simple and straightforward, we have certainly seen it in the last year and a half. Scientists, for their part, continue to study methods and solutions – sometimes a bit exotic – to understand the problem in all its facets. In a recent article published in Science Advances , the origin of some molecules known as polycyclic aromatic hydrocarbons ( Pah), fundamental in the formation processes of molecules in our galaxy, but also involved in the fossil combustion processes that occur, among other things, in the exhaust gases of our cars. The answer, therefore, could come from the stars.

Let’s proceed in order. For nearly half a century, astrophysicists and organic chemists have been hunting for the origins of C6H6, the benzene ring– an elegant hexagonal molecule composed of 6 carbon and 6 hydrogen atoms, which according to astrophysicists would be the fundamental building block of the Pah. In space, Pahs are among the most basic compounds produced by the explosion of dying and carbon-rich stars and are the basis for the synthesis of the first forms of carbon – as well as the precursors of the molecules involved in the formation of the first forms of life on Earth. The Pahs, however, also have a dark side. The industrial processes that take place in crude oil refineries and the operation of gas combustion engines, in fact, also emit these compounds, which are transformed into toxic air pollutants such as soot.

Exactly how these two processes happen – that is, how the first benzene ring was generated in stars in the early universe and how combustion engines trigger the chemical reaction that alters the benzene ring into polluting particles – is still unclear to scientists. .

The most accredited explanation involves a particular type of extremely reactive free radical, propargyl (C3H3): its propensity to lose an electron would lead it, according to scientists, to easily recombine with a similar one, giving rise to the first aromatic ring, benzene. .

In the new study, researchers from Lawrence Berkeley National Laboratory (Berkeley Lab), the University of Hawaii and Florida International University conducted the first real-time laboratory measurement of unstable particles called free radicals that react under similar conditions. occurring in the cosmos, causing elemental carbon and hydrogen atoms to fuse into primary benzene rings. It is therefore the first demonstration of the so-called “self-reaction of the propargyl radical” – the suspect mentioned above – in astrochemical and combustion conditions.

The environmental conditions similar, in pressure and temperature, to those that occur in combustion engines, as well as in the hydrocarbon-rich atmosphere of Titan – one of Saturn’s moons, for example – were reproduced in the laboratory using a chemical reactor at high temperature and the size of a coin, called a “hot nozzle”. Scientists directly observed the formation of isomers – molecules with the same chemical formula but different atomic structures – by two propargyl radicals that lead to the benzene ring, also managing to stop the self-reaction of the propargyl radical – which takes place in microseconds – just before the larger Pahs and subsequent soot formed .

This is a first step towards understanding how carbon compounds have evolved in the universe and – why not – a helping hand to the automotive industry so that cleaner combustion engines can begin. Having more efficient gas engines, experts say, is still important, because it could take another 25 years before we can replace the entire fleet of gas cars with electric vehicles. Furthermore, equipping airplanes and the gas component of hybrid vehicles with cleaner combustion engines could help significantly reduce CO2 emissions.

Finally, as far as astrophysics is concerned, these results would be fundamental to map the carbon in the universe, and to understand the cosmic origins of the carbon structures of DNA.

Featured image: Authors Musahid Ahmed (left) and Wenchao Lu at the Berkeley Lab, the laboratory where they managed to stop the “propargyl radical self-reaction” before soot formation. Credits: Thor Swift / Berkeley Lab


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Provided by INAF

How Primordial Black Holes Forms From Inflation With Solo or Multiple Bumps? (Cosmology / Quantum Physics)

Ruifeng Zheng and colleagues investigated the formation of primordial black holes (PBHs) from inflation model with bumpy potential, which has multiple bumps. They found that, the potential can give rise to power spectrum with single or multiple peaks in small scales, which can in turn predict the production of primordial black holes. Their study recently appeared in Arxiv.

There are several inflation models which discuss the possibility of the production of primordial black holes in inflation process of the early universe. But, the production of PBHs requires the violation of slow-roll condition. For this reason, slow-roll violating models become an interesting alternative, including ultra-slow-roll (USR) inflation, inflation with inflection points or bumps and others.

Previous studies have already discussed the case of potential with one bump. Now, Ruifeng and colleagues discussed the extended case of multiple bumps, which can generate PBHs at different mass ranges.

Fig 1: The evolution of φ with the parameter N, which enters the USR-like stage three times near N = 20, N = 35 and N = 50. © Zheng et al.

Specifically, they considered the power-law potential as the basic potential, and add one or several bumps of Gaussian type which makes the inflaton roll from the slow-roll stage to USR-like stage.

“These multiple bumps are quite different from the solo-bumpy ones, we have to take care of not only the shape of each bump like height, width, etc., but also the relative distance of the bumps. This is important because, when the inflaton field passes through one bump, it will lose kinetic energy, and if the bumps are far from each other, it may not have enough energy to pass through the next ones. For this reason, we set the bumps close to each other.”

