How Would Be Fuzzballs Shadow? (Quantum / Astronomy / Cosmology)

Last week, I wrote an article entitled, “Can black holes reflect light?” in which we saw that a horizonless quantum blackhole (BH) called “fuzzballs”, reflect light. Now, Fabio Bacchini and colleagues studied the behavior of null geodesics (light rays) in four-dimensional fuzzball geometries and used this to obtained the first images of fuzzball shadows as they would be perceived by a distant observer.

They first constructed a novel axisymmetric scaling solution which they named the “ring fuzzball”. The ring fuzzball solution allows for the “scaling limit” λ → 0, in which it approaches the metric of the static, supersymmetric BH with

V = L_I = 0, K^I = 1 + 2P/r , M = − 1/2 + (P³ − q0)/ r

This BH has mass 2M_BH = 3P +q0−P³ and a horizon at r = 0 with area A_BH = 16π P³(q0 − P³). The angular momentum of the (static) BH vanishes while the ring fuzzball has J = 2P³(1 − 3P²)λ. Note that this ring fuzzball represents the first ever explicitly constructed (exactly) scaling solution that is axisymmetric.

Thus, their analysis of this (axisymmetric scaling solution) confirms that, as far as the behavior of geodesics is concerned, fuzzballs in the scaling limit can resemble BH geometries arbitrarily well. It also reveals the key features and mechanisms of fuzzballs through which such phenomenological horizon behavior emerges.

FIG. 1: From left to right columns: visualizations of diagnostics for the ring fuzzball (P = 2 and q0 = 50) for decreasing values of λ, compared to the λ → 0 BH in the rightmost column. Rows from top to bottom: four-color screen indicating the portion of the celestial sphere from which geodesics originate; coordinate time t elapsed at the end of the numerical integration (normalized to MBH); strongest redshift experienced by the geodesic (normalized to the redshift at the camera position); strongest curvature encountered (normalized to K at the BH horizon). © Bacchini et al.

The images presented in their paper are the first visualizations of fuzzball geometries. They confirmed several physical properties of microstate geometries which had generally been anticipated but never verified, such as their trapping behavior. They found that, as the ring fuzzball approaches the BH limit, its microstructure induces increasingly chaotic motion of geodesics (light-rays) straying in the near-center region. Infalling geodesics that reach the microstructure/fuzzball will be heavily blueshifted and subsequently backreact with the structure and/or be heavily scattered. The light that will emanate from this region will then be too redshifted to be detectable. In this way, the fuzzball/microstructure conspires to create a shadow very much like that of a BH, while avoiding the paradoxes associated with an event horizon.

FIG. 2: Left panel: three-dimensional visualization of a representative geodesic in the near-center region of the ring fuzzball geometry with P = 2, q0 = 50 and λ = 0.01. The on-axis centers and the charged ring are shown in red. Middle column: a short portion of the same trajectory projected on the φ = π/2 plane, colored by elapsed time (top) an local redshift (bottom). Right column: the full chaotic trajectory shown until the final integration time. © Bacchini et al.
FIG. 3: Visualization of ring fuzzballs with P = 1/4, λ = 0.1 (top left), P = 307/500, λ = 0.3 (top right), P = 7/8, λ = 0.11 (bottom left), compared to an extremal Kerr-Newman BH (bottom right) of equal mass (and same angular momentum as the bottom left fuzzball). All images are darkened according to the maximal redshift encountered by each geodesic. The two bottom pictures exhibit minimal but non-zero differences. © Bacchini et al.

You can see in fig 3, it clearly shows that, depending on the value of P, λ, fuzzballs can mimic black holes to different degree. In particular, fuzzball shadows can appear very dark, but with a much smaller area (top left); or, while the shadow size can be within observational uncertainty bounds, a weak redshift may make fuzzballs appear too bright (top right). With the appropriate parameters, fuzzballs can also appear indistinguishable from actual black holes (Bottom left)


Their results indicates that fuzzballs sufficiently near the scaling limit yield a theoretically appealing and phenomenologically viable BH alternative. Vice versa, observations of a faint residual glow in the object’s shadow, or of its shadow’s size compared to its mass, have the potential to discriminate between BHs and fuzzballs somewhat away from the scaling limit. These should therefore be prime targets for current and future imaging missions such as the EHT.

“Observations of the shadow size and residual glow can potentially discriminate between fuzzballs away from the scaling limit and alternative models of black compact objects.

— told Bacchini, first author of the study.

This motivates a more detailed investigation of the characteristics that differentiate fuzzballs from BHs through the intricate structure of their shadows. This will require not only further advances in the construction of more realistic fuzzballs but also an accurate modeling of the plasma in a realistic accretion disk, coupled to full radiative transfer methods. This approach has been employed for BH geometries considered by the EHT, as well as for more exotic objects, and researchers intend to report on this elsewhere.

More broadly, the chaotic behaviour of geodesics on the would-be horizon scales also suggested that gravitational waves propagating in this region will similarly be chaotically dispersed. Therefore one expects the resulting gravitational wave signal that leaks out to be chaotic and dispersed over extended time intervals. This suggested that the post-ringdown phase of gravitational waves generated in fuzzball mergers will not exhibit a markedly clear echo structure.


