ALETHEIA: A New Low-mass Dark Matter Detection Project (Physics / Cosmology)

Astronomical evidence of many types, including cluster and galaxy rotation curves, lensing studies and spectacular observations of galaxy cluster collisions, and cosmic microwave background (CMB) measurements, all point to the existence of cold dark matter (CDM) particles. Cosmological simulations based on the CDM model have been remarkably successful at predicting the actual structures we see in the Universe.

Alternative explanations involving modification of general relativity have not been able to explain this large body of evidence across all length scales.
Recent results from Gaia showing consistency with many previous experiments therefore much more securely pinned down than ever on: (a) DM dominates the mass of the Milky Way Galaxy, and (b) the local DM mass density in the Solar system is around 0.3 GeV/c2 · cm¯3.

Weakly Interactive Massive Particles (WIMPs) and Axions are among the two most prominent DM candidates. WIMPs are a hypothesized class of DM particles that would freeze out of thermal equilibrium in the early Universe with a relic density that matches observation. The so-called “WIMP miracle” is the coincident emergence of WIMPs with similar characteristics both from the solution of the gauge hierarchy problem and from the observed relic density of dark matter. Axions are motived by the strong Charge Parity (CP) problem, essentially to solve a fine-tuning problem of 1 part in ∼ 1010. Axions are much lighter and require different experimental techniques than WIMPs to detect them as in the Axion Dark Matter eXperiment (ADMX).

There are several viable strategies to detect DM. Indirect detection experiments aim to observe high-energy particles resulting from the self-annihilation of DM. Collider experiments look for the production of DM particles in high energy collisions. Direct detection experiments aim to observe the rare scatters of DM on the low threshold, very low background detectors operated in deep underground Laboratories. Table I categorizes currently active DM experiments.

© Liao et al.

The low-mass WIMPs region (100s MeV/c2 – 10 GeV/c2 ) has not been fully exploited comparing to high-mass WIMPs (10 GeV/c2 – 1 TeV/c2 ) experiments which implement liquid xenon or argon TPCs (Time Projection Chambers). The ALETHEIA experiment aims to hunt for low-mass WIMPs with liquid helium-filled TPCs. In the recently published paper in Arxiv, Liao and colleagues have gone through the physics motivation of low-mass DM, the ALETHEIA detector’s design, a series of R&D programs that should be launched to address a liquid helium TPC’s functionality, and possible analysis channels available for DM searches.

INTRODUCTION TO ALETHEIA

The ALETHEIA project is an instrumental background-free experiment with the ROI (Research Of Interest) of ∼ 100s MeV/c² – 10 GeV/c². With the S2 only analysis, the ALETHEIA project could be sensitive to 10s MeV/c² WIMPs.

Here, instrumental background-free means in the range of ROI, a small number of background events (for instance, < 0.1 events) are expected, such that zero background events are observed. The instrumental backgrounds include radioactive particles due to the materials in the detector system (including dust) and the particles generated by cosmological muons hitting the rocks near the detector or the detector itself. For low-mass WIMPs searches, there is another background which is registered by 8B solar neutrinos. The 8B events can’t be discriminated from low-mass WIMPs signals. Consequently, in a WIMPs detector that is free of instrumental background like the ALETHEIA, by subtracting (theoretically estimated) 8B events from the observed events, we can figure out how many WIMPs events were observed and this quantity’s uncertainty.

WHY ALETHEIA?

None of the leading high-mass DM experiments is sensitive to low-mass WIMPs due to their relative heavy target material, xenon, or argon. The ALETHEIA was inspired by both high-mass and low-mass WIMPs experiments in the community. Although there existed quite a few low-mass DM experiments, researchers believe the ALETHEIA is a competitive project in the race of hunting for low-mass DM thanks to the following advantages.

(a) Being able to discriminate Electron Recoil (ER) and Nuclear Recoil (NR) (ER/NR) events with ”S1/S2” analysis (where “S1” refers to prompt scintillation while “S2” is the electroluminescence light originated from an ionization by recoiled target nuclei) and possibly PSD ( Pulse Shape Discrimination ) technologies.

(b) LHe (liquid helium) could achieve extremely low or even zero intrinsic backgrounds. At 4 K temperature, 3He is the only solvable material in LHe while it is very rare in Nature; any other impurities would show in the solid-state. Impurities are supposed to be purified completely with getter and cold-trap technologies.

(c) 4He only has two nucleons and four electrons. Therefore the intrinsic ER background induced by (background) gammas and neutrinos would be significantly smaller than heavier noble elements like Ar and Xe.

(d) TPC is a technology demonstrated for LXe and LAr; it could possibly be employed on LHe. If an LHe TPC were made successfully, its fiducial volume is expected to achieve very few or even zero backgrounds by self-shielding and other data-analyzing technologies. and

(e), being capable of scaling up to a ton or multi-tons size to fully touch down the B-8 neutrino floor.

THE DESIGN OF THE ALETHEIA PROJECT

Unlike earlier concepts like HERON, the ALETHEIA project will use liquid helium at ∼ 4 K, which is above the Lambda curve, instead of superfluid helium. W. Guo and D. N. McKinsey also proposed and simulated a liquid helium TPC hunting for DM in 2013 with “S1/S2” analysis, where “S1” refers to prompt scintillation while “S2” is the electroluminescence light originated from an ionization by recoiled target nuclei. Besides the “S1/S2” analysis, the ALETHEIA will also implement the S2O analysis to reach the sensitive WIMPS mass all the way down to 10s MeV/c².

