Category: 7. Science

Platelets are probably best known for their role in blood clotting, making scabs and related, if less salubrious, contributions to heart attacks and strokes. But these tiny, saucer-shaped blood cells have other physiological duties as well, including surveillance for viral or bacterial infections, the recruitment of immune cells to the site of a suspected incursion and even the direct destruction of pathogens. Now, thanks to the findings of a Ludwig Cancer Research study, we can add to this rich portfolio an additional and critically important function.

Researchers led by Ludwig Oxford’s Bethan Psaila and postdoc Lauren Murphy report in the current issue of Science that platelets may also help suppress systemic inflammation. Better yet, the way they do so can be readily harnessed to significantly improve the early and minimally invasive detection of cancer and the sensitivity of prenatal screening.

While platelets do not have their own nuclei, we discovered that they act like sponges, mopping up the fragments of DNA that are released by dead and dying cells. Our bodies employ multiple mechanisms to clear these bits of DNA from the bloodstream, as they can provoke inflammatory and autoimmune disorders if they accumulate. Our findings suggest platelets play an important role in limiting the abundance of DNA fragments in plasma. Fascinatingly, we also discovered that they then release these pieces of DNA when they are activated, suggesting that platelets can deploy their DNA cargo in a manner that prevents nonspecific inflammation yet elicits targeted inflammatory responses where they’re needed, such as, say, at a site of injury.”

Bethan Psaila, Ludwig Oxford

Cell-free (cf) DNA can also include traces of circulating tumor cell-derived DNA (ctDNA). An increasingly sophisticated suite of technologies now exists to isolate and analyze ctDNA for the noninvasive detection of cancers and monitoring of responses to therapy. But ctDNA levels are very low, especially in the earliest stages of disease, when cancers are best detected. Its rarity reduces the sensitivity of cancer screening by such “liquid biopsies”.

As it happens, the cfDNA collected for these diagnostics is currently isolated from blood plasma after all the blood cells, including platelets, have been discarded. The findings of this study suggest that a substantial proportion of cfDNA, including that derived from tumor cells, is contained within platelets, and this important source of information is therefore being missed.

“We’ve demonstrated that platelets take up DNA fragments that bear the mutational signatures of cancer cells,” said Murphy. “This is true not only in patients with advanced cancer but, remarkably, also in people who have pre-cancerous polyps in their colon, suggesting that platelets may offer an additional and so far untapped reservoir of cfDNA that could significantly improve the sensitivity of liquid biopsies.”

The finding that circulating platelets bear the genetic signatures of cancer has significant implications for cancer prevention.

What prompted the researchers to look for DNA in cells that lack a nucleus?

Platelets have a notable morphological quirk: they’re shot through, like sponges, with a network of membrane-lined channels called the open canalicular system. These channels allow them to release certain biomolecules essential to clotting and tissue repair upon activation and to pick up others, like viral RNA and DNA, as they circulate. Given the latter capability, Psaila hypothesized several years ago at a multi-institutional, cross-disciplinary brainstorming session organized by the philanthropy Cancer Research UK that platelets might also be picking up genomic cfDNA.

In partnership with senior author Chris Gregory at the University of Edinburgh, Psaila prepared a pitch, winning a small award that allowed her to hire a research assistant, Murphy, to validate this hypothesis. A year later, the researchers had exciting data that helped Murphy secure a position in a PhD program and a major early detection project grant from Cancer Research UK.

They and their colleagues, including Ludwig Oxford’s Benjamin Schuster-Böckler, whose lab conducted computational analysis for this study, showed that platelets indeed mop up human cfDNA in lab cultures and clinical samples. To prove that they weren’t just seeing residual DNA from megakaryocytes-nucleated cells from which platelets are derived-the researchers examined DNA from the platelets of pregnant women known to be carrying males. They report that they could predict the sex of the baby in every blood sample they analyzed by detecting fragments of the Y chromosome in the platelets, which could only have come from fetal cfDNA they’d mopped up in their travels.

“Given their abundance, ease of isolation and tissue-wide perfusion, platelets are ideally positioned to serve as biosensors for genetic perturbations across tissues,” said Psaila.