Reference: Fabio Bacchini, Daniel R. Mayerson, Bart Ripperda, Jordy Davelaar, Héctor Olivares, Thomas Hertog, Bert Vercnocke, “Fuzzball Shadows: Emergent Horizons from Microstructure”, pp. 1-6, ArXiv, 22 Mar 2021. https://arxiv.org/abs/2103.12075


Copyright of this article totally belongs to our author S. Aman. One is allowed to reuse it only by giving proper credit either to him or to us

Stressed Brain Linked to Broken heart (Medicine)

Heightened activity in the brain, caused by stressful events, is linked to the risk of developing a rare and sometimes fatal heart condition, according to research published today (Friday) in the European Heart Journal [1].

The study found the greater the activity in nerve cells in the amygdala region of the brain, the sooner the condition known as Takotsubo syndrome (TTS) can develop. The researchers suggest that interventions to lower this stress-related brain activity could help to reduce the risk of developing TTS; these could include drug treatments or techniques for lowering stress.

TTS, also known as “broken heart” syndrome, is characterised by a sudden temporary weakening of the heart muscles that causes the left ventricle of the heart to balloon out at the bottom while the neck remains narrow, creating a shape resembling a Japanese octopus trap, from which it gets its name. Since this relatively rare condition was first described in 1990, evidence has suggested that it is typically triggered by episodes of severe emotional distress, such as grief, anger or fear, or reactions to happy or joyful events. Patients develop chest pains and breathlessness, and it can lead to heart attacks and death. TTS is more common in women with only 10% of cases occurring in men. [2]

The amygdala is the part of the brain that controls emotions, motivation, learning and memory. It is also involved in the control of the autonomic nervous system and regulating heart function.

“The study suggests that the increased stress-associated neurobiological activity in the amygdala, which is present years before TTS occurs, may play an important role in its development and may predict the timing of the syndrome. It may prime an individual for a heightened acute stress response that culminates in TTS,” said Dr Ahmed Tawakol, co-director of the Cardiovascular Imaging Research Center at Massachusetts General Hospital and Harvard Medical School (Boston, USA), who led the study.

“We also identified a significant relationship between stress-associated brain activity and bone marrow activity in these individuals. Together, the findings provide insights into a potential mechanism that may contribute to the ‘heart-brain connection’.”

In the first study to look at brain scans using F-fluorodeoxyglucose positron emission tomography/computed tomography (PET-CT) to assess brain activity before TTS develops, Dr Tawakol and colleagues analysed data on 104 people with an average age of 68 years, 72% of whom were women.

Image of TTS heart showing the classic Japanese octopus trap shape © European Heart Journal

The patients had undergone scans at Massachusetts General Hospital (Boston, USA) between 2005 and 2019. Most of them had the scans to see if they had cancer and the scans also assessed the activity of blood cells in bone marrow. The researchers matched 41 people who went on to develop TTS between six months and five years after the scan with 63 who did not. The interval between the scan, the onset of TTs, last follow-up or death was an average (median) of 2.5 years for the 104 patients.

Dr Tawakol said: “Areas of the brain that have higher metabolic activity tend to be in greater use. Hence, higher activity in the stress-associated tissues of the brain suggests that the individual has a more active response to stress. Similarly, higher activity in the bone marrow reflects greater bone marrow metabolism. The PET/CT scans produce images that reflect the distribution of glucose metabolism. The brain images thereby yield a map of brain metabolic activity: the higher the values, the greater the activity in those brain regions.”

The researchers found that people who went on to develop TTS had higher stress-related amygdalar activity on initial scanning (measured as a ratio of amygdalar activity to activity of brain regions that counter stress) compared to individuals who did not subsequently develop TTS. Further, the higher the amygdalar signal, the greater the risk of developing TTS. Among the 41 patients who developed TTS, the average interval between the scan and TTS was 0.9 months, whereas among the control group of 63 patients, the average interval between the scan and last follow-up or death was 2.9 years.

“It was notable that among the 41 patients who developed TTS, the top 15% with the very highest amygdalar activity developed TTS within a year of imaging, while those with less elevated activity developed TTS several years later,” said Dr Tawakol.

He said future studies should investigate whether reducing stress-related brain activity could decrease the chances of TTS recurring among patients who have experienced TTS previously.

“These findings add to evidence of the adverse effect of stress-related biology on the cardiovascular system. Findings such as these underscore the need for more study into the impact of stress reduction or drug interventions targeting these brain regions on heart health. In the meantime, when encountering a patient with high chronic stress, clinicians could reasonably consider the possibility that alleviation of stress might result in benefits to the cardiovascular system.”

The process by which stress induces TTS is not well understood but may involve a multi-organ mechanism starting with activation of the stress-sensitive tissues of the brain. This brain activity in turn triggers several further events, including release of stress hormones, activation of the sympathetic nervous system and release of inflammatory cells, each of which can contribute to the development of TTS.