FIG. 1: The schematic drawing of the ALETHEIA detector (not to scale). From outside to inside: The light blue area represents the water tank surrounding the whole detector system, with a diameter of a few meters; the four purple rectangles on the edge of the water tank are the PMTs to detect background signals insides of the water tank; the dark green is the Gd-doped liquid scintillator veto, with thickness of ∼ half-meter; the four purple rectangles at the edge of veto (green area) are PMTs to detect signals insides of it; the cyan area is the active volume of the TPC, filled with liquid helium; the two horizontal dark blue stripes on the top and bottom of the active volume represent the SiPMs to detect scintillation and electroluminescence; the pink region represents the fiducial volume of the TPC where extremely low backgrounds are expected there. Red dots represent background neutrons. Black dots are background γs. © Liao et al.

The design of the dual-phase ALETHEIA has been significantly inspired by other successful experiments like DarkSide-50, LUX/LZ, PandaX, XENON-100, and XENON-1T, and others. The photon sensors would be SiPMs to achieve the highest possible photon detection efficiency. Figure 1 shows the schematic drawing of such a detector.

As shown in Fig. 1, the core of the ALETHEIA experiment is a dual-phase liquid helium TPC (in cyan). The TPC center is in pink representing the fiducial volume where extremely low or zero background is expected. On the top and bottom of the TPC are SiPMs (purple). The TPC was surrounded by a Gd-doped scintillator detector, which acts as a veto. The outmost is a water tank with a diameter of a few meters to shield neutrons and gammas outside of the detector system.

For neutrons that come from outside of the water tank, a few meters of water should thick enough to thermalize them. The ∼ half-meter Gd-doped liquid scintillator would capture thermalized neutrons. For neutrons originated from the TPC inside, it could be identified by the feature of multiple hits in the TPC and (or) liquid scintillator. Typical WIMPs signal would only have one hit registered due to a much lower coupling constant between WIMPs and helium nuclei than the strong interaction between a neutron and helium nuclei. For γs from outside of the water, the water tank can block them from entering the central detector; for γs from inside of the TPC, “S1/S2”, or PSD (Pulse Shape Discrimination), or a hybrid analysis combined both could discriminate from nuclear recoils induced by a neutron or a WIMPs.

WHY 4HE?

4He is suitable for low-mass WIMPs search thanks to several advantages:

(1) High recoil energy. The same kinetic energy of incident WIMPs would result in greater recoil energy than any other heavier elements. Hydrogen is even lighter, but the quenching factor of Hydrogen is more than one order smaller than Helium at the recoil energy of ∼1 keV_nr. ( ‘_’ is base)

(2) The Quenching Factor (QF) of LHe is quite high. For instance, for a 16 keV nuclear recoil, the measured QF of LHe is ∼ 65%; while LAr is ∼ 24%, which is a factor of 3 smaller. The measured Quenching Factor (QF) of Helium at 1.5 keV recoil energy is up to 22%. As a comparison, the measured QF of Hydrogen at 100 keV is only 2%, and the estimated QF at 1.5 keV nuclear recoils would be much lower. As a result, the QF of Hydrogen is guaranteed to be at least one order smaller than 4He. Thus, Hydrogen is not an appropriate material for low-mass WIMPs search with the method of ionization, while Helium is.

(3) 4He only has 4 electrons. Therefore the intrinsic ER background induced by (background) gammas would be significantly smaller than other widely used heavier noble elements like Argon and Xenon.

(4) At 4 K, only 3He is solvable in LHe, and 3He is very few in nature; other elements become a solid state at this low temperature. So, it would be easy to purify LHe with getter and cold trap technologies to achieve very high level purification.

(5) LHe is relatively cheaper. The price of LHe is ∼ 1/7 of LXe. (3He is very expensive, which is partially the reason why it has been ruled out for consideration as a material for low-mass WIMPs search.).

First 30 g LHe detector

Although lots of theoretical and experimental research have been launched to understand the particle characters of LHe, most of those experimental results focused on 100s keV_nr energy or higher, which are out of the ROI of the proposed LHe TPC: ∼ 0.5 –10 keV_nr. Therefore, researchers have to launch a complete set of Experimental tests to verify that an LHe TPC is suitable for low-mass DM hunting. The first 30 g LHe detector is assembled at CIAE in Beijing, China, and they are ready to launch tests soon.

FIG. 2: The first 30 g LHe cell is assembled at CIAE in Beijing, China, and ready to launch tests. Left: The first 30 g LHe cell manufactured and assembled at CIAE. (Right): Some of the parts of our first 30 g LHe cell before assembly. © Liao et al.

Featured image: The mechanical drawing of their first 30 g LHe cell. The left plot shows the test bench. The right one is the internal structure of the whole 30 g LHe cell. The unit for “D:130” and “H:42” on the right plot is mm. © Liao et al.


Reference: Junhui Liao, Yuanning Gao, Zhuo Liang, Zhaohua Peng, Lifeng Zhang, Lei Zhang, “A low-mass dark matter project, ALETHEIA: A Liquid hElium Time projection cHambEr In dArk matter”, ArXiv, pp. 1-32, 2021. https://arxiv.org/abs/2103.02161


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Nano-mapping Phase Transitions in Electronic Materials (Material Science)

“Phase transitions” are a central phenomenon in physical sciences. Despite being technical-sounding, they are actually something we all experience in everyday life: ice melting into liquid water, or hot water evaporating as steam. Solid, liquid, and gas are three well known “phases” and, when one turns into another, that is a phase transition.