With the potential, they constructed the power spectrum with single or multiple peaks in small scales, while keeping the large scale power spectrum consistent with CMB data. Later, they numerically calculated the abundances of PBHs (fraction to dark matter) at the mass range given by the solo-bumpy potential, as well as three mass ranges given by the multi-bumpy potential. Finally, they found that, PBHs can be formed at different mass ranges, including asteroid mass range (10¯16 − 10¯14M), planet mass range (10¯6 − 10¯3M) and solar mass range (around 1M), some of which can reach significant abundance.

FIG. 2: They plot fP BH for potential (21) given in paper with p = 2 using different threshold densities δc, where the yellow line corresponds to δc = 0.41, the purple line corresponds to δc = 0.46, and the blue line corresponds to δc = 0.486. Their results are consistent with the constraints from current observations. © Zheng et al.

They also found that, the larger threshold energy density (δc) is, the smaller the abundance will be, and this is easy understanding: the larger the threshold energy is, the more difficult it is to form black holes. For the small value of threshold energy density, the abundance of PBHs can reach around 10% of dark matter. The mass range of the PBHs formed is around 10¯15 M, namely the asteroid mass.

Moreover, they also considered the possibility of formation of primordial black holes (PBHs) in the early universe, through ellipsoidal collapse instead of spherical collapse. The difference between these two collapse models is that the threshold density for forming PBH is different. Because compared with the spherical collapse, the PBHs formed by the ellipsoidal collapse will increase the ellipticity of the formed PBHs, which will lead to the correction of the threshold density. Thus, abudance of ellipsoidal PBHs is lower than that of spherical PBHs, due to difference in their threshold densities.

FIG. 3: The figures above show the constraints on primordial black holes acting as dark matter, in which the colored region is excluded by various observations. The blue line correspond to fPBH, and the red line correspond to fe-PBH. The plot is for potential and δc = 0.465. From left to right, the masses of PBHs are 3.6975 × 10¯27 M, 5.8601 × 10¯16 M and 3.6975 × 10¯3 M respectively. Constraints are obtained from the publicly available Python code PBHbounds. © Zheng et al.

Finally, it has been suggested that, considering the age of the universe, PBHs with initial mass less than 1015g (∼ 10¯18 M) has been completely evaporated today. But, the PBHs of mass 3.6975 × 10¯27 (as shown in figure 3 above) may actually be vanishing, and cannot explain the dark matter today. But, although they can’t explain today’s dark matter they may still have a significant impact on the early universe, such as the process of Big Bang Nucleosynthesis, reheating, baryogenesis and so on.

Ruifeng and colleagues suggested that, we can be able to detect the traces left by such PBHs with future observation techniques, to find more evidence of their existence. Meanwhile, for other mass ranges, the PBHs are hardly evaporated till now and thus can act as dark matter.

“We will explore further details on the influences of the PBHs in our model in the future work.”

— concluded authors of the study

Reference: Ruifeng Zheng, Jiaming Shi, Taotao Qiu, “On Primordial Black Holes generated from inflation with solo/multi-bumpy potential”, Arxiv, pp. 1-14, 2021. https://arxiv.org/abs/2106.04303


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What Are The Effects Of Different Dark Matter Candidates On Compact Binary Systems? (Cosmology)

Ebrahim Hassani and colleagues investigated the effects of different dark matter candidates on the properties of compact binary systems due to the accretion of dark matter particles into them. They found that, the low-mass DM candidates has the potential to change the period of compact binary systems more than the observed values. Their study recently appeared in Arxiv.

As compact binary star systems move inside the halo of our Galaxies, they interact with dark matter particles. The interaction between dark matter particles and baryonic matter causes dark matter particles to lose some part of their kinetic energy. After dark matter particles have lost part of their kinetic energy, they gravitationally bound to stars and stars start to accrete dark matter particles from the halo. The accretion of dark matter particles inside compact binary systems increases the mass of the binary components and then, the total mass of the binary systems increases too. According to Kepler’s third law, increased mass by this way can affect other physical parameters (e.g. semi-major axes and orbital periods) of these systems too.

Thus, Ebrahim Hassani and colleagues now investigated the effects of different dark matter candidates on the properties of known compact binary systems (such as NS-NS, NS-WD, WD-WD, where, NS is neutron star and WD is white dwarf) due to the accretion of dark matter particles into them.

Initially, they considered four DM particles candidates which are axions with mass in the range 10¯15 −10¯12 (𝐺𝑒𝑉.𝑐¯2), Neutrinos with mass in the range 10¯12 − 10¯10 (𝐺𝑒𝑉.𝑐¯2), SuperWIMPs with mass in the range 10¯6 − 104 (𝐺𝑒𝑉.𝑐¯2), and WIMPs with mass in the range 10¯1 − 105 (𝐺𝑒𝑉.𝑐¯2).

Later, they estimated the periodic change of some known compact binary systems due to the accretion of dark matter particles inside them and then compared the results with the period change of these systems due to dynamical friction and gravitational wave emission.