Limitations of the study include that it was a single-centre, retrospective study that consisted mainly of patients with a diagnosis of cancer, a known TTS risk factor, which may limit the generalisability of the findings. The researchers were unable to measure instantaneous changes in brain activity in response to a stressful event that led to TTS and so cannot directly show a causal relationship. Nor were they able to measure changes in activity in other regions of the brain, which could also play a role.

An accompanying editorial by researchers not involved with this study has already been published [3].

Featured image: Scan of brain of someone who did not develop TTS © European Heart Journal


Notes:

[1] “Stress-associated neurobiological activity associates with the risk for and timing of subsequent Takotsubo syndrome”, by Azar Radfar et al. European Heart Journal. doi:10.1093/eurheartj/ehab029

[2] TTS affects less than 3% of people who suffer a heart attack and tends to occur between the ages of 60-75.

[3] “Brain-heart connection in Takotsubo syndrome before onset”, by Hideaki Suzuki, Satoshi Yasuda, Hiroaki Shimokawa. European Heart Journal. doi:10.1093/eurheartj/ehab026


Provided by European Society of Cardiology

Study Links Genes With Function Across the Human Brain (Neuroscience)

Comparing two neural maps reveals the roles of genes in cognition, perception and feeling

Many psychiatric disorders have genetic causes, but the exact mechanism of how genes influence higher brain function remains a mystery. A new study provides a map linking the genetic signature of functions across the human brain, a tool that may provide new targets for future treatments.

Led by Bratislav Misic, a researcher at The Neuro (Montreal Neurological Institute-Hospital) of McGill University, a group of scientists performed machine learning analysis of two Open Science datasets: the gene expression atlas from the Allen Human Brain Atlas and the functional association map from Neurosynth. This allowed them to find associations between gene expression patterns and functional brain tasks such as memory, attention, and mood.

Interestingly, the team found a clear genetic signal that separated cognitive processes, like attention, from more affective processes, like fear. This separation can be traced to gene expression in specific cell types and molecular pathways, offering key insights for future research into psychiatric disorders. Cognition, for example, was linked more to the gene signatures of inhibitory or excitatory neurons. Affective processes, however, were linked to support cells such as microglia and astrocytes, supporting a theory that inflammation of these cells is a risk factor in mental illness. The genetic signature related to affect was centred on a brain region called the anterior cingulate cortex, which has been shown to be vulnerable in mental illness.

Published in the journal Nature Human Behaviour on March 25, 2021, this study draws a direct link between gene expression and higher brain function, by mapping gene signatures to functional processes across the human brain.

“In this work we found molecular signatures of different psychological processes,” says Misic. “This is exciting because it provides a first step to understand how human thoughts and emotions arise from specific genes, biological pathways and cell types.”

This research was funded by the Canada First Research Excellence Fund, awarded to McGill University for the Healthy Brains, Healthy Lives initiative, the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs Program, the National Institutes of Health, the Canadian Institute for Advanced Research, and Google.

Featured image: A new study provides a map linking the genetic signature of functions across the human brain © The Neuro


Reference: Hansen, J.Y., Markello, R.D., Vogel, J.W. et al. Mapping gene transcription and neurocognition across human neocortex. Nat Hum Behav (2021). https://doi.org/10.1038/s41562-021-01082-z


Provided by McGill University

A Clue to How Some Fast-growing Tumors Hide in Plain Sight (Medicine)

New LJI research could guide the development of more effective cancer immunotherapies

The glow of a panther’s eyes in the darkness. The zig-zagging of a shark’s dorsal fin above the water.

Humans are always scanning the world for threats. We want the chance to react, to move, to call for help, before danger strikes. Our cells do the same thing.

The innate immune system is the body’s early alert system. It scans cells constantly for signs that a pathogen or dangerous mutation could cause disease. And what does it like to look for? Misplaced genetic material.

The building blocks of DNA, called nucleic acids, are supposed to be hidden away in the cell nucleus. Diseases can change that. Viruses churn out genetic material in parts of the cell where it’s not supposed to be. Cancer cells do too.

“Cancer cells harbor damaged DNA,” says Sonia Sharma, Ph.D., an associate professor at the La Jolla Institute for Immunology (LJI). “Mislocated DNA or aberrant DNA is a danger signal to the cell. They tell the cell, ‘There’s a problem here.’ It’s like the first ringing of the alarm bell for the immune system.”

Now Sharma and her colleagues have published a new Nature Immunology study describing the process that triggers this alert system directly inside tumor cells. Their research shows that a tumor-suppressor enzyme called DAPK3 is an essential component of a multi-protein system that senses misplaced genetic material in tumor cells, and slows tumor growth by activating the fierce-sounding STING pathway.

In the world of cancer immunotherapy, the STING pathway is well-known as a critical activator of cancer-killing T cells that kicks off the body’s powerful adaptive immune response. The new study shows that through DAPK3 and STING, the tumor’s own innate immune system plays a greater role in cancer immunity than previously appreciated.

“The tumor-intrinsic innate immune response plays an important role in natural tumor growth and cancer immunotherapy response,” says Sharma.

Tumors evolve mutations in tumor-suppressor genes that allow them to grow faster than normal tissue. Discovery of the critical role that DAPK3 plays in the STING pathway highlights a distinct problem in cancer and cancer immunotherapy. Tumor cells can acquire mutations that allow them to evade the immune system by keeping cells from sensing red flags such as misplaced DNA.