Rare-earth nickelate oxides, also called nickelates, have attracted a lot of interest from researchers because they display an electronic phase transition, which may be exploited in future electronic devices. This particular phase transition consists of turning from a metallic state that conducts electricity into an electrically-insulating state as temperature drops.

Behind this behaviour is a strong interaction between the electronic properties of these compounds and their “lattice” structure – the well-ordered arrangement of atoms that forms a crystal. However, uncovering the true nature of this metal to insulator phase transition in nickelates, and being able to control it for potential electronic devices, requires knowing how each characteristic phase emerges and evolves across the transition.

Atomic resolution STEM image showing the perfect crystal structure of a nickelate thin film, coloured to represent the two compounds. © Bernat Mundet.

Now, scientists from EPFL and the University of Geneva have combined two cutting-edge techniques to achieve nanoscale mapping of each distinct electronic phase. Published in the journal Nano Letters, the study was led by Dr Duncan Alexander at EPFL’s School of Basic Sciences and the group of Professor Jean-Marc Triscone at the University of Geneva.

The study’s first author, Dr Bernat Mundet, says: “To fully understand the physics displayed by novel electronic materials and to control them in devices, new atomic-scale characterization techniques are required. In this regard, we have been able for the first time to precisely determine the metallic and insulating regions of atomically engineered devices made from two nickelate compounds with near atomic resolution. We believe that our methodology will help to better understand the physics of this important family of electronic materials.”

The researchers combined aberration-corrected scanning transmission electron microscopy (STEM) with monochromated electron energy-loss spectroscopy (EELS).

In STEM, images are formed by scanning a beam of electrons, focused to a spot of about 1 Ångstroms in size, across a sufficiently thin specimen – in this case a sliver of nickelate – and collecting the transmitted and scattered electrons with the use of annular detectors. Though technically demanding, this technique allows researchers to precisely visualise a crystal’s lattice structure, atomic row by atomic row.

For the second technique, EELS, those electrons passing through the central hole of the annular detector are instead collected. Some of these electrons have previously lost some energy due to their interaction with the Ni atoms of the nickelate crystal. By measuring how this energy difference changes, we can determine the metallic or insulating state of the nickelate compound.

Since all electrons are scattered and collected simultaneously, the researchers were able to correlate the electronic state changes with the associated lattice positions in the different nickelate compounds. This approach allowed them to map, for the first time, the spatial configuration of their metallic or insulating regions, reaching a very high spatial resolution of around 3.5 Ångstroms (0.35 nanometers). The technique will be a valuable tool for studying and guiding the atomic engineering of these novel electronic materials.

“The latest electron microscopes give us an amazing ability to measure a variety of materials physical properties with atomic or nanometric spatial resolution,” says Duncan Alexander. “Here, by pushing the capabilities of EPFL’s Titan Themis microscope to the limits, we take an exciting step forward in this domain, by proving that we can measure the changes in electronic state across a thin film structure precisely made from two different nickelates. Our approach opens up new avenues for investigating the physics of these nickelate compounds, which have sparked research interest worldwide.”

“The combination of amazing artificial materials that display a metal to insulator transition and very advanced electron microscopy has allowed unprecedented detailed investigations of their electronic properties,” adds Jean-Marc Triscone. “In particular, it revealed, at the atomic scale, whether the material is conducting or insulating – an important question for better understanding these materials that may be used in future computing approaches.”

Featured image: Schematic illustration of a STEM probe scanning across the interface of two nickelate compounds, with the nature of the scattered electrons changing as the electronic phase of the material goes from being metallic to insulating. Atomic structure model rendered using Vesta. © Duncan T.L. Alexander


Reference: Bernat Mundet, Claribel Dominguez, Jennifer Fowlie, Marta Gibert, Jean-Marc Triscone, Duncan T. L. Alexander. Near-atomic-scale mapping of electronic phases in rare earth nickelate superlattices. Nano Letters 08 March 2021. DOI: 10.1021/acs.nanolett.0c04538


Provided by EPFL

Face Masks Are A Ticking Plastic Bomb (Biology)

Every minute of the day we throw away 3 million face masks. Many end up as potentially toxic micro- and nanoplastic or carriers for other toxicants in the environment, researchers warn.

Recent studies estimate that we use an astounding 129 billion face masks globally every month – that is 3 million a minute. Most of them are disposable face masks made from plastic microfibers.

– With increasing reports on inappropriate disposal of masks, it is urgent to recognize this potential environmental threat and prevent it from becoming the next plastic problem, researchers warn in a comment in thescientific journal Frontiers of Environmental Science & Engineering.

The researchers are Environmental Toxicologist Elvis Genbo Xu from University of Southern Denmark and Professor of Civil and Environmental Engineering Zhiyong Jason Ren from Princeton University.

No guidelines for mask recycling

Disposable masks are plastic products, that cannot be readily biodegraded but may fragment into smaller plastic particles, namely micro- and nanoplastics that widespread in ecosystems.

The enormous production of disposable masks is on a similar scale as plastic bottles, which is estimated to be 43 billion per month.