Future work in the lab will seek to clarify the role of platelets in the physiological management of cfDNA and the fate and consequences of DNA fragments released upon platelet activation.

This study was funded by Ludwig Cancer Research, Cancer Research UK, the UK Medical Research Council, Rosetrees Trust, Kidani Memorial Trust and Yosemite.

Bethan Psaila is an associate member of the Oxford Branch of the Ludwig Institute for Cancer Research and an associate professor in hematology at the University of Oxford.

Scientists from Trinity College Dublin have discovered that electrically stimulating “macrophages” – one of the immune systems key players – can “reprogram” them in such a way to reduce inflammation and encourage faster, more effective healing in disease and injury. 

This breakthrough uncovers a potentially powerful new therapeutic option, with further work ongoing to delineate the specifics.

Macrophages are a type of white blood cell with several high-profile roles in our immune system. They patrol around the body, surveying for bugs and viruses, as well as disposing of dead and damaged cells, and stimulating other immune cells – kicking them into gear when and where they are needed.

However, their actions can also drive local inflammation in the body, which can sometimes get out of control and become problematic, causing more damage to the body than repair. This is present in lots of different diseases, highlighting the need to regulate macrophages for improved patient outcomes. 

In the new study, just published in the international journal Cell Reports Physical Science, the Trinity team worked with human macrophages isolated from heathy donor blood samples provided via the Irish Blood Transfusion Board, St James’s Hospital. They stimulated these cells using a custom bioreactor to apply electrical currents and measured what happened.

The scientists discovered that this stimulation caused a shift of macrophages into an anti-inflammatory state that supports faster tissue repair; a decrease in inflammatory marker (signalling) activity; an increase in expression of genes that promote the formation of new blood vessels (associated with tissue repair as new tissues form); and an increase in stem cell recruitment into wounds (also associated with tissue repair).

We have known for a very long time that the immune system is vital for repairing damage in our body and that macrophages play a central role in fighting infection and guiding tissue repair.” 

Dr. Sinead O’Rourke, Research Fellow in Trinity’s School of Biochemistry and Immunology, and first author of the research article

“As a result, many scientists are exploring ways to ‘reprogram’ macrophages to encourage faster, more effective healing in disease and to limit the unwanted side-effects that come with overly aggressive inflammation. And while there is growing evidence that electrical stimulation may help control how different cells behave during wound healing, very little was known about how it affects human macrophages prior to this work.”

“We are really excited by the findings. Not only does this study show for the first time that electrical stimulation can shift human macrophages to suppress inflammation, we have also demonstrated increased ability of macrophages to repair tissue, supporting electrical stimulation as an exciting new therapy to boost the body’s own repair processes in a huge range of different injury and disease situations.”

The findings from the interdisciplinary team led by Trinity investigators, Professor Aisling Dunne (School of Biochemistry and Immunology) and Professor Michael Monaghan (School of Engineering) is especially significant given that this work was performed with human blood cells (showing its effectiveness for real patients), electrical stimulation is relatively safe and easy in the scheme of therapeutic options, and the outcomes should be applicable to a wide range of scenarios.

Corresponding author Prof. Monaghan added: “Among the future steps are to explore more advanced regimes of electrical stimulation to generate more precise and prolonged effects on inflammatory cells and to explore new materials and modalities of delivering electric fields. This concept has yielded compelling effects in vitro and has huge potential in a wide range of inflammatory diseases.”

SLAC National Accelerator Laboratory and University of Nevada, Reno scientists have debunked a 40-year-old theory by heating solid gold to 14 times its normal melting point without melting it!

The scientists achieved this feat and rewrote the rules of high-temperature physics using a combination of ultrafast lasers and X-rays.

Understanding Entropy Catastrophe

For nearly 40 years, physicists have believed there is a hard limit to how hot a solid can get without spontaneously breaking apart. 

Known as the “entropy catastrophe,” this theory holds that once a material reaches around three times its melting point, the increased entropy overwhelms its structure, causing it to liquefy.

Hotter Than the Sun

SLAC’s recent experiment, however, challenges this long-standing belief.