Sharma and her colleagues with the LJI Center for Cancer Immunotherapy, Max-Planck Institute of Biochemistry and UC San Diego found that loss of DAPK3 expression or function in tumor cells severely hindered STING activation. Their research in mouse models shows that these tumors were hidden from the immune system, and the researchers observed very few cancer-targeting CD8+ “killer” T cells in DAPK3-deficient tumors. As a result, loss of DAPK3 in tumors decreased responsiveness to cancer immunotherapy.

“Tumors lacking DAPK3 grow faster in vivo because they evade the immune system. They are also resistant to certain immunotherapy regimens, including combination therapies using the immune checkpoint blocker anti-PD1 to target anti-tumor T cells,” says Sharma.

Pharmaceutical companies are pursuing immunotherapies to activate STING, which are intended to be used in combination with immune checkpoint blockers. The new findings emphasize the importance of activating STING in tumor cells themselves–to properly set off that early alert system.

“Tumor-intrinsic immune responses are important,” says study co-first author Mariko Takahashi, Ph.D., a former LJI postdoctoral associate who now serves at Massachusetts General Hospital Cancer Center.

The researchers are now looking for additional proteins that play a role in the early innate immune response to cancer. “There are many players in the tumor microenvironment,” says Takahashi.

The study, “The tumor suppressor kinase DAPK3 drives tumor-intrinsic immunity through the STING-IFN-β pathway,” was supported by the National Institutes of Health (grants R01CA199376, U01DE028227, U54CA260591, S10OD020025 and R01ES027595), a Cancer Research Institute Irvington Postdoc Fellowship and the National Institute of General Medical Sciences (grant T32 GM007752).

Additional study authors include co-first author Chan-Wang J. Lio, Anaamika Campeau, Martin Steger, Ferhat Ay, Matthias Mann, David J. Gonzalez and Mohit Jain. DOI: 10.1038/s41590021-00896-3

Featured image: Misplaced or aberrant genetic material sends a danger signal. © La Jolla Institute for Immunology


Provided by LA Jolla Institute for Immunology

Scientists Observe Unusual Melting Of Diamond (Physics)

X-ray laser rips atomic bonds apart in a flash

An international team of scientists has found evidence of an unconventional melting process in diamond induced by an X-ray laser beam. While in conventional melting the atoms of a sample start moving stronger and stronger until their bonds break due to heating, the incredibly intense X-ray laser flashes ripped the bonds apart straight away, and only afterwards the atoms started moving due to heating. The scientists around Ichiro Inoue from the RIKEN SPring-8 Center in Japan, Eiji Nishibori from University of Tsukuba in Japan and DESY scientist Beata Ziaja report their observations in the journal Physical Review Letters.

X-rays are routinely used for scanning bags at airports and capturing medical images. In both cases, X-rays are produced by X-ray tubes (the X-ray equivalent of the electric light bulb). The X-ray beams from these tubes are weak because the waves making up the beams are out of sync. For more demanding applications, such as taking picosecond (trillionths of a second) snapshots of chemical reactions and studying the structures of small biomolecules, viruses, and smart materials, researchers need much more intense X-ray beams whose waves are in sync. For these applications, they use X-ray facilities known as X-ray free-electron lasers (XFELs).

XFELs generate X-ray flashes (called pulses) with femtosecond (quadrillionths of a second) durations and a peak brilliance of more than a billion times that of X-ray tubes. When the XFEL pulse is focused to micrometer- or nanometer-scale spots on a sample, many electrons are excited at once, causing irreversible structural changes. Understanding how matter responds to these intense X-ray pulses is essential for all applications. Now, the team has visualised the XFEL-matter interaction processes by using XFEL beams from the SPring-8  Angstrom Compact free electron LAser (SACLA).

The researchers used diamond as a sample and introduced a “pump-probe” technique using twin XFEL pulses: “The first pulse (pump pulse) excites the diamond and the second pulse (probe pulse) with a controlled delay time was used to investigate the structure of the sample,” explains Inoue. By carefully analysing the diffraction intensity of the probe pulse, the researchers determined the spatial electron density in diamond after the excitation with the pump pulse.

About five femtoseconds after the pump pulse, the electron distribution around each atom becomes almost uniform in all directions (isotropic). Credit: Inoue, Ziaja, Nishibori et al.

The measurement reveals that the strong ‘covalent’ bonds between the carbon atoms of the diamond are broken and the electron distribution around each atom becomes almost uniform in all directions (isotropic) within about five femtoseconds after the pump pulse, followed by the onset of the atomic movement underway to the melting. “Interestingly, the temporal order of the bond breaking and the atomic disordering is opposite to the conventional melting process, where the application of heat or pressure causes large thermal vibrations of atoms at first and later the bond breaking,” says Inoue.