Collection of photos of disposed facemasks in the environment in the city of Odense, Denmark. © Elvis Genbo Xu/SDU

However, different from plastic bottles, (of which app. 25 pct. is recycled), there is no official guidance on mask recycle, making it more likely to be disposed of as solid waste, the researchers write.

Greater concern than plastic bags

If not disposed of for recycling, like other plastic wastes, disposable masks can end up in the environment, freshwater systems, and oceans, where weathering can generate a large number of micro-sized particles (smaller than 5 mm) during a relatively short period (weeks) and further fragment into nanoplastics (smaller than 1 micrometer).

– A newer and bigger concern is that the masks are directly made from microsized plastic fibers (thickness of ~1 to 10 micrometers). When breaking down in the environment, the mask may release more micro-sized plastics, easier and faster than bulk plastics like plastic bags, the researchers write, continuing:

– Such impacts can be worsened by a new-generation mask, nanomasks, which directly use nano-sized plastic fibers (with a diameter smaller than 1 micrometer) and add a new source of nanoplastic pollution.

“We know that, like other plastic debris, disposable masks may also accumulate and release harmful chemical and biological substances, such as bisphenol A, heavy metals, as well as pathogenic microorganisms”

— Elvis Genbo Xu, Environmental Toxicologist

– The researchers stress that they do not know how masks contribute to the large number of plastic particles detected in the environment – simply because no data on mask degradation in nature exists.

– But we know that, like other plastic debris, disposable masks may also accumulate and release harmful chemical and biological substances, such as bisphenol A, heavy metals, as well as pathogenic micro-organisms. These may pose indirect adverse impacts on plants, animals and humans, says Elvis Genbo Xu.

What can we do?

Elvis Genbo Xu and Zhiyong Jason Ren have the following suggestions for dealing with the problem:

  •  Set up mask-only trash cans for collection and disposal
  •  consider standardization, guidelines, and strict implementation of waste management for mask wastes
  •  replace disposable masks with reusable face masks like cotton masks
  •  consider development of biodegradable disposal masks.

Featured image: Collected face masks in city of Odense, Denmark © Elvis Genbo Xu/SDU


Reference: Xu, E.G., Ren, Z.J. Preventing masks from becoming the next plastic problem. Front. Environ. Sci. Eng. 15, 125 (2021). https://link.springer.com/article/10.1007/s11783-021-1413-7 https://doi.org/10.1007/s11783-021-1413-7


Provided by SDU

I Ain’t Afraid of No Ghosts: People With Mind-blindness Not So Easily Spooked (Psychology)

The link between mental imagery and emotions may be closer than we thought.

People with aphantasia – that is, the inability to visualise mental images – are harder to spook with scary stories, a new UNSW Sydney study shows. 

The study, published today in Proceedings of the Royal Society B, tested how aphantasic people reacted to reading distressing scenarios, like being chased by a shark, falling off a cliff, or being in a plane that’s about to crash.

The researchers were able to physically measure each participant’s fear response by monitoring changing skin conductivity levels – in other words, how much the story made a person sweat. This type of test is commonly used in psychology research to measure the body’s physical expression of emotion. 

According to the findings, scary stories lost their fear factor when the readers couldn’t visually imagine the scene – suggesting imagery may have a closer link to emotions than scientists previously thought.

“We found the strongest evidence yet that mental imagery plays a key role in linking thoughts and emotions,” says Professor Joel Pearson, senior author on the paper and Director of UNSW Science’s Future Minds Lab

“In all of our research to date, this is by far the biggest difference we’ve found between people with aphantasia and the general population.”

Finding yourself trapped in a room full of spiders – and feeling them slowly crawl over you – was one of the scary stories used in the experiment. Photo: Unsplash.

To test the role of visual imagery in fear, the researchers guided 46 study participants (22 with aphantasia, and 24 with imagery) to a blackened room before attaching several electrodes to their skin. Skin is known to become a better conductor of electricity when a person feels strong emotions, like fear.

The scientists then left the room and turned the light off, leaving the participants alone as a story started to appear in the screen in front of them.  

At first, the stories started innocuously – for example, ‘You are at the beach, in the water’ or ‘You’re on a plane, by the window’. But as the stories continued, the suspense slowly built, whether it was a dark flash in the distant waves and people on the beach pointing, or the cabin lights dimming as the plane starts to shake. 

“Skin conductivity levels quickly started to grow for people who were able to visualise the stories,” says Prof Pearson. “The more the stories went on, the more their skin reacted.

“But for people with aphantasia, the skin conductivity levels pretty much flatlined.”

To check that differences in fear thresholds didn’t cause the response, the experiment was repeated using a series of scary images instead of text, like a photo of a cadaver or a snake bearing its fangs.

But this time, the pictures made the skin crawl equally in both groups of people.

“These two sets of results suggest that aphantasia isn’t linked to reduced emotion in general, but is specific to participants reading scary stories,” says Prof. Pearson. “The emotional fear response was present when participants actually saw the scary material play out in front of them.

“The findings suggest that imagery is an emotional thought amplifier. We can think all kind of things, but without imagery, the thoughts aren’t going to have that emotional ‘boom’.”

Do you want to hear a scary story? Photo: Shutterstock

Living with aphantasia

Aphantasia affects 2-5 per cent of the population, but there is still very little known about the condition. 

A UNSW study published last year found that aphantasia is linked to a widespread pattern of changes to other cognitive processes, like remembering, dreaming and imagining.