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Fig. 1: Calculated mass change of different types of compact binary systems and for different DM particle candidates. sub-plots (a)-(d) are for WD-WD type, sub-plots (e)-(h) for WD-NS type and sub-plots (i)-(l) for NS-NS type compact binary systems. In all sub-plots horizontal axes are the mass range of different DM particle candidates and vertical axes are the mass change of the compact binary systems. Only SuperWIMP particles have the potential to change the period of the compact binary systems in the range of the observed period change values for the observed period change values © Ebrahim Hassani et al.

They found that, low-mass DM candidates has the potential to change the period of compact binary systems more than the observed values. They also found that intermediate-mass DM candidates has the ability to change the period of compact binary systems as comparable as the observed values. But high-mass DM candidates can not change the period of compact binary systems as much as the observed values.

“Because of lack of knowledge about the exact physical nature of DM we can not speak with confidence that which DM candidate can be the best source of period change in compact binary systems


Moreover, they deduced that, gravitational wave emission from compact binary systems and the accretion of dark matter (DM) particles inside the compact binary systems can be considered as the main reasons of the observed periodic decay or change in these systems.

Finally, from results obtained, they suggested that, DM candidates with mass in the range, 𝑚𝜒 ∝ 10¯1−105 (𝐺𝑒𝑉.𝑐¯2) are the best DM candidates for this observed period changes.


Reference: Ebrahim Hassani, Amin Rezaei Akbarieh, Yousef Izadi, “The effects of dark matter on compact binary systems”, Arxiv, 2021. https://arxiv.org/abs/2106.05043


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How Much Water Was Delivered From The Asteroid Belt To The Earth After Its Formation? (Planetary Science)

How much water could have been brought to the Earth through asteroid collisions after the formation of earth? Rebecca Martin and Mario Livio now answered this question by using N-body simulations and by comparing the relative impact efficiencies of 3 radially narrow regions of the asteroid belts. Their study recently appeared in Arxiv.

As we all know, the planets in the inner solar system are relatively dry. The precise amount of water in and on the Earth is unknown, but is thought to be between one and ten “oceans”, where one ocean is about 2.5 × 10¯4 M or the mass of water on the Earth’s surface. The question is, how the Earth could have formed with its current amount of water, as it is not possible for Earth to form water by its own. Thus, there have been several suggestions: through adsorption of hydrogen molecules on to silicate grains, delivery of water through meteorites and icy pebbles etc. But, the current leading scenario for the majority of the water delivery is by external pollution from the outer parts of the asteroid belt.

So, by considering this, Martin and Livio now described their n-body simulations in which they modeled three radially narrow regions of the asteroid belt: the ν6 resonance (at about 2.1 au), the 2:1 mean motion resonance with Jupiter (at about 3.3 au) and the chaotic region outside of the asteroid belt. Next, they compared the relative impact
efficiencies between asteroids in these regions and the Earth.

“Our analysis assumed that the asteroid belt contained its primordial mass after the Earth had formed and the giant planets were on their current day orbits. Thus, we have skewed the assumptions to estimate an upper limit to the amount of water that could have been delivered to the Earth.”

They showed that the majority of asteroid collisions with the Earth originate from the ν6 resonance at the inner edge of the asteroid belt. About 2% of asteroids from the resonance collide with the Earth. While, the collision probability from the 2:1 mean motion resonance is about one hundred times smaller and from the chaotic region about a thousand times smaller.

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Figure 1. The outcomes of the n-body simulations in time binned into 0.5 Myr intervals. Note that the points are slightly offset from the centre of the time bin so that they don’t completely overlap. The upper panels have the Earth radius of REarth = 1 R⊕ while the lower panels have Earth radius of REarth = 10 R⊕. The left panels show the simulation of the ν6 resonance in the range a = 2.0-2.1 au. The middle panels show the 2:1 resonance in the range a = 3.3 – 3.35 au. The right panels show the simulation in the region 4 – 4.1 au. The blue points show asteroids that are ejected. The red points show asteroids that hit the Sun. The green points show asteroids that hit the Earth. The magenta points show asteroids that hit Jupiter or Saturn. © Martin and Livio

They also estimated that, if the majority of asteroids in the primordial asteroid belt were moved into the ν6 resonance either through asteroid-asteroid interactions or gas drag, or the Yarkovsky effect, then at most, the asteroid belt could have delivered about eight oceans worth of water. Thus, the delivery of one ocean’s worth from the asteroid belt was certainly possible.

“However, the delivery of 10 oceans worth could have been difficult and if the Earth’s mantle contains such significant amounts of water then the Earth likely formed with a good fraction of it.”

— concluded authors of the study

Reference: Rebecca G. Martin and Mario Livio, “How much water was delivered from the asteroid belt to the Earth after its formation?”, Arxiv, pp. 1-5, 2021. https://arxiv.org/abs/2106.03999


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