The measured results were interpreted on the basis of dedicated theoretical simulations provided by a team including DESY members and international collaborators. These simulations showed that the observed displacement of carbon atoms was due to an ultrafast transition of the diamond’s crystal structure caused just by the presence of many electrons excited by the intense X-ray FEL pulse. The structure transition forced atoms to quickly relocate their positions. “This femtosecond transition is called ‘non-thermal’ as it is not triggered by a much-longer-taking, ‘thermal’ heating of atoms in the crystal lattice,” explains Ziaja. “The simulations allowed to unambiguously identify the mechanism and the stages of the observed transition which ended in rapid diamond melting.”

Additional theory considerations confirmed the correct interpretation of the information contained in the so-called diffraction patterns that the X-ray pulses leave on the detector after being scattered by the diamond’s crystal lattice. This supported the conclusion on the observed structural transition.

“The X-ray-induced non-thermal melting should be ubiquitous for many experiments with high-intensity XFEL pulses,” comments Nishibori. “In particular, our finding can make a huge impact on developing methodologies for structure determination with high-intensity XFEL pulses, as in this intensity regime, the X-ray-induced damage occurring during the irradiation cannot be neglected.”

Featured image: The X-ray laser breaks the bonds in the diamond immediately and only then the atoms start moving (artist’s impression). Credit: DESY, Gesine Born


Reference:
Atomic-scale visualization of ultrafast bond breaking in x-ray-excited diamond; Ichiro Inoue, Yuka Deguchi, Beata Ziaja, Taito Osaka, Malik M. Abdullah, Zoltan Jurek, Nikita Medvedev, Victor Tkachenko, Yuichi Inubushi, Hidetaka Kasai, Kenji Tamasaku, Eiji Nishibori, and Makina Yabashi; Physical Review Letters, 2021; DOI: 10.1103/PhysRevLett.126.117403


Provided by DESY

Astronomers Spotted Third Largest and Longest Lived Oval In Jupiter (Planetary Science)

Summary:

⦿ Barrado-Izagirre and colleagues studied a color changing anticyclone in Jupiter from 2012 to 2019.

⦿ They referred this anticyclone as NTrZ-Oval. It is the third largest and long lived oval after great red spot (GRS) and BA oval.

⦿ It’s tangential velocity and vorticity are below half the value of GRS and BA.

⦿ Despite being a weak vortex it has survived for years after mergers and disturbances.


The ubiquitous presence of vortices at cloud level is one of the most important characteristics of the meteorology of the giant planets along with the zonal winds organized in a multiple jet system. Jupiter is the most prolific planet in showing a great variety of closed circulation vortices. Vortices with sizes above 2,000 km are observed at all latitudes of the Jovian disk except very close to the Equator. Recent observations obtained by the Juno mission show also stable cyclones close to both poles. The vortices can be visually distinguished by their reflectivity contrast with respect to adjacent clouds and by their shape, showing an oval form that encircles a region of closed or nearly-closed vorticity. The surrounding cloud patterns make them appear as “bright” or “dark” ovals with sizes ranging from one hundred kilometers to 40,000 km, the maximum size measured at the end of the XIX century for the largest oval in Jupiter, the well-known Great Red Spot (GRS).

Vortices are classified according to their relative vorticity as cyclones or anticyclones. In the Northern Hemisphere, cyclones show anti-clockwise rotation while anticyclones rotate clockwise. Anticyclones appear in a great number and a variety of sizes in the anticyclonic domains of the Jovian zonal wind profile, being more stable than cyclones, except at polar latitudes where cyclones are the stable vortices. The most apparent and well known vortices, due to their longevity and size, are the Great Red Spot (GRS, planetographic mean latitude 22ºS) and oval BA (planetographic mean latitude 33ºS) (Figure 1), both anticyclones.

Figure 1: The three longest-lived and largest Jupiter ovals: GRS, oval BA and the NTrO. Observation from HST on 20th of September, 2012 in F763M filter. © Barrado–Izagirre et al.

The essential properties to understand a vortex are its vorticity distribution and its relation with the environment flow shear. Other aspects that can be important in Jovian vortices are their color, possible changes in time, and interactions with other vortices, which may include mergers (constructive interactions) or destructive interactions with eddies. In the giant planets, where the mechanisms powering the zonal winds are mostly unknown, the interaction between vortices, eddies and jets are one of the mechanisms proposed to have an important role in forcing and maintaining the zonal jets.

The first vorticity measurements in Jupiter’s atmosphere were obtained for the GRS using ground-based photographic observations. These were later much improved with precise measurements from the Voyager 1 and 2 flybys including accurate measurements of the detailed flow field. The Voyagers also obtained precise measurements of the local vorticity for White Oval BC (at 33ºS) and for a cyclone “barge” at 16ºN. Images obtained by the Galileo obiter allowed to measure the wind field of the GRS and a few smaller vortices. Currently, HST images can also be used to retrieve the internal flow field of the largest vortices such as the GRS or oval BA and JunoCam has provided data with enough spatial resolution and temporal separation to measure the wind field of the GRS and polar vortices.

Figure 2: Zonal wind profile of Jupiter and location of the NTrO. The zonal wind profile is from Barrado-Izagirre et al. and the ellipse shows the location and approximate size of the NTrO within it. © Barrado–Izagirre et al.