But while most previous aphantasia research focused on behavioural studies, this study used an objective measure of skin conductance.

“This evidence further supports aphantasia as a unique, verifiable phenomenon,” says study co-author Dr Rebecca Keogh, a postdoctoral fellow formerly of UNSW and now based at Macquarie University.

“This work may provide a potential new objective tool which could be used to help to confirm and diagnose aphantasia in the future.”

The idea for this experiment came after the research team noticed a recurring sentiment on aphantasia discussion boards that many people with the condition didn’t enjoy reading fiction.

While the findings suggest that reading may not be as emotionally impactful for people with aphantasia, Prof. Pearson says it’s important to note that the findings are based on averages, and not everyone with aphantasia will have the same reading experience. 

The study was also focused on fear, and other emotional responses to fiction could be different.

While some people with aphantasia only experience a lack of visual imagery, others also have trouble imagining other senses, like sounds, tastes, and touch. Photo: Unsplash.

“Aphantasia comes in different shapes and sizes,” he says. “Some people have no visual imagery, while other people have no imagery in one or all of their other senses. Some people dream while others don’t.

“So don’t be concerned if you have aphantasia and don’t fit this mould. There are all kinds of variations to aphantasia that we’re only just discovering.”

Next, Prof. Pearson and his team at the Future Minds Lab plan to investigate how disorders like anxiety and Post Traumatic Stress Disorder might be experienced differently by people with aphantasia.

“Aphantasia is neural diversity,” says Prof. Pearson. “It’s an amazing example of how different our brain and minds can be.”

Featured image: It turns out seeing really is believing when it comes to scary stories. Photo: Unsplash.


Reference: “The critical role of mental imagery in human emotion: insights from fear-based imagery and aphantasia”,
Marcus Wicken, Rebecca Keogh and Joel Pearson, Proceedings of the Royal Society B
Published:10 March 2021. https://doi.org/10.1098/rspb.2021.0267


Provided by University of New South Wales

A CNIO Team Discovers How Telomere Involvement in Tumour Generation is Regulated (Biology)

The protein TRF1, which is part of the ‘protective shield’ at the ends of chromosomes, or telomeres, is regulated by the PI3K/AKT pathway, one of the most frequently affected pathways in numerous tumorigenic processes

When the researchers created human cancer lines that prevented AKT from modifying telomeres, they observed shorter telomeres and a reduced ability to generate tumours

The results show for the first time that telomeres respond to external signals that induce cell proliferation and that blocking these signals can interfere with immortality of cancer cells

The Telomeres and Telomerase Group led by Maria A. Blasco at the Spanish National Cancer Research Centre (CNIO) continues to make progress in unravelling the role that telomeres –the ends of chromosomes that are responsible for cellular ageing as they shorten– play in cancer. The CNIO team was among the first to propose that shelterins, proteins that wrap around telomeres and act as a protective shield, might be therapeutic targets for cancer treatment. Subsequently, they found that eliminating one of these shelterins, TRF1, blocks the initiation and progression of lung cancer and glioblastoma in mouse models and prevents glioblastoma stem cells from forming secondary tumours.  Now, in a study published in PLOS Genetics, they go one step further and describe for the first time how telomeres can be regulated by signals outside the cell that induce cell proliferation and have been implicated in cancer. The finding opens the door to new therapeutic possibilities targeting telomeres to help treat cancer.

The CNIO group was also the first to find a link between TRF1 and the PI3K/AKT signalling pathway. This metabolic pathway, which also encompasses mTOR, is one of the pathways most frequently affected in numerous tumorigenic processes. However, it was not known whether preventing TRF1 regulation by this pathway can have an impact on telomere length and its ability to form tumours. AKT acts as a transmitter of extracellular signals triggered by, among others, nutrients, growth factors and immune regulators, to the interior of cells. CNIO researchers Raúl Sánchez and Paula Martínez, directed by Maria A Blasco, set out to determine the involvement of telomeres in this signalling pathway.

To do this, the researchers modified the TRF1 protein in cells to make it unresponsive to AKT, using the gene-editing tool CRISPR/Cas9. This way, TRF1 and the telomeres became invisible to any extracellular signals transmitted by AKT.  Telomeres in these cells shortened and accumulated more damage; most importantly, the cells were no longer able to form tumours, indicating that telomeres are important targets of AKT and its role in cancer development.

“Most importantly, we found that when TRF1 can’t be phosphorylated by AKT, the latter has a lower potential to generate tumours,” explains Blasco.

The paper shows that telomeres are among the most important intracellular targets of the AKT pathway to form tumours, since, although neither the function of AKT nor of any of the thousands of proteins that are regulated by it was altered, only blocking AKT’s ability to modify telomeres was sufficient to slow tumour growth.  

The next step will be to generate genetically modified mice with telomeres that are invisible to AKT. The authors anticipate that these mice will be more resistant to cancer.

The study was funded by the Spanish Ministry of Science and Innovation, the Carlos III Health Institute, the Spanish State Research Agency, the European Research Council, the European Regional Development Fund, the Autonomous Community of Madrid, the Botín Foundation and Banco Santander through Santander Universities, and World Cancer Research.