The scientists hit a wafer-thin gold film with a 45-femtosecond laser pulse. They followed it up with a flash from SLAC’s 2-mile-long Linac Coherent Light Source X-ray laser that functioned as an atomic thermometer.

While gold’s normal melting point is 1,337 kelvins (1,947°F), the scientists, by observing how the X-rays scattered off the vibrating gold atoms, calculated a mind-boggling 19,000 kelvins (33,740°F) — hotter than even the Sun’s surface (9,900°F)!

And the best part? By heating the material so fast, the atoms didn’t have time to reorganize into a liquid structure. SLAC’s process basically outran the material’s natural melting behavior.

The Future of Thermodynamics

Ask any particle scientist, and they’ll tell you how tough it is to measure and understand extreme states of matter, such as those found in the cores of gas giants like Jupiter or inside fusion reactors on Earth. Even if they do, it would be plagued by large error bars.

By shattering the temperature barrier, the SLAC-Nevada team has now shown it is possible to probe the inner temperatures within ultra-hot systems accurately.

Image credit: artshock/Shutterstock

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An increasing number of applications in exoplanetary science require spectrographs with high resolution and high throughput without the need for a broad spectral range.

Examples include the search for biosignatures through the detection of the oxygen A-band at 760 nm, and the study of atmospheric escape through the helium 1083 nm triplet. These applications align well with the capabilities of a spectrograph based on a Virtually Imaged Phased Array (VIPA), a high-throughput dispersive element that is essentially a modified Fabry-Perot etalon.

We are developing VIPER, a high-resolution, narrowband, multimode fiber-fed VIPA spectrograph specifically designed to observe the helium 1083 nm triplet absorption line in the atmospheres of gaseous exoplanets. VIPER will achieve a resolving power of 300,000 over a wavelength range of 25 nm, and will be cross-dispersed by an echelle grating. VIPER is intended for operation on the 1.5 m Tillinghast Telescope and potentially on the 6.5 m MMT, both located at the Fred Lawrence Whipple Observatory (FLWO) on Mount Hopkins, Arizona, USA.

In this paper, we present VIPER’s instrument requirements, derived from the primary science goal of detecting anisotropic atmospheric escape from exoplanets. We discuss the design methodology for VIPA-based spectrographs aimed at maximizing throughput and diffraction efficiency, and we derive a wave-optics-based end-to-end model of the spectrograph to simulate the intensity distribution at the detector.

We present an optical design for VIPER and highlight the potential of VIPA-based spectrographs for advancing exoplanetary science.

Matthew C. H. Leung, David Charbonneau, Andrew Szentgyorgyi, Colby Jurgenson, Morgan MacLeod, Surangkhana Rukdee, Shreyas Vissapragada, Fabienne Nail, Joseph Zajac, Andrea K. Dupree

Comments: 39 pages, 27 figures, SPIE Optics + Photonics 2025
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2508.20169 [astro-ph.IM](or arXiv:2508.20169v1 [astro-ph.IM] for this version)
https://doi.org/10.48550/arXiv.2508.20169
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From: Matthew Leung
[v1] Wed, 27 Aug 2025 18:00:04 UTC (4,856 KB)
https://arxiv.org/abs/2508.20169
Astrobiology

Polluted white dwarfs offer a unique way to directly probe the compositions of exoplanetary bodies.

We examine the water content of accreted material using the oxygen abundances of 51 highly polluted white dwarfs. Within this sample, we present new abundances for three H-dominated atmosphere white dwarfs that showed promise for accreting water-rich material.

Throughout, we explore the impact of the observed phase and lifetime of accretion disks on the inferred elemental abundances of the parent bodies that pollute each white dwarf. Our results indicate that white dwarfs sample a range of dry to water-rich material, with median uncertainties in water mass fractions of ≈15%.

Amongst the He-dominated white dwarfs, 35/39 water abundances are consistent with corresponding H abundances. While for any individual white dwarf it may be ambiguous as to whether or not water is present in the accreted parent body, when considered as a population the prevalence of water-rich bodies is statistically robust.

The population as a whole has a median water mass fraction of ≈25%, and enforcing chondritic parent body compositions, we find that 31/51 WDs are likely to have non-zero water concentrations. This conclusion is different from a similar previous analysis of white dwarf pollution and we discuss reasons why this might be the case.