When two vortices of the same vorticity type closely interact they can merge (when they are of similar sizes), or if they have very different sizes the smaller one might get absorbed totally or partially. Vortex mergers occur in different areas of the planet with the best well-known example being the chain of large vortex mergers in 1998 and 2000 that resulted in oval BA. The new white oval BA turned red in August 2005 with a very similar shade to that of the GRS. Extensive dynamic studies did not find dynamical differences linked to color. According to radiative transfer analysis models, the color change resulted from the diffusion of a colored compound that interacted with the solar photons at the upper levels of the oval. Partial absorptions have been observed in Jupiter’s Great Red Spot interactions with large ovals.

Color changes are relatively common in Jupiter’s atmosphere. Color changes in the red coloration of tropical anticyclones have been described in Sánchez-Lavega et al. Their analysis of tropical vortices concluded that the vertical structure and dynamics of the anticyclones are not the causes of their coloration, and they propose that the red chromophore forms when the background material is stirred and exposed to ultraviolet radiation or mixed with other chemical compounds inside the vortex. In addition, planetary scale disturbances in the Jovian atmosphere can modify the zonal albedo pattern of the planet as for example in the cycle of the South Equatorial Belt (SEB) with convective Disturbances, large-scale color changes and Fades. The North Temperate Belt (NTB) also experiences this kind of event leading to the entire band becoming totally disturbed. The NTB Disturbances (NTBD) start with the outbreak of one or more convective plumes seen as bright spots moving with a velocity slightly faster than the zonal wind that interacts with the surrounding cloud patterns altering them and forming turbulence in their wake. The last NTBD developed in October 2016 with an outburst of four plumes that disturbed the entire latitudinal band and led to the formation of a very different reddish band.

Fig 3: NTrO in detail before and after the 2016 NTBD event. All images from HST in F658N filter. Barrado–Izagirre et al.

Now, in the present work, Barrado–Izagirre and colleagues have followed the evolution of an anticyclone located in the boundary between the North Tropical Zone (NTrZ) and the North Equatorial Belt (NEB) at 19º N planetographic latitude (Figures 1 and 2). This oval has existed at least since 2008 but it is probably older than that, so it is one of the longest living ovals observed in Jupiter. The oval is interesting because of its large size and longevity (third after the GRS and oval BA), its color changes between white and red, and its interactions with close vortices including a major vortex merger in February 2013, and by the interaction with the NTBD in 2012, 2016 and 2020. They referred this anticyclone as NTrZ-Oval (NTrO).

In order to describe the historic evolution of the properties of NTrZ-Oval, astronomers used JunoCam and Hubble Space Telescope (HST) images to measure its size, obtaining a mean value of (10,500±1,000) x (5,800±600) km² and its internal rotation finding a value of –(2±1)·10¯51 for its mean relative vorticity.

Fig 4: Examples of measured wind field in NTrO in 2012 and 2017. These results were obtained with the image correlation software resulting in a dense network of measurements. These measurements were later interpolated over a regular grid. © Barrado–Izagirre et al.

Furthermore, they used HST and PlanetCam-UPV/EHU multi-wavelength observations to characterize its color changes and Junocam images to unveil its detailed structure. The color and the altitudeopacity indices showed that the oval is higher and has redder clouds than its environment but has lower cloud tops than other large ovals like the GRS, and it is less red than the GRS and oval BA.

They also showed that in spite of the dramatic environmental changes suffered by the oval during all these years, its main characteristics are stable in time and therefore must be related with the atmospheric dynamics below the observable cloud decks.

Figure 5: Appearance of NTrO in different filters and time periods © Barrado–Izagirre et al.

Featured image: The White Tropical Oval and its environment from JunoCam observations on June 21, 2019. The image was originally projected in planetocentric coordinates. The inset shows zonal winds as measured during the Cassini flyby in black or in purple with only minor changes in this latitude range. © Barrado–Izagirre et al.


Reference: N. Barrado-Izagirre, J. Legarreta, A. Sánchez-Lavega, S. Pérez-Hoyos, R. Hueso, P. Iñurrigarro, J. F. Rojas, I. Mendikoa, I. Ordoñez-Etxeberria, the IOPW Team, “Jupiter’s third largest and longest-lived oval: Color changes and Dynamics”, Icarus, Volume 361, June 2021, 114394. https://doi.org/10.1016/j.icarus.2021.114394 https://www.sciencedirect.com/science/article/abs/pii/S001910352100083X


Copyright of this article totally belongs to our author S. Aman. One is allowed to reuse it only by giving proper credit either to him or to us

How Teeth Sense the Cold? (Biology)

For people with tooth decay, drinking a cold beverage can be agony.

“It’s a unique kind of pain,” says David Clapham, vice president and chief scientific officer of the Howard Hughes Medical Institute (HHMI). “It’s just excruciating.”

Now, he and an international team of scientists have figured out how teeth sense the cold and pinpointed the molecular and cellular players involved. In both mice and humans, tooth cells called odontoblasts contain cold-sensitive proteins that detect temperature drops, the team reports March 26, 2021, in the journal Science Advances. Signals from these cells can ultimately trigger a jolt of pain to the brain.