Featured image: When TRF1 is phosphorylated by AKT, telomeres are normal (top); in the cell lines where AKT doesn’t modify TRF1, telomeres are shorter and have a lower potential to generate tumours (bottom). /PLOS Genetics


Reference article

AKT-dependent signaling of extracellular cues through telomeres impact on tumorigenesis. Raúl Sánchez-Vázquez, Paula Martínez, Maria A. Blasco (PLOS Genetics, 2021). DOI: doi.org/10.1371/journal.pgen.1009410


Provided by CNIO

New Study Links Protein Causing Alzheimer’s Disease With Common Sight Loss (Psychiatry)

Newly published research has revealed a close link between proteins associated with Alzheimer’s disease and age-related sight loss. The findings could open the way to new treatments for patients with deteriorating vision and through this study, the scientists believe they could reduce the need for using animals in future research into blinding conditions.

Amyloid beta (Ab) proteins are the primary driver of Alzheimer’s disease but also begin to collect in the retina as people get older. Donor eyes from patients who suffered from age-related macular degeneration (AMD), the most common cause of blindness amongst adults in the UK, have been shown to contain high levels of Ab in their retinas.

This new study, published in the journal Cells, builds on previous research which shows that Ab collects around a cell layer called the retinal pigment epithelium (RPE), to establish what damage these toxic proteins cause RPE cells.

The research team exposed RPE cells of normal mouse eyes and in culture to Ab. The mouse model enabled the team to look at the effect the protein has in living eye tissue, using non-invasive imaging techniques that are used in ophthalmology clinics. Their findings showed that the mouse eyes developed retinal pathology that was strikingly similar to AMD in humans.

Dr Arjuna Ratnayaka, a Lecturer in Vision Sciences at the University of Southampton, who led the study said, “This was an important study which also showed that mouse numbers used for experiments of this kind can be significantly reduced in the future. We were able to develop a robust model to study AMD-like retinal pathology driven by Ab without using transgenic animals, which are often used by researchers the field. Transgenic or genetically engineered mice can take up to a year and typically longer, before Ab causes pathology in the retina, which we can achieve within two weeks. This reduces the need to develop more transgenic models and improves animal welfare.”

The investigators also used the cell models, which further reduced the use of mice in these experiments, to show that the toxic Ab proteins entered RPE cells and rapidly collected in lysosomes, the waste disposal system for the cells. Whilst the cells performed their usual function of increasing enzymes within lysosomes to breakdown this unwanted cargo, the study found that around 85% of Ab still remained within lysosomes, meaning that over time the toxic molecules would continue to accumulate inside RPE cells.

Furthermore, the researchers discovered that once lysosomes had been invaded by Ab, around 20 percent fewer lysosomes were available to breakdown photoreceptor outer segments, a role they routinely perform as part of the daily visual cycle.

Dr Ratnayaka added, “This is a further indication of how cells in the eye can deteriorate over time because of these toxic molecules collecting inside RPE cells. This could be a new pathway that no-one has explored before. Our discoveries have also strengthened the link between diseases of the eye and the brain. The eye is part of the brain and we have shown how Ab which is known to drive major neurological conditions such as Alzheimer’s disease can also causes significant damage to cells in retina.”

The researchers hope that one of the next steps could be for anti-amyloid beta drugs, previously trialled in Alzheimer’s patients, to be re-purposed and trialled as a possible treatment for age-related macular degeneration. As the regulators in the USA and the European Union have already given approval for many of these drugs, this is an area that could be explored relatively quickly.

The study may also help wider efforts to largely by-pass the use of animal experimentation where possible, so some aspects of testing new clinical treatments can transition directly from cell models to patients.

This research was funded by the National Centre for the Replacement Refinement & Reduction of animals in research (NC3Rs). Dr Katie Bates, Head of Research Funding at the NC3Rs said:

‘This is an impactful study that demonstrates the scientific, practical and 3Rs benefits to studying AMD-like retinal pathology in vitro.’

Animal studies were overseen by the institutions’ Ethical Research Committee and carried out in accordance with the UK Animal (Scientific Procedures) Act of 1986. Experiments also conformed to the ARVO statement for the Use of Animals in Ophthalmic and Vision Research. The experimental protocol was approved by the University of Southampton Research Ethics Committee and work carried out under the UK Home Office project licence #P395C9E5F (licence approval date: 4 July 2016).

The study “Oligomeric Aβ1-42 Induces an AMD-Like Phenotype and Accumulates in Lysosomes to Impair RPE Function” has been published in Cells with DOI https://doi.org/10.3390/cells10020413


Provided by University of Southampton

Variant B.1.1.7 of COVID-19 Associated With a Significantly Higher Mortality Rate

Variant B.1.1.7 of COVID-19 associated with a significantly higher mortality rate, research shows

The highly infectious variant of COVID-19 discovered in Kent, which swept across the UK last year before spreading worldwide, is between 30 and 100 per cent more deadly than previous strains, new analysis has shown.

A pivotal study, by epidemiologists from the Universities of Exeter and Bristol, has shown that the SARS-CoV-2 variant, B.1.1.7, is associated with a significantly higher mortality rate amongst adults diagnosed in the community compared to previously circulating strains.

The study compared death rates among people infected with the new variant and those infected with other strains.

It showed that the new variant led to 227 deaths in a sample of 54906 patients – compared to 141 amongst the same number of closely matched patients who had the previous strains.

With the new variant already detected in more than 50 countries worldwide, the analysis provides crucial information to governments and health officials to help prevent its spread.