Pollution in H-dominated white dwarfs continues to be more water-poor than in their He-dominated cousins, although the sample size of H-dominated white dwarfs remains small and the two samples still suffer a disjunction in the range of host star temperatures being probed.

Isabella L. Trierweiler, Carl Melis, Érika Le Bourdais, Patrick Dufour, Alycia J. Weinberger, Boris T. Gänsicke, Nicola Gentile-Fusillo, Siyi Xu, Jay Farihi, Andrew Swan, Malena Rice, Edward D. Young

Comments: 30 pages, 14 figures Accepted to ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2508.20172 [astro-ph.EP] (or arXiv:2508.20172v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2508.20172
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From: Isabella Trierweiler
[v1] Wed, 27 Aug 2025 18:00:07 UTC (1,655 KB)
https://arxiv.org/abs/2508.20172
Astrobiology

For decades, humans have imagined that the universe might be filled with intelligent life. Yet despite billions of stars and galaxies, we have found no clear evidence of aliens. Now, scientists suggest a possible reason: Earth may be located in an enormous cosmic void—a vast, sparsely populated region of space. If true, our planet could be unusually isolated from the denser regions of the universe, giving the appearance that humanity is alone or even “ostracized” in the cosmic landscape.

This theory, presented at the Royal Astronomical Society’s National Astronomy Meeting, has been led by Dr. Indranil Banik of the University of Portsmouth. The discovery could have far-reaching implications for our understanding of the universe’s structure and expansion.

Dr. Banik’s team explained that the local void, also referred to as an underdensity, could be roughly one billion light-years wide and about 20% less dense than the average universe. This sparsity of matter would affect how we perceive galaxy movements, potentially making it appear that the universe is expanding faster than it actually is.

Possible Solution to the Hubble Tension

The idea of a local cosmic void provides a potential explanation for the long-standing Hubble Tension, which arises from discrepancies in measuring the universe’s expansion rate. Observations of distant galaxies suggest a slower expansion, while local measurements indicate a faster rate. According to Dr. Banik, if the Milky Way is located inside a vast void, gravitational effects from denser surrounding regions would pull matter outward, making local velocities seem larger.

“This model, based on two decades of baryon acoustic oscillation data, is significantly more likely than a void-free model,” Dr. Banik said, highlighting the consistency of his team’s findings with patterns left from the Big Bang.

Implications for Cosmology

If confirmed, the local void theory challenges the assumption that the universe is uniform on large scales. It would also have consequences for predictions about the universe’s future, including the timing of the so-called “heat death,” when energy is evenly distributed and no significant cosmic activity occurs.While the idea of humans living in a cosmic void is still debated, Banik’s research strengthens the possibility that our region of the universe may be lonelier than previously thought. By analyzing oscillations caused by the early universe, his team has provided evidence that supports the existence of this massive void.

Life in the Void

Living in a cosmic void could have indirect implications for humanity, as it affects how we perceive the universe around us. Although the void does not directly indicate alien activity or ostracization, it does suggest that our cosmic neighborhood is isolated compared to denser regions of the universe.

Further research, including comparisons with supernova data, will be necessary to fully validate this theory and understand its consequences for cosmology. For now, Earth’s place in a giant cosmic void remains a compelling possibility that may reshape how scientists view the universe.

A groundbreaking study by researchers from Wuhan University, York University (UK), and Peking University has uncovered how Escherichia coli (E. coli) persister bacteria survive antibiotics by protecting their genetic instructions. The work, published in Nature Microbiology, offers new hope for tackling chronic, recurring infections.

Persister bacteria, which enter a dormant state to survive antibiotics that target active cells, are linked to over 20% of chronic infections and resist current treatments. Understanding their survival mechanisms could lead to new ways to combat recurring infections. This study utilized E. coli bacteria as a model and found that prolonged stress leads to the increased formation of aggresomes (membraneless droplets) and the enrichment of mRNA (molecules that carry instructions for making proteins) within them, which enhances the ability of E. coli to survive and recover from stress.