The work offers an explanation for how one age-old home remedy eases toothaches. The main ingredient in clove oil, which has been used for centuries in dentistry, contains a chemical that blocks the “cold sensor”protein, says electrophysiologist Katharina Zimmermann, who led the work at Friedrich-Alexander University Erlangen-Nürnberg in Germany.

Developing drugs that target this sensor even more specifically could potentially eliminate tooth sensitivity to cold, Zimmermann says. “Once you have a molecule to target, there is a possibility of treatment.”

Mystery channel

Teeth decay when films of bacteria and acid eat away at the enamel, the hard, whitish covering of teeth. As enamel erodes, pits called cavities form. Roughly 2.4 billion people – about a third of the world’s population – have untreated cavities in permanent teeth, which can cause intense pain, including extreme cold sensitivity.

No one really knew how teeth sensed the cold, though scientists had proposed one main theory. Tiny canals inside the teeth contain fluid that moves when the temperature changes. Somehow, nerves can sense the direction of this movement, which signals whether a tooth is hot or cold, some researchers have suggested.

“We can’t rule this theory out,” but there wasn’t any direct evidence for it, says Clapham a neurobiologist at HHMI’s Janelia Research Campus. Fluid movement in teeth – and tooth biology in general – is difficult to study. Scientists have to cut through the enamel – the hardest substance in the human body – and another tough layer called dentin, all without pulverizing the tooth’s soft pulp and the blood vessels and nerves within it. Sometimes, the whole tooth “will just fall to pieces,” Zimmermann says.

Zimmerman, Clapham, and their colleagues didn’t set out to study teeth. Their work focused primarily on ion channels, pores in cells’ membranes that act like molecular gates. After detecting a signal – a chemical message or temperature change, for example – the channels either clamp shut or open wide and let ions flood into the cell. This creates an electrical pulse that zips from cell to cell. It’s a rapid way to send information, and crucial in the brain, heart, and other tissues.

About fifteen years ago, when Zimmermann was a postdoc in Clapham’s lab, the team discovered that an ion channel called TRPC5 was highly sensitive to the cold. But the team didn’t know where in the body TRPC5’s cold-sensing ability came into play. It wasn’t the skin, they found. Mice that lacked the ion channel could still sense the cold, the team reported in 2011 in the journal Proceedings of the National Academy of Sciences.

After that, “we hit a dead end,” Zimmermann says. The team was sitting at lunch one day discussing the problem when the idea finally hit. “David said, ‘Well, what other tissues in the body sense the cold?’ Zimmermann recalls. The answer was teeth.

The whole tooth

TRPC5 does reside in teeth – and more so in teeth with cavities, study coauthor Jochen Lennerz, a pathologist from Massachusetts General Hospital, discovered after examining specimens from human adults.

A novel experimental set up in mice convinced the researchers that TRPC5 indeed functions as a cold sensor. Instead of cracking a tooth open and solely examining its cells in a dish, Zimmermann’s team looked at the whole system: jawbone, teeth, and tooth nerves. The team recorded neural activity as an ice-cold solution touched the tooth. In normal mice, this frigid dip sparked nerve activity, indicating the tooth was sensing the cold. Not so in mice lacking TRPC5 or in teeth treated with a chemical that blocked the ion channel. That was a key clue that the ion channel could detect cold, Zimmermann says. One other ion channel the team studied, TRPA1, also seemed to play a role.

The team traced TRPC5’s location to a specific cell type, the odontoblast, that resides between the pulp and the dentin. When someone with a a dentin-exposed tooth bites down on a popsicle, for example, those TRPC5-packed cells pick up on the cold sensation and an “ow!” signal speeds to the brain.

That sharp sensation hasn’t been as extensively studied as other areas of science, Clapham says. Tooth pain may not be considered a trendy subject, he says, “but it is important and it affects a lot of people.”

Zimmermann points out that the team’s journey towards this discovery spanned more than a decade. Figuring out the function of particular molecules and cells is difficult, she says. “And good research can take a long time.”

Featured image: Odontoblasts containing the ion channel TRPC5 (green) tightly pack the area between the pulp and the dentin in a mouse’s molar. The cells’ long-haired extensions fill the thin canals in dentin that extend towards the enamel. © L. Bernal et al./Science Advances 2021


Reference: Laura Bernal, Pamela Sotelo-Hitschfeld, Christine König, Viktor Sinica, Amanda Wyatt, Zoltan Winter, Alexander Hein, Filip Touska, Susanne Reinhardt, Aaron Tragl, Ricardo Kusuda, Philipp Wartenberg, Allen Sclaroff, John D. Pfeifer, Fabien Ectors, Andreas Dahl, Marc Freichel, Viktorie Vlachova, Sebastian Brauchi, Carolina Roza, Ulrich Boehm, David E. Clapham, Jochen K. Lennerz, Katharina Zimmermann, “Odontoblast TRPC5 channels signal cold pain in teeth”, Science Advances  26 Mar 2021: Vol. 7, no. 13, eabf5567 DOI: 10.1126/sciadv.abf5567


Provided by Howard Hughes Medical Institute

Scientists Develop New Platelet-based Formulation for Combination Anticancer Therapy (Medicine)

Tumor targeting and intratumoral penetration are long-standing issues for cancer therapeutics.