The study is published in the British Medical Journal on Wednesday, 10 March 2021.

Robert Challen, lead author of the study from the University of Exeter said: “In the community, death from COVID-19 is still a rare event, but the B.1.1.7 variant raises the risk. Coupled with its ability to spread rapidly this makes B.1.1.7 a threat that should be taken seriously.”

The Kent variant, first detected in the UK in September 2020, has been identified as being significantly quicker and easier to spread, and was behind the introduction of new lockdown rules across the UK from January.

The study shows that the higher transmissibility of the Kent strain meant that more people who would have previously been considered low risk were hospitalised with the newer variant.

Having analysed data from 54609 matched pairs of patients of all age-groups and demographics, and differing only in strain detected, the team found that there were 227 deaths attributed to the new strain, compared to 141 attributable to earlier strains.

Leon Danon, senior author of the study from the University of Bristol said: “We focussed our analysis on cases that occurred between November 2020 and January 2021, when both the old variants and the new variant were present in the UK. This meant we were able to maximise the number of “matches” and reduce the impact of other biases. Subsequent analyses have confirmed our results.

“SARS-CoV-2 appears able to mutate quickly, and there is a real concern that other variants will arise with resistance to rapidly rolled out vaccines. Monitoring for new variants as they arise, measuring their characteristics and acting appropriately needs to be a key part of the public health response in the future.”

Ellen Brooks-Pollock from the University of Bristol expanded: “It was fortunate the mutation happened in a part of the genome covered by routine testing. Future mutations could arise and spread unchecked”.


Reference: Challen R, Brooks-Pollock E, Read J M, Dyson L, Tsaneva-Atanasova K, Danon L et al. Risk of mortality in patients infected with SARS-CoV-2 variant of concern 202012/1: matched cohort study BMJ 2021; 372 :n579 doi: 10.1136/bmj.n579


Provided by University of Exeter

The Secret of Catalysts that Increase Fuel Cell Efficiency (Chemistry)

POSTECH·UNIST joint research team reveals the phase transition and metal ex-solution phenomena to increase the catalytic activity

Fuel cells, which are attracting attention as an eco-friendly energy source, obtain electricity and heat simultaneously through the reverse reaction of water electrolysis. Therefore, the catalyst that enhances the reaction efficiency is directly connected to the performance of the fuel cell. To this, a POSTECH-UNIST joint research team has taken a step closer to developing high-performance catalysts by uncovering the ex-solution and phase transition phenomena at the atomic level for the first time.

A joint research team of Professor Jeong Woo Han and Ph.D. candidate Kyeounghak Kim of POSTECH’s Department of Chemical Engineering, and Professor Guntae Kim of UNIST have uncovered the mechanism by which PBMO – a catalyst used in fuel cells – is transformed from perovskite structure to layered structure with nanoparticles ex-solution*1 to the surface, confirming its potential as an electrode and a chemical catalyst. These research findings were recently published as an outside back cover paper of the Energy & Environmental Science, an international journal in the field of energy.

© POSTECH

Catalysts are substances that enhance chemical reactions. PBMO (Pr0.5Ba0.5MnO3-δ), one of the catalysts for fuel cells, is known as a material that stably operates even when directly used as a hydrocarbon, not hydrogen. In particular, it exhibits high ionic conductivity as it changes to a layered structure under a reduction environment that loses oxygen. At the same time, the ex-solution phenomenon occurs in which the elements inside the metal oxide segregate to the surface.

This phenomenon occurs voluntarily under a reduction environment without any particular process. As the elements inside the material rise to the surface, the stability and performance of the fuel cell improve immensely. However, it was difficult to design the materials because the process through which these high-performance catalysts were formed was unknown.

© POSTECH

Focusing on these features, the research team confirmed that the process goes through a progression of phase transition, particle ex-solution, and catalyst formation. This was proved using the first-principles calculation based on quantum mechanics and the in-situ XRD*2 experiment that allows the observation of real-time crystal structural changes in materials. The researchers also confirmed that the oxidation catalyst developed this way displays up to four times better performance than the conventional catalysts, verifying that this study is applicable to various chemical catalysts.

“We were able to accurately understand the materials in atomic units that were difficult to confirm in previous experiments, and successfully demonstrated it thus overcoming the limitations of existing research by accurately understanding materials in atomic units, which were difficult to confirm in existing experiments, and successfully demonstrating them,” explained Professor Jeong Woo Han who led the study. “Since these support materials and nanocatalysts can be used for exhaust gas reduction, sensors, fuel cells, chemical catalysts, etc., active research in numerous fields is anticipated in the future.”

This research was conducted with the support from the Samsung Research Funding & Incubation Center and the Korea Institute of Energy Technology Evaluation and Planning.
 


1. Ex-solution
An elution. An operation that heats metal mixtures to separate its components.

2. XRD (X-Ray Diffraction)
An analysis method that identifies the crystal structure of a material based on diffraction occurring at a specific angle when X-Ray is irradiated on a material.