Key findings

They used multiple approaches, including imaging, modeling, and transcriptomics, to show that prolonged stress leading to ATP(fuel for all living cells) depletion in Escherichia coli results in increased aggresome formation, their compaction, and enrichment of mRNA within aggresomes compared to the cytosol(the liquid inside of cells). Transcript length was longer in aggresomes compared to the cytosol. Mass spectrometry showed exclusion of mRNA ribonuclease(an enzyme that breaks down RNA) from aggresomes, which was due to negative charge repulsion. Experiments with fluorescent reporters and disruption of aggresome formation showed that mRNA storage within aggresomes promoted translation and was associated with reduced lag phases during growth after stress removal. These findings suggest that mRNA storage within aggresomes confers an advantage for bacterial survival and recovery from stress.

Future implications

This breakthrough illuminates how persister cells survive and revive after antibiotic treatment. By targeting aggresomes, new drugs could disrupt this protective mechanism, preventing bacteria from storing mRNA and making them more vulnerable to elimination, thus reducing the risk of infection relapse.

This white paper is a summary of the Uranus Flagship Workshop that took place 21 to 23 May 2024 at NASA’s Goddard Space Flight Center. Co-led by Goddard and Johns Hopkins Applied Physics Lab conveners, we had a broad, international, Science Organizing Committee, and a largely early career Local Organizing Committee from APL and GSFC.

From prior workshops, it was apparent that the community was wildly enthusiastic about starting a mission, but lacked focus on what was possible or where to begin. Thus, the purpose of our workshop was to discuss practical aspects of the next planetary flagship and how we can employ new paradigms to better enable robust outer planet exploration.

To enable this goal, we introduced the community to the best practices and lessons learned from previous missions and NASA-commissioned studies, and discussed the challenges involved with a mission so far from the Earth/Sun.

The underlying workshop purpose was to steward the community towards a more practical mission design approach that will enable the development of this mission, as well as future missions, on a shorter cadence by setting expectations and having difficult discussions early in development. Because of the time scales involved in this mission, special effort was made towards early career inclusion and participation.

Amy Simon, Louise Prockter, Ian Cohen, Kathleen Mandt, Lynnae Quick

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2508.21074 [astro-ph.IM] (or arXiv:2508.21074v1 [astro-ph.IM] for this version)
https://doi.org/10.48550/arXiv.2508.21074
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From: Amy Simon
[v1] Mon, 11 Aug 2025 12:57:46 UTC (2,876 KB)
https://arxiv.org/abs/2508.21074
Astrobiology,

The occurrence rate of close-in super-Earths is higher around M-dwarfs compared to stars of higher masses.

In this work we aim to understand how the super-Earth population is affected by both the stellar mass, the size of the protoplanetary disc, and viscous heating. We utilise a standard protoplanetary disc model with both irradiated and viscous heating together with a pebble accretion model to simulate the formation and migration of planets.

We find that if the disc is heated purely through stellar irradiation, inwards migration of super-Earths is very efficient, resulting in the close-in super-Earth fraction increasing with increasing stellar mass.

In contrast, when viscous heating is included, planets can undergo outwards migration, delaying migration to the inner edge of the protoplanetary disc, which causes a fraction of super-Earth planets to grow to become giant planets instead.

This results in a significant reduction of inner super-Earths around high-mass stars and an increase in the number of giant planets, both of which mirror observed features of the planet population around high-mass stars. This effect is most pronounced when the protoplanetary disc is large, since such discs evolve over a longer time-scale. We also test a model when we inject protoplanets at a fixed time early on in the disc lifetime.

In this case, the fraction of close-in super-Earths decreases with increasing stellar mass in both the irradiated case and viscous case, since longer disc lifetimes around high-mass stars allows for planets to grow into giants instead of super-Earths for most injection locations.

Jesper Nielsen, Anders Johansen

Comments: 19 Pages, 16 figures, accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2508.21627 [astro-ph.EP] (or arXiv:2508.21627v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2508.21627
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From: Jesper Nielsen
[v1] Fri, 29 Aug 2025 13:39:28 UTC (3,995 KB)
https://arxiv.org/abs/2508.21627
Astrobiology,