Researchers from the Institute of Process Engineering (IPE) of the Chinese Academy of Sciences and the University of Chinese Academy of Sciences (UCAS) have developed a new platelet-based formulation which demonstrated potent therapeutic effects against cancer in murine models.

The scientists utilized the aggregation and activation features of the platelets to address issues of tumor targeting and intratumoral penetration. Upon carrying photothermal nanoparticles and immunostimulators, this biomimetic formulation also achieves an efficient combination therapy against multiple types of cancer.

This study was published in Science Advances on March 26.

Recently, photothermal therapy (PTT) has attracted increasing attention. Although promising, efficient delivery of PTT still faces a series of issues. The accumulation of photosensitizers, specifically at tumor sites, and subsequent intratumoral penetration are restricted for most anticancer therapies, because of the cancer’s heterogeneity and the compact extracellular matrix.

As a new type of delivery vector, platelets have shown their capacity to deliver cargo to tumor sites via several mechanisms, suggesting they are reasonable candidates for tumor targeting and intratumoral penetration.

Anticancer effects in a sophisticated model based on humanized mouse and PDX © Wei Wei

Hyperthermia can induce tumor cells to release antigens. Such a response not only reveals the inherent relationship between the underlying mechanisms of PTT and immunoactivation, but also encourages the combination of PTT and immunotherapy for improved anticancer therapy.

In this new platelet-based formulation, photothermal nanoparticles and immunostimulators were simply, mildly and efficiently integrated into platelets.

“The photothermal conversion efficiency of this novel photothermal nanoparticle reached 69.2%. Thus, low-power near-infrared light (NIR) irradiation can generate enough local hyperthermia,” said Prof. TIAN Zhiyuan from UCAS.

The biomimetic platelets worked as circulating sentinels in the bloodstream and had a sensitive response to vascular damage. As a result, a portion of them acted as spearheads to prime adhesion at defective tumor vascular endothelial cells.

After irradiation with low-power NIR, local hyperthermia resulted in acute vascular damage, which subsequently induced an aggregation cascade of reinforced platelets to form a targeting arsenal in situ.

Subsequently, nanosized proplatelets (nPLTs) were further generated upon these activated platelets. “We observed that nPLTs relayed the cargo into deep tumor tissue, expanding the area of attack,” said Prof. WEI Wei from IPE.

Following tumor ablation induced by photothermal therapy, the immunostimulator enhanced the immunogenicity of released tumor-associated antigens, which further induced the body’s immunologic response to attack residual, metastatic and recurrent tumors.

The research demonstrated potent therapeutic effects with low-power NIR irradiation in nine different murine models, and, most notably, a sophisticated model based on human platelets, humanized mice and patient-derived tumor xenografts (PDX).

“These results show great promise for utilization of this novel biomimetic platelet platform in high-performance and combined anticancer therapies,” said Prof. MA Guanghui from IPE.

A peer reviewer from Science Advances said the study was “well organized and performed.” The reviewer also emphasized that “this system is very effective in tumor therapy and has been shown in different tumor models, and I would very much like to see this work translated into clinical applications.”

Featured image: Schematic illustration of the platelet-based formulation and anticancer application in photothermal-immunological combined therapy © Wei Wei


Reference: Yanlin Lv, Feng Li, Shuang Wang, Guihong Lu et al., “Near-infrared light–triggered platelet arsenal for combined photothermal-immunotherapy against cancer”, Science Advances  26 Mar 2021: Vol. 7, no. 13, eabd7614 DOI: 10.1126/sciadv.abd7614


Provided by Chinese Academy of Sciences

Using Prodrugs On Cancer Cells (Medicine)

Team of FAU researchers develops new substances

Prodrugs are substances that only release their effects once they have been metabolised. The prodrugs of the FAU research team led by Prof. Dr. Andriy Mokhir, Professorship of Organic Chemistry, are activated in the organism by means of a chemical reaction with specific molecules that contain oxygen, known as reactive oxygen species. These molecules are found in large numbers in cancer cells.

The researchers demonstrated that their prodrugs were effective both in cell lines and Nemeth‐Kellner lymphoma mouse models, which serve as a model for leukaemia in humans.

Prodrugs induce stress in the endoplasmic reticulum (ER) of cancer cells, the area within cells which produces proteins the organism requires. Inducing ER stress in this way inhibits cancer cell growth.

Other medicines which also increase this effect such as Bortezomib und Carilzomib,have so far resulted in undesired side effects. Prodrugs, however, have very little effect on normal cells.

Featured image credit: Colourbox.de


Further information

Mokhir, A., Xu, H., Schikora, M., Sisa, M., Daum, S., Janko, C., Alexiou, C., Bilyy, R., Klemt, I., Sellner, L., Gong, W., Schmitt, M. and Bila, G. (2021), An endoplasmic reticulum – specific pro‐amplifier of reactive oxygen species in cancer cells. Angew. Chem. Int. Ed.. Accepted Author Manuscript. https://doi.org/10.1002/anie.202100054 https://onlinelibrary.wiley.com/doi/10.1002/anie.202100054


Provided by FAU