Reference: Kyeounghak Kim et al. “Mechanistic insights into the phase transition and metal ex-solution phenomena of Pr0.5Ba0.5Mn0.85Co0.15O3−δ from simple to layered perovskite under reducing conditions and enhanced catalytic activity, Energy and Environmental Science, 2021. https://pubs.rsc.org/en/content/articlelanding/2021/EE/D0EE02875D#!divAbstract


Provided by POSTECH

Sonic Dirac Points And The Transition Towards Weyl Points (Physics)

Recently, the three-dimensional (3D) Dirac points and 3D Dirac semimetals have attracted tremendous attention in the field of topological physics. The 3D Dirac point is a fourfold band crossing in 3D momentum space, which can be view as the degeneracy of two opposite Weyl points. However, the 3D Dirac points can be described by the Z2 topological invariant other than the Chern number. The topological property of 3D Dirac point is not totally the same as Weyl point. Besides, the transition from Dirac points to Weyl points has not been experimentally studied in both photonic and acoustic systems so far. Therefore, the theoretical or experimental breakthrough of 3D Dirac points and the study on their transition is of great significance further research and application.

In a new paper published in Light Science & Application, a team of scientists, led by Professor Shuqi Chen from The Key Laboratory of Weak Light Nonlinear Photonics, School of Physics, Nankai University, China, and co-workers have achieved the theoretical and experimental realization of a pair of class I acoustic 3D Dirac points in a hexagonal sonic crystal and demonstrate how the exotic features of the surface states and interface states evolve in the transition towards Weyl points. The transition from two Dirac points to two pairs of Weyl points is realized by introducing chiral hopping into the Dirac sonic crystal. Correspondingly, the surface state dispersion evolves from connecting Dirac points to connecting Weyl points. Pseudospin-polarized helical states, which link the two Dirac points in momentum space, are created through particular interface design using sublattice pseudospin inversion.

a Band dispersion along the direction. b,c Band dispersion in the reduced 2D planes at and . d,e Equifrequency contours with for d the 3D Dirac sonic crystal and e the Weyl sonic crystal at frequencies of 12.76 kHz (WP1), 13.67 kHz (DP) and 14.06 kHz (WP2). The colour maps represent the strength of the states probed in the sonic crystal. The green dashed lines represent the calculated values obtained from full-wave simulations. © by Boyang Xie, Hui Liu, Hua Cheng, Zhengyou Liu, Jianguo Tian, and Shuqi Chen

The Dirac and Weyl sonic crystals were fabricated by 3D printing based on a layer-stacking strategy. Both the bulk and surface band structures are obtained, showing the topological feature in surface and interface states. The experiment results are consistent with the simulation results. These scientists summarize the principle results:

“We study the 3D Dirac sonic crystal for three purposes: (1) to realize a 3D Dirac point with band inversion in acoustics; (2) to realize the pseudospin-polarized interface states in acoustic semimetals; and (3) to experimentally study how the surface states act in the transition from Dirac points to Weyl points.”

a schematic of the interface formed by swapping the large and small tubes. b Measured real-space interface wave propagation excited by a point-like source at the Dirac frequency. The position of the sound source is indicated by a red star. c Fourier-transformed equifrequency contours for the data in b. The black spheres represent the projections of the Dirac points. d Interface band dispersion for kz = 0, 0.2π/h and 0.4π/h. The green solid lines represent the simulated interface states. The shaded areas represent the calculated projected bulk bands. e Schematic of the interface formed by swapping the large and small tubes and inverting the chirality of slanted tubes of the Weyl sonic crystal. f, g Equifrequency contours at f WP1 frequency and at g Dirac frequency. © by Boyang Xie, Hui Liu, Hua Cheng, Zhengyou Liu, Jianguo Tian, and Shuqi Chen

“The helical states from 3D Dirac sonic crystal can be inherited by the Weyl sonic crystal, while more exotic interface states can arise with the chirality inversion.” they added.

“The presented pseudospin-polarized interface states and the chiral interface states correspond to different regions in momentum space and different frequencies, which may further inspire the design of topological devices using both kinds of interface states. We hope our work will inspire the design of weak topological insulators, the realization of acoustic hinge states, and the design of other 3D topological devices.” the scientists forecast.

Featured image: a, A 3D Dirac sonic crystal and its transition to a Weyl sonic crystal. a Photograph of the 3D Dirac sonic crystal. b,c Geometry of the unit cells for b the 3D Dirac sonic crystal and c the Weyl sonic crystal with additional chiral hopping tubes. The insets of b and c show top-view images of the 3D Dirac and Weyl sonic crystals. One unit cell is outlined with a red hexagon for each sonic crystal. d The Brillouin zone (BZ) of the 3D Dirac sonic crystal. e The band structure of the 3D Dirac sonic crystal where a Dirac point (DP) is located on . f Tight-binding model of the 3D Dirac sonic crystal, including nearest-neighbour hopping and next-nearest-neighbour hopping. g The BZ of the Weyl sonic crystal, where each 3D Dirac point splits into a pair of Weyl points, WP1 and WP2, with charges of +1 and -1, respectively. h The band structure of the Weyl sonic crystal. States with positive orbital angular momentum (OAM) and negative OAM are represented by red and blue lines, respectively. i Additional chiral interlayer coupling in the Weyl sonic crystal. The arrows represent the direction of positive phase hopping. © by Boyang Xie, Hui Liu, Hua Cheng, Zhengyou Liu, Jianguo Tian, and Shuqi Chen


Reference: Xie, B., Liu, H., Cheng, H. et al. Dirac points and the transition towards Weyl points in three-dimensional sonic crystals. Light Sci Appl 9, 201 (2020). https://www.nature.com/articles/s41377-020-00416-2 https://doi.org/10.1038/s41377-020-00416-2


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